JP2009199962A - Separator-incorporated electrode, its manufacturing method, and power storage device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode structure capable of reducing resistance caused by ion-passing, wherein a separator is incorporated in advance. <P>SOLUTION: An electrode 10 and the separator 20 are incorporated by sticking each other in advance in a separator-incorporated electrode 100. The electrode 10 is incorporated in the separator via an electrode mixing agent layer 10a including an active material so as not to make both parties separate each other. The electrode mixing agent layer 10a is arranged by adhesively bringing into contact with both of a collector 10b forming the electrode 10 and the separator 20. Such the electrode 10 can be used for a lithium-ion battery and a lithium-ion capacitor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrode and separator technology, and is particularly effective when applied to a combination of an electrode and a separator.

  The technology described below has been studied by the present inventors in completing the present invention, and the outline thereof is as follows.

  Power storage devices such as batteries and electric double layer capacitors have electrodes inside as constituent elements. Such an electrode is configured separately from the separator. That is, the electrode and the separator are prepared separately and combined when assembling a power storage device such as a battery. For example, an electrode unit is manufactured by alternately laminating electrodes and separators or winding the electrodes and separators. Further, the power storage device is manufactured by impregnating the electrode and the separator with an electrolytic solution and sealing.

  Ions are present in the electrolytic solution. Due to charging / discharging of the accumulator, ions in the electrolyte retained in the separator are taken into the electrode and discharged from the electrode to the separator. That is, the electrolytic solution retained in the separator is an ion conductive layer.

  However, in the power storage device configured by combining the electrode and the separator by such means, there is a problem that the resistance (internal resistance) to the passing ions between the electrode surface and the separator is large.

  The above-mentioned problem is particularly remarkable in a polymer battery in which a lithium ion conductive polymer is bonded between a positive electrode and a negative electrode as an ion conductive layer. For this reason, various attempts to reduce the internal resistance have been proposed. As one of them, Patent Document 1 describes a configuration in which a binder resin layer provided on a separator and an active material layer provided on a current collector of an electrode are adhered to each other. The active material layer is rolled in a semi-dry state to form a laminate of the current collector and the active material layer. In such a configuration, it is stated that the laminate of the electrode and the separator can be manufactured by heating and evaporating the solvent of the binder resin layer on the separator to which the electrode is adhered.

That is, first, each active material layer of a positive electrode and a negative electrode is apply | coated on a collector, and each electrode is formed by drying an active material after that. In addition, a binder resin solution in which the main component polyvinylidene fluoride is dissolved in a solvent is applied to the separator. Each electrode separately formed as described above is overlaid on the separator. While the separator and the electrode are kept in close contact with each other, the solvent of the binder applied on the separator is evaporated to form a battery laminate. Thereafter, a method for manufacturing a lithium ion secondary battery by impregnating the battery stack with an electrolytic solution is described.
Japanese Patent No. 3225871

  Conventionally, a paint composed of an electrode mixture layer such as an active material is applied on a current collector constituting an electrode with a die coater or a comma coater and dried. The surface of the electrode mixture layer thus obtained had fine irregularities when viewed microscopically, and the adhesion with the separator was not good. The adhesion at the interface between the electrode mixture layer and the separator greatly affects the internal resistance when ions pass through. In addition, the power storage device itself may be short-circuited due to the unevenness on the surface of the electrode mixture layer.

  In order to prevent such a problem, the surface of the electrode mixture layer is smoothed. For example, there is a means for pressing an electrode mixture layer applied wet on a current collector. However, when viewed microscopically, the interface between the electrode mixture layer and the separator is still not sufficiently adhered. That is, a mechanically smooth surface cannot be formed on the surface of the electrode mixture layer and the surface of the separator, respectively, and each fine unevenness inhibits adhesion.

  In addition, providing a separate pressing step for smoothing the surface of the electrode mixture layer and suppressing unevenness leads to an increase in manufacturing cost. Therefore, there has been a demand for the development of a technique that can omit such a pressing process.

  In the configuration of Patent Document 1, the active material is rolled. Moreover, in order to make a separator and an electrode contact | adhere, the binder layer as a contact bonding layer is provided as an essential structure. However, in the present invention, unlike the example described in Patent Document 1, the adhesion between the electrode mixture layer and the separator is not provided without separately providing an adhesive layer and without smoothing the electrode mixture layer. The goal is to improve.

  An object of the present invention is to provide an electrode structure in which separators are combined in advance in order to reduce the internal resistance of ion passage at the interface between the electrode mixture layer and 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 inventions disclosed in the present application, the outline of typical ones will be briefly described as follows. That is, the electrode and the separator were combined so as not to be separated via an electrode mixture layer such as an active material.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  In the present invention, the separator is combined with the electrode mixture layer of the electrode in a wet state in advance. Therefore, the adhesiveness between the electrode mixture layer and the separator can be enhanced as compared with the conventional technique in which each is configured separately and the electrode mixture layer is dried and then combined with the separator.

