Battery control method, controller, battery pack and electric equipment

Abstract

The embodiment of the invention provides a battery control method, a controller, a battery pack and electric equipment. The method comprises the steps that when the temperature of a battery is lower than a first temperature, the battery is controlled to be heated automatically, and the heating current of the self-heating meets the following conditions; wherein the mass ratio of the negative electrode graphite secondary particles of the battery is marked as rho; the particle size of the negative electrode graphite D50 of the battery is recorded as d, the unit is [mu] m, and the multiplying power of the heating current is recorded as C. On the basis of improving the heating efficiency of self-heating, the lithium precipitation risk is reduced, the retention rate of the battery capacity is improved, the fast charging time is shortened, and the service life of the battery is prolonged.

Description

Technical Field

[0001] This application relates to the field of batteries, and more particularly to a battery control method, controller, battery pack, and electrical device. Background Technology

[0002] Fast charging of lithium-ion batteries at low temperatures can lead to battery life degradation. The core mechanism is that during fast charging, the lithium-ion concentration at the negative electrode interface increases sharply, significantly increasing interfacial polarization. This causes lithium metal to deposit on the negative electrode, exacerbating interfacial contact failure and creating a high-resistance interfacial layer that hinders lithium-ion transport. This impedes the lithium-ion insertion / extraction process, reducing the amount of usable active material in the lithium-ion battery and resulting in rapid capacity decay and low capacity retention.

[0003] To alleviate the aforementioned problems, related technologies employ self-heating with heating current. By increasing the current rate, the cell temperature is accelerated, allowing it to reach a higher temperature before charging. This enhances lithium-ion transport kinetics and suppresses lithium plating. However, using self-heating with heating current in these technologies presents challenges: excessively high current rates may exacerbate the risk of lithium plating, while excessively low current rates may reduce heating efficiency.

[0004] Therefore, there is an urgent need for a battery control method that, while meeting the heating efficiency requirements of self-heating, reduces the risk of lithium plating and maintains a high capacity retention rate to ensure a long battery life. Summary of the Invention

[0005] This application provides a battery control method, controller, battery pack, and electrical device to reduce the risk of lithium plating while maintaining high capacity retention and long battery life, while ensuring self-heating efficiency.

[0006] In a first aspect, embodiments of this application provide a battery control method, the method comprising:

[0007] When the battery temperature is lower than a first temperature, the battery is controlled to self-heat, wherein the heating current for self-heating satisfies: ;

[0008] Wherein, the mass ratio of the negative electrode graphite secondary particles of the battery is denoted as ρ; the particle size of the negative electrode graphite D50 of the battery is denoted as d, in μm; and the multiplier of the heating current is denoted as C.

[0009] In one possible implementation, the ratio of the heating current also satisfies: The mass percentage of the binder in the battery is denoted as ω.

[0010] In one possible implementation, .

[0011] In one possible implementation, the carbon coating thickness of the negative electrode graphite of the battery is m, in nm. .

[0012] In one possible implementation, the frequency of the heating current is denoted as f, and the unit is Hz. .

[0013] In one possible implementation, .

[0014] In one possible implementation, .

[0015] In one possible implementation, the first temperature is greater than or equal to -30°C and less than or equal to 20°C.

[0016] In one possible implementation, the bifacial areal density of the positive electrode of the battery is denoted as σ1, with units of g / m³. 2 300 1000; and / or, the double-sided areal density of the negative electrode of the battery is denoted as σ2, in g / m³. 2 130 460.

[0017] In one possible implementation, the waveform of the heating current includes at least one of the following: sine wave, square wave, trapezoidal wave, and triangular wave.

[0018] In one possible implementation, the mass percentage of the conductive agent is denoted as . 0 3%.

[0019] In one possible implementation, the compaction density of the positive electrode of the battery is denoted as γ1, with units of g / cm³. 3 2.2 3; and / or, the compaction density of the negative electrode of the battery is denoted as γ2, in g / cm³. 3 1.4 2.

[0020] Secondly, embodiments of this application provide a controller, including: a memory and a processor;

[0021] The memory stores computer-executed instructions;

[0022] The processor executes computer execution instructions stored in the memory, causing the processor to perform any of the methods described in the first aspect above.

[0023] Thirdly, embodiments of this application provide a battery pack, the battery pack including a battery and a controller as described in the second aspect above.

[0024] Fourthly, embodiments of this application provide an electrical device, including a battery pack as described in the third aspect above, or a controller as described in the second aspect above.

[0025] Fifthly, embodiments of this application provide a battery pack, including a battery;

[0026] When the battery temperature is below a first temperature, it self-heats, and the heating current for self-heating satisfies the following: ;

[0027] Wherein, the mass ratio of the negative electrode graphite secondary particles of the battery is denoted as ρ; the particle size of the negative electrode graphite D50 of the battery is denoted as d, in μm; and the multiplier of the heating current is denoted as C.

[0028] The battery control method, controller, battery pack, and electrical equipment provided in this application embodiment control the battery to self-heat when the battery temperature is lower than a first temperature. In this application embodiment, the mass ratio of secondary graphite particles in the negative electrode of the battery is denoted as ρ; the D50 particle size of the negative electrode graphite is denoted as d (in μm); and the heating current multiplier for self-heating is denoted as C. .

[0029] A higher proportion of secondary graphite particles in the negative electrode and a smaller graphite D50 particle size result in a larger specific surface area of ​​the battery, leading to a lower charge transfer resistance. Under the same lithium plating risk conditions, this allows for a higher current density, thus permitting higher heating rates to accelerate temperature rise efficiency. Conversely, a lower proportion of secondary graphite particles and a larger graphite D50 particle size result in a higher Rct (resistance to lithium plating), necessitating a reduction in the heating current rate to suppress lithium plating risk and improve battery life.

[0030] Therefore, in this embodiment of the application, the heating current rate is controlled when the temperature of the lithium-ion battery is lower than a first temperature. satisfy: The mass ratio of secondary graphite particles in the negative electrode of the battery And graphite D50 particle size The method controls the heating current rate C to ensure a balance between self-heating efficiency and lithium plating risk. While maintaining a constant lithium plating risk level, a higher heating current rate is used to heat the battery, improving self-heating efficiency. Based on the battery control method implemented in this application, the self-heating efficiency is improved, the lithium plating risk is reduced, the battery capacity retention rate is increased, fast charging time is shortened, and battery life is extended. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0032] Figure 1 A schematic flowchart illustrating the battery control method provided in an embodiment of this application;

[0033] Figure 2 A waveform diagram of the heating current provided in the embodiments of this application. Figure 1 ;

[0034] Figure 3 A waveform diagram of the heating current provided in the embodiments of this application. Figure 2 ;

[0035] Figure 4 A waveform diagram of the heating current provided in the embodiments of this application. Figure 3 ;

[0036] Figure 5 A waveform diagram of the heating current provided in the embodiments of this application. Figure 4 ;

[0037] Figure 6 A schematic diagram of the controller provided in this application.

[0038] The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0039] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0040] Lithium-ion batteries are widely used in electric vehicles, energy storage systems, and consumer electronics due to their high energy density, long cycle life, and low self-discharge rate. However, current technologies face the problem of rapid capacity decay during lithium-ion battery charging caused by increased polarization.

[0041] To alleviate the aforementioned problems, related technologies employ self-heating with heating current. By increasing the current rate, the cell temperature is accelerated, allowing it to reach a higher temperature before charging. This enhances lithium-ion transport kinetics and suppresses lithium plating. However, using self-heating with heating current in these technologies presents challenges: excessively high current rates may exacerbate the risk of lithium plating, while excessively low current rates may reduce heating efficiency.

[0042] Therefore, there is an urgent need for a battery control method that can reduce the risk of lithium plating and maintain a high capacity retention rate by controlling the heating current rate, thereby ensuring the battery has a long lifespan while meeting the heating efficiency requirements of self-heating.

[0043] Therefore, this application proposes a battery control method that controls the battery to self-heat when the battery temperature is lower than a first temperature, and limits the range of heating current rate based on the negative electrode graphite D50 particle size and secondary particle ratio.

[0044] A higher proportion of secondary graphite particles in the negative electrode and a smaller graphite D50 particle size result in a larger specific surface area of ​​the battery and a smaller charge transfer resistance (Rct). Under the same lithium plating risk conditions, the battery can withstand a higher current density, thus allowing for higher heating rates to accelerate temperature rise efficiency. Conversely, a lower proportion of secondary graphite particles and a larger graphite D50 particle size result in a higher Rct, necessitating a reduction in the heating current rate to suppress lithium plating risk and improve battery life.

