Surface Gradient Ni-rich Cathode for Li-ion Batteries.

Nickel-rich layered oxide cathode material LiNi x Co y Mn z O 2 (NCM) has emerged as a promising candidate for next-generation lithium-ion batteries (LIBs). These cathode materials possess high theoretical specific capacity, fast electron/ion transfer rate, and high output voltage. However, their potential has been impeded by interface instability, crystal irreversible phase transition, and the resultant significant capacity loss, limiting their practical application in LIBs. In this work, a simple and scalable approach is proposed to prepare gradient cathode material (M-NCM) with excellent structural stability and rate performance. Taking advantage of the strong coordination of Ni 2+ with ammonia and the reduction reaction of KMnO 4 , the elemental compositions of the Ni-rich cathode were reasonably adjusted during the precursor preparation stage with surficial Ni depletion and Mn enrichment. In-depth investigations utilizing in-situ and ex-situ technologies underscore that the gradient design of the components played a crucial role in stabilizing the crystal structure, which effectively mitigates Li/Ni mixing and suppresses unwanted parasitic reactions on the surface. As a result, our M-NCM cathode maintains a remarkable 98.6% capacity after 200 cycles, and a rapid charging ability of 107.5 mAh g -1 at 15 C. Furthermore, a 1.2Ah pouch cell configurated with graphite anode demonstrates a lifespan of over 500 cycles with only 8% capacity loss. This work provides a simple and scalable approach for the in-situ construction of gradient cathode materials via cooperative coordination and deposition reactions. This article is protected by copyright. All rights reserved.