Electrochemical device, charge-discharge method, and electronic device

Abstract

An electrochemical device, a charging / discharging method, and an electronic device are disclosed. The negative electrode active material of the electrochemical device comprises a first active material and a second active material. The theoretical specific capacity of the first active material is less than that of the second active material, and the upper limit of the discharge operating voltage of the first active material is higher than that of the second active material. At first and second ambient temperatures T1 and T2, the charging capacity of the electrochemical device in a single charge-discharge process within a first cycle interval is Q, respectively. 11 and Q 21 Each has a discharge cutoff voltage V 11 and V 21 Or discharge cutoff current I 11 and I 21 The charging capacity of a single charge-discharge process in the second cycle interval is Q. 12 and Q 22 Each has a discharge cutoff voltage V 12 and V 22 Or discharge cutoff current I 12 and I 22 Q 21 With Q 11 The difference is no greater than 20%, and at least one of conditions a) to c) satisfies: Q 12 ≤Q 11 V 12 >V 11 ;I 12 >I 11 At least one of conditions d) to f) satisfies: Q 22 ≤Q 21 V 22 >V 21 ;I 22 >I 21 .

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrochemical device, a charging and discharging method, and an electronic device. Background Technology

[0002] The cycle performance of an electrochemical device directly affects its service life and quality. Better cycle performance results in a longer lifespan for the electrochemical device, which not only reduces user operating costs but also minimizes resource consumption.

[0003] The cycle performance of electrochemical devices includes both room temperature and high temperature cycle performance. For silicon-based batteries and other electrochemical devices with low temperature coefficients, the high-temperature cycle performance differs significantly from their room temperature cycle performance. Taking silicon-based batteries as an example, due to their inherent characteristics—a lower voltage plateau and lower temperature coefficient—their charging capacity at high temperatures is higher than at room temperature, leading to excessive lithium desorption from the positive electrode and severely deteriorating their high-temperature cycle performance. Furthermore, during long-term use, the silicon material expands, affecting the overall cycle performance of the silicon-based battery throughout its lifespan. Summary of the Invention

[0004] In view of this, embodiments of this application provide an electrochemical device, a charging and discharging method, and an electronic device to at least partially solve the above-mentioned problems.

[0005] According to a first aspect of the embodiments of this application, an electrochemical device is provided. The negative electrode active material of the electrochemical device includes a first active material and a second active material. The theoretical specific capacity of the first active material is less than the theoretical specific capacity of the second active material, and the upper limit of the discharge operating voltage of the first active material is higher than the upper limit of the discharge operating voltage of the second active material.

[0006] At the first ambient temperature T1, the charging capacity of the electrochemical device in a single charge-discharge process during the first cycle interval is Q. 11 It has a discharge cutoff voltage V 11 Or discharge cutoff current I 11 ;

[0007] The charging capacity of the electrochemical device in a single charge-discharge process in the second cycle interval is Q. 12 It has a discharge cutoff voltage V 12 Or discharge cutoff current I 12 Among them, at least one of conditions a) to c) is satisfied:

[0008] a)Q 12 ≤Q 11 ;

[0009] b)V 12>V 11 ;

[0010] c)I 12 >I 11 ;

[0011] At the second ambient temperature T2, where T2 > T1, the charging capacity of the electrochemical device in a single charge-discharge process within the first cycle interval is Q. 21 , satisfy, Q 21 With Q 11 The difference is no greater than 20%; the electrochemical device has a discharge cutoff voltage V in the first cycle interval. 21 Or discharge cutoff current I 21 ;

[0012] The charging capacity of the electrochemical device in a single charge-discharge process in the second cycle interval is Q. 22 It has a discharge cutoff voltage V 22 Or discharge cutoff current I 22 Among them, at least one of conditions d) to f) is satisfied:

[0013] d)Q 22 ≤Q 21 ;

[0014] e)V 22 >V 21 ;

[0015] f)I 22 >I 21 .

[0016] In one possible implementation, in conjunction with the first aspect described above, the temperature coefficient of the second active material is less than 0.98.

[0017] In another possible implementation, in conjunction with the first aspect described above, the second active material comprises a transition metal oxide.

[0018] In another possible implementation, in conjunction with the first aspect above, a single charge-discharge process of the electrochemical device includes: charging the electrochemical device at a constant current to a first voltage with a charging current, and charging the electrochemical device at a constant voltage to a first current with the first voltage; charging the electrochemical device at a constant current to a second voltage with the first current, and charging the electrochemical device at a constant voltage to a second current with the second voltage; and charging the electrochemical device at a constant current to a third voltage with the second current, and charging the electrochemical device at a constant voltage to a target charging cutoff current with the third voltage.

[0019] In another possible implementation, in conjunction with the first aspect mentioned above, T1 < 35℃, 35℃ ≤ T2 ≤ 60℃.

[0020] In another possible implementation, combining the first aspect mentioned above, Q 22 With Q 12 The difference is no greater than 20%.

