Li Dendrite Growth Research Articles

Tuning the Unloading and Infiltrating Behaviors of Li-Ion by a Multiphases Gradient Interphase for High-Rate Lithium Metal Anodes.

The random distribution of organic-phases (OPs) and inorganic-phases (IOPs) in native solid electrolyte interface (SEI) derived a sluggish Li-ion de-solvation and transmission, impairing the high-rate performance of lithium metal anodes (LMAs). Herein, a multiphases gradient distribution hybrid interface is constructed on metallic Li by surface chemical reconstruction. Theoretical simulations and experiments verify that the Li-ion unloading and infiltrating behaviors are tuned by functional complementary effects, enabling speedy kinetics. The upper OPs with polar functional group (─COO-) convert near-surface solvation structure, pushing Li-ion to unload the solvation cluster. Simultaneously, the bottom IOPs with plenty of crystal boundary accelerates Li-ion infiltration. Moreover, flexible OPs cooperate with rigid IOPs to buffer volume fluctuation and suppress dendritic Li growth. Consequently, the lifespan of the composited electrode is significantly prolonged over 520h at 5mAcm-2. The full cells also exhibit an exhilarated rate performance and capacity retention even under a low N/P ratio (≈2.5). This work offers a characteristic insight for the rational design of gradient hybrid interface on the practical LMAs.

Improving Bulk and Interfacial Lithium Transport in Garnet-Type Solid Electrolytes through Microstructure Optimization for High-Performance All-Solid-State Batteries.

Garnet-type Li6.4La3Zr1.4Ta0.6O7 (LLZTO) is regarded as a highly competitive next-generation solid-state electrolyte for all-solid-state lithium batteries owing to reliable safety, a wide electrochemical operation window of 0-6 V versus Li+/Li, and a superior stability against Li metal. Nevertheless, insufficient interface contacts caused by pores, along with Li dendrite growth at these voids and grain boundary regions, have hindered their commercial application. Herein, we suggest a method to produce high-quality LLZTO using LiAlO2 (LAO) as a chemical additive that leads to an improved microstructure with larger grain size (∼25 μm), a high relative density (∼96%), lower porosity (∼3.7%), and continuous secondary phases in grain boundary regions. This improved structure results in (i) improved Li-ion conductivity and enhanced interfacial resistance between Li metal and LLZTO by a denser structure with fewer pores and (ii) suppression of Li dendrite penetration in the electrolyte by secondary phases in grain boundary regions.

Scalable Production of Thin and Durable Practical Li Metal Anode for High‐Energy‐Density Batteries

AbstractUtilization of thin Li metal is the ultimate pathway to achieving practical high‐energy‐density Li metal batteries (LMBs), but its practical implementation has been significantly impeded by formidable challenges of poor thinning processability, severe interphase instability and notorious dendritic Li growth. Here we report a practical thin (10–40 μm) Li/Mo/Li2Se with concurrently modulated interphase and mechanical properties, achieved via a scalable mechanical rolling process. The in situ generated Li2Se and Mo not only enhance the mechanical strength enabling the scalable fabrication of thin Li metal, but also promote homogeneous Li electrodeposition. Significantly, the Li/Mo/Li2Se demonstrates ultrahigh‐rate performance (15 mA cm−2) and ultralong‐lifespan cycling sustainability (2700 cycles) with exceptional anti‐pulverization capability. The Li|LiFePO4 cells show substantially prolonged cyclability over 1200 cycles with an ultralow decay rate of ~0.01 % per cycle. Moreover, the Li|LiNi0.8Co0.1Mn0.1O2 pouch cells deliver enhanced cycling stability even under the extremely harsh conditions of low negative‐to‐positive‐capacity (N/P) ratio of ~1.2 and lean electrolyte of ~0.95 g Ah−1, showing an exceptional energy density of 329.2 Wh kg−1. This work sheds light on facile pathway for scalable production of durable thin Li metal anode toward reliable practicability.

Achieving High Stability and Capacity in Micron-Sized Conversion-Type Iron Fluoride Li-Metal Batteries.

