Lyophilic modified cylindrical capillary structure and cylindrical battery

Abstract

The invention relates to the technical field of batteries, and provides a lyophilic modified cylindrical capillary structure and a cylindrical battery, the lyophilic modified cylindrical capillary structure comprises a liquid guide cylinder and a lyophilic modified layer; the liquid guide cylinder comprises an inner base layer and an outer base layer arranged on the periphery of the inner base layer, and the inner base layer and the outer base layer are in butt joint to form capillary channels distributed in the extending direction of the liquid guide cylinder. The lyophilic modification layer comprises a first modification layer arranged on the inner wall of the capillary channel and is used for improving the lyophilic performance of the inner wall of the capillary channel; wherein the lyophilic modification layer is formed by compounding a fluorine-containing polymer and nanometer aluminum oxide particles, and the coating thickness of the lyophilic modification layer is 1-5 [mu] m. The cylindrical battery comprises the lyophilic modified cylindrical capillary structure, and the lyophilic modified cylindrical capillary structure and the electrolyte can infiltrate and climb upwards along the capillary channel by a relatively high height to infiltrate the top of the battery cell, so that the problems that the resistance of the top of the battery cell is easily increased after the cylindrical battery is used for a long time, and the battery performance is influenced are effectively solved.

Description

Technical Field

[0001] This disclosure relates to the field of battery technology, and in particular to a hydrophilic modified cylindrical capillary structure and a cylindrical battery. Background Technology

[0002] With the global proliferation of long-life applications such as electric vehicles (EVs) and grid-scale energy storage systems (ESS), the performance degradation of lithium-ion batteries has become increasingly prominent, leading to higher demands on the energy density, fast-charging performance, and lifespan of lithium-ion batteries.

[0003] Cylindrical batteries are one of the most commonly used commercial battery types. During manufacturing, the electrode winding layers are inserted into the battery casing, impregnated with electrolyte, and then sealed. When the battery is stationary or in use, gravity causes the amount of electrolyte at the bottom of the cylindrical battery to be greater than that at the top. This results in insufficient electrolyte at the top of the cell during charge-discharge cycles, leading to increased resistance and increasing the likelihood of localized lithium deposition, ultimately causing a decrease in battery capacity.

[0004] Because traditional cylindrical batteries have a relatively large cell height, it is difficult for the electrolyte to naturally penetrate the cells. This results in a limited height of the electrolyte along the electrodes, and after prolonged use, the resistance at the top of the cell tends to increase, affecting battery performance. Summary of the Invention

[0005] This disclosure provides a hydrophilic modified cylindrical capillary structure and a cylindrical battery to address the problems in existing cylindrical batteries, such as limited natural wetting height of the electrolyte, uneven wetting, and increased resistance at the top of the cell that affects battery performance.

[0006] The hydrophilic modified cylindrical capillary structure provided in this embodiment includes a liquid-conducting tube and a hydrophilic modified layer; The liquid guiding tube includes an inner base layer and an outer base layer disposed on the periphery of the inner base layer, and the inner base layer and the outer base layer are connected to each other to form capillary channels distributed along the extension direction of the liquid guiding tube; The hydrophilic modification layer includes a first modification layer disposed on the inner wall of the capillary channel to improve the hydrophilic properties of the inner wall of the capillary channel. The hydrophilic modified layer is composed of a fluoropolymer and nano-alumina particles, and the coating thickness of the hydrophilic modified layer is 1 μm to 5 μm.

[0007] In one embodiment, the liquid guide tube is made of one or more materials selected from polypropylene, polytetrafluoroethylene, polyimide, polyphenylene ether, polyphenylene sulfide, and polyetheretherketone.

[0008] In one embodiment, the inner diameter of the capillary channel is 50 μm to 150 μm, and the wall thickness of the inner base layer and the outer base layer is 10 μm to 30 μm.

[0009] In one embodiment, the capillary channel has a porosity of 40% to 60% in the liquid guiding cylinder.

