CN109696111B - Method for testing expansion rate of electrode active material and application thereof - Google Patents
Method for testing expansion rate of electrode active material and application thereof Download PDFInfo
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- CN109696111B CN109696111B CN201811608794.4A CN201811608794A CN109696111B CN 109696111 B CN109696111 B CN 109696111B CN 201811608794 A CN201811608794 A CN 201811608794A CN 109696111 B CN109696111 B CN 109696111B
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Abstract
The invention provides a method for testing the expansion rate of an electrode active material and a method for evaluating the quality of an electrode and a battery. The method for testing the expansion rate of the electrode active material comprises the following steps: providing an original electrode plate, wherein the original electrode plate comprises a base body and an electrode material layer arranged on the surface of the base body, and the electrode material layer contains an electrode active material and an inactive material; pressurizing the original electrode plate, and measuring the effective original thickness of an electrode material layer in the original electrode plate in a pressurized state; assembling the original electrode plates into a battery and enabling the battery to work for a preset time to obtain expanded electrode plates; pressurizing the expansion electrode slice, and measuring the effective expansion thickness of the electrode material layer in the expansion electrode slice in a pressurized state; the expansion rate of the electrode active material is determined based on the effective original thickness and the effective expansion thickness. The method is simple and convenient, the test result eliminates errors caused by factors except expansion of electrode active materials in the electrode slice, and the method is high in accuracy and good in feasibility.
Description
Technical Field
The invention relates to the technical field of materials, in particular to a method for testing the expansion rate of an electrode active material, a method for evaluating the quality of an electrode and a method for evaluating the quality of a battery.
Background
In the related art, electrode active materials (such as silicon-based materials, silicon-carbon composite materials and the like) in power batteries such as lithium ion batteries and the like have higher expansion rate in the use process, so that the cycle life of the power batteries is reduced, and the safety performance is poorer. Therefore, accurately testing the expansion rate of the electrode active material is of great significance to the design and research of power batteries. However, the current measurement of the expansion ratio of the electrode active material is still not accurate, and the procedure is complicated and has poor feasibility.
Thus, the existing related art for testing the expansion rate of the electrode active material still remains to be improved.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, an object of the present invention is to provide a method for testing the expansion rate of an electrode active material, which is simple and convenient, can eliminate errors due to factors other than the expansion of the electrode active material in an electrode sheet according to a test result, and has high accuracy or good feasibility.
In one aspect of the present invention, the present invention provides a method of testing the expansion rate of an electrode active material. According to an embodiment of the invention, the method comprises: providing an original electrode sheet, wherein the original electrode sheet comprises a base body and an electrode material layer arranged on the surface of the base body, and the electrode material layer contains an electrode active material and an inactive material; pressurizing the original electrode plate, and measuring the effective original thickness L of the electrode material layer in the original electrode plate in a pressurized state; assembling the original electrode plates into a battery and enabling the battery to work for a preset time to obtain expanded electrode plates; pressurizing the expansion electrode slice, and measuring the effective expansion thickness D of the electrode material layer in the expansion electrode slice in a pressurized state; determining an expansion rate of the electrode active material based on the effective original thickness L and the effective expanded thickness D. The inventor finds that the method is simple and convenient, the test result eliminates errors caused by factors except expansion of the electrode active material in the electrode slice, and the method is high in accuracy and good in feasibility.
According to an embodiment of the invention, the effective raw thickness L is measured by: measuring the thickness X of the original electrode plate in a pressurized state; measuring the thickness L of the substrate in the original electrode sheet1The effective original thickness L ═ X-L1。
According to an embodiment of the invention, the effective raw thickness L is measured by: measuring the first height L of the pressure sheet die by using a vernier caliper0(ii) a Placing an original electrode slice sample into an inner cavity of the tabletting mold, and measuring a second height L of the tabletting mold by using the vernier caliper2(ii) a Pressurizing the original electrode plate sample in the thickness direction through the tabletting mold to obtain a stress-strain curve of the original electrode plate sample, and determining the electrode material according to the stress-strain curveAmount of non-elastic deformation L of the material layer3(ii) a Measuring the thickness L of the matrix in the original electrode slice sample by using a micrometer caliper1The effective original thickness L ═ L2-L1-L0-L3。
According to an embodiment of the invention, the effective expanded thickness D is measured by: measuring the thickness H of the expansion electrode sheet in a pressurized state; measuring the thickness D of the substrate in the expanded electrode sheet1The effective expansion thickness D ═ H-D1。
According to an embodiment of the invention, the effective expanded thickness D is measured by: measuring the first height D of the pressure sheet die by using a vernier caliper0(ii) a Placing the sample of the expanded electrode slice into the inner cavity of the tabletting mold, and measuring the second height D of the tabletting mold by using the vernier caliper2(ii) a Pressurizing the sample of the expanded electrode sheet in the thickness direction through the tabletting mold to obtain a stress-strain curve of the sample of the expanded electrode sheet, and determining the non-elastic deformation D of the electrode material layer according to the stress-strain curve3(ii) a Measuring the thickness D of the substrate in the sample of the expansion electrode slice by using a micrometer caliper1The effective expansion thickness D ═ D2-D1-D0-D3。
According to the embodiment of the invention, the size of the original electrode plate sample is consistent with the size of the inner cavity of the tabletting mold; the size of the sample of the expansion electrode plate is consistent with the size of the inner cavity of the tabletting mold.
