JP2006164783A - Electrode, battery, and their manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for improving the ion conductivity of a solid electrolyte, and to improve characteristics of a secondary battery. <P>SOLUTION: An electrode has an active material layer 40 which includes an active material 10, a solid electrolyte 30, and a solid electrolyte particle 20 higher in ion conductivity than the solid electrolyte 30; and a collector 50 laminated in conjunction with the active material layer 40. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrode and a battery. The electrode and battery of this invention are used suitably for the secondary battery as a motor drive power supply, such as an electric vehicle.

  In recent years, there has been a strong demand for the introduction of electric vehicles (EV), hybrid vehicles (HEV), and fuel cell vehicles (FCV) against the background of the increasing environmental protection movement, and these motor drive batteries have been developed. Yes. As these motor drive batteries, the use of rechargeable secondary batteries has been studied.

  As a secondary battery, a lithium secondary battery whose electrolyte is a liquid has been widely used. Usually, a non-aqueous electrolyte containing a lithium salt is used as the electrolyte. However, problems such as the occurrence of liquid junctions and degradation of battery performance due to decomposition of the electrolytic solution may occur during long-term use or in a high-temperature environment. Therefore, a solid electrolyte secondary battery in which a solid electrolyte membrane made of a polymer is disposed between electrodes has been proposed as a power source for automobiles. The solid electrolyte used is divided into a gel polymer electrolyte and an intrinsic polymer electrolyte. The gel polymer electrolyte is an electrolyte that has been gelated by the incorporation of a plasticizer. An intrinsic polymer electrolyte refers to an electrolyte that is substantially solid.

A solid electrolyte secondary battery usually has a unit structure in which a current collector, a positive electrode, a solid electrolyte membrane, a negative electrode, and a current collector are stacked. As described above, the solid electrolyte membrane is composed of a solid electrolyte. However, since the solid electrolyte has lower ion conductivity than the liquid electrolyte, various means for improving the battery characteristics by improving the ion conductivity have been developed. ing. For example, a technique in which an ion conductive solid electrolyte is contained in a positive electrode and a negative electrode in order to ensure ion conductivity has been proposed (see Patent Document 1).
JP 2004-71405 A

  However, the ionic conductivity of a solid electrolyte is currently lower than that of a liquid electrolyte, and development of a technique for further improving the ionic conductivity is required in order to improve battery characteristics.

  Accordingly, an object of the present invention is to provide a means for improving the ionic conductivity of a solid electrolyte and to improve battery characteristics.

  An electrode having an active material, a solid electrolyte, an active material layer including solid electrolyte particles having higher ion conductivity than the solid electrolyte, and a current collector stacked on the active material layer.

  Since the electrode of the present invention includes solid electrolyte particles having high ion conductivity, it contributes to the realization of a battery having high ion conductivity and excellent battery characteristics.

  In the electrode of the present invention, a solid electrolyte is present in the electrode, and solid electrolyte particles having better ion conductivity than the solid electrolyte are dispersed. FIG. 1 is a schematic sectional view of an electrode of the present invention. The electrode has a structure in which an active material layer 40 and a current collector 50 are stacked. The active material layer 40 includes an active material 10, solid electrolyte particles 20, and a solid electrolyte 30. Although the ionic conductivity in the electrode is improved by the solid electrolyte 30 having ionic conductivity, the ionic conductivity of the solid polymer is lower than that of the liquid electrolyte. In the present invention, by further including solid electrolyte particles 20 having higher ion conductivity than the solid electrolyte 30, ion conductivity in the electrode is increased, and battery characteristics are improved.

  About the dispersion | distribution aspect of a solid electrolyte particle, Preferably, there exists a density | concentration distribution in which the density | concentration of the solid electrolyte particle in the site | part close | similar to a collector is low in an active material layer. FIG. 2 is a schematic cross-sectional view of an electrode having a concentration distribution of solid electrolyte particles. In the battery of FIG. 2, in the active material layer 40, there is a concentration distribution in which the concentration of the solid electrolyte particles 20 decreases as the current collector 50 is approached from the side where the polymer electrolyte membrane is disposed. By providing a concentration distribution in which the concentration of the solid electrolyte particles 20 becomes higher as the solid polymer particle 20 is closer to the solid polymer membrane side, it is possible to improve battery characteristics.

  The mechanism by which the battery characteristics are improved by the concentration distribution is not clear, but it is presumed that the utilization efficiency of the active material is improved by the concentration distribution. For example, in a lithium polymer secondary battery, lithium ions enter from a solid electrolyte present on the side opposite to the current collector. At this time, if the ion conductivity in the electrode is low, it is difficult for lithium ions to penetrate into the electrode, and the utilization efficiency of the active material in the vicinity of the current collector decreases. This tendency seems to be particularly noticeable when generating or charging at high output. In the present invention, since the ion conductivity on the side of the solid electrolyte membrane into which lithium ions enter is high, lithium ions are likely to enter the inside of the electrode, and the use efficiency of the active material is expected to improve. However, the above mechanism is merely speculation, and the technical scope of the present invention is not limited to the electrode having this mechanism.

