【作者】 张帅；

【导师】 武长城； 李贺；

【作者基本信息】 天津工业大学 ， 材料与化工（专业学位）， 2023， 硕士

【摘要】 超级电容器是一款高功率密度与长循环寿命的电化学储能装置,被广泛应用于军工、储能、交通等多个领域。与其他常见的储能器件相比,受限于双电层电容器物理吸附的电荷储能机制,其较低的能量密度严重限制其在储能领域的应用,因此如何在保持优点的同时提高其能量密度就成为如今研究的热点。现今市场上的电解液与电极材料种类繁多,然而对于如何充分发挥这些电解液与电极材料性能却少有研究。本文从电解液离子尺寸大小的角度入手,首先构造不同阳离子与阴离子尺寸的电解液对照组,探究电容器电极电势分配不均对电压的影响,然后通过对电容器构型的调整对提高工作电压,最终实现超级电容器能量密度的提升。首先选择性的合成N,N-二甲基吡咯烷四氟硼酸盐（DMP-BF₄）与二氟草酸硼酸双螺环季铵盐（SBP-DFOB）两种电解质盐。在常规浓度1mol L^-1的PC溶剂中,分别单独配置阴离子相同而阳离子不同（TEA-BF₄、SBP-BF₄、DMP-BF₄）与阳离子相同而阴离子不同（SBP-BF₄、SBP-DFOB）的二组电解液。电化学数据表明不同阳离子尺寸的对照组中,DMP-BF₄电解液具有更优异的电容性能,不同阴离子尺寸的对照组中,SBP-DFOB电解液具有3.4V的高工作电压;结合分子轨道能级模拟计算与实际电化学窗口测试分析发现,PC体系中电解液还原与氧化电位是由阴离子与PC分子决定的,阳离子尺寸变化对电化学窗口的贡献明显小于阴离子变化。三电极数据分析发现,不同种类的电解液均表现出正负极电位分配不均的现象,且阴阳离子尺寸差异越大,分配不均现象越明显。在第一章的基础上,为改善正负极电位分配不均现象并进一步提高工作电压,选取正负极电位分布区间最为均匀的N,N-二甲基吡咯烷四氟硼酸盐（DMP-BF₄）电解液,通过三电极装置测得1mol L^-1的DMP-BF₄/PC电解液理论最高耐受工作电压为3.2V。通过构造正负极质量比为1:1、1:1.1、1:1.2、1:1.3的非对称型超级电容器,通过质量调控来改变电极的相对容量,进而影响两个电极的电位增长速率,平衡正负极的电势分配。发现当正负极电极质量比为1:1.2时,可达到3.2V的理论工作电压窗口,在3.2V、1A g^-1的电流密度下充放电10000圈容量保持率达87.8%,器件单电极的最高能量密度和功率密度分别可达40.1Wh kg^-1与18.7k W kg^-1,实现能量密度的大幅提高。更多还原

【Abstract】 Supercapacitors are an electrochemical energy storage device with high power density and long cycle life,widely used in various fields such as military industry,energy storage,and transportation.Compared with other common energy storage devices,the low energy density of double layer capacitors,which are limited by the charge storage mechanism of physical adsorption,seriously limits their application in the field of energy storage.Therefore,how to improve their energy density while maintaining their advantages has become a hot research topic nowadays.There are many types of electrolytes and electrode materials in the current market,but there is little research on how to fully utilize the performance of these electrolytes and electrode materials.This article starts from the perspective of electrolyte ion size.Firstly,a control group of electrolytes with different cation and anion sizes is constructed to explore the impact of uneven distribution of capacitor electrode potential on voltage.Then,by adjusting the capacitor configuration,the working voltage is improved,and finally,the energy density of supercapacitors is improved.Firstly,two electrolyte salts,N,N-dimethylpyrrolidine tetrafluoroborate（DMP-BF₄）and difluorooxalate borate bisspirocyclic quaternary ammonium salt（SBP-DFOB）,were selectively synthesized.In a conventional concentration of 1mol L^-1 PC solvent,two sets of electrolytes with the same anions but different cations（TEA-BF₄,SBP-BF₄,DMP-BF₄）and the same cations but different anions（SBP-BF₄,SBP-DFOB）were prepared separately.Electrochemical data shows that DMP-BF₄ electrolyte has better capacitive performance in control groups with different cation sizes,while SBP-DFOB electrolyte has a high working voltage of 3.4V in control groups with different anion sizes;Combined with molecular orbital energy level simulation calculation and actual electrochemical window test analysis,it is found that the reduction and oxidation potential of electrolyte in PC system is determined by anions and PC molecules,and the contribution of cation size change to the electrochemical window is significantly less than that of anion change.Three electrode data analysis found that different types of electrolytes exhibit uneven distribution of positive and negative electrode potentials,and the larger the difference in the size of negative and positive ions,the more obvious the uneven distribution phenomenon.On the basis of Chapter 1,in order to improve the uneven distribution of positive and negative electrode potentials and further increase the working voltage,the N,N-dimethylpyrrolidine tetrafluoroborate（DMP-BF₄）electrolyte with the most uniform distribution range of positive and negative electrode potentials was selected.The theoretical maximum withstand working voltage of 1mol L-1 DMP-BF₄/PC electrolyte was measured through a three electrode device,which was 3.2V.By constructing asymmetric supercapacitors with a mass ratio of 1:1,1:1.1,1:1.2,and 1:1.3 for positive and negative electrodes,the relative capacity of the electrodes is changed through mass control,thereby affecting the potential growth rate of the two electrodes and balancing the potential distribution between the positive and negative electrodes.It was found that when the mass ratio of positive and negative electrodes is 1:1.2,a theoretical working voltage window of 3.2V can be reached.At a current density of 3.2V and 1A g^-1,the capacity retention rate of 10000 cycles of charging and discharging reaches 87.8%.The highest energy density and power density of a single electrode of the device can reach40.1Wh kg^-1 and 18.7k W kg^-1,respectively,achieving a significant increase in energy density.更多还原