Progress on Lithium Dendrite Suppression Strategies from the Interior to Exterior by Hierarchical Structure Designs

Development and Optimization of Thin-Lithium-Metal Anodes with a Lithium Lanthanum Titanate Stabilization Coating for Enhancement of Lithium-Sulfur Battery Performance

Lithium-ion batteries are dominating high-energy-density energy storage for 30 years. However, their development approaches theoretical limits, spurring the development of lithium-sulfur cells that achieve high energy densities through reversible electrochemical conversion reactions. Nevertheless, the commercialization of lithium-sulfur cells is hindered by practical challenges associated primarily with the use of thick-lithium anodes, low-loading sulfur cathodes, and high electrolyte-to-sulfur ratios, which prevent realization of the cells' full potential in terms of electrochemical and material performance. To solve these extrinsic and intrinsic problems, the effect of lithium-metal thickness on the electrochemical behavior of lithium-sulfur cells with high-loading sulfur cathodes in lean-electrolyte configurations is investigated. Specifically, lithium lanthanum titanate (LLTO), a solid electrolyte, is utilized to form an ionically/electronically conductive coating to stabilize lithium-metal anodes, thereby enhancing their lithium-ion pathways and interfacial charge transfer. Electrochemical analyses reveal that an LLTO coating significantly reduces excessive reactions between lithium metal and an electrolyte, thereby minimizing lithium consumption and electrolyte depletion. Further, LLTO-stabilized lithium anodes improve lithium-sulfur cell performance, and most importantly, allow the fabrication of thin-lithium, high-loading-sulfur cells that open a pathway toward high-energy-density batteries.

Covalent Organic Framework-Based Materials for Advanced Lithium Metal Batteries

Lithium metal batteries (LMBs), with high energy densities, are strong contenders for the next generation of energy storage systems. Nevertheless, the unregulated growth of lithium dendrites and the unstable solid electrolyte interphase (SEI) significantly hamper their cycling efficiency and raise serious safety concerns, rendering LMBs unfeasible for real-world implementation. Covalent organic frameworks (COFs) and their derivatives have emerged as multifunctional materials with significant potential for addressing the inherent problems of the anode electrode of the lithium metal. This potential stems from their abundant metal-affine functional groups, internal channels, and widely tunable architecture. The original COFs, their derivatives, and COF-based composites can effectively guide the uniform deposition of lithium ions by enhancing conductivity, transport efficiency, and mechanical strength, thereby mitigating the issue of lithium dendrite growth. This review provides a comprehensive analysis of COF-based and derived materials employed for mitigating the challenges posed by lithium dendrites in LMB. Additionally, we present prospects and recommendations for the design and engineering of materials and architectures that can render LMBs feasible for practical applications.

Accelerated Selective Li+ Transports Assisted by Microcrack-Free Anionic Network Polymer Membranes for Long Cyclable Lithium Metal Batteries

Rechargeable Li metal batteries have the potential to meet the demands of high-energy density batteries for electric vehicles and grid-energy storage system applications. Achieving this goal, however, requires resolving not only safety concerns and a shortened battery cycle life arising from a combination of undesirable lithium dendrite and solid-electrolyte interphase formations. Here, a series of microcrack-free anionic network polymer membranes formed by a facile one-step click reaction are reported, displaying a high cation conductivity of 3.1 × 10-5 S cm-1 at high temperature, a wide electrochemical stability window up to 5 V, a remarkable resistance to dendrite growth, and outstanding non-flammability. These enhanced properties are attributed to the presence of tethered borate anions in microcrack-free membranes, which benefits the acceleration of selective Li+ cations transport as well as suppression of dendrite growth. Ultimately, the microcrack-free anionic network polymer membranes render Li metal batteries a safe and long-cyclable energy storage device at high temperatures with a capacity retention of 92.7% and an average coulombic efficiency of 99.867% at 450 cycles.

