MgO nanosheets modified carbon foam@carbon nanotubes for lithium-sulfur battery cathode

The article reports a facile method to prepare a novel 3D flexible multifunctional nitrogen-doped carbon nanotube electrode. The carbon nanotubes were simultaneously modified by MgO nanosheets. The researchers prepared CF@CNTs/MgO complexes by using a facile liquid-phase impregnation/adsorption method in combination with the pyrolysis of commercially available inexpensive melamine foam (MF). This method allows for efficient control of sulfur loading. Various characterizations such as SEM, TEM, HRTEM, XRD, XPS, and electrochemical tests were performed for different complexes with loadings ranging from 3.8 mg/cm2 to 14.4 mg/cm2 (see figure presentation) to finally obtain suitable complexes with high sulfur loadings.

This is analyzed accordingly in the article. The presence of a three-dimensional foam carbon skeleton with extraordinary elasticity and mechanical strength eliminates the need for binders in the prepared complexes, while the porous framework provides sufficient internal space to mitigate the problem of large sulfur volume changes during the lithium-sulfur battery cycle. The tight CNT coating on the foam carbon backbone promotes electron or ion transport and reaction rate, and also provides efficient active sites with a view to increasing sulfur loading rate. The modification of ultrathin MgO nanosheets promotes the chemisorption of lithium polysulfides during the reaction, and the in situ heteroatomic nitrogen doping of the foam carbon also facilitates the trapping of lithium polysulfides.

This study provides a relatively simple idea for the preparation of CF@CNTs/MgO complexes, which provides a new direction for the preparation of flexible electrodes for applications in wearable devices.

In this work, the researchers explored a relatively simple method for synthesizing 3D CF@CNTs/MgO The complex is used as an electrode for lithium-sulfur batteries, which can increase the sulfur loading rate and can mitigate the shuttle effect. A dense CNTs coating was introduced on the foam carbon backbone, and the complex exhibited high conductivity and elasticity. The modification of ultra-thin MgO nanosheets and the utilization of nitrogen-doped functional groups promote the chemisorption of lithium polysulfides. The electrode thus exhibited an intrinsic discharge capacity of 911 mAh/g at a sulfur loading of 2.4 mg/cm2, retaining 68% performance after 350 cycles at a multiplicity of 1C, (0.06% capacity loss after 800 cycles at a multiplicity of 2C), and a Coulomb efficiency of 0.05 when the sulfur loading was 14.4 mg/cm2 and the elemental sulfur content was 78 wt%. C, the electrode still maintains a high mass specific capacity of 612 mAh/g and area specific capacity of 8.8 mAh/cm2 after 50 cycles, which is nearly twice as high as that of today\’s commercial lithium-ion batteries. This study provides a new direction for the preparation of flexible electrodes for application in wearable devices.