Battery cell heating system and thermal simulation method of heating device

Abstract

The invention discloses a battery cell heating system which comprises a heating device, and the heating device comprises a current input interface, a current output interface, a rectangular coil and a rectangular heating cavity. The current input interface and the current output interface are both used for connecting a high-frequency alternating current source; the rectangular coil is formed by winding a rectangular copper pipe; the rectangular heating cavity is a cavity enveloped by the rectangular coil and is used for accommodating a battery cell; and when high-frequency alternating current is introduced into the rectangular coil, a space magnetic field is generated in the rectangular heating cavity, so that the battery core arranged in the rectangular heating cavity induces eddy current and is heated. The shape of a rectangular heating cavity formed by the rectangular coil in an enveloping mode is matched with the height of a common rectangular battery cell. By adopting the structure, the distribution of the generated space magnetic field is matched with the appearance of the battery cell, eddy current can be more uniformly distributed in the battery cell body, the problem of local overheating or heating dead angles is effectively avoided, the heating quality is improved, and the service life of the battery is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery thermal management, in particular to a battery cell heating system and a heating device thermal simulation method. BACKGROUND

[0002] In recent years, thanks to the rapid development of new energy technology, new energy batteries, especially lithium batteries, have become a hot topic in research and engineering applications due to their high energy density and long cycle life. However, the working performance, cycle life, and safety of lithium batteries are closely related to temperature. In low temperature environments (usually below 0℃), the effective available capacity of lithium batteries is greatly reduced, the charge and discharge power is decreased, and lithium precipitation occurs, which can even prevent the battery from working normally. The above factors make the ideal working temperature window a major problem restricting the development of lithium batteries. To expand the ideal working temperature window of lithium batteries, one effective way is to artificially heat the battery cells to have a more suitable working temperature in low temperature environments. To evaluate the feasibility of the battery cell heating method, stable heating temperature and good heating uniformity must be obtained in a laboratory environment, and a series of battery cell tests must be conducted on this basis.

[0003] Currently, the methods for heating lithium batteries in low temperature environments mainly include external heating and internal heating. The external heating method wraps a heating film or arranges a PTC heater outside the battery module to transfer heat to the battery cells through conduction and convection. However, this method has low heat conduction efficiency, slow heating speed, and uneven temperature distribution. The internal heating method includes self-heating and electromagnetic induction heating. The self-heating method generates Joule heat inside the battery by applying an alternating current, but this method cannot accurately control the heating effect and may cause irreversible damage to the battery. The electromagnetic induction heating method uses electromagnetic induction principles to arrange excitation coils outside or inside the battery cells to generate eddy currents for heating. This method has the advantages of high heating efficiency and fast heating speed, and is currently the most commonly used method.

[0004] The existing electromagnetic induction heating method generally uses a large area coil to heat multiple lithium batteries at the same time. For example, as shown in patent CN202323450142.1, this method cannot accurately control the heating effect of a single battery cell, and the heating uniformity is poor. In addition, the current design of induction heating coils lacks specificity and usually relies on experience for general design, which cannot guarantee the heating effect. Moreover, there is a lack of efficient and accurate multi-physical field coupling simulation to predict and evaluate the heating temperature and uniformity effect. SUMMARY

[0005] To overcome the above technical defects, the present application provides a battery cell heating system and a heating device thermal simulation method.

[0006] To solve the above problems, the present invention is implemented according to the following technical solution:

[0007] In a first aspect, the present invention provides a battery cell heating system, the battery cell heating system comprising a heating device, the heating device comprising: a current input interface, a current output interface, a rectangular coil, and a rectangular heating cavity; the current input interface and the current output interface are both used to connect to a high-frequency alternating current source; the rectangular coil is wound from a rectangular copper tube; the rectangular heating cavity is a cavity enclosed by the rectangular coil and is used to accommodate the battery cell; wherein, when a high-frequency alternating current is applied to the rectangular coil, a spatial magnetic field is generated within the rectangular heating cavity, causing the battery cell placed therein to be heated by induced eddy currents.

[0008] In conjunction with the first aspect, the present invention provides a first specific implementation of the first aspect, wherein the shape of the rectangular heating cavity is adapted to the rectangular structure of the battery cell to be heated so that the spatial magnetic field is uniformly distributed, thereby ensuring that the eddy currents induced by the battery cell to be heated are uniformly distributed.

[0009] In conjunction with the first aspect, the present invention provides a third specific implementation of the first aspect. Specifically, a plurality of temperature sensors and a main controller are provided. The plurality of temperature sensors are respectively arranged on the inner and outer sides of the battery cell to be heated. The temperature sensors are all connected to the main controller, which performs on / off control of the high-frequency alternating current source by judging the temperature.

