Although hydrogen fuel cells have gained momentum for growth, the automotive industry still pays more attention to battery energy. According to the International Energy Agency (IEA), about 3 million electric vehicles (EVs) will be sold in 2020, while a report released by Canalys.com in August 2021 pointed out that about 2.6 million EVs will be sold worldwide in the first half of 2021, reaching more than 160% of the sales in the first half of 2020.

In the first half of 2021, electric vehicles accounted for 12% and 15% of all vehicles sold in China and Europe respectively, while electric vehicles accounted for only 3% of new vehicles sold in the United States in the same period.

According to the report issued by the International Energy Agency (IEA) in April 2021, the number of electric vehicles, buses, vans and heavy trucks operating on the road is expected to reach 145 million by 2030. According to the data released in July 2020, the target of mainstream automobile manufacturers is: by 2025, 50% of the vehicles sold by Volvo will be electric vehicles; By 2030, 50% of the vehicles sold by Daimler will be electric vehicles; By 2030, 40% of the vehicles sold by Volkswagen will be electric vehicles.

Battery box 

By reducing the weight of the battery box, the composite material helps to offset the heavy weight of the battery. An example is the CFRP battery box developed by TRB Lightweight Structures (hereinafter referred to as TRB) for electric buses. Each of these electric buses is equipped with six 74kW batteries. The weight of each battery including the battery box is 550kg. However, to meet the overall weight requirements, the battery box is only 15kg, which is significantly lower than the previous 64kg aluminum battery box. In order to meet the requirements of other aspects, including manufacturing in the United States and reaching an annual output of 40000 pieces, TRB and Toyota Tsusho America jointly built a special production plant in Richmond, Kentucky, the United States. The plant uses high surface weight carbon fiber fabric to make 2m × 1 m battery box. In the factory, a 2min cured epoxy resin is first used to prepreg the fabric, then the prepreg is cut immediately, and a pick and place robot is used to automatically put the cut prepreg into the matching metal mold for rapid press curing (FPC) processing, with a cycle time of 11 minutes. The formed parts are subsequently processed and assembled by robots, including trimming, bonding inserts and placing washers. The design of the component also includes adding additional layers on the lower housing for thermal insulation, electrical insulation and electromagnetic shielding. The project is planned to be fully put into production in 2021. At the same time, TRB is still discussing with other potential customers more medium - and high-yield battery box production projects.

SGL Carbon in Germany also started a production in 2021, mainly producing the upper and lower layers of carbon fiber and glass fiber composite battery shells for a North American automobile manufacturer. This high-yield application is a key part of an electric vehicle chassis, meeting strict requirements for weight reduction, rigidity, crash protection, thermal management, and fire, water, and gas resistance. This contract was signed after it was announced in 2019 that SGL Carbon successfully produced a prototype composite battery shell for the Chinese automobile manufacturer Weilai. SGL Carbon said that it may have more orders, or even larger orders, with this manufacturer. At the same time, SGL Carbon also obtained a small batch supply contract from a European sports car manufacturer, which is planned to start in the middle of 2020, to produce the base material of composite battery shells in batch.

Another company supplying battery boxes is SHD Composites in the UK. Its prepreg uses a bio based polyfurfuryl alcohol (PFA) thermosetting resin with phenolic properties. Its PS200 prepreg meets the fire protection requirements for aircraft batteries specified by the European Aviation Safety Agency (EASA) and has been adopted by general aviation aircraft manufacturers. The simulated battery ignition test shows that when the internal temperature reaches 1100 ℃, the external temperature never exceeds 250 ℃, and the battery box never burns or decomposes. Composites Evolution of the United Kingdom also provides bio based polyfurfuryl alcohol (PFA) prepreg. The reinforcement materials used include flax fiber, glass fiber, aramid fiber, basalt fiber or carbon fiber, and have passed the flame, smoke and toxicity (FST) test required by aircraft and railway departments.

