Poly(ethylene oxide)-based composite solid polymer electrolyte containing Li7La3Zr2O12 and poly(ethylene glycol) dimethyl ether

We have synthesized a self-standing, flexible, highly ion conductive, and electrochemically stable composite solid polymer electrolyte (CSPE) composed of a poly(ethylene oxide) matrix, Li7La3Zr2O12 ceramic filler, and poly(ethylene glycol) dimethyl ether (PEGDME) plasticizer for all-solid-state Li-ion batteries. The CSPE containing 10 wt% PEGDME (CSPE10) shows the highest ionic conductivity of 4.7 × 10-4 S cm-1 at 60 °C. Additionally, all the CSPEs are stable up to 5.0 V vs. Li/Li+, and CSPE10 shows a high Li-ion transference number of 0.48 at 60 °C. When Li/CSPE/Li symmetric cells are cyclically polarized, the cell with CSPE10 shows the smallest overpotential because of the high ionic conductivity of CSPE10 and the low interfacial resistance between Li and CSPE10. The all-solid-state full cell with the Li/CSPE10/LiNi0.6Co0.2Mn0.2O2 configuration delivers an initial discharge capacity of 157 mA h g-1 at 0.1C at 60 °C. Even after 100 cycles at a higher C-rate of 0.5C, the full cell maintains high discharge capacity of 116 mA h g-1 corresponding to a capacity retention of ~86%. The full cell with a high LiNi0.6Co0.2Mn0.2O2 mass loading of 7.7 mg cm-2 shows an initial discharge capacity of ~160 mA h g-1 and maintains high discharge capacity of 140 mA h g-1 even after 60 cycles.