CN115843396A

CN115843396A - Electrochemical device, charging method thereof, and electronic device

Info

Publication number: CN115843396A
Application number: CN202280004899.7A
Authority: CN
Inventors: 刘云启; 罗明
Original assignee: Dongguan Poweramp Technology Ltd
Current assignee: Dongguan Poweramp Technology Ltd
Priority date: 2022-03-31
Filing date: 2022-03-31
Publication date: 2023-03-24
Also published as: WO2023184390A1

Abstract

The embodiment of the application provides an electrochemical device and a charging method thereof. The charging method comprises the following steps: in response to the current temperature being less than the reference temperature, performing constant current charging to a first cut-off voltage with a first charging current in a first charging stage; charging in a stage constant current mode in a second charging stage; in a third charging stage, constant current charging is carried out to a second cut-off voltage by using a second charging current; and charging to a third cut-off voltage with the third charging current in a fourth charging stage. The second charging phase includes a plurality of sub-phases in which the charging cutoff voltage is the first cutoff voltage. The first cutoff voltage is less than the second cutoff voltage, which is less 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. The charging method is suitable for low-temperature charging, avoids lithium precipitation and has high charging efficiency.

Description

Electrochemical device, charging method thereof, and electronic device

Technical Field

Embodiments of the present disclosure relate to the field, and more particularly, to an electrochemical device, a charging method thereof, and an electronic device including the electrochemical device.

Background

The lithium battery has the advantages of good rate capability, high voltage, light weight, long cycle life and no memory effect, and is widely applied to the fields of consumer products, digital products, power products, medical treatment, security and the like. How to charge lithium batteries is one of the key technologies in lithium battery applications. The lithium battery adopting the lithium iron phosphate system has long cycle life and good stability, but has poor low-temperature performance and cannot well take low-temperature and high-temperature applications into consideration. Lithium batteries of lithium iron phosphate systems are usually prohibited to be charged at low temperature, or the low-temperature charging rate of lithium iron phosphate batteries is set to be 0.1C or even lower, and the charging time is longer, even reaching more than 10 h. Because the bearing capacity of the electrochemical device is limited, if the charging rate is increased blindly, lithium precipitation of the negative electrode can be caused by charging with too high rate, and even the electrochemical device is short-circuited, ignited and exploded, thereby causing certain potential safety hazard.

Disclosure of Invention

In view of the above, embodiments of the present application provide an electrochemical device, a charging method thereof, a computer storage medium, and an electronic device including the electrochemical device, so as to at least partially solve the above problems and improve charging efficiency of a lithium iron phosphate battery at a low temperature.

According to a first aspect of embodiments herein, there is provided an electrochemical device. The electrochemical device is connected with a controller, and in response to the current temperature being less than the reference temperature, the controller is configured to: to determine whether the current temperature is less than the reference temperature, the controller causes the charging module to charge the electrochemical device in response to the current temperature being less than the reference temperature in the following manner. Charging the electrochemical device with a first charge current to a first cutoff voltage during a first charging phase; charging the electrochemical device in a multi-stage constant current manner in a second charging stage, wherein the second charging stage comprises N sub-stages in sequence, and N is a positive integer; during an (i) th sub-phase (i =1, 2, …, N-1), constant current charging the electrochemical device to the first cut-off voltage with an (i) th sub-phase charging current, and during an (i + 1) th sub-phase, constant current charging the electrochemical device to the first cut-off voltage with an (i + 1) th sub-phase charging current, the (i) th sub-phase charging current being less than the first charging current and greater than the (i + 1) th sub-phase charging current; charging the electrochemical device to a second cutoff voltage with a second charging current in a third charging phase, the second charging current being less than the nth sub-phase charging current; and in a fourth charging phase, charging the electrochemical device to a third cutoff voltage with a third charging current, the third charging current being less than the second charging current. Wherein the third cutoff voltage is greater than the second cutoff voltage, which is greater than the first cutoff voltage.

In some embodiments, 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 a plurality of constant current charging phases, the charging currents of the plurality of constant current charging phases decreasing gradually, and the cutoff voltages of the plurality of constant current charging phases increasing gradually.

In some embodiments, the reference temperature is a temperature value in the range of 10 ℃ to 25 ℃.

