JP2017004914A - All-sold battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sulfide-based all-solid battery capable of suppressing local heat generation due to charging, short-circuit, etc.SOLUTION: Disclosed is an all-solid battery includes; a positive electrode layer and a negative electrode layer obtained by coating a mixture on one surface of each current collector foil of a positive electrode current collector foil and a negative electrode current collector foil; and a sulfide solid electrolyte layer between the positive electrode layer and the negative electrode layer. A copper foil is provided on the positive electrode current collector foil of the positive electrode layer. A positive electrode mixture, the positive electrode current collector foil and the copper foil are laminated on the positive electrode layer side in this order. The sulfide solid electrolyte layer is provided in the positive electrode mixture. The positive electrode current collector foil has a through-hole. The through-hole is filled with resin melted at a predetermined temperature.SELECTED DRAWING: None

Description

  The present invention relates to an all-solid-state battery, and more particularly to a sulfide-based all-solid battery that can suppress local heat generation due to charging, short-circuiting, or the like by using a specific structure.

In recent years, lithium batteries have been put into practical use as batteries having high voltage and high energy density. Due to the expansion of the use of lithium batteries in a wide range of fields and the demand for high performance, various studies have been conducted to further improve the performance of lithium batteries.
Among them, since the electrolyte is not used compared to the conventional non-aqueous electrolyte lithium battery, the system required for improving the safety when using the non-aqueous electrolyte can be simplified. Therefore, it is expected that the all-solid-state battery will be put to practical use because it can have many advantages such as an increased degree of freedom and a reduced number of auxiliary devices.

However, various improvements are necessary in order to realize practical use of all solid state batteries.
One of them is technical development that can suppress local heat generation of the battery due to overcharge or short circuit of the all-solid-state battery.
On the other hand, a technique that is estimated to be applicable to the technique of the all-solid battery has been proposed.

For example, Patent Document 1 includes a plurality of electrode elements including a current collector divided into a plurality of parts and an active material layer formed on the current collector, and a conductive element that connects the current collectors. A secondary battery electrode is described, and as a specific example, a secondary battery electrode having an electrolyte layer composed of a separator impregnated with a lithium salt such as LiPF ₆ is shown.

  Patent Document 2 discloses a lithium battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer between both layers, wherein at least one of the layers is ionized more than a sulfide solid electrolyte material and hydrogen. A lithium battery containing a Li ion conductive material having a hydrogen sulfide generation suppressing material containing a metal element having a small tendency is described. As a specific example, a lithium battery containing 30% by weight of copper oxide as a hydrogen sulfide generation suppressing material is described. An ion conductive material is shown.

  Furthermore, Patent Document 3 discloses an all-solid battery having a positive electrode body, a negative electrode body, and a sulfide solid electrolyte layer between the positive electrode body and the negative electrode body, and at least one of the positive electrode body and the negative electrode body. An all-solid battery is described in which the porosity of the electrode active material layer increases as it approaches the current collector interface side from the sulfide solid electrolyte layer interface side in the thickness direction of the electrode active material layer.

  However, the sulfide-based all-solid battery obtained by applying these known techniques, when the battery is overcharged and a minute short-circuit path due to lithium deposition occurs, heat is generated due to current concentration in the minute short-circuit portion. There is a fear.

JP 2010-097729 A JP 2011-113720 A JP 2012-104270 A

  Accordingly, an object of the present invention is to provide a sulfide-based all-solid-state battery that can suppress local heat generation due to charging or short-circuiting.

The present invention provides a positive electrode layer and a negative electrode layer in which a mixture is applied to one surface of each of the positive electrode current collector foil and the negative electrode current collector foil, and a sulfide solid electrolyte layer between the positive electrode layer and the negative electrode layer. An all solid state battery comprising:
Having a copper foil on the positive electrode current collector foil of the positive electrode layer,
It is laminated in the order of the positive electrode mixture, the positive electrode current collector foil and the copper foil on the positive electrode layer side,
The positive electrode mixture has a sulfide solid electrolyte,
The positive electrode current collector foil has a through hole,
The battery is characterized in that the through hole is filled with a resin that melts at a predetermined temperature.

