JP2005340175A - Lithium primary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium primary battery having a long preservation life. <P>SOLUTION: This lithium primary battery is equipped with a separator 9, a negative electrode active material layer 5 and a positive electrode active material layer 6 mutually separated by the separator 9, a pair of frame-like sheet members 2, 3 to individually surround these electrode active material layers 5, 6 on the main surface of the separator, and a pair of collectors 7, 8 fixed to each of the frame-like sheet members 2, 3 to hold the electrode active material layers 2, 3 between the separator and them. The negative electrode active material layer 5 is formed of lithium foil. A frame-like wall member 10 is disposed between the frame-like sheet member 3 on the positive electrode side and the positive electrode active material layer 6, and the visible outline 6p of the positive electrode active material layer 6 is housed in the inside of the visible outline 5p of the lithium foil 5, in a projection drawing in the battery thickness direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lithium primary battery.

Lithium primary batteries using lithium as a negative electrode are in demand mainly for low-load backup applications because of their extremely low self-discharge and stable characteristics for long-term storage. Among them, those disclosed in the following Patent Documents 1 and 2 are commonly called paper batteries, and demand for IC cards with display functions, active RFIDs, and the like is expected to increase.
Japanese Patent No. 2935427 Japanese Patent Laid-Open No. 08-055627

  The lithium primary battery as described above is required to have a long shelf life. For example, in future IC card applications, prevention of a decrease in output voltage is strongly demanded. Therefore, an object of the present invention is to provide a lithium primary battery that has a long shelf life and is particularly excellent in output voltage stability.

Means for Solving the Problems and Effects of the Invention

  The inventors conducted an acceleration test on the lithium primary battery 50 of FIG. 13 at 70 ° C. indoor humidity. Among them, there was one showing a result like the graph of FIG. As can be seen from the graph, the voltage drop started around the seventh and eighth months.

  A schematic cross-sectional view of FIG. 13 shows a lithium primary battery 50 that has been subjected to the acceleration test. Reference numerals 52 and 53 are resin frame-like sheet members, reference numerals 57 and 58 are metal current collectors, reference numeral 59 is a separator, reference numeral 55 is a lithium foil constituting the negative electrode active material layer, and reference numeral 56 is a positive electrode active material layer. Is shown. On the negative electrode side, a gap is formed between the lithium foil 55 and the frame-shaped sheet member 52, whereas on the positive electrode side, the positive electrode active material layer 56 fills the opening of the frame-shaped sheet member 53 with almost no gap. Yes. The positive electrode active material layer 56 is formed by printing a paste-like mixture composed of a positive electrode active material, a conductive additive, an electrolytic solution, and the like, and is in-plane direction by pressurization in a subsequent process such as a sealing process. Because it spreads to.

On the other hand, immediately after the positive electrode mixture is produced by kneading, the positive electrode active material such as MnO ₂ is very active and decomposes the electrolytic solution. Therefore, stabilized discharge is performed promptly after the battery is manufactured. However, with the arrangement as shown in FIG. 13, the active positive electrode active material tends to remain at the end of the positive electrode active material layer 56 protruding from the lithium foil 55 in the in-plane direction.

  In general, the positive and negative electrodes of a battery are ideally equal in electrochemical capacity, but are industrially difficult. In a lithium primary battery, when the negative electrode capacity is larger than the positive electrode capacity, lithium remains even after complete discharge and causes electrolyte decomposition. Therefore, in the lithium primary battery, the positive electrode capacity is made larger than the negative electrode capacity. The conventional lithium primary battery 50 shown in FIG. 13 employs a structure in which the entire surface of the lithium foil 55 faces the positive electrode active material layer 56 with the separator 59 interposed therebetween. It has no design philosophy from the viewpoint of ensuring complete discharge and preventing battery deterioration during long-term storage. The present inventors have found such findings and have completed the following present invention.

  That is, the present invention for solving the problem includes a separator, a negative electrode active material layer and a positive electrode active material layer separated from each other by the separator, and a frame-shaped sheet member that surrounds the electrode active material layer on the main surface of the separator. A plate-like lithium primary battery comprising a current collector fixed to a frame-shaped sheet member and holding an electrode active material layer between the separator and a negative electrode active material layer made of lithium metal foil, A frame-shaped wall member is disposed between the sheet-like sheet member and the positive electrode active material layer, and in the projection view in the battery thickness direction, the outer shape line of the positive electrode active material layer matches the outer shape line of the lithium metal foil or on the inner side. The main feature is that it fits. Lithium metal means lithium or a lithium alloy.

  In the present invention, the wall member is provided so that the entire positive electrode active material layer faces the lithium metal foil via the separator. Therefore, the stabilized discharge is uniformly performed throughout the positive electrode active material layer, and the positive electrode active material having high activity does not remain. Therefore, decomposition of the electrolytic solution is suppressed, and battery deterioration during long-term storage is reduced. In addition, since the stabilized discharge is performed uniformly over the entire positive electrode, the amount of discharge when performing the stabilized discharge can be reduced, and a substantial improvement in battery capacity can be expected.

