Charging method and device

Abstract

The invention provides a charging method and equipment, the charging method is applied to the equipment, the equipment comprises a battery, and the method comprises the following steps: charging the battery in a first stage of a charging period; charging the battery in a second stage of the charging cycle; the charging period is a process of charging the battery from the first preset charge capacity to the second preset charge capacity; the charging period is composed of a first stage and a second stage, and the second stage is after the first stage; the second stage comprises a constant-current charging step and / or a constant-power charging step, and the ratio of the duration of the constant-current charging step and / or the constant-power charging step to the duration of the second stage is larger than or equal to a first threshold value. While the volume energy density of the battery is improved, the influence on the cycle life of the battery is reduced, so that the mechanical failure of active substance particles of the battery can be slowed down, and the cycle performance and life of the battery are improved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and in particular to a charging method and device. Background Art

[0002] The positive electrode of batteries such as lithium batteries and sodium batteries includes alkali metal materials, which can be called alkali metal batteries. Alkali metal batteries have a relatively high volumetric energy density, and can improve the endurance time while maintaining a small volume, so they are widely used in electronic devices.

[0003] Generally, the charging voltage of the alkali metal battery can be increased to increase the amount of alkali metal removed from the positive electrode of the alkali metal battery, and thus the volumetric energy density of the alkali metal battery can be improved. However, the increase in the charging voltage and the amount of alkali metal removed will result in a decrease in the cycle life of the alkali metal battery. Therefore, how to improve the volumetric energy density of the alkali metal battery while reducing the impact on the cycle life is a technical problem that those skilled in the art need to solve urgently. Summary of the Invention

[0004] The present application provides a charging method and device, which can improve the volumetric energy density of the battery while reducing the impact on the battery cycle life, thereby slowing down the mechanical failure of the battery and improving the battery cycle performance and life.

[0005] In a first aspect, the present application provides a charging method. The foregoing charging method is applied to a device, and the foregoing device includes a battery. The foregoing method includes:

[0006] Charging the foregoing battery in the first stage of a charging cycle; the foregoing charging cycle is a process of charging the foregoing battery from a first preset state of charge to a second preset state of charge;

[0007] Charging the foregoing battery in the second stage of the foregoing charging cycle; the foregoing charging cycle is composed of the foregoing first stage and the foregoing second stage, and the foregoing second stage is after the foregoing first stage;

[0008] The foregoing second stage includes a constant current charging step and / or a constant power charging step, and the ratio of the duration of the foregoing constant current charging step and / or the constant power charging step to the duration of the foregoing second stage is greater than or equal to a first threshold.

[0009] In this solution, the device charges the battery in the first stage to increase the battery's power level, and charges the battery in the second stage, with the ratio of the constant current charging step and / or the constant power charging step to the duration of the second stage being greater than or equal to a first threshold, so that the duration of constant voltage charging during the second stage of battery charging is reduced. It should be noted that increasing the charging voltage of the device to charge the battery can, on the one hand, increase the volumetric energy density of the battery, and on the other hand, cause greater stress on the positive electrode material of the battery, affecting the battery's cycle performance. Therefore, in the embodiments of this application, the device can charge the battery in the first stage to increase the battery's power level, and by reducing the duration of constant voltage charging of the battery during the second stage, it is possible to reduce the stress accumulation of the positive electrode material while increasing the charging voltage and volumetric energy density, thereby improving the cycle performance and lifespan of the battery.

[0010] In one possible implementation, the aforementioned first threshold is 25%.

[0011] In this solution, by making the ratio of the duration of the constant current charging step and / or the constant power charging step in the second stage to the duration of the second stage greater than or equal to 25%, the device can effectively reduce the stress accumulation inside the positive electrode material caused by constant voltage charging, slow down the mechanical failure of the battery, and extend the cycle life of the battery.

[0012] In one possible implementation, the ratio of the duration of the aforementioned second stage to the aforementioned charging cycle is 0.2.

[0013] In this solution, by making the ratio of the duration of the second stage to the charging cycle 0.2, the device can make the duration of the second stage shorter than that of the first stage, so that the device has more time in the first stage to charge more power into the battery. And by reducing the duration of the constant voltage charging step in the second stage before the end of charging, it is possible to reduce the stress accumulation inside the positive electrode material without affecting the amount of power charged into the battery.

[0014] In one possible implementation, the positive electrode of the aforementioned battery includes an alkali metal. After charging the aforementioned battery in the second stage of the aforementioned charging cycle, the amount of alkali metal removed from the positive electrode of the aforementioned battery is greater than or equal to 60%.

[0015] In this solution, after the device finishes charging the alkali metal battery, the amount of alkali metal removed from the positive electrode of the alkali metal battery is greater than or equal to 60%. That is, when the device charges the alkali metal battery according to the charging method provided in this solution, the alkali metal battery can achieve a relatively high volumetric energy density.

[0016] In one possible implementation, the charging voltage for charging the aforementioned battery in the aforementioned first stage is less than or equal to the charging voltage for charging the aforementioned battery in the aforementioned second stage.

[0017] In this solution, the charging voltage of the battery in the second stage is greater than that in the first stage, which can gradually increase the charging voltage of the battery during the charging cycle to achieve a higher volumetric energy density at the end of charging. At the same time, since the increase in the charging voltage will increase the internal stress of the battery cathode material, the charging method of the embodiments of the present application can effectively reduce the stress accumulation of the cathode material caused by the increase in the charging voltage by reducing the duration of the constant-voltage charging step in the second stage.

[0018] In a possible implementation, the aforementioned charging cycle includes N charging steps, the aforementioned first stage is composed of a part of the N charging steps, and the aforementioned second stage is composed of the other part of the N charging steps; N is a positive integer; the aforementioned N charging steps include a first charging step and a second charging step, and the aforementioned second charging step is the charging step after the aforementioned first charging step; the charging current for charging the aforementioned battery in the aforementioned second charging step is greater than or equal to the charging current for charging the aforementioned battery in the aforementioned first charging step.

[0019] In this solution, the device can increase the charging current of the battery during the charging cycle, that is, there is a charging step during the charging cycle where the charging current of the battery is greater than the charging current of the previous charging step. At this time, the charging speed of the battery is accelerated, and then the duration of the constant-voltage charging step can be reduced, and the stress accumulation can be reduced, thereby improving the cycle performance and life of the battery.

[0020] In a possible implementation, the aforementioned N charging steps further include a third charging step and a fourth charging step, and the aforementioned fourth charging step is the charging step after the aforementioned third charging step;

[0021] The charging current for charging the aforementioned battery in the aforementioned fourth charging step is less than the charging current for charging the aforementioned battery in the aforementioned third charging step.

[0022] In a possible implementation, the last charging step in the aforementioned second stage is any one of the aforementioned constant-current charging step or the aforementioned constant-power charging step.

[0023] In this solution, since the higher the charging voltage of the battery during constant-voltage charging, the greater the stress generated inside the battery cathode material. Therefore, in order to avoid the large stress caused by the high charging voltage, the last charging step before the end of the second stage can be a constant-current charging step or the aforementioned constant-power charging step, so as to reduce the duration of constant-voltage charging of the battery at the high charging voltage and slow down the mechanical failure of the battery.

[0024] In a possible implementation, in the last charging step of the aforementioned charging cycle, the multiple of the charging current for charging the aforementioned battery is in the range of 0.025 times to 1.5 times.

[0025] In this solution, the device can select a charging current with an appropriate current rate in the last charging step of the second stage according to different application scenarios to charge the battery, so as to achieve fast charging or slow charging of the battery. Among them, when the rate of the charging current in the last charging step of the device is relatively large, the charging speed of the battery is relatively fast, and thus the duration of the constant voltage charging of the battery can be reduced, and the cycle life of the battery can be improved.

[0026] In a possible implementation, after the battery is charged in the second stage of the foregoing charging cycle, the state of charge of the foregoing battery is greater than or equal to 90%.

[0027] In this solution, after the battery is charged, the state of charge is greater than or equal to 90%. Since the closer the state of charge of the battery is to 100% after charging, the more electricity is charged into the battery, the longer the battery life. Therefore, the battery can meet the requirements of the battery life after charging, ensuring that the device can work.

[0028] In a possible implementation, when the positive electrode material of the foregoing battery is lithium cobaltate material, when the charging voltage for charging the foregoing battery in the foregoing second stage is within the range of 4.5 volts to 4.75 volts, the charging of the foregoing battery ends.

[0029] In this solution, by raising the charging voltage at the end of the charging of the lithium cobaltate battery to within the range of 4.5 volts to 4.75 volts, the device can improve the volumetric energy density of the lithium cobaltate battery. At the same time, since the duration of the constant voltage charging step of the lithium cobaltate battery is also reduced in the second stage of this solution, the impact of the increase in the charging voltage on the cycle life of the lithium cobaltate battery can be reduced, and the cycle performance of the battery can be improved.

[0030] In a possible implementation, when the positive electrode material of the foregoing battery is ternary lithium material, when the charging voltage for charging the foregoing battery in the foregoing second stage is within the range of 4.3 volts to 4.5 volts, the charging of the foregoing battery ends.

[0031] In this solution, by raising the charging voltage at the end of the charging of the ternary lithium battery to within the range of 4.3 volts to 4.5 volts, the device can improve the volumetric energy density of the ternary lithium battery. At the same time, since the duration of the constant voltage charging step of the ternary lithium battery is also reduced in the second stage of this solution, the impact of the increase in the charging voltage on the cycle life of the ternary lithium battery can be reduced, and the cycle performance of the battery can be improved.

[0032] In a possible implementation, when the positive electrode material of the foregoing battery is a sodium-based layered oxygen positive electrode material, when the charging voltage for charging the foregoing battery in the foregoing second stage is within the range of 4.1 volts to 4.5 volts, the charging of the foregoing battery ends.

[0033] In this solution, by increasing the charging voltage at the end of sodium battery charging to the range of 4.1 V to 4.5 V, the volumetric energy density of the sodium battery can be improved. At the same time, since the duration of the constant-voltage charging step of the sodium battery is reduced in the second stage of this solution, the impact of the increased charging voltage on the cycle life of the sodium battery can be reduced, and the cycle performance of the battery can be improved.

[0034] In a second aspect, the present application also provides a device, which includes:

[0035] A first charging unit for charging the battery in the first stage of the charging cycle; the charging cycle is a process of charging the battery from a first preset state of charge to a second preset state of charge;

[0036] A second charging unit for charging the battery in the second stage of the charging cycle; the charging cycle consists of the first stage and the second stage, and the second stage follows the first stage; the second stage includes a constant-current charging step and / or a constant-power charging step, and the ratio of the duration of the constant-current charging step and / or the constant-power charging step to the duration of the second stage is greater than or equal to a first threshold.

[0037] In a possible implementation, the first threshold is 25%.

[0038] In a possible implementation, the ratio of the duration of the second stage to the charging cycle is 0.2.

[0039] In a possible implementation, the positive electrode of the battery includes an alkali metal. After the battery is fully charged in the second stage of the charging cycle, the amount of alkali metal removed from the positive electrode of the battery is greater than or equal to 60%.

[0040] In a possible implementation, the charging voltage for charging the battery in the first stage is less than or equal to the charging voltage for charging the battery in the second stage.

[0041] In a possible implementation, the charging cycle includes N charging steps, the first stage consists of a part of the N charging steps, and the second stage consists of the other part of the N charging steps; N is a positive integer; the N charging steps include a first charging step and a second charging step, and the second charging step is the charging step after the first charging step; the charging current for charging the battery in the second charging step is greater than or equal to the charging current for charging the battery in the first charging step.

[0042] In a possible implementation, the N charging steps further include a third charging step and a fourth charging step, and the fourth charging step is the charging step after the third charging step;

[0043] The charging current for charging the battery in the foregoing fourth charging step is less than the charging current for charging the battery in the foregoing third charging step.

