Preparation Of Metal Oxide/Sulfide Composites And Their Energy Storage Properties

The anxieties with respect to the unsustainable nature of fossil fuels and the increasingly pressing environmental issues have attracted increasing attention to sustainable,clean and efficient energy for all people.In recent years,rechargeable lithium-ion batteries?LIBs?,as environmentally friendly storage devices,have been widely used in portable electronic products?such as laptops,mobile phones?,and further developed into the electric vehicle market.However,the lower theoretical capacity of current commercial carbon anodes for lithium-ion batteries cannot satisfy the demand of high-energy and high-power lithium-ion batteries for electric vehicles.The transition metal oxides and sulfides are considered to be ideal candidates for lithium ion batteries anodes because of their high theoretical capacity and low cost.However,transition metal oxide and sulfide materials have lower conductivity and the inevitable volume change of the lithium ion insertion/extraction cycle process,which limits their application in lithium ion batteries.At present,high-rate performance and excellent cycle stability of anode materials have been achieved by effective strategies such as exploring the construction of new metal oxide/sulfide materials with different morphologies,and compounding with conductive carbon materials.In this paper,Co₃O₄/Ti₃C₂T_X nanocomposite and core-shell Cu_7.2S₄/C@MoS₂nanocomposite were designed and synthesized,and their morphologies and the electrochemical performance were tested,and two new anode composites with excellent performance were obtained.The research work is divided into the following two main parts:1.The Co₃O₄/Ti₃C₂T_X composites were prepared by using the obtained Ti₃C₂T_X nanomaterials and Co?NO₃?₂?6H₂O as raw materials.It can be clearly observed that the Co₃O₄nanoparticles are uniformly attached to the Ti₃C₂T_X layers through morphological structure analysis of the synthesized Co₃O₄/Ti₃C₂T_X nanocomposite.When the prepared materials were used as the anode material of lithium ion battery,the discharge specific capacity of the Co₃O₄/Ti₃C₂T_X nanocomposite was 1002.7 mAh g^-11 after 171 cycles under the current density of 200 mA g^-1,which showed better electrochemical performance than the pure Co₃O₄nanoparticle electrode.Therefore,It can be speculated that the Co₃O₄/Ti₃C₂T_X nanocomposite designed can reduce the transmission path of lithium ions and effectively adapt to the volume change during charge/discharge cycles.2.The three-dimensional core-shell Cu_7.2S₄/C@MoS₂ nanocomposite was synthesized through the vulcanization reaction using the obtained Cu₂O octahedron as the initial template.It can be clearly observed that MoS₂ nanosheets are randomly and uniformly grown on Cu_7.2S₄/C carrier through its morphological structure analysis.When was used as the anode material of lithium ion battery,the discharge specific capacity of the 200th cycle was observed to be 1502.4 mAh g^-11 for the three-dimensional core-shell Cu_7.2S₄/C@MoS₂nanocomposite electrode at the current density of 1 A g^-1,which showed superior electrochemical performance than the pure MoS₂ nanosheets electrode.Therefore,it can be inferred that the designed three-dimensional core-shell Cu_7.2S₄/C@MoS₂ nanocomposite can effectively improve the re-stacking of MoS₂ nanosheets and shorten the ion transport path.At the same time,the synergy between the two active materials can help to adapt to volume changes of the nanocomposite during charge/discharge cycles.