Enabling an intrinsically safe and high-energy-density 4.5 V-class Li-ion battery with nonflammable electrolyte

Developing nonflammable electrolyte with a wide electrochemical window has become an urgent demand for high-energy-density and high-safe lithium-ion batteries(LIBs).Herein,a fluorinated nonflammable phosphate electrolyte is developed to construct a safe 4.5 V-class LIB(Si-SiC-C/0.35Li2MnO3-0.65LiNi0.5Mn0.5O2).The proposed fluorinated phosphate electrolyte,0.8 M LiPF6/tris(2,2,2-trifluoroethyl)phosphate(TFEP)+5 vol%fluoroethylene carbonate(FEC)+5 vol%vinylene carbonate(VC),is not only completely nonflammable but also exhibits excellent oxidative/reductive stability on 0.35Li2MnO30.65LiNi0.5Mn0.5O2 cathode and Si-SiC-C anode.The in situ differential electrochemical mass spectrometry and X-ray photoelectron spectroscopy proved that TFEP-based electrolyte does not decompose into gases but forms a high-quality electrode-electrolyte interface on cathode surface at high working potential.The 4.5 V-class LIBs using 0.8 M LiPF6 TFEP-based nonflammable electrolyte shed some light on potential application for high-safe and low-cost larger-scale energy storage.

Designing safer lithium-based batteries with nonflammable electrolytes:A review

Lithium-based batteries have had a profound impact on modern society through their extensive use in portable electronic devices,electric vehicles,and energy storage systems.However,battery safety issues such as thermal runaway,fire,and explosion hinder their practical application,especially for using metal anode.These problems are closely related to the high flammability of conventional electrolytes and have prompted the study of flameretardant and nonflammable electrolytes.Here,we review the recent research on nonflammable electrolytes used in lithium-based batteries,including phosphates,fluorides,fluorinated phosphazenes,ionic liquids,deep eutectic solvents,aqueous electrolytes,and solid-state electrolytes.Their flame-retardant mechanisms and efficiency are discussed,as well as their influence on cell electrochemical performance.We conclude with a summary of future prospects for the design of nonflammable electrolytes and the construction of safer lithium-based batteries.

High-safety and high-voltage lithium metal batteries enabled by nonflammable diluted highly concentrated electrolyte

Lithium metal batteries(LMBs)show great promise for achieving energy densities over 400 Wh·kg^(-1).However,highly flammable organic electrolytes are a long-lasting problem that triggers safety hazards and hinders the commercial application of LMBs.Here,a nonflammable diluted highly concentrated electrolyte(DHCE)with ethoxy(pentafluoro)cyclotriphosphazene(PFPN)as a diluent is developed to simultaneously achieve high safety and cycling stability of high-voltage LMBs.The optimal DHCE not only ensures reversible Li deposition/dissolution behavior with a superior average Coulombic efficiency(CE)over 99.1%on lithium metal anode(LMA),but also suppresses side reactions and stress crack on the LiCoO_(2)(LCO)under high cut-off voltage.The newly developed DHCE exhibits high thermal stability,showing complete nonflammability and reduced heat generation between the electrolyte and delithiated LCO/cycled LMA.This work offers an opportunity for rational designing nonflammable electrolytes toward high-voltage and safe LMBs.

A multifunctional electrolyte with highly-coordinated solvation structure-in-nonsolvent for rechargeable lithium batteries

Rechargeable lithium-based battery is hailed as next-generation high-energy-density battery systems.However, growth of lithium dendrites, shuttle effect of lithium polysulfides intermediates and unstable interphase of high-voltage intercalation-type cathodes largely prevent their practical deployment.Herein, to fully conquer the three challenges via one strategy, a novel electrolyte with highlycoordinated solvation structure-in-nonsolvent is designed. On account of the particular electrolyte structure, the shuttle effect is completely suppressed by quasi-solid conversion of S species in Li-S batteries,with a stable cycle performance even at lean electrolyte(5μL mg^(-1)). Simultaneously, in-situ-formed highly-fluorinated interphases can not only lower Li+diffusion barrier to ensure uniform nucleation of Li but also improve stability of NCM cathodes, which enable excellent capacity retention of Lik LiNi(0.5)Co(0.2)Mn(0.3)O2 batteries under conditions toward practical applications(high loading of 2.7 m Ah cm^(-2) and lean electrolyte of 5 m L Ah^(-1)). Besides, the electrolyte is also nonflammable. This electrolyte structure offers useful guidelines for the design of novel organic electrolytes for practical lithium-based batteries.

Molecule‑Level Multiscale Design of Nonflammable Gel Polymer Electrolyte to Build Stable SEI/CEI for Lithium Metal Battery

The risk of flammability is an unavoidable issue for gel polymer electrolytes(GPEs).Usually,flameretardant solvents are necessary to be used,but most of them would react with anode/cathode easily and cause serious interfacial instability,which is a big challenge for design and application of nonflammable GPEs.Here,a nonflammable GPE(SGPE)is developed by in situ polymerizing trifluoroethyl methacrylate(TFMA)monomers with flame-retardant triethyl phosphate(TEP)solvents and LiTFSI–LiDFOB dual lithium salts.TEP is strongly anchored to PTFMA matrix via polarity interaction between-P=O and-CH_(2)CF_(3).It reduces free TEP molecules,which obviously mitigates interfacial reactions,and enhances flame-retardant performance of TEP surprisingly.Anchored TEP molecules are also inhibited in solvation of Li^(+),leading to anion-dominated solvation sheath,which creates inorganic-rich solid electrolyte interface/cathode electrolyte interface layers.Such coordination structure changes Li^(+)transport from sluggish vehicular to fast structural transport,raising ionic conductivity to 1.03 mS cm^(-1) and transfer number to 0.41 at 30℃.The Li|SGPE|Li cell presents highly reversible Li stripping/plating performance for over 1000 h at 0.1 mA cm^(−2),and 4.2 V LiCoO_(2)|SGPE|Li battery delivers high average specific capacity>120 mAh g^(−1) over 200 cycles.This study paves a new way to make nonflammable GPE that is compatible with Li metal anode.