[0010] In conjunction with the first aspect, the present invention provides a fourth specific implementation of the first aspect. Specifically, the main controller is configured to: push the battery cell to be heated into the rectangular heating cavity and detect the initial temperature of the battery cell to be heated; preset a temperature threshold and a heating non-uniformity threshold; when the initial temperature is less than the preset temperature threshold, control the rectangular coil to pass a high-frequency alternating current to put the rectangular coil into a heating state to heat the battery cell to be heated; during the heating process, detect the real-time temperature and real-time heating non-uniformity of the battery cell to be heated; when the real-time temperature is not less than the preset temperature threshold or the real-time heating non-uniformity is not less than the heating non-uniformity threshold, control the rectangular coil to disconnect the high-frequency alternating current to put the rectangular coil into a zero-current steady state and end the heating.

[0011] In conjunction with the first aspect, the present invention provides a fifth specific implementation of the first aspect, wherein the heating non-uniformity is defined as the ratio of the absolute value of the difference between the inner and outer temperatures of the battery cell to be heated to a preset temperature threshold; wherein the preset temperature threshold is the final temperature value that the battery cell to be heated is expected to reach at the end of the heating process.

[0012] Secondly, the present invention also provides a thermal simulation method for a heating device, comprising the following steps:

[0013] Step 1: Model Building

[0014] A rectangular induction coil model and a battery cell model are established in a multiphysics simulation software. The rectangular induction coil model includes parameters such as length, width, number of coil turns, and cross-sectional dimensions of a rectangular copper tube.

[0015] Step 2: Setting Material Properties

[0016] Assign copper material properties to the rectangular induction coil model, including electrical conductivity and relative permeability; assign material properties to the battery cell model;

[0017] Step 3: Setting up the physics field

[0018] The rectangular heating cavity enveloped by the rectangular induction coil is set as the magnetic field calculation domain to solve for the spatial magnetic field distribution;

[0019] A high-frequency alternating current excitation is applied to the rectangular induction coil model, the current amplitude and frequency are set, and the current input interface and current output interface are set as the current inflow end and the current outflow end, respectively.

[0020] Electromagnetic field equations are set for the battery cell model to simulate eddy current induction and to couple electromagnetic thermophysical fields.

[0021] Step 4: Thermal Setup

[0022] The initial temperature and ambient temperature are set for the battery cell model, and the thermal convection coefficient on the surface of the battery cell is defined;

[0023] The area outside the rectangular induction coil is set as a thermally insulating boundary condition.

[0024] Step 5: Solver Setup

[0025] The cell model is meshed, and the mesh is refined at the edges and corners of the cell.

[0026] The solver is configured to first perform frequency domain electromagnetic field analysis to obtain eddy current distribution and heat sources;

[0027] Then, transient thermal analysis is performed, and the total simulation time and time step are set to obtain the time-varying temperature distribution of the battery cell during the heating process.

[0028] Step Six: Results Analysis

[0029] The heating non-uniformity of the battery cell is calculated based on the simulation results, and a dynamic temperature change curve and a temperature distribution cloud map are generated.

[0030] In conjunction with the second aspect, the present invention provides a first specific implementation of the second aspect. Specifically, the cell model adopts a layered equivalent model, which includes at least an inner layer and an outer layer of the cell, and assigns different electrical conductivity, specific heat capacity, density and thermal conductivity properties to each layer respectively.

[0031] In conjunction with the second aspect, the present invention provides a second specific implementation of the second aspect, specifically, the solver configuration includes step-by-step setting of frequency domain and transient states to handle high-frequency alternating current and time-varying heating processes.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] By employing a rectangular coil wound with a rectangular copper tube and passing a high-frequency alternating current through it, eddy currents are directly generated inside the battery cell using the principle of electromagnetic induction for heating. This achieves non-contact internal heating, where heat energy is generated within the battery cell itself, avoiding heat loss associated with traditional external heat conduction methods, thus significantly improving heating efficiency and speed. The rectangular heating cavity formed by the rectangular coil is highly compatible with the shape of common rectangular battery cells. This structure ensures that the generated spatial magnetic field distribution matches the shape of the battery cell, guaranteeing a more uniform distribution of eddy currents within the cell and effectively avoiding localized overheating or heating dead zones, thereby improving heating quality and battery life.

[0034] Using rectangular cross-section copper tubing as the coil material not only provides excellent conductivity but also offers higher structural strength than round wires of the same size, resulting in a more stable coil that is less prone to deformation. Furthermore, the rectangular cross-section allows for a larger conductor cross-sectional area and tighter winding within a limited space, contributing to improved power density and space utilization.

