Dynamics of Li ions in an intercalated polymer electrolyte: a ⁷Li nuclear magnetic resonance study

Abstract

The ⁷Li nuclear magnetic resonance spectra and spin-lattice relaxation rates of lithium ions in an intercalated polymer electrolyte, Li-polyethylene-oxide confined within the galleries of an inorganic layered solid CdPS₃, are reported. The spectra show an unusual feature, the appearance above 330 K of quadrupolar satellites, whose splitting increases linearly with temperature, and their absence below this temperature. This behavior is also reflected in the temperature variation of the spin-lattice relaxation rates, which show a minimum at 300 K but above 330 K start decreasing again. Using an anisotropic quantum oscillator model, the observed variation in the ⁷Li quadrupolar coupling constant is shown to arise from changes in the time average of the electric field gradient as seen by a ⁷Li nucleus associated with mobile segments of the intercalated polymer.