Stable surface construction of the Ni-rich LiNi0.8Mn0.1Co0.1O2 cathode material for high performance lithium-ion batteries

Abstract

The nickel-rich layered material LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) is a promising candidate cathode material for next generation lithium-ion batteries due to its high energy density and relatively low cost. Unfortunately, NCM suffers from capacity fading upon cycling and poor rate capability that seriously limit its wide application. To overcome these drawbacks, we present an effective inorganic coating strategy for a complex Li_xNi_1−yFe_yO₂&NiFe₂O₄ (LNFO&NFO) in situ surface modified NCM cathode material by a sample wet-chemical method, which could effectively stabilize the layer structure and eliminate lithium impurities. As a result, LNFO&NFO surface modified NCM shows excellent electrochemical performance. For example, the optimized NFO-2 cathode not only shows an excellent rate performance with a discharge capacity of 140.56 mA h g⁻¹ at 10C, but also exhibits outstanding cycling stability with an improved capacity retention of 87.43% and 74.32% at 1C after 250 and 100 cycles at room and elevated temperatures of 25 and 55 °C. The superior electrochemical performance is attributed to the dual functions of NiFe₂O₄ modification. The formed LNFO&NFO coating layer bonds with the surface oxygen vacancies of the bulk material which could effectively stabilize the surface structure and bulk structure associated with capacity degradation as well as the electrical and ionic conductivity at the interface. Therefore, ingenious design of the LNFO&NFO surface coating layer is a key approach for improving the durability of the NCM cathode material during the cycling process.