Chemically Anchored Liquid-PEO Based Block Copolymer Electrolytes for Solid-State Lithium-Ion Batteries

Abstract

Solid-state electrolytes are being considered the keystone element for the development of safer all-solid-state lithium-ion batteries. While poly(ethylene oxide) (PEO) solid-state polymer electrolytes are known to support a lithium ions flux, satisfying conductivities are reached only above the melting point of the PEO crystallites rendering PEO unpractical. Herein, by means of block copolymer engineering, we design a mechanically clamped liquid-PEO electrolyte that combines the high ionic conductivity of a low molecular mass PEO while retaining the dimensional integrity of a solid material (1). Attractive ionic conductivities of about 0.01 mS/cm are attained at room temperature without compromising mechanical properties. The electrolyte shows a wide electrochemical stability window and help in building a stable interface with lithium metal. Competitive performances are attained when integrating the developed materials into operational/functional prototype batteries highlighting the provided potential. Next, we discuss a three step synthesis procedure of self-doped solid block copolymer electrolyte, combining a single-ion poly(lithium methacrylate-co-oligoethylene glycol methacrylate) ion conducting block (P(MALi-co-OEGMA)) and a structuring polystyrene block (PS) (2). The macromolecular design allows the formation of a self-standing film with excellent mechanical properties provided by the PS anchoring nanodomains while attaining attractive ionic conductivities of up to 0.02 mS/cm at room temperature. Moreover, the single-ion configuration based on polyanionic backbone affords high transference numbers, close to unity, and alleviates the power limitation encountered in salt-doped solid polymer electrolyte (SPE). The electrolyte exhibits a wide electrochemical stability window up to 4.5 V vs. Li+/Li and promote the formation of stable interfaces at the electrodes. (1) J. Rolland, J. Brassinne, J.-P. Bourgeois, E. Poggi, A. Vlad and J.-F. Gohy, J. Mater. Chem. A, 2014, 2, 11839–11846 (2) J. Rolland, E. Poggi, A. Vlad, J.-F. Gohy, Polymer 2015, 68, 344-352