Terahertz thickness measuring method and device based on multiple coatings of lithium ion electrode

Abstract

The invention discloses a terahertz thickness measuring method and device based on a lithium ion electrode multi-coating, and relates to the technical field of terahertz, the thickness measuring device comprises a transmitting probe, a receiving probe and an arc-shaped slide rail, and the transmitting probe and the receiving probe are arranged on the arc-shaped slide rail. According to the terahertz thickness measuring method and device based on the multiple coatings of the lithium ion electrode, a reflective terahertz time-domain spectrum detection system is utilized, the junction of a sample to be measured is measured at the same time, and echo signals generated when terahertz waves penetrate through air, penetrate through a detected coating and are reflected by the surface of the coating are measured at the same time; the refractive index of the lithium ion electrode coating and the refractive index of the material can be calculated as a reference signal of the terahertz time-domain spectroscopy, the material thickness and the refractive index can be measured at the same time without knowing the refractive index of the material and establishing a complex thickness measurement algorithm, and the detection method is simple and easy to implement. Measurement errors caused by position inconsistency when echo signals are extracted through multiple times of measurement are avoided.

Description

Technical Field

[0001] The present invention relates to the field of terahertz technology, and in particular to a terahertz thickness measurement method and device based on lithium ion electrode multi-coating. Background Art

[0002] Lithium-ion batteries have been widely used in portable battery products due to their high energy density, high operating voltage, long cycle life, environmental protection and safety. Coating is the process of evenly coating the positive and negative electrode slurries (composed of active particles, binders, conductive agents and solvents) on aluminum or copper foil current collectors. The uniformity and integrity of the coating are the key to ensuring the performance of the coating. Therefore, quantitative testing of key parameters such as thickness is required during the preparation, use and maintenance of the coating.

[0003] At present, there are mainly "comparison plate" method and eddy current method in the detection of multi-coating of lithium-ion electrodes. Among them, the "comparison plate" method estimates the lithium-ion electrode coating by making a standard substrate, calculating the spraying time and spraying amount, and the accuracy cannot be guaranteed; the eddy current method can only detect metal materials or non-metallic materials on metal substrates, and can only detect a single layer, which cannot meet the requirements for multi-layer coating detection on the surface of non-metallic substrates. Terahertz (THz) is a new technology used for lithium-ion electrode coating detection in the new energy industry.

[0004] Currently, the time-of-flight method is mostly used to detect lithium-ion electrode coatings using terahertz. It is necessary to predict the refractive index of the material in advance, and then calculate the thickness information based on the time difference between the reflected echoes of different interfaces. It is impossible to measure multiple coatings of lithium-ion electrodes with unknown refractive index. Summary of the invention

[0005] The present invention provides a terahertz thickness measurement method and device based on lithium ion electrode multi-coating to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A terahertz thickness measurement method and device based on lithium ion electrode multi-coating, the thickness measurement device comprises: a transmitting probe, a receiving probe and an arc-shaped slide rail, the transmitting probe and the receiving probe are arranged on the arc-shaped slide rail, and slide along the arc-shaped slide rail to adjust the transmitting angle and the receiving angle.

[0008] Preferably, the transmitting probe and the receiving probe are synchronously adjusted on both sides of the symmetry axis of the arc-shaped slide rail.

[0009] Preferably, a test platform is included, the arc-shaped slide rail is placed perpendicular to the test platform, and the sample to be measured is placed horizontally on the test platform.

[0010] A terahertz thickness measurement method based on lithium ion electrode multi-coating is implemented based on a terahertz thickness measurement device based on lithium ion electrode multi-coating, and the thickness measurement method includes:

[0011] Obtain a first duration, which is the time required for the transmitting probe to transmit the first terahertz wave at a preset angle θ to the first measuring point of the sample to be measured, and for the receiving probe to receive the first echo. down0 ; The first measuring point is located on the surface of the i-th coating layer on the sample to be measured; the first echo is a reflected echo of the first terahertz wave at the first measuring point;

[0012] The second time length and the third time length are obtained, wherein the second time length is the time length T required for the transmitting probe to transmit the second terahertz wave to the second measuring point of the sample to be measured at the preset angle θ and for the receiving probe to receive the second echo. up1 The third duration is the time required for the receiving probe to receive the third echo T' down0 ; The second measuring point is located on the surface of the i+1th coating layer on the sample to be measured, and the i+1th coating layer covers the i-th coating layer; the second echo is the reflected echo of the second terahertz wave at the second measuring point; the third echo is the reflected echo of the second terahertz wave on the surface of the i-th coating layer.

