JP2013065531A - Method of manufacturing nonaqueous electrolyte battery and nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery which includes an active material layer obtained by pressure molding an active material powder and a solid electrode powder and in which reduction of a short circuit and a discharge capacity hardly occur even if a battery is thinned by forming solid electrolyte layer by a gas phase method.SOLUTION: The nonaqueous electrolyte battery includes: a positive electrode active material layer 12 obtained by pressure molding an active material powder and a solid electrolyte powder; a negative electrode active material layer 22 obtained by pressure molding an active material powder and a solid electrolyte powder; and a solid electrolyte layer (SE layer 3) provided between the active material layers. The nonaqueous electrolyte battery includes an interface layer (negative electrode interface layer 23) consisting of only an active material formed by a gas phase method, provided on at least either between the positive electrode active material layer 12 and the SE layer 3, or between the negative electrode active material layer 22 and the SE layer 3.

Description

  The present invention provides a non-aqueous solution comprising a positive electrode active material layer and a negative electrode active material layer obtained by pressure molding an active material powder and a solid electrolyte powder, and a solid electrolyte layer interposed between these active material layers. The present invention relates to an electrolyte battery and a manufacturing method thereof.

  A nonaqueous electrolyte battery including a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between these electrode layers is used as a power source on the premise that charging and discharging are repeated. The electrode layer included in the battery further includes a current collector having a current collecting function and an active material layer containing an active material. Among such non-aqueous electrolyte batteries, in particular, a non-aqueous electrolyte battery that charges and discharges by movement of Li ions between the positive and negative electrode bodies has a high discharge capacity while being small.

  In the non-aqueous electrolyte battery described above, it has been proposed to make the electrolyte layer solid in order to suppress a short circuit between the positive electrode and the negative electrode caused by dendrites. For example, Patent Document 1 discloses a nonaqueous electrolyte battery including a solid electrolyte layer obtained by pressure-molding sulfide solid electrolyte powder. Moreover, in the nonaqueous electrolyte battery of this patent document 1, the active material layer is formed by press-molding the active material powder and the sulfide solid electrolyte powder, thereby improving the discharge capacity of the battery.

JP 2009-238636 A

  In recent years, electric devices have been reduced in size and thickness, and it is desired that non-aqueous electrolyte batteries serving as power sources for the electric devices be also reduced in size and thickness. However, the non-aqueous electrolyte battery of Patent Document 1 is difficult to reduce in thickness because all of its constituent elements are obtained by pressure-molding powder.

  Therefore, in a non-aqueous electrolyte battery including an active material layer obtained by pressure molding an active material powder and a solid electrolyte powder, the solid electrolyte layer is formed by a vapor phase method, and the solid electrolyte layer is thinned. It has been studied to achieve a thin battery. However, as a result of the study by the present inventors, it has been found that a solid electrolyte layer formed by a vapor phase method may cause a short circuit or a reduction in discharge capacity.

  The present invention has been made in view of the above circumstances, and one of its purposes is a solid electrolyte in a non-aqueous electrolyte battery including an active material layer obtained by pressure molding an active material powder and a solid electrolyte powder. It is an object of the present invention to provide a non-aqueous electrolyte battery that is unlikely to cause a short circuit or a reduction in discharge capacity even when the battery is thinned by forming a layer by a vapor phase method, and a method for manufacturing the same.

  As a result of the inventor's investigation of the above problems, in a battery including an active material layer obtained by pressure molding, an in-plane distribution of current occurs, and the in-plane distribution of the current is short-circuited or reduced in discharge capacity. It turned out to be the cause. The cause will be described with reference to FIG.

First, as shown in FIG. 4A, positive electrode active material particles (for example, LiCoO ₂ ) are dispersed in the positive electrode active material layer 12, and negative electrode active material particles (for example, TiS) are dispersed in the negative electrode active material layer 22. ₂ ) is dispersed. Therefore, the distance between the positive electrode active material particles and the negative electrode active material particles varies, and as a result, an in-plane distribution of current occurs. Here, as shown in FIG. 4 (A), when the solid electrolyte layer (SE layer) 3 is thick (for example, 100 μm), the relative value of the difference between the distances is small, so the in-plane distribution of current is almost a problem. It is not to the extent. However, as shown in FIG. 4B, when the SE layer 3 is formed by a vapor phase method and the SE layer 3 is thinned (for example, 10 μm), the relative value of the difference between the distances increases. The in-plane distribution of current becomes large. The present invention is defined below based on the above findings.

