Interfacial Engineering of P2-Type Ni/Mn-Based Layered Oxides by a Facile Water-Washing Method for Superior Sodium-Ion Batteries

Owing to the strong basicity and reactivity, residual sodium compounds (RSCs) on the surface of Na-based layered oxides for sodium-ion batteries (SIBs) cause the deterioration of the electrochemical performance and processability of the oxide cathode materials. Herein, considering P2-type Na0.66Ni0.26Zn0.07Mn0.67O2 as the model material, the water-washing treatment is proven to be a facile, economic, and highly efficient method to improve the electrochemical performance of P2-type Ni/Mn-based layered oxides. Experimental results show that RSCs on material surfaces can be effectively removed by water washing without causing severe damage to the bulk structure. Notably, water washing triggers the formation of an ultrathin (2-3 nm thick) Na-poor disordered interfacial layer on the surface of Na0.66Ni0.26Zn0.07Mn0.67O2. This layer plays a passivating role in further enhancing the material's resistance to water and reduces the reactivity of the material surface with the electrolyte. These compositional and structural optimizations for P2-type Na0.66Ni0.26Zn0.07Mn0.67O2 effectively suppress the release of gaseous CO2, formation of thick cathode-electrolyte interphase films, and consumption of active Na+, enabling good Na+ transport kinetics during cycling. The water-washed Na0.66Ni0.26Zn0.07Mn0.67O2 exhibits significantly improved cycling stability with a capacity retention of 89.1% at 100 mA g-1 after 100 cycles and rate capability with a discharge capacity of 76.3 mA g-1 at 2000 mA g-1; these values are higher than those of the unwashed Na0.66Ni0.26Zn0.07Mn0.67O2 (83.3%, 71.4 mA h g-1). This work provides fundamental insights into the detrimental effect of RSCs on the electrochemical performance of layered oxides and highlights the importance of regulating interfacial compositions for developing high-performance layered-oxide cathode materials for SIBs.

Boosting the Interfacial Stability of the Li6PS5Cl Electrolyte with a Li Anode via In Situ Formation of a LiF-Rich SEI Layer and a Ductile Sulfide Composite Solid Electrolyte

Due to its good mechanical properties and high ionic conductivity, the sulfide-type solid electrolyte (SE) can potentially realize all-solid-state batteries (ASSBs). Nevertheless, challenges, including limited electrochemical stability, insufficient solid-solid contact with the electrode, and reactivity with lithium, must be addressed. These challenges contribute to dendrite growth and electrolyte reduction. Herein, a straightforward and solvent-free method was devised to generate a robust artificial interphase between lithium metal and a SE. It is achieved through the incorporation of a composite electrolyte composed of Li6PS5Cl (LPSC), polyethylene glycol (PEG), and lithium bis(fluorosulfonyl)imide (LiFSI), resulting in the in situ creation of a LiF-rich interfacial layer. This interphase effectively mitigates electrolyte reduction and promotes lithium-ion diffusion. Interestingly, including PEG as an additive increases mechanical strength by enhancing adhesion between sulfide particles and improves the physical contact between the LPSC SE and the lithium anode by enhancing the ductility of the LPSC SE. Moreover, it acts as a protective barrier, preventing direct contact between the SE and the Li anode, thereby inhibiting electrolyte decomposition and reducing the electronic conductivity of the composite SE, thus mitigating the dendrite growth. The Li|Li symmetric cells demonstrated remarkable cycling stability, maintaining consistent performance for over 3000 h at a current density of 0.1 mA cm-2, and the critical current density of the composite solid electrolyte (CSE) reaches 4.75 mA cm-2. Moreover, the all-solid-state lithium metal battery (ASSLMB) cell with the CSEs exhibits remarkable cycling stability and rate performance. This study highlights the synergistic combination of the in-situ-generated artificial SE interphase layer and CSEs, enabling high-performance ASSLMBs.

High-Fluidity/High-Strength Dual-Layer Gel Electrolytes Enable Ultra-Flexible and Dendrite-Free Fiber-Shaped Aqueous Zinc Metal Battery

Fiber-shaped aqueous zinc-ion batteries (FAZIBs) with intrinsic safety, highcapacity, and superb omnidirectional flexibility hold promise for wearable energy-supply devices. However, the interfacial separation of fiber-shaped electrodes and electrolytes caused by Zinc (Zn) stripping process and severe Zn dendrites occurring at the folded area under bending condition seriously restricts FAZIBs' practical application. Here, an advanced confinement encapsulation strategy is originally reported to construct dual-layer gel electrolyte consisting of high-fluidity polyvinyl alcohol-Zn acetate inner layer and high-strength Zn alginate outer layer for fiber-shaped Zn anode. Benefiting from the synergistic effect of inner-outer gel electrolyte and the formation of solid electrolyte interphase on Zn anode surface by lysine additive, the resulting fiber-shaped Zn-Zn symmetric cell delivers long cycling life over 800 h at 1 mA cm-2 with dynamic bending frequency of 0.1 Hz. The finite element simulation further confirms that dual-layer gel electrolyte can effectively suppress the interfacial separation arising from the Zn stripping and bending process. More importantly, a robust twisted fiber-shaped Zn/zinc hexacyanoferrate battery based on dual-layer gel electrolyte is successfully assembled, achieving a remarkable capacity retention of 97.7% after bending 500 cycles. Therefore, such novel dual-layer gel electrolyte design paves the way for the development of long-life fiber-shaped aqueous metal batteries.

Preparation and Properties of Gel Polymer Electrolytes with Li1.5Al0.5Ge1.5(PO4)3 and Li6.46La3Zr1.46Ta0.54O12 by UV Curing Process

Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolytes (GPEs) are considered a promising electrolyte candidate for polymer lithium-ion batteries (LIBs) because of their free-standing shape, versatility, security, flexibility, lightweight, reliability, and so on. However, due to problems such as low ionic conductivity, PVDF-HFP can only be used on a small scale when used as a substrate alone. To overcome the above shortcomings, GPEs were designed and synthesized by a UV curing process by adding NASICON-type Li1.5Al0.5Ge1.5(PO4)3 (LAGP) and garnet-type Li6.46La3Zr1.46Ta0.54O12 (LLZTO) to PVDF-HFP. Experimentally, GPEs with 10% weight LLZTO in a PVDF-HFP matrix had an ionic conductivity of up to 3 × 10-4 S cm-1 at 25 °C. When assembled into LiFePO4/GPEs/Li batteries, a discharge-specific capacity of 81.5 mAh g-1 at a current density of 1 C and a capacity retention rate of 98.1% after 100 cycles at a current density of 0.2 C occurred. Therefore, GPEs added to LLZTO have a broad application prospect regarding rechargeable lithium-ion batteries.

An Ultrahigh Modulus Gel Electrolytes Reforming the Growing Pattern of Li Dendrites for Interfacially Stable Lithium-Metal Batteries

Gel polymer electrolytes (GPEs) have aroused intensive attention for their moderate comprehensive performances in lithium-metal batteries (LMBs). However, GPEs with low elastic moduli of MPa magnitude cannot mechanically regulate the Li deposition, leading to recalcitrant lithium dendrites. Herein, a porous Li7 La3 Zr2 O12 (LLZO) framework (PLF) is employed as an integrated solid filler to address the intrinsic drawback of GPEs. With the incorporation of PLF, the composite GPE exhibits an ultrahigh elastic modulus of GPa magnitude, confronting Li dendrites at a mechanical level and realizing steady polarization at high current densities in Li||Li cells. Benefiting from the compatible interface with anodes, the LFP|PLF@GPE|Li cells deliver excellent rate capability and cycling performance at room temperature. Theoretical models extracted from the topology of solid fillers reveal that the PLF with unique 3D structures can effectively reinforce the gel phase of GPEs at the nanoscale via providing sufficient mechanical support from the load-sensitive direction. Numerical models are further developed to reproduce the multiphysical procedure of dendrite propagation and give insights into predicting the failure modes of LMBs. This work quantitatively clarifies the relationship between the topology of solid fillers and the interface stability of GPEs, providing guidelines for designing mechanically reliable GPEs for LMBs.

