A Mixed Lithium‐Ion Conductive Li2S/Li2Se Protection Layer for Stable Lithium Metal Anode

Constructing artificial solid‐electrolyte interphase (SEI) on the surface of Li metal is an effective approach to improve ionic conductivity of surface SEI and buffer Li dendrite growth of Li metal anode. However, constructing of homogenous ideal artificial SEI is still a great challenge. Here, a mixed lithium‐ion conductive Li₂S/Li₂Se (denoted as LSSe) protection layer, fabricated by a facile and inexpensive gas–solid reaction, is employed to construct stable surface SEI with high ionic conductivity. The Li₂S/Li₂Se‐protected Li metal (denoted as LSSe@Li) exhibits a stable dendrite‐free cycling behavior over 900 h with a high lithium stripping/plating capacity of 3 mAh cm^?2 at 1.5 mA cm^?2 in the symmetrical cell. Compared to bare Li anode, full batteries paired with LiFePO₄, sulfur/carbon, and LiNi_0.6Co_0.2Mn_0.2O₂ cathodes all present better battery cycling and rate performance when LSSe@Li anode is used. Moreover, Li₂Se exhibits a lower lithium‐ion migration energy barrier in comparison with Li₂S which is proved by density functional theory calculation.     

3D Porous Cu Current Collector/Li‐Metal Composite Anode for Stable Lithium‐Metal Batteries

Lithium‐metal batteries are of particular interest for next‐generation electrical energy storage because of their high energy density on both volumetric and gravimetric bases. Effective strategies to stabilize the Li‐metal anode are the prerequisite for the progress of these exceptional storage technologies, such as Li–S and Li–O₂ batteries. Various challenges, such as uneven Li electrodeposition, anode volume expansion, and dendrite‐induced short‐circuit have hindered the practical application of rechargeable Li‐metal batteries. Herein, a one‐step facile and cost‐effective strategy for stabilizing lithium‐metal batteries via 3D porous Cu current collector/Li‐metal composite anode is reported. The porous structure of the composite electrode provides a “cage” for the redeposition of “hostless” lithium and accommodates the anode volume expansion during cycling. Compared with planar Cu foil, its high specific surface area favors the electrochemical reaction kinetics and lowers the local current density along the anode. It leads to low interfacial resistance and stabilizes the Li electrodeposition. On this basis, galvanostatic measurements are performed on both symmetric cells and Li/Li₄Ti₅O₁₂ cells and it is found that the electrodes exhibit exceptional abilities of promoting cell lifetime and stabilizing the cycling behavior. Although this work focuses on lithium metal, this novel tactic is easy to generalize to other metal electrodes.     

Stabilizing Polymer–Lithium Interface in a Rechargeable Solid Battery

Solid polymer electrolytes (SPEs) are promising candidates for developing high‐energy‐density Li metal batteries due to their flexible processability. However, the low mechanical strength as well as the inferior interfacial regulation of ions between SPEs and Li metal anode limit the suppress ion of Li dendrites and destabilize the Li anode. To meet these challenges, interfacial engineering aiming to homogenize the distribution of Li⁺/electron accompanied with enhanced mechanical strength by Mg₃N₂ layer decorating polyethylene oxide is demonstrated. The intermediary Mg₃N₂ in situ transforms to a mixed ion/electron conducting interlayer consisting of a fast ionic conductor Li₃N and a benign electronic conductor Mg metal, which can buffer the Li⁺ concentration gradient and level the nonuniform electric current distribution during cycling, as demonstrated by a COMSOL Multiphysics simulation. These characteristics endow the solid full cell with a dendrite‐free Li anode and enhanced cycling stability and kinetics. The innovative interface design will accelerate the commercial application of high‐energy‐density solid batteries.     

