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.     

All‐Solid‐State Batteries with a Limited Lithium Metal Anode at Room Temperature using a Garnet‐Based Electrolyte

Metallic lithium (Li), considered as the ultimate anode, is expected to promise high‐energy rechargeable batteries. However, owing to the continuous Li consumption during the repeated Li plating/stripping cycling, excess amount of the Li metal anode is commonly utilized in lithium‐metal batteries (LMBs), leading to reduced energy density and increased cost. Here, an all‐solid‐state lithium‐metal battery (ASSLMB) based on a garnet‐oxide solid electrolyte with an ultralow negative/positive electrode capacity ratio (N/P ratio) is reported. Compared with the counterpart using a liquid electrolyte at the same low N/P ratios, ASSLMBs show longer cycling life, which is attributed to the higher Coulombic efficiency maintained during cycling. The effect of the species of the interface layer on the cycling performance of ASSLMBs with low N/P ratio is also studied. Importantly, it is demonstrated that the ASSLMB using a limited Li metal anode paired with a LiFePO₄ cathode (5.9 N/P ratio) delivers a stable long‐term cycling performance at room temperature. Furthermore, it is revealed that enhanced specific energies for ASSLMBs with low N/P ratios can be further achieved by the use of a high‐voltage or high mass‐loading cathode. This study sheds light on the practical high‐energy all‐solid‐state batteries under the constrained condition of a limited Li metal anode.     

Bulk Nanostructured Materials Design for Fracture‐Resistant Lithium Metal Anodes

Li metal is an ideal anode for next‐generation batteries because of its high theoretical capacity and low potential. However, the unevenly distributed stress in Li metal anodes (LMAs) induced by volume fluctuation may cause the electrode to fracture easily, especially during high‐rate plating/stripping processes. Here fracture‐resistant LMAs using the concept of bulk nanostructured materials are designed via a metallurgical process. In bulk nanostructured Li (BNL), ionic conducting phases exist at grain boundaries, which promote Li⁺ transport. The refined Li grain size and precipitation hardening in BNL enhances the mechanical strength and fatigue endurance, alleviating the unevenly distributed stress and preventing electrode pulverization. Density functional theory is used to investigate the binding energy between Li and various kinds of oxides and SiO₂ is found to be optimal additive among screened oxides. BNL has 91% of the theoretical capacity of Li metal. In full cells with BNL anode, LiFePO₄ could deliver capacity of 90 mAh g^?1 at 10C, an order of magnitude higher than that in full cells with Li foil anode. This strategy is expected to pave the way for fracture‐resistant LMAs in high‐rate cycling with maximum capacity.     

A High-Performance Carbonate-Free Lithium|Garnet Interface Enabled by a Trace Amount of Sodium

Garnet-type solid-state electrolytes (SSEs) are promising for the realization of next-generation high-energy-density Li metal batteries. However, a critical issue associated with the garnet electrolytes is the poor physical contact between the Li anode and the garnet SSE and the resultant high interfacial resistance. Here, it is reported that the Li|garnet interface challenge can be addressed by using Li metal doped with 0.5 wt% Na (denoted as Li*) and melt-casting the Li* onto the garnet SSE surface. A mechanistic study, using Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) as a model SSE, reveals that Li₂CO₃ resides within the grain boundaries of newly polished LLZTO pellet, which is difficult to remove and hinders the wetting process. The Li* melt can phase-transfer the Li₂CO₃ from the LLZTO grain boundary to the Li*’s top surface, and therefore facilitates the wetting process. The obtained Li*|LLZTO demonstrates a low interfacial resistance, high rate capability, and long cycle life, and can find applications in future all-solid-state batteries (e.g., Li*|LLZTO|LiFePO₄).     

