A liquid injection process optimization method and system

Abstract

The application provides a liquid injection process optimization method and system. The method comprises the following steps: initial process setting; liquid injection cycle execution; real-time ultrasonic detection; dynamic threshold determination; process closed-loop regulation; and cycle termination according to cycle termination conditions. The application solves the technical problems of being unable to quantitatively detect the liquid injection and infiltration state in real time, lacking of bubble detection methods, and lacking of data support for process adjustment.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing technology, specifically to a method and system for optimizing the liquid injection process. Background Technology

[0002] The electrolyte filling process for lithium-ion batteries is a crucial step determining the quality of battery wetting. Traditional processes employ multiple cycles of negative pressure vacuuming followed by positive pressure electrolyte filling, typically 3-5 cycles in total. This vacuum environment removes internal gases to ensure thorough electrolyte wetting. However, existing technologies suffer from the following key drawbacks:

[0003] 1. Inability to quantify injection and infiltration status in real time. Current mainstream solutions rely on offline testing. For example, the existing invention patent application document CN114993888A, entitled "A Method for Testing the Wetting Properties of Battery Electrolyte," requires disassembling the battery after electrolyte injection to observe the wetting effect, which has the following drawbacks: Detection lag: By the time a problem is discovered, the battery already has quality defects; Destructive analysis and disassembly would render the battery completely unusable.

[0004] 2. Lack of bubble detection methods Bubbles in the electrolyte, such as those with an equivalent diameter of 100-999 μm, can block ion channels, but existing sensors cannot penetrate the metal casing to detect the distribution of bubbles inside.

[0005] 3. Lack of data support for process adjustments Current electrolyte injection processes typically use a fixed number of cycles, ignoring the porosity differences between individual cells. This leads to some cells being over- or under-injected. Correspondingly, optimization of the electrolyte injection process often relies on determining the amount of residual electrolyte in the injection cup. This manual observation of the residual electrolyte level is used to adjust the number of injection cycles, which results in significant errors.

[0006] The existing invention patent application document CN116481974A, entitled "Method for Testing the Wetting Properties of a Battery Cell," includes the following steps: providing a battery cell, which includes a housing and a core, with temperature measuring points set along the thickness and height directions of the core; subjecting the battery cell to constant temperature treatment; repeatedly injecting liquid into the core after constant temperature treatment, and acquiring the temperature of each measuring point multiple times during each liquid injection cycle; acquiring the temperature difference ΔT between the first and last measured temperatures Tinitial and Tfinal of each measuring point during each liquid injection cycle, and determining whether the temperature difference ΔT is within a preset temperature difference range Tpreset; if so, it indicates that the battery cell has completed wetting.

[0007] This patent uses point-to-point detection of the temperature difference after electrolyte injection to infer whether the electrolyte has reached that point, thus determining the effectiveness of electrolyte wetting. However, it has the following drawbacks: 1. To test whether the electrolyte has reached the specified level, this patent also requires reverse calculation. 2. When using the existing solution, temperature measuring instruments such as thermocouples are still placed inside the battery, which may damage the battery casing. Even if it does not damage the casing, it may introduce dust or other conductive materials into the battery, causing a short circuit and reducing the battery yield. 3. Difficulties in mass production. This patent requires heating, which makes it difficult to apply in actual production.

[0008] In summary, existing technologies suffer from technical problems such as the inability to quantify the injection and wetting status in real time, a lack of bubble detection methods, and a lack of data support for process adjustments. Summary of the Invention

[0009] The technical problem to be solved by this invention is: how to solve the technical problems in the prior art that cannot quantify the injection and wetting state in real time, lack of bubble detection methods, and lack of data support for process adjustment.

[0010] The present invention solves the above-mentioned technical problems by adopting the following technical solution: a method for optimizing the injection process includes: S1. Perform initial process settings: In the vacuum chamber of the injection equipment, integrate an ultrasonic transducer array circumferentially and set the target injection volume. and the maximum number of loops ; S2. Perform the electrolyte injection cycle, and perform the i-th positive and negative pressure cycle on the battery; S3. When the number of positive and negative pressure cycles meets the preset conditions, ultrasonic testing is performed at the end of the cycle to collect and calculate acoustic parameters. S4. Based on the acoustic parameters, perform dynamic threshold determination. When the set acoustic parameter conditions are met, stop the current injection cycle and calculate the wetting compliance rate. ; S5. Implement closed-loop process control based on the wetting compliance rate. The injection procedure is terminated. S6. Set the cycle termination condition. When the cumulative injection volume and the number of positive and negative pressure cycles reach the cycle termination condition, terminate the injection operation.