Iron fluoride, a conversion-type cathode material with high energy density and low-cost iron, holds promise for Li-ion batteries but faces challenges in synthesis, conductivity, and cycling stability. This study addresses these issues by synthesizing micron-sized iron-fluoride using a simple solid-state synthesis. Despite a large particle size, a high capacity of 571mAhg-1 is achieved, which is attributed to the unique surface and internal pores within the iron-fluoride particles, which provided a large surface area. This is the first study to demonstrate the feasibility of using large iron fluoride particles to enhance the energy density of the electrode and achieve an iron fluoride full cell with high capacity. Also, the cause of the capacity fading is investigated. Electrode delamination from the current collector, which is the main cause of capacity fading in early cycles, is resolved using a carbon-coated aluminum (C/Al) current collector. Moreover,iron (Fe) dissolution and the deposition of dissolved Fe on the Li metal also contributed significantly to the degradation. Localized high-concentration electrolytes (LHCEs)suppress iron dissolution and Li dendrite growth, resulting in long-cycle stability for 300 cycles. This study provides insights into the further development of conversion-type metal fluorides across various compositions.

Designing Bilayer Heterostructure Functional Polymer Electrolytes with Interfacial Engineering Strategy for High‐Performance Lithium Metal Batteries

AbstractThe uncontrollable lithium (Li) dendrites growth and complex electrode/electrolyte interface (EEI) problems are hindering the further application of high energy density lithium metal batteries (LMBs) in practice. Herein, a bilayer heterostructure gel polymer electrolyte (BGPE) is designed by directly curing functional boron‐containing monomers on the electrode surface to ensure excellent conductivity while solving the interface problems, achieving durable high voltage resistance and Li dendrites suppression. The unoccupied p‐orbital boron moiety of the 3D crosslinked network in BGPE not only improves the Li+ transference number (0.78), but also enhances the interfacial stability of the Li metal and inhibits the dendrites growth by anchoring PF6− anions and regulating the uniform Li deposition, thus ensuring a long cycle for Li/BGPE/Li cells. In addition, the functional additives tris(trimethylsilyl) phosphite and tris(pentafluorophenyl)borane can preferentially oxidize and decompose to form stable B, F, and Si‐rich EEIs, and effectively regulate the uniform growth of EEI. Thus, the LiNi0.5Co0.2Mn0.3O2/BGPE/Li and LiFePO4/BGPE/Li full cells exhibit stable cycling and excellent rate performance. This work provides a guiding design direction to address the EEI problems for high energy density LMBs.

A covalently bonded, LiF-rich solid electrolyte interphase for Li metal batteries with superior low-temperature performance

The solid electrolyte interphase (SEI) layer plays a critical role in determining the performance of lithium metal batteries (LMBs). Here, we show that treating Li foils with 4,4,5,5,5-pentafluoropentanol (PFPO) results in the formation of a novel LiF-rich organic/inorganic SEI layer (designated as LiF-PO) that enhances the performance of LMBs. Compared to the native SEI layer that is electrochemically formed in LMBs, the LiF-PO SEI layer is mechanically robust, adopts a compact structure, and exhibits high Li+ conductivity. These features enable Li//Li symmetric cells to exhibit superior performance metrics, even at low temperatures, including inhibited Li dendrite growth, reduced polarization voltage, and elongated cycling lifetime. Moreover, compared to lithium–sulfur cells prepared using bare Li foils, the cells prepared using PFPO-treated Li foils also exhibit markedly improved performance at low temperatures in terms of specific capacity (796 mA h g−1 vs. 559 mA h g−1 at 0.1 C and −20 °C), rate capability (519 mA h g−1 vs. 222 mA h g−1 at 3 C and 0 °C), and cycling stability (504 mA h g−1 vs. 253 mA h g−1 at 0.1 C after 100 cycles at −20 °C). The lessons learned from our study establish new principles for designing high-performance SEI layers and may be extended to other types of metal batteries.

Dendrite Growth and Dead Lithium Formation in Lithium Metal Batteries and Mitigation Using a Protective Layer: A Phase-Field Study.

