Diluent decomposition-assisted formation of Li F-rich solid-electrolyte interfaces enables high-energy Li-metal batteries

Passivation by the inorganic-rich solid electrolyte interphase(SEI),especially the LiF-rich SEI,is highly desirable to guarantee the durable lifespan of Li metal batteries(LMBs).Here,we report a diluent with the capability to facilitate the formation of LiF-rich SEI while avoiding the excess consumption of Li salts.Dissimilar to most of reported inert diluents,heptafluoro-l-methoxypropane(HM) is firstly demonstrated to cooperate with the decomposition of anions to generate LiF-rich SEI via releasing Fcontaining species near Li surface.The designed electrolyte consisting of 1.8 M LiFSI in the mixture of1,2-dimethoxyethane(DME)/HM(2:1 by vol.) achieves excellent compatibility with both Li metal anodes(Coulombic efficiency~99.8%) and high-voltage cathodes(4.4 V LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)(NMC811) and 4.5 V LiCoO_(2)(LCO) vs Li^(+)/Li).The 4.4 V Li(20μm)‖NMC811(2.5 mA h cm^(-2)) and 4.5 V Li(20μm)‖LCO(2.5 mA h cm^(-2)) cells achieve capacity retentions of 80% over 560 cycles and 80% over 505 cycles,respectively.Meanwhile,the anode-free pouch cell delivers an energy density of~293 W h kg^(-1)initially and retains 70% of capacity after 100 deep cycles.This work highlights the critical impact of diluent on the SEI formation,and opens up a new direction for designing desirable interfacial chemistries to enable high-performance LMBs.

Current status and reflection on the development of high-speed maglev transportation

Purpose–High-speed maglev technology can address the issues of adhesion,friction,vibration and highspeed current collection in traditional wheel-rail systems,making it an important direction for the future development of high-speed rail technology.Design/methodology/approach–This paper elaborates on the demand and significance of developing high-speed maglev technology worldwide and examines the current status and technological maturity of several major high-speed maglev systems globally.Findings–This paper summarizes the challenges in the development of high-speed maglev railways in China.Based on this analysis,it puts forward considerations for future research on high-speed maglev railways.Originality/value–This paper describes the development status and technical maturity of several major high-speed maglev systems in the world for the first time,summarizes the existing problems in the development of China’s high-speed maglev railway and on this basis,puts forward the thinking of the next research of China’s high-speed maglev railway.

类空气浓度的二氧化碳的高效电还原

近十年来,电化学转化二氧化碳受到越来越多的关注和研究,其最终目标是利用可再生能源得到电能来实现碳中和,以及经济和能源效益.为实现这一目标,电还原二氧化碳不仅需要较高的选择性和转化率,也需要考虑其大规模应用的成本和经济价值.尽管近年空气中二氧化碳的浓度达到了历史最高值(415 ppm),但仍仅占了空气气体中较少的一部分.从空气中捕获和浓缩二氧化碳需要耗费大量的能量(~8.65 GJ/t),这不可避免地增加了工业成本和复杂性.另外在更负电位的二氧化碳还原反应下存在氧气(O_(2))还原竞争反应,也为二氧化碳电还原带来更大的挑战.因此,目前几乎所有研究报道的二氧化碳电还原体系都是使用高浓度(通常是纯的)二氧化碳作为反应物,只有少数几篇近期文献研究了低浓度二氧化碳(如~10%二氧化碳浓度的烟道气)的电还原性能.此外,在二氧化碳电还原中,中性或者碱性溶液常被用来作为电解液,而气体扩散电极通常用来提高二氧化碳的传质,但在这样的条件下,一部分二氧化碳不可避免地会与碱性或中性的电解液反应或者被吸收,大大降低还原效率.本文设计了一种气相电化学电解槽,并使用低成本的铜或纳米铜催化剂,实现电还原浓度为0.03%或0.04%的二氧化碳.在此过程中,气相二氧化碳与水蒸气混合并直接传递到铜催化剂表面,在气-固界面上被还原为一氧化碳,且在反应过程中二氧化碳不会被水溶液或碱性电解质吸收或发生反应.通过对催化剂和实验参数的调整,当反应气体为0.03%的二氧化碳,在气体流速为0.5 mL/min的条件下,二氧化碳的转化效率可高达95%.此外,本文还成功实现了直接电还原空气中的二氧化碳(0.04%的二氧化碳),由于铜催化剂的氧气还原活性极差,空气中较高浓度的氧气并不会对二氧化碳还原产生较大影响.因此,在空气流速为0.5 mL/min的条件下,二氧化碳的最佳转化效率可达~79%.综上,本文为直接电还原转化二氧化碳提供了具有较好发展前景的方法.

