Electrochemical properties of spinel compound LiNi_（0.5）Mn_（1.2）Ti_（0.3）O_4 as cathode materials for lithium ion batteries

The electrochemical properties of spinel compound LiNi0.5Mn1.2Ti0.3O4 were investigated in this study.The chemicals LiAc·2H2O,Mn(Ac)2·2H2O,Ni(Ac)2·4H2O,and Ti(OCH3)4 were used to synthesize LiNi0.5Mn1.2Ti0.3O4 by a simple sol-gel method.The discharge capacity of the sample reached 134 mAh/g at a current rate of 0.1C.The first and fifth cycle voltammogram almost overlapped,which showed that the prepared sample LiNi0.5Mn1.2Ti0.3O4 had excellent good cycle performance.There were two oxidation peaks at 4.21 V and 4.86 V,and two reduction peaks at 4.55 V and 3.88 V in the cycle voltammogram,respectively.By electrochemical impedance spectroscopy and its fitted result,the lithium ion diffusion coefficient was measured to be approximately 7.76 × 10?11 cm2/s.     

Electrochemical hydrogen storage performance of AB<Subscript>5</Subscript>-CoB composites synthesized by a simple mixing method

AB₅ (MlNi_4.0Al_0.3Cu_0.5Zn_0.2) alloy and CoB alloy were prepared by arc melting. AB₅-CoB composites were synthesized by simple mixing of AB₅ alloy powders and CoB alloy powders, and their electrochemical hydrogen storage properties were studied as negative electrodes in KOH aqueous solution. The maximum discharge capacity of the AB₅-CoB(50%) composite (the content of CoB in the composite is 50 wt.%) reached 365.3 mAh·g⁻¹. After 100 charge-discharge cycles, the discharge capacity of the AB₅-CoB(50%) composite was still much higher than that of the AB₅ alloy. The high rate discharge capability (HRD) and potentiodynamic polarization were also tested.     

Synthesis and electrochemical properties of Li<Subscript>2</Subscript>MnSiO<Subscript>4</Subscript>/C nanoparticles via polyol process

Carbon-coated lithium manganese silicate (Li₂MnSiO₄/C) nanoparticles were synthesized by polyol process. X-ray diffraction (XRD) patterns of the obtained materials exhibit a good fit with that of the Li₂MnSiO₄ phase. Field emission scanning electron microscopy (FESEM) images of the obtained samples show that the particle size is only tens of nanometers. The high resolution transmission electron microscopy (HRTEM) analysis shows that the Li₂MnSiO₄ nanoparticles are surrounded by a very thin film of amorphous carbon. The composite prepared through polyol process shows good performance as cathode materials in lithium cells at room temperature. The charge capacity of the Li₂MnSiO₄/C samples is 219 mAh/g (about 1.3 Li⁺ per unit formula extracted), and the discharge capacity is 132 mAh/g (about 0.8 Li⁺ per unit formula inserted) in the first cycle in the voltage range of 1.5–4.8 V. A good capacity cycling maintenance of 81.8% after 10 cycles was obtained.     

Effect of heat treatment of titanium substrates on the properties of IrO<Subscript>2</Subscript>-Ta<Subscript>2</Subscript>O<Subscript>5</Subscript> coated anodes

The Ti substrates of IrO 2 -Ta 2 O 5 coated anodes were treated by solid-solution and aging, stress relieving annealing, and recrystallization annealing, and the coatings were prepared by thermal decomposition of a mixture of H 2 IrCl 6·6H 2 O dissolved in hydrochloric acid and TaCl 5 dissolved in alcohol. Scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and accelerated life test (ALT) were employed to study the microstructure and electrochemical properties of the anodes. Compared with the anode without heat treatment, the anodes with heat treatment are of higher electrochemical activity and longer accelerated life; especially, the anode with recrystallization annealing treatment has the best electrochemical properties and the longest accelerated life.     

