Understanding the Structural and Electrochemical Properties of LiNi0.9Co0.1O2 Ni-Rich Cathode in Lithium Ion Batteries

Abstract

Advances in next generation Li-ion battery technology have been trending towards utilizing Nickel-rich cathode materials. One of the Ni-rich compositions, LiNi0.9Co0.1O2, have the potential to increase energy density while further reducing costs due to the reduced Cobalt content. This composition forms a highly layered structure, which provides superior electrochemical performance. In particular, it showed > 220 mAh/g initial discharge capacity at 0.1C rate but the capacity fades quickly with cycling. The main factors behind this performance deterioration with cycling are structural transformation of the cathode to the rock salt phase, parasitic reactions between the Nickel-rich cathode and electrolyte and gas release. Here, we report physical and electrochemical properties of industrial grade LiNi0.9Co0.1O2 cathode material synthesized by utilizing continuous co-precipitation reaction in a Taylor Vortex Reactor.A thorough investigation of the mechanisms that make this material underperform other similar compositions was performed. In particular, the rate and long term cycling performance of the cathode material in half and full cell configuration were investigated. Synchrotron X-ray diffraction and X-ray absorption spectroscopy (XAS) of pristine and cycled cathodes after long term cycling will be discussed to understand the degradation mechanism. In-situ XAS at Nickel and Cobalt K-edge during the first two initial cycles will be discussed in detail to unravel the local structural changes and redox activity of Ni and Co in LiNi0.9Co0.1O2 cathode. Overall, this presentation will give a detailed understanding of this material’s synthesis, structure-property relationships, chemistry and electrochemical performance, which give new insights into the roles of Co and Mn in Ni-rich cathode materials.