Preparation Of Biomass Sisal-derived Carbon Materials And Its Electrochemical Energy Storage

With the increasing exhaustion of non-renewable energy sources such as fossil fuels,people have continuously turned their attention to the research and development of renewable energy sources.Biomass materials,as a huge resource library,use biomass resources or agricultural waste and other renewable resources to prepare biomass-based derived carbon materials for energy storage,which has become a current research hotspot.In this paper,activated carbon fibers and hard carbon materials were prepared by using renewable biomass sisal fibers as precursors,which were used as electrode materials for supercapacitors and sodium ion batteries,respectively.Through some characterization methods,including SEM,TEM,XRD,Raman,BET,etc.,the structure and phase of the sample were analyzed,and the electrochemical performance of the sample was evaluated by electrochemical testing.Activated carbon fibers at different activation temperatures were prepared using the extracted sisal fiber as a precursor,through the carbonization and activated by KOH.The study found that all samples at the activation temperature can maintain the structure and morphology of the raw materials,and the fibrous structure is conducive to the infiltration of the electrolyte and shorten the ion channels.As the activation temperature increases,the specific surface area and pore size distribution of the sample also change.At 750°C,the specific surface area and pore size distribution of activated carbon fibers are optimal.SC-750 has high specific surface area(S_BET:2289 m² g^-1)and excellent pore size distribution?2-10 nm?,with a total pore size of 1.23 cm³ g^-1.This pore size distribution is the ideal pore size for double-layer capacitors.It provides low-resistance channels for electrolyte ions to move inside the material,and can quickly form an electrochemical double layer.When the current density is 0.5 A g^-1,the specific capacitance of the SC-750 is 415 F g^-1;the SC-750 has a capacitance retention of 93%after 10,000 long cycles at a current density of 10 A g^-1.Similarly,sisal fiber is used as a precursor,and after pre-oxidation treatment,high-temperature cracking is directly performed to prepare a biomass hard carbon material with a specified shape.By changing the cracking temperature,the effect of temperature change on the sodium storage performance of hard carbon materials was studied.Increasing temperature causes the surface of the sample to become smooth,and the specific surface area of the corresponding sample is decreasing.However,excessive temperature will cause the destruction of the material structure and form more defects.It was found through electrochemical tests that an increase in temperature would lead to the appearance of the platform area of the sample,and the corresponding charge and discharge process would appear in two parts:the slope area and the platform area.The slope region corresponds to the adsorption of sodium ions on the surface of the carbon layer and defect sites,and the platform region corresponds to the storage of sodium ions in the nanoholes.As the temperature increases,the electrochemical performance of the sample is gradually improved.When the temperature reaches 1500°C,the sodium storage performance of the sample is the best.In the first-cycle of TCF1500,the coulomb efficiency was 42.1%,and its reversible specific capacity reached a maximum of 184.2 mAh/g.