JP2010230355A - Analysis system, electrochemical cell for analysis, and analysis method - Google Patents

Abstract

An internal state of an electrochemical cell using a solid or quasi-solid electrolyte is analyzed.
In the analysis system of the present invention, an analytical electrochemical cell 160a disposed in a magnet bore B of a nuclear magnetic resonance imaging apparatus is surrounded by an RF coil 130, and a solid or quasi-solid electrolyte and non-magnetic material. An electrochemical cell structure including the electrodes of the non-metallic material that supports the electrochemical cell structure from both sides, and a connection structure that electrically connects the electrode of the electrochemical cell structure to the outside. . Further, in the analysis system, filters 190a and 190b that block signal noise in a frequency band including the resonance frequency of the measurement target nuclide are interposed between the terminal of the electrochemical measurement device and the connection structure. The present analysis system thereby images the spatial distribution of the measurement nuclide in the electrolyte of the electrochemical cell structure.
[Selection] Figure 2

Description

  The present invention relates to an analysis technique for an electrochemical cell, and more particularly to an analysis system, an analytical electrochemical cell, and an analysis method for analyzing an internal state of an electrochemical cell in which a solid or quasi-solid electrolyte is used.

  Lithium ion secondary batteries are widely used as batteries for mobile phones, laptop computers, and the like, and are expected to be applied to large power supply applications such as hybrid cars and electric cars in the future. However, the liquid lithium ion secondary battery has a safety concern such as a fire due to the flammability of the organic solvent of the electrolytic solution, which is an obstacle to its application.

  Among various lithium ion secondary batteries, all solid lithium ion polymer secondary batteries can be constructed using a flame retardant polymer electrolyte, which is advantageous in ensuring safety and is composed of solid materials. Therefore, there is no worry of liquid leakage and the moldability is high, and it is attracting attention. In recent years, it has been demonstrated that by optimizing the molecular design of the polymer electrolyte, a capacity comparable to that of a liquid lithium ion secondary battery can be achieved even under relatively high power conditions. However, the lithium ion polymer secondary battery has a property that the battery capacity rapidly deteriorates with a charge / discharge cycle, which is an obstacle to practical use.

  Up to now, electrochemical measurement by an alternating current impedance method, structural analysis by an X-ray diffraction method and an electron microscope have been performed for the purpose of elucidating the deterioration mechanism of a lithium ion polymer secondary battery. The AC impedance method is a method of obtaining information on ion movement in a solid from a response by applying an AC electrical signal to a battery. Until now, it has been clarified that the internal resistance due to the positive electrode / electrolyte interface is remarkably increased by repeating the charge / discharge cycle in response to the deterioration of the battery capacity. In the X-ray diffraction method and the electron microscope, the battery is disassembled after performing a predetermined charge / discharge cycle, and analyzed to change the crystal structure of the electrode material, and to change the element having an atomic number larger than fluorine in the battery. Changes in the spatial distribution can be observed.

  However, since the X-ray diffraction method and the electron microscope observation are destructive inspections, it is difficult to obtain in situ information, and it is not possible to observe lithium which is a light metal. According to the AC impedance method, it is possible to obtain non-destructive information on the ion movement inside the polymer electrolyte, but it is impossible to distinguish the lithium ion from its counter anion and capture the ion movement. The obtained result is also an indirect guess, and the internal state of the lithium ion secondary battery cannot be sufficiently evaluated.

  Until now, in order to analyze the ion transport phenomenon inside the lithium ion polymer secondary battery, the present inventors have used a pulse field gradient NMR method (PGSE-NMR: Pulse Field-gradient Stimulated-echo Nuclear Magnetic Resonance). We have succeeded in measuring the diffusion coefficient of fluoride ions of lithium ions and counter anions and discussing the relationship between the mobility of ionic species and battery characteristics. In addition, Non-Patent Document 1 is disclosed as a report of studying the diffusion coefficient of a polymer electrolyte by PGSE-NMR. According to these methods, information on ion migration inside the electrolyte can be obtained in a nondestructive manner by distinguishing lithium ions and their counter anions. However, since only limited information such as the diffusion coefficient of ion species and the degree of salt dissociation can be obtained, it cannot be said that the internal state of the lithium ion secondary battery can be sufficiently evaluated.

  Although the above-described degradation mechanism has not yet been fully elucidated, the analysis results so far have shown that in order to avoid capacity degradation and provide a higher performance lithium ion polymer secondary battery, It is considered important to grasp the details of ion migration inside the secondary battery, particularly in the reaction field at the electrode / electrolyte interface, and to optimize the battery configuration accordingly.

H. Kataoka et al., “Ionic Conduction Mechanism of PEO-Type Polymer Electrolytes Investigated by the Carrier Diffusion Phenomenon Using PGSE-NMR”, Macromolecules, 35, 6239-6244 (2002).

  In other words, the development of a novel analysis technology that enables non-destructive and real-time analysis of the movement and spatial distribution of ion species in the electrolyte inside an electrochemical cell such as a lithium ion polymer secondary battery in the operating state. It was desired.

  The present invention has been made in view of the above-described prior art, and the present invention distinguishes ion migration phenomena and spatial distribution in a solid or quasi-solid electrolyte inside an electrochemical cell in an operating state by distinguishing ionic species. However, an object of the present invention is to provide an analysis system that can measure and image nondestructively in real time. Another object of the present invention is to provide an electrochemical cell for analysis used in the above analysis system. Still another object of the present invention is to measure, in an operating state, non-destructive and real-time ion migration phenomena and spatial distribution in a solid or quasi-solid electrolyte inside an electrochemical cell while distinguishing ionic species. It is to provide an analysis method for imaging.