Lithium metal batteries (LMBs) are considered one of the most promising next-generation rechargeable batteries due to their high specific capacity. However, severe dendrite growth and subsequent formation of dead lithium (Li) during the battery cycling process impede its practical application. Although extensive experimental studies have been conducted to investigate the cycling process, and several theoretical models were developed to simulate the Li dendrite growth, there are limited theoretical studies on the dead Li formation, as well as the entire cycling process. Herein, we developed a phase-field model to simulate both electroplating and stripping process in a bare Li anode and Li anode covered with a protective layer. A step function is introduced in the stripping model to capture the dynamics of dead Li. Our simulation clearly shows the growth of dendrites from a bare Li anode during charging. These dendrites detach from the bulk anode during discharging, forming dead Li. Dendrite growth becomes more severe in subsequent cycles due to enhanced surface roughness of the Li anode, resulting in an increasing amount of dead Li. In addition, it is revealed that dendrites with smaller base diameters detach faster at the base and produce more dead lithium. Meanwhile, the Li anode covered with a protective layer cycles smoothly without forming Li dendrite and dead Li. However, if the protective layer is fractured, Li metal preferentially grows into the crack due to enhanced Li-ion (Li+) flux and forms a dendrite structure after penetration through the protective layer, which accelerates the dead Li formation in the subsequent stripping process. Our work thus provides a fundamental understanding of the mechanism of dead Li formation during the charging/discharging process and sheds light on the importance of the protective layer in the prevention of dead Li in LMBs.

Revealing the Failure Mechanisms of Lithium Metal Solid‐State Batteries with Solid Inorganic Electrolytes by In situ Electron Microscopy

Lithium metal solid‐state batteries (LMSSBs) are considered to be one of the ultimate choices for future energy storage systems because of their high theoretical energy density and enhanced safety. However, the development of LMSSBs has been seriously hindered by some practical issues, such as Li dendrite penetration in the solid‐state electrolytes (SSEs) and uncontrolled interphase growth at the Li/SSE interface, which can cause severe battery degradation, failure, and even safety hazards. To construct safe high‐performance LMSSBs, it is crucial to gain an in‐depth understanding of the failure mechanisms induced by these challenges, especially through direct visualization of the failure processes. In this review, the recent progress on the mechanistic study of LMSSBs by in situ electron microscopy is summarized. In situ transmission electron microscopy (TEM) and scanning electron microscopy (SEM) offer an opportunity to probe the battery failure mechanism by observing the associated physical and chemical processes at nano/atomic resolution. The failure causes of Li dendrites growth and interphase formation are classified and discussed, followed by the corresponding solutions to address these issues. Additionally, the emerging perspectives on future research directions in this field are also summarized.

Anode-Free Li Metal Batteries: Feasibility Analysis and Practical Strategy.

Energy storage devices are striving to achieve high energy density, long lifespan, and enhanced safety. In view of the current popular lithiated cathode, anode-free lithium metal batteries (AFLMBs) will deliver the theoretical maximum energy density among all the battery chemistries. However, AFLMBs face challenges such as low plating-stripping efficiency, significant volume change, and severe Li-dendrite growth, which negatively impact their lifespan and safety. This study provides an overview and analysis of recent progress in electrode structure, characterization, performance, and practical challenges of AFLMBs. The deposition behavior of lithium is categorized into two stages: heterogeneous and homogeneous interface deposition. The feasibility and practical application value of AFLMBs are critically evaluated. Additionally, key test models, evaluation parameters, and advanced characterization techniques are discussed. Importantly, practical strategies of different battery components in AFLMBs, including current collector, interface layer, solid-state electrolyte, liquid-state electrolyte, cathode, and cycling protocol, are presented to address the challenges posed by the two types of deposition processes, lithium loss, crosstalk effect and volume change. Finally, the application prospects of AFLMBs are envisioned, with a focus on overcoming the current limitations and unlocking their full potential as high-performance energy storage solutions.

An artificial layer enables in situ generation of a homogeneous inorganic/organic composite solid electrolyte interphase for stable lithium metal batteries.

