Comprehensive Electrochemical, Calorimetric Heat Generation and Safety Analysis of Na$_{0.53}$MnO$_{2}$ Cathode Material in Coin Cells

The sodium ion cells were assembled by using Na$_{0.5}$3MnO$_{2}$ as cathode material, pure sodium metal as anode in case of half coin cells and coconut shell-derived hard carbon in case of full coin cells. Cyclic voltammetry, galvanostatic charge-discharge, and self-discharge analysis were conducted. A good rate capability, capacity retention, coulombic efficiency (99.5%), reproducibility and reversible Na-ion intercalation revealed a satisfactory performance of this cathode material. The safety related parameters including the heat generation during charging-discharging and thermal abuse tests have been executed by the means of sophisticated calorimetry instruments. It was observed that during the charging process less heat was generated than during discharging process. The exothermic reactions during thermal runaway were identified by using an accelerating rate calorimeter and pressure measurements during this thermal abuse test were performed as well. The thermal runaway of full coin cells occurred beyond 190 °C with a temperature rate (dT/dt) of 2.5 °C min$^{−1}$. Such detailed analysis of heat generation and thermal abuse helps finding new and quantitative correlations between different critical thermal and safety related issues in future post Li batteries that are a prerequisite for the design of safer batteries, the safe upscaling and for the adaptation of the thermal management system.