掺杂改性PMMA/PVDF共混聚合物基复合介质的储能性能提升

张昌海, 闫炜东, 张统钦, 张天栋, 迟庆国, 刘献礼

张昌海, 闫炜东, 张统钦, 等. 掺杂改性PMMA/PVDF共混聚合物基复合介质的储能性能提升[J]. 复合材料学报, 2023, 40(7): 3950-3963. DOI: 10.13801/j.cnki.fhclxb.20220913.004
引用本文: 张昌海, 闫炜东, 张统钦, 等. 掺杂改性PMMA/PVDF共混聚合物基复合介质的储能性能提升[J]. 复合材料学报, 2023, 40(7): 3950-3963. DOI: 10.13801/j.cnki.fhclxb.20220913.004
ZHANG Changhai, YAN Weidong, ZHANG Tongqin, et al. Improved energy storage performance of PMMA/PVDF blend polymer matrix composites by doping modification[J]. Acta Materiae Compositae Sinica, 2023, 40(7): 3950-3963. DOI: 10.13801/j.cnki.fhclxb.20220913.004
Citation: ZHANG Changhai, YAN Weidong, ZHANG Tongqin, et al. Improved energy storage performance of PMMA/PVDF blend polymer matrix composites by doping modification[J]. Acta Materiae Compositae Sinica, 2023, 40(7): 3950-3963. DOI: 10.13801/j.cnki.fhclxb.20220913.004

掺杂改性PMMA/PVDF共混聚合物基复合介质的储能性能提升

基金项目: 国家自然科学基金青年科学基金(52007042);黑龙江省自然科学基金联合引导项目(LH2020 E091);电子薄膜与集成器件国家重点实验室开放项目(KFJJ201904)
详细信息
    通讯作者:

    张天栋,博士,副教授,博士生导师,研究方向为聚合物电容器薄膜 E-mail: tdzhang@hrbust.edu.cn

  • 中图分类号: TM211;TB332

Improved energy storage performance of PMMA/PVDF blend polymer matrix composites by doping modification

Funds: National Natural Science Foundation of China Youth Science Foundation (52007042); Natural Science Foundation of Heilongjiang Province (LH2020 E091); Open Project of National Key Laboratory of Electronic Thin Films and Integrated Devices (KFJJ201904)
  • 摘要: 薄膜电容器在高压输电换流站、新能源汽车电驱动控制器、电磁武器脉冲功率电源等电气工程和电子器件领域具有重要应用。当前薄膜电容器正向着高能量密度、耐电压、耐高温等技术方向发展,对电容薄膜的电气性能提出了更高要求。本文选择铁电聚偏氟乙烯(PVDF)和聚甲基丙烯酸甲酯(PMMA)共混物作为储能聚合物基体,以具有高介电常数的纳米粒子BaTiO3和具有高电子亲和能的有机分子半导体[6, 6]-苯基C61丁酸甲酯(PCBM)作为掺杂相,综合利用BaTiO3的高介电特性及PCBM的捕获电荷能力,提高复合介质的极化强度与击穿场强,显著改善储能性能。研究表明,单掺杂BaTiO3时,掺杂含量为3wt%时复合介质综合性能最优;在此基础上,随着PCBM掺杂含量增大其储能密度和充放电效率提升明显。当PCBM掺杂含量为2wt%时,含有3wt%BT的PMMA/PVDF复合介质具有优异的储能性能,当电场为579.67 kV/mm时,放电能量密度达到15.60 J/cm3且充放电效率为75.30%。本文首次提出基于少量无机高介电协同有机分子半导体功能填料的聚合物薄膜储能性能改性研究,通过加入少量的BaTiO3,既避免了由于BaTiO3含量过高而导致的绝缘性能下降问题,又保证了BaTiO3粒子对复合介质介电常数和极化性能的提升。同时,为了进一步改善因低介电常数基体与高介电常数BaTiO3颗粒之间的电场畸变所导致的击穿强度下降问题,考虑在复合介质中加入一定量的PCBM,利用PCBM强大的电子亲和能力,在复合介质中构筑深陷阱以捕获和束缚载流子,抑制载流子的迁移,提升复合介质的击穿场强,从而综合提升了复合介质的储能性能,这为开发储能性能优异的聚合物复合介质提供了一种新思路。
    Abstract: Thin film capacitors have important applications in the fields of electrical engineering and electronic devices such as high voltage transmission converter stations, new energy vehicle electric drive controllers, electromagnetic weapon pulse power supply and so on. At present, thin-film capacitors are developing towards the technical direction of high energy density, voltage resistance, high temperature resistance and so on, which put forward higher requirements for the electrical performance of capacitor films. In this study, ferroelectric polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA) blends were selected as the energy storage polymer matrix, and BaTiO3 nanoparticles with high dielectric constant and organic molecular semiconductor [6, 6]-phenyl C61 methyl butyrate (PCBM) with high electron affinity were used as the doping phase. The high dielectric properties of BaTiO3 and the ability of PCBM to capture charge are comprehensively utilized to improve the polarization strength and breakdown field strength of the composite medium and significantly improve the energy storage performance. The results show that when the doping content is 3wt%, the composite media has the best comprehensive performance. On this basis, with the increase of PCBM doping content, its energy storage density and charge-discharge efficiency improved significantly. When PCBM doping content is 2wt%, PMMA/PVDF composite medium containing 3wt% BaTiO3 has excellent energy storage performance. When the electric field is 579.67 kV/mm, the discharge energy density reaches 15.60 J/cm3 and the charge-discharge efficiency is 75.30%. First proposed in this paper, based on a small amount of inorganic high dielectric organic molecules together semiconductor filler modified polymer film energy storage performance of the function, by adding a small amount of BaTiO3 particles, avoids insulation performance degradation caused by the high content of BaTiO3, and ensures the BaTiO3 particle on the properties of composite dielectric permittivity and polarization. At the same time, in order to further improve due to the low dielectric constant substrate with high dielectric constant BaTiO3 particles between the electric field distortion caused by the breakdown strength degradation, consider joining a certain amount of PCBM in a composite medium, use PCBM electron affinity ability, strong in composite medium build deep traps to capture and carrier, inhibit the transfer of carrier.The breakdown field strength of the composite medium is improved, so as to comprehensively improve the energy storage performance of the composite medium, which provides a new idea for the development of polymer composite medium with excellent energy storage performance.
  • 聚合物电介质薄膜凭借其低介电损耗、易加工成型、高击穿强度等优点,已广泛应用于医用除颤设备、柔性电子器件、脉冲功率系统、摩擦纳米发电机等[1-2]。随着混合电动汽车、油气勘探技术、航天电力系统的发展及应用环境的复杂化,对聚合物基电介质薄膜宽温域内的介电性能和击穿强度提出更高要求[3-4]。目前广泛使用的聚合物电介质薄膜为双向拉伸聚丙烯(BOPP),但由于BOPP的热稳定性欠佳,高温下的介电稳定性和击穿强度急剧下降,无法满足上述应用需求[5]

