A centrally cooled battery cell, its manufacturing method, and battery system

Abstract

This invention discloses a centrally directly cooled battery cell, its manufacturing method, and a battery system, belonging to the field of new energy battery technology. The battery cell includes an electrode winding body with an axially penetrating central cooling channel, and a three-layer integrated functional coating simultaneously applied to its outer surface, upper surface, and the inner wall of the channel. The core of its manufacturing method lies in using a tubular core mold (such as a ceramic tube) filled with a phase change support material (such as paraffin wax) for electrode film winding, thus solving the manufacturing problem of core mold damage. A central channel is formed through hot-melt dewaxing, followed by simultaneous internal and external coating. This method provides two channel forming paths: removing the core mold and assembling an independent insert, or retaining the core mold as a permanent channel. This invention also discloses a battery system comprising multiple such battery cells, a parallel liquid cooling circuit, multi-stage filtration, and safety components. This invention achieves efficient core direct cooling, all-around equal-height protection, and high-yield manufacturing, improving system safety and reliability.

Description

Technical Field

[0001] This invention relates to the field of new energy battery technology, specifically to a battery cell with a central direct cooling heat dissipation channel, a high-yield manufacturing method thereof, and a high-safety battery system containing the battery cell. Background Technology

[0002] As electric vehicles and energy storage systems place increasingly higher demands on battery energy density, power density, and safety, battery heat dissipation has become a key bottleneck restricting its performance. Traditional battery packs mostly use external cooling methods, which have long heat dissipation paths and low efficiency, making it difficult to cope with the huge heat generated by high-rate charging and discharging. This can easily lead to excessive battery temperature rise, lifespan reduction, and even thermal runaway. To address this issue, existing technologies have proposed solutions involving cooling channels within the battery cell, such as pre-drilling central channels during winding or stacking. However, this approach faces a critical manufacturing challenge in industrialization: under the immense tension of the electrode film (or electrode sheet) winding / stacking, the hollow tube (such as a ceramic tube) used as the forming core mold is highly susceptible to cracking and deformation due to its brittle structure and hollow interior. This results in uneven electrode structure, internal stress concentration, extremely low production yield, and an inability to achieve stable mass production. This manufacturing bottleneck severely hinders the practical application of this efficient heat dissipation structure. Furthermore, existing technologies lack systematic solutions for how to implement high-performance, consistent protective coatings on the complex internal and external surfaces of pre-formed hollow battery cells (especially the inner walls with large depth-to-diameter ratios), and how to reliably integrate such cells into battery systems with multiple safety functions such as efficient heat dissipation, pressure relief, and fault isolation. Summary of the Invention

