Research On Lithium Battery Testing Technology Based On Air-coupling Ultrasound

Due to the increasingly serious problems of energy shortage and environmental pollution,lithium batteries as a new type of green energy are widely used in various fields such as electronic products,energy transportation,etc.due to their advantages of large energy and long life.In the production and service of lithium batteries,the existence of hidden safety hazards will lead to various combustion and explosion accidents,so it is very important to detect their safety performance.At present,the problems in the detection methods of lithium batteries are:(1)high cost,low efficiency and damage to the lithium battery monomer;(2)the problem that dynamic online monitoring cannot be achieved.In view of the above problems,this paper proposes to use non-contact,non-destructive,non-polluting air-coupled ultrasonic technology to detect lithium batteries.By building an air-coupled ultrasonic lithium battery detection system,the vertical transmission method combined with ultrasonic C scanning was used to realize online detection of defects such as bubbles and electrolyte unevenness.The effects of probe detection frequency,scanning speed and other factors on the detection results are analyzed through experiments to obtain the optimal experimental parameters.In order to improve the detection accuracy,this paper uses wavelet threshold denoising technology and adaptive noise reduction algorithm to perform noise reduction on the acoustic transmission signal of lithium battery to improve the signal to noise ratio.And by using spatial domain filtering,frequency domain filtering,direct gray scale change and histogram equalization and other methods for image processing of the lithium battery air-coupled ultrasonic C-scan imaging map,the problem of low contrast and low defect recognition is solved.The results show that the 400 kHz probe and the scanning speed of 250mm/s can identify the self-made bubble defect of ?1mm in the lithium battery;For the natural bubble defects,the distribution position of the bubbles and the bubble defects of different depths that cannot be distinguished from the outside can be accurately detected.The relative error of the detected defect size is less than 5.5%.When the sym11 wavelet-based decomposition layer is used to process 9 pairs of lithium battery air-coupled ultrasonic transmission signals,the signal-to-noise ratio is 13.593 dB,and the signal-to-noise ratio reaches 13.758 dB after being processed by an adaptive noise reduction algorithm.Through comparative analysis of image processing methods,it is concluded that Gaussian low-pass filtering has better processing effects,and the image signal-to-noise ratio can reach 44.9393 dB,which improves the contrast of imaging results and has wide application value in the field of safety performance testing of lithium batteries.