# Patent

## Title
Analytical cell

## Abstract

An analytical cell includes first and second holders. The first and second holders each contain a substrate having a through-hole and a transmission membrane with an electron beam permeability so as to cover the through-hole. The first and second holders are stacked to form an overlapping portion such that the transmission membranes face each other. The through-holes face each other across the transmission membranes to form an observation window. Negative and positive electrode active materials are separated from each other and contact the electrolytic solution in the observation window. The negative and positive electrode active materials are electrically connected to negative and positive electrode collectors, respectively, in the overlapping portion. At least one of the negative and positive electrode collectors has an electrically insulating isolation membrane for avoiding contact with the electrolytic solution.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-080427 filed on Apr. 9, 2014, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an analytical cell suitable for use, e.g., in an electrode reaction analysis in an analytical equipment.
Description of the Related Art
As is well known, in an electric cell, a negative electrode active material and a positive electrode active material undergo electrode reactions in the charge-discharge process. In recent years, the electrode reactions have been analyzed during the charge-discharge process using analytical equipment. For example, an analytical cell that can be observed by a transmission electron microscope (TEM) has been proposed in In-situ Electron Microscopy of Electrical Energy Storage Materials [online], 2014, Retrieved on Jan. 30, 2014 from the Internet <URL: http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2011/electrochemical_storage/es095_unocic_2011_o.pdf>.
This analytical cell contains a pair of silicon substrates, each of which has a rectangular observation window having a size of about 50 μm×100 μm. The silicon substrates are stacked at a predetermined distance from each other to form an overlapping portion in such a manner that the observation windows face each other. A negative electrode active material containing a highly oriented graphite and a positive electrode active material containing LiCoO2 are deposited on one of the silicon substrates by an ion beam deposition method, so that the negative electrode active material and the positive electrode active material are located between the observation windows. Incidentally, the negative electrode active material and the positive electrode active material are each extracted from a bulk body using a focused ion beam (FIB).
The negative electrode active material and the positive electrode active material are electrically connected to a negative electrode collector and a positive electrode collector respectively in the overlapping portion. The negative electrode collector and the positive electrode collector each extend from the inside of the overlapping portion and are exposed to the outside. Therefore, the negative electrode active material and the positive electrode active material can be electrically connected to the outside of the overlapping portion by the negative electrode collector and the positive electrode collector.
The electrode reactions and the like of the negative electrode active material and the positive electrode active material can be analyzed by observing the analytical cell using the transmission electron microscope (TEM). Specifically, first, the analytical cell is placed in an end of a TEM holder having a passage for introducing an electrolytic solution to the overlapping portion. Then, the electrolytic solution is introduced from the passage of the TEM holder into the overlapping portion, and the negative electrode collector and the positive electrode collector are each connected to a charge-discharge tester or the like, whereby the negative electrode active material and the positive electrode active material undergo the electrode reactions. The TEM observation is carried out while transmitting an electron beam through the observation window to analyze the electrode reactions of the negative electrode active material and the positive electrode active material.
SUMMARY OF THE INVENTION
In the above-described analytical cell, the electrolytic solution is introduced into the overlapping portion, whereby the negative electrode active material and the positive electrode active material are brought into contact with the electrolytic solution to carry out the electrode reactions. In this process, also portions of the negative electrode collector and the positive electrode collector located in the overlapping portion are brought into contact with the electrolytic solution. Therefore, a side reaction, different from the electrode reactions of the negative electrode active material and the positive electrode active material, may be caused on the negative electrode collector and the positive electrode collector. In this case, it is difficult to accurately observe the electrode reactions of the analysis subjects.
A principal object of the present invention is to provide an analytical cell capable of inhibiting or suppressing side reactions on a negative electrode collector and a positive electrode collector, thereby highly accurately analyzing electrode reactions of a negative electrode active material and a positive electrode active material.
According to an aspect of the present invention, there is provided an analytical cell, through which an electron beam is transmitted to perform an analysis, comprising a first holder and a second holder stacked with an electrolytic solution interposed therebetween, wherein
the first holder and the second holder each contain a substrate including a through-hole and a transmission membrane having an electron beam permeability, the through-hole extends in a thickness direction of the substrate, the transmission membrane is disposed on one surface of the substrate, such that one end of the through-hole is covered with the transmission membrane,
the first holder and the second holder are stacked to form an overlapping portion in such a manner that the surfaces of the substrates with the transmission membranes formed thereon face each other,
the through-holes face each other across the transmission membranes in the overlapping portion to form an observation window, through which an electron beam is transmitted,
a negative electrode active material and a positive electrode active material are arranged at a distance from each other and respectively in contact with the electrolytic solution between the transmission membranes in the observation window,
the negative electrode active material and the positive electrode active material are electrically connected to a negative electrode collector and a positive electrode collector, respectively, in the overlapping portion,
the negative electrode collector and the positive electrode collector each extend from inside of the overlapping portion and are exposed to outside, and
at least one of the negative electrode collector and the positive electrode collector has an electrically insulating isolation membrane configured to avoid contact with the electrolytic solution in the overlapping portion.
In the analytical cell of the present invention, the isolation membrane for avoiding contact with the electrolytic solution is formed on at least one of the negative electrode collector and the positive electrode collector in the overlapping portion. Therefore, side reactions, which are different from the electrode reactions of the negative electrode active material and the positive electrode active material, can be suppressed on the negative electrode collector and the positive electrode collector. Consequently, the electrode reactions of the analysis subjects can be highly accurately analyzed by observing the negative electrode active material, the positive electrode active material, or the like while transmitting the electron beam through the analytical cell.
In the above analytical cell, each of the negative electrode collector and the positive electrode collector may have a layer structure with one surface contacting the first holder and the other surface having the isolation membrane. In this case, in production of the analytical cell, the negative electrode collector and the positive electrode collector may be formed only on the first holder. The one surface of the negative electrode collector and the one surface of the positive electrode collector are in contact with the first holder (e.g., the transmission membrane) and are not in contact with the electrolytic solution. Therefore, the contact of the negative electrode collector and the positive electrode collector with the electrolytic solution can be avoided by forming the isolation membranes only on the other surfaces. Consequently, the analytical cell can be easily and efficiently obtained by a simple production process.
In the above analytical cell, the negative electrode collector may have a layer structure with one surface contacting the first holder and the other surface having the isolation membrane, and the positive electrode collector may have a layer structure with one surface contacting the second holder and the other surface having the isolation membrane. In this case, the negative electrode active material and the positive electrode active material are disposed on each of the first holder and the second holder. Therefore, even when the negative electrode active material and the positive electrode active material are disposed in a small space, the negative electrode active material and the positive electrode active material are not arranged excessively close to each other and are not in contact with each other. Consequently, the negative electrode active material and the positive electrode active material can be effectively prevented from short-circuiting.
