JP2018045779A - All-solid lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an all-solid lithium ion secondary battery which has a high volume energy density, and which can absorb a volume change of a negative electrode active material layer when a charge-and-discharge cycle is repeated.SOLUTION: An all-solid lithium ion secondary battery 10 comprises a negative electrode current collector layer 1, a negative electrode active material layer 2, a solid electrolyte layer 3, a positive electrode active material layer 4 and a positive electrode current collector layer 5 in this order. In the all-solid lithium ion secondary battery 10, the negative electrode active material layer 2 comprises an alloy material including at least one kind selected from silicon and tin. As to the solid electrolyte layer 3, a packing rate is 85% or less, which is calculated from the following mathematical expression: Packing rate (%)=[{Weight (g) of the solid electrolyte layer÷True specific gravity (g/cm) of the solid electrolyte layer}÷{Apparent volume (cm) of the solid electrolyte layer}]×100. The negative electrode current collector layer 1 is 7.0% or more in elongation according to a tensile test. The positive electrode current collector layer 5 is 4.0% or more in elongation according to a tensile test.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an all solid lithium ion secondary battery.

  In recent years, high-performance batteries have been demanded in various industries. For example, in the automobile industry, development of a high-output and high-capacity battery for an electric vehicle or a hybrid vehicle is underway. In particular, an all-solid battery in which the electrolyte in the battery is replaced with a solid electrolyte has attracted attention. Since the electrolyte solution is not used in the all solid state battery, unlike the secondary battery using the electrolyte solution, the decomposition of the electrolyte solution due to overcharge does not occur. The all solid state battery is further characterized by having high cycle durability and high energy density.

  In an all-solid-state lithium ion secondary battery, as a negative electrode active material, for example, an alloy-based material containing silicon, tin or the like; or a carbon material such as graphite is used.

  Among these negative electrode active materials, alloy materials containing silicon, tin, and the like are materials that can occlude and release lithium ions by alloying with lithium and have a large theoretical discharge capacity. It is an effective material for increasing the capacity of secondary batteries.

  All-solid lithium ion secondary batteries using these alloy-based negative electrode active materials exhibit desired excellent battery performance at the beginning of manufacture. However, when the charge / discharge cycle is repeated, the battery performance may be drastically reduced, the battery shape may be deformed, and the like. One of the causes is considered to be related to the volume change of the negative electrode active material due to insertion and extraction of lithium ions accompanying the charge / discharge cycle.

In this regard, Patent Document 1 discloses that
Including a positive electrode, a negative electrode, a polymer layer and a lithium ion permeable insulating layer;
The positive electrode includes a positive electrode active material layer containing a positive electrode active material capable of inserting and extracting lithium and a positive electrode current collector,
The negative electrode includes a negative electrode active material layer formed by a vapor phase method and containing an alloy-based negative electrode active material and a negative electrode current collector,
The polymer layer is formed on a surface of the negative electrode active material layer, contains a first polymer and first inorganic oxide particles, and the lithium ion permeable insulating layer is interposed between the positive electrode and the negative electrode A lithium ion secondary battery arranged in such a manner is disclosed.

  In Patent Document 1, the polymer layer is present between the negative electrode active material layer and the lithium ion permeable insulating layer (separator) to absorb the volume expansion of the negative electrode active material layer and suppress deformation of the battery. ing.

JP 2010-250968 A

  However, according to the technique of Patent Document 1, although the volume expansion of the negative electrode active material associated with the charge / discharge cycle can be absorbed, a polymer that does not contribute to charge / discharge is used, so the volume energy density of the obtained battery is The inventors have found that this is not sufficient.

  Accordingly, an object of the present invention is to provide an all solid lithium ion secondary battery that can absorb the volume expansion of the negative electrode active material layer and has a high volumetric energy density.

  The above object of the present invention is achieved by the following all solid lithium ion secondary battery.

