Electrochemical device, method of charging the same, and electronic device

Abstract

This application provides an electrochemical device and its charging method. The charging method includes: in response to the current temperature being lower than a reference temperature, constant current charging with a first charging current to a first cutoff voltage in a first charging stage; charging in a staged constant current manner in a second charging stage; constant current charging with a second charging current to a second cutoff voltage in a third charging stage; and charging with a third charging current to a third cutoff voltage in a fourth charging stage. The second charging stage includes multiple sub-stages where the charging cutoff voltage is the first cutoff voltage. The first cutoff voltage is lower than the second cutoff voltage, and the second cutoff voltage is lower than the third cutoff voltage. The first charging current is greater than the sub-stage charging current of the second charging stage, the sub-stage charging current of the second charging stage is greater than the second charging current, and the second charging current is greater than the third charging current. This charging method is suitable for charging at low temperatures, avoids lithium plating, and has high charging efficiency.

Description

Technical Field

[0001] The embodiments of this application relate to the field of electrochemical devices and their charging methods, as well as electronic devices including electrochemical devices. Background Technology

[0002] Lithium-ion batteries possess advantages such as good rate performance, high voltage, light weight, long cycle life, and no memory effect, and are widely used in consumer products, digital products, power products, medical and security fields. How to charge lithium-ion batteries is one of the key technologies in their application. Lithium-ion batteries using the lithium iron phosphate (LFP) system have long cycle life and good stability, but poor low-temperature performance, making them unsuitable for both low-temperature and high-temperature applications. LFP batteries are generally prohibited from being charged at low temperatures, or the low-temperature charging rate is set to 0.1C or even lower, resulting in long charging times, sometimes exceeding 10 hours. Due to the limited capacity of electrochemical devices, blindly increasing the charging rate can cause lithium plating on the negative electrode, and may even lead to short circuits, fires, and explosions, posing significant safety hazards. Summary of the Invention

[0003] In view of this, embodiments of this application provide an electrochemical device and its charging method, a computer storage medium, and an electronic device including an electrochemical device, to at least partially solve the above-mentioned problems and improve the charging efficiency of lithium iron phosphate batteries at low temperatures.

[0004] According to a first aspect of the embodiments of this application, an electrochemical device is provided. The electrochemical device is connected to a controller, and in response to a current temperature being lower than a reference temperature, the controller is configured to: in order to determine whether the current temperature is lower than the reference temperature, in response to the current temperature being lower than the reference temperature, the controller causes a charging module to charge the electrochemical device in the following manner. In the first charging stage, the electrochemical device is charged to a first cutoff voltage using a first charging current. In the second charging stage, the electrochemical device is charged using a multi-stage constant current method, wherein the second charging stage includes N sequential sub-stages, where N is a positive integer. In the (i)th sub-stage (i = 1, 2, ..., N-1), the electrochemical device is charged to the first cutoff voltage using the (i)th sub-stage charging current. In the (i+1)th sub-stage, the electrochemical device is charged to the first cutoff voltage using the (i+1)th sub-stage charging current. The (i)th sub-stage charging current is less than the first charging current and greater than the (i+1)th sub-stage charging current. In the third charging stage, the electrochemical device is charged to a second cutoff voltage using a second charging current, which is less than the Nth sub-stage charging current. In the fourth charging stage, the electrochemical device is charged to a third cutoff voltage using a third charging current, which is less than the second charging current. The third cutoff voltage is greater than the second cutoff voltage, and the second cutoff voltage is greater than the first cutoff voltage.

[0005] In some embodiments, in response to a current temperature greater than the reference temperature, the controller is further configured to cause the charging module to charge the electrochemical device in a plurality of constant current charging stages, wherein the charging current of the plurality of constant current charging stages gradually decreases and the cutoff voltage of the plurality of constant current charging stages gradually increases.

[0006] In some embodiments, the reference temperature is a temperature value between 10°C and 25°C.

[0007] In some embodiments, the charging method ends when the electrochemical device is charged to the third cutoff voltage.

[0008] In some embodiments, the lower the current temperature, the smaller the first cutoff voltage and the first charging current.

[0009] In some embodiments, the electrochemical device further includes a memory configured to store a first cutoff voltage, a second cutoff voltage, a third cutoff voltage, a first charging current, a second charging current, a third charging current, and sub-stage charging currents of N sub-stages of the second charging stage.

