Al-incorporation into Li7La3Zr2O12 solid electrolyte keeping stabilized cubic phase for all-solid-state Li batteries

We observe the influence of AI occupancies in Li sites on the formation process of the garnet solid elec- trolyte of Li_7La_3Zr_2O_12 （LLZO）. A direct incorporation of AI is first promoted in a Li-insufficient garnet solid electrolyte during the calcination process of 850 ℃ and then the cubic phase of LLZO is obtained after successive annealing step of 1000 ℃. Comparing to pristine LLZO, AI incorporated LLZO shows less formation of Li_2CO_3, keeping crystallographic and physicochemical properties. This AI incorporation im- proves both the ionic conductivity and interfacial resistance to poisoning procedure.

In situ formation of lithiophilic Li_(22)Sn_(5) alloy and high Li-ion conductive Li_(2)S/Li_(2)Se via metal chalcogenide SnSSe for dendrite-free Li metal anodes

Lithium metal has gained extensive attention as the most ideal candidate for next-generation battery anode owing to the ultrahigh specific capacity and the lowest electrochemical potential.However,uncontrollable dendrite growth and huge volume variation extremely restrict the future deployment of lithium metal batteries.Herein,we report metal chalcogenide SnSSe with unique nanoplate stacking structure as a robust substrate for stable Li metal anode.During the initial Li plating process,lithiophilic Li_(22)Sn_(5) alloy and Li_(2)S/Li_(2)Se sites are obtained via in-situ electrochemical reaction of Li metal and SnSSe.Density functional theory(DFT)calculation demonstrates that the formed Li_(2)S/Li_(2)Se achieves low Li diffusion energy barrier,ensuring rapid Li~+migration.Li_(22)Sn_(5) alloy provides strong nucleation sites,promoting uniform Li nucleation.Furthermore,in-situ optical microscopy analysis suggests that the synthesized effect fundamentally inhibits lithium dendrite growth.Consequently,SnSSe modified Cu foil delivered an ultralow nucleation overpotential,superior cycling stability with 450 cycles(Coulombic efficiency,>98%),and excellent plating/stripping behavior over 2200 h at 0.5 mA cm^(-2).Moreover,the brilliant reversible cycles and rate capability were also realized in Li@SnSSe//LiFePO_(4)(LFP)full cell,shedding light on the feasibility of SnSSe for stable and dendrite-free lithium metal anode.

Structural Characteristic of CdS Thin Films and Their Influences on Cu(In,Ga)Se_2(CIGS) Thin Film Solar Cells

Deposition and structural characteristics of cadmium sulfide (CdS) thin films by chemical bath deposition (CBD) technique from a bath containing thiourea,cadmium acetate,ammonium acetate and ammonia in an aqueous solution are reported.Researches are made on the influence of the fundamental parameters including pH,temperature,and concentrations of the solution involved in the chemical bath deposition of CdS and titration or dumping of the thiourea solution on the structure characteristic of CdS thin films.The pH of the solution plays a vital role on the characteristic of the CdS thin films.The XRD patterns show that the change in the pH of the solution results in the change in crystal phase from predominant hexagonal phase to predominant cubic phase.The CdS thin films with the two different crystal phases have different influences on CIGS thin film solar cells.The crystal mismatch and the interface state density of the c-CdS(cubic phase CdS) and CIGS are about 1 419% and 8 507×10 12cm -2 respectively,and those of the h-CdS(hexagonal phase CdS) and CIGS are about 32 297% and 2 792×10 12cm -2 respectively.It is necessary for high efficiency CIGS thin film solar cells to deposit the cubic phase CdS thin films.

