Methods for determining battery charging capability boundaries, charging optimization methods and systems

Abstract

This invention proposes a method for determining the boundary of battery charging capability, a charging optimization method, and a system, relating to the field of lithium battery charging technology. The method includes: classifying the battery charging ambient temperature; assembling the battery into a three-electrode configuration and charging at different rates corresponding to different temperature ranges; plotting the anode-to-lithium potential table under different temperature ranges, charging rates, and dynamic SOCs; pre-classifying the anode-to-lithium potential; disassembling the charged batteries with different anode-to-lithium potentials; verifying lithium plating at the anode interface to determine the anode potential during lithium plating within the cell; fitting anode-to-lithium potential curves across the entire temperature range, full-rate charging, and different dynamic SOCs; and confirming the charging rate at different charge levels in the anode-to-lithium potential curves based on the actual lithium plating anode potential to determine the charging capability boundary. This invention precisely controls the lithium battery charging current and charging time, effectively reducing the risk of lithium plating and shortening the charging time.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a method for determining the boundary of battery charging capability, a charging optimization method, and a system. Background Technology

[0002] Lithium-ion batteries have advantages such as high energy density, light weight, high voltage, and environmental friendliness, and are therefore widely used in devices such as mobile phones, digital cameras, UPS power supplies, and electric vehicles. At the same time, consumers have also put forward higher requirements for the balance between battery fast charging time, cycle life, and environmental suitability.

[0003] The charging process of lithium-ion batteries involves complex interconversion of positive and negative electrode materials, interfacial electrochemical reactions, and polarization, which vary with ambient temperature and battery charge. This poses challenges to charging strategies under different ambient temperatures. Currently, the commonly used charging method for lithium-ion battery applications and testing is constant current and constant voltage charging. This method is convenient to operate, has low system requirements, and is easy to implement, but it has drawbacks such as long charging time, low charging efficiency, and high safety risks, affecting the end-user experience. Therefore, developing a fast and safe lithium-ion battery charging strategy is of great significance.

[0004] Chinese invention patent CN113285132A, entitled "Method and Application for Formulating a Stepped Charging System for Lithium-ion Batteries," describes a method for determining a stepped charging system for lithium-ion batteries. This method involves testing the charging performance of lithium-ion batteries at different rates to generate voltage-capacity (SOC) curves; then differentiating these SOC curves to generate dV / dQ-SOC curves for different charging rates; finally, performing a DCIR test and generating a DCIR-SOC curve; and ultimately outputting a stepped charging system for specific fast-charging needs. While this method is simple to operate, it fails to effectively characterize the battery's charging capacity at different charge levels and still carries the risk of lithium deposition at the anode during high-rate charging.

[0005] Chinese invention patent CN117565748A, entitled "A Method for Charging Control of Lithium-ion Batteries," describes a method that first measures the maximum allowable charging current of a target battery cell at different temperatures and SOCs, then measures the charging current of the target battery cell at different temperatures with maximum charging efficiency. Based on the number of target battery cells connected in parallel within the lithium-ion battery system, it obtains the maximum allowable charging current and the maximum charging current of the lithium-ion battery at different temperatures and SOCs, respectively. When the lithium-ion battery is charged at the target temperature, the specific charging current value is adjusted in real time based on the two charging current measurements to optimize charging efficiency. This method has few influencing variables and a short optimization process; however, as cycling progresses, battery capacity decreases and the DCR increases at the end of the cycle, posing a significant risk of lithium plating. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a method for determining the battery charging capability boundary, a charging optimization method, and a system. Based on dynamic SOC-OCV, static SOC-OCV databases, charging capability boundary tables at different temperatures, and combined with sensor data, the system precisely controls the lithium battery charging current and charging time, accurately identifies the lithium battery state, and provides the optimal charging method, effectively reducing the risk of lithium plating and shortening the charging time.

[0007] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0008] The first aspect of the present invention provides a method for determining the boundary of battery charging capability.

[0009] The method for determining the battery charging capability boundary includes the following steps:

[0010] The ambient temperature for battery charging is categorized into different levels.

[0011] The battery was assembled into a three-electrode system and charged at different rates at different temperatures. The anode-to-lithium potential and dynamic SOC of the three electrodes were monitored, and a table of anode-to-lithium potentials was plotted at different temperatures, charging rates, and dynamic SOCs.

[0012] The anode-to-lithium potential is pre-classified, and batteries with different anode-to-lithium potentials after charging are disassembled. Lithium plating is verified at the anode interface to determine the true lithium plating anode potential.

[0013] The anode-to-lithium potential curves were fitted under full temperature range, full rate charging, and different dynamic SOCs.

[0014] Based on the actual lithium plating anode potential, the charging rate under different charge levels in the anode-to-lithium potential curve is confirmed, thereby determining the charging capacity boundary.

[0015] As alternative technical solutions, the following also include:

[0016] Pre-measure the static SOC-OCV of the battery at different temperatures, as well as the dynamic SOC-OCV at different temperatures and different rates;

[0017] When monitoring the dynamic SOC of the three electrodes of a charging lithium-ion battery, the dynamic SOC of the lithium-ion battery is obtained by measuring the open-circuit voltage value and combining it with the pre-measured dynamic SOC-OCV meter.

[0018] As an optional technical solution, the static SOC-OCV table is a table showing the relationship between the initial SOC value and the open-circuit voltage OCV of the battery when it is not charged; the dynamic SOC-OCV table is a table showing the relationship between the dynamic SOC value and the open-circuit voltage OCV of the battery when it is charged at different charging rates.

[0019] As an alternative technical solution, an anode-to-lithium potential meter at a set temperature is used to measure the anode-to-lithium potential of a lithium-ion battery under different dynamic SOCs when the battery is charged at multiple different charging rates.

[0020] As an alternative technical solution:

[0021] Based on the anode-to-lithium potential under different temperatures, different charging rates, and different dynamic SOCs when charging the battery, the anode-to-lithium potential curves under different dynamic SOCs during full-temperature range and full-rate charging are fitted.