(1) The non-aqueous electrolyte battery of the present invention includes a positive electrode active material layer and a negative electrode active material layer obtained by pressure molding an active material powder and a solid electrolyte powder, and a solid electrolyte disposed between these active material layers. A layer. This non-aqueous electrolyte battery of the present invention is composed only of an active material formed by a vapor phase method at least one of between a positive electrode active material layer and a solid electrolyte layer and between a negative electrode active material layer and a solid electrolyte layer. An interface layer is provided.

  According to the configuration of the present invention, the in-plane distribution of current can be reduced. The reason why the in-plane distribution of the current can be reduced will be described by taking, for example, a configuration in which the negative electrode interface layer 23 made of the negative electrode active material is provided between the negative electrode active material layer 22 and the SE layer 3 shown in FIG. become. As shown in FIG. 1, the presence of the negative electrode interface layer 23 allows the distance between the positive and negative active materials (that is, the negative electrode interface layer 23 made of the negative electrode active material and each positive electrode active material in the positive electrode active material layer 12). It can be seen that the variation in the distance between the substance particles) can be made smaller than in the state of FIG.

  As is apparent from the description with reference to FIG. 1, even when a positive electrode interface layer made of a positive electrode active material is formed between the positive electrode active material layer 12 and the SE layer 3, the effect of reducing the in-plane distribution of current is obtained. I understand that there is. If the in-plane distribution of current is to be made smaller, a configuration including both the positive electrode interface layer and the negative electrode interface layer may be used.

(2) As one form of the nonaqueous electrolyte battery of the present invention, an interface layer (negative electrode interface layer) can be formed only between the negative electrode active material layer and the solid electrolyte layer.

In order to reduce the in-plane distribution of current, it is preferable to provide both the positive electrode interface layer and the negative electrode interface layer. However, from the viewpoint of reducing the thickness, it is better to use one interface layer. In that case, it is preferable to employ the negative electrode interface layer rather than the positive electrode interface layer. This is because the negative electrode interface layer has better adhesion to the active material layer and the solid electrolyte layer adjacent to the interface layer than the positive electrode interface layer, and the battery performance is less likely to deteriorate due to delamination. As the positive electrode active material, an oxide such as LiCoO ₂ is often used, and as the negative electrode active material, a sulfide such as TiS ₂ is often used, and as the solid electrolyte contained in the active material layer and the solid electrolyte layer, Since sulfide is often used, if the negative electrode interface layer is made of sulfide, high adhesion can be provided between the negative electrode interface layer, the negative electrode active material layer, and the solid electrolyte layer.

(3) As one form of this invention nonaqueous electrolyte battery, it is preferable that the thickness of an interface layer is 1-10 micrometers.

  If it is the thickness of the said range, sufficient active material can be contained in an interface layer, and it can avoid that an interface layer becomes thick too much.

(4) Moreover, the manufacturing method of the nonaqueous electrolyte battery of the present invention includes a positive electrode active material layer and a negative electrode active material layer obtained by pressure molding an active material powder and a solid electrolyte powder, and between these active material layers. A non-aqueous electrolyte battery manufacturing method for manufacturing a non-aqueous electrolyte battery including: a solid electrolyte layer disposed; and including the following steps α to γ.
[Step α] A positive electrode body comprising a positive electrode active material layer and a first solid layer that becomes a part of the solid electrolyte layer is produced.
[Step β] A negative electrode body including a negative electrode active material layer and a second solid layer that becomes a part of the solid electrolyte layer is prepared.
[Step γ]... The first solid layer and the second solid layer are formed by pressing and heat-treating the positive electrode body and the negative electrode body so that the first solid layer and the second solid layer face each other. A solid electrolyte layer is formed by integration.
In the method for producing a nonaqueous electrolyte battery of the present invention, at least one of step α and step β includes a step of forming an interface layer made of only the active material by a vapor phase method between the active material layer and the solid layer. It is characterized by including.

