JP2014082021A - Observation cell and lithium ion battery observation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an observation cell in which a bubble, generated during charge/discharge test, can be removed by a simple operation, and to provide a lithium ion observation system.SOLUTION: An observation cell includes a cell body (1) having a stage (32) for supporting a test lithium ion cell, a flange (2) having a transparent plate (10) facing the stage and constituting an observation window, and engaging with the cell body, and sealing means (36) surrounding the whole circumference of the stage. When attaching the flange (2) to the cell body (1), a sealed space (50) for housing the test lithium ion cell is formed by the flange, the cell body and the sealing means. The cell body is provided with first and second passages (51, 52) communicating with the sealed space (50), and an electrolyte is supplied to the sealed space via the first port and first passage.

Description

  The present invention relates to an observation cell and a lithium ion battery observation system capable of observing a change in state of an active material layer formed on an electrode plate of a lithium ion battery during operation under a microscope.

  Lithium ion secondary batteries are used as power supply devices for electric vehicles and portable terminals, and research and development of lithium ion batteries are rapidly progressing. In the development of a lithium ion battery, if development of the internal structure of the battery over time can be observed, acquisition of useful development data is expected. For example, the color and shape of the positive electrode and the negative electrode active material change depending on the state of charge and the concentration of Li ions. Therefore, if the color change or shape change of the active material can be observed from the outside, the generation state of Li ions and the distribution state of Li ions in the positive electrode and negative electrode active material layers can be grasped, which is useful for the development of new battery materials. Data can be collected.

  Furthermore, when the ion concentration of Li ions locally increases or battery deterioration progresses, Li ions segregate as metallic lithium, and dendrites are deposited. Dendrites are often acicular crystals at the beginning of production, and when dendrites grow, there is a risk that the positive electrode and the negative electrode may be short-circuited through the separator that separates the positive electrode and the negative electrode. When the positive electrode and the negative electrode are short-circuited due to the growth of dendrites, partial heat generation occurs, and if the growth reaction is accelerated, there is a risk of thermal runaway. Therefore, if the generation state of dendrite can be observed over time from the outside of the battery, it is expected to obtain useful information for improving the safety of the lithium ion battery.

  As a method for observing the internal structure of a lithium ion battery, a button-type simple evaluation cell is known. In this evaluation cell, a positive electrode plate, a separator, and a negative electrode plate are arranged in a recess formed in a stainless steel pot, and after injecting an electrolytic solution, a metal lid is arranged to form a test lithium ion battery. Yes. Then, after charging and discharging are repeated for a predetermined time or a predetermined number of times, the inside is opened and data such as the progress of deterioration of the battery material is acquired.

  Furthermore, as a modification of the simple evaluation cell described above, a method of fitting a glass plate into a metal lid and observing the inside of the battery from the direction orthogonal to the negative electrode plate and the positive electrode plate via the glass plate is also known. .

  When the button-type simple evaluation cell described above is used, a sealed lithium ion battery is formed. Therefore, after repeated charging and discharging, the battery structure and the like are deteriorated by disassembling and observing the internal structure. You can keep track of your progress. However, since the internal structure of the lithium ion battery in the cell cannot be observed directly from the outside, there is a drawback that the operating lithium ion battery cannot be observed continuously over time.

  When observing the internal structure of an operating lithium ion battery, the lithium ion battery to be observed is placed in a sealed observation cell, and the internal structure is observed through a glass window under a microscope. In this case, in order to observe with high magnification and high resolution, it is necessary to observe using an objective lens having a large numerical aperture. However, since an objective lens having a large numerical aperture has a short distance from the front end of the lens to the focal plane, it is difficult to match the observation site of the lithium ion battery with the focal plane of the objective lens. In particular, when observing through a glass window, the working distance is restricted, which is particularly difficult. Therefore, in order to perform high-resolution microscope observation, it is necessary to optimally maintain the interval between the objective lens of the microscope and the test lithium ion battery housed in the observation cell.

  Furthermore, when the test lithium ion battery is arranged in the observation cell, it must be assembled in a glove box filled with an inert gas such as argon. In this case, when the positive electrode plate and the negative electrode plate are impregnated with the electrolytic solution in the glove box, the positive electrode plate and the negative electrode plate impregnated with the electrolytic solution are accommodated in the observation cell, and the charge / discharge test is started. This causes a problem that air bubbles are generated. The generated bubbles often stay between the transparent plate forming the observation window and the test lithium ion battery. In this case, the image picked up by the microscope is superimposed with the image due to the bubbles, and a situation in which the state change of each active material in the active material layer is not clearly picked up occurs. Furthermore, the generation of bubbles often occurs not only immediately after the start of the charge / discharge test but also after a considerable time has elapsed after the start of the test. Therefore, in order to accurately observe the internal state of the operating lithium ion battery, it is an urgent task to develop bubble removing means for removing bubbles generated during the test.

An object of the present invention is to realize an observation cell in which the generation of bubbles due to charge / discharge operations is suppressed.
Another object of the present invention is to provide an observation cell that can remove bubbles by a simple operation even if bubbles are generated during a charge / discharge test.
Furthermore, another object of the present invention is to provide a lithium ion battery observation system capable of removing bubbles with a simple operation even when bubbles are suppressed during the charge / discharge test. There is.

