JP2012122834A - Thickness measurement apparatus for battery electrode material and thickness measurement method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thickness measurement apparatus which can simply perform evaluation for a battery electrode material and a thickness measurement method thereof.SOLUTION: A thickness measurement apparatus in one embodiment is a thickness measurement apparatus for a battery electrode material in which an active material layer 22 including an active material 23 is provided on a collector 21 and includes a measuring head 31 for jetting air onto the surface of the battery electrode material in order to form an air gap between the measuring head 31 and the battery electrode material, a coil 41 provided on the measuring head 31 and an oscillator 50 connected to the coil 41.

Description

  TECHNICAL FIELD The present invention relates to a battery electrode material thickness measuring device and a thickness measuring method, and more particularly, to a battery electrode material thickness measuring device having a current collector provided with an active material layer, and a thickness measurement. Regarding the method.

  Lithium ion batteries have been developed as batteries for electric vehicles. In a lithium ion battery, an electrode material in which an active material is provided on a current collector is used. For example, in the positive electrode material, an aluminum foil (Al) is used as a current collector, and lithium manganate or the like is used as an active material. On the other hand, in the negative electrode material, copper foil (Cu) is used as a current collector, and graphite is used as an active material.

  The configuration of the electrode material will be described with reference to FIG. In FIG. 9, the cross-sectional structure of the positive electrode material which is one electrode material 20 is shown typically. The electrode material 20 includes a current collector 21 and an active material layer 22 provided on the current collector 21. The current collector 21 has a thickness of about 20 μm, for example, and the active material layer 22 has a thickness of about 50 to 100 μm. The active material layer 22 is formed by applying the active material 23, the binder 24, and the conductive additive (also referred to as a conductive material) 25 in a mixed state.

In the case of the positive electrode material, the active material 23 is, for example, lithium manganate (LiMn ₂ O ₄ ) or lithium cobaltate (LiCoO ₂ ) having a particle diameter of 1 to 10 μm. The binder 24 is, for example, polyvinylidene fluoride (PVDF) or styrene butadiene rubber (SBR). The conductive auxiliary agent 25 is, for example, graphite fine powder having a particle diameter of 1 μm to submicron, carbon black, or carbon fiber. The active material 23, the binder 24, and the conductive assistant 25 are mixed and applied onto the current collector 21. Although not shown, the active material layer 22 is formed on both surfaces of the current collector 21. And a positive electrode material and a negative electrode material are arrange | positioned alternately, and a separator is arrange | positioned among them. And these laminated structures are immersed in electrolyte solution (electrolyte).

  An apparatus for evaluating such a lithium ion battery is disclosed. For example, in Patent Documents 1 and 2, the thickness of the electrode material is measured by a contact displacement sensor. Moreover, in patent document 3, the porous film is image | photographed with a color image and the film thickness is calculated | required with the color tone. However, the methods of Patent Documents 1 and 2 can measure only the thickness of the entire electrode material. Furthermore, since the contact type sensor is used, the surface may be damaged. Moreover, in patent document 3, a measuring object is limited to a porous membrane. Furthermore, since the film thickness is obtained from the color tone of the color image, it is difficult to measure accurately.

JP 2000-337859 A JP 2001-126719 A JP 2007-66821 A

  In order to improve battery performance, it is desired to measure the thickness of the active material layer 22 and the homogeneity of the active material layer. For example, it is desired to measure the thickness distribution of the active material layer 22. Furthermore, it is desired to measure that the active material 23, the binder 24, and the conductive additive 25 are uniformly distributed in the active material layer 22. By measuring these, the battery electrode material can be evaluated from various viewpoints. For example, by measuring the thickness distribution of the active material layer 22, application unevenness of the active material layer 22 can be evaluated. Furthermore, as shown in FIG. 10, in the active material layer 22, the conductive auxiliary agent 25 may be densely packed or metal foreign matter may be mixed. Alternatively, as shown in FIG. 11, voids or chips may occur in the active material layer 22. If there is such a heterogeneous portion, the current density is non-uniform or concentrated, causing a decrease in battery performance or deterioration. Therefore, by measuring the film pressure distribution and homogeneity of the active material layer and evaluating the battery electrode material, it is possible to contribute to the improvement of the battery performance.

  The present invention has been made in view of the above problems, and can easily measure the thickness of a battery electrode material. Therefore, the thickness measuring device that can contribute to the improvement of battery performance, and An object is to provide a thickness measurement method.

  A thickness measuring apparatus according to a first aspect of the present invention is a thickness measuring apparatus for a battery electrode material in which an active material layer containing an active material is provided on a current collector, the battery electrode material and In order to form an air gap therebetween, a head for ejecting air to the surface of the battery electrode material, a coil provided on the head, and an oscillator connected to the coil are provided. Thereby, since the thickness of the battery electrode material can be measured easily, it can contribute to the improvement of battery performance.

  A thickness measuring apparatus according to a second aspect of the present invention is the above-described thickness measuring apparatus, wherein the active material layer containing the active material according to an oscillation frequency when the oscillator and the coil are connected is provided. Thickness is measured. Thereby, the thickness of an active material layer can be measured easily and it can contribute to the improvement of battery performance.

  A thickness measuring apparatus according to a third aspect of the present invention is the above-described thickness measuring apparatus, wherein the electrode is provided on the head and forms a capacity electrode that forms a capacity with the battery electrode material, and outputs the oscillator. A switch for switching from the coil to the capacitive electrode. Thereby, since the homogeneity of the active material layer can be measured, evaluation from various viewpoints becomes possible.

  A thickness measuring apparatus according to a fourth aspect of the present invention is the above-described thickness measuring apparatus, comprising: an arm that supports the head; and a height adjusting mechanism that adjusts the height of the head on the arm. Is provided. Thereby, thickness measurement can be performed about the battery electrode material of various thickness.

  A thickness measuring apparatus according to a fifth aspect of the present invention is the above-described thickness measuring apparatus, wherein the head is supported by the arm via a leaf spring parallel link mechanism. Thereby, a fixed air gap can be obtained stably.

