JP2011086546A - Lithium battery and electronic equipment using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium battery made from a battery element which hardly generates curves, distortion, peeling-off, and cracks at the time of releasing pressure. <P>SOLUTION: In the lithium battery having a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, package pressure is 0-1 MPa, and a capacity maintenance rate is 80% or more at the time of the twentieth cycle. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lithium secondary battery, and further relates to an electronic device including the lithium secondary battery.

In recent years, with the widespread use of portable devices such as video cameras, mobile phones, and portable personal computers, the demand for secondary batteries has increased. In the current lithium ion secondary battery, an organic electrolyte is mainly used as an electrolyte.
Although the organic electrolyte exhibits high ionic conductivity, there is a concern about the risk of leakage, ignition, etc. when used as a battery because the electrolyte is liquid and flammable. Development of a safer solid electrolyte is expected as an electrolyte for next-generation lithium ion secondary batteries.
In order to realize an all-solid-state battery, solid electrolytes have been energetically developed, but the ionic conductivity is generally smaller than that of organic electrolytes, and the practical use is difficult.

As a solid electrolyte, lithium ion conductive ceramics based on Li ₃ N have been reported as materials exhibiting high ionic conductivity at room temperature (10 ⁻³ Scm ⁻¹ ). It was difficult to construct a solid state battery.

As a sulfide-based solid electrolyte, 10 ⁻⁴ Scm ⁻¹ solid electrolyte is disclosed in Patent Document 1, and in Patent Document 2, an electrolyte synthesized from Li ₂ S and P ₂ S ₅ is similarly 10 ^-4 Scm- ¹ ion conductivity is disclosed. In Patent Document 3, an ion conductivity of 10 ⁻³ Scm ⁻¹ is realized by a sulfide-based crystallized glass in which Li ₂ S and P ₂ S ₅ are synthesized in a ratio of 68 to 74 mol%: 26 to 32 mol%. ing.

Various oxide-based solid electrolytes have been proposed, but the ion conductivity of 10 ^{−4 to} 5 ^{Scm −1} units was not satisfactory.

  When the powder is applied to the positive electrode, the negative electrode, and the solid electrolyte as in the above patent document, it is necessary to increase the filling rate of each particle layer in order to improve the battery performance (high capacity, high voltage, cycle characteristics). Therefore, it was necessary to mold under high pressure. Further, the battery described in the above-mentioned patent document has a problem that it does not drive as a battery unless a high package pressure is applied.

In Patent Document 4, the positive density and the solid electrolyte layer are molded at a high pressure of 750 to 2000 MPa in an atmosphere of room temperature to about 250 ° C., thereby making the apparent density 95% or more and the same performance as the battery to which the electrolyte is applied. It is disclosed to enhance. However, since the pressurizing condition is very high pressure, the area of the battery that can be manufactured is limited, and the pressurizing apparatus also requires a special press machine.
Further, a method of applying pressure (package pressure) during driving has been studied.

Patent Document 5 proposes a battery in which a pressure of 50 to 1000 kgf / cm ² is applied to the all-solid battery element to bring it into close contact with the exterior body.
Patent Document 6 discloses a method of preventing an interface from being lost by disposing a support plate that sandwiches an all-solid battery element, applying a pressure of 1.5 to 200 MPa, and tightening.

  As described above, in the all solid electrolyte, it is necessary to maintain the interface contact by pressurizing with a sandwich plate and screws including maintaining the performance. However, in order to maintain the tightened state during driving, an extra clamping plate and screws are required, and space saving cannot be achieved. In addition, a mobile device such as a mobile device is undesirably increased in weight.

JP-A-4-202024 JP 2002-109955 A JP 2005-228570 A JP 2008-91328 A JP 2000-106154 A JP 2008-103284 A

  It is an object of the present invention to provide an all solid lithium battery that can be driven even when the package pressure is zero or small.