[0045] Therefore, in this embodiment of the application, when the battery temperature is lower than the first temperature, a multiplier greater than or equal to is used. and less than or equal to The battery is self-heated using a heating current. The heating current rate C is controlled by the mass ratio ρ of the secondary graphite particles in the negative electrode and the D50 particle size d of the graphite, thereby ensuring a balance between self-heating efficiency and lithium plating risk. While maintaining a constant lithium plating risk level, a higher heating current rate is used to heat the battery, improving the self-heating efficiency. Based on the battery control method implemented in this application, the self-heating efficiency is improved, the lithium plating risk is reduced, the battery capacity retention rate is increased, fast charging time is shortened, and battery life is extended.

[0046] The battery control method of this application embodiment can be applied to any battery charging scenario, such as charging scenarios for electric vehicles and energy storage systems. The battery control method of this application embodiment can be applied to both fast charging and non-fast charging scenarios. In both fast charging and non-fast charging scenarios, any charging strategy (constant current charging, stepped charging, etc.) can be adopted.

[0047] The positive electrode active material used in the battery of this application includes, but is not limited to, at least one of lithium iron phosphate (LiFePO4), NCM ternary positive electrode material, lithium manganese oxide (LiMn2O4), and lithium-rich manganese-based materials, and the negative electrode active material includes graphite.

[0048] The executing entity in this application embodiment can be the battery management system (BMS) of the battery, or any controller or control device outside the battery management system that can control the charging current. For example, the executing entity can be the control module on the side of the device where the battery is located (e.g., electrical equipment, electrical appliance, etc.). The electrical appliance mentioned here can be, for example, an electric vehicle or other electric vehicle. The following embodiment uses the BMS as the executing entity for illustration.

[0049] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0050] Figure 1 This is a schematic flowchart illustrating the battery control method provided in an embodiment of this application. Figure 1 As shown, the method includes:

[0051] S101. When the battery temperature is lower than a first temperature, control the battery to self-heat. The self-heating current satisfies: The mass percentage of secondary graphite particles in the negative electrode of the battery is denoted as ρ; the particle size of the D50 graphite in the negative electrode of the battery is denoted as d, in μm; and the heating current ratio is denoted as C.

[0052] The first temperature is the threshold temperature at which the battery begins to self-heat. When the battery temperature is below the first temperature, it indicates that the battery is in a low-temperature environment and needs to self-heat.

[0053] The heating current is the current applied during the battery's self-heating process. The heating current is used to raise the battery temperature. The heating current is an alternating current (AC) current, and its value changes periodically over time. For example, the heating current's current rating can be 1C, 2C, 3C, 4C, 5C, 6C, 7C, 8C, or any combination thereof.

[0054] The mass percentage of secondary graphite particles in the negative electrode of a battery refers to the percentage of the mass of secondary particles in the total graphite mass of the negative electrode active material. Secondary particles are polycrystalline composite particles formed by the fusion and aggregation of multiple graphite microcrystals at high temperatures, containing internal pores and grain boundaries.

[0055] The D50 particle size of the negative electrode graphite in a battery is the particle size value corresponding to a cumulative particle size distribution of 50%, which characterizes the particle size distribution of the graphite negative electrode material. It can also be called the median diameter or median particle size.

[0056] The heating current ratio is the ratio of the heating current value to the battery's rated capacity, used to measure the charging and discharging speed. For sine / cosine wave heating currents, it refers to the effective value, i.e., the ratio of the peak current to the square root of two; for square wave and other waveforms, it is the peak current. When a battery pack contains multiple batteries, the heating current ratio of each battery is the heating current ratio of the entire battery pack. The specific calculation method for the heating current ratio is the same as described above.

[0057] At low temperatures, the charge-discharge performance of lithium-ion batteries deteriorates, lithium-ion transport kinetics decrease, and lithium plating easily occurs on the negative electrode surface. The lithium dendrites produced by lithium plating react with the electrolyte in the battery, consuming active lithium and electrolyte, leading to lithium loss and consequently battery capacity decay. Heating the lithium-ion battery with a heating current to raise its temperature before charging can enhance lithium-ion transport kinetics, thereby suppressing lithium plating and improving battery life.

[0058] The inventors discovered that during the self-heating process, due to the high frequency of the current, the reaction is approximately limited to the first layer of graphite. The Rct of the electrode approximately exhibits an inverse relationship with the particle size ratio of the secondary particles and the graphite.

[0059] A higher proportion of secondary graphite particles in the negative electrode and a smaller D50 particle size result in a larger specific surface area of ​​the battery. This increased specific surface area provides more reaction sites for charge transfer, leading to a smaller Rct (response rate). Under the same lithium plating risk conditions, the battery can withstand a higher current density, allowing for higher heating rates to accelerate temperature rise. Conversely, a lower proportion of secondary graphite particles and a larger D50 particle size result in a higher Rct, necessitating a reduction in the heating current rate to suppress lithium plating risk and improve battery life. In summary, by limiting the range of charging rate variations based on the proportion of secondary graphite particles in the negative electrode and the D50 particle size, it is possible to maintain rapid temperature rise while suppressing lithium plating, thus improving battery safety.

[0060] Therefore, based on Determining the heating current rate is crucial for battery self-heating. When the proportion of secondary graphite particles in the negative electrode is high and the graphite D50 particle size is small, a higher heating current rate can be used to accelerate temperature rise efficiency. Conversely, when the proportion of secondary graphite particles in the negative electrode is low and the graphite D50 particle size is large, a lower heating current rate can be used to suppress lithium plating risk and improve battery life.

[0061] In this embodiment of the application, according to The heating current ratio is determined by the mass ratio of secondary graphite particles in the negative electrode and the D50 particle size of the graphite, so as to adapt to batteries with different mass ratios of secondary graphite particles in the negative electrode and the D50 particle size of the graphite.

[0062] Based on the mass ratio of secondary graphite particles in the negative electrode and the limiting ratio of heating current by graphite D50 particle size, heating efficiency can be improved to maintain the battery's fast charging capability and keep the fast charging time stable. On the other hand, the risk of lithium plating can be suppressed, thereby reducing battery polarization, improving battery capacity retention, and extending battery life.

[0063] The battery control method provided in this application embodiment controls the battery to self-heat when the battery temperature is lower than a first temperature. In this application embodiment, the mass ratio of secondary graphite particles in the negative electrode of the battery is denoted as ρ; the D50 particle size of the negative electrode graphite is denoted as d (in μm); and the heating current multiplier for self-heating is denoted as C. .

[0064] A higher proportion of secondary graphite particles in the negative electrode and a smaller graphite D50 particle size result in a larger specific surface area of ​​the battery, leading to a smaller Rct. Under the same lithium plating risk conditions, this allows for a higher current density, thus permitting higher heating rates to accelerate temperature rise efficiency. Conversely, a lower proportion of secondary graphite particles and a larger graphite D50 particle size result in a higher Rct, necessitating a reduction in the heating current rate to suppress lithium plating risk and improve battery life.

[0065] Therefore, the embodiment of this application controls the multiplier of the heating current. satisfy The mass ratio of secondary graphite particles in the negative electrode of the battery And graphite D50 particle size The method controls the heating current rate C to ensure a balance between self-heating efficiency and lithium plating risk. While maintaining a constant lithium plating risk level, a higher heating current rate is used to heat the battery, improving self-heating efficiency. Based on the battery control method implemented in this application, the self-heating efficiency is improved, the lithium plating risk is reduced, the battery capacity retention rate is increased, fast charging time is shortened, and battery life is extended.

[0066] Optionally, when the battery self-heats to the second temperature, the BMS can charge the battery using the charging current.

[0067] The charging current can be the current value of the battery under fast charging or non-fast charging. For example, the charging current multiplier can be 0.1C, 1C, 2C, 3C, 4C, 5C, 6C, 7C, 8C, 10C, 15C, or any combination thereof. The charging current is used to provide charging energy to the battery. When the battery pack contains multiple batteries, the charging current of each battery is the charging current of the entire battery pack.

[0068] The second temperature is the battery temperature threshold at the end of self-heating. For example, the second temperature is within a range of 15°C, 18°C, 20°C, 25°C, 30°C, or any combination thereof. The second temperature is greater than or equal to the first temperature.

[0069] For example, taking a second temperature of 20°C as an example, when the battery is at 5°C, the BMS can apply a heating current to the battery to heat it, and the rate of increase of the heating current is greater than or equal to... and less than or equal to The heating current is applied until the battery temperature reaches 20°C. Then, the BMS stops applying the heating current and begins applying a charging current to charge the battery. For example, the BMS can apply a 3C charging current for fast charging.

