Preparation And Performance Test Of New Functional Lithium Battery Electrolytes

Lithium batteries with high energy density,high operating voltage,long service life and low self-discharge are considered to be the most promising candidate for non-renewable energy storage devices.However,high-temperature and low-temperature electrochemical performance of LIBs were seriously destroyed.Nowadays,LIBs using in wide temperature range are increasingly required for special applications such as military aerospace and space.So,it is necessary to develop a new lithium battery system.Electrolyte is an important part of lithium batteries and plays a vital role in the operation of batteries.Herein,the development of new functional lithium battery electrolytes has always been the focus and core task to develop high performance lithium batteries.Herein,methyl acetate?MA,T_m=-98.1°C?co-solvent?50 vt.%?is blended with three carbonate solvents to obtain a high-conductivity LiPF₆-based quaternary ester-based electrolyte(-60°C,0.095 mS cm^-1),which contains tris?trimethylsilyl?phosphite?TMSP?and 1,3-propanediolcyclic sulfate?PCS?functional additives to significantly enhance the electrochemical performances of a high-voltage?5 V-class?LiNi_0.5Mn_1.5O₄/MCMB battery system over a wide temperature range operation?-60°C-50°C?.At-5°C and a charge/discharge rate of 0.3C,LiNi_0.5Mn_1.5O₄/MCMB full cell using BE+MA+TMSP+PCS exhibits high capacity retention(99.7%,101.7 mAh g^-1/102 mAh g^-1)and most stable voltage plateaus after 200 cycles.High reactivity between MA co-solvent and MCMB anode is proposed to be associated with MCMB catalytic formation of methoxy free radical.It is revealed that the high reactivity can be greatly suppressed by binary functional additives of TMSP and PCS.The flammable and volatile organic solvent used in LIBs frequently lead to safety issues.Solid electrolytes are considered to address safety issues of LIBs significantly.Due to the ex-situ assembly technology of solid-state electrolyte,solid-state lithium batteries commonly show a poor electrolyte/electrode interfacial contact.Herein,we report an in-situ polymerized poly?tetrahydrofuran?-based solid polymer electrolyte?PTSPE?to resolve the poor interfacial contact problem in solid state lithium batteries.The in-situ formed PTSPE exhibits a high ionic conductivity(2.3×10^-4 S cm^-1)and a wide electrochemical window?4.5 V?at 60 ^oC.More importantly,the in-situ formed PTSPE improves interfacial compatibility remarkably,suppressing the growth of lithium dendrites.The LiFePO₄/Li cell employing this in-situ formed PTSPE delivers a high discharge capacity of 142.3 mA h g^-1(153mA h g^-1,142.3 mA h g^-1)even after 100 cycles.This manuscript will provide valuable perspectives for developing next generation high energy density Lithium batteries with safety property over a wide temperature range.