Lithium (Li) metal anodes are considered one of the most promising anodes for high-performance batteries with ultra-high specific energy density. However, uncontrolled dendrite growth and the unsuitability of common systems for high voltage hinder the development of Li metal batteries with long cycle life. Herein, we report a rationally designed artificial solid electrolyte interphase (SEI) for Li metal anodes, incorporating LiNO3 and lithium difluoro(oxalato)borate (LiDFOB) as additives within a porous poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer skeleton (referred to as PNF). LiNO3 and LiDFOB can release and synergistically react at the electrode surface, leading to the in situ generation of a homogeneously distributed inorganic/organic SEI during the electrochemical process. This SEI improves homogeneity, ionic conductivity and mechanical stability, contributing to the suppression of electrolyte side reactions and Li dendrite growth. Moreover, a uniform CEI with high Li+ conductivity can be constructed on the NCM811 particles, further enhancing the structural integrity of the NCM811 cathode. As a result, the artificial SEI layer on Li metal anodes enables stable cycling of Li-Cu half cells in an ester-based electrolyte and Li-LiNi0.8Mn0.1Co0.1O2 full cell even at a high voltage of 4.5 V. This work provides new insights into designing homogeneous SEIs for Li metal batteries.

A biomass-based protective layer with rigid structure and ion conductivity for high-performance lithium metal batteries

Lithium (Li) metal has been considered as an effective anode material because of its high theoretical capacity, but the uncontrolled dendrite growth and the unstable electrode/electrolyte interface limit its practical application. In this work, proanthocyanidin (PA), a natural extracted biomass, was designed and developed as a coating material to guide homogeneous deposition and restrain side reaction for lithium metal batteries. The rigid benzene ring structure of PA can increase the mechanical strength to restrain dendrite growth on Li surface. Moreover, the spontaneous formation of organolithium (PA-Li) structure from the reaction of phenolic hydroxyl group with Li metal increase the ion transportation ability of PA layer and induce the uniform deposition of Li+ ions to hinder the growth of Li dendrites, as well as prevent the direct contact of organic electrolyte with Li metal to suppress the interface side reaction. As a result, Li metal anode with PA-Li exhibits stable cycling properties for 2800 h at 2 mA cm-2 and 2 mAh cm-2, better that of bare Li (200 h). Li-sulfur full battery with PA-Li can still achieve a capacity of 570 mAh g-1 after 300 cycles. This work provides an effective strategy for the construction a natural functional layer on Li surface to enhance the electrochemical performance, as well as the implementation of high-value utilization for natural biomass.

Unravelling the O-doping effect on chemical/electrochemical stability of Li5.5PS4.5Cl1.5 for all-solid-state lithium batteries

Chlorine-rich Li-argyrodite sulfide solid electrolytes Li5.5PS4.5Cl1.5 are applied in all-solid-state batteries (ASSBs) due to the promising ionic transport and structural stability. However, the poor air/moisture stability and incompatibility to Li metal impede their practical applications. Herein, we synthesized a Li5.5PS4.5Cl1.5-based argyrodite exhibiting improved moisture stability and electrochemical performance to metallic Li, as well as high-voltage cathodes through O doping. The prepared oxygen-doped Li5.5PS4.5Cl1.5 samples (Li5.5PS4.425O0.075Cl1.5) possess significantly enhanced air stability and lower migration barrier in comparison with pristine Li5.5PS4.5Cl1.5. Moreover, Li5.5PS4.425O0.075Cl1.5 exhibits lower polarization voltage and better compatibility with lithium metal in the constant current charge-discharge tests of Li-Li symmetrical cell. This is attributed to the Cl-O coexistence coating interface that observed in the interface of Li/Li5.5PS4.425O0.075Cl1.5. To fully leverage the ultrafast ionic conductivity of Li5.5PS4.5Cl1.5, we construct ASSBs using optimized Li5.5PS4.425O0.075Cl1.5 as buffer layer between pristine LiNi0.6Mn0.2Co0.2O2 cathode materials and Li5.5PS4.5Cl1.5, leading to higher discharge capacities and elevated capacity retention. Based on above results, we further introduce LiNbO3-coated LiCoO2 as cathode, combined with Li5.5PS4.425O0.075Cl1.5 as an isolating layer between Li anode and Li5.5PS4.5Cl1.5 to suppress the growth of Li dendrite and achieve superior cyclability at wide voltage windows. Consequently, the all-solid-state lithium batteries exhibit promising application in a wide temperature range. This work provides a compelling strategy for achieving improved Chlorine-rich Li-argyrodite solid electrolytes with excellent air stability, high ionic conductivity and Li dendrite suppression capability, hence enabling all-solid-state batteries with high energy density and superior cyclability.

