A dynamic compensation liquid injection method and system for lithium ion battery electrolyte and lithium ion battery

Abstract

The application discloses a dynamic compensation liquid injection method and system of a lithium ion battery electrolyte and a lithium ion battery, and relates to the field of lithium ion battery production and manufacturing. The dynamic liquid injection method provided by the application first obtains a reference curve of internal pressure change after battery liquid injection under the premise of fixed battery batch and specified production conditions, and determines a steady-state internal pressure threshold and a steady-state critical change rate as the judgment standard of dynamic compensation based on the reference curve. Then, in actual mass production, a dynamic compensation mode of liquid injection-detection-judgment-liquid compensation-circulation is adopted, and the actual internal pressure change rate reaching the steady state and the actual internal pressure value being stable within the steady-state internal pressure threshold are taken as double control targets, so that the liquid injection amount is accurately controlled to gradually approach the optimal liquid injection amount, the bottleneck of the traditional quantitative liquid injection mode is broken through, the single battery is accurately injected on demand, the influence of individual battery process differences is weakened, and the consistency of the battery after liquid injection is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing technology, specifically to a dynamic compensation electrolyte injection method, system, and lithium-ion battery. Background Technology

[0002] Current lithium battery electrolyte filling technology employs a fixed-volume injection method, meaning that all batteries are injected with the same fixed volume or weight of electrolyte. However, due to inherent micron-level differences in the porosity and compaction density of materials such as electrodes and separators within the battery, their actual electrolyte absorption and retention capabilities vary. This fixed-volume injection method leads to differences in the actual wetting state and electrolyte saturation level within each battery. This is one of the fundamental reasons for the insufficient consistency in performance characteristics such as capacity, internal resistance, and cycle life within the same batch of batteries. Battery consistency is a crucial factor affecting the safety and lifespan of battery packs.

[0003] To compensate for the aforementioned inconsistencies and ensure wetting effectiveness under worst-case conditions, existing processes often employ an over-filling strategy. This not only wastes expensive electrolyte raw materials but may also lead to excessive unwetting free electrolyte remaining inside the battery, causing battery swelling after encapsulation and, in extreme cases, increasing the risk of leakage and creating safety hazards.

[0004] Therefore, it is necessary to study a more precise method and system for injecting electrolyte into lithium-ion batteries, breaking away from the previous fixed-volume injection method, in order to improve the performance consistency of batteries in the same batch. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies and achieve precise on-demand electrolyte injection for each battery, this application proposes a dynamic compensation electrolyte injection method, system, and lithium-ion battery. By real-time monitoring of the rate of change of internal gas phase pressure after insufficient electrolyte injection, automatic electrolyte replenishment is performed based on the monitoring results, thereby achieving precise on-demand electrolyte injection through dynamic compensation.

[0006] In a first aspect, this application proposes a dynamic compensation electrolyte injection method for lithium-ion batteries, comprising: S1. Based on battery batch and production conditions, obtain the corresponding baseline curve of internal gas phase pressure change, steady-state internal pressure threshold and steady-state critical change rate. S2. Place the batch of batteries in the electrolyte injection station and inject a first preset amount of electrolyte into the batteries under the production conditions. S3. After standing for a first preset time, perform in-situ online detection to obtain the current value of the gas phase pressure inside the battery and calculate the current rate of change of the gas phase pressure inside the battery. S4. Determine whether fluid replenishment is needed based on the current rate of change. If fluid replenishment is needed, calculate the amount of fluid to be added based on the difference between the current internal pressure value and the baseline curve. If fluid replenishment is not needed, proceed directly to step S6. S5. Refill the battery with the additional electrolyte of the specified amount. S6. Repeat S3-S5 until the current rate of change is less than the steady-state critical rate of change and is maintained for a second preset time, then stop the injection. S7. Detect the internal pressure of the battery after stopping the electrolyte injection. If it is within the steady-state internal pressure threshold range, the battery quality is considered to be up to standard. If it is less than the steady-state internal pressure threshold range, proceed to step S4 to continue adding electrolyte. If it is greater than the steady-state internal pressure threshold range, the battery is considered to be faulty.

[0007] The technical solution provided in this application first obtains the internal pressure change benchmark curve, steady-state internal pressure threshold, and steady-state critical change rate of a fixed batch of batteries under specified operating conditions. Then, during mass production, a dynamic compensation process of injection-detection-judgment-replenishment-circulation is used to make the actual internal pressure change curve gradually approach the benchmark curve, moving from insufficient injection to optimal injection. Finally, the battery internal pressure reaches a steady state and stabilizes within the steady-state internal pressure threshold, thus achieving the optimal injection volume. This breaks through the quantitative injection mode and achieves the goal of precise injection on demand.

