Powder Coatings Provide Sustainable Surface Solutions for Electric Vehicles

By Shelley Bausch

Based on the characteristics and capabilities of powder coatings, as momentum for electric vehicles (EVs) builds, powder will play a significant role in the rapidly evolving ecosystem. Powder coatings have a unique ability to support a wide spectrum of customer priorities including safety, efficiency, durability, and sustainability. Although it is difficult to predict the size of the ultimate market for powder in these automotive applications and in the supporting infrastructure, they will be a critical part of the expansion.

In 2021, the global consumption of powder coating was estimated at approximately $11.8 billion while the use in automotive manufacturing was estimated to be $1.2 billion, about 10% of the total value and 7% of the volume (Orr and Boss, 2021 Global Powder Newsletter). Of the powder coatings used in the automotive industry, 25% is used on wheels, 15% on exterior trim parts, and 40% for under the hood components, leaving 20% in miscellaneous applications (IHS Markit, 2021 Paint and Coatings Industry Overview). Powder coatings used for under the hood components will gradually shift from protecting the drive train for internal combustion engines (ICE) to protecting components for the electric powertrain, which is why it is critical for powder coating material and equipment suppliers to understand the electric vehicle evolution.

Over 6.5 million EVs were sold in 2021—a 109% increase year-over-year—and all indications are that the electric vehicle market will continue to grow at double digit rates as EV infrastructure expands and user acceptance increases. This move from ICE vehicles to EVs will drive significant change throughout the automotive powertrain, on battery design, the number of components, platform design, materials of construct, and the need for more efficient electric motors. The challenges facing the value chain are numerous and center on elements such as vehicle range, overall vehicle performance, end user cost, and safety.

Battery Pack EVolution
The battery pack itself is a core component of an electrified powertrain; it stores and provides energy to power the electric motor. Design and improvement of battery packs and cells are focus areas on the development of EVs. Most development today is on lithium-ion batteries, but new battery technologies continue to be explored to address challenges of size, weight, range, safety, and recyclability. Battery energy density and
its performance range are key determinants in how this technology will evolve and will be influenced by the end application priorities and requirements such as the relative trade offs of power versus energy cells and density.

Because light vehicle EVs will grow to be the dominant vehicle type, current battery development and evolution is focused on light vehicle requirements. Several development paths are emerging, led by lithium-ion liquid or gel technology, varying based on targeted market, performance level, and design requirements. For applications requiring higher energy density, longer range, and faster charging, batteries will use high nickel cathode chemistries with no cobalt or very low cobalt levels. In these cases, high silicon containing anodes are used so that the anode does not become a limitation on energy density performance. Where there is a focus on lowering cost and changing designs to achieve reasonable vehicle ranges, lower cost cathode chemistry is used and will leverage mainly graphite anodes. In parallel, there is a high level of interest in solid state batteries, particularly for light duty vehicles and anything involving air mobility like vertical take-off and landing vehicles (eVTOLs).

Another alternative design for electrically driven vehicles is hydrogen fuel cell technology. Thus far, the technology has been limited by process issues and hydrogen fuel infrastructure and transport challenges. However, there are examples of it reaching commercial scale in areas like long haul trucking. There are also options to use hydrogen fuel cells in combination with smaller lithium-ion batteries to give the fuel cells a buffer and more power when needed. The evolution of fuel cell technology will depend on how quickly lithium-ion technology and solid-state batteries evolve as well as how quickly the various end markets develop. It is reasonable to expect significant breakthroughs in this area in the next few years.

Powder Provides Protection and Performance
Regardless of approach, the battery packs that enable EVs consist of highly sophisticated components. Protecting these components is critically important to high performance and safety. PET films, paper, sheets, and tapes can be employed for fulfilling tasks such as the prevention of electrical short circuits, heat propagation, or flame spreading. However, there are inherent limitations and application challenges with these protective solutions such as the presence of air gaps and bubbles. In addition, new geometric designs produce surfaces and edges that create potential failure points for film or sheet- based protection. For these reasons, specialized coatings are becoming an increasingly popular solution for battery protection.