[0070] The method of this application embodiment, when the battery is heated to a second temperature based on the heating current, charges the battery with the charging current. By heating the battery cell to a higher temperature before charging, the battery in the current state is charged. Compared with charging the battery before heating, the lithium-ion transport dynamics during the charging process can be enhanced, the charging efficiency can be improved, the charging time can be shortened, lithium plating can be suppressed, the battery capacity retention rate can be improved, and the battery life can be improved.

[0071] The following describes an embodiment of the present application in which the battery is controlled to self-heat when the battery temperature is lower than a first temperature.

[0072] Optionally, the first temperature is greater than or equal to -30°C and less than or equal to 20°C.

[0073] Optionally, the first temperature can be -30, -25, -20, -15, -10, -5, 0, 5, 10, 15, 20 or within any two of the above values.

[0074] For example, if the first temperature is greater than or equal to -30°C and less than or equal to 20°C, the BMS can obtain the battery temperature. If the battery temperature is lower than the first temperature, it can obtain the mass ratio ρ of the negative electrode graphite secondary particles and the carbon coating thickness m of the negative electrode graphite. The heating current rate is determined to control the battery's self-heating. Once the battery has self-heated to a second temperature, the charging current is used to charge it. If the battery temperature exceeds 20°C, the charging current is used to charge the battery. For example, the BMS can apply a 3C charging current for fast charging.

[0075] For example, when the battery is a battery pack, the BMS can obtain the temperature of any cell in the battery, or the average temperature of multiple cells, to obtain the battery temperature.

[0076] For example, if the battery is a battery pack and multiple sensors are installed inside the battery pack, the BMS can obtain the lowest temperature among the multiple temperatures measured by the multiple sensors to obtain the temperature of the battery.

[0077] For example, when the battery is a single cell, the BMS can obtain the temperature of the cell near the negative terminal post on the negative side of the cell to obtain the battery temperature.

[0078] Because the electrolyte may solidify when the battery temperature is below -30°C, the battery cannot function properly and cannot be heated by applying a heating current. When the battery temperature is above 20°C, the lithium ion diffusion rate and electrolyte conductivity are both at a good level, the risk of lithium plating is low, and no heating current is needed. Therefore, in this embodiment, the first temperature is greater than or equal to -30°C and less than or equal to 20°C.

[0079] When the battery temperature is greater than or equal to -30°C and less than or equal to 20°C, the electrolyte viscosity increases significantly, increasing ion migration resistance. This prevents lithium ions from being promptly inserted into the negative electrode during charging, easily leading to lithium plating. Furthermore, the battery's charge / discharge efficiency decreases dramatically, power performance degrades, and charging time is prolonged. Therefore, when the battery temperature is greater than or equal to -30°C and less than or equal to 20°C, controlling the battery to self-heat and utilizing the internal resistance heat generation mechanism to achieve rapid temperature rise before charging can more effectively enhance lithium-ion transport kinetics and suppress lithium plating.

[0080] Optionally, the waveform of the heating current includes at least one of the following: sine wave, square wave, trapezoidal wave, and triangular wave.

[0081] For example, the heating current value includes a first value and a second value. The heating current value rises from the initial value to the first value, then falls from the first value to the second value, and then rises from the second value back to the initial value.

[0082] For example, during the period when the battery is heated using a heating current, the first value corresponding to the heating current is i. C The second value is i DThe heating current is determined by the initial value i. A Rise to the first value i C Then from the first value i C Decrease to the second value i D Then from the second value i D Rise to the initial value i A For example, the waveform of the heating current may be a symmetrical waveform that rises first and then falls, or an asymmetrical waveform.

[0083] Figure 2 A waveform diagram of the heating current provided in the embodiments of this application. Figure 1 .like Figure 2 As shown, the waveform of the heating current can be a sine wave, where the heating current rises from an initial value of 0 to a first value i. C Then from the first value i C Decrease to the second value i D Then from the second value i D It rises to the initial value of 0. Where t... A To t C During the charging phase, t C To t D This is the discharge phase.

[0084] The battery is heated by a sinusoidal heating current. The continuous and smooth characteristics of the sinusoidal wave can reduce the impact of sudden current changes on the battery interior, reduce polarization effect, avoid local overheating or overcooling, and improve the uniformity of battery temperature distribution.

[0085] Figure 3 A waveform diagram of the heating current provided in the embodiments of this application. Figure 2 .like Figure 3 As shown, the waveform of the heating current can be a square wave.

[0086] The battery is heated by a square wave heating current. The pulsed high current of the square wave can instantly generate a large amount of Joule heat, which accelerates the overall temperature rise and increases the heating rate.

[0087] Figure 4 A waveform diagram of the heating current provided in the embodiments of this application. Figure 3 .like Figure 4 As shown, the waveform of the heating current can be a trapezoidal wave.

[0088] The battery is heated by a trapezoidal wave heating current. The trapezoidal wave generates heat rapidly in the early stage, and the thermal shock is reduced in the later stage by the ramp current, thus balancing the heating rate and the uniformity of temperature distribution.

[0089] Figure 5 A waveform diagram of the heating current provided in the embodiments of this application. Figure 4 .like Figure 5As shown, the waveform of the heating current can be a triangular wave.

[0090] The battery is heated by a triangular wave heating current. The current amplitude of the triangular wave changes linearly, which can realize heating regulation and achieve high-precision heating through linear temperature control.

[0091] The method in this application embodiment uses a heating current waveform that includes at least one of a sine wave, a square wave, a trapezoidal wave, and a triangular wave. By providing heating currents with multiple waveforms to heat the battery, the heating efficiency can be optimized based on the characteristics of different waveforms.

[0092] Optionally, the frequency of the heating current is denoted as f, and the unit is Hertz (Hz). .

[0093] Optionally, the frequency f of the heating current can be 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 50, or any combination thereof.

[0094] For example, when the battery temperature is below a first temperature, the BMS can obtain the mass ratio ρ of the negative electrode graphite secondary particles and the carbon coating thickness m of the negative electrode graphite, determine the heating current rate C, and obtain the heating current frequency f, where the heating current frequency f is greater than or equal to 1 Hz and less than or equal to 50 Hz. The battery is then self-heated using a heating current with rate C and frequency f.

[0095] Since the frequency f of the heating current is greater than or equal to 1, it ensures that the heating current based on this frequency can quickly generate sufficient Joule heat inside the battery, achieving a rapid temperature rise. If the frequency f of the heating current is less than or equal to 10, it prevents overheating caused by the Joule heat generated by the heating current based on this frequency, which could damage the battery. Therefore, based on... Using a specific heating current to heat the battery can achieve rapid temperature rise and improve heating efficiency while ensuring battery safety. When the battery pack contains multiple batteries, the frequency of the battery's heating current is the same as the frequency of the battery pack's heating current.

[0096] The following describes an embodiment in which the battery is charged using a charging current when the battery self-heats to a second temperature.

[0097] Optionally, the charging current can be a constant current. When the battery self-heats to a second temperature, the BMS uses a constant current to charge the battery.

[0098] Optionally, the charging current can be a curved waveform. A corresponding charging current value is set for each charging stage, and charging is performed based on the charging current corresponding to each charging stage.

[0099] For example, the charging current used by the BMS can be a dynamically changing current. The charging current can be related to the charging duration. For instance, the charging current used during charging period t1 is linearly related to the charging duration, and the heating current can be expressed as I1(t1).

[0100] It should be understood that the charging current used during a charging period can be related to the charging duration. The charging current used during a charging period... With charging time The relationship is based on function representation, and the embodiments of this application do not limit the function form.

[0101] For example, With time The functional form can be expressed as , can also be expressed as Where a, b, A, B, C, and D can be positive real constants, negative real constants, or 0, and can be determined based on the battery's state of charge. Taking the battery's state of charge under constant current charging as an example... =0, This is the current value of the charging current.

[0102] Taking the charging state of a battery under fast charging as an example, the relationship between the charging current and the charging time during the charging period can be determined based on the preset relationship between the charging current and the charging time under the fast charging state of the battery. That is, the relationship between the charging current and the charging time under the fast charging state of the battery is determined as the relationship between the charging current and the charging time during the charging period in this embodiment of the application.

[0103] The method of this application embodiment involves heating the battery to a second temperature using a heating current, and then charging the battery using a charging current. Since the battery temperature is heated to the second temperature, charging the battery in its current state, compared to charging the battery before heating, enhances lithium-ion transport kinetics during charging, improves charging efficiency, shortens charging time, suppresses lithium plating, and improves battery capacity retention.

