Cassia seed-derived N-P double-doped porous carbon as an efficient sulfur host material for high-performance Li-S batteries

As biochar exhibits a unique structure and electrical conductivity, application of biochar in batteries arouses huge attention. In the present study, the cassia seed-derived N-P double-doped porous carbon which acts as a carrier of sulfur cathode is prepared based on a fast, powerful puffing of cassia seed with subsequent annealing treatment route. After loading sulfur into the porous carbon, the carbon–sulfur composite is employed as the cathode material of lithium-sulfur batteries. It is found that by puffing process with the popcorn machine, cassia seeds can successfully change into porous carbon with numerous mesopores based on considerable large pores. This special architecture can effectively capture the lithium polysulfide intermediates and inhibit the volume of sulfur from expanding simultaneously. Meanwhile, the N-P double-doped carbon can alter the hybridization orbital of carbon and facilitate the chemical adsorption of lithium polysulfide, thereby expediting the cycle of S cathode. The N-P doped carbon–sulfur composite exhibits a maximum discharge capacity of 1464.4 mAh/g at 0.1C and maintains a high discharge capacity of 825.8 mAh/g after 100 cycles at 5C. This study presents an economical, green and sustainable method to synthesis N-P double-doped porous carbon–sulfur composite which has large-scale application prospects in lithium-sulfur batteries.