MAGNETIC FORCE DILATOMETRE

Abstract

A dilatometer (110) configured to measure the dilation of an electrode in a battery (20), the dilatometer (110) comprising: a first holder (114) configured to support the battery (20); a magnet (40) positioned adjacent to the first holder (114); a magnetic force sensor (120) configured to measure the strength of the magnetic force between the magnet (40) and a magnetic spacer within the battery (20) supported by the first holder (114); a second holder (122) configured to move the magnet (40) relative to the magnetic spacer of the battery (20) supported by the first holder (114);and a controller (50) configured to: receive calibration force measurements (510) from the magnetic force sensor (120), wherein the calibration force measurements (510) comprise the strength of the magnetic force between the magnet (40) and the magnetic spacer at various calibration distances resulting from the movement of the magnet (40) relative to the magnetic spacer over a distance range during calibration; assign a position value to each of the calibration force measurements (510), wherein the position value is a distance between the magnet (40) and the magnetic spacer of the battery (20); predict the strength of the magnetic force between the magnet (40) and the magnetic spacer over the entire distance range based on the position values ​​of the and perform a dynamic time distortion (DTW) on the calibration force measurements (510);Normalizing the calibration force measurements (510) to normalized calibration data (550) and creating an idealized calibration pattern (610) based on the calibration force measurements (510); basis of the calibration force measurements (510), the normalized calibration data (550) and the idealized calibration pattern (610).;

Description

INTRODUCTION The present disclosure relates to a magnetic force dilatometer. A battery pack comprises one or more battery modules, each containing a number of battery cells. The battery cells undergo expansion as the battery is charged and discharged. During charging and discharging, chemical reactions within the battery cells cause the anode or cathode electrodes to expand or contract. Monitoring the expansion of the battery cells is useful for preventing electrode drying, improving battery cell lifespan, developing battery cells, estimating energy density, and / or designing battery modules and battery packs. DE 10 2023 120 823 A1 discloses a system for measuring battery expansion and comprises a battery cell, a magnet, and a magnetic force sensor. The strength of the magnetic force between the magnet and the magnetic force sensor changes as the battery cell expands. The magnetic force sensor detects this change in the strength of the magnetic force between the magnet and the magnetic force sensor. A control module connected to the magnetic force sensor measures the degree of expansion of the battery cell based on the change in the strength of the magnetic force between the magnet and the magnetic force sensor. Further state of the art is described in DE 10 2021 212 386 A1, DE 10 2017 215 144 A1 and DE 10 2021 202 154 A1. The object of the invention is to create a dilatometer with which it is possible to improve the calibration of the dilatometer in such a way that a reliable measurement of the dilation of an electrode in a battery is always guaranteed. The problem is solved by the subject matter of claim 1. Advantageous embodiments of the invention are described in the dependent claims. SUMMARY The present disclosure comprises, in various features, a dilatometer configured to measure the dilation of an electrode in a battery. The dilatometer comprises: a first holder configured to support the battery; a magnet attached adjacent to the first holder; a magnetic force sensor configured to measure the strength of the magnetic force between the magnet and a magnetic spacer within the battery supported by the first holder; a second holder configured to move the magnet relative to the magnetic spacer of the battery supported by the first holder; and a controller.The controller is configured to: receive calibration force readings from the magnetic force sensor, wherein the calibration force readings comprise the strength of the magnetic force between the magnet and the magnetic spacer at various calibration distances resulting from the movement of the magnet relative to the magnetic spacer over a distance range during calibration; assign a position value to each of the calibration force readings, wherein the position value is a distance between the magnet and the battery's magnetic spacer; and predict the strength of the magnetic force between the magnet and the magnetic spacer over the entire distance range based on the position values ​​of the calibration force readings. In other respects, the battery is a button cell battery. Other features include different calibration distances in intervals of 10 µm. Other features include different calibration distances in intervals of 50 µm. In other respects, the calibration force measurements include multiple measurements at each of the different calibration distances. In other characteristics, the spacing range is 250 µm. In other respects, the magnetic force sensor is a load sensor. In further features, a sliding table is configured to move the second holder and the magnet relative to the first holder and the magnetic spacer of the battery supported by the first holder. In other features, the controller is configured to: normalize the calibration force measurements to normalized calibration data and create an idealized calibration pattern based on the calibration force measurements; and perform dynamic time warping (DTW) based on the calibration force measurements, the normalized calibration data, and the idealized calibration pattern. In other features, the controller is configured to further process the calibration force measurements by truncating or clipping the calibration force measurements based on the DTW and removing noise from the calibration force measurements. Further features include the assignment of the position value to each of the calibration force measurements, the arrangement of the calibration force measurements into groups, and the identification or labeling of the groups with the position values. In other features, the controller is configured to predict the strength of the magnetic force between the magnet