Charging method, charging chip, battery and electric equipment

Abstract

A charging method comprises at least two charging phases, each charging phase comprising alternating first and second steps. The first step applies a first current to the battery for a first time, and the second step applies a second current to the battery for a second time. Wherein the first current is the charging current and is greater than the second current, and the first time and / or the second time are / is 1-60 seconds.

Description

Technical Field

[0001] The present application relates to the field of energy technology, and in particular to a charging method, a charging chip, a battery and an electrical device. Background Art

[0002] With the continuous improvement of modern science and technology, people are becoming more and more dependent on electronic products. As the energy supply for most electronic products, lithium-ion batteries are becoming more and more important. People have put forward various requirements for lithium-ion batteries, such as faster charging speed, longer battery life, and longer cycle life.

[0003] At the current stage, as the fast charging power becomes higher and higher, high-power charging generates high heat and large temperature rise, and polarization accumulation is serious, resulting in a narrow lithium plating window, which in turn restricts the charging speed. Summary of the invention

[0004] The embodiments of the present application provide a charging method, a charging chip, a battery and an electrical device. The charging method reduces polarization accumulation during the charging process and widens the lithium precipitation window, thereby increasing the charging speed. In addition, the charging method has low hardware requirements for the charging chip and is suitable for consumer electronic electrical devices.

[0005] In a first aspect, an embodiment of the present application provides a charging method, which includes at least two charging stages, each charging stage including an alternating first step and a second step; the first step applies a first current to the battery for a first time, and the second step applies a second current to the battery for a second time; wherein the first current is a charging current and is greater than the second current, and the first time and / or the second time is 1 second to 60 seconds.

[0006] In this embodiment, based on the fact that the first current is a charging current and is greater than the second current, the first step and the second step are alternated, so that a relatively small second current is interspersed in the process of charging with a relatively large first current, which is conducive to reducing polarization phenomenon and reducing charging temperature rise, thereby improving the problem that large current charging easily leads to lithium precipitation, widening the lithium precipitation window, and is conducive to improving the charging speed and cycle life. In addition, the charging process includes at least two charging stages, and each charging stage is provided with a corresponding charging step, and the charging step is adapted to the charging stage, which is conducive to further reducing polarization phenomenon and improving charging speed and cycle life. In addition, the first time and / or the second time is 1 second to 60 seconds, so that the duration of the first current and / or the second current is long and the alternation frequency is low. In this way, the hardware requirements of the charging chip are low, and it is suitable for consumer electronic electrical equipment.

[0007] In some embodiments, the first time and / or the second time is 10 seconds to 60 seconds. That is, the duration of the first current and / or the second current is 10 seconds to 60 seconds, which further reduces the frequency of alternation between the first step and the second step, thus reducing the hardware requirements for the charging chip and being suitable for consumer electronic devices.

[0008] In some embodiments, the second current is a charging current, and the current value of the second current is zero, or the second current is a discharging current. When the second current is a charging current, in each charging stage, high current charging (first current) and low current charging (second current) are charged alternately, and the high current charging lasts for a long time; when the current value of the second current is zero, high current charging (first current) and standing are performed alternately, and the high current lasts for a long time; when the second current is a discharging current, high current charging (first current) and discharging are performed alternately, and the high current lasts for a long time. In this embodiment, low-power charging, standing or discharging are interspersed in the high-power charging process, so that the polarization impedance is reduced, thereby reducing the heat generation, widening the lithium precipitation window, and increasing the charging speed.

[0009] In some embodiments, in the aforementioned at least two charging stages, the first current of the current charging stage is less than or equal to the first current of the previous charging stage. In this embodiment, the first current generally shows a decreasing trend throughout the charging stage, that is, as the power increases, the power of high-power charging decreases. As the battery power increases, the ability to receive charging decreases, thereby reducing the first current, so that the charging efficiency is improved, and in addition, heat generation is reduced to extend the battery life.

[0010] In some embodiments, in at least two charging stages, the second current of the current charging stage is less than or equal to the second current of the previous charging stage. In this embodiment, the second current generally shows a decreasing trend throughout the charging stage. That is, as the charge increases, the power of low-power charging decreases. As the battery charge increases, the ability to receive charging decreases, thereby reducing the second current, so that the charging efficiency is improved, and in addition, heat generation is reduced to extend the battery life.

[0011] In some embodiments, the first current is 0.01 C to 10 C. Preferably, the first current is 5 C to 10 C. In this embodiment, the first current can reach 10 C, achieving high-power charging and improving the charging rate.

