Battery charging method and apparatus

Abstract

Embodiments of the present application provide a battery charging method and apparatus. The method comprises: charging a battery sequentially using a first current and a second current, the second current having a current value less than that of the first current, the current value of the second current being greater than zero, the second current comprising a descending-current segment, a starting point current value of the descending-current segment being less than an ending point current value of the first current, and the descending-current segment having a non-zero slope. The embodiments of the present application avoid continuous battery charging at a high current, thereby reducing the rate of electrochemical reactions in the interior of the battery, decreasing the degree of polarization, and, in turn, prolonging the service life of the battery.

Description

Battery charging method and charging device

[0001] The present application claims priority to the Chinese patent application No. 202411366657X, filed on September 27, 2024, and titled "Battery charging method and device", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of battery, in particular to a battery charging method, a battery charging device, an electronic device and a computer readable storage medium. BACKGROUND

[0003] With the rapid development of new energy vehicles, battery technology has become an indispensable part of modern society. The performance of the battery, especially the energy density, charging and discharging efficiency and service life, will affect the performance and cost-effectiveness of new energy vehicles.

[0004] However, due to the limitation of the service life of the battery by some factors, in order to improve the charging efficiency of the battery, a large current is used for fast charging of the battery, which further reduces the service life of the battery. SUMMARY

[0005] The purpose of the embodiments of the present application is to provide a battery charging method to solve the problem of prolonging the service life of the battery in the prior art. The specific technical solutions are as follows:

[0006] In the first aspect of the present application, a battery charging method is provided. The battery is charged in sequence according to a first current and a second current. The current value of the second current is less than the current value of the first current, and the current value of the second current is greater than 0.

[0007] The second current includes a descending current segment. The starting current value of the descending current segment is less than the ending current value of the first current, and the slope of the descending current segment is not 0.

[0008] In another aspect of the present application, a computer readable storage medium is provided. The computer readable storage medium stores instructions. When the instructions are executed on a computer, the computer executes the battery charging method described above.

[0009] In another aspect of the present application, an electronic device is provided. The electronic device includes a memory and a processor. The memory is configured to store a computer program. When the processor executes the computer program, the battery charging method described above is implemented.

[0010] In another aspect of the embodiments of the present application, a computer program product containing instructions, which, when executed on a computer, cause the computer to perform the charging method of the battery described above.

[0011] In another aspect of the embodiments of the present application, a charging device is provided, which is configured to sequentially charge the battery with a first current and a second current, the current value of the second current being less than the current value of the first current, and the current value of the second current being greater than 0.

[0012] The second current includes a falling current segment, the starting current value of the falling current segment being less than the ending current value of the first current, and the slope of the falling current segment being other than 0.

[0013] In another aspect of the embodiments of the present application, an electric device is provided, which includes the battery and the battery management system described above or the charging device described above.

[0014] In another aspect of the embodiments of the present application, a battery management system is provided, which includes the electronic device described above or the charging device described above.

[0015] In another aspect of the embodiments of the present application, a vehicle is provided, which includes the battery management system described above.

[0016] In the embodiments of the present application, the battery is sequentially charged with a first current and a second current, the current value of the second current being less than the current value of the first current, and the current value of the second current being greater than 0; the second current includes a falling current segment, the starting current value of the falling current segment being less than the ending current value of the first current, and the slope of the falling current segment being other than 0. In the charging process, the battery is sequentially charged with the first current and the second current less than the first current, and in the process of charging the battery, the slope of the falling current segment of the second current is other than 0, i.e., the second current does not directly decrease to a small current value instantaneously, so that the use of a large current to continuously charge the battery can be avoided, the electrochemical reaction rate in the battery can be reduced, the degree of polarization of the battery can be reduced, and the service life of the battery can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced below.

[0018] FIG. 1 is a step flowchart of a charging method of a battery provided in the embodiments of the present application;

[0019] FIG. 2 is a charging schematic diagram of a second current of a triangular wave provided in the embodiments of the present application;

[0020] FIG. 3 is a charging schematic diagram of a second current of a sine wave provided in an embodiment of the present application;

[0021] FIG. 4 is a charging schematic diagram of a second current of a square wave + sine wave provided in an embodiment of the present application;

[0022] FIG. 5 is a charging schematic diagram of a second current of a triangular wave + sine wave provided in an embodiment of the present application;

[0023] FIG. 6 is a charging current timing diagram of a charging method provided in an embodiment of the present application;

[0024] FIG. 7 is a schematic diagram of a battery management system and a power consumption device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application.

[0026] Referring to FIG. 1, it is a step flow chart of a charging method of a battery provided in an embodiment of the present application, as shown in FIG. 1, the method can specifically include the following steps:

[0027] Step 101, sequentially charging the battery according to a first current and a second current, the current value of the second current is less than the current value of the first current, and the current value of the second current is greater than 0;

[0028] The second current includes a falling current section, the starting current value of the falling current section is less than the ending current value of the first current, and the slope of the falling current section is not 0.

[0029] The charging method of the battery in the embodiments of the present application can be applied to a battery management system (BMS) of a vehicle, or other systems that need to be charged, which is not limited in the embodiments of the present application.

[0030] In the embodiments of the present application, when charging the battery through a charging pile or other charging devices, the battery can be sequentially charged according to a first current and a second current, the first current is usually referred to as a charging current, the second current can be referred to as a pulse current, and the current value of the second current is less than the current value of the first current, and the current value of the second current is greater than 0.

[0031] In the embodiments of the present application, considering the hardware of the charging device such as the charging pile and the charging safety, the current will not directly jump from a larger current to a smaller current, for example, directly drop from the first current to the second current. Therefore, in the embodiments of the present application, the second current can include a falling current section, the falling current section is a current section from the first current to the second current, and the starting current value of the falling current section is less than the ending current value of the first current. The slope of the falling current section from the first current to the second current can be a preset slope, and the preset slope is not 0. This ensures that the charging method disclosed in the embodiments of the present application will not damage the charging pile when applied to the charging pile, and ensures that the charging method disclosed in the embodiments of the present application can be implemented in a conventional charging pile.

[0032] In the embodiments of the present application, the first current and the second current smaller than the first current are used in turn during the charging process. During the charging of the battery, the slope of the falling current section of the second current is not 0, that is, the second current will not directly decrease to a small current value, thus reducing the rate of electrochemical reaction inside the battery, thereby reducing the degree of battery polarization, and further improving the battery life.

[0033] In the actual charging process of the battery, when a larger current (for example, a first current greater than 1C) is used to charge the battery, the charging speed of the battery can be improved to achieve fast charging. However, if a larger current is continuously used to charge the battery, it will cause the battery to polarize, thereby affecting the service life of the battery. The polarization of the battery can involve active polarization, concentration polarization, and ohmic polarization, etc.

[0034] In specific implementation, since the current value of the first current is large, that is, greater than 1C, the active material in the negative thickness direction has uneven reaction, and the reaction rate of the side away from the current collector is greater than the current collector side, resulting in a higher state of charge (SOC) of the side away from the current collector. Since the current value of the second current is smaller than the first current, the current reduction will improve the reaction uniformity in the negative thickness direction. At this time, the region with higher state of charge away from the current collector no longer performs a positive lithium intercalation electrochemical reaction, but a negative discharge electrochemical reaction. Therefore, the second current applied can cause the side of the battery negative active material away from the current collector to discharge to the current collector side, thereby reducing the thickness direction concentration polarization and achieving overall polarization reduction of the battery.

[0035] In addition, in the above embodiments, the first current greater than or equal to 1C means that the current value corresponding to any time of the first current should be greater than or equal to 1C to ensure that the effect of reducing the thickness direction concentration polarization can be improved when charging with the second current, and the overall polarization of the battery is reduced.

[0036] In addition, in the above embodiment, the first current greater than 1C means that the current value corresponding to any moment of the first current should be greater than the current value corresponding to charging the battery at a charging rate of 1C, so as to ensure that the thickness direction concentration polarization effect can be reduced when charging at the second current, and the overall polarization of the battery is reduced.

[0037] In the embodiments disclosed in the present application, if the second current is a dynamically changing current, the current value of the second current can be an average current value or a minimum current value. Specifically, if the second current is a sinusoidal current signal, the current value of the second current is the average current value of the sinusoidal current signal. If the second current is a triangular wave current signal, the current value of the second current is the minimum current value of the triangular wave current signal. In addition, if the second current is a constant current, the current value of the second current is the actual current value.

[0038] Further, in the above embodiment, the current value of the first current is the current value at the end of the first current, or the current value of the first current at the moment when the first current is converted to the second current.

[0039] In addition, when charging the battery according to the second current, the consumption rate of the reactant on the negative electrode surface is reduced, so that the reactant on the current collector side can be supplemented in time, thereby reducing the concentration polarization.

[0040] When charging the battery according to the second current, the negative active material of the battery on the side away from the current collector discharges to the current collector side, so that the battery has a more uniform state of charge and current density distribution in the thickness direction of the negative active material, improves the uniformity of the active material reaction in the thickness direction of the negative electrode, thereby reducing the concentration polarization.

[0041] It should be noted that the charging time of the first current is usually ≥ 30s (seconds). Because when the charging time of the first current is less than 30s, the polarization of the battery is still small, the state of charge in the thickness direction of the negative electrode is uniform, the second current cannot make the negative electrode surface (the side away from the current collector) discharge to the current collector side, and the polarization effect is not reduced. Therefore, the second current needs to be applied after the charging time of the first current is ≥ 30s, so as to achieve a better polarization reduction effect.

