Battery degradation could start at the nanoscale

Researchers have identified nanoscale changes in ageing lithium-ion batteries that could be responsible for their degradation over time.

Lithium-ion batteries are used in mobile phones, notebook computers and electric vehicles, and use lithium ions to carry the current from the negative to positive electrode.

They may then be recharged by an external electrical power source that forces ions to move in the reverse direction, from the positively charged cathode to the negative anode.

Giorgio Rizzoni and colleagues at the Ohio State University have dissected and examined batteries that had reached their end of life under experimental conditions.

They found that in dead batteries, a fraction of lithium was irreversibly lost from the cathode to the anode, and no longer participated in charging and discharging.

"We can clearly see that an aged sample versus and unaged sample has much lower lithium concentration in the cathode," Rizzoni explained.

"It has essentially combined with anode material in an irreversible way."

Using infrared thermal imaging and a range of microscopy techniques, the researchers discovered that finely-structured nanomaterials on dead batteries' electrodes had coarsened in size.

They suspected that the coarsening of the cathode may be responsible for the loss of lithium, although they have not yet proved this theory.

The study was being conducted in collaboration with Oak Ridge National Laboratory and the National Institute of Standards Technology.

Results were expected to increase batteries' longevity and improve their potential to power future electric vehicles.