[0044] In a possible implementation, the last charging step in the foregoing second stage is any one of the foregoing constant current charging step or the foregoing constant power charging step.

[0045] In a possible implementation, in the last charging step of the foregoing charging cycle, the multiple of the charging current for charging the battery is in the range of 0.025 times to 1.5 times.

[0046] In a possible implementation, after charging the battery in the second stage of the foregoing charging cycle, the state of charge of the battery is greater than or equal to 90%.

[0047] In a possible implementation, when the positive electrode material of the foregoing battery is lithium cobaltate material, when the charging voltage for charging the battery in the foregoing second stage is in the range of 4.5 volts to 4.75 volts, the charging of the battery ends.

[0048] In a possible implementation, when the positive electrode material of the foregoing battery is ternary lithium material, when the charging voltage for charging the battery in the foregoing second stage is in the range of 4.3 volts to 4.5 volts at the end of charging in the second stage, the charging of the battery ends.

[0049] In a possible implementation, when the positive electrode material of the foregoing battery is sodium layered oxygen positive electrode material, when the charging voltage for charging the battery in the foregoing second stage is in the range of 4.1 volts to 4.5 volts at the end of charging in the second stage, the charging of the battery ends.

[0050] In a third aspect, the present application provides a device, which includes a processor and a memory. The memory is coupled to the processor, and when the processor executes the computer program or computer instructions stored in the memory, the method described in any item of the foregoing second aspect can be implemented. The device may further include a communication interface, and the communication interface is used for the device to communicate with other devices. Exemplarily, the communication interface may be a transceiver, a circuit, a bus, a module or other types of communication interfaces.

[0051] In a possible implementation, the device may include:

[0052] A memory for storing computer programs or computer instructions;

[0053] A processor for:

[0054] Charge the battery in the first stage of the charging cycle; the charging cycle is a process of charging the battery from a first preset state of charge to a second preset state of charge;

[0055] Charge the battery in the second stage of the charging cycle; the charging cycle consists of the first stage and the second stage, and the second stage comes after the first stage;

[0056] The second stage includes a constant current charging step and / or a constant power charging step, and the ratio between the duration of the constant current charging step and / or the constant power charging step and the duration of the second stage is greater than or equal to a first threshold.

[0057] It should be noted that the computer programs or computer instructions in the memory of the present application can be pre-stored or stored after being downloaded from the Internet when using the device. The present application does not specifically limit the source of the computer programs or computer instructions in the memory. The coupling in the embodiments of the present application is an indirect coupling or connection between devices, units or modules, which can be electrical, mechanical or other forms for information interaction between devices, units or modules.

[0058] In a fourth aspect, the present application provides a computer-readable storage medium storing computer programs or computer instructions, and the computer programs or computer instructions are executed by a processor to implement the method described in any item of the first aspect above.

[0059] In a fifth aspect, the present application provides a computer program product, and when the computer program product is executed by a processor, the method described in any item of the first aspect above will be executed.

[0060] In a sixth aspect, an embodiment of the present application provides a chip including a processor, wherein the processor is configured to execute computer programs or computer instructions stored in a memory, so that the chip executes the method described in any item of the first aspect above.

[0061] The solutions provided in the second to sixth aspects above are used to implement or cooperate with the methods correspondingly provided in the first aspect, so the same or corresponding beneficial effects can be achieved as those of the corresponding methods in the first aspect, and details are not described herein again. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a schematic structural diagram of a device provided by an embodiment of the present application;

[0063] Figure 2 It is a schematic flowchart of a charging method provided by an embodiment of the present application;

[0064] Figure 3 It is a schematic diagram of the relationship between the charging voltage and the charging time of a lithium cobalt oxide battery provided by an embodiment of the present application;

[0065] Figure 4 Another structural schematic diagram of the device provided by the embodiment of the present application;

[0066] Figure 5 A hardware structural schematic diagram of the device provided by the embodiment of the present application. Detailed implementation manners

[0067] In the embodiments of the present application, "a plurality of" means two or more. In the embodiments of the present application, "and / or" is used to describe the association relationship of associated objects, indicating three relationships that can exist independently. For example, A and / or B can mean: A exists alone, B exists alone, or both A and B exist simultaneously. In the embodiments of the present application, descriptions such as "at least one (or at least one) of a1, a2,..., and an" include the case where any one of a1, a2,..., and an exists alone, and also include any combination of any plurality of a1, a2,..., and an, and each case can exist alone; for example, the description manner of "at least one of a, b, and c" includes the cases of a alone, b alone, c alone, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b, and c.

[0068] In each embodiment of the present application, if there is no special description and logical conflict, the terms and / or descriptions among the various embodiments are consistent and can be referenced to each other, and the technical features in different embodiments can be combined to form new embodiments according to their inherent logical relationships.

[0069] First, the technical terms related to the embodiments of the present application will be introduced below.

[0070] Alkali metal battery: It refers to a battery in which the positive electrode of the battery includes an oxide of an alkali metal element and a transition metal element. The structural general formula of the above-mentioned oxide of the alkali metal element and the transition metal element includes AMO2, where A represents an alkali metal element, and M includes at least a transition metal element. The above-mentioned alkali metals include six metal elements: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Exemplarily, the alkali metal battery can be a lithium battery, a sodium battery, a potassium battery, etc.

[0071] Volume energy density: It refers to the ratio of the energy of the battery to the volume of the battery, and can be used to characterize the ability of the battery to release electrical energy through chemical reactions. In the case of the same battery volume, the larger the volume energy density, the higher the energy of the battery, that is, the stronger the ability of the battery to release electrical energy.

[0072] Alkali metal extraction amount: It represents the ratio of the molar amount of alkali metal in the cathode material to the molar amount of other metals after the charging of the alkali metal battery is completed, and can be used to characterize the volumetric energy density of the alkali metal battery. The higher the alkali metal extraction amount, the higher the volumetric energy density of the alkali metal battery.

[0073] Lithium cobalt oxide material: It represents an alkali metal material composed of lithium cobalt oxide, and the chemical formula includes LiCoO 2 . The lithium cobalt oxide material is a commonly used cathode material in lithium-ion batteries.

[0074] Lithium ternary material: It represents an alkali metal material composed of ternary oxides of lithium. Exemplarily, the lithium ternary material includes lithium nickel cobalt manganate (abbreviated as NCM, and the chemical formula includes LiNi a Co b Mn 1-a-b O 2 , 0 < a < 1, 0 < b < 1, 0 < 1 - a - b < 1), lithium nickel cobalt aluminate (abbreviated as NCA, and the chemical formula includes LiNi a Co b Al 1-a-b O 2 , 0 < a < 1, 0 < b < 1, 0 < 1 - a - b < 1), etc., but not limited to this.

[0075] Sodium-ion battery layered oxide cathode material: It represents an alkali metal material composed of layered sodium oxides, and the layered sodium oxides contain sodium element and transition metals. Exemplarily, the above sodium-ion battery layered oxide cathode material includes: sodium nickel iron manganate (abbreviated as NFM, and the chemical formula includes NaNi a Fe b Mn 1-a-b O 2 , 0 < a < 1, 0 < b < 1, 0 < 1 - a - b < 1) or sodium copper iron manganate (the chemical formula includes NaCu a Fe b Mn 1-a-b O 2 , 0 < a < 1, 0 < b < 1, 0 < 1 - a - b < 1), etc., but not limited to this.

[0076] Constant voltage charging: It means charging the battery with a constant voltage. For example, by applying a constant DC signal across the battery terminals, the battery can be charged with a constant voltage.

[0077] Constant current charging: It means charging the battery with a constant current. For example, by inputting a constant DC signal to the battery, the battery can be charged with a constant current.

[0078] Constant power charging: It means charging the battery with a constant power.

[0079] Charging step: It can be understood as the steps of charging the battery within a charging cycle. For example, assume that the charging cycle includes three charging steps, namely the first charging step, the second charging step, and the third charging step. Then, when charging the battery within the charging cycle, the first charging step can be executed first to charge the battery, then the second charging step can be executed to charge the battery, and then the third charging step can be executed to charge the battery.

[0080] Current rate: It refers to the ratio of the charging current or discharging current of the battery to the rated capacity of the battery, which is used to characterize the speed of battery charging and discharging, and is abbreviated as C. Exemplarily, assume that the rated capacity of the battery is 100Ah. When the charging current rate of the battery is 0.2C, it indicates that the charging current of the battery is 20A. Since the embodiments of the present application introduce the charging method of the battery, for the convenience of description, the charging current rate is characterized by the current rate in the following content.

[0081] The embodiments of the present application will be introduced below in conjunction with the accompanying drawings.

[0082] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of the device provided by the embodiments of the present application. Figure 1 The device 100 shown includes a battery 110. The device 100 is connected to a charger. Among them, data signals and power signals can be transmitted between the device 100 and the charger. The connection method between the device 100 and the charger can be wired connection or wireless connection, and the present application does not limit this.

[0083] It can be understood that Figure 1 the charger in can provide a power signal to the device 100 so that the device 100 charges the battery 110 according to the power signal. In addition, the device 100 can send a data signal to the charger, thereby controlling the type and magnitude of the power signal provided by the charger, and further changing the charging method for charging the battery 110.

[0084] Exemplarily, the above device 100 can include but is not limited to any rechargeable electronic product, such as a battery device, a vehicle-mounted system, a smart home device, a smart phone, a tablet personal computer (Tablet PC), a handheld computer, a wearable electronic device, a personal computer (PC), etc. The embodiments of the present application will not list them one by one here.

[0085] It should be noted that as the requirements of the user of the electronic device for the volume size and battery life of the electronic device continue to increase, the volumetric energy density of the battery needs to be further improved. Specifically, since alkali metal materials have a relatively high material density and electrode compaction density, when applied to the positive electrode of the battery, the volumetric energy density of the battery can be increased. Further, in addition to using alkali metal materials as the positive electrode material, the volumetric energy density of the battery can also be increased by increasing the charging voltage of the battery. Exemplarily, assuming that the above alkali metal battery is a lithium cobalt oxide battery, by increasing the charging cut-off voltage of the lithium cobalt oxide battery from 4.2 V when it was first widely used to 4.5 V, the volumetric energy density of the lithium cobalt oxide battery can exceed 700 Wh / L, thereby achieving an increase in the volumetric energy density of the battery. Among them, the charging cut-off voltage refers to the charging voltage of the battery at the end of the charging cycle. In some application scenarios, the charging cut-off voltage can also be understood as the charging voltage when the battery reaches the fully charged state. It can be understood that when the device increases the charging voltage of the battery, it also means increasing the charging cut-off voltage. Therefore, the device can increase the volumetric energy density of the battery by increasing the charging cut-off voltage of the battery.

[0086] In some feasible embodiments, in order to increase the charging voltage of the battery, the device can charge the battery through the following conventional boost charging methods. For ease of understanding, the embodiments of the present application take the positive electrode material of the battery as lithium cobalt oxide material as an example to illustrate the above conventional boost charging methods. Specifically, in the actual application scenario, the device can execute the charging steps (1a) to (6a) in the following conventional boost charging methods:

[0087] (1a) Constantly charge the battery with a charging current of 3.5C until the voltage reaches 4.21V, and then constantly charge the battery with a charging voltage of 4.21V until the current decreases to 3.0C;

[0088] (2a) Constantly charge the battery with a charging current of 3.0C until the voltage reaches 4.25V, and then constantly charge the battery with a charging voltage of 4.25V until the current decreases to 2.5C;

[0089] (3a) Constantly charge the battery with a charging current of 2.5C until the voltage reaches 4.35V, and then constantly charge the battery with a charging voltage of 4.35V until the current decreases to 2.0C;

[0090] (4a) Constantly charge the battery with a charging current of 2.0C until the voltage reaches 4.4V, and then constantly charge the battery with a charging voltage of 4.4V until the current decreases to 1.5C;

[0091] (5a) Constantly charge the battery with a charging current of 1.5C until the voltage reaches 4.5V, and then constantly charge the battery with a charging voltage of 4.5V until the current decreases to 1.2C;

[0092] (6a) The battery is charged at a constant current of 1.2C until the voltage reaches 4.53V, and then it is charged at a constant voltage of 4.53V until the current decreases to 0.025C, at which point the battery is fully charged and its state of charge (SOC) reaches 100%.