  Note that the concentration distribution may be gradually changed as shown in FIG. 2, or a structure in which layers having different concentrations are stacked may be employed. Preferably, there is no interface where the concentration of the solid electrolyte particles changes, and the concentration gradually changes. Interfaces with different compositions may become an obstacle to ionic conduction, and ionic conductivity can be increased by not having a clear interface.

  Next, the constituent materials of the electrode of the present invention will be described in detail.

The active material 10 is a positive electrode active material if the electrode is a positive electrode, and a negative electrode active material if the electrode is a negative electrode. What is necessary is just to select a positive electrode active material and a negative electrode active material suitably according to the kind of battery. For example, if the battery is the lithium secondary battery, as a cathode active material, Li · Co-based composite oxide such as LiCoO _2, Li · Ni-based composite oxide such as LiNiO _2, spinel LiMn ₂ O ₄ Li · Mn based composite oxide, Li · Fe based composite oxide such as LiFeO _2, and the like. In addition, transition metal and lithium phosphate compounds and sulfate compounds such as LiFePO ₄ ; transition metal oxides and sulfides such as V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , and MoO ₃ ; PbO ₂ , AgO, NiOOH etc. are mentioned. In some cases, two or more positive electrode active materials may be used in combination.

  The particle size of the positive electrode active material may be smaller than the particle size generally used in a solution type battery in which the electrolyte is not solid in order to reduce electrode resistance. Specifically, the average particle diameter of the positive electrode active material is preferably 0.1 to 5 μm.

  Examples of the negative electrode active material include a crystalline carbon material and an amorphous carbon material. Specific examples include natural graphite, artificial graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, and hard carbon. In some cases, two or more negative electrode active materials may be used in combination. The particle size of the active material is not particularly limited, but is usually about 0.1 to 5 μm.

The solid electrolyte particles 20 are not particularly limited as long as the solid electrolyte particles 20 are particles that are more excellent in ion conductivity than the solid electrolyte 30. Examples of the particles having excellent ion conductivity include Li _3.25 Ge _0.25 P _0.75 S ₄ , LiI—Li ₂ S—P ₂ S ₅ , Li ₂ S—GeS ₂ —P ₂ S ₅ , Li etc. _{2 O-B 2 O 3 -P} 2 O 5, LiO-V 2 O 5 -SiO 2, Li 2 O-TiO 2 -P 2 O 5 and the like. The particle size of the solid electrolyte particles is not particularly limited, but is usually about 0.01 to 10 μm. The ionic conductivity of the solid electrolyte particles 20 and the ionic conductivity of the solid electrolyte 30 can be evaluated using a bipolar cell or the like.

The solid electrolyte 30 is not particularly limited as long as it is a material having ion conductivity. Examples of the polymer having ion conductivity include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. Such polyalkylene oxide polymers can well dissolve lithium salts such as LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ C ₂ F ₅ ) ₂ . Moreover, excellent mechanical strength is exhibited by forming a crosslinked structure. The solid electrolyte is included in at least one of the positive electrode active material layer and the negative electrode active material layer, but is preferably included in both in order to further improve battery characteristics. Preferably, the solid electrolyte 30 has a function as a binder for holding the active material 10 and the solid electrolyte particles 20. By allowing the solid electrolyte to exist between the active materials, ion conduction in the active material layer becomes smooth, and the output of the battery can be improved.

  As an effect obtained by using the solid electrolyte 30 and the solid electrolyte particles 20 in combination, the solid electrolyte 30 can be thermally polymerized or photopolymerized on the electrode. That is, conventionally, a sheet-like solid electrolyte has been proposed, but the conductivity is lowered at the mating surface, that is, at the interface with the positive electrode and the negative electrode. This problem can be somewhat improved by improving the adhesion between the positive electrode and the negative electrode using a method of curing the solid electrolyte on the electrode. From this viewpoint, the solid electrolyte 30 is preferably a polymer that can be formed by thermal polymerization or photopolymerization. Since the solid electrolyte particles 20 are vitrified at a very high temperature such as 500 ° C., it is difficult to vitrify the electrodes on the electrode. Therefore, it is preferable to use an inorganic material vitrified in advance as the solid electrolyte particles 20. By adopting a method of forming a solid electrolyte film on the electrode, it is possible to obtain both effects of improving the ionic conductivity of the solid electrolyte particles 20 and improving the ionic conductivity by eliminating the interface of the solid electrolyte 30.

The active material layer preferably contains a lithium salt. As the lithium salt, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or a mixture thereof can be used. However, it is not necessarily limited to these.

  The active material layer preferably further contains a conductive agent such as acetylene black, carbon black, and graphite. By including a conductive agent, conductivity of electrons generated in the active material layer can be increased, and battery performance can be improved.

  The compounding amount of the constituent material of the active material layer such as the active material, solid electrolyte, lithium salt, and conductive aid should be determined in consideration of the purpose of use of the battery (output priority, energy priority, etc.) and ion conductivity. . For example, if the amount of the solid electrolyte in the active material layer is too small, the ion conduction resistance and the ion diffusion resistance in the active material layer increase, and the battery performance deteriorates. On the other hand, if the amount of the solid electrolyte in the active material layer is too large, the energy density of the battery is lowered. Therefore, in consideration of these factors, the solid electrolytic mass meeting the purpose is determined.

