Lithium carbon fluoride battery capable of continuously discharging at high power and manufacturing method of lithium carbon fluoride battery

Abstract

The invention belongs to the technical field of lithium primary batteries, and particularly discloses a lithium carbon fluoride battery pack capable of continuously discharging at high power and a manufacturing method of the lithium carbon fluoride battery pack. The battery pack comprises at least one unit battery formed by a plurality of single batteries, a battery shell and a sheet-shaped heat management interlayer, the sheet-shaped heat management interlayer is arranged between adjacent single batteries in the unit battery, and / or between different unit batteries, and / or between the unit battery and the battery shell; the sheet-shaped heat management interlayer is made of a graphene skeleton phase change composite material and is composed of a three-dimensional porous graphene network and a composite phase change material filled in pores of the network. By integrating the flexible interlayer with high heat conduction and high heat storage functions, heat can be actively and quickly absorbed and homogenized during high-power discharge, the temperature rise of the battery pack is effectively inhibited, and local hot spots are eliminated, so that continuous and stable high-power output of the lithium carbon fluoride battery is realized, and the safety and reliability of a system are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium primary battery technology, specifically relating to a lithium fluoride carbon battery with excellent thermal management capabilities and its manufacturing method, which is particularly suitable for high energy density applications requiring long-term, high-current discharge. Background Technology

[0002] Lithium-ion fluoride (CFC) batteries possess extremely high theoretical specific energy (approximately 2180 Wh / kg), making them one of the highest energy density primary battery systems currently available. They have irreplaceable applications in specialized fields such as spacecraft, military equipment, medical implants, and exploration instruments. However, with the ever-increasing power demands of electrical equipment, CFC batteries often need to be connected in series or parallel to form battery packs to meet voltage and capacity requirements. However, battery packs face more severe thermal challenges than individual cells during high-power discharge. 1. Heat accumulation effect: The heat generated by the simultaneous high-current discharge of multiple batteries is superimposed, resulting in severe heat accumulation inside the battery pack; 2. Uneven heat distribution: Due to the limitations of the battery pack structure, heat dissipation is difficult in the center, easily forming a temperature gradient. This leads to uneven performance of individual cells, affecting the overall discharge capacity and voltage plateau stability. Localized overheating may cause internal short circuits, posing a risk of combustion or explosion.

[0003] 3. Risk of thermal runaway propagation: Overheating of a single cell may trigger a chain reaction of temperature increases in adjacent cells, increasing safety risks; 4. Power output degradation: To prevent overheating, battery management systems often forcibly limit the discharge current or terminate the discharge prematurely, resulting in the actual usable power being far lower than the theoretical value.

[0004] 5. Performance degradation: High temperatures accelerate electrolyte decomposition and irreversible side reactions of electrode materials, severely damaging battery performance.

[0005] In existing technologies, battery pack thermal management mainly relies on external heat dissipation systems, such as air cooling, liquid cooling, or phase change material (PCM) encapsulation. However, these methods have significant drawbacks: air cooling and liquid cooling systems increase volume, weight, and energy consumption; traditional PCM materials (such as paraffin plates) have low thermal conductivity, cannot be adjusted in shape, have poor contact with the battery, and cannot actively control the direction of heat flow. Especially for lithium fluoride carbon battery packs, the heat generation during discharge is non-uniform over time, making it difficult for traditional heat dissipation solutions to achieve dynamic matching.

[0006] Therefore, developing a novel thermal management structure that can efficiently manage heat from within and ensure continuous high-power discharge of the battery pack has become the key to promoting the development of lithium fluoride battery pack technology. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a lithium fluoride carbon battery with high thermal management efficiency and the ability to ensure continuous high-power discharge, as well as a method for manufacturing the same.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a lithium fluoride carbon battery capable of continuous high-power discharge, comprising at least two unit cells and a battery casing, wherein the unit cell comprises multiple individual cells and a unit casing, and further comprising: A sheet-like thermal management interlayer is disposed between adjacent individual cells within the unit cell, and / or between different unit cells, and / or between the unit cell and the battery casing; The sheet-like thermal management interlayer is mainly a sheet-like graphene framework phase change composite material composed of a three-dimensional porous graphene network and a composite phase change material filling the pores of the network.

