Innovative fluorinated boron-based electrolyte harmonizes interface chemistry-electrochemistry of Mg anode for accessible rechargeable Mg battery

The development of promising boron-based electrolyte for rechargeable magnesium batteries (RMBs) is constrained by high costs and cumbersome synthesis. Herein, an accessible and innovative magnesium phenyl fluoroborate complex electrolyte (MPFBC) has been designed, which employs cheap boron trifluoride as both the boron and fluorine source, utilizing a facile Lewis acid-base reaction for synthesis. The MPFBC electrolyte is capable of stable cycling of Mg||Mg cells at 0.5 mA cm −2 with low overpotential (<100 mV) and maintains a decent discharge specific capacity of 62.6 mAh g −1 after 1000 cycles of the Mg||Mo 6 S 8 battery at 0.5C. Further, the complementary advantages of chemistry and electrochemistry have been highlighted for the first time to harmonizes interface chemistry of Mg anode. A complementation combining the in-situ pre-corrosion driven by chemical process and the Mg 2+ -conducting layer formed through electrochemical process enables controllable interface chemistry and interface evolution. The design and synthesis of MPFBC pave a feasible way for commercialization of boron-based electrolytes, and simultaneously the interface regulation strategy of chemistry-electrochemistry complementary advantages enriches the interface theories of RMBs.