[0008] Furthermore, the acquisition of the baseline curve of the internal gas phase pressure change, the steady-state internal pressure threshold, and the steady-state critical rate of change based on battery batches and production conditions specifically includes: S11. Select experimental batteries and fix experimental conditions according to battery batch and production conditions; S12. Conduct the injection experiment and collect the experimental data; S13. Based on experimental data, establish a curve of the change of internal gas phase pressure value over time for each experimental battery. S14. Select the internal gas phase pressure change curve of the battery that meets the set standard. S15. Smoothly fit the internal gas phase pressure change curve of the screened and qualified batteries, and add an envelope band to generate a baseline curve of internal gas phase pressure change of the battery. S16. Based on the benchmark curve, determine the steady-state internal pressure threshold and the steady-state critical rate of change.

[0009] This solution establishes an internal pressure variation baseline curve through experiments, under the premise of fixed batches of batteries and specified operating conditions. It can accurately capture key characteristic parameters such as internal pressure amplitude, rate of change, and steady-state inflection point. The steady-state internal pressure threshold and steady-state critical rate of change set based on the experimental curve are closer to the actual process requirements than the theoretically derived values. At the same time, the baseline curve and envelope are formed by statistically smoothing the parallel experimental data of multiple cells. This can filter out interference factors such as random anomalies and detection noise of individual cells, forming a fluctuation range that is allowed by the process, and providing a stable and reliable reference standard for online electrolyte replenishment judgment.

[0010] Furthermore, the process of conducting the injection experiment and collecting experimental data specifically includes: S121. Group all experimental batteries and set different experimental injection volumes for each group. S122. Inject the experimentally set amount of electrolyte into the experimental battery and let it stand for a third preset time. S123. During the liquid injection and settling process, the internal pressure value of the experimental battery is continuously monitored at a preset frequency.

[0011] In this experiment, the battery groups were injected with electrolyte of different experimental values. The gradient experiment was used to make the experimental results show a certain degree of dispersion. Based on the discrete samples, a baseline center line and extreme value envelope can be constructed to define a reasonable process allowable range.

[0012] Furthermore, the step of determining whether fluid resuscitation is needed based on the current rate of change specifically includes:

[0013] in, The steady-state critical rate of change, This represents the current rate of change.

[0014] Furthermore, the specific formula for calculating the additional liquid volume based on the difference between the current value and the baseline curve is as follows:

[0015]

[0016] in, This is the additional volume of liquid to be added; The gain coefficient is the one calibrated in the experiment; This is the adjustment coefficient for each round; This is the baseline curve value for the current time. This represents the actual internal pressure value at the current time. This represents the difference between the actual time pressure value and the baseline curve value. This represents the minimum standard pressure difference corresponding to the current time. This is the maximum limit for a single fluid resuscitation. This is the minimum fluid replacement volume.

[0017] This scheme employs a dual-judgment logic for dynamic compensation electrolyte injection, with the internal pressure change rate as the primary criterion and the internal pressure value as the secondary criterion. The internal pressure change rate is used as the primary criterion; when the measured internal pressure change rate exceeds the steady-state critical change rate, it is determined that the battery has a tendency for insufficient electrolyte wetting. The internal pressure value is used as the secondary criterion to determine whether the conditions for immediate electrolyte replenishment are met and to calculate the replenishment amount. This dual-judgment logic avoids misjudgment and omission, improving the accuracy of electrolyte replenishment.

[0018] Furthermore, after the first preset time of settling, in-situ online detection is performed to obtain the current value of the internal gas phase pressure of the battery and calculate the current rate of change of the internal gas phase pressure of the battery. Specifically, after the first preset time of settling, the internal gas phase pressure value of the battery is collected online multiple times in situ within a specified time window. The average internal pressure collected within the time window is used as the current value of the internal gas phase pressure of the battery; the average rate of change of internal pressure at multiple points within the time window is used as the current rate of change of the internal gas phase pressure of the battery.

[0019] This solution uses a specified time window to collect pressure data at multiple points, process the average value, and calculate the average rate of change. It can filter out sampling spikes, instantaneous disturbances, and interference from replenishment pressure peaks, restore the true gas phase pressure and change trend of the battery, and improve the stability and accuracy of data acquisition.

