JP5168768B2 - Electrode structure - Google Patents

Description

The present invention relates to an electrode structure having grooves on the electrode surface.

In the conventional electrode structure of a lithium battery, the electrode surface is formed as smoothly as possible, so that the electrode material constitutes one large region. This electrode material is, for example, a roll as disclosed in JP-A-9-115504 (Patent Document 1), JP-A-2002-025542 (Patent Document 2), JP-A-2002-164043 (Patent Document 3), etc. It is uniformly coated on the current collector using a mold coater. In the electrode manufacturing process using this roll type coating machine, separate coating machines are required for the positive electrode and the negative electrode, the production line is large, and the production takes a long time.
JP-A-9-115504 JP 2002-025542 A JP 2002-164043 A

  By the way, in the conventional electrode structure, since the electrode material constituted one large region, when a micro short circuit occurs in a part of the electrode, current is concentrated from the entire electrode to the micro short circuit part, and self-discharge is promoted. The battery life may be shortened.

  Further, since the electrode material is uniformly coated on the current collector, it is difficult to reduce the vibration of the specific part.

  Furthermore, it is very difficult to manufacture an extremely thin electrode of about several μm due to the accuracy limitation of the roll type coating machine. For example, a high output is obtained like a high output battery for a vehicle. Therefore, it has not been possible to deal with a battery that requires a thin electrode thickness.

The present invention has been made in order to solve the above-described problems of the prior art, and can achieve a long battery life and can improve vibration isolation. and an object thereof is to provide a structure.

Electrode structure according to the present invention for achieving the above object, so that the two or more regions in which a part of the region of at least the electrode surface is divided, the electrode active material is laminated on a substrate, wherein Some areas have grooves with a depth of more than half of the electrode average thickness on the electrode surface, and the some areas having the grooves on the electrode surface side have vertices passing through the center of gravity of the electrode surface. It is a shape located along the connecting line, or a shape located along a line connecting the midpoints passing through the center of gravity of the electrode surface, or connects vertices and midpoints passing through the center of gravity of the electrode surface a shape which is located along the line, the part of the region, from one end to the other end of the electrode surface is characterized Rukoto formed by grooves that are not contiguous.

According to the electrode structure according to the present invention configured as described above, the electrode active material is laminated on the base material so that at least a part of the region on the electrode surface side is divided into two or more regions. The partial area has a groove having a depth of more than half of the average electrode thickness on the electrode surface, and the partial area having the groove on the electrode surface side is a vertex passing through the center of gravity of the electrode surface. It is a shape located along a line connecting each other, or a shape located along a line connecting the middle points passing through the center of gravity of the electrode surfaces, or vertices and middle points passing through the center of gravity of the electrode surfaces a shape which is located along a line connecting the portion of the region, said one end of the electrode surface to the other is formed by a groove which is not contiguous Runode, reduced self-discharge of the battery by micro short circuit Battery life can be achieved. It is possible to improve the vibration-proof.

Embodiments of an electrode structure according to the present invention will be described below in detail with reference to the drawings. A reference embodiment of a method for manufacturing an electrode structure , a secondary battery, an assembled battery, a composite assembled battery, and a vehicle equipped with these batteries will also be described in detail with reference to the drawings. In the drawings cited in the following embodiments, the thickness and shape of each layer constituting the secondary battery are exaggerated, but this is done to facilitate understanding of the contents of the invention. Therefore, it is not consistent with the thickness and shape of each layer in an actual secondary battery.

  1A is a plan view of a secondary battery according to the present embodiment, FIG. 1B is a side view thereof, and FIG. 1C is a sectional view thereof. As shown in the drawing, the secondary battery 10 has a rectangular flat shape, and a positive electrode tab 20A and a negative electrode tab 20B for taking out electric power are drawn out from both sides thereof. The power generation element 30 is wrapped by an exterior material (for example, a laminate film) 40 of the secondary battery 10, and the periphery thereof is heat-sealed 50. The power generation element 30 is sealed with the positive electrode tab 20A and the negative electrode tab 20B pulled out. ing.

  The secondary battery 10 according to the present embodiment is particularly characterized in the structure of the electrode, and has a fine groove on the electrode surface as will be described later. Therefore, since it is necessary to form a fine groove on the electrode surface, among the layers constituting the power generating element 30 of the secondary battery 10, at least the electrode material constituting the negative electrode layer and the positive electrode layer is simply changed by the volume change of the piezoelectric element. It is preferable that the fine coated fine particles are produced by extruding each particle independently. Specifically, for example, the material necessary for layer formation is intermittently ejected from a plurality of nozzle holes, as in the case of printing an image using an inkjet printer system. However, it is possible to form fine grooves by secondary processing using a cutting machine or the like after applying an electrode material with a coater or the like without using an ink jet printer system.