[0010] In some embodiments, the battery cell includes a positive electrode, which includes lithium iron phosphate.

[0011] According to a second aspect of the embodiments of this application, a charging method for an electrochemical device is provided. The charging method includes: determining whether a current temperature is lower than a reference temperature; and, in response to the current temperature being lower than the reference temperature, charging the electrochemical device in the following manner:

[0012] In the first charging stage, the electrochemical device is charged to a first cutoff voltage using a first charging current; in the second charging stage, the electrochemical device is charged using a multi-stage constant current method, wherein the second charging stage includes N sequential sub-stages, where N is a positive integer; in the (i)th sub-stage (i = 1, 2, ..., N-1), the electrochemical device is charged to the first cutoff voltage using the (i)th sub-stage charging current; in the (i+1)th sub-stage, the electrochemical device is charged to the first cutoff voltage using the (i+1)th sub-stage charging current; the (i)th sub-stage charging current is less than the first charging current and greater than the (i+1)th sub-stage charging current; in the third charging stage, the electrochemical device is charged to a second cutoff voltage using a second charging current, where the second charging current is less than the Nth sub-stage charging current; and in the fourth charging stage, the electrochemical device is charged to a third cutoff voltage using a third charging current, where the third charging current is less than the second charging current.

[0013] Wherein, the third cutoff voltage is greater than the second cutoff voltage, and the second cutoff voltage is greater than the first cutoff voltage.

[0014] In some embodiments, the charging method further includes: charging the electrochemical device through a plurality of constant current charging stages in response to the current temperature being greater than the reference temperature, wherein the charging current of the plurality of constant current charging stages gradually decreases and the cutoff voltage of the plurality of constant current charging stages gradually increases.

[0015] In some embodiments, the reference temperature is a temperature value between 10°C and 25°C.

[0016] In some embodiments, the charging method ends when the electrochemical device is charged to the third cutoff voltage.

[0017] In some embodiments, the lower the current temperature, the smaller the first cutoff voltage and the first charging current.

[0018] According to a third aspect of the embodiments of this application, a computer storage medium is provided. The computer storage medium has computer instructions that, when executed on a controller of an electrochemical device, cause the electrochemical device to perform the charging method as described in the second aspect.

[0019] According to a fourth aspect of the embodiments of this application, an electronic device is provided, including the electrochemical device of the first aspect.

[0020] According to the electrochemical device and charging method, computer storage medium, and electronic device provided in the embodiments of this application, the charging method is determined according to the current temperature. When the temperature is lower than the reference temperature, a larger charging current is used to perform constant current charging on the electrochemical device in the first charging stage. In the second charging stage, a multi-stage constant current charging method is used to charge the electrochemical device, with the charging current decreasing in each of the multiple sub-stages of the second charging stage, and each sub-stage having the same cutoff voltage (the same as the cutoff voltage of the first charging stage). In the third and fourth charging stages, a smaller charging current is used to perform constant current charging on the electrochemical device, and the cutoff voltage is increased. By setting the multiple sub-stages of the first and second charging stages to have the same cutoff voltage, the charging time of the third and fourth charging stages is shortened, and the potential of the positive electrode can be more effectively controlled, avoiding lithium plating and effectively reducing the safety risks of the battery charging process, making it suitable for lithium battery charging at low temperatures. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0022] Figure 1 This is a schematic block diagram of an electrochemical device according to an embodiment of this application.

[0023] Figure 2 A lookup table for charging parameters in the memory is shown.

[0024] Figure 3 This is a flowchart of a charging method for an electrochemical device according to an embodiment of this application.

[0025] Figure 4 The relationship between battery voltage, charging current, and capacity during the charging process is shown.

[0026] Figure 5 The battery voltage and charging current during the charging process are shown.

[0027] Figure 6 The comparison of charging time between the charging method and the constant current constant voltage charging method according to embodiments of this application is shown.

[0028] Figure 7 The present application illustrates a comparison of battery voltage and anode-to-lithium potential between the charging method and the constant current-constant voltage charging method according to embodiments of this application.

[0029] Figure 8 The image shows a battery cell after 10 charge-discharge cycles at -20°C according to the charging method of this application.

[0030] Figure 9A and 9B The present application illustrates a comparison of battery voltage and charging time between the charging method of this application and the charging methods of related technologies.

[0031] Figure 10A and 10B The present application illustrates a comparison of battery voltage and positive electrode potential to lithium in the charging method of the present application and the charging method of related technologies. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of this application.

