过渡金属二硼化物作为高容量负极的研究

碱性溶液中,VB2和TiB2分别发生了 11电子和 6电子氧化反应,释放出 3 100mAh/g和 1 600mAh/g的超常电化学容量.对此,初步的解释是:在二硼化物中过渡金属与硼的电子转移使硼元素电负性增强,引起硼的电化学活化.使得合金的电极电势钳制在较负区域,导致某些过渡金属元素处于活化态,进而发生电化学氧化释放出电化学能量.     

中性水溶液高容量TiB_2负极的电氧化反应

本文报道了TiB2作为阳极材料在中性水溶液中的电化学行为.结果表明TiB2在KF水溶液中释放出超高电化学容量:在电流密度为50 mA/g时,容量可以达到1300 mAh/g,超过目前报道的所有金属电极的容量.在放电过程中,二硼化钛中的硼发生电化学氧化反应生成硼氟酸根,而其中的钛则形成金属单质.因此二硼化钛可以作为一种阳极材料构建高比容量中性化学电源体系.     

高铁酸钾电化学性能研究

主要研究正极材料高铁酸钾的合成以及用它作为正极活性物质在一次性碱性电池中 ,于不同浓度电解质溶液和不同放电电流下的放电性能 .发现其在 9mol/L- 1KOH溶液中放电容量最高 ,并表现出良好的放电平台特性 .0 .4C时 ,放电容量可达 5 2 1 .3mAh/ g .XRD分析表明 ,放电后产物为Fe3O4 ,由此提出相关可能的放电反应机理     

有序介孔磷酸钛锂离子电池正极材料制备及电化学性能

选用合适模板剂由溶胶凝胶法合成高度有序介孔结构的磷酸钛正极材料.研究煅烧温度对材料孔结构及材料的电化学性能的影响,合成样品的结构形貌和比表面分别用XRD、BET、TEM及元素分析仪表征.充放电测试结果表明,该介孔结构正极材料表现出优越的电化学性能,以150 mA/g充放电,首次放电容量高达94 mAh/g,而不含模板剂无孔结构的材料放电容量仅37 mAh/g.     

LiNi_(0.8)Co_(0.2)O_2的络合法合成及其电化学性能研究

采用络合法制备了锂离子电池的活性正极材料LiNi0.8Co0.2O2粉体,该合成材料结晶良好,层状结构发育完善.电池充放电测试表明,作为锂离子电池正极,其电化学性能与LiNi0.8Co0.2O2粉体的合成温度有关,其中以900℃下合成得到的材料性能最优:第1次放电比容量高达142mAh/g,循环30次后可逆比容量仍高达122mAh/g,容量损失为14.5%.文中对容量退化的原因进行了分析.     

B对Sn-Co合金结构及电化学性能的影响

采用固相法合成了Sn-Co/B复合材料, 考察了B对材料的结构和电化学性能的影响. XRD分析结果表明, Sn-Co合金由CoSn相组成, 添加B能使晶粒细化并且形成CoSn2. 恒流充放电测试表明, B的添加提高了Sn-Co合金的循环性能, 但使放电容量略有降低. 当B质量分数为4%时, Sn-Co/B复合物的首次放电容量为216 mA·h/g, 经过30次循环后容量保持率达82.9%, 表现出良好的结构稳定性.     

锂硫二次电池硫-碳纳米管正极的合成和性能

由单质硫与碳纳米管合成一种新型含碳复合材料.XRD、SEM、BET比表面和孔径分布表征观察硫-碳纳米管复合材料,循环伏安法和电池充放电测试材料的电化学性能.结果表明:以硫-碳纳米管作正极组装的2016型扣式电池有较好的电化学性能,其初始放电比容量达680mAh/g(室温),30次循环放电比容量仍稳定在500mAh/g.     

贮氢电极合金ZrCr_(0.4)Mn_(0.2)V_(0.1)Co_(0.1)Ni_(1.2)高温电化学性能的研究

研究了AB2型Laves相贮氢电极合金ZrCr0.4Mn0.2V0.1Co0.1Ni1.2在不同温度下的放电容量、活化、高倍率和自放电等电化学性能.实验表明:25℃下,合金电极经13次循环后其最大放电容量为336mAh/g,在70℃下,仅需4次循环就达到298mAh/g;该合金在70℃,300mA/g电流下的高倍率放电性能比25℃时提高了约16%,但自放电性能却从3%/d下降到17%/d,虽然温度升高,合金的循环性能有所下降,但还是相当稳定的.这主要是因为循环过程中合金表面形成的氧化膜阻碍了合金元素进一步溶解造成的.     

