JP2012043753A - Lithium ion secondary battery and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery whose electrode core material and a mixture layer formed thereon have a sufficient peel strength and a method of manufacturing the same.SOLUTION: In preparing cathode coating liquid, a cathode active material grain PX in large particle size, as well as a cathode active material in ordinary particle size, are dispersed in a solvent. This large particle size is 90% or more in diameter of the overall thickness of a cathode mixture layer PA after a cathode core material PB has had cathode coating liquid applied thereto and dried and was then roll-pressed. The cathode coating liquid prepared that way is used to create a cathode plate P. Cathode active material grains PX are embedded into the cathode core material PB as it is subjected to a roll press. The same applies to an anode too.

Description

  The present invention relates to a lithium ion secondary battery and a method for manufacturing the same. More specifically, the present invention relates to a lithium ion secondary battery having a sufficient peel strength between an electrode core material and a composite material layer formed thereon and a method for manufacturing the same.

  In a lithium ion secondary battery, an electrode plate (a positive electrode plate and a negative electrode plate) in which an active material is applied to an electrode core material (a positive electrode core material and a negative electrode core material) such as a metal foil may be used. In the manufacture of such an electrode plate, a coating liquid in which an active material and a binder are kneaded is applied to both surfaces of the electrode core material, and then the coating layer (mixture layer) is dried. This binder is for binding an active material layer to the electrode core.

  The electrode plate manufactured in this way may be peeled off near the boundary between the electrode core material and the composite material layer in subsequent manufacturing processes (such as a winding process and a can insertion process). When the composite material layer is peeled off, charge transfer between the peeled composite material layer and the electrode core material hardly occurs. Along with this, the exchange of lithium ions hardly occurs between the composite layer and the electrolyte. For this reason, the current collecting property in the separated composite layer is significantly reduced. Therefore, the composite layer of the electrode plate needs to have a certain degree of peel strength.

  Further, in the composite material layer, the volume of the active material is repeatedly changed due to insertion and extraction of ions during use as a battery. If the peel strength is low, the composite layer may peel microscopically due to the volume change of the active material. In the exfoliated mixture layer, there is almost no chemical reaction on the surface of the active material. That is, the battery performance decreases. For this reason, it is necessary to make the peeling strength of a compound material layer high.

  To increase the peel strength, there is a method to increase the binder. In addition, there is a method using an active material having a small active material specific surface area, that is, an active material having a large particle size. Furthermore, as in Patent Document 1, it is conceivable to subject the electrode core material to a roughening treatment. According to Patent Document 1, the unevenness on the surface of the roughened electrode core material bites into the composite material layer, and the anchor effect is exhibited (see paragraph [0015] of Patent Document 1). As a result, the composite material layer is unlikely to peel off.

JP 2009-215604 A

  However, increasing the amount of the binder increases the volume of the electrode body. That is, the volume energy density is low. Also, the binder can be a cause of hindering the movement of charges. For this reason, the internal resistance of a battery using an electrode plate with a large amount of binder is large. In addition, the reaction area of an active material having a small active material specific surface area is smaller than the reaction area of an active material having a large active material specific surface area. In other words, the electrode reaction hardly occurs on the surface. And like patent document 1, performing a roughening process to an electrode core means that the manufacturing process of an electrode core increases. That is, the manufacturing cost is high.

  The present invention has been made to solve the above-described problems of the prior art. That is, the problem is to provide a lithium ion secondary battery having sufficient peel strength between the electrode core material and the composite layer formed thereon, and a method for manufacturing the lithium ion secondary battery.

  The lithium ion secondary battery according to one aspect of the present invention, which has been made for the purpose of solving this problem, includes a positive electrode plate having a positive electrode mixture layer formed on at least one surface of the positive electrode core material, and at least one side of the negative electrode core material. It has a negative electrode plate having a negative electrode mixture layer formed on its surface and a separator disposed between the positive electrode plate and the negative electrode plate. And at least one of the positive electrode composite material layer and the negative electrode composite material layer includes particles having a diameter of 90% or more of the film thickness of the composite material layer. In such a lithium ion secondary battery, the peel strength of the composite material layer containing the particles is high. Therefore, the battery performance hardly deteriorates due to the peeling of the composite material layer.

  In the lithium ion secondary battery described above, the ratio Y / X of the weight Y of the binder to the weight X of the active material is preferably 0.05 or less in the composite layer containing the particles. This is because the peel strength of the electrode plate of the lithium ion secondary battery is high without increasing the amount of the binder.

  In the lithium ion secondary battery described above, in the mixture layer containing particles, the amount of particles mixed is in the range of 1 to 5% of the total weight of the mixture layer containing particles. It should be within. This is because the peel strength of the composite layer is sufficient and the density of the active material is sufficient.