Applications, prospects and challenges of metal borides in lithium sulfur batteries

Although the lithium-sulfur (Li-S) battery has a theoretical capacity of up to 1675 mA h g-1, its practical application is limited owing to some problems, such as the shuttle effect of soluble lithium polysulfides (LiPSs) and the growth of Li dendrites. It has been verified that some transition metal compounds exhibit strong polarity, good chemical adsorption and high electrocatalytic activities, which are beneficial for the rapid conversion of intermediate product in order to effectively inhibit the "shuttle effect". Remarkably, being different from other metal compounds, it is a significant characteristic that both metal and boron atoms of transition metal borides (TMBs) can bind to LiPSs, which have shown great potential in recent years. Here, for the first time, almost all existing studies on TMBs employed in Li-S cells are comprehensively summarized. We firstly clarify special structures and electronic features of metal borides to show their great potential, and then existing strategies to improve the electrochemical properties of TMBs are summarized and discussed in the focus sections, such as carbon-matrix construction, morphology control, heteroatomic doping, heterostructure formation, phase engineering, preparation techniques. Finally, the remaining challenges and perspectives are proposed to point out a direction for realizing high-energy and long-life Li-S batteries.

Semi-Embedded Structured Bi Nanospheres for Boosted Self-Heating-Induced Healing of Li-Dendrites

It is reported that self-heating-induced healing on lithium metal anodes (LMAs) provides a mitigation strategy for suppressing Li dendrites. However, how to boost the self-heating-induced healing of Li-dendrites and incorporate it into Li-host design remains an imminent problem that needs to be solved. Herein, a new bismuth nanosphere semi-buried carbon cloth (Bi-NS-CC) material with a 3D flexible host structure is proposed. The ultrasmall Bi nanospheres are uniformly and densely distributed on carbon fiber, providing active sites to form uniform Li3 Bi alloy with molten lithium, thereby guiding the injection of molten metallic lithium into the 3D structure to form a self-supporting composite LMAs. The ingenious semi-embedded structure with strong interfacial C─Bi ensures superior mechanical properties. Interestingly, when the current density reaches up to 10 mA cm-2 , the lithium dendrites undergo self-heating. Carbon cloth as a host can quickly and uniformly transfer heat, which induces the uniform migration of Li on anodes. The semi-embedded structure with strong C─Bi ensures Bi nanospheres guide the formation of smooth morphology even under these harsh conditions (high-temperature, high-rate, etc.). Consequently, at 10 mA cm-2 /10 mAh cm-2 , the Li/Li3 Bi-NS-CC realizes ultra-long cycles of 1500 h and ultra-low overpotential of 15 mV in a symmetric cell.

A Review on Covalent Organic Frameworks as Artificial Interface Layers for Li and Zn Metal Anodes in Rechargeable Batteries

Li and Zn metals are considered promising negative electrode materials for the next generation of rechargeable metal batteries because of their non-toxicity and high theoretical capacity. However, the uneven deposition of metal ions (Li+ , Zn2+ ) and the uncontrolled growth of dendrites result in poor electrochemical stability, unsatisfactory cycle life, and rapid capacity decay of batteries assembled with Li and Zn electrodes. Owing to the unique internal directional channels and abundant redox active sites of covalent organic frameworks (COFs), they can be used to promote uniform deposition of metal ions during stripping/electroplating through interface modification strategies, thereby inhibiting dendrite growth. COFs provide a new perspective in addressing the challenges faced by the anodes of Li metal batteries and Zn ion batteries. This article discusses the stability and types of COFs, and summarizes some novel COF synthesis methods. Additionally, it reviews the latest progress and optimization methods of using COFs for metal anodes to improve battery performance. Finally, the main challenges faced in these areas are discussed. This review will inspire future research on metal anodes in rechargeable batteries.