Regulating the Electrical Double Layer with Supramolecular Cyclodextrin Anions for Dendrite-Free Zinc Electrodeposition

The interfacial stability of a Zn battery is dependent on the electrical double layer (EDL) that forms at the interface between the electrolyte and the Zn metal anode. A fundamental understanding of the regulation of the EDL structure and stability on the Zn surface is highly desirable for practical applications of aqueous batteries. Herein, the interfacial chemistry of the EDL is regulated by the adsorption of supramolecular cyclodextrin anions in the inner Helmholtz plane (IHP). The nucleation overpotential and the charge transfer activation energy for Zn2+ to go through the OHP (Ea1) and IHP (Ea2) are increased, leading to slower Zn2+ transfer kinetics. The electric field distribution and Zn2+ flux in the proximity of the Zn metal surface are homogenized, thus suppressing the growth of dendrites. The mechanism is supported with theoretical and experimental analyses. Consequently, a Zn||Zn symmetric cell achieves an ultrahigh cumulative capacity of 10000 and 4250 mAh cm-2 at a respective current density of 10 and 50 mA cm-2, and an average Coulombic efficiency of 99.5% over 1000 cycles under harsh conditions (at a high current density of 10 mA cm-2 with a high capacity of 10 mAh cm-2). This work provides insight into the introduction of supramolecular anions to regulate the electrical double layer EDL structure and improve the interfacial stability.

In Situ Constructing Robust and Highly Conductive Solid Electrolyte with Tailored Interfacial Chemistry for Durable Li Metal Batteries

Employing nanofiber framework for in situ polymerized solid-state lithium metal batteries (SSLMBs) is impeded by the insufficient Li+ transport properties and severe dendritic Li growth. Both critical issues originate from the shortage of Li+ conduction highways and nonuniform Li+ flux, as randomly-scattered nanofiber backbone is highly prone to slippage during battery assembly. Herein, a robust fabric of Li0.33 La0.56 Ce0.06 Ti0.94 O3-δ /polyacrylonitrile framework (p-LLCTO/PAN) with inbuilt Li+ transport channels and high interfacial Li+ flux is reported to manipulate the critical current density of SSLMBs. Upon the merits of defective LLCTO fillers, TFSI- confinement and linear alignment of Li+ conduction pathways are realized inside 1D p-LLCTO/PAN tunnels, enabling remarkable ionic conductivity of 1.21 mS cm-1 (26 °C) and tLi+ of 0.93 for in situ polymerized polyvinylene carbonate (PVC) electrolyte. Specifically, molecular reinforcement protocol on PAN framework further rearranges the Li+ highway distribution on Li metal and alters Li dendrite nucleation pattern, boosting a homogeneous Li deposition behavior with favorable SEI interface chemistry. Accordingly, excellent capacity retention of 76.7% over 1000 cycles at 2 C for Li||LiFePO4 battery and 76.2% over 500 cycles at 1 C for Li||LiNi0.5 Co0.2 Mn0.3 O2 battery are delivered by p-LLCTO/PAN/PVC electrolyte, presenting feasible route in overcoming the bottleneck of dendrite penetration in in situ polymerized SSLMBs.

Low-cost BPO4 In Situ Synthetic Li3 PO4 Coating and B/P-Doping to Boost 4.8 V Cyclability for Sulfide-Based All-Solid-State Lithium Batteries

Structural damage of Ni-rich layered oxide cathodes such as LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) and serious interfacial side reactions and physical contact failures with sulfide electrolytes (SEs) are the main obstacles restricting ≥4.6 V high-voltage cyclability of all-solid-state lithium batteries (ASSLBs). To tackle this constraint, here, a modified NCM811 with Li3 PO4 coating and B/P co-doping using inexpensive BPO4 as raw materials via the one-step in situ synthesis process is presented. Phosphates have good electrochemical stability and contain the same anion (O2- ) and cation (P5+ ) as in cathode and SEs, respectively, thus Li3 PO4 coating precludes interfacial anion exchange, lessening side reactivity. Based on the high bond energy of B─O and P─O, the lattice O and crystal texture of NCM811 can be stabilized by B3+ /P5+ co-doping, thereby suppressing microcracks during high-voltage cycling. Therefore, when tested in combination with Li─In anode and Li6 PS5 Cl solid electrolytes (LPSCl), the modified NCM811 exhibits extraordinary performance, with 200.36 mAh g-1 initial discharge capacity (4.6 V), cycling 2300 cycles with decay rate as low as 0.01% per cycle (1C), and 208.26 mAh g-1 initial discharge capacity (4.8 V), cycling 1986 cycles with 0.02% per cycle decay rate. Simultaneously, it also has remarkable electrochemical abilities at both -20 °C and 60 °C.

Stable Lithium-Sulfur Batteries Ensured by GeS2 and α-S8 Lattice Matching During the Charge Process

The charge process of lithium-sulfur batteries (LSBs) is a process in which molecular polarity decreases and the volume shrinks gradually, which is the process most likely to cause lithium polysulfides (LiPSs) loss and interfacial collapse. In this work, GeS2 is utilized, whose (111) lattice plane exactly matches with the (113) lattice of α-S8 , to solve these problems. GeS2 can regulate the interconversion-deposition behavior of S-species during the charge process. Soluble LiPSs can be spontaneously adsorbed on the GeS2 surface, then obtain electrons and eventually convert to α-S8 molecules. More importantly, the α-S8 molecules will crystallize uniformly along the (111) lattice plane of GeS2 to maintain a stable cathode-electrolyte interface. Therefore, outstanding charge/discharge LSBs are successfully accomplished.

Single-Crystal Growth of P2-Type Layered Oxides with Increased Exposure of {010} Planes for High-Performance Sodium-Ion Batteries

An increase in the size of single-crystal particles can effectively reduce the interfacial side reactions of layered oxides for sodium-ion batteries at high voltages but may result in sluggish Na+ transport. Herein, single-crystal Na0.66Ni0.26Zn0.07Mn0.67O2 with increased proportions of {010} planes is synthesized by adding low-cost NaCl as the molten salt. With the assistance of a NaCl molten salt, the median diameter (D50) of single-crystal Na0.66Ni0.26Zn0.07Mn0.67O2 increases to 10.46 μm relative to that of the comparison sample without NaCl (6.57 μm). Electrolyte decomposition on the surface of single-crystal Na0.66Ni0.26Zn0.07Mn0.67O2 is considerably suppressed, owing to a decrease in the specific surface area. Moreover, the increased exposure of {010} planes is favorable for improving the Na+ transport kinetics of single-crystal particles. Therefore, at 100 mA g-1, single-crystal Na0.66Ni0.26Zn0.07Mn0.67O2 exhibits a high-capacity retention of 96.6% after 100 cycles, which is considerably greater than that of the comparison sample (86.8%). Moreover, the rate performance of single-crystal Na0.66Ni0.26Zn0.07Mn0.67O2 (average discharge capacity of 81.2 mAh g-1) is superior to that of the comparison sample (average discharge capacity of 61.2 mAh g-1) at 2000 mA g-1. This work provides a new approach for promoting the single-crystal growth of layered oxides for highly stable interfaces at high voltages without compromising Na+ transport kinetics.

Structural properties of Phoenix oolong tea polysaccharide conjugates and the interfacial stability in nanoemulsions

BACKGROUND

Tea polysaccharide conjugate (TPC) is a naturally occurring active substance that is extracted from tea. Owing to its benefits in enhancing human immunity and antioxidant effects, TPC is widely used in culinary products. The binding mode of polysaccharides and proteins in TPC, however, has not been well studied; it may be closely related to their functional properties, especially emulsification.

RESULTS

The molecular weights and monosaccharide compositions of TPC were determined by ion chromatography and high-performance gel permeation chromatography. Although the functional groups of polysaccharides and proteins were confirmed by infrared spectroscopy, the presence of proteins could not be detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis and ultraviolet spectroscopy. It was hypothesized that the hydrophobic groups of the proteins in TPC were wrapped by polysaccharide chains, thus making the proteins undetectable. The rheology and interfacial protein adsorption results show that TPC forms a viscoelastic film at the oil-water interface to prevent the aggregation of oil droplets, thereby enhancing the stability of the emulsion. Based on these structural and emulsifying properties of TPC, the binding mode of polysaccharides and proteins along with their phase behavior at the oil-water interface of the emulsion was speculated.

