JP2024108327A - All-solid-state battery and method for manufacturing the all-solid-state battery - Google Patents

Abstract

An all-solid-state battery capable of improving reliability and a method for manufacturing the all-solid-state battery are provided.
[Solution] The battery comprises a positive electrode collector 100, a negative electrode 200, and an active material composite 310 arranged between the positive electrode collector 100 and the negative electrode 200, wherein the negative electrode 200 has silicon nanowires and a lithium film covering the surface of the silicon nanowires, and the active material composite 310 has an active material forming body 320 made of lithium cobalt oxide, and a first solid electrolyte 330 covering the periphery of the active material forming body 320.
[Selected figure] Figure 2

Description

The present invention relates to an all-solid-state battery and a method for manufacturing an all-solid-state battery.

Patent Document 1 discloses the structure of silicon nanowires and a method for producing silicon nanowires using an etching solution. Silicon nanowires are applied to energy storage devices such as solid-state lithium secondary batteries.

Patent Document 2 discloses the configuration of an electrode composite that constitutes a lithium secondary battery and a manufacturing method of the electrode composite. A lithium secondary battery can be made highly efficient and have a high capacity by manufacturing the battery by crystallizing the electrolyte from a glassy state.

Patent No. 6383412 Patent No. 6624892

However, the configuration described in Patent Document 1 has the problem that it is difficult to maximize the battery capacity and durability at the same time, because it is necessary to form a silicon nanostructure within the microstructure of the silicon alloy, and the direction and size of the nanowires are nonuniform at each crystal grain boundary. In addition, the configuration described in Patent Document 2 has the problem that the battery capacity decreases and the internal resistance increases as the battery is repeatedly charged and discharged. In other words, even if the nanowires described in Patent Document 1 are applied to the electrode composite described in Patent Document 2, it is difficult to improve durability against charging and discharging.

The all-solid-state battery comprises a positive electrode collector, a negative electrode, and an active material composite disposed between the positive electrode collector and the negative electrode, the negative electrode having a silicon nanowire and a lithium film coated on the surface of the silicon nanowire, and the active material composite having an active material forming body made of lithium cobalt oxide and a first solid electrolyte surrounding the active material forming body.

The method for manufacturing an all-solid-state battery includes the steps of forming an active material composite, forming silicon nanowires on the surface of a silicon substrate using the MACE method, forming a lithium film on the surface of the silicon nanowires to form a negative electrode, preparing a positive electrode collector, and joining the positive electrode collector, the active material composite, and the negative electrode.

FIG. 1 is a perspective view showing a configuration of an all-solid-state battery. FIG. 1 is a cross-sectional view showing a configuration of an all-solid-state battery. FIG. 2 is a perspective view showing the configuration of a silicon substrate that constitutes a negative electrode. FIG. 1 is a cross-sectional view showing a structure of a silicon nanowire. FIG. 4 is a cross-sectional view showing a configuration of an electrode composite. FIG. 2 is a perspective view showing a method for manufacturing an all-solid-state battery. 1A to 1C are cross-sectional views illustrating a method for manufacturing an all-solid-state battery. 1A to 1C are cross-sectional views illustrating a method for manufacturing an all-solid-state battery. 1A to 1C are cross-sectional views illustrating a method for manufacturing an all-solid-state battery. FIG. 2 is a perspective view showing a method for manufacturing an all-solid-state battery. FIG. 2 is a perspective view showing a method for manufacturing an all-solid-state battery. FIG. 2 is a perspective view showing a method for manufacturing an all-solid-state battery. FIG. 2 is a perspective view showing a method for manufacturing an all-solid-state battery. 1A to 1C are cross-sectional views illustrating a method for manufacturing an all-solid-state battery. 1A to 1C are cross-sectional views illustrating a method for manufacturing an all-solid-state battery. FIG. 2 is a perspective view showing a method for manufacturing an all-solid-state battery. FIG. 13 is a perspective view showing the configuration of another example of an all-solid-state battery. FIG. 13 is a perspective view showing the configuration of another example of an all-solid-state battery.

First, the configuration of the all-solid-state battery 1000 will be described with reference to FIG.

As shown in FIG. 1, the all-solid-state battery 1000 is an all-solid-state secondary battery, such as a lithium-ion battery, formed in a disk shape and used in, for example, wearable devices. Note that the all-solid-state battery 1000 is not limited to being disk-shaped, and may be a polygonal disk shape.