[0021] In another possible implementation, in conjunction with the first aspect described above, the electrochemical device is connected to a processor, the processor being configured to: acquire the current temperature of the electrochemical device; determine a target charging cut-off current for the electrochemical device based on the current temperature and a pre-established first mapping relationship between temperature and charging cut-off current, the first mapping relationship including N temperatures and corresponding N charging cut-off currents, wherein the N charging cut-off currents increase as the N temperatures increase, and N is an integer greater than or equal to 2; and control the electrochemical device to charge until the target charging cut-off current is reached.

[0022] In another possible implementation, in conjunction with the first aspect above, the processor is specifically configured to: determine the temperature in the first mapping relationship that is closest to the current temperature as the target temperature, and determine the charging cut-off current corresponding to the target temperature as the target charging cut-off current.

[0023] In one possible implementation, in conjunction with the first aspect described above, the processor is further configured to: acquire the current charge-discharge cycle number of the electrochemical device; determine a target cycle interval of the electrochemical device based on the current charge-discharge cycle number; determine the target discharge cut-off voltage or target discharge cut-off current based on the target cycle interval and a pre-established second mapping relationship between the cycle interval and the discharge cut-off voltage or discharge cut-off current, wherein the second mapping relationship includes M sequential cycle intervals and corresponding M discharge cut-off voltages or discharge cut-off currents, and the cycle interval with a larger charge-discharge cycle number corresponds to a larger discharge cut-off voltage or discharge cut-off current, where M is a number greater than or equal to two integers; and control the discharge of the electrochemical device until the target discharge cut-off voltage or the target discharge cut-off current is reached.

[0024] In one possible implementation, in conjunction with the first aspect described above, the difference between the discharge cutoff voltages corresponding to two adjacent cycle intervals is greater than a first voltage amplitude, which is between 0.1V and 0.2V.

[0025] According to a second aspect of the embodiments of this application, a charging and discharging method for an electrochemical device is provided. The negative electrode active material of the electrochemical device includes a first active material and a second active material. The theoretical specific capacity of the first active material is less than the theoretical specific capacity of the second active material, and the upper limit of the discharge operating voltage of the first active material is higher than the upper limit of the discharge operating voltage of the second active material. The method includes:

[0026] At a first ambient temperature T1, the charging capacity of the electrochemical device in a single charge-discharge process during the first cycle interval is controlled to be Q. 11 It has a discharge cutoff voltage V 11 Or discharge cutoff current I 11 ;

[0027] The charging capacity of the electrochemical device during a single charge-discharge process in the second cycle interval is controlled to be Q. 12 It has a discharge cutoff voltage V 12 Or discharge cutoff current I 12 Among them, at least one of conditions a) to c) is satisfied:

[0028] a)Q 12 ≤Q 11 ;

[0029] b)V 12 >V 11 ;

[0030] c)I 12 >I 11 ;

[0031] At the second ambient temperature T2, where T2 > T1, the charging capacity of the electrochemical device in a single charge-discharge process within the first cycle interval is controlled to be Q. 21 , satisfy, Q 21 With Q 11 The difference is no greater than 20%; the electrochemical device has a discharge cutoff voltage V in the first cycle interval. 21 Or discharge cutoff current I 21 ;

[0032] The charging capacity of the electrochemical device during a single charge-discharge process in the second cycle interval is controlled to be Q. 22 It has a discharge cutoff voltage V 22 Or discharge cutoff current I 22 Among them, at least one of conditions d) to f) is satisfied:

[0033] d)Q 22 ≤Q 21 ;

[0034] e)V 22 >V 21 ;

[0035] f)I 22 >I 21 .

[0036] According to a third aspect of the embodiments of this application, an electronic device is provided, the electronic device including an electrochemical device as described in any of the first aspects.

[0037] Based on the above technical solution, the negative electrode active material of the electrochemical device includes a first active material and a second active material. The theoretical specific capacity of the first active material is less than that of the second active material, and the upper limit of the discharge operating voltage of the first active material is higher than that of the second active material. At the first ambient temperature T1, the charging capacity of the electrochemical device in a single charge-discharge process in the first cycle interval is Q. 11 At a second ambient temperature T2 greater than T1, the charging capacity of the electrochemical device in a single charge-discharge process during the first cycle is Q. 21 And Q 21 With Q 11 The difference is no greater than 20%. That is, the capacity of the electrochemical device charged at the higher second ambient temperature is essentially the same as the capacity charged at the first ambient temperature, thereby avoiding excessive lithium removal from the negative electrode of the electrochemical device at high temperatures and improving the high-temperature cycling performance of the electrochemical device. Meanwhile, at the first ambient temperature T1, the charging capacity of the electrochemical device in a single charge-discharge process in the first cycle interval is Q. 11 It has a discharge cutoff voltage V 11 Or discharge cutoff current I 11 The charging capacity of a single charge-discharge process in the second cycle interval is Q. 12 It has a discharge cutoff voltage V 12 Or discharge cutoff current I 12 And satisfy at least one of conditions a) to c): Q 12 ≤Q 11 V 12 >V 11 ;I 12 >I 11 At a second ambient temperature T2, which is greater than T1, the charging capacity of the electrochemical device in a single charge-discharge process during the first cycle is Q. 21 It has a discharge cutoff voltage V 21 Or discharge cutoff current I 21 The charging capacity of a single charge-discharge process in the second cycle interval is Q. 22 It has a discharge cutoff voltage V 22 Or discharge cutoff current I 22 And satisfy at least one of conditions d) to f): Q 22 ≤Q 21 V 22 >V 21 ;I 22 >I 21That is, by using different discharge cut-off voltages or discharge cut-off currents in different cycle intervals, the discharge cut-off voltage of the electrochemical device is gradually increased, so as to achieve optimal use of the electrochemical device throughout its entire life cycle, thereby improving the cycle performance of the electrochemical device throughout its entire life cycle. Attached Figure Description

[0038] 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.

