Fluoroethylene Carbonate Research Articles

Quasi‐Localized High‐Concentration Electrolytes for High‐Voltage Lithium Metal Batteries

The poor compatibility with Li metal and electrolyte oxidation stability preclude the utilization of commercial ester‐based electrolytes for high‐voltage lithium metal batteries. This work proposes a quasi‐localized high‐concentration electrolyte (q‐LHCE) by partially replacing solvents in conventional LiPF6 based carbonated electrolyte with fluorinated analogs (fluoroethylene carbonate (FEC), 2,2,2‐trifluoroethyl methyl carbonate (FEMC)) with weakly‐solvating ability. The q‐LHCE enables the formation of an anion‐rich solvation sheath, which functions like LHCE but differs in the partial participation of weakly‐solvating cosolvent in the solvation structure. With this optimized electrolyte, inorganic‐dominated solid electrolyte interphases are achieved on both the cathode and anode, leading to uniform Li deposition, suppressed electrolyte decomposition and cathode deterioration. Consequently, q‐LHCE supports stable cycling of Li | LiCoO2 (≈3.5 mAh cm−2) cells at 4.5 V under the whole climate range (from −20 to 45 °C) with limited Li consumption. A practical ampere‐hour level graphite | LiCoO2 pouch cell at 4.5 V and aggressive Li | LiNi0.5Mn1.5O4 cell at 5.0 V with excellent capacity retention further reveals the effectiveness of q‐LHCE. The refinement of old‐fashioned carbonate electrolytes provides new perspectives toward practical high‐voltage battery systems.

Synergistic dual electrolyte additives for fluoride rich solid-electrolyte interface on Li metal anode surface: Mechanistic understanding of electrolyte decomposition

Improving the quality of the solid-electrolyte interphase (SEI) layer is highly imperative to stabilize the Li-metal anodes for the practical application of high-energy–density batteries. However, controllably managing the formation of robust SEI layers on the anode is challenging in state-of-the-art electrolytes. Herein, we discuss the role of dual additives fluoroethylene carbonate (FEC) and lithium difluorophosphate (LiPO2F2, LiPF) within the commercial electrolyte mixture (LiPF6/EC/DEC) considering their reactivity with Li metal anodes using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. Synergistic effects of dual additives on SEI formation mechanisms are explored systematically by invoking different electrolyte mixtures including pure electrolyte (LP47), mono-additive (LP47/FEC and LP47/LiPF), and dual additives (LP47/FEC/LiPF). The present work suggests that the addition of dual additives accelerates the reduction of salt and additives while increasing the formation of a LiF-rich SEI layer. In addition, calculated atomic charges are applied to predict the representative F1s X-ray photoelectron (XPS) signal, and our results agree well with the experimentally identified SEI components. The nature of carbon and oxygen-containing groups resulting from the electrolyte decompositions at the anode surface is also analyzed. We find that the presence of dual additives inhibits undesirable solvent degradation in the respective mixtures, which effectively restricts the hazardous side products at the electrolyte-anode interface and improves SEI layer quality.

Effect of Fluoroethylene Carbonate Electrolyte Additives on the Electrochemical Performance of Nickel-Rich NCM Ternary Cathodes

It has been well established recently that fluorinated electrolyte additives such as fluoroethylene carbonate (FEC) could promote the formation of LiF-based solid electrolyte interphases that can stabilize lithium metal anodes. Meanwhile, the impact of FEC additives on the cathode side, particularly for the high energy density nickel-rich LiNi1–x–yCoxMnyO2 (NCM) ternary cathodes, remains unclear. In this study, we investigated the structural and chemical composition of a cathode electrolyte interphase (CEI) and its electrochemical performance to elucidate the effect of FEC additives on the LiNi0.9Co0.05Mn0.05O2 (NCM90) cathode for high energy lithium-ion batteries. It is discovered that the FEC additive in carbonate electrolyte (BE-FEC) can produce a LiF-based CEI, which could stabilize the NCM90 surface and improve the cycle performance at low cut-off voltage. The formation of a thick LiF layer under high cut-off voltage and high rate has been observed to result in increased polarization and slower Li+ transport kinetics, ultimately leading to a deterioration in battery performance. On the other hand, in a carbonate electrolyte (BE) and under low voltage, the unstable Li2CO3-based CEI components on the NCM90 surface with an intermediate rock salt phase in between contribute to poor long-term performance and reduced reliability. While under high voltage, the BE sample shows superior electrochemical performance due to the formation of a thin LiF layer from the decomposition of LiPF6. Our work provides a comprehensive understanding of the role of FEC in the CEI of nickel-rich cathodes, offering practical guidance for the design of electrolytes for high-energy high-voltage nickel-rich cathodes.

