成果報告書詳細
管理番号20130000000349
タイトル*平成24年度中間年報 安全・低コスト大規模蓄電システム技術開発/共通基盤研究/過渡現象を利用する大規模蓄電システムの非破壊劣化診断技術の開発
公開日2013/5/29
報告書年度2012 - 2012
委託先名学校法人同志社 同志社大学
プロジェクト番号P11007
部署名スマートコミュニティ部
和文要約
英文要約 An estimation method of circuit parameters of a Lithium-ion battery model has been proposed. The model consists of a DC voltage source and an internal impedance. The proposed method gives the circuit parameters from a measured voltage and current waveforms during its operation. The internal voltage is a function of the State Of Charge (SOC). The internal impedance can be expressed by a resistor, which expresses the voltage drop in a high frequency region, and some RC parallel circuits, which express the transient characteristic of the battery. Their parameters are estimated from the impedance in z-domain. The proposed method gives satisfactory accurate parameters without initial values. The accuracy of the proposed method is confirmed by a comparison with the measured transient characteristic of a battery.
 The voltage waveform of a battery installed in an electrical bike shows an identical tendency to that of a laboratory test. A transient characteristic of a deteriorated laminate-type battery also shows an identical tendency to that of an 18650-type battery. These results indicate that the proposed method is applicable to practical apparatuses.
 The transient characteristic of a battery heavily depends on its temperature, which is difficult to measure. The temperature, however, can be estimated from the battery current and the internal impedance with a thermal equivalent circuit. The method reduces the number of thermal sensors for an assembled battery system.
 Accelerated degradation tests (high temperature and high voltage) were carried out for coin-type half cells using a graphite anode and LMO, NCA, and NCM cathodes, and the variations of impedance components were summarized. The increase in impedance of the graphite anode was mainly due to the growth of the surface film made of organic materials (and LiF), while that of all the cathodes was attributed to an increase in the coverage of highly resistive surface film, probably made of LiF.
 The propriety of the proposed method was investigated by comparing the data obtained by the proposed method and the conventional impedance method. The estimated impedance by the proposed method did not completely agree with that measured by the impedance method, and some problems to be improved became clear.
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