[0035] Compared to a circular solenoid structure, a rectangular coil is better suited to the rectangular structure of the battery cell to be heated, and can induce a more uniform spatial magnetic field in the heating cavity, thereby ensuring the uniformity of heating. When heating the same battery cell, the cross-sectional area of ​​the rectangular coil is significantly smaller than that of the circular solenoid, and the required copper tube length will be significantly shorter than that of the circular solenoid, thereby reducing the cost of the coil and maximizing the balance between cost and heating effect. Attached Figure Description

[0036] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein:

[0037] Figure 1 This is a schematic diagram of the overall structure of the heating device of the present invention. Figure 1 .

[0038] Figure 2 This is a schematic diagram of the heating device of the present invention;

[0039] Figure 3 This is a simulation result of the actual cell temperature during the cell heating process according to the present invention;

[0040] Figure 4 This is a schematic diagram of the overall structure of the heating device of the present invention. Figure 2 .

[0041] In the diagram: 1-Current input interface; 2-Current output interface; 3-Rectangular coil; 4-Rectangular heating cavity; 5-Battery cell tab; 6-Battery cell to be heated. Detailed Implementation

[0042] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0043] like Figures 1-4 As shown, this invention provides a thermal simulation method for a battery cell heating system and heating device.

[0044] Example 1

[0045] like Figure 1 As shown, a battery cell heating system includes a heating device, characterized in that the heating device comprises: a current input interface 1, a current output interface 2, a rectangular coil 3, and a rectangular heating cavity 4; the current input interface 1 and the current output interface 2 are both used to connect to a high-frequency alternating current source; the rectangular coil 3 is wound from a rectangular copper tube; the rectangular heating cavity 4 is a cavity enclosed by the rectangular coil 3, used to accommodate the battery cell 6; wherein, when a high-frequency alternating current is applied to the rectangular coil 3, a spatial magnetic field is generated in the rectangular heating cavity 4, causing the battery cell 6 placed therein to be heated by induced eddy currents.

[0046] Specifically, the heating device includes a rectangular coil 3, a current input interface 1, a current output interface 2, and a rectangular heating cavity 4. The rectangular coil 3 is made of copper tubing with a rectangular cross-section tightly wound into a rectangular planar shape; the rectangular heating cavity 4 is located in the central area enclosed by the rectangular coil 3, and is a rectangular space matching the shape of the coil, used to fix the battery cell to be heated, i.e., the shape of the battery cell to be heated is rectangular; the current input interface 1 and the current output interface 2 are used to connect an external high-frequency alternating current source to the rectangular coil 3.

[0047] Working (Heating) Principle: When a high-frequency alternating current is supplied to the rectangular coil through the current interface, a rapidly changing spatial alternating magnetic field is generated inside and around the coil. This high-frequency magnetic field passes through the battery cell (conductor) placed within the rectangular heating cavity 4. According to Faraday's law of electromagnetic induction, the changing magnetic field induces eddy currents within the battery cell. The battery cell itself has resistance; when strong eddy currents flow within it, according to Joule's law, electrical energy is converted into heat energy, causing the battery cell to heat up rapidly and uniformly from the inside. Utilizing the principle of electromagnetic induction, heat is generated directly within the lithium battery cell to be heated, avoiding the thermal resistance and delay of traditional external heat conduction, thus resulting in high heating efficiency and speed. The relatively uniform magnetic field distribution generated by the rectangular coil also ensures a relatively uniform eddy current induction within the battery cell, achieving uniform heating of the rectangular battery and effectively preventing localized overheating, which is beneficial for protecting battery performance and lifespan. The design of the rectangular coil and rectangular heating cavity 4 is highly compatible with the common square battery cell shape, maximizing space utilization and resulting in a compact heating device structure with more direct and efficient magnetic energy transfer. The heating process is "non-contact," requiring no physical connection between the coil and the battery cell to be heated. This avoids the risks of short circuits and sparks that may arise from direct electrical connections, improving the system's safety and reliability. Using high-frequency alternating current and low-resistance copper tubing, and leveraging the skin effect, the current is concentrated on the coil surface, reducing heat loss from the coil itself and concentrating more energy on heating the battery cell.

[0048] In a preferred embodiment, the cell to be heated is the actual lithium battery cell that needs to be heated, and it is placed completely in the rectangular heating cavity; the heating cell is provided with two cell tabs, which are clamped by a clamp when the cell to be heated is heated, so that the clamp does not have to directly contact the cell and does not affect the cell.

[0049] In a preferred embodiment, the shape of the rectangular heating cavity 4 is adapted to the rectangular structure of the battery cell to make the spatial magnetic field distribution uniform, thereby ensuring that the eddy currents induced by the battery cell are evenly distributed.

