WO2016071967A1

WO2016071967A1 - Lithium-ion cell and method for manufacturing same

Info

Publication number: WO2016071967A1
Application number: PCT/JP2014/079298
Authority: WO
Inventors: 祐介加賀; 利光野口; 和明直江; 新平尼崎
Original assignee: 株式会社日立製作所
Priority date: 2014-11-05
Filing date: 2014-11-05
Publication date: 2016-05-12

Abstract

The present invention makes it possible to improve the output of a lithium-ion cell, and to prevent the occurrence of short circuiting between the positive and negative electrodes caused by dislodging of the electrode active material. A means for accomplishing the above is a lithium-ion cell having a positive electrode, a negative electrode, and a separator for separating the electrodes, wherein a slit section is formed extending in the longitudinal direction of the separator, the slit section being a groove passing from the front surface to the back surface of the separator. The width of the slit section in the short direction is less than the average diameter of the active material, and the length in the long direction is equal to or greater than the average diameter of the active material.

Description

Lithium ion battery and manufacturing method thereof

The present invention relates to a lithium ion battery and a method for producing the same, and more particularly to a lithium ion battery in which a positive electrode and a negative electrode are separated by a separator.

With the development of portable electronic devices and the like, small secondary batteries that can be repeatedly charged are used as a power supply source for these devices. Among these, lithium ion secondary batteries have been attracting attention because they have the advantages of high energy density, long cycle life, low self-discharge characteristics, and high operating voltage. Lithium ion secondary batteries have the advantages described above, and are therefore widely used in portable electronic devices such as digital cameras, notebook personal computers, and mobile phones.

Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-280724) has a laminate formed by sequentially laminating a positive electrode, a separator, and a negative electrode, and at least one of the positive electrode and the negative electrode has a grain structure in consideration of high output. A lithium ion battery is described as an electrochemical device including active material particles having a small diameter. In a lithium ion battery, discharging or charging is performed by moving lithium ions between a positive electrode and a negative electrode through pores opened in a separator.

JP 2007-280724 A

If the pore diameter of the separator through which lithium ions pass is small and the passage route of lithium ions in the separator is not linear, the movement of lithium ions is hindered and the internal resistance of the lithium ion battery (lithium ion secondary battery) Get higher. In order to solve this problem, Patent Document 1 provides pores that penetrate the laminate in the stacking direction of the laminate. Moreover, in patent document 1, in order to prevent that a short circuit arises when an active material falls from a positive electrode or a negative electrode, the average diameter of the said pore is made smaller than the average particle diameter of active material particle.

However, when the average diameter of the pores opened in the separator is limited to be smaller than the average particle diameter of the active material particles, in order to reduce the internal resistance of the lithium ion battery and improve the output performance of the lithium ion battery It is difficult to improve the diffusibility of lithium ions in the separator.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

Of the embodiments disclosed in the present application, the outline of typical ones will be briefly described as follows.

A lithium ion battery according to a typical embodiment has a positive electrode and a negative electrode containing an electrode active material, and a separator that separates the electrodes, and is a groove that penetrates from the front surface to the back surface of the separator, and has a short direction. The slit width is less than the average diameter of the electrode active material and the length in the longitudinal direction is not less than the average diameter of the electrode active material.

Furthermore, in the method for manufacturing a lithium ion battery according to a typical embodiment, the width in the short direction is less than the average diameter of the electrode active material, and the length in the longitudinal direction is greater than or equal to the average diameter of the electrode active material. After the slit portion is opened in the separator, the positive electrode and the negative electrode containing the electrode active material and the separator separating the electrodes are overlapped.

According to a typical embodiment, it is possible to reduce the internal resistance of the battery and improve the output performance while preventing a short circuit due to the dropping of the active material, thereby improving the performance and reliability of the lithium ion battery. Can do.

It is a top view of the positive electrode plate which comprises the lithium ion battery which is this Embodiment 1 of this invention. It is a top view of the negative electrode plate which comprises the lithium ion battery which is this Embodiment 1 of this invention. It is the schematic which shows the laminated structure of the laminated body which comprises the lithium ion battery which is this Embodiment 1 of this invention. It is an overhead view which shows the winding body which comprises the lithium ion battery which is this Embodiment 1 of this invention. It is a bird's-eye view which permeate | transmits and shows partially the lithium ion battery which is this Embodiment 1 of this invention. It is the schematic explaining operation | movement of a lithium ion battery. It is the schematic which shows the manufacturing method of the lithium ion battery which is embodiment of this invention. FIG. 8 is an overhead view showing a method for manufacturing the lithium ion battery following FIG. 7. FIG. 9 is an overhead view showing a method for manufacturing a lithium ion battery following FIG. 8. FIG. 10 is an overhead view showing a method for manufacturing the lithium ion battery following FIG. 9. It is an overhead view which shows the manufacturing method of the lithium ion battery following FIG. It is the schematic which shows the laminated structure of the laminated body which comprises the lithium ion battery which is this Embodiment 2 of this invention. It is an overhead view which shows the winding body which comprises the lithium ion battery which is this Embodiment 2 of this invention. It is the schematic which shows the manufacturing method of the lithium ion battery which is embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. In the embodiments, the description of the same or similar parts will not be repeated in principle unless particularly necessary.

