Lithium secondary battery and battery-embedded card
阅读说明:本技术 锂二次电池及电池内置卡 (Lithium secondary battery and battery-embedded card ) 是由 大塚春男 藤田雄树 下野真弘 于 2019-02-27 设计创作,主要内容包括:本发明提供一种膜外装形态的锂二次电池,其中,具备作为正极板的锂复合氧化物烧结体板,并且,即便反复弯曲也不容易在电极端部产生褶皱。该锂二次电池具备:正极板,该正极板为锂复合氧化物烧结体板;负极;隔板;电解液;以及1对外装膜,该1对外装膜的外周缘彼此被密封而形成出收纳电池要素的内部空间,外周缘的合计厚度T<Sub>1</Sub>为110μm以下,外装膜的正极板侧的隆起高度T<Sub>2p</Sub>满足T<Sub>2p</Sub>≥1.3T<Sub>1</Sub>的关系,外装膜的负极侧的隆起高度T<Sub>2n</Sub>满足T<Sub>2n</Sub>≥1.3T<Sub>1</Sub>的关系,隔板的正极板侧表面上的、正极板端部与外装膜之间的分离距离W<Sub>p</Sub>为200μm以下,隔板的负极侧表面上的、负极端部与外装膜之间的分离距离W<Sub>n</Sub>为200μm以下。(The invention provides a lithium secondary battery in a membrane-exterior form, which is provided with a lithium composite oxide sintered plate as a positive electrode plate and is less prone to wrinkle at an electrode end even when repeatedly bent. The lithium secondary battery includes: a positive electrode plate which is a lithium composite oxide sintered plate; a negative electrode; a partition plate; an electrolyte; and 1 pair of outer films, 1The outer peripheral edges of the outer coating films are sealed to each other to form an internal space for housing the battery elements, and the total thickness T of the outer peripheral edges 1 A bulge height T of 110 μm or less on the positive plate side of the outer coating film 2p Satisfy T 2p ≥1.3T 1 In relation to (3), the bulge height T of the outer coating film on the negative electrode side 2n Satisfy T 2n ≥1.3T 1 A separation distance W between the positive electrode plate end and the outer coating on the positive electrode plate side surface of the separator p 200 μm or less, and a separation distance W between the negative electrode end part and the outer coating film on the negative electrode side surface of the separator n Is 200 μm or less.)
1. A lithium secondary battery is provided with:
a positive electrode plate which is a lithium composite oxide sintered plate;
a negative electrode comprising carbon, and having a size larger than that of the positive electrode plate;
a separator interposed between the positive electrode plate and the negative electrode, the separator having a size larger than that of the positive electrode plate and the negative electrode;
an electrolyte solution impregnated in the positive electrode plate, the negative electrode and the separator; and
1 pair of outer films, wherein outer peripheries of the 1 pair of outer films are sealed to each other to form an internal space, and the positive electrode plate, the negative electrode, the separator, and the electrolyte are accommodated in the internal space,
the lithium secondary battery is characterized in that,
an outer peripheral portion of the separator is in close contact with at least the outer peripheral edge of the exterior film on the positive electrode plate side or a peripheral region in the vicinity thereof to separate a region for housing the positive electrode plate and a region for housing the negative electrode,
the total thickness T of the sealed outer peripheries of the 1 pair of outer films1Is less than 110 mu m in the thickness of the film,
a height of a bulge on the positive electrode plate side of the outer coating filmT2pSatisfy T2p≥1.3T1In the context of (a) or (b),
a ridge height T of the negative electrode side of the outer coating film2nSatisfy T2n≥1.3T1In the context of (a) or (b),
a separation distance W between the positive electrode plate end and the outer coating on the positive electrode plate side surface of the separatorpIs less than 200 mu m in the weight ratio,
a separation distance W between the negative electrode end portion and the outer coating film on the negative electrode side surface of the separatornIs 200 μm or less.
2. The lithium secondary battery according to claim 1,
the lithium secondary battery is a thin secondary battery that can be built into a card.
