Polyacrylonitrile fibers network reinforced polymer electrolyte with Li-Sn alloy layer protected Li anode toward ultra-long cycle lifespan for room-temperature solid-state batteries

Poly(ethylene oxide) polymer electrolyte composited with high content of succinonitrile organic plasticizer has excellent ionic conductivity at room temperature. Unfortunately, the poor interface stability between this novel solid polymer electrolyte (SPE) and Li metal anode leads to limited cycling performance, which seriously hinders its commercial applications. Herein, the electrospun nanofibers framework of polyacrynitrile (PAN) is introduced as a three-dimensional polymer filler, which can not only provide a robust skeleton for improved mechanical stability, but also inhibit the growth of Li dendrites with increased Li ion transference number from 0.28 to 0.41. Meanwhile, the Li anode is modified via constructing a dense Li-Sn alloy layer, offering a perfectly passivated anode surface and eliminating the side reaction between metallic Li and SPE efficiently. Hence, the interface compatibility and structure stability between the anode and the polymer electrolyte are greatly improved in the prolongated cyclic testing due to the synergistic effect of PAN reinforced SPE and Li-Sn alloy layer coated Li. As a result, the symmetrical battery can cycle stably for 2400 h at 25 °C under 0.1 mA cm−2 and 0.1 mAh cm−2, while the LiFePO4 based full battery can keep a good capacity retention of 85 % even after 500 cycles at 0.5 C. This work demonstrates that the combination of modifying SPE and building advanced interface layer on the Li anode is an effective measure to optimize the room temperature cycling performance of polymer solid-state Li battery.