JP4968768B2 - Cylindrical non-aqueous electrolyte battery - Google Patents

Description

  The present invention relates to a cylindrical nonaqueous electrolyte battery, and more particularly to a cylindrical nonaqueous electrolyte battery having a high capacity and excellent pulse discharge characteristics.

  As the cylindrical non-aqueous electrolyte battery, a high-capacity bobbin type battery such as a memory backup and a wound battery compatible with a heavy load such as a camera power source are widely known. The former bobbin type batteries are lithium manganese batteries and lithium thionyl chloride batteries, but they can be manufactured at a low cost with a simple structure, and can be filled with many active materials. Since the electrode area is small and the load characteristics are inferior, there is a disadvantage that the capacity is reduced when discharging with a large current is performed.

  The latter type of wound battery with heavy load characteristics has been commercialized as a lithium manganese battery or a lithium fluorinated graphite battery. This type of battery has an electrode wound body formed by winding a thin long electrode as a battery element, so that a large electrode area can be secured and a large discharge capacity can be taken out even when a large current is discharged. There is. However, since many separators and current collectors that do not directly contribute to improving battery characteristics are provided in the electrode body, the filling amount of the active material has to be reduced, and it is inevitable that the battery capacity is reduced. In addition, while a large current can be taken out, there is a disadvantage in that when an abnormality such as a short circuit occurs, heat generation is severe and there is a danger of ignition, various safety measures are required, the battery structure is complicated and the manufacturing cost increases. is there.

  Due to recent diversification of applied devices, not only light load applications such as memory backup, heavy load applications such as cameras, but also medium load applications such as data transmission and reception are increasing. There has been a demand for the development of a battery that can be used.

  In order to meet these demands, the present inventors have developed a wound battery with improved medium load discharge characteristics and have already filed a patent application (Patent Document 1). With the technique of this patent document 1, the improvement of a medium load discharge characteristic is achieved by the selection regarding the conductive support agent in a positive mix, and the optimization of a positive mix sheet density.

JP 2005-38708 A

  By the way, in the battery mainly applied to the medium load application as disclosed in Patent Document 1, there is a demand for further higher capacity, and it is possible to repeat discharge in a very short time. Characteristics (pulse discharge characteristics) are also required.

  However, it is very difficult to simultaneously achieve higher capacity and improved pulse discharge characteristics for the following reasons.

  Increasing the capacity of the non-aqueous electrolyte battery can be achieved, for example, by increasing the positive electrode mixture sheet, increasing the occupied volume ratio of the positive electrode in the battery, and increasing the filling amount of the positive electrode active material. Here, since the volume of the electrode that can be loaded in the battery outer can is limited, the surface area of the positive electrode itself is reduced by increasing the thickness of the positive electrode mixture sheet to increase the capacity. Since the discharge reaction of the battery occurs at a position where the positive electrode and the negative electrode face each other, the surface area of the negative electrode also decreases as the surface area of the positive electrode decreases due to the increase in the thickness of the positive electrode mixture sheet.

  However, in order to improve the pulse discharge characteristics in a nonaqueous electrolyte battery, it is necessary to increase the opposing area of the positive and negative electrodes. As described above, the thickness of the positive electrode mixture sheet is increased to increase the capacity. Therefore, it is extremely difficult to improve the pulse discharge characteristics.

  The non-aqueous electrolyte battery disclosed in Patent Document 1 has a relatively high capacity and is excellent not only in medium-load discharge characteristics but also in pulse discharge characteristics. The non-aqueous electrolyte battery is expected to require further higher capacity and improved pulse discharge characteristics. The present invention has been made in view of the above circumstances, and an object thereof is to provide a cylindrical non-aqueous electrolyte battery having a high capacity and excellent pulse discharge characteristics.

  The cylindrical nonaqueous electrolyte battery of the present invention that has achieved the above object is a cylinder having an electrode winding body formed by winding a sheet-like positive electrode and a sheet-like negative electrode through a separator in a cylindrical outer can. Type non-aqueous electrolyte battery, wherein the sheet-like positive electrode is formed by laminating two positive electrode mixture sheets through a current collector, and one positive electrode mixture sheet. The sheet-like negative electrode has a thickness corresponding to 4 to 9% of the inner diameter of the outer can, and the sheet-like negative electrode has a metallic lithium layer and a surface of the metallic lithium layer on the side facing the positive electrode through the separator. The lithium-aluminum alloy is at least partially included.

  In the present invention, as described above, the positive electrode mixture sheet relating to the sheet-like positive electrode has a sheet-like negative electrode having a metal lithium layer (for example, a negative electrode active material on the surface of the negative electrode current collector) while increasing the capacity with the specific thickness. In a sheet-like negative electrode having a metal lithium layer as a material), the lithium-aluminum alloy is present on a part of the surface of the metal lithium layer facing the positive electrode, thereby improving the pulse discharge characteristics. .

  The lithium-aluminum alloy according to the sheet-like negative electrode can be formed, for example, by laminating an aluminum foil on the surface of a metal lithium foil for constituting a metal lithium layer and electrochemically alloying it in the battery. Since such a lithium-aluminum alloy is pulverized, the surface area of the sheet-like negative electrode can be increased. In addition, when metallic lithium is used as the negative electrode active material, an organic film is formed on the surface of the negative electrode due to the reaction with the electrolytic solution, which increases the interfacial resistance of the negative electrode and reduces battery characteristics such as pulse discharge characteristics. One factor is that the lithium-aluminum alloy has a lower reactivity with the electrolytic solution than lithium, so that the formation of the organic film is suppressed, and the deterioration of battery characteristics due to this is suppressed.

  In the battery of the present invention, as described above, the presence of the lithium-aluminum alloy on the surface of the negative electrode facing the positive electrode achieves an increase in the surface area of the negative electrode and suppresses the occurrence of organic coatings that cause a decrease in battery characteristics. Thus, the pulse discharge characteristics can be improved while increasing the capacity by increasing the thickness of the positive electrode mixture sheet.

