JP4954468B2 - Winding electrode, manufacturing method thereof, and battery manufacturing method - Google Patents

Description

  The present invention relates to a wound electrode, a method for manufacturing the same, and a method for manufacturing a battery.

  In recent years, the importance of mobile devices such as mobile phones, PDAs, and notebook computers has increased, and the importance of batteries mounted on them has also increased. In particular, due to environmental considerations, the importance of secondary batteries that can be repeatedly charged is increasing. Application of secondary batteries to automobiles, electric bicycles, household power storage systems, commercial power storage systems, and the like has been studied.

  A pair of strip-like electrodes (positive electrode and negative electrode) constituting a battery usually has a structure in which an active material layer containing an active material and a binder is formed on both surfaces of a metal foil. For example, a strip-shaped polyethylene microporous film called a separator is disposed between the positive electrode and the negative electrode, and on the opposite side of the negative electrode on the positive electrode side. The laminate including the positive electrode, the negative electrode, and the two separators is wound into, for example, a cylindrical shape or a flat shape, and is stored in the container together with the electrolytic solution. The separator insulates the positive electrode and the negative electrode. In a rectangular Li-ion battery normally used for a mobile phone or the like, a wound electrode in which a laminate is wound in a flat shape is used in order to effectively use the volume inside the can.

By the way, it has been proposed to use a thinner separator to reduce the volume occupied by the separator in the wound body and to increase the amount of active material filling (high capacity). For example, instead of an independent film such as the polyethylene microporous membrane, a porous insulating layer formed by applying an insulating material to an active material layer of either the positive electrode or the negative electrode can be used as a separator. For example, the thickness of the separator can be further reduced (see, for example, Patent Documents 1 to 5).
Japanese Patent Laid-Open No. 1-167948 JP-A-10-284065 WO 98/38688 pamphlet JP-A-11-288874 JP 2000-149906 A

  However, in the laminate before winding, when the two porous insulating layers are each integrated with one of the active material layers of the positive electrode and the negative electrode, and the positive electrode and the negative electrode are in a non-bonded state, When the integrated product in which the porous insulating layers are formed on both surfaces of the negative electrode and the positive electrode are in a non-bonded state, there are the following problems.

  When the laminate is wound, the negative electrode active material layer may be cracked in a portion having a large curvature, particularly in the vicinity of the innermost periphery of the wound body. In such a case, cracks also occur in the porous insulating layer integrated with the negative electrode. If a crack occurs in the porous insulating layer, a short circuit may occur between the positive electrode and the negative electrode. The cracking of the porous insulating layer is more likely to occur particularly when the wound electrode is flat. In the conventional method for manufacturing a wound electrode, it has been difficult to suppress the occurrence of a short circuit by suppressing the cracking of the porous insulating layer while enabling a high capacity.

  The present invention can increase the capacity, suppress the occurrence of a short circuit, and easily provide a more reliable wound electrode and battery.

  The method for producing a wound electrode according to the present invention includes: (a) a strip-shaped positive electrode including a pair of positive electrode active material layers and a positive electrode current collector disposed between the pair of positive electrode active material layers; A first paint containing a first resin on any one of a strip-like negative electrode including a pair of negative electrode active material layers and a negative electrode current collector disposed between the pair of negative electrode active material layers Is applied to form a first porous insulating layer, and one of the positive electrode and the negative electrode includes a second resin having a softening point higher than that of the first resin. Is applied to form a second porous insulating layer, the first porous insulating layer is disposed between the positive electrode and the negative electrode, and the second porous insulating layer is one of the outermost layers. A step of stacking the positive electrode and the negative electrode so as to form an outer layer; and (b) the first resin while pressing the laminate. Heating at a temperature not lower than the softening point and lower than the softening point of the second resin to bond the positive electrode and the negative electrode through the first porous insulating layer; and (c) the step (b). And winding the laminated body after.

  The battery manufacturing method of the present invention includes a wound electrode and an electrolyte prepared by the wound electrode manufacturing method of the present invention in a container containing a resin, and after sealing the container, The method includes a step of joining the positive electrode or the negative electrode and the second porous insulating layer by heating the wound product obtained by winding the laminate from the outside while applying pressure.

  In this specification, the softening point is a value measured in accordance with JIS K 7206.

  According to the present invention, it is possible to easily provide a more reliable wound electrode and battery that can have a higher capacity and suppress the occurrence of a short circuit.

  Hereinafter, an example of a wound electrode and a method for manufacturing the wound electrode according to the present invention and an example of a method for manufacturing a battery will be described with reference to the drawings.

(Embodiment 1)
In the present embodiment, a wound electrode constituting a Li ion battery will be described as an example.

  First, as shown in FIG. 1A, a strip-shaped positive electrode 4 including a pair of positive electrode active material layers 4a and 4b and a positive electrode current collector 4c disposed between the pair of positive electrode active material layers 4a and 4b. Make it.

  On the other hand, as shown in FIG. 1A, a strip-shaped negative electrode 3 including a pair of negative electrode active material layers 3a and 3b and a negative electrode current collector 3c disposed between the pair of negative electrode active material layers 3a and 3b. Is made.

  Next, as shown in FIG. 1B, a first paint containing a first resin is applied on the negative electrode active material layer 3a to form a first porous insulating layer 2a.

  Next, as shown in FIG. 1C, a second coating material containing a second resin having a softening point higher than that of the first resin is applied onto the negative electrode active material layer 3b, so that a second porous insulating layer is formed. 2b is formed.

  Next, as shown in FIG. 1D, the first porous insulating layer 2a is disposed between the positive electrode 4 and the negative electrode 3, and the second porous insulating layer 2b is one outermost layer. 4 and the negative electrode 3 are stacked to form a laminate.

