Method and device for determining temperature boundary of lithium ion battery and battery pack

Abstract

The method for determining the temperature boundary of the lithium ion battery comprises the step of determining the temperature boundary corresponding to the current dead lithium precipitation amount based on a preset corresponding relation between the dead lithium precipitation amount of the lithium ion battery and the temperature boundary. According to the method, the to-be-detected lithium ion battery does not need to be disassembled, the dead lithium precipitation amount of the to-be-detected lithium ion battery is determined in situ, and the temperature boundary corresponding to the current dead lithium precipitation amount is determined based on the preset corresponding relation between the dead lithium precipitation amount of the lithium ion battery and the temperature boundary. After the temperature boundary is determined, the temperature which does not exceed the temperature boundary is used as the safe temperature interval, so that the lithium ion battery to be detected is ensured to work in the safe temperature interval, the thermal runaway fault caused by the reduction of the thermal stability of the battery cell is avoided, and the safety and reliability of the whole life cycle of the battery cell are improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a method, apparatus and battery pack for determining the temperature boundary of a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries have been widely used in electric vehicles, unmanned aerial vehicles, energy storage devices, and power tools due to their advantages such as low cost and high energy density. To address range anxiety and slow charging issues, the development of fast charging technology has become a consensus among new energy companies. However, fast charging can easily lead to lithium plating in the battery cell, which can induce internal short circuits, thermal runaway, and other faults, resulting in a decrease in cell safety.

[0003] It is understood that in this application, a single lithium-ion battery may be referred to as a single cell (hereinafter referred to as "cell"). Summary of the Invention

[0004] The purpose of this application is to provide a method, apparatus, and battery pack for determining the temperature boundary of a lithium-ion battery, so as to achieve real-time determination of the temperature boundary of the battery cell. The specific technical solution is as follows:

[0005] The first aspect of this application provides a method for determining the temperature boundary of a lithium-ion battery, the method comprising:

[0006] The current amount of dead lithium deposition in the lithium-ion battery under test is obtained. Based on a preset temperature boundary model of the lithium-ion battery, the temperature boundary corresponding to the current amount of dead lithium deposition is determined. The preset temperature boundary model of the lithium-ion battery is configured to reflect the mapping relationship between the amount of dead lithium deposition and the temperature boundary, and the operating temperature of the lithium-ion battery under test is controlled to not exceed the temperature boundary.

[0007] Based on a pre-defined correlation between the amount of dead lithium deposition in a lithium-ion battery and its temperature boundary, the temperature boundary corresponding to the current amount of dead lithium deposition is determined. This method eliminates the need to disassemble the lithium-ion battery under test. The amount of dead lithium deposition is determined in situ, and the corresponding temperature boundary is established using the pre-defined correlation. Once the temperature boundary is determined, the temperature range not exceeding this boundary is considered the safe temperature range. This ensures the lithium-ion battery operates within a safe temperature range, preventing thermal runaway failures caused by reduced cell thermal stability and contributing to improved cell lifecycle safety and reliability.

[0008] In one or more embodiments of this application, before determining the temperature boundary corresponding to the current dead lithium deposition amount based on a preset lithium-ion battery temperature boundary model, a sample battery pack is obtained. For each sample battery pack, at least one first three-electrode battery and at least one first two-electrode battery are obtained. Cyclic aging tests are performed on the first three-electrode battery and the first two-electrode battery based on the cyclic aging test conditions of the pack. The cyclic aging test is stopped when the dead lithium deposition amount of the first three-electrode battery and the first two-electrode battery reaches a preset threshold, thus obtaining a first sample three-electrode battery and a first sample two-electrode battery. The first dead lithium deposition amount of the first sample three-electrode battery is then obtained. Based on the first dead lithium deposition amount and the first temperature boundary of the first sample two-electrode battery, and the first dead lithium deposition amount of the first sample three-electrode battery and the first temperature boundary of the first sample two-electrode battery, the temperature boundary corresponding to the dead lithium deposition amount under the corresponding environmental conditions and / or operating conditions of the sample battery pack is determined. Cyclic aging tests are performed on the first three-electrode battery and the first two-electrode battery of each sample battery pack to obtain the temperature boundary corresponding to the dead lithium deposition amount under the corresponding environmental conditions and / or operating conditions of each sample battery pack. Based on the temperature boundary corresponding to the dead lithium deposition amount under the corresponding environmental conditions and / or operating conditions of each sample battery pack, a temperature boundary model of lithium-ion battery is constructed.

[0009] Each of the sample battery packs includes a three-electrode battery and a two-electrode battery. The cycle aging test conditions are the same for batteries in the same group. The cycle aging test conditions include environmental conditions and / or operating conditions.

[0010] A temperature boundary model for lithium-ion batteries was constructed to determine the temperature boundary corresponding to the amount of dead lithium deposition. After determining the temperature boundary, the temperature range not exceeding the temperature boundary was defined as the safe temperature range. This ensures that the lithium-ion battery under test operates within a safe temperature range, reduces thermal runaway failures caused by the decrease in the thermal stability of the cell material, and helps improve the safety and reliability of the cell throughout its entire life cycle.

[0011] In one or more embodiments of this application, the first sample three-electrode battery is disassembled to determine the amount of dead lithium deposited in the first sample three-electrode battery. Based on the amount of dead lithium deposited in the first sample three-electrode battery, a first amount of dead lithium deposited is obtained, a heating rate is determined, and the first sample two-electrode battery is heated based on the heating rate. The state of the first sample two-electrode battery is monitored in real time. When the first sample two-electrode battery is in a thermal runaway fault, the temperature at this time is recorded to obtain the temperature boundary of the first sample two-electrode battery. A first temperature boundary is determined based on the temperature boundary of the first sample two-electrode battery.

