Extending the cycle life of Na3V2(PO4)(3) cathodes in sodium-ion batteries through interdigitated carbon scaffolding

摘要

The increasing interest in Na-ion batteries is based on their lower projected cost relative to Li-ion batteries and hence are more economically viable for the large-scale storage of electrical energy. Similar to Li-ion batteries, the capacity of Na-ion batteries is cathode-limited. Na3V2(PO4)(3) (NVP), a prevalent cathode candidate and one of the most stable Na-ion host materials, still exhibits capacity losses in prolonged cycling. We report herein a method which can improve the durability of NVP in extended use. This is done by using a carbon scaffold to constrain the movement of NVP during charge and discharge reactions. The procedure consists of the sol-gel synthesis of densely aligned dense NVP nanofibers under hydrothermal conditions, followed by sucrose infiltration into the interstices of these fibers to form an interdigitated carbon scaffold after calcination. The NVP-carbon nanocomposite fabricated as such shows ultra-stable cycling performance at very high C-rates, 99.9% capacity retention at 20C for more than 10 000 cycles, thereby demonstrating the effectiveness of the materials design principles behind this modification strategy.