[0012] In some embodiments, the second current is -5C to 10C. Preferably, the second current is -5C to 5C. In this embodiment, for example, in the late stage of charging, the degree of polarization accumulation is relatively large, and when the second current is a discharge current of 5C discharge, high-power discharge is achieved, which is conducive to reducing polarization accumulation and improving charging speed. For example, in the early stage of charging, the degree of polarization accumulation is relatively small, and when the second current is a charging current of 10C, high-power charging is achieved, further improving the charging speed.

[0013] In some embodiments, the charging method includes: in response to the voltage of the battery reaching the cut-off voltage of the current charging stage, entering the next charging stage from the current charging stage. In this embodiment, each charging stage corresponds to a cut-off voltage, and when the battery voltage reaches the cut-off voltage of the charging stage, the next charging stage is entered. In this way, the battery overcharge can be reduced, the battery time under high voltage can be reduced, thereby reducing polarization accumulation, and improving the charging speed and cycle life.

[0014] In some embodiments, the charging method includes: in response to the number of alternations between the first step and the second step in the current charging stage reaching the alternation cutoff number, entering the next charging stage from the current charging stage. In this embodiment, each charging stage corresponds to an alternation cutoff number, and when the number of alternations between the first step and the second step reaches the alternation cutoff number, entering the next charging stage. In this way, overcharging of the battery can be reduced, and the time the battery is under high voltage can be reduced, thereby reducing polarization accumulation and improving charging speed and cycle life.

[0015] In some embodiments, before charging the battery, the charging method includes: obtaining at least two charging stages and charging parameters of each charging stage, the charging parameters including a first current, a second current, a first time, a second time, a cut-off voltage, or an alternating cut-off number of times. In this embodiment, the charging parameters are pre-stored in the memory of the charging chip, and when entering the charging operation, the processor of the charging chip calls and obtains the entire charging program (including at least two charging stages and charging parameters of each charging stage) from the memory.

[0016] In some embodiments, the aforementioned obtaining of at least two charging stages and charging parameters of each charging stage includes: obtaining at least two charging stages corresponding to the current number of cycles of the battery and charging parameters of each charging stage. In this embodiment, the effect of the number of cycles on polarization is considered, so that the charging procedure is adapted to the number of cycles, and overcharging is in accordance with the battery aging condition.

[0017] In some embodiments, the aforementioned at least two charging stages and the charging parameters of each charging stage are determined after balancing the lithium precipitation window, the charging speed and the charging temperature rise. In this embodiment, the charging procedure is determined after comprehensively considering the lithium precipitation window, the charging speed and the charging temperature rise, which can achieve fast charging while taking into account the cycle life.

[0018] In a second aspect, an embodiment of the present application provides a charging chip, comprising a memory and a processor; the memory is used to store executable program code; the processor is used to read the executable program code stored in the memory to execute the charging method in the first aspect.

[0019] In a third aspect, an embodiment of the present application provides a battery, including a battery management system, which includes the charging chip in the second aspect.

[0020] In a fourth aspect, an embodiment of the present application provides an electrical device, comprising the battery in the third aspect.

[0021] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the structure of a battery in some embodiments of the present application;

[0023] Figure 2 is a schematic diagram of the structure of batteries in other embodiments of the present application;

[0024] Figure 3 is a schematic diagram of the structure of a charging chip in some embodiments of the present application;

[0025] Figure 4 is a schematic flow chart of a charging method in some embodiments of the present application;

[0026] Figure 5 is a schematic diagram of charging parameters at various charging stages in some embodiments of the present application;

[0027] Figure 6 is a schematic diagram of the relationship between battery impedance and SOC in some embodiments of the present application;

[0028] Figure 7 is a flow chart of a charging method in other embodiments of the present application;

[0029] Figure 8 is a flow chart of a charging method in other embodiments of the present application;

[0030] Fig. 9 is a residual diagram of charging temperature rise in some embodiments of the present application;

[0031] Fig.10 is a residual graph filled with time in some embodiments of the present application;

[0032] Fig.11 is a schematic diagram of the fitting results of the DOE model in some embodiments of the present application;

[0033] Fig. 12A and 12B Schematic diagram of lithium deposition of battery pole pieces in some embodiments of the present application;

[0034] Fig.13 It is a schematic diagram of temperature and voltage under two charging modes in some embodiments of the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and in detail in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] The technical features involved in the various embodiments of the present application described below do not conflict with each other and can be combined with each other.