[0022] As an alternative technical solution, based on the actual lithium plating anode potential, the charging rate under different charge levels in the anode-to-lithium potential curve is confirmed, thereby determining the charging capacity boundary, specifically:

[0023] Step 1: Based on the anode-to-lithium potential curves under different dynamic SOCs during full-temperature and full-rate charging, find the anode-to-lithium potential curves under different dynamic SOCs during full-rate charging at the current ambient temperature, and use them as benchmark comparison curves;

[0024] Step 2: Determine the initial charging rate. Using the actual lithium plating anode potential as the benchmark comparison value, determine the dynamic SOC boundary point corresponding to when the anode lithium potential reaches the benchmark comparison value under the initial charging rate. This is the first SOC boundary point. Then, charge at the initial charging rate until the first SOC boundary point is reached and stop.

[0025] Step 3: Determine the secondary charging rate. Repeat the process in Step 2 above to find the second SOC boundary point. Charge from the first SOC boundary point to the second SOC boundary point using the secondary charging rate.

[0026] Step 4: Repeat the process in Step 3 above until the Nth charging rate is determined, find the Nth SOC boundary point, and charge from the (N-1)th SOC boundary point to the Nth SOC boundary point at the Nth charging rate. The Nth SOC boundary point is the preset SOC charging target value.

[0027] As an alternative technical solution:

[0028] The charging capability boundary is: charging to the first SOC boundary point at the initial charging rate, charging from the first SOC boundary point to the second SOC boundary point at the second charging rate, ... charging from the (N-1)th SOC boundary point to the Nth SOC boundary point at N charging rates;

[0029] The battery charging capability boundary under the entire temperature range was determined, and a charging capability boundary table was prepared.

[0030] A second aspect of the present invention provides a battery charging optimization method.

[0031] The battery charging optimization method based on the battery charging capability boundary determination method described in the first aspect includes the following steps:

[0032] Obtain the initial SOC value of the battery when it is not charged;

[0033] Obtain the current battery charging ambient temperature and find the battery charging capacity boundary corresponding to the current battery charging ambient temperature in the charging capacity boundary table.

[0034] Starting from the initial SOC value, the battery is charged in stages according to the battery charging capacity boundary;

[0035] During the phased charging process, the dynamic SOC value of the battery is acquired in real time to determine whether the SOC threshold value of each phase has been reached (I = 1...N). If so, the phase ends and the next phase begins, until the preset SOC charging target value is reached, thus completing the entire charging process.

[0036] As an alternative technical solution:

[0037] The initial SOC value of the battery is obtained through the static SOC-OCV table;

[0038] The dynamic SOC value of the battery is obtained through the dynamic SOC-OCV table.

[0039] The current ambient temperature for battery charging is obtained by collecting data from sensors.

[0040] A third aspect of the present invention provides a battery charging optimization system.

[0041] The battery charging optimization system includes:

[0042] The initial SOC acquisition module is configured to acquire the initial SOC value of the battery when it is not charged.

[0043] The query module is configured to: obtain the current battery charging ambient temperature and search for the battery charging capacity boundary corresponding to the current battery charging ambient temperature in the charging capacity boundary table;

[0044] The phased charging module is configured to charge the battery in stages according to the battery charging capacity boundary, starting from the initial SOC value.

[0045] The SOC boundary point judgment module is configured to: acquire the dynamic SOC value of the battery in real time during the phased charging process, and determine whether the SOC boundary point I is reached in each phase, where I = 1...N; if so, the phase ends and the next phase begins, until the preset SOC charging target value is reached, thus completing the entire charging process.

[0046] The above one or more technical solutions have the following beneficial effects:

[0047] This invention provides a method for determining the battery charging capability boundary, a charging optimization method, and a system. First, the battery charging capability boundary across the entire temperature range is determined experimentally, identifying the first SOC boundary point and initial charging rate, the second SOC boundary point and secondary charging rate, ..., the Nth SOC boundary point and Nth charging rate, thus enabling staged charging of the battery. Then, based on dynamic SOC-OCV, static SOC-OCV tables, and charging capability boundary tables at different temperatures, combined with sensor data, the lithium battery charging current and charging time are precisely controlled, and the lithium battery state is accurately identified, thereby providing the optimal charging method, effectively reducing the risk of lithium plating and shortening the charging time.

[0048] This invention, when determining the battery charging capability boundary across the entire temperature range through experimental methods, first determines the actual lithium-plating anode potential. A more accurate lithium-plating anode potential can be obtained by disassembling the battery. Then, based on an anode-to-lithium potential table, anode-to-lithium potential curves are fitted under the full temperature range, full-rate charging, and different dynamic SOC conditions. Finally, using the actual lithium-plating anode potential as a benchmark, the charging rate at different charge levels in the anode-to-lithium potential curve is confirmed, determining the SOC boundary points corresponding to when the anode-to-lithium potential reaches the benchmark value at multiple charging rates. This method yields a more accurate charging capability boundary value.

[0049] The charging method of the present invention can effectively reduce the risk of lithium plating, improve the cycle stability of the product, reduce electrical safety risks, and extend the product's service life.

[0050] This invention can effectively shorten charging time and improve the user experience for end users.

[0051] The charging strategy of this invention is easy to implement in the system, which is conducive to the promotion and application of the product.

[0052] Advantages of additional aspects 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

[0053] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0054] Figure 1 A diagram showing the anode-to-lithium potential of a lithium-ion battery at 25°C and 1C charging rate.

[0055] Figure 2 The second embodiment is a flowchart of the charging strategy. Detailed Implementation

[0056] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0057] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0058] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0059] As mentioned earlier, developing a fast and safe lithium-ion battery charging strategy is of great significance. Addressing the technical problems of existing technologies that fail to effectively characterize the charging capacity of batteries at different charge levels, leading to a significant risk of lithium plating at high charging rates, and the issue that with increasing charging cycles and decreasing battery capacity, improper charging methods, if not precisely controlled, can result in severe lithium plating risks and rapid degradation of battery cycle performance, this embodiment discloses a method for determining the boundary of battery charging capacity.

