Carbonate coprecipitation preparation of Li-rich layered oxides using the oxalate anion ligand as high-energy, high-power and durable cathode materials for lithium-ion batteries

Abstract

Rechargeable lithium-ion batteries (LIBs) present an urgent demand to develop cathode materials that combine high-energy and high-power density with long cycle life. For meeting the demand, dual ligands (ammonia and oxalate anion) by hydroxide coprecipitation have been introduced to prepare spherical precursors for the above desired cathode in our previous study, in which low efficiency, toxic and volatile ammonia is still utilized as one of the ligands and an inert atmosphere is needed due to the high content of Mn. Thus, in this work, the feasibility of using the oxalate anion as a single ligand by carbonate coprecipitation for Li-rich layered oxides is investigated. Consequently, they deliver a high volumetric energy density of about 2000 W h L⁻¹, a high-power density of over 940 W h L⁻¹ at a current density of 1000 mA g⁻¹, and superior cycling stability with a capacity retention of 98.1% after 80 cycles, indicating much better performances than the Li-rich oxides prepared via the ammonia ligand. Also, their performances approach the level for the sample prepared via dual ligands. The enhanced properties are likely ascribed to the smaller primary particles and the possibly suppressed phase transformation from layered to spinel phases due to a large amount of stacking faults, lower cation mixing and higher Mn oxidation state according to SEM, TEM, XRD and XPS experiments. These findings demonstrate that the oxalate anion is a desired ligand to prepare Li-rich layered oxides as high-energy, high-power and durable cathode materials for LIBs.