Electrochemical co-deposition of magnesium based alloy from molten salts

Magnesium based alloys with aluminum and zinc were obtained through electrochemical co-deposition from LiCl-NaCl-MgCl2 melt. The possibility of electrochemical co-deposition was discussed in detail by electro-analytical methods including cyclic voltametry, square wave voltametry, and chronopotentiometry. The co-deposition happens when the concentration of aluminum and zinc ions is kept at low value and the current density is high enough. The components of alloy elements can be controlled by fixing the components of the feeding salts. A laboratory experiment of the preparation by step-current co-deposition was also performed and certain compositions of the Mg-Al, and Mg-Zn were obtained. The alloys obtained from the co-deposition show a typical as-cast microstructure. The best conditions of electrolysis such as temperature, amount of addition and mode of feeding were discussed in detail.     

Preparation and optical properties of Y<Subscript>2</Subscript>O<Subscript>3</Subscript>/SiO<Subscript>2</Subscript> powder

Y(NO3)3 and NH3·H2O were used as a raw materials,and nano-Y2O3 powder was successfully synthesized by a precipitation method.Employing TEOS as a raw material,SiO2 powder was successfully prepared by a alkoxide-hydrolysis method,and a Y2O3/SiO2 composite powder was obtained by coating.The Y2O3,SiO2,and Y2O3/SiO2 powders were characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),and Fourier transform infrared spectrophotometer(FT-IR);the Y2O3 and Y2O3/SiO2 powders were further examined ...     

LiTFSi/KTf熔盐电解质中锂在铝电极上的电化学行为(英文)

采用循环伏安、计时电位和计时电流等电化学测试技术考察LiTFSI/KTf熔盐电解质中锂在铝电极上的电化学行为。结果表明:在该熔盐中,锂在铝电极上的电化学还原过程伴随着锂铝合金的成核过程,锂在铝电极上的嵌入过程平缓、稳定。恒电流充放电循环实验发现,首次循环的库仑效率很低,这主要归结于Li-Al合金对锂元素的持留能力。通过XRD和SEM表征了充放电前后铝电极的物相组成和表面形貌。计时电流实验发现,锂原子嵌入铝电极中形成α-Li-Al合金的过程受锂在铝基体内的扩散步骤控制,且该扩散系数为1.8×10-10cm2/s。     

Synthesis and electrochemical performance of YF<Subscript>3</Subscript>-coated LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> cathode materials for Li-ion batteries

Spinel LiMn₂O₄ cathodes were coated with 1 mol% YF₃. X-ray diffraction (XRD) analyses showed that Y and/or F did not enter the lattice of the LiMn₂O₄ crystal. Transmission electron microscopy (TEM) showed that a compact YF₃ layer of 5–20 nm in thickness was coated onto the surface of LiMn₂O₄ particles. Scanning electron microscopy (SEM) observation showed that the YF₃ coating caused the agglomeration of LiMn₂O₄ particles. The cycling test demonstrated that the YF₃ coating can improve the electrochemical performance of LiMn₂O₄ at both 20 and 55°C. Moreover, YF₃-coated LiMn₂O₄ exhibited an improved rate capability compared with the uncoated one at high rates over 5C. The immersion test in electrolytes showed that YF₃-coated LiMn₂O₄ is more erosion resistant than the uncoated one.     

Reduction behavior of cerium(Ⅲ) ions in NaCl-2CsCl melt

The cathodic process of cerium(Ⅲ) ions in NaCl-2CsCl melt was studied by cyclic voltammetry and square wave voltammetry with tungsten and gold electrodes at 873 K. The two electroanalytical methods yield similar results. The cathodic process of cerium(Ⅲ) ions consists of two reversible steps: Ce3+ + e-= Ce2+ and Ce2+ + 2e-= Ce. The half wave potentials of Ce3+/Ce2+ and Ce2+/Ce were determined as -2.525 V vs. Cl2/Cl- and -2.975 V vs. Cl2/Cl-, respectively. The diffusion coefficient of Ce3+ was also determined as 5.5 × 10-5 cm2·s-1.     