[0050] Specifically, when the magnetic field lines generated by the rectangular coil need to pass through the battery cell placed in the heating chamber, the rectangular-to-rectangular design ensures that every surface area of ​​the rectangular battery cell maintains a substantially consistent and closest distance to the direction of the coil's magnetic field. This achieves "effective coupling" of the maximum area between the magnetic field and the battery cell, reducing leakage and loss of magnetic field lines in unused spaces, thereby efficiently transferring more magnetic field energy to the battery cell and converting it into heat energy.

[0051] The rectangular coil is a multi-turn rectangular coil that generates a relatively uniform magnetic field in its central region (i.e., the rectangular heating cavity 4). If a mismatched cylindrical battery cell is placed inside the rectangular coil, the distance between the edge of the cell and the center of the coil will vary, resulting in significant differences in the induced magnetic field strength at different locations. However, if a matching rectangular battery cell is placed inside the rectangular coil, the entire outer surface of the cell is within the "uniform intensity region" where the magnetic field strength generated by the coil is most uniform. This ensures from the outset that the excitation magnetic field acting on the battery cell is uniform. According to the law of electromagnetic induction, the intensity of the induced eddy current is proportional to the intensity of the local magnetic field change. A uniformly distributed excitation magnetic field is a prerequisite for ensuring a uniform distribution of the induced eddy currents. Uniform eddy currents mean uniform heat source distribution. This fundamentally avoids the problems of overheating at the corners of the battery cell (hot spots) or insufficient heating at the center (cold spots) caused by shape mismatch. Localized overheating can seriously damage battery life and safety, while uniform heating is key to achieving rapid and safe preheating. The design of both the heating chamber and the battery cell as rectangular is not a simple mechanical fit, but an active design aimed at optimizing the electromagnetic field distribution. By utilizing the uniform magnetic field region of the rectangular coil, it ensures the uniform distribution of the eddy current heat source, thereby directly resulting in high heating uniformity, excellent energy efficiency, and minimal impact on battery life.

[0052] In a preferred embodiment, the rectangular coil has a rectangular cross-section, with its length and width corresponding to the shortest and second shortest sides of the battery cell, respectively.

[0053] Specifically, the long side of the rectangular cross-section is aligned with the shortest side of the battery cell, and the flat, wide face of the coil conductor faces the two sides of the battery cell with the largest surface area. The main "emitting surface" for generating the magnetic field is aligned with the area most critical for energy exchange. This alignment allows the generated high-frequency magnetic field to penetrate the battery cell's interior with the largest effective area and shortest distance, greatly enhancing the coupling between the magnetic field and the battery cell material, thereby improving energy transfer efficiency. Eddy currents tend to circulate on the conductor surface (here, the battery cell) in a direction perpendicular to the magnetic field. By aligning the long side of the cross-section parallel to the shortest side of the battery cell, a wider and more uniform eddy current loop is induced within the battery cell. This avoids excessive concentration of eddy currents in narrow areas, ensuring a more uniform distribution of heat sources (heat generated by eddy currents) within the battery cell volume, further consolidating heating uniformity and preventing internal "cold core" problems due to insufficient penetration. This oriented cross-section design allows the coil to be made thinner in a spatially limited dimension (the direction of the shortest side of the battery cell), while distributing more conductor material in the direction that needs to cover a large area of ​​the battery cell. This makes the entire heater structure very compact and efficient, achieving optimal magnetic field coverage and heating effect with minimal materials and space, meeting the requirements of high energy density and compact layout in modern electronic devices.

[0054] The rectangular cross-section of the rectangular coil is not arbitrarily arranged; its design, where the longest side corresponds to the shortest side of the cell, is a sophisticated system-level optimization. Through directional coupling and a focused magnetic field, it achieves the following: more magnetic energy is delivered into the cell; eddy currents and heat are generated uniformly in three-dimensional space; and performance is maximized within a limited space.

[0055] In a preferred embodiment, a plurality of temperature sensors and a main controller are provided. The temperature sensors are respectively arranged on the inner and outer sides of the cell to be heated. The temperature sensors are all connected to the main controller, which performs on / off control of the high-frequency alternating current source based on temperature judgment.

