Enhancing the Electrochemical Performance of Ni-Rich Layered Oxide Cathodes by Combination of the Gradient Doping and Dual-Conductive Layers Coating

Abstract

Currently, there is an urgent demand for Ni-rich cathode materials with excellent electrochemical properties under harsh conditions; however, obtaining such materials is very challenging. Here, we propose an innovative modification strategy that combines gradient phosphate polyanion doping and dual-conductive layer (Li3PO4-PANI) coating. The phosphate polyanion gradient doping can be described as acting in a “support role” to optimize the crystal structure. Moreover, the dual-conductive (Li3PO4-PANI) layers can be described as acting in a “palisade role” to inhibit side reactions and enhance the ionic/electronic conductivity of the NCM cathode. For the NCM cathode, this strategy synergistically achieves three main objectives: enhancement of structure stability, improvement of the ionic/electronic conductivity of the interface, and reduction of residual lithium salts. The modified NCM cathode delivers superior cycling stability, with 81.4% capacity retention after 100 cycles (4.5 V/55 °C), whereas the original NCM shows only a quite low capacity retention (57.7%). Moreover, this strategy also significantly improves the rate performance of the NCM cathode. These results indicate that this innovative modification strategy can be utilized to enhance the electrochemical performance of the NCM cathode at 4.5 V and 55 °C.