[0104] The parameters of the battery for which charging control is performed using the method of the embodiments of this application will be described below.

[0105] In the above embodiments, when the battery temperature is lower than a first temperature, the BMS can control the battery to self-heat, and obtain the mass ratio ρ of the negative electrode graphite secondary particles and the carbon coating thickness m of the negative electrode graphite, and control the heating current rate. satisfy .

[0106] Preferably, the mass ratio ρ of secondary graphite particles in the negative electrode of the battery is... .

[0107] Optionally, the mass ratio ρ of the negative electrode graphite secondary particles in the battery can be 0.3, 0.325, 0.35, 0.375, 0.4, 0.425, 0.45, 0.475, 0.5, 0.525, 0.55, 0.575, 0.6, or any combination of the above values.

[0108] The proportion of secondary graphite particles can be measured using image analysis. A small amount of graphite powder is uniformly dispersed on a conductive adhesive, and excess powder is gently blown away to ensure that the particles are dispersed without overlapping. Then, a gold sputtering process is performed to enhance conductivity. Under a scanning electron microscope, a representative area is selected, and multiple backscattered electron (BSE) images are captured at a preset magnification. The BSE mode is sensitive to composition and can better distinguish the boundaries between primary and secondary particles. Image analysis software from related technologies is used to perform threshold segmentation on the images to separate the particles from the background. Based on a preset size threshold, particles larger than a certain threshold are identified as "secondary particles," and those smaller than the threshold are identified as "primary particles" or fragments. The software automatically calculates the area or equivalent circle diameter of all identified particles. The particle proportion is obtained by calculating: (Number of secondary particles / Total number of particles) × 100%.

[0109] For example, the preset magnification can be in the range of 500x to 2000x, such as taking more than 10 BSE images at a magnification of 1000x. The image analysis software can be Image-Pro Plus, ImageJ, or the instrument's built-in software. The preset threshold can be determined according to the material system, and the preset threshold can be, for example, 8μm, 10μm, or 15μm.

[0110] In this embodiment, the proportion of secondary graphite particles in the negative electrode of the battery is greater than or equal to 30%, which can improve lithium-ion transport efficiency, reduce electrode internal resistance, and thus accelerate the temperature rise rate during the self-heating process. The proportion of secondary graphite particles in the negative electrode of the battery is less than or equal to 60%, which can prevent excessively high proportions from causing a decrease in compaction density, cracking of the bonding interface between secondary particles during cycling, and capacity decay. Therefore, for a battery with a secondary graphite particle proportion in the negative electrode greater than or equal to 30% and less than or equal to 60%, the battery control method of this embodiment can improve the efficiency of battery heating based on heating current while maintaining battery life, further shortening the battery charging time.

[0111] Preferably, the graphite D50 particle size for the battery , .

[0112] Optionally, the graphite D50 particle size of the battery It can be 8, 8.5, 9, 10, 11, 12, 12.5, 13, 14, 14.5, 15, 16, 17, 17.5, 18, 19, 19.5, 20, or any combination of the above values.

[0113] Optionally, the D50 particle size of graphite can be obtained using laser diffraction (laser particle size analyzer). Deionized water is used, a small amount of surfactant is added, and graphite particles are added to prepare a suspension of appropriate concentration. Typically, the opacity should be within the instrument's recommended range. The prepared suspension is thoroughly dispersed in an ultrasonic cleaner and then quickly transferred into the instrument's sample cell. Measurement is initiated, and the instrument automatically cycles, collects data, and calculates to obtain a volume-based particle size distribution curve and report, from which the D50 value is obtained.

[0114] For example, in the process of obtaining the D50 particle size of graphite described above, the shading rate can be in the range of 10-20%, and the prepared suspension can be dispersed in an ultrasonic cleaner for 1-3 minutes.

[0115] In this embodiment, the graphite D50 particle size d of the battery is greater than or equal to 8 μm, which makes its structure stable. During the repeated insertion / extraction of lithium ions, structural instability prevents the battery from easily breaking and failing, thus helping to maintain battery life. The graphite D50 particle size d of the battery is less than or equal to 20 μm, which increases the number of reactive sites. Under the same heating current, the higher effective reaction area results in a faster initial temperature rise and improved heating efficiency. Therefore, for batteries with a graphite D50 particle size d greater than or equal to 8 μm and less than or equal to 20 μm, the battery control method of this embodiment can improve the efficiency of battery heating based on heating current and shorten battery charging time while maintaining battery life.

[0116] Optionally, the mass percentage of the battery binder is denoted as ω, and the heating current ratio also satisfies: .

[0117] The mass percentage of the binder in a battery refers to the proportion of the binder in the electrode slurry, which affects the coverage of active sites and charge transfer resistance. Binders include at least one of carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE).

[0118] For example, the mass percentage of the binder in the negative electrode sheet can be measured by thermogravimetric analysis. For instance, an inert atmosphere of nitrogen (N2) or argon (Ar) is used to study the pyrolysis behavior of the material in an oxygen-free environment. The temperature is raised from room temperature to ~120°C and held constant to remove physically adsorbed water, and the mass loss m1 is recorded. The temperature is then further increased to 500-800°C in the inert atmosphere, depending on the type of binder; the mass loss m2 at this stage is mainly due to the pyrolysis and volatilization of the binder. Under an inert atmosphere, the mass percentage of the binder is obtained using the formula: Binder mass percentage ≈ m2 / initial sample mass × 100%.

[0119] The inventors discovered that when the binder content increases, the active sites for lithium intercalation in the negative electrode are covered by the binder, leading to an increase in the Rct of the negative electrode. Under the same self-heating conditions, the risk of lithium plating also increases. Therefore, the heating current ratio needs to be reduced to keep the risk of lithium plating controllable. Thus, in the method of this application embodiment, the heating current ratio decreases as the binder content increases.

[0120] The method in this application embodiment, the heating current multiplier Greater than or equal to This ensures that the heating current can effectively heat the battery, improving heating efficiency. The heating current ratio... Less than or equal to To maintain the risk of lithium plating under control. Through When the binder content increases, the rate of increase is reduced to keep the risk of lithium plating under control, thereby achieving a more efficient heating process while keeping the risk of lithium plating under control.

[0121] Optionally, ω is denoted as the mass percentage of the binder for the battery. .

[0122] Optionally, the mass percentage ω of the battery binder can be 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any combination thereof.

[0123] In the method of this application embodiment, when the binder mass percentage is greater than or equal to 0.5%, it can ensure that the electrode maintains structural integrity during heating, prevents active material from falling off, and reduces capacity decay. When the binder mass percentage is less than or equal to 5%, it avoids excessively high binder mass percentages that could encapsulate the active material and conductive agent, hindering lithium-ion transport. The battery can achieve a balance between electrode structure stability and lithium plating risk, and improve the reliability of heating and charging the battery.

[0124] Optionally, the carbon coating thickness of the graphite in the negative electrode of the battery is m, in nm. .

[0125] Optionally, the carbon coating thickness m of the graphite in the negative electrode of the battery can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, or any combination of the above values.

[0126] The carbon coating thickness of graphite is the distance from the graphite surface to the outer surface of the coating layer. High-resolution transmission electron microscopy (HRTEM) is typically used to determine the carbon coating thickness. Graphite particles are ultrasonically dispersed in ethanol, and a drop of the suspension is placed on a copper grid with a carbon support film. Thin regions at the particle edges are located under HRTEM, and the system is adjusted to high-resolution mode. The distance from the end of the core lattice fringes to the outermost edge of the particle is measured, thus obtaining the carbon coating thickness.

[0127] In the method of this application embodiment, the carbon coating thickness of graphite is greater than or equal to 10 nm, which can enhance structural stability and inhibit electrolyte decomposition, reduce the rate of battery capacity decay, and improve battery capacity retention. A carbon coating thickness of less than or equal to 30 nm ensures that the battery has sufficient capacity. Based on... Heating and charging the battery can improve the battery capacity retention rate while ensuring that the battery has sufficient capacity.

[0128] Optionally, the areal density of the positive electrode of the battery is denoted as σ1, with units of g / m³. 2 300 1000; and / or, the areal density of the negative electrode of the battery is denoted as σ², with units of g / m³. 2 130 460.

[0129] For example, the bifacial density σ1 of the positive electrode of the battery can be 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, or any combination of the above values.

[0130] For example, the areal density σ2 of the negative electrode of the battery can be 130, 135, 140, 145, 150, 160, 170, 180, 190, 200, 250, 300, 350, 400, 430, 460, or any combination of the above values.

