Process for preparing metal difluorochelatoborates and use as battery electrolytes or additives in electrochemical cells

Abstract

The invention relates to a process for preparing metal difluorochelatoborates, in which a metal bis(chelato)borate of the formula M[BL] is reacted with boron trifluoride and a metal fluoride (MF) and/or a metal salt of the chelating ligand (ML) where M+ is a monovalent cation selected from the group consisting of lithium, sodium, potassium and ammonium NR, where R═H, alkyl (C1 to C8) and L is a chelating agent having two terminal oxygen atoms and having the general formula (II), where: when m=1 and Yand Ytogether with Cform a carbonyl group, n=0 or 1 and o=0 or 1 and Rand Rare each, independently of one another, H or alkyl having from one to eight carbon atoms (C1-C8) and Y, Yare each, independently of one another, OR(R═C1-C8-alkyl), then n or o≠1: p=0 or 1 and when n and o=0, p=1; or Y, Y, Y, Yare each, independently of one another, OR(R═C1-C8-alkyl), m=1, n=0 or 1, o=1 and p=0; or Cand Care members of a 5- or 6-membered aromatic or heteroaromatic ring (with N, O or S as heteroelement) which can optionally be substituted by alkyl, alkoxy, carboxy or nitrile, where R, R, Yand Yare absent, m=0 or in the case of 1, Yand Ytogether with Cform a carbonyl group and p is 0 or 1, in an organic, aprotic solvent.