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

In some embodiments, the lower the present temperature, the smaller the first off voltage and the first charging current.

In some embodiments, the electrochemical device further comprises a memory configured to store the first cutoff voltage, the second cutoff voltage, the third cutoff voltage, the first charging current, the second charging current, the third charging current, and the sub-phase charging currents of the N sub-phases of the second charging phase.

In some embodiments, the cell comprises a positive pole piece comprising lithium iron phosphate.

According to a second aspect of embodiments of the present application, there is provided a method of charging an electrochemical device. The charging method comprises the following steps: judging whether the current temperature is less than the reference temperature; and in response to the current temperature being less than the reference temperature, charging the electrochemical device by:

charging the electrochemical device to a first cutoff voltage with a first charging current in a first charging phase; charging the electrochemical device in a multi-stage constant current manner in a second charging stage, wherein the second charging stage comprises N sub-stages in sequence, and N is a positive integer; in an (i) th sub-stage (i =1, 2, …, N-1), constant current charging the electrochemical device to the first off-voltage with an (i) th sub-stage charging current, and in an (i + 1) th sub-stage, constant current charging the electrochemical device to the first off-voltage with an (i + 1) th sub-stage charging current, the (i) th sub-stage charging current being less than the first charging current and greater than the (i + 1) th sub-stage charging current; charging the electrochemical device to a second cutoff voltage with a second charging current in a third charging phase, the second charging current being less than the nth sub-phase charging current; and in a fourth charging phase, charging the electrochemical device to a third cutoff voltage with a third charging current, the third charging current being less than the second charging current.

Wherein the third cutoff voltage is greater than the second cutoff voltage, which is greater than the first cutoff voltage.

In some embodiments, the charging method further comprises: and in response to the current temperature being greater than the reference temperature, charging the electrochemical device through a plurality of constant current charging phases, wherein the charging currents of the plurality of constant current charging phases gradually decrease and the cut-off voltages of the plurality of constant current charging phases gradually increase.

According to a third aspect of embodiments herein, there is provided a computer storage medium. The computer storage medium has computer instructions that, when run on a controller of an electrochemical device, cause the electrochemical device to perform a charging method as in the second aspect.

According to a fourth aspect of embodiments herein, there is provided an electronic device comprising the electrochemical device of the first aspect.

According to the electrochemical device, the charging method thereof, the computer storage medium and the electronic device provided by the embodiment of the application, the charging mode is determined according to the current temperature, when the temperature is lower than the reference temperature, the electrochemical device is subjected to constant current charging by using a large charging current in the first charging stage, the electrochemical device is charged by using a plurality of sub-stage constant current charging modes in the second charging stage, the charging currents of the plurality of sub-charging stages in the second charging stage are decreased progressively, the plurality of sub-stages have the same cut-off voltage (the same as the cut-off voltage of the first charging stage), and the electrochemical device is subjected to constant current charging by using a smaller charging current in the third charging stage and the fourth charging stage, and the cut-off voltage is increased. The multiple sub-stages of the first charging stage and the second charging stage are provided with the same cut-off voltage, so that the charging time of the third charging stage and the fourth charging stage is shortened, the potential of the positive pole piece can be more effectively controlled, lithium analysis is avoided, the safety risk of the battery charging process is effectively reduced, and the lithium battery charging method is suitable for lithium battery charging at low temperature.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the embodiments of the present application, and other drawings can be obtained by those skilled in the art according to the drawings.

Fig. 1 is a schematic block diagram of an electrochemical device according to an embodiment of the present application.

Fig. 2 shows a charging parameter look-up table in memory.

Fig. 3 is a flowchart of a charging method of an electrochemical device according to an embodiment of the present application.

Fig. 4 shows the relationship between the battery voltage and the charging current and the capacity during charging.

Fig. 5 shows the battery voltage and the charging current during charging.

Fig. 6 shows a comparison of charging periods of the charging method and the constant-current constant-voltage charging method of the embodiment of the present application.

Fig. 7 shows a comparison of cell voltages and a comparison of anode-to-lithium potentials of the charging method and the constant current and constant voltage charging method of the embodiment of the present application.

Fig. 8 shows the cell after 10 cycles of charging and discharging at-20 ℃ according to the charging method of the present application.