An all-solid lithium ion secondary battery comprising a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order,
The negative electrode active material layer contains an alloy material containing at least one selected from silicon and tin,
For the solid electrolyte layer, the filling rate calculated by the following formula (1) is 85% or less,
Filling rate (%) = [{weight of solid electrolyte layer (g) ÷ true specific gravity of solid electrolyte layer (g / cm ³ )} ÷ {apparent volume of solid electrolyte layer (cm ³ )}] × 100 (1)
The elongation in the tensile test of the negative electrode current collector layer is 7.0% or more, and
The elongation percentage in the tensile test of the positive electrode current collector layer is 4.0% or more,
An all-solid-state lithium ion secondary battery.

  The all-solid-state lithium ion secondary battery of the present invention can absorb the volume change of the negative electrode active material layer when the charge / discharge cycle is repeated, and has a high volume energy density.

FIG. 1 is a conceptual diagram for explaining the effect of the present invention. FIG. 2 is a graph showing the relationship between the rate of change in thickness of the all-solid-state lithium ion secondary battery and the filling rate of the solid electrolyte layer evaluated in Examples and Comparative Examples. FIG. 3 is a graph showing the relationship between the rate of change in thickness of the all-solid-state lithium ion secondary battery and the elongation rate of the negative electrode current collector layer (copper foil) evaluated in Examples and Comparative Examples. FIG. 4 is a graph showing the relationship between the rate of change in thickness of the all-solid-state lithium ion secondary battery and the rate of elongation of the positive electrode current collector layer (aluminum foil) evaluated in Examples and Comparative Examples.

  Hereinafter, a preferred embodiment (this embodiment) of the all solid lithium ion secondary battery of the present invention will be described in detail.

<All-solid lithium ion secondary battery>
The all-solid-state lithium ion secondary battery of this embodiment is
An all-solid lithium ion secondary battery comprising a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order,
The negative electrode active material layer contains an alloy material containing at least one selected from silicon and tin,
For the solid electrolyte layer, the filling rate calculated by the following formula (1) is 85% or less,
Filling rate (%) = [{weight of solid electrolyte layer (g) ÷ true specific gravity of solid electrolyte layer (g / cm ³ )} ÷ {apparent volume of solid electrolyte layer (cm ³ )}] × 100 (1)
The elongation in the tensile test of the negative electrode current collector layer is 7.0% or more, and
The elongation percentage in the tensile test of the positive electrode current collector layer is 4.0% or more,
It is characterized by that.

  In the all solid lithium ion secondary battery of the present embodiment, the solid electrolyte layer has a filling rate of 85% or less, so that the solid electrolyte layer has a significant volume of voids. When the negative electrode active material layer expands as the charge / discharge cycle is repeated, the voids are crushed so that the volume change of the negative electrode active material layer can be absorbed.

  Furthermore, in this embodiment, the flexibility of the current collector layer can be obtained by using a negative electrode current collector layer having an elongation rate of 7.0% or more and a positive electrode current collector layer having an elongation rate of 4.0% or more. Is guaranteed to be sufficiently high. These soft current collector layers can follow the expansion and deformation of the negative electrode active material layer due to repeated charge / discharge cycles, and the accompanying deformation of the battery structure, and can suppress damage to the battery. it can.

  In FIG. 1, the effect of the all-solid-state lithium ion secondary battery of this embodiment was shown notionally.

  The all solid lithium ion secondary battery 10 in FIG. 1 includes a negative electrode current collector layer 1, a negative electrode active material layer 2, a solid electrolyte layer 3, a positive electrode active material layer 4, and a positive electrode current collector layer 5. They are stacked in this order.

  In the all solid lithium ion secondary battery 10 of FIG. 1, the thickness of the negative electrode active material layer 2 before the cycle (a) is a predetermined value as designed. However, after repeating the charge / discharge cycle many times (b), the negative electrode active material layer 2 expands in the thickness direction t.

  However, since the voids in the solid electrolyte layer 3 having a relatively low filling rate are crushed, the expansion and deformation of the negative electrode active material layer 2 can be absorbed, and the flexible negative electrode current collector layer 1 and positive electrode current collector can be further absorbed. Since each of the electric conductor layers 5 can follow the deformation of the battery structure, an increase in the thickness of the entire solid lithium ion secondary battery 10 can be suppressed.

The all-solid-state lithium ion secondary battery of this embodiment is
The unit battery may include a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order,
A stacked battery in which a plurality of the unit batteries are stacked may be used.