[0037] Although the device schematic diagram is divided into functional modules and the flowchart shows a logical sequence, in some cases, the steps may be divided differently from the modules in the device or may be executed in an order different from that shown in the flowchart.

[0038] When an element is referred to as being “connected to” another element, it can be directly connected to the other element, or one or more intervening elements may be present therebetween.

[0039] The terms "first", "second", etc. in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more.

[0040] In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the previously and subsequently associated objects are in an "or" relationship.

[0041] When the battery is provided with charging service, the battery is electrically and communicatively connected with a charging device (such as a charging pile or a charger). The battery sends a charging request to the charging device, and the charging device responds to the charging request by providing current to charge the battery.

[0042] The charging chip in the battery determines the charging parameters (including charging current, charging voltage and charging time, etc.) based on the actual situation of the battery, and the charging request carries the charging parameters. The charging device provides charging services for the battery according to the charging parameters in the charging request.

[0043] At present, common charging schemes include: constant current charging to a certain voltage, and then constant voltage charging to the cut-off current. During the charging process, the battery anode potential continues to decrease, and the cathode potential continues to rise. If a larger current is used for charging (constant current charging), the anode potential will drop rapidly due to the large concentration polarization. When the anode potential is too low, it is possible that lithium ions will be reduced to metallic lithium (Li) on the anode surface. This will lead to a decrease in the performance of lithium-ion batteries and bring safety risks.

[0044] Some other charging schemes use pulse charging to charge to a certain voltage, and then charge to a cut-off current at a constant voltage. That is, use a large current to charge for a certain period of time, then discharge for a short time, and charge to the cut-off voltage in this cycle to improve the problem of lithium deposition caused by large current. However, in the later stage of battery charging, the voltage rises, and high current charging is still used. Even if a short discharge is performed, the structure of the anode material will be damaged, resulting in the risk of lithium deposition. The lithium deposition window is narrow, which in turn restricts the charging speed.

[0045] Based on this, some embodiments of the present application provide a charging method, a charging chip, a battery and an electrical device. The charging method is executed by the charging chip in the battery management system, so that the polarization accumulation of the battery during the charging process can be reduced and the lithium precipitation window can be widened, thereby improving the charging speed. In addition, the charging method has low hardware requirements for the charging chip and is suitable for consumer electronic electrical devices.

[0046] Based on the application of the charging chip in the battery management system, the battery management system is installed in the battery. In order to facilitate understanding of the role of the battery management system in the battery, here, the structure of the battery in some embodiments of the present application is first introduced.

[0047] Battery

[0048] Some embodiments of the present application provide a battery 100, see Figure 1The battery 100 includes: at least one battery module 10, which is composed of one or more battery cells and can be charged and discharged; a switch unit 20, which is connected in series to the positive terminal side or the negative terminal side of the battery module 10 to control the flow of charging / discharging current of the battery module 10; and a battery management system (BMS) 30, which is used to control and manage the voltage, current, temperature, etc. of the battery 100 to prevent overcharging and overdischarging.

[0049] Among them, the switch unit 20 can be a mechanical switch element or a semiconductor switch element, which is used to control the flow of current for charging or discharging the battery module 10. In detail, the switch unit 20 may include: a charging switch element, which is controlled to be turned on during charging; and a discharging switch element, which is controlled to be turned on during discharging. However, this is only an example, and therefore, the switch unit 20 is not limited to MOSFET, etc., but a relay, etc. may be used instead. Among them, one or more battery cells in the battery module 10 may be connected in series, in parallel, or in mixed connection, which is not limited here.

[0050] The battery management system 30 is connected to the battery module 10 and can monitor data such as voltage, current, temperature, etc. of the battery module 10. Exemplarily, when the switch unit 20 is a semiconductor switch element, the battery management system 30 can measure or calculate the voltage and current of the gate, source, and drain of the semiconductor switch device.

[0051] In some embodiments, the current, voltage, temperature, etc. of the battery module 10 may also be measured using various sensors 40 disposed adjacent to the switch unit 20. As an input interface for receiving the measured values ​​of the above-mentioned various parameters, the battery management system 30 may include a plurality of terminals and circuits connected to these terminals to process the input values. In addition, the battery management system 30 may control the on / off of the switch unit 20 and may be connected to the battery module 10 to monitor the status of the battery module 10.

[0052] In some embodiments, the battery management system 30 is further used to determine charging parameters and control the charging current to provide a suitable charging current for the battery module 10 .

