Lithium ion battery charging strategy determination method and battery charging method

Abstract

The invention discloses a lithium ion battery charging strategy determination method and a charging method.The charging strategy determination method comprises the steps that the average charging rate C'is determined according to the calibrated capacity, the target SOC interval and the target charging time of a lithium ion battery to be charged, and then the minimum value Cmin and the maximum value Cmax of the charging rate are determined; c 'is more than Cmin and less than Cmax; determining the current charging time for completing the target SOC interval under the current charging strategy; in the current charging strategy, n stepped charging stages are set, and the charging multiplying power C ''is continuously reduced along the charging sequence; c ''is larger than or equal to Cmin and smaller than or equal to Cmax, at least one C'' is larger than C ', n is larger than or equal to 2, if the current charging time is smaller than or equal to the target charging time, the current charging strategy is the target charging strategy, and if the current charging time is larger than the target charging time, correction is carried out to form a new current charging strategy, and the last step is returned.

Description

Technical Field

[0001] The present 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 Art

[0002] At present, the charging system used in the application and testing of lithium-ion batteries is mainly the constant current and constant voltage method. This charging method is simple and easy to operate. However, as the market and users' demand for fast charging of lithium-ion batteries increases, the current and voltage values ​​need to be continuously increased. However, high current constant current and constant voltage charging easily leads to lithium deposition, which directly affects the service life of lithium-ion batteries.

[0003] At present, the step charging system has become an effective method to achieve fast charging of batteries. The step charging system can be simply understood as performing different constant current and constant voltage charging in different battery SOC (State of Charge) intervals. Considering the convenience of operation, the constant voltage step is often omitted in the middle. However, while meeting the needs of fast charging, lithium plating cannot occur during the step charging process to prevent affecting battery safety and cycle life. Therefore, under the premise of the step charging system, it is necessary to optimize charging parameters such as charging current to avoid lithium plating, so as to maximize the battery charging speed and improve the user experience while ensuring battery safety and life.

[0004] However, how to optimize charging parameters needs to be determined based on the basic charging properties of lithium-ion batteries. Currently, in the lithium-ion battery industry, charging strategies are mostly determined based on continuous charging tests of lithium-ion batteries. However, this method is inefficient and has low accuracy. Summary of the invention

[0005] In order to solve the problems of the prior art, the present application provides a lithium-ion battery charging strategy determination method and a battery charging method to solve one or more technical problems existing in the prior art.

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

[0007] (11) determining an average charging rate C' corresponding to the target SOC interval according to the lithium ion battery calibrated capacity of the lithium ion battery to be charged, the target SOC interval and the target charging time corresponding to the target SOC interval;

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

[0009] (15) determining the current charging time required to complete the charging of the target SOC interval under the current charging strategy; in the current charging strategy, the target SOC interval corresponds to n step charging stages, and along the charging sequence, the charging rate C" corresponding to the step charging stage is continuously reduced; 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 preset rules to form a new current charging strategy and return to step (15).

[0011] Optionally, the step (13) includes:

[0012] Based on C'±kC (0.1≤k≤2), the minimum value C of the charging rate corresponding to the target SOC interval is determined min and the 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 a first charging strategy; the method further comprises the steps of:

[0014] (12) Based on the minimum value C of the charging rate corresponding to the target SOC interval min and the maximum value C max , and set the number of step charging stages n in the first charging strategy and the charging rate C" corresponding to each step charging stage in an arithmetic progression.

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

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

[0017] and / or,

[0018] The charging rate of at least one step charging stage of the current charging strategy is increased.

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

[0020] At least one step charging stage is added 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 When the charging process is performed, at least one step charging stage is added before the first step charging stage;

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

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

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

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

[0025] The step (15) comprises:

[0026] In the first n-1 step charging stages, the negative reference potential of the current step charging stage is determined by using the reference electrode, and when the negative reference potential is less than or equal to the cut-off 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 reference potential is determined by using the reference electrode, and when the negative reference potential is less than or equal to the cut-off voltage or reaches the maximum value of the target SOC range, the charging in the nth step charging stage is terminated.

