Dynamic Ion Sieve as the Buffer Layer for Regulating Li+ Flow in Lithium Metal Batteries

How to realize uniform Li⁺ flow is the key to achieve even Li deposition for lithium metal batteries (LMBs). In this study, a concept of dynamic ion sieve is proposed to design the buffer layer nearby Li anode surface to regulate Li⁺ spatial arrangement by introducing tributylmethylphosphonium bis(trifluoromethanesulfonyl)imide (TMPB) into the carbonate electrolyte. The buffer layer induced by TMP⁺ can adjust the velocity of arriving solvated Li⁺ that gives solvated Li⁺ sufficient time to redistribute and accumulate on Li anode surface, resulting in a uniform and higher concentrated Li⁺ flow. Besides, TFSI⁻ can participate in the generation of inorganic component-rich solid electrolyte interphase (SEI) with Li₃N, which can facilitate the Li⁺ conductivity of SEI. Consequently, the stable and uniform Li deposition can be obtained, achieving the excellent cycling performance up to 1000 h at 0.5 mA cm⁻² in the Li||Li symmetric cell. Besides, the Li||NCM622 full cell also possesses excellent cycling stability with a high-capacity retention rate of 66.7% after 300 cycles.     

Hexafluoroisopropyl Trifluoromethanesulfonate-Driven Easily Li+ Desolvated Electrolyte to Afford Li||NCM811 Cells with Efficient Anode/Cathode Electrolyte Interphases

Solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) with optimized components and structures are considered to be crucial for lithium-ion batteries. Here, gradient lithium oxysulfide (Li₂SO_x, x = 0, 3, 4)/uniform lithium fluoride (LiF)-type SEI is designed in situ by using hexafluoroisopropyl trifluoromethanesulfonate (HFPTf) as electrolyte additive. HFPTf is more likely to be reduced on the surface of Li anode in electrolytes due to its high reduction potential. Moreover, HFPTf can make Li⁺ desolvated easily, leading to the increase in the flux of Li⁺ on the surface of Li anode to avoid the growth of Li dendrites. Thus, the cycling stability of Li||Li symmetric cells is improved to be 1000 h at 0.5 mA cm⁻². In addition, HFPTf-contained electrolyte could make Li||NCM811 batteries with a capacity retention of 70% after 150 cycles at 100 mA g⁻¹, which is attributed to the formation of uniform and stable CEI on the cathode surface for hindering the dissolvation of metal ions from the cathode. This study provides effective insights on the strong ability of additives to adjust electrolytes in “one phase and two interphases” (electrolyte and SEI/CEI).     

Ultrathin and Non-Flammable Dual-Salt Polymer Electrolyte for High-Energy-Density Lithium-Metal Battery

Rechargeable batteries with Li-metal anodes and Ni-rich LiNi_xMn_yCo_zO₂ (x + y + z = 1, NMC) cathodes promise high-energy-density storage solutions. However, commercial carbonate-based electrolytes (CBEs) induce deteriorative interfacial reactions to both Li-metal and NMC, leading to Li dendrite formation and NMC degradation. Moreover, CBEs are thermally unstable and flammable, demonstrating severe safety risks. In this study, an ultrathin and non-flammable dual-salt polymer electrolyte (DSPE) is proposed via lightweight polytetrafluoroethylene scaffold, poly(vinylidene fluoride-co-hexafluoropropylene) polymeric matrix, dual-salt, and adiponitrile/fluoroethylene carbonate functional plasticizers. The as-obtained DSPE exhibits an ultralow thickness of 20 µm, high room temperature ionic conductivity of 0.45 mS cm⁻¹, and a large electrochemical window (4.91 V versus Li/Li⁺). The dual-salt synergized with functional plasticizers is used to fabricate a stable interface layer on both anode and cathode. In-depth experimental and theoretical analyses have revealed the formation of stable interfaces between the DSPE and the anode/cathodes. As a result, the DSPE effectively prevents Li/DSPE/Li symmetric cell from short-circuiting after 1200 h, indicating effective suppression of Li dendrites. Moreover, the Li/DSPE/NMC cell delivers outstanding cyclic stability at 2 C, maintaining a high capacity of 112 mAh g⁻¹ over 1000 cycles.     

