Method for detecting metal elements of current collector of lithium ion battery

Abstract

The invention relates to the technical field of lithium battery current collector detection, in particular to detection of metal elements of a lithium ion battery current collector. The detection method comprises the following steps: mixing a prepared lithium ion battery current collector sample with a digestion reagent, then carrying out microwave digestion by adopting a gradient heating mode to obtain a digestion solution, and determining the element content by adopting an inductively coupled plasma device, the dosage ratio of the lithium ion battery current collector sample to the digestion reagent is (0.1-0.5) g: (5-8) mL, and the digestion reagent is selected from one or more of hydrochloric acid, nitric acid and hydrogen peroxide. According to the method, the pretreatment period is shortened, pollution is reduced through batch sealing treatment, meanwhile, the aluminum foil and the copper foil are well digested through microwave assistance, the proportion of the content of all metal elements in the product can be accurately obtained through optimization of the detection method, and quality control over raw materials is better completed.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery current collector detection, and particularly to the detection of metal elements in the current collector of lithium-ion batteries. Background Art

[0002] In recent years, new energy vehicles have become the main trend in the future development of the automotive market. As the core component of new energy vehicles, the market demand for lithium batteries will inevitably increase rapidly. With the development of lithium batteries, battery aluminum foil, as the positive current collector material for the current mainstream lithium battery technology, will be widely used, thus triggering a sharp increase in market demand. The current collector, one of the core components of lithium batteries, refers to the structural part that collects current. Its main function is to collect the current generated by the battery active material to form a larger current for external output, and it needs to be in full contact with the active material. It has performance requirements such as high conductivity, strong corrosion resistance, good toughness, certain stiffness, and easy processing and forming. The chemical and physical properties of aluminum foil and copper foil just meet the above requirements. Therefore, the lithium battery industry usually uses aluminum foil as the positive current collector and copper foil as the negative current collector. The metal element content of aluminum foil and copper foil has a significant impact on their microstructure and mechanical properties, and thus affects the performance of lithium-ion batteries, such as aspects such as the alternating current internal resistance (ACR), direct current resistance (DCR), rate charge and discharge, cycle performance, and rate cycle performance of the battery.

[0003] At present, there is no detection method for the metal elements of copper foil and aluminum foil in lithium-ion batteries. The existing technologies mainly focus on aluminum alloy and copper alloy products, and the metal elements are tested by wet acid digestion. On the one hand, the steps are relatively cumbersome, time-consuming, and easy to introduce impurity pollution; on the other hand, the PET film of the aluminum foil and copper foil used in the battery current collector cannot be processed, and the contents of the main elements aluminum and copper cannot be obtained, and there are deviations in the remaining trace elements, lacking corresponding means for the quality control of raw materials. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a detection method for the metal elements in the current collector of lithium-ion batteries, which detects the metal elements of the aluminum foil and copper foil used in the current collector of lithium-ion batteries. The method of the present invention shortens the pretreatment cycle, and the batch closed treatment reduces pollution. At the same time, good digestion of aluminum foil and copper foil is completed through microwave assistance. Through the optimization of the detection method, the proportion of the content of each metal element in the product can be accurately obtained, and better quality control of raw materials can be completed.

[0005] In a first aspect, the present invention provides a method for detecting metal elements in a current collector of a lithium-ion battery, comprising: mixing a sampled current collector sample of the lithium-ion battery with a digestion reagent, and then performing microwave digestion in a gradient heating manner to obtain a digestion solution, and measuring the element content by means of an inductively coupled plasma device; the dosage ratio of the current collector sample of the lithium-ion battery to the digestion reagent is 0.1-0.5 g: 5-8 mL, and the digestion reagent is selected from one or more of hydrochloric acid, nitric acid and hydrogen peroxide. In view of the blank in the test method for metal elements in the positive and negative current collectors (aluminum foil and copper foil) used in lithium-ion batteries, and in combination with the principle of microwave digestion, by optimizing various influencing factors such as sample dosage, digestion acids, and digestion procedures, the best test scheme is obtained, achieving precise control of product quality and filling the industry gap.

[0006] Preferably, the heating program of the microwave digestion includes: heating at a rate of 2-20 °C / min to 100-150 °C, maintaining for 2-10 min, and then heating at a rate of 1-15 °C / min to 155-200 °C for 10-60 min. By optimizing the heating program of the microwave digestion, the digestion efficiency and element solubility are improved, ensuring the sufficiency and stability of sample digestion, thereby improving the detection accuracy.

