Electrolyte-Dependent Assembly of Silk Nanofibrils Rewrites Interfacial Regulation of Zinc Anodes

Abstract The development of aqueous zinc-ion batteries (AZIBs) is hindered by challenges such as zinc dendrite growth, parasitic side reactions, and zinc corrosion during cycling. Employing electrolyte additives to form a protective layer on electrodes represents an effective strategy to mitigate these issues. Natural biomaterials are increasingly attracting attention as environmentally friendly alternatives to conventional toxic additives. This study investigates “top-down” silk nanofibrils (TD SNF) and “bottom-up” silk nanofibrils (BU SNF), prepared via different processing methods, as functional additives. These two types of silk nanofibrils (SNF) display distinct behaviors depending on the electrolyte system. In ZnSO 4 electrolyte, both types of SNF aggregate into microgel particles. Conversely, in Zn(OTF) 2 electrolyte, BU SNF maintains its nanofibrous structure and forms a homogeneous hydrogel network. These SNF form a protective gel layer on the Zn anode surface, which modulates zinc nucleation and growth. As a result, the TD SNF additive in ZnSO 4 electrolyte enables stable cycling for 2750 h at 2 mA cm −2 with a capacity of 2 mAh cm −2 . Similarly, the BU SNF additive in Zn(OTF) 2 achieves a cycle life of 700 h under more demanding conditions of 10 mA cm −2 and 10 mAh cm −2 . This work provides insights into the application of SNF as sustainable electrolyte additives for high-performance AZIBs.