[0009] Preferably, as an improvement, the thermal management interlayer is a multi-layer composite flexible sheet, and further includes: The porous polymer interface layer is a hydrophobically modified porous polymer film with a porosity >50% and a thickness of 10~50μm. It covers the upper and lower surfaces of the sheet-like thermal management interlayer and is used to encapsulate the phase change material and achieve adaptive contact with the battery surface. The flexible sealing layer is a flexible sealing strip that is resistant to electrolyte corrosion and covers the perimeter of the sheet.

[0010] Preferably, as an improvement, the composite phase change material comprises a main phase change component with a phase change temperature of 50℃ to 90℃ and a thermally conductive enhanced nanofiller. The thermally conductive enhanced component is carbon nanotubes or boron nitride nanoparticles.

[0011] Preferably, as an improvement, thermally conductive silicone grease is also filled between adjacent individual cells within the cell.

[0012] Preferably, as an improvement, the contact area between the sheet-like thermal management interlayer and the side of the individual battery cell accounts for more than 80%. All individual batteries are thermally coupled to each other through the thermal management interlayer.

[0013] Preferably, as an improvement, the sheet-like thermal management interlayer has an in-plane thermal conductivity ≥15 W / (m·K) and a thickness of 0.5 mm to 10.0 mm. Its normal thermal conductivity is ≥5 W / (m·K), its radius of flexibility is ≤20 mm, and its heat capacity per unit area (including latent heat) is ≥150 kJ / (m²·K). 2 ·K).

[0014] Preferably, as an improvement, the main phase change component in the composite phase change material is selected from at least one of paraffin, fatty acids, polyols, or eutectic mixtures thereof.

[0015] Secondly, the present invention provides a method for manufacturing the lithium fluoride carbon battery capable of continuous high-power discharge, characterized by comprising the following steps: (1) Preparation of sheet-like graphene framework phase change material: a three-dimensional porous graphene framework is prepared, and molten composite phase change material is filled into the pores of the framework by vacuum impregnation. After hot pressing reduction treatment, sheet-like material is obtained. (2) Unit cell integration: After cutting the sheet material obtained in step (1), it is attached to the surface of the single cell, and multiple single cells and sheet materials are assembled into the unit shell to form a unit cell; (3) Battery module integration: At least two of the cell cells are spaced and thermally connected by the sheet material obtained in step (1) to assemble a battery module; (4) System integration: The temperature sensor is placed in the battery module, and then the battery casing is installed and the encapsulation is completed.

[0016] For cylindrical single-cell batteries, the sheet material is pre-formed into a matching arc or semi-enclosed structure; for square single-cell batteries, the sheet material is a flat plate structure.

[0017] Furthermore, the specific steps for preparing sheet-like graphene framework phase change materials are as follows: (1) Preparation of graphene framework: Using high-concentration uniformly dispersed graphene hydrogel as raw material and deionized water as solvent, the mixture is stirred at a high speed of 2000-3000 r / min for 60-150 min to obtain uniform and stable diluted graphene hydrogel; after freeze-drying, its porosity is controlled by pressure induction, and graphitization treatment at 2000-3000℃ is carried out to obtain a three-dimensional porous graphene framework. (2) Preparation of sheet-like graphene framework phase change material: The phase change material is placed in the device and fully melted into a liquid phase at a certain temperature; then the graphene framework is immersed in the molten phase change material, first vacuum degassing, then inert gas is introduced for pressurization, and the molten composite phase change material is filled into the pores of the framework through vacuum impregnation, and then the sheet-like material is obtained by hot pressing reduction treatment. (3) Unit cell integration: After cutting the sheet material obtained in step (2), attach it to the surface of the single cell, and assemble multiple single cells and sheet materials together into the unit shell to form a unit cell; (4) Battery module integration: At least two of the cell units are spaced and thermally connected by the sheet material obtained in step (2) to assemble a battery module; (5) System integration: The battery module is installed into the battery casing and encapsulated.