  Thereby, the internal resistance of ion passage can be reduced at the interface between the electrode mixture layer and the separator.

  In addition, it is possible to reduce the process of combining separate electrodes and separators when assembling the power storage device. Moreover, the press process after apply | coating an electrode compound-material layer to a collector can also be skipped.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing the structure of a separator-integrated electrode according to the present invention. FIG. 2A is a cross-sectional explanatory view for explaining the problems of the conventional configuration. (B) is sectional explanatory drawing explaining the interface state of the electrode compound-material layer of this invention, and a separator. FIGS. 3A and 3B are explanatory views showing a modification of the structure of the separator-integrated electrode. FIG. 4 is an explanatory view schematically showing a configuration of a power storage device using separator-integrated electrodes.

  The electrode 10 according to the present invention has a configuration in which the electrode 10 and the separator 20 are combined in advance. As shown in FIG. 1, the electrode 10 is composed of an electrode mixture layer 10a and a current collector 10b. The electrode 10 and the separator 20 are combined via the electrode mixture layer 10a so as not to be separated. In this way, the separator combined electrode 100 is configured.

  The electrode mixture layer 10a is in close contact with and combined with both the separator 20 and the current collector 10b, for example, by the components of the electrode mixture layer 10a. At least an adhesive layer for joining the electrode mixture layer 10 a and the separator 20 is not provided between the electrode mixture layer 10 a and the separator 20. An adhesive layer having a predetermined thickness is not uniformly provided on the surface of the separator 20.

  In the separator combined electrode 100 of the present invention, for example, a binder contained in the electrode mixture layer 10 a functions to hold the separator 20 together. The electrode mixture layer 10a is dried in contact with the separator 20 in an undried state, and the separator 20 is not peeled off from the electrode mixture layer 10a. Of course, as long as the electrode mixture layer 10a and the separator 20 are not peeled off as described above, the electrode mixture layer 10a does not necessarily include a binder.

  Thus, by combining the electrode 10 and the separator 20, the internal resistance related to the passage of ions between the electrode mixture layer 10 a and the separator 20 can be lowered.

  Even when a treatment such as pressing after applying to the current collector is performed as in the conventional example described above, microscopic irregularities still remain on the surface of the electrode mixture layer. The separator also has microscopic unevenness microscopically. Even when both are combined at the time of assembling the power storage device, a non-bonded portion is generated at the interface between the two, and there is a limit to the reduction of internal resistance related to ion passage. Such a state is schematically shown in FIG.

  In the present invention, the separator is brought into intimate contact with the surface of the wet electrode mixture layer, and dried while maintaining the state. Thereby, the surface of an electrode compound-material layer comes to follow a separator surface, and can make the adhesiveness of both interface stronger.

  That is, in the separator-integrated electrode according to the present invention, as shown in FIG. 2B, the electrode mixture layer is aligned with the separator 20 surface at the interface of the electrode mixture layer 10a in contact with the separator 20 surface. A surface 10a is formed. Thereby, generation | occurrence | production of the non-joining part to the separator 20 surface resulting from the fine surface unevenness | corrugation of the electrode compound-material layer 10a is suppressed.

  Therefore, the internal resistance related to ion passage can be kept low. In other words, the passage resistance at the interface between the electrode mixture layer 10a and the separator 20 can be reduced.

  The resistance value that can be measured with the separator-integrated electrode according to the present invention is the DC internal resistance. In general, the measured DC internal resistance includes the resistance of ions passing through the electrode mixture layer / separator interface, the resistance of ions passing through the separator, the liquid resistance, the charge transfer resistance of the electrode surface, the bulk resistance of the electrode, etc. It is the value as a whole. However, as described above, in the separator-integrated electrode in which only the adhesion between the electrode and the separator is improved, the resistance conditions other than the ion interface passage resistance can be considered to be substantially constant. Therefore, the reduction of the DC internal resistance in the separator combined electrode according to the present invention can be considered to be substantially due to the reduction of the ion interface passage resistance.

  The reduction of the ion passage resistance is greatly influenced by the characteristics of the separator used for the separator-integrated electrode.

  The separator has a gap for ions to pass through. As the characteristics of the separator to be combined, it is preferable to set the degree of ion passage to 5 sec / 100 mL or more when the air permeability is used as an index. Regarding the air permeability, there are some differences in measured values depending on the position of the separator on the ion passage surface. Therefore, it can obtain | require more correctly by dividing | segmenting the ion passage surface of a separator into plurality, and averaging each air permeability measured in the divided | segmented location.

  If the air permeability is less than 5 sec / 100 mL, the liquid can easily pass through, so that the wet electrode mixture layer penetrates the gap of the separator and leads to the opposite electrode, which may cause a short circuit. Therefore, it is necessary to keep the gap formed in the separator below to some extent.

