Editorial for special issue on advanced materials for energy storage and conversion

The ever-increasing environmental problems and energy challenges have called urgent demand for utilizing green,efficient,and sustainable energy,thus promoting the development of new technologies associated with energy storage and conversion systems.Amongst a wealth of energy storage devices,Li/Na/K/Zn/Mg ion batteries,metal-air batteries,and lithium-sulfur/all-solid-state batteries together with supercapacitors as advanced power sources have attracted considerable interest due to their conspicuous merits of high energy density,long cycle life,and good rate capability.

Microstructure and properties of Cu−2Cr−1Nb alloy fabricated by spark plasma sintering

Cu−2Cr−1Nb alloy was fabricated by spark plasma sintering(SPS)using close coupled argon-atomized alloy powder as the raw material.The optimal SPS parameters obtained using the L9(3^(4))orthogonal test were 950℃,50 MPa and 15 min,and the relative density of the as-sintered alloy was 99.8%.The rapid densification of SPS effectively inhibited the growth of the Cr_(2)Nb phase,and the atomized powder microstructure was maintained in the grains of the alloy matrix.Uniformly distributed multi-scale Cr_(2)Nb phases with grain sizes of 0.10−0.40μm and 20−100 nm and fine grains of alloy matrix with an average size of 3.79μm were obtained.After heat treatment at 500℃ for 2 h,the room temperature tensile strength,electrical conductivity,and thermal conductivity of the sintered Cu−2Cr−1Nb alloy were 332 MPa,86.7%(IACS),and 323.1 W/(m·K),respectively,and the high temperature tensile strength(700℃)was 76 MPa.

Effect of lithium content on electrochemical property of Li_(1+x)(Mn_(0.6)Ni_(0.2)Co_(0.2))_(1-x)O_2(0≤x≤0.3) composite cathode materials for rechargeable lithium-ion batteries

In order to confirm the optimal Li content of Li-rich Mn-based cathode materials(a fixed mole ratio of Mn to Ni to Co is0.6:0.2:0.2),Li1+x(Mn0.6Ni0.2Co0.2)1-xO2(x=0,0.1,0.2,0.3)composites were obtained,which had a typical layered structure with R3m and C2/m space group observed from X-ray powder diffraction(XRD).Electron microscopy micrograph(SEM)reveals that the particle sizes in the range of0.4-1.1μm increase with an increase of x value.Li1.2(Mn0.6Ni0.2Co0.2)0.8O2sample delivers a larger initial discharge capacity of275.7mA·h/g at the current density of20mA/g in the potential range of2.0-4.8V,while Li1.1(Mn0.6Ni0.2Co0.2)0.9O2shows a better cycle performance with a capacity retention of93.8%at0.2C after50cycles,showing better reaction kinetics of lithium ion insertion and extraction.

Selective recovery of Cu(Ⅱ) through polymer inclusion membranes mediated with 2-aminomethylpyridine derivatives

The Cu(Ⅱ) separation behaviors with polymer inclusion membranes(PIMs) are explored by modifying 2-aminomethylpyridine derivatives with hydrophobic alkyl chains, including 2-[N-(tert-butyloxycarbonylmethyl)-2-picolyamino]acetate(AMB), N,N-dioctyl-2-aminomethylpyridine(AMD), tert-butyl 2-(N-octyl-2-picolyamino) acetate(AMC), and N,N-didecyl-2-aminomethylpyridine(AME). The transport flux and selectivity of Cu(Ⅱ) are determined by optimizing composition and structure of carriers and plasticizers. The results show that the hydrophobic modification of 2-aminomethylpyridine derivatives can boost the selective transport of copper ions in PIMs and membrane stability. In the optimum composition of 30 wt.% PVC, 30 wt.% AME, and 40 wt.% NPOE, the initial flux of Cu(Ⅱ) is 5.8×10^(−6) mol·m^(−2)·s^(−1). The FT-IR and XPS spectra identify that the alkyl amine functional groups of AME involve in the transport of copper chloride species. The SAXS analysis demonstrates that the generated micro-channels in PIMs induced by the hydrophobic modification of 2-aminomethylpyridine derivatives can contribute to the enhanced Cu(Ⅱ) flux.

Using support vector machine for materials design

Materials design is the most important and fundamental work on the background of materials genome initiative for global competitiveness proposed by the National Science and Technology Council of America. As far as the methodologies of materials design, besides the thermodynamic and kinetic methods combing databases, both deductive approaches so-called the first principle methods and inductive approaches based on data mining methods are gaining great progress because of their suc- cessful applications in materials design. In this paper, support vector machine （SVM）, including support vector classification （SVC） and support vector regression （SVR） based on the statistical learning theory （SLT） proposed by Vapnik, is introduced as a relatively new data mining method to meet the different tasks of materials design in our lab. The advantage of using SVM for materials design is discussed based on the applications in the formability of perovskite or BaNiO3 structure, the prediction of energy gaps of binary compounds, the prediction of sintered cold modulus of sialon-corundum castable, the optimization of electric resistances of VPTC semiconductors and the thickness control of In203 semiconductor film preparation. The results presented indicate that SVM is an effective modeling tool for the small sizes of sample sets with great potential applications in materials design.

Ultra-stable carbon-coated sodium vanadium phosphate as cathode material for sodium-ion battery

Based on the excellent sodium ion mobility of sodium superionic conductor structures,Na_(3)V_(2)(PO_(4))_(3)materials have become promising cathode materials in sodium-ion batteries(SIBs).However,inadequate electronic transport of Na_(3)V_(2)(PO_(4))_(3)limits the cycling stability and rate performances in SIBs.In this work,high-performance conductive carbon-coated Na_(3)V_(2)(PO_(4))_(3)materials are obtained via a simple and facile ball-milling assisted solid-state method by utilizing citric acid as carbon sources.The carbon-coated composite electrodes display a high initial specific capacity of 111.6 mAh·g^(-1),and the specific capacity could retention reach 92.83%after 100 cycles at 1C with the high coulombic efficiency(99.95%).More importantly,the capacity of conductive carbon-coated nano-sized Na_(3)V_(2)(PO_(4))_(3)can remain 48.5 mAh·g^(-1) at 10℃after 3000 cycles(initial capacity of 101.2 mAh·g^(-1)).At the same time,high coulombic efficiency(near 100%)has little decay even at a high rate of 20℃during 1000 cycles,demonstrating the excellent cycling stability and remarkable rate performances,and showing potential in largescale productions and applications.