Lactulose modulation of the inner Helmholtz plane for stable and dendrite-free zinc anodes in aqueous Zn-ion batteries

Abstract

The performance of zinc metal anodes in aqueous zinc-ion batteries (AZIBs) is strongly influenced by the chemical composition of the inner Helmholtz plane (IHP), which plays a critical role in ensuring anode stability and reversibility. In aqueous environments, a water-dominant IHP induces undesirable side reactions and irregular zinc deposition, presenting significant challenges for the practical application of zinc anodes. This study introduces lactulose (LA), a polyhydroxy sugar, as a self-adsorptive additive to modify the IHP. LA effectively displaces water molecules, forming a drier IHP that mitigates water-induced decomposition reactions and improves the stability of the zinc anode. Moreover, LA adsorption promotes Zn (002) plane nucleation, effectively inhibiting dendrite formation and enhancing the reversibility of the zinc anode. As a result, the Zn‖Zn symmetric cell achieves stable operation for over 2200 hours at 1 mA cm⁻² and 0.5 mA h cm⁻². The Zn‖Cu half-cell demonstrates stable cycling performance, completing more than 1000 cycles with a coulombic efficiency of 99.4%. Similarly, the Zn‖MnO₂ full cell retains 85.31% of its initial capacity following 1100 cycles at a charge/discharge rate of 1 A g⁻¹. Under the same conditions, the Zn‖MnO₂ pouch cell retains 77.63% of its capacity after 480 cycles. These results underscore the significant potential of LA as an additive for enhancing the practical viability of zinc-ion batteries.