Tailored fluoroborate-based electrolyte with fast interphase formation kinetics toward stable Ah-level zinc batteries

Abstract

Solid electrolyte interphase (SEI) plays a critical role in stabilizing zinc batteries, yet insufficient attention has been given to its in-situ growth kinetics and the post-stripping morphology of zinc anodes, both affecting the SEI-forming quality. Herein, we showcase a synergistic effect between uniform Zn stripping and rapid SEI formation through introducing tetramethylurea (TMU) into Zn(BF₄)₂-based electrolytes. TMU participates in the Zn²⁺ solvation structure and reshapes the electrolyte hydrogen-bond network, enabling a water-poor electric double layer that mitigates the corrosion-induced stripping inhomogeneity. Subsequently, a multi-component and inorganic-rich SEI with high uniformity is rapidly deposited during the plating process. This SEI with abundant zincophilic sites activates instantaneous nucleation and hence guides dense and uniform Zn deposition. With enhanced Zn stripping/plating symmetry, the long-term effectiveness of SEI is guaranteed, contributing to the high reversibility over 3200 ​h at 1 ​mA ​cm⁻²/2 mAh cm⁻². Impressively, the Zn//NaV₃O₈ full cell (4.43 mAh cm⁻²) can be steadily cycled at 0.1 ​A ​g⁻¹ under an intermittent-rest protocol. The stable operation of an Ah-level pouch cell over 100 cycles further demonstrates the scalability of this strategy and highlights the significance of achieving high stripping/plating symmetry and a long-term effective SEI toward practical zinc batteries.