Optimal design and discharge operation of lithium-ion whole-cell

AIMO, CORINA. E.; HENQUÍN, EDUARDO. R.; AGUIRRE, PÍO. A.

Journal of Energy Storage

Elsevier

Año: 2019 vol. 24 p. 1 - 14

2352-152X

The optimal design of Li-ion whole-cells is presented for different discharge operating constraints: constantcurrent (CC), constant power (CP), and constant resistance (CR). In addition, a new Optimal TheoreticalOperation Policy (OTOP) is derived resorting to Variational Calculation. When applied to cell discharge, thispolicy relates equilibrium voltage, applied current, and discharge time. The considered design variables compriseelectrode thicknesses, porosity volume fractions, total solid volume fractions, and cell mass. The objectiveof the optimal design formulation is to maximize the total specific energy delivered for a set of given dischargetime values with the aim of relating delivered energy to delivered power. The simultaneous optimization ofmultiple design variables under different operating conditions is efficiently achieved by using a simple phenomenologicalmathematical model that predicts the main aspects of these systems. The importance of thisprocedure is reflected in remarkable improvements to total specific energy delivered. The optimized whole-celldesigns gained average improvements of more than 40%, depending on time discharge, when compared to theinitial design taken from the literature; and when the optimal designs obtained under the different operatingconditions are compared, an additional specific energy is obtained (OTOP results in the best operating condition,followed by CR, CC, and CP, with average differences of 7, 8, and 15%, respectively).