Creation of Lithium-Ion-Conducting Channels in Gel Polymer Electrolytes through Non-Solvent-Induced Phase Separation for High-Rate Lithium-Ion Batteries

Porous polymer membranes have been widely used as matrixes of gel polymer electrolytes (GPEs) for lithium-ion batteries (LIBs). This work demonstrates the creation of lithium-ion-conducting channels in GPEs made of porous membranes prepared by a non-solvent-induced phase separation (NIPS) process. Poly(ethylene glycol) (PEG)-grafted poly(vinyl butyral) (PVB-g-PEG) is employed as the raw material for the preparation of the porous membranes. In the NIPS process, the hydrophilic PEG segments appear at the pore walls of the resulting porous membranes to increase the liquid electrolyte uptake of the membranes. Moreover, the PEG segments covering the pore walls create a hydrophilic domain and lithium-ion-conducting channels, consequently to facilitate lithium-ion transportation through the membranes. The PVB-g-PEG-based GPEs exhibit high lithium-ion conductivities of 0.98-1.86 mS cm(-1), which are much higher than the value recorded for the neat PVB-based GPE (0.57 mS cm(-1)). Discharge capacities of 150 and 72 mAh g(-1) have been recorded for batteries employing the prepared GPE at charging rates of 0.2C and 10C, respectively. A 48% capacity retention ratio has been obtained at 10C charging rate. The battery also demonstrates a long-term stability in a charge-discharge cycling test at 0.5C. An effective approach for designing porous membrane-based GPEs for high-rate lithium-ion batteries has been demonstrated.