Na_(2)O对锂铝硅微晶玻璃析晶及性能的影响

采用熔融法制备了不同Na_(2)O含量的透明锂铝硅微晶玻璃,通过DSC、XRD、FESEM等测试方法研究了不同Na_(2)O含量对玻璃析晶及性能的影响。结果表明:Na_(2)O的引入能显著降低玻璃的转变温度和析晶温度,抑制LiAlSi_(4)O_(10)晶相的析出。但Na_(2)O的引入促使微晶玻璃中析出Li_(2)Si_(2)O_(5)新相,并且随着Na_(2)O引入量的增加,Li_(2)Si_(2)O_(5)转变为主晶相。由于晶体尺寸均为纳米级,主晶相的转变对透过率影响较小,微晶玻璃的可见光透过率均高于85%。主晶相的转变有效增强了微晶玻璃的机械性能,其弯曲强度由300 MPa提升至331 MPa。Na_(2)O的引入有效增强了Na-K交换,Na_(2)O含量为4%(质量分数)的Li 2O-Al_(2)O_(3)-SiO_(2)微晶玻璃在410℃的KNO_(3)熔盐中交换6 h后,维氏硬度由7.108 GPa提升至7.403 GPa,弯曲强度由331 MPa提升至470 MPa。

Li_(4)SrCa(SiO_(4))_(2)∶Eu^(3+)红色荧光粉的合成及其发光性能

采用硅酸盐作为基质材料,通过高温固相法合成了Li_(4)SrCa(SiO_(4))_(2)∶Eu^(3+)红色荧光粉。通过X射线粉末衍射、X射线光电子能谱、透射电镜和荧光光谱,对所得样品的物相、形貌及其发光性能进行了表征分析。结果表明,掺入Eu^(3+)后,Li_(4)SrCa(SiO_(4))_(2)的晶体结构并没有发生改变。在393 nm光激发下,荧光粉的荧光光谱中693 nm处发射峰强度最强。以693 nm作为监测波长,荧光激发峰分别为361 nm(7F0→5D4)、375 nm(7F0→5G3)、413 nm(7F0→5D3)、393 nm(7F0→5L6)和464 nm(7F0→5D2),即样品对近紫外和蓝光有较好的吸收。利用发射光谱研究了Eu^(3+)掺杂浓度(物质的量分数)对荧光粉发光强度的影响。当Eu^(3+)的掺杂浓度x=0.10时,样品发射强度最强,发射红光,其色坐标为(0.6375,0.3537)。通过Dexter强度与浓度关系分析了浓度猝灭机制。

Li_(2)O-Si_(3)N_(4)-AlN系统相关系和Li-α′-Sialon的形成

研究了 Li_2O-Si_3N_4-AlN 系统1750℃的等温截面。在 Si_3N_4-Li_2O∶3AlN 连线上,测定了 Li-α′-Sialon 固溶体(Li_(?)Si_(?)Al_(3n)O_nN_(?),2n≤2)区,其稳定范围为2n=0.25～1.50。研究了 Li-α′-Sialon的形成反应和致密化过程。发现在1300～1600℃范围内先生成一个中间相:Li-O′-Sialon,从1600℃才开始并快速地形成 Li-α′-Sialon,1700℃可获得接近理论密度的纯 Li-α′-Silon 相。对 Li-α′-Sialon 的高温稳定性也作了讨论。

Pb(Li_(1/4)Fe_(1/4)W_(1/2)O_3铁电体的有序结构和介电性质

用普通的电子陶瓷一次合成法，在903K下制备了高度有序的Pb（Li1/4Fe1/4W1/2）O3铁电体，介电特性测量显示该材料有明显的弥散相变现象。从X射线衍射和透射电镜的分析表明为面心立方钙钛矿结构，晶胞参数为8．024×10-10m。提出其有序化结构特点是Li+、Fe3+随机分布，同时它们与W6+相间在〈111〉方向作有序排列。