[0028] Optionally, the method further comprises the steps of:

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

[0030] In the step (17), if the current charging time is greater than the target charging time, correcting the current charging strategy according to a preset rule 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 the present application provides a lithium ion battery charging method, the lithium ion battery charging method comprising:

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

[0034] (23) determining a target step charging stage corresponding to the current SOC from a 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 according to any one of claims 1 to 8;

[0035] (25) Taking the target step charging stage as the starting step charging stage, charging is performed 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 intervals;

[0037] The step (23) comprises:

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

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

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

[0041] In the technical solution for implementing the present invention, the average charging rate C' corresponding to the target SOC interval is determined by the calibrated capacity of the lithium-ion battery, the target SOC interval and the target charging time corresponding to the target SOC interval, and the minimum value Cmin and the maximum value Cmax of the charging rate corresponding to the target SOC interval are further determined based on C'. Since the average charging rate C' used as a benchmark is obtained on the premise of meeting the target charging time, the charging rate determined based on this is a charging rate that can meet or approach meeting the target charging time. Compared with the prior art, which has no benchmark and relies entirely on charging experiments to determine the charging strategy, the present 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 so that targeted corrections can be made, thereby determining the target charging strategy that meets the target charging time. In this way, an efficient and accurate method for formulating a battery fast charging strategy is provided.

[0042] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In addition, similar numbers in the figures are used to represent similar components, among which:

[0044] Figure 1 is a flow chart of a method for determining a charging strategy for a lithium-ion battery in Embodiment 1 of the present application;

[0045] Figure 2 is a voltage-SOC curve diagram corresponding to the charging strategy in the first embodiment of the present application;

[0046] Figure 3 is the charging rate C"-t corresponding to the charging strategy in the first embodiment of the present application 累计 Relationship graph;

[0047] Figure 4 is a charging rate C″-SOC curve diagram of the charging strategy before and after correction in Example 1 of the present application;

[0048] Figure 5 This is a flow chart of the lithium-ion battery charging method in Example 2 of the present application. DETAILED DESCRIPTION

[0049] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0050] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in this application and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The terms "and / or" or "and / or" used in this application include any and all combinations of one or more related listed items.

[0051] For greater clarity, this application first briefly introduces the principle that step charging can reduce the risk of lithium plating under the premise of fast charging.

[0052] During the charging process, lithium batteries will polarize. When polarization reaches a certain degree and the negative electrode potential is zero, it means that lithium deposition occurs in theory. Different SOCs and charging rates have different effects on polarization and lithium deposition. The higher the SOC and the greater the charging rate, the more severe the polarization and the greater the risk of lithium deposition.

[0053] However, when switching the charging rate, the change in current reduces or eliminates polarization, the voltage rises, the negative electrode potential rises to greater than zero, and the risk of lithium plating is reduced, so that charging can continue at the new charging rate.

[0054] Step charging is based on the above characteristics of lithium batteries. When charging starts, 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 described in the background technology, although the step charging technology has been adopted in fast charging, how to quickly determine the optimal charging parameters, namely the number of steps and the charging rate of each step, is still an existing problem. In response to this, the present application innovatively proposes a new method for determining a step charging strategy, that is, according to the charging demand (charging of the target SOC interval within the target charging time), the average charging rate is determined, and the step charging strategy is determined based on the average charging rate. Since the average charging rate is obtained on the premise of meeting the charging demand, the step charging strategy determined based on this can meet or approach the charging rate that meets the target charging time. Compared with the prior art method of having no benchmark and relying entirely on charging experiments to determine the charging strategy, the present application fundamentally improves the accuracy and efficiency of the formulation of the charging strategy. Furthermore, the present application determines the direction of strategy correction based on the judgment of the charging time of the charging strategy, and carries out targeted strategy correction, so as to quickly determine the step charging strategy that meets the charging demand.

