# CNT-Coated Quartz Woven Fabric Electrodes for Robust Lithium-ion Structural Batteries
## 1 Introduction  
While energy technology has been intensively researched to meet the rapidly increasing energy demand around the world for the past 20 years, demand is increasing explosively for industrial energy as can be seen in the popularity of consumer portable electronics, wireless transmission, vehicle control system, uninterrupted power supply, and backup power and pulse, all of which require high economic efficiency [1; 2; 3]. As unmanned vehicle technology is actively applied industrially for the purpose of intelligent and economic operation of vehicles, the need for an optimal system for increasing the amount of onboard equipment and reducing the weight of the vehicle is also required. The demand for a breakthrough to overcome the limitation of conventional lithium-ion batteries (LIBs) has been accelerating [4]. On the other hand, eco-friendly policies, such as reducing carbon dioxide emissions related to global warming, have become hot topics in the traditional automobile industry, which generates a lot of smoke. Many efforts are being made to commercialize technologies in various fields for electric vehicles. This trend has seen the rise of energy-efficient transportation means based on economic feasibility. As such, there has been an increase in demand for reducing fuel economy, extending operating distance, and expertise for advanced system integration in fields such as the automobile and aerospace industries. To save costs in the energy efficiency of a vehicle, there have been attempts to increase the operating efficiency by reducing the weight of parts, or increasing the energy generation per unit weight by increasing the specific capacity of the battery required for the system. In line with this approach, various studies have been actively conducted in the last 20 years, particularly in the US and Europe. It is a concept that improves energy efficiency at the system level asa study on a multifunctional structure that can store and release energy while maintaining the structural materials' mechanical performance using fiber composites [5; 6; 7; 8]. Through weight reduction that maintains the strength of the structure, a space that can perform more functions or tasks in the same volume is obtained. At the same time, this space is used as an energy storage electrode, increasing the energy efficiency of the entire system. Eventually, from the perspective of the energy system, it is expected that the development of excellent energy efficiency will be possible through the correlation between mechanical strength and electrochemical performance [9; 10]. The most common fiber types in composites are glass and carbon, which can contribute to electrode support in a structural battery [11; 12; 13; 14]. There are some conflicting requirements in the electrode support. The continuity in the load path is required from an electric energy storage portion to the adjacent structure portion for the structural function, while the discontinuity in the electrical path is essential between these two portions of electrode support for proper battery function. In this regard, a glass fabric such as quartz woven fabric (QWF) is a better choice for electrode support if the fabric is modified in the energy storage portion by Li-storable and electric-conducting materials like carbon nanotube (CNT) forest. Silica, used as a fiber woven fabric, is a good candidate material, but still needs a 3D network shape that can provide continuous electron transport paths with adequate levels of electrical conduction. To date, the research has reported the performance of structural supercapacitors with potential applications, and the research on structural cells is at a basic stage that hardly deviates from conventional approaches [15; 16]. Research on a multifunctional robust battery to utilize the excellent mechanical and electrical properties of the composite material can suggest a new energy storage paradigm that can improve energy efficiency in various systems requiring mechanical strength.