[0010] In one embodiment, the hydrophilic modified layer further includes a second modified layer disposed on the inner wall of the inner base layer and a third modified layer disposed on the outer wall of the outer base layer.

[0011] In one embodiment, the mass percentage of the nano-alumina particles in the hydrophilic modified layer is 10% to 30%.

[0012] In one embodiment, the liquid wetting angle of the first modified layer in the capillary channel is ≤30°.

[0013] In one embodiment, the hydrophilic modified cylindrical capillary structure further includes a diffuser plate; The diffuser plate is disposed at the top of the liquid guiding cylinder and is correspondingly connected to the hydrophilic modification layer; Furthermore, the diffusion plate is composed of a fluoropolymer and nano-alumina particles.

[0014] In one embodiment, a plurality of first recesses are provided in the outer peripheral wall of the inner base layer; The outer base layer has a plurality of second recesses in its inner peripheral wall; When the outer base layer is wrapped around the outer periphery of the inner base layer, the first recess and the second recess are connected one-to-one to form multiple independently distributed capillary channels, or the first recess and the second recess are connected to each other in an alternating manner to form an integral capillary channel.

[0015] In addition, this disclosure also provides a cylindrical battery, which includes a battery body and the above-mentioned hydrophilic modified cylindrical capillary structure. The liquid guiding tube is concentrically arranged inside the battery body in a vertical direction, with one end connected to the bottom of the battery body and the other end connected to the top of the battery body.

[0016] The technical solution provided in this disclosure has the following advantages compared with related technologies: The hydrophilic modified cylindrical capillary structure provided in this embodiment forms a capillary channel through a porous structure in the liquid guiding cylinder, allowing the electrolyte to rise and wet upwards via capillary action. Furthermore, by providing a first modified layer with good hydrophilic properties on the inner wall of the capillary channel, the wetting angle of the electrolyte at the inner wall of the capillary channel is reduced, balancing the lifting force of capillary action with the liquid flow resistance of the electrolyte. This allows the electrolyte to rise and wet upwards along the capillary channel to a higher height, achieving the function of wetting the top of the battery cell. This effectively solves the problem that the resistance at the top of the battery cell easily increases after prolonged use of cylindrical batteries, affecting battery performance.

[0017] Furthermore, the cylindrical battery provided in this embodiment includes the above-mentioned hydrophilic modified cylindrical capillary structure, which can achieve all the beneficial effects of the above-mentioned hydrophilic modified cylindrical capillary structure, and will not be described in detail here.

[0018] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0019] The above and other objects, features, and advantages of this disclosure will become readily apparent from the following detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings. Several embodiments of this disclosure are illustrated in the drawings by way of example and not limitation, in which: In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0020] Figure 1 A schematic diagram of the hydrophilic modified cylindrical capillary structure provided in an embodiment of this disclosure is shown; Figure 2 An enlarged view of the top end of the hydrophilic modified cylindrical capillary structure provided in an embodiment of this disclosure is shown; Figure 3 A breakdown diagram of the liquid-conducting tube in the hydrophilic modified cylindrical capillary structure provided in the embodiments of this disclosure is shown; Figure 4 Another structural diagram of the liquid guiding tube in the hydrophilic modified cylindrical capillary structure provided in the embodiments of this disclosure is shown; Figure 5 A perspective view (including a diffuser plate) of a hydrophilic modified cylindrical capillary structure provided in an embodiment of this disclosure is shown. Figure 6 A schematic diagram of a cylindrical battery provided in an embodiment of this disclosure is shown; Figure 7 A schematic diagram of the wetting angle in an embodiment of this disclosure is shown.

