Advanced functional materials: 3000 h stable cycling at high current density and capacity based on cross-linked mxene lithium anode
lithium is considered as an ideal anode material for lithium because of its high theoretical specific capacity (3860 MAH g – 1) low redox potential (− 3.04 V vs. stard hydrogen electrode). However from the point of view of practical application lithium metal anode needs to be greatly improved in rate specific capacity charge discharge stability. On the one h the surface capacity of lithium anode is required to be greater than 10 MAH cm-2 in order to achieve the energy density of 500 whkg-1; on the other h the application of next-generation batteries requires the lithium anode to achieve rapid charge discharge at a current density greater than 10 Ma cm-2. However during the charge discharge cycle lithium metal is prone to produce uncontrollable dendrite growth volume expansion of electrodes instability of solid electrolyte boundary film. These problems will be more serious under the condition of high current density large capacity charge discharge which will greatly affect the cycle stability service life of the battery.
Professor Liang Jiajie of Nankai University firstly improved the mechanical strength toughness of mxene based three-dimensional framework by covalent crosslinking of polymers prepared metal lithium carriers with excellent conductivity lithium affinity mechanical stability which were used to deposit lithium metal to prepare lithium anode materials. Specifically the three-dimensional framework of mxene / silver nanowires was formed by silylation of mxene nanosheets with polysiloxane. Compared with the control sample (non crosslinked mxene framework) the covalently crosslinked mxene framework shows excellent mechanical strength toughness which is conducive to alleviating the impact of huge internal stress changes during rapid deep lithium deposition / stripping ensuring the structural integrity of the three-dimensional framework carrier in long-term charge discharge cycle. The results show that the lithium metal anode has a stable charge discharge cycle of more than 3000 cycles (3000 hours) in a symmetrical battery with a capacity of 10 MAH cm-2 a current density of 20 mA cm-2. The related work was published in advanced functional materials (DOI: 10.1002 / ADFM. 202008044).
the strategy of this work focuses on optimizing the mechanical stability of lithium metal framework so as to significantly improve the cycle life of lithium metal anode. The mxene / agnw framework with conductivity lithium affinity formed by the combination of weak van der Waals force will collapse due to the large stress change during the lithium deposition / stripping cycle. On the contrary covalent crosslinking was introduced through silicification reaction with polysiloxane in this work which significantly improved the mechanical strength toughness of the framework was conducive to maintaining the structural integrity of the framework in the long cycle process. Therefore the lithium metal composite anode prepared in this work shows excellent reversibility under ultra-high current density ultra-high surface capacity which makes the practical application of high-performance lithium metal battery possible.
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