PVdF-HFP QSSEs and the role of inorganic fillers preventing HF formation

The increasing need of efficient energy storage, necessary for the progressive green transition, is leading to a plethora of different new solution to improve lithium ion batteries safety, capacity, time durability and recycling. PVdF-HFP based quasi-solid-state electrolytes (QSSEs) offer a great opportunity to get safer and long-lasting batteries [1]. This kind of electrolytes contain lithium salts with fluorine-based anions, such as LiPF6, LiFSI and LiTFSI that, in presence of moisture, due to problem during battery production or accidental breaking, could hydrolyze producing HF [2]. This acid is very harmful for the battery because it attacks the cathode, decreasing significantly the battery capacity and life. The use of specific inorganic fillers added in the polymeric matrix could help prevent these reactions, assuring a longer life for the battery even in case of moisture presence. In the first part of the study, different lithium salts had been considered for the QSSEs, evaluating the performance and choosing LiFSI for its best conductivity. After that, cerium oxide nanoparticles, properly functionalized to increase the compatibility with the polymeric environment, were added. The electrolytes obtained where tested thermally, mechanically an electrochemically in different conditions, finally adding water to verify the actual material behaviour in preventing HF formation. The so produced QSSE could be successfully used in a complete cell, showing good ability in maintaining battery capacity and efficiency even in presence of considerable amount of water.