Phase change material and micro-channel liquid cooling composite lithium battery enhanced heat dissipation device

Abstract

The invention relates to a phase change material and micro-channel liquid cooling composite lithium battery enhanced heat dissipation device, and belongs to the technical field of lithium battery thermal management. The device comprises a composite phase change material (CPCM) arranged between battery units and a tree-shaped micro-channel liquid cooling plate located on the outer side of the CPCM, and a metal packaging structure is arranged outside a battery pack. According to the method, heat generated by discharging of the battery is directly absorbed through the CPCM, the heat is conducted out in time through flowing of cooling liquid in the tree-shaped forked micro-channel liquid cooling plate, and the problem that the heat absorption performance of the CPCM is reduced due to temperature rise is effectively solved. The invention has the advantages of latent heat absorption and liquid cooling efficient heat conduction, can obviously improve the heat dissipation efficiency in high-rate discharge and high-temperature environments, ensures the temperature uniformity and working safety of the battery pack, and is suitable for the fields of power batteries, energy storage systems and the like.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature heat dissipation of lithium batteries, and specifically relates to a lithium battery enhanced heat dissipation device that combines phase change material with microchannel liquid cooling. Background Technology

[0002] Lithium-ion batteries, due to their high energy density, long cycle life, high power handling capacity, and low self-discharge rate, have become the mainstream energy source in the current power and energy storage fields, and are widely used in new energy vehicles, energy storage power stations, and portable electronic devices. However, under high-temperature environments, the electrochemical reaction rate inside the battery accelerates significantly, leading to problems such as electrolyte decomposition, electrode material aging, and SEI film instability, thereby accelerating performance degradation and shortening cycle life. Studies have shown that to ensure battery safety and performance, the ideal operating temperature should be maintained between 25℃ and 45℃; if the temperature is too high or too low, it will adversely affect the battery's capacity retention and safety.

[0003] To address the heat generated by lithium-ion batteries during operation, common battery thermal management systems (BTMS) mainly include three methods: air cooling, liquid cooling, and phase change material (PCM) cooling. Air cooling is simple in structure and low in cost, but its heat dissipation efficiency is relatively low; liquid cooling has excellent heat transfer performance and can quickly remove heat, but the system is complex and consumes more energy; PCM cooling utilizes the latent heat of phase change of materials to achieve passive temperature control, which can effectively delay temperature rise and improve temperature uniformity, but its thermal conductivity is low and its heat dissipation speed is limited. To overcome the limitations of a single cooling method, researchers have proposed a hybrid BTMS that combines PCM cooling and liquid cooling technologies, possessing advantages such as high-efficiency heat dissipation, fast response, and low energy consumption, becoming an important development direction for improving the thermal management performance of lithium batteries.

[0004] Currently, most research focuses on battery performance analysis under medium discharge rate (3C) and room temperature conditions. However, effectively reducing the maximum temperature of battery modules and improving temperature uniformity remains a key issue under high discharge rate and extreme temperature environments. To address this challenge, this study proposes a lithium-ion battery enhanced heat dissipation device combining phase change materials (PCM) and microchannel liquid cooling. This device combines a high thermal conductivity PCM with a tree-like distributed microchannel liquid cooling plate structure to form a synergistic mechanism of active and passive heat dissipation, which can significantly improve thermal conductivity and temperature consistency, providing an efficient, safe, and stable thermal management solution for high-power battery systems. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium battery enhanced heat dissipation device that combines phase change material (PCM) with microchannel liquid cooling. This device can reduce battery pack temperature and improve temperature uniformity under high discharge rates and extreme temperature conditions. By adjusting the percentage of expanded graphite added to the PCM, the melting rate of the PCM is significantly slowed down, enhancing heat transfer and solving the problems of insufficient heat absorption during melting and inadequate heat absorption uniformity in traditional PCM cooling methods. Simultaneously, this invention can also improve heat dissipation by adjusting the flow rate of the liquid cooling plate to cool the PCM in a timely manner. This composite cooling structure has a simple connection and a short coolant path, enabling the battery to operate within its optimal temperature range, ensuring temperature consistency during battery operation, and improving the system's mass energy density and volumetric energy density.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a lithium battery enhanced heat dissipation device combining phase change material (PCM) and microchannel liquid cooling. This device mainly includes an outer protective aluminum frame, PCM inside the aluminum frame, and a microchannel dendritic liquid cooling plate embedded with the PCM. These three components together constitute a composite heat dissipation system. The PCM absorbs and stores the heat generated by the battery discharge, while the liquid cooling plate carries away the heat stored within the PCM through the flow of coolant, allowing the PCM to recover its latent heat and heat absorption capacity, thus ensuring that the battery temperature operates within a reasonable range.

