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What is the essence of the average voltage of lithium batteries? How to improve?

Generally speaking, the higher the specific capacity of the electrode, or the higher the average battery voltage, it is undoubtedly beneficial to the improvement of battery energy density. where the average cell voltage is determined by the free enthalpy of the lithium-ion exchange reaction, which includes the intercalation and disengagement of the lithium ions on the active electrode material. For ordinary cathode materials, the electrode reaction appears to be a redox reaction at first glance, however, this view does not take into account the interaction of electrons and ions in the material. It is because of these interactions that the electronic state of the transition metal ions involved in the reaction depends on the degree of lithium ion intercalation.

In view of the lack of understanding of the average voltage of batteries in traditional methods, in this paper, Professor Wolfram Jaegermann of the Technical University of Darmstadt, Germany, proposes a new method to analyze the average electrode potential of batteries. As shown in the figure above, the schematic diagram of the Fermi level and the density of states (DOS) of the electrode can be seen that under normal conditions, the Fermi level of the cathode material is located in the TM-3d derivative band and moves with the change of the charge state, and its displacement is related to the corresponding displacement of the electrochemical potential. However, the information obtained from this diagram alone is also incomplete, as it does not take into account the difference between the lithium-ion chemical potential in lithium metal and other anodes.