Lithium ion secondary battery

Abstract

To provide a lithium ion secondary battery in which no active material is used in a negative electrode.SOLUTION: A lithium ion secondary battery according to an aspect of the present invention comprises a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive and negative electrodes. In the lithium ion secondary battery, the negative electrode has a negative electrode current collector; the negative electrode current collector has a region where it is in direct contact with at least one of the electrolyte and the separator; the electrolyte contains a fluorine; and the negative electrode current collector has the function of allowing a precipitate having lithium to deposit on its surface during a charge operation. The lithium ion secondary battery may further comprise a spacer between the separator and the negative electrode. The electrolyte may further contain an organic compound having fluorine. Supplying fluorine to lithium deposited from the electrolyte to the negative electrode surface can prevent deposition of lithium like a dendrite (whisker) during further deposition.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] One embodiment of the present invention relates to a lithium ion secondary battery and a method for manufacturing the same.

[0002] Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one aspect relates to an article, a method, or a manufacturing method. One aspect of the present invention is a process, machine, manufacture, or composition. Therefore, the present invention more specifically disclosed herein The technical field of one embodiment of the present invention is a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, The driving method thereof or the manufacturing method thereof can be given as an example. [Background technology]

[0003] Secondary batteries include nickel-metal hydride batteries, lead secondary batteries, and lithium-ion secondary batteries. Some examples include:

[0004] These secondary batteries are used as power sources for mobile information terminals such as mobile phones. Among them, lithium-ion secondary batteries are being actively developed because they have high capacity and can be made small. This is being carried out in many places.

[0005] Lithium-ion secondary batteries consist of an electrode collector, an electrode active material, an electrolyte, a separator, and an outer casing. Lithium-ion secondary batteries consist of a variety of components, such as electrodes, and are manufactured through a number of processes. Considering the wide range of applications, it is important to be able to manufacture at low cost. The fewer the number of steps and time required for manufacturing, the lower the manufacturing costs. can.

[0006] The negative electrode of a lithium ion secondary battery generally has an active material made of a carbon material on a negative electrode current collector. The active material is the material that inserts the ions (lithium ions) that act as carriers. The active material layer, which is made by coating the active material on the current collector, contains In addition to the substance, conductive additives, binders, etc. may be included.

[0007] Materials suitable for the negative electrode have a low redox potential and a specific capacity per unit volume and weight. However, in secondary batteries, metallic lithium has the following characteristics: During charging, lithium in the electrolyte precipitates in the form of dendrites (whiskers) on the lithium metal. This may cause a short circuit by breaking through the separator, and may also cause dendrites to form during discharge. The roots of the whiskers dissolve into the electrolyte, generating isolated lithium, which reduces the cycle characteristics. Therefore, in the lithium-ion secondary batteries that are in practical use, In the present case, an active material layer is formed by coating an active material made of a carbon material on a current collector, and lithium ions are The absorption and release reaction of ions is utilized as the negative electrode reaction (Non-Patent Document 1).

[0008] However, when preparing the active material layer, a kneading machine for preparing the slurry, a slurry grinding machine, etc. are used as the equipment. Many pieces of equipment are required, such as a coater for applying the coating and a dryer for drying the slurry. In addition, each process using these devices requires time. Materials such as electrical auxiliaries and binders are also costly. In addition, in the case of electrodes using active material layers, In secondary batteries, the cell potential decreases by the reaction potential of the active material, resulting in a decrease in energy density. On the other hand, if a method of directly depositing lithium on the current collector could be adopted, The negative electrode has the lowest potential among all the systems in the battery, making it the secondary battery with the highest energy density. can be produced. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 4-328277 [Patent Document 2] JP 2007-106634 A [Non-patent literature]

[0010] [Non-Patent Document 1] Zenpachi Ogumi (ed.), "Lithium Secondary Batteries", 1st edition, Ohmsha Co., Ltd., March 20, 2008, p.104 Summary of the Invention [Problem to be solved by the invention]

[0011] One aspect of the present invention aims to produce a negative electrode without using an active material made of a carbon-based material. The present invention aims to provide a method for producing lithium without incurring the time and financial costs associated with forming a negative electrode active material layer. The present invention aims to provide a lithium-ion secondary battery that can reduce the amount of metal oxide in the negative electrode during charging. Reduces lithium dendritic (whisker-like) deposits on the lithium surface. Another object of the present invention is to provide a lithium-ion secondary battery having good cycle characteristics. Another object of the present invention is to provide a secondary battery having a large capacity per unit mass and volume. Another object of the present invention is to provide a novel secondary battery, To provide a new electricity storage device, a new method for manufacturing a secondary battery, or a new method for manufacturing an electricity storage device One of the goals is to