(Embodiment 1)
The configuration of the lithium ion battery according to the embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a plan view of a positive electrode plate constituting the lithium ion battery of the present embodiment. FIG. 2 is a plan view of the positive electrode plate constituting the lithium ion battery of the present embodiment. FIG. 2 is a plan view of the negative electrode plate constituting the lithium ion battery of the present embodiment. FIG. 3 is a schematic view showing a laminated structure of a laminated body constituting the lithium ion battery of the present embodiment. FIG. 4 is an overhead view showing a wound body constituting the lithium ion battery according to the present embodiment. FIG. 5 is a bird's-eye view showing a part of the lithium ion battery of the present embodiment. FIG. 6 is a schematic diagram for explaining the operation of the lithium ion battery.

FIG. 1 shows a positive electrode sheet PEL constituting the positive electrode of the lithium ion battery of the present embodiment. The positive electrode sheet PEL has a foil-like positive electrode plate PEP. Further, the positive electrode sheet PEL has an electrode material film PEF that is in contact with the positive electrode plate PEP so as to cover the surface of the positive electrode plate PEP and the back surface opposite to the front surface. That is, the positive electrode plate PEP is sandwiched between the pair of electrode material films PEF. In the figure, the electrode material film PEF on the back surface side of the positive electrode plate PEP is not shown.

The electrode material film PEF is formed by, for example, applying a slurry obtained by mixing a positive electrode active material PAS made of lithium cobalt oxide with carbon as a conductive additive and a binder to a positive electrode plate PEP, and then drying and solidifying the slurry. Film. The binder (binder) between the positive electrode plate PEP and the positive electrode active material PAS is made of, for example, polyvinylidene fluoride. The slurry of the positive electrode is formed by a solution in which the binder, the positive electrode active material PAS, and carbon as a conductive additive are dissolved in N methylpyrrolidone (NMP).

The average particle diameter of the plurality of particles (active material particles) constituting the positive electrode active material PAS is, for example, 10 μm. The film thickness of the electrode material film PEF in contact with one surface of the positive electrode plate PEP is, for example, 10 to 100 μm. That is, the particles constituting the plurality of positive electrode active materials PAS are stacked on the surface of the positive electrode plate PEP.

The positive electrode sheet PEL made of the positive electrode plate PEP and the electrode material film PEF is a thin sheet extending in one direction. That is, the positive electrode plate PEP and the electrode material film PEF extend in the above-described direction, that is, the longitudinal direction. Hereinafter, the longitudinal direction of a sheet such as the positive electrode sheet PEL may be simply referred to as an X direction (first direction). The surface of the electrode material film PEF, that is, the surface opposite to the surface in contact with the positive electrode plate PEP is smoothed.

A rectangular positive electrode that is cut in one direction along the surface of the positive electrode plate PEP and that is perpendicular to the longitudinal direction of the positive electrode plate PEP and that protrudes in the short direction. A plurality of current collecting tabs PTAB are formed. Hereinafter, the short direction of a sheet such as the positive electrode sheet PEL may be simply referred to as a Y direction (second direction). The plurality of positive electrode current collecting tabs PTAB are arranged along one side of the end of the positive electrode plate PEP in the Y direction, and are formed in an uncoated portion of the positive electrode active material PAS. That is, the positive electrode current collection tab PTAB is exposed from the positive electrode active material PAS, and a plurality of the positive electrode current collection tabs PTAB are arranged in the X direction along one side of the positive electrode sheet PEL.

FIG. 2 shows a negative electrode sheet NEL constituting the negative electrode of the lithium ion battery of the present embodiment. The negative electrode sheet NEL has a foil-like negative electrode plate NEP. The negative electrode sheet NEL has an electrode material film NEF that is in contact with the negative electrode plate NEP so as to cover the surface of the negative electrode plate NEP and the back surface opposite to the surface. That is, the negative electrode plate NEP is sandwiched between the pair of electrode material films NEF. In the figure, the electrode material film NEF on the back side of the negative electrode plate NEP is not shown.

For example, the electrode material film NEF is formed by applying a slurry obtained by mixing carbon as a conductive additive and a binder (binder) to a negative electrode active material NAS made of a carbon material (carbon material) and then drying the slurry on the negative electrode plate NEP. This is a solidified film. The binder (binder) between the negative electrode plate NEP and the negative electrode active material NAS is made of, for example, polyvinylidene fluoride. The slurry of the negative electrode is formed by a solution in which the binder, the negative electrode active material NAS, and carbon as a conductive additive are dissolved in N methylpyrrolidone (NMP).

The average particle diameter of the plurality of particles (active material particles) constituting the negative electrode active material NAS is, for example, 10 μm. The film thickness of the electrode material film NEF in contact with one surface of the negative electrode plate NEP is, for example, 10 to 100 μm. That is, the particles constituting the plurality of negative electrode active materials NAS are stacked on the surface of the negative electrode plate NEP.

The negative electrode sheet NEL made of the negative electrode plate NEP and the electrode material film NEF is a thin sheet extending in one direction. That is, the negative electrode plate NEP and the electrode material film NEF extend in the above-described direction, that is, the longitudinal direction (X direction). The surface of the electrode material film NEF, that is, the surface opposite to the surface in contact with the negative electrode plate NEP is smoothed.

One end of the short direction (Y direction) that is along the surface of the negative electrode plate NEP and perpendicular to the longitudinal direction of the negative electrode plate NEP is cut and protruded in the Y direction. A plurality of tabs NTAB are formed. The plurality of negative electrode current collecting tabs NTAB are arranged along one side of the end of the negative electrode plate NEP in the Y direction, and are formed in an uncoated portion of the negative electrode active material NAS. That is, the negative electrode current collecting tab NTAB is exposed from the negative electrode active material NAS.

Next, the structure of the electrode winding body WRF (see FIG. 4) constituting the lithium ion battery will be described with reference to FIGS.

