Taking cotton stalk as a biomass source,KOH as an activator,and sulfur as an energy storage material,a high-performance carbon sulfur composite is prepared through a carbonization activation high-pressure three-step method.The effect of changes in KOH dosage on the structure of activated carbon and the electrochemical performance of the composite is investigated.It is indicated from the results that the KOH activation mainly promotes the development of pores with a size below 10 nm in activated carbon.Tthe specific surface area and pore volume of activated carbon reach their maximum,reaching 3 068.15 m2·g-1 and 1.68 cm3·g-1,respectively when the ratio of carbon to KOH is 1∶4.Excessive KOH activation leads to the collapse of partial pores with a size of 3-9 nm,causing micropores/small mesopores to transform into large mesopores or macropores,further resulting in a reduction in specific surface area and pore volume.The electrochemical performance of the composite shows a positively correlation with the pore volume of activated carbon.The carbon sulfur composite prepared under a carbon/KOH ratio of 1∶4 exhibits the best electrochemical performance.The composite can retain a discharge capacity of 787 mAh·g-1 after it has been reused for 100 cycles at a current density of 0.1 C.At a current density of 2 C,the composite can deliver a high specific capacity of 582 mAh·g-1.
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