A method for increasing the surface wetting tension of aluminum foil for batteries

Abstract

The present invention provides a method for increasing the surface wetting tension of aluminum foil for batteries, belonging to the field of new energy battery technology. The aluminum foil for batteries is subjected to a secondary rolling process, wherein the secondary rolling process sequentially includes rough rolling and finish rolling. The rolling oil used in the rolling process comprises the following components: a base oil, an alcohol, an ester, and a modified polyvinyl alcohol. The structural formula of the modified polyvinyl alcohol is shown below, wherein m = 50-100 and n = 11-17. The present invention, through the secondary rolling process, increases the surface wetting tension of the aluminum foil, thereby improving the surface performance of batteries, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy batteries, and in particular to a method for improving the surface wetting tension of aluminum foil for batteries. Background Art

[0002] With the rapid development of the domestic electronics and electric vehicle industries, demand for various types of batteries has rapidly increased, and so has demand for related products. Battery aluminum foil is one such product. The battery foil described in this article refers to aluminum foil used as the positive electrode material for lithium-ion batteries. It serves as both the current collector electrode and as a carrier for the positive electrode material (lithium battery material is coated on the surface). Battery foil (H18 state) has been widely used in recent years. This type of battery foil product is unannealed and is typically cut directly into coating specifications after rolling. After finishing, the battery foil surface retains a certain amount of oil (oil film). The amount of oil present affects the battery's storage performance and safety after coating with lithium battery material. When the overall surface of the battery foil is heavily oiled (thick oil film), the coating material adheres poorly, resulting in a thin or uneven coating, which affects the battery's storage capacity. Excessive oil on individual spots prevents the electrode material from being coated. Once the finished battery is produced, these spots will discharge, causing the battery to fail to charge or even explode.

[0003] Battery foil typically uses surface wetting tension to measure oil content. This tension is expressed in dynes, a mechanical unit. The wetting tension on both the top and bottom surfaces of battery foil is generally required to be no less than 32 dynes.

[0004] There are two unqualified aspects in the surface wetting tension of battery foil produced by conventional technology during the rolling process: one is that the initial dyne value of the finished battery foil after rolling is less than 32 dynes, which does not meet the requirements; the second is that the initial value is greater than 32 dynes, but the dyne value decays rapidly after standing for 12 hours, and even falls below 30 dynes after 24 hours, which does not meet the requirements.

[0005] Domestic aluminum foil manufacturers typically address these two issues by: first, they clean the rolled battery foil through a cleaning process to remove the oil film on the foil surface, thereby increasing the surface dyne value; second, they use rolling oils with no or minimal additives to increase the dyne value of the rolled battery foil.

[0006] Both methods can reduce oil carryover, but both have drawbacks: adding a cleaning step reduces yield and increases costs by over 25%. Using pure rolling oil results in poor rolling stability, difficulty controlling plate shape, slow speeds, rapid oil evaporation, and an increase in rolling oil consumption of approximately 20%. Summary of the Invention

[0007] The purpose of the present invention is to propose a method for improving the surface wetting tension of aluminum foil for batteries. Through the secondary rolling method, the surface wetting tension of the aluminum foil is improved, thereby improving the surface performance of the battery, and has broad application prospects.

[0008] The technical solution of the present invention is achieved as follows:

[0009] The present invention provides a method for improving the surface wetting tension of aluminum foil for batteries. The aluminum foil for batteries is subjected to secondary rolling, wherein the secondary rolling sequentially includes rough rolling and finish rolling. The rolling oil used for the rolling comprises the following components: base oil, alcohol, ester and modified polyvinyl alcohol. The structural formula of the modified polyvinyl alcohol is shown in Formula I:

[0010]

[0011] Wherein, m=50-100, and n=11-17.

[0012] As a further improvement of the present invention, the rolling oil for rolling is prepared from the following raw materials in parts by weight: 50-60 parts of base oil, 2-4 parts of alcohol, 5-7 parts of ester, and 70-90 parts of modified polyvinyl alcohol.

[0013] As a further improvement of the present invention, the rolling oil for rolling is prepared from the following raw materials in parts by weight: 55 parts of base oil, 3 parts of alcohol, 6 parts of ester, and 80 parts of modified polyvinyl alcohol.

[0014] As a further improvement of the present invention, the base oil is 82# base oil.

[0015] As a further improvement of the present invention, the alcohol includes dodecyl alcohol and octadecyl alcohol in a mass ratio of 4-6:2.

[0016] As a further improvement of the present invention, the ester includes methyl dodecanoate and ethyl hexadecanoate in a mass ratio of 3-5:2.

