Bridging Zn2+/Ca2+‐Storage Chemistries by Hetero‐Solvation Electrolyte toward High‐Voltage Ca2+‐Based Hybrid Batteries

Via hybrid electrolytes with [Ca²⁺(H₂O)(acetonitrile)(CF₃SO₃)⁻] hetero-solvation unit, a new Ca²⁺-based hybrid battery is established by bridging Zn²⁺/Ca²⁺-storage chemistries, achieving a high voltage plateau and decent cycle life.

Abstract

Earth-rich Ca²⁺ ions for energy storage can endow batteries with low-cost and high-energy merits, yet remain hampered by difficult Ca²⁺ plating/stripping and (de)intercalation. Herein, by bridging Zn²⁺/Ca²⁺-storage chemistries, a high-voltage and stable Ca²⁺-based hybrid battery (CHB) in a hetero-solvation electrolyte (HSE) is initially achieved. With a [Ca²⁺(H₂O)(acetonitrile)(CF₃SO₃)⁻] hetero-solvation unit, the HSE not only allows a reversible in situ Zn stripping/plating to circumvent the low-capacity/high-potential limitation of non-stripping/plating-type anodes for Ca²⁺ storage but also effectively overcomes kinetics-sluggish Ca²⁺ (de)intercalation usually occurring in conventional organic electrolytes. The acetonitrile-rich water-lean anode interface synergized by the electrostatic shielding effect of Ca²⁺ ions plays a conducive role in facilitating highly reversible Zn stripping/plating. Moreover, the lubricating/shielding properties of water molecules in the hetero-solvation unit effectively boost the Ca²⁺/Zn²⁺ co-insertion/extraction into/from the KNiMnPB/G cathode. Consequently, the HSE affords an endurable Zn stripping/plating over 1600 h, endows KNiMnPB/G//Zn battery with a high operating voltage of up to 1.85 V at 0.1 A g⁻¹, and demonstrates decent stability over 400 cycles at 1 A g⁻¹, outperforming most aqueous Ca²⁺-based batteries with non-stripping/plating-type anodes. This work sheds new light on the development of high-voltage aqueous CHBs by bridging Zn²⁺/Ca²⁺-storage chemistries, which would boost to pursue other high-energy multivalent-ion batteries.