Improving the electrochemical performance of layered lithium-rich cathode materials by fabricating a spinel outer layer with Ni3+

Surface modification and fabrication of composite structures have been reported to be efficient strategies to obtain cathode materials with satisfactory electrochemical performance. Herein, a combined method to fabricate an oxidized spinel outer layer containing Ni3+ is demonstrated to be an effective method to improve the rate capability as well as cyclability of Li-rich cathode materials. Such a surface modification process is carried out through a facile treatment with ammonium persulfate, and a homogeneous layered-spinel structure is thus obtained, which contains intimately connected layered bulk and an oxidized spinel outer layer. The thus-obtained material delivers a charge/discharge capacity of 330.5/308.7 mA h g(-1), with an enhanced coulombic efficiency up to 93.4% and a rather fascinating rate capability of 169.1 mA h g(-1), 100.8 mA h g(-1), and 68.2 mA h g(-1) at 10 C, 20 C and 30 C, respectively, and a much superior cycle performance, which is a stable capacity with no fading after prolonged 200 cycles.