  The present inventors can solve the above-mentioned problems by applying NMR imaging to an electrochemical measurement system and non-destructively measuring in situ the ion migration phenomenon and spatial distribution in the electrolyte in the electrochemical cell structure. Based on the idea of being able to do this, we have made an intensive study and studied the structure of the electrochemical cell placed in the high magnetic field and radio wave detection region and the connection with the electrochemical measurement system. The present inventors have found that it is feasible and have reached the present invention. That is, the present inventors made the electrode material and the connection structure out of a non-magnetic material, removed metal elements as much as possible from within the radio wave detection region, and further between the electrochemical measuring device and the electrochemical cell. In addition, a low-pass filter that blocks signal noise in the frequency band that includes the resonance frequency of the target nuclide is inserted close to the radio wave detection region, enabling in situ measurement of the ion migration phenomenon and spatial distribution. As a result, the present invention was achieved.

  According to the present invention, an analysis system for analyzing an electrochemical cell structure by a nuclear magnetic resonance imaging method is provided. In the analysis system of the present invention, an electrochemical cell structure surrounded by an RF coil and including an electrode of a solid or quasi-solid electrolyte and a nonmagnetic material, and a set of support members of a nonmetallic material that supports the electrochemical cell structure from both sides And an electrochemical cell for analysis that includes a connection structure that electrically connects an electrode of the electrochemical cell structure and the outside.

  In the analysis system, the electrochemical cell for analysis is placed in the magnet bore of the nuclear magnetic resonance imaging apparatus, and the signal in the frequency band including the resonance frequency of the nuclide to be measured is connected between the terminal of the electrochemical measurement apparatus and the connection structure. A spatial filter of the nuclide to be measured in the electrolyte of the electrochemical cell structure is imaged with a filter that blocks noise.

  According to the above configuration, metal elements are eliminated from the radio wave detection region as much as possible, and signal noise in a frequency band including the resonance frequency of the measurement target nuclide is suitably cut off. Imaging within the electrolyte of the electrochemical cell structure can be realized.

Furthermore, the analysis system can image the spatial distribution of the measurement target nuclide using a pulse sequence by the gradient echo method. By using a pulse sequence by the gradient echo method, imaging in the electrolyte of the electrochemical cell structure can be accelerated. Further, in the present invention, the electrochemical cell structure includes a polymer material electrolyte containing lithium ions, and a first electrode and a second electrode arranged on both sides of the electrolyte to constitute a secondary battery. be able to. Furthermore, in the present invention, the analysis system can set one or more nuclides selected from the group consisting of ⁷ Li, ¹⁹ F, ³¹ P, and ¹ H as measurement target nuclides. Accordingly, it is possible to image the spatial distribution of various elements in a solid or quasi-solid electrolyte.

  Further, in the present invention, the electrochemical cell for analysis is connected to a filter, constitutes a connection structure, and the electrochemical cell structure is sealed in a sample tube together with a seal member, and a set of support members is sandwiched from both sides. It can further include a set of magnetic and conductive blocks. In this case, the support member can exclude this block from the detection range of the RF coil.

  Furthermore, in the present invention, the electrode of the electrochemical cell structure can include a current collector made of a non-magnetic metal material each having a thickness of 0.1 mm or less, and the connection structure is connected to the current collector. A lead wire of a nonmagnetic metal material having a diameter of 5 mm or less can be included. By using a member of the above size, it is possible to satisfactorily reduce noise that can affect NMR imaging. The nuclear magnetic resonance imaging apparatus can also include a superconducting magnet, an RF coil, a gradient coil, an NMR spectrometer with a magnetic field gradient control function, and a measurement computer.

  Furthermore, according to the present invention, an electrochemical cell for analysis is provided for analyzing an electrochemical cell structure by a nuclear magnetic resonance imaging method. The present invention also provides an analysis method for analyzing an electrochemical cell structure by nuclear magnetic resonance imaging.

The figure which shows the outline of the analysis system by embodiment of this invention. The figure which shows the outline of the battery cell set for analysis of embodiment of this invention. The figure which shows the detailed structure inside the electrochemical cell for analysis of embodiment of this invention. The photograph which shows the external appearance of the battery cell for analysis of this embodiment. The figure which shows the outline of the battery cell set for analysis in other embodiment of this invention. The figure which shows the outline of the battery cell set for analysis in other embodiment of this invention. The flowchart which shows the analysis method by embodiment of this invention. The figure which shows typically the waveform of the pulse sequence by a gradient echo method. The graph which shows the charging / discharging characteristic of the produced battery cell structure. The image which shows distribution on the plane horizontal to the z-axis of the fluorine ion in a lithium ion polymer secondary battery. The image which shows distribution on the plane perpendicular | vertical to the z-axis of the fluorine ion in a lithium ion polymer secondary battery.

  Hereinafter, although this invention is demonstrated with specific embodiment, this invention is not limited to embodiment mentioned later.

  FIG. 1 schematically illustrates an analysis system 100 according to an embodiment of the present invention. The analysis system 100 shown in FIG. 1 includes a superconducting magnet 110, a nuclear magnetic resonance (hereinafter referred to as NMR) spectrometer 120, a measurement computer 140, and an electrochemical measurement device 150. . The measurement computer 140 is installed with a measurement application for executing NMR imaging measurement. The measurement computer 140 controls the operation of the NMR spectrometer 120 and generates an n-dimensional image from the measured NMR signal. Data is composed and recorded in a storage area such as a hard disk.