  For example, in the experiment of the present inventor, when the gap through which ions of the separator pass is regarded as a circular through hole, it has been found that the diameter of the through hole may be set to 10 μm or less. When the diameter is larger than 10 μm, the electrode mixture layer passes through the separator to the opposite electrode, which may cause a short circuit.

  The separator combined electrode 100 having such a configuration can be manufactured as follows. For example, the electrode mixture layer 10a in contact with both the electrode 10 and the separator 20 can be manufactured in a step of drying from a wet state.

  That is, the current collector 10b and the separator 20 are attached to the wet electrode mixture layer 10a formed by application of slurry or the like. In a state where the electrode mixture layer 10a is moist, the surface of the electrode mixture layer 10a is formed so as to adapt to the fine unevenness of the surface of the separator 20 attached. With the surface of the electrode mixture layer 10a and the surface of the separator 20 in close contact with each other as described above, the electrode mixture layer 10a is placed in a drying apparatus or the like and maintained while maintaining this state. Thereby, the separator 20 is fixed in a state in which the electrode mixture layer 10a is in close contact with the electrode mixture layer 10a.

  For example, a slurry of the electrode mixture layer 10a is applied to the current collector 10b with a predetermined thickness, and the separator 20 is placed on the electrode mixture layer 10a before the applied electrode mixture layer 10a is dried, and then dried. What is necessary is just to dry with an apparatus.

  Regarding the fixing, as described above, it is considered that the binder component in the electrode mixture layer 10a is involved and the adhesion between the electrode mixture layer 10a and the separator 20 is secured. Such a binder component is originally added in order to provide a connection between the active material and the conductive material. However, the present inventors have found that such a binder can also be used for bonding with a separator. However, as described above, the electrode mixture layer 10a does not necessarily include a binder. The component which exhibits the function as a binder which has adhesiveness with a separator substantially should just be contained.

  As described above, the wet electrode mixture layer 10a may be prepared, for example, as a slurry in a state where the electrode mixture layer 10a can be applied to the current collector 10b or the like with a predetermined layer thickness.

  For example, when the power storage device is a battery, the electrode mixture layer 10a made of an active material, a conductive material, a binder, etc. involved in the electrode reaction is mixed in a slurry with a solvent such as water. There may be a configuration in which no binder is inserted as long as it has a function of a binder.

  On the other hand, when the power storage device is a capacitor using an electric double layer, a substance such as activated carbon that does not participate in redox is used instead of the active material that participates in the redox reaction in the battery. Others are the same as the components used for the electrode mixture layer 10a such as a battery.

  Note that in this specification, a material such as activated carbon that does not participate in the oxidation-reduction reaction provided on the current collector of the electrode used in the capacitor as the power storage device is also defined as an active material within a range that does not cause any particular problem for convenience of explanation. I will call it.

  For example, as shown in FIG. 1, the separator-integrated electrode 100 is configured such that one electrode 10 and one separator 20 are used as a unit, and the two are bonded together with an electrode mixture layer 10 a. The separator-integrated electrode 100 may be a negative electrode, a positive electrode, or any case.

  Alternatively, for example, as illustrated in FIGS. 3A and 3B, the current collectors 10 b and the separators 20 may be alternately stacked with the electrode mixture layer 10 a interposed therebetween. FIG. 3A shows a configuration in which separators 20 are provided at both ends, and a current collector 10b and an electrode mixture layer 10a provided on both surfaces of the current collector 10b are provided between both separators 20.

  Alternatively, for example, as shown in FIG. 3B, both current collectors 11a and 12a of a negative electrode 11 and a positive electrode 12 are provided at both ends, and an electrode mixture layer 11b between the current collectors 11a and 12a, One separator 20 may be provided through 12b.

  3A and 3B show the case where the total number of current collectors and separators is three, the number of current collectors and separators may be three or more.

  As shown in FIG. 4, the separator combined electrode 100 having such a configuration is provided in, for example, a lithium ion battery 200 a or a lithium ion capacitor 200 b as the power storage device 200. In the example shown in FIG. 4, the separator combined electrode 100 having the configuration shown in FIG. 1 used for the negative electrode 11 is used as one unit, and a plurality of units are alternately stacked with the positive electrode 12.

  The negative electrode 11 includes a negative electrode current collector 11a having a through hole 13 and an electrode mixture layer 11b for the negative electrode. A terminal 11c is provided on the negative electrode current collector 11a. Each terminal 11c is connected to form a negative external connection terminal 11d. Similarly, a plurality of positive electrodes 12 are provided corresponding to the plurality of units of the negative electrode 11. The positive electrode 12 includes a positive electrode current collector 12a having a through hole 14 and a positive electrode mixture layer 12b. A terminal 12c is provided on the positive electrode current collector 12a. Each terminal 12c is connected to form a positive external connection terminal 12d.