  In the lithium ion secondary battery described above, the particles may be a positive electrode active material covered with a conductive film. This is because the positive electrode active material layer has a sufficient density of the positive electrode active material.

  In the lithium ion secondary battery described above, the particles may be aggregates in which conductive materials are aggregated. This is because the conductivity of the positive electrode mixture layer of the positive electrode plate is sufficient.

  Further, the battery manufacturing method according to still another aspect of the present invention includes a positive electrode coating liquid preparation step of preparing a positive electrode coating liquid in which at least a positive electrode active material and a binder are mixed in a solvent, and at least a positive electrode core material. A positive electrode plate coating and drying step in which a positive electrode coating solution is applied to one side and then dried to form a positive electrode plate; a positive electrode plate pressing step in which the positive electrode plate is roll-pressed; and at least a negative electrode active material and a binder; A negative electrode coating liquid preparation step for preparing a negative electrode coating liquid mixed with a solvent, and a negative electrode plate coating and drying process by coating the negative electrode coating liquid on at least one surface of the negative electrode core material and then drying it. A negative electrode plate pressing step in which the negative electrode plate is roll-pressed, a laminated electrode body forming step in which a positive electrode plate and a negative electrode plate are laminated with a separator interposed therebetween, and a laminated electrode body Insert into the battery container and inject electrolyte A method and a battery assembly step of sealing. And at least one of the positive electrode coating liquid preparation process and the negative electrode coating liquid preparation process is 1-1 of the thickness of the composite layer of the positive electrode plate after the positive electrode plate pressing step or the negative electrode plate after the negative electrode plate pressing step. Mix particles with a diameter of 5 times in a solvent to prepare a coating solution. In such a battery manufacturing method, a battery having a high peel strength of the composite material layer can be manufactured. Therefore, in the battery manufactured in this way, the battery performance hardly deteriorates due to the peeling of the composite material layer.

  In the battery manufacturing method described above, in at least one of the positive electrode coating liquid preparation step and the negative electrode coating liquid preparation step, the ratio Y / X of the weight Y of the binder to the weight X of the active material is 0.05. A coating solution may be prepared as follows. This is because a battery including an electrode plate with sufficient peel strength can be manufactured without increasing the amount of the binder.

  In the battery manufacturing method described above, at least one of the positive electrode coating liquid preparation step and the negative electrode coating liquid preparation step, the amount of particles mixed in the solvent is set to the total weight of the solute material mixed in the solvent. It is good to make a coating liquid as 1 to 5% of range. This is because it is possible to manufacture a battery in which the peel strength of the composite layer is sufficient and the density of the active material is sufficient.

  In the battery manufacturing method described above, a positive electrode active material covered with a conductive film may be used as the granular material in the positive electrode coating liquid preparation step. This is because it is possible to manufacture a battery in which the peel strength of the composite layer is sufficient and the density of the active material is sufficient.

  In the battery manufacturing method described above, in the positive electrode coating liquid preparation step, an aggregate in which conductive materials are aggregated may be used as the granular body. This is because a battery in which the positive electrode mixture layer of the positive electrode plate has sufficient conductivity can be manufactured.

  ADVANTAGE OF THE INVENTION According to this invention, the lithium ion secondary battery with sufficient peeling strength of an electrode core material and the composite material layer formed in it, and its manufacturing method are provided.

It is sectional drawing for demonstrating the structure of the lithium ion secondary battery which concerns on embodiment. It is a perspective view for demonstrating the winding electrode body and current collecting plate of the lithium ion secondary battery which concern on embodiment. It is an expanded view for demonstrating the winding structure of the lithium ion secondary battery which concerns on embodiment. It is a perspective sectional view for explaining the positive electrode plate and the negative electrode plate of the lithium ion secondary battery according to the first embodiment. It is a schematic block diagram for demonstrating the electrode manufacturing apparatus used for the manufacturing method of the lithium ion secondary battery which concerns on embodiment. It is a perspective sectional view showing a thing in the middle of preparation of a positive electrode plate and a negative electrode plate used for a lithium ion secondary battery concerning an embodiment. It is a schematic block diagram for demonstrating the winding apparatus used for the manufacturing method of the lithium ion secondary battery which concerns on embodiment. It is a perspective sectional view for explaining a positive electrode plate and a negative electrode plate of a lithium ion secondary battery according to a second embodiment.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In the present embodiment, the present invention is embodied with respect to a lithium ion secondary battery and a manufacturing method thereof.

(First embodiment)
1. Lithium ion secondary battery The battery according to the present embodiment is a cylindrical lithium ion secondary battery. FIG. 1 shows a cross-sectional view of the battery 10 of the present embodiment. As shown in FIG. 1, the battery 10 is sealed by a battery case including a battery container 11 and a lid 12. The battery 10 includes a wound electrode body 100, a positive current collector 110, and a negative current collector 120. In addition, an electrolytic solution is injected into the battery container 11.