[0012] The description of these problems does not preclude the existence of other problems. The embodiment does not necessarily have to solve all of these problems. The above will become apparent from the description in the specification, drawings, claims, etc. It is possible to extract other issues from the descriptions in the patent, claims, etc. [Means for solving the problem]

[0013] One aspect of the present invention is a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator between the positive electrode and the negative electrode. The negative electrode has a negative electrode current collector, and the negative electrode current collector is at least one of the electrolyte solution or the separator. The negative electrode current collector has an area in direct contact with one of the electrodes, the electrolyte contains fluorine, and the negative electrode current collector is A lithium ion secondary battery having a function of depositing lithium on its surface. Next battery.

[0014] Another aspect of the present invention is a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator between the positive electrode and the negative electrode. The negative electrode has a negative electrode current collector, and a spacer between the separator and the negative electrode. The current collector is in direct contact with the spacer, the electrolyte contains fluorine, and the separator and the negative electrode current collector The lithium-containing precipitate can be formed in the region between the electrode and the body. It is a lithium-ion secondary battery.

[0015] Another aspect of the present invention is a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator between the positive electrode and the negative electrode. and a sheet-like spacer between the separator and the negative electrode, The negative electrode has a negative electrode current collector, and the negative electrode current collector is provided with a spacer. The electrolyte contains fluorine and is in direct contact with the separator and the negative electrode current collector. A lithium ion secondary battery having a function of depositing lithium in the battery. It is a pond.

[0016] Another aspect of the present invention is a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator between the positive electrode and the negative electrode. a separator and a spacer between the separator and the negative electrode, the negative electrode having a negative electrode current collector, The negative electrode current collector is in direct contact with the spacer, and the electrolyte contains fluorine. The separator and the spacer are flexible and are disposed between the separator and the negative electrode current collector. A lithium-ion secondary battery having a function of depositing a precipitate containing lithium. be.

[0017] In one embodiment of the present invention, fluorine is contained in an organic compound or an inorganic salt in the electrolyte. In the electrolyte, organic compounds or inorganic salts are contained in an amount of 2 wt% or less based on the weight of the electrolyte. The organic compound may be a fluorocarbon. The inorganic salt may be ethylene carbonate. A lithium-ion secondary battery that is lithium tetrafluoroborate or lithium hexafluorophosphate. The negative electrode may be a lithium ion secondary battery having no active material layer. The negative electrode current collector may be a lithium ion secondary battery containing copper. The precipitate may be lithium fluoride, forming a lithium ion secondary battery.

[0018] Without using an active material layer made of a carbon material, for example, lithium is directly applied to a negative electrode current collector made of copper. When lithium is deposited on the current collector, a film of lithium is formed, and the film grows with charging. However, when lithium is deposited on the negative electrode current collector, it tends to form dendrites. This creates problems with lithium whiskers. As a result of examining the conditions under which whiskers cannot be formed, it was found that the presence of fluorine on the current collector surface suppresses the formation of whiskers. It was found that:

[0019] That is, the electrolyte of the secondary battery contains a salt further containing fluorine as a salt having lithium, e.g. For example, when lithium tetrafluoroborate or lithium hexafluorophosphate is used, the surface of the negative electrode current collector It was confirmed that the formation of dendritic (whisker-like) lithium on the surface can be suppressed. In addition, the cycle characteristics of secondary batteries are improved, and the capacity of the batteries per unit weight and volume is also increased. I was able to do it.

[0020] Furthermore, an organic compound having fluorine, such as fluoroethylene carbonate, may be added to the electrolyte as an additive. The addition of carbonate further improved the cycle characteristics, and the power per unit weight and volume was It was also confirmed that the capacity of the battery was further increased. At least, the presence of an organic compound having fluorine as an additive in the electrolyte can improve the negative electrode Fluorine is supplied to the surface, improving cycle characteristics.

[0021] In addition, if a spacer is provided between the separator and the negative electrode current collector, the separator and the negative electrode current collector A region where lithium can be deposited between the electrode and the spacer can be secured. Although lithium can be deposited on the surface of the negative electrode current collector without the spacer, the spacer prevents lithium from being deposited on the surface of the negative electrode current collector. In addition, by making the area larger, it is possible to increase the area in which the metal can be precipitated. In order to secure the required space, it is preferable that the volume occupied by the spacer is small. For example, the spacer is formed in a sheet shape. When using spacers with high porosity, it is desirable to have a high porosity. This also makes it possible to reduce the weight of the lithium-ion secondary battery.

