Ionic Liquid Based Electrolytes for High Energy Electrochemical Storage Devices
Ionic Liquid Based Electrolytes for High Energy Electrochemical Storage Devices
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用于高能电化学存储装置的离子液体电解质
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
M. Conte
中科院分区：
文献类型：
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作者：
S. Passerini;F. Alessandrini;G. Appetecchi;M. Conte
室温离子液体（RTIL）-在室温或低于室温下为液体的盐-首先被报道用于硝酸乙基铵[1]，近年来被广泛报道。RTIL是不挥发的，不可燃的，并且通常具有优异的热稳定性。这些材料引起了研究人员对各种应用的兴趣，包括燃料电池，电化学电容器，染料敏感太阳能电池，电化学器件和电池[2-7]。RTIL作为高能量电化学装置电池中的电解质的使用是非常有前途的，因为这可以解决传统液体电解质的挥发性和可燃性的许多问题。使用RTIL作为液体电解质中常规溶剂的替代品[6-8]以及将RTIL掺入固体聚合物电解质[9，10]正在全球范围内进行研究。在RTIL的大家族中，具有咪唑鎓基阳离子的盐由于其高导电性而受到广泛关注。不幸的是，由于酸性阳离子质子的存在，基于咪唑钥的RTIL具有不利的与锂金属的化学和电化学性质。最近，MacFarlane等人[11]和我们[12-15]已经报道了由N-烷基-N-甲基吡咯烷鎓阳离子（PYR 1 R）（下标表示阳离子的烷基中的碳数）和双（三氟甲磺酰基）酰亚胺阴离子（TFSI）（PYR 1 RTFSI）组成的RTIL。一些吡咯烷鎓盐如PYR 13 TFSI和PYR 14 TFSI具有低于环境温度的熔点和高的室温离子电导率。高能量密度电池需要作为诸如电信、便携式电子设备和混合动力电动车辆（HEV）的应用的电源。锂离子电池目前或很快将成为实现这些目标的首选电池。下一代锂金属电池（具有锂金属阳极而不是碳嵌入阳极）需要不同的电解质，优选固态电解质。为了实现更轻、更安全、更长寿命和更高能量密度的电池，聚合物电解质似乎是最有前途的候选者，但它们在环境温度下的离子电导率太低（~10 S/cm）。在最近的工作中，我们证明了将PYR 13 TFSI掺入P（EO）20 LiTFSI聚合物电解质中导致具有显著增加的室温离子电导率的自支撑膜[12-14]。我们还报道了在聚合物电解质和阴极中加入PYR 13 TFSI的Li/LiFePO 4电池即使在中等温度下也可以可逆地操作，具有高放电容量。超级电容器由于其在几秒或更长时间内提供高比功率的能力，目前被认为是用于平滑由燃料电池或电池供电的运输和家用应用中所需的强和短时间电力请求的电能存储设备的选择，以及用于分布式网络中的电压补偿的能量存储变电站。离子液体显示出宽的电化学稳定性窗口和良好的导电性，使得它们可以用作高压超级电容器的无溶剂“绿色”电解质[1618]。已经在DLCS [3，19 -20]和混合超级电容器[21]中研究了IL的使用，但是它们在这些电能转换系统所需的大量循环中的循环稳定性仍然需要证明。在最近的一项工作中，对具有PYR 14 TFSI的活性炭（AC）//聚（3-甲基噻吩）（pMeT）混合超级电容器进行了超过15，000次循环的循环测试结果，工作温度为60°C，电极质量负载适合实际应用[22]。在目前的工作中，我们将报告在ENEA获得的关于电池和超级电容器的IL的最新结果。还将简要介绍欧盟项目ILHYPOS（离子液体混合动力超级电容器）。
Room temperature ionic liquids (RTILs) – salts which are liquids at or below room temperature – were first reported for ethylammonium nitrate [1] and have been extensively reported in recent years. RTILs are nonvolatile, nonflammable and often have excellent thermal stability. These materials have aroused the interests of researchers for a wide variety of applications including fuel cells, electrochemical capacitors, dye-sensitive solar cells, electrochemical device and batteries [2-7]. The use of RTILs as electrolytes in high energy electrochemical devices batteries is very promising because this may solve many of the problems of traditional liquid electrolytes that are volatility and flammability. The use of RTILs as replacements for conventional solvents in liquid electrolytes [6-8] and the incorporation of RTILs into solid polymer electrolytes [9,10] are under investigation worldwide. Among the large family of RTILs, salts with imidazolium based cations have received extensive attention due to their high conductivity. Unfortunately, imidazolium based RTILs have unfavorably chemical and electrochemical properties with lithium metal due to the presence of acidic cation protons. Recently, RTILs composed of N-alkyl-N-methylpyrrolidinium cations (PYR1R) (the subscript indicates the number of carbons in the alkyl group of the cation) and bis(trifluoromethanesulfonyl)imide anions (TFSI) (PYR1RTFSI) have been reported by MacFarlane et al. [11] and us [12-15]. Some of the pyrrolidinium salts such as PYR13TFSI and PYR14TFSI, have sub-ambient melting points and a high room temperature ionic conductivity. High energy density batteries are required as power source for applications such as telecommunications, portable electronic devices and hybrid electric vehicles (HEVs). Lithium-ion batteries are currently or soon will be the batteries of choice to obtain these objectives. The next generation lithium metal batteries (with lithium metal anodes rather than carbon intercalation anodes) require different, preferably solid-state, electrolytes. To achieve lighter, safer, longer life and higher energy density batteries, polymer electrolytes appear to be the most promising candidates, but their ionic conductivity at ambient-moderate temperatures is much too low (~10 S/cm). In recent work, we demonstrated that the incorporation of PYR13TFSI into P(EO)20LiTFSI polymer electrolytes results in free-standing membranes with a considerably increased room temperature ionic conductivity [12-14]. We also reported that Li/LiFePO4 batteries incorporating PYR13TFSI in the polymer electrolyte and the cathode can be reversibly operated even at moderate temperatures with a high discharge capacity. Supercapacitors, due to their capability to deliver high specific power during a few seconds or more, are presently considered as the electrical energy storage devices of choice for smoothing the strong and short-time power solicitations required in transportation and domestic applications powered by fuel cells or batteries, as well as for energy storage substations for voltage compensation in distributed networks. ILs display wide electrochemical stability windows and good conductivities so that they can be used as solvent-free “green” electrolytes for high voltage supercapacitors [1618]. The use of ILs has been investigated both in DLCSs [3,19-20] and in hybrid supercapacitors [21], but their cycling stability over a high number of cycles required by these power energy conversion systems still needed to be proven. In a recent work, the results of cycling tests over more than 15,000 cycles for an activated carbon (AC)//poly(3-methylthiophene) (pMeT) hybrid supercapacitor with PYR14TFSI, operating at 60°C and with an electrode mass loading suitable for practical applications [22]. In the present work we will report on the most recent results obtained at ENEA on IL for batteries and supercapacitors. A brief overview of the EU Project ILHYPOS (Ionic Liquid Hybrid Power Supercapacitors) will be also given.