Electrochemical device, method for controlling electrochemical device, storage medium, and electronic apparatus

Abstract

The invention provides an electrochemical device. The discharge capacity per unit mass of a first active material of a negative electrode active layer is smaller than that of a second active material; a charging process of the electrochemical device comprises a first charging stage, a second charging stage, a third charging stage, a fourth charging stage and a fifth charging stage which are carried out in sequence; the rate of the first charging stage, the rate of the second charging stage, the rate of the third charging stage, the rate of the fourth charging stage and the rate of the fifth charging stage are v1, v2, v3, v4 and v5 respectively; wherein v1 and v2 are larger than zero, v3, v4 and v5 are smaller than zero, and v1 > v2 > v4 > v3 > v5. The invention further provides an electrochemical control method, a storage medium and electronic equipment. According to the electrochemical device provided by the invention, the short charging time and the long cycle life of the electrochemical device are taken into account at the same time on the basis of recognition of the aging of the electrochemical device and the negative electrode active material.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to an electrochemical device and its control method, a storage medium, and an electronic device. Background Art

[0002] Lithium-ion batteries have advantages such as high working voltage, no memory effect, high energy density, high power density, and low self-discharge rate. Therefore, lithium-ion batteries are popular in consumer and energy storage electronic products. With the development of new energy, lithium-ion batteries have become the main energy source. However, how to charge lithium-ion batteries quickly and effectively to meet the growing demand remains a technical problem.

[0003] The traditional constant current-constant voltage (CCCV) charging strategy is a widely used charging method. It first charges at a constant current during the charging process, and then switches to constant voltage charging when the battery voltage reaches a certain value until the battery is fully charged. However, the above-mentioned constant current-constant voltage charging strategy has limited effects in practical applications and cannot fully meet the demand for fast charging.

[0004] To ensure the performance of lithium-ion batteries and extend their service life, an effective charging strategy is needed. Fast charging is an urgent need for users, but too high a charging rate may cause problems such as battery overheating and overvoltage, thereby shortening the battery life. Therefore, it is extremely urgent for researchers to provide a charging strategy that takes into account both extending the battery life and shortening the charging time. Summary of the Invention

[0005] In view of this, the embodiments of the present application provide an electrochemical device and its control method, an electronic device, and a storage medium, which can take into account the extension of the cycle life of the electrochemical device while shortening the charging time.

[0006] The present application provides an electrochemical device, including a positive electrode sheet, a separator, and a negative electrode sheet stacked. The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer provided on the surface of the negative electrode current collector. The negative electrode active layer includes a first active material and a second active material, and the discharge capacity per unit mass of the first active material is less than that of the second active material;

[0007] The charging process of the electrochemical device includes a first charging stage, a second charging stage, a third charging stage, a fourth charging stage, and a fifth charging stage that are sequentially carried out;

[0008] The rate of the first charging stage is v1, the rate of the second charging stage is v2, the rate of the third charging stage is v3, the rate of the fourth charging stage is v4, and the rate of the fifth charging stage is v5;

[0009] Among them, both v1 and v2 are greater than zero, v3, v4, and v5 are all less than zero, and v1 > v2 > v4 > v3 > v5;

[0010] The rate is the ratio of the change in the charging rate to the change in the state of charge during the charging stage.

[0011] In some specific embodiments, the first active material includes a carbon-based material, the second active material includes a silicon-based material, and the silicon element content in the silicon-based material is 0.5 to 20 wt%.

[0012] In some specific embodiments, the state of charge of the battery corresponding to the starting point of the first charging stage is 0, and the state of charge of the battery corresponding to the end point of the first charging stage and the state of charge of the battery corresponding to the starting point of the second charging stage ≤ 25.0%; the state of charge of the battery corresponding to the end point of the second charging stage and the state of charge of the battery corresponding to the starting point of the third charging stage ≤ 60.0%; the state of charge of the battery corresponding to the end point of the third charging stage and the state of charge of the battery corresponding to the starting point of the fourth charging stage ≤ 80.0%; the state of charge of the battery corresponding to the end point of the fourth charging stage and the state of charge of the battery corresponding to the starting point of the fifth charging stage ≤ 97.0%; the state of charge of the battery corresponding to the end point of the fifth charging stage is 100.0%;

[0013] And / or, v1 is 10 to 80, preferably, v1 is 20 to 60; v2 is 1 to 8, preferably, v2 is 2 to 7; v3 is -50 to -10, preferably, v3 is -32 to -15; v4 is -5 to 0, preferably, v4 is -3.5 to -1.5; v5 is -100 to -60, preferably, v5 is -85 to -70.

[0014] In some specific embodiments, the rate of the second charging stage is v2, and the calculation expression used is as follows:

[0015] v2 = [(T + 273.15) / (SOC * V)] * m2;

[0016] Among them, T is the battery temperature in the second charging stage, SOC is the state of charge in the second charging stage, V is the voltage in the second charging stage, and m2 is the second parameter;

[0017] The rate of the third charging stage is v3, and the calculation expression used is as follows:

[0018] v3 = [(T + 273.15) / (SOC * V)] * m3;

[0019] Among them, T is the battery temperature in the third charging stage, SOC is the state of charge in the third charging stage, V is the voltage in the third charging stage, and m3 is the third parameter;

[0020] The rate of the fourth charging stage is v4, and the calculation expression used is as follows:

[0021] v4 = [(T + 273.15) / (SOC * V)] * m4;

[0022] Among them, T is the battery temperature in the fourth charging stage, SOC is the state of charge in the fourth charging stage, V is the voltage in the fourth charging stage, and m4 is the fourth parameter;

[0023] The rate of the fifth charging stage is v5, and the calculation expression used is as follows:

[0024] v5 = [(T + 273.15) / (SOC * V)] * m5;

[0025] Among them, T is the battery temperature in the fifth charging stage, SOC is the state of charge in the fifth charging stage, V is the voltage in the fifth charging stage, and m5 is the fifth parameter.

[0026] In some specific embodiments, the value range of the second parameter is from 2.0 to 4.0;

[0027] And / or, the value range of the third parameter is from -30 to -15;

[0028] And / or, the value range of the fourth parameter is from -6 to -1;

[0029] And / or, the range of the fifth parameter is from -110 to -100.

[0030] In some specific embodiments, the first charging stage includes N1 charging steps; the second charging stage includes N2 charging steps; the third charging stage includes N3 charging steps; the fourth charging stage includes N4 charging steps; the fifth charging stage is constant current charging and / or constant voltage charging. When the fifth charging stage is constant current charging, the fifth charging stage includes N5 charging steps; N2 > N1, N2 > N3, N4 > N1, N4 > N3, N5 > N2, N5 > N4;

[0031] Each of the N1 to N4 charging steps is constant current charging.

