Thermal management device and thermal management method of vehicle-mounted lithium battery

Abstract

The invention discloses a thermal management device and a thermal management method of a vehicle-mounted lithium battery, and belongs to the technical field of lithium battery thermal management, and the thermal management device comprises a heat pump circulation unit which is arranged at the negative electrode end of a lithium battery stack and is connected with the lithium battery stack so as to realize refrigeration / heating circulation; and the first vacuum heat insulation layer is connected with one end, far away from the lithium battery stack, of the heat pump circulation unit. According to the thermal management device and the thermal management method for the vehicle-mounted lithium battery, the influence of the external environment on the vehicle-mounted lithium battery can be effectively isolated, and the risks that the capacity of the lithium battery is greatly attenuated in a low-temperature environment and thermal runaway spontaneous combustion is generated in a high-temperature environment are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal management of lithium batteries, and in particular relates to a thermal management device and a thermal management method for a vehicle-mounted lithium battery. Background Art

[0002] Lithium-ion batteries are the most widely used batteries in electric vehicles and energy storage systems. They are extremely sensitive to the ambient temperature during operation. The ambient temperature has a great impact on the working performance, cycle capacity, and operating efficiency of lithium batteries. The optimal working temperature of lithium batteries is 15-45°C, but the actual working temperature is between -10°C and 60°C, far exceeding the optimal operating temperature. Excessively high or low ambient temperatures and increased temperature differences within the battery pack will have a significant negative impact on the overall working performance and service life of the lithium-ion battery pack. In addition, if the battery works in a high temperature environment for a long time and the heat cannot be effectively dissipated, it will lead to thermal runaway of the battery, which will not only cause serious economic losses, but also pose a threat to personal safety.

[0003] In order to reduce the impact of the environment on lithium batteries and ensure that the batteries can maintain a safe and stable temperature range under extreme conditions, adding a lithium battery thermal management system to electric vehicles is currently a common method.

[0004] The thermal management of lithium batteries in the prior art focuses more on battery cooling, which can be divided into active cooling and passive cooling according to different cooling methods; the former achieves better thermal management effects by consuming additional work, while the latter only dissipates heat through its own structure; according to the different cooling media used, the battery thermal management system can also be divided into air cooling, liquid cooling, phase change material cooling, etc.; phase change material cooling belongs to passive cooling, which has the characteristics of simple structure, high thermal energy density, and uniform temperature, but it only plays the role of simple heat absorption and energy storage. When the latent heat of phase change in the system is exhausted, it will affect the overall heat dissipation of the battery; air cooling has a simple structure and is economical, but its heat dissipation efficiency is low and it is difficult to cope with high temperature environments. At the same time, high noise is also a problem; compared with air cooling, liquid cooling has greatly improved heat dissipation efficiency, but it has a complex structure, high cost, and there is a risk of leakage during use.

[0005] In addition to the above methods, air-to-energy heat pumps are also an advanced thermal management technology widely used in automotive lithium battery systems. They use the principle of heat pumps to achieve heat movement through the phase change process of the circulating working fluid. At the same time, changing the flow direction of the circulating working fluid can take into account both battery cooling and heating, thereby effectively controlling the battery temperature. The heating efficiency of air-to-energy heat pumps is three times that of common electric heaters, and they are highly efficient and energy-saving. Compared with liquid cooling, the risk of leakage is greatly reduced. However, air-to-energy heat pumps still perform poorly under extreme climate conditions and require additional insulation systems to assist.

[0006] In terms of thermal insulation, the commonly used thermal insulation materials in lithium battery thermal management are aerogel, polyurethane foam and ceramic fiber. Aerogel is an ultra-lightweight material with low thermal conductivity (0.013-0.03) and has excellent thermal insulation performance, but its high manufacturing cost and poor mechanical strength limit its large-scale application. Polyurethane foam, as a common thermal insulation material, has good mechanical properties and low thermal conductivity (0.02-0.04), but may burn at high temperatures, and additional flame retardants need to be added to improve safety, and the service life is short. Ceramic fiber has high temperature stability and low thermal conductivity (0.03-0.08), but its processing is more difficult, requiring special manufacturing technology, and ceramic fiber materials are easy to break. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a thermal management device for a vehicle-mounted lithium battery, which adopts the following technical solutions:

[0008] A thermal management device for a vehicle-mounted lithium battery, comprising:

[0009] A heat pump circulation unit, which is arranged at the negative terminal of the lithium battery stack and connected to the lithium battery stack to realize a cooling / heating cycle;

[0010] A first vacuum insulation layer is connected to an end of the heat pump circulation unit away from the lithium battery stack.