[0012] In one or more embodiments of this application, before performing a cycle aging test on the first three-electrode battery and the first two-electrode battery based on the cycle aging test conditions of the group, a second sample three-electrode battery is obtained for each sample battery group, and a cycle aging test is performed on the second sample three-electrode battery to obtain the maximum dead lithium deposition amount of the lithium-ion battery under the corresponding environmental conditions and / or operating conditions of the sample battery group, and the preset threshold is determined based on the maximum dead lithium deposition amount of the lithium-ion battery.

[0013] In one or more embodiments of this application, a preset step size is calculated according to the following formula;

[0014]

[0015] Where X is the preset step size, Q is the maximum amount of dead lithium deposited, a is the preset first multiple, and a is a positive number less than 1;

[0016] Calculate the preset threshold using the following formula;

[0017]

[0018] Where Y is a preset threshold and b is a non-negative number that satisfies Y≤Q.

[0019] In one or more embodiments of this application, when at least two first sample three-electrode batteries and at least two first sample two-electrode batteries are obtained, the average value of the dead lithium deposition amount of each first sample three-electrode battery is determined as the first dead lithium deposition amount, and the temperature boundary of each first sample two-electrode battery is determined as the first temperature boundary.

[0020] In one or more embodiments of this application, when one first sample three-electrode battery and one first sample two-electrode battery are obtained, the amount of dead lithium deposited in the first sample three-electrode battery is determined as the first dead lithium deposited amount, and the temperature boundary of the first sample two-electrode battery is determined as the first temperature boundary.

[0021] The second aspect of this application provides a lithium-ion battery manufacturing apparatus for implementing the method for determining the temperature boundary of a lithium-ion battery according to any one of the first aspects above.

[0022] A third aspect of this application provides a battery pack that includes the temperature boundary determination device for the lithium-ion battery provided in the second aspect above.

[0023] In another aspect of this application, an electronic device is provided, including: a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other via the communication bus. The memory stores computer programs; the processor, when executing the program stored in the memory, implements any of the above-described methods for determining the temperature boundary of a lithium-ion battery.

[0024] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements any of the above-described methods for determining the temperature boundary of a lithium-ion battery.

[0025] This application also provides a computer program product containing instructions that, when run on a computer, cause the computer to execute any of the above-described methods for determining the temperature boundary of a lithium-ion battery.

[0026] Beneficial effects of the embodiments in this application:

[0027] This application provides a method, apparatus, and battery pack for determining the temperature boundary of a lithium-ion battery. Based on a preset correspondence between the amount of dead lithium deposition in the lithium-ion battery and the temperature boundary, the method determines the temperature boundary corresponding to the current amount of dead lithium deposition. This method eliminates the need to disassemble the lithium-ion battery under test. The amount of dead lithium deposition in the battery is determined in situ, and the temperature boundary corresponding to the current amount of dead lithium deposition is determined based on the preset correspondence between the amount of dead lithium deposition and the temperature boundary. After determining the temperature boundary, the temperature range not exceeding the temperature boundary is considered a safe temperature range. This ensures that the lithium-ion battery under test operates within a safe temperature range, avoiding thermal runaway failures caused by reduced cell thermal stability, and contributing to improved cell lifecycle safety and reliability.

[0028] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0030] Figure 1 A flowchart illustrating a method for determining the temperature boundary of a lithium-ion battery provided in some embodiments of this application;

[0031] Figure 2A schematic diagram of a first structure of a temperature boundary determination device for a lithium-ion battery provided in some embodiments of this application;

[0032] Figure 3 A second structural schematic diagram of a temperature boundary determination device for a lithium-ion battery provided in some embodiments of this application;

[0033] Figure 4 This is a schematic diagram of the structure of an electronic device provided in some embodiments of this application. Detailed Implementation

[0034] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. The technical solutions described herein are only some embodiments of this application. All other embodiments or other technical solutions obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0035] To determine the temperature boundary of a lithium-ion battery, this application provides a method, apparatus, and battery pack for determining the temperature boundary of a lithium-ion battery. The method for determining the temperature boundary of a lithium-ion battery is described first. This method can be applied to electronic devices that provide temperature boundary determination services for lithium-ion batteries, such as smart charging devices, computers, and servers, including local and cloud servers.

[0036] Lithium-ion batteries are classified into several types based on their cathode materials, such as lithium cobalt oxide batteries, lithium manganese oxide batteries, lithium nickel oxide batteries, ternary lithium batteries, lithium iron phosphate batteries, lithium manganese iron phosphate batteries, or batteries that combine different types of materials (ternary hybrid lithium iron phosphate batteries, ternary hybrid lithium manganese iron phosphate batteries, etc.). Lithium-ion batteries can also be classified according to their shape or structure: cuboid (square-shell cells), prismatic, cylindrical (cylindrical cells), and pouch (soft-pack cells), etc.

[0037] During the charging and discharging process of a lithium-ion battery, lithium ions should be released from the positive electrode during charging, migrate through the electrolyte to the negative electrode, and embed themselves in the layered structure of the negative electrode material. During discharging, they should be released from the negative electrode and return to the positive electrode. If lithium ions are not embedded in the layered structure of the negative electrode material, but instead deposit on the surface of the negative electrode and form metallic lithium, this phenomenon is called lithium plating in lithium-ion batteries.