Synergistic regulation of Li deposition on F-doped hollow carbon spheres toward dendrite-free lithium metal anodes

The notorious issues of lithium (Li) dendrite growth and volume change hinder the practical applications of Li metal anodes. LiF as a key component of the solid electrolyte interface (SEI) governs Li+ transport and deposition, yet the formation of LiF consumes the anions (PF6-/TFSI-) in the electrolyte, preventing the stable cycling of Li anodes. Herein, fluorine (F)-doped hollow carbon (FHC) was synthesized and used to construct a composite current collector with FHC as an F-rich buffer layer for modifying the Cu foil. The F content provided by FHC not only mitigates the anion (PF6-/TFSI-) consumption but also enhances the stability of SEI. The hollow structure of FHC with abundant internal space can accommodate deposited Li to relieve the volume change during cycling. Besides, the significantly improved specific surface area of the electrode effectively reduces the local current density to achieve a homogeneous Li deposition. Due to the above cooperation, the symmetrical cell of Cu@FHC-Li||Cu@FHC-Li maintains stable cycling for more than 1800 h with a hysteresis voltage of 19 mV. In addition, full cell coupling with LiFePO4 cathode delivers excellent long-term cycling and rate performance. This work provides an effective route for developing stable Li metal anodes.

A Forceful "Dendrite-Killer" of Polyoxomolybdate with Reusability Effectively Dominating Dendrite-Free Lithium Metal Anode

In this work, a series of Mo-containing polyoxometalates (POMs) modified separators to inhibit the growth of lithium dendrites, and thus improving the lifespan and safety of the cells is proposed. When the deposited lithium forms dendrites and touches the separator, the optimized Dawson-type POM of (NH4 )6 [P2 Mo18 O62 ]·11H2 O (P2 Mo18 ) with the stronger oxidizability, acts like a "killer", is more inclined to oxidize Li0 into Li+ , thus weakening the lethality of lithium dendrites. The above process is accompanied by the formation of Lix [P2 Mo18 O62 ] (x = 6-10) in its reduced state. Converting to the stripping process, the reduced state Lix [P2 Mo18 O62 ] (x = 6-10) can be reoxidized to P2 Mo18 , which achieves the reusability of P2 Mo18 functional material. Meanwhile, lithium ions are released into the cell system to participate in the subsequent electrochemical cycles, thus the undesired lithium dendrites are converted into usable lithium ions to prevent the generation of "dead lithium". As a result, the Li//Li symmetrical cell with P2 Mo18 modified separator delivers exceptional cyclic stability for over 1000 h at 3 mA cm-2 and 5 mAh cm-2 , and the assembled Li-S full cell maintains superior reversible capacity of 600 mAh g-1 after 200 cycles at 2 C.

Solvation Structure Tuning Induces LiF/Li3 N-Rich CEI and SEI Interfaces for Superior Li/CFx Batteries

The electrode/electrolyte interfaces play an important role in the electrochemical reaction kinetics to alleviate the severe polarization and voltage hysteresis in lithium primary batteries. Herein, C5 F5 N is proposed as an electrolyte additive to tune the characteristics of the electrode/electrolyte interfaces. The Li/CFx primary battery with C5 F5 N additive exhibits an excellent discharge-specific capacity of 981.4 mAh g-1 (0.1 C), a remarkable high-rate capability of 598 mAh g-1 (15 C), and an outstanding energy/power density of 1068.7 Wh kg-1 /24362.5 W kg-1 . It also shows remarkable storage performance with 717.2 mAh g-1 at 0.1 C after storage at 55 °C for 2 months. The excellent performance of the Li/CFx batteries is closely related to the improved and stable Li3 N/LiF-rich homogeneous interfaces induced by the C5 F5 N additive, which results in uniform distribution of Li+ flux, facilitated electrochemical kinetics, and increased rate capability of Li/CFx battery. Therefore, C5 F5 N is expected to be a promising electrolyte additive, and the related electrode/electrolyte interface engineering provides an effective and facile strategy to increase the performance of the lithium primary battery.

Mechanistic study of Al2O3 coating effects on lithium deposition and dissolution reaction

