A method for simulating the self-heating thermal runaway of a battery

Abstract

The present invention relates to a method for simulating the self-heating out-of-control of a battery. The method includes adjusting the diameter of lithium metal particles according to the simulation conditions of a lithium-ion battery; wrapping a layer of phase change material outside the lithium metal particles to prepare a lithium metal-phase change material composite; adjusting the quantity of the lithium metal-phase change material composite and setting the lithium metal-phase change material composite at different positions on the negative electrode of the lithium-ion battery to determine the battery to be simulated; subjecting the battery to be simulated to tests and simulations under different triggering conditions and high-temperature environments, and collecting the voltage, temperature, and impedance of the self-heating out-of-control of the battery to be simulated. The present invention has the advantages of controllable damage degree, high repeatability, conforming to the actual failure scenario, and being reproducible.

Description

Technical Field

[0001] The present invention relates to the field of battery self-heating runaway simulation, and particularly to a method for simulating battery self-heating runaway. Background Art

[0002] For the experimental simulation methods of self-heating runaway caused by local overheating inside the battery, current researchers have explored experimental simulation methods such as implanting shape memory alloy, implanting low-melting-point metal foil, implanting metal powder wrapped with phase change material, defective separator, artificially induced lithium dendrites, and acupuncture. Among them, the literature "Internal Short Circuit Trigger Method for Lithium-Ion Battery Based on Shape Memory Alloy" triggers internal short circuit in the battery by implanting shape memory alloy and external heating. The literature "Experimental triggers for internal short circuits in lithium-ion cells" simulates internal short circuit by implanting low-melting-point metal foil and successfully triggers thermal failure of button cells and 18650 cells. The patent application "An internal short circuit trigger element, an internal short circuit trigger battery and an internal short circuit trigger method (CN201911215355.1)" proposes a method to trigger internal short circuit in the battery by placing metal powder wrapped with phase change material inside the battery, which has the advantages of flexible arrangement position of the trigger element and little influence on battery performance. The patent application "Internal short circuit trigger battery and battery internal short circuit trigger method (CN201811203104.7)" discloses a method to simulate internal short circuit in the battery by making holes in the lithium-ion battery separator and covering the holes with phase change filler. The literature "Mechanism of the entire overdischarge process and overdischarge-induced internal short circuit in lithium-ion batteries" artificially induces the generation of dendrites by over-discharging, and it is found that when the state of charge SOC is 12%, the copper current collector dissolves and dendrites are generated. The literature "Experimental and numerical study on penetration-induced internal short-circuit of lithium-ion cell" uses acupuncture to simulate the occurrence of internal short circuit in the battery, and it is found that the penetration depth of the acupuncture needle, the diameter of the acupuncture needle, etc. have a great impact on the occurrence of thermal failure. The literature "Safety issues caused by internal short circuits in lithium-ion batteries" simulates internal short circuit by extrusion, and different types of internal short circuits are simulated by adjusting the SOC and extrusion depth of the battery.

[0003] Although various methods for reproducing self-heating failure have been proposed by researchers, they have their own advantages and disadvantages in terms of repeatability, controllability, implementation difficulty, etc. Generally speaking, the method of foreign object implantation has good repeatability and controllability, but there are still significant differences from the scenario of actual battery self-heating runaway. The method of defective separator has limitations such as great implementation difficulty and large differences from the scenario of actual battery self-heating runaway. The method of artificially inducing dendrite growth causes less damage to the battery and has low implementation difficulty, but the dendrite growth position and process are uncontrollable. The acupuncture method is simple and highly controllable, but its repeatability is relatively poor, and there are also significant differences from the scenario of actual battery self-heating runaway.

[0004] Therefore, how to improve the test method and propose a simulation method for lithium-ion battery self-heating runaway caused by local overheating with controllable damage degree, high repeatability and in line with the actual failure scenario is an urgent problem to be solved at present, and it is also the basis for studying the self-heating failure mechanism and then overcoming the problem of lithium-ion battery spontaneous combustion. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for simulating battery self-heating runaway, which has the advantages of controllable damage degree, high repeatability, in line with the actual failure scenario and being able to reproduce.

