Glucose‐Induced Synthesis of 1T‐MoS₂/C Hybrid for High‐Rate Lithium‐Ion Batteries

Abstract

commercial LIBs with graphite-based materials as anode cannot meet the above requirements due to the limitation of graphite itself. It shows a low theoretical capacity of 372 mAh g −1 , [2] rapid capacity decay, and possible safety issues during cycling process. Recently, transition metal dichalcogenides (TMDs) have attracted widespread attention in the energy storage fields, especially its application in electrodes of LIBs. As a representative of TMDs, MoS 2 has shown fascinating and superior electrochemical performance due to its unique layered structure. [3,4] MoS 2 always exists in the following three phases: 2H, 1T, and 3R phase according to different coordinations of Mo and S atoms. [5][6][7][8][9] The 2H and 1T phase MoS 2 exhibit notable energy storage and conversion performance due to their characteristic structure and rich physical and chemical properties. 2H-MoS 2 is a semiconducting phase with trigonal prismatic structure. Its high theoretical capacity of 670 mAh g −1 renders it fit to be considered as a promising anode material for LIBs. [10,11] However, two severe issues of 2H-MoS 2 electrode still need to be taken into account: 1) the structure destruction induced by the large volume change during lithium-ions intercalating and deintercalating process; 2) the poor electronic conductivity, arising from a large bandgap of about 1.9 eV. [12,13] To overcome these shortcomings, a large amount of efforts was devoted to modify the electrochemical performance of 2H-MoS 2 . Two general ways are: 1) designing nanostructure materials, such as nanotubes, [14] nanosheets, [15] and nanospheres [16] ; 2) hybridizing 2H-MoS 2 with carbonaceous materials, such as graphene. [17,18] Compared with 2H phase MoS 2 , 1T phase MoS 2 presents a metallic transport behavior and its electric conductivity is approximately 5 orders of magnitudes higher than that in semiconducting 2H-MoS 2 . [19] This contributes to the transfer of electrons and ions in the electrode material. Furthermore, 1T-MoS 2 owns an expanded interlayer spacing of about 1 nm, which is nearly 1.5 times larger than that in 2H-MoS 2 (about 0.65 nm). [20,21] Such an expanded interlayer spacing makes lithium ions embedding and de-embedding much easier. However, the conventional methods to fabricate 1T-MoS 2 require an alkali metal intercalation or exfoliation process, which is unstable, dangerous, complicated, and time-consuming. [22] Preparing 1T phase MoS 2 possesses higher conductivity than the 2H phase, which is a key parameter of electrochemical performance for lithium ion batteries (LIBs). Herein, a 1T-MoS 2 /C hybrid is successfully synthesized through facile hydrothermal method with a proper glucose additive. The synthesized hybrid material is composed of smaller and fewer-layer 1T-MoS 2 nanosheets covered by thin carbon layers with an enlarged interlayer spacing of 0.94 nm. When it is used as an anode material for LIBs, the enlarged interlayer spacing facilitates rapid intercalating and deintercalating of lithium ions and accommodates volume change dur...

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“…Bai et al fabricated a1 T-MoS 2 /C hybrid,i nw hich the interlayer spacingo fa s-prepared 1T MoS 2 was expanded significantly from 0.65 to 0.94 nm. [10] As uperior rate performance with ar eversible capacity of 600 mAh g À1 at 10 Ag À1 was achieved ( Figure 7a). Jiao et al synthesized porous nanotubes assembled with metallic 1T MoS 2 nanosheets through as olvothermalm ethod.…”

“…d) Cycling performance of as‐synthesized samples, e) cycling performance of graphene@MoS 2 @TiO 2 samples. (reproduced with permission, Copyright Wiley‐VCH, 2019).…”

“…Bai et al. fabricated a 1T‐MoS 2 /C hybrid, in which the interlayer spacing of as‐prepared 1T MoS 2 was expanded significantly from 0.65 to 0.94 nm . A superior rate performance with a reversible capacity of 600 mAh g −1 at 10 A g −1 was achieved (Figure a).…”

“…d) Cycling performance of assynthesized samples, e) cycling performance of graphene@MoS 2 @TiO 2 samples. (reproduced with permission, [10] Copyright Wiley-VCH,2 019). ly,t he K + intercalation/extraction process in microsized MoS 2 was proved to be highly dependento nt he charge/discharge rate.…”

“…[5] Besides, it has advantages of high theoretical capacityand low cost as electrode materials.Nevertheless, pristine MoS 2 electrodes suffer from poor cycling stabilitya nd huge voltage polarization. [6] Many strategies have been proposed to improve the electrochemical performance of MoS 2 , such as compositing with ac onductive carbonaceous matrix, [7] doping with heteroatoms, [8] defectengineering, [9] enlarging the interlayer spacingo f( 002), [10] synthesizingf ew-layer MoS 2 , [11] or fabricating specialn anostructures. [12] These modified MoS 2 electrodes show excellent cycling stability and rate performance.…”