According to the present invention, the following lithium batteries and the like are provided.
1. A lithium battery comprising a positive electrode layer, a solid electrolyte layer and a negative electrode layer,
The package pressure is 0 to 1 MPa,
A lithium battery having a capacity retention rate of 80% or more at the 20th cycle.
2. The lithium battery according to 1, wherein a change in discharge start voltage during 20 cycles is 0.5 V or less.
3. A lithium battery comprising a positive electrode layer, a solid electrolyte layer and a negative electrode layer,
The package pressure is 0 to 1 MPa,
The ratio of the peeled area and the element area of the horizontal cross section where the peeled area is the maximum among the horizontal cross sections perpendicular to the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer at atmospheric pressure is the following formula: (2) The lithium battery characterized by satisfy | filling.
E / F × 100 ≦ 20 (2)
(In formula, E shows the peeling area (mm < ² >) of the horizontal cross section from which a peeling area becomes the maximum.
F represents the element area (mm ² ) of the horizontal cross section where the peeled area is maximized. )
4). A lithium battery comprising a positive electrode layer, a solid electrolyte layer and a negative electrode layer,
The package pressure is 0 to 1 MPa,
The projected area of the peeled portion in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer under atmospheric pressure, and the projected area of the solid electrolyte layer in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are expressed by the following formula (3 A lithium battery.
100 × H / (H + I) <50 (3)
(I indicates a projected area (mm ² ) obtained by removing the projected area of the peeling portion from the projected area of the solid electrolyte layer in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer. H is the positive electrode layer, the solid electrolyte layer. And the projected area (mm ² ) of the peeled portion of the projected area of the solid electrolyte layer in the stacking direction of the negative electrode layer.)
5). 5. The lithium battery according to any one of 1 to 4, wherein at least one of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer contains particles.
6. An electronic apparatus comprising the lithium battery according to any one of items 1 to 5.

  ADVANTAGE OF THE INVENTION According to this invention, the all-solid-state lithium battery which can drive even if a package pressure is zero or small can be provided.

It is a perspective view which shows one Embodiment of the lithium battery of this invention. It is XX longitudinal cross-sectional view of the lithium battery of FIG. It is XX longitudinal cross-sectional view which shows the crack which generate | occur | produced in the lithium battery, (a) shows the crack in an interface, (b) shows the crack in a layer, (c) shows the crack in an edge part. FIG. 2 is an abbreviated XX vertical sectional view of the lithium battery of FIG. 1. FIG. 4 is a horizontal sectional view corresponding to a dotted line in FIG. 3. FIG. 2 is an abbreviated XX vertical sectional view of the lithium battery of FIG. 1. It is a figure which shows the measuring method of an element peeling part projected area. It is a figure which shows the projection area of the solid electrolyte layer except the element peeling part projection area and the element peeling part projection area. It is XX longitudinal cross-sectional view which shows the maximum distortion of a lithium battery, (a) is an arcuate deformation maximum distortion, (b) is a drum-shaped deformation maximum distortion, (c) shows a waveform deformation maximum distortion. It is a vertical sectional view of the lithium battery obtained in Example 1 by X-ray CT observation. It is the vertical sectional view and horizontal sectional view of the lithium battery obtained in Example 1 by X-ray CT observation. It is a vertical sectional view of the lithium battery obtained in Example 2 by X-ray CT observation. It is the vertical sectional view and horizontal sectional view of the lithium battery obtained in Example 2 by X-ray CT observation. It is a vertical sectional view of the lithium battery obtained in Comparative Example 1 by X-ray CT observation. It is the vertical sectional view and horizontal sectional view of the lithium battery obtained by the comparative example 1 by X-ray CT observation. It is a vertical sectional view of the lithium battery obtained in Comparative Example 2 by X-ray CT observation. It is the vertical sectional view and horizontal sectional view of the lithium battery obtained by the comparative example 2 by X-ray CT observation. It is a vertical sectional view of the lithium battery obtained in Comparative Example 3 by X-ray CT observation. It is the vertical sectional view and horizontal sectional view of the lithium battery obtained by the comparative example 3 by X-ray CT observation.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments.
FIG. 1 is a perspective view showing an embodiment of a lithium battery of the present invention.
FIG. 2 is an XX longitudinal sectional view of the lithium battery of FIG.
In FIG. 2, the lithium battery 1 includes a battery element 3 sandwiched between a positive electrode current collector 5 and a negative electrode current collector 7. The battery element 3 includes a solid electrolyte layer 20 between a pair of electrode layers including the positive electrode layer 10 and the negative electrode layer 30.
In the present invention, the package pressure is 0 to 1 MPa. The package pressure refers to a pressure applied during charge / discharge driving, and is a pressure applied in a uniaxial direction perpendicular to the battery stack surface.