[0038] When lithium ions are deposited on the surface of the negative electrode to form metallic lithium, some of the metallic lithium loses electrical contact with the electrode due to physical or chemical reasons, or is encapsulated by electrolyte decomposition products or SEI (solid electrolyte interphase), and can no longer be converted back into lithium ions to participate in the cycle through electrochemical reactions. In this application, this type of "inactive" metallic lithium is referred to as "dead lithium".

[0039] Dead lithium deposited in lithium-ion batteries is chemically reactive and readily reacts with the electrolyte at high temperatures or localized hot spots, generating significant heat and triggering self-heating, potentially leading to thermal runaway. Furthermore, dead lithium typically exists in dendritic or granular form, often exhibiting non-uniform structures that can cause uneven current distribution during charging and discharging, resulting in localized overheating. Increased temperature accelerates side reactions, creating a positive feedback loop: heat → faster reaction → even hotter → more vigorous reaction. Therefore, cells with dead lithium deposits exhibit higher localized hot spot temperatures during charging and discharging compared to cells without dead lithium deposits, easily exceeding the thermal stability boundary of the lithium-ion battery and triggering thermal runaway. For ease of explanation, the thermal stability boundary will be referred to as the temperature boundary below.

[0040] The method for determining the temperature boundary of lithium-ion batteries in related technologies is as follows:

[0041] After fully charging the lithium-ion battery using the standard operating procedure (SOP), test it according to the following procedure:

[0042] First, attach the temperature sensing wire to the center of the battery cell surface;

[0043] The lithium-ion battery is then placed horizontally in a hot box and heated to a certain temperature at a rate of 5±2℃ / minute and maintained for 60 minutes. If the lithium-ion battery experiences thermal runaway at this temperature, the temperature recorded by the temperature sensing wire is recorded as the temperature boundary.

[0044] During the research and development process, the inventors discovered that the amount of dead lithium deposition affects the temperature boundary of lithium-ion batteries. Based on this, the inventors developed a method for determining the temperature boundary of lithium-ion batteries based on the correspondence between the amount of dead lithium deposition and the temperature boundary of lithium-ion batteries.

[0045] like Figure 1 As shown, Figure 1 This is a flowchart illustrating the method for determining the temperature boundary of a lithium-ion battery according to this application. The method includes:

[0046] S110, obtain the current amount of dead lithium deposition in the lithium-ion battery to be tested;

[0047] S120, based on the preset temperature boundary model of lithium-ion battery, determines the temperature boundary corresponding to the current amount of dead lithium deposition. The preset temperature boundary model of lithium-ion battery is configured to reflect the mapping relationship between the amount of dead lithium deposition and the temperature boundary.

[0048] S130 controls the operating temperature of the lithium-ion battery under test to not exceed the temperature boundary.

[0049] The temperature at which a lithium-ion battery operates in a target device is called its operating temperature. Target devices include, but are not limited to, electric vehicles, unmanned aerial vehicles (UAVs), home energy storage devices, commercial and industrial energy storage devices, uninterruptible power supplies (UPS), and mobile energy storage devices that utilize lithium-ion batteries. For example, when a lithium-ion battery is flying or charging in an UAV, it is discharged at a rate of 3C or charged at a rate of 1.8C. The temperature of the battery measured by a temperature sensor during the charging and discharging process is recorded as the operating temperature.

[0050] In some optional examples of this application, the current dead lithium deposition of the lithium-ion battery under test can be determined based on the negative electrode potential of the lithium-ion battery under test. Optionally or additionally, the negative electrode potential of the lithium-ion battery under test can be determined based on methods such as Gaussian process regression, symbolic regression, neural networks, convolutional neural networks, recurrent neural networks, empirical formulas, electrochemical mechanism models, etc.

[0051] After obtaining the negative electrode potential of the lithium-ion battery under test, the current amount of dead lithium deposition in the lithium-ion battery under test is calculated by using the lithium deposition side reaction control equation.

[0052] For example, the governing equations for lithium plating side reactions include the Bavo's equation and its variations, the Tafel equation and its variations, etc.

[0053] In this application, a pre-defined temperature boundary model for lithium-ion batteries reflects the mapping relationship between the amount of dead lithium deposition and the temperature boundary under different environments and / or operating conditions. Based on this pre-defined temperature boundary model, the temperature boundary corresponding to the current amount of dead lithium deposition is determined. This eliminates the need to disassemble the lithium-ion battery under test, enabling real-time determination of the amount of dead lithium deposition and the determination of the corresponding temperature boundary based on the pre-defined temperature boundary model. After determining the temperature boundary, temperatures not exceeding this boundary are considered a safe temperature range, ensuring the lithium-ion battery operates within this range. This reduces thermal runaway failures caused by decreased thermal stability of the cell materials, contributing to improved safety and reliability throughout the cell's lifespan. It is understood that in this document, "cell" refers to a single lithium-ion battery.

[0054] The following section describes the method for constructing the pre-defined temperature boundary model for lithium-ion batteries. For ease of explanation, several commonly used terms in this application will be introduced first:

[0055] Lithium-ion batteries include two-electrode batteries and three-electrode batteries. Two-electrode batteries consist of a positive electrode and a negative electrode, which form a closed circuit through an electrolyte. Two-electrode batteries are the most common type of battery in electrochemical research and practical commercial applications.

[0056] A three-electrode battery includes a positive electrode, a negative electrode, and a reference electrode. The reference electrode is an electrode with a stable and known potential, which serves as a reference for accurately measuring the potentials of the positive and negative electrodes.