  When the all solid lithium ion secondary battery of the present embodiment is a laminated battery, the laminated battery may have a structure having a plurality of unit batteries. The unit battery is a laminate in which a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer are laminated in this order. In the laminated battery, adjacent unit batteries may be configured to share the negative electrode current collector layer, the positive electrode current collector layer, or both. That is, the laminated battery includes, for example, a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode You may have two unit batteries which share a positive electrode active material layer in the lamination | stacking order of a collector layer. The laminated battery may be housed in an exterior body such as a laminate or a can.

[Solid electrolyte layer]
The solid electrolyte layer in this embodiment has a filling rate calculated by the following mathematical formula (1) of 85% or less.
Filling rate (%) = [{weight of solid electrolyte layer (g) ÷ true specific gravity of solid electrolyte layer (g / cm ³ )} ÷ {apparent volume of solid electrolyte layer (cm ³ )}] × 100 (1)

  In the above formula (1), the apparent volume of the solid electrolyte layer can be obtained by multiplying the area of the solid electrolyte layer by the thickness. The thickness of the solid electrolyte layer is calculated by subtracting the thickness of the negative electrode current collector layer, the negative electrode active material layer, the positive electrode active material layer, and the positive electrode current collector layer from the thickness of the all solid lithium ion secondary battery. Can do.

  The filling rate of the solid electrolyte layer may preferably be 83% or less, 80% or less, or 75% or less.

  On the other hand, in order to maintain the mechanical strength of the solid electrolyte layer and exhibit the function as the electrolyte layer in the battery, the filling rate of the solid electrolyte layer is 30% or more, 40% or more, 50% or more, or 60 % Or more is preferable.

  The filling rate of the solid electrolyte layer is adjusted to a desired value by adjusting the pressing pressure in at least one of the molding of the solid electrolyte layer and the molding of the all-solid lithium ion secondary battery (described later). Can be adjusted.

  The thickness of the solid electrolyte layer may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more, and may be 100 μm or less, 50 μm or less, or 30 μm or less.

The solid electrolyte layer preferably contains a sulfide, for example. Examples of the sulfide contained in the solid electrolyte layer include Li ₂ S, P ₂ S _{5 and the} like, and it is preferable to use one or more selected from these.

[Negative electrode current collector layer]
The negative electrode current collector layer in the all solid lithium ion secondary battery of the present embodiment has an elongation percentage of 7.0% or more in a tensile test. This elongation rate is a value that represents the percentage of the elongation at break when the tensile test is performed on the sample of the negative electrode current collector layer with respect to the sample length (distance between marked lines) before the tension, in percentage.

Specifically, it is calculated | required by following Numerical formula (2) using the data of the tensile test measured based on IPC-TM-650.
Elongation rate (%) = Elongation at break (mm) ÷ Distance between marked lines (mm) × 100 (2)

  The elongation rate of the negative electrode current collector layer needs to be 7.0% or more, preferably 7.2% or more, or 7.5% or more from the above-mentioned purpose.

  The elongation percentage of the negative electrode current collector layer can be adjusted by, for example, heat treatment.

  Examples of the material constituting the negative electrode current collector layer include stainless steel (SUS), copper (Cu), nickel (Ni), iron (Fe), titanium (Ti), cobalt (Co), and zinc (Zn). Metal foils, in particular copper foils, can be used.

  The thickness of the negative electrode current collector layer can be 1 μm or more, 5 μm or more, or 10 μm or more, and can be 100 μm or less, 50 μm or less, or 35 μm or less. Specifically, the thickness of the negative electrode current collector layer can be, for example, 15 μm, but is not limited thereto.

[Positive electrode current collector layer]
The positive electrode current collector layer in the all solid lithium ion secondary battery of the present embodiment has an elongation percentage of 4.0% or more in the tensile test, and may be 4.5% or more or 4.8 or more. The definition of the elongation rate is the same as that of the elongation rate in the negative electrode current collector layer.

  The elongation percentage of the positive electrode current collector layer can be adjusted by, for example, heat treatment.

  Examples of the material constituting the positive electrode current collector layer include stainless steel (SUS), nickel (Ni), chromium (Cr), gold (Au), platinum (Pt), aluminum (Al), iron (Fe), and titanium. A metal foil made of (Ti), zinc (Zn) or the like, particularly an aluminum foil can be used.