  ADVANTAGE OF THE INVENTION According to this invention, the sulfide type all-solid-state battery which can suppress the local heat_generation | fever by charge, a short circuit, etc. can be obtained.

FIG. 1A is a cross-sectional view schematically showing an all solid state battery according to an embodiment of the present invention. FIG. 1B is a schematic cross-sectional view showing a state in which lithium deposition has occurred in the all solid state battery of the embodiment of the present invention shown in FIG. 1A. FIG. 1C is a cross-sectional view showing a state in which the reaction between Cu and the sulfide solid electrolyte occurs after lithium deposition occurs in the all solid state battery of the embodiment of the present invention shown in FIG. 1B. FIG. 1D is a cross-sectional view showing a state in which an electron conduction path is formed by growth of CuS after lithium deposition occurs in the all solid state battery of the embodiment of the present invention shown in FIG. 1C. FIG. 1E is a plan view of the positive electrode current collector foil in the all solid state battery of the embodiment of the present invention shown in FIG. 1A. FIG. 1F is a plan view of the positive electrode current collector foil showing a state in which lithium deposition occurs in the all-solid battery of the embodiment of the present invention shown in FIG. 1B and holes are generated by resin melting. FIG. 2A is a cross-sectional view schematically showing a conventional all-solid battery. FIG. 2B is a schematic cross-sectional view illustrating a state in which lithium deposition occurs in the all-solid battery according to the related art. FIG. 2C is a schematic cross-sectional view illustrating a state in which local heat generation occurs in the all-solid battery according to the related art. FIG. 3 is a graph showing the relationship between the heat generation rate and the short-circuit diameter in the all-solid-state battery. FIG. 4 is a schematic cross-sectional view of an all solid state battery manufactured in order to verify that local heat generation is suppressed by the all solid state battery according to the present invention. FIG. 5 is a graph comparing the charging behavior of the battery shown in FIG. 4 with the charging behavior of a conventional all solid state battery. FIG. 6 is a copy of a cross-sectional photograph in which the state of the battery shown in FIG. 4 before charging is observed by SEM and EDX. FIG. 7 is a copy of a cross-sectional photograph obtained by observing the state of the battery shown in FIG. 4 after charging with SEM and EDX.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As shown in FIGS. 1A and 1E, an all-solid battery 1 according to an embodiment of the present invention has a positive electrode layer in which a mixture is applied to one surface of each of the positive electrode current collector foil 2 and the negative electrode current collector foil 3. 4 and a negative electrode layer 5, and an all-solid-state battery including a sulfide solid electrolyte layer 6 between the positive electrode layer 4 and the negative electrode layer 5,
Having a copper foil 7 on the positive electrode current collector foil 2 of the positive electrode layer 4;
It is laminated in the order of the positive electrode mixture, the positive electrode current collector foil and the copper foil on the positive electrode layer side,
The positive electrode mixture has a sulfide solid electrolyte,
The positive electrode current collector foil 2 has a plurality of through holes 8;
By filling the through-hole 8 with a resin that melts at a predetermined temperature, local heat generation due to charging, short-circuiting, or the like can be prevented or suppressed.

The all-solid-state battery of the embodiment of the present invention has not been sufficiently theoretically elucidated to prevent or suppress local heat generation due to overcharge, for example, charging or short-circuiting by the all-solid-state battery of the embodiment of the present invention. It can be considered as follows using FIGS. 1A to 1F showing a mechanism of preventing or suppressing local heat generation due to.
In the all solid state battery shown in FIG. 1A of the embodiment of the present invention, as shown in FIG. 1B, when overcharge, short circuit, etc. occur and lithium precipitation occurs, the battery temperature rises and the melting temperature of the resin, for example, 80 to When the temperature reaches 140 ° C., the resin filled in the through holes in the positive electrode current collector foil is heated and melted as shown in FIG. 1E. Since the volume of the resin is reduced by melting the resin as compared with the solid resin, holes are generated as shown in FIG. 1F. As a result, as shown in FIG. 1C, the copper (Cu) on the positive electrode current collector foil and the sulfide solid electrolyte (SE) in the positive electrode mixture come into contact with each other through the generated holes, and an electrochemical reaction occurs. CuS with high electron conductivity is generated. Then, as shown in FIG. 1D, it is considered that the growth of CuS forms an electron conduction path between the solid electrolyte layer and the positive electrode current collector foil, thereby preventing or suppressing local heat generation.