[0022] On the other hand, the spacer does not need to support the structure of the lithium-ion secondary battery, so it can be of a fixed shape. It is not necessary to use a spacer, and a flexible spacer can be used. The spacer having the above structure can be applied to a flexible lithium ion secondary battery. The spacer can also deform in response to deformation of the lithium ion secondary battery.

[0023] The negative electrode can be used in a lithium-ion secondary battery without providing an active material layer. It is possible to manufacture a secondary battery while reducing the equipment, time, and financial costs involved in the process of forming an active material layer. It can be made. Effect of the Invention

[0024] According to one embodiment of the present invention, a negative electrode can be produced without using an active material made of a carbon-based material. The lithium ion can be charged without incurring the time and financial costs associated with forming a negative electrode active material layer. In addition, the lithium secondary battery can be provided by depositing the lithium metal on the surface of the negative electrode during charging. This can reduce the amount of lithium dendritic (whisker-like) formed by the lithium ion implantation. It is also possible to provide a lithium ion secondary battery having good cycle characteristics. In addition, it is possible to provide a secondary battery having a large capacity per unit mass and volume. One embodiment of the present invention is a novel secondary battery, a novel power storage device, a novel method for manufacturing a secondary battery, and It is possible to provide a novel method for manufacturing an electricity storage device.

[0025] The description of these effects does not preclude the existence of other effects. An embodiment does not necessarily have to have all of these effects. Effects other than these may also be included. The above is self-evident from the description, drawings, claims, etc. Other effects can be extracted from the claims and other descriptions. [Brief description of the drawings]

[0026] [Figure 1] 1A and 1B are diagrams illustrating a secondary battery according to one embodiment of the present invention. [Diagram 2] FIG. 2 shows the results of an XPS analysis of the negative electrode surface of a secondary battery according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a SEM image of a surface of a negative electrode of a secondary battery according to one embodiment of the present invention. [Figure 4] FIG. 2 is a graph showing charge and discharge curves of a secondary battery according to one embodiment of the present invention. [Diagram 5] FIG. 2 is a graph showing charge and discharge curves of a secondary battery according to one embodiment of the present invention. [Figure 6] FIG. 13 shows cycle characteristics of a secondary battery according to one embodiment of the present invention. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] 1A to 1C are diagrams illustrating electronic devices including a secondary battery according to one embodiment of the present invention. [Figure 10] 1A to 1C are diagrams illustrating electronic devices including a secondary battery according to one embodiment of the present invention. [Figure 11] 1A and 1B are diagrams illustrating an electronic device including a secondary battery according to one embodiment of the present invention, as viewed from the side. [Figure 12] FIG. 2 is a SEM image of the surface of a negative electrode of a secondary battery. [Figure 13] 1A and 1B are diagrams illustrating a secondary battery according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description, and various modifications in form and details are possible by those skilled in the art. The present invention is not limited to the description of the following embodiments. It is not something that can be done.

[0028] In each of the drawings described in this specification, the positive electrode, the negative electrode, the active material layer, the separator, the exterior body, etc. The dimensions of each component, such as the size and thickness of each component, have been exaggerated for clarity of illustration. Therefore, each component is not necessarily limited to its size. The present invention is not limited to the relative size between the

[0029] In addition, in this specification, ordinal numbers such as 1st, 2nd, 3rd, etc. are used for convenience. The order of steps and the vertical positional relationship are not shown. It does not indicate a specific name as an item for identifying the invention.

[0030] In addition, in the configuration of one embodiment of the present invention described in this specification, etc., The same reference numerals are used in different drawings for the parts having the same configuration, and the repeated explanations are omitted. In addition, when referring to parts with similar functions, the same hatch pattern is used and symbols are used. In some cases, the number may not be added.

[0031] In addition, the contents described in the description of the embodiment of the present invention can be used in appropriate combination. Cut.

