Electrochemical device, control method thereof, electronic device, and storage medium

Abstract

Embodiments of the present application provide an electrochemical device, a control method thereof, an electronic device and a storage medium. The negative active material of the electrochemical device includes a first active material and a second active material. The specific capacity of the first active material is less than that of the second active material. The discharge working voltage range of the first active material includes a first voltage range which is not greater than the upper limit of the discharge working voltage of the second active material. The electrochemical device operates at a first discharge cut-off voltage and a first charge cut-off voltage in a first time period. The electrochemical device operates at a second discharge cut-off voltage and a second charge cut-off voltage in a second time period. The first discharge cut-off voltage and the second discharge cut-off voltage are both located in the first voltage range. The first discharge cut-off voltage is less than the second discharge cut-off voltage, and / or the first charge cut-off voltage is greater than the second charge cut-off voltage. The present scheme can improve the volume energy density of the electrochemical device while prolonging the service life of the electrochemical device.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to an electrochemical device and its control method, electronic device and storage medium. Background Technology

[0002] With the widespread use of electronic products such as laptops, mobile phones, tablets, power banks, and drones, the requirements for their electrochemical devices are becoming increasingly stringent. These devices not only need to be lightweight but also possess high volumetric energy density and long lifespan. Lithium-ion batteries and sodium-ion batteries are commonly used electrochemical devices in electronic products. Silicon, with its high reversible capacity, is considered a potential anode material for rechargeable batteries to further improve their volumetric energy density. However, silicon anode materials undergo significant volume expansion during cycling, which negatively impacts the lifespan of the rechargeable battery. Summary of the Invention

[0003] In view of this, embodiments of this application provide an electrochemical device and its control method, electronic device and storage medium, which can improve the volumetric energy density of the electrochemical device while enabling the electrochemical device to have a longer service life.

[0004] 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 specific capacity of the first active material is less than that of the second active material. The discharge operating voltage range of the first active material includes a first voltage range not greater than the upper limit of the discharge operating voltage of the second active material. The electrochemical device operates at a first discharge cutoff voltage and a first charge cutoff voltage during a first time period. The electrochemical device operates at a second discharge cutoff voltage and a second charge cutoff voltage during a second time period. Both the first discharge cutoff voltage and the second discharge cutoff voltage are located within the first voltage range. The first discharge cutoff voltage is less than the second discharge cutoff voltage, and / or the first charge cutoff voltage is greater than the second charge cutoff voltage.

[0005] The electrochemical device operates at a first discharge cutoff voltage and a first charge cutoff voltage in a first time period, and at a second discharge cutoff voltage and a second charge cutoff voltage in a second time period. Both the first discharge cutoff voltage and the second discharge cutoff voltage are within a first voltage range. When the discharge cutoff voltage is within the first voltage range, a greater amount of the first active material and a greater amount of the second active material participate in the discharge in the negative electrode active material. By adjusting the discharge cutoff voltage and the charge cutoff voltage of the electrochemical device, the first discharge cutoff voltage is made less than the second discharge cutoff voltage, and / or the first charge cutoff voltage is made greater than the second charge cutoff voltage. By adjusting the capacity contributed by the second active material, the capacity contributed by the second active material is made to correspond to the health status of the electrochemical device, thereby extending the service life of the electrochemical device. Therefore, it is possible to increase the volumetric energy density of the electrochemical device and enable it to have a longer service life.

[0006] In one possible implementation, the discharge operating voltage range of the first active material includes a second voltage range greater than the upper limit of the discharge operating voltage of the second active material, and the electrochemical device operates at a third discharge cutoff voltage and a third charge cutoff voltage during a third time period; wherein the third discharge cutoff voltage is located within the second voltage range, and / or the second charge cutoff voltage is greater than the third charge cutoff voltage.

[0007] Within the second voltage range, when the discharge cutoff voltage is within the second voltage range, a large amount of the first active material in the negative electrode active material participates in the discharge, while little or no second active material participates in the discharge. By adjusting the discharge cutoff voltage and charging cutoff voltage of the electrochemical device, so that the third discharge cutoff voltage is within the second voltage range, and / or the second charging cutoff voltage is greater than the third charging cutoff voltage, the second active material can be prevented from participating in the discharge process of the electrochemical device, or only a small amount of the second active material can participate in the discharge process of the electrochemical device. Thus, after the second active material undergoes significant expansion, it can be prevented from participating in the discharge process of the electrochemical device, thereby inhibiting further expansion of the electrochemical device and extending its service life.

[0008] In one possible implementation, the electrochemical device performs at least one of the following operations during a fourth time period: (i) stopping charging and discharging; (ii) issuing information to indicate that charging and discharging operations on the electrochemical device should be stopped.

[0009] As the number of cycles of an electrochemical device increases, its battery life and safety performance decrease, impacting the user experience. Because the secondary active material expands during cycling, the device's volume also expands significantly with each cycle, increasing the risk of damage. To improve user experience and enhance safety, the electrochemical device should stop charging and discharging when its battery life and safety performance deteriorate to a certain level, or when its volume expands to a certain extent. Alternatively, it could issue a message indicating the cessation of charging and discharging operations to prompt the user to replace the device.

[0010] In one possible implementation, the first time period, the second time period, the third time period, and the fourth time period are arranged sequentially in chronological order throughout the life cycle of the electrochemical device.

[0011] The first, second, third, and fourth time periods are arranged chronologically within the lifecycle of the electrochemical device. The discharge cutoff voltage of the electrochemical device gradually increases according to the time sequence of each time period, while the charging cutoff voltage gradually decreases according to the time sequence of each time period. In the early stage of the electrochemical device cycle, the high specific capacity advantage of the second active material is fully utilized to improve the volumetric energy density of the electrochemical device. In the later stage of the electrochemical device cycle, the capacity contributed by the second active material is reduced, the expansion rate of the electrochemical device is slowed down, and the service life of the electrochemical device is extended. Finally, the charging and discharging operation of the electrochemical device is stopped or a prompt is made to stop the charging and discharging operation of the electrochemical device, thereby improving the user experience of the electrochemical device and ensuring the safety of the electronic equipment in which the electrochemical device is located.

[0012] In one possible implementation, the second active material comprises silicon, the first voltage range is no greater than 3.5V, and the second voltage range is greater than 3.5V.

[0013] When the second active material includes silicon, during the discharge process of the electrochemical device, when the discharge voltage is above 3.5V, the first active material mainly participates in the discharge process, with little or no participation from the second active material. However, when the discharge voltage is below 3.5V, both the first and second active materials participate in a larger quantity. The first and second voltage ranges are divided by 3.5V. In the first time period, the high specific capacity of the second active material can be fully utilized to improve the volumetric energy density of the electrochemical device. In the second time period, the expansion rate of the electrochemical device can be slowed down, extending its service life.

[0014] In one possible implementation, the electrochemical device operates within different ranges of its State of Health (SOH) parameter during different time periods.

[0015] When an electrochemical device operates at different times, its surface area (SOH) parameter falls within different ranges. Specifically, the first, second, third, and fourth time periods can be determined based on the SOH parameter. Since the SOH parameter characterizes the health status of the electrochemical device, determining the operating time periods based on the SOH parameter is equivalent to determining the operating time periods based on the device's health status. This allows the electrochemical device to operate at different discharge cutoff voltages and / or charge cutoff voltages within different time periods. This fully utilizes the high specific capacity of the second active material, increasing the volumetric capacity density of the electrochemical device while ensuring a long service life.

[0016] In one possible implementation, the SOH parameter includes at least one of the following: (i) the internal resistance of the electrochemical device; (ii) the reversible capacity of the electrochemical device; (iii) the thickness of the electrochemical device; and (iii) the pressure or stress between the electrochemical device and the housing for housing the electrochemical device.

[0017] During the cycling process of an electrochemical device, its internal resistance, reversible capacity, thickness, and pressure or stress between it and the casing can all reflect its health status. By using one or more of these parameters as SOH (State of Health) parameters, the SOH parameters can accurately reflect the health status of the electrochemical device. Furthermore, different time periods can be determined based on the SOH parameters. By adjusting the discharge cutoff voltage and charging cutoff voltage of the electrochemical device during different time periods, the high specific capacity performance of the second active material can be fully utilized, thereby extending the service life of the electrochemical device while improving its volumetric energy density.

[0018] In one possible implementation, the SOH parameter is the pressure between the electrochemical device and the housing; when the pressure between the electrochemical device and the housing is less than a first threshold, the electrochemical device operates in the first time period; when the pressure between the electrochemical device and the housing is greater than or equal to the first threshold and less than a second threshold, the electrochemical device operates in the second time period; when the pressure between the electrochemical device and the housing is greater than or equal to the second threshold and less than a third threshold, the electrochemical device operates in the third time period; when the pressure between the electrochemical device and the housing is greater than or equal to the third threshold, the electrochemical device operates in the fourth time period.

