JP2009081140A - Secondary battery, and manufacturing method of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inorganic solid electrolyte secondary battery having excellent battery characteristics, and to provide a simple manufacturing method of the inorganic solid electrolyte secondary battery. <P>SOLUTION: The secondary battery is equipped with a positive electrode 1, a negative electrode 2 and an inorganic solid electrolyte 3, of which, the positive electrode 1 is constituted of a positive electrode active material layer 4 and a positive electrode current collector layer 5, the negative electrode 2 is constituted of a negative electrode active material layer 6 and a negative electrode current collector layer 7. The positive electrode current collector layer 5 or the negative electrode current collector layer 7 is a conductive metal oxide layer, and the negative electrode active material layer 6 is lithium metal or a lithium alloy, or the negative electrode active material layer is a material in which an operating potential of the negative electrode is nobler than 1.0 V to a potential of the lithium metal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a secondary battery using an inorganic solid electrolyte and a manufacturing method thereof.

  As electronic devices become smaller and lighter, there is an increasing demand for smaller and lighter batteries. As batteries that meet this demand, ultra-small and ultra-thin batteries born by the fusion of thin film technology and battery material technology are being studied. These thin batteries are expected to be mounted on power supplies such as IC cards and tags, or on LSI substrates.

  On the other hand, as a high-power secondary battery, a lithium ion secondary battery in which a lithium cobalt oxide is combined in the positive electrode, a carbon material in the negative electrode, and a solution in which a lithium salt is dissolved in a nonaqueous solvent is combined has been put into practical use. Yes. These are manufactured by various methods, but each of the positive electrode and negative electrode materials is slurried and applied, a process involving drying, a process of cutting them into a predetermined shape, a rolling process, a winding process, and an electrolyte solution. The manufacturing method including the step of injecting liquid is mainly used, leading to practical use. However, these processes and manufacturing methods have limitations in making the battery thinner and smaller.

For this reason, in order to make it smaller and thinner, lithium and carbon were used for the negative electrode, LiCoO ₂ and LiMn ₂ O ₄ were used for the positive electrode, an inorganic solid electrolyte was used for the electrolyte, and semiconductor processes such as sputtering and vapor deposition and patterning methods were introduced. Thin solid electrolyte secondary batteries have been devised. (For example, see Patent Document 1 and Patent Document 2)

  However, since such a conventional solid electrolyte battery is formed by a thin film process such as sputtering, it takes a long time to form a film, and it is difficult to form a multi-layer, resulting in a high manufacturing cost. In addition, since conventional solid electrolyte batteries use metals such as copper, aluminum, gold, and palladium as current collectors, heat treatment after film formation cannot be sufficiently performed, the crystallinity of the active material does not increase, and battery characteristics are improved. There was an inadequate problem.

JP 2000-106366 A JP 2004-127743 A

  The present invention has been made in view of such problems, and it is an object of the present invention to provide a secondary battery excellent in battery characteristics and suitable for downsizing and thinning using a simple process and a method for manufacturing the same. And

  As a result of earnest research on the form of a secondary battery that can be manufactured by a simple process without impairing battery performance, the present inventors have found that an inorganic solid electrolyte as an electrolyte, a conductive metal as a positive electrode current collector or a negative electrode current collector When applied in combination with an oxide and a specific negative electrode active material, a battery element precursor comprising a positive electrode, a negative electrode, an inorganic solid electrolyte, etc. can be sintered together to obtain a secondary battery. Compared to battery manufacturing methods using sputtering or other film-forming methods, the process and manufacturing equipment are simple and low-cost, and small batteries can be created, and each component of the resulting secondary battery has a high density. It has been found that each member exhibits sufficient ionic conductivity and conductivity, and sufficient battery characteristics can be obtained.

The secondary battery of the present invention is
A positive electrode in which a positive electrode active material layer and a positive electrode current collector layer are laminated;
A negative electrode in which a negative electrode active material layer and a negative electrode current collector layer are laminated;
An inorganic solid electrolyte containing lithium sandwiched between the positive electrode and the negative electrode,
The negative electrode active material layer uses a negative electrode active material in which the negative electrode operating potential is nobler than 1.0 V with respect to the potential of metallic lithium, and at least one of the positive electrode current collector and the negative electrode current collector is conductive. It is a metal oxide layer.