The lithium battery of the present invention has a cycle characteristic in which the capacity retention rate with respect to the initial discharge capacity after 20 cycles is preferably 80% or more, more preferably 83% or more.
Here, the one-time cycle refers to performing charging and discharging once.
Therefore, the cycle of 20 times means performing charging and discharging 20 times each.

The capacity maintenance rate is obtained as follows. After charging the batteries at a current density of 0.2 mA / cm ^2, and discharged at 0.2 mA / cm ^2, to measure the discharge capacity at that time. This charge / discharge process is repeated 20 times.
Here, the cut voltage at the time of charging is 4.2V, and the cut voltage at the time of discharging is 1.5V. The discharge capacity is a value obtained by dividing the amount of current (mAh) obtained every hour by the weight (g) of the positive electrode active material, and the unit is mAh / g.
The capacity maintenance rate follows the following formula (1).
A = B / C × 100 (1)
Here, A is the capacity retention rate (%), B is the discharge capacity (mAh / g) at the time of discharge after the 20th cycle, and C is the discharge capacity (mAh / g) at the time of discharge at the first cycle. g).

Preferably, the voltage change after 20 cycles is 0.5 V or less. This voltage is a voltage value immediately after the start of discharge, and is the difference between the discharge start voltage at the first cycle and the discharge start voltage after the 20th cycle. Preferably it is 0.1 V or less.
Here, when the battery is first charged after the battery is manufactured and then discharged, one cycle is completed when it is performed once in the order of charging and discharging. As such a battery, the positive electrode is a positive electrode which is a substance containing Li such as LCO, and the negative electrode is a negative electrode containing graphite or the like.
On the other hand, when the battery is first discharged after manufacturing and then charged, one cycle is completed when it is performed once in the order of discharging and charging. As such a battery, a negative electrode is a negative electrode which is a substance containing Li like Li metal, and a positive electrode is a positive electrode containing indium etc.

The lithium battery of the present invention is preferably a lithium battery comprising a positive electrode layer, a solid electrolyte layer and a negative electrode layer, wherein the package pressure is 0 to 1 MPa, and the positive electrode layer, the solid electrolyte layer and the negative electrode layer are at atmospheric pressure. A lithium battery characterized in that a ratio of a peeled area and an element area of a horizontal cross section having a maximum peeled area among horizontal cross sections perpendicular to the stacking direction satisfies the following formula (2).
E / F × 100 ≦ 20 (2)
(In formula, E shows the peeling area (mm < ² >) of the horizontal cross section from which a peeling area becomes the maximum.
F represents the element area (mm ² ) of the horizontal cross section where the peeled area is maximized. )

The horizontal cross section that is a cross section perpendicular to the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer corresponds to, for example, the YY cross section of the lithium battery in FIG.
A lithium battery may have an element peeling portion that occurs in a manufacturing process or the like in the battery element portion. FIG. 3 is a diagram showing a crack in the element. As a crack in the element, a crack at the interface shown in FIG. 3A, a crack inside the layer shown in FIG. 3B, and a crack shown in FIG. There are roughly three types of cracks at the end of the element.

The horizontal cross section where the peeled area is maximized is that the area occupied by the element peeled portion (crack portion) is the maximum among any horizontal cross section perpendicular to the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer. It is a horizontal cross section.
The peeling area of the horizontal cross section where the peeling area is maximized (hereinafter sometimes referred to as the maximum peeling area) is an area occupied by the element peeling portion in the horizontal cross section where the peeling area is maximized. Further, the element area of the horizontal cross section where the peeling area is maximized is the area of the horizontal cross section where the peeling area is maximized.

4 is an abbreviated XX vertical cross-sectional view of the lithium battery of FIG. 1, and a horizontal cross section corresponding to a dotted line is a horizontal cross section in which the peeling area of the element peeling portion 40 is maximized.
FIG. 5 is a diagram showing a horizontal section corresponding to the dotted line in FIG. 4. In FIG. 5, the peeling area E of the horizontal cross section where the peeling area is maximum is the area of the element peeling portion b, and the element area F of the horizontal cross section where the peeling area is maximum is the area of the element horizontal cross section a. In the present invention, the maximum peel area ratio α represented by b / a × 100 is preferably 20 or less.
In FIG. 5, there is one element peeling portion, but when there are a plurality of element peeling portions, the total area of the plurality of element peeling portions is defined as a peeling area E.