[0033] It should be noted that, unless otherwise specified, the embodiments mentioned herein can be combined to form new technical solutions. In this invention, unless otherwise specified, all technical features mentioned herein can be combined to form new technical solutions. In this invention, unless otherwise specified, the numerical range "a to b" represents any real number between a and b. For example, the numerical range "6 to 22" means that all real numbers between "6 to 22" have been listed herein; "6 to 22" is merely a shortened representation of these numerical combinations.

[0034] The constant current-constant voltage (CC-CV) charging method in related technologies first uses a constant current for charging. As charging progresses, the state of charge of the cell increases, the internal polarization of the cell gradually increases, and the lithium potential at the anode continuously decreases. When the lithium deposition potential is reached, lithium ions will be deposited at the anode, causing irreversible lithium loss (capacity loss) and posing serious safety hazards. In addition, the charging time is relatively long, the current remains basically constant throughout the charging cycle, and the charging efficiency is low.

[0035] The staged charging method in related technologies adjusts the charging current based on the cutoff voltage. When the set cutoff voltage is reached, the charging current is switched to proceed to the next stage of charging. The cutoff voltage increases gradually in each stage, while the charging current decreases gradually in each stage. In the early stages, the charging current is relatively large, resulting in greater internal polarization and a lower actual charging capacity of the battery. This leads to longer charging times for subsequent low-current charging, resulting in a longer overall charging time.

[0036] Figure 1 This is a schematic block diagram of an electrochemical device according to an embodiment of this application. Figure 1 As shown, the electrochemical device 10 includes: a battery cell 100, a controller 200, a charging module 300, a discharging module 400, a temperature sensor 500, and a memory 600. The battery cell is also called a battery. The battery cell 100 includes: a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive and negative electrodes. The positive electrode is a lithium compound, such as lithium iron phosphate (LiFePO4). The negative electrode is graphite. When the electrochemical device 10 is charged, under the action of an electric field, lithium ions are deintercalated from the positive electrode and intercalated into the negative electrode, storing energy. When the electrochemical device 10 is discharged, lithium ions are deintercalated from the negative electrode and flow to the positive electrode, making the positive electrode in a lithium-rich state; this process forms an electric current. The charging module 300 is used to charge the electrochemical device 10, i.e., to charge the battery cell 100. The charging module 300 can be connected to an external charging device (e.g., a charger). The discharge module 400 is connected to an external load to discharge the electrochemical device 10, i.e., the battery cell 100 supplies power to the load. The discharge module 400 includes, for example, a DC-DC converter and a DC-AC converter. The controller 200 controls the operating modes of the charging module 300 and the discharge module 400, for example, controlling the method by which the charging module 300 charges the electrochemical device 10. The controller 200, charging module 300, and discharge module 400 can also be referred to as a battery management system. The temperature sensor 500 senses the ambient temperature. The memory 600 stores the code corresponding to the charging method, charging parameters, etc. The electrochemical device 10 also includes a current sensor and a voltage sensor. The current sensor monitors the charging current and discharging current of the battery cell 100. The voltage sensor monitors the voltage of the battery cell 100.

[0037] Figure 3 This is a flowchart of a charging method for an electrochemical device according to an embodiment of this application. This charging method can be used for... Figure 1 The electrochemical device 10 shown is charged. Figure 4 The relationship between battery voltage, charging current, and capacity during the charging process is shown. Figure 4 The horizontal axis represents the state of charge reached at each charging stage during the charging process. Figure 4 The vertical axis on the left represents the voltage of cell 100, and the vertical axis on the right represents the charging current. Figure 4 Curve 1 and curve 2 are shown. Figure 5 Curve 1 represents the voltage change of cell 100 during the charging process. Figure 5Curve 2 shows the magnitude of the charging current at each stage of the charging process. State of charge (SOC) characterizes the state of available electrical energy in a battery cell, usually expressed as a percentage. Charging current is typically expressed as a charging rate, which is a representation of the charging current relative to the battery capacity. Battery capacity is generally expressed in Ah or mAh. For example, when the battery capacity is 1200mAh, a 1C charging current is 1200mA, and a 0.2C charging current is equal to 240mA.

[0038] Taking the charging method of charging cell 100 from 0% to 80% as an example, the charging method includes the following steps.