[0056] Some embodiments of the present application are described below. It should be noted that the following description is for illustrative purposes and is not intended to limit the scope of protection of the present application.

[0057] Embodiment 1 Embodiment 1 of the present invention provides a method for determining a charging strategy for a lithium-ion battery. Figure 1 , the method comprises the following steps:

[0058] 11. Determine an average charging rate C' corresponding to the target SOC interval according to the lithium ion battery calibrated capacity of the lithium ion battery to be charged, the target SOC interval and the target charging time corresponding to the target SOC interval.

[0059] In the embodiment of the present application, the formula (1) can be used: C' = (SOC max -SOC min )*C0 / t0 / C0 to calculate the average charging rate C'.max -SOC min Used to calculate the target SOC range; C0 is the rated capacity, and t0 is the target charging time corresponding to the target SOC range. C can be obtained by constant capacity of the lithium-ion battery under set conditions. min and SOC max The fast charging boundary conditions are defined according to the materials and performance of lithium-ion batteries. min is the minimum SOC for fast charging, SOC max The maximum SOC of fast charge, lower than SOC min Fast charging can easily lead to lithium ion deposition inside the battery, which is higher than SOC max It is easy to cause lithium deposition in lithium-ion batteries. The SOC can be determined according to the different lithium-ion batteries. min and SOC max 13. Based on the average charging rate C', determine the minimum value C of the charging rate corresponding to the target SOC interval min and the maximum value C max ; C min <C'<C max .

[0060] Combined with the charging characteristics of lithium-ion batteries discussed in the full text, it can be seen that the charging rate corresponding to the target SOC interval is not a fixed value, but tends to decrease as the SOC increases. When the SOC is at the starting value of the target SOC interval, it has a maximum value C max , when SOC is at the maximum value of the target SOC range, it has a minimum value C min The average charge rate C' is suitable for the average SOC in the target SOC range, so C min <C'<C max It is understandable that C min With C max Both are greater than zero.

[0061] In some embodiments of the present application, step (13) specifically includes: determining the minimum value C of the charging rate corresponding to the target SOC interval based on the formula C'±kC (0.1≤k≤2) min and the maximum value C max ; Where C is the ratio of the current required by the lithium-ion battery to charge and discharge its rated capacity within a specified time. Further, according to the chemical composition, health status, safety considerations, etc. of the lithium-ion battery, it is preferred to take k = 1, then C max =C'+C, and C min=C'-C. Of course, in order to further determine the maximum and minimum values, the maximum and minimum values ​​can be further corrected, such as combining C' with past empirical values ​​to determine the maximum and minimum values. This application does not make specific restrictions on this. According to the above method, the minimum and maximum values ​​of the charging rate can be determined simply and quickly, providing a basis for the subsequent determination of the step charging rate without relying on charging experiments.

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

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

[0064] Table 1

[0065]

[0066] It can be seen from the table that the number of step charging stages n of the first charging strategy is 5, and the charging rate C" corresponding to each step charging stage ranges from the maximum value C max Arithmetic decreases to the minimum value C min .

[0067] It can be understood that in the above-mentioned arithmetic decreasing method, the arithmetic difference value is pre-set to obtain the number of step charging stages n, where q≤k, and the arithmetic difference value is determined according to the range of the maximum and minimum values ​​of the charging rate, and then the number of step charging stages is determined to avoid the q value being too large and resulting in too few step charging stages, affecting the charging efficiency. A small number of charging stages may also result in a higher charging rate being used in some stages, increasing the risk of battery aging and lithium precipitation, and may also increase the battery temperature rise and affect the battery performance. Optionally, q≤0.5k. Further, q≥0.2k, to avoid the q value being too small and resulting in too many step charging stages, and the charging efficiency is reduced due to the conversion of each charging stage.

[0068] It should be noted that the number of step charging stages n should be a positive integer. Therefore, in the above arithmetic decreasing method, in some cases, the arithmetic decreasing is not a strict arithmetic decrease, such as C max and C min They are 4.5C and 2.4C respectively, and the arithmetic progression is 0.5C. At this time, an integer n cannot be obtained, so the difference between the last two step charging stages can be set to 0.6C.

