Development of Cathode Materials of Lithium-Ion Secondary Batteries for High Energy and Safety

Abstract

As a consequence of shortage of fossil fuels, development of electrified vehicles (EVs) has further raised the performance requirements of rechargeable battery system. The research and development efforts in meeting these challenges have focused on identifying and designing new cathode materials with capacity higher than 200 mAh g −1 and improved safety characteristics. In order to improve the thermal and structural stability of the Ni-rich layered cathode materials, cathodes enriched in Mn at the outer layer were proposed to suppress the undesired Ni 4+ reduction because Mn 4+ is naturally stable (MnO2 is a stable compound) and does not participate in the redox reaction during the charge and discharge cycle. Recently, we developed a high-energy cathode material with not only full concentration gradient materials but also two-sloped full concentration gradient materials, in which the Ni concentration decreases and the Mn concentration increases toward the particle surface. These cathode materials are synthesized via a specially designed batch-type reactor. The cathode delivers high discharge capacity with excellent capacity retention. The cathode materials exhibits the best cycling stability, rate capability, and thermal stability compared to conventional cathode (CC) and Li[Ni0.8Co0.15Al0.05]O2 (NCA). While the chemical partitioning of the composition generated the observed high capacity and thermal stability, the unique microstructure of the FCG secondary particle provided excellent cycle stability and rate capability.