Charging method and device

Abstract

Provided in the present application are a charging method and device. The charging method is applied to a device, wherein the device comprises a battery. The method comprises: charging a battery in a first stage of a charging period, and charging the battery in a second stage of the charging period, wherein the charging period is a process during which the battery is charged from a first preset state-of-charge to a second preset state-of-charge, the charging period consists of the first stage and the second stage, 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 greater than or equal to a first threshold value. The present application can increase the volume energy density of a battery, and can also reduce the influence on the cycle life of the battery, so that the mechanical failure of active substance particles of the battery can be slowed down, thereby improving the cycle performance of the battery and prolonging the service life of the battery.

Description

Charging method and equipment

[0001] This application claims priority to the Chinese patent application with application number 202311634464.3 filed with the State Intellectual Property Office of China on November 30, 2023, and priority to the Chinese patent application with the invention name “Charging Method and Device”, all contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a charging method and device. Background Art

[0003] Lithium batteries, sodium batteries, and other batteries whose positive electrodes contain alkali metal materials are referred to as alkali metal batteries. Alkali metal batteries have a high volumetric energy density, which allows them to extend battery life while maintaining a small size, leading to their widespread use in electronic devices.

[0004] Typically, increasing the charging voltage of an alkali metal battery can increase the amount of alkali metal released from the positive electrode, thereby improving the volumetric energy density of the alkali metal battery. However, increasing the charging voltage and the amount of alkali metal released can reduce the cycle life of the alkali metal battery. Therefore, how to increase the volumetric energy density of alkali metal batteries while minimizing the impact on cycle life is a technical problem that needs to be solved by those skilled in the art.

[0005] Summary of the Invention

[0006] The present application provides a charging method and device that can improve the volume 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.

[0007] In a first aspect, the present application provides a charging method, which is applied to a device, the device including a battery, and the method comprising:

[0008] 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 charge to a second preset charge;

[0009] charging the battery in a second stage of the charging cycle; the charging cycle consisting of the first stage and the second stage, the second stage following the first stage;

[0010] The aforementioned second stage includes a constant current charging step and / or a constant power charging step, and the ratio between the duration of the aforementioned constant current charging step and / or constant power charging step and the duration of the aforementioned second stage is greater than or equal to a first threshold.

[0011] In this solution, the device increases the battery power by charging the battery in the first stage, and charges the battery in the second stage, and makes the ratio of the constant current charging step and / or constant power charging step in the second stage to the duration of the second stage greater than or equal to the first threshold value, so that the battery reduces the duration of constant voltage charging when charging in the second stage. It should be noted that the device increases the charging voltage of the battery, which can increase the volume energy density of the battery on the one hand, and on the other hand, it can also cause the positive electrode material of the battery to generate greater stress, affecting the battery cycle performance. To this end, in the embodiment 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 can reduce the stress accumulation of the positive electrode material while increasing the charging voltage and volume energy density, thereby improving the cycle performance and life of the battery.

[0012] In a possible implementation, the first threshold is 25%.

[0013] In this solution, 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 by making the ratio of the duration of the constant current charging step and / or constant power charging step in the second stage to the duration of the second stage greater than or equal to 25%.

[0014] In a possible implementation, the ratio of the duration of the second stage to the duration of the charging cycle is 0.2.

[0015] In this solution, the device sets the duration ratio of the second phase to the charging cycle to 0.2, making the second phase shorter than the first phase. This allows the device to charge the battery more during the first phase. Furthermore, by reducing the duration of the constant-voltage charging step in the second phase before the end of charging, stress accumulation within the positive electrode material is reduced without affecting the battery's charge capacity.

[0016] In one possible implementation, the positive electrode of the battery includes an alkali metal, and after the battery is charged in the second stage of the charging cycle, the amount of alkali metal released from the positive electrode of the battery is greater than or equal to 60%.

[0017] In this solution, after the device completes charging the alkali metal battery, the amount of alkali metal released 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 by this solution, the alkali metal battery can achieve a higher volume energy density.

[0018] In a possible implementation, the charging voltage of the battery in the first stage is less than or equal to the charging voltage of the battery in the second stage.

[0019] In this solution, the battery's charging voltage in the second stage is greater than that in the first stage, allowing the battery's charging voltage to gradually increase during the charging cycle, thereby achieving a higher volumetric energy density at the end of charging. Furthermore, because increasing the charging voltage increases the internal stress of the battery's positive electrode material, the charging method of this embodiment of the application can effectively reduce the stress accumulation in the positive electrode material caused by the increase in charging voltage by reducing the duration of the constant-voltage charging step in the second stage.

[0020] In one possible implementation, the charging cycle includes N charging steps, the first stage consists of a portion of the N charging steps, and the second stage consists of another portion 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; and 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.

[0021] In this solution, the device can increase the battery's charging current during the charging cycle. Specifically, the battery's charging current at one charging step within the cycle is greater than the charging current at the previous charging step. This speeds up the battery's charging speed, shortening the constant-voltage charging step and reducing stress accumulation, thereby improving the battery's cycle performance and lifespan.

[0022] In one possible implementation, the N charging steps further include a third charging step and a fourth charging step, and the fourth charging step is a charging step subsequent to the third charging step.

[0023] The charging current for charging the battery in the fourth charging step is smaller than the charging current for charging the battery in the third charging step.

[0024] In a possible implementation, the last charging step in the aforementioned second stage is any one of the aforementioned constant current charging step and the aforementioned constant power charging step.

[0025] In this solution, the higher the charging voltage during constant voltage charging, the greater the stress generated within the battery's positive electrode material. Therefore, to avoid the significant stress caused by high charging voltages, the final charging step before the end of the second phase can be a constant current charging step or the aforementioned constant power charging step. This can reduce the duration of constant voltage charging at high charging voltages and mitigate mechanical failure.

[0026] In a possible implementation, in the last charging step of the charging cycle, a charging current rate for charging the battery is in a range from 0.025 times to 1.5 times.

[0027] In this solution, the device can select an appropriate current rate in the final charging step of the second phase to achieve fast or slow charging of the battery, depending on the application scenario. When the device uses a higher current rate in the final charging step, the battery charges faster, which can reduce the duration of constant voltage charging and improve the battery's cycle life.

[0028] In a possible implementation, after the battery is charged in the second stage of the charging cycle, the charge of the battery is greater than or equal to 90%.

[0029] In this solution, after charging is complete, the battery's charge is greater than or equal to 90%. Since the closer the battery's charge is to 100% after charging, the more energy is stored in the battery, the longer the battery life. Therefore, after charging is complete, the battery can meet the required battery life and ensure that the device can operate.

[0030] In one possible implementation, when the positive electrode material of the battery is lithium cobalt oxide, the charging of the battery is completed when the charging voltage of the battery in the second stage is within the range of 4.5 volts to 4.75 volts.

[0031] In this solution, the device increases the volumetric energy density of lithium cobalt oxide batteries by increasing the charging voltage at the end of charging to a range of 4.5 volts to 4.75 volts. Furthermore, because the second stage of this solution also reduces the duration of the constant-voltage charging step for lithium cobalt oxide batteries, the impact of the increased charging voltage on the cycle life of the lithium cobalt oxide batteries can be reduced, thereby improving the battery's cycling performance.

[0032] In one possible implementation, when the positive electrode material of the battery is a ternary lithium material, the charging of the battery is completed when the charging voltage of the battery in the second stage is within the range of 4.3 volts to 4.5 volts.

[0033] In this solution, the device increases the volumetric energy density of ternary lithium batteries by increasing the charging voltage to a range of 4.3 to 4.5 volts at the end of charging. Furthermore, because the second stage of this solution also reduces the duration of the constant-voltage charging step for ternary lithium batteries, the impact of the increased charging voltage on the cycle life of ternary lithium batteries can be reduced, thereby improving the battery's cycling performance.

[0034] In one possible implementation, when the positive electrode material of the aforementioned battery is a sodium-electrolyte-layer oxygen positive electrode material, the charging voltage of the aforementioned battery in the aforementioned second stage is within the range of 4.1 volts to 4.5 volts, and the charging of the aforementioned battery is completed.

[0035] In this solution, the device increases the volumetric energy density of sodium batteries by raising the charging voltage at the end of charging to a range of 4.1 to 4.5 volts. Furthermore, because the second stage of this solution also reduces the duration of the constant-voltage charging step, the impact of the increased charging voltage on the cycle life of the sodium battery can be reduced, thereby improving the battery's cycling performance.

[0036] In a second aspect, the present application further provides a device, the aforementioned device comprising:

[0037] a first charging unit configured to charge the battery in a first stage of a charging cycle; wherein the charging cycle is a process of charging the battery from a first preset charge to a second preset charge;

[0038] A second charging unit is used to charge the battery in the second stage of the aforementioned charging cycle; the aforementioned charging cycle consists of the aforementioned first stage and the aforementioned second stage, and the aforementioned second stage is after the aforementioned first stage; the aforementioned second stage includes a constant current charging step and / or a constant power charging step, and the ratio between the duration of the aforementioned constant current charging step and / or constant power charging step and the duration of the aforementioned second stage is greater than or equal to a first threshold.

[0039] In a possible implementation, the first threshold is 25%.

[0040] In a possible implementation, the ratio of the duration of the second stage to the duration of the charging cycle is 0.2.

[0041] In one possible implementation, the positive electrode of the battery includes an alkali metal, and after the battery is charged in the second stage of the charging cycle, the amount of alkali metal released from the positive electrode of the battery is greater than or equal to 60%.