铜掺杂的羟基氧化镍用于高效电催化乙醇氧化

醇的电化学氧化反应是能源和化学转化领域的一个研究热点,它在燃料电池、生物质利用和精细化学品合成等领域展示出了广阔的应用前景.其中,乙醇是绿色、无毒的液体燃料,与其相关的电催化氧化反应也在直接乙醇燃料电池、电催化乙醇重整制备高附加值的产物(如乙酸盐)等方面得到了广泛的研究.目前广泛使用的乙醇氧化的电催化剂以铂、钯、铑等贵金属为主,但其自然界储量较低,成本高昂,同时会因电催化乙醇氧化过程中产生的一氧化碳等中间产物而中毒失活.因此,研究人员致力于开发具有高活性、高稳定性和高选择性的非贵金属基乙醇氧化电催化剂.镍基催化剂不仅展示出电催化乙醇氧化的活性,也可以活化水产生OHads用于解决CO中间体引起的催化剂中毒问题.铜基材料具有优异的本征电导率.受之前研究的启发,本文在镍基材料中掺杂铜以形成高价态的镍位点,如Ni^(3+)物种,从而使镍基材料获得更好的电催化乙醇氧化性能.通过原位电化学重建策略,开发了一种以铜镍合金为前驱体的铜均匀掺杂的羟基氧化镍电催化剂.铜掺杂改善了羟基氧化镍的导电性,促进高价镍物种的产生,从而改善了羟基氧化镍在电催化乙醇氧化中的性能.采用X射线粉末衍射、拉曼光谱、扫描电子显微镜、X射线光电子能谱和透射电子显微镜等技术表征了所制电催化剂的物构性质.可以发现,引入铜掺杂物后,羟基氧化镍中高价态Ni^(3+)物种的比例(72%)相较于掺杂前(35%)提高了1倍,且表现出优异的电催化乙醇氧化制备乙酸盐的性能.在1.72 V(相对于RHE)下的电流密度可达227 mA·cm^(‒2),具有较高活性,生产乙酸盐的法拉第效率达到98%以上;使用32 h后,催化剂仍然保持了最初活性的73%,具有较高的稳定性.通过电化学活性面积、电化学阻抗、塔菲尔斜率等一系列的电化学手段研究,也证明了铜的引入是羟基氧化镍电催化乙醇氧化性能提高的关键.此外,本文使用了电化学原位拉曼光谱实时监测了电催化乙醇到乙酸盐的反应过程,在所有给定电位下均可以观察到乙醇、乙醛和乙酸盐的特征峰.结合核磁共振氢谱分析结果,表明乙酸盐是铜掺杂的羟基氧化镍电催化乙醇氧化过程中的主要产物,而乙醛可能是该过程中生成的重要中间体.本工作为设计用于乙醇电化学氧化生产高附加值产品的非贵金属催化剂提供了一条有潜力的途径.

通过双活化策略在Ag-CeO_(2)电催化剂上用苯乙酮高效固定CO_(2)

