Sol/Antisolvent Coating for High Initial Coulombic Efficiency and Ultra-stable Mechanical Integrity of Ni-Rich...

The Ni-rich cathode holds great promise for high energy density lithium-ion batteries because of its high capacity and operating voltage. However, crucial problems such as cation disorder, structural degradation, side reactions, and microcracks become serious with increasing nickel content. Herein, a novel and facile sol/antisolvent coating modification of Ni-rich layered oxide LiNi_0.85Co_0.1Mn_0.05O₂ (NCM) is developed where we use ethanol to disperse the nanosized LiBO₂ to form the sol and adopt tetrahydrofuran (THF) as antisolvent to prepare the cluster of nanoparticles to be coated on the surface of NCM. The coating thickness can be tuned through the THF addition amount. The LiBO₂ nanorod deposition is formed as well over the crack of the NCM cathode, likely acting as a patch to repair the original defect of the intrinsic crack. The uniform LiBO₂ nanospherical particle coating together with LiBO₂ nanorod wrapping provides a double protection against electrolytes. Compared with the raw material, LiBO₂-coated LiNi_0.85Co_0.1Mn_0.05O₂ (LiBO₂-coated NCM) exhibits a high initial Coulombic efficiency of 90.3% at 0.2 C between 2.8 and 4.3 V vs Li⁺/Li, a superior rate capability, enhanced fast charge property at 3 C, and restricted microcrack formation. This simple in-site modification and repairing technology guarantees a good mechanical integrity of the polycrystalline Ni-rich cathode.