[0006] To achieve the above object, the present invention provides the following solution:

[0007] A method for simulating battery self-heating runaway, comprising:

[0008] Adjust the diameter of lithium metal particles according to the simulation conditions of the lithium-ion battery; the simulation conditions include: simulating lithium-ion batteries in different aging states or simulating lithium-ion batteries charged below 0°C for different numbers of times;

[0009] Wrap a layer of phase change material outside the lithium metal particles to prepare a lithium metal-phase change material composite;

[0010] Adjust the quantity of the lithium metal-phase change material composite and place the lithium metal-phase change material composite at different positions on the negative electrode surface of the lithium-ion battery to determine the battery to be simulated;

[0011] Subject the battery to be simulated to test simulations under different triggering conditions and high-temperature environments, and collect the voltage, temperature and impedance of the battery self-heating runaway of the battery to be simulated; the triggering conditions include: making the battery to be simulated in a state where internal exothermic side reactions continuously occur, including the battery being at high temperature, high SOC of the battery or being at high temperature and high-rate charge and discharge at the same time; the battery high-temperature condition is higher than or equal to 45°C; the range of high SOC of the battery is 80% - 100%; high-rate charge and discharge is greater than or equal to 1C rate.

[0012] Optionally, adjusting the diameter of the lithium metal particles according to the simulation conditions of the lithium-ion battery specifically includes:

[0013] If the simulation conditions of the lithium-ion battery are to simulate lithium-ion batteries in different aging states, then for every 5% reduction in the state of health (SOH) of the lithium-ion battery, the corresponding adjusted diameter of the lithium metal particles increases by 100 microns;

[0014] If the simulation conditions of the lithium-ion battery are to simulate lithium-ion batteries that have undergone low-temperature charging below 0°C for different numbers of times, then for every 10 times of charging below 0°C of the lithium-ion battery, the corresponding adjusted diameter of the lithium metal particles increases by 100 microns.

[0015] Optionally, the diameter range of the lithium metal particles is from 100 microns to 500 microns.

[0016] Optionally, the phase change material is paraffin wax.

[0017] Optionally, wrapping a layer of phase change material outside the lithium metal particles to prepare a lithium metal-phase change material composite specifically includes:

[0018] In an inert gas atmosphere environment, make the heating temperature of the paraffin wax higher than the phase change temperature;

[0019] In an inert gas atmosphere environment, place the lithium metal particles in the melted paraffin wax, make the ambient temperature lower than the phase change temperature, and after a set time, the outside of the lithium metal particles is wrapped with solid paraffin wax;

[0020] Cut the paraffin wax outside the lithium metal particles until the thickness of the paraffin wax is less than 1 mm.

[0021] Optionally, adjusting the quantity of the lithium metal-phase change material composite and setting the lithium metal-phase change material composite at different positions on the surface of the negative electrode of the lithium-ion battery to determine the battery to be simulated specifically includes:

[0022] In an inert gas atmosphere environment, open the battery core of the lithium-ion battery and place the lithium metal-phase change material composite between the negative electrode and the separator of the lithium-ion battery;

[0023] Rewind the battery core of the lithium-ion battery and place it in the battery core housing of the lithium-ion battery or wrap it with an aluminum-plastic film, refill the electrolyte, encapsulate it, and perform formation again, and control the battery temperature to be always more than 10°C lower than the phase change temperature of the phase change material.

[0024] Optionally, making the battery to be simulated be in different triggering conditions and high-temperature environments for test simulation, and collecting the voltage, temperature, and impedance of the battery self-heating runaway of the battery to be simulated specifically includes:

[0025] Adjust the battery state of charge (SOC) to a high SOC of the battery;

[0026] Place the battery to be simulated in a high-temperature environment, and collect the voltage, temperature, and impedance of the battery's self-heating thermal runaway to be simulated.

[0027] Optionally, the battery to be simulated is placed under different triggering conditions and in a high-temperature environment for test simulation, and the voltage, temperature, and impedance of the battery's self-heating thermal runaway to be simulated are collected. Specifically, it includes:

[0028] Place the battery to be simulated in a high-temperature environment. When the battery temperature of the battery to be simulated remains unchanged, perform high-rate charge and discharge, and collect the voltage, temperature, and impedance of the battery's self-heating thermal runaway to be simulated.