[0042] In a possible implementation, the charging voltage of the battery in the first stage is less than or equal to the charging voltage of the battery in the second stage.

[0043] In one possible implementation, the charging cycle includes N charging steps, the first stage consists of a portion of the N charging steps, and the second stage consists of another portion 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; and 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.

[0044] In one possible implementation, the N charging steps further include a third charging step and a fourth charging step, and the fourth charging step is a charging step subsequent to the third charging step.

[0045] The charging current for charging the battery in the fourth charging step is smaller than the charging current for charging the battery in the third charging step.

[0046] In a possible implementation, the last charging step in the aforementioned second stage is any one of the aforementioned constant current charging step and the aforementioned constant power charging step.

[0047] In a possible implementation, in the last charging step of the charging cycle, a charging current rate for charging the battery is in a range from 0.025 times to 1.5 times.

[0048] In a possible implementation, after the battery is charged in the second stage of the charging cycle, the charge of the battery is greater than or equal to 90%.

[0049] In one possible implementation, when the positive electrode material of the battery is lithium cobalt oxide, the charging of the battery is completed when the charging voltage of the battery in the second stage is within the range of 4.5 volts to 4.75 volts.

[0050] In one possible implementation, when the positive electrode material of the aforementioned battery is a ternary lithium material, the charging of the aforementioned battery is completed when the charging voltage of the aforementioned battery in the aforementioned second stage is within the range of 4.3 volts to 4.5 volts at the end of the aforementioned second stage charging.

[0051] In one possible implementation, when the positive electrode material of the aforementioned battery is a sodium-electrolyte-oxygen positive electrode material, the charging voltage of the aforementioned battery in the aforementioned second stage is a charging voltage at the end of the aforementioned second stage charging in the range of 4.1 volts to 4.5 volts, and the charging of the aforementioned battery is completed.

[0052] In a third aspect, the present application provides a device comprising a processor and a memory. The memory is coupled to the processor, and when the processor executes a computer program or computer instructions stored in the memory, the method described in any one of the second aspects above can be implemented. The device may also include a communication interface for communicating between the device and other devices. Exemplarily, the communication interface may be a transceiver, circuit, bus, module, or other type of communication interface.

[0053] In one possible implementation, the device may include:

[0054] Memory for storing computer programs or computer instructions;

[0055] Processor for:

[0056] The battery is charged in the first stage of a charging cycle; a charging cycle is a process of charging the battery from a first preset charge to a second preset charge;

[0057] charging the battery in a second phase of a charging cycle; the charging cycle consists of a first phase and a second phase, the second phase following the first phase;

[0058] The second stage includes a constant current charging step and / or a constant power charging step, and a 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.

[0059] It should be noted that the computer programs or computer instructions in the memory of this application can be pre-stored or downloaded from the Internet when the device is used and stored. This application does not specifically limit the source of the computer programs or computer instructions in the memory. The coupling in the embodiments of this application is an indirect coupling or connection between devices, units or modules, which can be electrical, mechanical or other forms, and is used for information exchange between devices, units or modules.

[0060] In a fourth aspect, the present application provides a computer-readable storage medium, which stores a computer program or computer instructions, and the aforementioned computer program or computer instructions are executed by a processor to implement any method described in the first aspect above.

[0061] In a fifth aspect, the present application provides a computer program product. When the computer program product is executed by a processor, the method described in any one of the first aspects above will be executed.

[0062] In a sixth aspect, an embodiment of the present application provides a chip, which includes a processor, wherein the processor is used to execute a computer program or computer instructions stored in a memory, so that the chip executes any method described in the first aspect.

[0063] The solutions provided in the second to sixth aspects are used to implement or cooperate with the corresponding methods provided in the first aspect, and therefore can achieve the same or corresponding beneficial effects as the corresponding methods in the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] FIG1 is a schematic diagram of a structure of a device provided in an embodiment of the present application;

[0065] FIG2 is a schematic diagram of a flow chart of a charging method provided in an embodiment of the present application;

[0066] FIG3 is a schematic diagram showing the relationship between the charging voltage and charging time of a lithium cobalt oxide battery provided in an embodiment of the present application;

[0067] FIG4 is another schematic diagram of the structure of the device provided in an embodiment of the present application;

[0068] FIG5 is a schematic diagram of a hardware structure of a device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0069] In the embodiment of the present application, "multiple" refers to two or more. In the embodiment 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 represent: A exists alone, B exists alone, or A and B exist at the same time. The description methods such as "at least one (or at least one) of a1, a2, ... and an" adopted in the embodiment of the present application include the situation where any one of a1, a2, ... and an exists alone, and also include any combination of any multiple of a1, a2, ... and an, each of which can exist alone; for example, the description method of "at least one of a, b and c" includes the situation where a is alone, b is alone, c is alone, a and b combination, a and c combination, b and c combination, or a, b, c combination.

[0070] In the various embodiments of the present application, unless otherwise specified or there is a logical conflict, the terms and / or descriptions between the various embodiments are consistent and can be referenced by each other. The technical features in different embodiments can be combined to form new embodiments according to their inherent logical relationships.

[0071] The following is an introduction to the technical terms involved in the embodiments of this application.

[0072] Alkali metal battery: refers to a battery whose positive electrode includes oxides of alkali metal elements and transition metal elements. The general structural formula of the oxides of the above-mentioned alkali metal elements and transition metal elements includes AMO2, wherein 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, or a potassium battery.

[0073] Volumetric energy density: This refers to the ratio of a battery's energy to its volume, and can be used to characterize a battery's ability to release electrical energy through chemical reactions. For batteries of the same volume, a higher volumetric energy density indicates a higher energy content, meaning a greater ability to release electrical energy.

[0074] Alkali metal release amount: The ratio of the molar amount of alkali metal in the positive electrode material to the molar amount of other metals after the charging of the alkali metal battery is completed can be used to characterize the volume energy density of the alkali metal battery. The higher the alkali metal release amount, the higher the volume energy density of the alkali metal battery.

[0075] Lithium cobalt oxide material: It refers to an alkali metal material composed of lithium cobalt oxide, and its chemical formula includes LiCoO2. The lithium cobalt oxide material is a commonly used cathode material in lithium-ion batteries.

[0076] Lithium ternary material: It refers to an alkali metal material composed of ternary oxides of lithium. Exemplarily, the lithium ternary material includes lithium nickel cobalt manganese oxide (abbreviated as NCM, chemical formula includes LiNi a Co b Mn 1-a-b O2, 0 < a < 1, 0 < b < 1, 0 < 1 - a - b < 1), lithium nickel cobalt aluminum oxide (abbreviated as NCA, chemical formula includes LiNi a Co b Al 1-a-b O2, 0 < a < 1, 0 < b < 1, 0 < 1 - a - b < 1), etc., but not limited to this.

[0077] Sodium-based layered oxide cathode material: It refers to an alkali metal material composed of layered sodium oxides, and the layered sodium oxides contain sodium element and transition metals. Exemplarily, the above sodium-based layered oxide cathode material includes: sodium nickel iron manganese oxide (abbreviated as NFM, chemical formula includes NaNi a Fe b Mn 1-a-b O2, 0 < a < 1, 0 < b < 1, 0 < 1 - a - b < 1) or sodium copper iron manganese oxide (chemical formula includes NaCu a Fe b Mn 1-a-b O2, 0 < a < 1, 0 < b < 1, 0 < 1 - a - b < 1), etc., but not limited to this.

[0078] 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.

[0079] 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.

[0080] Constant power charging: It means charging the battery with a constant power.

[0081] Charging step: It can be understood as the steps of charging the battery within a charging cycle. For example, assuming 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.

[0082] Current rate: refers to the ratio of a battery's charging or discharging current to its rated capacity, and is used to characterize the speed of the battery's charging and discharging. It is abbreviated as C. For example, assuming a battery with a rated capacity of 100Ah, a charging current rate of 0.2C represents a charging current of 20A. Since the embodiments of this application focus on battery charging methods, for ease of explanation, the current rate will be used to characterize the charging current rate in the following content.

[0083] The embodiments of the present application will be described below with reference to the accompanying drawings.

[0084] Please refer to Figure 1, which is a schematic diagram of the structure of a device provided in an embodiment of the present application. The device 100 shown in Figure 1 includes a battery 110. The device 100 is connected to a charger. Data signals and power signals can be transmitted between the device 100 and the charger. The connection between the device 100 and the charger can be wired or wireless, which is not limited by this application.

[0085] It is understood that the charger in FIG1 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 to control the type and size of the power signal provided by the charger, thereby changing the charging method for charging the battery 110.

[0086] Exemplarily, the above-mentioned device 100 may include but is not limited to any rechargeable electronic product, such as battery equipment, vehicle-mounted systems, smart home devices, smart phones, tablet personal computers (Tablet PCs), handheld computers, wearable electronic devices, personal computers (Personal computers, PCs), etc. The embodiments of the present application will not illustrate them one by one here.

[0087] It should be noted that as user requirements for the size and battery life of electronic devices continue to increase, the volumetric energy density of batteries needs to be further improved. Specifically, due to the high material density and electrode compaction density of alkali metal materials, when used in battery positive electrodes, they can increase the battery's volumetric energy density. Furthermore, in addition to using alkali metal materials as positive electrode materials, the battery's volumetric energy density can also be increased by increasing the battery's charging voltage. For example, assuming the alkali metal battery is a lithium cobalt oxide battery, by increasing the charge cut-off voltage from 4.2 volts, which was initially widely used, to 4.5 volts, the volumetric energy density of the lithium cobalt oxide battery can be increased to over 700 Wh / L, thereby achieving an increase in the battery's volumetric energy density. The charge cut-off voltage refers to the battery's charge voltage at the end of the charge cycle. In some application scenarios, the charge cut-off voltage can also be understood as the charge voltage when the battery reaches a fully charged state. It is understandable that when a device increases the battery's charge voltage, it also means increasing the charge cut-off voltage. Therefore, by increasing the battery's charge cut-off voltage, the device can increase the battery's volumetric energy density.

