NaBF4对锂离子电池石墨负极性能的影响

利用恒流充放电、循环伏安、交流阻抗、SEM、EDS等测试技术研究了在锂离子电池石墨负极和浆过程中加入NaBF₄对其电化学性能的影响。结果表明:NaBF₄的最佳添加量为2%,可明显提高石墨电极的首次放电比容量和充放电效率;电极的自放电性能和循环稳定性得到明显改善。室温条件下,添加了2% NaBF₄的电极以放电容量计算的自放电率为0.87%·d^-1,比未添加时降低了15%;循环伏安、EDS以及SEM测试结果表明,四氟硼酸钠参与了石墨电极的成膜过程,改变了SEI膜的组分和形貌。     

采用新颖喷墨打印技术制备的薄膜LiCoO2电极及其电化学性能

采用喷墨打印技术制备了LiCoO2薄膜电极. 用X射线衍射、扫描电镜(SEM)、循环伏安和恒电流充放电试验对薄膜电极进行结构表征和电化学性能测试. SEM结果表明, 所制备的薄膜电极表面粒子分布均匀, 厚度约为1.27 μm. 经过轻微热处理(450 ℃, 30 min)的薄膜LiCoO2电极呈现出稳定的充放电循环性能. 当以20 μA/cm2进行充放电时, 第50次循环容量保持率约为首次放电容量(81 mA·h/g)的87%, 10次循环后的充放电过程的充放电效率均接近100％.     

纳米ZnO的固相合成及其对锌电极的改性作用

利用固相配位化学反应制备了纳米ZnO粉体 ,借助XRD、TEM进行了表征 ,并采用循环伏安法和循环充放电法对电化学性能进行了分析。循环伏安测试表明 ,在较慢扫速 (1mV s)下 ,不同组成电极的峰形相差较大 ,添加 5 0 %纳米ZnO的混配电极展示出良好的循环可逆性。恒流充放电测试结果表明 ,添加 5 0 %的ZnO对锌电极具有较好的改性作用 ,提高了锌电极的循环充放电性能 ,但纳米ZnO对锌电极的改性效果明显优于普通粒径ZnO。在循环充放电第 2 5周和 3 0周时放电容量分别为 2 2 0mA·h g和 1 98mA·h g。     

LiF和LiCl对石墨电极电化学性能的影响

六氟磷酸锂是目前商品化锂离子电池中使用最广泛的电解质锂盐,LiF和LiCl是除水和酸之外六氟磷酸锂产品中最重要的杂质.运用扫描电子显微镜（SEM）、充放电、循环伏安法（CV）以及电化学阻抗谱测试（EIS）等研究了LiF和LiCl对石墨电极电化学性能的影响.充放电结果表明,在1 mol/L LiPF₆-EC：DEC：DMC电解液中添加饱和的LiF,可以显著提高石墨电极的充放电可逆容量并改善其循环性能,而在1 mol/L LiPF₆-EC：DEC：DMC电解液中添加饱和的LiCl,虽也可提高石墨电极的首次充电容量,但严重恶化石墨电极的充放电循环稳定性.CV结果表明,电解液中LiF、LiCl的存在对EC的还原分解过程影响较小.但SEM和EIS的结果指示,LiF、LiCl对石墨电极表面SEI膜的形成过程影响较大.在添加饱和LiF的电解液中石墨电极表面形成的SEI膜较薄且电阻较小,进而提高了石墨电极的可逆循环容量及改善了其循环稳定性;但在饱和的LiCl电解液中石墨电极表面形成的SEI膜较厚且电阻较大,严重恶化石墨电极的电化学循环稳定性.     

新型锂离子电池三维结构泡沫NiO电极的制备及电化学性能

通过固相氧化方法,以三维结构泡沫镍为基体和金属镍源,制备了三维结构泡沫氧化镍负极。XRD和SEM结果表明,经500℃氧化处理,泡沫镍基体上形成了NiO微米级的致密活性氧化层。通过充放电测试和循环伏安测试研究了电极的电化学性能,结果表明,三维结构泡沫氧化镍在放电电位区间0.05～3.2VvsLi/Li+,0.2C倍率下充放电,初始容量损失为20%,且经40次循环后,质量比容量为950mAh·g-1,三维泡沫氧化镍电极具有优异的循环容量保持性能。三维泡沫氧化镍具有的大的活性表面积,降低了界面反应的极化,从而提高了NiO电极的倍率放电性能。     

