Rechargeable aqueous metal-ion batteries (RAMB) made from low-cost and abundant electrode materials are attractive for large-scale energy storage. Up to now, a variety of RAMB based on monovalent ions (e.g., Li⁺, Na⁺ and K⁺) intercalation chemistry have been explored. However, due to the low average operation voltage (< 1.25 V), most of them suffer from the problem of low energy density which greatly hinders their application. Consequently, new fundamental concepts are urgently needed to build high-voltage RAMB with high energy density to meet the demands from large-scale energy storage. In this presentation, recent progresses on the development of high-voltage RAMB in our group are introduced.

Firstly, we have succeeded in employing a unique concept of “mixed-metal-ions” including Li⁺/Na⁺, Li⁺/K⁺ and Na⁺/K⁺ to construct a series of RAMB (Na_0.22MnO₂/LiMn₂O₄, TiP₂O₇/Na_0.44MnO₂, TiP₂O₇/Ni₁Zn₁HCF and NaTi₂(PO₄)₃/Ni₁Zn₁HCF). Among them, the NaTi₂(PO₄)₃/Ni₁Zn₁HCF battery has an average operation voltage of 1.45 V, which is higher than other aqueous batteries based on sodium-ion and/or potassium-ion technologies.

Secondly, a new kind of aqueous zinc ion battery (Zn/ZnHCF) with an average operation voltage of 1.7 V has been demonstrated. Owning to the high operation voltage, its specific energy is up to 100.4 Wh kg^-1 based on the total mass of active electrode materials, make it a viable alternative to commercial aqueous batteries for large-scale energy storage

In a word, the establishments of aqueous mixed-metal-ion batteries together with Zn/ZnHCF battery not only provide new members to the family of RAMB, but also greatly broaden our horizons for battery research.