  The wound electrode body 100 repeats charging and discharging in the electrolytic solution and directly contributes to power generation. The positive electrode current collector plate 110 is a positive electrode current collector connected to a positive electrode core material of a wound electrode body 100 described later. The material is aluminum. The negative electrode current collector plate 120 is a negative electrode current collector connected to a negative electrode core material of a wound electrode body 100 described later. Its material is copper. FIG. 2 is a perspective view of the wound electrode body 100 extracted from FIG. 1 to which the positive electrode current collector plate 110 and the negative electrode current collector plate 120 are connected.

The electrolyte injected into the battery container 11 is obtained by dissolving an electrolyte in an organic solvent. Examples of organic solvents include ester solvents such as propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), ester solvents such as γ-butylactone (γ-BL), di- An organic solvent containing an ether solvent such as ethoxyethane (DEE) can be used. As the electrolyte salt, lithium salts such as lithium perchlorate (LiClO ₄ ), lithium borofluoride (LiBF ₄ ), and lithium hexafluorophosphate (LiPF ₆ ) can be used.

  FIG. 3 is a development view showing a wound structure of the wound electrode body 100. As shown in FIG. 3, the wound electrode body 100 is wound in a state where the positive electrode plate P, the separator S, the negative electrode plate N, and the separator T are stacked in this order from the inside. Here, the separator S and the separator T are made of the same material. For the understanding of the above winding order, only the codes are distinguished as S and T.

  The positive electrode plate P is obtained by applying a composite material containing a positive electrode active material capable of inserting and extracting lithium ions to an aluminum foil as a positive electrode core material. The surface of the positive electrode active material may be coated with a conductive material such as a carbon material. The negative electrode plate N is obtained by applying a composite material containing a negative electrode active material capable of occluding and releasing lithium ions to a copper foil as a negative electrode core material.

  As shown in FIG. 3, the positive electrode plate P has a positive electrode coating portion P1 and a positive electrode non-coating portion P2. The positive electrode coating part P1 is a place where a positive electrode active material or the like is applied to the positive electrode core material. The positive electrode non-coating portion P2 is a portion where a positive electrode active material or the like is not applied to the positive electrode core material. Therefore, the thickness of the positive electrode coating part P1 is thicker than the thickness of the positive electrode non-coating part P2.

  The negative electrode plate N includes a negative electrode coating portion N1 and a negative electrode non-coating portion N2. The negative electrode coating portion N1 is a portion where a negative electrode active material or the like is applied to the negative electrode core material. The negative electrode non-coating portion N2 is a portion where a negative electrode active material or the like is not applied to the negative electrode core material. Therefore, the thickness of the negative electrode coating part N1 is thicker than the thickness of the negative electrode non-coating part N2.

  An arrow A in FIG. 3 indicates the width direction (vertical direction in FIG. 2) of the positive electrode plate P, the negative electrode plate N, and the separators S and T. An arrow B in FIG. 3 indicates the longitudinal direction of the positive electrode plate P, the negative electrode plate N, and the separators S and T (the circumferential direction of the wound electrode body 100 in FIG. 2).

  FIG. 4 is a perspective sectional view of the positive electrode plate P (or the negative electrode plate N). In FIG. 4, each symbol outside the parentheses indicates each part in the case of the positive electrode, and each symbol in the parenthesis indicates each part in the case of the negative electrode. The direction indicated by arrow A in FIG. 4 is the same as the direction indicated by arrow A in FIG. That is, it is the width direction of the positive electrode plate P. The direction indicated by arrow B in FIG. 4 is the same as the direction indicated by arrow B in FIG. That is, it is the longitudinal direction of the positive electrode plate P.

  As shown in FIG. 4, the positive electrode plate P is obtained by forming a positive electrode mixture layer PA on a part of both surfaces of a strip-like positive electrode core material PB. On the left side in FIG. 4, a positive electrode non-coated portion P2 of the positive electrode plate P protrudes in the width direction. The positive electrode non-coated portion P2 is formed in a strip shape. The positive electrode non-coated portion P2 is a region where the positive electrode active material is not applied to both surfaces of the positive electrode core material PB. Therefore, in the positive electrode non-coating portion P2, the positive electrode core material PB is still exposed. On the other hand, on the right side in FIG. 4, there is no protrusion corresponding to the positive electrode non-coated portion P2. In the positive electrode coating part P1, the positive electrode mixture layer PA is formed with a uniform thickness on both surfaces of the positive electrode core material PB.

  As shown in FIG. 4, positive electrode active material particles PX are contained in the positive electrode mixture layer PA. The positive electrode active material particles PX are positive electrode active materials having a larger particle diameter than other positive electrode active materials. That is, the material is the same, but only the particle size is different. The particle diameter of the positive electrode active material particles PX is substantially the same as the film thickness of the positive electrode mixture layer PA. More specifically, the particle diameter of the positive electrode active material particles PX is 90% or more of the total thickness of the positive electrode mixture layer PA.