[0021] Explanation of the labels in the diagram: 1. Liquid guide tube; 11. Inner layer; 111. First recess; 12. Outer layer; 121. Second recess; 13. Capillary channel; 2. Liquid guiding tube; 21. First modified layer; 22. Second modified layer; 23. Third modified layer; 3. Diffuser plate; 4. Battery body. Detailed Implementation

[0022] To make the objectives, features, and advantages of this disclosure more apparent and understandable, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0023] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0024] Combination Figure 1 and Figure 2 As shown, this embodiment of the present disclosure provides a hydrophilic modified cylindrical capillary structure, which includes a liquid guiding tube 1 and a hydrophilic modified layer 2; the liquid guiding tube 1 includes an inner base layer 11 and an outer base layer 12 disposed around the inner base layer 11, and the inner base layer 11 and the outer base layer 12 are connected to each other to form capillary channels 13 distributed along the extension direction of the liquid guiding tube 1; the hydrophilic modified layer 2 includes a first modified layer 21 disposed on the inner wall of the capillary channel 13, which is used to improve the hydrophilic properties of the inner wall of the capillary channel 13; wherein, the hydrophilic modified layer 2 is composed of a fluoropolymer and nano-alumina particles, and the coating thickness of the hydrophilic modified layer 2 is 1μm to 5μm.

[0025] In practical use, the hydrophilic modified cylindrical capillary structure provided in this embodiment can be vertically positioned at the center of a cylindrical battery, and the liquid guiding cylinder 1 can be wound around the stacked battery cells. Since the inner base layer 11 and outer base layer 12 of the liquid guiding cylinder 1 are connected to form capillary channels 13 distributed along the extension direction of the liquid guiding cylinder 1, the electrolyte at the bottom of the battery can be lifted upwards along the capillary channels 13 by the "capillary action" to a higher height, thus achieving the function of wetting the top of the battery cells.

[0026] In addition, the hydrophilic modified cylindrical capillary structure also has a first modified layer 21 on the inner wall of the capillary channel 13 to improve the hydrophilic properties of the inner wall of the capillary channel 13. The first modified layer 21 is composed of a fluoropolymer (e.g., PVDF-HFP) and nano-alumina particles, and has a thickness of 1μm to 5μm. In this way, through the composite coating structure of "fluoropolymer + nano-alumina", the chemical stability of the fluoropolymer and the roughening effect of the nano-alumina particles are utilized to ensure the chemical stability of the inner wall of the capillary channel 13, while significantly reducing the wetting angle of the electrolyte at the inner wall of the capillary channel 13. This balances the lifting force of "capillary action" and the liquid flow resistance of the electrolyte, effectively improving the uniformity of electrolyte wetting and cycle performance of the cylindrical battery.

[0027] In addition, combined Figure 7 To further explain the "wetting angle" mentioned above, for example, when a tiny spherical droplet falls onto a surface to be wetted, the easier the surface is to be wetted, the more the droplet merges with the surface. The wetting angle α is formed by the line connecting the center of the droplet and the edge of the merged part and the plane parallel to the surface to be wetted. The smaller the wetting angle α, the easier the surface to be wetted (e.g., the surface of paper). The larger the wetting angle α, the less easily the surface to be wetted (e.g., the surface of a lotus leaf).

[0028] Therefore, in summary, the hydrophilic modified cylindrical capillary structure provided in this embodiment forms a capillary channel 13 through a porous structure in the liquid guiding cylinder 1, which allows the electrolyte to rise and wet upwards via capillary force. Furthermore, by providing a first modified layer 21 with good hydrophilic properties on the inner wall of the capillary channel 13, the wetting angle of the electrolyte at the inner wall of the capillary channel 13 is reduced, balancing the lifting force of capillary action and the liquid flow resistance of the electrolyte. This allows the electrolyte at the bottom of the cylindrical battery to rise and wet upwards along the capillary channel 13 to a higher height, effectively achieving the function of wetting the top of the cell. This effectively solves the problem that the resistance at the top of the cell easily increases and affects the battery performance after long-term use of cylindrical batteries.

[0029] In one embodiment, the liquid guide tube 1 is made of one or more materials selected from polypropylene, polytetrafluoroethylene, polyimide, polyphenylene ether, polyphenylene sulfide, and polyetheretherketone.