[0011] Further, the heat pump circulation unit includes a first heat exchanger and a second heat exchanger; the water outlet of the first heat exchanger is connected to the water inlet of the second heat exchanger through a first pipe, and the first pipe is provided with an expansion valve; the water inlet of the first heat exchanger is connected to the water outlet of the second heat exchanger through a second pipe, and the second pipe is provided with a compressor;

[0012] The first heat exchanger is connected to the bottom of the lithium battery stack; the second heat exchanger is arranged at an end away from the lithium battery stack; and the first vacuum insulation layer is transversely arranged on an end of the first heat exchanger away from the lithium battery stack.

[0013] Furthermore, the first vacuum insulation layer includes a vacuum layer inner core, non-woven fabric and a desiccant; the vacuum layer inner core is a porous structure; the desiccant is inserted in the vacuum inner core; the non-woven fabric is sleeved outside the vacuum layer inner core; the non-woven fabric outer sleeve is provided with a metal polymer film.

[0014] Furthermore, the desiccant is laterally inserted at the end of the vacuum inner core.

[0015] Furthermore, the inner core of the vacuum layer is a porous structure.

[0016] Furthermore, a second vacuum insulation layer is provided between two adjacent lithium batteries in the lithium battery stack, and the two adjacent lithium batteries are connected via the second vacuum insulation layer.

[0017] Furthermore, a thermal management method for a vehicle-mounted lithium battery is a thermal management method for a thermal management device for a vehicle-mounted lithium battery as described in any one of the above items, and the thermal management method is as follows:

[0018] In the cooling mode, the steam from the first heat exchanger enters the compressor for compression, becomes high-temperature steam, and then enters the second heat exchanger for heat exchange. After the heat exchange, the steam is condensed into liquid, enters the first heat exchanger through the expansion valve, and absorbs heat in the first heat exchanger to provide cooling for the lithium battery stack. The evaporated steam enters a new cycle.

[0019] In the heating mode, the steam refrigerant in the heat pump circulation unit flows in the opposite direction. The high-temperature steam flowing out of the compressor enters the first heat exchanger to provide heat for the lithium battery stack, enters the second heat exchanger through the expansion valve, evaporates in the second heat exchanger, absorbs heat from the low-temperature environment, and finally the steam enters a new cycle.

[0020] Beneficial effects:

[0021] (1) The present invention provides a thermal management device for an on-vehicle lithium battery. The vacuum insulation layer equipped in the on-vehicle lithium battery stack can effectively isolate the battery from the influence of the external environment, thereby reducing the risk of significant capacity attenuation of the lithium battery in a low temperature environment (-15°C) and thermal runaway and spontaneous combustion in a high temperature environment (≥40°C).

[0022] (2) The thermal management device for a vehicle-mounted lithium battery provided by the present invention is equipped with a heat pump circulation unit, which can effectively reduce the preheating energy consumption required when the electric vehicle is restarted after being parked for a long time (≥10 hours) in a low temperature environment (-15°C). When combined with an air energy heat pump, it can reduce the risk of leakage while greatly reducing the energy consumption required for preheating.

[0023] (3) The thermal management device for a vehicle-mounted lithium battery provided by the present invention has a relatively simple structure and does not require additional energy input. The thickness, vacuum degree and material composition of the vacuum insulation layer can be reasonably adjusted according to different lithium battery operating conditions, external ambient temperature and other factors, and multiple parameters can be optimized to adapt to local conditions.