Uniform Lithium Nucleation/Growth Induced by Lightweight Nitrogen‐Doped Graphitic Carbon Foams for High‐Performance Lithium Metal Anodes

The lithium metal anode has attracted soaring attention as an ideal battery anode. Unfortunately, nonuniform Li nucleation results in uncontrollable growth of dendritic Li, which incurs serious safety issues and poor electrochemical performance, hindering its practical applications. Herein, this study shows that uniform Li nucleation/growth can be induced by an ultralight 3D current collector consisting of in situ nitrogen‐doped graphitic carbon foams (NGCFs) to realize suppressing dendritic Li growth at the nucleating stage. The N‐containing functional groups guide homogenous growth of Li nucleus nanoparticles and the initial Li nucleus seed layer regulates the following well‐distributed Li growth. Benefiting from such favorable Li growth behavior, superior electrochemical performance can be achieved as evidenced by the high Coulombic efficiency (≈99.6% for 300 cycles), large capacity (10 mA h cm^?2, 3140 mA h g^?1_NGCF‐Li), and ultralong lifespan (>1200 h) together with low overpotential (<25 mV at 3 mA cm^?2); even under a high current density up to 10 mA cm^?2, it still displays low overpotential of 62 mV.     

High Performance Low-Temperature Lithium Metal Batteries Enabled by Tailored Electrolyte Solvation Structure

The electrochemical performances of lithium metal batteries are determined by the kinetics of interfacial de-solvation and ion transport, especially at low-temperature environments. Here, a novel electrolyte that easily de-solvated and conducive to interfacial film formation is designed for low-temperature lithium metal batteries. A fluorinated carboxylic ester, diethyl fluoromalonate (DEFM), and a fluorinated carbonate, fluoroethylene carbonate (FEC) are used as solvents, while high concentrated lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is served as the solute. Through tailoring the electrolyte formulation, the lithium ions in the high concentrated fluorinated carboxylic ester electrolyte are mainly combined with anions, which weakens the bonding strength of lithium ions and solvent molecules in the solvation structure, beneficial to the de-solvation process at low temperature. The fluorinated carboxylic ester (FCE) electrolyte enables the LiFePO₄ (LFP) | Li half-cell achieves a high capacity of 91.9 mAh g⁻¹ at −30 °C, with high F content in the interface. With optimized de-solvation kinetics, the LFP | Li full cell remains over 100 mAh g⁻¹ at 0 °C after cycling 100 cycles. Building new solvents with outstanding low-temperature properties and weaker solvation to match with Li metal anode, this work brings new possibilities of realizing high energy density and low temperature energy storage batteries.     

Facile Synthesis of Ant‐Nest‐Like Porous Duplex Copper as Deeply Cycling Host for Lithium Metal Anodes

Suppressing the dendrite formation and managing the volume change of lithium (Li) metal anode have been global challenges in the lithium batteries community. Herein, a duplex copper (Cu) foil with an ant‐nest‐like network and a dense substrate is reported for an ultrastable Li metal anode. The duplex Cu is fabricated by sulfurization of thick Cu foil with a subsequent skeleton self‐welding procedure. Uniform Li deposition is achieved by the 3D interconnected architecture and lithiophilic surface of self‐welded Cu skeleton. The sufficient space in the porous layer enables a large areal capacity for Li and significantly improves the electrode–electrolyte interface. Simulations reveal that the structure allows proper electric field penetration into the connected tunnels. The assembled Li anodes exhibit high coulombic efficiency (97.3% over 300 cycles) and long lifespan (>880 h) at a current density of 1 mA cm^?2 with a capacity of 1 mAh cm^?2. Stable and deep cycling can be maintained up to 50 times at a high capacity of 10 mAh cm^?2.     

