Study On Modified Horn-based Porous Carbon For Lithium-Sulfur Battery

With the urgent demand for energy storage devices,lithium-sulfur(Li-S)battery with high specific energy(2800 Wh L-1)has approached to the scene view of human.The dissolution and shuttle of lithium polysulfide(LiPSs)hinder the application of Li-S battery.Therefore,this work designed and prepared a high specific surface area(SBET)nitrogen-,sulfur-rich horn-based porous carbon(HNS-HPC),loaded with manganese dioxide(MnO2@HNS-HPC),to achieve surface modification of porous carbon.Using to the MnO2@HNS-HPC-modified separator in Li-S battery,because of the synergistic effect of N,S doping and MnO2,adsorption capacity for LiPSs was not only enhanced,but also the reaction kinetics of sulfur was promoted.Besides,residence time of LiPSs was shortened and the diffusion of ions was promoted.Eventually,the discharge capacity,cycle life and rate performance of Li-S battery were improved.This work is mainly as follows:Firstly,orthogonal experiment was designed to study the influence factors of the SBET for carbonization conditions.The SBET of the optimum carbon was as high as 3106.49 m2 g-1,and the orthogonal experiment provided a basis for the preparation of porous carbon with SBET.the N and S atoms were successfully doped into the carbon framework,and the atomic ratio were up to 3.01%and 0.58%.And the layered structure was retained,which was beneficial to the stability of structure and the formation of interconnected pore structure.These results provided the condition for the loading of the manganese dioxide.Secondly,MnO2 was loaded onto the horn-based porous carbon(HNS-HPC)to form MnO2-modified nitrogen-and sulfur-rich horn-based porous carbon(MnO2@HNS-HPC)composite with SBET by using the advantages of strong adsorption,catalytic conversion and good ion diffusion of MnO2.Reaction time on the loading was considered,the reaction of the optimum dispersion of MnO2 was 5 h,and the best electrochemical performance of Li-S battery with MnO2@HNS-HPC-modified separator was obtained.In addition,by studying the adsorption properties of MnO2@HNS-HPC and the reaction kinetics of liquid-liquid and solid-liquid conversion of sulfide,the MnO2@HNS-HPC not only has a strong adsorption capacity to LiPSs,but also effectively promotes reaction kinetics of phase transition of sulfur.Finally,MnO2@HNS-HPC-modified separator was successfully prepared,which had good wettability and mechanical strength.At 1.0 C,the initial capacity reaches 957.3 mAh g-1,a specific capacity of 529.1 mAh g-1 and a low capacity fading rate of 0.056%after 600 cycles were obtained.And the rate performance is very stable.Because of the synergistic effect of N,S doping and MnO2,the reaction kinetics of sulfur could be effectively promoted,and the"shuttle effect" can be effectively alleviated by physical barrier and chemical adsorption.Finally,the electrochemical performance of the battery was obviously improved.