Method for measuring longitudinal elongation percentage of pole piece

Abstract

The invention relates to the technical field of pole piece elongation measurement, and particularly provides a method for measuring the longitudinal elongation of a pole piece. The measuring method comprises the following steps: forming a plurality of straight lines extending along the length direction of a pole piece on the surface of the pole piece; n non-rolling samples of the pole piece are obtained and weighed, and the non-rolling samples cover the two straight lines; n rolled samples of the pole piece are obtained and weighed, and the n rolled samples are in one-to-one correspondence with the n non-rolled samples; measuring the distance between the two straight lines covered by the rolled sample; and calculating the longitudinal extension rate = the comprehensive extension rate-the transverse extension rate of the pole piece. According to the invention, the comprehensive extension rate and the transverse extension rate are combined, the longitudinal extension rate of the pole piece can be measured, a plurality of straight lines are formed on the pole piece, so that the sample for calculating the comprehensive extension rate covers the same two straight lines, and the transverse extension rate is calculated according to the distance variation between the two straight lines. The measurement accuracy of the longitudinal elongation rate can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of pole piece elongation measurement, and specifically provides a method for measuring the longitudinal elongation of a pole piece. Background Art

[0002] In the existing battery manufacturing process, the rolling process will compact the coated electrode and reduce the porosity between the active materials in order to increase the compaction density of the active materials on the electrode, thereby cramming more electrode layers into the same volume and increasing the capacity of the battery.

[0003] During the rolling process, the coated electrode is deformed and thinned by the pressure of the roller. During the deformation process, the active material in the electrode changes in the length and width of the electrode due to the existence of porosity, thus becoming longer and wider. The part of the electrode that increases in the length direction is the longitudinal elongation.

[0004] Most existing technologies use weighing measurement to detect the elongation of the pole piece, that is, using the same sampling area to sample and weigh the pole piece before rolling to obtain W1, and sample and weigh the pole piece after rolling to obtain W2, then the elongation = (W1-W2) / W2.

[0005] However, the elongation obtained by the weighing measurement method is the comprehensive elongation of the pole piece, which includes the longitudinal elongation and the transverse elongation. The measured elongation is greater than the required elongation (ie, the longitudinal elongation).

[0006] Therefore, this field needs a new technical solution to solve the above problems. Summary of the invention

[0007] The present invention aims to solve the above technical problem, that is, to solve the problem that the longitudinal extension rate of the pole piece cannot be measured by the weighing measurement method in the prior art.

[0008] In a first aspect, the present invention provides a method for measuring the longitudinal elongation of a pole piece, the measuring method comprising the following steps:

[0009] A plurality of straight lines extending along the length direction of the electrode piece to be tested are formed on the surface of the electrode piece to be tested, and the plurality of straight lines are spaced and parallel along the width direction of the electrode piece to be tested;

[0010] Obtain n unrolled samples of the electrode to be tested and weigh them, wherein each of the unrolled samples covers two of the straight lines, and n is a positive integer;

[0011] Obtaining n rolled samples of the electrode to be tested and weighing them, wherein the n rolled samples correspond to the n unrolled samples one by one, and the corresponding rolled samples and the corresponding unrolled samples cover the same two straight lines and have the same area;

[0012] measuring the distance between the two straight lines covered by the sample after rolling;

[0013] Calculate the longitudinal elongation of the electrode to be tested = comprehensive elongation - transverse elongation;

[0014] Wherein, the comprehensive elongation is calculated based on the weight of the unrolled sample and the weight of the rolled sample, and the lateral elongation is calculated based on the distance between the two straight lines covered by the unrolled sample and the distance between the two straight lines covered by the rolled sample.

[0015] In the preferred technical solution of the above-mentioned method for measuring the longitudinal extension rate of the pole piece, the measuring method further comprises:

[0016] Obtaining the weight loss of each of the rolled samples relative to the corresponding non-rolled sample;

[0017] According to the obtained multiple weight loss amounts, discard the rolled samples whose weight loss amounts do not meet the preset conditions and the corresponding unrolled samples;

[0018] The discarded rolled samples and the unrolled samples do not participate in the calculation of the longitudinal elongation.

