Battery cell thermal runaway source inhibition method and structure based on temperature-sensitive interface layer

Abstract

The invention discloses a cell thermal runaway source inhibition method and structure based on a temperature sensitive interface layer. Thermal runaway is a typical chain reaction-positive feedback process: inducement (such as short circuit) heat production, temperature rise, triggering, more severe heat release side reaction, generation of more heat, temperature explosive rise and thermal runaway. The patent technology mainly solves the problem of thermal runaway from the source (inducement (such as short circuit)). A special material is firstly laid on double surfaces of positive and negative aluminum foils and copper foils, and then conductive layers are coated on the laid positive and negative aluminum foils and copper foils. The special material is in a conductive state when the temperature is lower than 90 DEG C, and the battery cell can be normally charged and discharged, and when the temperature of the battery cell reaches 90 DEG C or above, the special material has an insulating characteristic, is non-conductive, and inhibits the short circuit phenomenon in the battery cell, so that the phenomena of heat production and temperature rise in the battery cell and heat loss inhibition control are inhibited.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, specifically to a method and structure for suppressing the source of thermal runaway in battery cells based on a temperature-sensitive interface layer. Background Technology

[0002] With the rapid development of new energy vehicles, large-scale energy storage, and portable electronic devices, the energy density of lithium-ion batteries is constantly increasing, and their safety issues are becoming increasingly prominent. Thermal runaway is the most serious safety accident involving lithium-ion batteries, and once it occurs, it often leads to catastrophic consequences. Currently, industry-wide protective measures against battery thermal runaway mostly focus on "post-accident management" or "process intervention," for example: External thermal management system: It dissipates heat through liquid cooling, air cooling, etc., but when intense heat is generated internally, its heat dissipation efficiency is often insufficient to suppress the temperature rise.

[0003] Pressure relief device (Vent): Releases pressure when the internal pressure of the battery cell is too high to prevent explosion, but cannot prevent thermal runaway.

[0004] Thermal insulation materials: Thermal insulation layers are placed between cells or modules to slow down the spread of heat, but they cannot protect the inside of individual cells.

[0005] Electrolyte additives: The thermal stability of the electrolyte can be improved by adding film-forming additives or flame retardants, but the effect is limited and may affect the electrochemical performance.

[0006] High-stability diaphragm: The use of ceramic-coated diaphragm or closed diaphragm is intended to prevent internal short circuits caused by diaphragm shrinkage, but it cannot solve the problem of positive and negative electrode contact short circuits caused directly by dendrite puncture, metal impurities, mechanical abuse, etc.

[0007] These technical solutions all intervene or alleviate the problem after the "chain reaction" of thermal runaway has started (i.e., heat generation has already begun), which is a passive defense and fails to fundamentally cut off the initial cause of thermal runaway—internal short circuit.

[0008] With the increasing sales and ownership of electric vehicles, the collision safety of electric vehicle power batteries, as a core component, has become one of the most pressing concerns for consumers. Currently, the most common industry approach to ensure collision safety is through structural reinforcement. However, when a battery pack experiences thermal runaway in a collision, the thermal runaway can easily propagate within the battery pack, resulting in lower overall safety.

[0009] Technical drawbacks: For example, Chinese patent CN223245680U, which describes a battery pack thermal runaway protection device, power battery system, and electrical equipment, uses a control module and current devices to form a detection element. This detection element surrounds the battery pack within the battery compartment. The control module determines the risk of thermal runaway by detecting changes in the detection signal from the detection element. Specifically, when the detection signal from the detection element is interrupted, the control module generates a control signal, connects to a switching module to acquire the control signal, and disconnects the connections between battery packs based on this signal to prevent the spread of thermal runaway within the battery pack. This solution requires high sensitivity, transmission speed, and control accuracy from the detection elements. If any part of this process fails, the risk of thermal runaway remains. Most importantly, it cannot address the root cause of thermal runaway.

[0010] Therefore, it is necessary to provide a method and structure for suppressing the source of thermal runaway in battery cells based on a temperature-sensitive interface layer. Summary of the Invention

[0011] To address the problems existing in the prior art, this invention provides a method and structure for suppressing the source of thermal runaway in battery cells based on a temperature-sensitive interface layer. This invention aims to solve the fundamental problem that existing technologies cannot suppress the initiation of a thermal runaway chain reaction at its source. Through an innovative internal structure design of the battery cell, the current path inside the cell is actively and intelligently cut off during the initial heat generation stage of thermal runaway (i.e., when the temperature rises but before violent side reactions occur), thereby terminating the positive feedback loop of "heat generation → temperature rise → more violent heat generation" and fundamentally preventing the occurrence of thermal runaway.

