Alleviating the Storage Instability of LiNi0.8Co0.1Mn0.1O2 Cathode Materials by Surface Modification with Poly(acrylic acid)

The storage stability of the nickel-rich ternary cathode materials deteriorates with the increase of Ni content, which has become a major obstacle in the practical application process of the materials. In this work, a handy and effective surface modification method with poly(acrylic acid) is developed to solve this issue, and the air sensitivity of LiNi0.8Co0.1Mn0.1O2 materials is alleviated successfully by the protective poly(acrylic acid) coating. The poly(acrylic acid) coating can not only reduce the surface alkalinity of NCM811 materials but also prevent direct contact between the materials and H2O/CO2 in the air. Compared with the pristine materials, the modified materials show smaller weight increase, higher capacity and coulomb efficiency, and less change of morphology and structure after storage in the same conditions (55 °C, 80% RH). The fewer surface impurities, more stable near-surface structure, and better electrochemical performance for the modified materials benefit from the protective layer constructed by poly(acrylic acid). This work provides a new perspective and possibility for the improvement of storage stability of nickel-rich materials, showing that modifications with other polymers containing acidic groups are also likely to be feasible for nickel-rich cathode materials.