An efficient electrolyte additive of tetramethylammonium sulfate hydrate for Dendritic-Free zinc anode for aqueous Zinc-ion batteries

Recently, zinc metal has been considered as a promising metal anode for aqueous rechargeable metal ion batteries due to its low electrochemical potential and high theoretical capacity. However, zinc metal suffers from hydrogen evolution reaction (HER) and dendrite growth during plating/stripping. Here, we propose a low-cost, effective and non-toxic electrolyte additive, tetramethylammonium sulfate hydrate (TMA2SO4), as a simple cationic surfactant additive for zinc-ion batteries, to trigger the smooth Zn deposition during charging and discharging process. It is found that TMA2SO4 enable the realization of the deposition of Zn ions along the surface of zinc foil laterally without stacking and thus dendrite growth and side reactions are greatly mitigated by the electrolyte additive of TMA2SO4 even when the amount of the additive is as low as 0.25 mM. As a result, the TMA2SO4 additive induces excellent cycling stability over 1800 h at the current density of 0.5 mA cm-2 with the limited capacity of 0.5 mAh cm-2 for the Zn-Zn symmetrical cell. Moreover, the electrolyte with TMA2SO4 can well match with MnO2 cathode, which achieves the high initial capacity of 181.3 mAh g-1 at 0.2 A g-1 and long-term cycling stability with the capacity retention of 98.72 % after 200 cycles for the Zn/MnO2 full cell. This work provides a general electrolyte design strategy to suppress zinc dendrite growth and side reactions to achieve long-lifespan zinc metal anodes for aqueous zinc ion batteries by electrostatic shielding effect.