The measuring method of the peeling area E of the horizontal cross section where the peeling area is maximum is not particularly limited, but can be measured by, for example, the following method.
Decompress the molded lithium ion battery, and observe the X-ray CT cross section of the horizontal cross section perpendicular to the stacking direction of the battery element consisting of the negative electrode layer, solid electrolyte layer, and negative electrode layer of the lithium ion battery under atmospheric pressure. (See FIGS. 10 and 12).
A vertical sectional view of the device (see FIGS. 10, 12, 14, 16 and 18) is obtained by X-ray CT observation, and the peeled portion is measured. Next, the horizontal cross section is observed at intervals of 70 μm in the horizontal direction with respect to the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer, and a plurality of horizontal cross-sectional views are obtained (the horizontal cross section indicates the battery element). It may be the entire horizontal cross section or a single field of view (eg, 15.5 mm × 9.6 × 10 ⁻² mm). And a peeling part is specified from the sectional view of the horizontal section with reference to the vertical sectional view.

  Among the cross-sectional views of the plurality of horizontal cross sections, the one having the largest peeled portion (the sum of the areas of the peeled portions in the horizontal cross section when there are a plurality of peeled portions in an arbitrary horizontal cross section) is selected. The area of the horizontal cross section of the element and the area of the peeled portion can be measured by using image software manufactured by Yamato Kagaku.

In addition to the above, after the molded battery element is depressurized (pressure is released) and appropriately sealed with a laminate film or the like, it can also be measured by observing a horizontal section by the X-ray CT method. In the horizontal cross-section observation, observation is performed sequentially from the top of the battery element at intervals of 70 μm, the peeled portion is identified from the image and an arbitrary vertical cross-sectional view, and an image having the maximum peeled area is extracted from the horizontal cross-sectional observation image. . Using the extracted image, the element cross-sectional area F (mm ² ) and the maximum peeled area E (mm ² ) are measured by image processing. The maximum peel area ratio α is obtained by the following formula (2).
Maximum peel area ratio α = 100 × E / F (2)

In the lithium battery of the present invention, the maximum peel area ratio of the formula (2) is preferably E / F × 100 ≦ 20, more preferably E / F × 100 <10, and most preferably E / F ×. 100 <5.
By satisfy | filling Formula (2) E / Fx100 <= 20, the lithium battery of this invention can make ion conduction easy, and can maintain battery performance. On the other hand, when E / F × 100 of the formula (2) is more than 20, ion conduction between the positive electrode and the negative electrode during battery driving becomes difficult, and the battery performance may be deteriorated.

The lithium battery of the present invention is a lithium battery including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, and has a package pressure of 0 to 1 MPa, and is stacked in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer under atmospheric pressure. It is preferable that the projected area of the peeling portion and the projected area of the solid electrolyte layer in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer satisfy the following formula (3).
H / (H + I) × 100 <50 (3)
(I indicates a projected area (mm ² ) obtained by removing the projected area of the peeled portion from the projected area of the solid electrolyte layer in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer.
H represents the projected area (mm ² ) of the peeled portion of the projected area of the solid electrolyte layer in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer. )
More preferably, H / (H + I) × 100 <10, and most preferably H / (H + I) × 100 <5.

The projected area of the peeled portion in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer, and the projected area of the solid electrolyte layer in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer can be measured by, for example, the following method. .
6 is a schematic XX vertical cross-sectional view of the lithium battery of FIG. 1 when there are a plurality of element peeling portions.
In FIG. 6, there are three element peeling portions, and the area of the peeling portions of the horizontal cross sections X, Y, and Z is measured by the same method as in the above-described E measuring method. By superimposing the obtained horizontal sections X, Y and Z so as to constitute a battery element, an element peeling portion projection view can be obtained, and the projected area of the element peeling portion can be measured (FIG. 7).
FIG. 8 is a diagram showing the projected area of the element peeling portion of FIG. 7 and the projected area of the solid electrolyte layer excluding the projected area of the element peeling portion. In the present invention, the projected area of the element peeling portion is H. When the projected area of the solid electrolyte layer excluding the projected area of the element peeling portion is I, the thickness direction occupied peeling area ratio β represented by 100 × H / (H + I) is preferably less than 50.
More preferably, β is less than 10, most preferably less than 5. If β is 50 or more, ion conduction between the positive electrode and the negative electrode when the battery is driven becomes difficult, and the battery performance may be extremely deteriorated.