Electrolytes Enriched by Crown Ethers for Lithium Metal Batteries

Lithium (Li) metal battery is considered the most promising next-generation battery due to its low potential and high theoretical capacity. However, Li dendrite growth causes serious safety problems. Herein, the 15-Crown-5 (15-C-5) is reported as an electrolyte additive based on solvation shell regulation. The strong complex effect between Li⁺ ion and 15-C-5 can reduce the concentration of Li ions on the electrode surface, thus changing the nucleation, and repressing the growth of Li dendrites in the plating process. Significantly, the strong coordination of Li⁺/15-C-5 would be able to make them aggregate around the Li crystal surface, which could form a protective layer and favor the formation of a smooth and dense solid electrolyte interphase with high toughness and Li⁺ ion conductivity. Therefore, the electrolyte system with 2.0 wt% 15-C-5 achieves excellent electrochemical performance with 170 cycles at 1.0 mA cm⁻² with capacity of 0.5 mA h cm⁻² in symmetric Li|Li cells. The obviously enhanced cycle and rate performance are also achieved in Li|LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) full cells. The 15-C-5 demonstrates to be a promising additive for the electrolytes toward safe and efficient Li metal batteries.     

Inorganic Filler Enhanced Formation of Stable Inorganic-Rich Solid Electrolyte Interphase for High Performance Lithium Metal Batteries

Lithium metal (LM) is a promising anode material for next generation lithium ion based electrochemical energy storage devices. Critical issues of unstable solid electrolyte interphases (SEIs) and dendrite growth however still impede its practical applications. Herein, a composite gel polymer electrolyte (GPE), formed through in situ polymerization of pentaerythritol tetraacrylate with fumed silica fillers, is developed to achieve high performance lithium metal batteries (LMBs). As evidenced theoretically and experimentally, the presence of SiO₂ not only accelerates Li⁺ transport but also regulates Li⁺ solvation sheath structures, thus facilitating fast kinetics and formation of stable LiF-rich interphase and achieving uniform Li depositions to suppress Li dendrite growth. The composite GPE-based Li||Cu half-cells and Li||Li symmetrical cells display high Coulombic efficiency (CE) of 90.3% after 450 cycles and maintain stability over 960 h at 3 mA cm⁻² and 3 mAh cm⁻², respectively. In addition, Li||LiFePO₄ full-cells with a LM anode of limited Li supply of 4 mAh cm⁻² achieve capacity retention of 68.5% after 700 cycles at 0.5 C (1 C = 170 mA g⁻¹). Especially, when further applied in anode-free LMBs, the carbon cloth||LiFePO₄ full-cell exhibits excellent cycling stability with an average CE of 99.94% and capacity retention of 90.3% at the 160th cycle at 0.5 C.     

Stable Non-flammable Phosphate Electrolyte for Lithium Metal Batteries via Solvation Regulation by the Additive

The application of lithium metal batteries (LMBs) is impeded by safety concerns. Employing non-flammable electrolytes can improve battery reliability while the cost and performance deterioration limit their popularization. Herein, a high-performance non-flammable electrolyte is designed, 1.5 m LiTFSI in propylene carbonate (PC)/triethyl phosphate (TEP) (4:1 by vol.) with 4-nitrophenyl trifluoroacetate (TFANP) as the additive, which can facilitate the construction of LiF-rich solid electrolyte interphase (SEI) on Li anode surface and cathode electrolyte interphase (CEI) on cathode surface through its prioritized decomposition. In TFANP-containing electrolyte, the decreased TEP coordination number in the solvation sheath relieves the adverse effect of active TEP on both the SEI and CEI for suppressing the growth of Li dendrites and reducing the continuous electrolyte consumption. Thus, the Li||LiNi_0.6Co_0.2Mn_0.2O₂ battery with such an electrolyte can deliver 132 mAh g⁻¹ after 150 cycles with high coulombic efficiency (99.5%) and superior rate performance (110 mAh g⁻¹ at 5 C, 1 C = 200 mA g⁻¹). This work provides a new additive insight on non-flammable electrolyte for reliable LMBs.     