    为了制备高温、强电场等极端环境中具有良好稳定性的聚合物电介质薄膜,有学者选择具有高玻璃化转变温度(Tg)的芳香族聚合物,如聚酰亚胺(PI)、聚醚酰亚胺(PEI)、聚芳醚酮(PEEK)、聚芳醚脲(PEEU)等制备了高温电介质薄膜,但研究发现虽然其在高温、强电场环境中的介电性能保持稳定,但击穿强度迅速下降[6]。这可归因于温度场-电场耦合环境中芳香族聚合物分子结构中苯环的π-π耦合作用引起的高漏电流密度[7]。为了降低漏电流对芳香族聚合物电介质薄膜的影响,Duan等[8]将交联结构引入到PEI分子结构中制备不同交联度的c-PEI,交联结构在增加PEI内部电子陷阱能级和陷阱密度的同时,打破了分子结构的规整性,降低了π-π耦合效应,抑制了高温、强电场环境中漏电流的形成,所制备c-PEI高温下的击穿强度较非交联PEI显著提升。此外,采用密度泛函理论(DFT)分析发现,PI分子结构中酸酐上的苯环带有正电性,PEI分子中连接醚键的苯环带有负电性,因此,Zhang等[9]将PI和PEI共混,利用分子链间静电作用降低了PI和PEI分子链间距以及内部自由体积,所制备的PI-PEI共混薄膜的最高击穿强度超过1000 MV/m。但需要指出的是,由于聚合物的击穿强度(E)与其介电常数(ε)存在内禀矛盾关系(E~1/ε0.65),即击穿强度的提升往往伴随着介电常数的下降,进而影响到聚合物电介质薄膜储能特性的改善[10]。因此,如何制备同时具有高介电常数和高击穿强度的聚合物电介质薄膜是目前的研究热点。

    为了打破介电常数与击穿强度间的内禀矛盾,有学者基于不同聚合物功能层(极化层、绝缘层、过渡层等),通过调控空间组装工艺构筑了多层聚合物电介质薄膜[11]。在多层结构中,特殊的空间电场分布机制赋予绝缘层更高的电场强度,而极化层和多尺度界面结构则通过偶极子极化和Maxwell-Wagner-Sillars (MWS)界面极化提升了介电常数[12-13]。Wang等[14]通过PEI和聚(偏氟乙烯-三氟乙烯-三氟氯乙烯)(PTVC)构筑了顺式三层结构和反式三层结构的全有机聚合物电介质薄膜,研究发现顺式三层结构的最大击穿强度达到504 MV/m,并且介电常数在室温−100℃范围内保持稳定。但遗憾的是,目前多层结构电介质薄膜的研究大多局限于铁电聚合物,无法满足高温应用需求[11, 15]

    近期,Su等[16]采用去质子化法制备了芳纶纳米纤维(ANF)并抽滤得到ANFm,研究发现ANFm具有较高的介电常数和优异的高温稳定性,所制备的ANFm能够满足高温环境的应用需求,但由于ANFm表面粗糙度较高,易诱导空间电荷聚集,导致击穿强度较低。Vu等[17]基于ANF与氟化石墨烯(GF)制备了ANFm-GF电介质薄膜,结果表明,由于GF的高本征击穿强度(~1000 MV/m) ANFm-GF电介质薄膜在室温下最大击穿强度提升至507 MV/m。但在高温下,电极处注入的电子以及空间电荷在ANFm表面缺陷处的聚集诱导了电树枝的形成并引发电击穿,引起ANFm击穿强度迅速降低(<300 MV/m)[18]。因此,改善ANFm的表面粗糙度有助于提升其高温击穿强度。

    本文选用ANFm和可溶性PI,采用浸渍提拉法构筑了具有三明治结构的全有机PI-ANFm-PI (P-A-P)复合薄膜。ANFm具有较高的介电常数以及出众的热学稳定性能;PI具有极高的击穿强度和玻璃化温度,能够满足高温电介质材料的应用需求。研究结果发现,ANFm表面粗糙度的降低以及P-A-P复合薄膜内部电子-空穴对的构建有效抑制了漏电流的形成;同时ANFm的高极化率可为P-A-P复合薄膜提供高介电常数;本文通过分析P-A-P复合薄膜的介电性能、电导损耗和击穿强度以期为制备新型高温电介质薄膜提供新思路和新方法。

    芳纶(PPTA),日本帝人芳纶公司;二甲基亚砜(DMSO),分析纯,天津市科密欧化学试剂有限公司;聚酰亚胺(PI),型号P84,美国杜邦公司;KOH,纯度98%,阿拉丁试剂(上海)有限公司;N-甲基吡咯烷酮(NMP),分析纯,上海凌峰化学试剂有限公司。上述试剂直接使用,无需提纯。

