A defective battery screening method based on an implanted temperature information card

Abstract

This invention provides a defective battery screening method based on an implantable temperature information card, belonging to the field of battery defect diagnosis technology. The method embeds an implantable temperature information card, powered and communicated via ultrasound, into the battery, enabling passive, wireless, and rapid acquisition of the battery's internal temperature via an external temperature acquisition card. Based on this, a two-step screening process is constructed, including electrical signal analysis and assessment of the temperature change rate during the formation stage, thereby achieving efficient and accurate screening of defective batteries.

Description

Technical Field

[0001] This invention belongs to the field of battery defect diagnosis technology, specifically relating to a defect battery screening method based on an implanted temperature information card. Background Technology

[0002] Lithium-ion batteries, due to their high energy density and long cycle life, have become key power components in consumer electronics, electric vehicles, and energy storage systems. However, in the context of large-scale applications, thermal runaway and the resulting fires still occur frequently and pose significant risks. A major cause of thermal runaway stems from process defects in battery manufacturing and assembly, such as electrode burrs, separator inclusions, and uneven or inconsistent electrolyte distribution. These defects can lead to localized short circuits and further trigger thermal runaway. Therefore, conducting efficient screening of defective batteries before they leave the factory is crucial for reducing the risk of thermal runaway and improving product safety.

[0003] Formation is a crucial step in lithium-ion battery manufacturing, electrochemically activating the cells and directly impacting core indicators such as initial efficiency, internal resistance, capacity retention, and consistency. Its results often determine whether a cell can proceed to subsequent capacity grading, sorting, and shipping. As formation is a critical end-stage in the production chain, timely screening of potentially defective batteries at this stage not only prevents defective cells from flowing into subsequent processes and wasting costs but also helps to intercept risks under conditions closest to actual use. However, some minute internal defects may initially manifest as microampere-level leakage or slight micro-short circuits. Their impact on external electrical signals such as voltage and current is easily masked by current fluctuations and measurement noise during the formation process, making reliable identification difficult solely based on electrical signals. In contrast, defects causing localized increases in internal resistance and micro-short circuits typically lead to abnormal heating, with temperature information more directly reflecting the internal state. Furthermore, significant thermal resistance and heat transfer hysteresis exist between the cell's interior and exterior surfaces, and surface temperature is easily affected by environmental and contact conditions, making it difficult to accurately characterize internal thermal behavior. Therefore, precise acquisition of internal temperature is more valuable for screening.

[0004] To overcome the lag and degradation issues in surface temperature monitoring, direct sensing technology for battery internal temperature has gained increasing attention. However, existing solutions still have shortcomings in terms of production line adaptability. On the one hand, some internal temperature monitoring solutions require data transmission via leads, which can easily damage the cell's sealed structure and may introduce risks such as short circuits and corrosion, thereby affecting the battery's long-term performance and safety. On the other hand, while wireless solutions can avoid interference from wiring, such as patent CN202410325654.5 which uses ultrasound for wireless data transmission, its internal circuitry still relies on the battery's own power supply, which consumes the battery's effective capacity. Furthermore, the charging current during the formation stage is relatively small and cannot support the normal operation of active devices, thus hindering large-scale screening during the formation stage. Patent CN202410325653.0 proposes to use ultrasound to simultaneously achieve wireless power supply and data transmission, thereby realizing passive built-in monitoring. However, its external transmitter is usually composed of a function generator connected to an ultrasonic probe, which results in high equipment cost and limited integration. More importantly, this type of configuration is difficult to carry out synchronous and parallel temperature acquisition of multiple cells under single-station conditions, making it difficult to match the actual needs of the batching and capacity testing process for multiple cells and high-frequency detection.

[0005] Therefore, for the scenario of multiple cells operating in parallel at a single workstation on a production line, a passive wireless rapid acquisition method for the internal temperature of cells during the formation stage is constructed. By extracting and comparing parameters such as battery voltage, current, and internal temperature change rate during the formation process, and combining them with threshold discrimination, defective batteries can be quickly identified and eliminated. This has important engineering application value and research significance. Summary of the Invention

[0006] To address the problems existing in the background technology, the purpose of this invention is to provide a defective battery screening method based on an implantable temperature information card during the battery formation stage. This method embeds an implantable temperature information card, powered and communicated via ultrasound, into the battery, and uses an external temperature acquisition card to achieve passive, wireless, and rapid acquisition of the battery's internal temperature. Based on this, a two-step screening process is constructed, including electrical signal analysis and assessment of the temperature change rate during the formation stage, thereby achieving efficient and accurate screening of defective batteries.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A defective battery screening method based on an implanted temperature information card includes the following steps:

[0009] Step 1: Insert a temperature information card into the battery cell, and then seal it.