[0030] Specifically, the inner base layer 11 and the outer base layer 12 in the liquid guiding tube 1 can be made separately from one or more materials selected from polypropylene, polytetrafluoroethylene, polyimide, polyphenylene ether, polyphenylene sulfide, and polyether ether ketone. After they are made, they are connected in a corresponding manner to form a capillary channel 13.

[0031] Alternatively, the inner base layer 11 and the outer base layer 12 can be simultaneously formed by molding one or more materials selected from polypropylene, polytetrafluoroethylene, polyimide, polyphenylene ether, polyphenylene sulfide, and polyether ether ketone, and capillary channels 13 can be formed at the same time.

[0032] The liquid guide tube 1 is made of one or more of the above materials, which has the advantages of mature molding process, low manufacturing cost and stable structure and shape.

[0033] In one embodiment, the inner diameter of the capillary channel 13 is 50 μm to 150 μm, and the wall thickness of the inner base layer 11 and the outer base layer 12 is 10 μm to 30 μm.

[0034] The inner diameter of the capillary channel 13 is selected within the range of 50μm to 150μm, such as 50μm, 70μm, 110μm, 150μm, etc. This not only ensures that the electrolyte generates sufficient capillary lifting force in the capillary channel 13 (theoretical climbing height ≥15cm), but also avoids the problem of a surge in liquid flow resistance caused by the small pore size of the capillary channel 13.

[0035] The wall thickness of the inner base layer 11 and the outer base layer 12 is selected to be between 10μm and 30μm. This not only ensures the structural shape stability of the liquid guide tube 1, but also reduces the space occupancy of the liquid guide tube 1 inside the battery, thus avoiding the problem of a significant reduction in battery energy density.

[0036] In one embodiment, the porosity of the capillary channel 13 in the liquid guiding cylinder 1 is 40% to 60%.

[0037] The porosity of the capillary channel 13 in the liquid guiding cylinder 1 is selected to be between 40% and 60%. This not only ensures that there is a sufficient number of capillary channels 13 to allow enough electrolyte to climb upwards and effectively wet the top of the battery cell, but also avoids the problem that too many capillary channels 13 will lead to poor structural stability of the liquid guiding cylinder 1 and deformation after long-term use, resulting in blockage of the capillary channels 13.

[0038] In one embodiment, the hydrophilic modified layer 2 further includes a second modified layer 22 disposed on the inner wall of the inner base layer 11 and a third modified layer 23 disposed on the outer wall of the outer base layer 12.

[0039] Specifically, in combination Figure 2In further detail, the hydrophilic modified layer 2 also includes a second modified layer 22 disposed on the inner wall of the inner base layer 11 and a third modified layer 23 disposed on the outer wall of the outer base layer 12. In this way, the second modified layer 22 and the third modified layer 23 can respectively reduce the wetting angle of the electrolyte on the inner and outer walls of the liquid guiding cylinder 1, so that the electrolyte can efficiently wet the inner and outer surfaces of the liquid guiding cylinder 1, thereby playing a gathering function of "adsorbing" the electrolyte towards the liquid guiding cylinder 1, so that the electrolyte can be more efficiently lifted and wetted upward by the capillary channel 13.

[0040] In one embodiment, the mass percentage of nano-alumina particles in the hydrophilic modified layer 2 is 10% to 30%.

[0041] Specifically, the mass percentage of nano-alumina particles in the hydrophilic modified layer 2 is selected to be between 10% and 30%. This way, the roughening effect of the nano-alumina particles reduces the wetting angle of the hydrophilic modified layer 2, while also ensuring that there is a sufficient amount of fluoropolymer to ensure the chemical stability of the hydrophilic modified layer 2, thus avoiding the problem of corrosion and peeling after long-term use.

[0042] In one embodiment, the liquid wetting angle of the first modified layer 21 in the capillary channel 13 is ≤30°.

[0043] Specifically, by controlling the mass ratio of nano-alumina particles in the hydrophilic modified layer 2, the wetting angle of the hydrophilic modified layer 2 can be reduced. Thus, when the liquid wetting angle of the first modified layer 21 is ≤30°, it is better than the 40°~60° wetting angle of the traditional PP material capillary tube, thereby ensuring that the electrolyte generates sufficient capillary lifting force in the capillary channel 13 and achieves the effect of a theoretical climbing height ≥15cm.

