Method for measuring thickness of copper foil for lithium ion battery

Abstract

The invention discloses a method for measuring the thickness of a copper foil for a lithium ion battery, and the method comprises the following steps: carrying out the vacuum packaging of a vacuum bag, measuring the thickness of the vacuum bag after the vacuum packaging, obtaining the original thickness a of the vacuum bag, opening the vacuum bag again, laminating and fixing N copper foils to be measured (N is greater than or equal to 2), putting the laminated copper foils into the vacuum bag, and carrying out the measurement of the thickness a of the vacuum bag. And then air in the vacuum bag is extracted so that negative pressure can be formed in the vacuum bag, the thickness b of the vacuum bag containing the copper foil is measured through a thickness measuring instrument, and the thickness # imgabs0 # of the single copper foil is obtained according to a formula. The precision and reliability of thickness measurement of the ultrathin lithium battery copper foil are remarkably improved, deformation and creases of the ultrathin copper foil in the measurement process are inhibited through physical fixation, the problem of local depression caused by pressure of a probe of a contact type thickness gauge is solved, meanwhile, the harsh requirement of non-contact type optical measurement for the flatness of the copper foil is lowered, and the measurement accuracy of the thickness of the ultrathin lithium battery copper foil is improved. And the compatibility is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of thickness measurement, in particular to a method for measuring the thickness of copper foil for lithium ion batteries. Background Art

[0002] With the global energy transition and the rapid development of the new energy vehicle industry, lithium-ion batteries have been widely used as core energy storage devices. The negative electrode, a crucial component of lithium-ion batteries, directly determines its charge and discharge efficiency and safety. The negative electrode of a traditional lithium-ion battery is typically made by coating a copper foil current collector with graphite. As a carrier for electron transfer, copper foil must simultaneously meet the requirements of high conductivity, mechanical strength, and lightweight. In recent years, to increase battery energy density and reduce manufacturing costs, ultra-thinning of the negative electrode current collector copper foil has become a mainstream trend in the lithium-ion battery industry. Its thickness has gradually decreased from the early 12-15 μm (micrometers) to 6 μm or even below 4.5 μm. The use of ultra-thin copper foil can significantly reduce the proportion of inactive materials, improve the battery's mass energy density, and reduce raw material costs, meeting the lightweight and long-range requirements of new energy vehicles and other new energy devices.

[0003] However, the continuous reduction in copper foil thickness poses significant challenges to manufacturing processes and quality inspection. For thickness measurement during quality inspection, conventional methods typically utilize contact thickness gauges to directly measure single-layer copper foil. However, due to the low mechanical strength and easy deformation of ultra-thin copper foil (e.g., 4.5 μm), improper handling or environmental stress can easily cause creases and wrinkles in the foil during measurement, leading to deviations from the true thickness. Especially when creases are present on the foil surface, the pressure exerted by the contact thickness gauge's probe can exacerbate localized deformation, causing depressions or protrusions at the measurement point. This can lead to thickness measurement errors exceeding 10%. Furthermore, while some non-contact optical thickness measurement technologies can avoid mechanical contact damage, they place extremely high demands on the copper foil's surface flatness. In actual production, this inherent curling of ultra-thin copper foil due to its extreme flexibility is difficult to avoid, often resulting in insufficient surface flatness during measurement.

[0004] In existing technologies, to address the aforementioned issues with copper foil thickness measurement and improve the stability of ultra-thin copper foil thickness measurement, some solutions propose stacking multiple layers of copper foil, measuring the total thickness, and then calculating the thickness of a single layer through arithmetic averaging. However, the core difficulty of this method lies in the fact that if air gaps or local wrinkles exist between the copper foils during the stacking process, the interlayer contact will be loose, resulting in nonlinear accumulation of stacked thickness and ultimately amplifying measurement errors. Therefore, how to achieve non-destructive stacking and fixation of ultra-thin copper foil, eliminate creases and air interference, and thus accurately measure the thickness of the copper foil, has become the key to improving thickness measurement accuracy. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a method for measuring the thickness of copper foil for lithium-ion batteries, which can solve the problems described in the background art.