[0060] This embodiment defines the charging capability boundary and divides the charging method of lithium-ion batteries and electrical devices into N sub-stages. Each sub-stage controls the charging amount by charging time, ultimately reaching the target SOC threshold value for each sub-stage to reduce polarization. By using sensors to quickly feedback the cell status, the charging amount and charging time can be adjusted in a timely manner to improve charging efficiency, shorten charging time, and reduce the risk of lithium plating during charging, thereby enhancing the end-user experience and improving product competitiveness.

[0061] like Figure 1 As shown, the battery charging capability boundary determination method proposed in this embodiment may include the following steps:

[0062] The ambient temperature for battery charging is categorized into different levels.

[0063] The battery was assembled into a three-electrode system and charged at different rates at different temperatures. The anode-to-lithium potential and dynamic SOC of the three electrodes were monitored, and a table of anode-to-lithium potentials was plotted at different temperatures, charging rates, and dynamic SOCs.

[0064] The anode-to-lithium potential is pre-classified, and batteries with different anode-to-lithium potentials after charging are disassembled. Lithium plating is verified at the anode interface to determine the true lithium plating anode potential.

[0065] The anode-to-lithium potential curves were fitted under full temperature range, full rate charging, and different dynamic SOCs.

[0066] Based on the actual lithium plating anode potential, the charging rate under different charge levels in the anode-to-lithium potential curve is confirmed, thereby determining the charging capacity boundary.

[0067] The purpose of this invention is to provide an optimal fast charging method for lithium-ion batteries, enabling the batteries to be charged quickly and efficiently under different ambient temperatures and different charge levels, avoiding rapid degradation of battery cycle performance caused by improper charging methods, thereby greatly improving the end-user experience.

[0068] The technical solution of this embodiment will be described in detail below, specifically including the following steps:

[0069] 1) As shown in Table 1, the common ambient temperatures of lithium-ion batteries are divided into the following categories (the following categories are only examples).

[0070] Table 1 provides examples of ambient temperature gradations.

[0071] Classification 1 2 3 4 5 6 7 Ambient temperature -30℃＜T≤-20℃ -20℃＜T≤-10℃ -10℃＜T≤0℃ 0℃＜T≤10℃ 10℃＜T≤25℃ 25℃＜T≤45℃ 45℃＜T≤55℃

[0072] As can be seen from Table 1 above, this embodiment divides the ambient temperature into 7 levels, among which:

[0073] First setting: Ambient temperature -30℃ to -20℃;

[0074] Second setting: Ambient temperature -20℃ to -10℃;

[0075] Third setting: Ambient temperature -10℃ to 0℃;

[0076] Fourth level: Ambient temperature 0℃ to 10℃;

[0077] Fifth level: Ambient temperature 10℃ to 25℃;

[0078] Level 6: Ambient temperature 25℃ to 45℃;

[0079] Level 7: Ambient temperature 45℃ to 55℃.

[0080] The left endpoint value of each level is classified into the level above.

[0081] 2) Also includes:

[0082] Pre-measure the static SOC-OCV of the battery at different temperatures, as well as the dynamic SOC-OCV at different temperatures and different rates;

[0083] When monitoring the dynamic SOC of the three electrodes of a charging lithium-ion battery, the dynamic SOC of the lithium-ion battery is obtained by measuring the open-circuit voltage value and combining it with the pre-measured dynamic SOC-OCV meter.

[0084] Specifically, the static SOC-OCV of the battery at different temperatures and the dynamic SOC-OCV at different temperatures and rates are measured and entered into the system.

[0085] Table 2 shows the static SOC-0CV data.

[0086] SOC (%) OCV(V) SOC (%) OCV(V) SOC (%) OCV(V) 0 3.044 35 3.647 70 3.956 5 3.315 40 3.681 75 4.012 10 3.42 45 3.724 80 4.067 15 3.462 50 3.775 85 4.084 20 3.516 55 3.822 90 4.09 25 3.568 60 3.87 95 4.102 30 3.614 65 3.918 100 4.101

[0087] Table 3 shows the dynamic SOC-OCV data at different magnifications under 25℃ conditions.

[0088]

[0089] The static SOC-OCV table above shows the relationship between the initial SOC value and the open-circuit voltage (OCV) of the battery when it is not charged. By measuring the open-circuit voltage and combining it with the static SOC-OCV data table for different ambient temperatures, the initial SOC value can be determined.

[0090] The above dynamic SOC-OCV table shows the relationship between the dynamic SOC value and the open-circuit voltage (OCV) of a battery under different charging rates. By measuring the open-circuit voltage and combining it with the dynamic SOC-OCV data table for different ambient temperatures and charging rates, the dynamic SOC value corresponding to that open-circuit voltage at a set ambient temperature and a set charging rate can be determined. The dynamic SOC value is the SOC value during the charging process.

[0091] For example:

[0092] In this embodiment, when the battery is charged at a rate of 4.0C at 25°C, the dynamic SOC value is 30% when the open circuit voltage is measured to be 3.86.

[0093] At 25°C, when the battery is charged at a rate of 3.0C, the dynamic SOC value is 30% when the open circuit voltage is measured to be 3.81.

[0094] At 25°C, when the battery is charged at a rate of 2.0C, the dynamic SOC value is 35% when the open circuit voltage is measured to be 3.8V.

[0095] 3) Assemble the batteries that require a charging strategy into a three-electrode configuration; charge at different rates for different ambient temperatures, while monitoring the lithium potential of the anode in the three electrodes.

[0096] The table below shows the anode-to-lithium potential at the set temperature, which represents the anode-to-lithium potential of a lithium-ion battery under different dynamic SOCs when the battery is charged at multiple different charging rates, as shown in Tables 4 and 5.