When the negative electrode active material, the positive electrode active material, and the like in the analytical cell are observed, the electron beam needs to be transmitted through the observation window. In this process, the electrolytic solution may inhibit the transmission of the electron beam. Therefore, it is preferred that the thickness of the electrolytic solution layer formed between the transmission membranes in the observation window is reduced, and the electron beam transmission distance in the electrolytic solution is shortened, to improve the observation accuracy. Thus, in the above analytical cell, it is preferred that the isolation membrane has an electron beam permeability (electron beam transparency) and extends from at least one of the negative electrode collector and the positive electrode collector in such a manner that the isolation membrane is interposed between the transmission membrane and at least one of the negative electrode active material and the positive electrode active material in the observation window.
In this analytical cell, as described above, the electron beam-permeable isolation membrane is interposed between the transmission membrane and at least one of the negative electrode active material and the positive electrode active material in the observation window, whereby the electron beam transmission distance in the electrolytic solution can be shortened. Consequently, the electrode reactions of the negative electrode active material and the positive electrode active material, etc. can be more highly accurately analyzed.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an overall schematic perspective view of an analytical cell according to a first embodiment of the present invention;
FIG. 2 is a cross-sectional view of the analytical cell of FIG. 1 taken along the line II-II in the direction of the arrows;
FIG. 3 is a plan view of a transmission membrane side of a first holder in the analytical cell of FIG. 1;
FIG. 4 is a plan view of a transmission membrane side of a second holder in the analytical cell of FIG. 1;
FIG. 5A is a plan view of a transmission membrane precursor side of a substrate with a transmission membrane precursor formed on one surface and a covering membrane precursor formed on the other surface, FIG. 5B is a cross-sectional view taken along the line VB-VB in FIG. 5A in the direction of the arrows, and FIG. 5C is a cross-sectional view taken along the line VC-VC in FIG. 5A in the direction of the arrows;
FIG. 6A is a plan view of a photoresist formed on the one surface of the substrate of FIG. 5A, FIG. 6B is a cross-sectional view taken along the line VIB-VIB in FIG. 6A in the direction of the arrows, and FIG. 6C is a cross-sectional view taken along the line VIC-VIC in FIG. 6A in the direction of the arrows;
FIG. 7A is a plan view of collector-shaped portions formed by patterning the photoresist of FIG. 6A, so that the transmission membrane precursor is exposed in the portions, FIG. 7B is a cross-sectional view taken along the line VIIB-VIIB in FIG. 7A in the direction of the arrows, and FIG. 7C is a cross-sectional view taken along the line VIIC-VIIC in FIG. 7A in the direction of the arrows;
FIG. 8A is a plan view of thinned portions in the transmission membrane precursor corresponding to the collector-shaped portions of FIG. 7A, FIG. 8B is a cross-sectional view taken along the line VIIIB-VIIIB in FIG. 8A in the direction of the arrows, and FIG. 8C is a cross-sectional view taken along the line VIIIC-VIIIC in FIG. 8A in the direction of the arrows;
FIG. 9A is a plan view of a collector precursor formed on the one surface of the substrate of FIG. 8A, FIG. 9B is a cross-sectional view taken along the line IXB-IXB in FIG. 9A in the direction of the arrows, and FIG. 9C is a cross-sectional view taken along the line IXC-IXC in FIG. 9A in the direction of the arrows;
FIG. 10A is a plan view of a negative electrode collector and a positive electrode collector obtained by removing the photoresist of FIG. 9A, FIG. 10B is a cross-sectional view taken along the line XB-XB in FIG. 10A in the direction of the arrows, and FIG. 10C is a cross-sectional view taken along the line XC-XC in FIG. 10A in the direction of the arrows;
FIG. 11A is a plan view of a photoresist formed on the one surface of the substrate of FIG. 10A, FIG. 11B is a cross-sectional view taken along the line XIB-XIB in FIG. 11A in the direction of the arrows, and FIG. 11C is a cross-sectional view taken along the line XIC-XIC in FIG. 11A in the direction of the arrows;
FIG. 12A is a plan view of photoresist residues remaining only on the negative electrode collector, the positive electrode collector, and portions corresponding to spacers formed by patterning the photoresist of FIG. 11A, FIG. 12B is a cross-sectional view taken along the line XIIB-XIIB in FIG. 12A in the direction of the arrows, and FIG. 12C is a cross-sectional view taken along the line XIIC-XIIC in FIG. 12A in the direction of the arrows;
FIG. 13A is a plan view of a transmission membrane formed by thinning the exposed portions of the transmission membrane precursor around the photoresist residues of FIG. 12A, FIG. 13B is a cross-sectional view taken along the line XIIIB-XIIIB in FIG. 13A in the direction of the arrows, and FIG. 13C is a cross-sectional view taken along the line XIIIC-XIIIC in FIG. 13A in the direction of the arrows;
FIG. 14A is a plan view of first spacer-shaped portions of the transmission membrane precursor obtained by removing the patterned photoresist of FIG. 13A, FIG. 14B is a cross-sectional view taken along the line XIVB-XIVB in FIG. 14A in the direction of the arrows, and FIG. 14C is a cross-sectional view taken along the line XIVC-XIVC in FIG. 14A in the direction of the arrows;
FIG. 15A is a plan view of a photoresist formed on the one surface of the substrate of FIG. 14A, FIG. 15B is a cross-sectional view taken along the line XVB-XVB in FIG. 15A in the direction of the arrows, and FIG. 15C is a cross-sectional view taken along the line XVC-XVC in FIG. 15A in the direction of the arrows;
FIG. 16A is a plan view of a negative electrode active material formation portion (formed on the transmission membrane and the negative electrode collector) and the first spacer-shaped portions exposed by patterning the photoresist of FIG. 15A, FIG. 16B is a cross-sectional view taken along the line XVIB-XVIB in FIG. 16A in the direction of the arrows, and FIG. 16C is a cross-sectional view taken along the line XVIC-XVIC in FIG. 16A in the direction of the arrows;