[0003] Purpose of the invention The present invention aims to solve at least one or more problems existing in the aforementioned background art. Specifically, the objective is: This invention provides a method for manufacturing battery cells with a central cooling channel in a stable and high-yield manner, particularly addressing the problem of easy damage to the molding core. A coating method is provided to achieve synchronous, equal-height, and high-performance protection on the inner and outer surfaces of the battery cell. A battery cell and battery system with excellent heat dissipation and safety performance are provided by the above method. Technical solution To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for manufacturing a centrally directly cooled battery cell, characterized by comprising the following sequential steps: S1. Core mold wax injection reinforcement: Select a tubular core mold, inject molten phase change support material into its cavity, and after cooling and solidification, form a solid support body inside the tubular core mold to obtain a reinforced core mold. S2. Electrode film winding: With the reinforced core mold as the central axis, the battery electrode film is evenly wound around its outer wall to form a battery cell blank; S3. Hot melt dewaxing and channel forming: The battery cell blank is heated to melt and discharge the phase change support material, thereby forming a central cooling channel that runs through the battery cell blank; S4. Integrated coating: The outer surface, upper surface and inner wall of the central cooling channel of the battery cell blank are simultaneously surface treated, and then an impregnation process is used for simultaneous coating to form a multi-layer functional coating. As a further definition of the first aspect of the technical solution, the forming of the central cooling channel in step S3 includes the following two implementation methods: Implementation Method A: The tubular core mold is extracted from the battery cell blank to form a pre-formed channel; subsequently, an independent hollow tube made of corrosion-resistant insulating material is assembled into the pre-formed channel; the inner wall of the hollow tube constitutes the final inner wall of the central cooling channel. Implementation Method B: After the phase change support material is discharged, the tubular core mold is permanently retained and encapsulated in the battery cell blank; the inner wall of the tubular core mold itself directly constitutes the inner wall of the central cooling channel. Preferably, the tubular mandrel is a ceramic tube. The phase change support material is paraffin wax, microcrystalline wax, or polyethylene wax. Preferably, in step S4, the impregnation process includes multiple impregnation and curing cycles, and each coating layer undergoes surface smoothing treatment after curing. The multi-layer functional coating includes at least a high-adhesion primer layer, an insulating and flame-retardant intermediate layer, and a high-hardness topcoat layer bonded sequentially from the inside out, with a total coating thickness of 0.5-0.7 mm. In a second aspect, the present invention provides a centrally directly cooled battery cell prepared by the method described in the first aspect, characterized in that it comprises: An integrated electrode winding body has an axially continuous central cooling channel at its center; A three-layer integrated composite coating is simultaneously applied to the outer surface, upper surface, and inner wall of the central cooling channel of the electrode winding body. The composite coating includes a high-adhesion primer layer, an insulating and flame-retardant functional layer, and a high-hardness wear-resistant surface layer, which are stacked sequentially from the inside to the outside. In embodiment A, the inner wall of the central cooling channel is the inner wall of an independent hollow tube assembled in the electrode winding body; in embodiment B, the inner wall of the central cooling channel is the inner wall of a tubular mandrel permanently encapsulated in the electrode winding body. Thirdly, the present invention provides a battery system, characterized in that it comprises: Multiple battery cells as described in the second aspect; A battery box, including a shell and a bottom support, wherein a plurality of battery cells are arranged in an array inside the battery box and separated from each other by elastic insulating spacers disposed therebetween; The liquid cooling circulation assembly includes an inlet pipe, an outlet pipe, at least one stage filter connected in series in the inlet pipe, and a filter element disposed on the outlet pipe. The inlet pipe is connected to the inlet of the central cooling channel of each battery cell through an inlet manifold, and the outlet pipe is connected to the outlet of the central cooling channel of each battery cell through an outlet manifold. Safety components include a pressure relief valve located on top of the battery compartment; Electrical components, including a positive terminal and a negative terminal disposed on the battery box. Beneficial effects Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: Effectively solves manufacturing bottlenecks: By using the "wax-filled reinforced core mold" process, the temporary support of phase change materials is utilized to enable the brittle tubular core mold to withstand the huge tension during the electrode film winding process, thereby achieving high yield and large-scale stable production of battery cells with central cooling channels. Two feasible process paths are provided: This invention clarifies two channel forming methods, Implementation Method A and Implementation Method B. Implementation Method A facilitates the reuse of mandrels and independent optimization of insertion materials; Implementation Method B simplifies the process flow and improves structural integrity and production efficiency. The two methods provide flexible choices for different application needs. Achieving efficient core direct cooling: The manufactured battery cells have a built-in central cooling channel, and the coolant can flow directly through the core heat-generating area of ​​the cell. The heat dissipation path is short and efficient, which can effectively suppress the temperature rise of the battery and meet the needs of high-power application scenarios. Achieving comprehensive and consistent protection: Through simultaneous immersion coating on the inner and outer surfaces and meticulous post-processing, it is ensured that all surfaces of the battery (including the inner hole walls) receive a composite coating with consistent performance, forming a continuous, sealed three-dimensional protective shell, which significantly improves the battery's inherent safety and environmental tolerance. Building a multi-layered system safety: From functional coating protection for individual battery cells to multiple designs such as system-level buffer intervals, multi-stage filtration, and active pressure relief, a safety protection system from the inside out is formed. Combined with the integrated large-cell structure, the safety and reliability of the entire battery system are improved. Attached Figure Description

[0004] Figure 1 This is a schematic cross-sectional view of the battery system according to an embodiment of the present invention. Figure 2 This is a partial cross-sectional schematic diagram of one embodiment of the battery cell center hole insertion tube assembly structure of the present invention (corresponding to embodiment A). Figure 3 This is a partially enlarged schematic diagram of the three-layer integrated coating structure of the battery cell of the present invention. The labels in the figures are as follows: 101. Battery cell; 102a. Center hole (in Embodiment A, refers to the pre-formed channel formed after the core mold is extracted); 102b. Center hole insertion tube (in Embodiment A) or tubular component constituting the channel (in Embodiment B); 103. Battery upper surface; 104. Inner wall of the central cooling channel; 105. First coating layer (high adhesion primer layer); 106. Second coating layer (insulating and flame-retardant functional layer); 107. Third coating layer (high hardness and wear-resistant surface layer); 201. Battery spacer; 301. Battery box shell; 302. Battery box bottom support; 401. First filter membrane; 402. Second filter membrane; 403. Water-absorbing sponge in coolant; 501. Battery box bottom filter; 502. Pressure relief valve; 601. First terminal (positive); 602. Second terminal (negative); 701. Water inlet pipe; 702. Water outlet pipe. Detailed Implementation