    首先将剪切得到的PPTA短纤(长度约1 mm)分别用丙酮、乙醇超声处理30 min,以除去表面污染物;随后将0.08 g芳纶短纤分散于含有0.16 g KOH的40 mL DMSO∶H2O(体积比为25∶1)混合溶液中,室温下超声处理4 h后得到暗红色ANF/DMSO溶液。将适量去离子水加入到ANF/DMSO溶液中,高速搅拌后形成ANF胶体悬浮液,随后采用真空抽滤方法制备ANFm,并在80℃下干燥12 h。

    将PI粉末溶解于NMP中分别制备1wt%、3wt%、5wt%、7wt%和10wt%的PI溶液,随后将ANFm垂直浸渍于PI溶液中,并采用浸渍5 min,提拉静置1 min的方式循环5次;将浸渍得到的ANFm至于100℃中干燥12 h,并在10 MPa,180℃条件下热压5 min。为了方便描述所制备的PI-ANFm-PI (P-A-P)复合薄膜,根据溶液中PI的质量分数分别将P-A-P复合薄膜命名为P-A-P-1、P-A-P-3、P-A-P-5、P-A-P-7、P-A-P-10 (表1);单层ANF薄膜命名为ANFm。所制备的ANFm和P-A-P复合薄膜的厚度约为15 μm,PI单层厚度为0~0.2 μm。此外,需要指出的是,对比发现P-A-P-10中PI层的厚度反而略低于P-A-P-7,这可能是由于PI溶液浓度过高后,分子链间缠结点增加,导致黏附或进入ANFm的PI减少。ANFm和P-A-P复合薄膜的制备流程如图1所示。

    表  1  材料参数
    Table  1.  Materials parameters
    Samples outer
    layer
    Middle
    layer
    Thickness of
    sample/μm
    Concentration of
    PI solution/wt%
    P-A-P-1 PI ANF 14.7 1
    P-A-P-3 14.9 3
    P-A-P-5 15.2 5
    P-A-P-7 15.0 7
    P-A-P-10 14.6 10
    Notes: PI—Polyimide; ANF—Aramid nanofiber.
    下载: 导出CSV 
    | 显示表格
    图  1  芳纶纳米纤维薄膜 (ANFm)和PI-ANFm-PI (P-A-P)薄膜的制备流程图
    Figure  1.  Scheme of fabrication procedures for aramid nanofiber film (ANFm) and polyimide-ANFm-polyimide (P-A-P) films
    PPTA—Poly-p-phenylene terephthamide; NMP—N-methylpyrrolidone; DMSO—Dimethyl sulphoxide

    红外测试:采用Nicolet 6700型傅里叶变换红外光谱仪(FTIR,美国赛默飞世尔科技公司),测试波数范围为4000~500 cm−1。X射线衍射(XRD)测试:D/max-2550PC型,日本理学公司,靶材Cu,管电压40 V,管电流40 mA,扫描范围为5°~90°,波长0.154 nm。AFM测试:Dimension FastScan型,德国布鲁克公司,采用敲击模式,扫描范围2 μm×2 μm。SEM测试:S4800型场发射扫描电子显微镜,日本Hitachi公司。TEM测试:JEM-2100型透射电子显微镜,日本电子株式会社。介电性能测试:Concept 40型宽频介电阻抗谱仪,德国Novocontrol公司,频率范围101~106 Hz,测试温度分别为25℃和150℃。击穿强度测试:CS9916BX型程控超高压分析仪,南京长盛公司,每个样品测试12次,并通过Weibull分布拟合得到Weibull击穿强度。

    采用Gaussview5.0和Gaussian09 W计算了ANF和PI的电子结构和能级分布。在密度泛函理论(DFT)计算中,所用基组为B3LYP/6-31G(d),并且仅使用ANF和PI分子结构中的一个结构单元进行计算。通过Multiwfn程序分析了ANF和PI的静电势(ESP)分布[19-21]

    图2(a)为去质子化过程中ANF/DMSO分散液的光学图片,从图中可以看到,随着时间的增加,ANF/DMSO溶液的颜色逐渐变深,4 h后变为暗红色均相溶液。这是由于在KOH作用下,PPTA分子链上的氢原子逐渐去质子化,削弱了分子链间的氢键作用,PPTA纤维逐渐转变为ANF。Yang等[22]研究发现,由于PPTA分子链中π-π堆叠效应及分子链间范德华力相互作用,PPTA纤维无法完全溶解于DMSO,而是以纳米纤维的形式存在。从图2(b)中可以看到,所制备的ANF具有高长径比。上述结果表明,通过调控DMSO和H2O的比例能够在短时间内制备得到ANF,比仅采用纯DMSO溶剂制备ANF的方法更高效[16]。对比ANF与PPTA的FTIR谱图发现(图2(c)),ANF和PPTA中特征峰位置基本相同,表明采用去质子化方法制备的ANF化学结构没有发生明显变化,这有利于保持其高强度、高绝缘和高温稳定性能。图2(d)为ANF和PPTA的XRD图谱。在PPTA的XRD谱图中2θ=21.1°、23.5°和28.5°的特征峰分别对应(110)、(200)和(004)晶面;在ANF的XRD谱图中,只在2θ=21.1°处出现了(110)晶面的特征衍射峰,而(200)和(004)晶面的衍射峰强度显著下降,表明ANF内部晶体结构与PPTA一致,只是晶粒尺寸发生了变化[23]。采用谢乐公式(D=0.89λ/(βcosθ),其中D为晶粒尺寸,λ为波长,β为半峰宽,θ为衍射角)计算了PPTA和ANF的晶粒尺寸,结果发现PPTA中(110)晶面对应的晶粒尺寸为5.27 nm,而ANF中(110)晶面对应的晶粒尺寸降低至1.46 nm。晶粒尺寸的降低可归因于去质子化过程中分子链间氢键网络的破坏扰乱了PPTA分子链的规整排列,进而引起分子链从有序结构转变为无序结构[24]