The observation cell according to the present invention is an observation cell in which an active material layer formed on an electrode plate of a test lithium ion battery in operation can be observed with a microscope through an observation window,
A cell body having a stage for supporting a test lithium ion battery;
A flange that faces the stage and constitutes an observation window; a flange that engages with the cell body;
Sealing means for enclosing the entire circumference of the stage;
An insulating stopper ring that is disposed between the cell body and the flange, electrically insulates the cell body and the flange and defines a distance between the stage and the transparent plate;
Having first and second connection terminals provided on the cell body and the flange, respectively;
The test lithium ion battery is configured as a laminate in which a first electrode plate, a separator, and a second electrode plate are stacked on the stage,
When a flange is attached to the cell body, a sealed space for accommodating the test lithium ion battery is formed by the flange, the cell body, and sealing means,
The cell body is provided with first and second flow paths communicating with the sealed space, and first and second ports formed in the first and second flow paths, respectively.
An electrolyte solution is supplied to the sealed space through the first port and the first flow path.

  As a result of various experiments and analysis by the present inventor on the cause of bubble generation, inert gas and a small amount of water adsorbed on the positive electrode plate and negative electrode plate constituting the test lithium ion battery are the cause of bubble generation. It turned out to be. That is, the test lithium ion battery is assembled in a glove box filled with an inert gas such as argon gas, and stored in an observation cell. Therefore, when the positive electrode plate or negative electrode plate is impregnated with the electrolyte in the clove box and stored in the observation cell, the electrolyte solution is impregnated with the inert gas adsorbed on the positive electrode plate or negative electrode plate. When charging and discharging are repeated, an inert gas appears as bubbles. Similarly, when a small amount of moisture is adsorbed, the moisture is decomposed, and hydrogen gas or oxygen gas appears as bubbles.

  Based on the analysis results described above, in the present invention, a sealed space is formed by a flange having an observation window, a stage provided in the cell body, and a sealing means surrounding the stage, and a test lithium ion battery is formed in the sealed space. Place. The cell body is formed with first and second flow paths and first and second ports communicating with a sealed space in which a test lithium ion battery is accommodated, and the first port is connected to an electrolyte supply means. The second port is connected to a decompression means such as a vacuum device. Prior to the charge / discharge test, the sealed space is depressurized, so that the test lithium ion battery stored in the sealed space is maintained in a vacuum state or in a reduced pressure atmosphere. Inert gas and the like are removed and maintained in a clean state. Therefore, after the positive electrode plate and the negative electrode plate are in a clean state, the electrolytic solution is supplied through the first port and the first flow path so that the clean state lithium ion battery is impregnated with the electrolytic solution. It becomes possible to make it. That is, by maintaining the positive electrode plate and the negative electrode plate constituting the test lithium ion battery in a reduced-pressure atmosphere, a minute amount of water, inert gas, and the like that cause generation of bubbles are removed. Can be prevented from occurring.

  In a preferred embodiment of the observation cell according to the present invention, first and second valves are provided in the first and second flow paths, respectively, and an electrolyte supply means is connected to the first port. A pressure reducing means is connected to the second port, and when supplying the electrolyte solution to the sealed space, the space from the first valve to the second port is decompressed by the pressure reducing means, and the electrolyte solution is decompressed. The electrolytic solution is supplied from the supply means to the sealed space through the first port and the first flow path. When the entire flow path including the sealed space in which the test lithium ion battery is accommodated is decompressed, the pressure difference between the sealed space and the external space is utilized by using an electrolyte supply means such as a syringe pump. Thus, the electrolytic solution can be smoothly supplied to the sealed space. As a result, the observation cell including the test lithium-ion battery is taken out of the glove box and maintained in a clean state from which the adsorbed inert gas and a small amount of moisture are removed, and then the electrolyte is supplied to the test lithium-ion battery. It becomes possible to do.

  In another preferred embodiment of the observation cell according to the present invention, the electrolyte supply means is constituted by a syringe pump in which the electrolyte is accommodated, and when bubbles are generated in the sealed space during the charge / discharge test, The second valve is maintained in the closed state and the first valve is maintained in the open state, and the syringe pump is operated so that the space formed between the second valve and the first port is depressurized. By operating, the generated bubbles move to the syringe side through the first flow path and the first port. As a result of various experiments and analysis on the method for removing bubbles generated by the charge / discharge test by the present inventor, the generated bubbles are excluded from the sealed space by reducing the pressure in the sealed space where the bubbles are present. Turned out to be. That is, by appropriately operating the syringe pump connected to the first port, alternately reducing the pressure in the sealed space and the step of returning from the reduced pressure state to the normal pressure one or more times, The generated bubbles can be removed from the sealed space. Therefore, even if bubbles are generated during observation, it is possible to remove the bubbles only by operating the syringe pump.

  In another preferred embodiment of the observation cell according to the present invention, the laminate constituting the test lithium ion battery is positioned on the stage of the cell body, and the observation formed on the second electrode plate and the separator, respectively. Two positioning pins for aligning the holes are provided. These two positioning pins are provided as pop-up type positioning pins that can be displaced in a direction orthogonal to the stage. When the flange is engaged with the cell body, It is characterized by being displaced in a direction away from the head. When observing the active material layer formed on the first electrode plate, an observation hole is formed in the second electrode plate and the separator disposed on the side close to the transparent plate, and illumination light is transmitted through the observation hole. It is necessary to enter the first electrode plate. In this case, when the observation hole formed in the second electrode plate and the observation hole formed in the separator are not aligned, the observation area is shifted, or the first electrode plate and the second electrode plate are in direct contact with each other and short-circuited. There is a risk of malfunction. Therefore, in the present invention, two positioning pins are provided on the stage that supports the test lithium ion battery, and the positioning pins are provided as pop-up positioning pins. This pop-up pin achieves the effect that the observation holes formed in the electrode plate and the separator are accurately aligned, and the problem that the observation area is shifted or the two electrode plates are in direct contact is eliminated.

