An immersion liquid cooling mechanism for square lithium-ion batteries and a lithium-ion battery module

Abstract

This invention relates to the field of energy storage battery technology, specifically disclosing an immersion liquid cooling mechanism for a square lithium-ion battery module. The liquid cooling mechanism includes a housing for holding square lithium-ion battery cells. The top surface of the housing is open, and a cover is provided to close the top surface. Several baffles are arranged side-by-side at intervals on the bottom surface of the cover, all along the length of the cover, thereby forming multiple flow channels on the bottom surface of the cover. Multiple liquid inlets are provided on the cover, each corresponding to a flow channel, for introducing coolant. A plurality of liquid outlets are provided on the bottom of the side wall of the housing at one end opposite the liquid inlets for discharging the cooled coolant after heat exchange. This invention effectively improves the uniformity of coolant distribution, avoids the generation of local hot spots and eddies, and improves the cooling effect of the square lithium-ion battery.

Description

Technical Field

[0001] This invention belongs to the field of energy storage battery technology, and relates to square lithium-ion batteries, specifically to an immersion liquid cooling mechanism and a lithium-ion battery module for square lithium-ion batteries. Background Technology

[0002] With the increasing severity of global energy shortages and environmental pollution, energy storage technology has been widely promoted and rapidly applied due to its ability to ensure the stability of green and renewable energy supplies such as solar and wind power, thereby improving the reliability, flexibility, and efficiency of energy systems. Electrochemical energy storage, with its advantages of mature technology, high efficiency and flexibility, rapid response, and strong integration capabilities, has become a focus of research and application in the energy storage field. Among these, lithium-ion battery energy storage technology, with its advantages of high specific energy, light weight, and low maintenance costs, is currently the most popular and mature form of electrochemical energy storage.

[0003] Temperature is the most significant factor affecting the performance, lifespan, and safety of lithium batteries. Typically, lithium batteries operate within a temperature range of -20°C to 60°C, with an optimal range of 15°C to 35°C. Temperatures that are too high or too low can negatively impact battery operation and even trigger thermal runaway. Therefore, efficient thermal management of batteries is essential.

[0004] Compared to other cooling methods, liquid cooling is currently the fastest-growing form of battery thermal management due to its higher heat exchange efficiency and more compact structure. Based on the contact method between the heat transfer medium and the battery pack, liquid cooling thermal management can be divided into indirect cold plate type and direct immersion type. Immersion liquid cooling, by directly contacting the battery with the electrically insulating working fluid (coolant), achieves higher heat exchange efficiency, better temperature uniformity, and faster thermal response capabilities, and has received more attention in high-power and high-density energy storage systems.

[0005] Existing immersion liquid cooling mechanisms differ somewhat from actual applications and are primarily designed for cylindrical batteries. The geometry and cycle life of prismatic energy storage batteries differ from those of cylindrical and power batteries, resulting in different heat distribution patterns. Existing immersion liquid cooling mechanisms suffer from uneven coolant distribution and the presence of localized hot spots and eddies, leading to poor battery cooling performance. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide an immersion liquid cooling mechanism and a lithium-ion battery module for square lithium-ion batteries. This invention can effectively improve the uniformity of coolant distribution, avoid the generation of local hot spots and eddies, and improve the cooling effect of square lithium-ion batteries.

[0007] The technical solution of this invention is implemented as follows:

[0008] An immersion liquid cooling mechanism for square lithium-ion batteries includes a housing for holding square lithium-ion battery cells. The top surface of the housing is open, and a cover is provided on the top surface of the housing to close the top surface of the housing. Several baffles are arranged side by side at intervals on the bottom surface of the cover, and all baffles are arranged along the length of the cover, thereby forming multiple flow channels on the bottom surface of the cover. Multiple liquid inlets are provided on the cover, and all liquid inlets are arranged one-to-one with the flow channels for introducing coolant. A plurality of liquid outlets are provided on the bottom of the side wall of the housing at one end opposite to the liquid inlets for discharging the coolant after heat exchange.