Lithiophilic Protective Dual Layer Enabling Stable Electrodeposition of Lithium at High Current Density

Lithium (Li) is an ideal anode material for rechargeable batteries and thus manufacturing Li metal is crucial for the practical development of Li metal batteries. Electrodeposition is an efficient technique for producing ultrathin and scalable Li metal electrodes. However, the dendritic growth and the side reactions of Li with electrolyte during the electrodeposition are the main obstacles to overcome. In this study, we designed a pre-coated protective dual layer (PDL) composed of a poly(ethylene oxide)-based solid polymer electrolyte (SPE) and a polydopamine-coated cellulose membrane (PD-CM). The adhesive and ion-conductive SPE layer suppressed the growth of Li dendrites and side reactions with liquid electrolyte. The PD-CM layer with high porosity and lithiophilicity promoted a facile and uniform Li-ion flux. By applying the pre-coated PDL, Li was uniformly electrodeposited on the Ag-coated Cu at a high current density of 6 mA cm−2. The Li/LiFePO4 cell composed of an electrodeposited Li anode with PDL and a LiFePO4 cathode was assembled without an additional separator, and its cycling performance was evaluated. The cell initially delivered a high discharge capacity of 154.8 mAh g−1 at 45 °C and exhibited excellent cycling stability with a capacity retention of 97.0% after 200 cycles.

Bilayer Interphase for Air-Stable and Dendrite-Free Lithium Metal Anode Cycling in Carbonate Electrolytes.

The intrinsic reactivity of lithium (Li) toward ambient air, combined with insufficient cycling stability in conventional electrolytes, hinders the practical adoption of Li metal anodes in rechargeable batteries. Here, a bilayer interphase for Li metal is introduced to address both its susceptibility to corrosion in ambient air and its deterioration during cycling in carbonate electrolytes. Initially, the Li metal anode is coated with a conformal bottom layer of polysiloxane bearing methacrylate, followed by further grafting with poly(vinyl ethylene carbonate) (PVEC) to enhance anti-corrosion capability and electrochemical stability. In contrast to single-layer applications of polysiloxane or PVEC, the bilayer design offers a highly uniform coating that effectively resists humid air and prevents dendritic Li growth. Consequently, it demonstrates stable plating/stripping behavior with only a marginal increase in overpotential over 200 cycles in carbonate electrolytes, even after exposure to ambient air with 46% relative humidity. The design concept paves the way for scalable production of high-voltage, long-cycling Li metal batteries.

Reversible Li plating regulation on graphite anode through a barium sulfate nanofibers-based dielectric separator for fast charging and high-safety lithium-ion battery

