Dendrite-free zinc anode enabled by bifunctional additive coupling electrostatic shielding and zincophilic leveling

The development of aqueous zinc-based batteries is hindered by the dendrite formation and side reactions. To address the issues, a novel bifunctional sodium citrate (Na₃CA) electrolyte additive is developed, in which sodium ion forms an electrostatic shielding layer on the zinc surface to suppress the growth of zinc dendrites, while zincophilic citrate ion replaces water molecules in the solvent shell through leveling effect to reduce side reactions and adsorb onto the electrode surface to promote the uniform zinc deposition. Results show that in the symmetrical tests, the addition of Na₃CA additive decreases the nucleation overpotential from 64.3 mV to 31.6 mV, enabling the battery to be stably cycled for more than 3500 h at the current density of 0.5 mA cm⁻², which is 14 times higher than that with the traditional electrolyte. In the half-battery test, the Na₃CA additive significantly improves the reversibility of the zinc anode with the average coulombic efficiency increasing from 87 % to 95 %. Full battery test shows that after 500 cycles, the capacity retention rate of the battery with Na₃CA additive is 1.6 times that of the traditional battery. This work offers a facile and effective strategy of designing bifunctional electrolyte additive to achieve high-performance aqueous zinc-based batteries.