Electrochemical mechanism of electrolysis codeposition of Mg-Sr alloy in molten salt

The electrochemical process of Mg-Sr codeposition was studied in MgCl₂-SrCl₂-KCl melts containing different MgCl₂ concentrations at 700 °C by cyclic voltammetry, chronopotentiometry and chronoamperometry. The results show that the actual precipitation potential of Sr reduces by nearly 0.5 V because of the depolarization effects of Sr activity reduced by forming Mg-Sr alloy. The codeposition potential condition of Mg and Sr to form Mg-Sr alloy is as follows: When electrode potential is more negative than ?1.5 V, the magnesium will precipitate; when electrode potential is more negative than ?2.0 V, the magnesium and strontium will both deposit. The control step of codeposition process of Mg and Sr is not diffusion control step. The codeposition current condition of Mg and Sr to form Mg-Sr alloy by chronoptentiometry is as follows: cathode current densities are higher than 0.71, 1.57 and 2.83 A/cm² in MgCl₂-SrCl₂-KCl melts with MgCl₂ concentrations of 2%, 5% and 10% (mass fraction), respectively.     

Preparation of zirconium by electro-deoxidization in molten salt

Metal zirconium was prepared by electro-deoxidization method. Using CaCl2 molten salt as electrolyte, sintered ZrO2 pallets as cathode, graphite rod as anode, the pallets were electrolyzed at 900 ℃ and 3.1 V for 8, 10 and 12 h, respectively. The mechanism of electro-deoxidization of ZrO2 was studied preliminarily. The results show that the morphologies of cathode pallets affect the forming process of products. The process of electro-deoxidization ofZrO2 in the molten salt is conducted step by step, from exterior of cathode to its interior and from high valence oxide to low valence oxide until to metal.     

LiF-NaF-KF-K2 TiF6-KBF4熔体中电沉积TiB2的阴极过程

采用循环伏安法研究了700℃时46.5LiF-11.5NaF-42KF(摩尔分数,%)熔盐中Ti(Ⅳ)(c(K2TiF6)=0.2 mol/L)和B(Ⅲ)(c(KBF4)=0.4 mol/L)在铂电极上的电化学还原机理,计算了各还原步骤传递的电子数。研究了LiF-NaF-KF-K2TiF6-KBF4(c(K2TiF4)=0.3 mol/L,c(KBF4)=0.3,0.6,0.9 mol/L)熔盐中电化学合成TiB2的阴极过程机理。结果表明:Ti(Ⅳ)的电化学还原为三步电荷传递反应,且阴极过程近似可逆;B(Ⅲ)在铂电极上的电化学反应机理为简单的三电子一步反应,阴极过程近似可逆;Ti(Ⅳ)和B(Ⅲ)可在同一电位下发生共沉积并反应生成TiB2。     

Preparation,characterization and electrochemical properties of mesoporous LiFe<Subscript>0.99</Subscript>Mo<Subscript>0.01</Subscript>PO<Subscript>4</Subscript>/C

A mesoporous LiFe_0.99Mo_0.01PO₄/C composite was synthesized by the sol-gel method using (NH₄)₂MoO₄ as a doping starting material. The formation of conductive carbon, metal doping and mesopores was achieved simultaneously in the prepared material. The characterizations of crystal structures and microstructures were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), extended X-ray-absorption fine-structure (EXAFS) and X-ray-absorption near-structure spectroscopy (XANES), while the surface area was determined using N₂ adsorption techniques. Cyclic voltammetry (CV) and charge-discharge cycling performance were used to characterize its electrochemical properties. The sample possessed uniformly distributed mesopores with an average pore size of 4 nm, and the specific surface area was about 69.368 m²/g. The results show that the reversible capacity of mesoporous LiFe_0.99Mo_0.01PO₄/C is about 160 mAh/g at 0.1C, 135 mAh/g at 1C and 90 mAh/g at 5C, respectively. The capacity fading is neglectable.     

Electrochemical behavior of zirconium in the LiCl-KCl molten salt at Mo electrode

The electroreduction process of Zr(IV) was studied at molybdenum electrode in LiCl-KCl-K₂ZrF₆ molten salt. The transient electrochemical techniques, such as cyclic voltammetry and chronopotenimetry were used. The experimental results showed that the electrochemical reduction of Zr(II)/Zr and Zr(IV)/Zr(II) were both diffusion-controlled process. In the 773-973 K range, the diffusion coefficients of Zr(ii) and Zr(IV) were determined: D_Zr(II) = 0.15567exp{−69.65 × 10³RT(K)} cm²/s, D_Zr(IV) = 1.09 × 10⁻⁴ exp{−44.39 × 10³RT(K)} cm²/s. The activation energy values for the diffusion process were 69.65 kJ/mol and 44.39 kJ/mol, respectively.     