  The above-mentioned wall member is selected from the group of polyolefin resin, polyimide resin, polycarbonate resin, polyester resin, polyurethane resin, polysiloxane resin, polyamide resin, AS resin, ABS resin, and fluorine resin. What was comprised with 1 or more types of resin is suitable. These resins are particularly recommended as the material of the wall member of the present invention because they are excellent in electrolytic solution resistance and oxidation-reduction resistance.

  Moreover, it is preferable that a wall member has a porous structure which can hold | maintain electrolyte solution. When the wall member is provided, the volume thereof becomes a dead space, and the volume energy density decreases. However, when the wall member has a porous structure, the excess electrolyte can be held by the wall member, and a decrease in volume energy density can be suppressed. In addition, since the wall member holds the electrolytic solution, even if an unexpected seal breakage occurs, the leakage can be minimized. Furthermore, the process of sealing the frame-shaped sheet members to each other at the time of manufacturing the battery is performed, but when the wall member holds the electrolytic solution, excess electrolytic solution protrudes into the seal portion during the process, resulting in poor sealing. The problem of causing That is, the wall member contributes to the yield improvement.

  The wall member is preferably bonded to at least one of the positive electrode current collector and the separator. In this way, even if a certain amount of pressure is applied to the battery, it is possible to prevent the positive electrode mixture from protruding to the outside of the wall member. The wall member may be bonded by an adhesive or heat welding.

  In another aspect, in order to solve the problem, the present invention separately provides a separator, a negative electrode active material layer and a positive electrode active material layer separated from each other by the separator, and the electrode active material layer on the main surface of the separator. A pair of frame-shaped sheet members to be surrounded, and a pair of current collectors fixed to each of the frame-shaped sheet members and holding an electrode active material layer between the separators, the negative electrode active material layer being a lithium metal foil In the projection view of the battery thickness direction, the opening of the frame-shaped sheet member on the positive electrode side is made smaller than the opening of the frame-shaped sheet member on the negative electrode side. The main feature is that the outline of the material layer matches or falls within the outline of the lithium metal foil.

  In the present invention described above, the positive electrode active material layer is entirely opposed to the lithium metal foil through the separator by providing a size in the opening of the frame-shaped sheet member. Therefore, a stabilized discharge is performed on the entire positive electrode active material layer, and the positive electrode active material does not remain active. Therefore, decomposition of the electrolytic solution is suppressed, and battery deterioration during long-term storage is reduced. In addition, since the stabilized discharge is performed uniformly over the entire positive electrode, the amount of discharge when performing the stabilized discharge can be reduced, and a substantial improvement in battery capacity can be expected.

  In addition, as the inventors have made further studies, it has been found that the cause of the battery deterioration exists other than the fact that the stabilized discharge is not sufficiently performed.

Generally, in a lithium primary battery, it is known that self-discharge of a negative electrode proceeds by the following reaction.
2Li + 2H ₂ O = 2LiOH + H ₂

  Referring to the conventional lithium primary battery 50 shown in FIG. 13, as shown in FIG. 14, during the long-term storage or use, moisture enters the battery through the frame-like sheet members 52 and 53 little by little. This is because the frame-like sheet members 52 and 53 as the sealing material are made of a resin having a high water vapor barrier property such as polypropylene, but it is difficult to completely prevent the water vapor from passing therethrough. However, even if hydrogen is generated by the above-described reaction, the hydrogen is released to the outside through the frame-shaped sheet members 52 and 53, so that the battery performance is not greatly affected. In addition, lithium hydroxide has no special problem.

On the other hand, since the lithium primary battery 50 in FIG. 13 has a structure in which the positive electrode active material layer 56 extends to a position where the positive electrode active material layer 56 contacts the frame-shaped sheet member 53, the water WA enters the positive electrode active material layer 56. The water WA that has entered the positive electrode active material layer 56 locally creates an acidic state in the voids between the active material particles (for example, MnO ₂ particles). As a result, the following reaction occurs.
Li ⁺ + H ₂ O = LiOH + H ⁺
MnO ₂ + 4H ⁺ = 2H ₂ O + Mn ⁴⁺

  As the above reaction proceeds, tetravalent manganese is eluted in the electrolyte. Tetravalent manganese eluted in the electrolyte is very active and immediately decomposes the electrolyte. Carbon dioxide gas is generated by the decomposition of the electrolyte. The generated carbon dioxide gas stays inside the battery, impairs the contact between the separator 59 and the active material layers 55 and 56, or the contact between the active material layers 55 and 56 and the current collectors 57 and 58, or creates pores in the positive electrode active material. The battery performance is greatly deteriorated by blocking or forming a passive film on the surface of the positive electrode active material particles or the negative electrode active material particles. In order to improve such problems, the present inventors propose the following lithium primary battery.

  That is, in order to solve the problem, the lithium primary battery of the present invention is located between the positive electrode active material layer and the frame-shaped sheet member to isolate both, and the water that has entered the battery through the frame-shaped sheet member. The main feature is that a moisture protection wall is provided to prevent the metal from moving toward the positive electrode active material layer.