[0097] Table 4 shows the lithium potential at different charging rates and SOCs of lithium-ion batteries at 25℃.

[0098]

[0099] As can be seen from Table 4 above, at 25℃ and a charging rate of 4.0C, the SOC value reached is 30% when the anode-to-lithium potential reaches 13mV.

[0100] This means that when charging at a rate of 4.0C at 25℃, the charge level is 30% when the anode-to-lithium potential reaches 13mV.

[0101] At 25°C, when charged at a 2.0C rate, the SOC value reaches 60% when the anode-to-lithium potential reaches 11mV.

[0102] This means that when charging at a rate of 2.0C at 25℃, the charge level is 60% when the anode-to-lithium potential reaches 11mV.

[0103] Table 5 shows the lithium potential of the anode at different charging rates and SOCs of lithium-ion batteries at 0℃.

[0104]

[0105] As can be seen from Table 5 above, when charged at 4.0C rate at 0℃, the SOC value reached is 30% when the anode-to-lithium potential reaches -27mV.

[0106] This means that when charging at a rate of 4.0C at 0℃, the charge level is 30% when the anode-to-lithium potential reaches -27mV.

[0107] At 0°C, when charged at a 2.0C rate, the SOC value reaches 45% when the anode-to-lithium potential reaches 7mV.

[0108] This means that when charging at a rate of 2.0C at 0℃, the charge level is 45% when the anode-to-lithium potential reaches 7mV.

[0109] 4) As shown in Table 6, the lithium potential of the anode is pre-classified (the following classification is only an example), the batteries with different lithium potentials of the anode are disassembled, the lithium plating at the anode interface is verified, and the true lithium plating anode potential is determined.

[0110] Table 6 provides examples of lithium potential grading for three-electrode anodes.

[0111] Tiering 1 2 3 4 5 6 Anode to lithium potential 30mV 20mV 10mV 0mV -10mV -20mV

[0112] In this embodiment, the actual lithium plating anode potential is determined by disassembling the pre-graded batteries and verifying lithium plating at the anode interface, for example, 10mV.

[0113] When lithium plating actually occurs, the anode potential is related to the charging temperature and the charging rate. Changes in both variables will lead to changes in the anode potential during actual lithium plating.

[0114] By determining the actual lithium plating anode potential, a lithium plating anode potential boundary is obtained. This boundary will be used in subsequent steps as a benchmark comparison value to ultimately determine multiple dynamic SOC boundary points.

[0115] 5) Use modeling software to process the above data and fit the anode-to-lithium potential at full rate and full temperature range.

[0116] Specifically:

[0117] Based on the anode-to-lithium potential under different temperatures, different charging rates, and different dynamic SOCs when charging the battery, the anode-to-lithium potential curves under different dynamic SOCs during full-temperature range and full-rate charging are fitted.

[0118] The model software was used to fit the anode-to-lithium potential curves of the battery under various set temperatures, set charging rates, and different dynamic SOCs when charging the battery. The curves were then used to fit the anode-to-lithium potential curves of the battery under different dynamic SOCs and at different temperatures and charging rates.

[0119] 6) The charging capacity boundary is determined by using the lithium plating anode potential boundary (i.e., the actual lithium plating anode potential) to confirm the rate of charge under different ambient temperatures and different charge levels.

[0120] In this embodiment, the charging process is equivalent to dividing the overall charging process into multiple charging sub-stages and determining the charging parameters for each charging sub-stage. The charging parameters for the I-th charging sub-stage include the I-th SOC boundary point and the corresponding charging rate.

[0121] Specifically, the following steps are included:

[0122] Step 1: Based on the anode-to-lithium potential curves under different dynamic SOCs during full-temperature and full-rate charging, find the anode-to-lithium potential curves under different dynamic SOCs during full-rate charging at the current ambient temperature, and use them as benchmark comparison curves;

[0123] Step 2: Determine the initial charging rate. Using the actual lithium plating anode potential as the benchmark comparison value, determine the dynamic SOC boundary point corresponding to when the anode lithium potential reaches the benchmark comparison value under the initial charging rate. This is the first SOC boundary point. Then, charge at the initial charging rate until the first SOC boundary point is reached and stop.

[0124] Although this embodiment uses the fitted anode-to-lithium potential curve as the benchmark comparison curve, since these curves are fitted by multiple discrete tables such as those shown in Table 5, for ease of understanding, please still refer to Table 5: lithium-ion battery anode-to-lithium potential at different SOCs when charged at different rates at 25°C.

[0125] As mentioned earlier, assuming the determined actual lithium plating anode potential is 10mV; please refer to Table 5. Assuming the initial charging rate is 4.0C, the 10mV actual lithium plating anode potential is used as a benchmark comparison value to determine when the anode-to-lithium potential at the initial charging rate of 4.0C will reach the boundary value of the lithium plating anode potential, i.e., when it will reach the actual lithium plating anode potential of 10mV. By referring to the last row of data in Table 5, we can see that there are two anode-to-lithium potential values: 13mV and -1mV. 13mV and -1mV just cross the actual lithium plating anode potential of 10mV, indicating that when the anode-to-lithium potential reaches 13mV during charging, lithium plating will not occur; when the anode-to-lithium potential continues to charge from 13mV to -1mV, lithium plating has already occurred.

[0126] The above analysis shows that the initial charging rate should be 4.0C until the anode-to-lithium potential reaches 13mV, and then this charging stage should be stopped, because continuing to charge will cause lithium plating. When the anode-to-lithium potential reaches 13mV, the corresponding dynamic SOC value is 30%.

[0127] That is, the first SOC threshold is 30%. Charge at the initial charging rate until the first SOC threshold, i.e., 30%, and then stop this charging phase.

[0128] Step 3: Determine the secondary charging rate. Repeat the process in Step 2 above to find the second SOC boundary point. Charge from the first SOC boundary point to the second SOC boundary point using the secondary charging rate.