[0019] In the preferred technical solution of the above-mentioned method for measuring the longitudinal elongation of the pole piece, the step of "discarding the rolled samples and the corresponding unrolled samples whose weight loss does not meet the preset conditions according to the obtained multiple weight loss amounts" specifically includes:

[0020] The rolled samples and the unrolled samples corresponding to the weight loss amounts different from the remaining weight loss amounts among the plurality of weight loss amounts are discarded.

[0021] In the preferred technical solution of the above-mentioned method for measuring the longitudinal elongation of the pole piece, the step of "discarding the rolled samples and the corresponding unrolled samples whose weight loss does not meet the preset conditions according to the obtained multiple weight loss amounts" specifically includes:

[0022] calculating a difference between every two of the weight loss amounts in the plurality of weight loss amounts;

[0023] comparing the difference with a preset value;

[0024] If the difference is greater than the preset value, the corresponding rolled sample and the unrolled sample are discarded.

[0025] In the preferred technical solution of the above-mentioned method for measuring the longitudinal elongation of the pole piece, in the case where the rolled sample and the unrolled sample are discarded, the measuring method further comprises:

[0026] The electrode to be tested is sampled again at the position corresponding to the discarded rolled sample and the unrolled sample.

[0027] In the preferred technical solution of the above-mentioned method for measuring the longitudinal elongation of the pole piece, in the case where the rolled sample and the unrolled sample are discarded, the measuring method further comprises:

[0028] comparing the number of the discarded unrolled samples or the rolled samples with the discardable number;

[0029] If the number of the discarded unrolled samples or the rolled samples is greater than the discardable number, resampling the electrode to be tested at the positions corresponding to the discarded rolled samples and the unrolled samples;

[0030] If the number of the discarded unrolled samples or the rolled samples is not greater than the discardable number, the electrode to be tested will not be sampled again.

[0031] In the preferred technical solution of the above method for measuring the longitudinal extension rate of the pole piece, the spacing between the two straight lines covered by each unrolled sample is equal.

[0032] In the preferred technical solution of the above-mentioned method for measuring the longitudinal elongation of the pole piece, n≥2.

[0033] In a preferred technical solution of the above method for measuring the longitudinal elongation of a pole piece, at least a portion of the plurality of unrolled samples are distributed along the width direction of the pole piece to be measured.

[0034] In the preferred technical solution of the above-mentioned method for measuring the longitudinal elongation of the pole piece, the line width of the straight line is not greater than 0.1 mm; and / or the shapes of the unrolled sample and the rolled sample are circular or rectangular.

[0035] When adopting the above-mentioned technical scheme, the elongation measurement method of the present invention combines the comprehensive elongation with the transverse elongation, and can measure the longitudinal elongation of the pole piece. Moreover, by forming multiple straight lines on the pole piece, the samples for comprehensive elongation calculation (unrolled samples and rolled samples) cover the same two straight lines, and the transverse elongation is calculated based on the change in the spacing between the two straight lines, thereby improving the accuracy of the longitudinal elongation measurement of the pole piece.

[0036] Furthermore, the present invention can effectively avoid the influence of surface density fluctuations and thickness fluctuations of the pole piece after rolling by discarding samples whose weight loss after rolling relative to the unrolled samples does not meet preset conditions, thereby further improving the accuracy of measuring the longitudinal elongation of the pole piece.

[0037] Furthermore, in the present invention, when rolled samples and unrolled samples are discarded, the electrode is resampled at positions corresponding to the discarded rolled samples and unrolled samples, which helps to avoid the situation where the accuracy of the measurement results is affected by the small number of samples.

[0038] Furthermore, the present invention makes it easier to calculate the lateral extension rate of the pole piece by setting the distance between the two straight lines covered by the unrolled sample to the same value.

