Enhancement in cycling stability of LiNi^sub 0.5^Mn^sub 1.5^O^sub 4^/Li cell under high temperature in gel polymer electrolyte system by Tris(trimethylsilyl) borate additive

Tris(trimethylsilyl) borate (TMSB) has been taken as solid electrolyte interface forming additive in carbonated liquid electrolyte of current lithium ion battery, but it has not been applied in Gel Polymer Electrolyte (GPE) yet. In this investigation, TMSB is selected to enhance the cyclic performance of high voltage cathode LiNi0.5Mn1.5O4 under elevated temperature in traditional poly(vinylidene fluoride-co-hexafluoropropylene) (P(VdF-HFP)) based GPE system. By addition of 1 wt% TMSB into GPE, 79% capacity retention ratio is kept at room temperature after 1000 cycles for Li/LiNi0.5Mn1.5O4 coin cell, whose retention value is almost the same as the GPE without additive. However, the discharge capacity retention is improved to 86% after 230 cycles with TMSB additive at high temperature of 55 °C, compared with 75% retention for the GPE without additive. From the physical and chemical characterization, it finds that the improvement in electrochemical performance of GPE with additive is caused by the formation of thin and uniform solid electrolyte interface layer between the GPE and cathode material, which is beneficial to inhibit the further decomposition of liquid component in GPE system and keep the structure integrity of LiNi0.5Mn1.5O4 cathode under high temperature environment.