[0039] Step S301: Obtain the current temperature. Temperature sensor 500 senses the current temperature and sends it to controller 200.

[0040] Step S302: Determine whether the current temperature is lower than the reference temperature. The reference temperature is a temperature value within the range of 10°C to 25°C. For example, the reference temperature is determined based on the material of the battery cell 100. In this embodiment, the positive electrode is lithium iron phosphate, and the reference temperature is 25°C.

[0041] In response to the current temperature being lower than the reference temperature, the controller 200 controls the charging module 300 to charge the battery cell 100 according to steps S303 to S306. The controller 200 retrieves the charging parameters corresponding to the current temperature from the memory 600, and the charging module 300 charges the battery cell 100 according to the charging parameters corresponding to the current temperature.

[0042] Step S303: In the first charging stage, the electrochemical device is charged to the first cutoff voltage V1 using a first charging current. This first charging stage is a constant current charging stage, using a relatively large first charging current to charge the cell 100 of the electrochemical device, causing the cell 100's voltage (battery voltage) and SOC to rise more rapidly. Figure 4 and Figure 5 As shown, in the first charging stage P1, the battery cell 100 is charged with a constant current using a first charging current I1. The charging cutoff voltage for the first charging stage P1 is a first cutoff voltage V1. The voltage of the battery cell 100 is monitored by a voltage sensor. When the voltage of the battery cell 100 rises to the first cutoff voltage V1, the first charging stage ends, and the state of charge (SOC) of the battery cell 100 reaches approximately 5%. The first charging current I1 can be selected based on the current temperature. Figure 4 and Figure 5 In the embodiment shown, the first charging current I1 is 0.4C and the first cutoff voltage V1 is 3.49±0.02V.

[0043] Step S304: In the second charging stage, the electrochemical device is charged to the first cutoff voltage V1 using a multi-stage constant current method. The second charging stage includes N sequential sub-stages, each corresponding to a charging current, where N is a positive integer. In the (i)th sub-stage (i = 1, 2, ..., N-1), the electrochemical device is charged to the first cutoff voltage V1 using the (i)th sub-stage charging current. In the (i+1)th sub-stage, the electrochemical device is charged to the first cutoff voltage V1 using the (i+1)th sub-stage charging current. The (i)th sub-stage charging current is less than the first charging current and greater than the (i+1)th sub-stage charging current. The cutoff voltage of all sub-stages in the second charging stage is the first cutoff voltage V1. In each sub-stage, the sub-charging stage ends when the voltage of the cell 100 rises to the first cutoff voltage V1. Figure 4 and Figure 5 The second charging stage P2 comprises five sub-stages. In the first sub-stage of the second charging stage, the charging current I is used. P21 When the electrochemical device is charged, the first sub-stage ends and the second sub-stage begins when the voltage of cell 100 rises to the first cutoff voltage V1. Similarly, in the second to fifth sub-stages of the second charging stage, the second sub-stage charging current I is used respectively. P22 The third sub-stage charging current I P23 The fourth sub-stage charging current I P24 The fifth sub-stage charging current I P25 To charge the electrochemical device. For example... Figure 4 As shown, the state of charge (SOC) of the electrochemical device is charged to over 40% through the second charging stage. In some embodiments, the sub-stage charging current of the second charging stage ranges from 0.35C to 0.15C. Figure 4 and Figure 5 In the embodiment shown, the first sub-stage charging current I P21 The second sub-stage charging current is 0.35C. P22 The charging current I in the third sub-stage is 0.3C. P23 The charging current I in the fourth sub-stage is 0.25C. P24 The charging current I in the fifth sub-stage is 0.2C. P25 It is 0.15C.

[0044] Step S305: In the third charging stage, the electrochemical device is charged to the second cutoff voltage V2 with a second charging current, wherein the second charging current I2 is less than the charging current I of the Nth sub-stage in the second charging stage. P2N The second cutoff voltage V2 is greater than the first cutoff voltage V1. For example... Figure 4 and 5As shown, in the third charging stage P3, the electrochemical device is charged to the second cutoff voltage V2 using the second charging current I2. Figure 4 and Figure 5 In the embodiment shown, the second charging current I2 is 0.1C, and the second cutoff voltage V2 is 3.55±0.02V.