Poor Li plating reversibility and high thermal runaway risks are key challenges for fast charging lithium-ion batteries with graphite anodes. Herein, a dielectric and fire-resistant separator based on hybrid nanofibers of barium sulfate (BS) and bacterial cellulose (BC) is developed to synchronously enhance the battery’s fast charging and thermal-safety performances. The regulation mechanism of the dielectric BS/BC separator in enhancing the Li+ ion transport and Li plating reversibility is revealed. (1) The Max-Wagner polarization electric field of the dielectric BS/BC separator can accelerate the desolvation of solvated Li+ ions, enhancing their transport kinetics. (2) Moreover, due to the charge balancing effect, the dielectric BS/BC separator homogenizes the electric field/Li+ ion flux at the graphite anode-separator interface, facilitating uniform Li plating and suppressing Li dendrite growth. Consequently, the fast-charge graphite anode with the BS/BC separator shows higher Coulombic efficiency (99.0% vs. 96.9%) and longer cycling lifespan (100 cycles vs. 59 cycles) than that with the polypropylene (PP) separator in the constant-lithiation cycling test at 2 mA cm−2. The high-loading LiFePO4 (15.5 mg cm−2)//graphite (7.5 mg cm−2) full cell with the BS/BC separator exhibits excellent fast charging performance, retaining 70% of its capacity after 500 cycles at a high rate of 2 C, which is significantly better than that of the cell with the PP separator (retaining only 27% of its capacity after 500 cycles). More importantly, the thermally stable BS/BC separator effectively elevates the critical temperature and reduces the heat release rate during thermal runaway, thereby significantly enhancing the battery’s safety.

In-situ construction of high-performance artificial solid electrolyte interface layer on anode surfaces for anode-free lithium metal batteries

The electrochemical performance of lithium metal batteries (LMBs) was hampered by the uncontrolled growth of lithium (Li) dendrites. To address this issue, the extensive application of artificial solid electrolyte interphase (SEI) coatings on anode surfaces emerged as an effective solution. Electrospinning, as an innovative technique for fabricating artificial SEI layers on the surface of copper (Cu) foil, effectively mitigated Li volume strain during cycling. In this study, an electrospun organic–inorganic composite nanofiber membrane was in-situ fabricated on Cu foil, serving as an artificial SEI layer (CuWs) for anode-free LMBs (AF-LMBs) to enhance battery performance. Lithiophilic polyvinylpyrrolidone was used as the polymer matrix, and Cu nitrate served as the inorganic functional particles capable of in-situ redox reactions. The CuWs with their three-dimensional (3D) network structure accommodated electrode volume changes and suppressed Li dendrite growth during Li deposition and stripping. Additionally, CuWs facilitated the in-situ generation of Li nitrate (LiNO3), which helped stabilize SEI layer and enhance Li utilization. The release sites of LiNO3 on the nanofibers enabled the in-situ reduction of metallic Cu, providing nucleation sites for Li deposition and forming the 3D ion–electron hybrid conductive networks. This CuWs layer reduced interfacial resistance and nucleation barriers, promoting uniform Li+ distribution on the anode surface. Li-Cu cells incorporating CuWs exhibited remarkable cycling stability, enduring over 460 cycles at 1.0 mA cm−2 and 1.0 mAh cm−2 with an average Coulombic efficiency of over 98.6 %. In Li-poor cells, the LFP|PE|CuWs achieved stable cycling for more than 30 cycles at 1.0 C, with a capacity retention rate of 92.0 %. These findings demonstrated that the CuWs membrane significantly enhanced the electrochemical performance of Li-poor cells and provided a novel artificial SEI protective strategy for advanced AF-LMBs with high energy density.

In Situ-Constructed Multifunctional Composite Anode with Ultralong-Life Toward Advanced Lithium-Metal Batteries.

Metallic lithium is the most competitive anode material for next-generation high-energy batteries. Nevertheless, the extensive volume expansion and uncontrolled Li dendrite growth of lithium metal not only cause potential safety hazards but also lead to low Coulombic efficiency and inferior cycling lifespan for Li metal batteries. Herein, a multifunctional dendrite-free composite anode (Li/SnS2) is proposed through an in situ melt-infusion strategy. In this configuration, the 3D cross-linked porous Li2S/Li22Sn5 framework facilitates the rapid penetration of electrolytes and accommodates the volume expansion during the repeated Li-plating process. Meanwhile, the lithiophilic Li2S phases with a low Li+ transport barrier ensure preferential Li deposition, effectively avoiding uneven electron distribution. Moreover, the Li22Sn5 electron conductors with appropriate Li+ bonding ability guarantee rapid charge transport and mass transfer. Most importantly, the steady multifunctional skeleton with sufficient inner interfaces (Li2S/Li22Sn5) in the whole electrode, not only realizes the redistribution of the localized free electron, contributing to the decomposition of Li clusters, but also induces a planar deposition model, thus restraining the generation of Li dendrites. Consequently, an unprecedented cyclability of over 6500h under an ultrahigh areal capacity of 10mAhcm-2 and a current rate of 20mAcm-2 is achieved for the prepared Li2S/Li22Sn5 composite anode. Moreover, the assembled Li/SnS2||LiFePO4 (LFP) pouch full-cells also demonstrate remarkable rate capability and a convincing cycling lifespan of more than 2000 cycles at 2 C.

