A battery swelling film, its preparation method and application

Abstract

This invention provides a battery swelling film, its preparation method, and its application. The battery swelling film is made of high-hardness TPU, low-hardness TPU, and an anhydride grafting agent. The raw materials for preparing the high-hardness TPU include component A and component B. Component A includes a polyester polyol and a small-molecule diol with a branched structure. Component B includes a diphenylmethane diisocyanate curing agent. The raw materials for preparing the low-hardness TPU include component C and component D. Component C includes a polyether-type linear diol and a small-molecule linear diol. Component D includes a toluene diisocyanate curing agent. By selecting and combining the above two types of TPU with different hardnesses, and simultaneously adding an anhydride grafting agent, a battery swelling film with a good swelling ratio, excellent adhesion, and high-temperature resistance is obtained.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery water treatment technology, specifically relating to a battery swelling membrane, its preparation method, and its application. Background Technology

[0002] Currently, the manufacturing process of lithium-ion batteries is mature and they are widely used in production. However, during the assembly of cylindrical batteries, a certain gap exists between the cell and the cylindrical casing. If the cell is not effectively secured within the casing, vibration or external impact can easily cause relative movement between the bare cell and the casing, leading to problems such as electrode damage, short circuits, and increased resistance. This affects the performance of the lithium battery and poses significant safety hazards. Therefore, it is necessary to bond the bare cell and the cylindrical casing and fill the gap between them.

[0003] TPU is increasingly popular due to its superior performance and environmental friendliness. TPU not only has excellent high tensile strength, high tear strength, toughness and aging resistance, but it is also a mature environmentally friendly material. At present, TPU has been widely used in: footwear, clothing, inflatable toys, water and underwater sports equipment, medical equipment, fitness equipment, car seat materials, umbrellas, suitcases, bags and other fields. CN111518481A discloses a swelling tape for lithium batteries and its manufacturing process, including a base layer and a pressure-sensitive adhesive layer. By adding TPU particles, EVA particles, styrene resin solution, and (titanium dioxide) color paste during the base layer manufacturing process, the base layer maintains a high area of ​​swelling even when the electrolyte is reduced or removed. The pressure-sensitive adhesive layer does not dissolve after being immersed in the electrolyte and remains sticky in the electrolyte environment. The swelling tape for lithium batteries prepared by this process can swell and deform in the length and width directions after contacting the lithium-ion battery electrolyte, increasing the area to more than 200% of the original area. However, this technology can only achieve swelling and deformation of the tape in the length and width directions to form folds and fill gaps, but it cannot fill the gaps in the cylindrical battery in all directions.

[0004] CN111995957A discloses an oriented polystyrene expanding tape and its preparation method, which is composed of a single-sided release oriented polystyrene film substrate and an acrylic adhesive layer. The tape has an expansion ratio of 400% in the thickness direction, but the tape has low temperature resistance and shrinks at high temperatures, making it unusable.

[0005] Therefore, providing a battery swelling film that can undergo high-rate expansion in area in electrolyte and has excellent adhesion and high-temperature resistance is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a battery swelling film, its preparation method, and its application. The battery swelling film is made of high-hardness TPU, low-hardness TPU, and an anhydride grafting agent. By selecting two types of TPU with different hardnesses and adding an anhydride grafting agent, the resulting battery swelling film can expand at a high rate in the electrolyte and has excellent adhesion and high-temperature resistance.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a battery swelling film, wherein the battery swelling film is made of high-hardness TPU, low-hardness TPU and an acid anhydride grafting agent;

[0009] The raw materials for preparing the high-hardness TPU include component A and component B. Component A includes polyester polyol and small molecule diol with branched structure, and component B includes diphenylmethane diisocyanate curing agent.

[0010] The raw materials for preparing the low-hardness TPU include component C and component D. Component C includes polyether-type linear diol and small molecule linear diol, and component D includes toluene diisocyanate curing agent.

