Homogeneous low-tortuosity membrane with fast ion transfer towards life-durable low-temperature zinc metal batteries

Abstract

Aqueous zinc metal batteries (AZMBs) have attracted significant attentions in the energy storage field due to their environmental safety. However, sluggish reaction kinetics of Zn(H₂O)₆²⁺ desolvation and corresponding Zn²⁺ ion transfer hinder the low-temperature performance of AZMBs. Herein, the boundary inhibition effect of ion-related pathway is initially uncovered, and a homogeneous low-tortuosity separator membrane (LTSM) with enhanced kinetics of ion desolvation and transfer is proposed. This low-tortuosity structure of LTSM significantly enhances the effectiveness of pore sieving effect toward large Zn(H₂O)₆²⁺ clusters, minimizing ion transfer barriers and homogenizing ion flux, as revealed by Raman and sum frequency generation spectroscopies. Encouragingly, the metallic Zn with LTSM exhibits lower nucleation overpotentials of ∼50 mV, showcasing an ultralong lifespan of over 10,000 h at 0 °C. Even under −10 °C, a cycle life up to 5000 h is also achieved. The as-prepared full cells assembled with LTSM display the specific capacity of 200 mAh g⁻¹ after 4000 cycles at 8 A g⁻¹ under 0 °C. Increasing to 6.3 mg cm⁻², the large areal pouch cell stabilizes for 160 cycles with retained capacity of 315 mAh g⁻¹, demonstrating feasibility of eliminating the boundary inhibition effect with low-tortuosity separator membrane for practical applications.