Researchers at the Norwegian University of Science and Technology (NTNU) are exploring the use of different materials in lithium-ion batteries to increase their energy density and improve safety. Lithium-ion batteries are crucial for decarbonizing transport networks and transitioning to renewable energy sources.
Traditionally, lithium-ion batteries use graphite as the anode material. However, the team at NTNU is investigating the use of silicon as an alternative, as it has the potential to store significantly higher amounts of lithium. By swapping graphite for silicon, the energy density of the battery can be substantially increased, enabling electric vehicles to cover longer distances without recharging.
One of the main challenges in lithium-ion batteries is their flammability. To address this issue, the researchers are exploring the use of ionic liquids as electrolytes. Ionic liquids are salts that remain in a liquid state at room temperature. By replacing traditional liquid electrolytes with ionic liquids, the risk of thermal events and battery fires can be reduced.
In a study published in the Journal of The Electrochemical Society, the team evaluated the performance of batteries with silicon anodes and ionic liquid electrolytes at high temperatures. They discovered that increasing the temperature of the battery enhances the conductivity of lithium ions within the electrolyte, overcoming the limitations of ionic liquids which have lower conductivity at room temperature. This finding suggests that operating large packs of batteries, which tend to overheat, could be made simpler without the need for additional cooling.
Furthermore, the researchers observed that some ionic liquid electrolytes performed better than others, and this could be attributed to the formation of a thin film, called a passivation layer, on the silicon surface. This passivation layer plays a crucial role in preventing the decomposition of the electrolyte and improving lithium ion mobility in the electrolyte.
Although promising, further research is needed before these advancements can be commercialized. The team used advanced equipment, such as X-ray photoelectron spectroscopy, to investigate the films formed on the electrodes.
This research by NTNU contributes to the ongoing efforts to develop safer and high-energy density lithium-ion batteries, which are essential for the transition to a sustainable and decarbonized future.
Source: Journal of The Electrochemical Society, DOI: 10.1149/1945-7111/ac9f78