Electrical Circuit Model for Sodium-ion Batteries

Sodium-ion batteries offer a promising alternative to lithium-ion ones thanks to their lower cost, smaller ecological footprint, and less stringent safety requirements. The development of an accurate model to reproduce their behaviors is still an open issue, despite being essential for enabling their efficient utilization. This work investigates the repurposing of lithium-ion equivalent circuit models for sodium-ion cells. Four models with 1, 2, 3, and 4 RC groups are considered to investigate their trade-off between accuracy and computational efficiency. The model parameters are identified with a pulse current test carried out on two nominally identical commercial cells. The performance of the models is evaluated using pulse current tests and a realistic electric vehicle current profile. In both cases, all the models achieve errors lower than 1% of the nominal cell voltage. These values are comparable with those obtained in lithium-ion cell models, suggesting the portability of model-based algorithms from lithium-ion batteries to sodium-ion ones. Moreover, the results highlight that the model with 2 RC groups is the best choice in low computational complexity systems. On the other hand, the model with 3 RC groups has the best trade-off between accuracy and computational complexity.