Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501 Japan.
J Am Chem Soc. 2013 Apr 17;135(15):5497-500. doi: 10.1021/ja312527x. Epub 2013 Apr 8.
The phase transition between LiFePO4 and FePO4 during nonequilibrium battery operation was tracked in real time using time-resolved X-ray diffraction. In conjunction with increasing current density, a metastable crystal phase appears in addition to the thermodynamically stable LiFePO4 and FePO4 phases. The metastable phase gradually diminishes under open-circuit conditions following electrochemical cycling. We propose a phase transition path that passes through the metastable phase and posit the new phase's role in decreasing the nucleation energy, accounting for the excellent rate capability of LiFePO4. This study is the first to report the measurement of a metastable crystal phase during the electrochemical phase transition of LixFePO4.
使用时间分辨 X 射线衍射实时跟踪非平衡电池运行过程中 LiFePO4 和 FePO4 之间的相变。随着电流密度的增加，除了热力学稳定的 LiFePO4 和 FePO4 相之外，还出现了亚稳晶相。亚稳相在电化学循环后开路条件下逐渐减少。我们提出了一条通过亚稳相的相转变路径，并假设新相在降低成核能方面的作用，这解释了 LiFePO4 优异的倍率性能。本研究首次报道了在 LixFePO4 的电化学相变过程中测量到亚稳晶体相。