and the magnetic spacer over the entire distance range by performing a linear regression over the groups. The present disclosure further comprises, in various features, a dilatometer configured to measure the dilation of an electrode in a battery. The dilatometer comprises: a first holder configured to support the battery; a magnet attached adjacent to the first holder; a magnetic force sensor configured to measure the strength of the magnetic force between the magnet and a magnetic spacer within the battery supported by the first holder; a second holder configured to move the magnet relative to the magnetic spacer of the battery supported by the first holder;and a controller. The controller is configured to: receive calibration force readings from the magnetic force sensor, where the calibration force readings comprise the strength of the magnetic force between the magnet and the magnetic spacer at various calibration distances resulting from the movement of the magnet relative to the magnetic spacer over a distance range during calibration; normalize the calibration force readings to normalized calibration data; create an idealized calibration pattern based on the calibration force readings; perform a dynamic time distortion based on the calibration force readings, the normalized calibration data, and the idealized calibration pattern to identify irrelevant parts of the calibration force readings;Assigning a position value to each of the calibration force measurements, wherein the position value is a distance between the magnet and the magnetic spacer of the battery; predicting the strength of the magnetic force between the magnet and the magnetic spacer over the entire distance range based on the position values ​​of the calibration force measurements; receiving a battery test force measurement from the magnetic force sensor, wherein the battery test force measurement contains the strength of the magnetic force between the magnet and the magnetic spacer of the battery during a battery dilation test; and identifying a dilation distance within the distance range that corresponds to the battery test force measurement, wherein the dilation distance corresponds to the dilation of the electrode in the battery. Further features include the assignment of the position value to each of the calibration force measurements, the arrangement of the calibration force measurements into groups, and the identification or labeling of the groups with the position values. In other features, the controller is configured to predict the strength of the magnetic force between the magnet and the magnetic spacer over the entire distance range by performing a linear regression over the groups. The present disclosure also includes, in various features, a method for measuring the dilation of an electrode in a battery using a dilatometer. The method comprises: receiving calibration force measurements at a controller of the dilatometer from a magnetic force sensor of the dilatometer, wherein the calibration force measurements comprise the strength of the magnetic force between a magnet of the magnetic force sensor and a magnetic spacer of the battery at various calibration distances resulting from the movement of the magnet relative to the magnetic spacer over a distance range during calibration; assigning a position value to each of the calibration force measurements using the controller, wherein the position value is a distance between the magnet and the magnetic spacer of the battery;Predicting the strength of the magnetic force between the magnet and the magnetic spacer over the entire distance range based on the position values ​​of the calibration force measurements with the controller; receiving a battery test force measurement from the magnetic force sensor on the controller, wherein the battery test force measurement contains the strength of the magnetic force between the magnet and the magnetic spacer of the battery during a battery dilation test; and identifying a dilation distance within the distance range corresponding to the battery test force measurement with the controller, wherein the dilation distance corresponds to a dilation of the electrode in the battery. The procedure further includes: normalizing the calibration force measurements with the controller to normalized calibration data and creating an idealized calibration pattern with the controller based on the calibration force measurements; and performing a dynamic time distortion with the controller based on the calibration force measurements, the normalized calibration data and the idealized calibration pattern. The procedure further includes assigning the position value to the individual calibration force measurements with the controller, including arranging the calibration force measurements into groups and labeling the groups with the position values ​​with the controller. The method also includes predicting the strength of the magnetic force between the magnet and the magnetic spacer over the entire distance range by performing a linear regression over the groups with the controller. Further applications of this disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and specific examples serve only for illustration and are not intended to limit the scope of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure will become more fully apparent from the detailed description and the accompanying drawings, wherein: Fig. 1A and Fig. 1B are side views of an example of a magnetic force dilatometer (MFD) for measuring the dilation of a battery cell according to the present disclosure; Fig. 2, Fig. 3 to Fig. 4 are side views of other examples of MFDs for measuring the dilation of a battery cell according to the present disclosure; Fig. 5 is a top view of another example of an MFD for measuring the dilation of a battery cell according to the present disclosure; Fig. 6 is a side view of the MFD of Fig. 5; Fig. 7 is a perspective side view of the MFD of Fig. 5; Fig. 8 is a cross-sectional view of the MFD of Fig. 5; Fig. 9 is a side view of an MFD for measuring the dilation of a pouch cell battery according to the present disclosure; Fig. 10 and Fig.Figure 11 shows side views of MFDs for measuring the dilation of a battery with prismatic cells according to the present disclosure; Figure 12 is a flowchart of an exemplary algorithm according to the present disclosure for calibrating an MFD and measuring the