锂离子电池Li_(2)FeP_(2)O_(7)正极材料的制备及其电化学性能

采用固相球磨法制备了Li_(2)FeP_(2)O_(7)/C正极材料,研究了烧结温度、碳包覆含量以及碳源对其结构、形貌以及电化学性能的影响。结果表明:高温固相烧结合成样品的适宜温度为680℃,以柠檬酸为碳源、碳包覆量为5%时,合成的Li_(2)FeP_(2)O_(7)/C晶型完整,晶粒较小且均匀,0.1C倍率下的放电比容量可达102.6 mAh/g,0.5C倍率下的初次放电比容量可达83.4 mAh/g,循环30次后放电比容量为80.7 mAh/g,展现了较好的循环性能以及倍率性能。

First-principles study on the alkali chalcogenide secondary compounds in Cu(In,Ga)Se_2 and Cu_2ZnSn(S,Se)_4 thin film solar cells

The beneficial effect of the alkali metals such as Na and K on the Cu（In.Ga）Se2 （CIGS） and Cu2ZnSn（S,Se）4 （CZTSSe） solar cells has been extensively investigated in the past two decades, however, in most of the studies the alkali metals were treated as dopants. Several recent studies have showed that the alkali metals may not only act as dopants but also form secondary phases in the absorber layer or on the surfaces of the films. Using the first-principles calculations, we screened out the most probable secondary phases of Na and K in CIGS and CZTSSe, and studied their electronic structures and optical properties. We found that all these alkali chalcogenide compounds have larger band gaps and lower VBM levels than CIGS and CZTSSe, because the existence of strong p-d coupling in CIS and CZTS pushes the valence band maximum （VBM） level up and reduces the band-gaps, while there is no such p-d coupling in these alkali chalcogenides. This band alignment repels the photo-generated holes from the secondary phases and prevents the electron-hole recombination. Moreover, the study on the optical properties of the secondary phases showed that the absorption coefficients of these alkali chalcogenides are much lower than those of CIGS and CZTSSe in the energy range of 0-3.4eV, which means that the alkali chalcogenides may not influence the absorption of solar light. Since the alkali metal dopants can passivate the grain boundaries and increase the hole carrier concentration, and meanwhile their related secondary phases have innocuous effect on the optical absorption and band alignment, we can understand why the alkali metal dopants can improve the CIGS and CZTSSe solar cell performance.

简易合成Cu_(2)Se/rGO水凝胶用于高性能锌离子混合电容器

环境友好和低成本的锌离子混合超级电容器在大规模储能方面受到了相当大的关注。过渡金属硒化物因其具有高的可逆容量、优越的导电性和多功能结构而受到了人们的广泛关注。在本研究中,通过一个简单的液相反应合成了三维Cu_(2) Se/rGO水凝胶复合物。在以锌片和Cu_(2) Se/rGO分别为负、正极材料的锌离子混合电容器(ZHICs)中Cu_(2) Se/rGO电极在0.1 A·g^(-1)时电容为130 F·g^(-1),远远大于Cu_(2) Se颗粒的54.5 F·g^(-1)。这显示着水凝胶rGO的加入能够提高锌离子的存储容量。

Unveiling the parasitic-reaction-driven surface reconstruction in Ni-rich cathode and the electrochemical role of Li_(2)CO_(3)

Nickel-rich transition-metal oxides are widely regarded as promising cathode materials for high-energydensity lithium-ion batteries for emerging electric vehicles. However, achieving high energy density in Ni-rich cathodes is accompanied by substantial safety and cycle-life obstacles. The major issues of Ni-rich cathodes at high working potentials are originated from the unstable cathode-electrolyte interface, while the underlying mechanism of parasitic reactions towards surface reconstructions of cathode materials is not well understood. In this work, we controlled the Li_(2)CO_(3) impurity content on LiNi_(0.83)Mn_(0.1)Co_(0.07)O_(2) cathodes using air, tank-air, and O_(2) synthesis environments. Home-built high-precision leakage current and on-line electrochemical mass spectroscopy experiments verify that Li_(2)CO_(3) impurity is a significant promoter of parasitic reactions on Ni-rich cathodes. The rate of parasitic reactions is strongly correlated to Li_(2)CO_(3) content and severe performance deterioration of Ni83 cathodes.The post-mortem characterizations via high-resolution transition electron microscope and X-ray photoelectron spectroscopy depth profiles reveal that parasitic reactions promote more Ni reduction and O deficiency and even rock-salt phase transformation at the surface of cathode materials. Our observation suggests that surface reconstructions have a strong affiliation to parasitic reactions that create chemically acidic environment to etch away the lattice oxygen and offer the electrical charge to reduce the valence state of transition metal. Thus, this study advances our understanding on surface reconstructions of Nirich cathodes and prepares us for searching for rational strategies.

