Basic Electrochemical Performance of Pure LiMnPO4 : a Comparison with Selected Conventional Insertion Materials

摘要

We compare the basic electrochemical performance of a LiMnPO4 battery material with the performance of its much more researched olivine counterpart - LiFePO4. To get a wider picture, we also included another well understood material, LiCoO2. Based on chronopotentiometric (galvanostatic) experiments, we discuss the materials performance in terms of cell energy efficiency and electrode polarization. We propose and justify the use of the "inflection point criterion" for determination of total overpotential (eta(total)). We further demonstrate that the general current-overpotential characteristics can be represented by introducing the total resistance of the cell - R-total. We find consistently that whereas in LCO the general current-overpotential characteristics is more or less linear, there is significant deviation from linearity in LiFePO4 and even bigger in LiMnPO4. The phenomenon is discussed in terms of state-of-the art knowledge about phase transformation phenomena in these materials.