Composite cylindrical battery thermal management system

Abstract

The invention discloses a composite cylindrical battery thermal management system which comprises a single battery, the single battery is nested in a sleeve, a plurality of transverse fins are uniformly distributed on the outer side of the sleeve, a shell is arranged on the outer sides of the sleeve and the transverse fins, phase change materials are filled among the sleeve, the transverse fins and the shell, and the transverse fins are in contact with the sleeve and the shell respectively; one part of heat generated by the single batteries is transmitted to the phase-change material and is absorbed by the phase-change material through the transmission of the sleeves, the transverse fins and the shell, and the other part of heat is transmitted to the external environment through the shell. By using the sleeve, a high-thermal-conductivity network can be formed to accelerate heat transfer, the problem of large temperature difference of the battery caused by traditional transverse fins is solved, the temperature uniformity of the battery is improved, the thermal conductivity of the phase-change material is improved, heat dissipation is enhanced, the defect of insufficient thermal conductivity of the phase-change material is overcome, and safe and efficient operation of the battery at high charge-discharge rate is ensured.

Description

Technical Field

[0001] The present invention relates to a composite cylindrical battery thermal management system, in particular to a composite cylindrical battery thermal management system combining a phase change material with a transverse fin-sleeve, and belongs to the technical field of lithium battery thermal management. Background Art

[0002] In the context of energy shortage and environmental pollution, electric vehicles have become an important sustainable solution for future transportation due to their low energy consumption and zero emissions. Lithium batteries are considered the best power source for electric vehicles due to their high power density, long service life, and no memory effect. However, lithium batteries are very sensitive to temperature. Lithium batteries generate huge heat at high discharge rates. The high temperature caused by the continuous accumulation of heat will lead to a decrease in the battery's discharge capacity and increase the risk of thermal runaway. In order to ensure that lithium batteries have optimal working efficiency, their operating temperature should be in the range of 20℃-40℃, and the maximum temperature difference of the battery should not exceed 5℃. Therefore, it is crucial to establish a stable and efficient battery thermal management system to ensure that the battery operates within a suitable operating temperature range.

[0003] Phase change materials have the potential to become an ideal choice for the next generation of battery thermal management technology due to their high thermal energy storage density and stable temperature uniformity. However, the low thermal conductivity of phase change materials severely limits the thermal performance of the battery thermal management system, especially under high discharge rate conditions, which can easily cause heat accumulation problems. Therefore, effective strategies, such as adding fins to improve the thermal conductivity of phase change materials, are needed to enhance the overall thermal management effect. Although the use of traditional transverse fins can effectively reduce the maximum temperature of the battery, there is a problem of excessive battery temperature difference (maximum temperature minus minimum temperature in the battery) at high discharge rates. Summary of the invention

[0004] The technical problem to be solved by the present invention is to solve the problem of large temperature difference in the battery caused by traditional transverse fins, improve the temperature uniformity of the battery, and at the same time compensate for the problem of low thermal conductivity of the phase change material, thereby reducing the maximum temperature of the battery and ensuring that the battery operates safely and efficiently at high charge and discharge rates.

[0005] In order to solve the above technical problems, the technical solution of the present invention is to provide a composite cylindrical battery thermal management system, which is characterized in that it includes a single cell, the single cell is nested in a sleeve, a plurality of transverse fins are evenly distributed on the outside of the sleeve, an outer shell is provided on the outside of the sleeve and the transverse fins, a phase change material is filled between the sleeve, the transverse fins and the outer shell, and the transverse fins are in contact with the sleeve and the outer shell respectively; the heat generated by the single cell is transferred through the sleeve, the transverse fins and the outer shell, a part of which is transferred to the phase change material and absorbed by the phase change material, and the other part is transferred to the external environment through the outer shell.

[0006] Preferably, the plurality of transverse fins separate the phase change material into a plurality of regions.

[0007] Preferably, the plurality of transverse fins are evenly distributed along the axial direction of the sleeve.

[0008] Preferably, when the temperature of the sleeve wall reaches the melting point of the phase change material, the latent heat of the phase change material takes effect and absorbs the heat generated by the single battery.

[0009] Preferably, the phase change material is an organic phase change material with high latent heat.

[0010] Preferably, the phase change material is paraffin with high latent heat, and the phase change temperature is between 29°C and 36°C.

[0011] Preferably, the sleeve, transverse fins and housing are all made of materials with high thermal conductivity.

[0012] Preferably, the height of the shell and the height of the sleeve are consistent with the height of the single battery; the inner wall of the sleeve is in close contact with the outer wall of the single battery.

[0013] Preferably, the transverse fin is a circular plate-shaped structure, and the single battery, the sleeve, the transverse fin, the phase change material and the shell are all provided with a same central axis; and the plane where the transverse fin is located is perpendicular to the central axis of the sleeve.

[0014] Preferably, the single cell is one of 18650, 21700 or 26650 cylindrical lithium-ion batteries.

