Surface modification of Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2oxide 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(Li_0.17Ni_0.25Mn_0.58)O₂ oxide with a large specific capacity is highly significant for high energy lithium-ion batteries. In this work, the Li-rich layered Li(Li_0.17Ni_0.25Mn_0.58)O₂ oxide is prepared by a spray-drying method. The surface modification with the Li–Mn–PO₄ is introduced onto Li-rich layered Li(Li_0.17Ni_0.25Mn_0.58)O₂ oxide for the first time. It is demonstrated that the surface of Li(Li_0.17Ni_0.25Mn_0.58)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(Li_0.17Ni_0.25Mn_0.58)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(Li_0.17Ni_0.25Mn_0.58)O₂ oxide during cycling. Apparently, the interface interaction between the amorphous Li–Mn–PO₄ layer and the top surface of Li(Li_0.17Ni_0.25Mn_0.58)O₂ grains is responsible for the improvement of the reaction kinetics and the electrochemical cycle stability of Li–Mn–PO₄-coated samples.