[0019] By continuously increasing the pressure between the electrochemical device and the casing, the life cycle of the electrochemical device can be divided into four time periods by successively increasing the first, second, and third thresholds. In the first three time periods, the electrochemical device operates with different discharge cutoff voltages and / or charge cutoff voltages. While increasing the volumetric capacity density of the electrochemical device, the expansion rate of the electrochemical device is slowed down, thus extending the service life of the electrochemical device. In the last time period, charging and discharging operations on the electrochemical device are stopped or a prompt is given to stop charging and discharging operations, thereby improving the user experience of the electrochemical device.

[0020] In one possible implementation, the first threshold is greater than or equal to 0.03 MPa, the second threshold is less than 0.5 MPa, the third threshold is greater than or equal to 0.5 MPa, and the second threshold is greater than the first threshold.

[0021] A first threshold is set to be greater than or equal to 0.03 MPa, a second threshold to be less than 0.5 MPa, and a third threshold to be greater than or equal to 0.5 MPa. The lifespan of the electrochemical device is divided into four time periods based on these thresholds. During the first three time periods, the electrochemical device operates with different discharge and / or charge cutoff voltages. This fully utilizes the energy density of the electrochemical device while slowing down the deterioration of its cycle state and extending its service life. During the last time period, charging and discharging operations on the electrochemical device are stopped, or the user is prompted to perform charging and discharging operations. This prevents the electrochemical device from undergoing excessive irreversible expansion that could cause crush damage to the casing.

[0022] In one possible implementation, the mass percentage of silicon in the negative electrode active material of the electrochemical device is in the range of (0%, 60%).

[0023] When silicon is used as the second active material, the volumetric energy density of the electrochemical device increases with the increase of silicon content in the negative electrode active material, but the cycle life of the electrochemical device decreases. To improve the volumetric energy density of the electrochemical device without excessively reducing its cycle life, the mass ratio of silicon in the negative electrode active material should be less than or equal to 60%. Furthermore, by controlling the electrochemical device to operate at different discharge cutoff voltages and / or charge cutoff voltages at different time periods, it is possible to ensure a longer cycle life of the electrochemical device while increasing its volumetric energy density.

[0024] In one possible implementation, the mass percentage of silicon in the negative electrode active material of the electrochemical device is in the range of [10%, 20%].

[0025] When silicon is used as the second active material, if the mass percentage of silicon in the negative electrode active material is in the range of [10%, 20%], the volumetric energy density of the electrochemical device can be improved based on the high specific capacity of silicon. Since the mass percentage of silicon is less than or equal to 20%, it will not have a significant impact on the cycle performance of the electrochemical device. By controlling the electrochemical device to operate at different discharge cutoff voltages and / or charge cutoff voltages at different time periods, the energy density of the electrochemical device can be fully utilized while ensuring that the electrochemical device has a long cycle life.

[0026] According to a second aspect of the present application, an electrochemical device control method is provided for controlling the charging and discharging process of the electrochemical device. The negative electrode active material of the electrochemical device includes a first active material and a second active material. The specific capacity of the first active material is less than that of the second active material. The discharge operating voltage range of the first active material includes a first voltage range not greater than the upper limit of the discharge operating voltage of the second active material. The electrochemical device control method includes: controlling the electrochemical device to operate at a first discharge cutoff voltage and a first charge cutoff voltage in a first time period, wherein the first discharge cutoff voltage is within the first voltage range; controlling the electrochemical device to operate at a second discharge cutoff voltage and a second charge cutoff voltage in a second time period, wherein the second discharge cutoff voltage is within the first voltage range; wherein the first discharge cutoff voltage is less than the second discharge cutoff voltage, and / or the first charge cutoff voltage is greater than the second charge cutoff voltage.

[0027] During a first time period, the electrochemical device is controlled to operate at a first discharge cutoff voltage and a first charge cutoff voltage. During a second time period, the electrochemical device is controlled to operate at a second discharge cutoff voltage and a second charge cutoff voltage. Both the first discharge cutoff voltage and the second discharge cutoff voltage are within a first voltage range. When the discharge cutoff voltage is within the first voltage range, a greater amount of first active material and a greater amount of second active material participate in the discharge in the negative electrode active material. By adjusting the discharge cutoff voltage and the charge cutoff voltage of the electrochemical device, the first discharge cutoff voltage is made less than the second discharge cutoff voltage, and / or the first charge cutoff voltage is made greater than the second charge cutoff voltage. This adjusts the capacity contributed by the second active material, making the capacity contributed by the second active material correspond to the health status of the electrochemical device, thus extending the service life of the electrochemical device. Therefore, it is possible to increase the volumetric energy density of the electrochemical device while enabling it to have a longer service life.

[0028] In one possible implementation, the discharge operating voltage range of the first active material includes a second voltage range greater than the upper limit of the discharge operating voltage of the second active material, and the electrochemical device control method further includes: controlling the electrochemical device to operate at a third discharge cutoff voltage and a third charge cutoff voltage during a third time period; wherein the third discharge cutoff voltage is located within the second voltage range, and / or the second charge cutoff voltage is greater than the third charge cutoff voltage.

[0029] In one possible implementation, the electrochemical device control method further includes controlling the electrochemical device to perform at least one of the following operations during a fourth time period: (i) stopping charging and discharging; (ii) issuing information to instruct the electrochemical device to stop charging and discharging operations.

[0030] In one possible implementation, the first time period, the second time period, the third time period, and the fourth time period are arranged sequentially in chronological order throughout the life cycle of the electrochemical device.

[0031] In one possible implementation, the electrochemical device control method further includes: determining the time period of the electrochemical device based on the range of values ​​of the SOH parameter of the electrochemical device.

[0032] In one possible implementation, the SOH parameter includes at least one of the following: (i) the internal resistance of the electrochemical device; (ii) the reversible capacity of the electrochemical device; (iii) the thickness of the electrochemical device; and (iii) the pressure or stress between the electrochemical device and the housing for housing the electrochemical device.

[0033] In one possible implementation, the mass percentage of silicon in the negative electrode active material of the electrochemical device is in the range of (0%, 60%).

[0034] In one possible implementation, the mass percentage of silicon in the negative electrode active material of the electrochemical device is in the range of [10%, 20%].

[0035] According to a third aspect of the embodiments of this application, an electrochemical device management system is provided, the electrochemical device management system being connected to an electrochemical device, the electrochemical device management system being used to execute the electrochemical device control method provided in the second aspect or any possible implementation thereof.

[0036] According to a fourth aspect of the embodiments of this application, an electronic device is provided, including the electrochemical device provided in the first aspect or any possible implementation thereof, or including the electrochemical device management system provided in the third aspect.

[0037] According to a fifth aspect of the embodiments of this application, a computer-readable storage medium is provided, on which a computer program is stored, which, when executed by a processor, implements the electrochemical device control method provided as described in the second aspect or any possible implementation thereof.

[0038] As can be seen from the above technical solution, the electrochemical device operates at a first discharge cutoff voltage and a first charge cutoff voltage in the first time period, and at a second discharge cutoff voltage and a second charge cutoff voltage in the second time period. Both the first discharge cutoff voltage and the second discharge cutoff voltage are within the first voltage range. When the discharge cutoff voltage is within the first voltage range, more of the first active material and more of the second active material participate in the discharge in the negative electrode active material. By adjusting the discharge cutoff voltage and the charge cutoff voltage of the electrochemical device, the first discharge cutoff voltage is made to be less than the second discharge cutoff voltage, and / or the first charge cutoff voltage is made to be greater than the second charge cutoff voltage. By adjusting the capacity contributed by the second active material, the capacity contributed by the second active material is made to correspond to the health status of the electrochemical device, thereby extending the service life of the electrochemical device. Therefore, it is possible to improve the volumetric energy density of the electrochemical device while enabling it to have a longer service life. Attached Figure Description

[0039] 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.

[0040] Figure 1 This is a schematic diagram of the electrochemical device for detecting shell pressure according to an embodiment of this application;

[0041] Figure 2 This is a schematic diagram of the expansion of an electrochemical device and the change in pressure on the casing as a function of the number of cycles, according to one embodiment of this application.

[0042] Figure 3 This is a flowchart of an electrochemical device control method according to an embodiment of this application. Detailed Implementation

[0043] 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.

[0044] In the following description, the control method, electronic equipment and storage medium of the electrochemical device in the embodiments of this application will be specifically described first. Then, some relevant experimental examples and comparative examples of the electrochemical device and its control method in the embodiments of this application will be given to illustrate the significant advantages of the electrochemical device and its control method, electronic equipment and storage medium in the embodiments of this application compared with the prior art.

[0045] The specific advantages of the embodiments of this application will be described below with reference to the accompanying drawings.

[0046] It should be noted that, in the content of the embodiments of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion batteries.