Lithium metal anodes show great promise for use in next-generation secondary batteries, but they suffer from lithium dendrite growth, as well as other issues, which cause safety problems and result in a loss of capacity with time. The use of artificial inorganic solid electrolyte interphase (SEI) layers, such as those comprising Al2O3, is a promising way to mitigate these disadvantages, but the mechanism behind these observed improvements remains poorly understood. Therefore, in this study, using pulsed laser deposition (PLD), the surface of a Cu electrode was coated with a physicochemically stable and mechanically strong Al2O3 thin film, and the effects of the film coating on the lithium deposition and dissolution behaviour were investigated. When the morphology of the deposits was evaluated by scanning electron microscopy, small lithium nuclei (approximately 0.2 μm in diameter) were observed to be deposited uniformly over the entire surface of the uncoated Cu electrode in the initial electrodeposition, and these grew into needle-like crystals from the nuclei. After 60 min of electrodeposition, the needle-like precipitates had aggregated and grown into three-dimensional structures with dendritic form. In contrast, on the surface of the Cu electrode modified with Al2O3 by PLD for 1 h, lithium clusters of about 50 μm in diameter were found to be aggregated and precipitated in the initial stages of electrodeposition. Notably, this is the first report of lithium deposition on Al2O3 thin films. With further cycling, the precipitates grew into two-dimensional flat plates. Analysis of the SEI film formed during the first deposition reaction revealed that the Al2O3 coating reduced the thickness of the SEI compared to that of the uncoated electrode. Therefore, the Al2O3 coating suppressed the decomposition of the electrolyte with the Cu electrode. The use of Al2O3 coatings results in (i) the growth of two-dimensional lithium clusters with an island shape on the Al2O3 thin film, and these could ensure a uniform electron conduction path to the electrode; in addition, (ii) the inhibited electrolyte decomposition caused by the low-surface-area lithium clusters and the low electronic conductivity of the Al2O3 thin film. These improve the coulombic efficiency and cycling behaviour.

Lithiophilic and Anticorrosive Cu Current Collector via Dual-Bonded Porous Polymer Coating for Stable Lithium-Metal Batteries

Li metal is the ultimate anode material for next-generation high-energy-density rechargeable batteries. However, the uncontrollable growth of Li dendrites and low Coulombic efficiency (CE) prevent it from practical applications in Li metal batteries (LMBs). Here, a facile and low-cost strategy is developed to decorate a Cu current collector with a self-assembled γ-aminopropyltrimethoxysilane (γ-APS) film. The thin polymer film with nanopores promotes the formation of cobblestone-like Li deposition and suppresses Li-dendrite formation due to its low surface energy. The protecting layer not only increases the lithiophilicity of the Cu current collector but also alleviates the ambient corrosion and galvanic corrosion in practical use. Owing to these advantages, the half cell using γ-APS-Cu collectors exhibits a high average CE value of 99.2% for 100 cycles. The symmetric cell of γ-APS-Cu@Li shows an improved lifespan of 1400 h with a small voltage hysteresis of 12 mV at 0.5 mA cm-2. The full cell assembled with LiFePO4 (LFP) cathodes and γ-APS-Cu@Li anodes delivers a high capacity of 136 mAh g-1 after 600 cycles at 0.5C.

Dual Vertically Aligned Electrode-Inspired High-Capacity Lithium Batteries

Lithium (Li) dendrite formation and poor Li⁺ transport kinetics under high-charging current densities and capacities inhibit the capabilities of Li metal batteries (LMBs). This study proposes a 3D conductive multichannel carbon framework (MCF) with homogeneously distributed vertical graphene nanowalls (VGWs@MCF) as a multifunctional host to efficiently regulate Li deposition and accelerate Li⁺ transport. A novel electrode for both Li|VGWs@MCF anode and LFP|VGWs@MCF (NCM₈₁₁ |VGWs@MCF) cathode is designed and fabricated using a dual vertically aligned architecture. This unique hierarchical structure provides ultrafast, continuous, and smooth electron transport channels; furthermore, it furnishes outstanding mechanical strength to support massive Li deposition at ultrahigh rates. As a result, the Li|VGWs@MCF anode exhibits outstanding cycling stability at ultrahigh currents and capacities (1000 h at 10 mA cm^-2 and 10 mAh cm^-2 , and 1000 h at 30 mA cm^-2 and 60 mAh cm^-2 ). Moreover, full cells made of such 3D anodes and freestanding LFP|VGWs@MCF (NCM₈₁₁ |VGWs@MCF) cathodes with conspicuous mass loading (45 mg cm^-2 for LFP and 35 mg cm^-2 for NCM₈₁₁ ) demonstrate excellent areal capacities (6.98 mAh cm^-2 for LFP and 5.6 mAh cm^-2 for NCM₈₁₁ ). This strategy proposes a promising direction for the development of high-energy-density practical Li batteries that combine safety, performance, and sustainability.