[0011] The hardness of the high-hardness TPU is higher than that of the low-hardness TPU.

[0012] The battery swelling film provided by this invention comprises high-hardness TPU, low-hardness TPU, and an anhydride grafting agent. The raw materials for preparing the high-hardness TPU include component A and component B. Component A includes polyester polyol and a small-molecule diol with a branched structure. Component B includes a diphenylmethane diisocyanate curing agent. The raw materials for preparing the low-hardness TPU include component C and component D. Component C includes a polyether-type linear diol and a small-molecule linear diol. Component D includes a toluene diisocyanate curing agent. By selecting two types of TPU with different hardnesses and adding an anhydride grafting agent, the resulting battery swelling film can fully absorb the solvent in the electrolyte, exhibiting a good swelling ratio, and possessing excellent adhesion and high-temperature resistance.

[0013] Preferably, the hardness of the high-hardness TPU is 95A to 64D, such as 100A, 45D, 50D, 55D or 60D.

[0014] Preferably, component A comprises the following components in parts by weight:

[0015] 20-75 parts by weight of polyester polyol

[0016] 5-20 parts by weight of small molecule diols with branched structures.

[0017] As a preferred technical solution of the present invention, selecting polyester polyol and small molecule diol with branched structure to be combined within a specific dosage range can ensure that the prepared TPU has high hardness.

[0018] The polyester polyol can be 30 parts by weight, 40 parts by weight, 50 parts by weight, 60 parts by weight, or 70 parts by weight, etc.

[0019] The branched small molecule diols can be 7 parts by weight, 9 parts by weight, 11 parts by weight, 13 parts by weight, 15 parts by weight, 17 parts by weight, or 19 parts by weight, etc.

[0020] Preferably, the mass ratio of component A to component B is 1:(0.02-0.5), for example, 1:0.05, 1:0.07, 1:0.09, 1:0.11, 1:0.13, 1:0.17, 1:0.2, 1:0.23, 1:0.28, 1:0.31, 1:0.38, 1:0.43, or 1:0.48, etc.

[0021] Preferably, the branched small molecule diol includes any one or a combination of at least two of 1,2-propanediol, methylpropanediol, 1,3-butanediol, or neopentyl glycol.

[0022] Preferably, the polyester polyol comprises a polyester diol.

[0023] Preferably, the polyester diol comprises any one or a combination of at least two of polyethylene adipate diol, polybutylene adipate diol, polyethylene adipate / butylene adipate diol, polyhexane adipate diol, or polytetrahydrofuran diol.

[0024] Preferably, the hardness of the low-hardness TPU is 70-85A, such as 72A, 74A, 76A, 78A, 70A, 71A, 72A, 73A or 74A.

[0025] Preferably, component C comprises the following components in parts by weight:

[0026] 5-20 parts by weight of polyether-type linear diol

[0027] 5-10 parts by weight of small molecule straight-chain diols.

[0028] As a preferred technical solution of the present invention, selecting polyether-type linear diols and small molecule linear diols in combination within the above-mentioned specific dosage range can result in TPU with lower hardness.

[0029] The polyether-type linear diol can be 7 parts by weight, 9 parts by weight, 11 parts by weight, 13 parts by weight, 15 parts by weight, 17 parts by weight, or 19 parts by weight, etc.

[0030] The small molecule straight-chain diol can be 7 parts by weight, 9 parts by weight, 11 parts by weight, 13 parts by weight, 15 parts by weight, 17 parts by weight, or 19 parts by weight, etc.

[0031] Preferably, the mass ratio of component C to component D is 1:(0.02-0.5), for example, 1:0.05, 1:0.07, 1:0.09, 1:0.11, 1:0.13, 1:0.17, 1:0.2, 1:0.23, 1:0.28, 1:0.31, 1:0.38, 1:0.43, or 1:0.48, etc.