  Next, the laminate is heated at a temperature not lower than the softening point of the first resin and lower than the softening point of the second resin while being pressed in the thickness direction using a hot roll press or the like, so that the first porosity is obtained. The positive electrode 4 and the negative electrode 3 are joined via the insulating layer 2a.

Although there is no restriction | limiting in particular about the pressure at the time of pressurizing a laminated body, 1 * 10 < ⁶ > Pa-1 * 10 < ⁹ > Pa is suitable. The heating temperature is preferably 60 ° C. or higher and lower than 200 ° C.

  Next, for example, the laminated body is wound so that the opposite side of the laminated body to the second porous insulating layer 2b side, that is, the positive electrode 4 side in the laminated body shown in FIG. (See FIG. 3).

  In the manufacturing method of the wound electrode of this embodiment, since the 1st porous insulating layer 2a and the 2nd porous insulating layer 2b are formed by apply | coating a coating material (refer FIG. 1B-C), for example, Rather than forming the first porous insulating layer 2a and the second porous insulating layer 2b by bonding the independently formed films, the first porous insulating layer 2a and the second porous insulating layer are thinner. Layer 2b can be formed. Therefore, the volume occupied by the first porous insulating layer 2a and the second porous insulating layer 2b in the wound electrode can be reduced to increase the filling amount of the active material, and the capacity can be increased. Become.

  Further, in the manufacturing method of the wound electrode of the present embodiment, the positive electrode 4, the first porous insulating layer 2a, and the negative electrode 3 are arranged in this order, and these are integrated before winding, The occurrence of cracks in the first porous insulating layer 2a due to winding can be suppressed, and thus the occurrence of a short circuit between the positive electrode 4 and the negative electrode 3 can be suppressed. Thereby, the reliability of the wound electrode can be increased.

  Furthermore, since the softening point of the second resin contained in the second porous insulating layer 2b is higher than the softening point of the first resin contained in the first porous insulating layer 2a, the positive electrode 4 and the negative electrode 3 The first porous insulating layer 2a is disposed between the positive electrode 4 and the negative electrode 3 so that the second porous insulating layer 2b is one outermost layer. The pressurization heating process to be performed can be directly performed by, for example, a hot roll press machine or a heating press machine. That is, in the present embodiment, the positive electrode 4, the first porous insulating layer 2a, and the negative electrode 3 can be easily integrated.

  From the above, according to the method for manufacturing a wound electrode of the present embodiment, a highly reliable wound electrode capable of increasing the capacity and suppressing occurrence of a short circuit can be easily provided.

  As shown in FIG. 1A, the positive electrode 4 may include a positive electrode current collecting tab 7 for electrically connecting the positive electrode current collector 4c and the positive electrode terminal of the battery. The positive electrode current collector tab 7 can be bonded to the positive electrode current collector 4c using, for example, a conductive adhesive (for example, aluminum paste). The positive electrode current collecting tab 7 is preferably bonded to, for example, a positive electrode active material layer lacking portion 4c ′ on the starting side of the positive electrode current collector 4c where the positive electrode active material layers 4a and 4b are not formed.

  The negative electrode 3 may include a negative electrode current collecting tab 8 for electrically connecting the negative electrode current collector 3c and the negative electrode terminal of the battery. The negative electrode current collecting tab 8 can be bonded to the negative electrode current collector 3c using, for example, a conductive adhesive (for example, silver paste). The negative electrode current collecting tab 8 is preferably joined to, for example, the negative electrode active material layer lacking portion 3c ′ on the side where the negative electrode current collector 3c is rolled and on which the negative electrode active material layers 3a and 3b are not formed.

  In the manufacturing method of the wound electrode according to the present embodiment, when the laminate is heated while being pressurized and the positive electrode 4 and the negative electrode 3 are bonded via the first porous insulating layer 2a, the first porous body is formed. The thickness of the conductive insulating layer 2a and the second porous insulating layer 2b may be reduced. If the thickness of the first porous insulating layer 2a and the second porous insulating layer 2b is reduced by pressurization, the capacity can be further increased.

  Moreover, in the manufacturing method of the wound electrode of this embodiment, the wound body obtained by winding the laminated body is heated at a temperature equal to or higher than the softening point of the second resin while being pressed, so that the second porous The conductive insulating layer 2b and the positive electrode 4 are preferably joined. If the 2nd porous insulating layer 2b and the positive electrode 4 are joined and a winding body is integrated, the handling property of a winding body (winding electrode) will become easy, and the winding electrode will be accommodated in the container. Becomes easy.

Although there is no restriction | limiting in particular about the pressure at the time of pressurizing a winding body, 1 * 10 < ⁶ > Pa-1 * 10 < ⁹ > Pa is suitable for a pressure.

The temperature at which the wound body is heated while being pressed (T ₃ ) is preferably lower than 200 ° C. When the first resin is a crystalline resin, for example, ethylene-vinyl acetate copolymer (EVA) or the like, the heating temperature T ₃ is determined from the viewpoint of maintaining the porosity of the first porous insulating layer. It is preferable that the temperature is lower than the melting point of one resin. When the first resin is an amorphous resin, for example, it is a cycloolefin polymer (for example, Nippon Zeon Co., Ltd., Zeonoa (registered trademark), Mitsui Chemicals, Inc., Appel (registered trademark), etc.). In this case, from the viewpoint of maintaining the porosity of the first porous insulating layer, it is preferable that the heating temperature T ₃ satisfies the relationship of T ₃ ≦ T ₁ + 20 ° C., for example. T ₁ is the softening point of the first resin.