[0093] It should be noted that during the process of the device charging the battery, the active ions at the positive electrode of the battery (such as alkali metal ions: lithium ions, sodium ions, etc.) can be removed from the positive electrode and embedded in the negative electrode after passing through the electrolyte and separator in the battery, thereby creating a potential difference between the positive and negative electrodes of the battery. The more active ions are removed from the positive electrode and embedded in the negative electrode of the battery, the higher the potential difference across the battery and the higher the energy of the battery. Thus, the amount of alkali metal removed from the positive electrode of the battery can be used to characterize the volumetric energy density of the battery.

[0094] Furthermore, in each of the above charging steps, when the device charges the battery at a constant current, due to the migration of active ions, the voltage across the battery will gradually increase. However, due to the polarization phenomenon inside the battery during constant current charging, after the device charges the battery at a constant current, the voltage across the battery is greater than the actual voltage of the battery. At this time, even though the voltage across the battery reaches the charging cut-off voltage, the battery is actually not fully charged. Therefore, the device can switch to constant voltage charging after charging the battery at a constant current to maintain the continuous migration of active ions inside the battery. It can be understood that when the device charges the battery at a constant voltage, the active ions are continuously embedded in the negative electrode, and at the same time, the positions available for the active ions to be embedded in the negative electrode decrease, resulting in a decrease in the rate of the electrochemical reaction, so the charging current will decrease during constant voltage charging. That is to say, during the process of charging the battery at a constant current, the voltage across the battery will gradually increase, and during the process of charging the battery at a constant voltage, the current passing through the battery will gradually decrease. It should be noted that in the embodiments of the present application, the voltage of the battery refers to the voltage across the battery, and the charging voltage of the battery refers to the voltage provided by the device for charging the battery.

[0095] Generally speaking, through the above conventional boost charging method, the device can switch between constant current charging and constant voltage charging multiple times when charging the battery, thereby gradually increasing the charging voltage of the battery, and further achieving a higher volumetric energy density when the SOC of the battery reaches 100%.

[0096] However, the inventors of the present application found in the practical process that the increase in the charging voltage would cause mechanical failure of the positive electrode material of the battery, affecting the cycle life of the battery. Specifically, for alkali metal batteries, the increase in the charging voltage would also increase the amount of alkali metal removed from the positive electrode. The increase in the charging voltage and the amount of alkali metal removed would cause large stresses inside the alkali metal material, and problems such as irreversible structural phase change, decreased stability, and decreased safety performance would occur. Further, as the alkali metal battery undergoes cyclic charge and discharge, the stresses inside the alkali metal material accumulate multiple times, and finally the material will fatigue, resulting in mechanical failure of the active material particles of the alkali metal battery.

[0097] It can be seen that although increasing the charging voltage can increase the volumetric energy density of the battery, it will also affect the cycle life of the battery. Among them, the cycle life of the battery refers to the maximum number of cycles before the battery capacity drops to the rated value under a certain charging method. It can be understood that one cycle refers to one charge and one discharge of the alkali metal battery.

[0098] It should be noted that for the same battery, when the device charges the battery according to different charging methods, the cycle life of the battery will also be different. Therefore, based on the above-mentioned technical problems, the embodiments of the present application provide a charging method, which can avoid the problems of fatigue and mechanical failure of the positive electrode material of the battery while increasing the volumetric energy density of the battery, thereby reducing the impact of the increase in the charging voltage on the cycle life of the battery.

[0099] The inventors of the present application found that as the charging voltage increases, when the device charges the battery at a constant voltage, the relatively high constant voltage is applied across the battery, which will cause the positive electrode material of the battery to enter the phase change stage, and further cause large stresses inside the positive electrode material. Further, if the device charges the battery at a constant voltage for a long time, the stress of the positive electrode material will accumulate for a long time, eventually leading to mechanical failure of the positive electrode material.

[0100] Therefore, the charging method provided by the embodiments of the present application proposes to reduce the stress accumulation generated in the positive electrode material of the battery by reducing the duration of the device charging the battery at a constant voltage, thereby reducing the impact on the cycle life of the battery.

[0101] Specifically, please refer to Figure 2 , Figure 2 which is a schematic flow chart of the charging method provided by the embodiments of the present application. Figure 2 The charging method shown can be executed by the Figure 1 device 100 shown, that is, the device 100 can charge the battery 110 according to the Figure 2 charging method shown. Specifically, Figure 2 the charging method shown at least includes the following steps:

[0102] S101. Charge the battery in the first stage of the charging cycle.

[0103] In some possible embodiments, the device charges the battery during the charging cycle. The charging cycle can be understood as a complete charging process of the battery. During this charging cycle, the device charges the battery so that the state of charge (SOC) of the battery is charged from a first preset charge level to reach a second preset charge level. Exemplarily, assuming that the first preset charge level is 0% and the second preset charge level is 100%, then the above charging cycle is the process of charging the battery from an SOC of 0% to 100%. Exemplarily, assuming that the first preset charge level is 0% and the second preset charge level is 90%, then the above charging cycle is the process of charging the battery from an SOC of 0% to 90%. It can be understood that the above content is only an example and does not constitute a limitation on the embodiments of the present application.

[0104] Furthermore, the above charging cycle may include a first stage and a second stage, and the first stage is before the second stage. Then when the device charges the battery during the charging cycle, it can first charge the battery within the first stage.

[0105] It should be noted that the above first stage includes at least one charging step, and the device can execute the at least one charging step to charge the battery. Exemplarily, assuming that the above first stage includes three charging steps arranged in sequence: a first constant current charging step, a second constant current charging step, and a constant voltage charging step. Then the device can execute the first constant current charging step to charge the battery with a constant current. In some application scenarios, as the first charging step of the battery, the above first constant current charging step can be a trickle charging step. The trickle charging step refers to the device charging the battery with a relatively low current for restorative charging to prevent damage to the battery due to a relatively high subsequent charging current. Exemplarily, the charging current of the above trickle charging step can be 0.2C. Further, after completing the first constant current charging step, the device executes the second constant current charging step to charge the battery with a constant current. After the trickle charging of the first constant current charging step, the device can increase the charging current so that the voltage of the battery continuously increases. Further, from the above content, it can be seen that when charging the battery with a constant current (the first constant current charging step and the second constant current charging step), due to the polarization phenomenon inside the battery, the voltage across the battery is not the same as the actual voltage of the battery. Therefore, after completing the second constant current charging step, the device executes the constant voltage charging step to charge the battery with a constant voltage to eliminate the polarization phenomenon inside the battery and enable the battery to charge more power. It can be understood that the above introduction of each charging step in the first stage is only an example and does not constitute a limitation on the present application. In some application scenarios, the first stage may also only include a constant current charging step or a constant voltage charging step, and the present application does not list them one by one here.

[0106] Generally speaking, in the embodiments of the present application, the device can execute at least one charging step in the first stage of the charging cycle to charge the battery and increase the battery power.

[0107] S102. Charge the battery in the second stage of the charging cycle.

[0108] As can be seen from the above, the charging cycle includes a first stage and a second stage, and the second stage is after the first stage. When the device charges the battery during the charging cycle, it can first charge the battery in the first stage and then charge the battery in the second stage after the first stage charging is completed. After charging in the first stage and the second stage, the battery charging is completed.

[0109] It should be noted that, as can be seen from the above, when the device performs constant voltage charging, a higher charging voltage will cause greater stress inside the battery positive electrode material, and the longer the constant voltage charging time, the more stress accumulates inside the battery positive electrode material, and the greater the impact on the battery cycle life. Therefore, the charging method provided in the embodiments of the present application can reduce the duration of constant voltage charging in the second stage of the charging cycle to reduce the stress accumulation inside the battery positive electrode material.

[0110] Specifically, the above second stage includes a constant current charging step and / or a constant power charging step. Exemplarily, the second stage may include at least one constant current charging step and at least one constant power charging step, or the second stage may include at least one constant current charging step, or the second stage may include at least one constant power charging step. For ease of description, in the following content of the embodiments of the present application, non-constant voltage charging steps are used to represent constant current charging steps and / or constant power charging steps. The non-constant voltage charging step can be understood as a charging step that charges in other charging methods except constant voltage charging in the charging steps.

[0111] It can be understood that the above second stage includes at least one non-constant voltage charging step. Further, the ratio of the duration of the above at least one non-constant voltage charging step, that is, the duration of the constant current charging step and / or the constant power charging step, to the duration of the second stage is greater than or equal to a first threshold. The first threshold can be understood as the minimum value of the ratio of the duration of the non-constant voltage charging step to the duration of the second stage when the stress influence inside the battery positive electrode material is significantly improved. That is to say, when the ratio of the duration of the above at least one non-constant voltage charging step to the duration of the second stage is greater than or equal to the above first threshold, the stress accumulation inside the battery positive electrode material is significantly reduced, and the battery cycle life can be greatly improved. Among them, the duration of the above at least one non-constant voltage charging step can be understood as the total duration of all non-constant voltage charging steps in the second stage.

[0112] Exemplarily, assume that the above second stage includes three charging steps: a constant current charging step, a constant voltage charging step, and a constant power charging step. Then, within the second stage, first, the device can execute the constant current charging step to charge the battery with a constant current. Then, after the constant current charging ends, the device can execute the constant voltage charging step to charge the battery with a constant voltage. Finally, after the constant voltage charging ends, the device can execute the constant power charging step to charge the battery with a constant power. It can be understood that both the above constant current charging step and the constant power charging step are non-constant voltage charging steps. Then, the sum of the duration of charging the battery with a constant current and the duration of charging the battery with a constant power by the device is the duration of at least one non-constant voltage charging step within the second stage. For example, assume that the duration of the above second stage is 10 minutes, the duration of the above constant current charging step is 2 minutes, and the duration of the above constant power charging step is 3 minutes. Then, the duration of the non-constant voltage charging step within the second stage is 2 + 3 = 5 minutes, and the ratio of the duration of the non-constant voltage charging step to the duration of the second stage is 50%. It can be understood that the above content is only an example and does not constitute a limitation to the embodiments of the present application.

[0113] Generally speaking, the charging method provided by the embodiments of the present application can improve the battery power by charging the battery in the first stage of the charging cycle, and by controlling the ratio of the duration of the non-constant voltage charging step to the duration of the second stage in the second stage of the charging cycle to be greater than or equal to a first threshold, the duration of charging the battery with a constant voltage within the second stage can be reduced, thereby reducing the stress accumulation inside the battery positive electrode material, and further reducing the influence of the increased charging voltage on the battery cycle life. The specific implementation process is described later and will not be elaborated here for the time being.

[0114] In some feasible implementation manners, from the above content, it can be known that the above first threshold is the minimum value of the ratio of the duration of the non-constant voltage charging step to the duration of the second stage when the stress influence inside the battery positive electrode material is significantly improved. Specifically, the first threshold can be 25%. That is to say, within the second stage of the charging cycle, the ratio of the duration of the non-constant voltage charging step to the duration of the second stage being greater than or equal to 25% can achieve a significant reduction in the stress accumulation inside the battery positive electrode material. In other words, the ratio of the duration of the non-constant voltage charging step to the duration of the second stage being greater than or equal to 25% can be understood as the ratio of the duration of the constant voltage charging step to the duration of the second stage being less than 75%. The charging method provided by the embodiments of the present application can effectively reduce the influence of the increased charging voltage on the battery life and extend the battery cycle life by controlling the duration of constant voltage charging within the second stage of the charging cycle to be within 75% of the duration of the second stage.

