Self-Propagating Enabling High Lithium Metal Utilization Ratio Composite Anodes for Lithium Metal Batteries

Constructing three-dimensional (3D) structural composite lithium metal anode by molten-infusion strategy is an effective strategy to address the severe problems of Li dendritic growth and huge volume changes. However, various challenges, including uncontrollable Li loading, dense inner structure, and low Li utilization, still need to be addressed for the practical application of 3D Li anode. Herein, we propose a self-propagating method, which is realized by a synergistic effect of chemical reaction and capillarity effect on porous scaffold surface, for fabricating a flexible 3D composite Li metal anode with high Li utilization ratio and controllable low Li loading. The composite 3D anode possesses controllable low loading (8.0-24.0 mAh cm^-2) and uniform grid structure, realizing a stable cycling over 600 h at a high Li metal utilization ratio over 75%. The proposed strategy for fabricating composite 3D anode could promote the practical application of Li metal batteries.

The fluorination-assisted dealloying synthesis of porous reduced graphene oxide-FeF2@carbon for high-performance lithium-ion battery and the exploration of its electrochemical mechanism

Based on the dealloying conception, a porous rGO-FeF₂@C is attained and shows a great electrochemical performance. An intriguing phenomenon has been that the decrease in charge cut-off voltage contributes to the higher discharge plateau.

Metal–organic framework-engaged synthesis of core–shell MoO2/ZnSe@N-C nanorods as anodes in high-performance lithium-ion batteries

A MoO₂/ZnSe@N-C nanorod was prepared through novel carbonization and selenization methods, shedding light on the design and application of metal selenides.

New rationally designed hybrid polypyrrole@SnCoS4 as an efficient anode for lithium-ion batteries

Three active materials containing binary metal sulfide (SnCoS₄) were obtained via a simple hydrothermal method. Also, the electrochemical performance of the anode materials was investigated in a lithium-ion half-cell.

Graphether: a reversible and high-capacity anode material for sodium-ion batteries with ultrafast directional Na-ion diffusion

Sodium-ion batteries (SIBs) have been attracting great attention as the most promising alternative to lithium-ion batteries (LIBs) for large-scale energy storage. However, the absence of suitable anode materials is the main bottleneck for the commercial application of SIBs. Herein, the adsorption and diffusion behaviors of Na on graphether are predicted by first-principles density functional calculations. Our results show that Na atoms can be adsorbed on graphether forming a uniform and stable coverage on both sides. Even at low intercalated Na concentrations, the semiconducting graphether can be changed to a metallic state, ensuring good electrical conductivity. Due to the structural anisotropy of graphether, the Na+ ions show a remarkable one-dimensional diffusion with an ultralow energy barrier of 0.04 eV, suggesting ultrafast charge/discharge characteristics. The graphether monolayer has a high theoretical specific capacity of 670 mA h g-1, which is much higher than commercial graphite anode materials. Furthermore, the average voltage is 1.58 V, comparable with that of commercial TiO2 anode materials for LIBs (1.5 V). During the charge/discharge process, graphether could mostly preserve the structural integrity upon the adsorption of Na even at the maximum concentration, suggesting its good reversibility. All these results show that graphether is a promising anode material for high-performance SIBs.

Designing conductive networks of hybrid carbon enables stable and long-lifespan cotton-fiber-based lithium–sulfur batteries

In modern society, flexible rechargeable batteries have become a burgeoning apodictic choice for wearable devices. Conventional lithium–sulfur batteries lack sufficient flexibility because their electrode materials are too rigid to bend. Along with the inherent high theoretical capacity of sulfur, lithium–sulfur batteries have some issues, such as dissolution and shuttle effect of polysulfides, which restricts their efficiency and practicability. Here, a flexible and “dead-weight”-free lithium–sulfur battery substrate with a three-dimensional structure was prepared by a simple strategy. With the cooperative assistance of carbon nanotubes and graphene attached to cotton fibers, the lithium–sulfur battery with 2.0 mg cm⁻² sulfur provided a high initial discharge capacity of 1098.7 mA h g⁻¹ at 1C, and the decay rate after 300 cycles was only 0.046% per cycle. The initial discharge capacity at 2C was 872.4 mA h g⁻¹ and the capacity was maintained 734.4 mA h g⁻¹ after 200 cycles with only a 0.079% per cycle decay rate.

A flexible, “dead weight”-free lithium–sulfur battery substrate was prepared, and batteries using these substrates showed great electrochemical performance.

General Liquid-Driven Coaxial Flow Focusing Preparation of Novel Microcapsules for Rechargeable Magnesium Batteries

Magnesium batteries have been considered promising candidates for next-generation energy storage systems owing to their high energy density, good safety without dendrite formation, and low cost of magnesium resources. However, high-performance cathodes with stable capacity, good conductivity, and fast ions transport are needed, since many conventional cathodes possess a low performance and poor preparation controllability. Herein, a liquid-driven coaxial flow focusing (LDCFF) approach for preparing a novel microcapsule system with controllable size, high loading, and stable magnesium-storage performance is presented. Taking the MoS2-infilled microcapsule as a case study, the magnesium battery cathode based on the microcapsules displays a capacity of 100 mAh g-1 after 100 cycles. High capacity retention is achieved at both low and high temperatures of -10, ‒5, and 45 °C, and a stable rate-performance is also obtained. The influences of the liquid flow rates on the size and shell thickness of the microcapsules are investigated; and electron and ion diffusion properties are also studied by first-principle calculations. The presented LDCFF method is quite general, and the high performance of the microcapsules enables them to find broad applications for making emerging energy-storage materials and secondary battery systems.