A lithium ion battery observation system according to the present invention includes an observation cell in which a test lithium ion battery is housed, a microscope that images the inside of the test lithium ion battery through an observation window formed in the observation cell, An observation system comprising a decompression device and an electrolyte solution supply device respectively connected to an observation cell and observing an active material layer formed on an electrode plate of a test lithium ion battery during operation, the observation system Cell
A cell body having a stage for supporting a test lithium ion battery;
A flange that faces the stage and constitutes an observation window; a flange that engages with the cell body;
Sealing means for enclosing the entire circumference of the stage;
An insulating member disposed between the cell body and the flange to electrically insulate the cell body and the flange;
Having first and second connection terminals provided on the cell body and the flange, respectively;
The test lithium ion battery is configured as a laminate in which a first electrode plate, a separator, and a second electrode plate are stacked on the stage,
When a flange is attached to the cell body, a sealed space for accommodating the test lithium ion battery is formed by the flange, the cell body, and sealing means,
The cell body is provided with first and second flow paths communicating with the sealed space, and first and second ports formed in the first and second flow paths, respectively.
An electrolyte supply means is connected to the first port, and a decompression device is connected to the second port.
The pressure reducing means decompresses the sealed space through the second port and the second flow path, and the electrolyte supply means electrolyzes the sealed space through the first port and the first flow path. A liquid is supplied.

  In the present invention, the cell body supporting the test lithium ion battery, the flange having the observation window, and the sealing means form a sealed space, and the two flow paths communicating with the sealed space are formed. The sealed space in which the test lithium ion battery is disposed can be decompressed via the first flow path, and then the electrolytic solution can be supplied to the sealed space via the second flow path. As a result, after removing the inert gas and a small amount of water adsorbed on the electrode plate constituting the test lithium ion battery, the test lithium ion battery can be impregnated with the electrolytic solution, and the generation of bubbles is greatly increased. It becomes possible to remove the generated bubbles with a simple operation as they decrease.

It is a figure which shows the whole structure of the cell for observation by this invention. It is a figure which shows an example of a flange. It is the top view and diagrammatic sectional view which show an example of a cell main body. It is a diagrammatic sectional view showing diagrammatically the state where the test lithium ion battery is stored in the sealed space. It is a figure which shows the approach state of illumination light. It is a diagram which shows an example of the lithium ion battery observation system by this invention.

  In the present invention, a sealed space is formed by a cell body that supports a test lithium ion battery, a flange having an observation window, and a sealing member (O-ring) that seals the entire circumference of the stage on which the test lithium ion battery is disposed. And forming a test lithium ion battery in the sealed space. Two flow paths (sealing paths) communicating with the sealed space are formed in the cell body. A first port is formed in the first flow path, and a second port is formed in the second flow path. A pressure reducing means such as a vacuum device is connected to the first port to reduce the pressure in the sealed space. The second port is connected to a syringe pump in which an electrolytic solution is accommodated, and the electrolytic solution is supplied from the syringe pump to the sealed space using a pressure difference.

  When the positive and negative electrode plates constituting the test lithium ion battery are exposed to the air, the performance of the positive electrode plate and the negative electrode plate deteriorates significantly. Therefore, when storing the test lithium ion battery in the observation cell, an inert gas such as argon gas is used. Need to work in a glove box filled with On the other hand, when the positive electrode plate, the negative electrode plate, and the separator are accommodated in the observation cell and sealed by impregnating the electrolytic solution by the operation in the glove box, the inert gas remains in the sealed space. Air bubbles are generated in the vicinity of the test lithium ion battery immediately after the start of the test, which hinders observation. In addition, factors other than the inert gas during charging / discharging, for example, when a minute amount of moisture or inert gas is adsorbed on the positive electrode plate or the negative electrode plate, it is decomposed by charging / discharging, and bubbles may be generated as well. . Therefore, in order to capture a clear image, it is necessary to take measures to prevent the generation of bubbles and remove the generated bubbles. Therefore, in the present invention, the first and second flow paths communicating with the sealed space that houses the test lithium ion battery are formed, the sealed space is depressurized via the first flow path, and the second The electrolyte is supplied to the sealed space through the flow path. With this configuration, the inert gas and the trace amount of water that are the cause of bubbles are removed by maintaining the sealed space in a reduced pressure state or a vacuum state, so that the test lithium ion battery is kept in a clean state. After that, it is possible to supply the electrolytic solution to the sealed space using an electrolytic solution supply means such as a syringe pump. Moreover, even if bubbles are generated near the test lithium-ion battery during the test, the electrolyte can be moved simply by operating the syringe pump to depressurize the sealed space. Moves to the syringe pump side, so that bubbles generated by a simple operation can be removed.

  1-4 is a figure which shows an example of the cell for observation by this invention, FIG. 1 is a figure which shows the relationship between the cell for observation during observation, and the objective lens of a microscope, FIG. 2 is an example of a flange. FIG. 3 shows an example of the cell body, and FIG. 4 shows the formation of the sealed space.

Referring to FIG. 1, an observation cell according to the present invention has a cell main body 1 in which a test lithium ion battery to be observed is arranged, and a flange 2 engaged with the cell main body. The cell body 1 and the flange 2 are engaged via a stopper ring 3 made of an electrically insulating material. The stopper ring 3 serves to electrically insulate the cell body 1 and the flange 2 from each other and to regulate the distance between the cell body and the flange. Further, the stopper ring 3 also serves to regulate the inclination of the flange 2 with respect to the cell body 1, and the flange can be stably and closely engaged with the cell body. That is, by interposing the stopper ring 3 over the entire periphery between the cell body 1 and the flange 2, the flange is brought into close contact with the entire circumference of the cell body even by fixing with a single screw. be able to. As a result, the transparent plate constituting the observation window and the test lithium ion battery can be maintained in parallel. The flange 2 is formed with two spot facing holes 4a and 4b, and at the corresponding position of the cell body, a spot facing hole formed in the electrically insulating material body is formed, and a screw (see FIG. The flange 2 is sealingly engaged with the cell body 1 by screwing. The screw head of the screw to be screwed is located inside the counterbore hole so that it does not protrude from the surface 2a of the flange 2 . In addition, it is also possible to use a screw made of an electrically insulating resin material as the screw. In this case, an insulating screw is formed on the metal cell body without forming a screw hole in the electrically insulating material body. Can be screwed directly. The flange 2 is formed with two fitting holes 5a and 5b into which positioning pins are fitted, and positioning pins 30a and 30b made of an insulating resin material provided in the cell body described later in these fitting holes (see FIG. 3). ) And relative positioning in the circumferential direction between the cell body 1 and the flange 2 is performed. Thus, in the present invention, since there is no member protruding upward from the surface 2a facing the objective lens of the microscope on the surface of the flange 2, even if the revolver supporting the objective lens is rotated, the objective lens There is no problem of interference between the tip and the observation cell.