As shown in FIG. 3, the electrode winding body WRF (see FIG. 4) is a laminate in which a positive electrode sheet PEL, a separator SP1, a negative electrode sheet NEL, and a separator SP2 are sequentially stacked, as shown in FIG. It is formed by winding. The length of the laminate in the X direction is, for example, several tens of centimeters to several meters. At this time, the slit part ST of the separator SP1 is opened between the positive electrode sheet PEL and the negative electrode sheet NEL. Further, the X direction and the Y direction are directions along the surface of the separator SP1 or SP2 facing the positive electrode sheet PEL or the negative electrode sheet NEL.

The separator SP1 and the separator SP2 shown in FIG. 3 are sheets made of an insulating material for insulating the positive electrode sheet PEL and the negative electrode sheet NEL. Specifically, each of the separators SP1 and SP2 is a sheet formed by stretching a resin film. The positive electrode current collecting tab PTAB formed on one side in the short direction of the positive electrode sheet PEL and the negative electrode current collecting tab NTAB formed on one side in the short direction of the negative electrode sheet NEL are arranged on the opposite sides in the Y direction. Has been.

In FIG. 3, the separator SP1 is enlarged and shown in the lower part of the figure. The separator SP2 has the same structure as the separator SP1. On the surface of the foil-shaped separator SP1, a plurality of slit portions ST are formed side by side in the Y direction. Each of the plurality of slit portions ST reaches from the surface of the separator SP1 to the back surface opposite to the surface. That is, the slit part ST penetrates the separator SP1 in the thickness direction of the separator SP1. Each slit part ST is a groove extending in the longitudinal direction of the separator SP1. The shape of the opening of the slit part ST in plan view is a rectangle. However, the shape of the opening of the slit part ST in plan view may be a polygon such as a trapezoid or a hexagon, or an ellipse.

The extending direction of the slit part ST, that is, the length L1 of each slit part ST in the X direction has a size equal to or larger than the respective average particle diameters of the positive electrode active material PAS and the negative electrode active material NAS, and in the X direction. It has a size smaller than the length of the separator SP1. Further, the width W1 of each slit portion ST in the Y direction is less than the average particle diameter of the positive electrode active material PAS and the negative electrode active material NAS. For example, the width W1 is 9 μm. A width W2 between adjacent slit portions ST in the Y direction is, for example, about 1 cm.

Since each of the separators SP1 and SP2 is a sheet formed by stretching a resin film, the resin film has a three-dimensional network structure. In addition to the slit portion ST, the resin film has a width larger than the width W1. A large number of small pores (not shown) are opened. The pore diameter is several tens to several hundreds nm. That is, the average diameter of the pores is less than the average particle diameter of each of the positive electrode active material PAS and the negative electrode active material NAS. As the material of the resin film, for example, polyolefin resin, polyester, polyimide, polyamide, cellulose, or the like can be used.

As shown in FIG. 4, the electrode winding body WRF is obtained by winding a laminated sheet (laminated body) in which a positive electrode sheet PEL, a separator SP1, a negative electrode sheet NEL, and a separator SP2 are superposed on an axis CR. Is formed. When the electrode winding body WRF is viewed from above in the extending direction of the axis CR, the positive electrode sheet PEL, the separator SP1, the negative electrode sheet NEL, and the separator SP2 are wound in a spiral shape around the axis CR. That is, the slit portion ST formed in the electrode winding body WRF extends in a spiral shape on the surface along the direction orthogonal to the extending direction of the shaft core CR.

Next, FIG. 5 shows an overhead view of the lithium ion battery LB of the present embodiment. In FIG. 5, the electrode winding body WRF and the like in the outer can CS are shown through the outer can CS and the cap CP, which are containers constituting the lithium ion battery LB.

As shown in FIG. 5, the lithium ion battery LB has an outer can CS and a cap CP that seals the upper portion of the outer can CS. An electrode winding body WRF is inserted into the outer can CS. Furthermore, the electrolyte EL is injected (filled) into the outer can CS so that the entire electrode winding body WRF is immersed therein.

A positive electrode current collection ring PR is provided at one end in a direction (Y direction) along the central axis of the cylindrical electrode winding body WRF. That is, the positive electrode current collection ring PR is disposed at one end in the extending direction of the shaft core CR (see FIG. 4). A plurality of positive current collecting tabs PTAB protruding from the positive electrode sheet PEL (see FIG. 4) constituting the electrode winding body WRF are connected to the positive current collecting ring PR. That is, the positive electrode current collection ring PR is electrically connected to the positive electrode sheet PEL (see FIG. 4) via the positive electrode current collection tab PTAB, and is not connected to the negative electrode sheet NEL.

Similarly, the negative electrode current collector ring NR disposed at the other end in the Y direction of the electrode winding body WRF is electrically connected to the negative electrode sheet NEL (see FIG. 4) via a plurality of negative electrode current collector tabs NTAB. It is connected to the.

The side wall of the cylindrical outer can CS is partially recessed to form a groove DT. The groove DT is formed along the side wall of the outer can CS so as to make one round around the central axis of the cylindrical outer can CS. The groove DT is provided to fix the electrode winding body WRF inserted in the outer can CS so as not to move in the vertical direction. The lithium ion battery LB of the present embodiment has a structure as described above.

