Preparation Of Nanoporous Carbon Materials As Host Materials In Lithium Sulfur Batteries

Lithium sulfur battery(LSBs)has high theoretical capacity and energy density, which plays an important role in the next generation of energy storage devices.However,However,some problems existing in LSBs(such as the volume change of shuttle effect S,etc.)seriously hinder its commercialization process.Therefore,we prepared two carbon materials using pomelo peel and ZIF-67 as the precursor system respectively and applied them in lithium sulfur batteries.On the one hand,both of these carbon materials have high specific surface areas,which can not only load a large amount of S as host materials for S,but also immobilize Li PS through well-developed pore structures.On the other hand,they can anchor Li PS by means of chemisorption using a large number of active sites provided by heterogeneous atoms.(1)The waste pomelo peel was used as carbon source,and a kind of nitrogen-oxygen doped porous activated carbon material(PACM)was prepared after high temperature alkaline activation.The high specific surface area of PACM(2326.4 m2 g-1)could not only load S 9 times of its own weight,but also effectively buffer the volume change of S The O element can provide a wealth of polar sites to enhance the anchoring ability of carbon materials to Li PS.Therefore,the prepared S@PACM₉composite anode with 90%S content can provide a high initial discharge specific capacity of 662.2 m Ah g^-1at 1 C current,and the capacity decay rate is only 0.068%in 300 cycles.(2)Cobalt oxynitrous doped porous carbon(NOCo ZIF)was obtained by step carbonization using urea and ZIF-67 as raw materials.Compared with the undoped porous carbon(CZIF),NOCo ZIF contains more N element and can provide more polar sites,thus enhancing the adsorption capacity of host material to Li PS and improving the utilization rate of S.Therefore,LSBs with NOCo ZIF as S host material showed excellent electrochemical performance.The S@NOCo ZIF composite anode can provide a high initial discharge capacity of 780.0 m Ah g^-1at 2 C current after being activated for 3 cycles at 0.1 C current.And after 500 cycles,the capacity retention rate is 78.65%,and the average capacity decay rate is only 0.043%.