[0069] Of course, in an alternative embodiment, C max and C min It can be regarded as a rough benchmark. The maximum and minimum values ​​of the first charging strategy can be roughly C max and C min Nearby. For example, C max and C min They are 4.5C and 2.4C respectively, and the arithmetic progression is 0.5C. At this time, an integer n cannot be obtained, so the charging rate of the last step charging stage can be adjusted to 2.5C.

[0070] The above-mentioned arithmetic difference method provides an easy-to-operate method for determining the charging strategy, and this method can provide a uniform and stably changing charging rate, and is a better method for determining the charging strategy.

[0071] In addition to the arithmetic method, it is also possible to min and C max , other methods are used to determine the first charging strategy. For example, a geometric progression method is used, where the charging rate of the next step charging stage is p times the charging rate of the previous step charging stage, and p < 1.

[0072] The above describes several feasible methods for determining the first charging strategy in an exemplary manner. However, it should be noted that as long as it is based on C max and C min Determining the first charging strategy is within the scope of protection of this application, and this application does not limit the specific method.

[0073] In this application, the maximum and minimum values ​​of the charging rate are determined by determining the average charging rate to determine the final number of step charging stages and the corresponding charging rate. The average charging rate is used as the basis to maximize the overall charging efficiency and improve the overall charging efficiency.

[0074] The first charging strategy is a preliminary trial, which does not necessarily guarantee that the charging needs can be met. Therefore, this application further needs to test the charging effect of the first charging strategy and make corrections based on the test results. Specifically, it includes:

[0075] Determine the charging time required to complete charging of the target SOC range under the first 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] When a new charging strategy is formed, the above process needs to be repeated to test the charging effect of the new charging strategy and make corrections based on the test results until a charging strategy meets the charging requirements.

[0078] Summarizing the above charging strategy formulation and correction cycle process, taking any charging strategy as the current charging strategy, the following steps 15 and 17 can be obtained:

[0079] 15. Determine the current charging time required to complete the charging of the target SOC interval under the current charging strategy; in the current charging strategy, the target SOC interval corresponds to n step charging stages, and along the charging sequence, the charging rate C" corresponding to the step charging stage is continuously reduced; the 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 preset rules to form a new current charging strategy and return to step (15).

[0081] In the above step 15, it is necessary to determine the charging time of each step charging stage to sum up and obtain the current charging time required to complete the charging of the target SOC interval. In the embodiment of the present application, the charging cutoff condition of each step charging stage is to reach or about to reach the theoretical lithium precipitation state. In order to better monitor the theoretical lithium precipitation state, in some embodiments of the present application, the lithium-ion battery to be charged can be a three-electrode lithium-ion battery, and the negative reference potential of the battery during the charging process can be measured by the three-electrode method. The negative reference potential reaches the cutoff voltage (theoretical lithium precipitation state) as the charging cutoff condition for each stage to calculate the charging time of each stage, wherein the cutoff voltage can specifically be zero.

[0082] To this end, a three-electrode lithium-ion battery is first prepared in this application. Copper wire is implanted as a reference electrode in the preparation of lithium battery winding or lamination stage to prepare a three-electrode lithium-ion battery. Specifically, the copper wire is implanted between the positive and negative electrodes of the second-to-last layer of lamination or winding, and the copper wire is separated from the positive and negative electrodes. The diameter of the selected copper wire is as small as possible, and in a preferred embodiment, the diameter is less than 50μm. Then the lithium-ion battery is charged and constant capacity. The lithium-ion battery is connected to a charge and discharge instrument to plate lithium on the copper wire, the positive terminal of the charge and discharge instrument is connected to the copper wire side, and the negative terminal of the charge and discharge instrument is connected to the positive or negative electrode of the battery. A small current constant current is used for charging. During the charging process, the lithium ions in the electrolyte are deposited on the copper wire, so that a uniform lithium layer is formed on the surface of the copper wire. The small current here is as small as possible. In a preferred embodiment, the current is less than or equal to 50μA, and the charging time is 4-8h. Specifically, the battery can be constant capacity for three weeks at room temperature, and the discharge capacity of the third week is taken as the calibration capacity C0.