  The electrode of the present invention is preferably used for a solid electrolyte battery, preferably a lithium polymer secondary battery. In that case, the electrode of this invention is used for at least one of a positive electrode and a negative electrode. Preferably, both the positive electrode and the negative electrode are the electrodes of the present invention.

  In a battery having a solid electrolyte membrane, it is preferable that the solid electrolyte membrane includes solid electrolyte particles having higher ion conductivity than the solid electrolyte constituting the solid electrolyte membrane. As described above for the electrode, the ionic conductivity of the solid electrolyte is relatively low, but it is possible to increase the ionic conductivity in the solid electrolyte membrane by including solid electrolyte particles with higher ionic conductivity in the solid electrolyte. is there.

The solid electrolyte membrane is composed of a polymer having ion conductivity, and the constituent material is not particularly limited as long as it exhibits ion conductivity. Examples of the material constituting the solid electrolyte membrane include known solid electrolytes such as polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. The solid electrolyte membrane preferably contains a lithium salt to ensure ionic conductivity. As the lithium salt, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or a mixture thereof can be used. However, it is not necessarily limited to these. As described above, polyalkylene oxide polymers such as PEO and PPO often dissolve lithium salts such as LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ C ₂ F ₅ ) _2. Yes. Moreover, excellent mechanical strength is exhibited by forming a crosslinked structure.

As the solid electrolyte particles contained in the solid electrolyte membrane, the same material as the solid electrolyte particles contained in the active material layer can be used. Specifically, Li _3.25 Ge _0.25 P _0.75 S ₄ , LiI—Li ₂ S—P ₂ S ₅ , Li ₂ S—GeS ₂ —P ₂ S ₅ , Li ₂ O—B ₂ O such as _{3 -P 2 O 5, LiO-} V 2 O 5 -SiO 2, Li 2 O-TiO 2 -P 2 O 5 and the like.

  The particle size of the solid electrolyte particles is not particularly limited, but is usually about 0.01 to 10 μm. In some cases, the solid electrolyte particles may be used as a holding material for the electrode by making the particle size of the solid electrolyte particles included in the solid electrolyte membrane equal to the film thickness. In that case, the average particle diameter of the solid electrolyte particles contained in the solid electrolyte membrane is preferably 0.7 to 1.0 when the thickness of the solid electrolyte membrane is 1.

  The thickness of the solid electrolyte membrane is not particularly limited. However, in order to obtain a compact battery, it is preferable to make it as thin as possible as long as the function as an electrolyte membrane can be secured. A typical solid electrolyte membrane has a thickness of about 5 to 200 μm.

  The batteries may be connected in series, in parallel, or a combination of series and parallel to form an assembled battery. For example, the assembled battery is placed in an outer case, and a terminal is drawn out from the outer case and used for connection with other devices. The assembled battery may be further connected in series, in parallel, or a combination of series and parallel to form a composite assembled battery.

  The number of batteries and the manner of connection in the assembled battery and the composite assembled battery may be determined according to the output and capacity required for the battery. When an assembled battery or a composite assembled battery is configured, the stability as a battery is increased as compared with a unit cell. By configuring the assembled battery or the composite assembled battery, the influence on the entire battery due to deterioration of one cell can be reduced.

  The battery, the assembled battery or the composite assembled battery can be preferably used for a vehicle. An assembled battery or a composite assembled battery mounted on a vehicle has excellent battery characteristics. For this reason, the performance of a vehicle increases.

  Then, the manufacturing method of the electrode of this invention is demonstrated. As a method for producing the electrode of the present invention, a coating method generally used for electrode production can be used. For example, a method of preparing a slurry by adding an electrode constituent material to a solvent and mixing it, and applying the slurry can be mentioned. The solid electrolyte that is a polymer may be present as a raw material in the slurry, and may be polymerized after being applied to the current collector. In that case, if necessary, a photopolymerization initiator or a thermal polymerization initiator is added to the slurry.

  Although the active material layer can be formed using a coating method, the active material layer is preferably formed by an inkjet method. The inventors of the present invention have created a method using an ink jet method as a method for providing a thin electrode having a high film thickness uniformity. By adopting a method in which an active material layer is formed by ejecting ink containing a constituent material of an active material layer such as an active material, a solid electrolyte or its raw material, solid electrolyte particles, and a conductive agent by an ink jet method, a uniform and thin active material is formed. It is possible to produce a material layer. In the case of ejecting by an inkjet method, ink including all of the constituent elements may be ejected, or a plurality of inks having different components may be ejected. When a mode in which a plurality of inks are ejected is used, it is easy to adjust the component ratio of the active material layer.

  Here, an active material layer manufactured using the inkjet method and advantages of the inkjet method will be described.

