纳米技术  >> Vol. 9 No. 3 (August 2019)

水系固态锌离子电池的制备与电化学性能研究
Preparation and Electrochemical Performance of Water-Based Solid-State Zinc Ion Batteries

DOI: 10.12677/NAT.2019.93009, PDF, HTML, XML, 下载: 687  浏览: 2,744  科研立项经费支持

作者: 袁 怡, 周永恒, 徐智渊, 张 雄*, 张传坤, 马亚楠, 曹明磊:湖北汽车工业学院理学院,湖北 十堰

关键词: 纳米α-MnO2锌离子电池固态电解质Nano α-MnO2 Zinc Ion Battery Solid Electrolyte

摘要: 水系固态锌离子电池(ZIB)因具有安全、柔性和低成本的特点,在可穿戴电子设备能源领域备受关注。开发具有高锌离子迁移率的固态电解质是水系固态锌离子电池研究的热点之一。本文以明胶、过硫酸钾、丙烯酰胺和 N,N’-亚甲基双丙烯酰胺为原料,采用自由基聚合反应,将聚丙烯酰胺枝接到明胶上,制备得到一种高机械强度和锌离子迁移率(0.37 mS•cm−1)的水系固态凝胶电解质。并以水热法制备得到的α-MnO2为正极材料,电沉积法合成的锌为负电极,组装得到三明治构型的水系固态锌离子电池。在3333 mA/g电流密度下首次放电比容量达到231.5 mAh/g,307 mA/g电流密度下最高比容量达314 mAh/g。
Abstract: The water-based solid state zinc ion battery (ZIB) has attracted much attention in the energy field of wearable electronic devices because of its safety, flexibility and low cost. The development of solid electrolytes with high zinc ion mobility is one of the hotspots for water-based solid state zinc ion batteries. In this paper, gelatin, potassium persulfate, acrylamide and N,N’-methylenebisacrylamide were used as raw materials, and the solid hydrogel electrolyte was prepared through grafting polyacrylamideonto gelatin via free radical polymerization method. The α-MnO2 fabricated by hydrothermal method was used as the positive electrode material, and the zinc synthesized by electrodeposition method was used as negative electrodematerial. As a result, a water-based solid zinc ion battery with a sandwich configuration was assembled. High ionic mobility of 0.37 mS•cm−1 was computed out from the electrochemical impedance spectroscopy. And at the current density of 3333 mA/g, the first specific discharge capacity reached 231.5 mAh/g, and the highest specific capacity at 307 mA/g current density reached 314 mAh/g.

文章引用: 袁怡, 周永恒, 徐智渊, 张雄, 张传坤, 马亚楠, 曹明磊. 水系固态锌离子电池的制备与电化学性能研究[J]. 纳米技术, 2019, 9(3): 79-85. https://doi.org/10.12677/NAT.2019.93009

1. 引言

环境和能源问题日益突出,因而新型绿色能源及装置的开发和使用成为当前的研究热点 [1] [2] 。随着柔性可穿戴电子设备的发展,人们对其能源存储设备提出了更高的要求,柔性、安全兼具高电化学性能和低成本的电池成为研究的焦点 [3] [4] [5] [6] 。当前,多种电化学储能设备(铅蓄电池、锂离子电池和超级电容器等)由于其固有的不足,例如体积笨重、价格昂贵、能量密度低等,这些极大地限制了它们在柔性电子设备上的实际应用 [7] - [13] 。相比传统的刚性电池,柔性器件所需的柔性储能设备还需具备良好耐磨损性和耐弯折性,因而其安全问题更加严重 [14] 。自锌/二氧化锰电池发明以后,凭借其高能量、功率密度和低成本以及环境友好等特点,迅速引起了人们的广泛关注 [15] [16] [17] [18] 。最近,据文献报道,研究者们将此经典的锌/二氧化锰一次电池转变成了一种高度可逆的二次电池,即锌离子电池。锌离子电池被认为是锂离子电池最具竞争力的替代品之一 [19] [20] [21] 。