  The thickness of the positive electrode current collector layer can be 1 μm or more, 5 μm or more, or 8 μm or more, and can be 100 μm or less, 50 μm or less, or 20 μm or less. Specifically, the thickness of the positive electrode current collector layer can be, for example, 15 μm, but is not limited thereto.

[Negative electrode active material layer]
The negative electrode active material layer in the all solid lithium ion secondary battery of the present embodiment can contain at least a negative electrode active material, preferably further contains a solid electrolyte, and further contains a conductive material, a binder and the like as desired. May be.

  The negative electrode active material layer in the all solid lithium ion secondary battery of the present embodiment contains an alloy-based material containing at least one selected from silicon and tin as the negative electrode active material. This alloy-based material is alloyed with lithium during charging and occludes lithium, and releases lithium during discharging.

  The alloy-based material containing silicon may be a known material, and examples thereof include silicon, silicon oxide, silicon carbide, silicon nitride, silicon-containing alloy, and solid solutions thereof. Some of the silicon atoms contained in these may be substituted with one or more elements.

Examples of the silicon oxide include silicon oxide represented by the composition formula: SiO _a (0.05 <a <1.95). Examples of silicon carbide include silicon carbide represented by the composition formula: SiC _b (0 <b <1). Examples of the silicon nitride include silicon nitride represented by a composition formula: SiN _c (0 <c <4/3). Examples of the silicon-containing alloy include alloys of silicon and elements other than silicon. Examples of elements other than silicon include Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti. Elements other than silicon can be used alone or in combination of two or more.

  Examples of the alloy-based material containing tin include tin, tin oxide, tin nitride, tin-containing alloy, and solid solutions thereof. Some of the tin atoms contained in these may be substituted with one or more elements.

Examples of the tin oxide include tin oxide represented by the composition formula: SnO _d (0 <d <2), tin dioxide (SnO ₂ ), and the like. Examples of the tin-containing alloy include a Ni—Sn alloy, a Mg—Sn alloy, a Fe—Sn alloy, a Cu—Sn alloy, and a Ti—Sn alloy. Examples of the tin compound include SnSiO ₃ , Ni ₂ Sn ₄ , and Mg ₂ Sn.

  Among alloy materials containing tin, tin oxide, tin-containing alloy, tin compound and the like are preferable.

  Among the above alloy materials, silicon, silicon oxide, tin, tin oxide and the like are preferable, and silicon, silicon oxide and the like are particularly preferable. An alloy type material can be used individually by 1 type or in combination of 2 or more types.

  As the solid electrolyte in the negative electrode active material layer, the same type of materials as those exemplified above as the sulfide contained in the solid electrolyte layer can be used.

  As the conductive material in the negative electrode active material layer, for example, known conductive carbon such as acetylene black can be preferably used. As the binder in the negative electrode active material layer, for example, a fluorine atom-containing resin typified by polyvinylidene fluoride (PVDF) can be preferably used.

  The thickness of the negative electrode active material layer is not particularly limited. For example, the range of 5 micrometers or more and 500 micrometers or less can be illustrated.

[Positive electrode active material layer]
The positive electrode active material layer in the all solid lithium ion secondary battery of the present embodiment can contain at least a positive electrode active material, preferably further contains a solid electrolyte, and further contains a conductive material, a binder, and the like as desired. May be.

  The positive electrode active material contained in the positive electrode active material layer in the all-solid-state lithium ion secondary battery of the present embodiment may be a known material, for example, lithium nickelate, lithium nickel cobalt aluminum oxide, nickel cobalt lithium manganate. Etc., and it is preferable to use one or more selected from these.

  As the solid electrolyte in the positive electrode active material layer, the same type of materials as those exemplified above as the sulfide contained in the solid electrolyte layer can be used.

  As the conductive material in the positive electrode active material layer, for example, conductive carbon, other carbon materials, metal materials, and the like can be used.

  As the binder in the positive electrode active material layer, for example, a fluorine atom-containing resin typified by polyvinylidene fluoride (PVDF) can be preferably used.

