Insight into the reaction mechanism of sulfur chains adjustable polymer cathode for high-loading lithium-organosulfur batteries

Small molecules with adjustable sulfur atoms in the confined structure were acted as precursor for the synthesis of polymer cathodes for lithium-organosulfur batteries.Among them,poly(diallyl tetrasulfide)(PDATtS)delivered a high capacity of 700 mAh g^(-1),stable capacity retention of 85%after 300 cycles,high areal capacity~4 m Ah cm^(-2) for electrode with up to 10.3 mg cm^(-2) loading.New insight into the reaction mechanism of PDATtS electrode that radicals arisen from the homolytic cleavage of S-S bond in PDATtS reacted with Li+to generate thiolates(RSLi)and insoluble lithium sulfides(Li_(2)S)or lithium disulfide(Li_(2)S_(2))was clearly verified by in-situ UV/Vis spectroscopy,nuclear magnetic resonance(NMR)studies and density-functional theory(DFT)calculations.Therefore,based on the unique reaction mechanism,problems of rapid capacity fading due to the formation of soluble polysulfide intermediates and their serious shuttle effect in conventional lithium-sulfur(Li-S)batteries was totally avoided,realizing the dendrite-free lithium sulfur batteries.This study sets new trends for avenues of further research to advance Li-S battery technologies.

Functional-selected LiF-intercalated-graphene enabling ultra-stable lithium sulfur battery

Using a functionally selective solid electrolyte interphase(SEI)as an anodic protection layer can effectively avoid the subsequent settlement of uneven lithium electrodeposits for lithium sulfur(Li-S)batteries.To address the issues of single functional,mechanical crushing and peeling of the conventional rigid LiF SEI,a unique functional-selected rigid-flexible-coupled LiF-intercalated-graphene(LiF-GN)SEI as anodic protection is constructed,which is verified by in-operando X-ray photoelectron spectroscopy(XPS)spectra.Owing to the synergistic effect of the LiF and graphene layer,this intercalated functionalselected SEI architecture exhibits a dramatic elastic modulus(rigid-flexible coupling with a shallow Young’s modulus(~430 MPa)and a tremendous Young’s modulus of~20 GPa),high mechanical strength,and can be repulsive to polysulfides,accompanied unprecedented trafficability of Li ions.Consequently,the forceful exclusion of polysulfides from the LiF-GN SEI,as confirmed by means of in-situ UV/vis analysis,Li2 S nucleation tests,and visual permeation experiments,is of profound significance for the effective protection of Li anodes and enables Li-S batteries to achieve remarkable electrochemical performance(ultralow capacity decay rate of 0.022%during 300 cycles at 1 C and high discharge capacity of 1092 mAh/g at 0.5 C).

模拟导弹制导约束系统实现锂全电池中锂金属的高效利用

金属锂的有效利用是实现锂金属全电池高安全性和高能量密度应用的关键.本文中,我们报道了一种仅含20%过量锂且可逆性和库仑效率显着提高的锂金属全电池.我们通过设计巧妙的模拟导弹制导约束系统(SMGCS),构建兼容的亲锂银位点和硝酸盐层来引导和限制锂的沉积.银位点充当有效的锂沉积位点,吸引锂离子,引导锂的初始成核.生成的硝酸盐层提供了有利于均匀限域且高容量锂沉积的界面环境,这在理论上已通过分子动力学(MD)模拟得到了验证.这两种优点相结合,实现了坚固且无枝晶的锂沉积以及含有极少量过量锂的锂金属全电池的应用.并且该锂金属在碳酸酯电解液中表现出优异的循环效率(300次以上的循环中库伦效率约99%),还可以在10 mA h cm^(-2)的高容量下进行深度循环.本文中锂金属前所未有的高利用率为未来高效锂金属全电池的发展开辟了一条新的道路.