JP2019061867A - Lithium battery, method of manufacturing lithium battery, and electronic apparatus - Google Patents

Abstract

To provide a lithium battery in which growth of lithium dendrites on a negative electrode side is suppressed and deviation in internal resistance is reduced and which has excellent charge and discharge characteristics and also to provide a method of manufacturing the lithium battery and an electronic apparatus equipped with the lithium battery.SOLUTION: A lithium battery 100 includes; a composite body 10 functioning as a positive electrode containing lithium; a negative electrode 30 containing lithium; an electrolyte layer 20 which is provided between the composite body 10 and the negative electrode 30 and composed of a first electrolyte 12; and a second electrolyte 22 containing iodine provided between the electrolyte layer 20 and the negative electrode 30. Ion conductivity of the second electrolyte 22 is smaller than that of the first electrolyte 12.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lithium battery, a method of manufacturing a lithium battery, and an electronic device.

  BACKGROUND In recent years, lithium batteries (including primary batteries and secondary batteries) have been used as power supplies for many electronic devices including portable information devices. A lithium battery comprises a positive electrode, a negative electrode, and an electrolyte layer disposed between these layers, which mediates lithium ion conduction while maintaining electrical insulation. In recent years, the energy density of lithium batteries has dramatically increased, but at the same time, the danger of smoke and ignition of the electrolyte has also increased. Therefore, there is a need for a safe lithium battery in which the organic electrolyte used for the electrolyte is nonflammable.

  For example, Patent Document 1 discloses a method of manufacturing an electrode complex which is suitably used for a lithium battery and can be made into a high power and high capacity lithium battery. In the method of producing an electrode complex of Patent Document 1, a forming material containing particulate lithium double oxide is compressed and molded, and heat treatment is performed at a temperature of 850 ° C. or higher and less than the melting point of the lithium double oxide. A step of obtaining a porous active material molded body, a liquid material containing a forming material of the inorganic solid electrolyte is applied to the surface of the active material molded body including the inside of the pores of the active material molded body and heat treated It has the process of forming a layer, and the process of joining a current collection object to the active material molded object exposed from a solid electrolyte layer.

  Further, Patent Document 1 shows an example of a lithium battery using an electrode complex as a positive electrode, and describes that metal lithium (Li) is selected as a forming material of an electrode functioning as a negative electrode.

JP, 2014-154236, A

  As disclosed in Patent Document 1 above, in a lithium battery using metal lithium as a negative electrode, metal lithium is deposited in a portion having a lower internal resistance than other portions during charging or in a concave portion or a convex portion on the negative electrode forming surface So-called dendrites may occur. When dendrite grows, the positive electrode and the negative electrode may be short-circuited inside the battery, or the interface between the solid electrolyte layer and the negative electrode may have a high resistance. In addition, when the lithium battery is discharged, a local reaction proceeds in the portion where the dendrite has grown, and thus the discharge capacity may be substantially reduced.

  In the embodiment of the method of manufacturing an electrode assembly shown in Patent Document 1, it is described that the negative electrode forming surface is polished and flattened. According to this, it is considered that the growth of dendrite is suppressed by flattening the negative electrode formation surface, but, on the other hand, the active material inside the solid electrolyte layer or the solid electrolyte layer and the positive electrode side is polished by polishing. There is a possibility that a crack may be generated at the interface between them and the internal resistance may become uneven. In other words, there has been a problem that a lithium battery or a method of manufacturing a lithium battery capable of reducing defects due to the growth of dendrite is required.

  The present invention has been made to solve at least a part of the above-described problems, and can be realized as the following modes or application examples.

  Application Example A lithium battery according to this application example includes a positive electrode containing lithium, a negative electrode containing lithium, an electrolyte layer provided between the positive electrode and the negative electrode and made of a first electrolyte, and the electrolyte layer. And a second electrolyte containing iodine provided between the anode and the negative electrode, wherein the ion conductivity of the second electrolyte is smaller than the ion conductivity of the first electrolyte.

  According to this application example, the second electrolyte containing iodine is present at the interface between the electrolyte layer and the negative electrode. Since the ion conductivity of the second electrolyte is lower than that of the first electrolyte, lithium, which is an active material, is deposited at a portion where the internal resistance on the negative electrode side is low at the time of the first charge. That is, lithium is deposited unevenly on the negative electrode side. In addition, a part of the lithium ion conducted reacts with iodine contained in the second electrolyte, and lithium iodide or a lithium iodide analog is produced on the negative electrode side. On the other hand, at the time of discharge, when the battery reaction starts from the portion where lithium is deposited nonuniformly, and the volume of lithium on the negative electrode side decreases, lithium iodide from lithium iodide or lithium iodide analogous substance in contact with nonuniformly deposited lithium Release begins and resistance increases. Therefore, in the interface between the electrolyte layer and the negative electrode, the portion where lithium is deposited unevenly is low and the internal resistance is made uniform, so that lithium can be produced even at the portion where lithium deposition did not occur on the negative electrode side. Discharge or discharge is initiated. In the next charging, charging is started from the state where the internal resistance is uniformed, so even if the interface between the electrolyte layer and the negative electrode is not flat, uneven precipitation of lithium is eliminated and generation of dendrite is suppressed. Be done. That is, the variation in internal resistance and the decrease in discharge capacity due to the growth of lithium dendrite are improved, and a lithium battery having excellent charge and discharge characteristics can be provided.

In the lithium battery described in the application example, the film thickness of the second electrolyte is preferably 100 nm or more and 800 nm or less.
According to this, by controlling the film thickness of the second electrolyte containing iodine, it is possible to prevent the internal resistance from becoming a high resistance while suppressing the formation of lithium dendrite.

In the lithium battery described in the application example, the positive electrode is a composite including an active material portion made of a particulate lithium composite metal oxide, and the first electrolyte is provided in a void inside the active material portion. Is preferred.
According to this configuration, in the composite functioning as the positive electrode, the area in which the particulate lithium composite metal oxide as the positive electrode active material and the first electrolyte are in contact is increased, and the conductivity of the charge is improved, thereby reducing the internal resistance. Thus, a lithium battery having excellent charge and discharge characteristics can be realized.

In the lithium battery described in the application example, it is more preferable that the first electrolyte and the third electrolyte having a larger ion conductivity than the first electrolyte be provided in a void inside the active material portion. .
According to this configuration, in addition to the first electrolyte and the third electrolyte in contact with the particulate lithium composite metal oxide as the positive electrode active material, more excellent conductivity of charge can be realized. .

In the lithium battery described in the application example, the second electrolyte may contain lithium iodide.
According to this configuration, generation of lithium dendrite can be effectively suppressed while suppressing variation in internal resistance.

In the lithium battery described in the application example, the first electrolyte is preferably a lithium composite oxide containing carbon and boron.
According to this configuration, since the lithium composite oxide containing carbon (C) and boron (B) can easily take an amorphous form, it is possible to eliminate the bias in the direction of ion conduction and to achieve excellent charge and discharge. A lithium battery having characteristics can be realized.

In the lithium battery described in the application example, the third electrolyte is preferably a lithium composite metal oxide containing lanthanum, zirconium and niobium.
According to this configuration, since the lithium composite metal oxide containing lanthanum (La), zirconium (Zr) and niobium (Nb) exhibits excellent ion conductivity, the variation in internal resistance is further reduced. A lithium battery having more excellent charge and discharge characteristics can be realized.

  In the method of manufacturing a lithium battery according to this application example, the step of forming an active material portion having a void inside using a particulate lithium composite metal oxide, and the first electrolyte in the void of the active material portion A step of filling to form a composite, a step of forming a film of the first electrolyte to cover at least one surface of the composite to form an electrolyte layer, and ions on the electrolyte layer rather than the first electrolyte. Forming a second electrolyte containing iodine, which has a low conductivity, forming a negative electrode by laminating on the second electrolyte, forming at least one of the other surface of the composite and the negative electrode Forming a current collector in contact with one side.

  According to this application example, the second electrolyte containing iodine is formed at the interface between the electrolyte layer and the negative electrode. Since the ion conductivity of the second electrolyte is lower than that of the first electrolyte, lithium, which is an active material, is deposited at a portion where the internal resistance is low on the negative electrode side at the time of the first charge. That is, lithium is deposited unevenly on the negative electrode side. In addition, a part of the lithium ion conducted reacts with iodine contained in the second electrolyte, and lithium iodide or a lithium iodide analog is produced on the negative electrode side. On the other hand, at the time of discharge, when the battery reaction starts from the portion where lithium is deposited nonuniformly, and the volume of lithium on the negative electrode side decreases, lithium iodide from lithium iodide or lithium iodide analogous substance in contact with nonuniformly deposited lithium Release begins and resistance increases. Therefore, in the interface between the electrolyte layer and the negative electrode, the portion where lithium is deposited unevenly is low and the internal resistance is made uniform, so that lithium can be produced even at the portion where lithium deposition did not occur on the negative electrode side. Discharge or discharge is initiated. In the next charging, charging is started from the state where the internal resistance is uniformed, so even if the interface between the electrolyte layer and the negative electrode is not flattened, uneven precipitation of lithium is eliminated and generation of dendrite is suppressed. Ru. That is, the variation in internal resistance and the decrease in discharge capacity caused by the growth of lithium dendrite are improved, and a lithium battery having excellent charge and discharge characteristics can be manufactured.