  The battery element is preferably under atmospheric pressure and has a maximum strain of 200 μm or less. More preferably, the maximum strain is 150 μm or less under atmospheric pressure. The maximum strain is the sum of the positive electrode side maximum displacement and the negative electrode side maximum displacement. There are three types of element distortion, for example, a bow shape shown in FIG. 9A, a drum shape shown in FIG. 9B, and a waveform shown in FIG. 9C. 9 (a) to 9 (c), the both ends A and A 'of the positive battery element and the both ends B and B' of the negative battery element are connected, and the positive maximum displacement a and the negative maximum displacement b are obtained. The vertical distance (a + b) from this straight line is obtained, the sum is obtained, and the sum is taken as the maximum distortion.

The maximum strain can be measured by depressurizing the molded battery element (in a state in which the pressure is released), sealing it with a laminate film or the like, and then observing a cross section by an X-ray CT method.
If the element itself collapses due to cracking or peeling when the element is taken out after pressure molding, depending on the thickness, it can be observed together with the jig for making the element (made of resin, insulator, metal, etc.) There is no need to take it out.
In the X-ray CT method, since a data image is obtained from an integrated image, an accurate distance value can be obtained on the image.

  In the lithium battery of the present invention, preferably, at least one of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer contains particles.

  For example, the solid electrolyte layer is formed by depositing solid electrolyte particles and applying an appropriate load. At this time, the thickness of the solid electrolyte layer is not particularly limited, but is preferably 10 to 1000 μm.

  For example, the electrode layers (positive electrode layer and negative electrode layer) include electrode active material particles and solid electrolyte particles, and are formed by depositing powder and then applying an appropriate load. At this time, the thickness of the electrode layer is not particularly limited, but is preferably 10 to 200 μm.

The solid electrolyte used for the solid electrolyte layer is not particularly limited, and for example, a material composed of a polymer electrolyte, an inorganic electrolyte compound, or a mixture thereof can be used. Preferably, it is a sulfide-based or oxide-based inorganic electrolyte compound, and more preferably a sulfide-based solid electrolyte containing at least sulfur, phosphorus, and lithium excellent in ion conductivity.
As an example of the sulfide-based solid electrolyte, a solid electrolyte described in JP-A-4-202024 can be used. Specifically, Li ₃ PO ₄ , halogen, and a halogen compound are appropriately added to a solid electrolyte composed of Li ₂ S and any of SiS ₂ , GeS ₂ , P ₂ S ₅ , and B ₂ S ₃ . As a method for producing a sulfide-based solid electrolyte comprising sulfur, phosphorus, and lithium, as described in JP-A-2005-228570, Li ₂ S and P ₂ S ₅ are used as raw materials, and mechanical milling (hereinafter referred to as MM method) is used. The synthesis method is simple and preferable. More specifically, a sulfide-based solid electrolyte glass can be obtained by MM method using a planetary ball mill by mixing Li ₂ S at a ratio of 70 mol% and P ₂ S ₅ at a ratio of 30 mol%.
Thereafter, the obtained sulfide-based solid electrolyte glass is heat-treated at a predetermined temperature to synthesize a sulfide-based solid electrolyte glass ceramic containing a crystal component. The heat treatment temperature is preferably 190 ° C to 340 ° C, more preferably 195 ° C to 335 ° C, and particularly preferably 200 ° C to 330 ° C.
The ionic conductivity of the sulfide-based solid electrolyte glass ceramic containing the crystal component thus obtained is about 7.0 × 10 ^{−4 to} 5.0 × 10 ⁻³ (S / cm).

As a positive electrode active material used in the positive electrode layer, it is not particularly _{limited, LiCoO 2, LiNiCoO 2, LiNiO} 2, LiNiMnCoO 2, LiFeMnO 2, LiMnNiO 4, LiMn 2 O 4, LiNiMnO 2, LiNiVO 4, LiCrMnO 4 , LiCoVO ₄ , LiCoPO ₄ , LiFePO ₄ , LiFe (SO ₄ ) ₃ , LiNi _0.8 Co _0.15 Al _0.05 O _{2 and} other transition metal complex oxide lithium salts are used. A positive electrode mixture which is a mixture of these positive electrode active materials and solid electrolytes can also be used.
The positive electrode mixture is prepared by mixing a positive electrode active material and a solid electrolyte. The ratio is preferably 50 wt% to 90 wt%, more preferably 60 wt% to 80 wt%, as the weight% of the positive electrode active material. The method of mixing is not particularly limited, and may be appropriately selected such as a method of mixing the dried powder in an agate mortar or the like, a method of adding an organic solvent and mixing.

