Application And Property Research Of Porous Coconut Shell Carbon For Lithium-Sulfur Batteries

Biomass resources are rich on the earth.Biomass carbon has all advantages of traditional activated carbon and its raw materials are non-polluting and diverse.Biomass carbon has achieved the concept of turning wastes into materials and sustainable development.In recent years,biomass carbon's application range and use are increasing and it's application in the battery area has also been concerned widely.The key for the development of high-performance lithium-sulfur batteries is to solve the inherent problems,such as the shuttle effect,the change of volume in the reaction,polysulfide dissolution and other issues.Biomass has a wide range of structural and physicochemical properties and provide a rich carbon source for production of carbon material with specific performance.In this thesis,coconut shell was used as the raw material to prepare coconut shell carbon(CSC)through carbonization,activation and drying steps.It has a wealth of microporous/mesoporous structures and high specific surface area.The test result shows that the average particle size of CSC is 14.25 ?m with a pore size distribution in the range of 1-3 nm.The large number of micropores and mesopores present in CSC led to a large specific surface area up to 2160 m2 g-1.The pore volume was 0.68 cm3g-1 The prepared CSC powders show an irregular massive structure with a typical disordered sp2 hybridized carbon network.The CSC is composed of carbon element,oxygen element mainly,but also contains some other metal elements,such as Na,Ca,Cu,Mg and so on.The ash content of CSC is 8.33%,pH of CSC is 9.58,iron content is 8.69%.The CSC has a large adsorption capacity to lithium polysulfide and plays the role of "molecular sponge".Sulfur was encapsulated in the micropores and mesopores of CSC by melting and infiltrating to form composite materials.The composite materials were applied to the cathode of lithium-sulfur battery.The sulfur-infiltrated CSC materials show superior discharge-charge capacity and cycling stability.High initial discharge capacities of 1599 and 1500 mA h g-1 were achieved at current rates of 0.5 and 2.0 C,respectively.A high reversible capacity of 517 mAh g-1 was retained at 2.0 C even after 400 cycles.The results demonstrate a high retention and a deep lithiation of the CSC-confined sulfur.The success of this strategy provides insight into seeking high-performance biochar materials for Li-S batteries from abundant bio-resources.