[0131] The areal density of the positive electrode of a battery refers to the total mass of active material coated per unit area on both sides of the positive electrode plate. The areal density of the negative electrode of a battery refers to the total mass of active material coated per unit area on both sides of the negative electrode plate.

[0132] Optionally, the areal density of the battery can be obtained based on battery disassembly. For example, the battery is disassembled in a dew point room or glove box, separating the positive and negative electrodes and the separator. Electrode samples of known area are cut. The total weight of the sample is accurately weighed. The binder and conductive agent are washed away with a specific solvent, leaving the active material, which is then dried and weighed. The areal density is obtained by calculating the ratio of the weight of the active material to the sample area. Simultaneously, coating thickness, compaction density, etc., can be calculated. Specific solvents include N-methyl-2-pyrrolidone (NMP).

[0133] In the method of this application embodiment, the double-sided areal density of the positive electrode of the battery is greater than or equal to 300 g / m². 2 And / or, the areal density of the negative electrode of the battery is greater than or equal to 130 g / m². 2 This allows for increased energy density while maintaining the same battery volume, and enhanced structural stability can reduce the rate of capacity decay and improve capacity retention. The areal density of the positive electrode is less than or equal to 1000 g / m³, and / or the areal density of the negative electrode is less than or equal to 1000 g / m³. 2 By controlling the surface density of the positive electrode, the low internal resistance of the battery can be maintained, thereby improving the battery's heating and charging efficiency. (Through 300...) 1000, and / or 130 A 460-cell battery can achieve a balance between improving battery heating and charging efficiency, as well as improving battery capacity retention.

[0134] Optionally, the mass percentage of the conductive agent in the battery is denoted as . 0 3%. Optionally, the mass percentage of the conductive agent in the battery. It can be 0, 0.25%, 0.5%, 0.85%, 1%, 1.25%, 1.5%, 1.85%, 2%, 2.25%, 2.5%, 2.75%, 3%, or any combination of the above values.

[0135] The mass percentage of the conductive agent in a battery refers to the percentage of the conductive agent's mass relative to the total mass of the mixture of electrode active materials and the conductive agent. The mass percentage of the conductive agent in a battery can be either the mass percentage of the positive electrode or the mass percentage of the negative electrode. Conductive agents can include at least one of carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphene.

[0136] Optionally, the mass percentage of the conductive agent can be obtained by disassembling the battery. Specifically, the binder is dissolved and washed away using N-methyl-2-pyrrolidone solvent to separate the active material and the conductive agent. The active material is then removed by high-temperature calcination or acid dissolution to obtain pure conductive agent, which is then accurately weighed. The mass percentage of the conductive agent is obtained by dividing the mass of the pure conductive agent by the total mass of the coating, based on the total mass of the electrode coating.

[0137] The conductive agent forms an interconnected three-dimensional network in the battery electrodes, which helps to conduct electrons. The mass percentage of the conductive agent in the battery is less than or equal to 3%. This avoids the problem that excessive conductive agent content may lead to increased slurry viscosity, cracking, and powdering during coating, thus improving the structural stability of the battery and consequently enhancing the reliability and stability of battery heating and charging.

[0138] Optionally, the compaction density of the positive electrode of the battery is denoted as γ1, with units of g / cm³. 3 2.2 3; The compaction density of the negative electrode of the battery is denoted as γ2, and the unit is g / cm³. 3 1.4 2.

[0139] Optionally, the compaction density γ1 of the positive electrode of the battery can be 2.2, 2.25, 2.3, 2.35, 2.4, 2.45, 2.5, 2.55, 2.6, 2.7, 2.8, 2.9, 2.95, 3, or any combination thereof.

[0140] Optionally, the compaction density γ2 of the negative electrode of the battery can be 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.95, 2, or any combination of the above values.

[0141] The compacted density of a battery's positive electrode refers to the mass per unit volume of the positive electrode material after it has been compacted under a specific pressure. The compacted density of a battery's negative electrode refers to the mass per unit volume of the negative electrode material after it has been compacted under a specific pressure.

[0142] For lithium-ion batteries, increasing the compaction density can increase the content of active material per unit volume, thereby improving the battery's energy density and capacity. Furthermore, the reduced volume of electrode materials during cycling can improve ion and electron transport efficiency, enhancing battery heating and charging efficiency. However, over-voltage of the electrode sheets can lead to reduced battery capacity and increased internal resistance. Therefore, based on 2.2... 3, 1.4 The battery, while ensuring sufficient capacity, achieves a balance between improving heating and charging efficiency, and enhancing capacity retention.

[0143] Optionally, the lithium salt in the battery electrolyte includes at least one of lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI), and the concentration of the electrolyte is 0.7-1.3 mol / L. The solvent includes at least one of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl acrylate (EA), and the conductivity of the electrolyte is 5-20 mS / cm.

[0144] Optionally, the concentration of the electrolyte can be 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, or any combination of the above values.

[0145] Optionally, the conductivity of the electrolyte can be 5, 5.5, 6, 6.5, 7, 8, 8.5, 9, 10, 11, 12, 12.5, 13, 14, 15, 16, 17, 17.5, 18, 18.5, 19, 19.5, 20, or any combination thereof.

[0146] For example, the electrolyte conductivity can be measured using a conductivity meter. Take an appropriate amount of the electrolyte to be tested into a clean, dry sample cell. Immerse the electrode in the electrolyte, agitating it to remove air bubbles and ensuring the platinum sheet is completely submerged. Place the sample cell in a preheated bath and let it stand for 10-15 minutes to allow the sample temperature to match the bath temperature. Select the correct measurement mode on the conductivity meter and read the solution temperature using the instrument. The solution temperature is measured using an external temperature probe. Wait for the reading to stabilize; the stabilization time is typically a few seconds to tens of seconds. Record the stable conductivity value and the corresponding temperature.

[0147] Electrolyte concentration is determined using ion chromatography to measure the concentration of anions, thereby indirectly determining the lithium salt concentration. For example, the concentrations of anions PF6⁻ and FSI⁻.

[0148] When the electrolyte concentration is too low, the number of lithium ions is insufficient, leading to a decrease in ion migration rate and an increase in internal resistance. Rapid charging and discharging are required during self-heating to generate Joule heat; low-concentration electrolytes cannot meet the ion conduction requirements under high current densities, thus failing to meet self-heating needs. Increasing the electrolyte concentration can shorten the heating time and improve heating efficiency. When the electrolyte concentration is too high, the intermolecular forces of the solvent increase, viscosity rises, leading to increased ion migration resistance, increased internal resistance, and reduced self-heating efficiency. Therefore, an electrolyte concentration of 0.7-1.3 mol / L can improve heating efficiency while meeting self-heating requirements.

[0149] The self-heating process relies on the rapid migration of lithium ions in the electrolyte to generate Joule heat. If the conductivity is too low, ion migration is hindered, increasing internal resistance and preventing the second temperature from being reached quickly enough. Therefore, increasing the electrolyte concentration can shorten the heating time and improve heating efficiency. If the conductivity is too high, the electrolyte viscosity increases, leading to increased resistance to ion migration and internal resistance, thus reducing self-heating efficiency. Therefore, a conductivity of 5-20 mS / cm is sufficient to improve heating efficiency while meeting the self-heating requirements.

[0150] Optionally, the base film layer of the battery includes at least one of polyethylene (PE), polypropylene (PP), cellulose, polyester film (PET), polyimide (PI), nonwoven fabric and electrospun separator, with a thickness of 2-22 μm.

[0151] Optionally, the thickness of the base film layer of the battery can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, or any combination thereof.

[0152] A thinner base film can improve ion transport efficiency and reduce internal resistance, thereby increasing heating efficiency. However, insufficient physical protection and decreased thermal stability increase the risk of thermal runaway and reduce battery life. Therefore, using a base film thickness of 2-22µm can ensure safety through moderate physical protection and thermal stability, while maintaining low internal resistance to improve heating efficiency.

[0153] Optionally, the functional layer material on the base film includes at least one of alumina, aramid, polyimide (PI), metal organic framework (MOF), magnesium oxide, and magnesium hydroxide, with a coating thickness of 0.3-8 μm.

[0154] Optionally, the coating thickness of the functional layer material on the base film can be 0.3, 0.8, 1.3, 1.8, 2.3, 2.8, 3.3, 3.8, 4.3, 4.8, 5.3, 5.8, 6.3, 6.8, 7.3, 7.8, 8, or any combination thereof.

[0155] While a thinner coating reduces ion transport resistance and improves heating efficiency, uneven coating coverage can lead to localized thermal inhomogeneity, potentially causing cycle life degradation. A thicker coating enhances thermal stability but significantly increases internal resistance due to prolonged ion migration paths. Therefore, a coating thickness of 0.3-8 μm is ideal, as it balances thermal stability with maintaining low internal resistance to improve heating efficiency.

