Three in One: Preparation of High-Performance High-Voltage\nLiCoO<sub>2</sub> Cathodes via Introducing High Concentrations of\nMg Ions

Lithium\ncobalt oxide (LCO) is widely used in the 3 C field due\nto its noteworthy volumetric and gravimetric energy densities. Howbeit,\nirreversible phase transitions and lattice oxygen oxidation may engender\nduring the state of deep lithium removal, limiting the application\nof high-energy-density batteries. Here, a MgO-coated LCO material\n(LM1CM2O) with Mg atom-substituted Li and Co atoms is achieved via\nthe rapid solvothermal and high-temperature calcination method. The\nresults, ex situ and in situ characterizations, and DTF calculation\nconfirmed that the introduction of Mg ions enhanced the structural\nstability and interface characteristics of LM1CM2O. The cycling performance\nshowed that capacity retentions are 91.36, 86.73, and 82.62% after\n100, 200, and 300 cycles (3.0–4.6 V) and 65.90% after 100 cycles\n(3.0–4.7 V) at a rate of 1 C, respectively. The improvement\ncan be attributed to the substitution of Mg into Co and Li sites,\neffectively regulating oxidation products of oxygen ions and enhancing\nthe structure stability, and the MgO coating layer increases the interface\nstability when charging at high charge voltage (≥4.6 V).