FIG. 17A is a plan view of a negative electrode active material precursor formed on the one surface of the substrate of FIG. 16A, FIG. 17B is a cross-sectional view taken along the line XVIIB-XVIIB in FIG. 17A in the direction of the arrows, and FIG. 17C is a cross-sectional view taken along the line XVIIC-XVIIC in FIG. 17A in the direction of the arrows;
FIG. 18A is a plan view of a negative electrode active material and second spacer-shaped portions obtained by removing the photoresist of FIG. 17A, FIG. 18B is a cross-sectional view taken along the line XVIIIB-XVIIIB in FIG. 18A in the direction of the arrows, and FIG. 18C is a cross-sectional view taken along the line XVIIIC-XVIIIC in FIG. 18A in the direction of the arrows;
FIG. 19A is a plan view of a photoresist formed on the one surface of the substrate of FIG. 18A, FIG. 19B is a cross-sectional view taken along the line XIXB-XIXB in FIG. 19A in the direction of the arrows, and FIG. 19C is a cross-sectional view taken along the line XIXC-XIXC in FIG. 19A in the direction of the arrows;
FIG. 20A is a plan view of a positive electrode active material formation portion (formed on the transmission membrane and the positive electrode collector) exposed by patterning the photoresist of FIG. 19A, FIG. 20B is a cross-sectional view taken along the line XXB-XXB in FIG. 20A in the direction of the arrows, and FIG. 20C is a cross-sectional view taken along the line XXC-XXC in FIG. 20A in the direction of the arrows;
FIG. 21A is a plan view of a positive electrode active material precursor formed on the one surface of the substrate of FIG. 20A, FIG. 21B is a cross-sectional view taken along the line XXIB-XXIB in FIG. 21A in the direction of the arrows, and FIG. 21C is a cross-sectional view taken along the line XXIC-XXIC in FIG. 21A in the direction of the arrows;
FIG. 22A is a plan view of a positive electrode active material obtained by removing the photoresist of FIG. 21A, FIG. 22B is a cross-sectional view taken along the line XXIIB-XXIIB in FIG. 22A in the direction of the arrows, and FIG. 22C is a cross-sectional view taken along the line XXIIC-XXIIC in FIG. 22A in the direction of the arrows;
FIG. 23A is a plan view of an isolation membrane precursor formed on the one surface of the substrate of FIG. 22A, FIG. 23B is a cross-sectional view taken along the line XXIIIB-XXIIIB in FIG. 23A in the direction of the arrows, and FIG. 23C is a cross-sectional view taken along the line XXIIIC-XXIIIC in FIG. 23A in the direction of the arrows;
FIG. 24A is a plan view of a photoresist formed on the one surface of the substrate of FIG. 23A, FIG. 24B is a cross-sectional view taken along the line XXIVB-XXIVB in FIG. 24A in the direction of the arrows, and FIG. 24C is a cross-sectional view taken along the line XXIVC-XXIVC in FIG. 24A in the direction of the arrows;
FIG. 25A is a plan view of photoresist residues remaining only on isolation membrane formation portions and the second spacer-shaped portions formed by patterning the photoresist of FIG. 24A, FIG. 25B is a cross-sectional view taken along the line XXVB-XXVB in FIG. 25A in the direction of the arrows, and FIG. 25C is a cross-sectional view taken along the line XXVC-XXVC in FIG. 25A in the direction of the arrows;
FIG. 26A is a plan view of a resultant obtained by removing the isolation membrane precursor in portions not covered with the photoresist of FIG. 25A, FIG. 26B is a cross-sectional view taken along the line XXVIB-XXVIB in FIG. 26A in the direction of the arrows, and FIG. 26C is a cross-sectional view taken along the line XXVIC-XXVIC in FIG. 26A in the direction of the arrows;
FIG. 27A is a plan view of isolation membranes and third spacer-shaped portions formed by removing the photoresist of FIG. 26A, FIG. 27B is a cross-sectional view taken along the line XXVIIB-XXVIIB in FIG. 27A in the direction of the arrows, and FIG. 27C is a cross-sectional view taken along the line XXVIIC-XXVIIC in FIG. 27A in the direction of the arrows;
FIG. 28A is a plan view of a photoresist formed on the other surface of the substrate of FIG. 27A, FIG. 28B is a cross-sectional view taken along the line XXVIIIB-XXVIIIB in FIG. 28A in the direction of the arrows, and FIG. 28C is a cross-sectional view taken along the line XXVIIIC-XXVIIIC in FIG. 28A in the direction of the arrows;
FIG. 29A is a plan view of an exposed portion in the covering membrane precursor, corresponding to a through-hole, formed by patterning the photoresist of FIG. 28A, FIG. 29B is a cross-sectional view taken along the line XXIXB-XXIXB in FIG. 29A in the direction of the arrows, and FIG. 29C is a cross-sectional view taken along the line XXIXC-XXIXC in FIG. 29A in the direction of the arrows;
FIG. 30A is a plan view of a resultant obtained by removing the exposed portion of the covering membrane precursor, exposed in the photoresist of FIG. 29A, FIG. 30B is a cross-sectional view taken along the line XXXB-XXXB in FIG. 30A in the direction of the arrows, and FIG. 30C is a cross-sectional view taken along the line XXXC-XXXC in FIG. 30A in the direction of the arrows;
FIG. 31A is a plan view of a through-hole formation portion of the substrate exposed by removing the photoresist of FIG. 30A, FIG. 31B is a cross-sectional view taken along the line XXXIB-XXXIB in FIG. 31A in the direction of the arrows, and FIG. 31C is a cross-sectional view taken along the line XXXIC-XXXIC in FIG. 31A in the direction of the arrows;
FIG. 32A is a plan view of a through-hole formed in the substrate of FIG. 31A, FIG. 32B is a cross-sectional view taken along the line XXXIIB-XXXIIB in FIG. 32A in the direction of the arrows, and FIG. 32C is a cross-sectional view taken along the line XXXIIC-XXXIIC in FIG. 32A in the direction of the arrows;
FIG. 33 is a cross-sectional view of an analytical cell according to a second embodiment of the present invention taken in the same direction as FIG. 2;
FIG. 34 is an overall schematic perspective view of an analytical cell according to a third embodiment of the present invention;
FIG. 35 is a cross-sectional view of the analytical cell of FIG. 34 taken along the line XXXV-XXXV in the direction of the arrows;
FIG. 36 is a plan view of a transmission membrane side of a first holder in the analytical cell of FIG. 34;
FIG. 37 is a plan view of a transmission membrane side of a second holder in the analytical cell of FIG. 34; and
FIG. 38 is a cross-sectional view of an analytical cell according to a fourth embodiment of the present invention taken in the same direction as FIGS. 2 and 35.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
Several preferred embodiments of the analytical cell of the present invention will be described in detail below with reference to the accompanying drawings.