In the secondary battery of the present invention,
The conductive metal oxide is preferably an oxide of at least one element selected from Sn, In, Zn, and Ti.

In the secondary battery of the present invention,
The conductive metal oxide is preferably at least one selected from SnO ₂ , In ₂ O ₃ , ZnO, and TiO _x (0.5 ≦ x ≦ 2).

  In the secondary battery of the present invention, the negative electrode active material in which the negative electrode operating potential is nobler than 1.0 V with respect to the potential of metallic lithium is tungsten oxide, molybdenum oxide, iron sulfide, lithium iron sulfide, titanium sulfide, It is desirable that it is at least one selected from lithium titanate.

In the secondary battery of the present invention, the negative electrode active material in which the negative electrode operating potential is nobler than 1.0 V with respect to the potential of metallic lithium is Li _x FeS _y (0 ≦ x ≦ 4, 0.9 ≦ y ≦ 2.1) and at least one selected from lithium iron sulfide having a spinel structure and Li _{4 + x} Ti ₅ O ₁₂ (0 ≦ x ≦ 3) and having a spinel structure It is desirable.

The method for producing the secondary battery of the present invention includes:
A lamination step of obtaining a laminate by laminating a positive electrode current collector layer, a positive electrode active material layer, an inorganic solid electrolyte layer containing lithium, a negative electrode active material layer, and a negative electrode current collector layer;
A method for producing a secondary battery, comprising performing a sintering step of sintering the laminate in an oxidizing atmosphere,
At least one of the positive electrode current collector layer and the negative electrode current collector layer is a conductive metal oxide layer, and the negative electrode active material layer has a negative electrode operating potential of 1.0 V or more with respect to the lithium metal potential. Is also characterized by using a noble negative electrode active material.

  In the first and second secondary batteries and the first and second secondary battery manufacturing methods of the present invention, a conductive metal oxide is used for the positive electrode or the negative electrode current collector, and a specific negative electrode active material is used. That is characteristic. Since this conductive metal oxide is not altered by heating, particularly heating in an oxidizing atmosphere, the production of battery elements by sintering can be applied. Moreover, it is excellent in reversibility of occlusion / release of lithium ions by selecting a specific negative electrode active material, and the battery has a good repeated life.

  According to the present invention, it is possible to provide a secondary battery that is excellent in battery characteristics and suitable for thinning by a simple manufacturing method.

  FIG. 1 illustrates an embodiment of a first secondary battery and a second secondary battery, and this embodiment will be described below with reference to the drawings.

First, a configuration common to the first secondary battery and the second secondary battery will be described.
As shown in FIG. 1, the battery cell is formed by laminating a positive electrode 1, a negative electrode 2, and an inorganic solid electrolyte layer 3 so that a positive electrode 1 and a negative electrode 2 face each other with an inorganic solid electrolyte layer 3 therebetween. The positive electrode 1 is formed by laminating a positive electrode active material layer 4 and a positive electrode current collector layer 5, and the negative electrode 2 is formed by laminating a negative electrode active material layer 6 and a negative electrode current collector layer 7. An inorganic solid electrolyte layer 3 is sandwiched between the positive electrode 1 and the negative electrode 2. The positive electrode 1 and the negative electrode 2 are laminated with external electrodes 8 and 9 each having a lead for extracting output to the outside. Particularly suitable for thin batteries, for example, the thickness of the positive electrode active material layer 4 is 500 to 0.1 μm, more preferably 50 to 1 μm, and the thickness of the positive electrode current collector layer 5 is 500 to 0.1 μm, more preferably. 50 to 1 μm, the thickness of the inorganic solid electrolyte layer 3 is 500 to 0.1 μm, more preferably 50 to 1 μm, and the thickness of the negative electrode active material layer 6 is 500 to 0.1 μm, more preferably 50 to 1 μm. The thickness of the electric body layer 7 is 500-0.1 micrometer, More preferably, the range of 50-1 micrometer is illustrated.