    图  2  (a)去质子化过程中ANF/DMSO分散液的光学图片;ANF的TEM图像(b)、PPTA和ANF的红外光谱(c)和XRD谱图(d)
    Figure  2.  (a) Digital photos of an aramid nanofiber (ANF)/DMSO dispersion during deprotonation process; TEM image of ANF (b), FTIR spectra (c) and XRD patterns (d) of PPTA and ANF

    图3(a)展示了ANFm横截面形貌,从图中可以看到,ANFm呈现致密的珍珠层状结构,而P-A-P-3 (图3(b))和P-A-P-7 (图3(c))具有明显的三层结构,其中上下层为PI (箭头所示),中间层为ANFm,并且PI层和ANFm层结合紧密,没有明显的孔隙。图3(d)~3(f)分别为ANFm、P-A-P-3和P-A-P-7的表面形貌,其中,ANFm表面凹凸不平,纤维堆积结构明显;而随着PI溶液浓度的增加,P-A-P-3和P-A-P-7的表面逐渐光滑平整,缺陷明显减少。从ANFm、P-A-P-3和P-A-P-7 (图3(g)~3(i))的光学图片可知,随着PI溶液浓度的增加,薄膜的颜色逐渐加深,间接表明PI层的厚度逐渐增大。Luo等[25]研究发现,当电介质薄膜表面粗糙程度较高时,空间电荷以及越过电极/电介质界面势垒的电子会聚集在电介质薄膜的缺陷处,长时间累积后诱导电击穿的发生。因此,减少电介质薄膜的表面缺陷,有助于阻碍电极中电子的注入以及电树枝的形成与发展,在提升击穿强度的同时,降低内部漏电流密度。

    图  3  横截面形貌:ANFm (a)、P-A-P-3 (b)、P-A-P-7 (c);表面形貌:ANFm (d)、P-A-P-3 (e)、P-A-P-7 (f);光学图片:ANFm (g)、P-A-P-3 (h)、P-A-P-7 (i)
    Figure  3.  Cross-sectional morphologies of ANFm (a), P-A-P-3(b), and P-A-P-7 (c); Surface morphologies of ANFm (d), P-A-P-3 (e), and P-A-P-7 (f); Digital photos of ANFm (g), P-A-P-3 (h), and P-A-P-7 (i)

    击穿强度是影响聚合物电介质薄膜储能特性的关键参数之一。采用威布尔分布函数分析了ANFm和P-A-P复合薄膜在25℃和150℃时的击穿强度,如图4(a)4(b)所示。可以看到,在宽温域范围内,三层结构复合薄膜的击穿强度均优于单层ANFm,表明PI层有助于提升ANFm的击穿强度。在图4(c)中,P-A-P复合薄膜在25℃和150℃时击穿强度分别为259.8 MV/m和242.3 MV/m,而P-A-P-7复合薄膜在相同温度下的击穿强度达411.6 MV/m和350.7 MV/m,相较于ANFm提升了58.4%和44.7%。研究表明,在多层电介质材料中,绝缘层承担更高的电场强度,极化层提供高介电常数[26]。在本文中,上下PI层为绝缘层,ANFm层为极化层,当三层结构形成后,PI层承担更高的电场强度,ANFm层上的电场强度迅速下降。由于聚合物的击穿机制主要包括电-机械击穿、热击穿、电击穿等[27]。因此,提升聚合物的杨氏模量、导热性能和绝缘性能均有助于改善其击穿强度。从图4(d)中可知,随着PI层溶液浓度的增加,P-A-P复合薄膜的杨氏模量从ANFm的1.59 GPa增加至P-A-P-7的2.87 GPa,而P-A-P-10杨氏模量下降的原因可归因于PI层厚度的降低。由于聚合物击穿强度与其杨氏模量成正比关系,即E=0.606(Y/(εrε0))1/2 (E为击穿强度,εr为聚合物本征介电常数,ε0为真空介电常数,Y为杨氏模量)[28]。因此,杨氏模量的提升有助于抑制电-机械击穿的发生。从图4(e)可知,P-A-P复合薄膜的漏电流密度也随着PI浓度的增加逐渐降低,这不但抑制了P-A-P复合薄膜内部电击穿的发生,同时降低了内部漏电流引起的热效应,避免了热击穿的发生。图4(f)为ANFm、P-A-P-3和P-A-P-7击穿强度、漏电流密度和杨氏模量的雷达图,可以看到,P-A-P-7的杨氏模量和击穿强度最高,漏电流密度最低,表明PI层厚度的增加有助于优化ANFm的电学性能。

    图  4  ANFm和P-A-P复合薄膜25℃ (a)和150℃ (b)的击穿强度威布尔分布、25℃和150℃的击穿强度对比图(c)、力学性能(d)和漏电流密度(e);(f) ANFm、P-A-P-3和P-A-P-7薄膜击穿强度、漏电流密度和杨氏模量的雷达图
    Figure  4.  Weibull distribution of breakdown strength at 25℃ (a) and 150℃ (b), comparison of breakdown strength at 25℃ and 150℃ (c), mechanical properties (d), and leakage current density (e) for ANFm and P-A-P composite films; (f) Radar chart of breakdown strength, leakage current density, and Young's modulus for ANFm, P-A-P-3, and P-A-P-7 films
    E—Breakdown strength; P—Polarization intensity

