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This paper presents a reduced-order electrochemical battery model designed for the online implementation of battery control systems. The model is based on porous-electrode and concentrated-solution theory frameworks and is able to predict voltage as well as the internal electrochemical variables of a battery. The reduction of the model leads to a physics-based one-dimensional discrete-time state-space reduced-order model (ROM), which is especially beneficial for online systems. Models optimized around different operational setpoints are combined to predict cell variables over a wide range of temperatures and state of charges (SOCs) using the output-blending method. A sigma-point Kalman filter is further used to manage inaccuracies generated by the reduction process and experimental-related issues such as measurement error (noise) in the current and voltage sensors. The state-estimation accuracies are measured against a full-order model (FOM) developed in COMSOL. The whole system is able to track the internal variables of the cell, as well as the cell voltage and SOC with very high accuracy, demonstrating its suitability for an online battery control system.

Electrochemical models are an incipient technique for estimation of battery cells internal variables, useful for cells design or state of function optimization. One of the non-trivial procedures that allow the use of this type of models is the estimation of model parameter values. This paper presents a review of the existing computational parameter estimation methods for rocking chair batteries electrochemical models, a crucial step for real case implementation. Physics-based models cannot reach accurate predictions if the parameters are not properly estimated, what highlights the necessity of reviewing the validity of these protocols, that are not extensively treated within literature. The gathered methods are explained and analyzed taking into account the accuracy and extent of the presented results, to give the most objective overview of their applicability within real case scenarios. The methods are classified into two different groups: single optimization analysis (using only one optimization procedure to estimate parameters) and multiple optimization analysis (methods using multiple optimizations). In addition, the need for at least some amount of physico-chemical characterization is analyzed as a common procedure for all the parameter estimation methods. The accuracy of each method is determined, taking as reference the best achievements found in literature. The results show that it is possible to estimate parameters with a high accuracy using non-invasive parameter estimation methods. Finally the potential of mixed (non invasive and physico-chemical based) methodologies is presented. These type of estimation procedures can potentially increase the accuracy of the procedures by lightening up the optimizations involved in the processes, and increasing the ability to estimate values for insensitive parameters. These mixed methods could achieve faster and cheaper estimation protocols, making them more efficient in general.

Safety issues related to lithium-ion batteries are a driving force in the search for new energy storage systems. Lithium-ion capacitors are becoming recognised as promising devices to address the question of safety. These products are a combination of lithium-ion batteries and electric double-layer capacitors in terms of energy and power density. The aim of this work is to assess lithium-ion capacitor safety under over-charge and under-discharge processes for pouch and prismatic cells. In the course of performing abuse tests, no evidence was found of severe hazard (explosion, fire or flame, rupture or major leakage). Quantitative external parameters (thickness, resistance and mass) and electro-thermal measurements showed an increase of swelling and internal resistance, which caused a decrease of capacity and energy efficiency in all cases. The ultrasound characterization technique confirmed that there were irreversible physical modifications of the materials under abuse conditions on prismatic cells, which could not be seen with the commonly used magnitudes (U, I, T). This technique was also used for the identification of the start of cell degradation. In post-mortem analysis, were observed different degradation phenomena such as melting of the separator and delamination in the electrodes.