[0047] Electrochemical device

[0048] Electrochemical devices provide power to electronic products such as laptops, mobile phones, tablets, power banks, and drones. Lithium-ion batteries and sodium-ion batteries both use graphite anode systems. As requirements for reducing the weight, size, and battery life of electronic devices cannot be significantly increased, there is a need to improve the volumetric energy density of electrochemical devices. Materials with large specific capacity, such as silicon and phosphorus, also have high reversible capacity. Therefore, using silicon and phosphorus as anode materials in electrochemical devices can further improve the volumetric energy density. However, large-specific-capacity anode materials undergo significant expansion during cycling, affecting the lifespan of the electrochemical device. Therefore, a technical solution is needed that can improve the volumetric energy density of electrochemical devices while ensuring a long service life.

[0049] Embodiments of the present application provide an electrochemical device, wherein a negative electrode active material of the electrochemical device comprises a first active material and a second active material, the specific capacity of the first active material is less than that of the second active material, and a discharge working voltage range of the first active material comprises a first voltage range not greater than an upper limit of a discharge working voltage of the second active material. The electrochemical device operates at a first discharge cut-off voltage and a first charge cut-off voltage in a first time period, and operates at a second discharge cut-off voltage and a second charge cut-off voltage in a second time period, and both the first discharge cut-off voltage and the second discharge cut-off voltage are located in the first voltage range. Wherein, the first discharge cut-off voltage is less than the second cut-off voltage, and / or the first charge cut-off voltage is greater than the second charge cut-off voltage.

[0050] Specific capacity refers to the ratio of the electric capacity that can be released by the active material inside the battery to the mass of the active material, and the unit of specific capacity is milliampere-hour per gram (mA·h / g). The specific capacity of the first active material is less than that of the second active material. When the first active material and the second active material of the same mass are used as the negative electrode active material of the battery, the amount of electricity that can be released by the first active material is less than that can be released by the second active material.

[0051] The first active material may be graphite, mesocarbon microbeads (MCMB) or Li₄Ti₅O 12 and the like, and the second active material may be SiO x (0<x<2), micron silicon, silicon nanowires, SiC, transition metal oxides (such as MnO, SnO₂, CoO, etc.) or phosphorus, etc. The above first active material and second active material can be freely combined, and the negative electrode active material of the electrochemical device may include a plurality of first active materials and / or a plurality of second active materials.

[0052] The second active material has a discharge working voltage range, within which both the first active material and the second active material contribute a relatively large capacity. Above the upper limit of the discharge working voltage range of the second active material, capacity is mainly contributed by the first active material, and a small amount of capacity is also contributed by the second active material, for example, the capacity contributed by the first active material is greater than 80%. Below the upper limit of the discharge working voltage range of the second active material, capacity is mainly contributed by the second active material, and a small amount of capacity is also contributed by the first active material, for example, the capacity contributed by the second active material is greater than 80%.

[0053] The operating voltage range of the first active material includes a first voltage range that is no greater than the upper limit of the discharge operating voltage of the second active material. The upper limit of the discharge operating voltage of the second active material refers to the upper limit of its discharge operating voltage range. For example, if the discharge operating voltage range of the second active material is [2.3V, 3.5V] and its upper limit is 3.5V, then the first voltage range is [2.3V, 3.5V]. The first voltage range is no greater than the upper limit of the discharge operating voltage of the second active material, meaning that any voltage value within the first voltage range is less than or equal to the upper limit of the discharge operating voltage of the second active material. Within the first voltage range, both the first and second active materials contribute a significant amount of capacity. That is, when the discharge voltage of the electrochemical device is within the first voltage range, a greater amount of the first active material and a greater amount of the second active material participate in the discharge process of the electrochemical device. The first voltage range can be the same as the discharge operating voltage range of the second active material.

[0054] The first and second time periods can be the first and second cycle stages within the entire lifespan of the electrochemical device. That is, the first and second time periods correspond to different charge-discharge cycles of the electrochemical device. For example, the first time period might be from the 300th to the 450th charge-discharge cycle, and the second time period might be from the 451st to the 600th charge-discharge cycle. The first and second time periods can include one or more charge-discharge cycles of the electrochemical device, and the number of charge-discharge cycles included in the first and second time periods can be the same or different.

[0055] In this embodiment, the electrochemical device operates at a first discharge cutoff voltage and a first charge cutoff voltage during a first time period, and at a second discharge cutoff voltage and a second charge cutoff voltage during a second time period. Both the first discharge cutoff voltage and the second discharge cutoff voltage are within a first voltage range. When the discharge cutoff voltage is within the first voltage range, a greater amount of first active material and a greater amount of second active material participate in the discharge in the negative electrode active material. By adjusting the discharge cutoff voltage and the charge cutoff voltage of the electrochemical device, the first discharge cutoff voltage is made less than the second discharge cutoff voltage, and / or the first charge cutoff voltage is made greater than the second charge cutoff voltage. By adjusting the capacity contributed by the second active material, the capacity contributed by the second active material corresponds to the health status of the electrochemical device, thereby extending the service life of the electrochemical device. Therefore, it is possible to improve the volumetric energy density of the electrochemical device while enabling it to have a longer service life.

[0056] In one possible implementation, the discharge operating voltage range of the first active material includes a second voltage range greater than the upper limit of the discharge operating voltage of the second active material, and the electrochemical device operates at a third discharge cutoff voltage and a third charge cutoff voltage during a third time period. The third discharge cutoff voltage is located within the second voltage range, and / or the second charge cutoff voltage is greater than the third charge cutoff voltage.

[0057] The discharge operating voltage range of the first active material includes not only the first voltage range but also a second voltage range greater than the upper limit of the discharge operating voltage of the second active material. For example, the discharge operating voltage range of the second active material is [2.3V, 3.5V], the upper limit of the discharge operating voltage of the second active material is 3.5V, and the second voltage range is (3.5V, 4.5V). The second voltage range is greater than the upper limit of the discharge operating voltage of the second active material, meaning that any voltage value within the second voltage range is greater than the upper limit of the discharge operating voltage of the second active material. Because the second voltage range is greater than the upper limit of the discharge operating voltage of the second active material, within the second voltage range, the capacity is mainly contributed by the first active material, while the second active material contributes little or no capacity. For example, the capacity contributed by the first active material is greater than 80%. That is, when the discharge voltage of the electrochemical device is within the second voltage range, more of the first active material participates in the discharge process of the electrochemical device, while less or no second active material participates in the discharge process of the electrochemical device.

[0058] Since the first discharge cutoff voltage and the second discharge cutoff voltage are within the first voltage range, and the third discharge cutoff voltage is within the second voltage range, the first voltage range is not greater than the upper limit of the discharge working voltage of the second active material, and the second voltage range is greater than the upper limit of the discharge working voltage of the second active material, therefore the third discharge cutoff voltage is greater than the first discharge cutoff voltage and the second discharge cutoff voltage.

[0059] In this embodiment, the electrochemical device operates at a third discharge cutoff voltage and a third charge cutoff voltage during a third time period. The third discharge cutoff voltage is within the second voltage range. When the discharge cutoff voltage is within the second voltage range, a large amount of the first active material in the negative electrode active material participates in the discharge, while little or no second active material participates in the discharge. By adjusting the discharge cutoff voltage and charge cutoff voltage of the electrochemical device, the third discharge cutoff voltage is made to be within the second voltage range, and / or the second charge cutoff voltage is greater than the third charge cutoff voltage. This can prevent the second active material from participating in the discharge process of the electrochemical device, or allow only a small amount of the second active material to participate in the discharge process of the electrochemical device. As a result, after the second active material undergoes significant expansion, it is prevented from participating in the discharge process of the electrochemical device, thereby inhibiting further expansion of the electrochemical device and extending its service life.

[0060] In one possible implementation, the electrochemical device can perform at least one of the following operations in the fourth time period:

[0061] (i) Stop charging and discharging;

[0062] (ii) Issue a message to instruct the cessation of charging and discharging operations on the electrochemical device.

[0063] In this embodiment, as the number of cycles of the electrochemical device increases, its battery life and safety performance decrease, affecting the user experience. Because the second active material expands during cycling, the volume of the electrochemical device expands significantly with increasing cycle count, increasing the risk of damage to the electronic device. Stopping charging and discharging the electrochemical device when its battery life and safety performance decline to a certain level, or when its volume expands to a certain extent, or issuing a message indicating the cessation of charging and discharging operations to prompt the user to replace the device, can improve the user experience and enhance the safety of the electrochemical device during use.

[0064] In one possible implementation, the first time period, the second time period, the third time period, and the fourth time period are arranged sequentially in time throughout the life cycle of the electrochemical device.