A modified separator based on ternary mixed-oxide for stable lithium metal batteries

Li metal batteries (LMBs) are among the most promising options for next-generation secondary batteries under the rapidly growing demand for high-energy–density electrochemical energy storage. However, the implementation of LMBs are hindered by major obstacles such as dentritic Li deposition and low cycling Coulombic efficiency. A practical functional separator is developed in this study, which consists of a Lewis acidic mixed oxide of ZrO2-SiO2-Al2O3 as a functional coating with anion anchoring ability to modulate ion transport in the vicinity of the Li metal anode, delivering a high Li+ transference number of 0.88 in carbonate electrolytes that suppresses dendrite formation. The strong Lewis acid sites in ZrO2-SiO2-Al2O3 originate from coordinatively unsaturated Zr4+ ions, which immobilize anions and reduce their decomposition rate. This significantly improves the chemical stability of the electrolyte and induces a more stable solid electrolyte interphase layer. The modified separator enables an anode-free cell containing a high-loading LiNi0.8Co0.1Mn0.1O2 cathode to present stable charge and discharge cycling for 150 cycles at 0.5C. By effectively suppressing Li dendrite growth and supporting the long-term operation of anode-free LMBs, this study offers a novel approach to rationally design mixed oxides with high Lewis acidity for functional separators.

Supramolecular polymer cross-linking gel electrolyte for highly stable quasi-solid-state lithium metal batteries

Lithium (Li) metal batteries have the advantage of high energy density, but the Li dendrites risk piercing the separator and causing a short circuit in the battery. Replacing the liquid electrolytes with gel electrolytes is considered an effective strategy to solve the issues. Herein, a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel electrolyte, improved with multifunctional supramolecular polymer (MSP), was prepared to enhance the cycling stability and energy density of quasi-solid-state Li metal batteries. The MSP addictive constructs a cross-linked network structure with PVDF-HFP matrix and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) through hydrogen bonding, improving the mechanical strength of the composite gel electrolyte (PH-10%MSP-GE) to against the growth of Li dendrites. Moreover, the pre-lithiated sulfonic acid groups, conductive polyether groups of MSP, and the attraction of TFSI– anions, promote the Li-ion transportation of the composite gel electrolyte. Finally, the Li||Li symmetric cell cycle stably for over 450 h. The Li||LiFePO4 full cell demonstrates a high energy density and excellent cycling stability for over 600 cycles, with a capacity retention rate of up to 98.7%. This work provides valuable insights into the preparation of multifunctional composite gel polymer electrolytes and competitive quasi-solid-state Li metal batteries.

H3PO4-Impregnated Covalent Organic Framework Membrane on Separators to Prevent Lithium Metal Anode Dendrite Growth.

Inhibiting the growth of lithium dendrites is crucial for battery safety. For separators, their favorable electrolyte wettability, uniform current density, and high ionic conductivity are beneficial for avoiding Li dendrite growth. In this work, we propose a separator (PA@COF/PP) by modifying a polypropylene separator with H3PO4-functionalized covalent organic frameworks. The uniform channels of the covalent organic frameworks and H3PO4 can homogenize the current and act as ionic conductors for efficient Li+ migration. The synthesized separator effectively suppresses the growth of lithium dendrites and improves the stability of the batteries. A symmetric cell with the PA@COF/PP separator exhibits a stable life span over 4000 hours at a high current density of 5 mA cm-2, compared to the commercial PP separator, which lasts only 159 hours. This work provides an efficient method and novel inspiration for the construction of dendrite-free lithium metal batteries.