[0039] Figure 1 This is a schematic diagram of the cycling performance of an electrochemical device in the relevant technology at a normal temperature of 25°C and at a high temperature of 45°C.

[0040] Figure 2 This is a schematic diagram of the cycling curves of the electrochemical device provided in the embodiments of this application under different discharge cutoff voltages;

[0041] Figure 3 This is a schematic diagram of the cycling performance of the electrochemical device provided in this application embodiment before and after capacity limitation at a high temperature of 45°C;

[0042] Figure 4 This is a schematic flowchart of the charging method for the electrochemical device provided in the embodiments of this application;

[0043] Figure 5 This is a schematic diagram of the structure of the electronic device provided in the embodiments of this application. Detailed Implementation

[0044] 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 thoroughly 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.

[0045] Electrochemical devices exhibit polarization during charging. Factors influencing this polarization include not only current but also ambient temperature. Higher ambient temperatures weaken the polarization. Reduced polarization leads to a higher positive electrode potential during charging, resulting in a higher charging capacity at higher temperatures compared to room temperature. This can cause excessive lithium desorption from the positive electrode, degrading the device's high-temperature performance. This is particularly pronounced in silicon-based electrochemical devices and similar devices with low temperature coefficients.

[0046] Taking silicon-based batteries as an example, such as Figure 1 As shown, comparing the cycle performance of electrochemical devices with the same Si content at room temperature (25°C) and at high temperature (45°C), it can be found that the cycle life at room temperature (25°C) is significantly better than that at high temperature (45°C). When 800 cycles are reached, the capacity retention differs by approximately 8%. Furthermore, as shown in Table 1, which compares the cycle capacity of Si materials at room temperature (25°C) and high temperature (45°C), for the same Si silicon material and the same chemical system, the cycle capacity of the electrochemical device at room temperature (45°C) is greater than that at high temperature (25°C), leading to over-lithiation in the electrochemical device. Figure 1 The degradation of cycling performance at a high temperature of 45°C is shown. The main reason for the above problem is that silicon itself has a low voltage plateau (sometimes referred to as the discharge operating voltage in the following text) and a low temperature coefficient, resulting in a higher charge and discharge capacity at a high temperature of 45°C, which leads to over-lithiation at the positive electrode of the electrochemical device.

[0047] Table 1

[0048]

[0049]

[0050] In addition, silicon has poor cycle performance. During long-term use, silicon-based materials will undergo significant volume expansion. Large volume changes can easily cause active materials to fall off from the current collector, reducing electrical contact with the current collector, resulting in a decline in electrode cycle performance and affecting the cycle performance of silicon-based batteries throughout their entire life cycle.

[0051] Therefore, embodiments of this application provide an electrochemical device, a charging method for the electrochemical device, and an electronic device to at least partially solve the above-mentioned technical problems.

[0052] The specific implementation of the embodiments of this application will be further described below with reference to the accompanying drawings.

[0053] Reference Figures 1 to 3As shown in the embodiments of this application, an electrochemical device is provided. The negative electrode active material of the electrochemical device includes a first active material and a second active material. The theoretical specific capacity of the first active material is less than that of the second active material, and the upper limit of the discharge operating voltage of the first active material is higher than that of the second active material. In some embodiments, the first active material includes graphite, and the second active material includes silicon or a silicon-based material. The upper limit of the operating voltage of graphite is 4.3V or higher. The upper limit of the operating voltage of silicon is generally 3.5V.

[0054] At the first ambient temperature T1, the charging capacity of the electrochemical device in a single charge-discharge process during the first cycle is Q. 11 It has a discharge cutoff voltage V 11 Or discharge cutoff current I 11 ;

[0055] The charging capacity of the electrochemical device in a single charge-discharge process during the second cycle is Q. 12 It has a discharge cutoff voltage V 12 Or discharge cutoff current I 12 Among them, at least one of conditions a) to c) is satisfied:

[0056] Q 12 ≤Q 11 ;

[0057] V 12 >V 11 ;

[0058] I 12 >I 11 ;

[0059] At the second ambient temperature T2, where T2 > T1, the charging capacity of the electrochemical device in a single charge-discharge process during the first cycle is Q. 21 , satisfy, Q 21 With Q 11 The difference is no greater than 20%; the electrochemical device has a discharge cutoff voltage V in the first cycle interval. 21 Or discharge cutoff current I 21 ;

[0060] The charging capacity of the electrochemical device in a single charge-discharge process during the second cycle is Q. 22 It has a discharge cutoff voltage V 22 Or discharge cutoff current I 22 Among them, at least one of conditions d) to f) is satisfied:

[0061] Q 22 ≤Q 21 ;

[0062] V22 >V 21 ;

[0063] I 22 >I 21 .

