Nanodiamond Regulated Electrolyte Enhances Thermal, Chemical and Structural Properties for Highly Reversible Zn Metal Anodes

Aqueous zinc-ion batteries (AZIBs) suffer from inevitable internal resistance-induced heat generation and competing hydrogen evolution, leading to high external cooling energy consumption and potential safety hazards. In this report, an electrolyte engineering strategy is proposed, involving nanodiamond (ND) additives to the commercial electrolyte. The ND particles assist in the reconstruction of the hydrogen bond network, reducing the desolvation energy of Zn²⁺, promoting the preferential deposition of (002) oriented Zn crystals, and effectively inhibiting water decomposition, Zn dendrite growth and heat-induced side reactions. Importantly, compared to commercial counterparts, ND-related electrolytes show relatively low impedance and high specific heat capacity (thermal conductivity), resulting in much reduced heat evolution and temperature rise. Such improvements are due to the key properties of nanodiamond, including its large specific surface area, abundant surface functional groups, and exceptional thermal conductivity. These collective enhancements not only minimize thermal and chemical side reactions but also reduce the internal pressure build-up, as evidenced by only a 26% volume-change in ND-based pouch batteries, compared to a 76% rise with commercial electrolytes. Consequently, both coin cells and pouch batteries with the ND-modified electrolyte exhibit much improved long-term cyclability, specific capacity, rate capacity and coulombic efficiency, compared to those without NDs.