[0039] Furthermore, the present invention helps to improve the accuracy of elongation measurement by distributing the unrolled samples along the width direction of the pole piece. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings, in which:

[0041] Figure 1 It is a flow chart of the method for measuring the longitudinal extension rate of the pole piece of the present invention;

[0042] Figure 2 It is a schematic structural diagram of obtaining a non-rolled sample of a pole piece to be tested according to the present invention;

[0043] Figure 3 It is a schematic structural diagram of obtaining a rolled sample of a pole piece to be tested according to the present invention.

[0044] List of reference numerals:

[0045] 1. Pole; 2. Straight line. DETAILED DESCRIPTION

[0046] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0047] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that, in the description of the present invention, although the various steps of the measuring method of the present invention are described in a specific order in this application, these orders are not restrictive, and those skilled in the art may perform the steps in different orders without departing from the basic principles of the present invention.

[0048] It should be noted that, in the description of the present invention, terms such as "front", "rear", "left" and "right" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0049] Specifically, the present invention provides a method for measuring the longitudinal extension rate of a pole piece, such as Figure 1 As shown, the measuring method of the present invention comprises the following steps:

[0050] S100: forming a plurality of straight lines extending along the length direction of the electrode piece on the surface of the electrode piece to be tested.

[0051] The plurality of straight lines are spaced and parallel along the width direction of the electrode to be tested.

[0052] For example, Figure 2 As shown, 10 straight lines 2 extending along the length direction of the pole piece 1 (left-right direction in the figure) are formed on the surface of the pole piece 1, and the 10 straight lines 2 are spaced and parallel along the width direction of the pole piece 1 (front-back direction in the figure).

[0053] It should be noted that the present invention does not limit the number of straight lines 2 to the above 10. For example, the number of straight lines 2 may also be set to 2, 4, 8, 12 or more.

[0054] In addition, it should be noted that, in actual applications, a person skilled in the art can draw lines on the surface of the pole piece 1 with a pen, or can draw lines on the surface of the pole piece 1 by spraying, or can form multiple straight lines on the surface of the pole piece 1 by laser engraving, etc. Such adjustments and changes to the specific formation method of the straight line 2 do not deviate from the principle and scope of the present invention, and should be limited within the scope of protection of the present invention.

[0055] S200: Obtain n unrolled samples of the electrode to be tested and weigh them.

[0056] Wherein, each unrolled sample covers two straight lines, and n is a positive integer.

[0057] It should be pointed out that the unrolled samples refer to the samples obtained by sampling the pole pieces that have not been rolled.

[0058] For example, Figure 2 As shown, Figure 2The pole piece 1 shown is a pole piece to be tested that has not been rolled. The number of unrolled samples is 5, that is, n=5. From front to back, they are unrolled sample 1, unrolled sample 2, unrolled sample 3, unrolled sample 4 and unrolled sample 5. The weights of unrolled sample 1, unrolled sample 2, unrolled sample 3, unrolled sample 4 and unrolled sample 5 are A1, A2, A3, A4 and A5 respectively. The spacing between the two straight lines covered by unrolled sample 1 is B1, the spacing between the two straight lines covered by unrolled sample 2 is B2, the spacing between the two straight lines covered by unrolled sample 3 is B3, the spacing between the two straight lines covered by unrolled sample 4 is B4, and the spacing between the two straight lines covered by unrolled sample 5 is B5.

[0059] It should be noted that the number of unrolled samples is not limited to the above 5, for example, it can also be 1, 2, 3, 4, 6 or more.

[0060] Preferably, n≥2. More preferably, n≥5.

[0061] In addition, it should be noted that, in practical applications, those skilled in the art preferably use an electronic scale to weigh the unrolled sample, wherein the accuracy of the electronic scale is preferably 0.0001 g.

[0062] In addition, it should be noted that in step S100, multiple straight lines can be formed on the surface of the pole piece according to a pre-set spacing, or multiple straight lines can be first formed on the surface of the pole piece and then the spacing between two straight lines is measured, etc. Such flexible adjustments and changes do not deviate from the principles and scope of the present invention and should be limited within the scope of protection of the present invention.

