JP2015018777A - Method for manufacturing electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode capable of giving an electrode having improved mobility in a Li ion electrode by a simple step.SOLUTION: A method for manufacturing an electrode in which an active material and a solid electrolyte are continuously and vertically arranged in an active material layer introduces the solid electrolyte into the active material layer formed in advance.

Description

  The present invention relates to an electrode manufacturing method, and more particularly to an electrode manufacturing method that improves the mobility of Li ions in an electrode and that has a simple manufacturing process.

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, the use of non-flammable electrolytes compared to the conventional non-aqueous electrolyte type lithium batteries eliminates the need for flammable electrolytes, so the safety is high, the degree of freedom of the cell shape is high, the degree of freedom of the structure is increased, and the number of auxiliary devices Therefore, it is expected that the solid state battery will be put to practical use.

However, in order to realize the practical application of solid state batteries, various improvements such as the creation of a solid electrolyte capable of providing high capacity and high output and / or the creation of electrodes capable of realizing high electrode utilization efficiency are required. is there.
As one of the technologies for improving the battery characteristics of this solid state battery, in order to realize a low resistance that lowers the resistance when Li ions move at the interface between the electrode active material and the solid electrolyte in the electrode during charging and discharging. An electrode in which an active material and a solid electrolyte are continuously arranged vertically has been proposed.

  For example, in Patent Document 1, a mixture of a solid electrolyte material made of an amorphous polyanion compound or an amorphous phosphate compound and an electrode active material having a specific capacity lowering temperature is heated and fired in a pressurized state. An electrode manufacturing method is described. As a specific example, a schematic diagram of an electrode having an active material layer in which an active material and a solid electrolyte are continuously arranged vertically is shown in FIG.

  Furthermore, Patent Document 2 discloses that when an electrode is obtained by arranging a columnar body of an electrode active material and a columnar body of an electrode solid electrolyte alternately in a direction intersecting a plane of the solid electrolyte constituting the separator, An electrode manufacturing method is described which includes a step of forming a substance slurry and a solid electrolyte slurry adjacent to each other to form a columnar shape.

  However, since it is not recognized that the solid electrolyte is introduced into the active material layer by a conventionally known technique, the contact between the active material layer and the solid electrolyte is insufficient, and the active material layer and the solid electrolyte It has been difficult to secure sufficient contact to improve the mobility of Li ions in the electrode and to obtain an electrode by a simple manufacturing process.

JP 2009-140910 A JP 2009-181877 A

  Accordingly, an object of the present invention is to provide an electrode manufacturing method capable of providing an electrode with improved mobility within the electrode of Li ions by a simple process.

The present invention is an electrode manufacturing method in which an active material and a solid electrolyte are continuously arranged vertically in an active material layer,
Introducing a solid electrolyte into a pre-formed active material layer;
And to the method.

  ADVANTAGE OF THE INVENTION According to this invention, the electrode which improved the mobility in the electrode of Li ion can be obtained with a simple manufacturing process.

FIG. 1 is a copy of a cross-sectional SEM image of an active material layer of an electrode obtained according to an embodiment of the present invention. FIG. 2 is a copy of a cross-sectional SEM image of the active material layer of the electrode obtained in Example 1 of the present invention. FIG. 3 is a copy of a cross-sectional SEM image of the active material layer of the electrode obtained in Example 2 of the present invention. FIG. 4 is a copy of a cross-sectional SEM image of the active material layer of the electrode obtained in Example 3 of the present invention. FIG. 5 is a table showing the relationship between the stirring time for introducing the solid electrolyte into the active material layer and the ratio between the average width of the solid electrolyte layer and the average width of the active material layer in the example of the present invention. FIG. 6 is a schematic diagram showing a method for evaluating Li ion conductivity. FIG. 7 is a bar graph comparing the Li ion conductivity of electrodes obtained by the present invention and methods outside the scope of the present invention.

In particular, in the present invention, the following embodiments can be mentioned.
1) The method for producing the electrode, wherein the introduction of the solid electrolyte is performed by mixing the particles of the solid electrolyte with the active material layer without fragmentation.
2) The manufacturing method of the said electrode whose said active material layer formed in advance is a layer containing the solid electrolyte (B) which has a particle diameter smaller than the film thickness of an electrode.
3) The manufacturing method of the said electrode in which the particle | grains of the solid electrolyte in introduction | transduction of the said solid electrolyte have a particle diameter more than the film thickness of an electrode.