[0029] According to the specific embodiments provided by the present invention, the following technical effects are disclosed by the present invention:

[0030] A method for simulating the self-heating thermal runaway of a battery provided by the present invention can control the damage degree of a lithium-ion battery during the process of simulating the self-heating thermal runaway of the battery by adjusting the diameter of the lithium metal particles, the quantity and position of the lithium metal-phase change material composite. During simulation, by wrapping the phase change material outside the lithium metal particles, before the lithium-ion battery reaches the phase change temperature, the lithium metal particles will not react with other components inside the lithium-ion battery. Once the phase change temperature is reached, after the phase change material melts, the lithium metal particles come into contact with the electrolyte and the positive and negative electrode materials inside the battery, and an exothermic side reaction occurs, realizing the accurate simulation of local overheating. Since the battery SOC and the battery temperature can be accurately controlled simultaneously at this time, the starting state of the battery's self-heating thermal runaway can be controlled. The parameters such as the diameter of the lithium metal particles, the quantity and position of the lithium metal-phase change material composite, the phase change temperature of the phase change material, the battery SOC, and the battery temperature of the present invention can all be precisely controlled. Therefore, the high repeatability of the experimental results can be ensured. According to the characteristics obtained by disassembling the actual failed battery cells, the lithium-ion battery provided with the lithium metal-phase change material composite is directly, quantitatively, and controllably simulated, which can be more in line with the actual failure scenarios. Brief Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 It is a schematic flow chart of a method for simulating the self-heating thermal runaway of a battery provided by the present invention. Detailed Embodiments

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] The object of the present invention is to provide a method for simulating the self-heating out-of-control of a battery, which has the advantages of controllable damage degree, high repeatability, conforming to the actual failure scenario, and being reproducible.

[0035] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 A schematic flow chart of a method for simulating the self-heating out-of-control of a battery provided by the present invention is as Figure 1 shown. A method for simulating the self-heating out-of-control of a battery provided by the present invention includes:

[0037] S101, adjusting the diameter of lithium metal particles according to the simulation conditions of the lithium-ion battery; the simulation conditions include: simulating lithium-ion batteries in different aging states or simulating lithium-ion batteries charged below 0 °C for different numbers of times; the diameter range of the lithium metal particles is 100 micrometers to 500 micrometers. By increasing the diameter of the lithium metal particles to simulate batteries in different aging states and batteries with different low-temperature charging times, the relationship between the internal heat accumulation level determined by the diameter of the lithium metal particles and the self-heating out-of-control of the battery is judged by analyzing the relationship between the diameter of the lithium metal particles and the self-heating out-of-control phenomenon of the battery.

[0038] S101 specifically includes:

[0039] If the simulation condition of the lithium-ion battery is to simulate lithium-ion batteries in different aging states, then for every 5% decrease in the state of health (SOH) of the lithium-ion battery, the diameter of the corresponding lithium metal particles is increased by 100 micrometers;

[0040] If the simulation condition of the lithium-ion battery is to simulate lithium-ion batteries charged below 0 °C for different numbers of times, then for every 10 times the lithium-ion battery is charged below 0 °C, the diameter of the corresponding lithium metal particles is increased by 100 micrometers.

[0041] S102. Wrap a layer of phase change material around the lithium metal particles to prepare a lithium metal-phase change material composite. By wrapping a layer of phase change material around the lithium metal particles, the stable existence of the lithium metal particles inside the lithium-ion battery at room temperature is achieved. Preferably, the phase change material is paraffin wax, and according to the reaction triggering temperature of different lithium metals and other materials inside the battery, the phase change temperature of the paraffin wax is preferably 40 °C.

[0042] S102 specifically includes:

[0043] In an inert gas atmosphere, adjust the ambient temperature of the paraffin wax so that the temperature of the paraffin wax is greater than the phase change temperature.

[0044] Place the lithium metal particles in the melted paraffin wax, adjust the ambient temperature of the paraffin wax so that the temperature of the paraffin wax is less than the phase change temperature. After a set time, the outer surface of the lithium metal particles is wrapped with solid paraffin wax. Among them, the temperature difference between the ambient temperature and the phase change temperature is greater than or equal to 10 °C.

[0045] Cut the paraffin wax on the outer surface of the lithium metal particles until the thickness of the paraffin wax is less than 1 mm.

[0046] S103. Adjust the quantity of the lithium metal-phase change material composite and place the lithium metal-phase change material composite at different positions on the surface of the negative electrode of the lithium-ion battery to determine the battery to be simulated.

[0047] S103 specifically includes:

[0048] In an inert gas atmosphere, open the lithium-ion battery core and place the lithium metal-phase change material composite between the negative electrode and the separator of the lithium-ion battery.

[0049] Rewind the lithium-ion battery core and place it in the outer shell of the lithium-ion battery core or wrap it with an aluminum-plastic film. Then, refill the electrolyte, seal, and form the battery, and control the battery temperature to be less than or equal to 30 °C.

[0050] For a lithium-ion battery with the same-side output tabs, the position of the lithium metal-phase change material composite should be close to the tab side. Under this condition, the risk of self-heating runaway of the battery is higher.