In the method of manufacturing a lithium battery according to the application example, in the step of forming the second electrolyte, it is preferable to form a film of lithium iodide having a thickness of 100 nm to 800 nm by an evaporation method.
According to this method, even if the surface of the electrolyte layer on the side facing the negative electrode is not flat, the film is formed using the vapor deposition method with excellent coverage, so lithium iodide as the second electrolyte is formed uniformly. It can be a film. In addition, since the film thickness of lithium iodide is 100 nm or more and 800 nm or less, it is possible to provide a method for manufacturing a lithium battery capable of reducing variation in internal resistance while suppressing the formation of lithium dendrite during charging. be able to.

In the method of manufacturing a lithium battery described in the application example, it is preferable to include a step of filling the voids of the active material portion with a third electrolyte having higher ion conductivity than the first electrolyte.
According to this method, in the inside of the active material portion, the particulate lithium composite metal oxide as the positive electrode active material comes into contact with the third electrolyte in addition to the first electrolyte, so the interface at which the charge moves Further, it is possible to manufacture a lithium battery having excellent charge and discharge characteristics.

  Application Example Another method of manufacturing a lithium battery according to this application example includes the steps of: forming a composite by mixing a positive electrode active material containing lithium and a first electrolyte, forming the mixture, and firing the mixture; Forming an electrolyte layer on one of the surfaces, forming a second electrolyte containing iodine, having a smaller ion conductivity than the first electrolyte, on the electrolyte layer, and laminating on the second electrolyte. And forming a current collector in contact with at least one of the other surface of the composite and the negative electrode.

  According to this application example, the second electrolyte containing iodine is formed at the interface between the electrolyte layer and the negative electrode. Since the ion conductivity of the second electrolyte is lower than that of the first electrolyte, lithium, which is an active material, is deposited at a portion where the internal resistance on the negative electrode side is low at the time of the first charge. That is, lithium is deposited unevenly on the negative electrode side. In addition, a portion of the lithium ion conducted reacts with iodine contained in the second electrolyte, and lithium iodide or a lithium iodide analog is produced on the negative electrode side. On the other hand, at the time of discharge, when the battery reaction starts from the portion where lithium is deposited nonuniformly, and the volume of lithium on the negative electrode side decreases, lithium iodide from lithium iodide or lithium iodide analogous substance in contact with nonuniformly deposited lithium Release begins and resistance increases. Therefore, in the interface between the electrolyte layer and the negative electrode, the portion where lithium is deposited unevenly is low and the internal resistance is made uniform, so that lithium can be produced even at the portion where lithium deposition did not occur on the negative electrode side. Discharge or discharge is initiated. In the next charging, charging is started from the state where the internal resistance is uniformed, so even if the interface between the electrolyte layer and the negative electrode is not flattened, uneven precipitation of lithium is eliminated and generation of dendrite is suppressed. Ru. In addition, since a composite is formed by mixing the positive electrode active material and the first electrolyte, molding, and firing, the composite is formed, so that the active material portion made of the positive electrode active material is filled with the first electrolyte later. A complex including the positive electrode active material and the first electrolyte can be easily formed. That is, the variation in internal resistance and the decrease in discharge capacity caused by the growth of dendrites of lithium are improved, and a lithium battery having excellent charge and discharge characteristics can be easily manufactured.

In the method of manufacturing a lithium battery according to the application example, in the step of forming the second electrolyte, it is preferable to form a film of lithium iodide having a thickness of 100 nm to 800 nm by an evaporation method.
According to this method, even if the surface of the electrolyte layer on the side facing the negative electrode is not flat, the film is formed using the vapor deposition method with excellent coverage, so lithium iodide as the second electrolyte is formed uniformly. It can be a film. In addition, since the film thickness of lithium iodide is 100 nm or more and 800 nm or less, it is possible to provide a method for manufacturing a lithium battery capable of reducing variation in internal resistance while suppressing the formation of lithium dendrite during charging. be able to.

In the method of manufacturing a lithium battery according to the application example, the step of forming the composite includes mixing the positive electrode active material, the first electrolyte, and a third electrolyte having a larger ion conductivity than the first electrolyte. The composite is preferably formed by molding and firing.
According to this method, since the positive electrode active material, the first electrolyte, and the third electrolyte are mixed to form a complex, the positive electrode active material, the first electrolyte, and the third electrolyte are brought into contact with each other in the composite. Therefore, it is possible to secure an interface where charges move, and to manufacture a lithium battery having a further reduced internal resistance.

Application Example An electronic device according to this application example is characterized by including the lithium battery described in the above application example.
According to this application example, since the lithium battery having excellent charge and discharge characteristics is provided which is less likely to cause variation in internal resistance and decrease in discharge capacity due to the growth of dendrite of lithium, charging is repeated using the lithium battery as a power supply. By discharging, an electronic device that can be used for a long time can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic perspective view which shows the structure of the lithium battery of 1st Embodiment. BRIEF DESCRIPTION OF THE DRAWINGS The schematic sectional drawing which shows the structure of the lithium battery of 1st Embodiment. The enlarged view which shows the positive electrode active material in the composite of 1st Embodiment, 1st electrolyte, and 3rd electrolyte. 3 is a flowchart showing a method of manufacturing the lithium battery of the first embodiment. Schematic which shows the process in the manufacturing method of the lithium battery of 1st Embodiment. Schematic which shows the process in the manufacturing method of the lithium battery of 1st Embodiment. Schematic which shows the process in the manufacturing method of the lithium battery of 1st Embodiment. The enlarged view which shows the internal structure of the active material part containing the positive electrode active material of 1st Embodiment. Schematic which shows the process in the manufacturing method of the lithium battery of 1st Embodiment. Schematic which shows the process in the manufacturing method of the lithium battery of 1st Embodiment. Schematic which shows the process in the manufacturing method of the lithium battery of 1st Embodiment. Schematic which shows the process in the manufacturing method of the lithium battery of 1st Embodiment. Schematic which shows the process in the manufacturing method of the lithium battery of 1st Embodiment. The schematic sectional drawing which shows the structure of the lithium battery of 2nd Embodiment. The flowchart which shows the manufacturing method of the lithium battery of 2nd Embodiment. Schematic which shows the process in the manufacturing method of the lithium battery of 2nd Embodiment. Schematic which shows the process in the manufacturing method of the lithium battery of 2nd Embodiment. The graph which shows the discharge characteristic in the lithium battery of Example 1- Example 3. FIG. The perspective view which shows the structure of the wearable apparatus as an electronic device of 3rd Embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the drawings to be used are appropriately enlarged or reduced and displayed so that the parts to be described can be recognized.

First Embodiment
<Lithium battery>
An example of the lithium battery of the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic perspective view showing the configuration of the lithium battery of the first embodiment, FIG. 2 is a schematic cross section showing the structure of the lithium battery of the first embodiment, and FIG. 3 is a positive electrode active in the composite of the first embodiment It is an enlarged view which shows a substance, a 1st electrolyte, and a 3rd electrolyte.

  As shown in FIG. 1, the lithium battery 100 of the present embodiment includes a composite 10 that functions as a positive electrode, an electrolyte layer 20 sequentially stacked on the composite 10, and a negative electrode 30. Further, the current collector 41 in contact with the composite 10 and the current collector 42 in contact with the negative electrode 30 are provided. Since all of the composite 10, the electrolyte layer 20, and the negative electrode 30 are formed of a solid phase containing lithium, the lithium battery 100 is a chargeable / dischargeable solid secondary battery.

  The lithium battery 100 of the present embodiment is, for example, a disk shape, and the outer size is, for example, 10 mmφ, and the thickness is, for example, approximately 0.3 mm. Since it is a solid secondary battery that can be charged and discharged while being small and thin, it can be suitably used as a power source of a portable information terminal such as a smartphone. The size and thickness of the lithium battery 100 are not limited to this value as long as it can be molded. The thickness when the external dimension is 10 mmφ as in the present embodiment is estimated to be about 0.1 mm from the viewpoint of formability if thin, and from the viewpoint of lithium ion conductivity of the electrolyte if thick, to about 1 mm If it is too thick, it will lower the utilization efficiency of the active material. The shape of the lithium battery 100 is not limited to the disk shape, and may be a polygonal disk shape. Each layer will be described in detail below.

