Extracting more from lithium-ion and other energy storage technologies is a focus of attention for scientists worldwide. Batteries have already made valuable contributions to the energy transition, but many challenges and improvements remain to be made.
While much research has focused on novel materials showing promise for energy storage applications, for many, the prospect of extracting more from existing technologies and understanding the mechanisms behind their limitations is also valuable. Faster charging presents challenges for today's batteries, particularly those related to electric vehicle applications, and understanding how the higher currents required for fast charging cause damage and performance loss within batteries has been a recent focus of research by scientists led by Argonne National Laboratory.
The team used a "raw" graphite anode that had not been cycled in the battery or even exposed to the electrolyte, and compared it to another anode taken from a battery that had undergone several fast-charging cycles. Both anodes were examined using sophisticated imaging and characterization techniques. Apart from electroplating—where lithium from the electrolyte was permanently deposited on the surface of the anode instead of being reversibly stored in the graphite particles—the team noted that the change in anode structure further reduced its capacity.
Argonne scientist Daniel Abraham explained, “Basically, what we’re seeing is a distorted network of atoms in the graphite, which prevents lithium ions from finding their ‘home’ inside the particles. Instead, they hover over the particles, and this effect appears to increase the battery’s charging speed, even after just a few cycles. The key is to find ways to prevent this loss of organization, or to modify the graphite particles in some way so that lithium ions can embed themselves more efficiently.”
The team suggests that increasing the cell's cutoff voltage or increasing the space within the graphite particle lattice might be potential solutions, but each has its own drawbacks. However, a deeper understanding of the mechanisms behind electroplating and performance loss should open new doors for researchers to find solutions.