  In the configuration in which the separator 20 is combined with the negative electrode 11, when the sizes of the negative electrode 11 and the separator 20 are substantially the same, that is, when the edge portions of the two are substantially the same, the size of the positive electrode 12 provided via the separator 20. Is preferably different from the negative electrode 11. For example, as shown in FIG. 5, the outer periphery of the negative electrode 11 is set to be 2 mm or more larger than the outer periphery of the positive electrode 12. This is preferable because both can be prevented from being short-circuited. FIG. 5 schematically shows the sizes of the negative electrode 11 and the positive electrode 12 in comparison.

  When the outer periphery of the negative electrode 11 is less than 2 mm from the outer periphery of the positive electrode 12, both edge portions are close to each other, and there is a possibility that both of them are short-circuited. On the other hand, if the difference between the positive electrode and the negative electrode exceeds 15 mm, the energy density is lowered, which is not preferable. Therefore, for example, the difference between the outer periphery of the negative electrode 11 and the outer periphery of the positive electrode 12 is set to be 15 mm or less. That is, as shown in FIG. 5, the difference in the outer periphery is preferably 2 mm or more and 15 mm or less.

  In addition, the restriction | limiting of the magnitude | size of the said negative electrode and a positive electrode is a case where the negative electrode is united with the separator. However, since the present invention is naturally applicable to the positive electrode, when the positive electrode is combined with the separator, the separator is approximately the same size or larger than the negative electrode, and the outer periphery of the positive electrode is 2 mm or more and 15 mm or less than the negative electrode. Small in range.

  Further, in the lithium ion battery 200 a shown in FIG. 4, a lithium electrode 15 used for doping lithium ions into the negative electrode 11 in advance is provided separately from the negative electrode 11 and the positive electrode 13. As shown in FIG. 4, the lithium electrode 15 is made of, for example, metallic lithium 15a and is provided on the lithium electrode current collector 15b. It arrange | positions facing the negative electrode 11 located in the outermost part of a laminated structure through the separator 20. FIG. The lithium electrode current collector 15b is provided with a lithium electrode terminal. The lithium electrode terminal is connected together with the terminal 11c of the negative electrode 11 and connected to the external connection terminal 11d.

  As shown in FIG. 4, the negative electrode 11, the positive electrode 12, and the lithium electrode 15 constitute a three-pole laminated unit 30. The three-pole laminated unit 30 is accommodated in the outer container 40 of the deeply drawn laminated film container 40a. The laminated film container 40a in which the three-pole laminated unit 30 is stored is filled with an electrolytic solution, and the three-pole laminated unit 30 is impregnated with the electrolytic solution. As shown in FIG. 4, the external connection terminals 11 d and 12 d are brought out from the laminated film container 40 a having such a configuration, and necessary external terminal connection is performed.

  The material configuration of the separator combined electrode 100 is as follows.

  For the electrode mixture layer used in the power storage device 200, a material that can be doped or dedoped with ions such as lithium ions is used as the negative electrode active material. For example, graphite, various carbon materials, polyacene-based substances including PAS, tin oxide, silicon compounds, and the like. Such a negative electrode active material is formed into a powder form, a granular form, a short fiber form, etc., mixed with a binder or the like to be described later to form a slurry, and is applied onto a negative electrode current collector or the like.

  As the positive electrode active material, a material that can be reversibly doped or dedoped with lithium ions or anions is used. For example, activated carbon, conductive polymers, polyacene-based materials including PAS, and the like. When the power storage device is configured as a lithium ion secondary battery, a lithium-containing metal oxide, particularly a lithium-containing transition metal oxide or lithium sulfide is used.

  As the binder, for example, a rubber-based binder such as SBR, a fluorine-containing resin such as polytetrafluoroethylene or polyvinylidene fluoride, or a thermoplastic resin such as polypropylene or polyethylene is used.

  Further, as the conductive material, for example, acetylene black, graphite, metal powder, or the like is used. The conductive material may be used in an appropriate amount as necessary.

  As the current collector, one provided with a through hole penetrating the front and back surfaces of the current collector is used. For example, expanded metal, punch metal, net, foam and the like. The shape and number of the through holes are not particularly limited as long as they do not hinder the movement of ions such as lithium ions. For the negative electrode current collector, for example, stainless steel, copper, nickel or the like is used. For the positive electrode current collector, for example, aluminum, stainless steel, or the like is used.

  A separator having durability without reacting with an electrolytic solution, a negative electrode active material, a positive electrode active material, or the like is used. Any porous body having pores communicating with the front and back surfaces of the separator and having no electrical conductivity may be used so that ions can pass through. As the material, for example, cellulose such as paper, polyethylene, polypropylene, or the like is used.

  The electrolyte is selected from the viewpoint of preventing electrolysis even at a high voltage and allowing lithium ions to exist stably. For example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxysolane, methylene chloride, sulfolane, or the like may be used alone or in an appropriate mixture.

