Fluoroethylene Carbonate Research Articles

Effective SEI Formation via Phosphazene‐Based Electrolyte Additives for Stabilizing Silicon‐Based Lithium‐Ion Batteries

AbstractSilicon, as potential next‐generation anode material for high‐energy lithium‐ion batteries (LIBs), suffers from substantial volume changes during (dis)charging, resulting in continuous breakage and (re‐)formation of the solid electrolyte interphase (SEI), as well as from consumption of electrolyte and active lithium, which negatively impacts long‐term performance and prevents silicon‐rich anodes from practical application. In this work, fluorinated phosphazene compounds are investigated as electrolyte additives concerning their SEI‐forming ability for boosting the performance of silicon oxide (SiOx)‐based LIB cells. In detail, the electrochemical performance of NCM523 || SiOx/C pouch cells is studied, in combination with analyses regarding gas evolution properties, post‐mortem morphological changes of the anode electrode and the SEI, as well as possible electrolyte degradation. Introducing the dual‐additive approach in state‐of‐the‐art electrolytes leads to synergistic effects between fluoroethylene carbonate and hexafluorocyclotriphosphazene‐derivatives (HFPN), as well as enhanced electrochemical performance. The formation of a more effective SEI and increased electrolyte stabilization improves lifetime and results in an overall lower cell impedance. Furthermore, gas chromatography‐mass spectrometry measurements of the aged electrolyte with HFPN‐derivatives as an additive compound show suppressed ethylene carbonate and ethyl methyl carbonate decomposition, as well as reduced trans‐esterification and oligomerization products in the aged electrolyte.

Mechanistic understanding of aging behaviors of critical-material-free Li4Ti5O12//LiNi0.9Mn0.1O2 cells with fluorinated carbonate-based electrolytes for safe energy storage with ultra-long life span

Behind-the-meter storage (BTMS) systems—a viable method to minimize potential risk of blackout events and stabilize the grid—require a different type of cost-effective energy storage with excellent safety, ultra-long (>20 years) cycle life and reasonable energy density compared that of electric vehicles. To increase the energy density and reduce the cost of a long-term cyclable lithium-titanate-based cell, it is required to employ a critical-material-free high voltage cathode and an electrolyte with good electrochemical and transport properties. Here, the long-term electrochemical performance and behaviors of selected critical-material-free Li4Ti5O12 (LTO)//LiNi0.9Mn0.1O2 (LNMO) full cells for BTMS applications are evaluated and analyzed in the optimized voltage range of 1.4–2.7 V at 45 °C with different fluorinated carbonate-based electrolytes. The fluoroethylene carbonate (FEC)-based electrolyte cell shows the highest capacity retention of 57.9 % and Coulombic efficiency (CE) of 99.96 % after 1000 cycles, potentially attributed to a dense, homogenous and less resistive LiF-rich solid-electrolyte interphase (SEI) layer formed on the surface of LTO that may mitigate electrolyte decomposition and maintain relatively low cell impedance during cycling. The 3,3,3-fluoroethylmethyl carbonate (F-EMC)-based electrolyte cell, however, presents the worst performance with lower capacity and a sharp decrease of CE, due to unstable and non-uniform SEI formation and continuous oxidative electrolyte decomposition. This mechanistic understanding of cell aging behaviors and failure mechanisms with detailed analysis of surface chemistry and electrode morphology can guide design of new electrode chemistries and electrolyte formulations for the development of BTMS batteries.

Dual-Salt Localized High-Concentration Electrolyte for Long Cycle Life Silicon-Based Lithium-Ion Batteries.

Silicon-based materials are considered the most promising anodes for next-generation lithium-ion batteries (LIBs) owing to their high specific capacity. However, poor interfacial stability due to enormous volume changes severely restricts their mass application in LIBs. Here, we design a fluoroethylene carbonate (FEC)-containing dual-salt (LiFSI-LiPF6) ether-based localized high-concentration electrolyte (D-LHCE-F) for enhancing the interfacial stability of silicon-based electrodes. It is revealed that the dominating LiFSI salt of superior chemical and thermal stability prevents the formation of corrosive HF, while the addition of FEC improves the interface stability by promoting the formation of protective LiF-rich SEI and increasing the flexibility of the interface. This robust and flexible SEI layer can adapt to substantial variations in the volume of silicon electrodes while preserving the integrity of the interface. The SiOx/C electrode using the unique D-LHCE-F retains up to 78.5% of its initial capacity after 500 cycles at 0.5C, well surpassing that of the control electrolyte (3.4% capacity retention). More notably, the cycle life of the SiOx/C||NCM90 (LiNi0.9Co0.05Mn0.05O2) full batteries is effectively enhanced thanks to the stabilized electrode/electrolyte interfaces. The key findings of this work offer crucial knowledge for rationally designing electrolyte chemistry to enable the practical application of high-energy-density LIBs adopting silicon-based anodes.