  The lithium primary battery of the present invention focuses on limiting the movement path of water that has passed through the frame-shaped sheet member by the moisture prevention wall. The moisture prevention wall prevents the positive electrode active material layer from coming into direct contact with the frame-shaped sheet member, and at the same time forms an electrolyte film with the frame-shaped sheet member. The electrolytic solution transports water toward the negative electrode side. That is, the moisture prevention wall has an effect of guiding water to the negative electrode side. As a result, the ratio of water entering the positive electrode active material layer can be greatly reduced. Since the positive electrode active material can be prevented from becoming active by reducing the ratio of water entering the positive electrode active material layer, the generation of carbon dioxide gas due to decomposition of the electrolyte is suppressed. Therefore, battery deterioration during long-term storage or use is unlikely to occur.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view of a lithium primary battery 1A of the present invention, and FIG. 2 is a cross-sectional view taken along line AA in FIG. As shown in FIGS. 1 and 2, the lithium primary battery 1 </ b> A has a rectangular plate shape, and includes a separator 9, a negative electrode active material layer 5 and a positive electrode active material layer 6 separated from each other by the separator 9, and electrodes thereof. Between a pair of window frames 2 and 3 (frame-like sheet members) individually enclosing the active material layers 5 and 6 on the main surface of the separator 9 and the separators 9 fixed to each of the window frames 2 and 3 A pair of current collectors 7 and 8 sandwiching the electrode active material layers 5 and 6 and strip-shaped lead terminals 7t and 8t (tabs) integrally formed with each of the current collectors 7 and 8 are provided. Each lead terminal 7t, 8t functions as a power extraction part.

  In the opening 3q of the window frame 3 on the positive electrode side, a frame-like wall member 10 configured as a separate member from the window frame 3 is disposed so as to surround the positive electrode active material layer 6. FIG. 4 is a projection view in the thickness direction of the lithium primary battery 1A. As shown in this projection view, the openings 2q and 3q of the window frames 2 and 3 and the opening 10q of the wall member 10 have a square shape similar to each other. If each part is rectangular, the material is less wasteful and the cost is low.

  The current collectors 7 and 8 are metal plates that also serve as the exterior material of the lithium primary battery 1A. The window frames 2 and 3, the window frame 2 on the negative electrode side and the current collector 7, and the window frame 3 on the positive electrode side and the current collector 8 are bonded to form a seal portion 11 that maintains the airtightness inside the battery. ing. The peripheral edge of the separator 9 is sandwiched between a pair of window frames 2 and 3 and bonded to one of the window frames 2 and 3. The pair of window frames 2 and 3 sandwich the separator 9 on the inner peripheral side and are bonded to each other on the outer peripheral side.

  The window frames 2 and 3 are made of, for example, ethylene vinyl acetate (EVA) on both sides of a base material made of a thermoplastic resin having low water vapor permeability such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET). A hot-melt adhesive layer such as ethylene / methacrylic acid copolymer (EMAA), acid-modified polyethylene (PE-a), or acid-modified polypropylene (PP-a) is formed. In the present embodiment, a resin sheet having a three-layer structure in which biaxially stretched polypropylene (OPP) is sandwiched between ethylene / methacrylic acid copolymers is used for the window frames 2 and 3. When the lithium primary battery 1A of the present invention is used for an ISO standard (ISO / IEC 7810) IC card, the thickness of the window frames 2 and 3 is preferably adjusted to 90 μm or more and 150 μm or less, for example. Adhesion between the window frames 2 and 3 and the current collectors 7 and 8 and adhesion between the window frames 2 and 3 and the separator 9 are performed through the adhesive layer.

  The negative electrode active material layer 5 can be a lithium foil or a lithium alloy foil. In this embodiment, the lithium foil 5 is used. In the case of a lithium primary battery used for an ISO standard IC card, the thickness of the lithium foil 5 is adjusted to, for example, 50 μm or more and 150 μm or less. The positive electrode active material layer 6 includes, for example, a positive electrode active material of 60% by mass or more and 70% by mass or less, a conductive auxiliary agent of 1% by mass or more and 5% by mass or less, and an electrolyte solution of 25% by mass or more and 35% by mass or less. It is comprised with the positive electrode compound material containing. The masses of the positive electrode active material layer 6 and the lithium foil 5 are adjusted so that the positive electrode capacity is larger than the negative electrode capacity. This prevents the lithium foil 5 from remaining after complete discharge.

As the positive electrode active material, a transition metal oxide powder that forms a composite oxide with lithium such as MnO ₂ can be used. A carbon material such as acetylene black can be used for the conductive assistant. Examples of the electrolytic solution include an organic solvent such as dimethoxyethane (DME), ethylene carbonate (EC), and propylene carbonate (PC), and lithium such as lithium perchlorate salt (LiClO ₄ ) and lithium triflate salt (LiCF ₃ SO ₃ ). What dissolved the salt can be used.

  The separator 9 is a thin film-like member that separates the positive electrode and the negative electrode and allows the electrolyte to penetrate sufficiently. The separator 9 is a sheet piece having a porous and multilayer structure made of a resin such as polyethylene or polypropylene. In the present embodiment, the separator 9 is made of a polyethylene porous sheet. The thickness of the separator 9 is, for example, 10 μm or more and 60 μm or less in the case of an ISO standard lithium primary battery for IC card use.