[0015] Compared with pure phase change material heat dissipation, the use of traditional transverse fins for heat dissipation can significantly reduce the maximum temperature of the battery, but it also increases the temperature difference of the battery. This is because the high thermal conductivity of the transverse fins will cause local low temperatures in the battery, thereby increasing the overall temperature difference. The present invention can solve the problem of large battery temperature difference (maximum temperature minus minimum temperature in the battery) caused by traditional transverse fins, while further reducing the maximum temperature of the battery and achieving more efficient thermal management performance. This is because the addition of the sleeve can, on the one hand, avoid the problem of increased temperature difference caused by direct contact between the transverse fins and the battery, and on the other hand, it can further improve the thermal conductivity of the phase change material.

[0016] The present invention uses a sleeve to form a high thermal conductivity network to accelerate heat transfer, solve the problem of large temperature difference in the battery caused by traditional transverse fins, improve the temperature uniformity of the battery, and at the same time improve the thermal conductivity of the phase change material, enhance heat dissipation, and make up for the disadvantage of insufficient thermal conductivity of the phase change material, ensuring that the battery operates safely and efficiently at high charge and discharge rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of a composite cylindrical battery thermal management system;

[0018] Figure 2 It is a schematic diagram of an exploded view of a composite cylindrical battery thermal management system;

[0019] Figure 3 It is a schematic diagram showing the maximum temperature variation over time of a pure phase change battery, a battery with a traditional transverse fin, and a battery combining the transverse fin and the sleeve of the present invention;

[0020] Figure 4 It is a schematic diagram of the temperature difference variation over time for a pure phase change battery, a battery with traditional transverse fins, and a battery combining the transverse fins and sleeves of the present invention.

[0021] In the figure: 1 - single cell; 2 - casing; 3 - transverse fins; 4 - phase change material; 5 - casing. DETAILED DESCRIPTION

[0022] In order to make the present invention more clearly understood, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0023] The present invention provides a composite cylindrical battery thermal management system, such as Figure 1 , Figure 2 As shown, it includes a single cell 1, a sleeve 2, a transverse fin 3, a phase change material 4 and a shell 5; the single cell 1 is a cylindrical lithium battery, the single cell 1 is nested in the sleeve 2 (that is, the sleeve 2 tightly wraps the single cell 1), a plurality of identical transverse fins 3 are evenly distributed along the axial direction of the sleeve 2 (in this embodiment, there are three transverse fins 3 on the sleeve 2), the phase change material 4 is filled between the sleeve 2, the transverse fin 3 and the shell 5, and the inner and outer walls of the transverse fin 3 are in contact with the sleeve 2 and the shell 5 respectively, which not only separates the phase change material 4 into multiple areas, but also forms a heat conduction network to accelerate heat transfer; under high charge and discharge rates, the sleeve 2 can effectively improve the uniformity of the temperature of the single cell 1, the sleeve 2 and the transverse fin 3 can enhance the heat transfer between the single cell 1 and the phase change material 4, and compensate for the low thermal conductivity of the phase change material 4; the heat generated by the single cell 1 is transferred through the sleeve 2, the transverse fin 3 and the shell 5, a part of which is transferred to the phase change material 4 and absorbed by the phase change material 4, and a part of which is transferred to the external environment through the shell 5. The inner wall of the shell 5 is in contact with the transverse fins 3 and the phase change material 4, and there is natural convection heat exchange between the outer wall of the shell 5 and the external environment. When the wall temperature of the sleeve 2 reaches the melting point of the phase change material 4, the latent heat of the phase change material 4 takes effect to absorb the heat generated by the single battery 1; the phase change material 4 selects an organic phase change material with high latent heat, which helps to absorb the heat generated by the battery; the sleeve 2, the transverse fins 3 and the shell 5 are all made of materials with high thermal conductivity to enhance heat transfer. The phase change material 4 fills the remaining space in the shell 5, fully absorbs the heat conducted from the sleeve 2, the transverse fins 3 and the shell 5, and is heated on all four sides, so it can melt more evenly.

[0024] The organic phase change material with high latent heat selected by the phase change material 4 can be paraffin, or a composite phase change material composed of paraffin and other materials (such as graphite, silicon, etc.). The phase change temperature of paraffin is between 29°C and 36°C. The material with high thermal conductivity can be metal aluminum, which has a high thermal conductivity coefficient, and other materials with high thermal conductivity can also be selected.

[0025] In one embodiment, the transverse fin 3 may be a circular plate structure, and the single cell 1, the sleeve 2, the transverse fin 3, the phase change material 4 and the shell 5 are all provided with the same central axis; the plane where the transverse fin 3 is located is perpendicular to the central axis of the sleeve 2. The transverse fin 3 may also be a structure of other shapes, as long as the transverse fin 3 is connected to the sleeve 2 and the shell 5. The single cell 1 may be a 18650 cylindrical lithium-ion battery, or a battery of other models such as 21700, 26650, etc.

