Jianqiu Deng

Structure and electrochemical performance of nanosized Li1.1(Ni0.35Co0.35Mn0.30)O2 powders for lithium-ion battery

Pure Li1.1Ni0.35Co0.35Mn0.30O2 nanosized powders have been successfully synthesized by improved hydroxide co-precipitation method, and characterized with X-ray powder diffraction and scanning electron microscopy (SEM). The electrochemical properties of cathodes and Li1.1Ni0.35Co0.35Mn0.30O2/Li4Ti5O12 full cells have been studied by charge–discharge tests and cyclic voltammetry. The Li1.1Ni0.35Co0.35Mn0.30O2 powders have a typical layered hexagonal crystal structure with an average particle size of about 780 nm. The cathodes exhibit high capacities and good cycling performance. The initial discharge capacity of the cathodes is 154.8 mAhg-1 at 0.5 C between 2.5 V and 4.3 V, and the capacity retention keeps 80.6% after 50 charge–discharge cycles. The Li1.1Ni0.35Co0.35Mn0.30O2/Li4Ti5O12 cells also deliver high specific capacities, good cycling stability and rate capability. This work demonstrates that Li1.1Ni0.35Co0.35Mn0.30O2 is a promising cathode material for lithium-ion batteries.

Effect of rapid solidification treatment on structure and electrochemical performance of low-Co AB5-type hydrogen storage alloy

The effect of rapid solidification on structure and electrochemical performance of the LaNi4.5Co0.25Al0.25 hydrogen storage alloy was investigated by X-ray powder diffraction and a simulated battery test, including maximum capacity, cycling stability, self-discharge, and high-rate discharge ability (HRD). All the melt-spun alloys were single-phase with the CaCu5-type structure (space group P6/mmm). In comparison to the as-cast alloy, the rapidly quenched alloys manifested an improved homogeneity of composition and expanded lattice parameters. The electrochemical measurements showed that the activation property, cycling stability and self-discharge of the alloy electrodes were also improved for the rapid solidified alloys. The HRD of the as-cast alloy was better than those of all the rapidly solidified alloys. As the quenching rate increased, the HRD and exchange current density first decreased and then increased.

Effects of Magnetic Heat Treatment on Microstructure and Hydrogen Permeation Properties of Nb–Ti–Ni Alloy Membranes

In this paper, effects of magnetic heat treatment (MHT) on structure and hydrogen permeation properties of Nb49Ni25Ti26 alloy membrane have been investigated. XRD and SEM were employed to characterize its phases and microstructure. Also, hydrogen diffusion coefficients (DH) of the alloy membrane were measured in Devanathan-Stachurski (D-S) dual-cell system. The results indicate that MHT-treated alloys still maintain their two-phase structure, consisting of the primary bcc-Nb (Ni, Ti) solid solution phase and (bcc-Nb(Ni, Ti) + β2-NiTi) eutectic phase, with their DH increment after MHT at 0° and 90° respectively. The maximum value of DH is 6.3822 × 10−9 H2 m2/s for the alloy membrane treated by MHT at 0° angle (magnetic field direction is parallel to membrane surface), the increase of DH is possibly due to the grain orientation, and the formation of smaller solid solution phase region with higher specific area. Such results suggest that reasonable MHT benefits to the improvement of hydrogen permeation properties of Nb49Ni25Ti26 alloy membrane.

Crystal structure and phase relations of Pr2Fe14B-La2Fe14B system

Abstract The crystal structure and phase relations of the Pr 2 Fe 14 B-La 2 Fe 14 B system were investigated by X-ray powder diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The crystal structure parameters were determined by full-profile Rietveld refinements. The results revealed that all alloys of (Pr 1– x La x ) 2 Fe 14 B crystallized the Nd 2 Fe 14 B-type structure with the space group P 4 2 / mnm and formed a continuous solid solutions between x =0.0 and 1.0. The lattice parameter a, c , unit-cell volume V and c/a ratio increased linearly with the La concentration. Determined by thermogravimetry analysis, the Curie temperature ( T C ), phase transition temperature and melting temperature of (Pr 1– x La x ) 2 Fe 14 B decreased linearly upon the La content. Based on the results of DSC measurements and X-ray powder diffraction examinations, the phase diagram of the Pr 2 Fe 14 B-La 2 Fe 14 B system was built up.

Effects of surface treatment on electrochemical properties of AB3.8-type hydrogen storage alloy in alkaline electrolyte

The La0.8Mg0.2Ni3.2Co0.3Mn0.1Al0.2 has been treated by the HF and KF etching solution and Ni coating solutions with the different concentrations. The surface structure and the electrochemical properties of the untreated and the treated hydrogen storage alloys have been investigated in details. The results show that the surface oxide layer on the alloys is removed after fluoridation and the surface of the alloy powders becomes smooth with electroless Ni plating. The maximum discharge capacity of the alloy electrodes is increased from 359.5 mA h g−1 (M1) to 370.1 mA h g−1 (M5) and the cycling stability is improved slightly after the surface treatment. At a discharge current density of 900 mA g−1, the high rate dischargeability (HRD) is enhanced from 38.3% (M1) to 77.0% (M5) and the M5 electrode still keeps at a high value of 55.9% at a discharge current density of 1500 mA g−1. In addition, the exchange current density I0 and the hydrogen diffusion coefficient D are also increased by the surface treatment.

