A modified trilayer membrane for suppressing Li dendrite growth in all-solid-state lithium-metal batteries

Abstract

Mechanically robust trilayer HSE membrane modified with an optimized amount of functionalized vapor-grown carbon fiber (f-VGCF) is prepared using a solution-casting method. This trilayer membrane had the structure SPE0 (PVDF-HFP/LiTFSI/SN)|SPE2 (PVDF-HFP/Al-doped-LLZO/LiTFSI/SN)|SPE1 (PVDF-HFP/LiTFSI/SN/f-VGCF). The SPE0 (unmodified) and SPE1 (modified) layers faced the cathode and anode sides, respectively; SPE2 is the same as SPE0 but loaded with needle-like Li6.25Al0.25La3Zr2O12 filler. The modified trilayer HSE membrane possessed an ionic conductivity (4.72 × 10–4 S cm−1) and a Li transference number (0.52) higher than unmodified trilayer HSE membrane (3.68 × 10–4 S cm−1 and 0.41, respectively). A Li/SPE1-SPE2-SPE1/Li symmetric cell displayed extremely stable Li plating/stripping performance when tested sequentially at 0.1, 0.2, 0.5, and 1 mA cm−2 for 800 h (200 h for each current density). A 2032 coin cell incorporating NCM622/SPE0-SPE2-SPE1/Li delivered a desirable capacity output with excellent cycling stability (85.04% capacity retention after 627 cycles with an average coulombic efficiency of 99.17% at a rate of 0.5C at room temperature). A pouch cell based on NCM622/SPE0-SPE2-SPE1/Li also achieved excellent capacity retention of 95.37% after 100 cycles with an average coulombic efficiency of 99.81% at 0.2C at room temperature. Thus, ASSLMBs incorporating such modified trilayer HSE membranes have potential for practical applications.