  A thickness measuring apparatus according to a sixth aspect of the present invention is the above-described thickness measuring apparatus, wherein a plate-like member that adsorbs and fixes the battery electrode material is provided below the battery electrode material. It is what. Thereby, it can measure stably.

  A thickness measuring method according to a seventh aspect of the present invention is a method for measuring a thickness of a battery electrode material in which an active material layer containing an active material is provided on a current collector, the battery electrode material and A step of ejecting air to the surface of the battery electrode material in order to form an air gap, a step of generating an alternating magnetic field in a coil provided in the head by an oscillator, and an oscillation frequency of the oscillator And a step. Thereby, the thickness of the battery electrode material can be measured easily, and it can contribute to the improvement of battery performance.

  A thickness measurement method according to an eighth aspect of the present invention is the thickness measurement method described above, wherein an active material layer is formed according to an oscillation frequency distribution of the oscillator when the measurement head and the electrode are relatively moved. The thickness distribution is measured. Thereby, the thickness of an active material layer can be measured easily and it can contribute to the improvement of battery performance.

  A thickness measuring method according to a ninth aspect of the present invention is the above-described thickness measuring method, wherein the head is provided with a capacity electrode that forms a capacity with the battery electrode material, and the output of the oscillator is obtained. The coil is switched to the capacitive electrode. Thereby, since the homogeneity of the active material layer can be measured, evaluation from various viewpoints becomes possible.

  A thickness measuring method according to a tenth aspect of the present invention is the above-described thickness measuring method, wherein the head is instructed by an arm, and the arm has a height adjusting mechanism for adjusting the height of the head. It is provided. Thereby, thickness can be measured about the battery electrode material of various thickness.

  A thickness measuring method according to an eleventh aspect of the present invention is the above-described thickness measuring method, wherein the head is supported by the arm via a leaf spring parallel link mechanism. Thereby, a fixed air gap can be obtained stably.

  A thickness measuring method according to a twelfth aspect of the present invention is the above-described thickness measuring method, wherein a specific resistance of the current collector is higher than a specific resistance of the active material layer. It is.

  A thickness measuring method according to a thirteenth aspect of the present invention is the above-described thickness measuring method, wherein a plate-like member for adsorbing and fixing the battery electrode material is provided below the battery electrode material. It is what. Thereby, it can measure stably.

  ADVANTAGE OF THE INVENTION According to this invention, the electrode material for batteries can be evaluated easily and the thickness measuring apparatus and thickness measuring method which can contribute to the improvement of battery performance can be provided.

It is a figure which shows typically the whole structure of the thickness measuring apparatus concerning this Embodiment. It is a figure which shows typically the structure of the measurement arm of a thickness measuring apparatus. It is a side view which shows typically the measuring head of a thickness measuring apparatus. It is a bottom view which shows typically the measuring head of a thickness measuring apparatus. It is a figure explaining the measuring method of a thickness measuring device. It is a side view which shows typically the measurement circuit of a thickness measuring apparatus. It is a figure which shows the relationship between surface distance and an oscillation frequency in a thickness measuring apparatus. It is side surface sectional drawing which shows the structure of the thickness measuring apparatus provided with the plate-shaped member. It is sectional drawing which shows the structure of the electrode material for batteries typically. It is sectional drawing which shows the example which abnormality generate | occur | produced in the active material layer of the battery electrode material. It is sectional drawing which shows the example which abnormality generate | occur | produced in the active material layer of the battery electrode material.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description shows preferred embodiments of the present invention, and the scope of the present invention is not limited to the following embodiments. In the following description, the same reference numerals indicate substantially the same contents.

  In the thickness measurement apparatus according to the present embodiment, the electrode material 20 that is a measurement object is, for example, an electrode material for a lithium ion battery. Therefore, as shown in FIG. 9, the electrode material 20 includes a current collector 21 and an active material layer 22. As the current collector 21, an aluminum foil is used in the case of a positive electrode material, and a copper foil is used in the case of a negative electrode material. The active material layer 22 is provided with the active material 23, the binder 24, and the conductive assistant 25 as described above. Aluminum foil (Al) is used as the current collector, and lithium manganate or the like is used as the active material. On the other hand, in the negative electrode material, copper foil (Cu) is used as the current collector, and graphite is used as the active material 23. The binder 24 is, for example, polyvinylidene fluoride (PVDF) or styrene butadiene rubber (SBR). The conductive auxiliary agent 25 is, for example, graphite fine powder having a particle diameter of 1 μm to submicron, carbon black, or carbon fiber. The active material 23, the binder 24, and the conductive assistant 25 are mixed and applied onto the current collector 21. The thickness measuring device measures the thickness distribution of the active material layer 22. By measuring the thickness distribution, thickness unevenness can be reduced. Therefore, it is possible to prevent a decrease in battery capacity and contribute to an improvement in battery performance. Further, the thickness measuring apparatus can measure unevenness in conductivity or voids of the active material layer. Therefore, it is possible to prevent a decrease in battery capacity and contribute to an improvement in battery performance.

  First, the overall configuration of the thickness measuring apparatus will be described with reference to FIG. FIG. 1 is a perspective view schematically showing the overall configuration of the thickness measuring apparatus. As shown in FIG. 1, the thickness measuring device includes a stage 11, a cover 12, a movable part 13, a clamp 14, and a measuring arm 30. A battery electrode material 20 is placed on the stage 11. The cover 12 is provided so as to be openable and closable with respect to the stage 11. When the measurement is performed on the electrode material 20, the cover 12 is closed. On the other hand, when taking out or installing the electrode material 20, the cover 12 is opened. The stage 11 is provided with a jet port 15. And the jet nozzle 15 ejects gas (air). Thereby, the electrode material 20 which is a measuring object floats. By using the spout 15, the electrode material 20 can be brought into non-contact with the stage surface. Therefore, damage or the like of the electrode material 20 can be prevented.