  As shown in parentheses in FIG. 4, the negative electrode plate N is obtained by forming a negative electrode mixture layer NA on part of both surfaces of a strip-shaped negative electrode core material NB. Similarly to the positive electrode, there are a negative electrode coating portion N1 and a negative electrode non-coating portion N2. However, as shown in FIG. 3, at the time of winding, the positive electrode non-coated portion P2 and the negative electrode non-coated portion N2 are wound in a state of protruding to the opposite side.

  As shown in FIG. 4, negative electrode active material particles NX are included in the negative electrode mixture layer NA. The negative electrode active material granule NX is a negative electrode active material having a larger particle size than other negative electrode active materials. That is, the material is the same, but only the particle size is different. The particle diameter of the negative electrode active material granules NX is substantially the same as the film thickness of the negative electrode mixture layer NA. More specifically, the particle diameter of the negative electrode active material granules NX is a value of 90% or more of the total thickness of the negative electrode mixture layer NA.

2. Method for Manufacturing Battery The method for manufacturing a lithium ion secondary battery according to the present embodiment includes the following steps.
(A) Electrode plate making process (A-1) Coating liquid creating process (A-2) Coating drying process (A-3) Pressing process (B) Laminated electrode body creating process (C) Battery assembly process

(A) Electrode plate preparation process Here, an electrode plate preparation process is demonstrated. The electrode plate creation process includes a coating liquid creation process, a coating drying process, and a pressing process.

(A-1) Coating liquid preparation process (A-1-1) Positive electrode coating liquid preparation process In a coating liquid preparation process, the coating liquid for positive electrodes and the coating liquid for negative electrodes are created. First, a method for preparing a positive electrode coating solution will be described. The positive electrode coating solution is prepared by stirring the solute material for the positive electrode in a solvent. Here, the solute material for the positive electrode is a positive electrode active material including the positive electrode active material particles PX, a conductive material, a binder, and a thickener. The particle size of the positive electrode active material particles PX is 1 to 1.5 times the film thickness of the positive electrode mixture layer PA after the (A-3) pressing step. And the weight Y of the binder put into the solvent is 0.05 or less of the weight X of the positive electrode active material put into the solvent.

The positive electrode active material is a material that can occlude / release lithium ions in the aluminum foil that is the positive electrode core material PB. As the positive electrode active material, lithium composite oxides such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), lithium cobaltate (LiCoO ₂ ), and lithium iron phosphate (LiFePO ₄ ) are used. These are preferably covered with a conductive film.

  Carbon materials such as carbon powder and carbon fiber can be used as the conductive material for the positive electrode. For example, carbon powder such as acetylene black, furnace black, ketjen black, etc., graphite powder, etc.

  The binder for the positive electrode is preferably a polymer that is insoluble (or hardly soluble) in the electrolyte and is dispersed in the solvent used for the positive electrode paste. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoro Fluorine resin such as ethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene rubber (SBR), acrylic acid-modified SBR resin (SBR latex), rubber such as gum arabic can be used. Alternatively, a combination of these may be used. The binder is not necessarily limited to the above polymer.

  As the thickener for the positive electrode, cellulose such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), hydroxypropylmethylcellulose phthalate (HPMCP) or the like is used. However, it is not necessarily limited to cellulose as described above, and can be used.

  An example of the solvent is water. In addition, N-methyl-2-pyrrolidone (NMP, hereinafter referred to as NMP) may be used. Other lower alcohols and lower ketones can also be used.

(A-1-2) Negative electrode coating liquid preparation step Subsequently, a method of preparing the negative electrode coating liquid will be described. The negative electrode coating solution is prepared by stirring the solute material for the negative electrode in a solvent. Here, the solute material for the negative electrode is a negative electrode active material, a binder, and a thickener including the negative electrode active material particles NX. The particle diameter of the negative electrode active material granules NX is 1 to 1.5 times the film thickness of the negative electrode mixture layer NA after the (A-3) pressing step. And the weight Y of the binder put into the solvent is 0.05 or less of the weight X of the negative electrode active material put into the solvent.

  The negative electrode active material is a material that can occlude and release lithium ions. As the negative electrode active material, a carbon-based material containing a graphite structure at least partially is used. For example, amorphous carbon, non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), graphite (graphite), or a carbon material having a combination thereof can be used.

  The binder for the negative electrode may be a polymer that is insoluble (or hardly soluble) in the electrolyte and is dispersed in the solvent used for the negative electrode paste. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoro Fluorine resin such as ethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene rubber (SBR), acrylic acid-modified SBR resin (SBR latex), rubber such as gum arabic can be used. Alternatively, a combination of these may be used. The binder is not necessarily limited to the above polymer.