  As the material of the current collectors 7 and 8 and the lead terminals 7t and 8t, one kind selected from a highly conductive metal group consisting of copper, copper alloy, stainless steel, aluminum, nickel and nickel alloy is preferably used. Can do. In particular, stainless steel is preferable because it is excellent in workability, corrosion resistance, and economy. When the lithium primary battery 1A is used for backup purposes, it is important that the constituent material of the current collector does not elute into the battery. In this regard, stainless steel has a minute. Specifically, SUS301, SUS304, SUS316, SUS316L, which are typical as austenitic stainless steel, and SUS631, which is typical as precipitation hardened stainless steel, are also excellent in spring properties, and therefore their use is recommended.

  As shown in the cross-sectional view of FIG. 2, on the positive electrode side, the positive electrode active material layer 6 fills the opening 10q of the wall member 10 without a gap. This maximizes the positive electrode capacity. Further, the positive electrode active material layer 6 is adjusted to have such a size and shape that the outline 6p is accommodated inside the outline 5p of the lithium foil 5 in the projection view of FIG. That is, the lithium foil 5 is larger than the positive electrode active material layer 6 on the surface facing the separator 9.

  In the case of the above arrangement, the stabilized discharge treatment at the time of manufacturing the battery can be sufficiently performed up to the end of the positive electrode active material layer 6. In view of this, it is also preferable that the outline 6p of the positive electrode active material layer 6 matches the outline 5p of the lithium foil 5 in the projection view of FIG. However, considering the assembly accuracy of the parts, it can be said that it is preferable to design the outer shape line 6 p of the positive electrode active material layer 6 to be inside the outer shape line of the lithium foil 5. Moreover, since the outline 5p of the lithium foil 5 is adjusted to a size that fits inside the outline 10p of the wall member 10, the peripheral portion of the lithium foil 5 is not easily consumed.

  The wall member 10 is selected from the group consisting of polyolefin resin, polyimide resin, polycarbonate resin, polyester resin, polyurethane resin, polysiloxane resin, polyamide resin, AS resin, ABS resin, and fluorine resin. Any resin can be used. In this embodiment, the wall member 10 is comprised with the porous sheet | seat made from a polypropylene. Polypropylene is suitable because it has been used as a separator material in an environment inside the battery. Of course, you may comprise the wall member 10 with the composite resin containing 2 or more types of resin selected from the above.

The average diameter of the holes formed in the wall member 10 is about 1 μm, and is adjusted to be much smaller than the average particle diameter (about 50 μm) of the powder material of the positive electrode active material layer 6. Therefore, the positive electrode active material hardly penetrates into the pores of the wall member 10, but the electrolytic solution penetrates easily. If the wall member 10 has a function of holding the electrolytic solution, an effect of preventing liquid leakage when an unexpected seal breakage can be expected. If the average diameter of the pores of the wall member 10 is 0.5 μm or more and 3 μm or less and the average particle diameter of the powder material of the positive electrode active material layer 6 is in the range of 30 μm or more and 60 μm or less, the above effect can be obtained while maintaining the battery performance. It is preferable because it can be obtained sufficiently. The average particle diameter of MnO ₂ powder and conductive additive powder may be an average particle diameter measured by a laser diffraction particle sizer. The average diameter of the holes in the wall member 10 can be obtained by a mercury porosimeter press-fitting method.

  In a normal battery design, the electrolyte solution is excessively added in an amount of about 5 vol% of the initial required amount in consideration of the decrease of the electrolyte solution over time. When the wall member 10 has a porous structure, the wall member 10 can be made to hold the 5 vol% excess electrolyte solution, so that a decrease in volume energy density due to the provision of the wall member 10 can be suppressed. .

In order to obtain the effect that the reduced amount is quickly replenished by the excess electrolytic solution held in the wall member 10 when the electrolytic solution involved in the battery reaction is reduced by evaporation / decomposition or the like, It is desirable that at least one of the requirements (a) and (b) is satisfied, particularly that the requirement (b) is satisfied. This is because the electrolytic solution retention is a capillary phenomenon and is considered to be governed by the requirement (b) rather than the requirement (a).
(A) The wettability between the wall member 10 and the electrolytic solution is the wettability between the electrolytic solution and the positive electrode active material (MnO ₂ powder), the wettability between the electrolytic solution and the lithium foil 5, and the wettability between the electrolytic solution and the separator 9. Smaller than any of sex.
(B) The average diameter of the holes in the wall member 10 is larger than the average diameter of the holes in the separator 9.

  The resin material used for the wall member 10 in this embodiment is a polypropylene porous sheet having an average pore diameter of about 1 μm that has been subjected to a modification treatment to impart adhesion. On the other hand, for the separator 9, a polyethylene porous sheet having an average pore diameter of about 20 nm is used. Therefore, the wall member 10 has an electrolyte solution holding power smaller than that of the separator 9 and exhibits an effect of supplying an excess electrolyte solution. When the average diameter of the pores of the wall member 10 is 0.5 μm or more and 3 μm or less, the above effect can be sufficiently obtained while maintaining the battery performance if the average diameter of the pores of the separator 9 is in the range of 10 nm or more and 50 nm or less. This is preferable.