[0042] In addition, since the battery cannot be charged for an unlimited length of time, the charging time of the first current should be less than the charging time of the battery at the first current when the voltage of the battery reaches the cutoff voltage of the battery, that is, the charging cutoff time. When the actual voltage of the battery exceeds the cutoff voltage of the battery, there is a risk of lithium precipitation in the battery. Generally, in the embodiments disclosed in the present application, the charging time of the first current should be less than or equal to 250s. If the first current charging time exceeds 250s, the cutoff voltage of the battery may be exceeded, resulting in overcharge lithium precipitation and affecting the service life of the battery.

[0043] In the above embodiment 1C, the charging rate of the battery is referred to, specifically, the charging rate refers to the current value required by the battery to charge to its rated capacity within a specified time. The charging rate is represented by C, and the calculation formula is charging rate C = charging current (A) / battery rated capacity (Ah). For example, a battery with a rated capacity of 100 Ah is charged with a current of 100 A, and the charging rate is 1C.

[0044] In the embodiments of the present application, the current value of the second current is less than the current value of the first current, that is, the current value of the first current at any time is greater than the current value of the second current at any time, and then the second current applied can make the negative active material of the battery away from the side of the current collector to the side of the current collector, thereby reducing the thickness direction concentration polarization and achieving overall polarization reduction of the battery.

[0045] In an embodiment of the present application, after charging the battery with the first current and the second current in turn, the battery is further charged with a third current, wherein the current value of the second current is less than the current value of the third current, and the third current is greater than 1C. By applying the third current after the second current in the embodiments of the present application, the current value of the second current is less than the current value of the third current, which can further optimize the charging strategy and shorten the charging time, reduce the polarization reaction of the battery, and improve the service life of the battery.

[0046] In an embodiment of the present application, the current value of the second current is less than the current value of the third current, which includes the following cases: 1. When the second current is a constant current, the current value of the second current at any time is less than the current value of the third current at any time. 2. When the second current is a dynamic current, the current value of the third current at any time is greater than the minimum current value in the second current. In the above two cases, the third current can be a constant current or a dynamic current.

[0047] In an embodiment of the present application, the second current further includes a rising current segment, the end current value of the rising current segment is less than the end current value of the third current, and the slope of the rising current segment is not 0.

[0048] In the embodiments of the present application, considering the hardware of the charging device such as the charging pile and the charging safety, the current will not directly jump from a larger current to a smaller current, for example, from the first current directly to the second current, or from the second current directly to the third current, so in the embodiments of the present application, the second current can include a falling current segment and a rising current segment. The falling current segment is from the first current to the second current, and the starting current value of the falling current segment is less than the ending current value of the first current. The rising current segment is from the second current to the third current, and the ending current value of the rising current segment is less than the starting current value of the third current. The slope of the falling current segment from the first current to the second current and the slope of the rising current segment from the second current to the third current can be a preset slope, and the slope is not 0. In some examples, the slopes of the falling current segment and the rising current segment of the second current can be values set according to relevant parameters of the charging device, the battery, etc. In addition, in the above embodiments, the ending current value of the falling current segment is equal to the starting current value of the rising current segment.

[0049] The charging time of the rising current segment is greater than the charging time of the falling current segment, which can further reduce the polarization of the battery and improve the charging efficiency and the service life of the battery.

[0050] Further, in the present example, the slopes of the rising current segment and the falling current segment can be average slopes, that is, the slopes after connecting the starting current value and the ending current value of the corresponding current segment. The starting current value and the ending current value of the corresponding current segment can also be determined by judging whether they are at the same time. If they are at the same time, the slope is 0, and if they are not at the same time, the slope is not 0. The corresponding current segment refers to one of the rising current segment and the falling current segment.

[0051] In addition, the charging time of the falling current segment can be the time length between the time corresponding to the boundary point of the first current and the second current and the time when the second current first appears the minimum current value (or the trough value), and the slope of the falling current segment can also be determined according to the current between the above time lengths. Similarly, the charging time of the rising current segment can be determined according to the time length between the time when the second current last appears the minimum current value (or the trough value) and the time corresponding to the boundary point of the second current and the third current, and the slope of the rising current segment can also be determined according to the current between the above time lengths.

[0052] In an embodiment of the present application, the second current comprises a falling current segment, a transition current segment and a rising current segment in sequence, the starting current value of the transition current segment is equal to the ending current value of the falling current segment, the ending current value of the transition current segment is equal to the starting current value of the rising current segment, and the current value of the transition current segment at any time is less than the maximum current value in the falling current segment and the rising current segment. The charging duration of the transition current segment is greater than the charging duration of the rising current segment and the charging duration of the falling current segment.

[0053] In the above embodiment, the charging duration of the falling current segment can be the duration between the time corresponding to the demarcation point of the first current and the second current and the time when the second current first appears the minimum current value (or the trough value), and the slope of the falling current segment can also be determined according to the current between the above durations. Similarly, the charging duration of the rising current segment can be determined according to the duration between the time when the second current last appears the minimum current value (or the trough value) and the time corresponding to the demarcation point of the second current and the third current, and the slope of the rising current segment can also be determined according to the current between the above durations. The transition current segment is the charging current segment between the falling current segment and the rising current segment, so the charging duration of the transition current segment can be determined according to the duration between the time corresponding to the demarcation point of the second current and the time when the second current first appears the minimum current value (or the trough value) to the time when the second current last appears the minimum current value (or the trough value).

[0054] In an embodiment of the present application, the second current comprises a falling current segment, a transition current segment and a rising current segment in sequence, the transition current segment is the current segment between the falling current segment and the rising current segment of the second current, and the current of the transition current segment can cause the negative electrode surface active material of the battery to discharge to the side of the current collector. Specifically, the transition current segment has a balanced thickness direction state of charge, balances the distribution of the active material, promotes the discharge of the active material to the side of the current collector, and thus reduces the effect of negative polarization. In addition, the charging duration of the rising current segment of the second current and the charging duration of the falling current segment depend on the ability of the charging pile to reduce current and to rise current. Generally, the longer the charging duration of the transition current segment of the second current compared to the charging duration of the rising current segment and the charging duration of the falling current segment, the better the effect of reducing polarization. Therefore, the charging duration of the transition current segment of the second current is greater than the charging duration of the rising current segment, and the charging duration of the rising current segment is greater than the charging duration of the falling current segment.

[0055] In a specific embodiment, the functional relationship of the rising current segment satisfies one of the following: I n =a×t n +b; I n =A×B C×t +D;

[0056] And / or, the functional relationship of the falling current segment satisfies one of the following: In = a x t n + b; I n = A x B C×t + D.

[0057] wherein, I n is the current from the first current to the second current, or from the second current to the third current, t n is the charging time of each charging strategy, C is the charging rate, t is the overall charging time of the battery, and a, b, A, B, and D are preset coefficients. Specifically, a, b, A, B, and D can be positive or negative real numbers, or zero, and the specific values can be determined according to the actual design of the battery cell.

[0058] Specifically, battery polarization refers to the phenomenon that the internal potential of the battery differs from the external measured potential due to the nonlinear characteristics of electrochemical reactions and the existence of internal impedance during the charging and discharging process. If a larger current is used for charging the battery, the battery polarization will be further increased. Therefore, the embodiments of the present application add a second current to charge the battery on the basis of originally charging the battery in turn according to the first current and the third current. Since the current value of the second current is smaller than the current value of the first current and the current value of the third current, the smaller current can reduce the rate of electrochemical reactions inside the battery, thereby reducing the degree of battery polarization, and further improving the battery life.

[0059] In some specific embodiments, the battery can be a lithium ion battery. The lithium ion battery is widely used in energy storage and electric vehicles and other fields due to its high energy density, high average output voltage, large output power, small self-discharge, superior cycle performance, fast charge and discharge, wide operating temperature range, and long service life. Of course, the battery can also be other types of batteries. The following will mainly take the lithium ion battery as an example for illustration, but it should not be understood as a limitation of the embodiments of the present application.

[0060] Wherein, the charging duration is the main obstacle restricting the further development of lithium ion batteries, therefore, lithium ion battery manufacturers are actively developing super-fast charging capability of the battery from the battery design and battery management. Specifically, one of the key factors limiting the fast charging of lithium ion batteries is that the negative electrode is prone to deposit lithium metal on the surface during fast charging, the deposited lithium metal reacts with the electrolyte of the lithium ion battery on the one hand, consuming the active lithium of the positive electrode, on the other hand, the lithium metal continues to grow and easily pierces the separator of the lithium ion battery, causing serious safety problems. In order to solve the problem of lithium metal deposition, the current market through self-heating method, heating the battery of the lithium ion battery to a high temperature (usually heated to 45-60℃ (Celsius)), improve the kinetics of lithium ion battery charging and discharging, reduce the risk of lithium metal deposition of the positive electrode of the lithium ion battery, however, the lithium ion battery under high temperature conditions will exist the problem of increasing side reaction and lithium ion battery life attenuation.

[0061] In a specific implementation, the lithium ion battery includes a positive electrode and a negative electrode, and the charging pile and other charging equipment can charge the lithium ion battery through the positive electrode and the negative electrode of the lithium ion battery. Specifically, the positive active material of the positive electrode of the lithium ion battery can include but is not limited to any one or combination of lithium iron phosphate (LiFePO4), NCM (Nickel-Cobalt-Manganese, nickel-cobalt-manganese) ternary positive electrode material, lithium manganate, and lithium-rich manganese-based. The negative active material of the negative electrode of the lithium ion battery can include but is not limited to any one or combination of graphite, silicon, and lithium titanate. A current collector is usually covered on the negative electrode of the lithium ion battery, and the material of the current collector is usually a metal foil, such as a copper foil. The current collector provides a conductive substrate, so that the negative active material of the lithium ion battery can effectively conduct current.