dilation of a battery with the MFD; Figure 13 is a graph showing the calibration force measurements of a force transducer that identifies the strength of the magnetic force between a magnet of the MFD and a magnetic spacer of a battery for a variety of samples at different calibration distances; Figure 14 is a graph showing the data from Figure 13, with the calibration force measurements normalized; Figure 15 is a graph of an idealized calibration pattern for the calibration force measurements; Figure 16 is a graph of the calibration force measurements ordered and labeled according to the strength of the magnetic force; FigureFigure 17 is a graph of the force transducer value as a function of the distance between the dilatometer magnet and the magnetic spacer of a battery, on which the calibration force measurements are plotted; and Figure 18 is a graph similar to that of Figure 17, wherein the graph of Figure 18 also includes the slope of the calibration force measurements. Reference numbers can be reused in the drawings to designate similar and / or identical elements. DETAILED DESCRIPTION Battery cells, such as lithium-ion batteries (LIBs), undergo reversible and irreversible expansion or dilation during cycle operation. A thorough understanding of battery cell expansion or dilation can be used to prevent electrode drying, improve battery cell lifetime, develop battery cells, estimate energy density, and / or design a battery pack. With next-generation anode materials, such as silicon, battery cell expansion or dilation is a much greater concern, as some electrode materials experience a volume change of approximately 300% during cycle operation. The present disclosure relates to a magnetic force dilatometer (MFD) configured to measure the dilation of battery cells during cycle operation. In DE 10 2023 120 823 A1, an MFD is configured to measure the dilation of battery cells during cycle operation. According to the present disclosure, a calibration process for an MFD comprises measuring various calibration forces of a magnetic force sensor at different calibration distances between a magnet of the MFD and a magnetic spacer of the battery under test. For this purpose, the magnet of the MFD is often manually moved to different positions, and several measurements of the magnetic force sensor are recorded at each distance. The calibration force measurements are used to create a graph of the magnetic force measured by the magnetic force sensor as a function of the distance between the dilatometer magnet and the magnetic spacer of the battery. Changes in the strength of the magnetic force correspond to changes in the distance, which in turn correspond to a degree of expansion of an electrode in the battery under test.As described herein, the controller of the present disclosure is configured to automate various aspects of calibration and testing. Figures 1A and 1B show an MFD 10 for measuring battery dilation. The MFD 10 contains a battery cell 20 (e.g., a lithium-ion battery cell). The battery cell 20 comprises a housing 22 that encloses one or more sets of first electrodes 24, second electrodes 26, and separators 28. A magnetic spacer 30 is arranged next to the second electrode 26. The magnetic spacer 30 (e.g., a permanent magnet, an electromagnet, or a ferromagnetic material) is arranged such that it moves within the housing 22 when the first electrode 24 or the second electrode 26 expands during the dilation of the battery cell 20. A preload element 32 (e.g., a spring) is arranged between the magnetic spacer 30 and an inner surface of the housing 22. The preload element 32 holds the magnetic spacer 30 against the second electrode 26 and is flexible to accommodate the movement of the magnetic spacer 30 when the first electrode 24 and / or the second electrode 26 expand during dilation. The MFD 10 further comprises an external magnet 40, which is arranged outside the housing 22 of the battery cell 20 and at a distance from the housing 22. The external magnet 40 can be a hemispherical magnet, a spherical magnet, a conical magnet, a cylindrical magnet, a square magnet, a rectangular magnet, or any other suitable magnet. The external magnet 40 and the magnetic spacer 30 are arranged within each other's magnetic fields. The MFD 10 also includes a sensor 42 configured to measure the strength of the magnetic force between the external magnet 40 and the magnetic spacer 30. The sensor 42 can be any suitable force sensor, such as a load cell sensor, a strain gauge sensor, a pressure sensor, etc. In some applications, the external magnet 40 and the sensor 42 can be replaced by a Hall sensor, a magnetometer, a fluxgate sensor (or Earth magnetic field detector), a superconducting quantum interference device (SQUID), a resonant sensor, an induction magnetometer, a reed contact sensor, a Wiegand wire sensor, or a magnetic force sensor. A controller 50 communicates with the sensor 42. The controller 50 is configured to determine the dilation of the battery cell 20 based on changes in the strength of the magnetic force between the external magnet 40 and the magnetic spacer 30. The change in dilation occurs, for example, in response to the expansion of the first electrode 24 and / or the second electrode 26. This expansion or dilation causes a movement of the magnetic spacer 30 relative to the external magnet 40. In Fig. 1A, the battery cell 20 is shown in an unstretched state, with the external magnet 40 positioned at a distance d1 from the magnetic spacer 30. The second electrode 26 has a thickness t1. In Fig. 1B, the battery cell 20 is shown in a stretched state. The thickness of the second electrode 26 increased from t1 to t2. As the thickness of the second electrode 26 (and / or the first electrode 24) increases, the magnetic spacer 30 moves further away from the external magnet 40. In the unstretched state of Fig. 1A, for example, the magnetic spacer 30 is positioned at a distance d1 from the external magnet 40. In the stretched state of Fig. 1B, the second electrode 26 is positioned at a distance d2 from the external magnet 40, which is greater than the distance d1. At distance d2, the magnetic attraction between the external magnet 40 and the magnetic spacer 30 is less than at distance d1. In some examples, the controller 50 uses one or more formulas that relate the dilation to the force transducer measurement and / or the temperature. In other examples, the