[0057] For a three-electrode battery, the full cell potential can be characterized by the potential of the positive electrode relative to the negative electrode. The positive electrode potential can be characterized by the potential of the positive electrode relative to the reference electrode, and the negative electrode potential can be characterized by the potential of the negative electrode relative to the reference electrode.

[0058] First, obtain the sample battery set.

[0059] The sample battery set includes multiple sample batteries. The sample batteries in the sample battery set are grouped according to a preset partitioning rule to obtain M sample battery groups. The preset partitioning rule includes environmental conditions and / or battery operating conditions. M is determined based on actual conditions, and this application does not impose specific limitations on it.

[0060] Optional or additional environmental conditions may include ambient temperature and ambient humidity.

[0061] Optional or additional operating conditions may include battery charge and discharge schemes. Charge and discharge schemes include charging schemes and / or discharging schemes. Charging schemes include at least one of the following charging methods: constant current charging, constant current-constant voltage charging, multi-stage constant current charging, pulse charging, etc. Discharging schemes include at least one of the following discharging methods: constant current discharging, pulse discharging, dynamic current discharging, etc.

[0062] As some specific examples, each charging scheme may include at least one charging rate, and each discharging scheme may include at least one discharging rate.

[0063] In one example, environmental conditions include ambient temperature. For instance, the ambient temperature range is -25°C to 65°C.

[0064] In some optional examples of this application, batteries with the same environmental conditions and / or the same operating conditions are grouped together to obtain multiple sample battery packs.

[0065] For example, taking temperature conditions as an example, the ambient temperature range is -25℃ to 65℃. For example, the temperature is divided into 5℃ intervals, and 19 temperature points are tested: -25℃, -20℃, -15℃, -10℃, -5℃, 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃ and 65℃. That is, the sample batteries in the same group are subjected to cyclic aging tests at the same ambient temperature.

[0066] Optionally or additionally, the preset classification rules may further consider battery information, including battery specifications. For example, battery specifications may include at least one of the following: battery type, battery capacity, etc.

[0067] Batteries are classified into several types based on electrolyte composition, positive and negative electrode composition, and separator. Batteries are also classified into several capacities based on their capacity.

[0068] In some cases, battery specifications include the type of battery. When grouping sample batteries in a sample battery set based on battery specifications, sample batteries of the same type are grouped together.

[0069] In other examples, battery specifications include battery capacity. When grouping sample batteries in a sample battery set based on battery specifications, sample batteries with the same capacity are grouped together.

[0070] In other examples, battery specifications include the type of battery and the capacity of the battery. When grouping sample batteries in a sample battery set based on battery specifications, sample batteries of the same type and capacity are grouped together.

[0071] For each group of sample battery packs, a three-electrode battery is assembled to obtain a three-electrode battery with defined positive and negative electrode materials, electrolyte, and structure. A two-electrode battery is assembled to obtain a two-electrode battery with defined positive and negative electrode materials, electrolyte, and structure. A sample dataset is determined based on each sample battery pack.

[0072] For each sample battery pack, at least one first three-electrode battery and at least one first two-electrode battery are obtained. Cyclic aging tests are performed on the first three-electrode battery and the first two-electrode battery of the group. The cyclic aging test is stopped when the amount of dead lithium deposited in the first three-electrode battery and the first two-electrode battery reaches a preset threshold, thus obtaining the first sample three-electrode battery and the first sample two-electrode battery.

[0073] The preset threshold can be determined based on actual conditions. For example, the maximum amount of dead lithium deposited in each sample battery pack can be determined using sample battery packs, and then the preset threshold can be determined based on the maximum amount of dead lithium deposited. To make the solution of this application clearer, the determination of the preset threshold is described in detail below.

[0074] In this application, cycle aging refers to the phenomenon of performance degradation in lithium-ion batteries after repeated charge-discharge cycles, caused by irreversible chemical and structural changes, resulting in capacity decay, increased internal resistance, and decreased charge-discharge efficiency. Cycle aging leads to changes in the battery's operating performance parameters, which include at least one of the following: voltage, current, and temperature. Optionally, the battery's operating performance parameters may also include: magnetic field and electrochemical AC impedance. Voltage includes the full-cell potential value, and current includes charging current and discharging current values. During the lithium-ion battery cycle aging test, cycle aging test data is obtained by collecting the battery's operating performance parameters.

[0075] For the determination of dead lithium deposition in lithium-ion batteries, the amount of dead lithium deposition in the first sample three-electrode battery can be determined based on offline characterization methods. Offline characterization methods include, but are not limited to, optical microscopy, neutron diffraction, nuclear magnetic resonance, mass spectrometry titration, etc.

[0076] A temperature rise test was performed on the first sample two-electrode battery until thermal runaway occurred, and the temperature at this point was recorded to obtain the temperature boundary of the first sample two-electrode battery. A first temperature boundary was determined based on the temperature boundary of the first sample two-electrode battery.

[0077] Since the first sample three-electrode battery and the first sample two-electrode battery were subjected to cyclic aging tests under the same cyclic aging test conditions, and the cyclic aging test stop conditions for the first sample three-electrode battery and the first sample two-electrode battery were the same, the first temperature boundary can be used as the temperature boundary corresponding to the first dead lithium deposition amount under the environmental conditions and / or the operating conditions corresponding to the sample battery pack.