[0009] Furthermore, the baffle is composed of a first baffle segment and a second baffle segment. The lower edges of the first baffle segment and the second baffle segment are located on the same horizontal plane. The first baffle segment is close to the liquid inlet end and the upper edge of the first baffle segment is connected to the bottom surface of the cover. The bottom surface of the cover corresponding to the second baffle segment has a slope, and the distance from the bottom surface of the cover to the top surface of the cover increases linearly along the direction from the liquid inlet to the liquid outlet. Correspondingly, the upper edge of the second baffle segment is inclined so as to be connected to the bottom surface of the cover.

[0010] Furthermore, the length of the first baffle segment is Where d is the total length of the baffle.

[0011] Furthermore, it also includes several flow guiding components, which are located between two adjacent battery cells. The flow guiding components are composed of horizontally arranged horizontal blocks and vertically arranged vertical blocks at both ends of the horizontal blocks, forming a U-shaped groove structure. A flow guiding hole penetrating the outer and inner sides of one of the vertical blocks is provided at the lower end of the vertical block.

[0012] Furthermore, the width of the flow guiding component corresponds to the length of the battery cell to be cooled.

[0013] Further, the coolant is HQ-EJ1, YL-70, or PMX-200. Preferably, the coolant is YL-70.

[0014] Furthermore, the coolant inlet temperature is 27-29℃.

[0015] The present invention also provides a square lithium-ion battery module, including a number of battery cells, and also includes the aforementioned immersion liquid cooling mechanism for square lithium-ion batteries. All battery cells are divided into several rows, and each row of batteries is clamped and fixed in the housing by end plates set at the ends. Each baffle is correspondingly set between two rows of batteries.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The bottom surface of the cover of the present invention is provided with several baffles arranged side by side along the length direction to form multiple flow channels, and the liquid inlet corresponds to each flow channel. This allows the coolant to flow into each flow channel more evenly, so as to cool the square lithium-ion battery cells in the box in a comprehensive and uniform manner, avoid local overheating or overcooling, effectively improve the consistency of the overall battery temperature, help maintain the stability of battery performance, and extend the battery life.

[0018] Meanwhile, the inlet is located on the cover, and the outlet is located at the bottom of the side wall of the housing at the end opposite the inlet. This design facilitates a reasonable flow path for the coolant within the housing. The coolant enters the housing through the inlet, flows through various channels to exchange heat with the battery, and then exits through the outlet at the bottom. This design fully utilizes gravity, allowing the coolant to flow naturally, reducing energy consumption, and ensuring sufficient residence time for heat exchange within the housing.

[0019] 2. The baffle on the bottom surface of the cover of this invention consists of a first baffle section and a second baffle section. The upper and lower edges of the first baffle section are both horizontally positioned. When the coolant enters the housing from the inlet, it acts as a buffer and guide, allowing the coolant to enter the flow channel smoothly, avoiding turbulence and eddies, and ensuring that the coolant flows evenly to the battery surface along a predetermined path to quickly absorb heat and achieve cooling. The bottom surface of the cover corresponding to the second baffle section has a slope, and the distance from the bottom surface to the top surface of the cover gradually increases along the direction from the inlet to the outlet. That is, the cover corresponding to the second baffle section gradually thickens from the inlet to the outlet, while the baffle corresponding to the second baffle section becomes narrower and narrower, allowing the coolant to flow forward and downward along the flow channel, resulting in more uniform cooling of the battery pack and improving the temperature uniformity of the battery module.

[0020] 3. The present invention provides a flow guiding component between two adjacent battery cells and between a battery cell and an end plate. The flow guiding component has a U-shaped groove structure, which facilitates the coolant to enter the U-shaped groove of the flow guiding component to cool the large surface of the battery cell. By providing a flow guiding hole at the lower end of the vertical block, the coolant in the flow guiding component can overflow from the flow guiding hole and flow into the bottom surface of the battery to cool the bottom surface of the battery.

[0021] 4. By selecting a suitable coolant and determining the optimal coolant inlet speed and temperature through orthogonal experiments, this invention can effectively reduce the maximum temperature and temperature difference on the battery surface. Attached Figure Description

[0022] Figure 1 - A schematic diagram of the structure of the present invention.

[0023] Figure 2-Figure 1 The left-side view.

[0024] Figure 3 - Top view of the box.

[0025] Figure 4 - Bottom view of the cover.

[0026] Figure 5 - Cross-sectional view of the cover.

[0027] Figure 6 - A schematic diagram of the flow guiding component.

[0028] Figure 7-3 Fluid trace diagram of a battery module.