According to the embodiment of the invention, a plurality of original electrode plate samples or expanded electrode plate samples which are arranged in a stacked mode are placed in the inner cavity of the tabletting mold.
According to an embodiment of the present invention, before placing the sample of the expanded electrode sheet into the inner cavity of the sheet pressing mold, the method further comprises: and preprocessing the sample of the expansion electrode plate.
According to an embodiment of the invention, the original electrode sheet sample or the expanded electrode sheet sample is obtained by punching the original electrode sheet or the expanded electrode sheet, and the middle part of the original electrode sheet or the expanded electrode sheet constitutes the original electrode sheet sample or the expanded electrode sheet sample.
In another aspect of the invention, a method of evaluating the quality of an electrode is provided. According to an embodiment of the present invention, the method includes the step of testing the expansion rate of the electrode active material using the method described above. The inventor finds that the method is simple and convenient, the error caused by factors except the expansion of the electrode active material in the electrode plate is eliminated according to the test result of the expansion rate of the electrode active material, the accuracy is high, the feasibility is good, and all the characteristics and advantages of the method for testing the expansion rate of the electrode active material are provided, and redundant description is omitted.
In yet another aspect of the invention, a method of evaluating battery quality is provided. According to an embodiment of the invention, the method comprises the step of evaluating the quality of the electrode using the method described above. The inventor finds that the method is simple and convenient, has high accuracy and good feasibility, has all the characteristics and advantages of the method for evaluating the quality of the electrode, and is not repeated herein.
Drawings
Fig. 1 shows a schematic flow chart of a method of testing the swelling rate of an electrode active material according to an embodiment of the present invention.
Fig. 2 shows a schematic cross-sectional structure of an original electrode sheet or an expanded electrode sheet according to an embodiment of the present invention.
FIG. 3 shows a schematic flow chart of measuring the effective raw thickness L according to one embodiment of the present invention.
Fig. 4 shows a schematic flow chart of measuring the effective raw thickness L according to another embodiment of the present invention.
Fig. 5a and 5b show a schematic flow chart of measuring the effective raw thickness L or the effective expanded thickness D according to an embodiment of the present invention.
Fig. 6 shows stress-strain curves for a raw electrode sheet sample and an expanded electrode sheet sample in one embodiment of the invention.
Fig. 7 shows a schematic plan structure of an original electrode sheet or an expanded electrode sheet and a sample of the original electrode sheet or the expanded electrode sheet according to an embodiment of the present invention.
FIG. 8 shows a schematic flow chart of measuring the effective inflated thickness D according to one embodiment of the present invention.
Fig. 9 shows a schematic flow chart of measuring the effective expansion thickness D according to another embodiment of the present invention.
Fig. 10 shows a schematic flow chart of measuring the effective inflated thickness D according to yet another embodiment of the present invention.
Reference numerals:
10: original electrode sheet, expanded electrode sheet 11: substrate 12: electrode material layer 20: original electrode sheet sample, expanded electrode sheet sample 100: a tabletting mold 110: a body 120: pressing portion 130: inner cavity
Detailed Description
The following describes embodiments of the present invention in detail. The following examples are illustrative only and are not to be construed as limiting the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
The present invention has been completed based on the following findings of the inventors:
in the related art, when the electrode sheet is assembled into a battery and used, the electrode active material therein has a high expansion rate during use, which may result in a reduction in cycle life and poor safety performance of the battery. Therefore, accurately testing the expansion rate of the electrode active material is meaningful for the design and research of power cells. However, it is well known to those skilled in the art that inactive materials such as a conductive agent (e.g., conductive carbon black, etc.) and a binder (e.g., polytetrafluoroethylene, etc.) are inevitably present in the electrode material layer in addition to the electrode active materials described above. In the related art, the influence of the conductive agent and the binder in the electrode material layer on the test results is not considered when the expansion rate of the electrode active material is tested. However, after extensive and intensive investigation and experimental verification, the inventors found that the errors of the conductive agent and the binder in the electrode material layer on the expansion ratio test results are not negligible.
