Surfactant Induced Crystal Regulation and Dual Layer Carbon Coating Formation for Enhanced Performance of High Voltage Olivine-Type Lithium Cobalt Phosphate Cathode Materials

In recent years, the rapid development of new electric vehicles has ushered in a golden age of lithium-ion battery research. In this research, surfactant induced carbon-decorated nanoplates LiCoPO4 were successfully prepared using a combination of solvothermal treatment and the carbonization process. The results show that the incorporation of cetyltrimethylammonium bromide (CTAB) surfactant presents dual influences on the preparation process of LiCoPO4 cathode materials. The first one is that CTAB could introduce micelles into the hydrothermal synthesis system to facilitate the reduction of grain size, therefore shortening the lithium-ion transmission path. Another is a unique carbon coating with dual layer structure that was formed during a sintering process due to the presence of a carbon substance derived from CTAB in the solvothermal treatment, resulting in nitrogen doping in the carbon layer and the formation of Co–N bonds on the surface. After optimization of the preparation, LiCoPO4 with the incorporation of 0.2 mmol of CTAB exhibited a high lithium-ion diffusion coefficient of 5.99 × 10–14 cm2 s–1 and an initial specific capacity of 120.1 mAh g–1 at 1 C, and its capacity retention ratio was 84.6% after 400 cycles. Furthermore, this material also delivered an initial specific capacity of 113.0 mAh g–1 at a high current rate of 5 C. The preparation method of materials presented here offers a promising strategy to enhance the feasibility of industrial application for high voltage olivine LiCoPO4.