The all-solid-state battery 1000 has, for example, a positive electrode collector 100 and a negative electrode 200 arranged with a solid electrolyte 300 sandwiched between them. The stack of the positive electrode collector 100, the negative electrode 200, and the solid electrolyte 300 is referred to as a battery cell 1000a. The all-solid-state battery 1000 shown in FIG. 1 is configured by connecting three battery cells 1000a. The battery cell 1000a alone also functions as a battery.

The solid-state battery 1000 is constructed by covering three stacked battery cells 1000a with an aluminum laminate film 400, which is an aluminum laminate exterior material. The aluminum laminate film 400 is made of an insulating base material such as polyamide resin, with aluminum foil on the front side (the surface that will become the outer surface when packaged) and a bonding layer on the inner side (the surface that will become the inner surface when packaged).

Next, the configuration of the all-solid-state battery 1000, i.e., the battery cell 1000a, will be described in detail with reference to Figures 2 to 5.

As shown in FIG. 2, the battery cell 1000a includes a positive electrode collector 100, a negative electrode 200, and a solid electrolyte 300 disposed between the positive electrode collector 100 and the negative electrode 200.

The negative electrode 200 includes a silicon substrate 210. As shown in FIG. 3, the silicon substrate 210 includes a base material 211 made of silicon and silicon nanowires 212 arranged on one side of the base material 211. As shown in FIG. 4, the silicon nanowires 212 include silicon nanowires 212a and a lithium film 212b coated on the surface of the silicon nanowires 212a.

The solid electrolyte 300 includes an active material composite 310. The active material composite 310 includes an active material forming body 320 made of lithium cobalt oxide, and a first solid electrolyte 330 that surrounds the active material forming body 320. The first solid electrolyte 330 is, for example, lithium lanthanum zirconium niobate. In other words, the active material forming body 320 is formed in contact with the first solid electrolyte 330. The solid electrolyte 300 includes a second solid electrolyte 340 in addition to the active material composite 310.

The positive electrode current collector 100 is provided in contact with one surface (one side) 310a of the active material composite 310. In other words, the positive electrode current collector 100 is in contact with the active material forming body 320 exposed on the one surface 310a. The positive electrode current collector 100 functions as a positive electrode, with the active material forming body 320 being composed of a positive electrode active material.

The material of the positive electrode current collector 100 may be, for example, one metal (single metal) selected from the group consisting of copper (Cu), magnesium (Mg), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), indium (In), gold (Au), platinum (Pt), silver (Ag), and palladium (Pd), or an alloy containing two or more metal elements selected from this group. The positive electrode current collector 100 and the active material complex 310 are collectively referred to as the electrode complex 301 (see FIG. 5).

As shown in FIG. 5, the active material forming body 320 is a forming body formed by three-dimensionally connecting multiple active material particles 321 made of single crystals. The active material particles 321 contain an active material made of a lithium composite oxide as a transition metal oxide.

Examples of lithium double oxides include _LiCoO2 (lithium cobalt oxide), _LiNiO2 , _LiMn2O4 , _{LiNi0.5Mn1.5O4 ,} LiNi1/3Co1/3Mn1/ _{3O2 ,} Li2Mn2O3, LiNi0.8Co0.16Al0.04O2 _{, LiFePO4} , _{Li2FeP2O7 , LiMnPO4 , LiFeBO3} , _Li3V2 ( _PO4 ) ₃ , _{Li2CuO2 , LiFeF3 , Li2FeSiO4 , Li2MnSiO4 ,} and _the like.

Among these, it is preferable to contain a compound containing lithium and at least one of cobalt, manganese, and nickel as the main material, and specifically, it is preferable to contain a compound selected from the group consisting of lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel oxide, and lithium nickel cobalt aluminum oxide as the main component.

By containing such a lithium composite oxide, the active material particles 321 transfer electrons between the active material particles 321 and transfer lithium ions between the active material particles 321 and the first solid electrolyte 330, thereby functioning as an active material.

The first solid electrolyte 330 is composed of a solid electrolyte that has lithium ion conductivity and is vitrified at room temperature. The first solid electrolyte 330 is in contact with the active material forming body 320. The active material composite 310 is in contact with the negative electrode 200 on the other surface 310b side via the second solid electrolyte 340. On the other surface 310b side, the active material forming body 320 is not exposed, and the first solid electrolyte 330 is exposed alone. This makes it possible to prevent a short circuit between the active material forming body 320 and the negative electrode 200.