In order to make the test result of the present invention more accurate, the inventor further keenly noticed that when the electrode tab is detached from the battery, since the electrode tab is not subjected to charge and discharge cycles (i.e., the original electrode tab herein) and is subjected to charge and discharge cycles (i.e., the expanded electrode tab herein), the types of the electrode active materials in the electrode material layer are different, and the electrode active materials in the electrode material layer before the charge and discharge cycles are subjected to chemical reactions after undergoing charge and discharge cycles and electrode reactions. Therefore, the kind of the material of the electrode active material in the electrode material layer is different before and after the charge-discharge cycle (i.e., the occurrence of the electrode reaction). After the electrode plate on the battery is disassembled, the electrode material layer can generate self expansion due to the disappearance of stress, and the electrode material layer loses self expansion generated by extrusion due to the disassembly from the battery before and after charge and discharge cycles due to the different elastic moduli of different materials, so that errors can be brought to the test result of the expansion rate of the electrode active material. After extensive and intensive studies and experimental verification, the inventors found that the error is not negligible when the expansion rate of the electrode active material is tested.
Furthermore, the inventors have found that, before and after the electrode sheet undergoes charge and discharge cycles, on one hand, the electrode active material in the electrode material layer expands, so that a dense packing manner cannot be formed between particles of the electrode active material, gaps between particles of the electrode active material increase, and errors may also occur in the measurement result of the expansion rate of the electrode active material; on the other hand, after the electrode reaction occurs, a passivation film (e.g., SEI film, etc.) may be formed on the surface of the electrode material layer, and since the passivation film has a certain thickness, it may have a certain influence on the result of the measurement of the expansion rate of the electrode active material, thereby causing errors.
In summary, the expansion rate test method of the electrode active material in the related art does not consider errors due to the expansion of the conductive agent and the binder, errors due to the self-expansion of the electrode material layer due to the loss of the compression, errors due to the increase of the gaps between particles in the electrode active material due to the expansion of the electrode active material, and errors due to the product of the electrode reaction. The inventors have conducted intensive studies on a method for testing an electrode active material, and have surprisingly found, after a plurality of experiments, that, among the above-mentioned sources of error, the electrode material layer expands by itself due to the loss of extrusion, and the particle-to-particle gaps in the electrode active material increase, both from the electrode material layer itself, so that the above-mentioned expansion or gap increase is very easily compressed back; in addition, since the elastic modulus of the product of the reaction of the conductive agent, the binder and the electrode is much smaller than that of the electrode active material, the conductive agent, the binder and the electrode reaction product are easily compressed while being expanded. That is, after a great deal of research, the inventors found that the above-mentioned errors can be eliminated in the test results of the expansion ratio by pressurizing the electrode sheet when testing the expansion ratio of the electrode active material, so that the test results have high accuracy and good feasibility, and the operation is simple and convenient.
Based on this, in one aspect of the present invention, the present invention provides a method of testing the expansion rate of an electrode active material. According to an embodiment of the present invention, referring to fig. 1, the method includes:
s100: providing a primary electrode sheet 10 (the structure schematic diagram refers to fig. 2), wherein the primary electrode sheet 10 comprises a base body 11 and an electrode material layer 12 arranged on the surface of the base body, and the electrode material layer 12 contains an electrode active material and an inactive material.
According to an embodiment of the present invention, the original electrode sheet 10 refers to an electrode sheet that is not soaked in an electrolyte and is not subjected to a charge and discharge cycle, and the source thereof is not particularly limited, and for example, an electrode sheet directly purchased from an electrode sheet manufacturer may be used as the original electrode sheet 10 according to the present invention as long as the electrode sheet is not soaked in an electrolyte and is not subjected to a charge and discharge cycle. Therefore, the test material has wide source and is easy to obtain, and industrialization is easy to realize.
