Cellulose-based gel-type electrolyte fabricated by lyophilization to enable uniform Li+ ion flux distribution for stable Li metal anodes with high-rate capability

Abstract

Lithium metal has been extensively investigated as the optimal anode for the next-generation rechargeable batteries. However, the high reactivity of Li with liquid electrolytes and the undesired dendrite growth predisposes the battery to destruction and even safety problems. Herein, a methyl cellulose-based gel polymer electrolyte (MC-GPE) with three-dimensional (3D) networks fabricated via lyophilization is implemented to guide the uniform Li+ deposition and suppress dendrite growth. Owing to the high absorption to LiPF6-based liquid electrolyte, the ionic conductivity of MC-GPE can reach up to around 0.7 mS cm–1 at ambient temperature, almost twice as large as the Polyethylene (PE) separator (Celgard 2730) immersed by the same electrolyte (0.43 mS cm–1). Accordingly, highly reversible Li plating/stripping with a stable polarization (< 40 mV), high coulombic efficiency (CE) (99%) and long lifespan (>400 h) can be obtained (1 mA cm−2, 1 mAh cm−2). The assembled Li-metal cells coupled with LiFePO4 cathodes show remarkable cycling stability and rate performance (157 mAh g–1 after 200 cycles at 1 C and 115 mAh g–1 after 400 cycles at 5 C) with high CE (∼100%). These results indicate the obtained MC-GPE can promote uniform Li+ ion flux distribution, suppress growth of Li dendrite and improve the cycle stability of Li metal anodes. This work paves a way for the application of the cellulose-based GPEs in the future Li-metal batteries.