High density capacitors: bridging the performance gap between conventional capacitors and electric double layer capacitors

电解电容器的低电容密度正成为电路板外形和电路性能的限制因素。当前一代双电层超级电容器的电容密度要高出几个数量级，但它们的充放电速率限制在1秒左右，或者特征频率为1赫兹，因此不适合那些需要在数百赫兹到千赫兹范围内运行的电容器的电路应用。换句话说，就电容/频率而言，目前可用的超级电容器与传统电路电容器技术之间存在显着的性能差距。提出的研究旨在通过研究开发具有新型纳米结构电极和高电容密度的超快超级电容器来解决这一性能差距，这些电容密度在数百赫兹到千赫兹范围内运行，适合于电路应用。这项研究如果成功，将给电容器设计带来颠覆性的变化，并在去耦、定时、滤波、电源和调理等关键电路功能上带来突破性的应用。所提出的纳米结构电极还可以用于电池和电催化剂的应用。教育和外展活动被纳入这个项目，以培养本科生和研究生。除了支持本科生项目学生的研究经验外，一些本科生将通过他们的项目实验室课程参与该项目，以激发他们对高级研究的兴趣。将注意招收女性和少数民族学生，特别是第一代大学生，以确保多样性和广泛参与。将开发用于能源技术的纳米材料外展部分，以教育学生，这些学生将在德克萨斯理工大学T-STEM中心协调的后续外展工作中担任大使。提出的研究将表征和演示在数百赫兹到千赫兹频率范围内运行的高密度电容器。这代表了电容器技术的颠覆性进步，紧凑高效的超快双电层电容器作为分立元件，用于线频交流电滤波，以及片上集成高密度微电容器的需求。所提出的电极是基于在纤维素纳米纤维支架上生长的垂直边缘定向多层石墨烯。这种新型材料具有浅、直、宽的孔结构，确保了高频率响应，而其大的比表面积，特别是高密度的完全暴露的石墨烯边缘，为大电容提供了可能。边缘取向多层石墨烯生长和纤维素纤维碳化成碳纳米纤维的过程只需要几分钟的时间。与用于滤波的低压铝电解电容器相比，基于这种新材料的超快双电层电容器可以使体积缩小至少两个数量级。所得到的独立电极也可以转移到基板或集成电路芯片上，用于封装内或片上电容器集成。该项目包括全面的纳米材料和电荷存储研究、器件建模、制造和性能测试。如果成功，它将最终弥合现有电路电容器和超级电容器之间的频率/电容差距。此外，本研究的结果将增进对相关材料和器件领域的理解。

The low capacitance density of electrolytic capacitors is becoming a limiting factor on circuit board profile and circuit performance. The capacitance density of the current generation of electric double layer supercapacitors is several orders of magnitude higher, but they are limited to a charge-discharge rate of about 1 second, or a characteristic frequency of 1 hertz, and thus not suitable for those circuit applications requiring capacitors that must run in the hundreds of hertz to kilohertz range. In other words, there exists a significant performance gap, in terms of capacitance/frequency, between currently available supercapacitor and traditional circuit capacitor technologies. The proposed research addresses this performance gap through studies aimed at developing ultrafast supercapacitors with novel nanostructured electrodes and a high capacitance density that run in the hundreds of hertz to kilohertz range and are suitable for circuit applications. This research, if successful, will bring about disruptive change in capacitor design and ground-breaking applications in crucial circuit functions like decoupling, timing, filtering, and power supply and conditioning. The proposed nanostructured electrodes can additionally be utilized in battery and electrocatalyst applications. Education and outreach activities are integrated in this project for the training of undergraduate and graduate students. In addition to supported Research Experiences for Undergraduates program students, several undergraduate students will be involved in the project through their Project Lab course work, to inspire their interest in advanced studies. Attention will be paid to recruiting female and minority students, particularly first-generation college students, to secure diversity and broad participation. An outreach component on nanomaterials for energy technologies will be developed to educate students who will serve as ambassadors in subsequent outreach efforts coordinated by the T-STEM Center of Texas Tech University.The proposed research will characterize and demonstrate high-density capacitors running in the hundreds of hertz to kilohertz frequency range. This represents a disruptive advance in capacitor technology for compact and efficient ultrafast electric double layer capacitors as discrete components, for line-frequency alternating current filtering, and on-chip integrated high-density micro-capacitor needs. The proposed electrode is based on perpendicularly edge-oriented multilayer graphene grown on a cellulose nanofiber scaffold. This novel material has a shallow, straight forward, wide-open pore structure that ensures high frequency response while its large specific surface area and especially high density of fully exposed graphene edges offer the possibility of large capacitance. Edge-oriented multilayer graphene growth and cellulose fiber carbonization into carbon nanofiber are implemented in a process that requires only a few minutes' time. The ultrafast electric double layer capacitors based on this new material could allow at least two orders of volume reduction compared to low-voltage aluminum electrolytic capacitors for filtering. The resulting freestanding electrodes can also be transferred to a substrate or an integrated circuit chip for in-package or on-chip capacitor integration. This project comprises comprehensive nanomaterial and charge storage studies, device modeling, fabrication and performance testing. If successful, it will ultimately bridge the frequency/capacitance gap between existing circuit capacitors and supercapacitors. The outcomes of this study will in addition enhance understanding in the areas of related materials and devices.