[0063] S300: Obtain n rolled samples of the electrode to be tested and weigh them.

[0064] There are n rolled samples corresponding to n unrolled samples one by one, the corresponding rolled samples and unrolled samples cover the same two straight lines, and the corresponding rolled samples and unrolled samples have the same area.

[0065] It should be pointed out that the rolled samples refer to the samples obtained by sampling the rolled pole pieces. The sampling positions of the rolled samples and the unrolled samples are corresponding, and the two corresponding rolled samples and the unrolled samples cover the same two straight lines.

[0066] For example, Figure 3 As shown, Figure 3The pole piece 1 shown is the pole piece to be tested after rolling. The number of rolled samples is the same as that of unrolled samples, which is also 5. From front to back, they are rolled sample 1, rolled sample 2, rolled sample 3, rolled sample 4 and rolled sample 5. The weights of rolled sample 1, rolled sample 2, rolled sample 3, rolled sample 4 and rolled sample 5 are a1, a2, a3, a4 and a5 respectively. Among them, rolled sample 1, rolled sample 2, rolled sample 3, rolled sample 4 and rolled sample 5 correspond to unrolled sample 1, unrolled sample 2, unrolled sample 3, unrolled sample 4 and unrolled sample 5 respectively.

[0067] It should be noted that, similar to the weighing of the unrolled sample, those skilled in the art in the art in practical applications preferably use an electronic scale to weigh the rolled sample, wherein the accuracy of the electronic scale is preferably 0.0001 g.

[0068] The number of the rolled samples is the same as the number of the unrolled samples, and the area of ​​the rolled samples is the same as the area of ​​the unrolled samples.

[0069] In order to ensure that the area of ​​the rolled sample is the same as that of the unrolled sample, it is preferred to use a sampler for sampling, and the unrolled sample and the rolled sample are sampled using the same sampler.

[0070] In addition, it should be noted that the order of steps S200 and S300 is not fixed. In actual applications, those skilled in the art may first execute step S300 and then execute step S200, that is, first obtain n rolled samples and weigh them, and then obtain n unrolled samples and weigh them. Such flexible adjustments and changes do not deviate from the principle and scope of the present invention and should be limited within the scope of protection of the present invention.

[0071] S400: Measure the distance between two straight lines covered by the sample after rolling.

[0072] After the pole piece 1 is rolled, the spacing between the straight lines 2 will become larger, and it is necessary to measure the spacing between the plurality of straight lines 2 on the pole piece 1 after rolling, wherein the measurement accuracy is preferably 0.01 mm.

[0073] It should be noted that the order of steps S300 and S400 is not fixed. In actual applications, those skilled in the art may first execute step S400 and then step S300, that is, first measure the distance between the straight lines at the sampling positions, and then sample and weigh the samples after rolling. Such flexible adjustments and changes do not deviate from the principle and scope of the present invention and should be limited within the protection scope of the present invention.

[0074] S500: Obtain the weight loss of each rolled sample relative to the corresponding non-rolled sample.

[0075] After obtaining the weight of the unrolled sample and the weight of the rolled sample, it is also necessary to obtain the weight loss of the rolled sample relative to the unrolled sample. The rolled sample and the unrolled sample are two samples covering the same two straight lines.

[0076] For example, Figure 2 and Figure 3 As shown, the rolled sample 1 and the unrolled sample 1 cover two identical straight lines, and the weight loss of the rolled sample 1 relative to the unrolled sample 1 is calculated as Δ1=A1-a1. Similarly, it is also necessary to calculate the weight loss of the rolled sample 2 relative to the unrolled sample 2 as Δ2=A2-a2, the weight loss of the rolled sample 3 relative to the unrolled sample 3 as Δ3=A3-a3, the weight loss of the rolled sample 4 relative to the unrolled sample 4 as Δ4=A4-a4, and the weight loss of the rolled sample 5 relative to the unrolled sample 5 as Δ5=A5-a5.