3. The lithium secondary battery according to claim 1 or 2,
said thickness T1Is 90 to 110 μm.
4. The lithium secondary battery according to any one of claims 1 to 3,
the lithium secondary battery satisfies 1.3T1≤T2p≤2.0T1And 1.3T1≤T2n≤2.4T1The relationship (2) of (c).
5. The lithium secondary battery according to any one of claims 1 to 4,
the separation distance WpIs 50 to 200 μm and the separation distance WnIs 50 to 200 μm.
6. The lithium secondary battery according to any one of claims 1 to 5,
the external film is: a laminate film comprising a resin film and a metal foil.
7. The lithium secondary battery according to any one of claims 1 to 6,
the separator is made of polyolefin, polyimide, or cellulose.
8. The lithium secondary battery according to any one of claims 1 to 7,
the thickness of the lithium secondary battery is 0.45mm or less.
9. The lithium secondary battery according to any one of claims 1 to 8,
the lithium composite oxide is lithium cobaltate.
10. The lithium secondary battery according to any one of claims 1 to 9,
the lithium composite oxide sintered body plate is an oriented positive electrode plate that includes a plurality of primary particles made of the lithium composite oxide, and the plurality of primary particles are oriented at an average orientation angle of more than 0 ° and 30 ° or less with respect to a plate surface of the positive electrode plate.
11. The lithium secondary battery according to any one of claims 1 to 10,
the lithium secondary battery further includes a positive electrode current collector and a negative electrode current collector.
12. A card with a built-in battery, comprising:
a resin base material; and
the lithium secondary battery according to any one of claims 1 to 11 embedded in the resin base material.
Technical Field
The present invention relates to a lithium secondary battery and a battery built-in card.
Background
In recent years, smart cards with built-in batteries have been put to practical use. An example of a smart card with a built-in primary battery is a credit card with a one-time password display function. Examples of the smart card having a secondary battery built therein include: a card with fingerprint authentication and wireless communication functions, which is provided with a wireless communication IC, a fingerprint analysis ASIC, and a fingerprint sensor. A battery for a smart card is generally required to have a thickness of less than 0.45mm, a high capacity and a low resistance, have a bending resistance, and be able to withstand a process temperature.
Secondary batteries or secondary battery-mounted cards for the above-described applications have been proposed. For example, patent document 1 (japanese patent application laid-open No. 2017-79192) discloses a secondary battery built in a plate member such as a card, the secondary battery having sufficient strength even when the plate member is bent and deformed. The secondary battery includes: an electrode body including a positive electrode and a negative electrode; a sheet-like laminate film exterior body whose outer peripheral side is welded in a state of covering the electrode body; and a positive electrode connection terminal and a negative electrode connection terminal, one end sides of which are connected to the electrode body and the other end sides of which extend outward from the laminate film package. Further, patent document 2 (jp 2006-331838 a) discloses a thin battery having a surface that is less likely to have large wrinkles and excellent in bending resistance. The thin battery includes: a battery body part having a separator, a positive electrode layer and a negative electrode layer accommodated between a positive electrode current collector and a negative electrode current collector, and a sealing part including a resin frame member for sealing the periphery of the battery body part satisfy the requirements that D1 is 100 [ mu ] m or more and 320 [ mu ] m or less and D1/D2 is 0.85 or less, when the thickness of the sealing part is D1 and the maximum thickness of the battery center part is D2. In the secondary batteries disclosed in patent documents 1 and 2, the following are adopted: a powder dispersion type positive electrode is produced by applying a positive electrode mixture containing a positive electrode active material, a conductive assistant, a binder, and the like, and drying the applied mixture.