[0056] Specifically, temperature sensors (such as thermocouples or thermistors) are placed at key locations on the inner and outer sides of the battery cell to directly and in real-time monitor the radial temperature difference of the lithium battery cell. All temperature sensors are connected to a main controller (usually an MCU or PLC). The main controller continuously reads the inner and outer temperature values ​​and calculates the heating non-uniformity according to the preferred formula: d = |T|. 内 -T 外 | / T, where d is the heating non-uniformity, T 内 T represents the internal temperature of the battery cell. 外 The external temperature is T, and the preset temperature threshold T (the final temperature value that the cell to be heated is expected to reach at the end of the heating process) is D. The current heating non-uniformity is calculated in real time. The calculated real-time temperature and non-uniformity are compared with the preset temperature threshold T and the heating non-uniformity threshold D, and the predetermined control logic is executed. Based on the judgment result, the main controller sends a command to the high-frequency alternating current source to control its on and off states, thereby precisely driving the rectangular coil to switch between the "heating state" and the "zero current steady state". In the entire heating process, from the insertion of the cell and the start of heating to reaching the temperature target or safely stopping due to non-uniformity, everything is completed automatically by the system. The system not only focuses on whether the heating is in place, but also pays close attention to whether the "heating process is safe". Once an abnormality is detected (non-uniformity exceeds the standard), the power supply is immediately cut off.

[0057] In a preferred embodiment, the main controller is configured to: push the battery cell to be heated into the rectangular heating cavity 4 and detect the initial temperature of the battery cell; preset a temperature threshold T and a heating non-uniformity threshold D; when the initial temperature is less than the preset temperature threshold, control the rectangular coil to pass a high-frequency alternating current to put the rectangular coil in a heating state to heat the battery cell; during the heating process, detect the real-time temperature and real-time heating non-uniformity of the battery cell; when the real-time temperature is not less than the preset temperature threshold or the real-time heating non-uniformity is not less than the heating non-uniformity threshold, control the rectangular coil to disconnect the high-frequency alternating current to put the rectangular coil in a zero-current steady state and end the heating.

[0058] Specifically, the battery cell to be heated is pushed into the heating cavity enclosed by the rectangular coil through a fixture or clamp; the actual temperature of the battery cell to be heated is detected, and the initial state temperature T0 is obtained and transmitted to the main controller. At the same time, the temperature threshold T and the heating non-uniformity threshold D are preset through the main controller; the main controller compares the initial state temperature T0 with the preset temperature threshold T (the final temperature value that the battery cell to be heated is expected to reach at the end of the heating process). When T0≥T, the external alternating current does not flow into the coil and is in a zero-current steady state; when T0<T, the external alternating current flows into the rectangular coil 3 through the current input port and flows out from the current output port 2. The induction coil is in a heating state, a spatial magnetic field is induced in the rectangular heating cavity 4, and eddy currents are induced in the battery cell, and induction heating begins; during the heating process, the temperature value t of the battery cell and the heating non-uniformity d are detected in real time. When t≥T or d>D, the external alternating current is disconnected, the spatial magnetic field and the eddy currents disappear, the battery cell stops heating, and the induction coil returns to the zero-current steady state, and the induction heating process ends.

[0059] Taking the example of heating the battery cell to be heated to 45°C, the temperature threshold is preset to 45°C through the main controller, and the preset heating non-uniformity threshold is 0.15. When the battery cell is pushed into the heating cavity, the temperature sensor immediately detects the actual temperature. If the temperature < 45°C, the main controller will control the external alternating current to flow into the rectangular coil 3 through the current input port and flow out from the current output port. A spatial magnetic field is induced in the rectangular heating cavity 4, and eddy currents are induced in the battery cell, and induction heating begins. During the heating process, the temperature sensor continues to detect the temperature of the battery cell in real time. When the temperature ≥ 45°C or the heating non-uniformity > 0.15, it means that the temperature of the battery cell has reached the preset value or the heating non-uniformity exceeds the expectation. The main controller controls the external alternating current to be disconnected, and the induction heating process stops immediately.

[0060] More specifically, the battery cell to be heated is pushed into the rectangular heating cavity 4 to complete the physical preparation; the system detects the initial temperature (T0) of the battery cell as the control reference. Two key thresholds are preset: the preset temperature threshold and the heating non-uniformity threshold. The preset temperature threshold is the final temperature value that the battery cell to be heated is expected to reach at the end of the heating process. The heating non-uniformity threshold is the maximum allowable temperature difference, which is a key indicator to ensure heating quality and safety. When the initial temperature is less than the preset temperature threshold, the system determines that heating is required; the control system turns on the high-frequency alternating current source to make the rectangular coil enter the heating state and starts to perform induction heating on the battery cell to be heated. During the heating process, the system continuously detects two real-time parameters: the real-time temperature and the real-time heating non-uniformity (usually referring to the maximum temperature difference between different points on the surface or inside of the battery cell); when any of the following conditions is met, the heating stops.

[0061] Condition 1 (heating up to standard): The real-time temperature is not less than the preset temperature threshold, that is, the heating has been completed.

[0062] Condition 2 (Protecting the heating device): The real-time heating unevenness is not less than the heating unevenness threshold, that is, the heating uniformity deteriorates, which may cause safety risks or damage the battery life.

[0063] When any termination condition is met, the system immediately cuts off the high-frequency current, the coil enters a zero-current steady state, and the heating process ends safely.

