The DC internal resistance of battery cannot be measured directly because charging and discharging with a DC current will change the state of the battery: its temperature and charge level. To determine the change of battery internal resistance at low temperature, this paper measured the AC impedance of the battery placed in a −40 ☌ thermostatic enclosure. For battery-packtesting, a string of three cells is constructed.īattery internal resistance is one of the important parameters. Its measurement frequency range and AC amplitude are 10 μHz-4 MHz and 1 mV-1 V respectively with frequency accuracy of 0.0025%.The tested battery is a LiMn 2O 4 cell, with cathode of spinel structure LiMn 2O 4, anode of artificial graphite, and shell of Al-plastic film. The electrochemical workstation produced by the Zahner Company in Germany is used to measure the AC impedance spectra of the battery and the impedance value at a fixed frequency. The function of the thermostatic enclosure is to provide the environment for the tests. Its maximum current and voltage of charge-discharge are 500 A and 500 V respectively. Battery-pack testing is performed by the Digatron EVT500-500 which is manufactured by the Digatron Company in Germany. Its maximum voltage of charge-discharge is 5 V, and its measurement precision can reach 0.1 mV. Cell-level charge-discharge testing is performed by the HT-V5C200D200 which is manufactured by the LTD company in Guangzhou. Experimental results prove that the wide-line metal film heating method can significantly improve the low-temperature performance of the battery.Ī diagram of the test platform is shown in Fig. Awide-line metal film is proposed to heat the battery so as to meet the low-temperature operating requirements of the 8×8 wheeled electric vehicle. This paper studies the charge-discharge performance of a LiMn 2O 4 battery in a 8×8 wheeled electric vehicle from 20 ☌ to −40 ☌. Therefore, auxiliary methods to improve the low-temperature performance of lithium-ion batteries become an important research direction, i.e., the AC heating method, preheating method, heating plate method and heating bag method. So far, it is difficult to improve their performance through innovations in the batteries’ materials. Generally, the solid electrolyte interface film, surface charge transfer impedance and Li+ diffusion in the electrode are the main influences on low-temperature performance of lithium-ion batteries. At low temperature, the charge-discharge performance of lithium-ion batteries significantly reduces. With their increased use, the low-temperature performance of lithium-ion batteries begins to attract attention. Lithium-ion is gradually replacing other chemistries to become the most common battery technology found in electric vehicles due to its advantages of high power, high energy density, long cycle life, low self-discharge rate, long shelf life and low pollution. Currently, battery chemistries used in electric vehicles include lead-acid, nickel cadmium, nickel metal hydride, lithiumion, and supercapacitors. The performance and cost of an electric vehicle depends strongly on the performance and service life of its battery. Battery energy storage is one of the key components in electric vehicles, so it receives strong research attention and has developed rapidly as a result. In-depth research work in many countries has improved all aspects of electric vehicle technology so that urban pollution can be reduced, and fruitful results have been achieved. However, lithium deposits were observed on all the anodes after 5000 pulse sequences with 10 s pulses at ± 20 C.In recent years, electric vehicles have developed rapidly. Negative anode voltages do not necessarily mean that lithium plating has occurred. For anodes, the maximum charge current to avoid a negative voltage was 3–5 C. Most of the cells were rated for a 10 C continuous discharge, and the cathode charging voltage at 10 C was around 4.2 V. On anodes, the third process can also be lithium plating. Pulse power tests at high rates typically showed three limiting processes within a 10 s pulse an instantaneous resistance increase, a solid state diffusion limited stage, and then electrolyte depletion/saturation. Tests on coin cell half cells included rate tests (continuous and pulsed), resistance measurements, and extended pulse tests. Commercial lithium ion cells with different power: energy ratios were disassembled, to allow the electrochemical performance of their electrodes to be evaluated.
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