A New Type of Ni-Rich Cathode for High-Energy Lithium-Ion Batteries

Abstract

Lithium-ion batteries (LIB) have become the main power source for electric vehicles (EVs). To satisfy a driving range threshold of 300 miles per single charge, strong demand for the higher energy density of LIBs has mandated the development of advanced cathode materials, which largely determine the capacity of LIBs. Currently, Archetypal cathodes deployed in current EVs, layered Li[NixCoy(Al or Mn)1−x−y]O2 (Al = NCA or Mn = NCM) oxide materials, has achieved the best performances for commercialization. However, these cathodes are still insufficient to meet the requirement of the energy density for EVs, which weaken the competitiveness of the driving range compared to that of internal combustion engine vehicles.1 Ni-enriched NCM and NCA cathode materials, delivering ever-closer to their theoretical specific capacity, come to the fore with a gradual increase of Ni content up to more than 90%. Although Ni-rich NCA and NCM cathodes are adequate to provide the required driving range, increasing Ni content largely compromises battery lifetime and thermal stability due to rapid capacity fading and an abundance of unstable Ni4+ species, as observed in LiNiO2.2,3 It has recently been shown that microcracks develop from anisotropic volume changes during charging of the Ni-rich NCM cathodes, which compromises the mechanical stability of the cathodes and aggravates chemical degradation due to an electrolyte attack.To overcome these inherent instabilities of Ni-rich NCM and NCA cathodes, we propose a new type of layered oxide cathode, Li[NixCoyW1−x−y]O2. In this study, we show that replacement of Al ions with W ions in a Ni-rich NCA layered oxide cathode markedly modifies the cathode microstructure through particle refinement and greatly improves the cycling stability of the cathode. We demonstrate its superior structural and thermal stability compared to the commercialized NCA cathode. References D. Andre, S.-J. Kim, P. Lamp, S. F. Lux, F. Maglia, O. Paschos and B. Stiaszny, J. Mater. Chem. A 2015, 3, 6709.H.-H. Ryu, K.-J. Park, C. S. Yoon and Y.-K. Sun, Chem. Mater. 2018, 30, 1155.G. W. Nam, N.-Y. Park, K.-J. Park, J. Yang, J. Liu, C. S. Yoon and Y.-K. Sun, ACS Energy Lett. 2019, 4, 2995.