Ultra-stable carbon-coated sodium vanadium phosphate as cathode material for sodium-ion battery

Based on the excellent sodium ion mobility of sodium superionic conductor structures, Na3V2(PO4)3 materials have become promising cathode materials in sodium-ion batteries (SIBs). However, inadequate electronic transport of Na3V2(PO4)3 limits the cycling stability and rate performances in SIBs. In this work, high-performance conductive carbon-coated Na3V2(PO4)3 materials are obtained via a simple and facile ball-milling assisted solid-state method by utilizing citric acid as carbon sources. The carbon-coated composite electrodes display a high initial specific capacity of 111.6 mAh·g−1, and the specific capacity could retention reach 92.83% after 100 cycles at 1C with the high coulombic efficiency (99.95%). More importantly, the capacity of conductive carbon-coated nano-sized Na3V2(PO4)3 can remain 48.5 mAh·g−1 at 10C after 3000 cycles (initial capacity of 101.2 mAh·g−1). At the same time, high coulombic efficiency (near 100%) has little decay even at a high rate of 20C during 1000 cycles, demonstrating the excellent cycling stability and remarkable rate performances, and showing potential in large-scale productions and applications. 基于钠超离子导体结构的优异钠离子迁移速率, Na3V2(PO4)3材料已成为钠离子电池 (SIBs) 中极有发展前景的正极材料。然而, Na3V2(PO4)3的导电性不佳会限制钠离子电池的循环稳定性和速率性能。在这项工作中, 利用柠檬酸作为碳源, 通过一种简单而又容易的球磨辅助固相法, 制备了高性能导电碳包覆的Na3V2(PO4)3材料。碳包覆复合电极的初始比容量高, 为111.6 mAh•g-1。在1C的电流密度下, 循环100次后, 容量保持率达到92.83%, 库仑效率高达99.95%。更重要的是, 在10C下经过3000次循环后, 导电碳涂覆纳米级Na3V2(PO4)3的容量仍可保持48.5 mAh•g-1 (初始容量为101.2 mAh•g-1)。同时, 即使在20C的高倍率下循环1000次, 高库仑效率 (接近100%) 也几乎没有衰减, 证明该材料具有优异的循环稳定性和出色的倍率性能, 并在大规模生产和应用中展现出潜力。