    为了进一步分析ANFm和P-A-P复合薄膜漏电流密度变化的内在机制,采用密度泛函理论(DFT)分析了PI和ANF的电子轨道能级和静电势(ESP)分布。PI和ANF的ESP分布如图5(a)5(b)所示。可以看出,ANF的最高静电势达到45,而PI最高仅为20,表明ANF具有更强的吸引电子的能力,可以作为电子陷阱位点捕获电极处注入以及内部形成的自由电子[29]。在图5(c)中,PI的最高占据分子轨道(HOMO)能级为−6.01 eV,最低占据分子轨道(LUMO)能级为−3.27 eV,禁带宽度为2.74 eV;ANF的HOMO能级为−5.63 eV,LUMO能级为−1.99 eV,禁带宽度为3.64 eV。虽然PI的禁带宽度低于ANF,高温下易形成自由电子,但由于PI的LUMO能级与ANF的HOMO能级差别较小(2.36 eV),PI层的电子与ANF的空穴在库仑力的作用下形成电子-空穴对(图5(d)),并作为电子陷阱捕获空间电荷[30-31]

    图  5  PI (a)和ANF (b)的静电势分布及各静电势范围内的面积百分比;(c) PI和ANF的分子轨道能级示意图;(d)电子-空穴对的形成与作用机制
    Figure  5.  Electrostatic potential (ESP) distributions and normalized ESP area distribution statistics of PI (a) and ANF (b); (c) Molecular orbital energy levels of PI and ANF; (d) Formation and mechanism of action of electron-hole pairs
    LUMO—Lowest unoccupied molecular orbital; HOMO—Highest occupied molecular orbital

    ANFm和P-A-P复合薄膜的介电性能如图6所示。在图6(a)中,ANFm的介电常数高达7.2(102 Hz),这归因于ANF表面丰富的极性基团以及内部高偶极矩酰胺键(~3.7 D)的存在。此外,P-A-P复合薄膜的介电常数对频率的依赖性明显降低。由于聚合物介电常数主要源于空间电荷极化,偶极子极化,原子极化和离子极化;其中原子极化和离子极化发生在高频率范围内(>108 Hz)[32-33]。因此,本文中P-A-P复合薄膜介电常数主要源于空间电荷极化(<104 Hz)和偶极子极化(104~106 Hz)。在低频率范围内,PI层的形成不但抑制了界面处空间电荷的聚集,同时PI和ANF内部电子-空穴对以及分子链间氢键网络的构建阻碍了载流子的迁移,降低了P-A-P复合薄膜的空间电荷密度,因此,P-A-P复合薄膜在低频率范围内的空间电荷极化强度随着PI溶液浓度的增加逐渐降低。同时,PI层的形成还引起P-A-P复合薄膜介电常数的降低。另外,PI较低的介电常数也会引起P-A-P复合薄膜介电常数的下降[34]。介电损耗会将电介质电容器储存的电能转化为焦耳热,降低电介质薄膜的使用寿命和效率。图6(b)为ANFm和P-A-P复合薄膜介电损耗与频率的关系。可以看到,在频率范围内,随着PI溶液浓度的增加,P-A-P复合薄膜的介电损耗逐渐降低,表明PI层的形成有助于降低P-A-P复合薄膜服役过程中能量的损耗以及抑制热效应的形成。图6(c)为ANFm和P-A-P复合薄膜在频率范围内的交流电导率。ANFm和P-A-P复合薄膜的交流电导率均与测试频率呈良好的线性关系,表明其均具有优异的绝缘性能[35]。此外,10 Hz时,ANFm和P-A-P复合薄膜的交流电导率随着PI层厚度的增加不断下降,如样品的交流电导率从2.88×10−13 S/cm(ANFm)降至3.63×10−14 S/cm (P-A-P-7),说明PI层的形成有助于进一步提升P-A-P复合薄膜的绝缘性能。

    图  6  ANFm和P-A-P复合薄膜的介电常数(a)、介电损耗(b)和电导率(c);P-A-P-7在25℃和150℃下的介电常数(d)、介电损耗(e)和电导率(f)
    Figure  6.  Dielectric constant (a), dielectric loss (b) and conductivity (c) of ANFm and P-A-P films; Dielectric constant (d), dielectric loss (e) and conductivity (f) of P-A-P-7 at 25℃ and 150℃

    此外,在25℃和150℃时对比分析了P-A-P-7的介电性能。在图6(d)中,P-A-P-7在150℃时的介电常数均高于25℃时的介电常数,尤其是在102~103 Hz范围内提升显著。这是由于随着温度的升高,从电极处注入的电子以及被束缚的电子热激发形成自由电子引起空间电荷极化强度增大;同时,PI和ANF分子链段的运动能力也随着温度的升高逐渐增加,进而增强了偶极子的取向极化。在图6(e)中,当频率低于104 Hz时,P-A-P-7的电导损耗在150℃时增加显著,这主要源于空间电荷的增加。在25℃时,电极处的电子无法越过电极/电介质间的界面势垒进入电介质,同时PI和ANF形成的电子-空穴对以及分子链间的氢键网络均会抑制空间电荷的迁移;但150℃时,电极处的电子吸收热能越过界面势垒,同时被电子-空穴对束缚的电荷热激发形成自由电子,引起电导损耗迅速增大。在图6(f)中,10 Hz时,P-A-P-7的电导率从25℃时的3.63×10−14 S/cm增加至150℃时的1.45×10−12 S/cm,也进一步表明高温下漏电流密度的增加。但需要指出的是,虽然P-A-P-7在150℃时介电损耗和电导率均有所增大,但依然保持在较低的范围,满足电介质薄膜的使用要求。

    本文基于芳纶纳米纤维薄膜(ANFm)和聚酰亚胺(PI)溶液,采用浸渍提拉法构筑了具有三明治结构的全有机PI-ANFm-PI (P-A-P)复合薄膜,并研究了宽温域内P-A-P复合薄膜的击穿强度、电导损耗和介电性能,主要结论如下:

    (1) ANFm表面粗糙度的降低以及PI与ANF形成的电子-空穴对有助于降低P-A-P复合薄膜的漏电流密度,减低电导损耗;

    (2)随着PI浓度的增加以及内部漏电流密度的降低,P-A-P复合薄膜的在25℃和150℃下的击穿强度达411.6 MV/m和350.7 MV/m,较ANF薄膜分别提升了58.4%和44.7%;