  The NMR spectrometer 120 includes a gradient magnetic field control unit, and in the bore B of the superconducting magnet 110, gradient coils 132x, y, and z in the three-axis directions of the x axis, the y axis, and the z axis are arranged. The NMR spectrometer 120 generates a slice selection gradient magnetic field control signal, a phase encode gradient magnetic field control signal, and a frequency encode gradient magnetic field control signal, and outputs a drive current to the gradient coil 132z, the gradient coil 132y, and the gradient coil 132x, The gradient magnetic field applied to the space to be measured is controlled, and position information is added to the NMR signal. Here, the z axis is an axis in the direction of the static magnetic field generated by the superconducting magnet 110, and the y axis and the x axis are two axes in a plane perpendicular to the z axis.

  In the bore B of the superconducting magnet 110, an RF (Radio Frequency) coil 130 is further arranged inside the set of gradient coils 132, and inside the RF coil 130 is used for NMR imaging analysis of the embodiment of the present invention. A battery cell (hereinafter simply referred to as an analytical battery cell) 160a is arranged.

  The NMR spectrometer 120 includes an irradiation channel for connecting the RF coil 130, generates an RF pulse waveform corresponding to the gradient magnetic field control signal in accordance with a predetermined pulse sequence, and outputs a drive current to the RF coil 130. Then, a radio wave pulse is irradiated. The NMR spectrometer 120 receives the NMR signal induced in the RF coil 130 from the analytical battery cell 160a. The measurement computer 140 reconstructs the image data by the projection reconstruction method or the Fourier transform method together with the NMR signal and the position information added by the gradient magnetic field control. In the present embodiment, the superconducting magnet 110, the NMR spectrometer 120, the RF coil 130, the gradient coil 132, and the measurement computer 140 constitute an NMR imaging apparatus.

  The analysis battery cell 160a according to the embodiment of the present invention has a battery cell structure disposed therein, and the battery cell structure is a measurement target of the analysis system 100. The electrode of the internal battery cell structure is connected to the connection terminal of the electrochemical measuring device 150 via a wiring. The electrochemical measurement device 150 operates as a potentiostat, a galvanostat, or a charge / discharge test device, and can perform direct current polarization measurement such as cyclic voltammetry measurement, potentiometry, charge / discharge test, and the like. For example, in a charge / discharge test, according to a specified measurement sequence, a constant voltage or a constant current is applied between electrodes of the battery cell structure of the analytical battery cell 160a to charge and discharge, and a storage capacity such as a charge capacity can be measured. it can.

  In addition, the electrochemical measurement device 150 can incorporate a frequency response analyzer (FRA) or a lock-in amplifier, whereby AC impedance measurement can be performed. The electrochemical measurement device 150 can be connected to the measurement computer 140 via an appropriate interface such as GPIB (General Purpose Interface Bus), and the battery cell structure is a measurement target in cooperation with the NMR imaging measurement. In situ NMR imaging measurements can be performed. Alternatively, the electrochemical measurement device 150 can be controlled by another independent computer or control unit.

  Hereinafter, the structure of an electrochemical cell for NMR imaging analysis according to an embodiment of the present invention will be described. FIG. 2 shows an outline of the analytical battery cell set 160 according to the embodiment of the present invention. Note that FIG. 2 schematically shows the analytical battery cell set 160, and it should be noted that the vertical and horizontal scale ratios do not necessarily match.

  The analysis battery cell set 160 shown in FIG. 2 includes an analysis battery cell 160a and noise cut filters 190a and 190b connected to external terminals of the analysis battery cell 160a. More specifically, the analysis battery cell 160a includes a cylindrical sample tube 162 having both ends open, a set of spacers 168 and 172 inserted into the sample tube 162, and a set of blocks 164, 166, and 174. including. The sample tube 162 has a shape that can be disposed in the RF coil 130. For example, a cylindrical Pyrex (registered trademark) glass tube or a quartz glass tube can be used. The analysis battery cell set 160a shown in FIG. 2 is arranged so that the direction in which the sample tube 162 extends is along the direction of the bore B of the superconducting magnet 110.

  Between the upper and lower spacers 168 and 172, a battery chamber 170 for storing the battery cell structure to be measured is configured, and the RF coil 130 is disposed so as to surround the battery chamber 170. Note that the RF coil 130 shown in FIG. 2 is a saddle type coil. The spacers 168 and 172 support the battery cell structure stored in the battery chamber 170 from both sides. The spacers 168 and 172 are made of a non-magnetic and non-metallic material, and eliminate as much of the metal material that can generate noise as possible from the radio wave detection range surrounded by the RF coil 130. The spacers 168 and 172 constitute the support member of this embodiment. Specific thicknesses of the spacers 168 and 172 can be appropriately set in consideration of the size and shape of the RF coil 130 to be used. For example, by inserting a metal into the sample tube 162 and monitoring the noise level, changing the position of the RF coil 130 relative to the metal, and adopting a distance at which the noise level is reduced to a practical level. it can.

  As such non-magnetic and non-metallic materials, fluororesins such as Teflon (registered trademark) and Daiflon (registered trademark) are preferably used from the viewpoint of chemical resistance and ease of handling. Other resin materials, glass materials, ceramic materials, etc. can be used. The spacers 168 and 172 are processed into a shape suitable for the sample tube 162. When a cylindrical sample tube is used, the spacers 168 and 172 are processed into a columnar shape having a diameter less than the inner diameter of the cylindrical shape.

  Blocks 164 and 166 and a block 174 are inserted outside the spacer 168 and the spacer 172 of the sample tube 162, respectively, and the spacers 168 and 172 and the battery cell structure inside thereof are sandwiched from both sides. The blocks 164, 166, and 174 are processed into a shape suitable for the sample tube 162. When a cylindrical sample tube is used, the blocks 164, 166, and 174 are processed into a cylindrical shape having a diameter less than the inner diameter of the cylindrical shape.