  In the present embodiment, a case will be described in which each layer of the power generation element 30 of the secondary battery 10 is overcoated with a predetermined adhesion pattern using an inkjet printer system. In the case of using the ink jet printer method, the power generation element 30 can be created by forming layers in order from the lower layer so as to draw a picture layer by layer. In other words, in the present embodiment, the unit cell 150 is overcoated in order from the first layer to the upper layer on the foil-like negative electrode current collector 110 as in the case of forming a color image with an inkjet printer. And the power generation element 30 is formed by repeatedly stacking the unit cells 150 three times. Here, each layer constituting the power generation element 30 will be described, and the detailed structure of the electrode itself will be described later.

  That is, on the negative electrode current collector (conductive material) 110 as a base material, a negative electrode active material is printed as a negative electrode material in the central portion, a conductive material is printed in a part thereof, and an insulating material is printed in an outer peripheral portion thereof. . An adhesion pattern such as which part of the negative electrode current collector 110 is to be printed with a material such as a negative electrode active material, a conductive material, and an insulating material is set in advance for each layer, and a printer that controls jetting of the material uses this adhesion pattern. In response, a conductive material or an insulating material is selectively sprayed in each region.

  When printing of the first layer is completed, printing of the second layer is started. On the first layer, an ion conductive material as an electrolyte layer 120 for exchanging lithium ions is printed at the central portion thereof, and a conductive material is printed on a portion thereof, and an insulating material is printed on the outer peripheral portion thereof.

  When the second layer printing is completed, the third layer printing is started. On the second layer, a positive electrode active material that forms an electrode layer serving as a positive electrode is printed at the central portion thereof, and a conductive material is printed on a part thereof, and an insulating material is printed on an outer peripheral portion thereof.

  When printing of the third layer is completed, printing of the fourth layer is started. A conductive material to be the positive electrode current collector 130 is printed on the entire surface of the third layer.

  When printing of the fourth layer is completed, printing of the fifth layer is started. On the fourth layer, an ion conductive material serving as an electrolyte layer 120 for exchanging lithium ions is printed at the central portion thereof, and a conductive material is printed on a portion thereof and an insulating material is printed on the outer peripheral portion thereof.

  When printing of the fifth layer is completed, printing of the sixth layer is started. The sixth layer is printed on the fifth layer, and the sixth layer printing is the same as the first layer printing. That is, on the fifth layer, a negative electrode active material for forming a negative electrode layer is printed at the central portion, a conductive material is printed on a part thereof, and an insulating material is printed on an outer peripheral portion thereof.

  Thereafter, the seventh and eighth layers are printed in the same manner as the second and third layers.

  In FIG. 1, the layer between the negative electrode current collector 110 and the positive electrode current collector 130 is a unit cell 150, 170 is a connecting portion between the tab and the current collector, 180 is the current collector width, and 190 is the tab. The width is shown.

  The printing for each unit cell 150 as described above is repeated three times in total to form a set of power generation elements 30.

Here, examples of the material for forming the positive electrode include a positive electrode active material, a conductive auxiliary agent, and the like. As the positive electrode active material, a composite oxide of lithium and transition metal (lithium-transition metal composite oxide) which is a constituent material of a general lithium ion battery is preferably used. Specifically, Li—Mn composite oxides such as LiMnO ₂ and LiMn ₂ O ₄ , Li—Co composite oxides such as LiCoO _2, and Li—Cr such as Li ₂ Cr ₂ O ₇ and Li ₂ CrO _4. system composite oxide, Li-Ni-based composite oxide such as LiNiO _2, Li x FeO _y and Li-Fe-based composite oxides such as _{LiFeO 2, Li x V y O} z Li-V based composite oxides such as, In addition, those obtained by substituting a part of these transition metals with other elements (for example, LiNi _x Co _1-x O ₂ (0 <x <1), etc.) can be used. Thus, although it selects from Li metal oxide, this invention is not limited to these materials. The lithium-transition metal composite oxide is a low-cost material that is excellent in reactivity and cycle durability. Therefore, the use of these materials for the electrodes is advantageous in that a secondary battery having excellent output characteristics can be formed. In addition, transition metal and lithium phosphate compounds such as LiFePO ₄ , sulfate compounds (V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ ), transition metal oxides such as MoO ₃ and sulfides (PbO ₂₎ , AgO, NiOOH) and the like.

  In particular, when a Li—Mn composite oxide is used as the positive electrode material, the voltage-SOC profile can be tilted. As a result, the state of charge (SOC) of the battery can be determined by measuring the voltage, which makes it possible to detect and deal with particularly unstable overcharge and overdischarge conditions, improving battery reliability. Can be made. In addition, it can be said that the Li—Mn-based composite oxide has a mild reaction even when the battery fails due to overcharge and overdischarge, and has high reliability in an abnormal state.