Dendrite-Free Li-Metal Anode Enabled by Dendritic Structure

The practical application of Li-metal anode in high-energy rechargeable Li batteries is still hindered by the uncontrollable formation of Li dendrites. Here, a facile way is reported to stabilize Li-metal anode by building dendrite-like Li₃Mg₇ alloys enriched with Li-containing polymers as the physical protecting layer and LiH as the Li-ion conductor. This unique dendritic structure effectively reduces local current density and accommodates volume change during the repeated Li plating/stripping process. More importantly, lithiophilic Li₃Mg₇ alloys not only guide the uniform Li deposition down into the below Li metal upon Li deposition, but also thermodynamically promote the extraction of Li during the reverse Li stripping process, which suppresses the parasitic reactions occurring on the surface of Li metal and hence inhibits the formation of Li dendrites. Moreover, the facile diffusion of Mg from Li₃Mg₇ alloys toward Li metal below is thermodynamically permitted, which leads to a uniform distribution of LiMg alloys inside the whole electrode and thus benefits long-term deep cycling stability. As a result, the protected Li-metal anode delivers stable and dendrite-free cycling performance at 10 mA h cm⁻² for over 900 h. When coupling this anode with LiFePO₄ and S cathodes, the thus-assembled full cells exhibit superior cycling stability.     

In Situ Formation of Li3P Layer Enables Fast Li+ Conduction across Li/Solid Polymer Electrolyte Interface

Solid‐state polymer electrolytes provide better flexibility and electrode contact than their ceramic counterparts, making them a worthwhile pursuit for all‐solid‐state lithium‐metal batteries. However, their large Li/solid state electrolyte interfacial resistance, small critical current density, and rapid lithium dendrite growth during cycling still limit their viability. Owing to these restrictions, all‐solid‐state cells with solid polymer electrolytes must be cycled above room‐temperature and with a small current density. These problems can be mitigated with an in situ formed artificial solid electrolyte interphase that rapidly conducts Li⁺ ions. Herein, a Li₃P layer formed in situ at the Li‐metal/solid polymer electrolyte interphase is reported that significantly reduces the electrode/electrolyte interfacial resistance. Additionally, this layer increases the wettability of the solid polymer by the metallic lithium anode, allowing for the critical current density of lithium symmetric cells to be doubled by homogenizing the current density at the interface. All‐solid‐state Li/Li symmetric cells and Li/LiFePO₄ cells with the Li₃P layer show improved cycling performance with a high current density.     

Empowering Metal Phosphides Anode with Catalytic Attribute toward Superior Cyclability for Lithium‐Ion Storage

Due to high capacity, moderate redox voltage, and relatively low polarization, metal phosphides (MPs) attract much attention as viable anode materials for lithium‐ion storage. However, severe capacity decay induced by the poor reversibility of discharge product (Li₃P) in these anodes suppresses their practical applications. Herein, it is first revealed that N‐doped carbon can effectively catalyze the oxidation of Li₃P by density functional theory calculations and activation experiments. By anchoring Ni₂P nanoparticles on N‐doped carbon sheets (Ni₂P@N‐C) via a facile method, an MP‐based anode rendered with a catalytic attribute is successfully fabricated for improving the reversibility of Li₃P during lithium‐ion storage. Benefiting from this design, not only can high capacity and rate performance be reached, but also an extraordinary cyclability and capacity retention be realized, which is the best among all other phosphides reported so far. By employing such a Ni₂P@N‐C composite and a commercialized active carbon as the anode and cathode, respectively, hybrid lithium‐ion capacitors can be fabricated with an ultrahigh energy density of 80 Wh kg^?1 at a power density of 12.5 kW kg^?1. This strategy of designing electrodes may be generalized to other energy storage systems whose cycling performance needs to be improved.     

Quaternary Diamond‐Like Chalcogenidometalate Networks as Efficient Anode Material in Lithium‐Ion Batteries

An improvement of lithium‐ion batteries with regard to their reversible capacity, cycling stability, rate performance, and safety under repetitive charge and discharge still requires considerable research activity. However, graphite has remained the unexcelled material for the anode so far. Here, it is shown that two novel quaternary lithium‐chalcogenidometalate phases, Li₄MnGe₂S₇ ( 1 ) and Li₄MnSn₂Se₇ ( 2 ), represent very promising new anode materials for lithium‐ion cells in that they achieve specific lithium storage capacities higher than that of the commercially used graphite, and display an excellent stability during cycling. These properties are based on the structural peculiarities of the phases, which adopt Wurtzite‐related topologies and provide high structural flexibility of the metal sulfide or selenide bonds as advantageous pre‐requisitions for a large ion accessible volume.     

