Fiber lithium-ion batteries represent a promising power strategy for rising wearable electronics. However, most fiber current collectors are solid, with vastly increased weights of inactive materials and sluggish charge transport. This results in low energy densities, which have hindered the development of fiber lithium-ion batteries in the past decade; particularly in long fibers, energy density is far too low to be useful.
A team of researchers at the Fudan University in Shanghai (China) has now discovered that redesigning the current collector of the electrode could solve this problem. The team replaced the current collector, which is a continuous, thin metal wire inside the graphite electrode, with a braid made of several much thinner metal threads.
To produce the braid, they unwound several ultra-thin metal threads from spindles and braided them into a central braided thread, which was then coated with graphite over the whole electrode.
The new braided current collector was just as stable as the continuous wire but made it possible to increase the energy density by interacting with the graphite. “The designed braiding structure leads to channels filled with active materials, reducing obstruction to lithium-ion transport and increasing loading capability of active materials,” the team explains.
This increased energy density was also demonstrated in tests – a woven textile was produced containing 40 one-meter-long Fiber Lithium-Ion Batteries (FLIBs) with braided current collectors. This FLIB-based textile was able to charge a smartphone from 30 to 57%, whereas the conventional FLIB design using a continuous current collector wire only managed to reach 52%.
This increase in efficiency was achieved by a relatively simple change in the design of the current collector. This is particularly important for long fiber batteries, which must be robust, stable, and light.
- Xinlin Huang, Chuang Wang, Dr. Chuanfa Li, Dr. Meng Liao, Jiaxin Li, Haibo Jiang, Yao Long, Xiangran Cheng, Kun Zhang, Pengzhou Li, Prof. Bingjie Wang, Prof. Huisheng Peng. Braided Fiber Current Collectors for High-Energy-Density Fiber Lithium-Ion Batteries. Angewandte Chemie, 2023; DOI: 10.1002/anie.202303616