[0032] In some specific embodiments, the cut-off voltage of the charging process ≥ 4.48V.

[0033] The present application also provides a method for controlling an electrochemical device, which is used to control the charging process of the electrochemical device. The electrochemical device includes a stacked positive electrode sheet, a separator, and a negative electrode sheet. The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer provided on the surface of the negative electrode current collector. The negative electrode active layer includes a first active material and a second active material, and the discharge capacity per unit mass of the first active material is less than that of the second active material;

[0034] The method for controlling the electrochemical device includes:

[0035] Controlling the electrochemical device to sequentially perform a first charging stage, a second charging stage, a third charging stage, a fourth charging stage, and a fifth charging stage during the charging process;

[0036] The rate of the first charging stage is v1, the rate of the second charging stage is v2, the rate of the third charging stage is v3, the rate of the fourth charging stage is v4, and the rate of the fifth charging stage is v5;

[0037] Wherein, both v1 and v2 are greater than zero, v3, v4, and v5 are all less than zero, and v1 > v2 > v4 > v3 > v5;

[0038] The rate is the ratio of the change in the charging rate of the charging stage to the change in its state of charge.

[0039] The present application also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the above-mentioned method for controlling the electrochemical device is implemented.

[0040] The present application also provides an electronic device, including the above-mentioned electrochemical device.

[0041] The present application provides an electrochemical device, which includes a first charging stage, a second charging stage, a third charging stage, a fourth charging stage, and a fifth charging stage that are sequentially carried out during the charging process; in the first charging stage, the lithium ions of the second active material diffuse relatively fast, the specific capacity is released relatively fast, and the swelling rate changes little. In this stage, a large-rate charging method is considered; in the second charging stage, the second active material has good tolerance to high-rate charging and is not prone to polarization. However, considering the swelling rate of the second active material, the charging rate can be appropriately reduced; in the third charging stage, the swelling rate of the second active material further increases, and the charging rate needs to be reduced to slow down the swelling rate of the second active material, balance the charging rate and the safety of the electrochemical device, and avoid overheating and overvoltage of the electrochemical device caused by high charging rates; in the fourth charging stage, a lower charging rate can slow down the metal deposition on the negative electrode surface, avoid the formation of lithium dendrites, and maintain the stability of the electrochemical device; in the fifth charging stage, lithium deposition, overheating, and the swelling rate of the second active material reach the maximum. Using a low-rate charging can control the voltage of the electrochemical device, reduce the material stress and side reactions of the second active material, and help extend the life of the electrochemical device; therefore, the electrochemical device provided by the present application selects the second active material in the negative electrode active material layer and combines the changes of the second active material in different charging stages. By using different charging rates in different charging stages, the charging rate, the safety and life of the electrochemical device are reasonably balanced, thereby achieving the balance between the fast charging and the extended life of the electrochemical device.

[0042] Experimental results show that compared with the charging methods of the prior art, the charging time of the charging method of the electrochemical device provided by the present application is shortened by up to >60%, and the cycle life of the charging method of the electrochemical device provided by the present application is extended by up to >91%. Brief Description of the Drawings

[0043] Figure 1 It is a schematic diagram showing the relationship between the charging rate and the SOC in the charging method of Embodiment 1 of the present invention;

[0044] Figure 2 It is a schematic diagram showing the relationship between the charging rate and the SOC in the charging methods provided by the embodiments and comparative examples of the present invention;

[0045] Figure 3 It is a schematic diagram showing the relationship between the SOC and the charging time in the charging methods provided by the embodiments and comparative examples of the present invention. Detailed Embodiments

[0046] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0047] In the content of the embodiments of the present application, a lithium-ion battery is taken as an example of an electrochemical device to explain the technical solutions of the present application. However, the electrochemical device of the present application is not limited to lithium-ion batteries.

[0048] In the following content, the electrochemical device, its control method, computer-readable storage medium, and electronic device of the present application will be specifically described in sequence.

[0049] For the electrochemical device

[0050] An electrochemical device is a device that provides electrical energy for consumer electronic products such as mobile phones, laptops, tablets, mobile power supplies, and electric vehicles. Lithium-ion batteries, sodium-ion batteries, etc. generally adopt a constant current-constant voltage (CCCV) charging strategy. With the continuous improvement of the battery life and application volume of electronic devices, the balance between the fast charging and service life of electrochemical devices can no longer meet the requirements. Therefore, there is an urgent need for a technical solution that can improve the fast charging of electrochemical devices and ensure the cycle life of electrochemical devices.

[0051] In view of this, an embodiment of the present application provides an electrochemical device, which includes a stacked positive electrode sheet, a separator, and a negative electrode sheet. The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer provided on the surface of the negative electrode current collector. The negative electrode active layer includes a first active material and a second active material, and the specific discharge capacity per unit mass of the first active material is less than that of the second active material;

[0052] The charging process of the electrochemical device includes a first charging stage, a second charging stage, a third charging stage, a fourth charging stage, and a fifth charging stage that are carried out in sequence;

[0053] The rate of the first charging stage is v1, the rate of the second charging stage is v2, the rate of the third charging stage is v3, the rate of the fourth charging stage is v4, and the rate of the fifth charging stage is v5;

[0054] Among them, both v1 and v2 are greater than zero, v3, v4, and v5 are all less than zero, and v1 > v2 > v4 > v3 > v5;

[0055] The rate is the ratio of the change amount of the charging rate of the charging stage to the change amount of its state of charge.

[0056] Among them, the rate of the charging stage in which the electrochemical device is located is used to represent the ratio relationship between the change amount of the charging rate of this charging stage and the change amount of its state of charge; for any charging stage, the relationship between the rate of this charging stage, the change amount of the charging rate, and the change amount of the state of charge satisfies the following expression:

[0057] v = δ(C / C_max) / δ(SOC) * 1000;

[0058] Wherein, v represents the rate of this charging stage, δ(C / C_max) represents the change amount of the charging rate of this charging stage, δ(SOC) represents the change amount of the state of charge of this charging stage, C represents the charging rate of this charging stage, and C_max represents the maximum charging rate of this charging stage.

[0059] In this application, the rate has a positive rate and a negative rate. Among them, the positive rate represents the rising rate, and the negative rate represents the falling rate.

