JP2019207750A - Lithium ion battery - Google Patents

Abstract

To provide a lithium ion battery capable of inhibiting reduction in a battery characteristic by improving charging performance into a frame body of at least one of a positive electrode active material layer and a negative electrode active material layer.SOLUTION: On surfaces of a sheet-like positive electrode collector and negative electrode collector are formed along their margins an annular positive electrode frame body and negative electrode frame body, respectively. On inner sides of the positive electrode frame body and negative electrode frame body are formed a positive electrode active material layer and negative electrode active material layer, respectively. The positive electrode active material layer is a non-binding body of positive electrode active material particles; the negative electrode active material layer is a non-binding body of negative electrode active material particles. An inner wall surface of the positive electrode frame body, the positive electrode frame body's side in contact with the positive electrode active material layer, is formed as a surface not orthogonal to a separator's first surface in contact with the positive electrode active material layer and/or an inner wall surface of the negative electrode frame body, the negative electrode frame body's side in contact with the negative electrode active material layer, is formed as a surface not orthogonal to the separator's second surface in contact with the negative electrode active material layer.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lithium ion battery.

  Lithium ion (secondary) batteries have been widely used in various applications in recent years as high-capacity, small and lightweight secondary batteries. Among these, as a small and thin lithium ion battery, a positive electrode in which a positive electrode active material layer containing a positive electrode active material and an electrolyte solution is formed on the surface of the positive electrode current collector, and a negative electrode active material similarly containing a negative electrode active material and an electrolyte solution A negative electrode having a layer formed on the surface of the negative electrode current collector is laminated with a separator interposed therebetween to produce a substantially flat lithium secondary cell, and a plurality of the lithium secondary cells are laminated to form a laminated battery module A lithium ion battery configured as is conventionally known.

  In such a lithium ion battery, for the purpose of improving flex resistance, a sheet-like frame member surrounding the separator, the positive electrode active material layer, and the negative electrode active material layer is provided, and this frame member is a resin material having rubber elasticity. A lithium ion battery formed from the above has been proposed (see Patent Document 1).

JP 2006-338904 A JP 2017-147222 A

  One of the applicants of the present application aims to provide a lithium ion battery capable of achieving both flexibility and high capacity capable of exhibiting sufficient charge / discharge characteristics even when greatly deformed. A lithium ion battery that is a non-binding body of positive electrode active material particles and whose negative electrode active material layer is a non-binding body of negative electrode active material particles has been proposed (see Patent Document 2).

  Since the positive electrode active material layer and the negative electrode active material layer having such a configuration are not fixed by the electrode binder, the separator, the positive electrode active material layer, and the negative electrode active material layer are formed by the frame member as disclosed in Patent Document 1 described above. In order to manufacture the surrounding lithium ion battery, the positive electrode active material layer and the negative electrode active material layer may be filled in the frame member.

  However, in the above-described conventional lithium ion battery, since the angle formed between the inner wall and the separator surface at the contact portion between the inner wall of the frame member and the separator surface is substantially a right angle, the positive electrode active material layer and the negative electrode active material layer Depending on the fluidity, the positive electrode active material layer and the negative electrode active material layer may not be filled up to the contact portion between the inner wall of the frame member and the separator surface. In this case, there is a possibility that voids are generated in the positive electrode active material layer and the negative electrode active material layer, resulting in deterioration of battery characteristics.

  Therefore, the present invention provides a lithium ion battery capable of suppressing deterioration in battery characteristics by improving the filling property of at least one of the positive electrode active material layer and the negative electrode active material layer into the frame. It is the purpose.

  In order to achieve this object, the present invention includes a positive electrode in which a positive electrode active material layer is formed on the surface of a sheet-like positive electrode current collector, and a negative electrode active material layer formed on the surface of a sheet-like negative electrode current collector. In a lithium ion battery having a lithium secondary cell in which a negative electrode is laminated via a separator, the surface of the positive electrode current collector and the negative electrode current collector are respectively provided with an annular positive electrode frame along the edge thereof, and A negative electrode frame is formed, the positive electrode active material layer and the negative electrode active material layer are respectively formed inside the positive electrode frame and the negative electrode frame, and the positive electrode active material layer is a non-binding body of positive electrode active material particles. The material layer is a non-binding body of the negative electrode active material particles, and the inner wall surface of the positive electrode frame that is in contact with the positive electrode active material layer is a surface that is not orthogonal to the first surface of the separator that is in contact with the positive electrode active material layer. Formed and / or on the side in contact with the negative electrode active material layer The inner wall surface of the Fukyokuwaku body, characterized in that it is formed on a surface that is not orthogonal with respect to second surface in contact with the negative electrode active material layer of the separator.

  Here, in the present invention, the non-binding body means that the electrode active material is positioned in the active material layer with a known solvent (dispersion medium) dry-type lithium ion battery binder (also referred to as an electrode binder). It means not fixed irreversibly.

  Known binders for solvent (dispersion medium) dry type lithium ion batteries include starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose, polyvinylpyrrolidone, tetrafluoroethylene, styrene-butadiene rubber, polyethylene, polypropylene and styrene-butadiene. Known binders for lithium ion batteries such as copolymers can be mentioned.

These binders for lithium ion batteries are used by being dissolved or dispersed in water or an organic solvent, and they are dried and solidified by volatilizing the solvent (dispersion medium) component to fix the binder irreversibly. However, since the electrode active material is not fixed by the electrode binder in the non-binding body in the present invention, the electrode active material contained in the active material layer can be separated without being destroyed. Note that the non-binding body is preferable because the active material particles are not firmly fixed in the active material layer, so that even if there is a volume change due to charge / discharge, it can be moderated.