[0010] Step 2: Perform formation processing on the packaged batteries. During the formation process, the voltage and current signals of each battery are continuously collected through the charging cabinet. At the same time, the temperature data reported by each temperature information card is collected at fixed time intervals through an external temperature acquisition card, and the rate of temperature change of the battery is calculated.

[0011] Step 3: Based on the voltage and current signals collected in Step 2, filter out batteries with abnormal electrical signals and remove them, while keeping batteries with normal electrical signals.

[0012] Step 4: For batteries with normal electrical signals, compare the temperature change rate of the battery during the formation stage. If it is less than the preset temperature change rate threshold, the battery is considered qualified; otherwise, the battery is considered abnormal and is rejected.

[0013] Furthermore, the specific process of step 1 is as follows:

[0014] Step 1.1. Fix the battery cell and temperature information card on the same layer of aluminum-plastic film. The temperature information card is fixedly set below the battery cell, and the temperature sensor in the temperature information card is set in the center area of ​​the battery cell core.

[0015] Step 1.2: Encapsulate the battery cell after implanting the temperature information card:

[0016] Step 1.2.1: Cover the battery cell and temperature information card with another layer of aluminum-plastic film, and use a hot press to hot press and seal the area between the battery cell and temperature information card to achieve physical isolation between the battery cell and the information card, and complete the hot press sealing of the aluminum-plastic film at the bottom of the battery.

[0017] Step 1.2.2. Hot-press seal one side and top of the battery, leaving one side unsealed for now;

[0018] Step 1.2.3. Inject electrolyte from the side of the battery that is not thermo-sealed, and then perform vacuum thermo-sealing on that side.

[0019] Furthermore, the temperature information card includes a first piezoelectric ceramic, a second piezoelectric ceramic, a temperature sensor, a rectifier bridge, a constant current source, a linear regulator, a first microcontroller, and a first amplifier;

[0020] The temperature acquisition card includes a third piezoelectric ceramic, a fourth piezoelectric ceramic, a DC power supply, a power management module, a self-excited oscillation circuit, a second microcontroller, and a second amplifier; the third piezoelectric ceramic of the temperature acquisition card is aligned with the first piezoelectric ceramic of the temperature information card, and the fourth piezoelectric ceramic of the temperature acquisition card is aligned with the second piezoelectric ceramic of the temperature information card.

[0021] During temperature measurement, the DC power supply powers the power management module and the self-excited oscillation circuit; the power management module is used to step down and filter the voltage before outputting it to the first microcontroller.

[0022] The self-excited oscillation circuit generates sinusoidal alternating current and excites the third piezoelectric ceramic. Based on the inverse piezoelectric effect, the third piezoelectric ceramic converts the sinusoidal alternating current into ultrasonic waves and emits them. After penetrating the aluminum-plastic film of the battery, the ultrasonic waves are received by the first piezoelectric ceramic of the temperature information card. Based on the piezoelectric effect, the first piezoelectric ceramic converts the ultrasonic waves into alternating current and transmits them to the rectifier bridge. The rectifier bridge rectifies the alternating current into direct current and transmits it to the linear voltage regulator. The linear voltage regulator provides a stable voltage output to the first microcontroller and a constant current source as a power supply. The constant current source is used for outputting a constant current.

[0023] The temperature sensor is used to detect the temperature inside the battery cell. The sensor converts the temperature signal into a resistance signal, and then converts the resistance signal into a voltage signal under the action of a constant current. The voltage signal is amplified by the first amplifier and acquired by the first microcontroller. The acquired voltage signal is modulated into a PWM wave. The PWM wave drives the second piezoelectric ceramic to emit ultrasonic waves carrying temperature information. The ultrasonic waves penetrate the aluminum-plastic film of the battery and are received by the fourth piezoelectric ceramic, which generates alternating current based on the piezoelectric effect. The alternating current is amplified by the second amplifier and received and decoded by the second microcontroller to obtain the detected temperature data.

[0024] Furthermore, the temperature acquisition card also includes a Bluetooth module, which transmits the detected temperature data decoded by the second microcontroller to an external computer for display and storage.

[0025] Furthermore, the temperature sensor is one of the following: a thin-film resistance temperature sensor, a thermistor sensor with corrosion-resistant encapsulation, or a MEMS temperature sensor based on the thermistor principle.