[0045] Step S306: In the fourth charging stage, the electrochemical device is charged to a third cutoff voltage V3 using a third charging current. The third charging current I3 is less than the second charging current I2, and the third cutoff voltage V3 is greater than the second cutoff voltage V2. Figure 4 and Figure 5 As shown, in the fourth charging stage P4, the electrochemical device is charged to the third cutoff voltage V3 using the third charging current I3. Figure 4 and Figure 5 In the embodiment shown, the third charging current I3 is 0.05C, and the third cutoff voltage V3 is 3.6±0.02V.

[0046] The charging parameters stored in memory 600 include: a first cutoff voltage V1, a second cutoff voltage V2, a third cutoff voltage V3, a first charging current I1, a second charging current I2, a third charging current I3, and sub-stage charging currents (I1, I2, I3) of the N sub-stages of the second charging stage. P21 to I P2N The charging parameters are stored in memory 600 in the form of a lookup table. For example... Figure 2 As shown, the memory 600 stores n lookup tables LUT1 to LUTn. Each lookup table corresponds to a temperature. The charging parameter values ​​may differ for different temperatures. For example, the lower the temperature, the smaller the first cutoff voltage V1 and the first charging current I1. The controller 200 retrieves the lookup table corresponding to the current temperature from the memory 600 to determine the charging parameters. The first cutoff voltage, second cutoff voltage, and third cutoff voltage can be determined based on the rated voltage of the battery cell 100 and do not change with temperature.

[0047] It should be understood that between the third and fourth charging stages, there may be one or more charging stages, in which the charging current gradually decreases and the charging current of the one or more charging stages is less than the second charging current and greater than the third charging current. The cutoff voltage of these charging stages gradually increases and the cutoff voltage of these charging stages is greater than the second cutoff voltage and less than the third cutoff voltage.

[0048] It should be understood that during the charging process, the voltage of the battery cell 100 is detected by a voltage sensor. When the detected value of the voltage sensor reaches the cutoff voltage, the next charging stage or charging sub-stage begins. However, the voltage value detected by the voltage sensor is the sum of the voltage of the battery cell 100 and the voltage across the equivalent charging resistance. Therefore, when entering the next charging stage or charging sub-stage, the detected value of the voltage sensor decreases as the charging current is reduced.

[0049] Furthermore, in response to the determination in step S302 that the current temperature is greater than the reference temperature, the controller 200 controls the charging module 300 to charge the electrochemical device in multiple constant current charging stages, wherein the charging current of the multiple constant current charging stages gradually decreases and the cutoff voltage of the multiple constant current charging stages gradually increases. The charging current and cutoff voltage of the multiple constant current charging stages are also stored in the memory 600.

[0050] First, by sensing the current temperature and determining the corresponding charging method and parameters, the charging efficiency and safety of the electrochemical device can be improved. Even in low-temperature environments, the electrochemical device can be charged quickly and safely. Furthermore, a larger charging current is used for constant current charging of the cell in the first charging stage, and multi-stage constant current charging is used in the second charging stage. The cutoff voltages of the multiple sub-stages are also configured to be the first cutoff voltage. This allows the actual voltage of the cell at the end of the second charging stage to be closer to the first cutoff voltage, shortening the time of the third and fourth charging stages. Because the charging current used in the first charging stage is larger, the voltage across the charging equivalent resistance is larger at the end of the first charging stage, resulting in a larger difference between the actual voltage of the cell and the first cutoff voltage. Through the constant current charging of the multiple sub-stages in the second charging stage, the actual voltage of the cell is closer to the first cutoff voltage. For the third and fourth charging stages, due to the smaller charging current, the voltage across the charging equivalent resistance is smaller, and the actual voltage of the cell is basically equal to the cutoff voltage corresponding to the third and fourth charging stages. To improve charging efficiency, the charging current is reduced and the cutoff voltage is increased in the third and fourth charging stages. Furthermore, as the state of charge (SOC) of the battery cell increases, the cell voltage increases, and the potential of the positive electrode decreases. Using the same first cutoff voltage as the first charging stage in the sub-stage of the second charging phase allows for more effective control of the positive electrode potential, preventing lithium plating and effectively reducing safety risks during battery charging, making it suitable for charging lithium batteries at low temperatures.