[0088] 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 method. For ease of understanding, the embodiment of the present application takes the battery's positive electrode material as an example of lithium cobalt oxide material to illustrate the above conventional boost charging method. Specifically, in actual application scenarios, the device can perform the following conventional boost charging method (1a) to (6a) charging steps:

[0089] (1a) Charge the battery at a constant current of 3.5C to a voltage of 4.21V, then charge the battery at a constant voltage of 4.21V until the current decreases to 3.0C.

[0090] (2a) The battery is charged at a constant current of 3.0C to a voltage of 4.25V, and then the battery is charged at a constant voltage of 4.25V until the current decreases to 2.5C.

[0091] (3a) Charge the battery at a constant current of 2.5C to a voltage of 4.35V, and then charge the battery at a constant voltage of 4.35V until the current decreases to 2.0C.

[0092] (4a) The battery is charged at a constant current of 2.0C to a voltage of 4.4V, and then the battery is charged at a constant voltage of 4.4V until the current decreases to 1.5C.

[0093] (5a) Charge the battery at a constant current of 1.5C to a voltage of 4.5V, and then charge the battery at a constant voltage of 4.5V until the current decreases to 1.2C.

[0094] (6a) The battery is charged at a constant current of 1.2C to a voltage of 4.53V, and then at a constant voltage of 4.53V until the current decreases to 0.025C. The battery is then fully charged and the battery's state of charge (SOC) reaches 100%.

[0095] It should be noted that during the process of charging the battery, the active ions (such as alkali metal ions: lithium ions, sodium ions, etc.) at the positive electrode of the battery can be released from the positive electrode and embedded in the negative electrode after passing through the electrolyte and diaphragm in the battery, thereby forming a potential difference between the positive and negative electrodes of the battery. If more active ions are released from the positive electrode of the battery and more active ions are embedded in the negative electrode, the higher the potential difference between the two ends of the battery, the higher the energy of the battery. It can be seen that the amount of alkali metal released from the positive electrode of the battery can be used to characterize the volumetric energy density of the battery.

[0096] Furthermore, during each of the above charging steps, when the device charges the battery at a constant current, the voltage across the battery gradually increases due to the migration of active ions. However, due to polarization within the battery during constant current charging, the voltage across the battery after the device charges the battery at a constant current is greater than the actual battery voltage. In this case, even if the voltage across the battery reaches the charge cutoff voltage, the battery is not actually fully charged. To this end, the device can switch to constant voltage charging after constant current charging to maintain the continuous migration of active ions within the battery. It is understandable that when the device charges the battery at a constant voltage, active ions continuously embed into the negative electrode, and the space available for active ion embedding at the negative electrode decreases, resulting in a decrease in the electrochemical reaction rate. Consequently, the charging current decreases during constant voltage charging. In other words, during constant current charging, the voltage across the battery gradually increases, and during constant voltage charging, the current through the battery gradually decreases. It should be noted that in the embodiments of the present application, the battery voltage refers to the voltage across the battery, and the battery charging voltage refers to the voltage provided by the device for charging the battery.

[0097] In general, through the above-mentioned 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 then achieving a higher volume energy density when the battery SOC reaches 100%.

[0098] However, the inventors of this application discovered in practice that increasing the charging voltage can cause mechanical failure of the battery's positive electrode material, affecting the battery's cycle life. Specifically, for alkali metal batteries, increasing the charging voltage will also increase the amount of alkali metal released from the positive electrode. The increase in charging voltage and alkali metal release will cause greater stress within the alkali metal material, resulting in irreversible structural phase transitions, decreased stability, and decreased safety performance. Furthermore, as the alkali metal battery undergoes cyclic charge and discharge, the stress within the alkali metal material accumulates multiple times, eventually causing material fatigue and leading to mechanical failure of the active material particles in the alkali metal battery.

[0099] This shows that while increasing the charging voltage can increase the volumetric energy density of a battery, it also affects its cycle life. A battery's cycle life refers to the maximum number of cycles, under a specific charging method, before the battery capacity drops to its rated value. It's understood that one cycle refers to one charge and one discharge for an alkali metal battery.

[0100] It should be noted that for the same battery, the battery cycle life will also be different if the device is charged using different charging methods. Therefore, based on the above technical issues, the embodiments of the present application provide a charging method that can improve the volumetric energy density of the battery while avoiding the problems of fatigue and mechanical failure of the battery positive electrode material, thereby reducing the impact of the increase in charging voltage on the battery cycle life.

[0101] The inventors of this application have discovered that as the charging voltage increases, when the device is charging the battery at a constant voltage, the higher constant voltage applied to the battery terminals causes the battery's positive electrode material to enter a phase transition phase, which in turn generates significant stress within the positive electrode material. Furthermore, if the device performs constant voltage charging for a long time, the stress in the positive electrode material accumulates over time, ultimately leading to mechanical failure of the positive electrode material.

[0102] To this end, the charging method provided in the embodiment of the present application proposes that the stress accumulation generated by the positive electrode material in the battery can be reduced by reducing the time for the device to charge the battery at a constant voltage, thereby reducing the impact on the battery cycle life.

[0103] Specifically, please refer to Figure 2, which is a flow chart of a charging method provided in an embodiment of the present application. The charging method shown in Figure 2 can be performed by the device 100 shown in Figure 1, that is, the device 100 can charge the battery 110 according to the charging method shown in Figure 2. Specifically, the charging method shown in Figure 2 includes at least the following steps:

[0104] S101 . Charging the battery in the first stage of a charging cycle.

[0105] In some feasible embodiments, the device charges the battery during a charging cycle. The charging cycle can be understood as a complete charging process of the battery. During the charging cycle, the device charges the battery so that the SOC of the battery is charged from a first preset charge to a second preset charge. Exemplarily, assuming that the above-mentioned first preset charge is 0% and the above-mentioned second preset charge is 100%, the above-mentioned charging cycle is a process of charging the battery from an SOC of 0% to 100%. Exemplarily, assuming that the above-mentioned first preset charge is 0% and the above-mentioned second preset charge is 90%, the above-mentioned charging cycle is a 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 to the embodiments of the present application.

[0106] Furthermore, the charging cycle may include a first stage and a second stage, and the first stage precedes the second stage. When the device charges the battery during the charging cycle, the device may first charge the battery during the first stage.

[0107] It should be noted that the first stage includes at least one charging step, and the device can perform this at least one charging step to charge the battery. For example, assuming that the first stage includes three charging steps in sequence: a first constant current charging step, a second constant current charging step, and a constant voltage charging step. The device can then perform the first constant current charging step to charge the battery with constant current. In some application scenarios, as the first charging step for the battery, the first constant current charging step can be a trickle charging step. This trickle charging step involves the device performing a restorative charge on the battery at a low current to prevent damage from subsequent higher charging currents. For example, the charging current in the trickle charging step can be 0.2C. Furthermore, after completing the first constant current charging step, the device performs a second constant current charging step to charge the battery with constant current. After the trickle charging in the first constant current charging step, the device can increase the charging current to continuously increase the battery voltage. Furthermore, it can be seen from the above content that when the battery is charged 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 at both ends of the battery is different from the actual voltage of the battery. For this reason, after completing the second constant current charging step, the device performs a constant voltage charging step to charge the battery at a constant voltage to eliminate the polarization phenomenon inside the battery and charge the battery with more electricity. It will be understood that the above introduction to the various charging steps in the first stage is only an example and does not constitute a limitation to this application. In some application scenarios, the first stage may also include only one constant current charging step or one constant voltage charging step, which are not illustrated one by one in this application.

[0108] In general, in the embodiments of the present application, the device can perform at least one charging step in the first stage of the charging cycle to charge the battery and increase the battery power.

[0109] S102 : Charging the battery in the second stage of the charging cycle.

[0110] As can be seen from the above, a charging cycle consists of a first stage and a second stage, with the second stage following the first stage. Therefore, when charging a battery during a charging cycle, the device may first charge the battery in the first stage and then, after the first stage, in the second stage. After the first and second stages, the battery is fully charged.

[0111] It should be noted that, as can be seen from the above content, when the device is charging at a constant voltage, a higher charging voltage will cause greater stress to be generated inside the battery's positive electrode material, and the longer the constant voltage charging time, the more stress accumulates inside the battery's positive electrode material, and the greater the impact on the battery's cycle life. Therefore, the charging method provided in the embodiment 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's positive electrode material.

[0112] Specifically, the above-mentioned 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 explanation, the embodiments of the present application characterize the constant current charging step and / or the constant power charging step as a non-constant voltage charging step in the following content. The non-constant voltage charging step can be understood as a charging step in which charging is performed in a manner other than constant voltage charging.

[0113] It is understandable that the above-mentioned second stage includes at least one non-constant voltage charging step. Furthermore, the ratio between the duration of the above-mentioned 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, and the duration of the second stage is greater than or equal to the first threshold. The first threshold can be understood as the minimum value of the ratio between the duration of the non-constant voltage charging step and the duration of the second stage when the stress effect inside the positive electrode material of the battery is significantly improved. That is to say, when the ratio between the duration occupied by the above-mentioned at least one non-constant voltage charging step and the duration of the second stage is greater than or equal to the above-mentioned first threshold, the stress accumulation inside the positive electrode material of the battery is significantly reduced, which can greatly improve the cycle life of the battery. Among them, the duration of the above-mentioned 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.