[0005] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Example 1: Manufacturing battery cells and system integration using Implementation Method A (removing tubes and assembling independent inserts). Battery cell molding: A high-temperature resistant ceramic tube with an inner diameter of 20mm is selected and filled with molten paraffin wax. After cooling, it forms a solid support. Using this reinforced core mold as the axis, the lithium iron phosphate positive electrode film, separator, and graphite negative electrode film are evenly wound on a winding machine to an outer diameter of 80mm to form a cylindrical battery cell blank. Hot melt dewaxing and core pulling: The green body was heated in a constant temperature environment of 90℃ for 45 minutes to completely melt and remove the internal paraffin. After cooling, the hollowed-out ceramic tube was carefully pulled out from the center of the green body, forming a pre-made center hole with a smooth inner wall and an inner diameter of 20mm (102a, see [reference]). Figure 2 ). Independent cannulation assembly: A polyetheretherketone (PEEK) tube with an outer diameter of 19.8 mm and a wall thickness of 2 mm was selected as the central hole insertion tube (102b). After applying high-temperature sealant to its outer wall, it was precisely pressed into the central hole (102a) formed in step 2 to achieve an interference fit and adhesive seal. Thus, the inner wall of this PEEK insertion tube constitutes the working inner wall (104) of the final central cooling channel. Three-layer integrated coating: A rubber support rod is inserted into the central hole insertion tube (102b). The outer surface, upper surface (103), and inner wall of the channel (104) of the battery cell (101) are simultaneously sandblasted, ultrasonically cleaned, and dried. Then, an impregnation process is employed (see...). Figure 3 ): a) Dip-coating epoxy high adhesion primer (first layer 105): Dip 3 times, each time curing at room temperature for 25 minutes, followed by ultrasonic fine water grinding for 10 minutes. b) Dip coating with halogen-free flame-retardant epoxy insulating varnish (second layer 106): Dip three times, each time curing at 80°C for 30 minutes, followed by ultrasonic fine water grinding for 10 minutes. c) Dip-coating with high-hardness epoxy topcoat (third layer 107): Dip three times, each time curing at 100℃ for 35 minutes, followed by ultrasonic fine water grinding for 15 minutes. After coating, the support rod is removed and the channel is cleaned. The total thickness of the resulting coating is 0.5-0.7 mm, and the pencil hardness of the coating on both the outer surface of the battery and the inner wall of the channel reaches 5H or higher. System integration and assembly: Multiple battery cells (101) are placed inside an aluminum alloy battery case shell (301), with silicone battery spacers (201) arranged between the cells. The bottom is fixed by a battery case bottom bracket (302) made of engineering plastic. A 400-mesh first filter membrane (401) and a 600-mesh second filter membrane (402) are installed in series in the coolant inlet pipe. The battery case is filled with hydrophilic polyurethane absorbent sponge (403). The central cooling channels of all battery cells are connected in parallel to the inlet pipe (701) and the outlet pipe (702), and a battery case bottom filter (501) is installed in the outlet pipe. A mechanical pressure relief valve (502) and copper first and second terminals (601) are installed on the top of the battery case. After sealing the battery case, an ethylene glycol aqueous solution is injected as coolant to complete the battery system assembly (see [link]). Figure 1 ). Example 2: Manufacturing battery cells using Implementation Method B (Chip-Mold Integration) The core difference between this embodiment and Embodiment 1 lies in the molding method of the central cooling channel; the subsequent coating and system integration processes are the same. After completing step 1 (electrode film winding) to form the battery cell blank, the following operations are performed: Hot melt dewaxing and integrated channel molding: The blank is heated to melt and expel the internal paraffin wax. In this embodiment, the special ceramic tube, which serves as the molding core and possesses long-term resistance to coolant corrosion and high insulation properties, is not extracted but is permanently retained and encapsulated in the center of the electrode winding body. This ceramic tube is directly used as the central hole insertion tube (102b) and the central cooling channel. Its inner wall constitutes the inner wall (104) of the channel to be coated. The subsequent three-layer integrated coating (step 4) and system integration assembly (step 5) processes are exactly the same as in Embodiment 1. The scope of protection of this invention is not limited to the above embodiments. Any equivalent structural transformations made based on the concept of this invention and the description and drawings of this invention, or direct / indirect applications in other related technical fields, should be included within the patent protection scope of this invention.