[0006] The technical solution for achieving the purpose of the present invention is: a method for measuring the thickness of copper foil for lithium ion batteries, comprising the following steps: The vacuum bag is vacuum sealed, and the thickness of the vacuum bag after vacuum sealing is measured to obtain the original thickness a of the vacuum bag. Open the vacuum bag again, stack and fix N copper foils to be measured (N≥2), put the stacked copper foils into the vacuum bag, and then extract the air in the vacuum bag to form a negative pressure inside the vacuum bag. Use a thickness gauge to measure the thickness b of the vacuum bag containing copper foil, and use the following formula to get the thickness of a single copper foil: :

[0007] Thus completing the measurement of copper foil thickness.

[0008] Furthermore, 3≤N≤200.

[0009] Furthermore, the specifications of each copper foil are the same, including the material and size. Furthermore, the copper foil includes rolled copper foil and electrolytic copper foil, and also includes modified copper foil based on both rolled copper foil and electrolytic copper foil.

[0010] Furthermore, the size of each copper foil is .

[0011] Furthermore, the thickness of a single copper foil is 1 μm-100 μm.

[0012] Furthermore, the vacuum bag is made of one or more combinations of polyethylene, polypropylene, polyester, nylon, aluminum foil and ethylene-vinyl alcohol copolymer.

[0013] Furthermore, the thickness measuring instrument is a two-point thickness measuring instrument or a non-contact thickness measuring instrument.

[0014] Furthermore, a vacuum sealer is used to extract the air in the vacuum bag, and the air in the vacuum bag is extracted to form a negative pressure inside the vacuum bag.

[0015] Beneficial effects of the present invention: The present invention significantly improves the accuracy and reliability of the thickness measurement of ultra-thin lithium battery copper foil by introducing a pre-processing process of sample cutting-neat stacking-vacuum packaging. First, the vacuum packaging technology effectively eliminates the air gaps and local wrinkles between the copper foil stacks, so that the multi-layer copper foil fits tightly, avoiding the nonlinear cumulative error of thickness caused by the looseness between layers in the traditional superposition method, and the calculation deviation of the single-layer thickness can be reduced to less than 1%. Second, this method suppresses the deformation and creases of the ultra-thin copper foil during the measurement process through physical fixation, solves the problem of local depression caused by the pressure of the contact thickness gauge probe, and reduces the stringent requirements of non-contact optical measurement on the flatness of the copper foil, and has stronger compatibility. Third, the pre-processing process simplifies the difficulty of operation, reduces the random errors caused by human intervention, and is suitable for batch detection of ultra-thin copper foils of 4.5 μm and below. Fourth, through high-precision stacking packaging, multi-point measurement and data averaging can be achieved simultaneously, further improving the stability of the results. This solution combines high precision, high efficiency and low cost, providing a standardized solution for quality control under the trend of ultra-thin lithium battery copper foil, and has significant industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: As shown in the figure, a method for measuring the thickness of copper foil for lithium-ion batteries includes the following steps: The vacuum bag is vacuum-sealed, and the thickness of the vacuum bag after vacuum sealing is measured to obtain the original thickness a of the vacuum bag.

[0018] The purpose of vacuum packaging the vacuum bag is to completely flatten the vacuum bag to form a flat surface, so that the original thickness a of the vacuum bag can be measured more accurately to avoid the measurement accuracy being insufficient due to the presence of trace air inside the vacuum bag or unevenness of the vacuum bag.

[0019] Open the vacuum bag again, stack and fix N copper foils to be measured (N≥2), put the stacked copper foils into the vacuum bag, and then extract the air in the vacuum bag to form a negative pressure inside the vacuum bag.

[0020] Among them, the air in the vacuum bag can be extracted through a vacuum sealing machine, that is, the air in the vacuum bag is extracted to form a negative pressure (i.e. vacuum) inside the vacuum bag, so that there is no air between the copper foil layers in the vacuum bag, and then the copper foils are tightly attached together, so that the end faces of each copper foil maintain a high flatness plane, and then the planes are attached to each other, and finally the copper foils are tightly stacked together.

