Lu Yihua, Li Jiagen, Zhao Yu, Zhu Xi
Shenzhen Institute of Artificial Intelligence and Robotics for Society (AIRS), The Chinese University of Hong Kong, Shenzhen, 14-15F, Tower G2, Xinghe World, Rd Yabao, Longgang District, Shenzhen 518172, P. R. China.
Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 199 Ren'ai Road, Suzhou 215123, P. R. China.
ACS Omega. 2019 Nov 25;4(24):20612-20617. doi: 10.1021/acsomega.9b02694. eCollection 2019 Dec 10.
Olivine-structured LiFePO is one of the most popular cathode materials in lithium-ion batteries (LIBs) for sustainable applications. Significant attention has been paid to investigating the dynamics of the lithiation/delithiation process in Li FePO (0 ≤ ≤ 1), which is crucial for the development of high-performance LiFePO material. Various macroscopic models based on experimental evidence have been proposed to explain the mechanism of phase transition from LiFePO to FePO, such as the shrinking core (i.e., core-shell) model, Laffont's (i.e., new core-shell) model, domino-cascade model, phase transformation wave, solid solution model, many-particle models, etc. However, these models, unfortunately, contradict each other and their validity is still under debate. An atomistic model is urgently required to depict the lithiation/delithiation process in Li FePO. In this article, we reveal the lithiation/delithiation process in LiFePO simulated by a computational model using the generalized gradient approximation (GGA + ) method. We find that the clustered configuration is the most energetically favorable, leading to co-operative Jahn-Teller distortion among the inter-polyhedrons that can be observed clearly from the bond patterns. This atomistic model not only offers answers to experimental results obtained at moderate or high rates but also gives the direction to further improve the rate capability of LiFePO cathode material for high-power LIBs.
橄榄石结构的LiFePO是可持续应用的锂离子电池（LIBs）中最受欢迎的正极材料之一。人们已高度关注研究LiFePO（0≤x≤1）中锂化/脱锂过程的动力学，这对高性能LiFePO材料的开发至关重要。基于实验证据已提出各种宏观模型来解释从LiFePO到FePO的相变机制，如收缩核（即核壳）模型、拉丰特（即新核壳）模型、多米诺级联模型、相变波、固溶体模型、多粒子模型等。然而，不幸的是，这些模型相互矛盾，其有效性仍在争论中。迫切需要一个原子模型来描述LiFePO中的锂化/脱锂过程。在本文中，我们揭示了使用广义梯度近似（GGA+U）方法通过计算模型模拟的LiFePO中的锂化/脱锂过程。我们发现簇状构型在能量上最有利，导致多面体间协同的 Jahn-Teller 畸变，这可以从键型中清楚地观察到。这个原子模型不仅为在中等或高速率下获得的实验结果提供了答案，还为进一步提高高功率LIBs的LiFePO正极材料的倍率性能指明了方向。