[0007] More preferably, heating at a rate of 5-15 °C / min to 110-130 °C, maintaining for 3-8 min, and then heating at a rate of 3-9 °C / min to 170-190 °C for 20-40 min, and then cooling down. By further optimizing and controlling the heating rate and temperature range, the digestion process becomes more efficient and gentle, which helps to further reduce sample loss and element volatilization and improve the recovery rate of metal elements.

[0008] More preferably, heating at a rate of 10±2 °C / min to 120±5 °C, maintaining for 5±2 min, and then heating at a rate of 6±2 °C / min to 180±5 °C for 30±5 min, and naturally cooling down.

[0009] Preferably, the current collector sample of the lithium-ion battery is aluminum foil or copper foil.

[0010] Preferably, the hydrochloric acid is a reagent of guaranteed reagent grade, with a concentration of 35%-40%, such as 36%, 37%, 38%, etc., and the nitric acid is a reagent of guaranteed reagent grade, with a concentration of 60%-68%, such as 64%, 65%, 66%, etc. At the preferred concentrations of hydrochloric acid and nitric acid, the effective digestion of the current collector sample and the element dissolution rate can be further ensured.

[0011] Preferably, when the lithium-ion battery current collector sample is aluminum foil, the digestion reagent is hydrochloric acid and hydrogen peroxide; preferably, the ratio of the lithium-ion battery current collector sample, hydrochloric acid, and hydrogen peroxide is 0.1 - 0.5 g : 5 - 6 mL : 1 - 2 mL. By optimizing the digestion conditions and reagent ratio of the aluminum foil sample, the digestion efficiency and detection accuracy of metal elements in the aluminum foil are further improved.

[0012] Preferably, when the lithium-ion battery current collector sample is copper foil, the digestion reagent is nitric acid; preferably, the ratio of the lithium-ion battery current collector sample to nitric acid is 0.1 - 0.5 g : 5 - 6 mL. By optimizing the digestion conditions of the copper foil, the full digestion of the copper foil sample is ensured, interference that may be caused during the reaction is avoided, and the accuracy of the detection results is guaranteed.

[0013] Preferably, the sample preparation includes: processing the lithium-ion battery current collector sample into lithium-ion battery current collector debris with a particle size ≤ 1 mm. Preferably, 0.1 - 0.5 g of the lithium-ion battery current collector debris is mixed with the digestion reagent. By optimizing the sample particle size and dosage, it helps with subsequent processing, ensures full reaction during digestion, and reduces the error in sample processing and determination.

[0014] Further preferably, the method for detecting metal elements in the lithium-ion battery current collector further includes the steps of acid expulsion and volume fixation of the digestion solution after microwave digestion.

[0015] Preferably, the digestion solution is subjected to acid expulsion treatment in an acid expulsion device at a temperature of 155 - 165 °C, and after cooling, it is fixed to 45 - 55 mL with pure water. Acid expulsion and volume fixation under the preferred conditions help to further improve the stability and accuracy of the digestion solution, avoid problems such as excessive acid content or uneven concentration generated during the reaction, and provide a more reliable sample for elemental analysis.

[0016] Preferably, the inductively coupled plasma device is an inductively coupled plasma optical emission spectrometer and / or an inductively coupled plasma mass spectrometer.

[0017] Further preferably, the method for detecting metal elements in the lithium-ion battery current collector includes: 1) Processing the lithium-ion battery current collector into lithium-ion battery current collector debris with a particle size ≤ 1 mm.

[0018] 2) Putting 0.1 - 0.5 g of the lithium-ion battery current collector debris into a digestion tank. When the lithium-ion battery current collector debris is copper foil, add 5 - 6 mL of nitric acid; when the lithium-ion battery current collector debris is aluminum foil, add 5 - 6 mL of hydrochloric acid, and then add 1 - 2 mL of hydrogen peroxide after the violent reaction.

[0019] 3) Place the digestion tank into a microwave digester and digest it according to the following procedure: Heat it up to 120 ± 5 °C at a rate of 10 ± 2 °C / min, keep it for 5 ± 2 min, then heat it up to 180 ± 5 °C at a rate of 6 ± 2 °C / min and keep it for 30 ± 5 min, and then let it cool naturally.

[0020] 4) Place the digestion tank into an acid evaporation instrument, evaporate the acid at a temperature of 160 ± 2 °C, and after cooling, dilute it to a volume of 45 - 55 mL with pure water to obtain the digestion solution to be measured.