  Here, in the present invention, the lithium secondary cell means a positive electrode in which a positive electrode active material layer is formed on the surface of a positive electrode current collector and a negative electrode in which a negative electrode active material layer is formed on the surface of a negative electrode current collector. It has a structure in which a positive electrode and a negative electrode are laminated via a separator and is not equipped with a battery container, terminal arrangement, electronic control device, etc. (Reference: Japanese Industrial Standard JIS C8715-2 “Industrial use” Lithium secondary battery cell and battery system "). Note that a lithium secondary cell may be abbreviated as a cell.

  Here, the positive electrode frame when the inner wall surface of the positive electrode frame that is in contact with the positive electrode active material layer is formed on a surface that is not orthogonal to the first surface of the separator and is cut perpendicularly to the first surface of the separator It is preferable that at least a part of the inner wall surface of the body is formed in a straight line passing through the contact point between the inner wall surface and the first surface, and the straight line and the first surface form an obtuse angle.

  Alternatively, the negative electrode when the inner wall surface of the negative electrode frame that is in contact with the negative electrode active material layer is formed on a surface that is not orthogonal to the second surface of the separator and is cut perpendicularly to the second surface of the separator It is preferable that at least a part of the inner wall surface of the frame is formed in a straight line passing through the contact point between the inner wall surface and the second surface, and the straight line and the second surface form an obtuse angle.

  Furthermore, the positive electrode frame when the inner wall surface of the positive electrode frame that is in contact with the positive electrode active material layer is formed on a surface that is not orthogonal to the first surface of the separator and is cut perpendicularly to the first surface of the separator It is preferable that at least a part of the inner wall surface is formed in a curve passing through the contact point between the inner wall surface and the first surface, and all tangents in the curve form an obtuse angle with respect to the first surface of the separator.

  Alternatively, the inner wall surface of the negative electrode frame that is in contact with the negative electrode active material layer is formed on a surface that is not orthogonal to the second surface that contacts the negative electrode active material layer of the separator, and is perpendicular to the second surface of the separator. At least a part of the inner wall surface of the negative electrode frame when cut into two is formed into a curve passing through the contact point between the inner wall surface and the second surface, and all the tangent lines in the curve form an obtuse angle with respect to the second surface of the separator. Is preferred.

  Such a lithium ion battery of the present invention is formed such that the inner wall surface of the positive electrode frame that is in contact with the positive electrode active material layer is a surface that is not orthogonal to the first surface that is in contact with the positive electrode active material layer of the separator, and / or Alternatively, the inner wall surface of the negative electrode frame that is in contact with the negative electrode active material layer is formed on a surface that is not orthogonal to the second surface that is in contact with the negative electrode active material layer of the separator.

  With the above-described configuration, it is possible to improve the filling property of at least one of the positive electrode active material layer and the negative electrode active material layer into the frame body, thereby suppressing deterioration in battery characteristics.

It is a partially broken perspective view which shows the lithium secondary cell used for the lithium ion battery which is embodiment of this invention. It is sectional drawing which shows the lithium secondary cell which is embodiment. It is sectional drawing which shows the lithium ion battery which is embodiment. It is a perspective view which shows the lithium ion battery which is embodiment. It is process drawing which shows the manufacturing method of the lithium ion battery which is embodiment. It is sectional drawing which shows the modification of the lithium secondary cell used for the lithium ion battery which is embodiment.

  Hereinafter, a lithium ion battery according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 3 is a cross-sectional view showing a lithium ion battery according to an embodiment of the present invention, and FIG. 4 is a perspective view showing the lithium ion battery according to the embodiment.

  In these drawings, the lithium ion battery L of the present embodiment is a stacked type in which a plurality of substantially flat unit cells 1 are stacked in series in a flexible container 20 that forms the outer shell of the lithium ion battery L. The battery module 21 is housed and configured.

  As shown in detail in FIGS. 1 and 2, the unit cell 1 includes a positive electrode 2 in which a positive electrode active material layer 5 is formed on the surface of a positive electrode current collector 7 that is a substantially flat (sheet-like) resin current collector. And the negative electrode 3 in which the negative electrode active material layer 6 is formed on the surface of the negative electrode current collector 8 which is also a substantially flat (sheet-like) resin current collector. It is configured by being laminated via a separator 4 and is formed in a substantially flat plate shape as a whole.

  The positive electrode active material layer 5 and the negative electrode active material layer 6 are a positive electrode active material layer and a negative electrode active material layer containing positive electrode active material particles or negative electrode active material particles and an electrolytic solution. In addition, the positive electrode active material layer 5 and the negative electrode active material layer 6 obtained by mixing the electrolytic solution and the positive electrode active material particles or the negative electrode active material particles may be in the form of a slurry, and have a lower fluidity than the slurry. (For example, a semi-solid state like okara which is also called a funicular state or a pendular state).

  On the surfaces of the positive electrode current collector 7 and the negative electrode current collector 8 (the lower surface of the positive electrode current collector 7 and the upper surface of the negative electrode current collector 8 in FIG. 1), the outer shape extends along these edges. A rectangular frame-like positive electrode frame 9 and negative electrode frame 10 that are substantially equal to the body 7 and the negative electrode current collector 8 are formed, respectively.

  The positive electrode active material layer 5 and the negative electrode active material layer 6 are formed and arranged inside the positive electrode frame body 9 and the negative electrode frame body 10, respectively. Between the positive electrode active material layer 5 and the negative electrode active material layer 6, A separator 4 whose end extends between the positive electrode frame 9 and the negative electrode frame 10 is disposed.

  The distance between the positive electrode current collector 7 and the separator 4 and the distance between the negative electrode current collector 8 and the separator 4 are determined by the heights of the positive electrode frame body 9 and the negative electrode frame body 10, respectively. The heights of the body 9 and the negative electrode frame 10 are adjusted in accordance with the capacity of the lithium ion battery L, and the positional relationship among the positive electrode current collector 7, the negative electrode current collector 8 and the separator 4 can be obtained at a necessary interval. It has been established.