[0032] Preferably, the polyether-type linear diol includes polypropylene glycol and / or polytetrahydrofuran diol.

[0033] Preferably, the small molecule straight-chain diol includes ethylene glycol and / or propylene glycol.

[0034] Preferably, the anhydride grafting agent comprises POE grafted with maleic anhydride.

[0035] Preferably, the material of the battery swelling film comprises the following components in parts by weight:

[0036] High-hardness TPU 10-50 parts by weight

[0037] Low-hardness TPU 10-50 parts by weight

[0038] 5-20 parts by weight of acid anhydride grafting agent.

[0039] The high-hardness TPU can be 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, or 45 parts by weight, etc.

[0040] The low-hardness TPU can be in quantities of 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, or 45 parts by weight.

[0041] The anhydride grafting agent can be 7 parts by weight, 9 parts by weight, 11 parts by weight, 13 parts by weight, 15 parts by weight, 17 parts by weight, 19 parts by weight, 19.5 parts by weight, or 20 parts by weight, etc.

[0042] Preferably, the material of the battery swelling film further includes a thermal crosslinking agent.

[0043] Preferably, the thermal crosslinking agent comprises an organic peroxide and / or diethylenetriamine.

[0044] Preferably, the content of thermal crosslinking agent in the material of the battery swelling film is 1 to 5 parts by weight, such as 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight or 4.5 parts by weight.

[0045] In a second aspect, the present invention provides a method for preparing a battery swelling film as described in the first aspect, the method comprising the following steps:

[0046] (1) React components A and B in high-hardness TPU to obtain high-hardness TPU; react components C and D in low-hardness TPU to obtain high-hardness TPU.

[0047] (2) The high-hardness TPU, low-hardness TPU, acid anhydride grafting agent and optional geothermal crosslinking agent obtained in step (1) are introduced into a twin-screw extruder to obtain a molten colloid, and then the molten colloid is cast into a film to obtain the battery swelling film.

[0048] Thirdly, the present invention provides an application of the battery swelling film as described in the first aspect in a lithium-ion battery.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The battery swelling film provided by the present invention comprises high-hardness TPU, low-hardness TPU and an anhydride grafting agent; the raw materials for preparing the high-hardness TPU include component A and component B, component A includes polyester polyol and small molecule diol with branched structure, and component B includes isocyanate curing agent; the raw materials for preparing the low-hardness TPU include component C and component D, component C includes polyether type linear diol and small molecule linear diol, and component D includes isocyanate prepolymer curing agent; the hardness of the high-hardness TPU is higher than that of the low-hardness TPU; by selecting the above two hardness TPUs and anhydride grafting agent, and limiting the raw materials for preparing the above two hardness TPUs, by selecting two hardness TPUs to match, and adding anhydride grafting agent, the obtained battery swelling film can fully absorb the solvent in the electrolyte and exhibit a good swelling ratio, and has excellent adhesion and high temperature resistance.

[0051] (2) Specifically, the peeling force of the battery swelling film provided by the present invention is 1.45 to 1.55 N / 25 mm, the swelling rate at 45°C is 173 to 184%, and the swelling rate at 85°C is 198 to 208%. Detailed Implementation

[0052] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0053] Example 1

[0054] A battery swelling film, the material comprising the following components by weight:

[0055]

[0056] The high-hardness TPU has a hardness of 50D. Its preparation raw materials include component A and component B in a mass ratio of 1:0.25. Component A includes 30 parts by weight of polyethylene adipate diol (molecular weight of 2000) and 10 parts by weight of 1,2-propanediol. Component B includes diphenylmethane diisocyanate curing agent.

[0057] The low-hardness TPU has a hardness of 80A. Its preparation raw materials include component C and component D in a mass ratio of 1:0.25. Component C includes 10 parts by weight of polypropylene glycol (molecular weight of 2000) and 5 parts by weight of ethylene glycol. The preparation raw materials of component D include toluene diisocyanate curing agent.

