A method for evaluating the stability of battery slurry

Abstract

This invention provides a method for testing the stability of battery slurry. The method uses ICP-OES and TG-MS to quantitatively analyze the material composition of the battery slurry. The stability of the slurry is evaluated by the percentage change in the mass of the slurry material at a set height after the slurry has been left to stand. The method has high accuracy and can clearly identify which materials play a significant role in the stability of the slurry. The stability of the slurry system can be improved by adjusting the physicochemical properties of the materials.

Description

Technical Field

[0001] This invention belongs to the field of battery slurry technology, specifically relating to a method for evaluating the stability of battery slurry. Background Technology

[0002] Battery slurry is a suspension system composed of different substances, each with different sedimentation rates. The interactions between different particles are complex, making stability monitoring extremely difficult. Even with uniform mixing, slurry stratification will occur after a certain period due to sedimentation. Furthermore, particle aggregation can occur, leading to uneven distribution of different substances throughout the system and poor dispersion.

[0003] If the slurry has poor stability, stratification will occur during subsequent coating processes, and particle agglomeration will lead to poor dispersion, resulting in a significant decrease in the performance of the final battery (e.g., specific capacity and cycle performance). Therefore, the stability of the battery slurry is crucial for battery performance. Conventional methods include testing the slurry's flowability, viscosity, solid content, and particle size.

[0004] The example disclosed in patent document CN106124363B is: by testing the viscosity change of the positive and negative electrode slurry from small to large shear rate and the viscosity change from large to small shear rate, the stability of the slurry is characterized by comparing the coincidence of the two viscosity-shear rate curves.

[0005] The example disclosed in patent document CN109884161A is: by collecting ceramic slurry at a certain height after standing for a certain period of time, the stability of the slurry is represented by detecting the elemental changes in the collected slurry bucket through a mass spectrometer.

[0006] The above-mentioned testing methods are all relatively crude and cannot accurately characterize the stability of battery slurry, nor can they clearly define the influence of various materials on the stability of the slurry, and cannot provide effective technical assistance for the subsequent improvement of the stability of battery slurry. Summary of the Invention

[0007] To address the aforementioned problems in existing technologies, this invention attempts to provide a method for testing the stability of battery slurry, achieving a more accurate characterization of the stability of battery slurry, clarifying the influence of various materials on slurry stability, and providing technical assistance for subsequent improvement of battery slurry stability.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] This invention provides a method for testing the stability of battery slurry, the method comprising the following steps:

[0010] Step 1, Battery slurry preparation: Place the freshly prepared or evenly dispersed battery slurry of known actual proportions into a container and seal it for standing.

[0011] Step 2, Slurry composition detection: After standing for a set time, a fixed mass of slurry is taken out at the cross-section of the slurry at the set height, and after processing, ICP-OES quantitative analysis and TG-MS quantitative analysis are performed to calculate the mass percentage of the metal element in the material, and the mass percentage of the binder, conductive agent and thickener are calculated to obtain the slurry ratio in the set height area, and then the percentage of the material ratio is calculated.

[0012] Step 3, Stability Evaluation: Compare the measured proportion of the slurry in the selected height area with the corresponding theoretical value. If the change rate of the mass percentage of each material in the slurry proportion is not greater than the specified value, the slurry is considered to have good stability. If the change rate of the mass percentage of any material is greater than the specified value, the slurry is considered to have poor stability, indicating that this material has a significant impact on the stability of the slurry.

[0013] Further preferably, the slurry treatment in step 2 includes: first drying, then digestion, filtration, dilution, and volume adjustment.

[0014] In a further preferred embodiment, in step 2, samples are taken from any region on the cross-section of the slurry at a set height, and measurements are taken from each region. The average of the multiple measurements is then compared with the theoretical value.

[0015] In a further preferred embodiment, in step 2, the total height of the slurry in the cylinder is set to H, and the stability of the slurry is evaluated by measuring the rate of change in the material composition of the slurry from 1 / 2 the height from the bottom of the cylinder.

