Effects of thermal annealing on the Li(+) intercalation properties of V(2)O(5) x nH(2)O xerogel films

V(2)O(5) x nH(2)O xerogel films with n = 1.6, 0.6, and 0.3 have been prepared from the sol-gel route by reacting V(2)O(5) with H(2)O(2) followed by drying under ambient conditions and thermal annealing at 110 and 250 degrees C, respectively. After dehydration, V(2)O(5) crystallizes at 300-330 degrees C, as revealed by thermal gravimetric analysis and X-ray diffraction. Electrochemical characterization demonstrated that V(2)O(5) x 0.3H(2)O film exhibits the best Li(+) intercalation performance, with an initial capacity of 275 mAh/g and a stabilized capacity of 185 mAh/g under a high current density of 100 microA/cm(2) after 50 cycles. Under a low current density of 10 microA/cm(2), the capacity of this film can reach 390 mAh/g. Such an enhanced electrochemical property by thermal treatment is ascribed to the reduced water content, the retained interlayer spacing, and the dominant amorphous phase in the film.     

钒酸盐化合物NaV_2O_5的水热合成及电化学性质

应用水热合成法制备NaV2O5晶体,XRD、SEM、拉曼光谱和XPS分析测试及电化学表明,该材料属正交晶系,空间群为Pmmn,呈纯相的棒状结构,长度约有20μm,宽度大约200 nm.该材料的V离子均价为+4.5价.首次放电容量达到120 mAh/g,放电平台为2.0 V.经过20个循环,容量保持率98 mAh/g,表现了良好的循环性能.     

脉冲激光沉积非晶态Ni-V2O5 复合薄膜及其电化学性能研究

首次报道了用355 nm脉冲激光沉积非晶态Ni-V2O5复合薄膜电极的电化学性能.采用不同摩尔比的NixV2O5 靶(x=0.1,0.3,0.5),在不同的基片温度(Ts)和O2气压力下制备了Ni-V2O5复合薄膜.XRD 和SEM测定表明, 在不锈钢基片上, Ts=300℃和氧气压力为14 Pa沉积0.5 h得到的是非晶态的Ni-V2O5薄膜.将此非晶态的Ni0.3V2O5薄膜电极用于锂电池的正极,与纯V2O5薄膜相比,不仅具有良好的放电速率性能和高的比容量,而且其充放电循环稳定性优异.该薄膜电极在放电速率为20 C时测得的比容量达200 mAh/g,并经1000次以上的充放电循环无明显的衰减.     

Enhanced electrochemical performance of submicron LiCoO<Subscript>2</Subscript> synthesized by polymer pyrolysis method

Submicron LiCoO₂ was synthesized by a polymer pyrolysis method using LiOH and Co(NO₃)₂ as the precursor compounds. Experimental results demonstrated that the powders calcined at 800 °C for 12 h appear as well-crystallized, uniform submicron particles with diameter of about 200 nm. As a result, the as-prepared LiCoO₂ electrode displayed excellent electrochemical properties, with an initial discharge capacity of 145.5 mAh/g and capacity retention of 86.1% after 50 cycles when cycled at 50 mA/g between 3.5 and 4.25 V. When cycled between 3.5 and 4.5 V, the discharge capacity increased to 177.9 mAh/g with capacity retention of 85.6% after 50 cycles.     

Ni-V2O5.nH2O core-shell nanocable arrays for enhanced electrochemical intercalation

We have prepared Ni-V(2)O(5).nH(2)O core-shell nanocable arrays for Li(+) intercalation applications. Ni-V(2)O(5).nH(2)O nanocables were prepared via formation of Ni nanorod arrays through the template based electrochemical deposition, followed by coating of V(2)O(5).nH(2)O on Ni nanorods through electrophoretic deposition. Transmission electron microscopy (TEM) micrograph clearly shows the Ni core was covered completely by a V(2)O(5).nH(2)O shell. Electrochemical analysis demonstrates that in a current density of 1.6 A/g, the Li(+) intercalation capacity of Ni-V(2)O(5).nH(2)O nanocable array is approximately 10 times higher than that of single-crystal V(2)O(5) nanorod array and 20 times higher than that of sol-gel-derived V(2)O(5) film. Both energy density and power density of such nanocable-array electrodes are higher than the V(2)O(5) film electrode by at least 1 order of magnitude. Such significant improvement in electrochemical performance is due to the large surface area and short diffusion path offered by the nanostructured V(2)O(5).nH(2)O.     