[0020] Furthermore, the first preset time is 2-5 minutes.

[0021] The first preset time set in this solution can avoid the disorderly pressure fluctuations in the early stage of liquid replenishment, obtain a more stable pressure change trend, and at the same time take into account the efficiency of the production line cycle.

[0022] Furthermore, the first preset amount is 70%-90% of the theoretical injection volume.

[0023] The first preset amount set in this scheme can not only ensure the efficiency of the initial stage of insufficient liquid injection and wetting, but also reserve sufficient adjustment margin for the subsequent dynamic liquid replenishment stage.

[0024] Secondly, this application provides a dynamic compensation electrolyte injection system for lithium-ion batteries, the system comprising: The control unit includes a programmable logic controller and is connected to other units in the system for implementing the injection method as described in any of the first aspects; Battery clamps and transfer units are used to fix batteries and enable the transfer of batteries between workstations under the control of the control unit; The sensing and detection unit includes an internal pressure tester, which is used to detect the internal gas phase pressure value of the battery located in the battery clamp and the transmission unit under the control of the control unit, and transmit the internal pressure value to the control unit; The electrolyte injection unit, including a high-precision metering pump and an injection needle valve, is used to inject a specified amount of electrolyte into the battery located in the battery clamp and transfer unit under the control of the control unit.

[0025] Thirdly, this application provides a lithium-ion battery manufactured using a dynamic compensation electrolyte injection method as described in any one of the first aspects.

[0026] The dynamic electrolyte injection method proposed in this application first obtains a baseline curve of internal pressure change after electrolyte injection under fixed battery batches and specified production conditions. Based on this baseline curve, a steady-state internal pressure threshold and a steady-state critical change rate are determined as the criteria for dynamic compensation. In actual mass production, a dynamic compensation method of electrolyte injection-detection-judgment-replenishment-circulation is adopted. The dual control objectives are that the internal pressure change rate reaches a steady state and the internal pressure value stabilizes within the steady-state internal pressure threshold. The electrolyte injection volume is precisely controlled to gradually approach the optimal injection volume, breaking through the bottleneck of traditional quantitative electrolyte injection methods. This enables precise on-demand electrolyte injection for single cells, weakens the impact of individual battery process differences, and improves the consistency of batteries after electrolyte injection. Attached Figure Description

[0027] Figure 1 This is an overall flowchart of the dynamic compensation electrolyte injection method for lithium-ion batteries according to the present invention; Figure 2 This is a flowchart of the present invention for obtaining the reference curve of battery internal pressure drop; Figure 3 This is a structural diagram of the dynamic compensation electrolyte injection system for lithium-ion batteries of the present invention. Detailed Implementation

[0028] To make the objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0030] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0031] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0032] Furthermore, in the description of this application, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] The internal pressure of the battery mentioned in this application refers to the gas phase pressure inside the battery, specifically the pressure formed in the electrode pores and the gas phase space inside the sealed lithium battery cavity that is not filled with electrolyte. Its value change directly reflects the wetting progress and filling saturation of the electrode pores by the electrolyte, and is clearly distinguished from physical quantities such as the external expansion force of the battery cell and the pressure of the equipment cavity.

[0034] Based on theoretical analysis and production experience, the change in battery internal pressure is strongly correlated with the electrolyte injection operation and the amount of electrolyte injected. During the electrolyte injection process, the battery internal pressure initially jumps sharply. In the early stage after injection, the electrolyte begins to rapidly permeate into the pores of the electrodes and separator, gradually releasing pressure in the internal gas phase space, and the internal pressure drops rapidly. In the middle stage after injection, the trend of internal pressure change shows obvious differentiation. In the under-electrolyte state, the electrolyte continues to wet the pores, and the internal pressure continues to decrease slowly. In the optimal injection volume state, the wettation tends to be saturated, and the internal pressure gradually levels off and enters a steady state. In the over-electrolyte state, the pores are filled and there is no space for permeation, so the internal pressure drop is limited, and it stabilizes earlier or even rises slightly. When there is abnormal internal gas generation, the gas generation rate is greater than the pressure release due to wettation, and the internal pressure rises instead of falling. In the later stage after injection, the internal pressure is basically stable. Analyzing the above process, it can be seen that detecting the rate of change of internal pressure in the middle stage after injection can identify whether the battery is in the optimal injection volume state.

