Graphene Oxide Enabled Flexible PEO-Based Solid Polymer Electrolyte for All-Solid-State Lithium Metal Battery

Exploring high performance solid electrolytes is essential for the practical application of solid-state lithium–metal batteries. Here, graphene oxide (GO) is employed to improve the electrochemical performance, thermal stability, and mechanical strength of the poly(ethylene oxide) (PEO) based electrolyte. The ionic conductivity of the hybrid electrolyte containing 1 wt % GO reaches 1.54 × 10 –5 S cm –1 at 24 °C, which is 7 times that of the electrolyte without GO, and the activation energy decreases from 1.01 to 0.64 eV. It is found that GO can suppress the formation of crystalline nuclei of PEO, thus increase the amorphous regions, and improve the movement ability of the PEO segments. Importantly, GO-modified PEO electrolyte not only has a wide electrochemical window (∼5 V) but also increases the lithium ion migration number to 0.42. Taking advantage of the decent GO–PEO solid electrolyte, the symmetric Li/Li cell can stably cycle for 600 h with a very small overpotential (27 mV) at 0.1 mA cm –2, showing excellent performance in inhibiting lithium dendrites. Most importantly, the LiFePO 4 //GO–PEO//Li full battery also delivers superior cycle and rate properties, with an initial discharge capacity of 142 mAh g –1 at 0.5 C and 91% capacity retention after 100 cycles. Moreover, the full battery can stably cycle for more than 450 charge–discharge cycles at 1 C. It is anticipated that PEO polymer electrolyte modified by GO has great practical application potential.