Facile Synthesis of Crumpled Nitrogen‐Doped MXene Nanosheets as a New Sulfur Host for Lithium–Sulfur Batteries

Abstract

shuttle effect of polysulfide. [3] The suppression of the polysulfide shuttle effect is the primary challenge that has hindered the development of lithium-sulfur batteries. The ideal sulfur cathode host should have: (i) a highly porous structure with interconnected architecture to encapsulate sulfur, (ii) strong capability to restrain soluble polysulfides, (iii) high electronic conductivity, and (iv) flexible but robust mechanical properties.Carbon materials with well-designed pore structures, such as mesoporous carbon [4] and carbon nanotubes, [5] have been utilized to restrain the migration of soluble polysulfides from the cathode. Carbon materials can effectively improve the electronic conductivity of sulfur cathodes, and the as-fabricated lithium-sulfur cells showed high specific capacities during the initial few cycles. However, there has been a serious decay of capacity during long-term cycling. It is mainly ascribed to the weak intrinsic interactions between nonpolar carbon and polar polysulfides intermediate, and the large volume expansion/extraction of sulfur compounds during the discharge/ charge processes. [6] The physical barriers provided by sequestration and adsorption in carbon materials can only slow down diffusion of lithium polysulfides out of cathodes in the shortto medium-term of cycling (<100 cycles). Additionally, weak interaction can cause the detachment and separation of lithium sulfides (Li 2 S x , 1 < x < 2, the fully discharged products), from carbon matrix, which will induce irreversible active mass loss and isolation of electrical contacts. Therefore, strong physical and chemical interactions between sulfur/lithium polysulfides and the host materials are crucial to suppress polysulfides shuttling effects and capacity decay. It has been discovered that surface functionalized host materials, such as reduced graphene oxides, [1] polar metal oxides (MnO 2 , [7] Ti 4 O 7[8] ), metal-organic frameworks (MOFs), [9] and metal carbide MXene, [10] showed much better properties because of their hydrophilic surfaces that can bind lithium polysulfides via polar-polar interactions.Recently, a large family of ternary metal carbides, nitrides, or carbonitrides has been successfully prepared. These are termed as "MXene" and are denoted as M n + 1 X n T x , where M is an transition metal such as Ti or V, X is C and/or N, and T is a surface termination group (e.g., O, OH, and F). [11] They have been emerged as brand-new 2D materials with potential applications as electrode materials. Owing to layered structure, high electronic conductivity, remarkable chemical durability, Crumpled nitrogen-doped MXene nanosheets with strong physical and chemical coadsorption of polysulfides are synthesized by a novel one-step approach and then utilized as a new sulfur host for lithium-sulfur batteries. The nitrogendoping strategy enables introduction of heteroatoms into MXene nanosheets and simultaneously induces a well-defined porous structure, high surface area, and large pore volume. The as-prepared nitrogen-dope...

2D Metal Carbides and Nitrides (MXenes) as High‐Performance Electrode Materials for Lithium‐Based Batteries

“…[100] As shown in the synthesis procedure (Figure 13a), the Ti 3 C 2 MXene nanosheets were rolled with lithium metal to fabricate an elongated film, which was then folded to increase the number of layers. [96] Copyright 2018, Wiley-VCH. Figure 13b Figure 10.…”

“…The multilayered Ti 3 C 2 MXene-Li hybrid film electrode shows flat voltage profiles, a reduced overpotential (32 mV at 1.0 mA cm −2 ) and superior cycling performance ( Figure 13d). [100] As discussed above, MXenes indeed improve the electrochemical performance of lithium-sulfur batteries, as summarized in Table 3 Ti 2 CT x Cathode host 70 1200 mAh g −1 at C/5 650 cycles at C/2 0.05% per cycle [26] Ti 3 C 2 T x @ Meso-C Cathode host 73 1225 mAh g −1 at C/2 300 cycles at C/2 0.14% per cycle [90] Ti 3 C 2 T x Interlayer on separator 100 1225 mAh g −1 at 0.5 A g −1 100 cycles at 0.5 A g −1 0.12% per cycle [99] Ti 3 C 2 T x Interlayer on separator 68 1047 mAh g −1 at C/5 500 cycles at 1C 0.062% per cycle [98] Ti 3 C 2 T x /RGO Cathode host 70 1144 mAh g −1 at C/2 300 cycles at C/2 0.077% per cycle [91] MXene/CNT Cathode host 83 1263 mAh g −1 at C/20 1200 cycles at C/2 0.043% per cycle [92] N-doped Ti 3 C 2 T x Cathode host 74 1144 mAh g −1 at C/5 1000 cycles at 2C 0.026% per cycle [96] Ti 3 C 2 T x nanoribbon Cathode host and interlayer 68 1062 mAh g −1 at C/5 200 cycles at C/2 0.24% per cycle [101] Ti 3 C 2 T x /MoS 2 -C Cathode host 79.6 1195 mAh g −1 at C/10 300 cycles at C/2 0.07% per cycle [102] Even after 100 cycles, a capacity of 841 mAh g −1 is retained.…”

Novel 2D Sb2S3 Nanosheet/CNT Coupling Layer for Exceptional Polysulfide Recycling Performance

“…[1,2] Compared with other battery systems, [3][4][5][6][7][8][9][10] lithium sulfur batteries (LSBs) are considered an attractive choice alternative to LIBs as next-generation batteries thanks to their high theoretical energy density of 2567 Wh kg −1 and exceptional specific of Li 2 S x species. [30] Among various potential coupling materials, 2D layer-structured materials with high surface-volume ratios and abundant active binding sites have attracted considerable attention, such as graphene, [31] MXene, [32,33] metal (hydro)oxides, [34] and metal sulfides. [30] Among various potential coupling materials, 2D layer-structured materials with high surface-volume ratios and abundant active binding sites have attracted considerable attention, such as graphene, [31] MXene, [32,33] metal (hydro)oxides, [34] and metal sulfides.…”

MXene‐Based Composites: Synthesis and Applications in Rechargeable Batteries and Supercapacitors

“…[74] With MXene-based composite cathode materials, the hydrophilic surfaces of MXene, can constrain the LiPSs. [258] In general, a large amount of sulfur can be adsorbed by MXene and its volume expansion is inhibited by the layered MXene, leading to the excellent electrochemical performance of the MXene/S electrode. [153] Following these predicted advantages, MXene-based composite materials have been synthesized and used as a sulfur carrier to improve Li-S battery performance.…”

“…[153] Following these predicted advantages, MXene-based composite materials have been synthesized and used as a sulfur carrier to improve Li-S battery performance. [258] Other materials also can insert between the MXene layers, such as porous carbon, [66] rGO, [143] and CNTs, [153] which improves the conductivity of MXene and inhibits MXene from restacking during cycling. The MOF precursors can insert into the interlaminations of the Ti 3 C 2 T x layers and form into the MOF to increase the Ti 3 C 2 T x surface areas.…”