  As shown in FIG. 2, the negative electrode 3 is wider than the positive electrode 4, and the negative electrode 3 and the positive electrode 4 are preferably overlapped so that both edges 3 f in the width direction of the negative electrode 3 protrude from the positive electrode 4. In the lithium ion battery, the lithium dendrite deposited on the peripheral edge of the negative electrode 3 with the use of the battery penetrates the first porous insulating layer 2a or the second porous insulating layer 2b and contacts the positive electrode 4 to cause a short circuit. This causes a problem that the battery life is shortened. If the positive electrode 4 and the negative electrode 3 are arranged so that the width of the negative electrode 3 is larger than that of the positive electrode 4 and both edge portions 3f in the width direction of the negative electrode 3 protrude from the positive electrode 4, both edge portions 3f of the negative electrode 3f. Precipitation of lithium dendrite in can be suppressed, and as a result, short circuit can be further suppressed.

  When the width of the negative electrode 3 is larger than that of the positive electrode 4, the first porous insulating layer 2 a and the second porous insulating layer 2 b are preferably formed on the negative electrode 3. In this case, since the first porous insulating layer 2a and the second porous insulating layer 2b wider than the width of the positive electrode 4 can be formed, the negative electrode 3 and the positive electrode 4 can be more reliably insulated.

  When the first porous insulating layer 2a and the second porous insulating layer are formed on the negative electrode 3, and the laminate is wound so that the positive electrode 3 is inside, the laminate is wound. It is preferable to use the positive electrode 4 whose length in the longitudinal direction is longer than that of the negative electrode 3 so that the outermost periphery of the wound body is formed from the end of the positive electrode 4. If the outermost periphery of the wound body is the end portion of the positive electrode 4, even if the wound body is directly sandwiched by a heating press or the like when the wound body is heated and integrated while being pressed, the second Therefore, the winding body can be easily integrated.

  The material of the positive electrode current collector 4c is not particularly limited, and is, for example, an Al foil.

  The positive electrode active material layers 4a and 4b are formed by, for example, applying a slurry obtained by mixing a positive electrode active material and a binder to the positive electrode current collector 4c, drying the slurry applied to the positive electrode current collector 4c, and then adding a thickness. It can be formed by pressing in the direction. The slurry can be applied by, for example, a doctor blade method or a spray coating method. The slurry may further contain a conductive material as necessary.

As the positive electrode active material, for example, an inorganic oxide such as LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiNi _1/3 Co _1/3 Mn _1/3 O, LiFePo _4, or the like can be used.

  Examples of binders include fluorine resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), rubber resins such as styrene butadiene rubber (SBR) and ethylene propylene diene multiblock polymer, and carboxymethyl cellulose (CMC). Cellulose-type resin etc. are mentioned. These binders can be used alone or in combination.

  Examples of the conductive material include carbon materials such as acetylene black (AB), ketjen black (KB), graphite, and amorphous carbon. These conductive materials can be used alone or in combination.

  The material of the positive electrode current collecting tab 7 is not particularly limited, and examples thereof include Al and Ni. Although there is no restriction | limiting in particular about the shape of the positive electrode current collection tab 7, For example, it is strip shape.

  The material of the negative electrode current collector 3c is not particularly limited, and is, for example, Cu foil.

  The negative electrode active material layers 3a and 3b are formed by, for example, applying a slurry obtained by mixing a negative electrode active material and a binder to the negative electrode current collector 3c, then drying the slurry applied to the negative electrode current collector 3c, and then the thickness. It can be formed by pressing in the direction. The slurry can be applied by, for example, a doctor blade method or a spray coating method. The slurry may further contain a conductive material as necessary.

Examples of the negative electrode active material include metals that can be alloyed with Li such as Sn and Si, metallic lithium, LiAl alloy, amorphous carbon, artificial graphite, natural graphite, fullerene, and carbon that can occlude and release lithium. Lithium titanate that can occlude and release lithium, such as a system material, Li ₄ Ti ₅ O ₁₂ , Li ₂ Ti ₃ O _7, etc. can be used.

  Examples of the binder include PVDF, PTFE, SBR, carboxymethyl cellulose (CMC) and the like. These binders can be used alone or in combination.

  Examples of the conductive material include carbon materials such as AB, KB, and amorphous carbon. These conductive materials can be used alone or in combination.

  The material of the negative electrode current collecting tab 8 is not particularly limited, and examples thereof include Cu and SUS. Although there is no restriction | limiting in particular about the shape of the negative electrode current collection tab 8, For example, it is a strip shape.

  As the first resin contained in the first paint, one having a softening point of 60 ° C. or higher and lower than 200 ° C. is preferable. If the softening point of the first resin is too low, the first resin may be softened and the battery characteristics may be deteriorated when the wound electrode is used. If the softening point of the first resin is too high, the heating temperature when joining the positive electrode 4 and the negative electrode 3 through the first porous insulating layer 2a becomes too high. If the heating temperature is too high, the binder contained in the negative electrode active material layers 3a and 3b and the positive electrode active material layers 4a and 4b deteriorates, and the negative electrode active material layers 3a and 3b are separated from the negative electrode current collector 3c. There arises a problem that 4a and 4b are peeled off from the positive electrode current collector 4c, and the electrode characteristics may be deteriorated. If the softening point of the first resin is lower than the softening point of the second resin to be described later and is in the range of 60 ° C. or higher and lower than 200 ° C., the laminate is heated at a temperature of 60 ° C. or higher and lower than 200 ° C. Thus, the positive electrode 4 and the negative electrode 3 can be joined via the first porous insulating layer 2a while suppressing deterioration of the electrode characteristics due to heat.