[0115] Exemplarily, assume that the above-mentioned second stage includes three charging steps: a constant current charging step, a constant voltage charging step, and a constant power charging step. It can be understood that both the above-mentioned constant current charging step and the constant power charging step are non-constant voltage charging steps. Then, the sum of the duration of the device charging the battery at a constant current and the duration of charging the battery at a constant power is the duration of at least one non-constant voltage charging step within the second stage. If the duration of the above-mentioned second stage is 10 minutes, the duration of the constant current charging step is 3 minutes, the duration of the constant voltage charging step is 4 minutes, and the duration of the constant power charging step is 3 minutes, then the duration of the non-constant voltage charging step within the second stage is 3 + 3 = 6 minutes. The ratio of the duration of the non-constant voltage charging step to the duration of the second stage is 60%, which is greater than or equal to the above-mentioned first threshold of 25%, and the ratio of the duration of the constant voltage charging step to the duration of the second stage is 40%. At this time, since the duration of the constant voltage charging step within the second stage is relatively short, the stress accumulation inside the positive electrode material of the battery is also relatively small, and the problem of mechanical failure of the battery after multiple cycles can be avoided. It can be understood that the above content is only an example and does not constitute a limitation to the embodiments of the present application.

[0116] In some feasible embodiments, the ratio between the duration of the non-constant voltage charging step and the duration of the second stage can be equal to 100%. At this time, the second stage only includes non-constant voltage charging steps and does not include constant voltage charging steps.

[0117] Exemplarily, assume that the above-mentioned second stage can include two charging steps: a constant current charging step and a constant power charging step. It can be understood that both the above-mentioned constant current charging step and the constant power charging step are non-constant voltage charging steps. Then, the sum of the duration of the device charging the battery at a constant current and the duration of charging the battery at a constant power is the duration of at least one non-constant voltage charging step within the second stage. If the duration of the above-mentioned second stage is 10 minutes, the duration of the constant current charging step is 6 minutes, and the duration of the constant power charging step is 4 minutes, then the duration of the non-constant voltage charging step within the second stage is 6 + 4 = 10 minutes. The ratio of the duration of the non-constant voltage charging step to the duration of the second stage is 100%, which is greater than or equal to the above-mentioned first threshold of 25%. At this time, the duration of the constant voltage charging step within the second stage is 0, and the stress accumulation inside the positive electrode material of the battery is greatly reduced, and the problem of mechanical failure of the battery after multiple cycles can be avoided. It can be understood that the above content is only an example and does not constitute a limitation to the embodiments of the present application.

[0118] Exemplarily, assume that the above-mentioned second stage may include a charging step: a constant current charging step or a constant power charging step. It can be understood that both the above-mentioned constant current charging step and the constant power charging step are non-constant voltage charging steps. Then, the duration of the device charging the battery with a constant current or charging the battery with a constant power is the duration of at least one non-constant voltage charging step within the second stage. If the duration of the above-mentioned second stage is 10 minutes, and the duration of the constant current charging step or the constant power charging step is 10 minutes, then the duration of the non-constant voltage charging step within the second stage is 10 minutes, and the ratio of the duration of the non-constant voltage charging step to the duration of the second stage is 100%, which is greater than or equal to the above-mentioned first threshold of 25%. At this time, the duration of the constant voltage charging step within the second stage is 0, and the stress accumulation inside the positive electrode material of the battery is greatly reduced, which can avoid the problem of mechanical failure of the battery after multiple cycles. It can be understood that the above content is only an example and does not constitute a limitation to the embodiments of the present application.

[0119] Generally speaking, the charging method provided by the embodiments of the present application can reduce the duration of constant voltage charging within the second stage by making the ratio of the duration of the non-constant voltage charging step within the second stage to the duration of the second stage greater than or equal to 25%, thereby reducing the stress accumulation inside the positive electrode material caused by constant voltage charging, slowing down the mechanical failure of the battery, and prolonging the cycle life of the battery.

[0120] In some feasible implementation manners, as can be seen from the above content, the device charges the battery in the first stage of the charging cycle according to step S101 to increase the battery's power, and then charges the battery in the second stage of the charging cycle according to step S102, and reduces the duration of the constant voltage charging step within the second stage to reduce the impact of constant voltage charging on the positive electrode material of the battery. It should be noted that since the device charging the battery with a constant voltage can effectively eliminate the polarization phenomenon inside the battery, enabling the battery to charge more power, while the duration of constant voltage charging in the second stage of the embodiments of the present application is reduced. Therefore, in order to reduce the stress impact on the positive electrode material caused by constant voltage charging while ensuring that the battery charges sufficient power, in the charging method provided by the embodiments of the present application, the ratio of the duration of the above-mentioned second stage to the charging cycle can be 0.2.

[0121] It can be understood that if the ratio of the duration between the above-mentioned second stage and the charging cycle is 0.2, then the ratio of the duration between the first stage and the charging cycle is 0.8. That is to say, assuming the charging cycle is T, the part from the start of the charging cycle to 0.8T is the first stage, and the part from 0.8T to the end of the charging cycle is the second stage. During the first stage, the device can charge the battery through a constant voltage charging step and a constant current charging step to enable the battery to charge more power. Then, during the second stage, by reducing the duration of the constant voltage charging step, the device can reduce the stress accumulation inside the positive electrode material. At this time, since the duration of the second stage only accounts for 0.2 of the charging cycle duration, it can be ensured that the battery charges sufficient power during the first stage of the charging cycle, and the reduction in the duration of the constant voltage charging step during the second stage will not affect the power charged into the battery.

[0122] Exemplarily, assuming the above-mentioned charging cycle T is 60 minutes, the duration of the first stage is 0.8T = 48 minutes, and the duration of the second stage is 0.2T = 12 minutes. Then the device can charge the battery through a constant voltage charging step and a constant current charging step from the start of the charging cycle to 48 minutes to enable the battery to charge sufficient power. Then, the device can charge the battery through a constant current charging step or a constant power charging step within 12 minutes before the end of the charging to reduce the impact of constant voltage charging on the positive electrode material. It can be understood that the above is only for illustration and does not constitute a limitation on the embodiments of the present application.

[0123] Generally speaking, the charging method provided by the embodiments of the present application makes the ratio of the duration between the second stage and the charging cycle be 0.2, so that the duration of the second stage is less than that of the first stage, which enables the device to have more time to charge more power into the battery during the first stage. And by reducing the duration of the constant voltage charging step during the second stage before the end of the charging, the stress accumulation inside the positive electrode material can be reduced while not affecting the power charged into the battery.

[0124] In some feasible embodiments, as can be seen from the above content, the requirements of the user for the volume and battery life of the device are constantly increasing, and the volumetric energy density of the battery needs to be further improved. In this regard, in addition to increasing the charging voltage, the device can also use an alkali metal material as the positive electrode material of the battery to improve the volumetric energy density of the battery. Among them, the positive electrode of the alkali metal battery includes an alkali metal, and this alkali metal is the active ion released by the above positive electrode during charging. Thus, it can be seen that for an alkali metal battery, increasing the charging voltage will also increase the amount of alkali metal released from the positive electrode, and the amount of alkali metal released can be used to characterize the volumetric energy density of the alkali metal battery. For specific reference to the above description, it will not be elaborated here.

[0125] It can be understood that after the alkali metal battery is fully charged, the higher the amount of alkali metal removed from the positive electrode, the higher the volumetric energy density of the alkali metal battery. In this regard, after the alkali metal battery is charged according to the charging method provided in the embodiments of the present application, the amount of alkali metal removed from the positive electrode of the alkali metal battery is greater than or equal to 60%.

[0126] It should be noted that when the amount of alkali metal removed from the positive electrode of the alkali metal battery is greater than or equal to 60%, it indicates that the volumetric energy density of the alkali metal battery is relatively high, and thus the requirements for the volume size and battery life of the device can be met.

[0127] In some feasible embodiments, in order to verify the amount of alkali metal removed from the positive electrode of the alkali metal battery, after the device finishes charging the alkali metal battery, the positive electrode of the alkali metal battery can be disassembled. Then, the separator on the surface of the positive electrode plate is cleaned, and the positive electrode plate is subjected to elemental analysis testing by an inductively coupled plasma emission spectrometer. Further, after the elemental analysis testing, the ratio of the alkali metal element to other metal elements in the positive electrode plate can be determined, and this ratio is the amount of alkali metal removed.

[0128] In some feasible embodiments, the above alkali metal battery can be a cobalt acid lithium battery, a ternary lithium battery, a sodium battery, or other batteries whose positive electrode includes oxides of alkali metal elements and transition metal elements. The embodiments of the present application will not list them one by one here.

[0129] Generally speaking, the charging method provided in the embodiments of the present application can make the amount of alkali metal removed from the positive electrode of the alkali metal battery greater than or equal to 60% after the battery is fully charged, so that the alkali metal battery can achieve a relatively high volumetric energy density.

[0130] In some feasible embodiments, in order to improve the volumetric energy density of the battery, the charging method provided in the embodiments of the present application can gradually increase the charging voltage of the battery during the charging cycle, so that more electric charge can be charged into the battery during the charging cycle. Specifically, the device can make the charging voltage for charging the battery in the first stage less than or equal to the charging voltage for charging the battery in the second stage, thereby increasing the charging voltage of the battery and increasing the volumetric energy density of the battery. Among them, the charging voltage of the device for charging the battery in the first stage can be understood as the average charging voltage of multiple charging steps in the first stage, and the charging voltage of the device for charging the battery in the second stage can be understood as the average charging voltage of multiple charging steps in the second stage.

[0131] Alternatively, the charging voltage at which the device charges the battery during the first stage can be understood as the charging voltage of any charging step within the first stage, and the charging voltage at which the device charges the battery during the second stage can be understood as the charging voltage of any charging step within the second stage. At this time, the charging voltage at which the device charges the battery during the first stage is less than or equal to the charging voltage at which the device charges the battery during the second stage, which can be understood as the maximum charging voltage of the battery among all charging steps in the first stage is less than the minimum charging voltage of the battery among all charging steps in the second stage.

[0132] Among them, the charging voltage of the battery in the constant voltage charging step refers to the constant charging voltage of the battery in this constant voltage charging step. The charging voltage of the battery in the constant current charging step refers to the maximum charging voltage of the battery in this constant current charging step. Since the charging voltage of the battery in the constant current charging step gradually increases, the charging voltage of the battery at the end of the constant current charging step is the maximum charging voltage. The charging voltage of the battery in the constant power charging step refers to the maximum charging voltage of the battery in this constant power charging step. Since the charging voltage of the battery in the constant power charging step gradually increases, the charging voltage of the battery at the end of the constant power charging step is the maximum charging voltage.

[0133] In some feasible embodiments, when the first stage includes multiple charging steps, the charging voltage of any charging step within the first stage is less than the charging voltage of the subsequent charging step, that is, when the battery is charged in multiple charging steps of the first stage, the charging voltage gradually increases. Similarly, when the second stage includes multiple charging steps, the charging voltage of any charging step within the second stage is less than the charging voltage of the subsequent charging step, that is, when the battery is charged in multiple charging steps of the second stage, the charging voltage gradually increases. It can be understood that by gradually increasing the charging voltage of the battery in multiple charging steps, the device can increase the voltage at the end of the charging cycle, thereby achieving a high volumetric energy density of the battery.