[0013] Preferably, according to the first time difference ΔT i1 and the second time difference ΔT r1 , using formula 1, obtain the thickness d of the i+1th layer of coating on the sample to be measured i .

[0014] Preferably, wherein n 0 is the refractive index of air, c is the speed of light, sin(θ) represents the sine value of the preset angle θ, ΔT i1 =T′ down0 -T up1 ; The value of i is a non-negative integer. When i is 0, the i-th coating surface is the uncoated surface of the sample to be measured.

[0015] Preferably, after obtaining the thickness di of the i+1th layer of coating on the sample to be measured, the method further comprises:

[0016] The refractive index acquisition module is configured to obtain the thickness d of the i+1th coating layer according to the thickness d of the i+1th coating layer. i , using formula 2, obtain the refractive index n of the i+1th layer of coating i+1 .

[0017] Due to the adoption of the above technical solution, the present invention has the following technical advances compared with the prior art:

[0018] 1. The present invention provides a terahertz thickness measurement method and device based on lithium ion electrode multi-coating, which improves the traditional fixed-angle detection probe and can freely change the angle of the transmitting end and the receiving end to realize variable-angle measurement of the terahertz system.

[0019] 2. The present invention provides a terahertz thickness measurement method and device based on lithium ion electrode multi-coating, which uses a reflective terahertz time-domain spectroscopy detection system to simultaneously measure the interface of the sample to be measured, and simultaneously measures the echo signal of the terahertz wave passing through the air, the coating to be detected and the coating surface reflected. The refractive index of the lithium ion electrode coating and the material can be calculated as a reference signal of the terahertz time-domain spectrum. There is no need to know the refractive index of the material, and there is no need to establish a complex thickness measurement algorithm. The material thickness and refractive index can be measured simultaneously. The detection method is simple, and the measurement error caused by the position inconsistency when extracting the echo signal during multiple measurements is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the process of the present invention;

[0021] Figure 2 It is a structural schematic diagram of the reflective terahertz time-domain spectroscopy detection system of the present invention;

[0022] Figure 3 A schematic diagram of the interaction between the terahertz wave and the coating substrate of the present invention;

[0023] Figure 4 This is a timing diagram of the echo of the terahertz wave of the present invention;

[0024] Figure 5 is a schematic diagram of Formula 1 of the present invention;

[0025] Figure 6 It is a schematic diagram of Formula 2 of the present invention;

[0026] Figure 7 It is a schematic diagram of Formula 3 of the present invention;

[0027] Figure 8 It is a schematic diagram of Formula 4 of the present invention;

[0028] Fig. 9 It is a schematic diagram of Formula 5 of the present invention.

[0029] In the figure: 1. Transmitting probe; 2. Receiving probe; 3. Arc slide rail; 4. Sample to be measured. DETAILED DESCRIPTION

[0030] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0031] like Figure 2 As shown, a terahertz thickness measuring device based on lithium ion electrode multi-coating includes: a transmitting probe 1, a receiving probe 2 and an arc-shaped slide rail 3. The transmitting probe 1 and the receiving probe 2 are arranged on the arc-shaped slide rail 3 and slide along the arc-shaped slide rail 3 to adjust the transmitting angle and the receiving angle.

[0032] The transmitting probe 1 and the receiving probe 2 are synchronously adjusted on both sides of the symmetry axis of the arc-shaped slide rail 3 .

[0033] The test platform comprises an arc-shaped slide rail 3 which is vertically placed on the test platform, and a sample 4 to be measured is horizontally placed on the test platform.