  As shown in FIG. 2, the composite 10 functioning as a positive electrode includes a positive electrode active material 11, a first electrolyte 12, and a third electrolyte 13 whose ion conductivity is higher than that of the first electrolyte 12. The positive electrode active material 11 is in the form of particles, and when the positive electrode active materials 11 are in contact with each other in the inside of the composite 10, the composite 10 is in a state in which the electron conductivity is given. Further, the current collector 41 is provided in contact with the plurality of positive electrode active materials 11.

  The electrolyte layer 20 provided between the composite 10 and the negative electrode 30 does not contain the positive electrode active material 11 and contains an electrolyte. In other words, the composite 10 and the negative electrode 30 do not have an electrical short circuit between the composite 10 and the negative electrode 30 which are given the electron conductivity by sandwiching the electrolyte layer 20, and charge (lithium ions or electrons) between the composite 10 and the negative electrode 30 Conduction is performed.

  In the present embodiment, the second electrolyte 22 is provided between the electrolyte layer 20 and the negative electrode 30. Although the details will be described later, the second electrolyte 22 is a lithium compound containing iodine, and a material having a smaller ion conductivity than the first electrolyte 12 is selected. Therefore, in consideration of the internal resistance, the film thickness of the second electrolyte 22 is extremely thin compared to the film thickness of the electrolyte layer 20, and a material that can be stably formed during film formation is selected.

  In the lithium battery 100 of the present embodiment, hereinafter, the surface of the composite 10 in contact with the electrolyte layer 20 will be described as one surface 10 a, and the surface of the composite 10 in contact with the current collector 41 will be described as the other surface 10 c.

<Complex>
As shown in FIG. 3, the positive electrode active material 11 and the third electrolyte 13 in the composite 10 are both in the form of particles, and the particle diameter of the third electrolyte 13 is overwhelmingly larger than the particle diameter of the positive electrode active material 11. Small. The third electrolyte 13 is in contact with the surface of the particulate positive electrode active material 11 and is present between particles of the positive electrode active material 11. Further, the first electrolyte 12 is present so as to fill the gaps between the particles of the positive electrode active material 11. In the present embodiment, the positive electrode active material 11 and the third electrolyte 13 are crystalline, whereas the first electrolyte 12 is amorphous. In addition, in FIG. 3, although the particle shape of the positive electrode active material 11 and the 3rd electrolyte 13 was made into spherical shape on account of illustration, the actual particle shape is not necessarily spherical shape, but each is amorphous.

  From the viewpoint of bringing the particles of the positive electrode active material 11 into contact with each other to exhibit electron conductivity, the particle diameter of the positive electrode active material 11 is preferably, for example, 500 nm or more and less than 10 μm in median diameter d50. On the other hand, the particle diameter of the third electrolyte 13 is, for example, at a submicron level with a median diameter d50 in relation to the manufacturing method described later. Although FIG. 3 illustrates the particles of the third electrolyte 13 in a distinguishable state, in reality, fine particles of submicron level are in contact with each other to constitute the third electrolyte 13.

The positive electrode active material 11 contained in the composite 10 contains at least Li, and is a lithium mixed metal oxide containing at least one transition metal selected from V, Cr, Mn, Fe, Co, Ni, and Cu as a constituent element. It is preferable to use a substance because it is chemically stable. Examples of such a lithium composite metal oxide, for _{example, LiCoO 2, LiNiO 2, LiMn} 2 O 4, Li 2 Mn 2 O 3, Li (Ni x Mn y Co 1-xy) O 2 [0 <x + y <1 _{], Li (Ni x Co y} Al 1-xy) O 2 [0 <x + y <1], LiCr 0.5 Mn 0.5 O 2, LiFePO 4, Li 2 FeP 2 O 7, LiMnPO 4, LiFeBO 3, Li 3 V 2 _{(PO 4) 3, Li 2} CuO 2, Li 2 FeSiO 4, such as Li ₂ MnSiO ₄ can be cited. In addition, lithium complex metal oxides include solid solutions in which some atoms in the crystals of these lithium complex metal oxides are substituted with typical metals, alkali metals, alkaline earth metals, lanthanoids, chalcogenides, halogens, and the like. These solid solutions can also be used as the positive electrode active material 11.

  The method of forming the positive electrode (positive electrode active material layer) using the above-mentioned positive electrode active material 11 is a thin film by a vapor deposition method such as press sintering, CVD, PLD, sputtering or aerosol deposition, in addition to the green sheet method. You may form. Furthermore, a single crystal grown from a melt or solution may be used.

<Electrolyte>
The first electrolyte 12 and the third electrolyte 13 contained in the composite 10, and the electrolyte layer 20 are solid electrolytes, and they are crystalline materials comprising oxide, sulfide, halide, nitride, hydride, boride and the like. Alternatively, amorphous can be used.

As an example of oxide crystalline materials, Li _0.35 La _0.55 TiO ₃ , Li _0.2 La _0.27 NbO ₃ , and some of the elements of these crystals are substituted with N, F, Al, Sr, Sc, Ta, lanthanoid elements, etc. Perovskite-type crystals or perovskite-like crystals, Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₅ La ₃ Nb ₂ O ₁₂ , Li ₅ BaLa ₂ TaO ₁₂ , and some of the elements of these crystals are N, F, Al, Sr, Garnet-type crystal or garnet-type crystal substituted with Sc, Ta, lanthanoid element, etc., Li _1.3 Ti _1.7 Al _0.3 (PO ₄ ) ₃ , Li _1.4 Al _0.4 Ti _1.6 (PO ₄ ) ₃ , Li _1.4 Al _0.4 Ti _1.4 Ge _0.2 (PO ₄ ) ₃ , and NASICON-type crystals in which some of these crystals are substituted with N, F, Al, Sr, Sc, Ta, a lanthanoid element, etc., Li ₁₄ ZnGe ₄ Other crystalline materials such as LISICON-type crystals such as O ₁₆ , Li _3.4 V _0.6 Si _0.4 O ₄ , Li _3.6 V _0.4 Ge _0.6 O ₄ , Li _{2 + x} C _1-x B _x O ₃ , etc. may be mentioned it can.

Examples of sulfide crystalline materials include Li ₁₀ GeP ₂ S ₁₂ , Li _9.6 P ₃ S ₁₂ , Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 , Li ₃ PS _{4 and the} like.

Also. Examples of other _{amorphous, Li 2 O-TiO 2,} La 2 O 3 -Li 2 O-TiO 2, LiNbO 3, LiSO 4, Li 4 SiO 4, Li 3 PO 4 -Li 4 SiO 4, Li ₄ GeO ₄ -Li ₃ VO ₄ , Li ₄ SiO ₄ -Li ₃ VO ₄ , Li ₄ GeO ₄ -Zn ₂ GeO ₂ , Li ₄ SiO ₄ -LiMoO ₄ , Li ₃ PO ₄ -Li ₄ SiO ₄ , Li ₄ SiO ₄ -Li ₄ ZrO ₄ , SiO ₂ -P ₂ O ₅ -Li ₂ O, SiO ₂ -P ₂ O ₅ -LiCl, Li ₂ O-LiCl-B ₂ O ₃ , LiAlCl ₄ , LiAlF ₄ , LiF-Al ₂ O ₃ , LiBr-Al ₂ O ₃ , Li _2.88 PO _3.73 N _0.14 , Li ₃ N-LiCl, Li ₆ NBr ₃ , Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -P ₂ S _{5 and the} like be able to. Above all, as the electrolyte used for the first electrolyte 12, the covering property to the surface and the lumen of the active material portion (porous active material sintered body) described later is high, and the melting point is lower than that of the positive electrode active material 11 described above In particular, Li _{2 + x} C _1-x B _x O ₃ which is a lithium composite oxide containing carbon (C) and boron (B), and similar substances are preferably used.

  The method of forming the electrolyte layer 20 using the above solid electrolyte is a solution process such as a so-called sol-gel method or an organic metal thermal decomposition method involving a hydrolysis reaction of an organic metal compound, or a CVD method in an appropriate metal compound and gas atmosphere. ALD method, green sheet method and screen printing method using slurry of solid electrolyte particles, aerosol deposition method, sputtering method using appropriate target and gas atmosphere, PLD method, flux method using melt or solution, etc. Any of these may be used.

  In the present embodiment, the same solid electrolyte is used as the first electrolyte 12 and the electrolyte layer 20 contained in the composite 10, but different solid electrolytes may be used.

