A lithium ion battery charging strategy determination method and a battery charging method

Abstract

The application discloses a lithium ion battery charging strategy determination method and a charging method. The charging strategy determination method comprises the following steps: determining an average charging rate C' according to the rated capacity of a lithium ion battery to be charged, a target SOC interval and a target charging time, and then determining a minimum charging rate C min and a maximum charging rate C max ; C min <C' < C max ; determining a current charging time for completing the target SOC interval under a current charging strategy; in the current charging strategy, n step charging stages are set, and the charging rate C'' continuously decreases along the charging sequence; C min ≤C'' ≤ C max , and at least one C'' > C'; n≥2; if the current charging time is less than or equal to the target charging time, the current charging strategy is the target charging strategy; if the current charging time is greater than the target charging time, correction is performed to form a new current charging strategy and the previous step is returned. The application improves the accuracy and efficiency of the charging strategy.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a method for determining a lithium-ion battery charging strategy and a battery charging method. Background Technology

[0002] Currently, the charging method used in lithium-ion battery applications and testing is mainly the constant current / constant voltage method. This charging method is simple, easy to implement, and convenient to operate. However, as the market and users demand faster charging of lithium-ion batteries, it is necessary to continuously increase the current and voltage values. High-current constant current / constant voltage charging can easily lead to lithium plating, directly affecting the lifespan of lithium-ion batteries.

[0003] Currently, tiered charging has become an effective method for achieving fast battery charging. Tiered charging can be simply understood as performing different constant current and constant voltage charging within different battery SOC (State of Charge) ranges. For ease of operation, the constant voltage step is often omitted. However, while meeting the demand for fast charging, lithium plating must not occur during tiered charging to prevent affecting battery safety and cycle life. Therefore, under the premise of tiered charging, it is necessary to optimize charging parameters such as charging current to avoid lithium plating, so as to maximize battery charging speed and improve user experience while ensuring battery safety and lifespan.

[0004] However, optimizing charging parameters requires determining the fundamental charging properties of lithium-ion batteries. Currently, the lithium-ion battery industry largely relies on continuous charging tests to determine charging strategies. However, this method is inefficient and inaccurate. Summary of the Invention

[0005] To address the problems in the prior art, this application provides a method for determining a lithium-ion battery charging strategy and a battery charging method to solve one or more technical problems existing in the prior art.

[0006] In a first aspect, this application provides a method for determining a lithium-ion battery charging strategy, the method comprising the following steps:

[0007] (11) Determine the average charging rate C' corresponding to the target SOC range based on the lithium-ion battery's rated capacity, target SOC range, and target charging time corresponding to the target SOC range;

[0008] (13) Based on the average charging rate C', determine the minimum value C of the charging rate corresponding to the target SOC range. min and maximum value C max C min <C'<C max ;

[0009] (15) Determine the current charging time required to complete charging of the target SOC range under the current charging strategy; in the current charging strategy, the target SOC range corresponds to n stepped charging stages, and along the charging sequence, the charging rate C” corresponding to the stepped charging stage continuously decreases; the C” min ≤C”≤C max And at least one C” > C'; n ≥ 2;

[0010] (17) If the current charging time is less than or equal to the target charging time, the current charging strategy is determined to be the target charging strategy; if the current charging time is greater than the target charging time, the current charging strategy is corrected according to the preset rules to form a new current charging strategy and the process returns to step (15).

[0011] Optionally, step (13) includes:

[0012] The minimum charging rate C corresponding to the target SOC range is determined based on C'±kC (0.1≤k≤2). min and maximum value C max C is the ratio of the current required for a lithium-ion battery to charge and discharge its rated capacity within a specified time.

[0013] Optionally, the current charging strategy is an initial charging strategy; the method further includes the step of:

[0014] (12) Based on the minimum charging rate C corresponding to the target SOC range min and maximum value C max And in accordance with the arithmetic progression, the number of tiered charging stages n and the charging rate C corresponding to each tiered charging stage are set in the initial charging strategy.

[0015] Optionally, in step (17), correcting the current charging strategy according to preset rules includes:

[0016] Before the last step charging stage of the current charging strategy, at least one additional step charging stage is added.

[0017] and / or,

[0018] Increase the charging rate of at least one step of the current charging strategy.

[0019] Optionally, adding at least one tiered charging stage before the last tiered charging stage of the current charging strategy includes:

[0020] Add at least one additional charging stage between the first two charging stages of the current charging strategy; or, the first charging stage of the current charging strategy is not C. max At the same time, at least one additional step charging stage is added before the first step charging stage;

[0021] The improvement of the charging rate of at least one step of the current charging strategy includes:

[0022] Increase the charging rate of at least one of the first m charging stages of the current charging strategy; where m is a positive integer and m ≤ n / 2; or, the first charging stage of the current charging strategy is not C. max At the same time, the charging rate of the first step charging stage is increased.

