现代化工

现代化工 ›› 2025, Vol. 45 ›› Issue (12) : 204-209. DOI: 10.16606/j.cnki.issn0253-4320.2025.12.035

科研与开发

高导电高保湿几丁质-聚乙烯醇凝胶电解质柔性锌空气电池

李帆 ¹ ,
罗文龙 ² ,
贾中悦 ³ ,
诸葛祥群 ¹ ,
罗鲲 ¹

作者信息 +

Highly conductive and moisturizing chitin-polyvinyl alcohol gel electrolytes for flexible zinc-air batteries

Author information +

文章历史 +

Received		Published
2025-02-28		2025-12-20
Issue Date	Revised Date
2025-12-15	2025-02-28

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摘要

以几丁质(CHI)改性聚乙烯醇(PVA)制成复合凝胶电解质(PVA-CHI-5),将离子电导率提升至104 mS/cm,且在空气中暴露25 h水分损失小于15%。由PVA-CHI-5制成的FZABs峰值功率密度可达51 mW/cm²,循环使用寿命超60 h,明显优于PVA凝胶电解质FZABs,为高性能FZABs开发提供了新思路。

Abstract

Composite gel electrolyte,PVA-CHI-5,is synthesized through using chitin (CHI) to modify polyvinyl alcohol (PVA).Its ionic conductivity is increased to 104 mS/cm,and the moisture loss is less than 15% after it has been exposed in the air for 25 hours.Flexible zinc-air batteries (FZABs) prepared with the PVA-CHI-5 electrolyte exhibits a peak power density of 51 mW/cm²,a cycle life of more than 60 hours,which is significantly better than the FZABs prepared with PVA gel electrolyte,providing a new idea for the development of high-performance FZABs.

Graphical abstract

关键词

几丁质 / 柔性锌空气电池 / 凝胶电解质 / 聚乙烯醇

Key words

chitin / flexible zinc-air battery / gel electrolyte / polyvinyl alcohol

Author summay

李帆(1998-),女,硕士生,研究方向为电化学储能;罗鲲(1966-),男,博士,教授,博士生导师,研究方向为电化学储能与电池材料回收,luokun@cczu.edu.cn。

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School of Materials Science & Engineering, Changzhou University, Changzhou 213164, China), AuthorCompanyExt(id=1241417269072327597, tenantId=1226480274814496768, journalId=1226484258170171394, articleId=1240720232613900762, companyId=1241417269063938987, language=CN, country=null, province=null, city=null, postcode=null, companyName=null, departmentName=null, remark=1.常州大学材料科学与工程学院,江苏常州 213164)])])] 李帆,罗文龙,贾中悦,诸葛祥群,罗鲲. 高导电高保湿几丁质-聚乙烯醇凝胶电解质柔性锌空气电池[J]. 现代化工, 2025, 45(12): 204-209 DOI:10.16606/j.cnki.issn0253-4320.2025.12.035

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随着便携式和可穿戴电子设备的快速发展,灵活、轻便且高效的能源存储系统需求日益增长^[1-3]。柔性锌空气电池(flexible zinc-air batteries,FZABs)因高能量密度、环境友好性和成本低受到广泛关注,在柔性电子设备中的应用潜力巨大^[4-9]。目前,FZABs使用的凝胶电解质在离子导电率、机械柔性和电化学稳定性等方面仍有提升空间^[10-12]。为此,研究者提出了许多创新的凝胶电解质设计^[13-14]。例如,Wu等^[15]报道了一种具有快速自修复功能的导电水凝胶,通过将改性海藻酸钠与聚乙烯醇结合而获得,并引入氯化钠使水凝胶具有良好的导电性;Fan等^[10]制备了PVA-KOH GPE并应用于柔性锌空气电池(FZAB),该GPE具有较高的离子电导率(30.3 mS/cm)和良好性能,但在环境暴露下,水分和离子电导率损失影响了电池循环和放电性;左丹英等^[16]制备了基于MCC、HEC和PVA的蜂巢状三维网络GPE,所制GPE具有优异的力学性能(0.24 MPa)和离子电导率(58.5 mS/cm),显示出较好的循环稳定性和应用潜力。

本文中提出并研究了一种基于几丁质/聚乙烯醇复合凝胶电解质(PVA-CHI)的新型材料,以同时提升离子导电性、机械性能和柔性。通过实验验证,优化后的PVA-CHI-5表现出高达104 mS/cm的离子电导率,在空气中暴露25 h后的重量损失小于15%,展现出优异的电解质吸收和保持性能。进一步测试表明,采用该电解质的FZAB具有良好的电化学性能,峰值功率密度达51 mW/cm²,电池寿命超过60 h。该研究为开发兼具高效能量存储和柔性特性的锌空气电池提供了新方案。