[0051] For a lithium-ion battery with the same-side output tabs, when the position of the lithium metal-phase change material composite is arranged close to the tab side, it should be arranged close to the negative electrode tab. Under this condition, the risk of self-heating runaway of the battery is higher.

[0052] For a lithium-ion battery with different-side output tabs, the position of the lithium metal-phase change material composite should be close to both sides of the tabs. Under this condition, the risk of self-heating runaway of the battery is higher.

[0053] For a lithium-ion battery with different side-out tabs, when the position of the lithium metal-phase change material composite is arranged close to one side of the tab, it should be arranged close to the negative tab. Under this condition, the risk of self-heating runaway of the battery is higher.

[0054] The number of lithium metal-phase change material composites arranged inside the lithium-ion battery is 1 - 4 to simulate the influence of multiple internal defects of the battery on the probability of self-heating runaway of the battery.

[0055] For arranging multiple lithium metal-phase change material composites inside the lithium-ion battery, by adjusting the number of composites near the tab, the influence of the arrangement position of the composites on the probability of self-heating runaway of the battery is simulated.

[0056] When arranging the lithium metal-phase change material composite inside the lithium-ion battery, it can be arranged at multiple different positions on the same negative electrode surface or on the surfaces of different layers of the negative electrode.

[0057] S104. Subject the battery to be simulated to different triggering conditions and high-temperature environments for test simulation, and collect the voltage, temperature, and impedance of the battery self-heating runaway of the battery to be simulated; the triggering conditions include: making the battery to be simulated in a state of internal exothermic side reaction, and the battery is simultaneously in a high-temperature, high-SOC state or simultaneously in a high-temperature, high-rate charge-discharge state; the high-temperature condition of the battery is higher than or equal to 45°C; the range of high-SOC of the battery is 80% - 100%; the high-rate charge-discharge is greater than or equal to 1C.

[0058] S104 specifically includes:

[0059] Adjust the battery SOC to battery SOC = 100%.

[0060] Place the battery to be simulated in a 60°C high-temperature environment and collect the voltage, temperature, and impedance of the battery self-heating runaway of the battery to be simulated.

[0061] Adjust the battery SOC and battery temperature to smaller values to judge the influence degree of the combination of internal defects of the battery and external states of the battery on whether the battery undergoes thermal runaway. The specific steps are as follows:

[0062] Set the battery SOC to 95%, 90%, 85%, and 80% respectively, and set the battery temperature to 55°C, 50°C, and 45°C respectively. Set the above battery states as 12 groups of orthogonal tests, where the size, number, and position of the lithium metal-phase change material composites inside the battery remain the same, and verify them respectively.

[0063] S104 specifically includes:

[0064] Place the battery to be simulated in a high-temperature environment. When the battery temperature of the battery to be simulated remains unchanged, perform high-rate charge and discharge cycles, and collect the voltage, temperature, and impedance of the battery self-heating runaway of the battery to be simulated. The combinations of high-rate charge and discharge cycles are 2C constant current charging, 2C constant current discharging, or 1.75C constant current charging, 1.75C constant current discharging, or 1.5C constant current charging, 1.5C constant current discharging.

[0065] The evaluation criterion for the battery temperature to be stable is that the battery temperature change rate is always less than 1 °C / min within 30 minutes.

[0066] Adjust the charge and discharge rate and battery temperature of the lithium-ion battery to smaller values to determine the influence degree of the combination of internal battery defects and external battery states on whether the battery undergoes thermal runaway. The specific steps are as follows:

[0067] Set the battery charge and discharge rate to 1.25C constant current charging, 1.25C constant current discharging, or 1C constant current charging, 1C constant current discharging respectively, and set the battery temperature to 55 °C, 50 °C, 45 °C respectively. Set the above battery states as 12 groups of orthogonal tests, where the size, quantity, and arrangement position of the lithium metal-insulating layer composite inside the battery remain the same, and verify them respectively.

[0068] The present invention realizes the quantitative analysis of the local overheat level inside the battery and the probability of the battery self-heating runaway. At the same time, the probability of accidental fire during the sample preparation process is small, and the test safety risk is small. The technical solution proposed by the present invention has important reference significance for locating the inducement of lithium-ion battery self-ignition and obtaining characteristic data such as voltage, temperature, and impedance during the self-heating runaway process of lithium-ion batteries, and can promote the development of safety warning and thermal diffusion protection technologies using power battery operation data, and has the conditions for highly engineered applications.

[0069] Each embodiment in this specification is described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other.