  According to the present invention, it is possible to provide a cylindrical non-aqueous electrolyte battery having a high capacity and excellent pulse discharge characteristics.

  In FIG. 1, the vertical side view showing one Embodiment of the nonaqueous electrolyte battery of this invention is shown. In FIG. 1, a nonaqueous electrolyte battery 1 includes a bottomed cylindrical outer can 2 having an upper opening, a sheet-like positive electrode 4 and a sheet-like negative electrode 5 loaded in the outer can 2 via a separator 6. A wound structure that seals the upper opening of the outer can 2, the wound electrode body 3 (see FIG. 2), a non-aqueous electrolyte (hereinafter simply referred to as “electrolyte”), Yes. In other words, the non-aqueous electrolyte battery 1 in FIG. 1 includes the sheet-like positive electrode 4 and the sheet-like negative electrode 5 in a space surrounded by the outer can 2 and the sealing structure that seals the upper opening of the outer can 2. It has a power generation element such as an electrode winding body 3 wound around a separator 6 and an electrolytic solution. The outer can 2 is made of iron or stainless steel.

  The sealing structure is attached to the cover plate 8 fixed to the inner peripheral edge of the upper opening of the outer can 2 and the opening formed in the center of the cover plate 8 through an insulating packing 9 made of polypropylene or the like. Terminal body 10 and insulating plate 11 disposed below cover plate 8. The insulating plate 11 is formed in a round plate shape that opens upward with an annular side wall 13 standing on the periphery of the disk-shaped base portion 12, and a gas passage 14 is opened at the center of the base portion 12. Yes. The cover plate 8 is fixed to the inner peripheral edge of the upper opening of the outer can 2 by laser welding or a crimp seal through packing while being received by the upper end of the side wall 13. As a countermeasure when the battery internal pressure suddenly increases, a thin portion (vent) can be provided on the lid 8 or the can bottom 2a of the outer can 2. The positive electrode 4 and the lower surface of the terminal body 10 are connected by a positive electrode lead body 15. Further, the negative electrode lead body 16 attached to the negative electrode 5 is welded to the upper inner surface of the outer can 2.

  FIG. 2 shows a cross-sectional plan view of the nonaqueous electrolyte battery shown in FIG. As shown in FIG. 2, the electrode winding body 3 is formed by winding a positive electrode 4 and a negative electrode 5 with a separator 6 interposed therebetween, and is formed in a substantially cylindrical shape as a whole. In the non-aqueous electrolyte battery shown in FIG. 2, the positive electrode 4 has a structure in which two positive electrode mixture sheets 20 and 21 are laminated via a current collector 22. The negative electrode 5 has a structure in which a metal lithium layer 25 and a current collector 26 are laminated. Although not shown, the metal lithium layer 25 is on the side facing the positive electrode 4 with the separator 6 interposed therebetween. A lithium-aluminum alloy is provided on at least a part of the surface. Here, in FIG. 2, C is a winding center portion of the electrode winding body 3, S is a winding start end portion of the positive electrode 4 in the electrode winding body 3, and E is a winding end portion of the electrode winding body 3. (Details will be described later). 1 and 2 show the case where the battery of the present invention is cylindrical.

  In FIG. 3, sectional drawing which expanded the principal part of the electrode winding body which concerns on the nonaqueous electrolyte battery of this invention is shown. In FIG. 3, in order to facilitate understanding, each component of the electrode winding body is illustrated as being stacked horizontally. Also in FIG. 3, as in FIG. 2, the lithium-aluminum alloy present on the surface of the metallic lithium layer 25 on the side facing the positive electrode 4 through the separator 6 is not shown. The separator 6 shown in FIG. 3 does not have the single-layer structure shown in FIG. 1 or FIG. 2, but has a microporous film 28 and a nonwoven fabric 29 as constituent elements, and the microporous film 28 is the negative electrode 5. The nonwoven fabric 29 is disposed so as to be in contact with the positive electrode 4.

  1, 2 and 3 conceptually show the arrangement of each component, and their dimensions (thickness, width, etc.) are different from the actual ones (the same applies to FIGS. 4 and 5 described later). .

  The positive electrode according to the present invention is a sheet-like positive electrode having a structure in which two positive electrode mixture sheets are laminated via a current collector. In the sheet-like positive electrode having such a structure, for example, the current collector is overlapped by three mm so that the current collector is located several mm inward from the two positive electrode mixture sheets, and the length direction in which the winding start end S is formed. It can produce by pressing a 3-10 mm part from the edge part of this. From the viewpoint of work, it is preferable that the two positive electrode mixture sheets and the positive electrode current collector are integrated prior to the production of the electrode winding body. The sheet and the current collector may be integrated when the electrode winding body is wound, and there is no particular problem in terms of characteristics even by such a manufacturing method.

  As the positive electrode mixture sheet, for example, a positive electrode mixture (slurry) obtained by blending a positive electrode active material with a conductive additive or a binder and adding water or the like as necessary is rolled using a roll or the like. Then, a pre-sheet can be formed, and a product obtained by drying and pulverizing the sheet can be roll-rolled again to form a sheet shape. Examples of the positive electrode active material include manganese dioxide, carbon fluoride, lithium cobalt composite oxide, spinel-type lithium manganese composite oxide, and the like. Examples of the conductive assistant include graphite, carbon black (Ketjen black, etc.) and acetylene black. These may be used alone or in combination of two or more. As the binder, polytetrafluoroethylene (PVDF), a rubber-based binder, or the like can be used. In the case of PVDF, a dispersion type or a powder type may be used, but a dispersion type is particularly preferable.

  In the positive electrode mixture sheet, for example, the content of the positive electrode active material is 92 to 97% by mass, the content of the conductive additive is 2 to 4% by mass, and the content of the binder is 1 to 4% by mass. preferable.