[0058] The method for preparing the battery swelling film provided in this embodiment includes the following steps:

[0059] (1) Polyethylene adipate diol, 1,2-propanediol and diphenylmethane diisocyanate curing agent are fed into a twin-screw extruder for extrusion only, and the extrusion temperature is set to 200℃ to obtain high-hardness TPU; polypropylene glycol, ethylene glycol and toluene diisocyanate curing agent are fed into a twin-screw extruder for extrusion only, and the extrusion temperature is set to 120℃ to obtain low-hardness TPU;

[0060] (2) The high-hardness TPU, low-hardness TPU, POE-grafted maleic anhydride and diethylenetriamine obtained in step (1) are introduced into a twin-screw extruder to obtain a molten colloid, and then the molten colloid is cast into a film to obtain the battery swelling film.

[0061] Example 2

[0062] A battery swelling film, the material comprising the following components by weight:

[0063]

[0064] The high-hardness TPU has a hardness of 95A. Its raw materials include component A and component B in a mass ratio of 1:0.05. Component A includes 20 parts by weight of polyethylene adipate diol (molecular weight of 2000) and 5 parts by weight of 1,2-propanediol. Component B includes diphenylmethane diisocyanate.

[0065] The low-hardness TPU has a hardness of 70A. Its preparation raw materials include component C and component D in a mass ratio of 1:0.05. Component C includes 5 parts by weight of polypropylene glycol (molecular weight of 2000) and 5 parts by weight of ethylene glycol. The preparation raw materials of component D include toluene diisocyanate curing agent.

[0066] The preparation method of the battery swelling film provided in this embodiment is the same as that in Embodiment 1.

[0067] Example 3

[0068] A battery swelling film, the material comprising the following components by weight:

[0069]

[0070] The high-hardness TPU has a hardness of 64D. Its raw materials include component A and component B in a mass ratio of 1:0.5. Component A includes 75 parts by weight of polyethylene adipate diol (molecular weight of 2000) and 20 parts by weight of 1,2-propanediol. Component B includes diphenylmethane diisocyanate.

[0071] The low-hardness TPU has a hardness of 85A. Its preparation raw materials include component C and component D in a mass ratio of 1:0.5. Component C includes 20 parts by weight of polypropylene glycol (molecular weight of 2000) and 20 parts by weight of ethylene glycol. The preparation raw materials of component D include toluene diisocyanate curing agent.

[0072] The preparation method of the battery swelling film provided in this embodiment is the same as that in Embodiment 1.

[0073] Example 4

[0074] A battery swelling film differs from Example 1 only in that it uses polybutylene adipate diol with a molecular weight of 2000 instead of polyethylene adipate diol with a molecular weight of 2000. All other components, amounts, and preparation methods are the same as in Example 1.

[0075] Example 5

[0076] A battery swelling film differs from Example 1 only in that a polytetrahydrofuran diol with a molecular weight of 2000 is used instead of a polypropylene glycol with a molecular weight of 2000. All other components, amounts, and preparation methods are the same as in Example 1.

[0077] Example 6

[0078] A battery swelling film differs from Example 1 only in that it does not contain diethylenetriamine; all other components, dosages, and preparation methods are the same as in Example 1.

[0079] Comparative Example 1

[0080] A battery swelling film, the material comprising the following components by weight:

[0081] High-hardness TPU 50 parts by weight

[0082] 13 parts by weight of anhydride grafting agent

[0083] 2.5 parts by weight of diethylenetriamine;

[0084] The high-hardness TPU has a hardness of 50D. Its preparation raw materials include component A and component B in a mass ratio of 1:0.25. Component A includes 30 parts by weight of polyethylene adipate diol (molecular weight of 2000) and 10 parts by weight of 1,2-propanediol. Component B includes diphenylmethane diisocyanate curing agent.

