Improved cycling stability of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2 through microstructure consolidation by TiO_2 coating for Li-ion batteries

摘要

The commercial deployment of Ni-rich layered oxide cathodes is hampered by both contaminating species on the surface and mechanical degradation associated to the microcracks. To resolve both issues, a series of TiO2-modified LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode materials is constructed and studied. As expected, TiO2 could trap the residual lithium on the surface, minimizing the undesired side reaction. In addition, infiltrative layer with Ti gradient concentration from the outer to inner is also acquired, which strengthens the primary particles, reduces the gaps between randomly oriented grains and stabilizes the structure of NCM622 during charge discharge cycles. As a result, the NCM622 with TiO2 incorporation thus displays a high capacity of 168.7 mAh g(-1), with 96% retention after 200 cycles, which is 18% higher than that of the bare NCM622. Structural and compositional characterization (i.e., in-situ Raman, EIS and depth XPS) further reveal the electrochemical mechanism and kinetics of the designed NCM622-TiO2 cathode.