Freudenberg Sealing Technologies has introduced cell caps and nonwoven cell stack envelopes for prismatic battery cells, designed to provide manufacturers with technical advantages and support the global shift to battery-powered mobility.
The company’s battery cell envelopes consist of innovative nonwoven materials that wrap the cell stack (much like conventional films), protect it during the assembly, and provide the necessary electrical insulation.
The nonwoven cell envelopes
The new nonwoven envelopes consist of a fiber network forming an ultra-homogeneous pore structure. The fibers are surface treated for permanent electrolyte “wettability.” This results in a lower risk of entrapping gas bubbles as the cell is filled and helps to keep the cell stack wetted over the lifetime.
Compared to conventional foils, nonwoven materials filled with electrolytes also lead to improved heat management within the cell — due to the resulting higher thermal conductivity.
Similar to a sponge, the absorbed electrolyte in the nonwoven creates an additional electrolyte reservoir in the cell. The electrolyte is released when the nonwoven is compressed, which happens during the aging of the cell when the stack swells.
When acting as an in-cell compression element, thicker layers of nonwoven envelopes can absorb a large portion of the cell stack growth within the cell, allowing thinner compression elements between single cells. In addition, absorbing cell stack growth inside the cell results in a more even load distribution on the cell stack, reducing the risk of dendrite formation and Lithium-plating. All these additional functions contribute to a longer cycle life and help to resolve a big challenge in battery technology.
The cell caps
Freudenberg offers custom-designed cell caps, developed in collaboration with cell manufacturers. All necessary functions are integrated, including rupture disks that dissipate escaping gases in case of a thermal runaway of the cell. These are manufactured on site for the local market with the lowest possible carbon footprint and in accordance with automotive standards such as IATF 16949.
Cell caps that are welded to the inner electrodes effectively seal and insulate the battery cells. They’re tested to be gas-tight and maintain this capacity throughout the cycle life of the battery. This ensures optimum performance under a range of operating conditions, minimizes the risk of gas leakage and increases safety. They also offer exceptional mechanical resistance to peak loads and fatigue. Their compatibility with various electrolytes, any coolants from outside and gases enables seamless integration into different EV systems.
Filed Under: Batteries, Technology News