Synthesis of Ni-rich NMC cathode material by redox-assisted deposition method for lithium ion batteries

Abstract

This work demonstrates a new synthesis method for NCM powder and surface modification at the same time. Cobalt manganese oxyhydroxide forms uniform precipitation on the surface of Ni(OH)2 through redox reaction. KMnO4 is used as a strong oxidant and the source of manganese. This is different from the conventional process that metal ions in the precursors have the same valence state as products. A slight amount of Ni2+is oxidized to Ni3+on the surface of Ni(OH)2. This surface oxidation process is proved to enhance the structural stability and the rate capacity of Ni-rich cathode materials. The reaction takes place spontaneously under a mild condition. The impurity-free LiNi0.96Co0.03Mn0.01O2(NMC-R) with high crystallinity is successfully fabricated. Uniform distribution of elements is formed after calcination. NMC-R exhibits low cation mixing degree and order surface structure. The material synthesized by redox-assisted deposition displays a high capacity of ~197 mAh g − 1 at the beginning and the capacity retention is about 93% after 100 cycles. It also provides 68 mAh g − 1 higher than the LiNiO2 sample at a high rate of 10C. In summary, a novel solvent-based preparation method for cathode material with a stable structure is developed, which is very promising for practical industrial scale.