[0078] After obtaining the amount of dead lithium deposition and temperature boundaries of lithium-ion batteries under different temperatures and operating conditions, a pre-defined construction algorithm is used to establish the correspondence between the amount of dead lithium deposition and temperature boundaries at different temperatures, so that each amount of dead lithium deposition has a corresponding temperature boundary. The pre-defined construction algorithm strategy includes, but is not limited to, machine learning algorithms such as linear regression, nonlinear regression, and Gaussian process regression.

[0079] A temperature boundary model for lithium-ion batteries was constructed to determine the temperature boundary corresponding to the amount of dead lithium deposition. After determining the temperature boundary, the temperature range not exceeding the temperature boundary was defined as the safe temperature range. This ensures that the lithium-ion battery under test operates within a safe temperature range, reduces thermal runaway failures caused by the decrease in the thermal stability of the cell material, and helps improve the safety and reliability of the cell throughout its entire life cycle.

[0080] Regarding the preset threshold for the amount of dead lithium deposited in lithium-ion batteries as described above, in some optional examples of this application, for each sample battery pack, a second sample three-electrode battery is obtained, and a cycle aging test is performed on the second sample three-electrode battery to obtain the maximum amount of dead lithium deposited in the lithium-ion battery under the corresponding environmental conditions and / or operating conditions of the sample battery pack. Then, the preset threshold is determined based on the maximum amount of dead lithium deposited in the lithium-ion battery.

[0081] The maximum amount of dead lithium deposited in the lithium-ion batteries of each sample battery pack was obtained under different environmental conditions and / or operating conditions. Then, a preset threshold was determined based on the maximum amount of dead lithium deposited.

[0082] In one example, the preset threshold is any value that is not greater than the maximum amount of dead lithium deposited.

[0083] In another example, the preset step size is calculated according to the following formula;

[0084]

[0085] Where X is the preset step size, Q is the maximum amount of dead lithium deposited, a is the preset first multiple, and a is a positive number less than 1;

[0086] Calculate the preset threshold using the following formula;

[0087]

[0088] Where Y is a preset threshold and b is a non-negative number that satisfies Y≤Q.

[0089] For example, the preset first multiple includes, but is not limited to, 1%, 2%, 3%, 10%, etc., and the specific multiple is determined based on the actual situation.

[0090] In one example, the first multiple is preset to 10%. Integer multiples of the preset step size are used as preset thresholds. For example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% of the maximum dead lithium precipitation are set as preset thresholds.

[0091] For each preset threshold, the cycle aging test will stop when the amount of dead lithium deposited in the first three-electrode battery and the first two-electrode battery reaches the preset threshold, thus obtaining the first sample three-electrode battery and the first sample two-electrode battery.

[0092] In some embodiments of this application, before performing a temperature rise test on the first sample two-electrode battery, a temperature rise rate is determined, and the temperature rise test on the first sample two-electrode battery is performed based on the temperature rise rate.

[0093] For example, the temperature rise test is performed at a rising rate, which can be 1℃ / h or 2℃ / h. In one example, the rising rate is 1℃ / h.

[0094] In some optional examples of this application, multiple first three-electrode cells and multiple first two-electrode cells are used to test the amount of dead lithium deposited and the temperature boundary.

[0095] When the amount of dead lithium deposited in multiple first three-electrode batteries and multiple first two-electrode batteries reaches a preset threshold, the cyclic aging test is stopped, resulting in at least one first sample three-electrode battery and at least one first sample two-electrode battery.

[0096] Optional or additional, in the case of obtaining at least two first sample three-electrode cells and at least two first sample two-electrode cells:

[0097] The average value of dead lithium deposition in each of the first sample three-electrode batteries is taken as the first dead lithium deposition.

[0098] The average temperature at which the two-electrode batteries of each first sample experience thermal runaway is determined as the first temperature boundary.

[0099] The first dead lithium deposition amount and the first temperature boundary are thus determined based on multiple sample cells, thereby improving the accuracy of the determined first dead lithium deposition amount and the first temperature boundary.

[0100] Optionally or additionally, in the case of obtaining one first sample three-electrode battery and one first sample two-electrode battery, the amount of dead lithium deposition in the first sample three-electrode battery is determined as the first dead lithium deposition amount, and the temperature boundary of the first sample two-electrode battery is determined as the first temperature boundary.

[0101] Optionally or additionally, the amount of dead lithium deposited in a lithium-ion battery can be assessed based on a preset potential evaluation method and cycle aging test data to evaluate the battery's negative electrode potential.

[0102] Preset potential assessment methods may include Gaussian process regression, symbolic regression, neural network models, empirical formulas, electrochemical mechanism models, etc. Neural network models include, but are not limited to, convolutional neural networks and recurrent neural networks.

[0103] For example, the negative electrode potential of a battery is evaluated based on cyclic aging test data using a neural network algorithm.

[0104] Optionally or additionally, the neural network algorithm is implemented through a pre-trained negative electrode potential prediction model. This model reflects the mapping relationship between historical cycle aging test data and the actual negative electrode potential value, and is used to predict the negative electrode potential value of the battery at historical moments. Cycle aging test data characterizes the battery's performance parameters, including at least one of the following: voltage, current, and temperature. Optionally, the battery's performance parameters may also include: magnetic field and electrochemical AC impedance. Voltage includes the full-cell potential value, and current includes charging current and discharging current values, etc.

[0105] In other words, after obtaining the pre-trained negative electrode potential prediction model, the cyclic aging test data during the actual application of the battery can be acquired in real time. This cyclic aging test data can be input into the pre-trained negative electrode potential prediction model, because the pre-trained negative electrode potential prediction model can reflect the mapping relationship between the cyclic aging test data of the battery at historical moments and the actual negative electrode potential value. After receiving the cyclic aging data during the battery's cyclic aging process, the pre-trained negative electrode potential prediction model can determine the actual negative electrode potential value corresponding to the cyclic aging data, thereby predicting the battery's negative electrode potential.