Deciphering the Thermal Failure Mechanism of Anode‐Free Lithium Metal Pouch Batteries

AbstractAnode‐free lithium metal batteries (AFLMBs) are the subject of increasing attention due to their ultrahigh energy density, simplified structure, reduced cost, and relatively high safety, but their thermal runaway performance under abuse conditions has been rarely explored, and a clear understanding of whether the absence of a highly‐reactive lithium metal anode is equal to thermal runaway free remains elusive. Herein, by systematically examining the thermal runaway characteristics of a 2.0 Ah AFLMB, it is revealed that under elevated temperatures, discharged anode‐free pouch cell is safe while the fully‐charged one indeed undergoes thermal runaway, but with a milder intensity than that of a lithium metal battery with the same capacity. Moreover, mechanistic investigations demonstrate that thermal runaway of an AFLMB employing a conventional electrolyte is triggered and dominated by anode‐induced exothermic interactions and the broken separator induced electrodes interaction. Moreover, it is shown for the first time that adding fluoroethylene carbonate in an electrolyte leads to ring‐opening repolymerization at 170 °C to form a thermal‐stable solid layer between anode and cathode, which inhibits the direct contact of electrodes and effectively postpones violent self‐heating. This comprehensive exploration of thermal runaway characteristics and mechanisms of large format AFLMBs sheds fresh light on developing high energy density and safety‐enhanced lithium metal batteries.

Partially fluorinated electrolyte for high-voltage cathode with sulfurized carbon anode from polyacrylonitrile for lithium-ion battery

A new lithium-ion battery is configured by coupling sulfurized carbon anode and high voltage LiNi0.5Mn1.5O4 (LNMO) cathode. The anode is derived from sulfurized polyacrylonitrile (S-C(PAN)). Severe capacity fading usually becomes unavoidable due to the oxidative decomposition of solvents, primarily when a conventional carbonate electrolyte with 1 M lithium hexafluorophosphate (LiPF6) is employed. Fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and 1, 1, 2, 2-Tetrafluoroethyl-2, 2, 3, 3-tetrafluoropropyl ether (TTE) are formulated as the best electrolyte (3:2:5 in vol. ratio) for this new high-voltage lithium-ion battery to mitigate this capacity fading and improve the adaptability of the S-C(PAN) and LNMO. The discharge capacity of full cell made with 1 M lithium hexafluorophosphate (LiPF6) in FEC/EMC/TTE (3:2:5) electrolyte reaches 688 mAh g−1 at a rate of 2 C, while 19 mAh g−1 for the control electrolyte. X-ray photoelectron spectroscopy (XPS) results confirm that the fluorinated electrolyte stabilizes both surfaces of S-C(PAN) and LNMO in the full cell effectively. Compared to the control electrolyte, the developed electrolyte enhances the cyclic stability and rate capability of both half cells (Li//S-C(PAN and Li//LiNi0.5Mn1.5O4) and S-C(PAN)//LiNi0.5Mn1.5O4 full cells.

Electrolyte modification method induced atomic arrangement in FeOx/NF nanosheets for efficient overall water splitting.

To explore transition metal-based electrocatalysts with remarkable energy storage and conversion performance, the rational design and synthesis of electrodes with rich active sites and favorable electrical conductivity are crucial. Herein, using fluoroethylene carbonate (FEC) additive in electrochemical conversion reaction (electrolyte modification method) is proposed as an effective strategy to enhance the catalytic activity of FeOx/NF. The optimal sample FeOx/NF-Li-FEC1 shows optimized HER activity with remarkably low overpotential of 222 mV at a current density of 200 mA cm-2. By employing FeOx/NF-Li-FEC1 as bifunctional electrocatalysts, the overall water-splitting device reaches a current density of 10 mA cm-2 at a low cell voltage of 1.56 V. The outstanding performance is mainly attributed to the atomic arrangement to offer rich active sites as well as the evolved electronic structure and the thin SEI layer to accelerate charge transfer process. This study opens up a novel avenue to rationally design and synthesize low-cost and high-performance electrode materials for electrochemical energy conversion and storage devices.

