Enhancing the Structural Stability and Electrochemical Performance of High-Nickel Cathode Materials through Ti Doping with an Exothermic Non-oxide Precursor.

ABSTRACT

The foreseeable global cobalt (Co) crisis has driven the demand for cathode materials with less Co dependence, where high-nickel layered oxides are a promising solution due to their high energy density and low cost. However, these materials suffer from poor cycling stability and rapid voltage decay due to lattice displacement and nanostrain accumulation. Here, we introduced an exothermic TiN dopant via a scalable coating method to stabilize LiNi0.917Co0.056Mn0.026O2 (NCM92) materials. The exothermic reaction of TiN conversion generates extra heat during the calcination process on the cathode surface, promotes the lithiation process, and tunes the morphology of the cathode material, resulting in compact and conformal smaller particle sizes to provide better particle integration and lithium diffusion coefficient. Moreover, the Ti dopant substitutes the Ni3+ site to generate stronger Ti-O bonding, leading to higher structural stability and extended cycle life. The Ti-doped NCM (NCM92_TiN) shows a remarkable cycling stability of maintaining 80% capacity retention for 400 cycles, while bare NCM92 can only reach 88 cycles. Furthermore, the NCM92_TiN cathodes demonstrate an enhanced rate capability and achieve a discharge capacity of over 168 mAh g-1 at 5C.