JP2005190913A - Lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery wherein the battery size can be made small or battery capacity can be made large in the same battery size. <P>SOLUTION: In this lithium secondary battery, a group of electrode plates 3 wherein a positive electrode plate 4 and a negative electrode plate 5 wherein plain parts 42, 52 not coated with the active material are formed at one end parts in a width direction are wound while active material coating parts 41, 51 are disposed facing each other through a separator 6 and the plain parts 42, 52 of the positive and negative electrode plates 4, 5 are projected in a counter direction, the width of the active material coating part 51 of the negative electrode plate 5 is larger than the width of the active material coating part 41 of the positive electrode plate 4, and winding is performed in a state that the boundary of the active material coating part 51 and the plain part 52 in the negative electrode plate 5 and a side edge of the separator 6 are almost adjusted to form the group of electrode 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lithium secondary battery, and more particularly to a lithium secondary battery including an electrode plate group formed by winding a positive electrode plate and a negative electrode plate through a separator.

  A secondary battery such as a lithium ion secondary battery has an electrode plate group in which a positive electrode plate and a negative electrode plate are wound through a separator, and one end in the width direction of the positive electrode plate and the negative electrode plate in the electrode plate group It is known that a plain part not coated with an active material is formed on the part, the plain parts of the positive electrode plate and the negative electrode plate protrude in opposite directions, and a current collector plate is joined to the edge of each plain part. (For example, refer to Patent Document 1).

  In such an electrode plate group, as shown in FIG. 5, an active material application portion 41 applied with an active material of the positive electrode plate 4 and an active material application portion 51 applied with an active material of the negative electrode plate 5 are provided. It is configured to obtain a charging / discharging action by facing each other through the separator 6 and inserting or extracting lithium ions between both active materials. Furthermore, the width dimension n of the active material application part 51 of the negative electrode plate 5 is set larger than the width dimension p of the active material application part 41 of the positive electrode plate 4, and the active material application part of the negative electrode plate 5. By projecting both side edges of 51 by dimensions e and f to the outside of both side edges of the active material coating portion 41 of the positive electrode plate 4, metal lithium is deposited in the active material coating portion 51 of the negative electrode plate 5. It is prevented. That is, when a portion where the lithium ions released from the active material of the positive electrode plate 4 cannot be completely occluded is generated in the active material application portion 51 of the negative electrode plate 5, metallic lithium is deposited in the shape of the needle, and this metal Since lithium may break through the separator 6 and cause a short circuit, this is prevented.

  Further, in order to ensure insulation between the positive and negative electrode plates 4 and 5, the width dimension of the separator 6 is set larger than the width dimension of the active material coated portion 51 of the wide negative electrode plate 5. Both side edges are configured to protrude by dimensions b and c, respectively, outside the side edges of the active material application part 51 of the negative electrode plate 5. The plain portions 42 and 52 of the positive electrode plate 4 and the negative electrode plate 5 are outside the side edges of the separator 6 by the dimensions a and d necessary to ensure a reliable joining operation with the current collectors 7 and 8. The width dimension is set so as to protrude.

Therefore, as described above, the protruding dimension of the plain portion 42 of the positive electrode plate 4 from the side edge of the separator 6 is a, the protruding dimension of the separator 6 from the side edge of the negative electrode plate 5 opposite to the uncoated portion 52 is b, The protruding dimension of the separator 6 from the boundary between the active material coating part 51 and the plain part 52 of the negative electrode plate 5 is c, the protruding dimension from the side edge of the separator 6 of the plain part 52 of the negative electrode plate 5 is d, and The width dimension of the active material application part 41 is p, the width dimension of the active material application part 51 of the negative electrode plate 5 is n, and the active material application of the negative electrode plate 5 from both side edges of the active material application part 41 of the positive electrode plate 4 The width dimension D of the electrode plate group 3 from the side edge of the uncoated portion 42 of the positive electrode plate 4 to the side edge of the uncoated portion 52 of the negative electrode plate 5 is defined as e and f, respectively. With reference to the width n of the active material coated portion 51, D = n + (a + b + c + d).
JP 2001-185120 A