Although it does not specifically limit as a negative electrode active material used for a negative electrode layer, Carbon materials, such as graphite and graphite, Sn metal, In metal, Li metal, etc. can be used suitably. More specifically, natural graphite, various graphites, metal powders such as Sn, Si, Al, Sb, Zn, Bi, Sn ₅ Cu ₆ , Sn ₂ Co, Sn ₂ Fe, Ti—Sn, Ti—Si, etc. Examples include metal alloy powders, oxides (Li _4/3 Ti _5/3 O), nitrides (LiCoN), and the like, and a negative electrode mixture that is a mixture of these and a solid electrolyte can also be used.
The negative electrode mixture is prepared by mixing a negative electrode active material and a solid electrolyte. The ratio is preferably 40 wt% to 80 wt%, more preferably 50 wt% to 80 wt%, as the weight% of the negative electrode active material. As a mixing method, a method of mixing the dried powder with an agate mortar or a method of adding and mixing an organic solvent may be selected as appropriate.

  As the current collector, a plate or foil made of Cu, Mg, SUS steel, Ti, Fe, Co, Ni, Zn, Al, Ge, In, Li, or an alloy thereof can be used. The positive electrode current collector and the negative electrode current collector may be the same or different.

The battery element used in the present invention can be produced by bonding and molding a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. As a method of molding, after depositing each member, a method of pressurizing and pressing in a lump, a method of pressurizing between rolls, a method of molding each layer individually and then molding in a lump, etc. There is.
The battery element that suppresses the peeled area differs depending on the material type and lamination method, but the method of adjusting the pressure during molding, the method of laminating each layer independently after molding, the method of performing heat treatment under pressure, the charge / discharge cycle under pressure It can be obtained by a method of performing the treatment several times.

  You may shape | mold through an adhesive substance to such an extent that the ionic conductivity in a joining surface is not impaired. Further, heat fusion treatment may be performed to such an extent that the solid electrolyte and the crystal structure of the active material do not change.

  According to this invention, the electronic device carrying the above-mentioned lithium battery is provided. Although it does not specifically limit as an electronic device, Mobile devices, such as a mobile telephone and a mobile personal computer, Mobile devices, such as an electric vehicle and an electric bicycle, An electric tool etc. are mentioned.

Example 1
Commercially available Li ₂ S and P ₂ S ₅ (manufactured by Aldrich) were mixed at a molar ratio of 70:30, and a sulfide-based solid electrolyte glass was obtained by a planetary ball mill. Then, it processed at 300 degreeC for 2 hours, and obtained the sulfide type solid electrolyte glass ceramic containing a crystal component. The ionic conductivity of the obtained sulfide-based solid electrolyte glass ceramic was 1.3 × 10 ⁻³ S / cm.
The obtained solid electrolyte glass ceramic particles and the positive electrode active material LiNi _0.8 Co _0.15 Al _0.05 O ₂ were mixed at a weight ratio of 30 wt%: 70 wt% to obtain a positive electrode mixture.
The obtained solid electrolyte glass ceramic particles and graphite powder as the negative electrode active material were mixed at a weight ratio of 40 wt%: 60 wt% to obtain a negative electrode mixture.
200 mg of the produced solid electrolyte glass ceramic particles were put into a metal mold having a diameter of 15.5 mm and subjected to pressure molding at a pressure of 20 MPa. Further, 100 mg of the positive electrode mixture was added and pressure-molded again at 60 MPa, and 62.4 mg of the negative electrode mixture was charged from the opposite side of the positive electrode mixture and again pressure-molded at 60 MPa to form a lithium secondary battery element. Got.

The element was placed on a metal pedestal, sealed with aluminum laminate, and observed with X-ray CT (package pressure was 0 MPa). FIG. 10 shows a vertical cross-sectional view of the manufactured lithium secondary battery element as a result of X-ray CT observation. The upper side is the positive electrode and the lower side is the negative electrode. As a result of connecting the both ends of the element and measuring each maximum displacement in the vertical direction, the positive electrode side maximum displacement was 0 μm and the negative electrode side maximum displacement was 53 μm, and the maximum strain defined by the sum thereof was 53 μm.
The horizontal cross-sectional observation result by the said X-ray CT observation is FIG. Of these, No. At the edge of the image 5, a slight peeling site was observed. The maximum peeled area ratio calculated from the peeled portion and the entire area was 3.4. Moreover, the thickness direction occupation peeling area ratio was 3.9.