CONCLUSION

In TPC, the hydrophilic groups of the proteins are linked to polysaccharides by covalent interactions, where the hydrophobic groups are wrapped with the polysaccharide chains with the help of hydrophobic forces to form a hydrophobic core. The unique binding of polysaccharides and proteins in TPC enhances its amphiphilic properties, which can be effectively distributed at the oil-water interface and form stable emulsions. © 2023 Society of Chemical Industry.

Constructing Ionic Self-Concentrated Electrolyte via Introducing Montmorillonite Toward High-Performance Aqueous Zn-MnO2 Batteries

Aqueous zinc metal batteries are regarded as one of the most promising alternatives to lithium-ion batteries for large-scale energy storage due to the abundant zinc resources, high safety, and low cost. Herein, an ionic self-concentrated electrolyte (ISCE) is proposed to enable uniform Zn deposition and reversible reaction of MnO₂ cathode. Benefitting from the compatibility of ISCE with electrodes and its adsorption on the electrode surface for guidance, the Zn/Zn symmetrical batteries exhibit the long-life cycle stability with more than 5000 and 1500 h at 0.2 and 5 mA cm^-2 , respectively. The Zn/MnO₂ battery also exhibits a high capacity of 351 mA h g^-1 at 0.1 A g^-1 and can enable a stability over 2000 cycles at 1 A g^-1 . This work provides a new insight into electrolyte design for stable aqueous Zn-MnO₂ battery.

Cross-Linked Gel Polymer Electrolyte Based on Multiple Epoxy Groups Enabling Conductivity and High Performance of Li-Ion Batteries

The low ionic conductivity and unstable interface of electrolytes/electrodes are the key issues hindering the application progress of lithium-ion batteries (LiBs). In this work, a cross-linked gel polymer electrolyte (C-GPE) based on epoxidized soybean oil (ESO) was synthesized by in situ thermal polymerization using lithium bis(fluorosulfonyl)imide (LiFSI) as an initiator. Ethylene carbonate/diethylene carbonate (EC/DEC) was beneficial for the distribution of the as-prepared C-GPE on the anode surface and the dissociation ability of LiFSI. The resulting C-GPE-2 exhibited a wide electrochemical window (of up to 5.19 V vs. Li⁺/Li), an ionic conductivity (σ) of 0.23 × 10^-3 S/cm at 30 °C, a super-low glass transition temperature (T_g), and good interfacial stability between the electrodes and electrolyte. The battery performance of the as-prepared C-GPE-2 based on a graphite/LiFePO₄ cell showed a high specific capacity of ca. 161.3 mAh/g (an initial Coulombic efficiency (CE) of ca. 98.4%) with a capacity retention rate of ca. 98.5% after 50 cycles at 0.1 C and an average CE of about ca. 98.04% at an operating voltage range of 2.0~4.2 V. This work provides a reference for designing cross-linking gel polymer electrolytes with high ionic conductivity, facilitating the practical application of high-performance LiBs.

In Situ Polymerized Flame Retardant Gel Electrolyte for High-Performance and Safety-Enhanced Lithium Metal Batteries

A flame retardant gel electrolyte (FRGE) is deemed as one of the most promising electrolytes to relieve the problems of safety hazards and interfacial incompatibility of Li metal batteries. Herein, a novel solvent triethyl 2-fluoro-2-phosphonoacetate (TFPA) with outstanding flame retardancy is introduced in the polymer skeleton synthesized by in situ polymerization of the monomer polyethylene glycol dimethacrylate (PEGDMA) and the cross-linker pentaerythritol tetraacrylate (PETEA). The FRGE exhibits superb interfacial compatibility with Li metal anodes and inhibits uncontrolled Li dendrite growth. This can be ascribed to the restriction of free phosphate molecules by the polymer skeleton, thus realizing a stable cycling performance over 500 h at 1 mA cm^-2 and 1 mAh cm^-2 in the Li||Li symmetric cell. In addition, the high ionic conductivity (3.15 mS cm^-1) and Li⁺ transference number (0.47) of the FRGE further enhance the electrochemical performance of the correspondent battery. As a result, the LiFePO₄|FRGE|Li cell exhibits excellent long-term cycling life with a capacity retention of 94.6% after 700 cycles. This work points to a new pathway for the practical development of high-safety and high-energy-density Li metal-based batteries.

Correlation between the Protein Pharmaceutical Surface Activity and Interfacial Stability

The interaction of protein drugs with the air-liquid interface plays a crucial role in the overall stability in aqueous formulations, particularly when the adsorbed proteins are subjected to the surface flow. Nonionic surfactants are usually added into the formulation solutions to address this issue. A diversity of studies have been focused on the usage of surfactants, the stability mechanism of surfactants, or seeking new pharmaceutical surfactants. However, the real protagonist, the basic properties of protein drugs, was neglected, which may play a vital role in the stability of protein drugs. Herein, we aim to clarify the correlation between the surface behavior of proteins and the interfacial stability. A force tensiometer is used to track the surface tension reduction and the competition between surfactants and proteins at the surface. We find that the surface behaviors of proteins vary with storage temperature and protein types including monoclonal antibodies (mAb), bispecific monoclonal antibodies (BsAb), and antibody-drug conjugates (ADCs). Especially for the protein stored at 5 °C, the surface activity of proteins is better than that of surfactants. It indicates that the ability of proteins to adsorb at the interface should not be ignored compared to surfactants. The significant difference in the interfacial stability of protein pharmaceuticals formulated in the same buffer and excipients as well as the surfactants with the same concentration further confirms the interfacial adsorption capacity of proteins that should not be ignored. These findings provide a new angle and valuable insights into the correlation between the surface activity of the proteins and interfacial stability, which may pave the way for future preformulation studies on therapeutic proteins and broaden the thoughts of formulation development.

Building K-C Anode with Ultrahigh Self-Diffusion Coefficient for Solid State Potassium Metal Batteries Operating at -20 to 120 °C

Solid state potassium (K) metal batteries are intriguing in grid-scale energy storage, benefiting from the low cost, safety, and high energy density. However, their practical applications are impeded by poor K/solid electrolyte (SE) interfacial contact and limited capacity caused by the low K self-diffusion coefficient, dendrite growth, and intrinsically low melting point/soft features of metallic K. Herein, a fused-modeling strategy using potassiophilic carbon allotropes molted with K is demonstrated that can enhance the electrochemical performance/stability of the system via promoting K diffusion kinetics (2.37 × 10^-8 cm² s^-1 ), creating a low interfacial resistance (≈1.3 Ω cm² ), suppressing dendrite growth, and maintaining mechanical/thermal stability at 200 °C. A homogeneous/stable K stripping/plating is consequently implemented with a high current density of 2.8 mA cm^-2 (at 25 °C) and a record-high areal capacity of 11.86 mAh cm^-2 (at 0.2 mA cm^-2 ). The enhanced K diffusion kinetics contribute to sustaining intimate interfacial contact, stabilizing the stripping/plating at high current densities. Full cells coupling ultrathin K-C composite anodes (≈50 µm) with Prussian blue cathodes and β/β″-Al₂ O₃ SEs deliver a high energy density of 389 Wh kg^-1 with a retention of 94.4% after 150 cycles and fantastic performances at -20 to 120 °C.

Dual-Salt Localized High-Concentration Electrolyte for Long Cycle Life Silicon-Based Lithium-Ion Batteries

Silicon-based materials are considered the most promising anodes for next-generation lithium-ion batteries (LIBs) owing to their high specific capacity. However, poor interfacial stability due to enormous volume changes severely restricts their mass application in LIBs. Here, we design a fluoroethylene carbonate (FEC)-containing dual-salt (LiFSI-LiPF₆) ether-based localized high-concentration electrolyte (D-LHCE-F) for enhancing the interfacial stability of silicon-based electrodes. It is revealed that the dominating LiFSI salt of superior chemical and thermal stability prevents the formation of corrosive HF, while the addition of FEC improves the interface stability by promoting the formation of protective LiF-rich SEI and increasing the flexibility of the interface. This robust and flexible SEI layer can adapt to substantial variations in the volume of silicon electrodes while preserving the integrity of the interface. The SiO_x/C electrode using the unique D-LHCE-F retains up to 78.5% of its initial capacity after 500 cycles at 0.5C, well surpassing that of the control electrolyte (3.4% capacity retention). More notably, the cycle life of the SiO_x/C||NCM90 (LiNi_0.9Co_0.05Mn_0.05O₂) full batteries is effectively enhanced thanks to the stabilized electrode/electrolyte interfaces. The key findings of this work offer crucial knowledge for rationally designing electrolyte chemistry to enable the practical application of high-energy-density LIBs adopting silicon-based anodes.