However, in general, since the powder dispersion type positive electrode contains a relatively large amount (for example, about 10% by weight) of a binder that does not contribute to capacity, the packing density of the lithium composite oxide as the positive electrode active material is lowered. Thus, the powder dispersion type positive electrode has a large room for improvement in capacity and charge/discharge efficiency. Therefore, attempts have been made to improve the capacity and the charge/discharge efficiency by forming a positive electrode or a positive electrode active material layer using a lithium composite oxide sintered plate. In this case, since the positive electrode or the positive electrode active material layer does not contain a binder, the packing density of the lithium composite oxide is increased, and thus a high capacity and good charge-discharge efficiency are desired. 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 bonded to the positive electrode current collector via a conductive bonding layer. The positive electrode active material layer includes: a lithium composite oxide sintered plate having a thickness of 30 [ mu ] m or more, a porosity of 3 to 30% and an open pore ratio of 70% or more. Patent document 4 (international publication No. 2017/146088) discloses that an oriented sintered body plate is used as a positive electrode of a lithium secondary battery having a solid electrolyte, and the oriented sintered body plate is used as the positive electrodeThe plate comprises a lithium cobaltate (LiCoO)2) And a plurality of primary particles made of the lithium composite oxide, wherein the plurality of primary particles are oriented at an average orientation angle of more than 0 DEG and not more than 30 DEG with respect to the plate surface of the positive electrode plate.
Disclosure of Invention
However, the cards incorporating a sintered plate of lithium complex oxide (positive electrode plate) as disclosed in patent documents 3 and 4 have a problem that wrinkles are likely to occur on the surface of the card when subjected to hundreds of repeated bending tests as specified in JIS (japanese industrial standards). That is, if a ceramic sintered body plate having high rigidity is used as an electrode, the shape of the card when bent is a shape close to a trapezoid, rather than an arc, and as a result, the curvature of the end portion of the electrode plate becomes large, and wrinkles are likely to occur.
The present inventors have recently obtained a finding that, in a lithium secondary battery in the form of a film-encased battery provided with a positive electrode sintered body plate, the total thickness T of the outer peripheral edge is reduced1The protrusion height T of the exterior film on the positive electrode plate side2pThe height T of the bulge on the negative electrode side of the outer coating film2nAnd a separation distance W between the end of the positive electrode plate and the outer filmpAnd a separation distance W between the negative electrode end portion and the outer coatingnSatisfies a predetermined condition, and is less likely to cause wrinkles at the electrode end even when repeatedly bent. In particular, it is found that even when a film-encased lithium secondary battery satisfying the above conditions is subjected to a repeated bending test of hundreds of times specified in JIS in the form of an in-battery card, wrinkles are less likely to occur at the electrode end portions.
Accordingly, an object of the present invention is to provide a lithium secondary battery in a membrane exterior form, which includes a lithium composite oxide sintered plate as a positive electrode plate and in which wrinkles are not easily generated at an electrode end portion even when repeated bending (particularly, in a form of a battery-embedded card) is performed.
According to one aspect of the present invention, there is provided a lithium secondary battery including:
a positive electrode plate which is a lithium composite oxide sintered plate;
a negative electrode comprising carbon, and the negative electrode having a size larger than that of the positive electrode plate;
a separator interposed between the positive electrode plate and the negative electrode, the separator having a size larger than that of the positive electrode plate and the negative electrode;
an electrolyte solution impregnated in the positive electrode plate, the negative electrode and the separator; and
1 pair of outer films, wherein outer peripheries of the 1 pair of outer films are sealed to each other to form an internal space, and the positive electrode plate, the negative electrode, the separator, and the electrolyte are accommodated in the internal space,
the lithium secondary battery is characterized in that,
an outer peripheral portion of the separator is in close contact with at least the outer peripheral edge of the exterior film on the positive electrode plate side or a peripheral region in the vicinity thereof to separate a region for housing the positive electrode plate and a region for housing the negative electrode,
the total thickness T of the sealed outer peripheries of the 1 pair of outer films1Is less than 110 mu m in the thickness of the film,
a protrusion height T of the exterior film on the positive electrode plate side2pSatisfy T2p≥1.3T1In the context of (a) or (b),
a ridge height T of the negative electrode side of the outer coating film2nSatisfy T2n≥1.3T1In the context of (a) or (b),
a separation distance W between the positive electrode plate end and the outer coating on the positive electrode plate side surface of the separatorpIs less than 200 mu m in the weight ratio,
a portion between the negative electrode end portion and the outer coating film on the negative electrode side surface of the separatorDistance WnIs 200 μm or less.