Scientific Challenges and Improvement Strategies of Zn-Based Anodes for Aqueous Zn-Ion Batteries

Aqueous zinc-ion batteries (ZIBs) have attracted widespread attention due to the intrinsic features of Zn-based anodes, mainly including high capacity, low cost, and low working potential together with high over-potential for hydrogen evolution reaction. Aqueous ZIBs are considered to be strong competitors and substitutes for lead-acid, nickel-metal hydrogen, nickel-cadmium, and even lithium-ion batteries. Great efforts have been made in the past few years towards the issues existed in aqueous ZIBs, mainly including alkaline and mild acidic systems. In this perspective, we illustrate the advantages, the main challenges, and the corresponding solution strategies of Zn-based anodes in various aqueous rechargeable ZIBs with alkaline and mild acidic electrolytes. Furthermore, feasible aqueous ZIBs for practical use are prospected.

Built-In Stable Lithiophilic Sites in 3D Current Collectors for Dendrite Free Li Metal Electrode

Stable lithiophilic sites in 3D current collectors are the key to guiding the uniform Li deposition and thus suppressing the Li dendrite growth, but such sites created by the conventional surface decoration method are easy to be consumed along with cycling. In this work, carbon fiber (CF)-based 3D porous networks with built-in lithiophilic sites that are stable upon cycling are demonstrated. Such heterostructured architecture is constructed by the introduction of zeolitic imidazolate framework-8-based nanoparticles during the formation of the 3D fibrous carbonaceous network and the following annealing. The introduced Zn species are found to be re-distributed along the entire individual CF in the 3D network, and function as lithiophilic sites that favor the homogenous lithium nucleation and growth. The 3D network also presents a multi-scale porous structure that improves the space utilization of the host. The corresponding symmetric cells adopting such 3D anode demonstrate excellent cycling performance, especially at a high rate (300 cycles at 10 mA cm^-2 with a capacity of 5 mA h cm^-2 ). A full cell with LiFePO₄ cathode shows a capacity retention of 98% after cycling at 1C for 300 cycles. This method provides an effective design strategy for 3D hosting electrodes in dendrite-free alkali metal anode applications.

Charge-Discharge Mechanism of High-Entropy Co-Free Spinel Oxide Toward Li+ Storage Examined Using Operando Quick-Scanning X-Ray Absorption Spectroscopy

Transition metal high-entropy oxides (HEOs) are an attractive class of anode materials for high-performance lithium-ion batteries (LIBs). However, owing to the multiple electroactive centers of HEOs, the Li+ storage mechanism is complex and debated in the literature. In this work, operando quick-scanning X-ray absorption spectroscopy (XAS) is used to study the lithiation/delithiation mechanism of the Cobalt-free spinel (CrMnFeNiCu)3 O4 HEO. A monochromator oscillation frequency of 2 Hz is used and 240 spectra are integrated to achieve a 2 min time resolution. High-photon-flux synchrotron radiation is employed to increase the XAS sensitivity. The results indicate that the Cu2+ and Ni2+ cations are reduced to their metallic states during lithiation but their oxidation reactions are less favorable compared to the other elements upon delithiation. The Mn2+/3+ and Fe2+/3+ cations undergo two-step conversion reactions to form metallic phases, with MnO and FeO as the intermediate species, respectively. During delithiation, the oxidation of Mn occurs prior to that of Fe. The Cr3+ cations are reduced to CrO and then Cr0 during lithiation. A relatively large overpotential is required to activate the Cr reoxidation reaction. The Cr3+ cations are found after delithiation. These results can guide the material design of HEOs for improving LIB performance.

