National Special Superfine Powder Engineering Research Center, School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
Key Laboratory of Soft Chemistry and Functional Materials of Education Ministry, School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
ACS Appl Mater Interfaces. 2023 Apr 19;15(15):19075-19084. doi: 10.1021/acsami.3c03535. Epub 2023 Mar 30.
LiNiCoMnO (NCM) is identified as the most classical cathode material on account of its outstanding specific capacity, moderate price, and high safety. However, the surface stability of the high nickel cathode material is poor, which is extremely sensitive to air. Herein, we discover that the electron donor functional groups of organic polymers can form a stable coordination anchoring effect with nickel atoms in the cathode material that can provide an empty orbit through electron transfer, which not only enhances the mutual interface stability between the polymer coating and NCM but also greatly inhibits the decomposition of metal ions in the deintercalation/intercalation process. Density functional theory calculations and first principles reveal that there are coordination bonds and charge transfers between poly(3,4-ethylenedioxythiophene) (PEDOT) and NCM. Consequently, the modified material displayed excellent cyclic stability, with a capacity retention of 91.93% at 1 C after 100 cycles and a rate property of 143.8 mA h g at 5 C. Moreover, structural analysis indicated that the enhanced cycling stability resulted from the suppression of irreversible phase transitions of PEDOT-coated NCM. This unique mechanism provides a thought for organic coating and surface modification of NCM materials.
层状镍钴锰酸锂（NCM）因其比容量高、价格适中、安全性好而被认为是最经典的正极材料。然而，高镍正极材料的表面稳定性较差，对空气极其敏感。在此，我们发现有机聚合物的给电子功能基团可以与正极材料中的镍原子形成稳定的配位锚定效应，通过电子转移提供空轨道，不仅增强了聚合物涂层与 NCM 之间的相互界面稳定性，而且极大地抑制了脱嵌/嵌入过程中金属离子的分解。密度泛函理论计算和第一性原理表明，聚（3,4-乙二氧基噻吩）（PEDOT）与 NCM 之间存在配位键和电荷转移。因此，改性材料表现出优异的循环稳定性，在 1 C 下循环 100 次后容量保持率为 91.93%，在 5 C 下倍率性能为 143.8 mA h g。此外，结构分析表明，增强的循环稳定性源于抑制了 PEDOT 涂层 NCM 的不可逆相转变。这种独特的机制为 NCM 材料的有机涂层和表面改性提供了一种思路。