Growth and structural characteristics of metastableβ-In2Se3 thin films on H-terminated Si(111)substrates by molecular beam epitaxy

Epitaxial growth and structural characteristics of metastableβ-In2Se3 thin films on H-terminated Si(111)substrates are studied.The In2Se3 thin films grown below theβ-to-αphase transition temperature(453 K)are characterized to be strainedβ-In2Se3 mixed with significantγ-In2Se3 phases.The pure-phased single-crystallineβ-In2Se3 can be reproducibly achieved by in situ annealing the as-deposited poly-crystalline In2Se3 within the phase equilibrium temperature window ofβ-In2Se3.It is suggeted that the observedγ-to-βphase transition triggered by quite a low annealing temperature should be a rather lowered phase transition barrier of the epitaxy-stabilized In2Se3 thin-film system at a state far from thermodynamic equilibrium.

Thermal stability and thermoelectric properties of Cd-doped nano-layered Cu2Se prepared using NaCl flux method

Cu2Se is a promising"phonon liquid-electron crystal"thermoelectric material with excellent thermoelectric performance.In this work,Cd-doped Cu2-xSeCdx(x=0,0.0075,0.01,and 0.02)samples were prepared using NaCl flux method.The solubility of Cd in Cu2Se at room temperature was less than 6%,and a second phase of CdSe was found in the samples with large initial Cd content(x=0.01 and 0.02).Field-emission scanning electron microscopic image showed that the arranged lamellae formed a large-scale layered structure with an average thickness of approximately 100 nm.Transmission electron microscopy demonstrated that doping of Cd atoms did not destroy the crystal integrity of Cu2Se.A small amount of Cd in Cu2Se could reduce the electrical and thermal conductivities of the material,thus significantly enhancing its thermoelectric performance.With the increase in Cd content in the sample,the carrier concentration decreased and the mobility increased gradually.Thermogravimetric differential thermal analysis showed that no weight loss occurred below the melting point.Excessive Cd doping led to the emergence of the second phase of CdSe in the sample,thus significantly increasing the thermal conductivity of the material.A maximum ZT value of 1.67 at 700 K was obtained in the Cu1.9925SeCd0.0075 sample.

植物补光用蓝绿色荧光粉Li_(2)Ca_(2)Si_(2)O_(7):Eu^(2+)的合成与光谱性能研究

该文采用高温固相法制备一种植物补光用蓝绿色Li_(2)Ca_(2)Si_(2)O_(7):Eu^(2+)荧光粉,并对其结构、光谱性能及色度坐标进行表征。结果表明,荧光粉Li_(2)Ca_(2)Si_(2)O_(7):Eu^(2+)加入10%的NH4Cl时的最佳合成温度为900℃,该荧光粉在330 nm的紫外激发下发射光谱位于450~520 nm的宽峰。荧光粉Li_(2)Ca_(2(1-x))Si_(2)O7:2x Eu^(2+)中Eu^(2+)的最佳浓度为0.07,Eu^(2+)离子之间的能量传递机制为电多级相互作用。

NaBH4-induced phase transition of CoSe_(2) with abundant Se deficiency for acidic oxygen reduction to hydrogen peroxide