As the electrolyte dissolved in the electrolytic solution, for example, LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiPF ₆ , LIN (C ₂ F ₅ SO ₂ ) ₂ or the like is used.

  Moreover, as an exterior container, the laminated film of aluminum is used, for example. Alternatively, a three-layer laminate film having a nylon film on the outside, an aluminum foil in the center, and a modified polypropylene on the inside is used.

  The configuration according to the present invention described above was verified in detail by the following examples.

Example 1
[Production of Negative Electrode] Furfuryl alcohol, which is a raw material of furan resin charcoal, was held at 60 ° C. for 24 hours to cure the resin, thereby obtaining a black resin. The black resin was placed in an electric furnace, heated to 1200 ° C. in 3 hours in a nitrogen atmosphere, and held at that temperature for 2 hours. After cooling by cooling, the sample taken out was pulverized by a ball mill to obtain non-graphitizable carbon powder (hydrogen atom / carbon atom = 0.008) having D50% (50% volume cumulative diameter) = 5.0 μm.

  86 parts by weight of the sample was sufficiently mixed with 6 parts by weight of acetylene black powder, 5 parts by weight of an acrylic resin binder, 3 parts by weight of carboxymethyl cellulose, and 200 parts by weight of water. This obtained the slurry used as the electrode compound-material layer for negative electrodes.

The obtained slurry was coated on both sides of a copper expanded metal having a thickness of 32 μm (porosity 50%) as a negative electrode current collector. Thereby, the electrode compound material layer for negative electrodes was formed. Before the electrode mixture layer was dried, a cellulose-based separator having a maximum aperture of 1 μm and an air permeability of 10 sec / 100 mL was stacked and dried in a dryer set at 60 ° C. As a result, a separator-integrated negative electrode was obtained. The value (weight per unit area of the negative electrode active material) obtained by dividing the amount of the negative electrode active material contained in the electrode mixture layer by the area of the negative electrode including both the front and back surfaces was 4.0 mg / cm ² . Note that almost all through holes of the current collector were blocked by the electrode mixture layer.

[Production of positive electrode] 85 parts by weight of a commercially available activated carbon powder having a specific surface area of 2000 m ² / g, 5 parts by weight of acetylene black powder, 6 parts by weight of an acrylic resin binder, 4 parts by weight of carboxymethyl cellulose and 200 parts by weight of water, Mix well. This obtained the slurry used as the electrode compound-material layer for positive electrodes.

  A non-aqueous carbon conductive paint was coated on both sides of an aluminum expanded metal having a thickness of 35 μm (porosity 50%) by a spray method and dried. This obtained the positive electrode electrical power collector in which the conductive layer was formed. The total thickness (the sum of the current collector thickness and the conductive layer thickness) was 52 μm.

While pulling the positive electrode current collector in the vertical direction, the slurry as the electrode mixture layer was uniformly coated on both surfaces of the positive electrode current collector with a die coater. This was dried and pressed to obtain a positive electrode having a thickness of 129 μm. The thickness of the electrode mixture layer was 77 μm. Moreover, the value (weight per unit area of the positive electrode active material) obtained by dividing the amount of the positive electrode active material contained in the electrode mixture layer by the area of the positive electrode including both the front and back surfaces was 3.5 mg / cm ² . Note that almost all through holes of the current collector were blocked by the electrode mixture layer.

  [Capacitance Measurement per Unit Weight of Negative Electrode] As a negative electrode for evaluation, the separator-integrated negative electrode was cut into a size of 1.5 cm × 2.0 cm. Further, a polyethylene nonwoven fabric having a thickness of 50 μm was prepared as a separator. Moreover, as a counter electrode of the negative electrode for evaluation, metallic lithium having a size of 1.5 cm × 2.0 cm and a thickness of 200 μm was prepared. A simulation cell was assembled by making the negative electrode for evaluation and metallic lithium face each other via a separator.

Metallic lithium was used as a reference electrode. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ in propylene carbonate at a concentration of 1.2 mol / L was used. The negative electrode active material was charged with 500 mAh / g of lithium ions at a charging current of 1 mA. Thereafter, discharging was performed at a discharge current of 1 mA until the negative electrode potential reached 1.5V. The electrostatic capacity per unit weight of the negative electrode was determined based on the discharge time until a potential change of 0.2 V further occurred from the negative electrode potential one minute after the start of discharge. The capacitance was 4286 F / g.

  [Capacitance Measurement per Unit Weight of Positive Electrode] The positive electrode was cut into a size of 1.5 cm × 2.0 cm as a positive electrode for evaluation. Further, a polyethylene nonwoven fabric having a thickness of 50 μm was prepared as a separator. Moreover, as a counter electrode of the positive electrode for evaluation, metallic lithium having a size of 1.5 cm × 2.0 cm and a thickness of 200 μm was prepared. A simulation cell was assembled by making an evaluation positive electrode and metallic lithium face each other via a separator.

