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    Home > Ji Xiaobo team of Central South University has made new progress in the field of anode materials for binary transition metal oxide lithium ion batteries

    Ji Xiaobo team of Central South University has made new progress in the field of anode materials for binary transition metal oxide lithium ion batteries

    • Last Update: 2020-01-10
    • Source: Internet
    • Author: User
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    Recently, the research group of Professor Ji Xiaobo of Central South University has made new progress in improving the cycle stability, activating its reversible conversion and optimizing its lithium storage performance Relevant research results were published on nano energy (DOI: 10.1016 / j.nanoen 2019.104333) under the title of "reviewing the activation effects of high value cobalt in comoo4towards high reversible conversion" Professor Ji Xiaobo is the corresponding author of this paper, and Zhang Yang, a 2017 graduate student of master's degree, is the first author of this paper Transition metal oxide (TMOS) is considered as one of the promising anode materials for lithium-ion batteries because of its high theoretical specific capacity, good safety and simple preparation Because of its high theoretical specific capacity, molybdenum based metal oxides have attracted extensive attention in the field of energy storage This kind of materials do not follow the mechanism of lithium ion intercalation / de intercalation in layered graphite electrode, but carry out conversion reaction Therefore, like most transition metal oxides with large theoretical specific capacity, molybdenum based metal oxides are facing two serious problems as the anode of lithium-ion batteries The first problem is that the volume of the material changes greatly during the charging and discharging process, which leads to a significant decrease in the capacity, resulting in the electrode material pulverization and poor cycle performance Another disadvantage is the irreversible conversion of Li 2O, which leads to capacity loss In view of the above problems, the team studied the molybdenum based bimetal oxide material cobalt molybdate (comoo4: 980 MAH g-1) Compared with the single metal oxide, bimetal oxide has more complex metal components and more metal valence, which is conducive to the conversion reaction with lithium In this study, one-dimensional rod like cobalt molybdate with different sizes was obtained by controlling hydrothermal reaction time It has been proved that the material is irreversibly converted into molybdenum and cobalt in the first cycle of discharge, and further evolved into the redox reaction of CO / CoO and Mo / MoO3 in the subsequent charge discharge cycle The conversion of divalent cobalt ions to high valence cobalt was detected by non in situ cyclic voltammetry In this system, high valence cobalt not only provides additional capacity, but also promotes the electrochemical reversible reaction between MoO3 and Li2O, and stimulates the release of irreversible capacity In this study, a smaller size distribution can effectively limit the volume expansion, reduce the electron transfer resistance, improve the structural stability, and promote the rapid charge transfer In addition, the optimized size effect can further promote the conversion of divalent cobalt ions to high valence cobalt, thus achieving better cycle stability After 400 cycles at the current density of 1A g-1, the material still shows a capacity of nearly 1000 MAH g-1 and a capacity retention rate of nearly 100% This work is expected to provide an in-depth understanding of the process of cobalt ion valence change and its impact on lithium storage performance, and provide ideas for optimizing the electrochemical performance of transition metal oxides.
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