The thermal desorption (TD) technique is widely employed in modern mass spectrometry to facilitate the detection of non-volatile analytes. In this study, we developed a compact TD device based on a small resistance wire and coupled it with a self-aspirating corona discharge ionization (CDI) source to conduct direct MS analysis of various liquid and solid samples. Due to its small size and low heat capacity, the temperature of the TD module can be flexibly and rapidly modulated by controlling the power sequence. Multiple heating modes, including pulse heating (PH), isothermal heating, and step heating (SH), are realized and characterized, and then applied for the detection of different real samples. In particular, the PH mode is suitable for the simultaneous detection of multiple components in samples with relatively simple matrices, while the SH mode is capable of component separation. In addition, the sensitivity and quantitative capability of the TD-CDI system for DEP solutions were tested, showing acceptable stability with a relative standard deviation of about 6.7% and a detection limit of 0.088 ng. Overall, the developed TD-CDI system provides a simple, convenient, and versatile tool for direct mass spectrometry analysis of real samples.
Mislabeling the geographical origin of coffee is a prevalent form of fraud. In this study, a rapid, nondestructive, and high-throughput method combining mass spectrometry (MS) analysis and intelligence algorithms to classify coffee origin was developed. Specifically, volatile compounds in coffee aroma were detected using self-aspiration corona discharge ionization mass spectrometry (SACDI-MS), and the acquired MS data were processed using a customized deep learning algorithm to perform origin authentication automatically. To facilitate high-throughput analysis, an air curtain sampling device was designed and coupled with SACDI-MS to prevent volatile mixing and signal overlap. An accuracy of 99.78% was achieved in the classification of coffee samples from six origins at a throughput of 1 s per sample. The proposed approach may be effective in preventing coffee fraud owing to its straightforward operation, rapidity, and high accuracy and thus benefit consumers.
Deep Learning , Volatile Organic Compounds , Coffee/chemistry , Odorants/analysis , Mass Spectrometry/methods , Algorithms , Volatile Organic Compounds/analysis
P2-phase layered cathodes play a pivotal role in sodium-ion batteries due to their efficient Na+ intercalation chemistry. However, limited by crystal disintegration and interfacial instability, bulk and interfacial failure plague their electrochemical performance. To address these challenges, a structural enhancement combined with surface modification is achieved through trace Y doping. Based on a synergistic combination of experimental results and density functional theory (DFT) calculations, the introduction of partial Y ions at the Na site (2d) acts as a stabilizing pillar, mitigating the electrostatic repulsions between adjacent TMO2 slabs and thereby relieving internal structural stress. Furthermore, the presence of Y effectively optimizes the Ni 3d-O 2p hybridization, resulting in enhanced electronic conductivity and a notable rapid charging ability, with a capacity of 77.3 mA h g-1 at 40 C. Concurrently, the introduction of Y also induces the formation of perovskite nano-islands, which serve to minimize side reactions and modulate interfacial diffusion. As a result, the refined P2-Na0.65 Y0.025 [Ni0.33 Mn0.67 ]O2 cathode material exhibits an exceptionally low volume variation (≈1.99%), an impressive capacity retention of 83.3% even at -40 °C after1500 cycles at 1 C.
Sodium-ion batteries (SIBs) have been recognized as one of the most promising new energy storage devices for their rich sodium resources, low cost and high safety. The electrolyte, as a bridge connecting the cathode and anode electrodes, plays a vital role in determining the performance of SIBs, such as coulombic efficiency, energy density and cycle life. Therefore, the overall performance of SIBs could be significantly improved by adjusting the electrolyte composition or adding a small number of functional additives. In this review, the fundamentals of SIB electrolytes including electrode-electrolyte interface and solvation structure are introduced. Then, the mechanisms of electrolyte additive action on SIBs are discussed, with a focus on film-forming additives, flame-retardant additives and overcharge protection additives. Finally, the future research of electrolytes is prospected from the perspective of scientific concepts and practical applications.