Ultrafast Charging of a 4.8 V Manganese-Rich Cathode-Based Lithium Metal Cell by Constructing Robust Solid Electrolyte Interphases

Fast charging of Li-metal battery (LMB) is a challenging issue owing to the interfacial instability of Li-metal anode in liquid electrolyte and Li-dendrites growth, resulting in fire hazard. Those issues motivated to pioneer a stabilization strategy of liquid electrolyte-derived solid electrolyte interphase (SEI) layer that enables dendrites-free Li-metal anode under extremely high current density, which solid-state battery cannot. Here, the novel electrolyte formulation is reported including trace-level pentafluoropropionic anhydride (PFPA) combined with fluoroethylene carbonate (FEC) additives, and the SEI stabilization in Li//Mn-rich LMB, achieving unprecedented ultrafast charging under simultaneous extreme conditions of 20 C (charged in 3 min), 4.8 V and 45 °C, delivering 118 mAh g⁻¹ for long reversible 400 cycles, and unprecedented high stability of Li//Li cell under extremely high current 10 mA cm⁻² (Li stripping/plating in 6 min) for a prolonged time of 200 h. The SEI analysis results reveal that the PFPA, which has a symmetric 10 F-containing molecular structure, is a strong F source for promptly producing thin, uniform, and robust F- and organics-enriched SEI layers at both Li-metal anode and Mn-rich cathode, preventing Li-dendrites. This study provides a potential concept for ultrafast charging, long-cycled, and safer high-energy LMBs and LIBs.     

Perfluoro Macrocyclic Ether as an Ambifunctional Additive for High-Performance SiO and Nickel 88%-Based High-Energy Li-ion Battery

State-of-the-art lithium (Li)-ion batteries employ silicon anode active material at a limited fraction while strongly relying on fluoroethylene carbonate (FEC) electrolyte additive exceeding 10 wt.% to enable stable cycling. The swelling issue of silicon in the aspect of solid electrolyte interphase (SEI) instability and a risk of safety hazards and high manufacturing cost due to FEC has motivated the authors to design a well-working fluorinated additive substitute. High-capacity cells employing nickel-rich oxide cathode are pursued by operating at > 4.2 V versus Li/Li⁺, for which anodic stability of electrolyte is required. Herein, a highly effective new ambifunctional additive of icosafluoro-15-crown 5-ether is proposed at a little fraction of 0.4 wt.% for the stabilized interfaces and reduced swelling of high capacity (3.5 mAh cm⁻²) 5 wt.% SiO-graphite anode and LiNi_0.88Co_0.08Mn_0.04O₂ cathode. Utilizing together with a lowered fraction of FEC, reversible long 300 cycles at 4.35 V and 1 C (225 mA g⁻¹) are achieved. Material characterization results reveal that such stabilization is derived from the surface passivation of both anode and cathode with perfluoro ether, LiF, and Li_xPF_y species. The present study gives insight into electrolyte formulation design with lower cost and both-side stabilization strategies for silicon and nickel-rich active materials and their interfaces.     

A Salt-in-Metal Anode: Stabilizing the Solid Electrolyte Interphase to Enable Prolonged Battery Cycling

Metallic lithium (Li) is the ultimate anode candidate for high-energy-density rechargeable batteries. However, its practical application is hindered by serious problems, including uncontrolled dendritic Li growth and undesired side reactions. In this study a concept of “salt-in-metal” is proposed, and a Li/LiNO₃ composite foil is constructed such that a classic electrolyte additive, LiNO₃, is embedded successfully into the bulk structure of metallic Li by a facile mechanical kneading approach. The LiNO₃ reacts with metallic Li to generate Li⁺ conductive species (e.g., Li₃N and LiN_xO_y) over the entire electrode. These derivatives afford a stable solid electrolyte interphase (SEI) and effectively regulate the uniformity of the nucleation/growth of Li on initial plating, featuring a low nucleation energy barrier and large crystalline size without mossy morphology. Importantly, these derivatives combined with LiNO₃ can in-situ repair the damaged SEI from the large volume change during Li plating/stripping, enabling a stable electrode-electrolyte interface and suppressing side reactions between metallic Li and electrolyte. Stable cycling with a high capacity retention of 93.1% after 100 cycles is obtained for full cells consisting of high-loading LiCoO₂ cathode (≈20 mg cm⁻²) and composite metallic Li anode with 25 wt% LiNO₃ under a lean electrolyte condition (≈12 µL) at 0.5 C.     

Facile Li+ Transport in Interpenetrating O- and F-Containing Polymer Networks for Solid-State Lithium Batteries