[0129] In step two above, the first SOC threshold has been determined to be 30%. The charging is stopped at the initial charging rate until the first SOC threshold, i.e., 30%. The next process will start from the SOC of 30% in step two and continue the charging process of the next sub-stage.

[0130] As shown in Table 5 above, the next sub-stage is charged at a secondary charging rate of 3.0C. Assuming that the actual lithium plating anode potential corresponding to this sub-stage is still 10mV (for ease of understanding, this is just an example), corresponding to the second row of the derivative in Table 5, there are two anode-to-lithium potential values ​​of 12mV and 2mV during the secondary charging process at a secondary charging rate of 3.0C. Similar to the aforementioned step two, the two anode-to-lithium potential values ​​of 12mV and 2mV just cross the actual lithium plating anode potential of 10mV, indicating that when the anode-to-lithium potential reaches 12mV during the charging process, lithium plating will not occur. When the anode-to-lithium potential continues to be charged from 12mV to 2mV, lithium plating has already occurred.

[0131] Similarly, as the above analysis shows, the battery should be charged at a secondary charging rate of 3.0C until the anode-to-lithium potential reaches 12mV, and then this charging stage should be stopped, because continuing to charge will result in lithium plating. When the anode-to-lithium potential reaches 12mV, the corresponding dynamic state of charge (SOC) value is 45%.

[0132] That is, the second SOC threshold is 45%. Charge at a secondary charging rate of 3.0C until the second SOC threshold, i.e., 45%, and then stop this charging phase.

[0133] Step 4: Repeat the process in Step 3 above until the Nth charging rate is determined, find the Nth SOC boundary point, and charge from the (N-1)th SOC boundary point to the Nth SOC boundary point at the Nth charging rate. The Nth SOC boundary point is the preset SOC charging target value.

[0134] In this embodiment, for example, if the preset SOC charging target value is 100%, that is, until fully charged, then according to the above process, the parameters for each charging sub-stage determined in this embodiment are as follows:

[0135] First charging stage: initial charging rate 4.0C, first SOC threshold 30%;

[0136] Second charging stage: Second charging rate 3.0C, second SOC threshold 45%;

[0137] The third charging stage: three charging rates of 2.0C, and the third SOC threshold of 65%;

[0138] The fourth charging stage: four charging cycles at a rate of 1.0C, with the fourth SOC threshold at 85%;

[0139] Fifth charging stage: five charging cycles at a rate of 0.75C, with the fifth SOC threshold at 90%;

[0140] The sixth charging stage: six charging cycles at a rate of 0.5C, with the sixth SOC threshold at 95%;

[0141] The seventh charge stage: seven charge rates of 0.33C, and the seventh SOC threshold of 100%.

[0142] This completes the entire charging process for each sub-stage. In the charging strategy proposed in this embodiment, the charging of each sub-stage will not reach the lithium potential threshold for lithium plating, thus ensuring that lithium plating does not occur as much as possible during each sub-stage, thereby avoiding lithium plating during the overall charging process and improving charging stability.

[0143] In the above specific embodiments, it is assumed that the actual lithium plating anode potential corresponding to each sub-stage is 10mV. However, in actual processes, the anode potential during lithium plating is related to both the charging temperature and the charging rate. At the same charging temperature, using different charging rates, the actual lithium plating anode potential will deviate from the 10mV in this embodiment. In actual processes, the actual lithium plating anode potential of each charging sub-stage can be compared and adjusted accordingly.

[0144] Furthermore, this embodiment also considers using the anode-to-lithium potential to effectively characterize the battery's charging capability (i.e., the ability to detect significant lithium plating risk) at different charge levels. A more accurate true lithium plating anode potential is obtained through experimental disassembly. This true lithium plating anode potential is then applied in subsequent comparisons to accurately identify the SOC boundary value for each charging sub-stage. The resulting charging strategy is more precise, safe, and scientific.

[0145] It can be understood that the charging capability boundary is: charging to the first SOC boundary point at the initial charging rate, charging from the first SOC boundary point to the second SOC boundary point at the second charging rate, ... charging from the (N-1)th SOC boundary point to the Nth SOC boundary point at N charging rates;

[0146] To improve subsequent practicality, after determining the battery charging capability boundary across the entire temperature range, a charging capability boundary table is also prepared.

[0147] It is understandable that the charging rate in the charging capacity boundary table is a commonly used charging rate for easy reference.

[0148] 7) Before the battery starts charging, the sensor feeds back the cell temperature to the host, and the SOC-OCV table (static) that has been entered into the system feeds back the SOC of the cell at that time (i.e. the initial SOC when the battery is not charging), and the appropriate charging current cx is given by the corresponding charging capacity boundary table.

[0149] 8) When the battery begins charging, the entire charging process is divided into n sub-stages (n1, n2, n3…nx), with charging currents of c1, c2, c3…cx, and charging times of t1, t2, t3…tx. This charging time can be understood as the time it takes for the battery's State of Charge (SOC) to reach the SOC threshold of each sub-stage. Each stage is a constant current charging process.

[0150] ① The first charging stage n1: The battery is charged with the charging current of c1 for a duration of t1. During the charging process, the sensor provides feedback on the charging current, cell temperature, and battery voltage. The system compares the real-time dynamic SOC-OCV meter with the accurate SOC of the battery at this time. After reaching the next SOC range or protection voltage, the system jumps to the next charged stage n2.

[0151] ② The second charging stage n2: The battery is charged using the charging current of c2 for a charging time of t2. During the charging process, the sensor provides feedback on the charging current, cell temperature, and battery voltage. The system compares the real-time dynamic SOC-OCV meter with the accurate SOC of the battery at this time. After reaching the next SOC range or protection voltage, it jumps to the next charged stage n3.