Next, the operation of the lithium ion battery of this embodiment will be described with reference to FIG. As shown in FIG. 6, the lithium ion battery is a kind of non-aqueous electrolyte secondary battery, and is a secondary battery in which lithium ions in the electrolyte are responsible for electrical conduction. A lithium metal oxide is used for the positive electrode active material PAS, which is the amount of the positive electrode material, and a carbon material such as graphite is used for the negative electrode active material NAS, which is the negative electrode material. In addition, for example, an organic solvent such as ethylene carbonate and a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ) are used for the electrolyte EL made of an electrolyte. The electrolyte EL is a liquid filled in order to cause a charge / discharge reaction between the positive electrode PE and the negative electrode NE when a voltage is applied to the positive electrode PE or the negative electrode NE.

In the battery, lithium ions exit from the positive electrode PE and enter the negative electrode NE during charging, and conversely during discharge, the lithium ions exit from the negative electrode NE and enter the positive electrode PE. An Al foil made of Al (aluminum) is used for the positive electrode plate PEP that is the current collector foil of the positive electrode PE, and a Cu foil made of Cu (copper) is used for the negative electrode plate NEP that is the current collector foil of the negative electrode NE. It has been. At the time of charging or discharging, the lithium ion battery passes through the slit portion ST opened in the separator SP between the positive electrode PE and the negative electrode NE.

Next, the effect of the lithium ion battery of this embodiment will be described using a lithium ion battery of a comparative example. In the lithium ion battery of the comparative example used for the description here, the separator that separates the positive electrode and the negative electrode is made of a resin film, and the slit portion ST as shown in FIG. 3 is not formed in the separator.

Here, since the separator of the comparative example is a sheet formed by stretching a resin film, the resin film has a three-dimensional network structure, and a lot of very small pores are opened in the resin film. The pore diameter of the pores is several tens to several hundreds nm and is very small. Since the resin film has a three-dimensional network structure, the pores do not penetrate linearly from the front surface to the back surface of the separator. When charging / discharging in the lithium ion battery of such a comparative example, lithium ions move between the electrodes through the pores.

At this time, the lithium ion battery cannot move linearly in the separator, but moves while meandering in the maze-like pores in the resin film having a three-dimensional network structure. For this reason, there is a problem that the internal resistance of the lithium ion battery increases due to the fact that the linear movement of lithium ions is hindered. As described above, when the movement path between the electrodes of lithium ions is only the pores formed in the gaps of the three-dimensional network structure of the separator, the three-dimensional network structure of the separator is changed when lithium ions move. Since it becomes an obstacle, it is disadvantageous in terms of diffusing lithium ions.

In addition, since the pore diameter is very small as described above, the area in which lithium ions can move between the electrodes is small, which also causes the internal resistance of the lithium ion battery to increase.

In order to solve these problems, it is conceivable to process the separator and provide a hole that penetrates the separator in the thickness direction of the separator. The larger the diameter of the hole, the larger the area in which lithium ions can move between the electrodes. In addition, by providing the hole portion, lithium ions can move linearly without being obstructed by an obstacle. Therefore, the internal resistance of the lithium ion battery can be reduced.

Here, the positive electrode or negative electrode active material of the lithium ion battery is fixed by a binder and is in close contact with an electrode plate such as a positive electrode plate or a negative electrode plate. In some cases, particles of the material may fall off the electrode plate.

Therefore, when the separator is processed to form a hole that penetrates the separator, the active material particles peeled off as described above when the diameter of the hole is equal to or larger than the average diameter of the active material particles. May accumulate between the electrodes, causing a short circuit between the positive electrode and the negative electrode. On the other hand, by making the average diameter of the holes formed by processing the separator smaller than the average diameter of the active material, it is possible to prevent the active material from passing through the holes of the separator. Thereby, it is possible to prevent the occurrence of a short circuit between the electrodes due to the dropping of the active material. In this case, the shape of the opening of the hole of the separator is considered to be, for example, a circle.

However, when the average diameter of the pores of the separator is smaller than the average diameter of the active material, the area where lithium ions can move between the electrodes is small, so that the internal resistance of the lithium ion battery can be effectively reduced. Have difficulty.

Therefore, in the present embodiment, as shown in FIG. 3, the separator SP1 and the separator SP2 are provided with slit portions ST extending in one direction. The size of the width W1 in the short direction of the slit part ST is less than the average particle diameter of a plurality of particles constituting the positive electrode active material PAS and the negative electrode active material NAS. Therefore, it is possible to prevent the particles of the positive electrode active material PAS or the negative electrode active material NAS, which have been peeled off, from passing through the slit portions ST opened in the separators SP1 and SP2, and therefore, between the electrodes due to the loss of the active material. The occurrence of a short circuit can be prevented. Thereby, the reliability of a lithium ion battery can be improved and the lifetime of a lithium ion battery can be extended.

Also, the average diameter of the slit portion ST is very large compared to the diameter of the pores formed in the three-dimensional network structure constituting the separators SP1 and SP2. Moreover, the size of the length L1 of the slit part ST is equal to or larger than the average particle diameter of a plurality of particles constituting the positive electrode active material PAS and the negative electrode active material NAS. That is, the average diameter of the slit part ST is not less than the average particle diameter of the plurality of particles constituting the positive electrode active material PAS and the negative electrode active material NAS. Therefore, compared with the case where the average diameter of the hole part formed in the separator is smaller than the average diameter of an active material, the area which can move a lithium ion between electrodes can be expanded significantly.

Further, the slit portion ST linearly penetrates from the front surface to the back surface of each of the separators SP1 and SP2 in the thickness direction of the separators SP1 and SP2. Therefore, since lithium ions can move linearly between the electrodes, the internal resistance of the lithium ion battery can be greatly reduced. Therefore, the performance of the lithium ion battery can be improved.

