Constructing heterostructured Li-Fe-Ni-Mn-O cathodes for lithium-ion batteries: effective improvement of ultrafast lithium storage.

Abstract

Surface modification is proved to be an effective strategy to improve the power density of lithium-ion batteries (LIBs) applied in electric vehicles. In this article, a protective modification layer (FeF3/LiF) is successfully deposited onto the surface of a low-cost cathode material, Li6/5[Fe1/10Ni3/20Mn11/20]O2, for realizing the improvement of ultrafast lithium storage. The reversible specific capacity and ultrahigh rate capability are effectively improved. The modified sample can achieve a higher reversible discharge specific capacity of 171.8 mA h g-1 at 0.2C. A discharge specific capacity of 150.4 mA h g-1 is delivered at 1C after 60 cycles. Even at 2C and 5C, the discharge specific capacities are still maintained at 135.7 and 124.5 mA h g-1. Notably, when charged and discharged at 20C, a discharge specific capacity of 73.4 mA h g-1 can be achieved after 200 cycles by the heterostructured Li-Fe-Ni-Mn-O cathode, almost twice that of the bare material. The good fast lithium storage capability can be ascribed to the effective suppression of interfacial side reactions, the conversion reaction from the FeF3 phase, and the harmonious coexistence of layered and spinel phases. The triple benefits from the heterostructured cathode provide a promising route for constructing advanced LIBs.