[0062] During the charging process of the lithium ion battery, especially during the charging process using a large charging current, lithium ions are deposited on the positive electrode of the lithium ion battery, and the deposited lithium ions are reduced to lithium metal on the negative electrode of the lithium ion battery, thereby depositing lithium metal on the negative electrode of the lithium ion battery. Due to the large charging current, the current density of lithium insertion on the surface of the negative electrode of the lithium ion battery is high, and it is easy to reach the saturation of lithium insertion. At this time, the deposited lithium metal reacts with the electrolyte of the lithium ion battery on the one hand, consuming the active lithium of the positive electrode, on the other hand, the lithium metal continues to grow and easily pierces the separator of the lithium ion battery, causing serious safety problems.

[0063] In the process of determining the first current based on the charging strategy of each segment and charging the lithium ion battery through the charging device, the second current with a shorter time and smaller than the first current and the third current can be applied to balance the state of charge in the thickness direction of the negative electrode of the lithium ion battery, thereby reducing the saturation of lithium metal on the surface of the negative electrode of the lithium ion battery, reducing the risk of lithium metal deposition, and achieving better fast charging capability.

[0064] In the practical application of the present application, when the lithium ion battery is charged using the second current which is not 0, the positive and negative active materials of the battery will undergo electrochemical reactions. Due to the large current value of the first current, the active material reaction of the battery negative electrode in the thickness direction is not uniform, and the reaction rate far from the current collector side is higher than that close to the current collector side, resulting in a higher state of charge far from the current collector side. Since the current value of the second current is smaller than that of the first current, and in practice, the reduction of current helps to improve the uniformity of the negative electrode in the thickness direction, at this time, the area far from the current collector side with higher state of charge no longer undergoes positive lithium intercalation reaction, but negative discharge reaction. Therefore, the second current applied after the first current can promote the discharge of the battery negative electrode active material from the side far from the current collector to the current collector side, which can reduce the concentration polarization in the thickness direction and achieve the reduction of the overall polarization of the battery.

[0065] In addition, when charging using the second current which is not 0, the consumption rate of the reactant on the surface of the battery negative electrode is reduced, so that the reactant close to the current collector side can be replenished in time, thereby reducing the concentration polarization. The battery negative electrode active material discharges from the side far from the current collector to the current collector side, so that the battery negative electrode active material has a more uniform state of charge and current density distribution in the thickness direction, improves the uniformity of the active material reaction in the negative electrode thickness direction, and further reduces the concentration polarization.

[0066] Therefore, the charging method provided by the embodiments of the present application inserts the second current between the first current and the third current, and the current value of the second current is smaller than that of the first current and the third current. The second current can promote the discharge of the battery negative electrode sheet close to the surface of the separator to the current collector side, reduce the polarization of the battery, and thus ensure the service life of the battery.

[0067] In an embodiment of the present application, the charging method comprises: N charging stages, N≥2 and is an integer; wherein each charging stage comprises: charging the battery in turn according to the first current and the second current, the current value of the second current is smaller than that of the first current, the charging time according to the first current is≥30s, and the current value of the second current is greater than 0;

[0068] The current value of the second current of the N-1th charging stage is smaller than the current value of the first current of the Nth charging stage.

[0069] Exemplarily, the charging scheme can at least include a step charging scheme (step fast charging scheme) and a constant current charging scheme (constant current fast charging scheme). Specifically, the step charging scheme (I1→I2→I3→...→In) is a charging scheme that gradually adjusts the charging current, and the charging process of the battery can be divided into several charging stages (i.e., a multi-stage charging strategy). For example, in a step charging scheme, the charging stages can be divided into a constant current fast charging stage, a constant current decreasing charging stage, a constant voltage charging stage, a floating charging stage, and a temperature monitoring stage, and each charging stage uses a different current T. The current value of the current T of each charging stage can be from I1→I2→I3→...→In, where I1≥I2≥I3≥...≥In, that is, the charging current of the step charging scheme starts from a larger charging current, and then gradually reduces the charging current as the battery voltage rises during the charging process, which can avoid overcharging of the battery and reduce battery heating. The constant current charging scheme refers to keeping the charging current unchanged during the entire charging process of the battery. It should be noted that the constant current charging scheme can be divided into a multi-stage charging strategy according to time or other ways, where the current value of the current of each stage is the same.

[0070] wherein the current value of the first current and the current value of the third current can be correspondingly set according to the current value corresponding to each charging strategy in the charging scheme of the battery. Illustratively, in the embodiments of the present application, if the charging scheme of the battery is a step charging scheme, the current value of the first current can be I1 and the current value of the third current can be I2 in the constant current fast charging stage, the current value of the first current can be I2 and the current value of the third current can be I3 in the constant current decreasing charging stage, and so on. If the charging scheme of the battery is a constant current charging scheme, the current value of the first current and the current value of the third current can be the same.

[0071] In the embodiments of the present application, when charging the battery, the battery is charged according to the charging order, i.e., the N charging stages corresponding to the step charging scheme or the constant current charging scheme, respectively, N≥2 and is an integer. When entering the current charging stage (the Nth charging stage), the battery can be first charged according to the first current, and then charged according to the second current, wherein the current value of the second current is less than the current value of the first current and the current value of the second current is greater than 0, and the first current in the next charging stage is taken as the third current. Therefore, the current value of the second current is less than the current value of the first current in the next charging stage. After completing the charging of the current charging stage, the next charging stage is entered according to the charging order, until the charging of the battery is completed.

[0072] The third current of the N-1th charging stage can be the first current of the Nth stage. That is, in the Nth charging stage, the current value of the first current is greater than the current value of the second current in the N-1th charging stage, and less than the current value of the first current in the N-1th charging stage. The charging time of the first current is greater than or equal to 30 seconds, that is, the charging time of the third current is greater than or equal to 30 seconds.

[0073] In an embodiment of the present application, when the first current and the second current are both constant currents, the starting current value and the terminal current value of the first current are equal to the current value at any time of the first current, and the starting current value and the terminal current value of the second current are equal to the current value at any time of the second current. Therefore, the charging stages are divided according to the starting current value of the first current, and each charging stage sequentially includes the first current and the second current.

[0074] In some embodiments, the current waveform of the first current and the second current can be a curve waveform. A target current value is set in each charging stage. In the case that the current value of the charging current in the charging stage is less than the target current value, the charging current is the second current, otherwise it is the first current, wherein the target current value can be determined according to the actual demand, for example, it can be determined according to the charging current in the charging stage. Further, in an embodiment, the target current value can be determined according to the current value corresponding to the trough of the charging current (wherein if the charging current has multiple troughs with different current values, the trough with the minimum current value is used as the reference), in other embodiments, when the charging time of the first current defined according to the current value corresponding to the trough of the charging current is less than 30 seconds, the current value at the moment when the charging time of the charging current is equal to 30 seconds can be used as the target current value. Of course, the target current value defined based on the above rules needs to ensure that after the target current value is determined, the charging current in the stage can be divided into A current curve and B current curve, the charging process B current curve is after the A current curve, and the current value at any moment of the A charging curve is greater than the current value at any moment of the B current curve.

[0075] Specifically, taking FIG. 6 as an example, in the charging stage, the waveform of the current I1 and the waveform of the current i1 are both curve waveforms. It should be noted that the waveform of the current I1 and the waveform of the current i1 can be a sine wave, a triangular wave or other curve waveforms, and are not limited to the waveforms shown in FIG. 6.

[0076] The battery is charged according to the charging current, and a first charging phase starts from a starting time. In the first charging phase, the current value corresponding to the trough of the charging current is I1-min, that is, the target current value is I1-min. Therefore, in the first charging phase, the current waveform with a current value greater than I1-min is a current I1 waveform, and the current waveform with a current value less than I1-min is a current i1 waveform. The boundary point of the current I1 and the current i1 can be set as an N1 point, and the time corresponding to the N1 point is t-N1. Therefore, the charging current before t-N1 (that is, the charging current between t-N0 and t-N1) can be set as the first current of the first charging phase, that is, the current I1. In addition, the current value corresponding to the trough of the charging current is I1-min, that is, the target current value is I1-min. The boundary point N2 between the first charging phase and the second charging phase can also be determined, and the time corresponding to the N2 point is t-N2. The second charging phase is the charging phase after the first charging phase. Therefore, the charging current between t-N1 and t-N2 can be set as the second current of the first charging phase, that is, the current i1. The charging current after t-N2 can be set as the first current of the second charging phase, that is, the current I2. Similarly, the boundary points between the first current and the second current of the Nth charging phase and the boundary points between the second current of the (N-1)th charging phase and the first current of the Nth charging phase are determined according to the above embodiment.

[0077] In addition, if the first current charging duration divided by N1 is less than 30s in the above embodiment, the charging duration can be extended, for example, in FIG. 4, the first current and the second current are divided by the N1' point as the boundary point. The division method is consistent with the above method, and will not be described in detail here. Similarly, the boundary points between the first current and the second current of the Nth charging phase and the boundary points between the second current of the (N-1)th charging phase and the first current of the Nth charging phase are determined according to the above embodiment.

