Stable, robust and customizable 3D printed decoupled structural lithium-ion batteries

The widespread adoption of electric vehicles relies heavily on the development of robust, fast-charging battery technologies that can support their continuous operation for long periods. One proposed energy storage solution to improve the endurance of electric vehicles involves the use of so-called structural batteries.

Structural batteries are batteries that can serve two purposes, both as structural components of vehicles and as energy storage solutions. Instead of being external components added to an electronic or electrical device, these batteries are thus directly integrated into the structure.

Researchers at Shanghai University and their collaborators have recently developed a promising strategy for fabricating high-performance structural batteries with customizable geometric configurations. Their strategy, described in a paper published in Composites Science and Technologyenables 3D printing of structural lithium-ion batteries for different geometric configurations.

“This study aims to design an integrated energy storage and charge-carrying structure with high charge capacity and high energy storage,” Yinhua Bao, corresponding author of the paper, told Tech Xplore.

“In terms of structural energy storage design, materials science mainly focuses on the synthesis and utilization of materials, as well as the secondary design of components for energy storage.

“For example, carbon fiber or fiberglass structures can be used, and modifications can be made to the battery’s electrodes, separators, or electrolytes to improve the charging performance of the structural energy storage.”

Despite their potential benefits, many structural energy storage solutions fabricated to date have had significant limitations, including relatively low energy densities and poor electromechanical cycling performance.

In their study, Bao and his colleagues sought to make more efficient structural batteries using a scalable manufacturing strategy. In particular, they explored the possibility of making these batteries using 3D printing, which is now widely used to manufacture various electronic products and components.

“By leveraging 3D printing, we aim to create customizable structural frames that, when combined with energy storage materials, form components with integrated energy storage and load-bearing functions, exhibiting high energy density and load-bearing capacity,” Bao said.

“The structure is expected to play the main role of load support, minimizing or reducing damage to energy storage materials during charging, thereby ensuring excellent energy storage capacity.”

The structural framework presented by Bao and colleagues could be adapted to enable the 3D printing of structural batteries for a variety of applications, going beyond electric vehicles. In fact, it could also be used to produce structural energy storage components for specific autonomous robots and warehouse logistics vehicles.

The 3D printing strategy developed by the researchers focuses on two key aspects of structural lithium-ion batteries: the energy storage unit and the structure.

“By designing a decoupled structure, it is possible to effectively reduce the deformation of the energy storage unit under load, thereby improving the mechanical stability of the battery,” Bao explained.

“We are using 3D printing technology to create the structure because it allows for rapid production and precise control of structural components. We have selected high-performance electrode materials and electrolytes to further improve the energy density and battery life.”

Bao and his colleagues also simulated damage to an energy storage unit under load using finite element software. This allowed them to optimize the structural design of the batteries to limit the predicted damage.

“We also adopt a distributed layout of battery cells to avoid the drawback of global failure due to localized damage,” Bao said. “Our tests demonstrate that by adopting a decoupled structural battery design approach, structural batteries with high energy density and charge capacity as well as mechanical-electrochemical robustness can be realized. In addition, 3D printing technology enables customizable structural batteries.”

The researchers used their proposed approach to fabricate a composite structural battery sample. In initial tests, this battery was shown to be able to withstand significant tensile and bending stresses, while exhibiting a high energy density of 120 Wh kg^-1 and 210 Wh L^-1 (3.5 mA cm^-2).

It is worth noting that the battery retained up to 92% of its capacity after 500 operating cycles. It also retained 98.7% of its capacity under a tensile stress of 80 MPa and 97% of its capacity under a bending stress of 96.3 MPa, losing approximately 0.18% of its capacity per operating cycle.

“In practical applications, different material selections can be made for different components, and using finite element simulations in real-world scenarios can optimize the structural design,” Bao said. “Our approach thus enables the fabrication of decoupled structural batteries that can be applied to various use cases.”

In the future, the 3D printing-based manufacturing strategy introduced by this team of researchers could facilitate the large-scale production of high-performance structural energy storage components for a wide range of applications. These could include stable, high-capacity structural batteries for electric vehicles, as well as smaller-scale batteries for robotic systems.

“The next step of our research will be to explore the application of decoupled structural batteries, such as unmanned aerial vehicles (UAVs) and robots,” Bao added. “We will make them more reliable by changing the material of the structures.”

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