The positive electrode active material layer 4 of the positive electrode 1 will be described.
As the positive electrode active material used for the positive electrode active material layer 4, various metal oxides, metal sulfides, and the like can be used. In particular, when a metal oxide is used, secondary battery sintering can be performed in an oxygen atmosphere, and the obtained secondary battery can obtain an active material with few oxygen defects and high crystallinity. Therefore, it is desirable because a battery having a high capacity close to the theoretical capacity can be manufactured.

Specific examples of the positive electrode active material include manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), and lithium nickel composite oxide. (e.g. _Li x _NiO 2), lithium cobalt composite oxide _(Li x _CoO 2), lithium nickel cobalt composite oxide (e.g., _{LiNi 1-y Co y O 2} ), lithium manganese cobalt composite oxides (e.g. LiMn _y Co _{1 -y} O _2), spinel type lithium-manganese-nickel composite oxide _{(Li x Mn 2-y Ni} y O 4), lithium phosphates having an olivine structure _{(Li x FePO 4, Li x} Fe 1-y Mn y PO _4, such as _Li x CoPO _4), iron sulfate _{(Fe 2 (SO 4) 3} ), vanadium At least one selected from such product (e.g. _V 2 _{O 5)} can be mentioned. In these chemical formulas, x and y are preferably in the range of 0-1.

More preferable positive electrode active materials include lithium manganese composite oxide (LixMn ₂ O ₄ ), lithium nickel composite oxide (Li _x NiO ₂ ), lithium cobalt composite oxide (Li _x CoO ₂ ), and lithium nickel cobalt having a high battery voltage. complex oxide _{(Li x Ni 1-y Co} y O 2), spinel type lithium-manganese-nickel composite oxide _{(Li x Mn 2-y Ni} y O 4), lithium manganese cobalt composite oxide _(Li x _Mn y Co _{1 -y} O _2), lithium iron phosphate _(Li x FePO _4), and the like. (Note that x and y are preferably in the range of 0 to 1.) These positive electrode active materials have improved crystallinity and improved battery characteristics by sintering in an oxidizing atmosphere.

The positive electrode current collector layer 5 and the negative electrode current collector layer 7 will be described.
At least one of the positive electrode current collector layer 5 and the negative electrode current collector layer 7 uses a conductive metal oxide layer. The conductive metal oxide layer refers to a layered shape in which conductive metal oxides are integrated with each other. It may be a porous body having fine pores in the layer. By applying this material, it is possible to simultaneously sinter the electrode, electrolyte and current collector, thereby increasing the crystallinity of the active material and further improving the electrical conductivity. Very suitable.

  When a conductive metal oxide is not used for either the positive electrode current collector layer 5 or the negative electrode current collector layer 7, a metal or alloy collection such as copper or nickel that does not react with lithium at the charge / discharge potential of the negative electrode Although it is possible to use an electric body, it is not preferable because high-temperature baking after film formation tends to react with the positive electrode / negative electrode active material layer and may deteriorate battery performance. It is particularly desirable to use a conductive metal oxide layer for both the positive electrode current collector layer 5 and the negative electrode current collector layer 7.

Examples of the conductive metal oxide include oxides of at least one element selected from Sn, In, Zn, and Ti. More _{specifically, SnO 2, In 2 O 3} , ZnO, TiO x (0.5 ≦ x ≦ 2) and the like. These conductive metal oxides may contain a trace element (for example, 10 at% or less) for enhancing conductivity such as Sb, Nb, Ta in the structure.

The inorganic solid electrolyte 3 will be described.
The inorganic solid electrolyte 3 is made of a material that has ionic conductivity and is so small that electronic conductivity can be ignored. The inorganic solid electrolyte 3 uses lithium, and in this secondary battery, lithium ions are movable ions. For example, Li ₃ PO ₄ , Li ₃ PO ₄ mixed with nitrogen, LiPO _4-x N _x (x is 0 <x ≦ 1), Li ₂ S—SiS ₂ , Li ₂ S—P ₂ S ₅ , Lithium ion conductive glassy solid electrolytes such as Li ₂ S—B ₂ S ₃ , and lithium ion conductive solid electrolytes obtained by doping these glasses with lithium halides such as LiI and lithium oxyacid salts such as Li ₃ PO ₄ Etc. have high lithium ion conductivity and are effective. Among them, a titanium oxide type solid electrolyte containing lithium, titanium, and oxygen, for example, Li _x La _y TiO ₃ (x is 0 <x <1, y is 0 <y <1) is fired in an oxygen atmosphere. Is preferable because it exhibits stable performance.