[0023] Optionally, the current charging time is determined based on simulation or the actual charging process.

[0024] Optionally, the lithium-ion battery to be charged includes a three-electrode lithium-ion battery with a reference electrode;

[0025] Step (15) includes:

[0026] In the first n-1 step charging stages, the negative parameter potential of the current step charging stage is determined using the reference electrode, and when the negative parameter potential is less than or equal to the cutoff voltage, the next step charging stage is entered and the charging time of the current step charging stage is recorded.

[0027] In the nth step charging stage, the negative parameter potential is determined using the reference electrode, and the charging of the nth step charging stage ends when the negative parameter potential is less than or equal to the cutoff voltage or reaches the maximum value of the target SOC range.

[0028] Optionally, the method further includes the step of:

[0029] (16) Form a correlation curve between each charging rate and its corresponding cumulative charging time under the current charging strategy;

[0030] In step (17), the step of correcting the current charging strategy according to a preset rule if the current charging time is greater than the target charging time includes:

[0031] If the current charging time is greater than the target charging time, the current charging strategy is corrected based on the correlation curve to form a corrected charging strategy.

[0032] A second aspect of this application provides a lithium-ion battery charging method, the lithium-ion battery charging method comprising:

[0033] (21) Upon receiving a charging request, determine the current SOC of the lithium-ion battery to be charged;

[0034] (23) Determine the target step charging stage corresponding to the current SOC from the preset lithium-ion battery charging strategy; the preset lithium-ion battery charging strategy is obtained by the lithium-ion battery charging strategy determination method according to any one of claims 1-8;

[0035] (25) Starting from the target step charging stage, charge according to the preset lithium-ion battery charging strategy.

[0036] Optionally, there are at least two preset lithium-ion battery charging strategies, and different lithium-ion battery charging strategies correspond to different target SOC ranges.

[0037] Step (23) includes:

[0038] (231) Determine the target lithium-ion battery charging strategy corresponding to the current SOC;

[0039] (233) Determine the target stepped charging stage corresponding to the current SOC from the target lithium-ion battery charging strategy.

[0040] The above-described technical solutions of the present invention have at least one or more of the following beneficial effects:

[0041] In implementing the technical solution of this invention, the average charging rate C' corresponding to the target SOC range is determined by the lithium-ion battery's calibrated capacity, the target SOC range, and the target charging time corresponding to the target SOC range. Furthermore, based on C', the minimum value Cmin and the maximum value Cmax of the charging rate corresponding to the target SOC range are determined. Since the average charging rate C', serving as a benchmark, is obtained under the premise of meeting the target charging time, the charging rate determined based on this is a charging rate that can meet or closely approximate the target charging time. Compared to the prior art, which relies entirely on charging experiments to determine the charging strategy without any benchmark, this application fundamentally improves the accuracy and efficiency of charging strategy formulation. Furthermore, by judging the charging time of the formulated fast charging strategy, the direction of strategy correction can be determined for targeted correction, thereby determining the target charging strategy that meets the target charging time. This provides an efficient and accurate method for formulating a battery fast charging strategy.

[0042] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0043] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Furthermore, similar numbers in the drawings are used to denote similar components, wherein:

[0044] Figure 1 This is a flowchart of the lithium-ion battery charging strategy determination method in Embodiment 1 of this application;

[0045] Figure 2 This is the voltage-SOC curve corresponding to the charging strategy in Embodiment 1 of this application;

[0046] Figure 3 The charging rate C”-t corresponding to the charging strategy in Embodiment 1 of this application. 累计 Relationship curve diagram;

[0047] Figure 4 This is a charging rate C”-SOC curve of the charging strategy before and after correction in Embodiment 1 of this application;

[0048] Figure 5 This is a flowchart of the lithium-ion battery charging method in Embodiment 2 of this application. Detailed Implementation

[0049] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0050] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application and in its specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The terms "and / or" or "and / or" as used in this application include any and all combinations of one or more of the associated listed items.

[0051] To make it clearer, this application will first briefly introduce the principle that stepped charging can reduce the risk of lithium plating while allowing for fast charging.

[0052] During charging, lithium batteries undergo polarization. When polarization reaches a certain level, and the negative electrode potential becomes zero, theoretically, lithium plating occurs. Different states of charge (SOC) and charging rates have varying effects on polarization and lithium plating. Higher SOC and higher charging rates result in more severe polarization and a greater risk of lithium plating.

[0053] However, when switching charging rates, the change in current reduces or eliminates polarization, increases voltage, raises the negative electrode potential to above zero, reduces the risk of lithium plating, and allows charging to continue at the new charging rate.

