Textile Lithium Battery offers high energy density and flexibility

Researchers at The Hong Kong Polytechnic University (PolyU) have developed a ‘Textile Lithium Battery’ that offers a stable, durable and safe energy supply for wearable electronics.

Described in the journal Nature Communications, the battery was awarded three prizes — a Gold Medal and two Special Merit Awards — at the 47th International Exhibition of Inventions of Geneva, held in April this year. It has potential applications in healthcare monitoring, intelligent textiles, smartphones, GPS tracking and the Internet of Things (IoT).

Lithium batteries are currently the dominant rechargeable batteries in the market due to their relatively high energy density and long cycle life. Conventional lithium batteries are bulky and heavy, making them unsuitable for use in wearable devices, so scientists have spent the past decade developing bendable lithium batteries — often by using metal foils as current collectors. However, it is only with the emergence of the Textile Lithium Battery, developed by PolyU’s Institute of Textiles and Clothing (ITC), that bottlenecks over energy density, flexibility, mechanical robustness and cycling stability are able to be addressed.

Applying PolyU’s patented Polymer-Assisted Metal Deposition (PAMD) technology, highly conductive metal, copper and nickel are uniformly and conformally deposited onto pre-treated fabrics. Such fabricated metallic fabrics, featuring low sheet resistance and large surface area, serve as current collectors in the battery. After adding active materials to act as the cathode and anode, the metallic fabrics, together with a separator and electrolyte, are assembled into the Textile Lithium Battery.

Laboratory tests conducted by the ITC team have proven the extremely high mechanical stability, durability and safety of the Textile Lithium Battery under deformation. When the battery was repeatedly folded in half, twisted at different angles or freely crumpled, its voltage window remained unchanged. Bending tests showed that the battery can be bent over 1000 times with marginal capacity degradation. Safety tests conducted by continuous hammering, trimming with scissors and penetrating with a nail proved the battery can stably provide power output for the electronic components with no risk of catching fire.

Overall, the lightweight Textile Lithium Battery demonstrates high energy density of more than 450 Wh/L. It also boasts excellent flexibility, with a bending radius of less than 1 mm and foldability of over 1000 cycles with marginal capacity degradation. In comparison, existing bendable lithium batteries can only reach a bending radius of about 25 mm, with a much lower performance of less than 200 Wh/L. The Textile Lithium Battery, which measures less than 0.5 mm thick, also possesses fast charging/discharging capability and long cycle life comparable with conventional lithium batteries.

“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,” said Professor Zheng Zijian, who leads the ITC research team. “As all wearable electronics will require a wearable energy supply, our … Textile Lithium Battery offers a promising solution to a wide array of next-generation applications, ranging from health care, infotainment, sports, aerospace, fashion and IoT to any sensing or tracking uses that may even exceed our imagination of today.”

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