1 实验部分

1.1 材料试剂

乙醇(纯度≥99.7%)、异丙醇(IPA,纯度 ≥99.7%)、丙酮(纯度≥99.5%)、炭黑(Vulcan XC-72)、醋酸锌[(CH₃COO)₂Zn,纯度≥99.0%]、几丁质(纯度≥99.7%)购自国药集团化学试剂有限公司。氢氧化钾(KOH,纯度≥90.0%)、氢氧化钾(NaOH,纯度≥90.0%)、尿素(纯度≥90.0%)购自上海阿拉丁生化科技股份有限公司。聚乙烯醇(PVA,分子质量约19 500)购自上海麦克林生化科技有限公司。四氧化三钴纳米颗粒(Co₃O₄,纯度 ≥99.5%)、锌箔(厚度0.3 mm)购自长沙春新能源科技有限公司。亲水碳布(WOS1002)购自昆山电子科技有限公司。所有水溶液均用去离子水(<0.055 μS/cm)配制。所有这些试剂均为分析纯,无需进一步处理。

1.2 几丁质/聚乙烯醇复合凝胶(PVA-CHI)的制备

1.2.1 CHI分散液制备

首先,将6.0 g NaOH和10.0 g尿素溶于80 mL水中。然后将2.25 g几丁质粉分散在上述溶剂中。在-20℃下保存24 h后,将溶液在室温下搅拌和解冻。在10 000 r/min下离心7 min消泡,得到澄清透明的碱性几丁质溶液。然后将样品浸泡在去离子水中以进行溶剂置换。每30 min更换一次去离子水,直到达到中性pH,得到几丁质分散液。

1.2.2 几丁质/聚乙烯醇复合凝胶(PVA-CHI)的制备

在90℃下将5 g PVA粉末缓慢加入到40 mL 3%、5%、7%几丁质分散液的溶液中,在450 r/min下搅拌1.5 h至溶液呈白色黏稠状。将混合物倒入模具中后放入冷冻室冷却10 h进行冷冻交联。随后,将制备的凝胶在6 mol/L KOH中浸泡8 h,即可得到PVA-CHI-3、PVA-CHI-5和PVA-CHI-7碱性凝胶聚合物电解质。制备过程如图1(a)所示。上述制备过程中不加入CHI制备的凝胶聚合物电解质记为Pure PVA。

1.3 表征

1.3.1 结构测试

利用场发射扫描电子显微镜(FESEM,SEU8010)研究了PVA-CHI的形态和结构。采用FTIR8400S型傅里叶变换红外光谱仪探究PVA-CHI中含有的官能团。使用电子万能试验机-10 kN(WDT-1010 KN)进行拉伸应变试验,拉伸间距 20 mm,拉伸速率为50 mm/min。

电化学阻抗谱(EIS)测试在电化学工作CHI 660上进行,将测试模式设置为交流阻抗模式,操作频率为0.1~100 kHz,电压幅值为5 mV,离子电导率计算公式为:

(1)

σ = l / (E S R * A)

其中,l、A分别代表参与测试的聚合物电解质的厚度、电解质与不锈钢片之间的接触面积,而等效串联电阻(ESR)的值可从交流阻抗谱图像与实轴的交点处获得。

1.3.2 凝胶聚合物电解质的环境稳定性测试

在50%相对湿度和室温条件下,采用精密电子天平,每隔5 h记录一次,分析浸泡在足量氢氧化钾电解液中的样品的解析过程。

PVA-CHI对电解液的解吸速率(M_t)根据以下公式进行计算:

(2)

M t = M 2 / M 1

其中,M₁为在电解液中充分吸收达到饱和时凝胶聚合物电解质的质量;M₂为电解液解吸后凝胶聚合物电解质的质量。

1.3.3 柔性锌空气电池的性能测试

首先,将碳布裁剪成1.5 cm×2 cm大小的片材,依次用丙酮、乙醇和去离子水冲洗,然后置于60℃的烘箱中烘干。通过将27 mg Co₃O₄、63 mg炭黑以及0.9 mL全氟磺酸树脂(Nafion)溶液加入到由 7.2 mL去离子水和1.8 mL异丙醇组成的混合液中,超声处理30 min来制备催化剂墨水。将该墨水以0.3 mg/cm²的质量负载量喷涂到经过预处理的碳布上,然后置于60℃的烘箱中烘干。