[0054] Stepped charging is based on the aforementioned characteristics of lithium batteries. At the beginning of charging, the SOC is low, and the corresponding risk of lithium plating is low, so a larger charging rate can be used to achieve fast charging. As the charging process progresses, the SOC increases, the negative electrode potential gradually drops to zero, and the risk of lithium plating increases. At this time, switching to a lower charging rate can reduce or eliminate polarization, increase the negative electrode potential, and reduce the risk of lithium plating, so that charging can continue at the lower charging rate.

[0055] However, as mentioned in the background section, although stepped charging technology is currently used in fast charging, quickly determining the optimal charging parameters, i.e., the number of steps and the charging rate of each step, remains a challenge. To address this, this application innovatively proposes a new method for determining a stepped charging strategy. This method determines the average charging rate based on the charging demand (completing charging within the target SOC range within the target charging time), and then uses this average charging rate as a benchmark to determine the stepped charging strategy. Since the average charging rate is obtained under the premise of meeting the charging demand, the stepped charging strategy determined based on this can meet or closely meet the charging rate required for the target charging time. Compared to existing technologies that rely entirely on charging experiments to determine the charging strategy without any benchmark, this application fundamentally improves the accuracy and efficiency of charging strategy formulation. Furthermore, based on the judgment of the charging time of the charging strategy, this application determines the direction of strategy correction and performs targeted strategy correction, thereby quickly determining a stepped charging strategy that meets the charging demand.

[0056] The following describes some embodiments of this application. It should be noted that the following description is for illustrative purposes and is not intended to limit the scope of protection of this application.

[0057] Example 1 of this application provides a method for determining a lithium-ion battery charging strategy. (Refer to...) Figure 1 The method includes the following steps:

[0058] 11. Based on the lithium-ion battery's rated capacity, target SOC range, and target charging time corresponding to the target SOC range, determine the average charging rate C' corresponding to the target SOC range.

[0059] In this embodiment of the application, it can be specifically expressed by formula (1): C' = (SOC) max -SOC min The average charge rate C' is calculated by multiplying C0 by t0 / C0. Where SOC...max -SOC min This is used to calculate the target SOC range; C0 is the calibrated capacity, and t0 is the target charging time corresponding to the target SOC range. C can be obtained by calibrating the lithium-ion battery under specified conditions. SOC... min and SOC max SOC is a fast-charging boundary condition defined based on the materials and performance of lithium-ion batteries. min Minimum SOC for fast charging, SOC max The maximum SOC for fast charging, below the SOC min Fast charging can easily lead to lithium-ion deposition inside the battery, exceeding the state of charge (SOC). max This can easily lead to lithium plating in lithium-ion batteries. The State of Charge (SOC) can be determined based on the specific type of lithium-ion battery. min and SOC max 13. Based on the average charging rate C', determine the minimum charging rate C corresponding to the target SOC range. min and maximum value C max C min <C'<C max .

[0060] Based on the discussion of lithium-ion battery charging characteristics throughout the text, it can be seen that the charging rate corresponding to the target SOC range is not a constant value, but rather decreases as the SOC increases. It reaches its maximum value C at the beginning of the target SOC range. max When the SOC is at the maximum value of the target SOC interval, it has a minimum value C. min The average charging rate C' is suitable for the average SOC within the target SOC range, therefore C min <C'<C max C is understandable. min With C max All are greater than zero.

[0061] In some embodiments of this application, step (13) specifically includes: determining the minimum value C of the charging rate corresponding to the target SOC range based on the formula C'±kC (0.1≤k≤2). min and maximum value C max Where C is the ratio of the current required for a lithium-ion battery to charge and discharge its rated capacity within a specified time. Furthermore, based on the chemical composition, health status, and safety considerations of the lithium-ion battery, k = 1 is preferably chosen, then C... max =C'+C, and C min=C'-C. Of course, to further determine the maximum and minimum values, the maximum and minimum values ​​can be further modified, for example, by combining C' with past empirical values ​​to determine the maximum and minimum values. This application does not specifically limit this. Based on the above method, the minimum and maximum values ​​of the charging rate can be determined simply and quickly, providing a basis for determining the subsequent stepped charging rate without relying on charging experiments.

[0062] Determine the minimum value C min With the maximum value C max After that, it can be based on C min and C max Further determine the initial charging strategy. In some embodiments of this application, the number of charging stages n and the charging rate C” corresponding to each charging stage can be determined based on an arithmetic progression. If the arithmetic progression is qC, then the charging rate C” of the x-th charging stage is... x =C” x-1 -qC, where x is greater than or equal to 2, and q is the arithmetic progression adjustment factor.

[0063] For example, if the target SOC range is 10%-80%, C' is 3.5C, k=1, C max and C min The initial charging rates are 4.5C and 2.5C respectively. Taking an arithmetic progression qC of 0.5C, the initial charging strategy is determined as shown in Table 1 below:

[0064] Table 1

[0065]

[0066] As can be seen from the table, the number of charging stages n in the initial charging strategy is 5, and the charging rate C” corresponding to each charging stage ranges from the maximum value C. max Arithmetic progression decreasing to the minimum value C min .