[0078] Further, in other embodiments of the present application, the first current and the second current can also be periodic currents, for example: the first current and the second current are sine currents, triangular wave currents or square wave currents. In an embodiment of the present application, the charging method comprises: the charging method comprises: N charging phases, N≥2 and is an integer; each charging phase comprises: charging the battery according to the first current, charging the battery according to the second current, at least one first period and a second period are set for each charging phase, and the second period is after the at least one first period, each charging phase comprises:

[0079] The battery is charged with a first current in a first time period and charged with a second current in a second time period, wherein the second current of the N-1th charging stage has a current value less than the first current of the Nth charging stage.

[0080] The battery is charged with a first current in a first time period and charged with a second current in a second time period, wherein the second current of the N-1th charging stage has a current value less than the first current of the Nth charging stage.

[0081] In the embodiments of the present application, each charging stage is also provided with a time period corresponding to the first current and the second current, i.e., a charging duration. When charging the battery in each charging stage, the battery is charged with the first current in the first time period corresponding to the charging stage, and then charged with the second current in the second time period corresponding to the charging stage. Then, the next charging stage is entered according to the charging sequence, until the charging of the battery is completed. The first time period corresponding to each charging stage is the first time period, and the last time period corresponding to each charging strategy is the second time period.

[0082] The first time period can be one or multiple. When the first time period is multiple, the second time period is also multiple. The multiple first time periods can be spaced apart according to a preset condition (for example, a preset time interval). Correspondingly, the second time period is after the corresponding first time period.

[0083] It should be noted that the time period (i.e., the first time period and the second time period) can be pre-set as a fixed value, or dynamically determined according to the battery, the charging device, the surrounding environment and other factors. The embodiments of the present application do not need to be limited in this regard.

[0084] Further, in the above embodiment, in one charging stage, when the first current is a dynamic current, for example, the first current is a sine current, a triangular wave current or a square wave current. When the first current includes a plurality of time periods in turn, the corresponding time periods can be divided according to a preset rule. The preset rule can be determined according to actual needs. Further, in an embodiment of the present application, taking the first current including a plurality of sine currents with different amplitudes as an example, if the first current includes a plurality of sine currents with different amplitudes, a plurality of first current charging time periods can be divided by the trough values of each sine current. For example, the first current charges the battery, and three sine currents appear in turn in the entire charging process. The time points at which the trough values of the three sine currents match are time point A, time point B and time point C. Therefore, the charging stage includes the following three first time periods: a time period from the starting time point of the first current to time point A, a time period from time point A to time point B, and a time period from time point B to time point C.

[0085] In an embodiment of the present application, the second current further includes a rising current segment, an end current value of the rising current segment is less than an end current value of the third current, and a slope of the rising current segment is not 0. A charging time length of the rising current segment is greater than a charging time length of the falling current segment.

[0086] In an embodiment of the present application, an end current value of the rising current segment of the second current is less than an end current value of the third current, that is, the second current is less than the third current, and a slope of the rising current segment is a preset slope, and the slope of the rising current segment is not 0.

[0087] In an embodiment of the present application, the second current includes a falling current segment, a transition current segment and a rising current segment in turn, a start current value of the transition current segment is equal to an end current value of the falling current segment, and an end current value of the transition current segment is equal to a start current value of the rising current segment. A current value of the transition current segment at any time point is less than a maximum current value in the falling current segment and the rising current segment. A charging time length of the transition current segment is greater than a charging time length of the rising current segment and a charging time length of the falling current segment.

[0088] In an embodiment of the present application, the second current includes a falling current segment, a transition current segment and a rising current segment, and a current value of the transition current segment at any time point is less than a current value in the falling current segment and the rising current segment. A charging time length of the transition current segment is greater than a charging time length of the rising current segment, and a charging time length of the rising current segment is greater than a charging time length of the falling current segment. The transition current segment has a balanced thickness direction state of charge, thereby reducing the effect of negative polarization. The longer the charging time length of the transition current segment is compared with the charging time lengths of the rising current segment and the falling current segment, the better the effect of negative polarization is.

[0089] Further, in the examples of the present application, the slope of the rising current segment and the falling current segment can be an average slope, i.e., the slope of the line connecting the starting current value and the ending current value of the corresponding current segment, or can be determined by judging whether the starting current value and the ending current value of the corresponding current segment are at the same time, if at the same time, the slope is 0, if not at the same time, the slope is not 0. Wherein, the corresponding current segment refers to one of the rising current segment and the falling current segment.

[0090] In an embodiment of the present application, the first current is a constant current. In the embodiment of the present application, the first current corresponding to each charging stage can be a constant current. Specifically, the first current can be set as a constant current, i.e., the fast charging of the battery can be realized according to the constant current in the first time period. The charging method can apply the second current on the basis of the charging strategy of each constant current to realize the polarization reduction of the lithium ion battery.

[0091] In other embodiments, the first current can also be set as a current with varying current values, i.e., a non-constant current, and the current value of the first current can change with time. The corresponding relationship between the current value In of the first current and the time t can be In = A*BC*t + D, wherein a, b, A, B, C, and D can be positive or negative real numbers, or zero. The specific values of a, b, A, B, C, and D can be determined according to the actual design of the battery cell.

[0092] In other embodiments of the present application, the transition current segment of the second current segment can be a constant current.

[0093] In an embodiment of the present application, the ratio of the current value of the second current to the current value of the first current ranges from 0.1 to 0.9. Preferably, the ratio of the current value of the second current to the current value of the first current ranges from 0.5 to 0.7.

[0094] Specifically, the ratio is used to determine the current value of the second current applied to the battery on the basis of the first current applied to the battery by each charging strategy. The ratio range is generally [0.1-0.9], and the preferred ratio range can be [0.5-0.7].

[0095] In the above embodiments, if the second current is a dynamic current, the current value of the second current can be an average current value or a minimum current value. Specifically, if the second current is a sinusoidal current signal, the current value of the second current is the average current value of the sinusoidal current signal. If the second current is a triangular wave current signal, the current value of the second current is the minimum current value of the triangular wave. In addition, if the second current is a constant current, the current value of the second current is the actual current value.

[0096] In further, in the above embodiments, the current value of the first current is the current value at the first current end point, or the current value of the first current at the time when the first current is converted into the second current.

[0097] After the ratio is obtained, the current value of the first current and the ratio can be multiplied to obtain the current value of the second current, or the current value of the second current is obtained based on the ratio by weighting or the like, that is, the current value of the second current in, n = 1, 2, 3, 4, …, wherein the current value of the second current is less than the current value of the first current In, that is, in < In. Exemplarily, in = 0.1-0.9 * In, wherein n = 1, 2, 3, 4, ….

[0098] In an embodiment of the present application, the ratio is determined according to the battery parameter of the battery and / or the strategy parameter of each charging strategy.

[0099] Specifically, the battery parameter of the battery can at least include the negative electrode material area density, compaction, and temperature, and the like battery parameters; and the strategy parameter of the charging strategy can generally include the current of the charging and the time of the charging, and the like strategy parameters.

[0100] Wherein, if the charging strategy is a step charging scheme, the strategy parameter of the charging strategy can at least further include a charging rate (C), specifically, the charging rate refers to a measure of the charging rate of the battery, which is expressed as a multiple of the rated capacity of the battery, and the charging rate corresponding to each charging strategy can be set according to the type of the battery, the charging requirement, and the safety requirement, and the like, and generally the charging rate corresponding to each charging strategy is different. For example, in the constant current fast charging phase, a higher charging rate (such as 2C) can be used to quickly increase the battery power, and in the constant voltage charging phase, the charging rate can be reduced (such as 1C) to stabilize the battery voltage, so as to avoid the problems of overcharging and overheating of the battery.

[0101] In some embodiments of the present application, the ratio of the current value of the second current to the current value of the first current is in the range of [0.1-0.9]. Specifically, when the ratio of the current value of the second current to the current value of the first current is in the range of [0.1-0.9] and the charging method disclosed in the present application can further shorten the fast charging time, reduce the problem of battery polarization, and further improve the reduction speed of the battery capacity retention rate.

[0102] Further, in an embodiment of the present application, the ratio of the current value of the second current to the current value of the first current is in the range of [0.5-0.7]. Specifically, when the ratio of the current value of the second current to the current value of the first current is in the range of [0.5-0.7] and the charging method disclosed in the present application can further shorten the fast charging time, reduce the problem of battery polarization, and further improve the reduction speed of the battery capacity retention rate.

[0103] In the above embodiments, if the second current is a dynamic current, the current value of the second current can be an average current value or a minimum current value. Specifically, if the second current is a sinusoidal current signal, the current value of the second current is the average current value of the sinusoidal current signal. If the second current is a triangular wave current signal, the current value of the second current is the minimum current value of the triangular wave. In addition, if the second current is a constant current, the current value of the second current is the actual current value.

[0104] Further, in the above embodiments, the current value of the first current is the current value at the first current end point, or the current value of the first current at the time when the first current is converted into the second current, or the current value corresponding to the boundary point of the first current and the second current, which can be determined with reference to the foregoing part.

[0105] In addition, in the above embodiments, the ratio of the current value of the second current to the current value of the first current can be determined according to the charge rate of the second current and the charge rate of the first current. Specifically, since the charge rate of the battery is equal to the current / battery capacity, when the battery capacity is consistent, the ratio of the current is equal to the ratio of the charge rate.

[0106] In an embodiment of the present application, the ratio of the current value of the second current to the current value of the first current is M, and M is negatively correlated with at least one of a battery tab parameter and a temperature of the battery, wherein the battery tab parameter includes at least one of the conductivity, the area density, the compactness density and the thickness of the battery tab. For example, the larger the parameter of the battery tab is, the smaller the value of M should be, so as to ensure the best SOC balancing effect, reduce the risk of lithium precipitation in the fast charging process, and prolong the service life of the battery.