[0053] The battery 100 in the present application improves the battery management system 30, such as Figure 2 As shown, the battery management system 30 also includes a charging chip 31. The charging chip 31 determines the charging parameters according to the battery 100, so that the polarization accumulation of the battery 100 during the charging process is reduced and the lithium precipitation window is widened, thereby improving the charging speed. In addition, the charging method has low hardware requirements for the charging chip 31 and is suitable for consumer electronic devices.

[0054] Hereinafter, the charging chip 31 and the charging method executed by the charging chip 31 will be described in detail.

[0055] Charging chip

[0056] Some embodiments of the present application provide a charging chip 31, see Figure 3 The charging chip 31 includes a memory 311 , a processor 312 , and a computer program stored in the memory 311 and executable on the processor 312 .

[0057] In some embodiments, the processor 312 may include a central processing unit (CPU), or an application specific integrated circuit (ASIC), or may be configured to implement one or more integrated circuits of the embodiments of the present application.

[0058] The memory 311 may include a read-only memory (ROM), a random access memory 311 (RAM), a magnetic disk storage medium device, an optical storage medium device, a flash memory device, an electrical, optical or other physical / tangible memory 311 storage device. Therefore, generally, the memory 311 includes one or more tangible (non-transitory) computer-readable storage media (e.g., memory devices) encoded with software including computer executable instructions, and when the software is executed (e.g., by one or more processors 312), it is operable to perform the charging method described with reference to the following.

[0059] The processor 312 runs a computer program corresponding to the executable program code by calling the executable program code stored in the memory 311 to implement the charging method described below.

[0060] The charging chip 31 also includes an interface circuit 313 and a bus 314. Figure 3As shown, the memory 311, the processor 312, and the interface circuit 313 are connected through the bus 314 and communicate with each other. In some embodiments, the processor 312 receives and executes computer instructions from other memories of the BMS 30 through the interface circuit 313 to implement the charging method described below. The bus 35 includes hardware, software, or both, coupling the components of the charging chip 31 to each other. By way of example and not limitation, bus 314 may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), a Hyper Transport (HT) interconnect, an Industrial Standard Architecture (ISA) bus, an InfiniBand interconnect, a Low Pin Count (LPC) bus, a Memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local Bus (VLB) bus, or other suitable bus or a combination of two or more of these. Where appropriate, a bus may include one or more buses. Although the present application describes and illustrates a specific bus, the present application contemplates any suitable bus or interconnect.

[0061] It should be noted that although the above-mentioned charging chip 31 only shows the memory 311, the processor 312, and the interface circuit 313, in the specific implementation process, those skilled in the art should understand that the charging chip 31 may also include other devices necessary for normal operation. At the same time, according to specific needs, those skilled in the art should understand that the charging chip 31 may also include hardware devices for implementing other additional functions. In addition, those skilled in the art should understand that the charging chip 31 may also only include the devices necessary to implement the embodiments of the present application, and does not necessarily include Figure 3 All devices shown in .

[0062] Charging method

[0063] The charging method provided in the embodiment of the present application is implemented in a charging chip having the above hardware structure. Figure 4 The charging method includes at least two charging stages, each charging stage includes a first step and a second step alternately. The first step applies a first current to the battery for a first time, and the second step applies a second current to the battery for a second time.

[0064] Each charging stage has its own first step and second step, and the first step and second step of each charging stage are not completely the same, and the number of alternations is not completely the same. For example, the first step step1-1 and the second step step1-2 corresponding to the first charging stage alternate 40 times, and the first step step2-1 and the second step step2-2 corresponding to the second charging stage alternate 30 times, and the first current and / or the first time in the first step step1-1 of the first charging stage are greater than the first current and / or the first time in the first step step2-1 of the second charging stage, or the second current and / or the second time in the second step step1-2 of the first charging stage are greater than the second current and / or the second time in the second step step2-2 of the second charging stage.

[0065] For the first step and the second step in each charging stage, the first current is the charging current and is greater than the second current. That is, in each charging stage, the relatively small second current is interspersed in the process of charging with a relatively large first current, which is conducive to reducing polarization and lowering the charging temperature rise, thereby improving the problem of lithium deposition caused by high current charging, widening the lithium deposition window, and is conducive to improving the charging speed and cycle life.

[0066] In some embodiments, the first current is 0.01 C to 10 C. Preferably, the first current is 5 C to 10 C. In this embodiment, the first current can reach 10 C, achieving high-power charging and improving the charging rate.

