Reconstruction of helmholtz plane to stabilize zinc metal anode/electrolyte interface

Abstract

Dendrites proliferation and parasitic side reactions on zinc metal anodes (ZMAs) severely weaken the energy efficiencies of aqueous zinc metal batteries (AZMBs). Herein, an effective Helmholtz plane (HP) reconstruction mechanism on ZMAs in ZnSO4 electrolyte activated by zinc pyrrolidone carboxylate (PCA-Zn) additive is proposed. Systematical experiments together with numerical simulations identified that the dissociated PCA− anions featuring bis-zincophilic-terminal preferentially adhere to the ZMAs surface with carboxyls serving as anchors to replace H2O and SO42−, reshaping an H2O/SO42−-repellent HP to restrain water-triggered side reactions. Meanwhile, the other free zincophilic carbonyl terminals of PCA− anions endow the restructured HP with spatial confinement effect on Zn2+, effectively suppressing their rampant in-plane diffusion and homogenizing ions flux during Zn deposition. Moreover, the HP exhibits a self-repair behavior against unexpected electrode surface damage upon cycling. Benefiting from the multifunctional HP that enables more stable ZMAs/electrolyte interphasial chemistry, an excellent Zn||Zn symmetric electroplating/stripping cyclic durability exceeding 300 h under a depth of discharge up to 40% (20 mA cm−2/20 mAh cm−2) is achieved, accounting for significantly boosted rechargeability (89.7% capacity holding ratio after 5000 cycles) of the carbon-cloth@polyaniline||ZMA full AZMBs compared to that without PCA-Zn additive (malfunction after only 960 cycles).