二氧化碳(CO_(2))是一种主要的温室气体,对全球气候变化和生态环境造成了很大影响.同时,CO_(2)也是一种无毒、廉价、丰富的C_(1)资源,可用于合成用作燃料和药物的各种有机化合物.因此,模拟植物光合作用对CO_(2)进行固定成为了众多科研工作者的研究热点.电化学羧化是将CO_(2)固定在有机分子上的一种有效方法,并且已被证明可以通过构建新的C–C键,使CO_(2)与各种底物(包括酮、二烯和类卤化物等)发生电羧化反应,形成羧酸化合物.然而,由于CO_(2)分子本身的热力学和动力学惰性,使得CO_(2)分子的活化颇具挑战性,难以实现高效转化.目前,许多研究致力于开发各种用于CO_(2)转化的反应模型和催化剂.例如,结合单个CO_(2)分子形成不同羧酸的单羧基化反应.酮类化合物与CO_(2)的电羧化反应是实现CO_(2)固定并合成羧酸的一种有效途径,得到的羧酸产物可作为许多生物活性化合物的来源.然而,在CO_(2)和芳香酮的电羧化反应中,由于二者的活化具有较大的过电位差异,会严重阻碍电羧化反应的效率并导致产物收率较低.研究表明可以通过同时激活CO_(2)分子和有机底物以促进目标羧化产物的形成.该策略为改善CO_(2)和芳族酮之间的电羧化反应效率提供了思路.本文合成了一种Ag掺杂的CeO_(2)纳米线(Ag-CeO_(2)NWs)作为催化苯乙酮和CO_(2)进行电羧化反应的催化剂.该催化剂能够起到同时活化CO_(2)和苯乙酮分子的作用,实现双重活化的目的.在双重活化策略下,苯乙酮与CO_(2)的电羧化反应可以通过将CO_(2)活化为CO_(2)^(•−),然后通过自由基的形式加成到苯乙酮的双键上;或者,苯乙酮分子被活化成苯乙酮自由基阴离子,苯乙酮自由基阴离子通过亲核反应与CO_(2)偶联,最终形成羧酸产物.与银箔、银纳米颗粒和CeO_(2)纳米线相比,Ag-CeO_(2)纳米线催化剂可以有效降低CO_(2)和苯乙酮分子活化之间的起始电位差,从而能够有效地电羧化形成2-苯乳酸.在-1.8 V vs.Ag/AgI电位下,生成2-苯乳酸的法拉第效率高达91%,收率为83.2%.综上,本文同时激活CO_(2)和有机底物分子的双重活化策略有利于指导催化剂的设计,从而提高CO_(2)固定效率,进而提高电羧化反应的活性和选择性.

Biochar amendments increase soil organic carbon storage and decrease global warming potentials of soil CH4 and N2O under N addition in a subtropical Moso bamboo plantation

Background: Nitrogen(N) deposition affects soil greenhouse gas(GHG) emissions, while biochar application reduces GHG emissions in agricultural soils. However, it remains unclear whether biochar amendment can alleviate the promoting effects of N input on GHG emissions in forest soils. Here, we quantify the separate and combined effects of biochar amendment(0, 20, and 40 t·ha) and N addition(0, 30, 60, and 90 kg N·ha·yr) on soil GHG fluxes in a long-term field experiment at a Moso bamboo(Phyllostachys edulis) plantation.Results: Low and moderate N inputs(≤60 kg N·ha·yr) significantly increase mean annual soil carbon dioxide(CO) and nitrous oxide(NO) emissions by 17.0%–25.4% and 29.8%–31.2%, respectively, while decreasing methane(CH) uptake by 12.4%–15.9%, leading to increases in the global warming potential(GWP) of soil CHand NO fluxes by 32.4%–44.0%. Moreover, N addition reduces soil organic carbon(C;SOC) storage by 0.2%–6.5%. Compared to the control treatment, biochar amendment increases mean annual soil CO2emissions, CHuptake, and SOC storage by 18.4%–25.4%, 7.6%–15.8%, and 7.1%–13.4%, respectively, while decreasing NO emissions by 17.6%–19.2%, leading to a GWP decrease of 18.4%–21.4%. Biochar amendments significantly enhance the promoting effects of N addition on soil COemissions, while substantially offsetting the promotion of N2O emissions, inhibition of CHuptake, and decreased SOC storage, resulting in a GWP decrease of 9.1%–30.3%.Additionally, soil COand CHfluxes are significantly and positively correlated with soil microbial biomass C(MBC) and pH. Meanwhile, NO emissions have a significant and positive correlation with soil MBC and a negative correlation with pH.Conclusions: Biochar amendment can increase SOC storage and offset the enhanced GWP mediated by elevated N deposition and is, thus, a potential strategy for increasing soil C sinks and decreasing GWPs of soil CHand NO under increasing atmospheric N deposition in Moso bamboo plantations.

