Technicians diagnosing and disassembling lithium-ion car batteries. The new study may make it possible to perform diagnostics without disassembling the battery in the future (image: Shutterstock)
Published on 09/14/2026
By José Tadeu Arantes | Agência FAPESP – Monitoring the lifespan of a lithium-ion battery without disassembling it is possible. This prospect was opened up by a study published in May in the journal Cell Reports Physical Science by researchers at the State University of Campinas (UNICAMP) in the state of São Paulo, Brazil, and their collaborators. The scientists created an advanced computational model to investigate these energy sources and discovered that natural voltage fluctuations act as an “X-ray” of the system. This reveals the microscopic structure of its materials and the speed of the chemical reactions occurring within it. This finding paves the way for rapid, low-cost diagnostics in energy storage.
Lithium-ion batteries are found in a wide variety of devices, ranging from small electronics – such as cell phones, laptops, cameras, and portable tools – to electric vehicles. On an even larger scale, they are used in stationary energy storage systems, including those that store electricity generated by intermittent sources, such as solar and wind power. This helps balance supply and demand in electrical grids.
The study was funded by FAPESP through three projects (20/12632-5, 23/08663-0, and 24/03807-7). It was coordinated by Raphael Nagao, a professor at the Institute of Chemistry (IQ) at UNICAMP. The first author is doctoral student Eduardo Parma, who is advised by Nagao.
“The oscillations reveal characteristics of the nanostructure of the electrodes and the speed at which lithium ions move from one electrode to another. This relationship could serve as the basis for simple and inexpensive methods to monitor battery aging and health,” says Parma. “The goal is to take advantage of this spontaneous behavior to extract information that’s normally very difficult to access,” Nagao adds.
The researcher emphasizes that this oscillatory behavior is present in many natural systems. For example, the heartbeat corresponds to a periodic variation in electrical voltage, which is recorded by an electrocardiogram. This phenomenon was first observed in batteries in 2018. However, until now, no one had explained how the process occurs. “Eduardo translated that oscillatory behavior into mathematical equations. By solving the equations, he was able to reproduce the behavior observed experimentally in simulations,” says Nagao.
What happens inside the electrode
To understand the process, it is important to remember that electrodes are not solid blocks, as is often imagined, but rather highly complex, porous structures. “We can think of them as a kind of foam made up of billions of tiny solid particles separated by pores filled with a liquid electrolyte. The particles correspond to the battery’s active material, while the electrolyte functions as a network of pathways through which lithium ions move until they reach the surface of each particle,” Parma explains.
The ions enter the particles through a process called intercalation, settling into available positions within the structure. The key to understanding the oscillatory behavior is that the charge does not distribute uniformly throughout the entire set of particles but rather couples to a subset at a time. These groups transition almost simultaneously from a lightly charged state to a highly charged one. Each transition produces a peak in the battery’s electrical voltage. The succession of these transitions generates the oscillatory behavior observed experimentally.
“A typical electrode contains about 10 billion particles. During each oscillation, approximately 1% of them – about 100 million – transition from a low-charge state to a high-charge state almost simultaneously, producing the small voltage spike observed experimentally,” Parma explains.
The study focused on electrodes made of lithium titanate (Li₄Ti₅O₁₂, or LTO), a material known for its high structural stability that is considered promising for applications requiring high currents. The simulations showed that the particles do not all incorporate lithium at the same time. Instead, they undergo this transition in groups that shift almost simultaneously from a less-lithiated state to a more-lithiated state, producing voltage oscillations.
To simulate this mechanism, the researchers used a technique known as phase-field modeling. Unlike traditional models based on the pseudo-two-dimensional (P2D) approximation, which represent each particle in a simplified manner, the new method directly solves the equations describing how the lithium concentration evolves within the particles using multidimensional computational grids. According to the authors, this approach overcomes the significant limitations of previous models and accurately reproduces the physical mechanisms responsible for the experimentally observed oscillations.
Information hidden in the voltage
The main contribution of this work was to demonstrate that the characteristics of the oscillations carry quantitative information about the fundamental properties of the battery.
For example, the simulations showed that the size distribution of the electrode particles directly influences the period of the oscillations. Conversely, this means that analyzing the period of the oscillations can provide information about the microstructure of the material.
The researchers also found a relationship between the period and amplitude of the oscillations and the rate at which lithium ions enter and exit the electrode particles during the intercalation reaction. This rate, known as “intercalation current density,” is a key parameter used to characterize the kinetics of electrochemical reactions. According to the authors, it may someday be estimated simply by analyzing the battery’s voltage oscillations.
“Today, many of these properties can only be determined using sophisticated experimental techniques, some of which rely on large scientific facilities, such as synchrotron light sources. Our model suggests that some of that information can be obtained simply by analyzing the voltage oscillations of the battery itself,” Nagao emphasizes.
Diagnosis without dismantling the battery
The authors point out that this possibility still needs to be validated experimentally, but it is a promising prospect. If the relationship predicted by the model is confirmed, accurately measuring the small electrical oscillations during battery operation will suffice to estimate the internal characteristics of the electrode and monitor its degradation over charge and discharge cycles. This could lead to inexpensive methods of assessing the health of batteries without disassembling them or using advanced characterization techniques.
In addition to explaining a phenomenon that has been poorly understood since its discovery, the study provides a new tool for investigating electrochemical materials. By transforming small voltage oscillations into quantitative indicators of the internal structure and dynamics of the electrodes, the model expands the possibilities for developing more efficient, durable, and reliable batteries.
The article “Role of electrode microstructure and kinetics in oscillations in Li-ion batteries revealed by phase-field simulations” can be accessed at cell.com/cell-reports-physical-science/fulltext/S2666-3864(26)00234-1.
Source: https://agencia.fapesp.br/59186