[0114] Exemplarily, it is assumed 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. Then, in the second stage, first, the device can perform a constant current charging step to charge the battery with a constant current. Then, after the constant current charging is completed, the device can perform a constant voltage charging step to charge the battery with a constant voltage. Finally, after the constant voltage charging is completed, the device can perform a constant power charging step to charge the battery with a constant power. It can be understood that the above-mentioned constant current charging step and constant power charging step are both non-constant voltage charging steps, then the sum of the duration of the device charging the battery with a constant current and the duration of the device charging the battery with a constant power is the duration of at least one non-constant voltage charging step in the second stage. For example, assuming that the duration of the second stage is 10 minutes, the duration of the constant current charging step is 2 minutes, and the duration of the constant power charging step is 3 minutes, then the duration of the non-constant voltage charging step in 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 should be understood that the above content is only an example and does not constitute a limitation of the embodiments of the present application.

[0115] In general, the charging method provided in the embodiments of the present application can increase the battery's charge level by charging the battery in the first stage of the charging cycle, and by controlling the ratio between the duration of the non-constant voltage charging step and the duration of the second stage to be greater than or equal to a first threshold in the second stage of the charging cycle, thereby reducing the duration of constant voltage charging of the battery in the second stage, thereby reducing the stress accumulation within the battery's positive electrode material, and further reducing the impact of the increase in charging voltage on the battery's cycle life. The specific implementation process will be described in the subsequent section and will not be detailed here.

[0116] In some feasible embodiments, it can be seen from the above content that the above-mentioned first threshold value is the minimum value of the ratio between the duration of the non-constant voltage charging step and the duration of the second stage when the stress effect inside the positive electrode material of the battery is significantly improved. Specifically, the first threshold value can be 25%. That is to say, in the second stage of the charging cycle, the ratio between the duration of the non-constant voltage charging step and the duration of the second stage is greater than or equal to 25%, which can achieve a significant reduction in the stress accumulation inside the positive electrode material of the battery. In other words, the ratio between the duration of the non-constant voltage charging step and the duration of the second stage is greater than or equal to 25%, which can be understood as the ratio between the duration of the constant voltage charging step and the duration of the second stage is less than 75%. The charging method provided in the embodiment of the present application can effectively reduce the impact of the charging voltage increase on the battery life and extend the cycle life of the battery by controlling the duration of the constant voltage charging in the second stage of the charging cycle to within 75% of the duration of the second stage.

[0117] For example, it is assumed that the 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 the constant current charging step and the constant power charging step are both non-constant voltage charging steps. The sum of the duration of the constant current charging of the battery and the duration of the constant power charging of the battery by the device is the duration of at least one non-constant voltage charging step in the second stage. If the duration of the 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 in the second stage is 3+3=6 minutes, and 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 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 constant voltage charging step in the second stage is relatively short, the stress accumulation inside the positive electrode material of the battery is relatively small, which can avoid the problem of mechanical failure of the battery after multiple cycles. It should be understood that the above content is only an example and does not constitute a limitation of the embodiments of the present application.

[0118] In some feasible implementations, the ratio between the duration of the non-constant voltage charging step and the duration of the second stage may be equal to 100%. In this case, the second stage only includes the non-constant voltage charging step but does not include the constant voltage charging step.

[0119] For example, it is assumed that the second stage can include two charging steps: a constant current charging step and a constant power charging step. It is understandable that the constant current charging step and the constant power charging step are both non-constant voltage charging steps. The sum of the duration of the constant current charging of the battery by the device and the duration of the constant power charging of the battery is the duration of at least one non-constant voltage charging step in the second stage. If the duration of the 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 in the second stage is 6+4=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 first threshold value of 25%. At this time, the duration of the constant voltage charging step in 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 is understandable that the above content is only an example and does not constitute a limitation to the embodiments of the present application.

[0120] For example, it is assumed that the above-mentioned second stage can include a charging step: a constant current charging step or a constant power charging step. It is understandable that the above-mentioned constant current charging step or constant power charging step are both non-constant voltage charging steps, then the duration of the device's constant current charging of the battery or the duration of the constant power charging of the battery is the duration of at least one non-constant voltage charging step in the second stage. If the duration of the above-mentioned second stage is 10 minutes, the duration of the above-mentioned constant current charging step or the duration of the constant power charging step is 10 minutes, then the duration of the non-constant voltage charging step in 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 value of 25%. At this time, the duration of the constant voltage charging step in 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 is understandable that the above content is only an example and does not constitute a limitation to the embodiments of the present application.

[0121] In general, the charging method provided in the embodiment of the present application can reduce the duration of constant voltage charging in the second stage by making the ratio of the duration of the non-constant voltage charging step in 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 extending the cycle life of the battery.

[0122] In some feasible embodiments, it can be seen from the above content that 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 in the second stage to reduce the impact of constant voltage charging on the battery's positive electrode material. It should be noted that, since the device can effectively eliminate the polarization phenomenon inside the battery by constant voltage charging of the battery, the battery is charged with more power, and the second stage in the embodiment of the present application reduces the duration of constant voltage charging. Therefore, in order to reduce the stress effect of constant voltage charging on the positive electrode material while ensuring that the battery is charged with sufficient power, in the charging method provided in the embodiment of the present application, the duration ratio between the above-mentioned second stage and the charging cycle can be made to be 0.2.

[0123] It can be understood that the ratio of the duration between the above-mentioned second stage and the charging cycle is 0.2, and the ratio of the duration between the first stage and the charging cycle is 0.8. That is to say, assuming that the charging cycle is T, the part from the beginning 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. In the first stage, the device can charge the battery through the constant voltage charging step and the constant current charging step to charge the battery with more electricity. Then, in the second stage, the device can reduce the stress accumulation inside the positive electrode material by reducing the duration of the constant voltage charging step. At this time, since the duration of the second stage only accounts for 0.2 of the charging cycle, it can be ensured that the battery is charged with enough electricity in the first stage of the charging cycle, and the reduction in the duration of the constant voltage charging step in the second stage will not affect the amount of electricity charged to the battery.

[0124] For example, assuming that 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. 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, so that the battery is charged with sufficient electricity. 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 charging to reduce the impact of constant voltage charging on the positive electrode material. It will be understood that the above is only an example and does not constitute a limitation to the embodiments of the present application.

[0125] In summary, the charging method provided in the embodiments of the present application achieves a duration ratio of 0.2 between the second stage and the charging cycle, making the second stage shorter than the first stage. This allows the device to charge the battery more during the first stage. Furthermore, by reducing the duration of the constant-voltage charging step in the second stage before the end of charging, stress accumulation within the positive electrode material is reduced without affecting the battery's charge capacity.

[0126] In some feasible embodiments, it can be seen from the above content that the user's requirements for the size and battery life of the device are constantly increasing, and the volume 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 alkali metal materials as the positive electrode material of the battery to increase the volume energy density of the battery. Among them, the positive electrode of the alkali metal battery includes alkali metal, and the alkali metal is the active ion released from the above-mentioned positive electrode during the charging process. It can be seen that for alkali metal batteries, the increase in 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 volume energy density of the alkali metal battery. Please refer to the above description for details, which will not be repeated here.

[0127] It is understood that after the alkali metal battery is charged, the higher the amount of alkali metal released from the positive electrode, the higher the volumetric energy density of the alkali metal battery. In this regard, after the device charges the alkali metal according to the charging method provided in the embodiment of the application, the amount of alkali metal released from the positive electrode of the alkali metal battery is greater than or equal to 60%.

[0128] It should be noted that when the amount of alkali metal released from the positive electrode of the alkali metal battery is greater than or equal to 60%, it indicates that the volume energy density of the alkali metal battery is relatively high, thereby meeting the requirements of the device for volume size and battery life.

[0129] In some feasible embodiments, to verify the amount of alkali metal released from the positive electrode of an alkali metal battery, the positive electrode of the alkali metal battery can be disassembled after the device completes charging the alkali metal battery. The separator on the surface of the positive electrode is then cleaned, and the positive electrode is then subjected to elemental analysis using an inductively coupled plasma optical emission spectrometer. Furthermore, after the elemental analysis, the ratio of alkali metal elements to other metal elements in the positive electrode can be determined; this ratio is the amount of alkali metal released.

[0130] In some feasible embodiments, the alkali metal battery may be a lithium cobalt oxide battery, a ternary lithium battery, or a sodium battery, etc., the positive electrode of which includes oxides of alkali metal elements and transition metal elements. The embodiments of the present application will not illustrate them one by one here.

[0131] In general, the charging method provided in the embodiment of the present application can ensure that the amount of alkali metal released from the positive electrode of the alkali metal battery is greater than or equal to 60% after charging is completed, thereby enabling the alkali metal battery to achieve a higher volume energy density.

[0132] In some feasible implementations, in order to improve the volume 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 the battery can be charged with more electricity during the charging cycle. Specifically, the device can make the charging voltage of the battery charged in the first stage less than or equal to the charging voltage of the battery charged in the second stage, thereby increasing the charging voltage of the battery and increasing the volume energy density of the battery. Among them, the charging voltage of the battery charged by the device 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 battery charged by the device in the second stage can be understood as the average charging voltage of multiple charging steps in the second stage.