Enhancing the Interfacial Stability of the Li2S-SiS2-P2S5 Solid Electrolyte toward Metallic Lithium Anode by LiI Incorporation

Chalcogenide solid-state electrolytes (SEs) have been regarded as promising candidates for lithium dendrite suppression due to their high ionic conductivity, suitable mechanical strength, and large Li⁺ ion transference number. However, the wide applications of SEs in pragmatic all-solid-state batteries are still retarded by their limited interface stability, which leads to lithium dendrite growth and formation of interphase with high resistance. In addition, the interphase evolution mechanism between SEs and metallic Li anodes remains unclear. Herein, this work demonstrates that the interfacial stability of Li₂S-SiS₂-P₂S₅ SEs can be effectively enhanced by tuning the interphase through LiI incorporation. This strategy contributes to a high ionic conductivity of the SEs and electronic insulation interphase containing LiI. Thus, the 70(60Li₂S-28SiS₂-12P₂S₅)-30 LiI SEs prepared by melt-quenching exhibit a high ionic conductivity of 1.74 mS cm^-1 at room temperature and a larger critical current density of 1.65 mA cm^-2 at 65 °C. The cycling life of the symmetric Li|SEs|Li cell is up to 200 h without significant resistance growth at 0.1 mA cm^-2 at room temperature. This enhanced interface stability is revealed to originate from the in situ-formed LiI within the interphase, which prevents continual SEs degradation and suppresses lithium dendrite growth. This work provides a vital understanding of interphase evolution, which is valuable for designing SEs with long cycling stability.

Examining Electrolyte Compatibility on Polymorphic MnO2 Cathodes for Room-Temperature Rechargeable Magnesium Batteries

Rechargeable magnesium batteries are promising candidates for post-lithium-ion batteries, owing to the large source abundance and high theoretical energy density. However, there remain few reports on constructing practical cells with oxide cathodes and Mg anodes at room temperature. In this work, we compare the reaction behavior of various MnO₂ polymorph cathodes in two representative electrolytes: Mg[TFSA]₂/G3 and Mg[Al(hfip)₄]₂/G3. In Mg[TFSA]₂/G3, discharge capacities of the MnO₂ cathodes are well consistent with the changes in Mg composition, where nanorod-like α-MnO₂ and λ-MnO₂ show the capacities of about 100 mA h g^-1 at room temperature. However, this electrolyte has the disadvantage that the Mg anodes are easily passivated. In contrast, Mg[Al(hfip)₄]₂/G3 allows highly reversible deposition/dissolution of Mg anodes, whereas the discharge process of the MnO₂ cathodes involves a large part of side reactions, in which the MnO₂ active material takes part in some reductive reaction together with electrolyte species instead of the expected Mg²⁺ intercalation. Such an unstable electrode/electrolyte interface would lead to continuous degradation on/near the cathode surface. Thus, the interfacial stability between the oxide cathodes and the electrolytes must be improved for practical applications.

High Transverse Thermoelectric Performance and Interfacial Stability of Co/Bi0.5Sb1.5Te3 Artificially Tilted Multilayer Thermoelectric Devices

Artificially tilted multilayer thermoelectric devices (ATMTDs) have attracted extensive attention because of their numerous advantages, such as high integration, great structural freedom, and large transverse Seebeck coefficients. ATMTDs are composed of numerous alternating stackings of two types of materials with large differences in electrical and thermal transport. Therefore, it is of great interest to find ATMTDs with both high transverse thermoelectric performance and good interfacial stability to develop their practical application. In this work, cobalt (Co) and Bi_0.5Sb_1.5Te₃ (BST) are chosen to prepare Co/BST ATMTDs. The interfacial structure and composition of Co/BST are characterized, and its interfacial stability and transverse thermoelectric performance are evaluated. The results show that the thickness of the Co/BST interfacial reaction layer is about 4 μm. Annealing at 473 K for 32 h does not increase the thickness, which indicates better interfacial stability than Ni/BST. After structure optimization, Co/BST ATMTD has ZT_zx = 0.41, which is second only to YbAl₃/BST ATMTDs. Meanwhile, the transverse Seebeck coefficient reaches -120.38 μV/K. The outstanding interfacial stability and transverse thermoelectric performance promise excellent thermal response and refrigeration performance with Co/BST ATMTDs.

Strengthening the Interfacial Stability of the Silicon-Based Electrode via an Electrolyte Additive─Allyl Phenyl Sulfone

Silicon-based anodes have received widespread attention because of their high theoretical capacity, which, however, still faces challenges for practical applications due to the large volume changes during repeated charge/discharge processes, despite being developed for many years. Herein, we explore an electrolyte additive, allyl phenyl sulfone (APS), to enhance the interfacial stability and long-term durability of the SiO_x/C electrode. It is revealed that additive APS contributes to forming a dense and robust solid electrolyte interphase film with high mechanical strength and favorable lithium-ion diffusion kinetics, which effectively suppresses the parasitic side reactions at the electrode-electrolyte interface. Meanwhile, the strong interaction between APS and trace water/acid in the electrolyte is further beneficial for enhancing the interfacial stability. By incorporating 0.5 wt% APS, the cycling stability of the silicon-based electrode is significantly improved, reserving a capacity of 777 mAh g^-1 after 200 cycles at 0.5C and 30 °C (79.3% capacity retention), which well exceeds that of the baseline electrolyte (57.8% capacity retention). More importantly, additive APS effectively promotes the cycling performance of the corresponding SiO_x/C||NCM90 (LiNi_0.9Co_0.05Mn_0.05O₂) full battery. This work provides valuable understanding in developing new electrolyte additives to enable the commercial application of high-energy density lithium-ion batteries using silicon-based anodes.

Modularly Integrated System for Spatiotemporally Separated Solar Energy Storage and Release

The sun is regarded as an endless source of clean energy. However, the intermittent supply and dynamically changeable demand of solar energy, as well as its uneven regional distribution, have been continually motivating the technological research of practical strategies to realize the spatiotemporally separated solar energy harvest and utilization. Accordingly, we here developed an integrated system for efficient solar energy capture, stable storage, and on-demand release, which corresponds to the intricate design of three distinct modules, namely, a photothermal conversion module, a latent heat storage module, and a mechanical trigger module. Moreover, efficient heat transfer and long-term supercooled stability necessitate interfacial passivation to coordinate the physical coupling of different modules. In addition to providing an integrated prototype that demonstrates a closed energy cycle in practice, this study may further inspire a new paradigm for advanced solar utilization in both theory and methodology.

In Situ Construction of a LiF-Enriched Interfacial Modification Layer for Stable All-Solid-State Batteries

All-solid-state batteries (ASSBs), particularly based on sulfide solid-state electrolytes (SSEs), are expected to meet the requirements of high-energy-density energy storage. However, the unstable interface between the ceramic pellets and lithium (Li) metal can induce unconstrained Li-dendrite growth with safety concerns. Herein, we design a carbon fluoride-silver (CF_x-Ag) composite to modify the SSEs. As lithium fluoride (LiF) nanocrystals can be in situ formed through electrochemical reactions, this LiF-enriched modification layer with high surface energy can more effectively suppress Li dendrite penetration and interfacial reactions between the SSEs and anode. Remarkably, the all-solid-state symmetric cells using a lithium-boron alloy (LiB) anode can stably work to above 2,500 h under 0.5 mA cm^-2 and 2 mAh cm^-2 at 60 °C without shorting. A modified LiB||LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) full cell also demonstrates an improved capacity retention and high Coulombic efficiency (99.9%) over 500 cycles. This work provides an advanced solid-state interface architecture to address Li-dendrite issues of ASSBs.