Metallic lithium was used as a reference electrode. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ in propylene carbonate at a concentration of 1.2 mol / L was used. The battery was charged to 3.6 V at a charging current of 1 mA. Thereafter, constant voltage charging was performed. After a total charging time of 1 hour, discharging was performed at a discharge current of 1 mA until the positive electrode potential reached 2.5V. Based on the discharge time until the positive electrode potential reached from 3.5V to 2.5V, the capacitance per unit weight of the positive electrode was determined. The capacitance was 140 F / g.

  [Preparation of Tripolar Laminate Unit] A separator-integrated negative electrode was cut into a size of 6.2 cm × 7.7 cm (excluding the terminal welded portion) with a roll cutter, and 12 negative electrodes were prepared. The positive electrode was cut out with a size of 5.8 cm × 7.3 cm (excluding the terminal welded portion) to prepare 11 positive electrodes. The separator is integrated with the negative electrode, and the edge of the separator and the edge of the negative electrode coincide with each other on the three sides other than the terminal welded portion by cutting out the negative electrode.

  The positive electrode and the negative electrode were alternately laminated so that the terminal welds of the positive electrode current collector and the negative electrode current collector were on opposite sides. At this time, the outer periphery of the positive electrode was arranged to be 2 mm smaller than the outer periphery of the negative electrode.

  In addition, it laminated | stacked so that the outermost part of an electrode might become a negative electrode. The uppermost part and the lowermost part have separators integrated with the negative electrode. Four sides of the laminated positive and negative electrode assemblies were fastened with tape. The terminal welded portions (11 sheets) of the positive electrode current collector were collectively ultrasonically welded to an aluminum positive electrode terminal having a width of 50 mm, a length of 50 mm, and a thickness of 0.2 mm. The terminal welded portions (12 sheets) of the negative electrode current collector were collectively ultrasonically welded to a copper negative electrode terminal having a width of 50 mm, a length of 50 mm, and a thickness of 0.2 mm. Thereby, the electrode lamination unit was constituted.

  A stainless steel net having a thickness of 80 μm was prepared as a lithium electrode current collector. A metal lithium foil was pressure-bonded to a stainless steel mesh to form a lithium electrode. One lithium electrode was placed on top of the electrode stack unit so as to completely face the outermost negative electrode. Thereby, a three-pole laminated unit was obtained. The terminal welding part of the lithium electrode current collector was resistance welded to the negative electrode terminal welding part.

[Preparation of Cell and Impregnation with Electrolytic Solution] Two laminate films deep-drawn to 3.5 mm in accordance with the shape of the three-pole laminated unit were prepared. This laminate film was put together to form a laminate film container. In the meantime, the three-pole laminated unit was installed, and three sides of the laminated film container were heat-sealed to form a bag. As an electrolytic solution, a solution in which LiPF ₆ was dissolved so as to have a concentration of 1 mol / L with respect to propylene carbonate was prepared.

  A funnel was inserted into the remaining side of the laminate film container that was not heat-sealed, and a small amount of electrolyte was injected with a dropper, and vacuum impregnation was repeated to impregnate a total amount of 15 g. Then, the remaining one side was heat-sealed under reduced pressure, and the film type cell was completed. Four film type cells were assembled. In addition, the metallic lithium arrange | positioned in a cell is equivalent to 500 mAh / g per weight of a negative electrode active material.

  [Initial Evaluation of Cell] After impregnating with the electrolytic solution, the cell was allowed to stand for 20 days, and 1 cell out of 4 cells was decomposed. In the decomposed cell, the lithium metal was completely lost. From this, it was judged that the negative electrode active material was pre-doped (pre-doped) with 500 mAh / g lithium ions per unit weight.

  [Evaluation of cell characteristics] The battery was charged at a constant current of 1000 mA until the cell voltage reached 3.8V. After that, constant current-constant voltage charging for applying a constant voltage of 3.8 V was performed for 30 minutes. Next, the battery was discharged at a constant current of 500 mA until the cell voltage was 2.2V. This cycle of 3.8V-2.2V was repeated, and the cell capacity and DC internal resistance in the 10th discharge were evaluated.

  Subsequently, after being left in a thermostatic bath at −20 ° C. for 2 hours, the same cycle of 3.8 V to 2.2 V was repeated 500 times, and the cell capacity was evaluated by returning to room temperature. The results are shown in FIG. 6 together with the capacity retention after 500 cycles at −20 ° C. However, the data is an average of 3 cells.

(Comparative Example 1)
[Production of Negative Electrode] A copper expanded metal having a thickness of 32 μm (porosity 50%) was prepared as a negative electrode current collector. On both surfaces, the slurry of the electrode mixture layer for the negative electrode was uniformly coated with a die coater. This obtained the negative electrode which has a negative electrode compound material layer whose negative electrode active material is 4.0 mg / cm < ² >.

