| As a potential energy storage device,lithium-ion batteries（LIBs）have attracted extensive attention due to their high energy density,ultra high-power density,extremely long cycling life and environmental friendliness.Graphite was used as anode material for conventional commercial lithium ion batteries.However,due to the low capacity of graphite,the further development of commercial graphite has been hampered.Transition metal oxides（TMOs）have attracted extensive attention because of their high capacity.Nonetheless,TMOs as anode materials for lithium ion batteries still face great challenges.Among them,large volume expansion and poor electrical conductivity are the important factors restricting their development.Constructing mesoporous electrode materials could not only increase the contact area between electrode material and electrolyte but also buffer the volume expansion problem during cycling.In addition,electronic structure regulation of transition metal oxides can effectively change its electronic structure and enhance the electronic conductivity of transition metal oxides.In this paper,we took molybdenum dioxide and molybdenum phosphide composite material（meso-Mo O2/Mo P-NBs）as the research object.As the anode materials of lithium ion battery,the advantages of heterogeneous structure compared with single material are clarified.Meanwhile,the energy storage mechanism of heterogeneous structure and single material is explored and analyzed.The main results are as follows:（1）Meso-MoO2/Mo P-NBs was synthesized by high temperature calcination,and two comparison samples were obtained by controlling the amount of phosphorus source during calcination.Three kinds of materials were assembled into lithium ion half cells for electrochemical performance test.The meso-Mo O2/Mo P-NBs shows the best cycling performance(515 m Ah g-1 after 1000 cycles at 1 A g-1)and rate capability(291 m Ah g-1 at 8 A g-1).（2）The ion and electronic transport properties of the three materials were studied by a series of electrochemical analysis and density functional theory calculations（DFT）.For the three comparison samples,meso-Mo O2/Mo P-NBs has the highest lithium ion diffusion coefficient,the smallest charge transfer impedance and the best electronic conductivity,which benefit for rapid lithium-ion transport properties.（3）It is revealed that the lithium-ion storage mechanism of meso-Mo O2/Mo P-NBs is partial conversion for Mo O2 and finite solid solution reaction for Mo P by in-situ XRD and ex-situ TEM analysis.In addition,based on in-situ XRD calculation,little volume expansion was observed during Li+insertion/extraction process in meso-Mo O2/Mo P-NBs,which contribute to good structural stability and reversibility. |
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