Stabilizing the Li1.3 Al0.3 Ti1.7 (PO4 )3 |Li Interface for High Efficiency and Long Lifespan Quasi-Solid-State Lithium Metal Batteries

To tackle the poor chemical/electrochemical stability of Li_1+x Al_x Ti_2-x (PO₄ )₃ (LATP) against Li and poor electrode|electrolyte interfacial contact, a thin poly[2,3-bis(2,2,6,6-tetramethylpiperidine-N-oxycarbonyl)norbornene] (PTNB) protection layer is applied with a small amount of ionic liquid electrolyte (ILE). This enables study of the impact of ILEs with modulated composition, such as 0.3 lithium bis(fluoromethanesulfonyl)imide (LiFSI)-0.7 N-butyl-N-methylpyrrolidinium bis(fluoromethanesulfonyl)imide (Pyr₁₄ FSI) and 0.3 LiFSI-0.35 Pyr₁₄ FSI-0.35 N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr₁₄ TFSI), on the interfacial stability of PTNB@Li||PTNB@Li and PTNB@Li||LiNi_0.8 Co_0.1 Mn_0.1 O₂ cells. The addition of Pyr₁₄ TFSI leads to better thermal and electrochemical stability. Furthermore, Pyr₁₄ TFSI facilitates the formation of a more stable Li|hybrid electrolyte interface, as verified by the absence of lithium "pitting corrosion islands" and fibrous dendrites, leading to a substantially extended lithium stripping-plating cycling lifetime (>900 h). Even after 500 cycles (0.5C), PTNB@Li||LiNi_0.8 Co_0.1 Mn_0.1 O₂ cells achieve an impressive capacity retention of 89.1 % and an average Coulombic efficiency of 98.6 %. These findings reveal a feasible strategy to enhance the interfacial stability between Li and LATP by selectively mixing different ionic liquids.

Improving Cyclability of All-Solid-State Batteries via Stabilized Electrolyte-Electrode Interface with Additive in Poly(propylene carbonate) Based Solid Electrolyte

In this study, tetraethylene glycol dimethyl ether (TEGDME) is demonstrated as an effective additive in poly(propylene carbonate) (PPC) polymers for the enhancement of ionic conductivity and interfacial stability and a tissue membrane is used as a backbone to maintain the mechanical strength of the solid polymer electrolytes (SPEs). TEGDME in the PPC allows the uniform distribution of conductive LiF species throughout the cathode electrolyte interface (CEI) layer which plays a critically important role in the formation of a stable and efficient CEI. In addition, the high modulus of SPEs suppresses the formation of a protrusion-type CEI on the cathode. The SPE with the optimized TEGDME content exhibits a high ionic conductivity of 0.89 mS cm^-1 , an adequate potential stability of up to 4.89 V, and a high Li-ion transference number of 0.81 at 60 °C. Moreover, the Li/SPE/Li cell demonstrates excellent cycling stability for 1650 h, and the Li/SPE/LFP full cell exhibits an initial reversible capacity of 103 mAh g^-1 and improved stability over 500 cycles at a rate of 1 C. The TEGDME additive improves the electrochemical properties of the SPEs and promotes the creation of a stable interface, which is crucial for ASSLIBs.

Computational Investigation of the Interfacial Stability of Lithium Chloride Solid Electrolytes in All-Solid-State Lithium Batteries

All-solid-state Li-ion batteries (ASSLIBs) with solid electrolytes (SEs) are promising next-generation batteries owing to their high energy density and high safety. Recently, lithium chloride SEs have attracted increasing attention because of their high ionic conductivity and broad electrochemical stability window. However, only a few studies have been reported for the application of lithium chloride SEs in high-energy ASSLIBs employing lithium metal anodes and high-voltage cathode materials. This study examines the interfacial stability of lithium chloride SEs toward lithium metal anodes and high-voltage cathode materials using first-principles calculations. Calculation results indicate the chemical instability of lithium chloride SEs toward lithium metal anodes. Metallic phases are formed by reduction reactions resulting in the continuous decomposition of lithium chloride SEs. In addition, lithium chloride SEs exhibit high reactivity toward high-voltage cathode materials, resulting in interfacial resistance by decomposition reactions. Computational screening is performed to explore coating materials to stabilize the interfaces, demonstrating that binary halides are appropriate for the anode and 54 compounds are discovered for the cathode. Among the coating materials for the cathode, several ternary oxides such as LiAl₅O₈, Li₂MoO₄, and LiTaO₃ are found to be promising for enhancing the interfacial stability between lithium chloride SEs and high-voltage cathode materials.

Progress in Solid Polymer Electrolytes for Lithium-Ion Batteries and Beyond

Solid-state polymer electrolytes (SPEs) for high electrochemical performance lithium-ion batteries have received considerable attention due to their unique characteristics; they are not prone to leakage, and they exhibit low flammability, excellent processability, good flexibility, high safety levels, and superior thermal stability. However, current SPEs are far from commercialization, mainly due to the low ionic conductivity, low Li⁺ transference number (t_Li+ ), poor electrode/electrolyte interface contact, narrow electrochemical oxidation window, and poor long-term stability of Li metal. Recent work on improving electrochemical performance and these aspects of SPEs are summarized systematically here with a particular focus on the underlying mechanisms, and the improvement strategies are also proposed. This review could lead to a deeper consideration of the issues and solutions affecting the application of SPEs and pave a new pathway to safe, high-performance lithium-ion batteries.

Formation of LiF Surface Layer During Direct Fluorination of High-Capacity Co-Free Disordered Rocksalt Cathodes

Disordered rocksalt (DRX) cathodes have attracted interest due to their high capacity and compositional flexibility (e.g., Co-free chemistries). However, the sloping voltage profile and gradual capacity fade during cycling have hindered the widespread adoption of these materials. Simulations predict that fluorine substitution in DRX cathodes will improve their capacity, rate performance, and cyclability. In this study, we use a fluidized bed reactor to fluorinate a model Li-rich DRX composition (Li_1.15Ni_0.375Ti_0.375Mo_0.1O₂, NTMO) to investigate how fluorine content impacts the cathode's structure and electrochemical performance. Instead of substituting O with F to form oxyfluoride phases, direct fluorination of DRX cathodes leads to the formation of LiF surface films, which improves the specific energy and capacity retention. This study demonstrates the feasibility of direct fluorination to improve the electrochemical performance of high-voltage cathodes by tuning the material's surface chemistry.

Robust Li6PS5I Interlayer to Stabilize the Tailored Electrolyte Li9.95SnP2S11.95F0.05/Li Metal Interface

All-solid-state lithium-metal batteries (ASSLMBs) with sulfide electrolytes have attracted attention owing to their superior safety and high energy density. However, interfacial instability of sulfide electrolytes against Li metal still hinders their applications. Herein, F-doping is adopted to optimize the structure of Li₁₀SnP₂S₁₂. It is demonstrated that the Li_9.95SnP₂S_11.95F_0.05 (LSPSF) electrolyte exhibits a high ionic conductivity of 6.4 mS cm^-1 because of F-doping, which can reduce the impurity Li₂SnS₃ and generate Li⁺ vacancies. In addition, the Li₆PS₅I (LPSI) glass-ceramic interlayer is employed to enhance the interfacial stability between the sulfide electrolyte and Li metal by restraining the reduction of Sn⁴⁺ cations, as indicated by X-ray photoelectron spectroscopy (XPS). As a result, the assembled ASSLMBs with the LPSI interlayer deliver high initial discharge capacity and remarkable cycling stability. This work provides a new design route for manufacturing high-performance ASSLMBs.

Stabilizing Lithium Metal Anode Enabled by a Natural Polymer Layer for Lithium-Sulfur Batteries

The lithium-sulfur (Li-S) battery with a high theoretical energy density (2560 Wh kg^-1) is one of the most promising candidates in next-generation energy storage systems. However, its practical application is impeded by the shuttle effect of lithium polysulfides, huge volume expansion, and overgrowth dendrite of lithium. Herein, we propose an artificial conformal agar polymer coating on a lithium anode (marked as A-Li). The functional layer facilitating the formation of a compact interphase on the lithium anode can effectively accommodate expansive volume and restrain the growth of dendritic lithium. The Li/Li symmetric cell with A-Li delivers stable plating/stripping cycling over 300 h at a high current density of 3.0 mA cm^-2 and a high fixed areal capacity of 3.0 mAh cm^-2. The cycle life of Li-Cu cells with A-Li is twice longer than that of pristine cells, and the Li-S batteries equipped with A-Li anodes also deliver an enhanced specific capacity and high Coulombic efficiencies. This work provides a pathway to protect metal Li anodes and contributes to the development of high-performance Li-S batteries.

