450Wh/L Bendable Textile Lithium Battery Developed for Wearables

May 28, 2019 by Scott McMahan

Lithium batteries are currently the dominant rechargeable battery in the market due to their relatively high energy density and long cycle life. However, the conventional heavy and bulky lithium battery is difficult to use in wearable devices.

Researchers at The Hong Kong Polytechnic University (PolyU) have created a highly flexible, high-energy textile lithium battery. (See image above of Professor Zheng Zijian holding up the textile lithium battery).

While others have attempted to devise bendable lithium batteries using metal foils as current collectors, the researchers contend that only PolyU's textile lithium battery overcomes the limitations in energy density, mechanical robustness, flexibility, and cycling stability. According to the researchers, the textile lithium battery offers a safer, more stable, and durable power supply for wearable electronics.

The team anticipates that the unique battery technology could be used in a myriad of applications including intelligent textiles, healthcare monitoring, smartphones, GPS tracking, and IoT.

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PolyU's novel lightweight textile lithium battery demonstrated high energy density of more than 450Wh/L, and it has a bending radius of less than 1mm, and foldability of over 1,000 cycles with marginal capacity degradation.

Existing bendable lithium batteries, on the other hand, can only reach a bending radius of about 25 mm, and they have much lower performance of less than 200 Wh/L.

The textile lithium battery, which is less than 0.5mm thick, also allows fast charging/discharging, and boasts a long cycle life that is said to be comparable with conventional lithium batteries.

The innovation that the research team of PolyU's Institute of Textiles and Clothing (ITC) developed won three prizes at the 47th International Exhibition of Inventions of Geneva in April this year, a Gold Medal and two Special Merit Awards.

Professor Zheng Zijian, who leads the ITC research team, said, "Wearable technology has been named as the next global big market opportunity after smartphones. Global market revenues for wearable devices are forecasted to grow by leaps and bounds, of over 20% annually, to reach US$100 billion by 2024. As all wearable electronics will require wearable energy supply, our novel technology in fabricating textile lithium battery offers promising solution to a wide array of next-generation applications, ranging from healthcare, infotainment, sports, aerospace, fashion, IoT to any sensing or tracking uses that may even exceed our imagination of today."

The team utilized PolyU's patented technology of Polymer-Assisted Metal Deposition (PAMD) that uniformly deposits highly conductive metal, copper (Cu) and nickel (Ni) onto pre-treated fabrics.

Such metallic fabrics, featuring low sheet resistance and large surface area, serve as current collectors in the battery. After the active materials are added to serve as the cathode and anode, the metallic fabrics, together with separator and electrolyte, are assembled into the textile lithium battery.

Bending tests revealed that the battery can be bent more than 1,000 times with only marginal capacity degradation. The battery was able to withstand even continuous hammering, trimming with scissors, and penetrating with nail and still stably deliver power output for the electronic components with no risk of catching fire or bursting.

The group published their findings in Nature Communications.

Reference Material

Chang, J., et al. Flexible and stable high-energy lithium-sulfur full batteries with only 100% oversized lithium. Nature Communications, 2018, 9(1): 4480.