Bridging multiscale interfaces for developing ionically conductive high-voltage iron sulfate-containing sodium-based battery positive electrodes

Non-aqueous sodium-ion batteries (SiBs) are a viable electrochemical energy storage system for grid storage. However, the practical development of SiBs is hindered mainly by the sluggish kinetics and interfacial instability of positive-electrode active materials, such as polyanion-type iron-based sulfates, at high voltage. Here, to circumvent these issues, we proposed the multiscale interface engineering of Na2.26Fe1.87(SO4)3, where bulk heterostructure and exposed crystal plane were tuned to improve the Na-ion storage performance. Physicochemical characterizations and theoretical calculations suggested that the heterostructure of Na6Fe(SO4)4 phase facilitated ionic kinetics by densifying Na-ion migration channels and lowering energy barriers. The (11-2) plane of Na2.26Fe1.87(SO4)3 promoted the adsorption of the electrolyte solution ClO4− anions and fluoroethylene carbonate molecules, which formed an inorganic-rich Na-ion conductive interphase at the positive electrode. When tested in combination with a presodiated FeS/carbon-based negative electrode in laboratory- scale single-layer pouch cell configuration, the Na2.26Fe1.87(SO4)3-based positive electrode enables an initial discharge capacity of about 83.9 mAh g−1, an average cell discharge voltage of 2.35 V and a specific capacity retention of around 97% after 40 cycles at 24 mA g−1 and 25 °C.

LiF-Rich Interfacial Protective Layer Enables Air-Stable Lithium Metal Anodes for Dendrite-Free Lithium Metal Batteries.

Lithium (Li) metal is considered as a promising anode candidate for high-energy-density batteries. However, the high reactivity of Li metal leads to poor air stability, limiting its practical application. Additionally, the interfacial instability, such as dendrite growth and an unstable solid electrolyte interphase layer, further complicates its utilization. Herein, a dense lithium fluoride (LiF)-rich interfacial protective layer is constructed on the Li surface through a simple reaction between Li and fluoroethylene carbonate (denoted as LiF@Li). The LiF-rich interfacial protective layer consists of both organic (ROCO2Li and C-F-containing species, which only exist on the outer layer) and inorganic (LiF and Li2CO3, distribute throughout the layer) components with a thickness of ∼120 nm. Specifically, chemically stable LiF and Li2CO3 play an important role in blocking air and hence improve the air durability of LiF@Li anodes. Notably, LiF with high Li+ diffusivity facilitates uniform Li+ deposition, while organic components with high flexibility relieve volume change upon cycling, thereby enhancing the dendrite inhibition capacity of LiF@Li. Consequently, LiF@Li exhibits remarkable stability and excellent electrochemical performance in both symmetric cells and LiFePO4 full cells. Moreover, LiF@Li maintains its initial color and morphology even after air exposure for 30 min, and the air-exposed LiF@Li anode still retains its superior electrochemical performance, further establishing its outstanding air-defendable capability. This work proposes a facile approach in constructing air-stable and dendrite-free Li metal anodes toward reliable Li metal batteries.

Multifunctional Additive Ethoxy(pentafluoro)cyclotriphosphazene Enables Safe Carbonate Electrolyte for SiOx‐Graphite/NMC811 Batteries

AbstractThe silicon (Si) or silicon monoxide (SiOx)‐graphite (Gr)/nickel‐rich LiNixMnyCozO2 (NMC, x+y+z=1, with x≥80 %) cell chemistry is currently regarded as a promising candidate to further improve the energy density of rechargeable lithium‐ion batteries, but is confronted with safety and cycling stability issues. Here, the flame retardant ethoxy(pentafluoro)cyclotriphosphazene (PFPN) is studied as electrolyte additive in the SiOx‐Gr/NMC811 full cell system. We find that PFPN in combination with an increased lithium hexafluorophosphate (LiPF6) concentration renders carbonate‐based electrolytes non‐flammable based on a very low self‐extinguishing time of 3.1 s g−1 while the electrolyte maintains a high ionic conductivity of 8.4 mS cm−1 at 25 °C. Importantly, PFPN in combination with fluoroethylene carbonate (FEC) also stabilizes the solid‐electrolyte interphase of Si‐based anodes beyond the level achieved only with FEC. Furthermore, PFPN improves the wetting property of the electrolyte, rendering it a multifunctional additive. As a result, excellent capacity retention of 87 % after 200 cycles at 1 C was achieved for SiOx‐Gr/NMC811 pouch cells with a relatively high SiOx content of 20 %. Our work provides a promising avenue for developing safe and high‐performance electrolytes for lithium‐ion batteries with silicon‐based anodes.

