Beyond the battery capacity, the impedance of the battery also has a large impact on the performance of the battery. In order to study the change of the impedance of the batteries in electrolyte with different acidity, the electrochemical impedance spectroscopy (EIS) test was carried out. The impedance of the battery consists of three parts, namely internal resistance, electric double layer capacitance and Faraday impedance. The internal resistance refers to the internal resistance of the electrolyte and the electrode, which is determined by the properties of the electrolyte and the electrode material and is a constant. The electric double layer capacitor exists because except for the active ions, there are also inactive ions exist in the electrolyte. The inactive ions do not undergo a redox reaction, only changing the charge distribution in the electrolyte and causing the electric double layer capacitance. The Faraday impedance is derived from the redox reaction and charge transfer occurring in the active ions in the electrolyte. The Faraday process can be further divided into two processes, a charge transfer process and a mass transfer process. These two processes produce charge transfer resistance and mass transfer resistance, respectively. When the scanning frequency is low, the mass transfer resistance is dominant. When the scanning frequency is high, the time period of the change is too short, so that the material transfer does not take place, and the charge transfer resistance is dominant. In the impedance diagram, the semicircle represents the charge transfer resistance, and the diameter of the semicircle represents the interface resistance. The larger the diameter of the semicircle, the larger the interface resistance, and the more difficult the redox reaction occurs.Sometimes there will be more than one semicircle in the impedance map, indicating that there are multiple interface resistors in the battery system. At the same time, the straight line after the semicircle represents the mass transfer impedance. The greater the slope of the line, the lower the impedance. Furthermore, the mass transfer resistance of the battery changes with the scanning frequency.The lower the scanning frequency, the larger the mass transfer resistance. Fig. compared the impedance of battery in electrolyte of different acidity under the scan rate from 200kHz to 100mHz.