  An observation window 6 including a transparent plate is formed on the flange 2, and the active material layer of the positive electrode plate or the negative electrode plate of the lithium ion battery disposed in the observation cell is observed through the observation window 6 with a microscope. That is, the illumination light emitted from the objective lens 7 of the microscope enters the inside of the observation cell through the transparent plate provided in the observation window 6 and illuminates the observed active material layer of the test lithium ion battery. . The reflected light emitted from the test lithium ion battery is condensed by the objective lens 7 of the microscope through the observation window 6. A confocal microscope is preferably used as the microscope. The confocal microscope forms an omnifocal image focused over a considerably wide distance range along the optical axis direction by capturing a plurality of two-dimensional images while moving the objective lens along the optical axis direction. Can do. Therefore, it is possible to capture a focused two-dimensional image and a three-dimensional image of each active material laminated along the optical axis direction of the active material layer, and the color change of each active material due to charge / discharge And shape changes can be observed in real time. In particular, since the color of each active material changes according to the Li ion concentration contained in the active material, the distribution state of Li ions and the generation state of dendrite can be observed from the outside.

  It is desirable to use an objective lens with thickness correction as the objective lens of the microscope. In the present invention, an illumination lens is projected through the transparent plate of the observation window, and the reflected light that has passed through the transparent plate is detected by the objective lens, so that an objective lens with plate thickness correction is used. On the other hand, since the working distance of the high-resolution and high-magnification objective lens with thickness correction is as short as several millimeters (for example, about 1.8 mm), the test lithium ion battery is brought closer to the transparent plate of the observation window. Arrange so that.

  A first connection terminal 8 a is attached to the cell body 1, and a second connection terminal 8 b is provided on the flange 2. These connection terminals are made of brass plated with gold and are connected to the charge / discharge controller 9. In the state in which the test lithium ion battery is housed, the first connection terminal 8a is connected to the current collector foil of one electrode plate of the test lithium ion battery via the metal cell body 1, and the second connection. The terminal 8b is connected to the current collector foil of the other electrode plate of the test lithium ion battery via a metal flange. The connection terminals 8a and 8b can be formed not on the side walls of the cell main body and the flange, but in such a manner that a recess is formed in the cell main body and the flange and the recess is located in the recess. During the test of the lithium ion battery, a charge / discharge test is performed under the control of the charge / discharge controller 9 provided outside the observation cell, and the internal state of the lithium ion battery being charged / discharged is observed through the observation window 6. Observed under a microscope.

  FIG. 2 shows an example of a flange, FIG. 2 (A) is a plan view, and FIG. 2 (B) is a sectional view taken along the line II-II in FIG. 2 (A). A circular observation window 6 is formed in the center of the flange 2. An optically transparent glass plate 10 having a thickness of about 1 mm is attached to the observation window via an adhesive. Illumination light emitted from the objective lens of the microscope enters the observation area of the lithium ion battery via the transparent plate 10, and reflected light emitted from the observation area is collected by the objective lens 7 of the microscope via the transparent plate 10. .

  A ring-shaped protrusion 11 is formed on the flange 2 so as to surround the circular transparent plate 10. This ring protrusion 11 engages with a groove in the ring formed on the cell body side, and serves to grip the peripheral edges of the sheet-like positive electrode plate, negative electrode plate and separator constituting the test lithium ion battery. . Further, two recesses 12a and 12b are formed in the flange 2 so as to face each other with the transparent plate 10 interposed therebetween. These recesses are provided on the cell body side, engage with positioning pins for positioning the sheet-like test lithium ion battery, and function as escape holes.

  3A and 3B are diagrams showing an example of the cell body. FIG. 3A is a diagrammatic plan view viewed from the flange side, and FIG. 3B is a cross-sectional view taken along the line II-II in FIG. is there. FIG. 4 is a diagrammatic sectional view schematically showing a state in which the flange 2 is hermetically engaged with the cell body 1 and the test lithium ion battery 20 is accommodated in the sealed space. The cell body 1 is provided with two electrically insulating positioning pins 30a and 30b. These positioning pins 30a and 30b engage with fitting holes 5a and 5b formed in the flange 2, and relative positioning in the circumferential direction between the cell body 1 and the flange 2 is performed. Furthermore, two screw holes 31a and 31b into which two screws for fixing the flange 2 are screwed are formed in the cell body.