[0007] The outer protective shell aluminum frame is made of aluminum, a metallic material with excellent thermal conductivity. Aluminum's high thermal conductivity helps reduce the temperature gradient inside the battery pack, allowing the aluminum frame to efficiently conduct heat generated inside the battery to the outer shell surface. Once the heat is conducted to the aluminum frame surface, it can be more effectively dissipated into the surrounding air through natural convection. The entire outer surface of the aluminum frame becomes a heat dissipation surface. Simultaneously, the aluminum alloy provides sufficient mechanical strength to protect the battery pack from impacts, compression, and vibration, while also fulfilling its heat dissipation function. Both structural strength and heat dissipation are thus achieved.

[0008] The composite phase change material is composed of paraffin wax and expanded graphite. It can be pressed into flexible sheets, filler blocks, or sandwich structures and directly bonded to the battery surface. While maintaining high heat storage capacity, the addition of expanded graphite accelerates the heat absorption and release processes, improving temperature control efficiency. This addresses three major pain points in battery heat dissipation: poor temperature uniformity, slow response, and leakage risk, combining high efficiency, safety, and engineering feasibility. The composite phase change material can promptly absorb the heat generated by the battery pack, maintaining the temperature of the battery pack during discharge.

[0009] Furthermore, the tree-like microchannel liquid cooling plate is made of aluminum, a metallic material with excellent thermal conductivity. Mimicking the branching structure of plant leaf veins, the main channel progressively splits into secondary microchannels, covering the entire cooling plate area. Coolant flow is distributed as needed, eliminating dead zones and hot spots found in traditional flow channels. Branch channels shorten single-path lengths, reduce the number of bends, and lower turbulent energy loss. The flow channel and support structure are integrated, resulting in a thin cooling plate suitable for phase change materials and battery packs.

[0010] Furthermore, the heat source is provided by a lithium battery, with selectable discharge rates of 1C, 2C, and 3C, and durations of 3600s, 1800s, and 1200s, respectively. These heat generation rates and durations are technical parameters belonging to the fields of electrochemical energy storage and new energy vehicles. The heat source of the battery discharge is absorbed by the phase change material and carried away by the coolant flowing through the liquid cooling plate.

[0011] Furthermore, the thermal regulation mechanism of the composite battery thermal management system is studied using a multiphysics coupling modeling method. To accurately characterize the multi-field transport behavior of the battery system, the thermal effect energy equation of the lithium battery is:

[0012] Wherein, ρ and C p λ represents the battery's density and specific heat, λx, λy, and λz are the battery's thermal conductivity in the x, y, and z directions, respectively. T and t are temperature and time, respectively, and q is the battery's volumetric heating rate.

[0013] Furthermore, the battery heat generation rate was calculated using the battery heat generation rate per unit volume model proposed by Bernardi, and the expression is as follows:

[0014] In the formula, I is the battery current, V is the battery volume, U is the battery open-circuit voltage, U0 is the battery load voltage, and T is the battery load voltage. b The initial temperature of the battery; dU0 / dT b is the coefficient of voltage variation with temperature.