According to the embodiment of the present invention, the electrode material layer 12 in the original electrode sheet 10 may be disposed on one surface of the base 11 (the structural schematic diagram refers to fig. 2), or may be disposed on both surfaces of the base 11. Therefore, the test material has wide source and is easy to obtain, and industrialization is easy to realize.
According to the embodiment of the invention, the material of the base body 11 may be the material of the base body in a conventional electrode sheet, and may be a metal sheet or the like, for example. In some embodiments of the present invention, the material of the substrate 11 may be aluminum foil or copper foil. Therefore, the test material has wide source and is easy to obtain, and industrialization is easy to realize.
S200: the original electrode sheet 10 is subjected to a pressing process (a schematic structural diagram refers to fig. 2), and an effective original thickness L of the electrode material layer 12 in the original electrode sheet 10 is measured in a pressed state.
According to the embodiment of the present invention, the process parameters of the pressurization treatment are not particularly limited as long as the pressurization treatment can cause the expansion or increase derived from the above-described error to be compressed, as described above, and the pressure or the like of the pressurization treatment is not particularly limited.
According to an embodiment of the present invention, it should be noted that the effective original thickness L refers to a thickness infinitely close to the true thickness of the electrode active material in the electrode material layer 12 after the error described herein is eliminated. It has been previously mentioned that only the swelling of the electrode active material is of interest for the development and design of electrodes when tested for swelling ratio. Therefore, in step S200, the effective original thickness L is the thickness of the electrode active material in the electrode material layer 12, and after the thickness of the electrode active material in the electrode material layer 12 in the original electrode sheet 10 is measured, the expansion rate of the electrode active material can be directly calculated, and the method has high accuracy and good feasibility.
In some embodiments of the present invention, referring to fig. 2 and 3, the effective raw thickness L is measured by:
s210: the thickness X of the original electrode sheet 10 was measured in a pressurized state.
According to the embodiment of the present invention, referring to fig. 2, the thickness X of the original electrode sheet 10 refers to the sum of the thicknesses of the electrode material layer 12 and the base 11 in the original electrode sheet 10, and the specific manner of measuring the thickness X is not particularly limited, and one skilled in the art can flexibly select the thickness X as needed as long as the requirement is met. In some embodiments of the present invention, the thickness X may be measured with a ruler, or with a vernier caliper or a micrometer screw, etc. Therefore, the method is simple and convenient to operate and easy to industrialize.
S220: measuring the thickness L of the base body in the original electrode sheet 101The effective original thickness L ═ X-L1。
According to the embodiment of the invention, the thickness L of the base body in the original electrode sheet 10 is measured1The effective original thickness L can be obtained, so that the influence of the matrix 11 in the original electrode sheet 10 on the test result of the expansion rate of the electrode active material is eliminated, and by this calculation, when the expansion rate is tested, the original electrode sheet and the expansion electrode sheet used in the test are not required to use the same matrix, because the error caused by the matrix on the expansion rate is deducted in the final test result. Therefore, the test material has wide sources and flexible selection, and is easy to realize industrialization.
In other embodiments of the present invention, further, with reference to fig. 4, 5 a-5 b, the effective raw thickness L is measured by:
s210': measuring the first height L of the sheeting die 100 with a vernier caliper0(the structural schematic view refers to FIG. 5 a).
According to an embodiment of the present invention, a first height L of a tableting mold 100 is measured0Can be measured with a vernier caliper. Therefore, the method is simple and convenient to operate, and the measuring accuracy is high.
According to an embodiment of the present invention, the tablet pressing mold 100 at least includes a body 110, a pressing portion 120, and an inner cavity 130 (referring to fig. 5a for a schematic structural diagram), so as to press the original electrode sheet 10.
According to the embodiment of the present invention, the specific type of the tablet pressing mold 100 is not particularly limited as long as the pressing process can be achieved, and the specific type can be flexibly selected by those skilled in the art according to actual needs. In some embodiments of the present invention, the sheeting die 100 may be a sheeting die used in infrared spectroscopy. Thus, the tableting mold having a wide source and in infrared spectroscopic analysis is directly used without separately manufacturing the tableting mold 100 for testing the expansion rate of the electrode active material.
S220': placing the original electrode sheet sample (including the electrode material layer 12 and the substrate 11) into the inner cavity 130 of the tabletting mold 100, and measuring the second height L of the tabletting mold 100 by using the vernier caliper2(the structural schematic view is shown in FIG. 5 b).