Bi‐affinity Electrolyte Optimizing High‐Voltage Lithium‐Rich Manganese Oxide Battery via Interface Modulation Strategy

AbstractThe practical implementation of high‐voltage lithium‐rich manganese oxide (LRMO) cathode is limited by the unanticipated electrolyte decomposition and dissolution of transition metal ions. The present study proposes a bi‐affinity electrolyte formulation, wherein the sulfonyl group of ethyl vinyl sulfone (EVS) imparts a highly adsorptive nature to LRMO, while fluoroethylene carbonate (FEC) exhibits a reductive nature towards Li metal. This interface modulation strategy involves the synergistic use of EVS and FEC as additives to form robust interphase layers on the electrode. As‐formed S‐endorsed but LiF‐assisted configuration cathode electrolyte interphase with a more dominant −SO2− component may promote the interface transport kinetics and prevent the dissolution of transition metal ions. Furthermore, the incorporation of S component into the solid electrolyte interphase and the reduction of its poorly conducting component can effectively inhibit the growth of lithium dendrites. Therefore, a 4.8 V LRMO/Li cell with optimized electrolyte may demonstrate a remarkable retention capacity of 97 % even after undergoing 300 cycles at 1 C.

Bi-affinity Electrolyte Optimizing High-Voltage Lithium-Rich Manganese Oxide Battery via Interface Modulation Strategy.

The practical implementation of high-voltage lithium-rich manganese oxide (LRMO) cathode is limited by the unanticipated electrolyte decomposition and dissolution of transition metal ions. The present study proposes a bi-affinity electrolyte formulation, wherein the sulfonyl group of ethyl vinyl sulfone (EVS) imparts a highly adsorptive nature to LRMO, while fluoroethylene carbonate (FEC) exhibits a reductive nature towards Li metal. This interface modulation strategy involves the synergistic use of EVS and FEC as additives to form robust interphase layers on the electrode. As-formed S-endorsed but LiF-assisted configuration cathode electrolyte interphase with a more dominant -SO2 - component may promote the interface transport kinetics and prevent the dissolution of transition metal ions. Furthermore, the incorporation of S component into the solid electrolyte interphase and the reduction of its poorly conducting component can effectively inhibit the growth of lithium dendrites. Therefore, a 4.8 V LRMO/Li cell with optimized electrolyte may demonstrate a remarkable retention capacity of 97 % even after undergoing 300 cycles at 1 C.

All-fluorinated electrolyte for non-flammable batteries with ultra-high specific capacity at 4.7 V

Li metal batteries (LMBs) with LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes could release a specific energy of >500 Wh kg−1 by increasing the charge voltage. However, high-nickel cathodes working at high voltages accelerate degradations in bulk and at interfaces, thus significantly degrading the cycling lifespan and decreasing the specific capacity. Here, we rationally design an all-fluorinated electrolyte with addictive tri(2,2,2-trifluoroethyl) borate (TFEB), based on 3, 3, 3-fluoroethylmethylcarbonate (FEMC) and fluoroethylene carbonate (FEC), which enables stable cycling of high nickel cathode (LiNi0.8Co0.1Mn0.1O2, NMC811) under a cut-off voltage of 4.7 V in Li metal batteries. The electrolyte not only shows the fire-extinguishing properties, but also inhibits the transition metal dissolution, the gas production, side reactions on the cathode side. Therefore, the NMC811||Li cell demonstrates excellent performance by using limited Li and high-loading cathode, delivering a specific capacity >220 mA h g−1, an average Coulombic efficiency >99.6% and capacity retention >99.7% over 100 cycles.

Organic Cathode with Dual-Type Multielectron Reaction Centers for High-Energy-Density Lithium Primary Batteries.