多元醇法合成纳米LiCoPO4及其电化学性能

采用多元醇法合成了高电位LiCoPO4正极材料.以甲苯为碳源,在LiCoPO4表面化学气相沉积包覆一层厚度约3 nm的导电碳层.通过XRD、SEM、TEM、CV以及恒流充放电曲线等方法分析、观察和测试样品的晶体结构、微观形貌以及电化学性能.结果表明,多元醇法合成的样品为纯相LiCoPO4,碳包覆LiCoPO4/C电极0.1C倍率首次放电容量达到132 mAh·g-1,50周期循环容量保持78%.循环伏安和微分容量曲线表明LiCoPO4/C电极的充放电过程Li+脱出和嵌入均为两步步骤.     

钛和锆的添加对MgNi型合金电极电化学性能的影响

用机械球磨法（MA）成功合成了镁基储氢合金MgNi, Mg0.9Ti0.1Ni和Mg0.9Ti0.1Ni0.9Co0.1。研究了其结构和电化学性能。X射线衍射（XRD）和扫描电镜（SEM）结果表明合金为非晶结构，并有少量的Ni衍射峰存在。充放电测试结果表明这一系列合金具有很好的电化学活性。Ti和Co的替代使合金的循环稳定性好于MgNi合金。50周充放电循环后，Mg0.9Ti0.1Ni0.9Co0.1合金的放电容量明显好于MgNi合金，Mg0.9Ti0.1Ni0.9Co0.1的放电容量比MgNi合金高102.8%，比Mg0.9Ti0.1Ni合金高45.49%。在充放电循环过程中，合金电极容量衰减的主要原因是在合金电极表面Mg变成了Mg(OH)2。Tafel极化测试表明Ti和Co的添加可以提高合金电极在碱液中的抗腐蚀性能和提高合金电极的循环稳定性。EIS测试结果表明Ti和Co的替代可以明显提高MgNi型合金表面的电催化活性。     

0/1/2维混合纳米形貌V2 O5的制备与储锂性能

以P123为结构导向剂,采用溶胶-凝胶法结合冷冻干燥技术制备了0/1/2维混合纳米形貌的正交相V₂O₅电极活性材料.利用XRD和SEM表征了样品的结构和形貌,通过循环伏安法、恒流充放电和交流阻抗谱测试研究了样品的储锂性能.结果显示,这种0/1/2维混合纳米形貌V₂O₅具有较高的储锂容量、优异的电化学循环稳定性和出色的大倍率充放电性能,在1 A/g电流密度下循环500次后放电比容量稳定在117.5 mA·h/g,容量保持率为94.4%,在5 A/g大电流密度下,其放电比容量仍保持在88.2 mA·h/g,性能明显优于未添加P123制备的2D片状V₂O₅材料.     

稀土镧掺杂MnO2电极的制备及性能研究

以Mn(CH3COO)2·4H2O为原料,利用直流电沉积法合成MnO2电极材料,在制备过程中向溶液中添加h(NO3)3·6H2O对MnO2电极进行改性.分别采用X射线衍射(XRD)、扫描电子显微镜(SEM)和原子吸收方法分析了电极的结构、形貌以及组成.通过BET分析,发现掺La后MnO2的比表面积明显增大.采用循环伏安(CV)和恒流充放电技术测试了MnO2的电化学性能.结果表明,MnO2比容量为198.72 F·g-1,掺La后MnO2的电化学性能显著改善,其比容量为276.60 F·g-1.     

LiFePO4/C正极材料的液相合成及电化学性能研究

尝试对共沉淀法进行改进, 利用自制的加料装置合成了橄榄石型LiFePO₄/C复合正极材料. 应用X射线衍射(XRD)、扫描电镜(SEM)、X射线能谱(EDS)、循环伏安(CV)以及恒电流充放电测试等方法对目标材料进行了结构表征和电化学性能测试. 实验结果表明采用该法得到的样品具有单一的橄榄石结构, 样品形貌规则, 粒径细小均匀. 改性后的材料具有较高的首放容量及良好的循环稳定性能. 0.1C倍率下充放电测试表明, 其首次放电比容量超过145 mAh•g^－1, 50次循环后, 容量没有明显衰减. 0.2C和0.5C倍率下的平均放电容量分别为130及120 mAh•g^－1, 循环过程中样品表现出较好的循环稳定性.     

