Transport Properties of Solid Polymer Electrolytes Prepared from Oligomeric Fluorosulfonimide Lithium Salts Dissolved in High Molecular Weight Poly(ethylene oxide)

Abstract

Transport properties such as ionic conductivity, lithium transference number, and apparent salt diffusion coefficient are reported for solid polymer electrolytes (SPEs) prepared using several oligomeric bis[(perfluoroalkyl)sulfonyl]imide (fluorosulfonimide) lithium salts dissolved in high molecular weight poly(ethylene oxide) (PEO). The salt series consists of polyanions in which two discrete fluorosulfonimide anions are linked together by [(perfluorobutylene)disulfonyl]imide linker chains. The restricted diffusion technique was used to measure the apparent salt diffusion coefficients in SPEs, and cationic transference numbers were determined using both potentiostatic polarization and electrochemical impedance spectroscopy methods. A general trend of diminished salt diffusion coefficient with increasing anion size was observed and is opposite to the trend observed in ionic conductivity. This unexpected finding is rationalized in terms of the cumulative effects of charge carrier concentration, anion mobility, ion pairing, host plasticization by the anions, and salt phase segregation on the conductivity.

Negative Transference Numbers in Poly(ethylene oxide)-Based Electrolytes

“…It is based on the measurement of conductivity by ac impedance, salt diffusion coefficient by restricted diffusion, steady-state current under dc polarization, and the thermodynamic factor using concentration cells. Our approach, based on concentrated solution theory, is very similar to that proposed by Ma et al 33 A majority of t + values reported in the literature [41][42][43][44][45][47][48][49]58,59,61 are based on the steady-state current method pioneered by Bruce and Vincent. 42,57 In a few cases [34][35][36][37] where the approach of Ma et al is used to determine t + , there is no attempt to relate t + values thus obtained with those that might be obtained using the steady-state current method.…”

“…It is now fairly routine to report both σ and t +,SS of newly-developed polymer electrolytes. 41,44,45,47,48,[58][59][60] The question of limits on i ss /i 0 , or equivalently, t +,SS is an interesting open question. While most papers have reported i ss /i 0 values between 0 and 1, there is at least one report wherein i ss /i 0 obtained from an electrolyte was greater than 1.…”

Synthesis and properties of polysiloxanes containing polyhedral oligomeric silsesquioxane (POSS) and oligo (ethylene oxide) groups in the side chains

“…[15][16][17] However, the practical application of PEO for electrolyte materials is limited due to its low ionic conductivity at room temperature; the ionic conduction occurs mostly in the amorphous phase while PEO is highly crystalline at room temperature. [18][19][20] To decrease the crystallinity or to increase the conductivity by increasing the free volume or the mobility of polymer chains, comb-like or hairy-rod-like polymers and inorganic scaffolds having oligomeric ethylene oxide groups were prepared. 16,[21][22][23][24][25] Especially polysiloxanes having oligo(ethylene oxide) have been extensively studied because they have reasonably high ionic conductivity due to the high mobility of the siloxane backbone, although they are not solid polymer electrolytes.…”

Biopolymer agar‐agar doped with NH4SCN as solid polymer electrolyte for electrochemical cell application

“…Diffusion coefficient, also called diffusivity, is an important parameter indicative of the diffusion mobility. The diffusion coefficients of cations and anions of each polymer electrolyte have been calculated from the measured values of conductivity and cation transference number ( t + ), using the following equations …”