[0133] Alternatively, the charging voltage used by the device to charge the battery in the first stage can be understood as the charging voltage of any charging step in the first stage, and the charging voltage used by the device to charge the battery in the second stage can be understood as the charging voltage of any charging step in the second stage. In this case, the charging voltage used by the device to charge the battery in the first stage is less than or equal to the charging voltage used to charge the battery in the second stage, which can be understood as the maximum charging voltage of the battery in all charging steps in the first stage being less than the minimum charging voltage of the battery in all charging steps in the second stage.

[0134] Among them, the charging voltage of the battery in the constant voltage charging step refers to the constant charging voltage of the battery in the 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 the constant current charging step. Since the charging voltage of the battery gradually increases in the constant current charging step, the charging voltage of the battery is the maximum charging voltage at the end of the constant current charging step. The charging voltage of the battery in the constant power charging step refers to the maximum charging voltage of the battery in the constant power charging step. Since the charging voltage of the battery gradually increases in the constant power charging step, the charging voltage of the battery is the maximum charging voltage at the end of the constant power charging step.

[0135] In some feasible embodiments, when the first stage includes multiple charging steps, the charging voltage of any charging step in the first stage is lower than the charging voltage of the subsequent charging step, that is, the charging voltage of the battery gradually increases as it is charged through the multiple charging steps in the first stage. Similarly, when the second stage includes multiple charging steps, the charging voltage of any charging step in the second stage is lower than the charging voltage of the subsequent charging step, that is, the charging voltage of the battery gradually increases as it is charged through the multiple charging steps in the second stage. It is understood that by gradually increasing the battery charging voltage through 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.

[0136] For example, assume that the first stage includes five charging steps, where 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 lower than the charging voltage of the subsequent charging step, and the charging voltage of the five charging steps gradually increases. Meanwhile, 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 in the second stage is higher than the charging voltage of the battery in each charging step in the first stage.

[0137] In general, the charging method provided in the embodiments of the present application can gradually increase the battery's charging voltage during the charging cycle by increasing the battery's charging voltage in the second stage to a greater value than the battery's charging voltage in the first stage, thereby achieving a higher volumetric energy density at the end of charging. Furthermore, because increasing the charging voltage increases the internal stress of the battery's positive electrode material, the charging method provided in the embodiments of the present application can effectively reduce the stress accumulation in the positive electrode material caused by the increase in charging voltage by reducing the duration of the constant-voltage charging step in the second stage.

[0138] In some feasible embodiments, the charging cycle may include N charging steps, wherein the first stage consists of a portion of the N charging steps, and the second stage consists of another portion of the N charging steps. Furthermore, the charging method provided in the embodiments of the present application can increase the charging speed of the battery, reduce the duration of the constant voltage charging step, and thereby mitigate mechanical failure of the battery by making the charging current of one of the N charging steps greater than the charging current of the previous charging step.

[0139] The battery charging current in each charging step can be understood as the maximum charging current of the battery in that charging step. In this case, if the charging current of one of the N charging steps is greater than the charging current of the previous charging step, it can be understood that the maximum charging current of the battery in that charging step is greater than the maximum charging current of the previous charging step.

[0140] It is understood that the battery charging current is constant during the constant current charging step, and thus the battery charging current during this constant current charging step is a constant current. At the same time, since the battery charging current gradually decreases during the constant voltage charging step, the battery charging current during the constant voltage charging step refers to the battery charging current at the start of the constant voltage charging step.

[0141] In some feasible implementations, when a charging cycle includes N charging steps, there is a case where the charging current used to charge the battery in the jth charging step is greater than or equal to the charging current used to charge the battery in the j-1th charging step. The jth charging step can be understood as one of the N charging steps, and the j-1th charging step can be understood as the charging step before the jth charging step.

[0142] In some feasible implementations, when a charging cycle includes N charging steps, there is a case where the charging current for charging the battery in the i-th charging step is less than the charging current for charging the battery in the i-1-th charging step. The i-th charging step can be understood as one of the N charging steps, and the i-1-th charging step can be understood as the charging step before the i-th charging step. Thus, it can be seen that among the N charging steps in 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.

[0143] For example, in the case where the charging cycle includes 6 charging steps, it is assumed that the first stage includes 5 charging steps and the second stage includes 1 charging step. Among the 7 charging steps, the charging current of the first charging step is 1C, the charging current of the second charging step is 0.5C, the charging current of the third charging step is 1.5C, the charging current of the fourth charging step is 1.5C, the charging current of the fifth charging step is 1C, and the charging current of the sixth charging step is 0.7C. It can be seen that the charging current of the second charging step is less than the charging current of the first charging step, the charging current of the third charging step is greater than the charging current of the second charging step, the charging current of the fourth charging step is equal to the charging current of the third charging step, and the charging current of the sixth charging step is less than the charging current of the fifth charging step.

[0144] It should be noted that within the battery's rated charging current, the higher the charging current the device applies to the battery, the faster the active ions and electrons at both ends of the battery move, allowing the battery's charge to increase rapidly in a short period of time, thus increasing the battery's charging speed. The rated charging current of the battery mentioned above refers to the battery's maximum charging current. Charging a battery at a current greater than the rated current may damage the battery. Therefore, when charging the battery, the device can keep the charging current less than the rated current to avoid damaging the battery.

[0145] In contrast, in the charging steps (1a) to (6a) of the conventional boost charging method described above, the charging current of the device for charging the battery gradually decreases until it is finally reduced 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 embodiment of the present application, the device can increase the charging current of the battery during the charging cycle, that is, the battery charging current of the charging step in the charging cycle is greater than the battery charging current of the previous charging step. At this time, the battery charging speed is accelerated, and the duration of the constant voltage charging step can be reduced, reducing stress accumulation, thereby improving the cycle performance and life of the battery.

[0146] In some feasible implementations, the 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.

[0147] 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 lower than the battery charging voltage of the next charging step, that is, the charging voltage of the battery by the device is gradually increased. The battery charging voltage of the last charging step before the end of the second stage is the highest charging voltage of the battery in the entire charging cycle. At the same time, since the higher the charging voltage of the battery during constant voltage charging, the greater the stress generated inside the positive electrode material 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.

[0148] In some feasible implementations, the non-constant voltage charging step includes a constant current charging step and a constant power charging step. The last charging step of the second phase can be a constant current charging step or a constant power charging step.

[0149] For example, it is assumed 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 in the second stage is a constant power charging step. Specifically, in the second stage, first, the device can perform a constant current charging step to charge the battery with a constant current. Then, after the constant current charging is completed, the device can perform a constant voltage charging step to charge the battery with a constant voltage. Finally, after the constant voltage charging is completed, the device can perform a constant power charging step to charge the battery with a constant power. After the constant power charging is completed, the battery charging is completed.

[0150] For example, 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 in the second stage is a constant current charging step. Specifically, in the second stage, the device can first perform a constant voltage charging step to charge the battery at a constant voltage. Then, after the constant voltage charging is completed, the device can perform a constant current charging step to charge the battery at a constant current. After the constant current charging is completed, the battery charging is completed. It will be understood that the above content is only an example and does not constitute a limitation of the embodiments of the present application.

[0151] In general, the charging method provided in the embodiment 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 mechanical failure, and thereby improving the battery cycle performance and life.

[0152] In some feasible implementations, in the first charging step of the charging cycle, that is, the first charging step of the first stage, the charging current of the device for charging the battery is in the range of 0.1C to 5C. Specifically, when the device charges the battery with a charging current with a lower current rate within the above-mentioned range of 0.1C to 5C in the first charging step, for example, when the battery is charged with a charging current of 0.1C, the charging speed of the battery is slow. On the contrary, when the device charges the battery with a charging current with a higher current rate within the above-mentioned range of 0.1C to 5C, for example, when the battery is charged with a charging current of 5C, the charging speed of the battery is fast. It can be seen from this that the device can select a charging current with a suitable current rate in the first charging step of the first stage for charging according to different application scenarios, so as to achieve fast charging or slow charging of the battery.

[0153] In some feasible implementations, in the last charging step of the charging cycle, that is, the last charging step of the second stage, the charging current of the device for charging the battery is in the range of 0.025C to 1.5C. Specifically, when the device charges the battery with a charging current with a lower current rate within the above-mentioned range of 0.025C to 1.5C in the last charging step, for example, when the battery is charged with a charging current of 0.025C, the charging speed of the battery is slow. On the contrary, when the device charges the battery with a charging current with a higher current rate within the above-mentioned range of 0.025C to 1.5C, for example, when the battery is charged with a charging current of 1.5C, the charging speed of the battery is fast. It can be seen from this that the device can select a charging current with a suitable current rate in the last charging step of the second stage for charging according to different application scenarios, so as to achieve fast charging or slow charging of the battery.

[0154] It should be noted that in the conventional boost charging method described above, the charging current of the battery charged by the device is gradually reduced, so the charging current of the battery in the last charging step is usually relatively low. For example, the charging current of the last charging step in the conventional boost charging method described above is 0.025C. In contrast, since the charging current of the battery charged by the device during the charging cycle can be increased in the charging method provided in the embodiment of the present application, the charging current of the battery in the last charging step can be relatively high. For example, the charging current of the last charging step can be 1.5C. Therefore, the charging method provided in the embodiment of the present application can further improve the charging speed compared to the conventional boost charging method described above, thereby reducing the duration of constant voltage charging and improving the cycle life of the battery.

[0155] In some feasible implementations, after the device completes charging the battery in the second stage of the charging cycle, the charge of the battery is greater than or equal to 90%. That is, in the embodiment of the present application, the battery charge can reach more than 90% after the first and second stages of charging. It is understandable that after the battery is charged, the closer the battery charge is to 100%, the more electricity is charged into the battery, and the longer the battery life. In the embodiment of the present application, after the battery is charged, the charge is greater than or equal to 90%, then the battery can meet the battery life requirement and ensure that the device can work.