锂钛复合氧化物锂离子电池负极材料的研究

采用 3种化学方法合成锂钛复合氧化物 .应用X -射线衍射分析对其结构进行表征以及电化学性能测试 ,结果表明 :由Li2 CO3、TiO2 高温合成的锂钛复合氧化物为尖晶石结构的Li4Ti5 O12 .Li4Ti5 O12 电极在 1 .5V左右有一放电平台 ,充放电可逆性良好 ,即充电电压平台与此接近 ,且电极的比容量较大 ,循环性能良好 .以 0 .30mA·cm- 2 充放电时 ,首次放电容量可达 30 0mAh·g- 1,可逆比容量为 1 0 0mAh·g- 1,经多次充放电循环后 ,其结构仍保持稳定性 .试验电池测试表明 ,Li4Ti5 O12 可选作Li4Ti5 O12 /LiCoO2 锂离子电池的负极材料 .     

二氧化钛纳米管的制备与光催化活性

用阳极氧化法,室温条件下在含NH4F和H2O的电解液(丙三醇+NH4F+H2O;乙二醇+NH4F+H2O)中制备了TiO2纳米管阵列。用环境扫描电子显微镜(SEM)、X射线衍射仪(XRD)表征二氧化钛纳米管阵列的微观形貌和物相结构。在丙三醇电解液中,电压为60 V,65 V,70 V,75 V制备的纳米管直径依次为160、170、190、220 nm。对甲基橙(10 mg/L)降解测试TiO2纳米管阵列的光催化性能。研究结果表明:在100 V阳极电压制备经过500℃退火处理后的TiO2纳米管阵列的光催化效果最好,其光催化降解率在光照时间120 min时达到89.2%。     

Free-standing vanadium pentoxide nanoribbon film as a high-performance cathode for rechargeable sodium batteries

Vanadium pentoxide(V_2O_5·nH_2O) nanoribbons are synthesized via a hydrothermal process. These ribbons are 20 nm thick, 200 nm to 1 μm wide and several tens of micrometers long. Free-standing binder-free films are prepared by using these nanoribbons with multi-walled carbon nanotubes(MWCNTs) and used as the cathode for rechargeable sodium batteries. The large interlayer space between the V_2O_5 bilayers can enhance the kinetics of sodium ion intercalation/deintercalation. In addition, the intertwining network of the V_2O_5·0.34 H_2O film provides efficient electron conduction pathways and shortens diffusion distances of sodium ion. The electrochemical tests prove that the freestanding V_2O_5 · 0.34 H_2O film cathode delivers high reversible specific capacities(190 mAh/g) and good cycling stabilities(170 mAh/g after 150 cycles) in the voltage range between 1.5 V and 3.5 V.     

花状NH4V4O10微纳米结构的水热制备及电化学嵌锂性能

通过水热法制备了花状NH4V4O10微纳米结构. 采用XRD,SEM,TEM,XPS等测试手段对样品结构、形貌和组成进行了表征. 实验结果表明,所制得的NH4V4O10花状结构是由直径约100 nm,长度为几微米的纳米带团簇而形成. 研究了反应体系中温度、时间等因素对NH4V4O10产物形貌的影响. 将制备的NH4V4O10组装成锂模拟扣式电池,考察了其电化学嵌锂性能. 研究结果显示,所制备的花状NH4V4O10具有较高的比容量（307 mAh?g-1）,有望作为锂离子电池的新型正极材料.     

纳米TiO_2的电化学嵌锂研究

应用苛性钠水热法制备粒度均匀、分散性好、质子钛酸盐纳米管(直径约10～15nm).经加热烧结脱水后,该纳米管逐渐转变成具有锐钛矿相结构的纳米柱(直径约15～20nm).初步研究表明,这种具有锐钛矿相结构的纳米柱,其电化学可逆嵌/脱锂容量较高,但循环稳定性还有待改进提高.     

Ag4V2O6F2 (SVOF): a high silver density phase and potential new cathode material for implantable cardioverter defibrillators

The electrochemical reactivity of the cathode material Ag 4V 2O 6F 2 (SVOF) versus lithium, with a particular emphasis on the lithium insertion mechanism, was studied by means of the complementary techniques in situ X-ray diffraction, electron paramagnetic resonance, and high-resolution transmisssion electron microscopy. This study confirms the initial reports of a high capacity for SVOF of 148 mAh/g above 3 V and that the reduction of silver above 3 V (vs Li (+)/Li (0)) leads to a loss of SVOF crystallinity until it becomes completely amorphous between the third and fourth lithiums inserted. Next, vanadium is reduced between 2.5 and 1.5 V (vs Li (+)/Li (0)) for the fifth and sixth lithiums inserted. In addition, the polarization within the cathode is significantly lower for the vanadium reduction than for the silver reduction. The silver metal morphologies consisted of nanoparticles ( approximately 5 nm diameter) and dendrites and were both seen in samples of lithiated SVOF.     

