Researchers at the State University of Campinas (Unicamp) in Brazil, working with collaborators, have developed an advanced computational model that can monitor the lifespan of lithium-ion batteries without the need to take them apart. The study was published in the journal Cell Reports Physical Science.
The scientists found that the natural voltage oscillations inside a battery act as a kind of X-ray of the system. These oscillations can reveal microscopic characteristics of the battery's materials and the speed of the chemical reactions taking place inside it.
The finding opens the way for fast, low-cost methods of assessing the condition of batteries used in energy storage.
Where lithium-ion batteries are used
Lithium-ion batteries are found in a wide range of equipment, including mobile phones, laptops, cameras and portable tools, as well as electric vehicles.
They are also used in stationary energy storage systems, including systems that store electricity generated by intermittent sources such as solar and wind power. This storage helps balance supply and demand on electrical grids.
What happens inside the electrode
Lithium ions enter battery particles through a process called intercalation, in which they occupy available spaces within the material's structure. It is during this process that the information explaining the oscillatory behaviour observed by the researchers emerges.
Charge does not spread evenly across all particles. Instead, it concentrates in a subset of particles, which shift almost simultaneously from a low-charge state to a highly charged one.
To reproduce this mechanism, the researchers used a technique known as phase-field modelling. Unlike traditional models, which simplify the way particles are represented, the new method solves equations describing how lithium concentration evolves inside the particles, using multidimensional computational models.
According to the study's authors, the approach overcomes the limitations of earlier models and is able to reproduce the physical mechanisms responsible for the oscillations observed in experiments.
Still needs experimental confirmation
The study notes that the possibility still needs to be confirmed experimentally, but it represents a promising outlook. If the relationship predicted by the model is confirmed, small electrical oscillations could be measured while a battery is operating in order to estimate internal characteristics of the electrode and track its degradation over charge and discharge cycles.
The technology could, in future, contribute to cheaper methods for evaluating the health of batteries, without the need to disassemble them or use advanced characterisation techniques.
