Reversible Deposition of Lithium Particles Enabled by Ultraconformal and Stretchable Graphene Film for Lithium Metal Batteries

Originating from inhomogeneous Li deposition and dissolution, the formation of dendritic and/or dead Li lies as a fundamental barrier to the practical implementation of Li metal anodes for high-energy Li-ion batteries. Here, an ultraconformal and stretchable solid-electrolyte interphase (SEI) composed of parallelly stacked few-layer defect-free graphene nanosheets, which can deform to remain ultraconformal during the expansion and shrinkage of micro-sized Li metal particles is reported. The shape-adaptive graphene protective skin is prepared via a facile mechanical method followed by Li stripping, which enables fast Li-ion diffusion, and inhibits Li dendrites and Li pulverization. The interlayer slips and wrinkles of the graphene film endow the robust protective skin with high stretchability. This work represents a unique strategy of building ultraconformal and stretchable 2D-materials-based protective skins on the surface of Li metal toward high-energy, long-life, and safe Li metal batteries.     

A Polymer‐Reinforced SEI Layer Induced by a Cyclic Carbonate‐Based Polymer Electrolyte Boosting 4.45 V LiCoO2/Li Metal Batteries

Lithium (Li) metal batteries (LMBs) are enjoying a renaissance due to the high energy densities. However, they still suffer from the problem of uncontrollable Li dendrite and pulverization caused by continuous cracking of solid electrolyte interphase (SEI) layers. To address these issues, developing spontaneously built robust polymer‐reinforced SEI layers during electrochemical conditioning can be a simple yet effective solution. Herein, a robust homopolymer of cyclic carbonate urethane methacrylate is presented as the polymer matrix through an in situ polymerization method, in which cyclic carbonate units can participate in building a stable polymer‐integrated SEI layer during cycling. The as‐investigated gel polymer electrolyte (GPE) assembled LiCoO₂/Li metal batteries exhibit a fantastic cyclability with a capacity retention of 92% after 200 cycles at 0.5 C (1 C = 180 mAh g^?1), evidently exceeding that of the counterpart using liquid electrolytes. It is noted that the anionic ring‐opening polymerization of the cyclic carbonate units on the polymer close to the Li metal anodes enables a mechanically reinforced SEI layer, thus rendering excellent compatibility with Li anodes. The in situ formed polymer‐reinforced SEI layers afford a splendid strategy for developing high voltage resistant GPEs compatible with Li metal anodes toward high energy LMBs.     

Lithium Foam for Deep Cycling Lithium Metal Batteries

Li metal anode has been recognized as the most promising anode for its high theoretical capacity and low reduction potential. But its large-scale commercialization is hampered because of the infinite volume expansion, severe side reactions, and uncontrollable dendrite formation. Herein, the self-supporting porous lithium foam anode is obtained by a melt foaming method. The adjustable interpenetrating pore structure and dense Li₃N protective layer coating on the inner surface enable the lithium foam anode with great tolerance to electrode volume variation, parasitic reaction, and dendritic growth during cycling. Full cell using high areal capacity (4.0 mAh cm⁻²) LiNi0.8Co0.1Mn0.1 (NCM811) cathode with the N/P ratio of 2 and E/C ratio of 3 g Ah⁻¹ can stably operate for 200 times with 80% capacity retention. The corresponding pouch cell has <3% pressure fluctuation per cycle and almost zero pressure accumulation.     

Highly Thermostable Interphase Enables Boosting High-Temperature Lifespan for Metallic Lithium Batteries

In consideration of high specific capacity and low redox potential, lithium metal anodes have attracted extensive attention. However, the cycling performance of lithium metal batteries generally deteriorates significantly under the stringent conditions of high temperature due to inferior heat tolerance of the solid electrolyte interphase (SEI). Herein, controllable SEI nanostructures with excellent thermal stability are established by the (trifluoromethyl)trimethylsilane (TMSCF₃)-induced interface engineering. First, the TMSCF₃ regulates the electrolyte decomposition, thus generating an SEI with a large amount of LiF, Li₃N, and Li₂S nanocrystals incorporated. More importantly, the uniform distributed nanocrystals have endowed the SEI with enhanced thermostability according to the density functional theory simulations. Particularly, the sub-angstrom visualization on SEI through a conventional transmission electron microscope (TEM) is realized for the first time and the enhanced tolerance to the heat damage originating from TEM imaging demonstrates the ultrahigh thermostability of SEI. As a result, the highly thermostable interphase facilitates a substantially prolonged lifespan of full cells at a high temperature of 70 °C. As such, this work might inspire the universal interphase design for high-energy alkali-metal-based batteries applicated in a high-temperature environment.     