[0064] By comparing real-time temperature feedback with preset temperature thresholds, precise control of the heating endpoint is achieved, avoiding underheating or overheating and ensuring the battery remains within its optimal temperature range. The core advantage of this method lies in using heating non-uniformity as a critical termination condition parallel to temperature. It proactively prevents localized overheating (a precursor to thermal runaway) caused by internal cell defects, coil malfunctions, or external interference, significantly enhancing the system's safety redundancy. By strictly controlling heating uniformity and the final temperature, irreversible damage to lithium batteries caused by high temperatures, overheating, or non-uniform thermal stress is effectively avoided, contributing to extended battery life.

[0065] In a preferred embodiment, the heating non-uniformity is defined as the ratio of the absolute value of the difference between the inner and outer temperatures of the battery cell to a preset temperature threshold; wherein the preset temperature threshold is the final temperature value that the battery cell to be heated is expected to reach at the end of the heating process.

[0066] Example 2

[0067] A thermal simulation method for a heating device includes the following steps:

[0068] Step 1: Model Building

[0069] A rectangular induction coil model and a battery cell model are established in a multiphysics simulation software. The rectangular induction coil model includes parameters such as length, width, number of coil turns, and cross-sectional dimensions of a rectangular copper tube.

[0070] Specifically, based on actual design drawings, accurate geometric models of coils and layered cells are created in the software. The layered cell model is crucial, as it more realistically reflects the different responses of various materials inside the battery (such as positive and negative electrodes, separators, and current collectors) to electromagnetic and thermal fields.

[0071] Step 2: Setting Material Properties

[0072] The rectangular induction coil model is given copper material properties, including electrical conductivity and relative permeability; the battery cell model is given material properties.

[0073] Specifically, the model is given realistic physical properties. The coil is set as a good conductor (such as copper), while the battery cell needs to be set in layers with its conductivity, permeability, density, specific heat capacity, and thermal conductivity. The accuracy of this step directly determines the reliability of the simulation results.

[0074] The conductivity and relative permeability of a coil determine its electromagnetic properties; the material properties of the battery cell (including anisotropic conductivity, thermal conductivity, specific heat capacity, etc.) directly affect eddy current generation and heat transfer.

[0075] Step 3: Setting up the physics field

[0076] The rectangular heating cavity 4 enveloped by the rectangular induction coil is set as the magnetic field calculation domain to solve the spatial magnetic field distribution; a high-frequency alternating current excitation is applied to the rectangular induction coil model, the current amplitude and frequency are set, and the current input interface 1 and the current output interface 2 are set as the current inflow end and the current outflow end, respectively; an electromagnetic field equation is set for the cell model to simulate eddy current induction and couple the electromagnetic thermophysical field.

[0077] Specifically, the rectangular heating cavity 4 enveloping the coil is defined as the magnetic field calculation domain. When the coil is energized, a relatively uniform spatial alternating magnetic field generated by current excitation will be established within this region. A high-frequency alternating current is applied to the coil, the inflow and outflow ports of the current are defined, and its frequency and amplitude are set. Electromagnetic field control equations such as Ampere's law are applied to the battery cell to induce eddy currents in the changing magnetic field.

[0078] Step 4: Thermal Setup

[0079] The initial temperature and ambient temperature are set for the battery cell model, and the thermal convection coefficient on the surface of the battery cell is defined;

[0080] The area outside the rectangular induction coil is set as a thermally insulating boundary condition.

[0081] Specifically, the initial temperature of the battery cell and the thermophysical parameters of the material (thermal conductivity, etc.) are defined. The outer region of the coil is set as thermally insulated. It focuses on the self-generated heat produced by the eddy currents inside the battery cell, while ignoring the complex heat exchange between the coil and the environment, effectively reducing the simulation complexity while ensuring the accuracy of the core physical processes.

[0082] Step 5: Solver Setup

[0083] The cell model is meshed, and the mesh is refined at the edges and corners of the cell.

[0084] The solver is configured to first perform frequency domain electromagnetic field analysis to obtain eddy current distribution and heat sources;

[0085] Then, transient thermal analysis is performed, and the total simulation time and time step are set to obtain the time-varying temperature distribution of the battery cell during the heating process.

[0086] Specifically, the model is discretized, and the mesh needs to be refined in key areas (such as the edge of the battery cell) to ensure accuracy. First, a stable electromagnetic field and eddy current heat source distribution are calculated in the frequency domain; then, this heat source is used as input to perform transient analysis and calculate the temperature change over time.

[0087] Step Six: Results Analysis

[0088] The heating non-uniformity of the battery cell is calculated based on the simulation results, and a dynamic temperature change curve and a temperature distribution cloud map are generated.

