Discharge Rate Capability in Aged Li-Ion Batteries

Abstract

A dataset is presented containing the rate capability measured for Lithium-ion cells obtained from old notebook batteries. The experimental results show an intersection of rate capabilities, related to degraded cells that exhibit high reversible capacities compared to the rated value and measured at 0.1C discharge rate, but a fast voltage decay and a constrained discharge capacity measured at 1C. With the aid of an electrochemical model it is shown that this intersection is possible if cells containing a lower concentration of Lithium salt in the electrolyte are compared to others that experienced a higher damage in the electrodes during their first use. This article casts doubts on the validity of a state of health determined from the discharge capacity measured at one rate for the classification of Li-ion batteries for a second life, if applied to datasets containing batteries experiencing diverse degradation paths.