controller 50 includes a memory containing a first calibration table, which stores the dilation as a function of the force transducer measurement, and a second calibration table, which stores dilation compensation values ​​as a function of the temperature. The first calibration table contains the known strength of the magnetic force between the external magnet 40 and the magnetic spacer 30 at various distances d (see, for example, graph 750 in Fig. 18). The second calibration table stores the dilation compensation values ​​at different temperatures.In some examples, the first and second calibration tables are combined into a single table, indexed by the load cell measurement and the measured temperature and / or strain, which is a function of temperature. Using the first and / or the second calibration table, the controller 50 determines the distance d2 between the external magnet 40 and the second electrode 26, which corresponds to the magnetic strength measured by the sensor 42 and compensated for by the measured temperature. The distance d2 corresponds to the expansion of the second electrode 26 (and / or the first electrode 24). The dilation data can be used for a variety of purposes. For example, knowing the extent to which battery cell 20 has expanded after a certain number of charge / discharge cycles and / or under different conditions can be useful for developing batteries that are less susceptible to electrode drying and have a longer lifespan. The information can also be used in the design of the battery cells, the estimation of energy density, and the development of various battery modules and packs. An example calibration procedure is explained in more detail below. As shown in Fig. 2, the sensor 42 is arranged between the external magnet 40 and the housing 22. The sensor 42 is in direct contact with the housing 22 and detects a pressure sensor. In Figures 3 and 4, the sensor 42 comprises a magnetic sensor. In some examples, the sensor 42 is selected from a group consisting of a Hall sensor, a magnetic resistance sensor, a fluxgate sensor or Earth magnetic field detector, a sensor with a superconducting quantum interference device (SQUID), a resonant sensor, an induction magnetometer, a reed contact sensor, a Wiegand wire sensor, and / or a magnetic force sensor. The sensor 42 is spaced apart from the housing 22. In Fig. 4, the positions of the sensor 42 and the magnetic spacer 30 are reversed. The sensor 42 is arranged inside the housing 22 between the second electrode 26 and the preload element 32, and the magnetic spacer 30 is arranged outside the housing 22 at a distance from or in contact with the housing 22. Figures 5-8 show another dilatometer 110 according to the present disclosure, configured to measure the dilation with temperature compensation of each suitable battery cell during charging and discharging. For example, the dilatometer 110 is configured to measure the dilation of battery cell 20 from Figures 1A, 1B, 2, 3, and 4 in real time. The dilatometer 110 comprises a frame 112 (e.g., a base plate) and a battery cell holder 114 attached to the frame 112. The battery cell holder 114 is configured to accommodate a button cell battery or any other suitable type of battery cell. Leads are connected to the battery cell 20 for charging and discharging. A sliding table 116 is attached to the battery cell holder 114 to support a load cell 120. The load cell 120 can be any suitable load cell, such as a miniature S-Bear Jr. load cell 2.0 (model LSB201) from Futek Advanced Sensor Technology, Inc., of Irvine, CA. The dilatometer 110 includes a micrometer 130 for adjusting the vertical height of the sliding table 116 and for adjusting the vertical position of the load cell 120 mounted on the sliding table 116. A magnet holder 122 is arranged on the load cell 120, serving to hold the external magnet 40. In this example, the external magnet 40 comprises a spherical magnet (e.g., Fig. 8). As can be seen, the magnet holder 122 can be configured to hold external magnets with other suitable shapes. The battery cell 20 is held in the battery cell holder 114 between the external magnet 40 and a compression element 124, which holds the battery cell 20 in position. Figure 9 shows a system 210 for measuring the battery expansion of a pouch cell battery 212. The pouch cell battery 212 includes battery terminals 214 and is mounted on a stationary plate 216. The pouch cell battery 212 is located between the stationary plate 216 and a magnet in the form of a floating compression plate 218. The compression plate 218 can be made of any suitable magnetic material (e.g., steel) or may have a magnet or magnetic material embedded in or attached to a surface of the compression plate 218. The compression plate 218 is mounted on supports 220. Opposite the compression plate 218 is a sensor 230 configured to measure the magnetic force, e.g., a magnetic field sensor or a load cell (e.g., the load cell 120).The sensor 230 is mounted on a stationary plate 232, thus rendering the sensor 230 stationary. The sensor 230 communicates with the controller 50. The stationary plate 232 is mounted on the supports 220 and secured in position by fasteners 234. Springs 236 are located between the stationary plate 232 and the compression plate 218 to allow movement of the compression plate 218 during expansion. A sensor 180, e.g., a temperature or strain sensor, measures the temperature or strain (and derives the temperature from the strain). As the pouch cell battery 212 expands during dilation, the distance d1 between the sensor 230 and the compression plate 218 decreases, and the strength of the magnetic field between the compression plate 218 and the sensor 230 changes. The controller 50 is configured to measure the degree of dilation of the pouch cell battery 212 based on the change in the strength of the magnetic force between the compression plate 218 and the sensor 230. The system 210 can be calibrated according to the present disclosure, but modified so that the distance d1 decreases during dilation instead of increasing. The system 210 can be calibrated in any other suitable way that correlates a measured magnetic field strength between the compression plate 218 and the sensor 230 with the degree of dilation of the pouch cell 212. Figure 10 shows a system 310A for measuring the battery expansion of a battery 312 with prismatic cells. The battery 312 with prismatic