  The cell body 1 has a stage 32 that supports the test lithium ion battery 20. As shown in FIG. 4, the test lithium ion battery 20 includes a first electrode plate (for example, negative electrode plate) 21, a separator 22, and a second electrode plate (for example, positive electrode plate) 23. These electrode plates and separators are composed of circular sheet-like members and are stacked on the stage 32. The stage 32 is provided with two positioning pins 33 a and 33 b for positioning the electrode plate and the separator. These positioning pins are pop-up positioning pins that can be displaced with respect to the surface of the stage 32. That is, as shown in FIG. 3B, recesses are formed in the cell body, and elastically deformable springs 34a and 34b (only the spring 34a is shown) are arranged in these recesses, and positioned above these springs. Pins 33a and 33b are arranged, respectively. Therefore, when the flange is not engaged, the tip of the positioning pin protrudes greatly above the surface of the stage 32. When the flange 2 is engaged, the flange 2 is inserted into the recesses 12a and 12b formed in the flange, and is pushed downward by the flange to be displaced downward. A stopper (not shown) is provided and set so that the pin does not jump upward.

  As shown in FIG. 4, each of the first and second electrode plates 21 and 23 and the separator 22 constituting the test lithium ion battery has two pieces so as to correspond to the positions of the positioning pins 33a and 33b, respectively. Positioning holes 21a and 21b, 22a and 22b, 23a and 23b are formed. When assembling the test lithium ion battery, the electrode plate and the separator are placed on the stage so that the two positioning pins are inserted into the positioning holes formed in the first electrode plate 21, the separator 22 and the second electrode plate 23. Laminated and arranged.

  Further, in order to observe the inside of the test lithium ion battery, that is, to observe the active material layer of the first electrode plate 21 located on the lowermost side, the separator 22 and the second electrode plate 23 have a diameter. Observation holes 22c and 23c which are through holes of about 1 mm are formed. The first electrode plate 21 is formed with a through hole 21c having a diameter of about 0.3 mm at the center thereof. The through hole 21c formed in the first electrode plate is a hole for forming a flow path through which the electrolytic solution flows, and is formed as necessary.

  FIG. 5 is a diagrammatic cross-sectional view showing an enlarged observation site of the test lithium ion battery. In this example, a negative electrode plate is used as the first electrode plate 21 and an active material layer formed on the negative electrode plate is observed. As shown in FIG. 5, the positive electrode plate (second electrode plate) 23, the separator 22 and the negative electrode plate 21 (first electrode plate) are sequentially placed on the stage 32 from the side close to the transparent plate 10 constituting the observation window. Laminate. At this time, the positive electrode plate 23 is disposed such that the current collector foil is in direct contact with the flange and the active material layer is adjacent to the separator 22. The negative electrode plate 21 is disposed so that the current collector foil is in direct contact with the stage 32 (cell body) and the active material layer is adjacent to the separator. Further, the positive electrode plate 23 and the separator 22 positioned on the side close to the transparent plate 10 constituting the observation window are positioned so that the observation holes 23c and 22c are aligned with each other.

  Illumination light emitted from the objective lens of the microscope passes through the transparent plate 10 and illuminates the active material layer of the negative electrode plate 21 through observation holes 23c and 22c formed in the positive electrode plate 23 and the separator 22, respectively. In this example, the observation holes formed in the electrode plate 23 and the separator 22 are positioned using the two positioning pins 33a and 33b so that they are aligned with each other. The problem of short circuit due to direct contact between the first electrode plate and the second electrode plate is eliminated. That is, as will be described later, the assembly operation of the observation cell is performed in a glove box filled with an inert gas. In this case, since the workability of the glove box is poor, it is difficult to align the electrode plate and the separator so that the positioning holes fit into the positioning pins 33a and 33b. However, in this example, since the two positioning pins 33 a and 33 b are configured as pop-up pins that can move up and down, a considerably long portion protrudes from the stage 32. As a result, the electrode plate and the separator can be easily attached to the positioning pins. In addition, when the flange is engaged with the cell body, the positioning pin is pushed down, so the thickness of the portion of the flange facing the stage can be reduced, and the test lithium-ion battery and the microscope objective lens As a result, an objective lens having a large numerical aperture (high resolution) can be used. When the flange 2 is hermetically engaged with the cell body 1, the current collector foil of the positive electrode plate 23 and the flange 2 are in electrical contact, and the current collector foil of the negative electrode plate 21 and the cell body 1 are electrically connected. The drive voltage supplied from the charge / discharge controller 9 is applied between the current collector foil of the positive electrode plate and the current collector foil of the negative electrode plate via the connection terminals 8a and 8b and the cell body and the flange, The state of the active material layer of the negative electrode plate during operation is observed.

  Referring to FIG. 3, a ring-shaped groove 35 is formed on the periphery of the stage 32 of the cell body 1. The ring-shaped groove 35 engages with the ring-shaped protrusion 11 formed in the flange 2. The sizes of the electrode plates 21 and 22 and the separator 22 are set to be larger than the ring-shaped groove 35. Therefore, when the electrode plate and the separator are positioned on the stage 32 and subsequently the flange 2 is engaged with the cell body, the ring-shaped protrusion 11 formed on the flange has the ring groove 35 formed on the cell body. When inserted into the sheet-like electrode plate and separator are gripped while acting in a radial outward direction from the center, the electrode plate and separator are not formed with wrinkles or undulations, Positioned parallel to the transparent plate 10 and the stage 30. As a result, even if an objective lens having a short working distance and a large numerical aperture is used, the focal point of the objective lens can be formed on the electrode plate.

  A ring-shaped O-ring 36 that functions as a sealing means is disposed so as to surround the stage 32 that supports the test lithium ion battery. By providing the O-ring 36, when the flange 2 is engaged with the cell body 1, a sealed space is formed by the cell body 1 including the stage, the flange 2 including the observation window, and the O-ring 36. A test lithium ion battery is disposed inside.

