• Journal of Electrochemical Science and Technology
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• v.15 no.3
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• pp.414-420
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• 2024

Lithium-ion batteries are widely used in many applications due to their high energy density, high efficiency, and excellent cycle ability. Once an unknown Li-ion battery is reusable, it is important to measure its lifetime and state of health. The most favorable measurement method is the cycle test, which is accurate but time- and capacity-consuming. In this study, instead of a cycle test, we present an empirical model based on the C-rate test to understand the state of health of the battery in a short time. As a result, we show that the partially accelerated charge/discharge condition of the Li-ion battery is highly effective for the degradation of battery capacity, even when half of the charge/discharge conditions are the same. This observation provides a measurable method for predicting battery reuse and future capacity degradation.

• Journal of Information Processing Systems
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• v.12 no.3
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• pp.436-454
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• 2016

This research presents the battery discharge rate models for the energy consumption of mobile phone batteries based on machine learning by taking into account three usage patterns of the phone: the standby state, video playing, and web browsing. We present the experimental design methodology for collecting data, preprocessing, model construction, and parameter selections. The data is collected based on the HTC One X hardware platform. We considered various setting factors, such as Bluetooth, brightness, 3G, GPS, Wi-Fi, and Sync. The battery levels for each possible state vector were measured, and then we constructed the battery prediction model using different regression functions based on the collected data. The accuracy of the constructed models using the multi-layer perceptron (MLP) and the support vector machine (SVM) were compared using varying kernel functions. Various parameters for MLP and SVM were considered. The measurement of prediction efficiency was done by the mean absolute error (MAE) and the root mean squared error (RMSE). The experiments showed that the MLP with linear regression performs well overall, while the SVM with the polynomial kernel function based on the linear regression gives a low MAE and RMSE. As a result, we were able to demonstrate how to apply the derived model to predict the remaining battery charge.

• Clean Technology
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• v.18 no.3
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• pp.320-324
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• 2012

In the present study, the discharge characteristics of a lithium-ion battery was evaluated to calculate the rate of heat generation under various discharge rates by mathematical modeling. The modeling and simulation of a pseudo-two dimensional ionic transport system for governing Butler-Volmer equation were carried out by using FEMLAB as a PDE (partial differential equation) solver, where the discharge rate was changed from 5 $A/m^2$ to 25 $A/m^2$. The computational results showed that the concentration of consumed solid-phase lithium at the surface of electrode was increased with increasing discharge rates. While the resulting diffusion limitation occurred shortly, it increased the rate of heat generation even more rapidly for the internal voltage to approach the cutoff voltage of the lithium-ion battery.

• Journal of IKEEE
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• v.18 no.1
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• pp.96-105
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• 2014

This paper proposes a battery lifetime enhancement method based on the nonlinear discharge charisteristics called recovery effect. In general, the stored energy in a battery is considered in the prediction of battery lifetime. However, due to the chemical reaction in a battery, more energy can be drawn from a battery when it is not continuously but intermittently discharged, which is called recovery effect. In the proposed method, several battery cells are alternately discharged, and some battery cells rest while maintaining the system power supply. This makes recovery effect of battery cells, which extends battery lifetime. In the experiment, battery lifetime increases about 7% in the alternating discharge of two battery cells, when compared with conventional parallel discharge.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.12
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• pp.819-828
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• 2022

Sensitivity of aircraft sizing depending on battery performance was studied for a generic quad tilt rotor type electric vertical takeoff and landing vehicle. The mission requirements proposed by Uber Elevate and NASA were used for initial sizing, and the calculated gross weight is ranged between 5,000lb and 11,000lb for battery specific energy range of 200-400Wh/kg in pack level and continuous discharge rate range of 4-5C. For the assumed gross weight of 7,000lb, the required battery performance was calculated with two different criteria: available power and energy, and the effects of battery specific energy and discharge rate are analyzed. The maximum discharge rate is also recommended considering failure cases such as one battery pack inoperative and one prop rotor inoperative.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1129-1131
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• 2002

