A New Lithium Salt with a Chelate Complex of Phosphorus for Lithium Battery Electrolytes

摘要

A new Li salt, lithium tris(1, 2-benzenediolato (2)-O,O') phosphate, was synthesized and utilized in Li batteryelectrolytes for Li/V2O5 cells. This Li salt has a hexacoordinatedchelate-type phosphorus anion produced from a pentacoordinatedorganophosphorus compound as a useful intermediate. It isthermally stable due to the chelating effect with the bidentateligands of the anion which is a feature distinct from the commonLi battery salt LiPF6. The thermal decomposition temperature ishigher than that of The pentacoordinated intermediate, and thedecomposition process is proven to occur in two steps withrelease of the benzene moiety from the anion. The specificconductivity (3.89 mS cm-1) in an ethylene carbonate-tetrahydrofuran binary mixture (mole fraction of tetrahydrofuranis 0.7) is somewhat low, which can be explained by their highviscosities based on the large anion size. In spite of the lowconductivity, the discharge capacity approaches the theoreticalvalue, and a high energy density (410 Wh kg-1) is obtained for aLi/V2O5 cell discharged to a cutoff potential of 2.5V vs. Li/Li+.