An Ostwald ripening route towards Ni-rich layered cathode material with cobalt-rich surface for lithium ion battery

Abstract

An Ostwald ripening-based route is proposed to prepare Ni-rich layered cathodes with Co-rich surface for lithium-ion batteries (LIBs). Commercially available Ni0.8Co0.1Mn0.1(OH)2 and spray pyrolysis derived porous Co3O4 are used as mixed precursors. During the lithiation reaction process under high-temperature, the porous Co3O4 microspheres scatter primary particles and spontaneously redeposit on the surface of Ni-rich spheres according to Ostwald ripening mechanism, forming the Ni-rich materials with Co-rich outer layers. When evaluated as cathode for LIBs, the resultant material shows ability to inhibit the cation disorder, relieves the phase transition from H2 to H3 and diminishes side reactions between the electrolyte and Ni-rich cathode material. As a result, the obtained material with Co-rich outer layers exhibits much more improved cycle and rate performance than the material without Co-rich outer layers. Particularly, NCM-Co-1 (molar ratio of Ni0.8Co0.1Mn0.1(OH)2/Co3O4 is 60:1) delivers a reversible capacity of 159.2 mA h g−1 with 90.5% capacity retention after 200 cycles at 1 C. This strategy provides a general and efficient way to produce gradient substances and to address the surface problems of Ni-rich cathode materials.