Evaluating Transport Properties and Ionic Dissociation of LiPF6 in Concentrated Electrolyte. Issue 12 (17th August 2017)

• Record Type: Journal Article
• Authors: Feng, Zhange; Higa, Kenneth; Han, Kee Sung; Srinivasan, Venkat
• Is Part Of: Journal of the Electrochemical Society. Volume 164:Issue 12(2017)
• Page Start: A2434
• Page End: A2440
• Publication Date: 2017-08-17
• Subjects: concentrated solution theory -- electrolytes -- ionic dissociation -- lithium ion battery -- pulsed field gradient NMR -- transport properties; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0941712jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : The presence of lithium hexafluorophosphate (LiPF6 ) ion pairs in carbonate-based electrolyte solutions is widely accepted in the field of battery electrolyte research and is expected to affect solution transport properties. No existing techniques are capable of directly quantifying salt dissociation in these solutions. Previous publications by others have provided estimates of dissociation degrees using dilute solution theory and pulsed field gradient nuclear magnetic resonance spectroscopy (PFG-NMR) measurements of self-diffusivity. However, the behavior of a concentrated electrolyte solution can deviate significantly from dilute solution theory predictions. This work, for the first time, instead uses Onsager–Stefan–Maxwell concentrated solution theory and the generalized Darken relation with PFG-NMR measurements to quantify the degrees of dissociation in electrolyte solutions (LiPF6 in ethylene carbonate/diethyl carbonate, 1:1 by weight). At LiPF6 concentrations ranging from 0.1 M to 1.5 M, the salt dissociation degree is found to range from 61% to 37%. Transport properties are then calculated through concentrated solution theory with corrections for these significant levels of ion pairing.