水系固态锌离子电池有望解决有机电解质和刚性电池的固有安全问题,并且由于具有较高的能量与功率密度等特点,其在柔性设备储能装置领域展现出极大的应用潜力。然而,由于高锌离子导电固态电解质的缺乏,水系固态锌离子电池一直难以实现优异的电化学性能。针对此问题,本文以ZnSO4、MnSO4、明胶、过硫酸钾、丙烯酰胺和N,N’-亚甲基双丙烯酰胺为原料,采用自由基聚合反应,将聚丙烯酰胺枝接到明胶上,开发制备得到一种高机械强度和锌离子迁移率的水系固态电解质。在此基础上,以水热法合成的α-MnO2为正极材料,电沉积法制备得到的锌为负电极材料,组装得到三明治构型的水系固态锌离子电池。在3333 mA/g电流密度下首次放电比容量达到231.5 mAh/g,307 mA/g电流密度下最高比容量达314 mAh/g。

2. 实验部分

2.1. 水系固态凝胶电解质的制备

采用自由基聚合法制备水系固态凝胶电解质,其制备流程如图1所示。首先,将2 g明胶(照相级,阿拉丁)加入到20 mL的2.77 mmol/L K2S2O8 (分析纯,阿拉丁)、ZnSO4 (1 mol/L)和MnSO4 (0.1 mol/L)的混合溶液中,在60℃下油浴加热并搅拌至完全溶解。然后,加入2.11 mol/L丙烯酰胺(分析纯,阿拉丁)和4.86 mmol/L N,N’-亚甲基双丙烯酰胺(化学纯,阿拉丁),并在40℃下搅拌2 h,得到水系固态电解质。接着,将洁净100%棉织物(2 cm *2 cm)放入胶体溶液中在60℃下搅拌2 h~3 h,取出织物将其浸泡在1 mol/L ZnSO4和0.1 mol/L MnSO4混合溶液中10 h~12 h,得到电解质混合隔膜,待用(制备得到的电解质溶液如图2(a),冷却后凝胶电解质如图2(b)所示)。

Figure 1. Flow chart for the preparation of an aqueous solid electrolyte

图1. 水系固态电解质的制备流程图

Figure 2. (a) (b) Aqueous solid gel electrolyte; (c) Battery assembly schematic diagram

图2. (a) (b) 水系固态凝胶电解质;(c) 电池组装示意图

2.2. 正极材料的制备

采用简易水热法制备二氧化锰纳米棒,组装正极。首先,配置0.08 mol/L Mn(CH3COO)2·4H2O (分析纯,阿拉丁)溶液,并将此溶液滴加入80 mL的0.1 mol/L KMnO4溶液中,搅拌0.5 h后。然后,取上述混合溶液75 mL加入到100 mL的反应釜中,在120℃下分别保温9 h、12 h、15 h、18 h、21 h、24 h,反应结束后在自然条件下冷却。接着,采用离心分离法对反应后的溶液进行处理,得到黑色粉末并将其放置在60℃的真空干燥箱中12 h。最后,按照MnO2:乙炔黑质量比75:25混合,并将其涂敷在2 cm *2 cm的泡沫镍片上,在60℃下真空干燥处理12 h,得到正极。

2.3. 负极材料的制备

采用电沉积法制备锌电极。首先,剪取2 cm *3 cm铜箔(锂电池级)使用去离子水、无水乙醇清洗数次。然后,以铜箔作为阴极,纯锌片(99.994%主成分含量)作为阳极,采用双电极法(安捷伦E3631A恒流源仪),在0.01 A/cm2电流密度下沉积3000 s,得到负极。

2.4. 锌离子电池的组装

在空气中,按照MnO2正极、电解质混合隔膜和锌负极顺序依次叠放组装得到锌离子电池,组装示意图如图2(c)所示。

3. 材料表征

二氧化锰的XRD分析及形貌表征

图3描述的是采用水热法在不同反应时间(9 h、12 h、15 h、18 h、21 h、24 h)下合成的MnO2的XRD图谱。从图中可以看出,所有样品的XRD图谱在12.75˚、18.06˚、28.64˚和37.77˚四处有明显的衍射峰,分别对应着晶面(110)、(200)、(310)和(121),与标准卡片α-MnO2 (PDF#72-1982)的四个主峰相对应。这表明本文中采用水热法合成的产物是MnO2,且其主相为四方相,即α-MnO2图4(a)、图4(b)为不同放大倍数下α-MnO2的SEM图,图中样品为水热反应9 h制备得到的α-MnO2。从图中可以看出,水热法合成的α-MnO2形貌为纳米棒,其直径约40 nm,长度约2 μm。

Figure 3. XRD patterns of MnO2 synthesized by hydrothermal method at different reaction times (9 h, 12 h, 15 h, 18 h, 21 h, 24 h)