  As the thickener for the negative electrode, cellulose such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), and hydroxypropylmethylcellulose phthalate (HPMCP) is used. However, it is not necessarily limited to cellulose as described above, and can be used.

  An example of the solvent is water. NMP may be used. Other lower alcohols and lower ketones can also be used.

(A-2) Coating / drying step (A-2-1) Positive electrode plate coating / drying step A positive electrode plate PO shown in FIG. 6 is prepared using the electrode manufacturing apparatus 1000 shown in FIG. In FIG. 6, each symbol outside the parentheses indicates each part in the case of the positive electrode, and each symbol in the parenthesis indicates each part in the case of the negative electrode. First, as shown in FIG. 6, the positive electrode core material PB is sent out from the unwinding reel 1101 of the unwinding portion 1100. Next, the positive electrode coating liquid is applied to the positive electrode core material PB from the die 1210 of the coating unit 1200. During this coating, the backup roller 1220 is transporting while supporting the positive electrode core material PB.

  Next, the positive electrode core material PB coated with the coating liquid is conveyed into the drying furnace 1300. In the drying furnace 1300, the coating liquid applied to the positive electrode core material PB is dried. Specifically, hot air is blown from the air nozzle 1301 to the coating layer on the positive electrode core material PB. Alternatively, heating using infrared rays may be performed. In addition, another heating device can be used. In this way, the positive electrode mixture layer PA is formed on the positive electrode core material PB from which the coating liquid has been dried. Thereafter, the positive electrode core material PB on which the positive electrode mixture layer PA is formed is taken up by the take-up reel 1401 of the take-up unit 1400.

  An electrode manufacturing apparatus 1000 shown in FIG. 5 is an apparatus that coats and dries only one side of an electrode core material (a positive electrode core material and a negative electrode core material). Therefore, in order to apply both surfaces of the positive electrode core material PB, after forming the positive electrode mixture layer PA on one surface thereof, the positive electrode mixture layer PA may be formed on the opposite surface. That is, the negative electrode core material NB may be passed through the electrode manufacturing apparatus 1000 twice. Thereby, the positive electrode plate PO shown in FIG. 6 is produced.

  However, if an electrode manufacturing apparatus that coats and dries both sides instead of the electrode manufacturing apparatus 1000 of FIG. 5 is used, the number of times the positive electrode core material PB is passed through the electrode manufacturing apparatus 1000 may be one. The electrode manufacturing apparatus that performs the double-side coating may be any device as long as a die for coating on the surface opposite to the coating surface and a drying furnace downstream of the drying oven 1300 in FIG. 5 are arranged.

(A-2-2) Negative electrode plate coating / drying step The negative electrode plate NO can also be prepared in the same manner as the positive electrode plate PO. However, the negative electrode core material NB is used instead of the positive electrode core material PB, and the negative electrode coating liquid is used instead of the positive electrode coating liquid. Moreover, the drying conditions of the coating liquid applied to the negative electrode core material NB may be different from the drying conditions of the coating liquid applied to the positive electrode core material PB. Moreover, whichever order may be sufficient as the order which produces positive electrode plate PO and negative electrode plate NO.

(A-3) Pressing step (A-3-1) Positive electrode plate pressing step Subsequently, a roll press is applied to the positive electrode plate PO and the negative electrode plate NO that have undergone the coating and drying step. As shown in FIG. 6, a part of the positive electrode active material particles PX may protrude from the positive electrode active material layer PA of the positive electrode plate PO. Then, a roll press is applied to the positive electrode plate PO. Thereby, the positive electrode mixture layer PA is pressed in the film thickness direction. The positive electrode active material particles PX are also pressed in the same manner. However, the positive electrode active material particles PX have a hardness that does not crush when compressed by the pressing process. Then, the positive electrode active material particles PX slightly sink into the positive electrode core material PB. Due to this anchor effect, the peel strength of the positive electrode plate PO becomes high. Then, the positive electrode plate PO is slit along the line L in FIG. Thereby, the positive electrode plate P is created.

(A-3-2) Negative electrode plate pressing step The negative electrode plate N can be prepared in the same manner as the positive electrode plate P.

(B) Laminate electrode body preparation process Then, the separators S and T are wound on the positive electrode plate P and the negative electrode plate N using the winding device 2000 shown in FIG. The winding device 2000 includes a positive electrode plate supply unit 2001, a negative electrode plate supply unit 2002, separator supply units 2003 and 2004, and a winding shaft 2005. Here, as shown in FIG. 3, the positive electrode plate P, the separator S, the negative electrode plate N, and the separator T are stacked and wound in order from the inside. The wound electrode body 100 is created by rotating the wound shaft 2005 in the direction of arrow F in FIG.