[0085] The method for preparing the battery swelling film provided in this embodiment includes the following steps:

[0086] (1) Polyethylene adipate diol, 1,2-propanediol and diphenylmethane diisocyanate curing agent are fed into a twin-screw extruder for extrusion only. The extrusion temperature is set to 200℃ to obtain high-hardness TPU.

[0087] (2) The high-hardness TPU, POE grafted maleic anhydride and diethylenetriamine obtained in step (1) are introduced into a twin-screw extruder to obtain a molten colloid, and then the molten colloid is cast into a film to obtain the battery swelling film.

[0088] Comparative Example 2

[0089] A battery swelling film, the material comprising the following components by weight:

[0090] Low-hardness TPU 50 parts by weight

[0091] 13 parts by weight of anhydride grafting agent

[0092] 2.5 parts by weight of diethylenetriamine;

[0093] The low-hardness TPU has a hardness of 80A. Its preparation raw materials include component C and component D in a mass ratio of 1:0.25. Component C includes 10 parts by weight of polypropylene glycol (molecular weight of 2000) and 5 parts by weight of ethylene glycol. The preparation raw materials of component D include toluene diisocyanate curing agent.

[0094] The method for preparing the battery swelling film provided in this embodiment includes the following steps:

[0095] (1) Polypropylene glycol, ethylene glycol and toluene diisocyanate curing agent are fed into a twin-screw extruder for extrusion only. The extrusion temperature is set to 120°C to obtain low-hardness TPU.

[0096] (2) The low-hardness TPU, POE-grafted maleic anhydride and diethylenetriamine obtained in step (1) are introduced into a twin-screw extruder to obtain a molten colloid, and then the molten colloid is cast into a film to obtain the battery swelling film.

[0097] Comparative Example 3

[0098] A battery swelling film differs from Example 1 only in that it does not contain diethylenetriamine; all other components, dosages, and preparation methods are the same as in Example 1.

[0099] Performance testing:

[0100] (1) Adhesion performance: The test method for peel force on steel plates refers to the standard GB / T 2792-2014;

[0101] (2) Swelling rate: Refer to the standard GB / T 7125-2014 to test the total thickness h0 of the sample. Cut the test sample into 50×50mm pieces and prepare 5 pieces. Put the cut tape into a PE bottle, pour in electrolyte to cover the sample, and bake in an environment of 45℃ and 85℃ for 36h respectively. After that, take out the sample, flatten the sample, and use a 30cm steel ruler to test the length a and width b of the sample (confirm that the shrinkage in the length and width directions is ≤10%). At the same time, refer to the standard GB / T 7125-2014 to test the thickness h1 of the sample after soaking and baking in electrolyte. Swelling rate = h1 / h0×100%.

[0102] The battery swelling films provided in Examples 1-6 and Comparative Examples 1-3 were tested according to the above test methods. The test results are shown in Table 1.

[0103] Table 1

[0104] Peel force / N / 25 mm Swelling rate at 45℃ / % Swelling rate at 85℃ / % Example 1 1.55 182 208 Example 2 1.45 184 207 Example 3 1.55 183 204 Example 4 1.5 179 202 Example 5 1.55 173 201 Example 6 1.5 178 198 Comparative Example 1 1.35 110 135 Comparative Example 2 1.25 120 Dissolve Comparative Example 3 1.45 98 107

[0105] As can be seen from the data in Table 1, the battery swelling film provided by the present invention has excellent adhesion, high swelling ratio and excellent high temperature resistance.

[0106] Specifically, the peel strength of the battery swelling film provided in Examples 1 to 6 is 1.45 to 1.55 N / 25 mm, the swelling rate at 45°C is 173 to 184%, and the swelling rate at 85°C is 198 to 208%.

[0107] Comparing the data of Example 1 and Comparative Example 1, it can be seen that the battery swelling film containing only high-hardness TPU has lower peel strength and lower swelling rate in electrolyte.