The analytical cell is suitable for use, e.g., in an analysis of electrode reactions in a negative electrode active material and a positive electrode active material under electron beam transmission in analytical equipment. For example, the analytical equipment may be a transmission electron microscope (TEM). In this case, the analytical cell is attached to an end of a TEM holder, and then an observation process is performed. For example, the observation subject (i.e., the analytical cell) may be a lithium-ion secondary cell, a nickel-hydrogen cell, an alkaline-manganese cell, or the like. Examples of the analytical cell of the lithium-ion secondary cell will be described below.
First Embodiment
An analytical cell 10 according to a first embodiment will be described below with reference to FIGS. 1 to 4. FIG. 1 is an overall schematic perspective view of the analytical cell 10. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1 in the direction of the arrows. FIG. 3 is a plan view of a transmission membrane (electron beam permeable membrane or electron beam transparent membrane) 14 side of a first holder 12 in the analytical cell 10. FIG. 4 is a plan view of a transmission membrane (electron beam permeable membrane or electron beam transparent membrane) 18 side of a second holder 16 in the analytical cell 10. To facilitate understanding, the X-axis, Y-axis, and Z-axis directions shown in FIGS. 1 to 4 are defined as the width, depth, and height directions respectively in the following description. In addition, in the X-axis, Y-axis, and Z-axis directions, the tip of the arrow is defined as one end, and the base end of the arrow is defined as the other end.
The analytical cell 10 contains the first holder 12 and the second holder 16 stacked with an electrolytic solution interposed therebetween. Specifically, the first holder 12 and the second holder 16 are stacked to form an overlapping portion 20, and spacers 11 (see FIG. 3) for forming a space are interposed therebetween. The overlapping portion 20 is sealed by a sealant 22 such as an epoxy-based resin adhesive (see FIG. 1) while the space is filled with the electrolytic solution. Incidentally, the sealant 22 is omitted in FIG. 2.
Thus, in the analytical cell 10, a small amount of the electrolytic solution is enclosed (stored) in the overlapping portion 20. It is not necessary to additionally introduce the electrolytic solution. Therefore, the pressure of the electrolytic solution acting on the first holder 12 and the second holder 16, i.e., the inner pressure of the analytical cell 10, can be lowered. Consequently, it is not necessary to increase the distance between the first holder 12 and the second holder 16, and the analytical cell 10 can be a small size. In this embodiment, for example, the electrolytic solution preferably contains propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), or the like.
As shown in FIGS. 2 and 3, the first holder 12 contains a substrate 24 and the transmission membrane 14. For example, the substrate 24 contains silicon (Si), borosilicate glass, quartz (SiO2), or the like. A through-hole 26 penetrating in the thickness direction is formed approximately at the center of the substrate 24. The transmission membrane 14 is formed on one surface of the substrate 24 to cover the through-hole 26, and a covering membrane 28 is formed on the other surface of the substrate 24, such that the through-hole 26 is exposed. The through-hole 26 has a truncated quadrangular pyramid shape tapered in the direction from the covering membrane 28 toward the transmission membrane 14 of the substrate 24.
For example, the transmission membrane 14 contains a material having an electron beam permeability (electron beam transparency) such as silicon nitride (Si3N4), silicon carbide (SiC), silicon (Si), carbon (C), or graphite (C). The covering membrane 28 may contain the same material as the transmission membrane 14.
As shown in FIGS. 2 and 4, the second holder 16 contains a substrate 30 and the transmission membrane 18. The substrate 30 contains the same material as the substrate 24, has approximately the same depth and height as the substrate 24, and has a width smaller by 2L (L×2) than that of the substrate 24. A through-hole 32 penetrating in the thickness direction is formed approximately at the center of the substrate 30, and has the same shape as the through-hole 26. The transmission membrane 18 is formed on one surface of the substrate 30 to cover the through-hole 32, and a covering membrane 34 is formed on the other surface of the substrate 30, such that the through-hole 32 is exposed. The transmission membrane 18 and the covering membrane 34 may contain the same material as the transmission membrane 14.
The first holder 12 and the second holder 16 are stacked to form the overlapping portion 20 in such a manner that the through-holes 26, 32 face each other across the transmission membranes 14, 18. Since the substrate 24 has a width larger by 2L than that of the substrate 30 as described above, the width direction end portions having a width of L in the first holder 12 are exposed and extended from the overlapping portion 20 formed in this manner (see FIGS. 1 and 2).
In the overlapping portion 20, an observation window 36, through which an electron beam is satisfactorily transmitted, is formed in the overlap of the through-hole 26 and the transmission membrane 14 in the first holder 12 and the through-hole 32 and the transmission membrane 18 in the second holder 16. In the analytical cell 10, a negative electrode active material 38 and a positive electrode active material 40 are arranged at a distance from each other while being in contact with the electrolytic solution between the transmission membranes 14, 18 in the observation window 36, so that the electrode reactions and the like are analyzed using the electron beam transmission through the observation window 36. The overlapping portion 20 other than the observation window 36, i.e., the portion in which the substrates 24, 30 face each other across the transmission membranes 14, 18, is referred to also as the facing portion in the following description.
Specifically, as shown in FIGS. 2 and 3, both of the negative electrode active material 38 and the positive electrode active material 40 are formed on the transmission membrane 14 in the first holder 12. A negative electrode collector 42, a positive electrode collector 44, and the spacers 11 are further formed on the transmission membrane 14, and the negative electrode collector 42 and the positive electrode collector 44 are electrically connected to the negative electrode active material 38 and the positive electrode active material 40, respectively.
For example, the spacers 11 contain an electrically insulating material, have a cuboid shape, and are positioned around four corners of the overlapping portion 20. The arrangement and the shape of the spacers 11 are not particularly limited as long as a desired space can be easily formed in the overlapping portion 20 by the spacers 11. It is not necessary to form the spacers 11 in a case where the desired space can be formed in the overlapping portion 20 without the spacers 11.
The negative electrode active material 38 has a layer structure extending from the observation window 36 to the facing portion on one end side in the width direction. The negative electrode active material 38 can be preferably formed from a substance such as Li4Ti5O12, C, Si, or Ge.
The positive electrode active material 40 has a layer structure extending from the observation window 36 to the facing portion on the other end side in the width direction. The positive electrode active material 40 can be preferably formed from a substance such as LiCoO2, LiMn2O2, LiNiO2, LiFePO4, Li2FePO4F, LiCo1/3Ni1/3Mn1/3O2, or Li (LiαNixMnyCoz)O2.