According to an embodiment of the present invention, the second height L of the tableting mold 100 is measured2Can be measured with a vernier caliper. Therefore, the method is simple and convenient to operate, and the measuring accuracy is high.
According to an embodiment of the present invention, the first height L of the tableting mold 100 has been obtained as a result of the foregoing steps0And a second height L of the sheeting mold 100 after placing the original electrode sheet sample into the interior cavity 130 of the sheeting mold 1002Therefore, the thickness of the original electrode plate sample can be obtained, the operation is simple, the accuracy is high, the industrialization is easy to realize, and the subsequent pressurization treatment of the original electrode plate sample is convenient.
In some embodiments of the present invention, the dimensions of the original electrode sheet sample correspond to the dimensions of the interior cavity 130 of the sheeting mold 100. Therefore, when the original electrode plate sample is subjected to subsequent pressure treatment, the original electrode plate sample does not expand in the direction perpendicular to the thickness direction, so that the calculation accuracy is ensured when the expansion rate is calculated by using the thickness of the original electrode plate sample, and the accuracy of the method for measuring the expansion rate is further improved.
According to an embodiment of the present invention, a plurality of original electrode sheet samples arranged in a stacked manner may also be directly placed in the inner cavity 130 of the tablet die 100. Therefore, due to the fact that a plurality of original electrode plate samples arranged in a stacked mode are placed, uncertainty caused by a single sample to a measurement result is eliminated, and after the original electrode plate samples arranged in the stacked mode are placed in the inner cavity 130, measurement of subsequent steps is conducted, and the expansion rate test result of the electrode active material can be further improved.
According to an embodiment of the present invention, referring to fig. 7, the original electrode sheet sample 20 may be obtained by punching the original electrode sheet 10 (it should be noted that, since fig. 7 is a schematic plan view, only the electrode material layer 12 is shown in the original electrode sheet 10, and the base is not shown), and the middle portion of the original electrode sheet 10 constitutes the original electrode sheet sample 20. Therefore, the thickness of the middle portion of the original electrode sheet 10 is uniform, and the thickness of the electrode sheet which swells after use is also uniform, so that the test result of the swelling rate of the electrode active material by the method can be further improved by adopting the middle portion of the original electrode sheet sample 20.
S230': the original electrode sheet sample 20 is subjected to pressure treatment in the thickness direction by the pressing mold 100 to obtain a stress-strain curve of the original electrode sheet sample 20 (see fig. 6), and the amount of non-elastic deformation L of the electrode material layer is determined according to the stress-strain curve3。
According to the embodiment of the present invention, it has been described that, in the electrode material layer 12, the conductive agent and the binder are expanded in the expansion rate test method of the electrode active material, the electrode material layer 12 is self-expanded due to the loss of the compression, the electrode active material is expanded to increase the gaps between particles in the electrode active material, and the thickness of the product of the electrode reaction is easily compressed compared to the electrode active material. That is, the elastic modulus of the aforementioned expansion, gap enlargement, and thickness is much smaller than that of the electrode active material (it should be noted that although the expansion and gap are not theoretically physical, those skilled in the art will understand that the elastic modulus of the expansion and gap can be considered as zero herein). Therefore, the original electrode sheet can be subjected to pressurization treatment to eliminate errors caused by the factors on the test result of the expansion rate.
According to the embodiment of the present invention, since the elastic modulus of the expansion, the increase in the gap, and the thickness of the product of the electrode reaction is much smaller than that of the electrode active material, when the raw electrode sheet sample 20 is subjected to the pressure treatment, the expansion, the increase in the gap, and the thickness of the product of the electrode reaction are all non-elastic deformation, and the electrode active material is elastic deformation. Therefore, when the original electrode plate sample is subjected to pressure treatment, the electrode active material is subjected to elastic deformation during the pressure treatment, a stress-strain curve of the original electrode plate sample is recorded, and the stress and the strain of the electrode active material with elastic deformation are in a linear relationship. Further, a stress-strain curve is linearly fitted (see fig. 6) according to hooke's law and the stress-strain theory of the material to obtain intersection points (i.e., points a and b in fig. 6) with the strain coordinate axis, and the line segments oa and ob are inelastic deformation amounts. Therefore, when the original electrode sheet sample is tested, as can be understood by those skilled in the art, the non-elastic deformation L of the original electrode sheet sample can be obtained according to the corresponding relationship between the strain and the non-elastic deformation3I.e. the length corresponding to line oa in fig. 6 (hereinafter in the case of the test on the sample of the expanded electrode sheet, the amount of non-elastic deformation D of the sample of the expanded electrode sheet is obtained3I.e. the length corresponding to the line segment ob in fig. 6). Thus, the foregoing errors in the expansion rate test result caused by the expansion of the conductive agent and binder, the self-expansion of the electrode material layer due to the loss of compression, the expansion of the electrode active material resulting in the increase of the gaps between particles in the electrode active material, and the thickness of the product of the electrode reaction are obtained.