  The electrode material 20 is held by the clamp 14. That is, the clamp 14 holds one end of the electrode material 20. The clamp 14 is slidably attached to the movable portion 13. The clamp 14 moves in the Y direction with respect to the movable portion 13. The movable part 13 is slidably attached to the stage 11. The movable part 13 moves on the stage 11 in the X direction. By driving the clamp 14 in the Y direction and the movable portion 13 in the X direction, the electrode material 20 freely moves in the XY direction. The movement of the electrode material 20 may be automatically controlled by controlling the clamp 14 and the movable portion 13 with a computer or the like. Thereby, the whole surface measurement of the electrode material 20 can be performed automatically.

  Further, a measurement arm 30 is attached to the stage 11. The measurement arm 30 extends from the back side (−Y side) end of the stage 11 to the center of the stage 11. The distal end portion of the measurement arm 30 is disposed on the electrode material 20. That is, the electrode material 20 is disposed immediately below the measurement head provided at the tip of the measurement arm 30. The measurement head performs measurement on the electrode material 20. Then, the relative position between the measurement head and the electrode material 20 is changed by moving the electrode material 20 in the XY directions by the clamp 14 and the movable portion 13. An arbitrary position of the electrode material 20 can be measured. By gradually shifting the measurement head and the electrode material 20, the entire surface of the electrode material 20 can be measured.

  Next, the configuration of the measurement arm 30 will be described with reference to FIG. FIG. 2 is a side view schematically showing the configuration of the measurement arm 30. The measurement arm 30 serving as a measurement unit includes a measurement head 31, a leaf spring 32, a base 33, a tip arm 34, a base arm 35, a height adjustment mechanism 38, and a differential transformer 60.

  A base 33 is erected at the end of the stage 11. A base arm 35 is attached to the base 33. That is, the base 33 supports the base arm 35. The base arm 35 extends from the base 33 in the Y direction. A tip arm 34 extending in the Y direction is disposed on the tip side of the base arm 35. The tip arm 34 and the base arm 35 are connected by a pair of leaf springs 32. That is, the base arm 35 supports the tip arm 34 via the leaf spring 32.

  A pair of leaf | plate spring 32 is spaced apart and arrange | positioned. The leaf spring 32 is attached to the upper and lower surfaces of the tip arm 34. The pair of leaf springs 32 constitute a leaf spring type parallel link mechanism. Thereby, the measuring head 31 is pressed against the electrode material 20 with a substantially constant force. When the leaf spring 32 is bent, the tip arm 34 is displaced up and down with respect to the base arm 35. A measuring head 31 is attached to the tip of the tip arm 34. The leaf spring 32 is bent according to the weight of the tip arm 34 and the measurement head 31. Of course, the structure is not limited to the leaf spring type parallel link, and any structure may be used as long as the measurement head 31 is displaced up and down according to the surface height of the electrode material 20.

  The measurement head 31 is provided with a circuit for performing measurement. Further, the measurement head 31 is provided with a jet nozzle. Air is ejected from the ejection port to the electrode material 20. When the air flows along the surface of the electrode material 20, an air gap (gap) is formed between the measurement head 31 and the surface of the electrode material 20. The air gap varies with the air pressure. Further, when the air pressure is kept constant and the surface height of the electrode material 20 changes, the measuring head 31 moves up and down so that the air gap becomes constant. The amount of bending of the leaf spring 32 changes according to the surface height of the electrode material 20 and the air gap length. For example, the amount of bending of the leaf spring 32 becomes the largest when the air is stopped. When the air pressure is increased and the air gap is increased, the amount of bending of the leaf spring 32 is decreased. The pair of leaf springs 32 constitutes a parallel leaf spring link mechanism. When the air pressure is made constant, the leaf spring 32 generates a substantially constant elastic force in the downward direction (−Z direction). The measuring head 31 is pressed against the electrode material 20 by this elastic force, and the air gap becomes constant. A constant air gap can be obtained stably. Furthermore, a desired air gap length can be obtained by adjusting the air pressure. Therefore, the measurement head 31 can be air-lifted while maintaining an appropriate air gap. The detailed configuration of the measurement head 31 will be described later.

  A height adjustment mechanism 38 is attached to the base arm 35. The height adjustment mechanism 38 is a micrometer, for example, and can send out the base arm 35 in the vertical direction (Z direction). Alternatively, a linear guide mechanism and a motor may be used as the height adjustment mechanism 38, and the base arm 35 may be automatically fed. The base arm 35 moves in the Z direction with respect to the base 33. The distance between the measuring head 31 and the electrode material 20 is changed by the height adjusting mechanism 38. By adjusting the height according to the electrode material 20, the electrode material 20 of various thicknesses can be evaluated. The attachment position of the height adjustment mechanism 38 is not limited to the base arm 35. For example, the height adjustment mechanism 38 may be attached to the tip arm 34 or the measurement head 31.

  The base arm 35 is provided with a main portion of a differential transformer 60 that measures the flying height of air. Specifically, a primary coil 63 and a secondary coil 62 are attached to the base arm 35. Secondary coils 62 are arranged on both upper and lower sides of the primary coil 63. The secondary coils 62 are arranged symmetrically with the primary coil 63 interposed therebetween. A resin support 39 is provided on the distal arm 34. The resin support 39 supports the core 61 of the differential transformer 60. The core 61 is interlocked with the tip arm 34. In order to realize a high-frequency differential transformer, for example, a ferrite core is used as the core 61. The core 61 is disposed inside the primary coil 63. Similarly, the core 61 is disposed inside the secondary coil 62. When the core 61 is at a reference height, the core 61 is arranged symmetrically with respect to the secondary coils 62 provided on the upper and lower sides of the primary coil 63.