Fig. 9A and 9B show a battery voltage comparison and a charging time comparison of the charging method of the embodiment of the present application and the charging method of the related art.

Fig. 10A and 10B show a battery voltage comparison and a positive electrode tab-to-lithium potential comparison of the charging method of the embodiment of the present application and the charging method of the related art.

Detailed Description

In order to make those skilled in the art better understand the technical solutions in the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, but not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application shall fall within the scope of the protection of the embodiments in the present application.

It should be noted that: in the present invention, the embodiments mentioned herein can be combined with each other to form a new technical solution, if not specifically stated. In the present invention, all the technical features mentioned herein may be combined with each other to form a new technical solution, if not specifically stated. In the present invention, unless otherwise stated, the numerical range "a to b" means any real number between a and b. For example, a numerical range of "6 to 22" means that all real numbers between "6 to 22" have been listed herein, and "6 to 22" is only a shorthand representation of the combination of these numbers.

In a constant current and constant voltage (CC-CV) charging method in the related art, a constant current is used for charging, as the charging progresses, the state of charge of a battery cell increases, the internal polarization of the battery cell gradually increases, the potential of an anode to lithium decreases all the time, and when the potential reaches a lithium deposition potential, lithium ions are deposited at the anode, so that irreversible lithium loss (capacity loss) is caused, and a serious potential safety hazard is caused. In addition, the charging time is long, the current is basically kept unchanged in the whole charging period, and the charging efficiency is low.

In the stage charging method in the related art, regulation and control are performed according to the cut-off voltage, the charging current is switched when the set cut-off voltage is reached, the charging in the next stage is performed, the cut-off voltage is increased stage by stage, and the charging current is decreased stage by stage. In a plurality of stages in the early stage, the charging current is large, the internal polarization is large, the actual charging capacity of the battery is low, the subsequent low-current charging time is long, and the overall charging time is long.

Fig. 1 is a schematic block diagram of an electrochemical device according to an embodiment of the present application. As shown in fig. 1, the electrochemical device 10 includes: the battery pack 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 cells are also referred to as batteries. The battery cell 100 includes: the lithium ion battery comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm arranged between the positive pole piece and the negative pole piece. The positive electrode plate is a lithium compound, such as lithium iron phosphate (L i FePO 4). The negative pole piece is graphite. When the electrochemical device 10 is charged, under the action of the electric field, lithium ions are extracted from the positive electrode plate and inserted into the negative electrode plate to store energy. When the electrochemical device 10 discharges, lithium ions are extracted from the negative electrode plate and flow to the positive electrode plate, so that the positive electrode plate is in a lithium-rich state, and a current is formed in the process. The charging module 300 is used to realize charging of the electrochemical device 10, that is, charging of the battery cells 100. The charging module 300 may be connected with an external charging device (e.g., a charger). The discharge module 400 is connected to an external load, and is configured to discharge the electrochemical device 10, that is, the battery cells 100 supply power to the load. The discharge module 400 includes, for example, a dc-dc converter and a dc-ac converter. The controller 200 is used to control the operation modes of the charging module 300 and the discharging module 400, for example, the method of the charging module 300 for charging the electrochemical device 10. The controller 200, the charging module 300, and the discharging module 400 may also be referred to as a battery management system. The temperature sensor 500 is used to sense the ambient temperature. The memory 600 is used for storing codes, charging parameters and the like corresponding to the charging method. The electrochemical device 10 also includes a current sensor and a voltage sensor. The current sensor is used to monitor the charging current and the discharging current of the battery cell 100. The voltage sensor is used to monitor the voltage of the battery cell 100.

Fig. 3 is a flowchart of a charging method of an electrochemical device according to an embodiment of the present application. This charging method may be used to charge the electrochemical device 10 shown in fig. 1. Fig. 4 shows the relationship between the battery voltage and the charging current and the capacity during charging. The horizontal axis of fig. 4 represents the state of charge achieved during each charging phase of the charging process. The vertical axis on the left side of fig. 4 represents the voltage of the battery cell 100, and the vertical axis on the right side represents the charging current. Fig. 4 shows

curves

1 and 2. Curve 1 of fig. 5 is a change in voltage of the battery cell 100 during charging. Curve 2 of fig. 5 is the magnitude of the charging current at each stage in the charging process. The state of charge (SOC) characterizes the state of available electrical energy in a cell, typically expressed as a percentage. The charging current is generally expressed in terms of a charging rate, which is a representation of the charging current with respect to the battery capacity. The battery capacity is generally expressed by Ah or mAh. For example, when the battery capacity is 1200mAh, the charging current at 1C is 1200mA, and the charging current at 0.2C is 240mA.

