Enabling LiNi<sub>0.88</sub>Co<sub>0.09</sub>Al<sub>0.03</sub>O<sub>2</sub> Cathode Materials with Stable Interface by Modifying Electrolyte with Trimethyl Borate
Zhenxue Xiao, Shao‐Lun Cui, Yangyang Wang, Sheng Liu, Guoran Li, Xueping Gao
Abstract
As one of the most promising cathode materials in lithium-ion batteries, nickel-rich cathode materials have been widely studied due to their high specific capacity and high operating voltage to realize the energy density of 300 Wh kg –1 . However, the oxidative decomposition of electrolyte catalyzed by transition metal ions and the crack of secondary particles have brought great challenges to their further development. In order to solve this problem, functionalized electrolyte is often used to stabilize the interface and structure of cathode materials. Herein, it is proposed to add trimethyl borate (TMB) in commercial electrolyte to enhance the interfacial stability of LiNi 0.88 Co 0.09 Al 0.03 O 2 cathode material. By adjusting the content of TMB in the electrolyte, it is found that a volume ratio of 10% can achieve the best electrochemical performance. In the voltage range of 3.0–4.3 V, the LiNi 0.88 Co 0.09 Al 0.03 O 2 electrode with the 10% TMB-containing electrolyte can achieve a capacity retention of up to 82% after 300 cycles at 1C rate (1C = 200 mA g –1 ), while the electrode with blank electrolyte is only 61%. Through a systematic analysis toward cycled electrode materials, it is indicated that the cracking degree of secondary particles decreases and a thin, stable, and conductive cathode electrolyte interface film is formed on the electrode with 10% TMB-containing electrolyte. This simple and effective method of improving the interfacial and structural stability of nickel-rich cathode materials via adding TMB in the electrolyte provides a practical strategy for the development of high-performance lithium-ion batteries.