“锂硫电池”专辑序言

锂硫电池是指采用硫或含硫复合物作为正极,锂或含锂材料为负极,以硫-硫键的断裂/生成来实现电能与化学能相互转换的一类电池体系。由于活性物质具有质轻、多电子反应等特性,从而能够实现高达1675m Ah·g-1的理论比容量和2600 Wh·kg-1的质量比能量。这比传统的锂离子电池的能量密度高出7倍左右,极有潜力成为新一代高能量密度电化学储能体系,近年来一直是高能锂金属电池领域的研究热点之一。

“锂硫电池”专辑序言

锂硫电池是指采用硫或含硫复合物作为正极,锂或含锂材料为负极,以硫-硫键的断裂/生成来实现电能与化学能相互转换的一类电池体系。由于活性物质具有质轻、多电子反应等特性,从而能够实现高达1675m Ah·g^(-1)的理论比容量和2600 Wh·kg^(-1)的质量比能量。这比传统的锂离子电池的能量密度高出7倍左右,极有潜力成为新一代高能量密度电化学储能体系,近年来一直是高能锂金属电池领域的研究热点之一。然而,锂硫电池的实用化依然存在着诸多问题。

Coercivity enhancement of sintered Nd–Fe–B magnets by grain boundary diffusion with Pr_(80-x)Al_(x)Cu_(20)alloys

A grain boundary diffusion(GBD)process with Pr_(80-x)Al_(x)Cu_(20)(x=0,10,15,20)low melting point alloys was applied to commercial 42M sintered Nd–Fe–B magnets.The best coercivity enhancement of a diffused magnet was for the Pr_(65)Al_(15)Cu_(20)GBD magnet,from 16.38 kOe to 22.38 kOe.Microstructural investigations indicated that increase in the Al content in the diffusion source can form a continuous grain boundary(GB)phase,optimizing the microstructure to enhance the coercivity.The coercivity enhancement is mainly due to the formation of a continuous GB phase to separate the main phase grains.Exchange decoupling between the adjacent main phase grains is enhanced after the GBD process.Meanwhile,the introduction of Al can effectively promote the infiltration of Pr into the magnet,which increases the diffusion rate of rare-earth elements within a certain range.This work provides a feasible method to enhance coercivity and reduce the use of rare-earth resources by partial replacement of rare-earth elements with non-rare-earth elements in the diffusion source.

Effect of TbF_(3)diffusion on the demagnetization behavior and domain evolution of sintered Nd-Fe-B magnets by electrophoretic deposition

We studied the magnetic properties and domain evolution of annealed and TbF3-diffused sintered Nd-Fe-B magnets using the electrophoretic deposition method.After TbF_(3)diffusion,the coercivity increased significantly by 9.9 kOe and microstructural analysis suggested that Tb favored the formation of the(Nd,Tb)_(2)Fe_(14)B shell phase in the outer region of the matrix grains.The first magnetization reversal and the dynamic successive domain propagation process were detected with a magneto-optical Kerr microscope.For the TbF_(3)-diffused magnet,the magnetization reversal appeared at a larger applied field and the degree of simultaneous magnetization reversal decreased compared with an annealed magnet.During demagnetization after full magnetization,the occurrence of domain wall motion(DWM)in the reproduced multi-domain regions was observed by the step method.The maximum polarization change resulting from the reproduced DWM was inversely related to the coercivity.The increased coercivity for the diffused magnet was mainly attributed to the more difficult nucleation of the magnetic reversed region owing to the improved magneto-crystalline anisotropy field as a result of Tb diffusion.

Effect of CeO_(2)doping on the coercivity of 2:17 type SmCo magnets

The effects of CeO_(2)doping on the magnetic properties and microstructure of 2:17 type SmCo magnets are studied.With the increase of CeO_(2)from 0 wt.%to 3 wt.%,the coercivity of the magnets increases from 22.22 kOe to over 29.37 kOe,which is an increase of more than 30%.When the doping content is lower than 1 wt.%,the remanence and magnetic energy product of the magnets remain almost constant.Both decrease sharply as the doping concentration further increases.After CeO_(2)doping,the oxide content in the magnet increases significantly and the Ce element is uniformly distributed in the magnet.Observing the magnetic domains reveals that doping with CeO_(2)can refine the magnetic domains and make the magnetic domain wall more stable,resulting in a significant increase in the coercivity of the magnets.