[0089] Specifically, it visualizes the output temperature distribution cloud map and temperature dynamic change curve. It quantitatively extracts the highest / lowest temperatures and calculates the previously defined heating non-uniformity based on them, providing accurate data support for evaluating heating performance, optimizing design parameters (such as coil structure and current frequency), and setting control thresholds.

[0090] More specifically, the specific steps of the step-by-step modeling process for the electro-magnetic-thermal coupling simulation during the induction heating process of the battery cell are as follows:

[0091] ① Geometric modeling: Based on the actual shape and size of the coil and the size of the battery cell, the rectangular induction coil and the layered geometric model of the battery cell are established in the multiphysics simulation software.

[0092] ② Material properties: Set the material properties of current input interface 1, rectangular coil 3 and current output interface 2 according to the actual coil material. Consult the datasheet of the battery cell and set the battery cell material in layers to make it as consistent as possible with the actual properties.

[0093] ③ Magnetic field setting: After obtaining the model with material properties, the rectangular heating cavity 4 enclosed by the rectangular coil is set as a free magnetic field space. At this time, relatively uniform magnetic lines of force will pass through the heating cavity, generating a spatial magnetic field.

[0094] ④ Electric field setting: First, apply alternating current to rectangular coil 3, set current input interface 1 and current output interface 2 as the external excitation inflow end and outflow end respectively, and set the specific current frequency and amplitude; then set Ampere's law to the electric cell to be heated placed in rectangular heating cavity 4, at which time the electric cell will have the ability to induce eddy currents.

[0095] ⑤ Temperature field setting: Set the temperature field for the battery cell placed in the heating chamber. Give the initial temperature value of the battery cell and set the corresponding thermal conductivity and heat flux properties. Approximate the area outside the rectangular coil as a thermal insulation area to reduce the simulation difficulty.

[0096] ⑥ Solver configuration and simulation: Mesh the set model, configure the simulation solver step by step, first set the frequency domain, then set the transient state, and you can get the temperature distribution of the battery cell at each moment during the heating process.

[0097] ⑦ Post-processing of results: After obtaining the simulation results, the highest and lowest temperature distribution of the battery cell during the heating process is further obtained, the heating non-uniformity is calculated, and the dynamic temperature change curve and image of the battery cell during the heating process are generated to obtain the required relevant parameters and visualization results.

[0098] Continuing with the example of heating the battery cell to 45°C, the simulation results of the battery cell temperature are obtained by establishing an electro-magnetic-thermal coupling simulation model step by step, as shown below. Figure 4 As shown.

[0099] When the battery cell to be heated reaches 45°C within 20 seconds, excluding the tabs, the internal temperature difference of the battery cell is within 5°C, and the non-uniformity is less than 0.15. Therefore, it can be seen that the rectangular induction coil structure of this invention can effectively guarantee heating effect and heating uniformity.

[0100] In a preferred embodiment, the cell model adopts a layered equivalent model, which includes at least an inner layer and an outer layer of the cell, and assigns different electrical conductivity, specific heat capacity, density and thermal conductivity properties to each layer.

[0101] In a preferred embodiment, the solver is configured to include step-by-step frequency domain and transient settings to handle high-frequency alternating current and time-varying heating processes.

[0102] Specifically, frequency domain analysis is used to solve for the electromagnetic field generated by high-frequency alternating current excitation and the resulting eddy current distribution in the battery cell. For a sinusoidal excitation with a fixed frequency, the system eventually reaches a steady-state electromagnetic response. Frequency domain analysis assumes that all field quantities vary sinusoidally, thus transforming the complex time-domain partial differential equations (Maxwell's equations) into relatively easy-to-solve frequency-domain complex equations. Through this step, the eddy current loss (Joule heat) distribution inside the battery cell can be directly calculated and output as a steady-state heat source, preparing for subsequent thermal analysis.

[0103] Transient analysis is used to simulate the dynamic process of temperature field changes over time in a battery cell under the influence of an eddy current heat source. This step solves the classical heat conduction equation. It uses the eddy current loss distribution obtained from frequency domain analysis as the internal heat source and, combined with initial temperature conditions and boundary conditions (such as convective heat dissipation), calculates the temperature change at every point in the battery cell throughout the entire time history from the start to the end of heating. The final result is a time-varying temperature distribution contour map, a heating curve, and time-varying data that can be used to calculate heating non-uniformity.

[0104] Example 3

[0105] In addition to the first embodiment, the rectangular induction coil of the present invention can be compatible with different heating methods for the battery cell, provided that the coil size is selected appropriately.