(C) Battery Assembly Step Subsequently, the wound electrode body 100 is inserted into the battery container 11. Then, an electrolytic solution is injected into the battery container 11. The lid 12 is then sealed. Thereby, the battery cell 10 of this embodiment is assembled. After this, it is advisable to perform processing such as conditioning and aging and various inspection processes. Through the above steps, the battery cell 10 of this embodiment is manufactured.

  As described above in detail, in the battery manufacturing method according to this embodiment, in the coating liquid preparation step, the positive electrode active material having a particle diameter of 1 to 1.5 times the film thickness of the positive electrode mixture layer PA after pressing. The positive electrode coating liquid was prepared by mixing the substance particles PX. Therefore, in the pressing process, the positive electrode active material particles PX are embedded in the positive electrode core material PB. Thereby, the positive electrode plate P with high peeling strength is produced. The same applies to the negative electrode plate N.

3. Summary As described above in detail, in the method of manufacturing a lithium ion secondary battery according to the present embodiment, the film thickness of the positive electrode mixture layer PA after pressing is changed to 1-1. The positive electrode active material particles PX having a particle size of 5 times were mixed to prepare a positive electrode coating solution. Therefore, in the pressing process, the positive electrode active material particles PX are embedded in the positive electrode core material PB. Thereby, the positive electrode plate P with high peeling strength is produced. The same applies to the negative electrode plate N. Thereby, the manufacturing method of the lithium ion secondary battery with which a composite material layer cannot peel easily from an electrode core material is implement | achieved.

  In the lithium ion secondary battery according to the present embodiment, positive electrode active material particles PX having a larger particle diameter than other positive electrode active materials are included in positive electrode mixture layer PA. The particle size of the positive electrode active material particles PX is a value of 90% or more of the total thickness of the positive electrode mixture layer PA. A part of the positive electrode active material particles PX is embedded in the positive electrode core material PB. The same applies to the negative electrode plate N.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, an electrode body used for a battery is not limited to a wound electrode body. Therefore, the present invention can be applied even to a battery having flat electrode bodies. Any secondary battery using stacked electrode bodies stacked and stacked can be applied. The present invention can be applied not only to a cylindrical battery but also to a square battery.

  In addition, the positive electrode mixture layer PA and the negative electrode mixture layer NA are formed on both sides of the positive electrode core material PB and the negative electrode core material NB, respectively. However, the composite material layer may be formed on only one side. The present invention can also be applied to a case where two or more composite layers are formed on at least one of the positive electrode plate and the negative electrode plate.

(Second Embodiment)
A second embodiment will be described. The lithium ion secondary battery according to this embodiment is different from the lithium ion secondary battery according to the first embodiment in the positive electrode plate. In the positive electrode mixture layer PA of the positive electrode plate P of this embodiment, an aggregate of conductive material is included instead of the positive electrode active material particles PX. Therefore, description of matters common to the first embodiment is omitted.

1. Lithium ion secondary battery The positive electrode plate PP of this embodiment is shown in FIG. The positive electrode plate PP has conductive material aggregated particles PY. As shown in FIG. 8, conductive material aggregated particles PY are contained in the positive electrode mixture layer PA. The conductive material aggregate PY is an aggregate formed by aggregating conductive materials. The particle size is substantially the same as the film thickness of the positive electrode mixture layer PA. More specifically, the particle diameter of the conductive material aggregated particles PY is 90% or more of the total thickness of the positive electrode mixture layer PA. That is, the particle diameter of the conductive material aggregated particles PY is approximately the same as the particle size of the positive electrode active material particles PX described in the first embodiment. In other respects, the battery of this embodiment is the same as the battery 10 of the first embodiment.

2. Manufacturing Method of Lithium Ion Secondary Battery The manufacturing method of the lithium ion secondary battery according to the present embodiment is substantially the same as that of the first embodiment. Only the coating liquid preparation process is different. In the coating liquid preparation process of this embodiment, the positive electrode active material particles PX are not mixed when the positive electrode coating liquid is prepared.

  Instead, when the materials are mixed in the solvent and kneaded, an aggregate of conductive material is created. Aggregates of conductive material are easily formed. For this reason, the conductive material aggregated particles PY can be created without particular conditions. In this way, a positive electrode coating liquid containing the conductive material aggregated particles PY is created.

3. Summary As described above in detail, in the method of manufacturing a lithium ion secondary battery according to the present embodiment, the film thickness of the positive electrode mixture layer PA after pressing is changed to 1-1. The conductive material agglomerate PY having a particle size 5 times larger was prepared. Therefore, in the pressing process, the conductive material aggregated particles PY are embedded in the positive electrode core material PB. Thereby, the positive electrode plate P with high peeling strength is produced. The negative electrode plate N is the same as in the first embodiment. Thereby, the manufacturing method of the lithium ion secondary battery with which a composite material layer cannot peel easily from an electrode core material is implement | achieved.