The second electrolyte 22 is provided between the electrolyte layer 20 and the negative electrode 30 in order to suppress the growth of dendrites resulting from the uneven deposition of Li on the negative electrode 30 side during charging of the lithium battery 100. It is a thing. Such a second electrolyte 22 is a lithium compound containing iodine and having no electron conductivity, and is preferably amorphous. For example, LiI, LiI-CaI ₂ , Li ₃ NI ₂ , Li ₃ N -LiI-LiOH, etc. Li ₂ S-SiS ₂ -LiI can be mentioned. In addition, the second electrolyte 22 made of a lithium compound containing iodine has smaller ion conductivity than the electrolyte containing a metal element such as the transition metal described above. Therefore, in consideration of the internal resistance of the lithium battery 100, it is preferable that the film thickness of the second electrolyte 22 be uniform, with as little variation as possible. The film thickness range of the second electrolyte 22 in the present embodiment is preferably 100 nm or more and 800 nm or less, and more preferably 100 nm or more and 400 nm or less. Therefore, it is preferable that stable film formation be possible at the time of film formation, and among the lithium compounds described above, it is preferable to use lithium iodide (LiI) which is chemically stable and has a relatively high vapor pressure.

  As a method of forming such a second electrolyte 22 (film forming method), suitable metal compounds and gas may be used in addition to solution processes such as so-called sol-gel method and organic metal thermal decomposition method involving hydrolysis reaction of organic metal compounds. CVD method in atmosphere, ALD method, green sheet method or screen printing method using slurry of solid electrolyte particles, aerosol deposition method, sputtering using appropriate target and gas atmosphere, PLD, flux using melt or solution Law etc. can be mentioned. The vapor deposition method (vacuum vapor deposition method) is particularly preferably used in consideration of the coverage with the formation surface on which the second electrolyte 22 is formed and the uniformity of the film thickness at the time of film formation.

  In the present embodiment, in the composite 10, the positive electrode active material 11 is exposed on the other surface 10c in contact with the current collector 41, and the plurality of exposed positive electrode active materials 11 and the current collector 41 are electrically connected. There is.

<Negative electrode>
Examples of negative electrode active materials that can be used as the negative electrode 30 include Nb ₂ O ₅ , V ₂ O ₅ , TiO ₂ , In ₂ O ₃ , ZnO, SnO ₂ , NiO, ITO (Indium Tin Oxide), and AZO (Al-doped). Zinc Oxide), FTO (F-doped Tin Oxide), anatase phase of TiO ₂ , lithium double oxide such as Li ₄ Ti ₅ O ₁₂ , Li ₂ Ti ₃ O ₇ , Li, Si, Sn, Si-Mn, Si Examples thereof include metals such as -Co, Si-Ni, In and Au and alloys containing these metals, carbon materials, and materials in which lithium ions are inserted between layers of carbon materials. In consideration of the discharge capacity in the small and thin lithium battery 100, the negative electrode 30 is preferably a single metal or an alloy forming metal Li or a lithium alloy. The alloy is not particularly limited as long as it can occlude and release lithium, but is preferably one containing a metal other than Group 13 and Group 14 carbon or a metalloid element, and more preferably a single metal of aluminum, silicon and tin It is an alloy or a compound containing these atoms. These may be used alone, or two or more may be used in any combination and ratio. Examples of alloys include lithium alloys such as Li-Al, Li-Ni, Li-Si, Li-Sn, and Li-Sn-Ni, silicon alloys such as Si-Zn, Sn-Mn, Sn-Co, Sn-Ni, Examples thereof include tin alloys such as Sn-Cu and Sn-La, Cu ₂ Sb, La ₃ Ni ₂ Sn _{7 and the} like.

  The method of forming the negative electrode 30 using the above negative electrode active material is a solution process such as a so-called sol-gel method or an organic metal thermal decomposition method involving hydrolysis reaction of an organic metal compound, or a CVD method in an appropriate metal compound and gas atmosphere. ALD method, green sheet method and screen printing method using slurry of solid negative electrode active material, aerosol deposition method, sputtering method using appropriate target and gas atmosphere, PLD method, vacuum evaporation method, plating method, thermal spraying method Any or the like may be used.

<Current collector>
The current collectors 41 and 42 are, for example, copper (Cu), magnesium (Mg), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), One metal (a single metal) selected from the metal group of germanium (Ge), indium (In), gold (Au), platinum (Pt), silver (Ag), and palladium (Pd), or the metal group An alloy or the like composed of two or more selected metals is used.

  In the present embodiment, copper (Cu) is used as the current collectors 41 and 42. The thickness of the current collectors 41 and 42 is, for example, 20 μm to 40 μm. The lithium battery 100 may not necessarily include the pair of current collectors 41 and 42, and may include one of the pair of current collectors 41 and 42. For example, in the case where a plurality of lithium batteries 100 are stacked and electrically connected in series, the lithium battery 100 may be configured to include only the current collector 41 of the pair of current collectors 41 and 42. .

<Method of Manufacturing Lithium Battery (Manufacturing Method of Composite)>
Next, a method of manufacturing the lithium battery 100 according to the present embodiment will be described with reference to FIGS. FIG. 4 is a flowchart showing the method of manufacturing the lithium battery of the first embodiment, and FIGS. 5 to 13 are schematic views showing steps in the method of manufacturing the lithium battery of the first embodiment. In addition, FIG. 8 is an enlarged view which shows the internal structure of the active material part containing the positive electrode active material of 1st Embodiment.

  As shown in FIG. 4, in the method of manufacturing the lithium battery 100 according to this embodiment, a step of forming an active material portion including the positive electrode active material 11 (step S1), and a step of filling the active material portion with the third electrolyte 13. (Step S2), the step of filling the first electrolyte 12 in the active material portion (Step S3), the step of polishing the composite (Step S4), the step of forming the electrolyte layer 20 (Step S5), and the second A film forming process (step S6) of the electrolyte 22, a forming process (step S7) of the negative electrode 30, and a forming process (step S8) of the current collectors 41 and 42 are provided.

In step S1, an active material portion having a void inside is formed using the positive electrode active material 11. Specifically, in the present embodiment, LiCoO ₂ (lithium cobaltate; hereinafter referred to as LCO), which is a lithium composite metal oxide containing cobalt (Co), is used as the positive electrode active material 11. Slurry mixed with 1,4-dioxane (90 g) as a solvent in which polypropylene carbonate (10 g) as a binder (binding agent) is dissolved, and LCO powder (15 g) having a median diameter d50 of about 5 μm in particle size distribution As shown in FIG. 5, the sheet 10s was formed by coating on a polyethylene terephthalate film (PET) substrate 55 using a fully automatic film applicator (manufactured by Kotec Co., Ltd.).

  The composition of the slurry at this time can have an arbitrary value in accordance with the desired thickness of the sheet 10s and the performance of the coating apparatus. Moreover, auxiliary agents such as dispersants, antifoaming agents, and pore forming agents may be added to the slurry as required.

  By removing the sheet 10s thus formed using a suitable punch, as shown in FIG. 6, a disk-shaped pellet 10p having a diameter of, for example, 10 mm is obtained. The pellets 10p are degreased at about 300 ° C., placed on a substrate, and fired using, for example, an electric muffle furnace. The firing temperature is preferably 850 ° C. or more and less than the melting point of the positive electrode active material 11. In this case, since LCO is used as the positive electrode active material 11, the firing temperature is set to 875 ° C. or more and 1000 ° C. or less. The firing time is preferably, for example, 5 minutes or more and 36 hours or less. More preferably, it is 4 hours or more and 14 hours or less.

  Thereby, the LCO particles are sintered to obtain pellets 10p as an active material portion which is a porous active material sintered body having a void (internal cavity) inside. Hereinafter, the sintered pellet 10p is referred to as an active material portion 10p. The material of the substrate used at the time of firing is not particularly limited, but it is preferable to use a material such as magnesium oxide which is less likely to react with LCO particles.

  By setting the firing temperature to 850 ° C. or more, sintering proceeds sufficiently and electron conductivity in the crystals of LCO particles is secured. By setting the firing temperature to less than the melting point of the positive electrode active material 11, excessive volatilization of lithium ions in the crystals of LCO particles is suppressed, and the conductivity of lithium ions is maintained. That is, the capacity of the complex 10 can be secured. Therefore, in the lithium battery 100 using the composite 10, appropriate output and capacity can be provided.

  Although the above pellets may be formed by containing an organic substance such as a binder (binding agent) for connecting LCO particles to each other or a pore forming material for adjusting the porosity of the active material portion 10p, these pellets may be formed after firing It is preferable to burn off the organic substance surely by firing, since the remaining organic substance affects the charge conductivity. In other words, it is desirable to form the pellet without containing an organic substance such as a binder or a pore former. In addition, the porosity of the active material portion 10p can be controlled by adjusting the LCO particles, that is, the average particle diameter of the positive electrode active material particles, and the sintering conditions such as pressure and baking temperature at the time of forming the pellets. . In the present embodiment, the porosity of the active material portion 10 p is adjusted to be 40% or more and 60% or less in order to ensure sufficient contact between the electrolyte to be filled later and the positive electrode active material 11.

  The method for forming the pellets is not limited to the method using the slurry containing the positive electrode active material 11. For example, LCO particles are filled in a die of φ 10 mm (forming die), pressure is applied, and uniaxial pressing is performed. You may produce. Then, the process proceeds to step S2.

