The high-voltage battery has now become a goal in order to meet the demands for high energy density.However,the severe side reactions between Li metal and carbonate-based electrolytes in this system result in unstable...The high-voltage battery has now become a goal in order to meet the demands for high energy density.However,the severe side reactions between Li metal and carbonate-based electrolytes in this system result in unstable interphase,leading to non-uniform Li-ion flux and thus aggravating the dendrite growth of Li.The protect interphase,traditional solid electrolyte interface(SEI),is a loose solid layer consisted of many components,which generally does not possess the function of preventing the lithium budding.Herein,based on polysulfide solubility in ester,we proposed a strategy to eliminate the dendrite by constructing a unique SEI in which the dynamic polysulfides were in situ formed and encapsuled.For this purpose,a 2-fluorophenylsulfur pentafluoride(2-FSPF)was employed as an additive in carbonate-based electrolyte that can be decomposed electrochemically during battery operation to form such a polysulfide-rich interphase.These polysulfides with certain fluidity can adhere to dynamically the budding tip of Li metal,as a so-called tip-inhibitor,when the local current density of the tip rising,thus to hinder Li^(+)diffusion toward the tip,resulting in inhibiting the further growth of Li dendrites and leveling the Li deposition.At the current density of 1 mA cm^(-2),the average Coulombic efficiency of Li//Cu cells is as high as 98.39%during 600 cycles,and the stable cycling of Li//Li symmetric cell reaches 3500 h.Furthermore,due to the high anodic stability,the Li//high-voltage LiCoO_(2)(LCO)full cells and Li–O_(2)battery achieve excellent cycle performance with lean electrolyte.展开更多
We present here a systematic theoretical study to explore the underlying mechanisms of the H abstraction reaction from methane. Various abstracting agents have been modeled, using oxygen radicals and a set of high val...We present here a systematic theoretical study to explore the underlying mechanisms of the H abstraction reaction from methane. Various abstracting agents have been modeled, using oxygen radicals and a set of high valence metal oxo compounds. Our calculations demonstrate that although H abstraction from CH3-H by metal oxoes can be satisfactorily fitted into the Polanyi correlation on the basis of oxygen radicals, the mechanisms behind are significantly different. The frontier orbital analyses show that there are three electrons and three active orbitals (3e, 3o) involved in H abstraction by oxygen radicals; whereas an additional orbital of pi(M-O)* is involved in H abstraction by M = O, resulting in a (4e, 4o) interaction. In terms of valence bond state correlation diagram, we find that H abstraction by a metal oxo may benefit from the contribution of ionic resonance structures, which could compensate the penalty of opening the M-O pbond. We believe that these findings can help to design more effective catalysts for the activation of light alkanes. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B. V. and Science Press. All rights reserved.展开更多
Lithium-oxygen(Li-O) battery is considered as one of the most promising alternatives because of its ultrahigh theoretical energy density. However, their cycling stability is severely restricted by the uncontrollable d...Lithium-oxygen(Li-O) battery is considered as one of the most promising alternatives because of its ultrahigh theoretical energy density. However, their cycling stability is severely restricted by the uncontrollable dendrite growth and serious oxygen corrosion issue on Li surface. Herein, a sulfur-modified Li surface can be successfully constructed via chemical reaction of guanylthiourea(GTU) molecule on Li,which can induce the selectively fast decomposition of lithium bis(trifluoromethanesulfonyl)imide(LiTFSI) to form a smooth and stable inorganics-rich solid-electrolyte interphase(IR-SEI) during the subsequent electrochemical process. Such an IR-SEI cannot only offer a highly reversible and stable Li plating/stripping chemistry with dendrite-free property(10 mA cm^(-2)-10 mAh cm^(-2), > 0.5 years;3 mA cm^(-2)-3 m Ah cm^(-2), > 1 year) but also endows the Li metal an anti-oxygen corrosion function, thereby significantly improving the cycling stability of Li-Obatteries. This work provides a new idea for constructing functional solid-electrolyte interphase(SEI) to achieve highly stable Li metal anode.展开更多