[0134] Exemplarily, assume that the first stage includes five charging steps. Among them, the charging voltage of the first charging step is 4.21 volts, the charging voltage of the second charging step is 4.25 volts, the charging voltage of the third charging step is 4.35 volts, the charging voltage of the fourth charging step is 4.4 volts, and the charging voltage of the fifth charging step is 4.5 volts. It can be seen that the charging voltage of each charging step in the first stage is less than the charging voltage of the subsequent charging step, and the charging voltages of the five charging steps gradually increase. At the same time, the second stage includes one charging step, and the charging voltage of the battery in this charging step is 4.54 volts. It can be understood that the charging voltage of the battery within the second stage is greater than the charging voltage of the battery in each charging step of the first stage.

[0135] Generally speaking, the charging method provided by the embodiments of the present application can gradually increase the charging voltage of the battery during the charging cycle by making the charging voltage of the battery in the second stage greater than that in the first stage, so as to achieve a higher volumetric energy density at the end of charging. At the same time, since the increase in the charging voltage will increase the internal stress of the battery cathode material, the charging method of the embodiments of the present application can effectively reduce the stress accumulation of the cathode material caused by the increase in the charging voltage by reducing the duration of the constant-voltage charging step in the second stage.

[0136] In some feasible embodiments, the above charging cycle may include N charging steps. Among them, the first stage is composed of a part of the N charging steps, and the second stage is composed of another part of the N charging steps. Further, the charging method provided by the embodiments of the present application can increase the charging speed of the battery by making the charging current of one charging step among the N charging steps greater than the charging current of the previous charging step of this charging step, reduce the duration of the constant-voltage charging step, and thus slow down the mechanical failure of the battery.

[0137] Among them, the charging current of the battery within each charging step can be understood as the maximum charging current of the battery within this charging step. At this time, the charging current of one charging step among the N charging steps being greater than the charging current of the previous charging step of this charging step can be understood as the maximum charging current of the battery in this charging step being greater than the maximum charging current of the previous charging step.

[0138] It can be understood that the charging current of the battery in the constant-current charging step is constant, so the charging current of the battery in this constant-current charging step is the constant current. At the same time, since the charging current of the battery in the constant-voltage charging step gradually decreases, the charging current of the battery in the constant-voltage charging step refers to the charging current of the battery at the start of the constant-voltage charging step.

[0139] In some feasible embodiments, when the charging cycle includes N charging steps, there is a charging current for charging the battery in the jth charging step that is greater than or equal to the charging current for charging the battery in the (j - 1)th charging step. The above jth charging step can be understood as one of the N charging steps, and the above (j - 1)th charging step can be understood as the previous charging step of the above jth charging step.

[0140] In some feasible embodiments, when the charging cycle includes N charging steps, there is a charging current for charging the battery in the i-th charging step, which is less than the charging current for charging the battery in the (i - 1)-th charging step. The above-mentioned i-th charging step can be understood as one of the N charging steps, and the above-mentioned (i - 1)-th charging step can be understood as the previous charging step of the i-th charging step. Thus, among the N charging steps of the charging cycle, the charging current of any charging step can be greater than, equal to, or less than the charging current of the subsequent charging step.

[0141] Exemplarily, when the charging cycle includes 6 charging steps, assume that the first stage includes 5 charging steps and the second stage includes 1 charging step. Among them, the charging current of the 1st charging step among the above 7 charging steps is 1C, the charging current of the 2nd charging step is 0.5C, the charging current of the 3rd charging step is 1.5C, the charging current of the 4th charging step is 1.5C, the charging current of the 5th charging step is 1C, and the charging current of the 6th charging step is 0.7C. It can be seen that the charging current of the 2nd charging step is less than that of the 1st charging step, the charging current of the 3rd charging step is greater than that of the 2nd charging step, the charging current of the 4th charging step is equal to that of the 3rd charging step, and the charging current of the 6th charging step is less than that of the 5th charging step.

[0142] It should be noted that within the rated charging current of the battery, the greater the charging current of the device for charging the battery, the faster the movement of active ions and electrons at both ends of the battery, and the battery power can rise rapidly in a short time, so the charging speed of the battery is accelerated. Among them, the rated charging current of the above battery refers to the maximum charging current of the battery. When the battery charging current is greater than this rated charging current, it may cause damage to the battery. Therefore, when the device charges the battery, it can keep the charging current less than the rated charging current to avoid damaging the battery.

[0143] In contrast, in the charging steps (1a) to (6a) of the above conventional boost charging method, the charging current of the device for charging the battery gradually decreases until it finally decreases to 0.025C. When the device charges the battery according to this conventional boost charging method, the charging speed is relatively slow. In the charging method provided in the embodiments of the present application, the device can increase the charging current of the battery within the charging cycle, that is, there is a charging step within the charging cycle where the battery charging current is greater than the battery charging current of the previous charging step. At this time, the battery charging speed is accelerated, and thus the duration of the constant voltage charging step can be reduced, and the stress accumulation can be reduced, thereby improving the cycle performance and life of the battery.

[0144] In some feasible embodiments, the above-mentioned second stage includes at least one non-constant voltage charging step, and the last charging step of the second stage is a non-constant voltage charging step.

[0145] It should be noted that, as can be seen from the above content, when the charging cycle includes multiple charging steps, the battery charging voltage of each charging step is less than that of the subsequent charging step, that is, the charging voltage for charging the battery by the device gradually increases. Then, the battery charging voltage of the last charging step before the end of the second stage is the highest charging voltage of the battery during the entire charging cycle. At the same time, since the stress generated inside the battery positive electrode material is greater when the battery is charged at a constant voltage and the higher the charging voltage of the battery, in order to avoid the huge stress caused by the high charging voltage, the last charging step before the end of the second stage can be a non-constant voltage charging step, thereby avoiding the stress caused by the high charging voltage and slowing down the mechanical failure of the battery.

[0146] In some feasible embodiments, the above-mentioned non-constant voltage charging step includes a constant current charging step and a constant power charging step. Then, the last charging step of the second stage can be a constant current charging step or a constant power charging step.

[0147] Exemplarily, assume that the second stage includes three charging steps: a constant current charging step, a constant voltage charging step, and a constant power charging step. Then, the last charging step of the second stage is a constant power charging step. Specifically, within the second stage, first, the device can execute the constant current charging step to charge the battery at a constant current. Then, after the constant current charging ends, the device can execute the constant voltage charging step to charge the battery at a constant voltage. Finally, after the constant voltage charging ends, the device can execute the constant power charging step to charge the battery at a constant power. After the constant power charging ends, the battery charging is completed.

[0148] Exemplarily, assume that the second stage includes two charging steps: a constant voltage charging step and a constant current charging step. Then, the last charging step of the second stage is a constant current charging step. Specifically, within the second stage, first, the device can execute the constant voltage charging step to charge the battery at a constant voltage. Then, after the constant voltage charging ends, the device can execute the constant current charging step to charge the battery at a constant current. After the constant current charging ends, the battery charging is completed. It can be understood that the above content is only an example and does not constitute a limitation to the embodiments of the present application.

[0149] Generally speaking, the charging method provided by the embodiments of the present application can reduce the duration of constant voltage charging of the battery at a high charging voltage by making the last charging step in the second stage a non-constant voltage charging step, thereby reducing the stress accumulation of the positive electrode material, slowing down the mechanical failure, and further improving the battery cycle performance and lifespan.

[0150] In some feasible embodiments, in the first charging step of the charging cycle, that is, the first charging step of the first stage, the charging current for charging the battery by the device is in the range of 0.1C to 5C. Specifically, when the device charges the battery with a charging current having a lower current rate within the above range of 0.1C to 5C during the first charging step, for example, when charging the battery with a charging current of 0.1C, the charging speed of the battery is slower. On the contrary, when the device charges the battery with a charging current having a higher current rate within the above range of 0.1C to 5C, for example, when charging the battery with a charging current of 5C, the charging speed of the battery is faster. Thus, it can be seen that the device can select a charging current with an appropriate current rate to charge the battery in the first charging step of the first stage according to different application scenarios, so as to achieve fast charging or slow charging of the battery.

[0151] In some feasible embodiments, in the last charging step of the charging cycle, that is, the last charging step of the second stage, the charging current for charging the battery by the device is in the range of 0.025C to 1.5C. Specifically, when the device charges the battery with a charging current having a lower current rate within the above range of 0.025C to 1.5C during the last charging step, for example, when charging the battery with a charging current of 0.025C, the charging speed of the battery is slower. On the contrary, when the device charges the battery with a charging current having a higher current rate within the above range of 0.025C to 1.5C, for example, when charging the battery with a charging current of 1.5C, the charging speed of the battery is faster. Thus, it can be seen that the device can select a charging current with an appropriate current rate to charge the battery in the last charging step of the second stage according to different application scenarios, so as to achieve fast charging or slow charging of the battery.

[0152] It should be noted that in the above conventional boost charging method, the charging current for charging the battery by the device gradually decreases, so the charging current of the battery in the last charging step is usually relatively low. For example, the charging current in the last charging step of the above conventional boost charging method is 0.025C. In contrast, since in the charging method provided by the embodiments of the present application, the charging current for charging the battery by the device within the charging cycle can increase, therefore, the charging current of the battery in the last charging step can be relatively high. For example, the charging current in the last charging step can be 1.5C. Then, compared with the above conventional boost charging method, the charging method provided by the embodiments of the present application can further improve the charging speed, thereby reducing the duration of constant voltage charging and improving the cycle life of the battery.

[0153] In some feasible embodiments, after the device completes charging the battery in the second stage of the charging cycle, the state of charge of the battery is greater than or equal to 90%. That is to say, in the embodiments of the present application, through the charging in the first stage and the second stage, the state of charge of the battery can reach more than 90%. It can be understood that after the battery is charged, the closer the state of charge of the battery is to 100%, the more electricity is charged into the battery, and the longer the battery life is. In the embodiments of the present application, after the battery is fully charged, the state of charge is greater than or equal to 90%, so the battery can meet the requirement of battery life and ensure that the device can work.

[0154] In some feasible embodiments, for the specific implementation of the device to charge the battery, the embodiments of the present application take the alkali metal battery as an example for illustration. Specifically, the alkali metal battery can be a lithium cobalt oxide battery, a ternary lithium battery, a sodium battery, etc. In the following content of the embodiments of the present application, the lithium cobalt oxide battery, the ternary lithium battery and the sodium battery are taken as examples for illustration respectively, and other types of alkali metal batteries are not elaborated here.

[0155] In some feasible embodiments, when the above alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 1 in the charging method to charge the battery. The charging cycle of Example 1 includes charging steps (1b) to (11b):

[0156] (1b) Constant current charge the lithium cobalt oxide battery at a charging current of 3.5C until the voltage reaches 4.21V;

[0157] (2b) Constant voltage charge the lithium cobalt oxide battery at a charging voltage of 4.21V until the current decreases to 3.0C;

[0158] (3b) Constant current charge the lithium cobalt oxide battery at a charging current of 3.0C until the voltage reaches 4.25V;

[0159] (4b) Constant voltage charge the lithium cobalt oxide battery at a charging voltage of 4.25V until the current decreases to 2.5C;

[0160] (5b) Constant current charge the lithium cobalt oxide battery at a charging current of 2.5C until the voltage reaches 4.35V;

[0161] (6b) Constant voltage charge the lithium cobalt oxide battery at a charging voltage of 4.35V until the current decreases to 2.0C;

[0162] (7b) Constant current charge the lithium cobalt oxide battery at a charging current of 2.0C until the voltage reaches 4.4V;

[0163] (8b) Constant voltage charge the lithium cobalt oxide battery at a charging voltage of 4.4V until the current decreases to 1.5C;

[0164] (9b) Constant current charge the lithium cobalt oxide battery at a charging current of 1.5C until the voltage reaches 4.5V;

[0165] (10b) Constant voltage charge the lithium cobalt oxide battery at a charging voltage of 4.5V until the current decreases to 1.2C;

[0166] (11b) Constant current charge the lithium cobalt oxide battery at a charging current of 1.2C until the voltage reaches 4.54V, and the charging is completed.