  In the present invention, an electrode manufacturing method in which an active material and a solid electrolyte are continuously arranged vertically in an active material layer, and it is necessary to introduce the solid electrolyte into a previously formed active material layer Thus, an electrode with improved mobility within the electrode of Li ions can be obtained by a simple manufacturing process.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the electrode obtained by the embodiment of the present invention has an active material (black) and a solid electrolyte (gray) in an active material layer with a thickness of typically about 50 μm on a current collector foil. Are continuously arranged vertically.

In other words, the electrode obtained by the embodiment of the present invention has a solid electrolyte continuously present in the active material layer in a direction perpendicular to the active material.
And the solid electrolyte which exists continuously perpendicularly | vertically as mentioned above with respect to the active material may penetrate the active material layer, and does not need to penetrate.
The width of the solid electrolyte layer continuously present in the active material layer can be, for example, about 17 μm to 100 μm in FIGS.

In the electrode, the active material layer may include not only a layer made of pure active material but also a layer rich in an active material containing a small amount of solid electrolyte, that is, an active material rich layer.
When the active material layer is a layer rich in active material (active material rich layer), as shown in FIGS. 2 to 4, the solid electrolyte is continuously arranged perpendicular to the active material layer. The average value of the layer width (that is, the average width of the solid electrolyte layer) / the average value of the width of the layer rich in the active material (that is, the average width of the active material layer) = about 0.7 to 2 may be appropriate.

The electrode is a method of manufacturing an electrode in which an active material and a solid electrolyte are continuously arranged vertically in an active material layer,
The solid electrolyte can be obtained by a solid electrode manufacturing method in which a solid electrolyte is introduced into a previously formed active material layer.
In the above method, the introduction of the solid electrolyte is preferably performed by mixing the solid electrolyte particles with the active material layer without fragmentation.
In this specification, without solidifying the particles of the solid electrolyte, not only when the particles of the solid electrolyte are not pulverized but also when they are pulverized a little, for example, about 50% or more of the particle diameter may be maintained. Is included.
In the specification, the particle diameter of the solid electrolyte particles means the length of the longest part in the particles regardless of the shape of the particles (for example, plate shape, spherical shape, columnar shape, etc.).
Moreover, in this specification, the particle diameter of particle | grains shows a secondary particle diameter.

In the above method, it is preferable that the previously formed active material layer is a layer containing a solid electrolyte having a particle diameter less than the film thickness of the electrode.
In the above method, it is preferable that the particles of the solid electrolyte introduced into the pre-formed active material layer have a particle diameter equal to or greater than the film thickness of the electrode.

  In an embodiment of the present invention, first, a solid electrolyte having a particle diameter less than the film thickness of the electrode, for example, assuming that the electrode film thickness is typically about 50 μm, a solid electrolyte having a particle diameter of less than about 50 μm; A mixer, such as an ultrasonic homogenizer, in which the active material (solid) is in the range of 2 to 100 times by mass of this solid electrolyte, for example 2 to 10 times by mass, and an inert solvent such as a hydrocarbon solvent such as heptane or hexane. Or using an ultrasonic homogenizer and a shaker in combination to form a mixture (coating paste) containing an active material layer. During this mixing, the added solid electrolyte may be fragmented.

  The embodiment of the present invention then assumes that the obtained mixture containing the pre-formed active material layer has a solid electrolyte having a particle diameter equal to or larger than the film thickness of the electrode, for example, the film thickness of the electrode is about 50 μm. A solid electrolyte having a particle size (secondary particle size) of about 50 μm or more, for example, 50 to 150 μm, for example, 50 to 100 μm, typically about 90 μm (sometimes referred to as solid electrolyte large particles). , In the range of 0.1 to 1 relative to the total mass 1 of the total solid electrolyte, such as in the range of 0.1 to 0.95, such as in the range of 0.2 to 0.7, typically 0.5. Add an amount of solid electrolyte comparable to the amount added initially. Next, the added solid electrolyte particles are mixed with the active material layer without fragmentation, for example, by mixing with a shaker, the solid electrolyte is introduced into the active material layer, and the resulting mixture is applied to the current collector foil. For example, it is performed by coating to 100 to 300 μm, typically 200 μm thickness, and drying.

When the solid electrolyte is introduced into the preformed active material layer by the above method, as shown in FIGS. 2 to 5, after adding the solid electrolyte large particles to the mixture including the preformed active material layer, The average width of the solid electrolyte layer / the average width of the active material layer is changed by changing the time of stirring and mixing by a shaker in a range of 1 minute or more, for example, in the range of 5 to 60 minutes, typically in the range of 10 to 30 minutes. The value can be varied in the range of 0.7 to 2.2.
Then, by changing the value of the average width of the solid electrolyte layer / the average width of the active material layer as described above, an electrode having high Li ion conductivity can be obtained as shown in FIG.