A battery was obtained by sandwiching both surfaces of the element as current collectors with Ti foil (package pressure was 0 MPa). The battery was evaluated according to the following method.
After charging the batteries at a current density of 0.2 mA / cm ^2, and discharged at 0.2 mA / cm ^2, to measure the discharge capacity at that time. This charge / discharge process was repeated 20 times, and the capacity retention rate was determined from the change in the discharge capacity at the first time and the 20th time.
The cut voltage during charging was 4.2V, and the cut voltage during discharging was 1.5V. The capacity was measured by mAh / g obtained by normalizing the amount of current obtained every hour with the weight of the positive electrode active material. As the discharge start voltage, a voltage value immediately after the start of discharge was measured.
For comparison, the battery was charged at a current density of 0.2 mA / cm ² with a pressure of 10 MPa applied, and then discharged at 0.2 mA / cm ² , and the discharge capacity at that time was also measured. This charge / discharge process was repeated 20 times, and the capacity retention rate was determined from the discharge capacity at the first cycle and the discharge capacity at the 20th cycle.
The results are shown in Tables 1 and 2.
In addition, the warp, distortion, peeling, and crack generated at the time of producing the battery element were improved so that the contact could be taken by the package pressure of 22 MPa, and the performance was almost recovered.

Example 2
Implemented except that a metal mold with a diameter of 15.5 mm was used, the molding pressure of the solid electrolyte was 10 MPa, the molding pressure after charging the positive electrode mixture on one side was 40 MPa, and the molding pressure after charging the negative electrode mixture on the other side was 40 MPa. In the same manner as in Example 1, a lithium secondary battery element was obtained.
The obtained lithium secondary battery element was observed by X-ray CT. The result of X-ray CT observation is shown in FIG. The upper side is a negative electrode, and the lower side is a positive electrode. Although the pedestal is distorted and the level is not maintained, both end portions of the element are connected in the same manner as in Example 1, and each maximum displacement in the vertical direction is measured. As a result, the positive electrode side maximum displacement was 0 μm and the negative electrode side maximum displacement was 53 μm, and the maximum strain defined by the sum thereof was 53 μm.
The horizontal cross-sectional observation result by the said X-ray CT observation is FIG. Of these, No. Some peeling sites were observed at 15 image edges. The maximum peeled area ratio calculated from the peeled portion and the entire area was 1.6. Moreover, the thickness direction occupation peeling area ratio was 4.4.
A battery was prepared and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 1
Other than using a PET mold with a diameter of 15.5 mm, the molding pressure of the solid electrolyte was 20 MPa, the molding pressure after the positive electrode mixture was charged on one side was 70 MPa, and the molding pressure after the negative electrode mixture was charged on the other side was 70 MPa. A lithium secondary battery element was obtained in the same manner as Example 1.
Since it was difficult to extract after molding, FIG. 14 shows the result of X-ray CT observation of the obtained lithium secondary battery element as it is. The upper side is a negative electrode, and the lower side is a positive electrode. Similarly to Example 1, both end portions of the element were connected, and each maximum displacement in the vertical direction was measured. As a result, the maximum displacement on the positive electrode side was 386 μm and the maximum displacement on the negative electrode side was 562 μm, and the maximum strain defined by the sum thereof was 948 μm.
The horizontal cross-sectional observation result by the said X-ray CT observation is FIG. Of these, No. At the 12 image edges, a maximum peeled site was observed at the center. The maximum peeled area ratio calculated from this peeled portion and the entire area was 76.3. Moreover, the thickness direction occupation peel area ratio was 94.1.
A battery was prepared and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 2
Other than using a PET mold with a diameter of 15.5 mm, the molding pressure of the solid electrolyte was 10 MPa, the molding pressure after charging the positive electrode mixture on one side was 20 MPa, and the molding pressure after charging the negative electrode mixture on the other side was 20 MPa. A lithium secondary battery element was obtained in the same manner as Example 1.
FIG. 16 shows the result of X-ray CT observation of the obtained lithium secondary battery element as it is. The upper side is a negative electrode, and the lower side is a positive electrode. Similarly to Example 1, both end portions of the element were connected, and each maximum displacement in the vertical direction was measured. As a result, the maximum displacement on the positive electrode side was 246 μm and the maximum displacement on the negative electrode side was 387 μm, and the maximum strain defined by the sum thereof was 633 μm.
The horizontal cross-sectional observation result by the said X-ray CT observation is FIG. Of these, No. At 11 image edges, a maximum peeled site was observed at the center. The maximum peeled area ratio calculated from the peeled portion and the entire area was 70.5. Moreover, the thickness direction occupation peel area ratio was 96.1.
A battery was prepared and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 3
Other than using a PET mold with a diameter of 15.5 mm, the molding pressure of the solid electrolyte was 10 MPa, the molding pressure after charging the positive electrode mixture was 60 MPa on one side, and the molding pressure after charging the negative electrode mixture was 60 MPa on the other side. A lithium secondary battery element was obtained in the same manner as Example 1.
FIG. 18 shows the result of X-ray CT observation of the obtained lithium secondary battery element as it is. The upper side is a negative electrode, and the lower side is a positive electrode. Similarly to Example 1, both end portions of the element were connected, and each maximum displacement in the vertical direction was measured. As a result, the maximum displacement on the positive electrode side was 316 μm and the maximum displacement on the negative electrode side was 457 μm, and the maximum strain defined by the sum thereof was 773 μm.
The horizontal cross-sectional observation result by the said X-ray CT observation is FIG. Of these, No. At the 12 image edges, a maximum peeled site was observed at the center. The maximum peeled area ratio calculated from the peeled portion and the entire area was 58.9. Moreover, the thickness direction occupation peeling area ratio was 95.6.
A battery was prepared and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