The external electrodes 8 and 9 will be described.
The material constituting the external electrodes 8 and 9 is not particularly limited. For example, Ag, Ag / Pd alloy, Ni plating, Cu by vapor deposition, and the like can be mentioned. Further, solder plating for mounting may be performed on the surface of the external electrode. The connection form of the external electrodes 8 and 9 is not limited to that shown in FIG. 1. The battery element including the positive electrode 1, the negative electrode 2, and the inorganic solid electrolyte 3 is covered with a resin or the like and connected to a part of the positive electrode and negative electrode A configuration in which the output is drawn to the outside by a line may be used.

Even if an inorganic material such as SiO ₂ , Al ₂ O ₃ , PbO, or MgO is mixed with the positive electrode 1 constituting the secondary battery, the negative electrode 2 described later, the inorganic solid electrolyte 3, the external electrodes 8 and 9, etc. It may also contain organic substances such as PVB and MEK.

  Regarding the shape of the secondary battery, FIG. 1 shows an example of a planar secondary battery in which a flat layered electrode and an electrolyte are stacked, but the battery shape is not limited to this. For example, a cylindrical shape, a rod shape, or the like may be used.

  Next, the negative electrode active material used for the negative electrode active material layer 6 which is not a common structure in the first secondary battery and the second secondary battery will be described. Even when a production method for producing a secondary battery by applying a negative electrode active material used in the first secondary battery and the second secondary battery to sinter battery element precursors at the same time is applied. Good battery characteristics are exhibited without deterioration of the active material characteristics.

(1) First Secondary Battery The negative electrode active material used for the negative electrode active material layer 6 in the first secondary battery uses metallic lithium or a lithium alloy. As the lithium alloy, lithium and at least one alloy selected from Sn, In, and Zn have a large capacity, so that the thickness can be reduced and the stress at the interface can be suppressed. Specific examples of the alloy composition include Li _4.4 Sn, LiIn, LiZn, and the like, and particularly Li _4.4 Sn is desirable because it has a high capacity and can be thinned.

  The negative electrode active material layer 6 made of metallic lithium or lithium alloy can be deposited at the time of initial charge after the secondary battery is assembled. A material (for example, tin oxide, indium oxide, zinc oxide) in which the conductive metal oxide which is the negative electrode current collector layer 7 reacts with lithium ions released from the positive electrode active material layer 4 or the inorganic solid electrolyte layer 3 In this case, a lithium alloy layer to be the negative electrode active material layer 6 is formed between the inorganic solid electrolyte layer 3 and the negative electrode current collector layer 7. When the conductive metal oxide that is the negative electrode current collector layer 7 is a material that does not react with lithium ions released from the positive electrode (for example, titanium oxide), the inorganic solid electrolyte layer 3 and the negative electrode current collector A metal lithium layer that becomes the negative electrode active material layer 6 is formed between the layers 7. The negative electrode active material layer 6 formed by such charging forms a good interface rich in bondability with the adjacent inorganic solid electrolyte 3 or the negative electrode current collector layer 7. As a result, an excellent battery with low interface resistance can be produced.

(2) Second Secondary Battery In the first secondary battery, the negative electrode active material used for the negative electrode active material layer 6 has an operating potential of the negative electrode 2 nobler than 1.0 V with respect to the potential of metallic lithium. A negative electrode active material is used. The potential at which the conductive metal oxide used for the negative electrode current collector 7 inserts and desorbs lithium ions is 1.0 V or less. Therefore, the conductive metal oxide of the negative electrode current collector layer 7 does not react with lithium ions at a potential at which the insertion / extraction reaction of lithium ions proceeds in the negative electrode active material layer 6. Therefore, the reaction of the conductive metal oxide in the current collector layer 7 does not hinder the electrode reaction of the negative electrode active material itself, and the repetitive life of the battery is improved as compared with the first battery.

