Lithium ion battery thermal management system and method based on phase change material and liquid cooling

Abstract

The invention belongs to the technical field of lithium ion battery thermal management, and discloses a lithium ion battery thermal management system and method based on a phase change material and liquid cooling. The system comprises a lithium battery for generating electric power; the cold plate is clamped between two adjacent lithium batteries and is used for absorbing heat and cooling the lithium batteries; a liquid cooling channel is arranged on the cold plate; the liquid cooling channel is provided with an inlet and an outlet and used for being connected with a cooling liquid circulation system. A PCM layer is integrated on the cold plate, and the PCM layer is filled with a phase change material. By combining the phase-change material and the liquid cooling technology, a light, efficient and energy-saving hybrid thermal management system is designed, and the occurrence of thermal runaway accidents of the battery is effectively prevented. Turbulence and heat exchange efficiency is enhanced through the design of the Z-shaped cooling channel, cooling liquid flow is dynamically adjusted in combination with an intermittent cooling strategy, the temperature and gradient of the battery are remarkably reduced, meanwhile, the weight and energy consumption of the system are reduced, and the safety and service life of the battery are effectively improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion battery thermal management, and particularly relates to a hybrid battery thermal management system (HBTMS) and method based on phase change material (PCM) and liquid cooling. BACKGROUND

[0002] Energy storage is a necessary condition for supporting large-scale development and utilization of new energy, and is an important infrastructure and strong support for building a new power system dominated by new energy. Various new energy storage technologies dominated by lithium ion batteries are rapidly developing, and energy storage lithium batteries have great market potential. With the rapid development of renewable energy, the energy storage industry is gradually emerging.

[0003] Lithium ion batteries are favored due to their high energy density, low self-discharge rate, long life, light weight, and compact design. In order to maintain optimal performance and safety, lithium ions must be operated within a specific temperature range of 20 ℃~40 ℃, and a temperature gradient of less than 5 ℃ can lead to reduced efficiency, accelerated degradation, and safety risks. Therefore, an effective battery thermal management system (BTMS) is crucial for maintaining the battery within its optimal temperature range, thereby maintaining its performance and life.

[0004] Lithium ion batteries are prone to performance degradation and thermal runaway risk at high temperatures or uneven temperatures; the existing technology has the following problems: 1) Air cooling efficiency is low and difficult to meet high-power charging and discharging requirements.

[0005] 2) Liquid cooling is efficient but complex in structure, high in energy consumption, and requires continuous pumping of cooling liquid.

[0006] 3) Single phase change material (PCM) loses its heat absorption ability after complete melting, and cannot meet the dynamic thermal load demand.

[0007] 4) Existing hybrid systems mostly use separate PCM and cooling plate designs, resulting in increased volume and weight.

[0008] Therefore, designing an effective thermal management system for lithium ion batteries is crucial for ensuring their safety and reliability, while minimizing weight and operating costs. SUMMARY

[0009] The purpose of this invention is to provide a thermal management system and method for lithium-ion batteries based on phase change materials and liquid cooling, so as to solve the technical problems of thermal runaway risk and performance degradation of lithium-ion batteries in high-rate charge and discharge scenarios.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a lithium-ion battery thermal management system based on phase change materials and liquid cooling, comprising: Lithium batteries; A cold plate, sandwiched between two adjacent lithium batteries, is used to absorb heat and cool the lithium batteries; the cold plate is provided with a liquid cooling channel; the liquid cooling channel has an inlet and an outlet for connecting to the coolant circulation system; a phase change material (PCM) layer is integrated on the cold plate, and the PCM layer is filled with phase change material.

[0011] A further improvement of the present invention is that the liquid cooling channels in the cold plate adopt a Z-shaped layout.

[0012] A further improvement of the present invention is that the liquid cooling channel in the cold plate has four or more bends.

[0013] A further improvement of the present invention is that the cold plate is made of aluminum and the coolant flowing into the liquid cooling channel is water.

[0014] A further improvement of the present invention is that the phase change material is RT-35, which accounts for more than 70% of the volume of the cold plate.

[0015] A further improvement of the present invention is that it also includes a control unit and a coolant circulation system; the coolant circulation system is connected to the inlet and outlet of the liquid cooling channel; The control unit is used to control the operating status of the coolant circulation system, and the specific control methods include: Obtain the battery temperature T; Melting fraction calculated based on battery temperature T λ ; Based on melt fraction λ Controls the start and stop of the coolant circulation system and the flow rate of the coolant.