Taking the charging of the SOC of the battery cell 100 from 0% to 80% by this charging method as an example, the charging method includes the following steps.

In step S301, the current temperature is acquired. The temperature sensor 500 senses the current temperature and transmits the current temperature to the controller 200.

Step S302, judging whether the current temperature is less than the reference temperature. The reference temperature is a temperature value in the range of 10 ℃ to 25 ℃. For example, the reference temperature is determined according to the material of the battery cell 100. In this embodiment, the positive electrode plate is lithium iron phosphate, and the reference temperature is 25 ℃.

In response to that the current temperature is less than the reference temperature, the controller 200 controls the charging module 300 to charge the battery cell 100 according to the methods of steps S303 to S306. The controller 200 searches for a charging parameter corresponding to the current temperature from the memory 600 according to the current temperature, and the charging module 300 charges the battery cell 100 according to the charging parameter corresponding to the current temperature.

In step S303, in the first charging phase, the electrochemical device is charged to the first cut-off voltage V1 with the first charging current. The first charging phase is a constant-current charging phase, and the battery cell 100 of the electrochemical device is charged with a larger first charging current, so that the voltage (battery voltage) and the SOC of the battery cell 100 increase faster. As shown in fig. 4 and 5, in the first charging phase P1, the battery cell 100 is subjected to constant current charging using the first charging current I1. The charge cutoff voltage of the first charge phase P1 is the 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 cut-off voltage V1, the first charging stage is ended, and the SOC of the battery cell 100 reaches about 5%. The first charging current I1 may be selected according to the present temperature. In the embodiment shown in fig. 4 and 5, the first charging current I1 is 0.4C, and the first off-voltage V1 is 3.49 ± 0.02V.

In step S304, in the second charging stage, the electrochemical device is charged to the first off-voltage V1 in a multi-stage constant current manner. The second charging stage comprises N sub-stages in sequence, each sub-stage corresponds to a charging current, and N is a positive integer. In the (i) th sub-stage (i =1, 2, …, N-1), the electrochemical device is subjected to constant current charging to a first cut-off voltage V1 with an (i) th sub-stage charging current, and in the (i + 1) th sub-stage, the electrochemical device is subjected to constant current charging to the first cut-off voltage V1 with an (i + 1) th sub-stage charging current, wherein the (i) th sub-stage charging current is smaller than the first charging current and larger than the (i + 1) th sub-stage charging current. The cutoff voltages of the plurality of sub-phases in the second charge phase are all the first cutoff voltage V1. In each sub-phase, when the voltage of the battery cell 100 rises to the first cut-off voltage V1, the sub-charging phase is ended. Fig. 4 and 5 comprise 5 sub-stages in the second charging phase P2And (5) a stage. In the 1 st sub-phase of the second charging phase, the 1 st sub-phase charging current I is used _P21 And charging the electrochemical device, and ending the 1 st sub-stage and entering the 2 nd sub-stage when the voltage of the battery cell 100 rises to the first cut-off voltage V1. Similarly, in the sub-phase 2 to the sub-phase 5 of the second charging phase, the sub-phase 2 charging current I is used respectively _P22 3 rd sub-stage charging current I _P23 4 th sub-stage charging current I _P24 5 th sub-stage charging current I _P25 The electrochemical device is charged. As shown in fig. 4, the SOC of the electrochemical device is charged to 40% or more by the second charging stage. In some embodiments, the sub-phase charging current of the second charging phase ranges from 0.35C to 0.15C. In the embodiment shown in fig. 4 and 5, the 1 st sub-phase charging current I _P21 0.35C, sub-phase 2 charging current I _P22 0.3C, sub-phase 3 charging current I _P23 0.25C, 4 th sub-stage charging current I _P24 0.2C, the 5 th sub-stage charging current I _P25 It was 0.15C.