Phase engineering of cobalt hydroxide toward cation intercalation

Multi-cation intercalation in aqueous and neutral media is promising for the development of high-safety energy storage devices. However, developing a new host matrix for reversible cation intercalation as well as understanding the relationship between cation intercalation and the interlayer structure is still a challenge. In this work, we demonstrate layered cobalt hydroxides as a promising host for cation interaction, which exhibit high metal ion (Li+, Na+, K+, Mg2+ and Ca2+) storage capacities after phase transformation. Moreover, it is found that α-Co(OH)2 with an intercalated structure is more conducive to phase transition after electrochemical activation than β-Co(OH)2. As a result, the activated α-Co(OH)2 delivers four times higher capacity in multi-cation storage than activated β-Co(OH)2. Meanwhile, the α-Co(OH)2 after activation also shows an ultralong cycle life with capacity retention of 93.9% after 5000 cycles, which is also much superior to that of β-Co(OH)2 (∼74.8%). Thus, this work displays the relationship between cation intercalation and the interlayer structure of layered materials, which is important for designing multi-ion storage materials in aqueous media.

Environmentally Benign, Intrinsically Coordinated, Lithium-Based Solid Electrolyte with a Modified Purine as Supporting Ligand

Bioinspired materials have become increasingly competitive for electronic applications in recent years owing to the environment-friendly alternatives they offer. The notion of biocompatible solid organic electrolytes addresses the issues concerning potential leakage of corrosive liquids, volatility and flammability of electrolyte solvents. This study presents a new intrinsically coordinated Li^I adenine complex that exhibits electrical conductivity as a solid electrolyte capable of self-sustained supply of Li^I ions. It exhibits conductivity through moisture-assisted Li^I ion motion up to 373 K, and possibly by an ion-hopping mechanism beyond 373 K. This purine-derived solid electrolyte shows enhanced conductivity and transference number demonstrating the potential of purine-based ligands and their coordination complexes in interesting materials applications.

Sulfate-Containing Composite Based on Ni-Rich Layered Oxide LiNi0.8Mn0.1Co0.1O2 as High-Performance Cathode Material for Li-ion Batteries

Composite positive electrode materials (1−x) LiNi_0.8Mn_0.1Co_0.1O₂∙xLi₂SO₄ (x = 0.002–0.005) for Li-ion batteries have been synthesized via conventional hydroxide or carbonate coprecipitation routes with subsequent high-temperature lithiation in either air or oxygen atmosphere. A comparative study of the materials prepared from transition metal sulfates (i.e., containing sulfur) and acetates (i.e., sulfur-free) with powder X-ray diffraction, electron diffraction, high angle annular dark field transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electron energy loss spectroscopy revealed that the sulfur-containing species occur as amorphous Li₂SO₄ at the grain boundaries and intergranular contacts of the primary NMC811 crystallites. This results in a noticeable enhancement of rate capability and capacity retention over prolonged charge/discharge cycling compared to their sulfur-free analogs. The improvement is attributed to suppressing the high voltage phase transition and the associated accumulation of anti-site disorder upon cycling and improving the secondary agglomerates’ mechanical integrity by increasing interfacial fracture toughness through linking primary NMC811 particles with soft Li₂SO₄ binder, as demonstrated with nanoindentation experiments. As the synthesis of the (1−x) LiNi_0.8Mn_0.1Co_0.1O₂∙xLi₂SO₄ composites do not require additional operational steps to introduce sulfur, these electrode materials might demonstrate high potential for commercialization.

Recent Advancements of N-Doped Graphene for Rechargeable Batteries: A Review

Graphene, a 2D carbon structure, due to its unique materials characteristics for energy storage applications has grasped the considerable attention of scientists. The highlighted properties of this material with a mechanically robust and highly conductive nature have opened new opportunities for different energy storage systems such as Li-S (lithium-sulfur), Li-ion batteries, and metal-air batteries. It is necessary to understand the intrinsic properties of graphene materials to widen its large-scale applications in energy storage systems. In this review, different routes of graphene synthesis were investigated using chemical, thermal, plasma, and other methods along with their advantages and disadvantages. Apart from this, the applications of N-doped graphene in energy storage devices were discussed.

Probing the electrode-solution interfaces in rechargeable batteries by sum-frequency generation spectroscopy

An in-depth understanding of the electrode-electrolyte interaction and electrochemical reactions at the electrode-solution interfaces in rechargeable batteries is essential to develop novel electrolytes and electrode materials with high performance. In this perspective, we highlight the advantages of the interface-specific sum-frequency generation (SFG) spectroscopy on the studies of the electrode-solution interface for the Li-ion and Li-O₂ batteries. The SFG studies in probing solvent adsorption structures and solid-electrolyte interphase formation for the Li-ion battery are briefly reviewed. Recent progress on the SFG study of the oxygen reaction mechanisms and stability of the electrolyte in the Li-O₂ battery is also discussed. Finally, we present the current perspective and future directions in the SFG studies on the electrode-electrolyte interfaces toward providing deeper insight into the mechanisms of discharging/charging and parasitic reactions in novel rechargeable battery systems.

