Preparation And Performance Of Bio-Carbon Materials Based On Symmetric Supercapacitor Electrodes

Due to the rapid consumption of global fossil fuel energy and the explosive growth of the world's population,there is an urgent need to develop clean,low-cost and efficient alternative energy sources.The supply of new energy sources?such as wind,solar,hydropower and biomass?is unstable and cannot be used as a provider of sustainable energy technologies.Sustainable power batteries and supercapacitors remain the main carriers of global energy use.Compared with batteries,supercapacitors have a faster charging speed,a longer life,a wider temperature range and are non-toxic,which have become a hot topic in energy research.Among the factors affecting the performance of supercapacitors,the choice of electrolyte and electrode materials is vital.From the perspective of environmental protection and renewable,this paper chooses bio-carbon material as the electrode material of symmetrical supercapacitors.The research content is as follows:1.A series of porous carbon-based supercapacitor electrode materials?GCK?were synthesized from dead leaves of Ginkgo biloba by carbonization and KOH activation.The morphology and structure of porous carbon derived from Ginkgo biloba were characterized in detail.The specific surface area of the best porous carbon electrode GCK2 was 1013 m²g^-1.Explored the effect of acid and alkaline electrolytes on electrode performance,the results show that the specific capacitance of the GCK2 electrode can reach 563.5 and 436.5 F g^-1 at 1.0 A g^-11 in 1.0 M H₂SO₄ and 6.0 M KOH electrolytes,respectively,and it shows excellent rate performance and cycle stability in both electrolytes.It is worth noting that the symmetrical supercapacitors assembled with porous carbon materials show excellent performance,which is superior to other previously reported porous carbon derived from Ginkgo biloba.It shows that GCK2 has certain application potential in energy storage equipment with high energy and power density.2.The chestnut shell was selected as the carbon source?CC?and ZnCl₂?-Cl?,KOH?-OH?and K₂CO₃?-CO₃?were used to activate the carbonization products,respectively.The morphology and performance of electrode materials?CC700-Cl??CC700-OH??CC700-CO₃?activated by different activators were compared.It was found that CC700-OH has a layered structure with holes/sheets interspersed,with a specific capacitance of 520 F g-1 at 1 A g^-1.CC700-Cl has a 3D channel network structure,with a specific capacitance of 506 F g^-1 at 1 A g^-1 and a specific surface area of 813.9 m2g^-1.The network structure formed by mesopores and micropores provides a channel for electronic transmission.Although the specific capacitance of CC700-Cl is slightly lower than CC700-OH,its stability is better than CC700-OH.Therefore,in a two-electrode system,a symmetrical capacitor was assembled with CC700-Cl-11.The symmetric capacitor has a specific capacitance of 118 F g^-1 at 1 A g^-1,the scan rate of CV can be increased to 220 mV s^-1,and the potential window width is 0 to 1.6 V.When the power density is 900 W kg^-1,the energy density is 53.1 Wh kg^-1 and when the power density is increased to 27000 W kg^-1,the energy density can still be maintained at 27 Wh kg^-1.The above research results show that it is feasible to prepare symmetrical supercapacitor electrode materials using chestnut shell as carbon source.3.Using grapefruit peel as a carbon source?GC?,through high temperature oxidative carbonization?GCO?and hydrothermal carbonization?GCS?after sulfuric acid treatment,the effects of two carbonization methods on the properties of carbonized products were compared,and the carbonization temperature was optimized.The results show that GCO600 had better performance.The GCO600-14,activated product of GCO600 by K₂CO₃,has rich network pores and a specific surface area of 661.7 m²g^-1.In the three-electrode system,the specific capacitance of GCO600-14 is 413 F g^-1 at 1 A g^-1,and the specific capacitance can still reach 289 F g^-1 when the current density is increased by 30 times,which is 70%of the initial value.The specific capacitance did not decrease significantly after 5,000 cycles.And the symmetrical capacitor GCO600-14//GCO600-14 has a power density of 720 and 20800 W kg^-1,the corresponding energy density is 26 and 20.2 Wh kg^-1,respectively.The above information shows that GCO600-14 has potential application prospects as a new,environmentally friendly energy storage material.