[0067] Understandably, in the aforementioned arithmetic progression method, a pre-set arithmetic progression value is used to determine the number of charging stages n, where q ≤ k. This arithmetic progression value is determined based on the range of the maximum and minimum charging rates, thus determining the number of charging stages. This avoids an excessively large q value, which would result in too few charging stages and affect charging efficiency. A fewer charging stage might also lead to some stages using higher charging rates, increasing the risk of battery aging and lithium plating, and potentially increasing battery temperature rise, thus affecting battery performance. Optionally, q ≤ 0.5k. Further, q ≥ 0.2k is used to avoid an excessively small q value, which would result in too many charging stages and decrease charging efficiency due to the transitions between each stage.

[0068] It should be noted that the number of charging stages n should be a positive integer. Therefore, in the above arithmetic progression method, in some cases, the arithmetic progression is not strictly arithmetic, for example, C. max and C min The values ​​are 4.5C and 2.4C respectively, with an arithmetic progression of 0.5C. Since an integer n cannot be obtained at this point, the difference between the last two step charging stages can be set to 0.6C.

[0069] In alternative embodiments, C max and C min This can be considered a rough benchmark; the maximum and minimum values ​​of the first-charge strategy can be roughly within C. max and C min Nearby is fine. For example, C. max and C min The rates are 4.5C and 2.4C respectively, with an arithmetic progression of 0.5C. Since an integer n cannot be obtained at this point, the charging rate of the last step charging stage can be adjusted to 2.5C.

[0070] The above-mentioned arithmetic progression method provides an easy-to-operate way to determine the charging strategy, and this method can provide a uniform and stable charging rate, which is a better way to determine the charging strategy.

[0071] Besides arithmetic progressions, it can also be based on C. min and C max Alternatively, other methods can be used to determine the initial charging strategy. For example, a geometric progression method can be used, where the charging rate of the later charging stage is p times the charging rate of the previous charging stage, where p < 1.

[0072] The above examples illustrate several feasible methods for determining the first charging strategy. However, it should be noted that any method based on C... max and C min The determination of the initial charging strategy falls within the scope of protection of this application, and this application does not limit the specific method.

[0073] In this application, by determining the average charging rate, the maximum and minimum values ​​of the charging rate are determined to determine the final number of tiered charging stages and the corresponding charging rates. Based on the average charging rate, the overall charging efficiency is maximized and improved.

[0074] The initial charging strategy is a preliminary trial and may not guarantee that charging needs will be met. Therefore, this application further requires testing the charging effect of the initial charging strategy and making adjustments based on the test results. Specifically, this includes:

[0075] Determine the charging time required to complete charging of the target SOC range under the initial charging strategy;

[0076] If the charging time is less than or equal to the target charging time, the first charging strategy is determined to be the target charging strategy; if the charging time is greater than the target charging time, the first charging strategy is corrected according to a preset rule to form a new charging strategy.

[0077] Once a new charging strategy is developed, the above process needs to be repeated to test the charging effect of the new strategy and make corrections based on the test results until a certain charging strategy meets the charging requirements.

[0078] Summarizing the above-mentioned cyclical process of formulating and correcting charging strategies, and taking any one of the charging strategies as the current charging strategy, we can obtain the following steps 15 and 17:

[0079] 15. Determine the current charging time required to complete charging of the target SOC range under the current charging strategy; in the current charging strategy, the target SOC range corresponds to n stepped charging stages, and along the charging sequence, the charging rate C” corresponding to the stepped charging stage continuously decreases; C” min ≤C”≤C max And at least one C” > C'; n ≥ 2.

[0080] 17. If the current charging time is less than or equal to the target charging time, the current charging strategy is determined to be the target charging strategy; if the current charging time is greater than the target charging time, the current charging strategy is corrected according to a preset rule to form a new current charging strategy and the process returns to step (15).

[0081] In step 15 above, the charging time for each step of the charging process needs to be determined to sum the current charging time required to complete the charging of the target SOC range. In this embodiment, the charging cutoff condition for each step of the charging process is reaching or about to reach the theoretical lithium plating state. To better monitor this theoretical lithium plating state, in some embodiments of this application, the lithium-ion battery to be charged can be a three-electrode lithium-ion battery. The negative parameter potential of the battery during the charging process is measured using the three-electrode method. The charging cutoff condition for each stage is calculated by using the negative parameter potential reaching the cutoff voltage (theoretical lithium plating state). Specifically, the cutoff voltage can be zero.