  As shown in FIGS. 1 and 2, the positive electrode 2 and the negative electrode 3 are arranged facing each other with the separator 4 therebetween, and the positive electrode 2 and the negative electrode 3 are stacked with the separator 4 interposed therebetween. As a result, the unit cell 1 of the present embodiment is configured.

  Here, in the present embodiment, as shown in detail in FIG. 2, the inner wall surface 9 a of the positive electrode frame 9 that is in contact with the positive electrode active material layer 5 is a surface in contact with the positive electrode active material layer 5 of the separator 4. At least part of the inner wall surface 9a of the positive electrode frame 9 when cut perpendicularly to the first surface 4a of the separator 4 is formed between the inner wall surface 9a and the first wall 4a. A straight line passing through the contact point P1 with the one surface 4a is formed, and the straight line and the first surface 4a form an obtuse angle.

  Further, the inner wall surface 10a of the negative electrode frame 10 that is in contact with the negative electrode active material layer 6 is formed on a surface that is not orthogonal to the second surface 4b that is a surface in contact with the negative electrode active material layer 6 of the separator 4. 4 at least a part of the inner wall surface 10a of the negative electrode frame 10 when cut perpendicularly to the second surface 4b is formed in a straight line passing through the contact point P2 between the inner wall surface 10a and the second surface 4b. The second surface 4b forms an obtuse angle.

  More specifically, as shown in FIG. 2, in a cross section in which the inner wall surface 9a of the positive electrode frame 9 is cut perpendicularly to the first surface 4a of the separator 4, the inner wall surface 9a is a straight line passing through the contact P1. The straight line and the first surface 4a form an obtuse angle. In other words, in the cross section shown in FIG. 2, the inner wall surface 9a is formed in a straight line that goes inward of the positive electrode frame 9 as it goes downward in the figure.

  Similarly, in a cross section obtained by cutting the inner wall surface 10a of the negative electrode frame 10 perpendicularly to the second surface 4b of the separator 4, the inner wall surface 10a is formed in a straight line passing through the contact P2, and the straight line and the second surface are formed. 4b forms an obtuse angle. In other words, in the cross section shown in FIG. 2, the inner wall surface 10 a is formed in a straight line that goes inward of the negative electrode frame 10 as it goes upward in the drawing.

  The angles formed by the inner wall surface 9a of the positive electrode frame 9 and the first surface 4a of the separator 4 and the angles formed by the inner wall surface 10a of the negative electrode frame 10 and the second surface 4b of the separator 4 at the contacts P1 and P2 are obtuse angles. That is, it may be larger than 90 ° and smaller than 180 °, but as an example, in the range of 95 ° to 135 °, preferably 100 ° to 120 °, the positive electrode active material layer 5 and the negative electrode active material at the contacts P1 and P2 The filling property of the material layer 6 can be sufficiently secured, and the occurrence of voids at the contact points P1 and P2 can be sufficiently suppressed.

  The positive electrode frame 9 and the negative electrode frame 10 may be integrally formed as shown in FIGS. 1 and 2, but when the positive electrode frame 9 and the negative electrode frame 10 are configured separately, The upper surface in the drawing of the positive electrode frame 9 and the lower surface in the drawing of the negative electrode frame 10 are preferably sealed with a seal member (not shown) in FIGS.

  The material constituting the sealing member is a material that has adhesiveness to the upper surface of the positive electrode frame 9 and the lower surface of the negative electrode frame 10 and can be integrally fixed thereto, and is heat resistant at the battery operating temperature. Thermoplastic resin and thermosetting resin, etc. that have an insulating property and an electrolyte does not penetrate, such as a urethane resin, an epoxy resin, a polyethylene resin, a polypropylene resin, and a polyimide resin. it can. Moreover, the material which comprises a sealing member can be used with forms, such as a liquid sealing material, an adhesive tape type sealing material, and a hot-melt type sealing material. A hot melt adhesive available from the market can also be used.

  Further, when the positive electrode frame body 9 and the negative electrode frame body 10 are configured separately, the seal member is disposed on at least one of the upper surface of the positive electrode frame body 9 in the drawing and the lower surface of the negative electrode frame body 10 in the drawing, and then the seal. The separator 4 may be disposed on the member, and heat may be applied to the separator 4 by a heat sealer or the like to fix the separator 4 to the positive electrode frame 9 or the negative electrode frame 10.

  Alternatively, a sealing member is attached to both surfaces (first surface 4a, second surface 4b) of the end portion of the separator 4, and heat is applied to the separator 4 with a heat sealer or the like, so that the separator 4 is connected to the positive electrode frame 9 or the negative electrode frame. 10 may be fixed.

  The unit cell 1 shown in FIG. 1 is stacked in series so that the upper surface of the positive electrode current collector 7 and the lower surface of the negative electrode current collector 8 of the adjacent unit cells 1 are adjacent to each other to form a stacked battery module 21. The laminated battery module 21 is housed in the container 20 preferably sealed under reduced pressure, so that the lithium ion battery L of the present embodiment shown in FIGS.

  The container 20 constituting the lithium ion battery L of the present embodiment shown in detail in FIG. 3 is divided into an upper container 20a and a lower container 20b. The upper container 20a and the lower container 20b are formed in substantially the same shape, and the left and right ends of the upper container body 20c and the lower container body 20d whose upper surfaces are open and the upper container body 20c and the lower container body 20d in FIG. A pair of upper container edge 20e and lower container edge 20f protruding sideways from the portion.

  The container 20 constituting the lithium ion battery L is not limited to the container shown in FIG. 3, and may be a container divided into a pair of sheets and a container formed in a bag shape.

  In the container 20 shown in FIG. 3, the stacked battery module 21 is housed in an internal space formed by arranging the upper container 20a and the lower container 20b to face each other, and this internal space is preferably decompressed. In this state, the upper container edge 20e and the lower container edge 20f are sealed with a seal member (not shown), whereby the lithium ion battery L of the present embodiment is configured. As the seal member for sealing the upper container edge 20e and the lower container edge 20f, the same seal member as that for sealing the frame can be used.