Porous carbon architectures with different dimensionalities for lithium metal storage

Lithium metal batteries have recently gained tremendous attention owing to their high energy capacity compared to other rechargeable batteries. Nevertheless, lithium (Li) dendritic growth causes low Coulombic efficiency, thermal runaway, and safety issues, all of which hinder the practical application of Li metal as an anodic material. In this review, the failure mechanisms of Li metal anode are described according to its infinite volume changes, unstable solid electrolyte interphase, and Li dendritic growth. The fundamental models that describe the Li deposition and dendritic growth, such as the thermodynamic, electrodeposition kinetics, and internal stress models are summarized. From these considerations, porous carbon-based frameworks have emerged as a promising strategy to resolve these issues. Thus, the main principles of utilizing these materials as a Li metal host are discussed. Finally, we also focus on the recent progress on utilizing one-, two-, and three-dimensional carbon-based frameworks and their composites to highlight the future outlook of these materials.

Remedies to Avoid Failure Mechanisms of Lithium-Metal Anode in Li-Ion Batteries

Rechargeable lithium-metal batteries (LMBs), which have high power and energy density, are very attractive to solve the intermittence problem of the energy supplied either by wind mills or solar plants or to power electric vehicles. However, two failure modes limit the commercial use of LMBs, i.e., dendrite growth at the surface of Li metal and side reactions with the electrolyte. Substantial research is being accomplished to mitigate these drawbacks. This article reviews the different strategies for fabricating safe LMBs, aiming to outperform lithium-ion batteries (LIBs). They include modification of the electrolyte (salt and solvents) to obtain a highly conductive solid–electrolyte interphase (SEI) layer, protection of the Li anode by in situ and ex situ coatings, use of three-dimensional porous skeletons, and anchoring Li on 3D current collectors.

Suppressing Li Dendrite Puncture with a Hierarchical h-BN Protective Layer

Lithium metal has been perceived as an extremely attractive anode due to its superior energy density and low redox potential. However, great challenges affiliated with the operating security of Li metal batteries (LMBs) posed by growing Li dendrites hamper the widespread application of rechargeable LMBs. In this study, hierarchical hairball-like boron nitride (h-BN) was fabricated on a Li metal anode using the pulsed laser deposition (PLD) method. The chemically inert and mechanically robust dielectric h-BN coating on the Li anode can act as an interfacial layer conducive to enhancing the stability and extending the battery lifetime of LMBs by suppressing the formation and propagation of dendrites during the recurrent plating and stripping process. Moreover, the h-BN layer favors the drift of Li ions and mitigates electrolyte depletion, therefore demonstrating a reduced polarization in the voltage profiles, which further facilitates the uniform deposition of Li ions during battery operation. As proof, the Li/BN || BN/Li symmetrical cells can circulate steadily for 1800 h with no observable polarization at constant current density. Thus, the three-dimensional h-BN interface layer is efficacious for Li dendrite suppression during the practical application of LMBs, and it may also be promising for tackling dendrite issues in other metal ion battery systems.

The Defect Chemistry of Carbon Frameworks for Regulating the Lithium Nucleation and Growth Behaviors in Lithium Metal Anodes

Carbon materials have been widely considered as the frameworks in lithium (Li) metal anodes due to their lightweight, high electrical conductivity, and large specific surface area. Various heteroatom-doping strategies have been developed to enhance the lithiophilicity of carbon frameworks, thus rendering a uniform Li nucleation in working Li metal batteries. The corresponding lithiophilicity chemistry of doping sites has been comprehensively probed. However, various defects are inevitably introduced into carbon materials during synthesis and their critical role in regulating Li nucleation and growth behaviors is less understood. In this contribution, the defect chemistry of carbon materials in Li metal anodes is investigated through first-principles calculations. The binding energy towards a Li atom and the critical current density are two key descriptors to reveal the defect chemistry of carbon materials. Consequently, a diagram of designing carbon frameworks with both high lithiophilicity and a large critical current density is built, from which the Stone-Wales defect is predicted to possess the best performance for delivering a uniform Li deposition. This work uncovers the defect chemistry of carbon frameworks and affords fruitful insights into defect engineering for achieving dendrite-free Li metal anodes.

