Surface modification of Li-rich layered Li(Li0.17Ni0.25Mn0.58)O-2 oxide with Li-Mn-PO4 as the cathode for lithium-ion batteries

Enhancement of the discharge capacity, high-rate capability, and cycle stability of the Li-rich layered Li(Li0.17Ni0.25Mn0.58)O-2 oxide with a large specific capacity is highly significant for high energy lithium-ion batteries. In this work, the Li-rich layered Li(Li0.17Ni0.25Mn0.58)O-2 oxide is prepared by a spray-drying method. The surface modification with the Li-Mn-PO4 is introduced onto Li-rich layered Li(Li0.17Ni0.25Mn0.58)O-2 oxide for the first time. It is demonstrated that the surface of Li(Li0.17Ni0.25Mn0.58)O-2 grains is coated with the thin amorphous Li-Mn-PO4 layer (5 wt%). With increasing calcination temperature after the surface coating, a strong interaction can be induced on the interface between the amorphous Li-Mn-PO4 layer and the top surface of Li(Li0.17Ni0.25Mn0.58)O-2 grains. As anticipated, the discharge capacity and high-rate capability are obviously improved for the Li-Mn-PO4-coated sample after calcination at 400 degrees C, while excellent cycle stability is obtained for the Li-Mn-PO4-coated sample after calcination at 500 degrees C as compared with the as-prepared Li(Li0.17Ni0.25Mn0.58)O-2 oxide during cycling. Apparently, the interface interaction between the amorphous Li-Mn-PO4 layer and the top surface of Li(Li0.17Ni0.25Mn0.58)O-2 grains is responsible for the improvement of the reaction kinetics and the electrochemical cycle stability of Li-Mn-PO4-coated samples.