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Zr-doped LiNi0.5Mn1.49Zr0.01O4 and pristine LiNi0.5Mn1.5O4 with ordered and disordered structures were prepared by a low-temperature solution combustion synthesis method. The phase compositions, structural ordering and micro-morphologies of the products were characterized by X-ray diffraction, energy-dispersive spectroscopy, inductive coupled plasma, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy measurements. The electrochemical performances of the products were investigated by charge/discharge testing, cyclic voltammetry, and electrochemical impedance spectroscopy. The results indicate that the effects of Zr doping on ordered or disordered LiNi0.5Mn1.5O4 are different. Ordered LiNi0.5Mn1.49Zr0.01O4 shows much better cycling stability and rate capability than that of ordered LiNi0.5Mn1.5O4. In contrast, the cycling stability of disordered LiNi0.5Mn1.5O4 changes little, and the rate capability decreases after Zr doping. After 200 cycles at 1 C, the capacity retentions of ordered LiNi0.5Mn1.49Zr0.01O4 and LiNi0.5Mn1.5O4 are 95.0% and 78.0%, respectively, while the capacity retentions of disordered LiNi0.5Mn1.49Zr0.01O4 and LiNi0.5Mn1.5O4 are 98.6% and 95.1%, respectively. In particular, the specific capacity of ordered LiNi0.5Mn1.49Zr0.01O4 is as high as 129.4 mA h/g and retains 94.5% after 100 cycles at 10 C, whereas the specific capacity of ordered LiNi0.5Mn1.5O4 is only 103.0 mA h/g and retains 84.0% at the same conditions. The excellent electrochemical performance of ordered LiNi0.5Mn1.49Zr0.01O4 could be attributed to its better crystallinity, higher lithium diffusion coefficient (DLi), and lower polarization.

A series of Cu-doped LiNi 0.5 Mn 1.5−x Cu x O 4 (x = 0, 0.03, 0.05, 0.10, 0.15) spinel samples have been successfully prepared using a modified low temperature solution combustion synthesis method. X-ray diffraction(XRD) and infrared spectroscopy(FT-IR) analysis are used to characterize the phase structure. Scanning electron microscopy(SEM) is used to observe the microstructure of the products. The electrochemical performance are studied by galvanostatic charge-discharge testing, cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS). No obvious secondary phases were observed in XRD patterns of as-synthesized LiNi 0.5 Mn 1.5−x Cu x O 4 powders. The samples have a combination structure of ordered and disordered space group and the order degree increases with the increase of Cu doping content obtained from FT-IR spectra. The electrochemical performances show that although the specific capacity decreases with the Cu-doping content, the cycle-life both at room temperature and 55 °C and the C-rate performance are remarkably improved. The factors of stable structure, grain refinement, better crystallinity and lower charge transfer resistance lead to the excellent performance of Cu-doped samples.

SmBaCo2−x−yMnxMgyO5+δ (x = 0.5, 1, 1.5 and y = 0.05, 0.1) samples are synthesized by sol-gel method. The influence of different substitution of Mn and Mg for Co on crystal structures, thermal expansion coefficient (TEC), electrical conductivities and electrochemical performances have been investigated. The generation of the secondary phase BaMnO3 is suppressed with Mg2+ increasing. Demonstrated by temperature-dependent X-ray diffraction from 25 °C to 700 °C, the structure of SmBaCo0.4Mn1.5Mg0.1O5+δ in high temperature is stable. The TEC of SmBaCo1.45Mn0.5Mg0.05O5+δ, SmBaCo0.95MnMg0.05O5+δ, SmBaCo0.45Mn1.5Mg0.05O5+δ and SmBaCo0.4Mn1.5Mg0.1O5+δ are 15.77 × 10−6 K−1, 16.20 × 10−6 K−1, 12.19 × 10−6 K−1 and 12.58 × 10−6 K−1, respectively, which are much lower than those of cobalt-based layered perovskites and more compatible with the thermal expansion of SDC electrolyte. Although the electrochemical performances of SmBaCo2−x−yMnxMgyO5+δ (x = 0.5, 1, 1.5 and y = 0.05, 0.1) decrease slightly with Mn increasing, the polarization resistances of the SmBaCo1.45Mn0.5Mg0.05O5+δ and SmBaCo0.4Mn1.5Mg0.1O5+δ are 0.17 Ω cm2 and 0.30 Ω cm2 at 800 °C, respectively, which can meet the electrochemical performance requirements of cathode materials. Among the samples, the SmBaCo1.45Mn0.5Mg0.05O5+δ and SmBaCo0.4Mn1.5Mg0.1O5+δ show better tradeoff properties between TEC and electrochemical performance as cathode materials for IT-SOFCs.