[0167] Among them, the state of charge of the lithium cobalt oxide battery at the end of charging is 100%, and within the entire charging cycle T from (1b) to (11b) above, in the last 0.2T, that is, in the second stage, 43% of the time is the constant voltage charging step, and 57% of the time is the constant current charging step. That is, the proportion of the time of the non-constant voltage charging step in the second stage is greater than the above first threshold of 25%.

[0168] Further, when the lithium cobalt oxide battery is charged according to the first embodiment above, the schematic diagram of the relationship between the charging voltage and the charging time of the lithium cobalt oxide battery can be referred to Figure 3 as shown. Specifically, please refer to Figure 3 , Figure 3 which is a schematic diagram of the relationship between the charging voltage and the charging time of the lithium cobalt oxide battery provided by the embodiment of the present application. Figure 3 The comparison curve shown is the curve when the device charges the battery according to the above charging steps (1a) to (6a), Figure 3 and the optimized curve shown is the curve when the device charges the battery according to the above charging steps (1b) to (11b).

[0169] It can be understood that, from Figure 3 it can be seen that the charging cycle of the comparison curve is 64 minutes, while the charging cycle corresponding to the optimized curve is 40 minutes. Thus, it can be seen that the charging method provided by the embodiment of the present application can accelerate the charging speed of the battery. At the same time, from the 24th minute to the 64th minute, the charging voltage corresponding to the comparison curve remains unchanged, that is, the device performs constant voltage charging on the battery. From the above content, it can be known that when the device performs constant voltage charging on the battery with a high charging voltage, the internal stress of the battery cathode material will accumulate for a long time. Therefore, when the device charges the battery according to the charging steps of the comparison curve, it will cause mechanical failure of the battery, and the cycle performance and life of the battery will be affected.

[0170] In contrast, Figure 3The optimized curve shown does not have a long constant-voltage charging step. Especially when the charging voltage is relatively high (for example, greater than 4.5), the optimized curve significantly reduces the duration of the constant-voltage charging step. Among them, when the charging voltage of the battery reaches 4.53 volts, the corresponding charging step in the optimized curve is a constant-current charging step or a constant-power charging step, which can reduce the duration of constant-voltage charging when the charging voltage of the battery is relatively high. Therefore, when the device charges the battery according to Figure 3 the optimized curve shown, it can reduce the stress accumulation of the positive electrode material, slow down mechanical failure, and thus improve the cycle performance and life of the battery, and can also improve the charging speed.

[0171] In some feasible embodiments, when the above alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 2 in the charging method to charge the battery. The charging cycle of this Example 2 includes charging steps (1c) to (11c). Among them, the specific implementation manners of charging steps (1c) to (10c) can refer to the above charging steps (1b) to (10b), which will not be elaborated here. The charging step (11c) is:

[0172] (11c) Constant-current charge the lithium cobalt oxide battery at a charging current of 1.2C to a voltage of 4.6V, and the charging ends.

[0173] Among them, the state of charge of the lithium cobalt oxide battery at the end of charging is 100%. And in the entire charging cycle T from (1c) to (11c) above, in the last 0.2T, that is, in the second stage, 40% of the duration is a constant-voltage charging step, and 60% of the duration is a constant-current charging step. That is, in the second stage, the proportion of the duration of the non-constant-voltage charging step is greater than the above first threshold of 25%.

[0174] In some feasible embodiments, when the above alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 3 in the charging method to charge the battery. The charging cycle of this Example 3 includes charging steps (1d) to (14d). Among them, the specific implementation of charging steps (1d) to (7d) can refer to the above charging steps (1b) to (7b), which will not be elaborated here. The charging steps (8d) to (14d) are as follows:

[0175] (8d) Constant-current charge the lithium cobalt oxide battery at a charging current of 2.0C to a voltage of 4.53V;

[0176] (9d) Constant-voltage charge the lithium cobalt oxide battery at a charging voltage of 4.53V until the current decreases to 1.5C;

[0177] (10d) Constant-current charge the lithium cobalt oxide battery at a charging current of 1.5C to a voltage of 4.6V;

[0178] (11d) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.6 V until the current decreases to 0.6 C;

[0179] (12d) Constantly charge the lithium cobalt oxide battery at a charging current of 0.6 C until the voltage reaches 4.65 V;

[0180] (13d) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.65 V until the current decreases to 0.4 C;

[0181] (14d) Constantly charge the lithium cobalt oxide battery at a charging current of 0.4 C until the voltage reaches 4.7 V, and the charging is completed.

[0182] Among them, the state of charge of the lithium cobalt oxide battery at the end of charging is 100%, and in the entire charging cycle T from (1d) to (14d) above, in the last 0.2T, that is, in the second stage, 25% of the time is for the constant voltage charging step, and 75% of the time is for the constant current charging step. That is, in the second stage, the proportion of the time of the non-constant voltage charging step is greater than the above first threshold of 25%.

[0183] In some feasible embodiments, when the above alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 4 in the charging method to charge the battery. The charging cycle of this Example 4 includes charging steps (1e) to (14e). Among them, charging steps (1e) to (7e) can refer to the above charging steps (1b) to (7b), which will not be elaborated here. Charging steps (8e) to (14e) are as follows:

[0184] (8e) Constantly charge the lithium cobalt oxide battery at a charging current of 1.5 C until the voltage reaches 4.5 V;

[0185] (9e) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.5 V until the current decreases to 1.2 C;

[0186] (10e) Constantly charge the lithium cobalt oxide battery at a charging current of 2 C until the voltage reaches 4.53 V;

[0187] (11e) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.53 V until the current decreases to 0.7 C;

[0188] (12e) Constantly charge the lithium cobalt oxide battery at a charging current of 0.7 C until the voltage reaches 4.55 V;

[0189] (13e) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.55 V until the current decreases to 0.5 C;

[0190] (14e) Constantly charge the lithium cobalt oxide battery at a charging current of 0.5 C until the voltage reaches 4.7 V, and the charging is completed.

[0191] Among them, the state of charge of the lithium cobalt oxide battery at the end of charging is 90%, and in the entire charging cycle T from (1e) to (14e) above, in the last 0.2T, that is, in the second stage, the duration of 0% is the constant voltage charging step, and the duration of 100% is the constant current charging step, that is, in the second stage, the proportion of the duration of the non-constant voltage charging step is greater than the above first threshold of 25%.

[0192] In some feasible embodiments, when the above alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 5 in the charging method to charge the battery. The charging cycle of this Example 5 includes charging steps (1f) to (14f). Among them, the charging steps (1f) to (7f) can refer to the above charging steps (1b) to (7b), which will not be elaborated here. The charging steps (8f) to (14f) are as follows:

[0193] (8f) Constantly charge the lithium cobalt oxide battery at a charging current of 1.7C until the voltage reaches 4.55V;

[0194] (9f) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.55V until the current decreases to 1.5C;

[0195] (10f) Constantly charge the lithium cobalt oxide battery at a charging current of 1.5C until the voltage reaches 4.57V;

[0196] (11f) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.57V until the current decreases to 1.2C;

[0197] (12f) Constantly charge the lithium cobalt oxide battery at a charging current of 1.5C until the voltage reaches 4.6V;

[0198] (13f) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.6V until the current decreases to 0.7C;

[0199] (14f) Constantly charge the lithium cobalt oxide battery at a charging current of 0.7C until the voltage reaches 4.7V, and the charging ends.

[0200] Among them, the state of charge of the lithium cobalt oxide battery at the end of charging is 97%, and in the entire charging cycle T from (1f) to (14f) above, in the last 0.2T, that is, in the second stage, the duration of 0% is the constant voltage charging step, and the duration of 100% is the constant current charging step, that is, in the second stage, the proportion of the duration of the non-constant voltage charging step is greater than the above first threshold of 25%.

[0201] In some feasible embodiments, when the above alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 6 in the charging method to charge the battery. The charging cycle of this Example 6 includes charging steps (1g) to (12g). Among them, charging steps (1g) to (7g) can refer to the above charging steps (1b) to (7b), which will not be elaborated here. Charging steps (8g) to (12g) are as follows:

[0202] (8g) Constantly charge the lithium cobalt oxide battery at a charging current of 1.5C until the voltage reaches 4.5V;

[0203] (9g) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.5V until the current decreases to 1.2C;

[0204] (10g) Constantly charge the lithium cobalt oxide battery at a charging current of 1.2C until the voltage reaches 4.6V;

[0205] (11g) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.6V until the current decreases to 0.15C;

[0206] (12g) Constantly charge the lithium cobalt oxide battery at a charging current of 0.15C until the voltage reaches 4.61V, and the charging ends.

[0207] Among them, the state of charge of the lithium cobalt oxide battery at the end of charging is 100%. And in the entire charging cycle T from (1g) to (12g) above, in the last 0.2T, that is, in the second stage, 75% of the time is for the constant voltage charging step, and 25% of the time is for the constant current charging step. That is, in the second stage, the proportion of the time of the non-constant voltage charging step is equal to the above first threshold of 25%.

[0208] In some feasible embodiments, when the above alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 7 in the charging method to charge the battery. The charging cycle of this Example 7 includes charging steps (1h) to (13h). Among them, charging steps (1h) to (7h) can refer to the above charging steps (1b) to (7b), which will not be elaborated here. Charging steps (8h) to (13h) are as follows:

[0209] (8h) Constantly charge the lithium cobalt oxide battery at a charging current of 1.2C until the voltage reaches 4.5V;

[0210] (9h) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.5V until the current decreases to 1C;

[0211] (10h) Constantly charge the lithium cobalt oxide battery at a charging current of 1.5C until the voltage reaches 4.6V;

[0212] (11h) Constantly charge the lithium cobalt oxide battery at a charging voltage of 4.6V until the current decreases to 1C;

[0213] (12h) Constant current charge the lithium cobalt oxide battery at a charging current of 1C until the voltage reaches 4.66V.

[0214] (13h) Constant power charge the lithium cobalt oxide battery at a charging power of 9.52 watts (W) until the voltage reaches 4.7V, and the charging ends.

[0215] Among them, the state of charge of the lithium cobalt oxide battery at the end of charging is 100%. And in the entire charging cycle T from (1h) to (13h) above, in the last 0.2T, that is, in the second stage, 14% of the time is for the constant voltage charging step, 16% of the time is for the constant current charging step, and 70% of the time is for the constant power charging step. That is, in the second stage, the proportion of the time of the non-constant voltage charging step is greater than the above first threshold of 25%.

[0216] Generally speaking, when the device charges the lithium cobalt oxide battery according to the charging method provided in the embodiments of the present application, the charging cut-off voltage of the lithium cobalt oxide battery can reach within the range of 4.5 volts to 4.75 volts. Among them, the charging cut-off voltage of the lithium cobalt oxide battery can be understood as the charging voltage of the lithium cobalt oxide battery at the end of the charging cycle. Since the charging voltage of the lithium cobalt oxide battery gradually increases during the charging cycle, the charging cut-off voltage of the lithium cobalt oxide battery can also be understood as the highest charging voltage of the lithium cobalt oxide battery during the charging cycle. In contrast, in the above conventional boost charging method, the charging cut-off voltage of the battery charging is only 4.53 volts, while in the embodiments of the present application, the charging cut-off voltage of the lithium cobalt oxide battery can be increased to more than 4.54 volts. It can be understood that as the charging cut-off voltage increases, the volumetric energy density of the lithium cobalt oxide battery also increases. Therefore, the charging method provided in the embodiments of the present application can improve the volumetric energy density of the lithium cobalt oxide battery by increasing the charging cut-off voltage of the lithium cobalt oxide battery. At the same time, since the charging method provided in the embodiments of the present application also reduces the duration of the constant voltage charging step of the lithium cobalt oxide battery, the influence of the increase in the charging cut-off voltage on the cycle life of the lithium cobalt oxide battery can be reduced.