Step S305, in a third charging phase, charging the electrochemical device to a second cut-off voltage V2 with a second charging current, wherein the second charging current I2 is less than the charging current I of the Nth sub-phase in the second charging phase _P2N The second cut-off voltage V2 is greater than the first cut-off voltage V1. As shown in fig. 4 and 5, in the third charging phase P3, the electrochemical device is charged to the second cutoff voltage V2 using the second charging current I2. In the embodiment shown in fig. 4 and 5, the second charging current I2 is 0.1C, and the second cutoff voltage V2 is 3.55 ± 0.02V.

Step S306, in a fourth charging phase, the electrochemical device is charged to a third cut-off voltage V3 with a third charging current, where the third charging current I3 is smaller than the second charging current I2, and the third cut-off voltage V3 is greater than the second cut-off voltage V2. As shown in fig. 4 and 5, in the fourth charging phase P4, the electrochemical device is charged to the third cut-off voltage V3 using the third charging current I3. In the embodiment shown in fig. 4 and 5, the third charging current I3 is 0.05C, and the third cutoff voltage V3 is 3.6 ± 0.02V.

In the memory 600The stored charging parameters include: a first cut-off voltage V1, a second cut-off voltage V2, a third cut-off voltage V3, a first charging current I1, a second charging current I2, a third charging current I3 and a sub-phase charging current (I) of N sub-phases of the second charging phase _P21 To I _P2N ). The charging parameters are stored in the memory 600 in the form of a look-up table (l ook up tab l e). As shown in fig. 2, the memory 600 stores therein n look-up tables LUT1 to LUTn. One for each temperature. The charging parameters may have different values for different temperatures. For example, the lower the temperature, the smaller the first off voltage V1 and the first charging current I1. The controller 200 obtains the lookup table corresponding to the current temperature from the memory 600, and determines the charging parameter. The first cut-off voltage, the second cut-off voltage, and the third cut-off voltage may be determined according to a rated voltage of the battery cell 100, and may not change with temperature.

It is to be understood that one or more charging phases may also be included between the third charging phase and the fourth charging phase, the charging current of the one or more charging phases being gradually reduced, and the charging current of the one or more charging phases being smaller than the second charging current and larger than the third charging current, the cut-off voltages of the charging phases being gradually increased, and the cut-off voltages of the charging phases being larger than the second cut-off voltage and smaller than the third cut-off voltage.

It should be understood that, during the charging process, the voltage of the battery cell 100 is detected by the voltage sensor, and when the detection value of the voltage sensor reaches the cut-off voltage, the next charging phase or sub-charging phase is entered. The voltage value detected by the voltage sensor is the sum of the voltage of the battery cell 100 and the voltage across the charge equivalent resistance. Therefore, when the next charging stage or sub-charging stage is entered, the charging current is reduced, and then the detection value of the voltage sensor is reduced.

Further, in response to determining that the current temperature is greater than the reference temperature at step S302, the controller 200 controls the charging module 300 to charge the electrochemical device in a plurality of constant current charging phases in which the charging current is gradually decreased and the cut-off voltages are gradually increased. The charging currents and cutoff voltages for the plurality of constant current charging phases are also stored in memory 600.

Firstly, the charging efficiency and the charging safety of the electrochemical device can be improved by sensing the current temperature and determining the charging method and the charging parameters corresponding to the current temperature according to the current temperature. The electrochemical device can be charged quickly and safely even in a low-temperature environment. Further, the battery cell is subjected to constant current charging by using a larger charging current in the first charging stage, the battery cell is subjected to constant current charging by using multiple sub-stages in the second charging stage, and the cut-off voltages of the multiple sub-stages are also configured to be the first cut-off voltage, so that the actual voltage of the battery cell is closer to the first cut-off voltage when the second charging stage is finished, and the time of the third charging stage and the time of the fourth charging stage are shortened. Because the charging current used in the first charging stage is large, when the first charging stage is finished, the voltage on the charging equivalent resistor is large, the difference value between the actual voltage of the battery cell and the first cut-off voltage is large, and the actual voltage of the battery cell is closer to the first cut-off voltage through the constant current charging of the plurality of sub-stages of the second charging stage. For the third and fourth charging stages, the charging current is small, the voltage on the charging equivalent resistor is small, and the actual voltage of the battery cell is substantially equal to the cut-off voltage corresponding to the third and fourth charging stages. To improve the charging efficiency, the charging current in the third and fourth charging phases is reduced and the cut-off voltage is increased. Further, as the SOC of the battery cell increases, the voltage of the battery cell increases, and the potential of the positive electrode plate decreases. The first cut-off voltage which is the same as that of the first charging stage is used in the sub-stage of the second charging stage, so that the potential of the positive pole piece can be more effectively controlled, lithium analysis is avoided, the safety risk of the battery charging process is effectively reduced, and the lithium battery charging method is suitable for lithium battery charging at low temperature.

