Multifunctional "liquid-solid" interconvertible electrolytes for aqueous zinc-ion batteries with dendrite suppression and impact resistance capabilities.

Short-circuits induced by Zn dendrite growth and external impacts can lead to the failure of aqueous zinc-ion batteries (AZIBs). To enhance the mechanical safety of aqueous batteries, most of the work focuses on strengthening the external packaging, while comparatively limited attention has been directed toward the properties and optimization of the internal electrolyte. Herein, a smart multifunctional fluid [polymethyl methacrylate dispersed in Zn(OTf) aqueous solution] is developed as both a highly ionic conductive electrolyte and an intrinsic mechanical protector for AZIBs. This electrolyte exhibits dynamic "liquid-solid" interconversion due to its non-Newtonian fluid properties. Under normal circumstances, the fluid's high ionic conductivity (25.2 mS cm) supports efficient electrochemical kinetics and interfacial compatibility. Upon high current rates or sudden external impacts, the electrolyte stiffens to suppress Zn dendrite growth and prevent internal short circuits. An AZIB (Zn||VO) using this electrolyte achieves a specific capacity of 353.6 mAh g at 0.1 A g, good rate capability (206.9 mAh g at 5 A g), and excellent cyclability with 85 % capacity retention after 3000 cycles at 5 A g. Additionally, the electrolyte's shear-thickening effect ensures stable operation of the cell under impacts. This work highlights the dual functionality of the electrolyte in enhancing both electrochemical performance and mechanical safety in AZIBs.