Trace-amount triple-doping of Ti, Mg, and B for improving the stability of lattice structure and discharge capacity of LiCoO2 at 4.6V

Lithium cobaltate (LiCoO2) is the favored cathode material due to its exceptional volumetric energy density. An effective approach to enhancing the energy density of lithium-ion batteries is to elevating the operating voltage of LiCoO2. However, lithium cobalt oxide will experience unfavorable phase transitions from O3 phase to H1–3 phase, as well as irreversible oxygen oxidation reactions at high voltages, which deteriorate its electrochemical performance. Here, we propose a triple-doping strategy involving metal elements Ti, Mg, and non-metal elements B. Introducing Mg and Ti into the LiCoO2 lattice not only suppress hazardous phase transitions during high-voltage cycling, but also enhance surface lattice oxygen stability and prevent the escape of lattice oxygen during high voltage cycling. Moreover, it increases the c-axis spacing, which improve the diffusion rate of Li+ ions during cycling. The B doping helps metal elements Mg and Ti better diffuse into the particle interiors, while reducing the size of LiCoO2 particles. After Ti-Mg-B triple-doping, the LiCoO2 cathode material has an initial discharge capacity of 233.7 mAh·g−1 within the range of 3.0 - 4.6 V at 0.5 C, with the residual capacity of 183 mAh·g−1 after 100 cycles. The modified sample still remain a reversible capacity of 94.7mAh·g−1 at a current density of 10 C. Our studied doping strategy significantly improves the cycling stability of LiCoO2 at 4.6 V, while further enhancing the capacity of lithium batteries.