[0015] Furthermore, the coolant within the liquid-cooled plate channels is water, which is considered an incompressible laminar fluid. The mass, energy, and momentum conservation equations for the liquid flow in the microchannels are as follows:

[0016]

[0017]

[0018] Where ρ c (kg / m3) is the density of the coolant, ν (m / s) is the velocity of the coolant, and λc (W / m·K) is the thermal conductivity of the coolant, c w (J / kg·K) is the specific heat capacity of the coolant, T w (°C) is the temperature of the coolant, and P (Pa) is the static pressure of the coolant.

[0019] Furthermore, this invention selects paraffin wax as the phase change material (PCM), based on its economic advantages and engineering application potential. In the numerical modeling process, the PCM is defined as an incompressible laminar medium to characterize its dynamic heat transfer properties during the phase change process. The heat transfer within the phase change material is controlled by the following formula: β=

[0020] In the formula, ρ CPCM H CPCM and K CPCM The density, enthalpy, and thermal conductivity of CPCM are respectively; T0, T, and C. CPCM These represent ambient temperature, CPCM temperature, and specific heat capacity, respectively; L is the latent heat of phase change; and β is the liquid phase fraction of the CPCM.

[0021] Furthermore, to improve energy efficiency, the flow rate of the coolant in the liquid cooling plate can be dynamically adjusted according to the amount of heat generated by the battery. In this way, the liquid can dynamically and directly contact the phase change material, resulting in high heat exchange efficiency and good cooling effect.

[0022] The beneficial effects of this invention are: (1) The invention incorporates a phase change material to carry away the heat transferred from the battery pack, thereby reducing the risk of thermal failure of internal circuits and electrical components due to the rise in external temperature of the battery casing; (2) Install the liquid cooling plate in the middle of the phase change material, add an auxiliary cooling device and phase change material, the liquid cooling plate is in direct contact with the phase change material, and removes excess heat in time, resulting in good cooling effect; (3) The liquid cooling plate directly exchanges heat in the middle of the phase change material. The liquid cooling plate and the phase change material are arranged alternately. The coolant flows from top to bottom along the tree-shaped channel. On the one hand, the contact area between the tree-shaped channel and the liquid is large, which increases the heat exchange efficiency. On the other hand, the flow guiding effect of the tree-shaped channel is better, and the flow velocity increases after the flow is guided, which removes heat faster. (4) A sealing structure is provided at the opening of the liquid cooling plate cooling device. The opening of the liquid cooling plate cooling device is supplied with coolant by the external water pipe. While ensuring the sealing effect, the flow rate can be dynamically adjusted to reduce energy consumption. It is easy to install, disassemble and maintain. (5) The heat dissipation system of the present invention adds a liquid cooling plate cooling device on the basis of the original phase change material, which is equivalent to adding a branch for cooling the phase change material, which is easy to implement and control, and can achieve continuous heat dissipation of the battery pack at high temperature. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the tree-shaped liquid cooling plate model of the present invention; Figure 2 This is a diagram of a traditional phase change material heat dissipation system; Figure 3 This is a temperature distribution diagram of a traditional phase change material-cooled battery module; Figure 4 It shows the temperature distribution of a battery module with different EG phase change materials and a dendritic liquid cooling plate. Figure 5 Temperature distribution of battery modules at different coolant flow rates; Figure 6 These are diagrams showing different coolant flow paths; Figure 7 This is a temperature distribution diagram of battery modules with different coolant flow schemes. Detailed Implementation