The negative electrode active material is a material in which the operating potential of the negative electrode is nobler than 1.0 V with respect to the potential of metallic lithium, has conductivity, and has high reversibility of lithium ion insertion / extraction reactions. It is desirable to use a substance that has a small volume change upon occlusion / release of lithium ions and that does not change greatly upon heating. Specifically, tungsten oxide (for example, WO _a (1.8 <a <2.2), negative electrode operating potential 1.0 to 1.4 V), molybdenum oxide (for example, MoO _b (1.8 <b <2.2), negative electrode operating potential 1.0 to 1.4 V), Iron sulfide (for example, Fe _c S (0.9 <c <1.1), negative electrode operating potential of about 1.8 V), lithium iron sulfide (Li _x FeS _y (0 ≦ x ≦ 4, 0.9 ≦ y ≦ 2.1), negative electrode working potential of about 1.8V), titanium sulfide (eg TiS _d (1.8 <d <2.2), negative electrode operating potential 1.5 to 2.7 V), lithium titanate (for example, Li _{4 + z} Ti ₅ O ₁₂ (0 ≦ z ≦ 3), negative electrode operation) A metal oxide or metal sulfide having a potential of about 1.55 V) can be used. These may be used alone or in combination of two or more. In particular, it is preferably a composite sulfide containing lithium and iron, or a composite oxide containing lithium and titanium, and is represented by Li _x FeS _y (0 ≦ x ≦ 4, 0.9 ≦ y ≦ 2.1). Iron sulfide (negative electrode operating potential of about 1.8 V) or lithium titanate represented by the chemical formula Li _{4 + x} Ti ₅ O ₁₂ (0 ≦ x ≦ 3) and having a spinel structure (negative electrode operating potential of about 1.55 V) This is desirable because the amount of occlusion of lithium ions is large and the battery capacity is increased.

  By adopting the configuration of the first and second secondary batteries as described above, a manufacturing process in which the positive electrode, the negative electrode, and the inorganic solid electrolyte are sintered together can be adopted. For example, the following simple process Thus, an inorganic solid electrolyte secondary battery can be completed.

  Next, the manufacturing method of the 1st, 2nd secondary battery is demonstrated using FIG. FIG. 2 is a schematic cross-sectional view showing an embodiment of a secondary battery manufacturing process.

  In FIG. 2, for example, an inorganic solid electrolyte layer 3, a positive electrode active material layer 4, a positive electrode current collector layer 5, a negative electrode active material layer 6, and a negative electrode current collector layer 7 are prepared on a carrier sheet 10. However, it is not necessary to prepare the negative electrode active material layer 6 in advance in the case of a secondary battery formed by depositing the negative electrode active material layer by the initial charge in the subsequent process.

Each layer is formed by, for example, using a constituent material of each member as a binder (for example, polyvinylidene fluoride,
This can be done by applying a slurry kneaded with styrene-butadiene rubber or the like and a solvent (N-methylpyrrolidone, water, etc.) to the required thickness by screen printing or doctor blade method, and then removing the carrier sheet. it can. It is desirable that the positive electrode current collector layer 5 and the negative electrode active material layer 6 made of a conductive metal oxide do not contain a material such as a metal that forms an insulating layer by oxidation or be deposited on the surface.

  If the materials constituting each layer are not compatible with each other, for example, the positive electrode active material layer 4 and the positive electrode current collector layer 5 are sequentially stacked on the same carrier sheet. You may laminate and form on top. Further, all of the positive electrode active material layer 4, the positive electrode current collector layer 5, the negative electrode active material layer 6 (not necessary when the negative electrode active material layer is formed by initial charging), the negative electrode current collector layer 7, and the inorganic solid electrolyte 3 are all included. It is also possible to sequentially laminate the members in the slurry state by applying a screen printing method or the like.

  Next, after removing the carrier sheet from each dried layer, the solid electrolyte layer 3 is sandwiched between the positive active material layer 4 and the negative active material layer 6, and the positive electrode current collector layer 5, the negative electrode active material layer are disposed outside the positive electrode active material layer 4. The battery element precursor is formed by stacking so that the negative electrode current collector layer 7 is positioned outside the material layer 6. At this time, it is desirable to perform it while thermocompression bonding. Further, the battery element precursor is put in a predetermined jig for integrating the layers and subjected to a hydrostatic pressure treatment. Then, dicing is performed.