[0065] During the first and second time periods, both the first and second active materials participate in the discharge process of the electrochemical device. The high specific capacity of the second active material is fully utilized. As the number of cycles increases, the second active material gradually expands. Increasing the discharge cutoff voltage reduces the participation of the second active material during discharge, thus slowing the expansion rate of the electrochemical device. In the third time period, the first active material primarily participates in the discharge process. Since the expansion of the second active material during cycling is greater than that of the first active material, further increasing the discharge cutoff voltage after significant expansion of the electrochemical device can prevent the second active material from participating in the discharge process, further reducing the expansion rate and extending the device's lifespan. In the fourth time period, the expansion of the electrochemical device affects the safety of the electronic equipment. Stopping the charging and discharging operation or prompting a message to stop the operation improves the user experience and ensures the safety of the electronic equipment containing the electrochemical device.

[0066] Corresponding to increasing the discharge cutoff voltage of the electrochemical device, decreasing the charging cutoff voltage of the electrochemical device can also reduce the participation of the second active material during the cycle of the electrochemical device, thereby reducing the expansion rate of the electrochemical device and extending its service life.

[0067] In this embodiment, the first time period, the second time period, the third time period, and the fourth time period are arranged sequentially in the life cycle of the electrochemical device. The discharge cutoff voltage of the electrochemical device gradually increases in the order of each time period, and the charging cutoff voltage of the electrochemical device gradually decreases in the order of each time period. In the early stage of the electrochemical device cycle, the high specific capacity advantage of the second active material is fully utilized to improve the volumetric energy density of the electrochemical device. In the later stage of the electrochemical device cycle, the capacity contributed by the second active material is reduced, the expansion rate of the electrochemical device is reduced, and the service life of the electrochemical device is extended. Finally, the charging and discharging operation of the electrochemical device is stopped or a prompt is made to stop the charging and discharging operation of the electrochemical device, thereby improving the user experience of the electrochemical device and ensuring the safety of the electronic equipment in which the electrochemical device is located.

[0068] In one possible implementation, the second active material comprises silicon, with a first voltage range of no more than 3.5V and a second voltage range of more than 3.5V.

[0069] In this embodiment, when the second active material includes silicon, during the discharge process of the electrochemical device, when the discharge voltage is above 3.5V, the first active material mainly participates in the discharge process, with little or no participation from the second active material. However, when the discharge voltage is below 3.5V, both the first and second active materials participate in the discharge process in larger quantities. The first and second voltage ranges are divided by 3.5V. In the first time period, the high specific capacity of the second active material can be fully utilized to improve the volumetric energy density of the electrochemical device. In the second time period, the expansion rate of the electrochemical device can be slowed down, extending its service life.

[0070] In one possible implementation, the State of Health (SOH) parameter of the electrochemical device falls within different ranges when the device operates at different times.

[0071] In this embodiment, the SOH parameter of the electrochemical device falls within different value ranges during different time periods of operation. Specifically, the first, second, third, and fourth time periods can be determined based on the SOH parameter. Since the SOH parameter characterizes the health status of the electrochemical device, determining the operating time periods based on the SOH parameter is equivalent to determining the operating time periods based on the health status of the electrochemical device. This allows the electrochemical device to operate at different discharge cutoff voltages and / or charge cutoff voltages during different time periods. This fully utilizes the high specific capacity of the second active material, improving the volumetric capacity density of the electrochemical device while ensuring a long service life.

[0072] In one possible implementation, the SOH parameter of the electrochemical device may include at least one of the following:

[0073] (i) The internal resistance of the electrochemical device;

[0074] (ii) The reversible capacity of the electrochemical device;

[0075] (iii) The thickness of the electrochemical device;

[0076] (iiii) The pressure or force between the electrochemical device and the housing used to house the electrochemical device.

[0077] In this embodiment, during the cycling process of the electrochemical device, the internal resistance, reversible capacity, thickness, and pressure or stress between the electrochemical device and the casing can all reflect the health status of the electrochemical device. By using one or more of these parameters as SOH parameters, the SOH parameters can accurately reflect the health status of the electrochemical device. Based on the SOH parameters, different time periods can be determined. By adjusting the discharge cutoff voltage and charging cutoff voltage of the electrochemical device in different time periods, the high specific capacity performance of the second active material can be fully utilized, thereby extending the service life of the electrochemical device while improving its volumetric energy density.

[0078] As the number of cycles in an electrochemical device increases, the volume of the negative electrode active material expands, leading to an increase in the thickness of the electrochemical device. Therefore, the thickness of the electrochemical device can be used as a surface-to-oxide (SOH) parameter reflecting its health status. When the electrochemical device is located inside the casing of an electronic device, such as a mobile phone, the expansion of the electrochemical device changes the pressure between it and the casing. Therefore, the pressure between the electrochemical device and the casing containing it can be used as an SOH parameter reflecting its health status.

[0079] Figure 1 This is a schematic diagram of the electrochemical device for detecting housing pressure according to an embodiment of this application. Figure 1 As shown, the electrochemical device 11 is disposed within the housing 12, and a pressure sensor 13 is disposed between the electrochemical device 11 and the lower side wall of the housing 12. As the number of cycles of the electrochemical device 11 increases, its volume expands. When the electrochemical device 11 expands to contact the upper side wall of the housing 12, further expansion increases the pressure exerted by the electrochemical device 11 on the housing 12. Therefore, the degree of expansion of the electrochemical device 11 can be determined based on the pressure value detected by the pressure sensor 13. Furthermore, after obtaining the pressure value detected by the pressure sensor 13, the electrochemical device management system divides it by the contact area between the pressure sensor 13 and the electrochemical device 11 to determine the pressure between the electrochemical device 11 and the housing 12.

[0080] In one possible implementation, when the SOH parameter represents the pressure between the electrochemical device and the casing, a first threshold, a second threshold, and a third threshold are set for this pressure. The first threshold is less than the second threshold, and the second threshold is less than the third threshold. When the pressure between the electrochemical device and the casing is less than the first threshold, the electrochemical device operates in a first time period. When the pressure between the electrochemical device and the casing is greater than or equal to the first threshold and less than the second threshold, the electrochemical device operates in a second time period. When the pressure between the electrochemical device and the casing is greater than or equal to the second threshold and less than the third threshold, the electrochemical device operates in a third time period. When the pressure between the electrochemical device and the casing is greater than or equal to the third pressure, the electrochemical device operates in a fourth time period.

[0081] Figure 2 This is a curve showing the expansion of an electrochemical device and the change in pressure on the casing as a function of the number of cycles, according to one embodiment of this application. Figure 2 As shown, curve 201 represents the percentage expansion of the electrochemical device as a function of the number of cycles, and curve 202 represents the pressure exerted by the electrochemical device on the casing as a function of the number of cycles. Curve 201 shows that as the number of cycles increases, the percentage expansion of the electrochemical device gradually increases, meaning the volume of the device gradually increases, and the health of the device continuously deteriorates. Curve 202 shows that as the number of cycles increases, the pressure exerted by the electrochemical device on the casing gradually increases. Figure 1It is evident that the expansion percentage of the electrochemical device is positively correlated with the pressure exerted by the device on the casing. The degree of expansion of the electrochemical device can reflect its health status. Therefore, based on the pressure exerted by the device on the casing, the life cycle of the electrochemical device can be divided into multiple time periods. The health status of the electrochemical device varies in different time periods. By adjusting the discharge cutoff voltage and charging cutoff voltage of the electrochemical device in different time periods, the lifespan of the electrochemical device can be guaranteed while increasing its volumetric capacity density.

[0082] In this embodiment, as the number of cycles of the electrochemical device increases, the health status of the electrochemical device deteriorates continuously, and the volume of the electrochemical device expands continuously, causing the pressure between the electrochemical device and the casing to increase continuously. Therefore, the life cycle of the electrochemical device can be divided into four time periods by sequentially increasing the first threshold, the second threshold, and the third threshold. In the first three time periods, the electrochemical device operates with different discharge cutoff voltages and / or charge cutoff voltages. While increasing the volumetric capacity density of the electrochemical device, the expansion rate of the electrochemical device is slowed down, and the service life of the electrochemical device is extended. In the last time period, the charging and discharging operation of the electrochemical device is stopped or a prompt is given to stop the charging and discharging operation of the electrochemical device, thereby improving the user experience of the electrochemical device.

[0083] In one possible implementation, a first threshold, a second threshold, and a third threshold are set for the pressure between the electrochemical device and the casing, wherein the first threshold is greater than or equal to 0.03 MPa, the second threshold is less than 0.5 MPa, and the third threshold is greater than or equal to 0.5 MPa.