In an embodiment of the present invention, the active material includes lithium cobaltate (Li _x CoO ₂ ), lithium nickelate (Li _x NiO ₂ ), nickel manganese lithium cobaltate (Li _{1 + x} Ni _1/3 Mn _1/3). Co _1/3 O ₂ ), nickel lithium cobaltate (LiCo _0.3 Ni _0.7 O ₂ ), lithium manganate (Li _x Mn ₂ O ₄ ), lithium titanate (Li _4/3 Ti _5/3 O) _4), lithium manganese oxide compound _{(Li 1 + x M y Mn} 2-x-y O 4; M = Al, Mg, Fe, Cr, Co, Ni, Zn), lithium titanate _(Li x _TiO y), phosphoric acid metallic lithium _{(LiMPO 4, M = Fe,} Mn, Co, Ni), vanadium oxide _{(V 2 O} 5), molybdenum oxide (MoO3), titanium sulfide ( iS _2), lithium cobalt nitride (LiCoN), lithium silicon nitride (LiCoN), lithium metal, lithium alloy (LiM, M = Sn, Si , Al, Ge, Sb, P), lithium storage intermetallic compound ( (MgxM, M = Sn, Ge, Sb, or XySb, X = In, Cu, Mn) and their derivatives, carbon materials (C) such as graphite and hard carbon. Here, there is no clear distinction between the positive electrode active material and the negative electrode active material, and the positive and negative potentials are compared for the positive electrode and the negative potential is used for the negative electrode by comparing the charge and discharge potentials of the two types of compounds. Thus, an electrode having an arbitrary voltage can be formed.
For example, Li _x CoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , Li _x Ni _1/2 Mn _1/2 O ₂ , Li _x Ni _1/3 Co _1/3 Mn _1/3 O ₂ , Li _x [Ni _y Li _{1 / 3-2y / 3} ] O ₃ (0 ≦ x ≦ 1, 0 <y <1/2) and lithium or transition metal of these lithium transition metal oxides were substituted with other elements Lithium transition metals such as LiNiMnCoO ₂ can be mentioned as the positive electrode active material.
Moreover, carbon materials (C), such as graphite and hard carbon, are preferably used as the negative electrode active material.

Examples of the solid electrolyte include Li ₂ S—SiS ₂ , LiI—Li ₂ S—SiS ₂ , liI-li ₂ S—P ₂ S ₅ , LiI—Li ₂ S—B ₂ S ₃ , Li ₃ PO ₄ —. _{Li 2 S-Si 2 S,} Li 3 PO 4 -Li 2 S-SiS 2, LiPO 4 -Li 2 S-SiS, LiI-Li 2 S-P 2 O 5, LiI-Li 3 PO 4 -P 2 S ₅ , sulfide-type amorphous solid electrolytes such as Li ₃ PS ₄ and Li ₂ S—P ₂ S ₅ .

The Li ₂ S—P ₂ S ₅ can be obtained from lithium sulfide and diphosphorus pentasulfide and / or simple phosphorus and simple sulfur. For example, these raw materials are melt-reacted and then rapidly cooled or the raw materials are used. It can be obtained by heat-treating sulfide glass obtained by processing by a mechanical milling method. The mixing molar ratio of lithium sulfide to diphosphorus pentasulfide or simple phosphorus and simple sulfur is usually 50:50 to 80:20, preferably 60:40 to 75:25, and preferably Li ₂ S: P _2. S ₅ = 70: 30~75: is about 25 (mole ratio).

In the embodiment of the present invention, the negative electrode active material, the solid electrolyte, and a commonly used conductive agent can be used.
Examples of the conductive agent include carbon materials and metals that are difficult to be alloyed with lithium, such as aluminum and conductive polymer materials, and aluminum and carbon materials are preferable. As the carbon material, graphite, carbon black, carbon nanotube, carbon nanofiber, fullerene and the like can be used alone or in combination of two or more.

  In order to obtain a solid battery using the electrode of the solid battery obtained by the embodiment of the present invention, the electrode obtained by the embodiment of the present invention is applied as a negative electrode, a solid sulfide electrolyte is laminated, It can be produced by applying an electrode obtained by the method or an electrode other than the electrode described above.

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.
In each of the following examples, Li conductivity was measured by the method shown in the schematic diagram of FIG.

