Host-Guest Interactions in Single-Ion Lithium Polymer Electrolyte

Abstract

The complex interplay between the ionic conductivity and structure of the LiCF 3 SO 3 :PEO polymer electrolyte, induced by the calix͓6͔pyrrole anion receptor, has been investigated by different experimental methods, including ac impedance, calorimetry, X-ray diffraction, and Fourier-transform infrared spectroscopy. It was found that calix͓6͔pyrrole, even at low concentrations, can form stable bidentate complexes with triflate anions, thus making cation transport dominating, which results in t + close to unity. It should be noted that the incorporation of an anion trap does not suppress the bulk ionic conductivity of polymer electrolytes at above 60°C. We attribute this effect to the dissociation of ion aggregates and structural changes imposed by the additive. Stable solid electrolyte interface resistance was achieved in the polymer electrolytes containing calix͓6͔pyrrole.

Influence of calix[2]‐p‐benzo[4]pyrrole on the electrochemical properties of poly(ethylene oxide)‐based electrolytes for lithium batteries

“…27 It is interesting to note that no discernible peak has been identified in the high-energy narrow peak at 845 cm À1 in the PEOþCBPþLiCF 3 SO 3 system, which suggests that the basic lithium-polyether backbone interactions remain unaltered. 28 A similar trend has been observed by Golodnitsky et al, 7 who studied the electrochemical properties of calix [6]pyrrole.…”

“…According to Fuoss-Kraus calculations, 20 in the range where a rise in conductivity is noted, the contribution of free ions decreases due to generation of positively charged triplets. 21 According to Golodnitsky et al, 7 this trend breaks down when such triplets aggregate into more complex species, making macroscopic viscosity the predominant factor in conductivity. Furthermore, bulky molecules in the electrolyte cannot only provide steric hindrance for segmental motion of the polyether chains but also render transport of ions more difficult.…”

“…Both anions and cations are mobile in PEs, with cationic transference numbers nearly always below 0.5. According to Golodnitsky et al, 7 who studied the effect of calix [6]pyrrole on the electrochemical properties of PEO-LiN(CF 3-SO 2 ) 2 (LiTFSI) complexes, the anionic mobility reduces the limiting current density and forms an undesirable salt concentration gradient across the PE. Subsequently, this leads to a voltage drop during constant current operation, which in turn, affects the high-power capability of the battery.…”

A search for a single-ion-conducting polymer electrolyte: Combined effect of anion trap and inorganic filler

“…In our recent work [10,11], we have shown, by dc-ac techniques, that addition of calix [6]pyrrole (C6P) to polyether-based lithium triflate electrolytes results in a considerable increase in the cation transport number, t Li+ . Contrary to the case of calixarene compounds [12], the increase in the lithium transference number is observed upon incorporation of even a small amount of C6P.…”

Salt-in-Polymer Electrolytes for Lithium Ion Batteries Based on Organo-Functionalized Polyphosphazenes and Polysiloxanes

“…Interestingly, an increase of the transference number of lithium ions has been achieved by dispersing nanoparticles, or by dissolving crown ethers or other molecules with specific ionic interactions [48,87,88]. A completely different approach was suggested and investigated by Bruce et al which relies on ordered domains of PEO based electrolytes with fast transport of lithium ions along helix channels formed by the PEO backbone [89,90].…”