Next-generation magnesium-ion batteries: The quasi-solid-state approach to multivalent metal ion storage

Abstract

Mg-ion batteries offer a safe, low-cost, and high–energy density alternative to current Li-ion batteries. However, nonaqueous Mg-ion batteries struggle with poor ionic conductivity, while aqueous batteries face a narrow electrochemical window. Our group previously developed a water-in-salt battery with an operating voltage above 2 V yet still lower than its nonaqueous counterpart because of the dominance of proton over Mg-ion insertion in the cathode. We designed a quasi-solid-state magnesium-ion battery (QSMB) that confines the hydrogen bond network for true multivalent metal ion storage. The QSMB demonstrates an energy density of 264 W·hour kg −1 , nearly five times higher than aqueous Mg-ion batteries and a voltage plateau (2.6 to 2.0 V), outperforming other Mg-ion batteries. In addition, it retains 90% of its capacity after 900 cycles at subzero temperatures (−22°C). The QSMB leverages the advantages of aqueous and nonaqueous systems, offering an innovative approach to designing high-performing Mg-ion batteries and other multivalent metal ion batteries.

Recent advances in all-solid-state batteries for commercialization

“…To improve the cyclability of ASSMIBs, Leong et al fabricated and tested ASSMIBs using PEO in an aqueous electrolyte. 173 The SSE showed an excellent chemical stability at high voltage (2.6 to 2.0 V plateau). Furthermore, the cell displayed a superior cyclability over 900 cycles with a good capacity retention of 88% owing to the anchoring ability of hydrogen bonds in the PEO structure.…”

Redesigning Solvation Structure toward Passivation-Free Magnesium Metal Batteries

“…1 Owing to this dendrite-free merit as well as its high capacity (2205 mAh g −1 and 3833 mAh cm −3 ), affordability, and abundant resources of Mg metal, rechargeable Mg metal batteries (RMBs) are considered a promising candidate for future energy storage. 2 Nevertheless, the implementation of RMBs is plagued by a notorious passivation layer. Highly active Mg metal engages in reactions with most electrolyte components (including solvents, salts, and additives) to produce a dense passivation layer, which impedes any potential chemical reaction.…”

“…In striking contrast to the dendritic Li deposition behavior, Mg metal delivers smooth plating/stripping morphology during electrochemical cycles . Owing to this dendrite-free merit as well as its high capacity (2205 mAh g –1 and 3833 mAh cm –3 ), affordability, and abundant resources of Mg metal, rechargeable Mg metal batteries (RMBs) are considered a promising candidate for future energy storage . Nevertheless, the implementation of RMBs is plagued by a notorious passivation layer.…”