[0082] Therefore, this application first prepares a three-electrode lithium-ion battery. During the lithium battery winding or stacking stage, copper wire is implanted as a reference electrode to prepare the three-electrode lithium-ion battery. Specifically, the copper wire is implanted between the positive and negative electrodes of the penultimate layer of the stack or winding, and is separated from the positive and negative electrodes. The diameter of the selected copper wire is as small as possible; in a preferred embodiment, the diameter is less than 50 μm. Next, the lithium-ion battery is charged and capacitated. The lithium-ion battery is connected to a charge-discharge apparatus to plate lithium onto the copper wire. The positive terminal of the charge-discharge apparatus is connected to the copper wire side, and the negative terminal of the apparatus is connected to the positive or negative electrode of the battery. A small constant current is used for charging. During the charging process, lithium ions in the electrolyte are deposited on the copper wire, forming a uniform lithium layer on the surface of the copper wire. The small current is as small as possible; in a preferred embodiment, the current is less than or equal to 50 μA, and the charging time is 4-8 hours. Specifically, the battery can be capacitated at room temperature for three weeks, and the discharge capacity of the third week is taken as the calibrated capacity C0.

[0083] The three-electrode lithium-ion battery is then charged according to the current charging strategy, and the negative parameter potential of the current step charging stage is monitored using a reference electrode during the charging process. In the first n-1 step charging stages of the current charging strategy, when the negative parameter potential reaches the cutoff voltage (e.g., zero), the next step charging stage begins, and the charging time of the current step charging stage is recorded. When entering the nth step charging stage, it is possible that the battery has already been charged to the maximum value of the target SOC range before reaching the theoretical lithium plating state. Therefore, when entering the nth step charging stage, it is necessary to determine whether the negative parameter potential is less than or equal to the cutoff voltage or whether the battery has been charged to the maximum value of the target SOC range. If either condition is met first, the charging of the nth step charging stage ends, and the charging time is calculated.

[0084] In addition to determining the charging time based on the actual charging process as described above, in alternative embodiments, the relevant parameters of the lithium-ion battery and the current charging strategy can be input into charging simulation software to simulate the charging process, and the charging time of each stage can be determined based on the simulated process changes, thereby determining the charging time corresponding to the current charging strategy.

[0085] If the current charging time is greater than the target charging time, the current charging strategy needs to be corrected according to preset rules to form a new current charging strategy. In this application, the charging rate can be adjusted by adjusting the number of stages n and the arithmetic progression adjustment factor 1 to achieve strategy correction. This application does not limit the specific correction method, but it should be clear that the new current charging strategy aims to further shorten the charging time. In some embodiments, correcting the current charging strategy according to preset rules includes:

[0086] Before the last step of the current charging strategy, at least one additional step charging stage is added. The charging rate of this additional step charging stage is naturally higher than the lowest charging rate in the original charging strategy. Compared to the original charging strategy, this new charging strategy can utilize a higher charging rate to achieve charging within the same SOC range, thereby reducing charging time.

[0087] Adding at least one step charging stage before the last step charging stage of the current charging strategy includes: adding at least one step charging stage between the first two step charging stages of the current charging strategy; or, the first step charging stage of the current charging strategy is not C. max At the same time, at least one additional step charging stage is added before the first step charging stage.

[0088] The charging rate for the added tiered charging stages must satisfy the overall charging strategy's decreasing trend. In one embodiment, the charging rate for the added tiered charging stages can still be determined using the arithmetic progression method, where C... x =C” x-1 -q'C, and q' is less than q. For example, in Table 1, when k=1, q=0.5, q'=0.2, and C'=3.5C, we take 3.5C+1C-0.2C=4.3C and add it between stages 1 and 2 in Table 1 to form a new stage 2. This results in 6 charging stages, with the corresponding charging rates for each stage being: 4.5C, 4.3C, 4C, 3.5C, 3C, 2.5C.

[0089] In an alternative embodiment, the charging rate of a newly added charging stage can be determined by using an arithmetic progression method to decrease the charging rate between multiple charging stages. For example, if q = 0.5 in Table 1, then q' can be 0.4. This method allows the newly added charging rate to vary evenly and be interspersed among the original charging rates, while also avoiding duplication with the original charging rates. For example, taking q' = 0.4 and adding two stepped charging stages as an example, Table 2 can be formed based on Table 1, where the second and fourth stages are the newly added charging stages:

[0090] Table 2

[0091]

[0092]

[0093] In addition to changing the number of charging stages, alternative embodiments of this application may increase the charging rate of at least one charging stage of the current charging strategy to form a new charging strategy. Specifically, this may include:

[0094] Increase the charging rate of at least one of the first m charging stages of the current charging strategy; where m is a positive integer and m ≤ n / 2; or, the first charging stage of the current charging strategy is not C. max At the same time, the charging rate of the first charging stage is increased. It is easy to understand that increasing the charging rate can correspondingly shorten the charging time.