  A ring-shaped insulating ring 37 made of an electrically insulating resin is disposed outside the ring-shaped O-ring 36. Further, a stopper ring 38 is disposed on the outside thereof. The stopper ring 38 is made of an electrically insulating material, maintains the cell body 1 and the flange 2 in an electrically insulated state, and defines an interval between the cell body 1 and the flange 2. It also functions as an adjusting means and an inclination adjusting means. That is, when the flange is engaged with the cell body and screwed, the outer peripheral portion of the flange and the stopper ring are engaged with each other, and the interval between the flange and the cell body is defined, which is undesirable. The problem of tilting is also eliminated. As a result, the distance between the transparent plate 10 of the flange and the stage 32 of the cell body is also defined, so that an appropriate pressing force is applied to the test lithium ion battery 20 disposed between the transparent plate and the stage. It becomes possible to carry out the test. Further, when testing various thicknesses of test lithium ion batteries, a charge / discharge test is performed in an optimum state according to the thickness of the test lithium ion batteries by preparing stopper rings of various heights d. It becomes possible. For example, when a test is performed on a test lithium ion battery having a half-cell structure, which will be described later, a lithium foil is used as the second electrode plate. By using a stopper ring having a height corresponding to the thickness of the lithium foil, an optimum is obtained. A charge / discharge test is performed under the conditions. Furthermore, since it also functions as an inclination adjusting means, the test lithium ion battery can be maintained parallel to the transparent plate 10.

  Next, the two flow paths communicating with the sealed space in which the test lithium ion battery is accommodated will be described with reference to FIGS. The first flow path functions to supply an electrolytic solution to a sealed space in which the test lithium ion battery is accommodated, and the second flow path functions to depressurize the sealed space. One end of the first flow path is formed at the tip of the first positioning pin 33a. The first positioning pin 33a is constituted by a pop-up type hollow pin, and its internal space is configured to allow the electrolytic solution to flow therethrough. The tip of the first positioning pin is cut obliquely so that the flow path is not closed when the flange 2 is engaged. The tip of the first positioning pin protrudes from the stage 32. The first positioning pin 33 a is disposed in a recess provided in the cell body 1 via a spring 34 a, and the recess communicates with the first flow path 39. A first valve 40 is connected to the first flow path 39. The first valve 40 is attached to a Teflon valve seat 40a provided in the cell body. In FIG. 3A, a draw bolt that supports the valve and a countersunk screw 40b are shown. A first port 41 is provided in the flow path on the other end side of the first valve 40. The first port 41 is connected to an electrolyte supply means such as a syringe pump, for example, and the electrolyte supplied from the first port 41 includes the first valve 40, the first flow path 39, and the first port 41. It flows into the sealed space from the tip of the positioning pin 32a through the first flow path formed by the positioning pin 33a. The electrolyte flowing into the sealed space passes through the gap between the second electrode plate and the transparent plate, the observation hole 23c formed in the second electrode plate, and the observation hole 22c formed in the separator, and then enters the first electrode plate. To reach. As a result, the second electrode plate, the separator, and the first electrode plate are immersed in the electrolytic solution, and the test lithium ion battery is in a chargeable / dischargeable state. A part of the electrolytic solution reaches the second flow path through the hole 21c formed in the first electrode plate.

  The second flow path is configured by an L-shaped second flow path 42 formed in the cell body. One outlet of the second flow path is located on the stage 32. A second valve 43 is connected to the second flow path 42. The second valve 43 is attached to a Teflon valve seat 43a provided in the cell body. In FIG. 3A, a draw bolt and a disc spring 43b for supporting the valve are shown. A second port 44 is provided in the flow path on the other end side of the second valve 43. The second port 44 is connected to a decompression device such as a vacuum device, for example, and decompresses the sealed space in which the test lithium ion battery is accommodated and the communicating flow path.

  FIG. 6 is a diagram showing an example of a lithium ion battery observation system according to the present invention. In this example, the observation cell shown in FIG. 1 to FIG. 5 is used as an observation cell for storing a test lithium ion battery, and details are omitted. In addition, the same code | symbol is attached | subjected and demonstrated to the component same as the component used in FIGS. The observation cell includes a cell main body 1 and a flange 2 that engages with the cell main body. When the flange 2 is engaged with the cell body 1, a sealed space 50 is formed by the cell body 1, the flange 2 including the transparent plate 10 constituting the observation window, and the ring-shaped O-ring 36. On the stage 32 that forms the sealed space 50, the test lithium ion battery 20 including the first electrode plate, the separator, and the second electrode plate is disposed. In the drawing, the test lithium ion battery 20 is illustrated as being separated from the cell body and the flange, but actually, the current collector foil of the first electrode plate is in electrical contact with the cell body, and the second The current collector foil of the electrode plate is in electrical contact with the flange.

  First and second flow paths 51 and 52 are communicated with the sealed space 50. The first flow path 51 includes a first flow path 39, a first valve 40, and a first port 41. The second flow path 52 includes a second flow path 42, a second valve 43, and a second port 44. For example, a syringe pump 53 that functions as an electrolyte supply unit is connected to the first port. For example, a decompression device 54 such as a vacuum device is connected to the second port.

  Next, an operation process of the lithium ion battery observation system shown in FIG. 6 will be described. First, a glove box filled with an inert gas such as argon gas is prepared. The glove box is connected to a pass box that can be decompressed. In the glove box, a positive electrode plate, a negative electrode plate, and a separator, which are cut into a predetermined size, which is a constituent element of the lithium ion battery, and have positioning holes and observation holes are disposed. Moreover, the cell main body 1, the flange 2, and the syringe pump 53 which comprise the observation cell of this invention are also arrange | positioned. In addition, a beaker containing an electrolytic solution is disposed in the glove box.