Synthesis of (Li2Fe1-yMny)SO Antiperovskites with Comprehensive Investigations of (Li2Fe0.5Mn0.5)SO as Cathode in Li-ion Batteries

A series of solid solutions (Li₂Fe_1-yMn_y)SO with a cubic antiperovskite structure was successfully synthesized. The composition (Li₂Fe_0.5Mn_0.5)SO was intensively studied as a cathode in Li-ion batteries showing a reversible specific capacity of 120 mA h g^-1 and almost a 100% Coulombic efficiency after 50 cycles at 0.1C meaning extraction/insertion of 1 Li per formula unit during 10 h. Operando X-ray absorption spectroscopy confirmed the redox activity of both Fe²⁺ and Mn²⁺ cations during battery charge and discharge, while operando synchrotron X-ray diffraction studies revealed a reversible formation of a second isostructural phase upon Li-removal and insertion at least for the first several cycles. In comparison to (Li₂Fe)SO, the presence of Mn stabilizes the crystal structure of (Li₂Fe_0.5Mn_0.5)SO during battery operation, although post mortem TEM studies confirmed a gradual amorphization after 50 cycles. A lower specific capacity of (Li₂Fe_0.5Mn_0.5)SO in comparison to (Li₂Fe)SO is probably caused by slower kinetics, especially in the two-phase region, as confirmed by Li-diffusion coefficient measurements.

Encapsulation of Se into Hierarchically Porous Carbon Microspheres with Optimized Pore Structure for Advanced Na-Se and K-Se Batteries

Sodium-selenium (Na-Se) and potassium-selenium (K-Se) batteries have emerged as promising energy storage systems with high energy density and low cost. However, major issues such as huge Se volume changes, polyselenide shuttling, and low Se loading need to be overcome. Although many strategies have been developed to resolve these issues, the relationship between the carbon host pore structure and electrochemical performance of Se has not been studied extensively. Here, the effect of the carbon host pore structure on the electrochemical performance of Na-Se and K-Se batteries is investigated. N, S-co-doped hierarchically porous carbon microspheres with different pore structures that can incorporate a large amount of amorphous Se (∼60 wt %) are synthesized by spray pyrolysis and subsequent chemical activation at different temperatures. By optimizing the amount of micropore volume and micropore-to-mesopore ratio, high reversible capacity and cycling stability are achieved for the Se cathode. The optimized cathode delivers a reversible capacity of 445 mA h g^-1 after 400 cycles at 0.5C for Na-Se batteries and 436 mA h g^-1 after 120 cycles at 0.2C for K-Se batteries. This study marks the importance of developing conductive carbon matrices with delicately designed pore structures for advanced alkali metal-chalcogen battery systems.

Shaping Li Deposits from Wild Dendrites to Regular Crystals via the Ferroelectric Effect

Manipulating the Li plating behavior remains a challenging task toward Li-based high-energy batteries. Generally, the Li plating process is kinetically controlled by ion transport, concentration gradient, local electric field, etc. A myriad of strategies have been developed for homogenizing the kinetics; however, such kinetics-controlled Li plating nature is barely changed. Herein, a ferroelectric substrate comprised of homogeneously distributed BaTiO₃ was deployed and the Li plating behavior was transferred from a kinetic-controlled to a thermodynamic-preferred mode via ferroelectric effect. Such Li deposits with uniform hexagonal and cubic shapes are highly in accord with the thermodynamic principle where the body-centered cubic Li is apt to expose more (110) facets as possible to maximally minimize its surface energy. The mechanism was later confirmed due to the spontaneous polarization of BTO particles trigged by an applied electric field. The instantly generated reverse polarized field and charged ends not only neutralized the electric field but also leveled the ion distribution at the interface.

Boosting potassium-ion storage in large-diameter carbon nanotubes/MoP hybrid

Potassium-ion batteries (KIBs) as a substitute for lithium ion batteries have attracted tremendous attention in recent years thanks to the cost-effectiveness and abundance of potassium resources. However, the current lack of suitable electrode materials is a major obstacle against the practical application of KIBs. Hence, design and preparation of capable anode materials are critical for the development of KIBs. In this study, a promising electrode based on N, P-codoped large diameter hollow carbon nanotubes decorated with ultrasmall MoP nanoparticles (MoP@NP-HCNTs) were prepared. The hollow carbon nanotubes facilitate the rapid electron and ion transfer, and release the huge volume expansion during discharge/charge. The MoP@NP-HCNT electrode delivers high initial capacity of 485, 482 and 463 mAh g^-1 corresponding to 100, 200 and 1000 mA g^-1, respectively. The discharge specific capacity still maintains 300 mAh g^-1 at 100 mA g^-1 after over 80 cycles. It still shows ultralong cycling stability with a discharge capacity of 255 mAh g^-1 at a high current density of 1000 mA g^-1 after 120 cycles. This study opens up a new routine to develop high reversible capacity and promising electrode materials for KIBs.

