Inhibition of Structural Transformation and Surface Lattice Oxygen Activity for Excellent Stability Li-Rich Mn-Based Layered Oxides

Li-rich Mn-based layered oxides (LLOs) are one of the most promising cathode materials, which have exceptional anionic redox activity and a capacity that surpasses 250 mA h/g. However, the change from a layered structure to a spinel structure and unstable anionic redox are accompanied by voltage attenuation, poor rate performance, and problematic capacity. The technique of stabilizing the crystal structure and reducing the surface oxygen activity is proposed in this paper. A coating layer and highly concentrated oxygen vacancies are developed on the material's surface, according to scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. In situ EIS shows that structural transformation and oxygen release are inhibited during the first charge and discharge. Optimized 3@LRMA has an average attenuation voltage of 0.55 mV per cycle (vs 1.7 mV) and a capacity retention rate of 93.4% after 200 cycles (vs 52.8%). Postmortem analysis indicates that the successful doping of Al ions into the crystal structure effectively inhibits the structural alteration of the cycling process. The addition of oxygen vacancies reduces the surface lattice's redox activity. Additionally, surface structure deterioration is successfully halted by N- and Cl-doped carbon coating. This finding highlights the significance of lowering the surface lattice oxygen activity and preventing structural alteration, and it offers a workable solution to increase the LLO stability.

Automated summary

A technique of stabilizing the crystal structure and reducing the surface oxygen activity is proposed, achieving better voltage attenuation and capacity retention. The addition of a coating layer and highly concentrated oxygen vacancies inhibits structural transformation and oxygen release during the charge and discharge process.