[0032] (Embodiment 1) A method for manufacturing a lithium-ion secondary battery 110 according to one embodiment of the present invention will be described with reference to FIGS. FIG. 1(B) is a cross-sectional view of a lithium-ion secondary battery 110. 1 is a diagram showing a positive electrode current collector 101a, a positive electrode active material layer 101b, a separator 104, and a negative electrode The current collector 102 is stacked, and the electrolyte 105 is sealed in the exterior body 106. It is also possible for the secondary battery to have a laminated structure. The positive electrode current collector 101a and the positive electrode active material layer 101b are included, while the negative electrode has a negative electrode active material layer. Therefore, the negative electrode current collector 102 is the main component constituting the negative electrode. The negative electrode current collector 102 may be in direct contact with the separator 104. In that case, the negative electrode current collector 102 is in contact with the separator. The separator 104 directly contacts the electrolyte 105 present in the openings of the separator 104. When the negative electrode current collector 102 is not in contact with the electrolyte 104, the electrolyte 105 is At least one entire surface of the negative electrode current collector 102 is in contact with the negative electrode current collector 102 .

[0033] The negative electrode will be described. The negative electrode does not have an active material layer, and the negative electrode current collector 102 is the main component of the negative electrode. It is an essential component.

[0034] The negative electrode current collector 102 may be made of stainless steel, gold, platinum, zinc, iron, copper, aluminum, titanium, Metals such as tantalum and their alloys are highly conductive and have carrier ions such as lithium. Materials that do not alloy with silicon, titanium, neodymium, and scandium can also be used. The aluminum alloy contains elements such as tungsten and molybdenum that improve heat resistance. It can also be formed from a metal element that reacts with silicon to form a silicide. Metal elements that react with silicon to form silicide include zirconium, titanium, and , hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, Cobalt, nickel, etc.

[0035] Metallic lithium is popular due to its low redox potential and high specific capacity per unit volume and weight. Although it has favorable properties, due to the reactivity of metallic lithium in the atmosphere, it is not recommended for safety reasons. Therefore, metallic lithium must not be used for the negative electrode current collector. Even if metallic lithium is deposited on the current collector by charging the secondary battery, the secondary battery Because the pond is sealed, this problem does not arise.

[0036] The negative electrode current collector 102 is not covered with an active material layer, but is in direct contact with the electrolyte 105 or the separator. Then, the negative electrode current collector 102 has at least a region where the negative electrode current collector 102 can be charged by a reaction caused by charging. However, as charging progresses, lithium in the electrolyte is deposited on the lithium. As charging continues, the ions precipitate in the form of dendrites (whiskers). Lithium grows in the form of whiskers and breaks through the separator, causing a short circuit. In addition, the roots of the dendrites (whiskers) may dissolve into the electrolyte during discharge and become isolated. Lithium is generated, and the capacity is reduced by the lithium that is lost in the electrolyte without undergoing a battery reaction. This causes a problem of deterioration in cycle characteristics.

[0037] This problem can be avoided by providing an active material layer made of, for example, a carbon material on the negative electrode current collector. However, when preparing the active material layer, it is necessary to use a device for preparing the slurry. a kneading machine for mixing the slurry, a coater for applying the slurry, and a dryer for drying the slurry. Many pieces of equipment are required. In addition, each process using these devices takes time. In addition, the active material, conductive additive, binder, and other materials are also costly. In the secondary battery according to the present invention, since an active material layer is not provided on the negative electrode current collector, A part of the equipment can be omitted, and the manufacturing cost can be reduced.

[0038] In the case of an electrode using an active material layer, the cell potential is increased by the reaction potential of the active material in the secondary battery. On the other hand, in the secondary battery according to one embodiment of the present invention, In this case, the negative electrode is the most important component of all the systems inside the secondary battery because lithium is deposited directly on the current collector. Since the potential is the lowest in the battery, it is possible to fabricate a secondary battery with the highest energy density.

[0039] Through the above steps, a negative electrode for a lithium ion secondary battery can be produced.

[0040] The positive electrode 101 will be described.

[0041] The positive electrode 101 includes at least a positive electrode current collector 101a and a positive electrode active material layer 101b.

[0042] The positive electrode active material is a material capable of inserting and extracting carrier ions such as lithium ions. For example, an olivine type crystal structure, a layered rock salt type crystal structure, or a spinel type crystal structure can be used. Examples of such materials include lithium-containing materials having a tetracyclic crystal structure.

[0043] Lithium-containing materials with an olivine structure (general formula LiMPO 4 (M is Fe(II), Mn( Representative examples of the cations are LiFePO4 , Li NiPO 4 , LiCoPO 4 , LiMnPO 4 , LiFe a Ni b PO 4 , LiFe a C o b PO 4 , LiFe a Mn b PO 4 , LiNi a Co b PO 4 , LiNi a Mn b PO 4 (a + b is less than or equal to 1, 0 < a < 1, 0 < b < 1), LiFe c Ni d Co e PO 4 , Li Fe c Ni d Mn e PO 4 , LiNi c Co d Mn e PO 4 (c + d + e is less than or equal to 1, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFe f Ni g Co h Mn i PO 4 (f + g + h + i is less than or equal to 1, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1), etc. exist.

