CN111886746A - Lithium secondary batteries and cards with built-in batteries - Google Patents

Abstract

Provided is a film-form lithium secondary battery which, despite having a lithium composite oxide sintered plate as a positive electrode plate, is less likely to have wrinkles in the vicinity of the end of the positive electrode plate even when repeatedly bent. The lithium secondary battery includes: the lithium composite oxide sintered body plate includes a positive electrode plate, a negative electrode layer, a separator, an electrolyte, and 1 pair of outer packaging films, wherein the outer peripheries of the 1 pair of outer packaging films are sealed with each other to form an inner space for accommodating a battery element, the thickness of the lithium secondary battery is 350-500 [ mu ] m, the thickness of the positive electrode plate is 70-120 [ mu ] m, and the distance between the end of the positive electrode plate and the end of the negative electrode layer is 50-2000 [ mu ] m over the entire peripheries of the positive electrode plate and the negative electrode layer.

Description

Lithium secondary batteries and cards with built-in batteries

technical field

The present invention relates to a lithium secondary battery and a card with a built-in battery.

Background technique

In recent years, smart cards with built-in batteries are being put into practical use. As an example of a smart card with a built-in primary battery, a credit card with a one-time password display function can be cited. An example of a smart card with a built-in secondary battery is a card with a fingerprint authentication/wireless communication function, which includes a wireless communication IC, an ASIC for fingerprint analysis, and a fingerprint sensor. Batteries for smart cards are generally required to have a thickness of less than 0.45 mm, high capacity, low resistance, flexibility, and process temperature resistance.

A secondary battery for this application and a card on which the secondary battery is mounted have been proposed. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2017-79192) discloses a secondary battery which is built in a plate-shaped member such as a card, and has enough strength. The secondary battery includes: an electrode body including a positive electrode and a negative electrode; a sheet-like laminate film outer body whose outer peripheral side is welded while covering the electrode body; and a positive electrode connection terminal and a negative electrode connection terminal, one end side of which is It is connected to the electrode body, and the other end side extends from the laminate film outer package to the outside. In addition, Patent Document 2 (Japanese Patent Laid-Open No. 2006-331838 ) discloses a thin battery in which large wrinkles are hardly generated on the surface and which is excellent in buckling resistance. The thin battery includes: a battery main body in which a separator, a positive electrode layer, and a negative electrode layer are accommodated between a positive electrode current collector and a negative electrode current collector; The frame member satisfies 100 μm≦D1≦320 μm and D1/D2≦0.85, when the thickness of the sealing portion is D1 and the maximum thickness of the battery center portion is D2. In the secondary batteries disclosed in these Patent Documents 1 and 2, a powder-dispersed positive electrode is used, and the powder-dispersed positive electrode is prepared by applying a positive electrode mixture containing a positive electrode active material, a conductive aid, a binder, and the like, and making it made dry.

However, in general, powder-dispersed positive electrodes contain a large amount (for example, about 10% by weight) of components that do not contribute to capacity (binders, conductive additives), so the packing density of the lithium composite oxide as the positive electrode active material becomes low. Therefore, there is still much room for improvement in the capacity and charge-discharge efficiency of the powder-dispersed cathode. Therefore, attempts have been made to improve the capacity and charge-discharge efficiency by forming the positive electrode or the positive electrode active material layer from a lithium composite oxide sintered body plate. In this case, since the positive electrode or the positive electrode active material layer does not contain a binder or a conductive aid, the packing density of the lithium composite oxide becomes high, and high capacity and good charge-discharge efficiency can be expected. For example, Patent Document 3 (Japanese Patent No. 5587052 ) discloses a positive electrode for a lithium secondary battery including: a positive electrode current collector; and a positive electrode active material layer which is connected to the positive electrode current collector via a conductive bonding layer engage. The positive electrode active material layer is composed of a lithium composite oxide sintered body plate having a thickness of 30 μm or more, a porosity of 3 to 30%, and an open pore ratio of 70% or more. In addition, Patent Document 4 (International Publication No. 2017/146088) discloses the use of an oriented sintered body plate containing lithium composed of lithium cobalt oxide (LiCoO ₂ ) or the like as a positive electrode of a lithium secondary battery provided with a solid electrolyte The plurality of primary particles composed of the composite oxide are oriented at an average orientation angle of more than 0° and 30° or less with respect to the plate surface of the positive electrode plate.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2017-79192

Patent Document 2: Japanese Patent Laid-Open No. 2006-331838

Patent Document 3: Japanese Patent No. 5587052

Patent Document 4: International Publication No. 2017/146088

SUMMARY OF THE INVENTION

However, cards incorporating a film-coated battery including a lithium composite oxide sintered body plate (positive electrode plate) as disclosed in Patent Documents 3 and 4 have the following problem. In the case of several hundreds of repeated bending tests, wrinkles are likely to occur on the surface of the card near the end of the positive electrode plate.

The inventors of the present invention have now obtained the knowledge that, in a lithium secondary battery in the form of a film-coated battery provided with a positive electrode sintered body plate, by adjusting the thickness of the lithium secondary battery, the thickness of the positive electrode plate, and the relationship between the edge of the positive electrode plate and the negative electrode layer The distance between the ends satisfies a predetermined condition, and even if bending is repeated, wrinkles are not easily generated near the ends of the positive electrode plate. It has also been found that it is not easy to perform the repeated bending test required by the JIS standard for as many as several hundred times in the form of a card with a built-in battery for a film-coated lithium secondary battery that satisfies the above conditions. Wrinkles occur near the ends of the positive plate.

Therefore, an object of the present invention is to provide a lithium secondary battery in the form of a film, which has a lithium composite oxide sintered body plate as a positive electrode plate, which is not effective even if it is repeatedly bent (especially in the form of a card with a built-in battery). Wrinkles are easily generated near the ends of the positive plate.

According to an aspect of the present invention, a lithium secondary battery is provided, comprising:

a positive electrode plate, the positive electrode plate is a lithium composite oxide sintered body plate;

A carbon-containing negative electrode layer, the size of the negative electrode layer is larger than the size of the positive electrode plate;

a separator, the separator is interposed between the positive electrode plate and the negative electrode layer, and the size is larger than the size of the positive electrode plate and the negative electrode layer;

an electrolyte that is impregnated into the positive plate, the negative layer, and the separator; and

1 an outer packaging film, the outer peripheries of the 1 outer packaging film are sealed with each other to form an inner space, and the positive electrode plate, the negative electrode layer, the separator and the electrolyte are accommodated in the inner space,

in,

The outer peripheral portion of the separator is in close contact with at least the outer peripheral edge of the outer packaging film on the positive electrode plate side or a surrounding area near the outer periphery, and the partition housing the positive electrode is separated from the partition housing the negative electrode,

The thickness of the lithium secondary battery is 350-500 μm, the thickness of the positive electrode plate is 70-120 μm, and the distance between the end of the positive electrode plate and the end of the negative electrode layer is between the positive electrode plate and the negative electrode layer. The entire outer circumference of the negative electrode layer is 50 to 2000 μm.