According to another aspect of the present invention, there is provided a battery built-in card including: a resin base material, and the lithium secondary battery implanted in the resin base material.
Drawings
Fig. 1 is a schematic cross-sectional view of an example of a lithium secondary battery of the present invention.
Fig. 2A is a diagram showing a first half of an example of a process for manufacturing a lithium secondary battery.
Fig. 2B is a diagram showing the latter half of an example of a process for manufacturing a lithium secondary battery, and is a diagram showing a process subsequent to the process shown in fig. 2A. A photograph of the film-encased battery was included at the right end of fig. 2B.
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 in a cross-section of the oriented positive plate shown in fig. 3.
Fig. 5 is a histogram showing distribution of orientation angles of primary particles in the EBSD image of fig. 4 on an area basis.
Fig. 6 is a schematic view of the surface profile for explaining the height H of the convex portion generated on the card surface by the repeated bending test.
Fig. 7 is a schematic cross-sectional view (right side in the figure) illustrating a mechanism of occurrence of wrinkles in a film-encased electrode provided with a positive electrode sintered body plate, and shows a case where wrinkles occur in the vicinity of an electrode end (portion surrounded by a circle) when the film-encased battery is bent as shown in the left side in the figure.
Detailed Description
Lithium secondary battery
Fig. 1 schematically shows an example of a lithium secondary battery of the present invention. The lithium secondary battery 10 shown in fig. 1 includes:
That is, as described above, the cards incorporating a lithium composite oxide sintered plate (positive electrode plate) as disclosed in patent documents 3 and 4 have a problem that wrinkles are likely to occur on the surface of the card when subjected to hundreds of repeated bending tests specified in JIS. That is, if a ceramic sintered plate having high rigidity is used as an electrode, the shape of the card when bent is a shape close to a trapezoid, not an arc, and as a result, the curvature of the end portion of the electrode plate becomes large as in the film-encased battery 100 shown in fig. 7, and wrinkles W are likely to occur. In addition, since the film-encased battery 100 is wrinkled, the battery pack in which the film-encased battery 100 is implanted into the resin substrate is also wrinkled on the surface. In this regard, according to the lithium secondary battery of the present invention, the above-described wrinkles can be effectively suppressed. Therefore, the lithium secondary battery 10 of the present invention is preferably: a thin secondary battery that can be incorporated in a card, more preferably: a thin secondary battery is embedded in a resin substrate and made into a card. That is, according to another preferred aspect of the present invention, there is provided a battery built-in card including: a resin base material and a lithium secondary battery implanted in the resin base material. The typical scheme of the battery built-in card is as follows: the lithium secondary battery is preferably provided with 1 pair of resin films and the 1 pair of resin films sandwiched therebetween, and the resin films are preferably thermally bonded to each other by heating and pressing.
The
According to a preferred embodiment of the present invention, the
The oriented
Each
As shown in fig. 4 and 5, the average value of the orientation angles of the
The average orientation angle of the
As shown in fig. 5, the orientation angle of each
Since each
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
The density of the oriented sintered body constituting the oriented
From the viewpoint of increasing the active material capacity per unit area to improve the energy density of the lithium secondary battery 10, the thickness of the
The
The
The electrolyte solution 24 is not particularly limited, and any commercially available electrolyte solution for lithium batteries may be used, as long as: by reacting lithium salts (e.g. LiPF)6) An electrolyte solution such as a liquid obtained by dissolving a salt in an organic solvent (for example, a mixed solvent of Ethylene Carbonate (EC) and ethyl methyl carbonate (MEC), a mixed solvent of Ethylene Carbonate (EC) and diethyl carbonate (DEC), or a mixed solvent of Ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC)).