  The thickness of the positive electrode active material layer is not particularly limited. For example, the range of 5 micrometers or more and 500 micrometers or less can be illustrated.

<Manufacture of all-solid-state lithium ion secondary batteries>
The all-solid-state lithium ion secondary battery of the present embodiment may be manufactured by any method as long as it has the above configuration. However, for example, the following production methods can be exemplified.

Preparing a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer, respectively (step 1);
A negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer are laminated to obtain a laminate (step 2), and the laminate is pressed. (Step 3)
A method for producing an all-solid-state lithium ion secondary battery.

[Step 1]
In Step 1 of the method for producing an all solid lithium ion secondary battery of the present embodiment, a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer are respectively prepared. To do. The negative electrode active material layer contains an alloy material containing at least one selected from silicon and tin.

  Each of the negative electrode current collector layer and the positive electrode current collector layer is subjected, for example, to the above-described metal foil as a material constituting each current collector layer, subjected to appropriate heat treatment, and subjected to the elongation rate in the tensile test of the foil. It can be prepared by adjusting the shape to a predetermined value.

The negative electrode active material layer and the positive electrode active material layer can be obtained, for example, by pressing and molding the above-described materials or mixtures thereof as contained in each active material layer. The pressing pressure can be typically about 2.0 ton / cm ² (196 MPa), but is not limited thereto. Pressing pressure, for example, 0.5ton ^/ cm 2 (49MPa) above, 1.0ton ^/ cm 2 (98MPa) above, or 1.5 ton ^/ cm 2 can be a (147 MPa) or more,, 3.5 ton / Cm ² (343 MPa) or less, 3.0 ton / cm ² (294 MPa) or more, or 2.5 ton / cm ² (245 MPa) or less.

The solid electrolyte layer can be obtained by, for example, pressing and molding the sulfide described above as contained therein. The pressing pressure is typically about 0.1 ton / cm ² (9.8 MPa), but is not limited thereto. Pressing pressure, for ^example, be a 0.01ton / cm 2 (0.98MPa) above or 0.05ton ^/ cm 2 (4.9MPa) or more, 1.0ton ^/ cm 2 (98MPa) less or 0. 5 ton / cm ² (49 MPa) or less. This press pressure may be appropriately set by those skilled in the art in consideration of a desired filling rate, a desired thickness, and the like for the solid electrolyte layer.

[Step 2]
In step 2 of the method for producing an all solid lithium ion secondary battery of the present embodiment, the negative electrode current collector layer, the negative electrode active material layer, the solid electrolyte layer, the positive electrode active material layer, and the positive electrode current collector prepared in step 1 above. A body layer is laminated to obtain a laminate.

  In this step 2, according to the desired layer configuration in the obtained all-solid-state lithium ion secondary battery, the above layers are stacked in a predetermined order to obtain a stacked body.

[Step 3]
And in the process 3, the all-solid-state lithium ion secondary battery of this embodiment can be obtained by pressing said laminated body.

  The pressing pressure in this case can typically be about 10 MPa, for example, but is not limited thereto. For example, it can be 1 MPa or more, 3 MPa or more, or 5 MPa or more, and can be 50 MPa or less, 30 MPa or less, or 20 MPa or less.

<Use of all-solid lithium ion secondary battery>
When using the all-solid-state lithium ion secondary battery of the present embodiment, it may be used after being restricted by a predetermined pressure.

<Example 1>
1. Preparation of Solid Electrolyte Li ₂ S (manufactured by Nippon Chemical Industry Co., Ltd.) 0.7656 g and P ₂ S ₅ (manufactured by Aldrich) 1.2344 g were weighed and mixed in an agate mortar for 5 minutes to obtain a mixture. 4 g of heptane was added to this mixture, mechanical milling was performed using a planetary ball mill for 40 hours, and then the mixture was allowed to stand in an argon atmosphere at 25 ° C. for 3 hours to dry to obtain a solid electrolyte.

2. Preparation of negative electrode mixture A mixture of 2.18 mg of silicon powder as a negative electrode active material, 0.14 mg of VGCF (registered trademark, manufactured by Showa Denko KK, conductive carbon) and 2.18 mg of the solid electrolyte obtained in the above 1 Used as a mixture.