Self‐Standing Porous LiCoO2 Nanosheet Arrays as 3D Cathodes for Flexible Li‐Ion Batteries

Self‐standing electrodes are the key to realize flexible Li‐ion batteries. However, fabrication of self‐standing cathodes is still a major challenge. In this work, porous LiCoO₂ nanosheet arrays are grown on Au‐coated stainless steel (Au/SS) substrates via a facile “hydrothermal lithiation” method using Co₃O₄ nanosheet arrays as the template followed by quick annealing in air. The binder‐free and self‐standing LiCoO₂ nanosheet arrays represent the 3D cathode and exhibit superior rate capability and cycling stability. In specific, the LiCoO₂ nanosheet array electrode can deliver a high reversible capacity of 104.6 mA h g^?1 at 10 C rate and achieve a capacity retention of 81.8% at 0.1 C rate after 1000 cycles. By coupling with Li₄Ti₅O₁₂ nanosheet arrays as anode, an all‐nanosheet array based LiCoO₂//Li₄Ti₅O₁₂ flexible Li‐ion battery is constructed. Benefiting from the 3D nanoarchitectures for both cathode and anode, the flexible LiCoO₂//Li₄Ti₅O₁₂ battery can deliver large specific reversible capacities of 130.7 mA h g^?1 at 0.1 C rate and 85.3 mA h g^?1 at 10 C rate (based on the weight of cathode material). The full cell device also exhibits good cycling stability with 80.5% capacity retention after 1000 cycles at 0.1 C rate, making it promising for the application in flexible Li‐ion batteries.     

Microstructure Controlled Porous Silicon Particles as a High Capacity Lithium Storage Material via Dual Step Pore Engineering

To overcome the lithium storage barriers of current lithium‐ion batteries, it is imperative that conventional low capacity graphite anodes be replaced with other higher capacity anode materials. Silicon is a promising alternative anode material due to its huge energy densities; however, its lithium‐concentration‐dependent volumetric changes can induce severely adverse effects that lead to drastic degradations in capacity during cycling. The dealloying of Si–metal alloys is recently suggested as a scalable approach to fabricate high‐performance porous Si anode materials. Herein, a microstructure controlled porous Si is developed by the dealloying in conjunction with wet alkaline chemical etching. The resulting 3D networked structure enables enhancement in lithium storage properties when the Si‐based material is applied not only as a single active material but also in a graphite‐blended electrode.     

Building Artificial Solid‐Electrolyte Interphase with Uniform Intermolecular Ionic Bonds toward Dendrite‐Free Lithium Metal Anodes

Li metal has been widely regarded as a promising anode for next‐generation batteries due to its high theoretical capacity and low electrochemical potential. The unstable solid‐electrolyte interphase (SEI) and uncontrollable dendrite growth, however, incur severe safety hazards and hamper the practical application of Li metal anodes. Herein, an advanced artificial SEI layer constructed by [LiNBH]_n chains, which are crosslinked and self‐reinforced by their intermolecular Li? N ionic bonds, is designed to comprehensively stabilize Li metal anodes on a molecular level. Benefiting from its polymer‐like structure, the [LiNBH]_n layer is flexible and effectively tolerates the volume change of Li metal anodes. In addition, this layer with high polarity in its structure, helps to regulate the homogeneous distribution of the Li⁺ flux on Li electrodes via the further formation of Li? N bonds. The designed [LiNBH]_n layer is electrically nonconductive but highly ionically conductive, thus facilitating Li⁺ diffusion and confining Li deposition beneath the layer. Therefore, under the protection of the [LiNBH]_n layer, the Li metal anodes exhibit stable cycling at a 3 mA cm^?2 for more than 700 h, and the full cells with high lithium iron phosphate and sulfur cathodes mass loading also present excellent cycling stability.     

A Li–Al–O Solid‐State Electrolyte with High Ionic Conductivity and Good Capability to Protect Li Anode

Using a solid‐state electrolyte (SSE) to stabilize the Li metal anode is widely considered a promising route to develop next‐generation high energy density lithium batteries. Here, a new polycrystalline aluminate‐based SSE (named Li–Al–O SSE) with good capability is introduced to protect Li metal. The SSE is formed on the Li metal surface via a chemical reaction between LiOH and triethylaluminum (TEAL) with the existence of LiTFSI‐based electrolyte. It is a continuous film that consists of polycrystalline LiAlO₂, Li₃AlO₃, Al₂O₃, Li₂CO₃, LiF, and some organic compounds. Such Li–Al–O SSE possesses a room‐temperature ionic conductivity as high as 1.42 × 10^?4 S cm^?1. Meanwhile, it effectively protects the Li anode from the corrosion of H₂O, O₂, and organic solvent, and suppresses the growth of Li dendrite. With the protection of the Li–Al–O SSE, the cycle life of Li|Li symmetric cell and Li|O₂ cell is substantially elongated, indicating that the SSE exhibits an excellent protective effect under both inert and oxidizing circumstances.     