[0077] S600: According to the obtained multiple weight loss amounts, discard the rolled samples whose weight loss amounts do not meet the preset conditions and the corresponding non-rolled samples.

[0078] After obtaining the weight loss of each rolled sample relative to the unrolled sample, it is necessary to determine whether the weight loss of each rolled sample relative to the unrolled sample meets the preset conditions. If the preset conditions are not met, the samples that do not meet the preset conditions need to be discarded, that is, they will not be involved in the calculation of the longitudinal elongation of the electrode.

[0079] By discarding samples whose weight loss does not meet the preset conditions, the influence of the surface density fluctuation of the pole piece and the thickness fluctuation after rolling can be effectively avoided, thereby improving the accuracy of the measurement of the longitudinal elongation of the pole piece.

[0080] For example, if the weight loss Δ1 of the rolled sample 1 relative to the unrolled sample 1 does not meet the preset condition, the rolled sample 1 and the unrolled sample 1 are discarded and do not participate in the subsequent calculation of the elongation.

[0081] It should be noted that the present invention does not limit the specific content of the preset conditions, and those skilled in the art can flexibly set them in practical applications, as long as the setting of the preset conditions can effectively avoid the influence of the pole piece surface density fluctuation and the thickness fluctuation after rolling.

[0082] Regarding step S600, two preferred examples are described below.

[0083] Preferred example 1, the step of "discarding the rolled samples and the corresponding non-rolled samples whose weight loss amounts do not meet the preset conditions according to the multiple weight loss amounts obtained" specifically includes: discarding the rolled samples and the non-rolled samples corresponding to the weight loss amounts that are different from the rest of the weight loss amounts among the multiple weight loss amounts.

[0084] Among the multiple weight loss amounts obtained, there are weight loss amounts with the same values. When one or several weight loss amounts are different from the rest, it means that the weight loss amounts of the corresponding samples fluctuate. By discarding the corresponding samples, the influence of the fluctuation of the pole piece surface density and the fluctuation of the thickness after rolling can be effectively avoided, thereby improving the accuracy of the measurement of the longitudinal elongation of the pole piece.

[0085] Taking the above-mentioned example in which the number of unrolled samples and rolled samples are both 5, after calculation, the values ​​of Δ2, Δ3, Δ4 and Δ5 are the same, and only the value of Δ1 is different from the other four. In this case, the rolled sample 1 and the unrolled sample 1 are discarded and do not participate in the subsequent calculations.

[0086] It should be noted that if there are multiple groups of identical values, for example, if the values ​​of Δ1 and Δ2 are the same, and the values ​​of Δ3, Δ4 and Δ5 are all the same, then the samples corresponding to Δ1 and Δ2 will be discarded, that is, the samples with a smaller number will be discarded.

[0087] Preferred Example 2, step S600, the step of "discarding the rolled samples whose weight loss does not meet the preset conditions and the corresponding unrolled samples according to the obtained multiple weight loss amounts" specifically includes:

[0088] S610: Calculate the difference between every two weight loss amounts in the plurality of weight loss amounts;

[0089] S620: Compare the difference with a preset value;

[0090] S630: If the difference is greater than a preset value, the corresponding rolled samples and unrolled samples are discarded.

[0091] When the difference between the two weight loss amounts is greater than the preset value, it means that the weight loss amounts of the corresponding two groups of samples fluctuate greatly. By discarding the corresponding samples, the influence of the surface density fluctuation of the pole piece and the thickness fluctuation after rolling can be effectively avoided, thereby improving the accuracy of the measurement of the longitudinal elongation rate of the pole piece.

[0092] Taking the above-mentioned example in which the number of unrolled samples and rolled samples is 5, where the preset value is 0.0002g, after calculation and comparison, only the difference between Δ1 and Δ2 = |Δ1-Δ2|>0.0002g, and the differences between the remaining weight loss amounts are no more than 0.0002g. In this case, rolled sample 1, unrolled sample 1, rolled sample 2 and unrolled sample 2 are discarded and do not participate in subsequent calculations.