[0067] In some embodiments, the first time and / or the second time is 1 second to 60 seconds, so that the duration of the first current and / or the second current is long and the alternation frequency is low, so that the hardware requirements for the charging chip are low, and it is suitable for consumer electronic electrical equipment. In some embodiments, the first time and / or the second time is 10 seconds to 60 seconds. That is, the duration of the first current and / or the second current is long between 10 seconds and 60 seconds, which further makes the alternation frequency of the first step and the second step low, so that the hardware requirements for the charging chip are low, and it is suitable for consumer electronic electrical equipment.

[0068] It can be understood that compared to the scheme in which the entire charging process is not divided into charging stages, the first step or the second step is always the same (such as pulse charging), the charging process in the present application includes at least two charging stages, each charging stage is provided with a corresponding charging step, and the charging step is adapted to the charging stage, which is beneficial to further reduce polarization phenomenon and improve charging speed and cycle life.

[0069] In some embodiments, the second current is a charging current, a current value of the second current is zero, or the second current is a discharging current.

[0070] Exemplarily, the second current is a charging current. In each charging stage, the first current and the second current are charged alternately, that is, high-power charging is performed for a first duration in an alternating manner, and then low-power charging is performed for a second duration, thereby reducing the polarization accumulation of the battery through low-power charging.

[0071] Exemplarily, the current value of the second current is zero. In each charging stage, high-power charging is performed for a first time period in an alternating manner, and then charging is stopped for a second time period. That is, the battery is left at rest during the second time period, thereby reducing the polarization accumulation of the battery by resting.

[0072] Exemplarily, the second current is a discharge current. In each charging stage, high-power charging is performed for a first duration and then discharged for a second duration in an alternating manner, and polarization accumulation of the battery is reduced by discharging.

[0073] In this embodiment, when the second current is a charging current, in each charging stage, high current charging (first current) and low current charging (second current) are charged alternately, and the high current charging lasts for a long time; when the current value of the second current is zero, high current charging (first current) and standing are performed alternately, and the high current lasts for a long time; when the second current is a discharge current, high current charging (first current) and discharging are performed alternately, and the high current lasts for a long time. In this embodiment, low-power charging, standing or discharging are interspersed in the high-power charging process, so that the polarization impedance is reduced, thereby reducing the heat generation, widening the lithium precipitation window, and increasing the charging speed.

[0074] In some embodiments, the second current is -5C to 10C. Preferably, the second current is -5C to 5C. In this embodiment, for example, in the late stage of charging, the degree of polarization accumulation is relatively large, and when the second current is a discharge current of 5C discharge, high-power discharge is achieved, which is conducive to reducing polarization accumulation and improving charging speed. For example, in the early stage of charging, the degree of polarization accumulation is relatively small, and when the second current is a charging current of 10C, high-power charging is achieved, further improving the charging speed.

[0075] In some embodiments, in at least two charging stages, the first current of the current charging stage is less than or equal to the first current of the previous charging stage. Figure 5 As shown, the entire charging process includes three charging stages. The first currents corresponding to the three charging stages are Ia, Ic and Ie, respectively. Then, Ic≤Ia, Ie≤Ic.

[0076] In this embodiment, during the entire charging stage, the first current generally shows a decreasing trend, that is, as the power increases, the power of high-power charging decreases. As the battery power increases, the ability to receive charging decreases, and thus, the first current is reduced, so that the charging efficiency is improved. In addition, heat generation is reduced, and the battery life is extended.

[0077] In some embodiments, in at least two charging stages, the second current in the current charging stage is less than or equal to the second current in the previous charging stage. Figure 5 As shown, the entire charging process includes three charging stages. The second currents corresponding to the three charging stages are I b, I d and If, respectively, then I d≤I b, If≤I d.

[0078] In this embodiment, the second current generally shows a decreasing trend during the entire charging stage. That is, as the charge increases, the power of low-power charging decreases. As the battery charge increases, the ability to receive charging decreases, and thus, the second current is reduced, so that the charging efficiency is improved, and in addition, heat generation is reduced, thereby extending the battery life.

[0079] In some embodiments, during the entire charging process, the second current changes from a positive value (charging current) to zero, to a negative value (discharging current). For example, in the first charging stage, the second current is 5C; in the second charging stage, the second current is 0C; in the third charging stage, the second current is -3C. It is understandable that as the battery capacity gradually increases, the risk of electrode polarization increases, the second current gradually decreases, and the second current being negative (discharging current) is better than being static, and being static is better than the second current being positive (charging current). In this way, polarization accumulation is reduced, making the charging process safer.