[0064] In this embodiment, the upper limit of the discharge operating voltage of the first active material is higher than the upper limit of the discharge operating voltage of the second active material, so that the first active material discharges before the second active material during the discharge of the electrochemical device. In one embodiment of this application, the first active material may be graphite, and the second active material may be elemental silicon, silicon oxide, silicon-carbon composite, or silicon alloy, or other negative electrode materials whose discharge operating voltage (also called voltage plateau) is lower than the discharge operating voltage of the first active material and whose temperature coefficient is lower than 0.98. For example, in one implementation, the second active material may include a transition metal oxide. For ease of description, silicon (Si) is used as an example to describe the embodiments of this application in detail below. It should be understood that the embodiments of this application are also applicable to electrochemical devices having other second active materials as described above.

[0065] At the first ambient temperature T1, the charging capacity of the electrochemical device in a single charge-discharge process during the first cycle is Q. 11 This can be understood as follows: During a single charge-discharge process in the first cycle interval, the full charge capacity of the electrochemical device at the first ambient temperature T1 is Q. 11 The full-charge capacity describes the capacity of an electrochemical device when it is charged to the charging limit voltage and the charging cutoff current.

[0066] Similarly, at the second ambient temperature T2, where T2 > T1, the charging capacity of the electrochemical device in a single charge-discharge process during the first cycle is Q. 21 This can be understood as follows: During a single charge-discharge process in the first cycle interval, the full-charge capacity of the electrochemical device at the second ambient temperature T2 is Q. 21 .

[0067] Due to Q 21 With Q 11 The difference is no more than 20%, that is, in the first cycle interval, the full charge capacity of the electrochemical device charged at the higher second ambient temperature T2 is basically the same as that charged at the first ambient temperature T1. This effectively reduces the over-lithiation of the positive electrode of the electrochemical device in the first cycle interval at a higher temperature, reduces the deterioration of the positive electrode voltage of the electrochemical device on the high voltage cycle, and improves the high temperature cycle performance of the electrochemical device.

[0068] Furthermore, in one embodiment of this application, similar to the case of the first cyclic interval, Q 22 With Q 12The difference is no more than 20%, that is, in the second cycle interval, the full charge capacity of the electrochemical device charged at the higher second ambient temperature T2 is basically the same as that charged at the first ambient temperature T1, thereby further effectively reducing the over-lithiation of the positive electrode of the electrochemical device in the second cycle interval at a higher temperature.

[0069] In one implementation of this application, T1 < 35℃, and 35℃ ≤ T2 ≤ 60℃. Therefore, a charging process with an ambient temperature less than 35℃ can be understood as a room temperature charging process, and a process with an ambient temperature greater than or equal to 35℃ and less than or equal to 60℃ can be understood as a high temperature charging process.

[0070] Q 21 With Q 11 The difference is no greater than 20% and / or Q 22 With Q 12 The difference is no more than 20%, which can be understood as the electrochemical device maintaining a basically consistent charging capacity during both room temperature and high temperature charging processes. That is, in the embodiments of this application, the capacity of the electrochemical device charged at high temperature is consistent with that charged at room temperature, so as to effectively reduce the positive electrode over-lithiation in the electrochemical device under high temperature environment, reduce the deterioration of the positive electrode voltage of the electrochemical device on high voltage cycling, and improve the high temperature cycling performance of the electrochemical device.

[0071] In this embodiment, the charging capacity of the electrochemical device can be made substantially consistent across different ambient temperatures by controlling the charging to a target charging cutoff voltage or target charging cutoff current corresponding to each ambient temperature. Specifically, the charging capacity of the electrochemical device at room temperature can be substantially consistent. The target charging cutoff voltage can be equal to or greater than the charging limit voltage of the electrochemical device, or it can be less than the charging limit voltage of the electrochemical device. Adjusting the target charging cutoff voltage involves issues related to the execution of the entire electronic device using the electrochemical device. For example, it requires adjusting the charger power, which is relatively complex. In contrast, adjusting the target charging cutoff current only requires monitoring the temperature of the electrochemical device and can be achieved using a combination of hardware and software control, which is simpler.

[0072] For example, in one implementation of this application, an electrochemical device is connected to a processor, which is configured to: acquire the current temperature of the electrochemical device; determine the target charging cut-off current of the electrochemical device based on the current temperature and a pre-established first mapping relationship between temperature and charging cut-off current, wherein the first mapping relationship includes N temperatures and corresponding N charging cut-off currents, and the N charging cut-off currents increase with the increase of the N temperatures, where N is an integer greater than or equal to 2; and control the electrochemical device to charge until the target charging cut-off current is reached.

[0073] Specifically, the target charging cut-off current of the electrochemical device is determined based on the current temperature and a pre-established first mapping relationship between temperature and charging cut-off current, including: determining the temperature closest to the current temperature in the first mapping relationship as the target temperature, and determining the charging cut-off current corresponding to the target temperature as the target charging cut-off current.