S240': measuring the raw electricity with a micrometerThickness L of the matrix in the Pole piece sample1The effective original thickness L ═ L2-L1-L0-L3。
According to the embodiment of the invention, the thickness L of the matrix in the original electrode slice sample is measured1The effective original thickness L can be obtained, so that the influence of the matrix in the original electrode plate sample on the test result of the expansion rate of the electrode active material is eliminated, and by the calculation mode, the original electrode plate sample and the expanded electrode plate sample used in the test are not required to use the same matrix when the expansion rate is tested, because the error caused by the matrix on the expansion rate is deducted in the final test result. Therefore, the test material has wide sources and flexible selection, and is easy to realize industrialization.
According to an embodiment of the present invention, the first height L of the tableting mold 100 is obtained in the foregoing measurement0A second height L of the tablet pressing mold 100 after the original electrode sheet is placed in the inner cavity 130 of the tablet pressing mold 1002The amount of non-elastic deformation L of the electrode material layer3And the thickness L of the base body in the original electrode sheet sample1Based on the above formula (I), the effective original thickness L ═ L2-L1-L0-L3. Therefore, the thickness of the electrode active material in the electrode material layer is obtained, the expansion rate of the electrode active material can be directly calculated after the thickness of the electrode active material in the electrode material layer in the original electrode plate is measured, and errors caused by the factors are deducted, so that the accuracy is high, and the feasibility is good.
According to an embodiment of the invention, after measuring the effective raw thickness L, the method further comprises:
s300: and assembling the original electrode plates into a battery and enabling the battery to work for a preset time to obtain the expanded electrode plates.
According to an embodiment of the present invention, the primary electrode sheet is operated for a predetermined time after being assembled into a battery in order to obtain an expanded electrode sheet, so that the expansion rate of the electrode active material is obtained according to the effective expansion thickness L of the electrode material layer in the primary electrode sheet and the effective expansion thickness D of the electrode material layer in the expanded electrode sheet.
According to the embodiment of the invention, the preset time may be the time for the conventional battery to work, as long as it is ensured that the expanded electrode sheet is obtained after the original electrode sheet is completely expanded, the specific preset time is not particularly limited, and a person skilled in the art can flexibly select the expanded electrode sheet according to actual needs, and redundant description is omitted here.
S400: and pressurizing the expansion electrode plate, and measuring the effective expansion thickness D of the electrode material layer in the expansion electrode plate in a pressurized state.
According to the embodiment of the invention, all steps and processes for performing the pressurization treatment on the expanded electrode sheet can be performed by referring to the steps and processes for performing the pressurization treatment on the original electrode sheet, and are not described in detail herein.
In some embodiments of the invention, referring to fig. 2 and 8, the effective expanded thickness D of the electrode material layer in the expanded electrode sheet is measured by:
s410: the thickness H of the expanded electrode sheet 10 was measured in a pressurized state.
S420: measuring the thickness D of the base body in the expanded electrode sheet 101The effective expansion thickness D ═ H-D1。
According to the embodiment of the invention, all the steps and processes described above can be performed with reference to the steps (S210 and S220) and processes of the original electrode sheet, and are not described in detail herein.
In other embodiments of the present invention, further, with reference to fig. 5 a-5 b and fig. 9, the effective expanded thickness D is measured by:
s410': measuring the first height D of the sheeting mold 100 with a vernier caliper0(the structural schematic view refers to FIG. 5 a).
And S420': the sample of the expanded electrode sheet (including the electrode material layer 12 and the base 11) is placed into the inner cavity 130 of the sheeting mold 100, and the second of the sheeting mold 100 is measured with the vernier caliperHeight D2(the structural schematic view is shown in FIG. 5 b).