  By the way, at both side edges of the separator 6, a short circuit between the side edge of the active material application part 51 of the negative electrode plate 5 opposite to the plain part 52 and the positive electrode plate 4 is prevented. It is required to have a function of preventing a short circuit between the side edge of the landing portion 41 opposite to the plain portion 42 and the negative electrode plate 5. The separator 6 protrudes from the active material coating portion 51 of the negative electrode plate 5 by the dimension b between the side edge of the active material coating portion 51 of the negative electrode plate 5 opposite to the plain portion 52 and the positive electrode plate 4. However, the active material coating portion of the negative electrode plate 5 is between the side edge of the active material coating portion 41 of the positive electrode plate 4 opposite to the uncoated portion 42 and the negative electrode plate 5. The short circuit is prevented by projecting the separator 6 by a dimension (f + c) from 51.

  However, as the protruding dimension of the separator for preventing a short circuit between the side edge of the active material coated portion 41 of the positive electrode plate 4 opposite to the uncoated portion 42 and the negative electrode plate 5, the dimension c or the dimension f is c. Is larger than the dimension f, and the dimensions c and f are usually set to substantially the same size. Therefore, the separator 6 is dimensioned from the active material coating portion 51 of the negative electrode plate 5. In the state of projecting by (f + c), the projecting dimension is excessive. As a result, the width dimension D of the electrode plate group is excessively large, and accordingly the battery size is increased. Conversely, when the same battery size is used, there is a problem that the battery capacity is relatively decreased.

  In view of the above-described conventional problems, an object of the present invention is to provide a lithium secondary battery that can reduce the battery size or increase the battery capacity with the same battery size.

  In the lithium secondary battery of the present invention, a positive electrode plate and a negative electrode plate, which are formed with a plain portion not coated with an active material at one end in the width direction, are opposed to each other with a respective active material coated portion interposed therebetween. In addition, in the lithium secondary battery including the electrode plate group formed by winding the plain portions of the positive and negative electrode plates in a state of protruding in opposite directions, the width of the active material coating portion of the negative electrode plate is Set larger than the width of the active material coated portion of the positive electrode plate, and wind the electrode plate group in a state where the boundary between the active material coated portion and the plain portion of the negative electrode plate and the side edge of the separator are substantially matched. It is composed.

  According to this configuration, the electrode plate group is configured by winding in a state in which the boundary between the active material coated portion and the plain portion in the negative electrode plate and the side edge of the separator are substantially matched, but the active material of the negative electrode plate The width of the coated portion is larger than the width of the active material coated portion of the positive electrode plate, and both side portions of the active material coated portion of the negative electrode plate protrude a predetermined width dimension from the side edge of the active material coated portion of the positive electrode plate. Therefore, by extending the side edge of the separator to the side edge, a short circuit between the side edge of the active material coating portion of the positive electrode plate and the negative electrode plate can be prevented by this separator. In addition, since the separator does not protrude from the boundary between the active material coated portion and the plain portion of the negative electrode plate, it is possible to reduce the protruding dimension of the separator that has conventionally protruded from the boundary between the active material coated portion and the plain portion of the negative electrode plate. In addition, since the protruding dimension of the plain portion protruding from the separator does not change, the width dimension of the electrode plate group can be reduced by the reduction of the protruding dimension of the separator, and the battery size can be reduced accordingly, or the same battery With the size, the size of the active material application part can be increased and the battery capacity can be increased.

  According to the lithium secondary battery of the present invention, the side edge of the separator is substantially matched with the boundary between the active material coated portion and the plain portion of the negative electrode plate, and the protruding dimension of the separator protruding from the boundary is reduced. Therefore, the battery size can be reduced accordingly, or the same battery size can increase the size of the active material coating portion and increase the battery capacity.

  Hereinafter, an embodiment of the prismatic battery of the present invention will be described with reference to FIGS.

  1 and 2, reference numeral 1 denotes a prismatic battery made of a lithium secondary battery, and an electrode plate as a power generation element in a rectangular case 2 having a flat cross-sectional shape, or a rounded rectangular shape or an oval rectangular tube shape. Group 3 is contained with the electrolyte.