  Here, as shown in FIG. 3, electrode terminals 13 and 14 are interposed between the upper container 20 a and the lower container 20 b and the laminated battery module 21, respectively, and a part 13 a of the electrode terminals 13 and 14. , 14a extend to the outside of the lithium ion battery L through the upper container edge 20e and the lower container edge 20f.

  Here, in this specification, “the positive electrode active material layer and the negative electrode active material layer are formed inside the positive electrode frame body and the negative electrode frame body” means that the positive electrode current collector 7 and the negative electrode current collector 8 are on the surface. It means a state in which an active material layer corresponding to the inside of the formed positive electrode frame 9 and negative electrode frame 10 is disposed. Preferably, the positive electrode active material layer 5 and the negative electrode active material layer 6 are the positive electrode frame 9, This means that the inside of the negative electrode frame 10 is filled. The positive electrode active material layer 5 disposed inside the positive electrode frame 9 is in a state where the positive electrode active material particles and the electrolyte are mixed, and the negative electrode active material layer 6 disposed inside the negative electrode frame 10 is the negative electrode active material layer. In this state, the substance particles and the electrolytic solution are mixed.

  In the present invention, in order for the positive electrode active material layer 5 and the negative electrode active material layer 6 to be disposed inside the positive electrode frame 9 and the negative electrode frame 10, the powdered positive electrode active material particles and the negative electrode active material particles are used. A mixture comprising positive electrode active material particles and an electrolyte solution (also referred to as positive electrode slurry) and a mixture comprising negative electrode active material particles and an electrolyte solution, which may be directly placed inside the frames 9 and 10, respectively. You may carry out by putting (it is also mentioned negative electrode slurry) inside the frames 9 and 10, respectively. When powdered positive electrode active material particles and negative electrode active material particles are directly placed inside the frames 9 and 10, the positive electrode active material layer 5 and the negative electrode active material 5 are placed inside the frames 9 and 10 by subsequently adding an electrolyte solution. A material layer 6 is arranged.

  When the positive electrode active material particles or the positive electrode slurry and the negative electrode active material particles or the negative electrode slurry are put inside the frames 9 and 10, vibration and impact may be applied to the positive electrode current collector 7 and the negative electrode current collector 8. preferable. In the present invention, since the inner wall surface of the frame is not orthogonal to the separator, the positive electrode active material particles or the positive electrode slurry, and the negative electrode active material particles or the negative electrode slurry are removed from the frames 9, 10 by applying vibration and impact. This is preferable because it can be more uniformly filled without forming a gap to the corner formed by the frame and the separator on the inside.

  In addition, the positive electrode slurry and the negative electrode slurry (hereinafter referred to as the electrode slurry when referring to the positive electrode slurry and the negative electrode slurry) obtained by mixing the positive electrode active material particles or the negative electrode active material particles and the electrolytic solution are liquid (electrolytic solution). ) Is a fluid mixture in which the active material particles are uniformly suspended, but is less fluid than the slurry by adjusting the weight ratio of the positive electrode active material particles or the negative electrode active material particles to the electrolytic solution. (For example, a semi-solid state such as a funicular state or a pendular state such as okara) or an aggregate formed by absorbing the liquid by the active material particles may be used.

As the positive electrode active material particles contained in the positive electrode active material layer 5, known positive electrode active material particles that can be used for lithium ion batteries can be used, and composite oxides of lithium and transition metals (for example, LiCoO ₂ , LiNiO) ₂ , LiMnO ₂ and LiMn ₂ O ₄ ), transition metal oxides (eg MnO ₂ and V ₂ O ₅ ), transition metal sulfides (eg MoS ₂ and TiS ₂ ) and conductive polymers (eg polyaniline, polypyrrole, polythiophene). , Polyacetylene, poly-p-phenylene and polycarbazole).

Further, as the negative electrode active material particles contained in the negative electrode active material layer 6, known negative electrode active material particles that can be used for lithium ion batteries can be used, and graphite, non-graphitizable carbon, amorphous carbon, polymer Compound fired bodies (for example, those obtained by firing and carbonizing phenol resins and furan resins, etc.), cokes (for example, pitch coke, needle coke, petroleum coke, etc.), carbon fibers, conductive polymers (for example, polyacetylene and polyquinoline) , Tin, silicon, and metal alloys (for example, lithium-tin alloys, lithium-silicon alloys, lithium-aluminum alloys, lithium-aluminum-manganese alloys), and complex oxides of lithium and transition metals (for example, Li ₄ Ti ₅ O ₁₂ ) and the like.

  In the lithium ion battery of the present invention, the positive electrode active material particles or the negative electrode active material particles are coated positive electrode active material particles or coated negative electrode active material particles having a coating layer containing a coating resin composition on at least a part of the surface thereof. Preferably there is.

  It is preferable that the surface of the active material particle has a coating layer because the volume change of the electrode that occurs during charge and discharge is alleviated and the expansion of the electrode can be suppressed.

  As the coating resin included in the coating layer, those described in JP 2017-0547703 A as a resin for coating a non-aqueous secondary battery active material can be suitably used.

  The coating layer may further contain a conductive filler, and the conductive filler is selected from materials having conductivity.

  Specific examples of conductive materials include metals [aluminum, stainless steel (SUS), silver, gold, copper, titanium, etc.], carbon [graphite, carbon black (acetylene black, ketjen black, furnace black, channel). Black, thermal lamp black, etc.), carbon nanotubes (single-walled, multilayered, and mixtures thereof, etc.)], and mixtures thereof, but are not limited thereto.

  These conductive fillers may be used alone or in combination of two or more. Moreover, these alloys or metal oxides may be used. From the viewpoint of electrical stability, aluminum, stainless steel, carbon, silver, gold, copper, titanium and mixtures thereof are preferred, silver, gold, aluminum, stainless steel and carbon are more preferred, and carbon is more preferred. is there. These conductive fillers are non-conductive particles (particles made of a ceramic material or a resin material) coated with a conductive material (metal among the above-mentioned conductive auxiliary materials) by plating or the like. But you can.