Endoplasmic-reticulum-like catalyst coating on separator to enhance polysulfides conversion for lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries with high theoretical specific energy of 2600 Wh kg^(-1) are one of promising candidates for next-generation energy storage devices.However,the severe shuttle effect of intermediate polysulfides leads to rapid capacity decay during battery cycling,especially at high sulfur loading and high current density.Herein,the MnO nanoparticles covered carbon with endoplasmic-reticulum-like structure(MnO@ERC)as separator coating for Li-S batteries is proposed.The MnO@ERC coating can act as upper current collector to enhance electrical conductivity of cathode and decrease the interface impedance of the whole battery.More importantly,both the polar MnO nanoparticles and Mn_(3)O_(4) formed at the end of the charging process can catalyze the conversion of lithium polysulfides,which is convinced by the high adsorption energy and the elongate S–S bond.As a result,Li-S batteries based on MnO@ERC coating separator showed stable cycle for 350 cycles under 0.5C,high discharge specific capacity of 783.6m Ah g^(-1) after 100 cycles at 0.2 C,534.7 m Ah g^(-1) after 100 cycles under the sulfur loading of 5.26 mg cm;and low self-discharge rate of 9.1%after resting 48 h..

Effects of post-sinter annealing on microstructure and magnetic properties of Nd–Fe–B sintered magnets with Nd–Ga intergranular addition

We investigate the effects of post-sinter annealing on the microstructure and magnetic properties in B-lean Nd–Fe–B sintered magnets with different quantities of Nd–Ga intergranular additions. The magnet with fewer Nd–Ga additions can enhance 0.2 T in coercivity, with its remanences nearly unchanged after annealing. With the further increase of the Nd–Ga addition, the annealing process leads coercivity to increase 0.4 T, accompanied by a slight decrease of remanence. With the Nd–Ga addition further increasing and after annealing, however, the increase of coercivity is basically constant and the change of remanence is reduced. Microstructure observation indicates that the matrix grains are covered by continuous thin grain boundary phase in the magnets with an appropriate Nd–Ga concentration after the annealing process. However, the exceeding Nd–Ga addition brings out notable segregation of grain boundary phase, and prior formation of part RE6 Fe13 Ga phase in the sintered magnet. This prior formation results in a weaker change of remanence after the annealing process.Therefore, the diverse changes of magnetic properties with different Nd–Ga concentrations are based on the respective evolution of grain boundary after the annealing process.

Magnetic properties and resistivity of a 2:17-type SmCo magnet doped with ZrO_(2)

In order to counteract the demagnetization caused by eddy current loss,widespread attention has been devoted to increasing the resistivity of permanent magnets.We prepared 2:17-type Sm Co magnets doped with different ZrO_(2)contents and investigated the influence of the ZrO_(2)content on the magnetic properties and resistive anisotropism.The results showed that not only was the resistivity of the magnet improved,but,in addition,the coercivity of the magnet was significantly increased.The microstructure was studied with TEM,which showed that ZrO_(2)doping was able to cause a decrease in the lamellar phase density and the growth of cellular structures.The increased grain boundaries and Sm_(2)O_(3)phases were favorable to the improvement of resistivity.The decrease of the lamellar phases caused a narrowing of the resistive anisotropism.The additional Cu in the center of the cellular boundaries was the main reason for the enhancement of Hcj.However,an excessive amount caused an increase of the Zr_6(Fe Co)_(23)phase and a deterioration of the cellular structure,thereby leading to a decrease in coercivity.

Coercivity and microstructure of sintered Nd-Fe-B magnets diffused with Pr-Co,Pr-Al,and Pr-Co-Al alloys

The commercial 42 M Nd-Fe-B magnet was treated by grain boundary diffusion(GBD)with Pr_(70)Co_(30)(PC),Pr_(70)Al_(30)(PA)and Pr_(70)Co_(15)Al_(15)(PCA)alloys,respectively.The mechanism of coercivity enhancement in the GBD magnets was investigated.The coercivity was enhanced from 1.63 T to 2.15 T in the PCA GBD magnet,higher than the 1.81 T of the PC GBD magnet and the 2.01 T of the PA GBD magnet.This indicates that the joint addition of Co and Al in the diffusion source can further improve the coercivity.Microstructural investigations show that the coercivity enhancement is mainly attributed to the exchange-decoupling of the GB phases.In the PCA GBD magnet,the wider thin GB phases can be formed and the thin GB phases can still be observed at the diffusion depth of 1500μm due to the combined action of Co and Al.At the same time,the formation of the Pr-rich shell can also be observed,which is helpful for the coercivity enhancement.