[0029] Figure 8-3 Temperature cloud map of the battery surface of this battery module.

[0030] Figure 9-3 Vector diagram of fluid velocity in a battery module.

[0031] Figure 10-3 Velocity vector distribution and temperature vector distribution diagram of the battery module.

[0032] Figure 11 - Cloud map of battery surface temperature distribution for the three battery modules under optimal operating conditions.

[0033] Figure 12 - Velocity cloud map of three battery modules at a height of 0.1m under optimal operating conditions.

[0034] Figure 13 - Calculation results of evaluation indicators for the three battery modules under optimal operating conditions.

[0035] Wherein: 1-cover; 2-liquid inlet; 3-box; 4-liquid outlet; 5-cell battery; 6-flow guide assembly; 7-battery plate; 8-tab; 9-baffle; 10-flow guide hole. Detailed Implementation

[0036] The existing immersion liquid cooling mechanism used in square energy storage batteries has a lot of unorganized fluid flow when cooling the battery, which leads to uneven distribution of coolant and the generation of local hot spots and eddies, resulting in poor cooling effect.

[0037] Based on this, the present invention provides an immersion liquid cooling mechanism for square lithium-ion batteries, see [link to relevant documentation]. Figures 1-6 The immersion liquid cooling mechanism includes a housing 3 for placing square lithium-ion battery cells. The top surface of the housing 3 is open, and a cover 1 is provided on the top surface of the housing 3 to close the top surface of the housing 3. Several baffles 9 are arranged side by side at intervals on the bottom surface of the cover 1. All baffles 9 are arranged along the length of the cover 1, thereby forming multiple flow channels on the bottom surface of the cover 1. Multiple liquid inlets 2 are provided on the cover 1, and all liquid inlets 2 are arranged one-to-one with the flow channels for introducing coolant. A plurality of liquid outlets 4 are provided at the bottom of the side wall of the housing at one end of the housing opposite to the liquid inlets for discharging the coolant after heat exchange.

[0038] Here, several baffles are arranged side by side along the length of the bottom surface of the cover to form multiple flow channels, and the liquid inlet corresponds one-to-one with the flow channel. After the battery cells are placed in, the battery cells are arranged in several rows inside the box. Each baffle is located between two rows of batteries. In this way, two adjacent baffles, as well as the baffles located on the two edges and the corresponding edges of the cover, form flow channels, so that the coolant can flow into each flow channel more evenly, and provide comprehensive and uniform cooling to the square lithium-ion battery cells inside the box. This avoids local overheating or overcooling, effectively improves the uniformity of the overall battery temperature, helps maintain the stability of battery performance, and extends battery life.

[0039] Meanwhile, the inlet is located on the cover, and the outlet is located at the bottom of the side wall of the housing at the end opposite the inlet. This design facilitates a reasonable flow path for the coolant within the housing. The coolant enters the housing through the inlet, flows through various channels to exchange heat with the battery, and then exits through the outlet at the bottom. This design fully utilizes gravity, allowing the coolant to flow naturally, reducing energy consumption, and ensuring sufficient residence time for heat exchange within the housing.

[0040] During use, the inlet and outlet are connected to the coolant circulation equipment through pipelines. In this way, the low-temperature coolant enters the tank from the inlet and exchanges heat with the battery cells. Then, the high-temperature coolant after heat exchange flows out from the outlet and enters the coolant circulation equipment for cooling before entering the tank.

[0041] In specific implementation, the baffle 9 is composed of a first baffle section and a second baffle section. The lower edges of the first baffle section and the second baffle section are located on the same horizontal plane. The first baffle section is close to the liquid inlet end and the upper edge of the first baffle section is connected to the bottom surface of the cover. The bottom surface of the cover corresponding to the second baffle section has a slope, and the distance from the bottom surface of the cover to the top surface of the cover increases linearly along the direction from the liquid inlet to the liquid outlet. Correspondingly, the upper edge of the second baffle section is inclined so as to be connected to the bottom surface of the cover.

