Du Yuhao, Zhao Wenguang, Li Zijian, Ren Hengyu, Yi Haocong, Wu Shengyu, Wang Jun, Pan Feng, Zhao Qinghe
School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China.
College of Physics and Energy, Fujian Normal University, Fuzhou 350117, China.
ACS Nano. 2025 Jul 22;19(28):25951-25961. doi: 10.1021/acsnano.5c05981. Epub 2025 Jul 12.
The applied cathodes in lithium-ion batteries usually suffer from severe structural degradation upon fast charging, and the correlated mechanism still remains vague. Here, we reveal the surface structural evolution of LiCoO (LCO) during cycling at 4.6 V vs Li/Li with an extreme high fast-charging current of 10 C. Fast charging induces surface heterogeneous delithiation, promoting nonuniform surface phase transitions and resulting in the formation of a triphase hybrid on the charged surface. The triphase hybrid consists of the layered, spinel, and rock-salt (RS) phases. As cycling proceeds, this triphase hybrid propagates gradually toward the bulk, accompanied by a progressive thickening of the surface RS phase, leading to deteriorated Li transport kinetics and accelerated capacity fading. Thus, suppressing the heterogeneous Li delithiation of LCO is crucial for enhancing fast-charging durability. By applying a uniform and robust surface coating, the surface delithiation homogeneity upon extreme fast charging is significantly improved, and the thickening of the surface Li-blocking RS phase is greatly reduced, thereby achieving enhanced cycling stability of LCO. This work benefits the development of more advanced LCO cathodes tailored for fast-charging applications.
锂离子电池中使用的阴极在快速充电时通常会遭受严重的结构退化，相关机制仍不明确。在此，我们揭示了LiCoO（LCO）在相对于Li/Li为4.6 V且具有10 C的极高快速充电电流下循环过程中的表面结构演变。快速充电会引发表面不均匀脱锂，促进不均匀的表面相变，并导致在充电表面形成三相混合相。三相混合相由层状、尖晶石和岩盐（RS）相组成。随着循环的进行，这种三相混合相逐渐向体相传播，同时表面RS相逐渐增厚，导致锂传输动力学恶化和容量快速衰减。因此，抑制LCO的不均匀锂脱锂对于提高快速充电耐久性至关重要。通过施加均匀且坚固的表面涂层，在极快速充电时表面脱锂的均匀性得到显著改善，表面锂阻挡RS相的增厚也大大减少，从而实现了LCO循环稳定性的增强。这项工作有助于开发更先进的用于快速充电应用的LCO阴极。