  It is also possible to use conductive fibers as the conductive filler. Examples of conductive fibers include carbon fibers such as PAN-based carbon fibers and pitch-based carbon fibers, conductive fibers obtained by uniformly dispersing highly conductive metal or graphite in synthetic fibers, and metals such as stainless steel. Examples thereof include fiberized metal fibers, conductive fibers obtained by coating the surface of organic fibers with metal, and conductive fibers obtained by coating the surfaces of organic fibers with a resin containing a conductive substance. Among these conductive fibers, carbon fibers are preferable.

  When the coating layer of the coated active material particles contains a conductive filler, the weight of the coating layer is 3 to 3 times the total weight of the active material particles, the coating resin composition, and the conductive filler used if necessary. It is preferably 25% by weight.

  The coated active material particles can be produced by a known method (mixing a coating resin composition, active material particles, and a conductive filler used if necessary) described in JP-A-2017-0547703 and the like. It may be produced by mixing a coating agent obtained by mixing a coating resin and a conductive filler used if necessary, and active material particles, and a coating resin, a conductive filler and active material particles used if necessary May be produced by mixing them simultaneously. In addition, when mixing the active material particles, the coating resin, and the conductive filler used if necessary, the mixing order is not particularly limited, but after mixing the active material particles and the coating resin, the conductive filler is further added. In addition, it is preferable to further mix. The coating resin is preferably mixed as a coating resin solution. For example, in a state where the active material particles are put in a universal mixer and stirred at 30 to 500 rpm, the coating resin solution is added over 1 to 90 minutes. It can be obtained by dropping and mixing, further mixing a conductive additive, raising the temperature to 50 to 200 ° C. while stirring, reducing the pressure to 0.007 to 0.04 MPa, and holding for 10 to 150 minutes.

  As an electrolytic solution used for the electrode slurry, a known electrolyte used for manufacturing a lithium ion battery and an electrolytic solution containing a nonaqueous solvent can be used.

As the _{electrolyte, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6 , and lithium salts of inorganic acids LiClO _{4, etc., LiN (CF 3 SO 2)} 2, LiN (C 2 F 5 SO 2) 2 and LiC (CF ₃ And a lithium salt of an organic acid such as SO ₂ ) ₃ . Among these, LiPF ₆ is preferable from the viewpoint of battery output and charge / discharge cycle characteristics.

  As the non-aqueous solvent, a lactone compound, a cyclic or chain carbonate ester, a chain carboxylate ester, a cyclic or chain ether, a phosphate ester, a nitrile compound, an amide compound, a sulfone, a sulfolane, or a mixture thereof may be used. it can.

  A non-aqueous solvent may be used individually by 1 type, and may use 2 or more types together.

  Among the nonaqueous solvents, lactone compounds, cyclic carbonates, chain carbonates, and phosphates are preferable from the viewpoint of battery output and charge / discharge cycle characteristics, and more preferable are lactone compounds, cyclic carbonates, chains. A carbonic acid ester and a mixture thereof are more preferable, and a cyclic carbonate, a chain carbonate, and a mixture of a cyclic carbonate and a chain carbonate are more preferable. Particularly preferred are propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC) and a mixture of two or more carbonates selected from these.

  The electrode slurry is obtained by mixing and dispersing the active material particles in the electrolytic solution using a known dispersing device, and the weight of the active material particles contained in the electrode slurry is 10 to 60% by weight based on the weight of the electrolytic solution. It is preferable to prepare by dispersing at a concentration of. When the above-described coated active material particles are used as the active material particles contained in the electrode slurry, the weight of the active material particles contained in the electrode slurry is calculated using the weight of the coated active material particles.

  At least one of the positive electrode active material layer 5 and the negative electrode active material layer 6 may further contain a conductive auxiliary agent in addition to the conductive filler contained in the coating layer of the coated active material particles. The same conductive aid as the conductive filler can be used. If the active material layer contains a conductive filler and a conductive aid, if the active material layer is dispersed in a solvent in which the coating resin does not dissolve, only the conductive aid is extracted into the solvent. The remaining conductive filler and conductive auxiliary agent can be separated and distinguished.

  Furthermore, the positive electrode active material layer 5 and the negative electrode active material layer 6 containing a conductive auxiliary agent are formed by using an electrode slurry containing a conductive auxiliary agent obtained by mixing and dispersing active material particles, an electrolytic solution and a conductive auxiliary agent. be able to. In the positive electrode active material layer 5 and the negative electrode active material layer 6 containing a conductive auxiliary agent, a conductive path is formed between the active material particles by the conductive auxiliary agent, thereby improving electron transfer in the active material.

  In the present invention, the electrode slurry used for forming the positive electrode active material layer 5 and the negative electrode active material layer 6 does not contain the electrode binder (also referred to as a binder or a binder) used in known lithium ion batteries. Is preferred.

  In the present invention, when the coated active material particles are used as the active material particles forming the positive electrode active material layer 5 and the negative electrode active material layer 6, the function of the coating resin can be achieved without fixing the active material particles by the electrode binder. Is preferable because the conductive path can be maintained.

  As the separator 4, a known separator for a lithium ion battery can be used. A microporous film made of polyolefin (polyethylene, polypropylene, etc.), a multilayer film in which a polyolefin porous film is laminated, polyester fiber, aramid fiber, glass fiber And non-woven fabrics made of the same, and those having ceramic fine particles such as silica, alumina, titania and the like attached to the surface thereof. Examples of known separators for lithium ion batteries include separators made of porous polyolefin [Hypore manufactured by Asahi Kasei Co., Ltd., Celgard manufactured by Asahi Kasei Co., Ltd., Upore manufactured by Ube Industries, Ltd.] and the like.