  According to the above method for producing a nonaqueous electrolyte battery of the present invention, the nonaqueous electrolyte battery of the present invention can be produced.

  According to the configuration of the non-aqueous electrolyte battery of the present invention, it is possible to obtain a battery in which short-circuiting or reduction in discharge capacity does not easily occur even after repeated charge and discharge.

It is explanatory drawing explaining the effect of the structure of this invention. 1 is a schematic diagram of a nonaqueous electrolyte battery shown in Embodiment 1. FIG. FIG. 3 is an explanatory view illustrating a method for manufacturing the nonaqueous electrolyte battery shown in Embodiment 1. (A), (B) is explanatory drawing explaining the problem of a prior art.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Overall configuration of nonaqueous electrolyte battery>
As shown in FIG. 2, the nonaqueous electrolyte battery 100 of Embodiment 1 includes a positive electrode layer 1, a solid electrolyte layer (SE layer) 3, and a negative electrode layer 2. The positive electrode layer 1 further includes a positive electrode current collector 11 and a positive electrode active material layer 12, and the negative electrode layer 2 further includes a negative electrode current collector 21 and a negative electrode active material layer 22. The most characteristic feature of the nonaqueous electrolyte battery 100 is that only at least one of the active material is formed between the positive electrode active material layer 12 and the SE layer 3 and between the negative electrode active material layer 22 and the SE layer 3. The interface layer is provided (in FIG. 2, only the negative electrode interface layer 23 between the negative electrode active material layer 22 and the SE layer 3 is illustrated). Hereinafter, each configuration provided in the battery 100 will be described in detail.

≪Positive electrode current collector≫
As the positive electrode current collector 11, a conductive material such as Al, Ni, alloys thereof, and stainless steel can be used.

≪Positive electrode active material layer≫
The positive electrode active material layer 12 is a powder molding layer obtained by pressure molding a positive electrode active material powder and a solid electrolyte powder. The positive electrode active material layer 12 may contain a conductive additive and a binder in addition to the positive electrode active material powder and the solid electrolyte powder.

  The thickness of the positive electrode active material layer 12 may be appropriately selected depending on the required discharge capacity of the battery 100. For example, the thickness of the positive electrode active material layer 12 may be 30 to 200 μm.

As the positive electrode active material powder, a material having a layered rock salt type crystal structure, for example, Liα _X β _(1-X) O ₂ (α is one selected from Co, Ni, Mn, β is Fe, Al, A material selected from Ti, Cr, Zn, Mo, Bi, Co, Ni, and Mn, α ≠ β, and X is 0.5 or more. In particular, LiCoO ₂ is preferable for the positive electrode active material. In addition, a positive electrode active material having a spinel crystal structure and a positive electrode active material having an olivine crystal structure can also be used. The average particle diameter of each particle constituting these positive electrode active material powders is preferably 2 to 20 μm.

On the other hand, as the solid electrolyte powder, for example, a sulfide such as Li ₂ S—P ₂ S ₅ can be used. In addition, oxides such as V ₂ O ₅ can be used. The average particle diameter of each particle constituting these solid electrolyte powders is preferably 1 to 10 μm. In particular, sulfide is preferable because of its high Li ion conductivity. The sulfide may contain elements such as oxygen, germanium, and silicon.

≪Negative electrode current collector≫
As the negative electrode current collector 21, a conductive material such as Cu, Ni, Fe, Cr, Al, and alloys thereof (for example, stainless steel) can be suitably used.

≪Negative electrode active material layer≫
Similarly to the positive electrode active material layer 12, the negative electrode active material layer 22 is also a powder molding layer obtained by pressure molding a negative electrode active material powder and a solid electrolyte powder. The negative electrode active material layer 22 may also contain a conductive additive, a binder, and the like.

  The thickness of the negative electrode active material layer 22 may be appropriately selected depending on the required discharge capacity of the battery 100. For example, the thickness of the negative electrode active material layer 22 may be 30 to 200 μm.

As the negative electrode active material powder, sulfides such as TiS ₂ and FeS ₂ can be used. The average particle diameter of each particle constituting the negative electrode active material powder is preferably 2 to 20 μm.

