Polyanionic electrolytes with high alkali ion conductivity

We describe the synthesis of chain polymers that contain Lewis base or Lewi s acid groups in the backbone that can then be reacted with acidic or basic groups to form polyanions with weak binding sites for alkali cations. We r eview both 'base-in-chain' and 'acid-in-chain' approaches to this type of p olyanion. When the anionic groups are optimally separated, the conductiviti es of the polymers are found to be high relative to those of most single io nic conducting polymers and even most non-imide salt-in-polymer electrolyte s. The concentration of ionic groups, can be varied using polyethylene glyc ol links (spacers) of variable length. The conductivity is found to maximiz e near the value which maximizes the conductivity in simple salt-in-fully a morphous polyether polymers (the number of the ethyleneoxy repeating unit n = 12). Finally a novel process, which achieves the same objective by a dif ferent route, will be described. This class of weakly coordinating polyanio nic electrolyte, in which the coulomb traps for Li+ are little if at all st ronger than the polyether chelation traps, is seen as a promising developme nt in the solid polymer electrolyte field. Except for the case of 'weak tra p' acid-in-chain polymers, all these electrolytes are unicationic in their conduction.