[0084] A first threshold is set to be greater than or equal to 0.03 MPa and less than 0.5 MPa, allowing the electrochemical device to operate with a lower discharge cutoff voltage and / or a higher charge cutoff voltage when the cycling condition is good, thus fully utilizing the energy density of the electrochemical device. A second threshold is set to be greater than the first threshold and less than 0.5 MPa. When the cycling condition of the electrochemical device deteriorates to a certain extent, the discharge cutoff voltage of the electrochemical device is increased and / or the charge cutoff voltage is decreased to prevent the electrochemical device from undergoing significant irreversible expansion, which could severely degrade its cycle life. A third threshold is set to be greater than or equal to 0.5 MPa to ensure that the electrochemical device can charge and discharge when the cycling condition is good, fully utilizing its energy density. Furthermore, if the electrochemical device undergoes significant expansion, charging and discharging operations are stopped to prevent excessive irreversible expansion from causing crush damage to the casing.

[0085] In this embodiment, a first threshold is set to be greater than or equal to 0.03 MPa, a second threshold to be less than 0.5 MPa, and a third threshold to be greater than or equal to 0.5 MPa. The lifespan of the electrochemical device is divided into four time periods using these thresholds. During the first three time periods, the electrochemical device operates with different discharge cut-off voltages and / or charge cut-off voltages. This fully utilizes the energy density of the electrochemical device while slowing down the deterioration of its cycle state and extending its service life. In the last time period, charging and discharging operations on the electrochemical device are stopped, or the user is prompted to perform charging and discharging operations, which avoids damage to the casing caused by excessive irreversible expansion of the electrochemical device.

[0086] In one possible implementation, the mass percentage of silicon in the negative electrode active material of the electrochemical device is in the range of (0%, 60%), for example, the mass percentage of silicon in the negative electrode active material is 1%, 10%, 20%, 30% or 60%, etc.

[0087] In the embodiments of this application, when silicon is used as the second active material, the volumetric energy density of the electrochemical device increases with the increase of silicon content in the negative electrode active material, but the cycle life of the electrochemical device decreases. Therefore, the mass ratio of silicon in the negative electrode active material is less than or equal to 60%, which can improve the volumetric energy density of the electrochemical device without causing excessive decrease in the cycle life of the electrochemical device. Furthermore, by controlling the electrochemical device to operate at different discharge cutoff voltages and / or charge cutoff voltages in different time periods, it is possible to ensure that the electrochemical device has a long cycle life while improving the volumetric energy density of the electrochemical device.

[0088] In one possible implementation, the mass percentage of silicon in the negative electrode active material of the electrochemical device is in the range of [10%, 20%], for example, the mass percentage of silicon in the negative electrode active material is 1%, 10%, or 20%, etc.

[0089] In the embodiments of this application, when silicon is used as the second active material, and the mass percentage of silicon in the negative electrode active material is in the range of [10%, 20%], the volumetric energy density of the electrochemical device can be improved based on the high specific capacity of silicon. Since the mass percentage of silicon is less than or equal to 20%, it will not have a significant impact on the cycle performance of the electrochemical device. By controlling the electrochemical device to operate at different discharge cutoff voltages and / or charge cutoff voltages at different time periods, the energy density of the electrochemical device can be fully utilized while ensuring that the electrochemical device has a long cycle life.

[0090] Electrochemical device control methods

[0091] Figure 3This is a flowchart of an embodiment of an electrochemical device control method, used to control the charging and discharging process of the electrochemical device. The negative electrode active material of the electrochemical device includes a first active material and a second active material. The specific capacity of the first active material is smaller than that of the second active material. The discharge operating voltage range of the first active material includes a first voltage range that is not greater than the upper limit of the discharge operating voltage of the second active material. Figure 3 As shown, the control method for this electrochemical device includes the following steps:

[0092] Step 301: Control the electrochemical device to operate at a first discharge cutoff voltage and a first charge cutoff voltage during the first time period.

[0093] The electrochemical device's life cycle includes a first time period, during which the electrochemical device is controlled to operate at a first discharge cutoff voltage and a first charge cutoff voltage, wherein the first discharge cutoff voltage is within a first voltage range.

[0094] Step 302: Control the electrochemical device to operate at the second discharge cutoff voltage and the second charge cutoff voltage during the second time period.

[0095] The electrochemical device includes a second time period different from the first time period in its life cycle. The electrochemical device is controlled to operate at a second discharge cutoff voltage and a second charge cutoff voltage in the second time period, wherein the second discharge cutoff voltage is within a first voltage range, and the first discharge cutoff voltage is less than the second discharge cutoff voltage and / or the first charge cutoff voltage is greater than the second charge cutoff voltage.

[0096] In this embodiment, the electrochemical device is controlled to operate at a first discharge cutoff voltage and a first charge cutoff voltage during a first time period, and at a second discharge cutoff voltage and a second charge cutoff voltage during a second time period. Both the first discharge cutoff voltage and the second discharge cutoff voltage are within a first voltage range. When the discharge cutoff voltage is within the first voltage range, a greater amount of first active material and a greater amount of second active material participate in the discharge in the negative electrode active material. By adjusting the discharge cutoff voltage and the charge cutoff voltage of the electrochemical device, the first discharge cutoff voltage is made less than the second discharge cutoff voltage, and / or the first charge cutoff voltage is made greater than the second charge cutoff voltage. This adjusts the capacity contributed by the second active material, making the capacity contributed by the second active material correspond to the health status of the electrochemical device, thus extending the service life of the electrochemical device. Therefore, it is possible to improve the volumetric energy density of the electrochemical device and enable it to have a longer service life.

[0097] In one possible implementation, the discharge operating voltage range of the first active material includes a second voltage range greater than the upper limit of the discharge operating voltage of the second active material, and the electrochemical device control method further includes:

[0098] The electrochemical device is controlled to operate at a third discharge cutoff voltage and a third charge cutoff voltage during a third time period. The third discharge cutoff voltage is located within a second voltage range, and / or the second charge cutoff voltage is greater than the third charge cutoff voltage.

[0099] In one possible implementation, the electrochemical device control method further includes controlling the electrochemical device to perform at least one of the following operations during a fourth time period:

[0100] (i) Stop charging and discharging;

[0101] (ii) Issue a message to instruct the cessation of charging and discharging operations on the electrochemical device.

[0102] In one possible implementation, when the life cycle of the electrochemical device includes the aforementioned first time period, second time period, third time period, and fourth time period, the first time period, second time period, third time period, and fourth time period are arranged sequentially in chronological order within the life cycle of the electrochemical device.

[0103] In one possible implementation, the electrochemical device control method further includes: determining the time period of the electrochemical device based on the range of values ​​of the health status parameters of the electrochemical device.

[0104] In one possible implementation, the health status parameter includes at least one of the following: (i) the internal resistance of the electrochemical device; (ii) the reversible capacity of the electrochemical device; (iii) the thickness of the electrochemical device; and (iii) the pressure or stress between the electrochemical device and the housing used to house the electrochemical device.

[0105] In one possible implementation, the mass percentage of silicon in the negative electrode active material of the electrochemical device is in the range of (0%, 60%).

[0106] In one possible implementation, the mass percentage of silicon in the negative electrode active material of the electrochemical device is in the range of [10%, 20%].

[0107] It should be noted that the details of the above-mentioned electrochemical device control method have been described in detail in the electrochemical device embodiments of the present application. The specific process can be found in the description of the aforementioned electrochemical device embodiments, and will not be repeated here.

[0108] Electrochemical device management system

[0109] One embodiment of this application provides an electrochemical device management system connected to an electrochemical device, which is used to execute the electrochemical device control method in the foregoing embodiments.

[0110] It should be noted that, since the electrochemical device and the electrochemical device control method have been described in detail in the foregoing embodiments, the process of the electrochemical device management system controlling the operation of the electrochemical device can be referred to the description in the foregoing embodiments, and will not be repeated here.

[0111] electronic devices

[0112] One embodiment of this application provides an electronic device, including the electrochemical device or electrochemical device management system described in the above embodiments. The electronic device can be a mobile phone, drone, etc. The negative electrode active material of the electrochemical device in the electronic device includes a first active material and a second active material. The specific capacity of the first active material is smaller than that of the second active material. The presence of the second active material can increase the volumetric energy density of the electrochemical device, giving the electronic device a longer battery life. Controlling the electrochemical device in the electronic device to operate at different discharge cutoff voltages and / or charge cutoff voltages at different time periods can slow down the decay of the electrochemical device's cycle life, thereby extending the lifespan of the electrochemical device and improving the user experience of the electronic device.

[0113] Computer-readable storage media

[0114] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the electrochemical device control method of any of the above embodiments. Specifically, a system or apparatus equipped with a storage medium storing software program code that implements the functions of any of the above embodiments can be provided, and the computer (or CPU or MPU) of the system or apparatus can read and execute the program code stored in the storage medium.

[0115] In this case, the program code read from the storage medium can itself implement the function of any of the above embodiments, and therefore the program code and the storage medium storing the program code constitute part of this application.