Claims

1. A method for manufacturing a centrally directly cooled battery cell, characterized in that, The process includes the following sequential steps: S1, Core mold reinforcement: Select a tubular core mold, pour molten phase change support material into its cavity, and after cooling and solidification, form a solid support body inside the tubular core mold to obtain a reinforced core mold; S2, Electrode film winding: With the reinforced core mold as the central axis, uniformly wind the battery electrode film around its outer wall to form a battery cell blank; S3, Hot melt dewaxing and channel forming: Heat the battery cell blank to melt and discharge the phase change support material, thereby forming a central cooling channel that runs through the battery cell blank; S4, Integrated coating: Simultaneously surface treat the outer surface, upper surface, and inner wall of the central cooling channel of the battery cell blank, and then simultaneously coat them using an impregnation process to form a multi-layer functional coating.

2. The manufacturing method according to claim 1, characterized in that, In step S3, the central cooling channel is formed in any of the following ways: Method 1: The tubular core mold is extracted from the battery cell blank to form a pre-formed channel; subsequently, an independent hollow tube made of corrosion-resistant insulating material is assembled into the pre-formed channel, and the inner wall of the hollow tube constitutes the final inner wall of the central cooling channel; or, Method 2: After the phase change support material is discharged, the tubular core mold is permanently retained and encapsulated in the battery cell blank, and the inner wall of the tubular core mold itself directly constitutes the inner wall of the central cooling channel.

3. The manufacturing method according to claim 1 or 2, characterized in that, The tubular core mold is a ceramic tube; the phase change support material is paraffin wax, microcrystalline wax, or polyethylene wax.

4. The manufacturing method according to claim 1 or 2, characterized in that, In step S4, the impregnation process includes multiple impregnation and curing cycles for each functional coating, and surface smoothing treatment is performed after each coating layer is cured.

5. The manufacturing method according to claim 4, characterized in that, The multilayer functional coating includes at least a high-adhesion primer layer, an insulating and flame-retardant intermediate layer, and a high-hardness topcoat layer, which are bonded together sequentially from the inside out.

6. The manufacturing method according to claim 5, characterized in that, The total thickness of the coating is 0.5-0.7 mm.

7. A centrally directly cooled battery cell, characterized in that, include: An integrated electrode winding body has an axially continuous central cooling channel at its center; A three-layer integrated composite coating is simultaneously applied to the outer surface, upper surface, and inner wall of the central cooling channel of the electrode winding body. The composite coating includes a high-adhesion primer layer, an insulating and flame-retardant functional layer, and a high-hardness wear-resistant surface layer, which are stacked sequentially from the inside to the outside.

8. The center-cooled direct-cooled battery cell according to claim 7, characterized in that, The central cooling channel is constructed in one of the following ways: Method A: The central cooling channel includes a pre-formed channel located in the electrode winding body, and an independent hollow tube tightly fitted in the pre-formed channel, the inner wall of the independent hollow tube forming the inner wall of the central cooling channel; or, Method B: The inner wall of the central cooling channel is formed by the inner wall of a tubular mandrel permanently encapsulated in the electrode winding body.

9. A battery system, characterized in that, include: The battery includes a plurality of centrally cooled battery cells as described in claim 7 or 8; a battery case, comprising a housing and a bottom support, wherein the plurality of battery cells are arranged in an array within the battery case and separated from each other by elastic insulating spacers disposed therebetween; a liquid cooling circulation assembly, comprising an inlet pipe, an outlet pipe, at least one stage filter connected in series in the inlet pipe, and a filter element disposed in the outlet pipe, wherein the inlet pipe is connected to the central cooling channel inlet of each battery cell via an inlet manifold, and the outlet pipe is connected to the central cooling channel outlet of each battery cell via an outlet manifold; a safety component, comprising a pressure relief valve disposed on the top of the battery case; and an electrical component, comprising a positive terminal and a negative terminal disposed on the battery case.

10. The battery system according to claim 9, characterized in that, The at least one stage of filter includes a first filter membrane and a second filter membrane arranged in series.

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