Model-Based Investigation of Porosity Profiles in Graphite Anodes Regarding Sudden-Death and Second-Life of Lithium Ion Cells

Abstract

The second-life concept helps to reduce the cost for electric vehicles by adding monetary value to disused automotive batteries. However, the sudden-death effect, a change in ageing behaviour limits the total lifetime and might reduce the second-life timespan. In this paper, we utilize a common pseudo two-dimensional (P2D) cell model to investigate the influence of different porosity profiles in the graphite electrode on the battery’s ageing. Ageing is modeled by two irreversible side reactions at the anode, the formation of solid electrolyte interface (SEI) and lithium plating. We use parameters of a high-energy cell with thick electrodes. A constant initial anode porosity as a reference is compared with two optimized porosity profiles. Simulation results show that by using a layered anode, a two-stage porosity profile with higher porosity at the separator side, the cycle count until sudden-death and especially the cycles for second-life applications can both almost be doubled.

Keywords

• Li-ion cells
• ageing-induced lithium plating
• sudden-death
• second-life
• modelling
• porosity profiles
• graded porosity
• graphite anode