Impact of in coin cell atmosphere on lithium metal battery performance

Research on lithium metal as a high-capacity anode for future lithium metal batteries (LMBs) is currently at an all-time high. To date, the different influences of a highly pure argon glovebox (GB) and an industry-relevant ambient dry room (DR) atmosphere have received little attention in the scientific community. In this paper, we report on the impact of in coin cell atmosphere (ICCA) on the performance of an LMB as well as its interphase characteristics and properties in combination with three organic carbonate-based electrolytes with and without two well-known interphase-forming additives, namely fluoroethylene carbonate (FEC) and vinylene carbonate (VC). The results obtained from this carefully executed systematic study show a substantial impact of the ICCA on solid electrolyte interphase (SEI) resistance (RSEI) and lithium stripping/plating homogeneity. In a transition metal cathode (NMC811) containing LMBs, a DR ICCA results in an up to 50% increase in lifetime due to the improved chemical composition of the cathode electrolyte interphase (CEI). Furthermore, different impacts on electrode characteristics and cell performance were observed depending on the utilized functional additive. Since this study focuses on a largely overlooked influential factor of LMB performance, it highlights the importance of comparability and transparency in published research and the importance of taking differences between research and industrial environments into consideration in the aim of establishing and commercializing LMB cell components.

Vital roles of fluoroethylene carbonate in electrochemical energy storage devices: a review

The origin, synthesis, application and challenge of FEC electrolyte additive as a vital role used in different electrodes for LIBs have been reviewed.

Synergistic role of functional electrolyte additives containing phospholane-based derivative to address interphasial chemistry and phenomena in NMC811||Si-graphite cells

Herein, we report on the 2-phenoxy-1,3,2-dioxaphospholane (PhEPi) molecule as a novel functional phospholane-based electrolyte additive. The presence of PhEPi in optimal concentration in the baseline electrolyte (EC:EMC 3:7, 1 M LiPF6) significantly enhances the electrochemical performance of the NMC811||Si-graphite cell chemistry. To further optimize the cell's overall performance, two well-known film-forming additives, namely, vinylene carbonate (VC) and fluoroethylene carbonate (FEC), were used as co-additives with PhEPi, and the resulting cells thoroughly characterized by selected electrochemical and spectroscopic techniques. The addition of PhEPi to the VC-containing electrolytes showed the complementary advantages of high specific discharge capacity and prolonged cycle life of the considered cells and outperformed the overall performance of the FEC counterpart. To gain better understanding of the role of each additive on the individual positive and negative electrode interphases, we conducted a systematic investigation of both electrodes, which were pre-cycled against Li-metal electrode. Post mortem spectroscopic investigations of the corresponding interphases provided insights into the synergistic effect of VC and PhEPi in the NMC811||Si-graphite cell chemistry.

ZnF2 -Riched Inorganic/Organic Hybrid SEI: in situ-Chemical Construction and Performance-Improving Mechanism for Aqueous Zinc-ion Batteries.

Uncontrolled dendrites growth and serious parasitic reactions in aqueous electrolytes, greatly hinder the practical application of aqueous zinc-ion battery. On the basis of in situ-chemical construction and performance-improving mechanism, multifunctional fluoroethylene carbonate (FEC) is introduced into aqueous electrolyte to construct a high-quality and ZnF2 -riched inorganic/organic hybrid SEI (ZHS) layer on Zn metal anode (ZMA) surface. Notably, FEC additive can regulate the solvated structure of Zn2+ to reduce H2 O molecules reactivity. Additionally, the ZHS layer with strong Zn2+ affinity can avoid dendrites formation and hinder the direct contact between the electrolyte and anode. Therefore, the dendrites growth, Zn corrosion, and H2 evolution reaction on ZMA in FEC-included ZnSO4 electrolyte are highly suppressed. Thus, ZMA in such electrolyte realize a long cycle life over 1000 h and deliver a stable coulombic efficiency of 99.1 % after 500 cycles.