Reference example 1
1. Synthesis Li ₂ S solid electrolyte and (Nippon Chemical Industrial Co., Ltd.) _P 2 _{S 5} and (Aldrich) and LiI (Aldrich) as a starting _{material, Li 2 S0.558g, P 2 S} 5 0.900g, LiI0. 542 g was mixed for 5 minutes in an agate mortar, then 4 g of heptane was added, and ball milling was performed at a platform rotation speed of 500 rpm for 40 hours using a planetary ball mill (container: 45 ml of ZrO ₂ , ball: 53 g of ZrO ₂ φ5 mm), The solid electrolyte precursor was obtained by drying at 100 ° C.
After 0.5 g of the obtained glass sample was weighed and placed in a glass tube, and further placed in a sealed container made of SUS, heat treatment was performed at various temperatures in a desktop muffle furnace to obtain a glass ceramic electrolyte.
The weighing and synthesis were all performed in Ar gas.

Examples 1-3
2. Preparation of Electrode 2-1 Negative Electrode 1) Weighing 1100 mg of graphite (Mitsubishi Chemical Corporation), 473 mg of the obtained solid electrolyte (small particle size) and 46 mg of aluminum (High Purity Chemical) were weighed.
2) Stirring and mixing Each weighed material was dispersed in heptane and stirred and mixed using an ultrasonic homogenizer and a shaker.
3) Weighing 473 mg of the solid electrolyte was weighed. At this time, the solid electrolyte having a secondary particle diameter of 90 μm was used.
4) Mixing by stirring In order to perform only dispersion without crushing the solid electrolyte added the second time, stirring and mixing were performed using only a shaker.
The shaking time was 10 minutes (Example 1), 20 minutes (Example 2), or 30 minutes (Example 3).
5) Coating The mixture was subjected to a 200 μm GAP meter and dried to produce an electrode.

The cross-sectional SEM images measured for the obtained negative electrode are shown in FIG. 2, FIG. 3, and FIG.
Moreover, the relationship between the stirring time for introducing the solid electrolyte into the active material layer and the ratio between the average width of the solid electrolyte layer and the average width of the active material layer, obtained from FIGS. The results are shown in FIG.

2-2 Production of Positive Electrode LiNiI / 3Co1 / 3Mn1 / 3O ₂ (Nichia Corporation) 1700 mg, VGCF (Showa Denko) 51 mg, and the obtained solid electrolyte 541 mg were weighed, mixed, and coated to form a film.

3. Measurement of Li ion conductivity Between the positive electrode and the negative electrode, which are considered to be the structure of a normal battery, a target negative electrode was installed as shown in FIG. 6 with 50 mg of the obtained solid electrolyte powder sandwiched between them.
DC resistance was measured between the positive electrode (positive electrode mixture) and the negative electrode (negative electrode mixture) at an arbitrary current (for example, 1 mA / cm ² ).
Separately, a cell containing no target compound was produced, and the direct current resistance was measured at the same current.
The difference in resistance due to the presence or absence of the target compound was taken as the direct current resistance derived from the target, and the Li ion conductivity was determined. It is assumed that the target compound / separate layer (sometimes abbreviated as a separate layer) has a low junction resistance.

  The Li ion conductivity of the obtained Examples 1 and 3 is shown together with other results in FIG.

Comparative Example 1
A negative electrode was produced in the same manner as in Example 1, except that the solid electrolyte was not added at the second time, the entire amount of solid electrolyte was added at the first time, and the mixture was stirred and mixed using an ultrasonic homogenizer and a shaker. did.
The Li ion conductivity obtained using the obtained negative electrode is shown together with other results in FIG.

  From FIG. 7, it was confirmed that an electrode with improved mobility in the Li ion electrode can be easily obtained by a simple manufacturing process.

  According to the present invention, an electrode with improved mobility in the Li ion electrode can be easily obtained by a simple manufacturing process.

Claims (4)

In the active material layer, an active material and a solid electrolyte are continuously and vertically manufactured electrodes,
Introducing a solid electrolyte into a pre-formed active material layer;
And said method.   The method for producing an electrode according to claim 1, wherein the introduction of the solid electrolyte is performed by mixing the particles of the solid electrolyte with the active material layer without fragmentation.   The method for producing an electrode according to claim 1, wherein the pre-formed active material layer is a layer containing a solid electrolyte having a particle diameter less than the film thickness of the electrode.   The method for producing an electrode according to claim 2, wherein the solid electrolyte particles have a particle diameter equal to or greater than a film thickness of the electrode.