| Biomass-based carbon materials are widely used as supercapacitor electrode due to the characteristic of high specific surface area,excellent stability and friendly environmental.However,the unmodified pure carbon materials have poor hydrophilicity,weak electrical conductivity and lacking of active sites,which limit their application in some fields.While graphene oxide is used in electrochemistry field due to its excellent electrical conductivity,electron mobility,large specific surface area and other characteristics.But graphene sheets are easy to stack,which greatly reduced the specific surface area of graphene materials.At the same time,the interior of the agglomerated graphene cannot be infiltrated by the electrolyte,which makes the electrochemical performance of the graphene electrode much lower than expected.Therefore,people are devoted to study the composite of biomass-based carbon material and graphene to explore the interaction of different materials with graphene materials.In this paper,combining the advantages of biomass-based carbon and GO materials,the specific capacitance of electrode materials was improved by preparing biomass-based carbon/GO composite carbon materials,and the energy density of supercapacitor was further improved through the adjustment and control of structure.The research contents are as follows:（1）Preparation and performance of chitosan/graphene oxide composite carbon materials.Sandwich-like chitosan/r GO composites（CRG）were prepared by microwave-assisted hydrothermal method,without further carbonization or activation,it can be directly used as an additive free electrode material,which can effectively reduce the resistance of the material and is conducive to practical application.The presence of chitosan inhibits the stacking of graphene sheets and effectively improved the dispersion of CRG.The presence of GO enhances the electrical conductivity of the composites and provided a large accessible specific surface area with hierarchical pore structure.When used as additive-free electrode,CRG exhibited a high specific capacitance of 274 F/g（0.5 A/g）in three-electrode system using 1 M H2SO4 electrolyte,it also shows good rate performance and cycling stability.Solid-state supercapacitor device was assembled with CRG electrode and lignin hydrogel electrolytes,high gravimetric energy densities of 8.4 Wh/kg at the power density of 50 W/kg was achieved.（2）Preparation and performance of double modified chitosan/graphene oxide composite carbon materials.Due to the poor solubility of chitosan in water and the uneven reaction between chitosan and GO,dimethyl sulfoxide was used as the solvent to modify chitosan by adding succinic anhydride to increase the content of carboxyl and hydroxyl in chitosan surface,which improving the water solubility of chitosan.On the other hand,the presence of chitosan inhibited the stacking of GO to some extent,but it did not eliminate the phenomenon.In addition,the graphene oxide sheet is large and dense,which makes it difficult to pass through for gas and ions.When used as an electrode material,electrolyte ions need to bypass the whole graphene oxide sheet to carry out ion transport,which is not conducive to charge transport.Therefore,the pore formation of GO sheets greatly reduces the ion transport path.The porous structure not only weaken the interaction force between graphene sheets by increasing the defect area,which effectively alleviated the stacking of graphene sheets,but also exposed the active surface and improved the ion transport capacity of the material.High performance of double modified chitosan/graphene oxide composites were prepared by one-step microwave hydrothermal method.In the three-electrode system with 1 M H2SO4 electrolyte,the specific capacitance of MCHG is up to 432 F/g（0.5 A/g）and the MCHG has good rate performance and cycle stability.When assembled into solid capacitor devices,it has a high energy density of 14.8 Wh/kg at a power density of 100W/kg.（3）Preparation and performance of activated carbon/graphene oxide composite carbon materials.With the development of portable electronic devices,the higher volume performance of electrode materials is required.Therefore,biomass-based activated carbon prepared from straw was introduced to compound with GO,and the biomass-based carbon composites（AC3/G）were obtained by capillary drying method,which has the structure of sunflower-like shape and hierarchical pore dense network with the density is 1.23 g/cm3.When used 1 M H2SO4 as electrolyte in a three-electrode system,the gravimetric capacitance of AC3/G is up to 628 F/g（0.5 A/g）,and the corresponding volumetric capacitance is 775 F/cm3.A flexible solid-state supercapacitor device was assembled into AC3/G with lignin hydrogel electrolytes,the high volumetric energy density of 9.7 Wh/cm3 can be obtained at power density is 62W/cm3. |
