Microorganism-moulded pomegranate-like Na₃V₂(PO₄)₃/C nanocomposite for advanced sodium-ion batteries

Na₃V₂(PO₄)₃ (NVP) with a NASICON crystal structure is a promising cathode material for sodium-ion batteries; however, it has a low rate performance due to its poor electric conductivity. Herein, pomegranate-like NVP/C composites were proposed and prepared via a simple and cost-efficient method using yeast as the mould. Owing to the strong adsorption ability of yeast, high tolerance to extreme conditions and high nitrogen and phosphorus content, a hierarchically structured material composed by NVP particles embedded within a N-/P-doped carbon framework was formed in situ. In the NVP/C composites, the nanoscaled NVP grains coated by carbon, derived from the cytoplasm, and micron-sized carbon capsules, which resulted from the carbonization of the sturdy cell walls, were formed to further accommodate dozens of the carbon-coated NVP grains, resulting in a pomegranate-like architecture. This unique structure and the N-/P-doped carbon framework can provide superior electrochemical kinetics and stability, with efficient electron pathways, and can also buffer volume changes during Na⁺ insertion/extraction. As a result, the NVP/C composites exhibit a good rate performance (113.9 mA h g^-1 at 10C) and an outstanding long-term cycling stability (capacity retention of around 74.7% after 10000 cycles). The properties of the pomegranate-like structure moulded by yeast microorganisms are remarkable and the NVP/C composite is believed to be a promising electrode material for sodium-ion batteries.