Research On Novel Energy Storage Cathode Materials Based On Oxygen Anion Redox Reaction

The specific capacity of conventional Li/Na-ion batteries is limited by the limited number of metal cations in the cationic charge compensation mechanism.Facing the eager demand for large-capacity batteries,increasing the anionic charge compensation mechanism is an effective way to provide additional capacity.However,the irreversible and unstable problems of oxygen anion redox have also become obstacles to its real implementation.Aiming at these problems,this paper takes a classical Na_0.6[Li_0.2Mn_0.8]O₂ material that can undergo oxygen anion redox as the research object,and studies the coating and modification of it and its derivative lithium-rich oxide.The result is as follows:（1）The Na_0.6[Li_0.2Mn_0.8]O₂ material is coated with O group elements（S、Se、Te）,and the effect of the Se coating treatment at 600°C is the best.Electrochemical tests were performed on the 1%Se sample,and the capacity retention rate increased from 39.02%to 83.86%for 50 cycles at a cut-off voltage of 4.5V-3.5V and a current density of 25m A/g.The XRD results show that the 1%Se sample inhibits the phase transition of the structure.XPS results show that the 1%Se sample improves the reversibility of oxygen anion redox,and Se redox occurs during charge-discharge cycling.The Na_0.6[Li_0.2Mn_0.8]O₂ material was coated with different organic substances,and the results showed that the capacity retention rate of the 1%PAN-coated sample for 30 cycles at a cut-off voltage of 4.5V-3.5V and a current density of 25m A/g Increased from42.45%to 70.29%.SEM and TEM results showed that PAN was successfully coated on the surface of the material.（2）The Na_0.6[Li_0.2Mn_0.8]O₂ material was ion-exchanged by the lithium nitrate molten salt method to obtain the O3 type Li_0.6[Li_0.2Mn_0.8]O₂ material,and the material was co-doped with 1.0%Al and 0.5%B Heterogeneous modification.The electrochemical performance test shows that the capacity retention rate of the modified material at 0.1C for 80 cycles is increased from 62.48%of the bare material to 82.48%,and the rate performance is also improved.Through XRD and TEM tests,it was found that the modified samples inhibited the transformation of the structure from the layered phase to the spinel phase and stabilized the crystal structure of the material.This co-doping method provides an idea for the modification of other cathode materials.This paper contains 39 figures,8 tables,and 90 references...