[0070] Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for simulating the self-heating out-of-control of a battery, characterized in that, Including: Adjusting the diameter of lithium metal particles according to the simulation conditions of a lithium-ion battery; The simulation conditions include: simulating lithium-ion batteries in different aging states or simulating lithium-ion batteries that have been charged below 0°C for different numbers of times; Wrapping a layer of phase change material outside the lithium metal particles to prepare a lithium metal-phase change material composite; Adjusting the quantity of the lithium metal-phase change material composite and placing the lithium metal-phase change material composite at different positions on the surface of the negative electrode of the lithium-ion battery to determine the battery to be simulated; Subjecting the battery to be simulated to different triggering conditions and a high-temperature environment for test simulation, and collecting the voltage, temperature, and impedance of the battery self-heating runaway of the battery to be simulated; the triggering conditions include: making the battery to be simulated in a state where internal exothermic side reactions continuously occur, including the battery being simultaneously at a high temperature, the battery having a high state of charge (SOC), or being simultaneously at a high temperature and high-rate charge and discharge states; the battery high-temperature condition is higher than or equal to 45°C; the range of the battery high SOC is 80% - 100%; the high-rate charge and discharge is greater than or equal to 1C rate.

2. The method for simulating the self-heating out-of-control of a battery according to claim 1, wherein The adjusting the diameter of the lithium metal particles according to the simulation conditions of the lithium-ion battery specifically includes: If the simulation condition of the lithium-ion battery is to simulate lithium-ion batteries in different aging states, then for every 5% reduction in the state of health (SOH) of the battery aging state of the lithium-ion battery, the diameter of the corresponding adjusted lithium metal particles increases by 100 microns; If the simulation condition of the lithium-ion battery is to simulate lithium-ion batteries that have been charged below 0°C for different numbers of times, then for every 10 times the lithium-ion battery is charged below 0°C, the diameter of the corresponding adjusted lithium metal particles increases by 100 microns.

3. A method for simulating self-heating thermal runaway of a battery according to claim 2, characterized in that, The diameter range of the lithium metal particles is from 100 microns to 500 microns.

4. A method for simulating self-heating thermal runaway of a battery according to claim 1, characterized in that, The phase change material is paraffin wax.

5. A method for simulating self-heating runaway of a battery according to claim 4, characterized in that, The wrapping a layer of phase change material outside the lithium metal particles to prepare a lithium metal-phase change material composite specifically includes: In an inert gas atmosphere environment, making the heating temperature of the paraffin wax higher than the phase change temperature; In an inert gas atmosphere environment, placing the lithium metal particles in the melted paraffin wax, making the ambient temperature lower than the phase change temperature, and after a set time, the outside of the lithium metal particles is wrapped with solid paraffin wax; Cutting the paraffin wax outside the lithium metal particles until the thickness of the paraffin wax is less than 1 mm.

6. A method for simulating self-heating out-of-control of a battery according to claim 1, characterized in that, The adjusting the quantity of the lithium metal-phase change material composite and setting the lithium metal-phase change material composite at different positions on the surface of the negative electrode of the lithium-ion battery to determine the battery to be simulated specifically includes: In an inert gas atmosphere environment, opening the battery core of the lithium-ion battery and placing the lithium metal-phase change material composite between the negative electrode and the separator of the lithium-ion battery; Rewinding the battery core of the lithium-ion battery and placing it in the outer shell of the battery core of the lithium-ion battery or wrapping it with an aluminum-plastic film, refilling, encapsulating, and forming again, and controlling the battery temperature to be less than or equal to 30°C.

7. A method for simulating self-heating thermal runaway of a battery according to claim 1, characterized in that, The subjecting the battery to be simulated to different triggering conditions and a high-temperature environment for test simulation, and collecting the voltage, temperature, and impedance of the battery self-heating runaway of the battery to be simulated specifically includes: Adjusting the battery SOC to the battery high SOC; Placing the battery to be simulated in a high-temperature environment and collecting the voltage, temperature, and impedance of the battery self-heating runaway of the battery to be simulated.

8. A method for simulating self-heating out-of-control of a battery according to claim 1, characterized in that, Subject the battery to be simulated to different triggering conditions and high-temperature environments for test simulation, and collect the voltage, temperature, and impedance of the battery thermal runaway of the battery to be simulated, specifically including: Place the battery to be simulated in a high-temperature environment. When the battery temperature of the battery to be simulated remains unchanged, perform high-rate charge and discharge, and collect the voltage, temperature, and impedance of the battery thermal runaway of the battery to be simulated.

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