ZnF2‐Riched Inorganic/Organic Hybrid SEI: in situ‐Chemical Construction and Performance‐Improving Mechanism for Aqueous Zinc‐ion Batteries

AbstractUncontrolled dendrites growth and serious parasitic reactions in aqueous electrolytes, greatly hinder the practical application of aqueous zinc‐ion battery. On the basis of in situ‐chemical construction and performance‐improving mechanism, multifunctional fluoroethylene carbonate (FEC) is introduced into aqueous electrolyte to construct a high‐quality and ZnF2‐riched inorganic/organic hybrid SEI (ZHS) layer on Zn metal anode (ZMA) surface. Notably, FEC additive can regulate the solvated structure of Zn2+ to reduce H2O molecules reactivity. Additionally, the ZHS layer with strong Zn2+ affinity can avoid dendrites formation and hinder the direct contact between the electrolyte and anode. Therefore, the dendrites growth, Zn corrosion, and H2 evolution reaction on ZMA in FEC‐included ZnSO4 electrolyte are highly suppressed. Thus, ZMA in such electrolyte realize a long cycle life over 1000 h and deliver a stable coulombic efficiency of 99.1 % after 500 cycles.

Molecular dynamics simulations of fluoroethylene carbonate and vinylene carbonate as electrolyte additives for Li-ion batteries

ABSTRACT Contemporary electrolyte additives have captivated the attention of researchers since additives were reported to play a very crucial role in supporting the formation of an effective solid electrolyte interphase (SEI) in the case of silicon if used as an anode. The choice of a good solvent with additives demonstrates a significant impact on the solvation and diffusivity of lithium ions. Fluoroethylene carbonate (FEC) and Vinylene carbonate (VC) were extensively used additives for increasing the lifespan of Li-ion batteries (LIBs). In the current study, structural, dynamical, and transport properties of six different systems were investigated by applying classical molecular dynamics (MD) simulations. The properties obtained from the simulations suggested system E consisting of DMC, 1M LiPF, and 10% FEC, to be the best medium for the electrolytes for LIBs, since the diffusion coefficient of Li ions and ionic conductivity of LiPF were estimated to be of high values for the system E. However, before the evaluation of the transport properties, the structural properties in terms of radial distribution functions and spatial distribution functions were evaluated for DMC molecules with reference to DMC, Li, and PF ions. The structure data were also found to be in fair agreement with experimental and previous simulation results reported so far. Based on the finding of this study, it was suggested that DMC as a solvent with a 10% FEC additive could be considered a good medium for electrolytes for the improved performance of LIBs compared to VC as an additive to DMC.

Consequences of Different Pressures and Electrolytes on the Irreversible Expansion of Lithium Metal Half Cells

AbstractLithium metal is considered as the ‘holy‐grail’ among anode materials for lithium‐ion batteries, but it also has some serious drawbacks such as the formation of dendritic and dead lithium. In this study, the interplay of external pressure and different carbonate‐ and ether‐based electrolytes on the (ir)reversible expansion of lithium metal during cycling against lithium titanate and lithium iron phosphate is studied. In carbonate‐based electrolytes without any additives, lithium metal shows tremendous irreversible expansion and significant capacity reduction at elevated current densities due to the formation of mossy and dead lithium. The addition of fluoroethylene carbonate can reduce irreversible expansion and capacity reduction, especially when a high external pressure is applied. When an ether‐based electrolyte is used, the irreversible dilation of the lithium metal is suppressed when applying increased external pressures. Overall, increased external pressure appears to reduce the formation of mossy and dead lithium and improve the performance.

Tracking the Oxidation of Silicon Anodes Using Cryo-EELS upon Battery Cycling.

Silicon is a high-capacity material for the anode of a rechargeable lithium-ion battery. One of the fundamental challenges for using Si in anodes is capacity fading, which has been revealed to be partially associated with the interfacial instability between the Si and liquid electrolyte due to the large volume swing of Si upon charging and discharging. Smart nanoscale design concepts, either presynthesized or formed in situ, have led to the mitigation of the detrimental factors associated with the volume swing of Si. However, it has never been clear how the chemical state of Si evolves and contributes to the capacity fading upon battery cycling. Here, we use cryo-electron energy loss spectroscopy to directly monitor, at a subnanometer scale, the chemical evolution of Si upon battery cycling. We discover that during the cycling process Si particles are progressively oxidized to form SiO2, which is initiated from the particle surface and gradually penetrates toward the interior of the particle, directly contributing to the capacity fading. Possible mechanisms of Si oxidation are postulated. We further show how the cycling stability can be improved by an electrolyte additive to form an effective passivation layer, representatively, even a small concentration of fluoroethylene carbonate causes the formation of an LiF layer on the Si nanoparticle surface that prevents Si oxidation and improves cycling stability. The present work unveils Si oxidation as a previously unrecognized factor that contributes to capacity fading, therefore providing insight into the design of anodes with Si-based materials.