[0060] In the electrochemical device of this application, the negative electrode active layer includes a first active material and a second active material, and the discharge capacity per unit mass of the first active material is less than that of the second active material; during the charging process of the electrochemical device, the expansion rate of the second active material is greater than that of the first active material. The charging process of the electrochemical device includes five different charging stages, and different rates are used for charging in each charging stage. As the charging time progresses, the change amount of the charging rate and the change amount of the state of charge change at different rates.

[0061] The researchers of this application found that: for the electrochemical device provided in this application, in the first charging stage of the charging process, the lithium ions of the second active material diffuse faster, the specific capacity is released faster, and the expansion rate changes little. Therefore, it is considered to charge at a large rate; in the second charging stage of the charging process, the second active material has better tolerance to high-rate charging and is not prone to polarization phenomena. However, considering the expansion rate of the second active material, the charging rate can be appropriately reduced; in the third charging stage, the expansion rate of the second active material further increases, and the charging rate needs to be reduced to slow down the expansion rate of the second active material, balance the charging rate and the safety of the electrochemical device, and avoid overheating and overvoltage of the electrochemical device caused by high charging rates; in the fourth charging stage, using a lower charging rate can slow down the metal deposition on the surface of the negative electrode, avoid the formation of lithium dendrites, and maintain the stability of the electrochemical device; in the fifth charging stage, lithium precipitation, overheating, and the expansion rate of the second active material reach the maximum. Using a low-rate charging can control the voltage of the electrochemical device, reduce the material stress and side reactions of the second active material, and help extend the life of the electrochemical device.

[0062] In some specific embodiments, the first active material includes a carbon-based material. Further, the carbon-based material includes one or more of artificial graphite, natural graphite, hard carbon, soft carbon, and mesophase microspheres. The second active material includes a silicon-based material. Further, the silicon-based material includes one or more of silicon carbide materials, silicon chloride materials, elemental silicon, and silicon alloys. The content of silicon element in the silicon-based material is 0.5 wt% to 20 wt%. In some specific embodiments, the content of silicon element in the silicon-based material is 1 wt% to 15 wt%. More specifically, the content of silicon element in the silicon-based material is 3.5 wt% to 10.5 wt%. In this application, the content of silicon element in the silicon-based material is 1.5 wt%, 2.1 wt%, 2.4 wt%, 2.6 wt%, 2.9 wt%, 3.0 wt%, 3.1 wt%, 3.3 wt%, 3.6 wt%, 3.7 wt%, 4.0 wt%, 4.1 wt%, 4.3 wt%, 4.6 wt%, 4.8 wt%, 5.0 wt%, 5.1 wt%, 5.2 wt%, 5.4 wt%, 5.6 wt%, 6.5 wt%, 6.9 wt%, 7.3 wt%, 7.6 wt%, 8.0 wt%, 8.3 wt%, 8.7 wt%, 8.9 wt%, 9.1 wt%, 9.3 wt%, 9.6 wt%, 10.0 wt%, 10.6 wt%, 10.9 wt%, 11.0 wt%, 11.3 wt%, 11.8 wt%, 12.2 wt%, 12.8 wt%, 13.0 wt%, 13.5 wt%, 13.6 wt%, 13.9 wt%, 14.1 wt%, 14.2 wt%, 14.8 wt%, 15.3 wt%, 15.6 wt%, 15.9 wt%, 16.3 wt%, 16.6 wt%, 16.8 wt%, 17.0 wt%, 17.2 wt%, 17.4 wt%, 17.7 wt%, 17.9 wt%, 18.2 wt%, 18.6 wt%, 18.9 wt%, 19.1 wt%, 19.3 wt%, 19.6 wt%, 19.9 wt%. The content of silicon element in the silicon-based material is obtained by the TAG method (thermogravimetric analysis method). Silicon in the silicon-based material usually exists in the form of elemental silicon, silicon dioxide, or other silicon compounds. The TAG method obtains the content of silicon element by heating the sample and measuring its mass change.

[0063] In a possible implementation, the state of charge of the battery corresponding to the starting point of the first charging stage is 0, and the state of charge of the battery corresponding to the ending point of the first charging stage and the state of charge of the battery corresponding to the starting point of the second charging stage ≤ 25.0%. Specifically, the state of charge of the battery corresponding to the ending point of the first charging stage and the state of charge of the battery corresponding to the starting point of the second charging stage are 10.0% to 25.0%. More specifically, the state of charge of the battery corresponding to the ending point of the first charging stage and the state of charge of the battery corresponding to the starting point of the second charging stage are 13.0% to 20.0%.

[0064] In a possible implementation, the state of charge of the battery corresponding to the ending point of the second charging stage and the state of charge of the battery corresponding to the starting point of the third charging stage ≤ 60.0%. Specifically, the state of charge of the battery corresponding to the ending point of the second charging stage and the state of charge of the battery corresponding to the starting point of the third charging stage are 50.0% to 60.0%. More specifically, the state of charge of the battery corresponding to the ending point of the second charging stage and the state of charge of the battery corresponding to the starting point of the third charging stage are 52.0% to 59.0%.

[0065] In a possible implementation, the state of charge of the battery corresponding to the ending point of the third charging stage and the state of charge of the battery corresponding to the starting point of the fourth charging stage ≤ 80.0%. Specifically, the state of charge of the battery corresponding to the ending point of the third charging stage and the state of charge of the battery corresponding to the starting point of the fourth charging stage are 70.0% to 80.0%. More specifically, the state of charge of the battery corresponding to the ending point of the third charging stage and the state of charge of the battery corresponding to the starting point of the fourth charging stage are 73.0% to 78.0%.

[0066] In a possible implementation, the state of charge of the battery corresponding to the ending point of the fourth charging stage and the state of charge of the battery corresponding to the starting point of the fifth charging stage ≤ 97.0%. Specifically, the state of charge of the battery corresponding to the ending point of the fourth charging stage and the state of charge of the battery corresponding to the starting point of the fifth charging stage are 90% to 97%. More specifically, the state of charge of the battery corresponding to the ending point of the fourth charging stage and the state of charge of the battery corresponding to the starting point of the fifth charging stage are 92% to 95%.

[0067] The state of charge of the battery corresponding to the ending point of the fifth charging stage is 100.0%.