In the lithium primary battery 1 </ b> A of the present embodiment, the amount of the electrolyte is determined based on the positive electrode material powder (active material powder, conductive assistant powder, etc.) and the pore volume of the separator 9. Furthermore, an extra amount is added in advance, taking into consideration the years of use, the amount permeated through the seal portion 11 and dissipated to the outside, and the reduction amount due to disassembly. Then, it has been described that the decrease in the energy density of the battery can be reduced by holding the excess electrolyte in the holes of the wall member 10. Therefore, the amount of electrolyte used can be converted from the pore volume of the wall member 10, the positive electrode material powder, and the separator 9.
(Amount of electrolyte) ≧ (hole volume of wall member 10) + (pore volume of positive electrode material powder and separator)

  It is not essential to produce the wall member 10 with a resin sheet having a porous structure. Of course, the wall member 10 may be produced with a resin sheet having no porous structure, such as a polypropylene sheet or a polyethylene sheet. It is.

  Next, a manufacturing method of the lithium primary battery 1A will be described with reference to FIG. First, the current collector 7 on the negative electrode side is brought into surface contact with the window frame 2 and the adhesive layer of the window frame 2 is melted by an ultrasonic welding method or a heat welding method to bond the current collector 7 to the window frame 2. (6-1). Next, the assembly of the window frame 2 and the current collector 7 is turned over, and the lithium foil 5 as the negative electrode active material is placed on the current collector 7. Further, the separator 9 is placed on the lithium foil 5 so that the peripheral edge thereof is in surface contact with the window frame 2 (6-2). At this time, it is preferable that the separator 9 and the window frame 2 are preliminarily heat-welded so that the position shift of the separator 9 does not occur. A wall member 10 is bonded to the separator 9 in advance.

  Next, the positive electrode mixture is printed on the main surface of the separator 9 surrounded by the wall member 10 by a printing method using a metal mask to form the positive electrode active material layer 6 (6-3). Next, the positive electrode current collector 8 previously bonded to the window frame 3 is placed on the positive electrode active material layer 6 (6-4). Then, a heat welding jig 60 such as an ultrasonic horn is brought into contact with the current collector 8 while sucking air from the vacuum atmosphere or between the window frames 2 and 3 to weld the window frames 2 and 3 together. Thereby, the lithium primary battery 1A of the present invention is obtained (6-5). The lithium primary battery 1A is subjected to a stabilized discharge treatment immediately after assembly. Thereby, the activity of the positive electrode active material is lowered, and the occurrence of problems such as decomposition of the electrolyte solution during long-term storage, liquid erosion, and formation of an inactive film is prevented. 6, the thickness of the wall member 10 is larger than the thickness of the window frame 3, but half the thickness of the separator 9 is subtracted from the thickness of the window frame 3 as shown in FIG. 2. The thickness may be the thickness of the wall member 10. Or the thickness of the window frame 3 and the thickness of the wall member 10 may correspond.

(Second embodiment)
Next, FIG. 3 is a schematic cross-sectional view of the lithium primary battery 1B of the present invention, and FIG. 5 is a projection view of the lithium primary battery 1B in the battery thickness direction. The lithium primary battery 1B of this embodiment is the same in appearance as the lithium primary battery 1A of FIG. The difference is that the opening 30q of the window frame 30 on the positive electrode side is made smaller than the opening 2q of the window frame 2 on the negative electrode side. That is, the wall member 10 shown in FIG.

  As can be seen from the projection of FIG. 5, the openings 2q and 30q of the window frames 2 and 30 are similar to each other. The positive electrode active material layer 6 fills the openings 30q of the window frame 30 on the positive electrode side without any gaps. The window frame 30 is adjusted to have a size such that the opening 30q fits inside the outline 5p of the lithium foil 5. That is, the window frame 30 on the positive electrode side and the lithium foil 5 are overlapped in the battery thickness direction. As a result, the lithium foil 5 is larger than the positive electrode active material layer 6 on the surface facing the separator 9.

  The lithium primary battery 1B shown in FIG. 3 matches the lithium primary battery 1A shown in FIG. 2 in terms of the obtained effects and the objects that can be achieved. However, since the wall member 10 is also used as the window frame 30, the number of parts is small and manufacturing is easy. That is, it can be manufactured at low cost. On the other hand, when the wall member 10 is provided as a separate member from the window frame 3 as in the lithium primary battery 1A of FIG. 2, the room for material selection becomes large, and a porous material is used to hold the excess electrolyte. It is possible to provide a higher performance lithium primary battery.

(Third embodiment)
FIG. 7 is a schematic cross-sectional view of the lithium primary battery according to the third embodiment. The lithium primary battery 1 </ b> C includes a separator 9, a negative electrode active material layer 5 and a positive electrode active material layer 26 separated from each other by the separator 9, and a negative electrode active material layer 5 and a positive electrode active material layer 26. It is common to the previous two embodiments, for example, in that the current collectors 7 and 8 are held. As shown in an enlarged view in FIG. 8, the negative electrode active material layer 5 and the positive electrode active material layer 26 are such that the outer peripheral edge 26 h of the positive electrode active material layer 26 is more outward in the in-plane direction than the outer peripheral edge 5 h of the negative electrode active material layer 5. However, this may be the same as in the previous embodiment. In addition, by fixing the current collectors 7 and 8 to the window frames 22, 23 and 24 (frame-like sheet members) that function as a seal material, a seal portion 21 that maintains the airtightness inside the battery is formed. This is a matter common to the previous two embodiments, but the structures of the window frames 22, 23, 24 themselves are slightly different.