[0035] Meanwhile, batteries from the same batch, with consistent manufacturing processes, designs, and environmental conditions, will eventually converge and tend towards the same steady-state threshold range under the premise of optimal electrolyte injection volume and no abnormal gas generation. In a state of insufficient electrolyte injection, the steady-state internal pressure will be lower; conversely, in a state of excessive electrolyte injection, the steady-state internal pressure will be higher. Therefore, in addition to the rate of change in internal pressure, the steady-state internal pressure value is also a standard for determining whether the optimal electrolyte injection volume has been reached.

[0036] Based on the above analysis, before implementing the dynamic compensation electrolyte injection method of this application on the mass production line, it is necessary to first establish a baseline curve for the internal pressure change of batteries under the same operating conditions and in the same batch. Simultaneously, based on the baseline curve, the steady-state internal pressure threshold and the steady-state internal pressure change rate should be determined as the criteria for dynamic compensation. During mass production electrolyte injection, the same ambient temperature and operating conditions are maintained. The batteries are first subjected to a first-stage under-filling pre-injection; after the under-filling pre-injection is completed, the dynamic replenishment stage begins, through electrolyte injection... Detection judge The compensation control of electrolyte replenishment and circulation gradually brings the actual internal pressure change curve of the battery closer to the reference curve. Under ideal conditions, before reaching the optimal electrolyte level, the battery is always in a state of insufficient electrolyte and unsaturated wetting. During the resting phase, the actual internal pressure continues to decline, the rate of change of internal pressure is negative, and the actual internal pressure change curve is generally below the reference curve. Through multiple small-increment precise electrolyte replenishments, the actual internal pressure change curve converges and rises in a sawtooth pattern. The rate of decrease in internal pressure gradually slows down, the rate of change of internal pressure gradually approaches 0, and the actual internal pressure value gradually falls into the preset stable internal pressure threshold range. This process is the process by which the battery gradually approaches the optimal saturated electrolyte state from insufficient wetting and finally reaches the optimal electrolyte level. After the rate of change of internal pressure tends to stabilize and electrolyte replenishment stops, it is also necessary to determine whether the internal pressure value has entered the steady-state internal pressure threshold range to achieve the determination of dual control objectives and avoid the failure of a single control objective.

[0037] Example 1 To achieve the above-mentioned inventive concept, reference is made to Figure 1 This application provides the following exemplary embodiments: S1. Based on battery batch and production conditions, obtain the corresponding baseline curve of internal gas phase pressure change, steady-state internal pressure threshold, and steady-state critical change rate.

[0038] For example, refer to Figure 2 A baseline curve for battery internal pressure variation was established experimentally, including the following steps: S11. Select experimental batteries and fix the experimental conditions according to the battery batch and production conditions. Specifically... Several standard qualified batteries from the same batch were selected as experimental batteries to ensure that the experimental batteries were in the same state as the mass-produced batteries in the previous process and that the casing seals were the same. Based on actual production conditions, fixed experimental conditions are maintained, including consistent ambient temperature and humidity; consistent vacuum level of the battery cavity before liquid injection; and consistent static posture and placement environment after liquid injection.

[0039] S12. Conduct the injection experiment and collect experimental data, specifically including: S121. Group all experimental batteries into groups, and set different experimental injection volumes for each group; for example, the experimental batteries can be divided into 7 groups, and the experimental injection volumes can be set in gradients: theoretical volume, theoretical volume +1%, theoretical volume +2%, theoretical volume +3%, theoretical volume -1%, theoretical volume -2%, and theoretical volume -3%; the theoretical volume is the theoretical injection volume of this batch of batteries, and is generally calculated using the following formula in the industry:

[0040] Since batteries in the same batch are produced using the same structural design, the same raw materials and the same process, the theoretical liquid injection volume is the same. However, due to process reasons, there will be slight differences in the internal structure of the batteries produced in actual production, resulting in the actual optimal liquid injection volume of batteries in the same batch being a value that fluctuates slightly around the theoretical volume. S122. Inject the experimentally set amount of electrolyte into the experimental battery and let it stand for a third preset time. When injecting the experimentally determined amount of electrolyte into the experimental battery, the injection mode is involved, including the injection sequence, single injection volume, and settling interval. Since the primary purpose of establishing the baseline curve in this method is to determine the steady-state critical rate of change and the steady-state internal pressure threshold, serving as a criterion for dynamic compensation and guiding the direction and trend of dynamic internal pressure control during production, it is not required that the curve match the baseline curve in the early stages of dynamic electrolyte replenishment. Therefore, the injection mode in the experimental phase can differ from the injection mode in the mass production process. Furthermore, since staged injection will inevitably cause the internal pressure change curve to exhibit a sawtooth-like upward trend, to obtain a relatively smooth baseline curve, a slow, single injection or two-stage injection can be considered during the experimental phase.