  An excitation cable 66 is connected to the primary coil 63. As will be described later, an oscillator is connected to the cable 66. A detection cable 67 is connected to the secondary coil 62. The cable 66 and the cable 67 are coaxial cables, for example. By supplying an AC voltage via the cable 66, the primary coil 63 is excited. When the tip arm 34 moves up and down relative to the base arm 35, the core 61 moves up and down relative to the secondary coil 61. When the core 61 is at a reference height, AC voltages (induced voltages) induced in the upper and lower secondary coils 62 are equal. Therefore, the differential voltage becomes zero. When the core 61 deviates vertically from the reference height, the position of the core 61 with respect to the secondary coil 63 becomes symmetric. Therefore, a difference is generated between the induced voltages of the upper and lower secondary coils 62, and an AC voltage (differential voltage) corresponding to the difference appears. By detecting the differential voltage via the cable 67, the height change of the core 61 can be measured. That is, a change in the position of the tip arm 34 with respect to the base arm 35 can be measured.

  The differential transformer 60 can measure the flying height due to air. For example, when the air pressure changes, the air gap between the measurement head 31 and the electrode material 20 changes. Accordingly, the position of the measurement head 31 with respect to the base arm 35 and the position of the tip arm 34 that supports the measurement head 31 change vertically. That is, the amount of bending of the leaf spring 32 that supports the tip arm 34 changes. Accordingly, the position of the core 61 with respect to the secondary coil 61 changes up and down. The position change of the core 61 is measured by the differential voltage of the secondary coil 61. By doing in this way, the relationship between the air pressure and the flying height by air can be obtained.

  For example, measurement with the differential transformer 60 is performed in a state where the ejection of air is stopped and the electrode material 20 and the measurement head 31 are in contact with each other. Further, measurement is performed by the differential transformer 60 in a state where air of a predetermined pressure is blown and air is floated. By comparing these two measured values, the air flying height at a certain air pressure can be measured. This air flying height is the air gap length between the electrode material 20 and the measuring head 31. Furthermore, the relationship between the air pressure and the air flying height can be obtained by gradually changing the air pressure. In the differential transformer 60, the core 61 on the tip arm 34 side and the coil on the base arm side 45 are not in contact with each other. That is, the differential transformer 60 is a non-contact type sensor that can perform measurement without contact with the measurement target. By using a non-contact sensor, the influence on the air gap can be suppressed. That is, since the differential transformer 60 that is a non-contact sensor is used, no force is applied to the leaf spring 32 from the differential transformer side. The leaf spring 32 can be softened and the operation can be made supple. Therefore, the air gap can be kept constant. Of course, the vertical position of the measuring head 31 relative to the base arm 35 may be measured by a sensor other than the differential transformer 60.

  Further, when the electrode material 20 to be measured is placed on the stage 11, the measuring head 31 is lowered by the height adjusting mechanism 38. In the state where the measuring head 31 is sufficiently separated from the surface of the electrode material 20, the air does not float. Then, the measurement head 31 is lowered, and when the measurement head 31 approaches a certain distance with respect to the electrode material 20, the air floats. Then, the height of the measuring head 31 with respect to the base arm 35 changes. Therefore, the height of the air floating can be confirmed by the differential transformer 60. When the height is automatically controlled by a motor or the like, the height at which the air floats may be detected by a contact or the like. For example, a contact or the like is provided on the tip arm 34 or the base arm 35. By doing so, it is possible to detect that the air has floated. Then, the measurement head 31 is lowered by a predetermined amount from the time when air levitation is detected. By doing so, the pressure to the air gap by the parallel link of the leaf spring 32 can be made constant, and the air gap length can be accurately controlled.

  The measurement head 31 performs measurement on the electrode material 20. Measurement with respect to the electrode material 20 can be performed at a position immediately below the measurement head 31. When the measurement at that position is completed, the electrode material 20 is displaced in the XY directions by a predetermined amount. That is, as shown in FIG. 1, the electrode material 20 is moved in the XY directions. And it measures similarly in the position after movement. By repeating this, it is possible to measure the entire electrode material 20.

  Next, the configuration of the measuring head 31 will be described with reference to FIGS. FIG. 3 is a side view schematically showing the configuration of the measuring head 31, and FIG. 4 is a bottom view.

  The measurement head 31 includes a main body 40, a coil 41, a jet nozzle 42, and a capacitive electrode 43. The main body 40 is a substantially cylindrical member, for example, and is formed of a plastic material. A cylindrical convex portion 44 is provided below the main body portion 40. The protrusion 44 protrudes downward, and the protrusion amount is about 0.5 mm. In the XY plane, the convex portion 44 is disposed at the center of the main body portion 40. The convex portion 44 has a cylindrical shape with a diameter of about 3 mm to 5 mm.

  Furthermore, a capacitive electrode 43 is provided on the convex portion 44. The capacitive electrode 43 is exposed on the lower surface of the convex portion 44. The lower surface of the capacitive electrode 43 is flat and faces the electrode material 20. The capacitive electrode 43 is a circular thin plate. A capacitance (capacitor) is formed by the capacitance electrode 43 and the electrode material 20. In the XY plane, the main body portion 40, the convex portion 44, and the capacitor electrode 43 are arranged concentrically. The capacitive electrode 43 or the tip of the capacitive electrode 43 may be made of graphite. By using graphite, metal contamination when the capacitive electrode 43 comes into contact with the electrode material 20 can be prevented. When measuring the air gap, it is possible to easily measure that the capacitive electrode 43 is in contact with the electrode material 20 by stopping the oscillation of the oscillator 50.

  Further, the measurement head 31 is provided with an air outlet 42. A through hole provided in the capacitive electrode 43 serves as an air outlet 42. The spout 42 passes through the center of the capacitive electrode 43. Air (air) is ejected downward from the ejection port 42. That is, air is ejected in the direction of the arrow in FIG. The air flows outward along the surface of the electrode material 20. Thereby, an air gap is formed between the convex portion 44 of the measurement head 31 and the electrode material 20. That is, the measurement head 31 floats on the electrode material 20. For example, air is ejected with a pressure such that the air gap is 10 μm. The gas ejected from the ejection port 42 is not limited to air (air) but may be other gas such as nitrogen.