无镨钕AB5型Mm（Ni,Co,Mn,Al）5合金储氢及电化学性能研究

镍氢电池是目前国内外混合动力汽车的首选电池,但随着稀土价格的不断上涨,稀土元素占其成本的比例约由14%逐步提升到55%,开发无镨、钕的高丰度镧铈稀土元素AB5型储氢材料,有助降低混合动力车用镍氢电池负极材料的成本。采用中频感应熔炼配合快淬甩带工艺制备了LaxCe1-x(NiCoMnAl)5(x=0.8,0.6,0.4)合金,并研究了合金A,B侧各元素的比例以及制备工艺对合金储氢性能及电化学性能的影响。结果表明,随着x的降低,合金的储氢量和放电容量逐渐降低。当x=0.6时,合金电极具有较好的综合电化学性能,最大放电容量达到332.81 mAh.g-1,充放电循环寿命达(715 mA.g-1,80%容量保持率,下同)215次。对该合金B侧Mn,Al含量进行优化后,原材料中的Co含量减少,合金的最高电化学容量可达319.01 mAh.g-1。合金在氩气氛保护下进行退火处理后,结晶度和均匀性上升,电化学容量有所降低,但循环稳定性得到明显改善。其中,经950℃/2 h退火处理的LaxCe1-x(NiCoMnAl)5(x=0.8)合金的最大放电容量达328.07 mAh.g-1,充放电循环寿命达364次。     

类凝胶法制备锂离子二次电池正极材料镍钴酸锂

以LiOH.H2O,Ni(NO3)2,6H2O,Co(NO3)2.6H2O,NH3.H2O为原料,在不同条件下以类凝胶法制备层状化合物LiNixCo1-xO2,并以此作正极材料进行电化学测试,结果表明,首次充电比容量达192mAh/g,首次放电比容量达140mAh/g,循环22次后其放电比容量保持在119mAh/g。     

Drastically enhanced cycle life of Co-B alloy electrode by 8-hydroxyquinoline at elevated temperature

The effect 8-hydroxyquinoline (8-HQ) additive in electrolyte on the cyclic stability of Co-B alloy electrode was investigated at elevated temperature (55 °C). Charge–discharge measurements show that 8-HQ can drastically enhance the cycle life of Co-B alloy electrode. Specifically, in the electrolyte containing 0.028 M 8-HQ additive, the discharge capacity of Co-B alloy electrode after 100 cycles are still up to 385.8 mAh/g at 55 °C. However, for the electrode in 8-HQ-free electrolyte, its discharge capacity is sharply decreased to only 138.5 mAh/g after 100 cycles. ICP-OES, XRD and ATR/FT-IR measurements were used to clarify the reason of the improvement in the cyclic stability. These results show that beneficial effect of 8-HQ on cycle life of Co-B alloy electrode can be attributed to the formation of insoluble complex (8-HQ)₂Co(II)·2H₂O protective layer that can suppress the dissolution of Co(OH)₂ into electrolyte at elevated temperature.     

Chemical preparation and investigation of Fe-P-B ultrafine amorphous alloy particles

A series of Fe-P-B ultrafine amorphous alloy particles has been prepared by the chemical reduction method The composition and size of the particles have been effectively adjusted.Mossbauer spectroscopy in addition to sonic other techniques has been used to investigate the reaction process,the factors that influence the preparation,the crystallization of the particles,and the interactions between the components within them.The results indicate that the co-deposition of iron,phosphorus and boron atoms in the solution at room temperature forms Fe-P-B amorphous alloy particles,and a preferential bonding of Fe-P bond to Fe-B one exists in the particles.     

Li-ion charge storage performance of wood-derived carbon fibers@MnO as a battery anode

Wood-derived carbons have been demonstrated to have large specific capacities as the anode materials of lithium-ion batteries(LIBs). However, these carbons generally show low tap density and minor volumetric capacity because of high specific surface area and pore volume. Combination with metal oxide is one of the expected methods to alleviate the obstacles of wood-derived carbons. In this work, the composites of Mn O loaded wood-derived carbon fibers(CF@Mn O) were prepared via a simple and envir...     

A mesoporous non-precious metal boride system: synthesis of mesoporous cobalt boride by strictly controlled chemical reduction

Generating high surface area mesoporous transition metal boride is interesting because the incorporation of boron atoms generates lattice distortions that lead to the formation of amorphous metal boride with unique properties in catalysis. Here we report the first synthesis of mesoporous cobalt boron amorphous alloy colloidal particles using a soft template-directed assembly approach. Dual reducing agents are used to precisely control the chemical reduction process of mesoporous cobalt boron nanospheres. The Earth-abundance of cobalt boride combined with the high surface area and mesoporous nanoarchitecture enables solar-energy efficient photothermal conversion of CO₂ into CO compared to non-porous cobalt boron alloys and commercial cobalt catalysts.

Generating high surface area mesoporous transition metal boride is challenging but interesting because incorporation of boron atoms can generate lattice distortion to form amorphous metal boride which has unique properties in catalysis.     