[0024] (4) The thermal management device for an on-vehicle lithium battery provided by the present invention adds a vacuum insulation layer between battery cells, which can effectively prevent the propagation of thermal runaway between batteries and significantly reduce the economic losses and threats to personal safety caused by battery thermal runaway. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic structural diagram of the thermal management device of the vehicle-mounted lithium battery of the present invention;

[0026] Figure 2 for Figure 1 The enlarged schematic diagram at A in the middle;

[0027] Figure 3 This is a schematic structural diagram of a heat pump circulation unit of a thermal management device for a vehicle-mounted lithium battery of the present invention;

[0028] Figure 4 A schematic diagram of the structure of a lithium battery stack of a thermal management device for a vehicle-mounted lithium battery of the present invention;

[0029] Among them, 1. lithium battery stack; 2. first heat exchanger; 3. first vacuum insulation layer; 4. second heat exchanger; 5. lithium battery thermal management system; 6. vacuum layer inner core; 7. non-woven fabric; 8. metal polymer film; 9. desiccant; 10. compressor; 11. expansion valve; 12. second vacuum insulation layer. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside" and "outside" etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0032] Example 1

[0033] Reference Figures 1 to 3 , a thermal management device for a vehicle-mounted lithium battery, comprising:

[0034] A heat pump circulation unit, which is arranged at the negative terminal of the lithium battery stack 1 and is detachably connected to the lithium battery stack 1 to realize a cooling / heating cycle;

[0035] The first vacuum insulation layer 3 is connected to an end of the heat pump circulation unit away from the lithium battery stack 1 .

[0036] Through the above technical solution, the heat pump circulation unit and the first vacuum insulation layer 3 realize the thermal management of the lithium battery stack 1; the first vacuum insulation layer 3 has lower thermal conductivity, stronger stability, is not easy to burn at high temperature, has good safety, and has a long service life; the configuration of the heat pump circulation unit can effectively reduce the preheating energy consumption required when the electric vehicle is restarted after being parked for a long time (≥10 hours) in a low temperature environment (-15°C), and when combined with the air energy heat pump, it can reduce the risk of leakage while greatly reducing the energy consumption required for preheating;

[0037] The first vacuum insulation layer 3 has a low thermal conductivity (about 0.002W / (m·K)), and has a good insulation effect on outdoor high temperature environment or low temperature environment, which greatly reduces the impact of the vehicle's surrounding environment on the lithium battery thermal management system 5, wherein the lithium battery thermal management system 5 includes a first heat exchanger 2, a first vacuum insulation layer 3 and a lithium battery stack 1; the vacuum insulation layer equipped on the vehicle-mounted lithium battery stack can effectively isolate it from the impact of the external environment, reducing the risk of lithium battery capacity being greatly attenuated in a low temperature environment (-15°C) and thermal runaway and spontaneous combustion in a high temperature environment (≥40°C).

[0038] In this embodiment, the heat pump circulation unit includes a first heat exchanger 2 and a second heat exchanger 4; the water outlet of the first heat exchanger 2 is connected to the water inlet of the second heat exchanger 4 through a first pipe, and a compressor 1 is provided on the first pipe; the water inlet of the first heat exchanger 2 is connected to the water outlet of the second heat exchanger 4 through a second pipe, and an expansion valve 110 is provided on the second pipe;

[0039] The first heat exchanger 2 is connected to the bottom of the lithium battery stack 1 ; the second heat exchanger 4 is arranged at one end away from the lithium battery stack 1 ; the first vacuum insulation layer 3 is transversely arranged on one end of the first heat exchanger 2 away from the lithium battery stack 1 .

[0040] Through the above technical scheme, the first heat exchanger 2, the compressor 10, the second heat exchanger 4, and the expansion valve 11 are connected end to end in sequence to form a circulating heat pump circulation unit, wherein the first heat exchanger 2, the compressor 10 and the expansion valve 11 are arranged together on the inner side of the heat pump circulation unit, and the second heat exchanger 4 is arranged on the outer side of the heat pump circulation unit (the first heat exchanger 2 and the second heat exchanger 4 are arranged in different spaces), and the two modes of cooling and heating are realized through the principle of air energy heat pump; the heat pump circulation unit uses a low-temperature refrigerant (such as R-22 refrigerant) as the working fluid, wherein the cooling mode provides cooling to the lithium battery stack 1, and the heating mode provides heat to the lithium battery stack 1, and the heat provided by the low-temperature environment is composed of outdoor heat and heat generated by the thermal management device itself, which greatly improves the system energy efficiency.