[0152] ③ The third charging sub-stage n3: The battery is charged using the charging current of c3 for a charging time of t3. During the charging process, the sensor provides feedback on the charging current, cell temperature, and battery voltage. The system compares the real-time dynamic SOC-OCV meter with the accurate SOC of the battery at this time. After reaching the next SOC range or protection voltage, it jumps to the next charged sub-stage n4.

[0153] …

[0154] ④ The xth charging sub-stage nx: The battery is charged with the charging current cx for a charging time of tx. During the charging process, the sensor provides feedback on the charging current, cell temperature, and battery voltage. The system compares the real-time dynamic SOC-OCV meter with the accurate SOC of the battery at this time. The charging process ends after the next SOC range or protection voltage is reached.

[0155] This embodiment defines the charging capability boundary and divides the charging method of lithium-ion batteries and electrical devices into N sub-stages. Each sub-stage uses charging time to control the charging amount, thereby reducing polarization. The sensor quickly feeds back the cell status and adjusts the charging amount and charging time in a timely manner, improving charging efficiency, shortening charging time, and reducing the risk of lithium plating during charging. This enhances the end-user experience and improves product competitiveness.

[0156] The present invention will now be described in further detail.

[0157] In this invention, all equipment and raw materials are available from the market or are commonly used in the industry. Unless otherwise specified, the methods in the following embodiments are conventional methods in the field.

[0158] 1. The battery operating temperature range is divided into 7 levels. In this embodiment, the ambient temperature is divided into 7 levels.

[0159] II. Fabricate the three electrodes of a single lithium-ion battery cell and test them at seven different charging rates (0.33C, 0.5C, 0.75C, 1.0C, 1.5C, 2.0C, 3.0C, 4.0C) at the above seven temperature levels; record the changes in anode-to-lithium potential, and plot the anode-to-lithium potential curves and anode-to-lithium potential table for charging at different rates at the seven temperature levels; categorize the cells according to their anode-to-lithium potential. Figure 1 The diagram shows the lithium potential at the anode of a lithium-ion battery under 1C charging conditions at 25℃.

[0160] 3. Test the static SOC-OCV curve and plot the static SOC-OCV table.

[0161] IV. Measure the dynamic SOC-OCV curves at 7 temperature levels and plot the dynamic SOC-OCV table.

[0162] Example 1:

[0163] The batteries used in the following examples and comparative cases have a nominal capacity of 30Ah. Charging was performed according to the first level of the anode-to-lithium potential (30mV) standard, at an ambient temperature of 0°C. The specific charging process is as follows:

[0164] ① The system detects that the voltage of the electrical device is 3.044V and the temperature is 0℃. It starts charging from 0% SOC and uses a 4C (120A) current for 1.5 minutes.

[0165] ② Charge using a 3C (90A) current for 2 minutes; the system detects a maximum temperature of 3℃ for the electrical device.

[0166] ③ Charge using a 2C (60A) current for 3 minutes; the system detects a maximum temperature of 8℃ for the electrical device.

[0167] ④ Charge with a 1.5C (45A) current for 2 minutes; the system detects the maximum temperature of the electrical device as 11℃, which is the 4th temperature range. Switch to search the database of different SOC anode-to-lithium potentials when charging at different rates within the 4th temperature range.

[0168] ⑤ Charge with a 1.5C (45A) current for 6 minutes; the system detects the maximum temperature of the electrical device as 15℃.

[0169] ⑥ Charge using a 1.0C (30A) current for 9 minutes; the system detects the maximum temperature of the electrical device as 16℃.

[0170] ⑦ Charge with a current of 0.75C (22.5A) for 12 minutes; the system detects the maximum temperature of the electrical device as 16.5℃.

[0171] ⑧ Charge with a current of 0.5C (15A) for 12 minutes; the system detects the maximum temperature of the electrical device as 17℃.

[0172] ⑦ Charge with a current of 0.33C (10A) for 18 minutes; the system detects the maximum temperature of the electrical device as 18.5℃.

[0173] Charging is completed based on dynamic SOC-OCV.

[0174] Example 2:

[0175] The batteries used in the following examples and comparative examples have a nominal capacity of 30Ah. Charging was performed according to the third level (10mV) of the anode lithium potential standard at an ambient temperature of 0°C. The specific charging process is as follows:

[0176] ① The system detects that the voltage of the electrical device is 3.044V and the temperature is 0℃. It starts charging from 0% SOC and uses a 4C (120A) current for 1.5 minutes.

[0177] ② Charge using a 3C (90A) current for 2 minutes; the system detects a maximum temperature of 3℃ for the electrical device.

[0178] ③ Charge with 2C (60A) current for 6 minutes; the system detects the maximum temperature of the electrical device as 12℃; the temperature range is level 4, and the database of different SOC anode-to-lithium potentials during charging at different rates within the level 4 temperature range is switched to search.

[0179] ④ Charge using a 2C (60A) current for 3 minutes; the system detects a maximum temperature of 14℃ for the electrical device.

[0180] ⑤ Charge with a 1.5C (45A) current for 4 minutes; the system detects the maximum temperature of the electrical device as 16℃.

[0181] ⑥ Charge using a 1.0C (30A) current for 12 minutes; the system detects the maximum temperature of the electrical device as 18℃.

[0182] ⑦ Charge with a current of 0.75C (22.5A) for 8 minutes; the system detects the maximum temperature of the electrical device as 18.5℃.

[0183] ⑧ Charge with a current of 0.5C (15A) for 6 minutes; the system detects the maximum temperature of the electrical device as 19.5℃.

[0184] ⑦ Charge with a current of 0.33C (10A) for 9 minutes; the system detects a maximum temperature of 21℃ for the electrical device.

[0185] Charging is completed based on dynamic SOC-OCV.

[0186] Example 3:

[0187] The batteries used in the following examples and comparative cases have a nominal capacity of 30Ah. Charging was performed according to the sixth level (-20mV) of the anode lithium potential standard, at an ambient temperature of 0℃. The specific charging process is as follows:

[0188] ① The system detects that the voltage of the electrical device is 3.044V and the temperature is 0℃. It starts charging from 0% SOC and uses a 4C (120A) current for 3 minutes.

