锂离子电容器用Li3VO4基负极材料的可控制备及性能研究

Supercapacitor has a good application prospect in the energy storage field. However, low energy density of supercapacitor limits its wide applications. Li3VO4 is a promising electrode material with great potential, which features a range of unique attributes such as high theoretical capacity and low voltage during charge and discharge. In this project, hydrothermal method will be chosen for the synthesis of hollow Li3VO4 nanocubes. The formation mechanism of structure, morphology of hollow Li3VO4 nanocubes and controllable synthesis of Li3VO4 nanocubes will be studied. And the energy storage mechanism of Li3VO4 as anode for Li-ion supercapacitor will be deeply discussed. Three-dimensional electrospun carbon nanofibers/N doped-graphene composite (CNGFA) with hierarchical porous structures will be prepared by a surface-induced co-assembly strategy and chemical reduction. On the basis of this, hollow Li3VO4 nanocubes will be precipitated in the holes of CNGFA. Then Li-ion supercapacitor based hollow Li3VO4/CNGFA composite as anode will be fabricated. The regulation of the reaction condition in the structure, composition, morphology of hollow Li3VO4/CNGFA composite will be investigated. Influence of structure, composition, doping, defect, interface of Li3VO4/CNGFA composite on porosity, conductivity, electrochemical properties of Li3VO4/CNGFA composite will be systematically studied to reveal the relationship of structure-electrochemical properties of Li3VO4/CNGFA composite. This work will provide experimental and theoretical basis for the preparation of electrode materials for supercapacitor with high energy density and high power density.

超级电容器在储能领域具有良好的应用前景，但能量密度低制约了它的广泛应用。正钒酸锂(Li3VO4)具有比容量高、嵌/脱锂电位低等优点，是很有潜力的电极材料。因此，本项目拟采用水热法合成中空Li3VO4纳米立方体，探索Li3VO4结构、形貌的形成机制及可控生长，深入探讨Li3VO4作为锂离子电容器负极材料的储能机理。采用表面诱导协同组装-还原法制备具有层级孔结构的三维电纺碳纳米纤维-氮掺杂石墨烯复合材料(CNGFA)，负载中空Li3VO4纳米立方体，以Li3VO4/CNGFA为负极材料构筑锂离子电容器。研究反应条件对Li3VO4/CNGFA的结构、组成、形貌的调控作用，系统考察Li3VO4/CNGFA的结构、组成、掺杂、缺陷、界面等对其孔隙率、电导率、电化学性能的影响，揭示Li3VO4/CNGFA的结构与电化学性能的内在联系，为制备高能量密度、高功率密度的超级电容器电极材料提供实验和理论依据。

锂离子电容器（LIC）是一种非常有潜力的储能器件。理想的电极材料对于锂离子电容器性能具有决定性作用。正钒酸锂(Li3VO4) 因为具有大的比容量、较低且安全的电位平台而被认为是一种很有前景的新型嵌入型锂离子电容器负极材料。然而，Li3VO4固有较低的电子导电率限制其在锂离子电容器上的应用。针对Li3VO4电子导电性差的缺点，本项目分别以石墨烯和Mxene为基体负载Li3VO4，提高Li3VO4基复合材料的电子导电率。研究了Li3VO4/石墨烯和Li3VO4/Mxene复合材料的结构与电化学性能的关系。对于Li3VO4/石墨烯复合材料，石墨烯明显提高了Li3VO4电子导电率。电流密度为200mA/g, Li3VO4/石墨烯的初始放电比容量达到320mAh/g, 700次循环后放电比容量为240mAh/g, 容量保持率达到75％。采用溶胶凝胶法制备了Li3VO4/Mxene复合材料，Mxene具有优异的电子导电能力和独特的二维层状结构，可以较好地负载Li3VO4粒子，因此Li3VO4/Mxene复合材料展现了优异的倍率性能。电流密度为2000mA/g, Li3VO4/Mxene复合材料的初始放电比容量为187mAh/g, 1000次循环后放电比容量为146mAh/g，远高于相同条件下1000次循环后纯Li3VO4的比容量(40mAh/g)和商业石墨的比容量(71mAh/g)。相关研究为制备高能量密度、高功率密度的锂离子电容器电极材料提供了丰富的实验依据。项目实施三年来，项目组在Energy Storage Materials， Journal of Materials Chemistry A等期刊共发表相关SCI论文12篇，培养硕士研究生6人，顺利完成了各项研究内容和指标。