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

Abstract

Although lithium metal is an ultimate anode material for lithium-based batteries owing to its high theoretical capacity, the uncontrollable dendrites and infinite volume change associated with poor rate capabilities are stagnating its practical applications. Here, a new type of perpendicular MXene-Li array is developed with tunable MXene walls and constant space in between as anodes for lithium metal batteries. Such perpendicular MXene arrays possess dual periodic interspaces, i.e., nanometer-scale interspaces in MXene walls and micrometer-scale interspaces between MXene walls. The former interspaces are favorable for the fast transfer of lithium ions upon stripping and plating, and the latter enables efficiently homogenization of the electric field, leading to a good high-rate capability up to 20 mA cm −2 . More importantly, the notorious lightning rod effect and volume change are efficiently inhibited in such perpendicular MXene arrays, giving rise to a dendrite-free lithium anode with a low potential of 25 mV, a high capacity of 2056 mAh g −1 , and good cycle stability up to 1700 h. layers [10,11] ), advanced electrolytes (solid electrolytes, [12] hybrid electrolytes [13,14] ) and 3D hosts (nickel foams, [15,16] graphene oxide foams, [17][18][19][20] etc.) have been exploited. In particular, 3D hosts enable to significantly promote the transfer of lithium ions or electrons, dramatically improving the cycle life and inhibiting the volume change during repeated stripping and plating processes. To date, 3D hosts can be simply divided into two categories: insulated hosts and electrically conductive hosts. The insulated 3D hosts commonly include glass fiber (GF) cloths, [21] ZnO coated polyimide matrix, [22] and oxidized polyacrylonitrile nanofiber networks, [23] which can homogenize the lithium flux and enhance the transportation of lithium ions. In comparison, electrically conductive 3D hosts are common carbon nanotube sponges, [24] Cu frameworks, [25] reduced graphene oxide foams, [26] 3D graphitic carbon foams, [27] which enable to homogenize both electrical field and lithium ion flux. However, for above 3D hosts, their pores were usually disordered, far from the ideal ordered structures. Very recently, some hosts with periodic and uniform pores or channels have been explored, including vertically aligned 3D hosts including porous polyimide/lithium arrays, [28] glass fiber/ lithium arrays, [29] Cu microchannels, [30] and vertically oriented lithium-copper-lithium arrays. [31] These periodic upright structures are not only favorable for the fast transfer of both lithium ion and electron, but providing abundant interior spaces for lithium plating. Thus, these vertically aligned hosts show improved high-rate capabilities as applied for lithium-based batteries. Unfortunately, in such 3D hosts, the lightning rod effect becomes more severe, causing substantial lithium dendrites growing at the top end of the aligned walls. [30,31] Moreover, upon deep stripping and plating, lithium is still prone to mainly grow on the ...

A 3D Hydroxylated MXene/Carbon Nanotubes Composite as a Scaffold for Dendrite‐Free Sodium‐Metal Electrodes

“…[22] Theh ydroxylated MXene (h-MXene) materials possess fibrous morphology and more content of oxygenic functional groups,c ompared with twodimensional MXene materials, [23][24][25][26][27] as well as high electric and thermal conductivity. [28][29][30] Among all the MXene materials,T i 3 C 2 is most typical one and has been widely studied. [24] Previous studies have shown that loading with oxygenic functional groups can improve the sodiophilic/lithiophilic nature of the carbon hosts,r esulting in relatively low overpotential for Na/Li nucleation.…”

Recent Advances of Emerging 2D MXene for Stable and Dendrite‐Free Metal Anodes

“…The perpendicular MXene arrays could not only Reproduced with permission. [214] Copyright 2020, Wiley-VCH.…”

“…Recently, Yang and co‐workers designed perpendicular MXene–Li arrays with adjustable MXene walls and constant space in between by a rolling‐cutting method ( Figure a). [ 214 ] They first fabricated a flexible Ti 3 C 2 T x MXene film by a vacuum filtration method. Then the MXene film and Li strip were pressed together and manually rolled into a MXene–lithium cuboid.…”

Self-propagating fabrication of 3D porous MXene-rGO film electrode for high-performance supercapacitors

“…In order to facilitate fast ion transport and fully utilize the active surface, several strategies have been proposed to overcome the restacking problem, such as adding "spacers" between MXene layers [14][15][16] , creating pores [17][18][19][20] , establishing three-dimensional (3D) structures and fabricating vertical alignments [21][22][23][24][25] . Fabricating 2D MXene nanosheets into 3D structure has been focused as a significant and effective approach for increasing the ion accessibility to the active sites, and many ways have been reported including template methods [ 13 , 26 , 27 ], freeze-drying [28][29][30] , loading on 3D matrix [31][32][33] .…”