[0116] Examples of storage media used to provide program code include floppy disks, hard disks, magneto-optical disks, optical disks (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), magnetic tapes, non-volatile memory cards, and ROMs. Alternatively, program code can be downloaded from a server computer via a communication network.

[0117] Furthermore, it should be clear that not only can the program code read by the computer be executed, but also the operating system or other components operating on the computer can be instructed based on the program code to perform some or all of the actual operations, thereby realizing the function of any of the embodiments described above.

[0118] Furthermore, it is understood that the program code read from the storage medium is written to the memory set in the expansion board inserted into the computer or to the memory set in the expansion module connected to the computer. Then, based on the instructions of the program code, the CPU or other components installed on the expansion board or expansion module execute some and all of the actual operations, thereby realizing the function of any of the above embodiments.

[0119] Computer program products

[0120] This application also provides a computer program product stored on a computer-readable medium and including computer-executable instructions, which, when executed, cause at least one processor to perform the electrochemical device control method of any of the above embodiments. It should be understood that the solutions in this embodiment have the corresponding technical effects in the above method embodiments, and will not be repeated here.

[0121] Experimental examples and comparative examples

[0122] The following uses a lithium-ion battery as an example of an electrochemical device to illustrate some experimental examples and comparative examples of the embodiments of this application. Through these experimental examples and comparative examples, the significant advantages of the electrochemical device and its control method, electronic device, and storage medium in the embodiments of this application compared with the prior art can be more easily seen. It should be understood that the following experimental examples and comparative examples are only used to better illustrate the embodiments of this application, and are not intended to limit the embodiments of this application.

[0123] <Comparative Example 1>

[0124] Preparation of the positive electrode sheet: Lithium cobalt oxide, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97:1.4:1.6. N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred until homogeneous to form a positive electrode slurry (solid content of 72 wt%). The positive electrode slurry was uniformly coated onto the positive electrode current collector aluminum foil to a thickness of 80 μm, dried at 85 °C, and then cold-pressed, cut, and slit. Finally, it was dried under vacuum at 85 °C for 4 hours to obtain the positive electrode sheet.

[0125] Preparation of the negative electrode sheet: Artificial graphite, binder polyacrylic acid, and sodium carboxymethyl cellulose (CMC) were dissolved in deionized water at a weight ratio of 97:1.5:1.5 to form a negative electrode slurry (solid content 40wt%). A 10μm thick copper foil was used as the negative electrode current collector. The negative electrode slurry was coated onto the current collector to a thickness of 50μm and dried at 85℃. After cold pressing, cutting, and slitting, the negative electrode sheet was dried under vacuum at 120℃ for 12 hours to obtain the negative electrode sheet.

[0126] Preparation of the separator: The separator is made of 7 μm thick polyethylene (PE).

[0127] Preparation of electrolyte: In a dry argon atmosphere glove box, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed in a mass ratio of EC:PC:DEC = 1:1:1. After dissolving and stirring thoroughly, lithium salt LiPF6 was added and mixed evenly to obtain the electrolyte, wherein the concentration of LiPF6 was 1 mol / L.

[0128] Preparation of lithium-ion batteries: Positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes for isolation. The electrodes are then wound to form an electrode assembly. The electrode assembly is placed in an outer aluminum-plastic film package, and after dehydration at 80°C, the electrolyte is injected and the battery is sealed. Following formation, degassing, and edge trimming processes, a lithium-ion battery is obtained.

[0129] Cyclic conditions: A single, unchanging cyclic condition is used, where the discharge cutoff voltage is 3.0V and the charging cutoff voltage is 4.45V.

[0130] The testing methods for parameters in various embodiments of this application are described below.

[0131] (1) Testing of charging cut-off voltage and discharging cut-off voltage: A battery voltage internal resistance tester or a multimeter can be used for testing.

[0132] (2) Testing of the pressure between the electrochemical device (lithium-ion battery) and the casing: such as Figure 1 As shown, a pressure sensor is built into the housing. With the increase in the number of cycles of the electrochemical device, irreversible expansion occurs. After the electrochemical device comes into contact with the housing and the pressure sensor, a certain pressure is generated. The value of this pressure is the pressure between the electrochemical device and the housing at the contact area between the sensor and the electrochemical device. Figure 2 It can be seen that there is a one-to-one correspondence between the pressure between the electrochemical device and the shell and the expansion volume of the electrochemical device during the cycle.

[0133] (3) Electrochemical Cycle Count Test: A cycle tester is used to perform constant current and constant voltage charge / discharge tests on individual battery cells at the set charge / discharge cutoff voltages. For example, if a single battery cell has charge / discharge cutoff voltages of 4.45V and 3.0V respectively, the cycle tester charges the cell at 25°C with a constant current and constant voltage of 3C to 4.45V, and then discharges it at 0.5C to 3.0V as one cycle. This cycle count is repeated continuously to determine the different cycle counts for each battery cell. Cycle Count Test at 80% Capacity Decay: After formation, the battery cell is charged at 25°C with a constant current and constant voltage of 3C, and then discharged at 0.5C. The capacity at this point is recorded as the initial capacity. The cycle count corresponding to the first capacity decay to 80% (or less than 80% of the initial capacity) is recorded as the cycle count at 80% capacity decay.

[0134] (4) Energy density test: At 25°C, the prepared lithium-ion battery is fully charged at a constant current and constant voltage of 0.2C and fully discharged at a constant current and voltage of 0.2C. The discharge capacity at this time is recorded. The ratio of the discharge capacity of the lithium-ion battery to the volume of the lithium-ion battery is the volumetric energy density of the lithium-ion battery.

[0135] It should be noted that the testing of lithium-ion battery voltage, internal resistance, and cycle life is a well-known technique to those skilled in the art and will not be described in detail here. Furthermore, the testing methods are not limited to those described in this application, and other suitable testing methods may also be used.

[0136] Comparative Examples 2-7

[0137] The difference between Comparative Examples 2 to 7 and Comparative Example 1 is that some of the artificial graphite in the negative electrode active material is replaced with silicon-based material Si-C. Specifically, in Comparative Example 2, the mass ratio of Si element in the negative electrode active material is 1%; in Comparative Example 3, the mass ratio of Si element in the negative electrode active material is 10%; in Comparative Example 4, the mass ratio of Si element in the negative electrode active material is 20%; in Comparative Example 5, the mass ratio of Si element in the negative electrode active material is 30%; in Comparative Example 6, the mass ratio of Si element in the negative electrode active material is 60%; and in Comparative Example 7, the mass ratio of Si element in the negative electrode active material is 90%.

[0138] Table 1 below shows the energy density test results and the number of cycles required to reduce capacity to 80% for Comparative Examples 1 to 7.

[0139] Table 1

[0140]

[0141] As shown in Table 1 above, the energy density of the electrochemical device increases with the increase of Si content in the negative electrode active material, but the cycle life of the electrochemical device decreases significantly with the increase of Si content in the negative electrode active material.

[0142] <Comparative Example 8-13>

[0143] The difference between Comparative Examples 8 to 13 and Comparative Example 1 is that some of the artificial graphite in the negative electrode active material was replaced with silicon-based material Si-C, so that the mass ratio of Si element in the negative electrode active material was 30%. The discharge cutoff voltage of Comparative Example 8 was 2.3V, that of Comparative Example 9 was 2.5V, that of Comparative Example 10 was 2.8V, that of Comparative Example 11 was 3.2V, that of Comparative Example 12 was 3.4V, and that of Comparative Example 13 was 3.5V. The charging cutoff voltage of Comparative Examples 8 to 13 remained the same as that of Comparative Example 5, at 4.45V.

[0144] Table 2 below shows the energy density test results and the number of cycles required to reduce capacity to 80% for Comparative Examples 5 and 8-13.

[0145] Table 2

[0146]

[0147]

[0148] As shown in Table 2 above, the energy density of the electrochemical device decreases with increasing discharge cutoff voltage, while the cycle life of the electrochemical device improves significantly with increasing discharge cutoff voltage.

[0149] <Comparative Examples 14-17>

[0150] The difference between Comparative Examples 14 to 17 and Comparative Example 1 is that some of the artificial graphite in the negative electrode active material was replaced with silicon-based material Si-C, so that the mass ratio of Si element in the negative electrode active material was 30%. The charging cutoff voltage of Comparative Example 14 was 4.2V, that of Comparative Example 15 was 4.3V, that of Comparative Example 16 was 4.6V, and that of Comparative Example 17 was 4.9V. The discharge cutoff voltage of Comparative Examples 14 to 17 remained the same as that of Comparative Example 5, at 3.0V.

[0151] Table 3 below shows the energy density test results and the number of cycles required to reduce capacity to 80% for Comparative Examples 5 and 14-17.

[0152] Table 3

[0153]

[0154] As shown in Table 3 above, the energy density of the electrochemical device increases with the increase of the charging cut-off voltage, while the cycle life of the electrochemical device decreases with the increase of the charging cut-off voltage.