[0217] In some feasible embodiments, when the above alkali metal battery is a ternary lithium battery, the device can execute Embodiment 8 in the charging method to charge the battery. The charging cycle of Embodiment 8 includes charging steps (1k) to (5k):

[0218] (1k) Constant current charge the ternary lithium battery at a charging current of 2C until the voltage reaches 4V.

[0219] (2k) Constant voltage charge the ternary lithium battery at a charging voltage of 4V until the current decreases to 1.5C.

[0220] (3k) Constant current charge the ternary lithium battery at a charging current of 1.5C until the voltage reaches 4.2V.

[0221] (4k) Constantly charge the ternary lithium battery at a charging voltage of 4.2 V until the current decreases to 0.5 C.

[0222] (5k) Constantly charge the ternary lithium battery at a charging current of 0.5 C until the voltage reaches 4.3 V, and the charging ends.

[0223] Among them, the state of charge of the ternary lithium battery at the end of charging is 100%, and in the entire charging cycle T from (1k) to (5k) above, in the last 0.2T, that is, in the second stage, 30% of the duration is the constant-voltage charging step, and 70% of the duration is the constant-current charging step. That is, in the second stage, the proportion of the duration of the non-constant-voltage charging step is greater than the above first threshold of 25%.

[0224] In some feasible embodiments, when the device charges the ternary lithium battery according to the charging method provided in the embodiments of the present application, the charging cut-off voltage of the ternary lithium battery can reach within the range of 4.3 V to 4.5 V. It can be understood that as the charging cut-off voltage increases, the volumetric energy density of the ternary lithium battery also increases. Therefore, the charging method provided in the embodiments of the present application can increase the volumetric energy density of the ternary lithium battery by increasing the charging cut-off voltage. At the same time, since the charging method provided in the embodiments of the present application also reduces the duration of the constant-voltage charging step of the ternary lithium battery, the influence of the increase in the charging cut-off voltage on the cycle life of the ternary lithium battery can be reduced.

[0225] In some feasible embodiments, when the above alkali metal battery is a sodium battery, the device can execute Embodiment Nine in the charging method to charge the battery. The charging cycle of Embodiment Nine includes charging steps (1n) to (5n):

[0226] (1n) Constantly charge the sodium battery at a charging current of 2 C until the voltage reaches 3.9 V.

[0227] (2n) Constantly charge the sodium battery at a charging voltage of 3.9 V until the current decreases to 1.5 C.

[0228] (3n) Constantly charge the sodium battery at a charging current of 1.5 C until the voltage reaches 3.95 V.

[0229] (4n) Constantly charge the sodium battery at a charging voltage of 3.95 V until the current decreases to 0.5 C.

[0230] (5n) Constantly charge the sodium battery at a charging current of 0.5 C until the voltage reaches 4.20 V, and the charging ends.

[0231] Among them, the state of charge of the sodium battery at the end of charging is 100%, and in the entire charging cycle T from (1n) to (5n) above, in the last 0.2T, that is, in the second stage, 56% of the duration is the constant voltage charging step, and 44% of the duration is the constant current charging step. That is, the proportion of the duration of the non-constant voltage charging step in the second stage is greater than the above first threshold of 25%.

[0232] In some feasible embodiments, when the device charges the sodium battery according to the charging method provided in the embodiments of the present application, the charging cut-off voltage of the sodium battery can reach within the range of 4.1 volts to 4.5 volts. It can be understood that as the charging cut-off voltage increases, the volumetric energy density of the sodium battery also increases. Therefore, the charging method provided in the embodiments of the present application can improve the volumetric energy density of the sodium battery by increasing the charging cut-off voltage of the sodium battery. At the same time, since the charging method provided in the embodiments of the present application also reduces the duration of the constant voltage charging step of the sodium battery, the influence of the increase in the charging cut-off voltage on the cycle life of the sodium battery can be reduced.

[0233] In some feasible embodiments, in order to facilitate the understanding of the differences between Embodiments 1 to 9 and the above conventional boost charging method in the above charging method, please refer to the following table:

[0234]

[0235]

[0236] It should be noted that in the table, Comparative Example 1 refers to the device charging the lithium cobalt oxide battery to an SOC of 95% with the above conventional boost charging method and a charging cut-off voltage of 4.55V. Comparative Example 2 refers to the device charging the lithium cobalt oxide battery to an SOC of 97% with the above conventional boost charging method and a charging cut-off voltage of 4.6V. Comparative Example 3 refers to the device charging the sodium battery to an SOC of 100% with the above conventional boost charging method and a charging cut-off voltage of 4.15V. The cycle performance refers to the number of cycles when the battery capacity decays to the target capacity.

[0237] It can be understood that in Comparative Example 1 and Comparative Example 2 above, the duration ratio of the constant-voltage charging step in the second stage is equal to 100%, and the charging voltage in the second stage is relatively high. From the above content, it can be seen that the internal stress of the positive electrode material will accumulate for a long time in the second stage, resulting in mechanical failure of the battery and a decline in cycle performance. Exemplarily, in Comparative Example 1, the cycle performance is ~700 cls@80%, indicating that after 700 cycles of the lithium cobalt oxide battery, the battery capacity decays to 80%. In Comparative Example 2, the cycle performance is ~200 cls@80%, indicating that after 200 cycles of the lithium cobalt oxide battery, the battery capacity decays to 80%. In Comparative Example 3, the cycle performance is ~120 cls@80%, indicating that after 120 cycles of the sodium battery, the battery capacity decays to 80%. Thus, it can be seen that the lithium cobalt oxide battery has poor cycle performance when performing cyclic charging based on the above conventional step-up charging method.

[0238] In contrast, the duration ratio of the constant-voltage charging step in the second stage corresponding to each of the above embodiments is less than or equal to 75%, that is, the duration ratio of the non-constant-voltage charging step is greater than the first threshold of 25%. From the above content, it can be seen that at this time, the stress accumulation inside the positive electrode material of the battery is reduced, which can effectively slow down the mechanical failure of the battery and improve the cycle performance and life of the battery. For example, in Embodiment 1, the cycle performance is ~800 cls@80%, indicating that after 800 cycles of the lithium cobalt oxide battery, the battery capacity decays to 80%; in Embodiment 2, the cycle performance is ~1500 cls@80%, indicating that after 1500 cycles of the lithium cobalt oxide battery, the battery capacity decays to 80%. Therefore, compared with the charging method of Embodiment 1, the lithium cobalt oxide battery has better cycle performance when charged by the charging method of Embodiment 2.

[0239] It can be understood that the alkali metal extraction amount and cycle performance corresponding to each of the above embodiments can be different. The higher the alkali metal extraction amount, the higher the volumetric energy density of the battery. Then, according to different actual application scenarios and battery types, the device can select different embodiments to charge the battery, and the embodiments of the present application are not exemplified one by one here.

[0240] In summary, in this solution, the device charges the battery in the first stage to increase the battery's power. And in the second stage, the device charges the battery and makes the duration of the non-constant-voltage charging step in the second stage, that is, the duration ratio of the constant-current charging step and / or the constant-power charging step to the duration of the second stage, greater than or equal to the first threshold, so as to reduce the duration of constant-voltage charging when the battery is charged in the second stage. It should be noted that increasing the charging voltage of the device to charge the battery can, on the one hand, improve the volumetric energy density of the battery, and on the other hand, it will also cause greater stress on the positive electrode material of the battery, affecting the battery cycle performance. Therefore, in the embodiments of this application, the device can charge the battery in the first stage to increase the battery power, and by reducing the duration of constant-voltage charging of the battery in the second stage, it can, while increasing the charging voltage and volumetric energy density, reduce the stress accumulation of the positive electrode material, slow down the mechanical failure of the battery, and thus improve the cycle performance and life of the battery.

[0241] The above mainly introduces the charging method provided by the embodiments of this application. It can be understood that in order for the device to implement the corresponding functions above, it includes the corresponding hardware structures and / or software modules for executing each function. Combining the units and steps of each example described in the embodiments disclosed in this article, this application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a certain function is executed in the way of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the embodiments of this application.

[0242] The embodiments of this application can divide the functional modules according to the above method examples of the device. For example, each functional module can be divided corresponding to each function, or two or more functions can be integrated into one module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiments of this application is illustrative, only a logical function division, and there may be other division methods in actual implementation.

[0243] In the case of dividing each functional module corresponding to each function, please refer to Figure 4 , Figure 4 which is another structural schematic diagram of the device provided by the embodiments of this application. The device 400 includes a first charging unit 410 and a second charging unit 420. Among them:

[0244] The first charging unit 410 is used to charge the battery in the first stage of the charging cycle; the charging cycle is the process of charging the battery from the first preset state of charge to the second preset state of charge;

[0245] A second charging unit 420 for charging the battery in the second stage of a charging cycle; the charging cycle consists of a first stage and a second stage, with the second stage following the first stage; the second stage includes a constant current charging step and / or a constant power charging step, and the ratio of the duration of the constant current charging step and / or the constant power charging step to the duration of the second stage is greater than or equal to a first threshold.

[0246] In a possible implementation, the first threshold is 25%.

[0247] In a possible implementation, the ratio of the duration of the second stage to the charging cycle is 0.2.

[0248] In a possible implementation, the positive electrode of the battery includes an alkali metal, and after the battery is fully charged in the second stage of the charging cycle, the amount of alkali metal removed from the positive electrode of the battery is greater than or equal to 60%.

[0249] In a possible implementation, the charging voltage for charging the battery in the first stage is less than or equal to the charging voltage for charging the battery in the second stage.

[0250] In a possible implementation, the charging cycle includes N charging steps, the first stage consists of a part of the N charging steps, and the second stage consists of the other part of the N charging steps, where N is a positive integer;

[0251] The N charging steps include a first charging step and a second charging step, and the second charging step is the next charging step after the first charging step; the charging current for charging the battery in the second charging step is greater than or equal to the charging current for charging the battery in the first charging step.

[0252] In a possible implementation, the N charging steps further include a third charging step and a fourth charging step, and the fourth charging step is the next charging step after the third charging step;

[0253] The charging current for charging the battery in the fourth charging step is less than the charging current for charging the battery in the third charging step.

[0254] In a possible implementation, in the last charging step of the charging cycle, the multiple of the charging current for charging the battery is in the range of 0.025 times to 1.5 times.

[0255] In a possible implementation, after the battery is fully charged in the second stage of the charging cycle, the state of charge of the battery is greater than or equal to 90%.

[0256] In a possible implementation, when the positive electrode material of the battery is lithium cobaltate material, when the charging voltage for charging the battery in the second stage is in the range of 4.5 volts to 4.75 volts, the battery charging ends.

[0257] In a possible implementation, when the cathode material of the battery is a ternary lithium material, when the charging voltage for charging the battery in the second stage is in the range of 4.3 volts to 4.5 volts, the battery charging ends.

[0258] In a possible implementation, when the cathode material of the battery is a sodium-based layered oxide cathode material, when the charging voltage for charging the battery in the second stage is in the range of 4.1 volts to 4.5 volts, the battery charging ends.

[0259] Figure 4 For the specific operations and beneficial effects of each unit in the device 400 shown, reference can be made to the Figure 2 description in the above-mentioned method and its possible implementation manners, which will not be elaborated here.

[0260] Please refer to Figure 5 , Figure 5 which is a schematic hardware structure diagram of the device provided by the embodiment of the present application. The device 500 may be the device in the above-mentioned charging method, or may be a chip in the device, or may be a processing system in the device, etc. The device 500 includes: a processor 501, a memory 502, and a communication interface 503. The processor 501, the communication interface 503, and the memory 502 may be connected to each other or connected to each other through a bus 504.