Synthesis and Manipulation of Single-Crystalline Lithium Nickel Manganese Cobalt Oxide Cathodes: A Review of Growth Mechanism

Lithium nickel manganese cobalt oxide (NMC) cathodes are of great importance for the development of lithium ion batteries with high energy density. Currently, most commercially available NMC products are polycrystalline secondary particles, which are aggregated by anisotropic primary particles. Although the polycrystalline NMC particles have demonstrated large gravimetric capacity and good rate capabilities, the volumetric energy density, cycling stability as well as production adaptability are not satisfactory. Well-dispersed single-crystalline NMC is therefore proposed to be an alternative solution for further development of high-energy-density batteries. Various techniques have been explored to synthesize the single-crystalline NMC product, but the fundamental mechanisms behind these techniques are still fragmented and incoherent. In this manuscript, we start a journey from the fundamental crystal growth theory, compare the crystal growth of NMC among different techniques, and disclose the key factors governing the growth of single-crystalline NMC. We expect that the more generalized growth mechanism drawn from invaluable previous works could enhance the rational design and the synthesis of cathode materials with superior energy density.

Metal-organic framework based bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries: current progress and prospects

Zinc-air batteries (ZABs) are regarded as ideal candidates for next-generation energy storage equipment due to their high energy density, non-toxicity, high safety, and environmental friendliness. However, the slow oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics on the air cathode limit their efficiency and the development of highly efficient, low cost and stable bifunctional electrocatalysts is still challenging. Metal-Organic Framework (MOF) based bifunctional oxygen electrocatalysts have been demonstrated as promising alternative catalysts due to the regular structure, tunable chemistry, high specific surface area, and simple and easy preparation of MOFs, and great progress has been made in this area. Herein, we summarize the latest research progress of MOF-based bifunctional oxygen electrocatalysts for ZABs, including pristine MOFs, derivatives of MOFs and MOF composites. The effects of the catalysts' composites, morphologies, specific surface areas and active sites on catalytic performances are specifically addressed to reveal the underlying mechanisms for different catalytic activity of MOF based catalysts. Finally, the main challenges and prospects for developing advanced MOF-based bifunctional electrocatalysts are proposed.

Preparation of Poly-1-butene Nanofiber Mat and Its Application as Shutdown Layer of Next Generation Lithium Ion Battery

Nonwoven nanofiber webs from polyolefin show great potential in various fields such as nanofilters, high performance membranes and separators in lithium ion batteries (LiB). Although nonwoven microfiber webs can be obtained by the well-established melt-blown method, it is relatively difficult to produce nonwoven nanofiber web using polyolefin (polyethylene and polypropylene). There have been several reports on the preparation of polyolefin nanofibers by melt-electrospinning, although this approach presents several intrinsic disadvantages, i.e., high processing costs, the requirement of complex equipment, and poor control over pore size or fiber diameter. Solution-based electrospinning has the potential to overcome the drawbacks of melt-electrospinning, but the solubility of most polyolefin is poor. In this study, we found that poly-1-butene, a member of the poly(alpha-olefin) family, can be used in the electrospinning process. We set the concentration of the polymeric solution for electrospinning at 0.65–1.7 g/mL. Here, we report on the fabrication of nonwoven fiber webs composed of poly-1-butene and their copolymers. The diameter of the nonwoven fiber mat was 0.2–0.4 μm, which can be applicable for shutdown layer. As a representative application, we prepared a poly-1-butene nanofiber separator with an appropriate pore size by electrospinning for use as the shut-down layer of a next-generation LiB. The PB-based nanofiber mat provided shutdown ability at around 100 to 120 °C.

Three-Dimensional Porous Alginate Fiber Membrane Reinforced PEO-Based Solid Polymer Electrolyte for Safe and High-Performance Lithium Ion Batteries

The rational design and optimization of solid polymer electrolytes (SPEs) are critical for the application of safety and high efficiency lithium ion batteries (LIBs). Herein, we synthesized a novel poly(ethylene oxide) (PEO)-based SPE (PEO@AF SPE) with a cross-linking network by the introduction of alginate fiber (AF) membranes. Depending on the high-strength supporting AF skeleton and the cross-linking network formed by hydrogen bonds between the PEO matrix and AF skeleton, the obtained PEO@AF SPE exhibits an excellent tensile strength of 3.71 MPa, favorable heat resistance (close to 120 °C), and wide electrochemical stability window (5.2 V vs Li/Li⁺). Meanwhile, the abundant oxygen-containing groups in alginate macromolecular and the three-dimensional (3D) porous structure of the AF membrane can greatly increase Li⁺ anchor points and provide more Li⁺ migration pathways, leading to the enhancement of Li⁺ conduction and interfacial stability between the SPE and Li anode. Furthermore, the assembled LiFePO₄/PEO@AF SPE/Li cells also exhibit satisfactory electrochemical performance. These results reveal that PEO incorporating with AFs can boost the mechanical strength, thermostability, and electrochemical properties of the SPE simultaneously. Furthermore, one will expect that the newly designed PEO@AF SPE with cross-linked networks thus provides the possibility for future applications of safety and high-performance LIBs.