[0026] Furthermore, in step 1.2, the temperature for hot pressing is 180℃-190℃, and the hot pressing time is 3-5 seconds.

[0027] Furthermore, in step 2, the specific process for calculating the battery's temperature change rate is as follows: the temperature data is differentiated with respect to time to obtain the temperature change rate.

[0028] Furthermore, in step 4, the preset temperature change rate threshold is preferably 1 ℃ / h.

[0029] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0030] 1. This invention achieves passive, wireless, and convenient acquisition of the internal temperature of a pouch battery through the collaborative design of an implanted temperature information card and an external miniature temperature acquisition card. This solution not only avoids the problem of data cable wiring damaging the battery's structural integrity, but also, by employing a miniaturized temperature acquisition card, establishes a stable ultrasonic energy transmission and data feedback channel between the external temperature acquisition card and the implanted temperature information card, thus providing a reliable data foundation for subsequent high-precision defect screening processes.

[0031] 2. This invention introduces the internal temperature of the battery as a core criterion for quantitative screening of defective batteries during the formation stage. Compared to traditional methods that rely solely on electrical signals or battery surface temperature, internal temperature can more directly and earlier reflect abnormal states within the battery, thereby achieving accurate and early identification of defects and potential problems. This invention constructs a dual-progressive defect screening method for the formation stage, improving the accuracy and specificity of defect judgment. The formation stage is a crucial process where the battery cell undergoes electrochemical activation and interface formation for the first time, and it is also an important screening stage where minor process defects are more likely to manifest as abnormal thermal behavior. Therefore, defect identification at this stage has high engineering value. Specifically, this invention first eliminates batteries with obvious process defects based on abnormal electrical signals such as voltage and current. Subsequently, for batteries with normal electrical signals, further discrimination is made based on the rate of change of internal temperature during the formation process, thereby identifying defective batteries that, although not showing obvious electrical signal abnormalities, have already exhibited internal thermal anomalies. Through this progressive screening scheme, earlier and more accurate risk interception can be achieved before the battery enters the subsequent capacity grading, sorting, and usage stages. Attached Figure Description

[0032] Figure 1 A cross-sectional schematic diagram of a pouch battery structure with an embedded temperature information card.

[0033] Figure 2 This is a circuit logic diagram of the temperature information card and temperature acquisition card during use of the present invention.

[0034] Figure 3 This is a flowchart of the screening method in the battery formation stage of the present invention.

[0035] Figure 4 This is a bar chart comparing the maximum internal temperature change rate of normal and defective batteries during the formation stage, obtained through a temperature acquisition card.

[0036] The attached diagram is labeled as follows: 1 is aluminum-plastic film, 2 is battery cell, 3 is temperature sensor, 4 is temperature information card, and 5 is piezoelectric ceramic. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0038] A defective battery screening method based on an implanted temperature information card, wherein the device on which the method is based includes a temperature information card and a temperature acquisition card;

[0039] A cross-sectional diagram of the soft-pack battery with an implanted temperature information card is shown below. Figure 1 As shown, the soft-pack battery is encapsulated by an aluminum-plastic film 1, which contains a battery cell 2. A temperature information card 4 is fixedly installed at the bottom of the battery cell 2. The temperature information card 4 includes a temperature sensor 3 and two piezoelectric ceramics 5. The sensitive grid of the temperature sensor 3 extends to the central area of ​​the core of the battery cell 2, and is used to directly collect the temperature signal inside the battery.

[0040] Figure 2 This is a circuit logic diagram of the temperature information card and temperature acquisition card during use of the present invention. Figure 2 As shown, the circuit flow of the temperature information card and temperature acquisition card working together can be divided into two parts: a power supply link and an information feedback link. During temperature measurement, the third piezoelectric ceramic of the temperature acquisition card is aligned with the first piezoelectric ceramic of the temperature information card, and simultaneously, the fourth piezoelectric ceramic of the temperature acquisition card is aligned with the second piezoelectric ceramic of the temperature information card. The DC power supply, after processing by the power management module, powers the microcontroller. Simultaneously, the DC power supply directly powers the self-excited oscillation circuit. After startup, the self-excited oscillation circuit outputs a high-frequency sinusoidal AC excitation signal and drives the third piezoelectric ceramic to emit ultrasonic waves. The ultrasonic waves pass through the aluminum-plastic film of the battery and are received by the first piezoelectric ceramic of the temperature information card, converted into an AC signal based on the piezoelectric effect. This AC signal is rectified and filtered by a rectifier bridge to form DC power, which is then regulated to 3.3V by a linear regulator to power the microcontroller and constant current source of the temperature information card. A constant current source continuously generates a constant current. Under the action of this constant current, the temperature sensor converts the resistance signal into a voltage signal. The voltage signal is amplified 20 times by the first amplifier and then sampled by the first microcontroller ADC of the temperature information card. The first microcontroller uses a timer to modulate the sampling result in an OOK mode and generate a PWM wave drive signal to drive the second piezoelectric ceramic to generate an ultrasonic return signal carrying temperature information. The ultrasonic return signal also penetrates the aluminum-plastic film of the battery and is received by the fourth piezoelectric ceramic of the temperature acquisition card. The fourth piezoelectric ceramic converts it back into an AC signal based on the piezoelectric effect. The AC signal is amplified by the second amplifier and then input into the second microcontroller of the temperature acquisition card for demodulation and decoding. The decoded temperature data is then sent to the host computer via Bluetooth for data recording and subsequent analysis.