Management scheme influence and nitrogen addition effects on soil CO_(2),CH_(4),and N_(2)O fluxes in a Moso bamboo plantation

Background:It is still not clear whether the effects of N deposition on soil greenhouse gas(GHG)emissions are influenced by plantation management schemes.A field experiment was conducted to investigate the effects of conventional management(CM)versus intensive management(IM),in combination with simulated N deposition levels of control(ambient N deposition),30 kg N·ha^(−1)·year^(−1)(N30,ambient+30 kg N·ha^(−1)·year^(−1)),60 kg N·ha^(−1)·year^(−1)(N60,ambient+60 kg N·ha^(−1)·year^(−1)),or 90 kg N·ha^(−1)·year^(−1)(N90,ambient+90 kg N·ha^(−1)·year^(−1))on soil CO_(2),CH_(4),and N_(2)O fluxes.For this,24 plots were set up in a Moso bamboo(Phyllostachys edulis)plantation from January 2013 to December 2015.Gas samples were collected monthly from January 2015 to December 2015.Results:Compared with CM,IM significantly increased soil CO_(2) emissions and their temperature sensitivity(Q_(10))but had no significant effects on soil CH_(4) uptake or N_(2)O emissions.In the CM plots,N30 and N60 significantly increased soil CO_(2) emissions,while N60 and N90 significantly increased soil N_(2)O emissions.In the IM plots,N30 and N60 significantly increased soil CO_(2) and N_(2)O emissions,while N60 and N90 significantly decreased soil CH_(4) uptake.Overall,in both CM and IM plots,N30 and N60 significantly increased global warming potentials,whereas N90 did not significantly affect global warming potential.However,N addition significantly decreased the Q_(10) value of soil CO_(2) emissions under IM but not under CM.Soil microbial biomass carbon was significantly and positively correlated with soil CO_(2) and N_(2)O emissions but significantly and negatively correlated with soil CH_(4) uptake.Conclusion:Our results indicate that management scheme effects should be considered when assessing the effect of atmospheric N deposition on GHG emissions in bamboo plantations.

Development and evaluation of an online monitoring single-particle optical particle counter with polarization detection

We developed a single-particle optical particle counter with polarization detection(SOPC)for the real-time measurement of the optical size and depolarization ratio(defined as the ratio of the vertical component to the parallel component of backward scattering)of atmospheric particles,the polarization ratio(DR)value can reflect the irregularity of the particles.The SOPC can detect aerosol particles with size larger than 500 nm and the maximum particle count rate reaches~1.8×10^(5)particles per liter.The SOPC uses a modulated polarization laser to measure the optical size of particles according to forward scattering signal and the DR value of the particles by backward S and P signal components.The sampling rate of the SOPC was 106#/(sec·channel),and all the raw data were processed online.The calibration curve was obtained by polystyrene latex spheres with sizes of 0.5-10μm,and the average relative deviation of measurement was 3.96% for sub 3μm particles.T-matrix method calculations showed that the DR value of backscatter light at 120°could describe the variations in the aspect ratio of particles in the above size range.We performed insitu observations for the evaluation of the SOPC,the mass concentration constructed by the SOPC showed good agreement with the PM_(2.5)measurements in a nearby state-controlled monitoring site.This instrument could provide useful data for source appointment and regulations against air pollution.

Novel Zr-doped β-Li_(3)PS_(4) solid electrolyte for all-solid-state lithium batteries with a combined experimental and computational approach

