Regulating the helmholtz plane by trace polarity additive for long-life Zn ion batteries

Abstract

Zinc (Zn) metal possesses broad prospects because of its strong water-stability, intrinsic safety and high theoretical specific capacity, however, the instability of the interface between Zn electrode and electrolyte prevents its practical application. Herein, a trace maltose (Malt) additive with strong zincophilicity, firm inter-molecular hydrogen bond and abundant exposure of high-electronegativity hydroxyl is introduced to dynamically adjust the components in the Helmholtz plane (HP) to achieve highly stable and reversible Zn anode for aqueous zinc-ion batteries (AZIBs). Especially, Malt molecules are preferentially adsorbed on (100) and (101) crystal planes to promote uniform and dense Zn2+ deposition along with (002) crystal plane. Benefiting from the unique dynamic HP, the Zn||Zn symmetric cell demonstrates the outstanding performance over 5300 h at 2 mA cm−2, and achieves the cumulative discharge capacity of 3.6 Ah cm−2 at 30 mA cm−2 and a high depth of discharge (DOD) of 51.3%. Meanwhile, the Zn//KVO full cell can operate stably for 800 cycles in a low negative-to-positive capacity ratio (N/P). This study provides a new perspective for the design of advanced aqueous electrolyte additives towards long-life AZIBs by dynamically regulating the Helmholtz plane near the surface of Zn metal.