[0041] Example 1

[0042] In this embodiment, temperature sensor 3 is a flexible thin-film resistance temperature sensor. The sensitive grid is made of copper with a thickness of 12μm and the size of the sensitive grid area is 9mm×9mm. The temperature sensor is encapsulated with polyimide, with thicknesses of 27.5μm and 25μm on both sides, respectively. In this embodiment, the battery is an NCM / graphite system soft-pack lithium-ion battery with a rated capacity of 1Ah. The temperature information card 4 is 20mm×60mm in size.

[0043] A defective battery screening method based on an implanted temperature information card includes the following steps:

[0044] Step 1: Assemble the temperature information card and the temperature acquisition card; wherein, the temperature information card is embedded inside the battery, and the temperature acquisition card is set outside the battery; the sensitive grid of the temperature sensor is set in the central area of ​​the core of cell 2;

[0045] Step 2: Fix the temperature information card to the bottom of the battery, below the battery cell; place the battery cell and the temperature information card together on the same layer of aluminum-plastic film, and use double-sided tape to fix the temperature information card to the aluminum-plastic film;

[0046] Step 3: Cover the battery cell and temperature information card with another layer of aluminum-plastic film, and use a hot press to hot press and seal the area between the battery cell and temperature information card to achieve physical isolation between the battery cell and the information card, and complete the vacuum seal at the bottom of the battery; then, hot press and seal one side and the top of the battery, leaving the side with the air bladder unsealed for the time being.

[0047] Step 4: Inject electrolyte from the side of the battery airbag, and then perform vacuum hot pressing to seal the side to obtain a normal battery with integrated temperature information card, numbered 1;

[0048] Step 5: Simulate the preparation of 4 defective cell samples. The separator of these 4 cells is partially damaged to simulate the risk of internal short circuit caused by process burrs or uneven electrode size. All 4 defective cells are prepared by implanting temperature information cards and encapsulating the battery according to the process described in Steps 1 to 4. Finally, defective battery samples with internal temperature monitoring function are prepared and numbered 2 to 5.

[0049] Step 6: Perform formation processing on the normal cells obtained in Step 4 and the defective cells obtained in Step 5; a flowchart illustrating the defective cell screening method during the formation stage is shown below. Figure 3 As shown;

[0050] Step 7: During the formation process, the voltage and current signals of each battery are continuously collected through the charging cabinet; simultaneously, temperature data reported by each temperature information card is collected synchronously at fixed time intervals through 5 temperature acquisition cards, and the temperature change rate is calculated. The maximum temperature change rate of each battery is statistically analyzed, and the results are as follows: Figure 4 As shown;

[0051] Based on the collected electrical signal data, no batteries with abnormal voltage or current signals were detected, and all batteries successfully passed this stage of screening; according to Figure 3 The statistical results of the maximum temperature change rate shown are used to compare and analyze batteries numbered 1 to 5. Among them, the maximum temperature rise rate of battery number 1 is 0.26℃ / h, which is considered qualified. The maximum temperature rise rates of batteries numbered 2 to 5 are 4.04℃ / h, 5.26℃ / h, 4.8℃ / h and 6.24℃ / h respectively, all of which significantly exceed the threshold, so they are judged as unqualified and screened out.

[0052] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for screening defective batteries based on an implanted temperature information card, characterized in that, Includes the following steps: Step 1: Insert a temperature information card into the battery cell, and then seal it. Step 2: Perform formation processing on the packaged batteries. During the formation process, the voltage and current signals of each battery are continuously collected through the charging cabinet. At the same time, the temperature data reported by each temperature information card is collected at fixed time intervals through an external temperature acquisition card, and the rate of temperature change of the battery is calculated. Step 3: Based on the voltage and current signals collected in Step 2, filter out batteries with abnormal electrical signals and remove them, while keeping batteries with normal electrical signals. Step 4: For batteries with normal electrical signals, compare the temperature change rate of the battery during the formation stage. If it is less than the preset temperature change rate threshold, the battery is considered qualified; otherwise, the battery is considered abnormal and is rejected.