  The positive electrode current collector 7 and the negative electrode current collector 8 are a pair of current collectors, and a known current collector for a lithium ion battery can be used without limitation. A known metal current collector, a conductive material, and a resin can be used. A resin current collector (resin current collector described in JP 2012-150905 A and International Publication No. WO 2015/005116 etc.) and the like can be suitably used.

  Examples of the metal current collector include copper, aluminum, titanium, nickel, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, alloys containing one or more of these metals, and stainless steel alloys. One or more metal materials selected from These metal materials may be used in the form of a thin plate or a metal foil. Moreover, you may use what formed the said metal material by methods, such as sputtering, electrodeposition, and application | coating, on the base-material surface comprised other than the said metal material as a metal electrical power collector.

  The resin current collector is a current collector including a conductive layer made of a conductive polymer material, and the conductive resin layer is formed into a sheet shape by a known method. It can be obtained by molding. In the lithium ion battery of the present invention, another conductive layer (metal layer or other conductive resin) is added to the conductive resin layer obtained by molding a conductive polymer material into a sheet shape by a known method. Layer) may be laminated.

  As a polymer material having conductivity that constitutes the conductive resin layer included in the resin current collector, a polymer material in which a conductive filler is dispersed in a polymer having no conductivity is used. it can.

  Non-conductive polymer materials include aliphatic polyolefins [polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyisobutylene. , Polybutadiene and polymethylpentene (PMP) and copolymers thereof, etc.], alicyclic polyolefin [polycycloolefin (PCO) etc.], polyester resin [polyethylene terephthalate (PET) etc.], polyether nitrile (PEN), Synthetic rubber [styrene butadiene rubber (SBR), etc.], acrylic resin [polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), etc.], polyvinylidene fluoride (PVdF), epoxy tree , Silicone resins and mixtures thereof.

  From the viewpoint of electrical stability, polyethylene (PE), polypropylene (PP), polymethylpentene (PMP) and polycycloolefin (PCO) are preferable, and polyethylene (PE), polypropylene (PP) and polymethylpentene are more preferable. (PMP).

  The conductive filler is selected from materials having conductivity. Preferably, from the viewpoint of suppressing ion permeation in the current collector, it is preferable to use a material that does not have conductivity with respect to ions used as the charge transfer medium. Specific examples include, but are not limited to, carbon materials, aluminum, gold, silver, copper, iron, platinum, chromium, tin, indium, antimony, titanium, nickel, and the like.

  These conductive fillers may be used alone or in combination of two or more. Moreover, these alloy materials, such as stainless steel (SUS), may be used. From the viewpoint of corrosion resistance, aluminum, stainless steel, carbon material, nickel, and more preferably carbon material are preferred. In addition, these conductive fillers may be those obtained by coating the metal shown above with a plating or the like around a particulate ceramic material or resin material.

  The resin current collector can be obtained by a known method described in JP 2012-150905 A and International Publication No. WO 2015/005116, and specific examples include 5 to 5 acetylene black as a conductive filler in polypropylene. Examples thereof include 20 parts dispersed and then rolled with a hot press. Moreover, the thickness is not particularly limited, and can be applied in the same manner as known ones or with appropriate changes.

  The material constituting the frames 9 and 10 is not particularly limited as long as it is a material that can be fixed to the surface of the current collectors 7 and 8 and is durable to the electrolytic solution. Materials, particularly thermosetting resins are preferred. Specific examples include epoxy resins, polyolefin resins, polyester resins, polyurethane resins, and polyvinylidene fluoride resins. Epoxy resins are preferred because they are durable and easy to handle.

  Next, with reference to FIG. 5, the manufacturing method of the cell 1 used for the lithium ion battery L of this embodiment is demonstrated.

  First, as shown in FIG. 5A, the positive electrode frame 9 is formed on the upper surface of the base 30 in the drawing. Although the method of forming the positive electrode frame 9 on the upper surface of the base 30 is arbitrary, an example is a method of laminating the positive electrode frame 9 on the upper surface of the base 30. As a method of laminating the positive electrode frame 9, a method of printing a material constituting the frame body 9 at a predetermined location on the upper surface of the base 30 using screen printing, a nozzle capable of discharging the material constituting the positive electrode frame 9. 31 is moved to a predetermined position on the upper surface of the base 30 and a predetermined shape is formed by a method of discharging the material constituting the positive electrode frame 9 by a mechanism capable of discharging a predetermined amount of member, injection molding using a predetermined mold, or the like. A method of forming the positive electrode frame 9 and laminating it on the upper surface of the base 30 is preferable. Regardless of which method is employed, it is necessary to form the positive electrode frame 9 so that the inner wall surface 9a of the positive electrode frame 9 has the predetermined shape described above.

  Next, as shown in FIG. 5B, after the positive electrode frame 9 formed in FIG. 5A is inverted upside down on the base 30, the positive electrode frame 9 in FIG. In the drawing, a seal member 11 is disposed on the upper surface 9b, and the separator 4 is placed so that the end portion is placed on the seal member 11. The method of placing the separator 4 on the upper surface 9 b of the positive electrode frame 9 is arbitrary, and as an example, the upper surface of the separator 4 is held by a vacuum chuck 32, and the separator 4 is attached to the positive electrode frame 9 by using the vacuum chuck 32. A method of removing the chuck 32 from the separator 4 after being placed on the upper surface 9b is preferable.

  Thereafter, heat is applied to the separator 4 from the upper surface (second surface) 4b of the separator 4 in FIG. 5B by means of a heat sealer (not shown), and the separator 4 and the positive electrode frame 9 are fused by the seal member 11. Let

  Next, as shown in FIG. 5C, the negative electrode frame 10 is formed on the upper portion of the positive electrode frame 9 in the figure while holding the positive electrode frame 9 and the separator 4 from below by the holder 33. The method of forming the negative electrode frame 10 on the upper part of the positive electrode frame 9 is also arbitrary. Like the positive electrode frame 9, the nozzle 34 capable of discharging the material constituting the negative electrode frame 10 is controlled to move to a predetermined location. For example, a method of discharging a material constituting the negative electrode frame 10 by a mechanism capable of discharging a predetermined amount of member is publicly cited. Regardless of which method is employed, it is necessary to form the negative electrode frame 10 so that the inner wall surface 10a of the negative electrode frame 10 has the predetermined shape described above.