Solid polymer electrolytes (SPEs) provide an intimate contact with electrodes and accommodate volume changes in the Li-anode, making them ideal for all-solid-state batteries (ASSBs); however, confined chain swing, poor ion-complex dissociation, and barricaded Li⁺-transport pathways limit the ionic conductivity of SPEs. This study develops an interpenetrating polymer network electrolyte (IPNE) comprising poly(ethylene oxide)- and poly(vinylidene fluoride)-based networked SPEs (O-NSPE and F-NSPE, respectively) and lithium bis(fluorosulfonyl) imide (LiFSI) to address these challenges. The  CF₂ / CF₃ segments of the F-NSPE segregate FSI⁻ to form connected Li⁺-diffusion domains, and  C O C segments of the O-NSPE dissociate the complexed ions to expedite Li⁺ transport. The synergy between O-NSPE and F-NSPE gives IPNE high ionic conductivity (≈1 mS cm⁻¹) and a high Li-transference number (≈0.7) at 30 °C. FSI⁻ aggregation prevents the formation of a space-charge zone on the Li-anode surface to enable uniform Li deposition. In Li||Li cells, the proposed IPNE exhibits an exchange current density exceeding that of liquid electrolytes (LEs). A Li|IPNE|LiFePO₄ ASSB achieves charge–discharge performance superior to that of LE-based batteries and delivers a high rate of 7 mA cm⁻². Exploiting the synergy between polymer networks to construct speedy Li⁺-transport pathways is a promising approach to the further development of SPEs.     

Controlling Solvation and Solid-Electrolyte Interphase Formation to Enhance Lithium Interfacial Kinetics at Low Temperatures

Operation of lithium-based batteries at low temperatures (<0 °C) is challenging due to transport limitations as well as sluggish Li⁺ kinetics at the electrode interface. The complicated relationships among desolvation, charge transfer, and transport through the solid electrolyte interphase (SEI) at low temperatures are not well understood, hindering electrolyte development. Here, an ether/hydrofluoroether and fluoroethylene carbonate (FEC)-based ternary solvent electrolyte is developed to improve Li cycling at low temperatures (Coulombic efficiency of 93.3% at -40 °C), and the influence of the local solvation structure on interfacial Li⁺ kinetics and SEI chemistry is further revealed. The hydrofluoroether cosolvent allows for modulation of the solvation structure, thereby enabling facile Li⁺ desolvation while forming an inorganic-rich SEI, which are both beneficial for lowering Li⁺ kinetic barriers at the interface. This cosolvent also increases the oxidative stability of the electrolyte to over 4.0 V versus Li/Li⁺, thereby enabling cycling of NMC-based full cells at −40 °C. This study advances the understanding of the influence of Li⁺ solvation structure, SEI chemistry, and interfacial Li⁺ kinetics on Li electrochemistry at low temperatures, providing new design considerations for creating effective low-temperature electrolyte systems.     

Electrolyte Interphase Built from Anionic Covalent Organic Frameworks for Lithium Dendrite Suppression

Lithium (Li) metal batteries hold considerable promise for numerous energy-dense applications. However, the dendritic Li anode produced during Li⁺/Li deposition-stripping endangers battery safety and shortens cycle lifespan. Herein, an electrolyte interphase built from 2D anionic covalent organic frameworks (ACOF) is coated on Li for dendrite suppression. The ACOF with Li⁺-affinity facilitates rapid and exclusive passage of Li-ions from the electrolyte, yielding near-unity Li⁺ transference number (0.82) and ionic conductivity beyond 3.7 mS cm^-1 at the interphase. Such high transport efficiency of Li-ions can fundamentally circumvent the Li⁺ deficiency that results in dendrite formation. Pairing the ACOF-coated Li against a high-voltage LiCoO₂ cathode (4.5 V) achieves exceptional cycle stability, mitigated polarization, as well as improved rate capability. Accordingly, this strategy vastly expands the pool of electrolyte interphases that can be used for coating and protecting Li anode.     

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.     

Fluorinated Bifunctional Solid Polymer Electrolyte Synthesized under Visible Light for Stable Lithium Deposition and Dendrite-Free All-Solid-State Batteries

Solid polymer electrolytes (SPEs) that can offer flexible processability, highly tunable chemical functionality, and cost effectiveness are regarded as attractive alternatives for liquid electrolytes (LE) to address their safety and energy density limitations. However, it remains a great challenge for SPEs to stabilize Li⁺ deposition at the electrolyte–electrode interface and impede lithium dendrite proliferation compared with LE-based systems. Herein, a design of solid-state fluorinated bifunctional SPE (FB-SPE) that covalently tethers fluorinated chains with polyether-based segments is proposed and synthesized via photo-controlled radical polymerization (photo-CRP). In contrast to the conventional non-fluorinated polyether-derived SPEs, FB-SPE is able to provide conducting Li⁺ transport pathways up to ≈5.0 V, while simultaneously forming a Li F interaction that can enhance Li anode compatibility and prevent Li dendrites growth. As a result, the FB-SPE exhibits outstanding cycling stability in Li||Li symmetrical cells of over 1500 operating hours at as high current density as 0.2 mA cm⁻². A thin and uniform Li deposition layer and LiF-rich SEI at the surface of Li anode are found, and stable cycling with average coulombic efficiencies of 99% is demonstrated in Li||LFP and Li||NCM all-solid-state batteries based on such bifunctional fluorinated SPEs. The interesting fluorine effect and effective self-suppression of lithium dendrites will inform rational molecular design of novel electrolytes and practical development of all-solid-state Li metal batteries.     