One-pot coating of LiCoPO4/C by a UiO-66 metal-organic framework

LiCoPO4 (LCP) is a promising high voltage cathode material but suffers from low conductivity and poor electrochemical properties. These properties can be improved by coating with a conductive carbon layer. Ongoing research is focused on the protective layer with good adhesion and inhibition of electrolyte decomposition reactions. In the present work, we suggest a new robust one-pot procedure, featuring the introduction of UiO-66 metal-organic framework (MOF) nanoparticles during LCP synthesis to create a metal-carbon layer upon annealing. The LiCoPO4/C@UiO-66 was synthesized via the microwave-assisted solvothermal route, and 147 mA h g-1 discharge capacity was obtained in the first cycle. The MOF acts as a source of both carbon and metal atoms, which improves conductivity. Using operando X-ray absorption spectroscopy upon cycling, we identify two Co-related phases in the sample and exclude the olivine structure degradation as an explanation for a long-term capacity fade.

Multidimensional B4N materials as novel anode materials for lithium ion batteries

Based on first-principles calculations and ab initio molecular dynamics simulations, multidimensional B4N materials are investigated as anode materials for lithium ion batteries. The present results show that the monolayer B4N can reach a remarkably high specific capacity of 1874.27 mA h g-1 and possesses a low diffusion barrier (0.29 eV). Testing of bilayer B4N and bulk B4N reveals that the materials exhibit irreversible structural phase transformation. They are transformed from a layered structure to the more stable cavity-channel structure due to the adsorption of Li atoms. The volume expansions of their saturated lithiation cavity-channel structures are about 12%, which is close to that of graphite (10%). Moreover, it is found that the energy barriers of the bilayer and bulk B4N are less than 0.5 eV in the cavity-channel. The saturated adsorption of bulk B4N yields a specific capacity of 468.57 mA h g-1, which is higher than that of commercial graphite (372 mA h g-1). More importantly, all the lithiation structures in the monolayer, bilayer, and bulk B4N are verified to be thermodynamically stable at 350 K. These findings may encourage further experimental investigation in the design of multidimensional B4N materials as novel candidate anode materials for lithium ion batteries.

Regulation of Cathode-Electrolyte Interphase via Electrolyte Additives in Lithium Ion Batteries

As the power supply of the prosperous new energy products, advanced lithium ion batteries (LIBs) are widely applied to portable energy equipment and large-scale energy storage systems. To broaden the applicable range, considerable endeavours have been devoted towards improving the energy and power density of LIBs. However, the side reaction caused by the close contact between the electrode (particularly the cathode) and the electrolyte leads to capacity decay and structural degradation, which is a tricky problem to be solved. In order to overcome this obstacle, the researchers focused their attention on electrolyte additives. By adding additives to the electrolyte, the construction of a stable cathode-electrolyte interphase (CEI) between the cathode and the electrolyte has been proven to competently elevate the overall electrochemical performance of LIBs. However, how to choose electrolyte additives that match different cathode systems ideally to achieve stable CEI layer construction and high-performance LIBs is still in the stage of repeated experiments and exploration. This article specifically introduces the working mechanism of diverse electrolyte additives for forming a stable CEI layer and summarizes the latest research progress in the application of electrolyte additives for LIBs with diverse cathode materials. Finally, we tentatively set forth recommendations on the screening and customization of ideal additives required for the construction of robust CEI layer in LIBs. We believe this minireview will have a certain reference value for the design and construction of stable CEI layer to realize desirable performance of LIBs.

Mirror-Like Electrodeposition of Lithium Metal under a Low-Resistance Artificial Solid Electrolyte Interphase Layer

Nonuniform electrodeposition and dendritic growth of lithium metal coupled to its chemical incompatibility with liquid electrolytes are largely responsible for poor Coulombic efficiency and safety hazards preventing the successful implementation of energy-dense Li metal anodes. Artificial solid electrolyte interface (ASEI) layers have been proposed to address the morphological evolution and chemical reactions in Li metal anodes. In this study, an ASEI layer consisting of a lithium phosphorus oxynitride (LiPON) thin film electrolyte and gold-alloying interlayer was developed and shown to promote the electrodeposition of smooth, homogeneous, mirror-like Li metal morphologies. The Au layer alloyed with Li, reducing the nucleation overpotential and resulting in a more spatially uniform metal deposit, while the LiPON layer provided a physical barrier between the Li metal and aprotic liquid electrolyte. The effectiveness and integrity of the LiPON protective layer was assessed using in operando impedance spectroscopy and ex situ SEM/EDS characterization. Smooth, homogeneous Li morphologies were realized in capacities up to 3 mAh cm^-2 plated at 0.1 mA cm^-2. At higher current densities up to 1 mA cm^-2 or increased deposition capacities of 6 mAh cm^-2, the LiPON coating fractured due to the localized, nonuniform lithium deposits and rough, dendritic Li morphologies were observed. This approach represents a new strategy in the design of artificial SEIs to enable Li metal anodes with practical areal capacities.

Porous SnO2/C Nanofiber Anodes and LiFePO4/C Nanofiber Cathodes with a Wrinkle Structure for Stretchable Lithium Polymer Batteries with High Electrochemical Performance

Stretchable lithium batteries have attracted considerable attention as components in future electronic devices, such as wearable devices, sensors, and body-attachment healthcare devices. However, several challenges still exist in the bid to obtain excellent electrochemical properties for stretchable batteries. Here, a unique stretchable lithium full-cell battery is designed using 1D nanofiber active materials, stretchable gel polymer electrolyte, and wrinkle structure electrodes. A SnO2/C nanofiber anode and a LiFePO4/C nanofiber cathode introduce meso- and micropores for lithium-ion diffusion and electrolyte penetration. The stretchable full-cell consists of an elastic poly(dimethylsiloxane) (PDMS) wrapping film, SnO2/C and LiFePO4/C nanofiber electrodes with a wrinkle structure fixed on the PDMS wrapping film by an adhesive polymer, and a gel polymer electrolyte. The specific capacity of the stretchable full-battery is maintained at 128.3 mAh g-1 (capacity retention of 92%) even after a 30% strain, as compared with 136.8 mAh g-1 before strain. The energy densities are 458.8 Wh kg-1 in the released state and 423.4 Wh kg-1 in the stretched state (based on the electrode), respectively. The high capacity and stability in the stretched state demonstrate the potential of the stretchable battery to overcome its limitations.