[0189] ② Charge using a 3C (90A) current for 4 minutes; the system detects a maximum temperature of 6℃ for the electrical device.

[0190] ③ Charge with 2C (60A) current for 4.5 minutes; the system detects the maximum temperature of the electrical device as 11℃; the temperature range is level 4, and the database of different SOC anode-to-lithium potentials during charging at different rates within the level 4 temperature range is searched.

[0191] ④ Charge using a 2C (60A) current for 6 minutes; the system detects a maximum temperature of 16℃ for the electrical device.

[0192] ⑤ Charge with a 1.5C (45A) current for 4 minutes; the system detects the maximum temperature of the electrical device as 17.5℃.

[0193] ⑥ Charge using a 1.0C (30A) current for 6 minutes; the system detects the maximum temperature of the electrical device as 18.5℃.

[0194] ⑦ Charge with a current of 0.33C (10A) for 9 minutes; the system detects a maximum temperature of 21℃ for the electrical device.

[0195] Charging is completed based on dynamic SOC-OCV.

[0196] Comparative Example 1:

[0197] The electrical device is charged at 3.044V and 0℃, starting from 0% SOC. It is charged using a constant current and constant voltage method, with a constant current charging current of 0.5C (15A) and a constant voltage until 0.05C (1.5A). The charging cutoff voltage is 4.2V. Record the total charging time and charging capacity.

[0198] Comparative Example 2:

[0199] The electrical device is charged at 3.044V and 0℃, starting from 0% SOC. It is charged using a constant current and constant voltage method, with a constant current charging current of 1C (30A) and a constant voltage until 0.05C (1.5A). The charging cutoff voltage is 4.2V. Record the total charging time and charging capacity.

[0200] Comparative Example 3:

[0201] The electrical device is charged at 3.044V and 0℃, starting from 0% SOC. It is charged using a constant current and constant voltage method, with a constant current charging current of 1.5C (45A) and a constant voltage until 0.05C (1.5A). The charging cutoff voltage is 4.2V. Record the total charging time and charging capacity.

[0202] Comparative Example 4:

[0203] The electrical device is charged at 3.044V and 0℃, starting from 0% SOC. It is charged using a constant current and constant voltage method, with a constant current charging current of 2C (60A) and a constant voltage until 0.05C (1.5A). The charging cutoff voltage is 4.2V. Record the total charging time and charging capacity.

[0204] Comparative Example 5:

[0205] The electrical device is charged at 3.044V and 0℃, starting from 0% SOC. It is charged using a constant current and constant voltage method, with a constant current charging current of 3C (90A) and a constant voltage until 0.05C (1.5A). The charging cutoff voltage is 4.2V. Record the total charging time and charging capacity.

[0206] Comparative Example 6:

[0207] The electrical device is charged at 3.044V and 0℃, starting from 0% SOC. It is charged using a constant current and constant voltage method, with a constant current charging current of 4C (120A) and a constant voltage until 0.05C (1.5A). The charging cutoff voltage is 4.2V. Record the total charging time and charging capacity.

[0208] The above-mentioned electrical device was charged according to the charging methods in the embodiments and comparative examples, and the charging time was compared. The comparison results are shown in Table 7 below. Then, 10 charge-discharge cycles were performed, the device was disassembled, the anode interface was observed, and statistical comparisons were made. The comparison results are shown in Table 8 below.

[0209] Table 7 compares the charging time of the Example and Comparative Example from 0% to 100% SOC.

[0210]

[0211] Table 8 shows the interface lithium plating situation after 10 charge-discharge cycles for the examples and comparative examples.

[0212]

[0213] From Tables 7 and 8 above, we can conclude that:

[0214] The embodiments of this invention can balance charging time and charging safety. Charging time is shortened, and lithium plating does not occur at the cell interface.

[0215] Example 2

[0216] This embodiment discloses a battery charging optimization method.

[0217] like Figure 2 As shown, the battery charging optimization method based on the battery charging capability boundary determination method described in Embodiment 1 includes the following steps:

[0218] Obtain the initial SOC value of the battery when it is not charged;

[0219] Obtain the current battery charging ambient temperature and find the battery charging capacity boundary corresponding to the current battery charging ambient temperature in the charging capacity boundary table.

[0220] Starting from the initial SOC value, the battery is charged in stages according to the battery charging capacity boundary;

[0221] During the phased charging process, the dynamic SOC value of the battery is acquired in real time to determine whether the SOC threshold value of each phase has been reached (I = 1...N). If so, the phase ends and the next phase begins, until the preset SOC charging target value is reached, thus completing the entire charging process.

[0222] Furthermore, such as Figure 2 As shown:

[0223] The initial SOC value of the battery is obtained through the static SOC-OCV table;

[0224] The current battery charging ambient temperature is obtained by collecting data from sensors.

[0225] The dynamic SOC value of the battery is obtained through the dynamic SOC-OCV table.

[0226] Based on the charging capacity boundary table, multiple charging sub-stages are divided, and the charging parameters for each sub-stage are obtained, namely the charging rate and the charging SOC threshold value. The charging time is obtained through the charging SOC threshold value. It is then determined whether the current charging sub-stage is completed. If it is completed, the charging ends and the next charging sub-stage begins; otherwise, the charging process of the current sub-stage continues.

[0227] Example 3

[0228] This embodiment provides a battery charging optimization system.

[0229] The battery charging optimization system includes:

[0230] The initial SOC acquisition module is configured to acquire the initial SOC value of the battery when it is not charged.

[0231] The query module is configured to: obtain the current battery charging ambient temperature and search for the battery charging capacity boundary corresponding to the current battery charging ambient temperature in the charging capacity boundary table;

[0232] The phased charging module is configured to charge the battery in stages according to the battery charging capacity boundary, starting from the initial SOC value.