Dynamic Interfacial Stability Confirmed by Microscopic Optical Operando Experiments Enables High-Retention-Rate Anode-Free Na Metal Full Cells

Rechargeable alkali metal anodes hold the promise to significantly increase the energy density of current battery technologies. But they are plagued by dendritic growths and solid-electrolyte interphase (SEI) layers that undermine the battery safety and cycle life. Here, a non-porous ingot-type sodium (Na) metal growth with self-modulated shiny-smooth interfaces is reported for the first time. The Na metal anode can be cycled reversibly, without forming whiskers, mosses, gas bubbles, or disconnected metal particles that are usually observed in other studies. The ideal interfacial stability confirmed in the microcapillary cells is the key to enable anode-free Na metal full cells with a capacity retention rate of 99.93% per cycle, superior to available anode-free Na and Li batteries using liquid electrolytes. Contradictory to the common beliefs established around alkali metal anodes, there is no repeated SEI formation on or within the sodium anode, supported by the X-ray photoelectron spectroscopy elemental depth profile analyses, electrochemical impedance spectroscopy diagnosis, and microscopic imaging.

Surface Potential Regulation Realizing Stable Sodium/Na3 Zr2 Si2 PO12 Interface for Room-Temperature Sodium Metal Batteries

Inorganic Na₃ Zr₂ Si₂ PO₁₂ is prospective with a high ionic conductivity but suffers large interfacial resistance and stability issues against sodium metal, hindering its practical application in all-solid-state sodium batteries. A surface potential regulation strategy is adopted to address these issues. Na₃ Zr₂ Si₂ PO₁₂ (NZSP) ceramic with homogeneously-sintered surface is synthesized by a simple two-step sintering method to promote its uniform surface potential, which is favorable for mitigating the potential fluctuations at the interface against Na metal and enhancing interfacial compatibility. The Na/NZSP interface can be stabilized for over 4 months with a low interfacial resistance of 129 Ω cm² at 25 °C. The symmetrical Na/NZSP/Na cell exhibits ultra-stable sodium platting/stripping cycling for over 1000 cycles under 0.1 mA cm^-2 . Superior interfacial performance is well retained even under 0.2 mA cm^-2 at room temperature. The robust interface is further signified by its excellence under higher current densities of up to 0.85 mA cm^-2 at 60 °C. A 4 V all-solid-state Na₃ V_1.5 Cr_0.5 (PO₄ )₃ /NZSP/Na metal battery is demonstrated at ambient conditions, which exhibits superior rate capability and delivers a high reversible capacity of 103 mA h g^-1 under 100 mA g^-1 for over 400 cycles with a Coulombic efficiency of over 99%.

Cyclopropenium Cationic-Based Covalent Organic Polymer-Enhanced Poly(ethylene oxide) Composite Polymer Electrolyte for All-Solid-State Li-S Battery

Cyclopropenium cationic-based covalent organic polymer (iCP@TFSI) was successfully prepared through the SN₂ reaction and ion replacement process, which can be incorporated into the PEO/LiTFSI matrix as a filler. The obtained solid-state polymer electrolytes were utilized for an all-solid-state lithium-sulfur (Li-S) battery. Padding iCP@TFSI into the PEO matrix not only has a positive influence on both the ionic conductivity and the mechanical capacity of solid-state polymer electrolytes but also increases the stability of the lithium metal anode, which essentially improves the overall cycling ability of all-solid-state Li-S batteries. Among the membranes attained, the PEO-10%iCP@TFSI electrolyte displays the best ionic conductivity up to 1.2 × 10^-3 S·cm^-1 at 80 °C. The symmetrical lithium battery exhibits higher cycle stability (600 h) due to the higher mechanical properties related to more stable lithium metal interfaces. The Li-S battery based on the PEO-10%iCP@TFSI electrolyte exhibits excellent electrochemical performance with better Coulombic efficiency and outstanding cycling stability. Its capacity is maintained at 490 mAh·g^-1 after 500 cycles at 1 C with a 0.032% decay rate each cycle, and the Coulombic efficiency is close to 100% during the whole cycling.

Stabilizing Ni-Rich LiNi0.83Co0.12Mn0.05O2 with Cyclopentyl Isocyanate as a Novel Electrolyte Additive

Ni-rich layered structure materials are appealing cathodes for high-energy-density lithium-ion batteries developed for electric vehicles, drones, power tools, etc. However, poor interfacial stability between a Ni-rich cathode and carbonate electrolyte, especially at high temperatures, and fast capacity fading still hinder their mass market penetration. Here, we investigate cyclopentyl isocyanate (CPI) with a single isocyanate (-NCO) functional group as a bifunctional electrolyte additive for the first time to improve the interfacial stability of Ni-rich cathode LiNi_0.83Co_0.12Mn_0.05O₂ (NCM83). With an electrolyte containing 2 wt % CPI, the NCM83 cathode shows capacity retention of up to 92.3% after 200 cycles at 1C and 30 °C, much higher than that with the standard electrolyte (78.6%). It is demonstrated that the -NCO of CPI could largely inhibit the thermal decomposition of LiPF₆ salt and scavenge water and hydrogen fluoride (HF) species, improving electrolyte stability. More importantly, the additive CPI could be preferentially oxidized, forming a stabilized and protective cathode electrolyte interphase (CEI) layer on the surface of NCM83, which effectively suppresses the parasitic side reactions and maintains the superior interfacial charge-transfer and lithium-ion diffusion kinetics. Both functions enable a significant improvement in electrochemical performance at both 30 and 60 °C.

Improving the Stability of High-Voltage Lithium Cobalt Oxide with a Multifunctional Electrolyte Additive: Interfacial Analyses

In recent years, various attempts have been made to meet the increasing demand for high energy density of lithium-ion batteries (LIBs). The increase in voltage can improve the capacity and the voltage platform performance of the electrode materials. However, as the charging voltage increases, the stabilization of the interface between the cathode material and the electrolyte will decrease, causing side reactions on both sides during the charge–discharge cycling, which seriously affects the high-temperature storage and the cycle performance of LIBs. In this study, a sulfate additive, dihydro-1,3,2-dioxathiolo[1,3,2]dioxathiole 2,2,5,5-tetraoxide (DDDT), was used as an efficient multifunctional electrolyte additive for high-voltage lithium cobalt oxide (LiCoO₂). Nanoscale protective layers were formed on the surfaces of both the cathode and the anode electrodes by the electrochemical redox reactions, which greatly decreased the side reactions and improved the voltage stability of the electrodes. By adding 2% (wt.%) DDDT into the electrolyte, LiCoO₂ exhibited improved Li-storage performance at the relatively high temperature of 60 °C, controlled swelling behavior (less than 10% for 7 days), and excellent cycling performance (capacity retention rate of 76.4% at elevated temperature even after 150 cycles).

Simultaneous Enhancement of Interfacial Stability and Kinetics of Single-Crystal LiNi0.6Mn0.2Co0.2O2 through Optimized Surface Coating and Doping

Balancing interfacial stability and Li⁺ transfer kinetics through surface engineering is a key challenge in developing high-performance battery materials. Although conformal coating enabled by atomic layer deposition (ALD) has shown great promise in controlling impedance increase upon cycling by minimizing side reactions at the electrode-electrolyte interface, the coating layer itself usually exhibits poor Li⁺ conductivity and impedes surface charge transfer. In this work, we have shown that by carefully controlling postannealing temperature of an ultrathin ZrO₂ film prepared by ALD, Zr⁴⁺ surface doping could be achieved for Ni-rich layered oxides to accelerate the charge transfer yet provide sufficient protection. Using single-crystal LiNi_0.6Mn_0.2Co_0.2O₂ as a model material, we have shown that surface Zr⁴⁺ doping combined with ZrO₂ coating can enhance both the cycle performance and rate capability during high-voltage operation. Surface doping via controllable postannealing of ALD surface coating layer reveals an attractive path toward developing stable and Li⁺-conductive interfaces for single-crystal battery materials.

