A High Rate Lithium-Rich Layered MNC Cathode with Low Capacity Fade for Li-Ion Batteries

Abstract

We report a new synthesis method, termed self-sustaining combustion reaction, that resulted in a lithium-rich MNC (LLMNC) cathode material with high rate capability and excellent capacity maintenance during cycling compared to the lithium-rich metal oxide cathode materials previously reported in the literature ( 1-4 ). This porous, sponge-like composite metal oxide of the composition, 0.5Li2MnO3. 0.5LiMn0.5Ni0.35Co0.15O2, was characterized by means of its X-ray diffraction (XRD) pattern, FESEM (Field Emission Scanning Electron Microscopy) images and electrochemical data. The interconnected pore structure of the material with enhanced surface properties (figure 1, inset) compared to its previously known counterpart synthesized from the co-precipitation method provides higher rate capability with low capacity fade during long-term cycling.The XRD pattern of the material, with the Li2MnO3 region magnified, presented in Figure 1, perfectly matches with the literature data( 3 ) for the layered Li-rich MNC material of similar composition. We obtained discharge capacities of approximately 300, 250, 200 and 150 mAh/g at C/20, C/4, and C and 2C discharge rates for electrodes having an active material loading of approximately 7 mg/cm2. Remarkably, excellent capacities with practically zero capacity fade has been observed for hundreds of cycles at the C discharge rate as shown in Figure 2 for a Li half-cell cycling between 2-4.9V at room temperature. Detailed structural and electrochemical properties of the material characterized using cyclic voltammetry (CV), XRD, X-ray Absorption Spectrometry (XAS), FESEM and High Resolution Transmission Electron Microscopy (HRTEM) will be discussed.