Electrocatalytic oxygen reduction(ORR)via the 2e−pathway to form H_(2)O_(2) in acidic medium has attracted extensive attention.However,the low activity,insufficient selectivity and high cost of catalysts have been the bottlenecks.Herein,CoSe_(2) with abundant Se deficiency was synthesized by a simple hydrothermal method,and the addition of NaBH4-induced CoSe_(2) phase transition from orthorhombic to cubic phase with more Se deficiency.The cubic phase CoSe_(2) with abundant Se deficiency can effectively regulate the surface electronic structure with suitable binding energies of*OOH and*O,which shows high activity,selectivity and long-term stability for acidic ORR to H_(2)O_(2).The onset potential is as low as 0.73 V vs.reversible hydrogen electrode(RHE),the H_(2)O_(2) selectivity is 84%(0 V vs.RHE),and the average electron transfer number is about 2.3.Furthermore,the H_(2)O_(2) yield measured using a flow cell is as high as 115.92 mmol·gcat.^(−1)·h^(−1) and the Faradaic efficiency is 70%at 0 V vs.RHE,which presents high potential in electrocatalytic acidic ORR to H_(2)O_(2) and organic pollutant degradation using the electron-Fenton process.

Seed and Wasp Production in the Mutualism of Figs and Fig Wasps

Figs (Moracea: Ficus) and fig wasps (Hymenoptera: Chlocloids: Agaonideae) depend on each other to complete their reproduction. Monoecious fig species and their pollinating wasps are in conflict over the use of fig ovaries which can either produce one seed or one wasp. From observation on Ficus virens Ait., we showed that female flowers with outer layer of ovaries (near to the wall of syconium) had no significant difference from that with inner and interval layer of ovaries (near to the syconium cavity), in which most seeds and wasps were produced. This meant that fig tree provided the same potential resource for seed and wasps production. Observation indicated that there was usually only one foundress in syconium at female flower phase and no com- petition pollinators. Measurement of the style length of female flowers and the ovipositor of pollinators indicated that most ovaries could be reached by pollinator’s ovipositor. However, at the male flower phase, production of seeds was significantly more than that of wasps including non-pollinating wasps but there was no significant difference between seed and pollinating wasp production when without non-pollinating wasps produced. This result indicated that non-pollinating wasps competed ovaries not with seeds but with pollinating wasps for ovipositing. Bagged experiment showed that the sampling fig species was not self-sterile which was important for figs and wasps to survive bad season. Seed production in self-pollinated figs was not significantly different from total wasps in- cluding non-pollinating ones. This might be related with the weaker competition among wasps since bagged figs were not easy to reach by wasps from outside.

Li掺杂对铜锌锡硫硒太阳电池的影响研究

开展了基于二甲基亚砜溶剂体系的溶胶凝胶法制备铜锌锡硫硒薄膜中掺杂Li的相关研究。对不同Li掺杂量的CZTSSe薄膜分别进行了表截面形貌、晶体结构、成分比例测试,结果表明:在CZTSSe薄膜中掺杂Li可以提升薄膜的结晶质量,且随着Li掺杂量的增加,结晶质量变好。分析原因为,高温硒化过程中形成的Li_(2)Se相辅助生长改善了薄膜的结晶质量,抑制了ZnCu和SnCu等施主能级缺陷生成。但是,同样发现在Li/Cu摩尔比为1%~10%之间存在阈值,过量的Li并不能进入晶格而富集在晶界处。对不同Li掺杂的CZTSSe薄膜进行太阳电池的制备,结果表明Li/Cu为1%的太阳电池具有最高的转换效率,达到8.5%。

Lattice evolution, order transformation, and microwave dielectric properties of the Zn_(1-x)Li_(2x)TiO_(3)(0≤x≤1) system ceramics

