Polymer Precursor Derived Li_xPON Electrolytes: Toward Li–S Batteries

Efforts to develop polymer precursor electrolytes that offer properties anticipated to be similar or superior to (lithium phosphorus oxynitride, LiPON) glasses are reported. Such precursors offer the potential to be used to process LiPON-like thin glass/ceramic coatings for use in all solid state batteries, ASBs. Here, LiPON glasses provide a design basis for the synthesis of sets of oligomers/polymers by lithiation of OP(NH2)3–x(NH)x [from OP(NH)3],OP(NH2)3-x(NHSiMe3)x and [P═N]3(NHSiMe3)6–x(NH)x. The resulting systems have degrees of polymerization of 5–20. Treatment with selected amounts of LiNH2 provides varying degrees of lithiation and Li+ conducting properties commensurate with Li+ content. Polymer electrolytes impregnated in/on Celgard exhibit Li+ conductivities up to ∼1 × 10–5S cm–1 at room temperature and are thermally stable to ∼150 °C. A Li–S battery assembled using a Li6SiPON composition polymer electrolyte exhibits an initial reversible capacity of 1500 mAh gsulfur–1 and excellent cycle performance at 0.25 and 0.5 C rate over 120 cycles at room temperature.