Stepped phase change battery thermal management system

Abstract

The invention relates to a stepped phase change battery thermal management system which is characterized by comprising a battery module, a liquid cooling plate and a stepped phase change material, the battery module comprises more than one single battery, the single batteries are arranged adjacently, and a phase change space is reserved between the adjacent single batteries; the liquid cooling plates are arranged at the end parts of the single batteries; the stepped phase change material comprises a first phase change material and a second phase change material, the first phase change material and the second phase change material are arranged in the phase change space, the first phase change material is located in the direction, away from the liquid cooling plate, of the phase change space, and the second phase change material is located in the other direction of the phase change space and makes contact with the liquid cooling plate; the phase change temperature of the first phase change material is higher than that of the second phase change material. The method is characterized in that a stepped phase change material is adopted, in the process of cooling the battery by liquid cooling, the balance of the internal temperature of the battery is kept, the service life of the battery is prolonged, and the service power of the battery is guaranteed.

Description

Technical Field

[0001] The present invention relates to a stepped phase change battery thermal management system. Background Art

[0002] At present, new energy batteries are becoming more and more popular. Batteries will generate heat during use. In order to ensure that the temperature of the battery is within a controllable range during use, a liquid cooling plate is usually installed at one end of the battery to reduce the battery temperature during use. The above structure has the following situation: during the process of the liquid cooling plate cooling the battery, the temperature of the battery near the liquid cooling plate end will be lower than that of the end far from the liquid cooling plate, and the battery heat is not balanced. The consequences are as follows: 1. Capacity imbalance and power decline: The reaction rate of the battery in the high-temperature area accelerates, and the reaction rate in the low-temperature area decreases, resulting in an enlarged capacity difference between monomers (the capacity in the high-temperature area decreases rapidly, the capacity in the low-temperature area remains unchanged but the overall energy storage capacity decreases), the activity difference of the electrode material increases the internal resistance, the discharge rate is limited, and the system output power decreases; 2. Accelerate battery aging: Side reactions in the high-temperature area (such as lithium deposition and electrolyte decomposition) accelerate, the capacity utilization rate in the low-temperature area decreases, and the attenuation rate of the entire life cycle increases by more than 30% 57; During the cycle process, the temperature difference continues to expand, and the capacity attenuation rate shows a non-linear growth. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a stepped phase change battery thermal management system, which uses stepped phase change materials to keep the temperature inside the battery balanced during the process of liquid cooling to cool the battery, extend the life of the battery, and ensure the battery use power.

[0004] To achieve the above purpose, the technical solution of the present invention is realized as follows. It is a stepped phase change battery thermal management system, including a battery module and a liquid cooling plate; the battery module includes more than one single battery, each of the single batteries is arranged adjacent to each other, and a phase change space is left between adjacent single batteries; the liquid cooling plate is arranged at the end of the single battery; stepped phase change materials; the stepped phase change materials include a first phase change material and a second phase change material, the first phase change material and the second phase change material are respectively arranged in the phase change space, the first phase change material is located in the direction of the phase change space away from the liquid cooling plate, and the second phase change material is located in the other direction of the phase change space and contacts the liquid cooling plate; the phase change temperature of the first phase change material is greater than the phase change temperature of the second phase change material.

[0005] In this technical solution, the volume ratio of the first phase change material and the second phase change material in the phase change space is 7:3 to 3:7.

[0006] In this technical solution, the first phase change material is composed of sodium acetate trihydrate, polyethylene glycol, sodium pyrophosphate decahydrate, a thermal conductivity enhancer, urea and hydrogel.

[0007] In this technical solution, the mass percentage of the first phase change material is composed of 62-75wt% of sodium acetate trihydrate, 3-8wt% of polyethylene glycol, 3-8wt% of sodium pyrophosphate decahydrate, 3-5wt% of thermal conductivity enhancer, 2-5wt% of urea, and 20-25wt% of hydrogel.

[0008] In this technical solution, the second phase change material is composed of disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and hydrogel.

[0009] In this technical solution, the mass percentage of the second phase change material is composed of 55-65wt% of disodium hydrogen phosphate dodecahydrate, 10-20wt% of sodium carbonate decahydrate, and 20-25wt% of hydrogel.

[0010] In this technical solution, the hydrogel is composed of polyvinyl alcohol and sodium alginate.

[0011] In this technical solution, the dry basis mass ratio of polyvinyl alcohol to sodium alginate is 3:1-4:1.

[0012] The advantages of the present invention compared with the prior art are as follows: By using a stepped phase change material, during the process of cooling the battery by liquid cooling, the temperature inside the battery is kept balanced, the service life of the battery is extended, and the power of the battery during use is guaranteed. Description of the Drawings

[0013] Figure 1 is a schematic structural diagram of the present invention. Detailed Embodiments

[0014] The following further describes the detailed embodiments of the present invention with reference to the drawings. It should be noted here that the description of these embodiments is for helping to understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0015] In the description of the present invention, the orientation or positional relationship indicated by the terms "upper", "lower", "right", "inner", "left", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific orientation, so it cannot be understood as a limitation to the present invention.