[0041] In some embodiments, the electrolyte injection process during the baseline curve establishment experiment is divided into two stages. In the first stage, a first preset amount of electrolyte is injected. After the first stage of electrolyte injection is completed, the battery is left to stand for a first preset time. Then, the remaining electrolyte is slowly injected into the battery and left to stand for a third preset time. Correspondingly, the electrolyte injection process in the actual mass production process is also divided into two stages. In the first stage, a first preset amount of electrolyte is injected. After the first stage of electrolyte injection is completed, the battery is left to stand for a first preset time before entering the dynamic replenishment stage. The electrolyte injection mode in the first stage of the baseline curve establishment experiment is consistent with the electrolyte injection mode in the first stage of the actual mass production process. This allows the actual internal pressure change curve of the battery during the mass production process to roughly match the baseline curve in the early and middle stages, avoiding the risk of excessive replenishment caused by significant deviations in the feedback value during dynamic compensation and resulting in errors in the replenishment calculation. By limiting the electrolyte injection volume and standing time in the first stage to be consistent, the smoothness of the baseline curve and the comparability of the internal pressure trend in the early and middle stages of mass production are taken into account, improving the control stability and electrolyte injection accuracy of the dynamic replenishment algorithm.

[0042] In some embodiments, the first preset amount is 70%-90% of the theoretical liquid injection amount of this batch of batteries, which can ensure the efficiency of the first stage of insufficient liquid injection and wettability, and reserve sufficient adjustment margin for the subsequent dynamic liquid replenishment stage.

[0043] In some embodiments, the first preset time is 2-5 minutes. This duration is the short settling time after a stage of insufficient electrolyte injection. It needs to be adapted to the initial seepage of electrolyte, rapid rise and fall of internal pressure, and the entry into a stable decline stage.

[0044] In some embodiments, the third preset time is 2-4 hours. This duration is the long standing time after the second stage of electrolyte injection, which needs to be adapted to the full wetting of the electrolyte, the balance of gas production, and the entry of the battery internal pressure into the real steady state region.

[0045] S123. During the liquid injection and settling process, continuously monitor and record the internal pressure value of the experimental battery at a preset frequency; For example, during the experiment, a uniform detection frequency with a fixed 5-second sampling interval can be used throughout, balancing feature capture and data simplicity. In some embodiments, internal pressure detection can also employ time-segmented differentiated sampling frequencies: high-frequency sampling of 1–2 Hz is used during the rapid change phase of the injection process and the first preset time after injection; medium-frequency sampling of 10–30 seconds is used during the slow differentiation phase of internal pressure after the first preset time; and low-frequency sampling of 5–15 minutes is used after the steady-state phase begins 1 hour after injection. This approach ensures that no data is lost during the initial rapid changes, the differentiation slope is accurate in the middle stage, and the steady-state is smooth in the later stage, with a moderate amount of data that is easy to process and fit later.

[0046] S13. Based on the experimental data, establish a curve of the change of the internal gas phase pressure value of each experimental battery over time.

[0047] S14. Select a battery internal gas phase pressure change curve that meets the set criteria, the set criteria specifically include: The curve can be divided into four segments: during the injection process, the internal pressure jumps sharply and instantaneously, resulting in a significant pressure peak; in the initial stage after injection, the internal pressure drops rapidly from the peak, with a large rate of decline and a steep curve slope; in the middle stage after injection, the slope of the internal pressure decreases, and the curve changes from a steep drop to a gentle decline; in the later stage after injection, the internal pressure no longer declines significantly in one direction, gradually flattens out, and fluctuates only slightly within a very small threshold, without a sustained decline or significant rise. A curve that meets the above criteria can be considered the internal pressure change curve of a battery that has reached the optimal injection volume.

[0048] In some embodiments, the experimental batteries can be destructively disassembled for more precise curve selection. After the experimental batteries have been filled with electrolyte and allowed to stand, those with insufficient or excessive electrolyte filling are excluded. Batteries with no dry spots on the electrode cross-section, uniform color, no white areas, no free liquid, no liquid accumulation, no flow, and no liquid adhering to the separator edge are selected. The pressure change curves corresponding to these batteries are those that meet the set standards.