[0042] Here, the first baffle section has horizontally positioned upper and lower edges. This serves as a buffer and guide when the coolant enters the housing from the inlet, allowing it to flow smoothly into the channel and preventing turbulence and eddies. This ensures the coolant flows evenly to the battery surface along a predetermined path, laying the foundation for efficient heat exchange. Simultaneously, near the inlet, the low-temperature coolant can fully contact the battery via the horizontal edges, quickly absorbing heat and achieving cooling. The second baffle section corresponds to a cover with a sloped bottom surface. The distance from the bottom to the top surface of the cover increases linearly from the inlet to the outlet, meaning the cover gradually thickens from the inlet to the outlet, while the baffle itself becomes increasingly narrow. This allows the coolant to flow forward and downward along the channel, resulting in more uniform cooling of the battery pack and improving the temperature uniformity of the battery module.

[0043] Meanwhile, this baffle allows for more even distribution of coolant within the battery pack. The second baffle section and the corresponding cover structure guide the coolant forward and downward, preventing excessive or insufficient coolant in certain areas, thus balancing cooling across all battery cells, reducing temperature differences between cells, and improving battery pack consistency and overall performance. It also reduces internal thermal stress, lowers the risk of damage due to uneven thermal expansion and contraction, and extends battery life.

[0044] In specific implementation, the length of the first baffle segment is Where d is the total length of baffle 9.

[0045] Here, the lengths of the first and second baffle sections are limited. Experiments have shown that this helps to achieve a balanced distribution of coolant, enhance heat exchange efficiency, make the cooling of various parts of the battery more uniform, and improve heat exchange performance.

[0046] In specific implementation, it also includes several flow guiding components 6. The flow guiding components 6 are located between two adjacent battery cells. The flow guiding components 6 are composed of horizontal blocks arranged horizontally and vertical blocks arranged vertically at both ends of the horizontal blocks, forming a U-shaped groove structure. A flow guiding hole 10 penetrating the outer and inner sides of one of the vertical blocks is provided at the lower end of the vertical block.

[0047] Here, a flow guiding component is set between two adjacent battery cells, and the flow guiding component has a U-shaped groove structure, which facilitates the coolant to enter the U-shaped groove of the flow guiding component to cool the large surface of the battery cell. A flow guiding hole is set at the lower end of the vertical block, which allows the coolant in the flow guiding component to overflow from the flow guiding hole and flow into the bottom surface of the battery to cool the bottom surface of the battery.

[0048] In specific implementation, the coolant is HQ-EJ1, YL-70, or PMX-200. Preferably, the coolant is YL-70, the optimal flow rate of the coolant entering the tank is 0.55 m / s, and the optimal temperature is 28°C.

[0049] A square lithium-ion battery module includes several battery cells 5 and a submersible liquid cooling mechanism for square lithium-ion batteries as described above. All battery cells are divided into several rows. Each row of batteries is clamped and fixed in the housing 3 by end plates set at the ends. Each baffle 9 is set between two rows of batteries. At the same time, a flow guiding component 6 is also provided between the battery cells and end plates at both ends of each row of batteries.

[0050] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0051] The following lithium battery modules each have 52 square lithium iron phosphate hard-shell battery cells with a capacity of 280Ah connected in a series loop. Adjacent battery cells are connected by a plate. The 52 batteries are divided into four columns, with 13 battery cells in each column. They are clamped and fixed in the housing by end plates at both ends.

[0052] Battery Module 1: The water inlet and outlet of the battery module are located on the same side of the lower part of the box, with one inlet and one outlet.

[0053] Battery Module 2: The water inlet and outlet of the battery module are located on opposite sides of the lower part of the box, with dual inlet and dual outlet.

[0054] Battery Module 3: Figures 1-6 As shown, the bottom surface of the cover is provided with several baffles, all of which are arranged along the length of the cover, thereby forming multiple flow channels on the bottom surface of the cover. Each baffle is positioned between two rows of batteries. The cover also has multiple liquid inlets, each corresponding to a flow channel, for introducing coolant. At the bottom of the side wall of the housing opposite the liquid inlets, there are multiple liquid outlets for discharging the cooled coolant after heat exchange. The liquid inlets and outlets are connected to a coolant circulation system via pipelines. The baffles are composed of a first baffle section and a second baffle section, which are of equal length. The lower edges of the first and second baffle sections are on the same horizontal plane. The first baffle section is closer to the liquid inlet end, and its upper upper edge is connected to the bottom surface of the cover. The bottom surface of the cover corresponding to the second baffle section has a slope, and the distance from the bottom surface to the top surface of the cover increases linearly along the direction from the liquid inlet to the liquid outlet. Correspondingly, the upper edge of the second baffle section is inclined to connect to the bottom surface of the cover.