  In the circumferential direction of the side surfaces of the blocks 164 and 174, a groove is cut and an O-ring 180 is fitted, and the internal battery cell structure is sealed together with the sample tube 162 to be cut off from the outside air. A space is formed between the block 164 and the block 166, and this serves as an air escape place when the blocks 164 and 174 are sealed.

  Blocks 164, 166, and 174 include a non-magnetic and conductive material and provide an electrical connection between the battery cell structure disposed therein and the external electrochemical measurement device 150. As such a non-magnetic and conductive material, non-magnetic metal materials (including simple metals and alloys) such as brass, non-magnetic stainless steel, aluminum, and copper can be used. As long as the above can be obtained, it is possible to use a carbon material such as graphite or glassy carbon, or a conductive non-metallic material such as ceramic that is conductive and non-magnetic.

  A screw hole is formed through the block 164, and a screw hole having an appropriate depth is also formed in the block 166. A screw 176 is screwed into the screw holes of the blocks 164 and 166, and the spacer 168 is pressed by the screw 176. With the configuration of the blocks 164 and 166 and the screw 176, the battery cell structure can be placed under a pressurized state close to a practical use environment. The block 174 is also threaded with an appropriate depth, and a screw 178 is inserted there. These screws 176 and 178 are made of a nonmagnetic and conductive material, and constitute an external terminal of the analytical battery cell 160a.

  The noise cut filter 190 connected to the external terminal of the analysis battery cell 160a is configured using a filter circuit such as a low pass filter or a band pass filter, and cuts off a signal in a frequency band including the resonance frequency of the nuclide to be measured. To do. It is preferable that the noise cut filter 190 cuts off high frequency noise generated from the electrochemical measuring device 150 and the wiring connecting the terminal and the analytical battery cell 160a, and adversely affects the measurement on the NMR spectrometer 120 side. Can be prevented.

  The noise cut filter 190 is preferably interposed in the vicinity of the battery cell structure to be measured from the viewpoint of reducing noise. That is, it is more preferable that the connection distance connecting the noise cut filter 190 and the electrode in the battery cell structure is short. Since the electrochemical measuring device 150 and the analytical battery cell 160a in the superconducting magnet 110 are usually connected by drawing a relatively long wire, there is a possibility that large noise will be picked up from the external environment. By using the noise cut filter 190, it is possible to satisfactorily reduce noise that becomes a problem when combining the electrochemical measurement system and the NMR spectroscopy system.

The noise cut filter 190 can be manufactured using, for example, a coil L and a capacitor C having an inductance and a capacitance corresponding to the resonance frequency, but a filter circuit having any known circuit configuration may be used. it can. Hereinafter, typical resonance frequencies of nuclides will be exemplified. In superconducting magnets of 200 MHz class (corresponding to proton resonance frequency), 300 MHz class, and 400 MHz class, the resonance frequencies of ⁷ Li are 77.7 MHz, 116.6 MHz, and 155.5 MHz, respectively. The resonance frequency of ¹⁹ F is 188.1 MHz (200 MHz class), 282.2 MHz (300 MHz class), 376.3 MHz (400 MHz class). The resonance frequency of ³¹ P is 80.9 MHz (200 MHz class), 121.4 MHz (300 MHz class), and 161.923 MHz (400 MHz class). Since the electrochemical AC impedance measurement is performed in the range of about 10 mHz to 1 MHz, the noise cut filter 190 can be configured as a low-pass filter that blocks a signal of 5 MHz or more, for example.

  FIG. 3 is a diagram showing a detailed structure inside the electrochemical cell for analysis according to the embodiment of the present invention. Note also that FIG. 3 does not necessarily match the vertical and horizontal scale ratios. FIG. 3 shows elements constituting the analytical electrochemical cell internal structure 160b such as spacers 168 and 172, blocks 164 and 166 and 174, screws 176 and 178, and the like.

A battery cell structure 200 including a negative electrode 202, an electrolyte 204, and a positive electrode 206 is disposed between the spacers 168 and 172. The battery cell structure 200 includes an electrode material and an electrolyte material constituting an electrochemical cell such as a lithium ion polymer secondary battery (including a lithium ion polymer secondary battery using a lithium metal as a negative electrode). When the battery cell structure 200 is configured as a lithium ion polymer secondary battery, the negative electrode 202 includes a negative electrode active material such as metallic lithium, polyacetylene, graphite, lithium titanate, and the positive electrode 206 includes LiFePO ₄ , LiMn ₂ O. ₄ , and a positive electrode active material such as LiCoO ₂ .

  When the negative electrode 202 is made of metallic lithium, it is preferable to use a metallic lithium foil having a thickness of 0.2 mm or less from the viewpoint of reducing noise for NMR imaging, and the thickness of the metallic lithium foil is 0.1 mm or less. This is more preferable because the noise level can be considerably suppressed. For the positive electrode 206, for example, a mixture of the positive electrode active material, a conductive agent such as acetylene black or furnace black, and a binder such as lithium salt-containing polyethylene oxide (PEO) or polyvinylidene fluoride (PVdF) is used. be able to. In addition, the negative electrode 202 and the positive electrode 206 may include other nonmagnetic current collector materials. When the current collector contains a non-magnetic metal material such as an Al foil or Pt foil, the thickness is preferably 0.2 mm or less from the viewpoint of reducing noise for NMR imaging, and is 0.1 mm or less. More preferably, the film thickness is 0.02 mm or less because the noise level can be considerably suppressed.

When the battery cell structure 200 is configured as a lithium ion polymer secondary battery, the electrolyte 204 can be a solid or gel (quasi-solid) polymer electrolyte containing lithium ions. More specifically, the electrolyte 204 is a polymer of polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, or polymethyl methacrylate containing a lithium salt such as LiTFSI (LiN (SO ₂ CF ₃ ) ₂ ). An electrolyte can be used.