    (3) PI层的形成提升了P-A-P复合薄膜的介电稳定性,并且介电损耗随着PI溶液浓度的增加逐渐降低,绝缘性能随着PI溶液浓度的增加逐渐增大。

  • 图  1   BaTiO3颗粒的SEM图像

    Figure  1.   SEM image of BaTiO3 particles

    图  2   不同BaTiO3含量的PMMA/PVDF-xwt%-BaTiO3共混复合薄膜的SEM图像:(a) 1wt%;(b) 2wt%;(c) 3wt%;(d) 4wt%

    Figure  2.   SEM images of PMMA/PVDF-xwt%-BaTiO3 blended composite films with different BaTiO3 contents: (a) 1wt%; (b) 2wt%; (c) 3wt%; (d) 4wt%

    图  3   PMMA/PVDF-xwt%-BaTiO3共混复合薄膜的XRD图谱

    Figure  3.   XRD patterns of PMMA/PVDF-xwt%-BaTiO3 blended composite films

    图  4   PMMA/PVDF-xwt%-BaTiO3共混复合薄膜的FTIR图谱

    Figure  4.   FTIR spectra of PMMA/PVDF-xwt%-BaTiO3 blend composite films

    图  5   PMMA/PVDF-xwt%-BaTiO3共混复合薄膜的电学性能:(a) 介电常数;(b) 介电损耗;(c) 漏电流密度;(d) 击穿场强

    Figure  5.   Electrical properties of PMMA/PVDF-xwt%-BaTiO3 blend composite films: (a) Dielectric constant; (b) Dielectric loss; (c) Leakage current density; (d) Breakdown field strength

    P—Failure probability

    图  6   PMMA/PVDF-xwt%-BaTiO3共混复合薄膜的极化性能:(a) 电位移-电场强度(D-E)曲线;(b) 最大极化(Dmax)和剩余极化(Dr)的柱状图分布

    Figure  6.   Polarization properties of PMMA/PVDF-xwt%-BaTiO3 blend composite films: (a) Electric displacement-electric field intensity (D-E) curves; (b) Histogram distribution of maximum polarization (Dmax) and residual polarization (Dr)

    图  7   PMMA/PVDF-xwt%-BaTiO3共混复合薄膜的储能性能:(a) 储能密度(Ue)和储能效率(η)变化规律;(b) 储能密度和储能效率的柱状图分布

    Figure  7.   Energy storage performance of PMMA/PVDF-xwt%-BaTiO3 blend composite film: (a) Changing rule of energy storage density (Ue) and energy storage efficiency (η); (b) Histogram distribution of energy storage density and energy storage efficiency

    图  8   PMMA-ywt%PCBM@PVDF-3wt%BaTiO3共混复合薄膜的SEM截面图像:(a) 1wt%PCBM;(b) 1.5wt%PCBM;(c) 2wt%PCBM;(d) 2.5wt%PCBM

    Figure  8.   SEM cross sections images of PMMA-ywt%PCBM@PVDF-3wt%BaTiO3 composite films: (a) 1wt%PCBM; (b) 1.5wt%PCBM; (c) 2wt%PCBM; (d) 2.5wt%PCBM

    图  9   PMMA-ywt%PCBM@PVDF-3wt%BaTiO3共混复合薄膜XRD图谱

    Figure  9.   XRD patterns of PMMA-ywt%PCBM@PVDF-3wt%BaTiO3 blend composite films

    图  10   PMMA-ywt%PCBM@PVDF-3wt%BaTiO3共混复合薄膜FTIR图谱

    Figure  10.   FTIR spectra of PMMA-ywt%PCBM@PVDF-3wt%BaTiO3 blend composite films

    图  11   PMMA-ywt%PCBM@PVDF-3wt%BaTiO3共混复合薄膜的电学性能:(a)介电常数;(b) 介电损耗;(c) 漏电流密度;(d) 击穿场强

    Figure  11.   Electrical properties of PMMA-ywt%PCBM@PVDF-3wt%BaTiO3 blend composite films: (a) Dielectric constant; (b) Dielectric loss; (c) Leakage current density; (d) Breakdown field strength

    图  12   PMMA-ywt%PCBM@PVDF-3wt%BaTiO3混复合薄膜的极化性能:(a) 位移-电场(D-E)曲线;(b) DmaxDr的柱状图分布

    Figure  12.   Polarization properties of PMMA-ywt%PCBM@PVDF-3wt%BaTiO3 blend composite films: (a) Displacement-electric field (D-E) curves; (b) Histogram distribution of Dmax and Dr

    图  13   PMMA-ywt%PCBM@PVDF-3wt%BaTiO3共混复合薄膜的储能性能:(a) 储能密度和储能效率变化规律;(b) 储能密度和储能效率的柱状图分布

    Figure  13.   Energy storage performance of PMMA-ywt%PCBM@PVDF-3wt%BaTiO3 blend composite films: (a) Energy storage density and energy storage efficiency; (b) Histogram distribution of energy storage density and energy storage efficiency

    表  1   聚甲基丙烯酸甲酯(PMMA)-ywt%[6, 6]-苯基C61丁酸甲酯(PCBM)@聚偏氟乙烯(PVDF)-xwt%BaTiO3样品的命名

    Table  1   Naming of polymethyl methacrylate (PMMA)-ywt%[6, 6]-phenyl C61 (PCBM)@Polyvinylidene fluoride (PVDF)-xwt%BaTiO3 samples

