Implantation of Fe7S8 nanocrystals into hollow carbon nanospheres for efficient potassium storage

Recent advances in rational design for high-performance potassium-ion batteries

The growing global energy demand necessitates the development of renewable energy solutions to mitigate greenhouse gas emissions and air pollution. To efficiently utilize renewable yet intermittent energy sources such as solar and wind power, there is a critical need for large-scale energy storage systems (EES) with high electrochemical performance. While lithium-ion batteries (LIBs) have been successfully used for EES, the surging demand and price, coupled with limited supply of crucial metals like lithium and cobalt, raised concerns about future sustainability. In this context, potassium-ion batteries (PIBs) have emerged as promising alternatives to commercial LIBs. Leveraging the low cost of potassium resources, abundant natural reserves, and the similar chemical properties of lithium and potassium, PIBs exhibit excellent potassium ion transport kinetics in electrolytes. This review starts from the fundamental principles and structural regulation of PIBs, offering a comprehensive overview of their current research status. It covers cathode materials, anode materials, electrolytes, binders, and separators, combining insights from full battery performance, degradation mechanisms, in situ/ex situ characterization, and theoretical calculations. We anticipate that this review will inspire greater interest in the development of high-efficiency PIBs and pave the way for their future commercial applications.

Acetylcholine triggered enzymatic cascade reaction based on Fe7S8 nanoflakes catalysis for organophosphorus pesticides visual detection

BACKGROUND

Organophosphorus pesticides (OPs) play important roles in the natural environment, agricultural fields, and biological prevention. The development of OPs detection has gradually become an effective strategy to avoid the dangers of pesticides abuse and solve the severe environmental and health problems in humans. Although conventional assays for OPs analysis such as the bulky instrument required analytical methods have been well-developed, it still remains the limitation of inconvenient, inefficient and lab-dependence analysis in real samples. Hence, there is an urgent demand to develop efficient detection methods for OPs analysis in real scenarios.

RESULTS

Here, by virtue of the highly efficient catalytic performance in Fe7S8 nanoflakes (Fe7S8 NFs), we propose an OPs detection method that rationally integrated Fe7S8 NFs into the acetylcholine (ACh) triggered enzymatic cascade reaction (ATECR) for proceeding better detection performances. In this method, OPs serve as the enzyme inhibitors for inhibiting ATECR among ACh, acetylcholinesterase (AChE), and choline oxidase (CHO), then reduce the generation of H2O2 to suppress the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) that catalyzed by Fe7S8 NFs. Benefiting from the integration of Fe7S8 NFs and ATECR, it enables a sensitive detection for OPs (e.g. dimethoate). The proposed method has presented good linear ranges of OPs detection ranging from 0.1 to 10 μg mL-1. Compared to the other methods, the comparable limits of detection (LOD) of OPs are as low as 0.05 μg mL-1.

SIGNIFICANCE

Furthermore, the proposed method has also achieved a favorable visual detection performance of revealing OPs analysis in real samples. The visual signals of OPs can be transformed into RGB values and gathered by using smartphones, indicating the great potential in simple, sensitive, instrument-free and on-site analysis of pesticide residues in environmental monitoring and biosecurity research.

Interface Engineering of Fe7S8/FeS2 Heterostructure in situ Encapsulated into Nitrogen-Doped Carbon Nanotubes for High Power Sodium-Ion Batteries

Heterostructure engineering combined with carbonaceous materials shows great promise toward promoting sluggish kinetics, improving electronic conductivity, and mitigating the huge expansion of transition metal sulfide electrodes for high-performance sodium storage. Herein, the iron sulfide-based heterostructures in situ hybridized with nitrogen-doped carbon nanotubes (Fe7S8/FeS2/NCNT) have been prepared through a successive pyrolysis and sulfidation approach. The Fe7S8/FeS2/NCNT heterostructure delivered a high reversible capacity of 403.2 mAh g-1 up to 100 cycles at 1.0 A g-1 and superior rate capability (273.4 mAh g-1 at 20.0 A g-1) in ester-based electrolyte. Meanwhile, the electrodes also demonstrated long-term cycling stability (466.7 mAh g-1 after 1,000 cycles at 5.0 A g-1) and outstanding rate capability (536.5 mAh g-1 at 20.0 A g-1) in ether-based electrolyte. This outstanding performance could be mainly attributed to the fast sodium-ion diffusion kinetics, high capacitive contribution, and convenient interfacial dynamics in ether-based electrolyte.

Graphene supported FeS2 nanoparticles with sandwich structure as a promising anode for High-Rate Potassium-Ion batteries

Pyrite FeS₂ now emerges as a promising anode for potassium-ion batteries (PIBs) due to its low cost and high theoretical capacity. However, the significant volume expansion, low electrical conductivity, and the ambiguous mechanism related to potassium storage severely hinder its development for PIBs anodes. Herein, FeS₂ nanostructures are skillfully dispersed on the graphene surface layer by layer (FeS₂@C-rGO) to form a sandwich structure by using Fe-based metal organic framework (Fe-MOF) as precursors. The unique structural design can improve the transfer kinetics of K⁺ and effectively buffer the volume expansion during cycling, thereby enhancing the potassium storage performance. As a result, the FeS₂@C-rGO delivers a high capacity of 550 mAh/g at a current density of 0.1 A/g. At a high rate of 2 A/g, the capacity can maintain 171 mAh/g even after 500 cycles. Moreover, the electrochemical reaction mechanism and potassium storage behavior are revealed by in-situ X-ray diffractionand density functional theory calculations. This work not only provides a novel insight into the structural design of electrode materials for high-performance PIBs, but also proposes a valuable understanding of the potassium storage mechanism of the FeS₂-based anode.

An ultrastable sodium-ion battery anode enabled by carbon-coated porous NaTi2(PO4)3 olive-like nanospheres

NaTi₂(PO₄)₃ (NTP) is a promising anode material for sodium-ion batteries (SIBs). It has drawn wide attention because of its stable three-dimensional NASICON-type structure, proper redox potential, and large accommodation space for Na⁺. However, the inherent low electronic conductivity of the phosphate framework reduces its charge transfer kinetics, thus limiting its exploitation. Therefore, this paper proposes a material with carbon-coated porous NTP olive-like nanospheres (p-NTP@C) to tackle the issues above. Based on experimental data and theoretical calculations, the porous structure of the material is found to be able to provide more active sites and shorten the Na⁺ diffusion distance. In addition, the carbon coating can effectively improve the electron and Na⁺ diffusion kinetics. As the anode material for SIBs, the p-NTP@C olive-like nanospheres exhibit a high reversible capacity (127.3 mAh g^-1 at 0.1 C) and ultrastable cycling performance (84.8% capacity retention after 10,000 cycles at 5 C). Furthermore, the sodium-ion full cells, composed of p-NTP@C anode and Na₃V₂(PO₄)₂F₃@carbon cathode, also deliver excellent performance (75.7% capacity retention after 1000 cycles at 1 C). In brief, this nanostructure design provides a viable approach for the future development of long-life and highly stable NASICON-type anode materials.