| With its appearance, lithium battery has rapidly developed into one of the mostimportant rechargeable batteries for its advantages like high working voltage, highenergy density and small volume. However, the development of lithium battery isconstraint for the sake of its hidden danger, which calls for safety monitoring coming tobe a critical technology in the research of lithium battery. It is more accurate to describeperformances of a lithium battery by finding the impedance of it through research, sincechanges of a lithium battery’s impedance provides evidences for their safety prediction.Also, impedance is the critical parameter for battery sorting or evaluating consistency ofbatteries in a battery pack. Thus research on lithium battery’s impedance is of greatsignificance.In this paper, we study the impedance of lithium battery in two ways. First, wecorrect the initial model with data and impedance spectra, and then verify the correctedmodel with electrochemical software. EIS is an approach to know a battery’sperformance through its structure, thus Battery impedance model contains a largeamount of information indicating a battery’s performance. In our paper, we studybattery with impedance spectroscopy measurement system which was devised by usearlier, and get impedance spectra, as well as modify our initial model we establishedearlier. Finally, we came to the conclusion that a model of battery is composed ofparallel elements which contains double layer capacitance of the electrode surface andfaraday impedance (polarization resistance), another parallel element which contains ainductance and a resistance, and a equivalent components which indicates the battery’sohmic resistance, and all of which are series connected. We also tested the correctnessas well as accuracy of this model with impedance spectra. Second, we found a properway to construct a measuring platform of impedance spectroscopy through theoreticalanalysis of a lithium battery’s impedance spectroscopy, research on a battery’sperformances, and comparison of different approaches. A lithium battery’s innerstructure and chemical reactions are so complicated that common ways to preciselymeasure its resistance are impossible. So here we establish a impedance spectroscopy measurement system with AD5933Chip recently introduced by ADI Corporation afterhaving studied working principles of electrochemical workstation at home and abroad.A highly integrated impedance measurements chip incorporates functions required tomeasure a battery’s impedance, including excitation signal source, AD sampling andDTF. It simplifies circuit design, and satisfies design requirements at large. Since theerror of measurement is less than5percent, from the approach we adopted we mayknow more precisely about a battery’s impedance through measurement.In this paper, we apply EIS in the field of lithium battery monitoring, which opensup a new way to study the safety of batteries. And we have improved traditional ways ofdesigning, enhancing accuracy of measurement as well as simplifying circuit devisingthrough the impedance spectroscopy measurement system we established from theapproach we mentioned. This approach is of high practical value in fields of batteryassorting and battery’s safety monitoring. |