[0044] In one embodiment, the hydrophilic modified cylindrical capillary structure further includes a diffuser plate 3; the diffuser plate 3 is disposed at the top of the liquid guiding cylinder 1 and is correspondingly connected to the hydrophilic modified layer 2; and the diffuser plate 3 is composed of a fluoropolymer and nano-alumina particles.

[0045] Specifically, in combination Figure 5 In further detail, the aforementioned diffuser plate 3 can be made of the same material as the hydrophilic modified layer 2, also composed of a fluoropolymer and nano-alumina particles, thus ensuring that the diffuser plate 3 also possesses excellent wettability. Since the diffuser plate 3 is positioned at the top of the liquid guiding cylinder 1 and correspondingly connected to the hydrophilic modified layer 2, when the electrolyte rises to the top of the liquid guiding cylinder 1 through the capillary channel 13, it can diffuse radially from the inside out along the diffuser plate 3, allowing the electrolyte to subsequently and fully and uniformly wet the top of the battery cell under gravity.

[0046] In one embodiment, the outer peripheral wall of the inner base layer 11 is provided with a plurality of first recesses 111; the inner peripheral wall of the outer base layer 12 is provided with a plurality of second recesses 121; when the outer base layer 12 is wrapped around the outer peripheral portion of the inner base layer 11, the first recesses 111 and the second recesses 121 are connected one-to-one to form a plurality of independently distributed capillary channels 13, or the first recesses 111 and the second recesses 121 are interleaved to form an integral capillary channel 13.

[0047] Specifically, in combination Figure 3 In further detail, the outer peripheral wall of the inner base layer 11 may be provided with a plurality of first recesses 111 at intervals along the height direction, and the first recesses 111 may be configured as grooves with a semi-circular cross-section; the inner peripheral wall of the outer base layer 12 may be provided with a plurality of second recesses 121 at intervals along the height direction, and the second recesses 121 may also be configured as grooves with a semi-circular cross-section.

[0048] When the outer base layer 12 is wrapped around the outer periphery of the inner base layer 11, the first recess 111 and the second recess 121 can be connected one-to-one to form multiple independently distributed capillary channels 13; or as Figure 4 As shown, the first recess 111 and the second recess 121 interlock to form an integral capillary channel 13.

[0049] In addition, this disclosure also provides a cylindrical battery, which includes a battery body 4 and the above-mentioned hydrophilic modified cylindrical capillary structure; the liquid guiding tube 1 is concentrically disposed inside the battery body 4 in the vertical direction, and one end is connected to the bottom of the battery body 4, and the other end is connected to the top of the battery body 4.

[0050] Specifically, in combination Figure 6 In further detail, since the cylindrical battery includes the battery body 4 and the aforementioned hydrophilic modified cylindrical capillary structure, and the liquid guiding tube 1 is concentrically arranged inside the battery body 4 in the vertical direction, with its two ends corresponding to the bottom and top of the battery body 4, the capillary channel 13 in the liquid guiding tube 1 allows the electrolyte at the bottom of the cylindrical battery to rise and wet to a higher height along the capillary channel 13, effectively achieving the function of wetting the top of the cell. This solves the problem that the resistance at the top of the cell easily increases and affects the battery performance after long-term use of the cylindrical battery.

[0051] Since the cylindrical battery includes the aforementioned hydrophilic modified cylindrical capillary structure, the other beneficial effects of the aforementioned hydrophilic modified cylindrical capillary structure can also be achieved by the cylindrical battery, and will not be elaborated further here.

[0052] In addition, the embodiments of this disclosure also conduct charge-discharge tests on the cylindrical battery with the hydrophilic modified cylindrical capillary structure and the cylindrical battery without the hydrophilic modified cylindrical capillary structure: the battery is charged at a constant current of 1C to 4.20V, charged at a constant voltage to 0.05C cutoff, discharged at a constant current of 1C to 0.05V, until the capacity retention rate is recorded after 500 cycles.