The second solid electrolyte 340 is disposed between the active material complex 310 and the negative electrode 200. In this manner, the active material complex 310 and the negative electrode 200 are joined via the second solid electrolyte 340, improving the adhesion between the active material complex 310 and the negative electrode 200, thereby reducing the internal resistance of the battery.

An alloy film 220 of gold (Au) and lithium (Li) is disposed at the interface of the negative electrode 200, i.e., between the silicon nanowires 212 and the solid electrolyte 300. By disposing the alloy film 220 in this manner, if gold is used as the film that functions as a catalytic metal when forming the silicon nanowires 212, it is possible to suppress partial precipitation of lithium ions and to make the precipitation of lithium ions uniform.

Next, a method for manufacturing the all-solid-state battery 1000 will be described in detail with reference to Figures 6 to 16.

In the process shown in FIG. 6, a green sheet 320A composed of a positive electrode porous body is formed, and the green sheet 320A is punched out, for example by press processing, into the shape of the porous positive electrode 320a before it becomes the active material forming body 320.

In the process shown in Figures 7 and 8, the voids in the porous positive electrode 320a are impregnated with a precursor solution 330a of the first solid electrolyte 330 in dry air in a glove box, and then the precursor solution 330a is fired and crystallized. In this way, the active material composite 310 is formed.

The material of the first solid electrolyte 330 may be, for example, the aforementioned lithium oxide containing C, Si or B, which has lithium ion conductivity, and preferably uses lithium oxide containing B (Li-B-O or a material containing the constituent elements of Li-B-O). This makes it possible to obtain a first solid electrolyte 330 with excellent ion conductivity, and also ensures that the porous positive electrode 320a is dissolved in the precursor solution 330a of the first solid electrolyte 330.

In the process shown in FIG. 9, a second solid electrolyte 340 is formed on the surface of the active material composite 310 in a vacuum using a sputtering method.

Next, we will explain the manufacturing method for the negative electrode 200.

In the process shown in FIG. 10, a gold (Au) film 230a is formed on the silicon substrate 210. Specifically, the gold film 230a is formed on the silicon substrate 210 by sputtering, vapor deposition, displacement plating, or the like. The gold film 230a functions as a catalyst film for MACE (metal-assisted chemical etching) that forms silicon nanowires 212a on the silicon substrate 210. In addition, this gold film 230a remains on the surface of the silicon nanowires 212a and the surface of the substrate 211 on the silicon nanowire 212a side even after MACE, and forms an alloy film 220 with lithium by vapor deposition of lithium (Li) on the silicon nanowires 212a, becoming the material of the alloy film 220 that functions as a film that uniforms the deposition of lithium ions during charging and discharging of the all-solid-state battery 1000.

Next, although not shown, an aluminum film is formed on the gold film 230a, and pores are formed in the aluminum film using an anodization method.

In the process shown in FIG. 11, a gold film pattern 230b having pores 230c is formed. Specifically, the gold film 230a is etched using a sputtering method using argon (Ar) with the aluminum anodized film having the pores described above as a mask. As a result, a gold film pattern 230b is formed in the gold film 230a, which reflects the shape of the pores 230c.

In the process shown in FIG. 12, MACE processing is performed to form silicon nanowires 212a. MACE processing is a simple etching method that can be performed by simply immersing the substrate in a mixture of appropriate amounts of hydrofluoric acid and hydrogen peroxide at room temperature. The length of the silicon nanowires 212a can be easily controlled by adjusting the immersion time.

By using the MACE method, it is possible to form silicon nanowires 212a with a diameter of several nm to 100 nm and a high aspect ratio of approximately 5 μm in length.

In the process shown in FIG. 13, a lithium (Li) film is formed on the surface of the silicon nanowires 212a by deposition in a vacuum of an argon (Ar) atmosphere. This completes the silicon substrate 210.

In the process shown in FIG. 14, a positive electrode current collector 100 is formed on one surface 310a of the solid electrolyte 300. Furthermore, a negative electrode 200 is joined to the other surface 310c of the solid electrolyte 300.