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] Reference Appendix Figure 4 This invention proposes a lithium battery enhanced heat dissipation device combining phase change material (PCM) and microchannel liquid cooling. The basic structure of the device includes a PCM, a dendritic liquid cooling plate embedded within the PCM, and an aluminum frame encasing the device for external protection; these three components together constitute the heat dissipation system structure. The PCM is made of highly thermally conductive paraffin wax and expanded graphite, arranged in nine equidistant parallel sections, with the battery pack installed in the middle. The example dimensions are set to 100×8×135mm, but can be adjusted according to actual needs. Figure 1As shown, a tree-shaped liquid cooling plate is inserted in the middle of the phase change material. The liquid cooling plate is made of aluminum, a material with high thermal conductivity, to maximize the transfer of heat accumulated in the phase change material. The liquid cooling plate has an external water inlet, allowing for dynamic adjustment of the coolant flow rate. Its size can be adjusted according to specific application requirements; in this embodiment, the dimensions are 100×2.5×135mm. The protective aluminum frame, also made of aluminum with high thermal conductivity, firmly secures all internal components together, ensuring the module's airtightness and preventing deformation and damage during battery discharge. In this embodiment, the dimensions are 256.5×118×135mm. Eight battery packs are placed in the middle of the phase change material and fixed at equal intervals. Expanded graphite (EG) is added to the phase change material. By adjusting the percentage of EG added, the thermal conductivity of the phase change material can be changed. In this embodiment, the EG addition amounts are set to 6%, 12%, 20%, and 30%, respectively. The tree-shaped liquid cooling plate can dynamically adjust the coolant flow rate. By adjusting the flow rate, the heat accumulated in the phase change material can be removed more quickly. In this embodiment, the coolant flow rate is set to 0.10 m / s, 0.14 m / s, 0.18 m / s and 0.22 m / s, respectively, to experimentally evaluate the heat dissipation uniformity.

[0026] The heat source is a lithium battery, which is placed within a phase change material. Lithium-ion batteries are characterized by high energy density and strong power handling capacity. During battery discharge, the phase change material continuously absorbs the heat it generates, while the coolant in the liquid cooling plate promptly removes the heat accumulated in the phase change material, thus ensuring that the lithium battery maintains optimal performance during operation.

[0027] Reference Appendix Figure 3 To be continued Figure 4 Appendix Figure 2 A schematic diagram of cooling for traditional single-phase change materials is attached. Figure 3 The image shows the temperature distribution of the battery pack under traditional single-phase change material cooling methods. It can be seen that the heat source distribution is relatively concentrated, the temperature distribution is uneven, and there are obvious hot spots in certain areas of the battery. (Attached) Figure 4 A schematic diagram of a phase change material combined with a dendritic liquid cooling plate is attached. Figure 5 The diagram shows the temperature distribution of the battery pack when the percentage of EG added to the phase change material is 0%, 6%, 12%, 20%, and 39%, combined with heat dissipation using a dendritic liquid cooling plate. With increasing EG percentage, the overall heating uniformity of the battery pack significantly improves, and localized hot spots gradually diminish. The maximum battery temperature gradually decreases, reaching its lowest point at 20% EG content, and then rises again at 30% EG content.

[0028] Reference Appendix Figure 5The diagram shows the temperature distribution of the battery module at different coolant flow rates. When the inlet flow rate increases from 0.10 m / s to 0.18 m / s, the maximum temperature decrease reaches its maximum of 0.2℃. However, if the inlet flow rate is further increased, for example from 0.18 m / s to 0.22 m / s, the maximum temperature decrease is only 0.06℃. The rate of temperature decrease slows down with increasing inlet velocity, indicating that the improvement in heat dissipation becomes insignificant when the coolant inlet velocity exceeds 0.18 m / s.

[0029] Reference Appendix Figure 6 and 7 Appendix Figure 6 This diagram shows different coolant flow paths. The blue arrows indicate the coolant inlet direction, while the red arrows indicate the direction the coolant flows after passing the cold plate. (Attached) Figure 7 The battery module temperature distribution diagrams show different coolant flow schemes. The maximum battery temperature is roughly the same across the four schemes, with a maximum fluctuation of only 0.1℃. All four schemes demonstrate good effectiveness in controlling the maximum battery temperature. Scheme 2 shows better temperature and temperature difference control, with a maximum temperature of 45.29℃ and a temperature difference of 4.49℃. This is because the coolant flow direction in Scheme 2 is alternating; the opposing flow layout increases the effective coolant flow per unit time, thereby improving the fluidity between the coolant and the battery. The significant temperature difference between the inlet and outlet of the cooling section facilitates efficient heat transfer, resulting in a more uniform coolant temperature distribution.