[0018] Preferably, as an improvement, the temperature of the hot-press reduction treatment in step (2) is 150~250℃ and the pressure is 5~20 MPa.

[0019] Preferably, as an improvement, in step (2), the temperature of the vacuum impregnation is 90~120℃.

[0020] The beneficial effects of this invention are as follows: 1. Active internal thermal management: The graphene framework constructs an ultra-high-speed heat conduction path from the reaction point outward, rapidly diffusing local hot spots to the entire positive electrode; at the same time, the phase change material encapsulated in the framework absorbs a large amount of latent heat when the phase change temperature is reached, effectively "flattening" the temperature peak and making the internal temperature field distribution of the battery more uniform and mild.

[0021] 2. Achieve continuous high-power discharge: Through effective internal temperature control, the battery will not trigger protection or experience a sharp performance degradation due to overheating during high-current discharge, thus enabling it to continuously discharge at a stable high power level until its capacity is nearly depleted.

[0022] 3. Enhanced safety and performance: It fundamentally suppresses the risk of thermal runaway and mitigates high-temperature side reactions, significantly improving the safety and performance of the battery under harsh operating conditions.

[0023] 4. Structural stability: The three-dimensional graphene network plays a good role in encapsulating and confining the phase change material, preventing leakage during the phase change process and ensuring the long-term structural integrity of the composite material during battery cycling.

[0024] 5. A paradigm shift from "encasing for heat dissipation" to "interlayer heat absorption and temperature homogenization": Traditional thermal management involves encasing the battery in a heat dissipation medium, with heat being conducted from the inside out. This invention uses a sheet-like material with high thermal conductivity and high heat storage capacity as an interlayer inserted between the batteries. This material can instantly absorb the heat generated by adjacent batteries and rapidly homogenize it within the surface, effectively eliminating local hot spots and temperature differences between batteries, and controlling the maximum temperature difference of the battery pack to within 5°C.

[0025] 6. "Time-sequenced thermal management" capability: The composite phase change material in the sheet material undergoes a solid-liquid phase change at a specific temperature (e.g., 60℃), absorbing a large amount of heat. In the early stage of discharge, the material absorbs sensible heat; when the temperature rises to the phase change point, the latent heat absorption begins, forming a temperature plateau period. This creates a long-term, stable, optimal operating temperature window for the battery, which is key to achieving "continuous" high-power discharge.

[0026] 7. Integrated structural and functional design: The sheet material has the characteristics of high thermal conductivity (graphene skeleton), high heat storage (phase change material), flexible bonding (porous interface layer) and corrosion resistance (sealing layer). It is embedded in the battery pack as a standardized functional component without changing the internal structure of the individual battery. It has strong versatility and simple process.

[0027] 8. Enhanced safety and reliability: As a physical isolation layer, the sheet material also plays multiple safety roles, such as preventing the spread of thermal runaway, buffering mechanical stress, and providing insulation protection, which significantly improves the overall reliability and safety of the battery pack. Attached Figure Description

[0028] Figure 1 This is a comparison chart of the surface temperature change curves of the lithium fluoride carbon battery provided in Example 1 of the present invention and the comparative battery under continuous high-power discharge. Detailed Implementation

[0029] The following detailed description illustrates the specific implementation method: Example 1: Sheet-like thermal management interlayer (graphene framework phase change material), lithium fluoride carbon battery and its preparation 1. Preparation of oriented porous graphene hydrogels: A 5 mg / mL aqueous solution of graphene oxide (GO) was injected into a long strip of polytetrafluoroethylene mold.

[0030] Place the mold on a -30℃ cold table, control the cooling of the bottom, so that the ice crystals grow upwards from the bottom, and freeze for 24 hours.

[0031] The frozen sample was freeze-dried for 72 hours to obtain a GO aerogel block with vertically oriented pores and a density of approximately 15 mg / cm³. The GO aerogel block is a graphene framework with a porosity of 92.3%.