[0055] In addition, a flow guiding assembly is provided between two adjacent batteries and between a battery cell and an end plate. The flow guiding assembly consists of a horizontal block and vertical blocks arranged at both ends of the horizontal block, forming a U-shaped groove structure. A flow guiding hole is provided at the lower end of one of the vertical blocks, penetrating the outer and inner sides of the vertical block, so as to discharge the coolant in the U-shaped groove. The flow guiding holes of all flow guiding assemblies are located on the same side.

[0056] 1. The batteries of the above three battery modules operate at 0.5P discharge. YL-70 fluorinated liquid is used as the coolant, the coolant flow rate is 0.15m / s, and the coolant inlet temperature is 25℃ for simulation experiments.

[0057] (1) The fluid traces and battery surface temperature clouds of the three battery modules are respectively as follows: Figure 7 and Figure 8 As shown, where Figure 7 (a) and Figure 8 (a) is battery module one. Figure 7 (b) and Figure 8 (b) is battery module two. Figure 7 (c) and Figure 8 (c) shows battery module three, as can be seen from the figure:

[0058] (a) The flow of coolant in battery module 1 is subject to a short-circuit effect, and some coolant cannot be discharged, thus stagnating in local areas. Due to the fluid short-circuit effect, the flow area of ​​coolant in battery module 1 is mainly concentrated at the inlet. There is almost no obvious flow of coolant in the middle and rear of the battery pack. The temperature in the battery pack tab area is higher than 35°C, while there is local overcooling in the front of the battery pack, indicating that the cooling capacity is not effectively utilized.

[0059] (b) The highest temperature in battery module two is lower than that in battery module one, and the temperature uniformity is improved. However, the temperature in some areas still exceeds the recommended value of 35°C, and there is still localized overcooling at the front end of the battery pack. This is because the end plate obstructs the coolant. The coolant leaves the inlet at high speed, first undergoing jet impact heat exchange with the end plate and dispersing into multiple streams, resulting in a significant velocity gradient and energy loss, while consuming most of the cooling capacity. The remaining coolant bypasses to the outlet through the gaps between the battery cells, with only a small amount of coolant effectively exchanging heat across the surface of the battery pack.

[0060] (c) The highest temperature and maximum temperature difference of battery module three are 29.79℃ and 3.71℃, respectively, and the surface temperature gradient of the battery module is more gradual, indicating that this battery module can effectively distribute cooling and avoid the generation of local hot spots. Figure 7 (c) It can be seen that the flow channel structure of the cover avoids the flow and mixing of coolant, reduces the energy loss caused by fluid impacting the wall, and reduces the velocity decay of coolant when it flows out. Under the action of gravity, the coolant streamlines more fully sweep across the surface of the battery pack, providing more effective cooling for the battery pack, and preventing it from bypassing directly to the outlet through the gaps between the battery rows.

[0061] (2) Flow velocity vector diagrams for the three battery modules are shown below. Figure 9 As shown, where Figure 9 (a) is battery module one. Figure 9 (b) is battery module two. Figure 9 (c) is battery module three. As can be seen from the figure:

[0062] In battery modules 1 and 2, the coolant flow velocity at the inlet is significantly higher than in other areas, while the velocity around the battery pack is less than 0.04 m / s, forming a low-velocity, slow-flow zone. The inlets of battery modules 1 and 2 exhibit significant jet impact and backflow phenomena. Furthermore, the coolant flows vertically upwards at the top of the battery pack, preventing effective circulation and causing stagnation that negatively impacts the overall heat dissipation of the battery module. In battery module 3, the flow velocity around the battery pack is more uniform, with an average velocity higher than in battery modules 1 and 2, approaching 0.09 m / s, thus improving the heat exchange between the coolant and the battery pack.

[0063] The following table compares the data for the highest surface temperature Tmax, the maximum surface temperature difference ΔT, and the standard deviation σ of the average battery temperature within the three battery modules. It is evident that battery module three has a lower maximum temperature, below 30℃, and exhibits the best temperature uniformity.

