Lithium environment in dilute poly(ethylene oxide)/lithium triflate polymer electrolyte from REDOR NMR spectroscopy

The role of the lithium ion environment is of fundamental interest regarding transport and conductivity in lithium polymer electrolytes. X-ray crystallography has been used to characterize the lithium environment in completely crystalline poly(ethylene oxide) (PEO) electrolytes, but this approach cannot be used with dilute PEO electrolytes. Here, using solid-state NMR data collected with the rotational-echo double-resonance C-13{Li-7} (REDOR) pulse sequence, we have been able to characterize the crystalline microdomains of a PEO-lithium triflate sample with an oxygen/lithium ratio of 20: 1. Our data clearly demonstrates that the lithium crystalline microdomains are nearly identical to those of a completely crystalline 3: 1 sample, for which the crystal structure is known.