  Next, as illustrated in FIG. 5D, the negative electrode active material layer 6 including the negative electrode active material and the electrolytic solution is formed and arranged inside the negative electrode frame 10 to form the negative electrode 3. The method of forming the negative electrode 3 is arbitrary, and the negative electrode slurry containing the negative electrode active material 6 is applied to the surface of the upper surface (second surface) 4b of the separator 4. There are various methods such as injecting a negative electrode slurry containing the active material 6. The formation of the negative electrode active material layer 6 on the upper surface 4b of the separator 4 is performed by applying a mixture containing the negative electrode active material and the electrolytic solution to the surface of the separator 4 and removing the electrolytic solution from the back surface by suction as necessary. Can be done.

  Next, as shown in FIG. 5 (e), the negative electrode active material 6 forming the negative electrode 3 is covered with the upper surface in the drawing, and the end is placed on the upper surface 10 b of the negative electrode frame 10 in the drawing. The current collector 8 is placed. The method of placing the negative electrode current collector 8 on the upper surface of the negative electrode active material 6 is arbitrary, and as an example, the upper surface of the negative electrode current collector 8 in the figure is held by a vacuum chuck 36, and the negative electrode A method of removing the chuck 36 from the negative electrode current collector 8 after placing the current collector 8 on the upper surface of the negative electrode active material 6 is preferable.

  Next, as shown in FIG. 5 (f), the negative electrode 3 formed in FIG. 5 (e) is inverted upside down, and then the positive electrode active material layer 5 containing the positive electrode active material and the electrolytic solution is formed into the positive electrode frame. The positive electrode 2 is formed by being formed and arranged inside the body 9. Since the method of forming the positive electrode 2 is the same as the method of forming the negative electrode 3, the description thereof is omitted here.

  Then, as shown in FIG. 5G, the positive electrode active material 5 forming the positive electrode 2 is covered with the upper surface of the positive electrode active material 5 in the drawing, and the end portion is placed on the upper surface 9c of the positive electrode frame 9 in the drawing. By placing the electric body 7, the unit cell 1 of the present embodiment can be manufactured as shown in FIG. 5 (h). Since the method of placing the positive electrode current collector 7 is the same as the method of placing the negative electrode current collector 8, description thereof is omitted here.

  As described above, in the lithium ion battery L of the present embodiment, the inner wall surface 9 a of the positive electrode frame 9 that is in contact with the positive electrode active material layer 5 is in contact with the first surface 4 a that is in contact with the positive electrode active material layer 5 of the separator 4. The inner wall surface 10a of the negative electrode frame 10 that is formed on a surface that is not orthogonal to the negative electrode active material layer 6 is formed on a surface that is not orthogonal to the second surface 4b of the separator 4 that is in contact with the negative electrode active material layer 6. Yes.

  In addition, at least a part of the inner wall surface 9a of the positive electrode frame 9 when cut perpendicularly to the first surface 4a of the separator 4 is formed in a straight line passing through the contact point P1 between the inner wall surface 9a and the first surface 4a. Further, the straight line and the first surface 4a form an obtuse angle, and at least a part of the inner wall surface 10a of the negative electrode frame 10 when cut perpendicularly to the second surface 4b of the separator 4 is the inner wall surface 10a. And the second surface 4b are formed in a straight line passing through the contact point P2, and the straight line and the second surface 4b form an obtuse angle.

  Therefore, since the angles formed by the inner wall surface 9a of the positive electrode frame 9 and the inner wall surface 10a of the negative electrode frame 10 and the first surface 4a and the second surface 4b of the separator 4 at these contacts P1 and P2 are obtuse angles. The filling properties of the positive electrode active material layer 5 and the negative electrode active material layer 6 in P1 and P2 and the vicinity thereof are remarkably improved, and the possibility that voids are generated in the contact P1 and P2 portions can be suppressed to a very low level. Thereby, it becomes possible to suppress the deterioration of the battery characteristics of the lithium ion battery L.

  Moreover, since the positive electrode active material layer 5 is a non-binding body of positive electrode active material particles and the negative electrode active material layer 6 is a non-binding body of negative electrode active material particles, the cell 1 of the present embodiment has an active material. The particles can move while maintaining contact with adjacent active material particles. As a result, even when stress is applied to the lithium ion battery L and the lithium ion battery L is deformed, the positive electrode does not cause cracks in the active material layer and does not peel at the interface with the current collector. The conductive path between the current collector 7 and the negative electrode current collector 8 can be maintained, and sufficient charge / discharge characteristics can be continuously exhibited.

(Modification)
The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific configuration is not limited to the embodiment and the example, and the design change is within a range not departing from the gist of the present invention. Are included in the present invention.

  As an example, the shapes of the inner wall surfaces 9a and 10a of the positive electrode frame 9 and the negative electrode frame 10 are not limited to the above-described embodiments, and various modifications are possible. For example, at least a part of the inner wall surface 9a of the positive electrode frame 9 when cut perpendicularly to the first surface 4a of the separator 4 is formed in a curve passing through the contact point P1 between the inner wall surface 9a and the first surface 4a. All tangents in the curve form an obtuse angle with respect to the first surface 4a of the separator 4 and / or the inner wall surface 10a of the negative electrode frame 10 when cut perpendicularly to the second surface 4b of the separator 4. These positive electrode frames 9 are formed such that at least a part thereof is formed into a curve passing through the contact point P2 between the inner wall surface 10a and the second surface 4b, and all tangent lines in the curve form an obtuse angle with respect to the second surface 4b of the separator 4. The inner wall surfaces 9a and 10a of the negative electrode frame 10 may be formed.