[0017] As a further improvement of the present invention, the preparation method of the modified polyvinyl alcohol is as follows: polyvinyl alcohol is dissolved in dichloromethane, alkyl chloride and alkali are added, heated and stirred for reaction, water is added for precipitation, filtered, washed, and dried to obtain the modified polyvinyl alcohol.

[0018] As a further improvement of the present invention, the mass ratio of the polyvinyl alcohol, alkyl chloride and base is 10:7-12:3-5; and the base is selected from at least one of triethylamine, diethylamine, NaOH and KOH.

[0019] As a further improvement of the present invention, the roughness of the finishing roller is 0.05-0.07 μm, and the rolling temperature is 45-55°C.

[0020] As a further improvement of the present invention, the roughness of the rough rolling roll is 0.1-0.12 μm, and the rolling temperature is 40-50°C.

[0021] The present invention has the following beneficial effects:

[0022] Rolling oil is composed of base oil and additives. Additives include long-chain fatty acids, alcohols, and esters. The base oil currently used is a saturated hydrocarbon oil, which consists of normal alkanes, isoalkanes, and a small amount of cycloalkanes; the carbon number distribution is C9-C17, mainly concentrated in C11-C15 (measured by gas chromatography and mass spectrometry). After the aluminum foil is left for a period of time, some components in the surface rolling oil will evaporate and its surface tension will change. In the rolling oil, the volatility of the base oil is greater than that of the additives, which changes the component composition of the rolling oil and causes the wetting tension of the aluminum foil to change.

[0023] The present invention prepares a modified polyvinyl alcohol, and the synthesis route is as follows:

[0024]

[0025] The modified polyvinyl alcohol has a relatively high molecular weight. At the same time, a long-chain alkyl chain is connected to each unit through a nucleophilic substitution reaction, so that the prepared modified polyvinyl alcohol has good non-polarity and can compensate for the volatile base oil, thereby preventing a large change in the surface tension of the aluminum foil and maintaining a relatively high surface tension on the surface of the aluminum foil.

[0026] The present invention improves the surface wetting tension of the aluminum foil through the secondary rolling method, thereby improving the surface performance of the battery, and has broad application prospects. DETAILED DESCRIPTION

[0027] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment provides a method for improving the surface wetting tension of aluminum foil for batteries, wherein the aluminum foil for batteries is subjected to secondary rolling, wherein the secondary rolling sequentially includes rough rolling and finish rolling.

[0030] The roughness of the rollers in the rough rolling was 0.1 μm, and the rolling temperature was 40°C.

[0031] The roller roughness of the finish rolling is 0.05 μm, and the rolling temperature is 45°C.

[0032] The raw material composition of the rolling oil (parts by weight) is as follows: 50 parts 82# base oil, 2 parts alcohol, 5 parts ester, and 70 parts modified polyvinyl alcohol. The alcohol includes dodecyl alcohol and octadecyl alcohol in a mass ratio of 4:2. The ester includes methyl dodecanoate and ethyl hexadecanoate in a mass ratio of 3:2.

[0033] The preparation method of modified polyvinyl alcohol is as follows: 10 parts by weight of polyvinyl alcohol is dissolved in 50 parts by weight of dichloromethane, 7 parts by weight of dodecyl chloride and 3 parts by weight of KOH are added, heated to reflux, stirred and reacted for 3 hours, water is added for precipitation, filtered, washed, and dried to obtain modified polyvinyl alcohol.

[0034] Example 2

[0035] This embodiment provides a method for improving the surface wetting tension of aluminum foil for batteries, wherein the aluminum foil for batteries is subjected to secondary rolling, wherein the secondary rolling sequentially includes rough rolling and finish rolling.

[0036] The roughness of the rollers in the rough rolling was 0.12 μm, and the rolling temperature was 50° C.

[0037] The roller roughness of the finish rolling was 0.07 μm, and the rolling temperature was 55° C.

[0038] The raw material composition of the rolling oil (parts by weight) is as follows: 60 parts of 82# base oil, 4 parts of alcohol, 7 parts of ester, and 90 parts of modified polyvinyl alcohol. The alcohol includes dodecyl alcohol and octadecyl alcohol in a mass ratio of 6:2. The ester includes methyl dodecanoate and ethyl hexadecanoate in a mass ratio of 5:2.

[0039] The preparation method of modified polyvinyl alcohol is as follows: 10 parts by weight of polyvinyl alcohol is dissolved in 50 parts by weight of dichloromethane, 12 parts by weight of octadecyl chloride and 5 parts by weight of triethylamine are added, heated to reflux, stirred and reacted for 5 hours, water is added for precipitation, filtered, washed, and dried to obtain modified polyvinyl alcohol.

[0040] Example 3

[0041] This embodiment provides a method for improving the surface wetting tension of aluminum foil for batteries, wherein the aluminum foil for batteries is subjected to secondary rolling, wherein the secondary rolling sequentially includes rough rolling and finish rolling.

