Synthesis and cathode properties of a cubic rocksalt-type Si-doped Li2NiTiO4 for lithium-ion batteries

Li2NiSixTi1−xO4 was obtained by the sol-gel method under ambient pressure in the whole 0 ≤ x ≤ 0.2 regions. The lattice constant did not change, but the crystallinity decreased by increasing the Si doping level. The discharge capacities at the rate of 0.32 mA g−1 for the obtained Li2NiTiO4 and Li2NiSi0.1Ti0.9O4 were 153.4 mAh g−1 and 145.5 mAh g−1, respectively. The energy densities of the Li2NiTiO4 (598 mWh g−1) and Li2NiSi0.1Ti0.9O4 (567 mWh g−1) obtained at the rate of 0.32 mA g−1 were equivalent to that of LiCoO2. Moreover, the discharge capacities of Li2NiTiO4 and Li2NiSi0.1Ti0.9TiO4 remained at 57.1 mAh g−1 and 75.6 mAh g−1 even after 20 cycles, respectively. In addition, the framework of Li2NiTiO4 and Li2NiSixTi1−xO4 was stable enough to maintain its charge-discharge processes at the first cycle by expansion and contraction of the lattice accompanying the extraction/insertion of lithium.