US 12,379,421 B2
In-situ ultrasonic method for detecting the state of charge in soft-packaged lithium-ion batteries
Yan Lyu, Beijing (CN); Jie Gao, Beijing (CN); Xuan Liu, Beijing (CN); Bin Wu, Beijing (CN); and Cunfu He, Beijing (CN)
Assigned to BEIJING UNIVERSITY OF TECHNOLOGY, Beijing (CN)
Filed by BEIJING UNIVERSITY OF TECHNOLOGY, Beijing (CN)
Filed on Apr. 30, 2024, as Appl. No. 18/650,083.
Application 18/650,083 is a continuation of application No. PCT/CN2022/128499, filed on Oct. 31, 2022.
Claims priority of application No. 202111315012.X (CN), filed on Nov. 8, 2021.
Prior Publication US 2024/0361394 A1, Oct. 31, 2024
Int. Cl. G01R 31/387 (2019.01); G01N 29/07 (2006.01); G01N 29/24 (2006.01); G01R 31/367 (2019.01)
CPC G01R 31/387 (2019.01) [G01N 29/07 (2013.01); G01N 29/2437 (2013.01); G01R 31/367 (2019.01); G01N 2291/023 (2013.01)] 1 Claim
OG exemplary drawing
 
1. A method for in-situ detection of a state of charge (SOC) of a soft-packaged lithium-ion battery using an ultrasonic guided wave, wherein a detection device for implementing the method includes a computer, a set of circular piezoelectric patches, a charging and discharging equipment, an arbitrary waveform generator, and a digital oscilloscope; the computer is connected to the charging and discharging equipment and the digital oscilloscope, the circular piezoelectric patches are connected to the arbitrary waveform generator and the digital oscilloscope;
the set of circular piezoelectric patches includes two circular piezoelectric patches, a center frequency of the circular piezoelectric patches is 150 kHz, the two circular piezoelectric patches are symmetrically attached to a surface of the soft-packaged lithium-ion battery at a distance of 3/4 length of the soft-packaged lithium-ion battery, and a A0 mode of the ultrasonic guided wave is excited for the detection of the state of charge of the soft-packaged lithium-ion battery;
the method comprises the following steps:
obtaining frequency dispersion curves of the soft-packaged lithium-ion battery at different states of charge and determining, based on variation patterns of the frequency dispersion curves, a mode of the ultrasonic guided wave and an optimal excitation frequency range for detecting the state of charge (SOC) of the soft-packaged lithium-ion battery; identifying a most optimal excitation frequency, an excitation position and a reception position based on a finite element simulation result; producing, by the arbitrary waveform generator, a Hanning-window-modulated five-cycle sine signal to excite one of the two circular piezoelectric patches that is located at the excitation position on the surface of the soft-packaged lithium-ion battery; exciting the one of the two circular piezoelectric patches generates an ultrasonic guided wave within the soft-packaged lithium-ion battery, which is then received by another one of the two circular piezoelectric patches that is located at the reception position on the surface of the soft-packaged lithium-ion battery; a signal of the received ultrasonic guided wave is processed to extract time-domain characteristic parameters of the received ultrasonic guided wave, based on a correspondence between the time-domain characteristic parameters and the state of charge, the state of charge of the soft-packaged lithium-ion battery is detected;
using a charging and discharging protocol, the soft-packaged lithium-ion battery is subjected to three charge-discharge cycles, during a constant current discharge process, the circular piezoelectric patch located at the excitation position on the surface of the soft-packaged lithium-ion battery is repeatedly excited at 3-minute intervals to obtain transit time Tij of the received ultrasonic guided wave at predetermined states of charge of the soft-packaged lithium-ion battery, here, i represents the number of charge-discharge cycles, and j represents the state of charge;
the transit time Tij obtained in the three charge-discharge cycles at a same state of charge (j=m) are averaged using the following formula to obtain an average transit time Tm:

OG Complex Work Unit Math
where m ranges from 0 to 100, the average transit time Tm is then fitted against the predetermined states of charge to obtain a fitting curve of state of charge versus transit time for the soft-packaged lithium-ion battery;
after the fitting curve is established, using the charging and discharging protocol to perform a single charge-discharge cycle to charge the soft-packaged lithium-ion battery to another predetermined state of charge (SOC=n1), the another predetermined state of charge is calculated using the formula:

OG Complex Work Unit Math
the time-domain waveform of the ultrasonic guided wave signal at the another predetermined state of charge is obtained, from which transit time T of the A0 mode of the ultrasonic guided wave is extracted;
the transit time T is then substituted into the fitting curve to determine a state of charge (SOC=n2) corresponding to the transit time T;

OG Complex Work Unit Math
if the difference between the SOC=n2 calculated from the fitting curve and the SOC=n1 calculated using the formula is within 2%, the difference between the SOC=n2 and the SOC=n1 validates that an unknown state of charge of the same soft-packaged lithium-ion battery can be determined using the fitting curve and a transit time corresponding to the unknown state of charge.