[0021] 5) Measure the element content in the digestion solution by using an inductively coupled plasma optical emission spectrometer (ICP-OES) or an inductively coupled plasma mass spectrometer (ICP-MS) for the digestion solution to be measured.

[0022] A detection method for metal elements of a current collector of a lithium-ion battery provided by the present invention creates a new test method for metal elements in positive and negative current collectors (aluminum foil / copper foil) for lithium-ion batteries, optimizes aspects such as sample treatment and dosage, type of acid, digestion procedure, etc., comprehensively obtains the best test effect, fills the research gap in this field, the process is relatively closed, greatly reduces the possible introduction of impurity pollution, and can be used for the treatment of a large number of samples at the same time, meeting the needs of enterprise production quality control and helping the further development and growth of the new energy field. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a schematic diagram of the detection method provided by the embodiment of the present invention. Detailed Embodiments

[0025] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0026] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0027] If no specific technology or conditions are specified in the examples of the present invention, the technology or conditions described in the literature in the field or the product instructions are used. If the manufacturer of the devices, instruments, reagents, etc. is not specified, they are all conventional products that can be purchased through regular channels. The experimental reagents and raw materials involved are all commercially available, and the reagents are all analytically pure products.

[0028] In the following examples, the main experimental equipment involved: inductively coupled plasma emission spectrometer (Optima8300), inductively coupled plasma mass spectrometer (NexiON 300X), Anton Paar microwave digestion instrument (MWPRO). The hydrochloric acid is a high-grade pure reagent with a concentration of 37%, and the nitric acid is a high-grade pure reagent with a concentration of 65%.

[0029] Example 1 This embodiment provides a method for detecting metal elements in a lithium ion battery current collector. Figure 1 The specific steps are as follows: Step 1: Use ceramic scissors to cut the aluminum foil samples (samples 1-5) to obtain aluminum foil fragments with a diameter not greater than 1 mm.

[0030] Step 2: Weigh a certain amount of aluminum foil scraps (depending on the element content, the sample weight is 0.1g, 0.3g, 0.4g, 0.5g respectively), put them into a polytetrafluoroethylene digestion tank, add 6mL of hydrochloric acid first, and then add 1mL of hydrogen peroxide after the violent reaction is over.

[0031] Step 3: Place the digestion tank into the microwave digestion instrument and perform digestion according to the following procedure: heat to 120°C at a rate of 10°C / min, continue for 5 min, then heat to 180°C at a rate of 6°C / min, continue for 30 min, and then naturally cool to room temperature.

[0032] Step 4: Take out the digestion tank and put it into the acid removal instrument to remove excess acid at 160°C. After cooling, pour it into a 50mL plastic beaker and dilute it with pure water to obtain a pure digestion solution.

[0033] Step 5. Pass the obtained digestion solution through an inductively coupled plasma optical emission spectrometer (ICP-OES) - inductively coupled plasma mass spectrometer to obtain the accurate content of each element. The results for different sample weights are shown in Table 1. When the sample weight is 0.1 g, the detected amounts of heavy metals are the highest.

[0034] Table 1

[0035] Example 2 This example provides a method for detecting metal elements in a current collector of a lithium-ion battery. The specific steps are as follows: Step 1. Use ceramic scissors to cut the copper foil sample to obtain copper foil debris with a diameter not greater than 1 mm.

[0036] Step 2. Weigh a certain mass of the debris (determined according to the element content, usually 0.1 - 0.5 g), put it into a polytetrafluoroethylene digestion tank, and add 6 mL of nitric acid.

[0037] Step 3. Place the digestion tank into a microwave digestion instrument and digest it according to the following procedure: heat it to 120 °C at a rate of 10 °C / min, hold for 5 min, then heat it to 180 °C at a rate of 6 °C / min and hold for 30 min, and then naturally cool to room temperature.

[0038] Step 4. After taking out the digestion tank, place it into an acid-removing instrument to remove the excess acid at a temperature of 160 °C. After cooling, pour it into a 50 mL plastic beaker and make up the volume with pure water to obtain a pure digestion solution.

[0039] Step 5. Pass the obtained digestion solution through an inductively coupled plasma optical emission spectrometer (ICP-OES) / inductively coupled plasma mass spectrometer to obtain the accurate content of each element.

[0040] Comparative Example 1 This comparative example uses the treatment method for aluminum alloy in Standard GB / T 20975.25 - 2008 to treat the same sample (sample weight 0.1 g) in Example 1. The comparison results are shown in Table 2.