[0016] In the present invention, unless otherwise clearly defined and limited, terms such as "set" and "sheath" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, and it may be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0017] As Figure 1 shown, it is a stepped phase change battery thermal management system, which is characterized by including a battery module and a liquid cooling plate 2; the battery module includes more than one single battery 1, each of the single batteries 1 is arranged adjacent to each other, and a phase change space is left between adjacent single batteries 1; the liquid cooling plate 2 is arranged at the end of the single battery 1; a stepped phase change material; the stepped phase change material includes a first phase change material 3 and a second phase change material 4, the first phase change material 3 and the second phase change material 4 are respectively arranged in the phase change space, the first phase change material 3 is located in the direction away from the liquid cooling plate 2 in the phase change space, and the second phase change material 4 is located in the other direction of the phase change space and contacts the liquid cooling plate 2; the phase change temperature of the first phase change material 3 is greater than the phase change temperature of the second phase change material 4.

[0018] By adopting the stepped phase change material, during the process of cooling the battery by liquid cooling, the internal temperature of the battery is kept balanced, the service life of the battery is prolonged, and the power consumption of the battery is guaranteed.

[0019] First embodiment: The first phase change material 3 is composed of 21wt% of a hydrogel composed of polyvinyl alcohol and sodium alginate (dry basis mass ratio 4:1), 65wt% of sodium acetate trihydrate, 3wt% of urea, 3wt% of polyethylene glycol, 5wt% of sodium pyrophosphate decahydrate, and 3wt% of a thermal conductivity enhancer; The second phase change material 4 is composed of 25wt% of a hydrogel composed of polyvinyl alcohol and sodium alginate (dry basis mass ratio 4:1), 65wt% of disodium hydrogen phosphate dodecahydrate, and 10wt% of sodium carbonate decahydrate; The filling ratio is that the upper layer filling volume to the lower layer filling volume ratio is 6:4, and the liquid cooling plate 2 adopts a serpentine flow channel.

[0020] Stress buffering effect: The elongation at break, tensile strength, and Young's modulus of the first phase change material 3 are respectively: 115%, 0.61 MPa, and 5.43 Mpa, the phase change temperature is 45°C, and the enthalpy value is 201 kJ / kg; The elongation at break, tensile strength and Young's modulus of the second phase change material 4 are 119.5%, 0.59 MPa and 5.18 Mpa respectively, the phase change temperature is 32 °C, and the enthalpy value is 195 kJ / kg; When the battery pack starts to operate, the single cell 1 generates heat and the temperature gradually rises. When the temperature of the lower part of the battery (about 40% of the battery height) reaches 35 °C, the second phase change material 4 starts to absorb heat and melt, and the temperature at the bottom of the battery is maintained in the range of 35 - 38 °C; the temperature of the upper part of the battery (about 60% of the upper height of the battery) gradually rises to 48 °C, and the first phase change material 3 starts to absorb heat and melt, and the temperature at the top of the battery is maintained in the range of 42 - 50 °C; an ethylene glycol aqueous solution with a concentration of 50% is used in the liquid cooling plate 2, the inlet temperature is 25 °C, the coolant flow rate is set at 6 L / min, the liquid cooling plate 2 is in direct contact with the lower second phase change material 4, and the heat of the lower second phase change material 4 is taken away through the coolant circulation. The heat of the upper first phase change material 3 is taken away through the coolant circulation based on the heat conduction of the lower second phase change material 4, realizing the recycling of the upper first phase change material 3 and the lower second phase change material 4. The average temperature of the battery pack is controlled in the range of 35 - 42 °C, and the maximum temperature of the single cell is controlled below 50 °C. Example

[0021] The first phase change material 3 consists of 21 wt% of a hydrogel composed of polyvinyl alcohol and sodium alginate (dry basis mass ratio 4:1), 65 wt% of sodium acetate trihydrate, 5 wt% of urea, 1 wt% of polyethylene glycol, 6 wt% of sodium pyrophosphate decahydrate, and 2 wt% of a thermal conductivity enhancer; The second phase change material 4 consists of 21 wt% of a hydrogel composed of polyvinyl alcohol and sodium alginate (dry basis mass ratio 4:1), 68 wt% of disodium hydrogen phosphate dodecahydrate, and 11 wt% of sodium carbonate decahydrate; The filling ratio is that the upper filling volume to the lower filling volume ratio is 7:3, and the liquid cooling plate 2 adopts a serpentine flow channel.

