Building nickel-rich cathodes with large concentration gradient for high performance lithium-ion batteries

The construction of Nickel-rich layered oxide cathodes with concentration gradient structure (FCG) is still a tough challenge due to the adverse thermal-induced diffusion of the transition metal ions (TM) during sintering process. Here a series of full concentration gradient Li[Ni0.8Co0.1Mn0.1]O2 (FCG811) cathode materials with TiO2-regulation is constructed and studied. The introduction of TiO2 could effectively block the interdiffusion of TM in FCG811, and thus a large evolution of the composition from the central Li[Ni0.91Co0.06Mn0.03]O2 to the surficial Li[Ni0.55Co0.16Mn0.29]O2 is achieved. The larger gradient enables the FCG cathodes with higher electrochemical stability and smaller internal strain at highly charged state. In addition, the Ti4+ doping is also acquired, which is favorable for the structural durability of the NCM cathodes. As a result, the FCG811 with TiO2 incorporation displays high capacity of 169 mAh g−1, with 96% retention after 150 cycles, which is 18% higher than that of the conventional FCG811. Structural and compositional characterizations (i.e., in-situ XRD, EIS, XPS and HRTEM) further reveal the electrochemical mechanism and kinetics of the designed FCG811-TiO2 cathode.