[0032] 2. Vacuum impregnation lamination: Preparation of composite phase change materials: high-purity paraffin C 28 H 58 Straight-chain alkanes (phase transition point 62℃) and multi-walled carbon nanotubes (mass ratio 95:5) were melt-blended at 90℃.

[0033] Place the GO aerogel block in a vacuum impregnation tank, evacuate to below 10 Pa, inject molten composite phase change material, and impregnate under pressure for 2 hours.

[0034] 3. Heat reduction and compression molding: The impregnated composite material was placed in a hot press mold and heated to 200°C at a rate of 10°C / min under argon protection, and held at that temperature for 30 minutes for thermal reduction.

[0035] After the heat preservation is completed, a pressure of 15 MPa is applied and the material is held under pressure and cooled to room temperature to obtain a dense sheet with a thickness of 1.5 mm.

[0036] 4. Surface finishing and encapsulation: (1) Lay a polyethylene porous membrane (20 μm thick, 60% porosity) treated with polytetrafluoroethylene hydrophobic on both sides of the sheet.

[0037] Apply silicone rubber sealant to all four sides of the sheet, and after curing, cut it into 165mm×150mm square sheets for later use.

[0038] (2) Assembly of lithium fluoride carbon battery pack Unit cell integration: After the sheet material is cut, it is attached to the predetermined contact surface of the single cell stack with thermally conductive silicone grease, placed in the unit cell casing, and assembled into a unit cell; Battery module integration: After the sheet material is cut, it is attached to the predetermined contact surface of the cell using thermally conductive silicone grease, and then all the cell units and the sheet material are assembled together into a battery module. Battery pack integration: The battery module is placed into the battery pack casing, and sheet material is attached between the casing and the battery module to assemble a lithium fluoride battery pack.

[0039] Example 2: The difference from Example 1 is that high-purity C is used. 28 H 58 Straight-chain alkanes replaced with high-purity C 29 H 60 Straight-chain alkanes and high purity Stearic acid C 18 H 36 O 2.

[0040] Example 3: The difference from Example 1 is that high-purity C is used. 28 H 58 Straight-chain alkanes replaced with high-purity C 28 H 58 Straight-chain alkanes and high-purity C 32 H 66 A mixture of straight-chain alkane eutectic.

[0041] Comparative Example 1 Using the same single cell, unit cell, and battery casing as in the previous embodiment, the battery pack is assembled in a tightly arranged manner without thermal management interlayer, relying solely on the natural heat dissipation of the casing.

[0042] Comparative Example 2 Using the same single cell, unit cell, and battery casing as in Example 1, the thermal management interlayer in Example 1 is replaced with a thermal management interlayer without graphene framework. The rest is the same as in Example 1. The battery pack is assembled and heat dissipation relies on phase change materials and the casing.

[0043] Performance testing: The battery packs of Example 1, Comparative Example 1, and Comparative Example 2 were tested at an ambient temperature of 25°C.

[0044] Example 1 Battery Pack: During discharge, the temperature rises gradually, reaching a plateau of 55-65°C in the middle of the discharge (approximately 30 minutes), which lasts for about 50 minutes, with a maximum temperature of approximately 65°C. The total discharge time is 120 minutes, and the maximum temperature is 71°C.

[0045] Example 2 Battery Pack: During discharge, the temperature rises gradually, reaching a plateau of 58-68°C in the middle of the discharge (approximately 30 minutes), which lasts for about 45 minutes, with a maximum temperature of approximately 68°C. The total discharge time is 100 minutes, and the maximum temperature is 71°C.

[0046] Example 3 Battery Pack: During discharge, the temperature rises gradually, reaching a plateau of 58-68°C in the middle of the discharge (approximately 40 minutes), which lasts for about 75 minutes, with a maximum temperature of approximately 68°C. The total discharge time is 145 minutes, and the maximum temperature is 71°C.

[0047] Comparative Example 1 Battery Pack: The temperature rose rapidly, and the center temperature exceeded 71°C after about 35 minutes of discharge. The total discharge time was only 41 minutes, with a maximum temperature of 75°C.