Organic electrode materials are composed of abundant elements, have diverse and designable molecular structures, and are relatively easily synthesized, promising a bright future for low-cost and large-scale energy storage. However, they are facing low specific capacity and low energy density. Herein, we report a high-energy-density organic electrode material, 1,5-dinitroanthraquinone, which is composed of two kinds of electrochemically active sites of nitro and carbonyl groups. They experience six- and four-electron reduction and are transformed into amine and methylene groups, respectively, in the presence of fluoroethylene carbonate (FEC) in the electrolyte. Drastically increased specific capacity and energy density are demonstrated with an ultrahigh specific capacity of 1321 mAh g-1 and a high voltage of ∼2.62 V, corresponding to a high energy density of 3400 Wh kg-1. This surpasses the electrode materials in commercial lithium batteries. Our findings provide an effective strategy to design high-energy-density and novel lithium primary battery systems.

Dual Additives for Stabilizing Li Deposition and SEI Formation in Anode‐Free Li‐Metal Batteries

Anode‐free Li‐metal batteries are of significant interest to energy storage industries due to their intrinsically high energy. However, the accumulative Li dendrites and dead Li continuously consume active Li during cycling. That results in a short lifetime and low Coulombic efficiency of anode‐free Li‐metal batteries. Introducing effective electrolyte additives can improve the Li deposition homogeneity and solid electrolyte interphase (SEI) stability for anode‐free Li‐metal batteries. Herein, we reveal that introducing dual additives, composed of LiAsF6 and fluoroethylene carbonate, into a low‐cost commercial carbonate electrolyte will boost the cycle life and average Coulombic efficiency of NMC||Cu anode‐free Li‐metal batteries. The NMC||Cu anode‐free Li‐metal batteries with the dual additives exhibit a capacity retention of about 75% after 50 cycles, much higher than those with bare electrolytes (35%). The average Coulombic efficiency of the NMC||Cu anode‐free Li‐metal batteries with additives can maintain 98.3% over 100 cycles. In contrast, the average Coulombic efficiency without additives rapidly decline to 97% after only 50 cycles. In situ Raman measurements reveal that the prepared dual additives facilitate denser and smoother Li morphology during Li deposition. The dual additives significantly suppress the Li dendrite growth, enabling stable SEI formation on anode and cathode surfaces. Our results provide a broad view of developing low‐cost and high‐effective functional electrolytes for high‐energy and long‐life anode‐free Li‐metal batteries.

Decent Fast-Charging Performance of Li-Ion Battery Achieved by Modifying Electrolyte Formulation and Charging Protocol

In this work, two strategies have been attempted to achieve decent fast-charging performances of Li-ion batteries. The first is to combine lithium bis(fluorosulfonyl)imide (LiFSI) and dimethoxyethane (DME) into an electrolyte for high ionic conductivity of the bulk electrolyte and the electrolyte-electrode interphases, and the second is to limit charging capacity within 80% state-of-charge (SOC) for stable capacity retention by lowering charging rate without increasing total charging time in the standard constant current-constant voltage (CC-CV) charging protocol. It is found that using 5 wt% fluoroethylene carbonate (FEC) as an additive enables the hybridization of 20 wt% DME into the electrolyte without adverse effects on the initial formation cycles and ongoing cycling in terms of coulombic efficiency and reversible capacity, and adding 2 wt% LiPF6 is beneficial to reducing charge-transfer resistance and stabilizing capacity retention. As a result, decent fast-charging performances are obtained from the 200 mAh graphite/LiNi0.80Co0.15Al0.05O2 pouch cells by using a 1.2 m (molality) LiFSI 3:5:2 ethylene carbonate (EC)/ethylmethyl carbonate (EMC)/DME + 5% FEC + 2% LiPF6 electrolyte (all by wt) and a modified CC-CV charging protocol consisting of CC charging at 4 C for a total of 12 min, which is the charging time equivalent to a 5 C charging protocol.