[0108] Comparing the data from Example 1 and Comparative Example 2, it can also be seen that the battery swelling film containing only low-hardness TPU has lower peel strength and poorer high-temperature resistance.

[0109] Further comparison of the data from Example 1 and Comparative Example 3 also shows that the absence of anhydride grafting agent also affects the swelling performance of the battery swelling film.

[0110] Finally, comparing the data from Example 1 and Example 6, it can be seen that the addition of thermal crosslinking agent also affects the swelling performance of the battery swelling film.

[0111] The applicant declares that this invention illustrates a battery swelling film, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

Claims

1. A battery swelling film, characterized in that, The battery swelling film is made of high-hardness TPU, low-hardness TPU and an anhydride grafting agent; The raw materials for preparing the high-hardness TPU include component A and component B. Component A includes polyester polyol and small molecule diol with branched structure, and component B includes diphenylmethane diisocyanate curing agent. Component A comprises the following components in parts by weight: 20-75 parts by weight of polyester polyol 5-20 parts by weight of small molecule diols with branched structures; The mass ratio of component A to component B is 1:(0.02~0.5); the hardness of the high-hardness TPU is 95A~64D; The raw materials for preparing the low-hardness TPU include component C and component D. Component C includes polyether-type linear diol and small molecule linear diol, and component D includes toluene diisocyanate curing agent. Component C comprises the following components in parts by weight: 5-20 parts by weight of polyether-type linear diol 5-10 parts by weight of small molecule straight-chain diols; The mass ratio of component C to component D is 1:(0.02~0.5); The hardness of the low-hardness TPU is 70-85A.

2. The battery swelling film according to claim 1, characterized in that, The branched small molecule diols include any one or a combination of at least two of 1,2-propanediol, methylpropanediol, 1,3-butanediol, or neopentyl glycol.

3. The battery swelling film according to claim 1, characterized in that, The polyester polyol includes polyester diol.

4. The battery swelling film according to claim 3, characterized in that, The polyester diol includes any one or a combination of at least two of polyethylene adipate diol, polybutylene adipate diol, polyethylene adipate / butylene adipate diol, or polyhexane adipate diol.

5. The battery swelling film according to claim 1, characterized in that, The polyether-type linear diols include polypropylene glycol and / or polytetrahydrofuran diol.

6. The battery swelling film according to claim 1, characterized in that, The small molecule straight-chain diols include ethylene glycol and / or propylene glycol.

7. The battery swelling film according to claim 1, characterized in that, The anhydride grafting agent includes POE grafted with maleic anhydride.

8. The battery swelling film according to claim 1, characterized in that, The battery swelling film comprises the following components by weight: High-hardness TPU 10-50 parts by weight Low-hardness TPU 10-50 parts by weight 5-20 parts by weight of acid anhydride grafting agent.

9. The battery swelling film according to claim 1, characterized in that, The battery swelling film also includes a thermal crosslinking agent.

10. The battery swelling film according to claim 9, characterized in that, The thermal crosslinking agent includes organic peroxides and / or diethylenetriamine.

11. The battery swelling film according to claim 9, characterized in that, The content of thermal crosslinking agent in the material of the battery swelling film is 1 to 5 parts by weight.

12. A method for preparing a battery swelling film as described in any one of claims 1 to 11, characterized in that, The preparation method includes the following steps: (1) React components A and B in high-hardness TPU to obtain high-hardness TPU; react components C and D in low-hardness TPU to obtain low-hardness TPU. (2) The high-hardness TPU, low-hardness TPU, acid anhydride grafting agent and optional geothermal crosslinking agent obtained in step (1) are introduced into a twin-screw extruder to obtain a molten colloid, and then the molten colloid is cast into a film to obtain the battery swelling film.

13. The application of a battery swelling film as described in any one of claims 1 to 11 in a lithium-ion battery.

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