  The second resin contained in the second paint is not particularly limited as long as the softening point is higher than the softening point of the first resin, but those having a softening point lower than 200 ° C. are preferable. When the softening point of the second resin is too high, the negative electrode active material layers 3a and 3b and the positive electrode active material layers 4a and 4b are heated when the wound body is heated while being pressed to integrate the wound body. The contained binder deteriorates, causing problems such as separation of the negative electrode active material layers 3a and 3b from the negative electrode current collector 3c and separation of the positive electrode active material layers 4a and 4b from the positive electrode current collector 4c. This is because there is a risk of it. If the softening point of the second resin is lower than 200 ° C, the wound body can be integrated while suppressing deterioration of electrode characteristics due to heat by heating the wound body at a temperature lower than 200 ° C.

Here, T ₁ the softening point of the first resin, the softening point of the second resin and T _2, if T ₂ is greater than T _1, no particular limitation for the difference between T ₂ and T ₁ . However, from the viewpoint of ease of setting the heating temperature when the positive electrode 4 and the negative electrode 3 are bonded via the first porous insulating layer 2a and the heating temperature when the wound body is integrated, T It is preferable to select the first resin and the second resin so that the difference between ₂ and T ₁ is 20 ° C. or more.

  The first porous insulating layer 2a and the second porous insulating layer 2b are formed by, for example, applying a paint containing organic fine particles and a binder as necessary to the negative electrode active material layers 3a and 3b. it can. The application can be performed by a doctor blade method or a spray application method. It is preferable that the first porous insulating layer 2a and the second porous insulating layer 2b have a so-called shutdown function. The shutdown function means that when the temperature inside the battery rises too much, the pores of the first porous insulating layer 2a and the second porous insulating layer 2b are blocked, and the first porous insulating layer 2a and It refers to the function of eliminating the ionic conductivity of the second porous insulating layer 2b.

  Examples of the organic fine particle material include thermoplastic resins such as polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), and polylactic acid. Can be mentioned.

  The paint may further contain inorganic fine particles. Examples of the inorganic fine particles include inorganic oxides such as alumina and silica. The organic fine particles may be fine particles made of a composite material containing the thermoplastic resin and an inorganic oxide.

  Examples of the binder contained in the paint include PVDF, PTFE, SBR, and the like. In addition, when the organic fine particle itself has adhesiveness, for example, when the material of the organic fine particle is EVA or the like, the binder is not always necessary.

  The first porous insulating layer 2a and the second porous insulating layer 2b can also be formed by the following method. (1) A resin solution in which a resin is dissolved in a solvent (good solvent) is applied to, for example, the negative electrode active material layers 3a and 3b, and is then immersed in a poor solvent before the applied resin solution is dried. A microporous resin coating film (first porous insulating layer 2a and second porous insulating layer 2b) is coagulated and precipitated.

  (2) The resin solution is further mixed with a poor solvent or an inorganic salt, and the obtained paint is applied to, for example, the negative electrode active material layers 3a and 3b. Next, the good solvent is dried and removed from the paint applied to the negative electrode active material layers 3a and 3b, and then the poor solvent or inorganic salt is removed by a method such as drying or extraction, whereby the first porous insulating layer 2a. And the 2nd porous body insulating layer 2b is obtained.

  Examples of the resin in the resin solution include EVA, EEA, and chlorinated PP, examples of the good solvent include toluene and tetrahydrofuran (THF), and examples of the poor solvent include water, alcohol, and the like. As the salt, for example, LiBr, LiI or the like can be used. The above resin, good solvent, poor solvent, and inorganic salt may be used in combination of two or more.

  When the first coating material and the second coating material are the above-described coating materials including organic fine particles and a binder as necessary, the first resin and the second resin are resins contained in the organic fine particles. . When the first paint and the second paint are the above-described resin solution in which the resin is dissolved in a solvent (good solvent) (including those containing a poor solvent or an inorganic salt added), the first resin The second resin is a resin in the resin solution.

  The combination of the first resin and the second resin has a second resistance higher than the softening point of the first resin in consideration of the heat resistance of the binder contained in the negative electrode active material layer and the positive electrode active material layer. There is no particular limitation as long as the softening point of the resin is high.

  In general, when the resin is a copolymer, the softening point can be adjusted by adjusting the blending ratio of two types of monomers constituting the copolymer. For example, in an ethylene-vinyl acetate copolymer (EVA), the softening point decreases as the blending ratio of vinyl acetate is increased. Therefore, for example, of two types of EVA having different vinyl acetate content, EVA having a relatively large vinyl acetate content is used as the first resin, and EVA having a relatively small vinyl acetate content is the second. The resin may be selected.

  In addition, at least one of the first resin and the second resin is polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA). A polymer blend comprising at least one resin selected from the group consisting of polylactic acid and chlorinated PP, and at least one heat-resistant resin selected from the group consisting of polysulfone, polyethersulfone and polyphenylsulfone. Also good. At least one of the first resin and the second resin is polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), poly It may be a polymer blend containing at least one resin selected from the group consisting of lactic acid and chlorinated PP and a petroleum hydrocarbon resin, such as an aromatic modified aliphatic hydrocarbon resin. The polymer blend may contain both a heat resistant resin and a petroleum hydrocarbon resin. The softening point of the polymer blend can be adjusted by selecting the blending ratio and type of the heat resistant resin and petroleum hydrocarbon resin contained in the polymer blend.