The other end of the negative electrode collector 42 in the width direction is electrically connected to the negative electrode active material 38 in the facing portion in the overlapping portion 20, and the one end in the width direction is exposed to the outside of the overlapping portion 20. In the example of FIGS. 1 to 4, the exposed portion of the first holder 12 protruding or extending from the overlapping portion 20 has the width L, and thus also the exposed portion in the one end of the negative electrode collector 42 protruding or extending from the overlapping portion 20 has the width L. One surface of the negative electrode collector 42 is in contact with the transmission membrane 14, and the other surface is covered with an isolation membrane 46 inside the overlapping portion 20. The negative electrode collector 42 preferably contains a substance such as tungsten (W), copper (Cu), aluminum (Al), platinum (Pt), gold (Au), or carbon (C).
The isolation membrane 46 contains an electrically insulating substance such as silicon nitride, and acts to avoid the contact of the electrolytic solution with the negative electrode collector 42 inside the overlapping portion 20.
The positive electrode collector 44 has the same structure as the negative electrode collector 42 except that the one end in the width direction is electrically connected to the positive electrode active material 40 in the facing portion in the overlapping portion 20. Thus, the other end of the positive electrode collector 44 in the width direction is exposed and extended from the overlapping portion 20 by the width L. In the positive electrode collector 44, one surface is in contact with the transmission membrane 14, and the other surface is covered with an isolation membrane 48 inside the overlapping portion 20. The isolation membrane 48 has the same structure as the isolation membrane 46.
In the negative electrode collector 42 and the positive electrode collector 44, the portions protruding from the overlapping portion 20 are hereinafter referred to also as the exposed portions.
In the analytical cell 10 having the above structure, the negative electrode active material 38 and the positive electrode active material 40 can be electrically connected to the outside of the overlapping portion 20 (e.g., an external circuit) by the negative electrode collector 42 and the positive electrode collector 44. Thus, for example, in the step of forming the sealant 22, when metal wires for electrical connection (indicated with broken lines in FIG. 3) are interposed between the exposed portions and the sealant 22, the metal wires are electrically connected to the negative electrode collector 42 and the positive electrode collector 44, respectively.
For example, the metal wires are connected to an external circuit such as a charge-discharge tester. In this case, the negative electrode active material 38 and the positive electrode active material 40 can be electrically connected to the external circuit by the negative electrode collector 42 and the positive electrode collector 44. Consequently, desired electrode reactions such as charge-discharge reactions can be carried out in the cell containing the negative electrode active material 38, the positive electrode active material 40, and the electrolytic solution.
For example, in the TEM observation of the analytical cell 10, the analytical cell 10 is placed on the TEM holder in a manner such that the observation window 36 faces an electron beam irradiation part of the TEM. Then, the metal wires are connected to the charge-discharge tester or the like, and a potential difference is applied between the metal wires to cause the electrode reactions as the observation subject in the negative electrode active material 38 and the positive electrode active material 40.
In this process, in the overlapping portion 20, the negative electrode active material 38 and the positive electrode active material 40 are in contact with the electrolytic solution, while the negative electrode collector 42 and the positive electrode collector 44 are not in contact with the electrolytic solution, as described above. Therefore, side reactions, different from the electrode reactions as the observation subject, can be suppressed in the negative electrode active material 38 and the positive electrode active material 40. Consequently, the electrode reactions of the negative electrode active material 38 and the positive electrode active material 40 can be accurately analyzed while transmitting the electron beam through the observation window 36.
For example, in a specific method using the TEM for analyzing the electrode reactions, an electron diffraction pattern is obtained based on the electron beam transmitted through the observation window 36. When the negative electrode active material 38 or the positive electrode active material 40 is physically or chemically changed in the process of the electrode reaction, the change is shown in the electron diffraction pattern. Therefore, information on the changes of the negative electrode active material 38 and the positive electrode active material 40 can be obtained by observing the electron diffraction pattern during the electrode reactions. In this embodiment, the information accuracy deterioration due to the above-described side reaction can be prevented. Thus, so-called in-situ observation can be performed highly accurately.
The analytical cell 10 may be produced by a known semiconductor process (see, e.g., International Publication No. WO 2008/141147). A method for producing the analytical cell 10 will be described below with reference to FIGS. 5A to 32C.
The analytical cell 10 may be produced by separately preparing the first holder 12 and the second holder 16, and then by combining the first holder 12 and the second holder 16. First, a method for preparing the first holder 12 will be described below. In the following example, the substrate 24 and the negative electrode active material 38 are made of silicon (Si), the transmission membrane 14 and the covering membrane 28 are made of silicon nitride (Si3N4), the negative electrode collector 42 and the positive electrode collector 44 are made of tungsten (W), and the positive electrode active material 40 is made of lithium cobaltate (LiCoO2).
First, as shown in FIGS. 5A to 5C, both surfaces of the substrate 24 are polished, and are each covered with a silicon nitride membrane by chemical vapor deposition (CVD). The silicon nitride membrane formed on the one surface of the substrate 24 is used as a precursor of the transmission membrane 14 (a transmission membrane precursor 50), and the silicon nitride membrane formed on the other surface is used as a precursor of the covering membrane 28 (a covering membrane precursor 52).
As shown in FIGS. 6A to 6C, the transmission membrane precursor 50 is covered with a photoresist 54. As shown in FIGS. 7A to 7C, the photoresist 54 is removed by a photolithography process in portions corresponding to the negative electrode collector 42 and the positive electrode collector 44. Thus, a pair of collector-shaped portions 56, 56, which have the same shapes as the negative electrode collector 42 and the positive electrode collector 44, are formed by removing the photoresist 54, and the transmission membrane precursor 50 is exposed in the collector-shaped portions 56, 56.
As shown in FIGS. 8A to 8C, a reactive ion etching process is carried out using the photoresist 54 as a mask, whereby the height of the exposed transmission membrane precursor 50 is reduced in the collector-shaped portions 56, 56. Thus, in the transmission membrane precursor 50, the portions corresponding to the negative electrode collector 42 and the positive electrode collector 44 are thinned by the height of the negative electrode collector 42 and the positive electrode collector 44.
As shown in FIGS. 9A to 9C, the exposed portions of the transmission membrane precursor 50 and the photoresist 54 are covered with a tungsten membrane by physical vapor deposition (PVD). The tungsten membrane is used as a precursor of the negative electrode collector 42 and the positive electrode collector 44 (a collector precursor 58). As shown in FIGS. 10A to 10C, the entire photoresist 54 is removed (lifted off), whereby the negative electrode collector 42 and the positive electrode collector 44 are formed in the thinned portions of the transmission membrane precursor 50.