[0106] Another implementation example Figure 4 As shown, in this embodiment, the battery cell 6 is heated vertically. The battery cell to be heated is no longer placed horizontally in the rectangular heating cavity 4, but vertically. Since there is a free space magnetic field in the heating cavity, eddy currents can still be induced in the vertically placed battery cell, thereby inducing heating of the battery cell.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A battery cell heating system, the battery cell heating system comprising a heating device, characterized in that, The heating device includes: Current input interface, current output interface, rectangular coil, and rectangular heating cavity; Both the current input interface and the current output interface are used to connect to a high-frequency alternating current source. The rectangular coil is made by winding a rectangular copper tube; The rectangular heating cavity is the cavity enclosed by the rectangular coil and is used to house the battery cell; When a high-frequency alternating current is applied to the rectangular coil, a spatial magnetic field is generated inside the rectangular heating cavity, causing the battery cell to be heated inside to be heated by induced eddy currents.

2. The cell heating system according to claim 1, characterized in that: The shape of the rectangular heating cavity is adapted to the rectangular structure of the battery cell to be heated, so that the spatial magnetic field is evenly distributed and the eddy currents induced by the battery cell to be heated are evenly distributed.

3. The cell heating system according to claim 1, characterized in that: The rectangular coil has a rectangular cross-section, with its length and width corresponding to the shortest and second shortest sides of the battery cell to be heated, respectively.

4. The cell heating system according to claim 1, characterized in that... ,include: Several temperature sensors and a main controller, Several temperature sensors are respectively arranged on the inner and outer sides of the cell to be heated. All temperature sensors are connected to the main controller, which controls the on / off state of the high-frequency alternating current source based on temperature judgment.

5. A cell heating system according to claim 4, characterized in that, The main controller is configured as follows: The battery cell to be heated is pushed into the rectangular heating cavity, and the initial temperature of the battery cell to be heated is detected. Preset temperature threshold and heating unevenness threshold; When the initial temperature is less than the preset temperature threshold, a high-frequency alternating current is controlled to pass through the rectangular coil, so that the rectangular coil is in a heating state to heat the battery cell to be heated. During the heating process, the real-time temperature and real-time heating unevenness of the battery cell to be heated are detected; When the real-time temperature is not less than a preset temperature threshold or the real-time heating unevenness is not less than a heating unevenness threshold, the rectangular coil is controlled to disconnect the high-frequency alternating current, so that the rectangular coil is in a zero-current steady state and the heating ends.

6. A cell heating system according to claim 4, characterized in that, The heating non-uniformity is defined as the ratio of the absolute value of the difference between the inner and outer temperatures of the cell to be heated to a preset temperature threshold. The preset temperature threshold is the final temperature value that the battery cell to be heated is expected to reach at the end of the heating process.

7. A thermal simulation method for a heating device, used to simulate a cell heating system as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Model Building A rectangular induction coil model and a battery cell model are established in a multiphysics simulation software. The rectangular induction coil model includes parameters such as length, width, number of coil turns, and cross-sectional dimensions of a rectangular copper tube. Step 2: Setting Material Properties Assign copper material properties to the rectangular induction coil model, including electrical conductivity and relative permeability; assign material properties to the battery cell model; Step 3: Setting up the physics field The rectangular heating cavity enveloped by the rectangular induction coil is set as the magnetic field calculation domain to solve for the spatial magnetic field distribution; A high-frequency alternating current excitation is applied to the rectangular induction coil model, the current amplitude and frequency are set, and the current input interface and current output interface are set as the current inflow end and the current outflow end, respectively. Electromagnetic field equations are set for the battery cell model to simulate eddy current induction and to couple electromagnetic thermophysical fields. Step 4: Thermal Setup The initial temperature and ambient temperature are set for the battery cell model, and the thermal convection coefficient on the surface of the battery cell is defined; The area outside the rectangular induction coil is set as a thermally insulating boundary condition; Step 5: Solver Setup The cell model is meshed, and the mesh is refined at the edges and corners of the cell. The solver is configured to first perform frequency domain electromagnetic field analysis to obtain eddy current distribution and heat sources; Then, transient thermal analysis is performed, and the total simulation time and time step are set to obtain the time-varying temperature distribution of the battery cell during the heating process. Step Six: Results Analysis The heating non-uniformity of the battery cell is calculated based on the simulation results, and a dynamic temperature change curve and a temperature distribution cloud map are generated.

8. The thermal simulation method for a heating device according to claim 7, characterized in that, The cell model adopts a layered equivalent model, which includes at least an inner layer and an outer layer of the cell, and assigns different electrical conductivity, specific heat capacity, density and thermal conductivity properties to each layer.

9. The thermal simulation method for a heating device according to claim 7, characterized in that, The solver configuration includes step-by-step setting of the frequency domain and transient states to handle high-frequency alternating current and time-varying heating processes.

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