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.     

Solvent-Free Electrolyte for High-Temperature Rechargeable Lithium Metal Batteries

The formation of lithiophobic inorganic solid electrolyte interphase (SEI) on Li anode and cathode electrolyte interphase (CEI) on the cathode is beneficial for high-voltage Li metal batteries. However, in most liquid electrolytes, the decomposition of organic solvents inevitably forms organic components in the SEI and CEI. In addition, organic solvents often pose substantial safety risks due to their high volatility and flammability. Herein, an organic-solvent-free eutectic electrolyte based on low-melting alkali perfluorinated-sulfonimide salts is reported. The exclusive anion reduction on Li anode surface results in an inorganic, LiF-rich SEI with high capability to suppress Li dendrite, as evidenced by the high Li plating/stripping CE of 99.4% at 0.5  mA cm⁻² and 1.0 mAh cm⁻², and 200-cycle lifespan of full LiNi_0.8Co_0.15Al_0.05O₂ (2.0 mAh cm⁻²) || Li (20 µm) cells at 80 °C. The proposed eutectic electrolyte is promising for ultrasafe and high-energy Li metal batteries.     

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.     

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.     

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.     

The Restrained Li/Gel Polymer Electrolyte Interface Deterioration Enabled by the Synergetic Effect of Ultra-Lithiophilic Interphase and Interfacial Coupling Skeleton

Quasi-solid-state lithium metal batteries are deemed as one of the most promising next-generation energy storage devices due to their enhanced safety and high energy density. However, the Li/Gel polymer Electrolyte (GPE) interface deterioration induced by the side reactions, dendrite growth during Li plating, and contact loss during Li stripping will inevitably lead to the failure of the battery. Herein, a Li/Li₂₃Sr₆–Li₃N/Sr₂N anode structure (LSN) prepared by hot-rolling process is designed, where Sr₂N serves as an inert skeleton to retain the interfacial coupling and to avoid contact loss. At the same time, the Li₃N–Li₂₃Sr₆ interphase with high Li adsorption energy and fast Li⁺ transfer kinetics regulate the Li plating behavior. Benefitting from the design, when coupled with the carbonate-based GPE, the lifespan of the symmetric battery with the LSN is extended to 1300 h at 0.2 mA cm⁻²/0.2 mAh cm⁻². Furthermore, the LSN||LiFePO₄ (LFP) full cell exhibits a steady cycle with extremely low voltage polarization at 0.5 C after 200 cycles. This study provides a practical strategy to stabilize the Li/GPE interface and deepens the understanding of Li⁺ plating/stripping behaviors through the interphase.     

Multiscale Structural Gel Polymer Electrolytes with Fast Li+ Transport for Long-Life Li Metal Batteries

Li metal batteries (LMBs) are considered as promising candidates for future rechargeable batteries with high energy density. However, Li metal anode (LMA) is extensively sensitive to general liquid electrolytes, leading to unstable interphase and dendrites growth. Herein, a novel gel polymer electrolyte consisting of a micro-nanostructured poly(vinylidene fluoride-co-hexafluoropropylene) matrix and inorganic fillers of Zeolite Socony Mobil-5 (ZSM-5) and SiO₂ nanoparticles, is fabricated to expedite Li⁺ ions transport and suppress Li dendrite growth. Due to the Lewis acid interaction, SiO₂ can absorb amounts of PF₆⁻ and promote the dissociation of LiPF₆. The specific sub-nanometer pore structure of ZSM-5 greatly enhances the Li⁺ ion transference number. These structures can restrain the decomposition of electrolytes and build stable interphase on LMA. Therefore, the Li||Ni_0.8Co_0.1Mn_0.1O₂ full cell maintains 92% capacity retention after 300 cycles at 1 C (1 C ≈190 mAh g⁻¹) in carbonate electrolyte. This multiscale design provides an effective strategy for electrolyte exploration in high-performance LMBs.     

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).     