cells includes a battery terminal 314 and is attached to a stationary plate 316. A magnet 320 is attached to the battery 312 with prismatic cells. Supports 322 extend from the plate 316 and have brackets 330. The brackets 330 hold the battery 312 with prismatic cells to the plate 316. During expansion, the battery 312 with prismatic cells expands, causing the magnet 320 to move towards a sensor 340, which is attached to a stationary plate 342. The stationary plate 342 is rigidly attached to the supports 322 by fasteners 350. The sensor 340 is in communication link with the controller 50. Sensor 340 is configured to detect magnetic force. Sensor 340 can be, for example, a magnetic field sensor or a force transducer (e.g., force transducer 120). As the battery 312 with prismatic cells expands during dilation, the distance d1 between magnet 320 and sensor 340 decreases, and the strength of the magnetic field between magnet 320 and sensor 340 changes. Controller 50 is configured to measure the degree of dilation of battery 312 with prismatic cells based on the change in the strength of the magnetic force between magnet 320 and sensor 340. System 310A is calibrated according to the present disclosure and modified to take into account the decreasing, rather than increasing, distance d1 during dilation. Alternatively, system 310A can be calibrated in any other suitable manner that correlates a measured magnetic field strength between magnet 320 and sensor 340 with the degree of dilation of battery 312 with prismatic cells. System 310B of Fig. 11 is similar to system 310A of Fig. 8. In system 310B, the battery 312 with prismatic cells is positioned so that it can expand on two opposite sides during dilation, for example, on the top and bottom (or the front and back). To measure the expansion on both sides, a magnet 320A is located on one side of the battery 312 with prismatic cells, and a magnet 320B is located on the opposite side. A sensor 340A is located opposite magnet 320A. A sensor 340B is located opposite magnet 320B. Sensor 340A measures changes in the strength of the magnetic force of magnet 320A. Sensor 340B measures changes in the strength of the magnetic force of magnet 320B. System 310B is calibrated and modified according to the present disclosure such that the distances d1 decrease during dilation instead of increasing. Alternatively, System 310B can be calibrated in any other suitable manner that correlates the measured magnetic field strength between magnet 320A and sensor 340A and / or between magnet 320B and sensor 340B with the degree of dilation of battery 312 with prismatic cells. Fig. 12 shows an exemplary calibration procedure 410 according to the present disclosure. The controller 50 is configured to perform the calibration procedure 410. The procedure 410 is described here only by way of example in connection with the operation of the dilatometer 110. The procedure 410 can be performed with any other suitable dilatometer, such as any of the other dilatometers and systems 10, 210 and 310A / 310B of the present disclosure. Procedure 410 begins in block 412, and in block 414, calibration data is imported into the controller 50. An example of calibration data is shown in graph 510 in Fig. 13. The calibration data comprises a variety of calibration force measurements acquired by sensor 42, representing the strength of the magnetic force between magnet 40 and magnetic spacer 30. The calibration force measurements are performed at different calibration distances between magnet 40 and magnetic spacer 30. For example, and with reference to Fig. 13, seven groups 512A–512G of calibration force measurements can be performed at seven different calibration distances. The calibration distances can be arranged at any suitable interval over a distance range of any length. The interval can be, for example, 50 µm over a distance range of 300 µm. More precisely, the first group 512A of calibration force measurements can be taken at a base distance of the distance range where the strength of the magnetic force between the magnet 40 and the magnetic spacer 30 is 2.6 mV / V. The first group 512A can contain any number of calibration force measurements taken over any period of time. For example, about five samples can be taken over a period of about fifty seconds. After the samples of the first group 512A have been taken and recorded by the controller 50, the micrometer 130 is used to move the sliding stage 116 and the magnet 40 by a predetermined distance, e.g., 50 µm, closer to the magnetic spacer 30 of the battery 20. With the magnet 40 now 50 µm closer to the magnetic spacer 30, the second group 512B of calibration force measurements is taken and recorded. The calibration process is repeated with the third group 512C, the fourth group 512D, the fifth group 512E, the sixth group 512F, and the seventh group 512G. The calibration force measurements are imported into the controller 50 in a suitable format, e.g., in the form of graph 510 in Fig. 13. From block 414, procedure 410 continues with blocks 416 and 418. The controller 50 can be configured to perform the tasks of blocks 416 and 418 simultaneously or substantially simultaneously, or the tasks can be performed sequentially. In block 416, the calibration data of graph 510 is normalized. In particular, graph 510 is normalized to generate, for example, the normalized graph 550 of Fig. 14. Graph 550 is normalized so that the force sensor values, for example, lie within a range of 0.0 to 1.0. Normalization can be performed because, for example, the exact range of the force sensor values ​​in Fig. 13 is not known at the beginning of the calibration process. Normalizing graph 550 sets it to the same scale as the idealized calibration pattern of Fig. 15. The idealized calibration pattern of graph 610 is an idealized staircase, as this is the expected general appearance of graph 510 of the calibration force measurements. To perform the normalization, the controller 50 can be configured to use any suitable normalization formula, such as the following: Controller 50 is configured to identify points in block 420 of graph 550 that do not fit the constructed idealized calibration pattern of graph 610 in Fig. 15 and are therefore not relevant calibration force measurements. Any suitable comparison technique can be applied, e.g., dynamic time warping (DTW). Controller 50 performs a series of DTW comparisons