[0083] Afterwards, the three-electrode lithium-ion battery is charged according to the current charging strategy, and the negative reference potential of the current step charging stage is monitored using the reference electrode during the charging process. In the first n-1 step charging stages of the current charging strategy, when the negative reference potential reaches the cut-off voltage (such as zero), the next step charging stage is entered and the charging time of the current step charging stage is recorded; when entering the nth step charging stage, it is possible that it has been charged to the maximum value of the target SOC range before reaching the theoretical lithium precipitation state. For this reason, when entering the nth step charging stage, it is necessary to determine whether the negative reference potential is less than or equal to the cut-off voltage or whether it is charged to the maximum value of the target SOC range. When any one of them is satisfied first, the charging of the nth step charging stage is terminated and the charging time is calculated.

[0084] In addition to determining the charging time based on the actual charging process as described above, in an alternative embodiment, the relevant parameters of the lithium-ion battery and the current charging strategy can also be input into the charging simulation software to simulate the charging process, and the charging time for 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 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 is to further shorten the charging time. In some embodiments, correcting the current charging strategy according to preset rules includes:

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

[0087] The adding of 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 When the charging voltage is increased, at least one step charging stage is added before the first step charging stage.

[0088] The charging rate of the increased step charging stage must meet the overall charging strategy of the charging rate is decreasing trend. In one embodiment, the charging rate of the increased step charging stage can still be determined by the "'arithmetic decreasing 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, 3.5C+1C-0.2C=4.3C is taken and added between the 1st and 2nd stages in Table 1 to form a new 2nd stage. At this time, 6 charging stages are formed, and the corresponding charging rates of each charging stage are: 4.5C, 4.3C, 4C, 3.5C, 3C, and 2.5C.

[0089] In an alternative embodiment, the charging rate of the newly added charging stage can be determined by an arithmetic decreasing method between multiple charging stages. For example, if q=0.5 in Table 1, q' can be 0.4. This method can make the newly added charging rate change evenly and interspersed between the original charging rates, and can also avoid duplication with the original charging rate. For example, taking q'=0.4 and adding 2 step charging stages as an example, the following Table 2 can be formed on the basis of Table 1, where the 2nd and 4th are newly added charging stages:

[0090] Table 2

[0091]

[0092]

[0093] In addition to changing the number of step charging stages, in an alternative embodiment of the present application, the charging rate of at least one step charging stage of the current charging strategy may be increased to form a new charging strategy. Specifically, it may include:

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

[0095] This application does not specifically limit how to increase the charging rate. The average of the charging rates of two adjacent charging stages of the original charging strategy can be used as the charging rate of the next charging stage in the adjacent charging stages. For example, by using this method, the charging rates of the second and fourth stages in Table 1 are adjusted to obtain the following Table 3:

[0096] Table 3

[0097]

[0098] The new charging rate of the second stage is determined based on the average of the charging rates of the original first and second stages, and the new charging rate of the 42nd stage is determined based on the average of the charging rates of the original third and fourth stages.

[0099] In addition to the average value method shown in Table 3, the present application can also adopt an arithmetic difference method, and the specific arithmetic difference 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 the present application, the charging stage and the charging rate can also be adjusted at the same time.

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

[0104] In order to more intuitively display the relationship between the charging rate and the charging time, some embodiments of the present application further include the following steps:

[0105] 16. Form an association 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 includes the cumulative charging time of the charging rate itself and the charging rates of the previous stages. Based on the association curve, you can intuitively see the charging time that has been used when charging to a certain charging rate, and simply judge the gap relationship with the target charging time.