Phosphonium Bromides Regulating Solid Electrolyte Interphase Components and Optimizing Solvation Sheath Structure for Suppressing Lithium Dendrite Growth

Electrolyte additives play important roles in suppressing lithium dendrite growth and improving the electrochemical performance of long-life lithium metal batteries (LMBs), however, it is still challenging to design individual additive for adjusting the solid electrolyte interphase (SEI) components and changing lithium ion solvation sheath in the electrolyte at the same time for optimizing electrochemical performance. Herein, alkyl-triphenyl-phosphonium bromides (alkyl-TPPB) are designed as the electrolyte additive to enhance the stability of metallic Li anode under the guidance of multi-factor principle for electrolyte additive molecule design (EDMD). Both alkyl-TPP cations and Br⁻ anions produce positive influences on suppressing Li dendrite growth and stabilizing the unstable interphase between metallic Li anode/electrolyte. As expected, the optimized solvation sheath structure, and the stable SEI suppress Li dendrite growth. As a result, the Li||Li₄Ti₅O₁₂ cell reveals a long stable life over 1000 cycles with high Coulombic efficiency (99.9%). This work provides an insight on stabilizing SEI and optimizing solvation sheath structure with novel approach to develop long-term stability and safety LMBs.     

Unlocking the Potential of Lithium Metal Batteries With a Sulfite-Based Electrolyte

Lithium metal batteries (LMBs) have the potential to significantly increase the energy density of advanced batteries in the future. Nonetheless, the dendritic lithium structures and low Coulombic efficiency (CE) of LMBs currently impede their applied implementation. Herein, a sulfite-based electrolyte (SBE/FEC), including 1.0 m lithium bis(fluorosulfonyl)imide in a blend of ethylene sulfite and diethyl sulfite, and 5 wt% fluoroethylene carbonate is proposed. SBE/FEC is a highly efficient inhibitor against the growth of lithium dendrites through the formation of robust solid electrolyte interphase (SEI) layer. Raman spectroscopy and theoretical calculation indicate that in SBE/FEC, a significant portion of FSI⁻ exists in associated complexes, playing a vital role in the creation of LiF-rich passivation. Besides, the sulfite solvents decompose and yield polysulfide complexes in the SEI layer. A direct correlation between the proportion of cation–anion complexes and the contact angle between electrolyte and separator is elucidated through molecular dynamics simulations. The SBE/FEC system exhibits high CEs (98.3%) with Li||Cu cells, along with a steady discharge capacity of ≈137 mA h g⁻¹ in Li||LiFePO₄ cell. This study presents an effective approach for enhancing LMBs with sulfite-based electrolytes, which can lead to high-energy-density next-generation rechargeable batteries.     

TiO2-Induced Conversion Reaction Eliminating Li2CO3 and Pores/Voids Inside Garnet Electrolyte for Lithium–Metal Batteries

Garnet Li₇La₃Zr₂O₁₂ (LLZO) is regarded as a promising solid electrolyte due to its high Li⁺ conductivity and excellent chemical stability, but suffers from grain boundary resistance and porous structure which restrict its practical applications in lithium–metal batteries. Herein, a novel and highly efficient TiO₂-induced conversion strategy is proposed to generate Li ion-conductive Li_0.5La_0.5TiO₃, which can simultaneously eliminate the pre-existing pores/voids and contamination Li₂CO₃. The Li/LLZTO-5TiO₂/Li symmetric cell exhibits a high critical current density of 1.1 mA cm⁻² at 25°C, and the long-term lithium cycling stability of over 1500 h at 0.1 mA cm⁻². More importantly, the excellent performance of LLZTO-5TiO₂ electrolyte is verified by LiCoO₂/LiFePO₄ coupled full cells. For example, The LiCoO₂ coupled full cell exhibits a significant discharge rate capacity of 108 mAh g⁻¹ at 0.1 C, and a discharge capacity retention rate of 91.23% even after 150 cycles of charge and discharge. COMSOL Multiphysics and density functional theory calculation reveal that LLZTO-5TiO₂ electrolyte has a strong lithium affinity and uniform Li ions distribution, which can improve the cycle stability of Li–metal batteries by preventing dendrite growth.     