  As shown in FIG. 3, the electrode plate group 3 is wound around the outer periphery of a thin plate-shaped core material in a state where the strip-like positive electrode plate 4, the separator 6, the negative electrode plate 5, and the separator 6 are sequentially stacked. It is configured by pulling out the core material and compressing it flat, and the positive electrode plate 4 and the negative electrode plate 5 are stacked with the separator 6 interposed therebetween. The positive electrode plate 4 has an active material coating portion 41 formed by applying and drying a positive electrode mixture on a core material 4a made of aluminum foil, and the negative electrode plate 5 is made of a negative electrode mixture on a core material 5a made of copper foil. The separator 6 is formed of a porous polypropylene film or the like. Further, the outer periphery of the electrode plate group 3 is covered with an outer peripheral separator (not shown) as necessary to prevent a short circuit, or an insulating resin layer (not shown) is formed on the inner periphery of the case 2.

  In the electrode plate group 3, the core material 4a made of aluminum foil of the positive electrode plate 4 and the core material 5a made of copper foil of the negative electrode plate 5 are projected on opposite sides to form plain portions 42 and 52, respectively. The positive electrode current collector 7 is bonded to the positive electrode plain portion 42 by laser beam welding or electron beam welding, and the negative electrode current collector 8 is bonded to the protruding negative electrode uncoated portion 52 by laser beam welding or electron beam welding. ing.

  As shown in FIG. 1, the positive electrode current collector 7 also serves as a lower lid that closes the lower end opening of the case 2, and the planar shape is fitted to the inner periphery of the lower end of the case 2 as shown in FIG. 2. An annular rising portion 9 is formed to rise outward (on the opposite side to the electrode plate group 3) on the entire circumference of the outer periphery. The positive electrode current collector 7 is fitted to the lower end portion of the case 2, and the lower end edge of the case 2 and the end edge of the annular rising portion 9 are welded by laser beam welding or the like. It is joined. Further, in the semicircular part at both ends in the long side direction, a radial joint protrusion 11 protruding toward the inner side (electrode plate group 3 side) is protruded and formed at a substantially central part in the circumferential direction. A plurality of joining projections 12 extending substantially at the full width at appropriate intervals in the long side direction are formed so as to be in pressure contact with the plain portion 42 of the positive electrode plate 4 projecting from the electrode plate group 3. Thus, these joint projections 11 and 12 are joined to the plain portion 42 of the positive electrode plate 4 by performing laser beam welding or electron beam welding.

  As shown in FIG. 1, the negative electrode current collector 8 is disposed in a space between the upper lid 13 that closes the upper end opening of the case 2 and the upper end of the electrode plate group 3, as shown in FIG. In addition, the planar shape accommodated and disposed in the case 2 is configured by a substantially oval flat plate, and the semicircular portions at both ends in the long side direction have an inner side (electrode plate group) in the substantially central portion in the circumferential direction. 3) projecting in the radial direction projecting toward the third side), and projecting and projecting a plurality of joining projections 15 extending over almost the entire width at appropriate intervals between the two ends. 14 and 15 are pressed against the plain portion 52 of the negative electrode plate 5 projecting from the electrode plate group 3, and laser beam welding or electron beam welding is performed on the joint protrusions 14 and 15 to thereby form the negative electrode plate 5 It is joined to the plain part 52.

  The negative electrode current collector 8 is integrally bent with a substantially Ω-shaped or pantograph-shaped buffer portion 16 having a flat upper surface in the vicinity of one end in the long side direction. The buffer portion 16 may be separately molded and integrally joined to the flat-plate negative electrode current collector 8. A cylindrical protrusion 17 is formed by burring at the center of the upper surface of the buffer part 16, and a fitting hole 19 formed in the lower end surface of the electrode column 18 as a negative electrode terminal is fitted into the cylindrical protrusion 17. The electrode column 18 is integrally joined to the buffer portion 16 by resistance welding or the like in a state where the electrode column 18 is accurately positioned. Thus, the electrode column 18 is connected to the negative electrode current collector 8 through the buffer portion 16 in a state in which the displacement in the horizontal direction and the vertical direction and the swing in the horizontal direction are allowed.

