| In recent years,with the development of portable electronics and electric vehicles,lithium ion batteries anode materials with high energy density and high power density have gradually gained great effort.Compared with traditional graphite anode material,metal chalcogenides are considered as ideal candidates anode materials in terms of their higher specific capacity and better reversibility.Particularly,owing to the complex composition and synergistic effects of multiple metal species,multicomponent bimetal chalcogenides show their better electrochemical reactivity and structure stability However,the metal chalcogenides exhibit large volume change and poor conductivity during repeated charging and discharging processes,which would severely limit their practical applications.In view of the above issues,this paper prepares sulfur-selenium based metal compounds through different methods,optimizes their material structures and modifies them with different carbon sources,aiming to obtain the anode materials with excellent electrochemical performances.In addition,the detailed material characterizations and electrochemical performance tests are performed,and the relationship between material structure and electrochemical performance is studied in depthLi3VO4/MoS2 composite with mesoporous structure is prepared by solvothermal method.The synergetic effect between MoS2 with high specific capacity and Li3VO4 with high cycle stability enables Li3VO4/MoS2 composite to show excellent electrochemical performance.The heterostructures between MoS2 and Li3VO4 would effectively connect the Li+ conducting channels,and promote Li+ transmission during the charge and discharge process.In addition,the mesoporous structure can effectively increase lithium storage sites.The initial discharge capacity and charge capacity of Li3VO4/MoS2 composite are 951 mAh g-1 and 735 mAh g-1,respectively,corresponding to the initial coulombic efficiency of 77.2%.After cycling 200 times at a current density of 500 mA g-1,the capacity of 604 mAh g-1 is retained for Li3VO4/MoS2 composite,showing outstanding rate performance and long-term cycle stabilityThe porous ZnMoS4@C nanosheets composite is prepared through glucose-assisted supercritical water system.The ZnMoS4@C nanosheets composite shows large specific surface area,which can increase the contact area with the electrolyte and shorten the Li+transmission distance.Carbon modification can effectively buffer the volume change of the ZnMoS4@C electrode,and maintain its electronic conductivity during the repeated charge and discharge processes.Moreover,carbon matrix can effectively improve the electronic and ionic conductivity of the electrode material,making ZnMoS4@C electrode excellent electrochemical performance.After cycling 70 times at a current density of 100 mA g-1,the ZnMoS4@C electrode exhibits a high reversible capacity of 935.1 mAh g-1.The average lithium storage capacities of 967.8,818.4,723.1,645.5 and 562.9 mAh g-1 were delivered when the current densities are fixed at 100,200,400,800 and 1600 mA g-1,respectively.The porous LiInSe2@C composites are fabricated and the coal tar pitch is used as carbon source.Appropriate amount of carbon coating can make the optimal interface between LiInSe2@C composite and electrolyte,showing significantly reduced charge transport resistance and increased Li+diffusion coefficient.Besides,the porous structure of the LiInSe2@C composite is beneficial to maintaining the structural stability during the charge and discharge process,and large specific surface area would increase the contact area between electrode and electrolyte,and promote Li+transport as well.After cycling 50 times at a current density of 100 mA g-1,the LiInSe2@C composite exhibits a discharge capacity of 412.8 mAh g-1,which is much higher than that of LiInSe2(174.5 mAh g-1).Furthermore,a reversible capacity of 270 mAh g-1 can be remained after 1000 cycles at 1000 mA g-1.Using citric acid as carbon source and pre-forming a film on the surface of LiInSe2 nanoparticles,and the LiInSe2@C composites are prepared followed by high temperature annealing.The nano-scale thin carbon layers with uniform thickness are formed on the surface of the LiInSe2@C composites.The presence of the thin carbon layers can effectively improve the electronic and ionic conductivities of the LiInSe2 electrode,which makes the LiInSe2@C composite exhibit high initial coulombic efficiency,high lithium storage capacity and excellent rate performance.The initial discharge capacity and charge capacity of LiInSe2@C composite is 732.0 mAh g-1 and 545.2 mAh g-1 at 100 mA g-1,respectively,corresponding to the initial coulombic efficiency of 74.5%.In addition,after cycling 800 times at high current density of 1500 mA g-1,the capacity retention of the LiInSe2@C electrode is 333 mAh g-1,showing significantly excellent long-term cycling performance. |
PDF Full Text Request