[0107] Further, in an embodiment disclosed in the present application, the ratio of the current value of the second current to the current value of the first current is M, and the change amplitude of the negative correlation between M and the parameter of the negative electrode tab of the battery is greater than the change amplitude of the negative correlation between M and the parameter of the positive electrode tab of the battery. Specifically, since polarization and lithium precipitation mainly occur at the negative electrode tab of the battery, adjusting the positive and negative electrode tab parameters will have a greater change in the value of M than adjusting the positive electrode tab parameters, thereby shortening the fast charging time, reducing the risk of battery polarization, and thus prolonging the service life of the battery.

[0108] In an embodiment of the present application, the charging time range of charging the battery according to the second current is 1-20 seconds (s). Specifically, when the charging time range of charging the battery according to the second current is 1-20 s and the charging method disclosed in the present application can further shorten the fast charging time, reduce the problem of battery polarization, and thus improve the reduction speed of the battery capacity retention rate.

[0109] Preferably, the charging duration of charging the battery according to the second current ranges from 3 to 10 seconds. Specifically, when the charging duration of charging the battery according to the second current ranges from 3 to 10 seconds and the charging method disclosed in the present application can further shorten the fast charging time, reduce the problem of battery polarization, and thus improve the speed of reducing the battery capacity retention rate.

[0110] In the above embodiment, the charging duration of charging the battery according to the second current in the current charging stage can be determined according to the duration between the time point corresponding to the end current value of the first current in the current charging stage and the time point corresponding to the start current value of the first current in the next charging stage. Specifically, the charging duration of charging the battery according to the second current can be determined according to the demarcation point between the first current and the second current in the current charging stage and the demarcation point between the second current in the current charging stage and the first current in the next charging stage, for example, as shown in FIG. 6, the charging duration of charging the battery according to the second current is equal to the difference between the time point value corresponding to t-N2 and the time point value corresponding to t-N1. In an embodiment of the present application, the current value of the first current in the N-1th charging stage is greater than the current value of the first current in the Nth charging stage.

[0111] In an embodiment of the present application, the charging duration according to the first current is T1 and the charging duration according to the second current is T2, wherein T1 / T2≥5. Specifically, when the charging duration according to the first current is T1 and the charging duration according to the second current is T2, wherein T1 / T2≥5 and the charging method disclosed in the present application can further shorten the fast charging time, reduce the problem of battery polarization, and thus improve the speed of reducing the battery capacity retention rate.

[0112] In the above embodiment, the charging duration of charging the battery according to the first current in the current charging stage can be determined according to the duration between the time point corresponding to the start current value of the first current in the current charging stage and the time point corresponding to the end current value of the first current. Specifically, the charging duration of charging the battery according to the first current can be determined according to the demarcation point between the first current (or the initial charging time point) in the current charging stage and the second current in the previous charging stage and the demarcation point between the first current and the second current in the current charging stage, for example, as shown in FIG. 6, the charging duration of charging the battery according to the first current is equal to the difference between the time point value corresponding to t-N0 and the time point value corresponding to t-N1.

[0113] In the above embodiment, the charging time length of the battery in the current charging phase according to the second current can be determined according to the time length between the time point corresponding to the end current value of the first current in the current charging phase and the time point corresponding to the start current value of the first current in the next charging phase. Specifically, the charging time length of the battery according to the second current can be determined according to the demarcation point between the first current and the second current in the current charging phase and the demarcation point between the second current and the first current in the next charging phase, for example, as shown in FIG. 6, the charging time length of the battery according to the second current is equal to the difference between the time point corresponding to t-N2 and the time point corresponding to t-N1.

[0114] In the embodiment of the present application, according to the charging sequence, the current value of the first current corresponding to each charging phase gradually decreases, that is, the current value of the first current in the N-1th charging phase is greater than the current value of the first current in the Nth charging phase, that is, as the different charging phases are completed gradually, the current of the battery gradually fills up, and the current value of the first current gradually decreases. Using the first current with gradually decreasing current value to charge the battery can reduce the stress on the battery in the later charging stage, thereby prolonging the battery life.

[0115] In an embodiment of the present application, according to the charging sequence, the charging time corresponding to each charging phase gradually decreases.

[0116] In the embodiment of the present application, according to the charging sequence, the charging time corresponding to each charging phase gradually decreases, that is, as the different charging phases are completed gradually, the current of the battery gradually fills up, and the charging efficiency also gradually improves, and the charging time gradually decreases. Using the gradually decreasing charging time to charge the battery can complete the charging of the battery in a shorter time, thereby improving the overall charging efficiency of the battery.

[0117] In an embodiment of the present application, the charging time length of the second current is determined, and the battery is charged according to the current value of the second current according to the charging time length.

[0118] Optionally, the charging time length can be a preset charging time length, or can be determined according to the first current, the second current, the battery parameter of the battery, and / or the device parameter of the charging device used to charge the battery.

[0119] In the embodiment of the present application, the charging duration of the second current can be a preset charging duration, for example, the preset charging duration can be 1 second, 1.5 seconds, 3 seconds, 4 seconds, 6 seconds, etc. After switching from the first current to the second current, the battery is charged using the second current for a preset charging duration. If the current charging strategy is not completed, the battery can continue to be charged using the first current. If the current charging strategy has been completed, the battery can be charged using the third current, i.e., the first current in the next charging strategy.

[0120] Of course, the charging duration of the second current can be determined according to the first current, the second current, the battery parameters of the battery, and / or the device parameters of the charging device used to charge the battery, etc. Specifically, the device parameters of the charging device can include a controllable current range, which refers to the maximum and minimum charging currents that the charging device can safely provide. For example, assuming that the controllable current range of the charging device is 1A / s-500A / s (ampere / second), 1A is the minimum controllable current of the charging pile, and 500A is the maximum controllable current of the charging pile.

[0121] In the embodiment of the present application, in order to avoid the time of the applied second current being too long to affect the battery charging efficiency, a preset drop limit time is set in advance, i.e., the maximum time for reducing the charging current of the battery from the first current to the second current. In this way, it can be avoided that the time for charging the battery using the second current is too short to achieve the purpose of improving the battery polarization of the battery, and at the same time, it can be avoided that the battery charging efficiency is affected. Therefore, in the embodiment of the present application, the charging duration of the second current can be determined based on the current difference between the first current and the second current, and the minimum controllable current of the charging pile and the preset drop limit time. In determining the charging duration of the second current, the charging current of the battery can be reduced from the first current to the second current within the charging duration of the second current, so that the battery is charged using the second current.

[0122] In an embodiment of the present application, the waveform of the second current includes at least any one or combination of a square wave, a triangular wave, a sine wave, and a cosine wave. Of course, the waveform of the pulse charging current in the embodiment of the present application is not limited to the above waveforms and combinations, and can be selected as needed. The embodiment of the present application does not need to be limited in this regard. Taking a lithium ion battery as an example:

[0123] Referring to FIG. 2, it is a charging diagram of a second current of a triangular wave provided in the embodiment of the application, wherein the dashed line represents a step charging scheme, based on which a first current (I1→I2→I3→...→In) of the lithium ion battery can be determined, and the solid line represents an improved charging strategy of the embodiment of the application, based on which a second current (i1→i2→i3→...→in) can be applied on the basis of the corresponding charging current (the first current) of each segment of the step charging scheme, specifically, after the lithium ion battery is charged by the first current, the charging current of the lithium ion battery is decreased from the first current In to the second current in with a triangular wave.

[0124] Referring to FIG. 3, it is a charging diagram of a second current of a sine wave provided in the embodiment of the application, wherein the dashed line represents a step charging scheme, based on which a first current (I1→I2→I3→...→In) of the lithium ion battery can be determined, and the solid line represents an improved charging strategy of the embodiment of the application, based on which a second current (i1→i2→i3→...→in) can be applied on the basis of the corresponding charging current (the first current) of each segment of the step charging scheme, specifically, after the lithium ion battery is charged by the first current, the charging current of the lithium ion battery is decreased from the first current In to the second current in with a triangular wave. Wherein the second current is a half-period sine wave current, and the second current: i pulse = sin(t), wherein t is a pulse time (charging duration), and the value range is 1-20S (seconds).

[0125] Referring to FIG. 4, it is a charging diagram of a second current of a square wave + sine wave provided in the embodiment of the application, wherein the dashed line represents a step charging scheme, based on which a charging current (I1→I2→I3→...→In) of the lithium ion battery can be determined, and the solid line represents an improved charging strategy of the embodiment of the application, based on which a second current (i1→i2→i3→...→in) can be applied on the basis of the corresponding charging current (the first current) of each segment of the step charging scheme, specifically, after the lithium ion battery is charged by the first current, the charging current of the lithium ion battery is decreased from the first current In to the second current in with a square wave + sine wave. Wherein the second current is a half-period sine wave current + square wave current, and the sine wave current in the second current: i pulse = sin(t), wherein t is a pulse time, and the value range is 1-20S (seconds).

[0126] Referring to FIG. 5, it is a charging diagram of a second current of a triangular wave + sine wave according to an embodiment of the present application. The dashed line represents a step charging scheme, based on which the charging current (I1→I2→I3→...→In) of the lithium ion battery can be determined. The solid line represents the improved charging strategy according to the embodiment of the present application. Based on the charging current (first current) corresponding to the step of the step charging scheme, the second current (i1→i2→i3→...→in) can be applied. Specifically, after the first current completes charging the lithium ion battery, the charging current of the lithium ion battery is reduced from the first current In to the second current in with a waveform of a triangular wave + sine wave. The second current is a half-period triangular wave current + sine wave current, wherein the sine wave current in the second current is i pulse = sin(t), wherein t is the pulse time, and the value range is 1-20 seconds.