Effect of annealing temperature on coercivity of Nd-Fe-B magnets with TbFeAl doping by process of hot-pressing

The Nd-Fe-B magnets are pre-sintered and then processed with hot-pressing,and the resulting magnets are called the hot-pressed pretreated(HPP)magnets.The coercivity of the HPP magnets increases as the annealed temperature increases.When the annealing temperature is 900℃,the coercivity of the magnet is only 17.6 kOe(1 Oe=79.5775 A·m^-1),but when the annealing temperature rises up to 1060℃,the coercivity of the magnet reaches 23.53 kOe,which is remarkably increased by 33.7%.The microstructure analysis indicates that the grain surface of the HPP magnet becomes smoother as the annealed temperature increases.The microstructure factorαis changed according to the intrinsic coercivity model formula.Theαof the magnet at 900℃is only 0.578,but it is 0.825 at 1060℃.Microstructural optimization is due mainly to the increase of coercivity of the HPP magnet.

Magnetic properties of misch-metal partially substituted Nd–Fe–B magnets sintered by dual alloy method

The misch-metal （MM） partially substituted Nd-Fe-B sintered magnets were fabricated by the dual alloy method, and the crystal structure, microstructure, and magnetic properties were analyzed comprehensively. X-ray diffraction （XRD） reveals that the increasing content of the MM has an inconsiderable effect on the crystallographic alignment of the magnets. Grains of the two main phases are uniformly distributed, and slightly deteriorate on the grain boundary. Due to the diffusion between the adjacent grains, the MM substituted Nd-Fe-B magnets contain three types of components with different Ce/La concentrations. Moreover, the first-order reversal curve （FORC） diagram is introduced to analyze the magnetization reversal process, coercivity mechanism, and distribution of reversal field in magnetic samples. The analysis indicates that there are two major reversal components, corresponding to the two different main phases. The domain nucleation and growth are determined to be the leading mechanism in controlling the magnetization reversal processes of the magnets sintered by the dual alloy method.

Impact of Ambient Air Pollution on Public Health under Various Traffic Policies in Shanghai,China

Objective To investigate the potential impact of ambient air pollution on public health under various traffic policies in Shanghai. Methods The exposure level of Shanghai residents to air pollution under various planned traffic scenarios was estimated, and the public health impact was assessed using concentration-response functions derived from available epidemiological studies. Results Our results showed that ambient air pollution in relation to traffic scenarios had a significant impact on the future health status of Shanghai residents. Compared with the base case scenario, implementation of various traffic scenarios could prevent 759-1574, 1885-2420, and 2277-2650 PM10-related avoidable deaths （mean-value） in 2010, 2015, and 2020, respectively. It could also decrease the incidence of several relevant diseases. Conclusion Our findings emphasize the need to consider air pollution-related health effects as an important impact of traffic policy in Shanghai.

Effects of RFTVR and CO2 laser on symptoms improvement, QOL and vas of patients with early laryngeal cancer

Objective: To study the effect of RFTVR and CO2 laser on the improvement of symptoms, QOL and vas of patients with early laryngeal cancer. Methods: In this study, 120 patients with laryngeal cancer diagnosed and treated from January 2015 to December 2016 were taken as research objects. All patients were randomly divided into observation group and control group, 60 patients in each group. Patients in observation group were treated with RFTVR, and patients in control group were treated with new-type fiber-optic CO2 laser. The patients in the two groups were treated with cisplatin injection. The differences of perioperative indexes, swallowing function, pronunciation function, survival period, QOL score and VAS score between the two groups were compared. Results: There was no significant difference in the amount of intraoperative bleeding, operation time and hospitalization time between the two groups (P > 0.05);the correct swallowing of the observation group was significantly higher than that of the control group. After treatment, jitter, shimmer and HNR of the two groups were significantly improved, and jitter and shimmer of the observation group were significantly lower than that of the control group, and HNR was significantly higher than that of the control group (P < 0.05) The QOL score and VAS score of the two groups were significantly improved, and the QOL score of the observation group was significantly higher than that of the control group and the VAS score was significantly lower than that of the control group (P < 0.05);the total survival period and tumor free survival period of the observation group were significantly higher than that of the control group. Conclusion: Compared with CO2 laser treatment, the swallowing function and voice function of patients treated by low temperature plasma radiofrequency ablation were significantly improved, and the life quality of patients was significantly improved by prolonging the survival period of patients..