The Intercalation Potential Of The Electrode Materials For Lithium Ion Battery With Spinel Structures: A First Principles Study

The safety problem and the quantity demanded of energy density for the lithium ion battery are closely related the voltage of batteries,and the value of voltage decide to delithium/lithium potential of electrode materials.The potential of electrode materials influence the choice of electrolyte materials,it requires the charge/discharge potential of electrode materials should be located in window of the electrochemical electrolyte materials.The current commercial electrode materials are mainly organic electrolytes,while these kinds of electrolyte hidden trouble in safety.Energy density of lithium batteries is the product of potential and lithium capacity,the demands of market for energy density also ask for the high potential value of electrode materials.Chemically,the potential of electrode materials are decided by the redox potential of materials,while it can’t clearly explain that the element present different potential value in different structure of materials.Physically,it recognized that the potential depend on the change of Gibbs free energy before and after lithium extraction where the Gibbs free energy decides by structure,element and component of materials,but these effects how to influence the potential isn’t clear.Theoretically analyzes the potential of the battery,it is significance sums up the relationship between material potential value and the structure to further develop lithium ion batteries.In this study,we systematically studied the intercalation potential of the different spinel-type electrode materials for lithium ion battery by first principle calculations.The results show that the value of potential determined by valence electronic distribution of the valence-variable elements in the crystal field.First of all,we analyse the spinel and anti-spinel type electrode material LiM₂O₄（M=Mn,Co）,find the change of Fermi energy level during the delithiated/lithiated process determined the potential value of materials.For the redox of the same transition metal,the d-orbit electron shows different distribution in different crystal field,then the Fermi energy level have different reduce/increase degree,the potential value is different,and the same crystal field shows the same d-orbit electron distribution,then the reduce/increase of Fermi energy level are close,the voltage value roughly equal.Moreover,for the different transition metal,the voltage value also related to the reduce/increase level of Fermi energy.Next,we compare the spinel type LiNi0.5Mn1.5O4 and LiNi₂O₄ with LiMn₂O₄,it is hard to explain that thedelithium/lithium potential of LiMn₂O₄ lower than the former from the Fermi energy movement,the reason is that the redox potential of Ni is much higher than the Mn.