Research on doping modification of ZnTiO_(3) ceramics to enhance microwave dielectric properties has been hindered by poor performance,unclear structure-function mechanisms.To expand the applicability of ZnTiO_(3) ceramics,this study explores Zn_(1-x)Li_(2x)TiO_(3)(O≤×≤1)ceramics using a phase engineering strategy.Our findings reveal that the introduction of Lit into the ZnTiO_(3) system initiates a multiple phase transition,starting at x=0.1.Initially,ilmenite ZnTiO_(3) transforms into a cubic ordered spinel phase(space group P4332).Subsequently,a transition to a disordered spinel phase(space group Fd3m)occurs at x=0.5,culminating in the formation of a monoclinic rock salt-structured LizTiO3 phase.Significantly,two sets of ceramics with near-zero temperature coefficients of resonance frequency(t:)were obtained at x=0.1 and 0.75.Moreover,the quality factor(Qxf)demonstrated a 4.4-fold increase compared to that of ZnTiO_(3) ceramics at x=0.25(105,013 GHz).Additionally,it was observed that the Ti4 polarization in Zn_(1-x)Li_(2x)TiO_(3) ceramics was underestimated by 11.3%-13.3%,causing the measured dielectric constant(e.)exceeding the theoretical dielectric constant(eth).The ionic polarizability of Ti*was adjusted to stabilize around 3.29 A.Evaluation using multiple methods,including Phillips-van Vechten-Levine(P-V-L)theory,Raman vibrational mode analysis,bond valence,bond energy theory,and octahedral distortion,confirms that the Ti-O bonds within the octahedron predominantly affect&r,the increasing lattice energy(U)contributes to the enhancement of Qxf,and the strengthened Li-O bond energy effectively regulates Tr.

Highly insulating phase of Bi_(2)O_(2)Se thin films with high electronic performance

Bi_(2)O_(2)Se is highly competitive as a candidate of next-generation high-performance semiconductors.Though dubbed as semiconductor,Bi_(2)O_(2)Se films exhibited high conductance,i.e.,metallic behavior,due to spontaneously ionized defects.Semiconducting/insulating films are of practical importance in broad applications based on low-power,high-performance electronics,the existence of which lacks firm evidence.Here,we synthesized highly insulating films in a controlled way,which exhibit semiconducting behavior with channel resistance up to 1 TΩ.The electron chemical potential lies within the band gap,in some cases,even below the charge neutrality level,signifying the trace of hole-type semiconducting.The performance of insulating devices remains high,comparable to high-quality devices previously.Especially,the threshold voltage(Vth)is positive,contrary to common negative values reported.Calculations indicate that our synthesis conditions suppress electron donors(Se vacancies(VSe))and promote the formation of compensating acceptors(Bi vacancies(VBi)),leading to insulating behaviors.Our work offers insights into electron dynamics of Bi_(2)O_(2)Se,moves one step further towards p-type transistors and provides a valuable playground for engineering ferroelectricity in high-performance semiconductors.

Differentiated design strategies toward broadband achromatic and polarizationinsensitive metalenses

Metasurfaces have emerged as a flexible platform for shaping the electromagnetic field via the tailoring phase,amplitude,and polarization at will.However,the chromatic aberration inherited from building blocks’diffractive nature plagues them when used in many practical applications.Current solutions for eliminating chromatic aberration usually rely on searching through many meta-atoms to seek designs that satisfy both phase and phase dispersion preconditions,inevitably leading to intensive design efforts.Moreover,most schemes are commonly valid for incidence with a specific spin state.Here,inspired by the Rayleigh criterion for spot resolution,we present a design principle for broadband achromatic and polarization-insensitive metalenses using two sets of anisotropic nanofins based on phase change material Ge2Sb2Se4Te1.By limiting the rotation angles of all nanofins to either 0 deg or 90 deg,the metalens with a suitable numerical aperture constructed by this fashion allows for achromatic and polarization-insensitive performance across the wavelength range of 4–5μm,while maintaining high focusing efficiency and diffraction-limited performance.We also demonstrate the versatility of our approach by successfully implementing the generation of broadband achromatic and polarization-insensitive focusing optical vortex.This work represents a major advance in achromatic metalenses and may find more applications in compact and chip-scale devices.