In view of the separation and recycling of Pd(II) from multi-metal aqueous solution, a functionalized extractant of 2-[(2-ethylhexyl)thio]benzoxazole (EHBXS) with excellent selectivity for Pd(II) was synthesized and used to extract Pd(II) for the first time. The effects of EHBXS concentration, HCl concentration, organic/aqueous (O/A) phase ratio, contact time, and regeneration of EHBXS were investigated in detail. The extraction efficiency of Pd(II) was almost 100 % while the co-extraction efficiencies of Pt(IV), Rh(III), Cu(II), Fe(III) and Ni(II) existed in the aqueous solution were less than 10 %, which indicates that EHBXS is an effective extractant and can effectively remove Pd(II) from other metals at desired extraction conditions. Thiourea ((NH2)2CS) solution (1.0 mol/L) could be used as an effective Pd(II) stripping agent and the one-step stripping efficiency of Pd(II) was higher than 98 %. EHBXS has excellent regeneration ability and the extraction efficiency of Pd(II) with regenerated EHBXS reaches to 87% even after 7 cycles. Moreover, the coordination mechanism between EHBXS and Pd(II) has been proven via the slope method, FT-IR spectra, 1H NMR, 13C NMR and single X-ray diffraction. Pd(II) and EHBXS formed a 1:2 complex of Pd(EHBXS)2Cl2 during extraction. Pd(II) was coordinated with two Cl atoms and two EHBXS, and thus formed Pd(EHBXS)2Cl2 molecule, in which EHBXS was coordinated with Pd(II) via the N atom in the benzoxazole ring as neutral unidentate ligand.

Cobalt-free perovskite oxides NdBaCu2O5+δ (NBCO) and NdBa0.5Sr0.5Cu2O5+δ (NBSCO) has been investigated as cathode materials in intermediate-temperature solid fuel cells (IT-SOFCs). The crystal structure, thermal expansion, electrical conductivity and electrochemical properties have been characterized by X-ray diffraction (XRD), dilatometer, four-probe dc method, electrochemical impedance spectroscopy (EIS) and cathodic polarization examinations. The average thermal expansion coefficients (TEC) values of NBCO and NBSCO are 13.0 × 10−6/°C and 14.5 × 10−6/°C, which are more desirable on combining with the electrolytes than cobalt-based cathodes. The partly substitution of Sr on B-site increases the electron hole concentration and improves the conductivity. The polarization resistances values of NBSCO are 0.205 Ωcm2, 0.200 Ωcm2 and 0.135 Ωcm2, whereas the polarization resistances values of NBCO are 8.61 Ωcm2, 3.18 Ωcm2 and 0.83 Ωcm2 at 600 °C, 700 °C and 800 °C, respectively. The improved electrochemical performance of NBSCO should be ascribed to the higher conductivity as well as the improved oxygen adsorption/desorption and oxygen ions diffusion processes.