[0127] It should be noted that, compared with the step charging scheme (I1→I2→I3→...→In), the improved charging strategy according to the embodiment of the present application can improve the negative thickness direction non-uniformity of the lithium ion battery and reduce the polarization of the lithium ion battery by adding a second current in with a shorter time and a smaller value. Therefore, when the negative voltage of the lithium ion battery is used as the cutoff condition, a longer charging time can be obtained after charging by applying the second current, that is, the charging time of the next segment charging strategy In+1 can be extended, tn+1>t’n+1, wherein t’n+1 represents the charging time corresponding to the original next segment charging strategy, and tn+1 represents the charging time corresponding to the extended next segment charging strategy. In practical applications, extending the charging time of the next segment charging strategy can provide sufficient time for the lithium ion battery to absorb and stabilize the charge, avoid energy loss caused by too fast charging rate, and thus better achieve the charging of the battery. The extended charging time (tn+1-t’n+1) is determined by reaching the same cutoff condition, for example, the negative voltage of the lithium ion battery.

[0128] In order for those skilled in the art to better understand the embodiments of the present application, the following specific examples are used for illustration.

[0129] The lithium iron phosphate battery and the ternary lithium battery can be used as the battery participating in the experiment, and the fast charging time and the life attenuation of different charging strategies are compared as the technical effect to determine the preferred embodiment of the charging strategy.

[0130] The following is a specific test scheme. The battery of the experimental object is a lithium iron phosphate LiFePO4 / NCM ternary positive electrode material as the positive electrode material and graphite as the negative electrode material. The battery participating in the test is placed in a 25℃ environment and subjected to the following charging and discharging test.

[0131] In embodiment 1, the experimental method of battery fast charging includes: charging a battery with a chemical system of lithium iron phosphate LiFePO4 and a capacity of 100 AH at a large current I1 of 7C for 100s, and then charging at a small current I2 of 3.5C (i.e. the current value of the small current is 0.5 times the current value of the large current) for 1s; then charging at a large current I1 of 6.5C for 100s, and then charging at a small current I2 of 3.25C for 1s; then charging at a large current I1 of 6C for 100s, and then charging at a small current I2 of 3C for 1s, and so on (i.e. the current value of each large current is equal to the current value of the previous large current-0.5C, and the current value of the small current is 0.5 times the current value of the previous large current) until the battery is charged from 10% SOC to 80% SOC, and then stopped, and the time in the SOC interval is calculated, which is the fast charging time.

[0132] Cycle life test: charge according to the above charging method, and then discharge at a discharge current of 0.33C when the charge is 80% SOC, until the battery voltage reaches 2.0V. Repeat the above charging steps until the cycle number is greater than 500 / 1000 times (or the capacity retention rate of the battery is less than 80%), and calculate the capacity retention rate of the battery at the same time.

[0133] The capacity retention rate is calculated as follows: the capacity of the battery before testing is Q0 (in addition, the battery capacity Q0 can also be the nominal capacity of the battery), then the battery is charged from 10% SOC to 80% SOC based on the above charging method, and then discharged to 10% SOC at a discharge rate of 1 / 3C, and then cycled 500 times, and then the battery is tested at a rate of 1 / 3C after 500 cycles (capacity calibration), and the calibrated capacity is Q500, and the calibrated capacity after 1000 cycles is Q1000. The capacity retention rate of the 500th cycle is Q500 / Q0*100%, and the capacity retention rate of the 1000th cycle is Q1000 / Q0*100%.

[0134] Embodiments 2-42 and comparative examples 1-20 all perform charging and discharging tests on lithium iron phosphate batteries according to the steps of embodiment 1, wherein the difference lies in the charging rate of the large current (i.e. I1), the ratio between the charging rate of the small current (i.e. I2) and the charging rate of the large current, the charging time of the large current, the charging time of the small current, and the ratio between the charging time of the large current and the charging time of the small current. The following table (experimental data of lithium iron phosphate batteries) can be obtained, in which K1 can represent the ratio between the charging rate of the second current and the charging rate of the first current, T2 can represent the charging time of the second current, K2 can represent the ratio between the charging time of the first current and the charging time of the second current, and T1 can represent the charging time of the first current.

[0135] In Table 2, Examples 1-42 and Comparative Examples 1-20 are all subjected to charge-discharge test on the battery with NCM ternary system and capacity of 130 AH according to the procedure of Example 1 in Table 1 above, wherein the difference lies in the charge rate of the large current (i.e. I1) and the ratio between the charge rate of the small current (i.e. I2) and the charge rate of the large current, the charge time of the large current, the charge time of the small current and the charge time of the large current and the charge time of the small current are different. The following Table 2 (experimental data of ternary lithium battery) can be obtained. In Table 2, K3 can represent the ratio of the charge rate of the second current to the charge rate of the first current, T4 can represent the charge time of the second current, K4 can represent the ratio of the charge time of the first current to the charge time of the second current, and T3 can represent the charge time of the first current.

[0136] Table 1:

[0137] Table 2:

[0138] Referring to Table 1 and Table 2, it can be known from the comparison between Examples 1-16, 21-33 and Comparative Examples 12, 14, 16, 18-20 that, compared with charging according to the first current, then standing and then charging according to the first current, sequentially charging the battery according to the first current and the second current, wherein the current value of the second current is less than the current value of the first current and the current value of the second current is greater than 0, can improve the fast charging time, reduce the problem of battery polarization and further improve the reduction speed of the battery capacity retention rate. In addition, no matter 2C, 3C, or 4C or above, the charging method disclosed in the present application can shorten the fast charging time, reduce the problem of battery polarization and further improve the reduction speed of the battery capacity retention rate.

[0139] It can be known from the comparison between Examples 1-16, 21-33 and Comparative Examples 11, 13, 15, 17 that, compared with charging according to the first current, the charging method disclosed in the present application, i.e. sequentially charging the battery according to the first current and the second current, wherein the current value of the second current is less than the current value of the first current and the current value of the second current is greater than 0, can shorten the fast charging time, reduce the problem of battery polarization and further improve the reduction speed of the battery capacity retention rate. In addition, no matter 2C, 3C, or 4C or above, the charging method disclosed in the present application can shorten the fast charging time, reduce the problem of battery polarization and further improve the reduction speed of the battery capacity retention rate.

[0140] In the embodiments disclosed in the present application, the first current is greater than 1C, specifically, as can be seen from Comparative Examples 9 and 10, when the battery is charged at a first current of 1C, whether the battery is charged according to the charging method disclosed in the present application or directly charged by the first current, the charging time and capacity retention rate of the battery are not much different, and if the battery is charged at a first current of 1C, the fast charging time cannot be shortened, and the problem of battery polarization cannot be reduced to improve the speed of reduction of battery capacity retention rate. As can be seen from Example 12 and Comparative Example 13, when the first current of the battery is greater than 1C, the fast charging time can be shortened, and the problem of battery polarization can be reduced to improve the speed of reduction of battery capacity retention rate.

[0141] In the embodiments disclosed in the present application, the charging time of the first current is ≥ 30s, specifically, as can be seen from Examples 5, 34-36 and Comparative Examples 1-8, when the current of the first current is greater than or equal to 30s or more, the charging method disclosed in the present application can shorten the fast charging time, and reduce the problem of battery polarization to improve the speed of reduction of battery capacity retention rate.

[0142] In an embodiment disclosed in the present application, the ratio of the current value of the second current to the current value of the first current ranges from [0.1-0.9], that is, the charging rate of the second current and the charging rate of the first current range from [0.1-0.9]. Specifically, as can be seen from Examples 11-16 and 28-29, when the ratio of the current value of the second current to the current value of the first current ranges from [0.1-0.9], and the charging method disclosed in the present application can further shorten the fast charging time, and reduce the problem of battery polarization to improve the speed of reduction of battery capacity retention rate.

[0143] Further, in the embodiments disclosed in the present application, the ratio of the current value of the second current to the current value of the first current ranges from [0.5-0.7], that is, the charging rate of the second current and the charging rate of the first current range from [0.5-0.7]. Specifically, as can be seen from Examples 11-16, when the ratio of the current value of the second current to the current value of the first current ranges from [0.5-0.7], and the charging method disclosed in the present application can further shorten the fast charging time, and reduce the problem of battery polarization to improve the speed of reduction of battery capacity retention rate.

[0144] In an embodiment disclosed in the present application, the charging time of the second current ranges from [1s-20s]. Specifically, as can be seen from Examples 1-8, when the charging time of the second current ranges from [1s-20s], and the charging method disclosed in the present application can further shorten the fast charging time, and reduce the problem of battery polarization to improve the speed of reduction of battery capacity retention rate.

[0145] In further, the charging time of the second current is in the range of [3s-10s]. Specifically, from the comparison of embodiments 1-8, when the charging time of the second current is in the range of [3s-10s], and the charging method disclosed in the present application can further shorten the fast charging time, and reduce the problem of battery polarization, thereby improving the speed of reducing the battery capacity retention rate.

[0146] In addition, from the comparison between embodiments 1-16, 25-33, when the ratio of the current value of the second current to the current value of the first current is in the range of [0.1-0.9] and the charging time of the second current is in the range of [1s-20s], and the charging method disclosed in the present application can effectively shorten the fast charging time, and reduce the problem of battery polarization, thereby improving the speed of reducing the battery capacity retention rate.