[0064] Table 1. Comparison of Temperature Data

[0065] Battery Module 1 38.09 9.15 0.97 Battery Module 2 35.11 7.10 1.11 Battery Module 3 29.79 3.81 0.75

[0066] (3) Schematic diagram of unfavorable flow (velocity vector distribution and temperature vector distribution) in some areas of the three types of battery modules, as shown in the figure. Figure 10 As shown, where Figure 10 (a) is battery module one. Figure 10 (b) is battery module two. Figure 10 (c) Battery module three. As shown in the figure, there are significant localized unfavorable flow conditions in the coolant within battery modules one and two. Besides the jet impact at the end plate, battery module one also exhibits noticeable vortex phenomena. Although vortices can enhance convective heat transfer and thus improve heat transfer efficiency, the large velocity fluctuations and frequent changes in flow direction in the vortex region lead to unstable heat transfer in different areas, resulting in uneven temperature distribution. Figure 10 (a) The temperature vector distribution diagram shows that the temperature above the vortex region is about 3°C ​​higher than below. Simultaneously, the formation of vortices leads to more complex fluid flow, increasing flow resistance and energy loss. Significant fluid stagnation is also observed at the top of battery modules one and two. Due to the increased temperature of the coolant during heat exchange with the battery pack, the coolant exhibits an upward flow trend under the influence of thermal buoyancy, especially at the top of the battery modules where it flows vertically upwards, causing heat to accumulate in this area. Figure 10As shown in the temperature vector distribution diagrams in (a) and 10(b), the temperature at the top of the battery module is significantly higher than that in the middle and lower parts of the battery module. The problem of coolant stagnation at the top may exacerbate the local overheating phenomenon. The unfavorable local flow in battery module three is small and mainly manifested at the front end of the flow channel, resulting in low flow resistance, which is conducive to uniform coolant distribution and has significant advantages.

[0067] 2. Orthogonal experiments were conducted on the three battery modules under three levels of factors: different coolant types (HQ-EJ1, YL-70, PMX-200), coolant inlet flow rates (0.15m / s, 0.35m / s, 0.55m / s), and inlet temperatures (22.00℃, 25.00℃, 28.00℃). The optimal combination obtained is shown in Table 2 below.

[0068] Table 2 Optimal combination of factor levels for three battery modules

[0069] Battery Module 1 YL-70; 0.35m / s; 28.00℃ Battery Module 2 YL-70; 0.55m / s; 28.00℃ Battery Module 3 YL-70; 0.55m / s; 28.00℃

[0070] (1) The surface temperature distribution cloud map of the three battery modules under optimal operating conditions is shown in the figure. Figure 11 As shown, where Figure 11 (a) is battery module one. Figure 11 (b) is battery module two. Figure 11 (c) is battery module three. Figure 11 It can be known that:

[0071] Under optimal operating conditions, the highest surface temperature of battery module 1 still exceeded the recommended value of 35℃, and the battery pack exhibited significant uneven heating and cooling. The highest temperature of battery module 2 was below 35℃, but its maximum surface temperature difference exceeded 5℃. In contrast, the surface temperature and maximum temperature difference of battery module 3 were both within the recommended range. At the same time, the hot and cold spots on the surface of the battery pack were significantly reduced, and there was no obvious overheating at the top of the battery. This is because the flow path of the coolant allows it to prioritize cooling the top area of ​​the battery with higher heat generation, and then cool the lower surface areas and bottom areas after consuming some of the cooling capacity, thus ensuring a uniform temperature distribution.

[0072] (2) The velocity cloud diagrams of the three battery modules at a height of 0.1m under optimal operating conditions are shown below. Figure 12 As shown, where Figure 12 (a) is battery module one. Figure 12 (b) is battery module two. Figure 12 (c) is battery module three. Figure 11 It can be known that:

[0073] In battery modules one and two, distinct high- and low-speed zones emerged. Due to the impact of the coolant on the end plates and the bypass effect through the gaps between the battery rows, the high-speed zone was mainly concentrated at the coolant inlet and the gaps between the battery rows, with a velocity approaching 0.6 m / s. However, the velocity around the battery pack was close to 0 m / s. This significant velocity difference led to uneven cooling distribution and deteriorated heat transfer. For battery module three, the high-speed zone was mainly concentrated in the gaps between the battery rows and at the module ends. The velocity difference within the cooling module was only 0.11 m / s, and the coolant flowed sufficiently around the battery pack, thus ensuring effective and balanced heat exchange.