Synthesis and characterization of sodium vanadium oxide gels: the effects of water (n) and sodium (x) content on the electrochemistry of Na(x)V2O5·nH2O

Sodium vanadium oxide gels, Na(x)V(2)O(5)·nH(2)O, of varying sodium content (0.12 < x < 0.32) were prepared by careful control of an ion exchange process. The water content (0.23 > n > 0.01) and interlayer spacing were found to be inversely proportional to the sodium level (x), thus control of sodium (x) content provided a direct, chimie douce approach for control of hydration level (n) and interlayer spacing, without the need for high temperature treatment to affect dehydration. Notably, the use of high temperatures to modify hydration levels can result in crystallization and collapse of the interlayer structure, highlighting the distinct advantage of our novel chimie douce synthesis strategy. Subsequent to synthesis and characterization, results from an electrochemical study of a series of Na(x)V(2)O(5)·nH(2)O samples highlight the significant impact of interlayer water on delivered capacity of the layered materials. Specifically, the sodium vanadium oxide gels with higher sodium content and lower water content provided higher capacities in lithium based cells, where capacity delivered to 2.0 V under C/20 discharge ranged from 170 mAh/g for Na(0.12)V(2)O(5)·0.23H(2)O to 300 mAh/g for Na(0.32)V(2)O(5)·0.01H(2)O. The capacity differences were maintained as the cells were cycled.     

锂离子电池正极材料Li[Li_(0.167)Mn_(0.583)Ni_(0.25)]O_2的合成与性能研究

应用低热固相法制备镍锰复合正极材料Li[Li0.167Mn0.583Ni0.25]O2.XRD、FESEM和恒电流充放电测试表明,该材料结晶良好,可标定为α-NaFeO2型结构(空间群R3-m),颗粒粒径约为60~100 nm,粒度均匀细小.在2.5~4.4 V之间以0.5 C(100 mA/g)做充放电循环时,可逆比容量在120 mAh/g以上,循环性能非常稳定.如将截止电压升高到4.6 V,则比容量大大提高,最高可达234 mAh/g.上述充放电测试都出现了比容量随循环次数上升的现象.主要原因可归结为材料中Mn(Ⅳ)向Mn(Ⅲ)的转变,但在不同的电压范围内导致该转变的起因并不相同.     

The rechargeable aluminum-ion battery

We report a novel aluminium-ion rechargeable battery comprised of an electrolyte containing AlCl(3) in the ionic liquid, 1-ethyl-3-methylimidazolium chloride, and a V(2)O(5) nano-wire cathode against an aluminium metal anode. The battery delivered a discharge capacity of 305 mAh g(-1) in the first cycle and 273 mAh g(-1) after 20 cycles, with very stable electrochemical behaviour.     

喷墨打印制备LiMn2O4薄膜电极及其电化学性能

通过溶胶-凝胶法制备了尖晶石LiMn2O4. 用分散剂Lormar D, 经超声分散制得了含LiMn2O4粒子的打印“墨水”, 并使用计算机喷墨打印的方法制得LiMn2O4薄膜电极. 薄膜电极的厚度约为1.8 μm. 用XRD、TG-DTA、SEM、循环伏安、电化学阻抗谱和充放电等方法对材料和电极的性能进行了表征. 结果表明, 在较大电流100 μA·cm-2 (2C)的充放电情况下, 电极能保持好的稳定性,其首次放电容量为109 mAh·g-1, 充放电54次后, 其容量仍可保持97.4%, 为105 mAh·g-1, 这可归因于薄膜电极中尖晶石LiMn2O4的晶型完整, LiMn2O4粒子小以及稳定的超薄电极结构.     

Electrochemical insertion of magnesium ions into V2O5 from aprotic electrolytes with varied water content

The electrochemical performance of V2O5 has been studied in propylene carbonate (PC)-containing magnesium perchlorate [Mg(ClO4)2] electrolytes in view of their application as positive electrode in the rechargeable magnesium batteries. V2O5 exhibited good properties in hosting magnesium ions and its electrochemical performance depended on the amount of H2O in the electrolytes. The highest first discharge specific capacities of V2O5 electrode was up to 158.6 mAh/g in 1 mol dm(-3) Mg(ClO4)2 + 1.79 mol dm(-3) H2O/PC electrolytes. Electrochemical impedance spectroscopy (EIS) and charging-discharging tests showed that a reasonable amount of H2O in the electrolyte solution facilitated the electrochemical performance of V2O5 electrodes.     