  The positive electrode mixture sheet has a thickness corresponding to 4 to 9% of the inner diameter of the battery outer can per sheet. By providing a positive electrode having a thick positive electrode mixture sheet in this manner, the occupied volume ratio of the positive electrode in the battery is increased to reduce unnecessary gaps in the battery, and the filling amount of the positive electrode active material is increased to increase the battery capacity. Capacitance can be achieved. The specific thickness of each positive electrode mixture sheet varies depending on the size of the battery (the size of the outer diameter of the outer can), but is usually 0.5 to 1.0 mm.

Moreover, it is preferable that the density of a positive mix sheet is 2.1-2.8 g / cm < ³ >, for example. In addition, the density of the positive mix sheet as used in this specification is a value determined by the volume and weight of the dry positive mix sheet.

From the viewpoint of improving the load characteristics (especially the discharge characteristics at medium load) of the non-aqueous electrolyte battery, carbon black having a BET specific surface area of 400 to 2000 m ² / g (particularly ketjen black) is used as the conductive auxiliary. The content of the conductive additive in the positive electrode mixture sheet is set to 2.0 to 4.0% by mass, and the density of the positive electrode mixture sheet is further set to 2.2 to 2.7 g / cm ^3. preferable. In addition, the BET specific surface area of the conductive assistant referred to in this specification is a surface area measured and calculated using the BET formula which is a theoretical formula of multimolecular adsorption. is there. Moreover, the specific surface area measuring apparatus by the nitrogen adsorption method ("Macsorb HM model-1201" by Mounttech) was used for the measurement of the BET specific surface area of carbon black in the Example mentioned later.

  Examples of the current collector used for the positive electrode include those made of stainless steel such as SUS316, SUS430, and SUS444, and the forms thereof include plain weave metal mesh, expanded metal, lath net, punching metal, and foil (plate). Etc. can be exemplified. The thickness of the current collector is preferably, for example, 0.1 to 0.4 mm.

  Note that it is desirable to apply a paste-like conductive material to the surface of the positive electrode current collector. When a positive electrode current collector having a three-dimensional structure is used, as in the case of using an essentially flat material such as a metal foil or a punching metal, the current collecting effect is remarkable by applying a conductive material. Improvement is observed. This is because the route through the conductive material filled in the mesh is effectively used as well as the route in which the metal part of the mesh current collector is in direct contact with the positive electrode mixture sheet. It is estimated to be.

  As the conductive material, for example, silver paste or carbon paste can be used. In particular, the carbon paste is suitable for reducing the manufacturing cost of the non-aqueous electrolyte battery because the material cost is lower than that of the silver paste and the contact effect is almost the same as that of the silver paste. As the binder for the conductive material, it is preferable to use a heat resistant material such as water glass or an imide binder. This is because the drying treatment is performed at a high temperature exceeding 200 ° C. when moisture in the positive electrode mixture sheet is removed.

  The negative electrode according to the present invention is a sheet-like negative electrode in which a metal lithium layer is provided, for example, on the surface of a current collector, and the surface of the metal lithium layer facing the positive electrode through a separator (current collector side and Has a lithium-aluminum alloy on at least a part of the opposite surface.

  In the above lithium-aluminum alloy, for example, a metal lithium foil serving as a metal lithium layer is laminated with a current collector, and an aluminum foil is further laminated on the surface opposite to the current collector side of the metal lithium foil to form a sheet-like negative electrode ( The wound electrode prepared using the sheet-like negative electrode, the sheet-like positive electrode, and the separator is housed in an outer can together with the electrolytic solution, and lithium and aluminum are electrochemically contained in the battery. By forming an alloy, the layer is formed on the surface of the metal lithium layer.

  Since the lithium-aluminum alloy formed as described above is pulverized, the surface area of the sheet-like negative electrode increases. In addition, the lithium-aluminum alloy suppresses the reaction with the electrolytic solution on the surface of the sheet-like negative electrode, thereby suppressing the formation of an organic coating that causes a decrease in battery characteristics. With these functions, the pulse discharge characteristics can be improved in the battery of the present invention.

  In addition, when forming a lithium-aluminum alloy in a battery as mentioned above, it is preferable that the width | variety of aluminum foil is smaller than the width | variety of metal lithium foil. In addition, the “width” relating to the sheet-like negative electrode, the sheet-like positive electrode, the separator, their constituent elements, and their raw materials in the present specification is the width direction orthogonal to the longitudinal direction of the sheet-like negative electrode, the sheet-like positive electrode, and the separator. It means length.

  When a lithium-aluminum alloy is formed by the above method using an aluminum foil having a width larger than or equal to that of the metal lithium foil, the lithium-aluminum alloy is formed up to the end in the width direction of the metal lithium layer. Will be. However, since the lithium-aluminum alloy is pulverized as described above, for example, when an external impact is applied to the battery, the pulverized lithium-aluminum alloy is formed from the vicinity of the end in the width direction of the metal lithium layer. May drop, resulting in a decrease in the discharge capacity of the battery, or the dropped lithium-aluminum alloy powder may come into contact with the positive electrode to decrease the battery voltage and cause a voltage failure. In addition, when a lithium-aluminum alloy is formed by the above method using an aluminum foil having a width wider than that of the metal lithium foil, a portion where the aluminum foil protrudes from the metal lithium foil is not involved in the formation of the lithium-aluminum alloy. become.

  More specifically, when both the center of the width direction of the metal lithium foil and the center of the width direction of the aluminum foil are laminated, both ends in the width direction of the metal lithium foil are portions from the end to 1 mm. It is preferable to set the width of the metal lithium foil and the aluminum foil so that is exposed.

  The thickness of the metal lithium foil for forming the metal lithium layer according to the sheet-like negative electrode is preferably 0.05 to 0.4 mm, for example.

  Moreover, it is preferable that the thickness of the said aluminum foil used in order to laminate | stack with the said metal lithium foil and form a lithium-aluminum alloy is 3-15 micrometers, for example. If the aluminum foil is too thin, the amount of lithium-aluminum alloy formed may be reduced, and the effect of improving the pulse discharge characteristics of the battery may be reduced. Also, if the aluminum foil is too thin, cracks may occur during winding of the electrode winding body, and in this case, the distribution of aluminum becomes non-uniform, so that the discharge reaction progresses at each location of the negative electrode. Differences may occur, which may reduce the effect of improving the pulse discharge characteristics of the battery. On the other hand, if the aluminum foil is too thick, the amount of aluminum that does not contribute to the discharge increases, and the discharge capacity of the battery tends to decrease.

