The polymer composite electrolyte with polyethylene oxide-grafted graphene oxide as fillers toward stable highcurrent density lithium metal anodes

Abstract

Adding inorganic fillers to polymer electrolytes is one of the main means to improve ionic conductivity. However, the filler will aggregate, causing the problem of incompatibility between the electrolyte and the metal lithium negative electrode. According to reports, the flaky structure of graphene oxide (GO) has the characteristics of large specific surface area and stable performance, which has attracted widespread attention as a filler for polymer electrolytes. However, the electrolyte membrane has poor compatibility with lithium negative electrodes when GO as a filler, which is not conducive to the full performance of lithium batteries. In this paper, we grafted polyethylene oxide (PEO) on the surface of GO (the product is referred to as GO@PEO) to improving the dispersibility of the filler and the compatibility of the gel polymer electrolyte (GPE) with lithium metal . It is worth that after GO grafting PEO, the impedance of the interface between GPE and lithium metal is significantly reduced, and the compatibility of the electrolyte with the lithium negative electrode is significantly improved. Assembled into Li/ Li battery, the surface current cycle is stable, up to 1 mA cm−2. GO@PEO further improves the ionic conductivity of the ion conductivity up to 1.6 mS cm−1. Further prepared into LiFePO4 (LFP)/Li battery, GPE-GO@PEO showed excellent cycle stability and the discharge specific capacity retention rate was 95.6% after 100 cycles. The rate performance of the battery is also significantly improved. At 5C, the discharge specific capacity of the LFP/Li battery remains 40 mAh g−1.