[0012] To achieve the above objectives, the present invention is implemented through the following technical solution: a method for suppressing the source of thermal runaway in a battery cell based on a temperature-sensitive interface layer, comprising pre-laying a smart barrier material layer on both surfaces of the positive electrode current collector and the negative electrode current collector. The smart barrier material layer is made of PTC composite material, the matrix of which is a high molecular polymer, and conductive fillers are uniformly dispersed inside. By adjusting the crystallinity of the polymer matrix and the type, concentration, morphology and distribution of the conductive fillers, its switching temperature can be precisely set. The switch is set to a normal operating temperature between 70°C and 110°C. When the switch is at normal operating temperature, the polymer matrix is ​​crystalline, the conductive filler forms a continuous conductive network, and the material exhibits a low resistance state (e.g., sheet resistance <10Ω / cm²), ensuring the normal charging and discharging performance of the battery cell, with minimal impact on energy density and internal resistance. When the temperature exceeds the normal operating temperature, it is in the triggered state: When the local temperature of the cell rises to the triggered state temperature due to internal short circuit or other reasons, the polymer matrix undergoes a crystalline-amorphous transformation, the volume expands, the conductive network is destroyed, the resistivity jumps, and the material changes from a conductor to an insulator, a high-resistivity state, or a surface resistivity state.

[0013] Preferably, the method for preparing the multilayer composite electrode of the battery cell in this patent is as follows: Step 1: Prepare the intelligent barrier slurry by mixing polymer, conductive filler, dispersant and solvent in a specific ratio, and then dispersing and ball milling the mixture to form a uniform and stable slurry. Step 2: Laying the intelligent partition material layer. Using precision coating equipment, the above slurry is evenly coated on both surfaces of the positive and negative current collectors. Then, after drying and compaction, a dense intelligent partition film that is firmly bonded to the current collector is formed, with a thickness controlled at 1-10μm. Step 3: Coating the conductive layer and active material layer. On the cured smart barrier material layer, continue to coat the traditional electrode paste. The solvent in the paste cannot dissolve the underlying smart barrier material layer. After drying, rolling and cutting, the positive and negative electrode sheets of this battery cell are obtained. Step 4: Cell assembly. The prepared positive and negative electrode sheets and separator are made into a cell by winding or stacking, and then put into the casing, injected with electrolyte, and the encapsulation is completed.

[0014] Based on any one of claims 1 to 2, a cell thermal runaway source suppression structure based on a temperature-sensitive interface layer is adopted. The cell includes a positive current collector and a negative current collector, which are separated by a membrane. Both sides of the positive current collector and the negative current collector are coated with a conductive layer, an active material layer, and a smart isolation material layer in sequence.

[0015] Preferably, the positive current collector is a positive aluminum foil, and the negative current collector is a negative copper foil.

[0016] Preferably, when the switching temperature is above normal temperature, the resistivity of the smart partition material layer undergoes a jump of at least three orders of magnitude, and the material transforms from a conductor to an insulator with a resistance value greater than 10 ohms. 6 Ω / cm².

[0017] Preferably, the crystalline polymer matrix is ​​any one of polyethylene, polyvinylidene fluoride, or polyamide.

[0018] Preferably, the conductive filler is any one of carbon black, carbon nanotubes, graphene or metal particles.

[0019] Preferably, the electrode paste contains active material, conductive agent, and binder.

[0020] Preferably, the normal operating temperature of the switch is 90℃.

[0021] In summary, this invention provides a method and structure for suppressing the source of thermal runaway in battery cells based on a temperature-sensitive interface layer. The beneficial effects of this invention's technical solution are as follows: 1. Source suppression and proactive defense: directly addressing the cause of thermal runaway (internal short circuit), intervening at the first heat generation stage, transforming passive protection into proactive cutoff, resulting in higher safety.

[0022] 2. Comprehensive protection: Since the intelligent isolation material layer is laid on the entire current collector surface, it can provide equally effective protection for internal short circuits occurring at any location on the electrode sheet, with no blind spots in protection.

[0023] 3. Rapid response: The switching temperature is set at 90℃, which is far below the melting point of the diaphragm and the starting temperature of a large number of violent exothermic side reactions. The response is timely, which buys valuable time to stop the chain reaction.

[0024] 4. Dual blocking mechanism: It not only increases the resistance through the PTC effect, but more importantly, it physically cuts off the "highway" of electron transport (from the current collector to the active material), fundamentally solving the problem of electron short circuit.

[0025] 5. Minimal impact on cell performance: Under normal operating conditions, the resistance of the intelligent isolation material layer is extremely low, and its impact on the internal resistance, rate performance, and energy density of the cell is negligible.