All-solid-state lithium batteries(ASSLBs)are promising for safety and high-energy-density large-scale energy storage.In this contribution,we propose a Li_(3–4x)Zr_(x)PS_(4)(LZPS)by Zr-dopedβ-Li_(3)PS_(4)(LPS)as a novel solid electrolyte(SE)for ASSLBs based on experimental and simulation methods.The structure,electronic property,mechanical property,and ionic transport properties of LZPS(x=0,0.03,0.06,and 0.1)are investigated with first-principles calculations.Meanwhile,LZPS is prepared by solid states reaction method.By combining experimental analysis and first-principles calculations,it is confirmed that a small amount of Zr4+can be successfully doped into the framework ofβ-LPS composites without significantly compromising structural integrity.When the Zr^(4+)concentration is x=0.03,the doped material Li_(2.88)Zr_(0.03)PS_(4)exhibits the highest ionic conductivity(5.1×10^(−4)S·cm^(−1))at 30℃,and the Li-ion migration energy barrier is the lowest.The Li_(2.88)Zr_(0.03)PS_(4)SE has obtained the best mechanical properties,the good ductility,and shear deformation resistance,which can better maintain the structural stability of the battery.In addition,the Li/Li symmetrical cell is assembled,which shows excellent electrochemical stability of electrolyte against lithium.The constructed all-solid-state batteries(LiCoO_(2)-Li_(6)PS_(5)Cl|Li_(2.88)Zr_(0.03)PS_(4)|Li-In)delivers an initial discharge capacity of 130.4 mAh·g^(−1)at 0.2 C and a capacity retention of 85.1%after 100 cycles at room temperature.This study provides a promising electrolyte for the application of ASSLBs with high ionic conductivity and excellent stability against lithium.

Glycerol aerobic oxidation to glyceric acid over Pt/hydrotalcite catalysts at room temperature

Glycerol(GLY) aerobic oxidation in an aqueous solution is one of the most prospective pathways in biomass transformation, where the supported catalysts based on noble metals(mainly Au, Pd, Pt) are most commonly employed. Herein, Pt nanoparticles supported on rehydrated MgxAl1-hydrotalcite(denoted as re-MgxAl1-LDH-Pt) were prepared via impregnation-reduction method followed by an in situ rehydration process, which showed high activity and selectivity towards GLY oxidation to produce glyceric acid(GLYA) at room temperature. The metal-support interfacial structure and catalyst basicity were modulated by changing the Mg/Al molar ratio of the hydrotalcite precursor, and the optimal performance was achieved on re-Mg6Al1-LDH-Pt with a GLY conversion of 87.6% and a GLYA yield of 58.6%, which exceeded the traditional activated carbon and oxide supports. A combinative study on structural characterizations(XANES, CO-FTIR spectra, and benzoic acid titration) proves that a higher Mg/Al molar ratio promotes the formation of positively charged Ptd+species at metal-support interface, which accelerates bond cleavage of a-C–H and improves catalytic activity. Moreover, a higher Mg/Al molar ratio provides a stronger basicity of support that contributes to the oxidation of terminal-hydroxyl and thus enhances the selectivity of GLYA. This catalyst with tunable metal-support interaction shows prospective applications toward transformation of biomass-based polyols.

Real-time AGC dispatch units considering wind power and ramping capacity of thermal units

The high penetration of wind energy sources in power systems has substantially increased the demand for faster-ramping thermal units participating in the frequency regulation service.To fulfill the automatic generation control(AGC)and compensate the influence of wind power fluctuations simultaneously,ramping capacity should be considered in the dispatch model of thermals.Meanwhile,conventional methods in this area do not take the impact of transmission loss into the dispatch model,or rely on offline network model and parameters,failing to reflect the real relationships between the wind farms and thermal generators.This paper proposes an online approach for AGC dispatch units considering the above issues.Firstly,the power loss sensitivity is online identified using recursive least square method based on the real-time data of phasor measurement units.It sets up power balance constraint and results in a more accurate dispatch model.Then,an improved multi-objective optimization model of dispatch is proposed and a connection is established between the thermal units with fast ramping capacity and the wind farms with rapid fluctuations.Genetic algorithm is used to solve the dispatch model.The proposed method is compared with conventional methods in simulation case in the IEEE 30-bus system.Finally,simulation results verify the validity and the feasibility of identification method and optimization model.