[0074] In the above manner, the electrochemical device can be charged to the charging cutoff current corresponding to the first ambient temperature T1, so that the charging capacity of the electrochemical device in a single charge-discharge process in the first cycle interval is Q. 11 Furthermore, at the second ambient temperature T2, the electrochemical device is charged to the charging cutoff current corresponding to the second ambient temperature T2, so that the charging capacity of the electrochemical device in a single charge-discharge process in the first cycle interval is Q. 21 This method achieves a consistent charging capacity of the electrochemical device at various ambient temperatures in a simple manner, thereby effectively reducing the over-lithiation of the positive electrode in the electrochemical device at high temperatures, reducing the deterioration of the positive electrode voltage on high-voltage cycling, and improving the high-temperature cycling performance of the electrochemical device.

[0075] In one implementation of this application, a single charge-discharge process of the electrochemical device includes: charging the electrochemical device to a first voltage at a constant current with a charging current, and charging the electrochemical device to a first current at a constant voltage with the first voltage; charging the electrochemical device to a second voltage at a constant current with the first current, and charging the electrochemical device to a second current at a constant voltage with the second voltage; and charging the electrochemical device to a third voltage at a constant current with the second current, and charging the electrochemical device to a target charging cutoff current with the third voltage.

[0076] It should be noted that a cycle interval includes multiple charge-discharge cycles. In this application, the occurrence of a certain parameter (e.g., charging capacity, charging voltage, charging current, charging cut-off voltage, charging cut-off current, discharging cut-off voltage, discharging cut-off circuit, etc.) in a single charge-discharge cycle of a certain cycle interval is not intended to limit the parameter to be equal or the same value in every charge-discharge cycle within that cycle interval.

[0077] For example, within the first cycle interval at the first temperature, there may be multiple charge-discharge cycles. The charging capacity of the multiple charge-discharge cycles can be the same or different. As an example, the first cycle interval includes the i-th charge-discharge cycle and the (i+1)-th charge-discharge cycle, and the charging capacity of the i-th charge-discharge cycle is denoted as Q. 1i The charging capacity of the (i+1)th charge-discharge cycle is denoted as Q. 1(i+1) Q 1i Can be used with Q 1(i+1) Same. Or, Q 1iCan be used with Q 1(i+1) They are not the same, but the difference is within 20%. The difference between two objects is equal to the difference between the larger object and the smaller object, divided by the smaller object, and then multiplied by 100%. Similarly, within the two-cycle interval at the first temperature (or the one-cycle interval at the second temperature, and the two-cycle interval at the second temperature), multiple charge-discharge cycles can correspond to the same or different charging capacities.

[0078] Based on a single charge-discharge process of an electrochemical device, this implementation method allows for maintaining a relatively consistent charging capacity across different ambient temperatures by controlling the electrochemical device to charge to a target charging cutoff current corresponding to each ambient temperature. This approach is relatively simple to implement and can effectively improve the high-temperature cycling performance of the electrochemical device. For example... Figure 5 As shown, in a specific example, using the above charging equation, the target charging cutoff current is adjusted to limit the capacity at high temperatures, and the capacity retention rate increases by about 5% after 700 cycles.

[0079] Furthermore, in this embodiment of the application, at the first ambient temperature T1, the charging capacity of the electrochemical device in a single charge-discharge process during the first cycle interval is Q. 11 It has a discharge cutoff voltage V 11 Or discharge cutoff current I 11 The charging capacity of the electrochemical device in a single charge-discharge process during the second cycle is Q. 12 It has a discharge cutoff voltage V 12 Or discharge cutoff current I 12 Among them, at least one of conditions a) to c) is satisfied: Q 12 ≤Q 11 V 12 >V 11 ;I 12 >I 11 .

[0080] Furthermore, at the second ambient temperature T2, where T2 > T1, the charging capacity of the electrochemical device in a single charge-discharge process during the first cycle is Q. 21 , satisfy, Q 21 With Q 11 The difference is no greater than 20%; the electrochemical device has a discharge cutoff voltage V in the first cycle interval. 21 Or discharge cutoff current I 21 The charging capacity of the electrochemical device in a single charge-discharge process during the second cycle is Q. 22 It has a discharge cutoff voltage V 22 Or discharge cutoff current I 22 Among them, at least one of conditions d) to f) is satisfied: Q 22 ≤Q21 V 22 >V 21 ;I 22 >I 21 .

[0081] That is, regardless of the ambient temperature, different discharge cutoff voltages or discharge cutoff currents are used in different cycling ranges. As the number of cycles of the electrochemical device increases, the discharge cutoff voltage of the electrochemical device is gradually increased.

[0082] The cycling characteristics of electrochemical devices differ due to the use of different discharge cutoff voltages or discharge cutoff currents. For example... Figure 2 As shown, curves 310, 320, 330, and 340 represent the cycling curves of a silicon-based electrochemical device at discharge cutoff voltages of 3V, 3.2V, 3.3V, and 3.4V, respectively. For the silicon-based electrochemical device, the slopes of the cycling curves at discharge cutoff voltages of 3V, 3.2V, 3.3V, and 3.4V are all different. Higher cutoff voltages result in better cycling stability but lower initial capacity, while lower cutoff voltages result in poorer cycling stability but higher initial capacity. The cycling curves at different cutoff voltages will intersect at a specific number of cycles. It should be understood that this explanation uses a silicon-based electrochemical device as an example only; electrochemical devices with other secondary active materials exhibit similar characteristics, which will not be elaborated upon here.