[0068] Each charging stage includes a starting point and an ending point, and the state of charge corresponding to the starting point and the ending point respectively is the basis for the charging stage in which the electrochemical device is located; in some specific embodiments, the starting point and the ending point of the first charging stage are 0 and 19.0% respectively, the starting point and the ending point of the second charging stage are 19.0% and 58.9% respectively, the starting point and the ending point of the third charging stage are 58.9% and 73.3% respectively, the starting point and the ending point of the fourth charging stage are 73.3% and 95.2% respectively, and the starting point and the ending point of the fifth charging stage are 95.2% and 100% respectively.

[0069] In the present application, for adjacent charging stages, the state of charge corresponding to the ending point of the previous charging stage is the same as the state of charge corresponding to the starting point of the subsequent charging stage.

[0070] In some specific embodiments, the rate v1 of the first charging stage is 10 to 80, more specifically, v1 is 20 to 60, and more specifically, v1 is 34 to 45.

[0071] Exemplarily, when the electrochemical device enters the first charging stage, a stepped current charge is performed on the electrochemical device using a stepped-up charging rate determined when the rising rate of the first charging stage is 34 to 45.

[0072] In the first charging stage, at a low state of charge (SOC), the internal resistance of the electrochemical device is relatively low and can withstand a high current without causing an excessive voltage increase; at this time, the lithium ions of the second active material diffuse relatively fast and can be quickly embedded in the negative electrode material, reducing the risk of lithium plating. Although the charging rate is high in this stage, the temperature of the electrochemical device is relatively low at low SOC, and thermal management is relatively easy to control.

[0073] In some specific embodiments, the rate v2 of the second charging stage is 1 to 8, more specifically, v2 is 2 to 7, and more specifically, v2 is 3 to 5.

[0074] Exemplarily, when the electrochemical device enters the second charging stage, a stepped current charge is performed on the electrochemical device using a stepped-up charging rate determined when the rising rate of the second charging stage is 3 to 5.

[0075] In the second charging stage, the rate of the second charging stage is determined based on the battery temperature, state of charge, voltage, and second parameter of the second charging stage; the value range of the second parameter is 2.0 to 4.0, specifically, the value range of the second parameter is 2.5 to 3.2.

[0076] In some specific embodiments, the rate v2 of the second charging stage is calculated using the following expression:

[0077] v2 = [(T + 273.15) / (SOC * V)] * m2;

[0078] Wherein, T is the battery temperature (°C) in the second charging stage, SOC is the state of charge (%) in the second charging stage, V is the voltage (V) in the second charging stage, and m2 is the second parameter.

[0079] When the electrochemical device enters the second charging stage, following the progress of the charging stage, this stage belongs to the middle part of the capacity of the electrochemical device. A fast and stable charging rate can significantly shorten the charging time; meanwhile, the second active material in this stage has good tolerance to high-rate charging, is not prone to polarization phenomenon, and due to the anode material being able to effectively absorb lithium ions, the risk of lithium deposition is low.

[0080] In some specific embodiments, the rate v3 of the third charging stage is from -50 to -10, more specifically, v3 is from -32 to -15, and more specifically, v3 is from -25 to -16.

[0081] Exemplarily, when the electrochemical device enters the third charging stage, a stepped current charging is performed on the electrochemical device using a stepped-down charging rate determined to be from -25 to -16 in the third charging stage.

[0082] In the third charging stage, the rate of the third charging stage is determined based on the battery temperature, state of charge, voltage, and the third parameter in the third charging stage. The value range of the third parameter is from -30 to -15, specifically, the value range of the third parameter is from -28 to -20.

[0083] In some specific embodiments, the rate v3 of the third charging stage is calculated using the following expression:

[0084] v3 = [(T + 273.15) / (SOC * V)] * m3;

[0085] Wherein, T is the battery temperature (°C) in the third charging stage, SOC is the state of charge (%) in the third charging stage, V is the voltage (V) in the third charging stage, and m3 is the third parameter.

[0086] When the electrochemical device enters the third charging stage, following the progress of the charging stage, as the state of charge SOC increases, the aging of the electrochemical device and the stress of the anode material increase. In this stage, the charging rate is reduced to slow down the aging rate of the anode material; meanwhile, the reduced charging rate can balance the charging speed and the safety of the electrochemical device, and avoid overheating and overvoltage of the electrochemical device caused by high rate.

[0087] In some specific embodiments, the rate v4 of the fourth charging stage is from -5 to 0, more specifically, v4 is from -3.5 to -1.5.

[0088] Exemplarily, when the electrochemical device is in the fourth charging stage, a stepped current charge is performed on the electrochemical device using a stepped-down charging rate determined when the stepped-down rate in the fourth charging stage is from -3.5 to -1.5.

[0089] In the fourth charging stage, the rate of the third charging stage is determined based on the battery temperature, state of charge, voltage, and a fourth parameter in the fourth charging stage. The value range of the fourth parameter is from -6 to -1. Specifically, the value range of the fourth parameter is from -4 to -2.

[0090] In some specific embodiments, the rate v4 of the fourth charging stage is calculated using the following expression:

[0091] v4 = [(T + 273.15) / (SOC * V)] * m4;

[0092] Wherein, T is the battery temperature (°C) in the fourth charging stage, SOC is the state of charge (%) in the fourth charging stage, V is the voltage (V) in the fourth charging stage, and m4 is the fourth parameter.

[0093] When the electrochemical device enters the fourth charging stage, as the charging stage progresses, the risk of lithium plating on the negative electrode material increases under a high state of charge SOC. Reducing the charging rate can slow down the deposition of lithium metal on the negative electrode surface and avoid the formation of lithium dendrites. At the same time, as the SOC increases, the heat generation of the electrochemical device also increases. A lower charging rate is beneficial for controlling the temperature of the electrochemical device, protecting the negative electrode material of the electrochemical device, and helping to maintain the electrochemical stability of the electrochemical device and extend the life of the electrochemical device. In some specific embodiments, the rate of the fifth charging stage is from -100 to -60. More specifically, v5 is from -85 to -70.

[0094] Exemplarily, when the electrochemical device is in the fifth charging stage, a stepped current charge is performed on the electrochemical device using a stepped-down charging rate determined when the stepped-down rate in the fifth charging stage is from -85 to -70.

[0095] In the fifth charging stage, the rate of the fifth charging stage is determined based on the battery temperature, state of charge, voltage, and a fifth parameter in the fifth charging stage. The value range of the fifth parameter is from -110 to -100. Specifically, the value range of the fifth parameter is from -108 to -102.

[0096] In some specific embodiments, the rate v5 of the fifth charging stage is calculated using the following expression:

[0097] v5 = [(T + 273.15) / (SOC * V)] * m5;

[0098] Wherein, T is the battery temperature (°C) in the fifth charging stage, SOC is the state of charge (%) in the fifth charging stage, V is the voltage (V) in the fifth charging stage, and m5 is the fifth parameter.