According to another aspect of the present invention, there is provided a card with a built-in battery including a resin base material and the lithium secondary battery embedded in the resin base material.

Description of drawings

FIG. 1 is a schematic cross-sectional view of an example of the lithium secondary battery of the present invention.

2A is a diagram showing the first half of an example of a manufacturing process of a lithium secondary battery.

FIG. 2B is a diagram showing the second half of an example of a manufacturing process of a lithium secondary battery, the latter half being a process performed subsequent to the process shown in FIG. 2A . The right end of Figure 2B includes a photo of the film-covered cell.

FIG. 3 is an SEM image showing an example of a cross section perpendicular to the plate surface of the oriented positive electrode plate.

FIG. 4 is an EBSD image at a cross-section of the oriented positive plate shown in FIG. 3 .

FIG. 5 is a histogram showing the distribution of the orientation angles of primary particles in the EBSD image of FIG. 4 on an area basis.

FIG. 6 is a schematic diagram for explaining the surface profile of the height H of the convex portion generated on the card surface by repeated bending tests.

Detailed ways

Lithium secondary battery

An example of the lithium secondary battery of the present invention is schematically shown in FIG. 1 . The lithium secondary battery 10 shown in FIG. 1 includes a positive electrode plate 16 , a separator 18 , a negative electrode layer 20 , an electrolytic solution 24 , and an outer packaging film 26 . The positive electrode plate 16 is a lithium composite oxide sintered body plate. The negative electrode layer 20 contains carbon and is larger in size than the positive electrode plate 16 . The separator 18 is interposed between the positive electrode plate 16 and the negative electrode layer 20 , and the size is larger than that of the positive electrode plate 16 and the negative electrode layer 20 . The electrolyte 24 penetrates into the positive electrode plate 16 , the negative electrode layer 20 and the separator 18 . For the outer wrapping film 26, the outer peripheral edges thereof are sealed to each other to form an inner space, and the positive electrode plate 16, the negative electrode layer 20, the separator 18, and the electrolytic solution 24 are accommodated in the inner space. The outer peripheral portion of the separator 18 is in close contact with at least the outer peripheral edge of the outer film 26 on the positive electrode plate 16 side or the surrounding area in the vicinity thereof, and separates the partition housing the positive electrode plate 16 from the partition housing the negative electrode layer 20 . Further, the thickness of the lithium secondary battery 10 is 350 to 500 μm, and the thickness of the positive electrode plate 16 is 70 to 120 μm. Further, the distance D between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 is 50 to 2000 μm over the entire outer circumference of the positive electrode plate 16 and the negative electrode layer 20 . In this way, in the lithium secondary battery 10 of the film-coated battery type including the positive electrode sintered body plate, the thickness of the lithium secondary battery 10 , the thickness of the positive electrode plate 16 , and the distance between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 The distance D satisfies the predetermined condition, so that even if bending is repeated, wrinkles are less likely to be generated in the vicinity of the edge of the positive electrode plate. In particular, even when the lithium secondary battery 10 that satisfies the above conditions is subjected to the repeated bending test required by the JIS standard up to several hundreds of times in the form of a card with a built-in battery, it is not easy to get close to the edge of the positive electrode plate. Create wrinkles.

That is, as described above, the cards incorporating the film-coated batteries provided with the lithium composite oxide sintered body plates (positive electrode plates) disclosed in Patent Documents 3 and 4 have the following problem. In the case of hundreds of repeated bending tests, wrinkles are likely to occur on the card surface near the end of the positive electrode plate. In this regard, according to the lithium secondary battery of the present invention, these wrinkles can be effectively suppressed. The reason for this is not clear, but it is considered that, for example, the end portion of the positive electrode plate 16 becomes difficult to push up the outer packaging film 26 . Therefore, the lithium secondary battery 10 of the present invention is preferably a thin secondary battery that can be built into a card, and more preferably a thin secondary battery that is embedded in a resin base material and used to form a card. That is, according to another preferred aspect of the present invention, there is provided a card with a built-in battery including a resin base material and a lithium secondary battery embedded in the resin base material. A typical configuration of the above-mentioned card with a built-in battery includes a pair of resin films and a lithium secondary battery sandwiched by the pair of resin films. Press and heat bond.

The positive electrode plate 16 is a lithium composite oxide sintered body plate. The fact that the positive electrode plate 16 is a sintered body plate means that the positive electrode plate 16 does not contain a binder. This is because even if the binder is contained in the green sheet, the binder disappears or burns out during firing. Furthermore, since the positive electrode plate 16 does not contain a binder, there is an advantage that the deterioration of the positive electrode due to the electrolytic solution 24 can be avoided. In addition, the lithium composite oxide constituting the sintered body plate is particularly preferably lithium cobaltate (typically, LiCoO ₂ (hereinafter, abbreviated as LCO) in some cases). Various lithium composite oxide sintered body plates and LCO sintered body plates are known, for example, sintered bodies disclosed in Patent Document 3 (Japanese Patent No. 5587052 ) and Patent Document 4 (International Publication No. 2017/146088 ) can be used plate.

According to a preferred embodiment of the present invention, the positive electrode plate 16 , that is, the lithium composite oxide sintered body plate is an oriented positive electrode plate, and the oriented positive electrode plate contains a plurality of primary particles composed of lithium composite oxide, and the plurality of primary particles are opposite to the positive electrode. The plate surface of the plate is oriented at an average orientation angle of more than 0° and 30° or less. FIG. 3 shows an example of a cross-sectional SEM image perpendicular to the surface of the oriented positive plate 16 , while FIG. 4 shows electron backscatter diffraction (EBSD: Electron Backscatter Diffraction) at a cross-section perpendicular to the surface of the oriented positive plate 16 . Diffraction) image. In addition, FIG. 5 shows a histogram representing the distribution of the orientation angles of the primary particles 11 in the EBSD image of FIG. 4 on an area basis. In the EBSD image shown in Fig. 4, discontinuities in crystal orientation can be observed. In FIG. 4 , the orientation angle of each primary particle 11 is represented by the intensity of the color, and the darker the color, the smaller the orientation angle is. The orientation angle means the inclination angle of the (003) plane of each primary particle 11 with respect to the direction of the plate surface. In addition, in FIG. 3 and FIG. 4, the part shown in black inside the orientation positive electrode plate 16 is an air hole.