3. Production of negative electrode active material layer 3.7 mg of the negative electrode mixture obtained in 2 above was pressed at a pressure of 2.0 ton / cm ² (196 MPa) to obtain a negative electrode active material layer.

4). Preparation of Positive Electrode Mixture As the positive electrode active material, lithium nickel cobalt manganate (LiNi _3/5 Co _1/5 Mn _1/5 O ₂ ) subjected to surface treatment with LiNbO ₃ was used. A mixture of 12.03 mg of this positive electrode active material, 0.51 mg of VGCF (registered trademark), and 5.03 mg of the solid electrolyte obtained in the above 1 was used as a positive electrode mixture.

5. Production of positive electrode active material layer A positive electrode active material layer was obtained by pressing 12.3 mg of the positive electrode mixture obtained in 4 above at a pressure of 2.0 ton / cm ² (196 MPa).

6). Production of Solid Electrolyte Layer After placing 18 mg of the solid electrolyte obtained in 1 above on a ceramic mold having an area of 1 cm ² and pressing it at a pressure of 0.1 ton / cm ² (9.8 MPa) to form a layer. The solid electrolyte layer having a filling rate of 85% was manufactured by peeling from the mold.

7). Manufacture of negative electrode current collector layer The negative electrode current collector layer was obtained by heat treating a commercially available copper foil (elongation rate: 2.2%) to adjust the elongation rate to 7.0%. .

8). Production of positive electrode current collector layer The positive electrode current collector layer was obtained by heat treating a commercially available aluminum foil (elongation rate: 2.5%) to adjust the elongation rate to 5.4%. .

9. Production of Battery Negative electrode current collector layer obtained in 7 above, negative electrode active material layer obtained in 3 above, solid electrolyte layer obtained in 6 above, positive electrode active material layer obtained in 5 above, and positive electrode obtained in 8 above The current collector layers were stacked in this order, and pressed at a pressure of 10 MPa to produce an all solid lithium ion secondary battery.

6). Measurement methods for various evaluations (1) Filling rate of solid electrolyte layer The filling rate of the solid electrolyte layer is expressed by the following formula (1).
Filling rate (%) = [{weight of solid electrolyte contained in solid electrolyte layer (g) ÷ true specific gravity of solid electrolyte (g / cm ³ )} ÷ {apparent volume of solid electrolyte layer (cm ³ )}] × 100 (1)
Calculated by

In the above mathematical formula (1), the apparent volume of the solid electrolyte layer was obtained by multiplying the ceramic mold area (1 cm ² ) by the thickness of the solid electrolyte layer. The thickness of the solid electrolyte layer is obtained by reducing the thickness of the copper foil, the negative electrode active material layer, the positive electrode active material layer, and the aluminum foil, which have been measured in advance, from the measured value of the thickness of the all solid lithium ion secondary battery. Calculated.

(2) Elongation rate of the negative electrode current collector layer The elongation rate of the negative electrode current collector layer was determined by performing a tensile test in accordance with the international industry standard IPC-TM-650 standard. Calculated.
Elongation rate (%) = Elongation at break (mm) ÷ Distance between marked lines (mm) × 100 (2)

(3) Elongation rate of positive electrode current collector layer The positive electrode current collector layer was cut into a size of length: 80 mm × width: 8 mm to obtain a test piece, and using a Shimadzu autograph, the distance between grips: 90 mm, Tensile speed: A tensile test was performed under the condition of 50 mm / min, and the above result was calculated from the above formula (2).

(4) Thickness change rate of all-solid-state lithium ion secondary battery About the obtained all-solid-state lithium ion secondary battery, the initial thickness and the thickness after a charging / discharging cycle are measured as follows, respectively and following Formula (3) The calculated value was defined as the thickness change rate. The charge / discharge cycle was performed in a state where the battery was restrained at a pressure of 20 MPa.