[0051] The charging method described above is executed by the charging module 300 under the control of the controller 200. The controller 200 is, for example, a microcontroller unit (MCU) or an application-specific integrated circuit (ASIC). The memory 600 can be a non-volatile memory, such as a read-only memory (ROM). The charging method is stored in the memory 600 in the form of code, and the controller 200 executes the code to control the charging module 300 to perform the charging method. For example, the controller 200 determines whether to enter the next charging stage or charging sub-stage based on the detection value of the voltage sensor. When the voltage sensor detects a cutoff voltage, the controller 200 sends a control signal to the charging module 300, and the charging module 300 reduces the charging current.

[0052] It should be noted that the controller 200 is not necessarily located inside the electrochemical device 10. For example, the controller 200 can be located in a charging device or load connected to the electrochemical device, and communicate with the charging module 300 of the electrochemical device 10 to control the charging module 300 to charge the electrochemical device 10.

[0053] To compare the low-temperature charging performance of the charging method of this application and the constant current and constant voltage charging method in related technologies, charging experiments were conducted on cells with positive electrode sheets including lithium iron phosphate at -20°C using both the constant current and constant voltage charging method and the charging method of this application.

[0054] Figure 6 A comparison of the charging time of the charging method and the constant current constant voltage charging method according to embodiments of this application is shown. Figure 6 As shown, charging a battery cell from 0-0.5% SOC to 90% using a constant current and constant voltage charging method takes approximately 5.5 hours, while using the charging method of this application, it only takes less than 4 hours; charging a battery cell from 0-0.5% SOC to 80% using a constant current and constant voltage charging method takes approximately 250 minutes, while using the charging method of this application, it only takes approximately 150 minutes, saving 100 minutes, greatly reducing charging time and improving overall charging performance.

[0055] Figure 7 The present application illustrates a comparison of battery voltage and anode-to-lithium potential between the charging method and the constant current-constant voltage charging method according to embodiments of this application. Figure 7This includes curves 1, 2, 3, and 4. Curve 1 shows the change in battery voltage during charging of the electrochemical device using the charging method of this application. Curve 2 shows the change in battery voltage during charging of the electrochemical device using a constant current / constant voltage charging method. Curve 3 shows the change in the lithium potential of the positive electrode during charging of the electrochemical device using the charging method of this application. Curve 4 shows the change in the lithium potential of the positive electrode during charging of the electrochemical device using a constant current / constant voltage charging method. Figure 7 As shown, when using a constant current and constant voltage charging method, as the SOC increases, the potential of the positive electrode plate continuously decreases and eventually reaches the lithium plating potential. At this point, lithium plating occurs inside the cell, causing a safety hazard. Using the charging method of this application, the positive electrode plate is always above the lithium plating potential, and lithium plating does not occur inside the battery. The entire charging process is safe and efficient.

[0056] Figure 8 This image shows a disassembled view of a battery cell after 10 charge-discharge cycles at -20°C, performed according to the charging method of this application on a battery cell whose positive electrode includes lithium iron phosphate. Figure 7 As shown, the interface of the negative electrode plate is good, and no lithium plating occurs.

[0057] To compare the low-temperature charging performance of the charging method of this application and the staged charging method in the related art, the applicant conducted charging experiments on cells with positive electrode sheets including lithium iron phosphate at -10°C using the staged charging method in the related art and the charging method of this application, respectively.

[0058] <Comparative Example 1>

[0059] In related technologies, staged charging methods charge the electrochemical device through multiple stages, with the charging current gradually decreasing and the cutoff voltage gradually increasing in each stage. The staged charging methods in related technologies have eight charging stages, with the cutoff voltages of the first to eighth constant-current charging stages being V11, V21, ..., V81, respectively, where V81 > V71 > ... > V21 > V11. In the charging method of this application, the second charging stage includes five sub-stages.

[0060] Figure 9A A comparison of battery voltages for the two charging methods is shown. Figure 9B The comparison of charging time for the two charging methods is shown. Figure 9A Curves 1 and 2 are shown. Curve 1 is the battery voltage curve during the charging process of the electrochemical device using the charging method of this application, and curve 2 is the battery voltage curve during the charging process of the electrochemical device using the staged charging method in related technologies. Figure 9A As shown, using the charging method of this application, the cell SOC is charged to about 80% in the second charging stage. Figure 9BCurves 3 and 4 are shown. Curve 3 is the relationship between the cell's state of charge (SOC) and time when charging the electrochemical device using the charging method of this application. Curve 4 is the relationship between the cell's SOC and time when charging the electrochemical device using a staged charging method of related technology. Figure 9B As shown, the charging method of this application charges the battery cell from 0-0.5% SOC to 80% more than two hours faster than the staged charging method of related technologies. This is because in the staged charging method of related technologies, the first charging stage uses a constant large current to charge the battery cell, which leads to greater internal polarization of the battery cell and a smaller actual charging voltage (much smaller than the cutoff voltage of the first charging stage). This results in a longer duration for subsequent charging stages, ultimately leading to a longer total charging time. Therefore, the charging method of this application has higher charging efficiency.