[0044] In particular, lithium iron phosphate (LiFePO 4 ) is preferable because it satisfies the requirements for a cathode active material, such as safety, stability, high capacity density, high generation potential , the presence of lithium that can be extracted during initial oxidation (charging), etc., well.

[0045] Examples of lithium-containing materials having a layered rock salt type crystal structure include lithium cobalt oxide. (LiCoO 2 ), LiNiO 2 , LiMnO 2 , Li 2 MnO 3 , LiNi 0.8 Co 0.2 O 2 NiCo series (general formula: LiNi x Co 1-x O 2 (0 <x<1))、L iNi 0.5 Mn 0.5 O 2 NiMn series such as LiNi x Mn 1-x O 2 (0 <x<1))、LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 NiMnCo series (NMC and The general formula is LiNi x Mn y Co 1-x-y O 2 (x>0, y>0, x+y<1 In addition, Li(Ni 0.8 Co 0.15 Al 0.05 )O 2 , Li 2 MnO 3 -LiMO 2 (M is Co, Ni or Mn), etc.

[0046] In particular, LiCoO 2 The capacity is large, and LiNiO 2 It is more stable in air than and LiNiO 2 Since it has advantages such as being thermally stable as compared to

[0047] Examples of lithium-containing materials having a spinel-type crystal structure include LiMn2 O 4 , L i 1+x Mn 2-x O 4 , Li(MnAl) 2 O 4 , LiMn 1.5 Ni 0.5 O 4 etc. Some examples include:

[0048] LiMn 2 O 4 Lithium-containing materials having a spinel-type crystal structure containing manganese such as A small amount of lithium nickel oxide (LiNiO 2 Or LiNi 1-x MO 2 (M=Co, Al Mixing it with other materials has the advantage of suppressing the elution of manganese and the decomposition of the electrolyte. This is preferable.

[0049] In addition, the positive electrode active material is a compound having the general formula Li (2-j) MSiO 4 (M is Fe(II), Mn (II), Co(II), or Ni(II) (j is 0 to 2) The general formula Li (2-j) MSiO 4 A representative example is Li ( 2-j) FeSiO 4 , Li (2-j) NiSiO 4 , Li (2-j) CoSiO 4 , L i (2-j) MnSiO 4 , Li (2-j) Fe k Ni l SiO 4 , Li (2-j) Fe k Co l SiO 4 , Li (2-j)Fe k Mn l SiO 4 、Li (2-j) Ni k Co l SiO 4 、Li (2-j) Ni k Mn l SiO 4 (k + l is 1 or less, 0 < k < 1, 0 < l <1), Li (2-j) Fe m Ni n Co q SiO 4 、Li (2-j) Fe m Ni n Mn q SiO 4 、Li (2-j) Ni m Co n Mn q SiO 4 (m + n + q is 1 or less, 0 < m <1, 0 < n < 1, 0 < q < 1), Li (2-j) Fe r Ni s Co t Mn u SiO 4 ( r + s + t + u is 1 or less, 0 < r < 1, 0 < s < 1, 0 < t < 1, 0 < u < 1) etc. are mentioned.

[0050] Also, as the positive electrode active material, A x M 2 (XO 4 ) 3 (A is Li, Na, or Mg) (M is Fe, Mn, Ti, V, Nb, or Al) (X is S, P, Mo, W, As, or , Si) represented by the general formula of a NASICON-type compound can be used. NASICON-type compound As, Fe 2 (MnO 4 ) 3 , Fe 2 (SO 4 )3 , Li 3 Fe 2 (PO 4 ) 3 etc. In addition, Li 2 MPO 4 F, Li 2 MP 2 O 7 , Li 5 M O 4 (M is Fe or Mn), a compound represented by the general formula NaFeF 3 Perovskite etc. TiS type fluoride 2 , MoS 2 Metal chalcogenides (sulfides, selenides, terbium, etc.) LiMVO 4 Lithium-containing materials having an inverse spinel crystal structure such as NaO2 (V 2 O 5 , V 6 O 13 , LiV 3 O 8 etc.), manganese oxides, organic Sulfur-based materials and the like can be used.