[0083] Based on the above characteristics, this application embodiment uses different discharge cutoff voltages in different cycle intervals. As the number of cycles of the electrochemical device increases, the discharge cutoff voltage of the electrochemical device is gradually increased, thereby achieving optimal use of the electrochemical device throughout its entire life cycle and improving the cycle performance of the electrochemical device throughout its entire life cycle.

[0084] Specifically, in one implementation of this application, a processor that can be connected to the electrochemical device is further configured to: obtain the current charge-discharge cycle number of the electrochemical device; determine the target cycle interval of the electrochemical device based on the current charge-discharge cycle number; determine the target discharge cutoff voltage or target discharge cutoff current based on the target cycle interval and a pre-established second mapping relationship between the cycle interval and the discharge cutoff voltage or discharge cutoff current, wherein the second mapping relationship includes M sequential cycle intervals and corresponding M discharge cutoff voltages or discharge cutoff currents, and the cycle interval with a larger charge-discharge cycle number corresponds to a larger discharge cutoff voltage or discharge cutoff current, wherein M is greater than or equal to two integers; and control the discharge of the electrochemical device until the target discharge cutoff voltage or target discharge cutoff current is reached.

[0085] In one implementation of this application, the difference between the discharge cutoff voltages corresponding to two adjacent cycle intervals is greater than a first voltage amplitude, which is between 0.1V and 0.2V.

[0086] by Figure 2 Taking the silicon-based electrochemical device as an example, a 3.0V cycle is used when the cycle range of the electrochemical device is 1-200 cycles, a 3.2V cycle is used when the cycle range of the electrochemical device is 201-1000 cycles, and a 3.4V cycle is used when the cycle range of the electrochemical device is greater than 1000 cycles. In this way, the discharge cutoff voltage of the silicon-based electrochemical device is increased in stages, and the utilization of silicon is gradually reduced to achieve optimal use of the silicon-based electrochemical device, thereby improving the cycle performance of the silicon-based electrochemical device throughout its entire life cycle.

[0087] This application also provides a charging method for an electrochemical device, applicable to the electrochemical device provided in the aforementioned device embodiments. The negative electrode active material of the electrochemical device includes a first active material and a second active material. The theoretical specific capacity of the first active material is less than the theoretical specific capacity of the second active material, and the upper limit of the discharge operating voltage of the first active material is higher than the upper limit of the discharge operating voltage of the second active material. The method includes:

[0088] At the first ambient temperature T1, the charging capacity of the electrochemical device during a single charge-discharge process in the first cycle interval is Q. 11 It has a discharge cutoff voltage V 11 Or discharge cutoff current I 11 ;

[0089] The charging capacity of the electrochemical device during a single charge-discharge process in the second cycle interval is Q. 12 It has a discharge cutoff voltage V 12 Or discharge cutoff current I 12 Among them, at least one of conditions a) to c) is satisfied:

[0090] Q 12 ≤Q 11 ;

[0091] V 12 >V 11 ;

[0092] I 12 >I 11 ;

[0093] At the second ambient temperature T2, where T2 > T1, the charging capacity of the electrochemical device during a single charge-discharge process in the first cycle interval is Q. 21 , satisfy, Q 21 With Q 11 The difference is no greater than 20%; the electrochemical device has a discharge cutoff voltage V in the first cycle interval. 21 Or discharge cutoff current I 21 ;

[0094] The charging capacity of the electrochemical device during a single charge-discharge process in the second cycle interval is Q. 22 It has a discharge cutoff voltage V 22 Or discharge cutoff current I 22 Among them, at least one of conditions d) to f) is satisfied:

[0095] Q 22 ≤Q 21 ;

[0096] V 22 >V 21 ;

[0097] I 22 >I 21 .

[0098] like Figure 4 As shown, in one embodiment of this application, the charging method includes:

[0099] Step S401: Obtain the current temperature and current charge / discharge cycle number of the electrochemical device;

[0100] Step S402: Determine the target charging cut-off current of the electrochemical device based on the current temperature and the pre-established first mapping relationship between temperature and charging cut-off current, and determine the target discharge cut-off voltage or target discharge cut-off current based on the target cycle interval and the pre-established second mapping relationship between cycle interval and discharge cut-off voltage or discharge cut-off current. The first mapping relationship includes N temperatures and corresponding N charging cut-off currents, and the N charging cut-off currents increase with the increase of the N temperatures. The second mapping relationship includes M sequential cycle intervals and corresponding M discharge cut-off voltages or discharge cut-off currents, and the cycle interval with a larger number of charge and discharge cycles corresponds to a larger discharge cut-off voltage or discharge cut-off current. N and M are integers, and N≥2 and M≥2.

[0101] Step S403: Control the electrochemical device to charge in a charging mode until the target charging cutoff current is reached;

[0102] Step S404: Control the electrochemical device to discharge in a discharge mode until the target discharge cutoff voltage or target discharge cutoff current is reached.

[0103] In one implementation of this application, the charging method includes: charging the electrochemical device to a first voltage with a constant current using a charging current, and charging the electrochemical device to a first current with a constant voltage using the first voltage; charging the electrochemical device to a second voltage with a constant current using the first current, and charging the electrochemical device to a second current with a constant voltage using the second voltage; and charging the electrochemical device to a third voltage with a constant current using the second current, and charging the electrochemical device to a target charging cutoff current using the third voltage.