[0022] Stress buffering effect: The phase change temperature of the first phase change material 3 is 42 °C, and the enthalpy value is 189 kJ / kg; The phase change temperature of the second phase change material 4 is 33 °C, and the enthalpy value is 185 kJ / kg; When the battery pack starts to operate, the single cell 1 generates heat and the temperature gradually rises. The temperature of the lower part of the battery (about 30% of the battery height) reaches 35°C, and the second phase change material 4 begins to absorb heat and melt. The temperature at the bottom of the battery is maintained in the range of 35 - 39°C. The temperature of the upper part of the battery (about 70% of the upper height of the battery) gradually rises to 45°C, and the first phase change material 3 begins to absorb heat and melt. The temperature at the top of the battery is maintained in the range of 40 - 45°C. An ethylene glycol aqueous solution with a concentration of 50% is used in the liquid cooling plate 2, the inlet temperature is 25°C, and the coolant flow rate is set at 1.5 m / s. The liquid cooling plate is in direct contact with the lower second phase change material 4, and the heat of the lower second phase change material 4 is carried away through the coolant circulation. The heat of the upper first phase change material 3 is carried away through the coolant circulation by the heat conduction effect based on the lower second phase change material 4, realizing the recycling of the upper first phase change material 3 and the lower second phase change material 4. The average temperature of the battery pack is controlled within 35 - 43°C, and the maximum temperature of the single cell is controlled below 45°C.

[0023] In this embodiment, the volume ratio of the first phase change material 3 and the second phase change material 4 in the phase change space is 7:3 to 3:7.

[0024] In this embodiment, the first phase change material 3 is composed of disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and hydrogel.

[0025] In this embodiment, it is composed of 55 - 65 wt% of disodium hydrogen phosphate dodecahydrate, 10 - 20 wt% of sodium carbonate decahydrate, and 20 - 25 wt% of hydrogel.

[0026] In this embodiment, the second phase change material 4 is composed of sodium acetate trihydrate, polyethylene glycol, sodium pyrophosphate decahydrate, thermal conductivity enhancer, and hydrogel.

[0027] In this embodiment, it is composed of 65 - 75 wt% of sodium acetate trihydrate, 3 - 8 wt% of polyethylene glycol, 3 - 8 wt% of sodium pyrophosphate decahydrate, 3 - 5 wt% of thermal conductivity enhancer, and 20 - 25 wt% of hydrogel.

[0028] In this embodiment, the hydrogel is composed of polyvinyl alcohol and sodium alginate.

[0029] In this embodiment, the dry - basis mass ratio of polyvinyl alcohol and sodium alginate is 3:1 - 4:1.

[0030] The above has made a detailed description of the embodiments of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the described embodiments. For those of ordinary skill in the art, various changes, modifications, substitutions, and deformations to these embodiments still fall within the protection scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A stepped phase change battery thermal management system, characterized in that Comprising a battery module and a liquid cooling plate (2); the battery module includes more than one single battery (1), each of the single batteries (1) is arranged adjacent to each other, and a phase change space is left between adjacent single batteries (1); the liquid cooling plate (2) is arranged at the end of the single battery (1). A stepped phase change material; the stepped phase change material includes a first phase change material (3) and a second phase change material (4), the first phase change material (3) and the second phase change material (4) are respectively arranged in the phase change space, the first phase change material (3) is located in the direction away from the liquid cooling plate (2) of the phase change space, and the second phase change material (4) is located in the other direction of the phase change space and contacts the liquid cooling plate (2); the phase change temperature of the first phase change material (3) is greater than the phase change temperature of the second phase change material (4).

2. The stepped phase change battery thermal management system according to claim 1, wherein The volume ratio of the first phase change material (3) and the second phase change material (4) in the phase change space is 7:3 to 3:

7.

3. The stepped phase change battery thermal management system according to claim 1, characterized in that The first phase change material (3) is composed of sodium acetate trihydrate, polyethylene glycol, sodium pyrophosphate decahydrate, a thermal conductivity enhancer, urea and hydrogel.

4. The stepped phase change battery thermal management system according to claim 3, wherein The mass percentage of the first phase change material (3) is composed of 62-75wt% of sodium acetate trihydrate, 3-8wt% of polyethylene glycol, 3-8wt% of sodium pyrophosphate decahydrate, 3-5wt% of a thermal conductivity enhancer, 2-5wt% of urea and 20-25wt% of hydrogel.

5. The stepped phase change battery thermal management system according to claim 1, wherein The second phase change material (4) is composed of disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate and hydrogel.

6. The stepped phase change battery thermal management system according to claim 5, wherein The mass percentage of the second phase change material (4) is composed of 55-65wt% of disodium hydrogen phosphate dodecahydrate, 10-20wt% of sodium carbonate decahydrate and 20-25wt% of hydrogel.

7. The stepped phase change battery thermal management system according to claim 3 or 5, characterized in that The hydrogel is composed of polyvinyl alcohol and sodium alginate.

8. The stepped phase change battery thermal management system according to claim 7, characterized in that The dry basis mass ratio of polyvinyl alcohol and sodium alginate is 3:1-4:1.

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