As shown in FIGS. 11A to 11C, the one surface of the substrate 24 having the transmission membrane precursor 50, the negative electrode collector 42, and the positive electrode collector 44 is covered with a photoresist 60. As shown in FIGS. 12A to 12C, the photoresist 60 is patterned by a photolithography process, such that the photoresist 60 remains only on the negative electrode collector 42, the positive electrode collector 44, and portions corresponding to the spacers 11. Thus, spacer formation membranes 62 of the photoresist 60 are formed in the formation portions to be the spacer 11.
As shown in FIGS. 13A to 13C, a reactive ion etching process is carried out using the photoresist 60 as a mask. In this process, the negative electrode collector 42 and the positive electrode collector 44 are protected by the residues of the photoresist 60, and the height of the exposed portion of the transmission membrane precursor 50 is reduced around the spacer formation membranes 62. Thus, in the transmission membrane precursor 50, portions covered with the spacer formation membranes 62 protrude as first spacer-shaped portions 64. The first spacer-shaped portions 64 have approximately the same height as the negative electrode collector 42 and the positive electrode collector 44.
As shown in FIGS. 14A to 14C, the photoresist 60 is lifted off to obtain the transmission membrane 14. Then, as shown in FIGS. 15A to 15C, the one surface of the substrate 24 having the transmission membrane 14, the first spacer-shaped portions 64, the negative electrode collector 42, and the positive electrode collector 44 is covered with a photoresist 66.
As shown in FIGS. 16A to 16C, the photoresist 66 is patterned by a photolithography process, such that a portion corresponding to the negative electrode active material 38 on the transmission membrane 14 and the negative electrode collector 42 is exposed, and the first spacer-shaped portions 64 are further exposed. Thus, a negative electrode active material formation portion 68 is formed by removing the photoresist 66 along the shape of the negative electrode active material 38.
As shown in FIGS. 17A to 17C, the one surface of the substrate 24 having the photoresist 66, the first spacer-shaped portions 64, and the negative electrode active material formation portion 68 is covered with a silicon membrane by physical vapor deposition (PVD). The silicon membrane is used as a precursor of the negative electrode active material 38 (a negative electrode active material precursor 70). As shown in FIGS. 18A to 18C, the photoresist 66 is lifted off to obtain the negative electrode active material 38. Furthermore, second spacer-shaped portions 72 are obtained from the negative electrode active material precursor 70 remaining on the first spacer-shaped portions 64.
As shown in FIGS. 19A to 19C, the one surface of the substrate 24 having the negative electrode active material 38, the negative electrode collector 42, the positive electrode collector 44, the transmission membrane 14, and the second spacer-shaped portions 72 is covered with a photoresist 74. As shown in FIGS. 20A to 20C, the photoresist 74 is patterned by a photolithography process, such that a portion corresponding to the positive electrode active material 40 on the transmission membrane 14 and the positive electrode collector 44 is exposed. Thus, a positive electrode active material formation portion 76 is formed by removing the photoresist 74 along the shape of the positive electrode active material 40.
As shown in FIGS. 21A to 21C, the one surface of the substrate 24 having the photoresist 74 and the positive electrode active material formation portion 76 is covered with a lithium cobaltate membrane by physical vapor deposition (PVD). The lithium cobaltate membrane is used as a precursor of the positive electrode active material 40 (a positive electrode active material precursor 78). As shown in FIGS. 22A to 22C, the photoresist 74 is lifted off to obtain the positive electrode active material 40.
As shown in FIGS. 23A to 23C, the one surface of the substrate 24 having the negative electrode active material 38, the positive electrode active material 40, the negative electrode collector 42, the positive electrode collector 44, the transmission membrane 14, and the second spacer-shaped portions 72 is covered with a silicon nitride membrane by chemical vapor deposition (CVD). The silicon nitride membrane is used as a precursor of the isolation membranes 46, 48 (an isolation membrane precursor 80). As shown in FIGS. 24A to 24C, the one surface of the substrate 24 having the isolation membrane precursor 80 is covered with a photoresist 82.
As shown in FIGS. 25A to 25C, the photoresist 82 is patterned by a photolithography process, such that the photoresist 82 remains only on portions corresponding to the isolation membranes 46, 48 and the second spacer-shaped portions 72. The negative electrode collector 42 and the positive electrode collector 44 have the exposed portions protruding from the overlapping portion 20. The isolation membrane precursor 80 formed on the negative electrode collector 42 and the positive electrode collector 44 has portions corresponding to the exposed portions, and the photoresist 82 is removed in such portions. In other words, in the isolation membrane precursor 80 formed on the negative electrode collector 42 and the positive electrode collector 44, the portions having the width L from the ends of the width direction of the substrate 24 are exposed. Furthermore, the photoresist 82 is removed also in a portion corresponding to the observation window 36.
As shown in FIGS. 26A to 26C, a reactive ion etching process is carried out using the photoresist 82 as a mask. Thus, in the isolation membrane precursor 80, the portion exposed around the photoresist 82 is removed. As shown in FIGS. 27A to 27C, the residues of the photoresist 82 are lifted off to obtain the isolation membranes 46, 48. In the negative electrode collector 42 and the positive electrode collector 44, portions other than the exposed portions are covered with the isolation membranes 46, 48. Meanwhile, third spacer-shaped portions 84 are obtained from the isolation membrane precursor 80 remaining on the second spacer-shaped portions 72. Thus, the first spacer-shaped portions 64, the second spacer-shaped portions 72, and the third spacer-shaped portions 84 are stacked to form the spacers 11.
As shown in FIGS. 28A to 28C, the other surface of the substrate 24 having the covering membrane precursor 52 is covered with a photoresist 86. As shown in FIGS. 29A to 29C, the photoresist 86 is removed by a photolithography process, such that the covering membrane precursor 52 is exposed in a portion corresponding to the through-hole 26 of the substrate 24.
As shown in FIGS. 30A to 30C, a reactive ion etching process is carried out using the photoresist 86 as a mask. Thus, in the covering membrane precursor 52, the portion exposed in the photoresist 86 is removed from the substrate 24. In other words, in the substrate 24, a portion corresponding to the through-hole 26 is exposed. As shown in FIGS. 31A to 31C, the photoresist 86 is lifted off to obtain the covering membrane 28, and then the one surface of the substrate 24 having the transmission membrane 14, the spacers 11, and the isolation membranes 46, 48 is covered with an alkali-resistant surface protection layer (not shown).
As shown in FIGS. 32A to 32C, the other surface of the substrate 24 is subjected to a penetration etching process to form the through-hole 26. In this process, the one surface of the substrate 24 is protected by the alkali-resistant surface protection layer. Then, a reactive ion etching process is carried out to remove the alkali-resistant surface protection layer, whereby the first holder 12 is obtained. The first holder 12 contains the substrate 24 having the through-hole 26, and the transmission membrane 14 is disposed on the one surface of the substrate 24, such that one end of the through-hole 26 is covered with the transmission membrane 14.