[0030] In this embodiment, by adding EG percentage content, liquid cooling plate coolant flow rate and coolant flow direction, the heat dissipation utilization rate of phase change material is optimized, resulting in significant improvement in the battery pack's maximum temperature and temperature uniformity.

[0031] In addition, the device of the present invention is also equipped with a temperature monitoring module and a coolant flow rate regulating mechanism: Temperature monitoring module: It can detect the surface and internal temperature distribution of the battery pack in real time, providing data support for adjusting the percentage of EG added to the phase change material and the flow rate of the coolant.

[0032] Coolant flow rate adjustment mechanism: It adopts manual or electric adjustment method and can accurately adjust the optimal coolant flow rate according to the temperature requirements of the battery pack.

[0033] In summary, this invention enhances heat transfer by adding EG to increase the thermal conductivity of the phase change material, while dynamically adjusting the coolant flow rate, significantly improving the performance and flexibility of battery pack thermal management, and thus possessing high practical application value. It should be emphasized that although this invention has described the technical solutions in detail through multiple embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions in the embodiments without departing from the spirit of this invention. These modifications or substitutions will not change the core technical content and innovative points of this invention. Therefore, the scope of protection of this invention should be determined by the claims.

Claims

1. A lithium battery heat dissipation device with phase change material and micro-channel liquid cooling, characterized in that, The device comprises: (1) composite phase change material, paraffin is added with expanded graphite (EG) to increase the thermal conductivity of the phase change material, strengthen heat transfer, and finally obtain better cooling performance, which can quickly transfer heat to the cold plate on both sides; (2) tree-shaped liquid cooling plate, in order to solve the heat transfer and performance problem of PCM, a new type of bifurcated tree-shaped microchannel liquid cooling plate is designed, the tree-shaped structure has the characteristics of high strength, delicate design and high heat dissipation efficiency, in order to realize lightweight design, the cooling plate material is made of aluminum; (3) aluminum frame, the aluminum frame provides a solid mechanical skeleton for the whole battery module; the outermost layer of the battery cooling module is wrapped with a 1 mm thick aluminum frame to firmly fix all the internal hardware together, ensuring the sealing of the module and preventing deformation and damage during the discharge process of the battery pack. 2.The phase change material and micro-channel liquid cooling combined lithium battery heat dissipation device according to claim 1, wherein, The composite cooling system structure is composed of two pieces of phase change material embedded with a liquid cooling plate equidistantly and parallelly arranged 9 groups, and 8 battery grooves are arranged between the phase change materials to install the battery pack. 3.The lithium battery heat dissipation device of claim 1, wherein, The composite phase change material is a CPCM composed of paraffin / expanded graphite, which has chemical stability and non-corrosion characteristics, and its thermal conductivity is significantly improved, with excellent thermal stability and high latent heat of phase change, which can meet the heat dissipation requirements of power battery. 4.The device according to claim 1, wherein, The tree-shaped liquid cooling plate is made of aluminum, and its channel network imitates the branching structure of plant root system or leaf vein, with left-right symmetrical structure, cooling liquid flows into the single inlet trunk, and flows through the liquid cooling plate through multiple levels of symmetrical bifurcation.

5. The phase change material and micro-channel liquid cooling combined lithium battery heat dissipation device according to claim 3, characterized in that, The tree-shaped network greatly increases the contact area between the cooling liquid and the solid wall surface of the cooling plate through the tree-shaped branches, and the tree-shaped structure naturally concentrates the channels in the area needing heat dissipation, and the channel density can better match the heat source distribution. 6.The phase change material and micro-channel liquid cooling combined lithium battery heat dissipation device according to claim 1, wherein, The aluminum frame can be in close contact with the internal heat dissipation structure and become part of the heat dissipation path, the heat generated inside can be transferred to the aluminum frame through these structures, the aluminum frame itself has a large surface area and can be used as an auxiliary heat dissipation surface, which can dissipate part of the heat to the surrounding environment through convection and radiation, and the aluminum frame is the first physical defense line of the battery module, which protects the fragile battery structure inside, and the whole battery pack provides the necessary stiffness and strength.

Images