[0011] This invention addresses the technical pain points of traditional electrolyte injection processes, such as the inability to quantify the electrolyte wetting status in real time and the reliance on empirical parameters leading to bubble residue. It proposes embedding an ultrasonic detection module in the vacuum / positive pressure injection cycle, dynamically determining the wetting achievement rate through acoustic feature thresholds, thereby dynamically adjusting the injection process. This invention can directly emit ultrasonic waves to measure the wetting yield, which can reduce the production cost of lithium batteries and improve battery quality.

[0012] In a more specific technical solution, the probe includes: a transmitting probe and a receiving probe; Based on the battery thickness, the probe spacing in the integrated ring-shaped transducer array is set, as well as the number of probes, probe angle interval, probe tilt angle, and reference frequency of each probe.

[0013] This invention ensures uniform circumferential coverage of the transducer array by setting an angular interval θ; and avoids reflection interference caused by direct sound waves hitting the sidewall of the battery by setting the probe tilt angle α and the angle between the probe beam axis and the battery radial direction, thereby enhancing axial penetration.

[0014] In a more specific technical solution, in S2, during each cycle operation, in the negative pressure stage, the battery is evacuated to a preset negative pressure and a negative pressure holding range is set. During the positive pressure stage, electrolyte is injected, and the pressure is increased to the preset positive pressure, setting a positive pressure holding range.

[0015] In a more specific technical solution, in S3, during the ultrasonic testing process, the battery is evacuated to a preset negative pressure, the probe's emission reference frequency and ultrasonic intensity are set, the black spots on the battery in the defect area are detected, and the defect area is determined to be in a poor wetting state.

[0016] In a more specific technical solution, in S3, the acoustic parameters include: transmission attenuation and fundamental frequency offset; the transmission attenuation is used to characterize energy attenuation and quantify the degree of energy loss when ultrasound penetrates the battery, and the fundamental frequency offset is used to characterize the electrolyte wetting state.

[0017] In a more specific technical solution, in S4, the following logic is used to calculate the immersion compliance rate. :

[0018] In the formula, The number of times the immersion meets the standard.

[0019] In a more specific technical solution, in S5, if the immersion compliance rate... If the preset wetting conditions are not met, adjust the injection process parameters using the following logic:

[0020]

[0022] In a more specific technical solution, in S5, the correction time parameter is adjusted according to the upper limit of the pressure holding time, and the next injection cycle operation begins.

[0023] In a more specific technical solution, in S6, the loop termination condition is set using the following logic: or

[0024] In the formula, Indicates the target injection volume. This indicates the maximum number of iterations.

[0025] In a more specific technical solution, an injection process optimization system includes: The initial parameter setting module is used for initial process settings. An ultrasonic transducer array is integrated circumferentially within the vacuum chamber of the injection equipment to set the target injection volume. and the maximum number of loops ; The electrolyte injection circulation module is used to perform electrolyte injection circulation, performing the i-th positive and negative pressure cycle on the battery; The acoustic parameter acquisition module is used to perform ultrasonic testing, collect and calculate acoustic parameters when the number of positive and negative pressure cycles meets the preset conditions and the cycle ends. The liquid injection circulation module is connected to the liquid injection circulation module. The immersion status processing module is used to perform dynamic threshold determination based on acoustic parameters. When the set acoustic parameter conditions are met, the current injection cycle is stopped, and the immersion compliance rate is calculated. The immersion state processing module is connected to the acoustic parameter acquisition module; The closed-loop control module is used for closed-loop process control based on the wetting compliance rate. The injection operation is terminated upon determination, and the closed-loop control module is connected to the wetting state processing module. The injection termination module is used to set the cycle termination condition. When the cumulative injection volume and the number of positive and negative pressure cycles reach the cycle termination condition, the injection operation is terminated. The injection termination module is connected to the closed-loop control module.

[0026] The present invention has the following advantages over the prior art: This invention addresses the technical pain points of traditional electrolyte injection processes, such as the inability to quantify the electrolyte wetting status in real time and the reliance on empirical parameters leading to bubble residue. It proposes embedding an ultrasonic detection module in the vacuum / positive pressure injection cycle, dynamically determining the wetting achievement rate through acoustic feature thresholds, thereby dynamically adjusting the injection process, which can reduce the production cost of lithium batteries and improve battery quality.

[0027] This invention ensures uniform circumferential coverage of the transducer array by setting an angular interval θ; and avoids reflection interference caused by direct sound waves hitting the sidewall of the battery by setting the probe tilt angle α and the angle between the probe beam axis and the battery radial direction, thereby enhancing axial penetration.