[0156] Optionally, the coating adhesive layer on the base membrane includes at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polyolefins, hydroxyethyl methacrylate, acrylic acid, butyl acrylate, isooctyl acrylate, and butyl oleate, with a coating thickness of 0.2-5 μm and a membrane porosity of 25%-60%.

[0157] Optionally, the coating thickness of the adhesive layer on the base film can be 0.2, 0.7, 1.2, 1.7, 2.2, 2.7, 3.2, 3.7, 4.2, 4.7, 5, or any combination thereof.

[0158] Optionally, the porosity of the diaphragm can be 25, 27.5, 30, 32.5, 35, 37.5, 40, 42.5, 45, 47.5, 50, 52.5, 55, 57.5, 60, or any combination of the above values.

[0159] During battery self-heating, a lower coating thickness can reduce ion transport interface resistance and improve heating efficiency, but insufficient adhesion may lead to electrode-base film interface peeling, resulting in cycle life degradation. A higher coating thickness can improve battery structural stability, but excessive coating thickness increases ion migration path length, leading to increased internal resistance and reduced heating efficiency. Therefore, a coating thickness of 25%-60% is used to improve heating efficiency while enhancing battery structural stability and reducing cycle life degradation.

[0160] Optionally, when the battery pack contains multiple batteries, the battery parameters included in this application embodiment, such as the mass percentage of secondary graphite particles in the negative electrode, the D50 particle size of the negative electrode graphite, the mass percentage of the binder, the mass percentage of the conductive agent, the carbon coating thickness of the negative electrode graphite, the compaction density of the positive electrode, the compaction density of the negative electrode, the double-sided areal density of the positive electrode, the double-sided areal density of the negative electrode, the conductivity of the electrolyte, the concentration of the electrolyte, the thickness of the base film layer, the coating thickness of the functional layer material on the base film, the coating thickness of the adhesive layer on the base film, and the porosity of the separator, can be obtained based on the average value of the parameters of multiple batteries. Taking the mass percentage of the binder as an example, the mass percentage of the binder of three batteries can be randomly selected and measured, and the average value of the mass percentage of the binder of the three batteries can be calculated as the mass percentage of the binder of the battery in this application embodiment.

[0161] The battery control method of this application will be further described below based on experimental data.

[0162] In this embodiment, liquid lithium-ion batteries of different systems are used as the experimental subjects. Different self-heating strategies are used to heat and charge the batteries, and the heat generation efficiency and lifespan decay of the experimental subjects are compared.

[0163] Example 1:

[0164] The experimental subject was a cathode material made primarily of lithium iron phosphate. The coating also included 0.5% PVDF binder and 1% single-walled carbon nanotubes. After mixing, the mixture was coated onto a 13µm carbon-coated aluminum foil. After coating and compaction, the double-sided areal density of the cathode was 350 g / m². 2 The compacted density is 2.71 g / cm³. 3 The negative electrode is primarily made of graphite, with secondary graphite particles accounting for 50% and a D50 particle size of 8 μm. The graphite carbon coating thickness is 10 nm. The coating material includes 0.5% of a CMC and SBR mixed binder, applied to an 8 μm copper foil. The compacted electrode surface density is 161 g / m². 2 The compacted density is 1.57 g / cm³. 3 The separator is a PP separator with 30% porosity. The positive electrode, separator, negative electrode, separator and positive electrode are stacked in sequence, and after baking, liquid injection, formation and capacity testing are carried out to obtain a single cell with a capacity of 108Ah.

[0165] The following self-heating test was conducted on the above experimental subjects:

[0166] 1) Battery pretreatment: Charge the battery to 0.5% SOC at room temperature.

[0167] 2) Low-temperature standing: Place the pretreated battery in a test chamber that has been cooled to -10℃ and stand for at least 24 hours to ensure that the cell temperature is fully balanced with the ambient temperature, i.e., the temperature difference is ≤2℃.

[0168] 3) Perform self-heating test: Record the lowest cell temperature before startup as the starting temperature. Simulate vehicle commands through the test system to trigger the battery's self-heating function. Perform sinusoidal AC self-heating at a self-heating frequency of 1 Hz until reaching 25°C. Record cell voltage, current, battery SOC, and temperature in real time. Record data including the highest and lowest temperature points.

[0169] 4) Performance evaluation: Calculate the average temperature rise rate (°C / min) to evaluate the heat generation efficiency; let it stand for a period of time to ensure that the battery temperature recovers to -10°C, repeat the above test, and cycle 200 times to evaluate the impact on battery life.

[0170] For example, the battery capacity retention rate is calculated as follows:

[0171] Based on the cell capacity of Q0 before the test (the cell capacity Q0 can also be the nominal capacity of the cell), a cyclic test was performed using the self-heating test procedure described above, for 200 cycles. After 200 cycles, a Reference Performance Test (RPT) was performed on the battery at a 1 / 3C rate, and the calibrated capacity was Q200. The capacity retention rate after the 200th cycle was Q200 / Q0×100%.

[0172] Examples 2-25: The experimental subjects in Examples 2-21 were prepared in the same way as those in Example 1. The difference in the mixing ratio of the positive and negative electrodes in Examples 22-25 lies in the positive electrode coating ratio: 2.1% PVDF binder and 1.8% single-walled carbon nanotubes; and 3.7% CMC and SBR mixed binder for the negative electrode. All examples were tested using the self-heating test procedure of Example 1, with differences in the heating current rate, the proportion of secondary graphite particles, the graphite D50 particle size, the binder mass percentage, and the graphite coating thickness.

[0173] Comparative Examples 1-16: The experimental subjects of Comparative Examples 2-12 were prepared in the same manner as those in Example 1. The experimental subjects of Comparative Examples 13-16 had different positive and negative electrode mixing ratios. Specifically, the positive electrode coating consisted of 2.1% PVDF binder and 1.8% single-walled carbon nanotubes; the negative electrode consisted of 3.7% CMC and SBR mixed binder. All comparative examples were prepared according to the preparation method of Example 1, with differences in the heating current ratio, the proportion of secondary graphite particles, the graphite D50 particle size, the binder mass percentage, and the graphite coating thickness.

[0174] Specifically, the proportion of secondary graphite particles in Comparative Examples 1-4 The graphite D50 particle size d of Comparative Examples 9-16 is outside the range of 30%-60%; the particle size d of Comparative Examples 9-16 is outside the range of 8μm-20μm; the binder mass percentage of Comparative Examples 2, 4, 6, 8, 10, 12, and 16 is outside the range of 8μm-20μm. Outside the 0.5%-5% range, the heating current ratio is... to In addition, the graphite coating thickness *m* of Comparative Examples 3, 4, 7, 8, 11, 12, 14, and 15 is outside the range of 10 nm to 30 nm, and the heating current ratio of Comparative Examples 1 to 16 is within the range of... - In addition.

[0175] Examples 26-50: The experimental subject was a ternary liquid lithium-ion battery. The positive electrode used ternary NCM as the main material. The ternary material, 1.4% conductive agent (CNT), and 2.2% binder (PVDF) were mixed at high speed in an N-methylpyrrolidone solvent to form a uniform slurry. This slurry was then uniformly coated onto an aluminum foil current collector. The electrode was compacted using a roller press, achieving a compaction density and areal density of 2.71 g / cm³. 3 With 350g / m 2 The negative electrode uses graphite. Graphite, 2.8% conductive agent (SP), and 0.5-5% binder (CMC / SBR system) are mixed at high speed in deionized water in a specific ratio to form a uniform slurry. The areal density of the coated and rolled electrode is 161 g / m². 2 The compacted density is 1.57 g / cm³. 3 The positive and negative electrodes (separated by a separator) are stacked and assembled into a battery cell. After baking, the cell undergoes processes such as electrolyte injection, formation, and capacity testing to obtain a single battery cell with a capacity of 127 Ah. Specifically, the positive and negative electrode mixing ratios differ in Examples 47-50. Specifically, the positive electrode coating contains 2.1% PVDF binder and 1.8% single-walled carbon nanotubes; the negative electrode coating contains 3.7% CMC and SBR mixed binder. In Examples 26-50, each example is prepared according to the preparation method of Example 1, with differences in the proportion of secondary graphite particles, the graphite D50 particle size, the binder mass percentage, and the graphite coating thickness.

