Catastrophic battery failure can lead to enormous costs in damages and potentially even result in serious injuries. This is a major issue preventing the advancement of energy storage technologies. One approach to mitigate or prevent damage from battery failure is structural energy and power materials. These multifunctional materials can simultaneously bear a mechanical load and store energy creating more robust and energy storage devices. However, research in structural energy storage materials typically focuses on improving the electrode. Mechanically and thermally robust separators offer an alternative approach for preventing battery failure under extreme conditions such as high loads and temperatures. These separators could also mitigate the major problem of lithium dendrite formation due to the enhanced mechanical properties. Unfortunately, a robust separator must also maintain adequate ion transport properties and require easy processability to be a feasible replacement for commercial energy storage separators. The recently discovered aramid nanofibers (ANFs), nanoscale building blocks derived from Kevlar<sup>®</sup> fibers, have been used as a mechanical reinforcement filler for composite materials and show promise in battery separators. Here, we fabricate pure ANF separators through the dissolution of bulk Kevlar<sup>® </sup>fibers and vacuum-assisted self-assembly. We investigate the thermal behavior and degradation of ANF separators at high temperatures as well as mechanical properties of the separator at elevated temperatures. We also characterize ion transport properties and electrochemical performance of a Li-ion battery utilizing the ANF separator. Finally, we compare the pure ANF separator to common commercially available separators. ANF separators allow for producing safer batteries under extreme conditions while being easily processable and without diminish energy storage capabilities.

Aramid nanofiber separators for energy storage application

2019 Spring National Meeting

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