In the preparation of the second holder 16, both surfaces of the substrate 30 are polished in the same manner as the substrate 24 to be covered with the transmission membrane precursor 50 and the covering membrane precursor 52. The one surface of the substrate 30 is covered with a silicon nitride membrane used as the transmission membrane 18, and the other surface is covered with a silicon nitride membrane used as a covering membrane precursor. Then, the covering membrane 34 and the through-hole 32 are formed on the substrate 30 in the same manner as the processing of the other surface of the substrate 24. Thus, the through-hole 32 is formed in the substrate 30, and the transmission membrane 18 is disposed on the one surface of the substrate 30, such that one end of the through-hole 32 is covered with the transmission membrane 18, whereby the second holder 16 is prepared.
After the first holder 12 and the second holder 16 are prepared as described above, the electrolytic solution is applied to the one surface of the first holder 12 in such a manner that the negative electrode active material 38 and the positive electrode active material 40 are each brought into contact with the electrolytic solution. The second holder 16 is stacked on the first holder 12 as described above. Thus, the first holder 12 and the second holder 16 are stacked to form the overlapping portion 20, and the through-holes 26, 32 face each other across the transmission membranes 14, 18 to form the observation window 36. In this process, in each end of the first holder 12, the portion having the width L protrudes from the overlapping portion 20.
Then, the sealant 22 is formed around the overlapping portion 20, whereby the inner space of the overlapping portion 20 filled with the electrolytic solution is sealed. In the process of forming the sealant 22, the metal wires are fixed and electrically connected to the exposed portions of the negative electrode collector 42 and the positive electrode collector 44, protruding from the overlapping portion 20. The analytical cell 10 is produced in this manner. Thus, the analytical cell 10 can be produced more easily at lower cost by the known semiconductor process than by ion beam deposition methods, etc.
As described above, the negative electrode collector 42 and the positive electrode collector 44 each have the layer structure with the one surface contacting the transmission membrane 14 in the first holder 12 and the other surface having the isolation membrane 46, 48. Therefore, in the production of the analytical cell 10, the negative electrode collector 42 and the positive electrode collector 44 may be formed only on the first holder 12. In addition, the one surface of the negative electrode collector 42 and the one surface of the positive electrode collector 44 are in contact with the transmission membrane 14 in the first holder 12, and are not in contact with the electrolytic solution. Therefore, the contact of the negative electrode collector 42 and the positive electrode collector 44 with the electrolytic solution can be avoided by forming the isolation membranes 46, 48 only on the other surfaces.
Consequently, the analytical cell 10 can be easily and efficiently obtained by a simple production process.
Second Embodiment
An analytical cell 88 according to a second embodiment will be described below with reference to FIG. 33. FIG. 33 is a cross-sectional view of the analytical cell 88 taken in the same direction as FIG. 2. The components in FIG. 33, equal or similar in functions and effects to those in FIGS. 1 to 32C, are denoted by the same reference numerals, and detailed explanations thereof are omitted.
The analytical cell 88 contains isolation membranes 90, 92 instead of the isolation membranes 46, 48 in the analytical cell 10. The isolation membranes 90, 92 contain a substance having electrically insulating and electron beam permeable properties. Preferred examples of such substances include silicon nitride.
The isolation membranes 90, 92 are different from the isolation membranes 46, 48 in that the other end of the isolation membrane 90 and the one end of the isolation membrane 92 reach the inside of the observation window 36. Thus, each of the isolation membranes 90, 92 is interposed between the transmission membrane 18 and the negative electrode active material 38 or the positive electrode active material 40 in the observation window 36.
In this embodiment, the isolation membranes 90, 92 can act to avoid the contact of the negative electrode collector 42 and the positive electrode collector 44 with the electrolytic solution in the overlapping portion 20, and the electron beam transmission distance in the electrolytic solution can be shortened in the observation window 36. That is, since the electron beam permeable isolation membranes 90, 92 are disposed in the observation window 36, the electrolytic solution layer, which may inhibit the electron beam transmission, can be thinned, and the electron beam can be satisfactorily transmitted in the observation window 36. Consequently, the analytical cell 88 has the same advantageous effects as the analytical cell 10, and, in addition, is capable of analyzing the electrode reactions and the like in the negative electrode active material 38 and the positive electrode active material 40 more highly accurately.
For example, the analytical cell 88 may be produced in the same manner as the above analytical cell 10 except for performing the following photolithography process instead of the photolithography process for the photoresist 82 shown in FIGS. 25A to 25C. In this case, the photoresist 82 is patterned, such that the photoresist 82 remains also inside the observation window 36, to form portions to be covered with the isolation membranes 90, 92. As a result, in the final product of the analytical cell 88, each isolation membrane 90, 92 extends from the negative electrode collector 42 or the positive electrode collector 44 to the negative electrode active material 38 or the positive electrode active material 40.
Third Embodiment
An analytical cell 94 according to a third embodiment will be described below with reference to FIGS. 34 to 37. FIG. 34 is an overall schematic perspective view of the analytical cell 94. FIG. 35 is a cross-sectional view of the analytical cell 94 of FIG. 34 taken along the line XXXV-XXXV in the direction of the arrows. FIG. 36 is a plan view of a transmission membrane 14 side of a first holder 96 in the analytical cell 94. FIG. 37 is a plan view of a transmission membrane 18 side of a second holder 98 in the analytical cell 94. The components in FIGS. 34 to 37, equal or similar in functions and effects to those in FIGS. 1 to 33, are denoted by the same reference numerals, and detailed explanations thereof are omitted.
The analytical cell 94 contains the first holder 96 and the second holder 98 instead of the first holder 12 and the second holder 16 in the analytical cell 10. The first holder 96 contains a substrate 100 instead of the substrate 24, and the second holder 98 contains a substrate 102 instead of the substrate 30.
The substrate 100 is different from the substrate 24 in that the through-hole 26 is slightly shifted from the center of the substrate 100 toward one end in the width direction. The substrate 102 is different from the substrate 30 in that the substrate 102 has approximately the same shape as the substrate 100 in the first holder 96.
As described above, the first holder 96 and the second holder 98 are stacked to form the overlapping portion 20 in such a manner that the through-holes 26, 32 in the substrates 100, 102 face each other across the transmission membranes 14, 18. Therefore, in the analytical cell 94, one end of the first holder 96 and the other end of the second holder 98 protrude from the overlapping portion 20 in the width direction respectively to form exposed portions having the width L.
