American scientists put the rapid charging of lithium-ion batteries under a microscope and found that charging at a higher rate will quickly destroy the structure of the graphite negative electrode, even after a small amount of cycles will cause capacity loss. By identifying the mechanism that causes this performance loss, the team can help point the right direction for future research.
Intercalation of lithium ions (green) in graphite anodes
Making full use of lithium ion and other energy storage technologies is the focus of attention of scientists all over the world. Batteries have made valuable contributions to the energy transition, but there are still many challenges and improvements that need to be completed.
Although much of the focus of this research is to use brand-new materials that show promise for energy storage applications, squeezing more from existing technologies and understanding the mechanisms behind their limitations is a valuable prospect for many people. Faster charging presents a challenge for today’s batteries, especially related to electric vehicle applications-understanding how the higher current required for fast charging can lead to battery damage and performance loss is a recent report by a scientist led by Argonne National Laboratory MLA. America.
The team used an "as is" graphite anode that was not cycled in the battery or even exposed to the electrolyte, and compared it with another one taken from a battery that had undergone multiple rapid charging cycles. Both anodes were inspected using sophisticated imaging and characterization techniques, as described in the paper "Disordered increase in the edges of graphite particles revealed by multi-length-scale characterization of fast-charging lithium-ion batteries" published in the Journal of the Electrochemical Society describe.
In addition to electroplating—the lithium in the electrolyte is permanently deposited on the anode surface instead of being reversibly stored in graphite particles—the team noticed that changes in the anode’s structure further reduced its capacity. "Basically, what we are seeing is the distortion of the network of atoms in graphite, which prevents lithium ions from finding their'home' inside the particles-instead, they are plated on the particles," explained Argonne scientist Daniel Abraham. He added that this effect seems to increase as the battery charging speed increases, and is visible even after a few cycles. "The key is to find a way to prevent this loss of tissue or modify the graphite particles in some way so that lithium ions can be inserted more effectively."
The team suggests that increasing the battery cut-off voltage or increasing the space in the graphite particle lattice may be potential solutions, but each method has its own shortcomings. However, a better understanding of the mechanisms behind plating and performance loss should open new doors for researchers looking for solutions.
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