Challenge in manufacturing electrolyte solutions for lithium and lithium ion batteries quality control and minimizing contamination level

The quality of electrolytes for lithium batteries are a major topic in scie nce and battery industries. The solvents and lithium salts should be of hig hest purity. Therefore, during preparation and handling of electrolyte solu tions, the contamination level has to be minimized and the quality during p ackaging, storage and transportation has to be guaranteed. Especially, prot ic impurities are found to be very critical for LiPF6-based electrolytes. T he influence of water is reported to be tremendous. But also other protic i mpurities like alcohols are considered to play an important role in the ele ctrolyte quality. The reaction of the protic impurities with LiPF6 leads to the formation of HF which further reacts with cathode active materials (e. g., spinel) and the passivating films of the cathode and anode. For a bette r understanding of the protic impurities and their role in the electrolyte quality a systematic investigation of different impurities was carried out. Electrolytes were doped with different protic compounds. Then the electrol yte was analyzed for protic impurities and HF in dependence of time. First results showing the relation between protic impurities and HF are presented and discussed. In addition, different packaging materials for the electrol yte solutions were investigated. Storage tests were carried out at differen t temperatures and in different atmospheres. Results on contamination level s, influence of packaging, high temperature storage and handling are addres sed. (C) 1999 Elsevier Science S.A. All rights reserved.