Improved Performance of Silicon-Containing Anodes with Organic Solvent-Solubilized Lithium Nitrate

Three different organic solvents (dimethylacetamide (DMAc), dimethylformamide (DMF), and dimethyl sulfoxide (DMSO)) were used to improve the solubility of LiNO3 in a standard carbonate-based electrolyte with lithium difluoro(oxalato)borate (LiDFOB) as the salt. Together, the LiDFOB and organic-solvent solubilized LiNO3 preferentially reduce on the surface of silicon-containing anodes to create an SEI rich in oxalates, nitrate decomposition species, and B-F species. The improved stability of the SEI throughout the first 100 cycles results in silicon and silicon/graphite composite anodes with better capacity retention than observed with standard electrolytes or fluoroethylene carbonate (FEC) containing electrolytes. This study demonstrates the feasibility of the use of non-traditional electrolyte solvents in the improvement and optimization of lithium ion-battery electrolytes.

Boosting fast electrode reaction kinetics of silicon suboxide anodes by fluoroethylene carbonate-based electrolyte

The growing demand for electric vehicles has led to an urgent need for higher-energy-density batteries. Silicon (Si) has been regarded as an alternative to graphite as an anode material owing to its high theoretical capacity. Nevertheless, the large volume change in Si during repeated charge/discharge causes serious particle fracture, leading to rapid capacity degradation. Silicon suboxide (SiOx) anodes show better cycling performance than Si because of their alleviated volume variation, yet still have unsatisfactory electrode reaction kinetics. Herein, fluoroethylene carbonate (FEC)-based electrolyte is proposed to enhance the electrochemical properties of SiOx anodes. A higher specific capacity of ∼1500 mAh g−1 at 0.5 A g−1 and an excellent rate capability of ∼1050 mAh g−1 at 4 A g−1 are obtained for the SiOx anode, which ensures an 83.5% capacity retention of SiOx||LiFePO4 cells after 300 cycles. The theoretical calculations and experimental studies reveal that FEC forms a weakly solvating electrolyte, enabling easier Li-ion desolvation and fast electrode reaction kinetics. Moreover, FEC reinforces the Li+-anion coordination owing to its weak solvating capability, thus a LiF-rich electrode/electrolyte interphase is formed through the co-decomposition of FEC and PF6− anions, leading to a tough SEI film formation with rapid ionic conductivity and good mechanical property.

Multilayer structure solid-state electrolyte composite membranes for long-life quasi-solid-state battery

To reduce the impedance of the interface between solid electrolytes and electrodes and improve the interfacial stability, the liquid electrolyte (LE) is added between solid-state electrolytes and electrodes. We design LE containing different lithium salts, additives and a solid-state electrolyte membrane containing polyvinylidene fluoride (PVDF), Li1.3Al0.3Ti1.7(PO4)3 (LATP) and polypropylene membrane (PP) (LATP membrane), and systematically investigate the interfacial wettability, stability and safety through contact angle analysis, interfacial impedance measurements, and linear scanning voltammetry. The results show that the LE containing 1 M lithium hexafluorophosphate (LiPF6) salt, 1.3-propane sultone (1.3-PS) additive, adiponitrile, fluoroethylene carbonate (FEC), and that containing 0.575 M lithium bis(trifluoromethane sulfonimide) (LiTFSI)/0.575 M LiPF6 salt, trimethyl phosphate, FEC, and PS exhibit superior performance. The interfacial impedance of the Li|LE-LATP membrane-LE|Li coin cell is only ∼50 Ω. The LiNi0.6Co0.2Mn0.2O2 (NCM622)|LE-LATP membrane-LE|Si/C coin cell exhibits an initial specific discharge capacity of ∼163 mAh g−1 at 0.5 C and 25 °C, and the capacity retention rate is ∼87% after 100 cycles. Furthermore, the 5 Ah NCM622|LE–LATP membrane–LE|Si/C pouch battery exhibits a capacity retention rate of> 90% after 400 cycles at 25 °C and 1 C.

The Interaction in Electrolyte Additives Accelerates Ion Transport to Achieve High-Energy Non-Aqueous Lithium Metal Batteries.

Electrolyte engineering is a feasible strategy to realize high energy density lithium metal batteries. However, stabilizing both lithium metal anodes and nickel-rich layered cathodes is extremely challenging. To break through this bottleneck, a dual-additives electrolyte containing fluoroethylene carbonate (10vol.%) and 1-methoxy-2-propylamine (1vol.%) in conventional LiPF6 -containing carbonate-based electrolyte is reported. The two additives can polymerize and thus generate dense and uniform LiF and Li3 N-containing interphases on both electrodes' surfaces. Such robust ionic conductive interphases not only prevent lithium dendrite formation in lithium metal anode but also suppress stress-corrosion cracking and phase transformation in nickel-rich layered cathode. The advanced electrolyte enables Li||LiNi0.8 Co0.1 Mn0.1 O2 stably cycle for 80 cycles at 60mAg-1 with a specific discharge capacity retention of 91.2% under harsh conditions.

