A low-cost vanadium oxide nanofiber for full Ca-ion batteries over a 30,000-cycle lifespan

In the post-lithium-ion battery era, calcium-ion batteries (CIBs) are considered a desirable candidate due to their great physicochemical and economic properties. Unfortunately, the lack of high-performance cathode materials has limited the development of CIBs to a large extent. Metal oxides are the most studied CIB cathodes by virtue of their superior electrochemical performance, cost advantages, and scalable synthesis. Among numerous metal oxides, layered vanadium oxides are a popular option because of their unique structural properties and high Ca²⁺ storage capability. Herein, VO₂(B) nanofibers, a typical layered vanadium oxide, are synthesized by a simple one-step synthesis method using a commercial precursor. Employing as a CIB cathode, it could deliver high reversible capacities of 97.5 mAh·g^–1 at 5 A·g^–1 after 1000 cycles and 74.6 mAh·g^–1 at 10 A·g^–1 after 2000 cycles. Moreover, a CIB full battery assembled by perylene-3,4,9,10-tetracarboxylic diimide as an anode and the nanofiber as a cathode achieved a specific capacity of 38.8 mAh·g^–1 at a current density of 0.5 A·g^–1 even over 30,000 cycles. This work may provide CIBs with a promising cathode material that can be produced on a large scale and at a low cost.