Improved High-Voltage Stability of NCM523 Cathode Using Functional Electrolyte Additive

Abstract

Advanced portable electronics, electric vehicles and grid-based energy storage systems demand higher energy density Li-ion batteries than conventional ones as power sources. The energy density of Li-ion batteries can increase by increasing the specific capacity of cathode material, which can increase by raising the charge cut-off voltage. Among various cathode materials, nickel-rich three-components layered oxides of Li(Ni1-x-yCoxMny)O2 (NCM, 1-x-y ≥ 0.5) have been considered as prospective candidates for high-energy density Li-ion batteries because of higher capacity and lower cost than Ni-lean oxides. However, their high-voltage performance is difficult to achieve due to limited anodic stability of conventional electrolyte above 4.2 V vs. Li/Li+ and instability of cathode material at highly charged state. Under such an aggressive charge condition, cathode-electrolyte interfacial reactions often cause a degradation of cathode material and electrolyte consumption by oxidative decomposition of electrolyte, resulting in a rapid performance fade.1-3 We have demonstrated that the use of high-voltage electrolyte additive(s) is efficient and economic because they in situ form a surface protective layer at the cathode during high-voltage cycling, and improve the interfacial stability and cycling performance.1-3 Here we report the development of phosphorus-based additive for the NCM523 cathode to the charge cut-off voltage of 4.6 V. X-ray photoelectron spectroscopic and infrared spectroscopic studies on cathode-electrolyte interfacial phenomena and their correlation to cycling performance would be discussed in the meeting. Acknowledgements This research was supported by Ministry of Trade, Industry & Energy (R0004645) and Creative Human Resource Development Consortium for Fusion Technology of Functional Chemical/Bio Materials of BK Plus program by Ministry of Education of Korea.