柔性锌空气电池测试是使用武汉蓝电(LAND)多通道测试系统(LAND CT2001A)进行的。对于充放电测试,截止电压范围设定为0.5~2.5 V,充电和放电的恒定电流密度均为3 mA/cm²,每次持续 10 min。完全放电测试保持3 mA/cm²的相同电流密度,截止电压为0.6 V。

2 实验结果与讨论

2.1 PVA-CHI凝胶的结构表征

图1(a)说明了PVA-CHI电解质的制备过程。首先,通过NaOH/尿素碱溶液处理得到几丁质分散液。随后,将PVA溶解于几丁质分散体系中,并在 -18℃的低温条件下进行冷冻交联。此过程中,PVA长链分子通过物理交联形成聚合物网络结构,而几丁质长链分子则在PVA基骨架内转化为另一层聚合物网络,最终形成双网络水凝胶。

采用ATR-FTIR表征PVA-CHI的化学成分和键合信息。如图1(b)所示,PVA在3 600~3 200 cm^-1处显示出特征性的宽峰,这归因于O—H伸缩振动。1 140 cm^-1处的峰为C—O伸缩振动,2 950 cm^-1和 2 910 cm^-1处的峰分别为—CH₂的不对称和对称伸缩振动。PVA中1 430 cm^-1处的峰是—OH弯曲振动的结果^[17]。引入几丁质后,可以清晰地观察到几丁质特有的酰胺吸收峰:酰胺Ⅰ带(1 663 cm^-1)和酰胺Ⅱ带(1 624 cm^-1),分别归因于C=O伸缩振动和C—N—H弯曲振动。图1(c)、(d)表示冷冻干燥后观察到的制备水凝胶的凝胶网络形态。由于冷冻干燥过程中冰晶的升华,PVA-CHI-5显示出相互连接的多孔结构。结果证实了三维多孔网络结构的形成,可以看出,纳米甲壳素的加入使PVA凝胶形成更致密的网络结构,有助于提高PVA水凝胶的机械强度^[5-6,18-19]。

2.2 PVA-CHI的性能分析

在凝胶聚合物电解质中,离子电导率、保水率和抗拉强度是很关键的参数,对整体电池的放电电压、工作寿命和功率输出等有着很大的影响。为了定量评价PVA-CHI的机械性能,进行了拉伸应力-应变试验。图2(a)展示了不同比例PVA-CHI复合材料与纯PVA的抗拉强度测试结果。由于PVA和CHI链之间丰富的氢键相互作用和物理纠缠,当电解液吸收50%时,PVA-CHI-5的拉伸应力(285 kPa)和断裂应变(248%)与Pure PVA(175 kPa,176%)相比大大改善。所获得的PVA-CHI-5最大伸长率高达245%,这意味着其在各种变形下具有较好的柔韧性。通常,由纳米填料引起的复合材料机械强度的增强会导致韧性降低,从而导致断裂应变的减少。值得注意的是,在PVA中引入CHI不仅显著提高了拉伸应力(285 kPa),而且将断裂应变提高到248%。PVA-CHI电解质力学性能的增强主要归因于双网络结构中强烈而紧密的相互作用。一方面,富含羟基的几丁质通过氢键增强与PVA网络之间的相互作用,有效地将能量耗散到整个网络中,实现坚韧而有弹性的网络;另一方面,具有高面内模量的几丁质还可以增强聚合物基体以实现高机械强度^[20]。随着几丁质引入增多,过量的几丁质提高了水凝胶的交联密度,这导致在拉伸过程中水凝胶中的应力集中^[21]。

考虑到有效的电解质保留有助于稳定电解质-电极界面并提高FZABs的循环稳定性,还在周围环境中评估了不同凝胶的电解质保留能力。图2(b)展示了不同比例PVA-CHI复合材料与Prue PVA在不同时间(0~25 h)内的保水率。纯PVA的初始保水率接近100%,但在25 h后下降至约40%。相比之下,PVA-CHI复合材料的保水率明显优于纯PVA。PVA-CHI-3的初始保水率略高于纯PVA,但下降较快。PVA-CHI-5和PVA-CHI-7表现出更强的保水能力,其中PVA-CHI-5在空气中暴露25 h后仍保持85%以上的水分。这表明,CHI的高吸湿性以及与PVA之间的分子间氢键作用显著提高了凝胶电解质的水分保持能力,从而增强了长期稳定性和实用性。

