Effect of interface wetting on the performance of gel polymer electrolytes-based solid-state lithium metal batteries

Solid-state lithium metal batteries are the one of most promising energy storage devices. To date, however, it is still considered that the interface wetted by liquid electrolytes can enhance the performance of solid-state lithium batteries. In this work, the resistance of the batteries versus their cycle number is investigated using 1 M LiPF₆ EC/DMC (v/v = 1/1) (LE) and 1 M LiTFSI-PP13TFSI (IL) wetting the interface of the LiFePO₄ cathode and the ionic liquid gel polymer electrolyte (ILGPE). The results indicate that, compared with IL-wetting, LE-wetting treatment can more effectively lower the bulk resistance of the battery. The bulk resistance of the batteries does not alter after cycling, indicating that the ionic conductivity is stable during the charging/discharging. The interfacial resistance and charge transfer resistance of LE-wetted batteries increase by 50 times and 825 times after 50 cycles at C/3 and 23 °C, while the resistance of IL-wetted batteries increase by less than 20 times. Furthermore, the formation of the electrode electrolytes interphase during cycling, which probably accounts for the change of battery resistance observed in solid-state lithium batteries. The ILGPE had superior compatibility and stability with LiFePO₄ cathode, which is also the most basic guarantee for the battery's stable cycling.