  A D-cut portion 20 that forms a connection plane 20a is formed at the upper portion of the electrode column 18, and a shallow annular recess 21 for sealing having an arcuate cross section is formed at an appropriate distance below the D-cut portion 20. The annular recess 21 may not be formed depending on circumstances, or a very shallow multi-annular groove may be formed over a predetermined range.

  The upper lid 13 has an oval shape in which the planar shape is fitted to the inner periphery of the upper end of the case 2, and the annular rising portion 22 is directed outward (opposite to the electrode plate group 3) on the entire outer periphery. The upper lid 13 is fitted to the upper end portion of the case 2 and the upper end edge of the case 2 and the end edge of the annular rising portion 22 are welded by laser beam welding or the like. Are integrally joined in a sealed state.

  A holding cylinder portion 24 through which the electrode column 18 penetrates is integrally formed on the upper lid 13, and an insulating gasket 25 is interposed between the inner periphery of the holding cylinder portion 24 and the outer periphery of the electrode column 18. In the mounted state, the diameter of the portion corresponding to the annular groove 21 of the holding cylinder portion 24 is reduced to form the reduced diameter deformed portion 26 and the insulating gasket 25 is compressed, so that the electrode column 18 and the holding cylinder portion 24 are compressed. The space is sealed. In addition, as shown in FIG. 2, the upper lid 13 has a safety valve 27 that breaks and opens to the atmosphere when the internal pressure in the case 2 exceeds a certain level, and a liquid injection port that injects electrolyte into the case 2. 28 and its sealing plug 29 are provided.

  Further, in order to prevent the buffer portion 16 from coming into contact with the case 2 and short-circuiting, a buffer portion cover 30 covering the buffer portion 16 is provided integrally with the insulating gasket 25. The insulating gasket 25 and the buffer cover 30 may be configured separately. Further, in order to prevent the core member 5a of the negative electrode plate 5 exposed at the upper end portion of the electrode plate group 3 and the outer peripheral portion of the negative electrode current collector 8 from coming into contact with the case 2 and short-circuiting, the negative electrode current collector 8 is prevented. And the insulating frame 31 which covers at least the outer peripheral part of the exposed part of the core material 5a of the negative electrode plate 5 is provided.

  In the electrode plate group 3 of the square battery 1 having the overall configuration described above, as shown in FIGS. 3 and 4, the negative electrode is smaller than the width dimension p of the active material application portion 41 to which the active material of the positive electrode plate 4 is applied. The width n of the active material coated portion 51 coated with the active material of the plate 5 is set larger, and both side edges of the active material coated portion 51 of the negative electrode plate 5 are connected to the active material coated portion of the positive electrode plate 4. By being positioned outside both side edges of 41, precipitation of metallic lithium in the active material coated portion 51 of the negative electrode plate 5 is prevented. Further, the separator 6 interposed between the positive electrode plate 4 and the negative electrode plate 5 has one side portion protruding beyond the side edge of the negative electrode plate 5 opposite to the plain portion 52 of the active material coating portion 51, The other side edge is set larger than the width dimension of the active material coating portion 51 of the negative electrode plate 5 and its arrangement position is regulated so that the side edge substantially coincides with the boundary between the active material coating portion 51 and the plain portion 52. ing. The plain portions 42 and 52 of the positive electrode plate 4 and the negative electrode plate 5 protrude outward from both side edges of the separator 6 by a dimension necessary to ensure a reliable joining operation with the current collectors 7 and 8. The width dimension is set in

  Therefore, the protruding dimension of the plain plate 42 of the positive electrode plate 4 from the side edge of the separator 6 is a, the protruding dimension of the separator 6 from the side edge of the negative electrode plate 5 opposite to the uncoated part 52 is b, The projected dimension of the uncoated portion 52 of the negative electrode plate 5 from the boundary between the active material coated portion 51 and the uncoated portion 52 and the side edge of the separator 6 that substantially matches the boundary is d, and the width dimension of the coated portion of the positive electrode plate is p. When the width dimension of the coated portion of the negative electrode plate is n, and the projecting dimensions of the active material coated portion of the negative electrode plate from both side edges of the active material coated portion of the positive electrode plate are e and f, respectively, The width dimension D of the electrode plate group from the side edge of the portion 42 to the side edge of the uncoated portion 52 of the negative electrode plate 5 is D = n + (a + b + d), based on the width dimension n of the active material coated portion of the negative electrode plate. Given in.

