High‐Capacity Zinc Anode Enabled by a Recyclable Biomass Bamboo Membrane Separator

Abstract Aqueous zinc ion batteries have gained attention as viable energy storage systems, yet the occurrence of detrimental side reactions and Zn dendrite formation undermines the efficiency of Zn anodes. Controlling water activity have proven to be an effective strategy in mitigating these challenges. However, strategies such as electrolyte design and electrode protection layer show weakness to varying degrees. Here, a new oxygen‐functionalized biomass bamboo membrane separator (denoted as BM) is proposed to restrain the activity of water molecules. This BM separator features a unique, multi‐tiered 2D interlayer that facilitates rapid ion diffusion. Additionally, the oxygen functional groups of the BM separator can form hydrogen bonds with water molecules, effectively transforming water molecules from a free state to a bound state. Consequently, the Zn/Zn asymmetric coin cell using BM can work at the ultrahigh rate and capacity of 30 mA cm −2 and 30 mAh cm −2 for more than 80 h while its counterparts using glass fiber can barely work. Moreover, full cells using BM separator exhibited a capacity retention of 89.7% after 1000 cycles at 10 A g −1 . This study reveals the important influence of water‐limited activity on Zn anode protection and provides an avenue for the design of novel separator.