[0104] The charging method provided in this embodiment is applicable to the corresponding electrochemical devices in the foregoing embodiments and has the beneficial effects corresponding to the corresponding electrochemical devices, which will not be repeated here. Furthermore, the meaning and setting method of each parameter in this embodiment can be referred to the description of the corresponding part in the foregoing device embodiments, which will also not be repeated here.

[0105] To make the inventive objectives, technical solutions, and technical effects of this application clearer, the following detailed description is provided in conjunction with specific examples. The comparative examples and embodiments of this application employ electrochemical devices with a silicon content of 3%, a voltage of 4.48V, and a 3C system. It should be noted that the comparative examples and embodiments of this application may also employ electrochemical devices with other chemical systems, and this application is not limited thereto.

[0106] All comparative examples and embodiments of this application employ the following charging process: charging the electrochemical device to 4.25V using a constant current of 3C, charging the electrochemical device to 1.8C using a constant voltage of 4.25V, charging the electrochemical device to 4.35V using a constant current of 1.8C, charging the electrochemical device to 1.5C using a constant voltage of 4.35V, charging the electrochemical device to 4.53V using a constant current of 1.5C, and charging the electrochemical device to the cutoff current A using a constant voltage of 4.53V. All comparative examples and embodiments of this application employ a constant current of 0.5C for discharging. Here, C represents the charging rate, another measure of charging speed, referring to the current value required for the electrochemical device to charge to its rated capacity within a specified time, i.e., charging rate = charging current / rated capacity. It should be understood that the above charging process is merely an example, and any other suitable charging method can be applied to the embodiments of this application.

[0107] The following section compares the cycle performance of electrochemical devices using the charging methods of Comparative Examples 1-3 and those using the charging methods of the embodiments of this application.

[0108] Comparative Example 1

[0109] Test temperature: 45℃

[0110] The cutoff current A is 0.12C;

[0111] The discharge cutoff voltage for the entire life cycle is 3.0V.

[0112] Comparative Example 2

[0113] The cutoff current A is 0.25C;

[0114] The discharge cutoff voltage for the entire life cycle is 3.0V.

[0115] Comparative Example 3

[0116] The cutoff current A is 0.12C;

[0117] The discharge cutoff voltage is increased in stages throughout the entire life cycle. Specifically, the discharge cutoff voltage is 3.0V for the 1-500 cycle range, 3.2V for the 500-1000 cycle range, and 3.4V for the greater than 1000 cycle range.

[0118] Example

[0119] The cutoff current A is 0.25C;

[0120] The discharge cutoff voltage is increased in stages throughout the entire life cycle. Specifically, the discharge cutoff voltage is 3.0V for the 1-500 cycle range, 3.2V for the 500-1000 cycle range, and 3.4V for the greater than 1000 cycle range.

[0121] Table 2 records the test cycle performance of the electrochemical devices of each comparative example and embodiment of this application, including: capacity retention rate after 1200 cycles at 25°C, expansion rate after 1200 cycles at 25°C, capacity retention rate after 600 cycles at 45°C, and expansion rate after 600 cycles at 45°C.

[0122]

[0123] As can be seen from Table 2, the embodiments of this application can not only solve the problem of poor cycling trend of electrochemical devices at high temperature of 45°C, but also further improve the cycling performance and expansion rate of electrochemical devices at room temperature of 25°C by combining multiple stages to increase the discharge cutoff voltage, thereby improving the cycling performance of electrochemical devices throughout their entire life cycle.

[0124] Figure 5 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Figure 5 As shown, the electronic device 50 includes, but is not limited to, at least one processor 510 and an electrochemical device 520, and the above components can be connected via a bus or directly.

[0125] The electrochemical device 520 is the electrochemical device in the above-described device embodiments. The processor 510 can charge the electrochemical device 520 according to the charging method of the electrochemical device in the above-described method embodiments. Its technical principles and effects can be referred to the foregoing embodiments, and will not be repeated here.

[0126] It should be noted that, Figure 5The electronic device is merely an example; in other embodiments, it may include more or fewer elements, or may have different element configurations. The electronic device can be any suitable rechargeable device or component, such as a watch, mobile phone, tablet, personal digital assistant, Wireless Fidelity (WiFi) unit, Bluetooth unit, speaker, etc.

[0127] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention filed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not claimed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0128] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

[0129] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

[0130] It should be understood that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for the method embodiments, since they are basically similar to the methods described in the apparatus and system embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions of other embodiments.

[0131] It should be understood that the foregoing describes specific embodiments of this specification. Other embodiments are within the scope of the claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0132] It should be understood that the use of a singular form to describe an element or to show only one element in the accompanying drawings does not imply that the number of such element is limited to one. Furthermore, modules or elements described or shown as separate herein may be combined into a single module or element, and modules or elements described or shown as single herein may be broken down into multiple modules or elements.