[0099] When the electrochemical device enters the fifth charging stage, as the charging stage progresses, the fifth charging stage is the stage with the highest risk of lithium plating and overheating. Low-rate charging can precisely control the voltage of the electrochemical device to prevent overcharging. At the same time, side reactions are active at high SOC, and low-rate charging can reduce the decomposition of the electrolyte and lower gas generation; it can also minimize the stress and side reactions of the negative electrode material, contributing to the extension of the life of the electrochemical device.

[0100] In this application, the first charging stage, the second charging stage, the third charging stage, and the fourth charging stage each include at least 1 step number. The fifth charging stage is constant current charging and / or constant voltage charging. When the fifth charging stage is constant current charging, the fifth charging stage includes at least 1 step number; the step number represents the number of steps of the charging rate during the charging process. Specifically, the charging rate of each charging stage may experience multiple gradual increases or decreases, and each increase or decrease will add one level of steps. Therefore, when the charging rate of the charging stage changes from high to low or from low to high, the corresponding step number will increase accordingly to achieve precise control and optimized management of the battery charging process. This stepped charging method is beneficial to improving the cycle life of the electrochemical device. Of course, the more step numbers there are for each charging stage, the better, as this is more conducive to achieving precise control, but this method will reduce the charging efficiency.

[0101] In some specific embodiments, the first charging stage includes N1 charging steps, the second charging stage includes N2 charging steps, the third charging stage includes N3 charging steps, the fourth charging stage includes N4 charging steps, and the fifth charging stage includes N5 charging steps; and N2 > N1, N2 > N3, N4 > N1, N4 > N3, N5 > N2, N5 > N4. Specifically, N1 is 2 - 4, N2 is 4 - 6, N3 is 2 - 5, N4 is 4 - 6, and N5 is 5 - 8; each of the N1 to N5 charging steps is constant current charging.

[0102] In the embodiments of this application, a battery cell is provided, and the charging cut-off voltage of the battery cell ≥ 4.48V, such as 4.48V, 4.5V, or 4.53V. The term —— The charging cut-off voltage has the conventional meaning in the art and generally refers to the maximum voltage value that the battery cell can safely reach during the charging process.

[0103] When charging under a high-voltage system, the side reactions of silicon will intensify, which will further cause the battery to heat up faster and intensify internal gas generation, etc., affecting the safety and cycle life of the battery. By adjusting the charging rate of the battery at different charging stages under the high-voltage system, the silicon element in the battery can more stably intercalate and deintercalate lithium ions, thereby reducing the side reactions of the silicon-doped negative electrode battery under the high-voltage system and improving the safety and cycle life of the battery.

[0104] In the electrochemical device provided by the present application, the charging method of the electrochemical device is obtained by the researchers of the applicant through a large number of experiments under different aging conditions (different rates, different SOC) taking lithium-ion batteries as an example, and the understanding of the active substances and battery aging of lithium-ion batteries.

[0105] Furthermore, under different aging conditions (different charging rates, different SOC), the degradation of the battery cells is different; through a large number of aging tests by the researchers of the present application, it can be seen that the traditional CCCV charging method or the stage charging method known in the prior art cannot be well matched with the actual degradation law of the battery cells, and the actual aging process is a highly non-linear complex process.

[0106] The charging rates (C) in the aging tests of the present application include but are not limited to: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.8, 9, 10;

[0107] The SOC (%) in the aging experiments of the present application includes but is not limited to: 0 to 5, 5 to 10, 10 to 15, 15 to 20, 20 to 25, 25 to 30, 30 to 35, 35 to 40, 40 to 45, 45 to 50, 50 to 55, 55 to 60, 60 to 65, 65 to 70, 70 to 75, 75 to 80, 80 to 85, 85 to 90, 90 to 95, 95 to 100.

[0108] In view of the above-mentioned large number of aging experiments, the researchers of the applicant have reasonably designed a charging method suitable for the electrochemical device of the present application.

[0109] Based on this, the present application provides an electrochemical device. By selecting the first active material and the second active material in the negative electrode active layer of the electrochemical device and combining the changes in the expansion rate, stress, and tolerance of the second active material during the charging process, different charging rates are adopted in different SOC intervals during the charging process, reasonably balancing the charging speed with the safety and lifespan of the electrochemical device. Specifically, a higher charging rate is used in the medium and low SOC intervals to improve the charging efficiency and shorten the charging time; the charging rate in the high SOC interval is reduced to reduce the risk of lithium plating and overheating. Therefore, the electrochemical device provided by the present application matches a suitable charging method, ultimately effectively optimizing the fast charging ability and cycle life of the electrochemical device.

[0110] The experimental results show that compared with the charging methods of the prior art, when the cycle life is the same, the charging time of the charging method of the electrochemical device provided by the present application is shortened by up to >60%; when the charging duration is the same, the cycle life of the charging method of the electrochemical device provided by the present application is extended by up to >91%.

[0111] Electrochemical device control method

[0112] The present application also provides an electrochemical device control method for controlling the charging process of the electrochemical device. The electrochemical device includes a stacked positive electrode sheet, a separator, and a negative electrode sheet. The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer provided on the surface of the negative electrode current collector. The negative electrode active layer includes a first active material and a second active material, and the discharge capacity per unit mass of the first active material is less than that of the second active material.

[0113] The electrochemical device control method includes:

[0114] Controlling the electrochemical device to sequentially perform a first charging stage, a second charging stage, a third charging stage, a fourth charging stage, and a fifth charging stage during the charging process;

[0115] The rate of the first charging stage is v1, the rate of the second charging stage is v2, the rate of the third charging stage is v3, the rate of the fourth charging stage is v4, and the rate of the fifth charging stage is v5;

[0116] Wherein, both v1 and v2 are greater than zero, v3, v4, and v5 are all less than zero, and v1 > v2 > v4 > v3 > v5;

[0117] The rate is the ratio of the change in the charging rate of the charging stage to the change in its state of charge.

[0118] In this application, the charging process of the electrochemical device sequentially undergoes a first charging stage, a second charging stage, a third charging stage, a fourth charging stage, and a fifth charging stage, and further limits the rate numerical relationship of each of the above charging stages, so that the electrochemical device can take into account both short charging time and long cycle life.

