What influences the cycle life of batteries? And, most importantly, how can we expand it? An international research team lead by TU Delft showed that local irregularity in the oxide cathode material extends the number of times Li-ion batteries may be charged and discharged. The results were published in Nature.
Unstable electrode
Rechargeable batteries are an important part of the energy transition, especially as renewable energy becomes more widely available. Among the many types of rechargeable batteries, lithium-ion batteries are among the most powerful and popular. Layered oxides are frequently employed as electrodes for electrical connection. However, as the battery charges, its atomic structure becomes unstable. This eventually affects the battery’s cycle life.
The findings could result in a new generation of Li-ion batteries with reduced production costs and a lower CO2 footprint per unit of energy stored over their lifetime. The researchers will then study whether the same material design concepts can be applied to cathodes made from less scarce raw materials.
Marnix Wagemaker
Local disorder
To address this issue, the ‘Storage of Electrochemical Energy’ group at TU Delft collaborated with worldwide researchers. Qidi Wang, the paper’s primary author, writes, “The layered oxide used as cathode material for Li-ion batteries is neatly ordered.” We conducted a structure design study to incorporate chemical short-range disorder into this material using a more efficient synthesis approach. As a result, it became more stable while in battery mode.”
Longer cycle life, shorter charging time
The increased structural stability nearly doubled the battery’s capacity retention after 200 charging/discharging cycles. Furthermore, this chemical short-range instability facilitates charge transport in the electrode, leading in faster charging periods. The team proved these benefits for well-known commercial cathodes, including lithium cobalt oxide (LiCoO2) and lithium nickel manganese cobalt oxide (NMC811).
Critical materials
The disorder referred to here is likely “entropy.” In the context of batteries, particularly lithium-ion batteries commonly used in electronic devices, maintaining a certain level of disorder or entropy can indeed improve battery life. This concept relates to how ions move within the battery during charging and discharging cycles.
The findings could result in a new generation of Li-ion batteries with reduced production costs and a lower CO2 footprint per unit of energy stored over their lifetime. The researchers will then study whether the same material design concepts can be applied to cathodes made from less scarce raw materials. “Both cobalt and nickel are so-called critical materials for energy technologies, and it would be beneficial to reduce their use in batteries,” says Marnix Wagemaker, the paper’s principal author.
