RESUMEN
Complete encapsulation of high-content sulfur in porous carbon is crucial for high performance Li-S batteries. To this end, unlike conventional approaches to control the pore of carbon hosts, we demonstrate controlling the interfacial energy of the solution in the process of penetrating the sulfur-dissolved solution. We unveil, experimentally and theoretically, that the interfacial energy with the carbon surface of the sulfur solution is the key to driving complete encapsulation of sulfur. In the infiltration of sulfur solutions with N-methyl-2-pyrrolidone, we achieve complete encapsulation of sulfur, even up to 85 wt %. The sulfur fully encapsulated cathode achieves markedly high volumetric capacity and stable cycle operation in its Li-S battery applications. We achieve a volumetric capacity of 855 mAh/cm3 at 0.2C and a capacity reduction of 0.071% per cycle up to 300 cycles at 1C.
RESUMEN
The chemical stability and energy density of redox couples are crucial factors in enhancing the durability and cost competitiveness of aqueous flow batteries. This study proposed integrating functional groups to viologen anolyte to increase its solubility and, consequently, energy density and stability for prolonged performance. Specifically, sulfonate and ester groups were selectively incorporated at the nitrogen sites of viologen to enhance solubility, leveraging their asymmetry and double hydrophilicity. Furthermore, an alpha-methyl group was introduced between the bipyridine and ester groups to enhance the chemical stability by preventing stacking and dimerization that can lead to irreversible degradation. The modified viologen demonstrated a remarkable solubility of 3.0 M in deionized water, corresponding to a volumetric capacity of 80.404 Ah L-1. Additionally, the designed viologen exhibits outstanding retention of 92.4% after 200 cycles with a minimal capacity fading rate of 0.055% per cycle in a 0.1 M flow cell test.
RESUMEN
Lithium-sulfur (Li-S) batteries are promising as next-generation energy storage systems. Adsorbents for sulfide species are favorably applied to the cathode, but this substrate often results in a surface-passivating lithium sulfide(Li2 S) film with a strong adsorption of Li2 S. Here, an amorphous titanium suboxide (a-TiOx) is presented that strongly adsorbs lithium polysulfides (Li2 Sx , x < 6) but relatively weakly adsorbs to Li2 S. With these characteristics, the a-TiOx achieves high conversion of Li2 Sx and high sulfur utilization accompanying the growth of particulate Li2 S. The DFT calculations present a mechanism for particulate growth driven by the promoted diffusion and favorable clustering of Li2 S. The a-TiOx -coated carbon nanotube-assembled film (CNTF) cathode substrate cell achieves a high discharge capacity equivalent to 90% sulfur utilization at 0.2 C. The cell also delivers a high capacity of 850 mAh g-1 even at the ultra-high-speed of 10 C and also exhibits high stability of capacity loss of 0.0226% per cycle up to 500 cycles. The a-TiOx /CNTF is stacked to achieve a high loading of 7.5 mg S cm-2 , achieving a practical areal capacity of 10.1 mAh cm-2 .
RESUMEN
We present a simple but rationally designed anode composed of polydopamine-wrapped, Si nanoparticle-impregnated macroporous CNT particles for lithium-ion batteries; this anode is mass-producible and at the same time achieves an excellent capacity and its retention by effective stress relaxation and surface passivation.
RESUMEN
A carbon host capable of effective and uniform sulfur loading is the key for lithium-sulfur batteries (LSBs). Despite the application of porous carbon materials of various morphologies, the carbon hosts capable of uniformly impregnating highly active sulfur is still challenging. To address this issue, we demonstrate a hierarchical pore-structured CNT particle host containing spherical macropores of several hundred nanometers. The macropore CNT particles (M-CNTPs) are prepared by drying the aerosol droplets in which CNTs and polymer particles are dispersed. The spherical macropore greatly improves the penetration of sulfur into the carbon host in the melt diffusion of sulfur. In addition, the formation of macropores greatly develops the volume of the micropore between CNT strands. As a result, we uniformly impregnate 70 wt % sulfur without sulfur residue. The S-M-CNTP cathode shows a highly reversible capacity of 1343 mA h g-1 at a current density of 0.2 C even at a high sulfur content of 70 wt %. Upon a 10-fold current density increase, a high capacity retention of 74% is observed. These cathodes have a higher sulfur content than those of conventional CNT hosts but nevertheless exhibit excellent performance. Our CNTPs and pore control technology will advance the commercialization of CNT hosts for LSBs.
RESUMEN
The combination of the control of CNT assembly density and the control of intrinsic carbon properties by doping can synergistically improve the supercapacitor performance of CNT-based electrodes. We prepared a dense-packed CNT spherical assembly via emulsion-assisted evaporation and subsequently conducted nitrogen (N) doping to make CNT-based supercapacitors. The assembly of CNT spherical particles is applied as the supercapacitor electrode. We control the N doping content and obtain a specific capacity of 215 F/g at a current density of 0.2 A/g, which is 3.1 times higher than that of the untreated sample. The enhancement stems from high pseudocapacitance and high electrical conductivity that result from the N doping of the CNT assembly. In a comparison of the specific capacitance of N-CNT spherical particles with that of the CNT films prepared by conventional solution-coating, we found that N-CNT samples display a capacitance that is 1.8 times higher, thus confirming the morphological advantage provided by the CNT packing and the hierarchical porous structure in the CNT particle assembly. Our approach allows a facile and high throughput production of high performance electrodes based on CNTs that are commercially available. Moreover, our approach can be extended to produce spherical particles consisting of other nanostructured carbon materials and their composites.
RESUMEN
Carbon/silicon composite materials are a promising anode substrate for use in lithium-ion batteries. In this study, we suggest a new architecture for a composite electrode made of a woven-like carbon material decorated with silicon nanoparticles. The 3D woven-like carbon (WLC) structure was fabricated using direct carbonization of multi-beam interference lithography polymer patterns. Subsequent solution coating was applied to decorate the WLC with silicon nanoparticles (SiNPs). The SiNP/WLC electrode exhibited a specific capacity of 930â mAh g(-1) , which is three times higher than the specific capacity of the bare electrode. Specifically, the SiNP/WLC electrode exhibited an outstanding retention capacity of 81 % after 50â cycles and a Coulombic efficiency of more than 98 %. This rate capability performance was attributed to the WLC structure and the uniform decoration of the SiNPs.