On the other hand, the reason why local heat generation due to overcharging cannot be prevented or suppressed by the conventional all solid state battery is described below with reference to FIGS. 2A to 2C showing the mechanism of local heat generation due to overcharging of the conventional all solid state battery. You can think so.
In the conventional all-solid-state battery 10 shown in FIG. 2A, when overcharge, short-circuit, etc. occur and lithium is deposited as shown in FIG. 2B, local heat is generated due to a minute short-circuit caused by lithium as shown in FIG. 2C. To do. For this reason, it becomes an unstable mode.

Further, the prevention or suppression of the occurrence of local heat generation by the all solid state battery of the present invention can be explained from the relationship between the heat generation rate and the short-circuited portion diameter as follows.
Localized heating in all-solid-state cell is caused by the heat generation due to the current concentration of a micro short circuit portion, the heat generation rate ΔT is short section resistance ^{Rs = kl / πY 2/4} , the short-circuit current I = E / (Rs + Ri ), the heat generated by short circuit resistance ^{ws = I 2 Rs = E 2} Rs / (Ri + Rs) 2, when a short-circuit unit heat capacity C = cρπId ^2/4, is expressed by the following equation.
ΔT = Ws / 4.186 / C
[Where, k: specific resistance of short circuit, E: electromotive force, Ri: internal resistance, l: distance between electrode plates, d: short circuit diameter, c: specific heat, ρ: specific gravity]
Then, when the heat generation rate ΔT is taken on the vertical axis and the short-circuited part diameter d is taken on the horizontal axis, the graph of FIG. 3 is obtained.
From FIG. 3, it is understood that the smaller the diameter of the short-circuited portion, the higher the heat generation rate. Therefore, it is preferable that the diameter of the short-circuited portion is larger from the viewpoint of preventing local heat generation without considering the battery performance.
The present invention is an extension of this consideration. By giving the all-solid battery a function that causes a large short circuit in the battery, the battery performance is unexpectedly lowered as compared with the conventional all-solid battery. Thus, a sulfide-based all solid state battery capable of preventing or suppressing local heat generation can be realized.

  The all solid state battery according to the embodiment of the present invention includes a positive electrode layer and a negative electrode layer in which a mixture is applied to one surface of each of the positive electrode current collector foil and the negative electrode current collector foil, and a positive electrode layer and a negative electrode layer. A positive electrode current collector foil, a copper foil on the positive electrode current collector foil of the positive electrode layer, and a positive electrode mixture, a positive electrode current collector foil, and a copper foil are laminated in that order on the positive electrode layer side. The material has a sulfide solid electrolyte, the positive electrode current collector foil has a through hole, and the through hole is filled with a resin that melts at a predetermined temperature.

As the positive electrode active material contained in the positive electrode layer, a material capable of inserting Li, for example, _{Li (Ni a Co b Al 1} -a-b) O 2 [a, b is any number less than 1 is there. _{However, a + b ≦ 1],} Li (Ni a Co b Mn 2-a-b) O 4 [a, b is any number less than 2. However, for example, LiNi _1/2 Mn _1/2 O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _3/5 Co _1/5 Mn _1/5 O ₂ , etc. LiMn ₂ O ₄ , LiNi _1/2 Mn _3/2 O ₄ , LiNiPO ₄ , LiMnPO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , Li ₃ V ₂ (PO ₄ ) _3, etc., preferably LiCoO ₂ or LiNi _1/3 Co _1/3 Mn _1/3 O ₂ can be mentioned.

The composite material in the positive electrode layer of the embodiment of the present invention needs to contain a sulfide solid electrolyte as a solid electrolyte. As the sulfide solid electrolyte, for example, _{Li 2 S: P 2 S 5} = 50: 50~100: 0 ( mass ratio) and a way sulfide solid obtained by mechanical milling of Li ₂ S and _P 2 _{S 5} An electrolyte can be used.
In addition, a binder for binding, for example, a fluorine-containing resin such as polyvinylidene fluoride (PVDF), a butadiene-based rubber (for example, BR, SBR), or a conductive additive such as carbon such as acetylene black or ketjen black is used for the positive electrode layer. May be contained.
The thickness of the positive electrode layer is not particularly limited, but may be, for example, 0.1 to 1000 μm.

