Lithium-ion batteries are accompanying the progressive development of society, with relevant applications in everyday life, including consumer electronics, grid levelling, and automotive. Despite their favourable characteristics that enabled their establishment in the market, such as high energy density, superior cycling stability, and lightweight, the rapidly growing automotive sector calls for still higher specific energy and power, increased safety, and lower cost.
Metallic lithium is an ideal anode material for rechargeable batteries, thanks to its high theoretical specific capacity, low density, and low electrochemical potential. However, lithium metal batteries are still far from full industrial deployment because of interface instability and uncontrolled lithium dendritic growth. These metallic microstructures are responsible for the decrease of the coulombic efficiency of the cell and the shortening of operating life, because they generate internal short circuits, triggering fires or explosions.
To overcome these issues, liquid electrolytes can be replaced by solid-state ones, which exhibit good ionic conductivity and appropriate electrochemical stability, being at the same time sufficiently resistant to act as physical barriers. They can help in improving the interface stability, by inhibiting the dendritic growth. Finally, they can also improve the overall safety, decreasing the risk of thermal runaway and explosion.
In the article “PVDF-HFP Based, Quasi-Solid Nanocomposite Electrolytes for Lithium Metal Batteries” doi: 10.1002/smll.202311805, published in the journal Small (Wiley, Impact Factor 13.3, 2022 Journal Impact Factor, Journal Citation Reports (Clarivate Analytics, 2023)), the research group on electrochemical energy storage, led by Prof. Riccardo Ruffo e dal Prof. Piercarlo Mustarelli, with the important computational contribution by Prof.ssa Livia Giordano's group, proposes an innovative quasi-solid electrolyte, based on polyvinylidene fluoride and a functionalized silica nanofiller. The filler improves the mechanical, transport and electrochemical properties of the electrolyte, which shows good ionic conductivity values and high resistance to dendrite penetration, ensuring prolonged and safe operation of the battery containing LiFePO4 as cathode material.