High areal capacity and long-life Sn anode enabled by tuning electrolyte solvation chemistry and interfacial adsorbed molecular layer

Abstract

Tin (Sn) is an appealing metal anode for aqueous batteries (ABs) due to its high theoretical capacity, elevated hydrogen overpotential, affordability and environmentally friendly nature. However, the parasitic reaction and dead Sn formation are two critical issues that impede the practical application of Sn metal batteries. Herein, we demonstrate that the addition of trace amount of polyvinylpyrrolidone (PVP, 1 mM) into the pristine electrolyte can effectively solve these issues. Specifically, the PVP additive can reshape the structure of Sn²⁺ solvation sheath to accelerate cations migration and suppress water-induced side reaction and the formation of hydroxide sulfate. Additionally, the preferential adsorption of PVP at the interface also promotes the three-dimensional (3D) diffusion of Sn²⁺, facilitating uniform Sn deposition. As a result, symmetric cells with PVP additive in the electrolyte deliver stable cycling for up to 1800 h at 10 mA cm⁻²/1 mAh cm⁻² or 230 h at 5 mA cm⁻²/10 mAh cm⁻². The designed electrolyte also enables the MnO₂//Sn full battery to maintain a discharge capacity of 0.92 mAh cm⁻² over 3000 cycles at current density of 6 mA cm⁻² and supports the stable cycling of PbO₂//Sn full battery for 230 cycles under the high capacity of 10 mAh cm⁻².