Metal sulfides are emerging as a promising anode material for sodium-ion batteries with high reversible capacities and fast reaction kinetics, but achieving long-cycling-life remains a great challenge. Here, taking cobalt sulfide as an example, its electrochemical sodium-ion storage failure phenomenon is first reported, which indicates that the battery cannot reach the cutoff voltage during charging. Detailed analyses demonstrate that such failure may originate from the dissolution and escape of polysulfide intermediates, further reacting with the released copper-ions from the current collector and inducing the occurrence of the shuttle effect. Based on the explored failure mechanism, a sulfur-doped carbon matrix with polar carbon sulfur bonds, which can firmly immobilize the dissolved polysulfides, is deliberately introduced into the Co 1−x S active particles (Co 1−x S/s-C) to improve their cycle stability. Consequently, the cycle life of the Co 1−x S/s-C anode for sodium-ion storage is extended from the original 125 to present 2000 cycles, even at high-rate current densities. Moreover, utilizing the carbon current collector instead of traditional copper can effectively delay the occurrence of the failure phenomenon. The present work promotes better fundamental understanding of the structural evolution of metal sulfide anodes during cycles, and the solution strategy can be extended to apply in other metal sulfides (ZnS, NiS).

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Zinc oxide films with c-axis preferred orientation were deposited on silicon (100) substrates by radio frequency (RF) reactive sputtering. The properties of the samples were characterized by X-ray diffractometer, X-ray photoelectron spectroscopy and fluorescent-spectrophotometer. The effect of sputtering power and substrate temperature on the structural and photoluminescent (PL) properties of the ZnO films was investigated. The results indicated that when the sputtering power is 100 W and the substrate temperature is 300-400℃, it is suitable for the growth of high c-axis orientation and small strain ZnO films. A violet peak at about 380 nm and a blue band at about 430 nm were observed in the room temperature photoluminescence spectra, and the origin of blue emission was investigated.ZnO films, XRD spectra, PL spectra, substrate temperature, RF reactive sputtering ZnO has been widely used in the surface-acoustic apparatus, gas sensor, solar cell electrode and light emitters for its excellent optical and electronic properties [1] . As a kind of direct band semiconductor compound with hexagonal wurtzite structure, ZnO has a wide band gap E g (3.37 ev) and high excition binding energy ex b E (60 meV) at room temperature, compared with other wide band emission materials [2,3] such as ZnSe (E g = 2.7 eV, ex b E = 20 meV) and GaN (E g = 3.4 eV, ex b E = 21 meV), and it would be more suitable for the room temperature or high temperature ultra-violet emission material, so its emission properties have drawn much attention.The emission peaks of ZnO films mainly contain an excition peak (∼380 nm) [2][3][4][5][6][7] and a green peak (∼510 nm) [6,7] . With the further study of the ZnO films photoluminescent (PL) properties, blue peaks at various wavelengths have been reported, e.g. Wang et al. [8] reported the blue peak at 446

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The present study investigated the laser welding performance of Al-Fe aluminum alloy sheets with different contents of intermetallic compounds. Under the same welding parameters, the alloy of higher intermetallic compounds content has wide and deep weld pools with uniform sizes. The alloy of lower intermetallic compounds content has narrow and shallow weld pools with nonuniform sizes. The higher content of intermetallic compounds results in higher laser absorptivity and lower thermal conductivity, and then increases the effective absorbed energy during welding, which is beneficial to the formation of wide and deep weld pools. The distribution uniformity of intermetallic compounds influences the size uniformity of weld pools. In the alloy with lower content of intermetallic compounds, the nonuniform distribution of intermeallic compounds results in the formation of abnormal weld pool, leading to the nonuniform size of the weld pools. In the alloy with higher content of intermetallic compounds, uniform distribution of intermetallic compounds make the size of weld pools more uniform.

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A method to graphitize amorphous carbon was carried out by annealing pyrocarbon from cracked phenolic resin in molten sodium metal at a lower temperature and ambient pressure and the phase transformation of pyrocarbon from amorphous carbon to crystallized carbon was studied. X-ray diffraction (XRD), Raman scattering spectroscopy, transmission electron microscopy (TEM), and nitrogen gas physisorption by the Brunauer-Emmett-Teller (BET) method were used to probe the prepared samples for carbon composition, particle size, and morphology. The graphitization of amorphous carbon was obvious when being annealed in molten sodium metal in argon atmosphere at 800°C for 24 h. For the sample annealed at 900°C for 24 h, the degree of graphitization was 40% and the average thickness of the graphitized carbon layers was about 40 nm. The effect of sodium metal infiltration into the matrix of amorphous carbon on the graphitization is also discussed.