[0106] In step 17, if the current charging time is greater than the target charging time, the current charging strategy is corrected according to a preset rule, including: if the current charging time is greater than the target charging time, the current charging strategy is corrected based on the association curve to form a corrected charging strategy. For example, based on the association curve, if it is found that the cumulative charging time corresponding to the charging rate of one stage has exceeded the target charging time, it is necessary to increase the number of charging stages or increase the charging rate before this stage.

[0107] The following is a process of determining a charging strategy based on a specific charging scenario. Slightly different from the above embodiment, the above embodiment only involves charging parameters of the target SOC interval, while the specific charging scenario includes the entire process of the battery from 0 (SOC is 0%) to full charge (SOC is 100%):

[0108] A 100Ah battery cell of a certain model was used as the experimental object. A 100Ah three-electrode lithium-ion battery was prepared. Copper wire was implanted as the three electrodes during the winding stage of the lithium battery. The copper wire was implanted between the positive and negative electrodes of the penultimate layer of winding, and the copper wire was separated from the positive and negative electrodes. The three-electrode copper wire was selected to be 30μm. The battery was connected to a charge and discharge instrument to plate lithium on the copper wire. The positive terminal of the charge and discharge instrument was connected to the copper wire side, and the negative terminal of the charge and discharge instrument was connected to the positive or negative electrode of the battery. A constant current of 20μA was used for charging for 6h. At room temperature, 0.33C constant current and constant voltage charging and 0.33C discharge were used for 3 cycles to constant the battery capacity. The voltage range was 2.5-3.65V. The discharge capacity of the third week was taken as the calibrated capacity of 100.28Ah (i.e. C0).

[0109] According to the charging capacity requirements, the target charging time t0 of the target SOC range of 10-80% must not exceed 12 minutes. After calculation, the average charging rate C' required in the 10%-80% SOC range is (80%-10%)*C0 / t0 / C0=3.5C. Using k=1, the minimum charging rate C is determined by 3.5C±1C min 2.5C, maximum C maxis 4.5C. Determine the first charging strategy, where 0-10% SOC can adopt a charging rate range of 0.33C-1C, and specifically 1C can be used for charging for 10 minutes; in the 10%-80% SOC range, use the parameters shown in Table 1 above for charging, and use a negative reference potential of 0V as the cutoff condition, and 80% is also the cutoff condition; 80% SOC-100% SOC can adopt a charging rate range of 1C~0.33C, and specifically 2C, 1.5C, and 1C can be used for charging, and the negative reference potential is 0V as the cutoff condition, and 100% SOC is also the cutoff condition. It should be noted that in the 80% SOC-100% SOC stage, a step charging method can also be used to achieve charging. Use the first charging strategy to charge, and record the positive electrode potential, negative reference potential and corresponding SOC to further form Figure 2 The potential-SOC curve is shown. According to the charging cut-off condition, the charging time of each step charging stage and the corresponding cumulative SOC are recorded to obtain the following Table 5:

[0110]

[0111] The cumulative charging time corresponding to each step charging stage is calculated, and the C"-t relationship between each step charging stage (corresponding charging rate) and the cumulative charging time is established accordingly. 累计 Relationship curve, such as Figure 3 As shown. Corresponding to 10-80% SOC, t 累计 =t1+t2+t3+t4+t5=12.213min, which does not meet the requirement of t0≤12min. However, according to C”-t 累计 The relationship curve shows that between 4.5C and 1C, C"-t 累计 Satisfies the linear relationship. Between 4.5C-3.5C, increasing the number of steps can shorten the charging time to the greatest extent. Based on the original charging strategy, this application adds a 4.2C charging rate as a corrected charging strategy. And further monitor the charging process of the corrected charging strategy, record the charging time of each step charging stage and the corresponding cumulative SOC according to the charging cut-off condition, and obtain the following Table 6:

[0112] Table 6

[0113]

[0114] As can be seen from Table 6, after the correction, the charging time corresponding to 10% SOC-80% SOC is 11.989min<12min, which meets the charging demand of the target SOC range. Therefore, the corrected charging strategy is determined as the target charging strategy.

