State-of-charge and state-of-health estimation for lithium-ion battery using the direct wave signals of guided wave

With the development of new energy technology, lithium-ion battery, as a common energy storage and driving structure, has been widely used in many fields. It is significant to accurately monitor and evaluate the state of charge (SOC) and state of health (SOH) of lithium-ion battery. This paper presents the estimation method of SOC and SOH of lithium-ion battery based on ultrasonic guided wave technology. In the experiment, the guided wave signals are activated by a single fixed piezoelectric transducer and the propagating guided waves are rapidly captured using a scanning laser Doppler vibrometer system. The multi-parameter analysis of the direct wave signals including time-domain, frequency-domain and time-frequency distribution are performed, and thus three guided-wave parameters, namely signal amplitude, time of flight and power spectral density connected with the charge discharge cycle and aging of battery, are successively set to comprehensively evaluate SOC/SOH of lithium-ion battery. The results show that the guided wave parameters in time-domain, frequency-domain and time-frequency distribution have well consistent correspondence with SOC/SOH, and the differential curve analysis of signal amplitude can effectively reflect the phase transitions in the charge-discharge cycle and the aging process. In addition, the sensitivity of ultrasonic guided wave technology to estimation of SOC/SOH gradually decreases with the battery aging.