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Advanced energy materials: development history and latest progress of manganese based lithium spinel ion battery cathode

wallpapers News 2020-12-06

Nobel Prize in chemistry in 2019 was awarded to John B. goodenough M. Stanley Whittingham Akira Yoshino for their outsting contributions in the field of lithium ion batteries. Among them Professor goodenough the father of international lithium batteries has developed three kinds of cathode materials with different structures: layered lithium cobalt oxide (1980) spinel lithium manganese oxide (1983) olivine lithium iron phosphate (1997). Layered lithium cobalt oxide layered ternary olivine lithium iron phosphate are the most widely used cathode materials in the market but the use of spinel lithium manganate is relatively limited. This is mainly due to the manganese rich characteristics of LiMn2O4 which leads to the dissolution of manganese the significant Jahn teller effect of Mn3 resulting in the low specific capacity poor cycle performance of LiMn2O4. In the past 30 years researchers have used a variety of methods to improve the performance of lithium manganate including the use of Li Ni2 Mg2 CR2 Al3 Fe3 other single ion or multi ion bulk surface doping the use of oxide fluoride polymer surface coating the control of morphology particle size the use of solid electrolyte to solve the problem of liquid electrolyte Dissolution of manganese in electrolyte. Although these methods effectively improve the capacity cycling performance of spinel LiMn2O4 its energy density is still lower than that of layered ternary materials. However the structure of spinel is superior to that of layered olivine. Spinel (transition metal oxygen) framework has cubic symmetry large vacancy space three-dimensional lithium ion transport channel which has good structure thermal stability deep lithium extraction / insertion potential fast lithium ion transport rate. The great potential of these elements can be realized through their exquisite design spinel.

first of all the phase transition products of "bad spinel" are often observed on the surface of layered materials with high specific energy during cycling which is generally considered to be the main reason for the performance degradation of layered materials. Due to the surface oxygen loss other factors the composition of these "bad spinels" is generally transition metal: oxygen > 0.5 so the valence state of transition metal is low the transition metal occupies the tetrahedral sites in the three-dimensional lithium ion channel in spinel which leads to the problems of surface transition metal dissolution slow lithium ion transport rate. Therefore we need to design the surface composition synthesis method to induce the surface phase transition of layered materials into "good spinel" with transition metal: oxygen < 0.5 so as to restrain the attenuation problem. In addition the materials with cubic symmetry spinel like framework can also be used as electrode materials with high energy density high rate. This kind of materials can obtain more low barrier 0-tm structure easier multi-element doping more oxygen ion redox capacity by adjusting the proportion of lithium: transition metal cation: anion the type of element so as to achieve high specific capacity of 300 or even 400 MAH / g excellent rate performance.

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