S430': the expanded electrode sheet sample 20 is subjected to pressure treatment in the thickness direction by the pressing mold 100 to obtain a stress-strain curve of the expanded electrode sheet sample 20 (see fig. 6), and the amount of non-elastic deformation D of the electrode material layer is determined from the stress-strain curve3。
S440': measuring the thickness D of the substrate in the sample of the expansion electrode slice by using a micrometer caliper1The effective original thickness D ═ D2-D1-L0-D3。
According to the embodiment of the present invention, for the explanation of all the materials, steps, processes and principles described above, reference may be made to the explanation of the materials, steps (S210 ', S220', S230 ', and S240'), processes and principles of the original electrode sheet, and redundant description is not repeated here.
In other embodiments of the present invention, referring to FIG. 10, the first height D of the sheeting mold 100 is measured using a vernier caliper in the previous step0(S410'), thereafter, the sample of the expanded electrode sheet is placed in the inner cavity 130 of the tableting mold 100, and the second height D of the tableting mold 100 is measured using the vernier caliper2Before (S420'), the step further includes:
s450': and preprocessing the sample of the expansion electrode slice.
According to the embodiment of the invention, the pretreatment of the sample of the expanded electrode sheet can be specifically carried out by soaking the expanded electrode sheet, so that electrolyte absorbed by electrode reaction generated when the sample of the expanded electrode sheet is assembled into a battery in front before working is removed, the electrolyte is prevented from corroding a tabletting mold, the tabletting mold can be protected from being repeatedly used for a long time, and the accuracy of measuring the electrode active material is still high after the tabletting mold is repeatedly used for a long time.
According to the embodiment of the invention, the soaking treatment can be carried out by soaking the expansion electrode slice in DMC (dimethyl carbonate), the soaking treatment time can be 1 min-2 min, and the dew point is less than-35 ℃ and the ambient temperature can be (25 +/-2) DEG C when the soaking treatment is carried out. In some embodiments of the present invention, the time of the soaking treatment may be 1min, 1.2min, 1.4min, 1.6min, 1.8min, 2min, or the like. Therefore, the electrolyte absorbed by the expansion electrode slice can be completely removed, the pretreatment time is short, and the efficiency of the testing method is high.
S500: determining an expansion rate of the electrode active material based on the effective original thickness L and the effective expanded thickness D.
According to an embodiment of the present invention, the expansion ratio of the electrode active material is calculated as follows:
the expansion rate η ═ [ (D-L)/L ] × 100%, where D is the effective expansion thickness of the aforementioned expanded electrode sheet, and L is the effective original thickness of the aforementioned original electrode sheet;
therefore, after a great deal of research, the inventor finds that by performing pressure treatment on the electrode sheet when testing the expansion rate of the electrode active material, errors caused by the expansion of the conductive agent and the binder in the electrode material layer, errors caused by the self-expansion of the electrode material layer due to the loss of extrusion, errors caused by the increase of gaps between particles in the electrode active material due to the expansion of the electrode active material, and errors caused by products of electrode reaction can be eliminated in the test result of the expansion rate, so that the test result has high accuracy and good feasibility, and the operation is simple and convenient.
In another aspect of the invention, a method of evaluating the quality of an electrode is provided. According to an embodiment of the present invention, the method includes the step of testing the expansion rate of the electrode active material using the method described above. The inventor finds that the method is simple and convenient, the error caused by factors except the expansion of the electrode active material in the electrode plate is eliminated according to the test result of the expansion rate of the electrode active material, the accuracy is high, the feasibility is good, and all the characteristics and advantages of the method for testing the expansion rate of the electrode active material are provided, and redundant description is omitted.
According to the embodiment of the invention, the electrode can be an anode or a cathode, the shape, thickness or surface state and the like of the electrode are not particularly limited, and the expansion rate of the electrode active material can be tested by adopting the method provided by the invention as long as the requirements are met, so that the quality of the electrode can be evaluated.
According to the embodiments of the present invention, it can be understood by those skilled in the art that the method for evaluating the quality of the electrode may include other steps besides the step of testing the swelling rate of the electrode active material as described above, and thus, the description thereof is omitted.
In yet another aspect of the invention, a method of evaluating battery quality is provided. According to an embodiment of the invention, the method comprises the step of evaluating the quality of the electrode using the method described above. The inventor finds that the method is simple and convenient, has high accuracy and good feasibility, has all the characteristics and advantages of the method for evaluating the quality of the electrode, and is not repeated herein.
According to the embodiment of the present invention, it can be understood by those skilled in the art that the battery includes other structures of a conventional battery, such as electrodes, a battery separator, and an electrolyte, which are not described in detail herein.