[0074] The calculation results of the evaluation indicators of the three battery modules under optimal operating conditions are as follows: Figure 13 As shown, Figure 13 (a) represents the highest temperature and maximum temperature difference on the battery surface. Figure 13 (b) represents the standard deviation of battery module voltage drop and battery surface temperature. Figure 13 It can be seen that, under optimal operating conditions, the highest surface temperature and maximum temperature difference of battery module three are 31.21℃ and 2.45℃, respectively. Compared with battery modules one and two, the highest surface temperature and maximum temperature difference of battery module three are reduced by 14.89% and 57.46%, and 7.80% and 47.29%, respectively. Meanwhile, the standard deviation of the battery surface temperature of battery module three is only 0.57, which is reduced by 46.73% and 43.56% compared with battery modules one and two, respectively. Regarding voltage drop, battery module three exhibits the highest voltage drop at 608.19 Pa, while battery module one has the lowest at 219.65 Pa. This is because battery module one experiences significant coolant short-circuiting and bypassing. Although a lower voltage drop is beneficial for reducing pump power consumption, it is achieved under conditions detrimental to battery pack heat dissipation, thus hindering efficient thermal management of the battery pack.

[0075] Finally, it should be noted that the above embodiments of the present invention are merely illustrative examples and not intended to limit the implementation of the invention. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A submersible liquid cooling mechanism for square lithium-ion batteries, comprising a housing for holding square lithium-ion battery cells, the battery cells being arranged in several rows within the housing; the top surface of the housing is open, and a cover is provided on the top surface of the housing to close the top surface of the housing; characterized in that: Several baffles are arranged side by side at intervals on the bottom surface of the cover, and all baffles are arranged along the length of the cover, thereby forming multiple flow channels on the bottom surface of the cover. Each baffle is located between two rows of batteries, and adjacent baffles and baffles located on the two edges and the corresponding edges of the cover form flow channels. Multiple liquid inlets are provided on the cover, and all liquid inlets are arranged one-to-one with the flow channels for introducing coolant. Multiple liquid outlets are provided at the bottom of the side wall of the box at one end of the box opposite to the liquid inlets for discharging the coolant after heat exchange. The baffle is composed of a first baffle section and a second baffle section. The lower edges of the first baffle section and the second baffle section are located on the same horizontal plane. The first baffle section is close to the liquid inlet end, and the upper edge of the first baffle section is connected to the bottom surface of the cover. The bottom surface of the cover corresponding to the second baffle section has a slope, and the distance from the bottom surface of the cover to the top surface of the cover increases linearly along the direction from the liquid inlet to the liquid outlet. Correspondingly, the upper edge of the second baffle section is inclined so as to be connected to the bottom surface of the cover. It also includes several flow guiding components, which are located between two adjacent battery cells. The flow guiding components are composed of horizontal blocks and vertical blocks arranged at both ends of the horizontal blocks, forming a U-shaped groove structure. A flow guiding hole is provided at the lower end of one of the vertical blocks, penetrating the outer and inner sides of the vertical block, so that the coolant enters the U-shaped groove of the flow guiding component and overflows from the flow guiding hole into the bottom surface of the battery.

2. The immersion liquid cooling mechanism for a square lithium-ion battery according to claim 1, characterized in that, The length of the first baffle section is d, where d is the total length of the baffle.

3. The immersion liquid cooling mechanism for a square lithium-ion battery according to claim 1, characterized in that, The width of the flow guiding component corresponds to the length of the battery cell to be cooled.

4. The immersion liquid cooling mechanism for a square lithium-ion battery according to claim 1, characterized in that, The coolant is HQ-EJ1, YL-70, or PMX-200.

5. The immersion liquid cooling mechanism for a square lithium-ion battery according to claim 4, characterized in that, The coolant is YL-70.

6. The immersion liquid cooling mechanism for a square lithium-ion battery according to claim 5, characterized in that, The coolant inlet temperature is 27-29℃.

7. A square lithium-ion battery module, comprising a plurality of battery cells, characterized in that, It also includes an immersion liquid cooling mechanism for a square lithium-ion battery as described in any one of claims 1-6, wherein all battery cells are divided into several rows, each row of batteries is clamped and fixed in the housing by end plates provided at the ends, and each baffle is provided between two rows of batteries.

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