Lithium-Ion and Chloride-Ion Transfer in Chiral and Racemic 3-Hydroxyquinuclidinium Perchlorate: Influence of Defects and a Mixed Plastic Crystal Matrix

Abstract

Organic ionic plastic crystals (OIPCs) are promising solid electrolytes. To observe the effect of defects and a mixed OIPC matrix on ionic conductivity, lithium-ion transfer and chloride-ion transfer in chiral and racemic (+/±)-3-hydroxyquinuclidinium perchlorate plastic crystals were studied. The pure chiral material and racemic mixture and their corresponding doped mixtures showed different thermal behaviors. Powder X-ray diffraction revealed that the cubic crystal structure appeared in both the high-temperature phase of the pure chiral material and the whole temperature range for the racemic system. Solid-state nuclear magnetic resonance spectra indicated the possible ion mobility of the two undoped matrices. The lithiumion conductivity in the chiral material (above −10 °C) and racemic mixture (in the whole temperature region) increased 2.5−3 orders of magnitude, while the chloride-ion conductivity in the chiral material only increased obviously above 50 °C. Positron annihilation lifetime spectroscopy demonstrated the dependence of ionic conductivity on defect volumes of the pure chiral material and its doped mixtures, and the defects of the doped mixtures expanded largely. The ionic conductivity and defect volume of the doped mixtures containing lithium ions and chloride ions qualitatively obeyed the Cohen−Turnbull free volume theory.

Investigation of the Physicochemical Properties of Pyrrolidinium-Based Mixed Plastic Crystal Electrolytes

“…26,27 A recent study by Dong et al reported the interesting thermal and transport properties of pure chiral (+)-3hydroxyquinuclidinium perchlorate ((+)-[3-OH-QH]ClO 4 ) compared to racemic (±)-3-hydroxyquinuclidinium perchlorate ((±)-[3-OH-QH]ClO 4 ) and mixed systems. 28 Thermal phase behavior studies revealed that pure (+)-[3-OH-QH]-ClO 4 displayed one solid−solid transition, while racemic (±)-[3-OH-QH]ClO 4 showed no solid−solid transitions. Investigation of the transport properties of neat (+)-[3-OH-QH]ClO 4 showed increased ionic conductivity as the temperature is increased, with a sudden jump in values observed at the II−I phase transition (12 °C).…”

“…Thermal phase behavior studies revealed that pure (+)-[3-OH-QH]­ClO 4 displayed one solid–solid transition, while racemic (±)-[3-OH-QH]­ClO 4 showed no solid–solid transitions. Investigation of the transport properties of neat (+)-[3-OH-QH]­ClO 4 showed increased ionic conductivity as the temperature is increased, with a sudden jump in values observed at the II–I phase transition (12 °C) . The sudden increase in ionic conductivity was attributed to the increase in onset of rotational motions/change in crystal structure as the OIPC sample is heated.…”

“…A recent study by Dong et al reported the interesting thermal and transport properties of pure chiral (+)-3-hydroxyquinuclidinium perchlorate ((+)-[3-OH-QH]­ClO 4 ) compared to racemic (±)-3-hydroxyquinuclidinium perchlorate ((±)-[3-OH-QH]­ClO 4 ) and mixed systems . Thermal phase behavior studies revealed that pure (+)-[3-OH-QH]­ClO 4 displayed one solid–solid transition, while racemic (±)-[3-OH-QH]­ClO 4 showed no solid–solid transitions.…”

“…In contrast, the mixed OIPC (±)-[3-OH-QH]­ClO 4 shows a gradual increase in ionic conductivity values with increasing temperature, without sudden rises. It was concluded that the mixed OIPC (±)-[3-OH-QH]­ClO 4 system has a high-symmetry cubic lattice throughout the low- and high-temperature phases, with no structural changes occurring …”

“…Investigation of the transport properties of neat (+)-[3-OH-QH]ClO 4 showed increased ionic conductivity as the temperature is increased, with a sudden jump in values observed at the II−I phase transition (12 °C). 28 The sudden increase in ionic conductivity was attributed to the increase in onset of rotational motions/change in crystal structure as the OIPC sample is heated. In contrast, the mixed OIPC (±)-[3-OH-QH]ClO 4 shows a gradual increase in ionic conductivity values with increasing temperature, without sudden rises.…”