关键词: 椰壳, 磷掺杂, MnO _x, 硬碳, 赝电容

Abstract:

Phosphorus-doped hard carbon/MnO _x composites were synthesized by hydrothermal treatment and one-step pyrolysis using coconut shell as a biomass carbon source, phosphoric acid as a phosphorus source and a pore-forming agent, and manganese sulphate as a manganese source, and were used in the field of supercapacitors. The effects of the additions of phosphoric acid and manganese sulfate on the structural and electrochemical properties of the composites were analyzed, and the mechanism of the enhancement of the electrochemical properties of phosphorus-doped hard carbon/MnO _x composites was investigated. The etching of phosphoric acid contributed to the formation of a multistage pore structure of microporous-mesoporous composite, which provided not only the composites with bilayer capacitance, but also space for the growth of MnO _x and reduced its agglomeration, thus exposing more pseudocapacitive active sites. Phosphorus doping not only increased the layer spacing of the hard carbon and improved the defects in its structure, but also introduced phosphorus-containing functional groups such as C—P\stackrel{}{̿}O, C—P—O and C/P—O—P, which synergistically interacted with MnO _x to further enhance its electrochemical performance. The specific capacitance of the composite was as high as 302F/g, and the capacitance retention was still 70.5% after 10000 cycles at 10A/g. When assembled into a symmetric supercapacitor, the power density was up to 400W/kg at the energy density of 156Wh/kg, which indicated that it had a great potential for application in the field of supercapacitors.

Key words: coconut shell, phosphorus doping, MnO _x, hard carbon, pseudocapacitance