Other lithium salts in the electrolyte 204 include inorganic salts such as LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiCl, LiBr, LiCF ₃ SO ₃ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC ( Organic salts such as SO ₂ CF ₃ ) ₃ , LiC (SO ₂ C ₂ F ₅ ) ₃ , and other salts known as electrolytes for non-aqueous electrolytes can be used.

  In addition, the material structure of the negative electrode 202, the electrolyte 204, and the positive electrode 206 stored in the battery chamber 170 can be charged and discharged by transporting lithium ions and transferring charges when using a lithium ion polymer secondary battery. Any combination of electrolytes can be employed as long as the electrolyte is quasi-solid or solid and is made of a non-magnetic material.

  The spacer 168 is formed with a through hole 168a through which a lead wire connected to the negative electrode 202 in the battery chamber 170 is inserted, and the negative electrode 202 and the block 166 are connected by a lead wire passing through the through hole 168a. . Similarly, the spacer 172 is formed with a through hole 172a for inserting a lead wire from the positive electrode 206 in the battery chamber 170, and the positive electrode 206 and the block 174 are connected by the lead wire passing through the through hole 172a. .

  Screw holes 164a, 166a and screw holes 174a into which screws 176 and 178 of external terminals are screwed are formed in the blocks 164, 166 and the block 174, respectively. In the analysis battery cell 160a of the present embodiment, the lead wire passing through the through hole 168a, the conductive blocks 166 and 164, and the screw 176 form a connection structure from the battery cell structure to the outside of the analysis battery cell. Similarly, the lead wire passing through the through hole 172a, the block 174, and the screw 178 constitute the other connection structure.

  The lead wire is formed of a non-magnetic and conductive member, and provides electrical connection between the battery cell structure disposed inside and the external electrochemical measurement device 150. As such a member, a nonmagnetic metal wire can be used, and from the viewpoint of chemical stability, it is preferable to use a noble metal wire such as a platinum wire. From the viewpoint of reducing noise for NMR imaging, a metal wire having a diameter of 0.5 mm or less is preferably used, and a metal wire having a diameter of 0.2 mm or less is more preferably used.

  FIG. 4 is a photograph showing the appearance of the analytical battery cell 160a of this embodiment. In the photograph shown in FIG. 4, the corresponding elements of the analytical battery cell 160a shown in FIGS. 2 and 3 are indicated by reference numerals. Referring to FIG. 4, it can be seen that the battery cell structure 200 is supported by spacers 168 and 172 from both sides in the analytical battery cell 160a.

  Hereinafter, the configuration around the electrochemical cell for analysis according to another embodiment of the present invention will be described. FIG. 5 schematically shows the periphery of an analytical battery cell set 210 according to another embodiment of the present invention. Note also that FIG. 5 does not necessarily match the vertical and horizontal scale ratios. In the embodiment shown in FIG. 5, the analysis battery cell set 210 includes an analysis battery cell 210a and noise cut filters 220a and 220b connected to external terminals of the analysis battery cell 210a. The The analysis battery cell set 210 is arranged in a straight line with the direction of the sample tube in the direction of the bore B of the superconducting magnet 110. As shown in FIG. 5, if the length in the longitudinal direction (sample tube direction) of the analytical battery cell 210a is less than the diameter of the bore B of the superconducting magnet 110, it is installed horizontally, and further, a solenoid type RF coil By using 212, the sensitivity of NMR spectroscopy can be improved.

  FIG. 6 shows an outline around the analytical battery cell set 230 in still another embodiment of the present invention. The analysis battery cell set 230 shown in FIG. 6 includes an analysis battery cell 230a and noise cut filters 240a and 240b connected to the terminals of the analysis battery cell a.

  The analysis battery cell 230a shown in FIG. 6 has the sample tube 162 shown in FIG. 2 as an inner tube 232, and an outer tube 234 provided on the outer side thereof. In the analysis battery cell 160a shown in FIG. 2, the wiring from the lower terminal is routed downward as it is, and is drawn out from below the bore B of the superconducting magnet 110. In the battery cell a, the wiring from the lower terminal is routed upward through the space between the inner tube 232 and the outer tube 234. Depending on the experimental constraints, the embodiment shown in FIG. 6 can be adopted. However, since the routed wiring passes through the RF coil 236, from the viewpoint of reducing noise for NMR imaging. 2 and FIG. 5 are preferred.

  Hereinafter, an analysis method for analyzing a battery cell structure by the nuclear magnetic resonance imaging method in the analysis system 100 of the embodiment of the present invention will be described. FIG. 7 is a flowchart illustrating an analysis method according to an embodiment of the present invention. The analysis method shown in FIG. 7 is started from step S100. In step S101, a battery cell structure, a spacer, a block, and the like are inserted into the analysis battery cell 160a, the analysis battery cell 160a is set, and a superconducting magnet is provided. The analytical battery cell 160a is prepared at a predetermined position in the bore B of 110.

  In step S102, various measurement conditions in electrochemical measurement and NMR imaging measurement are set. As electrochemical measurement conditions, when measuring charge / discharge of a battery, it is possible to specify a charge method such as a constant current charge method, a constant voltage charge method, a constant current constant voltage control charge method, a pulse charge method, or a constant current discharge. Designation of a discharge method such as a method, a constant power discharge method, and a pulse discharge method, designation of whether or not there is a downtime, and the like are included. In addition, as measurement conditions for electrochemical measurement, for example, in the case of performing cyclic voltammetry, a starting potential, a running potential range, a running speed, and the like are included.

The measurement conditions of the NMR imaging measurement include designation of a measurement target nuclide, designation of a pulse sequence, measurement range (selection of a measurement plane in the case of a two-dimensional image, etc.), designation of resolution, and the like. The nuclide to be measured depends on the static magnetic field strength that can be generated by the superconducting magnet to be used. Examples include spin quantum nuclide, and more specifically, ⁷ Li, ¹⁹ F, ³¹ P, ¹ H, and the like. In NMR imaging, the spatial distribution of the measurement target nuclide is quantified, and can be imaged as a two-dimensional or three-dimensional real-time video image or as a still image at an arbitrary timing.

  The analysis method according to the embodiment of the present invention is based on a gradient echo method such as FLASH, SPGR, GRASS, and FISP from the viewpoint of achieving a high signal-to-noise ratio (SN ratio) and obtaining high accuracy and time resolution. It is preferable to image the spatial distribution of the nuclide to be measured, and thus the spatial distribution of the element to be measured, using the pulse sequence. In the gradient echo method, an echo signal is generated by inverting the gradient magnetic field instead of the 180 ° pulse of the spin echo method. FIG. 8 schematically shows a waveform of a pulse sequence by the gradient echo method. FIG. 8 schematically shows waveforms of a signal (RF) of a channel connected to the RF coil, a slice selection gradient magnetic field control signal (G (slice)), and a frequency encode gradient magnetic field control signal (G (read)). ing. The RF signal includes an irradiated 90 ° pulse waveform and an induced echo signal waveform.

  In step S103, according to the electrochemical measurement conditions set in step S102, the battery cell structure is energized through a noise cut filter that cuts off signal noise in the frequency band including the resonance frequency of the measurement target nuclide, and electrochemical measurement is performed. To start. In step S104, NMR spectroscopy measurement is started according to the NMR imaging measurement conditions set in step S102, and the spatial distribution of the measurement target nuclide is imaged with the inside of the battery cell structure electrolyte as the observation position. Then, after recording desired data, the analysis is terminated in step S105. Note that the NMR spectroscopic measurement in step S104 can be performed while the electrochemical measurement is in operation.

  According to the above-described analytical battery cells 160a, 210a, and 230a, since the electrode current collector and the connection structure are made of a nonmagnetic material, they can be handled safely and stably even in the superconducting magnet. Furthermore, since the metal material is excluded from the radio wave detection region of the RF coil 130 as much as possible, noise that acts on the NMR imaging measurement due to the metal material in the measurement target region is suitably reduced. Furthermore, the external terminals of the analytical battery cells 160a, 210a, and 230a are connected to the connection terminal of the electrochemical measuring device 150 via a noise cut filter 190 that blocks a noise signal in a frequency band including the resonance frequency of the measurement target nuclide. Connected. For this reason, it is effectively prevented that noise picked up by the electrochemical measuring apparatus 150 and the wiring between the terminals is transmitted to the NMR spectrometer side. Due to the above features, a high signal-to-noise ratio is achieved, and NMR imaging with the electrochemical cell structure in operation as the object of observation is realized.

  In the above description, the analysis battery cell in which the battery cell structure is disposed has been described as an example of the analysis electrochemical cell. However, the electrochemical cell structure that can be disposed in the analysis electrochemical cell. Is not particularly limited. The electrochemical cell structure may be another electrochemical cell structure using a solid or quasi-solid electrolyte containing the ion species of the measurement target nuclide. In the above description, the electrochemical cell structure is configured as a so-called bipolar cell. However, in other embodiments, in order to perform more accurate potential control, the electrochemical cell structure is provided at an appropriate location in the battery chamber 170. A reference electrode may be arranged to configure as a three-pole cell. In addition to the saddle type and solenoid type described above, other RF coils such as a birdcage type can also be adopted as the RF coil.

  Hereinafter, the analysis system and the analysis method of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to specific examples.

(Analysis system)
An NMR spectrometer (Avance 300) equipped with a Bruker micro-imaging accessory was used as the NMR spectrometer 120. An ultrashield (registered trademark) manufactured by Bruker, 300 MHz, and a superconducting magnet having a bore diameter of 89 mm was used as the superconducting magnet 110. In addition, the gradient coil 132 was configured using a gradient system of micro imaging probe manufactured by Bruker. A potentiostat (1287 type) manufactured by Solartron was used as the electrochemical measuring device 150. In addition, a personal computer manufactured by Hewlett-Packard Company with a 2.66 GHz CPU and 2 GB memory mounted thereon was used as the measurement computer 140.

(Analytical battery cell)
A straight pipe made of Pyrex (registered trademark) having a processing accuracy of ± 0.5 mm, an outer diameter of 9 mm, an inner diameter of 7 mm, and a length of 100 mm was used as the sample tube 162. A column made of Teflon (registered trademark) having a diameter of 6 mm, a height of 30 mm, and a through-hole of 0.8 mmφ in the center was produced as a spacer 168. In addition, a Teflon (registered trademark) cylinder having a diameter of 6 mm, a height of 11 mm, and a through hole of φ0.8 mm in the center was manufactured as the spacer 172.

  As the block 164, a brass cylinder having a diameter of 6 mm, a height of 20 mm, a φ3 mm screw hole penetrating in the center, and an O-ring groove cut in the center of the side surface was used. A brass cylinder having a diameter of 6 mm, a height of 5 mm, and a screw hole having a depth of 3 mm and a diameter of 3 mm in the center was formed as a block 166. Block 174 is a brass cylinder having a diameter of 6 mm, a height of 20 mm, a screw hole having a depth of 5 mm and a diameter of 3 mm formed in the center of one surface, and two O-ring grooves cut in the center of the side surface at intervals of 5 mm. Created as. A platinum wire of φ0.2 mm was inserted through the through holes of the spacers 168 and 172 and used as a lead wire. The screw 176 used as the external terminal was made of a nonmagnetic material having a diameter of 3 mm and 50 mm.

A low-pass filter (cutting off a high frequency of 5.8 MHz or higher) composed of a 1.1 μH coil L and a 680 pF capacitor C was used as the noise cut filter 190. In the 300 MHz class NMR spectroscopy system, when ⁷ Li is a measurement target nuclide, the resonance frequency is 116.6 MHz.

(Battery cell structure)
And Aldrich of LiFeP0 ₄ as the positive electrode active material, a conductive agent of acetylene black manufactured by Denki Kagaku Kogyo Co., Ltd., and Aldrich polyethylene oxide PEO (particle binder + lithium conductivity agent) as a binder , 88: 6: 6 (mass%) to produce a positive electrode. A metal lithium foil having a purity of 99.9% and a thickness of 0.37 mm manufactured by Aldrich was rolled to 0.2 mm or less and used as a negative electrode. Polyelectrolytes, _LiN the electrolytic salt (SO 2 _{CF 3) 2} (weight ratio 0.23) is used is plasticizer by the following general formula (1) in Nichiyu Co. boric acid represented (tri ( Oxyalkylene)) ester (n = 6-12, weight ratio 0.38), monomers polyethylene glycol monomethacrylate (molecular weight 400, manufactured by NOF Corporation, weight ratio 0.29) and polyethylene glycol dimethacrylate A polyethylene oxide polymer electrolyte produced by mixing in a solution (molecular weight 600, manufactured by NOF Corporation, weight ratio 0.10) and photopolymerizing with ultraviolet rays was used. And the lithium ion polymer secondary battery of the said structure was created, and it sealed in the battery cell for analysis. The lithium ion polymer secondary battery and the analytical battery cell were prepared in a glove box under a water content of 10 ppm or less and in an argon atmosphere.

(Charge / discharge measurement and NMR imaging measurement)
With respect to the prepared lithium ion polymer secondary battery, under the condition of a temperature of 60 ° C. and a current density of 1 C (that is, a condition that the LiFePO ₄ theoretical capacity of 170 mAhg ⁻¹ can be fully charged or fully discharged in one hour). Thus, a 100-cycle charge / discharge test was performed. FIG. 9A is a graph showing a change in voltage with respect to charge / discharge capacity in each charge / discharge cycle. FIG. 9B is a graph showing changes in battery capacity due to charge / discharge cycles. As shown in FIG. 9, the discharge average voltage was about 3.5 V, and the electrochemical behavior equivalent to that of a battery using ordinary LiFePO ₄ was confirmed.

  In the NMR imaging measurement, a pulse sequence of the gradient echo method shown in FIG. 8 was used. Note that the imaging parameters were repetition time (TR) = 503 ms, echo time (TE) = 6 ms, imaging time (TA) = 1: 4 [min], and NEX (Number of Excitations) = 1. FIGS. 10 to 12 show NMR imaging results measured using the battery cell structure having the above configuration as a measurement object before starting the charge / discharge cycle and after 50 cycles. FIG. 10 shows the distribution of fluorine ions on a plane parallel to the z-axis (the cross-sectional direction of the polymer electrolyte) in the lithium ion polymer secondary battery. FIG. 10 (A) shows an image before the charge / discharge cycle, FIG. 10 (B) shows an image after 50 cycles, and FIG. 10 (C) shows a measurement plane. FIG. 11 shows the distribution of fluorine ions on a plane perpendicular to the z-axis (the horizontal direction of the polymer electrolyte) in the lithium ion polymer secondary battery. FIG. 11 (A) shows the image after 50 cycles, and FIG. 11 (B) illustrates the measurement plane.

  Referring to FIGS. 10 and 11, it is shown that fluorine ions that were uniformly distributed throughout the polymer electrolyte before the charge / discharge cycle segregated to the positive electrode side after 50 cycles. Further, after 50 cycles, it was shown that segregation was concentrated on a specific portion even on the plane of the polymer electrolyte in the water direction.

(Summary)
As shown in FIGS. 10 to 12, by using the analytical battery cell configured as described above, it has been demonstrated that in situ measurement of NMR imaging of fluorine ion spatial distribution is feasible. Or, in an electrochemical cell structure using a quasi-solid electrolyte, it is possible to image in real time the spatial distribution of nuclide elements of half-integer or integer nuclear spin quantum number with a relatively high natural abundance ratio. It has been shown.

  According to the present invention, in an operating state, ion migration phenomenon and spatial distribution in a solid or quasi-solid electrolyte inside an electrochemical cell are measured and imaged in a non-destructive and real-time manner while distinguishing ionic species. An analysis system that can be provided can be provided. Moreover, according to this invention, the electrochemical cell for an analysis used with the said analysis system can be provided. According to the present invention, in an operating state, the ion transfer phenomenon and the spatial distribution in a solid or quasi-solid electrolyte inside an electrochemical cell are further measured in a non-destructive and real-time manner while distinguishing ionic species. An analysis method for imaging can be provided. The analysis system, analytical electrochemical cell, and analytical method of the present invention make it possible to grasp in real time the movement and spatial distribution of each ionic species in the electrolyte inside the electrochemical cell under various conditions. Development of a high-performance electrochemical cell (for example, a lithium ion polymer secondary battery in which capacity deterioration does not occur) can be supported.

  Although the embodiments and examples of the present invention have been described so far, the embodiments of the present invention are not limited to the above-described embodiments and specific examples, and other embodiments, additions, modifications, It can be changed within a range that can be conceived by those skilled in the art, such as deletion, and any aspect is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

DESCRIPTION OF SYMBOLS 100 ... Analytical system 110 ... Superconducting magnet, B ... Bore, 120 ... NMR spectrometer, 130 ... RF coil, 132 ... Gradient coil, 160 ... Analytical battery cell, 140 ... Computer for measurement, 150 ... Electrochemical measuring device , 160a ... analytical battery cell, 160 ... analytical battery cell set, 190 ... noise cut filter, 162 ... sample tube, 164 ... block, 166 ... block, 168 ... spacer, 170 ... battery chamber, 172 ... spacer, 174: Block, 176: Screw (external terminal), 178 ... Screw (external terminal), 180 ... O-ring, 200 ... Battery cell structure, 202 ... Negative electrode, 204 ... Electrolyte, 206 ... Positive electrode, 210 ... Battery cell for analysis Set, 210a ... Analysis battery cell, 212 ... RF coil, 220 ... Noise cut filter, 230 ... Analysis power Cell set, 230a ... analytical cell, 232 ... inner tube, 234 ... outer tube, 236 ... RF coil, 240 ... noise cut filter

Claims (11)

An analysis system for analyzing an electrochemical cell structure by a nuclear magnetic resonance imaging method, the analysis system comprising:
An electrochemical cell structure disposed in a magnetic bore of a nuclear magnetic resonance imaging apparatus, surrounded by an RF coil, including an electrode of a solid or quasi-solid electrolyte and a non-magnetic material, and supporting the electrochemical cell structure from both sides An analytical electrochemical cell comprising: a set of non-metallic material support members; and a connection structure for electrically connecting the electrode of the electrochemical cell structure to the outside;
A filter interposed between a terminal of an electrochemical measurement device and the connection structure and blocking signal noise in a frequency band including a resonance frequency of a nuclide to be measured, and the filter in the electrolyte of the electrochemical cell structure An analysis system that images the spatial distribution of the target nuclide.   The analysis system according to claim 1, wherein the analysis system images a spatial distribution of the measurement target nuclide using a pulse sequence by a gradient echo method. The electrochemical cell structure comprises a secondary battery including the electrolyte of a polymer material containing lithium ions, and a first electrode and a second electrode disposed on both sides of the electrolyte, and the analysis The analysis system according to claim 1, wherein the system uses one or more nuclides selected from the group consisting of ⁷ Li, ¹⁹ F, ³¹ P, and ¹ H as the measurement nuclide.   The analytical electrochemical cell is a non-magnetic and conductive block, is connected to the filter, constitutes the connection structure, and seals the electrochemical cell structure in a sample tube together with a seal member, and supports the support The analysis system according to claim 1, further comprising a set of blocks that sandwich the set of members from both sides, wherein the support member excludes the blocks from the detection range of the RF coil.   The electrode of the electrochemical cell structure includes a current collector made of a nonmagnetic metal material each having a thickness of 0.1 mm or less, and the connection structure is connected to the current collector and has a diameter of 0.5 mm or less. The analysis system according to claim 1, comprising a lead wire made of a nonmagnetic metal material. An analytical electrochemical cell for imaging the spatial distribution of a target nuclide in an electrolyte of an electrochemical cell structure by nuclear magnetic resonance imaging,
A sample tube in which an electrochemical cell structure including an electrode of a solid or quasi-solid material and a nonmagnetic material is inserted, and a nonmetallic material that is inserted in the sample tube and supports the electrochemical cell structure from both sides An analytical electrochemical cell, comprising: a set of members; and a connection structure that electrically connects the electrode of the electrochemical cell structure to a filter that blocks signal noise in a frequency band including a resonance frequency of an external measurement target nuclide. .   A non-magnetic and conductive block that is connected to the filter, constitutes the connection structure, and seals the electrochemical cell structure in a sample tube together with a seal member, and sets the support member from both sides The analytical electrochemical cell according to claim 6, further comprising a set of blocks to be sandwiched, wherein the support member excludes the block from the detection range of the RF coil. An analysis method for analyzing an electrochemical cell structure by a nuclear magnetic resonance imaging method, the analysis method comprising:
An electrochemical cell structure surrounded by an RF coil and including an electrode of a solid or quasi-solid electrolyte and a non-magnetic material; a set of non-metallic material support members for supporting the electrochemical cell structure from both sides; Preparing an analytical electrochemical cell in a magnet bore of a nuclear magnetic resonance imaging apparatus, including a connection structure for electrically connecting the electrode of the chemical cell structure to the outside;
Energizing the electrochemical cell structure through a filter that blocks signal noise in a frequency band including the resonance frequency of the measurement nuclide;
Imaging the spatial distribution of the nuclide to be measured in the electrolyte of the electrochemical cell structure.   The analysis method according to claim 8, wherein in the imaging step, the spatial distribution of the measurement target nuclide is imaged using a pulse sequence by a gradient echo method. In the preparing step, a secondary battery including the electrolyte of a polymer material containing lithium ions, and a first electrode and a second electrode disposed on both sides of the electrolyte is formed in the electrochemical The cell structure includes a step of loading into a sample tube of the analytical electrochemical cell, wherein the imaging step includes one or more selected from the group consisting of ⁷ Li, ¹⁹ F, ³¹ P, and ¹ H. The analysis method according to claim 8 or 9, wherein a nuclide is used as the measurement nuclide.   The preparing step includes inserting a set of non-magnetic and conductive blocks into a sample tube of the analytical electrochemical cell, sealing the electrochemical cell structure in a sample tube together with a seal member with the block, and supporting the support. The analysis method according to claim 8, further comprising a step of sandwiching a set of members from both sides, wherein the support member excludes the block from a detection range of the RF coil.