Grafting of Lithiophilic and Electron-Blocking Interlayer for Garnet-Based Solid-State Li Metal Batteries via One-Step Anhydrous Poly-Phosphoric Acid Post-Treatment

Garnet-based solid-state Li-metal batteries (GSSBs) have the merits of high energy density and high safety. However, the realization of a stable and well-matched Li|garnet interface for GSSBs remains challenging due to electron leakage and lithiophobic Li₂CO₃ impurity. To address these issues, herein, new surface chemistry is reported that converts the undesired Li₂CO₃ contaminant into an ultra-thin lithium polyphosphate (Li-PPA) layer through anhydrous polyphosphoric acid -induced in situ substitution reaction without damaging the water-sensitive garnet electrolyte. In particular, the Li-PPA interlayer not only facilitates the homogenous spreading of molten Li but also creates a robust electron-blocking shield to suppress Li dendrite formation. As a result, the assembled Li symmetric cell exhibits a low interfacial impedance (4 Ω cm²) and high critical current density (1.8 mA cm⁻²) at 25 °C, which enables the cell to continuously cycle over 2500 h at 0.2 mA cm⁻². Furthermore, the GSSBs paired with LiFePO₄ deliver a high capacity of 149.3 mAh g⁻¹ at 1 C and maintain 92.3% of the initial capacity after 500 cycles and can be used for solar energy storage, suggesting the feasibility of this interfacial engineering strategy for GSSBs.     

Dendrite-Free Reverse Lithium Deposition Induced by Ion Rectification Layer toward Superior Lithium Metal Batteries

Considerable endeavors are developed to suppress lithium (Li) dendrites and improve the cycling stability of Li metal batteries in order to promote their commercial application. Herein, continuous zinc (Zn) nanoparticles-assembled film with homogenous nanopores is proposed as a modified layer for separator via a scalable method. The in situ formed LiZn alloy film during initial Li plating can serve as a Li⁺ ion rectification and lithiophilic layer to regulate the nucleation and reverse deposition of Li. When applied in Li|LiFePO₄ full cells with traditional carbonate-based electrolyte, the modified separator enables outstanding cycling stability of up to 350 cycles without capacity loss at a large rate of 5 C (3.4 mA cm⁻²) and a remarkable reversible capacity of 144 mAh g⁻¹ after 120 cycles at a commercial mass loading as high as 19.72 mg cm⁻². The excellent electrochemical performances are ascribed to the dendrite-free reverse Li deposition induced by modified layer by means of its lithiophilic property for regulating homogeneous Li nucleation on the separator as well as its well-distributed nanopores for homogenizing Li⁺ ion flux and enhancing electrolyte wetting.     

In-Built Quasi-Solid-State Poly-Ether Electrolytes Enabling Stable Cycling of High-Voltage and Wide-Temperature Li Metal Batteries

Developing solid-state electrolytes with good compatibility for high-voltage cathodes and reliable operation of batteries over a wide-temperature-range are two bottleneck requirements for practical applications of solid-state metal batteries (SSMBs). Here, an in situ quasi solid-state poly-ether electrolyte (SPEE) with a nano-hierarchical design is reported. A solid-eutectic electrolyte is employed on the cathode surface to achieve highly-stable performance in thermodynamic and electrochemical aspects. This performance is mainly due to an improved compatibility in the electrode/electrolyte interface by nano-hierarchical SPEE and a reinforced interface stability, resulting in superb-cyclic stability in Li || Li symmetric batteries ( > 4000 h at 1 mA cm⁻²/1 mAh cm⁻²; > 2000 h at 1 mA cm⁻²/4 mAh cm⁻²), which are the same for Na, K, and Zn batteries. The SPEE enables outstanding cycle-stability for wide-temperature operation (15–100 ° C) and 4 V-above batteries (Li || LiCoO₂ and Li || LiNi_0.8Co_0.1Mn_0.1O₂). The work paves the way for development of practical SSMBs that meet the demands for wide-temperature applicability, high-energy density, long lifespan, and mass production.     

An Ultrafast and Stable Li-Metal Battery Cycled at −40 °C

Li-metal battery (LMB) suffers from the unexpected Li dendrite growth and unstable solid-electrolyte interphase (SEI), especially in the extreme conditions, such as high rates and low temperatures (LT). Herein, a high-rate and stable LT LMB is realized by regulating electrolyte chemistry. A weak Li⁺-solvating solvent 2-methyltetrahydrofuran is used as electrolyte solvent to mitigate the kinetic barrier for Li⁺ de-solvation. Moreover, a co-solvent tetrahydrofuran with a high donor number is incorporated to improve the LT solubility of Li salts, achieving an improved ionic conductivity while maintaining the weak Li⁺-solvation effect. Furthermore, abundant FSI^- anions in contact-ion pairs are presented, facilitating the formation of a stable LiF-enriched SEI. Consequently, the Li||Li battery can be operated at 10 mA cm^-2 with a small polarization of 154 mV at −40 °C. Meanwhile, an outstanding cumulative cycling capacity of 4000 mAh cm^-2 at 8.0 mA cm^-2 is achieved, reaching a record high level in LT alkali metal symmetric batteries. Also, rechargeable high-rate and stable full batteries are achieved at −40 °C. This work demonstrates the superiority of electrolyte chemistry for synergistic regulation of both ion transfer kinetics and SEI toward ultrafast and stable rechargeable LMBs at LT.     