Non-Flammable Electrolyte with Lithium Nitrate as the Only Lithium Salt for Boosting Ultra-Stable Cycling and Fire-Safety Lithium Metal Batteries

Lithium metal batteries (LMBs) attract considerable attention for their incomparable energy density. However, safety issues caused by uncontrollable lithium dendrites and highly flammable electrolyte limit large-scale LMBs applications. Herein, a low-cost, thermally stable, and low environmentally-sensitive lithium nitrate (LiNO₃) is proposed as the only lithium salt to incorporate with nonflammable triethyl phosphate and fluoroethylene carbonate (FEC) co-solvent as the electrolyte anticipated to enhance the performance of LMBs. Benefiting from the presence of NO₃⁻ and FEC with strong solvation effect and easily reduced ability, a Li₃N–LiF-rich stable solid electrolyte interphase is constructed. Compared to commercial electrolytes, the proposed electrolyte has a high Coulombic efficiency of 98.31% in Li-Cu test at 1 mA cm⁻² of 1.0 mAh cm⁻² with dendrite-free morphology. Additionally, the electrolyte system shows high voltage stability and cathode electrolyte interphase film-forming properties with stable cycling performances, which exhibit outstanding capacity retention rates of 96.39% and 83.74% after 1000 cycles for LFP//Li and NCM811//Li, respectively. Importantly, the non-flammable electrolyte delays the onset of combustion in lithium metal soft pack batteries by 255 s and reduces the peak heat release by 21.02% under the continuous external high-temperature heating condition. The novel electrolyte can contribute immensely to developing high-electrochemical-performance and high-safety LMBs.     

Uncovering the Function of a Five-Membered Heterocyclic Solvent-Based Electrolyte for Graphite Anode at Subzero Temperature

Ethylene carbonate (EC) is taken as the essential electrolyte component in lithium-ion batteries (LIBs) due to its high permittivity and film-forming ability. However, its high melting point (36.4 °C) and strong solvation energy severely hinder Li⁺ transportation and Li⁺ desolvation process under low temperatures, resulting in capacity loss and even Li plating on graphite anode. Herein, a five-membered heterocyclic compound isoxazole (IZ), similar to EC molecule, is well-formulated to substitute EC for low-temperature operation of graphite anode. It is revealed that IZ with dispersed charge distribution exhibits a weaker solvation ability than EC with highly polar carbonyl group, which induces relatively more anions into the solvation sheath to form contact ion pairs and aggregates. The tamed electrolyte not only exhibits high ionic conductivities over wide-temperature range but also generates an inorganic-rich interphase with low activation barrier for smooth Li⁺ ions threading. This enables graphite anode with an impressive reversible capacity of 263 mAh g^-1 at the low temperature of −30 °C (a room-temperature retention of as high as 71.5%), nearly twice higher than graphite with EC-based electrolyte. This study provides an alternative electrolyte recipe to relieve the anxiety of LIBs operated under harsh conditions.     

Hydrofluoric Acid-Removable Additive Optimizing Electrode Electrolyte Interphases with Li+ Conductive Moieties for 4.5 V Lithium Metal Batteries

High-voltage lithium metal batteries (LMBs) are capable to achieve the increasing energy density. However, their cycling life is seriously affected by unstable electrolyte/electrode interfaces and capacity instability at high voltage. Herein, a hydrofluoric acid (HF)-removable additive is proposed to optimize electrode electrolyte interphases for addressing the above issues. N, N-dimethyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) aniline (DMPATMB) is used as the electrolyte additive to induce PF₆⁻ decomposition to form a dense and robust LiF-rich solid electrolyte interphase (SEI) for suppressing Li dendrite growth. Moreover, DMPATMB can help to form highly Li⁺ conductive Li₃N and LiBO₂, which can boost the Li⁺ transport across SEI and cathode electrolyte interphase (CEI). In addition, DMPATMB can scavenge traced HF in the electrolyte to protect both SEI and CEI from the corrosion. As expected, 4.5 V Li|| LiNi_0.6Co_0.2Mn_0.2O₂ batteries with such electrolyte deliver 145 mAh g⁻¹ after 140 cycles at 200 mA g⁻¹. This work provides a novel insight into high-voltage electrolyte additives for LMBs.     