The separators SP1 and SP2 are made of a resin film having a three-dimensional network structure, and have pores in the gaps of the network structure. For this reason, when charging / discharging the lithium ion battery, lithium ions move between the electrodes through the pores as well as through the slit portions ST. For this reason, the internal resistance of a lithium ion battery can be reduced compared with the case where the slit part ST is provided in the film which does not have a three-dimensional network structure. Therefore, the performance of the lithium ion battery can be improved.

As described above, according to the present embodiment, the above-described slit portion is provided in the separator to improve the diffusibility of lithium ions in the separator, thereby suppressing a short circuit due to the dropping of the active material. On the other hand, it is possible to realize a lithium ion battery that can reduce the internal resistance of the battery and improve the output performance of the battery.

Hereinafter, a method of manufacturing the lithium ion battery according to the present embodiment will be described with reference to FIGS. 1 to 4 and FIGS. 7 to 11. FIG. 7 is a bird's-eye view illustrating the method for manufacturing the lithium ion battery of the present embodiment. 8 to 11 are schematic diagrams for explaining a method of manufacturing the lithium ion battery according to the present embodiment.

First, as shown in FIG. 1, a positive electrode sheet PEL constituting the lithium ion battery of the present embodiment is formed. Here, for example, a positive electrode active material PAS made of lithium cobalt oxide, carbon as a conductive additive, and a binder (binder) are mixed. A slurry is prepared from a solution obtained by dissolving the mixture thus formed in N-methylpyrrolidone (NMP), and the slurry is applied to the positive electrode plate PEP and dried, so that the electrode material film PEF containing the positive electrode active material PAS is formed. Form. Thereby, a positive electrode sheet PEL composed of the electrode material film PEF and the positive electrode plate PEP is formed.

The electrode material film PEF is in contact with the positive electrode plate PEP so as to cover each of the surface of the positive electrode plate PEP and the back surface opposite to the front surface. The binder (binder) with the positive electrode plate PEP is made of, for example, polyvinylidene fluoride. The positive electrode active material PAS is composed of a plurality of particles, and the average particle size of these particles is, for example, 10 μm.

The positive electrode sheet PEL formed as described above is pressurized to increase the density of the positive electrode active material PAS applied to the positive electrode plate PEP and smooth the surface. Moreover, after application | coating and smoothing of the said slurry, the positive electrode plate PEP of the uncoated part of positive electrode active material PAS is cut-processed, and several positive electrode current collection tab PTAB which has a rectangular shape is formed.

Moreover, as shown in FIG. 2, the negative electrode sheet NEL which comprises the lithium ion battery of this Embodiment is formed. Here, for example, a negative electrode active material NAS made of a carbon material (carbon material), carbon as a conductive additive, and a binder (binder) are mixed. A slurry is prepared from a solution in which the mixture thus formed is dissolved in N-methylpyrrolidone (NMP), and the slurry is applied to the negative electrode plate NEP and dried, whereby the electrode material film NEF containing the negative electrode active material NAS is formed. Form. Thereby, a negative electrode sheet NEL composed of the electrode material film NEF and the negative electrode plate NEP is formed.

The electrode material film NEF is in contact with the negative electrode plate NEP so as to cover each of the surface of the negative electrode plate NEP and the back surface opposite to the surface. The binder (binder) with the negative electrode plate NEP is made of, for example, polyvinylidene fluoride. The negative electrode active material NAS is composed of a plurality of particles, and the average particle size of these particles is, for example, 10 μm.

The negative electrode sheet NEL formed as described above is pressurized to increase the density of the negative electrode active material NAS applied to the negative electrode plate NEP and to smooth the surface. Moreover, after application | coating and smoothing of the said slurry, the positive electrode plate PEP of the uncoated part of negative electrode active material NAS is cut-processed, and the some negative electrode current collection tab NTAB which has a rectangular shape is formed.

Next, as shown in FIGS. 3, 4 and 7, the positive electrode sheet PEL and the negative electrode sheet NEL formed as described above are prepared, and further, separators SP1 and SP2 are prepared. Thereafter, an electrode winding body constituting a lithium ion battery is formed by winding the sheet NEL positive electrode sheet, the separator, and the negative electrode sheet NEL.

That is, as shown in FIG. 3, the electrode winding body WRF (see FIG. 4) is formed by sequentially superposing the positive electrode sheet PEL, the separator SP1, the negative electrode sheet NEL, and the separator SP2, and this laminated sheet is formed as shown in FIG. It is formed by winding. Separator SP1 and separator SP2 are used to insulate positive electrode sheet PEL and negative electrode sheet NEL. As a material for the separators SP1 and SP2, for example, a resin film containing polyolefin resin, polyester, polyimide, polyamide, cellulose, or the like can be used.

At this time, the positive electrode current collecting tab PTAB formed on the positive electrode sheet PEL and the negative electrode current collecting tab NTAB formed on the negative electrode sheet NEL are arranged on the opposite sides in the Y direction. Further, before winding as described above, a plurality of slit portions ST are formed in each of the separator SP1 and the separator SP2 as described later with reference to FIG.

In each of the separator SP1 and the separator SP2, a plurality of slit portions ST are arranged in the short direction (Y direction) of the separator SP1 and the separator SP2. Further, the slit portion ST penetrates from the front surface to the back surface of the separator SP1 and the separator SP2. The width W1 in the Y direction of the slit part ST is less than the average particle diameter of the positive electrode active material PAS and the negative electrode active material NAS, and is 9 μm, for example. The length L1 in the longitudinal direction (X direction) of the slit part ST is not less than the average particle diameter of the positive electrode active material PAS and the negative electrode active material NAS.