[0115] Figure 4The charging rate C”-SOC curve corresponding to the charging strategy before and after correction is intuitively shown. It can be seen that regardless of before and after correction, the charging rate changes smoothly in different SOC ranges, which helps to reduce the stress during the charging process and extend the battery life. At the same time, the corrected charging rate C”-SOC curve can shorten the charging time and improve the charging efficiency.

[0116] Based on the above embodiment, the present application determines the average charging rate C' corresponding to the target SOC interval based on the charging demand, and further determines the minimum value C of the charging rate corresponding to the target SOC interval based on C'. min and the maximum value C max . Since the average charging rate 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 is close to meeting the target charging time. Compared with the prior art, which has no benchmark and relies entirely on charging experiments to determine the charging strategy, the present application fundamentally improves the accuracy and efficiency of charging strategy formulation. At the same time, preliminarily determining the charging rate based on the average charging rate charging rate C' can not only maximize the charging efficiency, but also shorten the time for subsequent strategy formulation. Furthermore, by judging the charging time of the formulated fast charging strategy, the direction of strategy correction can be determined so that targeted corrections can be made, thereby determining the target charging strategy that meets the target charging time. In this way, an efficient and accurate method for formulating a battery fast charging strategy is provided.

[0117] Embodiment 2

[0118] Corresponding to the above-mentioned embodiment 1, the second embodiment of the present 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 charge 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 the second embodiment is not a three-electrode battery, but a lithium-ion battery with actual charging requirements.

[0121] In the embodiment of the present application, the current SOC of the lithium-ion battery to be charged can be determined based on the relevant methods of the prior art, and the present application does not make any specific limitations.

[0122] 23. Determine the target step charging stage corresponding to the current SOC from a 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 of the above-mentioned embodiment 1.

[0123] Considering the differences in charging characteristics of different types of lithium-ion batteries, the lithium-ion battery to be charged in the second embodiment of the present application should be of the same or similar type as the lithium-ion battery to be charged in the first embodiment.

[0124] 25. Taking the target step charging stage as the starting step charging stage, charging is performed according to the preset lithium-ion battery charging strategy.

[0125] In some embodiments of the present 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, the target charging strategy is used as the preset lithium-ion battery charging strategy for the lithium-ion battery to be charged. When it is determined that the current SOC of the lithium-ion battery to be charged is 50%, the fourth step charging stage in the corresponding table is used, and the 3.5C charging rate is used as the starting charging rate, and charging is performed in sequence according to 3.5C, 3C, and 2.5C in the charging strategy.

[0126] In other embodiments of the present application, there are at least two preset lithium-ion battery charging strategies, and different lithium-ion battery charging strategies correspond to different target SOC intervals. For example, according to the method of embodiment 1, the SOC interval less than 10%, the SOC interval of 10%-80%, and the SOC interval greater than 80% correspond to different charging strategies. At this time, step 23 includes:

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

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

[0129] For example, it is determined that the current SOC is 85%, corresponding to the target lithium-ion battery charging strategy for the SOC range greater than 80%. According to Table 6, it is determined that it belongs to the 7th charging stage, that is, charging starts at 2C.

[0130] Based on the above-mentioned embodiment 2, the present application can use the determined step charging strategy to realize fast charging of the battery.

[0131] Of course, in a further embodiment, the actual charging can also be recorded so as to analyze and determine whether the target charging strategy can truly meet the charging demand and provide feedback on the target charging strategy.

[0132] It should be noted that the methods in the above-mentioned Embodiment 1 and Embodiment 2 can be implemented by computer, can be implemented by manual operation, or can be implemented partially by computer and partially by manual operation. For the computer method, those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform. Based on this understanding, the technical solution of the present application can be essentially or partly in other words, the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer system (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment of the present application or some parts of the embodiments.

[0133] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The system and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0134] The technical solution provided by the present application is described in detail above. The principle and implementation method of the present application are described in detail using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present application.