[0051] In addition, the carrier ion is an alkali metal ion other than the lithium ion, an alkaline earth metal ion, etc. In the case of cations, beryllium ions, or magnesium ions, the above-mentioned compounds are used as the positive electrode active material. In the compounds and oxides, alkali metals (e.g., sodium and potassium) are used instead of lithium. Alkaline earth metals (e.g., calcium, strontium, barium, etc.), Lithium or magnesium may also be used. For example, NaFeO 2 Ya, Na 2 / 3 [F e 1 / 2 Mn 1 / 2 ]O 2 The sodium-containing layered oxide such as This can be done.

[0052] In addition, a material in which a plurality of the above materials are combined may be used as the positive electrode active material. A solid solution of the above materials can be used as the positive electrode active material. Co 1 / 3 Mn 1 / 3 Ni 1 / 3 O 2 and Li 2 MnO 3 The solid solution is used as the positive electrode active material. It is possible.

[0053] The positive electrode active material should preferably have an average primary particle size of 50 nm to 100 μm. .

[0054] Acetylene black (AB), graphite particles, and carbon black are used as conductive additives for the electrodes. Carbon nanotubes, graphene, fullerene, etc. can be used.

[0055] The conductive additive can form an electronic conduction network in the electrode. This makes it possible to maintain a path of electrical conduction between the positive electrode active materials. By adding an electric auxiliary agent, a positive electrode active material layer 101b having high electronic conductivity is realized. It is possible.

[0056] In addition to the typical polyvinylidene fluoride (PVDF), polyimide is also used as a binder. , polytetrafluoroethylene, polyvinyl chloride, ethylene propylene diene poly styrene-butadiene rubber, acrylonitrile-butadiene rubber, fluororubber, Uses polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, etc. It is possible.

[0057] The content of the binder in the total amount of the positive electrode active material layer 101b is 1 wt % or more and 10 wt % or less. Preferably, 2wt% or more and 8wt% or less is more preferable, and 3wt% or more and 5wt% or less is more preferable. The content of the conductive assistant with respect to the total amount of the positive electrode active material layer 101b is more preferably 1w The content is preferably t% or more and 10wt% or less, and more preferably 1wt% or more and 5wt% or less.

[0058] When the positive electrode active material layer 101b is formed by a coating method, the positive electrode active material, the binder, and the conductive material are mixed together. An auxiliary agent and a dispersion medium are mixed to prepare an electrode slurry, which is then applied onto the positive electrode current collector 101a and dried. In this embodiment, the positive electrode current collector 101a is made of a metal containing aluminum as a main component. Materials are used.

[0059] The positive electrode current collector 101a may be made of a metal such as stainless steel, gold, platinum, aluminum, or titanium. Materials with high electrical conductivity that do not alloy with carrier ions such as lithium, such as alloys of these Silicon, titanium, neodymium, scandium, molybdenum, etc. can also be used. Aluminum alloys containing elements that improve heat resistance, such as Alternatively, it may be formed of a metal element that reacts with silicon to form a silicide. Metal elements that react with the metal to form silicide include zirconium, titanium, hafnium, and barium. Nadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel The positive electrode current collector is available in foil, plate (sheet), mesh, punched metal, extract A shape such as a band metal shape can be appropriately used.

[0060] Through the above steps, a positive electrode for a lithium ion secondary battery can be produced.

[0061] The separator 104 will now be described.

[0062] The separator 104 may be made of paper, nonwoven fabric, glass fiber, or nylon (polyethylene). amide), Vinylon (polyvinyl alcohol fiber), polyester, acrylic, polyamide Synthetic fibers such as olefin and polyurethane can be used. However, they are soluble in the electrolyte solution described below. It is necessary to select materials that do not dissolve.

[0063] More specifically, the separator 104 may be made of a material such as a fluorine-based polymer or polyethylene. Polyethers such as ethylene oxide and polypropylene oxide, polyethylene, polypropylene Polyolefins such as ethylene glycol, polyacrylonitrile, polyvinylidene chloride, polymethylmethacrylate acrylate, polymethyl acrylate, polyvinyl alcohol, polymethacrylonitrile, Polyvinyl acetate, polyvinylpyrrolidone, polyethyleneimine, polybutadiene, Polystyrene, polyisoprene, polyurethane polymers and their derivatives, cellulose , paper, nonwoven fabric, glass fiber, either alone or in combination. It is possible.