  A coil 41 is wound around the outer periphery of the cylindrical main body 40. For example, the coil is wound with 30 to 40 turns. As will be described later, the coil 41 is supplied with a high-frequency voltage from an oscillator. Therefore, the coil 41 generates an alternating magnetic field. When a current flows through the coil 41, a magnetic field line is generated in the Z direction at the center of the coil 41. That is, at the center of the measurement head 31 on the XY plane, lines of magnetic force are generated in the direction toward the electrode material 20 or in the opposite direction.

  Next, the circuit configuration of the measuring head 31 will be described with reference to FIG. FIG. 5 is a circuit diagram showing a circuit configuration of the measurement head 31. The measuring head 31 is provided with the coil 41 and the capacitive electrode 43 as described above. Furthermore, one end of the coil 41 is connected to the switch 47, and the other end is connected to the ground. The capacitor electrode 43 is also connected to the switch 47. The current collector 21 facing the capacitor electrode 43 is connected to the ground. Therefore, the capacitor electrode 43 and the current collector 21 form a capacitor (capacitor). That is, the current collector 21 serves as the other capacitor electrode constituting the capacitor. The switch 47 is connected to the oscillator 50 via a cable 51 that is a conductive wire. In other words, the high frequency voltage generated by the oscillator 50 is supplied to the switch 47 via the cable 51. The switch 47 switches the output destination of the oscillator 50. That is, the switch 47 switches the connection destination of the oscillator 50 from the coil 41 to the capacitive electrode 43 or from the capacitive electrode 43 to the coil 41. A high frequency voltage from the oscillator 50 is applied to one of the coil 41 and the capacitor electrode 43 by the switch 47.

  For example, when measuring the thickness of the active material layer 22, the switch 47 connects the oscillator 50 to the coil 41. Thereby, the coil 41 generates an alternating magnetic field. The electrode material 20 is provided with a current collector 21 made of aluminum foil or the like. An alternating magnetic field is generated in the vicinity of the aluminum foil that is a diamagnetic material. That is, lines of magnetic force are generated in a direction orthogonal to the sheet-like current collector 21. Then, an eddy current is generated on the surface of the current collector 21, and the lines of magnetic force are reduced. That is, an eddy current is generated in a direction that cancels the change in the coil magnetic field. Since the number of magnetic field lines is reduced, the inductance is reduced. The amount of decrease in inductance changes according to the distance between the current collector 21 and the coil 41. That is, as the current collector 21 and the measurement head 31 provided with the coil 41 are closer, the inductance is greatly reduced. On the other hand, the air gap length is substantially constant by setting the air ejected from the ejection port 42 to a constant pressure. That is, the distance between the surface of the electrode material 20 and the measuring head 31 is substantially constant. Therefore, when the active material layer 22 is thinned, the distance between the current collector 21 and the measurement head 31 is reduced, and when the active material layer 22 is thickened, the distance between the current collector 21 and the measurement head 31 is increased. Thus, the distance between the current collector 21 and the measurement head 31 changes according to the thickness of the active material layer 22.

The specific resistance of the active material layer 22 is 1 × 10 ⁻² Ω · cm to 1 Ω · cm, and the specific resistance of aluminum or copper is about 2 × 10 ⁻⁶ Ω · cm. Therefore, the specific resistance of the active material layer 22 is about 10 ⁴ to 10 ⁶ higher than that of the current collector 21. The active material layer 22 has almost no diamagnetic property. There is almost no influence on the inductance by the active material layer 22. Even if the thickness of the active material layer 22 changes, the inductance hardly changes. Note that manganese Mn and cobalt Co contained in the active material layer 22 are ferromagnetic materials and have the property of increasing the lines of magnetic force. However, when compared with the diamagnetic strength of the aluminum foil or copper foil used as the current collector 21, it is almost negligible. There is almost no influence on the inductance by the active material layer 22.

  The inductance changes depending on the distance between the coil 41 and the current collector 21, that is, the distance between the measurement head 31 and the current collector 21. Therefore, the distance between the coil 41 and the current collector 21 can be measured by obtaining the oscillation frequency of the oscillator 50. The change in inductance can be determined by the oscillation frequency of the oscillator 50. The thickness of the active material layer 22 can be measured by subtracting the air gap from the distance between the coil 41 and the current collector 21. For example, when the active material layer 22 becomes thin under the condition that the air gap is constant, the distance between the measurement head 31 and the current collector 21 becomes small. On the other hand, when the active material layer 22 becomes thicker under the condition that the air gap is constant, the distance between the measuring head 31 and the current collector 21 increases. Therefore, by obtaining the oscillation frequency distribution of the oscillator 50, the in-plane distribution of the thickness of the active material layer 22 can be measured. Furthermore, the thickness distribution can be measured at high speed without contact.

  On the other hand, when measuring the unevenness of the active material layer 22, the switch 47 is switched to connect the oscillator 50 to the capacitor electrode 43. Thereby, a capacitance (capacitor) is formed by the capacitance electrode 43 and the electrode material 20. The capacitance changes depending on the dielectric constant between the capacitive electrodes and the distance between the capacitive electrodes. Therefore, the capacitance changes depending on the material and state of the active material layer 22 disposed between the current collector 21 and the capacitor electrode 43. For example, in the active material layer 22 where the conductive auxiliary agent 25 is densely packed, the conductivity is high. Therefore, the effective inter-electrode distance is reduced and the capacitance is increased.

  An in-plane distribution of the oscillation frequency of the oscillator 50 is obtained under conditions where the air gap is constant. By doing so, the unevenness and homogeneity of the active material layer 22 can be measured. For example, the capacitance shown in FIG. 10 and FIG. 11 is greatly different from that in the normal part in the abnormal part such as the conductive agent crowded part, the metallic foreign matter mixed part, the void generating part, and the chipping part. Furthermore, the mixing unevenness of the active material 23, the binder 24, and the conductive additive 25 in the active material layer 22 can also be measured. By obtaining the oscillation frequency distribution, the homogeneity of the active material layer 22 can be measured.