Covalent Organic Frameworks and Their Derivatives for Better Metal Anodes in Rechargeable Batteries

Metal anodes based on a plating/stripping electrochemistry such as metallic Li, Na, K, Zn, Ca, Mg, Fe, and Al are recognized as promising anode materials for constructing next-generation high-energy-density rechargeable metal batteries owing to their low electrochemical potential, high theoretical specific capacity, superior electronic conductivity, etc. However, inherent issues such as high chemical reactivity, severe growth of dendrites, huge volume changes, and unstable interface largely impede their practical application. Covalent organic frameworks (COFs) and their derivatives as emerging multifunctional materials have already well addressed the inherent issues of metal anodes in the past several years due to their abundant metallophilic functional groups, special inner channels, and controllable structures. COFs and their derivatives can solve the issues of metal anodes by interfacial modification, homogenizing ion flux, acting as nucleation seeds, reducing the corrosion of metal anodes, and so on. Nevertheless, related reviews are still absent. Here we present a detailed review of multifunctional COFs and their derivatives in metal anodes for rechargeable metal batteries. Meanwhile, some outlooks and opinions are put forward. We believe the review can catch the eyes of relevant researchers and supply some inspiration for future research.

Design of Robust, Lithiophilic, and Flexible Inorganic-Polymer Protective Layer by Separator Engineering Enables Dendrite-Free Lithium Metal Batteries with LiNi0.8 Mn0.1 Co0.1 O2 Cathode

As a promising candidate for the high energy density cells, the practical application of lithium-metal batteries (LMBs) is still extremely hindered by the uncontrolled growth of lithium (Li) dendrites. Herein, a facile strategy is developed that enables dendrite-free Li deposition by coating highly-lithiophilic amorphous SiO microparticles combined with high-binding polyacrylate acid (SiO@PAA) on polyethylene separators. A lithiated SiO and PAA (lithiated-SiO/PAA) protective layer with synergistic flexible and robust features is formed on the Li metal anode via the in situ reaction to offer outstanding interfacial stability during long-term cycles. By suppressing the formation of dead Li and random Li deposition, reducing the side reaction, and buffering the volume changes during the lithium deposition and dissolution, such a protective layer realizes a dendrite-free morphology of Li metal anode. Furthermore, sufficient ionic conductivity, uniform lithium-ion flux, and interface adaptability is guaranteed by the lithiated-SiO and Li polyacrylate acid. As a result, Li metal anodes display significantly enhanced cycling stability and coulombic efficiency in Li||Li and Cu||Li cells. When the composite separator is applied in a full cell with a carbonate-based electrolyte and LiNi_0.8 Mn_0.1 Co_0.1 O₂ cathode, it exhibits three times longer lifespan than control cell at current density of 5 C.

Integrated Structure of Cathode and Double-Layer Electrolyte for Highly Stable and Dendrite-Free All-Solid-State Li-Metal Batteries

All-solid-state batteries have become the most potential next-generation energy-storage devices. However, it is quite difficult to simultaneously achieve a single solid-state electrolytes (SSEs) layer with both dendrite-free Li metal plating and low interfacial resistance between the cathode and SSEs. Herein, an integrated structure of cathode and double-layer solid electrolyte membrane (IS-CDL) is designed, which greatly improves the interfacial contact and suppresses the Li dendrite growth. The first "polymer in ceramic" solid electrolyte layer (SL1) consists of 80 wt % Li_1.4Al_0.4Ti_1.6(PO₄)₃ (LATP) nanoparticles and 20 wt % polyethylene oxide (PEO), and the second polymer electrolyte layer is PEO-based solid electrolyte layer (SL2). The SL1 with high mechanical properties can hinder the growth of Li dendrites and reduce the interfacial resistance with the cathode. The SL2 can inhibit the side reaction between the Li metal and LATP. The Li symmetric cells with sandwich-type hierarchical electrolyte (SL2/SL1/SL2) can stably cycle over 3200 h at 0.1 mA cm^-2 at 45 °C. The obtained all-solid-state LiFePO₄-IS-CDL/Li batteries present a capacity of 142.6 mA h g^-1 at 45 °C with the capacity retention of 91.7% after 100 cycles, and all-solid-state NCM811-IS-CDL/Li batteries deliver a specific capacity of 175.5 mA h g^-1 at 60 °C. This work proposes an effective strategy to fabricate all-solid-state lithium batteries with high electrochemical performance.