  Examples of the material for the negative electrode current collector include copper, nickel, iron, and stainless steel. Since the internal volume of the outer can decreases by the thickness of the negative electrode current collector, the thickness dimension of the negative electrode current collector is preferably as small as possible, specifically, for example, 0.1 mm or less. Recommended. That is, if the negative electrode current collector is too thick, the amount of the metal lithium layer (metal lithium foil) that is the negative electrode active material has to be reduced, and the battery capacity may be reduced. Moreover, since it will be easy to tear when a negative electrode collector is too thin, it is desirable that the thickness of a negative electrode collector be 0.005 mm or more. The width of the negative electrode current collector is preferably the same as or wider than the width of the metal lithium foil, and the area is 100 to 130% of the area of the metal lithium foil disposed on one side. preferable. By making the area of the negative electrode current collector as described above, the width of the negative electrode current collector is the same as or wider than the width of the metal lithium foil, and the length becomes longer. It is possible to prevent the lithium foil from being cut and the electrical connection from being cut off.

  There is no restriction | limiting in particular as a separator which concerns on the battery of this invention, The separator made from a microporous film and the nonwoven fabric separator which are employ | adopted for the conventionally well-known nonaqueous electrolyte battery are applicable.

  In the battery of the present invention, a separator having a microporous film and a nonwoven fabric as constituent elements is preferably used. If the separator has a structure in which a microporous film and a non-woven fabric are laminated and these are laminated, the electrode winding body suppresses the breakthrough of the separator by the positive electrode active material on the positive electrode surface, thereby preventing the occurrence of a short circuit. Further, it is possible to prevent the battery characteristics from being deteriorated due to the drop-off of the finely divided lithium-aluminum alloy on the negative electrode surface.

  That is, if a microporous film and a non-woven fabric are used in combination, even if a microporous film alone causes a crack or the like and a short circuit occurs, a crack or the like does not easily occur and the penetration strength is high. Occurrence of a short circuit can be prevented by the presence of the nonwoven fabric.

  In addition, the finely divided lithium-aluminum alloy on the negative electrode surface may fall off the negative electrode, for example, when an external impact is applied to the battery. Such a dropped lithium-aluminum alloy passes through the separator. If it moves to the positive electrode, it reacts with the positive electrode active material, causing a voltage failure in which the voltage of the battery decreases. If a separator having the microporous film and the nonwoven fabric as constituent elements is used, the microporous film prevents the lithium-aluminum alloy that has fallen off from the negative electrode from moving to the positive electrode, thereby preventing the occurrence of the above voltage failure. It is possible to suppress the deterioration of battery characteristics.

  In addition, when the microporous film which concerns on a separator has a crack etc., the movement inhibitory effect to the positive electrode of the lithium-aluminum alloy which fell from the negative electrode will be greatly impaired. If it is a separator having a constituent element, as described above, since the breakthrough of the microporous film is suppressed by the presence of the nonwoven fabric, for example, compared to the case of using a separator composed only of a microporous film, The occurrence of the voltage failure can be suppressed to a higher degree.

  Further, in a separator having a microporous film and a non-woven fabric as constituent elements, a resin that constitutes the microporous film by heat generated in association with a sudden discharge such as a short circuit in a nonaqueous electrolyte battery. It is possible to ensure shutdown characteristics such as melting and sealing the pores of the separator to increase the internal resistance of the battery and ensure the safety of the battery. In addition, the nonwoven fabric also has an action as an electrolyte solution holding layer for increasing the amount of electrolyte solution held in the separator to further improve the battery capacity.

  In the battery of the present invention, when a separator having a microporous film and a nonwoven fabric as constituent elements is used, it is preferable that the microporous film is disposed so as to be in contact with the negative electrode and the nonwoven fabric is disposed so as to be in contact with the positive electrode. By arranging in this way, the breakage of the microporous film by the positive electrode active material on the positive electrode surface can be more highly suppressed by the action of the nonwoven fabric in contact with the positive electrode. The movement of the aluminum alloy to the positive electrode can be better prevented.

  The thickness of the nonwoven fabric in the separator having the microporous film and the nonwoven fabric as constituent elements is, for example, 10 μm or more, more preferably 20 μm or more, and 80 μm or less, more preferably 60 μm or less, and particularly preferably 50 μm or less. It is desirable that If the nonwoven fabric is too thin, the effect of preventing the occurrence of a short circuit or voltage failure due to the breakage of the microporous film in the electrode winding body may be reduced. In addition, if the nonwoven fabric is too thin, the amount of electrolyte retained in the separator is also reduced, and the battery capacity improvement effect may be reduced. On the other hand, if the nonwoven fabric is too thick, the battery capacity tends to decrease, and the resistance value of the separator increases, resulting in a decrease in load characteristics or sufficient discharge of electricity for the capacity of the battery. There is a case where a capacity is wasted such that it cannot be performed. When the nonwoven fabric has a thickness of 50 μm or less (that is, 10 μm or more, more preferably 20 μm or more and 50 μm or less) among the above thicknesses, it is particularly preferable because the capacity can be increased and the load characteristics can be improved.

  As the nonwoven fabric related to the separator, for example, polyolefins such as polyethylene (PE) and polypropylene (PP); polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT); polyphenylene sulfide (PPS); Those produced by various known production methods can be used.

  Further, the thickness of the microporous film is 10 μm or more, more preferably 20 μm or more, and preferably 40 μm or less. If the microporous film is too thin, a short circuit may occur due to the breakage of the microporous film in the electrode winding body, and the separator may be broken when the electrode is wound due to its low strength. May occur. On the other hand, if the microporous film is too thick, the effect of improving the battery capacity may be reduced, and the resistance value of the separator increases, leading to a decrease in load characteristics or a waste of the above capacity. May occur.

