High-Performance Li(Li0.18Ni0.15Co0.15Mn0.52)O2@Li4M5O12 Heterostructured Cathode Material Coated with a Lithium Borate Oxide Glass Layer

The continuous phase transformation to spinel LiMn2O4 seriously hinders the electrochemical properties of Li-excess layered oxides in lithium ion batteries. Herein, we prepared a heterostructured Li-excess layered cathode material consisting of a Li(Li0.18Ni0.15Co0.15Mn0.52)O-2 active material in conjunction with a surface Li4M5O12 spinel and a Li2O-LiBO2-Li3BO3 glass coating layer. The material showed improved electrochemical kinetic properties with respect to its pristine counterpart because the Li2O-LiBO2-Li3BO3 glass layer not only improved the ionic conductivity of the material but also depressed the side reactions of the electrode with the electrolyte. In addition, the surface Li4M5O12 spinel constantly grew inward the bulk of the material during long-term charge discharge cycling instead of the conventional LiMn2O4 transformation for the pristine Li(Li0.18Ni0.15Co0.15Mn0.52)O-2. As a result, the heterostructured cathode material showed overall improved electrochemical performance. An initial discharge capacity of 258.8 mAh g(-1) was obtained at the 0.2 C rate with remarkable capacity retention of 92.2% after 100 cycles. Moreover, the material showed excellent rate capacity delivering a high discharge capacity of 130.4 mAh g(-1) and 100.4 mAh g(-1) at the 10 and 20 C rates, respectively. Differential scanning calorirnetry showed that the exothermic temperature of the fully charged electrode was elevated to 324.2 degrees C with little thermal release of 232.5 J g(-1), demonstrating good thermal safety of the material.