Identifying Challenges and Methods for Mitigation in No-Cobalt LiNiO2 Cathode Materials

Abstract

Cathode materials such as layered oxides play a crucial role in determining the energy density and safety of lithium ion batteries. LiCoO2 based cathode materials, which have been dominating the batteries in portable devices for many years, are facing unique issues, such as high cost and child labor problems in cobalt mining. As an alternative solution, LiNiO2, isostructural to the commercial LiCoO2, extensively explored in the 1990s, has recently attracted renewed attention in quest of extremely low-Co or completely Co-free layered cathodes to reduce the reliance on high-cost toxic Co resource. However, with the high nickel content, the issues such as phase transformations, anisotropically periodic volume changes, highly reactive surfaces, oxygen release, and poor thermal stability have become pronounced. These challenges, associated with the unstable bulk and surface chemistry, have hindered the implementation of LiNiO2 in practical batteries over the last few decades. In this presentation, we will present the multiscale doping strategies in LiNiO2 to improve the electrochemical performance through bulk and surface stabilizer. We will also elaborate our approach to engineer the dopant distribution in individual battery particles. In addition, we systematically investigate how the surface chemistry of LiNiO2 based materials changes with various environments, including human exhalation, sample storage, sample preparation, electrochemical cycling, and surface doping. Our results demonstrate that the surface of these materials is highly reactive and prone to alter at various stages of sample handling and characterizations. We highlight that more efforts should be devoted towards the development of highly stable CEIs either by cathode surface coating, doping, electrolyte modification or combining multiple strategies.