Metal–Organic Frameworks Mediated Synthesis of One-Dimensional Molybdenum-Based/Carbon Composites for Enhanced Lithium Storage

Abstract

Molybdenum (Mo)-based compounds with properly engineered nanostructures usually possess improved reversible lithium storage capabilities, which offer great promise to boost the performance of lithium-ion batteries (LIBs). Nevertheless, a lack of efficient and high-yield methods for constructing rational nanostructures has largely restricted the application of these potentially important materials. Herein we demonstrate a metal-organic frameworks (MOFs) mediated strategy to successfully synthesize a series of one-dimensional Mo-based/carbon composites with distinct nanostructures. In this process, starting from well-designed MoO nanorods, the crystal control growth is first proposed that a layer of MOFs is achieved to be controllably grown on surfaces of MoO, forming an obvious core-shell structure, and then the adopted precursor can be in situ transformed into MoO or MoC which are both well confined in conductive porous carbons through direct carbonization at different temperatures, where the MOFs shell serve as both carbon sources and the reactant to react with MoO simultaneously. Benefiting from this design, all optimized products exhibit enhanced electrochemical performances when evaluated as anode materials for LIBs, especially the hollow MoO/C and core-shell MoC/C electrodes, show best reversible capacities up to 810 and 530 mAh g even after 600 cycles at a current density of 1 A g, respectively. So this work may broaden the application of MOFs as a kind of coating materials and elucidates the attractive lithium storage performances of molybdenum-based compounds.

Metal Oxides with Distinctive Valence States in an Electron‐Rich Matrix Enable Stable High‐Capacity Anodes for Li Ion Batteries

“…This process is accompanied with phase transitions from monoclinic to orthorhombic and back to monoclinic, resulting in the formation of Li x MoO 2 . The peaks at 1.44 and 1.73 V in the anodic sweep originate from the Li‐ion extraction in Li x MoO 2 . Besides the two redox peaks, the peaks located at 2.01 and 2.30 V represent the reduction of MoO 3 to MoO 2 .…”

A Bio‐Inspired Structurally‐Responsive and Polysulfides‐Mobilizable Carbon/Sulfur Composite as Long‐Cycling Life Li−S Battery Cathode

“…The capacitive effect of the battery system is calculated according to equations as below: i = av b , and log(i) = b log(v) + log(a), where b below 0.5 represents a diffusion-controlled process, while a larger b value means the ideal capacitive behavior. [47][48][49] In Figure 10b, the b values for the anodic (2.48 V) and cathodic (1.96 V) peaks are 0.6456 and 0.606, respectively, which indicates a capacitive rather than diffusion-controlled process. In Figure 10c, all the contribution ratios are displayed.…”

Recent Progress on Molybdenum Oxides for Rechargeable Batteries

“…[70] If the dosageo fd opamine-HClr eaches 300 mg, hollow pores can be achieved. [72] As depicted in Figure 9a,t he MOF shell can act as ac arbon source upon annealing at different temperatures. The composite electrode shows reversible specific capacities of 940 and 775 mA hg À1 at current densities of 100 and 1000 mA g À1 , respectively.T he rate capability of the electrode increases with the volume of hollow pores ( Figure 8c); this is associated with the shortened lithium-ion diffusion pathway.B ya nnealing prefabricated Mo-polydopamine hollow spheres,atriple-shelled MoO 2 /C composite electrode with hollow structure was also obtained by Lou et al [71] The triple-shelled MoO 2 /C hollow spheres exhibit an initial discharge capacity of 1139 mAh g À1 at 500 mA g À1 .H owever,t he coulombic efficiency is only 67 %f or the first cycle, which can be ascribed to the irreversible conver- Recently,aM OF modulation strategy was adopted to fabricate variousM o-based/carbon hybrid electrodes, including MoO 2 /C, acid-treated MoO 2 /C, and MoC/C composites.…”

“…The composite electrode shows reversible specific capacities of 940 and 775 mA hg À1 at current densities of 100 and 1000 mA g À1 , respectively.T he rate capability of the electrode increases with the volume of hollow pores (Figure 8c); this is associated with the shortened lithium-ion diffusion pathway.B ya nnealing prefabricated Mo-polydopamine hollow spheres,atriple-shelled MoO 2 /C composite electrode with hollow structure was also obtained by Lou et al [71] The triple-shelled MoO 2 /C hollow spheres exhibit an initial discharge capacity of 1139 mAh g À1 at 500 mA g À1 .H owever,t he coulombic efficiency is only 67 %f or the first cycle, which can be ascribed to the irreversible conver- Recently,aM OF modulation strategy was adopted to fabricate variousM o-based/carbon hybrid electrodes, including MoO 2 /C, acid-treated MoO 2 /C, and MoC/C composites. [72] As depicted in Figure 9a,t he MOF shell can act as ac arbon source upon annealing at different temperatures. The as-obtained 1D MoO 2 /C composite electrode delivers areversible capacity of up to 810 mA hg À1 after 600 charge/discharge cycles at 1000 mA g À1 .A fter acid treatment, the electrochemical properties are improved, to some extent, including the specific capacity and rate capability.A so bserved in Figure 9b,o ft he three samples, acid-treated MoO 2 /C exhibitst he best rate performance, which can be ascribed to reduced charge-transfer resistance and increased lithium-ion diffusionv elocity during cycling.…”

“…a) Cycling stability and b) rate capability of metal-organic framework (MOF)-derived MoC/C composites [72]. ZIF = zeolitic imidazolate framework, BMZIF = bimetallic zeolitic imidazolate framework.…”