Continental Structural Plastics (CPS), a subsidiary of Teijin Group, has been providing molded composite electric vehicle battery shells for nearly 10 years since it first started to provide upper and lower battery shells for Chevrolet Spark in 2012. Since then, the battery box cover of the company has become more and more popular, and the size of the battery box cover currently manufactured can reach 1.5m × 2m or more. In December 2020, Continental Structural Plastics (CSP) and Teijin demonstrated a full-size multi material electric vehicle battery box demonstration, which includes at least three structural components: a relatively thin composite upper cover, a thicker and more structured composite chassis, and a metal trapezoidal frame to provide additional support for the batteries inside the battery box. Continental Structural Plastics (CSP) has also developed an internal frame of an energy absorbing foam structure that can be used for higher crash protection. The upper cover and chassis are molded and can adopt various fire protection schemes developed by continental structural plastics. It is said that this multi material battery box is 15% lighter than the steel battery box and has better heat resistance than the aluminum battery box.

At present, Continental Structural Plastics (CSP) has developed and produced 34 types of battery box covers in the United States and China.

In May 2021, the carbon fiber manufacturer Toray Industries of Japan announced that it has developed a high thermal conductivity technology, which can improve the heat dissipation performance of carbon fiber reinforced plastics (CFRP) to the level of metal. When this technology is applied to CFRP, the heat can be effectively dissipated through the heat conduction inside the material. This helps to inhibit battery aging in mobile applications, while improving performance in electronic equipment applications. This breakthrough of Toray provides a technical solution to effectively dissipate the heat in the battery and electronic circuit while using CFRP to reduce weight. The company expects that CFRP applications that adopt its technology will include advanced vehicles, mobile electronic devices and wearable devices that require lightweight and heat dissipation performance.

The "Composites for sustainable mobility" (CosiMo) project, completed in 2021, aims to develop an intelligent thermoplastic resin transfer molding (T-RTM) process for the production of a challenging component of the battery box cover. The part is 1100 mm long and 530 mm wide, which was designed by the research center of Faurecia Green Motion Intelligent System in Augsburg, Germany. It is used to explore the limitations of materials and processes, including metal inserts and foam core layers, complex shapes and thickness changes of 2.5~10mm. These components are manufactured by the Lightweight Production Technology Center (ZLP) of the German Aerospace Center (DLR). The goal is to develop a fully automated process control method using the one-step process of RTM mold and hot press with sensors. More than 70 sensors are integrated in the RTM mold, so that the resin flow can be monitored during the injection of caprolactam monomer and its in-situ polymerization into PA6 composite. The sensor network contains dielectric sensors provided by Netzsch, Germany, and integrates pressure/temperature sensors from Kistler, Switzerland, and ultrasonic sensors developed by the University of Augsburg. The process parameter data from sensors are also used to optimize the process simulation model, and then the automatic process control driven by simulation data based on machine learning method is developed accordingly. ZLP has produced more than 100 high-quality components. The knowledge acquired in the process of project research and development will be used for industrial batch production and digital closed-loop control of other composite processes in the future.

Technical Fibre Products (hereinafter referred to as TFP) of the United States has been supplying nonwoven veils of various materials for many years. It is used for interlayer and surface of composite parts to increase electromagnetic interference (EMI) shielding, conductivity, reflectivity, wear resistance or fire resistance. As Nigel Walker, the company's technical director, explained, the battery box should be able to prevent electromagnetic interference, suppress fire, and ensure lightweight and made of composite materials while doing so. As many electric vehicle manufacturers gradually give up the use of metal battery boxes and turn to lightweight composite materials, some unexpected consequences may include the loss of metal based fire resistance or electromagnetic shielding performance. "For example, we can add a thin layer of nickel plating material, which can shield electric energy so as not to interfere with other systems in the car, while maintaining the necessary weight and thickness of components." John Haaland, president of TFP, said. "This is a good example of versatility." Walker added.

Another way to achieve the versatility of composite laminates is to use Supercomp, ZRT and Bimetal materials from Boston Materials of the United States. In the roll to roll processing, the magnetic positioning process patented by the company can make the crushed carbon fibers vertically oriented into sheets. Through out of plane oriented carbon fibers, Boston Materials overcomes the traditional limitations of composite materials on the conductivity through the laminate thickness. "We are showing thermal conductivity and conductivity comparable to aluminum." Anvesh Gurijala, founder of Boston Materials, said, "We have reached the performance level of nanofibers. Nickel veils and expanded metal foils can be used to prevent electromagnetic interference and lightning strikes, while the cost and processing performance have also been improved." When combined with thermoplastic films, ZRT materials can be molded into complex shapes and have thermal conductivity similar to that of aluminum. "Low cost, mass production thermoforming processes can be used to produce non-metallic heat exchanger panels with very small characteristic structures to increase surface area." Gurijala said.