[0156] In some feasible implementations, to facilitate the specific implementation of battery charging by the device, the embodiments of this application use alkali metal batteries as an example for illustration. Specifically, the alkali metal battery can be a lithium cobalt oxide battery, a ternary lithium battery, or a sodium battery. In the following description of the embodiments of this application, lithium cobalt oxide batteries, ternary lithium batteries, and sodium batteries are used as examples, and other types of alkali metal batteries are not described in detail.

[0157] In some feasible embodiments, when the alkali metal battery is a lithium cobalt oxide battery, the device may perform embodiment 1 of the charging method to charge the battery. The charging cycle of embodiment 1 includes charging steps (1b) to (11b):

[0158] (1b) Charge the lithium cobalt oxide battery with a constant current of 3.5C to a voltage of 4.21V;

[0159] (2b) charging the lithium cobalt oxide battery at a constant voltage of 4.21 V until the current decreases to 3.0 C;

[0160] (3b) The lithium cobalt oxide battery is charged at a constant current of 3.0C to a voltage of 4.25V;

[0161] (4b) charging the lithium cobalt oxide battery at a constant voltage of 4.25 V until the current decreases to 2.5 C;

[0162] (5b) The lithium cobalt oxide battery is charged at a constant current of 2.5C to a voltage of 4.35V;

[0163] (6b) charging the lithium cobalt oxide battery at a constant voltage of 4.35 V until the current decreases to 2.0 C;

[0164] (7b) The lithium cobalt oxide battery is charged at a constant current of 2.0C to a voltage of 4.4V;

[0165] (8b) charging the lithium cobalt oxide battery at a constant voltage of 4.4 V until the current decreases to 1.5C;

[0166] (9b) The lithium cobalt oxide battery is charged at a constant current of 1.5C to a voltage of 4.5V;

[0167] (10b) The lithium cobalt oxide battery is charged at a constant voltage of 4.5 V until the current decreases to 1.2 C;

[0168] (11b) The lithium cobalt oxide battery is charged at a constant current of 1.2C to a voltage of 4.54V, and the charging is completed.

[0169] Among them, the charge of the lithium cobalt oxide battery at the end of charging is 100%, and in the entire charging cycle T from (1b) to (11b) above, 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 duration of the non-constant voltage charging step in the second stage accounts for more than the first threshold 25%.

[0170] Furthermore, when the lithium cobalt oxide battery is charged according to the above embodiment 1, the relationship between the charging voltage and charging time of the lithium cobalt oxide battery can be shown in Figure 3. Specifically, please refer to Figure 3, which is a schematic diagram of the relationship between the charging voltage and charging time of the lithium cobalt oxide battery provided in the embodiment of the present application. The comparison curve shown in Figure 3 is the curve when the device charges the battery according to the above charging steps (1a) to (6a), and the optimization curve shown in Figure 3 is the curve when the device charges the battery according to the above charging steps (1b) to (11b).

[0171] It can be understood that, as shown in Figure 3, the charging cycle of the comparison curve is 64 minutes, while the charging cycle corresponding to the optimization curve is 40 minutes. It can be seen that the charging method provided in the embodiment of the present application can speed up 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. As can be seen from the above content, the device performs constant voltage charging of the battery with a high charging voltage, which will cause the internal stress of the battery positive electrode material to accumulate for a long time. Therefore, when the device charges the battery according to the charging step of the comparison curve, it will cause the battery to fail mechanically, and the cycle performance and life of the battery will be affected.

[0172] In contrast, the optimized curve shown in Figure 3 does not have a long constant voltage charging step, especially when the charging voltage is 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 of the battery when the charging voltage is high. Therefore, when the device charges the battery according to the optimized curve shown in Figure 3, it can reduce the stress accumulation of the positive electrode material, slow down mechanical failure, thereby improving the cycle performance and life of the battery, and can increase the charging speed.

[0173] In some feasible embodiments, when the alkali metal battery is a lithium cobalt oxide battery, the device can execute the second embodiment of the charging method to charge the battery. The charging cycle of the second embodiment includes charging steps (1c) to (11c). The specific implementation of charging steps (1c) to (10c) can refer to the above-mentioned charging steps (1b) to (10b), which will not be described in detail here. Charging step (11c) is:

[0174] (11c) The lithium cobalt oxide battery is charged at a constant current of 1.2C to a voltage of 4.6V, and the charging is completed.

[0175] Among them, the 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, the last 0.2T, that is, in the second stage, 40% of the time is the constant voltage charging step and 60% of the time is the constant current charging step, that is, the duration of the non-constant voltage charging step in the second stage accounts for more than the first threshold 25%.

[0176] In some feasible embodiments, when the alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 3 of the charging method to charge the battery. The charging cycle of Example 3 includes charging steps (1d) to (14d). The specific implementation of charging steps (1d) to (7d) can refer to the above-mentioned charging steps (1b) to (7b) and will not be repeated here. Charging steps (8d) to (14d) are as follows:

[0177] (8d) charging the lithium cobalt oxide battery with a constant current of 2.0C to a voltage of 4.53V;

[0178] (9d) charging the lithium cobalt oxide battery at a constant voltage of 4.53 V until the current decreases to 1.5C;

[0179] (10d) Constant current charging of the lithium cobalt oxide battery to a voltage of 4.6 V at a charging current of 1.5 C;

[0180] (11d) charging the lithium cobalt oxide battery at a constant voltage of 4.6 V until the current decreases to 0.6 C;

[0181] (12d) charging the lithium cobalt oxide battery at a constant current of 0.6C to a voltage of 4.65V;

[0182] (13d) charging the lithium cobalt oxide battery at a constant voltage of 4.65 V until the current decreases to 0.4C;

[0183] (14d) The lithium cobalt oxide battery is charged at a constant current of 0.4C to a voltage of 4.7V, and the charging is completed.

[0184] Among them, the 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, the last 0.2T, that is, in the second stage, 25% of the time is the constant voltage charging step, and 75% of the time is the constant current charging step, that is, the duration of the non-constant voltage charging step in the second stage accounts for more than the first threshold 25%.

[0185] In some feasible embodiments, when the alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 4 of the charging method to charge the battery. The charging cycle of Example 4 includes charging steps (1e) to (14e). Charging steps (1e) to (7e) can refer to the above-mentioned charging steps (1b) to (7b) and are not described in detail here. Charging steps (8e) to (14e) are as follows:

[0186] (8e) charging the lithium cobalt oxide battery with a constant current of 1.5C to a voltage of 4.5V;

[0187] (9e) charging the lithium cobalt oxide battery at a constant voltage of 4.5 V until the current decreases to 1.2 C;

[0188] (10e) Constant current charging of the lithium cobalt oxide battery to a voltage of 4.53 V at a charging current of 2 C;

[0189] (11e) charging the lithium cobalt oxide battery at a constant voltage of 4.53 V until the current decreases to 0.7 C;

[0190] (12e) charging the lithium cobalt oxide battery at a constant current of 0.7 C to a voltage of 4.55 V;

[0191] (13e) charging the lithium cobalt oxide battery at a constant voltage of 4.55 V until the current decreases to 0.5 C;

[0192] (14e) The lithium cobalt oxide battery is charged at a constant current of 0.5C to a voltage of 4.7V, and the charging is completed.

[0193] Among them, the 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, the last 0.2T, that is, in the second stage, 0% of the time is the constant voltage charging step, and 100% of the time is the constant current charging step, that is, the duration of the non-constant voltage charging step in the second stage accounts for more than 25% of the above first threshold.

[0194] In some feasible embodiments, when the alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 5 of the charging method to charge the battery. The charging cycle of Example 5 includes charging steps (1f) to (14f). Charging steps (1f) to (7f) can refer to the above-mentioned charging steps (1b) to (7b) and are not described in detail here. Charging steps (8f) to (14f) are as follows:

[0195] (8f) The lithium cobalt oxide battery is charged at a constant current of 1.7C to a voltage of 4.55V;

[0196] (9f) The lithium cobalt oxide battery is charged at a constant voltage of 4.55 V until the current decreases to 1.5 C;

[0197] (10f) The lithium cobalt oxide battery is charged at a constant current of 1.5C to a voltage of 4.57V;

[0198] (11f) The lithium cobalt oxide battery is charged at a constant voltage of 4.57 V until the current decreases to 1.2 C;

[0199] (12f) The lithium cobalt oxide battery is charged at a constant current of 1.5C to a voltage of 4.6V;

[0200] (13f) The lithium cobalt oxide battery is charged at a constant voltage of 4.6 V until the current decreases to 0.7 C;

[0201] (14f) The lithium cobalt oxide battery is charged at a constant current of 0.7C to a voltage of 4.7V, and the charging is completed.

[0202] Among them, the 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, the last 0.2T, that is, in the second stage, 0% of the time is the constant voltage charging step, and 100% of the time is the constant current charging step, that is, the duration of the non-constant voltage charging step in the second stage accounts for more than 25% of the above first threshold.

