High Capacity Magnesium Metal Rechargeable Battery Enabled By Dual Ion Chemistry

Electrochemical energy storage is the core technology for the success of green transportation and renewable energy. Among existing energy storage chemistries, magnesium metal rechargeable batteries (MRB) are receiving growing attention due to the abundance of magnesium and its highly reversible and dendrite-free deposition/dissolution in Grignard–based complex electrolyte, which enables the exploit of the high capacity magnesium anode(2233 mAh/g).These merits have made MRB a promising candidate system to store electrochemical energy. However, the strong coulombic interaction between an intercalation host and the bivalent Mg²⁺ makes the solid state diffusion of the latter rather sluggish, resulting in low Mg²⁺intercalation level, large polarization during charge/discharge and/or rapid capacity decay for common cathode materials.

To solve the problem, we developed a high capacity MRB by coupling TiS₂ with magnesium foil in a dual-ion chemistry(Mg²⁺/Li⁺). The battery operates by Li⁺ insertion/extraction at cathode and Mg deposition/dissolution at anode. The battery simultaneously combines high-capacity/high-voltage, fast Li⁺ intercalation of TiS₂ and the high-capacity/dendrite-free deposition of Mg anode.

Compared to other MRBs, the theoretical specific capacity and specific energy of the dual-ion battery is 161.0 mAh/g and 209.3 Wh/kg even when the weight of lithium salt was taken into account, which are 32.2% and 56.2% higher than 121.8 mAh/g and 134 Wh/kg of the state-of-the-art MRB(with Mo₆X₈ cathode). Noteworthily, there is still a huge potential to be exploited for this dual-ion battery concept. If a high voltage/capacity cathode compatible to electrolyte can be found, the specific energy could be increased largely. This could make it an alternative even competitive to the mainstream LIB technology, not mentioning the advantages of a dendrite-free Mg anode that is free of inert masses (current collector, binder, and conductive additives) and first cycle irreversible reaction associated with SEI formation.