In step S2, the third electrolyte 13 is filled in the space inside the active material portion 10p. Specifically, first, a precursor of the third electrolyte 13 is prepared. As a precursor, any of following (A)-(D) is used, for example.
(A) A composition containing a metal atom in a proportion according to the composition of the third electrolyte 13 and having a salt that becomes the third electrolyte 13 by oxidation.
(B) A composition having a metal alkoxide containing a metal atom in a proportion according to the composition of the third electrolyte 13.
(C) A dispersion in which the composition of (A) or (B) is dispersed in a solvent.
(D) A dispersion in which fine particles of the third electrolyte 13 or fine particles sol containing metal atoms in a proportion according to the composition of the third electrolyte 13 are dispersed in a solvent.
The salt contained in (A) contains a metal complex.

In this embodiment, Li _6.75 La ₃ Zr _1.75 Nb _0.25 O ₁₂ (hereinafter referred to simply as “LLZrNbO and LiZrNbO”, which is a lithium composite metal oxide, is used as the third electrolyte 13 exhibiting an ion conductivity higher than that of the positive electrode active material 11 (LCO). Name) was used. Crystal particles 13 p of LLZrNbO are dispersed in a solvent 51 and used as a precursor solution 50. The average particle size of LLZrNbO is, for example, 300 nm to 1 μm. The melting point of LLZrNbO is approximately 1000 ° C to 1100 ° C. Also, the ion conductivity of LLZrNbO is approximately 1 × 10 ^-4 [S / cm] (siemens per centimeter).

  Next, the precursor solution 50 is impregnated (impregnated) in the voids of the active material portion 10 p made of the positive electrode active material 11. Specifically, as shown in FIG. 7, for example, the precursor solution 50 is dropped from the nozzle 61 onto the active material portion 10 p disposed on the base material 56. Alternatively, the active material portion 10 p may be immersed in the precursor solution 50. In another example, the precursor solution 50 may be applied to the active material portion 10p. In still another example, the precursor solution 50 may be brought into contact with the end of the active material portion 10p, and the precursor solution 50 may be impregnated into the voids of the active material portion 10p by utilizing capillary action. At this time, the atmosphere surrounding the active material portion 10 p or the precursor solution 50 may be pressurized to promote the impregnation of the precursor solution 50. The substrate 56 is, for example, a transparent quartz substrate which is less likely to be deformed even if it is dried and fired at a high temperature thereafter.

  Then, the active material portion 10 p impregnated with the precursor solution 50 is dried in the air, and then heat treated and fired in a rare gas atmosphere. Thereby, as shown in FIG. 8, the third electrolyte 13 is deposited on the surface of the positive electrode active material 11 of the active material portion 10p. That is, in the inside of the active material portion 10 p, the third electrolyte 13 is filled in the voids of the sintered positive electrode active material 11. Then, the process proceeds to step S3.

  In step S3, the first electrolyte 12 is further filled in the voids of the active material portion 10p. Specifically, as shown in FIG. 9, first, the active material portion 10 p in which the third electrolyte 13 is filled is disposed in the crucible 91. The active material portion 10 p is supported by a support needle 92 provided on the bottom of the crucible 91. The crucible 91 is made of, for example, magnesium oxide, and the support needle 92 is made of, for example, gold (Au). A solid first electrolyte 12 is disposed on the active material portion 10 p. In the present embodiment, the surface of the active material portion 10p supported by the support needle 92 is the one surface 10a of the composite 10 described above. On the other hand, the surface of the active material portion 10p on which the first electrolyte 12 is disposed is referred to as the other surface 10b.

In the present embodiment, Li _{2+ x} C _{1 -x} B _x O ₃ (hereinafter referred to as LCBO) having a melting point lower than that of the third electrolyte 13 (LLZrNbO) is used as the first electrolyte 12. Since the melting point of LCBO is approximately 700 ° C., the crucible 91 is heated to approximately 800 ° C. in an atmosphere containing carbon dioxide (CO ₂ ) gas to melt the first electrolyte 12 placed on the active material portion 10 p. Thus, a melt of 12 m was obtained. The melt 12m penetrates into the porous active material portion 10p. Thereafter, the crucible 91 is cooled to room temperature to solidify the soaked melt 12m. In the inside of the active material portion 10 p in which the third electrolyte 13 is filled, the voids of the sintered positive electrode active material 11 are further filled with the first electrolyte 12. The surface of the active material portion 10 p is also covered with the first electrolyte 12 by adjusting the amount of the melt 12 m. As a result, the composite 10 in which the first electrolyte 12 and the third electrolyte 13 are filled in the porous active material portion 10 p is completed. The average thickness of the composite 10 at this time is approximately 110 μm. Then, the process proceeds to step S4. The ion conductivity of LCBO is approximately 1 × 10 ⁻⁶ [S / cm], which is smaller than the ion conductivity of the third electrolyte 13.

  In step S4, as shown in FIG. 10, the other surface 10b of the composite 10 filled with the first electrolyte 12 and the third electrolyte 13 is polished to expose the positive electrode active material 11. The surface where the positive electrode active material 11 is exposed is a polished surface, which corresponds to the other surface 10c of the composite 10 shown in FIG. Hereinafter, the other surface 10c may also be referred to as a polishing surface 10c. As a method of polishing the other surface 10b of the composite 10 in this manner, for example, chemical mechanical polishing (CMP) may be mentioned. After the active material portion 10p is filled with the first electrolyte 12 in step S3, if particles of the positive electrode active material 11 are sufficiently exposed on the other surface 10b, the polishing process is not necessarily performed. It is also good. That is, step S4 can be omitted. Then, the process proceeds to step S5.

  In step S5, as shown in FIG. 11, the electrolyte layer 20 is formed on one surface 10a that is the surface opposite to the polishing surface 10c of the composite 10. In the present embodiment, the same LCBO as the first electrolyte 12 is formed into a film by a sputtering method to form the electrolyte layer 20. The thickness of the electrolyte layer 20 may be 0.1 μm or more and 100 μm or less, and is 2.5 μm in the present embodiment. Then, the process proceeds to step S6.

In step S6, as shown in FIG. 12, the second electrolyte 22 is deposited on the electrolyte layer 20. In the present embodiment, the second electrolyte 22 is formed by vacuum evaporation using lithium iodide (LiI) as an evaporation source. As described above, the film thickness of the second electrolyte 22 may be in the range of 100 nm to 800 nm. In this case, the roughness (irregularities in the surface of the electrolyte layer 20 made of LCBO which is the formation surface of the second electrolyte 22) And 100 nm in consideration of. Then, the process proceeds to step S7. The ionic conductivity of lithium iodide (LiI) is 1 × 10 ⁻⁸ to 1 × 10 ⁻⁹ [S / cm], which is smaller than the ionic conductivity of the first electrolyte 12 made of LCBO.

  In step S7, as shown in FIG. 13, the negative electrode 30 is formed by laminating on the second electrolyte 22. In the present embodiment, metal lithium is deposited on the second electrolyte 22 by sputtering to form the negative electrode 30. The thickness of the negative electrode 30 may be in the range of 50 nm to 100 μm, and in the present embodiment, it is approximately 15 μm in consideration of the discharge capacity. Then, the process proceeds to step S8.

  In the step of forming the current collectors 41 and 42 in step S8, as shown in FIG. 2, the current collector 41 is formed in contact with the polishing surface 10c of the composite 10 and the current collector 42 is in contact with the negative electrode 30. Formed. In the present embodiment, the current collectors 41 and 42 are formed by sticking and pressing a copper foil having a thickness of approximately 20 μm. Thereby, the lithium battery 100 is completed.

According to the lithium battery 100 of the first embodiment and the method of manufacturing the same, the following effects can be obtained.
(1) The lithium battery 100 includes the composite 10 that functions as a positive electrode, the electrolyte layer 20 sequentially formed on one surface 10 a of the composite 10, the second electrolyte 22, the negative electrode 30, and the other of the composite 10. And a current collector 42 formed in contact with the negative electrode 30. The composite 10 is filled in the internal voids by impregnating the precursor solution 50 with the porous active material portion 10 p formed using the positive electrode active material 11 made of the particulate lithium composite metal oxide. A third electrolyte 13 and a first electrolyte 12 formed on the surface including internal voids by impregnating the melt 12 m are provided. The second electrolyte 22 is a lithium compound containing iodine, and has a smaller ion conductivity than the first electrolyte 12. Since the ion conductivity of the second electrolyte 22 is smaller than that of the first electrolyte 12, lithium, which is an active material, is deposited at a portion where the internal resistance on the negative electrode 30 side is low at the time of the first charge of the lithium battery 100. That is, lithium is deposited unevenly on the negative electrode 30 side. In addition, a part of the lithium ion conducted reacts with iodine contained in the second electrolyte 22, and lithium iodide or a lithium iodide analog is produced on the negative electrode 30 side. On the other hand, at the time of discharge, when the battery reaction starts from the portion where lithium is deposited nonuniformly, and the volume of lithium on the negative electrode 30 side decreases, lithium iodide or lithium iodide similar substance in contact with the nonuniformly deposited lithium The release of water starts to increase resistance. Therefore, in the interface between the electrolyte layer 20 and the negative electrode 30, the portion where the internal resistance is unevenly deposited is low and the internal resistance is uniformed, so the lithium does not precipitate on the negative electrode 30 side But the release or discharge of lithium is initiated. In the next charging, charging is started from the state where the internal resistance is uniformed, so even if the interface between the electrolyte layer 20 and the negative electrode 30 is not flat (in other words, the electrolyte layer 20 and the negative electrode 30 are formed) Even if one surface 10a of the composite 10 is not polished and flattened), the uneven precipitation of lithium is eliminated and the formation of dendrite is suppressed. That is, the variation in internal resistance and the decrease in discharge capacity due to the growth of lithium dendrite are improved, and the lithium battery 100 having excellent charge and discharge characteristics can be provided or manufactured.