[0203] In some feasible embodiments, when the alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 6 of the charging method to charge the battery. The charging cycle of Example 6 includes charging steps (1g) to (12g). Charging steps (1g) to (7g) can refer to the charging steps (1b) to (7b) above and are not described here. Charging steps (8g) to (12g) are as follows:

[0204] (8g) Charge the lithium cobalt oxide battery with a constant current of 1.5C to a voltage of 4.5V;

[0205] (9g) Charge the lithium cobalt oxide battery at a constant voltage of 4.5 V until the current decreases to 1.2 C;

[0206] (10g) Charge the lithium cobalt oxide battery at a constant current of 1.2C to a voltage of 4.6V;

[0207] (11g) The lithium cobalt oxide battery is charged at a constant voltage of 4.6 V until the current decreases to 0.15C;

[0208] (12g) The lithium cobalt oxide battery was charged at a constant current of 0.15C to a voltage of 4.61V, and the charging was completed.

[0209] Among them, the 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) mentioned above, the last 0.2T, that is, in the second stage, 75% of the time is the constant voltage charging step and 25% of the time is the constant current charging step, that is, the duration of the non-constant voltage charging step in the second stage is equal to the above-mentioned first threshold 25%.

[0210] In some feasible embodiments, when the alkali metal battery is a lithium cobalt oxide battery, the device can execute Example 7 of the charging method to charge the battery. The charging cycle of Example 7 includes charging steps (1h) to (13h). Charging steps (1h) to (7h) can refer to the above-mentioned charging steps (1b) to (7b) and are not described in detail here. Charging steps (8h) to (13h) are as follows:

[0211] (8h) Charge the lithium cobalt oxide battery with a constant current of 1.2C to a voltage of 4.5V;

[0212] (9h) Charge the lithium cobalt oxide battery at a constant voltage of 4.5V until the current decreases to 1C;

[0213] (10h) Charge the lithium cobalt oxide battery with a constant current of 1.5C to a voltage of 4.6V;

[0214] (11h) Charge the lithium cobalt oxide battery at a constant voltage of 4.6V until the current decreases to 1C;

[0215] (12h) Charge the lithium cobalt oxide battery with a constant current of 1C to a voltage of 4.66V;

[0216] (13h) The lithium cobalt oxide battery is charged at a constant power of 9.52 watts (W) to a voltage of 4.7 V, and charging is completed.

[0217] Among them, the 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) mentioned above, the last 0.2T, that is, in the second stage, 14% of the time is a constant voltage charging step, 16% of the time is a constant current charging step, and 70% of the time is a constant power charging step, that is, the duration of the non-constant voltage charging step in the second stage accounts for more than 25% of the above-mentioned first threshold.

[0218] In general, when the device charges a lithium cobalt oxide battery according to the charging method provided in the embodiment of the present application, the charging cut-off voltage of the lithium cobalt oxide battery can be increased to a range of 4.5 volts to 4.75 volts. 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 comparison, the charging cut-off voltage of the battery in the conventional boost charging method described above is only 4.53 volts, while the charging cut-off voltage of the lithium cobalt oxide battery in the embodiment of the present application can be increased to above 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 embodiment 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 embodiment of the present application also reduces the duration of the constant voltage charging step of the lithium cobalt oxide battery, it can reduce the impact of the increase in the charging cut-off voltage on the cycle life of the lithium cobalt oxide battery.

[0219] In some feasible embodiments, when the alkali metal battery is a ternary lithium battery, the device may execute Example 8 of the charging method to charge the battery. The charging cycle of Example 8 includes charging steps (1k) to (5k):

[0220] (1k) Charge the ternary lithium battery with a constant current of 2C to a voltage of 4V;

[0221] (2k) Charge the ternary lithium battery at a constant voltage of 4V until the current decreases to 1.5C;

[0222] (3k) Charge the ternary lithium battery with a constant current of 1.5C to a voltage of 4.2V;

[0223] (4k) Charge the ternary lithium battery at a constant voltage of 4.2V until the current decreases to 0.5C;

[0224] (5k) The ternary lithium battery is charged at a constant current of 0.5C to a voltage of 4.3V, and the charging is completed.

[0225] Among them, the charge of the ternary lithium battery at the end of charging is 100%, and in the entire charging cycle T from (1k) to (5k) mentioned above, the last 0.2T, that is, in the second stage, 30% of the time is the constant voltage charging step, and 70% of the time is the constant current charging step, that is, the duration of the non-constant voltage charging step in the second stage is greater than the above-mentioned first threshold 25%.

[0226] In some feasible embodiments, when the device charges the ternary lithium battery according to the charging method provided in the embodiment of the present application, the charging cut-off voltage of the ternary lithium battery can be made to be in the range of 4.3 volts to 4.5 volts. It can be understood that as the charging cut-off voltage increases, the volume energy density of the ternary lithium battery also increases. Therefore, the charging method provided in the embodiment of the present application can improve the volume energy density of the ternary lithium battery by increasing the charging cut-off voltage of the ternary lithium battery. At the same time, since the charging method provided in the embodiment of the present application also reduces the duration of the constant voltage charging step of the ternary lithium battery, the impact of the increase in the charging cut-off voltage on the cycle life of the ternary lithium battery can be reduced.

[0227] In some feasible embodiments, when the alkali metal battery is a sodium battery, the device may execute Example 9 of the charging method to charge the battery. The charging cycle of Example 9 includes charging steps (1n) to (5n):

[0228] (1n) Constant current charging of the sodium battery to a voltage of 3.9 V at a charging current of 2 C;

[0229] (2n) The sodium battery is charged at a constant voltage of 3.9 V until the current decreases to 1.5 C;

[0230] (3n) The sodium battery is charged at a constant current of 1.5C to a voltage of 3.95V;

[0231] (4n) charging the sodium battery at a constant voltage of 3.95 V until the current decreases to 0.5 C;

[0232] (5n) The sodium battery is charged at a constant current of 0.5C to a voltage of 4.20V, and the charging is completed.

[0233] Among them, the charge of the sodium battery at the end of charging is 100%, and in the entire charging cycle T from (1n) to (5n) above, the last 0.2T, that is, in the second stage, 56% of the time is the constant voltage charging step and 44% of the time is the constant current charging step, that is, the duration of the non-constant voltage charging step in the second stage accounts for more than the first threshold 25%.

[0234] In some feasible embodiments, when charging a sodium battery according to the charging method provided in the embodiments of this application, the device can achieve a charge cutoff voltage of the sodium battery within a range of 4.1 volts to 4.5 volts. It is understood that as the charge cutoff voltage increases, the volumetric energy density of the sodium battery also increases. Therefore, the charging method provided in the embodiments of this application can improve the volumetric energy density of the sodium battery by increasing the charge cutoff voltage. Furthermore, because the charging method provided in the embodiments of this application also reduces the duration of the constant-voltage charging step for the sodium battery, the impact of the increased charge cutoff voltage on the cycle life of the sodium battery can be reduced.

[0235] In some feasible implementations, to facilitate understanding of the differences between Examples 1 to 9 of the above-mentioned charging method and the above-mentioned conventional boost charging method, please refer to the following table:

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

[0237] It can be understood that in the above-mentioned comparative examples 1 and 2, the duration 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 decreased cycle performance. For example, in comparative example 1, the cycle performance is ~700cls@80%, indicating that the battery capacity of the lithium cobalt oxide battery decays to 80% after 700 cycles. In comparative example 2, the cycle performance is ~200cls@80%, indicating that the battery capacity of the lithium cobalt oxide battery decays to 80% after 200 cycles. In comparative example 3, the cycle performance is ~120cls@80%, indicating that the battery capacity of the sodium battery decays to 80% after 120 cycles. It can be seen that the cycle performance of the lithium cobalt oxide battery is poor when it is cyclically charged based on the above-mentioned conventional boost charging method.

[0238] In contrast, the duration 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 of the non-constant voltage charging step is greater than the first threshold of 25%. It can be seen from the above 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 Example 1, the cycle performance is ~800cls@80%, indicating that the battery capacity of the lithium cobalt oxide battery decays to 80% after 800 cycles; in Example 2, the cycle performance is ~1500cls@80%, indicating that the battery capacity of the lithium cobalt oxide battery decays to 80% after 1500 cycles. Therefore, compared with the charging method of Example 1, the lithium cobalt oxide battery has better cycle performance when charged using the charging method of Example 2.

[0239] It is understood that the alkali metal release and cycle performance corresponding to the above embodiments may vary. The higher the alkali metal release, the higher the volumetric energy density of the battery. Depending on the actual application scenario and battery type, the device can choose different embodiments to charge the battery. The embodiments of this application are not illustrated one by one here.

[0240] In summary, in this 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 value, so that the battery reduces the duration of constant voltage charging when charging in the second stage. It should be noted that the device increases the charging voltage of the battery, which can increase the volume energy density of the battery on the one hand, and on the other hand, it can also cause the positive electrode material of the battery to generate greater stress, affecting the battery cycle performance. To this end, in the embodiment 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 can reduce the stress accumulation of the positive electrode material while increasing the charging voltage and volume energy density, 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 in the embodiment of the present application. It is understandable that in order to realize the corresponding functions mentioned above, the device includes hardware structures and / or software modules corresponding to the execution of each function. In combination with the units and steps of the various examples described in the embodiments disclosed herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel 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 the present application.

[0242] The embodiment of the present application can divide the functional modules according to the device of the above method example. For example, each functional module can be divided according 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 embodiment of the present application is schematic and is only a logical function division. In actual implementation, there may be other division methods.

[0243] In the case of dividing each functional module into corresponding functional modules, please refer to FIG4 , which is another structural diagram of the device provided in an embodiment of the present application. The device 400 includes a first charging unit 410 and a second charging unit 420 . In particular:

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

[0245] The second charging unit 420 is used to charge the battery in the second stage of the charging cycle; the charging cycle consists of a first stage and a 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 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 the 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 one 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 released 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 one possible implementation, the charging cycle includes N charging steps, the first phase consists of a portion of the N charging steps, and the second phase consists of another portion 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, wherein the second charging step is the charging step following the first charging step; and a charging current for charging the battery in the second charging step is greater than or equal to a charging current for charging the battery in the first charging step.

