正极集流体对可充镁电池电化学性能的影响

以目前常用的Chevrel相Mo₆S₈作为正极材料, 涂覆在不同集流体(不锈钢、镍、铜、钛) 上, 以镁为负极,研究了在(PhMgCl)₂-AlCl₃/四氢呋喃(简称THF)“二代”电解液中集流体对可充镁电池电化学性能的影响. 恒流放电-充电结果显示在不锈钢集流体上电池电压极化最小, 并且具有较好的循环稳定性; 镍、铜次之; 钛集流体上的极化最大, 循环稳定性也最差. 并通过对比放电-充电循环前后电极和集流体表面的微观结构, 探讨了集流体对电池性能显著影响的原因. 电解液对集流体会造成腐蚀, 不同集流体在电解液中的稳定性有差异; 正极材料涂覆在不同集流体上, 电极表面状况有差异; 负载活性材料后集流体发生腐蚀的电位有所降低, 使集流体更易受到电解液的腐蚀.     

苯硫酚盐基溶液的可充镁电池电解液

将4-甲基苯硫酚、4-异丙基苯硫酚和4-甲氧基苯硫酚(RSH)分别与格氏试剂C₂H₅MgCl/THF(四氢呋喃)反应制得的苯硫酚氯化镁(RSMgCl)(分别标记为MBMC、IPBMC和MOBMC)/THF和进一步与Lewis 酸AlCl₃反应制得的(RSMgCl)_n-AlCl₃/THF(n=1,1.5,2)苯硫酚盐基溶液用作可充镁电池电解液,采用循环伏安和恒电流充放电测试研究了电解液的镁沉积-溶出性能和氧化分解电位. 结果表明,苯硫酚上的基团种类和RSMgCl与AlCl₃的比例对其电化学性能有影响. 其中,0.5 mol·L^-1(IPBMC)_1.5-AlCl₃/THF 溶液具有最佳的电化学性能,其氧化分解电位适宜(2.4 V(vs Mg/Mg²⁺)),镁沉积-溶出循环效率稳定,过电位低,电导率较高(2.48 mS·cm^-1),与正极材料Mo₆S₈兼容性良好,且具有一定的空气稳定性,配制方便,有希望应用于实际的可充镁电池体系中.     

吡唑基镁卤化物/四氢呋喃可充镁电池电解液

将不同配比的吡唑与格氏试剂反应制得的吡唑基镁卤化物/四氢呋喃（THF）溶液用作可充镁电池电解液,采用循环伏安和恒电流充放电测试研究了该电解液的镁沉积-溶出性能和氧化分解电位;并通过X射线衍射（XRD）和扫描电镜（SEM）对沉积物的组分和形貌进行了分析. 结果表明,吡唑上的取代基、吡唑与格氏试剂的反应配比对电解液的电化学性能都有影响. 1 mol·L^-1 1-甲基吡唑-PhMgCl（1：1摩尔比）/THF反应配制的电解液在不锈钢（SS）集流体的阳极氧化分解电位达到2.4 V（vs Mg/Mg²⁺）,并具有镁沉积-溶出电位低、循环稳定性高、配制方便的特点,有希望应用于实际的可充镁电池体系中.     

层状正极材料LiNi0.5Co0.25Mn0.25O2的结构及电化学行为

采用溶胶-凝胶方法制备了正极材料LiNi_0.5Co_0.25Mn_0.25O₂。XRD、XPS测试结果表明：LiNi_0.5Co_0.25Mn_0.25O₂中阳离子排列有序度较高，层状结构明显；Co、Mn分别以+3、+4价形式存在，Ni以+2、+3价形式存在，且Ni²⁺与Ni³⁺的含量之比约为1∶1。SEM测试结果表明：正极材料LiNi_0.5Co_0.25Mn_0.25O₂结晶粒径较均匀。充放电测试结果表明：与LiCoO₂相比，尽管LiNi_0.5Co_0.25Mn_0.25O₂的放电电压平台较低，但放电容量较高；在恒流充电模式下，当充电截止电压由4.35 V升高至4.75 V时，首次放电容量由179 mAh·g^-1增至201 mAh·g^-1，50次循环后，容量保持率由74.95%增至78.48%；在先恒流再恒压的充电模式下，电池首次放电容量为212 mAh·g^-1，50次循环后，容量保持率提高到87.71%。循环伏安测试表明：在2.80～4.80 V扫描范围内，该正极材料发生Ni²⁺/Ni³⁺，Co³⁺/Co⁴⁺两对电化学反应。EIS测试表明：随着充电截止电压的增大，该正极材料的传荷电阻变小。     