[0021] Use a thickness gauge to measure the thickness b of the vacuum bag containing copper foil, that is, use the thickness gauge to measure the upper and lower ends of the vacuum bag to measure the thickness of the vacuum bag containing copper foil. The thickness b includes the thickness of the laminated copper foil and the thickness of the vacuum bag, that is, the sum of the thicknesses of the two.

[0022] The thickness of a single copper foil is obtained according to the following formula: :

[0023] Thus completing the measurement of copper foil thickness.

[0024] For example, 3≤N≤200. Preferably, it is 10-30. For example, for each measurement, 10 copper foils are stacked together and placed in a vacuum bag, and then the thickness is measured. Alternatively, 30 copper foils are stacked together and placed in a vacuum bag, and then the thickness is measured.

[0025] Exemplarily, each copper foil has the same specifications, including the same material and size, and can be, for example, copper foil from the same batch produced on the same production line. Copper foil includes rolled copper foil and electrolytic copper foil, as well as modified copper foil based on both rolled copper foil and electrolytic copper foil.

[0026] The size of each copper foil is , that is, the length of the copper foil is between 0.2 cm (centimeter) and 50 cm, and the width of the copper foil is between 0.2 cm and 50 cm. Copper foil of this size is easy to put into the vacuum bag and makes it easier for the vacuum bag to form a negative pressure by extracting air. Copper foil that is too large or too small is not conducive to extracting air to form a negative pressure. For example, the size of the copper foil is For example, the length of the copper foil is 5 cm and the width is 1 cm. For another example, the length of the copper foil is 5 cm and the width is also 5 cm, and so on. I will not give examples one by one here.

[0027] Exemplarily, the thickness of a single copper foil is 1 μm-100 μm, for example, 3 μm-30 μm, and specifically, for example, the thickness of the copper foil is 3 μm or 30 μm.

[0028] Exemplarily, the vacuum bag is made of one or more of polyethylene, polypropylene, polyester, nylon, aluminum foil and ethylene-vinyl alcohol copolymer.

[0029] Exemplarily, the thickness measuring instrument is a two-point thickness measuring instrument or a non-contact thickness measuring instrument.

[0030] Example 1 A rolled copper foil with a standard thickness of 6μm, a cutting area of ​​1cm*1cm, and 20 layers; the vacuum bag is made of polyethylene; the thickness is measured by a Labthink C640 thickness gauge.

[0031] Example 2 A rolled copper foil with a standard thickness of 10μm, a cutting area of ​​2cm*2cm, and 10 layers; the vacuum bag is made of polypropylene; the thickness is measured by a Labthink C640 thickness gauge.

[0032] Example 3 A rolled copper foil with a standard thickness of 4.5μm, a cutting area of ​​2cm*2cm, and 16 layers (i.e., 16 copper foils stacked together); the vacuum bag is made of polypropylene; the thickness is measured by a Labthink C640 thickness gauge.

[0033] Example 4 The sample is an electrolytic copper foil with a standard thickness of 10μm, a cutting area of ​​1.5cm*1.5cm, and 20 layers. The vacuum bag is made of polyethylene. The thickness is measured using a Labthink C640 thickness gauge.

[0034] Example 5 An electrolytic copper foil with a standard thickness of 20μm, a cutting area of ​​5cm*5cm, and 25 layers; the vacuum bag material is an aluminum foil composite film; the thickness measurement instrument is a vernier caliper thickness gauge.

[0035] Example 6 An electrolytic copper foil with a standard thickness of 6μm, a cutting area of ​​3cm*3cm, and 10 layers; the vacuum bag is made of polypropylene; the thickness is measured by a high-precision micrometer.

[0036] Example 7 An electrolytic copper foil with a standard thickness of 4.5μm, a cutting area of ​​4cm*4cm, and 60 layers; the vacuum bag is made of polypropylene; the thickness is measured by a high-precision micrometer.

