Poly(ionic liquid)-functionalized graphene oxide towards ambient temperature operation of all-solid-state PEO-based polymer electrolyte lithium metal batteries

Endowing polyethylene oxide (PEO)-based electrolyte with low crystallinity and high efficient Li+ transport channels is urgently required for next generation all-solid-state lithium metal batteries (LMBs). Herein, a new type of oxyethyl containing poly(ionic liquid) modified graphene oxide nanoparticles (ox-PIL@GO) is coincidentally proposed for preparing PEO based organic-inorganic composite electrolyte membranes (CPEs). Both experimental and DFT simulation results indicate that the dissociation of the LiTFSI is significantly enhanced by the anticipated electrostatic interaction between imidazolium cation and TFSI- anions in CPEs. In addition, the formed electrostatic interaction can also inhibit the movement of TFSI-, giving rise to the increased lithium transference number of 0.61 from 0.21 for the neat PEO/LiTFSI electrolyte. Furthermore, the ion-dipole inter-action between imidazolium cation and PEO chain largely reduces the crystallinity of PEO and the ionic con-ductivity of 1.01 x 10(-4) S cm(-1) at 40 degrees C is successfully obtained. As a result, the ox-PIL@GO incorporated PEO electrolyte enables the Li parallel to Li symmetric cell with long-term, square-wave galvanostatic cycling test of 800 h at current density of 0.1 mA cm(-2) at 50 degrees C and the solid-state LiFePO4 vertical bar CPE vertical bar Li battery with high discharge specific capacity of 116 mAh g(-1) at 40 degrees C at 1C for 300 cycles.

Automated summary

To develop next generation all-solid-state lithium metal batteries, it is important to have polyethylene oxide (PEO)-based electrolyte with low crystallinity and high Li+ transport channels. This study proposes a new type of oxyethyl containing poly(ionic liquid) modified graphene oxide nanoparticles (ox-PIL@GO) for preparing PEO based organic-inorganic composite electrolyte membranes (CPEs). Experimental and simulation results show that ox-PIL@GO can enhance LiTFSI dissociation and inhibit TFSI- movement, resulting in improved lithium transference number and reduced crystallinity of PEO, leading to high ionic conductivity and cycling performance.