The above charging method is executed by the controller 200 controlling the charging module 300. The controller 200 is, for example, a Microcontroller (MCU), an application specific ic (ic I integrated C I rcu it, AS ic), or the like. The memory 600 may be a non-volatile memory, such as a Read-only memory (ROM). The above-described charging method is stored in the memory 600 in the form of codes, and the controller 200 executes the codes to control the charging module 300 to perform the above-described charging method. For example, the controller 200 determines whether to enter the next charging phase or the charging sub-phase according to the detection value of the voltage sensor. When the detection value of the voltage sensor is the off-voltage, the controller 200 transmits a control signal to the charging module 300, and the charging module 300 reduces the charging current.

It should be noted that the controller 200 is not necessarily provided inside the electrochemical device 10. For example, the controller 200 may be provided within a charging device or load connected to the electrochemical device. And communicates with the charging module 300 of the electrochemical device 10 to control the charging module 300 to charge the electrochemical device 10.

In order to compare the low-temperature charging performance of the charging method and the constant-current constant-voltage charging method in the related art, the constant-current constant-voltage charging method and the charging method are respectively used for carrying out a charging experiment on a battery cell of which the positive electrode plate comprises lithium iron phosphate at the temperature of minus 20 ℃.

Fig. 6 shows a comparison of charging periods of the charging method and the constant-current constant-voltage charging method of the embodiment of the present application. As shown in fig. 6, the SOC of the battery cell is charged from 0-0.5% to 90%, and the constant-current and constant-voltage charging method requires about 5.5 hours, while the charging method of the present application requires less than 4 hours; the battery cell is charged from 0-0.5% to 80% from SOC, the constant-current constant-voltage charging method needs about 250 minutes, and the charging method only needs about 150 minutes, saves 100 minutes, greatly reduces charging time and improves the overall charging performance.

Fig. 7 shows a comparison of cell voltages and a comparison of anode-to-lithium potentials of the charging method and the constant current and constant voltage charging method of the embodiment of the present application. Fig. 7 includes a curve 1, a curve 2, a curve 3, and a curve 4. Curve 1 is the variation of the cell voltage during charging of an electrochemical device using the charging method of the present application. Curve 2 is the variation curve of the cell voltage during charging of the electrochemical device using a constant current constant voltage charging method. Curve 3 is the change curve of the positive pole piece to the lithium potential during the charging process of the electrochemical device using the charging method of the present application. Curve 4 is the curve of the change of the positive electrode plate to the lithium potential during the charging of the electrochemical device using the constant current and constant voltage charging method. As shown in fig. 7, by using a constant-current constant-voltage charging method, as the SOC increases, the potential of the positive electrode plate decreases all the time and finally reaches the lithium-separation potential, and at this time, lithium separation occurs inside the battery cell, which causes potential safety hazards; by using the charging method, the positive pole piece is always higher than the lithium analysis potential, no lithium analysis occurs inside the battery, and the whole charging process is safe and efficient.

Fig. 8 shows a disassembled view of a cell after 10 charge-discharge cycles at-20 ℃ for a cell with a positive electrode plate comprising lithium iron phosphate, according to the charging method of the present application. As shown in fig. 7, the interface of the negative electrode plate was good, and no lithium deposition occurred.

In order to compare the low-temperature charging performance of the charging method of the present application and the stage charging method of the related art, the applicant performed a charging experiment on an electric core having a positive electrode plate including lithium iron phosphate at-10 ℃ using the stage charging method of the related art and the charging method of the present application, respectively.