  As the solid electrolyte powder, the same powder as that used for the positive electrode active material layer 12 can be used. The average particle diameter of each particle constituting the solid electrolyte powder is preferably 1 to 10 μm.

≪SE layer≫
The SE layer 3 is a layer made of a solid electrolyte formed by a vapor phase method. As the solid electrolyte to be used, the same material as the solid electrolyte powder used for the active material layers 12 and 22 can be used. The solid electrolytes used for the SE layer 3 and the active material layers 12 and 22 may be the same or different, but the former is preferred.

  The thickness of the SE layer 3 is preferably in the range of 1 to 20 μm. By setting the thickness of the SE layer 3 to 1 μm or more, sufficient insulation between the active material layers 12 and 22 can be secured. Moreover, the battery 100 can be made thin by setting the thickness of the SE layer 3 to 20 μm or less.

≪Interface layer≫
The interface layer is a layer formed by a vapor phase method made of only an active material, and is provided at at least one of the following positions [1] and [2].
[1] Between positive electrode active material layer 12 and SE layer 3 ... Positive electrode interface layer [2] Between negative electrode active material layer 22 and SE layer 3 ... Negative electrode interface layer * In FIG. 1, at the position [2] above Only the provided negative electrode interface layer 23 is shown.

The active material constituting the positive electrode interface layer is the same as the positive electrode active material contained in the positive electrode active material layer 12. For example, if the positive electrode active material is LiCoO ₂ , the positive electrode interface layer is also LiCoO ₂ . Similarly, the active material constituting the negative electrode interface layer 23 is the same as the negative electrode active material contained in the negative electrode active material layer 22. For example, if the negative electrode active material is TiS ₂ , the negative electrode interface layer 23 is also TiS ₂ .

  As already described with reference to FIG. 1, by providing the interface layer, the in-plane distribution of current can be reduced, and as a result, a short circuit and a reduction in discharge capacity can be suppressed. From the viewpoint of reducing the in-plane current distribution, it is preferable to provide both the positive electrode interface layer and the negative electrode interface layer 23. On the other hand, from the viewpoint of reducing the in-plane distribution of current and making the battery 100 thinner, it is preferable to provide only one of the positive electrode interface layer and the negative electrode interface layer 23. If only one of them is selected, the negative electrode interface layer 23 is preferably selected. The reason is that a typical negative electrode active material is sulfide, and a typical solid electrolyte is also sulfide. Therefore, the negative electrode interface layer 23 made of sulfide is adjacent to the negative electrode interface layer 23. This is because both the material 22 and the SE layer 3 are familiar and have high adhesion.

  The average thickness of the positive electrode interface layer and the negative electrode interface layer 23 is preferably 1 to 10 μm. By setting the thickness of the interface layer to 1 μm or more, the function as the interface layer can be sufficiently exhibited. In addition, by setting the thickness of the interface layer to 10 μm or less, it is possible to prevent the battery 100 from becoming thicker without lowering the Li ion conductivity in the thickness direction of the battery 100 by the interface layer.

<Method for producing non-aqueous electrolyte battery>
The non-aqueous electrolyte battery described above can be manufactured by a manufacturing method including the following steps (see FIG. 3).
[Step α] A positive electrode body (positive electrode layer 1) including the positive electrode active material layer 12 and the first solid layer 31 that becomes a part of the solid electrolyte layer 3 is produced.
[Step β] A negative electrode body (negative electrode layer 2) including the negative electrode active material layer 22 and the second solid layer 32 that becomes a part of the solid electrolyte layer 3 is prepared.
[Step γ] The positive electrode body (positive electrode layer 1) and the negative electrode body (negative electrode layer 2) are superposed and pressurized and heat-treated so that the first solid layer 31 and the second solid layer 32 face each other, The solid electrolyte layer 3 is formed by integrating the first solid layer 31 and the second solid layer 32.

<< Step α: Production of positive electrode body >>
When producing a positive electrode body (positive electrode layer 1), first, a positive electrode current collector 11 is placed in a mold, and a powder (positive electrode active material powder + solid electrolyte powder) as a raw material of the positive electrode active material layer 12 is placed thereon. What is necessary is just to arrange and press-mold. The positive electrode current collector 11 may be retrofitted to the positive electrode active material layer 12 after the above pressure forming.

