Application-MXene is used in lithium-sodium metal anodes-②

Research Background

Due to its unique physicochemical properties, MXene has been extensively studied and involves multiple fields . Metal lithium is expected as a next generation high energy density battery negative electrode material, a lithium sulfur, lithium-air battery. However, the charge-discharge cycle, lithium is repeated due to uneven deposition / dissolution of metal lithium negative electrode surface easily grows lithium dendrites, lithium dendrites loose structure, easy off electrochemically inactive form of " dead lithium " , leading to cell rapid decay reversible capacity, dendrite but also can cause the battery to short circuit , metal these problems limit the lithium applying the electrodes in the secondary battery. Specific structural design 3D host material, is expected to be no branches crystal growth to achieve higher security than the flexible energy of a lithium negative electrode metal. MXene is an emerging two-dimensional material, which has high conductivity and low diffusion barrier for lithium ions, and the groups adsorbed on the surface are lithium- philic . The sharing of MXene ‘s development in lithium metal and sodium metal anodes this time is only a part of the published articles, and other articles will be shared later .

Literature 1 :

Horizontal Growth of Lithium on Parallelly Aligned MXene Layers towards Dendrite-Free Metallic Lithium Anodes 

Adv. Mater. 2019, 31, 1901820 .

brief introduction

In order to adjust the lithium precision metal nucleation and growth, Beijing University of Aeronautics and Astronautics poplar bin TF , simple self-assembly mode, the preparation MXene film layer can be efficiently induce nucleation of lithium, such that lithium metal MXenes sheet The layer is deposited uniformly and grows in the horizontal direction instead of randomly nucleating and growing lithium dendrites . In addition, the F functional groups adsorbed on the MXenes nanosheets help to form a uniform and long-lasting SEI film . MXene- lithium metal mixed negative electrode has no lithium dendrite , high lithium content, and long cycle life (900 hours ) . When the discharge depth is greater than 5 mAh / cm 2 , lithium grows on the surface of Li-MXene , producing pebble-like lithium . When it is 35 mAh / cm 2 , the particle size of the pebble-like lithium becomes larger, but there is no lithium The generation of dendrites shows the controllable nucleation of two-dimensional nanosheets.Lithium metal batteries have huge application potential.

Literature 2 :

Perpendicular MXene Arrays with Periodic Interspaces toward Dendrite-Free Lithium Metal Anodes with High-Rate Capabilities  

Adv. Funct.  Mater. 2020, 30, 1908075 .

brief introduction

Recent research shows that thanks to the periodic structure, the 3D conductive host material not only significantly promotes the transfer of lithium ions or electrons, but also provides a rich internal space for the deposition and dissolution of lithium ions. Therefore, when these periodic 3D conductive hosts are applied to lithium batteries, their rate capability will be improved . Beijing University of Aeronautics and Astronautics INSTITUTE material poplar Bin TF , designed a unique MXene-Li array, which has two kinds of periodic intervals , by suction filtration deposition method, the prepared MXenes wall containing nanoscale The spacing, by alternately rolling the MXene film and the lithium metal sheet , forms a micron-level spacing between the MXene walls. In this carefully designed structure array, the thickness of the MXene layer and the lithium metal layer can be adjusted. The MXenes wall is a nano-scale gap, which is very beneficial for the rapid transportation of lithium ions. MXenes wall isThe micron-level gap effectively uniforms the electric field, which can effectively reduce the lightning rod effect during the cycle , thereby depositing lithium evenly inside the MXene array. Finally, a dendrite- free lithium anode was realized on the basis of the periodic MXene-Li array .

Literature 3 :

3D printing dendrite-free lithium anodes based on the nucleated MXene arrays

Energy Storage Materials 24 (2020) 670–675 .

brief introduction

3D printing as a rapid prototyping technology, more convenient in the preparation of the periodic structure, in view of MXenes hydrophilic, Beijing University of Aeronautics and Astronautics poplar Bin Task Force , through the 3D mode printing, the periodic preparation MXene of 3D arrays, and 3D lattice structure , by way of electrodeposition, can be prepared to yield the corresponding lithium metal negative electrode composite material was found during the deposition of lithium, the lithium is grown along the printing junction edge direction of the structure, rather than Growing on the substrate, with the deep deposition process, cobblestone-like lithium will appear between the 3D array and the 3D lattice , gradually filling the gap . Due to the large curvature of the 3D voids of the lattice structure , the sharp array effect is more obvious. The electrochemical performance of the 3D array structure is better than the electrochemical performance of the 3D lattice structure. When designing the host material of the periodic structure, you should pay attention to Consideration of curvature .

Source: MXene notes 

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