For the negative electrode layer, a material capable of inserting Li as a negative electrode active material, for example, known carbon such as graphite, preferably amorphous carbon, for example hard carbon, can be used. Moreover, the said sulfide solid electrolyte which can be applied to a positive electrode layer as a solid electrolyte can be used for a negative electrode layer.
In addition to the binder used for the negative electrode layer, for example, a fluorine-containing resin such as polyvinylidene fluoride (PVDF), butadiene rubber (for example, BR, SBR), other known binders and conductive auxiliary agents such as acetylene black And carbon such as ketjen black.
The thickness of the negative electrode layer is not particularly limited, but may be, for example, 0.1 to 1000 μm.

The sulfide solid electrolyte layer includes a sulfide solid electrolyte. As the sulfide solid electrolyte, the sulfide solid electrolyte that can be applied to the positive electrode layer and / or the negative electrode layer can be used.
The sulfide solid electrolyte layer may contain a binder, for example, a fluorine-containing resin such as polyvinylidene fluoride (PVDF), or a butadiene rubber (for example, BR or SBR).
The thickness of the sulfide solid electrolyte layer is not particularly limited, but may preferably be 0.1 to 1000 μm, particularly 0.1 to 300 μm.

As the positive electrode current collector foil, a metal foil such as an aluminum (Al) foil can be used, and as the negative electrode current collector foil, a metal foil such as a copper (Cu) foil can be used. Each of the positive electrode current collector foil and the negative electrode current collector foil may have a thickness of preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm.
A copper foil is provided on the positive electrode current collector foil of the positive electrode layer, and the positive electrode mixture, the positive electrode current collector foil, and the copper foil are laminated in this order on the positive electrode layer side. As the copper foil, a copper foil having a relatively large surface roughness can be used in consideration of adhesion at the time of lamination with the positive electrode current collector foil.
The positive electrode current collector foil needs to have a through hole. The positive electrode current collector foil has a through hole, for example, the total area of the through holes in the plan view of the positive electrode current collector foil is 0.1 to 5% of the total area of the positive electrode current collector foil (including the through holes). There may be a plurality of such ratios.

The through hole must be filled with a resin that melts at a predetermined temperature. The predetermined temperature varies depending on the battery performance required for the all-solid-state battery, but may be preferably 200 ° C. or lower and higher than 80 ° C.
Examples of the resin include polymers and oligomers such as polyolefin, polystyrene (PS), acrylonitrile-styrene resin (AS), ABS resin, polyvinyl chloride (PVC), acrylic resin (PMMA), and preferably have a melting point of 80 to What is in the range of about 140 ° C., for example, α-olefin homopolymer such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and two or more kinds of the above α-olefins are random Or block copolymer, ethylene and vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, one or more random or block copolymers of methyl methacrylate, ionomer resin, and mixtures of these polymers Is mentioned.
The positive electrode current collector foil is filled with the resin by a method known per se, such as filling a through-hole provided in a thin film with a fine powder, for example, coating a thin film provided with a through-hole with a solvent slurry containing a fine resin powder. Then, after filling, the solvent can be removed by evaporation.

  The all solid state battery can be obtained as follows. For example, a positive electrode mixture slurry containing a positive electrode active material, a sulfide solid electrolyte, a binder, and a solvent is applied to one surface of a positive electrode current collector foil in which a through hole is filled with a resin that melts at a predetermined temperature. Get a layer. On the other hand, a negative electrode mixture slurry containing a negative electrode active material, a solid electrolyte such as a sulfide solid electrolyte, a binder and a solvent is applied to one surface of the negative electrode current collector foil to obtain a negative electrode layer. A copper foil, said positive electrode layer, and negative electrode layer are laminated | stacked through sulfide solid electrolyte, and an all-solid-state battery can be obtained. The lamination can be performed by pressing at the final pressing pressure, for example, by cold isostatic pressing (CIP).