  Further, the battery element precursor is sintered at a high temperature under a temperature condition of 500 ° C. or higher and 1500 ° C. or lower, desirably 700 ° C. or higher and 900 ° C. or lower. The atmosphere during sintering is an oxidizing atmosphere because an oxide is used as a material. For example, the oxygen-containing atmosphere is good, and it is most convenient to carry out in an air atmosphere. However, depending on the raw material, there is no problem even if it is carried out by adjusting various atmospheres for the purpose of adjusting the oxidation-reduction reaction. The firing time is desirably in the range of 0.1 to 10 hours.

  Next, the external electrodes 8 and 9 connected to the positive electrode current collector layer 5 and the negative electrode current collector layer 7 are dried by bonding metal terminals to each other with a conductive paste or the like, and then coating the exterior with a resin coating by dipping or the like. Then, it can be cured to make a secondary battery.

  When the negative electrode active material layer 6 is formed by initial charging, the negative electrode active material layer 6 is deposited between the solid electrolyte layer 3 and the negative electrode current collector layer 7 by performing a charging step thereafter.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples as long as the gist of the invention is not exceeded.

Example 1
A secondary battery was prepared by the following procedure. FIG. 1 is a schematic cross-sectional view showing the structure of the secondary battery, and FIG.

<Preparation of inorganic solid electrolyte layer>
Inorganic solid lanthanum titanate lithium as an electrolyte _{(Li x} La y TiO ₃₎ powder 95 wt%, added to and mixed with polyvinylidene fluoride (PVdF) were added 5% by weight N-methylpyrrolidone (NMP) as a slurry, the slurry The inorganic solid electrolyte layer 3 was formed on the carrier sheet 10 by applying and drying on the carrier sheet 10.

<Preparation of positive electrode / negative electrode current collector layer>
Antimony-doped tin oxide (SnO ₂ ) powder 95% by weight and polyvinylidene fluoride (PVdF) 5% by weight are added to N-methylpyrrolidone (NMP) and mixed to form a slurry. Application and drying were performed to prepare a positive electrode current collector layer 5 and a negative electrode current collector layer 7 on the carrier sheet 10.

<Preparation of positive electrode active material layer>
As a positive electrode active material, 95% by weight of lithium cobaltate (LiCoO ₂ ) powder and 5% by weight of polyvinylidene fluoride (PVdF) are added to N-methylpyrrolidone (NMP) to form a slurry, and this slurry is applied onto a carrier sheet. Then, the positive electrode active material layer 4 was formed on the carrier sheet 10.

  A positive electrode current collector layer 5, a positive electrode active material layer 4, an inorganic solid electrolyte layer 3, and a negative electrode current collector layer 6 made of these constituent members are sequentially laminated to form a battery element precursor, which is then heated at 900 ° C. in an oxygen stream. Baked for 1 hour.

  The external electrodes 8 and 9 connected to the positive electrode current collector 5 and the negative electrode current collector 7 of the obtained battery element were attached, respectively, and then charged to 4.1 V to complete an inorganic solid electrolyte secondary battery.

  The completed battery was cut perpendicularly to the laminated surface and subjected to SEM-EDX analysis and XRD analysis, and as a result, Li-- which became the negative electrode active material layer 6 between the negative electrode current collector sheet 7 and the inorganic solid electrolyte layer 3 was obtained. The presence of the Sn alloy layer was confirmed.

(Example 2)
A battery similar to that of Example 1 was prepared, except that indium oxide (In ₂ O ₃ ) was used as the positive electrode and negative electrode current collector layer material.

  The completed battery was cut perpendicularly to the laminated surface and subjected to SEM-EDX analysis and XRD analysis, and as a result, Li-- which became the negative electrode active material layer 6 between the negative electrode current collector sheet 7 and the inorganic solid electrolyte layer 3 was obtained. The presence of the In alloy layer was confirmed.

(Example 3)
A battery similar to that of Example 1 was fabricated in addition to using zinc oxide (ZnO) as the positive electrode and negative electrode current collector layers.

  The completed battery was cut perpendicularly to the laminated surface and subjected to SEM-EDX analysis and XRD analysis, and as a result, Li-- which became the negative electrode active material layer 6 between the negative electrode current collector sheet 7 and the inorganic solid electrolyte layer 3 was obtained. The presence of the Zn alloy layer was confirmed.