Specifically, the positive electrode current collector 100 prepared separately may be joined to one surface 310a of the solid electrolyte 300, or the positive electrode current collector 100 may be formed on one surface 310a of the solid electrolyte 300 using a chemical vapor deposition (CVD) method or the like.

The silicon substrate 210, i.e., the negative electrode 200, is pressure-welded to the other surface 310c of the solid electrolyte 300 via a gold-lithium alloy film 220. This completes the battery cell 1000a.

In the process shown in FIG. 15, the battery cells 1000a are stacked and connected in parallel via the lead electrodes 501, 502. Specifically, the battery cells 1000a that are stacked vertically are stacked upside down. The all-solid-state battery 1000 can obtain a voltage of about 1.5 V by using approximately 14 or more layers of battery cells 1000a.

In the process shown in FIG. 16, the stacked battery cells 1000a are packaged in an aluminum laminate film 400. This completes the all-solid-state battery 1000.

Figures 17 and 18 show a method for extracting electrodes from a battery cell 1110, a method for fixing the battery cell 1110, and a method for packaging the battery cell 1110 in an all-solid-state battery 1001, which is an example of an embodiment.

As shown in FIG. 17, the battery cells 1110, positive electrode substrate (not shown), and negative electrode substrate 1124, which are stacked and housed in the case 1130, are held by the side walls 1131, 1132, and 1133, the protrusion 1140, and the bottom (not shown) of the case 1130. The side walls 1131, 1132, and 1133 have a notch 1150, which divides the side walls 1131 and 1132.

As shown in FIG. 18, the solid-state battery 1001 is covered from above and below with two aluminum laminate films 1161 and 1162.

The aluminum laminate films 1161 and 1162 are stretchable. Therefore, the aluminum laminate film 1161 covers the upper side of the all-solid-state battery 1001 along the outer shape of the all-solid-state battery 1001, such as the side of the all-solid-state battery 1001 (the side wall of the case 1130) and the upper surface of the all-solid-state battery 1001. The aluminum laminate film 1162 covers the lower surface of the all-solid-state battery 1001. The aluminum laminate films 1161 and 1162 are integrally formed by bonding the inner surfaces of the films together in a region that protrudes in an eave-like manner from the lower surface of the all-solid-state battery 1001.

The positive electrode tab 1122a and the negative electrode tab 1124a, which function as extraction electrodes, are pulled out from between the aluminum laminate films 1161 and 1162 in the above-mentioned overhanging area. The aluminum laminate films 1161 and 1162 are in close contact with the positive electrode tab 1122a and the negative electrode tab 1124a, and are integrated in the above-mentioned overhanging area. Therefore, the all-solid-state battery 1001 is sealed by the aluminum laminate films 1161 and 1162, except for the positive electrode tab 1122a and the negative electrode tab 1124a. By packaging the all-solid-state battery 1001 with the aluminum laminate films 1161 and 1162, the effects of moisture, gas, and the like can be reduced.

As described above, the all-solid-state battery 1000 of this embodiment includes a positive electrode collector 100, a negative electrode 200, and an active material composite 310 disposed between the positive electrode collector 100 and the negative electrode 200. The negative electrode 200 includes a silicon nanowire 212a and a lithium film 212b coated on the surface of the silicon nanowire 212a. The active material composite 310 includes an active material forming body 320 made of lithium cobalt oxide and a first solid electrolyte 330 that surrounds the active material forming body 320.

According to this configuration, since the negative electrode 200 is composed of silicon nanowires 212 coated with a lithium film 212b, the stress caused by expansion and contraction generated by repeated charging and discharging can be absorbed by the silicon nanowires 212, and damage to the negative electrode 200 during charging and discharging can be suppressed. Therefore, the durability of the all-solid-state battery 1000 can be improved. In addition, since the negative electrode 200 is composed of silicon nanowires 212, it is possible to increase the surface area of the negative electrode 200, and the charging and discharging capacity can be increased. Therefore, the life of the all-solid-state battery 1000 can be extended. In addition, since the battery cell 1000a can be made small, even if the battery cells 1000a are stacked, the all-solid-state battery 1000 can be prevented from becoming large.

In addition, in the all-solid-state battery 1000 of this embodiment, the active material composite 310 is preferably joined to the negative electrode 200 via the second solid electrolyte 340. With this configuration, the active material composite 310 and the negative electrode 200 are joined via the second solid electrolyte 340, so that the adhesion between the active material composite 310 and the negative electrode 200 is improved, and the internal resistance of the all-solid-state battery 1000 can be reduced.

