| Recently,the word “New Energy” has become a hot word due to environmental pollution and energy shortage problems,which arises the interests of researchers from all over the world to do research on energy technology and new energy materials development.New energy can be divided into two main parts,namely,energy harvesting and energy storage.While new energy storage can be roughly divided into batteries and capacitors.With the rapid development of wearable electronic equipments and new energy vehicles,it has put forward higher requirements for energy storage equipments with high energy density and power density,good safety and cycling stability.Thus,supercapacitors and lithium-sulfur batteries have become the research hotspots.Especially for porous carbon nanomaterials,they can be used as electrode materials for both supercapacitor and lithium-sulfur battery.In this thesis,silkworm excrements were used as the carbon source,and the biomass-based carbon nanomaterials with rich porous structure and high specific surface area were prepared by different methods,and the electrochemical properties of them were also studied.The contents of this thesis can be concluded as follows:?1?The porous carbon nanomaterials were prepared by an activation of KOH after a hydrothermal reaction?180 ?,12 h?of silkworm excrements.The phase and composition of as-synthesized sample were characterized by XRD,XPS and EELS;the structure and morphology of as-synthsized sample were characterized by SEM and TEM;the BET surface area and porosity of as-synthesized samples were studied by nitrogen absorption-desorption measurements.The results show that the carbon material prepared by hydrothermal method has a nano-network structure.More interesting,the self-doping of nitrogen,phosphorous and sulfur also can be observed.Besides,the as-synthesized sample also has a large number of micropores,and a small amount of mesopores and macropores.The BET surface area of the as-synthesized sample is up to 2258.45 m2·g-1.Furthermore,the as-prepared sample shows good supercapacitor characteristics used as the electrode.It presents the areal capacitance of 974.44 m F·cm-2 under a low current density of 1 mA·cm-2,and its areal capacitance is as high as 444.44 mF·cm-2 even at a high current density of 100 mA·cm-2.And it presents the gravimetric capacitance of 324.81 F·g-1 under a low current density of 0.333 A·g-1,and its gravimetric capacitance is as high as 148.15 F·g-1 even at a high current density of 33.33 A·g-1,indicating a good rate performance.?2?The porous carbon nanomaterials were prepared by an activation of KOH after a high temperature carbonization at 900 ? for 3 h under inert gas protection.The phase and composition of as-synthesized sample were characterized by XRD,XPS and EELS,the structure and morphology of as-synthesized sample were characterized by SEM and TEM,the BET surface area and porosity of the as-synthesized sample were studied by its nitrogen absorption-desorption properties.The results show that the carbon materials prepared by high temperature carbonization possess a nanosheet structure,which is different from the morphological structure of the target product prepared by hydrothermal method.The carbon material prepared by high temperature carbonization also contains a small amount of nitrogen,phosphorous and sulfur.Its nitrogen absorption-desorption properties show that the product also has a large number of micropores,a small amount of mesopores and macropores.It shows an excellent rate performance when used as supercapacitor electrode.Under a low current density of 1 mA·cm-2,the areal capacitance can reach 716.67 mF·cm-2,and its areal capacitance is as high as 444.44 mF·cm-2 even at a high current density of 100 mA·cm-2.And it presents the gravimetric capacitance of 238.89 F·g-1 under a low current density of 0.333 A·g-1,and its gravimetric capacitance is as high as 148.15 F·g-1 even at a high current density of 33.33 A·g-1,indicating a good rate performance.In addition,when it was used as a positive electrode for lithium-sulfur batteries after it was composited with elemental sulfur,the first discharge specific capacity of the sample is 620.1 mA·h·g-1?60% sulfur?and 656.6 mA·h·g-1?70% sulfur?,which are much higher than that of elemental sulfur(125.1 mA·h·g-1).It presents a good cycling stability with the capacity retention of 88%?60% sulfur?and 92%?70% sulfur?after 100 cycles under the condition of 0.2 C. |
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