[0026] 6. Good process compatibility: This preparation method can be achieved by adding a coating step to the existing electrode manufacturing process without disrupting the existing production line, making it easy to promote industrialization. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the battery cell electrode structure of the present invention; Figure 2 This is a schematic diagram of the multilayer composite electrode structure of the battery cell of the present invention; In the diagram: 1. Positive current collector; 2. Negative current collector; 3. Intelligent isolation material layer; 4. Conductive layer and active material layer. Detailed Implementation

[0028] The invention will now be further described with reference to the accompanying drawings.

[0029] like Figures 1 to 2 As shown: The present invention is as follows Figure 1 As shown, a method and structure for suppressing the source of thermal runaway in a battery cell based on a temperature-sensitive interface layer are disclosed. The battery cell sequentially includes a positive current collector, a positive intelligent isolation material layer, a positive conductive layer and an active material layer, a separator, a negative conductive layer and an active material layer, a negative intelligent isolation material layer, and a negative current collector.

[0030] The intelligent partition material layer is the core material layer of this patented technology. It is disposed between the positive electrode aluminum foil and the subsequently coated conductive layer / active material layer, and between the negative electrode copper foil and the subsequently coated conductive layer / active material layer, so that an intelligent partition material layer is pre-laid between the electrode metal foil and the conductive layer / active material layer.

[0031] The intelligent partition material layer uses PTC composite material, whose matrix is ​​a polymer, such as polyethylene, polyvinylidene fluoride, or polyamide. Conductive fillers are uniformly dispersed within the matrix, and these fillers can be such as carbon black, carbon nanotubes, graphene, or metal particles. By adjusting the crystallinity of the polymer matrix and the type, concentration, morphology, and distribution of the conductive fillers, the switching temperature can be precisely set. Switching temperature characteristics: The present invention preferably sets the switching temperature at 90℃. Its working principle is as follows: (1) Normal state (T<90℃): The polymer matrix is ​​crystalline, the conductive filler forms a continuous conductive network, and the material exhibits a low resistance state (such as surface resistance <10 Ω / cm²), ensuring the normal charging and discharging performance of the cell, and having minimal impact on energy density and internal resistance.

[0032] (2) Triggered state (T ≥ 90℃): When the local temperature of the cell rises to 90℃ due to internal short circuit or other reasons, the polymer matrix undergoes a crystalline-amorphous transformation, resulting in volume expansion, which destroys the conductive network and causes a transition in resistivity (such as an increase of 3-6 orders of magnitude). The material changes from a conductor to an insulator (or a high-resistivity state, with a surface resistivity > 10). 6 Ω / cm²).

[0033] Methods for preparing multilayer composite electrodes: Step 1: Preparation of intelligent barrier slurry. Polymer, conductive filler, dispersant, and solvent are mixed in a specific ratio, then dispersed by high-speed shearing and ball milling to form a uniform and stable slurry.

[0034] Step 2: Laying the intelligent barrier material layer. Using precision coating equipment, the above slurry is evenly coated on both surfaces of the positive electrode aluminum foil and the negative electrode copper foil. Subsequently, after drying and compaction processes, a dense intelligent barrier film that is firmly bonded to the current collector is formed, with a thickness controlled between 1-10 μm.

[0035] Step 3: Coating the conductive layer and active material layer. On top of the cured smart barrier material layer, a conventional electrode paste (containing active material, conductive agent, and binder) is applied. The solvent in this paste cannot dissolve the underlying smart barrier material layer. After drying, rolling, and slitting, the positive and negative electrode sheets of this invention are obtained.

[0036] Step 4: Cell Assembly. The prepared positive and negative electrode sheets and separator are wound or stacked to form a cell, which is then placed into a casing, injected with electrolyte, and encapsulated.

[0037] The working principle of this patented method for suppressing the source of thermal runaway in battery cells: When a local micro-short circuit is about to occur or has already occurred inside the battery cell due to any reason (such as dendrite puncture, metal impurities, mechanical deformation), a large amount of Joule heat will be generated at the short circuit point, causing the local temperature to rise sharply.

[0038] Traditional battery cells: The heat will be rapidly conducted to the surroundings, triggering exothermic side reactions such as SEI membrane decomposition and negative electrode reaction with electrolyte, which will further increase the temperature and eventually lead to membrane melting, large-area short circuit, and thermal runaway.

[0039] The battery cell of this invention: When the temperature at the short-circuit point rises to 90°C, the intelligent isolation material layer in that area (regardless of whether it is located at the positive or negative electrode) rapidly changes from conductive to insulating. This change physically cuts off the electron supply path from the current collector to the active material. Even if the positive and negative active materials are in direct contact due to separator failure, the short-circuit loop is fundamentally cut off because electrons cannot flow out from the current collector. The short-circuit heat generation process is immediately terminated, and the local temperature rise is effectively controlled, thus successfully blocking the positive feedback loop of "heat generation → temperature rise → more intense heat generation," nipping thermal runaway in the bud.