Decoupled Ce-Nd Isotopic Systematics of the Neoproterozoic Huangling Intrusive Complex and Its Geological Significance, Eastern Three Gorges, South China

Cerium is one of multivalent rear earth elements, which can transfer from trivalence to tretavalence at oxidizing environment. This process may cause variable degrees of fractionation of Ce from other trivalent rear earth elements, and thus may provide specific insight into the geological processes associated with marked redoxomorphism. Multiple geochemical tracing of Sr-Nd-Ce isotopes are performed on the felsic and mafic intrusives of the Neoproterozoic（~800 Ma） Huangling complex located at the eastern Three Gorges, South China. The intrusive rocks exclusively show various extents of negative Ce anomalies. On the εCe-εNd plot, most samples from the mafic intrusions scatter within the second quadrant, whereas those from the felsic intrusions within the fourth Quadrant. Both of the two groups exhibit relatively large range of ？Ce（t） variation but limited ？Nd（t） range, which cause a deviation from the ＂crustal array＂ and reveal a decoupled Nd-Ce isotope correlation. The intermediate-felsic suite have varied Ce/Ce＊ ratios but broadly proximate εCe（t） values, indicating that their negative Ce anomalies were generated during the magmatism; on the contrary, a positive correlation between εCe（t） and Ce/Ce＊ is observed for the intermediate-mafic suite, an indication of an origin of post-magmatic alteration or metamorphism for their Ce anomalies. Calculation of model age, the occurrence age of negative Ce anomalies（TCe） for the intermediate-mafic samples infers that the alteration events took place 〉350 Ma. Data showed that negative Ce anomalies of the felsic intrusions may reflect an increase of oxygen fugacity during magma ascending, rather than an inheritance from their source rocks. This explanation implies that the Neoproterozoic magmatism occurred at the continental nucleus of the Yangtze block were developing at a geodynamic context of rapidly regional uplifting.

M2M:A Simple Matlab-to-MapReduce Translator for Cloud Computing

MapReduce is a very popular parallel programming model for cloud computing platforms, and has become an effective method for processing massive data by using a cluster of computers. X-to-MapReduce （X is a program language） translator is a possible solution to help traditional programmers easily deploy an application to cloud systems through translating sequential codes to MapReduce codes. Recently, some SQL- to-MapReduce translators emerge to translate SQL-like queries to MapReduce codes and have good performance in cloud systems. However, SQL-to-MapReduce translators mainly focus on SQL-like queries, but not on numerical computation. Matlab is a high-level language and interactive environment for numerical computation, visualization, and programming, which is very popular in engineering. We propose and develop a simple Matlab-to-MapReduce translator for cloud computing, called M2M, for basic numerical computations. M2M can translate a Matlab code with up to 100 commands to MapReduce code in few seconds, which may cost a proficient Hadoop MapReduce programmer some days on coding so many commands. In addition, M2M can also recognize the dependency between complex commands, which is always confusing during hand coding. We implemented M2M with evaluation for Matlab commands on a cluster. Several common commands are used in our experiments. The results show that M2M is comparable in performance with hand-coded programs.

Spiking-free HGO-based DSC for flexible joint manipulator

The tracking control problem for Flexible Joint Manipulator Control System(FJMCS)with unmeasurable states is addressed in this paper.Firstly,a High-Gain Observer(HGO)is constructed to estimate the unmeasurable states and the uncertainties.Then,a Dynamic Surface Control(DSC)scheme is developed by using the estimation of HGO.The newly proposed controller has two advantages over the existing methods:(A)a novel Spike Suppression Function(SSF)is developed to avoid the estimation spike problem in the existing HGO-based controllers.(B)Unlike the existing observer-based partial feedback control scheme that can only estimate the unmeasurable states,the proposed HGO can estimate both the unmeasurable states and uncertainties.The closed-loop system stability is proved by the Lyapunov theory.Simulation results demonstrate the effectiveness of the proposed controller.

Dynamic-decision-based Real-time Dispatch for Reducing Constraint Violations

This paper proposes a dynamic-decision-based realtime dispatch method to coordinate the economic objective with multiple types of security dispatch objectives while reducing constraint violations in the process of adjusting the system operation point to the optimum.In each decision moment,the following tasks are executed in turn:①locally linearizing the system model at the current operation point with the online model identification by using measurements;②narrowing down the gaps between unsatisfied security requirements and their security thresholds in order of priority;③minimizing the generation cost;④minimizing the security indicators within their security thresholds.Compared with the existing real-time dispatch strategies,the proposed method can adjust the deviations caused by unpredictable power flow fluctuations,avoid dispatch bias caused by model parameter errors,and reduce the constraint violations in the dispatch decision process.The effectiveness of the proposed method is verified with the IEEE 39-bus system.