Preparation and Performance of the Heterostructured Material with a Ni-Rich Layered Oxide Core and a LiNi0.5Mn1.5O4-like Spinel Shell.

The LiNi1- x- yCo xAl yO2 (NCA)-layered materials are regarded as a research focus of power lithium-ion batteries (LIBs) because of their high capacity. However, NCA materials are still up against the defects of cation mixing and surface erosion of electrolytes. Herein, a novel design strategy is proposed to obtain a heterostructured cathode material with a high-capacity LiNi0.88Co0.09Al0.03O2 layer ( R3̅ m) core and a stable LiNi0.5Mn1.5O4-like spinel ( Fd3̅ m) shell, which is prepared through spontaneous redox reaction of the precursor with KMnO4 in an alkaline solution and subsequent calcination procedure. The structure, morphology, element distribution, and electrochemical performances of the as-prepared NCA are studied by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical techniques. The results show that the LiNi0.5Mn1.5O4-like spinel ( Fd3̅ m) shell layer with a robust cubic close-packed crystal structure is uniformly adhered to the surface of the NCA and can availably suppress the side reactions with the electrolyte and surface-phase transformation, which will facilitate insertion/extraction of Li+ ions during cycling. Benefiting from the enhanced structural stability and improved kinetics, the heterostructured NCA delivers a better cycling performance. The discharge specific capacity is as high as 153.7 mA h g-1 at 10 C, and even at high charge voltage of 4.5 V, the capacity retention can still increase 11% at 1 C (200 mA g-1) after 100 cycles. Besides, the material exhibits a prominent thermal stability of 248 °C at 4.3 V. Therefore, this novel structure design strategy can contribute to the development and commercialization of high-performance cathode materials for power LIBs.