[0016] Further optimization involves setting the set time for settling in step 2 to 48 hours.

[0017] Further optimization involves selecting the specified value for the percentage change rate of material mass in step 3 based on the requirements of the battery cell manufacturing process.

[0018] Further optimization, in step 3, the percentage change in mass is obtained by the following formula:

[0019] P 1A =(M 1A -M 0A ) / M 0A

[0020] Where: P 1A M is the percentage change in mass percentage of material A in the slurry taken at cross-section 1. 1A M is the mass percentage of material A in the slurry sample taken at cross-section 1; 0A It is the actual mass percentage of material A when preparing the slurry.

[0021] This invention employs ICP-OES and TG-MS quantitative analysis techniques. ICP-OES, or Inductively Coupled Plasma Optical Emission Spectrometry, can be used for qualitative and quantitative analysis of over seventy metallic elements and some non-metallic elements in samples from geological, environmental, chemical, biological, pharmaceutical, food, metallurgical, and agricultural fields. TG-MS is an analytical method combining thermogravimetric loss (TGA) information with mass spectrometry (MS). TG involves heating the sample via thermogravimetric analysis, which releases gases due to the presence of volatiles or combustion. MS detects the volatile components released during this heating process.

[0022] The advantages of this invention are as follows:

[0023] The method of this invention uses ICP-OES and TG-MS to quantitatively analyze the material composition of battery slurry. The stability of the slurry is evaluated by the change rate of the material ratio after the slurry has been left to stand. The method has high detection accuracy and can clearly identify which materials play a significant role in the stability of the slurry. The stability of the slurry system can be improved by adjusting the physicochemical properties of the materials. Attached Figure Description

[0024] Figure 1 This is a flowchart of one embodiment of the method for testing the stability of battery slurry. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided to provide a more thorough and complete understanding of the present invention. The accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Based on the embodiments of the present invention, technical solutions obtained by those skilled in the art without creative effort are all within the scope of protection of the present invention.

[0026] like Figure 1 As shown, one embodiment of the method for evaluating the stability of battery slurry according to the present invention specifically includes the following steps:

[0027] Step 1, Preparation of battery slurry: Place the freshly prepared or evenly dispersed electrode slurry with a known actual ratio into a container, seal it and let it stand. Use this known actual ratio as the theoretical value for subsequent comparisons.

[0028] Step 2, Slurry Composition Analysis: After standing for a certain period of time, a fixed mass of slurry is taken from a cross-section at a set height and dried. Through digestion, filtration, dilution, and volume adjustment, and then quantitative analysis using ICP-OES, the mass percentage of metal elements in the material can be calculated. The dried slurry is then quantitatively analyzed using TG-MS to calculate the mass percentages of binder, conductive agent, and thickener. This yields the optimal slurry composition for this height.

[0029] In this step, the settling time is set according to the cell manufacturing process; in this embodiment, the settling time is 48 hours.

[0030] In this step, the set height for taking the slurry is based on the combined influence of gravity and buoyancy, and the middle section is more representative of the overall stability of the slurry. It is preferable to take the cross section at 1 / 2 of the total height of the slurry.

[0031] As a preferred method, multiple areas at the same horizontal height are selected, each area is measured separately, the multiple measurements are averaged, and then compared with the theoretical value. This can improve the accuracy of the evaluation.

[0032] Step 3, Stability Evaluation:

[0033] In this step, the measured proportions of the extracted slurry are compared with the theoretical values. If the percentage change rate of all materials is not greater than the specified value, the slurry is considered to have good stability; if the percentage change rate of a certain material at a certain height is greater than the specified value, the slurry is considered to have poor stability. Here, the specified value for the percentage change rate of materials is selected based on the cell manufacturing process.

[0034] The percentage change rate of mass can be obtained by the following formula:

[0035] P 1A =(M 1A -M 0A ) / M 0A

[0036] Where: P 1A M is the percentage change in mass percentage of material A in the slurry taken at cross-section 1. 1A M is the mass percentage of material A in the slurry sample taken at cross-section 1; 0A It is the actual mass percentage of material A when preparing the slurry.