Zinc Air battery obtain their energy density advantage over the other batteries by utilizing ambient oxygen as the cathode materials, and reusing cathode as recycled form. And specific capacity of zinc powder is as high as 820mAh/g. When Zinc Air battery discharged by low rate current discharge voltage profile has very flat pattern until end of voltage. But, when Zinc Air battery discharged by high rate current discharge voltage and capacity become lower. Therefore, we focused on effects of catalyst size in cathode. So we examined performance of zinc air batteries, average discharge voltage, capacity, energy, resistance. And we also obtained resistance by the GSM pulse discharge. So we have got optimum size of catalyst for Zinc Air battery.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.852-856
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• 2011

The lithium ion diffusion coefficients of bare, carbon-coated and Cr-doped $LiFePO_4$ were obtained by fitting the discharge curves of each half cell with Li metal anode. Diffusion losses at discharge curves were acquired with experiment data and fitted to equations. Theoretically fitted equations showed good agreement with experimental results. Moreover, theoretical equations are able to predict lithium diffusion coefficient and discharge curves at various discharge rates. The obtained diffusion coefficients were similar to the true diffusion coefficient of phase transformation electrodes. Lithium ion diffusion is one of main factors that determine voltage drop in a half cell with $LiFePO_4$ cathode and Li metal anode. The high diffusion coefficient of carbon-coated and Cr-doped $LiFePO_4$ resulted in better performance at the discharge process. The performance at high discharge rate was improved much as diffusion coefficient increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.350-351
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• 2005

The electrochemical behavior of Si-C material synthesized by heating the mixture of silicon and polyvinylidene fluoride (PVDF). Coin cells of the type 2025 were made using the synthesized material and the electrochemical studies were performed. Si-C/Li cells were made by using the developed Si-C material. Charge/discharge test was performed at 0.1C hour rate. Initial charge and discharge capacities at Si-C material derived from 20 wt.% of PVDF was found to be 1,830 and 526 mAh/g respectively. Initial charge/discharge characteristics of the electrode were analyzed. The level of reversible specific capacity was about 216 mAh/g at Si-C material derived from 20 wt.% of PVDF, IIE, intercalation efficiency at initial charge/discharge, was 68 %. Surface irreversible specific capacity was 31 mAh/g, and average specific resistance was 2.6 ohm*g.

• Journal of Electrochemical Science and Technology
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• v.2 no.2
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• pp.97-102
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• 2011

Different amounts of excess lithium in the range of x = 0~0.3 were added to $Li_{1+x}[Mn_{0.720}Ni_{0.175}Co_{0.105}]O_2$ cathode materials synthesized using the co-precipitation method to investigate its microstructure and electrochemical properties. Pure layered structure without impurities was confirmed in the XRD pattern analysis and increasing peak intensity of $Li_2MnO_3$ was observed along with the addition of over 0.2 mol Li. The initial discharge capacity of the stoichiometric composition was determined to be 246 mAh/g, while the discharge capacity of the addition of 0.1 mol Li was obtained to be 241 mAh/g, which was not significantly different from that of the stoichiometric composition. However, the discharge capacities decreased dramatically after the addition of 0.2 and 0.3 mol Li to 162 mAh/g and 146 mAh/g, respectively. In the rate capability test, the active $Li_{1+x}[Mn_{0.720}Ni_{0.175}Co_{0.105}]O_2$ cathode material of the stoichiometric composition showed a dramatic decrease in its discharge capacity with increasing C-rate, as evidenced by the result that the discharge capacity at 5C was 13% compared with 0.1C. On the other hand, the discharge capacity of compositions containing excess lithium was improved at higher current rates. The cycling test showed that the composition containing an excess of 0.1 mol Li had the most outstanding capacity retention.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.1
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• pp.68-74
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• 2005

In this work, polymerization conditions of the gel polymer electrolyte (GPE) were studied to obtain better electrochemical performances in a lithium-ion polymer battery. When the polymerization temperature and time of the GPE were 70$^{\circ}C$ and 70 min, respectively, the lithium polymer battery showed excellent a rate capability and cycleability. The TMPETA (trimethylolpropane ethoxylate triacrylate)/TEGDMA (triethylene glycol dimethacrylate)-based cells prepared under optimized polymerization conditions showed excellent rate capability and low-temperature performances: The discharge capacity of cells at 2 Crate showed 92.1 % against 0.2C rate. The cell at -20 $^{\circ}C$ also delivered 82.4 % of the discharge capacity at room temperature.