[0053] The following performance comparison table was obtained:

[0054] Beneficial effects: The cylindrical battery with hydrophilic modified cylindrical capillary structure has a significantly higher capacity retention rate after 500 cycles than the conventional cylindrical battery without hydrophilic modified cylindrical capillary structure. At the same time, its DCIR and ACIR are lower than those of the conventional cylindrical battery without hydrophilic modified cylindrical capillary structure, which is mainly due to the sufficient wetting of the top of the cell.

[0055] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0056] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A hydrophilic modified cylindrical capillary structure, characterized in that, include: The liquid guiding tube (1) includes an inner base layer (11) and an outer base layer (12) disposed around the inner base layer (11), and the inner base layer (11) and the outer base layer (12) are connected to each other to form capillary channels (13) distributed along the extension direction of the liquid guiding tube (1). The hydrophilic modification layer (2) includes a first modification layer (21) disposed on the inner wall of the capillary channel (13) to improve the hydrophilic properties of the inner wall of the capillary channel (13); The hydrophilic modified layer (2) is composed of a fluoropolymer and nano-alumina particles, and the coating thickness of the hydrophilic modified layer (2) is 1 μm ~ 5 μm.

2. The hydrophilic modified cylindrical capillary structure according to claim 1, characterized in that, The liquid guide tube (1) is made of one or more of the following materials: polypropylene, polytetrafluoroethylene, polyimide, polyphenylene ether, polyphenylene sulfide, and polyether ether ketone.

3. The hydrophilic modified cylindrical capillary structure according to claim 1, characterized in that, The inner diameter of the capillary channel (13) is 50μm to 150μm, and the wall thickness of the inner base layer (11) and the outer base layer (12) is 10μm to 30μm.

4. The hydrophilic modified cylindrical capillary structure according to claim 1, characterized in that, The capillary channel (13) has a porosity of 40% to 60% in the liquid guiding tube (1).

5. The hydrophilic modified cylindrical capillary structure according to claim 1, characterized in that, The hydrophilic modified layer (2) further includes a second modified layer (22) disposed on the inner wall of the inner base layer (11) and a third modified layer (23) disposed on the outer wall of the outer base layer (12).

6. The hydrophilic modified cylindrical capillary structure according to claim 1, characterized in that, The mass percentage of the nano-alumina particles in the hydrophilic modified layer (2) is 10% to 30%.

7. The hydrophilic modified cylindrical capillary structure according to claim 6, characterized in that, The liquid wetting angle of the first modified layer (21) in the capillary channel (13) is ≤30°.

8. The hydrophilic modified cylindrical capillary structure according to claim 1, characterized in that, The hydrophilic modified cylindrical capillary structure also includes a diffuser plate (3). The diffuser plate (3) is disposed at the top of the liquid guide tube (1) and is correspondingly connected to the hydrophilic modification layer (2); Furthermore, the diffuser plate (3) is composed of a fluoropolymer and nano-alumina particles.

9. The hydrophilic modified cylindrical capillary structure according to any one of claims 1 to 8, characterized in that, The outer peripheral wall of the inner base layer (11) is provided with a plurality of first recesses (111). The outer base layer (12) has a plurality of second recesses (121) in its inner peripheral wall. When the outer base layer (12) is wrapped around the outer periphery of the inner base layer (11), the first recess (111) and the second recess (121) are connected one-to-one to form a plurality of independently distributed capillary channels (13), or the first recess (111) and the second recess (121) are interleaved to form an integral capillary channel (13).

10. A cylindrical battery, characterized in that, Includes the battery body (4) and the hydrophilic modified cylindrical capillary structure according to any one of claims 1 to 9; The liquid guide tube (1) is concentrically arranged inside the battery body (4) in the vertical direction, with one end connected to the bottom of the battery body (4) and the other end connected to the top of the battery body (4).

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