仿生与固态能源系统研究组知识库

基于电动汽车、混合动力车可再生制动系统亟待提高能量密度的实际需求，本论文主要从储能电池电极材料可控制备的角度出发，基于纳米过渡金属氮化物及其复合纳米材料，以构建电子/离子混合传输材料的为基本思路，通过材料设计结合结构设计，制备高性能电极材料，并对其电化学储能性能进行研究。主要取得了以下研究成果：

（1）TiN介孔微球的可控制备及其在锂离子电容器中的应用：通过无牺牲模板法设计合成了TiN介孔球，介孔微球粒径可通过前驱体组分调节。以TiN介孔球为电极构建了锂离子电容器。电化学表征结果显示，基于TiN介孔球电极的锂离子电容器表现出了较高的能量密度，在150 W kg^-1的功率密度下，能量密度可达45 W h kg^-1，高于目前商品化超级电容器的能量密度（< 10 Wh kg^-1）。该结果证明TiN 介孔球可以成为一种理想的锂离子电容器电极材料

（2）同轴MnO₂/TiN纳米管一维纳米阵列结构的制备及其在超级电容器中的应用：设计合成了同轴MnO₂/TiN纳米管一维纳米阵列复合材料，复合材料结构可以通过调节沉积电位实现。TiN纳米管阵列高的电子传输性能，使电活性材料MnO₂表现出了更高的比容量（在 2 A g^-1的电流密度下可达681.0 F g^-1），优异的倍率性能（从2 mV s^-1到2 V s^-1，容量保持率为55%）以及良好的循环性能（1000圈保持97%）。证明该纳米阵列复合材料在超级电容器中重要的潜在应用前景。

（3）同轴Pt/TiN 纳米管阵列结构（Pt/TiN NTA）的制备及其在锂空气电池中的应用：采用恒电位电沉积的方法设计制备了同轴Pt/TiN 纳米管阵列复合材料（Pt/TiN NTA）。该复合纳米结构兼备了一维纳米管状Pt层的结构优势与TiN纳米管阵列提供的导电骨架。同时TiN与Pt间的相互作用还有利于提供更多的0价Pt进一步促进电化学催化。与商品化Pt/C（20 wt. % Pt）催化剂相比，Pt/TiN NTA具备更高的质量比活性（2.1倍）与面积比活性（1.6倍）。该复合纳米阵列结构被用作双电解液体系锂空气电池的阴极。在0.02 mA cm^-2的电流密度下，充放电平台间的电势差仅为0.09 V。该结果表明该纳米阵列电极有望成为一种理想的双电解液体系锂空气电池。

（4）MoN/氮掺杂石墨烯复合材料的制备及其在锂空气电池中的应用：设计合成了MoN/氮掺杂石墨烯（MoN/NGS）复合材料。其中，MoN作为催化活性材料原位生长、均匀分布在氮掺杂石墨烯（NGS）的片层结构中，并被用作纯有机体系锂空气电池阴极材料。该有机体系锂空气电池表现出了很高的放电平台及较高的比容量。在3.1 V左右表现明显的放电平台，其比容量可达1050 mA h g^-1，充放电能量循环效率可达77%。实验结果表明MoN/NGS有望成为纯有机体系锂空气电池阴极材料的潜在选择。

To meet the demand for regenerative braking of hybrid-electric vehicles and power sources of pure electric vehicles, there is an increasing need of electrochemical devices with higher energy densities. In this study，electrodes for energy storage devices are designed based on the concept of fabricating mixed conducting materials for electron and ion. Nano-materials and nano-composites of transition metal nitrides are employed to fabricate high performance supercapacitor and Li-air batteries. The main contents are as follows:

(1) mesoporous TiN spheres with tunable diameter have been fabricated via a facile template-free strategy. Under ammonia atmosphere, mesoporous TiO₂ spheres are directly converted into mesoporous TiN spheres with the addition of cyanamide to retain the original morphology and untilized as electrode materials for Li-ion capacitor. The energy density of the resultant mesoporous TiN spheres can reach 45.0 Wh kg^-1 at a power density of 150 W kg^-1, which demonstrates that this material can be a promising electrode material for non-aqueous supercapacitors with high energy densities. 

(2) One dimensional MnO₂/ titanium nitride nanotube coaxial arrays have been designed for a high performance electrochemical capacitive energy storage system based on a concept of fabricating an efficiently, fast charge separation network. This nanostructured composite material was prepared by electrodepositing mesoporous MnO₂ into TiN nanotube arrays (TiN NTA), which is prepared by anodization of a Ti foil substrate and subsequent nitridation using ammonia annealing. The electrodeposited mesoporous MnO₂ inside the electrically conductive framework of TiN nanotube have tested to show high specific capacitance (681.0 F g^-1 at 2 A g^-1), excellent rate capability (55% capacitance retention from 2 mV s^-1 to 2000 mV s^-1), and long cycle life (3% capacitance loss after 1000 cycles). These results demonstrate that this coaxial composite nanostructure is very promising for high performance supercapacitors.

(3) One dimensional (1D) coaxial platinum/titanium nitride nanotube arrays are designed to achieve superior electrocatalytic activity of Pt based materials. The nanocomposite material is prepared by electrodepositing Pt into TiN nanotube arrays (TiN NTA). This nanostructured electrode combines the structural advantage of 1D Pt nanotube-like structure with the electrical conductive TiN NTA framework and offers more metallic Pt due to the favorable interaction between Pt and support. Compared with commercial Pt/C (20 wt. % Pt) catalyst, the Pt/TiN NTA deliver higher mass activity (2.1 times) and specific activity (1.6 times) for ORR and hence are utilized as cathode for hybrid electrolyte Li-O₂ batteries. The low overpotential characteristic of Pt/TiN NTA cathode indicates that this nanostructured electrode can be a potential candidate as cathode for hybrid electrolyte Li-air batteries.

(4) Molybdenum nitride/nitrogen-doped graphene nanosheets (MoN/GNS) are synthesized through hydrothermal reaction and subsequent ammonia annealing. In the nanocomposite, MoN as an electrocatalyst is integrated into the electronic conducting framework of GNS and directly used as O₂ cathode in Li-O₂ batteries. This hybrid cathode exhibits high discharge potential (around 3.1 V) and considerable large specific capacity, which can be served as an alternative O₂ electrode for Li-O₂ batteries.