Will Sulfide Electrolytes be Suitable Candidates for Constructing a Stable Solid/Liquid Electrolyte Interface?

Conversion-type batteries with electrode materials partially dissolved in a liquid electrolyte exhibit high specific capacity and excellent redox kinetics, but currently poor stability due to the shuttle effect. Using a solid-electrolyte separator to block the mass exchange between the cathode and the anode can eliminate the shuttle effect. A stable interface between the solid-electrolyte separator and the liquid electrolyte is essential for the battery performance. Here, we demonstrate that a stable interface with low interfacial resistance and limited side reactions can be formed between the sulfide solid-electrolyte β-Li₃PS₄ and the widely used ether-based liquid electrolytes, under both reduction and oxidation conditions, due to the rapid formation of an effective protective layer of ether-solvated Li₃PS₄ at the sulfide/liquid electrolyte interface. This discovery has inspired the design of a β-Li₃PS₄-coated solid-electrolyte Li₇P₃S₁₁ separator with a simultaneously high ion-conduction ability and good interfacial stability with the liquid electrolyte, so that hybrid lithium-sulfur (Li-S) batteries with this composite separator conserve a high discharge capacity of 1047 mA h g^-1 and a high second discharge plateau of 2.06 V after 150 cycles.

Polydopamine-Coated Garnet Particles Homogeneously Distributed in Poly(propylene carbonate) for the Conductive and Stable Membrane Electrolytes of Solid Lithium Batteries

Flexible membrane electrolytes consisting of Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) fillers in poly(propylene carbonate) (PPC) are considered promising for developing solid lithium batteries with high energy density and safety. However, LLZTO particles tend to agglomerate owing to their high surface energy, especially concerning their distribution in PPC that has low surface energy. Moreover, basic LLZTO particles attack PPC, resulting in its decomposition. Such problems make it difficult to achieve membrane electrolytes of PPC/LLZTO with high conduction and stability. In this work, continuous polydopamine (PDA) layers with a thickness of 4 nm are coated on LLZTO particles. Characterized by synchrotron X-ray microtomography and scanning electron microscopy, the PDA-coated LLZTO particles show homogeneous dispersion in PPC, which is attributed to the reduced surface energy of the LLZTO particles. Besides, this coating hinders the reaction between LLZTO and PPC, which improves the chemical stability of the membrane electrolytes. Consequently, the cells based on membrane electrolytes with PDA-coated LLZTO particles in PPC show improved electrochemical performance and cycling stability. These results demonstrate that the strategy of coating basic LLZTO particles is powerful for enhancing their usability in the high-performance membrane electrolytes for solid lithium batteries.

Interfacial Stability in Bi2Te3 Thermoelectric Joints

Bismuth telluride (Bi₂Te₃)-based thermoelectric materials are well-known for their high figure-of-merit (zT value) in the low-temperature region. Stable joints in the module are essential for creating a reliable device for long-term applications. This study used electroless Co-P to prevent a severe interfacial reaction between the joints of solder and Bi₂Te₃. A thick and brittle SnTe intermetallic compound layer was successfully inhibited. The strength of the joints improved, and the fracture mode became more ductile; furthermore, there was no significant degradation of thermoelectric properties after depositing the Co-P layer after long-term aging. The result suggests that electroless Co-P could enhance the interfacial stability of the joints and be an effective diffusion barrier for Bi₂Te₃ thermoelectric modules.

Effect of Orientation and Wetting Properties on the Behavior of Janus Particles at the Air-Water Interface

The adhesion force and contact angle of gold-capped silica Janus particles and plain silica particles at an air-water interface are studied via colloidal atomic force microscopy. Particles are attached to cantilevers at various orientations, and wetting properties of the gold surface are varied through modification with dodecanethiol. Thiol modification increases the hydrophobicity of the gold surface, thereby increasing the difference between the contact angles of the gold hemisphere and the silica hemisphere and, thus, increasing the degree of amphiphilicity of the Janus particle. Subsequently, the colloidal probe is pushed into a stationary bubble from the water phase followed by retraction back into the water phase. Adhesion force is found to be higher for Janus particles than isotropic silica particles, regardless of orientation of the anisotropic hemisphere. Particles with their polar half oriented toward the water and apolar half facing the air show an increase in adhesion force and contact angle as the degree of amphiphilicity of the particles increases. For particles of the reverse orientation, no significant difference is observed as wetting properties change. Both adhesion force and contact angle display an inverse relationship with a cap angle for particles with a higher degree of amphiphilicity. These results are of importance for using Janus particles to stabilize interfaces as well as for understanding the equilibrium height of Janus particles at the interface, which will impact capillary interactions and thus self-assembly.

Poly(vinylene carbonate)-Based Composite Polymer Electrolyte with Enhanced Interfacial Stability To Realize High-Performance Room-Temperature Solid-State Sodium Batteries

Solid-state rechargeable batteries using polymer electrolytes have been considered, which can avoid safety issues and enhance energy density. However, commercial application of the polymer electrolyte solid-state battery is still significantly limited by the low room-temperature ionic conductivity, poor mechanical properties, and weak interfacial compatibility between the electrolyte and electrode, especially for the room-temperature solid-state rechargeable battery. In this work, a poly(vinylene carbonate)-based composite polymer electrolyte (PVC-CPE) is reported for the first time to realize room-temperature solid-state sodium batteries with high performances. This in situ solidified PVC-CPE possesses superior ionic conductivity (0.12 mS cm^-1 at 25 °C), high Na⁺ transference number (t_Na⁺ = 0.60), as well as enhanced electrode/electrolyte interfacial stability. Notably, the composite cathode NaNi_1/3Fe_1/3Mn_1/3O₂ (c-NFM) is designed through the in situ growth of the polymer electrolyte inside the electrode to decrease interfacial resistance and facilitate effective ion transport in electrode/electrolyte interfaces. It is demonstrated that the solid-state c-NFM/PVC-CPE/Na battery assembled by a one-step in situ solidification method exhibits remarkably enhanced cell performances at room temperature compared with a reference NFM/PVC-CPE/Na assembled through a conventional ex situ method. The battery presents a high initial specific capacity of 104.2 mA h g^-1 at 0.2 C with a capacity retention of 86.8% over 250 cycles and ∼80.2 mA h g^-1 at 1 C. This study suggests that PVC-CPE is a very promising electrolyte for solid-state sodium batteries. This study also suggests a new method to design high-performance polymer electrolytes for other solid-state rechargeable batteries to realize high safety and considerable electrochemical performance at room temperature.

In Situ Lithiophilic Layer from H+/Li+ Exchange on Garnet Surface for the Stable Lithium-Solid Electrolyte Interface

Garnet-type solid-state electrolytes (SSEs) show a promising application in solid-state Li batteries. Poor interfacial contact with lithium causing large interfacial impedance and dendrite penetration is a problem. Inspired by unique H⁺/Li⁺ exchange of garnet electrolyte, we used an AgNO₃ aqueous solution induced strategy to construct a lithiophilic layer in situ on the garnet surface without any specific apparatus. Experimental analysis reveals the uniform distribution of Ag nanoparticles and significantly enhanced affinity between the solid state electrolyte (SSE) and Li anode for the Li-Ag alloying. As expected, the interfacial area specific resistance (ASR) is greatly reduced to ∼4.5 Ω cm², accompanying with long-cycling stability for ∼3500 h at 0.2 mA cm^-2 and high critical current density of 0.75 mA cm^-2. With modified SSEs, quasi-solid-state batteries with a LiFePO₄ or LiNi_0.5Co_0.2Mn_0.3O₂ cathode operate well at room temperature and an all-solid-state LiFePO₄/garnet/Li battery displays good cycling stability for over 200 cycles at 60 °C.

