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.

A Self-Healing and Nonflammable Cross-Linked Network Polymer Electrolyte with the Combination of Hydrogen Bonds and Dynamic Disulfide Bonds for Lithium Metal Batteries

The self-healing solid polymer electrolytes(SHSPEs)can spontaneously eliminate mechanical damages or micro-cracks generated during the assembly or operation of lithium-ion batteries(LIBs),significantly improving cycling performance and extending service life of LIBs.Here,we report a novel cross-linked network SHSPE(PDDP)containing hydrogen bonds and dynamic disulfide bonds with excellent self-healing properties and nonflammability.The combination of hydrogen bonding between urea groups and the metathesis reaction of dynamic disulfide bonds endows PDDP with rapid self-healing capacity at 28°C without external stimulation.Furthermore,the addition of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide(EMIMTFSI)improves the ionic conductivity(1.13×10^(−4)S cm^(−1)at 28°C)and non-flammability of PDDP.The assembled Li/PDDP/LiFePO_(4)cell exhibits excellent cycling performance with a discharge capacity of 137 mA h g^(−1)after 300 cycles at 0.2 C.More importantly,the self-healed PDDP can recover almost the same ionic conductivity and cycling performance as the original PDDP.

Advanced Nonflammable Localized High-Concentration Electrolyte For High Energy Density Lithium Battery

The key to realize long-life high energy density lithium batteries is to exploit functional electrolytes capable of stabilizing both high voltage cathode and lithium anode.The emergence of localized high-concentration electrolytes(LHCEs)shows great promise for ameliorating the above-mentioned interfacial issues.In this work,a lithium difluoro(oxalate)borate(LiDFOB)based nonflammable dual-anion LHCE is designed and prepared.Dissolving in the mixture of trimethyl phosphate(TMP)/1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether(D_(2)),the continuously consumption of LiDFOB is suppressed by simply introducing lithium nitrate(LiNO_(3)).Meantime,as most of the TMP molecular are coordinated with Li^(+),the electrolyte does not show incompatibility issue between neither metal lithium nor graphite anode.Therefore,it demonstrates excellent capability in stabilizing the interface of Ni-rich cathode and regulating lithium deposition morphology.The Li||LiNi_(0.87)Co_(0.08)Mn_(0.05)O_(2)(NCM87)batteries exhibit high capacity retention of more than 90%after 200 cycles even under the high cutoff voltage of 4.5 V,1 C rate.This study offers a prospective method to develop safe electrolytes suitable for high voltage applications,thus providing higher energy densities.

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.

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.

Oxidation behavior and improvement in nonflammability of LPSO-type Mg–Zn–Y–Sr alloy

Mg_(97)Zn_(1)Y_(2)alloys with high ignition temperatures were developed by adding Sr.The addition of Sr resulted in the formation of a uniform and thin Y_(2)O_(3)film.Mg–Zn–Y alloys containing at least 0.25 at.%Sr exhibited ignition temperatures of 1270–1320 K.As a result of EDS measurement,Sr was found to be concentrated in the Y_(2)O_(3)film.In addition,a mixed film of MgO and Sr O formed on the outer layer in the 1.5 at.%Sr-containing Mg_(97)Zn_(1)Y_(2)alloy.These findings suggest that the uniform and thin Y_(2)O_(3)film that maintains high soundness at high temperatures was formed owing to valence control and the formation of a protective outer oxide film.

Safe and Stable Lithium Metal Batteries Enabled by an Amide-Based Electrolyte

The formation of lithium dendrites and the safety hazards arising from flammable liquid electrolytes have seriously hindered the development of high-energy-density lithium metal batteries.Herein,an emerging amide-based electrolyte is proposed,containing LiTFSI and butyrolactam in different molar ratios.1,1,2,2-Tetrafluoroethyl-2,2,3,3-tetrafluoropropylether and fluoroethylene carbonate are introduced into the amide-based electrolyte as counter solvent and additives.The well-designed amide-based electrolyte possesses nonflammability,high ionic conductivity,high thermal stability and electrochemical stability(>4.7 V).Besides,an inorganic/organic-rich solid electrolyte interphase with an abundance of LiF,Li3N and Li-N-C is in situ formed,leading to spherical lithium deposition.The formation mechanism and solvation chemistry of amide-based electrolyte are further inves-tigated by molecular dynamics simulations and density functional theory.When applied in Li metal batteries with LiFePO4 and LiMn2O4 cathode,the amide-based electrolyte can enable stable cycling performance at room temperature and 60℃.This study provides a new insight into the development of amide-based electrolytes for lithium metal batteries.

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.

Analyses on performances of heat and multilayer reflection insulators

This research was conducted to study the performances of the heat and multilayer reflection insulators used for buildings in South Korea to realize eco-friendly, low-energy-consumption, green construction, and to contribute to energy consumption reduction in buildings and to the nation＇s greenhouse gas emission reduction policy （targeting 30% reduction compared to BAUCousiness as usual） by 2020）. The heat insulation performance test is about the temperatures on surfaces of test piece. The high air temperature and the low air temperature were measured to determine the overall heat transfer coefficient and thermal conductivity. The conclusions are drawn that the heat transmission coefficients for each type of existing reflection insulator are： A-1 （0.045 W/（m-K））, A-2 （0.031 W/（m.K））, A-3 （0.042 W/（m.K））, A-4 （0.078 W/（m.K））, and the average heat conductivity is 0.049 W/（m-K）; The heat conductivity for each type of Styrofoam insulator are 0.030 W/（m.K） for B-l, 0.032 W/（m-K） for B-2, 0.037 W/（m＇K） for B-3, 0.037 W/（m.K） for B-4, and the average heat conductivity is 0.035 W/（m＇K） regardless of the thickness of the insulator; The heat conductivity values of the multilayer reflection insulators are converted based on the thickness and type C-1 （0.020 W/（m.K））, C-2 （0.018 W/（m.K））, C-3 （0.016 W/（m.K））, and C-4 （0.012 W/（m.K））; The multilayer reflection insulator keeps the indoor-side surface temperature high （during winter） or low （in summer）, enhances the comfort of the building occupants, and conducts heating and moisture resistance to prevent dew condensation on the glass-outer-wall surface.

Enhanced safety of sulfone-based electrolytes for lithium-ion batteries:broadening electrochemical window and enhancing thermal stability

To meet the demands of high-voltage lithium-ion batteries(LIBs),we develop a novel electrolyte through theoretical calculations and electrochemical characterization.Triphenylphosphine oxide(TPPO)is introduced as a film-forming additive into a sulfone-based electrolyte containing 1 mol L^(−1) lithium difluoro(oxalate)borate.Density functional theory calculations show that TPPO has a lower reduction potential than the sulfone-based solvent.Hence,TPPO should be oxidized before the sulfone-based solvent and form a cathode electrolyte interphase layer on the Li-rich cathode.Our research findings demonstrate that adding 2 wt%TPPO to the sulfone-based electrolyte considerably enhances the ionic conductivity within a range of 20-60℃.In addition,it increases the discharge capacity of LIBs in a range of 2-4.8 V while maintaining excellent rate perfor-mance and cycling stability.Flammability tests and thermal gravimetric analysis results indicate excellent nonflammability and thermal stability of the electrolyte.