[0095] Regarding how to increase the charging rate, this application does not specify any particular method. The average charging rate of two adjacent charging stages in the original charging strategy can be taken as the charging rate of the next charging stage within that adjacent stage. For example, using this method, the charging rates of stages 2 and 4 in Table 1 can be adjusted to obtain the following Table 3:

[0096] Table 3

[0097]

[0098] The new charging rate for stage 2 is determined based on the average of the charging rates for stages 1 and 2, and the new charging rate for stage 42 is determined based on the average of the charging rates for stages 3 and 4.

[0099] In addition to the average value method shown in Table 3, this application can also use an arithmetic progression method, specifically where the arithmetic progression q” is less than q, for example, q” is 0.3. Using this method, the charging rate of the second stage in Table 1 is adjusted to obtain the following Table 4:

[0100] Table 4

[0101]

[0102] Of course, in some embodiments of this application, the charging stage and the charging rate can also be adjusted simultaneously.

[0103] All the charging strategies formed by the above corrections need to be verified cyclically until the charging time is less than the target charging time, then the target charging strategy is determined.

[0104] To more intuitively display the relationship between charging rate and charging time, some embodiments of this application further include the following steps:

[0105] 16. Form a correlation curve between each charging rate and its corresponding cumulative charging time under the current charging strategy. The corresponding cumulative charging time does not refer to the duration of each charging rate, but rather includes the cumulative charging time of that charging rate itself and the charging rates of previous stages. Based on this correlation curve, the charging time already used when charging to a certain charging rate can be visually observed, and the difference between the current charging rate and the target charging time can be easily determined.

[0106] Step 17, specifically the step of correcting the current charging strategy according to a preset rule if the current charging time is greater than the target charging time, includes: if the current charging time is greater than the target charging time, then based on the correlation curve, the current charging strategy is corrected to form a corrected charging strategy. For example, based on the correlation curve, if it is found that the cumulative charging time corresponding to the charging rate of a certain stage has exceeded the target charging time, then it is necessary to increase the charging stage order or increase the charging rate before that stage.

[0107] The following describes the process of determining a charging strategy based on a specific charging scenario. Slightly different from the embodiments described above, which only involve charging parameters within the target SOC range, the specific charging scenario includes the entire process of the battery charging from 0% (SOC is 0%) to full charge (SOC is 100%).

[0108] Using a 100Ah lithium-ion cell of a certain model as the experimental object, a 100Ah three-electrode lithium-ion battery was prepared. During the lithium battery winding stage, copper wires were embedded as the three electrodes, placed between the positive and negative electrodes in the penultimate layer of winding, and separated from the positive and negative electrodes. The copper wires selected for the three electrodes were 30μm. The battery was connected to a charge-discharge apparatus to plate the copper wires with lithium. The positive terminal of the apparatus was connected to the copper wire side, and the negative terminal was connected to either the positive or negative electrode of the battery. A constant current of 20μA was used for charging for 6 hours. At room temperature, the battery was charged at a constant current and voltage of 0.33C and discharged at 0.33C for 3 cycles to determine its calibrated capacity. The voltage range was 2.5-3.65V, and the discharge capacity of the third cycle was taken as the calibrated capacity of 100.28Ah (i.e., C0).

[0109] Based on the charging capacity requirements, the fast charging requirement needs to be met within the target SOC range of 10%-80%, with a target charging time t0 not exceeding 12 minutes. Calculations show that the average charging rate C' required in the 10%-80% SOC range is C' = (80%-10%)*C0 / t0 / C0 = 3.5C. Using k=1, the minimum charging rate C is determined to be 3.5C ± 1C. min It is 2.5C, and the maximum value is C. maxThe initial charging strategy is determined as follows: For the 0-10% SOC range, a charging rate range of 0.33C-1C can be used, specifically 1C for 10 minutes. In the 10%-80% SOC range, charging is performed using the parameters shown in Table 1 above, with a negative parameter potential of 0V as the cutoff condition, and also at 80%. For the 80%-100% SOC range, a charging rate range of 1C-0.33C can be used, specifically 2C, 1.5C, and 1C, with a negative parameter potential of 0V as the cutoff condition, and also at 100% SOC. It should be noted that a stepped charging method can also be used in the 80%-100% SOC stage. The initial charging strategy is used, and the positive electrode potential, negative parameter potential, and corresponding SOC are recorded to further form... Figure 2 The potential-SOC curve is shown below. Based on the charging cutoff condition, the charging time and corresponding cumulative SOC for each charging stage were recorded, resulting in Table 5 below:

[0110]