[0040] Specifically: The scope of this patent protection covers the application of cells containing the above structure in lithium batteries, as well as sodium batteries or other secondary batteries, particularly in high-energy-density power batteries and energy storage systems.

[0041] The embodiments described in this invention are for illustrative purposes only and do not constitute a limitation on the scope of the claims. Other substantially equivalent substitutions that can be conceived by those skilled in the art are all within the scope of protection of this invention.

Claims

1. A method for suppressing the source of thermal runaway in a battery cell based on a temperature-sensitive interface layer, characterized in that, A smart barrier material layer (3) is pre-laid on the double surfaces of the positive current collector (1) and the negative current collector (2). The smart barrier material layer (3) is made of PTC composite material. Its matrix is ​​a crystalline polymer, and the interior is uniformly dispersed with conductive fillers of carbon-based materials or metal particles. By adjusting the crystallinity of the polymer matrix, the type, concentration, morphology and distribution of the conductive fillers, its switching temperature can be precisely set. The switch is set to a normal operating temperature between 70°C and 110°C. When the switch is at normal operating temperature, the polymer matrix is ​​crystalline, the conductive filler forms a continuous conductive network, and the material exhibits a low resistance state (e.g., sheet resistance <10Ω / cm²), ensuring the normal charging and discharging performance of the battery cell, with minimal impact on energy density and internal resistance. When the temperature exceeds the normal operating temperature, it is in the triggered state: When the local temperature of the cell rises to the triggered state temperature due to internal short circuit or other reasons, the polymer matrix undergoes a crystalline-amorphous transformation, the volume expands, the conductive network is destroyed, the resistivity jumps, and the material changes from a conductor to an insulator, a high-resistivity state, or a surface resistivity state.

2. The method for suppressing the source of thermal runaway in a battery cell based on a temperature-sensitive interface layer according to claim 1, characterized in that, The preparation method of the multilayer composite electrode of this battery cell is as follows: Step 1: Prepare the intelligent barrier slurry by mixing polymer, conductive filler, dispersant and solvent in a specific ratio, and then dispersing and ball milling the mixture to form a uniform and stable slurry. Step 2: Laying the intelligent partition material layer (3), the above slurry is uniformly coated on the double surfaces of the positive electrode current collector (1) and the negative electrode current collector (2) through a precision coating equipment. Then, after drying and compaction, a dense intelligent partition film that is firmly bonded to the current collector is formed, with a thickness controlled at 1-10μm. Step 3: Coating the conductive layer and active material layer (4), on the solidified smart barrier material layer (3), continue to coat the traditional electrode paste. The solvent in the paste cannot dissolve the lower smart barrier material layer (3). After drying, rolling and cutting, the positive and negative electrode sheets of this battery cell are obtained. Step 4: Cell assembly. The prepared positive and negative electrode sheets and separator are made into a cell by winding or stacking, and then put into the casing, injected with electrolyte, and the encapsulation is completed.

3. Based on any one of claims 1 to 2, a cell thermal runaway source suppression structure based on a temperature-sensitive interface layer is characterized in that, This battery cell includes a positive current collector (1) and a negative current collector (2), with a membrane separating the positive current collector (1) and the negative current collector (2). Both sides of the positive current collector (1) and the negative current collector (2) are coated with a conductive layer, an active material layer (4), and an intelligent isolation material layer (3) in sequence.

4. The cell thermal runaway source suppression structure based on a temperature-sensitive interface layer according to claim 3, characterized in that, The positive current collector (1) is set as a positive aluminum foil, and the negative current collector (2) is set as a negative copper foil.

5. The method for suppressing the source of thermal runaway in a battery cell based on a temperature-sensitive interface layer according to claim 1, characterized in that, When the switching temperature exceeds the normal temperature, the resistivity of the intelligent partition material layer (3) undergoes a jump of at least 3 orders of magnitude, and the material changes from a conductor to an insulator with a resistance value greater than 10. 6 Ω / cm².

6. The method for suppressing the source of thermal runaway in a battery cell based on a temperature-sensitive interface layer according to claim 1, characterized in that, The crystalline polymer matrix is ​​any one of polyethylene, polyvinylidene fluoride, or polyamide.

7. The method for suppressing the source of thermal runaway in a battery cell based on a temperature-sensitive interface layer according to claim 1, characterized in that, The conductive filler can be any one of the following: carbon black, carbon nanotubes, graphene, or metal particles.

8. The method for suppressing the source of thermal runaway in a battery cell based on a temperature-sensitive interface layer according to claim 2, characterized in that, Electrode paste contains active materials, conductive agents, and binders.

9. In the method for suppressing the source of thermal runaway in a battery cell based on a temperature-sensitive interface layer according to claim 1, the preferred normal switching temperature is 90°C.

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