Physics-based modelling and analysis of various ageing mechanisms in sodium-ion batteries

Sodium-ion batteries are getting significant attention due to the abundance of raw materials. These batteries are anticipated to have their utility in the grid and electric vehicles. The prominent concern with these batteries is the capacity fade over time, which is generally caused by side reactions under varying operating conditions, leading to degradation mechanisms, such as unstable solid electrolyte interface layer formation and sodium plating. This study compares the three solid electrolyte interface degradation models: solvent-diffusion, reactionlimited, and ethylene carbonate reaction-limited, to predict capacity fade. These models are individually coupled with the reversible and irreversible sodium plating models. An application-based study is performed for lowspeed electric vehicles using Urban Dynamometer Driving Schedule and New York City Cycle drive cycles to assess battery life. The short-term (non-ageing) and long-term (ageing) cycling tests are performed using the drive cycles to assess the capacity fade by maintaining the battery at a higher voltage for a prolonged duration. The solvent-diffusion model predicted higher capacity fade among all models. The reaction-limited and ethylene carbonate reaction-limited models exhibit identical results, underscoring their concurrence in predictability. This study provides insights into sodium inventory loss and solid electrolyte interface growth and their effect on battery performance.