[0147] In an embodiment disclosed in the present application, the current value of the first current of the N-1 charging stage is greater than the current value of the first current of the N charging stage. Specifically, from the comparison of embodiments 3 / 7 / 11 / 13 / 16 and embodiments 17-24, compared with direct charging according to the first current, when the current value of the first current of the N-1 charging stage is greater than the current value of the first current of the N charging stage, the fast charging time can be further shortened, and the problem of battery polarization can be reduced, thereby improving the speed of reducing the battery capacity retention rate.

[0148] In an embodiment disclosed in the present application, the ratio of the charging time according to the first current to the charging time according to the second current is ≥5. Specifically, from embodiments 37-42, when the ratio of the charging time according to the first current to the charging time according to the second current is ≥5 and the charging method disclosed in the present application can further shorten the fast charging time, and reduce the problem of battery polarization, thereby improving the speed of reducing the battery capacity retention rate.

[0149] In addition, from the above description, for the embodiments in Table 1 and Table 2, the above relationship is satisfied, so it is known that whether it is an LFP system battery or a ternary system battery, the charging method disclosed in the present application can effectively shorten the fast charging time, and reduce the problem of battery polarization, thereby improving the speed of reducing the battery capacity retention rate. In further, for other system batteries (such as sodium ion batteries, solid state batteries, etc.), the charging method disclosed in the present application can also effectively shorten the fast charging time, and reduce the problem of battery polarization, thereby improving the speed of reducing the battery capacity retention rate.

[0150] The charging method provided by the embodiments of the present application can be applied to all conventional fast charging strategies of I1≥I2≥I3≥...≥In, and In can be selected according to the actual charging capacity of the lithium ion battery, that is, it is applicable to all charging rates within the safe charging current of the product.

[0151] Referring to FIG. 7, the battery management system 20 and the power utilization device 100 according to the embodiments of the present application include the electronic device or the charging device according to the embodiments of the present application. The power utilization device 100 can include the battery 10 and the battery management system 20 or the charging device according to the embodiments of the present application. The charging device includes, but is not limited to, an electric vehicle charging pile, a wireless charger, a mobile power supply, a charging cabinet, an energy storage cabinet, etc. The power utilization device 100 includes, but is not limited to, an electric vehicle, a household energy storage system, an uninterruptible power supply (UPS), a flywheel energy storage system, a pumped storage power station, etc.

[0152] The battery management system 20 and the power utilization device 100 according to the embodiments of the present application can charge the battery based on the charging method according to the embodiments of the present application, and the battery management system 20 and the power utilization device 100 include all technical effects of the charging method according to the embodiments of the present application, which are not described herein.

[0153] It should be noted that, for the method embodiments, in order to simply describe, they are all described as a combination of a series of actions, but those skilled in the art should know that the embodiments of the present application are not limited by the order of the actions described, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification all belong to preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present application.

[0154] Based on the charging method of the battery described above, the embodiments of the present application also disclose a charging device configured to sequentially charge the battery according to a first current and a second current, the current value of the second current being less than the current value of the first current, and the current value of the second current being greater than 0.

[0155] The second current includes a falling current segment, the starting current value of the falling current segment being less than the ending current value of the first current, and the slope of the falling current segment being not 0.

[0156] In an embodiment of the present application, after sequentially charging the battery according to the first current and the second current, the battery is further charged according to a third current, wherein the current value of the second current is less than the current value of the third current, and the third current is greater than 1C.

[0157] In an embodiment of the present application, the second current further includes a rising current segment, the ending current value of the rising current segment being less than the ending current value of the third current, and the slope of the rising current segment being not 0.

[0158] In an embodiment of the present application, the charging time length of the rising current segment is greater than the charging time length of the falling current segment.

[0159] In an embodiment of the present application, the second current comprises a falling current segment, a transition current segment and a rising current segment in sequence, the starting current value of the transition current segment is equal to the ending current value of the falling current segment, the ending current value of the transition current segment is equal to the starting current value of the rising current segment, and the current value of the transition current segment at any time is less than the maximum current value in the falling current segment and the rising current segment.

[0160] In an embodiment of the present application, the charging duration of the transition current segment is greater than the charging duration of the rising current segment and the charging duration of the falling current segment.

[0161] In an embodiment of the present application, the charging duration of the transition current segment is greater than the charging duration of the rising current segment, and the charging duration of the rising current segment is greater than the charging duration of the falling current segment.

[0162] In an embodiment of the present application, the charging method comprises N charging stages, N≥2 and is an integer; wherein each charging stage comprises: charging the battery in sequence according to a first current and a second current, the current value of the second current is less than the current value of the first current, the charging duration according to the first current is≥30s, and the current value of the second current is greater than 0.

[0163] The current value of the second current of the N-1th charging stage is less than the current value of the first current of the Nth charging stage.

[0164] In an embodiment of the present application, the charging method comprises N charging stages, N≥2 and is an integer; each charging stage comprises: charging the battery according to a first current and charging the battery according to a second current, at least one first time period and a second time period are set for each charging stage, and the second time period is after the at least one first time period, and each charging stage comprises:

[0165] charging the battery according to the first current in the first time period and charging the battery according to the second current in the second time period, wherein the current value of the second current of the N-1th charging stage is less than the current value of the first current of the Nth charging stage.

[0166] In an embodiment of the present application, the first time period corresponding to each charging strategy is the first time period, and the last time period corresponding to each charging strategy is the second time period.

[0167] In an embodiment of the present application, the second current further comprises a rising current segment, the ending current value of the rising current segment is less than the ending current value of the third current, and the slope of the rising current segment is not 0.

[0168] In an embodiment of the present application, the charging duration of the rising current segment is greater than the charging duration of the falling current segment.

[0169] In an embodiment of the present application, the second current comprises a falling current segment, a transition current segment and a rising current segment in sequence, the starting current value of the transition current segment is equal to the ending current value of the falling current segment, the ending current value of the transition current segment is equal to the starting current value of the rising current segment, and the current value of the transition current segment at any time is less than the maximum current value in the falling current segment and the rising current segment.

[0170] In an embodiment of the present application, the charging duration of the transition current segment is greater than the charging duration of the rising current segment and the charging duration of the falling current segment.

[0171] In an embodiment of the present application, the charging duration of the transition current segment is greater than the charging duration of the rising current segment, and the charging duration of the rising current segment is greater than the charging duration of the falling current segment.

[0172] In an embodiment of the present application, the first current is a constant current.

[0173] In an embodiment of the present application, the ratio of the current value of the second current to the current value of the first current ranges from 0.1 to 0.9.

[0174] In an embodiment of the present application, the ratio of the current value of the second current to the current value of the first current ranges from 0.5 to 0.7.

[0175] In an embodiment of the present application, the charging duration of the battery charged by the second current ranges from 1 to 20 seconds.

[0176] In an embodiment of the present application, the charging duration of the battery charged by the second current ranges from 3 to 10 seconds.

[0177] In an embodiment of the present application, the current value of the first current of the N-1th charging stage is greater than the current value of the first current of the Nth charging stage.

[0178] In an embodiment of the present application, the waveform of the second current comprises at least one of or a combination of a square wave, a triangular wave, a sine wave and a cosine wave.

[0179] In an embodiment of the present application, the waveform of the second current is selected to be adapted to the charging device for charging the battery.

[0180] In an embodiment of the present application, the current value of the first current is greater than or equal to 1C, and the charging duration of the first current is greater than or equal to 30s.

[0181] In an embodiment of the present application, the current value of the first current is less than or equal to the charging cutoff duration, the charging cutoff duration being a charging duration when the battery voltage reaches the battery cutoff voltage when the battery is charged according to the first current.

[0182] In an embodiment of the present application, the charging duration according to the first current is less than or equal to 250s.

[0183] In an embodiment of the present application, the current value of the first current is greater than or equal to 2C.

[0184] In an embodiment of the present application, the charging duration according to the first current is T1 and the charging duration according to the second current is T2, wherein T1 / T2≥5.

[0185] In an embodiment of the present application, the battery is a lithium ion battery.

[0186] In an embodiment of the present application, the functional relationship of the rising current section satisfies one of the following: I n =a×t n +b; I n =A×B C×t +D.

[0187] And / or, the functional relationship of the falling current section satisfies one of the following: I n =a×t n +b; I n =A×B C×t +D.

[0188] Wherein, I n is the current value from the first current to the second current, or from the second current to the third current, t n is the charging time of each charging strategy, C is the charging rate, t is the overall charging time, a, b, A, B, D are preset coefficients.

[0189] In an embodiment of the present application, the capacity of the battery is greater than or equal to 50AH.

[0190] In an embodiment of the present application, the ratio of the current value of the second current to the current value of the first current is M, and M is negatively correlated with at least one of the battery tab parameter and the temperature of the battery, wherein the battery tab parameter includes at least one of the conductivity, the area density, the compactness density and the thickness of the battery tab.

[0191] In an embodiment of the present application, the ratio of the current value of the second current to the current value of the first current is M, and the change amplitude of the negative correlation of M with the negative electrode tab parameter is greater than the change amplitude of the negative correlation of M with the positive electrode tab parameter.

[0192] For the above device embodiments, since they are basically similar to the method embodiments, they are described more simply, and the relevant parts refer to the part of the method embodiments.

[0193] In another embodiment provided by the present application, a computer readable storage medium is provided, which stores instructions, when running on a computer, causing the computer to perform the battery charging method in any of the above embodiments.

