Phenomenological Model-Based Analysis of Lithium Batteries: Discharge, Charge, Relaxation Times Studies, and Cycles Analysis

EDUARDO HENQUIN; AGUIRRE PIO

AICHE JOURNAL

JOHN WILEY & SONS INC

Lugar: New York; Año: 2015 vol. 61 p. 90 - 102

0001-1541

The operation of lithium ion batteries in discharge and charge processes is addressed. A simple phenomenologicalmodel is developed to predict all variables values. A set of algebraic and differential equations is derived taking intoaccount salt and lithium balances in electrodes, in the separator, and in particles. Balances are developed for finite volumesand appropriate average values of several variables such as concentrations, current densities, and electrochemicalreaction rates are introduced. Definitions of current densities as volume fraction functions are critical issues in the computations.Experimental values taken from the literature for discharge processes are predicted very accurately. Constantsalt concentration in the separator can be assumed and consequently, the model can be analytically solved. Charge anddischarge times, initial cell capacity, lost capacity, and relaxation times are easily estimated from simple equations andcell parameters. The limiting processes taking place during cell discharge can be determined. Energy efficiency andcapacity usage are quantified for cycles. VC 2014 American Institute of Chemical Engineers AIChE J, 61: 90?102, 2015Keywords: lithium ion batteries, cyclic processes, simplified mathematical modeling, capacity estimation, relaxation time