  Moreover, as a material which forms a negative electrode, there exists a negative electrode active material, and a crystalline carbon material and an amorphous carbon material are mentioned. 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 of the negative electrode active materials may be used in combination. By making the negative electrode material a crystalline carbon material or an amorphous carbon material, the voltage-SOC profile can be tilted. As a result, the state of charge (SOC) of the battery can be determined by measuring the voltage, which makes it possible to detect and deal with particularly unstable overcharge and overdischarge conditions, improving battery reliability. Can be made. This effect is particularly remarkable in amorphous carbon.

  Next, the electrode structure according to the present invention will be described with reference to FIGS. 2A is a plan view of the electrode structure according to the present invention, and FIG. 2B is a cross-sectional view taken along the line A-A ′. FIG. 3 is a diagram for explaining the state of movement of electrons during a minute short circuit. FIG. 4 is a diagram illustrating a state of absorption of distortion of the linear expansion coefficient. FIG. 5 is a schematic diagram showing the depth of the groove on the electrode surface.

  As shown in FIG. 2, for example, an electrode active material as an electrode material 220 is formed on a foil-like current collector 210 so that at least the electrode surface side is divided into two or more regions by the above-described inkjet printer method. The electrode 200 having a groove 230 that is laminated and deeper than half of the average electrode thickness is formed on the electrode surface.

  Conventionally, an electrode layer having a substantially uniform thickness is desired to be smooth without conscious irregularities on the electrode surface. However, if a minute short circuit occurs due to external stress input or peeling of a part of the electrode material, the electrons charged on the entire surface of the electrode are gradually consumed due to the minute short circuit. Will disappear and the battery will be completely discharged. For example, in the case of a lithium ion battery, when it reaches 0 volts, copper is likely to be deposited, and the function of the battery may be lost.

  In the electrode structure according to the present invention, by setting the groove 230 that forms at least two regions divided at least on the electrode surface side, even if a micro short circuit occurs in a certain part in the electrode 200, the region The electrons inside are selectively consumed. Therefore, it takes a long time for the electrons on the entire surface of the electrode to disappear, and as a result, the battery life when a micro short circuit occurs is extended. Conventionally, when electrons move, there are roughly two paths, a path for moving the electrode material and a path for moving the current collector, but in the case of the electrode structure according to the present invention, As shown in FIG. 3, since the fine groove 230 is provided on the electrode surface, the amount of electrons moving through the electrode material 220 is extremely reduced. That is, in FIG. 3, when a micro short-circuit occurs in a certain portion in the electrode 200, the groove 230 on the electrode surface is deeper as shown in (A), and the groove 230 on the electrode surface is shallow as shown in (B). As a result, the amount of electrons passing through the electrode material 220 can be reduced.

  In addition, the conventional smooth electrode has a different coefficient of linear expansion between the current collector and the electrode material due to external heat and self-heating, which may cause stress between the electrode material and the current collector. Was high. However, according to the electrode structure according to the present invention, as shown in FIGS. 4A and 4B, since the electrode surface has the fine groove 230, the width of the groove 230 changes. The distortion of the linear expansion coefficient can be absorbed, and the distortion due to the elongation of the current collector 210 that easily undergoes thermal expansion can be reduced.

  Here, the “electrode surface” means the surface of the electrode active material as the electrode material 220 applied on the current collector 210. Further, “two or more divided areas” means that one or more grooves 230 are set on the electrode surface, so that the areas divided by the grooves 230 are two or more.

  The depth of the fine groove 230 needs to be at least half the average electrode thickness. Here, the “average thickness of the electrode” means the average value when the thickness of the electrode material 220 applied on the current collector 210 varies. This is because electrons move through the electrode material other than the groove 230, and as described above, the deeper the groove 230, the more the movement of electrons is limited, and the life when a micro short circuit occurs can be improved. is there. This is because when the depth is less than half of the average electrode thickness, the amount of flowing current does not change so much and the effect on the battery life is reduced. Further, the effect of reducing the stress of the electrode 200 due to the difference in linear expansion coefficient is almost lost.

  More specifically, the depth of the groove 230 is preferably 70 to 100% of the average electrode thickness. This is because in the range of 70 to 100%, the battery life due to the micro short circuit and the heat resistance due to the difference in linear expansion coefficient are further improved. In the case of 100%, the current flow particularly in the case of a micro short circuit is only the current collector 210, so the battery life is remarkably improved. Further, since the electrode material 220 is placed on the current collector 210, the elongation of the current collector 210 due to the difference in the linear expansion coefficient almost completely moves as the behavior of the electrode material 220. The effect of reducing stress is increased. In FIG. 5, (A) shows the case where the groove depth is 90% of the average electrode thickness, (B) shows the case where the groove depth is 70% of the average electrode thickness, and (B) shows the groove. The case where the depth of the electrode is 50% of the average thickness of the electrode is shown, and these all satisfy the conditions of the present invention, but the embodiments of (A) and (B) are preferred.

