Developments in Polymer Electrolytes for Lithium Batteries

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Abstract
Recent developments in polymer electrolyte materials for lithium batteries are reviewed in this article. Four general classifications are recognized: (1) solvent-containing systems in which a liquid electrolyte solution either is fully miscible with a single-phase swollen polymer matrix (gel) or is a two-phase system in which “free” liquid occupies micropores within a swollen polymer network (hybrid), and conductivity (≥∼1 mS cm-1 at ambient temperature) is essentially independent of the polymer segmental motion (the thermal motion of segments of atoms along the backbone of a flexible polymer chain); (2) solvent-free, ion-coupled systems (typically polyether–Li salt complexes) in which both anions and cations are mobile within an amorphous, rubbery phase (conductivity ≤0.1 mS cm-1 at ambient temperature); (3) “single-ion” systems with anions fixed to the polymer backbone or systems with anion mobilities reduced by incorporation within larger molecules or by associations with the chain (conductivity ∼10-5 Scm-1 at ambient temperature); and (4) decoupled systems in which ionic mobility through channeled structures involves minimal local segmental displacements (conductivity 0.1–1 mS cm-1 at ambient temperature).