Strong anion receptor-assisted boron-based Mg electrolyte with wide electrochemical window and non-nucleophilic characteristic

- THFPB can effectively facilitate the partial dissolution of MgO in DME forming incipient acitive cation/anion species.
- This newly-explored Mg-ion electrolyte delivers high anodic stability (up to 4.2 V vs. Mg).
- The as-designed Mg-S batteries display high specific capacity and relatively less attenuation.

Herein we present a strong anion receptor-assisted Mg-ion electrolyte, which is synthesized from tris(2H-hexafluoroisopropyl) borate (THFPB) and MgO in 1,2-dimethoxyethane (DME). The as-prepared borate magnesium oxide complex (BMOC) electrolyte delivers exceptional electrochemical performances, including extremely high anodic stability (up to 4.2 V vs. Mg), non-corrosivity to stainless steel and aluminium foils, and reasonable ionic conductivity of 1.74 × 10− 4 S cm− 1. In addition, by virtue of the non-nucleophilic characteristic of the BMOC electrolyte, S ||BMOC ||Mg cells have been assembled, which show a high stable discharge capacity of 1030 mAh g− 1 for 15 cycles and one well-defined voltage plateau of ≈ 1.1 V vs. Mg, yielding a desirable energy density beyond 1100 Wh kg− 1 based on the weight of sulfur in cathodes.

The novel BMOC electrolyte is prepared by a simple one-step synthesis route and presents high reversibility for Mg deposition/dissolution, non-dendritic deposits, no corrosivity to conventional metallic current collectors and 4.2 V vs. Mg anodic stability on Al foil. Furthermore, good compatibility with conversion materials sulfur indicates that the BMOC electrolytes have great prospect in rechargeable Mg-S battery systems.217