Serge Pelissier

Study of graphite/NCA Li-ion cell degradation during accelerated aging tests — Data analysis of the SIMSTOCK project

This paper presents a preliminary analysis of aging data from the French SIMSTOCK program in order to evaluate the influence of several aging factors on capacity fade and impedance increase of graphite/NCA Li-ion batteries over accelerated aging tests. Test protocols (cycling and check-up) are presented, and the behavior of battery under aging is described. An equivalent-circuit model is used to extract the various contributions of the impedance spectra. Finally, the influence of the aging factors on capacity fade and impedance increase is discussed.

Measuring Reversible and Irreversible Capacity Losses on Lithium-Ion Batteries

In this paper we present an innovative and precise way to calculate the available capacity in a battery. This quantity is essential to assess the ageing process during real use or ageing tests. The most common way to measure the battery capacity consists on a constant current discharge. It is quite simple to implement but very dependent of impedance and relaxation state of the battery. Consequently, this method is not suitable to quantify reversible and irreversible capacity losses occurring on batteries. We propose an indirect measure of available capacity that reduces the distortion caused by battery relaxation and impedance changes.

Calendar and cycling ageing combination of batteries in electric vehicles

Abstract The battery is the most sensitive part in the powertrain of full electric vehicles because of its cost and weight. The full electric vehicle range and prize are highly determined by the battery performances. During its lifespan, the battery performances are degraded because of ageing mechanisms. Typically, there are two types of ageing: calendar and cycling ageing. In the electric vehicle application, both types of ageing coexist and interact. In this paper, we report the results of accelerated ageing tests and present a methodology to separate calendar from cycling ageing. With this analysis method, we demonstrate the interaction between calendar and cycling ageing when battery is cycled following representative current profiles of the electric vehicle application.

Impact of periodic current pulses on Li-ion batteries lifetime in vehicular application

Using the hybrid electric vehicle application as a reference, the possible impact of periodic current pulses on lithium ion secondary battery cycle life was evaluated. Several profile types, with and without pulses, were evaluated in a comparative study on cycle life of commercial graphite/LiFePO4 batteries. Results are presented, compared and analysed. Contrary to the well-known results on lead-acid batteries and to results in previously published work, there is no indication that periodic pulses could enhance the cycle life of Li-ion batteries. On the contrary, certain pulse patterns have been identified to be detrimental to Li-ion batteries.