Abstract
The limiting current is an important transport property of an electrolyte as it provides an upper bound on how fast a cell can be charged or discharged. We have measured the limiting current in lithium-lithium symmetric cells with a standard polymer electrolyte, a mixture of poly(ethylene oxide) and lithium bis(trifluoromethane) sulfonamide salt at 90°C. The cells were polarized with increasing current density. The steady-state cell potential was a smooth function of current density until the limiting current was exceeded. An abrupt increase in cell potential was taken as an experimental signature of the limiting current. The electrolyte mixture was fully characterized using electrochemical methods to determine the conductivity, salt diffusion coefficient, cation transference number, and thermodynamic factor as a function of salt concentration. We used Newman's concentrated solution theory to predict both cell potential and salt concentration profiles as functions of position in the cell at the experimentally applied current density. The theoretical limiting current was taken to be the current at which the calculated salt concentration at the cathode was zero. We see quantitative agreement between experimental measurements and theoretical predictions for the limiting current. This agreement is obtained without resorting to any adjustable parameters.
Highlights
Great efforts are being made to develop new electrolyte replacements53for rechargeable lithium batteries.[1,2,3,4,5,6,7,8] Traditional electrolytes used in lithium54batteries are mixtures of salts dissolved in cyclic carbonates
The time-dependence of the cell potential was recorded at fixed 388current densities
The steady-state cell potential was a smooth function of 389current density until a threshold; this threshold was taken as an indication 390that the applied current exceeded the limiting current
Summary
Great efforts are being made to develop new electrolyte replacements53for rechargeable lithium batteries.[1,2,3,4,5,6,7,8] Traditional electrolytes used in lithium54batteries are mixtures of salts dissolved in cyclic carbonates. Great efforts are being made to develop new electrolyte replacements. 53for rechargeable lithium batteries.[1,2,3,4,5,6,7,8] Traditional electrolytes used in lithium. 54batteries are mixtures of salts dissolved in cyclic carbonates. 55stability of these electrolytes at the operating potential of the batteries. 56affects both cycle life and safety.[9,10,11,12,13,14,15] There is considerable interest in. 57developing new electrolytes that overcome these limitations.[1,3,6,8,16,17,18] One. 58approach is to replace the solvent by a polymer.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have