  As used herein, the term “microporous film” refers to a film-like body made of resin (including so-called sheet-like bodies and plate-like bodies) that includes a large number of minute pores. Good, ions can pass inside the film. For example, fine particles (inorganic fine particles) are blended into a resin and molded into a film-like body, which is stretched uniaxially or biaxially to generate cracks in the vicinity of the fine particles to form pores Etc. can be used. Examples of the resin constituting the microporous film include polyolefins such as polyethylene (PE) and polypropylene (PP); polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT); polyphenylene sulfide (PPS); Can be mentioned. Examples of such commercially available microporous films include “Hypore” (trade name) manufactured by Asahi Kasei Corporation, “Setilla” (trade name) manufactured by Tonen Chemical Co., Ltd., and the like.

  The width of the separator may be set so that contact between the sheet-like positive electrode and the sheet-like negative electrode can be suppressed. However, in the separator having the microporous film and the nonwoven fabric as constituent elements, the width of the microporous film is the sheet. It is preferably larger than the width of the negative electrode. When the width of the microporous film according to the separator is larger than the width of the sheet-like negative electrode and the widest among the microporous film and the nonwoven fabric according to the sheet-like positive electrode, the sheet-like negative electrode, and the separator, By turning the microporous film protruding to both ends in the width direction of the rotating body inwardly, the movement of the lithium-aluminum alloy dropped from the negative electrode can be suppressed to a higher degree.

  On the other hand, in the separator having the microporous film and the non-woven fabric as constituent elements, the non-woven fabric has no effect by widening the microporous film as described above. Therefore, from the viewpoint of reducing the occupied volume of the nonwoven fabric in the battery, it is preferable to make the width of the nonwoven fabric smaller than that of the microporous film in the separator having the microporous film and the nonwoven fabric as constituent elements. More preferably, the width is about the same as that of the sheet-like positive electrode or sheet-like negative electrode.

For example, in the case of a nonaqueous electrolyte battery having a positive electrode in which the porosity of the positive electrode mixture sheet is 35 to 50%, the unevenness of the positive electrode surface in contact with the separator is large, so that the separator is broken through. Although it is likely to occur, even in such a case, the occurrence of a short circuit can be suppressed by employing the above separator having the microporous film and the nonwoven fabric as constituent elements. In addition, the porosity of a positive mix sheet is calculated | required as follows. For example, when the positive electrode mixture sheet is made of manganese dioxide, ketjen black, and PVDF, the true specific gravity is 4.5 g / cm ³ , 2.0 g / cm ³ , and 2.2 g / cm ^{3, respectively.} As the total X (g / cm 3) of the calculated mass of each constituent material contained per unit volume of the positive electrode mixture sheet, the difference from the actual density Y (g / cm ³ ) of the positive electrode mixture sheet is obtained. The porosity (%) is obtained as [(X−Y) / X] × 100.

  Further, the maximum unevenness on the positive electrode surface (that is, the vertical distance between the horizontal line passing through the highest position of the highest convex part and the horizontal line passing through the lowest position of the lowest concave part) is larger than the thickness of the microporous film. In the case of being large (more specifically, for example, 40 μm or more), since the unevenness of the positive electrode surface is large, the separator is likely to break through, but the above-mentioned components having a microporous film and a nonwoven fabric as constituent elements The separator is also effective for suppressing a short circuit in such a case.

Examples of the electrolyte solution according to the battery of the present invention include a solution prepared by dissolving LiPF ₆ , LiClO ₄ , LiCF ₃ SO _3, etc. as an electrolyte in a non-aqueous solvent such as an organic solvent.

Among the above electrolytes, LiCF ₃ SO ₃ is preferably used from the viewpoint of further improving battery safety. When metallic lithium is used for the negative electrode and LiCF ₃ SO ₃ is used for the solute, fluorine ionized from LiCF ₃ SO ₃ reacts with active lithium during storage of the battery, and the negative electrode surface is in a passive state. Since a certain lithium fluoride film is formed and the internal resistance of the battery is increased, the discharge characteristics are deteriorated. However, in the battery of the present invention, a part of the negative electrode has a lithium-aluminum alloy, and this lithium-aluminum alloy has lower activity than lithium alone, so that fluorine ions and lithium present during storage -It is hard to react with an aluminum alloy, the production | generation of the passive state film in the negative electrode surface is suppressed, and the fall of a discharge characteristic can be suppressed.

  The electrode winding body 3 can be produced, for example, according to a procedure as shown in FIGS. 4 (excluding the enlarged view) and FIG. 5, the separator 6 is shown in a single layer structure. As described above, the microporous film 29 and the nonwoven fabric are used as shown in the enlarged views of FIGS. 3 and 4. 28 is preferable. 25a is a laminate of metal lithium foil 25b and aluminum foil 25c (hereinafter referred to as "Li foil-Al foil laminate") for forming the metal lithium layer 25 and the lithium-aluminum alloy on the surface thereof. In addition to the enlarged view of FIG. 4 and FIG. 5, in order to avoid complication of the drawing, it is shown as if it is a single layer structure.

  First, as shown in FIG. 4, the heat-meltable tape 31 and then the separator 6 are placed on the upper surface of the central portion in the length direction of the negative electrode current collector 26. At this time, when the separator 6 is composed of the microporous film 28 and the nonwoven fabric 29, the microporous film 28 is on the negative electrode 5 side as shown in the enlarged view in the circle in FIG. It is preferable to arrange them. The separator 6 composed of the microporous film 28 and the nonwoven fabric 29 can be formed, for example, by superposing the microporous film 28 and the nonwoven fabric 29 and thermally welding only a part thereof.