  FIG. 3 is a schematic view of an embodiment of an electrode formed using an inkjet method. FIG. 3 shows an electrode in which an active material layer 60 formed using an inkjet method is stacked on a current collector 70. Note that FIG. 3 is exaggerated for understanding of the invention. For example, in order to show that the active material layer 60 is formed by adhering particles ejected by an ink jet method, the active material layer 60 is illustrated as if it is composed of a large number of particles. The active material layer 60 can be identified as one layer when viewed with the naked eye. The electrode is sealed in the exterior material, and the positive electrode tab and the negative electrode tab are drawn out of the exterior material. When the active material layer 60 is laminated on the current collector 70, in order to join the tab to the current collector 70, a portion 80 (hereinafter referred to as “ May also be provided). The uncoated portion may exist for the purpose other than the joining of the tab, but if the uncoated portion increases, the energy density of the battery is reduced. For this reason, it is preferable not to provide a non-application part as much as possible except the part to which a tab is joined. However, it is not intended to prohibit the occurrence of an uncoated portion that inevitably occurs in manufacturing.

  Conventionally, a coater such as a roll type coater has been used to form an active material layer. However, it has been difficult to form an extremely thin and highly uniform active material layer using a conventionally known coater. If thinness is demonstrated, when forming an active material layer with a coating machine, if the coating film to be formed does not have a certain thickness, there will be a portion where no film is formed. Explaining the uniformity, when the active material layer is formed by a coating machine, the film thickness tends to increase at the edge of the coating film. That is, the coating film tends to be thick at the interface between the site where the coating film is formed and the site where the coating film is not formed.

  The problem that cannot be achieved in the past, such as thinning and uniforming the active material layer, can be solved by adopting an ink jet method. The ink jet method means a printing method in which liquid ink is ejected from a nozzle and ink is attached to an object. The ink jet method is classified into a piezo method, a thermal ink jet method, and a bubble jet (registered trademark) method according to a method of ejecting ink.

  The piezo method is a method in which ink is ejected from nozzles by deformation of a piezo element that is arranged at the bottom of an ink chamber that stores ink and deforms when an electric current flows. The thermal ink jet method is a method in which ink is heated by a heat-generating heater, and the ink is ejected with the energy of steam explosion when the ink is vaporized. The bubble jet (registered trademark) method is a method in which ink is ejected by the energy of steam explosion when the ink is vaporized, similarly to the thermal ink jet method. The thermal ink jet method and the bubble jet (registered trademark) method are different in the portion to be heated, but the basic principle is the same.

  When an active material layer is manufactured using an inkjet method, the following effects can be obtained. First, the thickness of the active material layer becomes very uniform. For this reason, the heat generation from the electrode surface becomes uniform, and local deterioration is suppressed.

  Second, a battery having an active material layer manufactured by an inkjet method has high durability against vibration. Since the durability against vibration is high, a battery having an active material layer manufactured by an inkjet method can be suitably applied to an application where vibration is easily applied, for example, a vehicle. The durability against vibration is presumed to be due to the uniformity of the film and the microstructure of the active material layer produced by the inkjet method.

  Third, when the active material layer is thin, the energy density of the battery is improved. When a battery is applied to an application that requires high output, such as a vehicle power supply, an assembled battery in which a large number of batteries are connected is configured. If the battery is large, the assembled battery with a constant output also becomes large. The thin active material layer greatly contributes to the miniaturization of the assembled battery. Regarding the vehicle, the volume of the vehicle is limited, and the weight reduction of the assembled battery also affects the improvement of the fuel consumption of the vehicle. For this reason, downsizing of the assembled battery is particularly beneficial when used as a vehicle power source.

  As described above, an electrode having high uniformity is produced by ejecting an active material, a solid electrolyte or a raw material of the solid electrolyte, and solid electrolyte particles having higher ion conductivity than the solid electrolyte by an inkjet method. Is possible.

  The ink jet method can be applied not only to the production of the active material layer but also to the production of the solid electrolyte membrane. Preferably, the positive electrode active material, the solid electrolyte or the raw material of the solid electrolyte, and the step of ejecting solid electrolyte particles having higher ion conductivity than the solid electrolyte by the ink jet method, and the solid electrolyte or the raw material of the solid electrolyte, the ink jet method And a negative electrode active material, a solid electrolyte or a raw material of the solid electrolyte, and a solid electrolyte particle having higher ion conductivity than the solid electrolyte, and a method of ejecting the battery by an ink jet method. Is done.

  When the active material, the solid electrolyte or the raw material of the solid electrolyte, and the solid electrolyte particles having higher ion conductivity than the solid electrolyte are ejected by the ink jet method, an ink including all of these may be used. May be used. For example, when preparing an active material layer by preparing an electrode ink containing an active material, a solid electrolyte or a raw material of the solid electrolyte, and an electrolyte ink containing solid electrolyte particles having higher ion conductivity than the solid electrolyte. Both inks are supplied. The electrolyte ink can also be used for producing a solid electrolyte membrane.

  Hereinafter, a battery manufacturing method using an ink jet method will be described in detail in the order of steps.

  First, a base material for forming an active material layer is prepared. As the substrate, a member adjacent to the active material layer in the battery, for example, a current collector or a polymer electrolyte membrane is used. The general thickness of the current collector is 5 to 20 μm. However, a current collector having a thickness outside this range may be used.