[0048] Comparative Example 2 Battery Pack: The temperature rose rapidly, and the center temperature exceeded 71°C after about 55 minutes of discharge. The total discharge time was only 68 minutes, with a maximum temperature of 75°C.

[0049] The sheet-like thermal management interlayer obtained in Example 1 was tested to have an in-plane thermal conductivity of 25 W / (m·K), a normal thermal conductivity of 10 W / (m·K), and a heat capacity per unit area (including latent heat) of 300 kJ / (m²). 2 ·K).

Claims

1. A lithium-carbon fluoride battery capable of continuous high-power discharge, comprising at least two cell units and a battery casing, wherein the cell unit comprises multiple individual cells and a cell casing, characterized in that, Also includes: A sheet-like thermal management interlayer is disposed between adjacent individual cells within the unit cell, and / or between different unit cells, and / or between the unit cell and the battery casing; The sheet-like thermal management interlayer is mainly a sheet-like graphene framework phase change composite material composed of a three-dimensional porous graphene network and a composite phase change material filling the pores of the network.

2. The lithium fluoride carbon battery according to claim 1, characterized in that, The thermal management interlayer is a multi-layer composite flexible sheet, and also includes: A porous polymer interface layer covers the upper and lower surfaces of the sheet-like thermal management interlayer; A flexible sealing layer that covers the perimeter of the sheet.

3. The lithium fluoride carbon battery according to claim 1 or 2, characterized in that, The composite phase change material includes a main phase change component with a phase change temperature of 50℃~90℃ and a thermally conductive enhanced nanofiller.

4. The lithium fluoride carbon battery according to claim 1, characterized in that, Thermally conductive silicone grease is also filled between adjacent individual cells within the cell.

5. The lithium fluoride carbon battery according to claim 1, characterized in that, The contact area between the sheet-like thermal management interlayer and the side of the individual battery cell accounts for more than 80%.

6. The lithium fluoride carbon battery according to claim 1, characterized in that, The sheet-like thermal management interlayer has an in-plane thermal conductivity of ≥15 W / (m·K) and a thickness of 0.5 mm to 10.0 mm.

7. The lithium fluoride carbon battery according to claim 1, characterized in that, The main phase change component in the composite phase change material is selected from at least one of high-purity paraffin, fatty acids, or alkane eutectic mixtures.

8. A method for manufacturing a lithium-carbon fluoride battery capable of continuous high-power discharge as described in any one of claims 1, 2, 4 to 7, characterized in that, Includes the following steps: (1) Preparation of graphene framework: Using high-concentration uniformly dispersed graphene hydrogel as raw material and deionized water as solvent, the mixture is stirred at a high speed of 2000-3000 r / min for 60-150 min to obtain uniform and stable diluted graphene hydrogel; after freeze-drying, its porosity is controlled by pressure induction, and graphitization treatment at 2000-3000℃ is carried out to obtain a three-dimensional porous graphene framework. (2) Preparation of sheet-like graphene framework phase change material: The phase change material is placed in the device and fully melted into a liquid phase at a certain temperature; then the graphene framework is immersed in the molten phase change material, first vacuum degassing, then inert gas is introduced for pressurization, and the molten composite phase change material is filled into the pores of the framework through vacuum impregnation, and then the sheet-like material is obtained by hot pressing reduction treatment. (3) Unit cell integration: After cutting the sheet material obtained in step (2), attach it to the surface of the single cell, and assemble multiple single cells and sheet materials together into the unit shell to form a unit cell; (4) Battery module integration: At least two of the cell units are spaced and thermally connected by the sheet material obtained in step (2) to assemble a battery module; (5) System integration: The battery module is installed into the battery casing and encapsulated.

9. The manufacturing method according to claim 8, characterized in that, The temperature of the hot-press reduction treatment in step (2) is 150~250℃ and the pressure is 5~20 MPa.

10. The manufacturing method according to claim 8, characterized in that, In step (2), the temperature of the vacuum impregnation is 90~120℃.

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