Example 4
A battery similar to that of Example 1 was fabricated except that niobium-doped titanium oxide (TiO ₂ ) was used as the positive electrode and the negative electrode current collector layer.

  As a result of cutting the completed battery perpendicular to the laminated surface and performing SEM-EDX analysis and XRD analysis, the presence of a Li metal layer was confirmed between the negative electrode current collector layer and the inorganic solid electrolyte layer.

(Example 5)
As the positive electrode current collector layer 5, the positive electrode active material layer 4, the inorganic solid electrolyte layer 3, and the negative electrode current collector 7, the same materials as in Example 1 were used, and the negative electrode active material layer 6 was prepared as follows. The positive electrode current collector layer 5, the positive electrode active material layer 4, the inorganic solid electrolyte layer 3, the negative electrode active material layer 6, and the negative electrode current collector 6 layer are sequentially laminated to form a battery element precursor, Baked at 900 ° C. for 1 hour.

  After attaching the external electrodes 8 and 9 connected to the positive electrode current collector 5 and the negative electrode current collector 7 of the obtained battery element, respectively, the battery was charged to 2.8 V to complete an inorganic solid electrolyte secondary battery.

<Creation of negative electrode active material layer>
As a negative electrode active material, 95% by weight of lithium titanate (Li ₄ Ti ₅ O ₁₂ ) powder and ₅ % by weight of polyvinylidene fluoride (PVdF) are added to N-methylpyrrolidone (NMP) and mixed to form a slurry. It was applied and dried.

(Example 6)
A battery was prepared in the same manner as in Example 5 except that indium oxide (In ₂ O ₃ ) was used as the positive electrode and negative electrode current collector layer material.

(Example 7)
A battery was prepared in the same manner as in Example 5 except that zinc oxide (ZnO) was used as the positive electrode and negative electrode current collector layer material.

(Example 8)
A battery was prepared in the same manner as in Example 5 except that niobium-doped titanium oxide (TiO ₂ ) was used as the positive electrode and negative electrode current collector layer material.

Example 9
A battery was prepared in the same manner as in Example 5 except that iron sulfide (FeS) was used as the negative electrode active material.

(Example 10)
A battery was prepared in the same manner as in Example 5 except that titanium sulfide (TiS ₂ ) was used as the negative electrode active material.

(Example 11)
A battery was prepared in the same manner as in Example 5 except that tungsten oxide (WO ₂ ) was used as the negative electrode active material.

(Comparative Example 1)
An aluminum foil was used as the positive electrode current collector layer 5, a copper foil was used as the negative electrode current collector layer 7, and a negative electrode active material layer 6 was formed on the carrier sheet 10 using graphite as the negative electrode active material to produce a battery element. Thereafter, a battery similar to that of Example 1 was produced except that the negative electrode active material layer 6 was formed by sintering.

(Comparative Example 2)
An aluminum foil is used as the positive electrode current collector layer 5, a copper foil is used as the negative electrode current collector layer 7, and a negative electrode active material layer 6 is formed on the carrier sheet 10 using graphite as the negative electrode active material. After the production, a battery similar to Example 1 was produced except that the negative electrode active material layer 6 was formed by sintering in an argon atmosphere.

(Comparative Example 3)
The negative electrode active material layer 6 was formed on the carrier sheet 10 using graphite as the negative electrode active material to prepare the battery element precursor, and then the same as in Example 1 except that the negative electrode active material layer 6 was formed by sintering. A battery was prepared.

(Comparative Example 4)
A battery was prepared in the same manner as in Example 1 except that graphite was used as the negative electrode current collector layer 7 and sintering was performed in an argon atmosphere.

(Comparative Example 5)
A battery was prepared in the same manner as in Example 1 except that aluminum foil was used as the positive electrode current collector layer 5 and copper foil was used as the negative electrode current collector layer 7.

  Table 1 shows the results of measuring the battery capacities of the completed batteries of Examples 1 to 11 and Comparative Examples 1 to 5. The positive electrode active material used for each battery is the same, and since the same amount is applied, the battery capacity should be essentially the same. However, Comparative Examples 1 to 4 were found to have a significantly smaller battery capacity than Example 1.

