Stretchable electronics for portable or wearable applications may achieve a new level of flexibility with a supercapacitor that can bend and twist as it efficiently stores energy.

The pliability of 2D transition metal carbides, or MXenes, as electrode material was enhanced by researchers from Nanjing University, China. A titanium carbide MXene film designed with a crumpled and ridge-like texture was demonstrated to maintain the desired electrical properties of an electrode while imparting flexibility and stretchability to a supercapacitor.

After titanium aluminum carbide powder was decomposed into flakes with hydrofluoric acid, layers of pure titanium carbide nanosheets were captured as a roughly textured film on a filter. The film was placed on a piece of pre-stretched acrylic elastomer that was 800% its relaxed size. When released, the elastomer shrank to its original state and the adhered nanosheets crumpled into accordion-like wrinkles.

An electrode synthesized with a 3 µm-thick film could be repetitively stretched and relaxed without damage and without altering its ability to store an electrical charge. The material was used to fabricate a supercapacitor by sandwiching a polyvinyl(alcohol)-sulfuric acid gel electrolyte between a pair of the stretchable titanium carbide electrodes, resulting in a device with high energy capacity and extreme stretchability up to 800% without cracking. The supercapacitor described in Nano Letters maintained 90% of its energy storage capacity after being stretched 1,000 times, or after being bent or twisted.

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