图3. 不同反应时间(9 h、12 h、15 h、18 h、21 h、24 h)下水热法合成的MnO2的XRD图谱

Figure 4. Scanning electron microscope (SEM) image of MnO2 at different magnifications

图4. 不同放大倍数下MnO2的扫描电子显微镜(SEM)图

4. 电化学性能测试与分析

图5(a)为样品组装成标准纽扣电池通过电化学工站(上海辰华公司CHI660e)两电极测试方法下在1 mV/s、2 mV/s、5 mV/s的扫描速率下形成的循环伏安曲线,正极为α-MnO2材料(正极连接工作电极),负极使用铜箔镀锌材料(负极连接对电极和参比电极),电压窗口为0.9 V~1.85 V。锌离子电池的能量存储原理涉及到Zn2+在α-MnO2 2 × 2孔道中嵌入与吸附过程,其电池反应机理可以表示为 [22] :

MnO 2 + 1 2 Zn + 1 6 ZnSO 4 + x 6 H 2 O MnOOH + 1 6 ZnSO 4 [ Zn ( OH ) 2 ] 3 xH 2 O

Figure 5. (a) Cyclic voltammetry curves of zinc ion batteries at different scan rates; (b) Constant current charge and discharge curves of samples at different current densities; (c) Nyquist curves of sample AC impedance, the illustration is high frequency Area enlargement diagram and circuit simulation equivalent diagram

图5. (a) 锌离子电池在不同扫描速率下的循环伏安曲线;(b) 样品在不同电流密度下进行的恒电流充放电曲线;(c)样品交流阻抗的Nyquist曲线,插图为高频区放大图及电路模拟等效图

不同扫描速率下的CV曲线显示出明显的氧化还原峰,与基于水系电解质的传统锌离子电池CV曲线基本相同(如图5(a)所示)。还原峰的位置为1.25 V,主要原因是α-MnO2转变成MnOOH以及Zn随之被氧化成Zn2+;氧化峰的位置为1.7 V,其形成则主要归因于MnOOH转变为α-MnO2并伴随Zn2+还原成Zn。图5(b)描述的是锌离子电池在307 mA/g (1C)、615 mA/g (2C)和1.535 A/g (5C)电流密度下的恒电流充放电曲线,可以看出电池具有明显的充放电平台,根据比能量计算公式1 (C为比容量(mAh/g),I为放电电流大小(mA),t为放电时间(h),m为活性物质的质量(g))计算得到其对应的比容量分别为314 mAh/g、222.4 mAh/g和197.2 mAh/g。这说明该电池拥有良好的比容量及倍率性能。电化学阻抗谱可以用来较好地解释锌离子电池良好电化学性能的起因,如图5(c)所示。从该图可以明显地看出,电化学阻抗谱主要由两部分组成:中高频区域的半圆和低频区域的斜线。半圆展现的是SEI膜和界面电荷的传输特性,而斜线描述的是Zn2+在电极材料中的扩散行为。我们采用Zview软件,对电化学阻抗数据进行拟合,得到拟合电路图,如图5(c)中插图所示。拟合后,得出Rs和Rct值分别为4.9 Ω和71 Ω。对其电化学阻抗谱分析,公式(2) (d为电池隔膜厚度(cm),Rs是指欧姆电阻(Ω),Rct是指界面电荷转移电阻(Ω),A电池隔膜面积(cm−2))计算求得离子电导率为0.37 mS∙cm−1

C = I · t / m (1)

σ = d ( R c t R s ) 1 · A 1 (2)

本文采用简易水热法,以Mn(CH3COO)2·4H2O和高锰酸钾为原料,制备得到的长约2 μm和直径约40 nm的α-MnO2纳米棒,并以此作为正极材料;采用电镀法,以铜箔为基底,得到电镀锌作为负极材料;采用自由基聚合反应法,将聚丙烯酰胺枝接到明胶上,制备得到水凝胶,作为固态电解质。在此基础上,组装得到水系固态锌离子电池。在307 mA/g电流密度下,获得高达314 mAh/g的比容量,展现出良好的电化学性能,在柔性电子储能电源领域具有极大的应用潜力。

基金项目

感谢湖北高校2018年省级大学生创新创业训练计划项目(项目编号:201810525055, 201810525050)对本文的资助。

NOTES

*通讯作者。

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