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Owing to the variation between lithium-ion battery (LIB) cells, early discharge termination and overdischarge can occur when cells are coupled in series or parallel, thereby triggering a decrease in LIB module performance and safety. This study provides a modeling approach that considers the effect of cell variation on the performance of LIB modules in energy storage applications for improving the reliability of the power quality of energy storage devices and efficiency of the energy system. Ohm’s law and the law of conservation of charge were employed as the governing equations to estimate the discharge behavior of a single strand composing of two LIB cells connected in parallel based on the polarization properties of the electrode. Using the modeling parameters of a single strand, the particle swarm optimization algorithm was adopted to predict the discharge capacity and internal resistance distribution of 14 strands connected in series. Based on the model of the LIB strand to predict the discharge behavior, the effect of cell variation on the deviation of the discharge termination voltage and depth of discharge imbalance was modeled. The validity of the model was confirmed by comparing the experimental data with the modeling results.

In this study, we present a modeling approach to estimate the combined effects of cyclable lithium loss and electrolyte depletion on the capacity and discharge power fades of lithium-ion batteries (LIBs). The LIB cell based on LiNi0.6Co0.2Mn0.2O2 (NCM622) was used to model the discharge behavior in the multiple degradation modes. The discharge voltages for nine different levels of cyclable lithium loss and electrolyte depletion were measured experimentally. When there was no cyclable lithium loss, the 50% of electrolyte depletion brought about 5% reduction in discharge capacity at 0.05 C discharge rate, while it resulted in 46% reduction when it was coupled with 30% of cyclable lithium loss. The 50% of electrolyte depletion with no cyclable lithium loss caused 1% reduction in discharge power during 0.5 C discharge at the state of charge (SOC) level of 0.8, while it resulted in 13% reduction when it was coupled with 30% of cyclable lithium loss. The modeling results obtained by using the one-dimensional finite element method were compared with the experimental data. The justification of the modeling methods is demonstrated by the high degree of concordance between the predicted and experimental values. Using the validated modeling methodology, the discharge capacity and usable discharge power can be estimated effectively under various combined degradation modes of cyclable lithium loss and electrolyte depletion in the LIB cell.

This paper reports a modeling methodology to predict the electrical and thermal behaviors of a 2.7 V/650 F ultracapacitor (UC) cell from LS Mtron Ltd. (Anyang, Korea). The UC cell is subject to the charge/discharge cycling with constant-current between 1.35 V and 2.7 V. The charge/discharge current values examined are 50, 100, 150, and 200 A. A three resistor-capacitor (RC) parallel branch model is employed to calculate the electrical behavior of the UC. The modeling results for the variations of the UC cell voltage as a function of time for various charge/discharge currents are in good agreement with the experimental measurements. A three-dimensional thermal model is presented to predict the thermal behavior of the UC. Both of the irreversible and reversible heat generations inside the UC cell are considered. The validation of the three-dimensional thermal model is provided through the comparison of the modeling results with the experimental infrared (IR) image at various charge/discharge currents. A zero-dimensional thermal model is proposed to reduce the significant computational burden required for the three-dimensional thermal model. The zero-dimensional thermal model appears to generate the numerical results accurate enough to resolve the thermal management issues related to the UC for automotive applications without relying on significant computing resources.

This paper reports a modeling methodology to predict the effects of operating conditions on the thermal behavior of a lithium-ion battery (LIB) module. The potential and current density distributions on the electrodes of an LIB cell are predicted as a function of discharge time based on the principle of charge conservation. By using the modeling results of the potential and current density distributions of the LIB cell, the non-uniform distribution of the heat generation rate in a single LIB cell within the module is calculated. Based on the heat generation rate in the single LIB cell determined as a function of the position on the electrode and time, a three-dimensional thermal modeling of an LIB module is performed to calculate the three-dimensional velocity, pressure, and temperature distributions within the LIB module as a function of time at various operating conditions. Thermal modeling of an LIB module is validated by the comparison between the experimental measurements and the modeling results. The effect of the cooling condition of the LIB module on the temperature rise of the LIB cells within the module and the uniformity of the distribution of the cell temperatures are analyzed quantitatively based on the modeling results.

This paper reports a modeling methodology to predict the effect of the loss of cyclable lithium of a lithium-ion battery (LIB) cell comprised of a LiNi0.6Co0.2Mn0.2O2 cathode, natural graphite anode, and an organic electrolyte on the discharge behavior. A one-dimensional model based on a finite element method is presented to calculate the discharge behaviors of an LIB cell during galvanostatic discharge for various levels of the loss of cyclable lithium. Modeling results for the variation of the cell voltage of the LIB cell are compared with experimental measurements during galvanostatic discharge at various discharge rates for three different levels of the loss of cyclable lithium to validate the model. The calculation results obtained from the model are in good agreement with the experimental measurements. On the basis of the validated modeling approach, the effects of the loss of cyclable lithium on the discharge capacity and available discharge power of the LIB cell are estimated. The modeling results exhibit strong dependencies of the discharge behavior of an LIB cell on the discharge C-rate and the loss of cyclable lithium.

The zinc/bromine (Zn/Br2) flow battery is an attractive rechargeable system for grid-scale energy storage because of its inherent chemical simplicity, high degree of electrochemical reversibility at the electrodes, good energy density, and abundant low-cost materials. It is important to develop a mathematical model to calculate the current distributions in a Zn/Br2 flow cell in order to predict such quantities as current, voltage, and energy efficiencies under various charge and discharge conditions. This information can be used to design both of bench and production scale cells and to select the operating conditions for optimum performance. This paper reports a modeling methodology to predict the performance of a Zn/Br2 flow battery. The charge and discharge behaviors of a single cell is calculated based on a simple modeling approach by considering Ohm’s law and charge conservation on the electrodes based on the simplified polarization characteristics of the electrodes. An 8-cell stack performance is predicted based on an equivalent circuit model composed of the single cells and the resistances of the inlet and outlet streams of the positive and negative electrolytes. The model is validated by comparing the modeling results with the experimental measurements.

This paper reports a modeling methodology to predict the effects on the discharge behavior of the cathode composition of a lithium iron phosphate (LFP) battery cell comprising a LFP cathode, a lithium metal anode, and an organic electrolyte. A one-dimensional model based on a finite element method is presented to calculate the cell voltage change of a LFP battery cell during galvanostatic discharge. To test the validity of the modeling approach, the modeling results for the variations of the cell voltage of the LFP battery as a function of time are compared with the experimental measurements during galvanostatic discharge at various discharge rates of 0.1C, 0.5C, 1.0C, and 2.0C for three different compositions of the LFP cathode. The discharge curves obtained from the model are in good agreement with the experimental measurements. On the basis of the validated modeling approach, the effects of the cathode composition on the discharge behavior of a LFP battery cell are estimated. The modeling results exhibit highly nonlinear dependencies of the discharge behavior of a LFP battery cell on the discharge C-rate and cathode composition.