A new synthetic strategy for direct C(sp3)-H amination of carbonyl compounds at their α-carbon has been established employing molecular iodine and nitrogen-directed oxidative umpolung. In this transformation, iodine acts not only as an iodinating reagent but also as a Lewis acid catalyst, and both the nitrogen-containing moiety and the carbonyl group in the substrate play important roles. This synthetic approach is applicable to a broad variety of carbonyl substrates, including esters, ketones, and amides. Its features also include no requirement for transition metals, mild reaction conditions, short reaction times, and gram-scale synthesis.
Iodine , Nitrogen , Amination , Nitrogen/chemistry , Oxidation-Reduction , Oxidative Stress
Transition-metal phosphides (TMPs) as typical conversion-type anode materials demonstrate extraordinary theoretical charge storage capacity for sodium ion batteries, but the unavoidable volume expansion and irreversible capacity loss upon cycling represent their long-standing limitations. Herein we report a stress self-adaptive structure with ultrafine FeP nanodots embedded in dense carbon microplates skeleton (FeP@CMS) via the spatial confinement of carbon quantum dots (CQDs). Such an architecture delivers a record high specific capacity (778â mAh g-1 at 0.05â A g-1 ) and ultra-long cycle stability (87.6 % capacity retention after 10 000â cycles at 20â A g-1 ), which outperform the state-of-the-art literature. We decode the fundamental reasons for this unprecedented performance, that such an architecture allows the spontaneous stress transfer from FeP nanodots to the surrounding carbon matrix, thus overcomes the intrinsic chemo-mechanical degradation of metal phosphides.
P2-phase layered cathode materials with distinguished electrochemical performance for sodium-ion batteries have attracted extensive attention, but they face critical challenges of transition metal layer sliding and unfavorable formation of hydration phase upon cycling, thus showing inferior long cycle life. Herein, a new approach is reported to modulate the local structure of P2 material by constructing a state-of-the-art in-plane BO3 triangle configuration ((Na0.67 Ni0.3 Co0.1 Mn0.6 O1.94 (BO3 )0.02 ). Both are unveiled experimentally and theoretically that such a structure can serve as a robust pillar to hold up the entire structure, by inhibiting the H2 O insertion upon Na (de)intercalation and preventing the structure from deformation, which significantly boost the long cycle capability of P2-materials. Meanwhile, more Na ions in the architecture are enabled to site on the edge sharing octahedrons (Nae ), thus benefiting the Na+ transportation. Consequently, the as produced material demonstrates an ultralow volume variation (1.8%), and an outstanding capacity retention of 80.1% after 1000 cycles at 2 C. This work sheds light on efficient architecture modulation of layered oxides through proper nonmetallic element doping.
The application of sodium-based batteries in grid-scale energy storage requires electrode materials that facilitate fast and stable charge storage at various temperatures. However, this goal is not entirely achievable in the case of P2-type layered transition-metal oxides because of the sluggish kinetics and unfavorable electrode|electrolyte interphase formation. To circumvent these issues, we propose a P2-type Na0.78Ni0.31Mn0.67Nb0.02O2 (P2-NaMNNb) cathode active material where the niobium doping enables reduction in the electronic band gap and ionic diffusion energy barrier while favoring the Na-ion mobility. Via physicochemical characterizations and theoretical calculations, we demonstrate that the niobium induces atomic scale surface reorganization, hindering metal dissolution from the cathode into the electrolyte. We also report the testing of the cathode material in coin cell configuration using Na metal or hard carbon as anode active materials and ether-based electrolyte solutions. Interestingly, the Na||P2-NaMNNb cell can be cycled up to 9.2 A g-1 (50 C), showing a discharge capacity of approximately 65 mAh g-1 at 25 °C. Furthermore, the Na||P2-NaMNNb cell can also be charged/discharged for 1800 cycles at 368 mA g-1 and -40 °C, demonstrating a capacity retention of approximately 76% and a final discharge capacity of approximately 70 mAh g-1.
