A reversed strategy for designing high-performance anode materials from a traditional NaxV2O5 cathode†

Na_xV₂O₅ is one type of representative cathode material for Li-/Na-ion batteries owing to its relatively high potential vs. Li/Na. Herein, a novel Na_xV₂O₅ anode was successfully designed and synthesized via a reversed strategy, i.e., tuning the Na content in the Na_xV₂O₅ cathode. Orthorhombic α′-Na_xV₂O₅ (x ≈ 0.67) is firstly demonstrated to be a new high-performance anode for lithium-ion batteries (LIBs). Benefiting from its layered structure and the reasonably intercalated Na⁺, the as-synthesized α′-Na_xV₂O₅ displays a high reversible capacity (535.8 mA h g⁻¹ at 0.2 A g⁻¹), excellent rate capability and ultra-long cycle life (91.2% capacity retention after 10 000 cycles). Furthermore, the exceptional performance of the α′-Na_xV₂O₅ anode is showcased in an all-vanadium-based full cell. Importantly, ex situ XRD and XPS demonstrated that Li_zNa_xV₂O₅ is the main and stable active material during cycling, and the lithium-ion storage process is mainly determined by pseudocapacitive behavior. This work brings new insights into the field of vanadate-based anode materials for LIBs.