Poly(ethylene oxide)-Li10SnP2S12 Composite Polymer Electrolyte Enables High-Performance All-Solid-State Lithium Sulfur Battery

Composite polymer electrolyte membranes are fabricated by the incorporation of Li₁₀SnP₂S₁₂ into the poly(ethylene oxide) (PEO) matrix using a solution-casting method. The incorporation of Li₁₀SnP₂S₁₂ plays a positive role on Li-ionic conductivity, mechanical property, and interfacial stability of the composite electrolyte and thus significantly enhances the electrochemical performance of the solid-state Li-S battery. The optimal PEO-1%Li₁₀SnP₂S₁₂ electrolyte presents a maximum ionic conductivity of 1.69 × 10^-4 S cm^-1 at 50 °C and the highest mechanical strength. The possible mechanism for the enhanced electrochemical performance and mechanical property is analyzed. The uniform distribution of Li₁₀SnP₂S₁₂ in the PEO matrix inhibits crystallization and weakens the interactions among the PEO chains. The PEO-1%Li₁₀SnP₂S₁₂ electrolyte exhibits lower interfacial resistance and higher interfacial stability with the lithium anode than the pure PEO/LiTFSI electrolyte. The Li-S cell comprising the PEO-1%Li₁₀SnP₂S₁₂ electrolyte exhibits outstanding electrochemical performance with a high discharge capacity (ca. 1000 mA h g^-1), high Coulombic efficiency, and good cycling stability at 60 °C. Most importantly, the PEO-1%Li₁₀SnP₂S₁₂-based cell possesses attractive performance with a high specific capacity (ca. 800 mA h g^-1) and good cycling stability even at 50 °C, whereas the PEO/LiTFSI-based cell cannot be successfully discharged because of the low ionic conductivity and high interfacial resistance of the PEO/LiTFSI electrolyte.

Graphitic Hollow Nanocarbon as a Promising Conducting Agent for Solid-State Lithium Batteries

All-solid-state batteries (ASSBs) have lately received enormous attention for electric vehicle applications because of their exceptional stability by engaging all-solidified cell components. However, there are many formidable hurdles such as low ionic conductivity, interface instability, and difficulty in the manufacturing process, for its practical use. Recently, carbon, one of the representative conducting agents, turns out to largely participate in side reactions with the solid electrolyte, which finally leads to the formation of insulating side products at the interface. Although the battery community mentioned that parasitic reactions are presumably attributed to carbon itself or the generation of electronic conducting paths lowering the kinetic barrier for reactions, the underlying origin for such reactions as well as appropriate solutions have not been provided yet. In this study, for the first time, it is verified that the functional group on carbon is an origin for causing negative effects on interfacial stability and a graphitized hollow nanocarbon as a promising solution for improving-electrochemical performance is introduced. This work offers an invaluable lesson that a relatively minor part, such as a conducting agent, in ASSBs sometimes gives more positive impact on improving electrochemical performance than huge efforts for resolving other parts.

Stabilizing the Interface between Sodium Metal Anode and Sulfide-Based Solid-State Electrolyte with an Electron-Blocking Interlayer

Sulfide-based Na-ion conductors are promising electrolytes for all-solid-state sodium batteries (ASSSBs) because of high ionic conductivity and favorable formability. However, no effective strategy has been reported for long-duration Na cycling with sulfide-based electrolytes because of interfacial challenges. Here we demonstrate that a cellulose-poly(ethylene oxide) (CPEO) interlayer can stabilize the interface between sulfide electrolyte (Na₃SbS₄) and Na by shutting off the electron pathway of the electrolyte decomposition reaction. As a result, we achieved stable Na plating/stripping for 800 cycles at 0.1 mA cm^-2 in all-solid-state devices at 60 °C.

Constructing a Stable Lithium Metal-Gel Electrolyte Interface for Quasi-Solid-State Lithium Batteries

Interfacial problems, including interfacial stability and contact issues, severely plague the practical application of Li metal anodes. Here we report an interfacial regulation strategy that stabilizes the Li metal-gel electrolyte interface through in situ constructing a stable solid electrolyte interphase (SEI) layer. By stabilizing the interface of Li metal anodes, the gel electrolyte enables dendrite-free morphology and high plating/stripping efficiency. A systematic analysis further confirms that the formed SEI layer is responsible for homogeneous deposition and stable cycling performance. Benefiting from the interfacial stability between electrodes and electrolytes, the lifespan of Li metal batteries is extended.

11.2% All-Polymer Tandem Solar Cells with Simultaneously Improved Efficiency and Stability

All-polymer solar cells (all-PSCs) that contain both p-type and n-type polymeric materials blended together as light-absorption layers have attracted much attention, since the blend of a polymeric donor and acceptor should present superior photochemical, thermal, and mechanical stability to those of small molecular-based organic solar cells. In this work, the interfacial stability is studied by using highly stable all-polymer solar cell as a platform. It is found that the thermally deposited metal electrode atoms can diffuse into the active layer during device storage, which consequently greatly decreases the power conversion efficiency. Fortunately, the diffusion of metal atoms can be slowed down and even blocked by using thicker interlayer materials, high-glass-transition-temperature interlayer materials, or a tandem device structure. Learning from this, homojunction tandem all-PSCs are successfully developed that simultaneously exhibit a record power conversion efficiency over 11% and remarkable stability with efficiency retaining 93% of the initial value after thermally aging at 80 °C for 1000 h.

Lithium Dendrite Suppression and Enhanced Interfacial Compatibility Enabled by an Ex Situ SEI on Li Anode for LAGP-Based All-Solid-State Batteries

The electrode-electrolyte interface stability is a critical factor influencing cycle performance of All-solid-state lithium batteries (ASSLBs). Here, we propose a LiF- and Li₃N-enriched artificial solid state electrolyte interphase (SEI) protective layer on metallic lithium (Li). The SEI layer can stabilize metallic Li anode and improve the interface compatibility at the Li anode side in ASSLBs. We also developed a Li_1.5Al_0.5Ge_1.5(PO₄)₃-poly(ethylene oxide) (LAGP-PEO) concrete structured composite solid electrolyte. The symmetric Li/LAGP-PEO/Li cells with SEI-protected Li anodes have been stably cycled with small polarization at a current density of 0.05 mA cm^-2 at 50 °C for nearly 400 h. ASSLB-based on SEI-protected Li anode, LAGP-PEO electrolyte, and LiFePO₄ (LFP) cathode exhibits excellent cyclic stability with an initial discharge capacity of 147.2 mA h g^-1 and a retention of 96% after 200 cycles.

N-Allyl- N, N-Bis(trimethylsilyl)amine as a Novel Electrolyte Additive To Enhance the Interfacial Stability of a Ni-Rich Electrode for Lithium-Ion Batteries

Enhancing the electrode/electrolyte interface stability of high-capacity LiNi_0.8Co_0.15Al_0.05O₂ (LNCA) cathode material is urgently required for its application in next-generation lithium-ion battery. Herein, we demonstrate that enhanced interfacial stability of LNCA can be achieved by simply introducing 2 wt % N-allyl- N, N-bis(trimethylsilyl)amine (NNB) electrolyte additive. Electrolyte oxidation reactions and electrode structural destruction are greatly suppressed in the electrolyte with NNB additive, leading to improved cyclic stability of LNCA from 72.8 to 86.2% after 300 cycles. The mechanism of NNB on improving the cyclic stability of LNCA has been verified to its excellent solid electrolyte interface (SEI) film-forming capability. Moreover, the X-ray diffraction and X-ray photoelectron spectroscopy results indicate that the NNB-derived Si-containing SEI film restrains the Li/Ni disorder of LNCA during cycling, which further improves the cyclic stability of Ni-rich LNCA. Importantly, the charging/discharging test reveals that the NNB additive effectively improves the cyclic stability of the LNCA/graphite full cell.

Superior Blends Solid Polymer Electrolyte with Integrated Hierarchical Architectures for All-Solid-State Lithium-Ion Batteries

Exploration of advanced solid electrolytes with good interfacial stability toward electrodes is a highly relevant research topic for all-solid-state batteries. Here, we report PCL/SN blends integrating with PAN-skeleton as solid polymer electrolyte prepared by a facile method. This polymer electrolyte with hierarchical architectures exhibits high ionic conductivity, large electrochemical windows, high degree flexibility, good flame-retardance ability, and thermal stability (workable at 80 °C). Additionally, it demonstrates superior compatibility and electrochemical stability toward metallic Li as well as LiFePO₄ cathode. The electrolyte/electrode interfaces are very stable even subjected to 4.5 V at charging state for long time. The LiFePO₄/Li all-solid-state cells based on this electrolyte deliver high capacity, outstanding cycling stability, and superior rate capability better than those based on liquid electrolyte. This solid polymer electrolyte is eligible for next generation high energy density all-solid-state batteries.