  Further, in the lithium ion secondary battery according to the present embodiment, conductive material aggregated particles PY are included in the positive electrode mixture layer PA. The particle size of the conductive material aggregated particles PY is a value of 90% or more of the total thickness of the positive electrode mixture layer PA. A part of the conductive material aggregated particles PY is embedded in the positive electrode core material PB.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, an electrode body used for a battery is not limited to a wound electrode body. Therefore, the present invention can be applied even to a battery having flat electrode bodies. Any secondary battery using stacked electrode bodies stacked and stacked can be applied. The present invention can be applied not only to a cylindrical battery but also to a square battery.

  In addition, the positive electrode mixture layer PA and the negative electrode mixture layer NA are formed on both sides of the positive electrode core material PB and the negative electrode core material NB, respectively. However, the composite material layer may be formed on only one side. The present invention can also be applied to a case where two or more composite layers are formed on at least one of the positive electrode plate and the negative electrode plate.

  Embodiments according to the present invention will be described below. Here, positive plates were prepared under various conditions. And the peeling strength of these positive electrode plates was measured.

1. Creation of battery 1-1. The materials listed in Table 1 were used as materials for the artificial graphite positive electrode coating solution. That is, lithium iron phosphate (LiFePO ₄ ), acetylene black (AB), and polyvinylidene fluoride (PVD)
F). Moreover, NMP was used as a dispersion solvent. And lithium iron phosphate (Li
FePO ₄ ), acetylene black (AB), and polyvinylidene fluoride (PVDF) were dispersed in a weight ratio of 93%, 5%, and 2%, respectively, to prepare a positive electrode coating solution. Here, what was carbon-coated was used as lithium iron phosphate (LiFePO ₄ ).

In preparing the positive electrode coating solution, artificial graphite was mixed in a weight ratio of (a) 0%, (b) 1%, (c) 5%, and (d) 10%. The particle size of artificial graphite is U. The thickness of the positive electrode mixture layer after pressing is V. Here, the value of the grain size U and the thickness V of the positive electrode mixture layer after pressing was selected so as to satisfy the following formula.
U = 1.2 x V
35 μm ≦ U ≦ 55 μm
30 μm ≦ V ≦ 50 μm

  The materials listed in Table 2 were used as materials for the negative electrode coating solution. That is, natural graphite, styrene butadiene rubber (SBR), and carboxymethyl cellulose (CMC). Moreover, NMP was used as a dispersion solvent. Then, natural graphite, styrene butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were dispersed in 95%, 2.5%, and 2.5% solvent, respectively, in weight ratio to prepare a negative electrode coating solution.

  The ratio between the theoretical capacity of the positive electrode plate prepared as described above and the theoretical capacity of the negative electrode plate is 1: 1.5. In addition, a polypropylene / polyethylene composite porous membrane was used as a separator.

[Table 1]
Material Substance Weight ratio (%)
Cathode active material LiFePO ₄ 93
Conductive material AB 5
Binder PVDF 2
Dispersion solvent NMP −

[Table 2]
Material Substance Weight ratio (%)
Negative electrode active material Natural graphite carbon material 95
Binder SBR 2.5
Thickener CMC 2.5
Dispersion solvent NMP −

1-2. Aggregate In Example 2, a positive electrode plate and a negative electrode plate were prepared in substantially the same manner as in Example 1. The difference is that instead of mixing artificial graphite having a large particle size, a positive electrode plate was prepared using a conductive material, that is, a positive electrode coating solution containing an aggregate of acetylene black. The diameter of the aggregate is U. Thereby, the peel strength was measured in two cases of (e) no aggregate and (f) aggregate.

2. Evaluation Method The battery once prepared as described above was disassembled, and the peel strength of the positive electrode plate was measured. In measuring the peel strength, a 90 ° peel test was performed. In this measuring method, a tape is applied to a positive electrode plate which is a test piece, and the tape is pulled in a 90 ° direction on the plate surface of the positive electrode plate. Thereby, the force required for the positive electrode mixture layer to peel from the positive electrode core material is measured.

3. Result 3-1. Table 3 shows the peel strength of the positive electrode plate mixed with artificial graphite having a large particle size. As shown in Table 3, the peel strength of the sample added with artificial graphite is higher than the peel strength of the sample not added with artificial graphite. And as the addition amount increases, the peel strength tends to increase. However, when artificial graphite is mixed, the density of the positive electrode active material is lowered accordingly. Therefore, it is preferable to mix about 1 to 5% by weight.

[Table 3]
Sample Amount added (% by weight) Peel strength (N / m)
(A) 0 4.35
(B) 1 7.65
(C) 5 10.12
(D) 10 11.13

3-2. Aggregates Table 4 shows the peel strength of the positive electrode plates prepared using the acetylene black aggregates prepared in the positive electrode coating solution. As shown in Table 4, the peel strength of the sample with the acetylene black aggregate is lower than the peel strength of the sample without the acetylene black aggregate. The sample (e) is substantially the same as the sample (a) in Table 3.