[0037] Example 8 An electrolytic copper foil with a standard thickness of 15μm, a cutting area of ​​10cm*10cm, and 40 layers; the vacuum bag material is an aluminum foil composite film; the thickness measurement instrument is a high-precision micrometer.

[0038] Comparative Example 1 A rolled copper foil with a standard thickness of 4.5μm, a cutting area of ​​2cm*2cm, and 10 layers; the thickness is measured by a high-precision micrometer.

[0039] Comparative Example 2 A rolled copper foil with a standard thickness of 12μm, a cutting area of ​​3cm*3cm, and 15 layers; the thickness is measured by a Labthink C640 thickness gauge.

[0040] Comparative Example 3 An electrolytic copper foil with a standard thickness of 6μm, a cutting area of ​​3cm*3cm, and 20 layers; the thickness is measured by a high-precision micrometer.

[0041] The measured thicknesses of the copper foils for lithium ion battery negative electrode current collectors provided in Examples 1-8 and Comparative Examples 1-3 were compared, and the results are shown in Table 1.

[0042]

[0043] Table 1 Thickness data of copper foil for negative electrode current collector of lithium ion battery By comparing the data of the above 8 embodiments and 3 comparative examples, it can be seen that the non-destructive stacking fixed measurement method of the present invention can significantly improve the thickness measurement accuracy of the copper foil for the negative electrode current collector of the lithium ion battery.

[0044] The embodiment disclosed in this specification is merely an illustration of one aspect of the present invention. The scope of protection of the present invention is not limited to this embodiment. Any other functionally equivalent embodiments fall within the scope of protection of the present invention. Those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the scope of protection of the claims of the present invention.

Claims

1. A method for measuring the thickness of copper foil for lithium-ion batteries, characterized in that: The following steps are involved: The vacuum bag is vacuum sealed, and the thickness of the vacuum bag after vacuum sealing is measured to obtain the original thickness a of the vacuum bag. Open the vacuum bag again, stack and fix N copper foils to be measured (N≥2), put the stacked copper foils into the vacuum bag, and then extract the air in the vacuum bag to form a negative pressure inside the vacuum bag. Use a thickness gauge to measure the thickness b of the vacuum bag containing copper foil, and use the following formula to get the thickness of a single copper foil: : Thus completing the measurement of copper foil thickness.

2. The method for measuring the thickness of copper foil for lithium ion batteries according to claim 1, wherein: 3≤N≤200。 3. The method for measuring the thickness of copper foil for lithium ion batteries according to claim 1, wherein: The specifications of each copper foil are the same, including the material and size.

4. The method for measuring the thickness of copper foil for lithium ion batteries according to any one of claims 1 to 3, characterized in that: The copper foil includes rolled copper foil and electrolytic copper foil, and also includes modified copper foil based on both rolled copper foil and electrolytic copper foil.

5. The method for measuring the thickness of copper foil for lithium ion batteries according to any one of claims 1 to 3, characterized in that: The size of each copper foil is .

6. The method for measuring the thickness of copper foil for lithium ion batteries according to any one of claims 1 to 3, characterized in that: The thickness of a single copper foil is 1 μm-100 μm.

7. The method for measuring the thickness of copper foil for lithium ion batteries according to any one of claims 1 to 3, characterized in that: The vacuum bag is made of one or more of polyethylene, polypropylene, polyester, nylon, aluminum foil and ethylene-vinyl alcohol copolymer.

8. The method for measuring the thickness of copper foil for lithium ion batteries according to any one of claims 1 to 3, characterized in that: The thickness measuring instrument is a two-point thickness measuring instrument or a non-contact thickness measuring instrument.

9. The method for measuring the thickness of copper foil for lithium ion batteries according to any one of claims 1 to 3, characterized in that: A vacuum sealer is used to extract the air from the vacuum bag, and the air in the vacuum bag is extracted to form a negative pressure inside the vacuum bag.

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