Cost-effective, long-term aqueous rechargeable hybrid sodium/zinc batteries based on Zn anode and Na3MnTi(PO4)3 cathode

Aqueous rechargeable batteries have promising application in large-scale energy storage owing to their cost-effective, eco-friendly, high safety and good electrochemical performance. An aqueous rechargeable hybrid sodium/zinc battery with Zn anode, Na3MnTi(PO4)3 cathode and 0.5 mol L-1 CH3COONa and Zn(CH3COO)2 mixed electrolyte has been designed for the first time. The battery delivered a reversible and stable capacity of 95.0 mAh g−1 at 1.5 C for 50 cycles with a high and flat working voltage of 1.75 V vs. Zn2+/Zn. Impressively, the battery showed the excellent cycling performance and superior rate capability, which can be cycled at 10.0 C for 2000 cycles with a capacity retention of 93.6% and a reversible capacity of 55.6 mAh g−1 at 30.0 C. Meanwhile, the co-intercalation mechanism of hybrid Na+ and Zn2+ in the cathode is elucidated by cyclic voltammogram, ex-situ XRD, ex-situ XPS and Rietveld refinement analysis. This work gets insight into the charge/discharge processes of hybrid ions for NASICON-structured Na3MnTi(PO4)3, providing a feasible way to design cost-effective, high safety and long-term aqueous rechargeable batteries.