[0111] The cumulative charging time for each charging stage is calculated, and based on this, a relationship C”-t is established between each charging stage (corresponding charging rate) and the cumulative charging time. 累计 Relationship curve, such as Figure 3 As shown. Corresponding to 10-80% SOC, t 累计 = t1 + t2 + t3 + t4 + t5 = 12.213 min, which does not satisfy the requirement t0 ≤ 12 min. However, according to C”-t 累计 The relationship curve shows that between 4.5C and 1C, C”-t 累计 The linear relationship is satisfied. Between 4.5C and 3.5C, increasing the charging order can minimize the charging time. This application adds a 4.2C charging rate as a corrected charging strategy to the original charging strategy. Furthermore, the charging process of the corrected charging strategy is monitored, and the charging time and corresponding cumulative SOC for each charging stage are recorded according to the charging cutoff condition, as shown in Table 6 below:

[0112] Table 6

[0113]

[0114] As shown in Table 6, the corrected charging strategy results in a charging time of 11.989 min (<12 min) for the SOC range of 10% to 80%, which meets the charging requirements for this target SOC range. Therefore, this corrected charging strategy is determined as the target charging strategy.

[0115] Figure 4The charging rate C”-SOC curves before and after correction are visually displayed. It can be seen that, regardless of the correction, the charging rate changes smoothly across different SOC ranges, which helps reduce stress during charging and extend battery life. Simultaneously, the corrected charging rate C”-SOC curve shortens charging time and improves charging efficiency.

[0116] Based on the above embodiments, this application determines the average charging rate C' corresponding to the target SOC range based on charging demand, and further determines the minimum charging rate C' corresponding to the target SOC range based on C'. min and maximum value C max Since the average charging rate C' used as a benchmark is obtained under the premise of meeting the target charging time, the charging rate determined based on this is a charging rate that can meet or closely meet the target charging time. Compared with the existing technology, which relies entirely on charging experiments to determine the charging strategy without any benchmark, this application fundamentally improves the accuracy and efficiency of charging strategy formulation. Furthermore, determining the charging rate based on the average charging rate C' not only maximizes charging efficiency but also shortens the time for subsequent strategy formulation. Further, by judging the charging time of the formulated fast charging strategy, the direction of strategy correction can be determined for targeted correction, thereby determining the target charging strategy that meets the target charging time. This provides an efficient and accurate method for formulating battery fast charging strategies.

[0117] Example 2

[0118] Corresponding to Embodiment 1 above, Embodiment 2 of this application further provides a lithium-ion battery charging method, such as... Figure 5 As shown, the lithium-ion battery charging method includes:

[0119] 21. Upon receiving a charging request, determine the current SOC of the lithium-ion battery to be charged.

[0120] It should be noted that the lithium-ion battery to be charged in Example 2 is not a three-electrode battery, but a lithium-ion battery with actual charging requirements.

[0121] In the embodiments of this application, the current SOC of the lithium-ion battery to be charged can be determined based on relevant methods of existing technology. This application does not impose specific limitations on the comparison.

[0122] 23. Determine the target stepped charging stage corresponding to the current SOC from the preset lithium-ion battery charging strategy; the preset lithium-ion battery charging strategy is obtained according to the lithium-ion battery charging strategy determination method in Embodiment 1 above.

[0123] Considering the differences in charging characteristics among different types of lithium-ion batteries, the lithium-ion battery to be charged in Embodiment 2 of this application should be of the same or similar type as the lithium-ion battery to be charged in Embodiment 1.

[0124] 25. Starting from the target stepped charging stage, charge according to the preset lithium-ion battery charging strategy.

[0125] In some embodiments of this application, there is only one preset lithium-ion battery charging strategy. Taking the target charging strategy determined in Table 6 of Embodiment 1 as an example, this target charging strategy is used as the preset lithium-ion battery charging strategy for the lithium-ion battery to be charged. When the current SOC of the lithium-ion battery to be charged is determined to be 50%, corresponding to the fourth step of the charging stage in the table, the charging rate is 3.5C as the starting charging rate, and charging is carried out sequentially according to the charging strategy of 3.5C, 3C, and 2.5C.

[0126] In other embodiments of this application, the preset lithium-ion battery charging strategy is at least two, and different lithium-ion battery charging strategies correspond to different target SOC ranges. For example, according to Embodiment 1, the SOC range of less than 10%, the SOC range of 10%-80%, and the SOC range of greater than 80% correspond to different charging strategies. In this case, step 23 includes:

[0127] 231. Determine the target lithium-ion battery charging strategy corresponding to the current SOC;

[0128] 233. Determine the target stepped charging stage corresponding to the current SOC from the target lithium-ion battery charging strategy.

[0129] For example, if the current SOC is determined to be 85%, the target lithium-ion battery charging strategy corresponding to the SOC range of greater than 80% is determined according to Table 6 to belong to the 7th charging stage, that is, to start charging at 2C.

[0130] Based on the above embodiment 2, this application can utilize the determined stepped charging strategy to achieve fast charging of the battery.

[0131] Of course, in a further embodiment, the actual charging can be recorded so that subsequent analysis can be performed to determine whether the target charging strategy can truly meet the charging needs, and to provide feedback on the target charging strategy.