[0176] Comparative Examples 17-32: The experimental subjects were ternary liquid lithium-ion batteries. Comparative Examples 29-32 differed in the mixing ratio of the positive and negative electrodes. Specifically, the positive electrode coating consisted of 2.1% PVDF binder and 1.8% single-walled carbon nanotubes; the negative electrode consisted of 3.7% CMC and SBR mixed binder. All comparative examples were prepared according to the preparation method in Example 1, with differences in the proportion of secondary graphite particles, the graphite D50 particle size, the binder mass percentage, and the thickness of the graphite coating layer.

[0177] Specifically, the proportion of secondary graphite particles in Comparative Examples 17-20 The graphite D50 particle size d of Comparative Examples 25-32 is outside the range of 30%-60%; the particle size d of the graphite in Comparative Examples 25-32 is outside the range of 8μm-20μm; the binder mass percentage of Comparative Examples 18, 20, 22, 24, 26, 28, and 32 is outside the range of 8μm-20μm. Outside the 0.5%-5% range, the heating current ratio is... to In addition, the graphite coating thickness *m* of Comparative Examples 19, 20, 23, 24, 27, 28, 30, and 31 is outside the range of 10 nm to 30 nm, and the heating current ratio of Comparative Examples 13 to 16 is within the range of... - In addition.

[0178] Specific parameters and data are shown in Table 1:

[0179] Table 1

[0180]

[0181]

[0182] The capacity retention rate of a battery determines its remaining lifespan. A higher capacity retention rate indicates a longer remaining lifespan. For example, a capacity retention rate of over 95% after 200 cycles indicates a longer remaining lifespan. The above experiment uses the capacity retention rate after 200 cycles as the basis for analysis. A higher capacity retention rate after 200 cycles indicates less damage to the battery from the corresponding charging method and a longer battery lifespan; conversely, a lower capacity retention rate indicates that the charging method accelerates battery aging and shortens battery lifespan. The following analysis is based on the battery capacity retention rate:

[0183] The following analysis examines the heating efficiency and battery capacity retention based on the mass ratio of secondary graphite particles in the negative electrode, the D50 particle size of the negative electrode graphite, and the rate of heating current:

[0184] The data from Examples 1-25 are based on satisfying In this case, data from testing a first type of battery based on the battery control method of the embodiments of this application is used. Combined with Comparative Examples 1-16, the heating current multiplier is at... - In cases other than those described above, data from battery tests show that the battery control method based on the embodiments of this application charges the battery effectively. Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0185] The data from Examples 26-50 are based on satisfying In this case, data from testing a second type of battery based on the battery control method of the embodiments of this application is presented. Combined with Comparative Examples 17-32, the heating current multiplier is... - In cases other than those described above, data from battery tests show that the battery control method based on the embodiments of this application charges the battery effectively. Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0186] For the ratio of heating current The mass percentage of the battery binder The analysis of heating efficiency and battery capacity retention is as follows:

[0187] Examples 1-25, excluding Examples 10, 11, 14, and 25, are embodiments that satisfy the following conditions: In this case, the data from testing the first type of battery based on the battery control method of the embodiments of this application are used. In conjunction with Embodiments 10, 11, 14, 25, Comparative Examples 2, 4, 6, 8, 10, 12, and 16, the heating current multiplier is... to In cases other than those described above, data from battery tests show that the battery control method based on the embodiments of this application charges the battery effectively. Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0188] Examples 26-50, excluding Examples 35, 36, 39, and 50, are embodiments that satisfy... In this case, data from testing a second type of battery based on the battery control method of the embodiments of this application is used. In conjunction with Embodiments 35, 36, 39, 50, Comparative Examples 18, 20, 22, 24, 26, 28, and 32, the heating current multiplier is... In cases other than those described above, data from battery tests show that the battery control method based on the embodiments of this application charges the battery effectively. Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0189] Mass percentage of the binder for the battery The analysis of heating efficiency and battery capacity retention is as follows:

[0190] The data from Examples 1-10, 12, 13, and 15-24 are based on the mass percentage of the battery binder meeting the requirements. In this case, the data from testing the first type of battery based on the battery control method of the embodiments of this application are as follows. In conjunction with Examples 11, 14, 25, Comparative Examples 2, 4, 6, 8, 10, 12, and 16, the mass percentage of the battery binder is at... In cases other than those described above, data from battery tests show that the battery control method based on the embodiments of this application charges the battery effectively. Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0191] The data from Examples 26-35, 37, 38, and 40-49 are based on the mass percentage of the battery binder meeting the requirements. In this case, data from testing a second type of battery based on the battery control method of the embodiments of this application are used. In conjunction with Examples 36, 39, 50, Comparative Examples 18, 20, 22, 24, 26, 28, and 32, the mass percentage of the battery binder satisfies... In cases other than those described above, data from battery tests show that the battery control method based on the embodiments of this application charges the battery effectively. Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0192] Regarding the mass ratio of secondary graphite particles in the negative electrode of the battery The analysis of heating efficiency and battery capacity retention is as follows:

[0193] The data from Examples 1-14, Example 18, and Examples 22-25 pertain to the percentage of secondary graphite particles in the battery. satisfy In the case that, Data from tests conducted on a first type of battery under conditions of 30%-60% efficiency, based on the battery control method of this application embodiment. This data is combined with the percentage of secondary graphite particles in the batteries from Examples 15-17, Examples 19-21, and Comparative Examples 1-4. Data from battery tests conducted when the battery level is outside the 30%-60% range shows that the battery control method based on this application's embodiments effectively charges the battery. Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0194] The data from Examples 26-39, 43, and 47-50 pertain to the percentage of secondary graphite particles in the battery. satisfy In this case, data from testing a second type of battery based on the battery control method of the embodiments of this application are used. The percentage of graphite secondary particles in the battery is compared with that in Examples 40-42, Examples 44-46, and Comparative Examples 17-20. Data from battery tests conducted when the battery level is outside the 30%-60% range shows that the battery control method based on this application's embodiments effectively charges the battery. Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0195] The heating efficiency and battery capacity retention are analyzed for the carbon coating thickness *m* of the graphite anode in the battery, as follows:

[0196] The data from Examples 1-11, 15, 17, 18, 20, and 22-24 are based on the condition that the carbon coating thickness m of the graphite in the negative electrode of the battery satisfies... In the case of the battery control method according to the embodiments of this application, the test data of the first type of battery is presented. Combined with the test data of Examples 12-14, 16, 19, 21, 25, Comparative Examples 3, 4, 7, 8, 11, 12, 14, and 15, where the carbon coating thickness m of the negative electrode graphite of the battery is outside the range of 10nm-30nm, it can be seen that the battery charging based on the battery control method according to the embodiments of this application, in the case of the battery being charged, Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0197] The data from Examples 26-36, 40, 42, 43, 45, and 47-49 are based on the condition that the carbon coating thickness m of the graphite in the negative electrode of the battery satisfies... In the case of the battery control method according to the embodiments of this application, the test data of the second type of battery is presented. Combining the test data of Examples 37-39, 41, 44, 46, 50, Comparative Examples 19, 20, 23, 24, 27, 28, 30, and 31, where the carbon coating thickness m of the negative electrode graphite of the battery is outside the 10nm-30nm range, it can be seen that charging the battery based on the battery control method according to the embodiments of this application, in the case of the second type of battery, the test data of the battery is presented. Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0198] Let d be the particle size of the graphite D50 in the negative electrode of the battery. The analysis of the heating efficiency and battery capacity retention is as follows:

[0199] The data from Examples 1-14, 17, and 22-25 are based on the fact that the negative electrode graphite D50 particle size d of the battery meets the following conditions. In the case of the battery control method according to the embodiments of this application, the test data of the first type of battery is presented. Combining the test data of Examples 15, 16, 18-21, and Comparative Examples 9-16, where the negative electrode graphite D50 particle size d of the battery is outside the range of 8μm-20μm, it can be seen that the battery charging method according to the embodiments of this application, in the case of the battery being charged, Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0200] The data from Examples 26-39, 42, and 47-50 are based on the fact that the negative electrode graphite D50 particle size d of the battery satisfies... In the case of the battery control method according to the embodiments of this application, the data from testing the second battery is as follows. Combining the data from Examples 40, 41, 43-46, and Comparative Examples 25-32, where the negative electrode graphite D50 particle size d is outside the range of 8μm-20μm, it can be seen that the battery charging method according to the embodiments of this application, in the case of the second battery, is effective. Under these conditions, it achieves higher heating efficiency and battery capacity retention.