  (2) The second electrolyte 22 is formed using a vapor deposition method (vacuum vapor deposition method). Therefore, even if the surface of the electrolyte layer 20 on the side facing the negative electrode 30 is not flat, the film formation is performed using the vapor deposition method with excellent coverage, so the second electrolyte 22 can be formed uniformly. In addition, since the film thickness of the second electrolyte 22 is controlled to be 100 nm or more and 800 nm or less, generation of lithium dendrite during charging can be suppressed, and variation in internal resistance can be reduced. A manufacturing method can be provided.

  (3) Lithium iodide (LiI) is selected from lithium compounds containing iodine as the second electrolyte 22 to form a film. Lithium iodide is suitable for forming the second electrolyte 22 by vapor deposition because it is chemically stable and has a large vapor pressure as compared to other lithium compounds.

Second Embodiment
Next, a lithium battery according to a second embodiment and a method of manufacturing the same will be described with reference to FIGS. FIG. 14 is a schematic cross-sectional view showing the structure of the lithium battery of the second embodiment, FIG. 15 is a flow chart showing a method of manufacturing the lithium battery of the second embodiment, and FIGS. 16 and 17 are manufacture of the lithium battery of the second embodiment FIG. 2 is a schematic view showing steps in the method.

  The lithium battery 200 of the second embodiment is the same as the lithium battery 100 of the first embodiment in basic material configuration but different in the method of manufacturing a composite including the positive electrode active material 11. is there. Therefore, the same components as those of the lithium battery 100 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 14, in the lithium battery 200 of this embodiment, a composite 210 functioning as a positive electrode, an electrolyte layer 20 sequentially stacked on one surface 210 a of the composite 210, and a second electrolyte 22. , And the negative electrode 30. Further, the current collector 41 in contact with the other surface 210 b of the composite 210 and the current collector 42 in contact with the negative electrode 30 are provided. The composite 210, the electrolyte layer 20, the second electrolyte 22, and the negative electrode 30 are all formed of a solid phase containing lithium, so the lithium battery 200 is also a solid secondary battery that can be charged and discharged.

  The lithium battery 200 has, for example, a disk shape, and the outer size is, for example, 10 mmφ, and the thickness is, for example, approximately 0.3 mm. Since it is a solid secondary battery which is small and thin and chargeable and dischargeable, it can be suitably used as a power source of a portable information terminal such as a smartphone, as in the lithium battery 100 of the first embodiment. The size and thickness of the lithium battery 200 are not limited to this value as long as it can be molded. The shape of the lithium battery 200 is not limited to the disk shape, but may be a polygonal disk shape. Hereinafter, a composite 210 having a configuration different from that of the lithium battery 100 of the first embodiment will be described.

  The composite 210 functioning as a positive electrode includes a positive electrode active material 11, a first electrolyte 12, and a third electrolyte 13 having a higher ion conductivity than the first electrolyte 12. The positive electrode active material 11 and the third electrolyte 13 are in the form of particles, and are randomly disposed within the composite 210. When the positive electrode active materials 11 are in contact with each other in the inside of the complex 210, the complex 210 is in a state in which the electron conductivity is given. Further, the amorphous first electrolyte 12 is in contact with the positive electrode active material 11 and the third electrolyte 13 inside the composite 210. A detailed method of forming such a composite 210 will be described in the method of manufacturing the lithium battery 200 described later.

  The electrolyte layer 20 provided on one surface 210 a of the composite 210 is configured by the first electrolyte 12 without including the positive electrode active material 11. In addition, the electrolyte layer 20 is not limited to being formed using the first electrolyte 12, and among various electrolytes described in the first embodiment, a material having an ion conductivity larger than that of the second electrolyte 22 is selected. You may form using.

  The second electrolyte 22 is a lithium compound containing iodine as described in the first embodiment, and a material having a smaller ion conductivity than the first electrolyte 12 is selected. The second electrolyte 22 is provided between the electrolyte layer 20 and the negative electrode 30 in order to suppress the growth of lithium dendrite on the negative electrode 30 side. In consideration of the internal resistance of the lithium battery 200, the film thickness of the second electrolyte 22 is extremely thin compared to the film thickness of the electrolyte layer 20, and is controlled to 100 nm or more and 800 nm or less.

  The positive electrode active material 11 is exposed on the other surface 210 b of the composite 210, and the current collector 41 is provided in contact with the exposed positive electrode active material 11. In addition, another current collector 42 is provided in contact with the negative electrode 30.

  Next, a method of manufacturing the lithium battery 200 will be described with reference to FIG. As shown in FIG. 15, in the method of manufacturing the lithium battery 200 of the present embodiment, a step of forming a composite 210 including the positive electrode active material 11, the first electrolyte 12, and the third electrolyte 13 (step S 11); Step of forming electrolyte layer 20 (step S12), step of forming film of second electrolyte 22 (step S13), step of forming negative electrode 30 (step S14), and step of forming current collectors 41 and 42 (step S15) And have. Steps S12 to S15 of the present embodiment are basically the same as steps S5 to S8 in the method of manufacturing the lithium battery 100 of the first embodiment.

In step S11, as in the first embodiment, LiCoO ₂ (lithium cobaltate; LCO) is used as the positive electrode active material 11 which is a lithium composite metal oxide containing Li. In addition, LCBO was used as the first electrolyte 12, and LLZrNbO was used as the third electrolyte 13. A powder 11p (20 g) of LCO having a particle size distribution median diameter d50 of about 5 μm in 1,4-dioxane (90 g) as a solvent in which polypropylene carbonate (10 g) as a binder (binding agent) is dissolved As shown in FIG. 16, a powder 12p (4 g) of LCBO having a median diameter d50 of about 8 μm in the distribution and a powder 13 p (16 g) of LLZrNbO having a median diameter d50 of about 1 μm in the particle size distribution are mixed. The sheet 210s was formed by coating on a polyethylene terephthalate film (PET) substrate 55 using a fully automatic film applicator (manufactured by Kotec Co., Ltd.).

  The composition of the slurry at this time can have any value in accordance with the desired thickness of the sheet 210s and the performance of the coating apparatus. Moreover, you may add adjuvants, such as a dispersing agent and an antifoamer, to a slurry as needed.

  By removing the sheet 210s thus formed using a suitable punch, as shown in FIG. 17, a disc-shaped pellet 210p having a diameter of, for example, 10 mm is obtained. The pellets 210p are degreased at about 300 ° C., placed on a substrate, and fired using, for example, an electric muffle furnace. The firing temperature is preferably higher than the melting point of the first electrolyte 12, that is, LCBO, and lower than the melting point of LCO which is the positive electrode active material 11 and LLZrNbO which is the third electrolyte 13. In this case, the firing temperature is set to 850 ° C. or more and 1000 ° C. or less. The firing time is preferably, for example, 5 minutes or more and 36 hours or less. More preferably, it is 4 hours or more and 14 hours or less.

  Thereby, the composite 210 sintered in a state where the LCO particles are in contact with each other is obtained. The material of the substrate used at the time of firing is not particularly limited, but it is preferable to use a material such as magnesium oxide which is less likely to react with LCO particles.

  By setting the firing temperature to 850 ° C. or more, the LCBO is melted and sintering proceeds sufficiently to secure the electron conductivity in the crystals of LCO particles. By setting the firing temperature to less than the melting point of the positive electrode active material 11, excessive volatilization of lithium ions in the crystals of LCO particles is suppressed, and the conductivity of lithium ions is maintained. That is, the capacity of the complex 210 can be secured. Therefore, in the lithium battery 200 using the composite 210, appropriate output and capacity can be provided.

  The pellet 210p may be formed by containing an organic substance such as a binder (binding agent) for connecting LCO particles to one another, a dispersant, an antifoaming agent, etc. However, if such an organic substance remains after firing, the charge conductivity will be It is preferable to burn off the organic matter surely by firing. Then, the process proceeds to step S12.

