RESUMEN
Lithium-sulfur (Li-S) batteries are known as a prospective new generation of battery systems owing to their high energy density, low cost, non-toxicity, and environmental friendliness. Nevertheless, several issues remain in the practical application of Li-S batteries, such as low sulfur usage, poor rate performance, and poor cycle stability. Ordered microporous carbon materials and carbon nanotubes (CNTs) can effectively limit the diffusion of polysulfides (LiPSs) and have high electrical conductivity, respectively. Here, inspired by the evaporation of zinc at high temperatures, we constructed CNTs interpenetrating ordered microporous carbon nanospheres (CNTs/OMC NSs) by high-temperature calcination and used them as a sulfur host material. With the benefit from the excellent electrical conductivity of CNTs and OMC achieving uniform sulfur dispersion and effectively limiting LiPS dissolution, the S@CNTs/OMC NS cathodes show outstanding cycling stability (initial discharge capacity of 879 mAh g-1 at 0.5 C, maintained at 629 mAh g-1 for 500 cycles) and excellent rate performance (521 mAh g-1 at 5.0 C). Furthermore, the current study can serve as a significant reference for the synthesis of CNTs that interpenetrate various materials.
RESUMEN
The work describes dually-emissive silicon nanoparticles (Si NPs) in aqueous dispersion with two emissions. The Si NPs respond to different solvents independently with various wavelength fluorescence emissions (red to green). The fluorescence emission wavelengths and emissive color of Si NPs can be regulated by adjustment of the solvents. Based on the effect of the solvent, a series different emission color Si NPs is obtained (Si NPs A, B, C and D), which exhibit different fluorescence emission in various solvents. Notably, the Si NP-A (dispersed in water) exhibited excellent analytical performance in sensing Cu2+ ions with amazing fluorescent response from green to brilliant blue light. The much more enhancement at 436 nm than at 500 nm was due to the changing surface chemistry of Si NPs by Cu2+, which was dependent to the concentration of Cu2+ tightly. The excellent sensitivity of Si NP-A towards Cu2+ has been testified with the detection limit as low as 0.91 µM by good linear relationship between ratio of fluorescence intensity (I436/I500) and concentration of Cu2+ (2-30 µM). The Si NP-A can be exploited as a dual-fluorescence visualization agent for latent fingerprints imaging due to the feature of dual emission. The images exhibited green emission under excited at 254 nm, and emerged green light under 365 nm, which allowed the Si NP-A applying in development of latent finger prints at complex background. These acquired fingerprints revealed the particular second-level characteristics. Graphical abstractIllustration of the method for preparation of safranine-dyes silica nanoparticle (Si NPs), the evolution of Si NP-A (VSi NPs/Vwate = 1:2). Si NP-B (VSi NPs/Vdichloromethane = 1:1), Si NP-C (VSi NPs/Vethyl acetate = 1:1) and Si NP-D (VSi NPs/Vacetone = 1:1), and the application of water-dispersed silica nanoparticles (Si NP-A) to the detection and visualization of latent fingerprints (LFPs).
RESUMEN
The commercialization of lithium-sulfur batteries is facing great challenges, such as the "shuttle effect" and the poor conductivity of sulfur and Li2S2/Li2S, so it is extremely important to design new separator-modified materials with fast charge transfer capability and effective immobilization of polysulfides (LiPSs) to facilitate their conversion to address these challenges. In this paper, we propose a simple way to synthesize NiCo2O4 nanospheres containing oxygen vacancies (OV-NiCo2O4 NSs) and thus modify the separator. The synthesized OV-NiCo2O4 NSs accelerated the conversion of LiPSs through strong chemical interactions. In addition, the introduction of oxygen vacancies provided more active sites for LiPSs, which improved the electron conduction rate and accelerated the ion transport. Based on the above advantages, the battery with an OV-NiCo2O4 modified separator showed excellent electrochemical performance (the initial capacity of the battery was 801 mA h g-1 at 0.5 C, the specific capacity of discharge was maintained at 695 mA h g-1 after 500 cycles, and the capacity retention rate was as high as 87%).
RESUMEN
The solid-solid conversion of Li2S2 to Li2S is a crucial and rate-controlling step that provides one-half of the theoretical capacity of lithium-sulfur (Li-S) batteries. The catalysts in the Li-S batteries are often useless in the solid-solid conversion due to the poor contact interfaces between solid catalysts and insoluble solid Li2S2. Considering that ultrafine nanostructured materials have the properties of quantum size effects and unconventional reactivities, we design and synthesize for the pomegranate-like sulfur nanoclusters@nitrogen-doped carbon@nitrogen-doped carbon nanospheres (S@N-C@N-C NSs) with a seed-pulp-peel nanostructure. The ultrafine S@N-C subunits (diameter ≈5 nm) and effects of a spatial structure perfectly realize the rapid conversion of ultrafine Li2S2 to Li2S. The S@N-C@N-C seed-pulp-peel NS cathodes exhibit excellent sulfur utilization, superb rate performance (760 mAh g-1 at 10.0 C), and an ultralow capacity decay rate of about 0.016% per cycle over 1000 cycles at 4.0 C. The proposed strategy based on ultrafine nanostructured materials can also inform material engineering in related energy storage and conversion fields.