  Moreover, in this Embodiment, as shown in FIG. 2, the strip | belt-shaped straight groove | channel 230 which exhibits the cross-beam shape extended vertically and horizontally on the electrode surface is formed. It is preferable that the plurality of regions divided by the grooves 230 on the electrode surface have a rectangular parallelepiped shape. This is because the current collector 210 is also a rectangular parallelepiped in a broad sense, and therefore, there is a high possibility that stress resulting from external vibration or a linear expansion coefficient is generated in a portion that uses the rectangular parallelepiped as a source. Further, if the region is partitioned by a curve, a large stress is generated at the curved portion, and heat resistance and vibration resistance may be deteriorated. This is because, when the heat resistance or the like is lowered, the active material of the electrode is easily peeled off at that portion, and a cause of occurrence of a micro short circuit occurs.

  Furthermore, the length of the short side of the rectangular parallelepiped region is preferably in the range of 10 to 500 μm. This is because if the thickness is less than 10 μm, the total area of the grooves 230 that divide the region becomes too large, and a decrease in battery capacity cannot be ignored. Further, if it exceeds 500 μm, the degree of improvement in battery life is reduced.

  Here, the width of the groove 230 is preferably 1/100 to 1/10 of the area of the region, and the substantial width is about 1 μm to 100 μm. Since the portion where the groove 230 is formed is a portion where the electrode active material is small, the battery capacity is reduced accordingly. Therefore, it is desirable that the area of the groove 230 is as small as possible. The width of the groove 230 is determined by the manufacturing method of the groove 230 and the balance with the battery life, but is not particularly limited here.

  The regions divided by the fine grooves 230 are preferably distributed symmetrically on the electrode surface. In addition, it is preferable that a minute region including the minute groove 230 is located at the center of gravity of the electrode surface. Furthermore, it is preferable that the minute region including the minute groove 230 is located on a line connecting at least the vertex of the electrode surface and the midpoint of the side connecting the vertex.

  FIG. 6 is a diagram for explaining the vibration damping effect of the electrode structure according to the present invention. Since the electrode structure vibrates with the dotted line portion in the electrode structure as a node, the active material on the dotted line is most susceptible to the vibration. Further, the point where the dotted lines of the vibration nodes gather is also important for vibration, and the center of gravity is particularly susceptible to vibration because the vibration input is strongest. In addition, in FIG. 7, vertex 1 to vertex 4 are susceptible to vibration after the center of gravity, and midpoint 1-2, midpoint 2-3, midpoint 3-4, and midpoint 4-1 are also next. It becomes a part that is easy to receive. Here, the portion that is easily affected by the vibration is likely to cause a minute short circuit because the electrode material is likely to be peeled off by the vibration. Therefore, by providing the minute groove 230 in such a portion, the vibration resistance is improved and a minute short circuit is less likely to occur, and as a result, the vibration isolating property is improved.

  FIG. 7 to FIG. 9 are schematic views showing setting examples of the fine groove 230 based on the above consideration. With respect to the electrode structures of these A to G patterns, the vibration proof property is improved by setting a minute region including the minute groove 230 in a portion where the influence of vibration is large. In FIG. 7, A and A ′ patterns are obtained by positioning the groove 230 on the line connecting the vertex 1 and the vertex 3 and on the line connecting the vertex 2 and the vertex 3. In FIG. 7, the B and B ′ patterns have grooves 230 positioned on the line connecting the midpoint 1-2 and the midpoint 3-4 and on the line connecting the midpoint 4-1 and the midpoint 2-3. It is a thing. In FIG. 8, the C and C ′ patterns are on the line connecting the vertex 1 and the vertex 3, on the line connecting the vertex 2 and the vertex 3, and on the line connecting the midpoint 1-2 and the midpoint 3-4. The groove 230 is located on the surface. In FIG. 8, D and D ′ patterns are on the line connecting the vertex 1 and the vertex 3, on the line connecting the vertex 2 and the vertex 3, and on the line connecting the middle point 4-1 and the middle point 2-3. The groove 230 is located on the surface. In FIG. 9, E and E ′ patterns are on the line connecting the vertex 1 and the vertex 3, on the line connecting the vertex 2 and the vertex 3, on the line connecting the midpoint 1-2 and the midpoint 3-4, and 4 The groove 230 is positioned on a line connecting -1 and the midpoint 2-3. In FIG. 9, the F and G patterns are obtained by setting the grooves 230 in a grid pattern in the vertical and horizontal directions of the electrode surface.

  FIG. 10 is an explanatory diagram showing a vibration spectrum, in which an electrode having no fine groove is a conventional structure, and the electrode structure of the D pattern is an invention structure. As shown in the figure, it can be seen that the inventive structure greatly attenuates the vibration, suggesting the possibility of a small short circuit resulting therefrom.

  In addition, the size of the region divided by the fine groove 230 may be the same on the electrode surface, or various sizes may be mixed. In consideration of the effects of heat resistance and vibration proofing, the region is preferably as uniform as possible, but is not particularly limited.