  Electrode ink is ejected onto the substrate by an inkjet method, and prior to that, positive ink, negative ink, and electrolyte ink are prepared.

  The components contained in the positive electrode ink include a positive electrode active material, a solid electrolyte or a raw material thereof, solid electrolyte particles having higher ion conductivity than the solid electrolyte, a conductive agent, a dispersant, and a solvent. The positive ink may be one kind or plural kinds. The raw material is preferably used for the solid electrolyte. By using a compound that is polymerized to become a solid electrolyte, the viscosity of the ink can be kept low, and clogging in the ink jet apparatus can be prevented. When a solid electrolyte raw material is used, a polymerization initiator is added as necessary. In order to prevent aggregation of the positive electrode active material and the conductive agent, a dispersant may be used. As the dispersant, a compound having a dispersing action such as polyoxystearylamine can be used.

  Examples of the component contained in the negative electrode ink include a negative electrode active material, a solid electrolyte or a raw material thereof, solid electrolyte particles having higher ion conductivity than the solid electrolyte, a conductive agent, a dispersant, and a solvent. The negative electrode ink may be one type or a plurality of types. The raw material is preferably used for the solid electrolyte. By using a compound that becomes a polymerized solid electrolyte, the viscosity of the ink can be kept low, and clogging in the ink jet apparatus can be prevented. In order to prevent aggregation of the negative electrode active material and the conductive agent, a dispersant may be used. As the dispersant, a compound having a dispersing action such as polyoxystearylamine can be used.

  Examples of components contained in the electrolyte ink include a solid electrolyte or a raw material thereof, solid electrolyte particles having higher ion conductivity than the solid electrolyte, and a solvent. The electrolyte ink contains at least a solid electrolyte or a raw material thereof. Preferably, solid electrolyte particles are included in order to increase the ionic conductivity of the solid electrolyte membrane. The raw material is preferably used for the solid electrolyte. By using a compound that becomes a polymerized solid electrolyte, the viscosity of the ink can be kept low, and clogging in the ink jet apparatus can be prevented. In some cases, the electrolyte ink may be used to mix a solid electrolyte and solid electrolyte particles in the active material layer. In this case, the electrolyte ink also has a function as a positive electrode ink and / or a negative electrode ink.

  The solvent for each ink is not particularly limited, and examples thereof include N-methylpyrrolidone (NMP) and acetonitrile.

  The compounding ratio of the components contained in the positive ink, the negative ink, and the electrolyte ink is not particularly limited. However, the viscosity of the ink should be low enough to apply the inkjet method. On the other hand, from the viewpoint of improving working efficiency, the concentration of the contained component is preferably as high as possible. Examples of a method for keeping the viscosity low include a method for increasing the temperature of the ink. You may improve the compound contained so that a viscosity may become low. The viscosity of each ink supplied to the inkjet apparatus is not particularly limited, but is preferably about 1 to 100 cP.

  When each ink is prepared, the ink is ejected onto the substrate by an ink jet method to form an active material layer and a solid electrolyte membrane. The amount of ink ejected from the nozzles of the ink jet apparatus is very small, and an approximately equal volume can be ejected. Therefore, the active material layer and the solid electrolyte membrane formed by the adhesion of the electrode ink are very thin and uniform. Moreover, if an inkjet system is used, the thickness and shape of an active material layer and a solid electrolyte membrane can be precisely controlled.

  The ink ejection mechanism employed by the ink jet apparatus may be any of a piezo method, a thermal ink jet method, and a bubble jet (registered trademark) method. When forming the active material layer and the solid electrolyte membrane, the shapes of the active material layer and the solid electrolyte membrane are determined in advance. If the active material layer and the solid electrolyte membrane are formed based on the image created on the computer, the workability is excellent. The shape determination of the active material layer and the solid electrolyte membrane using a computer and the production of the active material layer and the solid electrolyte membrane are performed in the same manner as the image creation and printout operations using a computer and a printer, which are widely known. It is possible. Therefore, it can be said that the present invention is relatively easy to realize industrial production in that the knowledge developed in this field can be used.

  The volume of particles ejected from the inkjet device is preferably in the range of 1 to 100 picoliters. If the volume of the ejected particles is too small, vibration reduction may be insufficient. On the other hand, even if the volume of ejected particles is too large, there is a risk that vibration reduction will be insufficient. The volume of the particles ejected using the ink jet apparatus is substantially the same, and the manufactured electrodes and batteries are very uniform.

  The number of ejections by the inkjet method may be determined according to the thickness of the active material layer and the solid electrolyte membrane and the ratio of the constituent materials. If the thickness is insufficient in one printing, the printing may be repeated twice or more on the same surface. That is, the same ink is printed on the same base material. Thereby, an active material layer and a solid electrolyte membrane having a desired thickness are formed. When forming an active material layer and a solid electrolyte membrane by the inkjet method, the uniformity of the active material layer and the solid electrolyte membrane to be formed is very high, so even if they are laminated many times, a high uniformity Sex can be maintained.

  There are no particular limitations on the procedure for applying the ink when all of the positive electrode, the solid electrolyte membrane, and the negative electrode are manufactured by the inkjet method. All layers may be produced using a single ink jet device, or a positive electrode ink jet device, a solid electrolyte membrane ink jet device, and a negative electrode ink jet device are prepared, and a battery is manufactured by a flow operation. May be.