Claims

1. A method for determining a charging strategy for a lithium-ion battery, characterized in that: The lithium-ion battery charging strategy method comprises the following steps: (11) determining an average charging rate C' corresponding to the target SOC interval according to the lithium ion battery calibrated capacity of the lithium ion battery to be charged, the target SOC interval and the target charging time corresponding to the target SOC interval; (13) Based on the average charging rate C', determine the minimum value C of the charging rate corresponding to the target SOC interval min and the maximum value C max ; C min <C'<C max ; (15) determining a 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 interval corresponds to n set step charging stages, and along the charging sequence, the charging rate C" corresponding to the step charging stage is continuously reduced; 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 preset rules to form a new current charging strategy and return to step (15).

2. The method for determining a charging strategy for a lithium-ion battery according to claim 1, characterized in that: The step (13) comprises: Based on C'±kC (0.1≤k≤2), the minimum value C of the charging rate corresponding to the target SOC interval is determined min and the 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.

3. The method for determining a charging strategy for a lithium-ion battery according to claim 1, wherein: The current charging strategy is a first charging strategy; the method further comprises the steps of: (12) Based on the minimum value C of the charging rate corresponding to the target SOC interval min and the maximum value C max , and set the number of step charging stages n in the first charging strategy and the charging rate C" corresponding to each step charging stage in an arithmetic progression.

4. The method for determining a charging strategy for a lithium-ion battery according to any one of claims 1 to 3, characterized in that: In the step (17), correcting the current charging strategy according to a preset rule includes: Before the last step charging stage of the current charging strategy, at least one step charging stage is added, and / or, The charging rate of at least one step charging stage of the current charging strategy is increased.

5. The method for determining a charging strategy for a lithium-ion battery according to claim 4, characterized in that: The adding at least one step charging stage before the last step charging stage of the current charging strategy comprises: At least one step charging stage is added 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 When the charging process is performed, at least one step charging stage is added before the first step charging stage; The step of increasing the charging rate of at least one step charging stage of the current charging strategy includes: Increase the charging rate of at least one of the first m step charging stages of the current charging strategy; m is a positive integer and m≤n / 2; or, the first step charging stage of the current charging strategy is not C max When the charging rate of the first step charging stage is increased.

6. The method for determining a charging strategy for a lithium-ion battery according to any one of claims 1 to 3, characterized in that: The current charging time is determined based on a simulation or an actual charging process.

7. The method for determining a charging strategy for a lithium-ion battery according to any one of claims 1 to 3, characterized in that: The lithium-ion battery to be charged comprises a three-electrode lithium-ion battery with a reference electrode; The step (15) comprises: In the first n-1 step charging stages, the negative reference potential of the current step charging stage is determined by using the reference electrode, and when the negative reference potential is less than or equal to the cut-off 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 reference potential is determined by using the reference electrode, and when the negative reference potential is less than or equal to the cut-off voltage or reaches the maximum value of the target SOC range, the charging in the nth step charging stage is terminated.

8. The method for determining a charging strategy for a lithium-ion battery according to any one of claims 1 to 3, characterized in that: The method further comprises the steps of: (16) forming a correlation curve between each charging rate and its corresponding accumulated charging time under the current charging strategy; In the step (17), if the current charging time is greater than the target charging time, correcting the current charging strategy according to a preset rule 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.

9. A lithium ion battery charging method, characterized in that: The lithium-ion battery charging method comprises: (21) upon receiving a charging request, determining a current SOC of the lithium-ion battery to be charged; (23) determining a target step charging stage corresponding to the current SOC from a 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 according to any one of claims 1 to 8; (25) Taking the target step charging stage as the starting step charging stage, charging is performed according to the preset lithium-ion battery charging strategy.

10. The lithium-ion battery charging method according to claim 9, characterized in that: There are at least two preset lithium-ion battery charging strategies, and different lithium-ion battery charging strategies correspond to different target SOC intervals; The step (23) comprises: (231) determining a target lithium-ion battery charging strategy corresponding to the current SOC; (233) Determine a target step charging stage corresponding to the current SOC from the target lithium-ion battery charging strategy.

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