Dielectric properties are one of the first requirements of these specialized coatings. Depending on the specific battery design, position of the battery components, as well as the manufacturing process requirements, specialized coating options include thermoset and thermoplastic powder coating, electrocoat, intumescent coating, UV coating, and other specialty liquid coatings. These solutions can be applied as a single coat or can be combined in layering systems to achieve multifunctional performance. Performance benefits of coatings include the ability to cover sharp edges, maintain optimal temperatures, reduce the risk of fire, provide corrosion resistance, and prevent electromagnetic interference. For example, mid to heavy duty vehicles require battery cases to be protected with solutions offering corrosion and dielectric protection, weatherability, and even stone chip resistance. Traditionally these can be fulfilled by multiple layers of coatings with the primer layer addressing corrosion and dielectric protection and topcoats addressing weatherability and/or chip stone resistance. However, certain thermoplastic polyolefin powder coatings can meet all requirements in a single layer. With newer EV technologies and designs, having one coating able to deliver multiple functions will gain popularity due to both cost and performance.

Powder coatings yield additional benefits as compared to film- or sheet-based protection due to film thickness and application process control. For example, some substrates can have surface bumps, potentially impacting electrical insulation properties where preventing failures is critical. The risk of losing dielectric performance based on single layer defects or film thickness variation is a significant concern. Demonstrating the benefits of powder coatings will of course require specific test equipment related to electric insulation and thermal management. Material and equipment suppliers can support automotive customers with these capabilities to accelerate qualification and approval.

In addition to these functional performance benefits, it is important to recognize the sustainability benefits of powder coatings that support environmental and sustainability initiatives of supply chain participants, from corporate purpose statements to published sustainability metrics to regulatory compliance. Powder coatings have low to no VOCs, can be applied with extremely high transfer efficiency which reduces waste, and can be recycled/reused. When developed with the application process in mind, these coatings can provide versatility in film build and effectively cover challenging surfaces. This will require new investment or conversion of manufacturing capabilities if the change is from liquid to powder, and there will be opportunities for partnerships to design these equipment/material solutions. The benefit is clear, however, with their dielectric and corrosion resistant properties, powder coatings combine functional performance with sustainability to provide a leading solution to the needs of this market.

Other coatings critical to the advancement of electric vehicles include wire enamels, impregnating resins, and electric steel coatings that allow improved motor efficiency and durability. Coating solutions are used to insulate copper wire in electric motors, as well as magnetic circuits, electronic elements, and other electrical devices that are critical to motor and power efficiency. The increased efficiency from coating solutions is particularly valuable for EVs as it reduces the drain on the battery and allows smaller battery packs and/or longer range. This will be part of the overall evolution of electric vehicles as the design of the entire electrified powertrain changes to include a platform (skateboard), battery, and motors. All these elements need protection, function, and performance. Coating suppliers that can offer a total solution to enable the new electrified powertrain designs will win in this growing industry.

The Future of Mobility
The shift to EVs is more than just a change to the automobile itself. It is driving change across all aspects of the transportation environment. It is often described as “the future of mobility.” A future that includes changes in city infrastructure, parking and charging stations, micro- transportation options, vehicle interior requirements, electrical energy storage, and much more. This evolution lends itself to opportunities for innovation and new solutions to enable this infrastructure transformation in a cost-effective and user-friendly manner. The transition will also require more sustainable solutions, aligned with the overall move to electric vehicles as a more environmentally sustainable method of transportation as consumer preferences continue to shift.

Our team is focused on supporting the evolution and revolution of the future of mobility, and the entire coatings industry is well positioned to play a powerful role in its expansion. As one of the critical technologies, powder coatings provide a sustainable solution, supports sustainability-driven industry, and helps provide a sustainable future for all of us.

Shelley Bausch is senior vice president, industrial coatings for Axalta Coating Systems.