In the case of manufacturing a lithium secondary battery having excellent heat resistance, the electrolyte solution 24 preferably contains boron-containing lithium fluoride (LiBF) in a nonaqueous solvent4). In this case, the nonaqueous solvent may be a single solvent composed of γ -butyrolactone (GBL) or a mixed solvent composed of γ -butyrolactone (GBL) and Ethylene Carbonate (EC). The nonaqueous solvent contains gamma-butyrolactone (GBL), and thus the boiling point is increased, and the heat resistance is greatly improved. From this viewpoint, EC in the nonaqueous solvent: the volume ratio of GBL is preferably 0: 1-1: 1(GBL ratio)Rate 50 to 100 vol%), more preferably 0: 1-1: 1.5(GBL ratio 60 to 100 vol%), preferably 0: 1-1: 2(GBL ratio of 66.6 to 100 vol%), preferably 0: 1-1: 3(GBL ratio 75 to 100 vol%). Lithium borofluoride (LiBF) dissolved in non-aqueous solvent4) This also greatly improves heat resistance of the electrolyte having a high decomposition temperature. LiBF in the electrolyte 244The concentration is preferably 0.5 to 2mol/L, more preferably 0.6 to 1.9mol/L, still more preferably 0.7 to 1.7mol/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 Vinyl Ethylene Carbonate (VEC) as an additive. Both VC and FEC are excellent in heat resistance. Therefore, when the electrolyte solution 24 contains the additive, an SEI film having excellent heat resistance can be formed on the surface of the
The thickness of the lithium secondary battery 10 is preferably 0.45mm or less, more preferably 0.1 to 0.45mm, still more preferably 0.2 to 0.45mm, and particularly preferably 0.3 to 0.40 mm. If the thickness is within the above range, a thin lithium battery suitable for being built in a thin device such as a smart card can be obtained.
The outer peripheral edges of the 1 pair of
The
As described above, the size of the
The bulging height T of the
Separation distance W between end of
Method for manufacturing lithium cobaltate oriented sintered plate
The lithium secondary battery of the present invention is superior in thatThe oriented positive electrode plate or the oriented sintered plate to be optionally used can be produced by any production method, and is preferably produced by (1) LiCoO2Production of template particles, (2) production of matrix particles, (3) production of green sheets, and (4) production of oriented sintered plates.
(1)LiCoO2Preparation of template particles
Mixing Co3O4Raw material powder and Li2CO3And (4) mixing the raw material powder. Sintering the obtained mixed powder at 500-900 ℃ for 1-20 hours to synthesize LiCoO2And (3) powder. The obtained LiCoO2The powder is pulverized by a pot ball mill to a particle size of 0.1 to 10 μm based on the volume D50 to obtain a plate-like LiCoO which can conduct lithium ions parallel to the plate surface2Particles. The resulting LiCoO2The particles are in a state of being easily cleaved along the cleavage plane. LiCoO by Using fragmentation2Cleaving the particles to produce LiCoO2A template particle. The LiCoO2The particles can also be obtained by using LiCoO2A method of growing green chips by powder slurry and then crushing them, or a method of synthesizing plate-like crystals by flux method, hydrothermal synthesis, single crystal growth of molten solution, sol-gel method, or the like.
In this step, the profile of the
By adjusting LiCoO2At least one of the aspect ratio and the particle diameter of the template particles can control the total area ratio of the low-angle primary particles having an orientation angle of more than 0 ° and not more than 30 °. Specifically, LiCoO2The larger the aspect ratio of the template particles, and LiCoO2The larger the particle size of the template particles, the higher the total area ratio of the low-angle primary particles can be. LiCoO2The aspect ratio and the particle size of the template particles can be respectively adjusted by Co3O4Raw material powder and Li2CO3The particle diameter of the raw material powder, the pulverizing conditions (pulverizing time, pulverizing energy, pulverizing method, etc.) during pulverizing, and at least 1 of the classification after pulverizing are controlled。
By adjusting LiCoO2The aspect ratio of the template particles can be controlled to a total area ratio of the
By adjusting LiCoO2The average particle diameter of the
By adjusting LiCoO2The particle size of the template particles can control the compactness of the oriented
(2) Preparation of matrix particles
Mixing Co3O4The raw material powder is used as matrix particles. Co3O4The volume-based D50 particle size of the raw material powder is not particularly limited, and may be, for example, 0.1 to 1.0. mu.m, and is preferably smaller than LiCoO2The volume basis D50 particle size of the template particles. The matrix particles can also be prepared by mixing Co (OH)2The raw material is heat-treated at 500-800 ℃ for 1-10 hours. In addition, in the matrix particles, except for using Co3O4In addition, Co (OH) may be used2Particles, LiCoO may also be used2Particles.