  Next, when providing a positive electrode interface layer, a positive electrode active material is vapor-deposited on the positive electrode active material layer 12 by a vapor phase method such as a vacuum vapor deposition method or a laser ablation method. The positive electrode active material to be used is the same as the positive electrode active material included in the positive electrode active material layer 12.

  Finally, the first solid layer 31 is formed by a vapor phase method on the positive electrode active material layer 12 when the positive electrode interface layer is not provided, and on the positive electrode interface layer when the positive electrode interface layer is provided.

<< Step β: Production of negative electrode body >>
When producing a negative electrode body (negative electrode layer 2), first, a negative electrode current collector 21 is placed in a mold, and a powder (negative electrode active material powder + solid electrolyte powder) as a raw material of the negative electrode active material layer 22 is placed thereon. What is necessary is just to arrange | position and press-mold. The negative electrode current collector 21 may be retrofitted to the negative electrode active material layer 22 after the above pressure forming.

  Next, when providing the negative electrode interface layer 23, a negative electrode active material is vapor-deposited on the said negative electrode active material layer 22 by vapor phase methods, such as a vacuum evaporation method and a laser ablation method. The negative electrode active material used is the same as the negative electrode active material contained in the negative electrode active material layer 22.

  Finally, the second solid layer 32 is formed by a vapor phase method on the negative electrode active material layer 22 when the negative electrode interface layer is not provided, and on the negative electrode interface layer 23 when the negative electrode interface layer 23 is provided.

<< Step γ: Joining of positive electrode body and negative electrode body >>
A positive electrode body (positive electrode layer 1) and a negative electrode body (negative electrode layer 2) are laminated so that the first solid layer 31 and the second solid layer 32 face each other to produce a laminate. At that time, heat treatment is performed while the first solid layer 31 and the second solid layer 32 are pressed together, and the first solid layer 31 and the second solid layer 32 are integrated.

  The heat treatment conditions in the step γ vary depending on the effects of the composition of the first solid layer 31 and the second solid layer 32, but are preferably about 150 to 300 ° C. for 1 to 60 minutes. More preferable heat treatment conditions are 180 to 250 ° C. × 30 to 60 minutes.

  Although the pressure applied at the same time as the heat treatment is very small, there is an effect of promoting the integration of the first solid layer 31 and the second solid layer 32. However, the higher the pressure, the easier the integration is. However, when the pressure of the pressurization is increased, there is a possibility that defects such as cracking may occur in each layer provided in the positive electrode body (positive electrode layer 1) and the negative electrode body (negative electrode layer 2). In particular, the positive electrode active material layer 12 and the negative electrode active material layer 22 that are powder molding layers are likely to crack. Since the integration of the first solid layer 31 and the second solid layer 32 is only caused by heat treatment, a pressure of 10 to 20 MPa is sufficient.

  As described above, according to the method for manufacturing a nonaqueous electrolyte battery including the steps α to γ illustrated, the nonaqueous electrolyte battery 100 of the present invention described with reference to FIG. 2 can be manufactured.

≪Effect of nonaqueous electrolyte battery≫
The non-aqueous electrolyte battery 100 obtained through the steps described above is, for example, a non-aqueous electrolyte battery including an active material layer obtained by pressure-forming an active material powder and a solid electrolyte powder, and a solid formed by a gas phase method. A short circuit is less likely to occur than a battery including an electrolyte layer (SE layer). This is because the non-aqueous electrolyte battery 100 has an interface layer made of an active material between the active material layer and the SE layer, thereby reducing variations in the distance between the active materials between positive and negative. By reducing the variation in the distance between the positive and negative active materials, the in-plane current distribution becomes uniform, so that battery performance such as capacity characteristics is improved.

  While preparing the nonaqueous electrolyte battery 100 of FIG. 1 provided with the negative electrode interface layer 23, a conventional nonaqueous electrolyte battery not provided with the negative electrode interface layer 23 was prepared, and the battery characteristics of the two were compared.