[0016] A further improvement of this invention is that: the calculation of the melting fraction based on the battery temperature T... λ In the steps:

[0017] In the formula, T s The solidus temperature of the PCM; T l is PCM liquidus temperature; The melt fraction-based λ In the steps of controlling the start / stop of the coolant circulation system and the coolant flow rate, when λ When the temperature is ≥0.8, the coolant circulation system is activated, driving the coolant to flow in the liquid cooling channel at a flow rate of... for:

[0018] In the formula, V max This represents the maximum flow rate of the coolant.

[0019] Secondly, the present invention provides a thermal management method for lithium-ion batteries based on phase change materials and liquid cooling, comprising: Obtain the battery temperature T; Melting fraction calculated based on battery temperature T λ ; Based on melt fraction λ Control the flow rate of coolant in the liquid cooling channel.

[0020] A further improvement of this invention is that: the calculation of the melting fraction based on the battery temperature T... λ In the steps:

[0021] In the formula, T s The solidus temperature of the PCM; T l is PCM liquidus temperature.

[0022] A further improvement of the present invention is that: the melting fraction-based... λ In the step of controlling the flow rate of coolant in the liquid cooling channel, when λ When the value is ≥0.8, the coolant flows in the liquid cooling channel at a flow rate of for:

[0023] In the formula, V max This represents the maximum flow rate of the coolant. when λ When the value is ≤0.2, the coolant stops flowing in the liquid cooling channel. .

[0024] A further improvement of this invention is that: when 0.2 < λ When <0.8,

[0025] In the formula ，kp , k i , k d These are the PID control parameters.

[0026] Compared with the prior art, the present invention has the following unexpected technical effects: This invention provides a lithium-ion battery thermal management system based on phase change materials and liquid cooling, comprising: a lithium battery for generating electricity; a cold plate sandwiched between two adjacent lithium batteries for absorbing heat and cooling the lithium batteries; a liquid cooling channel on the cold plate; the liquid cooling channel having an inlet and an outlet for connecting to a coolant circulation system; and a PCM layer integrated on the cold plate, wherein the PCM layer is filled with phase change material. This invention, by combining phase change materials (PCM) and liquid cooling technology, designs a lightweight, high-efficiency, and energy-saving hybrid thermal management system (HBTMS), effectively preventing the technical problems of thermal runaway risk and performance degradation of lithium-ion batteries under high-rate charge and discharge scenarios. This invention enhances turbulence and heat exchange efficiency through a Z-shaped cooling channel design, and dynamically adjusts the coolant flow using an intermittent cooling strategy, significantly reducing battery temperature and gradient, while simultaneously reducing system weight and energy consumption, effectively improving battery safety and lifespan.

[0027] Furthermore, this invention employs a hybrid technology of PCM and liquid cooling. The PCM (RT-35) rapidly absorbs a large amount of heat during high-rate charging and discharging of the battery through phase change latent heat, while liquid cooling precisely removes the heat accumulated by the PCM, forming a synergistic effect of "rapid heat absorption + continuous heat dissipation".

[0028] Furthermore, the Z-shaped liquid cooling channel (4 bends or more) in this invention enhances the turbulence effect of the coolant, expands the heat exchange contact area, improves heat transfer efficiency, and reduces the battery temperature gradient.

[0029] Furthermore, in this invention, the PCM layer is directly integrated onto the cold plate, accounting for over 70% of its volume. It adheres tightly to the battery surface, enabling rapid response to temperature increases and timely suppression of localized hotspots, thus reducing the probability of thermal runaway from the source. The aluminum cooling plate combines excellent thermal conductivity with structural stability, and combined with the efficient heat dissipation of the water-based coolant, it can prevent performance degradation caused by the battery being exposed to high temperatures for extended periods.

[0030] Furthermore, this invention employs an intermittent cooling strategy based on the melting fraction λ. Coolant circulation is initiated only when λ ≥ 0.8 (PCM melts extensively) and stopped when λ ≤ 0.2, avoiding energy waste caused by continuous cooling. The coolant flow rate is dynamically adjusted with λ, eliminating the need to maintain maximum flow rate at all times, further reducing the energy consumption of the circulation system and extending the equipment's service life.

[0031] Furthermore, in this invention, the cold plate integrates a PCM layer and a liquid cooling channel, eliminating the need for an additional independent heat dissipation module, simplifying the system structure and reducing overall weight. The combination of the aluminum cooling plate and water-based coolant further optimizes the lightweight design of the system while ensuring heat dissipation performance.