[0041] In this embodiment, the first vacuum insulation layer 3 includes a vacuum layer core 6, a non-woven fabric 7 and a desiccant 9; the vacuum layer core 6 is a porous structure; the desiccant 9 is inserted in the vacuum core; the non-woven fabric 7 is sleeved on the outside of the vacuum layer core 6; and a metal polymer 8 film is disposed on the outer cover of the non-woven fabric 7.

[0042] Through the above technical scheme, the non-woven fabric 7 and the metal polymer 8 film ensure the sealing of the vacuum layer after the vacuum is evacuated, and it is preferably sealed by a heat sealing process; the desiccant 9 ensures the dry environment inside the vacuum layer; no additional energy input is required, and the thickness, vacuum degree and material composition of the vacuum insulation layer can be reasonably adjusted according to different lithium battery operating conditions, external ambient temperature and other factors, and multiple parameters can be optimized to adapt to local conditions.

[0043] In this embodiment, the desiccant 9 is inserted laterally at the end of the vacuum core.

[0044] In this embodiment, the vacuum layer inner core 6 is a porous structure.

[0045] Through the above technical solution, the inner core 6 of the vacuum layer is made of porous material, which provides mechanical strength when the vacuum layer is vacuumed. The inner core material can be replaced according to different insulation requirements. Currently, the more common inner core materials are glass fiber and meteorological silica.

[0046] The vacuum layer insulation material of a thermal management device for a vehicle-mounted lithium battery provided by the present invention has a lower thermal conductivity (0.002-0.08) and a longer service life compared to other materials, and has better cost-effectiveness than aerogel; the vacuum layer insulation material just makes up for the lack of insulation of air-source heat pumps under extreme climatic conditions. The combination of air-source heat pumps and vacuum layer insulation materials can develop a reliable and stable passive thermal management technology, which can greatly weaken the impact of the environment on the heat pump thermal management device, thereby ensuring that the vehicle-mounted lithium battery stack has higher performance and longer service life in various harsh environments.

[0047] Example 2

[0048] like Figure 4 As shown, the difference between this embodiment and embodiment 1 is that two adjacent lithium batteries in the lithium battery stack 1 are provided with a second vacuum insulation layer 12 and are connected through the second vacuum insulation layer 12 .

[0049] Through the above technical solution, in the lithium battery stack 1, the second vacuum insulation layer 12 arranged between two adjacent lithium batteries can prevent the spread of thermal runaway of a single battery to adjacent batteries, effectively prevent the spread of thermal runaway between lithium batteries, and greatly reduce the economic losses and threats to personal safety caused by battery thermal runaway.

[0050] Example 3

[0051] A thermal management method for a vehicle-mounted lithium battery is a thermal management method for a thermal management device for a vehicle-mounted lithium battery provided in Example 1. The low-temperature refrigerant is R-22 refrigerant as an example. The thermal management method is as follows:

[0052] In the cooling mode, the R-22 vapor coming out of the first heat exchanger 2 enters the compressor 10 for compression, becomes high-temperature vapor, and then enters the second heat exchanger 4 for heat exchange. After the heat exchange, the vapor is condensed into liquid, enters the first heat exchanger 2 through the expansion valve 11, and absorbs heat in the first heat exchanger 2 to provide cooling for the lithium battery stack 1. The evaporated R-22 enters a new cycle.

[0053] In the heating mode, the R-22 refrigerant in the heat pump circulation unit flows in the opposite direction. The high-temperature steam flowing out of the compressor 10 enters the first heat exchanger 2 to provide heat for the lithium battery stack 1, enters the second heat exchanger 4 through the expansion valve 11, evaporates in the second heat exchanger 4, absorbs heat from the low-temperature environment, and finally R-22 enters a new cycle.

