Reconstructing the Surface Structure of Li-Rich Cathodes for High-Energy Lithium-Ion Batteries

Reconstructing a favorable surface layer could contribute to superior charge transfer and stabilize bulk structure and thus achieve the excellent electrochemical performance of lithium- and manganese-rich oxides, but it is still challenging. In this work, the surface structures of Li-rich oxides have been successfully reconstructed via a facile strategy utilizing hydrothermal glucose carbonization and the subsequent reduction procedure. Surface microstructure and chemical state analyses reveal that the reconstruction process involves roughening of the surface connects with the extraction of lithium ions and the reduction of Mn ions as well as the formation of a spinel phase due to the distortion of oxygen anions or the presence of oxygen deficiencies. The reconstructed Co-free Li-rich oxide using 0.025 g of glucose exhibits superior electrochemical performance. Its maximum discharge capacities are 237 and 193 mAh/g at 100 and 600 mA/g, respectively, and their corresponding capacity retention ratios are higher than 93% at the 100th cycle. Furthermore, reconstructing the surface structure also enhances the discharge capacity and cycling performance of Co-containing Li-rich cathodes. The findings in this work would offer hints for surface structure reconstruction of many oxides used in energy and other fields.