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Synthesis And Electrochemical Performance Of Anode Materials (Carbonates, Cobaltates, Molybdenum Disulfide) For Lithium-ion Battery

Posted on:2018-10-25Degree:MasterType:Thesis
Country:ChinaCandidate:L LuFull Text:PDF
GTID:2321330512981736Subject:Inorganic Chemistry
Abstract/Summary:PDF Full Text Request
In this thesis,transition metal carbonates ZnCO3,spinel MCo2O4?M=Cu,Zn?,and MoS2were studied as anode materials for lithium-ion battery.The synthesis procedure,modification,structure and electrochemical properties of these materials were also studied.The important conclusions were drawn from our expriments.The main contents have been listed as follows:1.Transition metal carbonates ZnCO3 were synthesized by using ZnCl2 and NH4HCO3as raw materials by solvothermal method and ball milling-solvothermal combination method,respectively.The effects of the reaction temperature on crystal structure,morphology and formation mechanism,as well as electrochemical properties of the as-synthesized products through solvothermal method were deeply investigated.The effects of introduction of Co,and the molar ratio of Zn to Co?n Zn/Co?on the crystal structure,morphology and formation mechanism,and electrochemical properties of the as-synthesized products through ball milling-solvothermal combination method were also investigated.The results showed that compared with the synthesized temperature of 180??ZCCO-180?,the synthesized temperature of 200??ZCCO-200?exhibited higher discharge capacity?1530 mAh/g?and better rate performance with the reversible capacity of 876 mAh/g after 70 cycles.As anode materials for lithium ion battery?LIB?,all ZCCO electrodes possess high specific capacities and good cycle performance.The introduction of Co and molar ratio of Zn to Co play crucial roles on the morphology and electrochemical performance of the ZCCO.The as-obtained Zn0.5Co0.5CO3 electrode exhibits higher discharge capacity?1526 mAh/g?and better rate properties with the reversible capacity of 976 mAh/g after 100 cycles when the molar ratio of Zn/Co is 1:1.The growth mechanism of samples synthesized by different methods,and the mechanism of the electrochemical reactions in the electrodes was also investigated.The work provided experimental basis for developing novel anode material with high specific capacity and excellent cycling performances for lithium-ion battery.2.The precursors of CuCo2O4?CCO?were synthesized by ball-milling method and solvothermal method,respectively.The precursors were further heat-treated at a low temperature?450??in air to obtain CuCo2O4.The effects of synthesis methods on the crystal structure,morphology,formation mechanism,and electrochemical properties of the as-synthesized products were investigated.The results revealed that both the as-prepared CuCo2O4?S-CCO?synthesized by solvothermal method followed with pyrolysis and CuCo2O4?B-CCO?synthesized by ball-milling method followed with pyrolysis exhibited good electrochemical performance.Especially,the S-CCO behaved a large initial capacity of 1230m Ah/g,whose reversible capacity can maintain as high as 635 mAh/g after 100 cycles under a potential window from 3.0 to 0.01 V?vs.Li+/Li?at current density of 100 mA/g,showing better electrochemical properties compared with the B-CCO.The cyclic voltammetry?CV?and AC impedance test further confirmed the plateau change and the decrease of charge transfer resistance in the CCO electrodes.The chemical formation process and electrochemical mechanism of CCO were also analysized in brief presently.The good electrochemical performance suggested that CuCo2O4 could be a promising candidate as a novel anode material for LIB applications.Spinel ZnCo2O4?ZCO?microspheres were further obtained by pyrolysis of the previous relative ZCCO precursors via one-pot sovolthermal method at 450?.Difference on the structure,morphology and the electrochemical properties of the ZCO-180 and ZCO-200 samples was investigated.Compared with ZCO-180,ZCO-200exhibited better electrochemical performance with a high initial discharge capacity of 1416m Ah/g.After 70 cycles,the reversible capacity can be maintained as 741 mAh/g.And the electrochemical mechanism of ZCO was also analyzed in brief presently.The good electrochemical performance suggested that ZnCo2O4 could be a promising candidate as a novel anode material for LIB applications.3.SnO2-MoO3 composites were synthesized by using?NH4?6Mo7O24·4H2O and SnCl2·2H2O as raw materials through a simple solvothermal method followed by pyrolysis.Tin-doped MoS2?Sn/MoS2?was synthesized by a solvothermal method followed with annealing in Ar?H2?atmosphere,with SnO2-MoO3,and thioacetamide?TAA?as starting materials.The effects of Sn doping and the content of Sn-doping on the crystal structure,morphology,formation mechanism,and their electrochemical properties were investigated.As anode materials for LIB,all Sn/MoS2 composites exhibited both higher reversible capacity and better cycling performance at a current density of 200 mA/g,which was compared with MoS2 without Sn-doping.The achieved discharge capacity for Sn/MoS2 composites were above 1000 mAh/g after 100 cycles with nearly 100%coulombic efficiency.The cyclic voltammetry?CV?and AC impedance test further confirmed the doping of metal Sn in MoS2can improve the conductivity of MoS2,and the unique electrochemical mechanism of Sn/MoS2 composites were also analysized.Sn/MoS2 nanocomposite is a promising candidate as a novel anode material for LIBs.
Keywords/Search Tags:Lithium ion battery, Anode materials, ZnCO3, CuCo2O4, ZnCo2O4, MoS2, Doping
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