Lithium metal anodes have long been considered as "holy grail" in the field of energy storage batteries, but dendrite growth and large volume changes hinder their practical applications. Herein, a facile and eco-friendly CF 4 plasma treatment is employed for the surface modification of Li anodes, and an artificial layer consisting of LiF and Li 2 C 2 is fabricated for the first time. Experimental results and theoretical calculations reveal that the high adsorption energy of LiF and low Li + diffusion barriers in Li 2 C 2 induce uniform nucleation and planar growth of Li, guaranteeing a stable and dendrite-free Li structure during the repeated plating/stripping process of cycling. Symmetric cells using CF 4 plasma-treated Li operate stably for more than 6500 h (at 2 mA cm −2 and 1 mAh cm −2 ) or 950 h (at 1 mA cm −2 and 10 mAh cm −2 ). When paired with a LiFePO 4 cathode, full batteries deliver a high reversible capacity of 136 mAh g −1 (at 1 C) with considerable cycling stability (97.2% capacity retention over 200 cycles) and rate performance (116 mAh g −1 up to 5 C). This powerful application of plasma technology toward novel LiF-Li 2 C 2 artificial layers provide new routes for constructing environment-friendly and high-performance energy storage devices.
Two of the key questions in plasma medicine are how deep the reactive oxygen and nitrogen species (RONS) generated by a plasma can penetrate into tissue and how the liquid (extracellular and intracellular fluid) composition affects the concentration of RONS. In this paper, different thicknesses of pig muscle tissue are used as a tissue mode to investigate the effect of tissue thickness on the penetration of RONS through tissue. Six different types of liquid (inorganic group: double-distilled water (DDW), 1% phosphate-buffered saline, 0.9% NaCl; organic group: 5% glucose, 2% serum and 10% serum solution) are used in the receiving chamber under the tissue in order to try to understand the effect of liquid composition on the penetration of RONS (H 2 O 2 , NO − 2 and NO − 3 ) generated by the plasma. It is found that when a tissue thickness of 500 µm is used the H 2 O 2 concentrations in organic liquids are about 20-30 times higher than in DDW. The NO − 2 and NO − 3 concentrations in serum liquid are much higher than in all other liquids, which might be due to the plasma reacting with amino acids and proteins. Besides, the NO − 3 concentration in organic solution is higher than the NO − 2 concentration for the same experimental conditions. Furthermore, when the serum percentage is increased from 2% to 10%, the NO − 2 concentration increases dramatically but the NO − 3 concentration decreases significantly. This is especially true for a tissue thickness of 500 µm. One novel discovery is the RONS do not only penetrate the tissue by diffusion-there are also reactions between the plasma and the liquid which affect the final RONS concentration.
Cold atmospheric-pressure plasma jet generates rich reactive species including reactive oxygen species and reactive nitrogen species with gas temperature close to or at room temperature, which is very attractive for applications such as plasma medicine. However, under one atmospheric pressure, due to the high electron–neutral particles collision frequency (1011–12/s), it is difficult to generate atmospheric pressure plasma while keeping the gas temperature close to or at room temperature. Furthermore, when air rather than noble gases is used as working gas, due to the low energy levels of rotational and vibrational states of nitrogen and oxygen, it becomes extremely challenging to generate cold atmospheric pressure air plasma jet (CAAP-J) with gas temperature close to or at room temperature. Fortunately, after decades of research, several CAAP-Js have been reported. In this review, the state-of-the-art of the development of CAAP-Js is presented. The CAAP-Js are grouped into six categories based on their electrode configuration. A brief discussion on each group of the CAAP-Js is presented. Moreover, the physics of CAAP-Js is discussed, including the dynamics, the striation phenomenon, the temporal behavior of plasma parameters, and the nonequilibrium characteristic of CAAP-Js. Furthermore, the measurements of the reactive species generated by CAAP-Js are briefly reviewed. Finally, discussions and perspective of future research on CAAP-Js are presented.
In this work, reactive oxygen and nitrogen species (RONS) generated by a plasma jet penetrating through and left in the skin after the plasma treatment are measured, and the effects of stratum corneum (SC) on the penetration of the RONS are also investigated. It is found that the RONS generated by the plasma jet can penetrate through the skin, and that the penetration of some kinds of the RONS could be enhanced significantly by tape stripping the SC layer of the skin. Further investigations find that the typical reactive oxygen species, including OH, 1O2, O3, and H2O2, cannot penetrate through the mice skin at all (under the detection limit) no matter whether the SC layer of the skin is present or not, where the thickness of the mice skin is about 200–300 μm. This result is very different from the experimental results obtained from the muscle tissue model and gelatin model. Finally, it is found that high concentrations of long-lived RONS (H2O2, NO2−, and NO3−) are left in the skin after the plasma treatment, which means that the plasma treatment could have a long-time scale therapy effect. This finding is important for the applications of plasma medicine.
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