The influence of ion-pair transport in salt containing liquid electrolytes

C. Pfaffenhuber, J. Popovic

The influence of ion pairs to the overall conductivity in salt containing liquid electrolytes via an indirect (vehicular) transport mechanism has often been neglected, particularly in Li-based electrolytes.

Figure: Vehicular Li+ transport mechanism in Li-salt containing electrolytes involving ion-pairs. — Figure: Vehicular Li⁺transport mechanism in Li-salt containing electrolytes involving ion-pairs.

Figure: Vehicular Li⁺transport mechanism in Li-salt containing electrolytes involving ion-pairs.

In this context, individual conductivity contributions of cations (σ₊), anions (σ_-) and ion pairs (s) can be determined by engaging the concept of conservative ensembles and three experimental techniques (AC conductivity for σ_AC, DC polarization for σ_pol and PFG-NMR for s^*):

where s* is retrieved through tracer diffusion coefficient

Lithium triflate containing polyethylene glycol electrolyte solutions are currently investigated. The analysis can be extended to other electrolyte systems, including ionic liquids.

Publications:

J. Maier, Adv. Funct. Mater. , 2011, 21, 1448. DOI: 10.1002/adfm.201002153

C. Pfaffenhuber, J. Popovic, J. Maier, in preparation