  [Manufacture of Cells] Using the same negative electrode obtained above and the same positive electrode used in Example 1, four cell-type cells were assembled in the same manner as in Example 1. In addition, the same separator as that used in Example 1 was separately disposed between the positive electrode and the negative electrode. Moreover, the metallic lithium arrange | positioned in a cell is equivalent to 500 mAh / g per unit weight of a negative electrode active material.

  [Initial Evaluation of Cell] After being assembled for 20 days, one of the four cells was disassembled, and lithium metal was completely lost. Accordingly, it was determined that the negative electrode active material was previously doped with 500 mAh / g lithium ions per unit weight of the negative electrode active material.

  [Evaluation of cell characteristics] The battery was charged at a constant current of 1000 mA until the cell voltage reached 3.8V. After that, constant current-constant voltage charging for applying a constant voltage of 3.8 V was performed for 30 minutes. Next, the battery was discharged at a constant current of 500 mA until the cell voltage was 2.2V. This cycle of 3.8V-2.2V was repeated, and the cell capacity and DC resistance in the 10th discharge were evaluated.

  Subsequently, after being left in a constant temperature bath at −20 ° C., the same 3.8 V-2.2 V cycle was repeated 500 times, and the cell capacity was evaluated by returning to room temperature. The results are shown in FIG. 6 together with the capacity retention after 500 cycles at −20 ° C. However, the data is an average of 3 cells.

  Since Example 1 and Comparative Example 1 use the same basis weight positive electrode and negative electrode, the initial discharge capacity is the same. However, the capacity retention after 500 cycle tests at −20 ° C. was superior in Example 1. Further, when each cell after 500 cycles at −20 ° C. was disassembled, it was confirmed that some metallic lithium was deposited on the negative electrode surface of Comparative Example 1.

  This is presumably because the negative electrode configured in the separator-integrated type as in Example 1 had a low interface passage resistance because the separator and the negative electrode were in close contact with each other. Accordingly, the actually measured DC internal resistance is lowered.

  However, in the case of the comparative example 1, the electrode composite material layer slurry is directly applied to the expanded metal and dried to once configure the electrode. In the configuration of such an electrode, the surface of the electrode mixture layer is uneven due to the influence of the unevenness of the current collector. For this reason, it is considered that the resistance to ions passing therethrough is high, and the current density varies within the surface of the negative electrode active material. As a result, it was estimated that metallic lithium was deposited on the portion having a high resistance on the negative electrode surface. As a result, it is considered that the capacity retention rate decreased after 500 cycles at -20 ° C.

(Example 2)
[Preparation of Cell] Four film-type cells were assembled in the same manner as in Example 1 except that the negative electrode size was 6.0 cm × 7.5 cm (excluding the terminal welded portion). Note that the outer periphery of the positive electrode is 1 mm smaller than the outer periphery of the negative electrode. Moreover, the metallic lithium arrange | positioned in a cell is equivalent to 500 mAh / g per unit weight of a negative electrode active material.

  [Initial Evaluation of Cell] One cell was disassembled after being left for 20 days after the cell was assembled. Metallic lithium was completely lost. From this, it was judged that the negative electrode active material was previously doped with 500 mAh / g lithium ions per unit weight of the negative electrode active material.

  [Evaluation of cell characteristics] The battery was charged at a constant current of 1000 mA until the cell voltage reached 3.8V. After that, constant current-constant voltage charging for applying a constant voltage of 3.8 V was performed for 30 minutes. Next, the battery was discharged at a constant current of 500 mA until the cell voltage was 2.2V. This cycle of 3.8V-2.2V was repeated, and the cell capacity and DC internal resistance in the 10th discharge were evaluated.

  Subsequently, after being left in a constant temperature bath at −20 ° C., the same 3.8 V-2.2 V cycle was repeated 500 times, and the cell capacity was evaluated by returning to room temperature. The results are shown in FIG. 6 together with the capacity retention after 500 cycles at −20 ° C. However, since one of the three cells is short-circuited, the data is an average of two cells.

  In this example, the difference between the positive electrode outer periphery and the negative electrode outer periphery is 1 mm. For this reason, it is thought that it was short-circuited by dropping of the electrode mixture layer. Therefore, it was confirmed that it is desirable to set the size of the electrode so that the difference between the outer periphery of the positive electrode and the outer periphery of the negative electrode is 2 mm or more.

(Example 3)
[Preparation of Cell] In this example, a cellulose separator having a maximum aperture of 20 μm and an air permeability of 2 sec / 100 mL was used as the separator integrated with the negative electrode. Other than that, 4 film type cells were assembled in the same manner as in Example 1. In addition, the metallic lithium arrange | positioned in a cell is equivalent to 500 mAh / g per unit weight of a negative electrode active material.