[0155] <Experimental Examples 1-5>

[0156] The difference between Experimental Examples 1 to 5 and Comparative Example 5 is that some of the artificial graphite in the negative electrode active material was replaced with silicon-based material Si-C, so that the mass ratio of Si element in the negative electrode active material was 30%. The charging cutoff voltage was maintained at 4.45V, and the initial discharge cutoff voltage (first discharge cutoff voltage) was 3.0V. After the pressure between the electrochemical device and the shell reached the corresponding first threshold, the discharge cutoff voltage was increased by 0.2V, that is, the discharge cutoff voltage of the electrochemical device was adjusted to the second discharge cutoff voltage (3.2V). The first threshold corresponding to Experimental Example 1 was 0.03MPa, the first threshold corresponding to Experimental Example 2 was 0.05MPa, the first threshold corresponding to Experimental Example 3 was 0.08MPa, the first threshold corresponding to Experimental Example 4 was 0.10MPa, and the first threshold corresponding to Experimental Example 5 was 0.15MPa.

[0157] Table 4 below shows the test results of the number of cycles when the discharge cutoff voltage is increased for Comparative Example 5 and Experimental Examples 1-5, and the test results of the number of cycles when the capacity decays to 80%.

[0158] Table 4

[0159]

[0160]

[0161] When the pressure between the electrochemical device and the casing is less than the first threshold, it indicates that the irreversible expansion of the electrochemical device is small, and the cycle performance of the electrochemical device and the pressure on the casing are within a controllable range. Charge-discharge cycles can be performed according to the initial discharge cutoff voltage. Table 4 shows that if the first threshold is set too low (e.g., 0.01 MPa in Experimental Example 1), the electrochemical device will raise the discharge cutoff voltage after 50 cycles, which is not conducive to fully utilizing the energy density of the electrochemical device. If the first threshold is set too high (e.g., 0.15 MPa in Experimental Example 5), the electrochemical device will only raise the discharge cutoff voltage after 400 cycles, which is relatively limited in improving the cycle life of the electrochemical device and the irreversible expansion, because lithium-ion batteries typically require more than 800 cycles before the capacity decays to 80%.

[0162] <Experimental Example 6-11>

[0163] The difference between Experiment 6 and Experiment 3 is that when the pressure between the electrochemical device and the casing reaches the third threshold (0.5 MPa), the charge-discharge cycle of the electrochemical device is stopped, and the number of cycles of the electrochemical device at this time is recorded.

[0164] The difference between Experiment 7-11 and Experiment 3 is the addition of a second threshold. When the pressure between the electrochemical device and the casing reaches the first threshold (0.08 MPa) but not the corresponding second threshold, the first discharge cutoff voltage (3.0 V) is increased to the second discharge cutoff voltage (3.2 V). When the pressure between the electrochemical device and the casing reaches the corresponding second threshold, the discharge cutoff voltage is further increased by 0.2 V, that is, the second discharge cutoff voltage (3.2 V) is increased to the third discharge cutoff voltage (3.4 V). When the pressure between the electrochemical device and the casing reaches the third threshold (0.5 MPa), the charge-discharge cycle of the electrochemical device is stopped, and the number of cycles of the electrochemical device is recorded. The second threshold for Experiment 7 is 0.10 MPa, for Experiment 8 it is 0.15 MPa, for Experiment 9 it is 0.20 MPa, for Experiment 10 it is 0.25 MPa, and for Experiment 11 it is 0.30 MPa.

[0165] Table 5 below shows the test results of the number of cycles when the discharge cutoff voltage is increased to the second discharge cutoff voltage, the test results of the number of cycles when the discharge cutoff voltage is increased to the third discharge cutoff voltage, and the test results of the number of cycles when the electrochemical device stops charging and discharging in Experimental Examples 3 and 7-11.

[0166] Table 5

[0167] As shown in Table 5, according to Experiment 3, after 300 cycles, the pressure between the electrochemical device and the casing reaches the first threshold. As in Experiments 7-11, by setting a second threshold, when the pressure between the electrochemical device and the casing reaches the first threshold but not the second threshold, the discharge cutoff voltage of the electrochemical device is increased to the second discharge cutoff voltage (3.2V). This continues until the pressure between the electrochemical device and the casing reaches the second threshold, at which point the discharge cutoff voltage is further increased to the third discharge cutoff voltage (3.4V). This full-charge shallow-discharge method can improve the cycle life of the electrochemical device, reduce irreversible volume expansion, and thus reduce pressure damage to the casing. If the second threshold is set too low, it may cause the charging and discharging operation to stop when the electrochemical device is in good cycling condition, or trigger a signal to stop charging and discharging, shortening the cycle life of the electrochemical device. If the second threshold is set too high, its effectiveness in improving the cycle life and safety performance of the electrochemical device will be relatively limited.

[0168] <Experimental Example 12-16>

[0169] The difference between Experimental Examples 12 to 16 and Comparative Example 5 is that some of the artificial graphite in the negative electrode active material was replaced with silicon-based material Si-C, so that the mass ratio of Si element in the negative electrode active material was 30%. The discharge cutoff voltage was maintained at 3.0V, and the initial charging cutoff voltage (first charging cutoff voltage) was 4.45V. After the pressure between the electrochemical device and the casing reached the corresponding first threshold, the charging cutoff voltage was reduced by 0.05V, that is, the charging cutoff voltage of the electrochemical device was adjusted to the second charging cutoff voltage (4.4V). The first threshold corresponding to Experimental Example 12 was 0.01MPa, the first threshold corresponding to Experimental Example 13 was 0.05MPa, the first threshold corresponding to Experimental Example 14 was 0.08MPa, the first threshold corresponding to Experimental Example 15 was 0.10MPa, and the first threshold corresponding to Experimental Example 16 was 0.15MPa.

[0170] Table 6 below shows the test results of the number of cycles when the charging cutoff voltage of Comparative Example 5 and Experimental Examples 12-16 decreased, and the test results of the number of cycles when the capacity decayed to 80%.

[0171] Table 6

[0172]

[0173] When the pressure between the electrochemical device and the casing is less than the first threshold, it indicates that the irreversible expansion of the electrochemical device is small, and the cycle performance of the electrochemical device and the pressure on the casing are within a controllable range. Charge-discharge cycles can be performed according to the initial charging cut-off voltage. Table 6 shows that if the first threshold is set too low (e.g., 0.01 MPa in Experimental Example 12), the electrochemical device will lower the charging cut-off voltage after 50 cycles, which is not conducive to fully utilizing the energy density of the electrochemical device. If the first threshold is set too high (e.g., 0.15 MPa in Experimental Example 16), the electrochemical device will only lower the charging cut-off voltage after 400 cycles, which is relatively limited in terms of improving the cycle life and irreversible expansion of the electrochemical device. This is because lithium-ion batteries typically require more than 800 cycles to reach 80% capacity decay.

[0174] <Experimental Example 17-22>

[0175] The difference between Experiment 17 and Experiment 14 is that when the pressure between the electrochemical device and the casing reaches the third threshold (0.5 MPa), the charge-discharge cycle of the electrochemical device is stopped, and the number of cycles of the electrochemical device at this time is recorded.

[0176] The difference between Experiments 18-22 and Experiment 14 lies in the addition of a second threshold. When the pressure between the electrochemical device and the casing reaches the first threshold (0.08 MPa) but not the corresponding second threshold, the first charging cutoff voltage (4.45 V) is reduced to the second charging cutoff voltage (4.4 V). When the pressure between the electrochemical device and the casing reaches the corresponding second threshold, the charging cutoff voltage is further reduced by 0.05 V, that is, the second charging cutoff voltage (4.5 V) is reduced to the third charging cutoff voltage (4.35 V). When the pressure between the electrochemical device and the casing reaches the third threshold (0.5 MPa), the charging and discharging cycle of the electrochemical device is stopped, and the number of cycles of the electrochemical device at this time is recorded. Specifically, the second threshold for Experiment 18 is 0.10 MPa, for Experiment 19 it is 0.15 MPa, for Experiment 20 it is 0.20 MPa, for Experiment 21 it is 0.25 MPa, and for Experiment 22 it is 0.30 MPa.

[0177] Table 7 below shows the test results of the number of cycles when the charging cutoff voltage is reduced to the second charging cutoff voltage, the number of cycles when the charging cutoff voltage is reduced to the third discharging cutoff voltage, and the number of cycles when the electrochemical device stops charging and discharging in Experimental Examples 14 and 17-22.

