Flexible lithium battery can be integrated into textiles

May 28, 2019 //By Jean-Pierre Joosting
Flexible lithium battery for wearable electronics
Researchers at PolyU in Hong Kong have developed a lightweight flexible lithium battery with an energy density of more than 450 Wh/L and a bending radius of less than 1mm for wearable applications.

In comparison, the existing flexible lithium battery can only reach a bending radius of about 25 mm, and with much lower performance of less than 200 Wh/L. The Textile Lithium Battery is under 0.5 mm thickand has  sses fast charging/discharging capability and long cycle life comparable with conventional lithium batteries, as well as foldability of over 1,000 cycles with marginal capacity degradation. 

The innovation developed by the research team at the PolyU Institute of Textiles and Clothing (ITC) has won three prizes at the 47th International Exhibition of Inventions of Geneva held in April this year, namely 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 percent 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."

Over the past decade, scientists have looked to develop a flexible lithium battery, often by using metal foils as current collectors. However, it is only until the emergence of the Textile Lithium Battery that the bottlenecks over energy density, flexibility, mechanical robustness and cycling stability being addressed.

To create the battery, a patented novel technology of Polymer-Assisted Metal Deposition (PAMD) from PolyU, highly conductive metal, copper (Cu) and nickel (Ni) 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 battery. After adding active materials to act as cathode and anode, the metallic fabrics, together with separator and electrolyte, are assembled into the Textile Lithium Battery.

In general, the larger the surface areas for loading anode and cathode materials, the greater stability, higher charge/discharge speed and better flexibility is the battery. Applying the PolyU patented PAMD technology to control the deposition time, the thickness and sheet resistance of the metallic yarns can be easily controlled. By weaving the metallic yarns into a 3D metal fabric, its surface areas for loading the active materials, in comparison of a 2D metal foil sheet of the same size, is much enhanced.

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