Unveiling hybrid Li/Na ions storage mechanism of Na3V2(PO4)3@C cathode for hybrid-ion battery with high-rate performance and ultralong cycle-life

Developing Li/Na hybrid ion batteries that combine both the superiorities of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) is an unremitting pursuit for large-scale energy storage. Herein, hierarchical porous Na3V2(PO4)3@C (NVP@C) microspheres as Li/Na hybrid ion batteries (HIBs) cathode are presented, which is synthesized through a solvothermal method. The hierarchical porous microspheres composed by the nanosheets endow short Li/Na-ions diffusion paths and structural integrity, improve electron conductivity, and increase reaction active sites. As a result, the hierarchical porous NVP@C cathode exhibits a high discharge capacity (119.1 mAh g−1 at 0.2C), remarkable rate performance (74.3 mAh g−1 at 50C) and cycling stability (a capacity fade of 0.64% at 1C over 500 cycles). More importantly, the assembled NVP//G full cell using the NVP@C cathode and lithiated graphite anode releases a highest reversible capacity of 118.1 mAh g−1 based on the cathode active material mass at 5C and a capacity retention rate of 89.0% after 12,000 cycles. In addition, the Li/Na ions synergistic storage mechanism in the NVP@C cathode material has been elaborately clarified via in situ X-ray diffraction (XRD) and ex situ X-ray photoelectron spectroscopic (XPS) tests. This work demonstrate that our Li/Na HIBs are a prospective device for large-scale energy storage.