吡唑基镁卤化物/四氢呋喃可充镁电池电解液

将不同配比的吡唑与格氏试剂反应制得的吡唑基镁卤化物/四氢呋喃(THF)溶液用作可充镁电池电解液,采用循环伏安和恒电流充放电测试研究了该电解液的镁沉积-溶出性能和氧化分解电位;并通过X射线衍射(XRD)和扫描电镜(SEM)对沉积物的组分和形貌进行了分析.结果表明,吡唑上的取代基、吡唑与格氏试剂的反应配比对电解液的电化学性能都有影响.1 mol·L-11-甲基吡唑-PhMgCl(1:1摩尔比)/THF反应配制的电解液在不锈钢(SS)集流体的阳极氧化分解电位达到2.4 V(vs Mg/Mg2+),并具有镁沉积-溶出电位低、循环稳定性高、配制方便的特点,有希望应用于实际的可充镁电池体系中.     

大气压旋转螺旋状电极辉光放电等离子体催化甲烷偶联

采用新研制的具有旋转螺旋状电极的大气压辉光放电等离子体反应器催化甲烷偶联制碳二烃. 实验采用铜电极和不锈钢电极分别考察了输入电场峰值电压和甲烷、氢气进料流量等参数对甲烷转化率和碳二烃收率、选择性的影响. 在长时间连续反应无明显积碳的情况下, 最佳试验结果是电极材料为金属铜, 进料流量为60 mL•min^-1, V(CH₄ )/V(H₂)=1的条件下, 输入电场峰值电压为2.3 kV时, 甲烷转化率为70.64%, 碳二烃单程收率及其选择性分别为69.85%和 99.14%.     

乙烯硫脲-格氏试剂/THF电解液镁沉积-溶出性能

将乙烯硫脲与不同格氏试剂EtMgBr/THF、PhMgBr/THF、PhMgCl/THF反应制得了3种乙烯硫脲-格氏试剂/THF电解液. 通过循环伏安测试了在Pt电极的镁沉积-溶出性能. 结果表明,形成乙烯硫脲-格氏试剂/THF电解液不改变电解液的镁沉积-溶出性能,却拓宽了其电化学窗口. 如乙烯硫脲-PhMgBr/THF溶液的氧化分解电位可达2.3 V（vs. Mg/Mg²⁺）, 该电解液的电导率随溶液溶度增大先升后降,0.9 mol·L^-1时其电导率最高,可达615 μS·cm^-1. 比较乙烯硫脲-PhMgBr/THF在Pt、Ni、Cu和Al四种金属电极的电化学性能,发现在Ni电极的氧化分解电位最高,可达2.4 V（vs. Mg/Mg²⁺）,且具有良好的镁沉积-溶出性能. CR2016扣式电池的循环测试表明,Ni基底上的镁沉积-溶出电位较低,其循环效率可达到92%,适宜作为实用电池的集流体.     

碳酸乙烯酯添加剂对BMImBF4离子液体作为镁沉积—溶解电解液的改性研究

利用恒电流沉积-溶解、交流阻抗、XRD和SEM方法研究了在室温下EC(碳酸乙烯酯)添加剂对BMImBF₄离子液体作为镁沉积电解液的改善情况. 在Mg(CF₃SO₃)₂浓度为0.3 mol•L^－1的BMImBF₄电解液中加入w＝5%(质量分数)的EC后, 沉积—溶解循环过程更加稳定, 并且循环次数明显增加, 可以达到265次以上; 交流阻抗结果显示, 膜电阻和电荷转移电阻有所减少; 从SEM图可以观察到, 在沉积初期原本枝晶态的镁在加入EC后以颗粒状沉积. 可能是EC添加剂在反应中形成的低聚物覆盖在镁的表面, 抑制了枝晶的形成.     