2. The defective battery screening method as described in claim 1, characterized in that, The specific process of step 1 is as follows: Step 1.

1. Fix the battery cell and temperature information card on the same layer of aluminum-plastic film. The temperature information card is fixedly set below the battery cell, and the temperature sensor in the temperature information card is set in the center area of ​​the battery cell core. Step 1.2: Encapsulate the battery cell after implanting the temperature information card: Step 1.2.1: Cover the battery cell and temperature information card with another layer of aluminum-plastic film, and use a hot press to hot press and seal the area between the battery cell and temperature information card to achieve physical isolation between the battery cell and the information card, and complete the hot press sealing of the aluminum-plastic film at the bottom of the battery. Step 1.2.

2. Hot-press seal one side and top of the battery, leaving one side unsealed for now; Step 1.2.

3. Inject electrolyte from the side of the battery that is not thermo-sealed, and then perform vacuum thermo-sealing on that side.

3. The defective battery screening method as described in claim 1, characterized in that, The temperature information card includes a first piezoelectric ceramic, a second piezoelectric ceramic, a temperature sensor, a rectifier bridge, a constant current source, a linear regulator, a first microcontroller, and a first amplifier; The temperature acquisition card includes a third piezoelectric ceramic, a fourth piezoelectric ceramic, a DC power supply, a power management module, a self-excited oscillation circuit, a second microcontroller, and a second amplifier; the third piezoelectric ceramic of the temperature acquisition card is aligned with the first piezoelectric ceramic of the temperature information card, and the fourth piezoelectric ceramic of the temperature acquisition card is aligned with the second piezoelectric ceramic of the temperature information card. During temperature measurement, the DC power supply powers the power management module and the self-excited oscillation circuit; the power management module is used to step down and filter the voltage before outputting it to the first microcontroller. The self-excited oscillation circuit generates sinusoidal alternating current and excites the third piezoelectric ceramic. Based on the inverse piezoelectric effect, the third piezoelectric ceramic converts the sinusoidal alternating current into ultrasonic waves and emits them. After penetrating the aluminum-plastic film of the battery, the ultrasonic waves are received by the first piezoelectric ceramic of the temperature information card. Based on the piezoelectric effect, the first piezoelectric ceramic converts the ultrasonic waves into alternating current and transmits them to the rectifier bridge. The rectifier bridge rectifies the alternating current into direct current and transmits it to the linear voltage regulator. The linear voltage regulator provides a stable voltage output to the first microcontroller and a constant current source as a power supply. The constant current source is used for outputting a constant current. The temperature sensor is used to detect the temperature inside the battery cell. The sensor converts the temperature signal into a resistance signal, and then converts the resistance signal into a voltage signal under the action of a constant current. The voltage signal is amplified by the first amplifier and acquired by the first microcontroller. The acquired voltage signal is modulated into a PWM wave. The PWM wave drives the second piezoelectric ceramic to emit ultrasonic waves carrying temperature information. The ultrasonic waves penetrate the aluminum-plastic film of the battery and are received by the fourth piezoelectric ceramic, which generates alternating current based on the piezoelectric effect. The alternating current is amplified by the second amplifier and received and decoded by the second microcontroller to obtain the detected temperature data.

4. The defective battery screening method as described in claim 3, characterized in that, The temperature acquisition card also includes a Bluetooth module, which transmits the detected temperature data decoded by the second microcontroller to an external computer for display and storage.

5. The defective battery screening method as described in claim 3, characterized in that, The temperature sensor is one of the following: a thin-film resistance temperature sensor, a thermistor sensor with corrosion-resistant encapsulation, or a MEMS temperature sensor based on the thermistor principle.

6. The defective battery screening method as described in claim 1, characterized in that, In step 1.2, the temperature for hot pressing is 180℃-190℃, and the hot pressing time is 3-5 seconds.

7. The defective battery screening method as described in claim 1, characterized in that, In step 2, the specific process for calculating the battery's temperature change rate is as follows: the temperature data is differentiated with respect to time to obtain the temperature change rate.

8. The defective battery screening method as described in claim 1, characterized in that, In step 4, the preset temperature change rate threshold is 1 ℃ / h.

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