  Next, the manufacturing method of the electrode structure according to the present invention will be described in more detail.

  As described above, in order to manufacture the electrode structure according to the present invention, a method of independently extruding fine coated fine particles for each single particle by a volume change of the piezoelectric element, for example, an ink jet printer method is used. An electrode active material is laminated as the electrode material 220 on the current collector 210 made of metal foil so that the side is divided into two or more regions, and a groove 230 having a depth of more than half of the average electrode thickness is formed on the electrode surface. Form. The base material on which the electrode active material as the electrode material 220 is laminated is not limited to the current collector, and a polymer film may be used. As the electrode active material, a dispersion material is used as a binder, and it is possible to prepare a slurry of the electrode material as ink used in the ink jet printer system. The metal foil means a metal foil such as an aluminum foil, a copper foil, and a stainless steel foil (SUS foil) applicable to a battery current collector. In addition, the polymer film means a general battery separator material or an exterior laminate material. By applying an electrode active material to these substrates by inkjet, a low-resistance electrode resulting from high dispersibility can be obtained. Furthermore, since it has high adhesiveness due to the dispersing material, an electrode with high reliability against external stresses such as vibration can be obtained.

  The coated fine particles are preferably extruded by a predetermined amount in the range of 1 to 100 picoliters (pL). If it is less than 1 pL, even if a micro mass spring structure is formed, the mass is too small and satisfactory vibration reduction cannot be achieved. Moreover, if it exceeds 100 pL, it is difficult to form a bridge portion having a micro mass spring structure, and the vibration reduction effect may be reduced. Furthermore, even if a bridge portion having a micro mass spring structure is formed, the spring of the bridge portion becomes large, and the effect of reducing vibration becomes small.

  Regarding the layer thickness of the electrode material 220, it is preferable to increase the total thickness of the electrode material 220 by laminating the same electrode material (electrode active material) at a uniform thickness a plurality of times by the same method such as an inkjet printer method. . This is because a thick electrode can be manufactured by laminating the same electrode material (electrode active material) with a uniform thickness multiple times. Since the merit of the ink jet printer method is that thin coating can be performed with a uniform thickness, it cannot be said that the merit with respect to the thick coating is great. However, if the thickness is about 1 to 30 μm, the ink jet printer method can be laminated.

  However, the present invention is not limited to this, and the total thickness of the electrode material 220 can be increased by stacking different types of electrode materials multiple times with a uniform thickness by the same method. This is because, for example, when manufacturing an all-solid-state bipolar battery, a positive electrode material, an electrolyte, a negative electrode material, a metal foil, and the like can be applied in order. That is, an electrode for applying at least one of electrode element materials selected from a positive electrode material, a negative electrode material, an electrolyte material, and a conductive material on a base material selected from a metal foil or a polymer film. The electrode element material can be laminated to a substantially uniform thickness on the base material by independently ejecting each volume and allowing them to adhere independently on the base material.

  The electrode solvent is preferably an active material having a particle size of 0.01 to 1 μm. If the thickness is less than 0.01 μm, the size of the active material is smaller than the size of the dispersion material, so that the size of the micropores does not match the size of the dispersion material, and the adhesiveness decreases. On the other hand, if it exceeds 1 μm, the size of the active material is too large compared to the size of the dispersion material, and it becomes difficult to hold the active material as a binder, and the adhesiveness is lowered. For application by an ink jet printer method, it is preferable that the size of the active material is small. However, if it exceeds 1 μm, it becomes difficult to stably disperse the active material in the ink.

  In order to apply by an ink jet printer method, the electrode solvent preferably has a solid content in the range of 5 to 30 wt%. If it is less than 5 wt%, it is necessary to increase the number of times of coating in order to produce an electrode having a thickness of several microns, and the efficiency of electrode coating deteriorates. Further, if it exceeds 30 wt%, it is difficult to stably disperse in the ink. Here, when coating with a coater or the like without using the ink jet printer method, the higher the solid content, the better the coating efficiency. The solid content in this case is preferably in the range of 90 to 99 wt%, but is not limited.

  In order to apply by an ink jet printer system, the electrode active material dispersion is preferably in the range of 0.1 to 5 wt%. This is because if the content is less than 0.1 wt%, the dispersibility deteriorates and it may not be able to withstand long-term storage. On the other hand, if it exceeds 5 wt%, the relative amount of the active material decreases, and the efficiency for producing the electrode is poor. The dispersion material may be a single material or a plurality of materials. Further, NMP can be used as the ink solvent, but is not limited thereto. The invention achieves the object of the present invention as long as it has properties such as volatilization by heat treatment after application of the ink, and high compatibility with the active material and the dispersion material, and the active material and the dispersion material can be mixed well. . On the other hand, when coating with a coater or the like without using an ink jet printer method, the smaller the amount of the dispersing material, the better the coating efficiency and the amount of the active material of the electrode can be increased.