[0178] Table 7

[0179] As shown in Table 7, according to Experiment 14, after 300 cycles, the pressure between the electrochemical device and the casing reaches the first threshold. As in Experiments 18-22, by setting a second threshold, when the pressure between the electrochemical device and the casing reaches the first threshold but not the second threshold, the charging cutoff voltage of the electrochemical device will be reduced to the second charging cutoff voltage (4.4V). This continues until the pressure between the electrochemical device and the casing reaches the second threshold, at which point the charging cutoff voltage is further reduced to the third charging cutoff voltage (4.35V). This shallow charging method can improve the cycle life of the electrochemical device, reduce irreversible volume expansion, and thus reduce pressure damage to the casing.

[0180] <Experimental Examples 23-26>

[0181] The difference between Experiments 23-26 and Experiment 21 is that the first discharge cutoff voltage is 3.0V, the first charge cutoff voltage is 4.45V, the first threshold is 0.08MPa, the second threshold is 0.25MPa, and the third threshold is 0.5MPa. When the pressure between the electrochemical device and the casing reaches the first threshold but not the second threshold, the first discharge cutoff voltage (3.0V) is increased to the second discharge cutoff voltage by the corresponding first preset value, and the first charge cutoff voltage (4.45V) is decreased to the second charge cutoff voltage by the corresponding second preset value. When the pressure between the electrochemical device and the casing reaches the second threshold, the second discharge cutoff voltage is increased to the third discharge cutoff voltage by the corresponding first preset value, and the second charge cutoff voltage is decreased to the third discharge cutoff voltage by the corresponding second preset value. The first preset value for Experiment 21 is 0, and the corresponding second preset value is 0.05V. The first preset value for Experiment 23 is 0.1V, and the corresponding second preset value is 0.05V. The first preset value for Experiment 24 is 0.2V, and the corresponding second preset value is 0. The first preset value for Experiment 25 is 0.2V, and the second preset value is 0.025V. The first preset value for Experiment 26 is 0.2V, and the second preset value is 0.05V.

[0182] Table 8 below shows the test results of the number of cycles when the electrochemical devices of Experiment 21 and Experiment 23-26 stopped charging and discharging.

[0183] Table 8

[0184]

[0185] After the pressure between the electrochemical device and the casing reaches the first or second threshold, it is necessary to increase the discharge cutoff voltage and decrease the charging cutoff voltage. It is necessary to balance the ratio of the first preset value and the second preset value, and usually the first preset value needs to be greater than the second preset value.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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, wherein the second active material includes silicon. The specific capacity of the first active material is less than that of the second active material; The discharge operating voltage range of the first active material includes a first voltage range that is not greater than the upper limit of the discharge operating voltage of the second active material; The electrochemical device is configured as follows: The electrochemical device is divided into a first time period and a second time period arranged sequentially according to the pressure or stress between the electrochemical device and the housing used to contain the electrochemical device. The electrochemical device operates at a first discharge cutoff voltage and a first charge cutoff voltage during the first time period. and The electrochemical device operates at a second discharge cutoff voltage and a second charge cutoff voltage during the second time period. Both the first discharge cutoff voltage and the second discharge cutoff voltage are within the first voltage range; wherein, The first discharge cutoff voltage is less than the second discharge cutoff voltage, and the first charging cutoff voltage is greater than the second charging cutoff voltage.

2. The electrochemical device according to claim 1, wherein, The discharge operating voltage range of the first active material further includes a second voltage range that is greater than the upper limit of the discharge operating voltage of the second active material; The electrochemical device operates at a third discharge cutoff voltage and a third charge cutoff voltage during a third time period; wherein... The third discharge cutoff voltage is located within the second voltage range, and / or the second charge cutoff voltage is greater than the third charge cutoff voltage.

3. The electrochemical device according to claim 2, wherein, The first voltage range is no greater than 3.5V, and the second voltage range is greater than 3.5V.

4. The electrochemical device according to claim 2, wherein, The electrochemical device is configured to perform at least one of the following operations during the fourth time period: (i) Stop charging and discharging; (ii) Issue a message to instruct the cessation of charging and discharging operations on the electrochemical device.

5. The electrochemical device according to claim 4, wherein, The first time period, the second time period, the third time period, and the fourth time period are arranged in chronological order.

6. The electrochemical device according to claim 5, wherein, The electrochemical device is configured such that when the electrochemical device operates at different time periods, the health status parameters of the electrochemical device are within different value ranges.

7. The electrochemical device according to claim 6, wherein, The health status parameter includes at least one of the following: (i) The internal resistance of the electrochemical device; (ii) The reversible capacity of the electrochemical device; (iii) The thickness of the electrochemical device; (iiii) The pressure or force between the electrochemical device and the housing used to contain the electrochemical device.

8. The electrochemical device according to claim 7, wherein, The health status parameter is the pressure between the electrochemical device and the housing; the electrochemical device is configured as follows: When the pressure between the electrochemical device and the housing is less than a first threshold, the electrochemical device operates during the first time period; When the pressure between the electrochemical device and the housing is greater than or equal to the first threshold and less than the second threshold, the electrochemical device operates during the second time period; When the pressure between the electrochemical device and the housing is greater than or equal to the second threshold and less than the third threshold, the electrochemical device operates during the third time period. The electrochemical device operates during the fourth time period when the pressure between the electrochemical device and the housing is greater than or equal to the third threshold.

9. The electrochemical device according to claim 8, wherein, The first threshold is greater than or equal to 0.03 MPa, the second threshold is less than 0.5 MPa, the third threshold is greater than or equal to 0.5 MPa, and the second threshold is greater than the first threshold.

10. The electrochemical device according to any one of claims 1-9, wherein, The second active material includes silicon, and the mass percentage of silicon in the negative electrode active material is within the range of (0%, 60%).

11. The electrochemical device according to claim 10, wherein, The mass percentage of silicon in the negative electrode active material is within the range of [10%, 20%].

12. A method for controlling an electrochemical device, used to control the charging and discharging process of the electrochemical device, wherein the negative electrode active material of the electrochemical device includes a first active material and a second active material, the second active material includes silicon, the specific capacity of the first active material is less than that of the second active material, and the discharge operating voltage range of the first active material includes a first voltage range not greater than the upper limit of the discharge operating voltage of the second active material, the method for controlling the electrochemical device includes: The electrochemical device is divided into a first time period and a second time period arranged sequentially based on the pressure or stress between the electrochemical device and the housing used to contain the electrochemical device. The electrochemical device is controlled to operate at a first discharge cutoff voltage and a first charge cutoff voltage during the first time period, wherein the first discharge cutoff voltage is within the first voltage range; The electrochemical device is controlled to operate at a second discharge cutoff voltage and a second charge cutoff voltage during the second time period, wherein the second discharge cutoff voltage is within the first voltage range; Wherein, the first discharge cutoff voltage is less than the second discharge cutoff voltage, and the first charging cutoff voltage is greater than the second charging cutoff voltage.

13. The electrochemical device control method according to claim 12, wherein, The discharge operating voltage range of the first active material includes a second voltage range greater than the upper limit of the discharge operating voltage of the second active material, and the electrochemical device control method further includes: The electrochemical device is controlled to operate at a third discharge cutoff voltage and a third charge cutoff voltage during a third time period; Wherein, the third discharge cutoff voltage is located within the second voltage range, and / or, the second charge cutoff voltage is greater than the third charge cutoff voltage.

14. The electrochemical device control method according to claim 13, wherein, The electrochemical device control method further includes: During the fourth time period, the electrochemical device is controlled to perform at least one of the following operations: (i) Stop charging and discharging; (ii) Issue a message to instruct the cessation of charging and discharging operations on the electrochemical device.

15. The electrochemical device control method according to claim 14, wherein, The first time period, the second time period, the third time period, and the fourth time period are arranged in chronological order throughout the life cycle of the electrochemical device.

16. The electrochemical device control method according to claim 15, wherein, The electrochemical device control method further includes: The time period in which the electrochemical device is located is determined based on the range of values ​​of the health status parameters of the electrochemical device.

17. The electrochemical device control method according to claim 16, wherein, The health status parameter includes at least one of the following: (i) The internal resistance of the electrochemical device; (ii) The reversible capacity of the electrochemical device; (iii) The thickness of the electrochemical device; (iiii) The pressure or force between the electrochemical device and the housing used to contain the electrochemical device.

18. The method for controlling an electrochemical device according to any one of claims 12-17, wherein, The mass percentage of silicon in the negative electrode active material is within the range of (0%, 60%).

19. The electrochemical device control method according to claim 18, wherein, The mass percentage of silicon in the negative electrode active material is within the range of [10%, 30%].

20. An electrochemical device management system, the electrochemical device management system being connected to an electrochemical device, the electrochemical device management system being used to execute the electrochemical device control method as described in any one of claims 12-19.

21. An electronic device comprising an electrochemical device as claimed in any one of claims 1-11 or an electrochemical device management system as claimed in claim 20.

22. A computer-readable storage medium having a computer program stored thereon, the computer program being executed by a processor to implement the electrochemical device control method as described in any one of claims 12-19.

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