[0061] <Comparative Example 2>

[0062] In the staged charging method of related technologies, the electrochemical device is charged through multiple stages, with the charging current gradually decreasing in each stage. The multi-stage charging method has eight charging stages. The cutoff voltage for the first constant current charging stage is V11; the second to sixth constant current charging stages use the same cutoff voltage V21; the seventh charging stage uses a cutoff voltage V31; and the eighth charging stage uses a cutoff voltage V41, where V41 > V31 > V21 > V11. In contrast, the charging method of this application used in the comparative experiment has five sub-stages in its second charging stage.

[0063] Figure 10A A comparison of battery voltages for the two charging methods is shown. Figure 10B The comparison of the positive electrode potential to lithium is shown for two charging methods. Figure 10A Curves 1 and 2 are shown. Curve 1 is the battery voltage curve during the charging process of the electrochemical device using the charging method of this application, and curve 2 is the battery voltage curve during the charging process of the electrochemical device using the staged charging method in related technologies. Figure 10A As shown, using the charging method of this application, the cell's SOC is charged to slightly greater than 60% in the second charging stage. Figure 10A As shown, the cutoff voltage of the first charging stage in the charging method of this application is 0.07V lower than the cutoff voltage V11 of the first stage in the staged charging method of the related art. Figure 9B Curves 3 and 4 are shown. Curve 3 is the relationship between the cell's state of charge (SOC) and the positive electrode's lithium potential when the electrochemical device is charged using the charging method of this application. Curve 4 is the relationship between the cell's SOC and the positive electrode's lithium potential when the electrochemical device is charged using a staged charging method of related technologies. Figure 10BAs shown, when charging an electrochemical device using a staged charging method based on related technologies, lithium plating occurs when the cell's state of charge (SOC) is between 60% and 90%. However, using the charging method of this application, no lithium plating occurs during this charging process. Therefore, the charging method of this application has higher reliability.

[0064] As can be seen from the two comparative examples above, when the current temperature is lower than the reference temperature, the charging method of this application can not only improve the charging efficiency, but also avoid lithium plating.

[0065] This application also provides a non-transitory computer storage medium having computer instructions that, when executed on the controller 200 of the electrochemical device 10, cause the electrochemical device 10 to perform the aforementioned charging method. The non-transitory computer storage medium includes, but is not limited to, random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory, compact disc read-only memory (CD-ROM), digital video disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tapes, disk storage, or other magnetic storage devices.

[0066] This application also provides an electronic device, which includes the electrochemical device in any of the foregoing embodiments. The electrochemical device is used to power the electronic device. The electrochemical device provided by this application can be rapidly charged in low-temperature environments, ensuring the battery life of the electronic device. The electronic devices of this application include, but are not limited to: laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, over-ear stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors. It should be noted that the electrochemical device of this application is applicable not only to the electronic devices listed above, but also to energy storage power stations, maritime transport vehicles, and air transport vehicles. Air transport vehicles include air transport vehicles within the atmosphere and air transport vehicles outside the atmosphere.

[0067] According to the electrochemical device and charging method, computer storage medium, and electronic device provided in the embodiments of this application, the charging method is determined according to the current temperature. When the temperature is lower than the reference temperature, a larger charging current is used to perform constant current charging on the electrochemical device in the first charging stage. In the second charging stage, a multi-stage constant current charging method is used to charge the electrochemical device, with the charging current decreasing in each of the multiple sub-stages of the second charging stage, and each sub-stage having the same cutoff voltage (the same as the cutoff voltage of the first charging stage). In the third and fourth charging stages, a smaller charging current is used to perform constant current charging on the electrochemical device, and the cutoff voltage is increased. By setting the multiple sub-stages of the first and second charging stages to have the same cutoff voltage, the charging time of the third and fourth charging stages is shortened, and the potential of the positive electrode can be more effectively controlled, avoiding lithium plating and effectively reducing the safety risks of the battery charging process, making it suitable for lithium battery charging at low temperatures.