[0080] Low-power charging, standing or discharging are interspersed during the high-power charging process, and the high power tends to decrease during the charging process, so that high-power charging is mostly in the medium SOC stage (for example, SOC is in the range of 10% to 80%). The battery cell impedance in this medium SOC stage is low, which can effectively reduce charging heat and reduce charging temperature rise.

[0081] like Figure 6As shown, the relationship between cell impedance and SOC is bathtub-shaped. When the SOC is low or high, the cell impedance is high. When the SOC is in the medium range, the cell impedance is low, the charging heat generation is small, and the charging temperature rise is small, which is beneficial to reduce polarization accumulation.

[0082] In order to reduce the risk of battery overcharging, the end condition of each charging stage is set. If the end condition of the current charging stage is met, the current charging stage is terminated and the next charging stage is entered.

[0083] In some embodiments, Figure 7 As shown, the charging method further includes: in response to the voltage of the battery reaching the cut-off voltage of the current charging stage, entering the next charging stage from the current charging stage.

[0084] In this embodiment, a cut-off voltage is correspondingly set for each charging stage. As the charging stage proceeds, the battery voltage increases and the cut-off voltage also becomes higher and higher.

[0085] The current charging stage refers to the ongoing charging stage after charging starts. In the current charging stage, when the charging chip detects that the battery voltage reaches the corresponding cut-off voltage, the charging chip ends the current charging stage and enters the next charging stage. If the current charging stage is the last charging stage, charging stops.

[0086] In this embodiment, each charging stage corresponds to a cut-off voltage, and when the battery voltage reaches the cut-off voltage of the charging stage, the next charging stage is entered. In this way, overcharging of the battery can be reduced, and the time the battery is under high voltage can be reduced, thereby reducing polarization accumulation and improving charging speed and cycle life.

[0087] In some embodiments, Figure 8 As shown, the charging method further includes: in response to the alternation number of the first step and the second step in the current charging stage reaching the alternation cut-off number, entering the next charging stage from the current charging stage.

[0088] In this embodiment, each charging stage is correspondingly provided with an alternating cut-off number. For example, the alternating cut-off number of the current charging stage is 20 times. Then, in the current charging stage, when the charging chip detects that the alternating number of the first step and the second step reaches 20 times, the charging chip ends the current charging stage and enters the next charging stage. If the current charging stage is the last charging stage, charging is stopped.

[0089] In this embodiment, each charging stage corresponds to an alternating cutoff number, and when the alternating number of the first step and the second step reaches the alternating cutoff number, the next charging stage is entered. In this way, overcharging of the battery can be reduced, and the time the battery is under high voltage can be reduced, thereby reducing polarization accumulation and improving charging speed and cycle life.

[0090] In some embodiments, the number of charging stages (at least two charging stages) and the charging parameters of each charging stage can be stored in the memory of the BMS or the charging chip before the battery leaves the factory. The number of charging stages and the charging parameters of each charging stage are determined in advance through experiments. The determination of the charging stages and charging parameters will be described below.

[0091] Before charging the battery, the charging chip obtains at least two charging stages and charging parameters of each charging stage, where the charging parameters include a first current, a second current, a first time, a second time, a cut-off voltage, or a number of alternating cut-off times.

[0092] In this embodiment, the charging parameters are pre-stored in the memory of the charging chip or the BMS. When entering the charging operation, the processor of the charging chip calls and obtains the entire charging program (including at least two charging stages and the charging parameters of each charging stage) from the memory.

[0093] In some embodiments, considering the effect of battery aging on charging, a mapping relationship between the cycle number range and the charging stage and its charging parameters is set.

[0094] The aforementioned acquiring at least two charging stages and charging parameters of each charging stage includes: acquiring at least two charging stages corresponding to the current cycle number of the battery and charging parameters of each charging stage.

[0095] The number of cycles reflects the aging of the battery, a cycle number range into which the current cycle number falls is determined, and at least two charging stages corresponding to the cycle number range and charging parameters of each charging stage are obtained.

[0096] In this embodiment, the effect of the number of cycles on polarization is taken into consideration so that the charging procedure is adapted to the number of cycles and overcharging is in accordance with the battery aging condition.

[0097] In some embodiments, the aforementioned at least two charging stages and the charging parameters of each charging stage are determined after balancing the lithium precipitation window, the charging speed, and the charging temperature rise.