A New Strategy to Effectively Suppress the Initial Capacity Fading of Iron Oxides by Reacting with LiBH4

In this work, a new facile and scalable strategy to effectively suppress the initial capacity fading of iron oxides is demonstrated by reacting with lithium borohydride (LiBH₄) to form a B‐containing nanocomposite. Multielement, multiphase B‐containing iron oxide nanocomposites are successfully prepared by ball‐milling Fe₂O₃ with LiBH₄, followed by a thermochemical reaction at 25–350 °C. The resulting products exhibit a remarkably superior electrochemical performance as anode materials for Li‐ion batteries (LIBs), including a high reversible capacity, good rate capability, and long cycling durability. When cycling is conducted at 100 mA g^?1, the sample prepared from Fe₂O₃–0.2LiBH₄ delivers an initial discharge capacity of 1387 mAh g^?1. After 200 cycles, the reversible capacity remains at 1148 mAh g^?1, which is significantly higher than that of pristine Fe₂O₃ (525 mAh g^?1) and Fe₃O₄ (552 mAh g^?1). At 2000 mA g^?1, a reversible capacity as high as 660 mAh g^?1 is obtained for the B‐containing nanocomposite. The remarkably improved electrochemical lithium storage performance can mainly be attributed to the enhanced surface reactivity, increased Li⁺ ion diffusivity, stabilized solid‐electrolyte interphase (SEI) film, and depressed particle pulverization and fracture, as measured by a series of compositional, structural, and electrochemical techniques.     

A High‐Energy Li‐Ion Battery Using a Silicon‐Based Anode and a Nano‐Structured Layered Composite Cathode

High capacity electrodes based on a Si composite anode and a layered composite oxide cathode, Ni‐rich Li[Ni_0.75Co_0.1Mn_0.15]O₂, are evaluated and combined to fabricate a high energy lithium ion battery. The Si composite anode, Si/C‐IWGS (internally wired with graphene sheets), is prepared by a scalable sol–gel process. The Si/C‐IWGS anode delivers a high capacity of >800 mAh g^?1 with an excellent cycling stability of up to 200 cycles, mainly due to the small amount of graphene (～6 wt%). The cathode (Li[Ni_0.75Co_0.1Mn_0.15]O₂) is structurally optimized (Ni‐rich core and a Ni‐depleted shell with a continuous concentration gradient between the core and shell, i.e., a full concentration gradient, FCG, cathode) so as to deliver a high capacity (>200 mAh g^?1) with excellent stability at high voltage (～4.3 V). A novel lithium ion battery system based on the Si/C‐IWGS anode and FCG cathode successfully demonstrates a high energy density (240 Wh kg^?1 at least) as well as an unprecedented excellent cycling stability of up to 750 cycles between 2.7 and 4.2 V at 1C. As a result, the novel battery system is an attractive candidate for energy storage applications demanding a high energy density and long cycle life.     

High Voltage,Transition Metal Complex Enables Efficient Electrochemical Energy Storage in a Li‐Ion Battery Full Cell

Efficient energy storage systems impact profoundly the renewable energy future. The performance of current electrical energy storage technologies falls well short of requirements for using electrical energy efficiently in transportation, commercial, and residential applications. This paper explores the possibility by using transition‐metal‐based complexes as active materials in a Li‐ion battery full cell that synergizes the concept of both lithium‐ion batteries and redox flow batteries. A cathode made from transition metal complex, [Fe(bpy)₃](BF₄)₂, exhibits high discharge voltage approaching 4 V (vs Li/Li⁺). When coupled with a Li₄Ti₅O₁₂ anode, the Li‐ion full battery exhibits a cell voltage exceeding 2.2 V and decent cycling efficiencies with Coulombic efficiency and energy/voltage efficiencies above 99% and 92%/93%, respectively. Such a Li‐ion battery full cell offers distinct features such as low cost and flexibility in molecular structure design. The result reveals a generic design route toward iron‐based complexes as cathode materials with good electrochemical performances.     

