Cation replacement method enables high-performance electrolytes for multivalent metal batteries

High-performance, cost-efficient electrolyte systems are sought after for high-energy-density multivalent metal batteries. However, the expensive precursor and complex synthesis process hinders exploration of cathode electrode/electrolyte interfaces and solvation structures. Here we developed a universal cation replacement method to prepare low-cost, high-reversibility magnesium and calcium electrolytes derived from a zinc organoborate solvation structure. By rationally adjusting the precursor chain length and F-substitution degree, we can fine tune anion participation in the primary solvation shell. A completely dissociated Mg organoborate electrolyte enables high current endurance and enhanced electrochemical kinetics, whereas the Ca organoborate electrolyte with strong coordination/B-H inclusion offers a stable solid-electrolyte interphase with high coulombic efficiency. A rechargeable 53.4 Wh kg-1 Mg metal prototype is achieved with a 30 mu m Mg anode, a low electrolyte/sulfur ratio (E/S = 5.58 mu l mg-1) and a modified separator/interlayer. This work provides innovative strategies for reversible electrolyte systems and high-energy-density multivalent metal batteries. Cost-efficient electrolytes are important for the development of multivalent metal batteries, but expensive precursors and complex synthesis hinder progress. The authors present a cation replacement method for low-cost, high-reversibility magnesium and calcium electrolytes, advancing high-energy-density multivalent metal batteries.