    Sample nameSubstratex/wt%y/wt%
    PMMA/PVDF-1wt%-BaTiO3 PMMA/PVDF 1 0
    PMMA/PVDF-2wt%-BaTiO3 PMMA/PVDF 2 0
    PMMA/PVDF-3wt%-BaTiO3 PMMA/PVDF 3 0
    PMMA/PVDF-4wt%-BaTiO3 PMMA/PVDF 4 0
    PMMA-1.0wt%PCBM@PVDF-3wt%BaTiO3 PMMA/PVDF-3wt%-BaTiO3 3 1.0
    PMMA-1.5wt%PCBM@PVDF-3wt%BaTiO3 PMMA/PVDF-3wt%-BaTiO3 3 1.5
    PMMA-2.0wt%PCBM@PVDF-3wt%BaTiO3 PMMA/PVDF-3wt%-BaTiO3 3 2.0
    PMMA-2.5wt%PCBM@PVDF-3wt%BaTiO3 PMMA/PVDF-3wt%-BaTiO3 3 2.5
    Notes: x—Mass fraction of BaTiO3; y—Mass fraction of PCBM.
    下载: 导出CSV

    表  2   具有不同BT含量的PMMA/PVDF-xwt%-BaTiO3共混复合薄膜的电学性能参数

    Table  2   Electrical properties of PMMA/PVDF-xwt%-BaTiO3 blended composite films with different BT contents 100 Hz

    SampleεtanδEb/(kV·mm−1)β
    PMMA/PVDF5.500.0586593.3912.55
    PMMA/PVDF-1wt%-BaTiO35.800.0531554.7612.04
    PMMA/PVDF-2wt%-BaTiO36.000.0543522.6710.20
    PMMA/PVDF-3wt%-BaTiO36.370.0584511.9611.51
    PMMA/PVDF-4wt%-BaTiO36.900.0601434.529.84
    Notes: ε—Dielectric constant; tanδ—Dielectric loss; Eb—Breakdown electric field; β—Shape parameter.
    下载: 导出CSV

    表  3   不同PCBM含量的PMMA-ywt%PCBM@PVDF-3wt%BaTiO3共混复合薄膜的电学性能参数

    Table  3   Electrical properties of PMMA-ywt%PCBM@PVDF-3wt%BaTiO3 blends with different PCBM contents 100 Hz

    SampleεtanδEb/(kV·mm−1)β
    PMMA/PVDF-3wt%-BaTiO36.370.0584511.9611.51
    PMMA-1wt%PCBM@PVDF-3wt%BaTiO36.570.0620531.7010.98
    PMMA-1.5wt%PCBM@PVDF-3wt%BaTiO36.780.0585563.8310.02
    PMMA-2wt%PCBM@PVDF-3wt%BaTiO37.060.0546579.6711.17
    PMMA-2.5wt%PCBM@PVDF-3wt%BaTiO37.290.0653490.9410.99
    下载: 导出CSV
  • [1]

    PRATEEK, THAKUR V K, GUPTA R K. Recent progress on ferroelectric polymer-based nanocomposites for high energy density capacitors: Synthesis, dielectric properties, and future aspects[J]. Chemical Reviews,2016,116(7):4260-4317. DOI: 10.1021/acs.chemrev.5b00495

    [2]

    HUANG X, SUN B, ZHU Y, et al. High-k polymer nanocomposites with 1D filler for dielectric and energy storage applications[J]. Progress in Materials Science,2019,100:187-225. DOI: 10.1016/j.pmatsci.2018.10.003

    [3]

    TAN D Q. The search for enhanced dielectric strength of polymer-based dielectrics: A focused review on polymer nanocomposites[J]. Journal of Applied Polymer Science,2020,137(33):49379. DOI: 10.1002/app.49379

    [4]

    ZHENG M S, ZHENG Y T, ZHA J W, et al. Improved dielectric, tensile and energy storage properties of surface rubberized BaTiO3/polypropylene nanocomposites[J]. Nano Energy,2018,48:144-151. DOI: 10.1016/j.nanoen.2018.03.049

    [5]

    ZHANG Y, ZHANG C, FENG Y, et al. Energy storage enhancement of P(VDF-TrFE-CFE)-based composites with double-shell structured BZCT nanofibers of parallel and orthogonal configurations[J]. Nano Energy,2019,66:104195. DOI: 10.1016/j.nanoen.2019.104195

    [6]

    ZHANG Y, ZHANG C, FENG Y, et al. Excellent energy storage performance and thermal property of polymer-based composite induced by multifunctional one-dimensional nanofibers oriented in-plane direction[J]. Nano Energy,2019,56:138-150. DOI: 10.1016/j.nanoen.2018.11.044

    [7]

    LIU G, FENG Y, ZHANG T, et al. High-temperature all-organic energy storage dielectric with the performance of self-adjusting electric field distribution[J]. Journal of Materials Chemistry A,2021,9(30):16384-16394. DOI: 10.1039/D1TA02668B

    [8]

    WANG Z, WANG T, WANG C, et al. Poly(vinylidene fluoride) flexible nanocomposite films with dopamine-coated giant dielectric ceramic nanopowders, Ba(Fe0.5Ta0.5)O3, for high energy-storage density at low electric field[J]. ACS Applied Materials & Interfaces,2017,9(34):29130-29139. DOI: 10.1021/acsami.7b08664

    [9]

    CHU B, ZHOU Y. Energy storage properties of PVDF terpolymer/PMMA blends[J]. High Voltage,2016,1(4):171-174. DOI: 10.1049/hve.2016.0062

    [10]

    CHI Q, ZHOU Y, YIN C, et al. A blended binary composite of poly(vinylidene fluoride) and poly(methyl methacrylate) exhibiting excellent energy storage performances[J]. Journal of Materials Chemistry C,2019,7(45):14148-14158. DOI: 10.1039/C9TC04695J

    [11]

    THAKUR Y, LEAN M H, ZHANG Q M. Reducing conduction losses in high energy density polymer using nanocomposites[J]. Applied Physics Letters,2017,110(12):122905. DOI: 10.1063/1.4979040

    [12]

    MACHUI F, LANGNER S, ZHU X, et al. Determination of the P3 HT:PCBM solubility parameters via a binary solvent gradient method: Impact of solubility on the photovoltaic performance[J]. Solar Energy Materials and Solar Cells,2012,100:138-146. DOI: 10.1016/j.solmat.2012.01.005

    [13]

    ZHANG C, ZHANG T, FENG M, et al. Significantly improved energy storage performance of PVDF ferroelectric films by blending PMMA and filling PCBM[J]. ACS Sustainable Chemistry & Engineering,2021,9(48):16291-16303.