[0064] The separator 104 has an insulating property to prevent contact between the two electrodes, a property to retain the electrolyte, and a property to conduct ions. As a method for producing a membrane that functions as a separator, There is a method by stretching. For example, a molten polymer material is expanded to release heat, and the resulting film is One method is the stretching pore opening method, in which the membrane is stretched in two axial directions parallel to the membrane to form pores.

[0065] Next, as a method for incorporating the separator 104 into a secondary battery, the separator is Alternatively, a separator 104 may be placed on either the positive or negative electrode. However, it is also possible to combine the other of the positive electrode or the negative electrode. By housing the battery in an exterior body and impregnating it with an electrolyte, a secondary battery can be formed.

[0066] The separator 104 is made of a sheet having a size large enough to cover both sides of either the positive electrode or the negative electrode. If the electrode is formed in a tube or envelope shape and wrapped in a separator 104, the secondary During battery manufacturing, the electrodes can be protected from mechanical damage and the electrodes can be easily handled. The electrode wrapped in the separator and the other electrode are placed together in an outer casing, and the electrolyte is By incorporating the element, a secondary battery can be formed.

[0067] Additionally, the separator 104 may be multi-layered. The separator 104 may be formed in the manner described above. However, due to the materials of construction and the mechanical strength of the membrane, the range of membrane pore size and membrane thickness is limited. The first separator and the second separator are each produced by a stretching method, This can be used in combination in a secondary battery. The constituent materials may be selected from the above materials or one or more materials other than those listed above. The size of the pores in the film and the volume occupied by the pores can be controlled by the conditions of film formation and stretching. The properties of the membrane, such as the ratio of voids (also called porosity) and the thickness of the membrane, can be determined. By using different first and second separators in combination, one membrane can be used alone. Compared to the case of using it in Germany, it is possible to select the performance of the separator for the secondary battery in a wide range of options. become.

[0068] Furthermore, the secondary battery may be flexible. Even in such a case, the first separator and the second separator are in contact with each other at the interface therebetween. The sliding action relieves stress, so the structure using two separators is The laminated laminated body is also suitable as a separator for a flexible secondary battery.

[0069] In a lithium ion secondary battery in which an active material layer is not provided on the negative electrode, There is no active material layer between the separator and the negative electrode current collector. In some cases, the negative electrode current collector is filled with the separator, and at least a portion of the negative electrode current collector is in direct contact with the separator. If there were no spacer to keep the distance between the cathode and the anode current collector, the anode current collector would In some cases, at least a portion of the separator is in direct contact with the separator. In this case, the separator has holes. Therefore, the electrolyte in the pores comes into direct contact with the negative electrode current collector without passing through the active material layer. If it is desired to intentionally provide a distance between the negative electrode current collector and the separator, A spacer may be provided between the separator and the substrate.

[0070] The spacer will now be described.

[0071] In the lithium ion secondary battery according to one embodiment of the present invention, A spacer can be provided between the separator and the negative electrode current collector. By doing so, a region where lithium can be deposited is secured between the separator and the negative electrode current collector. Lithium can be deposited on the surface of the negative electrode current collector even without a spacer. The spacer allows a larger area onto which lithium can be deposited. Lithium can be deposited in the voids in the separator even without the spacer. The use of spacers prevents lithium deposits in the battery from shorting the positive and negative electrodes. It is possible.

[0072] FIG. 13 shows the structure of the present invention in which a spacer 108 is disposed between a separator 104 and a negative electrode current collector 106. FIG. 1 shows a cross-sectional view of a lithium-ion secondary battery according to one embodiment of the present invention.

[0073] In order to secure a larger region, the space between the separator and the negative electrode current collector is occupied by It is preferable that the volume of the spacer to be inserted is small. For example, a spacer formed in a sheet shape is used. When the separator is used, the porosity is preferably high, and is preferably higher than the porosity of the separator. A spacer with a high porosity increases the area on which lithium can be deposited. Not only can this be done, but the weight of the spacer can also be reduced, making it ideal for lithium-ion batteries. This eliminates the need to increase the weight of the next battery.

[0074] The spacer does not necessarily need to support the structure of the lithium-ion secondary battery, so it is not necessary to use a rigid spacer. It is not necessary to use a spacer having a fixed shape with high rigidity, and a flexible spacer can be used. The flexible spacer can be applied to a flexible lithium ion secondary battery. In addition, the spacer can be deformed in response to the deformation of the lithium ion secondary battery. Therefore, the spacer does not destroy the separator and the negative electrode current collector, and the spacer itself is not destroyed. However, the use of a highly rigid spacer is not excluded.

