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A new generation of battery packs with a recyclable epoxy SMC casing

An impact-resistant, yet lightweight, battery pack using an aluminium sandwich plate and glass fibre-reinforced epoxy SMC composites was developed by a consortium founded in 2019 including Lorenz Kunststofftechnik GmbH. This article has been published in the JEC Composites Magazine N°147.

A new generation of battery packs with a recyclable epoxy SMC casing
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5 minutes, 30 secondes

Faster, further, more efficient: Developers of e-vehicles and plug-in hybrids are aiming ever higher. The key element of these eff orts is the battery. On the one hand, it must be as ergonomic as possible to meet the increasing demands, but on the other hand, it must also have various safety-relevant properties as deformations or penetrating debris, such as they occur in accidents but also on uneven road surfaces, can trigger short circuits and dangerous fires that are difficult to extinguish. However, the materials that provide sufficient protection for the battery packs are often relatively heavy, which in turn has a negative impact on consumption and vehicle range. The new Pure Performance Battery now aims to solve this dilemma. A consortium consisting of companies from the automotive and mechanical engineering industries as well as from the chemical and plastics sectors, including Lorenz Kunststofftechnik GmbH, optimized the performance and resistance of proven high-voltage battery packs. The new Pure Performance Battery features a space-saving aluminium sandwich plate that prevents damage during ground impact and increases integration capability. The glass fibre-reinforced epoxy SMC casing offers high fire resistance and optimal crash performance while also being a fully integrated package solution.

Genesis

Back in 2019, Lorenz Kunststofftechnik GmbH joined forces with Vestaro GmbH, Forward Engineering GmbH, Evonik Resource Efficiency GmbH and LION Smart GmbH to form a development consortium, which was joined by Minth GmbH in 2021. Drawing on the accumulated expertise of its member companies, the group initially designed a cost-eff ective glass fibre-epoxy SMC cover for high-voltage batteries based on Evonik’s high-performance epoxy curing agent Vestalite® S. At that time, Lorenz Kunststofft echnik GmbH was already able to achieve a weight reduction of almost 10% for the battery housing compared to previous systems made of more cost-intensive materials. In addition, the state-of-the-art SMC materials allow complex geometries to be produced in a one-step process, making them ideal for semi-integral ergonomic design. Now, the partner companies have successfully developed a new generation of high-performance battery packs for electromobility.

Figure 1: The new Pure Performance Battery features a space-saving aluminium sandwich plate that prevents damage during ground impact and increases integration capability (source: Lorenz Kunststofftechnik GmbH)
Figure 1: The new Pure Performance Battery features a space-saving aluminium sandwich plate that prevents damage during ground impact and increases integration capability (source: Lorenz Kunststofftechnik GmbH)

Aluminium sandwich plate improves performance and vehicle integration

In most e-vehicles, the battery pack is located in the floor area in order to improve the centre of gravity and thus the driving performance, but also to provide more space in the vehicle cabin. However, this design increases the risk of dangerous battery damage due to impact situations or objects hitting the underside of the vehicle, such as loose stones or branches. Therefore, special protective measures must be taken to prevent deformation or the ingress of foreign objects. The bottom-impact use case and the vehicle integration are two major challenges for today’s battery packs. This is why the main focus in developing the new generation of performance battery packs lay on these two aspects. To fulfill the stringent requirements, the consortium designed a novel approach that takes maximum advantage of the design freedom of the proven SMC material.

The old floor structure was replaced by an aluminium sandwich plate developed by the youngest consortium member Minth. With this concept, the group was able to get rid of additional side-mounted deformation elements and use the freed space for battery cells instead. Using Forward Engineering’s BEV floor structure development tool, the Pure Performance Battery was configured and validated so that an improved impact behaviour of the sandwich floor could be achieved and the space required for the module assembly was reduced. In this way, the capacity could be increased by 10kWh to a total of 75kWh with approximately the same external dimensions of the battery pack. Thus, the aluminium sandwich plate not only improves performance in terms of bottom impact, but also plays a key role in the semi-integral vehicle concept.

Modular design and epoxy SMC housing boost performance

The new Pure Performance Battery can be for example 2.1 m long and 1.58 m wide or other dimensions, with a maximum height between 0.15 and 0.22 m, enabling a variety of vehicle architectures. In terms of ergonomic design, it competes with other high-end solutions, but surpasses them in terms of performance. The modular series design of the battery also allows flexible adjustment of the number of modules. The supercell concept based on LION Smart’s LIGHT Battery enables a calculated fast charging result of around 13 minutes for a charging power constantly above 200 kW (10 to 80% SOC). The system is currently being optimized in this respect to achieve a charging time of less than 10 minutes in the future. The glass fibre-reinforced epoxy SMC cover from Lorenz Kunststofft echnik not only stands out for its low weight, but at the same time provides a very high safety potential in terms of fire resistance and crash behaviour. It withstood all the relevant fire-related test set-ups, including thermal runaway tests conducted at a testing facility in southern Germany. In addition, all concerns regarding the EMI shielding performance of the glass fibre composites were tackled with a broad material toolbox and validated under OEM requirements. The process benefits were verified by manufacturing several complex demonstrator geometries. During these trials, cycle times of around 3 minutes were achieved, suggesting a high cost-saving potential.

Figure 2: The glass fibre-reinforced epoxy SMC casing offers high fire resistance and optimal crash performance while being a fully integrated package solution (source: Lorenz Kunststofftechnik GmbH)
Figure 2: The glass fibre-reinforced epoxy SMC casing offers high fire resistance and optimal crash performance while being a fully integrated package solution (source: Lorenz Kunststofftechnik GmbH)

Resource efficiency thanks to recycling system and “mix-and-match” service

The new generation of high-voltage battery packs has not only been improved in terms of performance. Future-proof solutions should be sustainable, this is why the consortium also addressed this topic with its developments. For example, the cover can be disassembled by undoing several screw connections to enable easy access to the battery modules and peripheral equipment. Unlike bonded systems, the Pure Performance Battery allows individual components to be replaced and repaired. The epoxy SMC battery cover itself can be recycled by Lorenz Kunststofftechnik and aferwards reused in new composite parts.

Overall, the consortium partners have once again learned a lot from each other during the development process of the new-generation battery pack in order to be able to supply customers with an allround finished battery pack. Given the dynamics of the industry, all project partners are prepared to handle requests from potential customers that deviate from the basic model and to offer a collaborative “mix-and-match” service. This offer presents a great opportunity for applications as the consortium makes it possible to address a company on a topic and benefit from the performance and know-how of the other members.

About the consortium: joint commitment to the future of electromobility:
In 2019, several companies from the automotive and mechanical engineering industries, as well as from the chemical and plastics sectors, organized themselves with the common goal of developing a battery concept for fully-electric vehicles that is suitable for series production. During the development, a new partner joined the consortium. As the European headquarters of the Chinese Minth Group, Minth GmbH, based in Unterschleißheim, Bavaria, now also supports the battery consortium, which consists of Lorenz Kunststofftechnik GmbH, Vestaro GmbH, Forward Engineering GmbH, Evonik Resource Efficiency GmbH and LION Smart GmbH.

This article has been published in the JEC Composites Magazine N°147.

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