The oriented positive electrode plate 16 is an oriented sintered body composed of a plurality of primary particles 11 bonded to each other. Each primary particle 11 is mainly plate-shaped, but may include primary particles formed in a rectangular parallelepiped shape, a cubic shape, a spherical shape, or the like. The cross-sectional shape of each primary particle 11 is not particularly limited, and may be a rectangle, a polygon other than a rectangle, a circle, an ellipse, or a complex shape other than these.

Each primary particle 11 is composed of a lithium composite oxide. The lithium composite oxide is an oxide represented by Li _x MO ₂ (0.05<x<1.10, M is at least one transition metal, and M typically contains one or more of Co, Ni, and Mn). The lithium composite oxide has a layered rock-salt structure. Layered rock-salt structure refers to a crystal structure in which lithium layers and transition metal layers other than lithium are alternately laminated with an oxygen layer interposed therebetween, that is, a crystal structure in which transition metal ion layers and lithium individual layers are alternately laminated with oxide ions (typical). It is α-NaFeO ₂ -type structure, that is, the structure in which transition metals and lithium are regularly arranged along the [111] axis of the cubic rock salt structure). Examples of lithium composite oxides include Li _x CoO ₂ (lithium cobalt oxide), Li _x NiO ₂ (lithium nickel oxide), Li _x MnO ₂ (lithium manganate), Li _x NiMnO ₂ (lithium nickel manganate) ), Li _x NiCoO ₂ (lithium nickel cobalt oxide), Li _x CoNiMnO ₂ (lithium cobalt nickel manganese oxide), Li _x CoMnO ₂ (lithium cobalt manganese oxide), etc., particularly preferably Li _x CoO ₂ (lithium cobalt oxide, typical is LiCoO ₂ ). The lithium composite oxide may contain Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ag, Sn, Sb, One or more elements of Te, Ba, Bi, and W.

As shown in FIGS. 4 and 5 , the average value of the orientation angles of the primary particles 11 , that is, the average orientation angle exceeds 0° and is 30° or less. This brings about the following various advantages. First, since each primary particle 11 is in a state of lying down in a direction inclined with respect to the thickness direction, the adhesiveness of each primary particle can be improved. As a result, the lithium ion conductivity between a certain primary particle 11 and other primary particles 11 adjacent to both sides in the longitudinal direction of the primary particle 11 can be improved, and thus the rate characteristic can be improved. Second, the magnification characteristic can be further improved. This is because, as described above, when lithium ions are taken in and out, expansion and contraction in the thickness direction of the oriented positive electrode plate 16 is dominant compared to the plate surface direction, so that when the oriented positive electrode plate 16 expands and contracts smoothly , the in and out of lithium ions also become smooth.

The average orientation angle of the primary particles 11 is obtained by the following method. First, in an EBSD image obtained by observing a rectangular area of 95 μm×125 μm at a magnification of 1000 times as shown in FIG. 4 , three horizontal lines that divide the orientation positive plate 16 into quarters in the thickness direction, and three vertical lines that bisect the orientation positive plate 16 in the direction of the plate surface. Next, the average orientation angle of the primary particles 11 is obtained by arithmetically averaging the orientation angles of all the primary particles 11 crossing at least one of the three horizontal lines and the three vertical lines. From the viewpoint of further improving the magnification characteristics, the average orientation angle of the primary particles 11 is preferably 30° or less, and more preferably 25° or less. From the viewpoint of further improving the magnification characteristics, the average orientation angle of the primary particles 11 is preferably 2° or more, and more preferably 5° or more.

As shown in FIG. 5 , the orientation angle of each primary particle 11 may be widely distributed from 0° to 90°, and most of the orientation angles are preferably distributed in a region exceeding 0° and 30° or less. That is, when the cross section of the oriented sintered body constituting the oriented positive electrode plate 16 is analyzed by EBSD, the orientation of the primary particles 11 included in the analyzed cross section with respect to the plate surface of the oriented positive electrode plate 16 The total area of primary particles 11 with an angle exceeding 0° and 30° or less (hereinafter referred to as low-angle primary particles) relative to the primary particles 11 included in the cross section (specifically, 30 primary particles for calculating the average orientation angle) The total area of the particles 11) is preferably 70% or more, and more preferably 80% or more. Thereby, since the ratio of the primary particle 11 with high mutual adhesiveness can be increased, the magnification characteristic can be improved further. In addition, it is more preferable that the total area of the primary particles having an orientation angle of 20° or less among the low-angle primary particles is 50% or more of the total area of the 30 primary particles 11 for calculating the average orientation angle. Further, it is more preferable that the total area of the primary particles having an orientation angle of 10° or less among the low-angle primary particles is 15% or more of the total area of the 30 primary particles 11 used for calculating the average orientation angle.

Since each primary particle 11 is mainly plate-shaped, as shown in FIGS. 3 and 4 , the cross section of each primary particle 11 extends in a predetermined direction, and is typically substantially rectangular. That is, when the cross section of the oriented sintered body is analyzed by EBSD, the total area of the primary particles 11 having an aspect ratio of 4 or more in the primary particles 11 included in the analyzed cross section is relative to the total area of the primary particles 11 in the cross section. The total area of the contained primary particles 11 (specifically, 30 primary particles 11 for calculating the average orientation angle) is preferably 70% or more, and more preferably 80% or more. Specifically, in the EBSD image shown in FIG. 4 , the mutual adhesion of the primary particles 11 can be further improved by this, and as a result, the magnification characteristic can be further improved. The aspect ratio of the primary particle 11 is a value obtained by dividing the maximum Feret diameter of the primary particle 11 by the minimum Feret diameter. The maximum Feret diameter is the maximum distance between the straight lines when the primary particle 11 is sandwiched by two parallel straight lines on the EBSD image at the time of cross-sectional observation. The minimum Feret diameter is the minimum distance between the straight lines when the primary particle 11 is sandwiched by two parallel straight lines on the EBSD image.

The average particle diameter of the plurality of primary particles constituting the oriented sintered body is preferably 5 μm or more. Specifically, the average particle diameter of the 30 primary particles 11 for calculating the average orientation angle is preferably 5 μm or more, more preferably 7 μm or more, and still more preferably 12 μm or more. Thereby, the number of grain boundaries between the primary particles 11 in the direction of lithium ion conduction is reduced, and the overall lithium ion conductivity is improved, so that the rate characteristics can be further improved. The average particle diameter of the primary particles 11 is a value obtained by arithmetically averaging the circle-equivalent diameters of the primary particles 11 . The equivalent circle diameter is the diameter of a circle having the same area as each primary particle 11 on the EBSD image.