[0119] Computer-readable storage medium

[0120] This application also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the electrochemical device control method in any one of the above embodiments. Specifically, a system or device equipped with the above storage medium is provided; the computer (or CPU or MPU) equipped with the system or device will read and execute the program code stored in the storage medium. In this storage medium, there is software program code that can implement the functions of any one of the above embodiments.

[0121] In this case, the program code read from the storage medium itself can implement the functions of any one of the above embodiments. Therefore, the program code and the storage medium storing the program code together constitute a part of this application.

[0122] Examples of the storage medium providing the program code include one or more of a floppy disk, a hard disk, a magneto-optical disk, an optical disk (such as CD-ROM, CD-R, CD-RW, DvD-ROM, DvD-RAM, DvD-RW, DvD+RW), a magnetic tape, a non-volatile memory card, and a ROM. Optionally, the program code can be downloaded from a server computer via a communication network.

[0123] In addition, for those skilled in the art, not only can the functions of any one of the above embodiments be implemented by executing the program code read by the computer, but also some or all of the actual operations can be completed by the operating system operating on the computer based on the instructions of the program code.

[0124] Further, the program code read from the storage medium is written to the memory provided in the expansion board inserted into the computer or to the memory provided in the expansion module connected to the computer, and then based on the instructions of the program code, the CPU etc. installed on the expansion board or the expansion module are made to execute some and all of the actual operations, so as to implement the functions of any one of the above embodiments.

[0125] Electronic device

[0126] This application also provides an electronic device, including the electrochemical device described in the above solution.

[0127] In some specific embodiments, the electronic device may be a mobile phone, an electric vehicle, a drone, etc. The present application provides an electrochemical device, in which the negative electrode active layer includes a first active material and a second active material, and the discharge capacity per unit mass of the first active material is less than that of the second active material. Considering the changes in lithium ion diffusion, swelling rate, stress, etc. of the second active material during the charging stage, and the charging process includes a first charging stage, a second charging stage, a third charging stage, a fourth charging stage, and a fifth charging stage in sequence, and the charging rates and rate relationships of the above-mentioned charging stages are defined, so that the determined charging rate can enable the electrochemical device to balance the charging time and long cycle life during the charging process.

[0128] By adopting the above charging strategy in the present application, when the cycle life is the same, the charging time can be shortened by up to more than 60% compared with the charging method of the prior art. When the charging duration is the same, the cycle life can be extended by up to more than 91% compared with the charging method of the prior art. Therefore, the electrochemical device provided by the present application can charge faster, safer, and more effectively.

[0129] To further understand the present invention, the electrochemical device, its control method, storage medium, and electronic device provided by the present invention will be described in detail below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0130] Embodiment 1

[0131] 1) Preparation of negative electrode sheet

[0132] Mix silicon-carbon negative electrode active material (silicon element content 5wt%), artificial graphite, conductive carbon black (SP), and styrene-butadiene rubber (SBR) in a mass ratio of 2:6:1:1, add deionized water, and obtain negative electrode active slurry under the action of a vacuum mixer; uniformly coat the negative electrode active slurry on both surfaces of an 8-μm-thick copper foil; dry the coated copper foil at room temperature, then transfer it to an oven at 60°C and dry for 24h, and then obtain the negative electrode sheet through cold pressing and slitting;

[0133] 2) Preparation of positive electrode sheet

[0134] Mix the positive electrode active material lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), and conductive carbon black (super P) in a mass ratio of 7:1:2, add N-methylpyrrolidone (NMP), and stir under the action of a vacuum mixer until the mixed system becomes a homogeneous and flowing positive electrode active slurry; uniformly coat the positive electrode active slurry on both surfaces of a 10-μm-thick aluminum foil; place the coated aluminum foil in an oven at 60°C and dry for 24h, and then obtain the required positive electrode sheet through rolling and slitting;

[0135] 3) Preparation of electrolyte

[0136] In a glove box filled with inert gas (argon) (H2O < 0.1 ppm, O2 < 0.1 ppm), a carbonate solvent (ethylene carbonate, propylene carbonate, and diethyl carbonate with a mass ratio of 1:1:1) and a carboxylate solvent (propyl propionate and ethyl propionate with a mass ratio of 1:1) were mixed evenly. Then, 1.25 mol / L of fully dried lithium hexafluorophosphate (LiPF6) was quickly added thereto, dissolved in a non-aqueous organic solvent, and stirred evenly. After passing the moisture and free acid tests, an electrolyte solution was obtained.

[0137] 4) Preparation of the separator

[0138] An 8-μm-thick coated polyethylene separator was selected.

[0139] 5) Preparation of the lithium-ion battery

[0140] The positive electrode sheet, separator, and negative electrode sheet prepared above were stacked in sequence, and then a non-injected bare battery cell was obtained by winding; the bare battery cell was placed in an outer packaging foil, and the corresponding electrolyte solution prepared above was injected into the dried bare battery cell. After processes such as vacuum packaging, standing, formation, shaping, and sorting, the corresponding lithium-ion battery was obtained.

[0141] The lithium-ion battery prepared above was charged in the first stage, and the voltage instantaneously increased from 3.0 V to 3.75 V. As the charging proceeded, the voltage continued to increase to 3.92 V, the v1 value was 34.4, and the number of steps in this stage was 3.

[0142] When the voltage continued to increase from 3.92 V and entered the second charging stage to 4.0 V, the v2 value was calculated from SOC2, V2, and T2 at the junction of the second stage and the third stage. The number of steps in this stage was 5.

[0143] When the voltage continued to increase from 4.0 V and entered the third charging stage to 4.2 V, the v3 value was calculated from SOC3, V3, and T3 at the junction of the third stage and the fourth stage. The number of steps in this stage was 3.

[0144] When the voltage continued to increase from 4.2 V and entered the fourth charging stage to 4.5 V, the v4 value was calculated from SOC4, V4, and T4 at the junction of the fourth stage and the fifth stage. The number of steps in this stage was 5.

[0145] When the voltage continued to increase from 4.5 V and entered the fifth charging stage to 4.3 V, the v5 value was calculated from SOC5, V5, and T5 at the end of the fifth stage. The number of steps in this stage was 6.

[0146] During the above charging process, the SOC, V, T, m, and v values of each charging stage are shown in Table 1.