  Preferably, a battery in which no clear interface exists between the positive electrode and the solid electrolyte membrane and / or between the solid electrolyte and the negative electrode is manufactured using an ink jet apparatus capable of ejecting a plurality of inks. The interface where the composition changes may be an obstacle to ionic conduction, and the ionic conductivity can be increased by not having a clear interface. For example, first, only positive electrode ink is ejected to form a positive electrode active material layer. When the positive electrode active material layer reaches a predetermined thickness, the electrolyte ink is ejected together with the positive electrode ink, and the ratio of the electrolyte ink is gradually increased. When only the electrolyte ink is ejected to form a coating film of the electrolyte ink having a predetermined thickness, ejection of the negative electrode ink is started, and the ratio of the negative electrode ink is gradually increased. In the case of manufacturing the battery in this mode, if the solid electrolyte particles are included only in the electrolyte ink, a concentration distribution is formed in the active material layer so that the concentration of the solid electrolyte particles in the portion close to the current collector is reduced. Is done.

  The ratio of each ink is possible by controlling the number of ejections from the ink jet apparatus. For example, when the positive electrode ink is ejected once, if the electrolyte ink is ejected three times, a layer in which the positive electrode ink and the electrolyte ink are supplied at 1: 3 is formed. In the case of forming a layer having a high proportion of the positive ink, this ratio may be changed.

  After the active material layer is formed, the solvent is removed by drying. When the raw material of the solid electrolyte is polymerized by this stage and does not become a solid electrolyte, the polymerization reaction may be advanced. For example, when a photopolymerization initiator is contained in the ink, the polymerization reaction of the raw material may be advanced by irradiating predetermined light.

In the following Examples and Comparative Examples, the following materials were used as the polymer electrolyte, lithium salt, solid electrolyte particles, positive electrode active material, and negative electrode active material. As the polymer electrolyte, macromers of ethylene oxide and propylene oxide were used. As the lithium salt, LiN (SO ₂ C ₂ F ₅ ) ₂ (hereinafter abbreviated as BETI) was used. As the solid electrolyte particles, LiI—Li ₂ S—P ₂ S ₅ having an average particle size of 1 μm was used. As the positive electrode active material, spinel type LiMn ₂ O ₄ having an average particle diameter of 0.6 μm was used. As the negative electrode active material, pulverized graphite having an average particle diameter of 0.7 μm was used. Ink preparation, application, and battery preparation were performed in a dry atmosphere with a dew point of -30 ° C or lower.

Example 1
1. Preparation of negative electrode ink 9% by mass of negative electrode active material, 3% by mass of polymer electrolyte raw material (hereinafter referred to as “polymer raw material”), 1% by mass of solid electrolyte particles, 2% by mass of lithium salt, light Benzyl dimethyl ketal as a polymerization initiator was added in an amount of 0.1% by mass of the polymer raw material, and 85% by mass of acetonitrile as a solvent was added thereto and stirred sufficiently to prepare a slurry. At this time, the viscosity of the ink was about 3 cP.

2. Preparation of positive electrode ink 7% by mass of positive electrode active material, 3% by mass of polymer raw material, 1% by mass of solid electrolyte particles, 2% by mass of lithium salt, 2% by mass of acetylene black as a conductive agent, and benzyl as a photopolymerization initiator Dimethyl ketal was added in an amount of 0.1% by mass of the polymer material, and 85% by mass of acetonitrile as a solvent was added thereto and stirred sufficiently to prepare a slurry. At this time, the viscosity of the ink was about 3 cP.

3. Electrolyte ink preparation 11% by mass of polymer material, 4% by mass of solid electrolyte particles, 8% by mass of lithium salt, 0.1% by mass of benzyl dimethyl ketal as a photopolymerization initiator, and acetonitrile as a solvent Was used to prepare a solution. At this time, the viscosity of the ink was 2 cP.

4). Production of Battery A positive electrode was produced by the following procedure using the prepared ink and a commercially available ink jet printer. When the above ink is used, there is a problem that acetonitrile as a solvent dissolves plastic parts in the ink introduction portion of the ink jet printer. Therefore, the parts in the ink introduction part were replaced with metal parts, and ink was directly supplied from the ink reservoir to the metal parts. Further, since there was a concern that the viscosity of the ink was low and the active material was precipitated, the ink reservoir was always stirred using a rotary blade.

  The inkjet printer was controlled by a commercially available computer and software. When preparing the positive electrode layer, the prepared positive electrode ink was used. The positive electrode layer was produced by printing a pattern created on a computer using an inkjet printer. In addition, since it was difficult to supply metal foil directly to a printer, these were stuck on A4 quality paper, supplied to the printer, and printed.

4-1. Negative electrode coating The prepared negative electrode ink was introduced into a commercially available modified inkjet printer, and a pattern created on a computer was printed on a stainless steel current collector foil. After printing, in order to dry the solvent, drying was performed in a vacuum oven at 60 ° C. for 2 hours. After drying, in order to polymerize the polymer electrolyte, it was photopolymerized by irradiation with ultraviolet rays for 20 minutes in a vacuum.

