【作者】 袁涛；

【导师】 姚春丽；

【作者基本信息】 北京林业大学 ， 生物质能源与材料， 2024， 博士

【摘要】 竹材作为我国产量最丰富的木质纤维素原料之一,对其在储能器件如超级电容器（SC）上的应用进行研究,不仅有利于缓解环境污染与能源枯竭问题,实现“双碳”目标的突破,同时也有利于高效储能器件向可持续能源的转型,但由于纤维素纳米材料其本身的绝缘特性以及与导电材料间的界面不稳定性,限制了其在电极材料中的应用,因此,如何将纤维素纳米材料与导电材料高效结合,以此制备高性能超级电容器是本文的研究重点。本文从纳米纤维素基导电材料的选择和复合材料的构筑出发,成功制备了具有高性能的纳米纤维素基复合电极材料。同时,也对该复合材料及其组装的超级电容器的各项性能进行了深入研究。主要结论如下:以低共熔溶剂（DES）体系制备得到的纤维素纳米纤丝（CNF）为基体,采用超声制备法,将镓铟液态金属材料（GI）和MXene材料结合以及CNF结合,制备得到CNF/MXene/GI柔性复合电极材料（CMG）,探讨了复合电极材料各项性能,将电极材料组装成对称柔性超级电容器并探究了其在储能器件中的应用。结果表明,CNF/MXene/GI薄膜在1 mA·cm^-2时具有871.3 mF·cm^-2的面积比电容,以及出色的循环稳定性（2000次循环后电容保持率为96.9%）。当使用CNF/MXene/GI薄膜作为超级电容器的电极时,在5 mA·cm^-2下获得了188.2 mF·cm^-2的高面积电容。此外,在0.83 mW·cm^-2的面积功率密度下,超级电容器的面积能量密度为37.6μWh·cm^-2。为提高复合材料电容性能,利用原位聚合策略,以CNF为导电支撑骨架制备CNF/（聚苯胺）PANI复合材料,增强了导电聚合物的结构稳定性,将其插入MXene片层中,制备CNF/MXene/PANI复合导电材料（CMP）,探究复合材料的形貌特征、结构形态及电化学性能,并使用PVA固态电解质将其组装成对称超级电容器,对器件的性能进行探究。结果显示,CNF/MXene/PANI膜在1 mA·cm^-2时具有2935 mF·cm^-2的高面积比电容,以及优异的循环稳定性（循环2000次后具有94%的电容保持率）。以CNF/MXene/PANI薄膜为电极的SC在5 mA·cm^-2下具有522 mF·cm^-2的高面积比电容。在0.83 mW·cm^-2的面积功率密度下,SC的面积能量密度为104.4μWh·cm^-2,且具有良好的循环稳定性（循环4000次后保持率为81.5%）。为了改善复合薄膜质量堆积效应,采用Fe₃O₄导电材料与CNF/MXene/GI复合,制备具有三明治结构的夹层电极材料CMG/F/CMG。研究Fe₃O₄夹层含量对复合材料形貌结构和力学性能的影响,进而分析其对电化学性能和电磁屏蔽性能的影响,以夹层导电材料为正负极组装对称超级电容器,并对器件的电化学性能进行探究。研究表明,CMG/F/CMG-15%复合导电薄膜,表现出良好的柔韧性和力学性能,且拉伸强度达到38.3 MPa,在1 mA·cm^-2时具有1430 mF·cm^-2的面积比电容,以及良好的循环稳定性（循环4000次后具有98%的电容保持率）,在X波段范围内,其最大电磁屏蔽效能达到65.7 dB,具有优异的电磁屏蔽性能。以CMG/F/CMG薄膜为电极的SC显示203 mF·cm^-2的面积比电容,并且具有良好的电稳定性。在0.33 mW·cm^-2的面积功率密度下,SC的面积能量密度达40.6μWh·cm^-2。通过水热法制备Fe₂O₃/MnO₂导电材料,将其作为夹层与CNF/MXene/PANI复合材料组合成为CMP/FM/CMP夹层材料,研究多层结构中各部分的比例及占比对CMP/FM/CMP复合导电薄膜形貌结构和电化学性能的影响机理,组装对称超级电容器,对超级电容器的电化学性能进行深入分析。研究结果表明,CMP/FM/CMP-20%复合导电薄膜在1 A·g^-1时具有445.6 F·g^-1的质量比电容,以及优异的循环稳定性,在X波段范围内,其最大电磁屏蔽效能达到59 dB,表现出了优秀的电磁屏蔽性能。以CMP/FM/CMP薄膜为电极的SC在5 mA·cm^-2下具有615 mF·cm^-2的面积比电容,并且SC也具有良好的电稳定性,在0.83 mW·cm^-2的面积功率密度下,SC的面积能量密度达到128.2μWh·cm^-2。为实现高工作电压,以CNF为柔性基底,利用一步还原法,制备CNF/还原氧化石墨烯（RGO）复合材料,研究复合材料形貌结构和电化学性能。同时,以CRG为正极,CNF基复合材料为负极,组装非对称超级电容器,并对其电化学性能进行探究。研究结果表明,以CNF/rGO为正极,CNF/MXene复合电极为负极组装的非对称超级电容器表现出优异的电化学性能,CRG//CMG/F/CMG表现出41.5 F·g^-1的质量比电容,以及在380.6 W·kg^-1的功率密度下能量密度达14.1 Wh·kg^-1,CRG//CMP/FM/CMP表现出107.2 F·g^-1的质量比电容,以及425.3 W·kg^-1的功率密度下45.6 Wh·kg^-1的高能量密度,研究展示了纳米纤维素基非对称超级电容器在柔性储能领域中的应用潜力。更多还原