  A feature of the lithium primary battery 1 </ b> C is that it includes a moisture prevention wall 25 that is located between the positive electrode active material layer 26 and the window frames 23 and 24 and isolates them. The wall member 10 and the like described in the previous embodiment are mainly for the purpose of preventing the positive electrode active material layer 6 from expanding in the in-plane direction. , 24 has the purpose and technical idea of preventing water that has entered the battery from moving toward the positive electrode active material layer 26. Of course, the moisture prevention wall 25 also has a function of preventing the positive electrode active material layer 26 from expanding in the in-plane direction, like the wall member 10 described in the previous embodiment.

  As shown in FIG. 7, the window frames 22, 23 and 24 constituting the seal portion 21 of the lithium primary battery 1C have a three-layer structure. Specifically, the positive electrode side adhesive layer 23 bonded to the positive electrode current collector 8, the negative electrode side adhesive layer 22 bonded to the negative electrode current collector 7, and the base material layer 24 positioned between the adhesive layers 22 and 23. It consists of. The adhesive layers 22 and 23 are layers composed of a resin excellent in adhesiveness with a metal such as acid-modified polypropylene. The base material layer 24 may be a resin having adhesiveness to the adhesive layers 22 and 23, and is a layer made of a resin such as polypropylene or polyethylene terephthalate.

  As shown in FIG. 8, the moisture prevention wall 25 is a component having an L-shaped cross section, and includes a first portion 251 sandwiched between the positive electrode side adhesive layer 23 and the base material layer 24, and a base material layer And a second portion 253 along the side surface 24p of 24. As the material of the moisture prevention wall 25, from the group of polyolefin resin, polyimide resin, polycarbonate resin, polyester resin, polyurethane resin, polysiloxane resin, polyamide resin, AS resin, ABS resin and fluorine resin. Any selected resin may be used. When emphasizing moisture barrier properties, it is advisable to use resins with excellent moisture barrier properties such as polypropylene and polyethylene terephthalate. It is also possible to form the moisture prevention wall 25 with a composite resin containing a plurality of types of resins selected from these resins in a predetermined ratio.

As shown in FIG. 8, the base material layer 24 and the moisture prevention wall 25 are partly bonded and fixed to each other so that a gap SH is formed between them. Alternatively, both may be completely non-adhered. The clearance SH between the base material layer 24 and the moisture prevention wall 25 is filled so that the electrolytic solution can flow. Therefore, the water WA that has reached the gap SH through the base material portion 24 is mixed into the electrolytic solution and quickly diffuses. The water WA mixed in the electrolytic solution is prevented from being diffused in the in-plane direction by the moisture prevention wall 25, and thus cannot be directly diffused into the positive electrode active material layer 26, but first diffuses into the separator 9. Then, it diffuses to the negative electrode side through the separator 9. Since the empty space 29 not filled with the negative electrode active material layer 5 is also filled with the electrolytic solution, the water WA diffuses in the electrolytic solution and reacts quickly with lithium constituting the negative electrode active material layer 5. There is also water WA that diffuses in such a way as to return to the positive electrode side through the separator 9, but the ratio is small. This is because most of the water WA is consumed by the reaction with lithium. In this way, it is possible to greatly reduce the rate at which water WA that has entered the battery reacts with the positive electrode active material (MnO ₂ ), thereby suppressing battery deterioration.

  The lithium primary battery 1C of FIG. 7 has a structure in which the adhesive layer 23 and the positive electrode active material layer 26 are in contact with each other, but the thickness of the adhesive layer 23 may be considerably smaller than that of the base material layer 24. Therefore, very little water enters the positive electrode active material layer 26 via the adhesive layer 23.

  As shown in FIGS. 7 and 8, in the lithium primary battery 1 </ b> C, the outer peripheral edge 26 h of the positive electrode active material layer 26 is located outside the outer peripheral edge 5 h of the negative electrode active material layer 5 in the in-plane direction. That is, the lithium primary battery 1C is not restricted by the positional relationship between the positive electrode active material layer 26 and the negative electrode active material layer 5 as in the previous embodiment, and the outer peripheral edges 26h and 5h are aligned in the plane. The shape of the moisture prevention wall 25 etc. can be devised. By doing so, it is possible to further reduce the rate at which the water WA diffuses into the positive electrode active material layer 26, so that it is possible to prevent further deterioration of the lithium primary battery 1C.

  In order to increase the volume of the positive electrode active material layer 26, it is desirable that the moisture prevention wall 25 be as thin as possible. When the positive electrode active material layer 26 is formed by printing a paste-like positive electrode mixture, the moisture prevention wall 25 needs to be self-supporting at the time of printing. It can be said that the L-shaped cross section is an effective shape. Even in the actual manufacture even if the cross section is L-shaped, the moisture prevention wall 25 is produced by overlapping two (a plurality of) resin sheets having different thicknesses, and the moisture prevention wall 25 is formed on the base material layer 24. It is possible to adopt an assembling procedure that arranges them so as to overlap each other. Note that, as described in the fourth embodiment, it is not essential to have an L-shaped cross section.