[0026] The height of the sleeve 2 is consistent with that of the single cell 1, both of which are 65mm, and the diameter is 18mm; the inner wall of the sleeve 2 is close to the outer wall of the single cell 1, which can increase the heat transfer area and accelerate the heat transfer. The sleeve 2 wraps the single cell 1 and has a thickness of 1mm; the number of transverse fins 3 is 3, the thickness is 2mm, and the length is 5mm, which is evenly distributed along the axial direction of the sleeve 2, and the inner and outer walls are in contact with the sleeve 2 and the shell 5 respectively; the phase change material 4 is divided into 4 sections by the transverse fins 3, and the height of each section is 14.75mm; the inner diameter of the shell 5 is 30mm, the thickness is 1mm, and the height is consistent with the single cell 1 and the sleeve 2.

[0027] like Figure 3 As shown, it shows the change of the maximum temperature of the battery when using different heat dissipation structures at a 5C discharge rate (wherein, the 5C discharge rate is only one example, and it is not necessarily applicable under the condition of a high discharge rate of 5C. The structure proposed by the present invention still has better effects than pure phase change materials and traditional transverse fins at other discharge rates). At the end of discharge, the maximum temperatures of the battery with pure phase change heat dissipation and the addition of traditional transverse fins for heat dissipation were 51.72°C and 43.2°C, respectively. Since the addition of transverse fins effectively improves the thermal conductivity of the phase change material, the maximum temperature of the battery is reduced by 8.52°C, but neither of these two heat dissipation methods keeps the battery within the optimal operating temperature range of 20°C to 40°C; and the composite structure of the transverse fins and sleeves of the present invention can make the battery work within the optimal operating temperature range. At the end of discharge, the maximum temperature is 39.1°C, because this structure can further improve the longitudinal thermal conductivity of the phase change material.

[0028] like Figure 4As shown, it shows the change of battery temperature difference when using different heat dissipation structures at a 5C discharge rate. At the end of discharge, the battery temperature difference of pure phase change heat dissipation is 4.2°C, which can meet the temperature difference control requirement within 5°C; but under the condition of using traditional transverse fins, the battery temperature difference rises to 6.79°C. Too high a temperature difference will accelerate the aging of battery materials, reduce cycle life, and increase the risk of thermal runaway; transverse fins can effectively improve the thermal conductivity of phase change materials and reduce battery temperature, but at the same time there is a problem of excessive battery temperature difference; the composite structure of the transverse fins and sleeves of the present invention can not only solve the problem of excessive battery temperature difference, but also further improve the thermal conductivity of the phase change material. At the end of discharge, the battery temperature difference is only 1.97°C.

Claims

1. A composite cylindrical battery thermal management system, characterized in that: The invention comprises a single cell (1), wherein the single cell (1) is nested in a sleeve (2), a plurality of transverse fins (3) are evenly distributed on the outside of the sleeve (2), a shell (5) is provided on the outside of the sleeve (2) and the transverse fins (3), a phase change material (4) is filled between the sleeve (2), the transverse fins (3) and the shell (5), and the transverse fins (3) are in contact with the sleeve (2) and the shell (5) respectively; heat generated by the single cell (1) is transferred through the sleeve (2), the transverse fins (3) and the shell (5), a part of which is transferred to the phase change material (4) and absorbed by the phase change material (4), and the other part is transferred to the external environment through the shell (5).

2. A composite cylindrical battery thermal management system as claimed in claim 1, characterized in that: The plurality of transverse fins (3) separate the phase change material (4) into a plurality of regions.

3. A composite cylindrical battery thermal management system as claimed in claim 1, characterized in that: The multiple transverse fins (3) are evenly distributed along the axial direction of the sleeve (2).

4. A composite cylindrical battery thermal management system as claimed in claim 1, characterized in that: When the wall temperature of the sleeve (2) reaches the melting point of the phase change material (4), the latent heat of the phase change material (4) takes effect and absorbs the heat generated by the single battery (1).

5. A composite cylindrical battery thermal management system as claimed in claim 4, characterized in that: The phase change material (4) is an organic phase change material with high latent heat.

6. A composite cylindrical battery thermal management system as claimed in claim 5, characterized in that: The phase change material (4) is paraffin with high latent heat, and the phase change temperature is between 29°C and 36°C.

7. A composite cylindrical battery thermal management system as claimed in claim 1, characterized in that: The sleeve (2), transverse fins (3) and shell (5) are all made of materials with high thermal conductivity.

8. A composite cylindrical battery thermal management system as claimed in claim 1, characterized in that: The height of the outer shell (5) and the height of the sleeve (2) are both consistent with the height of the single cell (1); the inner wall of the sleeve (2) is in close contact with the outer wall of the single cell (1).

9. A composite cylindrical battery thermal management system as claimed in claim 1, characterized in that: The transverse fin (3) is a circular plate-shaped structure; the single battery (1), the sleeve (2), the transverse fin (3), the phase change material (4) and the shell (5) are all provided with a same central axis; the plane where the transverse fin (3) is located is perpendicular to the central axis of the sleeve (2).

10. A composite cylindrical battery thermal management system as claimed in claim 1, characterized in that: The single cell (1) is one of 18650, 21700 or 26650 cylindrical lithium ion batteries.

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