  In step S12, the electrolyte layer 20 is formed on one surface 210a of the composite 210. In the present embodiment, as in the first embodiment, the same LCBO as the first electrolyte 12 is formed into a film by a sputtering method to form the electrolyte layer 20. The thickness of the electrolyte layer 20 may be in the range of 0.1 μm to 100 μm, and in the present embodiment, it is 2.5 μm. Then, the process proceeds to step S13.

  In step S13, the second electrolyte 22 is deposited on the electrolyte layer 20. In the present embodiment, as in the first embodiment, the second electrolyte 22 is formed by vacuum evaporation using lithium iodide (LiI) as an evaporation source. The film thickness of the second electrolyte 22 may be in the range of 100 nm to 800 nm, and in this case as well, it is approximately 100 nm in consideration of the surface state of the electrolyte layer 20 made of LCBO. Then, the process proceeds to step S14.

  In step S14, the negative electrode 30 is formed by laminating on the second electrolyte 22. Also in the present embodiment, metal lithium is deposited on the second electrolyte 22 by the sputtering method to form the negative electrode 30 as in the first embodiment. The thickness of the negative electrode 30 may be in the range of 50 nm to 100 μm, and in the present embodiment, the thickness is about 15 μm in consideration of the discharge capacity. Then, the process proceeds to step S15.

  In the process of forming the current collectors 41 and 42 in step S15, as shown in FIG. 14, the current collector 41 is formed to be in contact with the other surface 210b of the composite 210, and the current collector is in contact with the negative electrode 30. 42 were formed. In the present embodiment, the current collectors 41 and 42 are formed by sticking and pressing a copper foil having a thickness of approximately 20 μm. Thereby, the lithium battery 200 is completed. In the present embodiment, since the particulate positive electrode active material 11, the first electrolyte 12, and the third electrolyte 13 are mixed, formed, and fired to form the composite 210, the other surface 210b of the composite 210 is obtained. The LCO particles that are the positive electrode active material 11 are exposed to the Therefore, the step of polishing the composite 10 to expose the LCO particles as in the first embodiment is unnecessary.

  According to the lithium battery 200 of the second embodiment and the method for manufacturing the same, the effects (2) and (3) of the first embodiment can be obtained in addition to the effects (4) and (5) below.

  (4) The lithium battery 200 includes the composite 210 functioning as a positive electrode, the electrolyte layer 20 sequentially formed on one surface 210 a of the composite 210, the second electrolyte 22, the negative electrode 30, and the other of the composite 210. And the current collector 42 formed in contact with the negative electrode 30. The second electrolyte 22 is a lithium compound containing iodine, and has a smaller ion conductivity than the first electrolyte 12. Since the ion conductivity of the second electrolyte 22 is smaller than that of the first electrolyte 12, lithium, which is an active material, is deposited in a portion where the internal resistance on the negative electrode 30 side is low at the time of the first charge of the lithium battery 200. That is, lithium is deposited unevenly on the negative electrode 30 side. In addition, a part of the lithium ion conducted reacts with iodine contained in the second electrolyte 22, and lithium iodide or a lithium iodide analog is produced on the negative electrode 30 side. On the other hand, at the time of discharge, when the battery reaction starts from the portion where lithium is deposited nonuniformly, and the volume of lithium on the negative electrode 30 side decreases, lithium iodide or lithium iodide similar substance in contact with the nonuniformly deposited lithium The release of water starts to increase resistance. Therefore, in the interface between the electrolyte layer 20 and the negative electrode 30, the portion where the internal resistance is unevenly deposited is low and the internal resistance is uniformed, so the lithium does not precipitate on the negative electrode 30 side But the release or discharge of lithium is initiated. In the next charging, charging is started from the state where the internal resistance is uniformed, so even if the interface between the electrolyte layer 20 and the negative electrode 30 is not flat (in other words, the electrolyte layer 20 and the negative electrode 30 are formed) Even if one surface 210a of the composite 210 is not polished and flattened, the uneven precipitation of lithium is eliminated and the formation of dendrite is suppressed. That is, the variation in internal resistance and the decrease in discharge capacity caused by the growth of lithium dendrite are improved, and a lithium battery 200 having excellent charge and discharge characteristics can be provided or manufactured.

  (5) The composite 210 is formed by mixing and molding the positive electrode active material 11 made of particulate lithium composite metal oxide, the first electrolyte 12 and the third electrolyte 13, and firing. The LCO particles are exposed on the other surface 210 b of the obtained composite 210. Therefore, the third electrolyte 13 and the first electrolyte 12 are filled later into the porous active material portion 10p made of the positive electrode active material 11 as in the first embodiment, and the surface in contact with the current collector 41 is polished. The lithium battery 200 having excellent charge / discharge characteristics can be manufactured by a simpler method than in the case of

  Next, Examples 1 to 3 in which the film thickness of the second electrolyte 22 is made different by using the method for manufacturing the lithium battery 100 according to the first embodiment are shown, and evaluation results according to the battery characteristics of the lithium battery 100 This will be described with reference to FIG. FIG. 18 is a graph showing the discharge characteristics of the lithium batteries of Examples 1 to 3.

Example 1 is a lithium battery 100 in which the second electrolyte 22 is formed to have a film thickness of approximately 100 nm using lithium iodide (LiI). Example 2 is the lithium battery 100 which formed the 2nd electrolyte 22 into a film so that film thickness might be set to about 300 nm similarly using lithium iodide. Example 3 is the lithium battery 100 which formed the 2nd electrolyte 22 into a film so that film thickness might be set to about 800 nm similarly using lithium iodide. The battery area in each of the lithium batteries of Examples 1 to 3 is 0.385 cm ² .

In the evaluation of the discharge characteristics of the lithium batteries 100 of Examples 1 to 3, first, after leaving the lithium battery 100 to have a temperature of 25 ° C., the current density is set to 0.5 mA / cm ² and the upper limit time is set. It was set to 3.5 hours and charged. Thereafter, the discharge capacity density [mAh / g] and the voltage between the positive electrode and the negative electrode of lithium battery 100 when the current density is set to 0.5 mA / cm ² at 25 ° C. and the upper limit time is not set. The relationship with [mV] is confirmed. The horizontal axis in the graph of FIG. 18 represents the discharge capacity density [mAh / g] obtained by dividing the discharge capacity changing with the discharge time by the battery weight, and the vertical axis represents the voltage [mV] of the lithium battery 100. The evaluation of the discharge characteristics is performed in a constant current charge / discharge measurement mode in which the charge / discharge step is automatically switched when the set upper limit voltage is set to 4200 mV and the lower limit voltage to discharge is set to 2800 mV. The In view of the above-described battery area, the current density is set to 0.5 mA / cm ² by setting the amount of current to approximately 200 μA.

  As shown in FIG. 18, in Example 1 in which the film thickness of lithium iodide was about 100 nm, the discharge was started at an initial voltage of 3800 mV, and the voltage dropped to 3000 mV or less when the discharge time was about 3 hours. . The discharge capacity density of Example 1 in this case is approximately 150 mAh / g.

  In Example 2 in which the film thickness of lithium iodide was about 300 nm, the discharge was started at an initial voltage of 3800 mV, and the voltage dropped to 3000 mV or less when about 30 minutes of the discharge time elapsed. The discharge capacity density of Example 2 in this case is approximately 25 mAh / g.

In Example 3 in which the film thickness of lithium iodide was approximately 800 nm, the discharge was started at an initial voltage of 3400 mV, and the voltage dropped to 3000 mV or less after approximately 3 minutes of discharge time. In Example 3, assuming that the current density is set to 1/10 (one tenth) of 0.05 mA / cm ² , the voltage of the lithium battery 100 becomes 3000 mV or less when approximately 30 hours of discharge time has elapsed. The discharge capacity density of Example 3 in this case was about 123 mAh / g. The reason that the initial voltage in Example 3 is lower than in Example 1 and Example 2 is that the film thickness of lithium iodide is 800 nm, which is thicker than Example 1 or Example 2, and thus the internal resistance Is considered to have risen.

Although depending on the consumption current in the electronic device using the lithium battery 100 as a power source, when the film thickness of the second electrolyte 22 is thicker than 800 nm, for example, 1 μm, it is necessary to charge frequently in practice, which is preferable. Absent. When the current density required for discharge of the lithium battery 100 is 0.5 mA / cm ² or more, it is considered that the film thickness of the second electrolyte 22 is preferably 100 nm or more and 400 nm or less.