Li-Ion Transfer Mechanism of Gel Polymer Electrolyte with Sole Fluoroethylene Carbonate Solvent.

Although gel polymer electrolytes (GPEs) represent a promising candidate to address the individual limitations of liquid and solid electrolytes, their extensive development is still hindered due to the veiled Li-ion conduction mechanism. Herein, the related mechanism in GPEs is extensively studied by developing an in situ polymerized GPE comprising fluoroethylene carbonate (FEC) solvent and carbonate ester segments (F-GPE). Practically, although with high dielectric constant, FEC fails to effectively transport Li ions when acting as the sole solvent. By sharp contrast, F-GPE demonstrates superior electrochemical performances, and the related Li-ion transfer mechanism is investigated using molecular dynamics simulations and 7 Li/6 Li solid-state nNMR spectroscopy. The polymer segments are extended with the swelling of FEC, then an electron-delocalization interface layer is generated between abundant electron-rich groups of FEC and the polymer ingredients, which works as an electron-rich "Milky Way" and facilitates the rapid transfer of Li ions by lowering the diffusion barrier dramatically, resulting in a high conductivity of 2.47× 10-4 Scm-1 and a small polarization of about 20mV for Li//Li symmetric cell after 8000h. Remarkably, FEC provides high flame-retardancy and makes F-GPE remains stable under ignition and puncture tests.

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

AbstractOperation 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.

In-Situ-Polymerized 1,3-Dioxolane Solid-State Electrolyte with Space-Confined Plasticizers for High-Voltage and Robust Li/LiCoO2 Batteries.

In-situ-polymerized solid-state electrolytes can significantly improve the interfacial compatibility of Li metal batteries. Typically, in-situ-polymerized 1,3-dioxolane electrolyte (PDOL) exhibits good compatibility with Li metal. However, it still suffers from the narrow electrochemical window (4.1 V), limiting the application of high-voltage cathodes. Herein, a novel modified PDOL (PDOL-F/S) electrolyte with an expanded electrochemical window of 4.43 V and a considerable ionic conductivity of 1.95 × 10-4 S cm-1 is developed by introducing high-voltage stable plasticizers (fluoroethylene carbonate and succinonitrile) to its polymer network. The space-confined plasticizers are beneficial to construct a high-quality cathode-electrolyte interphase, hindering the decomposition of lithium salts and polymers in electrolytes at high voltage. The as-assembled Li|PDOL-F/S|LiCoO2 battery delivers superior cycling stability (capacity retention of 80% after 400 cycles) at 4.3 V, superior to that of pristine PDOL (3% after 120 cycles). This work provides new insights into the design and application of high-voltage solid-state lithium metal batteries by in situ polymerization.

Ameliorating Phosphonic-Based Nonflammable Electrolytes Towards Safe and Stable Lithium Metal Batteries.

High-energy-density lithium metal batteries with high safety and stability are urgently needed. Designing the novel nonflammable electrolytes possessing superior interface compatibility and stability is critical to achieve the stable cycling of battery. Herein, the functional additive dimethyl allyl-phosphate and fluoroethylene carbonate were introduced to triethyl phosphate electrolytes to stabilize the deposition of metallic lithium and accommodate the electrode-electrolyte interface. In comparison with traditional carbonate electrolyte, the designed electrolyte shows high thermostability and inflaming retarding characteristics. Meanwhile, the Li||Li symmetrical batteries with designed phosphonic-based electrolytes exhibit a superior cycling stability of 700 h at the condition of 0.2 mA cm-2, 0.2 mAh cm-2. Additionally, the smooth- and dense-deposited morphology was observed on an cycled Li anode surface, demonstrating that the designed electrolytes show better interface compatibility with metallic lithium anodes. The Li||LiNi0.8Co0.1Mn0.1O2 and Li||LiNi0.6Co0.2Mn0.2O2 batteries paired with phosphonic-based electrolytes show better cycling stability after 200 and 450 cycles at the rate of 0.2 C, respectively. Our work provides a new way to ameliorate nonflammable electrolytes in advanced energy storage systems.