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

[0253] The charging current for charging the battery in the fourth charging step is smaller 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 rate of the charging current for charging the battery is in a range from 0.025 times to 1.5 times.

[0255] In a possible implementation, after the battery is charged in the second stage of the charging cycle, the charge level 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 cobalt oxide, the battery charging is completed when the charging voltage of the battery in the second stage is within the range of 4.5 volts to 4.75 volts.

[0257] In a possible implementation, when the positive electrode material of the battery is a ternary lithium material, the battery charging is completed when the charging voltage of the battery in the second stage is within the range of 4.3 volts to 4.5 volts.

[0258] In a possible implementation, when the positive electrode material of the battery is a sodium-electrolyte-layer oxygen positive electrode material, the charging voltage of the battery in the second stage is within the range of 4.1 volts to 4.5 volts, and the battery charging is completed.

[0259] The specific operations and beneficial effects of each unit in the device 400 shown in FIG4 can be found in the description of the method and possible implementation methods shown in FIG2 above, and will not be repeated here.

[0260] Please refer to Figure 5, which is a schematic diagram of the hardware structure of a device provided in an embodiment of the present application. The device 500 can be the device used in the charging method described in the above embodiment, or can be a chip within the device, or can be a processing system within the device. 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 can be interconnected or connected via a bus 504.

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

[0262] The software or program codes required to implement the functions of all or part of the units of the method shown in FIG. 2 are stored in the memory 502 .

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

[0264] There may be multiple communication interfaces 503 , which are used to support the device 500 to communicate, such as receiving or sending data, signals or signaling.

[0265] Exemplarily, the processor 501 may 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 device, a transistor logic device, a hardware component, or any combination thereof. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a digital signal processor and a microprocessor, and the like. The processor 501 may be used to read the program stored in the memory 502 and execute the method described in FIG. 2 and the operations performed by the second node in the possible implementation. For example, the processor 501 may perform the following operations:

[0266] The battery is charged in the first stage of a charging cycle; a charging cycle is a process of charging the battery from a first preset charge to a second preset charge;

[0267] charging the battery in a second phase of a charging cycle; the charging cycle consists of a first phase and a second phase, the second phase following the first phase;

[0268] The second stage includes a constant current charging step and / or a constant power charging step, and a 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.

[0269] The specific operations and beneficial effects performed by the device 500 shown in FIG5 can be found in the description of the method and possible implementations shown in FIG2 above, and will not be repeated here.

[0270] An embodiment of the present application also provides a chip, which includes a processor, wherein the processor is used to execute a computer program or computer instructions stored in a memory, so that the chip performs the operations performed by the device in the method described in Figure 2 and any of its possible method embodiments.

[0271] An embodiment of the present application also provides a computer-readable storage medium, which stores a computer program. The computer program is executed by a processor to implement the operations performed by the device in the method described in Figure 2 and any of its possible method embodiments.

[0272] An embodiment of the present application also provides a computer program product. When the computer program product is read and executed by a computer, the operations performed by the device in the method described in Figure 2 and any of its possible method embodiments will be executed.

[0273] In summary, in this 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 value, so that the battery reduces the duration of constant voltage charging when charging in the second stage. It should be noted that the device increases the charging voltage of the battery, which can increase the volume energy density of the battery on the one hand, and on the other hand, it can also cause the positive electrode material of the battery to generate greater stress, affecting the battery cycle performance. To this end, in the embodiment 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 can reduce the stress accumulation of the positive electrode material while increasing the charging voltage and volume 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 the prefixes such as "first" and "second" used in this application are only for distinguishing different description objects, and do not have any limiting effect on the position, order, priority, quantity or content of the described objects. For example, if the described object is a "field", then the ordinal number before the "field" in the "first field" and the "second field" does not limit the position or order between the "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 the "first field" and the "second field". For another example, if the described object is a "level", then the ordinal number before the "level" in the "first level" and the "second level" does not limit the priority between the "levels". For another example, the number of described objects is not limited by the prefix and can be one or more. Taking "first device" as an example, the number of "devices" can be one or more. In addition, the objects modified by different prefixes may be the same or different. For example, if the described object is a "device", then the "first device" and the "second device" may be the same device, a device of the same type, or devices of different types; for another example, if the described object is "information", then the "first information" and the "second information" may be information of the same content or information of different contents. For example, without departing from the scope of the various described examples, the first node may be referred to as the second node, and similarly, the second node may be referred to as the first node. Both the first node and the second node may be nodes, and in some cases, may be separate and different nodes. In summary, the use of prefixes used to distinguish between description objects in the embodiments of the present application does not constitute a limitation on the described objects. For the statement of the described objects, please refer to the description in the context of the claims or embodiments, and no unnecessary limitation should be constituted due to the use of such prefixes.

[0275] It should be noted that the descriptions used in the embodiments of the present application, such as "at least one of a1, a2, ..., and an" and the like, include any one of a1, a2, ..., and an existing alone, and any combination of any multiple of a1, a2, ..., and an, each of which can exist alone. For example, the description "at least one of a, b, and c" includes a alone, b alone, c alone, a combination of a and b, a combination of a and c, a combination of b and c, or a combination of ab and c.

[0276] It should also be understood that in each embodiment of the embodiments of the present application, the size of the serial number of each process does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0277] It will also be understood that the term “comprise” (also known as “includes,” “including,” “comprises,” and / or “comprising”) when used in this specification specifies the presence of stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0278] It should also be understood that references throughout this specification to "one embodiment," "an embodiment," or "one possible implementation" mean that specific features, structures, or characteristics associated with that embodiment or implementation are included in at least one embodiment of the present application. Therefore, the appearance of "in one embodiment," "in an embodiment," or "one possible implementation" throughout this specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[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, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. These modifications or replacements do not cause the essence of the corresponding technical solutions to 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: The battery is charged in a first stage of a charging cycle; the charging cycle is a process of charging the battery from a first preset charge to a second preset charge; charging the battery in a second stage of the charging cycle; the charging cycle consists of the first stage and the second stage, the second stage being after the first stage; The second stage includes a constant current charging step and / or a constant power charging step, and a 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.

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 duration ratio between the second stage and the charging cycle is 0.

2.

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

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

6. The method according to any one of claims 1 to 5, characterized in that: The charging cycle includes N charging steps, 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, where N is a positive integer; The N charging steps include a first charging step and a second charging step, wherein the second charging step is a charging step subsequent to 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, wherein the fourth charging step is a charging step subsequent to the third charging step; The charging current for charging the battery in the fourth charging step is smaller 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 and the constant power charging step.

9. The method according to any one of claims 1 to 8, characterized in that: In the last charging step of the charging cycle, the rate 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 to 9, characterized in that: After the battery is charged completely in the second stage of the charging cycle, the charge level of the battery is greater than or equal to 90%.

11. The method according to any one of claims 1 to 10, characterized in that: In the case where the positive electrode material of the battery is lithium cobalt oxide material, the charging of the battery is completed when the charging voltage of the battery in the second stage is within the range of 4.5 volts to 4.75 volts.

12. The method according to any one of claims 1 to 10, characterized in that: In the case where the positive electrode material of the battery is a ternary lithium material, the charging of the battery is completed when the charging voltage of the battery in the second stage is within a range of 4.3 volts to 4.5 volts.

13. The method according to any one of claims 1 to 10, characterized in that: When the positive electrode material of the battery is a sodium-electrolyte-layer oxygen positive electrode material, the charging voltage of the battery in the second stage is within a range of 4.1 volts to 4.5 volts, and the battery charging is completed.

14. A device, characterized in that The device comprises: A first charging unit, used to charge the battery in a first stage of a charging cycle; the charging cycle is a process of charging the battery from a first preset charge to a second preset charge; A second charging unit is used to charge 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 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.

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

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

2.

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

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

19. The device according to any one of claims 14 to 18, characterized in that The charging cycle includes N charging steps, 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, where N is a positive integer; The N charging steps include a first charging step and a second charging step, wherein the second charging step is a charging step subsequent to 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 device according to claim 19, characterized in that The N charging steps further include a third charging step and a fourth charging step, wherein the fourth charging step is a charging step subsequent to the third charging step; The charging current for charging the battery in the fourth charging step is smaller than the charging current for charging the battery in the third charging step.

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

22. The device according to any one of claims 14 to 21, characterized in that In the last charging step of the charging cycle, the rate 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 to 22, characterized in that After the battery is charged completely in the second stage of the charging cycle, the charge level of the battery is greater than or equal to 90%.

24. The device according to any one of claims 14 to 23, characterized in that In the case where the positive electrode material of the battery is lithium cobalt oxide material, the charging of the battery is completed when the charging voltage of the battery in the second stage is within the range of 4.5 volts to 4.75 volts.

25. The device according to any one of claims 14 to 23, characterized in that In the case where the positive electrode material of the battery is a ternary lithium material, the charging of the battery is completed when the charging voltage of the battery in the second stage is within a range of 4.3 volts to 4.5 volts.

26. The device according to any one of claims 14 to 23, characterized in that When the positive electrode material of the battery is a sodium-electrolyte-layer oxygen positive electrode material, the charging voltage of the battery in the second stage is within a range of 4.1 volts to 4.5 volts, and the battery charging is completed.

27. A computer-readable storage medium, characterized in that: 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 to 13.

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