An Inorganic-Rich SEI Layer by the Catalyzed Reduction of LiNO3 Enabled by Surface-Abundant Hydrogen Bonding for Stable Lithium Metal Batteries

Lithium (Li) metal anodes (LMAs) are promising anode candidates for realizing high-energy-density batteries. However, the formation of unstable solid electrolyte interphase (SEI) layers on Li metal is harmful for stable Li cycling; hence, enhancing the physical/chemical properties of SEI layers is important for stabilizing LMAs. Herein, thiourea (TU, CH₄N₂S) is introduced as a new catalyzing agent for LiNO₃ reduction to form robust inorganic-rich SEI layers containing abundant Li₃N. Due to the unique molecular structure of TU, the TU molecules adsorb on the Cu electrode by forming Cu S bond and simultaneously form hydrogen bonding with other hydrogen bonds accepting species such as NO₃⁻ and TFSI⁻ through its N H bonds, leading to their catalyzed reduction and hence the formation of inorganic-rich SEI layer with abundant Li₃N, LiF, and Li₂S/Li₂S₂. Particularly, this TU-modified SEI layer shows a lower film resistance and better uniformity compared to the electrochemically and naturally formed SEI layers, enabling planar Li growth without any other material treatments and hence improving the cyclic stability in Li/Cu half-cells and Li@Cu/LiFePO₄ full-cells.     

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.     

Stable Metal Anode enabled by Porous Lithium Foam with Superior Ion Accessibility

Lithium (Li) metal anodes have attracted much interest recently for high‐energy battery applications. However, low coulombic efficiency, infinite volume change, and severe dendrite formation limit their reliable implementation over a wide range. Here, an outstanding stability for a Li metal anode is revealed by designing a highly porous and hollow Li foam. This unique structure is capable of tackling many Li metal problems simultaneously: first, it assures uniform electrolyte distribution over the inner and outer electrode's surface; second, it reduces the local current density by providing a larger electroactive surface area; third, it can accommodate volume expansion and dissipate heat efficiently. Moreover, the structure shows superior stability compared to fully Li covered foam with low porosity, and bulky Li foil electrode counterparts. This Li foam exhibits small overpotential (≈25 mV at 4 mA cm^?2) and high cycling stability for 160 cycles at 4 mA cm^?2. Furthermore, when assembled, the porous Li metal as the anode with LiFePO₄ as the cathode for a full cell, the battery has a high‐rate performance of 138 mAh g^?1 at 0.2 C. The beneficial structure of the Li hollow foam is further studied through density functional theory simulations, which confirms that the porous structure has better charge mobility and more uniform Li deposition.     

Decreasing Interfacial Pitfalls with Self-Grown Sheet-Like Li2S Artificial Solid-Electrolyte Interphase for Enhanced Cycling Performance of Lithium Metal Anode

Constructing a 3D composite Li metal anode (LMA) along with the engineering of artificial solid electrolyte interphase (SEI) is a promising strategy for achieving dendrite-free Li deposition and high cycling stability. The nanostructure of artificial SEI is closely related to the performance of the LMA. Herein, the self-grown process and morphology of in situ formed Li₂S during lithiation of Cu_xS is studied systematically, and a large-sized sheet-like Li₂S layer as an artificial SEI is in situ generated on the inner surface of a 3D continuous porous Cu skeleton (3DCu@Li₂S-S). The sheet-like Li₂S layer with few interfacial pitfalls (Cu/Li₂S heterogeneous interface) possesses enhanced diffusion of Li ions. And the continuous porous structure provides transport channels for lithium-ion transport. As a result, the 3DCu@Li₂S-S presents a high Coulombic efficiency (99.3%), long cycle life (500 cycles), and high-rate performance (10 mA cm⁻²). Furthermore, Li/3DCu@Li₂S anode fabricated by thermal infusion method inherits the synergistic advantages of sheet-like Li₂S and continuous porous structure. The Li/3DCu@Li₂S anode shows significantly enhanced cycling life in both liquid and solid electrolytes. This work provides a new concept to design artificial SEI for LMA with high safe and high performance.     