  [Initial Evaluation of Cell] After assembling the cell, the cell was disassembled after being left for 20 days. As a result, all of the metallic lithium was completely lost. From this, it was judged that 500 mAh / g lithium ion was previously doped per unit weight of the negative electrode active material.

  [Evaluation of cell characteristics] The battery was charged at a constant current of 1000 mA until the cell voltage reached 3.8V. After that, constant current-constant voltage charging for applying a constant voltage of 3.8 V was performed for 30 minutes. Next, the battery was discharged at a constant current of 500 mA until the cell voltage was 2.2V. This cycle of 3.8V-2.2V was repeated, and the cell capacity and DC resistance in the 10th discharge were evaluated. Subsequently, after being left in a constant temperature bath at −20 ° C., the same 3.8 V-2.2 V cycle was repeated 500 times, and the cell capacity was evaluated by returning to room temperature. The results are shown in FIG. 6 together with the capacity retention after 500 cycles at −20 ° C. However, since one of the three cells is short-circuited, the data is an average of two cells.

  Since the air permeability of the separator integrated with the negative electrode is as small as 2 sec / 100 mL, the interface passage resistance is low. Therefore, the measured DC internal resistance is small and excellent in characteristics. However, one of the three cells was shorted. This is considered that the electrode mixture layer penetrated through the opening of the separator and was short-circuited. Therefore, it was considered that the separator integrated with the electrode needs to have a maximum aperture of 10 μm or less and an air permeability of greater than 2 sec / 100 mL. As a practical range, it was judged that it is desirable that the air permeability is 5 sec / 100 mL or more with a margin.

  The present invention can be effectively used in the field of separator-integrated electrodes of power storage devices such as batteries and capacitors.

It is sectional drawing which shows the electrode structure of the separator united type which concerns on this invention. (A) is sectional explanatory drawing explaining the problem of a conventional structure. (B) is sectional explanatory drawing which showed typically the condition of the interface of the compound-material layer for electrodes of this invention, and a separator. (A), (b) is sectional drawing which shows the modification of the electrode structure of the separator united type which concerns on this invention. It is a section explanatory view showing typically the example of composition of the electrical storage device concerning the present invention. It is explanatory drawing which shows the ratio of the magnitude | size of a positive electrode and a negative electrode typically in contrast. It is explanatory drawing which shows the evaluation result of Example 1, 2, 3 and the comparative example 1 in a table format.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electrode 10a Electrode material layer 10b Current collector 11 Negative electrode 11a Negative electrode current collector 11b Electrode material layer 11c Terminal 11d External connection terminal 12 Positive electrode 12a Positive electrode current collector 12b Electrode material layer 12c Terminal 12d External connection terminal 13 Through hole DESCRIPTION OF SYMBOLS 14 Through-hole 15 Lithium electrode 15a Metal lithium 15b Lithium electrode current collector 20 Separator 30 Tripolar laminated unit 40 Exterior container 40a Laminate film container 100 Separator united electrode 200 Power storage device 200a Lithium ion battery 200b Lithium ion capacitor

Claims (10)

An electrode used in a power storage device,
The electrodes are combined so that the separator does not separate from the electrodes,
A separator-integrated electrode, wherein the gas permeability of the electrode combined with the separator is 5 sec / 100 mL or more. The separator-integrated electrode according to claim 1,
A separator-integrated electrode, wherein the electrode is closely bonded to the electrode so that the separator is not separated. The separator-integrated electrode according to claim 1 or 2,
A separator-integrated electrode characterized in that the electrode is bonded to an electrode mixture layer such as an active material layer for an electrode on a current collector constituting the electrode. In the separator coalescence type electrode according to any one of claims 1 to 3,
A separator-integrated electrode, wherein the current collector is provided with a through hole. In the separator coalescence type electrode according to any one of claims 1 to 4,
The separator is a combined separator type electrode having a diameter of a through-hole of 10 μm or less and a size larger than the size of the electrode. A method for producing a separator-integrated electrode that is combined so as not to separate the separator,
A step of drying an electrode mixture layer such as an active material layer for a wet electrode provided in contact with both the separator and the electrode is provided between the separator and the electrode. Manufacturing method of separator combined electrode. A method for producing a separator-integrated electrode that is combined so as not to separate the separator,
A method for producing a separator-integrated electrode, comprising a step of combining an electrode mixture layer such as an active material layer for a wet electrode with the separator. In the manufacturing method of the separator united electrode according to claim 6 or 7,
The electrode composite material layer is provided in contact with a current collector provided with a through-hole constituting the electrode, and a method for producing a separator combined electrode.   The separator-integrated electrode according to any one of claims 1 to 5, or the separator-integrated electrode manufactured by the method for manufacturing a separator-integrated electrode according to any one of claims 6 to 8. A power storage device including the power storage device. The power storage device according to claim 9, wherein
The power storage device is a lithium ion battery or a lithium ion capacitor.

Images