High‐Energy Ni‐Rich Cathode Materials for Long‐Range and Long‐Life Electric Vehicles
Been Namkoong, Nam‐Yung Park, Geon‐Tae Park, Ji‐Yong Shin, Thorsten Beierling, Chong Seung Yoon, Yang‐Kook Sun
Abstract
Abstract Li‐ion batteries (LIBs) in electric vehicles (EVs) are usually operated intermittently and maintained at high states of charge (SoCs) for long periods. Because the internal particles of Ni‐rich cathodes are easily exposed to the electrolyte at high SoCs owing to mechanical instability, the electrolyte exposure time—during which highly reactive Ni 4+ ions react with the electrolyte—critically affects the degradation of the cathode. Here, 1 mol% B doping of a core–shell concentration gradient (CSG) Li[Ni 0.88 Co 0.10 Al 0.02 ]O 2 cathode (CSG‐NCA88) is shown to dramatically alter the microstructure of the cathode and effectively protect the particle interior from parasitic electrolyte attack. The B‐doped CSG‐NCA88 cathode, CSG‐NCAB87, maintains its original microstructure even after holding for 500 h in the fully charged state, whereas irreversible structural damage occurs in the pristine CSG‐NCA88 cathode during the prolonged electrolyte exposure. The long‐term cycling results confirm that the capacity retention of the cathodes is determined by the electrolyte exposure time at a high SoC and that microstructural modification can effectively suppress the time‐dependent degradation from electrolyte attack. The proposed CSG‐NCAB87 cathode can be utilized at full capacity without restricting the SoC, thus realizing the development of economical high‐energy‐density LIBs.