[0041] Table 2 Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features. However, such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the present invention in each example.

Claims

1. A method for detecting metal elements in a current collector of a lithium-ion battery, characterized in that, Comprising: Mix the prepared lithium-ion battery current collector sample with a digestion reagent, then perform microwave digestion in a gradient heating manner to obtain a digestion solution, and use an inductively coupled plasma device to determine the element content; the dosage ratio of the lithium-ion battery current collector sample to the digestion reagent is 0.1 - 0.5 g : 5 - 8 mL, and the digestion reagent is selected from one or more of hydrochloric acid, nitric acid, and hydrogen peroxide.

2. The detection method of the metal element of the current collector of the lithium ion battery according to claim 1, characterized in that, The heating program of the microwave digestion includes: heating at a rate of 2 - 20 °C / min to 100 - 150 °C, maintaining for 2 - 10 min, and then heating at a rate of 1 - 15 °C / min to 155 - 200 °C for 10 - 60 min.

3. The detection method of the metal element of the current collector of the lithium ion battery according to claim 2, characterized in that, Heat at a rate of 5 - 15 °C / min to 110 - 130 °C, maintain for 3 - 8 min, then heat at a rate of 3 - 9 °C / min to 170 - 190 °C for 20 - 40 min, and then cool down.

4. The detection method of the metal element of the current collector of the lithium ion battery according to any one of claims 1-3, characterized in that, The lithium-ion battery current collector sample is aluminum foil or copper foil.

5. The detection method of the metal element of the current collector of a lithium-ion battery according to any one of claims 1-4, characterized in that, When the lithium-ion battery current collector sample is aluminum foil, the digestion reagent is hydrochloric acid and hydrogen peroxide; preferably, the ratio of the lithium-ion battery current collector sample, hydrochloric acid, and hydrogen peroxide is 0.1 - 0.5 g : 5 - 6 mL : 1 - 2 mL.

6. The detection method of the metal element of the current collector of the lithium-ion battery according to any one of claims 1-4, characterized in that, When the lithium-ion battery current collector sample is copper foil, the digestion reagent includes nitric acid; preferably, the ratio of the lithium-ion battery current collector sample to nitric acid is 0.1 - 0.5 g : 5 - 6 mL.

7. The detection method of the metal element of the current collector of the lithium ion battery according to any one of claims 1-6, characterized in that, The sample preparation includes: processing the lithium-ion battery current collector sample into lithium-ion battery current collector debris with a particle size ≤ 1 mm; preferably mixing 0.1 - 0.5 g of the lithium-ion battery current collector debris with the digestion reagent.

8. The detection method of the metal element of the current collector of the lithium-ion battery according to any one of claims 1-7, characterized in that, It also includes the steps of acid expulsion and volume fixation of the digestion solution after microwave digestion; preferably, the digestion solution is subjected to acid expulsion treatment in an acid expulsion device at a temperature of 155 - 165 °C, and after cooling, it is fixed to 45 - 55 mL with pure water.

9. The detection method of the metal element of the current collector of the lithium-ion battery according to any one of claims 1-8, characterized in that, The inductively coupled plasma device is an inductively coupled plasma emission spectrometer and / or an inductively coupled plasma mass spectrometer.

10. The detection method of the metal element of the current collector of a lithium-ion battery according to any one of claims 1-9, characterized in that, Comprising: 1) Process the lithium-ion battery current collector sample into lithium-ion battery current collector debris with a particle size ≤ 1 mm; 2) Put 0.1 - 0.5 g of the lithium-ion battery current collector debris into a digestion tank, add 5 - 6 mL of nitric acid, or add 5 - 6 mL of hydrochloric acid, and then add 1 - 2 mL of hydrogen peroxide after the violent reaction; 3) Put the digestion tank into a microwave digester and digest according to the following program: heat at a rate of 10 ± 2 °C / min to 120 ± 5 °C, maintain for 5 ± 2 min, and then heat at a rate of 6 ± 2 °C / min to 180 ± 5 °C for 30 ± 5 min, and cool naturally; 4) Put the digestion tank into an acid expulsion instrument, perform acid expulsion at a temperature of 160 ± 2 °C, and after cooling, fix it to 45 - 55 mL with pure water to obtain the digestion solution to be measured; 5) Determine the element content in the digestion solution by passing the digestion solution to be measured through an inductively coupled plasma emission spectrometer or an inductively coupled plasma mass spectrometer.

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