between the normalized calibration force measurements 550 and the idealized calibration pattern 610 in a single pass (“sweep”). Starting with the complete data set, an additional data point is removed from the beginning of the normalized calibration force measurements in each successive comparison, and the resulting distance values ​​are then stored in a field. Upon completion of the series, the minimum distance value corresponds to the beginning of the corresponding calibration profile.The process is then repeated with a reverse sweep to locate the end of the relevant calibration profile. The DTW results are applied to graph 510. As a result of the DTW comparison of graph 550 and graph 610, the portion of graph 510 with sample numbers greater than 40 and larger than group 512G is designated for removal because it does not fit the constructed idealized calibration pattern of Fig. 15. The portions of graph 510 with sample numbers smaller than the first group 512A are also designated for removal. The measured values ​​designated for removal may be the result of noises that occur when the battery 20 is inserted into and removed from the holder 114. From block 420, the controller proceeds to block 422. In block 422, controller 50 truncates graph 510 to remove the areas deemed irrelevant by the DTW. In block 424, graph 510 is further processed to remove noise from the calibration force measurements. The noise is determined by subtracting adjacent points on graph 510 in both directions and identifying irregularities. Points 514A–514E in Fig. 13 are examples of noise reduction performed by controller 50 in block 424. From block 424, the procedure 410 continues to block 426. In block 426, the calibration force measurements are organized into fields and labeled according to the calibration distance between the magnet 40 and the magnetic spacer 30 at which the measurements were taken. As shown in graph 650 in Fig. 16, for example, field 652A contains the calibration force measurements of group 512A, labeled with the initial distance of the distance range, which in this example is 250 µm. Field 652B contains the calibration force measurements of group 512B and is labeled with the second distance of the distance range, which in this example is 50 µm less than the base of 250 µm, or 200 µm. Field 652C contains the calibration force measurements of group 512C and is labelled with the nearest distance of the distance range, which in this example is 150 µm.Field 652D contains the calibration force measurements of group 512D and is labeled with the nearest distance in the range, which in this example is 100 µm. Field 652E contains the calibration force measurements of group 512E and is labeled with the nearest distance in the range, which in this example is 50 µm. Field 652F contains the calibration force measurements of group 512F and is labeled with the nearest distance in the range, which in this example is 0 µm from the base distance. Field 652G contains the calibration force measurements of group 512G and is labeled with the nearest distance in the range, which in this example is -50 µm relative to the base distance. Controller 50 is configured to detect in block 426 whether any of the predefined calibration intervals have been missed during manual operation of the micrometer 130. In graph 650, for example, none of the predefined calibration intervals were missed. Thus, the difference in the force cell reading between adjacent fields 652A–652G is 0.1 mV / V. However, if one of the predefined calibration intervals is missed, such as area 652D at 100 µm, the difference in the force cell reading between area 652C and area 652E would be 0.2 mV / V. Controller 50 is configured to use statistical methods to determine the typical step height and to correctly label field 652E with the correct interval of 100 µm, which corresponds to two steps of 0.1 mV / V.If the controller 50 were not configured to detect the difference of 0.2 mV / V between field 652C and field 652E, field 652E might not be labelled correctly at a distance of 50 µm. Whether one of the calibration distances was overlooked or missed during the manual operation of the micrometer device 130 can be determined in any suitable way. For example, the controller 50 is configured to calculate the difference between each data point of fields 652A–652G, where the data points of each of fields 652A–652G provide a difference value at or around 0, and the first data point on a new staircase or new field 652A–652G provides a value approximately equal to the step height. In the example of Fig. 16 (where, for simplicity, values ​​close to 0, such as 0.0001, are treated as 0), the series of difference values ​​might look like this: 0, 0, 0, 0, -0.1, 0, 0, 0, -0.1, 0, 0.... Thus, most of the values ​​are 0, while some are at the step height of -0.1. Controller 50 is configured to perform a kernel density estimate (KDE or kernel density estimate) on the data points.KDE estimates a continuous curve, where the height of the curve corresponds to the estimated frequency of the value occurring in the data. A higher peak value means the value occurs more frequently. An example KDE yields a high peak around 0 and a lower peak around -0.1, which corresponds to a typical step height. Controller 50 is configured to use the following formula to determine how many steps occurred between successive data points: `delta = round(diff_val / pk_two_loc)`. The value of `delta` is an integer indicating the number of steps that occurred. For example, if the difference value `diff_val` is -0.1, the calculation is: `delta = round(-0.1 / -0.1)`, resulting in a delta value of 1, meaning one step occurred. However, if the difference value is -0.2 (`delta = round(-0.2 / -0.1)`), the delta value is 2, meaning two steps occurred. If the controller 50 identifies the following difference series: 0, 0, 0, 0, -0,1, 0, 0, 0, 0, -0,2, 0, 0, 0, 0, -0,1, 0, 0, 0, 0, then the delta values ​​are: 0, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 1, 0, 0, 0. The number in the preceding series indicates how many levels occurred in the data.A value of 0 means that the analysis is at the same level as the previous data point, a value of 1 means that the analysis has moved by one level, a value of 2 means that the analysis has moved by two levels, and so on. And if the group of levels is known as 0 µm, 10 µm, 20 µm, 30 µm, 40 µm, 50 µm, etc., then the