[0147] Table 1 Data table of relevant parameters for each charging stage

[0148] Group SOC / % T / ℃ V / V m v / ％ N The first charging stage / / / / 34.4 3 The second charging stage 58.9 62.5 4.0 2.9 4.1 5 The third charging stage 73.3 64.9 4.2 -18.5 -20.3 3 The fourth charging stage 95.2 60.7 4.5 -4 -3.1 5 The fifth charging stage 100 53.0 4.53 -108 -77.8 6

[0149] As Figure 1 shown Figure 1 is a schematic diagram of the relationship between the ratio of the charging rate and the maximum charging rate corresponding to each charging stage during the charging process of the lithium-ion battery prepared in this embodiment and the SOC. As Figure 1 shown, in the first charging stage, 3 stepped-up charging rates are used. For example, when C_rate / C_rate(max) = 0.653, the battery SOC is charged from 0 to 19.0%; in the second charging stage, 5 stepped-up charging rates are used. For example, when C_rate / C_rate(max) = 0.164, the battery SOC is charged from 19.0% to 58.9%; in the third charging stage, 3 stepped-down charging rates are used. For example, when C_rate / C_rate(max) = -0.292, the battery SOC is charged from 58.9% to 73.3%; in the fourth charging stage, 5 stepped-down charging rates are used. When C_rate / C_rate(max) = -0.068, the battery SOC is charged from 73.3% to 95.2%; in the fifth charging stage, 6 stepped-down charging rates are used. When C_rate / C_rate(max) = -0.373, the battery SOC is charged from 95.2% to 100.0%.

[0150] Comparative Example 1

[0151] The above-prepared lithium-ion battery is charged by a 4C CCCV charging method, which specifically includes the following stages:

[0152] Constant current charging stage: At the beginning of charging, the lithium-ion battery is charged with a constant current of 4C. During the constant current charging stage, the battery voltage gradually rises. When the battery voltage approaches its full charge cut-off voltage, the constant current charging stage ends;

[0153] Constant voltage charging stage: After the constant current charging ends, the constant voltage charging stage is entered; at this time, the lithium-ion battery maintains the charging voltage at the rated full charge voltage of the battery (for example, the cut-off voltage of 4.53V), and the charging current gradually decreases as the battery charge increases. When the charging current drops to a certain extent, below 0.05C, the battery is basically fully charged and the charging process ends.

[0154] Comparative Example 2

[0155] The above-prepared lithium-ion battery is charged by a 6C CCCV charging method, which specifically includes the following stages:

[0156] Constant current charging stage: At the beginning of charging, the lithium-ion battery is charged with a constant current of 6C. During the constant current charging stage, the battery voltage gradually rises. When the battery voltage approaches its full charge cut-off voltage, the constant current charging stage ends;

[0157] Constant voltage charging stage: After the constant current charging ends, the constant voltage charging stage begins; at this time, the lithium-ion battery maintains the charging voltage at the rated full charge voltage of the battery (for example, the cut-off voltage of 4.53V), and the charging current gradually decreases as the battery charge increases. When the charging current drops to a certain level, below 0.05C, the battery is basically full and the charging process ends.

[0158] Comparative Example 3

[0159] The lithium-ion battery prepared above is charged using the following charging method, which specifically includes the following stages:

[0160] Starting from the initial voltage of 3.0V, the lithium-ion battery is first charged at a constant current of 6.5C to 4.15V, so that the battery SOC is charged from 0 to 20%; then charged at a constant current of 6C to 4.25V, so that the battery SOC is charged to 35%; then charged at a constant current of 5.5C to 4.35V, so that the battery SOC is charged to 50%; then charged at a constant current of 5C to 4.45V, so that the battery SOC is charged to 65%; then charged at a constant current of 4.5C to 4.5V, so that the battery SOC is charged to 78%; then charged at a constant current of 4.0C to 4.53V, so that the battery SOC is charged to 85%; finally, it is charged at a constant voltage until the SOC is 100%.

[0161] Figure 2 It is a schematic diagram of the relationship between the charging rate and SOC of the lithium-ion batteries of the embodiments and comparative examples of the present invention; from Figure 2 It can be seen that Embodiment 1 of the present application adopts a stepped charging method with different charging rates. Comparative Example 1 and Comparative Example 2 adopt a 4C constant current-constant voltage charging method and a 6C constant current-constant voltage charging method respectively. Comparative Example 3 also adopts a stepped charging method. The charging rates of the above four charging methods are completely different at different SOC%.

[0162] Figure 3 It is a schematic diagram of the relationship between SOC and charging time of the lithium-ion batteries of the embodiments and comparative examples of the present invention; from Figure 3It can be seen that the charging method of Example 1 makes the charging time of the lithium-ion battery at SOC 80% only 492s, at SOC 90%, the charging time is only 588s, and at SOC 100%, the charging time is only 847s; while the charging method of Comparative Example 1 makes the charging time of the lithium-ion battery at SOC 80% 742s, at SOC 90%, the charging time is 880s, and at SOC 100%, the charging time is 2263s; the charging method of Comparative Example 2 makes the charging time of the lithium-ion battery at SOC 80% 495s, at SOC 90%, the charging time is 602s, and at SOC 100%, the charging time is 1775s; the charging method of Comparative Example 3 makes the charging time of the lithium-ion battery at SOC 80% 525s, at SOC 90%, the charging time is 650s, and at SOC When the SOC is 100%, the charging time is 1815s; thus, when the lithium ions are charged to SOC 100%, the charging time provided by the charging method provided in Example 1 is shortened by 62.6% compared with the charging method provided in Comparative Example 1, the charging time is shortened by 52.3% compared with the charging method provided in Comparative Example 2, and the charging time is shortened by 53.3% compared with the charging method provided in Comparative Example 3.

[0163] The battery health status (SOH) test was performed using an electrochemical workstation, whereby the charge and discharge current (from each charging strategy of the above-mentioned Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3) was applied to the lithium-ion battery, and the current and time data during the charge and discharge process were measured. The actual capacity of the battery was calculated using the coulomb counting method, and compared with the initial capacity to obtain the SOH percentage; the calculation method is as follows:

[0164] Current integration formula: ΔQ = ∫I_b(t)dt

[0165] Where: ΔQ is the change in charge during the battery charge and discharge process (unit: ampere-hour, Ah);

[0166] I_b(t) is the battery charge and discharge current (unit: ampere, A);

[0167] T is time (unit: hour, h);

[0168] SOH calculation formula: SOH = (Q_actual / Q_initial) × 100%

[0169] Where: SOH is the battery health status (percentage);

[0170] Q_actual is the actual capacity calculated by current integration (unit: Ah);

[0171] Q_initial is the initial capacity of the battery (unit: Ah);

[0172] The capacity retention rates of the lithium-ion batteries provided in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 under different charging methods were calculated according to the above method, as shown in Table 2;

[0173] Table 2 Data table of the capacity retention rates of the lithium-ion batteries provided in the examples and comparative examples under different charging methods (%)

[0174]

[0175] Based on the above table as the data basis, taking 80% capacity retention rate as the standard, the cycle lives of the charging methods of the lithium-ion batteries provided in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were obtained, and the results are shown in Table 3;

[0176] Table 3 Data table of the cycle lives of the lithium-ion batteries in the examples and comparative examples under different charging methods

[0177] Group Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Cycle life (cycles) 1073 859 562 727

[0178] As can be seen from Table 3, under the condition of the same charging duration, compared with Comparative Example 1, the charging method of the present application extends the cycle life of the lithium-ion battery by 25%, compared with Comparative Example 2, the charging method of the present application extends the cycle life of the lithium-ion battery by 91%, and compared with Comparative Example 3, the charging method of the present application extends the cycle life of the lithium-ion battery by 48%.