As shown in FIG. 4, the electrode winding body WRF is formed by winding the positive electrode sheet PEL, the separator SP1, the negative electrode sheet NEL, and the separator SP2 around the shaft core CR. Specifically, as shown in FIG. 7, the positive electrode sheet PEL from the positive electrode roll PELR, the negative electrode sheet NEL from the negative electrode roll NELR, and the separator SP1 and the separator SP2 from the separator roll SPR are respectively rolled out, and these four sheets are After being stacked while being conveyed via the guide roller GRL, the electrode winding body WRF is formed by winding.

At this time, the separator SP1 and the separator SP2 are conveyed from the separator roll SPR to the slit forming unit STM before being wound. In the slit forming portion STM, for example, a slitter blade SCT1 made of a material such as stainless steel, carbon steel, high-speed steel, cemented carbide, ceramic, sapphire, or diamond is disposed. A plurality of cutting edges are provided on the surface of the slitter blade SCT1 and facing the surfaces of the separators SP1 and SP2 so as to be aligned in the short direction (Y direction) of the separators SP1 and SP2. The width of each cutting edge of the slitter blade SCT1 in the Y direction is less than the average particle diameter of the positive or negative active material particles, and is, for example, 9 μm.

Then, the slitter blade SCT1 is pressed against the respective surfaces of the separator SP1 and the separator SP2 while conveying the separator SP1 and the separator SP2 via the guide roller GRL. Thereby, a plurality of slit portions ST extending along the conveying direction of the separator SP1 and the separator SP2 are formed side by side in the Y direction. In this cutting process, the slitter blade SCT1 may be either rotating or fixed.

As described above, a laminated sheet in which the positive electrode sheet PEL and the negative electrode sheet NEL and the separators SP1 and SP2 in which the slit portions ST are opened can be wound. After winding the laminated sheet from several tens of cm to several m, the laminated sheet is cut with a cutter blade CT. Thereby, the electrode winding body WRF is formed.

Next, as shown in FIG. 8, the positive electrode current collecting tab PTAB protruding from the upper end of the electrode winding body WRF is connected to the positive electrode current collecting ring PR. Similarly, the negative electrode current collecting tab NTAB protruding from the lower end of the electrode winding body WRF is connected to the negative electrode current collecting ring NR. Here, the connection of the positive electrode current collector tab PTAB to the positive electrode current collector ring PR and the connection of the negative electrode current collector tab NTAB to the negative electrode current collector ring NR are performed by, for example, ultrasonic welding.

Next, as shown in FIG. 9, the electrode winding body WRF is inserted into the outer can CS. And as shown in FIG. 10, the exterior can CS is processed and the groove | channel DT is formed. The groove DT is provided to fix the electrode winding body WRF inserted in the outer can CS so as not to move in the vertical direction.

Next, as shown in FIG. 11, electrolyte EL is injected into the exterior can CS into which the electrode winding body WRF is inserted. Thereby, the electrode winding body WRF is immersed in the electrolytic solution EL. Then, the lithium ion battery in this Embodiment can be manufactured by sealing the upper part of the armored can CS with the cap CP.

Hereinafter, effects of the manufacturing method of the lithium ion battery according to the present embodiment will be described.

In the present embodiment, as shown in FIG. 3, the separator SP1 and the separator SP2 are provided with slit portions ST extending in one direction. Since the size of the width W1 in the short direction of the slit part ST is less than the average particle diameter of the plurality of particles constituting the positive electrode active material PAS and the negative electrode active material NAS, a short circuit between the electrodes due to the dropping of the active material Can be prevented. Thereby, the reliability of a lithium ion battery can be improved and the lifetime of a lithium ion battery can be extended.

Moreover, since the average diameter of the slit part ST is not less than the average particle diameter of the plurality of particles constituting the positive electrode active material PAS and the negative electrode active material NAS, the average diameter of the holes formed in the separator is larger than the average diameter of the active material. Compared to a small case, the area in which lithium ions can move between the electrodes can be greatly increased.

Moreover, since the slit portion ST linearly penetrates from the front surface to the back surface of each of the separators SP1 and SP2 in the thickness direction of the separators SP1 and SP2, lithium ions move linearly between the electrodes. Is possible. Therefore, since the internal resistance of the lithium ion battery can be greatly reduced, the performance of the lithium ion battery can be improved.

The separators SP1 and SP2 are made of a resin film having a three-dimensional network structure, and have pores in the gaps of the network structure. For this reason, the internal resistance of a lithium ion battery can be reduced compared with the case where the slit part ST is provided in the film which does not have a three-dimensional network structure. For this reason, the performance of a lithium ion battery can be improved.

Further, in the winding process described with reference to FIG. 7, conveyance and winding are performed while tension is applied to each sheet including the separators SP1 and SP2. For this reason, when the slit part ST is formed as a cut extending in the short direction (Y direction) of the separators SP1 and SP2, when the tension is applied to the separators SP1 and SP2 in the winding step, the separators SP1 and SP2 There is a risk of tearing. Further, even if the separators SP1 and SP2 are not broken, the opening width of the slit portion ST is widened by the tension, so that the active material can pass through the slit portion ST, and it is impossible to prevent a short circuit due to the dropping of the active material. Problems arise.

In contrast, in the present embodiment, the extending direction of the slit portions ST in the separators SP1 and SP2 is matched with the direction in which the separators SP1 and SP2 are pulled in the winding step, that is, the longitudinal direction (X direction). Thereby, it can be avoided that the separators SP1 and SP2 are broken as described above and that the width in the short direction of the slit portion ST is widened and the short-circuit preventing effect cannot be obtained.