In addition, in the all-solid-state battery 1000 of this embodiment, it is preferable that a gold-lithium alloy film 220 is disposed at the interface of the negative electrode 200. According to this configuration, since the gold-lithium alloy film 220 is disposed, when the film that functions as the catalytic metal used in MACE is gold, it is possible to form an Au/Li alloy by vapor deposition of lithium on the silicon nanowire surface that serves as the negative electrode interface by utilizing the trace amount of gold remaining on the surface of the silicon nanowire 212, and to suppress partial precipitation of lithium ions during repeated charging and discharging of the all-solid-state battery 1000, and to uniformize the precipitation of lithium ions and further relieve stress, thereby preventing a decrease in battery capacity due to repeated charging and discharging.

In addition, the all-solid-state battery 1000 of this embodiment preferably includes a laminate in which the positive electrode collector 100, the negative electrode 200, and the active material composite 310 are stacked in order, i.e., the battery cell 1000a, and the laminate is covered with an aluminum laminate film 400. According to this configuration, since the laminate of the above configuration is covered with an aluminum laminate film 400, it can be easily handled as an all-solid-state battery 1000 having a predetermined battery capacity.

The manufacturing method of the all-solid-state battery 1000 of this embodiment includes the steps of forming an active material composite 310, forming silicon nanowires 212a on the surface of a silicon substrate 210 using the MACE method, forming a lithium film 212b on the surface of the silicon nanowires 212a to form a negative electrode 200, preparing a positive electrode collector 100, and joining the positive electrode collector 100, the active material composite 310, and the negative electrode 200.

According to this method, the negative electrode 200 is formed of silicon nanowires 212 coated with a lithium film 212b, so that the stress caused by expansion and contraction generated by charging and discharging can be absorbed by the silicon nanowires 212, and damage to the negative electrode 200 during charging and discharging can be suppressed. This improves the durability of the all-solid-state battery 1000. In addition, because the negative electrode 200 is composed of silicon nanowires 212, it is possible to increase the surface area of the negative electrode 200, and the charging and discharging capacity can be increased. This allows the life of the all-solid-state battery 1000 to be extended.

100...positive electrode current collector, 200...negative electrode, 210...silicon substrate, 211...substrate, 212...silicon nanowire, 212a...silicon nanowire, 212b...lithium film, 220...alloy film, 230a...gold film, 230b...gold film pattern, 230c...pore, 300...solid electrolyte, 301...electrode composite, 310...active material composite, 310a...one side, 310b...other side, 310c...other side, 320...active material forming body, 320a...porous positive electrode, 320A...green 321...active material particles, 330...first solid electrolyte, 330a...precursor solution, 340...second solid electrolyte, 400...aluminum laminate film, 501, 502...drawing electrode, 1000...all-solid-state battery, 1000a...battery cell, 1001...all-solid-state battery, 1110...battery cell, 1122a...positive electrode tab, 1124...negative electrode substrate, 1124a...negative electrode tab, 1130...case, 1140...projection, 1161, 1162...aluminum laminate film.

Claims (5)

A positive electrode current collector;
A negative electrode;
an active material composite disposed between the positive electrode current collector and the negative electrode;
Equipped with
The negative electrode includes a silicon nanowire and a lithium film coated on a surface of the silicon nanowire,
The active material composite includes an active material forming body made of lithium cobalt oxide, and a first solid electrolyte that surrounds the active material forming body. The all-solid-state battery according to claim 1 ,
the active material composite is joined to the negative electrode via a second solid electrolyte. The all-solid-state battery according to claim 1 ,
The all-solid-state battery further comprises a gold-lithium alloy film disposed on an interface of the negative electrode. The all-solid-state battery according to claim 1 ,
a laminate in which the positive electrode current collector, the negative electrode, and the active material composite are laminated in this order;
The laminate is covered with an aluminum laminate exterior material. forming an active material composite;
forming silicon nanowires on a surface of a silicon substrate using a MACE method;
forming a lithium film on a surface of the silicon nanowire to form a negative electrode;
preparing a positive electrode current collector;
a step of joining the positive electrode current collector, the active material composite, and the negative electrode;
The present invention relates to a method for producing an all-solid-state battery.

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