[Table 4]
Sample Presence / absence of aggregate Peel strength (N / m)
(E) No aggregate 4.35
(F) There is an aggregate 12.25

  As described above in detail, the peel strength of the electrode plate to be produced is improved by mixing an active material or agglomerate having a large particle size into the coating liquid.

DESCRIPTION OF SYMBOLS 10 ... Battery 11 ... Battery container 12 ... Cover 100 ... Winding electrode body 1000 ... Electrode manufacturing apparatus 2000 ... Winding apparatus P ... Positive electrode plate PA ... Positive electrode compound material layer PB ... Positive electrode core material P1 ... Positive electrode coating part P2 ... Positive electrode Non-coated portion PX ... Positive electrode active material particles PY ... Conductive material aggregated particles N ... Negative electrode plate NA ... Negative electrode mixture layer NB ... Negative electrode core material N1 ... Negative electrode coated portion N2 ... Negative electrode non-coated portion NX ... Negative electrode active Material granules S, T ... Separator

Claims (10)

A positive electrode plate having a positive electrode mixture layer formed on at least one surface of the positive electrode core material;
A negative electrode plate having a negative electrode mixture layer formed on at least one surface of the negative electrode core;
In a lithium ion secondary battery having a separator disposed between the positive electrode plate and the negative electrode plate,
At least one of the positive electrode mixture layer and the negative electrode mixture layer,
A lithium ion secondary battery comprising particles having a diameter of 90% or more of the thickness of the composite material layer. The lithium ion secondary battery according to claim 1,
In the composite layer containing the granules,
A lithium ion secondary battery, wherein the ratio Y / X of the weight Y of the binder to the weight X of the active material is 0.05 or less. The lithium ion secondary battery according to claim 1 or 2,
In the composite layer containing the granules,
The lithium ion secondary battery, wherein the mixing amount of the particles is in the range of 1 to 5% of the total weight of the composite layer containing the particles. A lithium ion secondary battery according to any one of claims 1 to 3,
The granules are
A lithium ion secondary battery, which is a positive electrode active material covered with a conductive film. A lithium ion secondary battery according to any one of claims 1 to 3,
The granules are
A lithium ion secondary battery, wherein the conductive material is an agglomerated aggregate. A positive electrode coating liquid preparation step for preparing a positive electrode coating liquid in which at least a positive electrode active material and a binder are mixed in a solvent;
A positive electrode plate coating and drying step in which at least one side of the positive electrode core material is coated with the positive electrode coating solution and then dried to form a positive electrode plate;
A positive electrode plate pressing step for applying a roll press to the positive electrode plate;
A negative electrode coating liquid preparation step of preparing a negative electrode coating liquid in which at least a negative electrode active material and a binder are mixed in a solvent;
A negative electrode plate coating drying step in which the negative electrode coating liquid is applied to at least one surface of the negative electrode core material and then dried to form a negative electrode plate;
A negative electrode plate pressing step for subjecting the negative electrode plate to a roll press;
A laminated electrode body creating step in which the positive electrode plate and the negative electrode plate are laminated with a separator sandwiched therebetween,
In a battery manufacturing method including a battery assembly step of inserting the laminated electrode body into a battery container and injecting an electrolyte to seal the battery,
At least one of the positive electrode coating liquid preparation step and the negative electrode coating liquid preparation step,
Coating by mixing particles having a diameter of 1 to 1.5 times the thickness of the positive electrode plate after the positive electrode plate pressing step or the composite material layer of the negative electrode plate after the negative electrode plate pressing step A method for producing a battery, comprising producing a liquid. A method of manufacturing a battery according to claim 6,
At least one of the positive electrode coating liquid preparation step and the negative electrode coating liquid preparation step,
A method for producing a battery, characterized in that a coating liquid is prepared with a ratio Y / X of the weight Y of the binder to the weight X of the active material being 0.05 or less. A method of manufacturing a battery according to claim 6 or 7,
At least one of the positive electrode coating liquid preparation step and the negative electrode coating liquid preparation step,
A method for producing a battery, characterized in that a coating liquid is prepared by setting an amount of the particles mixed in a solvent within a range of 1 to 5% of a total weight of a solute material mixed in the solvent. A method for manufacturing a battery according to any one of claims 6 to 8, comprising:
In the positive electrode coating liquid preparation step,
As the granules,
A method for producing a battery, comprising using a positive electrode active material covered with a conductive film. A method for manufacturing a battery according to any one of claims 6 to 8, comprising:
In the positive electrode coating liquid preparation step,
As the granules,
A method for manufacturing a battery, comprising using an aggregate in which conductive materials are aggregated.

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