Scientists must study the processes inside an operating battery to understand battery failures. The observations guide the development of faster-charging and longer-lasting batteries.
Current techniques to study battery materials are complicated and expensive. They are not quick enough to capture the rapid changes in electrode materials.
To understand battery failures, the researchers studied micrometer-sized rod-like particles of one of the fastest charging anode materials available today (Nb14W3O44) during high-rate cycling using a low-cost, laboratory-based optical microscopy method.
First, the researchers introduced visible light into the battery via a small glass window. They observed the dynamic process within the active particles in real-time and under realistic non-equilibrium conditions. It revealed front-like lithium-concentration gradients moving through the individual active particles, causing internal strain and fracturing some particles.
Particle fracture is a problem in batteries because it can cause electrical disconnection of the fragments, reducing the battery’s storage capacity. Such spontaneous events have severe consequences leading to battery failures.
The researchers could analyze a large population of particles using optical microscopy. It revealed that particle cracking occurs more frequently with higher delithiation rates and in longer particles.
The novel technique offers rapid data acquisition, single-particle resolution, and high throughput capabilities. It could also facilitate further research into what happens when batteries fail (battery failures) and how to prevent it.