[0042] The roughness of the rollers in the rough rolling was 0.11 μm, and the rolling temperature was 45°C.

[0043] The roller roughness of the finish rolling is 0.06 μm, and the rolling temperature is 50° C.

[0044] The raw material composition of the rolling oil (parts by weight) is as follows: 55 parts of 82# base oil, 3 parts of alcohol, 6 parts of ester, and 80 parts of modified polyvinyl alcohol. The alcohol includes dodecyl alcohol and octadecyl alcohol in a mass ratio of 5:2. The ester includes methyl dodecanoate and ethyl hexadecanoate in a mass ratio of 4:2.

[0045] The preparation method of modified polyvinyl alcohol is as follows: 10 parts by weight of polyvinyl alcohol is dissolved in 50 parts by weight of dichloromethane, 10 parts by weight of hexadecyl chloride and 4 parts by weight of NaOH are added, heated to reflux, stirred and reacted for 4 hours, water is added for precipitation, filtered, washed, and dried to obtain modified polyvinyl alcohol.

[0046] Example 4

[0047] Compared with Example 3, the difference is that the alcohol is single dodecanol.

[0048] The details are as follows:

[0049] The raw material composition of the rolling oil (parts by weight) is as follows: 55 parts of 82# base oil, 3 parts of alcohol, 6 parts of ester, and 80 parts of modified polyvinyl alcohol. The alcohol is dodecyl alcohol. The ester includes methyl dodecanoate and ethyl hexadecanoate, with a mass ratio of 4:2.

[0050] Example 5

[0051] Compared with Example 3, the difference is that the alcohol is single octadecyl alcohol.

[0052] The details are as follows:

[0053] The raw material composition of the rolling oil (parts by weight) is as follows: 55 parts of 82# base oil, 3 parts of alcohol, 6 parts of ester, and 80 parts of modified polyvinyl alcohol. The alcohol is octadecyl alcohol. The ester includes methyl laurate and ethyl hexadecanoate, with a mass ratio of 4:2.

[0054] Example 6

[0055] Compared with Example 3, the difference is that the ester is single methyl dodecanoate.

[0056] The details are as follows:

[0057] The raw material composition of the rolling oil (parts by weight) is as follows: 55 parts of 82# base oil, 3 parts of alcohol, 6 parts of ester, and 80 parts of modified polyvinyl alcohol. The alcohols include dodecyl alcohol and octadecyl alcohol in a mass ratio of 5:2. The ester is methyl dodecanoate.

[0058] Example 7

[0059] Compared with Example 3, the difference is that the ester is single ethyl hexadecanoate.

[0060] The details are as follows:

[0061] The raw material composition of the rolling oil (parts by weight) is as follows: 55 parts of 82# base oil, 3 parts of alcohol, 6 parts of ester, and 80 parts of modified polyvinyl alcohol. The alcohols include dodecyl alcohol and octadecyl alcohol in a mass ratio of 5:2. The ester is ethyl hexadecanoate.

[0062] Comparative Example 1

[0063] Compared with Example 3, the difference is that the modified polyvinyl alcohol is replaced by an equal amount of polyvinyl alcohol.

[0064] The details are as follows:

[0065] The raw material composition of the rolling oil (parts by weight) is as follows: 55 parts of 82# base oil, 3 parts of alcohol, 6 parts of ester, and 80 parts of polyvinyl alcohol. The alcohol includes dodecyl alcohol and octadecyl alcohol in a mass ratio of 5:2. The ester includes methyl dodecanoate and ethyl hexadecanoate in a mass ratio of 4:2.

[0066] Comparative Example 2

[0067] Compared with Example 3, the difference is that the modified polyvinyl alcohol is replaced by an equal amount of 82# base oil.

[0068] The details are as follows:

[0069] The raw material composition of the rolling oil (parts by weight) is as follows: 135 parts of 82# base oil, 3 parts of alcohol, and 6 parts of ester. The alcohol includes dodecyl alcohol and octadecanol in a mass ratio of 5:2. The ester includes methyl dodecanoate and ethyl hexadecanoate in a mass ratio of 4:2.

[0070] Comparative Example 3

[0071] The difference compared with Example 3 is that no alcohol was added.

[0072] The details are as follows:

[0073] The raw material composition of the rolling oil (parts by weight): 55 parts of 82# base oil, 9 parts of ester, and 80 parts of modified polyvinyl alcohol. The alcohols include dodecyl alcohol and octadecyl alcohol in a mass ratio of 5:2. The esters include methyl dodecanoate and ethyl hexadecanoate in a mass ratio of 4:2.

