It's inspired by our spine.
Battery structure, alternating rigid with other flexible components. Image credit: Yuan Yang/Columbia Engineering
The rapid development of flexible and wearable electronic products (also known as wearable) are creating an interesting range of applications, from smart watches and flexible displays, such as smartphones, tablets and TVs, to fabrics, crystals, patches and smart sensors. This has led to an increased demand for flexible, high-performance batteries. Until recently, however, experts had had difficulty simultaneously obtaining a good flexibility index and high energy density in lithium-ion batteries.
Now, a team led by Yuan Yang of Columbia University has developed a prototype that addresses this challenge: a human spinal lithium battery that allows remarkable flexibility, high power density and stable voltage, no matter how it bends or spins.
The energy density of our prototype is one of the highest to date,"Yang explains in a statement. We have developed a simple and scalable approach to producing a large scale flexible lithium ion battery similar to the column with excellent electrochemical and mechanical properties. Our design is a very promising candidate for flexible batteries. We are currently optimizing the design and improving its performance.
Yang, whose group explores the composition and structure of battery materials for high performance, was inspired by the flexibility of the spine while doing squats in the gym. The human spine is highly flexible as well as mechanically robust, as it contains soft bone marrow components that interconnect the hard parts of the vertebra. Yang used this model to design a battery with a similar structure. Its prototype has a thick, rigid segment that stores energy by wrapping the electrodes (the vertebrae) around a thin, flexible area (the marrow). The design provides excellent flexibility for the entire battery.
"As the volume of the rigid part of the electrode is significantly greater than the flexible interconnection - concludes Yang - the energy density of such a flexible battery can be greater than 85% of a conventional battery. Due to the high proportion of active materials in the whole structure, our battery shows a very high energy density, higher than any other report we are aware of. The battery also successfully survived a tough dynamic mechanical load test due to our biomimetic design.