Sodium‐ion batteries offer a promising alternative to lithium‐ion batteries by addressing ecological and economic challenges. However, to assess the applicability of these cells for different sectors, understanding aging behavior, including degradation modes, is crucial. This work presents a comprehensive aging analysis of 67 commercial sodium‐ion batteries under various temperatures, C‐rates, and depths of discharge. We analyzed the initial cell‐to‐cell variance and the aging trajectories regarding capacity fade and resistance increase. We demonstrated that the cycling rate does not significantly influence the aging trajectories, whereas smaller depths of discharge significantly reduce degradation. The degradation gradients for 25 °C and 40 °C were similar; for −10 °C, we observed rapid capacity fading that can be attributed to irreversible sodium plating. Furthermore, we identified the degradation modes for four different aging categories. Since some aging tests stopped due to gas‐induced current interrupt device triggering at low current rates and states of charge, we proposed two hypotheses for the gassing under specific conditions, suggesting inadequate gas consumption in cathode‐electrolyte side reactions or solid electrolyte interphase instability as potential causes. Overall, this work provides a valuable in‐depth analysis of the aging behavior of a commercial sodium‐ion battery as a function of temperature, C‐rate, and depth of discharge, with data made available for further research.

An accurate estimation of the residual energy, i. e., State of Energy (SoE), for lithium‐ion batteries is crucial for battery diagnostics since it relates to the remaining driving range of battery electric vehicles. Unlike the State of Charge, which solely reflects the charge, the SoE can feasibly estimate residual energy. The existing literature predominantly focuses on showcasing diverse methods with a gap in conducting in‐depth analysis and comparison of the SoE. The scope of this work is to provide a comprehensive understanding of the SoE by discussing the feasibility and applicability of various definitions and estimation approaches from the literature. For the first time, we classify existing SoE definitions, considering the differences between the inherent stored and usable energy. In the absence of a unified definition in the literature, we propose two physically feasible definitions. Based on the proposed definitions, we critically analyze the practical challenges of SoE estimation. Additionally, to examine the accuracy of the most suitable SoE definition, we conduct an experimental evaluation using a commercial NCA/C+Si cell. Compared to the State of stored Energy, we demonstrate that the State of Charge underestimates the residual energy by more than 3 %, highlighting the importance of adequate SoE estimation.

This research paper presents a data-based energy management method for a vessel that predicts the upcoming load demands based on data from weather information and its automated tracking system. The vessel is powered by a hybrid propulsion system consisting of a high-temperature fuel cell system to cover the base load and a battery system to compensate for the fuel cell’s limited dynamic response capability to load fluctuations. The developed energy management method predicts the load demand of the next time steps by analyzing physical relationships utilizing operational and positional data of a real vessel. This allows a steadier operation of the fuel cell and reduces stress factors leading to accelerated aging and increasing the resource efficiency of the propulsion system. Since large ships record tracking data of their cruise and no a priori training is required to adjust the energy management, the proposed method can be implemented with small additional computational effort. The functionality of the energy management method was verified using data from a real ship and records of the water currents in the North Sea. The accuracy of the load prediction is 2.7% and the attenuation of the fuel cell’s power output could be increased by approximately 32%.