Ni3S2@碳纳米管复合材料的制备及其储钠性能

采用一步固相煅烧工艺制备了碳纳米管原位封装Ni₃S₂纳米颗粒（Ni₃S₂@CNT）,并研究了其作为钠离子电池（SIBs）负极材料的电化学性能. 通过X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、循环伏安测试、恒流充放电以及交流阻抗等研究了Ni₃S₂@CNT的物相结构、形貌特征以及电化学性能. 电化学测试表明,材料在100 mA·g ^-1电流密度下,放电容量可以达到541.6 mAh·g ^-1,甚至在2000 mA·g ^-1的大电流密度下其放电比容量也可以维持在274.5 mAh·g ^-1. 另外,材料在100 mA·g ^-1电流密度下,经过120周充放电循环后其放电和充电比容量仍然可以保持在374.5 mAh·g ^-1和359.3 mAh·g ^-1,说明其具有良好倍率性能和循环稳定性能. 良好的电化学性能归因于这种独特的碳纳米管原位封装Ni₃S₂纳米颗粒结构. 碳纳米管不但可以提高复合材料的导电性,也可以缓冲Ni₃S₂纳米颗粒在反复充放电过程中产生的体积膨胀效应,明显改善了Ni₃S₂@CNT负极复合材料的电化学性能.     

Peculiarities of the Transition to an Equilibrium State of Mechanically Alloyed Fe/Amorphous Phase Fe-B/B Nanocomposite with Composition Fe(68)B(32) upon Thermal Treatment

The methods of X-ray diffraction, Mossbauer spectroscopy, and magnetic measurements are employed to study the structural and phase transformations in the course of isochronous (1 h) annealing at 300–900°C and isothermal (350°C) annealing of a mechanically alloyed Fe/amorphous phase Fe-B/B_s nanocomposite with a total boron content of 32 at %. Common and specific regularities are established for the sequence of solid-phase reactions as compared to amorphous Fe-B alloys prepared by melt quenching. The observed differences are explained by a high thermal stability of the nanostructure in the mechanically alloyed Fe-B system due to the presence of boron atoms B_s segregated at the intergrain boundaries.     

A Ti-V-based bcc phase alloy for use as metal hydride electrode with high discharge capacity

The electrochemical characteristics of single bcc phase Ti-30V-15Cr-15Mn alloy were investigated. It was demonstrated that the single bcc phase alloy has high electrochemical discharge performance at high temperature. Its discharge capacity is closely related with temperature and discharge current. The first discharge capacities of 580-814 mAh g(-1) of the alloy powder were obtained at discharge current of 45-10 mA g(-1) in 6 M KOH solution at 353 K. Although the electrochemical cycle life of the alloy is unsatisfactory at present, it opens up prospects for developing a new hydrogen storage alloy with high hydrogen capacity for use as high performance metal hydride electrodes in rechargeable Ni-MH battery.     

Investigation of PZT-5H and PZT-8 type piezoelectric effect on cycling stability on Si-MWCNT containing anode materials

Silicon (Si) containing materials cannot be used in commercial lithium ion batteries due to the mechanical stress problem triggered by volume expansion during cycling. The high-volume change causes mechanical instability of Si anode materials during charging/discharging, resulting fast capacity fading. It is thought that piezoelectric materials can be a solution for the volume expansion problem because of their ability to generate electric field when pressure is applied on them. For this purpose, PZT-8 and PZT-5H type piezoelectric materials were mixed with silicon and multiwalled carbon nanotube (MWCNT) to obtain anode composites and tested electrochemically versus lithium metal. The piezoelectiric effect on the electrochemical activity of these anodes is investigated by preparing the anode composite without any piezoelectric material additive (Sample #3). At the end of the 50 charge/discharge cycles, the capacities reached 420 mAh/g, 300 mAh/g and 100 mAh/g for PZT-8-added, PZT-5H-added and no-PZT samples, respectively. These results showed that PZT addition improves capacity performance of Si-MWCNT anodes. Additionally, the obtained anode composites were characterized with X-ray diffraction and scanning electron microscopy.     

Hydrogenation of Furfural to Furfuryl Alcohol over Co-B Amorphous Catalysts Prepared by Chemical Reduction in Variable Media

Five Co-B amorphous alloy catalysts were prepared by chemical reduction in different media, including pure water and pure ethanol as well as the mixture of ethanol and water with variable ethanol content, Their catalytic properties were evaluated using liquid phase furfural hydrogenation to furfuryl alcohol as the probe reaction. It was found that the reaction media had no significant influence on either the amorphous structure of the Co-B catalyst or the electronic interaction between metallic Co and alloying B. This could successfully account for the fact that all the as-prepared Co-B catalysts exhibited almost the same selectivity to furfuryl alcohol and the same activity per surface area （ Rs ）, which could be considered as the intrinsic activity, since the nature of active sites remained unchanged. However, the activity per gram of Co （ R^mH ） of the as-prepared Co-B catalysts increased rapidly when the ethanol content in the water-ethanol mixture used as the reaction medium for catalyst preparation increased. This could be attributed to the rapid increase in the surface area possibly owing to the presence of more oxidized boron species which could serve as a support for dispersing the Co-B amorphous alloy particles.