[0201] This application also provides a charging current control method for an electric vehicle, the electric vehicle having a charging interface and a battery, comprising: controlling the battery to self-heat when the charging interface is connected to an external charging device and the battery temperature is lower than a first temperature, wherein the self-heating heating current satisfies: The mass percentage of secondary graphite particles in the negative electrode of the battery is denoted as ρ; the particle size of the D50 graphite in the negative electrode of the battery is denoted as d, in μm; and the heating current ratio is denoted as C.

[0202] The battery control method for electric vehicles provided in this application embodiment controls the battery to self-heat when the battery temperature is lower than a first temperature. In this application embodiment, the mass ratio of secondary graphite particles in the negative electrode of the battery is denoted as ρ; the D50 particle size of the negative electrode graphite is denoted as d (in μm); and the heating current rate is denoted as C. .

[0203] A higher proportion of secondary graphite particles in the negative electrode and a smaller graphite D50 particle size result in a larger specific surface area of ​​the battery, leading to a smaller Rct. Under the same lithium plating risk conditions, this allows for a higher current density, thus permitting higher heating rates to accelerate temperature rise efficiency. Conversely, a lower proportion of secondary graphite particles and a larger graphite D50 particle size result in a higher Rct, necessitating a reduction in the heating current rate to suppress lithium plating risk and improve battery life.

[0204] Therefore, the embodiment of this application controls the multiplier of the heating current. satisfy The mass ratio of secondary graphite particles in the negative electrode of the battery And graphite D50 particle size The method controls the heating current rate C to ensure a balance between self-heating efficiency and lithium plating risk. While maintaining a constant lithium plating risk level, a higher heating current rate is used to heat the battery, improving self-heating efficiency. Based on the battery control method implemented in this application, the self-heating efficiency is improved, the lithium plating risk is reduced, the battery capacity retention rate is increased, fast charging time is shortened, and the battery life of electric vehicles is extended.

[0205] This application also provides a battery control method applied to a charging device, comprising: when the charging interface is connected to an external electrical device and the battery temperature is lower than a first temperature, controlling the battery of the external electrical device to self-heat, wherein the self-heating heating current satisfies: The mass percentage of secondary graphite particles in the negative electrode of the battery is denoted as ρ; the particle size of the D50 graphite in the negative electrode of the battery is denoted as d, in μm; and the heating current ratio is denoted as C.

[0206] The battery control method for charging devices provided in this application embodiment controls the battery to self-heat when the battery temperature is lower than a first temperature. In this application embodiment, the mass ratio of secondary graphite particles in the negative electrode of the battery is denoted as ρ; the D50 particle size of the negative electrode graphite is denoted as d (in μm); and the heating current rate is denoted as C. .

[0207] A higher proportion of secondary graphite particles in the negative electrode and a smaller graphite D50 particle size result in a larger specific surface area of ​​the battery, leading to a smaller Rct. Under the same lithium plating risk conditions, this allows for a higher current density, thus permitting higher heating rates to accelerate temperature rise efficiency. Conversely, a lower proportion of secondary graphite particles and a larger graphite D50 particle size result in a higher Rct, necessitating a reduction in the heating current rate to suppress lithium plating risk and improve battery life.

[0208] Therefore, the embodiment of this application controls the multiplier of the heating current. satisfy The mass ratio of secondary graphite particles in the negative electrode of the battery And graphite D50 particle size The method controls the heating current rate C to ensure a balance between self-heating efficiency and lithium plating risk. While maintaining a constant lithium plating risk level, a higher heating current rate is used to heat the battery, improving self-heating efficiency. Based on the battery control method implemented in this application, the self-heating efficiency is improved, the lithium plating risk is reduced, the battery capacity retention rate is increased, fast charging time is shortened, and the battery life of external electrical devices is extended.

[0209] This application also provides a battery control device that can control the battery to self-heat when the battery temperature is lower than a first temperature, wherein the self-heating current satisfies: The mass percentage of secondary graphite particles in the negative electrode of the battery is denoted as ρ; the D50 particle size of the negative electrode graphite is denoted as d (in μm); and the heating current rate is denoted as C. This battery control device includes, but is not limited to, electric vehicle charging stations, wireless chargers, power banks, charging cabinets, and energy storage cabinets.

[0210] The battery control device provided in this application embodiment controls the rate of heating current. satisfy The mass ratio of secondary graphite particles in the negative electrode of the battery And graphite D50 particle size The heating current rate C is controlled to ensure a balance between self-heating efficiency and lithium plating risk. While maintaining a constant lithium plating risk level, a higher heating current rate is used to heat the battery, improving self-heating efficiency. The battery control device provided in this application improves self-heating efficiency, reduces lithium plating risk, increases battery capacity retention, shortens fast charging time, and extends battery life.

[0211] This application provides a battery pack including a battery; when the battery temperature is lower than a first temperature, it performs self-heating, and the self-heating current satisfies: 5⁄((ρ×d))≤C≤200⁄((ρ×d)); wherein, the mass ratio of the negative electrode graphite secondary particles of the battery is denoted as ρ; the negative electrode graphite D50 particle size of the battery is denoted as d, in μm, and the heating current ratio is denoted as C.

[0212] Figure 6 This is a schematic diagram of the controller provided in this application. Figure 6 As shown, the controller 600 provided in this embodiment includes at least one processor 601 and a memory 602. Optionally, the controller 600 further includes a communication component 603. The processor 601, memory 602, and communication component 603 are connected via a bus.

[0213] In a specific implementation, at least one processor 601 executes computer execution instructions stored in memory 602, causing at least one processor 601 to perform the above-described method.

[0214] The specific implementation process of processor 601 can be found in the above method embodiments, and its implementation principle and technical effect are similar, so it will not be repeated here. In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. A general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly manifested as execution by a hardware processor, or execution by a combination of hardware and software modules in the processor.

[0215] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0216] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0217] This application provides a battery management system, which includes the controller or battery control device described in the above embodiments.

[0218] This application provides a battery pack including a battery and a controller as described in the above embodiments.

[0219] This application provides an electrical device, including the battery pack of the above embodiments, or the controller of the above embodiments.

[0220] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0221] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0222] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0223] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0224] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0225] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0226] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0227] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0228] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0229] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A battery control method, characterized in that, The method includes: When the battery temperature is lower than a first temperature, the battery is controlled to self-heat, and the self-heating current satisfies: ; Wherein, the mass ratio of the negative electrode graphite secondary particles of the battery is denoted as ρ; the particle size of the negative electrode graphite D50 of the battery is denoted as d, in μm; and the multiplier of the heating current is denoted as C.

2. The method according to claim 1, characterized in that, The ratio of the heating current also satisfies: The mass percentage of the binder in the battery is denoted as ω.

3. The method according to claim 2, characterized in that, 。 4. The method according to any one of claims 1-3, characterized in that, The carbon coating thickness of the graphite anode in the battery is m, with the unit being nm. .

5. The method according to any one of claims 1-3, characterized in that, The frequency of the heating current is denoted as f, and the unit is Hz. .

6. The method according to any one of claims 1-3, characterized in that, 。 7. The method according to any one of claims 1-3, characterized in that, 。 8. The method according to any one of claims 1-3, characterized in that, The first temperature is greater than or equal to -30°C and less than or equal to 20°C.

9. The method according to any one of claims 1-3, characterized in that, The waveform of the heating current includes at least one of the following: sine wave, square wave, trapezoidal wave, and triangular wave.

10. The method according to any one of claims 1-3, characterized in that, The mass percentage of the conductive agent in the battery is denoted as . 0 3%.

11. The method according to any one of claims 1-3, characterized in that, The compaction density of the positive electrode of the battery is denoted as γ1, and the unit is g / cm³. 3 2.2 3; and / or, the compaction density of the negative electrode of the battery is denoted as γ2, in g / cm³. 3 1.4 2; And / or, the double-sided areal density of the positive electrode of the battery is denoted as σ1, with units of g / m³. 2 300 1000; and / or, the double-sided areal density of the negative electrode of the battery is denoted as σ2, in g / m³. 2 130 460.

12. A battery pack, characterized in that, Including batteries; When the battery temperature is below a first temperature, it self-heats, and the heating current for self-heating satisfies the following: ; Wherein, the mass ratio of the negative electrode graphite secondary particles of the battery is denoted as ρ; the particle size of the negative electrode graphite D50 of the battery is denoted as d, in μm; and the multiplier of the heating current is denoted as C.

13. A controller, characterized in that, include: Memory, processor; The memory stores computer-executed instructions; The processor executes computer execution instructions stored in the memory, causing the processor to perform the method as described in any one of claims 1-11.

14. A battery pack, characterized in that, Includes a battery, and a controller as described in claim 13.

15. An electrical appliance, characterized in that, This includes the battery pack as described in claim 14, or the controller as described in claim 13.

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