[0049] S15. The internal gas phase pressure change curve of the screened and qualified battery is smoothly fitted and an envelope band is added to generate a reference curve of internal gas phase pressure change of the battery. In some embodiments, the least squares method or B-spline curve (B-Spline) is used for curve fitting. The fitted curve is used as the center line of the internal pressure change reference curve, and the extreme value method is used to add upper and lower envelope bands on the fitted center line.

[0050] S16. Based on the benchmark curve, determine the steady-state internal pressure threshold and the steady-state critical rate of change.

[0051] Extract the steady-state time period when the internal pressure has stabilized from the baseline curve, and extract the pressure data of the fitted center line, the upper envelope zone and the lower envelope zone of the extreme value method within this time period; calculate the mean values ​​of the upper and lower envelope zones after smoothing the steady-state segment as the upper and lower limit thresholds of the steady-state pressure, and use the steady-state mean value of the fitted center line as the steady-state reference center threshold to form the steady-state pressure threshold range; A time period is extracted from the baseline curve after the injection is completed and the system has been allowed to stand for a first preset time. A fixed calculation time window is set. Within this time window, the average internal pressure change rate at multiple points along the baseline centerline, upper envelope, and lower envelope is calculated. The maximum value of these three rates is taken as the steady-state critical rate of change, denoted as [missing information]. In some embodiments, the width of this time window is 30-60 seconds.

[0052] S2. Place the batch of batteries in the electrolyte injection station, and inject a first preset amount of electrolyte into the batteries under the production conditions.

[0053] According to the set production conditions, the ambient temperature and humidity are controlled; the vacuum degree of the battery cavity is maintained before electrolyte injection; after electrolyte injection, the battery is placed in a static position and in the environment, and a first preset amount of electrolyte is injected into the battery casing. In some embodiments, this first preset amount is consistent with the amount of electrolyte injected in the first stage of the experiment; in other embodiments, the first preset amount is 70%-90% of the theoretical amount of electrolyte injected.

[0054] S3. After standing for a first preset time, perform in-situ online detection to obtain the current value of the gas phase pressure inside the battery and calculate the current rate of change of the gas phase pressure inside the battery.

[0055] After a first preset time, the internal gas phase pressure value of the battery is continuously collected within a specified time window. The average internal pressure collected within the time window is taken as the current value of the internal gas phase pressure of the battery. The average internal pressure change rate at multiple points within the time window is calculated as the current change rate of the internal gas phase pressure of the battery. The width of the time window is consistent with the width of the time window for determining the steady-state critical change rate during the experimental stage.

[0056] S4. Determine whether fluid replenishment is needed based on the current rate of change. If fluid replenishment is needed, calculate the amount of fluid to be added based on the difference between the current internal pressure value and the baseline curve. If fluid replenishment is not needed, proceed directly to step S6.

[0057] The dynamic compensation method used in this application employs a dual-judgment logic, primarily based on the rate of internal pressure change and secondarily on the internal pressure value. The rate of internal pressure change is used as the primary criterion; when the measured rate of internal pressure change exceeds the steady-state critical rate of change, the battery is determined to have a tendency for insufficient electrolyte wetting. The internal pressure value is used as the secondary criterion to determine whether immediate electrolyte replenishment is possible and to calculate the replenishment amount. The specific steps are as follows: S41. Determine whether fluid replacement is necessary based on the following conditions;

[0058] in, The steady-state critical rate of change, This represents the current rate of change. S42. If fluid replenishment is required, the volume of fluid to be added is calculated based on the difference between the current value and the baseline curve. The specific formula is as follows:

[0059]

[0060] in, This is the additional volume of liquid to be added; This is the pressure-injection volume gain coefficient calibrated for experiments, used to match the injection sensitivity of batteries in different systems; the default value is 1. This is a round adjustment coefficient used to match the nonlinear change characteristics of the internal pressure-injection volume sensitivity during the injection process with the wetting stage. It monotonically decreases with each injection round. When the sensitivity is low in the early stages, the coefficient is larger to improve injection efficiency. As the sensitivity increases in the later stages, the coefficient automatically decreases to achieve slow, micro-volume injection and avoid over-injection. For example, the first round of injection... Set the value to 2.0-3.0, second round. Take 1.2-1.8, third round. Set it to 1, and keep it at 1 thereafter; This is the baseline curve value for the current time. This represents the actual internal pressure value at the current time. This is the difference between the current internal pressure value and the baseline curve. The reference differential pressure threshold, physically defined as the critical internal pressure difference during the battery electrolyte filling process, represents the transition from the free wetting zone to the near-saturation pressure-sensitive zone. This threshold can be experimentally calibrated based on the sensitivity curve of differential pressure versus electrolyte volume, and in some cases, it can also be determined based on engineering experience. For example, in conventional medium-to-large capacity batteries... ; This is the maximum limit for a single fluid resuscitation volume to prevent the risk of excessive fluid resuscitation in a single instance. In some embodiments, ; The minimum compensation amount is determined by the liquid injection equipment on the production line. It is the minimum quantitative amount that the liquid injection equipment can control, and is generally 0.1% to 0.5% of the theoretical liquid injection amount.