The volume of the peeled part (no applied pressure) of the battery elements of Examples 1 and 2 and Comparative Examples 1 to 3 was measured. The results are shown in Table 3. From Table 3, it can be seen that in the battery elements of Comparative Examples 1 to ³ whose peel volume far exceeds 1 mm ³ , it is necessary to apply a high package pressure in order to maintain the battery performance.
The volume of the peeled portion was measured using a three-dimensional image obtained by an X-ray CT apparatus (TDM-1000IS manufactured by Yamato Scientific Co., Ltd.) and using analysis software (TRI / 3D-VOL manufactured by Ratoku System Engineering Co., Ltd.). did.

  The lithium battery of the present invention can be used for mobile devices such as mobile phones and mobile personal computers, mobile devices such as electric cars and electric bicycles, and electric tools.

DESCRIPTION OF SYMBOLS 1 Lithium electron 3 Battery element 5 Positive electrode collector 7 Negative electrode collector 10 Positive electrode layer 20 Solid electrolyte layer 30 Negative electrode layer 40 Element peeling part

Claims (6)

A lithium battery comprising a positive electrode layer, a solid electrolyte layer and a negative electrode layer,
The package pressure is 0 to 1 MPa,
A lithium battery having a capacity retention rate of 80% or more at the 20th cycle.   2. The lithium battery according to claim 1, wherein a change in the discharge start voltage during 20 cycles is 0.5 V or less. A lithium battery comprising a positive electrode layer, a solid electrolyte layer and a negative electrode layer,
The package pressure is 0 to 1 MPa,
The ratio of the peeled area and the element area of the horizontal cross section where the peeled area is the maximum among the horizontal cross sections perpendicular to the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer at atmospheric pressure is the following formula: (2) The lithium battery characterized by satisfy | filling.
E / F × 100 ≦ 20 (2)
(In formula, E shows the peeling area (mm < ² >) of the horizontal cross section from which a peeling area becomes the maximum.
F represents the element area (mm ² ) of the horizontal cross section where the peeled area is maximized. ) A lithium battery comprising a positive electrode layer, a solid electrolyte layer and a negative electrode layer,
The package pressure is 0 to 1 MPa,
The projected area of the peeled portion in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer under atmospheric pressure, and the projected area of the solid electrolyte layer in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are expressed by the following formula (3 A lithium battery.
100 × H / (H + I) <50 (3)
(I indicates a projected area (mm ² ) obtained by removing the projected area of the peeling portion from the projected area of the solid electrolyte layer in the stacking direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer. H is the positive electrode layer, the solid electrolyte layer. And the projected area (mm ² ) of the peeled portion of the projected area of the solid electrolyte layer in the stacking direction of the negative electrode layer.)   The lithium battery according to claim 1, wherein at least one of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer includes particles.   An electronic device comprising the lithium battery according to claim 1.