Bi基化合物膜包覆ZnO的制备和电化学性能

为提高锌镍电池ZnO的循环充放电性能,采用Bi(NO3)3水解沉积法对ZnO包覆Bi基化合物膜,系统研究了包覆ZnO的微结构和电化学性能。TEM,XRD和EDS表明由Bi6(NO3)4(OH)2O6·2H2O,BiO和Bi2O3组成的Bi基化合物膜包覆在ZnO表面。表面包覆能提高ZnO的循环性能和放电容量,含5.1wt%Bi的包覆ZnO循环性能稳定,平均放电容量为509mAh·g-1,利用率为78%,性能有较大改善。充放电曲线和循环伏安结果均表明包覆Bi基化合物膜能降低锌镍电池的充电平台,加宽放电平台,提高ZnO的电化学活性。包覆Bi基化合物膜能有效减小活性材料与碱性电解液的接触,抑制ZnO的溶解,提高循环稳定性;而包覆膜的微孔结构又可使活性材料接触到电化学反应必须的H2O和OH-,保证了高的放电容量。     

新型钛基镍电极对肼氧化反应的电催化活性

A novel titanium-supported nickel electrode(Ni/Ti) was fabricated by a hydrothermal process using NiSO4 and hydrazine as raw materials. The structure of Ni/Ti was characterized by SEM and EDS. Oxidation of hydrazine on the Ni/Ti electrode in 1 mol·L-1 NaOH solution was studied with cyclic voltammograms(CV) and chronoamperometry (CA).The results show that Ni/Ti electrode was electrochemically active towards hydrazine oxidation. The high current density was recorded on the Ni/Ti electrode,and the onset potential for the hydrazine oxidation was-0.3 V as the hydrazine concentration was 70 mmol·L-1. This novel nickel electrode would be a promising anodic material used in direct hydrazine fuel cells.     

Self-discharge behavior of LaNi5-based hydrogen storage electrodes in different electrolytes

Nickel–metal hydride (Ni–MH) batteries using hydrogen storage alloys as negative electrode materials have been developed and commercialized because of their high energy density, high rate capability and long cycle life, without causing environmental pollution (Song et al. J Alloys Comp 298:254, 2000; Jang et al. J Alloys Comp 268:290, 1998). However, the self-discharge rate is relatively higher than that of the Ni–Cd batteries, which would certainly be disadvantageous in practical applications. The capacity loss of a battery during storage is often related to self-discharge in the cells. Self-discharge takes place from a highly charged state of a cell to a lower state of charge (SOC) and is typically caused by the highly oxidizing or reducing characteristic of one or both of the electrodes in the cell. This self-discharge behavior may be affected by various factors such as gases, impurities, temperature, type of alloy electrode, electrolytes, or charge/discharge methods. The loss of capacity can be permanent or recoverable, depending on the nature of the mechanism (chemical or electrochemical) and aging condition. In this paper, the effects of electrolyte composition and temperature on self-discharge behavior of LaNi₅-based hydrogen storage alloy electrodes for Ni–MH batteries have been investigated. It was found that both reversible and irreversible capacity loss of MH electrode tested at 333 K were higher than that at 298 K. When tested at 298 K and 333 K, reversible capacity loss was mainly affected by the electrolyte, while the irreversible capacity loss was not affected. The dissolution of Al from the electrode can be reduced more effectively in an electrolyte with Al addition, compared with that in normal electrolyte. This resulted in a lower reversible capacity loss for the electrode exposed in the Al³⁺-rich electrolyte. SEM analysis has shown that some needle shape and hexagonal corrosion products were formed on the surface of the alloy electrodes, especially after storage at high temperature.     