  By repeating the above measurement, the film thickness distribution and homogeneity of the active material layer 22 can be measured. For example, the coil 41 and the oscillator 50 are connected, and the thickness of the active material layer 22 is measured from the oscillation frequency of the oscillator 50. Thereafter, the switch 47 is switched to connect the oscillator 50 and the capacitor electrode 43. From the oscillation frequency of the oscillator 50, the homogeneity of the active material layer 22 is measured. Thereby, the measurement in the position with the electrode material 20 is complete | finished. When the measurement at this position is completed, the electrode material 20 is moved, and the positions of the measurement head 31 and the electrode material 20 are shifted. Then, at another position of the electrode material 20, the switch 47 is switched to measure the oscillation frequency. By repeating this, measurement for the entire electrode material 20 is performed. In this way, non-contact and high-speed measurement is possible. Alternatively, after the switch 47 is connected to the coil 41 and the in-plane distribution of the oscillation frequency is measured, the switch 47 may be connected to the capacitor electrode 43 and the in-plane distribution of the oscillation frequency may be measured. Of course, conversely, the switch 47 may be connected to the capacitor electrode 43 to measure the in-plane distribution of the oscillation frequency, and then the switch 47 may be connected to the coil 41 to measure the in-plane distribution of the oscillation frequency.

  Next, a specific configuration of the measurement circuit will be described with reference to FIG. FIG. 6 is a circuit diagram illustrating an example of a measurement circuit. The oscillator 50 is an LC oscillation circuit, specifically a Colpitts oscillation circuit. The oscillator 50 includes a coil 52, a capacitor 53, a resistor 54, a transistor 55, and the like. Two capacitors 53 are connected in series between the output of the oscillator 50 and the ground. The coil 52 is connected in parallel with the two capacitors 53. In order to determine the oscillation frequency, on the output side of the oscillator 50, the transistor 55 of the oscillator 50 is connected to a frequency counter.

  The output terminal of the oscillator 50 is connected to the switch 47 via the cable 51. The coil 52 of the oscillator 50 is connected between the ground and the cable 51. Note that one end of the coil 41 is connected to the output terminal of the oscillator 50 via the switch 47, and the other end is connected to the ground via the coated wire of the coaxial cable that is the cable 51. Therefore, the coil 52 of the oscillator 50 and the coil 41 of the measuring head 31 are connected in parallel.

  The output of the oscillator 50 to the frequency counter is branched and connected to the buffer amplifier 56 and the synchronous detection circuit 57. The output of the buffer amplifier 56 is connected to the differential transformer 60 via the cable 66. The buffer amplifier 56 buffers the output of the oscillator 50 and outputs it to the differential transformer 60. Accordingly, the primary coil 63 of the differential transformer 60 is excited by the high frequency from the oscillator 50. Further, the output to the frequency counter of the oscillator 50 is supplied to the synchronous detection circuit 57. In addition, the differential voltage from the secondary coil 62 of the differential transformer 60 is input to the synchronous detection circuit 57 via the cable 67. The synchronous detection circuit 57 performs synchronous detection on these two signals. Thereby, the positional displacement of the measuring head 31, that is, the height can be measured. The position displacement measured by the synchronous detection circuit 57 becomes a position output and is input to the control PC. Thus, by using the output of the oscillator 50 for the differential transformer 60, it is possible to prevent the influence of high frequency interference. That is, when the output to the coil 41 and the output to the differential transformer 60 are made separate, they may interfere with each other. However, by sharing the output to the coil 41 and the output to the differential transformer 60, the influence of interference can be prevented. Therefore, the thickness can be measured accurately.

The inductance of the oscillator 50 is L _osc and the capacitance is C _osc . Here, L _osc = 3.99 μH and C _osc = 110 pF. The cable 51 is a coaxial cable. _Let the inductance L _{cable of the} cable 51 be the capacitance C _cable . Note that C _cable = 17.25 pF.

The combined inductance of the entire measurement circuit is L, and the inductance of the coil 41 of the measurement head 31 is L _gap . L _gap varies depending on the air gap. The combined inductance L ₁ when the switch 47 connects the oscillator 50 to the coil 41 is expressed by the following equation (1).
1 / L ₁ = 1 / L _osc + 1 / (L _cable + L _gap ) (1)

Also, when the switch 47 connects the oscillator 50 to the capacitor electrode 43, the combined inductance L ₂ is expressed by the following equation (2).
1 / L ₂ = 1 / L _osc + 1 / L _cable (2)

The capacity of the capacity electrode 43 and the electrode material 20 is C _gap . C _gap varies depending on the state of the active material layer 22. Combined capacitance C ₁ when connecting the switch 47 to the coil 41 is as Equation (3).
C ₁ = C _osc + C _cable (3)

Combined capacitance C ₂ when connecting the switch 47 to the capacitor electrode 43 is as shown in equation (4).
C ₂ = C _osc + C _cable + C _gap (4)

Here, the oscillation frequency f is expressed by the following equation (5).
f = 1 / (2π (LC) ^1/2 ) (5)

Therefore, by substituting C ₁ and L ₁ into equation (5), the oscillation frequency f when the oscillator 50 is connected to the coil 41 is obtained. Here, the inductance L _gap of the coil 41 depends on the thickness of the active material layer 22 as described above. In a state where the oscillator 50 and the coil 41 are connected, the oscillation frequency f is obtained by the frequency counter of the oscillator 50. Thereby, the thickness of the active material layer 22 can be measured.