[0093] It should be noted that the preset value of the present invention is not limited to the above-mentioned 0.0002g. For example, the preset value can also be set to 0.0001g or 0.0003g, etc. Those skilled in the art can flexibly set the specific numerical value of the preset value based on experiments or experience in actual applications.

[0094] In addition, it should be noted that, in actual applications, those skilled in the art can flexibly select the above-mentioned preferred example 1 and preferred example 2 according to actual conditions. For example, when the weight loss amounts with the same numerical value account for a large proportion, preferred example 1 can be used, otherwise, preferred example 2 can be used.

[0095] S700: Calculate the longitudinal elongation of the pole piece = comprehensive elongation - transverse elongation.

[0096] Among them, the comprehensive elongation of the pole piece is calculated based on the weight of the unrolled sample and the number of rolled samples, and the lateral elongation of the pole piece is calculated based on the spacing between the two straight lines covered by the unrolled sample and the spacing between the two straight lines covered by the rolled sample.

[0097] The comprehensive elongation of the pole piece = [(A1-a1) / a1+(A2-a2) / a2+...+(A n-1 -a n-1 ) / a n-1 +(A n -a n ) / a n ] / n, where A is the weight of the sample before rolling and a is the weight of the sample after rolling.

[0098] Transverse extension rate of pole piece = [(b1-B1) / b1+(b2-B2) / b2+...+(b n-1 -B n-1 ) / b n-1 +(b n -B n ) / b n ] / n, where B is the distance between the two straight lines covered by the unrolled sample, and b is the distance between the two straight lines covered by the rolled sample.

[0099] That is, the longitudinal extension rate of the pole piece = [(A1-a1) / a1+(A2-a2) / a2+...+(A n-1 -a n-1 ) / a n-1 +(A n -a n ) / a n ] / n-[(b1-B1) / b1+(b2-B2) / b2+...+(b n-1 -B n-1 ) / b n-1 +(b n -B n ) / b n ] / n.

[0100] That is to say, the longitudinal elongation of the pole piece = comprehensive elongation - transverse elongation, wherein the comprehensive elongation is calculated based on the weight change between the rolled sample and the unrolled sample, and the transverse elongation is calculated based on the change in the spacing between the two straight lines covered by the sample.

[0101] Taking the above-mentioned example in which the number of unrolled samples and rolled samples are both 5, and after calculation and comparison, it is determined that the 5 weight loss amounts all meet the preset conditions, then the longitudinal extension rate of the electrode = [(A1-a1) / a1+(A2-a2) / a2+(A3-a3) / a3+(A4-a4) / a4+(A5-a5) / a5] / 5-[(b1-B1) / b1+(b2-B2) / b2+(b3-B3) / b3+(b4-B4) / b4+(b5-B5) / b5] / 5.

[0102] It should be noted that the above steps S500 and S600 are not necessary. In some less preferred embodiments, those skilled in the art may cancel steps S500 and S600 in actual applications. Of course, the present invention preferably retains steps S500 and S600 to improve the accuracy of elongation measurement.

[0103] In a first preferred example, when rolled samples and unrolled samples are discarded, the measuring method of the present invention further comprises: resampling the pole piece at positions corresponding to the discarded rolled samples and unrolled samples.

[0104] That is, according to the determination in step S600 , some rolled samples and some unrolled samples are discarded. In this case, re-sampling is required.

[0105] Exemplarily, if the weight loss of the rolled sample 1 and the unrolled sample 1 does not meet the preset condition, the rolled sample 1 and the unrolled sample 1 are discarded, such as Figure 2 and Figure 3As shown, resampling is performed at the position corresponding to the unrolled sample 1, and the sample is the unrolled sample 6, whose weight is A6; resampling is performed at the position corresponding to the rolled sample 1, and the sample is the rolled sample 6, whose weight is a6.

[0106] That is, "re-sampling the pole piece at the position corresponding to the discarded rolled sample and the unrolled sample" means re-sampling the pole piece at the position covering the same two straight lines as the discarded rolled sample and the unrolled sample.