controller 50 is configured to accurately position and label the data points, even if the operator has accidentally missed a level, thus avoiding potential "off-by-one" or "off-by-one" errors. From block 426, the procedure 410 continues to block 428. In block 428, the controller 50 contains the data shown in graph 710 of Fig. 17, i.e., the force transducer value of the sensor 42 as a function of the distance between the magnet 40 and the magnetic spacer 30 relative to 0 µm, where the point 0 µm is the base distance. The controller 50 has a configurable parameter that specifies the step height or distance for each field 652A - 652G, as well as the force transducer value associated with each of the fields 652A - 652G, as explained above. Based on this information, the controller contains data from fields 652A - 652G in graph 710. The points of each field 652A - 652B are consolidated into a single point in graph 710 because the force sensor value and the distance value are the same or substantially the same for each data point. Controller 50 is configured to also determine the slope of the points on graph 710 in block 428. The slope can be determined in any suitable way, e.g., by linear regression. In the example shown in Fig. 18, the controller is configured to perform a linear regression and determines a slope of -520.72 (y-int of 1294.64; r2 of 0.999265) on graph 750. The calibration ends in block 430. The dilatometer 110 is configured to measure the dilation of battery cell 20, or another suitable battery, before or after calibration, as battery cell 20 undergoes charge and discharge cycles. Leads are connected to the dilatometer 110 to operate battery cell 20 cyclically. The controller 50 is configured to record data from the load cell 120 at any suitable time increment, e.g., in 5-second intervals. To determine the degree of dilation of electrode 24 and / or electrode 26, the controller 50 is configured to use graph 750 from Fig. 18 and the determined slope. Based on the calibration graph 750, the controller 50 assigns a distance measurement along the distance range to each measured value of the force transducer sensor 42. For example, a force transducer value of sensor 42 of 2.2 mV / V corresponds to a distance of 150 µm from the starting point of the distance range. In other words, a measured value of 2.2 mV / V corresponds to an increase in electrode thickness of 150 µm. Referring to the example in Fig. 1A and Fig. 1B, the thickness t1 of electrode 26 has increased by 150 µm to the thickness t2 shown in Fig. 1B. Similarly, a value of 2.25 mV / V corresponds to an increase in electrode thickness of approximately 125 µm.The calibration graph 750 can be used to determine the dilation distance of each electrode of any suitable battery configuration, including the battery configurations described above. The foregoing description is merely explanatory and is not intended to limit the revelation, its application, or use. The comprehensive teachings of revelation can be implemented in a multitude of ways. Although this disclosure contains certain examples, the true scope of the disclosure should not be so limited, since other modifications are apparent upon study of the drawings, the description, and the following claims. It is understood that one or more steps within a method may be performed in a different order (or simultaneously) without altering the principles of the present disclosure. Although each of the embodiments above is described with certain features, any one or more of these features described in relation to any embodiment of the disclosure may be implemented in one of the other embodiments and / or combined with features of another embodiment, even if such combination is not explicitly described.In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with each other remain within the scope of this disclosure. Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, such as "connected," "interlocking," "coupled," "adjacent," "next to," "on," "above," "below," and "arranged." If a relationship between a first and a second element is not explicitly described as "direct" in the above disclosure, this relationship may be a direct relationship in which no other intervening elements exist between the first and the second element, or it may be an indirect relationship in which one or more intervening elements (either spatial or functional) exist between the first and the second element.As used herein, the phrase “at least one of A, B and C” should be interpreted as a logical (A OR B OR C) using a non-exclusive logical OR and not as “at least one of A, at least one of B and at least one of C”. In the diagrams, the direction of an arrow, as indicated by the arrowhead, generally shows the flow of information (e.g., data or instructions) that is relevant to the illustration. For example, if Element A and Element B exchange a variety of information, but the information transferred from Element A to Element B is relevant to the illustration, the arrow may point from Element A to Element B. This unidirectional arrow does not imply that no further information is transferred from Element B to Element A. Furthermore, Element B may send requests for or acknowledgments of information to Element A in return for information sent from Element A to Element B. In this application, including the definitions below, the term "module" or the term "controller" may be replaced by the term "circuit". The term "module" may refer to, be part of, or include: an application-specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field-programmable gate array (FPGA); a processor circuit (common, dedicated, or group) that executes code; a memory circuit (common, dedicated, or group) that stores the code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, e.g., in a system-on-a-chip. The module may contain one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces connected to a local area network (LAN), the internet, a wide area network (WAN), or combinations thereof. The functionality of any module of this disclosure may be distributed across multiple modules connected via interface circuits. For example, multiple modules may enable load balancing. In another example, a server module (also called a remote or cloud module) may perform some functions on behalf of a client module. The term "code," as used above, can include software, firmware, and / or microcode, and can refer