Proton-driven bilateral interfacial chemistry and electrolyte structure reconstruction enable highly reversible zinc metal anodes

Uncontrolled dendrite growth, severe parasitic reactions on the Zn metal anode (ZMA), and the dissolution of cathode active materials have significantly limited the development of aqueous zinc ion batteries. Herein, 3-(Cyclohexylamino)-1-propanesulfonic acid (CAPS) featured with zwitterion as a multifunctional additive is introduced into the 2 M ZnSO4 aqueous electrolyte to simultaneously regulate the interfacial chemistry of the Zn anode and the cathode, as well as the solvated structure of Zn2+, thereby improving the interfacial and structural stability of both electrodes. Thereinto, the preferentially adsorbed CAPS zwitterion onto the ZMA surface favors for constructing a cationic protective layer originated from the electrostatic shielding effect of the cationic group (>NH2+), inhibiting the growth of dendrites. Meanwhile, the CAPS zwitterion can self-regulate the bilateral interfacial pH by forming the conjugate acid-base pair, suppressing hydrogen evolution reaction and Zn anode surface corrosion. Additionally, the CAPS zwitterion alters the solvated structure of Zn2+, weakening H2O molecule activity and reducing the dissolution of vanadium element from cathode. Consequently, the Zn||Zn symmetric cells harvest excellent cycling stability (1 mA cm−2, 1 mAh cm−2, 2300 h), and the Zn||Cu asymmetric cells display a high average Coulombic Efficiency of 99.7% after 1600 cycles in the ZnSO4+CAPS electrolyte.