Transparent and Stretchable Current Collectors: The Future of Flexible Batteries

Imagine a battery that bends and stretches with your body, powering your wearable devices seamlessly. My work at ETH Zürich under Prof. Markus Niederberger's supervision focused on developing such flexible batteries, paving the way for the next generation of wearable technology.

The Challenge

Modern wearable devices require components that are not just functional but also flexible and transparent. Traditional electronic parts are often opaque and rigid, making them unsuitable for truly wearable technology. The key challenge lies in developing electrodes that combine high transparency and electrical conductivity with mechanical flexibility. These devices need to withstand various deformations - from stretching and bending to twisting and folding - while maintaining their performance.

Our Innovation

We developed a hierarchical multiscale hybrid nanocomposite that combines the best properties of different materials:

• Gold nanowires (Au NWs) with small diameter (≈3 nm) and longer length (≈50-100 μm) for high electrical conductivity
• Multi-walled carbon nanotubes (MWCNTs) with larger diameter (≈11 nm) but shorter length (≈5-20 μm) for mechanical flexibility
• A unique three-layer structure: Au NWs/MWCNTs/Au NWs on a flexible PDMS membrane
• Hexagonal-structured channels in the PDMS substrate for enhanced stretchability

The Results

Our hybrid current collector achieved remarkable performance metrics:

• High conductivity with an average resistance of just 40-50 ohms
• Excellent transparency (80-85% light transmission)
• Impressive stretchability up to 100% strain
• Outstanding durability, maintaining performance over 1000 bending/stretching cycles

Why It Matters

This research represents a significant step forward in the field of flexible electronics. Our innovative current collector design could enable the development of truly wearable devices that combine transparency with mechanical flexibility - from smart glasses to electronic maps and flexible displays.

Looking Forward

While there are still challenges to overcome before this technology reaches commercial products, our research demonstrates a promising pathway forward. The hierarchical structure we've developed provides efficient multiscale electron transport paths, with Au NWs serving as the main current backbone collector and MWCNTs providing local elastic percolation networks. This combination shows superior performance compared to single-component materials, potentially paving the way for next-generation flexible electronic devices.