碳酸乙烯酯添加剂对BMImBF4离子液体作为镁沉积—溶解电解液的改性研究

利用恒电流沉积-溶解、交流阻抗、XRD和SEM方法研究了在室温下EC(碳酸乙烯酯)添加剂对BMImBF₄离子液体作为镁沉积电解液的改善情况. 在Mg(CF₃SO₃)₂浓度为0.3 mol•L^－1的BMImBF₄电解液中加入w＝5%(质量分数)的EC后, 沉积—溶解循环过程更加稳定, 并且循环次数明显增加, 可以达到265次以上; 交流阻抗结果显示, 膜电阻和电荷转移电阻有所减少; 从SEM图可以观察到, 在沉积初期原本枝晶态的镁在加入EC后以颗粒状沉积. 可能是EC添加剂在反应中形成的低聚物覆盖在镁的表面, 抑制了枝晶的形成.     

过充保护添加剂1,2-二甲氧基-4-硝基苯和1,4-二甲氧基-2-硝基苯在锂离子电池中的应用

在锂离子电池电解液1 mol·L^-1 LiPF₆/(碳酸乙烯酯(EC)+碳酸二乙酯(DEC)+碳酸甲乙酯(EMC) (1:1:1,体积比))中分别添加1,2-二甲氧基-4-硝基苯(DMNB1)和1,4-二甲氧基-2-硝基苯(DMNB2)作为防过充添加剂.采用循环伏安(CV)、恒流充放电、过充测试、电化学阻抗谱(EIS)、扫描电子显微镜(SEM)等手段研究了DMNB1和DMNB2 的防过充效果, 以及添加剂与LiNi_1/3Co_1/3Mn_1/3O₂材料的相容性. 结果表明: DMNB1 和DMNB2 的氧化电位都在4.3 V (vs Li/Li⁺)以上, 且均能显著提高电池的过充保护性能. 100%过充和5 V截止电压过充测试表明, DMNB1 的防过充性能优于DMNB2. 采用基础电解液、添加0.1 mol·L^-1 DMNB1 和添加0.1 mol·L^-1DMNB2 电解液的LiNi_1/3Co_1/3Mn_1/3O₂/Li 电池, 0.2C 倍率下循环100 次, 容量保持率分别为98.4%、95.9%和68.1%. 证明硝基在添加剂苯环上的取代位置和其电化学性能之间有着密切联系.     

Electrochemical‐Conditioning‐Free and Water‐Resistant Hybrid AlCl3/MgCl2/Mg(TFSI)2 Electrolytes for Rechargeable Magnesium Batteries

Rechargeable magnesium batteries are a promising alternative to Li‐based energy storage because of their abundant and inexpensive components. The high sensitivity and reactivity of the organic Mg²⁺ electrolyte makes their development challenging. Herein, we develop a new hybrid electrolyte, based on three simple inorganic salts of MgCl₂, AlCl₃, and Mg(TFSI)₂. The electrolyte exhibits unprecedented electrochemical performance for reversible deposition and stripping of Mg, with Coulombic efficiency up to 97 %, overpotential down to 0.10 V, good stability especially for aluminum and stainless‐steel current collectors. It maintained its activity even after introducing 2000 ppm water and it could be prepared from impure chemicals. A full cell with the hybrid electrolyte and Mg foil as anode, Mo₆S₈ as cathode gave a specific capacity of 98 mAh g^?1 and maintained 94 % capacity after 100 cycles at a rate of 0.20 C, indicating the good compatibility of the hybrid electrolyte.     

