High-performance lithium ion batteries (LIBs) are increasingly important to help achieve the global aim of carbon neutrality. As a promising cathode material for LIBs, LiVPO4F presents better thermal stability and higher theoretical specific energy than current LiFePO4. However, its practical performance is severely constrained by the low electric conductivity and sluggish electrochemical kinetics. Herein, a new type of mixed-polyanion LiV(SixP1−xO4)F/C (0 < x < 1) is designed and explored by lightly substituting phosphorous with silicon. The phase structure, particle size and morphology are not obviously affected, while some V3+ is oxidized to V4+ because of the charge compensation of SiO44- with PO43-. The optimized LiV(Si0.05P0.95O4)F/C shows noticeably enhanced electrochemical performance compared with pristine LiVPO4F/C and similar LiVPO4F/C materials reported in recent literature. The specific discharge capacities of 143 and 127 mA h g−1 are achieved at 0.1 and 8 C, respectively. In addition, LiV(Si0.05P0.95O4)F/C shows a capacity of 111 mA h g−1 after 1000 cycles at 1 C, corresponding to a capacity decay of only 0.019 % per cycle. The remarkable performance is ascribed to the reduced electrochemical resistance and significantly improved Li+ diffusivity. This work demonstrates the significance and feasibility of polyanion regulation for high-performance polyanionic battery materials.

中文翻译：

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用于锂离子电池的混合聚阴离子 LiV（SixP1−xO4）F/C （0 < x < 1） 正极材料


高性能锂离子电池 （LIB） 对于帮助实现全球碳中和目标越来越重要。作为一种很有前途的锂离子电池正极材料，LiVPO4F 比目前的 LiFePO4 具有更好的热稳定性和更高的理论比能。然而，其实用性能受到低电导率和缓慢的电化学动力学的严重制约。在此，通过用硅轻量取代磷，设计并探索了一种新型混合聚阴离子 LiV（SixP1−xO4）F/C （0 < x < 1）。物相结构、粒径和形貌没有明显影响，而一些 V3+ 由于 SiO44- 与 PO43- 的电荷补偿而被氧化成 V4+。与近期文献报道的原始 LiVPO4F/C 和类似的 LiVPO4F/C 材料相比，优化的 LiV（Si0.05P0.95O4）F/C 显示出明显增强的电化学性能。在 0.1 C 和 8 C 时分别实现了 143 和 127 mA h g-1 的比放电容量。此外，LiV（Si0.05P0.95O4）F/C 在 1 C 下循环 1000 次后显示容量为 111 mA h g−1，对应于每个循环的容量衰减仅为 0.019 %。卓越的性能归因于降低的电化学电阻和显著提高的 Li+ 扩散率。这项工作证明了聚阴离子调节对高性能聚阴离子电池材料的重要性和可行性。