    [14]

    ZHANG Y, CHI Q, LIU L, et al. PVDF-based dielectric composite films with excellent energy storage performances by design of nanofibers composition gradient structure[J]. ACS Applied Energy Materials,2018,1(11):6320-6329. DOI: 10.1021/acsaem.8b01306

    [15]

    SANG X, LI X, ZHANG D, et al. Improved dielectric properties and energy-storage densities of BaTiO3-doped PVDF composites by heat treatment and surface modification of BaTiO3[J]. Journal of Physics D: Applied Physics,2022,55(21):215501. DOI: 10.1088/1361-6463/ac4942

    [16]

    CAI X, LEI T, SUN D, et al. A critical analysis of the α, β and γ phases in poly(vinylidene fluoride) using FTIR[J]. RSC Advances,2017,7(25):15382-15389. DOI: 10.1039/C7RA01267E

    [17]

    MIAO B, LIU J, ZHANG X, et al. Ferroelectric relaxation dependence of poly(vinylidene fluoride-co-trifluoroethylene) on frequency and temperature after grafting with poly(methyl methacrylate)[J]. RSC Advances,2016,6(87):84426-84438. DOI: 10.1039/C6RA17977K

    [18]

    LI J, MENG Q, LI W, et al. Influence of crystalline properties on the dielectric and energy storage properties of poly(vinylidene fluoride)[J]. Journal of Applied Polymer Science,2011,122(3):1659-1668. DOI: 10.1002/app.34020

    [19]

    ELASHMAWI I S, HAKEEM N A. Effect of PMMA addition on characterization and morphology of PVDF[J]. Polymer Engineering & Science,2008,48(5):895-901.

    [20]

    SU J, ZHANG J. Recent development on modification of synthesized barium titanate (BaTiO3) and polymer/BaTiO3 dielectric composites[J]. Journal of Materials Science: Materials in Electronics,2018,30(3):1957-1975.

    [21]

    CHI Q, MA T, ZHANG Y, et al. Significantly enhanced energy storage density for poly(vinylidene fluoride) composites by induced PDA-coated 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 nanofibers[J]. Journal of Materials Chemistry A,2017,5(32):16757-16766. DOI: 10.1039/C7TA03897F

    [22]

    ZHU L, WANG Q. Novel ferroelectric polymers for high energy density and low loss dielectrics[J]. Macromolecules,2012,45(7):2937-2954. DOI: 10.1021/ma2024057

    [23]

    SUN L, SHI Z, WANG H, et al. Ultrahigh discharge efficiency and improved energy density in rationally designed bilayer polyetherimide-BaTiO3/P(VDF-HFP) composites[J]. Journal of Materials Chemistry A,2020,8(11):5750-5757. DOI: 10.1039/D0TA00903B

    [24]

    RU J, MIN D, LANAGAN M, et al. Energy storage properties of polyimide/BaTiO3 nanocomposite films and their breakdown mechanism in a wide content range[J]. Applied Physics Letters,2019,115(21):213901. DOI: 10.1063/1.5115766

    [25]

    LI Y, HO J, WANG J, et al. Understanding nonlinear dielectric properties in a biaxially oriented poly(vinylidene fluoride) film at both low and high electric fields[J]. ACS Applied Materials & Interfaces,2016,8(1):455-465. DOI: 10.1021/acsami.5b09368

    [26]

    YAO L, PAN Z, ZHAI J, et al. High-energy-density with polymer nanocomposites containing of SrTiO3 nanofibers for capacitor application[J]. Composites Part A: Applied Science and Manufacturing,2018,109:48-54. DOI: 10.1016/j.compositesa.2018.02.040

    [27]

    MARWAT M A, MA W, FAN P, et al. Ultrahigh energy density and thermal stability in sandwich-structured nanocomposites with dopamine@Ag@BaTiO3[J]. Energy Storage Materials,2020,31:492-504. DOI: 10.1016/j.ensm.2020.06.030

    [28]

    FENG Y, WU Y, XIE Y, et al. Tunable permittivity in polymer composites filled with Si-based semiconductors by regulating induced polarization[J]. Materials Science in Semiconductor Processing,2017,61:63-70. DOI: 10.1016/j.mssp.2016.12.029

    [29]

    YUAN C, ZHOU Y, ZHU Y, et al. Polymer/molecular semiconductor all-organic composites for high-temperature dielectric energy storage[J]. Nature Communications,2020,11(1):3919. DOI: 10.1038/s41467-020-17760-x

    [30]

    ARKHIPOV V I, REYNAERT J, JIN Y D, et al. The effect of deep traps on carrier hopping in disordered organic materials[J]. Synthetic Metals,2003,138(1-2):209-212. DOI: 10.1016/S0379-6779(02)01267-5

    [31]

    NENASHEV A V, VALKOVSKII V V, OELERICH J O, et al. Release of carriers from traps enhanced by hopping[J]. Physical Review B,2018,98(15):155207. DOI: 10.1103/PhysRevB.98.155207

  • 期刊类型引用(1)

    1. 刘晓军,战丽,邹爱玲,李志坤,赵俨梅,王绍宗. 纤维增强复合材料层间增韧技术研究进展. 复合材料科学与工程. 2022(01): 117-128 . 百度学术

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  • 收稿日期:  2022-07-24
  • 修回日期:  2022-08-27
  • 录用日期:  2022-09-04
  • 网络出版日期:  2022-09-13
  • 刊出日期:  2023-07-14

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