A hierarchical porous P-doped carbon electrode through hydrothermal carbonization of pomelo valves for high-performance supercapacitors

Porous carbon materials are synthesized from pomelo valves by the hydrothermal activation of H3PO4 followed by simple carbonization. The as-synthesized hierarchically porous carbon electrode exhibits a high specific capacitance of 966.4 F g-1 at 1 A g-1 and an ultra-high stability of 95.6% even after 10 000 cycles. Moreover, the supercapacitor also demonstrates a maximum energy of 36.39 W h kg-1 and a maximum power of 33.33 kW kg-1 with an energy retention of 25.56 W h kg-1, which paves the way for the development of high-performance, green supercapacitors for advanced energy storage systems.

In Situ Transformed Solid Electrolyte Interphase by Implanting a 4-Vinylbenzoic Acid Nanolayer on the Natural Graphite Surface

A solid electrolyte interphase (SEI) layer on a graphite anode plays a crucial role in deciding electrochemical properties of the electrode including the first Coulombic efficiency, rate capability, operating temperature, and long-term cycling stability. However, the ultrathin functional SEI layer is always naturally grown via electrolyte reduction decomposition reactions. Herein, we report a new strategy of in situ transformed solid electrolyte interphase of high stability by implanting a 4-vinylbenzoic acid (4-VBA) nanolayer on a mildly oxidized graphite surface. A 4-VBA layer of 40 nm contributes to the transformation of a robust and stable SEI layer, which not only significantly enhances the overall electrochemical performances of the natural graphite electrode but also greatly prolongs the cycle life of the full cell with the LiNi_0.6Co_0.2Mn_0.2O₂ cathode. The effectively suppressed surface evolution aroused from the stable organic SEI transformed from the implanted 4-VBA nanolayer explains the enhanced electrochemical properties.

A Comprehensive Review of Li-Ion Battery Materials and Their Recycling Techniques

In the context of constant growth in the utilization of the Li-ion batteries, there was a great surge in the quest for electrode materials and predominant usage that lead to the retiring of Li-ion batteries. This review focuses on the recent advances in the anode and cathode materials for the next-generation Li-ion batteries. To achieve higher power and energy demands of Li-ion batteries in future energy storage applications, the selection of the electrode materials plays a crucial role. The electrode materials, such as carbon-based, semiconductor/metal, metal oxides/nitrides/phosphides/sulfides, determine appreciable properties of Li-ion batteries such as greater specific surface area, a minimal distance of diffusion, and higher conductivity. Various classifications of the anode materials such as the intercalation/de- intercalation, alloy/de-alloy, and various conversion materials are illustrated lucidly. Further, the cathode materials, such as nickel-rich LiNixCoyMnzO2 (NCM), were discussed. NCM members such as NCM 333, NCM 523 that enabled to advance for NCM622 and NCM81are reported. The nanostructured materials bridged the gap in the realization of next-generation Li-ion batteries. Li-ion batteries’ electrode nanostructure synthesis, performance, and reaction mechanisms were considered with great concern. The serious effects of Li-ion batteries disposal need to be cut significantly to reduce the detrimental effect on the environment. Hence, the recycling of spent Li-ion batteries has gained much attention in recent years. Various recycling techniques and their effect on the electroactive materials are illustrated. The key areas covered in this review are anode and cathode materials and recent advances along with their recycling techniques. In light of crucial points covered in this review, it constitutes a suitable reference for engineers, researchers, and designers in energy storage applications.

Boosting Lithium Storage in Free-Standing Black Phosphorus Anode via Multifunction of Nanocellulose

Layer-structured black phosphorus (BP) demonstrating high specific capacity has been viewed as a very promising anode material for future high-energy-density Li-ion batteries (LIBs). However, its practical application is hindered by large volume change of BP and poor mechanical stability of BP anodes by traditional slurry casting technology. Here, a free-standing flexible anode composed of BP nanosheets and nanocellulose (NC) nanowires is fabricated via a facile vacuum-assisted filtration approach. The constructed free-standing BP@NC composite anode offers three-dimensional (3D) mixed-conducting network for Li⁺/e^- transports. The substrate of NC film has a certain flexibility up to 10.2% elongation that can restrain the volume change of BP and electrode during operation. In addition, molecular dynamic (MD) simulation and density function theory (DFT) show the greatly enhanced Li⁺ diffusion in BP@NC composite where the Li ions receive less repulsive force at the interface of BP interlayer and nanocellulose. Benefiting from above multifunction of nanocellulose, the BP@NC composite exhibits high capacities of 1020.1 mAh g^-1 at 0.1 A g^-1 after 230 cycles and 994.4 mAh g^-1 at 0.2 A g^-1 after 400 cycles, corresponding to high capacity retentions of 87.1% and 84.9%, respectively. Our results provide a low-cost and effective strategy to develop advanced electrodes for next-generation rechargeable batteries.