According to the embodiment of the present invention, the kind of the battery is not limited, and one skilled in the art can flexibly select the battery according to the requirement as long as the requirement is met, for example, the battery may include but is not limited to a lithium ion battery, etc.
According to the embodiment of the present invention, the use of the battery is not particularly limited, and those skilled in the art can flexibly select the battery according to the needs as long as the requirements are satisfied, and for example, the battery may be used in an electric vehicle.
According to the embodiment of the present invention, it can be understood by those skilled in the art that the method for evaluating the quality of the battery may include other steps besides the aforementioned step of evaluating the quality of the electrode by using the aforementioned method, and redundant description is omitted here.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (11)
1. A method of testing the expansion rate of an electrode active material, comprising:
providing an original electrode sheet, wherein the original electrode sheet comprises a base body and an electrode material layer arranged on the surface of the base body, and the electrode material layer contains an electrode active material and an inactive material;
pressurizing the original electrode plate, and measuring the effective original thickness L of the electrode material layer in the original electrode plate in a pressurized state;
assembling the original electrode plates into a battery and enabling the battery to work for a preset time to obtain expanded electrode plates;
pressurizing the expansion electrode slice, and measuring the effective expansion thickness D of the electrode material layer in the expansion electrode slice in a pressurized state;
determining an expansion rate of the electrode active material based on the effective original thickness L and the effective expanded thickness D.
2. The method of claim 1, wherein the effective raw thickness L is measured by:
measuring the thickness X of the original electrode plate in a pressurized state;
measuring the thickness L of the substrate in the original electrode sheet1The effective original thickness L ═ X-L1。
3. The method of claim 2, wherein the effective raw thickness L is measured by:
measuring the first height L of the pressure sheet die by using a vernier caliper0；
Placing an original electrode slice sample into an inner cavity of the tabletting mold, and measuring a second height L of the tabletting mold by using the vernier caliper2；
Pressurizing the original electrode plate sample in the thickness direction through the tabletting mold to obtain a stress-strain curve of the original electrode plate sample, and determining the non-elastic deformation L of the electrode material layer according to the stress-strain curve3；
Measuring the thickness L of the matrix in the original electrode slice sample by using a micrometer caliper1The effective original thickness L ═ L2-L1-L0-L3。
4. The method of claim 3, wherein the effective expanded thickness D is measured by:
measuring the thickness H of the expansion electrode sheet in a pressurized state;
measuring the thickness D of the substrate in the expanded electrode sheet1The effective expansion thickness D ═ H-D1。
5. The method of claim 4, wherein the effective expanded thickness D is measured by:
measuring the first height D of the pressure sheet die by using a vernier caliper0；
Placing the sample of the expanded electrode slice into the inner cavity of the tabletting mold, and measuring the second height D of the tabletting mold by using the vernier caliper2；
Pressurizing the sample of the expanded electrode sheet in the thickness direction through the tabletting mold to obtain a stress-strain curve of the sample of the expanded electrode sheet, and determining the non-elastic deformation D of the electrode material layer according to the stress-strain curve3；
Measuring the thickness D of the substrate in the sample of the expansion electrode slice by using a micrometer caliper1The effective expansion thickness D ═ D2-D1-L0-D3。
6. The method of claim 5, wherein the dimensions of the original electrode sheet sample are consistent with the dimensions of the interior cavity of the sheeting die; the size of the sample of the expansion electrode plate is consistent with the size of the inner cavity of the tabletting mold.
7. The method of claim 5, wherein a plurality of said raw or expanded electrode sheet samples are placed in a stack within the interior cavity of said sheeting die.
8. The method of claim 5, further comprising, prior to placing the sample of expanded electrode sheets into the interior cavity of the sheeting die:
and preprocessing the sample of the expansion electrode plate.
9. The method of claim 8, wherein the original electrode sheet sample or the expanded electrode sheet sample is obtained by die-cutting the original electrode sheet or the expanded electrode sheet, and a middle portion of the original electrode sheet or the expanded electrode sheet constitutes the original electrode sheet sample or the expanded electrode sheet sample.
10. A method of evaluating the quality of an electrode, comprising the step of testing the expansion rate of the electrode active material by the method according to any one of claims 1 to 9.
11. A method of evaluating the quality of a battery comprising the step of evaluating the quality of the electrode using the method of claim 10.
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| CN111928805A (en) * | 2020-07-31 | 2020-11-13 | 中国科学院宁波材料技术与工程研究所 | Method for testing and analyzing expansion rate of silicon-based negative electrode material |
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