[0233] The SOC boundary point judgment module is configured to: acquire the dynamic SOC value of the battery in real time during the phased charging process, and determine whether the SOC boundary point I is reached in each phase, where I = 1...N; if so, the phase ends and the next phase begins, until the preset SOC charging target value is reached, thus completing the entire charging process.

[0234] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for determining the boundary of battery charging capability, characterized in that, Includes the following steps: The ambient temperature for battery charging is categorized into different levels. The battery was assembled into a three-electrode system and charged at different rates at different temperatures. The anode-to-lithium potential and dynamic SOC of the three electrodes were monitored, and a table of anode-to-lithium potentials was plotted at different temperatures, charging rates, and dynamic SOCs. The anode-to-lithium potential is pre-classified, and batteries with different anode-to-lithium potentials after charging are disassembled. Lithium plating is verified at the anode interface to determine the actual lithium plating anode potential. The anode-to-lithium potential curves were fitted under full temperature range, full rate charging, and different dynamic SOCs. Based on the actual lithium plating anode potential, the charging rate under different charge levels in the anode-to-lithium potential curve is confirmed, thereby determining the charging capacity boundary. Based on the actual lithium plating anode potential, the charging rate under different charge levels in the anode-to-lithium potential curve is confirmed, thereby determining the charging capacity boundary, specifically: Step 1: Based on the anode-to-lithium potential curves under different dynamic SOCs during full-temperature and full-rate charging, find the anode-to-lithium potential curves under different dynamic SOCs during full-rate charging at the current ambient temperature, and use them as benchmark comparison curves; Step 2: Determine the initial charging rate. Using the actual lithium plating anode potential as the benchmark comparison value, determine the dynamic SOC boundary point corresponding to when the anode lithium potential reaches the benchmark comparison value under the initial charging rate. This is the first SOC boundary point. Then, charge at the initial charging rate until the first SOC boundary point is reached and stop. Step 3: Determine the secondary charging rate. Repeat the process in Step 2 above to find the second SOC boundary point. Charge from the first SOC boundary point to the second SOC boundary point using the secondary charging rate. Step 4: Repeat the process in Step 3 above until the Nth charging rate is determined, find the Nth SOC boundary point, and charge from the (N-1)th SOC boundary point to the Nth SOC boundary point at the Nth charging rate. The Nth SOC boundary point is the preset SOC charging target value.

2. The method for determining the battery charging capability boundary as described in claim 1, characterized in that, Also includes: Pre-measure the static SOC-OCV of the battery at different temperatures, as well as the dynamic SOC-OCV at different temperatures and different rates; When monitoring the dynamic SOC of the three electrodes of a charging lithium-ion battery, the dynamic SOC of the lithium-ion battery is obtained by measuring the open-circuit voltage value and combining it with the pre-measured dynamic SOC-OCV meter.

3. The method for determining the battery charging capability boundary as described in claim 2, characterized in that, The static SOC-OCV table is a table showing the relationship between the initial SOC value and the open-circuit voltage OCV of the battery when it is not charged; the dynamic SOC-OCV table is a table showing the relationship between the dynamic SOC value and the open-circuit voltage OCV of the battery when it is charged at different charging rates.

4. The method for determining the battery charging capability boundary as described in claim 3, characterized in that, The anode-to-lithium potential table at the set temperature shows the anode-to-lithium potential of a lithium-ion battery under different dynamic SOCs when the battery is charged at multiple different charging rates.

5. The method for determining the battery charging capability boundary as described in claim 4, characterized in that: Based on the anode-to-lithium potential under different temperatures, different charging rates, and different dynamic SOCs when charging the battery, the anode-to-lithium potential curves under different dynamic SOCs during full-temperature range and full-rate charging are fitted.

6. The method for determining the battery charging capability boundary as described in claim 3, characterized in that: The charging capability boundary is: charging to the first SOC boundary point at the initial charging rate, charging from the first SOC boundary point to the second SOC boundary point at the second charging rate, ... charging from the (N-1)th SOC boundary point to the Nth SOC boundary point at N charging rates; The battery charging capability boundary under the entire temperature range was determined, and a charging capability boundary table was prepared.

7. A battery charging optimization method based on the battery charging capability boundary determination method according to any one of claims 2-6, characterized in that, Includes the following steps: Obtain the initial SOC value of the battery when it is not charged; Obtain the current battery charging ambient temperature and find the battery charging capacity boundary corresponding to the current battery charging ambient temperature in the charging capacity boundary table. Starting from the initial SOC value, the battery is charged in stages according to the battery charging capacity boundary; During the phased charging process, the dynamic SOC value of the battery is acquired in real time to determine whether the SOC threshold value of each phase has been reached (I=1…N). If so, the phase ends and the next phase begins, until the preset SOC charging target value is reached, thus completing the entire charging process.

8. The battery charging optimization method as described in claim 7, characterized in that: The initial SOC value of the battery is obtained through the static SOC-OCV table; The dynamic SOC value of the battery is obtained through the dynamic SOC-OCV table. The current ambient temperature for battery charging is obtained by collecting data from sensors.

9. A battery charging optimization system, used to execute the battery charging capability boundary determination method as described in any one of claims 1-6, characterized in that, include: The initial SOC acquisition module is configured to acquire the initial SOC value of the battery when it is not charged. The query module is configured to: obtain the current battery charging ambient temperature and search for the battery charging capacity boundary corresponding to the current battery charging ambient temperature in the charging capacity boundary table; The phased charging module is configured to charge the battery in stages according to the battery charging capacity boundary, starting from the initial SOC value. The SOC boundary point judgment module is configured to: acquire the dynamic SOC value of the battery in real time during the phased charging process, and determine whether the SOC boundary point I is reached in each phase, I=1…N; if so, the phase ends and the next phase begins, until the preset SOC charging target value is reached, thus completing the entire charging process.

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