  As described above, the insulation between the positive electrode plate 4 and the negative electrode plate 5 can be realized while winding the side edge of the separator 6 in a state where the side edge of the separator 6 is substantially matched with the boundary between the active material coated portion 51 and the plain portion 52. The thickness of the active material coated portion 51 of the negative electrode plate 5 is, for example, about 160 to 200 μm in a conventional consumer lithium battery, but is as thin as about 80 to 100 μm. This is because the risk of falling off of the active material is reduced and the winding accuracy when the positive electrode plate 4, the negative electrode plate 5, and the separator 6 are wound in layers is increased.

  According to the prismatic battery 1 of the present embodiment described above, the electrode plate group is wound by winding in a state where the boundary between the active material coated portion 51 and the plain portion 52 in the negative electrode plate 5 and the side edge of the separator 6 are substantially matched. 3, the width dimension n of the active material application part 51 of the negative electrode plate 5 is larger than the width dimension p of the active material application part 41 of the positive electrode plate 4, and the active material application part of the negative electrode plate 5. Both side portions of 51 protrude from the side edges of the active material coated portion 41 of the positive electrode plate 4 by predetermined width dimensions e and f, respectively. Therefore, the side edge of the separator 6 is extended to the boundary between the active material coated portion 51 and the plain portion 52 in the negative electrode plate 5 by substantially the dimension f. A short circuit between the side edge of the landing portion 41 and the negative electrode plate 5 can be prevented.

  Moreover, since the separator 6 does not protrude from the boundary between the active material coated portion 51 and the plain portion 52 in the negative electrode plate 5, conventionally, the separator 6 has protruded from the boundary between the active material coated portion 51 and the plain portion 52 of the negative electrode plate 5. Since the protrusion dimension c of the separator 6 can be reduced and the protrusion dimension d of the plain portion 52 that protrudes from the separator 6 is basically unchanged, the width dimension D of the electrode plate group 3 is as follows: D = n + (a + b + d ), And can be reduced by the reduction of the protrusion dimension c of the separator 6 as compared with the prior art. Accordingly, the battery size can be reduced, or with the same battery size, the dimensions of the active material application portion can be increased, and the battery capacity can be increased. For example, in the case of a battery in which the width dimension of the active material application portion 41 of the positive electrode plate 4 is about 30 to 50 mm, the b dimension and the c dimension are about 2 to 3 mm. Therefore, in that case, the battery size is about 5%. It can be reduced or the battery capacity can be increased.

  Further, in the prismatic battery 1 of the present embodiment, an electrode column 18 as an electrode terminal is attached to the negative electrode current collector 8 joined to one end of the electrode plate group 3 accommodated in the case 2 via the buffer portion 16. A holding cylinder portion 24 is provided in the electrode column penetrating portion of the upper lid 13 integrally fixed to the case 2, and an insulating gasket 25 is interposed between the inner periphery of the holding cylinder portion 24 and the outer periphery of the electrode column 18 to hold it. Since the insulating gasket 25 interposed between the electrode column 18 and the holding cylinder portion 24 is compressed by the reduced diameter deformation portion 26 formed by caulking the cylinder portion 24, the sealing performance is ensured. The displacement of the electrode column 18 and the holding cylinder portion 24 due to the dimensional tolerance of the body 13 can be absorbed without difficulty by the displacement of the electrode column 18 by the buffer portion 16, and therefore, between the electrode column 18 and the holding cylinder portion 24. Insulated insulation gasket 25 presses unevenly No fear be problems such that they are, it is possible to ensure reliable sealing performance.

  Further, even when a shocking external force is applied to the electrode column 18, it can be absorbed by the electrode column 18 being easily oscillated and displaced around the sealing portion by the insulating gasket 25, and the sealing performance is not critically affected. , Stable sealing can be ensured.