  Until now, as a patent document disclosed in order to suppress the formation and growth of lithium dendrite, for example, in JP-A-2004-87402, a deposition substrate for depositing a light metal, and the deposition substrate provided on this deposition substrate There has been proposed a negative electrode for a lithium battery comprising an inorganic compound having ion conductivity. In addition, as the inorganic compound, at least one of the group consisting of lithium fluoride, lithium chloride, lithium iodide, lithium nitride, lithium phosphate, lithium silicate, lithium sulfide, lithium phosphide, lithium carbonate and lithium sulfolyl lithium. It is said that the lithium compound containing at least one of these is contained in the seed or raw material. In addition, although the thickness of the inorganic compound is preferably 5 μm or less, for example, in consideration of the impedance (internal resistance) of the lithium battery, the internal resistance becomes too high as described above when the thickness is in μm. However, there is a possibility that it may become an unsuitable lithium battery to use as a power supply practically.

  On the other hand, in the present invention, the second electrolyte 22 containing iodine is located between the electrolyte layer 20 and the negative electrode 30 on the surface 10 a side of the composite 10 that functions as the positive electrode, which tends to cause unevenness on the surface. It is formed. And since the film thickness of the second electrolyte 22 is 100 nm or more and 800 nm or less, more preferably 100 nm or more and 400 nm or less in consideration of the above-mentioned unevenness, a rise in internal resistance is suppressed, and a small size and thinness suitable for practical use Lithium battery 100 can be provided. The same effect can be obtained also in the lithium battery 200 of the second embodiment in which the method of forming the composite functioning as the positive electrode is different.

Third Embodiment
<Electronic equipment>
Next, the electronic device of the present embodiment will be described by using a wearable device as an example. FIG. 19 is a perspective view showing the configuration of the wearable device as the electronic device of the third embodiment.

  As shown in FIG. 19, a wearable device 300 as an electronic device according to the present embodiment is an information device which is mounted like a wristwatch on, for example, a wrist WR of a human body and can obtain information related to the human body. , A sensor unit 302, a display unit 303, a processing unit 304, and a battery 305.

  The band 301 is a belt made of a flexible resin such as rubber, for example, so as to be in close contact with the wrist WR at the time of wearing, and has a joint capable of adjusting the joint position at the end of the band. .

  The sensor 302 is, for example, an optical sensor, and is disposed on the inner surface side (wrist WR side) of the band 301 so as to touch the wrist WR when worn.

  The display unit 303 is, for example, a light receiving type liquid crystal display device, and is provided on the outer surface side of the band 301 (opposite to the inner surface to which the sensor 302 is attached) so that the wearer can read the information displayed on the display unit 303. It is arranged.

  The processing unit 304 is, for example, an integrated circuit (IC), is incorporated in the band 301, and is electrically connected to the sensor 302 and the display unit 303. The processing unit 304 performs arithmetic processing for measuring a pulse, a blood glucose level, and the like based on the output from the sensor 302. Further, the display unit 303 is controlled to display a measurement result and the like.

  The battery 305 is incorporated as a power supply source for supplying power to the sensor 302, the display unit 303, the processing unit 304, and the like in a detachable state with respect to the band 301. As the battery 305, the lithium battery 100 of the first embodiment is used. The lithium battery 200 of the second embodiment may be used as the battery 305.

  According to the wearable device 300 of the present embodiment, the sensor 302 electrically detects information related to the pulse and blood sugar level of the wearer from the wrist WR, and the processing unit 304 performs arithmetic processing and the like, and then the display unit 303 Can display the pulse and blood sugar levels. Not only the measurement result but also, for example, information indicating the condition of the human body predicted from the measurement result and time can be displayed on the display unit 303.

  In addition, since the lithium battery 100 (or the lithium battery 200) having excellent charge and discharge characteristics is used as the battery 305 in a small size, the wearable device 300 is lightweight and thin, and can withstand long-term repeated use. Can be provided. Further, since the lithium battery 100 is a solid secondary battery, it can be repeatedly used by charging, and there is no concern that the electrolyte leaks, so that the wearable device 300 can be used safely for a long period of time. it can.

  Although the wristwatch-type wearable device 300 is illustrated in the present embodiment, the wearable device 300 may be attached to, for example, an ankle, a head, an ear, a waist or the like.

  Further, the electronic device to which the lithium battery 100 as a power supply source is applied is not limited to the wearable device 300. For example, a head mounted display, a head up display, a mobile telephone, a personal digital assistant, a notebook computer, a digital camera, a video camera, a music player, a wireless headphone, a game machine, etc. are mentioned. Moreover, it is applicable not only to such a consumer (general consumer) apparatus but also an apparatus for industrial use. In addition, the electronic device of the present invention may have other functions such as a data communication function, a game function, a recording and reproducing function, and a dictionary function.

  The present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the scope or spirit of the invention as can be read from the claims and the entire specification, and a lithium battery with such a modification A method of manufacturing a lithium battery and an electronic device to which the lithium battery is applied are also included in the technical scope of the present invention. Various modifications can be considered other than the above embodiment. Hereinafter, a modification is given and demonstrated.

  (Modification 1) The composite 10 of the first embodiment and the composite 210 of the second embodiment, which function as a positive electrode, include a positive electrode active material 11, a first electrolyte 12, and a third electrolyte 13. However, the third electrolyte 13 may not necessarily be included.

  (Modification 2) According to the method of manufacturing the lithium battery 100 of the first embodiment, the composite 10 is prepared by adjusting the amount of the melt 12m of the first electrolyte 12 to be impregnated into the porous active material portion 10p. The composite 10 may include the electrolyte layer 20 because it is possible to simultaneously form the electrolyte layer 20 on one surface 10 a of the

  (Modification 3) The vapor deposition method as a method of forming the second electrolyte 22 is not only physical vapor deposition (PVD) such as vacuum vapor deposition, ion plating, ion beam vapor deposition, etc., but also thermal CVD, plasma CVD, etc. Chemical vapor deposition (CVD).

  10, 210: complex functioning as positive electrode, 10a, 210a: one surface of the complex, 10c, 210b: other surface of the complex, 10p, 210p: active material portion (pellets), 11: positive electrode active material, 12: first electrolyte, 13: third electrolyte, 20: electrolyte layer, 22: second electrolyte, 30: negative electrode, 41, 42: current collector, 100, 200: lithium battery, 300: wearable device as an electronic device .

Claims (14)

A positive electrode containing lithium,
A negative electrode containing lithium,
An electrolyte layer provided between the positive electrode and the negative electrode and comprising a first electrolyte;
And a second electrolyte containing iodine provided between the electrolyte layer and the negative electrode,
The lithium battery, wherein the ion conductivity of the second electrolyte is smaller than the ion conductivity of the first electrolyte.   The lithium battery according to claim 1, wherein a film thickness of the second electrolyte is 100 nm or more and 800 nm or less. The positive electrode is a composite including an active material portion made of particulate lithium composite metal oxide,
The lithium battery according to claim 1, wherein the first electrolyte is provided in a space inside the active material portion.   The lithium battery according to claim 3, wherein the first electrolyte and a third electrolyte having a higher ion conductivity than the first electrolyte are provided in a void inside the active material portion.   The lithium battery according to any one of claims 1 to 4, wherein the second electrolyte contains lithium iodide.   The lithium battery according to any one of claims 1 to 5, wherein the first electrolyte is a lithium composite oxide containing carbon and boron.   The lithium battery according to any one of claims 4 to 6, wherein the third electrolyte is a lithium mixed metal oxide containing lanthanum, zirconium and niobium. Forming an active material portion having a void therein by using a particulate lithium composite metal oxide;
Filling the voids of the active material portion with a first electrolyte to form a composite;
Forming an electrolyte layer by forming a film of the first electrolyte so as to cover at least one surface of the composite;
Forming a second electrolyte containing iodine having a smaller ion conductivity than the first electrolyte on the electrolyte layer;
Laminating on the second electrolyte to form a lithium-containing negative electrode;
Forming a current collector in contact with at least one of the other surface of the composite and the negative electrode.   The method of manufacturing a lithium battery according to claim 8, wherein in the step of forming the second electrolyte, lithium iodide having a thickness of 100 nm to 800 nm is formed by vapor deposition.   The method of manufacturing a lithium battery according to claim 8 or 9, further comprising the step of filling a third electrolyte in which the ion conductivity is larger than the first electrolyte in the void of the active material portion. Forming a composite by mixing a positive electrode active material containing lithium and a first electrolyte, forming the mixture, and firing;
Forming an electrolyte layer on one side of the composite;
Forming a second electrolyte containing iodine having a smaller ion conductivity than the first electrolyte on the electrolyte layer;
Laminating on the second electrolyte to form a lithium-containing negative electrode;
Forming a current collector in contact with at least one of the other surface of the composite and the negative electrode.   The method of manufacturing a lithium battery according to claim 11, wherein in the step of forming the second electrolyte, lithium iodide having a thickness of 100 nm to 800 nm is formed by vapor deposition.   In the step of forming the complex, the positive electrode active material, the first electrolyte, and a third electrolyte having a larger ion conductivity than the first electrolyte are mixed, shaped, and fired to form the complex. A method of manufacturing a lithium battery according to claim 11 or 12.   An electronic device comprising the lithium battery according to any one of claims 1 to 7.

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