Synergistic Anion-Solvent Engineering: Zinc Borohydride as a Multifunctional Additive for Non-Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries have been regarded as a promising energy storage system with cost-effectiveness and environmental sustainability. However, conventional aqueous electrolytes suffer from issues of zinc dendrite growth, hydrogen evolution, and cathode dissolution, leading to low Coulombic efficiency and poor reversibility of the zinc anode. Non-aqueous electrolytes with thermodynamic stability can improve reversibility, but the application is limited by the scarcity of high-performance zinc salts and sluggish electrochemical kinetics. Thus, this work proposes a synergistic anion-solvent engineering strategy by employing zinc borohydride as a multifunctional additive in a stable acetonitrile-triethyl phosphate-tetrahydrofuran (AN-TEP-THF) ternary non-aqueous electrolyte. The BH4 - anions effectively regulate Zn2+ solvation structures and induce uniform Zn deposition to suppress dendrites. Meanwhile, the ternary solvent system ensures superb solubility, ionic conductivity, and chemical stability. Benefiting from the synergistic effect, the symmetric cell achieves long cycling for over 400 h, and the full cell assembled with a potassium manganese hexacyanoferrate (KMnHCF) cathode exhibits an excellent capacity retention of 82.2% after 2000 cycles at 0.5 A g-1. The results demonstrate a feasible strategy to stabilize zinc anodes and boost electrochemical performance, providing new insights for developing high-safety rechargeable non-aqueous zinc-ion batteries.