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.     

Constructing a Multifunctional Interlayer toward Ultra-High Critical Current Density for Garnet-Based Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs), exhibiting great advantages of high energy density and safety, are proposed to be the next generation energy storage system. However, the successful commercialization of garnet-based ASSLBs is hindered by the poor contact between solid-state electrolytes (Li_6.25Ga_0.25La₃Zr₂O₁₂, LGLZO) and lithium anode, as well as low critical current density (CCD). Herein, an indium tin oxide (ITO) layer is prepared on LGLZO by ultrasonic spraying technique, where ITO reacts with molten lithium to form a composite interlayer, consisting of Li₁₃In₃, Li₂O, and LiInSn. Experiments and density functional theory calculations demonstrate that such a unique interlayer plays a multifunctional role in achieving simultaneously better interface wettability, uniform Li deposition, and dendrite suppression at Li/LGLZO interface. Consequently, the CCD of ITO-treated symmetric cell is increased to a record-high value of 12.05 mA cm⁻² at room temperature, which is expected to promote practical application of ASSLBs. Moreover, the Li/ITO@LGLZO/Li cell exhibits a low interfacial resistance of only 5.9 Ω cm² and performs stable electrochemical operations for over 2000 h at 2 mA cm⁻². The Li/ITO@LGLZO/LiFePO₄ full cell also delivers superior electrochemical performances, demonstrating the efficiency of the ITO layer.     

Dynamical SEI Reinforced by Open-Architecture MOF Film with Stereoscopic Lithiophilic Sites for High-Performance Lithium–Metal Batteries

A vulnerable solid–electrolyte interphase (SEI) layer cannot retard Li dendrite growth, electrolyte consumption, and anode volumetric expansion, which seriously hinders the development of high-safety Li-metal batteries (LMBs). Herein, a dynamical SEI reinforced by an open-architecture metal–organic framework (OA-MOF) film characterized by elastic expansion and contraction of the volume of stereoscopic lithiophilic sites, is designed. The self-adjustment distribution of lithiophilic sites on vertically grown Cu₂(BDC)₂ nanosheets enables the homogenization of Li-ion flux, smart control of Li mass transport, and compaction of Li deposition. The trapped N, N-dimethylformamide molecules in the open framework structure are favorable for the better wetting and dissolution effect of Li-ions accessing to Cu₂(BDC)₂. Combining these advantages, the featured OA-MOF/Cu@Li anode enables a high coulombic efficiency and low voltage hysteresis in Li||Cu cells even at an ultrahigh current density of 15 mA cm⁻².     

High‐Power Lithium Metal Batteries Enabled by High‐Concentration Acetonitrile‐Based Electrolytes with Vinylene Carbonate Additive

To enable next‐generation high‐power, high‐energy‐density lithium (Li) metal batteries (LMBs), an electrolyte possessing both high Li Coulombic efficiency (CE) at a high rate and good anodic stability on cathodes is critical. Acetonitrile (AN) is a well‐known organic solvent for high anodic stability and high ionic conductivity, yet its application in LMBs is limited due to its poor compatibility with Li metal anodes even at high salt concentration conditions. Here, a highly concentrated AN‐based electrolyte is developed with a vinylene carbonate (VC) additive to suppress Li⁺ depletion at high current densities. Addition of VC to the AN‐based electrolyte leads to the formation of a polycarbonate‐based solid electrolyte interphase, which minimizes Li corrosion and leads to a very high Li CE of up to 99.2% at a current density of 0.2 mA cm^‐2. Using such an electrolyte, fast charging of Li||NMC333 cells is realized at a high current density of 3.6 mA cm^‐2, and stable cycling of Li||NMC622 cells with a high cathode loading of 4 mAh cm^‐2 is also demonstrated.     

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.