Spectroelectrochemical studies of magnesium deposition by in situ FTIR spectroscopy

Magnesium can be reversibly deposited electrochemically from solutions of ethereal solvents, with Grignard reagents (RMgX) or complexes of Mg(AX_3−nR_n+1)₂ stoichiometry as the electrolytes (A=Al, B; X=Cl, Br; R=alkyl or aryl groups). These processes are far from being simple reactions of the Mg/Mg⁺⁺ couple, since the above electrolytes in solutions have complicated structures in which the ether molecules play an important stabilization role. In addition, Mg deposition processes in all of the above solutions are accompanied by adsorption phenomena. The surface chemistry of magnesium electrodes was studied in situ by FTIR spectroscopy, using an internal reflectance mode. The electrolyte solutions studied included tetrahydrofuran (THF) solutions of the RMgX electrolytes (R=butyl, ethyl, methyl benzyl, and X=Cl, Br); Mg(AlCl₂BuEt)₂; Mg(AlCl₃Bu)₂ and Mg(BPh₂Bu₂); Bu, Et, Ph=butyl, ethyl and phenyl groups, respectively. It was clear from these studies that Mg electrodes do not develop stable passivation in these solutions (i.e. formation of surface films). The nature of the adsorbed species in the above systems is discussed, based on the spectral results.     

可充镁电池正极材料PTMA/石墨烯

本文制备了聚4-甲基丙烯酸-2,2,6,6-四甲基哌啶-1-氮氧自由基酯(PTMA)/石墨烯纳米复合材料,并报道了其作为可充镁电池正极材料的电化学性能.通过傅里叶变换红外(FTIR)光谱、扫描电镜(SEM)、透射电镜(TEM)表征复合材料的结构和形貌;循环伏安和恒电流充放电测试其电化学性能.粒径10 nm左右的PTMA颗粒分散在具有导电作用的石墨烯表面;在"一代"电解液Mg(AlCl2BuEt)2/四氢呋喃(THF)(0.25 mol L-1)中,22.8mA g-1充放电电流密度下,PTMA/石墨烯复合材料的起始放电容量可达到81.2 mAh g-1.研究结果表明,含有自由基的有机化合物可以作为可充镁电池的一类新型正极材料,可以进一步通过使用具有高氧化分解电压的电解液来提高其放电容量.     

Reaction between [MgCl2(THF)2] and [MoOCl3(THF)2]. The Crystal Structures of [Mg(THF)6][MoOCl4THF]2 and [Mg2(m̈-Cl)3(THF)6][MoOCl4THF]

Two [MoOCl₃(THF)₂] molecules are used for detachment of two Cl atoms from [MgCl₂(THF)₂]. In such reaction a green crystalline salt [Mg(THF)₆][MoOCl₄THF]₂ IV is formed. Compound IV reacts further with 3 equivalents of bis(tetrahydrofuran)magnesium dichloride, yielding a green ionic [Mg₂(m?-Cl)₃(THF)₆][MoOCl₄THF] compound V . Compound IV and V vary only in a structure of cation what indicated that the tri-m?-chlorohexakis(tetrahydrofuran)dimagnesium(II) cation in V is really formed in reaction between [Mg(THF)₆]²⁺ cation and [MgCl₂(THF)₂]. The crystal structure of compounds IV and V has been solved by X-ray diffraction method. The [Mg(THF)₆]²⁺ cation forms the tetragonally distorted octahedron with the magnesium atom in the symmetry centre. In homobimetallic di-octahedral [Mg₂(m?-Cl)₃(THF)₆]⁺ cation the magnesium atoms are surrounded by three bridging chlorine atoms and three THF molecules. The structures of [MoOCl₄THF]^? in IV and V are similar. In those anions the molybdenum atom is hexacoordinated with four chlorine atoms in equatorial plane.     

Synthesis,Crystal Structure,and Electrochemical Properties of a Simple Magnesium Electrolyte for Magnesium/Sulfur Batteries

Most simple magnesium salts tend to passivate the Mg metal surface too quickly to function as electrolytes for Mg batteries. In the present work, an electroactive salt [Mg(THF)₆][AlCl₄]₂ was synthesized and structurally characterized. The Mg electrolyte based on this simple mononuclear salt showed a high Mg cycling efficiency, good anodic stability (2.5 V vs. Mg), and high ionic conductivity (8.5 mS cm⁻¹). Magnesium/sulfur cells employing the as‐prepared electrolyte exhibited good cycling performance over 20 cycles in the range of 0.3–2.6 V, thus indicating an electrochemically reversible conversion of S to MgS without severe passivation of the Mg metal electrode surface.