  In addition, since the buffer cover 30 that prevents the buffer 16 from contacting the case 2 is provided integrally with the insulating gasket 25, it is ensured that the buffer 16 contacts the case 2 and is short-circuited by the buffer cover 30. In addition, since it is provided integrally with the insulating gasket 25, the number of parts can be reduced, and the part cost and assembly man-hour can be reduced.

  Further, the insulating frame 31 is fitted so as to cover at least the outer peripheral portion of the negative electrode current collector 8 joined to one end of the electrode plate group 3 and the exposed portion of the core material 5a of the negative electrode plate 5 at one end portion of the electrode plate group 3. Therefore, the insulating frame 31 can surely prevent the exposed portion of the core material 5a of the negative electrode plate 5 of the electrode plate group 3 from coming into contact with the case 2 and short-circuiting.

  Further, since the joint protrusions 11, 12, 14, and 15 are provided on the positive electrode current collector 7 and the negative electrode current collector 8, they are collected with respect to the plain portions 42 and 52 of the positive electrode plate 4 and the negative electrode plate 5. The electric bodies 7 and 8 are surely press-contacted and can be reliably joined by welding at that portion, and a connection state with a small connection resistance can be secured. Particularly, the joint protrusions 11 are radially connected to the semicircular portions at both ends. , 14 is provided, it is possible to ensure high current collection efficiency even at the folded portion of the electrode plate group 3 wound in an oval cross-sectional shape.

  Further, since the positive electrode current collector 7 also serves as the lower lid of the case 2, the structure is simple, the number of parts can be reduced, and the number of assembly steps can be reduced, so that the cost can be reduced. The surface of the positive current collector 7, that is, the lower lid, can be increased by the joint protrusions 12 formed on the current collector 7 over almost the entire width at appropriate intervals, and the plate thickness of the positive current collector 7 can be increased. Even if not, the expansion when the internal pressure of the case 2 rises can be suppressed, and the cost and weight can be reduced.

  In the above description of the embodiment, the example of the prismatic battery 1 has been shown. However, the present invention is not limited to the prismatic battery but can be similarly applied to a cylindrical lithium battery, and the same effect is obtained again. It is clear without explanation.

  In the lithium secondary battery of the present invention, the side edge of the separator is substantially matched with the boundary between the active material coated portion and the plain portion of the negative electrode plate, so that the protruding dimension of the separator protruding from this boundary can be reduced, Therefore, the battery size can be reduced or the same battery size can increase the size of the active material coated part and increase the battery capacity, which is useful for various types of lithium secondary batteries such as cylinders and prisms. It is.

The whole structure of the square battery of one Embodiment of the lithium secondary battery of this invention is shown, (a) is a top view, (b) is a vertical front view. It is a disassembled perspective view of the square battery of the embodiment. It is a schematic diagram which shows the structure of the electrode group of the square battery of the embodiment. It is explanatory drawing which showed typically the dimensional relationship of the positive electrode plate, negative electrode plate, and separator in the electrode plate group of the embodiment, (a) is explanatory drawing of an unfolded state, (b) is sectional explanatory drawing. It is explanatory drawing which showed typically the dimensional relationship of the positive electrode plate in the electrode plate group of a prior art example, a negative electrode plate, and a separator, (a) is explanatory drawing of an unfolded state, (b) is sectional explanatory drawing.

Explanation of symbols

1 Square battery (lithium secondary battery)
3 Electrode plate group 4 Positive electrode plate 5 Negative electrode plate 6 Separator 41 Active material application part 42 Plain part 51 Active material application part 52 Plain part

Claims (1)

A positive electrode plate and a negative electrode plate on which a solid portion not coated with an active material is formed at one end in the width direction are opposed to each other through a separator, and each of the positive and negative bipolar plates In the lithium secondary battery including the electrode plate group formed by winding the plain portions in the opposite directions, the width of the active material coating portion of the negative electrode plate is the width of the active material coating portion of the positive electrode plate. The electrode plate group is constructed by winding the electrode plate in a state where the width is set larger than the width and the boundary between the active material coated portion and the uncoated portion in the negative electrode plate is substantially matched with the side edge of the separator. Next battery.

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