[0098] Among them, the lithium precipitation window refers to the maximum charging rate of the battery without lithium precipitation. It can be understood that the wider the lithium precipitation window, the greater the charging rate that the battery can withstand and the faster the charging speed. A large charging temperature rise will aggravate the polarization phenomenon and affect the charging performance and safety performance of the battery. Exemplarily, the lithium precipitation window, charging speed and charging temperature rise are considered by experimental design (DOE) to determine each charging stage and the charging parameters corresponding to the charging stage.

[0099] In this embodiment, the charging procedure is determined after comprehensively considering the lithium precipitation window, charging speed and charging temperature rise, which can achieve fast charging while taking into account the cycle life.

[0100] The following introduces the DOE experiment. Multiple batteries of the same batch and the same state are tested according to the following experimental design. The test results are analyzed using Mini-tab or JMP software. The battery is first charged at a constant current of 4.5C to a cut-off voltage of 4.25V, and then charged alternately in the first step and the second step until the cut-off voltage is 4.44V. Then, it is charged at a constant current of 2C to a cut-off voltage of 4.55V, and then charged at a constant voltage. Among them, the first step includes a first current C 1 Constant current charging first time T 1 The second step includes charging at a constant current of 4.5C for a second time period T 2 .

[0101] Among them, the first current C 1 , the first duration T 1 , the second duration T 2 , and the test results (full charge time and charging temperature rise) are shown in Table 1 below.

[0102] Table 1

[0103]

[0104]

[0105] In this DOE experiment, the full charge time and charging temperature rise are responses, and the first time, second time and first current are factors. Residual analysis is performed on the responses, such as Fig. 9 As shown in Figure 1, the temperature residual graph includes the normal probability graph of the charging temperature rise, the fitted value graph, the histogram, and the sequence graph. Fig.10 As shown, the time residual graph includes the normal probability graph of the filling time, the fitted value graph, the histogram, and the sequence graph. These residual graphs reflect whether the different assumptions of the model are met, including linearity, independence, homoscedasticity, and normality. By analyzing these images, possible problems in the model can be diagnosed, and the regression equations between the charging temperature rise and the factors, and the regression equations between the filling time and the factors can be obtained as follows:

[0106] Temp / ℃=19.691-0.1609T 1 +0.1911T 2 +1.987C 1 -0.000260T 1 *T 2 +0.02500T 1 *C 1 -0.03125T2 *C 1 -0.750C t *P t

[0107] Time / min=37.11+0.155T 1 -0.316T 2 -2.82C 1 +0.00036T 1 *T 2 -0.0659T 1 *C 1 +0.0779T 2 *C 1 -2.76C t *P t

[0108] Based on the above regression equation, the range and weight of the response can be determined as shown in Table 2 below.

[0109] Table 2

[0110] response Purpose Lower limit Target Upper limit Weight Importance Charging temperature rise / ℃ Minimum / 20 30.1 1 1 Filling time / min Look 23.5 26 39.3 1 1

[0111] The optimal solution is: the first duration is 50 seconds, the second duration is 2 seconds, and the first current is 3C. Fig.11 As shown, under the optimal solution, the fitting value of charging temperature rise is 21.525℃, the fitting value of full charge time is 26.3938, and the composite desirability is 0.9077.

[0112] Therefore, it can be known that the best charging method is to charge at a constant current of 4.5C to a cut-off voltage of 4.25V, then charge alternately with the first step and the second step until the cut-off voltage is 4.44V, and then charge at a constant current of 2C to a cut-off voltage of 4.55V, and charge at a constant voltage. The first step includes charging at a constant current of 3C for 50 seconds, and the second step includes charging at a constant current of 4.5C for 2 seconds.

[0113] After obtaining the best charging method, charge the battery 10 times using the best charging method, disassemble the battery cell, and confirm whether lithium deposition occurs. Fig. 12A This is a schematic diagram of the surface of the negative electrode after the battery is charged using the above-mentioned optimal charging method. Fig. 12B The schematic diagram of the negative electrode surface after the battery is disassembled after constant current and then constant voltage charging. By comparison, it can be seen that in the above optimal charging method, there is no lithium deposition on the negative electrode surface; in the traditional charging method of constant current and then constant voltage, lithium deposition is obvious on the negative electrode surface.

[0114] like Fig.13As shown, when charging in the charging method in the embodiment of the present application, the charging temperature rise is small and the voltage is at a high level for a short time, while when charging in the traditional charging method of constant current first and then constant voltage, the charging temperature rise is large and the voltage is at a high level for a long time. Some experiments have found that under the same charging time, compared with the traditional charging method, charging in the charging method in the embodiment of the present application can reduce the charging temperature rise by 4.5°C. If the charging temperature rise is the same, the charging time can be shortened by 2 minutes.