  As a result of disassembling and analyzing the battery whose capacity was confirmed, in the battery of Comparative Example 1, the current collector and the graphite as the negative electrode active material were oxidized, and various deteriorated layers were formed at the interface. It was thought that the generation of this altered phase deteriorated the battery characteristics.

  In the battery of Comparative Example 2, it was found that the oxidation of graphite as the current collector and the negative electrode active material was reduced, but the crystallinity of lithium cobaltate as the positive electrode active material was lowered. It was thought that firing in a reducing atmosphere reduced crystallinity and battery performance.

  In the battery of Comparative Example 3, oxidation of graphite as the negative electrode active material was observed as in Comparative Example 1, and in the battery of Comparative Example 4, the crystallinity of the positive electrode active material was decreased as in Comparative Example 2, and the battery performance was deteriorated. I found out that

  In the battery of Comparative Example 5, the oxidation of aluminum and copper as current collectors was confirmed, and it was found that the collapse of the current collecting layer lowered the battery performance.

  The results of measuring the cycle life of the batteries of Examples 1 to 11 are also shown in Table 1 below. The cycle life test is performed at 20 ° C., charging current is 1 C, discharging current is 1 C. For the batteries of Examples 1 to 4, the charging time is 3 hours, the charging and discharging end voltages are 4.1 V and 3 V, and the charging and discharging cycle is repeated. The capacity retention rate was measured. Regarding the batteries of Examples 5 to 11, the capacity retention rate was measured by repeating the charge and discharge cycles with a charge time of 3 hours and charge and discharge end voltages of 2.8 V and 1.5 V.

1 is a schematic cross-sectional view of a secondary battery according to the present invention. The schematic sectional drawing which shows the manufacturing method of the secondary battery concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Inorganic solid electrolyte layer 4 Positive electrode active material layer 5 Positive electrode collector layer 6 Negative electrode active material layer 7 Negative electrode collector layer 8 Positive electrode external electrode 9 Negative electrode external electrode

Claims (6)

A positive electrode in which a positive electrode active material layer and a positive electrode current collector layer are laminated;
A negative electrode in which a negative electrode active material layer and a negative electrode current collector layer are laminated;
An inorganic solid electrolyte containing lithium sandwiched between the positive electrode and the negative electrode,
The negative electrode active material layer uses a negative electrode active material in which the negative electrode operating potential is nobler than 1.0 V with respect to the potential of metallic lithium, and at least one of the positive electrode current collector and the negative electrode current collector is conductive. A secondary battery comprising a metal oxide layer.   2. The secondary battery according to claim 1, wherein the conductive metal oxide is an oxide of at least one element selected from Sn, In, Zn, and Ti. _{2. The} secondary battery according to claim 1, wherein the conductive metal oxide is at least one selected from SnO ₂ , In ₂ O ₃ , ZnO, and TiO _x (0.5 ≦ x ≦ 2).   The negative electrode active material having a negative electrode operating potential nobler than 1.0 V with respect to the potential of metallic lithium is at least selected from tungsten oxide, molybdenum oxide, iron sulfide, lithium iron sulfide, titanium sulfide, and lithium titanate. 2. The secondary battery according to claim 1, wherein the secondary battery is one type. The negative electrode active material in which the negative electrode operating potential is nobler than 1.0 V with respect to the potential of metallic lithium is represented by Li _x FeS _y (0 ≦ x ≦ 4, 0.9 ≦ y ≦ 2.1). 2. The lithium iron sulfide having a spinel structure and at least one selected from lithium titanate represented by Li _{4 + x} Ti ₅ O ₁₂ (0 ≦ x ≦ 3) and having a spinel structure. The secondary battery as described. A lamination step of obtaining a laminate by laminating a positive electrode current collector layer, a positive electrode active material layer, an inorganic solid electrolyte layer containing lithium, a negative electrode active material layer, and a negative electrode current collector layer;
A method for producing a secondary battery, comprising performing a sintering step of sintering the laminate in an oxidizing atmosphere,
At least one of the positive electrode current collector layer and the negative electrode current collector layer is a conductive metal oxide layer, and the negative electrode active material layer has a negative electrode operating potential of 1.0 V or more with respect to the lithium metal potential. A method for producing a secondary battery, comprising using a noble negative electrode active material.

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