Nylon-Based Composite Gel Membrane Fabricated via Sequential Layer-by-Layer Electrospinning for Rechargeable Lithium Batteries with High Performance

With the raw materials of poly(vinylidene-co-hexafluoropropylene) (P(VDF-HFP)) and polyamide 6 (PA6, nylon 6), a sandwich-structured composite membrane, PA6/P(VDF-HFP)/PA6, is fabricated via sequential layer-by-layer electrospinning. The nylon-based composite exhibits high absorption to organic liquid electrolyte (270 wt%) owing to its high porosity (90.35%), good mechanical property (17.11 MPa), and outstanding shut-down behavior from approximately 145 to 230 °C. Moreover, the dimensional shrink of a wet PA6 porous membrane immersed into liquid electrolyte is cured due to the existence of the P(VDF-HFP) middle layer. After swelling by the LiPF₆-based organic liquid electrolyte, the obtained PA6/P(VDF-HFP)/PA6-based gel polymer electrolytes (GPE) shows high ionic conductivity at room temperature (4.2 mS cm⁻¹), a wide electrochemical stable window (4.8 V), and low activation energy for Li⁺ ion conduction (4.68 kJ mol⁻¹). Benefiting from the precise porosity structure made of the interlaced electrospinning nanofibers and the superior physicochemical properties of the nylon-based composite GPE, the reversible Li⁺ ion dissolution/deposition behaviors between the GPE and Li anode are successfully realized with the Li/Li symmetrical cells (current density: 1.0 mA cm⁻²; areal capacity: 1.0 mAh cm⁻²) proceeding over 400 h at a polarization voltage of no more than 70 mV. Furthermore, the nylon-based composite GPE in assembled Li/LiFePO₄ cells displays good electrochemical stability, high discharge capacity, good cycle durability, and high rate capability. This research provides a new strategy to fabricate gel polymer electrolytes via the electrospinning technique for rechargeable lithium batteries with good electrochemical performance, high security, and low cost.

Should All Electrochemical Energy Materials Be Isomaterially Heterostructured to Optimize Contra and Co-varying Physicochemical Properties?

Sustainable energy and chemical/material transformation constrained by limited greenhouse gas generation impose a grand challenge and posit outstanding opportunities to electrochemical material devices. Dramatic advancements in experimental and computational methodologies have captured detailed insights into the working of these material devices at a molecular scale and have brought to light some fundamental constraints that impose bounds on efficiency. We propose that the coupling of molecular events in the material device gives rise to contra-varying or co-varying properties and efficiency improving partial decoupling of such properties can be achieved via introducing engineered heterogeneities. A specific class of engineered heterogeneity is in the form of isomaterial heterostructures comprised of non-native and native polymorphs. The non-native polymorph differs from their native/ground state bulk polymorph in terms of its discrete translational symmetry and we anticipate specific symmetry relationships exist between non-native and native structures that enable the formation of interfaces that enhance efficiency. We present circumstantial evidence and provide speculative mechanisms for such an approach with the hope that a more comprehensive delineation of proposed material design will be undertaken.

Boosting High-Performance in Lithium-Sulfur Batteries via Dilute Electrolyte

Polysulfide shuttle effects, active material losses, formation of resistive surface layers, and continuous electrolyte consumption create a major barrier for the lightweight and low-cost lithium-sulfur (Li-S) battery adoption. Tuning electrolyte composition by using additives and most importantly by substantially increasing electrolyte molarity was previously shown to be one of the most effective strategies. Contrarily, little attention has been paid to dilute and super-diluted LiTFSI/DME/DOL/LiNO₃ based-electrolytes, which have been thought to aggravate the polysulfide dissolution and shuttle effects. Here we challenge this conventional wisdom and demonstrate outstanding capabilities of a dilute (0.1 mol L^-1 of LiTFSI in DME/DOL with 1 wt. % LiNO₃) electrolyte to enable better electrode wetting, greatly improved high-rate capability, and stable cycle performance for high sulfur loading cathodes and low electrolyte/sulfur ratio in Li-S cells. Overall, the presented study shines light on the extraordinary ability of such electrolyte systems to suppress short-chain polysulfide dissolution and polysulfide shuttle effects.

Novel polymer coating for chemically absorbing CO2 for safe Li-ion battery

Gas evolution in Li-ion batteries remains a barrier for the implementation of high voltage materials in a pouch cell format; the inflation of the pouch cell is a safety issue that can cause battery failure. In particular, for manganese-based materials employed for fabricating cathodes, the dissolution of Mn²⁺ in the electrolyte can accelerate cell degradation, and subsequently gas evolution, of which carbon dioxide (CO₂) is a major component. We report on the utilization of a mixture of polymers that can chemically absorb the CO₂, including the coating of aluminum foils, which serve as trapping sheets, introduced into two Ah pouch cells—based on a LiMnFePO₄ (cathode) and a Li₄Ti₅O₁₂ (anode). The pouch cells with trapping sheets experienced only an 8.0 vol% inflation (2.7 mmol CO₂ per gram of polymers) as opposed to the 40 vol% inflation for the reference sample. Moreover, the cells were cycled for 570 cycles at 1 C and 45 °C before reaching 80% of their retention capacity.