4-2. Electrolyte Application Next, the prepared electrolyte ink was introduced into a commercially available inkjet printer that had been modified, and printed on the prepared negative electrode application part so as to protrude slightly from the negative electrode application part. The electrolyte ink solvent was dried in a vacuum oven at 60 ° C. for 2 hours. After drying, in order to polymerize the polymer electrolyte, it was photopolymerized by irradiation with ultraviolet rays for 20 minutes in a vacuum.

4-3. Positive electrode application Next, the prepared positive electrode ink was introduced into a commercially available inkjet printer that had been modified, and printed on the prepared electrolyte application part so as to be slightly smaller than the negative electrode application surface. did. Next, in order to dry the positive electrode ink solvent, it was dried in a vacuum oven at 60 ° C. for 2 hours. After drying, in order to polymerize the polymer electrolyte, it was photopolymerized by irradiation with ultraviolet rays for 20 minutes in a vacuum.

4-4. Assembly A stainless steel final foil was also arranged on the positive electrode side, and the negative electrode, electrolyte, and positive electrode were sandwiched between stainless steel foils. Finally, the battery was sealed and molded with an aluminum laminate so that only the positive and negative electrode leads were exposed.

5. Evaluation The produced battery was subjected to constant current constant voltage charging at ²⁰ μA / cm ^{2 at} an upper limit voltage of 4.2 V, and then constant current discharge at ²⁰ μA / cm ² was performed at a lower limit voltage of 2.5 V. Next, charging / discharging was performed at a current value of 3 C with reference to the capacity obtained at this time. The discharge rate [%] was obtained by dividing the 3C discharge capacity by the initial discharge capacity. The discharge rate was 37%.

(Example 2)
1. Preparation of negative electrode ink A slurry was prepared by sufficiently stirring 15% by mass of a negative electrode active material and 85% by mass of acetonitrile as a solvent. At this time, the viscosity of the ink was about 3 cP.

2. Preparation of positive electrode ink A slurry was prepared by sufficiently stirring 12% by mass of a positive electrode active material, 3% by mass of acetylene black as a conductive agent, and 85% by mass of acetonitrile as a solvent. At this time, the viscosity of the ink was about 3 cP.

3. Electrolyte ink preparation 11% by mass of polymer material, 4% by mass of solid electrolyte particles, 8% by mass of lithium salt, 0.1% by mass of benzyl dimethyl ketal as a photopolymerization initiator, and acetonitrile as a solvent Was used to prepare a solution. At this time, the viscosity of the ink was 2 cP.

4). Production of Battery A positive electrode was produced by the following procedure using the prepared ink and a commercially available ink jet printer. When the above ink is used, there is a problem that acetonitrile as a solvent dissolves plastic parts in the ink introduction portion of the ink jet printer. Therefore, the parts in the ink introduction part were replaced with metal parts, and ink was directly supplied from the ink reservoir to the metal parts. Further, since there was a concern that the viscosity of the ink was low and the active material was precipitated, the ink reservoir was always stirred using a rotary blade.

  The inkjet printer was controlled by a commercially available computer and software. When preparing the positive electrode layer, the prepared positive electrode ink was used. The positive electrode layer was produced by printing a pattern created on a computer using an inkjet printer. In addition, since it was difficult to supply metal foil directly to a printer, these were stuck on A4 quality paper, supplied to the printer, and printed.

4-1. Application The prepared negative electrode ink, electrolyte ink, and positive electrode ink were introduced into different nozzles of a commercially available inkjet printer that had been modified, and a pattern created on a computer was printed on a stainless steel current collector foil. At first, only the negative electrode ink was applied, and the ink jet printer was controlled so as to apply more electrolyte ink as the distance from the current collector foil increased. After applying the specified number of times, only the electrolyte ink was applied to form a separator layer. Thereafter, the positive electrode ink and the electrolyte ink were applied at the same time, and the printer was controlled so as to apply a larger amount of the positive ink away from the separator, and printing was performed. After printing, in order to dry the solvent, drying was performed in a vacuum oven at 60 ° C. for 2 hours. After drying, in order to polymerize the polymer electrolyte, it was photopolymerized by irradiation with ultraviolet rays for 20 minutes in a vacuum. By such application, each of the positive electrode active material layer, the solid electrolyte membrane, and the negative electrode active material layer contains solid electrolyte particles, and in the positive electrode active material layer and the negative electrode active material layer, a portion close to the current collector A battery having a concentration distribution in which the concentration of the solid electrolyte particles in the battery becomes low was obtained.

4-2. Assembly A stainless steel final foil was also arranged on the positive electrode side, and the negative electrode, electrolyte, and positive electrode were sandwiched between stainless steel foils. Finally, the battery was sealed and molded with an aluminum laminate so that only the positive and negative electrode leads were exposed.