The density of the oriented sintered body constituting the oriented positive electrode plate 16 is preferably 70% or more, more preferably 80% or more, and further preferably 90% or more. Thereby, since the mutual adhesion of the primary particles 11 can be further improved, the rate characteristic can be further improved. The density of the oriented sintered body was calculated by polishing the cross section of the positive electrode plate by CP (cross-section polishing) polishing, then performing SEM observation at a magnification of 1000, and binarizing the obtained SEM image to calculate the density. The average circle-equivalent diameter of the pores formed in the oriented sintered body is not particularly limited, but is preferably 8 μm or less. As the average circle-equivalent diameter of each pore is smaller, the mutual adhesion of the primary particles 11 can be further improved, and as a result, the rate characteristic can be further improved. The average circle-equivalent diameter of the pores is a value obtained by arithmetically averaging the circle-equivalent diameters of 10 pores on the EBSD image. The equivalent circle diameter is the diameter of a circle having the same area as each pore on the EBSD image. The pores formed inside the oriented sintered body may be open pores connected to the outside of the oriented positive electrode plate 16 , but preferably do not penetrate the oriented positive electrode plate 16 . In addition, each air hole may be a closed air hole.

The thickness of the positive electrode plate 16 is 70 to 120 μm, preferably 80 to 100 μm, more preferably 80 to 95 μm, and particularly preferably 85 to 95 μm. Within such a range, the active material capacity per unit area can be increased, the energy density of the lithium secondary battery 10 can be increased, and the deterioration of battery characteristics (in particular, the increase in resistance value) with repeated charge and discharge can be suppressed, and further The occurrence of wrinkles in the vicinity of the end portion of the positive electrode plate 16 due to repeated bending can be suppressed. In addition, the size of the positive electrode plate 16 is preferably 5 mm × 5 mm square or more, more preferably 10 mm × 10 mm to 200 mm × 200 mm square, further preferably 10 mm × 10 mm to 100 mm × 100 mm square; in other words, preferably 25 mm ² or more, more preferably 100 to 40000 mm ² , more preferably 100 to 10000 mm ² .

The anode layer 20 contains carbon as an anode active material. Examples of carbon include graphite, pyrolytic carbon, coke, fired resin body, mesophase spheroids, mesophase pitch, and the like, and graphite is preferred. The graphite may be any of natural graphite and artificial graphite. The negative electrode layer 20 preferably further contains a binder. Examples of the binder include styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and the like, preferably styrene-butadiene rubber (SBR) or polyvinylidene fluoride (PVDF) . In particular, when γ-butyrolactone (GBL), which is excellent in heat resistance, is used as the electrolyte solution 24, it is more preferable to use styrene-butadiene from the viewpoint that it is difficult to dissolve in GBL and can prevent deterioration of the binder function due to heating. Rubber (SBR) as binder.

The thickness of the negative electrode layer 20 is not particularly limited, but is preferably 70 to 160 μm, more preferably 80 to 150 μm, further preferably 90 to 140 μm, and particularly preferably 100 to 130 μm. Within such a range, the active material capacity per unit area can be increased, the energy density of the lithium secondary battery 10 can be increased, and the occurrence of wrinkles in the vicinity of the end portion of the positive electrode plate 16 due to repeated bending can be more effectively suppressed.

Separator 18 is preferably a separator made of polyolefin, polyimide, polyester (eg, polyethylene terephthalate (PET)) or cellulose. Examples of polyolefins include polypropylene (PP), polyethylene (PE), and combinations thereof. From the viewpoint of low cost, a separator made of polyolefin or cellulose is preferable. In addition, the surface of the separator 18 may be covered with ceramics such as aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), and silicon oxide (SiO ₂ ). On the other hand, from the viewpoint of being excellent in heat resistance, a separator made of polyimide or cellulose is preferable. Separators made of polyimide, polyester (eg, polyethylene terephthalate (PET)) or cellulose differ from widely used separators made of polyolefins, which have poor heat resistance, in that their own heat resistance Not only that, but also excellent wettability with respect to γ-butyrolactone (GBL), which is an electrolyte solution component excellent in heat resistance. Therefore, in the case of using an electrolytic solution containing GBL, the electrolytic solution can be sufficiently permeated into the separator (without being repelled). From the viewpoint of heat resistance, a particularly preferable separator is a separator made of polyimide. Separators made of polyimide are commercially available, and because of their extremely complex microstructure, they have the following advantages: they can more effectively prevent or delay the extension of lithium dendrites precipitated during overcharge and the resulting short circuit.

The electrolyte 24 is not particularly limited, and a lithium salt (for example, LiPF ₆ ) can be dissolved in an organic solvent (for example, a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (MEC), ethylene carbonate (EC) and Commercially available electrolyte solutions for lithium batteries, such as a mixed solvent of diethyl carbonate (DEC), or a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC)).

In the case of forming a lithium secondary battery excellent in heat resistance, the electrolyte solution 24 preferably contains lithium fluoroborate (LiBF ₄ ) in a non-aqueous solvent. In this case, the non-aqueous solvent may be a single solvent composed of γ-butyrolactone (GBL) or a mixed solvent composed of γ-butyrolactone (GBL) and ethylene carbonate (EC). By including γ-butyrolactone (GBL) in the non-aqueous solvent, the boiling point rises and the heat resistance is greatly improved. From such a viewpoint, the volume ratio of EC:GBL in the non-aqueous solvent is preferably 0:1 to 1:1 (GBL ratio of 50 to 100% by volume), and more preferably 0:1 to 1:1.5 (GBL ratio of 60% by volume). to 100 vol %), more preferably 0:1 to 1:2 (GBL ratio 66.6 to 100 vol %), particularly preferably 0:1 to 1:3 (GBL ratio 75 to 100 vol %). Lithium fluoroborate (LiBF ₄ ) dissolved in a non-aqueous solvent is an electrolyte with a high decomposition temperature, which also brings about a significant improvement in heat resistance. The LiBF ₄ concentration in the electrolyte 24 is preferably 0.5 to 2 mol/L, more preferably 0.6 to 1.9 mol/L, still more preferably 0.7 to 1.7 mol/L, and particularly preferably 0.8 to 1.5 mol/L.

The electrolyte 24 preferably further contains vinylene carbonate (VC) and/or fluoroethylene carbonate (FEC) and/or vinylethylene carbonate (VEC) as additives. Both VC and FEC are excellent in heat resistance. Therefore, by making the electrolyte solution 24 contain the above-mentioned additives, an SEI film excellent in heat resistance can be formed on the surface of the negative electrode layer 20 .