  1B to 1C, the first porous insulating layer 2a and the second porous insulating layer 2b are formed on the negative electrode 3. However, the method for manufacturing the wound electrode according to this embodiment is limited to this. Not. At least one of the first porous insulating layer 2 a and the second porous insulating layer 2 b may be formed on the positive electrode 4. When the second porous insulating layer 2b is formed on the positive electrode 4, when the wound body obtained by winding the laminate is heated at a temperature equal to or higher than the softening point of the second resin while being pressed, the second The porous insulating layer 2b and the negative electrode 3 are joined.

  In FIG. 1B, the first porous insulating layer 2a is formed only on the negative electrode active material layer 3a of the negative electrode 3a. However, the first porous insulating layer 2a is formed of the negative electrode active material of the negative electrode current collector 3c. You may form so that a part or all of the part in which the negative electrode active material layer 3a of the surface by the side of the layer 3a is not formed may further be covered. Similarly, the second porous insulating layer 2b shown in FIG. 1C is a part of the surface of the negative electrode current collector 3c on the negative electrode active material layer 3b side where the negative electrode active material layer 3b is not formed or You may form so that all may be covered further.

  Moreover, in the example demonstrated using FIG. 1D, although the laminated body is wound so that the positive electrode 4 side may become an inner side, the winding electrode is obtained, However, The manufacturing method of the winding electrode of this embodiment is not restrict | limited to this. . If the opposite side of the laminate from the second porous insulating layer side is on the inside, the laminate may be wound so that the negative electrode 3 is on the inside.

  FIG. 3 shows a wound electrode manufactured by the method for manufacturing a wound electrode according to this embodiment. The wound electrode of this embodiment includes a strip-shaped positive electrode 4, a strip-shaped negative electrode 3, a strip-shaped first porous insulating layer 2 a disposed between the positive electrode 4 and the negative electrode 3, and one of the laminated bodies. A laminated body including the band-shaped second porous insulating layer 2b arranged to be an outer layer is wound, for example, so that the opposite side of the laminated body to the second porous insulating layer 2b side is inside. ing. The first porous insulating layer 2a is formed by applying a first paint containing a first resin, and the second porous insulating layer 2b is a second paint containing a second resin. It is formed by apply | coating. The first porous insulating layer 2a is bonded to the positive electrode 4 and the negative electrode 3, and the softening point of the second resin is higher than the softening point of the first resin.

  Since the wound electrode of this embodiment is produced by the method for manufacturing a wound electrode of this embodiment, the reliability is high.

  In the wound electrode of this embodiment, the positive electrode 4 and the second porous insulating layer 2b may be joined.

  Next, the battery of this embodiment will be described with reference to the drawings.

  FIG. 4 shows an example (cross-sectional view) of a battery in which the wound electrode 1 manufactured by the above manufacturing method is housed in a container together with an electrolytic solution. In FIG. 4, the wound electrode 1 is simply illustrated for convenience of illustration, and hatching is also omitted. In FIG. 4, 3 is a negative electrode and 4 is a positive electrode.

  As shown in FIG. 4, in the battery according to the present embodiment, the container 9 including the lid 9a is formed of a metal such as aluminum (Al). An insulator 5 made of a synthetic resin such as a PTFE sheet is disposed at the bottom of the container 9. A metal terminal 11 made of stainless steel or the like is attached to the lid 9a via an insulating packing 10 made of synthetic resin such as PP, and a metal lead plate such as stainless steel is attached to the terminal 11 via an insulator 12. 13 is attached.

  In the example shown in FIG. 4, the positive electrode current collecting tab 7 is directly welded to the lid body 9 a, so that the container functions as a positive electrode terminal. Further, the negative electrode current collecting tab 8 is welded to the lead plate 13, and the negative electrode current collecting tab 8 and the terminal 11 are electrically connected via the lead plate 13. The terminal 11 functions as a negative terminal. Depending on the material of the container, the sign of the terminal may be reversed. The container may be made of, for example, stainless steel (SUS), or may contain a resin as in the container used in Embodiment 2 described later.

Although there is no restriction | limiting in particular as electrolyte solution, When a battery is a Li ion battery, what melt | dissolved Li salt in the organic solvent is used, for example. The Li salt is not particularly limited as long as it can be dissociated in an organic solvent to generate Li ⁺ ions and does not cause a side reaction such as decomposition in the voltage range of a battery having an electrolytic solution as a component.

Examples of the Li salt include inorganic compounds such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ). (SO ₂ C ₄ F ₉ ), LiC (SO ₂ CF ₂ ) ₃ , LiC (SO ₂ C ₂ F ₅ ) ₃ , LiPF _6-n (C ₂ F ₅ ) _n (n is an integer from 1 to 6) Organic compounds such as LiSO ₃ CF ₃ , LiSO ₃ C ₂ F ₅ , and LiSO ₃ C ₄ F ₈ can be used.

  The organic solvent is not limited as long as it can dissolve the Li salt and does not cause side reactions such as decomposition in the voltage range of the battery. Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, cyclic esters such as γ-butyrolactone, dimethoxyethane, and diglyme. And chain ethers such as triglyme and tetraglyme, cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran, and nitriles such as acetonitrile, propionitrile, methoxypropionitrile and ethoxypropionitrile. These organic solvents can be used alone or in combination.

  Among these, the organic solvent is preferably a mixed solvent of ethylene carbonate and chain carbonate. By using the above mixed solvent, high electrical conductivity can be obtained and good battery characteristics can be realized.

  For the purpose of improving characteristics such as safety, cycleability, and high-temperature storage properties, the electrolyte solution is appropriately vinylene carbonates, 1,3-propane sultone, diphenyl disulfide, cyclohexane, biphenyl, fluorobenzene, t-butyl. Additives such as benzene may be included.