锂离子电池正极材料xLi2MnO3·(1-x)Li[Ni1/3Mn1/3Co1/3]O2的制备及表征

以过渡金属乙酸盐和乙酸锂为原料,柠檬酸为螯合剂,通过溶胶-凝胶法结合高温煅烧法制备了锂离子电池富锂锰基正极材料xLi2MnO3·(1-x)Li[Ni1/3Mn1/3Co1/3]O2,采用X射线衍射(XRD),扫描电子显微镜(SEM)和电化学性能测试对所得样品的结构,形貌及电化学性能进行了表征.结果表明:x=0.5时,在900°C下煅烧12h得到颗粒均匀细小的层状xLi2MnO3·(1-x)Li[Ni1/3Mn1/3Co1/3]O2材料,并具有良好的电化学性能,在室温下以20mA·g-1的电流密度充放电,2.0-4.8V电位范围内首次放电比容量高达260.0mAh·g-1,循环40次后放电比容量为244.7mAh·g-1,容量保持率为94.12%.     

Alpha-CuV2O6 nanowires: hydrothermal synthesis and primary lithium battery application

We report on the synthesis, characterization, and electrochemical lithium intercalation of alpha-CuV2O6 nanowires, mesowires, and microrods that were prepared through a facile hydrothermal route. The diameters of the as-synthesized alpha-CuV2O6 nanowires, mesowires, and microrods were about 100 nm, 400 nm, and 1 microm, respectively. It was found that by simply controlling the hydrothermal reaction parameters, such as the reagent concentration and the dwell time, the transformation of microrods to nanowires was readily achieved via a "ripening-splitting" mechanism. Electrochemical measurements revealed that the as-prepared alpha-CuV2O6 nanowires and mesowires displayed high discharge capacities (447-514 mAh/g at 20 mA/g and 37 degrees C) and excellent high-rate capability. In particular, the alpha-CuV2O6 nanowires showed capacities much higher than those of alpha-CuV2O6 mesowires, microrods, and bulk particles. The mechanisms for the electrochemical lithium intercalation into the alpha-CuV2O6 nanowires were also discussed. From the Arrhenius plot of lithium intercalation into alpha-CuV2O6 nanowires, the activation energies were calculated to be 39.3 kJ/mol at 2.8 V (low lithium uptake) and 35.7 kJ/mol at 2.3 V (high lithium uptake). This result indicates that the alpha-CuV2O6 nanowires are promising cathode candidates for primary lithium batteries used in long-term implantable cardioverter defibrillators (ICD).     

Freestanding Carbon Nanotube Film for Flexible Straplike Lithium/Sulfur Batteries

Flexible lithium/sulfur (Li/S) batteries are promising to meet the emerging power demand for flexible electronic devices. The key challenge for a flexible Li/S battery is to design a cathode with excellent electrochemical performance and mechanical flexibility. In this work, a flexible strap-like Li/S battery based on a S@carbon nanotube/Pt@carbon nanotube hybrid film cathode was designed. It delivers a specific capacity of 1145 mAh g⁻¹ at the first cycle and retains a specific capacity of 822 mAh g⁻¹ after 100 cycles. Moreover, the flexible Li/S battery retains stabile specific capacity and Coulombic efficiency even under severe bending conditions. As a demonstration of practical applications, an LED array is shown stably powered by the flexible Li/S battery under flattened and bent states. We also use the strap-like flexible Li/S battery as a real strap for a watch, which at the same time provides a reliable power supply to the watch.     

Synthesis and electrochemical performance of nanoporous Li4Ti5O12 anode material for lithium-ion batteries

Nanoporous Li₄Ti₅O₁₂ (N-LTO) was prepared by sol–gel method using monodisperse polystyrene spheres as a template and followed by calcination process. The as-prepared N-LTO has a spinel structure, large special surface area, and nanoporous structure with the pore average diameter of about 100?nm and wall thickness of 50?nm. Electrochemical experiments show that N-LTO exhibits a high initial discharge capacity of 189?mAh?g^?1 at 0.1?C rate cycled between 0.5 and 3.0?V and excellent capacity retention of 170?mAh?g^?1 after 100?cycles. EIS and CV analysis show that N-LTO has a higher mobility for Li⁺ diffusion and a higher exchange current density, indicating an improved electrochemical performance. It is believed that the nanoporous structure has a larger electrode/electrolyte contact area, resulting in better electrochemical properties at high charge/discharge rates.