[0106] For each battery, after predicting the negative electrode potential in real time, the amount of dead lithium deposited in that battery is determined based on the predicted negative electrode potential.

[0107] The method for determining the amount of dead lithium deposited in a battery based on the predicted negative electrode potential is illustrated in the following embodiment.

[0108] In some optional examples of this application, after obtaining each negative electrode potential value, the lithium plating side reaction current density is calculated using the lithium plating side reaction governing equation. Exemplary examples include, but are not limited to, the Bavo's equation and its variations, the Tafel equation and its variations, etc.

[0109] Optionally, the lithium plating side reaction current density can be calculated using the Bavo's equation. The Bavo's equation is shown in the following formula:

[0110]

[0111] The current density for the lithium plating side reaction is... The reaction rate constant is... This refers to the electrolyte concentration. It is Faraday's constant. The negative pole transfer coefficient. The gas constant is For battery temperature, This is the negative electrode potential value.

[0112] After calculating the lithium plating side reaction current density, the lithium plating side reaction current is calculated using the following formula.

[0113]

[0114] This is the current for the lithium plating side reaction. The radius of the negative electrode particle is denoted as . It is twice the length of the negative electrode plate. The width of the negative electrode plate. The thickness of the negative electrode sheet. The negative solid phase porosity.

[0115] By combining the lithium plating side reaction current, the total amount of lithium plating over a historical period is calculated using the ampere-hour integration method.

[0116]

[0117] and These are the start and end times of the historical time period, respectively. This represents the total amount of lithium deposited due to lithium deposition side reactions.

[0118] Total lithium deposition includes reversible lithium deposition and dead lithium deposition. Reversible lithium will be reinserted into the battery during charging and discharging without causing battery capacity loss. Dead lithium, on the other hand, is difficult to re-participate in the reaction, causing battery capacity loss and affecting battery life.

[0119] After calculating the total lithium deposition, the predetermined ratio of dead lithium deposition to the total lithium deposition is obtained. Then, the product of the total lithium deposition and this ratio is calculated to obtain the dead lithium deposition.

[0120] The ratio of dead lithium deposition to total lithium deposition was determined based on prior testing.

[0121] In some optional examples of this application, for each sample battery pack, a third sample three-electrode battery is obtained, and a cycle aging test is performed on the third sample three-electrode battery to obtain the maximum dead lithium deposition and total lithium deposition of the lithium-ion battery under the corresponding environmental conditions and / or operating conditions of the sample battery pack. Based on the total lithium deposition corresponding to the dead lithium deposition under the corresponding environmental conditions and / or operating conditions of each sample battery pack, the total lithium deposition corresponding to the dead lithium deposition under different environmental conditions and / or different operating conditions of the lithium-ion battery is constructed, and then the ratio of dead lithium deposition to total lithium deposition under different environmental conditions and / or different operating conditions is determined.

[0122] Batteries under different environmental and operating conditions are obtained in advance, and after disassembly, the amount of dead lithium precipitation in a time period under different operating conditions is determined by mass spectrometry titration technology, nuclear magnetic resonance technology, etc.

[0123] In addition, for each operating condition, the total lithium deposition within the same time period under that operating condition is calculated according to the above method, and then the ratio of dead lithium deposition to total lithium deposition under the same operating condition is calculated.

[0124] Understandably, after obtaining the total lithium plating amount of the battery, the ratio of the battery's operating conditions is obtained, and the product of this ratio and the total lithium plating amount of the battery is calculated to obtain the dead lithium plating amount of the battery, as shown in the following formula:

[0125]

[0126] Indicates the amount of dead lithium deposited. This represents the ratio of dead lithium deposits to the total amount of lithium deposited.

[0127] The amount of dead lithium deposited was determined by the governing equation of the lithium plating side reaction.

[0128] This application provides a model training device for implementing any of the above-described methods for determining the temperature boundary of a lithium-ion battery.

[0129] like Figure 2 As shown, in some embodiments of this application, the device includes:

[0130] The acquisition module 210 is configured to acquire the current amount of dead lithium deposition in the lithium-ion battery under test.

[0131] The determination module 220 is configured to determine the temperature boundary corresponding to the current amount of dead lithium deposition based on a preset temperature boundary model of the lithium-ion battery. The preset temperature boundary model of the lithium-ion battery is configured to reflect the mapping relationship between the amount of dead lithium deposition and the temperature boundary.

[0132] The control module 230 is configured to control the operating temperature of the lithium-ion battery under test to not exceed the temperature boundary.

[0133] like Figure 3 As shown, in some optional examples of this application, the apparatus further includes:

[0134] Module 240 is configured as follows:

[0135] Before determining the temperature boundary corresponding to the current amount of dead lithium deposition based on a preset temperature boundary model of the lithium-ion battery, a temperature boundary model of the lithium-ion battery is constructed; the construction module 240 is specifically configured as follows:

[0136] Obtain sample battery packs, each sample battery pack including three-electrode batteries and two-electrode batteries; the cycle aging test conditions of batteries in the same group are the same, including environmental conditions and / or operating conditions.

[0137] For each sample battery pack, at least one first three-electrode battery and at least one first two-electrode battery are obtained;

[0138] Cyclic aging tests were performed on the first three-electrode battery and the first two-electrode battery based on the cyclic aging test conditions of this group. The cyclic aging test was stopped when the amount of dead lithium deposited in the first three-electrode battery and the first two-electrode battery reached a preset threshold, and the first sample three-electrode battery and the first sample two-electrode battery were obtained.