Ti3MC2 ternary compounds (M=Al or Si) have been prepared by a self-propagating high-temperature synthesis (SHS). The difference of synthesis mechanism between Ti3SiC2 and Ti3AlC2 using Ti/M/C(M=Al or Si) powder mixtures and some TiC or some intermetallic compounds as raw materials has been investigated. The phase composition and the relative content of Ti3MC2 materials in the final products were determined by X-ray diffraction (XRD). The results show that TiC and intermetallic compounds of TiAl have played an important role in synthesis of Ti3AlC2. The relative content of Ti3AlC2 in the products increases with increased addition of TiC or TiAl in the raw materials. In contrast, the relative content of Ti3SiC2 in the products changes less with increasing of TiSi2 content, even decreases with increasing of TiC content in the raw materials. The difference of synthesis mechanism between them has been explained thermodynamically.

The LiNi 0.5 Mn 1.5 O 4 (LNM) spinel lithium-ion battery cathodes were prepared by a modified low temperature solution combustion synthesis method at 600 °C for 3 h. Structural analyses reveal that the modified method is an effective process to eliminate an impurity phase. In comparison with the LNM prepared by a conventional method, the modified sample has higher purity, better crystallinity, smaller amount of Mn 3+ ions and higher structural ordering. It exhibits remarkably superior initial discharge specific capacity of 117.0 mAh/g, and delivers a reversible capacity of ~116.0, 116.6, 113.8, 108.9 and 85.9 mAh/g at 0.2 C, 0.5 C, 1 C, 2 C and 5 C, respectively. While the LNM prepared by the conventional method offers a lower reversible capacity of ~96.3, 95.4, 89.1, 77.0 and 40.6 mAh/g at the same rate. After 50 cycles, about 95.5% of reversible capacity is retained for the LNM prepared by modified method vs. 90.7% for the LNM prepared by the conventional method. It suggests that the modified method is a simple and effective method to prepare LiNi 0.5 Mn 1.5 O 4 with high performance at low temperature and in short time.

In order to simplify the template method for the synthesis of cathode materials for lithium ion batteries, a facile template method using plant stalks as bio-templates has been introduced. Based on this method, LiNi0.5Mn1.5O4 spinel with a significantly improved electrochemical performance has been synthesized using corn stalk as a template. X-ray diffraction (XRD), Fourier transform infrared pectroscopy (FTIR) and scanning electron microscope (SEM) have been used to investigate the phase composition and micro-morphologies of the products. Charge-discharge measurements in lithium cells, cyclic voltammetry (CV) and Electrochemical impedance spectroscopy (EIS) have been used to study the electrochemical performance of the products. The results indicate that the templated product exhibits higher crystallinity than that of non-templated product. Both of the templated product and the non-templated product are combination of the ordered space group P4332 and the disordered Fd-3 m. The specific BET surface area of the templated product is about twice larger than that of the non-templated product. Moreover, the electrochemical performances of the templated product including specific capacity, cycling stability and rate capability are significantly improved as compared with the non-templated product, due to its higher crystallinity, larger Li+ diffusion coefficient and lower charge transfer resistance.

High-voltage LiNi 0.5 Mn 1.5 O 4 spinels were synthesized by a low temperature solution combustion method at 400 °C, 600 °C and 800 °C for 3 h. The phase composition, structural disordering, micro-morphologies and electrochemical properties of the products were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and constant current charge–discharge test. XRD analysis indicated that single phase LiNi 0.5 Mn 1.5 O 4 powders with disordered Fd-3m structures were obtained by the method at 400 °C, 600 °C and 800 °C. The crystallinity increased with increasing preparation temperatures. XRD and FTIR data indicated that the degree of structural disordering in the product prepared at 800 °C was the largest and in the product prepared at 600 °C was the least. SEM investigation demonstrated that the particle size and the crystal perfection of the products were increased with increasing temperatures. The particles of the product prepared at 600 °C with ~200 nm in size are well developed and homogeneously distributed. Charge/discharge curves and cycling performance tests at different current density indicated that the product prepared at 600 °C had the largest specific capacity and the best cycling performance, due to its high purity, high crystallinity, small particle size as well as moderate amount of Mn 3+ ions.