The thickness of the lithium secondary battery 10 is 350 to 500 μm, preferably 380 to 450 μm, and more preferably 400 to 430 μm. With a thickness within such a range, a thin lithium battery suitable for being incorporated in thin devices such as smart cards can be formed. In addition, in the relationship between the thickness of the positive electrode plate 16 and the distance D between the end portion of the positive electrode plate 16 and the end portion of the negative electrode layer 20, it is helpful to suppress the occurrence of wrinkles near the end portion of the positive electrode plate 16 due to repeated bending. .

The outer peripheral edges of the outer packaging films 26 are sealed to each other to form an inner space, and the battery element 12 and the electrolyte 24 are accommodated in the inner space. That is, as shown in FIG. 1 , the contents of the lithium secondary battery 10 , ie, the battery element 12 and the electrolyte 24 , are packaged and sealed by an outer wrapping film 26 , and as a result, the lithium secondary battery 10 becomes a so-called film-coated battery. Here, the battery element 12 is defined as an element including a positive electrode plate 16 , a separator 18 , and a negative electrode layer 20 , and typically includes a positive electrode current collector (not shown) and a negative electrode current collector (not shown). The positive electrode current collector and the negative electrode current collector are not particularly limited, but metal foils such as copper foil and aluminum foil are preferable. The positive electrode current collector is preferably interposed between the positive electrode plate 16 and the outer packaging film 26 , and the negative electrode current collector is preferably interposed between the negative electrode layer 20 and the outer packaging film 26 . Further, the positive electrode terminal is preferably provided on the positive electrode current collector so as to extend from the positive electrode current collector, and the negative electrode terminal is preferably provided on the negative electrode current collector so as to extend from the negative electrode current collector. Preferably, the outer edges of the lithium secondary battery 10 are sealed by thermally bonding the outer packaging films 26 to each other. In the sealing by thermal bonding, it is preferable to use a heat bar (also referred to as a heat bar) generally used for heat sealing applications. Typically, the quadrangular shape of the lithium secondary battery 10 is preferably sealed at the outer periphery of the outer packaging film 26 over the entire outer periphery and 4 sides.

As the outer film 26, a commercially available outer film may be used. The thickness of the outer packaging film 26 is preferably 50 to 80 μm per sheet, more preferably 55 to 70 μm, further preferably 55 to 65 μm. The preferable outer packaging film 26 is a laminated film containing a resin film and a metal foil, and more preferably an aluminum laminated film containing a resin film and an aluminum foil. It is preferable that the laminated film is provided with resin films on both surfaces of metal foils such as aluminum foils. In this case, the resin film on one side of the metal foil (hereinafter referred to as a surface protective film) is preferably made of nylon, polyamide, polyethylene terephthalate, polyimide, polytetrafluoroethylene, The resin film on the other side of the metal foil is made of a heat-sealing material such as polypropylene.

As described above, the size of the negative electrode layer 20 is larger than the size of the positive electrode plate 16 , and on the other hand, the size of the separator 18 is larger than that of the positive electrode plate 16 and the negative electrode layer 20 . The outer peripheral portion of the separator 18 is in close contact with at least the outer peripheral edge of the outer film 26 on the positive electrode plate 16 side or the surrounding area in the vicinity thereof, and separates the partition for housing the positive electrode plate 16 and the partition for housing the negative electrode layer 20 . In addition, the outer peripheral portion of the separator 18 may be in close contact with the outer peripheral edge of the outer film 26 on the negative electrode layer 20 side or the surrounding area in the vicinity thereof.

The distance D between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 is 50 to 2000 μm, preferably 200 to 1500 μm, more preferably 200 to 1000 μm, and still more preferably 200 μm over the entire outer circumference of the positive electrode plate 16 and the negative electrode layer 20 . to 800 μm, particularly preferably 450 to 600 μm, and most preferably 450 to 550 μm. Here, as shown in FIG. 1 , the distance D between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 refers to the distance from the end of the positive electrode plate 16 to the end of the negative electrode layer 20 in its vicinity; in other words, It can also be said to be the width by which the negative electrode layer 20 extends from the positive electrode plate 16 .

Manufacturing method of lithium cobalt oxide oriented sintered plate

The oriented positive electrode plate or the oriented sintered plate preferably used in the lithium secondary battery of the present invention can be produced by any production method, but it is preferably through (1) production of LiCoO ₂ template particles, (2) preparation of matrix particles as shown in the following examples. Production, (3) production of green sheets, and (4) production of oriented sintered sheets were produced.

(1) Preparation of LiCoO ₂ template particles

The Co ₃ O ₄ raw material powder and the Li ₂ CO ₃ raw material powder are mixed. The obtained mixed powder is fired at 500 to 900° C. for 1 to 20 hours to synthesize LiCoO ₂ powder. The obtained LiCoO ₂ powder is pulverized into a volume-based D50 particle size of 0.1 to 10 μm with a jar ball mill to obtain plate-shaped LiCoO ₂ particles that can conduct lithium ions parallel to the plate surface. The obtained LiCoO ₂ particles were easily cleaved along the cleavage plane. LiCoO ₂ template particles are produced by cleaving the LiCoO ₂ particles by crushing. Such LiCoO ₂ particles can also be obtained by a method in which a green sheet using a LiCoO ₂ powder slurry is subjected to grain growth and then crushed, a flux method, hydrothermal synthesis, or single crystal growth using a melt , sol-gel method and other methods of synthesizing plate-like crystals.

In this step, the distribution of the primary particles 11 constituting the oriented positive electrode plate 16 can be controlled as described below.

- By adjusting at least one of the aspect ratio and particle size of the LiCoO ₂ template particles, the total area ratio of the low-angle primary particles whose orientation angle exceeds 0° and is 30° or less can be controlled. Specifically, the larger the aspect ratio of the LiCoO ₂ template particles and the larger the particle size of the LiCoO ₂ template particles, the more the total area ratio of the low-angle primary particles can be increased. _The aspect ratio and particle diameter _of the LiCoO template particles can be adjusted by adjusting the particle diameters _of the _Co3O4 raw material powder and the _Li2CO3 raw material powder, the grinding conditions during grinding (grinding time, grinding energy, grinding method, etc.), and At least one of the crushed classifications is controlled.

- By adjusting the aspect ratio of the LiCoO ₂ template particles, the total area ratio of the primary particles 11 having an aspect ratio of 4 or more can be controlled. Specifically, as the aspect ratio of the LiCoO ₂ template particles is increased, the total area ratio of the primary particles 11 having an aspect ratio of 4 or more can be increased. The method for adjusting the aspect ratio of the LiCoO ₂ template particles is as described above.