  An operation is performed from the outside, and the negative electrode plate 21, the separator 22, and the positive electrode plate 23 are arranged on the stage 32 of the cell body. At this time, the positions of the positioning through holes formed in the electrode plate and the separator are aligned with the positioning pins 33a and 33b formed on the stage, and the positioning pins 33a and 33b are connected to the negative electrode plate 21, the separator 22 and the positioning pins 33a and 33b. Positioning is performed so as to penetrate the positioning hole formed in the positive electrode plate 23. By this first positioning operation, the test lithium ion battery is positioned with respect to the stage, and also the observation holes formed in the separator 22 and the positive electrode plate (second electrode plate) 23 with respect to the negative electrode plate 21 to be observed Positioned with high accuracy. That is, the positioning operation using the positioning pins can align the positions of the observation holes formed in the positive electrode plate and the separator, thereby preventing the observation field from deviating and preventing the negative electrode plate and the positive electrode plate from coming into contact with each other. The trouble to do is also prevented.

  Next, the cell main body 1 and the flange 2 are positioned using positioning pins 30a and 30b provided on the cell main body 1, and two screws are screwed together to be sealingly engaged. By this second positioning operation, the flange 2 is positioned with respect to the cell body 1. By these two positioning operations, the observation site of the test lithium ion battery is positioned with respect to the observation window formed on the flange. By engaging a flange with the cell main body, the current collector foil of the electrode plate of the first electrode plate is connected to the cell main body, and the current collector foil of the second electrode plate is connected to the flange. Are electrically connected to the charge / discharge controller 9 via connection terminals provided on the cell body and the flange.

  Next, in the glove box, a syringe pump is operated to suck an appropriate amount of electrolyte. Subsequently, the first and second valves are closed in the glove box by an external operation. Thereafter, the syringe pump is connected to the first port 41, the observation cell connected to the syringe pump is taken out from the glove box, and the observation cell is arranged on the stage of the microscope apparatus.

  Subsequently, the decompression device 54 is connected to the second port 44, and the drive of the decompression device is started. Subsequently, the second valve 43 is opened, and the sealed space 50 in which the test lithium ion battery is accommodated and the flow path communicating therewith are decompressed. By this depressurization operation, the inert gas and a small amount of water adsorbed on the test lithium ion battery are removed, and the test lithium ion battery disposed in the sealed space 50 is made clean.

  After the sealed space 50 is depressurized, the second valve 43 is closed and the first valve is opened. When the first valve is opened, the electrolyte contained in the syringe pump 53 is sealed through the first port, the first valve, and the first flow path due to the pressure difference between the internal pressure and the external pressure. It is supplied to the space 50 and the test lithium ion battery 20 is impregnated with the electrolytic solution, and a charge / discharge test is possible.

  When bubbles are generated after the start of the charge / discharge test, the bubbles can be removed by operating the syringe pump 53. That is, when the operation is performed so that the plunger of the syringe pump 53 is pulled out, the sealed space and the communication channel are in a reduced pressure state, and the electrolyte moves to the syringe pump side. Along with the movement of the electrolytic solution, the generated bubbles also move to the syringe pump side via the sealed space 50 and the first flow path 51, and unwanted bubbles can be removed from the sealed space. In addition, when the inventor conducted an experiment using a prototype of the observation cell, it was confirmed that the bubbles generated in the sealed space were quickly removed by operating the plunger of the syringe pump. It was.

  The observation cell according to the present invention can also observe a lithium ion battery having a half cell structure. When observing a lithium ion battery having a half-cell structure, the second electrode plate located on the side close to the observation window is made of metal lithium foil, and the first electrode plate is made of a positive electrode plate or a negative electrode plate. In this case, the illumination light emitted from the microscope enters the active material layer of the first electrode plate (positive electrode plate or negative electrode plate) through the transparent plate 10, the holes formed in the metal lithium foil, and the holes formed in the separator. The state change of the active material layer of the half-cell lithium-ion battery in operation can be observed with a microscope.

DESCRIPTION OF SYMBOLS 1 Cell main body 2 Flange 3,38 Stopper ring 4a, 4b Counterbore hole 5a, 5b Engagement hole 6 Observation window 7 Microscope objective lens 8a, 8b Connection terminal 9 Charge / discharge controller
DESCRIPTION OF SYMBOLS 10 Transparent board 11 Ring-shaped protrusion 12a, 12b Escape hole 20 Lithium ion battery for a test
21 1st electrode plate 21a, 21b Positioning hole 21c Through-hole 22 Separator 22a, 22b Positioning hole 22c Observation hole 23 2nd electrode plate 23a, 23b Positioning hole 23c Observation hole 30a, 30b Positioning pin 31a, 31b Screw hole 32 Stage 33a, 33b Positioning pin 34a Spring 35 Ring-shaped groove 36 O-ring 37 Insulating ring 39 First flow path 40 First valve 40a First valve seat 40b First draw bolt / disc spring 41 First port 42 First 2nd flow path 43 2nd valve 43a 2nd valve seat 43b 2nd draw bolt and disc spring 44 2nd port 50 Sealing space 51 1st flow path 52 2nd flow path 53 Syringe pump 54 Pressure reducing device

Claims (13)