  Next, the tape 31 is heated from this state, and the separator 6 is melted and fixed to the negative electrode current collector 26 through the tape 31 in an integral manner. The tape 31 can be a single-sided or double-sided adhesive tape. Next, the two Li foil-Al foil laminates 25a and 25a are pressure-bonded and fixed at the longitudinal position of the negative electrode current collector 26 sandwiching the fixing portion of the separator 6. In other words, a portion where the negative electrode current collector 26 without the Li foil-Al foil laminate 25a as the negative electrode active material is exposed is provided on one side surface of the negative electrode current collector 26, and the separator 6 is fixed to the exposed portion 30. To do. At this time, it is preferable that the portion of the separator 6 fixed to the negative electrode current collector 26 includes a portion in which the microporous film and the nonwoven fabric are thermally welded. In this way, it is possible to obtain a laminated body 32 in which the negative electrode current collector 26, the Li foil-Al foil laminated body 25a, and the separator 6 are separated and integrated.

  Next, as shown in FIG. 5A, the laminate 32 is inserted between the transverse grooves 35 of the winding core 33. Here, the alignment is performed so that the exposed portion 30, that is, the portion where the separator 6 is fixed by the tape 31 is located between the transverse grooves 35 of the winding core 33. The winding core 33 is rotated about a half circumference in one direction (clockwise in FIG. 5), and the laminate 32 is wound around the outer peripheral surface of the winding core 33 as shown in FIG. Next, the positive electrode 4 composed of the positive electrode mixture sheets 20 and 21 and the current collector 22 is placed on the separator 6 so that the winding start end S side (see FIG. 2) is the winding core 33 side. Then, the laminate 32 is wound around the winding core 33. After winding the laminated body 32 and the positive electrode 4 with a winding core, the winding core 31 is extracted from the winding center C (see FIG. 2), and finally the winding end E (see FIG. 2) of the metal foil 26. Fasten with a fixing tape. In this way, as shown in FIG. 2, an electrode winding body 3 can be obtained in which the exposed portion 30 is the winding center C and the positive electrode 4 and the negative electrode 5 are wound through the separator 6.

  In addition, after the negative electrode current collector was previously wound around the winding core for about one turn, a folded electrode group was inserted so as to wrap the positive electrode by overlapping the Li foil-Al foil laminate and the separator constituting the negative electrode, It may be wound to form an electrode winding body. In this case, the Li foil-Al foil laminate (the metal lithium foil) is not pressure bonded to the negative electrode current collector at all.

  Since the non-aqueous electrolyte battery of the present invention has a high capacity and excellent pulse discharge characteristics, it can be used as a drive power source for equipment that requires repeated discharge in a very short time, particularly data communication equipment. It can be preferably applied to the power supply application of various devices such as the beginning.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention. In this example, a cylindrical lithium battery having an outer diameter of 17 mm and a height of 45 mm will be described as an example of a nonaqueous electrolyte battery. In addition, "%" used in a present Example is a mass reference | standard (mass%) unless there is particular notice.

Example 1
The non-aqueous electrolyte battery of Example 1 is described in the order of [Preparation of positive electrode], [Preparation of negative electrode], [Preparation of wound electrode body], [Assembly of battery], [Post-treatment (preliminary discharge, aging)]. To do.

[Production of positive electrode]
First, a positive electrode mixture (in mass ratio, solid content: water content = 100: 30) was prepared by the following procedure. Carbon black having a BET specific surface area of 600 m ² / g: 3% and manganese dioxide (manufactured by Tosoh Corporation): 92% were mixed by a dry method using a planetary mixer for 5 minutes, and then water was added to a solid content of 20% ( Mass ratio) and mixed for 5 minutes. PVDF dispersion ("D-1" manufactured by Daikin Industries, Ltd.) is prepared in an amount corresponding to 5% of the solid content of the positive electrode mixture, diluted with the remaining water, and added to the above mixture And mixed for 5 minutes to obtain a positive electrode mixture.

Using the above positive electrode mixture, two rolls having a diameter of 250 mm, adjusting the roll temperature to 125 ± 5 ° C., press pressure: 7 ton / cm, roll interval: 0.4 mm, rotation speed: 10 rpm The sheet was rolled and rolled. The positive electrode mixture (preliminary sheet) that passed through the roll was dried at 105 ± 5 ° C. until the residual moisture was 2% or less. Next, the dried preliminary sheet was pulverized using a pulverizer. At this time, the preliminary sheet was pulverized until it became twice or more the original apparent volume. Most of the particle diameter after pulverization was 1 mm or less, and PVDF added as a binder was also cut into fibers having a length of 1 mm or less. The pulverized material was formed into a sheet again by a roll. The interval between the rolls was adjusted to 0.6 ± 0.05 mm, and a positive electrode mixture sheet was obtained by forming into a sheet under the conditions of roll temperature: 125 ± 10 ° C., press pressure: 7 ton / cm, and rotation speed: 10 rpm. The obtained positive electrode mixture sheet has a thickness of 1.0 mm and corresponds to 5.9% of the inner diameter of the outer can. Moreover, the density of the positive mix sheet was 2.5 g / cm < ³ >, and the porosity calculated | required by the said method was 42%. The positive electrode mixture sheet is cut to obtain a positive electrode mixture sheet for inner circumference (20 in FIG. 2) having a width of 37 mm and a length of 51 mm, and a positive electrode mixture for outer periphery having a width of 37 mm and a length of 62 mm. An agent sheet (21 in FIG. 2) was obtained.

As the positive electrode current collector, an expanded metal made of stainless steel (SUS316) was used. The expanded metal was cut into a width of 34 mm and a length of 56 mm, and a stainless steel ribbon having a thickness of 0.1 mm and a width of 3 mm was attached to the center in the length direction by resistance welding as a positive electrode lead body. . Further, a carbon paste (manufactured by Nippon Graphite Co., Ltd.) was applied to the expanded metal so as not to crush the mesh, and then dried at a temperature of 105 ± 5 ° C. to obtain a positive electrode current collector. The coating amount of the carbon paste was set to 5 mg / cm ² after drying.