- By adjusting the particle size of the LiCoO ₂ template particles, the average particle size of the primary particles 11 can be controlled.

- By adjusting the particle size of the LiCoO ₂ template particles, the density of the oriented positive plate 16 can be controlled. Specifically, the smaller the particle size of the LiCoO ₂ template particles, the higher the density of the oriented positive electrode plate 16 can be.

(2) Preparation of matrix particles

_{Co3O4 raw} material powder was used as the matrix particle. The volume-based D50 particle size of the Co ₃ O ₄ raw material powder is not particularly limited, and may be set to, for example, 0.1 to 1.0 μm, but is preferably smaller than the volume-based D50 particle size of the LiCoO ₂ template particles. The matrix particles can also be obtained by subjecting the Co(OH) ₂ raw material to heat treatment at 500 to 800° C. for 1 to 10 hours. In addition to Co ₃ O ₄ , Co(OH) ₂ particles and LiCoO ₂ particles may also be used as the matrix particles.

In this step, the distribution of the primary particles 11 constituting the oriented positive electrode plate 16 can be controlled as described below.

- By adjusting the ratio of the particle size of the matrix particles to the particle size of the LiCoO template particles ₍ hereinafter referred to as "matrix/template particle size ratio"), it is possible to control the low-angle primary angle where the orientation angle exceeds 0° and is 30° or less The total area ratio of the particles. Specifically, the smaller the matrix/template particle size ratio, that is, the smaller the particle size of the matrix particles, the easier it is for the matrix particles to enter the LiCoO template particles in the calcination process described later, and thus the higher the low _- angle primary particles can be. percentage of the total area.

- By adjusting the matrix/template particle size ratio, the total area ratio of the primary particles 11 having an aspect ratio of 4 or more can be controlled. Specifically, the smaller the matrix/template particle size ratio, that is, the smaller the particle size of the matrix particles, the more the total area ratio of the primary particles 11 having an aspect ratio of 4 or more can be increased.

- By adjusting the matrix/template particle size ratio, the density of the oriented positive plate 16 can be controlled. Specifically, the smaller the matrix/template particle size ratio, that is, the smaller the particle size of the matrix particles, the higher the density of the oriented positive electrode plate 16 can be.

(3) Production of green sheets

The LiCoO ₂ template particles and the matrix particles are mixed at a ratio of 100:0 to 3:97 to obtain a mixed powder. The mixed powder, the dispersion medium, the binder, the plasticizer, and the dispersant are mixed, and the mixture is stirred under reduced pressure for defoaming, and adjusted to a desired viscosity to prepare a slurry. Next, the prepared slurry is molded using a molding method capable of applying shearing force to the LiCoO ₂ template particles, thereby forming a molded body. In this way, the average orientation angle of each primary particle 11 can be made to exceed 0° and be 30° or less. As a molding method capable of applying shearing force to the LiCoO ₂ template particles, a doctor blade method is preferable. In the case of using the doctor blade method, a green sheet as a molded body is formed by molding the prepared slurry on a PET film.

In this step, the distribution of the primary particles 11 constituting the oriented positive electrode plate 16 can be controlled as described below.

- By adjusting the molding speed, the total area ratio of the low-angle primary particles whose orientation angle exceeds 0° and is 30° or less can be controlled. Specifically, the higher the molding speed, the more the total area ratio of the low-angle primary particles can be increased.

- By adjusting the density of the molded body, the average particle diameter of the primary particles 11 can be controlled. Specifically, as the density of the molded body increases, the average particle diameter of the primary particles 11 can be increased.

- By adjusting the mixing ratio of LiCoO ₂ template particles and matrix particles, the density of the oriented positive plate 16 can also be controlled. Specifically, as the number of LiCoO ₂ template particles increases, the density of the oriented positive electrode plate 16 can be reduced.

(4) Fabrication of Oriented Sintered Plate

The formed body of the slurry is placed on a setter made of zirconia, and heat-treated (primary firing) at 500 to 900° C. for 1 to 10 hours to obtain a sintered plate as an intermediate body. The sintered plate is sandwiched up and down with lithium sheets (for example, sheets containing Li ₂ CO ₃ ), and in this state, the sintered plate is placed on a zirconia setter, and subjected to secondary firing, thereby obtaining a LiCoO ₂ sintered plate. Specifically, the setter plate on which the sintered plates sandwiched by the lithium sheets are placed is placed in an alumina saggar, fired at 700 to 850° C. in the atmosphere for 1 to 20 hours, and then sandwiched up and down with lithium sheets. The sintered plate is held and fired at 750 to 900° C. for 1 to 40 hours to obtain a LiCoO ₂ sintered plate. This calcination step may be divided into two or may be performed once. When firing is performed in two steps, it is preferable that the firing temperature of the first time is lower than the firing temperature of the second time. It should be noted that the total usage amount of lithium sheets in the secondary firing can be set so that the molar ratio of the Li amount in the green sheet and the lithium sheet to the Co amount in the green sheet, that is, the Li/Co ratio is 1.0. .

In this step, the distribution of the primary particles 11 constituting the oriented positive electrode plate 16 can be controlled as described below.

- The total area ratio of the low-angle primary particles whose orientation angle exceeds 0° and is 30° or less can be controlled by adjusting the heating rate during firing. Specifically, the faster the temperature rise rate is, the more the sintering of the matrix particles is suppressed, and the more the total area ratio of the low-angle primary particles can be increased.

- By adjusting the heat treatment temperature of the intermediate body, it is also possible to control the total area ratio of the low-angle primary particles whose orientation angle exceeds 0° and is 30° or less. Specifically, as the heat treatment temperature of the intermediate body is lowered, the sintering of the matrix particles is suppressed, and the total area ratio of the low-angle primary particles can be increased.

- The average particle diameter of the primary particle 11 can be controlled by adjusting at least one of the temperature increase rate at the time of sintering and the heat treatment temperature of the intermediate body. Specifically, the higher the temperature increase rate and the lower the heat treatment temperature of the intermediate body, the larger the average particle diameter of the primary particles 11 can be.

- The average particle diameter of the primary particles 11 can also be controlled by adjusting at least one of the amount of Li (eg, Li ₂ CO ₃ ) and the amount of sintering aids (eg, boric acid, bismuth oxide) during firing. Specifically, as the amount of Li increases and the amount of the sintering aid increases, the average particle diameter of the primary particles 11 can be increased.

- By adjusting the distribution during firing, the density of the oriented positive electrode plate 16 can be controlled. Specifically, the lower the firing temperature and the longer the firing time, the higher the density of the oriented positive electrode plate 16 can be.