[0179] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0180] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An electrochemical device, characterized in that, It includes a stacked positive electrode sheet, a separator, and a negative electrode sheet. The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer provided on the surface of the negative electrode current collector. The negative electrode active layer includes a first active material and a second active material, and the discharge capacity per unit mass of the first active material is less than that of the second active material; During the charging process of the electrochemical device, it includes a first charging stage, a second charging stage, a third charging stage, a fourth charging stage, and a fifth charging stage that are carried out in sequence; The rate of the first charging stage is v1, the rate of the second charging stage is v2, the rate of the third charging stage is v3, the rate of the fourth charging stage is v4, and the rate of the fifth charging stage is v5; Among them, both v1 and v2 are greater than zero, v3, v4, and v5 are all less than zero, and v1 > v2 > v4 > v3 > v5; The rate is the ratio of the change in the charging rate of the charging stage to the change in its state of charge.

2. The electrochemical device according to claim 1, characterized in that, The first active material includes a carbon-based material, the second active material includes a silicon-based material, and the silicon element content in the silicon-based material is 0.5 to 20 wt%.

3. The electrochemical device according to claim 1, wherein The state of charge of the battery corresponding to the starting point of the first charging stage is 0, and the state of charge of the battery corresponding to the end point of the first charging stage and the state of charge of the battery corresponding to the starting point of the second charging stage ≤ 25.0%; the state of charge of the battery corresponding to the end point of the second charging stage and the state of charge of the battery corresponding to the starting point of the third charging stage ≤ 60.0%; the state of charge of the battery corresponding to the end point of the third charging stage and the state of charge of the battery corresponding to the starting point of the fourth charging stage ≤ 80.0%; the state of charge of the battery corresponding to the end point of the fourth charging stage and the state of charge of the battery corresponding to the starting point of the fifth charging stage ≤ 97.0%; the state of charge of the battery corresponding to the end point of the fifth charging stage is 100.0%; And / or, v1 is 10 to 80, preferably, v1 is 20 to 60; v2 is 1 to 8, preferably, v2 is 2 to 7; v3 is -50 to -10, preferably, v3 is -32 to -15; v4 is -5 to 0, preferably, v4 is -3.5 to -1.5; v5 is -100 to -60, preferably, v5 is -85 to -70.

4. The electrochemical device according to claim 1, characterized in that, The rate of the second charging stage is v2, and the calculation expression used is as follows: v2 = [(T + 273.15) / (SOC * V)] * m2; Among them, T is the battery temperature in the second charging stage, SOC is the state of charge in the second charging stage, V is the voltage in the second charging stage, and m2 is the second parameter; The rate of the third charging stage is v3, and the calculation expression used is as follows: v3 = [(T + 273.15) / (SOC * V)] * m3; Among them, T is the battery temperature in the third charging stage, SOC is the state of charge in the third charging stage, V is the voltage in the third charging stage, and m3 is the third parameter; The rate of the fourth charging stage is v4, and the calculation expression used is as follows: v4 = [(T + 273.15) / (SOC * V)] * m4; Wherein, T is the battery temperature in the fourth charging stage, SOC is the state of charge in the fourth charging stage, V is the voltage in the fourth charging stage, and m4 is the fourth parameter; The rate of the fifth charging stage is v5, and the calculation expression used is as follows: v5 = [(T + 273.15) / (SOC * V)] * m5; Wherein, T is the battery temperature in the fifth charging stage, SOC is the state of charge in the fifth charging stage, V is the voltage in the fifth charging stage, and m5 is the fifth parameter.

5. The electrochemical device according to claim 4, characterized in that, The value range of the second parameter is from 2.0 to 4.0; And / or, the value range of the third parameter is from -30 to -15; And / or, the value range of the fourth parameter is from -6 to -1; And / or, the range of the fifth parameter is from -110 to -100.

6. The electrochemical device according to claim 1, characterized in that, The first charging stage includes N1 charging steps; the second charging stage includes N2 charging steps; the third charging stage includes N3 charging steps; the fourth charging stage includes N4 charging steps; the fifth charging stage is constant current charging and / or constant voltage charging. When the fifth charging stage is constant current charging, the fifth charging stage includes N5 charging steps; N2 > N1, N2 > N3, N4 > N1, N4 > N3, N5 > N2, N5 > N4; Each of the N1 to N4 charging steps is constant current charging.

7. The electrochemical device according to any one of claims 1 to 6, characterized in that, The cut-off voltage of the charging process ≥ 4.48V.

8. An electrochemical device control method for controlling the charging process of an electrochemical device. The electrochemical device includes a positive electrode sheet, a separator, and a negative electrode sheet stacked. The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer provided on the surface of the negative electrode current collector. The negative electrode active layer includes a first active material and a second active material, and the discharge capacity per unit mass of the first active material is less than that of the second active material; The electrochemical device control method includes: Controlling the electrochemical device to sequentially perform a first charging stage, a second charging stage, a third charging stage, a fourth charging stage, and a fifth charging stage during the charging process; The rate of the first charging stage is v1, the rate of the second charging stage is v2, the rate of the third charging stage is v3, the rate of the fourth charging stage is v4, and the rate of the fifth charging stage is v5; Wherein, both v1 and v2 are greater than zero, v3, v4, and v5 are all less than zero, and v1 > v2 > v4 > v3 > v5; The rate is the ratio of the change amount of the charging rate of the charging stage to the change amount of its state of charge.

9. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, it implements the electrochemical device control method as claimed in claim 8.

10. An electronic device, characterized in that, Including the electrochemical device as claimed in any one of claims 1 to 7.

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