Effect of Modified Li2MnO3 on Electrochemical Properties of Li-Rich Composite Layered Cathode

Abstract

xLi2MnO3-(1-x)LiMO2(M = Mn, Ni, Co, etc.) is a general formula representing composite layered cathode materials. Interestingly, this cathode exhibits surprisingly high reversible capacity and receives great attention for practical applications. Li2MnO3 is known to play an important role of providing extra Li source for stabilizing the layered structure. For single phase Li2MnO3, it shows limited capacity during charging/discharging reaction. Furthermore a characteristic 1st charging plateau corresponding to the extended capacity contribution from oxygen release in Li2MnO3. Accordingly, such oxygen release also causes the formation of oxygen defects (vacancies) and may cause the instability of Li2MnO3. Thus, the performance of Li-rich composite oxides cathode with layered structure is highly influenced by the electrochemical properties of Li2MnO3 Therefore, the main objective of this study is (i) to modify the electronic defects of Li2MnO3 through changing pO2, (ii) to add dopants to introduce more electrons to Li2MnO3 for better conduction, (iii) to assemble and test cells using Li2MnO3 as the cathode and Li metal as the anode, (iv) to characterize and understand the electrochemical properties of Li2MnO3. In this study, Li2MnO3 are prepared using sol gel/solid state reaction processes and treated by dopant addition and reducing atmospheres. Impedance of Li2MnO3 is measured using Electrochemical Impedance Spectroscopy (EIS). XRD analysis and SEM observation are performed for synthesized Li2MnO3 particles. A full cell based on Li/ Li2MnO3 and Li/ 0.5Li2MnO3-0.5LiMO2 using treated Li2MnO3 will be assembled and tested.