A Stable Solid Electrolyte Interphase for Magnesium Metal Anode Evolved from a Bulky Anion Lithium Salt

Rechargeable magnesium (Mg) metal batteries are a promising candidate for “post-Li-ion batteries” due to their high capacity, high abundance, and most importantly, highly reversible and dendrite-free Mg metal anode. However, the formation of passivating surface film rather than Mg²⁺-conducting solid electrolyte interphase (SEI) on Mg anode surface has always restricted the development of rechargeable Mg batteries. A stable SEI is constructed on the surface of Mg metal anode by the partial decomposition of a pristine Li electrolyte in the electrochemical process. This Li electrolyte is easily prepared by dissolving lithium tetrakis(hexafluoroisopropyloxy)borate (Li[B(hfip)₄]) in dimethoxyethane. It is noteworthy that Mg²⁺ can be directly introduced into this Li electrolyte during the initial electrochemical cycles for in situ forming a hybrid Mg²⁺/Li⁺ electrolyte, and then the cycled electrolyte can conduct Mg-ion smoothly. The existence of this as-formed SEI blocks the further parasitic reaction of Mg metal anode with electrolyte and enables this electrolyte enduring long-term electrochemical cycles stably. This approach of constructing superior SEI on Mg anode surface and exploiting novel Mg electrolyte provides a new avenue for practical application of high-performance rechargeable Mg batteries.     

Controllable Solid Electrolyte Interphase in Nickel‐Rich Cathodes by an Electrochemical Rearrangement for Stable Lithium‐Ion Batteries

The layered nickel‐rich materials have attracted extensive attention as a promising cathode candidate for high‐energy density lithium‐ion batteries (LIBs). However, they have been suffering from inherent structural and electrochemical degradation including severe capacity loss at high electrode loading density (>3.0 g cm^?3) and high temperature cycling (>60 °C). In this study, an effective and viable way of creating an artificial solid–electrolyte interphase (SEI) layer on the cathode surface by a simple, one‐step approach is reported. It is found that the initial artificial SEI compounds on the cathode surface can electrochemically grow along grain boundaries by reacting with the by‐products during battery cycling. The developed nickel‐rich cathode demonstrates exceptional capacity retention and structural integrity under industrial electrode fabricating conditions with the electrode loading level of ≈12 mg cm^?2 and density of ≈3.3 g cm^?3. This finding could be a breakthrough for the LIB technology, providing a rational approach for the development of advanced cathode materials.     

Revealing Structural Insights of Solid Electrolyte Interphase in High-Concentrated Non-Flammable Electrolyte for Li Metal Batteries by Cryo-TEM

High-concentrated non-flammable electrolytes (HCNFE) in lithium metal batteries prevent thermal runaway accidents, but the microstructure of their solid electrolyte interphase (SEI) remains largely unexplored, due to the lack of direct imaging tools. Herein, cryo-HRTEM is applied to directly visualize the native state of SEI at the atomic scale. In HCNFE, SEI has a uniform laminated crystalline-amorphous structure that can prevent further reaction between the electrolyte and lithium. The inorganic SEI component, Li₂S₂O₇, is precisely identified by cryo-HRTEM. Density functional theory (DFT) calculations demonstrate that the final Li₂S₂O₇ phase has suitable natural transmission channels for Li-ion diffusion and excellent ionic conductivity of 1.2 × 10^-5 S cm^-1.     

Dual‐Phase Single‐Ion Pathway Interfaces for Robust Lithium Metal in Working Batteries

The lithium (Li) metal anode is confronted by severe interfacial issues that strongly hinder its practical deployment. The unstable interfaces directly induce unfavorable low cycling efficiency, dendritic Li deposition, and even strong safety concerns. An advanced artificial protective layer with single‐ion pathways holds great promise for enabling a spatially homogeneous ionic and electric field distribution over Li metal surface, therefore well protecting the Li metal anode during long‐term working conditions. Herein, a robust dual‐phase artificial interface is constructed, where not only the single‐ion‐conducting nature, but also high mechanical rigidity and considerable deformability can be fulfilled simultaneously by the rational integration of a garnet Al‐doped Li_6.75La₃Zr_1.75Ta_0.25O₁₂‐based bottom layer and a lithiated Nafion top layer. The as‐constructed artificial solid electrolyte interphase is demonstrated to significantly stabilize the repeated cell charging/discharging process via regulating a facile Li‐ion transport and a compact Li plating behavior, hence contributing to a higher coulombic efficiency and a considerably enhanced cyclability of lithium metal batteries. This work highlights the significance of rational manipulation of the interfacial properties of a working Li metal anode and affords fresh insights into achieving dendrite‐free Li deposition behavior in a working battery.     