Porosity‐ and Graphitization‐Controlled Fabrication of Nanoporous Silicon@Carbon for Lithium Storage and Its Conjugation with MXene for Lithium‐Metal Anode

Silicon (Si) and lithium metal are the most favorable anodes for high‐energy‐density lithium‐based batteries. However, large volume expansion and low electrical conductivity restrict commercialization of Si anodes, while dendrite formation prohibits the applications of lithium‐metal anodes. Here, uniform nanoporous Si@carbon (NPSi@C) from commercial alloy and CO₂ is fabricated and tested as a stable anode for lithium‐ion batteries (LIBs). The porosity of Si as well as graphitization degree and thickness of the carbon layer can be controlled by adjusting reaction conditions. The rationally designed porosity and carbon layer of NPSi@C can improve electronic conductivity and buffer volume change of Si without destroying the carbon layer or disrupting the solid electrolyte interface layer. The optimized NPSi@C anode shows a stable cyclability with 0.00685% capacity decay per cycle at 5 A g^?1 over 2000 cycles for LIBs. The energy storage mechanism is explored by quantitative kinetics analysis and proven to be a capacitance‐battery dual model. Moreover, a novel 2D/3D structure is designed by combining MXene and NPSi@C. As lithiophilic nucleation seeds, NPSi@C can induce uniform Li deposition with buffered volume expansion, which is proven by exploring Li‐metal deposition morphology on Cu foil and MXene@NPSi@C. The practical potential application of NPSi@C and MXene@NPSi@C is evaluated by full cell tests with a Li(Ni_0.8Co_0.1Mn_0.1)O₂ cathode.     

Reversible Lithium Storage with High Mobility at Structural Defects in Amorphous Molybdenum Dioxide Electrode

This work demonstrates that structural defects in amorphous metal oxide electrodes can serve as a reversible Li⁺ storage site for lithium secondary batteries. For instance, molybdenum dioxide electrode in amorphous form (a‐MoO₂) exhibits an unexpectedly high Li⁺ storage capacity (up to four Li per MoO₂ unit), which is larger by a factor of four than that for the crystalline counterpart. The conversion‐type lithiation is discarded for this electrode from the absence of Mo metal and lithium oxide (Li₂O) in the lithiated a‐MoO₂ electrode and the retention of local structural framework. The sloping voltage profile in a wide potential range suggests that Li⁺ ions are inserted into the structural defects that are electrochemically nonequivalent. This electrode also shows an excellent cycle stability and rate capability. The latter feature is seemingly due to a rather opened Li⁺ diffusion pathway provided by the structural defects. A high Li⁺ mobility is confirmed from nuclear magnetic resonance study.     

Durable Li2CN2 Solid Electrolyte Interphase Wired by Carbon Nanodomains via In Situ Interface Lithiation to Enable Long-Cycling Li Metal Batteries

Lithium metal batteries (LMBs) are becoming the promising candidate of high-energy storage systems. However, the fragile natural solid electrolyte interphase (SEI) cannot retard the Li dendrite growth at anode, which will cause the low coulombic efficiency (CE) of Li plating/stripping and safety hazards in LMBs. Here, an in situ construction strategy of novel artificial SEI consisting of Li₂CN₂ ionic conductor wired by carbon nanodomains via dicyandiamide solution reaction method on Li metal surface is proposed. This lithiophilic Li₂CN₂ has the higher anti-reduction stability and longer critical length for Li dendrite, showing the excellent dendrite suppressing ability. The wired carbon domains promote the electron connection and charge homogenization in SEI, leading to the uniform Li nucleation around Li₂CN₂/C grains with enhanced interface kinetics and reduced polarization. This dual conductive Li₂CN₂/C network enables the durable preservation of high CE and low voltage hysteresis during Li plating/stripping, endowing LiNi_0.8Mn_0.1Co_0.1O₂/Li cells with ultralong cycling life exceeding 1000 cycles at high rate. The cycling stabilization effect is also remarkable even under thin Li anode and high-loading cathode conditions. This study provides a solution to robust SEI configuration of high conductivity via in situ interface lithiation reaction for high-performance LMBs.     