石墨烯-氧化钌纳米复合材料的水热法合成及电化学电容性能

通过水热法制备了石墨烯-氧化钌(G-RuO₂)纳米复合材料。对样品进行了X射线衍射(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM)和能量色散谱(EDS)表征。SEM结果表明氧化钌粒子均匀地分散在石墨烯层片上。TEM结果显示氧化钌纳米粒子的平均粒径约为3 nm。对样品进行了循环伏安和充放电性能测试,结果表明在1 A·g^-1的电流密度下,样品在H₂SO₄(1 mol·L^-1)溶液中具有219.7 F·g^-1的比电容。     

Study on surface adsorption from cationic surfactant–electrolyte mixed aqueous solution including BF 4 − ion

The surface tension of aqueous mixtures of dodecyltrimethylammonium tetrafluoroborate (DTABF₄) and sodium tetrafluoroborate (NaBF₄) was measured as a function of total molality and composition of DTABF₄ at 298.15 K. The results were analyzed by originally developed thermodynamic equations and compared with those of dodecyltrimethylammonium bromide (DTAB)–sodium bromide (NaBr) mixed system. It was indicated that BF₄⁻ ions reduce the repulsion between DTA⁺ ions more effectively than Br⁻ ions in the adsorbed film. To investigate this difference more closely, the surface tension of DTAB–NaBF₄ and DTABF₄–NaBr mixed system was also measured. The data analysis revealed that BF₄⁻ ions are adsorbed positively even for the pure NaBF₄ system and preferentially to Br⁻ ions in these mixtures. Furthermore, it was concluded that the side-by-side arrangement suggested in the adsorbed film of 1-hexyl-3-methylimidazolium tetrafluoroborate (HMIMBF₄) is due to not only the positive adsorption of BF₄⁻ ions but also the capability of hydrogen bond formation between imidazolium ion and BF₄⁻ ions.     

电解液添加剂硫酸亚乙酯对锂离子电池性能的影响

在1 mol/L LiPF₆/碳酸乙烯酯+碳酸二甲酯+碳酸甲乙酯（体积比1∶1∶1）电解液中,采用恒流充放电测试、循环伏安法（CV）、扫描电子显微镜（SEM）、能量散射光谱（EDS）、电化学阻抗谱（EIS）等测试技术,研究了添加剂硫酸亚乙酯（DTD）对锂离子电池性能及石墨化中间相碳微球（MCMB）电极/电解液界面性质的影响。 结果表明,在电解液中引入体积分数0.01%DTD后,MCMB/Li电池可逆放电容量从300 mA·h/g提高至350 mA·h/g,电池总阻抗降低,循环稳定性提高。CV测试发现,在首次还原过程中,DTD在电极电位1.4 V左右（vs Li/Li⁺）发生电化学还原,参与了MCMB电极表面固体电解质相界面膜（SEI膜）的形成过程。 同时,DTD对LiMn₂O₄电极性能无不良影响。     

Barium Sulfate Effects on the Electrochemical Behaviors of Nanostructured Lead Dioxide and Commercial Positive Plates of Lead-Acid Batteries

Positive electrode with uniform lead dioxide nanostructures directly synthesized by cyclic voltammetry (CV) method on the lead substrate in 1 M sulfuric acid solution including different concentration of barium sulfate. The effect of potential scan rate, sulfuric acid and barium sulfate concentration were studied on the morphology and particle size of lead dioxide using scanning electron microscopy (SEM) and X-ray diffraction techniques (XRD). The effect of barium sulfate was studied on the CV parameters including anodic peak current (I _p^a), cathodic peak current (I _p^c), anodic peak potential (E _p^a) and cathodic peak potential (E _p^c) during synthesis process. Finally, the effect of barium sulfate on the discharge capacity and cycle life of nanostructured positive electrodes and commercial positive plates was investigated. Both CV and battery test results showed that barium sulfate with concentration of 1 × 10⁻⁵ M can be used as suitable additive for positive paste of lead-acid batteries.     

Thermal studies of potassium tetrahydroborate−sodium tetrafluoroborate mixtures

The KBH₄?NaBF₄ mixture was studied by thermal analysis (differential scanning calorimetry). Chemical analysis, X-ray powder diffraction analysis, IR spectroscopy, and ¹¹B and ¹⁹F MAS NMR spectroscopy showed that the primary stage of the complex pyrolysis process is a metathesis reaction between components to form a new mixture, NaBH₄?KBF₄, the decomposition of which with the release of gaseous products and the formation of polyhedral borohydride compounds (mainly B₁₂H₁₂ ^2-) in the solid residue begins at a temperature of about 563 K. At a certain ratio between reactants in the initial mixture KBH₄?NaBF₄, the B₁₂H₁₂ ^2- anion can form with the material participation of the BF₄ ^- anion.