[0139] The first dead lithium deposition amount of the first sample three-electrode battery and the first temperature boundary of the first sample two-electrode battery were obtained.

[0140] Based on the first dead lithium deposition amount of the first sample three-electrode battery and the first temperature boundary of the first sample two-electrode battery, the temperature boundary corresponding to the dead lithium deposition amount under the corresponding environmental conditions and / or operating conditions of the sample battery pack is determined.

[0141] Cyclic aging tests were conducted on the first three-electrode battery and the first two-electrode battery of each sample battery pack to obtain the temperature boundary corresponding to the amount of dead lithium deposition under the environmental conditions and / or operating conditions of each sample battery pack.

[0142] A temperature boundary model for lithium-ion batteries is constructed based on the temperature boundary corresponding to the amount of dead lithium deposition under the environmental and / or operating conditions of each sample battery pack.

[0143] In some optional examples of this application, build module 240 is specifically configured as follows:

[0144] The first sample three-electrode battery was disassembled to determine the amount of dead lithium deposited in the first sample three-electrode battery;

[0145] The first dead lithium deposition amount is obtained based on the dead lithium deposition amount of the first sample three-electrode battery;

[0146] The heating rate is determined, and the temperature of the first sample two-electrode battery is increased based on the heating rate. The state of the first sample two-electrode battery is detected in real time. When the first sample two-electrode battery is in thermal runaway fault, the temperature at this time is recorded to obtain the temperature boundary of the first sample two-electrode battery.

[0147] The first temperature boundary is determined based on the temperature boundary of the first sample two-electrode battery.

[0148] In some optional examples of this application, build module 240 is specifically configured as follows:

[0149] Before performing cycle aging tests on the first three-electrode battery and the first two-electrode battery based on the cycle aging test conditions of the group, a preset threshold is determined; for each sample battery group, a second sample three-electrode battery is obtained, and a cycle aging test is performed on the second sample three-electrode battery to obtain the maximum amount of dead lithium deposition of the lithium-ion battery under the corresponding environmental conditions and / or operating conditions of the sample battery group.

[0150] A preset threshold is determined based on the maximum amount of dead lithium deposited in a lithium-ion battery.

[0151] In some optional examples of this application, build module 240 is specifically configured as follows:

[0152] Calculate the preset step size using the following formula;

[0153]

[0154] Where X is the preset step size, Q is the maximum amount of dead lithium deposited, a is the preset first multiple, and a is a positive number less than 1;

[0155] Calculate the preset threshold using the following formula;

[0156]

[0157] Where Y is a preset threshold and b is a non-negative number that satisfies Y≤Q.

[0158] In some optional examples of this application, build module 240 is specifically configured as follows:

[0159] Given at least two first sample three-electrode batteries and at least two first sample two-electrode batteries, the average value of the dead lithium deposition amount of each first sample three-electrode battery is determined as the first dead lithium deposition amount.

[0160] The temperature boundary of each first sample's two-electrode battery is defined as the first temperature boundary;

[0161] In some optional examples of this application, build module 240 is specifically configured as follows:

[0162] Given one first sample three-electrode battery and one first sample two-electrode battery, the amount of dead lithium deposited in the first sample three-electrode battery is determined as the first dead lithium deposited amount; the temperature boundary of the first sample two-electrode battery is determined as the first temperature boundary.

[0163] This application also provides an electronic device, such as... Figure 4As shown, it includes a processor 401, a communication interface 402, a memory 403, and a communication bus 404, wherein the processor 401, the communication interface 402, and the memory 403 communicate with each other through the communication bus 404.

[0164] Memory 403 is used to store computer programs;

[0165] When processor 401 executes the program stored in memory 403, it performs the following steps:

[0166] Obtain the current amount of dead lithium deposited in the lithium-ion battery under test;

[0167] Based on the preset temperature boundary model of lithium-ion battery, the temperature boundary corresponding to the current amount of dead lithium deposition is determined. The preset temperature boundary model of lithium-ion battery is configured to reflect the mapping relationship between the amount of dead lithium deposition and the temperature boundary.

[0168] The operating temperature of the lithium-ion battery under test should be controlled to not exceed the temperature limit.

[0169] The communication bus mentioned in the above electronic devices can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This communication bus can be divided into address bus, data bus, control bus, etc. For ease of illustration, only one thick line is used to represent it in the diagram, but this does not mean that there is only one bus or one type of bus.

[0170] The communication interface is used for communication between the aforementioned electronic devices and other devices.

[0171] The memory may include random access memory (RAM) or non-volatile memory (NVM), such as at least one disk storage device. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor.

[0172] The processors mentioned above can be general-purpose processors, including central processing units (CPUs), network processors (NPs), etc.; they can also be digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0173] In another embodiment provided in this application, a computer-readable storage medium is also provided, which stores a computer program that, when executed by a processor, implements the steps of any of the above-described methods for determining the temperature boundary of a lithium-ion battery.

[0174] In another embodiment provided in this application, a computer program product containing instructions is also provided, which, when run on a computer, causes the computer to execute any of the lithium-ion battery temperature boundary determination methods described in the above embodiments.

[0175] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid state disk (SSD)).