(Fourth embodiment)
FIG. 9 is a schematic cross-sectional view of the lithium primary battery according to the fourth embodiment. The lithium primary battery 1 </ b> D includes a separator 9, a negative electrode active material layer 5 and a positive electrode active material layer 36 separated from each other by the separator 9, and a negative electrode active material layer 5 and a positive electrode active material layer 36. The present embodiment is common to the previous three embodiments in that it includes the current collectors 7 and 8 to be held. Further, a pair of resin sheets are used as the window frames 32, 33, the negative electrode current collector 7 is fixed to the negative electrode side window frame 32, and the negative electrode current collector 8 is fixed to the positive electrode side window frame 33, thereby sealing. About the point which forms the part 31, it is common with 1st embodiment and 2nd embodiment. The window frames 32 and 33 have different opening sizes. Specifically, compared with the window frame 32 on the negative electrode side, the opening 33h of the window frame 33 on the positive electrode side is made larger. The size of the opening is just opposite to that of the second embodiment, and the separator 9 is fixed to the inner peripheral portion 32a of the window frame 32 on the negative electrode side adjusted to be narrow.

  The lithium primary battery 1D is characterized in that it includes a moisture prevention wall 35 that is located between the positive electrode active material layer 36 and the window frame 33 and isolates both. This moisture prevention wall 35 is different from the wall member 10 of the first embodiment in that it is made of a resin sheet (PP sheet, PET sheet, etc.) that does not hold the electrolytic solution or is at least harder to hold than the separator. Is different. In addition, a space 43 between the positive-side window frame 33 and the moisture prevention wall 35 that is not filled with an active material but is filled with an electrolytic solution. From the viewpoint of preventing the positive electrode active material layer 36 from spreading in the in-plane direction, it is desirable that the moisture prevention wall 35 is bonded to both of the positive electrode current collector 8 and the separator 9 in the entire periphery. Of course, you may make it fix to either one spotwise.

  As shown in FIG. 10, the moisture that has reached the inside of the battery through the window frame 33 on the positive electrode side quickly diffuses into the electrolyte solution that fills the void 43. The water WA diffused in the electrolytic solution diffuses into the separator 9. The thickness of the separator 9 is very small compared to the thickness of the moisture prevention wall 35 and the thickness of the positive electrode active material layer 36, but the separator 9 is impregnated with an electrolytic solution. Therefore, the speed at which the water WA having passed through the window frame 33 diffuses from the outer peripheral portion 9k of the separator 9 into the separator 9 is infinite compared to the speed at which the water WA diffuses into the moisture prevention wall 35. In other words, the moisture that has passed through the window frame 33 is guided to the void 41 on the negative electrode side by the separator 9 and the moisture prevention wall 35, and reacts promptly with lithium constituting the negative electrode active material layer 5. As a result, the rate at which the water WA that has entered the battery reacts with the positive electrode active material can be reduced.

  By the way, when there is no moisture prevention wall 35, the positive electrode active material layer 36 easily expands to a position in contact with the window frame 33. When the positive electrode active material layer 36 is formed by printing the paste-like positive electrode mixture, the positive electrode active material layer 36 applies a load in the thickness direction in the sealing step when forming the seal portion 31. Because it receives directly from. That is, the moisture prevention walls 25 and 35 are particularly effective for a thin lithium primary battery in which a positive electrode active material layer is formed by printing a paste-like positive electrode mixture.

  On the other hand, in the case of a lithium primary battery in which the positive electrode mixture is formed into a film in advance and cut into a desired shape to form a battery component, the positive electrode active material layer has appropriate hardness and self-supporting property, so that the in-plane direction Difficult to spread. Accordingly, although there is no problem that water that has entered the battery immediately diffuses into the positive electrode active material layer, by incorporating the technical idea of the present invention, water that has entered the battery is actively transported to the negative electrode side. Therefore, it is possible to reduce the amount of carbon dioxide generated due to the reaction between the positive electrode active material and water, thereby suppressing battery deterioration.

  Although several embodiments have been described above, it goes without saying that these embodiments may be combined with each other without departing from the spirit of the invention. For example, a moisture prevention wall that prevents water from flowing to the positive electrode active material layer is provided, and in the projection view in the battery thickness direction, the outline of the positive electrode active material layer coincides with the outline of the negative electrode active material layer or on the inner side. Can be fit. By doing so, it becomes possible to further reduce the ratio of water entering the positive electrode active material layer.

Experimental example

In order to confirm the effect of the present invention, the following experiment was conducted.
First, the lithium primary battery 1A of the present invention shown in FIG. 2 was produced by the method described with reference to FIG. The lithium primary battery 1A thus obtained was stored in an environment of 70 ° C. indoor humidity, and the closed circuit voltage was measured by a DC pulse discharge method every month. The resulting graph is shown in FIG. For comparison, the experimental results of the comparative product previously performed are also shown.

  The comparative product showed a decrease in the closed circuit voltage after about 7 months, and the closed circuit voltage reached 2.0 V after 10 months. On the other hand, the product of the present invention did not decrease the closed circuit voltage even after 10 months, and showed excellent long-term storage performance.