[0194] In another embodiment provided by the present application, a computer program product is provided, which contains instructions, when running on a computer, causing the computer to perform the battery charging method in any of the above embodiments.

[0195] In another aspect of the present application, a use electric device is provided, which comprises a battery and the above battery management system or the above charging device.

[0196] In another aspect of the present application, a battery management system is provided, which comprises the above electronic device or the above charging device.

[0197] In another aspect of the present application, a vehicle is provided, which comprises the above battery management system.

[0198] In the above embodiments, all or part of them can be realized by software, hardware, firmware or any combination thereof. When realized by software, all or part of them can be realized in the form of a computer program product. The computer program product comprises one or more computer instructions. When loaded and executed by a computer, all or part of them generate the processes or functions according to the embodiments of the present application. The computer can be a general-purpose computer, a special-purpose computer, a computer network or other programmable device. The computer instructions can be stored in a computer readable storage medium or transferred from one computer readable storage medium to another, for example, the computer instructions can be transferred from one website, computer, server or data center to another through wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.) mode. The computer readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. containing one or more available media sets. The available media can be magnetic media (such as floppy disk, hard disk, magnetic tape), optical media (such as DVD) or semiconductor media (such as solid state disk (SSD)) and the like.

[0199] It is to be noted that, as used in this document, the terminology "first", "second", etc. is merely used to differentiate one entity or action from another, and does not necessarily imply or require any actual relationship or order between or among the entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0200] Each of the embodiments in the present specification is described in a related manner, and the same or similar parts among the embodiments can be referred to each other. Each of the embodiments focuses on the difference from other embodiments. In particular, for the system embodiments, since they are basically similar to the method embodiments, they are described more simply, and the relevant parts can be referred to the part of the description of the method embodiments.

[0201] The preferred embodiments of the present application are merely used to illustrate the technical solutions of the present application, rather than limit the scope of the present application. Any modification, equivalent replacement, improvement, and the like made within the spirit and principle of the present application shall fall into the scope of the present application.

Claims

1. A method of charging a battery, characterized by, The method comprises: charging the battery in sequence according to a first current and a second current, the current value of the second current being less than the current value of the first current, and the current value of the second current being greater than 0; The second current comprises a falling current segment, the starting current value of the falling current segment being less than the ending current value of the first current, and the slope of the falling current segment being other than 0.

2. The charging method according to claim 1, characterized by, After the battery is charged in sequence according to the first current and the second current, the battery is further charged with a third current, wherein the current value of the second current is less than the current value of the third current, and the third current is greater than 1C.

3. The charging method according to claim 2, characterized by, The second current further comprises a rising current segment, the ending current value of the rising current segment being less than the ending current value of the third current, and the slope of the rising current segment being other than 0.

4. The charging method according to claim 3, characterized by, The charging time length of the rising current segment is greater than the charging time length of the falling current segment.

5. The charging method according to claim 3, characterized by, The second current comprises a falling current segment, a transition current segment and a rising current segment in sequence, the starting current value of the transition current segment is equal to the ending current value of the falling current segment, the ending current value of the transition current segment is equal to the starting current value of the rising current segment, and the current value of the transition current segment at any time is less than the maximum current value in the falling current segment and the rising current segment.

6. The charging method according to claim 5, characterized by, The charging time length of the transition current segment is greater than the charging time length of the rising current segment and the charging time length of the falling current segment.

7. The charging method according to claim 6, characterized by, The charging time length of the transition current segment is greater than the charging time length of the rising current segment, and the charging time length of the rising current segment is greater than the charging time length of the falling current segment.

8. The charging method according to claim 1, characterized by, The charging method comprises: N charging stages, N≥2 and is an integer; wherein each charging stage comprises: charging the battery in sequence according to a first current and a second current, the current value of the second current being less than the current value of the first current, the charging time length according to the first current being greater than or equal to 30s, and the current value of the second current being greater than 0; The current value of the second current in the N-1th charging stage is less than the current value of the first current in the Nth charging stage.

9. The charging method according to claim 1, characterized by, The charging method comprises: N charging stages, N≥2 and is an integer; each charging stage comprises: charging the battery according to a first current, charging the battery according to a second current, at least one first time period and a second time period are set for each charging stage, the second time period is after the at least one first time period, and each charging stage comprises: charging the battery according to the first current in the first time period and charging the battery according to the second current in the second time period, wherein the current value of the second current in the N-1th charging stage is less than the current value of the first current in the Nth charging stage.

10. The charging method according to claim 9, characterized by, The first time period corresponding to each charging strategy is the first time period, and the last time period corresponding to each charging strategy is the second time period.

11. The charging method according to claim 8 or 9, characterized by, The second current further comprises a rising current segment, the ending current value of the rising current segment being less than the ending current value of the third current, and the slope of the rising current segment being other than 0.

12. The charging method according to claim 11, characterized by, The charging duration of the rising current section is greater than the charging duration of the falling current section.

13. The charging method according to claim 11, characterized by, The second current comprises, in sequence, a falling current section, a transition current section, and a rising current section, the starting current value of the transition current section is equal to the ending current value of the falling current section, the ending current value of the transition current section is equal to the starting current value of the rising current section, and the current value of the transition current section at any time is less than the maximum current value in the falling current section and the rising current section.

14. The charging method according to claim 13, characterized by, The charging duration of the transition current section is greater than the charging duration of the rising current section and the charging duration of the falling current section.

15. The charging method according to claim 14, characterized by, The charging duration of the transition current section is greater than the charging duration of the rising current section, and the charging duration of the rising current section is greater than the charging duration of the falling current section.

16. The charging method according to any one of claims 1 to 10, characterized by, The first current is a constant current.

17. The charging method according to any one of claims 1 to 10, characterized by, The ratio of the current value of the second current to the current value of the first current ranges from 0.1 to 0.

9.

18. The charging method according to claim 17, wherein, The ratio of the current value of the second current to the current value of the first current ranges from 0.5 to 0.

7.

19. The charging method according to any one of claims 1 to 10, characterized by, The charging duration of the battery according to the second current ranges from 1 to 20 seconds.

20. The charging method according to any one of claim 19, characterized in that, The charging duration of the battery according to the second current ranges from 3 to 10 seconds.

21. The charging method according to claim 8 or 9, characterized by, The current value of the first current in the N-1th charging stage is greater than the current value of the first current in the Nth charging stage.

22. The charging method according to claim 1, wherein, The waveform of the second current comprises at least one of or a combination of a square wave, a triangular wave, a sine wave, and a cosine wave.

23. The charging method according to claim 22, wherein, The waveform of the second current is selected to be adapted to a charging device for charging the battery.

24. The charging method according to claim 1, wherein, The current value of the first current is greater than or equal to 1C, and the charging duration of the first current is greater than or equal to 30 seconds.

25. The charging method according to claim 24, wherein, The current value of the first current is greater than or equal to 2C.

26. The charging method according to claim 1, wherein, The charging duration according to the first current is T1, and the charging duration according to the second current is T2, where T1 / T2≥5.

27. The charging method according to claim 1, wherein, The battery is a lithium ion battery.

28. The charging method according to claim 3, wherein, The function relationship of the rising current section satisfies one of the following: I n = a x t n + b; I n = A x B C×t + D; And / or, the function relationship of the falling current section satisfies one of the following: I n = a x t n + b; I n = A x B C×t + D; wherein I n t is the time for the first current to drop to the second current, or for the second current to rise to the third current n t is the charging time of each segment, C is the charging rate, t is the overall charging time, a, b, A, B, D are preset coefficients.

29. The charging method according to claim 1, wherein, The capacity of the battery is greater than or equal to 50 AH.

30. The charging method according to claim 1, wherein, The ratio of the current value of the second current to the current value of the first current is M, and the M is negatively correlated with at least one of a parameter of a battery electrode sheet and a temperature of the battery, where the parameter of the battery electrode sheet comprises at least one of the conductivity, the area density, the compacted density, and the thickness of the battery electrode sheet.

31. The charging method according to claim 30, wherein, The ratio of the current value of the second current to the current value of the first current is M, and the variation amplitude of the negative correlation between the M and the parameter of the negative electrode sheet of the battery is greater than the variation amplitude of the negative correlation between the M and the parameter of the positive electrode sheet of the battery.

32. The charging method of claim 24, wherein, The charging duration according to the first current is less than or equal to a charging cutoff duration, and the charging cutoff duration is the charging duration when the battery voltage reaches a battery cutoff voltage during charging of the battery according to the first current.

33. The charging method according to claim 24 or 32, characterized by, The charging duration according to the first current is less than or equal to 250 seconds.

34. An electronic device, comprising: The electronic device comprises a memory configured to store a computer program and a processor, and the processor implements the method of any one of claims 1-33 when executing the computer program.

35. A charging device, comprising: The charging device is configured to charge the battery in sequence according to a first current and a second current, a current value of the second current being less than a current value of the first current, and the current value of the second current being greater than 0. The second current comprises a falling current section, a starting current value of the falling current section being less than an ending current value of the first current, and a slope of the falling current section being other than 0.

36. A battery management system, comprising: The battery management system comprises the electronic device of claim 34 or the charging device of claim 35.

37. An electrical device, comprising: The electric device comprises the battery and the battery management system of claim 36 or the charging device of claim 35.

38. A computer readable storage medium having stored thereon a computer program, characterized in that, The program is executed by a processor to implement the method of any one of claims 1-33.

39. A computer program product comprising computer programs / instructions, characterized in that, The computer program / instructions are executed by a processor to implement the method of any one of claims 1-33.

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