Fabrication And Application For Flexible Thermal Conductivity-regulated And Electrochemical Energy Storage Nanocomposites

In recent year,nanomaterials,especially transitional metal dichalcogenides(TMDs),which are similar to graphene structures,have been widely used as lithium ion and sodium ion batteries as novel electrode materials.There are many researches on the electrochemical properties of such materials,but there are few studies on the thermal management of these materials as lithium ion battery electrodes.Therefore,in this thesis,transition metal sulfide film materials were prepared by chemical vapor deposition(CVD)method.The electrochemical intercalation method was used to insert the hexammonium salt cation and lithium ion between the layers to prepare the regulated thermal conductivity nanocomposites,the issue of thermal management of electrode materials can be fulfilled.Metallic(1T)phase MoS₂ was prepared by alkali metal hydroxide-assisted method and the nanocomposites with electrochemical energy storage property by ball mill method.Electrochemical properties of conventional lithium ion batteries anodes including rate performance,cycle stability and kinetic problems can be improved.At the same time,in order to improve the thermal conductivity of electronic device and ensure its safety in use,high-quality one-dimensional silver nanowire materials were prepared.Ag NW can be used as a new thermal conductive filler in the process of film formation PVDF by internal filling and surface coating method.Finally,the Ag NW@Ag NW/PVDF composite film with high thermal conductivity was prepared and was used as a heat spreader for LED devices.A 150 nm molybdenum metal layer was deposited on a double-sided polished transparent sapphire substrate by magnetron sputtering,while MoS₂ film was prepared by a CVD method at.It was characterized by XRD,Raman,XPS,RBS,the results indicated the MoS₂was prepared successfully.RBS have characterized its composition and structure,showing its exact thickness of 153 nm.MoS₂[(HA)_x(H₂O)_y(DMSO)_z]and Li_xMoS₂ with regulated thermal conductivity property were prepared by electrochemical intercalation of hexammonium cations and lithium ions.The ICP method was used to characterized the chemical formula of intercalation compounds.Studies have shown that the thermal conductivity of the original MoS₂is 6.32 W m^-1K^-1,and the electric quantity loaded on MoS₂ was increased from 0 m Ah-8 m Ah,and its thermal conductivity was reduced from 6.32 W m^-1K^-1 to 2.41 W m^-1K^-1.For lithium ion intercalation compounds,as the concentration of lithium ions increased,the thermal conductivity decreased gradually from 6.32 W m^-1K^-1 to 1.83 W m^-1K^-1.A commercial TiS₂ single crystal film was characterized by XRD,Raman,XPS,SEM techniques.The hexammonium salt cation and lithium ion were intercalated between the TiS₂layers by electrochemical method to obtain TiS₂[(HA)_x(H₂O)_y(DMSO)_z]and Li_xTiS₂ with regulated thermal conductivity property.The results showed that the characteristic peaks of the composite TiS₂[(HA)_x(H₂O)_y(DMSO)_z]and Li_xTiS₂ are slightly reduced compared with TiS₂,in other words,the peak position is shifted to the left direction.These phenomena indicated that the insertion of lithium ions between the TiS₂ layers also increased the interplanar spacing,resulting in a decrease in 2?value.The chemical formula of intercalation compound was determined by ICP method,and its thermal conductivity was tested by TDTR method.Results showed thermal conductivity of the original TiS₂ film was 4.37 W m^-1K^-1,and for TiS₂[(HA)_x(H₂O)_y(DMSO)_z],the thermal conductivity decreased with the increase of the charged amount.Generally,the electric quantity increased from 0 m Ah to 8 m Ah,and its thermal conductivity decreased from 4.37 W m^-1K^-1 to 0.73 W m^-1K^-1.The Sn S film was deposited by ion milling evaporation with a 100 nm thick tin metal layer on the silicon substrate.The CVD method was used to prepare the Sn S film,which was characterized by XRD,XPS and Raman characterization methods.The hexammonium cation and lithium ion were intercalated between the Sn S layers by electrochemical intercalation method to obtain Sn S[(HA)_x(H₂O)_y(DMSO)_z]and Li_xSn S with with regulated thermal conductivity property.The crystal lattice structure was characterized by XRD and characteristic peaks disappearing.The chemical formula after intercalation was determined by ICP method,and its thermal conductivity was tested by TDTR method.For Sn S[(HA)_x(H₂O)_y(DMSO)_z],as the charged amount increased,the thermal conductivity was gradually reduced.The thermal conductivity of the pristine Sn S film was 4.70 W m^-1K^-1,and the electric quantity was increased from 0 m Ah to 8 m Ah,and its thermal conductivity is reduced from 4.70 W m^-1K^-1 to 0.83 W m^-1K^-1.For Li_xSn S,as the concentration of lithium ions increased from 0 to 1.0,its thermal conductivity decreased from 4.70 W m^-1K^-1 to 2.84 W m^-1K^-1.This indicated that the insertion of foreign ions changes the interlayer spacing of Sn S,thereby changing its thermal conductivity.The metallic 1T phase MoS₂ was prepared by calcination mixture solution of(NH₄)₂MoS₄and Li OH at high temperature under argon atmosphere,and the 1T MoS₂/Mn O nanocomposite was synthesized by a simple ball milling process for 1T MoS₂ and Mn O nanoparticle under argon,which is used for the anode in lithium ion battery.The prepared 1T MoS₂ and 1T MoS₂/Mn O nanocomposite were characterized by XRD,TEM,SEM,Raman,XPS.The results showed 1T MoS₂ had a crystal structure that was different from that of 2H phase MoS₂,and the diffraction pattern obtained by selected area electron diffraction are further proved its structure of 1T phase.Studies showed that Mn O was anchored on the edge of 1T MoS₂.Electrochemical charge and discharge test of composite electrode were conducted under 0.5 C and 10 C,respectively,presenting the capacity of 729.8 m Ah g^-1 and 493.7 m Ah g^-1,respectively.This nanocomposite electrode also had a long cycle life.Even at the 2000th cycle,the reversible charge and discharge capacities were still higher than 584.8 m Ah g^-1 and 589.6 m Ah g^-1,respectively,indicating that 1T MoS₂ improved the electrochemical properties of the Mn O anode.High-quality silver nanowire(AgNW)with a high aspect ratio and few impurities was prepared by reduction reaction for silver nitrate using glycerin,while polyvinyl pyrrolidone(PVP)was used as surfactant.Ag NW were added to the DMF solution dissolved with PVDF,and the Ag NW/PVDF transparent film was prepared by solvent evaporation method.Ag NW was further coated on the Ag NW/PVDF surface by wire-bar coating to form an Ag NW heat conduction network,thereby preparing an flexible Ag NW@Ag NW/PVDF composite film.The method improved the thermal conductivity of PVDF film from both inside and outside,and the thermal conductivity was as high as 127.6 W m^-1 K^-1,which can be used as a heat spreader for electronic materials.The pristine PVDF film and Ag NW@Ag NW/PVDF composite film were respectively used as the heat spreader in the heat dissipation system of the LED device.It had been found that the Ag NW@Ag NW/PVDF composite film presented better lateral heat transfer performance than pristine PVDF film due to its high thermal conductivity.