< comparative example 1>

In the step charging method in the related art, the electrochemical device is charged through a plurality of steps, the charging current used in the plurality of steps is gradually decreased, and the off-voltage of the plurality of steps is gradually increased. The number of the charging stages in the stage charging method in the related art is 8, the cut-off voltages from the 1 st constant current charging stage to the 8 th constant current charging stage are respectively V11, V21, … V81, and V81 > V71 > … > V21 > V11. In the charging method of the present application, the second charging phase includes 5 sub-phases.

Fig. 9A shows a battery voltage comparison of the two charging methods, and fig. 9B shows a charging time comparison of the two charging methods. Fig. 9A shows a curve 1 and a curve 2, the curve 1 being a curve of a cell voltage during charging of an electrochemical device using the charging method of the present application, and the curve 2 being a curve of a cell voltage during charging of an electrochemical device using a stage charging method in the related art. As shown in fig. 9A, the cell SOC is charged to about 80% in the second charging stage using the charging method of the present application. Fig. 9B shows a curve 3 and a curve 4, the curve 3 being a cell SOC versus time curve for charging an electrochemical device using the charging method of the present application, and the curve 4 being a cell SOC versus time curve for charging an electrochemical device using a related-art stage charging method. As shown in fig. 9B, the SOC of the cell is charged from 0-0.5% to 80%, and the charging method of the present application is faster than the phase charging method of the related art by 2 hours or more. This is because in the phase charging method in the related art, the first charging phase uses a constant large current to charge the battery cell, which results in a large polarization inside the battery cell, a small actual charging voltage of the battery cell (much smaller than the cutoff voltage of the first charging phase), a long time of the subsequent charging phase, and finally a long total charging time. Therefore, the charging method has higher charging efficiency.

< comparative example 2>

In the step charging method in the related art, the electrochemical device is charged through a plurality of steps, and the charging current used for the plurality of steps is gradually decreased. The number of charging stages in the multi-stage charging method is 8, the cutoff voltage of the 1 st constant current charging stage is V11, the same cutoff voltage is used from the 2 nd to 6 th constant current charging stages is V21, the cutoff voltage V31 is used in the 7 th charging stage, the cutoff voltage V41 is used in the 8 th charging stage, and V41 > V31 > V21 > V11. In comparison to the charging method of the present application used in the experiment, the second charging phase comprises 5 sub-phases.

Fig. 10A shows the battery voltage comparison for the two charging methods, and fig. 10B shows the positive pole piece to lithium potential comparison for the two charging methods. Fig. 10A shows a curve 1 and a curve 2, the curve 1 being a curve of a cell voltage during charging of an electrochemical device using the charging method of the present application, and the curve 2 being a curve of a cell voltage during charging of an electrochemical device using a stage charging method in the related art. As shown in fig. 10A, using the charging method of the present application, the cell SOC is charged to slightly more than 60% in the second charging stage. As shown in fig. 10A, the cutoff voltage of the first charging stage in the charging method of the present application is lower by 0.07V than the cutoff voltage V11 of the first stage of the stage charging method in the related art. Fig. 9B shows a curve 3 and a curve 4, where the curve 3 is a battery cell SOC and positive electrode tab versus lithium potential curve of an electrochemical device charged by the charging method of the present application, and the curve 4 is a battery cell SOC and positive electrode tab versus lithium potential curve of an electrochemical device charged by the phase charging method of the related art. As shown in fig. 10B, when the cell SOC is 60% to 90%, lithium deposition occurs using the related art phase charging method to charge the electrochemical device; with the charging method of the present application, no lithium precipitation occurs during this charging process. Therefore, the charging method has higher reliability.

According to the two comparative examples, when the current temperature is lower than the reference temperature, the charging method can improve the charging efficiency and can avoid lithium precipitation.

The present 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 charging method described above. Non-transitory computer storage media include, but are not limited to, random Access Memory (RAM), read-only Memory (ROM), electrically erasable programmable Read-only Memory (EEPROM), flash Memory, compact disk Read-only Memory (CD-ROM), digital versatile disk (D igi ta V ideo D i sc, DVD), or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage, or other magnetic storage devices.

The present application also provides an electronic device comprising the electrochemical device of any one of the foregoing embodiments. Electrochemical devices are used to power electronic devices. The application provides an electrochemical device can charge fast in low temperature environment, has ensured electron device's duration. Electronic devices of the present application include, but are not limited to: a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a cellular phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large-sized household battery, and a lithium ion capacitor. Note that the electrochemical device of the present application is applicable to an energy storage power station, a marine vehicle, and an air vehicle, in addition to the above-listed electronic devices. The air transport carrier device comprises an air transport carrier device in the atmosphere and an air transport carrier device outside the atmosphere.