On the other hand, when C ₂ and L ₂ are substituted into the equation (5), the oscillation frequency f when the oscillator 50 is connected to the capacitor electrode 43 is obtained. Here, the capacity of the capacitor electrode 43 depends on the density and unevenness of the active material 23 and the conductive additive 25 in the active material layer 22. In a state where the oscillator 50 and the capacitor electrode 43 are connected, the oscillation frequency f is obtained by the frequency counter of the oscillator 50. Thereby, the density and nonuniformity of the active material 23 and the conductive additive 25 in the active material layer 22 can be measured. For example, as shown in FIGS. 10 and 11, the oscillation frequency f changes greatly at a conductive agent densely packed portion, a metal foreign matter mixed portion, a void occurrence location, and a chip occurrence location as compared with a normal location. Therefore, these abnormal places can be detected. Further, in the active material layer 22, uneven mixing of the active material 23, the binder 24, and the conductive additive 25 can be evaluated. By comparing the measurement result with the coil 41 connected with the measurement result with the capacitor electrode 43 connected, the homogeneity of the active material layer 22 considering the thickness distribution can be comprehensively evaluated. Therefore, the battery electrode material can be evaluated from various viewpoints.

  Next, an actual measurement result is shown using FIG. FIG. 7 shows the measurement result of the oscillation frequency f with the coil 41 connected. FIG. 7 is a diagram showing a measurement result of a negative electrode material using a copper foil having a thickness of 15 μm as the current collector 21. Here, the negative electrode material in which the active material layer 22 of 70 μm is provided on one surface of the copper foil and the active material layer 22 of 120 μm is provided on the other surface is measured. Further, a copper foil having a thickness of 17 μm in which the active material layer 22 is not provided is measured for reference. In FIG. 7, the horizontal axis represents the surface distance (air gap) between the measurement head 31 and the surface of the electrode material 20, and the vertical axis represents the oscillation frequency f.

The surface distance can be changed by changing the air pressure of the measuring head 31. Then, the oscillation frequency f is measured by changing the surface distance. It can be seen from FIG. 7 that the oscillation frequency decreases as the surface distance increases. That is, (1) as in equation depending on the inductance _{L gap} of the coil 41, the combined inductance _{L 1} is changed. Therefore, the oscillation frequency f changes according to the inductance L _gap of the coil 41.

  In the measurement of the reference copper foil without the active material layer 22, the oscillation frequency is about 7.47 MHz when the surface distance is 0, that is, when the copper foil and the measuring head 31 are in contact with each other. As the surface distance increases, the oscillation frequency decreases. In the measurement of the negative electrode material, both surfaces have substantially the same inclination as the measurement of the copper foil. That is, when each curve is translated to the right side by the thickness of the active material layer 22, the curves substantially coincide. Thus, it can be seen that the oscillation frequency changes according to the thickness of the active material layer 22. Therefore, the thickness distribution of the active material layer 22 can be measured. The inclination of the relationship between the oscillation frequency and the surface distance can be adjusted by the number of turns of the coil.

  Of course, both the positive electrode material and the negative electrode material can be evaluated by using the thickness measuring apparatus according to the present embodiment. In the above description, the positive electrode material has been described on the assumption that the aluminum foil is used as the current collector 21 and lithium manganate is used as the active material. However, the measurement may be performed on the positive electrode material using other materials. . For example, you may evaluate the positive electrode material which used lithium cobaltate as an active material. Similarly, the negative electrode material may have a current collector 21 other than copper foil or an active material other than graphite. For example, silicon may be used as the negative electrode active material. Since measurement is performed in a non-contact manner, silicon chipping or the like can be prevented. Furthermore, the current collector 21 is suitable for a battery electrode material that is a diamagnetic material such as aluminum or copper. Of course, a current collector other than aluminum foil or copper foil may be used. The thickness measuring apparatus according to this embodiment is suitable for evaluating an electrode material having a current collector of a diamagnetic material. In the above description, the output to the coil 41 and the output to the differential transformer 60 are shared, but the output to the coil 41 and the output to the differential transformer 60 may be made separate. That is, an AC voltage different from the high frequency output from the oscillator 50 may be input to the differential transformer 60.

  Furthermore, the structure by which the adhesive sheet is provided between the electrical power collector 21 and the active material layer 22 may be sufficient. In this case, the total thickness of the adhesive sheet and the active material layer 22 can be measured. Furthermore, before the active material layer 22 is adhered to the adhesive sheet, the thickness distribution of the adhesive sheet can be measured. Of course, you may use for batteries other than a lithium ion battery. That is, by using the thickness measuring apparatus according to the present embodiment, it is possible to evaluate the battery electrode material in which the current collector 21 is provided with the active material layer 22. In particular, it is suitable for evaluation of a secondary battery in which the active material layer 20 including the active material 22 is provided on the current collector 21.

  The thickness measuring apparatus according to the present embodiment is also applicable to a configuration in which a metal sheet such as the current collector 21 is not provided. In this case, a sheet to be measured may be attached to a metal plate or the like by vacuum suction. Thereby, a separator, an active material layer sheet, an insulating sheet, etc. can be measured.

  Further, the measurement heads 31 may be arranged on both surfaces of the electrode material 20. Thereby, the active material layers 22 provided on both surfaces of the current collector 21 can be measured simultaneously. Therefore, the measurement time can be shortened. Note that the measurement heads 31 on both sides may be shifted. In this case, the two measuring heads 31 perform simultaneous double-sided measurement at different positions.

  When the electrode material 20 is measured on one side, a plate-like member made of plastic, metal, or the like may be provided under the electrode material 20. This configuration will be described with reference to FIG. 8A is a side cross-sectional view showing a state where there is no plate-like member, and FIG. 8B is a side cross-sectional view showing a state where a plastic plate-like member 17 is provided. (C) is side surface sectional drawing which shows the state in which the metal plate-shaped member 18 was provided.

  In the configuration in which the plate member shown in FIG. 8A is not provided, the clamp 14 clamps the electrode material 20. Then, air is ejected in the direction of the arrow from the ejection port 15 provided in the stage 11. As a result, the electrode material 20 clamped by the clamp 14 floats on the air. Therefore, it can prevent that the electrode material 20 and the stage 11 contact. In addition, at the end of the electrode material 20, there is a portion that protrudes from the metal foil that is the current collector 20. This projecting portion is sandwiched and fixed by a metal clamp 14. The clamp 14 is connected to the GND of the oscillator 50. Thereby, the current collector 20 can be grounded.