[0074] Comparative Example 4

[0075] The difference compared with Example 3 is that no ester is added.

[0076] The details are as follows:

[0077] The raw material composition of the rolling oil (parts by weight) is as follows: 55 parts of 82# base oil, 9 parts of alcohol, and 80 parts of modified polyvinyl alcohol. The alcohol includes dodecyl alcohol and octadecyl alcohol in a mass ratio of 5:2. The ester includes methyl dodecanoate and ethyl hexadecanoate in a mass ratio of 4:2.

[0078] Test Example 1

[0079] The contact angles of the aluminum foils prepared in Examples 1-7 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0080] Table 1

[0081] Group Water contact angle (°) Example 1 92 Example 2 94 Example 3 95 Example 4 88 Example 5 85 Example 6 82 Example 7 84 Comparative Example 1 72 Comparative Example 2 65 Comparative Example 3 75 Comparative Example 4 70

[0082] It can be seen from the above table that the aluminum foils prepared in Examples 1-3 of the present invention have good wettability.

[0083] Test Example 2

[0084] The aluminum foils prepared in Examples 1-7 and Comparative Examples 1-4 were placed in an oven at 80°C for 5 minutes (simulating the temperature during rolling to reduce the amount of oil on the surface). Finally, the surface wetting tension of the samples was measured using No. 30 and No. 32 dyne pens. The results are shown in Table 2.

[0085] Table 2

[0086] Group No. 30 Dyne pen No. 32 Dyne pen Example 1 No shrinkage No shrinkage Example 2 No shrinkage No shrinkage Example 3 No shrinkage No shrinkage Example 4 No shrinkage Slow contraction Example 5 No shrinkage Slow contraction Example 6 No shrinkage Slow contraction Example 7 No shrinkage Slow contraction Comparative Example 1 No shrinkage shrink Comparative Example 2 shrink shrink Comparative Example 3 Slow contraction after 15 seconds shrink Comparative Example 4 Slow contraction after 30 seconds shrink

[0087] It can be seen from the above table that the aluminum foils prepared in Examples 1-3 of the present invention have relatively high surface wetting tension.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for increasing the surface wetting tension of aluminum foil for batteries, characterized in that: The battery aluminum foil is subjected to secondary rolling, which includes rough rolling and finish rolling in sequence. The components of the rolling oil used for rolling are as follows: base oil, alcohol, ester and modified polyvinyl alcohol. The structural formula of the modified polyvinyl alcohol is shown in Formula I: Formula I; Wherein, m=50-100, and n=11-17.

2. The method for increasing the surface wetting tension of aluminum foil for batteries according to claim 1, characterized in that: The rolling oil is prepared from the following raw materials in parts by weight: 50-60 parts of base oil, 2-4 parts of alcohol, 5-7 parts of ester, and 70-90 parts of modified polyvinyl alcohol.

3. The method for increasing the surface wetting tension of aluminum foil for batteries according to claim 2, characterized in that: The rolling oil for rolling is prepared from the following raw materials in parts by weight: 55 parts of base oil, 3 parts of alcohol, 6 parts of ester, and 80 parts of modified polyvinyl alcohol.

4. The method for increasing the surface wetting tension of aluminum foil for batteries according to claim 2, characterized in that: The base oil is 82# base oil.

5. The method for increasing the surface wetting tension of aluminum foil for batteries according to claim 2, characterized in that: The alcohols include dodecyl alcohol and octadecyl alcohol in a mass ratio of 4-6:

2.

6. The method for increasing the surface wetting tension of aluminum foil for batteries according to claim 2, characterized in that: The esters include methyl dodecanoate and ethyl hexadecanoate in a mass ratio of 3-5:

2.

7. The method for increasing the surface wetting tension of aluminum foil for batteries according to claim 1, characterized in that: The preparation method of the modified polyvinyl alcohol is as follows: dissolving polyvinyl alcohol in dichloromethane, adding alkyl chloride and alkali, heating and stirring to react, adding water for precipitation, filtering, washing, and drying to obtain the modified polyvinyl alcohol.

8. The method for increasing the surface wetting tension of aluminum foil for batteries according to claim 7, characterized in that: The mass ratio of the polyvinyl alcohol, alkyl chloride and base is 10:7-12:3-5; and the base is selected from at least one of triethylamine, diethylamine, NaOH and KOH.

9. The method for increasing the surface wetting tension of aluminum foil for batteries according to claim 1, characterized in that: The roughness of the finishing roller is 0.05-0.07 μm, and the rolling temperature is 45-55°C.

10. The method for increasing the surface wetting tension of aluminum foil for batteries according to claim 1, characterized in that: The roughness of the rough rolling roll is 0.1-0.12 μm, and the rolling temperature is 40-50°C.

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