Industrial Waste Derived Separators for Zn‐Ion Batteries Achieve Homogeneous Zn(002) Deposition Through Low Chemical Affinity Effects

Abstract Designing a cost‐effective and multifunctional separator that ensures dendrite‐free and stable Zn metal anode remains a significant challenge. Herein, a multifunctional cellulose‐based separator is presented consisting of industrial waste‐fly ash particles and cellulose nanofiber using a facile solution‐coating method. The resulting fly ash‐cellulose (FACNF) separators enable a high ion conductivity (5.76 mS cm −1 ) and low desolvation energy barrier of hydrated Zn 2+ . These features facilitate fast ion transfer kinetics and inhibit water‐induced side reactions. Furthermore, experimental results and theoretical simulations confirm that the presence of fly ash particles in FACNF separators effectively accommodate the preferential deposition of Zn(002) planes, due to the weak chemical affinity between Zn(002) plane and fly ash, to mitigate dendrite formation and growth. Consequently, the utilization of FACNF separators causes an impressive cycling performance in both Zn||Zn symmetric cells (1600 h at 2 mA cm −2 /1 mAh cm −2 ) and Zn||(NH 4 ) 2 V 10 O 25 (NVO) full cells (4000 cycles with the capacity retention of 92.1% at 5 A g −1 ). Furthermore, the assembled pouch cells can steadily support digital thermometer over two months without generating gas and volume expansion. This work provides new insights for achieving crystallographic uniformity in Zn anodes and realizing cost‐effective and long‐lasting aqueous zinc‐ion batteries (AZIBs).