A high rate capability and long lifespan symmetric sodium-ion battery system based on a bipolar material Na2LiV2(PO4)3/C

Sodium ion batteries have been considered as one of the promising candidates for large-scale energy storage systems. From the application perspective of an integrated sodium ion full-cell system, it is important to develop a practical sodium-ion full-cell system with excellent cycling life, superior safety, and good rate capability to tolerate the frequent current impulses during the grid peak period. Therefore, exploring appropriate electrode materials with excellent electrochemical properties is the key issue. A rhombohedral structured two-phase Na2LiV2(PO4)3/C nanocomposite has been successfully synthesized and employed as both cathode and anode material. It exhibits excellent electrochemical performance, including high capacity, superior rate capability, and remarkable cycling performance. In particular, it shows excellent long-term cycling stability with a capacity retention of about 83% and 100% after 3000 cycles at 10C, for the cathode and anode, respectively. Moreover, the symmetric sodium-ion full cells made of the Na2LiV2(PO4)3/C nanocomposite have good rate capability and cycling stability, which verifies the feasibility of practical applications of the Na2LiV2(PO4)3/C nanocomposite in sodium-ion batteries.

Effect of Ce content on structure and electrochemical properties of La0.8–xCexPr0.1Nd0.1B5 (B = Ni, Co, Mn; 0 ⩽ x ⩽ 0.3) hydrogen storage alloys

The structure and electrochemical properties of La0.8–xCexPr0.1Nd0.1B5 (B5 ≡ Ni3.8Co1.1Mn0.1; x = 0, 0.1, 0.2, 0.3) hydrogen storage alloys have been investigated. The results show that all alloys consist of CaCu5-type single phase. The maximum discharge capacity of the alloy electrodes decreases from 368.7 mA h g–1 (x = 0) to 294.9 mA h g–1 (x = 0.30), the cyclic stability (S100) increases from 37.6% (x = 0) to 69.8% (x = 0.20) after 100 charge/discharge cycles, and the HRD1200 first increases from 69.5% (x = 0) to 85.2% (x = 0.20), then decreases to 80.8% (x = 0.30). Meanwhile, the electrochemical kinetic characteristics of the La0.8‒xCexPr0.1Nd0.1B5 alloy electrodes are also improved by increasing Ce content.

Effect of the temperature on electrode performance of the as cast La 0.7 Mg 0.3 (NiMnCo) 3.5 alloy

A series of experiments were performed to investigate the effect of the temperature on electrode performance of the as-cast La0.7Mg0.3(NiMnCo)3.5 alloy. XRD and SEM show that La0.7Mg0.3(NiMnCo)3.5 alloy has LaNi5 and La2Ni7 phase. The activation curves show that the as-cast La0.7Mg0.3(NiMnCo)3.5 alloy electrode can be activated in three times and the maximum discharge capacity is 358.74 mA h/g at 273 K. With increasing the temperature, the cyclic stability of the alloy electrode decreases obviously. And the capacity retention decreases from 96.14 to 63.53% when the temperature increases from 238 to 303 K. It also can be seen that the as-cast La0.7Mg0.3(NiMnCo)3.5 alloy electrode has the best self-discharge ability at 238 K and the best high-rate discharge ability at 273 K.

Effect of TiMn1.5 alloying on the structure, hydrogen storage properties and electrochemical properties of LaNi3.8Co1.1Mn0.1 hydrogen storage alloys

A series of experiments were performed to investigate the effect of TiMn1.5 alloying on the structure, hydrogen storage properties and electrochemical properties of LaNi3.8Co1.1Mn0.1 hydrogen storage alloys at 303 K. For simple, A, B, and C are used to represent alloys (x = 0 wt %, x = 4 wt % and x = 8 wt %) respectively. The results of XRD and SEM show that LaNi3.8Co1.1Mn0.1−xTiMn1.5 hydrogen storage alloys have LaNi5 phase and (NiCo)3Ti phase. Based on the results of PCT curves, the hydrogen storage capacities of LaNi3.8Co1.1Mn0.1−xTiMn1.5 hydrogen storage alloys are about 1.28 wt % (A), 1.16 wt % (B) and 1.01 wt % (C) at 303 K. And the released pressure platform and the pressure hysteresis decrease with the increase of TiMn1.5 content. Meanwhile the activation curves show that LaNi3.8Co1.1Mn0.1−xTiMn1.5 hydrogen storage alloy electrodes can be activated in three times and the maximum discharge capacity is 343.74 mA h/g at 303 K. In addition, with the increase of TiMn1.5 content, the cyclic stability of the hydrogen storage alloy electrodes decreases obviously and the capacity retention decreases from 76.70% to 70.00% when TiMn1.5 content increases from A to C. It also can be seen that LaNi3.8Co1.1Mn0.1−xTiMn1.5 hydrogen storage alloy electrode C and B have the best self-discharge ability and the best high-rate discharge ability from self-discharge curves and high-rate discharge curves.