[0034] like Figure 1-Figure 9 As shown, a terahertz thickness measurement method based on lithium ion electrode multi-coating is implemented based on a terahertz thickness measurement device based on lithium ion electrode multi-coating, and the thickness measurement method includes:

[0035] Obtain a first duration, which is the time required for the transmitting probe 1 to transmit the first terahertz wave at a preset angle θ to the first measuring point of the sample 4 to be measured, and for the receiving probe 2 to receive the first echo. down0 ; The first measuring point is located on the surface of the i-th coating layer on the sample 4 to be measured; the first echo is the reflected echo of the first terahertz wave at the first measuring point;

[0036] The second time length and the third time length are obtained. The second time length is the time length T required for the transmitting probe 1 to transmit the second terahertz wave to the second measuring point of the sample 4 to be measured at a preset angle θ, and for the receiving probe 2 to receive the second echo. up1 The third time length is the time length T' required for the receiving probe 2 to receive the third echo down0 ; The second measuring point is located on the surface of the i+1th coating layer on the sample 4 to be measured, and the i+1th coating layer covers the i-th coating layer; the second echo is the reflected echo of the second terahertz wave at the second measuring point; the third echo is the reflected echo of the second terahertz wave on the surface of the i-th coating layer.

[0037] According to the first time difference ΔT i1 and the second time difference ΔT r1 , using formula 1, obtain the thickness d of the i+1th layer of coating on the sample 4 to be measured i .

[0038] Among them, n 0 is the refractive index of air, c is the speed of light, sin(θ) represents the sine value of the preset angle θ, ΔT i1 =T′ down0 -T up1 ; The value of i is a non-negative integer. When i is 0, the surface of the i-th coating layer is the uncoated surface of the sample (4) to be measured.

[0039] After obtaining the thickness di of the i+1th coating layer on the sample 4 to be measured, the method further includes:

[0040] The refractive index acquisition module is based on the thickness d of the i+1th layer of coating. i , use formula 2 to obtain the refractive index n of the i+1th layer of coating i+1。

[0041] The terahertz pulse will reflect echoes on the front and back surfaces of the coating. By measuring the time difference of the echoes, the thickness information of the sample to be measured can be obtained; E initial is the original incident terahertz signal, and the incident angle is θ i , E down0 is the reflection signal of the metal substrate surface of the terahertz sample to be measured (i.e., the uncoated substrate, the 0th coating layer), and the corresponding first duration is recorded as T down0 ; E up1 The terahertz wave is the first layer of coating (i.e. Figure 3 Middle coating 1. Figure 4 The echo signal on the surface of the single-layer coating) is recorded as T up1 , E′ down0 is the echo signal of the terahertz wave on the substrate surface at the first coating layer (i.e., the bottom of the first coating layer), and the corresponding third duration is recorded as T′ down0。

[0042] The thickness model is derived based on the terahertz electromagnetic transmission characteristics.

[0043] Among them, d 1 is the first lithium-ion electrode coating, n 1 is the refractive index of the first coating layer, n 0 is the refractive index of air, sinθ i is the incident angle of the THz measurement coating, ΔT r1 Uncoated sample substrate echo T down0 The time difference T′ between the echo of the substrate of the sample to be measured and the coating down0 , ΔT i1 is the coating surface echo T of the sample to be measured containing coating up1 and base echo T′ down0 Through formulas 3 and 4, a set of equations based on the refractive index of the lithium ion electrode coating and the coating material is established, and the time difference ΔT is measured. r1 and ΔT i1 , the first layer of lithium ion electrode coating d is calculated using formula 4 1 , and then d 1 Substituting into formula 3, we can get the refractive index n of the first coating layer. 1 .

[0044] By way of example, the value of i is increased by 1, i=1, and the thickness measurement method is further described by taking the measurement of the thickness of the second coating layer of the sample to be measured as an example.

