Near-Equilibrium Control of Li2TiO3 Nanoscale Layer Coated on LiNi0.8Co0.1Mn0.1O2 Cathode Materials for Enhanced Electrochemical Performance. 
Ni-rich layered metal oxide of LiNi0.8Co0.1Mn0.1O2 is a promising cathode material for next-generation lithium ion batteries because of its capability to deliver a high capacity; however, intrinsic problems, especially the side reactions between Ni4+ ions and the electrolyte, adversely affect its electrochemical and thermal stability.  Surface coating by a protective and Li+-conducting Li2TiO3 layer is a strategic approach to remit those problems.  The normal deposition strategies depend on the hydrolysis of titanium alkoxides, making it difficult to control the reaction equilibrium.  Herein we report a near-equilibrium deposition tactic to achieve a uniform Li2TiO3 nanoscale layer coated on the surface of LiNi0.8Co0.1Mn0.1O2 microspheres to improve electrochemical performance and thermal stability.  With pH modulation and BO33- scavenger in the (NH4)2TiF6 precursor solution, the ion product for the coating layer is controlled to be slightly bigger than its solubility product.  The hydrolysis reaction chemistry can thus be manipulated at a near-equilibrium condition.  Within the critical pH range of 4.8-5.2, a uniform coating layer of Li2TiO3 with the thickness of about 4 nm can be successfully deposited on the surface of the LiNi0.8Co0.1Mn0.1O2 cathode material, which greatly enhances its capacity retention to 93.5% after 200 cycles at 0.5 C. The appropriate Li2TiO3 coating can increase the mobility of Li ions and suppress the side reactions between electrolytes and cathode materials, which further makes the modified cathode display the higher peak temperature in differential scanning calorimetry analysis and capacity enhancement at 60 °C, which are related to safety concerns.