Study On The Rechargeable Lithium Manganese Coin Cells

Lithiated manganese dioxide(Li_xMnO₂) was synthesized by melt-impregnation method using LiNO3 and treated EMD as raw materials. The morphology and structure were characterized by SEM, XRD, and particle size analysis, and the electrochemical properties were evaluated by constant-current charge/discharge cycling test. The effects of heat-treatment and acid-treatment on the properties of Li_xMnO₂ were systematically investigated. The cycling performance of the rechargeable 1ithium manganese coin cells using Li_xMnO₂ as cathode and lithium as anode was also studied.Li_xMnO₂ was synthesized by melt-impregnation method using LiNO3 and heat-treated EMD at 400℃for 10h as raw materials. Through single-factor experiment, sintering temperature, time and Li/Mn molar ratio were assessed, using the initial five discharge capacities as indicators, to achieve the optimal synthesis conditions, that is, Li/Mn molar ratio 0.30:1, sintering temperature 320℃and time 15h. It showed an initial discharge capacity of 186.1 mAh·g-1.In order to improve the purity of EMD, acid treatment was used to treat raw EMD. Through the orthogonal experiment of 3 factors and 3 levels, H2SO4 concentration, bathing temperature and reaction time were accessed, using the initial discharge capacity at 0.2C rate as indicator, the best acid treatment conditions of EMD were determined, that is, H2SO4 concentration 2mol·L-1, bathing temperature 30℃, reaction time 4h. It showed an initial discharge capacity of 186.7 mAh·g-1.Rechargeable lithium manganese coin cells were assembled by using Li_xMnO₂ prepared under optimal heat-treatment and acid-treatment conditions, lithium as anode, and LiPF6-EC/DMC(v:v=1:1) as electrolyte. This cell showed little capacity degradation after 300 cycles at 20%DOD and 3000 cycles at 5%DOD, respectively, exhibiting excellent cycling performance.