According to the electrochemical device, the charging method thereof, the computer storage medium and the electronic device provided by the embodiment of the application, the charging mode is determined according to the current temperature, when the temperature is lower than the reference temperature, the electrochemical device is subjected to constant current charging by using a large charging current in the first charging stage, the electrochemical device is charged by using a plurality of sub-stage constant current charging modes in the second charging stage, the charging currents of the plurality of sub-charging stages in the second charging stage are decreased progressively, the plurality of sub-stages have the same cut-off voltage (the same as the cut-off voltage of the first charging stage), and the electrochemical device is subjected to constant current charging by using a smaller charging current in the third charging stage and the fourth charging stage, and the cut-off voltage is increased. The multiple sub-stages of the first charging stage and the second charging stage are provided with the same cut-off voltage, so that the charging time of the third charging stage and the charging time of the fourth charging stage are shortened, the potential of the positive pole piece can be more effectively controlled, lithium analysis is avoided, the safety risk of the battery charging process is effectively reduced, and the lithium battery charging system is suitable for lithium battery charging at low temperature.

The above embodiments are only used for illustrating the embodiments of the present application, and not for limiting the embodiments of the present application, and those skilled in the relevant art can make various changes and modifications without departing from the spirit and scope of the embodiments of the present application, so that all equivalent technical solutions also belong to the scope of the embodiments of the present application, and the scope of patent protection of the embodiments of the present application should be defined by the claims.

Claims

1. An electrochemical device coupled to a controller, the controller configured to, in response to a current temperature being less than a reference temperature:

charging the electrochemical device to a first cutoff voltage with a first charging current in a first charging phase;

charging the electrochemical device in a multi-stage constant current manner in a second charging stage, wherein the second charging stage comprises N sub-stages in sequence, and N is a positive integer; in an (i) th sub-stage (i =1, 2, …, N-1), constant current charging the electrochemical device to the first off-voltage with an (i) th sub-stage charging current, and in an (i + 1) th sub-stage, constant current charging the electrochemical device to the first off-voltage with an (i + 1) th sub-stage charging current, the (i) th sub-stage charging current being less than the first charging current and greater than the (i + 1) th sub-stage charging current;

charging the electrochemical device to a second cutoff voltage with a second charging current in a third charging phase, the second charging current being less than the nth sub-phase charging current; and

charging the electrochemical device to a third cutoff voltage with a third charging current in a fourth charging phase, the third charging current being less than the second charging current,

2. The electrochemical device of claim 1, wherein in response to the present temperature being 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 phases with gradually decreasing charging currents and gradually increasing cutoff voltages.

3. The electrochemical device of claim 1, wherein the reference temperature is 10 ℃ to 25 ℃.

4. The electrochemical device according to claim 1, wherein the lower the present temperature is, the smaller the first off voltage and the first charge current are.

5. The electrochemical device of claim 1, further comprising a memory configured to store the first cutoff voltage, the second cutoff voltage, the third cutoff voltage, the first charging current, the second charging current, the third charging current, and sub-phase charging currents of the N sub-phases of the second charging phase.

6. The electrochemical device of claim 1, wherein the electrochemical device comprises a positive pole piece comprising lithium iron phosphate.

7. A method of charging an electrochemical device, comprising:

judging whether the current temperature is less than the reference temperature; and

in response to the current temperature being less than the reference temperature, charging the electrochemical device by:

charging the electrochemical device with a first charge current to a first cutoff voltage during a first charging phase;

8. The charging method of claim 7, wherein the charging method further comprises: and in response to the current temperature being greater than the reference temperature, charging the electrochemical device through a plurality of constant current charging phases, wherein the charging currents of the plurality of constant current charging phases gradually decrease and the cut-off voltages of the plurality of constant current charging phases gradually increase.

9. The charging method of claim 7, wherein the reference temperature is a temperature value in the range of 10 ℃ to 25 ℃.

10. An electronic device comprising the electrochemical device according to any one of claims 1 to 6.