Relationship Between Rate Performance And Electronic/Structural Changes During Oxygen Redox Of Lithium-Rich 4d/3d Transition Metal Oxides

Li-rich solid solution cathode materials having 3d transition metals or 4d transition metals are the candidate of next generation cathode material. In order to clarify the rate performance of 3d or 4d transition metal oxides, we focused two typical Li-rich solid solution cathodes; Li1.2Ni0.13Co0.13Mn0.54O2 as a model of 3d transition metal oxide and Li1.2Ni0.13Co0.13Ru0.54O2 cathode as a model solid solution cathode containing 4d transition metal. We have applied operando hard and soft X-ray absorption spectroscopies clarify electronic and local distortion of both cathodes. From the results of XAS measurements, the reaction mechanism of Li1.2Ni0.13Co0.13Ru0.54O2 cathode was clearly explained by reversible transition metal redox reaction without the oxygen redox process. The EXAFS analysis suggests that Li1.2Ni0.13Co0.13Ru0.54O2 cathode also had the small distorted structure around Ru compared with around Mn of Li1.2Ni0.13Co0.13Mn0.54O2 cathode. The small distorted structure takes advantages for Li+ diffusion, resulting in the high rate performance of the Li1.2Ni0.13Co0.13Ru0.54O2 cathode.