  In addition, the electrolytic solution is replaced with an organic solvent, such as ethyl-methylimidazolium trifluoromethylsulfonium imide, heptyl-trimethylammonium trifluoromethylsulfonium imide, pyridinium trifluoromethylsulfonium imide, guanidinium trifluoromethylsulfonium imide, etc. Of room temperature molten salt.

  Further, the electrolytic solution may be gelled with the following host polymer. The host polymer includes polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene oxide, polypropylene oxide, ethylene oxide-propylene oxide copolymer, crosslinked polymer containing an ethylene oxide chain in the main chain or side chain, photo And a (meth) acrylate copolymer which can be cross-linked by heat and has an oxetane compound or an alicyclic epoxy compound in the side chain.

(Embodiment 2)
In the present embodiment, an example of the battery manufacturing method of the present invention will be described.

  In the manufacturing method of the battery of this embodiment, after obtaining a laminated body, it is the same as that of the winding electrode manufacturing method of Embodiment 1 until the process of winding the laminated body. Therefore, the battery manufacturing method of the present embodiment also has the same effect as the winding electrode manufacturing method of the first embodiment.

  In the battery manufacturing method of the present embodiment, as shown in FIG. 5A, the wound body 1 obtained by winding the laminated body and the electrolytic solution are placed in a container 91 containing a resin, and the container is sealed. To do. Thereafter, as shown in FIG. 5B, from the outside of the container 91, the wound body 1 is heated while being pressurized with a heating press 14 or the like, and the positive electrode and the negative electrode are joined through the second porous insulating layer. The winding body 1 is integrated.

  The resin contained in the container 91 preferably contains a material capable of sealing the opening of the container 91 by heat welding or the like, for example, a polyolefin such as polyethylene or polypropylene. The container may have a laminate structure including the resin and the metal foil.

Although there is no restriction | limiting in particular about the pressure at the time of pressurizing the winding body 1 from the outer side of the container 91, 1 * 10 < ⁶ > Pa-1 * 10 < ⁹ > Pa is suitable.

The heating temperature (referred to as T ₄ ) when heating the wound body from the outside of the container is preferably less than 200 ° C. as in the first embodiment. This is because the wound body can be integrated while suppressing deterioration of the electrode characteristics due to heat. When the first resin is a crystalline resin, for example, ethylene-vinyl acetate copolymer (EVA), the heating temperature T ₄ is the first from the viewpoint of maintaining the porosity of the first porous insulating layer. The temperature is preferably lower than the melting point of the resin. When the first resin is an amorphous resin, for example, a cycloolefin polymer or the like, the heating temperature T ₄ is, for example, T ₄ from the viewpoint of maintaining the porosity of the first porous insulating layer. ≦ T ₁ + 20 ° C. is preferably satisfied. T ₁ is the softening point of the first resin.

  The materials and manufacturing methods of the positive electrode, the negative electrode, the first porous insulating layer, and the second porous insulating layer are the same as those of the first embodiment, and the material of the electrolytic solution is also the same as that of the first embodiment.

  After enclosing the wound body 1 and the electrolytic solution in the container 91, when the wound body 1 is heated while being pressurized, when the organic solvent contained in the electrolytic solution exceeds a predetermined temperature, the second porosity The second resin contained in the insulating layer starts to dissolve in the organic solvent. When the degree of dissolution of the second resin in the organic solvent is increased, the wound body 1 can be integrated at a lower heating temperature. The combination of the second resin and the organic solvent contained in the electrolyte is a combination that allows the winding body 1 to be integrated even when the winding body 1 is heated at a temperature lower than the softening point of the second resin. It is preferable. This is because deterioration of electrode characteristics due to heat can be further suppressed.

  Specifically, when the second resin is a polymer blend containing EVA, a heat-resistant resin such as polysulfone, and a petroleum hydrocarbon resin such as an aromatic modified aliphatic hydrocarbon resin, the organic solvent is ethylene. A mixed solvent of a cyclic carbonate such as carbonate or propylene carbonate and a chain carbonate such as dimethyl carbonate, ethylmethyl carbonate, or diethyl carbonate is preferable.

  Hereinafter, an example of the present invention will be described in more detail with reference to examples.

(Preparation of positive electrode)
LiCoO ₂ powder (positive electrode active material), graphite powder (conductive material), polyvinylidene fluoride (binder), and N-methyl-2-pyrrolidone (solvent) are mixed to form a slurry-like positive electrode active material mixture Got. This slurry was applied to both surfaces of an aluminum foil (positive electrode current collector, thickness: 20 μm) by a doctor blade method and dried. In this state, the thickness of the positive electrode active material mixture applied to both surfaces of the positive electrode current collector was 50 μm. Next, these are pressurized in the thickness direction with a press machine and heat-treated in a vacuum oven to remove moisture in the positive electrode active material mixture, and a positive electrode current collector is disposed between a pair of positive electrode active material layers A positive electrode having the above structure was produced.

(Preparation of negative electrode)
Graphite powder (negative electrode active material), polyvinylidene fluoride resin (binder), and N-methyl-2-pyrrolidone (solvent) were mixed to obtain a slurry-like negative electrode active material mixture. This slurry was applied to both sides of a copper foil (negative electrode current collector, thickness: 20 μm) by a doctor blade method and dried. In this state, the thickness of the negative electrode active material mixture applied to both surfaces of the negative electrode current collector was 50 μm. Next, pressurize them in the thickness direction with a press machine and heat-treat them in a vacuum oven to remove moisture in the negative electrode active material mixture, and a negative electrode current collector is placed between a pair of negative electrode active material layers A negative electrode having the above structure was produced.

(Preparation of the first porous insulating layer)
On one side of the negative electrode, an ethylene-vinyl acetate copolymer (Mitsui / Dipon Chemical Co., Ltd., P1905, vinyl acetate content: 19%, MFR value: 2.5 g / 10 min, softening point: 58 ° C., melting point: 84 The emulsion (average particle size: 2 μm) prepared using a high-pressure emulsification apparatus with a temperature of 0.1 ° C. (hereinafter abbreviated as “EVA1”) was applied by a doctor blade method to a thickness of 10 μm and dried. did.

(Preparation of the second porous insulating layer)
On the other side of the negative electrode, an ethylene-vinyl acetate copolymer (manufactured by Nippon Unicar Co., Ltd., NUC-5491, vinyl acetate amount: 6%, MFR value: 5.5 g / 10 min, softening point: 78 ° C., hereinafter “ Emulsion (average particle size: 2 μm) prepared using a high-pressure emulsifier using a raw material of “EVA2”) as a raw material was applied to a thickness of 10 μm by the doctor blade method and dried.

  Next, an integrated product (width 44 mm) composed of the negative electrode, the first porous insulating layer, and the second porous insulating layer, and the positive electrode (width: 43 mm) are placed between the positive electrode and the negative electrode. A laminated body was formed such that a porous insulating layer was disposed and the second porous insulating layer was one outermost layer. Next, the laminate was heated at 65 ° C. for 1 minute while being pressurized at 5 MPa by a hot press. Next, the positive electrode current collector tab was attached to the positive electrode current collector, and the negative electrode current collector tab was attached to the negative electrode current collector.

  Next, the laminate was wound in a flat shape so that the positive electrode side was on the inside to obtain a wound body. Next, the obtained wound body was heated at 80 ° C. for 2 minutes while being pressurized at 3 MPa using a heating press, and integrated with a thickness of 3.6 mm, a width of 32 mm, and a length of 46 mm. A wound electrode was obtained.

  Next, the wound body was inserted into an aluminum can having a thickness of 4 mm, a width of 34 mm, and a length of 50 mm, and the positive electrode collector tab was welded to the positive electrode terminal, and the negative electrode collector tab was welded to the negative electrode terminal.

Next, LiPF ₆ was dissolved in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a mass ratio of 1: 2 so that the concentration thereof was 1 mol / liter to obtain an electrolytic solution. After pouring this electrolyte solution into an aluminum can, the aluminum can was covered and sealed using a laser sealing device to obtain a square battery.

(Comparative Example 1)
A prismatic battery was produced in the same manner as in Example 1 except that the laminated body and the wound body were not heated and pressed by a hot press machine.

  A positive electrode and a negative electrode were produced in the same manner as in Example 1.

(Preparation of the first porous insulating layer)
On one negative electrode active material layer of the negative electrode, an emulsion (average particle size 2 μm) prepared using a high-pressure emulsifier using “EVA1” (softening point: 58 ° C., melting point: 84 ° C.) used in Example 1 as a raw material. It apply | coated so that it might become thickness 10 micrometers by the doctor blade method, it was dried, and the 1st porous insulating layer was obtained.

(Preparation of the second porous insulating layer)
Ethylene-vinyl acetate copolymer (manufactured by Exxon-Mobil Chemical Co., ESCORENE (registered trademark) ULTRA, UL 7840, vinyl acetate amount 33%, MFR value: 4.3 g / 10 min, melting point: 105 ° C.) 0.9 g, Escorez (Registered trademark) 2596 (aromatically modified aliphatic hydrocarbon resin) (manufactured by Exxon-Mobil Chemical Co., Ltd.) 0.36 g, and polysulfone (manufactured by Scientific Polymer Products Inc., weight average molecular weight (Mw): 80,000) 4.14 g was dissolved in 40 g of tetrahydrofuran (THF). To the obtained solution, 1.00 g of fumed silica was added, and the mixture was stirred overnight to obtain a slurry. Next, 7.00 g of lithium bromide (LiBr) was added to the slurry and dissolved. Next, the obtained slurry was applied to the other negative electrode active material layer of the negative electrode by a doctor blade method so as to have a thickness of 15 μm, and the applied slurry was left at room temperature to dry the THF naturally. Next, the dried slurry is immediately immersed in water for 1 hour to remove LiBr, and a polymer blend containing an ethylene-vinyl acetate copolymer, an aromatic modified aliphatic hydrocarbon resin, and polysulfone (softening point: A second insulating porous layer containing 125 ° C.) was obtained.

  Next, an integrated product (width 44 mm) composed of the negative electrode, the first porous insulating layer, and the second porous insulating layer, and the positive electrode (width 43 mm) are arranged between the first and the negative electrodes. The laminated body was formed such that the conductive insulating layer was disposed and the second porous insulating layer was one outermost layer. Next, the laminate was heated at 75 ° C. for 1 minute while being pressurized at 3 MPa by a hot press. Next, the positive electrode current collector tab was attached to the positive electrode current collector, and the negative electrode current collector tab was attached to the negative electrode current collector.

  Next, the laminate was wound in a flat shape so that the positive electrode side was on the inside to obtain a wound body. The wound body had a thickness of 3.6 mm, a width of 32 mm, and a length of 46 mm. This wound body was placed in a container made of a laminate film (polyester-aluminum-modified polyolefin) having a three-layer structure together with the electrolytic solution, and the container was sealed with heat. Next, using a hot press machine, the wound body was heated at 80 ° C. for 10 minutes while pressing at 1.5 MPa from the outside of the container to obtain a battery. The same electrolyte solution used in Example 1 was used as the electrolyte solution.

(Comparative Example 2)
A battery was fabricated in the same manner as in Example 2 except that the laminated body and the wound body were not hot-pressed by a hot press machine.