  Moreover, when the electrode material 20 has wrinkles, as shown in FIG.8 (b), wrinkles can be extended by using the plate-shaped member 17. FIG. In the configuration shown in FIG. 8B, a plastic plate-like member 17 is disposed under the electrode material 20. The electrode member 20 and the plate-like member 17 are clamped and held by the clamp 14. An adsorption groove 19 is provided on the upper surface of the plate member 17. The suction groove 19 is formed so that the peripheral edge of the electrode material 20 can be vacuum-sucked. Since the suction groove 19 sucks and fixes the electrode material 20, the wrinkles of the electrode material 20 can be extended. And the air from the jet nozzle 15 is ejected to the plate-shaped member 17, and the plate-shaped member 17 floats by air. Thus, the wrinkle of the electrode material 20 can be extended by providing the mode which sticks the plate-shaped member 17 made of plastic. Of course, the plate-like member 17 may be made of a material other than plastic.

  In the configuration shown in FIG. 8C, the plate-like member 17 having the configuration shown in FIG. 8B is replaced with a metal plate-like member 18. Furthermore, the electrode material 20 as a measurement target is replaced with a sheet 26 such as a conductive sheet or an insulator sheet. Accordingly, the metal plate-like member 18 is disposed below the sheet 26. A sheet 26 is sucked and fixed by a suction groove 19 provided in the plate member 18. In this way, by providing a mode for attaching the metal plate-like member 18, it is possible to measure a conductive sheet or an insulating sheet other than the electrode material. For example, the function similar to that of the current collector 21 of the electrode material 20 can be obtained by using the diamagnetic plate-like member 18. By measuring the oscillation frequency of the oscillator 50, the insulating sheet or the like on the plate-like member 18 can be measured. By connecting the coil, the thickness distribution of the sheet 26 can be measured.

  Furthermore, in the case of simultaneous measurement on both sides, it is preferable to connect an oscillator 50 having a greatly shifted frequency to the measuring head 31. That is, an oscillator is prepared separately, and the frequency of the high frequency output simultaneously is greatly shifted. Thereby, it is possible to prevent the oscillation frequency from being shifted due to high frequency interference. Moreover, when the measurement head 31 is arrange | positioned in the same XY position in both surfaces, it also becomes possible to measure the thickness of the measuring object in which conductive sheets, such as the electrical power collector 21, are not provided. In this case, the capacitive electrode provided on one measurement head 31 is used in place of the current collector 21. That is, a capacitor is formed by the capacitor electrode 32 of the measuring head 31 that is opposed. Then, the coil 41 and the oscillator 50 of the other measuring head 31 are measured to obtain the oscillation frequency. By doing so, the thickness of the measurement object can be measured. Measurement other than battery electrode material 20 can be performed in a non-contact manner. Therefore, it is possible to prevent the measurement object from being damaged.

  In the above description, the measurement position is changed by moving the electrode material 20. However, the measurement position may be changed by moving the measurement head 31. Furthermore, the measurement position may be changed by moving both the electrode material 20 and the measurement head 31.

DESCRIPTION OF SYMBOLS 11 Stage 12 Cover 13 Movable part 14 Clamp 15 Adsorption port 17 Plate-shaped member 18 Plate-shaped member 20 Electrode material 21 Current collector 22 Active material layer 23 Binder 24 Conductive auxiliary agent 26 Sheet 30 Measurement arm 31 Measurement head 32 Plate spring 33 Base 34 Base Arm 35 Tip Arm 40 Main Body 41 Coil 42 Spout 43 Capacitance Electrode 44 Convex 50 Oscillator 51 Cable 52 Coil 53 Capacitor 54 Resistor 55 Transistor 56 Buffer Amplifier 57 Synchronous Detection Circuit 60 Differential Transformer 61 Core 62 Secondary Coil 63 1 Next coil

Claims (13)

A thickness measuring device for a battery electrode material provided with an active material layer containing an active material on a current collector,
In order to form an air gap between the battery electrode material, a head for ejecting air to the surface of the battery electrode material;
A coil provided on the head;
A thickness measuring device comprising: an oscillator connected to the coil.   A thickness measuring device for measuring a thickness of an active material layer containing the active material according to an oscillation frequency when the oscillator and the coil are connected. A capacitive electrode provided on the head and constituting a capacity with the battery electrode material;
The thickness measuring device according to claim 1, further comprising: a switch that switches an output of the oscillator from the coil to the capacitive electrode. An arm for supporting the head;
The thickness measuring apparatus according to claim 1, wherein a height adjusting mechanism that adjusts a height of the head is provided on the arm.   The thickness measuring device according to any one of claims 1 to 4, wherein the head is supported by the arm via a leaf spring parallel link mechanism.   The thickness measuring device according to any one of claims 1 to 5, wherein a plate-like member for adsorbing and fixing the battery electrode material is provided below the battery electrode material. A method for measuring a thickness of a battery electrode material in which an active material layer containing an active material is provided on a current collector,
Injecting air onto the surface of the battery electrode material to form an air gap with the battery electrode material;
Generating an alternating magnetic field in a coil provided in the head by an oscillator;
And a step of obtaining an oscillation frequency of the oscillator.   The thickness measurement method according to claim 7, wherein the thickness distribution of the active material layer is measured according to an oscillation frequency distribution of the oscillator when the measurement head and the electrode are relatively moved. The head is provided with a capacity electrode that constitutes a capacity with the battery electrode material,
The thickness measuring method according to claim 7 or 8, wherein the output of the oscillator is switched from the coil to the capacitive electrode. The head is directed by an arm;
The thickness measuring method according to claim 7, wherein the arm is provided with a height adjusting mechanism that adjusts the height of the head.   The thickness measuring method according to claim 7, wherein the head is supported by the arm via a leaf spring parallel link mechanism.   The thickness measuring method according to claim 7, wherein a specific resistance of the current collector is higher than a specific resistance of the active material layer.   The thickness measuring method according to any one of claims 7 to 12, wherein a plate-like member for adsorbing and fixing the battery electrode material is provided below the battery electrode material.

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