Three in One: Preparation of High-Performance High-Voltage LiCoO₂ Cathodes via Introducing High Concentrations of Mg Ions

Lithium cobalt oxide (LCO) is widely used in the 3 C field due to its noteworthy volumetric and gravimetric energy densities. Howbeit, irreversible phase transitions and lattice oxygen oxidation may engender during the state of deep lithium removal, limiting the application of high-energy-density batteries. Here, a MgO-coated LCO material (LM1CM2O) with Mg atom-substituted Li and Co atoms is achieved via the rapid solvothermal and high-temperature calcination method. The results, ex situ and in situ characterizations, and DTF calculation confirmed that the introduction of Mg ions enhanced the structural stability and interface characteristics of LM1CM2O. The cycling performance showed that capacity retentions are 91.36, 86.73, and 82.62% after 100, 200, and 300 cycles (3.0–4.6 V) and 65.90% after 100 cycles (3.0–4.7 V) at a rate of 1 C, respectively. The improvement can be attributed to the substitution of Mg into Co and Li sites, effectively regulating oxidation products of oxygen ions and enhancing the structure stability, and the MgO coating layer increases the interface stability when charging at high charge voltage (≥4.6 V).