In this step, the profile of the
By adjusting the particle size of the matrix particles relative to LiCoO2The ratio of the particle diameters of the template particles (hereinafter referred to as "matrix/template particle diameter ratio") can control the total area ratio of the low-angle primary particles having an orientation angle of more than 0 ° and not more than 30 °. Specifically, the smaller the matrix/template particle diameter ratio, that is, the smaller the particle diameter of the matrix particles, the more easily the matrix particles enter LiCoO in the firing step described later2The template particles can therefore increase the total area ratio of the low-angle primary particles.
By adjusting the matrix/template particle diameter ratio, the total area ratio of the
The density of the oriented
(3) Production of Green sheet
Subjecting LiCoO to condensation2Template particles and matrix particles were measured at 100: 0-3: 97 to give a mixed powder. The mixed powder, the dispersion medium, the binder, the plasticizer, and the dispersant were mixed, stirred and defoamed under reduced pressure, and adjusted to a desired viscosity to prepare a slurry. Next, the method of using LiCoO can be applied2A molding method in which shear force is applied to the template particles, and the prepared slurry is molded, thereby forming a molded body. In this way, the average orientation angle of each
In this step, the profile of the
By adjusting the molding speed, the total area ratio of the low-angle primary particles having an orientation angle of more than 0 ° and not more than 30 ° can be controlled. Specifically, the higher the molding speed, the higher the total area ratio of the low-angle primary particles can be.
The average particle diameter of the
By adjusting LiCoO2The mixing ratio of the template particles and the matrix particles can also be controlledCompactness of the
(4) Production of oriented sintered plate
The molded body of the slurry is placed on a zirconia setter plate, and subjected to heat treatment (primary firing) at 500 to 900 ℃ for 1 to 10 hours to obtain a sintered plate as an intermediate. The sintered plate is formed by using a lithium sheet (for example, containing Li)2CO3Sheet of (b) was placed on a zirconia setter plate in a state of being sandwiched vertically, and secondary firing was performed to obtain LiCoO2And (5) sintering the plate. Specifically, a sintered plate is sandwiched by lithium sheets, the sintered plate on which the sintered plate is placed in an alumina sagger, and fired at 700 to 850 ℃ for 1 to 20 hours in the atmosphere, and then the sintered plate is further sandwiched by lithium sheets from above and below and fired at 750 to 900 ℃ for 1 to 40 hours to obtain LiCoO2And (5) sintering the plate. The firing step may be performed 2 times or 1 time. When firing is performed 2 times, the 1 st firing temperature is preferably lower than the 2 nd firing temperature. In addition, the total amount of lithium sheets used in the secondary firing may be set so long as the molar ratio of the amount of Li in the green sheet and the lithium sheets to the amount of Co in the green sheet, i.e., the Li/Co ratio, is 1.0.
In this step, the profile of the
By adjusting the temperature rise rate during firing, the total area ratio of the low-angle primary particles having an orientation angle of more than 0 ° and not more than 30 ° can be controlled. Specifically, as the temperature increase rate is higher, sintering of the matrix particles is suppressed, and the total area ratio of the low-angle primary particles can be increased.
By adjusting the heat treatment temperature of the intermediate, the total area ratio of the low-angle primary particles having an orientation angle of more than 0 ° and not more than 30 ° can be controlled. Specifically, as the heat treatment temperature of the intermediate is lowered, 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
By adjusting Li (e.g. Li) at firing2CO3) The average particle diameter of the
The densification of the oriented
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