[0032] Furthermore, in this invention, the control unit acquires the battery temperature in real time, calculates the PCM melting fraction λ, and dynamically adjusts the start / stop and flow rate of the coolant circulation to precisely match changes in battery thermal load. The control logic is based on the PCM solidus line. T s With liquidus line T l Temperature is adjusted to match the working characteristics of phase change materials to ensure the stability and adaptability of the thermal management system. Attached Figure Description

[0033] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of a lithium-ion battery thermal management system based on phase change materials and liquid cooling, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the cold plate in an embodiment of the present invention. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0035] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0036] This invention provides a lithium-ion battery thermal management system based on phase change materials and liquid cooling, comprising: A lithium battery 1 and a cold plate 2 are provided; the lithium battery 1 is used to generate electricity; the lithium battery 1 is provided with a positive electrode 11 and a negative electrode 12; the cold plate 2 is used to absorb heat and cool the lithium battery 1 to ensure that it is within a set temperature range.

[0037] The cold plate 2 is provided with a liquid cooling channel 21; the liquid cooling channel 21 has an inlet 210 and an outlet 211 for connecting to the coolant circulation system; a PCM layer 20 is integrated on the cold plate 2, and the PCM layer 20 is filled with phase change material PCM; the cold plate 2 is sandwiched between two lithium batteries 1.

[0038] In one specific embodiment, an embodiment of the present invention provides a lithium-ion battery thermal management system based on phase change materials and liquid cooling, comprising three lithium batteries 1 and two cold plates 2, with each cold plate 2 sandwiched between two adjacent lithium batteries 1 to form a sandwich structure.

[0039] In one specific embodiment, the liquid cooling channel 21 in the cold plate 2 adopts a Z-shaped (ZCP) layout, which enhances turbulence and heat exchange efficiency by increasing the number of bends in the liquid cooling channel 20; for example, four bends or more are adopted, preferably four bends.

[0040] In one specific embodiment, the phase change material PCM is selected as RT-35 (melting point 35°C, latent heat 160 kJ / kg). RT-35 has a solidus temperature of 302K (approximately 29°C) and a liquidus temperature of 309K (approximately 36°C). It has high latent heat, is non-toxic, has a long cycle life, matches the battery operating temperature, and occupies more than 70% of the volume of the cold plate 2, for example, 70%, 80% or 90%.

[0041] In one specific embodiment, the cold plate 2 is made of aluminum (lightweight and high thermal conductivity), and the coolant flowing into the liquid cooling channel 21 is water (low cost and high specific heat capacity).

[0042] This invention provides a lithium-ion battery thermal management system based on phase change materials and liquid cooling, applicable to electric vehicle power battery packs (such as 50kWh lithium iron phosphate battery packs), specifically including: The lithium battery module consists of three individual lithium batteries 1 connected in series. Each lithium battery 1 has a rated voltage of 3.2V and a capacity of 100Ah. The surface is provided with a positive electrode 11 and a negative electrode 12 (made of copper-aluminum composite material to reduce contact resistance). The individual lithium batteries 1 are rectangular blocks, and adjacent lithium batteries are spaced apart, with space reserved for the installation of the cold plate 2.

[0043] The cold plate assembly comprises two cold plates 2, each sandwiched between adjacent lithium batteries 1, forming a "lithium battery-cold plate-lithium battery" sandwich structure. The overall dimensions of the cold plate 2 are the same as those of the lithium battery 1, and it is made of 6061 aluminum alloy (thermal conductivity 201 W / (m²)). K), combining lightweight and high strength, weighing only 150g / piece, is sealed by laser welding process to prevent coolant leakage.

[0044] PCM Layer: The cold plate 2 integrates a PCM layer 20 (5mm thick), filled with phase change material RT-35 (solidspot temperature 35℃, latent heat of phase change 160kJ / kg), accounting for 75% of the total volume of the cold plate. RT-35 is a paraffin-based organic material with good compatibility with aluminum shells and excellent chemical stability in the range of -20℃ to 60℃. After 1000 phase change cycles, the latent heat loss rate is less than 5%, which can adapt to the battery operating temperature (25-45℃) for a long time.

[0045] Liquid cooling channel: A liquid cooling channel 21 (cross-sectional area 8mm×2mm) is reserved inside the cold plate 2, adopting a 4-bend Z-shaped layout (bending angle 60-90°), with a total channel length of 300mm. The inlet 210 and outlet 211 are located at opposite ends of the diagonal of the cold plate, respectively, and are connected to the external coolant circulation system (including water pump, water tank, and radiator) via silicone hoses. The coolant used is deionized water (with 2% ethylene glycol added for corrosion prevention), and the flow rate in the channel can be adjusted by the water pump (range 0.1-0.4m / s).