Furthermore, in the analytical cell 94, one surface of the negative electrode active material 38 and one surface of the negative electrode collector 42 are in contact with the transmission membrane 14 in the first holder 96, and one surface of the positive electrode active material 40 and one surface of the positive electrode collector 44 are in contact with the transmission membrane 18 in the second holder 98. Thus, the negative electrode active material 38, the negative electrode collector 42, and the isolation membrane 46 are formed on the first holder 96, and the positive electrode active material 40, the positive electrode collector 44, and the isolation membrane 48 are formed on the second holder 98. In this embodiment, the negative electrode active material 38 and the positive electrode active material 40 are formed on different holders (the first holder 96 and the second holder 98), whereby the negative electrode active material 38 and the positive electrode active material 40 are not arranged excessively close to each other and are not in contact with each other.
Consequently, the analytical cell 94 has the same advantageous effects as the analytical cell 10, and, in addition, is capable of effectively preventing short-circuit of the negative electrode active material 38 and the positive electrode active material 40 even when they are arranged in a small space.
For example, the analytical cell 94 may be produced in the same manner as the above analytical cell 10 except for using the substrate 102 instead of the substrate 100 in the steps of forming the positive electrode active material 40, the positive electrode collector 44, and the isolation membrane 48. As a result, in the final product of the analytical cell 94, the negative electrode active material 38 and the positive electrode active material 40 are formed on the different holders (the first holder 96 and the second holder 98).
Fourth Embodiment
An analytical cell 104 according to a fourth embodiment will be described below with reference to FIG. 38. FIG. 38 is a cross-sectional view of the analytical cell 104 taken in the same direction as FIGS. 2 and 35. The components in FIG. 38, equal or similar in functions and effects to those in FIGS. 1 to 37, are denoted by the same reference numerals, and detailed explanations thereof are omitted.
The analytical cell 104 contains the isolation membranes 90, 92 of the second embodiment instead of the isolation membranes 46, 48 in the analytical cell 94. The isolation membranes 90, 92 can act to avoid the contact of the negative electrode collector 42 and the positive electrode collector 44 with the electrolytic solution in the overlapping portion 20, and the electron beam transmission distance in the electrolytic solution can be shortened in the observation window 36. Consequently, the analytical cell 104 has the same advantageous effects as the analytical cells 10, 94, and, in addition, is capable of analyzing the electrode reactions and the like in the negative electrode active material 38 and the positive electrode active material 40 more highly accurately.
For example, the analytical cell 104 may be produced in the same manner as the above analytical cell 94 except for performing the following photolithography process instead of the photolithography process for the photoresist 82 shown in FIGS. 25A to 25C. In this case, the photoresist 82 is patterned, such that the photoresist 82 remains also inside the observation window 36, to form portions to be covered with the isolation membranes 90, 92. As a result, in the final product of the analytical cell 104, the negative electrode active material 38 and the positive electrode active material 40 are formed on the different holders (the first holder 96 and the second holder 98), and each isolation membrane 90, 92 extends from the negative electrode collector 42 or the positive electrode collector 44 to the negative electrode active material 38 or the positive electrode active material 40.
The present invention is not limited to the above embodiments, and various changes and modifications may be made therein without departing from the scope of the invention.
For example, the isolation membranes 46, 48 are formed on the negative electrode collector 42 and the positive electrode collector 44 in the analytical cell 10 of the above embodiment. However, the present invention is not limited thereto, and only one of the negative electrode collector 42 and the positive electrode collector 44 may have the isolation membrane 46 or the isolation membrane 48.
In a case where the analytical cell 10 or the like of the above embodiment is not the lithium-ion secondary cell but the nickel-hydrogen cell, for example, a negative electrode of nickel hydroxide, a positive electrode of a hydrogen storing alloy, and an electrolytic solution of an aqueous potassium hydroxide solution KOH(aq) may be used. In a case where the analytical cell 10 is the alkaline-manganese cell, for example, a negative electrode of manganese dioxide/graphite, a positive electrode of zinc, and an electrolytic solution of KOH(aq) may be used.
The analytical cell 10 and the like can be used in an analysis not only in the TEM but also in every analytical equipment using an electron beam.

## Claims

1. An analytical cell, through which an electron beam is transmitted to perform an analysis, comprising a first holder and a second holder stacked with an electrolytic solution interposed therebetween, wherein
the first holder and the second holder each contain a substrate including a through-hole and a transmission membrane having an electron beam permeability, the through-hole extends in a thickness direction of the substrate, the transmission membrane is disposed on one surface of the substrate, such that one end of the through-hole is covered with the transmission membrane,
the first holder and the second holder are stacked to form an overlapping portion in such a manner that the surfaces of the substrates with the transmission membranes formed thereon face each other,
the through-holes face each other across the transmission membranes in the overlapping portion to form an observation window, through which an electron beam is transmitted,
a negative electrode active material and a positive electrode active material are arranged at a distance from each other and respectively in contact with the electrolytic solution between the transmission membranes in the observation window,
the negative electrode active material and the positive electrode active material are electrically connected to a negative electrode collector and a positive electrode collector, respectively, in the overlapping portion,
the negative electrode collector and the positive electrode collector each extend from inside of the overlapping portion and are exposed to outside,
electrical leads are respectively connected to the negative and positive electrode collectors, and
at least one of the negative electrode collector and the positive electrode collector has an electrically insulating isolation membrane provided therewith such that the electrically insulating isolation membrane prevents said at least one of the negative and positive electrode collectors from contacting the electrolytic solution in the overlapping portion, and thereby inhibits any side reaction between the electrolyte solution and said at least one of the negative and positive electrode collectors when a potential difference is applied between the electrical leads to cause an electrode reaction in the positive and negative electrode active materials and the electrode reaction is observed using the electron beam transmitted through the observation window.

2. The analytical cell according to claim 1, wherein
the negative electrode collector and the positive electrode collector each have a layer structure with one surface contacting the first holder and the other surface having the isolation membrane.

3. The analytical cell according to claim 1, wherein
the negative electrode collector has a layer structure with one surface contacting the first holder and the other surface having the isolation membrane, and
the positive electrode collector has a layer structure with one surface contacting the second holder and the other surface having the isolation membrane.

4. The analytical cell according to claim 1, wherein
the isolation membrane has an electron beam permeability and extends from at least one of the negative electrode collector and the positive electrode collector in such a manner that the isolation membrane is interposed between the transmission membrane and at least one of the negative electrode active material and the positive electrode active material in the observation window.