Rubbery block copolymer electrolytes for solid-state rechargeable lithium batteries

For nearly 20 years, poly(ethylene oxide)-based materials have been researc hed for use as electrolytes in solid-state rechargeable lithium batteries. Technical obstacles to commercialization derive from the inability to satis fy simultaneously the electrical and mechanical performance requirements: h igh ionic conductivity along with resistance to Row. Herein, the synthesis and characterization of a series of poly(lauryl methacrylate)-b-poly[oligo( oxyethylene) methacrylate]-based block copolymer electrolytes (BCEs) are re ported With both blocks in the rubbery state (i.e., having glass transition temperatures well below room temperature) these materials exhibit improved conductivities over those of glassy-rubbery block copolymer systems. Dynam ic rheological testing verifies that these materials are dimensionally stab le, whereas cyclic voltammetry shows them to be electrochemically stable ov er a wide potential window, i.e., up to 5 V at 55 degrees C. A solid-state rechargeable lithium battery was constructed by laminating lithium metal, B CE, and a composite cathode composed of particles of LiAl0.25Mn0.75O2 (mono clinic), carbon black, and graphite in a BCE binder. Cycle testing showed t he Li/BCE/LiAl0.25Mn0.75O2 battery to have a high reversible capacity and g ood capacity retention. Li/BCE/Al cells have been cycled at temperatures as low as -20 degrees C. (C) 1999 The Electrochemical Society. S0013-4651(98) 05-005-8. All rights reserved.