[0046] The contact surface between the cold plate 2 and the lithium battery 1 can be coated with thermally conductive silicone grease (thermal conductivity 3.0 W / (m²)). K)), reducing contact thermal resistance; the edge of the cold plate 2 is provided with a positioning slot to match the protrusion of the lithium battery shell, ensuring a tight fit during installation and avoiding increased gap thermal resistance caused by vibration.

[0047] This invention provides a lithium-ion battery thermal management system based on phase change materials and liquid cooling, specifically for high-rate lithium batteries used in drones (such as ternary lithium battery packs with 20C discharge). The embodiment is as follows: The lithium battery module consists of 4 individual lithium batteries connected in parallel. Each battery has a rated voltage of 3.7V and a capacity of 20Ah, and supports continuous discharge at 20C (instantaneous power of 1.48kW). The surface of each battery cell is insulated (wrapped in a polyimide film).

[0048] The three cold plates 2 adopt a "double-sided clamping" design, meaning that each cold plate 2 is in contact with the lithium battery 1 on both sides. The material has been upgraded to an aluminum-copper composite material (the outer aluminum layer is corrosion-resistant, and the inner copper mesh enhances thermal conductivity, with an overall thermal conductivity of 300W / (m²). K).

[0049] The PCM layer 20 is filled with composite phase change material (RT-42), accounting for 80% of the volume, which can quickly absorb the instantaneous heat during high-rate discharge. The liquid cooling channel 21 adopts a 6-bend Z-shaped layout (each segment is 15mm long) to enhance the turbulence of the coolant.

[0050] The coolant is a 50% water-50% ethylene glycol mixture (freezing point -35℃, suitable for low-temperature environments) to ensure rapid dissipation of accumulated heat.

[0051] This invention provides a lithium-ion battery thermal management system based on phase change materials and liquid cooling, comprising: Lithium battery 1, used to generate electricity; The cold plate 2 is sandwiched between two adjacent lithium batteries 1 and is used to absorb heat and cool the lithium batteries 1. The cold plate 2 is provided with a liquid cooling channel 21. The liquid cooling channel 21 has an inlet and an outlet for connecting to the coolant circulation system. The cold plate 2 is integrated with a PCM layer, which is filled with a phase change material.

[0052] In one specific embodiment, the liquid cooling channel 21 in the cold plate 2 adopts a Z-shaped layout.

[0053] In one specific embodiment, the liquid cooling channel 21 in the cold plate 2 has four or more bends.

[0054] In one specific embodiment, the cold plate 2 is made of aluminum; the coolant flowing into the liquid cooling channel 21 is water. In one specific embodiment, the phase change material is RT-35, which accounts for more than 70% of the volume of the cold plate 2.

[0055] In one specific embodiment, it also includes a control unit and a coolant circulation system; the coolant circulation system is connected to the inlet and outlet of the liquid cooling channel 21; The control unit is used to control the operating status of the coolant circulation system, and the specific control methods include: Obtain the battery temperature T; Melting fraction calculated based on battery temperature T λ ; Based on melt fraction λ Controls the start and stop of the coolant circulation system and the flow rate of the coolant.

[0056] In one specific embodiment, the melting fraction is calculated based on the battery temperature T. λ In the steps:

[0057] In the formula, T s The solidus temperature of the PCM; T l is PCM liquidus temperature; The melt fraction-based λIn the steps of controlling the start / stop of the coolant circulation system and the coolant flow rate, when λ When the flow rate is ≥0.8, the coolant circulation system is activated, driving the coolant to flow in the liquid cooling channel 21 at a flow rate of... for:

[0058] In the formula, V max This represents the maximum flow rate of the coolant.

[0059] This invention provides a lithium-ion battery thermal management system based on phase change materials and liquid cooling. Its cooling strategy is to adopt intermittent cooling (IC), that is, to dynamically adjust the flow of coolant based on the PCM melting fraction (e.g., cooling starts when 80% melts and stops when 20% melts) to reduce energy consumption.

[0060] Specifically, this invention provides a thermal management method for lithium-ion batteries based on phase change materials and liquid cooling. The thermal management system for lithium-ion batteries based on phase change materials and liquid cooling includes the following steps: By combining the Equivalent Circuit Model (ECM) to predict battery heat generation in real time, the coolant flow rate (0.1–0.4 m / s) and start-up / shutdown sequence are dynamically adjusted to optimize the PCM phase change efficiency.

[0061] Battery heat generation is predicted in real time using an equivalent circuit model (ECM) and the energy conservation equation. The specific formula is as follows:

[0062] In the formula, The total heat generation rate; I This refers to the battery current. Battery voltage; This is the open-circuit voltage; T For battery temperature, , The conductivity represents the positive and negative electrodes; , Electrode potential; It is an entropy change; n The number of charges; F It is the Faraday constant (96485 C / mol).

