Construction organic composite gel polymer electrolyte for stable solid-state lithium metal batteries

Gel polymer electrolytes (GPEs) synergizing the advantages of both solid and liquid electrolytes are promising electrolyte candidates for lithium metal batteries (LMBs). However, due to the presence of the liquid medium, mechanical performance and thermal stability are compromised. To address this issue, we designed and prepared an organic composite GPEs by immersing a PVDF-HFP fiber membrane in a polyIL-in-salt ionic solution. This process imparts exceptional high-temperature stability (decomposition temperature of 340 °C) and enhanced mechanical performance (Young's modulus of about 6.7 MPa) to the GPEs. The incorporation of polyIL-in-salt ionic solutions is found to enhance the ionic conductivity of GPEs to 0.69 mS cm⁻¹ at 25 °C, facilitating a homogeneous distribution and accelerating ionic migration. The Li||Li battery utilizing this electrolyte effectively alleviates the concentration polarization and achieves the stable cycle performance over 1200 h at 0.25 mA cm⁻² at 50 °C. Additionally, the lithium metal battery, which incorporates the organic composite gel polymer electrolytes, has exhibited an extraordinary specific capacity of 167.3 mAh g⁻¹, accompanied by a retention rate of 99.1 % at 50 °C, even after 100 cycles. This study asserts that the innovative organic composite GPEs exhibit considerable potential for practical applications in lithium metal batteries (LMBs).