Design guidelines for secondary lithium-ion battery electrodes to overcome performance limitations of recycled cathode materials

Abstract

Today the ever-growing demand of lithium-ion batteries for electric vehicles is posing a terrible burden on materials availability. In particular, high performance cathode materials, such as LiNixMnyCozO2 (NMC), are becoming increasingly critical, thus requiring recycling processes to maximise their reutilisation. Recyclers are moving towards closed loop solutions, such as co-precipitation and direct recycling methods, which however can provide recycled materials with decreased electrochemical and transport properties compared to virgin ones. This work uses numerical modelling to provide design guidelines to overcome performance losses of recycled cathode materials. The model and its parametrisation are validated against experimental data of a virgin NMC cell. An impact assessment on battery performance is carried out showing that a plausible decrease in theoretical volumetric capacity and Li diffusivity in cathode active material leads to both lower accessible capacity during discharge and inferior performance during charge. Nevertheless, a design analysis indicates that recycling degradation can be effectively overcome by simple compensatory measures, such as a limited increase in electrode thicknesses and/or minor decrease in active material diameter, providing similar roundtrip efficiency, energy density, safe thermal operation and performance of the original cell made with virgin materials.