RESUMEN
Host materials that can physically confine and chemically adsorb/catalyze lithium polysulfides (LiPSs) are currently receiving intensive research interest for developing lithium-sulfur (Li-S) batteries. Herein, a novel host material made of micro-mesoporous carbon nanospheres (MMC NSs) with well-dispersed ultrafine NiS2-ZnS (uNiS2-ZnS) heterostructures is synthesized for the first time via a simple in situ sulfuration process. The uNiS2-ZnS/MMC materials achieve the synergistic effect of physical confinement and the efficient chemical adsorption/catalysis of LiPSs through a micro-mesoporous structure and well-dispersed uNiS2-ZnS heterostructures. In addition, compared with bulk heterostructured materials, the uNiS2-ZnS heterostructures greatly enhance the adsorption and catalytic ability toward LiPSs because the catalysis interface effect and naturally formed in-plane interfaces can be magnified by the ultrafine dispersed nanoparticles. As a result, the prepared uNiS2-ZnS/MMC-S cathodes exhibit outstanding rate capacity (675.5 mA h g-1 at 5.0C) and cyclic stability (710.5 mA h g-1 at 1.0C after 1000 cycles with a low capacity decay of 0.033% per cycle). This work provides a certain reference for the application of heterostructured materials in Li-S batteries.
RESUMEN
The carbon nanostructure with heteroatom doping having well-designed porosity and a large pore volume plays a vital role in high-performance supercapacitors. Herein, we synthesize hierarchical nitrogen and sulfur-codoped micromesoporous carbon nanospheres (N,S-HPCNSs) with an ultralarge pore volume of 3.684 cm3 g-1. The ultralarge pore volume in the N,S-HPCNSs can achieve fast charge storage and high electrochemical utilization due to the rapid mass transport. As a result, N,S-HPCNSs exhibit specific capacitances of 309.4 F g-1 at 0.5 A g-1 and 232.0 F g-1 at 50 A g-1 in a 1 M H2SO4 electrolyte, suggesting a superior rate property. Moreover, the N,S-HPCNSs exhibit a splendid cycling performance after 10,000 cycles with 98.5% capacitance retention. Furthermore, a symmetric supercapacitor reaches an excellent energy density of 27.8 W h kg-1 under 180.0 W kg-1 in a 1 M Na2SO4 electrolyte. The remarkable electrochemical properties of N,S-HPCNSs are caused by the ultralarge pore volume and hierarchical micromesoporous structures of the carbon NSs, which provide a significant way for designing energy storage systems.
RESUMEN
Red phosphorus (P) has been recognized as a promising material for lithium/sodium-ion batteries (LIBs/SIBs) because of their high theoretical capacity. However, tremendous volume variation and low conductivity limit its widespread applications. Hence, we design and synthesize uniformly distributed honeycomb-like hierarchical micro-mesoporous carbon nanospheres (HHPCNSs) with ultralarge pore volume (3.258 cm3 g-1) on a large scale through a facile way. The large pore volume provides enough space for loading of P and the expansion of P, and the uniform distribution of the micro-mesopores enables the red P to load uniformly. The resulting HHPCNSs/P composite exhibits extremely high capacity (2463.8 and 2367.6 mA h g-1 at 0.1 A g-1 for LIBs and SIBs, respectively), splendid rate performance (842.2 and 831.1 mA h g-1 at 10 A g-1 for LIBs and SIBs, respectively) and superior cycling stability (1201.6 and 938.4 mA h g-1 at 2 and 5 A g-1 after 1000 cycles for LIBs and 1269.4 and 861.8 mA h g-1 at 2 and 5 A g-1 after 1000 cycles for SIBs, respectively). More importantly, when coupled with LiFePO4 and Na3V2(PO4)3 cathode, lithium/sodium-ion full batteries display high capacity and superior rate and cycling performances, revealing the practicability of the HHPCNSs/P composite. The exceptional electrochemical performance is caused by the honeycomb-like carbon network with ultralarge pore volume, uniformly distributed hierarchical micro-mesoporous nanostructure, outstanding electronic conductivity, and excellent nanostructural stability, which is much better than currently reported P/C materials for both LIBs and SIBs.