5. Evaluation The produced battery was subjected to constant current constant voltage charging at ²⁰ μA / cm ^{2 at} an upper limit voltage of 4.2 V, and then constant current discharge at ²⁰ μA / cm ² was performed at a lower limit voltage of 2.5 V. Next, charging / discharging was performed at a current value of 3 C with reference to the capacity obtained at this time. The discharge rate [%] was obtained by dividing the 3C discharge capacity by the initial discharge capacity. The discharge rate was 44%.

(Comparative Example 1)
1. Preparation of negative electrode ink 9% by mass of negative electrode active material, 4% by mass of polymer raw material, 2% by mass of lithium salt, 0.1% by mass of benzyl dimethyl ketal as a photopolymerization initiator and 0.1% by mass of the polymer raw material, and solvent As a slurry, 85 mass% of acetonitrile was added and sufficiently stirred to prepare a slurry. At this time, the viscosity of the ink was about 3 cP.

2. Preparation of positive electrode ink 7% by mass of positive electrode active material, 4% by mass of polymer raw material, 2% by mass of lithium salt, 2% by mass of acetylene black as a conductive agent, and 0% of polymer raw material of benzyl dimethyl ketal as a photopolymerization initiator .1% by mass was added, and 85% by mass of acetonitrile as a solvent was added thereto, followed by thorough stirring to prepare a slurry. At this time, the viscosity of the ink was about 3 cP.

3. Electrolyte ink preparation 15% by mass of polymer material, 8% by mass of lithium salt, 0.1% by mass of benzyl dimethyl ketal as a photopolymerization initiator and 0.1% by mass of polymer material, and a solution using 77% by mass of acetonitrile as a solvent Prepared. At this time, the viscosity of the ink was 2 cP.

4). Production of Battery A battery was produced in the same procedure as in Example 1 using the prepared ink and a commercially available ink jet printer.

5. Evaluation The produced battery was subjected to constant current constant voltage charging at ²⁰ μA / cm ^{2 at} an upper limit voltage of 4.2 V, and then constant current discharge at ²⁰ μA / cm ² was performed at a lower limit voltage of 2.5 V. Next, charging / discharging was performed at a current value of 3 C with reference to the capacity obtained at this time. The discharge rate [%] was obtained by dividing the 3C discharge capacity by the initial discharge capacity. The discharge rate was 30%.

  Table 1 shows discharge rates at 3C of Example 1, Example 2, and Comparative Example.

  From the comparison between Example 1 and Comparative Example 1, it can be seen that the use of solid electrolyte particles increases the ionic conductivity and increases the discharge rate at 3C. Moreover, from the comparison between Example 1 and Example 2, it can be confirmed that the discharge rate is improved by increasing the concentration of the solid electrolyte particles in the active material layer as it is closer to the solid electrolyte membrane. This is due to the fact that ions are efficiently supplied to the active material far from the solid electrolyte membrane, and that the positive and negative electrode active material layers are continuously formed so that there is no interface between the layers, It is presumed that the ionic conductivity is high. However, the technical scope of the present invention is not limited to this mechanism.

  The electrode obtained by the production method of the present invention is used for a battery such as a lithium secondary battery. A preferred application of the lithium secondary battery is a vehicle.

It is a cross-sectional schematic diagram of the electrode of this invention. It is a cross-sectional schematic diagram of the electrode in which the concentration distribution of solid electrolyte particles exists. It is a schematic diagram of one Embodiment of the electrode formed using the inkjet system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Active material, 20 ... Solid electrolyte particle, 30 ... Solid electrolyte, 40 ... Active material layer, 50 ... Current collector, 60 ... Active material layer, 70 ... Current collector, 80 ... Uncoated part.

Claims (8)

An active material layer including an active material, a solid electrolyte, and solid electrolyte particles having higher ion conductivity than the solid electrolyte;
A current collector laminated on the active material layer;
Electrode.   2. The electrode according to claim 1, wherein in the active material layer, there is a concentration distribution in which the concentration of the solid electrolyte particles is low in a portion adjacent to the current collector.   The electrode according to claim 1, wherein the active material layer further contains a conductive agent.   A battery comprising a positive electrode, a solid electrolyte membrane, and a negative electrode, wherein at least one of the positive electrode and the negative electrode is the electrode according to any one of claims 1 to 3.   The battery according to claim 4, wherein the solid electrolyte membrane includes solid electrolyte particles having higher ion conductivity than the solid electrolyte constituting the solid electrolyte membrane.   The battery according to claim 5, wherein an average particle diameter of solid electrolyte particles contained in the solid electrolyte membrane is 0.7 to 1.0 when the thickness of the solid electrolyte membrane is 1.   An electrode manufacturing method including a step of ejecting an active material, a solid electrolyte, or a raw material of the solid electrolyte, and solid electrolyte particles having higher ion conductivity than the solid electrolyte by an inkjet method. Ejecting positive electrode active material, solid electrolyte or solid electrolyte raw material, and solid electrolyte particles having higher ion conductivity than the solid electrolyte by an inkjet method;
A step of ejecting a solid electrolyte or a raw material of the solid electrolyte by an ink jet method;
A step of ejecting a negative electrode active material, a solid electrolyte or a raw material of the solid electrolyte, and solid electrolyte particles having higher ion conductivity than the solid electrolyte by an inkjet method;
A method for producing a battery, comprising: