JP2014049370A - Flat type nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat type nonaqueous secondary battery with excellent reliability and productivity.SOLUTION: In a flat nonaqueous secondary battery, positive electrodes and negative electrodes are alternately laminated via separators, and in almost parallel to flat planes of an outer case and a sealing case in a space formed by caulking and sealing a positive electrode case and a negative electrode case via an insulation gasket. The flat nonaqueous secondary battery has an electrode group whose total number of the positive and negative electrodes is 3 or more, and nonaqueous electrolyte. Each collector tab part of the positive or negative electrode is collected, welded and integrated, and folded on an electrode with the same polarity on an outermost side of the electrode group, and its end is arranged at a specific portion. The integrated collector tab part of the positive or negative electrode is held between an outer face of the electrode group and an inner face of the positive electrode case or the negative electrode case.

Description

  The present invention relates to a flat nonaqueous secondary battery excellent in reliability and productivity.

  In a flat non-aqueous secondary battery generally referred to as a coin-type battery or a button-type battery, an electrode group in which a positive electrode and a negative electrode are opposed to each other with a separator interposed therebetween, and a non-aqueous electrolyte solution are provided in an outer case. And a structure accommodated in a space formed by a sealing case and an insulating gasket.

  In the flat non-aqueous secondary battery as described above, a positive electrode mixture layer or a negative electrode agent layer is formed on one or both surfaces of the current collector on the positive electrode and the negative electrode, and a part of the current collector is mixed with the positive electrode mixture. It is exposed without forming a layer or a negative electrode agent layer, and this is used as a current collecting tab. The current collecting tabs of each positive electrode and each negative electrode are welded together, and these collected current collecting tabs are connected to terminals. There are some which are used for electrical connection with the inner surface of an exterior case or a sealing case that also serves as a material (for example, Patent Document 1).

  In recent years, as the application range of flat non-aqueous secondary batteries has expanded, for example, there has been a demand for downsizing. However, in a flat non-aqueous secondary battery, depending on the shape of the battery, such as a small one, the inside of the battery is very narrow. Welding with the inner surface of the sealing case may be difficult, and battery productivity may be impaired.

  Therefore, the plurality of current collecting tabs welded together are folded and bonded to the outer surface side of the electrode group, and are brought into contact with the inner surfaces of the positive electrode case and the negative electrode case to be electrically connected to each other. There is also a proposal of a technique that enables the application of a small battery case while ensuring a certain degree (Patent Document 2).

JP 2003-142161 A JP 2011-141997 A

  With the technique described in Patent Document 2, even a small flat non-aqueous secondary battery can be produced satisfactorily, and a collection that is welded together by the inner surface of the positive electrode case or the negative electrode case and the outer surface of the electrode group. Because a part of the electric tab can be clamped, for example, even if the battery receives vibration, contact between the end of the current collecting tab that is welded together and a member such as a battery case on the counter electrode side can be suppressed. In addition, the reliability of the battery can be improved.

  However, the technique described in Patent Document 2 also has a problem that it is difficult to fit the positive electrode case and the negative electrode case, particularly in a thin flat non-aqueous secondary battery having a small thickness with respect to the diameter in plan view. This problem also affects productivity. In this respect, the technique described in Patent Document 2 still leaves room for improvement.

  This invention is made | formed in view of the said situation, The objective is to provide the flat non-aqueous secondary battery excellent in reliability and productivity.

  A positive electrode case that also serves as a positive electrode terminal and a negative electrode case that also serves as a negative electrode terminal are formed in a space formed by caulking and sealing via an insulating gasket. A flat non-aqueous secondary battery having a non-aqueous electrolyte and an electrode group in which the total number of positive and negative electrodes is three or more, and is laminated substantially parallel to the flat surface of the negative electrode case. ) Or (2).

(1) The negative electrode includes a main body portion and a current collecting tab portion that protrudes from the main body portion in a plan view and is narrower than the main body portion. A negative electrode layer containing a negative electrode active material is formed on one side or both sides of a current collector. In the current collector tab portion of the negative electrode, a negative electrode layer is not formed on the current collector. It has at least two negative electrodes, and the outermost electrode on the negative electrode case side in the electrode group is a negative electrode, and the current collecting tab portions of the negative electrodes are gathered together and welded together, and An integrated current collecting tab portion of the negative electrode is folded on the outermost negative electrode on the negative electrode case side in the electrode group, and an end portion of the integrated negative electrode current collecting tab portion is a plan view, Inside the outer periphery of the electrode group and the outermost part of the electrode group on the negative electrode case side The electrode group is located up to 2/3 of the diameter of the electrode group when the boundary between the main body part and the current collecting tab part of the electrode is the base point, and the outer surface of the electrode group and the inner surface of the negative electrode case It is pinched by.

(2) The positive electrode has a main body portion and a current collecting tab portion that protrudes from the main body portion in a plan view and is narrower than the main body portion. A positive electrode mixture layer containing a positive electrode active material is formed on one side or both sides of the current collector, and in the current collector tab portion of the positive electrode, a positive electrode mixture layer is not formed on the current collector, and the electrode group is , Having at least two positive electrodes, and the outermost electrode on the positive electrode case side in the electrode group is a positive electrode, and the current collecting tab portions of the positive electrodes are collected and welded together to be integrated The integrated current collecting tab portion of the positive electrode is folded on the outermost positive electrode on the positive electrode case side in the electrode group, and the end portion of the integrated positive current collecting tab portion is seen in a plan view. The outermost side of the positive electrode case side of the electrode group that is inside the outer periphery of the electrode group The outer surface of the electrode group and the inner surface of the positive electrode case are positioned up to 2/3 of the diameter length of the electrode group when the boundary between the main body part and the current collecting tab part of the positive electrode is used as a base point It is pinched by.

  In the battery industry, a flat battery with a diameter larger than the height is called a coin-type battery or a button-type battery, but there is a clear gap between the coin-type battery and the button-type battery. There is no difference, and the flat non-aqueous secondary battery of the present invention includes both coin-type batteries and button-type batteries.

  ADVANTAGE OF THE INVENTION According to this invention, the flat type non-aqueous secondary battery excellent in reliability and productivity can be provided.

It is a longitudinal cross-sectional view which represents typically an example of the flat non-aqueous secondary battery of this invention. It is a principal part expanded view of the flat non-aqueous secondary battery of FIG. It is a top view which represents typically an example of the negative electrode which concerns on the flat nonaqueous secondary battery of this invention. It is a top view which represents typically an example of the positive electrode which concerns on the flat nonaqueous secondary battery of this invention. It is a top view which represents typically an example of the electrode group which concerns on the flat nonaqueous secondary battery of this invention. It is a longitudinal cross-sectional view which represents typically the other example of the flat nonaqueous secondary battery of this invention. FIG. 7 is an enlarged cross-sectional view of a main part of the flat nonaqueous secondary battery in FIG. 6. It is a top view which represents typically an example of the separator which concerns on the flat nonaqueous secondary battery of this invention.

  1 and 2 schematically show an example of the flat non-aqueous secondary battery of the present invention. FIG. 1 is a longitudinal sectional view of a flat non-aqueous secondary battery, and FIG. 2 is an enlarged sectional view of a main part of FIG.

  As shown in FIG. 1 and FIG. 2, the flat non-aqueous secondary battery 1 includes a plurality of positive electrodes 5 and a plurality of negative electrodes 6 with separators 7 interposed therebetween, and their planes are substantially parallel (parallel) to the flat surface of the battery. And a non-aqueous electrolyte solution (not shown) are a positive electrode case 2 (exterior case in FIG. 1), and a negative electrode case 3 (also an outer case) (also shown in FIG. 1). In FIG. 1, it is accommodated in the space (sealed space) formed by the sealing case) and the insulating gasket 4. The negative electrode case 3 is fitted in the opening of the positive electrode case 2 via an insulating gasket 4, and the opening end of the positive electrode case 2 is tightened inward, whereby the insulating gasket 4 contacts the negative electrode case 3. Thus, the opening of the positive electrode case 2 is sealed, and the inside of the battery has a sealed structure. The positive electrode case 2 and the negative electrode case 3 are made of a metal such as stainless steel, and the insulating gasket 4 is made of an insulating resin such as polypropylene.

  1 and 2, as described above, the positive electrode case 2 that also serves as the positive electrode terminal is an outer case, and the negative electrode case 3 that also serves as a negative electrode terminal is a sealing case. In the battery of the present invention, for example, Depending on the configuration of the electrode group, the outer case may be a negative electrode case that also serves as a negative electrode terminal, and the sealing case may be a positive electrode case that also serves as a positive electrode terminal.

  3 schematically shows a plan view of the negative electrode 6. The negative electrode 6 has a width that is larger than the main body 600 and the main body 600 protruding from the main body 600 in plan view (up and down in FIG. 3). Current collecting tab portion 601 having a narrow direction length). The width of the current collecting tab portion 601 can be set to 5 to 60% of the width of the main body portion 600, for example.

  In the main body 600 of the negative electrode 6, a negative electrode agent layer 61 containing a negative electrode active material or the like is formed on one side or both sides of a current collector (62 in FIG. 1). And the current collection tab part 601 of the negative electrode 6 does not have the negative electrode agent layer formed in the surface of the electrical power collector 62, and the electrical power collector 62 is exposed.

  In the battery shown in FIG. 1 and FIG. 2, the upper and lower ends of the electrode group are negative electrodes 6B and 6B, and these negative electrodes 6B and 6B are provided on only one side of the current collector 62 (the inner surface of the battery). A layer 61 is provided. On the other hand, the negative electrode 6 </ b> A arranged on the electrode group other than the upper and lower ends has negative electrode agent layers 61 and 61 on both surfaces of the current collector 62. In addition, the negative electrode arrange | positioned at the outermost side of an electrode group may also have a negative electrode agent layer on both surfaces of a collector.

  4 schematically shows a plan view of the positive electrode 5. The positive electrode 5 has a width that is larger than the main body 500 and the main body 500 protruding from the main body 500 in plan view (upper and lower in FIG. 4). Current collecting tab portion 501 having a narrow direction length). The width of the current collecting tab portion 501 can be set to 5 to 60% of the width of the main body portion 500, for example.

  In the main body 500 of the positive electrode 5, a positive electrode mixture layer 51 containing a positive electrode active material or the like is formed on both surfaces of a current collector (52 in FIG. 1). In the current collecting tab portion 501 of the positive electrode 5, the positive electrode mixture layer is not formed on the surface of the current collector 52, and the current collector 52 is exposed. In the batteries shown in FIGS. 1 and 2, since the outermost electrode in the electrode group is a negative electrode, the positive electrode mixture is formed on both surfaces of the current collector 52 in the main body portion 500 of all the positive electrodes 5. Although the layer 51 is formed, for example, one of the electrodes on the outermost side in the electrode group (more specifically, the electrode on the exterior case side or the sealing case side that also serves as the positive electrode terminal) or both is used as the positive electrode. In this case, the outermost positive electrode in the electrode group may have a positive electrode mixture layer only on one side of the current collector (the inner surface of the battery) in the main body, and the positive electrode mixture layer on both sides. You may have an agent layer.

  Further, in the battery shown in FIG. 1, the current collecting tab portions of all the positive electrodes 5 constituting the electrode group are collected, and these are welded and integrated, and the end portions thereof are outside the electrode group in plan view ( It is bent so as to face the left side in the figure. The positive current collecting tab portion 501 a which is integrated and welded is welded to the inner surface of the positive electrode case 2.

  On the other hand, in the battery shown in FIG. 1 and FIG. 2, the current collecting tab portions 601 of all the negative electrodes 6 constituting the electrode group are integrated and welded together, and the outermost electrode on the negative electrode case 3 side in the electrode group. It is folded on the external negative electrode 6B and is sandwiched between the outer surface of the electrode group (upper surface in FIGS. 1 and 2) and the inner surface of the negative electrode case. Then, the end X of the integrated negative electrode current collecting tab portion 601a is a plan view of the battery (when the surface of the upper electrode group in FIGS. 1 and 2 is viewed downward in the drawing), This electrode group when the boundary between the main body portion 600 and the current collecting tab portion 601 of the outermost negative electrode 6B on the negative electrode case 3 side in the electrode group is inside the outer periphery of the electrode group. It is located up to 2/3 of the diameter length.

  FIG. 5 is a plan view schematically showing an example of an electrode group included in the flat nonaqueous secondary battery shown in FIGS. 1 and 2. FIG. 5 is a plan view of the electrode group of the flat nonaqueous secondary battery shown in FIGS. 1 and 2 as viewed from the upper surface in the figure, and the outermost surface is the negative electrode 6B (its current collector). 62 exposed surface). What is positioned around the negative electrode 6B is the outer peripheral portion of the separator 7 positioned below the negative electrode 6B. Further, a positive current collecting tab portion 501 located further below the separator 7 is located on the left side in the drawing, and the leading end portion of the current collecting tab portion 501 is below the electrode group (in the depth direction in the drawing). )

  In the electrode group shown in FIG. 5, a negative electrode current collecting tab portion 601 a integrated by being collected and welded is folded on the negative electrode 6 </ b> B on the outer surface side of the electrode group. In the drawing, the end portion on the right side of the integrated negative electrode current collecting tab portion 601a is a portion where the integrated negative electrode current collecting tab portion 601a is folded (bent). The end X of the integrated negative electrode current collecting tab 601a is inside the outer periphery of the electrode group, and the main body 600 of the outermost negative electrode 6B on the negative electrode case side of the electrode group and the current collector When the boundary with the electric tab portion 601 is used as a base point, the electrode group is positioned up to 2/3 of the diameter length.

  In this specification, “the end of the current collecting tab portion of the integrated negative electrode is based on the boundary portion between the main body portion and the current collecting tab portion of the outermost negative electrode on the negative electrode case side in the electrode group. "It is located up to 2/3 of the diameter length of this electrode group." Referring to FIG. 5, the outermost negative electrode on the negative electrode case side of the electrode group (negative electrode 6B shown) When a boundary portion (vertical dotted line portion in the figure) between the main body portion and the current collecting tab portion having a base point is used as a base point, a linear distance from the base point to an end portion X of the integrated negative electrode current collecting tab portion 601a ( This means that the length (a) in the drawing is 2/3 or less of the length (the length of b in the drawing) of the diameter of the electrode group (the portion indicated by the dotted line in the drawing) from this base point.

  The above-mentioned “diameter of the electrode group” related to the determination of the position of the end portion of the current collecting tab portion of the integrated negative electrode is the main body portion of the positive electrode and the negative electrode included in the electrode group, and the separator main body (the overhang) described later. In the case of a separator having a portion), it is determined without considering the current collecting tab portion of these electrodes and the presence of the protruding portion of the separator. Further, as will be described later, the positive electrode and the negative electrode used in the flat nonaqueous secondary battery of the present invention are not necessarily circular in planar shape (planar shape of the main body) as shown in FIGS. Accordingly, the planar shape of the separator may not be circular, but in the case of an electrode group using such a positive electrode, negative electrode, or separator, the collection of each positive electrode and each negative electrode in a plan view of the electrode group. About the part excluding the electric tab part, the middle point of the part where the linear distance is the longest among the two points on the line forming the outer periphery of the electrode group is the center in the plan view of the electrode group, and the base point is the starting point. A line passing through the center and reaching the outer periphery of the electrode group is regarded as the diameter, and the position of the end of the current collecting tab portion of the integrated negative electrode is estimated.

  Thus, the integrated negative electrode current collecting tab portion is folded over the outermost negative electrode on the negative electrode case side of the electrode group, and the end portion of the integrated negative electrode current collecting tab portion is an electrode in plan view. 2 of the diameter length of the electrode group when the boundary portion between the main body part and the current collecting tab part of the outermost negative electrode on the negative electrode case side in the electrode group is inside the outer periphery of the group. Even when a thin flat non-aqueous secondary battery is sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case, the productivity is maintained high. However, the reliability can be improved.

  That is, the integrated current collecting tab portion of the negative electrode is folded back on the outermost negative electrode on the negative electrode case side of the electrode group, and the end portion of the integrated negative electrode current collecting tab portion is inside the outer periphery of the electrode group. Is located between the outer surface of the electrode group and the inner surface of the negative electrode case, so that even if the battery is subjected to vibration, the internal negative electrode current collecting tab portion is misaligned. Since it is difficult to occur, for example, the contact between the current collecting tab portion of the negative electrode and the positive electrode member such as the positive electrode case can be satisfactorily suppressed, so that the reliability of the flat non-aqueous secondary battery is improved.

  However, the integrated current collector tab of the negative electrode tends to float without being along the outer surface of the electrode group due to its elasticity, but it is folded back and the portion located on the outermost negative electrode on the negative electrode case side of the electrode group is long. If it is too high, this floating part will also become long, and when assembling the battery, the workability when fitting the positive electrode case and the negative electrode case with the electrode group loaded decreases, and the occurrence rate of defective products increases. Or an operation for suppressing the occurrence of defective products may be required, which may reduce battery productivity.

  Therefore, in the flat non-aqueous secondary battery of the present invention, the end of the integrated negative electrode current collecting tab portion is formed between the main body portion and the current collecting tab portion of the outermost negative electrode on the negative electrode case side in the electrode group. Suppressing workability deterioration during battery manufacturing as described above by shortening the raised part so that it is located up to 2/3 of the diameter length of the electrode group when the boundary is used as the base point And increase its productivity.

  The end of the integrated negative electrode current collecting tab portion is the diameter length of the electrode group when the boundary between the main body portion and the current collecting tab portion of the outermost negative electrode on the negative electrode case side in the electrode group is used as a base point It is only necessary to be located up to 2/3 of the outermost part of the electrode group where the positive electrode, the negative electrode, and the separator all overlap (in the depth direction, all of these overlap) in plan view. It is preferable to be located inside. The positive electrode, the negative electrode and the separator used for the electrode group usually have different areas in plan view. Generally, the size of the positive electrode is smaller than the size of the negative electrode and separator. There is a portion where the positive electrode is not positioned in the depth direction in the vicinity of the outer periphery when viewed. Therefore, when the end portion of the current collecting tab portion of the integrated negative electrode is located at a place where the positive electrode, the negative electrode, and the separator all overlap, this integration is performed between the outer surface of the electrode group and the inner surface of the negative electrode case. Thus, the current collecting tab portion of the negative electrode can be clamped more favorably, and the displacement can be suppressed more favorably.

  The specific length of the portion of the integrated current collecting tab portion of the negative electrode that is sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case varies depending on the shape and size of the battery. It is preferable that it is 1.5 mm or more.

  Further, a part of the integrated current collecting tab portion of the negative electrode is sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case, so that each negative electrode and the negative electrode case serving as the negative electrode terminal are electrically connected. .

  FIG. 1 shows a case where both of the two electrodes on the outermost side of the electrode group are negative electrodes. As described above, in the battery of the present invention, the outermost side of the electrode group Either one or both may be a positive electrode.

  In this case, at least the outermost electrode on the side of the positive electrode case in the electrode group is the positive electrode, and the current collecting tab portions of the positive electrodes are gathered and integrated by welding together, and the integrated current collecting tab portion of the positive electrode, Fold over the outermost positive electrode on the positive electrode case side in the electrode group. Then, the end of the integrated current collecting tab portion of the positive electrode is inside the outer periphery of the electrode group in plan view and the main body portion of the outermost positive electrode on the positive electrode case side in the electrode group and the current collector. The electrode group is sandwiched between the outer surface of the electrode group and the inner surface of the positive electrode case so as to be positioned up to 2/3 of the diameter length of the electrode group with the boundary with the electric tab as a base point. As a result, the productivity and reliability of the battery are good as in the case where the current collecting tab portion of the integrated negative electrode is sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case as described above. Can be.

  In this specification, “the end portion of the current collecting tab portion of the integrated positive electrode is based on the boundary portion between the main body portion and the current collecting tab portion of the outermost positive electrode on the negative electrode case side in the electrode group. "It is located up to 2/3 of the diameter length of this electrode group" means that the positive electrode case in the electrode group is similar to the case described above with respect to the end of the current collecting tab portion of the integrated negative electrode. When the boundary between the main body portion and the current collecting tab portion of the outermost positive electrode on the side is the base point, the linear distance from this base point to the end of the current collecting tab portion of the integrated positive electrode is from this base point. It means that it is 2/3 or less of the length of the diameter of the electrode group. Further, the “diameter of the electrode group” related to the determination of the position of the end portion of the current collecting tab portion of the integrated positive electrode is the “diameter of the electrode group” related to the position of the end portion of the current collecting tab portion of the integrated negative electrode. The “diameter” is determined by the method described above.

  The integrated current collecting tab portion of the positive electrode is folded on the outermost positive electrode on the positive electrode case side of the electrode group, and the end portion of the integrated positive electrode current collecting tab portion is positioned on the inner side of the outer periphery of the electrode group. In addition, because the battery is subjected to vibrations, etc., the position of the current collecting tab portion of the integrated positive electrode is unlikely to be generated by being sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case. Accordingly, for example, contact between the current collecting tab portion of the positive electrode and the negative electrode member such as the negative electrode case can be satisfactorily suppressed, and thus the reliability of the flat non-aqueous secondary battery is improved.

  In addition, the end of the current collecting tab portion of the integrated positive electrode is based on the boundary portion between the main body portion and the current collecting tab portion of the outermost positive electrode on the positive electrode case side in the electrode group. By positioning it up to 2/3 of the length of the diameter, it is possible to shorten the floating part of the integrated current collector tab that does not follow the outer surface of the electrode group. It is possible to suppress the workability deterioration when fitting the positive electrode case and the negative electrode case, and increase the productivity.

  The end of the integrated current collecting tab portion of the positive electrode is the diameter length of the electrode group when the boundary between the main body portion and the current collecting tab portion of the outermost positive electrode on the positive electrode case side in the electrode group is used as a base point However, for the same reason as in the case of the end portion of the integrated current collecting tab portion, all of the positive electrode, the negative electrode, and the separator in the electrode group are seen in a plan view. It is preferable to be located inside the outermost part of the overlapping part (the part where all of them overlap in the depth direction). Accordingly, the integrated current collecting tab portion of the positive electrode can be more favorably sandwiched between the outer surface of the electrode group and the inner surface of the positive electrode case, and the positional deviation can be more effectively suppressed.

  The specific length of the portion of the integrated positive electrode current collecting tab portion sandwiched between the outer surface of the electrode group and the inner surface of the positive electrode case varies depending on the shape and size of the battery, but is, for example, 10 mm or less. It is preferable that it is 1.5 mm or more.

  In addition, a part of the integrated current collecting tab portion of the positive electrode is sandwiched between the outer surface of the electrode group and the inner surface of the positive electrode case, so that each positive electrode and the positive electrode case serving as the positive electrode terminal are electrically connected. .

  As shown in FIG. 1, when the two electrodes on the outermost side of the electrode group are both negative electrodes, the positive electrode case (the outer case in FIGS. 1 and 2) and the electrode group (the outermost negative electrode) An insulating seal (8 in FIG. 1) made of, for example, a tape formed of polyethylene terephthalate (PET) or polyimide may be disposed between them.

  Also, for example, when the two electrodes on the outermost side of the electrode group are both positive electrodes, the electrical connection between the negative electrode and the negative electrode case (exterior case or sealing case) associated with the electrode group is, for example, Collecting and collecting the current collecting tabs of all the negative electrodes together and integrating them together, as shown in FIGS. 1 and 2, the end portions and the like of the negative electrode are not folded over the negative electrode on the outer surface side of the electrode group. It can be performed by welding to the inner surface of the case.

  When the two electrodes on the outermost side of the electrode group are both positive electrodes, for example, a tape formed of PET or polyimide is formed between the negative electrode case and the electrode group (the outermost positive electrode). An insulating seal may be arranged.

  In the battery of the present invention, one of the two electrodes on the outermost side of the electrode group can be a negative electrode and the other can be a positive electrode. In this case, the current collecting tab portion of each negative electrode related to the electrode group has the same configuration as that described above in the case where the outermost two electrodes of the electrode group are both negative electrodes, and relates to the electrode group About the current collection tab part of each positive electrode, it can be set as the structure similar to the structure demonstrated previously about the case where all the two outermost electrodes of an electrode group are positive electrodes.

  As shown in FIGS. 1 and 2, when the integrated current collecting tab portion of the negative electrode is folded over the outermost negative electrode of the electrode group, the integrated negative electrode current collecting tab portion is directed toward the positive electrode case side. To some extent. In this case, the current collecting tabs of the individual negative electrodes can be lengthened to some extent. Therefore, particularly in the case of a small and thin flat non-aqueous secondary battery, the current collecting tabs of the respective negative electrodes are integrated. This improves the workability of the welding process. However, in this case, in order to prevent the current collecting tab portion of the integrated negative electrode from coming into contact with the positive electrode case, the length of the loosened portion is such that the end portion does not reach the positive electrode case ( For example, the thickness is preferably less than the thickness of the electrode group.

  On the other hand, when the integrated current collecting tab portion of the positive electrode is folded on the outermost positive electrode of the electrode group, the integrated positive electrode current collecting tab portion may have some slack toward the negative electrode case side. Good. In this case, since the current collecting tabs of individual positive electrodes can be made somewhat long, the current collecting tabs of each positive electrode are integrated, particularly in the case of a small and thin flat non-aqueous secondary battery. This improves the workability of the welding process. However, also in this case, in order to prevent the current collecting tab portion of the integrated positive electrode from coming into contact with the negative electrode case, the length of the loosened portion is long enough not to reach the negative electrode case. It is preferable to set the thickness (for example, less than the thickness of the electrode group).

  When the current collecting tabs of each negative electrode are integrated together and folded on the outermost negative electrode of the electrode group, the current collecting tab part of each negative electrode is placed on the outermost negative electrode of the electrode group before integrating. , Forcibly folded and folded, and then welded together to be integrated. When the current collecting tab portion of each negative electrode is integrated and then folded back on the outermost negative electrode of the electrode group, the length of the current collecting tab portion located on the outer side becomes insufficient when folded, and the folded negative electrode Return of the current collecting tab portion (a phenomenon of floating without being along the outer surface of the electrode group) is more likely to occur. On the other hand, if each current collection tab part is folded and then welded and integrated, it is more preferable because such a return can be suppressed.

  Also, when the current collecting tabs of each positive electrode are integrated together and folded back onto the outermost positive electrode of the electrode group, the current collecting tab part of each positive electrode must be integrated before the integration. It can be folded and bundled with a crease forcibly, and then welded together for integration. Also in this case, since the return (lifting) of the current collecting tab portion of the integrated positive electrode after welding can be suppressed more favorably, it is more preferable.

  In the battery of the present invention, the two separators arranged on both surfaces of the positive electrode can be welded to each other at at least a part of their peripheral portions to form a joint portion.

  6 and 7 schematically show another example of the flat non-aqueous secondary battery of the present invention. The battery shown in FIGS. 6 and 7 has a group of electrodes formed by forming joints at the peripheral edges of the two separators 7 and 7 arranged on both surfaces of the positive electrode 5, and FIG. FIG. 7 is a longitudinal sectional view showing a cross section of the positive electrode case 2, the negative electrode case 3, and the insulating gasket 4, and FIG. 7 is an enlarged view of the main part of FIG.

  FIG. 8 schematically shows a plan view of a separator in which a joining portion is formed on a part of the peripheral edge. In FIG. 8, assuming the case of a stacked electrode group in which the positive electrode, the negative electrode, and the separator are stacked together with the separator 7, the positive electrode 5 disposed under the separator 7 is indicated by a dotted line, A current collecting tab portion 601 relating to the negative electrode disposed on the lower side is indicated by a one-dot chain line, and a binding tape 9 for suppressing positional deviation of each component relating to the electrode group is indicated by a two-dot chain line. Further, the positive electrode 5 shown in FIG. 8 is one in which both sides (both sides) of the electrode group are opposed to the negative electrode. Although not shown in FIG. In the forward direction), at least a negative electrode is arranged.

  The separator 7 shown in FIG. 8 is joined to another separator disposed on the lower side (in the depth direction in the drawing) via the positive electrode 5 (indicated by a dotted line in the drawing), and a joint 7c (FIG. Middle). That is, the separator 7 and the separator disposed below the separator 7 are welded to each other at the peripheral edge to form a bag shape, and the positive electrode 5 is accommodated therein.

  The separator 7 shown in FIG. 8 includes a main body part 7a (that is, a main body part 7a having a larger area in plan view than the main body part 5a of the positive electrode 5) and the main body part 7a. It has a protruding portion 7b that protrudes and covers at least a portion of the current collecting tab portion 5b of the positive electrode 5 that includes a boundary portion with the main body portion 5a. Then, two separators (the separator 7 and the separator disposed below the positive electrode 5) disposed on both surfaces of the positive electrode 5 were welded to at least a part of the peripheral portion of the main body portion 7 a of the separator 7. A joint 7c is provided.

  As separators for non-aqueous secondary batteries, a microporous film made of a thermoplastic resin that is easily heat-shrinkable at high temperatures is generally used. In this way, two sheets arranged on both sides of the positive electrode are used. In this separator, the peripheral portions are welded to each other to form a joint portion, so that, for example, even if the inside of the battery becomes high temperature, the thermal contraction of the separator is suppressed, so that a safer battery is configured. be able to.

  In addition, as shown in FIG. 8, when using the separator which has a main-body part and an overhang | projection part, the junction part for joining two separators arrange | positioned on both surfaces of a positive electrode is a peripheral part of the main-body part of a separator However, a joining portion may also be provided at the peripheral portion of the separator overhanging portion (the portion of the peripheral edge portion of the separator overhanging portion along the protruding direction from the main body portion).

  The joining portion may be formed by directly welding the peripheral portions of the two separators, but a layer made of a thermoplastic resin is interposed between the two separators, and two sheets are interposed via this layer. The separator may be formed by welding. However, in the latter case, depending on the type of thermoplastic resin that constitutes the layer interposed between the separators and the type of thermoplastic resin that constitutes the separator, the strength of the joint may be reduced. It is preferable to use the layer made of the same kind of resin as the thermoplastic resin constituting the separator. That is, when the separators are welded directly, or when the separators are welded via a layer composed of the same type of resin as the thermoplastic resin that constitutes the separator, the strength of the joint is determined by the strength of the separator itself. Since they are almost the same, for example, separation at a joint portion that may occur due to vibration or the like when the battery is used can be satisfactorily suppressed, and a battery with higher reliability can be obtained.

  In addition, when using the separator which has a main-body part and an overhang | projection part as shown in FIG. 8, all the peripheral parts which concern on the main-body part of a separator may be a junction part, For example, it shows in FIG. Thus, you may leave a part of peripheral part as the non-welding parts 7d and 7d, without welding separators. After the two separators are welded to form a bag, the positive electrode is accommodated therein, the positive electrode is disposed on one separator, and the separator is further disposed on the positive electrode. When the positive electrode is housed in a separator that is welded to form a bag, air may remain in the separator. However, when manufacturing a battery using such a positive electrode, when the outer case and the sealing case are caulked, the residual air is well discharged outside the separator through the non-welded portions 7d and 7d. Occurrence of problems due to residual air in the separator (problems such as non-uniform reaction during power generation and reduced capacity) can be prevented.

  When providing a non-welding part in the peripheral part of a separator, it is preferable that the number shall be about 1-5 from a viewpoint of suppressing the productivity fall of a battery. Moreover, when providing a non-welding part in the peripheral part of a separator, the length of the outer edge of the non-welding part related to the main part of the separator is the total length of the outer edge related to the main part of the separator (the total length of the outer edge excluding the overhanging part) Is preferably about 15 to 60%. That is, in the main part of the separator, it is preferable that 40% or more (preferably 70% or more) of the entire length of the outer edge is a joined part, thereby ensuring good joining strength between the separators. Can do.

  In order to form a joint part at the peripheral part of two separators and to accommodate a positive electrode between these separators, when two separators are directly welded together to form a joint part, for example, one sheet It is possible to employ a method in which the positive electrode is overlaid on the separator, the separator is further overlaid thereon, and then the peripheral portions of these separators are welded. It is also possible to adopt a method in which two separators are stacked, the peripheral portions thereof are welded to join the separators, and then the positive electrode is inserted between these separators.

  On the other hand, when a layer composed of the same kind of resin as the constituent resin of the separator is interposed between the two separators and these are welded to form a joint, for example, the joint on one separator It is possible to adopt a method in which a film to be the layer is placed at a place where the layer is expected to be placed, a positive electrode is disposed on the separator, and a separator is further stacked thereon, and then the peripheral portions of these separators are welded. . In addition, a film to be the layer is placed in a place where it is planned to become a joint portion on one separator, and the separator and the film are previously welded. Adopting a method of laminating the peripheral portion by overlapping, or a method of inserting a positive electrode between these separators after forming a joined portion by interposing a film serving as the layer between two separators. You can also.

  For example, the peripheral edge of the separator can be welded by a hot press. In this case, the heating temperature may be a temperature higher than the melting point of the thermoplastic resin constituting the separator, but for example, the heating temperature is preferably 10 to 50 ° C. higher than the melting point. Moreover, about the time of a hot press, if a junction part can be formed satisfactorily, there will be no restriction | limiting, However, Usually, it shall be about 1 to 10 second.

  In addition, the planar shape of the separator used for the battery of the present invention is, for example, at least a part of the peripheral part of the separator as described above at least at the joint part (at least the peripheral part of the two separators arranged on both surfaces of the positive electrode). In the case of forming a joint portion formed by welding a part of each other, the shape shown in FIG. 8 is preferable. However, even when the joint portion is not formed, the shape shown in FIG. Is preferred.

  In the battery of the present invention, when forming the electrode group, separators are disposed on both sides of the positive electrode at least on both sides facing the negative electrode. As for the positive electrode facing the negative electrode, separators may be disposed on both sides thereof (joint portions may be formed on these two separators), or only on the surface facing the negative electrode. You may arrange. Furthermore, when all the outermost electrodes in the electrode group are positive electrodes, and no separator is disposed on both surfaces of these positive electrodes, the battery case that also serves as the negative electrode terminal and the outermost positive electrode of the electrode group are between As described above, an insulator such as an insulating seal made of tape or the like made of PET or polyimide is disposed.

  Heretofore, the flat non-aqueous secondary battery of the present invention has been described with reference to FIGS. 1 to 8, but FIGS. 1 to 8 were created to facilitate the description of the present invention. However, the shape and size of each member shown on the bottom are not necessarily accurate.

  The positive electrode mixture layer of the positive electrode according to the battery of the present invention is a layer containing a positive electrode active material, a conductive additive, a binder and the like.

Examples of the positive electrode active material according to the battery of the present invention include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y O ₂ , and Li _x Co _y M _1-y O _2. lithium transition metal composite such as _{Li x Ni 1-y M y} O 2, Li x Mn y Ni z Co 1-y-z O 2, Li x Mn 2 O 4, Li x Mn 2-y M y O 4 (However, in each of the above lithium transition metal composite oxides, M is at least one selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, Al, and Cr.) It is a metal element, and 0 ≦ x ≦ 1.1, 0 <y <1.0, and 2.0 ≦ z ≦ 2.2.) These positive electrode active materials may be used individually by 1 type, and may use 2 or more types together.

  Moreover, as a conductive support agent of a positive electrode, carbon black, scale-like graphite, ketjen black, acetylene black, fibrous carbon etc. are mentioned, for example. Furthermore, examples of the binder for the positive electrode include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxymethyl cellulose, and styrene butadiene rubber.

  For the positive electrode, for example, a positive electrode mixture obtained by mixing a positive electrode active material, a conductive additive, and a binder is dispersed in water or an organic solvent to prepare a positive electrode mixture-containing paste (in this case, the binder is preliminarily mixed with water or It may be dissolved or dispersed in a solvent and mixed with a positive electrode active material or the like to prepare a positive electrode mixture-containing paste), and the positive electrode mixture-containing paste is made of metal foil, expanded metal, plain weave metal mesh, etc. It is manufactured by forming a positive electrode mixture layer by applying it to one or both sides of a current collector, drying it, and then press-molding it. However, the method for manufacturing the positive electrode is not limited to the above-described method, and other methods may be used.

  As a composition of the positive electrode, for example, in 100% by mass of the positive electrode mixture constituting the positive electrode, the positive electrode active material is 75 to 90% by mass, the conductive additive is 5 to 20% by mass, and the binder is 3 to 15% by mass. Is preferred. Moreover, it is preferable that the thickness of a positive mix layer is 30-200 micrometers, for example.

  The material for the current collector of the positive electrode is preferably aluminum or an aluminum alloy. From the viewpoint of reducing the total thickness of the positive electrode and increasing the number of layers of the positive electrode and the negative electrode in the battery to increase the facing area between the positive electrode mixture layer and the negative electrode agent layer and improving the load characteristics of the battery, It is preferable to use a metal foil for the current collector. Moreover, it is preferable that the thickness of a collector is 8-20 micrometers, for example.

  Examples of the negative electrode according to the battery of the present invention include a negative electrode having lithium, a lithium alloy, a carbon material capable of occluding and releasing lithium ions, lithium titanate, and the like as an active material.

  Examples of the lithium alloy that can be used for the negative electrode active material include lithium alloys that reversibly alloy with lithium, such as lithium-aluminum and lithium-gallium, and the lithium content is, for example, 1 to 15 atomic%. Is preferred. Examples of the carbon material that can be used for the negative electrode active material include artificial graphite, natural graphite, low crystalline carbon, coke, and anthracite.

The lithium titanate that can be used for the negative electrode active material is represented by the general formula Li _x Ti _y O ₄ , and x and y are 0.8 ≦ x ≦ 1.4 and 1.6 ≦ y ≦ 2.2, respectively. Lithium titanate having a stoichiometric number is preferable, and lithium titanate having a stoichiometric number of x = 1.33 and y = 1.67 is particularly preferable. The lithium titanate represented by the general formula Li _x Ti _y O ₄ can be obtained, for example, by heat-treating titanium oxide and a lithium compound at 760 to 1100 ° C. As the titanium oxide, either anatase type or rutile type can be used, and examples of the lithium compound include lithium hydroxide, lithium carbonate, and lithium oxide.

  When the negative electrode active material is lithium or a lithium alloy, the negative electrode is formed by bonding the lithium or lithium alloy to a current collector such as a metal network to form a negative electrode layer made of lithium or lithium alloy on the surface of the current collector. Can be obtained. On the other hand, when a carbon material or lithium titanate is used as the negative electrode active material, for example, a negative electrode composite obtained by mixing a carbon material or lithium titanate with a binder as the negative electrode active material and, if necessary, a conductive additive. The negative electrode mixture-containing paste is prepared by dispersing the agent in water or an organic solvent (in this case, the binder is previously dissolved or dispersed in water or solvent, and mixed with the negative electrode active material or the like to contain the negative electrode mixture) The paste containing the negative electrode mixture may be applied to a current collector made of metal foil, expanded metal, plain weave metal mesh, etc., dried, and then pressed to form a negative electrode layer (negative electrode composite). The negative electrode can be produced by forming an agent layer. However, the manufacturing method of the negative electrode is not limited to the above-described method, and other methods may be used.

  In addition, as a binder and conductive support agent which concern on a negative electrode, the various binders and conductive support agent which were illustrated previously as what can be used for a positive electrode can be used.

  The composition of the negative electrode when a carbon material is used as the negative electrode active material is, for example, that the carbon material is 80 to 95% by mass and the binder is 3 to 15% by mass in 100% by mass of the negative electrode mixture constituting the negative electrode. Moreover, when using together a conductive support agent, it is preferable that a conductive support agent shall be 5-20 mass%. On the other hand, the composition of the negative electrode when lithium titanate is used as the negative electrode active material is, for example, 75 to 90% by mass of lithium titanate and 3 to 15% by mass of the binder in 100% by mass of the negative electrode mixture constituting the negative electrode. In addition, when a conductive auxiliary is used in combination, the conductive auxiliary is preferably 5 to 20% by mass.

  The thickness of the negative electrode layer (including the negative electrode mixture layer) in the negative electrode is preferably 40 to 200 μm, for example.

  The material for the current collector of the negative electrode is preferably copper or a copper alloy. From the viewpoint of reducing the total thickness of the negative electrode and increasing the number of layers of the positive electrode and negative electrode in the battery to increase the facing area between the positive electrode mixture layer and the negative electrode agent layer, and improving the load characteristics of the battery, It is preferable to use a metal foil for the current collector. Moreover, it is preferable that the thickness of a collector is 5-30 micrometers, for example.

  A separator made of a microporous film made of a thermoplastic resin is used. As the thermoplastic resin constituting the separator, for example, polyolefins such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, polymethylpentene, and the like are preferable. From the viewpoint of arranging and welding the same type of resin as the constituent resin, the melting point, that is, the melting temperature measured using a differential scanning calorimeter (DSC) in accordance with the provisions of JIS K 7121 is 100. A polyolefin of ˜180 ° C. is more preferable.

  As the form of the microporous film made of the thermoplastic resin constituting the separator, any form may be used as long as it has an ionic conductivity sufficient to obtain the required battery characteristics. Or the ion-permeable microporous film (microporous film currently used widely as a battery separator) which has many holes formed by the wet extending | stretching method etc. is preferable.

  The thickness of the separator is preferably, for example, 5 to 25 μm, and the porosity is preferably, for example, 30 to 70%.

  The positive electrode, the negative electrode, and the separator are stacked and used as a stacked electrode group as shown in FIG. 1, FIG. 2, FIG. 6, and FIG. 7. It is preferable that the electrodes are arranged so as to face in the same direction in the plan view of the group, and the current collecting tab portions of the respective negative electrodes are arranged so as to face in the same direction in the plan view of the electrode group. Thereby, current collection of the positive electrode and the negative electrode becomes easier.

  Furthermore, the current collecting tab portion of each positive electrode and the current collecting tab portion of each negative electrode only need to be arranged so as not to contact each other in a plan view of the electrode group, but these contacts are better suppressed, In addition, from the viewpoint of improving battery production, as shown in FIG. 8, the current collecting tab portion 501 of each positive electrode and the current collecting tab portion 601 of each negative electrode face each other in a plan view of the electrode group. More preferably, it is arranged at a position where

  Further, as shown in FIG. 8, the electrode group formed by laminating the positive electrode, the negative electrode, and the separator is bound to the outer periphery with a binding tape 9 made of polypropylene having chemical resistance, etc. It is preferable to suppress misalignment of the positive electrode and the negative electrode wrapped in the separator.

  The total number of positive electrodes and negative electrodes in the electrode group is at least 3, but it is also possible to increase the number (4, 5, 6, 7, 8, etc.). However, if the number of stacked positive and negative electrodes is increased too much, the merit as a flat battery may be reduced. Therefore, it is usually preferable that the number is 13 or less.

  Examples of non-aqueous electrolytes for batteries include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate, butylene carbonate, and vinylene carbonate; chain carbonate esters such as dimethyl carbonate, diethyl carbonate (DEC), and methyl ethyl carbonate. 1,2-dimethoxyethane, diglyme (diethylene glycol methyl ether), triglyme (triethylene glycol dimethyl ether), tetraglyme (tetraethylene glycol dimethyl ether), 1,2-dimethoxyethane, 1,2-diethoxymethane, tetrahydrofuran, etc. It is possible to use an electrolytic solution prepared by dissolving an electrolyte (lithium salt) in a concentration of about 0.3 to 2.0 mol / L in an organic solvent such as ether; That. The above organic solvents may be used alone or in combination of two or more.

Examples of the electrolyte include LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) Lithium salts such as ₂ are mentioned.

  The planar shape of the flat non-aqueous secondary battery of the present invention is not particularly limited, and may be a polygonal shape such as a square (quadrangle) in addition to the circular shape that is the mainstream of conventionally known flat batteries. In addition, the polygon such as a square as the planar shape of the battery in this specification includes a shape in which the corner is cut off and a shape in which the corner is curved. Moreover, the planar shape of the main body part of the positive electrode and the negative electrode may be a shape corresponding to the planar shape of the battery, and may be a substantially circular shape or a polygon such as a rectangle such as a rectangle or a square. In the case of a substantially circular shape, the portion corresponding to the location where the current collecting tab portion of the counter electrode is disposed is cut off as shown in FIGS. 3 and 4 in order to prevent contact with the current collecting tab portion of the counter electrode. It is preferable to use a different shape.

  The flat non-aqueous secondary battery of the present invention can be applied to the same use as a conventionally known flat non-aqueous secondary battery.

The flat non-aqueous secondary battery according to the present invention has, for example, a battery diameter d (when the planar view shape of the battery is not a circle, the planar view area assumes that the planar view shape is a circle. Is suitable for thin batteries with a thickness t (mm) to battery thickness t (mm) of 0.03 to 0.3, which is less than usual. However, high reliability can be secured. Further, the size of the battery of the present invention is not particularly limited, but it can be preferably applied to, for example, a very small size such as an opening area of an insulating gasket of 100 mm ² or less. However, since the battery having a very small opening area of the insulating gasket itself tends to be difficult to produce, the opening area of the insulating gasket according to the battery of the present invention is preferably 20 mm ² or more, for example.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
<Preparation of positive electrode>
A positive electrode was prepared using LiCoO ₂ as a positive electrode active material, carbon black as a conductive additive, and PVDF as a binder. First, LiCoO ₂ : 93 parts by mass and carbon black: 3 parts by mass were mixed, and the resulting mixture and PVDF: 4 parts by mass were previously dissolved in N-methyl-2-pyrrolidone (NMP). Were mixed to prepare a positive electrode mixture-containing paste. The obtained positive electrode mixture-containing paste was applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 15 μm by an applicator. When applying the positive electrode mixture-containing paste, the application part and the non-application part were continuously arranged every 5 cm, and the part that was the application part on the front surface was also the application part on the back surface. Subsequently, the applied positive electrode mixture-containing paste was dried to form a positive electrode mixture layer, and then roll-pressed and cut into a predetermined size to obtain a belt-like positive electrode. The positive electrode had a width of 40 mm, and the positive electrode mixture layer forming portion had a thickness of 140 μm.

  The belt-like positive electrode is such that the positive electrode mixture layer forming portion is the main body portion (arc portion diameter 15.1 mm), and the positive electrode mixture layer non-forming portion is the current collecting tab portion (width 3.5 mm). 3 was punched into the shape shown in FIG. 3 to obtain a positive electrode for a battery.

<Integration of battery positive electrode and separator>
A PE microporous membrane separator (thickness 16 μm) having the shape shown in FIG. 8 is disposed on both surfaces of the battery positive electrode, and the portion shown in FIG. 8 is welded by a heat press (temperature 170 ° C., press time 2 seconds). A joining part was formed in a part of the peripheral part of the main part and a part of the peripheral part of the overhanging part related to the two separators, and the battery positive electrode and the separator were integrated. Note that the width of the joint portion relating to the two separators was 0.3 mm for both the main portion and the overhang portion, and the length in the protruding direction from the main portion at the peripheral portion of the overhang portion was 0.5 mm. Of the outer edges of the main parts of the two separators, 90% of the length was used as the joint.

<Production of negative electrode>
A negative electrode was prepared using graphite as the negative electrode active material and PVDF as the binder. The graphite: 94 parts by mass, PVDF: 6 parts by mass, and a binder solution previously dissolved in NMP were mixed to prepare a negative electrode mixture-containing paste. The obtained negative electrode mixture-containing paste was applied to one or both sides of a negative electrode current collector made of a copper foil having a thickness of 10 μm by an applicator. In addition, when applying the negative electrode mixture-containing paste, when the coated part and the non-coated part are continuously applied every 5 cm and are applied to both sides of the current collector, the place where the coated part is the surface is the back side However, it was made to become an application part. Subsequently, the applied negative electrode mixture-containing paste was dried to form a negative electrode mixture layer, and then roll-pressed and cut into a predetermined size to obtain a strip-shaped negative electrode. The negative electrode had a width of 40 mm, and the negative electrode mixture layer forming portion had a thickness of 190 μm when formed on both sides of the current collector and 100 μm when formed on one side of the current collector.

  The strip-shaped negative electrode is shaped as shown in FIG. 4 so that the negative electrode mixture layer forming portion is a main body portion (arc portion diameter 16.3 mm) and the negative electrode mixture layer non-forming portion is a current collecting tab portion. The negative electrode for a battery having a negative electrode mixture layer on one side of the current collector and the negative electrode for a battery having a negative electrode mixture layer on both sides of the current collector were obtained. A part of the negative electrode for a battery having the negative electrode mixture layer on one side of the current collector was punched after a PET film having a thickness of 100 μm was attached to the exposed surface of the current collector of the strip-shaped negative electrode. .

<Battery assembly>
Three battery positive electrodes integrated with the separator, two battery negative electrodes with a negative electrode mixture layer formed on both sides of the current collector, and a battery negative electrode with a negative electrode mixture layer formed on one side of the current collector The battery negative electrode with a negative electrode mixture layer formed on one side of the current collector was used as the outermost electrode using two sheets (one of which was a PET film affixed to the exposed surface of the current collector) The battery positive electrode and the battery negative electrode were alternately stacked. And the current collection tab part of each battery positive electrode was collectively welded and integrated. In addition, the current collecting tab portion of each battery negative electrode is forcibly folded over each current collecting tab portion on one of the outermost battery negative electrodes, and these are then welded together. Thus, an electrode group was obtained.

The electrode group was placed in the outer case so that the PET film faced the inner surface of the outer case (positive electrode case), and the integrated current collecting tab portion of each battery positive electrode was welded to the inner surface of the outer case. In addition, an insulating gasket is attached to the sealing case (negative electrode case), and the nonaqueous electrolyte (LiPF ₆₎ is dissolved in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 1: 2 at a concentration of 1.2 mol / l. After adding 90 mg, the outer case containing the electrode group was put on, and the periphery was caulked, the diameter was 20 mm, the thickness was 1.6 mm, and flat non-aqueous water having a structure similar to that shown in FIGS. 6 and 7 A secondary battery was obtained.

  The flat non-aqueous secondary battery is designed to discharge at a current value of 6 mA and a discharge capacity of 30 mAh (the same applies to Example 2 and Comparative Examples 1 and 2 described later). ). Further, the end of the integrated negative electrode current collecting tab portion according to the flat non-aqueous secondary battery has a main body portion and a current collecting tab portion of the outermost negative electrode on the negative electrode case side of the electrode group in plan view. And the ratio a / b between the length of a and the length of b in FIG. 5 is 0. 2), the integrated current collecting tab portion of the negative electrode is sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case. Of the integrated current collecting tab portion of the negative electrode, the length of the portion sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case is 2.6 mm.

Example 2
The electrode when the end portion of the integrated current collecting tab portion of the negative electrode is based on the boundary between the main body portion and the current collecting tab portion of the outermost negative electrode on the positive electrode case side in the electrode group in plan view It was integrated so as to be located at 2/25 of the diameter length of the group (that is, the ratio a / b of the length of a to b in FIG. 5 was 0.08). A flat non-aqueous secondary battery was produced in the same manner as in Example 1 except that the current collecting tab portion of the negative electrode was sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case. Of the integrated current collecting tab portion of the negative electrode, the length of the portion sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case is 1.0 mm.

Comparative Example 1
The electrode when the end portion of the integrated current collecting tab portion of the negative electrode is based on the boundary between the main body portion and the current collecting tab portion of the outermost negative electrode on the positive electrode case side in the electrode group in plan view The integrated current collecting tab portion of the negative electrode is positioned at the other end of the diameter of the group (that is, the ratio a / b of the length a to b in FIG. 5 is 1). A flat non-aqueous secondary battery was produced in the same manner as in Example 1 except that it was sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case. Of the integrated current collecting tab portion of the negative electrode, the length of the portion sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case is 12.8 mm.

Comparative Example 2
The integrated current collecting tab portion of the negative electrode is hung to the positive electrode case side without being folded over the outermost negative electrode of the electrode group, and is not sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case, A flat nonaqueous secondary battery was produced in the same manner as in Example 1.

  When the occurrence state of defective products when 100 flat non-aqueous secondary batteries of Example 1 and Comparative Examples 1 and 2 were manufactured was examined, the number of defective products generated was that of Example 1 and Example 2. The number of batteries was 0, whereas that of Comparative Example 1 was 2, and that of Comparative Example 2 was 100. The battery of Example 1 was more productive than the battery of Comparative Example 1. It turned out to be excellent.

  In addition, the following vibration test was performed on each of the 25 flat non-aqueous secondary batteries of Examples 1 and 2 and Comparative Example 1.

  In the vibration test, first, the battery is firmly fixed to the platform of the vibration device so that the vibration is reliably transmitted without distorting the battery. For example, X, Y, Z when the plane axis direction of the battery is X The following vibrations were added to each of the three directions. The vibration applied to the battery is a sine curve waveform of logarithmic sweep from 7 Hz to 200 Hz, and it takes 15 minutes to return to 7 Hz (that is, the vibration is started from 7 Hz and increased to 200 Hz, and then the vibration is increased to 7 Hz. The total operation time to be reduced is 15 minutes). Therefore, the vibration applied in each of the X, Y, and Z directions of the battery is 3 hours, and the total vibration time is 9 hours. The logarithmic sweep speed in one cycle of the vibration was as follows. From 7 Hz to 18 Hz, the peak acceleration is maintained at 1 gn, then the vibration is kept at 0.8 mm (total displacement 1.6 mm), the vibration is increased until the peak acceleration is 8 gn, and further the vibration is 200 Hz. The peak acceleration of 8 gn is maintained until

  When the occurrence of a short circuit after the above vibration test was investigated, the number of short circuits generated was 0 for the battery of Example 1, 1 for the battery of Example 2, and 0 for the battery of Comparative Example 1. It was found that the batteries of Examples 1 and 2 (particularly the battery of Example 1) had very high reliability while having good productivity.

DESCRIPTION OF SYMBOLS 1 Flat type non-aqueous secondary battery 2 Positive electrode case 3 Negative electrode case 4 Insulation gasket 5 Positive electrode 500 Positive electrode main-body part 501 Positive electrode current collection tab part 6, 6A, 6B Negative electrode 600 Negative electrode main-body part 601 Negative electrode current collection tab part 7 Separator 7c Joint 8 Insulating material

Claims (10)

A positive electrode case that also serves as a positive electrode terminal and a negative electrode case that also serves as a negative electrode terminal are formed in a space formed by caulking and sealing via an insulating gasket. A flat non-aqueous secondary battery having a non-aqueous electrolyte and a group of electrodes having a total number of positive and negative electrodes of 3 or more, which are stacked substantially parallel to the flat surface of the negative electrode case,
The negative electrode has a main body portion and a current collecting tab portion that protrudes from the main body portion in a plan view and is narrower than the main body portion. The main body portion of the negative electrode includes a current collector. A negative electrode layer containing a negative electrode active material is formed on one side or both sides, and in the current collector tab portion of the negative electrode, the negative electrode layer is not formed on the current collector,
The electrode group has at least two negative electrodes, and the outermost electrode on the negative electrode case side in the electrode group is a negative electrode, and the current collecting tab portions of the negative electrodes are collected and welded together. The integrated negative electrode current collecting tab portion is folded over the outermost negative electrode on the negative electrode case side of the electrode group,
An end of the current collecting tab portion of the integrated negative electrode is inside the outer periphery of the electrode group in a plan view, and the main body portion and the current collector of the outermost negative electrode on the negative electrode case side in the electrode group It is located up to 2/3 of the diameter length of the electrode group when the boundary with the tab part is a base point, and is sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case. A flat non-aqueous secondary battery. A positive electrode case that also serves as a positive electrode terminal and a negative electrode case that also serves as a negative electrode terminal are formed in a space formed by caulking and sealing via an insulating gasket. A flat non-aqueous secondary battery having a non-aqueous electrolyte and a group of electrodes having a total number of positive and negative electrodes of 3 or more, which are stacked substantially parallel to the flat surface of the negative electrode case,
The positive electrode has a main body portion and a current collecting tab portion that protrudes from the main body portion in a plan view and is narrower than the main body portion. The main body portion of the positive electrode includes a current collector. A positive electrode mixture layer containing a positive electrode active material is formed on one side or both sides, and in the current collector tab portion of the positive electrode, a positive electrode mixture layer is not formed on the current collector,
The electrode group includes at least two positive electrodes, and the outermost electrode on the positive electrode case side in the electrode group is a positive electrode, and the current collecting tab portions of the positive electrodes are gathered and welded together. The integrated current collecting tab portion of the positive electrode is folded on the outermost positive electrode on the positive electrode case side in the electrode group,
An end of the integrated current collecting tab portion of the positive electrode is inside the outer periphery of the electrode group in a plan view, and a current collector and a current collector of the outermost positive electrode on the positive electrode case side in the electrode group It is located up to 2/3 of the diameter length of the electrode group when the boundary with the tab part is used as a base point, and is sandwiched between the outer surface of the electrode group and the inner surface of the positive electrode case. A flat non-aqueous secondary battery. The current collecting tab portions of the negative electrode are gathered together and integrated with each other, folded back on the outer surface of the negative electrode case side in the electrode group, and the end portion of the current collecting tab portion of the integrated negative electrode is In the plan view, the inner side of the outer periphery of the electrode group, and the electrode group with the base portion of the outermost negative electrode on the negative electrode case side of the electrode group and the current collecting tab portion as a base point It is located up to 2/3 of the diameter length and is sandwiched between the outer surface of the electrode group and the inner surface of the negative electrode case,
The current collecting tab portions of the positive electrode are gathered together and integrated with each other, folded on the outer surface of the positive electrode case side in the electrode group, and the end portion of the current collecting tab portion of the integrated positive electrode is In the plan view, the inner side of the outer periphery of the electrode group and the electrode group of the electrode group having a base portion of the outermost positive electrode on the positive electrode case side of the electrode group and the current collecting tab portion as a base point 3. The flat non-aqueous secondary battery according to claim 1, wherein the flat non-aqueous secondary battery is positioned up to 2/3 of the diameter length and is sandwiched between an outer surface of the electrode group and an inner surface of the positive electrode case.   The current collecting tab portions of the negative electrode are gathered together and integrated with each other, folded back on the outer surface of the negative electrode case side in the electrode group, and the end portion of the current collecting tab portion of the integrated negative electrode is When viewed from above, the outermost negative electrode on the negative electrode case side of the electrode group is located on the inner side of the outermost position at a position corresponding to a portion where all of the positive electrode, the negative electrode, and the separator overlap in the electrode group. It is located by 2/3 of the diameter length of the said electrode group from the boundary part of a main-body part and a current collection tab part, and is clamped by the outer surface of the said electrode group, and the inner surface of a negative electrode case. Item 4. The flat nonaqueous secondary battery according to item 1 or 3.   The current collecting tab portions of the positive electrode are gathered together and integrated with each other, folded on the outer surface of the positive electrode case side in the electrode group, and the end portion of the current collecting tab portion of the integrated positive electrode is In the plan view, the outermost positive electrode on the positive electrode case side in the electrode group is located on the inner side of the outermost position at the position corresponding to the location where all of the positive electrode, the negative electrode and the separator overlap in the electrode group. It is located by 2/3 of the diameter length of the said electrode group from the boundary part of a main-body part and a current collection tab part, and is clamped by the outer surface of the said electrode group, and the inner surface of a positive electrode case. Item 4. The flat nonaqueous secondary battery according to Item 2 or 3.   The flat non-aqueous secondary battery according to claim 1, wherein the total number of positive electrodes and negative electrodes is 13 or less. At least on both sides of the positive electrode facing the negative electrode, separators made of a microporous film made of thermoplastic resin are arranged,
The two separators include a main body that covers the entire surface of the main body of the positive electrode, and an overhang that protrudes from the main body and covers at least a portion of the current collecting tab of the positive electrode that includes a boundary with the main body. The flat separator is provided in any one of claims 1 to 6, wherein the two separators have joint portions welded to each other at least at a part of a peripheral edge portion of the main body portion. Water secondary battery.   The flat nonaqueous secondary battery according to claim 7, wherein a joint portion between two separators disposed on both surfaces of the positive electrode is formed by directly welding the two separators.   The joining portion of the two separators arranged on both surfaces of the positive electrode is formed by welding through a layer made of the same type of resin as the thermoplastic resin constituting the two separators. The flat non-aqueous secondary battery described.   The flat non-aqueous secondary battery according to any one of claims 7 to 9, wherein the thermoplastic resin constituting the separator is a polyolefin.

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