Dual-modification of Ni-rich cathode materials through strontium titanate coating and thermal treatment.

Ni-rich layered structure ternary oxides, such as LiNiCoMnO (NCM811), are promising cathode materials for high-energy lithium-ion batteries (LIBs). However, a trade-off between high capacity and long cycle life still obstructs the commercialization of Ni-rich cathodes in modern LIBs. Herein, a facile dual modification approach for improving the electrochemical performance of NCM811 was enabled by a typical perovskite oxide: strontium titanate (SrTiO). With a suitable thermal treatment, the modified cathode exhibited an outstanding electrochemical performance that could deliver a high discharge capacity of 188.5 mAh/g after 200 cycles under 1C with a capacity retention of 90%. The SrTiO (STO) protective layer can effectively suppress the side reaction between the NCM811 and the electrolyte. In the meantime, the pillar effect provided by interfacial Ti doping could effectively reduce the Li/Ni mixing ratio on the NCM811 surface and offer more efficient Li migration between the cathode and the coating layer after post-thermal treatment (≥600 °C). This dual modification strategy not only significantly improves the structural stability of Ni-rich layered structure but also enhances the electrochemical kinetics via increasing diffusion rate of Li. The electrochemical measurement results further disclosed that the 3 wt% STO coated NCM811 with 600 °C annealing exhibits the best performance compared with other control samples, suggesting an appropriate temperature range for STO coated NCM811 cathode is critical for maintaining a stable structure for the whole system. This work may offer an effective option to enhance the electrochemical performance of Ni-rich cathodes for high-performance LIBs.