[0132] It should be noted that the methods described in Embodiments 1 and 2 above can be implemented by a computer, by human operation, or by a combination of computer and human operation. Regarding the computer method, those skilled in the art will clearly understand that this application can be implemented using software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer system (which can be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or certain parts of the embodiments of this application.

[0133] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0134] The technical solutions provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for determining a lithium-ion battery charging strategy, characterized in that, The lithium-ion battery charging strategy method includes the following steps: (11) Determine the average charging rate C' corresponding to the target SOC range based on the lithium-ion battery calibrated capacity, target SOC range, and target charging time corresponding to the target SOC range; (13) Determine the minimum charging rate C corresponding to the target SOC range based on C'±kC (0.1≤k≤2). min and maximum value C max C represents the ratio of the current required to charge and discharge a lithium-ion battery to its rated capacity within a specified time. min <C'<C max ; (15) Determine the current charging time required to complete the charging of the target SOC range under the current charging strategy; In the current charging strategy, the target SOC range corresponds to n stepped charging stages, and along the charging sequence, the charging rate C'' corresponding to each stepped charging stage continuously decreases; the C min ≤C''≤C max And at least one C'' > C'; n ≥ 2; (17) If the current charging time is less than or equal to the target charging time, the current charging strategy is determined to be the target charging strategy; if the current charging time is greater than the target charging time, the current charging strategy is corrected according to the preset rules to form a new current charging strategy and the process returns to step (15). In step (17), correcting the current charging strategy according to preset rules includes: Before the last step charging stage of the current charging strategy, at least one additional step charging stage is added. and / or, Increase the charging rate of at least one step of the current charging strategy; The current charging strategy is the first charging strategy; the method further includes the step: (12) based on the minimum value C of the charging rate corresponding to the target SOC range. min and maximum value C max And in accordance with the arithmetic progression, the number of tiered charging stages n and the charging rate C'' corresponding to each tiered charging stage in the first charging strategy are set.

2. The lithium-ion battery charging strategy determination method according to claim 1, characterized in that, Adding at least one tiered charging stage before the last tiered charging stage of the current charging strategy includes: Add at least one additional charging stage between the first two charging stages of the current charging strategy; or, the first charging stage of the current charging strategy is not C. max At the same time, at least one additional step charging stage is added before the first step charging stage; The improvement of the charging rate of at least one step of the current charging strategy includes: Increase the charging rate of at least one of the first m charging stages of the current charging strategy; where m is a positive integer and m ≤ n / 2; or, the first charging stage of the current charging strategy is not C. max At the same time, the charging rate of the first step charging stage is increased.

3. The method for determining the charging strategy of a lithium-ion battery according to claim 1, characterized in that, The current charging time is determined based on simulation or the actual charging process.

4. The method for determining a lithium-ion battery charging strategy according to claim 1, characterized in that, The lithium-ion battery to be charged includes a three-electrode lithium-ion battery with a reference electrode. Step (15) includes: In the first n-1 step charging stages, the negative parameter potential of the current step charging stage is determined using the reference electrode, and when the negative parameter potential is less than or equal to the cutoff voltage, the next step charging stage is entered and the charging time of the current step charging stage is recorded. In the nth step charging stage, the negative parameter potential is determined using the reference electrode, and the charging of the nth step charging stage ends when the negative parameter potential is less than or equal to the cutoff voltage or reaches the maximum value of the target SOC range.

5. The method for determining a lithium-ion battery charging strategy according to claim 1, characterized in that, The method further includes the following steps: (16) Form a correlation curve between each charging rate and its corresponding cumulative charging time under the current charging strategy; In step (17), the step of correcting the current charging strategy according to a preset rule if the current charging time is greater than the target charging time includes: If the current charging time is greater than the target charging time, the current charging strategy is corrected based on the correlation curve to form a corrected charging strategy.

6. A method for charging a lithium-ion battery, characterized in that, The lithium-ion battery charging method includes: (21) Upon receiving a charging request, determine the current SOC of the lithium-ion battery to be charged; (23) Determine the target step charging stage corresponding to the current SOC from the preset lithium-ion battery charging strategy; the preset lithium-ion battery charging strategy is obtained by the lithium-ion battery charging strategy determination method according to any one of claims 1-5; (25) Starting from the target step charging stage, charge according to the preset lithium-ion battery charging strategy.

7. The lithium-ion battery charging method according to claim 6, characterized in that, The preset lithium-ion battery charging strategy is at least two, and different lithium-ion battery charging strategies correspond to different target SOC ranges. Step (23) includes: (231) Determine the target lithium-ion battery charging strategy corresponding to the current SOC; (233) Determine the target stepped charging stage corresponding to the current SOC from the target lithium-ion battery charging strategy.

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