A Highly Reversible,Dendrite-Free Lithium Metal Anode Enabled by a Lithium-Fluoride-Enriched Interphase

Metallic lithium is the most competitive anode material for next-generation lithium (Li)-ion batteries. However, one of its major issues is Li dendrite growth and detachment, which not only causes safety issues, but also continuously consumes electrolyte and Li, leading to low coulombic efficiency (CE) and short cycle life for Li metal batteries. Herein, the Li dendrite growth of metallic lithium anode is suppressed by forming a lithium fluoride (LiF)-enriched solid electrolyte interphase (SEI) through the lithiation of surface-fluorinated mesocarbon microbeads (MCMB-F) anodes. The robust LiF-enriched SEI with high interfacial energy to Li metal effectively promotes planar growth of Li metal on the Li surface and meanwhile prevents its vertical penetration into the LiF-enriched SEI from forming Li dendrites. At a discharge capacity of 1.2 mAh cm⁻², a high CE of >99.2% for Li plating/stripping in FEC-based electrolyte is achieved within 25 cycles. Coupling the pre-lithiated MCMB-F (Li@MCMB-F) anode with a commercial LiFePO₄ cathode at the positive/negative (P/N) capacity ratio of 1:1, the LiFePO₄//Li@MCMB-F cells can be charged/discharged at a high areal capacity of 2.4 mAh cm⁻² for 110 times at a negligible capacity decay of 0.01% per cycle.     

A 3D Lithiophilic Mo2N‐Modified Carbon Nanofiber Architecture for Dendrite‐Free Lithium‐Metal Anodes in a Full Cell

The pursuit for high‐energy‐density batteries has inspired the resurgence of metallic lithium (Li) as a promising anode, yet its practical viability is restricted by the uncontrollable Li dendrite growth and huge volume changes during repeated cycling. Herein, a new 3D framework configured with Mo₂N‐mofidied carbon nanofiber (CNF) architecture is established as a Li host via a facile fabrication method. The lithiophilic Mo₂N acts as a homogeneously pre‐planted seed with ultralow Li nucleation overpotential, thus spatially guiding a uniform Li nucleation and deposition in the matrix. The conductive CNF skeleton effectively homogenizes the current distribution and Li‐ion flux, further suppressing Li‐dendrite formation. As a result, the 3D hybrid Mo₂N@CNF structure facilitates a dendrite‐free morphology with greatly alleviated volume expansion, delivering a significantly improved Coulombic efficiency of ≈99.2% over 150 cycles at 4 mA cm^?2. Symmetric cells with Mo₂N@CNF substrates stably operate over 1500 h at 6 mA cm^?2 for 6 mA h cm^?2. Furthermore, full cells paired with LiNi_0.8Co_0.1Mn_0.1O₂ (NMC811) cathodes in conventional carbonate electrolytes achieve a remarkable capacity retention of 90% over 150 cycles. This work sheds new light on the facile design of 3D lithiophilic hosts for dendrite‐free lithium‐metal anodes.     

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.     

Roll-Pressed Silicon Anodes with High Reversible Volumetric Capacity Achieved by Interfacial Stabilization and Mechanical Strengthening of a Silicon/Graphene Hybrid Assembly

Application of Si anodes is hindered by severe capacity fading due to pulverization of Si particles during the large volume changes of Si during charge/discharge and repeated formation of the solid-electrolyte interphase. To address these issues, considerable efforts have been devoted to the development of Si composites with conductive carbons (Si/C composites). However, Si/C composites with high C content inevitably show low volumetric capacity because of low electrode density. For practical applications, the volumetric capacity of a Si/C composite electrode is more important than gravimetric capacity, but volumetric capacity in pressed electrodes is rarely reported. Herein, a novel synthesis strategy is demonstrate for a compact Si nanoparticle/graphene microspherical assembly with interfacial stability and mechanical strength achieved by consecutively formed chemical bonds using 3-aminopropyltriethoxysilane and sucrose. The unpressed electrode (density: 0.71 g cm⁻³) shows a reversible specific capacity of 1470 mAh g⁻¹ with a high initial coulombic efficiency of 83.7% at a current density of 1 C-rate. The corresponding pressed electrode (density: 1.32 g cm⁻³) exhibits high reversible volumetric capacity of 1405 mAh cm⁻³ and gravimetric capacity of 1520 mAh g⁻¹ with a high initial coulombic efficiency of 80.4% and excellent cycling stability of 83% over 100 cycles at 1 C-rate.