Improved cycling stability of high nickel cathode material for lithium ion battery through Al- and Ti-based dual modification

Abstract

The high nickel layered oxide cathode is considered to be one of the most promising cathode materials for lithium-ion batteries because of its higher specific capacity and lower cost. However, due to the increased Ni content, residual lithium compounds inevitably exist on the surface of the cathode material, such as LiOH, Li₂CO₃, etc. At the same time, the intrinsic instability of the high nickel cathode material leads to the structural destruction and serious capacity degradation, which hinder practical applications. Here, we report a simple and scalable strategy using hydrolysis and lithiation process of aluminum isopropoxide (C₉H₂₁AlO₃) and isopropyl titanate (C₁₂H₂₈O₄Ti) to prepare a novel α-LiAlO₂ and Li₂TiO₃ double-coated and Al³⁺ and Ti⁴⁺ co-doped cathode material (NCAT15). The Al and Ti doping stabilizes the layered structure due to the strong Al–O and Ti–O covalent bonds and relieves the Li⁺/Ni²⁺ cation disorder. Besides, the capacity of the cathode material for 100 cycles reaches 163.5 mA h g⁻¹ and the capacity retention rate increases from 51.2% to 90.6% (at 1C). The microscopic characterization results show that the unique structure can significantly suppress side reactions at the cathode/electrolyte interface as well as the deterioration of structure and microcracks. This innovative design strategy combining elemental doping and construction of dual coating layers can be extended to other high nickel layered cathode materials and help improve their electrochemical performance.