  Alternatively, as shown in FIG. 6A, the inner wall surfaces 9 a and 10 a of the positive electrode frame 9 and the negative electrode frame 10 excluding the vicinity of the contact P <b> 1 are substantially orthogonal to the first surface 4 a and the second surface 4 b of the separator 4. On the other hand, the positive electrode frame 9 and the inner wall surfaces 9a and 10a of the negative electrode frame 10 are formed on a curved surface so as to be flush with the first surface 4a of the separator 4 as it approaches the contact P1 in the vicinity of the contact P1. May be. In this case, since the vicinity of the contact point P1 of the negative electrode frame 10 is substantially the same flat surface as the first surface 4a of the separator 4, it is convenient to fuse the separator 4 to the negative electrode frame 10 and fix it.

  Moreover, as shown in FIG. 6B, the cross sections of the inner wall surfaces 9a and 10a of the positive electrode frame 9 and the negative electrode frame 10 may be formed as an integral inclined straight line. That is, the cross sections of the inner wall surfaces 9a and 10a of the positive electrode frame 9 and the negative electrode frame 10 may be formed as straight lines that inwardly incline from the upper side to the lower side in the figure. In this case, at the contact P2 between the inner wall surface 10a of the negative electrode frame 10 and the second surface 4b of the separator 4, the angle formed by the cross section of the inner wall surface 10a and the second surface 4b becomes an acute angle.

  Here, in the example shown in FIG. 6B, the end portion of the separator 4 is bent upward in the drawing, and is fused to the inner wall surface 9a of the positive electrode frame body 9 at the bent portion.

  In the example shown in FIG. 6 (b), the positive electrode frame 9 and the negative electrode frame 10 integrally formed on the upper surface of the negative electrode current collector 8 are bonded or integrally formed, and then the negative electrode active material layer 6 is filled in the negative electrode frame 10, the separator 4 is arranged on the upper surface of the negative electrode active material layer 6, the end thereof is fixed by fusion or the like, and the positive electrode active material layer 5 is further fixed on the upper portion of the separator 4. The lithium ion battery L can be manufactured by the procedure of filling the battery and covering with the positive electrode current collector 7.

  Further, as shown in FIG. 6C, only one of the inner wall surfaces 9a and 10a of the positive electrode frame 9 and the negative electrode frame 10 (in the illustrated example, the inner wall surface 9a of the positive electrode frame 9) is formed on an inclined surface. Furthermore, as shown in FIG. 6D, the inner wall surfaces 9a and 10a of the positive electrode frame 9 and the negative electrode frame 10 may be formed in a series of curved surfaces.

L Lithium ion battery P1, P2 Contact 1 Cell 2 Positive electrode 3 Negative electrode 4 Separator 4a First surface 4b Second surface 5 Positive electrode active material layer 6 Negative electrode active material layer 7 Positive electrode current collector 8 Negative electrode current collector 9 Positive electrode frame 9a 10a Inner wall surface 10 Negative electrode frame 21 Multilayer battery module

Claims (5)

A positive electrode having a positive electrode active material layer formed on the surface of a sheet-like positive electrode current collector and a negative electrode having a negative electrode active material layer formed on the surface of a sheet-like negative electrode current collector are laminated via a separator. A lithium ion battery having a lithium secondary cell,
On the surfaces of the positive electrode current collector and the negative electrode current collector, annular positive electrode frame bodies and negative electrode frame bodies are respectively formed along the edges thereof, and the positive electrode active material layer and the negative electrode active material layer are respectively formed on the positive electrode Formed inside the frame and the negative electrode frame,
The positive electrode active material layer is a non-binding body of positive electrode active material particles, the negative electrode active material layer is a non-binding body of negative electrode active material particles,
An inner wall surface of the positive electrode frame that is in contact with the positive electrode active material layer is formed on a surface that is not orthogonal to the first surface of the separator that is in contact with the positive electrode active material layer, and / or the negative electrode active material. A lithium ion battery in which an inner wall surface of the negative electrode frame that is in contact with a layer is formed on a surface that is not orthogonal to a second surface of the separator that is in contact with the negative electrode active material layer. The lithium ion battery according to claim 1,
The inner wall surface of the positive electrode frame that is in contact with the positive electrode active material layer is formed on a surface that is not orthogonal to the first surface of the separator,
At least a part of the inner wall surface of the positive electrode frame when cut perpendicularly to the first surface of the separator is formed in a straight line passing through a contact point between the inner wall surface and the first surface, A lithium ion battery in which the first surface forms an obtuse angle. The lithium ion battery according to claim 1 or 2,
The inner wall surface of the negative electrode frame that is in contact with the negative electrode active material layer is formed on a surface that is not orthogonal to the second surface of the separator,
At least a part of the inner wall surface of the negative electrode frame when cut perpendicularly to the second surface of the separator is formed in a straight line passing through a contact point between the inner wall surface and the second surface, A lithium ion battery in which the second surface forms an obtuse angle. The lithium ion battery according to claim 1,
The inner wall surface of the positive electrode frame that is in contact with the positive electrode active material layer is formed on a surface that is not orthogonal to the first surface of the separator,
At least a part of the inner wall surface of the positive electrode frame when cut perpendicularly to the first surface of the separator is formed in a curve passing through a contact point between the inner wall surface and the first surface, All tangents are lithium ion batteries that form an obtuse angle with respect to the first surface of the separator. The lithium ion battery according to claim 1 or 2,
The inner wall surface of the negative electrode frame that is in contact with the negative electrode active material layer is formed on a surface that is not orthogonal to the second surface of the separator that is in contact with the negative electrode active material layer,
At least a part of the inner wall surface of the negative electrode frame when cut perpendicularly to the second surface of the separator is formed in a curve passing through a contact point between the inner wall surface and the second surface, All tangents are lithium ion batteries that form an obtuse angle with respect to the second surface of the separator.