The perspective view of the lithium primary battery of this invention. The cross-sectional schematic diagram which shows 1st embodiment of the lithium primary battery of this invention. The cross-sectional schematic diagram which shows 2nd embodiment of the lithium primary battery of this invention. FIG. 3 is a projection view in the battery thickness direction of the lithium primary battery 1 </ b> A in FIG. 2. FIG. 4 is a projection view of the lithium primary battery 1 </ b> B in FIG. 3 in the battery thickness direction. Manufacturing process explanatory drawing of the lithium primary battery of FIG. The cross-sectional schematic diagram which shows 3rd embodiment of the lithium primary battery of this invention. FIG. 8 is an operation explanatory diagram of the lithium primary battery in FIG. 7. The cross-sectional schematic diagram which shows 4th embodiment of the lithium primary battery of this invention. FIG. 10 is a diagram illustrating the operation of the lithium primary battery in FIG. 9. The graph which shows the result of the acceleration test of a comparative product. The graph which shows the result of the acceleration test of this invention goods (lithium primary battery 1A). The cross-sectional schematic diagram of the conventional lithium primary battery. Explanatory drawing of the problem of the conventional lithium primary battery.

Claims (8)

  The separator (9), the negative electrode active material layer (5) and the positive electrode active material layer (6) separated from each other by the separator (9), and the electrode active material layers (5, 6) are separated from the main part of the separator (9). An electrode active material layer (5, 6) is held between the frame-shaped sheet member (2, 3) surrounding on the surface and the separator (9) fixed to the frame-shaped sheet member (2, 3). A plate-like lithium primary battery (1A) comprising a current collector (7, 8), wherein the negative electrode active material layer (5) is composed of a lithium metal foil (5), the frame-shaped sheet member ( 3) and a positive electrode active material layer (6) between which a frame-like wall member (10) is disposed, and in the projection view in the battery thickness direction, the outline (6p) of the positive electrode active material layer (6) In accordance with the outline (5p) of the lithium metal foil (5) or inside. Lithium primary batteries that (1A).   The wall member (10) is selected from the group of polyolefin resin, polyimide resin, polycarbonate resin, polyester resin, polyurethane resin, polysiloxane resin, polyamide resin, AS resin, ABS resin, and fluorine resin. The lithium primary battery (1A) according to claim 1, comprising at least one kind of resin.   The lithium primary battery (1A) according to claim 1 or 2, wherein the wall member (10) has a porous structure capable of holding an electrolytic solution.   The lithium primary battery (1) according to any one of claims 1 to 3, wherein the wall member (10) is bonded to at least one of the current collector (8) on the positive electrode side and the separator (9). 1A).   The lithium primary battery (1A) has a rectangular plate shape, and the positive electrode active material layer (6) is filled in the entire opening (10q) of the wall member (10). The lithium primary according to any one of claims 1 to 4, wherein the outer shape line (5p) of the lithium metal foil (5) is in a positional relationship within the outer shape line (10p) of the wall member (10). Battery (1A).   The separator (9), the negative electrode active material layer (5) and the positive electrode active material layer (6) separated from each other by the separator (9), and the electrode active material layers (5, 6) are separated from the main part of the separator (9). An electrode active material layer (between a pair of frame-like sheet members (2, 30) individually enclosing on the surface and the separator (9) fixed to each of the frame-like sheet members (2, 30) 5 and 6) and a pair of current collectors (7, 8), and the negative electrode active material layer (5) is composed of a lithium metal foil (5) in a plate-like lithium primary battery (1B) The opening (30q) of the frame-shaped sheet member (30) on the positive electrode side is made smaller than the opening (2q) of the frame-shaped sheet member (2) on the negative electrode side, and a projection view in the battery thickness direction The outer shape line (6p) of the positive electrode active material layer (6) is the outer shape of the lithium metal foil (5). Lithium primary battery, characterized in that to fit inside or matches (5p) (1B).   The lithium primary battery (1B) has a rectangular plate shape, and the positive electrode active material layer (6) is filled in the entire opening (30q) of the frame-shaped sheet member (30) on the positive electrode side, 7. The lithium according to claim 6, wherein in the projection view, the opening (30q) of the frame-shaped sheet member (30) on the positive electrode side is in a positional relationship within the outline (5p) of the lithium metal foil (5). Primary battery (1B).   The separator (9), the negative electrode active material layer (5) and the positive electrode active material layer (26, 36) separated from each other by the separator (9), and the electrode active material layers (5, 26, 36) are separated into separators ( 9) a frame-shaped sheet member (22, 23, 24, 32, 33) surrounding the main surface, and the separator (9) fixed to the frame-shaped sheet member (22, 23, 24, 32, 33). Current collector (7, 8) for holding the electrode active material layer (5, 26, 36) between the positive electrode active material layer (26, 36) and the frame-shaped sheet member (22, 23, 24, 32, 33) to isolate them from each other, and water that has penetrated into the battery through the frame-like sheet member (23, 24, 32, 33) is transferred to the positive electrode active material layer (26, 36) Moisture barrier that prevents movement towards ( Lithium primary batteries to 5 and 35), comprising the (1C, 1D).

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