  According to the electrode structure according to the present invention created as described above, the electrode material 220 is formed on the base material such as the current collector 210 so that at least the electrode surface side is divided into two or more regions. Since the electrode active material is laminated and formed so that the groove 230 having a depth more than half of the average electrode thickness exists on the electrode surface, if a micro short-circuit occurs, self-discharge caused by the micro short-circuit occurs. The amount of the electrode can be reduced, and the fine groove 230 suppresses the deterioration of the electrode structure due to the elongation during heat application due to the difference in the coefficient of linear expansion between the current collector 210 and the electrode material 220. By forming the region divided by the groove 230 on the electrode surface while controlling it, physical deterioration of the electrode material 220 at the time of vibration input can be reduced. As described above, in order to manufacture the electrode structure according to the present invention, it is desirable to use a method of extruding fine coated fine particles independently for each single particle by a volume change of the piezoelectric element, for example, an inkjet printer method, By using this method, an extremely thin electrode can be formed while having a fine groove 230 on the electrode surface, and therefore, the secondary battery 10 with high output and high reliability can be obtained.

  As shown in FIG. 11, a plurality of the secondary batteries 10 are connected in series or in parallel to form an assembled battery 250 and are housed in an external case 270 in a state where the terminals 260 are led out, and are assembled battery modules 280. Can be configured. Further, a plurality of the assembled battery modules 280 may be connected in series or in parallel to form the composite assembled battery 300.

  FIG. 12 shows a plan view (FIG. A), a front view (FIG. B), and a side view (FIG. C) of the composite assembled battery 300, but the assembled battery module 280 is an electrical device such as a bus bar. The battery module 280 is connected to each other using the connecting means, and the assembled battery module 280 is stacked in a plurality of stages using the connecting jig 310 and the fixing screw 320. How many secondary batteries 10 are connected to create the assembled battery module 280 and how many assembled battery modules 280 are stacked to create the composite assembled battery 300 depend on the vehicle (electric vehicle) ) Can be determined according to the battery capacity and output. In FIG. 12, reference numeral 330 denotes an external cushion material.

  Thus, the assembled battery 300 in which a plurality of assembled battery modules 280 are connected in series and parallel can obtain a high capacity and high output, and the reliability of each assembled battery module 280 is high. Long-term reliability of the battery 300 can be maintained. Even if some of the assembled battery modules 280 fail, the repair can be performed by simply replacing the failed part.

  In order to mount the composite battery pack 300 on the electric vehicle 400, it is mounted under the seat at the center of the vehicle body of the electric vehicle 400 as shown in FIG. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the composite battery pack 300 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 400 using the composite assembled battery 300 as described above has high durability and can provide sufficient output even when used for a long period of time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and running performance.

  In the present invention, not only the composite battery pack 300 but also only the battery pack module 280 may be mounted depending on the usage, or the composite battery pack 300 and the battery pack module 280 may be mounted in combination. It may be. Further, as the vehicle on which the assembled battery or the assembled battery module of the present invention can be mounted, the above-described electric vehicle and hybrid car are preferable, but are not limited thereto. For example, the present invention can be applied to other vehicles such as trains.

  Examples of the present invention will be described in detail below, but the present invention is not limited to these examples.

  In the following Examples 1 to 17, unless otherwise specified, as a polymer electrolyte raw material, a lithium salt, a positive electrode active material, a negative electrode active material, and a photopolymerization initiator constituting a power generation element of a secondary battery The following materials are used.

(1) Polymer electrolyte raw material: Macromer of ethylene oxide and propylene oxide (2) Lithium salt: LiN (SO ₂ C ₂ F ₅ ) ₂ (hereinafter referred to as “BETI”)
(3) Positive electrode active material: spinel type LiMn ₂ O ₄ (positive electrode 1: average particle diameter 0.2 μm, positive electrode 2: 1 μm). Here, the positive electrode 2 was pulverized by a wet pulverization method using an average particle diameter of 1 μm as a starting material to obtain a material having an average particle diameter.

(4) Negative electrode active material: pulverized graphite (average particle size: 0.2 μm)
(5) Photopolymerization initiator: benzyl dimethyl ketal In addition, the polymer electrolyte raw material was synthesize | combined according to the method of Unexamined-Japanese-Patent No. 2002-110239. Moreover, preparation, printing, and battery assembly of the negative electrode ink, the positive electrode ink, and the electrolyte ink were performed in a dry atmosphere with a dew point of −30 ° C. or less.

Example 1
7% by mass of a positive electrode active material, 2% by mass of acetylene black as a conductive material, and 1% by mass of a dispersant were dissolved in an NMP solvent. After sufficient stirring, the mixture was allowed to stand for several hours, and other than the precipitate was filtered with a filter to prepare a slurry as a positive electrode ink. The viscosity of this positive electrode ink was about 0.5 Ps.