Also, it is conceivable that a plurality of holes having an average diameter less than the average diameter of the active material are opened in the separator. In this case, unlike the slitter blade SCT1 shown in FIG. 7, a plurality of microneedles are attached to the surface of the roller, and the roller is pressed against the separator while rotating the roller according to the transport speed of the separator. It is conceivable to open the hole.

However, it is disadvantageous to use many microneedles that are easily broken and expensive from the viewpoint of reducing the manufacturing cost and improving the yield of the product. Furthermore, in order to form a hole using such a microneedle that is easily damaged, it is necessary to delay the separator conveyance speed in order to prevent the microneedle from being loaded. Therefore, there arises a problem that the production efficiency is lowered and the production cost is increased.

In contrast, in the present embodiment, the slitter blade SCT1 is made of a material such as stainless steel, carbon steel, high-speed steel, cemented carbide, ceramic, sapphire, or diamond, and is stronger than microneedles (see FIG. 7). Is used to form the slit portion ST (see FIG. 4). For this reason, it is not necessary to delay the conveying speed of the separators SP1 and SP2, and the possibility of damage to the slitter blade SCT1 is small. Therefore, the manufacturing cost of the lithium ion battery can be reduced.

(Embodiment 2)
In the present embodiment, opening a plurality of slit portions in the extending direction of the separator will be described with reference to FIGS. 12 and 13. FIG. 12 is a schematic view showing a laminated structure of a laminated body constituting the lithium ion battery of the present embodiment. FIG. 13 is an overhead view showing a wound body constituting the lithium ion battery of the present embodiment. The present embodiment is characterized in that a slit portion is formed intermittently (intermittently or discontinuously) in the separator using a slitter blade having an uneven edge.

As shown in FIG. 12, the electrode winding body WRF (see FIG. 13) is formed by winding the positive electrode sheet PEL, the separator SP1, the negative electrode sheet NEL, and the separator SP2 in an overlapping manner. In each of the separators SP1 and SP2, a plurality of slit portions ST extending in the extending direction (X direction) of the separators SP1 and SP2 are arranged side by side in the X direction. In the figure, the shape of each slit portion ST is a rectangle, but the shape may be a polygon such as a trapezoid or a hexagon or an ellipse.

The width W1 in the short direction of the slit part ST is less than the average particle diameter of the positive electrode active material PAS and the negative electrode active material NAS, for example, 9 μm. Further, the length L2 in the longitudinal direction of each slit part ST is equal to or larger than the average particle diameter of the positive electrode active material PAS and the negative electrode active material NAS, and is, for example, 5 cm. Moreover, the width W3 between the slit parts ST adjacent in the X direction is, for example, 1 cm. Further, a width W2 between the slit portions ST adjacent in the Y direction is, for example, 1 cm.

As shown in FIG. 13, the electrode wound body WRF is formed by winding the positive electrode sheet PEL, the separator SP1, the negative electrode sheet NEL, and the separator SP2 around the shaft core CR in an overlapped state. . The structure of the lithium ion battery of the present embodiment is the same as that of the first embodiment except for the aspect of the slit part ST.

As described above, the present embodiment is different from the first embodiment in that a plurality of slit portions ST extending in the X direction are arranged in the X direction in each of the separators SP1 and SP2. . Even if the slit portions ST are intermittently arranged in this way, the same effect as in the first embodiment can be obtained. Moreover, since the slit part ST is intermittently formed in each separator SP1, SP2, the mechanical strength in the longitudinal direction of the separators SP1, SP2 can be improved. Thereby, the reliability of a lithium ion battery can be improved.

Hereinafter, the manufacturing process of the lithium ion battery according to the present embodiment will be described with reference to FIGS. FIG. 14 is a schematic diagram showing a method for manufacturing a lithium ion battery according to an embodiment of the present invention. The manufacturing process of the lithium ion battery of the present embodiment is the same as the manufacturing process described in the first embodiment, except that the slitter blade SCT2 (see FIG. 14) is used to form the slit portion. That is, as shown in FIG. 13, the electrode winding body WRF is formed by winding the positive electrode sheet PEL, the separator SP1, the negative electrode sheet NEL, and the separator SP2 on the axis CR in a state where they are sequentially stacked.

Specifically, as shown in FIG. 14, a positive electrode sheet PEL from the positive electrode roll PELR, a negative electrode sheet NEL from the negative electrode roll NELR, a separator SP1 from the separator roll SPR, and a separator SP2 from the separator roll SPR, respectively, The electrode winding body WRF is formed by winding in an overlapping manner.

At this time, each of the separators SP1 and SP2 is conveyed from the separator roll SPR to the slit forming portion STM before being wound. In the slit forming part STM, for example, a slitter blade SCT2 made of a material such as stainless steel, carbon steel, high-speed steel, cemented carbide, ceramic, sapphire or diamond is disposed. The slitter blade SCT2 rotates corresponding to the transport speed of the separators SP1 and SP2 transported into the slit forming part STM. The width of a plurality of cutting edges attached to the surface of the slitter blade SCT2 and the width in the direction along the rotation axis of the slitter blade SCT2 is less than the average particle diameter of the positive or negative active material particles. The width of the cutting edge in the same direction is, for example, 9 μm.

Since the surface of the slitter blade SCT2 has a plurality of cutting edges arranged in the rotation direction of the slitter blade SCT2, the surface of the slitter blade SCT2 including the plurality of cutting edges is uneven.

