Chinese researchers have created a thin yarn-like battery that can be woven into fabric. It is flexible, waterproof, rechargeable, and can be cut into pieces and still work. As you can imagine, it has great potential for wearable electronics.

Wearable electronics, like smartwatches and exercise monitors, are becoming very popular. Now, researchers are developing ways to make even more flexible, durable, and smaller electronics. One way is to physically integrate electronics into clothing. Then, you could have an exercise shirt that monitors your heart rate, keeps you cool, and has lights that turn on in the dark.

The fibre-battery is promising because it is small, flexible, and lightweight. The battery that these researchers have invented in this study maintains its charge, is waterproof, and is flexible.

“The yarn batteries are integrated in parallel and in series by metal wire. We designed two special charge jacks for the cathode of the first battery and the anode of the last battery and integrated these charge jacks into the textile with good protection. The recharging of these batteries is conducted by connecting the charge jacks with the external charger,” said Chunyi Zhi, from the Department of Materials Science & Engineering at the City University of Hong Kong, to ZME Science.

First, the researchers twisted carbon nanotubules into a “yarn”. To make it into a battery, they coated one piece of yarn with zinc to form an anode and another in magnesium oxide to form a cathode. These two pieces were entwined together and coated with a polyacrylamide electrolyte and encased in silicone.

The battery was durable enough to be stretched (up to 300%) and knitted into clothing and still work optimally. One meter-long piece of yarn was cut into eight pieces, which were able to power a belt with 100 LED lights and an electroluminescent picture of a panda. In day-to-day life, weather can be unexpected and perhaps you get stuck in a surprise rain shower on the way home. You wouldn’t have to worry about the battery short-circuiting because it is waterproof thanks to it silicone coating. The battery is even machine-washable.

“One advantage of this yarn battery is this excellent waterproof capability. In this study, we fully immersed the yarn battery in water for 12 h. Surprisingly, the yarn battery still had 96.5% of its initial capacity, demonstrating good waterproof capability and high durability. We also tried to simulate the machine washing process– the yarn battery was immersed in water and stirred vigorously with a high power magnetic stirrer. Surprisingly, the battery retained 92.3% of its initial capacity after being stirred for over 5 min and was able to power an electronic watch after being stirred in water for over 30 min, demonstrating impressive waterproof performance and mechanical high durability,” said Zhi to ZME Science.

These fibre batteries could be useful for sportswear, pressure sensors, military uniforms, and medical devices. The possibilities are endless.

Li et al. 2018. Waterproof and tailorable elastic rechargeable yarn zinc ion batteries by a cross-linked polyacrylamide electrolyte. ACSNano.

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