Example

The present invention will be further specifically described by the following examples.

example 1

(1) Production of lithium secondary battery

The lithium secondary battery 10 in the form of a film-covered battery schematically shown in FIG. 1 was fabricated by the steps shown in FIGS. 2A and 2B . The details are as follows.

First, a LiCoO ₂ sintered body plate (hereinafter referred to as an LCO sintered body plate) having a thickness of 90 μm was prepared. The LCO sintered body plate is manufactured according to the above-described method for producing a lithium composite oxide sintered body plate, and satisfies each of the preferred conditions for the above-described lithium composite oxide sintered body plate. The sintered body plate was cut into a square of 10.5 mm×9.5 mm by a laser processing machine to obtain a plurality of chip-shaped positive electrode plates 16 .

As the outer wrapping film 26, two sheets of aluminum laminate films (manufactured by Showa Denko Packaging, 61 μm in thickness, three-layer structure of polypropylene film/aluminum foil/nylon film) were prepared. As shown in FIG. 2A , a plurality of chip-shaped positive electrode plates 16 were laminated on one outer wrapping film 26 with a positive electrode current collector 14 (aluminum foil having a thickness of 9 μm) interposed therebetween to prepare a positive electrode assembly 17 . In FIG. 2A , a plurality of chip-shaped positive electrode plates 16 are shown, but the present invention is not limited to this, and the positive electrode assembly 17 may be formed using one positive electrode plate 16 that is not divided into chip shapes. At this time, the positive electrode current collector 14 is fixed to the outer packaging film 26 with an adhesive. In addition, the positive electrode terminal 15 is fixed to the positive electrode current collector 14 in the form extended from the positive electrode current collector 14 by welding. On the other hand, the negative electrode layer 20 (carbon layer with a thickness of 130 μm) was laminated on the other outer wrapping film 26 with the negative electrode current collector 22 (copper foil with a thickness of 10 μm) interposed therebetween to prepare the negative electrode assembly 19 . At this time, the negative electrode current collector 22 was fixed to the outer packaging film 26 with an adhesive. In addition, the negative electrode terminal 23 is fixed to the negative electrode current collector 22 in the form extended from the negative electrode current collector 22 by welding. In addition, the carbon layer as the negative electrode layer 20 is a coating film containing a mixture of graphite as an active material and polyvinylidene fluoride (PVDF) as a binder.

As the separator 18, a porous polypropylene membrane (manufactured by Polypore, 25 μm in thickness, 55% in porosity) was prepared. As shown in FIG. 2A , the positive electrode assembly 17 , the separator 18 , and the negative electrode assembly 19 are sequentially stacked in such a manner that the positive electrode plate 16 and the negative electrode layer 20 are opposed to the separator 18 , so that both sides are covered by the outer packaging film 26 and the outer packaging film is obtained. The outer peripheral portion of 26 extends beyond the laminate 28 of the outer edge of the battery element 12 . The thickness of the battery element 12 (the positive electrode current collector 14, the positive electrode plate 16, the separator 18, the negative electrode layer 20, and the negative electrode current collector 22) thus constructed in the laminated body 28 is 0.33 mm, and its shape and size are 2.3 cm × 3.2cm quadrilateral.

As shown in FIG. 2A , the three sides A of the obtained laminate 28 are sealed. This sealing is performed by using an abutment jig (heat bar) adjusted to a sealing width of 2.0 mm, hot-pressing the outer peripheral portion of the laminate 28 at 200° C. and 1.5 MPa for 15 seconds, and making the outer peripheral portion The packaging films 26 (aluminum laminate films) are thermally bonded to each other. After sealing the three sides A, the laminate 28 is placed in the vacuum dryer 34 to remove moisture and to dry the adhesive.

As shown in FIG. 2B , in the glove box 38, a gap between the outer wrapping films 26 is formed at the unsealed remaining one side B of the laminate 28 whose outer edges A are sealed, and the injection tool 36 is inserted into the gap. Then, the electrolyte solution 24 was injected, and the side B was temporarily sealed using a simple sealer in a reduced-pressure atmosphere with an absolute pressure of 5 kPa. As the electrolytic solution, LiPF ₆ was dissolved at a concentration of 1.0 mol/L in a mixed solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (MEC) at a volume ratio of 3:7, and subcarbonate was further dissolved. An electrolyte solution obtained by dissolving vinyl ester (VC) at a concentration of 2% by weight. The laminated body in which the side B was temporarily sealed in this way was initially charged and aged for 7 days. Finally, the outer peripheral portion of the remaining one side B of the seal (excluding the end portion of the battery element) is cut off, and exhaust is performed.

As shown in FIG. 2B , in the glove box 38, under a reduced pressure atmosphere of an absolute pressure of 5 kPa, the side B' produced by the excision temporary sealing is sealed. This sealing is also performed by heat-pressing the outer peripheral portion of the laminate 28 at 200° C. and 1.5 MPa for 15 seconds, and thermally bonding the outer films 26 (aluminum laminate films) to each other in the outer peripheral portion. In this way, the side B' is sealed with an outer wrapping film 26 to produce a lithium secondary battery 10 in the form of a film-covered battery. The lithium secondary battery 10 was taken out from the glove box 38 , and the excess portion of the outer periphery of the outer film 26 was cut off to adjust the shape of the lithium secondary battery 10 . In this way, the lithium secondary battery 10 in which the outer edge 4 of the battery element 12 is sealed by the outer packaging film 26 and the electrolyte solution 24 is injected therein is obtained. The obtained lithium secondary battery 10 was a rectangle having a size of 38 mm×27 mm, a thickness of 0.45 mm or less, and a capacity of 30 mAh.

(2) Evaluation

The following evaluations were performed on the produced lithium secondary battery.

<Distance D between the end of the positive electrode plate and the end of the negative electrode layer>

The separation distance D between the end of the positive electrode plate and the end of the negative electrode layer was measured as follows. First, a transmission X-ray photograph of the lithium secondary battery was taken from the positive electrode side under the following conditions.

-Measuring device: Three-dimensional measurement X-ray CT device (TDM1300-IW/TDM1000-IW conversion type, manufactured by Yamato Scientific Co., Ltd.)