  The all solid state battery of the present invention has a sulfide solid electrolyte in the positive electrode mixture, the positive electrode current collector foil has a through hole, and the through hole is filled with a resin that melts at a predetermined temperature. Therefore, local heat generation can be prevented or suppressed without degrading the battery performance as compared with the all-solid battery of the prior art.

Examples of the present invention will be described below.
The following examples are for illustrative purposes only and are not intended to limit the invention.

Example 1
An all-solid battery for verification having the structure shown in FIG. 4 was prepared using the following materials, and a short circuit due to a reaction between Cu and a sulfide solid electrolyte (abbreviated as SE) was verified.
Copper foil (1mmφ)
Positive electrode layer (12.5mmφ)
1. 1. Positive electrode current collector foil: Al foil Positive core material: LiNi _1/3 Co _1/3 Mn _1/3 O ₂
3. 3. Solid electrolyte: sulfide solid electrolyte Binder: PVDF
5). Conductive aid: VGCF
Sulfide solid electrolyte layer (13.0mmφ)
1. 1. Solid electrolyte: sulfide solid electrolyte Binder: ABR
Negative electrode layer (13.0mmφ)
1. 1. Negative electrode current collector foil: Cu foil 2. negative electrode active material: carbon 3. Solid electrolyte: sulfide solid electrolyte Binder: PVDF

Using the obtained all-solid battery for verification, charging behavior was measured over about 10 hours.
The obtained results are shown together with the results of Comparative Example 1 in FIG.
Further, in the all-solid battery for verification, focusing on the Cu foil inserted with the positive electrode layer / SE interface, the cross-sectional photographs of the battery before and after charging are taken with a scanning electron microscope (SEM) and energy dispersive X-ray (EDX). It was measured by.
A copy of the resulting photograph is shown in FIGS. 6A (before charging) and 6B (after charging).

Comparative Example 1
The charging behavior of the conventional all solid state battery shown in FIG. 4 prepared by removing the copper foil from the all solid state battery for verification of Example 1 was measured.
The obtained results are shown together with the results of Example 1 in FIG.

From FIG. 5, it is confirmed that a short circuit occurs due to charging in the all-solid-state battery for verification in which the copper foil of Example 1 is inserted.
From FIG. 6A and FIG. 6B, in the all-solid battery for verification in which the copper foil of Example 1 was inserted, dissolution of Cu into the SE layer was not observed before charging, but dissolution of Cu into the SE layer after charging Was confirmed.
The above verification results show that according to the all solid state battery of the embodiment of the present invention, when overcharge, short circuit, etc. occur and the lithium deposition state occurs, the battery temperature rises and reaches the melting temperature of the resin. The resin filled in the through-holes in the foil is melted, and the resin is melted to generate holes. As a result, the copper (Cu) on the positive electrode current collector foil and the sulfide in the positive electrode mixture are generated through the generated holes. The solid solid electrolyte (SE) comes into contact and CuS having high electron conductivity is generated by an electrochemical reaction. And it is suggested that an electron conduction path is formed between the solid electrolyte layer and the positive electrode current collector foil by the growth of CuS, and local heat generation can be prevented or suppressed.

  According to the present invention, it is possible to provide a sulfide-based all-solid-state battery that can suppress local heat generation due to charging, short-circuiting, or the like.

DESCRIPTION OF SYMBOLS 1 All-solid-state battery of embodiment of this invention 2 Positive electrode current collection foil 3 Negative electrode current collection foil 4 Positive electrode layer 5 Negative electrode layer 6 Sulfide solid electrolyte layer 7 Copper foil 8 Through-hole 10 Conventionally known all solid state battery

Claims (1)

All-solid-state battery comprising a positive electrode layer and a negative electrode layer coated with a mixture on one surface of each of the positive electrode current collector foil and the negative electrode current collector foil, and a sulfide solid electrolyte layer between the positive electrode layer and the negative electrode layer Because
Having a copper foil on the positive electrode current collector foil of the positive electrode layer,
It is laminated in the order of the positive electrode mixture, the positive electrode current collector foil and the copper foil on the positive electrode layer side,
The positive electrode mixture has a sulfide solid electrolyte,
The positive electrode current collector foil has a through hole,
The battery, wherein the through-hole is filled with a resin that melts at a predetermined temperature.