[0054] A thermal management device and thermal management method for a vehicle-mounted lithium battery provided by the present invention combine an air-energy heat pump with a first vacuum insulation layer to achieve efficient and safe thermal management of the vehicle-mounted lithium battery stack; under the premise of ensuring the normal operation of the heat pump circulation unit and the lithium battery stack, the first vacuum insulation layer greatly weakens the impact of the environment on the thermal management of the vehicle-mounted lithium battery, enhances the stability of the lithium battery stack for long-term operation, and also reduces the preheating energy consumption (thermal runaway risk) of the lithium battery stack after long-term standing in a low temperature (high temperature) environment; a second vacuum insulation layer can be additionally provided between two adjacent lithium batteries to prevent the propagation of thermal runaway between batteries; in addition, the vacuum layer can adjust its parameters (core material, vacuum degree, thickness, etc.) according to different environmental conditions to achieve a balance between heat dissipation and heat insulation.

[0055] The above are only preferred embodiments of the present invention and do not limit the technical scope of the present invention. Therefore, any slight modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A thermal management device for a vehicle-mounted lithium battery, characterized in that: include: A heat pump circulation unit, which is arranged at the negative terminal of the lithium battery stack and connected to the lithium battery stack to realize a cooling / heating cycle; A first vacuum insulation layer is connected to an end of the heat pump circulation unit away from the lithium battery stack.

2. The thermal management device of a vehicle-mounted lithium battery according to claim 1, characterized in that: The heat pump circulation unit comprises a first heat exchanger and a second heat exchanger; the water outlet of the first heat exchanger is connected to the water inlet of the second heat exchanger through a first pipe, and a compressor is provided on the first pipe; the water inlet of the first heat exchanger is connected to the water outlet of the second heat exchanger through a second pipe, and an expansion valve is provided on the second pipe; The first heat exchanger is connected to the bottom of the lithium battery stack; the second heat exchanger is arranged at an end away from the lithium battery stack; and the first vacuum insulation layer is transversely arranged on an end of the first heat exchanger away from the lithium battery stack.

3. The thermal management device of a vehicle-mounted lithium battery according to claim 1, characterized in that: The first vacuum insulation layer includes a vacuum layer inner core, non-woven fabric and a desiccant; the vacuum layer inner core is a porous structure; the desiccant is inserted in the vacuum inner core; the non-woven fabric is sleeved outside the vacuum layer inner core; the non-woven fabric outer sleeve is provided with a metal polymer film.

4. The thermal management device of the vehicle-mounted lithium battery according to claim 3, characterized in that: The desiccant is laterally inserted at the end of the vacuum inner core.

5. The thermal management device of the vehicle-mounted lithium battery according to claim 3, characterized in that: The inner core of the vacuum layer is a porous structure.

6. The thermal management device for a vehicle-mounted lithium battery according to claim 1, characterized in that: A second vacuum insulation layer is provided between two adjacent lithium batteries in the lithium battery stack, and the two adjacent lithium batteries are connected via the second vacuum insulation layer.

7. A thermal management method for a vehicle-mounted lithium battery, which is a thermal management method for a thermal management device for a vehicle-mounted lithium battery according to any one of claims 1 to 6, characterized in that: The thermal management method is as follows: In the cooling mode, the steam from the first heat exchanger enters the compressor for compression, becomes high-temperature steam, and then enters the second heat exchanger for heat exchange. After the heat exchange, the steam is condensed into liquid, enters the first heat exchanger through the expansion valve, and absorbs heat in the first heat exchanger to provide cooling for the lithium battery stack. The evaporated steam enters a new cycle. In the heating mode, the steam refrigerant in the heat pump circulation unit flows in the opposite direction. The high-temperature steam flowing out of the compressor enters the first heat exchanger to provide heat for the lithium battery stack, enters the second heat exchanger through the expansion valve, evaporates in the second heat exchanger, absorbs heat from the low-temperature environment, and finally the steam enters a new cycle.

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