[0061] In some cases, after fluid replenishment, the internal pressure value will experience a rapid surge. After a first preset time of settling, although the internal pressure value decreases, the surge from fluid replenishment has not been fully absorbed. At this point, the rate of change of internal pressure will exceed the steady-state critical rate of change, indicating a low-fluid state. However, the internal pressure value will be greater than the baseline curve value, indicating an over-fluid state. The reason for this contradiction is that the "over-fluid state" at this time is a temporary, artificially inflated indicator, not a true over-fluid state, and should be avoided from being directly filtered out. In this embodiment, in When the time is reached, the fluid replenishment volume is set to 0, and the cycle begins again. The system is then allowed to stand for the first preset time, and the judgment is made again to avoid misjudgment.

[0062] S5. Add the amount of electrolyte to the battery.

[0063] S6. Repeat steps S3-S5 until the current rate of change is less than the steady-state critical rate of change and is maintained for a second preset time, then stop the injection. The second preset time is used to determine whether the battery internal pressure can be maintained in a stable state. In some embodiments, the second preset time is set to 2-4 hours. This duration allows the battery to achieve gas-liquid smoothing and wetting balance. The pressure value at this time is the true steady-state internal pressure, which can be used as a basis for determining whether the optimal injection volume has been reached.

[0064] S7. Detect the battery's internal pressure after stopping electrolyte injection. If it falls within the steady-state internal pressure threshold range, the battery quality is considered acceptable. If it falls below the steady-state internal pressure threshold range, proceed to step S4 to continue electrolyte injection. If it exceeds the steady-state internal pressure threshold range, the battery is considered faulty. After the internal pressure change rate stabilizes, the absolute internal pressure value needs to be determined again to avoid misjudgment and missed judgment. In most cases, through dynamic cyclic electrolyte injection in S3-S6, the battery internal pressure will fall within the steady-state internal pressure threshold range after reaching a steady state. If the change rate has reached a steady state but the internal pressure value is still below the steady-state internal pressure threshold range, it can be judged as a very small amount of electrolyte shortage. Proceed to step S42 for minimum electrolyte injection, and then perform cyclic detection and judgment again. If the internal pressure value finally exceeds the steady-state internal pressure threshold range, it is initially judged as over-injection, and a fault mark should be marked, and the battery should be transferred to the faulty battery judgment and processing procedure.

[0065] Example 2 Based on the method described in Embodiment 1, this embodiment provides a system for implementing the above method, as shown in the attached diagram. Figure 3 The system includes: The control unit includes a PLC (Programmable Logic Controller) that connects to other units in the system to implement the liquid injection method as described in Example 1. Battery clamps and transfer units are used to fix batteries and enable the transfer of batteries between workstations under the control of the control unit; The sensing and detection unit includes a battery internal gas phase pressure tester, which is used to detect the internal pressure value of the battery located in the battery clamp and the transmission unit under the control of the control unit, and transmit the internal pressure value to the control unit; The electrolyte injection unit, including a high-precision metering pump and an injection needle valve, is used to inject a specified amount of electrolyte into the battery located in the battery clamp and transfer unit under the control of the control unit.

[0066] Example 3 Based on Examples 1 and 2, this example provides a lithium-ion battery, which is manufactured using the dynamic compensation electrolyte injection method for lithium-ion batteries described in Example 1.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 this application.