  Ten batteries of Examples 1 and 2 and Comparative Examples 1 and 2 were prepared, respectively, and the charge / discharge characteristics were examined according to the following method. In the batteries of Examples 1 and 2, normal charging / discharging was possible, and no abnormality such as a short circuit was observed even after 100 cycles of charging / discharging. On the other hand, 5 of 10 batteries in Comparative Example 1 caused an internal short circuit and could not be charged / discharged. In the battery of Comparative Example 2, when the first charge / discharge was performed, 3 out of 10 were short-circuited, and 4 of the remaining 7 were short-circuited during the 30th charge / discharge. From these results, it was confirmed that the batteries of Examples 1 and 2 were more reliable than the batteries of Comparative Examples 1 and 2 because the short circuit was suppressed.

[Charge / discharge test]
In an atmosphere of 25 ° C., the battery was charged at a constant current of 500 mA until the battery voltage reached 4.2 V, and then charged by a constant voltage method until the current value reached 10 mA. Thereafter, the battery was discharged at a constant current of 500 mA until the battery voltage reached 3V. With this as one cycle, 100 cycles of charge / discharge were performed.

  In the present invention, since it is possible to provide a highly reliable wound electrode and battery capable of increasing the capacity and suppressing short-circuiting, the wound electrode and the manufacturing method thereof, and the manufacturing method of the battery of the present invention include: Useful.

AD is sectional drawing according to process which shows an example of the manufacturing method of the winding electrode of this invention. Schematic plan view of the laminate shown in FIG. 1D Sectional drawing which shows an example of the wound electrode of this invention Sectional drawing of the battery using an example of the wound electrode of this invention AB is sectional drawing according to process which shows an example of the manufacturing method of the battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Winding electrode 2a 1st porous insulating layer 2b 2nd porous insulating layer 3 Negative electrode 3a, 3b Negative electrode active material layer 3c Negative electrode collector 4 Positive electrode 4a, 4b Positive electrode active material layer 4c Positive electrode collector 7 Positive electrode Current collecting tab 8 Negative current collecting tab 9, 91 Container

Claims (14)

(A) a strip-shaped positive electrode including a pair of positive electrode active material layers and a positive electrode current collector disposed between the pair of positive electrode active material layers, a pair of negative electrode active material layers, and the one pair A first paint containing a first resin is applied to any one of a strip-like negative electrode including a negative electrode current collector disposed between the negative electrode active material layers of the first porous insulating material Forming a layer, and applying a second paint containing a second resin having a softening point higher than that of the first resin to one of the positive electrode and the negative electrode to form a second porous insulation Forming a layer, the first porous insulating layer is disposed between the positive electrode and the negative electrode, and the positive electrode and the negative electrode are arranged such that the second porous insulating layer is one outermost layer. Forming a laminate by stacking,
(B) heating the laminated body at a temperature not lower than the softening point of the first resin and lower than the softening point of the second resin while applying pressure to the positive electrode via the first porous insulating layer; And joining the negative electrode;
(C) After the step (b), a step of winding the laminate, and a method for manufacturing a wound electrode.   The method for manufacturing a wound electrode according to claim 1, wherein in the step (c), the laminate is wound in a flat shape.   In the step (c), the wound body obtained by winding the laminate is heated at a temperature equal to or higher than the softening point of the second resin while being pressurized, and the positive electrode or the negative electrode, The method for manufacturing a wound electrode according to claim 1, wherein two porous insulating layers are joined.   In the step (c), the wound body obtained by winding the laminate is heated at a temperature not lower than the melting point of the first resin and higher than the softening point of the second resin, while applying pressure. The manufacturing method of the winding electrode of Claim 1 which joins a positive electrode or the said negative electrode, and a said 2nd porous insulating layer. The negative electrode is wider than the positive electrode;
The method for producing a wound electrode according to claim 1, wherein in the step (a), the negative electrode and the positive electrode are overlapped so that both edges in the width direction of the negative electrode protrude from the positive electrode.   The method for producing a wound electrode according to claim 5, wherein in the step (a), the first porous insulating layer and the second porous insulating layer are formed on the negative electrode. In the step (a), in the step (a), the positive electrode having a longer length in the longitudinal direction than that of the negative electrode is formed so that the outermost periphery of the wound body obtained by winding the laminate is composed of the end portion of the positive electrode. Prepare
The manufacturing method of the winding electrode of Claim 6 which winds the said laminated body so that the said positive electrode may become an inner side in the said process (c).   The manufacturing method of the winding electrode of Claim 1 which heats the said laminated body at the temperature of 60 degreeC or more and less than 200 degreeC in the said process (b).   The manufacturing method of the winding electrode of Claim 3 which heats the said winding body at the temperature lower than 200 degreeC in the said process (c).   2. The wound electrode according to claim 1, wherein in the step (b), the laminate is heated while being pressed to reduce the thickness of the first porous insulating layer and the second porous insulating layer. Manufacturing method.   The method for manufacturing a wound electrode according to claim 1, wherein the first paint or the second paint further contains inorganic fine particles.   The wound electrode produced by the method for producing a wound electrode according to claim 1 and an electrolytic solution are placed in a container containing a resin, and after sealing the container, the laminate is formed from the outside of the container. A method for producing a battery, comprising: heating a wound body obtained by winding a body while applying pressure to join the positive electrode or the negative electrode and the second porous insulating layer.   The battery manufacturing method according to claim 12, wherein the wound body is heated at a temperature lower than a softening point of the second resin. The battery manufacturing method according to claim 13, wherein the wound body is heated at a temperature lower than the melting point of the first resin.

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