  9% by mass of the negative electrode active material and 1% by mass of Dispersant 1 were dissolved in an NMP solvent. After sufficient stirring, the mixture was allowed to stand for several hours, and other than the precipitate was filtered with a filter to prepare a slurry as a negative electrode ink. This negative electrode ink had a viscosity of about 0.3 Ps.

  A positive electrode was prepared based on the following procedure using the prepared ink and a commercially available ink jet printer. When the above ink was used, there was a problem that acetonitrile as a solvent softened the plastic part in the ink introduction part of the ink jet printer. Therefore, the parts in the ink introduction part were replaced with metal parts, and ink was supplied directly from the ink reservoir to the metal parts. Further, since there was a concern that the active material of the ink 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 producing the positive electrode layer, the above positive electrode ink was used. The positive electrode layer was produced by printing the electrode structure of the said A-G pattern (refer FIGS. 7-9) produced on the computer using the inkjet printer. In addition, since it was difficult to supply metal foil directly to a printer, these were affixed on the A4 quality paper and supplied to the printer for printing.

  In the electrode structure of the F pattern (see FIG. 9), the short side was set to 50 μm, the long side was set to 100 μm, the groove depth was set to 70% of the thickness, and the groove width was set to about 1 μm.

  The positive electrode ink was introduced into the ink-jet printer having the above-described devices, and a pattern structure created on a computer was printed on an aluminum foil having a thickness of 20 μm as a current collector. The volume of positive ink ink particles ejected from the ink jet printer was about 2 picoliters (pL). A positive electrode layer having a desired thickness was formed by printing the positive ink several times on the same surface. The thickness of each electrode material was about 10 μm. After printing, in order to dry the solvent, drying was performed in a vacuum oven at 60 ° C. for 2 hours.

  The same operation was performed on the surface of the current collector opposite to the positive electrode layer, whereby a positive electrode having a positive electrode layer formed on both surfaces of the current collector was obtained. Thereafter, the positive electrode was cut to a predetermined battery size.

  Thereafter, a negative electrode was prepared in the same manner.

  A battery was configured with two positive electrodes and three negative electrodes having an F-pattern electrode structure obtained in this manner, and a laminate material as an exterior. As the electrolytic solution, a 1: 1 solution of EC + PC was used. Similarly, a battery was constructed by using the aforementioned gel polymer.

(Example 2)
An electrode was prepared in the same manner as in Example 1 except that the groove depth on the electrode surface was 50% of the average electrode thickness.

(Example 3)
An electrode was prepared in the same manner as in Example 1 except that the groove depth on the electrode surface was set to 100% of the average electrode thickness.

Example 4
An electrode was prepared in the same manner as in Example 1 except that the rectangular parallelepiped region divided by the fine grooves had a short side of 10 μm and a long side of 20 μm.

(Example 5)
An electrode was prepared in the same manner as in Example 1 except that the rectangular parallelepiped-shaped region divided by the fine grooves had a short side of 200 μm, a long side of 200 μm, and a groove width of about 10 μm.

(Example 6)
An electrode was prepared in the same manner as in Example 1 except that the rectangular parallelepiped region divided by the fine grooves had a short side of 500 μm and a long side of 500 μm.

(Example 7)
An electrode was prepared in the same manner as in Example 1 except that the A-pattern electrode structure (see FIG. 7) was used.

(Example 8)
An electrode was prepared in the same manner as in Example 1 except that the electrode structure of A ′ pattern (see FIG. 7) was used.

Example 9
An electrode was prepared in the same manner as in Example 1 except that the B-pattern electrode structure (see FIG. 7) was used.

(Example 10)
An electrode was prepared in the same manner as in Example 1 except that the electrode structure having the B ′ pattern (see FIG. 7) was used.

(Example 11)
An electrode was prepared in the same manner as in Example 1 except that the C-pattern electrode structure (see FIG. 8) was used.

(Example 12)
An electrode was prepared in the same manner as in Example 1 except that the C ′ pattern electrode structure (see FIG. 8) was used.

(Example 13)
An electrode was prepared in the same manner as in Example 1 except that the D-pattern electrode structure (see FIG. 8) was used.

(Example 14)
An electrode was prepared in the same manner as in Example 1 except that the D ′ pattern electrode structure (see FIG. 8) was used.

(Example 15)
An electrode was prepared in the same manner as in Example 1 except that the E-pattern electrode structure (see FIG. 9) was used.

(Example 16)
An electrode was prepared in the same manner as in Example 1 except that the E ′ pattern electrode structure (see FIG. 9) was used.

(Example 17)
Initially, an electrode pattern was not formed, but after applying an electrode material by an ink jet printer, the electrode surface was shaved with a microcutter having a groove width of about 200 μm, and a G pattern electrode having a short side of 20 mm, a long side of 40 mm, and a groove width of 100% An electrode was prepared in the same manner as in Example 1 except that the structure was prepared by post-processing.