Claims

1. A dynamic compensation method for lithium-ion battery electrolyte, characterized in that, include: S1. Based on battery batch and production conditions, obtain the corresponding baseline curve of internal gas phase pressure change, steady-state internal pressure threshold and steady-state critical change rate. S2. Place the batch of batteries in the electrolyte injection station and inject a first preset amount of electrolyte into the batteries under the production conditions. S3. After standing for a first preset time, perform in-situ online detection to obtain the current value of the gas phase pressure inside the battery and calculate the current rate of change of the gas phase pressure inside the battery. S4. Determine whether fluid replenishment is needed based on the current rate of change. If fluid replenishment is needed, calculate the amount of fluid to be added based on the difference between the current internal pressure value and the baseline curve. S5. Refill the battery with the additional electrolyte of the specified amount. S6. Repeat S3-S5 until the current rate of change is less than the steady-state critical rate of change and is maintained for a second preset time, then stop the injection. S7. Detect the internal pressure of the battery after stopping the electrolyte injection. If it is within the steady-state internal pressure threshold range, the battery quality is considered to be up to standard. If it is less than the steady-state internal pressure threshold range, proceed to step S4 to continue adding electrolyte. If it is greater than the steady-state internal pressure threshold range, the battery is considered to be faulty.

2. The dynamic compensation injection method according to claim 1, characterized in that, The process of obtaining the baseline curve of the internal gas phase pressure change, the steady-state internal pressure threshold, and the steady-state critical rate of change based on battery batches and production conditions specifically includes: S11. Select experimental batteries and fix experimental conditions according to battery batch and production conditions; S12. Conduct the injection experiment and collect the experimental data; S13. Based on experimental data, establish a curve of the change of internal gas phase pressure value over time for each experimental battery. S14. Select the internal gas phase pressure change curve of the battery that meets the set standard. S15. Smoothly fit the internal gas phase pressure change curve of the screened and qualified batteries, and add an envelope band to generate a baseline curve of internal gas phase pressure change of the battery. S16. Based on the benchmark curve, determine the steady-state internal pressure threshold and the steady-state critical rate of change.

3. The dynamic compensation injection method according to claim 2, characterized in that, The process of conducting the injection experiment and collecting experimental data specifically includes: S121. Group all experimental batteries and set different experimental injection volumes for each group. S122. Inject the experimentally set amount of electrolyte into the experimental battery and let it stand for a third preset time. S123. During the liquid injection and settling process, the internal pressure value of the experimental battery is continuously monitored at a preset frequency.

4. The dynamic compensation injection method according to claim 1, characterized in that, The determination of whether fluid resuscitation is needed based on the current rate of change specifically includes: in, The steady-state critical rate of change, This represents the current rate of change.

5. The dynamic compensation injection method according to claim 4, characterized in that, The formula for calculating the additional liquid volume based on the difference between the current value and the baseline curve is as follows: in, This is the additional volume of liquid to be added; The gain coefficient is the one calibrated in the experiment; This is the adjustment coefficient for each round; This is the baseline curve value for the current time. This represents the actual internal pressure value at the current time. This represents the difference between the actual time pressure value and the baseline curve value. This represents the minimum standard pressure difference corresponding to the current time. This is the maximum limit for a single fluid resuscitation. This is the minimum fluid replacement volume.

6. The dynamic compensation injection method according to claim 1, characterized in that, After the first preset time of settling, the current value of the internal gas phase pressure of the battery is obtained by in-situ online detection, and the current rate of change of the internal gas phase pressure of the battery is calculated. Specifically, after the first preset time of settling, the internal gas phase pressure value of the battery is collected online multiple times in situ within a specified time window, and the average internal pressure collected within the time window is used as the current value of the internal gas phase pressure of the battery. The average internal pressure change rate at multiple points within this time window is taken as the current change rate of the gas phase pressure inside the battery.

7. The dynamic fluid replenishment method according to claim 1, characterized in that, The first preset time is 2-5 minutes.

8. The dynamic fluid replenishment method according to claim 1, characterized in that, The first preset amount is 70%-90% of the theoretical injection volume.

9. A dynamic compensation electrolyte injection system for lithium-ion batteries, characterized in that, The system includes: The control unit includes a PLC, which is connected to other units in the system to implement the liquid injection method as described in any one of claims 1-8; Battery clamps and transfer units are used to fix batteries and enable the transfer of batteries between workstations under the control of the control unit; The sensing and detection unit includes a battery internal gas phase pressure tester, which is used to detect the internal pressure value of the battery located in the battery clamp and the transmission unit under the control of the control unit, and transmit the internal pressure value to the control unit; The electrolyte injection unit, including a high-precision metering pump and an injection needle valve, is used to inject a specified amount of electrolyte into the battery located in the battery clamp and transfer unit under the control of the control unit.

10. A lithium-ion battery, characterized in that, It is manufactured using the dynamic compensation electrolyte injection method described in any one of claims 1-8 for lithium-ion batteries.

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