Surface modification of Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 oxide with Li–Mn–PO4 as the cathode for lithium-ion batteries

Abstract

Enhancement of the discharge capacity, high-rate capability, and cycle stability of the Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 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)O2 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)O2 oxide for the first time. It is demonstrated that the surface of Li(Li0.17Ni0.25Mn0.58)O2 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)O2 grains. As anticipated, the discharge capacity and high-rate capability are obviously improved for the Li–Mn–PO4-coated sample after calcination at 400 °C, while excellent cycle stability is obtained for the Li–Mn–PO4-coated sample after calcination at 500 °C as compared with the as-prepared Li(Li0.17Ni0.25Mn0.58)O2 oxide during cycling. Apparently, the interface interaction between the amorphous Li–Mn–PO4 layer and the top surface of Li(Li0.17Ni0.25Mn0.58)O2 grains is responsible for the improvement of the reaction kinetics and the electrochemical cycle stability of Li–Mn–PO4-coated samples.