Thickness change rate (%) = (Thickness after charge / discharge cycle−Initial thickness) ÷ Initial thickness × 100 (3)
Initial thickness: The obtained all-solid lithium ion secondary battery was charged at a constant current and a constant voltage up to 4.4 V at 0.5 mA, and then discharged at a constant current and a constant voltage up to 2.5 V at 0.5 mA. Charging / discharging was performed. The thickness of the battery after this initial charge / discharge was measured and used as the initial thickness.
Thickness after charge / discharge cycle: One cycle of constant-current charge to 3.0 V at 3 mA after constant current charge to 4.2 V at 3 mA for the all-solid lithium ion secondary battery after the initial charge / discharge. The cycle was repeated 1,500 times. Next, the thickness of the battery in the discharge state after performing one cycle of charge / discharge under the same conditions as the initial charge / discharge was determined as the thickness after the charge / discharge cycle.

<Examples 2-12 and Comparative Examples 1-3>
The all-solid-state lithium ion secondary battery in the same manner as in Example 1 except that the filling rate of the solid electrolyte and the elongation rates of the negative electrode current collector layer and the positive electrode current collector layer were as shown in Table 1, respectively. The change rate of the thickness of the battery after the charge / discharge cycle was measured.

  The filling rate of the solid electrolyte was adjusted to be a predetermined value by changing the press pressure in the above-mentioned “6. Production of solid electrolyte layer”. The elongation rates of the negative electrode current collector layer and the positive electrode current collector layer were each adjusted by changing the heat treatment conditions.

  The results are shown in Tables 1 to 3 and FIGS.

  Table 1 and FIG. 2 show that all solid lithium ions after the charge / discharge cycle when the filling rate of the solid electrolyte layer is varied under the condition that the elongation rate of the negative electrode current collector layer and the positive electrode current collector layer is constant. It is the result of investigating the thickness change rate of a secondary battery. From these results, in the case of Comparative Example 1 in which the filling rate of the solid electrolyte layer is 90%, the rate of change in thickness of the battery after the charge / discharge cycle is large, whereas the filling rate is 85% or less. In Examples 1 to 6, it was confirmed that the rate of change in thickness was kept low.

  Table 2 and FIG. 3 show the results after charging / discharging cycles when the filling rate of the solid electrolyte layer and the elongation rate of the positive electrode current collector layer were constant and the elongation rate of the negative electrode current collector layer was varied. It is the result of investigating the thickness change rate of a solid lithium ion secondary battery. From these results, in Comparative Example 2 in which the elongation rate of the negative electrode current collector layer was 5.0%, the rate of change in thickness of the battery after the charge / discharge cycle was large, whereas the elongation rate was 7. In the case of Examples 2, 7, and 8 which were 0% or more, it was confirmed that the rate of change in thickness was kept low.

  Table 3 and FIG. 4 show that the filling rate of the solid electrolyte layer was 81% (Comparative Example 3 and Examples 10, 2, 11, and 12) or 85% (Example 9), and the negative electrode current collector layer It is the result of investigating the thickness change rate of the all-solid-state lithium ion secondary battery after a charge / discharge cycle when the elongation rate of the positive electrode current collector layer is varied under a constant elongation rate. From these results, in Comparative Example 3 in which the elongation rate of the positive electrode current collector layer was 3.5%, the rate of change in thickness of the battery after the charge / discharge cycle was large, whereas the elongation rate was 4. In the case of Examples 2 and 9 to 12 which are 0% or less, it was confirmed that the rate of change in thickness was kept low.

DESCRIPTION OF SYMBOLS 1 Negative electrode collector layer 2 Negative electrode active material layer 3 Solid electrolyte layer 4 Positive electrode active material layer 5 Positive electrode collector layer 10 All-solid-state lithium ion secondary battery

Claims (1)

An all-solid lithium ion secondary battery comprising a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order,
The negative electrode active material layer contains an alloy-based material containing at least one selected from silicon and tin,
For the solid electrolyte layer, the filling rate calculated by the following mathematical formula is 85% or less,
Filling rate (%) = [{weight of solid electrolyte layer (g) ÷ true specific gravity of solid electrolyte layer (g / cm ³ )} ÷ {apparent volume of solid electrolyte layer (cm ³ )}] × 100
The elongation percentage in the tensile test of the negative electrode current collector layer is 7.0% or more, and
An all-solid-state lithium ion secondary battery, wherein an elongation percentage in a tensile test of the positive electrode current collector layer is 4.0% or more.

Images