An Aqueous Symmetric Sodium-Ion Battery with NASICON-Structured Na₃MnTi(PO₄)₃

A symmetric sodium-ion battery with an aqueous electrolyte is demonstrated; it utilizes the NASICON-structured Na₃MnTi(PO₄)₃as both the anode and the cathode. The NASICON-structured Na₃MnTi(PO₄)₃possesses two electrochemically active transition metals with the redox couples of Ti⁴⁺/Ti³⁺and Mn³⁺/Mn²⁺working on the anode and cathode sides, respectively. The symmetric cell based on this bipolar electrode material exhibits a well-defined voltage plateau centered at about 1.4 V in an aqueous electrolyte with a stable cycle performance and superior rate capability. The advent of aqueous symmetric sodium-ion battery with high safety and low cost may provide a solution for large-scale stationary energy storage.