[0133] It should also be understood that the terminology and expressions used herein are for descriptive purposes only, and one or more embodiments described herein should not be limited to these terms and expressions. The use of these terms and expressions does not exclude any illustrative and descriptive equivalent features (or parts thereof), and it should be recognized that various modifications that may exist should also be included within the scope of the claims. Other modifications, variations, and substitutions may also exist. Accordingly, the claims should be considered to cover all such equivalents.

Claims

1. An electrochemical device, characterized in that, The negative electrode active material of the electrochemical device includes a first active material and a second active material. The theoretical specific capacity of the first active material is less than that of the second active material, and the upper limit of the discharge operating voltage of the first active material is higher than that of the second active material. At the first ambient temperature T1 The charging capacity of the electrochemical device in a single charge-discharge process during the first cycle is Q. 11 It has a discharge cutoff voltage V 11 ; The charging capacity of the electrochemical device in a single charge-discharge process in the second cycle interval is Q. 12 It has a discharge cutoff voltage V 12 At least one of conditions a) to b) is satisfied: a)Q 12 ≤Q 11 ; b)V 12 >V 11 ; At the second ambient temperature T2, T2 > T1. The charging capacity of the electrochemical device in a single charge-discharge process within the first cycle interval is Q. 21 Q 21 With Q 11 The difference is no greater than 20%; The electrochemical device has a discharge cutoff voltage V in the first cycle interval. 21 ; The charging capacity of the electrochemical device in a single charge-discharge process in the second cycle interval is Q. 22 It has a discharge cutoff voltage V 22 At least one of conditions d) to e) is satisfied: d)Q 22 ≤Q 21 ; e) V 22 >V 21 。 2. The electrochemical device as described in claim 1, characterized in that, The temperature coefficient of the second active material is less than 0.

98.

3. The electrochemical device as described in claim 1, characterized in that, A single charge-discharge process of the electrochemical device includes: The electrochemical device is charged to a first voltage at a constant current, and then charged to a first current at a constant voltage using the first voltage. The electrochemical device is charged at a constant current to a second voltage using the first current, and then charged at a constant voltage to a second current using the second voltage; and The electrochemical device is charged at a constant current to a third voltage using the second current, and then charged at a constant voltage to a target charging cutoff current using the third voltage.

4. The electrochemical device as described in claim 1, characterized in that, T1<35℃, 35℃≤T2≤60℃.

5. The electrochemical device as described in claim 1, characterized in that, Q 22 With Q 12 The difference is no greater than 20%.

6. The electrochemical device as claimed in claim 1, characterized in that, The electrochemical device is connected to a processor, which is configured to: Obtain the current temperature of the electrochemical device; Based on the current temperature and the pre-established first mapping relationship between temperature and charging cut-off current, the target charging cut-off current of the electrochemical device is determined. The first mapping relationship includes N temperatures and corresponding N charging cut-off currents, with higher temperatures corresponding to larger charging cut-off currents, and N being an integer greater than or equal to 2. The electrochemical device is controlled to charge to the target charging cutoff current.

7. The electrochemical device according to claim 6, characterized in that, The processor is specifically configured as follows: The temperature closest to the current temperature in the first mapping relationship is determined as the target temperature, and the charging cut-off current corresponding to the target temperature is determined as the target charging cut-off current.

8. The electrochemical device according to claim 6, characterized in that, The processor is also configured to: Obtain the current charge-discharge cycle number of the electrochemical device; The target cycle range of the electrochemical device is determined based on the current charge-discharge cycle number. The target discharge cutoff voltage is determined based on the target cycle interval and the pre-established second mapping relationship between the cycle interval and the discharge cutoff voltage. The second mapping relationship includes M sequential cycle intervals and M corresponding discharge cutoff voltages, and the cycle interval with a larger number of charge and discharge cycles corresponds to a larger discharge cutoff voltage, where M is a number greater than or equal to 2 integers. The discharge of the electrochemical device is controlled until the target discharge cutoff voltage is reached.

9. An electronic device, characterized in that, The electronic device includes the electrochemical device as described in claims 1-8.

10. A charging and discharging method for an electrochemical device, characterized in that, The negative electrode active material of the electrochemical device includes a first active material and a second active material. The theoretical specific capacity of the first active material is less than that of the second active material, and the upper limit of the discharge operating voltage of the first active material is higher than that of the second active material. The method includes: At the first ambient temperature T1 The charging capacity of the electrochemical device during a single charge-discharge process in the first cycle interval is controlled to be Q. 11 It has a discharge cutoff voltage V 11 ; The charging capacity of the electrochemical device during a single charge-discharge process in the second cycle interval is controlled to be Q. 12 It has a discharge cutoff voltage V 12 At least one of conditions a) to b) is satisfied: a)Q 12 ≤Q 11 ; b)V 12 >V 11 ; At the second ambient temperature T2, T2 > T1. The charging capacity of the electrochemical device during a single charge-discharge process in the first cycle interval is Q. 21 , satisfy, Q 21 With Q 11 The difference is no greater than 20%; The electrochemical device has a discharge cutoff voltage V in the first cycle interval. 21 ; The charging capacity of the electrochemical device during a single charge-discharge process in the second cycle interval is controlled to be Q. 22 It has a discharge cutoff voltage V 22 Among them, at least one of conditions d) to e) is satisfied: d)Q 22 ≤Q 21 ; e) V 22 >V 21 。

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