Amino-Functionalized Interfacial Layer Enables an Ultra-Uniform Amorphous Solid Electrolyte Interphase for High-Performance Aqueous Zinc-Based Batteries

Aqueous rechargeable zinc-based batteries (ZBBs) are emerging as desirable energy storage systems because of their high capacity, low cost, and inherent safety. However, the further application of ZBBs still faces many challenges, such as the issues of uncontrolled dendrite growth and severe parasitic reactions occurring at the Zn anode. Herein, an amino-grafted bacterial cellulose (NBC) film is prepared as artificial solid electrolyte interphase (SEI) for the Zn metal anodes, which can significantly reduce zinc nucleation overpotential and lead to the dendrite-free deposition of Zn metal along the (002) crystal plane more easily without any external stimulus. More importantly, the chelation between the modified amino groups and zinc ions can promote the formation of an ultra-even amorphous SEI upon cycling, reducing the activity of hydrate ions, and inhibiting the water-induced side reactions. As a result, the Zn||Zn symmetric cell with NBC film exhibits lower overpotential and higher cyclic stability. When coupled with the V₂O₅ cathode, the practical pouch cell achieves superior electrochemical performance over 1000 cycles.     

Optimized Solid Electrolyte Interphase and Solvation Structure of Potassium Ions in Carbonate Electrolytes for High-Performance Potassium Metal Batteries

The introduction of electrolyte additives is one of the most potential strategies to improve the performance of potassium metal batteries (PMBs). However, designing an additive that can alter the K⁺ solvation shell and essentially inhibit K dendrite remains a challenge. Herein, the amyl-triphenyl-phosphonium bromide was introduced as an additive to build a stable solid electrolyte interphase layer. The amyl-TPP cations can form a cation shielding layer on the metal surface during the nucleation stage, preventing K⁺ from gathering at the tip to form K dendrites. Besides, the cations can be preferentially reduced to form K_xP_y with fast K⁺ transport kinetics. The Br⁻ anions, as Lewis bases with strong electronegativity, can not only coordinate the Lewis acid pentafluoride to inhibit the formation of HF, but also change the K⁺ solvation structure to reduce solvent molecules in the first solvation structure. Therefore, the symmetrical battery exhibits a low deposition overpotential of 123 mV at 0.1 mA cm⁻² over 4200 h cycle life. The full battery, paried with a perylene-tetracarboxylic dianhydride (PTCDA) cathode, possesses a cycle life of 250 cycles at 2 C and 81.9% capacity retention. This work offers a reasonable electrolyte design to obtain PMBs with long-term stablity and safety.     

High-Performance Solid Lithium Metal Batteries Enabled by LiF/LiCl/LiIn Hybrid SEI via InCl3-Driven In Situ Polymerization of 1,3-Dioxolane

The use of poly(1,3-dioxolane) (PDOL) electrolyte for lithium batteries has gained attention due to its high ionic conductivity, low cost, and potential for large-scale applications. However, its compatibility with Li metal needs improvement to build a stable solid electrolyte interface (SEI) toward metallic Li anode for practical lithium batteries. To address this concern, this study utilized a simple InCl₃-driven strategy for polymerizing DOL and building a stable LiF/LiCl/LiIn hybrid SEI, confirmed through X-ray photoelectron spectroscopy (XPS) and cryogenic-transmission electron microscopy (Cryo-TEM). Furthermore, density functional theory (DFT) calculations and finite element simulation (FES) verify that the hybrid SEI exhibits not only excellent electron insulating properties but also fast transport properties of Li⁺. Moreover, the interfacial electric field shows an even potential distribution and larger Li⁺ flux, resulting in uniform dendrite-free Li deposition. The use of the LiF/LiCl/LiIn hybrid SEI in Li/Li symmetric batteries shows steady cycling for 2000 h, without experiencing a short circuit. The hybrid SEI also provided excellent rate performance and outstanding cycling stability in LiFePO₄/Li batteries, with a high specific capacity of 123.5 mAh g⁻¹ at 10 C rate. This study contributes to the design of high-performance solid lithium metal batteries utilizing PDOL electrolytes.     

Early Lithium Plating Behavior in Confined Nanospace of 3D Lithiophilic Carbon Matrix for Stable Solid‐State Lithium Metal Batteries

Considerable efforts are devoted to relieve the critical lithium dendritic and volume change problems in the lithium metal anode. Constructing uniform Li⁺ distribution and lithium “host” are shown to be the most promising strategies to drive practical lithium metal anode development. Herein, a uniform Li nucleation/growth behavior in a confined nanospace is verified by constructing vertical graphene on a 3D commercial copper mesh. The difference of solid‐electrolyte interphase (SEI) composition and lithium growth behavior in the confined nanospace is further demonstrated by in‐depth X‐ray photoelectron spectrometer (XPS) and line‐scan energy dispersive X‐ray spectroscopic (EDS) methods. As a result, a high Columbic efficiency of 97% beyond 250 cycles at a current density of 2 mA cm^?2 and a prolonged lifespan of symmetrical cell (500 cycles at 5 mA cm^?2) can be easily achieved. More meaningfully, the solid‐state lithium metal cell paired with the composite lithium anode and LiNi_0.5Co_0.2Mn_0.3O₂ (NCM) as the cathode also demonstrate reduced polarization and extended cycle. The present confined nanospace–derived hybrid anode can further promote the development of future all solid‐state lithium metal batteries.