An observation cell in which an active material layer formed on an electrode plate of a test lithium ion battery during operation can be observed through a microscope through an observation window,
A cell body having a stage for supporting a test lithium ion battery;
A flange that faces the stage and constitutes an observation window; a flange that engages with the cell body;
Sealing means for enclosing the entire circumference of the stage;
An insulating stopper ring that is disposed between the cell body and the flange, electrically insulates the cell body and the flange and defines a distance between the stage and the transparent plate;
Having first and second connection terminals provided on the cell body and the flange, respectively;
The test lithium ion battery is configured as a laminate in which a first electrode plate, a separator, and a second electrode plate are stacked on the stage,
When a flange is attached to the cell body, a sealed space for accommodating the test lithium ion battery is formed by the flange, the cell body, and sealing means,
The cell body is provided with first and second flow paths communicating with the sealed space, and first and second ports formed in the first and second flow paths, respectively.
An observation cell, wherein an electrolytic solution is supplied to the sealed space through the first port and the first flow path.   2. The observation cell according to claim 1, wherein the first and second electrode plates and the separator of the test lithium ion battery are the first electrode plate, the separator, and the separator from the side far from the transparent plate that forms the observation window. The second electrode plate is laminated in the order, observation holes are formed in the second electrode plate and the separator, and the illumination light emitted from the microscope is observed on the transparent plate, the second electrode plate and the separator. An observation cell, wherein the cell enters the active material layer of the first electrode plate through a hole, and the active material layer of the first electrode plate is observed with a microscope. The observation cell according to claim 2, wherein first and second valves are provided in the first and second flow paths, respectively.
An electrolyte supply means is connected to the first port, a decompression means is connected to the second port,
When supplying the electrolytic solution to the sealed space, the space from the first valve to the second port is decompressed by the decompression unit, and the first port and the first flow are supplied from the electrolyte supply unit in a decompressed state. An observation cell, wherein an electrolyte is supplied to the sealed space through a path.   4. The observation cell according to claim 3, wherein when supplying the electrolyte solution to the sealed space, the first valve is closed and the second valve is opened, and in this state, the first port is connected to the first port. An observation characterized in that the internal space leading to the valve is depressurized, then the second valve is closed and the first valve is opened to supply the electrolytic solution to the sealed space, and then a charge / discharge test is performed. Cell.   5. The observation cell according to claim 3, wherein the electrolyte supply means is configured by a syringe pump in which an electrolyte is accommodated, and when bubbles are generated in the sealed space during a charge / discharge test, The second valve is maintained in the closed state and the first valve is maintained in the open state, and the syringe pump is operated so that the space formed between the second valve and the first port is depressurized. By operating, the bubble which generate | occur | produced moves to the syringe pump side via the said 1st flow path, The cell for observation characterized by the above-mentioned.   The observation cell according to any one of claims 2 to 5, wherein the stacked body constituting the test lithium ion battery is positioned on the stage of the cell main body, and the second electrode plate and the separator are positioned. Two positioning pins are provided for aligning the formed observation holes, and these two positioning pins are provided as pop-up type positioning pins that can be displaced in a direction perpendicular to the stage. An observation cell characterized by being displaced in a direction away from the flange when combined.   7. The observation cell according to claim 6, wherein at least one positioning pin of the positioning pin is configured as a hollow pin, and an internal space of the positioning pin constitutes a part of the first flow path, and the positioning pin An observation cell, wherein a tip of the pin communicates with the sealed space.   8. The observation cell according to claim 7, wherein the electrolyte supplied from the first port includes the first flow path, the positioning pin, an observation hole formed in a second electrode plate, and the separator. An observation cell, characterized in that it reaches the first electrode plate through an observation hole formed in the substrate.   9. The observation cell according to claim 1, wherein a ring-shaped groove is formed along a peripheral edge of the stage of the cell body, and a ring-shaped groove formed in the stage is formed on the flange. A ring-shaped ridge that engages with the battery, and the periphery of the laminate of the test lithium ion battery is between a ring-shaped groove formed on the cell body and a ring-shaped ridge formed on the flange. An observation cell characterized by being gripped.   10. The observation cell according to claim 2, wherein the second electrode plate of the test lithium ion battery is made of a metal lithium foil, and the first electrode plate is a positive electrode plate or a negative electrode. An observation cell comprising a plate, wherein a state of an active material layer formed on a positive electrode plate or a negative electrode plate of a test lithium ion battery having a half cell structure is observed. An observation cell in which the test lithium ion battery is housed, a microscope for imaging the inside of the test lithium ion battery through an observation window formed in the observation cell, and a decompression device connected to each of the observation cells And an electrolyte supply device, and a lithium ion battery observation system for microscopically observing an active material layer formed on an electrode plate of a test lithium ion battery in operation, the observation cell comprising:
A cell body having a stage for supporting a test lithium ion battery;
A flange that faces the stage and constitutes an observation window; a flange that engages with the cell body;
Sealing means for enclosing the entire circumference of the stage;
An insulating stopper ring that is disposed between the cell body and the flange and electrically insulates the cell body and the flange and defines a distance between the stage and the transparent plate;
Having first and second connection terminals provided on the cell body and the flange, respectively;
The test lithium ion battery is configured as a laminate in which a first electrode plate, a separator, and a second electrode plate are stacked on the stage,
When a flange is attached to the cell body, a sealed space for accommodating the test lithium ion battery is formed by the flange, the cell body, and sealing means,
The cell body is provided with first and second flow paths communicating with the sealed space, and first and second ports formed in the first and second flow paths, respectively.
An electrolyte supply means is connected to the first port, and a decompression device is connected to the second port.
The pressure reducing means decompresses the sealed space through the second port and the second flow path, and the electrolyte supply means electrolyzes the sealed space through the first port and the first flow path. A lithium ion battery observation system characterized by being supplied with a liquid.   12. The lithium ion battery observation system according to claim 11, wherein a test lithium ion battery is accommodated in the sealed space during a charge / discharge test, and the sealed space is decompressed via the second port and the second flow path. The lithium ion battery observation system is characterized in that the electrolyte is supplied to the sealed space through the first port and the first flow path. 13. The lithium ion battery observation system according to claim 11 or 12, wherein the electrolyte supply means is constituted by a syringe pump, and when a bubble is generated in the sealed space, the syringe pump is operated so that the sealed space is decompressed. By doing so, the generated bubbles move from the sealed space to the syringe pump side, and the bubbles are removed from the sealed space.

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