[0115] As shown in Table 3 below, for batteries of different systems, the two charging methods are used respectively. When charged to the same cut-off voltage in actual tests, the polarization impedance of the batteries charged by the charging method in the embodiment of the present application is reduced. The degree of reduction in polarization impedance of different systems is slightly different, and the reduction is approximately 9.8% to 23.48%.

[0116] Table 3

[0117]

[0118] In summary, in the embodiment of the present application, based on the first current being the charging current and being greater than the second current, the first step and the second step are alternated, so that the relatively small second current is interspersed in the process of charging with the relatively large first current, which is conducive to reducing polarization phenomenon and reducing charging temperature rise, thereby improving the problem that large current charging easily leads to lithium precipitation, widening the lithium precipitation window, and helping to improve the charging speed and cycle life. In addition, the charging process includes at least two charging stages, and each charging stage is provided with a corresponding charging step, and the charging step is adapted to the charging stage, which is conducive to further reducing polarization phenomenon and improving charging speed and cycle life. In addition, the first time and / or the second time is 1 second to 60 seconds, so that the duration of the first current and / or the second current is long and the alternation frequency is low. In this way, the hardware requirements of the charging chip are low, and it is suitable for consumer electronic electrical equipment.

[0119] Electrical equipment

[0120] Some embodiments of the present application also provide an electrical device, comprising the battery in any one of the above embodiments.

[0121] The electrical equipment of the present application is not particularly limited. In some embodiments, the electrical equipment may include a battery energy storage system, an electric motorcycle, an electric bicycle, an electric tool, a sweeping robot, an automatic guided vehicle (AGV), an uninterruptible power supply (UPS), etc.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A charging method, characterized in that: The charging method comprises at least two charging stages, each charging stage comprising alternating first and second steps; The first step applies a first current to the battery for a first time, and the second step applies a second current to the battery for a second time; The first current is a charging current and is greater than the second current, and the first time and / or the second time is from 1 second to 60 seconds.

2. The charging method according to claim 1, characterized in that: The first time and / or the second time is / are 10 seconds to 60 seconds.

3. The charging method according to claim 1, characterized in that: The second current is a charging current, a current value of the second current is zero, or the second current is a discharging current.

4. The charging method according to claim 1, characterized in that: In the at least two charging stages, a first current in a current charging stage is less than or equal to a first current in a previous charging stage.

5. The charging method according to claim 1, characterized in that: In the at least two charging stages, the second current in the current charging stage is less than or equal to the second current in the previous charging stage.

6. The charging method according to any one of claims 1 to 5, characterized in that: The first current is 0.01C to 10C.

7. The charging method according to claim 6, characterized in that: The first current is 5C to 10C.

8. The charging method according to any one of claims 1 to 5, characterized in that: The second current is -5C to 10C.

9. The charging method according to claim 8, characterized in that: The second current is -5C to 5C.

10. The charging method according to claim 1, characterized in that: The charging method includes: in response to the voltage of the battery reaching a cut-off voltage of a current charging stage, entering a next charging stage from the current charging stage.

11. The charging method according to claim 1, characterized in that: The charging method comprises: in response to the alternation number of the first step and the second step in the current charging stage reaching the alternation cut-off number, entering the next charging stage from the current charging stage.

12. The charging method according to claim 1, characterized in that: Before charging the battery, the charging method includes: acquiring the at least two charging stages and charging parameters of each charging stage, wherein the charging parameters include the first current, the second current, the first time, the second time, a cut-off voltage, or an alternating cut-off number of times.

13. The charging method according to claim 12, characterized in that: The acquiring the at least two charging stages and the charging parameters of each charging stage includes: The at least two charging stages corresponding to the current cycle number of the battery and the charging parameters of each charging stage are obtained.

14. The charging method according to claim 12 or 13, characterized in that: The at least two charging stages and the charging parameters of each charging stage are determined after balancing the lithium precipitation window, the charging speed and the charging temperature rise.

15. A charging chip, characterized in that: including memory and processor; The memory is used to store executable program code; The processor is used to read the executable program code stored in the memory to execute the charging method described in any one of claims 1-14.

16. A battery, characterized in that: It includes a battery management system, which includes the charging chip as claimed in claim 15.

17. An electrical equipment, characterized in that: Comprising the battery of claim 16.

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