A Quasi‐Solid Electrolyte by In Situ Polymerization of Selective Solvent for Lithium‐Metal Batteries

AbstractLithium (Li) metal is a competitive anode material for rechargeable high energy density batteries due to its high specific capacity and low reduction potential. However, great challenges remain in addressing uncontrollable Li dendrite growth and unstable interface. Herein, we report a quasi‐solid electrolyte enabled by in situ polymerization of polyethylene glycol methyl ether acrylate. Meanwhile, a LiF‐enriched solid electrolyte interphase (SEI) is built on Li‐metal surface by function of the fluoroethylene carbonate additive. The SEI with a good mechanical stability prompts the dense and uniform Li deposition behavior. The in situ polymerized gel polymer electrolyte exhibits an ionic conductivity of 1.71×10−4 S cm−1 at 30 °C, and a considerable oxidative stability up to 4.5 V (vs. Li/Li+). The Li||Li symmetric cells delivers a long‐term cycle life over 1400 h and a low voltage hysteresis at 0.5 mA cm−2, 1 mAh cm−2. To be paired with a LiFePO4 positive electrode, the cell shows a high discharge capacity of 135.6 mAh g−1 and capacity retention of 92.7 % after 300 cycles. This work provides a reference for the practical development of quasi‐solid electrolyte for lithium‐metal battery.

Stabilization of microsized Sn anode with carbon coating and fluoroethylene carbonate additive for high-performance Li-ion batteries

Metallic Sn is one of the promising alternatives to graphite for lithium-ion batteries because of its high theoretical capacity, low lithium alloying voltage, and high conductivity. However, the huge volume expansion due to repeated alloying-dealloying makes it unsuitable for commercial applications. Herein, we have proposed a single-step synthesis of carbon-coated Sn by catalytic decomposition of acetylene over Sn microparticles using the chemical vapor deposition technique. This modification of Sn has successfully controlled the volume expansion due to the higher availability of pores, resulting in very low capacity fading. Further, adding fluoroethylene carbonate (FEC) as an electrolyte additive results in very high structural stability. Postmortem studies carried out have confirmed the same. A specific discharge capacity of 390 mAh g−1 at a high current density of 0.5A g−1 is achieved for Sn/C in the presence of FEC additive, along with high rate capability and cyclic stability. The structural reconstruction in the presence of FEC additive, with superior capacity and stability, can pave the way for further building of Sn-based anodes for next-generation high-performance LIBs.

An ultra-thin polymer electrolyte for 4.5 V high voltage LiCoO2 quasi-solid-state battery

To achieve safe and high energy density solid-state batteries (SSBs), the weight of solid-state electrolyte (SSE) should be minimized and a high voltage and high specific capacity cathode should be used. Polyethylene oxide (PEO)-based polymer electrolytes (PEs) has been identified as the optimal SSE for SSBs owing to their versatile advantages. However, fabricating ultra-thin and high voltage stable PEO-based PEs is still challenging. Herein, an ultra-thin (8.1 µm) blending polymer electrolyte (BPE) is designed through blending PEO, Polymethyl methacrylate (PMMA) and Poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), and complexing with Succinonitrile (SN), Fluoroethylene carbonate (FEC) and LiTFSI plasticizers. Based on this design, Li|BPE|LiFePO4 quasi-solid-state battery (QSSB) can operate for 250 cycles with a capacity retention of 92.8%, 4.5 V high voltage Li|BPE|LiCoO2 QSSB exhibits 87% capacity retention after 80 cycles, with an average Coulombic efficiency ≥99.8%, which is much superior than 4.5 V Li|PEO|LiCoO2 SSB, whose capacity rapidly decays to 0 mAh/g after a dezen of cycles. DFT calculation suggests that blending PEO, PMMA and PVDF-HFP increase the electrochemical oxidation tolerance. Interface study by TEM and XPS discloses PEO-LiTFSI/LiCoO2 interface is unstable with a big amount of decomposed products from PEO-LiTFSI and from LiCoO2, while BPE/LiCoO2 interface is more stable without obvious decomposition, indicating the promising application of BPE for high energy density QSSBs.

