Lithium-Rich Layered Oxide Cathode Materials Modified for Lithium-Ion Batteries by CoS of a 3D Rock Salt Structure Assisted by PVP

Abstract

The problem of rapid degradation of the operating voltage and discharge specific capacity of lithium-rich layered oxide (LRMs) cathode materials is a major constraint for their commercial application. In this paper, CoS coating with a 3D layered structure assisted by PVP is used to enhance the cycle life and rate performance of the LRMs material. The introduction of PVP has the following effects: (1) it reduces the solubility of CoS in the electrolyte solution and forms a stable CoS coating, and (2) it acts as a nitrogen-containing carbon matrix material and the heteroatomic dopant, and can provide more active sites to improve the conductivity of CoS. In addition, the CoS coating is capable of efficaciously reducing the direct contact area between electrolyte solution and the LRMs material and alleviating the occurrence of harmful interface reactions. The result of this study manifests that after the modification through CoS modification by PVP, the problem of the capacity decay is obviously solved. When the current density is 0.2 C, the highest specific capacity of 248.87 mAh g^–1 can be provided. The capacity retention ratio of the LRMs@CoS material is 87.21% after 100 cycles, and the capacity decay is 0.3182 mAh g^–1 (1.1534 mAh g^–1 for the LRMs material) per cycle. When the current density is 1 C, the first discharge specific capacity of 220.91 mAh g^–1 is achieved, which demonstrates outstanding electrochemical performance. This study has come up with a simple and practical mentality to realize the modification of cathode materials for high-performance lithium-ion batteries.