In the slit forming part STM, the slitter blade is pressed against each of the separators SP1 and SP2 conveyed via the guide roller GRL. Thereby, slit part ST extended along the conveyance direction of separator SP1, SP2 is formed in each of separator SP1, SP2 intermittently (intermittently).

In addition, since the process after forming the electrode winding body WRF as described above is substantially the same as that described in the first embodiment, the description thereof is omitted.

If the manufacturing method of the lithium ion battery of the present embodiment is used, the slit portions ST can be intermittently formed along the longitudinal direction of the separators SP1 and SP2. Thereby, the same effect as the first embodiment can be obtained.

Furthermore, the mechanical strength in the longitudinal direction of the separator can be improved by intermittently arranging the slit portions ST in the X direction. Therefore, in the winding process described with reference to FIG. 14, even when tension is applied in the transport direction, the transport speed can be increased and productivity can be improved.

As mentioned above, the invention made by the present inventors has been specifically described based on the embodiment. However, the invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. is there.

In the first and second embodiments, the wound type lithium ion battery has been described as an example. However, the technical idea of the present invention is not limited to the wound type lithium ion battery, and includes a positive electrode, a negative electrode, And it can apply widely to an electrical storage device (for example, a battery or a capacitor etc.) provided with the separator which isolate | separates a positive electrode and a negative electrode electrically.

The present invention can be widely used in, for example, a manufacturing industry for manufacturing a battery typified by a lithium ion battery.

The present invention is effective when applied to a battery represented by a lithium ion battery.

NAS Negative electrode active material NEL Negative electrode sheet NEF Electrode material film NEP Negative electrode plate NTAB Negative electrode current collector tab PAS Positive electrode active material PEF Electrode material film PEL Positive electrode sheet PEP Positive electrode plate PTAB Positive electrode current collector tab SP1, SP2 Separator ST Slit part

Claims

A positive electrode;
A negative electrode,
A separator disposed between the positive electrode and the negative electrode and insulating the positive electrode and the negative electrode;
An electrolyte solution that causes a charge / discharge reaction between the positive electrode and the negative electrode;
Have
At least one of the positive electrode or the negative electrode includes a plurality of active material particles,
The separator has a slit portion that is opened between the positive electrode and the negative electrode and extends in a first direction;
The length of the slit portion in the first direction is not less than the average particle diameter of the plurality of active material particles,
The width of the slit portion in the second direction intersecting the first direction is less than the average particle diameter of the plurality of active material particles,
The lithium ion battery, wherein the first direction and the second direction are along a surface of the separator facing the positive electrode or the negative electrode.
The lithium ion battery according to claim 1,
A lithium ion battery in which a plurality of the slit portions are opened side by side in the first direction on the surface of the separator.
The lithium ion battery according to claim 1,
Said 1st direction is a lithium ion battery which is a direction along the longitudinal direction of the said separator.
The lithium ion battery according to claim 1,
A lithium ion battery in which a plurality of the slit portions are opened side by side in the second direction on the surface of the separator.
The lithium ion battery according to claim 1,
The separator has a three-dimensional network structure,
A hole is formed in the gap of the three-dimensional network structure,
The lithium ion battery, wherein an average diameter of the holes is less than an average particle diameter of the plurality of active material particles.
The lithium ion battery according to claim 1,
The separator is a lithium ion battery including a polyolefin resin, polyester, polyimide, polyamide, or cellulose.
The lithium ion battery according to claim 1,
The positive electrode, the separator and the negative electrode are stacked in order to form a laminate,
The said laminated body is a lithium ion battery wound.
A method for producing a lithium ion battery, comprising: a positive electrode; a negative electrode; and a first separator that insulates the positive electrode and the negative electrode.
(A) preparing the positive electrode, the negative electrode and the first separator;
(B) opening a slit portion extending in the first direction in the first separator;
(C) After the step (b), a step of stacking the positive electrode, the first separator, and the negative electrode to form a laminate;
(D) enclosing the laminate and the electrolyte in a container;
Have
At least one of the positive electrode or the negative electrode includes a plurality of active material particles,
The slit portion is opened between the positive electrode and the negative electrode,
The length of the slit portion in the first direction is not less than the average particle diameter of the plurality of active material particles,
The width of the slit portion in the second direction is less than the average particle diameter of the plurality of active material particles,
The method of manufacturing a lithium ion battery, wherein the first direction and the second direction are along a surface of the first separator facing the positive electrode or the negative electrode.
In the manufacturing method of the lithium ion battery according to claim 8,
In the step (a), the positive electrode, the negative electrode, the first separator and the second separator are prepared,
The step (b)
(B1) a step of conveying the positive electrode, the negative electrode, the first separator, and the second separator;
(B2) opening the slit portion by pressing a slitter blade whose blade edge is less than the average particle diameter of the active material particles on the surface of each of the first separator and the second separator to be conveyed;
Have
In the step (c), the positive electrode, the first separator, the negative electrode, and the second separator are sequentially stacked to form the laminate, and the laminate is wound to form a wound body,
In the step (d), a method for manufacturing a lithium ion battery, wherein the wound body and the electrolytic solution are sealed in a container.
In the manufacturing method of the lithium ion battery according to claim 9,
In the step (b2), a plurality of slit portions are opened along the transport direction of the first separator with respect to the first separator, and along the transport direction of the second separator with respect to the second separator. A method for producing a lithium ion battery, wherein a plurality of the slit portions are opened.
In the manufacturing method of the lithium ion battery according to claim 9,
The said slitter blade is a manufacturing method of a lithium ion battery containing stainless steel, carbon steel, high-speed steel, a cemented carbide, a ceramic, a sapphire, or a diamond.