基金financial support from the NSFC projects(U1805254,21773192,22072117,and 22179112)
文摘The high-voltage battery has now become a goal in order to meet the demands for high energy density.However,the severe side reactions between Li metal and carbonate-based electrolytes in this system result in unstable interphase,leading to non-uniform Li-ion flux and thus aggravating the dendrite growth of Li.The protect interphase,traditional solid electrolyte interface(SEI),is a loose solid layer consisted of many components,which generally does not possess the function of preventing the lithium budding.Herein,based on polysulfide solubility in ester,we proposed a strategy to eliminate the dendrite by constructing a unique SEI in which the dynamic polysulfides were in situ formed and encapsuled.For this purpose,a 2-fluorophenylsulfur pentafluoride(2-FSPF)was employed as an additive in carbonate-based electrolyte that can be decomposed electrochemically during battery operation to form such a polysulfide-rich interphase.These polysulfides with certain fluidity can adhere to dynamically the budding tip of Li metal,as a so-called tip-inhibitor,when the local current density of the tip rising,thus to hinder Li^(+)diffusion toward the tip,resulting in inhibiting the further growth of Li dendrites and leveling the Li deposition.At the current density of 1 mA cm^(-2),the average Coulombic efficiency of Li//Cu cells is as high as 98.39%during 600 cycles,and the stable cycling of Li//Li symmetric cell reaches 3500 h.Furthermore,due to the high anodic stability,the Li//high-voltage LiCoO_(2)(LCO)full cells and Li–O_(2)battery achieve excellent cycle performance with lean electrolyte.
基金financial support from the National Nature Science Foundation of China (21133004,21373167,21573178)the Fundamental Research Funds for the Central Universities (20720160046)the Program for Innovative Research Team in Chinese Universities (IRT_14R31)
文摘We present here a systematic theoretical study to explore the underlying mechanisms of the H abstraction reaction from methane. Various abstracting agents have been modeled, using oxygen radicals and a set of high valence metal oxo compounds. Our calculations demonstrate that although H abstraction from CH3-H by metal oxoes can be satisfactorily fitted into the Polanyi correlation on the basis of oxygen radicals, the mechanisms behind are significantly different. The frontier orbital analyses show that there are three electrons and three active orbitals (3e, 3o) involved in H abstraction by oxygen radicals; whereas an additional orbital of pi(M-O)* is involved in H abstraction by M = O, resulting in a (4e, 4o) interaction. In terms of valence bond state correlation diagram, we find that H abstraction by a metal oxo may benefit from the contribution of ionic resonance structures, which could compensate the penalty of opening the M-O pbond. We believe that these findings can help to design more effective catalysts for the activation of light alkanes. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B. V. and Science Press. All rights reserved.
基金the financial support from the National Natural Science Foundation of China(U1805254,21773192,22072117,22179112)。
文摘Lithium-oxygen(Li-O) battery is considered as one of the most promising alternatives because of its ultrahigh theoretical energy density. However, their cycling stability is severely restricted by the uncontrollable dendrite growth and serious oxygen corrosion issue on Li surface. Herein, a sulfur-modified Li surface can be successfully constructed via chemical reaction of guanylthiourea(GTU) molecule on Li,which can induce the selectively fast decomposition of lithium bis(trifluoromethanesulfonyl)imide(LiTFSI) to form a smooth and stable inorganics-rich solid-electrolyte interphase(IR-SEI) during the subsequent electrochemical process. Such an IR-SEI cannot only offer a highly reversible and stable Li plating/stripping chemistry with dendrite-free property(10 mA cm^(-2)-10 mAh cm^(-2), > 0.5 years;3 mA cm^(-2)-3 m Ah cm^(-2), > 1 year) but also endows the Li metal an anti-oxygen corrosion function, thereby significantly improving the cycling stability of Li-Obatteries. This work provides a new idea for constructing functional solid-electrolyte interphase(SEI) to achieve highly stable Li metal anode.