Fast Ion Transport in Li-Rich Alloy Anode for High-Energy-Density All Solid-State Lithium Metal Batteries

All-solid-state Li batteries (ASSLBs) with solid-polymer electrolytes are considered promising battery systems to achieve improved safety and high energy density. However, Li dendrite formation at the Li anode under high charging current density/capacity has limited their development. To tackle the issue, Li-metal alloying has been proposed as an alternative strategy to suppress Li dendrite growth in ASSLBs. One drawback of alloying is the relatively lower operating cell voltages, which will inevitably lower energy density compared to cells with pure Li anode. Herein, a Li-rich Li₁₃In₃ alloy electrode (LiRLIA) is proposed, where the Li₁₃In₃ alloy scaffold guides Li nucleation and hinders Li dendrite formation. Meanwhile, the free Li can recover Li's potential and facilitate fast charge transfer kinetics to realize high-energy-density ASSLBs. Benefitting from the stronger adsorption energy and lower diffusion energy barrier of Li on a Li₁₃In₃ substrate, Li prefers to deposit in the 3D Li₁₃In₃ scaffold selectively. Therefore, the Li–Li symmetric cell constructed with LiRLIA can operate at a high current density/capacity of 5 mA cm⁻²/5 mAh cm⁻² for almost 1000 h.     

Design Parameters for Ionic Liquid–Molecular Solvent Blend Electrolytes to Enable Stable Li Metal Cycling Within Li–O2 Batteries

Effective utilization of Li-metal electrodes is vital for maximizing the specific energy of lithium–oxygen (Li–O₂) batteries. Many conventional electrolytes that support Li–O₂ cathode processes (e.g._, dimethyl sulfoxide, DMSO) are incompatible with Li-metal. Here, a wide range of ternary solutions based on solvent, salt, and ionic liquid (IL) are explored to understand how formulations may be tailored to enhance stability and performance of DMSO at Li-metal electrodes. The optimized formulations therein facilitate stable Li plating/stripping performances, Columbic efficiencies >94%, and improved performance in Li–O₂ full cells. Characterization of Li surfaces reveals the suppression of dendritic deposition and corrosion and the modulation of decomposition reactions at the interface within optimized formulations. These observations are correlated with spectroscopic characterization and simulation of local solvation environments, indicating the persistent importance of DMSO–Li⁺-cation interactions. Therein, stabilization remains dependent on important molar ratios in solution and the 4:1 solvent-salt ratio, corresponding to ideal coordination spheres in these systems, is revealed as critical for these ternary formulations. Importantly, introducing this stable, non-volatile IL has negligible disrupting effects on the critical stabilizing interactions between Li⁺ and DMSO and, thus, may be carefully introduced to tailor other key electrolyte properties for Li–O₂ cells.     

A Bridge between Ceramics Electrolyte and Interface Layer to Fast Li+ Transfer for Low Interface Impedance Solid-State Batteries

Solid-state batteries (SSBs) are regarded as next generation advanced energy storage technology to provide higher safety and energy density. However, a practical application is plagued by large interfacial resistance, owing to solid-solid interface contact between ceramics electrolytes and Li anode. Introducing polymer-based coating between electrolytes and Li anode is a feasible strategy to solve this issue. Unfortunately, current polymer is hard to achieve intimate contact at the atomic scale and lacks of a bridge to transfer Li⁺ quickly between electrolytes and polymer coating. This gives rise to sluggish Li⁺ transfer dynamics, huge interface impedance and greatly limits the effectiveness of this strategy. Herein, Poly(lithium 4-styrenesulfonate)(PLSS) is introduced between Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO) electrolyte and Li anode. The theories and experiments prove the existence of strong coordinating interaction between  SO₃Li in PLSS and atoms on LLZTO surface. This interaction structures a bridge to migrate Li⁺ fast across LLZTO/PLSS interface and hence interface impedance is as low as 9 Ω cm². Moreover, the electron-blocking feature of PLSS can prevent electrons from tunneling the LLZTO/PLSS interface and combining with Li⁺ to form dendrite within LLZTO. PLSS-base cells show improved long-life cycling for 4700 h at 0.1 mA cm⁻² at room temperature.