In Situ Polymerization Anchoring Effect Enhancing the Structural Stability and Electrochemical Performance of the LiNi<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>O<sub>2</sub> Cathode Material
Yang Zhang, Ye Song, Jie Liu
Abstract
LiNi x Co y Mn 1– x – y O 2 (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 –1 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.