(Comparative example)
The ink slurry was applied to a metal foil with a bar coater to a thickness of about 10 μm to produce an electrode having a smooth electrode surface.

  About the above Examples 1-17 and a comparative example (conventional example), the self-discharge improvement rate (%), the average decay rate (%), and the decay rate after heating (%) were measured. The results are shown in Table 1 below.

[Self-discharge improvement rate]
The battery obtained in the comparative example (conventional example) was charged to 4.2 V and then left at room temperature. The voltage measured after about one month was used as the reference voltage. Thereafter, the batteries prepared in each Example were measured in the same manner, and the difference with respect to the reference voltage was defined as% improvement. Therefore, for example, the self-discharge improvement rate of 35% means that the voltage has decreased only to 65% when the voltage decrease rate of the reference electrode is 100%. That is, according to Examples 1-17, as shown in Table 1, it can confirm that the ratio of the self-discharge was reduced.

[Average reduction rate]
An acceleration pickup was set at a substantially central portion of the battery obtained by the method of each of the above embodiments, and the vibration spectrum of the acceleration pickup when hammered by an impulse hammer was measured. The setting method conformed to JIS B0908 (vibration and impact pickup calibration method / basic concept). The measured spectrum was analyzed by an FFT analyzer and converted to frequency and acceleration dimensions. The obtained frequency was averaged and smoothed to obtain a vibration transmissibility spectrum. The area ratio of the first peak of this acceleration spectrum with respect to the comparative example of the conventional example was taken as the average attenuation rate. A larger value means that vibration is reduced. That is, according to Examples 1 to 17, as shown in Table 1, good attenuation characteristics are shown.

[Attenuation rate after heating]
In accordance with the thermal cycle test defined in JIS C5961, 100 cycles of −25 ° C. (1 hour) and −60 ° C. (1 hour) were performed, and then the average attenuation rate was measured. That is, according to Examples 1 to 17, as shown in Table 1, good post-heating attenuation characteristics are shown.

  According to the present invention, it is possible to achieve a long battery life by forming a groove deeper than half of the average electrode thickness on the electrode surface and setting two or more regions divided at least on the electrode surface side. In addition, the vibration isolation can be improved, which is very useful for improving the reliability of secondary batteries such as bipolar batteries.

It is a top view, a side view, and a cross-sectional view of the secondary battery according to the present embodiment. It is a top view of an electrode structure concerning the present invention, and an A-A 'line sectional view. It is a figure explaining the movement state of the electron at the time of a micro short circuit. It is a figure explaining the absorption condition of distortion of a linear expansion coefficient. It is a schematic diagram which shows the depth of the groove | channel on the electrode surface. It is a figure explaining the vibration damping effect of the electrode structure which concerns on this invention. It is a schematic diagram which shows the example of a setting of a fine groove | channel. It is a schematic diagram which shows the example of a setting of a fine groove | channel. It is a schematic diagram which shows the example of a setting of a fine groove | channel. It is explanatory drawing which shows the spectrum of a vibration. It is a schematic block diagram of an assembled battery. It is a schematic block diagram of a composite assembled battery. It is a figure which shows the state with which the assembled battery was mounted in the vehicle.

Explanation of symbols

10 Secondary battery,
20A positive electrode tab,
20B negative electrode tab,
30 power generation elements,
40 exterior materials,
50 heat fusion,
110 negative electrode current collector,
120 electrolyte layer,
130 positive electrode current collector,
150 cells,
170 Connection between the tab and the current collector,
180 current collector width,
190 tab width,
200 electrodes,
210 current collector,
220 electrode material,
230 grooves,
250 battery packs,
260 terminals,
270 outer case,
280 battery module,
300 composite battery pack,
310 connection jig,
320 fixing screw,
330 external cushion,
400 Electric car.

Claims (4)

The electrode active material is laminated on the substrate so that at least a partial region on the electrode surface side is divided into two or more regions, and the partial region has at least half of the average electrode thickness on the electrode surface. The partial region having a groove having a depth and having the groove on the electrode surface side has a shape located along a line connecting vertices passing through the center of gravity of the electrode surface, or is formed on the electrode surface. It is a shape located along the line connecting the middle points passing through the center of gravity, or a shape located along the line connecting the vertices and the middle points passing through the center of gravity of the electrode surface, and the partial area is , electrode structure from one end to the other end of the electrode surface is characterized Rukoto formed by grooves that are not contiguous. Electrode structure according to claim 1 in which each area divided by the groove in the part of the region is characterized by having a rectangular parallelepiped shape.   3. The electrode structure according to claim 2, wherein a length of a short side of the rectangular parallelepiped region is in a range of 10 to 200 μm.   The depth of the said groove | channel is 70 to 100% of electrode average thickness, The electrode structure of any one of Claims 1-3 characterized by the above-mentioned.

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