[0028] This invention solves the technical problems existing in the prior art, such as the inability to quantify the injection and wetting status in real time, the lack of bubble detection methods, and the lack of data support for process adjustment. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the basic steps of an injection process optimization method according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the real-time ultrasound detection data stream processing in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the dynamic threshold determination data stream processing in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the loop termination determination data stream processing in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the battery ultrasonic probe distribution in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the defects of the battery under test after disassembly in Embodiment 1 of the present invention; Figure 7 This is a captured ultrasonic transmission image during the detection process of Embodiment 1 of the present invention; Figure 8 This is a diagram showing the ultrasonic testing effect of the battery after the liquid injection process in Embodiment 1 of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1 like Figure 1 As shown, the present invention provides a method for optimizing a liquid injection process, comprising the following basic steps: S1. Initial process settings: Integrate an ultrasonic transducer array circumferentially into the vacuum chamber of the injection equipment and set the target injection volume. and the maximum number of loops In this embodiment, a target injection volume is set. =120ml, maximum number of cycles =5; Number of probes n=14, including 7 transmitting probes and 7 receiving probes; In this embodiment, a prismatic lithium iron phosphate battery, model LF-54, manufactured by Company G, can be used. Structural parameters: length l = 105mm, height h = 45mm, thickness d = 28mm. The casing material can be, for example, aluminum alloy.

[0032] To address the blind zone and signal unevenness issues inherent in traditional linear / single-probe detection, this embodiment employs an integrated ring-shaped transducer array where the probe spacing is less than or equal to half the battery thickness. Taking a cylindrical battery as an example, with a thickness of Φ=50mm (the battery thickness being the radial length), the probe spacing must satisfy s ≤ 25mm. Furthermore, the value of s should ensure that the number of probes is even, facilitating a one-to-one correspondence between the transmitter and receiver. Specific design parameters are as follows: like Figure 5 As shown, the number of probes is set to n. Specifically, the total circumference of the transducer array ring is C=2πR, and the distance between a single probe and the battery casing is l=10mm. Then R=(50+10) / 2=30mm, and the number of probes is n=C / s. When s=20mm, n≈2×3.14×30 / 20≈9.4 → Take n=10 probes, of which 5 are transmitters and 5 are receivers.

[0033] Set the angle interval θ. Specifically, the center angle of adjacent probes can be set to, for example, θ=360° / n=36° to ensure uniform circumferential coverage.

[0034] Probe tilt angle α: The angle between the probe beam axis and the radial direction of the battery can be set to, for example, α = 30°~60°, to avoid the sound wave directly hitting the side wall of the battery and causing reflection interference, and to enhance axial penetration.

[0035] In this embodiment, the probe spacing can be set to, for example, s=14mm, satisfying s≤d / 2=14mm; the tilt angle can be set to, for example, α=45°, to enhance axial penetration. See the probe distribution diagram. Figure 5 .

[0036] In this embodiment, the reference frequency of a single probe is 0.5-5MHz.

[0037] The reference frequency affects the penetration depth and imaging resolution of ultrasound. Lower frequencies result in deeper penetration and reduced sound wave attenuation; higher frequencies provide better resolution and allow for the detection of smaller defects. The selection of the reference frequency in this invention should follow the following formula:

[0038] The velocity of sound for materials is 2200~2300 m / s for aluminum-cased batteries and lithium iron phosphate materials, and 2400-2600 m / s for ternary lithium materials.

[0039] Attenuation coefficient: 10~15 dB / cm / MHz² for lithium battery composite structures.

[0040] : Detect the depth of the target, i.e., the thickness of the battery.

[0041] In this embodiment, c=2250m / s, α=12dB / cm / MHz², and d=24mm are substituted into the reference frequency calculation formula: =3.9MHz For batteries thicker than 30mm, the calculated reference frequency in this embodiment is typically low. While ensuring the upper and lower limits are between 0.5-5MHz, the lower limit of the ultrasonic frequency can be reduced to allow for sufficient ultrasonic attenuation margin. Specifically, the lower limit of the ultrasonic frequency can be reduced to 50% of the original lower limit.

[0042] S2. Perform the electrolyte injection cycle, and perform the i-th positive and negative pressure cycle on the battery (i=1,2,...,N). In this embodiment, the battery undergoes the i-th cycle, and the specific steps for each cycle include: Negative pressure stage: The battery is evacuated to... Pressure holding

[0043] Positive pressure stage: Electrolyte injection Pressurized to Pressure holding .

[0044] Perform the i-th positive and negative pressure cycle on the battery (i=1,2,...,N); the specific cycle process parameters are shown in Table 1 below: Table 1

[0045] S3. Real-time ultrasonic detection, when At the end of each cycle, ultrasonic testing is performed to collect and calculate acoustic parameters; Specifically, such as Figure 2 As shown, when i=3, ultrasonic testing is performed on the battery. The vacuum is evacuated to -95kPa, and the reference frequency is emitted. 3.9MHz, ultrasonic intensity I0 = 1W / m². For example... Figure 6 As shown, after the tested battery was fully charged and disassembled, black spots were found in the defective area, which indicates poor wetting in that area.

[0046] In this embodiment, before performing ultrasonic testing after each cycle, the battery should be evacuated to a negative pressure. .

[0047] In this embodiment, acoustic parameters are collected and calculated, including transmission attenuation and fundamental frequency offset.

[0048] Among them, transmission attenuation characterizes energy attenuation: quantifies the degree of energy loss when ultrasound penetrates the battery.

[0049] Related to bubbles / pores: Bubbles or unwetted pores will scatter / reflect sound waves → significantly reduce → increase When the electrolyte is fully filled, the acoustic transmittance is high → approaching 0 dB. The calculation formula is as follows:

[0050] High sound wave transmittance, unit dB; ， Incident ultrasonic intensity, unit: W / m²; ， Transmitted ultrasonic intensity, unit: W / m²; Among them, the change in the standard velocity of sound due to the fundamental frequency offset: Electrolyte wetting alters the sound velocity in the medium → wavelength change → receiving frequency shift When wetting is good, the effect of solid-liquid coupling increases (positive offset). When bubbles remain, the offset decreases (negative shift). Microstructure correlation: Porosity of cathode increases → decreases → increases The calculation formula is as follows:

[0051] Reference frequency for transmitting ultrasonic waves, unit: MHz Reference frequency of transmitted ultrasonic waves, unit: MHz like Figure 7 The image shown is an ultrasonic transmission image captured during the detection process in this embodiment. The average value of the ultrasonic receiving area in the poorly infiltrated area is taken to obtain I. t =0.08W / m², =3.76MHz.

[0052] Acoustic parameter calculation:

[0053] S4. Dynamic threshold determination: When the set acoustic parameter conditions are met, the current injection cycle can be stopped, and the wetting compliance rate can be calculated. ; like Figure 3 As shown, in this embodiment, the set acoustic parameter threshold is: and When this threshold is met, the current injection cycle can be stopped.

[0054] In this embodiment, the formula for calculating the cumulative infiltration achievement rate is:

[0055] This refers to the number of times the immersion rate meets the standard. Specifically, when calculating the immersion rate, the number of injection cycles obtained during the first and second ultrasonic tests should be subtracted.

[0056] Specifically, the dynamic threshold can be set as follows: and , Cumulative achievement rate: If the aforementioned dynamic threshold is met, then the injection is deemed to have failed to meet the standard.

[0057] S5. Process closed-loop control, if If the solution reaches ≥95%, the injection process will be terminated. If the target is not met, adjust the injection process parameters:

[0058]

[0059] Specifically, Continue injection, adjusting the injection process parameters for the fourth cycle:

[0060] like Figure 4 As shown, due to the limitation of step S2 in the liquid injection cycle, during the negative pressure stage of the liquid injection process, the battery is evacuated to... Pressure holding Positive pressure stage: Injection of electrolyte Pressurized to Pressure holding Therefore, it is revised. The pressure holding time should be set to the upper limit of 180 seconds. After adjusting the process parameters, the next injection cycle can begin.

[0061] S6. Set the cycle termination condition when the cumulative injection volume... or Forced termination at that time.

[0062] In this embodiment, when i=4, Cumulative injection volume:

[0063] At this point, the injection process should be forcibly terminated.

[0064] like Figure 8 The image shown is an ultrasonic test of the battery wetting effect after the electrolyte injection process is completed. It can be seen that the battery has a good electrolyte wetting effect after the above process.

[0065] In summary, this invention addresses the technical pain points of traditional electrolyte injection processes, such as the inability to quantify the electrolyte wetting status in real time and the reliance on empirical parameters leading to bubble residue. It proposes embedding an ultrasonic detection module in the vacuum / positive pressure injection cycle, dynamically determining the wetting achievement rate through acoustic feature thresholds, thereby dynamically adjusting the electrolyte injection process. This can reduce the production cost of lithium batteries and improve battery quality.

[0066] This invention ensures uniform circumferential coverage of the transducer array by setting an angular interval θ; and avoids reflection interference caused by direct sound waves hitting the sidewall of the battery by setting the probe tilt angle α and the angle between the probe beam axis and the battery radial direction, thereby enhancing axial penetration.

[0067] This invention solves the technical problems existing in the prior art, such as the inability to quantify the injection and wetting status in real time, the lack of bubble detection methods, and the lack of data support for process adjustment.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for optimizing a liquid injection process, characterized in that, The method includes: S1. Perform initial process settings: In the vacuum chamber of the injection equipment, integrate an ultrasonic transducer array circumferentially and set the target injection volume. and the maximum number of loops ; S2. Perform the electrolyte injection cycle, and perform the i-th positive and negative pressure cycle on the battery; S3. When the number of positive and negative pressure cycles meets the preset conditions, at the end of the cycle, ultrasonic testing is performed to collect and calculate acoustic parameters. S4. Based on the acoustic parameters, perform dynamic threshold determination. When the set acoustic parameter conditions are met, stop the current injection cycle and calculate the immersion compliance rate. ; S5. Perform closed-loop process control based on the aforementioned wetting compliance rate. The injection procedure is terminated. S6. Set the cycle termination condition. When the cumulative injection volume and the number of positive and negative pressure cycles reach the cycle termination condition, terminate the injection operation.

2. The method for optimizing the injection process according to claim 1, characterized in that, S1 further includes setting the number of probes, wherein the probes include: a transmitting probe and a receiving probe; Based on the battery thickness, the probe spacing in the integrated ring-shaped transducer array is set, as well as the number of probes, probe angle interval, probe tilt angle, and reference frequency of each probe.

3. The method for optimizing the injection process according to claim 1, characterized in that, In S2, during each cycle, in the negative pressure stage, the battery is evacuated to a preset negative pressure and a negative pressure holding range is set.

4. The method for optimizing the injection process according to claim 1, characterized in that, In S2, during each cycle, in the positive pressure phase, electrolyte is injected, pressurized to a preset positive pressure, and a positive pressure holding range is set.

5. The method for optimizing the injection process according to claim 1, characterized in that, In step S3, during the ultrasonic testing process, the battery is evacuated to a preset negative pressure, the probe's emission reference frequency and ultrasonic intensity are set, and the black spots on the battery in the defect area are detected to determine that the defect area is in a poor wetting state.

6. The method for optimizing the injection process according to claim 1, characterized in that, In step S3, the acoustic parameters include: transmission attenuation and fundamental frequency offset. The transmission attenuation is used to characterize energy attenuation and quantify the energy loss when ultrasound penetrates the battery. The fundamental frequency offset is used to characterize the electrolyte wetting state.

7. The method for optimizing the injection process according to claim 1, characterized in that, In step S5, if the wetting rate meets the standard... If the preset wetting conditions are not met, the injection process parameters are adjusted using preset logic.

8. The method for optimizing the injection process according to claim 1, characterized in that, In step S5, the correction time parameter is adjusted according to the upper limit of the pressure holding time, and the next injection cycle operation begins.

9. The method for optimizing the injection process according to claim 1, characterized in that, In step S6, the cycle termination condition is set according to the target injection volume and the upper limit of the number of cycles.

10. A liquid injection process optimization system, characterized in that, The system includes: The initial parameter setting module is used for initial process settings. An ultrasonic transducer array is integrated circumferentially within the vacuum chamber of the injection equipment to set the target injection volume. and the maximum number of loops ; The electrolyte injection circulation module is used to perform electrolyte injection circulation, performing the i-th positive and negative pressure cycle on the battery; An acoustic parameter acquisition module is used to perform ultrasonic testing, collect and calculate acoustic parameters when the number of positive and negative pressure cycles meets a preset condition and the cycle ends. The liquid injection circulation module is connected to the liquid injection circulation module. The immersion status processing module is used to perform dynamic threshold determination based on the acoustic parameters. When the set acoustic parameter conditions are met, the current injection cycle is stopped, and the immersion compliance rate is calculated. The immersion state processing module is connected to the acoustic parameter acquisition module; The closed-loop control module is used for closed-loop process control, based on the stated wetting compliance rate. The decision is made to terminate the injection operation, and the closed-loop control module is connected to the immersion state processing module. The injection termination module is used to set the cycle termination condition. When the cumulative injection volume and the number of positive and negative pressure cycles reach the cycle termination condition, the injection operation is terminated. The injection termination module is connected to the closed-loop control module.

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