Researchers knit and weave yarn battery for wearables

August 22, 2017 // By Julien Happich
Removing the need for rigid and cumbersome batteries, a team of Chinese researchers has designed a rechargeable and flexible yarn-based battery that could be produced at scale on existing industrial knitting or weaving machines.


A free-standing solid-state yarn battery showing
two yarns electrodeposited with Zn (in grey) and
NCHO (shown in green) embedded into a
poly(vinyl alcohol)-based gel electrolyte.

Their paper "Weavable, Conductive Yarn-Based NiCo//Zn Textile Battery with High Energy Density and Rate Capability" recently published in the ACS Nano journal reports an intrinsically safe textile battery composed of pairs of stainless steel yarns electrodeposited with zinc (Zn) for the anode and nickel cobalt hydroxide (NCHO) for the cathode, jointly coated with a poly(vinyl alcohol)-based gel electrolyte.

The researchers used stainless steel 316L spun at high temperature to form micron-sized filaments, followed by a twist-bundle drawing technique, obtaining highly conductive continuous yarns (180 to 250μm in diameter) with a flexibility similar to that of cotton yarns. Those formed the basis for the two electrodes used in their yarn batteries.

Using industrial-grade knitting and weaving machines, the researchers demonstrated the dual (anode and cathode) yarns withstood well the conversion to highly conductive textiles.

For their conductive yarn-based NiCo//Zn textile battery, the researchers reported a high specific capacity of 5mAh cm−3 and energy densities of 0.12mWh cm−2 and 8mWh cm−3 and power densities of 32.8 mW cm−2 and 2.2 W cm−3 (all based on the solid battery).

These values are superior to most aqueous batteries and supercapacitors, claim the researchers.