<Invention product>
[Positive electrode body]
Positive electrode current collector 11: Al foil having a thickness of 20 μm Positive electrode active material layer 12 LiCoO _{2 having an} average particle diameter of 10 μm: Li ₂ S—P ₂ S ₅ = 70: 30 (mass%) having an average particle diameter of 4 μm; Powder molded layer / first solid layer 31 having a thickness of 100 μm. Li ₂ SP—S ₂ S ₅ film having an average thickness of 5 μm obtained by a laser ablation method [negative electrode body]
Negative electrode current collector 21: Al foil having a thickness of 20 μm Negative electrode active material layer 22: TiS _{2 having an} average particle diameter of 10 μm: Li ₂ S—P ₂ S _{5 having an} average particle diameter of 4 μm = 70: 30 (mass%); Powder molded layer / negative electrode interface layer 23 having a thickness of 100 μm: TiS ₂ film having an average thickness of 5 μm obtained by the laser ablation method, second solid layer 32, Li ₂ S- having an average thickness of 5 μm obtained by the laser ablation method P ₂ S ₅ film [Bonding conditions]
・ Pressure: 16 MPa
・ Heat treatment ... 190 ℃ × 2h

<Comparative product>
Same as the product of the present invention except that the negative electrode interface layer 23 is not provided.

<Test results>
About the produced this invention product and the comparative product, while measuring discharge capacity, the cycle test of 100 cycles was done. The conditions of the cycle test were a current density of 0.6 mA / cm ² and a cut-off voltage of 1.0 V to 2.2 V. The number of samples was 10 for each.

As a result, the average discharge capacity of the product of the present invention was 2.3 mAh / cm ² , and no sample caused a short circuit during 100 cycles. On the other hand, the average discharge capacity of the comparative product was 1.7 mAh / cm ² , and there were 3 out of 10 samples that caused a short circuit during 100 cycles.

  Note that the present invention is not limited to the above-described embodiment, and can be appropriately modified and implemented without departing from the gist of the present invention.

  The non-aqueous electrolyte battery of the present invention can be suitably used as a power source for electric devices based on repeated charge and discharge, for example, a power source for various electronic devices, and can also be expected to be used as a power source for hybrid vehicles and electric vehicles.

DESCRIPTION OF SYMBOLS 100 Nonaqueous electrolyte battery 1 Positive electrode layer 11 Positive electrode collector 12 Positive electrode active material layer 2 Negative electrode layer 21 Negative electrode collector 22 Negative electrode active material layer 23 Negative electrode interface layer 3 Solid electrolyte layer (SE layer)
31 1st solid layer 32 2nd solid layer

Claims (4)

A non-aqueous electrolyte battery comprising a positive electrode active material layer and a negative electrode active material layer obtained by pressure molding an active material powder and a solid electrolyte powder, and a solid electrolyte layer disposed between these active material layers. And
At least one of the positive electrode active material layer and the solid electrolyte layer and between the negative electrode active material layer and the solid electrolyte layer is provided with an interface layer made of only an active material formed by a vapor phase method. The nonaqueous electrolyte battery characterized by the above-mentioned.   The nonaqueous electrolyte battery according to claim 1, wherein the interface layer is formed only between the negative electrode active material layer and the solid electrolyte layer.   The non-aqueous electrolyte battery according to claim 1, wherein the interface layer has a thickness of 1 to 10 μm. Manufacturing a non-aqueous electrolyte battery comprising a positive electrode active material layer and a negative electrode active material layer obtained by pressure molding an active material powder and a solid electrolyte powder, and a solid electrolyte layer disposed between these active material layers A non-aqueous electrolyte battery manufacturing method comprising:
Producing a positive electrode body comprising the positive electrode active material layer and a first solid layer that becomes a part of the solid electrolyte layer; and
Producing a negative electrode body comprising the negative electrode active material layer and a second solid layer that is part of the solid electrolyte layer; and
The first solid layer and the second solid layer are integrated by superimposing the positive electrode body and the negative electrode body so that the first solid layer and the second solid layer face each other, and applying pressure and heat treatment. Step γ to form the solid electrolyte layer,
With
At least one of the step α and the step β includes a step of forming an interface layer made of only the active material by a vapor phase method between the active material layer and the solid layer. Method.

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