Abstract:

Internal short circuit （ISC） fault of lithim-ion batteries in new energy vehicles， as a critical stage in the evolution of battery thermal runaway， pose significant threats to battery safety. There is currently a lack of relevant technologies for real-time diagnosis of ISC in lithium-ion batteries，but electrochemical impedance spectroscopy （EIS） technology has shown great potential for ISC diagnosis. In this paper， a research on online ISC diagnosis strategies is conducted for lithium-ion batteries based on EIS measurement chips. A DNB chip based EIS online measurement scheme for lithium-ion batteries is constructed， and EIS measurement experiments for ISC batteries are completed. The EIS response and internal average temperature change laws under ISC are obtained， and temperature sensitive impedance characteristic frequencies are extracted. The experiments show that the measurement scheme has a relative error of impedance modulus less than 5% in the frequency range of 1 kHz-0.1 Hz， and an impedance phase angle measurement error less than 2° below 100 Hz. A model for estimating the average internal temperature of batteries based on impedance phase angle is established， and a real-time diagnosis strategy for ISC based on EIS temperature monitoring is developed. Four series connected LFP batteries experiments show that compared with traditional surface temperature based diagnosis strategies， this strategy shortened the diagnosis time by 1 400 s， with the accuracy of ISC resistance estimation increased by 30%.

Key words: lithium-ion battery, electrochemical impedance spectroscopy, internal temperature estimation, internal short circuit diagnosis