Improved high-temperature performance of LiNi0.5Co0.2Mn0.3O2/artificial graphite lithium ion pouch cells by difluoroethylene carbonate

A key issue in the development of lithium ion batteries (LIBs) is the stability of the electrolyte, especially at high temperature. This research compares three electrolyte solvents with different cyclic carbonate structures, i.e. ethylene carbonate (EC), fluoroethylene carbonate (FEC) and difluoroethylene carbonate (DFEC) to investigate their effect on the performance of LiNi0.5Co0.2Mn0.3O2/artificial graphite lithium ion pouch cells at high temperature. The results point out that DFEC is the most effective solvent in preventing interfacial impedance growth and electrolyte decomposition, and improving cycling performance, with capacity retention of 85 % after cycling 500 times at 45 °C. Comprehensive characterizations reveal that DFEC forms effective interphases with high thermal stability on both cathode and anode. This work highlights the important role of DFEC in electrolyte formulations for high−energy−density LIBs at elevated temperature.

Marrying a Non‐Flammable Phosphate Solvent with Lithium Nitrate: Novel Electrolyte for Intrinsically Safe and High Performance Lithium Metal Batteries

AbstractThe formation of lithium (Li) dendrites and deterioration of the mechanical integrity of Nickel (Ni)‐rich cathodes directly hinder the commercialization of high‐voltage Li metal batteries (LMBs) with Ni‐rich cathodes. Herein, a novel electrolyte was tailored by combining non‐flammable triethyl phosphate (TEP) solvent with easily‐synthesized lithium nitrate (LiNO3) as the main salt and fluoroethylene carbonate (FEC) additive. The preferential electrochemical decomposition of LiNO3 and FEC provides robust and conductive solid/cathode electrolyte interphase (SEI/CEI) layer on the surface of the anode/cathode, which can protect both electrodes effectively during long‐term cycling. Benefiting from the synergetic effect of LiNO3 and FEC, NFE−LiNO3 exhibited outstanding performances in the cells with LiNi0.6Mn0.2Co0.2O2 (Li||NMC622) under high voltage (4.3 V), achieving an extremely high average efficiency of ∼100 % with an exceptional capacity retention of 90 % after 250 cycles. This study provides useful insights into the rational design of highly efficient, non‐flammable, and low‐cost electrolyte for long‐lasting high‐voltage LMBs.

Tuning a Solvation Structure of Lithium Ions Coordinated with Nitrate Anions through Ionic Liquid‐Based Solvent for Highly Stable Lithium Metal Batteries

AbstractRational design of promising electrolyte is considered as an effective strategy to improve the cycling stability of lithium metal batteries (LMBs). Here, an elaborately designed ionic liquid‐based electrolyte is proposed that is composed of lithium bis(trifluoromethanesulfonyl)imide as the lithium salt, 1‐ethyl‐3‐methylimidazolium nitrate ionic liquid ([EMIm][NO3] IL) and fluoroethylene carbonate (FEC) as the functional solvents, and 1,2‐dimethoxyethane (DME) as the diluent solvent. Using [EMIm][NO3] IL as the solvent component facilitates a special Li+‐coordinated NO3− solvation structure, which enables the continues electrochemical reduction of solvated NO3− and the formation of remarkably stable and conductive solid electrolyte interface. With FEC as another functional solvent and DME as the diluent solvent, the formulated electrolyte delivers high oxidative stability and ionic conductivity, and endows improved electrochemical reaction kinetics. Therefore, the formulated electrolyte demonstrates exceedingly reversible and stable Li stripping/plating behavior with high average Coulombic efficiency (98.8%) and ultralong cycling stability (3500 h). Notably, the high‐voltage Li|LiNi0.8Co0.1Mn0.1O2 full cell with IL‐based electrolyte exhibits enhanced cyclability with a capacity retention of 65% after 200 cycles under harsh conditions of low negative/positive ratio (3.1) and lean electrolyte (2.5 µL mg−1). This study creates the first NO3−‐based ionic liquid electrolyte and evokes the avenue for practical high‐voltage LMBs.