  Next, in a state where the positive electrode current collector is interposed between the positive electrode mixture sheet for the inner periphery and the positive electrode mixture sheet for the outer periphery, only one end in the length direction is fixed and the three parties are integrated. . Specifically, the positive electrode mixture sheet for the inner periphery and the positive electrode mixture sheet for the outer periphery are aligned with one end in the length direction, and the end of the positive electrode current collector is composed of two positive electrode mixture sheets. Set the two so that they do not protrude from one end, and in that state, press the 5mm part of the two positive electrode mixture sheets from the end where both are aligned, so that the three parties are integrated. did. Then, the two positive electrode mixture sheets and the positive electrode current collector were integrated with hot air at 250 ± 10 ° C. for 6 hours to obtain a sheet-like positive electrode having a width of 37 mm.

[Preparation of negative electrode (negative electrode precursor)]
The negative electrode has a width: 37 mm, a length: 170 mm, a thickness: 10 μm on a copper foil (negative electrode current collector), a width: 37 mm, a length: 87 mm, a thickness: 0.30 mm metal lithium foil, and a width: 37 mm. A metal lithium foil having a length of 50 mm and a thickness of 0.30 mm is disposed, and further, a width: 35 mm, a length: 85 mm, a thickness: 6 μm, a width: 35 mm, a length: 48 mm, and a thickness: A 6 μm aluminum foil was arranged. First, a negative electrode lead made of nickel having a width of 3 mm, a length of 20 mm, and a thickness of 0.1 mm was pressure-bonded to a metal lithium foil having a length of 50 mm. Thereafter, as shown in FIG. 4, the two metal lithium foils are arranged on the copper foil in a separated state, and the aluminum foils are arranged on the two metal lithium foils, respectively. Thus, a sheet-like negative electrode (sheet-like negative electrode precursor before forming a lithium-aluminum alloy, hereinafter referred to as “sheet-like negative electrode” for convenience) was produced.

[Production of wound electrode body]
Laminate a microporous polyethylene film ["Hypore" (trade name) manufactured by Asahi Kasei Co., Ltd.] having a width: 44 mm, a length: 170 mm, and a thickness: 20 μm, and a non-woven fabric having a width: 42 mm, a length: 170 mm, and a thickness: 20 μm. The separator was manufactured by heat welding at a position 65 mm from one end in the length direction of the microporous polyethylene film, shifted by 10 mm from the nonwoven fabric.

  As shown in FIG. 4, the separator was affixed on the copper foil of the sheet-like negative electrode through the adhesive tape. In addition, when affixing a separator to a negative electrode, the nonwoven fabric surface was made into the positive electrode side, and the heat welding part of the microporous film of a separator and a nonwoven fabric was included in the adhesion part with an adhesive tape. Next, centering on the heat-welded portion between the microporous film of the separator and the nonwoven fabric, the separator was sandwiched between winding cores having a diameter of 3.5%: 3.5 mm [FIG. 5 (a), ( b)]. Next, after winding the negative electrode together with the separator once, the side on which the sheet-like positive electrode was fixed was placed on the winding core side and wound. After winding, the copper foil covered the outermost periphery. Thus, an electrode winding body as shown in FIG. 2 was obtained.

[Battery assembly]
The assembly process of the nonaqueous electrolyte battery will be described with reference to FIG. A polypropylene insulating plate having a thickness of 0.2 mm is inserted into the inner bottom portion 2a of the bottomed cylindrical outer can 2 made of nickel-plated iron can, and the electrode winding body 3 and the positive electrode lead body 15 are inserted thereon. Was inserted in a posture facing upward. The negative electrode lead body 16 of the electrode winding body 3 was resistance welded to the inner surface of the outer can 2, and the positive electrode lead body 15 was resistance welded to the lower surface of the terminal plate 10 after inserting the insulating plate 11. At this point, the insulation resistance was measured and it was confirmed that there was no short circuit.

As the electrolyte, a non-aqueous solution prepared by dissolving LiClO ₄ at a concentration of 0.5 mol / l in a mixed solvent of propylene carbonate and dimethoxyethane (volume ratio of 1: 2) was prepared, and this was used as an outer can. 3.5 ml was injected into 2. The injection was divided into three times, and the whole amount was injected while reducing the pressure in the final step. After the electrolyte solution is injected, the cover plate 8 is fitted into the upper opening of the outer can 2, and the inner peripheral portion of the opening end of the outer can 2 and the outer peripheral portion of the cover plate 8 are welded by laser welding. 2 openings were sealed.

[Post-treatment (preliminary discharge, aging)]
The sealed battery was pre-discharged with a resistance of 1Ω for 30 seconds, stored at 70 ° C. for 6 hours, then subjected to a secondary pre-discharge with a constant resistance of 1Ω for 1 minute, and lithium-aluminum on the separator-side surface of the sheet-like negative electrode. An alloy was formed. The battery after the preliminary discharge was aged at room temperature for 7 days, the open circuit voltage was measured to confirm that a stable voltage was obtained, and non-aqueous electrolysis with an outer diameter of 17.0 mm and a total height of 45.0 mm A liquid battery was obtained. The ratio of the negative electrode capacity to the positive electrode capacity of this nonaqueous electrolyte battery was 1.00.

Example 2
A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that the two aluminum foils used in the production of the sheet-like negative electrode were changed to those having a thickness of 2 μm.

Example 3
A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that the two aluminum foils used in the production of the sheet-like negative electrode were changed to those having a thickness of 15 μm.

Example 4
A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that the two aluminum foils used were changed to 30 μm in the production of the sheet-like negative electrode.

Example 5
A nonaqueous electrolyte battery was produced in the same manner as in Example 1 except that the microporous film surface was changed to the positive electrode side when the separator was attached to the negative electrode during the production of the electrode winding body.

Comparative Example 1
A nonaqueous electrolyte battery was produced in the same manner as in Example 1 except that two aluminum foils were not used in the production of the sheet-like negative electrode.

The non-aqueous electrolyte batteries of Examples 1 to 4 and Comparative Example 1 were subjected to the following discharge capacity measurement and pulse discharge characteristic evaluation. The results are shown in Tables 1 and 2.
[Discharge capacity]
About each non-aqueous electrolyte battery, it discharged continuously at 23 degreeC with the electric current value of 40 mA, and the discharge capacity until a battery voltage became 2.0V was measured. In addition, the number of samples of each battery was five, and the average value was made into the discharge capacity of the battery of each Example and a comparative example.