[0107] In a second preferred example, when the rolled samples and the unrolled samples are discarded, the measuring method of the present invention further comprises:

[0108] Compare the number of unrolled or rolled samples that are discarded with the number that can be discarded;

[0109] If the number of discarded unrolled samples or rolled samples is greater than the discardable number, the pole piece is resampled at the position corresponding to the discarded rolled samples and unrolled samples;

[0110] If the number of discarded unrolled samples or rolled samples is not greater than the discardable number, the pole piece will not be resampled.

[0111] That is to say, in this example, if some samples are discarded, it is not necessary to re-sampling. It is necessary to make a judgment based on the number of discarded samples. If the number of discarded unrolled samples or rolled samples is greater than the discardable number, it means that the number of discarded samples is relatively large, which may affect the accuracy of the elongation measurement. Therefore, re-sampling is required. On the contrary, if the number of discarded unrolled samples or rolled samples is not greater than the discardable number, it means that the number of discarded samples is relatively small, which will not affect the accuracy of the elongation measurement. Therefore, re-sampling is not required.

[0112] Exemplarily, according to the requirement, the number of unrolled samples for calculating the longitudinal elongation of the pole piece to be tested is not less than 5. When sampling is performed for the first time, the number of unrolled samples is 8, then 3 samples can be discarded. According to the judgment of step S600, if the number of discarded unrolled samples is 0, 1, 2 or 3, the pole piece will not be resampled. On the contrary, if the number of discarded unrolled samples is 4 or more, the pole piece needs to be resampled.

[0113] It should be noted that, when resampling is not required, the change in the spacing between the two straight lines covered by the discarded sample will no longer be involved in the calculation of the elongation. For example, if the rolled sample 1 and the unrolled sample 1 are discarded, B1 and b1 will no longer be involved in the calculation of the elongation.

[0114] Preferably, if Figure 2 As shown, the spacing between the two straight lines 2 covered by each unrolled sample is equal.

[0115] By setting the spacing between the two lines covered by the unrolled sample to the same value, it is easier to calculate the lateral extension of the pole piece.

[0116] Take the above-mentioned unrolled samples with 5 samples as an example. Figure 2 As shown, B1=B2=B3=B4=B5=10mm.

[0117] It should be noted that the distance between the two straight lines covered by the unrolled sample is not limited to the above 10 mm, for example, it can also be set to 8 mm, 9 mm, 11 mm or 12 mm, etc.

[0118] Preferably, if Figure 2 As shown, at least a portion of the plurality of unrolled samples are distributed along the width direction of the pole piece 1 .

[0119] More preferably, if Figure 2 As shown, a plurality of unrolled samples are distributed along the width direction of the pole piece 1 .

[0120] A plurality of unrolled samples are distributed along the width direction of the pole piece 1 , and correspondingly, a plurality of rolled samples are also distributed along the width direction of the pole piece 1 .

[0121] Distributing the samples along the width direction of the pole piece is helpful to improve the accuracy of elongation measurement.

[0122] Preferably, if Figure 2 As shown, the line width of the straight line 2 on the pole piece 1 is not greater than 0.1 mm.

[0123] The smaller the line width of the straight line 2 is, the more conducive it is to reducing the measurement error, thereby being more conducive to improving the accuracy of the elongation measurement.

[0124] For example, the width of the straight line 2 can be set to 0.005 mm, 0.008 mm, 0.01 mm, 0.02 mm, 0.05 mm, 0.08 mm or 0.1 mm. Further preferably, the line width of the straight line 2 on the pole piece 1 is not greater than 0.01 mm.

[0125] Preferably, if Figure 2 and Figure 3 As shown, the shapes of the unrolled sample and the rolled sample of the present invention are circular.

[0126] That is, those skilled in the art can use a sampler with a circular cross-section for sampling in practical applications.

[0127] Of course, those skilled in the art may also set the shapes of the unrolled samples and the rolled samples to be rectangular in practical applications, that is, use a sampler with a rectangular cross-section for sampling.