Zn(Cu)Si2+xP3 Solid Solution Anodes for High‐Performance Li‐Ion Batteries with Tunable Working Potentials

Si‐based anodes with a stiff diamond structure usually suffer from sluggish lithiation/delithiation reaction due to low Li‐ion and electronic conductivity. Here, a novel ternary compound ZnSi₂P₃ with a cation‐disordered sphalerite structure, prepared by a facile mechanochemical method, is reported, demonstrating faster Li‐ion and electron transport and greater tolerance to volume change during cycling than the existing Si‐based anodes. A composite electrode consisting of ZnSi₂P₃ and carbon achieves a high initial Coulombic efficiency (92%) and excellent rate capability (950 mAh g^?1 at 10 A g^?1) while maintaining superior cycling stability (1955 mAh g^?1 after 500 cycles at 300 mA g^?1), surpassing the performance of most Si‐ and P‐based anodes ever reported. The remarkable electrochemical performance is attributed to the sphalerite structure that allows fast ion and electron transport and the reversible Li‐storage mechanism involving intercalation and conversion reactions. Moreover, the cation‐disordered sphalerite structure is flexible to ionic substitutions, allowing extension to a family of Zn(Cu)Si_2+xP₃ solid solution anodes (x = 0, 2, 5, 10) with large capacity, high initial Coulombic efficiency, and tunable working potentials, representing attractive anode candidates for next‐generation, high‐performance, and low‐cost Li‐ion batteries.     

Intercalated Electrolyte with High Transference Number for Dendrite‐Free Solid‐State Lithium Batteries

Solid‐state lithium (Li) batteries using solid electrolytes and Li anodes are highly desirable because of their high energy densities and intrinsic safety. However, low ambient‐temperature conductivity and poor interface compatibility of solid electrolytes as well as Li dendrite formation cause large polarization and poor cycling stability. Herein, a high transference number intercalated composite solid electrolyte (CSE) is prepared by the combination of a solution‐casting and hot‐pressing method using layered lithium montmorillonite, poly(ethylene carbonate), lithium bis(fluorosulfonyl)imide, high‐voltage fluoroethylene carbonate additive, and poly(tetrafluoroethylene) binder. The electrolyte presents high ionic conductivity (3.5 × 10^?4 S cm^?1), a wide electrochemical window (4.6 V vs Li⁺/Li), and high ionic transference number (0.83) at 25 °C. In addition, a 3D Li anode is also fabricated via a facile thermal infusion strategy. The synergistic effect of high transference number intercalated electrolyte and 3D Li anode is more favorable to suppress Li dendrites in a working battery. The solid‐state batteries based on LiFePO₄ (Al₂O₃ @ LiNi_0.5Co_0.2Mn_0.3O₂), CSE, and 3D Li deliver admirable cycling stability with discharge capacity 145.9 mAh g^?1 (150.7 mAh g^?1) and capacity retention 91.9% after 200 cycles at 0.5 C (92.0% after 100 cycles at 0.2 C) at 25 °C. This work affords a splendid strategy for high‐performance solid‐state battery.     

Dual‐Salt Mg‐Based Batteries with Conversion Cathodes

Mg batteries as the most typical multivalent batteries are attracting increasing attention because of resource abundance, high volumetric energy density, and smooth plating/stripping of Mg anodes. However, current limitations for the progress of Mg batteries come from the lack of high voltage electrolytes and fast Mg‐insertable structure prototypes. In order to improve their energy or power density, hybrid systems combining Li‐driven cathode reaction with Mg anode process appear to be a potential solution by bypassing the aforementioned limitations. Here, FeS _x (x = 1 or 2) is employed as conversion cathode with 2–4 electron transfers to achieve a maximum energy density close to 400 Wh kg^?1, which is comparable with that of Li‐ion batteries but without serious dendrite growth and polysulphide dissolution. In situ formation of solid electrolyte interfaces on both sulfide and Mg electrodes is likely responsible for long‐life cycling and suppression of S‐species passivation at Mg anodes. Without any decoration on the cathode, electrolyte additive, or anode protection, a reversible capacity of more than 200 mAh g^?1 is still preserved for Mg/FeS₂ after 200 cycles.