[0063] Energy conservation equation (describing the battery temperature field):

[0064] In the formula, Battery density; This refers to the specific heat capacity of the battery. For battery thermal conductivity; An intermittent cooling strategy (IC) is adopted, based on the PCM melting fraction ( λ Dynamic start-stop of coolant flow, PCM melting fraction ( λ The calculation formula is:

[0065] In the formula, T s The solidus temperature of the PCM; T l is PCM liquidus temperature.

[0066] The formula for controlling the coolant flow rate is: Startup conditions: When λ When the temperature is ≥0.8, start the coolant flow, and the flow rate should be... Based on dynamic adjustment of heat load, the simplified control formula is as follows:

[0067] In the formula, V max This represents the maximum flow rate of the coolant.

[0068] When 0.2 < λ When <0.8,

[0069] In the formula ，k p , k i , k d These are the PID control parameters.

[0070] Stop condition: when λ When the value is ≤0.2, shut off the coolant flow. =0).

[0071] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

Claims

1. A lithium-ion battery thermal management system based on phase change materials and liquid cooling, characterized in that, include: Lithium battery (1); A cold plate (2) is sandwiched between two adjacent lithium batteries (1) for absorbing heat and cooling the lithium batteries (1); a liquid cooling channel (21) is provided on the cold plate (2); the liquid cooling channel (21) has an inlet and an outlet for connecting to the coolant circulation system; a phase change material (PCM) layer is integrated on the cold plate (2), and the PCM layer is filled with phase change material.

2. The lithium-ion battery thermal management system based on phase change materials and liquid cooling according to claim 1, characterized in that, The liquid cooling channel (21) in the cold plate (2) adopts a Z-shaped layout.

3. The lithium-ion battery thermal management system based on phase change materials and liquid cooling according to claim 1, characterized in that, The number of bends in the liquid cooling channel (21) of the cold plate (2) is 4 or more.

4. The lithium-ion battery thermal management system based on phase change materials and liquid cooling according to claim 1, characterized in that, The cold plate (2) is made of aluminum; the coolant flowing through the liquid cooling channel (21) is water.

5. The lithium-ion battery thermal management system based on phase change materials and liquid cooling according to claim 1, characterized in that, The phase change material is RT-35, and its volume accounts for more than 70% of the volume of the cold plate (2).

6. The lithium-ion battery thermal management system based on phase change materials and liquid cooling according to claim 1, characterized in that, It also includes a control unit and a coolant circulation system; The coolant circulation system connects the inlet and outlet of the liquid cooling channel (21); The control unit is used to control the operating status of the coolant circulation system, and the specific control methods include: Obtain the battery temperature T; Melting fraction calculated based on battery temperature T λ ; Based on melt fraction λ Controls the start and stop of the coolant circulation system and the flow rate of the coolant.

7. The lithium-ion battery thermal management system based on phase change materials and liquid cooling according to claim 6, characterized in that, The melting fraction is calculated based on the battery temperature T. λ In the steps: In the formula, T s The solidus temperature of the PCM; T l for PCM liquidus temperature; The melt fraction-based λ In the steps of controlling the start / stop of the coolant circulation system and the coolant flow rate, when λ When the flow rate is ≥0.8, the coolant circulation system is activated, driving the coolant to flow in the liquid cooling channel (21) at a flow rate of... for: In the formula, V max This represents the maximum flow rate of the coolant.

8. A thermal management method for lithium-ion batteries based on phase change materials and liquid cooling, characterized in that, The lithium-ion battery thermal management system based on phase change materials and liquid cooling according to any one of claims 1-5 includes: Obtain the battery temperature T; Melting fraction calculated based on battery temperature T λ ; Based on melt fraction λ Control the flow rate of coolant in the liquid cooling channel (21).

9. The lithium-ion battery thermal management method based on phase change materials and liquid cooling according to claim 8, characterized in that, The melting fraction is calculated based on the battery temperature T. λ In the steps: In the formula, T s The solidus temperature of the PCM; T l for PCM liquidus temperature.

10. The lithium-ion battery thermal management method based on phase change materials and liquid cooling according to claim 8, characterized in that, The melt fraction-based λ In the step of controlling the flow rate of coolant in the liquid cooling channel (21), when λ When the value is ≥0.8, the driving coolant flows in the liquid cooling channel (21) at a flow rate of for: In the formula, V max This represents the maximum flow rate of the coolant. when λ When the value is ≤0.2, the coolant stops flowing in the liquid cooling channel (21). .

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