[0176] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0177] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the embodiments of devices, battery packs, electronic devices, computer-readable storage media, and computer programs containing instructions are basically similar to the method embodiments, and therefore the descriptions are relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0178] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A method for determining the temperature boundary of a lithium-ion battery, characterized in that, The method includes: Obtain the current amount of dead lithium deposited in the lithium-ion battery under test; Based on a preset temperature boundary model of lithium-ion batteries, the temperature boundary corresponding to the current amount of dead lithium deposition is determined. The preset temperature boundary model of lithium-ion batteries is configured to reflect the mapping relationship between the amount of dead lithium deposition and the temperature boundary. The operating temperature of the lithium-ion battery under test is controlled to not exceed the temperature boundary.

2. The method according to claim 1, characterized in that, Before determining the temperature boundary corresponding to the current amount of dead lithium deposition based on the preset temperature boundary model of the lithium-ion battery, the method further includes: A temperature boundary model for a lithium-ion battery is constructed, and the method for constructing the temperature boundary model for a lithium-ion battery includes: Obtain sample battery packs, each of which includes three-electrode batteries and two-electrode batteries. The cycle aging test conditions for batteries in the same group are the same, including environmental conditions and / or operating conditions. For each of the sample battery packs, at least one first three-electrode battery and at least one first two-electrode battery are obtained; Cyclic aging tests were performed on the first three-electrode battery and the first two-electrode battery based on the cyclic aging test conditions of this group. The cyclic aging test was stopped when the amount of dead lithium deposited in the first three-electrode battery and the first two-electrode battery reached a preset threshold, and the first sample three-electrode battery and the first sample two-electrode battery were obtained. The first dead lithium deposition amount of the first sample three-electrode battery and the first temperature boundary of the first sample two-electrode battery are obtained. Based on the first dead lithium deposition amount of the first sample three-electrode battery and the first temperature boundary of the first sample two-electrode battery, the temperature boundary corresponding to the dead lithium deposition amount is determined under the environmental conditions and / or operating conditions corresponding to the sample battery pack. Cyclic aging tests were conducted on the first three-electrode battery and the first two-electrode battery of each sample battery pack to obtain the temperature boundary corresponding to the amount of dead lithium deposition under the environmental conditions and / or operating conditions of each sample battery pack. A temperature boundary model for lithium-ion batteries is constructed based on the temperature boundary corresponding to the amount of dead lithium deposition under the environmental and / or operating conditions of each sample battery pack.

3. The method according to claim 2, characterized in that, The process of obtaining the first dead lithium deposition amount of the first sample three-electrode battery and the first temperature boundary of the first sample two-electrode battery includes: The first sample three-electrode battery was disassembled to determine the amount of dead lithium deposited in the first sample three-electrode battery. Based on the amount of dead lithium deposited in the first sample three-electrode battery, the first amount of dead lithium deposited is obtained; The heating rate is determined, and the first sample two-electrode battery is heated based on the heating rate. The state of the first sample two-electrode battery is detected in real time. When the first sample two-electrode battery is in thermal runaway fault, the temperature at this time is recorded to obtain the temperature boundary of the first sample two-electrode battery. The first temperature boundary is determined based on the temperature boundary of the first sample two-electrode battery.

4. The method according to claim 2 or 3, characterized in that, Prior to the step of performing cycle aging tests on the first three-electrode battery and the first two-electrode battery based on the cycle aging test conditions of this set, the method further includes: Determining the preset threshold includes: For each sample battery pack, a second sample three-electrode battery is obtained, and a cycle aging test is performed on the second sample three-electrode battery to obtain the maximum amount of dead lithium deposition of the lithium-ion battery under the corresponding environmental conditions and / or operating conditions of the sample battery pack. The preset threshold is determined based on the maximum amount of dead lithium deposited in the lithium-ion battery.

5. The method according to claim 4, characterized in that, Determining the preset threshold based on the maximum dead lithium deposition of the lithium-ion battery includes: Calculate the preset step size using the following formula; Where X is the preset step size, Q is the maximum amount of dead lithium deposited, a is the preset first multiple, and a is a positive number less than 1; Calculate the preset threshold using the following formula; Where Y is a preset threshold and b is a non-negative number that satisfies Y≤Q.

6. The method according to claim 3, characterized in that, In the case of obtaining at least two first sample three-electrode batteries and at least two first sample two-electrode batteries, the step of obtaining the first dead lithium deposition amount based on the dead lithium deposition amount of the first sample three-electrode batteries includes: The average value of the dead lithium deposition amount of each of the first sample three-electrode batteries is determined as the first dead lithium deposition amount; The determination of the first temperature boundary based on the temperature boundary of the first sample two-electrode battery includes: The temperature boundary of each of the two electrode cells of the first sample is defined as the first temperature boundary.

7. The method according to claim 3, characterized in that, In the case of obtaining one first sample three-electrode battery and one first sample two-electrode battery, the step of obtaining the first dead lithium deposition amount based on the dead lithium deposition amount of the first sample three-electrode battery includes: The amount of dead lithium deposited in the first sample three-electrode battery is determined as the first dead lithium deposit amount; The determination of the first temperature boundary based on the temperature boundary of the first sample two-electrode battery includes: The temperature boundary of the first sample two-electrode battery is defined as the first temperature boundary.

8. A device for determining the temperature boundary of a lithium-ion battery, characterized in that, The device is used to implement the method for determining the temperature boundary of a lithium-ion battery as described in any one of claims 1-7.

9. A battery pack, characterized in that, Includes a temperature boundary determination device for a lithium-ion battery as described in claim 8.

10. An electronic device, characterized in that, It includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; A processor, when executing a program stored in memory, implements the steps of the method described in any one of claims 1-7.

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