Triple modification engineering to enhance structural stability and ionic-electronic transport kinetics of lithium-rich manganese-based cathode materials
Xingpeng Cai, Shiyou Li, Ningshuang Zhang, Jiawen Zhang, Jingxuan Yan, Xiaoling Cui
Abstract
The development of strategies to inhibit structural degradation and surface side reactions is the key to promoting the large-scale application of lithium-rich manganese-based cathode materials Li<sub>1.2</sub>Mn<sub>0.54</sub>Ni<sub>0.13</sub>Co<sub>0.13</sub>O<sub>2</sub> (LMNCO). Herein, LMNCO was triply modified from the inside to the outside, by bulk doping of Mo<sup>6+</sup>, fabricating oxygen vacancies (OVs) defects, and surface coating of S, N-doped carbon nanolayers (SNCN). The integration of Mo<sup>6+</sup> doping and OVs defects widens and stabilizes the Li<sup>+</sup> diffusion channel, and the surface coating of SNCN provides additional electrons for LMNCO in the conduction band region, achieving a simultaneous improvement in both ionic and electronic conductivity. Meanwhile, Mo<sup>6+</sup> doping and OVs mitigate the irreversible phase transitions caused by oxygen loss and transition metal (TM) out-of-plane migration, while SNCN inhibits the corrosion of the electrolyte on the material surface and enhances the stability of the surface structure. Benefiting from the synergistic effect of these modifications, the structural evolution of the modified material is highly reversible, and the layered structure remains intact during repeated lithiation/delithiation processes, while the mechanical properties of material are also improved, effectively suppressing crack generation and TM dissolution. As a result, at room temperature (25 °C), the modified cathode demonstrates a high capacity retention of 94.6% after 200 cycles at 1 C, and a high rate capacity of 161.0 mAh·g<sup>−1</sup> at 5 C. Especially, under harsh conditions, the capacity retention is 76.3% after 150 cycles at 55 °C and 1 C. This work provides a new solution for developing advanced LMNCO cathode materials.