Peng Hang, Zhao Shi-Xi, Huang Chao, Yu Lü-Qaing, Fang Zou-Qiang, Wei Guo-Dan
Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China.
School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
ACS Appl Mater Interfaces. 2020 Mar 11;12(10):11579-11588. doi: 10.1021/acsami.9b21271. Epub 2020 Feb 26.
Layered lithium-rich transition-metal oxides (LRMs) have been considered as the most promising next-generation cathode materials for lithium-ion batteries. However, capacity fading, poor rate performance, and large voltage decays during cycles hinder their commercial application. Herein, a spinel membrane (SM) was first in situ constructed on the surface of the octahedral single crystal LiMnNiCoO (O-LRM) to form the O-LRM@SM composite with superior structural stability. The synergetic effects between the single crystal and spinel membrane are the origins of the enhancement of performance. On the one hand, the single crystal avoids the generation of inactive LiMnO-like phase domains, which is the main reason for capacity fading. On the other hand, the spinel membrane not only prevents the side reactions between the electrolyte and cathode materials but also increases the diffusion kinetics of lithium ions and inhibits the phase transformation on the electrode surface. Based on the beneficial structure, the O-LRM@SM electrode delivers a high discharge specific capacity and energy density (245.6 mA h g and 852.1 W h kg at 0.5 C), low voltage decay (0.38 V for 200 cycle), excellent rate performance, and cycle stability.
层状富锂过渡金属氧化物（LRMs）被认为是最有前景的下一代锂离子电池正极材料。然而，容量衰减、倍率性能差以及循环过程中的大电压衰减阻碍了它们的商业应用。在此，首次在八面体单晶LiMnNiCoO（O-LRM）表面原位构建了尖晶石膜（SM），以形成具有优异结构稳定性的O-LRM@SM复合材料。单晶与尖晶石膜之间的协同效应是性能增强的根源。一方面，单晶避免了无活性的LiMnO类相域的产生，这是容量衰减的主要原因。另一方面，尖晶石膜不仅防止了电解质与正极材料之间的副反应，还提高了锂离子的扩散动力学，并抑制了电极表面的相变。基于这种有益的结构，O-LRM@SM电极具有高放电比容量和能量密度（0.5 C时为245.6 mA h g和852.1 W h kg）、低电压衰减（200次循环为0.38 V）、优异的倍率性能和循环稳定性。