[0261] Exemplarily, the memory 502 is used to store the computer programs and data of the device 500. The memory 502 may include but is not limited to a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or a compact disc read-only memory (CD-ROM), etc.

[0262] The software or program code required to implement all or part of the functions of the above-mentioned Figure 2 shown method is stored in the memory 502.

[0263] If the software or program code required for the functions of part of the units is stored in the memory 502, in addition to calling the program code in the memory 502 to implement part of the functions, the processor 501 may also cooperate with other components (such as the communication interface 503) to jointly complete Figure 3 the other functions (such as the function of receiving information) described in the above-mentioned method.

[0264] The number of communication interfaces 503 can be multiple, which is used to support the device 500 to communicate, such as receiving or sending data, signals or signaling, etc.

[0265] Exemplarily, the processor 501 can be a central processing unit, a general-purpose processor, a digital signal processor, an application-specific integrated circuit, a field-programmable gate array or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The processor can also be a combination that realizes computing functions, such as a combination including one or more microprocessors, a combination of a digital signal processor and a microprocessor, etc. The processor 501 can be used to read the program stored in the above-mentioned memory 502 and execute the Figure 2 method described above and the operations performed by the second node in possible implementation manners. For example, the processor 501 can perform the following operations:

[0266] Charge the battery in the first stage of the charging cycle; the charging cycle is the process of charging the battery from the first preset state of charge to the second preset state of charge;

[0267] Charge the battery in the second stage of the charging cycle; the charging cycle consists of the first stage and the second stage, and the second stage is after the first stage;

[0268] The second stage includes a constant current charging step and / or a constant power charging step, and the ratio of the duration of the constant current charging step and / or the constant power charging step to the duration of the second stage is greater than or equal to the first threshold.

[0269] Figure 5 For the specific operations performed by the device 500 shown and the beneficial effects, reference can be made to the description in the above-mentioned Figure 2 method and its possible implementation manners, which will not be elaborated here.

[0270] This application embodiment also provides a chip, which includes a processor. Among them, the processor is used to execute the computer program or computer instructions stored in the memory, so that the chip executes the Figure 2 operations performed by the device in any one of the above-mentioned

[0271] and its possible method embodiments. Figure 2 This application embodiment also provides a computer-readable storage medium, which stores a computer program. The computer program is executed by a processor to implement the

[0272] operations performed by the device in any one of the above-mentioned Figure 2The operations performed by the device in the method according to any one of the method embodiments and its possible method embodiments will be executed.

[0273] In summary, in the present solution, the device charges the battery in the first stage to increase the battery power, and charges the battery in the second stage, and makes the duration of the non-constant voltage charging step in the second stage, that is, the ratio of the duration of the constant current charging step and / or the constant power charging step to the duration of the second stage, greater than or equal to the first threshold, so that the duration of the constant voltage charging of the battery is reduced during the second stage charging. It should be noted that increasing the charging voltage of the device to charge the battery can, on the one hand, increase the volumetric energy density of the battery, and on the other hand, cause greater stress on the positive electrode material of the battery, affecting the battery cycle performance. For this reason, in the embodiments of the present application, the device can charge the battery in the first stage to increase the battery power, and by reducing the duration of the constant voltage charging of the battery in the second stage, it is possible to reduce the stress accumulation of the positive electrode material while increasing the charging voltage and the volumetric energy density, slow down the mechanical failure of the battery, and thus improve the cycle performance and life of the battery.

[0274] It should be noted that in the present application, prefix words such as "first" and "second" are only used to distinguish different described objects, and have no restrictive effect on the position, order, priority, quantity, or content of the described objects, etc. For example, if the described object is "field", the ordinal numbers before "field" in "first field" and "second field" do not limit the position or order between "fields", and "first" and "second" do not limit whether the "fields" they modify are in the same message, nor do they limit the order of "first field" and "second field". Again, if the described object is "level", the ordinal numbers before "level" in "first level" and "second level" do not limit the priority between "levels". Again, the quantity of the described object is not restricted by the prefix word and can be one or more. Taking "first device" as an example, the quantity of "device" can be one or more. In addition, the objects modified by different prefix words can be the same or different. For example, if the described object is "device", then "first device" and "second device" can be the same device, devices of the same type, or devices of different types; again, if the described object is "information", then "first information" and "second information" can be information with the same content or information with different content. For example, without departing from the scope of various examples, the first node can be called the second node, and similarly, the second node can be called the first node. The first node and the second node can both be nodes, and in some cases, can be separate and different nodes. In short, the use of prefix words for distinguishing described objects in the embodiments of the present application does not constitute a restriction on the described objects, and the statements of the described objects refer to the descriptions in the context of the claims or embodiments, and should not constitute redundant restrictions because of the use of such prefix words.

[0275] It should be noted that in the embodiments of the present application, descriptions such as "at least one (or at least one) of a1, a2,..., and an" include the case where any one of a1, a2,..., and an exists alone, and also include any combination of any plurality of a1, a2,..., and an, and each case can exist alone. For example, the description "at least one of a, b, and c" includes the cases of a alone, b alone, c alone, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b, and c.

[0276] It should also be understood that in each of the embodiments of the present application, the magnitude of the serial numbers of each process does not mean the sequence of execution, and the execution sequence of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0277] It should also be understood that the term "comprising" (also referred to as "includes", "including", "comprises", and / or "comprising") when used in this specification specifies the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or their groups.

[0278] It should also be understood that the "one embodiment", "an embodiment", and "a possible implementation" mentioned throughout the specification mean that the specific features, structures, or characteristics related to the embodiment or implementation are included in at least one embodiment of the embodiments of the present application. Therefore, the "in one embodiment" or "in an embodiment", "a possible implementation" that appear throughout the specification do not necessarily refer to the same embodiment. In addition, these specific features, structures, or characteristics can be combined in one or more embodiments in any suitable manner.

[0279] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the embodiments of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A charging method, characterized in that, the charging method is applied to a device, the device includes a battery, and the method includes: charging the battery in a first stage of a charging cycle; the charging cycle is a process of charging the battery from a first preset state of charge to a second preset state of charge; charging the battery in a second stage of the charging cycle; the charging cycle consists of the first stage and the second stage, and the second stage is after the first stage; the second stage includes a constant current charging step and / or a constant power charging step, and the ratio of the duration of the constant current charging step and / or the constant power charging step to the duration of the second stage is greater than or equal to a first threshold.

2. The method according to claim 1, characterized in that, the first threshold is 25%.

3. The method according to claim 1 or 2, characterized in that, the ratio of the duration between the second stage and the charging cycle is 0.

2.

4. The method according to any one of claims 1-3, characterized in that, the positive electrode of the battery includes an alkali metal, and after the battery is fully charged in the second stage of the charging cycle, the amount of alkali metal removed from the positive electrode of the battery is greater than or equal to 60%.

5. The method according to any one of claims 1-4, characterized in that, the charging voltage for charging the battery in the first stage is less than or equal to the charging voltage for charging the battery in the second stage.

6. The method according to any one of claims 1-5, characterized in that, the charging cycle includes N charging steps, the first stage consists of a part of the N charging steps, the second stage consists of the other part of the N charging steps, and N is a positive integer; the N charging steps include a first charging step and a second charging step, and the second charging step is the next charging step after the first charging step; the charging current for charging the battery in the second charging step is greater than or equal to the charging current for charging the battery in the first charging step.

7. The method according to claim 6, characterized in that, the N charging steps further include a third charging step and a fourth charging step, and the fourth charging step is the next charging step after the third charging step; the charging current for charging the battery in the fourth charging step is less than the charging current for charging the battery in the third charging step.

8. The method according to claim 1, characterized in that, the last charging step in the second stage is any one of the constant current charging step or the constant power charging step.

9. The method according to any one of claims 1-8, characterized in that, in the last charging step of the charging cycle, the multiple of the charging current for charging the battery is in the range of 0.025 times to 1.5 times.

10. The method according to any one of claims 1-9, characterized in that, after the battery is fully charged in the second stage of the charging cycle, the state of charge of the battery is greater than or equal to 90%.

11. The method according to any one of claims 1-10, characterized in that, when the cathode material of the battery is lithium cobaltate material, when the charging voltage for charging the battery in the second stage is in the range of 4.5 volts to 4.75 volts, the charging of the battery ends.

12. The method according to any one of claims 1-10, characterized in that, when the cathode material of the battery is ternary lithium material, when the charging voltage for charging the battery in the second stage is in the range of 4.3 volts to 4.5 volts, the charging of the battery ends.

13. The method according to any one of claims 1-10, characterized in that, when the cathode material of the battery is sodium layered oxide cathode material, when the charging voltage for charging the battery in the second stage is in the range of 4.1 volts to 4.5 volts, the charging of the battery ends.

14. An apparatus, characterized in that, the apparatus includes: a first charging unit for charging a battery in a first stage of a charging cycle; the charging cycle is a process of charging the battery from a first preset state of charge to a second preset state of charge; a second charging unit for charging the battery in a second stage of the charging cycle; the charging cycle consists of the first stage and the second stage, and the second stage is after the first stage; the second stage includes a constant current charging step and / or a constant power charging step, and the ratio of the duration of the constant current charging step and / or the constant power charging step to the duration of the second stage is greater than or equal to a first threshold.

15. The apparatus according to claim 14, characterized in that, the first threshold is 25%.

16. The apparatus according to claim 14 or 15, characterized in that, the ratio of the duration of the second stage to the charging cycle is 0.

2.

17. The apparatus according to any one of claims 14-15, characterized in that, the cathode of the battery includes an alkali metal, and after the battery is fully charged in the second stage of the charging cycle, the amount of alkali metal removed from the cathode of the battery is greater than or equal to 60%.

18. The apparatus according to any one of claims 14-15, characterized in that, the charging voltage for charging the battery in the first stage is less than or equal to the charging voltage for charging the battery in the second stage.

19. The apparatus according to any one of claims 14-18, characterized in that, the charging cycle includes N charging steps, the first stage consists of a part of the N charging steps, the second stage consists of another part of the N charging steps, and N is a positive integer; the N charging steps include a first charging step and a second charging step, and the second charging step is the next charging step after the first charging step; the charging current for charging the battery in the second charging step is greater than or equal to the charging current for charging the battery in the first charging step.

20. The apparatus according to claim 19, characterized in that, The N charging steps further include a third charging step and a fourth charging step, and the fourth charging step is the charging step following the third charging step; The charging current for charging the battery in the fourth charging step is less than the charging current for charging the battery in the third charging step.

21. The device according to claim 14, wherein, The last charging step in the second stage is any one of the constant current charging step or the constant power charging step.

22. The device according to any one of claims 14-21, wherein, In the last charging step of the charging cycle, the multiple of the charging current for charging the battery is in the range of 0.025 times to 1.5 times.

23. The device according to any one of claims 14-22, wherein, After charging the battery is completed in the second stage of the charging cycle, the state of charge of the battery is greater than or equal to 90%.

24. The device according to any one of claims 14-23, wherein, When the positive electrode material of the battery is a lithium cobalt oxide material, when the charging voltage for charging the battery in the second stage is in the range of 4.5 volts to 4.75 volts, the charging of the battery ends.

25. The device according to any one of claims 14-23, wherein, When the positive electrode material of the battery is a ternary lithium material, when the charging voltage for charging the battery in the second stage is in the range of 4.3 volts to 4.5 volts, the charging of the battery ends.

26. The device according to any one of claims 14-23, wherein, When the positive electrode material of the battery is a sodium-layered oxygen positive electrode material, when the charging voltage for charging the battery in the second stage is in the range of 4.1 volts to 4.5 volts, the charging of the battery ends.

27. A computer-readable storage medium, wherein, The computer-readable storage medium stores a computer program, and the computer program is executed by a processor to implement the method according to any one of claims 1-13.

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