由于离子电导率在电池的电化学性能中起着至关重要的作用,因此进一步应用交流阻抗测试来评估不同凝胶在电解质充分溶胀后的离子电导率^[22-24]。将水凝胶置于纽扣电池壳内,组装并测试了不同比例的PVA-CHI复合材料与纯PVA的电化学阻抗谱(EIS)及离子电导率(单位mS/cm),测试结果如图2(c)、(d)所示。纯PVA的离子电导率最低,仅为76 mS/cm。随着CHI比例的增加,离子电导率先升高后降低,PVA-CHI-5的离子电导率最大,达到104 mS/cm。相较之下,PVA-CHI-3和PVA-CHI-7的离子电导率较低,分别为88、96 mS/cm。结果表明,适量的几丁质添加能够显著提高离子电导率,这可能归因于几丁质增强了凝胶网络的结构稳定性和离子通道的形成。

2.3 柔性锌空气电池的性能分析

PVA-CHI Gels在FZAB中的实际应用通过三明治结构电池配置进行评估,该电池配置是通过在锌阳极和装有商用Co₃O₄的空气阴极之间夹接电解质制成的催化剂。从图3(a)可以看出,当该催化剂组装成电池后,通过电化学反应能够有效释放电能,从而为电子设备提供电力支持,实现充电功能。图3(b)展示了使用不同PVA-CHI凝胶电解质(PVA-CHI-3、PVA-CHI-5、PVA-CHI-7)以及纯PVA组装的柔性锌空气电池的奈奎斯特图。通过EIS阻抗图可以看出,不同凝胶的界面电阻存在显著差异。纯PVA的界面电阻最大,表现出最差的离子传导性。相比之下,PVA-CHI-5的界面电阻最小,显示出最佳的离子传导性能。PVA-CHI-7和PVA-CHI-3的阻抗介于两者之间,表明离子传导性有所提升,但仍不如PVA-CHI-5优异。

图3(c)展示了放电极化曲线和功率密度曲线的测试结果。使用PVA-CHI-5凝胶电解质时,功率密度达到51 mW/cm²,表现出最佳性能,表明其在高电流密度下依然能保持良好的电化学稳定性。PVA-CHI-3和PVA-CHI-7的性能分别为35、43 mW/cm²,虽然有所下降,但仍明显优于纯PVA(30 mW/cm²)。图3(d)展示了全放电测试的结果,使用PVA-CHI-5凝胶电解质的放电时间最长,达 58 h,表明其具备出色的储能性能和离子传导能力。PVA-CHI-7和PVA-CHI-3的放电时间分别为46、34 h,性能略逊一筹。纯PVA的放电时间最短,仅为25 h,电化学性能较差。图3(e)展示了在相同电流密度下,基于PVA-CHI-5的放电电压高于基于PVA-CHI-3、纯PVA以及PVA-CHI-7的放电电压。此外,在经历从0.5 mA/cm²到9 mA/cm²的不同放电电流密度速率性能测试循环后,PVA-CHI-5组装的FZAB仅表现出0.17 V的放电平台下降。这表明PVA-CHI-5在倍率性能方面具有优异的表现。图3(f)展示了充放电稳定性测试的结果,使用PVA-CHI-5凝胶电解质的电压平台最为稳定,循环过程中几乎没有明显衰减,且循环时间最长(64 h),表明其具有最佳的长期稳定性。PVA-CHI-3和PVA-CHI-7的循环时间分别为31、42 h,虽然低于PVA-CHI-5,但依然优于纯PVA。纯PVA的电压衰减最快,循环时间最短(25 h),显示其循环稳定性最差。

综上所述,PVA-CHI-5凝胶电解质在界面阻抗、放电时间、功率密度、能量密度及循环稳定性等电化学性能测试中均表现优异,适合作为高性能柔性电解质材料的候选材料。而纯PVA性能较差,仅能作为基体材料,需通过改性显著提升其性能^[25]。

3 结论

提出了一种简便且高效的几丁质/聚乙烯醇复合凝胶电解质(PVA-CHI)的合成策略。通过构建基于亲水网络与几丁质间丰富的物理缠结及超分子相互作用的复合结构,优化后的PVA-CHI-5展现出优异的性能,表现出高达104 mS/cm的离子电导率,并在空气中暴露25 h后重量损失低于15%,归因于其卓越的电解质吸收和保持能力。作为准固态电解质,PVA-CHI-5显著提升了柔性锌空气电池(FZABs)的电化学性能和结构稳定性,其峰值功率密度达到51 mW/cm²,电池寿命超过60 h,展现出卓越的耐久性、成本效益和生产可行性。这些研究成果为未来高性能凝胶电解质的设计提供了重要指导,并为高效稳定的柔性锌空气电池的开发奠定了坚实基础。

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