to programs, routines, functions, classes, data structures, and / or objects. The term "shared processor circuit" refers to a single processor circuit that executes some or all of the code of multiple modules. The term "group processor circuit" refers to a processor circuit that, in combination with other processor circuits, executes some or all of the code of one or more modules. References to "multiple processor circuits" include multiple processor circuits on discrete chips, multiple processor circuits on a single chip, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above.The term "shared memory circuit" refers to a single memory circuit that stores some or all of the code from multiple modules. The term "group memory circuit" refers to a memory circuit that, in combination with other memory devices, stores some or all of the code from one or more modules. The term "memory circuit" is a subset of the term "computer-readable medium." The term "computer-readable medium," as used here, does not include transitory electrical or electromagnetic signals that propagate through a medium (e.g., on a carrier wave); the term "computer-readable medium" can therefore be considered tangible / material and non-transient. Non-restrictive examples of a non-transient, tangible, computer-readable medium are non-volatile memory circuits (e.g., a flash memory circuit, a erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (e.g., a static random-access memory circuit or a dynamic random-access memory circuit), magnetic storage media (e.g., an analog or digital magnetic tape or a hard disk drive), and optical storage media (e.g.,a CD, a DVD or a Blu-ray Disc). The devices and methods described in this application can be implemented partially or completely by a specialized computer formed by configuring a general-purpose computer to perform one or more specific functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications that can be translated into computer programs through the routine work of an experienced technician or programmer. The computer programs contain processor-executable instructions stored on at least one non-transient, tangible, machine-readable medium. The computer programs may also contain or access stored data. The computer programs may include a basic input / output system (BIOS) that interacts with the hardware of the specialized computer, device drivers that interact with specific devices of the specialized computer, one or more operating systems, user applications, background services, background applications, etc. The computer programs can contain: (i) descriptive text to be parsed, e.g., HTML (Hypertext Markup Language), XML (Extensible Markup Language), or JSON (JavaScript Object Notation); (ii) assembly code; (iii) object code generated from the source code by a compiler; (iv) source code for execution by an interpreter; (v) source code for compilation and execution by a just-in-time compiler, etc. The source code can, for example, use the syntax of languages ​​such as C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, Simulink, and others. It must be written in Python®.

Claims

A dilatometer (110) configured to measure the dilation of an electrode in a battery (20), the dilatometer (110) comprising: a first holder (114) configured to support the battery (20); a magnet (40) positioned adjacent to the first holder (114); a magnetic force sensor (120) configured to measure the strength of the magnetic force between the magnet (40) and a magnetic spacer within the battery (20) supported by the first holder (114); a second holder (122) configured to move the magnet (40) relative to the magnetic spacer of the battery (20) supported by the first holder (114);and a controller (50) configured to: receive calibration force measurements (510) from the magnetic force sensor (120), wherein the calibration force measurements (510) comprise the strength of the magnetic force between the magnet (40) and the magnetic spacer at various calibration distances resulting from the movement of the magnet (40) relative to the magnetic spacer over a distance range during calibration; assign a position value to each of the calibration force measurements (510), wherein the position value is a distance between the magnet (40) and the magnetic spacer of the battery (20); predict the strength of the magnetic force between the magnet (40) and the magnetic spacer over the entire distance range based on the position values ​​of the and perform a dynamic time distortion (DTW) on the calibration force measurements (510);Normalizing the calibration force measurements (510) to normalized calibration data (550) and creating an idealized calibration pattern (610) based on the calibration force measurements (510); basis of the calibration force measurements (510), the normalized calibration data (550) and the idealized calibration pattern (610).; Dilatometer (110) according to claim 1, wherein the controller (50) is further configured to: receive a battery test force measurement from the magnetic force sensor (120), wherein the battery test force measurement includes the strength of the magnetic force between the magnet (40) and the magnetic spacer of the battery (20) during a dilation test of the battery (20); and identify a dilation distance within the distance range corresponding to the battery test force measurement, wherein the dilation distance corresponds to a dilation of the electrode in the battery (20). Dilatometer (110) according to claim 1, wherein the battery (20) is a button cell battery. Dilatometer (110) according to claim 1, wherein the different calibration distances are intervals of 10 µm. Dilatometer (110) according to claim 1, wherein the different calibration distances are intervals of 50 µm. Dilatometer (110) according to claim 1, wherein the calibration force measurements (510) comprise multiple measurements at each of the different calibration distances. Dilatometer (110) according to claim 1, wherein the distance range is 250 µm. Dilatometer (110) according to claim 1, wherein the magnetic force sensor (120) is a load sensor. Dilatometer (110) according to claim 1, further comprising a sliding table (116) configured to move the second holder (122) and the magnet (40) relative to the first holder (114) and the magnetic spacer of the battery (20) supported by the first holder (114).

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