[0128] Those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the claims of the present application, any one of the claimed embodiments may be used in any combination.

[0129] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for measuring the longitudinal elongation of a pole piece, characterized in that: The measuring method comprises the following steps: A plurality of straight lines extending along the length direction of the electrode piece to be tested are formed on the surface of the electrode piece to be tested, wherein the plurality of straight lines are spaced and parallel along the width direction of the electrode piece to be tested; Obtain n unrolled samples of the electrode to be tested and weigh them, wherein each of the unrolled samples covers two of the straight lines, and n is a positive integer; Obtaining n rolled samples of the electrode to be tested and weighing them, wherein the n rolled samples correspond to the n unrolled samples one by one, and the corresponding rolled samples and the unrolled samples cover the same two straight lines and have the same area; measuring the distance between the two straight lines covered by the sample after rolling; Calculate the longitudinal elongation of the electrode to be tested = comprehensive elongation - transverse elongation; Wherein, the comprehensive elongation is calculated based on the weight of the unrolled sample and the weight of the rolled sample, and the lateral elongation is calculated based on the spacing between the two straight lines covered by the unrolled sample and the spacing between the two straight lines covered by the rolled sample.

2. The method for measuring the longitudinal elongation of a pole piece according to claim 1, characterized in that: The measuring method further comprises: Obtaining the weight loss of each of the rolled samples relative to the corresponding non-rolled sample; According to the obtained multiple weight loss amounts, discard the rolled samples whose weight loss amounts do not meet the preset conditions and the corresponding unrolled samples; The discarded rolled samples and the unrolled samples do not participate in the calculation of the longitudinal elongation.

3. The method for measuring the longitudinal extension rate of a pole piece according to claim 2, characterized in that: The step of "discarding the rolled samples whose weight loss does not meet the preset conditions and the corresponding unrolled samples according to the obtained multiple weight loss amounts" specifically includes: The rolled samples and the unrolled samples corresponding to the weight loss amounts different from the remaining weight loss amounts among the plurality of weight loss amounts are discarded.

4. The method for measuring the longitudinal extension rate of a pole piece according to claim 2, characterized in that: The step of "discarding the rolled samples whose weight loss does not meet the preset conditions and the corresponding unrolled samples according to the obtained multiple weight loss amounts" specifically includes: calculating a difference between every two of the weight loss amounts in the plurality of weight loss amounts; comparing the difference with a preset value; If the difference is greater than the preset value, the corresponding rolled sample and the unrolled sample are discarded.

5. The method for measuring the longitudinal elongation of a pole piece according to claim 2, characterized in that: In the case where the rolled sample and the unrolled sample are discarded, the measuring method further comprises: The electrode to be tested is sampled again at the position corresponding to the discarded rolled sample and the unrolled sample.

6. The method for measuring the longitudinal extension rate of a pole piece according to claim 2, characterized in that: In the case where the rolled sample and the unrolled sample are discarded, the measuring method further comprises: comparing the number of the discarded unrolled samples or the rolled samples with the discardable number; If the number of the discarded unrolled samples or the rolled samples is greater than the discardable number, resampling the electrode to be tested at the positions corresponding to the discarded rolled samples and the unrolled samples; If the number of the discarded unrolled samples or the rolled samples is not greater than the discardable number, the electrode to be tested will not be sampled again.

7. The method for measuring the longitudinal elongation of a pole piece according to claim 1, characterized in that: The spacing between the two straight lines covered by each of the unrolled samples is equal.

8. The method for measuring the longitudinal extension rate of a pole piece according to claim 1, characterized in that: n≥2。 9. The method for measuring the longitudinal elongation of a pole piece according to claim 1, characterized in that: At least a portion of the plurality of unrolled samples are distributed along the width direction of the electrode piece to be tested.

10. The method for measuring the longitudinal elongation of a pole piece according to any one of claims 1 to 9, characterized in that: The shapes of the unrolled sample and the rolled sample are circular or rectangular; and / or The line width of the straight line is no greater than 0.1 mm.

Images