Infoscience

Journal article

Nanocomposites of titanium dioxide and polystyrene-poly(ethylene oxide) block copolymer as solid-state electrolytes for lithium metal batteries

There is considerable interest in developing solid electrolytes for rechargeable lithium batteries as they have the potential to increase both energy d. due to incorporation of a lithium metal anode and safety of batteries due to the fact that they are nonflammable. Block copolymers with a mech. hard nonconducting block and a soft ion-conducting block provide an avenue for obtaining highly conducting rigid solids. The authors add surface-modified TiO2 nanoparticles to a mixt. of polystyrene-block-poly(ethylene oxide) and bis(trifluoromethane)sulfonimide lithium salt. The presence of BF4- moieties on the surface of the particles was essential for obtaining macroscopically homogeneous electrolytes; macrophase sepn. was obsd. with the same nanoparticles with surfaces covered with oleic acid. The stability of these composite electrolytes against lithium metal electrodes was tested in sym. lithium-composite electrolyte-lithium cells. The surprising result was that electrolytes with 24% nanoparticles exhibited optimum stability; the amt. of charge passed before dendrite formation obsd. in the optimized composite electrolyte was a factor of 4.7 larger than that of the neat block copolymer electrolyte. Both tensile and shear moduli of the electrolytes were non-monotonic functions of particle concn. with peaks in the vicinity of 17 to 20%.

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