Understanding the Origin of Enhanced Li-Ion Transport in Nanocrystalline Argyrodite-Type Li6PS5I

Argyrodite-type Li₆PS₅X (X = Cl, Br) compounds are considered to act as powerful ionic conductors in next-generation all-solid-state lithium batteries. In contrast to Li₆PS₅Br and Li₆PS₅Cl compounds showing ionic conductivities on the order of several mS cm^-1, the iodine compound Li₆PS₅I turned out to be a poor ionic conductor. This difference has been explained by anion site disorder in Li₆PS₅Br and Li₆PS₅Cl leading to facile through-going, that is, long-range ion transport. In the structurally ordered compound, Li₆PS₅I, long-range ion transport is, however, interrupted because the important intercage Li jump-diffusion pathway, enabling the ions to diffuse over long distances, is characterized by higher activation energy than that in the sibling compounds. Here, we introduced structural disorder in the iodide by soft mechanical treatment and took advantage of a high-energy planetary mill to prepare nanocrystalline Li₆PS₅I. A milling time of only 120 min turned out to be sufficient to boost ionic conductivity by 2 orders of magnitude, reaching σ_total = 0.5 × 10^-3 S cm^-1. We followed this noticeable increase in ionic conductivity by broad-band conductivity spectroscopy and ⁷Li nuclear magnetic relaxation. X-ray powder diffraction and high-resolution ⁶Li, ³¹P MAS NMR helped characterize structural changes and the extent of disorder introduced. Changes in attempt frequency, activation entropy, and charge carrier concentration seem to be responsible for this increase.

A review of the α-Fe2O3 (hematite) nanotube structure: recent advances in synthesis, characterization, and applications

α-Fe2O3 nanotubes are exceptional one-dimensional transition metal oxide materials with low density, large surface area, promising electrochemical and photoelectrochemical properties, which are widely investigated in lithium-ion batteries, photoelectrochemical devices, gas sensors, and catalysis. They have drawn significant attention to the fields of energy storage and conversion, and environmental sensing and remediation due to the increase in the global energy crisis and environmental pollution. Many efforts have been made toward controlling the morphology or impurity doping to improve the intrinsic properties of α-Fe2O3 nanotubes. In this review, we introduce the synthesis methods and physicochemical properties of α-Fe2O3 nanotubes. The fabrication conditions, which are important for the physicochemical properties of materials, are also listed to describe the synthesis processes. Furthermore, the development and breakthrough of various applications in batteries, supercapacitors, photoelectrochemical devices, environmental remediation, and sensors are systematically reviewed. Finally, some of the current challenges and future perspectives for α-Fe2O3 nanotubes are discussed. We believe that this timely and critical mini-review will stimulate extensive studies and attract more attention, further improving the development of the α-Fe2O3 (hematite) nanotube structure.

Recent Advances and Applications of Inorganic Electrides

Electrides, accommodating excess electrons in lattice voids as anions, have attracted considerable attention in both fundamental research and application development because of their interesting properties, such as ultralow work functions, high electronic mobility, high catalytic activity, and anisotropic electronic and optical properties. Recently, much research progress has been made in both types and applications of inorganic electrides because of the high stability. In this Perspective, we aim to summarize the recent development of inorganic electrides discovered and proposed by experiment and theoretical calculations, highlighting the main applications, including catalysis, metal-ion batteries, superconductivity, magnetism, and organic light-emitting diodes. We provide insights into the role of anionic electrons in electrides playing in the stability and properties. Finally, the problems, challenges, and opportunities are presented, which provide an outlook for future research.

Carbon-Phosphorus Bonds-Enriched 3D Graphene by Self-Sacrificing Black Phosphorus Nanosheets for Elevating Capacitive Lithium Storage

Heteroatom-doping engineering has been verified as an effective strategy to tailor the electronic and chemical properties of materials. The high amount doping of nonmetal atoms to achieve desired performance, however, is always a grand challenge. Herein, a new strategy to achieve ultrahigh-level doping of phosphorus in a 3D graphene skeleton is proposed by sacrificing heterostructured two-dimensional black phosphorus on graphene. Via this approach, the phosphorus-loading in graphene hydrogel reached a record of 4.84 at. %, together with the formation of tunable pores of size 1.7-17.5 nm in graphene. During reaction kinetic analysis, the highly phosphorus-doped 3D graphene hydrogel anode exhibited more favorable capacitive-controlled ion storage behaviors, leading to a specific capacity as high as 1000 mA h g^-1 after 1700 cycles, which is superior to the pristine graphene hydrogel electrode. This simple but effective phosphorization offers an effective doping strategy for producing ultrahigh-level phosphorous doping but avoids the usual use of toxic phosphorous precursors. Furthermore, the modulation on the activation process over cycling investigated in this work gives us a new insight into designing stable anodes for carbonaceous electrode materials.

Emerging interfacial chemistry of graphite anodes in lithium-ion batteries

Emerging interfacial chemistry of the graphite anode in today's lithium-ion batteries paves the way to next-generation, high-performance energy storage devices.

Covalently cross-linked polymer stabilized electrolytes with self-healing performance via boronic ester bonds

This article reported a facile fabrication of self-healing solid polymer electrolytes via boronic ester bonds.