[0037] In this embodiment, to ensure greater accuracy of the measurement results, multiple samples of the slurry from the same cross-sectional area are taken, and the composition of the extracted slurry is analyzed. The average value of the multiple measurements is used as the evaluation basis. For multiple samples to be compared, the percentage of material mass in the slurry at the same height of each sample should be measured, and the rate of change of the percentage of material mass in the slurry should be calculated.

[0038] In a preferred embodiment, the total height of the slurry in the barrel is set to H, and the stability of the slurry is evaluated using the percentage change in the mass percentage of the slurry at a cross-section located at 1 / 2H from the bottom of the barrel. Using the percentage change in the mass percentage of the electrode slurry within this cross-sectional area allows for a more accurate evaluation of the battery slurry's stability. The worse the slurry stability, the greater the percentage change in the mass percentage of each material in the slurry at the 1 / 2H cross-section; conversely, if the slurry stability is good, the percentage change in the mass percentage of each material in the slurry at the 1 / 2H cross-section is smaller.

Claims

1. A method for testing the stability of battery slurry, characterized in that, The method includes: Step 1, Battery slurry preparation: Place the freshly prepared or evenly dispersed battery slurry with a known actual ratio into a container, seal it and let it stand. Use this known actual ratio as the theoretical value for subsequent comparisons. Step 2, Slurry composition detection: After a set set time of settling, a fixed mass of slurry is taken out from the cross-section at the set height of the slurry, and after processing, ICP-OES quantitative analysis and TG-MS quantitative analysis are performed. The mass percentage of the metal element is calculated by ICP-OES quantitative analysis, and the mass percentage of the binder, conductive agent and thickener is calculated by TG-MS quantitative analysis. Thus, the slurry ratio in the set height area is obtained, and the percentage of the material ratio is calculated. The process of taking a fixed mass of slurry at a cross-section at a set height of the slurry specifically involves taking samples from any area on the cross-section at the set height of the slurry, measuring each sample, averaging the measured values, and then comparing them with the theoretical value. The total height of the slurry in the barrel is set as H. The stability of the slurry is evaluated by the percentage change in the material mass of the slurry at a cross-section at a height of 1 / 2H from the bottom of the barrel after measurement. Step 3, Stability Evaluation: Compare the measured proportion of the slurry in the selected height area with the corresponding theoretical value. If the change rate of the mass percentage of each material in the slurry proportion is not greater than the specified value, the slurry is considered to have good stability. If the change rate of the mass percentage of any material is greater than the specified value, the slurry is considered to have poor stability, indicating that this material has a significant impact on the stability of the slurry.

2. The method for testing the stability of battery slurry according to claim 1, characterized in that, The slurry treatment in step 2 includes: drying, followed by digestion, filtration, dilution, and volume adjustment.

3. The method for testing the stability of battery slurry according to claim 1, characterized in that, In step 2, the set time for settling is 48 hours.

4. The method for testing the stability of battery slurry according to claim 1, characterized in that, In step 3, the specified value for the percentage change rate of material mass is determined based on the requirements of the cell manufacturing process.

5. The method for testing the stability of battery slurry according to claim 1, characterized in that, In step 3, the percentage change in mass is obtained by the following formula: ； in: It is the percentage change in mass of material A in the slurry taken at cross-section 1. It is the mass percentage of material A in the slurry taken at cross-section 1; It is the actual mass percentage of material A when preparing the slurry.

6. The method for testing the stability of battery slurry according to claim 1, characterized in that, In step 3, the greater the percentage change rate of each material mass in the cross-sectional area at the set height, the worse the slurry stability; conversely, the slurry stability is good.

7. The method for testing the stability of battery slurry according to claim 1, characterized in that, For multiple samples to be compared, the mass percentage of each material in the slurry samples in multiple 1 / 2H height cross-sectional areas should be measured, and the rate of change of the mass percentage of the material in the slurry should be calculated.

Images