Improving the electrochemical performance of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>/graphite batteries using LiF additive during fabrication

LiMn2O4/graphite batteries using LiF additive were fabricated and their electrochemical performance including discharge,cycling and storage performances were tested and compared with LiF-free LiMn2O4/graphite batteries.The LiMn2O4/graphite battery with LiF added shows better capacity (107.5 mAh/g),cycling performance (capacity retention ratio of 93% after 100 cycles),and capacity recovery ratio (98.1%) than the LiF-free battery.The improvement in electrochemical performance of the LiF-added LiMn2O4/graphite...     

Electrochemical behavior of nickel in HNO<Subscript>3</Subscript> and the effect of chloride ions

The electrochemical behavior of nickel in HNO₃ solutions of varying concentrations was examined using the cyclic voltammetry and potentiodynamic anodic polarization techniques. The anodic branch of the cyclic voltammogram is characterized by one anodic dissolution peak and a passivation region before oxygen evolution. The cathodic branch shows only one cathodic reduction peak corresponding to the reduction of HNO₃. Analysis of the anodic polarization data shows features of both reversible and irreversible reactions pointing to the complexity of the system. CT⁻ ions enhance the active dissolution of nickel in HNO₃ due to the adsorption on the bare metal surface and cause destruction of the passive film and initiation of pitting corrosion.     

Sol-gel preparation and characterization of Li1.3Al0.3Ti1.7（PO4）3 sintered with flux of LiBO2

Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellets sintered with different mole fractions of LiBO₂ were prepared by sol-gel method. The structural identification, surface morphology, ionic conductivity, and activation energy of the pellets were studied by X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopy. The results show that all the Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellets sintered with different mole fractions of LiBO₂ have similar X-ray diffraction patterns. The sintered pellet becomes denser and the boundary and corner of the particles become illegible with the increase of LiBO₂. Among the Li_1.3Al_0.3Ti_1.7(PO₃)₄ pellets sintered with different mole fractions of LiBO₂, the one sintered with 1 mol% LiBO₂ shows the highest ionic conductivity of 3.95×10⁻⁴ S.cm⁻¹ and the lowest activation energy of 0.2469 eV.     

Influence of CaF2 on the structure and dielectric properties of Ag（Nb0.8Ta0.2）O3 ceramics

Ag(Nb0.8Ta0.2)O3 ceramics were prepared by the traditional solid-state reaction method. The effect of CaF2 addition on the structure and di-electric properties of Ag(Nb0.8Ta0.2)O3 ceramics was investigated. The addition of CaF2 led the ceramics to a larger grain size and distortion of lattice. With the addition of 4.5 wt.% CaF2, the permittivity of the ceramics increased from 442 to 1028, the dielectric loss decreased sharply from 6.12 × 10-3 to 8.6 × 10-4, and the temperature coefficient of capacitance decreased from 1834 ppm/°C to-50 ppm/°C (at 1 MHz). These results indicated that the high permittivity was related with a large grain size, a low grain boundary density, and the weak Ta-O or Nb-O bond strength caused by the addition of CaF2.     

LiF-NaF-KF-K_2TiF_6熔盐中Ti(IV)的电化学还原及电结晶过程

采用循环伏安法和计时电流法研究了700℃时LiF-NaF-KF-K2TiF6熔盐中Ti(IV)在铂电极上阴极电化学还原机理以及电结晶过程。结果表明:Ti(IV)的电化学还原机理为三步骤电荷传递反应:Ti(IV)+e→Ti(III);Ti(III)+2e→Ti(I);Ti(I)+e→Ti(0),且阴极过程可逆;电结晶过程为瞬时形核。     

内蒙古发现大型富钛矿床

采用循环伏安法和计时电流法研究了700℃时LiF-NaF-KF-K2TiF6熔盐中Ti（Ⅳ）在铂电极上阴极电化学还原机理以及电结晶过程。结果表明：Ti（Ⅳ）的电化学还原机理为三步骤电荷传递反应：Ti（Ⅳ）＋e→Ti（Ⅲ）；Ti（Ⅲ）＋2e→Ti（Ⅰ）；Ti（Ⅰ）＋e→Ti（0），且阴极过程可逆：电结晶过程为瞬时形核。