[Pulse discharge characteristics]
About each nonaqueous electrolyte battery, the voltage after carrying out 100 ms pulse discharge at -40 degreeC with the predetermined | prescribed electric current value was measured. The nonaqueous electrolyte batteries of Example 1 and Comparative Example 1 were not discharged (undischarged battery) and were discharged after a current of 1300 mAh corresponding to 50% of the theoretical capacity (50% discharge battery). The current value of pulse discharge was set to 100 mA, 300 mA or 500 mA. Moreover, about the non-aqueous electrolyte battery of Examples 2-4, about the thing after discharging the electric current for 1300 mAh which is 50% of theoretical capacity | capacitance, the electric current value of pulse discharge was 300 mA.

  Moreover, about 100 each of the non-aqueous electrolyte batteries of Examples 1 to 4, the number of occurrences of defects during the production of the electrode winding body was examined. The defect at the time of producing the electrode winding body here means a crack in the aluminum foil generated at the time of winding. The results are also shown in Table 1.

  As shown in Table 1 and Table 2, the nonaqueous electrolyte batteries of Examples 1 to 4 have a large discharge capacity, a high voltage after a pulse discharge of 100 ms at 300 mA, and have good pulse discharge characteristics. . In addition, in the non-aqueous electrolyte battery of Example 2 using a thin aluminum foil as a negative electrode, although some defects occurred during the production of the electrode winding body, an example using a thicker aluminum foil as the negative electrode In each of the batteries 1, 3 and 4, such a defect of the electrode winding body does not occur. On the other hand, the nonaqueous electrolyte battery of Comparative Example 1 having a negative electrode produced without using an aluminum foil (that is, not having a lithium-aluminum alloy) has a pulse discharge as compared with the battery of the example. Later voltage is low and pulse discharge characteristics are inferior.

  In addition, the non-aqueous electrolyte battery of Example 1 in which the microporous film of the separator is disposed on the negative electrode side and the nonwoven fabric is disposed on the positive electrode side, and the microporous film of the separator is disposed on the positive electrode side and the nonwoven fabric is disposed on the negative electrode side. The non-aqueous electrolyte battery of Example 5 was subjected to the following vibration test.

  The vibration test was performed as follows. The open circuit voltage was measured for each non-aqueous electrolyte battery in which a stable voltage was obtained through the above preliminary discharge and aging (this is the initial voltage). After applying vibration to these batteries for a total of 6 hours, with a vibration frequency range of 10 to 55 Hz and a half amplitude of 0.5 mm for 1 minute in the X direction, similarly to the Y direction and the Z direction for 2 hours each, The open circuit voltage was measured again, and a product in which the voltage was lowered by 20 mV or more from the initial voltage was determined as a soft short product. The number of samples of each battery was 100, and the number of soft short products among them was examined. The results are shown in Table 3.

  As can be seen from Table 3, in the nonaqueous electrolyte battery of Example 1 in which the microporous film of the separator was arranged on the negative electrode side and the nonwoven fabric was arranged on the positive electrode side, no soft short occurred even in the vibration test. In the nonaqueous electrolyte battery of Example 5 in which the microporous film of the separator is disposed on the positive electrode side and the nonwoven fabric is disposed on the negative electrode side, a soft short is slightly caused by the vibration test. Therefore, it can be seen that it is preferable to dispose a separator like the battery of Example 1 in order to suppress the deterioration of the battery characteristics due to the vibration of the battery to a higher degree.

It is a vertical side view which shows an example of the nonaqueous electrolyte battery of this invention. It is a cross-sectional top view which shows an example of the nonaqueous electrolyte battery of this invention. It is principal part sectional drawing of the electrode winding body which concerns on the nonaqueous electrolyte battery of FIG. It is a figure for demonstrating the preparation methods of the electrode winding body which concerns on the nonaqueous electrolyte battery of this invention. It is a figure for demonstrating the preparation methods of the electrode winding body which concerns on the nonaqueous electrolyte battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte battery 2 Exterior can 3 Electrode wound body 4 Sheet-like positive electrode 5 Sheet-like negative electrode 6 Separator 20, 21 Positive electrode mixture sheet 22 Positive electrode current collector 25 Metal lithium layer 25a Metal lithium foil-aluminum foil laminate 25b Metallic lithium foil 25c Aluminum foil 26 Negative electrode current collector 28 Microporous film 29 Non-woven fabric 31 Tape 33 Winding core

Claims (5)

A cylindrical non-aqueous electrolyte battery having an electrode winding body formed by winding a sheet-like positive electrode and a sheet-like negative electrode through a separator in a cylindrical outer can,
The sheet-like positive electrode is formed by laminating two positive electrode mixture sheets via a current collector, and the positive electrode mixture sheet is 4 to 9% of the inner diameter of the outer can per sheet. Has a thickness equivalent to
The sheet-like negative electrode has a lithium-aluminum alloy on at least a part of the surface of the metal lithium layer and the surface of the metal lithium layer facing the positive electrode with a separator interposed therebetween. Non-aqueous electrolyte battery.   The lithium-aluminum alloy in the sheet-like negative electrode is formed by laminating an aluminum foil on the surface of a metal lithium foil for forming a metal lithium layer and electrochemically alloying it in the battery. A cylindrical non-aqueous electrolyte battery according to claim 1.   The cylindrical non-aqueous electrolyte battery according to claim 2, wherein the lithium-aluminum alloy in the sheet-like negative electrode is formed using an aluminum foil having a width smaller than that of the metal lithium foil.   The separator has a microporous film and a non-woven fabric as constituent elements, the microporous film is disposed so as to be in contact with the negative electrode, and the non-woven fabric is disposed so as to be in contact with the positive electrode. The cylindrical nonaqueous electrolyte battery according to any one of the above. The cylindrical nonaqueous electrolyte battery according to claim 4, wherein the positive electrode mixture sheet has a porosity of 35 to 50%.

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