【Abstract】 As one of the most abundant lignocellulosic raw materials in China,research on the application of bamboo in energy storage devices such as supercapacitors（SC）is not only conducive to easing environmental pollution and energy depletion,achieving a breakthrough in the goal of"double carbon",but also conducive to the transformation of efficient energy storage devices to sustainable energy.However,due to the insulating properties of nanocellulose and the interface instability between nanocellulose and conductive materials,its application in electrode materials is limited.Therefore,how to efficiently combine nanocellulose and conductive materials to prepare high-performance supercapacitors is the research focus of this paper.Based on the selection of nanocellulose based conductive material and the design of conductive composite material structure,the high performance nanocellulose based composite electrode material was prepared,and the properties of the composite material and the assembled supercapacitor were studied.The main conclusions are as follows:CNF/MXene/GI flexible composite electrode material（CMG）was prepared by combining gallium indium liquid metal material（GI）with MXene material and CNF with cellulose nanofibril（CNF）prepared in deep eutectic solvent（DES）system as matrix by ultrasonic preparation method.Various properties of the composite electrode material were discussed.Further,asymmetrical flexible supercapacitors were constructed by assembling electrode materials and their electrochemical properties were investigated.The results show that the CNF/MXene/GI film has an area specific capacitance of871.3 mF·cm^-2at 1 mA·cm^-2and excellent cycle stability（capacitance retention of 96.9%after 2000cycles）.When CNF/MXene/GI thin films were used as electrodes for supercapacitors,a high area capacitance of 188.2 mF·cm^-2was obtained at 5 mA·cm^-2.In addition,at a power density of 0.83 mW·cm^-2,the supercapacitor has an energy density of 37.6μWh·cm^-2,while maintaining good cycle stability.In order to improve the capacitive properties of composite materials,CNF/PANI composites were prepared using CNF as the conductive support framework by in-situ polymerization strategy,which enhanced the structural stability of the conductive polymer.Investigations were conducted into the morphological,structural,and electrochemical properties of CNF/MXene/PANI（CMP）composite conductive materials,which had been created by inserting CNF into MXene sheets.The PVA solid electrolyte was used to assemble it into a symmetrical supercapacitor,and the performance of device were analyzed.The results show that the CNF/MXene/PANI membrane has a high surface ratio capacitance of 2935 mFcm^-2at 1 mAcm^-2and excellent cyclic stability（94%capacitance retention after2000 cycles）.The SC electrode using CNF/MXene/PANI film has a high area-specific capacitance of522 mF·cm^-2at 5 mA·cm^-2.At a surface power density of 0.83 mW·cm^-2,SC has a surface energy density of 104.4μWh·cm^-2and good cycle stability（81.5%retention rate after 4000 cycles）.The sandwich electrode material CMG/F/CMG with sandwich structure was prepared by using Fe₃O₄conductive material and CNF/MXene/GI composite.The impact of the Fe₃O₄interlayer amount on the composite material’s shape,composition,and strength was examined,followed by an analysis of its effect on the electrochemical and electromagnetic shielding capabilities.The supercapacitor was built using the interlayer conductor material as both the anode and cathode,and this device was investigated for its electrochemical performance.The results show that the CMG/F/CMG-15%composite conductive film exhibits good flexibility and mechanical properties,and the tensile strength reaches 38.3 MPa,and the area specific capacitance at 1 mA·cm^-2is 1430 mF·cm^-2.And excellent cyclic stability（98%capacitance retention after 4000 cycles）,in the X-band range,its maximum electromagnetic shielding efficiency reaches 65.7 dB,showing good electromagnetic shielding performance.SC with CMG/F/CMG film as electrode has an area specific capacitance of 203 mF·cm^-2,and has good electrical stability.With a surface power density of 0.33 mW·cm^-2,the surface energy density of SC is 40.6μWh·cm^-2.Fe₂O₃/MnO₂conductive material was prepared by hydrothermal method,which was used as a sandwich and combined with CNF/MXene/PANI composite material to form CMP/FM/CMP sandwich material.The influence of the ratio and content of the sandwich on the morphology,structure and electrochemical performance of CMP/FM/CMP was studied,and symmetrical supercapacitors were assembled.The electrochemical performance of supercapacitor is investigated.The results show that the CMP/FM/CMP-20%composite conductive film has A mass specific capacitance of 445.6 F·g^-1at 1 A·g^-1,and excellent cyclic stability.In the X-band range,its maximum electromagnetic shielding efficiency reaches 59 dB,showing good electromagnetic shielding performance.SC with CMP/FM/CMP films as electrodes has an area specific capacitance of 615 mF·cm^-2at 5 mA·cm^-2,and SC also has good electrical stability.At the surface power density of 0.83 mW·cm^-2,the surface energy density of SC reaches 128.2μWh·cm^-2.To achieve high working voltage of capacitors,CNF/reduced graphene oxide（RGO）composites were prepared.The composites were examined for their morphology,structure,and electrochemical properties after being made with CNF as a flexible substrate through a one-step reduction process.Furthermore,an asymmetric supercapacitor was constructed with CRG as the anode and a CNF matrix composite as the cathode,and its electrochemical behavior was analyzed.The results show that the asymmetric supercapacitor with CNF/rGO as the positive electrode and CNF/MXene composite electrode as the negative electrode exhibits excellent electrochemical performance,and CRG//CMG/F/CMG exhibits a mass specific capacitance of 41.5 F/g.And the energy density reached14.1 Wh·kg^-1at 380.6 W·kg^-1power density,CRG//CMP/FM/CMP showed a mass specific capacitance of 107.2 F·g-1,and a high energy density of 45.6 Wh·kg^-1at 425.3 W·kg^-1power density.This study demonstrates the potential of nanocellulose based asymmetric supercapacitors in flexible energy storage.更多还原