Qu Long, Liu Pei, Yi Yikun, Wang Tao, Yang Pu, Tian Xiaolu, Li Mingtao, Yang Bolun, Dai Sheng
Shaanxi Key Laboratory of Energy Chemical Process Intensification, School of Chemical Engineering and Technology, Xi'an Jiaotong University, No. 28, Xianning West Road, Xi'an, Shaanxi, 710049, P. R. China.
Xi'an Jiaotong University Suzhou Academy, Suzhou, Jiangsu, 215123, P. R. China.
ChemSusChem. 2019 Jan 10;12(1):213-223. doi: 10.1002/cssc.201802449. Epub 2018 Nov 28.
Decay in electrochemical performance resulting from the "shuttle effect" of dissolved lithium polysulfides is one of the biggest obstacles for the realization of practical applications of lithium-sulfur (Li-S) batteries. To meet this challenge, a 2D g-C N /graphene sheet composite (g-C N /GS) was fabricated as an interlayer for a sulfur/carbon (S/KB) cathode. It forms a laminated structure of channels to trap polysulfides by physical and chemical interactions. The thin g-C N /GS interlayer significantly suppresses diffusion of the dissolved polysulfide species (Li S ; 2<x≤8) from the cathode to the anode, as proven by using an H-type glass cell divided by a g-C N /GS-coated separator. The S/KB cathode with the g-C N /GS interlayer (S/KB@C N /GS) delivers a discharge capacity of 1191.7 mAh g at 0.1 C after 100 cycles, an increase of more than 90 % compared with an S/KB cathode alone (625.8 mAh g ). The S/KB@C N /GS cathode shows good cycling life, delivering a discharge capacity as high as 612.4 mAh g for 1 C after 1000 cycles. According to XPS results, the anchoring of the g-C N /GS interlayer to Li S can be attributed to a coefficient chemical binding effect of g-C N and graphene on long-chain polysulfides. Generally, the improvement in electrochemical performance originates from a coefficient of the enhanced Li diffusion coefficient, increased charge transfer, and the weakening of the shuttle effect of the dissolved Li S as a result of the g-C N /GS interlayer.
溶解态多硫化锂的“穿梭效应”导致的电化学性能衰减是锂硫（Li-S）电池实现实际应用的最大障碍之一。为应对这一挑战，制备了二维g-C₃N₄/石墨烯片复合材料（g-C₃N₄/GS）作为硫/碳（S/KB）正极的中间层。它形成了通道的层状结构，通过物理和化学相互作用捕获多硫化物。薄的g-C₃N₄/GS中间层显著抑制了溶解的多硫化物物种（Li₂Sₓ；2＜x≤8）从正极扩散到负极，这通过使用由g-C₃N₄/GS涂层隔膜分隔的H型玻璃电池得到了证实。具有g-C₃N₄/GS中间层的S/KB正极（S/KB@C₃N₄/GS）在0.1 C下循环100次后放电容量为1191.7 mAh g，比单独的S/KB正极（625.8 mAh g）增加了90%以上。S/KB@C₃N₄/GS正极显示出良好的循环寿命，在1 C下循环1000次后放电容量高达612.4 mAh g。根据XPS结果，g-C₃N₄/GS中间层与Li₂Sₓ的锚固可归因于g-C₃N₄和石墨烯对长链多硫化物的协同化学结合作用。一般来说，电化学性能的改善源于增强的Li扩散系数、增加的电荷转移以及由于g-C₃N₄/GS中间层导致的溶解态Li₂Sₓ穿梭效应的减弱。