[0068] The above embodiments are only used to illustrate the embodiments of this application, and are not intended to limit the embodiments of this application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the embodiments of this application. Therefore, all equivalent technical solutions also fall within the scope of the embodiments of this application, and the patent protection scope of the embodiments of this application should be defined by the claims.

Claims

1. An electrochemical device, comprising a charging module, wherein, in response to a current temperature being lower than a reference temperature, a controller is configured to control the charging module to charge the electrochemical device in the following manner: During the first charging phase, the electrochemical device is charged to the first cutoff voltage with a first charging current; In the second charging stage, the electrochemical device is charged using a multi-stage constant current method, wherein... The second charging stage includes N sequential sub-stages, where N is a positive integer ≥ 2; In the (i)th sub-stage, the electrochemical device is charged at a constant current to the first cutoff voltage using the (i)th sub-stage charging current. In the (i+1)th sub-stage, the electrochemical device is charged at a constant current to the first cutoff voltage using the (i+1)th sub-stage charging current. The (i)th sub-stage charging current is less than the first charging current and greater than the (i+1)th sub-stage charging current. Wherein, i∈[1,2,…,N-1]; In the third charging stage, the electrochemical device is charged to a second cutoff voltage using a second charging current, the second charging current being less than the charging current of the Nth sub-stage; and In the fourth charging stage, the electrochemical device is charged to a third cutoff voltage using a third charging current, which is less than the second charging current. Wherein, the third cutoff voltage is greater than the second cutoff voltage, and the second cutoff voltage is greater than the first cutoff voltage; the reference temperature is 10°C to 25°C; the electrochemical device includes a positive electrode, and the positive electrode includes lithium iron phosphate; The controller is located inside the electrochemical device, or in a charging device or load connected to the electrochemical device, and communicates with the charging module.

2. The electrochemical device according to claim 1, wherein, In response to the current temperature being greater than the reference temperature, the controller is further configured to cause the charging module to charge the electrochemical device in multiple constant current charging stages, wherein the charging current of the multiple constant current charging stages gradually decreases and the cutoff voltage of the multiple constant current charging stages gradually increases.

3. The electrochemical device according to claim 1, wherein, The lower the current temperature, the smaller the first cutoff voltage and the first charging current.

4. The electrochemical device according to claim 1, wherein, The electrochemical device further includes a memory configured to store a first cutoff voltage, a second cutoff voltage, a third cutoff voltage, a first charging current, a second charging current, a third charging current, and sub-stage charging currents of N sub-stages of the second charging stage.

5. A charging method for an electrochemical device, comprising: Determine if the current temperature is lower than the reference temperature; as well as In response to the current temperature being lower than the reference temperature, the electrochemical device is charged in the following manner: wherein the reference temperature is a temperature value between 10°C and 25°C; the electrochemical device includes a positive electrode, which includes lithium iron phosphate; During the first charging phase, the electrochemical device is charged to the first cutoff voltage with a first charging current; In the second charging stage, the electrochemical device is charged in a multi-stage constant current manner, wherein the second charging stage includes N sequential sub-stages, where N is a positive integer ≥ 2; in the (i)th sub-stage, the electrochemical device is charged with a constant current to the first cutoff voltage using the charging current of the (i)th sub-stage; in the (i+1)th sub-stage, the electrochemical device is charged with a constant current to the first cutoff voltage using the charging current of the (i+1)th sub-stage; wherein the charging current of the (i)th sub-stage is less than the first charging current and greater than the charging current of the (i+1)th sub-stage; where i∈[1,2,… ,N-1]; In the third charging stage, the electrochemical device is charged to a second cutoff voltage using a second charging current, the second charging current being less than the charging current of the Nth sub-stage; and In the fourth charging stage, the electrochemical device is charged to a third cutoff voltage using a third charging current, which is less than the second charging current. Wherein, the third cutoff voltage is greater than the second cutoff voltage, and the second cutoff voltage is greater than the first cutoff voltage.

6. The charging method according to claim 5, wherein, The charging method further includes: in response to the current temperature being greater than the reference temperature, charging the electrochemical device through multiple constant current charging stages, wherein the charging current of the multiple constant current charging stages gradually decreases, and the cutoff voltage of the multiple constant current charging stages gradually increases.

7. An electronic device comprising the electrochemical device as claimed in any one of claims 1 to 4.

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