- Measurement mode: Microfocus X-ray transmission observation (DR method)

- Tube voltage: 70kV

- Tube current: 60μA

- Use Al filter (1mm)

- Irradiation time: 134 seconds

Since the outer packaging film 26 and the positive electrode current collector 14 (aluminum foil) can be penetrated by the transmission X-ray method, the contrast between the positive electrode plate 16 and the negative electrode current collector 22 (copper foil) can be observed. The area of the negative electrode current collector 22 (copper foil) is equivalent to the area of the negative electrode layer 20 , so it is possible to measure the end of the positive electrode plate 16 and the negative electrode layer 20 based on the contrast between the positive electrode plate 16 and the negative electrode current collector 22 (copper foil). The end of the separation distance D. Specifically, for each of the four sides of the lithium secondary battery 10 , three measurements were taken from the end of the positive electrode plate 16 (the positive electrode plate as a whole composed of a plurality of chip-shaped positive electrode plates) to the end of the negative electrode layer 20 . The separation distance of , and the average value D ₁ , D ₂ , D ₃ , and D ₄ of the separation distance of each of the four sides is obtained. The minimum value among D ₁ to D ₄ is shown in Table 1 as a representative value of the distance D between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 in the lithium secondary battery 10 .

<Repetitive bending test>

The obtained film-covered battery was embedded in epoxy resin to prepare a rectangular card with a built-in battery having a thickness of 0.76 mm and a size of 86 mm×54 mm. The card with built-in battery was subjected to a bending test in accordance with JIS X 6305-1. Specifically, the card was mounted on a card holder of a bending tester, and the card was subjected to 250 times of bending to make the surface protrude in the longitudinal direction, 250 times to make the surface convex in the short direction, and 250 times to bend the card in the longitudinal direction. 250 times of bending to make the back surface convex, 250 times of bending to make the back surface convex in the short-side direction, and a total of 1000 bending tests. Then, the surface profile of the battery-embedded portion of the card was measured using a surface roughness meter (manufactured by TAYLORHOBSON, Talysurf). That is, by repeating the bending test, convex portions having different degrees were generated in the outer packaging film in the vicinity of the battery embedded portion of the card, so the heights were measured. Specifically, as schematically shown in FIG. 6 , in the obtained surface profile, a peak corresponding to the convex portion is identified, a base line BL of the peak is drawn, and the distance from the base line BL to the peak top PT in the vertical direction is measured. As the height H of the convex portion, the presence or absence of wrinkles was determined on the basis of the following criteria. The results are shown in Table 1.

- No wrinkles: the height H of the convex portion is less than 40 μm

- Wrinkled: The height H of the convex portion is 40 μm or more.

Example 2

A battery was produced and evaluated in the same manner as in Example 1, except that the thickness of the positive electrode plate 16 was 70 μm and the thickness of the negative electrode layer 20 was 80 μm. The results are shown in Table 1.

Example 3

A battery was produced and evaluated in the same manner as in Example 1, except that the thickness of the positive electrode plate 16 was 120 μm and the thickness of the negative electrode layer 20 was 160 μm. The results are shown in Table 1.

Example 4

A battery was fabricated and evaluated in the same manner as in Example 1, except that the size of the negative electrode layer 20 was slightly reduced and the distance D between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 was changed to 200 μm. The results are shown in Table 1.

Example 5 (comparison)

A battery was fabricated and evaluated in the same manner as in Example 1, except that the size of the negative electrode layer 20 was further reduced and the distance D between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 was changed to 30 μm. The results are shown in Table 1.

Example 6 (comparison)

A battery was produced and evaluated in the same manner as in Example 1, except that the thickness of the positive electrode plate 16 was 130 μm and the thickness of the negative electrode layer 20 was 150 μm. The results are shown in Table 1.

Example 7

1) The thickness of the positive electrode plate 16 is 80 μm, and the thickness of the negative electrode layer 20 is 90 μm, and 2) The size of the negative electrode layer 20 is further reduced, and the distance between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 is set A battery was produced and evaluated in the same manner as in Example 1, except that D was changed to 50 μm. The results are shown in Table 1.

[Table 1]

Table 1

* indicates a comparative example.

Claims (13)

1. A lithium secondary battery is provided with:

a positive electrode plate which is a lithium composite oxide sintered plate;

a carbon-containing negative electrode layer having a size larger than that of the positive electrode plate;

a separator interposed between the positive electrode plate and the negative electrode layer, the separator having a size greater than the size of the positive electrode plate and the negative electrode layer;

an electrolyte impregnated into the positive electrode plate, the negative electrode layer, and the separator; and

1 pairs of outer packaging films, wherein the outer peripheries of the 1 pairs of outer packaging films are sealed with each other to form an inner space, and the positive electrode plate, the negative electrode layer, the separator and the electrolyte are accommodated in the inner space,

wherein,

an outer peripheral portion of the separator is in close contact with at least the outer peripheral edge of the outer film on the positive electrode plate side or a peripheral region in the vicinity thereof, and partitions a section for housing the positive electrode and a section for housing the negative electrode,

the thickness of the lithium secondary battery is 350-500 mu m, the thickness of the positive plate is 70-120 mu m, and the spacing distance between the end part of the positive plate and the end part of the negative layer is 50-2000 mu m on the whole periphery of the positive plate and the negative layer.

2. The lithium secondary battery according to claim 1,

the lithium secondary battery is a thin secondary battery that can be built in a card.

3. The lithium secondary battery according to claim 1 or 2,

the thickness of the lithium secondary battery is 380 to 450 μm.

4. The lithium secondary battery according to any one of claims 1 to 3,

the thickness of the positive plate is 80-100 mu m.

5. The lithium secondary battery according to any one of claims 1 to 4,

the spacing distance between the end of the positive plate and the end of the negative layer is 200-1500 mu m on the whole periphery of the positive plate and the negative layer.

6. The lithium secondary battery according to any one of claims 1 to 5,

the thickness of the negative electrode layer is 70-160 mu m.

7. The lithium secondary battery according to any one of claims 1 to 6,

the thickness of each outer packaging film is 50-80 mu m.

8. The lithium secondary battery according to any one of claims 1 to 7,

the outer packaging film is a laminated film comprising a resin film and a metal foil.

9. The lithium secondary battery according to any one of claims 1 to 8,

the separator is made of polyolefin, polyimide or cellulose.

10. The lithium secondary battery according to any one of claims 1 to 9,

the lithium composite oxide is lithium cobaltate.

11. The lithium secondary battery according to any one of claims 1 to 10,

the lithium composite oxide sintered body plate is an oriented positive electrode plate that includes a plurality of primary particles made of a lithium composite oxide, and the plurality of primary particles are oriented at an average orientation angle of more than 0 DEG and 30 DEG or less with respect to a plate surface of the positive electrode plate.

12. The lithium secondary battery according to any one of claims 1 to 11,

the lithium secondary battery further includes a positive electrode collector and a negative electrode collector.

13. A card with a built-in battery includes:

a resin base material; and

the lithium secondary battery according to any one of claims 1 to 12 embedded in the resin base.

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