[0045] The thickness measurement method of the second coating is the same as that of the first coating. Here, the surface echo signal E of the first coating on the sample to be measured is extracted. up1 The echo signal E′ on the first coating surface of the second coating layer of the sample to be measured up1 The time difference (T′ up1 -T up1 ), and the echo signal E′ on the first coating layer of the second coating layer of the sample to be measured up1 The second coating surface (i.e. Figure 3 Middle coating 2, Figure 4 The time difference of the echo signal Eup2 (T′up1-Tup2) of the double-layer coating. E″ down0 is the echo signal of the terahertz wave on the substrate surface at the second coating layer, and the corresponding third duration is recorded as T″ down0 The thickness model is derived based on the terahertz electromagnetic transmission theory.

[0046] Among them, d 2 is the second lithium ion electrode coating, n 2 is the refractive index of the second coating layer, n 0 is the refractive index of air, sinθ i Incident angle of the coating for THz measurements.

[0047] The provided terahertz-based lithium-ion electrode coating detection method can realize the measurement of multi-layer lithium-ion electrode coating and refractive index.

[0048] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A terahertz thickness measurement device based on lithium ion electrode multi-coating, characterized in that: The thickness measuring device comprises: a transmitting probe (1), a receiving probe (2) and an arc-shaped slide rail (3); the transmitting probe (1) and the receiving probe (2) are arranged on the arc-shaped slide rail (3) and slide along the arc-shaped slide rail (3) to adjust a transmitting angle and a receiving angle.

2. A terahertz thickness measurement device based on lithium ion electrode multi-coating according to claim 1, characterized in that: The transmitting probe (1) and the receiving probe (2) are synchronously adjusted on both sides of the symmetry axis of the arc-shaped slide rail (3).

3. A terahertz thickness measurement device based on lithium ion electrode multi-coating according to claim 2, characterized in that: It comprises a test platform, the arc-shaped slide rail (3) is placed vertically on the test platform, and the sample (4) to be measured is placed horizontally on the test platform.

4. A terahertz thickness measurement method based on lithium ion electrode multi-coating, implemented based on a terahertz thickness measurement device based on lithium ion electrode multi-coating according to claims 1-3, characterized in that: The thickness measurement method includes: A first time length is obtained, where the first time length is the time length T required for the receiving probe (2) to receive the first echo when the transmitting probe (1) transmits the first terahertz wave at a preset angle θ to the first measuring point of the sample (4) to be measured. down0 ; The first measuring point is located on the surface of the i-th coating layer on the sample to be measured (4); the first echo is a reflection echo of the first terahertz wave at the first measuring point; A second time length and a third time length are obtained, wherein the second time length is the time length T required for the transmitting probe (1) to transmit a second terahertz wave at the preset angle θ to the second measuring point of the sample to be measured (4), and for the receiving probe (2) to receive the second echo. up1 The third time length is the time length T′ required for the receiving probe (2) to receive the third echo down0 ; The second measuring point is located on the surface of the i+1th coating layer on the sample to be measured (4), and the i+1th coating layer covers the i-th coating layer; the second echo is the reflected echo of the second terahertz wave at the second measuring point; the third echo is the reflected echo of the second terahertz wave on the surface of the i-th coating layer.

5. The terahertz thickness measurement method based on lithium ion electrode multi-coating according to claim 4, characterized in that: According to the first time difference ΔT i1 and the second time difference ΔT r1 , using formula 1, obtain the thickness d of the i+1th layer of coating on the sample to be measured (4): i .

6. The terahertz thickness measurement method based on lithium ion electrode multi-coating according to claim 5, characterized in that: in, n0 is the refractive index of air, c is the speed of light, sin(θ) represents the sine value of the preset angle θ, ΔT i1 =T′ down0 -T up1 ; The value of i is a non-negative integer. When i is 0, the i-th coating surface is the uncoated surface of the sample (4) to be measured.

7. The terahertz thickness measurement method based on lithium ion electrode multi-coating according to claim 6, characterized in that: After obtaining the thickness di of the i+1th layer of coating on the sample to be measured (4), the method further comprises: The refractive index acquisition module is configured to obtain the thickness d of the i+1th coating layer according to the thickness d of the i+1th coating layer. i , using formula 2, obtain the refractive index n of the i+1th layer of coating i+1 .

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