Terminal sulfur atoms formation via defect engineering strategy to promote the conversion of lithium polysulfides  

作　　者：Yuanchang Li Wenda Li Xiujuan Yan Zhenfang Zhou Xiaosong Guo Jing Liu Changming Mao Zhonghua Zhang Guicun Li 

机构地区：[1]College of Materials Science and Engineering,Qingdao University of Science and Technology,Qingdao 266042,China

出　　处：《Journal of Materials Science & Technology》2022年第8期221-231,共11页材料科学技术（英文版）

基　　金：supported by the National Natural Science Foundation of China(21805157,51972187);Natural Science Foundation of Shandong Province(ZR2019MEM043,ZR2019MB037);Shandong Provincial Key Research and Development Program(2019GGX103034);Development Program in Science and Technology of Qingdao(19-6-2-12-cg)。

摘　　要：The defect engineering shows great potential in boosting the conversion of lithium polysulfides intermediates for high energy density lithium-sulfur batteries(LSBs),yet the catalytic mechanisms remain unclear.Herein,the oxygen-defective Li_(4)Ti_(5)O_(12)-xhollow microspheres uniformly encapsulated by N-doped carbon layer(OD-LTO@NC)is delicately designed as an intrinsically polar inorganic sulfur host for the research on the catalytic mechanism.Theoretical simulations have demonstrated that the existence of oxygen deficiencies enhances the adsorption capability of spinel Li_(4)Ti_(5)O_(12)towards soluble lithium polysulfides.Some-S-S-bonds of the Li2S6on the defective Li_(4)Ti_(5)O_(12)surface are fractured by the strong adsorption force,which allows the inert bridging sulfur atoms to be converted into the susceptible terminal sulfur atoms,and reduces the activation energy of the polysulfide conversion in some degree.In addition,with the N-doped carbon layer,secondary hollow microspheres architecture built with primary ultrathin nanosheets provide a large amount of void space and active sites for sulfur storage,adsorption and conversion.The as-designed sulfur host exhibits a remarkable rate capability of 547 m Ah g^(-1)at 4C(1 C=1675 m A g^(-1))and an outstanding long-term cyclability(519 m Ah g^(-1)after 1000 cycles at 3 C).Besides,a high specific capacity of 832 m Ah g^(-1)is delivered even after 100 cycles under a high sulfur mass loading of 3.2 mg cm^(-2),indicating its superior electrochemical performances.This work not only provides a strong proof for the application of oxygen defect in the adsorption and catalytic conversion of lithium polysulfides,but offers a promising avenue to achieve high performance LSBs with the material design concept of incorporating oxygen-deficient spinel structure with hierarchical hollow frameworks.

关 键 词：Lithium-sulfur batteries Oxygen deficiency Lithium titanate Hierarchical hollow microsphere Conversion kinetics 

分 类 号：TM912[电气工程—电力电子与电力传动] TQ131.11[化学工程—无机化工]