Synthesis and Processing of High Capacity, High Cycle life and High Discharge Rate Defective Manganospinel films for Rechargeable batteries

Abstract

AbstractSignificant effort to develop a robust rechargeable battery has been put in the past two decades. The efforts were mainly focused on developing rechargeable battery systems which exhibit high capacity, long cycle life and high discharge rate capabilities. LiMn2O4 based cathodes have been researched extensively as they are not only economical but also environmentally desirable. Research includes composition and doping variation, formation of novel phases and microstructural tailoring, but none of the material modifications have successfully satisfied all the above mentioned performance criteria. In this paper we show a correlation between processing parameters, microstructure and electrochemical performance of Li-Mn-O cathode films. In addition we discuss the formation of metastable oxygen-rich lithium manganospinels, using a unique ultraviolet assisted deposition process. These defective films exhibit high capacity (> 230 mAh/gm), long cycle life (less than 0.05 % capacity loss per cycle for the first 700 cycles), and high discharge rates (> 25 C for 25 % capacity loss). The long cycle life and high capacity was attributed to the ability to cycle the Mn+ valence to less than 3.5 without onset of Jahn-Teller structural transformation, while the high discharge rate was attributed to the extremely high diffusivity of Li+ in the defective Li1-δMn2-2δO4 phase.