[0075] In addition, even when a spacer is provided between the separator and the negative electrode current collector, It is not necessary to completely separate the separator from the negative electrode current collector. Of course, the separator and the negative electrode current collector do not have to be in direct contact with each other. Compared with the case where the electrode does not have a sintered body, the area where lithium can be deposited is larger. It would be good if we could do that.

[0076] The shape of the spacer may be a sphere or a column, in addition to the above-mentioned sheet shape. Spacers can be placed between the separator and the negative electrode current collector, and can be spherical or If the spacer is a columnar spacer, it can be provided by scattering it on the separator or negative electrode current collector. In addition, a film can be formed on the separator or negative electrode current collector and then patterned. It is also possible to provide spacers of a predetermined shape at predetermined positions.

[0077] The spacer material may be the same as that used for the separator, such as paper, nonwoven fabric, gasoline, etc. Lath fiber, nylon (polyamide), vinylon (polyvinyl alcohol fiber) ), polyester, acrylic, polyolefin, polyurethane and other synthetic fibers. In addition, it is possible to use aramid as a type of nylon (polyamide). However, it is necessary to select a material that does not dissolve in the electrolyte solution described below.

[0078] The electrolyte 105 will now be described.

[0079] In lithium-ion secondary batteries, the electrolyte is a lithium ion battery that transfers charge between the positive and negative electrodes. However, aqueous electrolytes are not considered to be electrolytes that are ... Therefore, it is not possible to use lithium salts dissolved in organic solvents. The resulting solution is used as the electrolyte.

[0080] The electrolyte solution 105 that can be used in the lithium ion secondary battery contains an electrolyte (solute). It is preferable to use a non-aqueous solution (solvent) containing the compound.

[0081] The solvent for the electrolyte 105 is preferably an aprotic organic solvent, for example, ethylene glycol. Carbonate (EC), Propylene Carbonate (PC), Butylene Carbonate, Chloroe Ethylene carbonate, vinylene carbonate, gamma-butyrolactone, gamma-valerolactone , Dimethyl carbonate (DMC), Diethyl carbonate (DEC), Ethyl methyl carbonate EMC, methyl formate, methyl acetate, methyl butyrate, 1,3-dioxane, 1 ,4-Dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether ter, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfur One of the following, or two or more of these in any combination and ratio: folane, sultone, etc. It can be used.

[0082] In addition, by using a polymer material that can be gelled as a solvent for the electrolyte 105, the electrolyte can be easily used without leakage. This improves safety. In addition, it is possible to make the lithium-ion secondary battery thinner and lighter. Representative examples of polymeric materials that can be polymerized are silicone gel, acrylic gel, and acrylonitrile. Polyurethane gel, polyethylene oxide, polypropylene oxide, fluorine-based polymers, etc. be.

[0083] In addition, as a solvent for the electrolyte solution 105, a flame-retardant and non-evaporative ionic liquid (a room temperature molten salt) is used. By using one or more of these, it is possible to prevent internal short circuits and overcharging of lithium-ion secondary batteries. Even if the internal temperature rises due to the above reasons, the lithium-ion secondary battery will not explode or catch fire. This makes it possible to improve the safety of the lithium-ion secondary battery.

[0084] The electrolyte to be dissolved in the above-mentioned solvent is an inorganic salt having fluorine, for example, LiP F 6 , LiAsF 6 , LiBF 4 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiC(C F 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiN(CF 3 SO 2 ) 2 , LiN(C 4 F 9 SO 2 )(CF 3 SO 2 ), LiN(C 2 F 5 SO 2 ) 2 A lithium salt such as Or, two or more of these may be used in any combination and ratio.

[0085] For example, lithium tetrafluoroborate (LiBF 4 ) or lithium hexafluorophosphate (LiP F 6 The electrolyte solution having the above structure was applied to a negative electrode current collector having an area where no active material was formed. When used in a secondary battery, lithium is deposited on the negative electrode current collector during the initial charging period, and lithium and fluorine are oxidized. The lithium fluoride is formed by the dendrites of the precipitated lithium. It was confirmed that the generation of nanoparticles (whiskers) was reduced. In a secondary battery that does not contain fluorine, when an inorganic salt having fluorine is used in the electrolyte, The initial charge capacity is larger than when no inorganic salt having the formula is used.

[0086] By using inorganic salts containing fluorine in the electrolyte, it is possible to develop a secondary battery that does not use an active material in the negative electrode. In batteries, the formation of dendrite-like (whisker-like) lithium on the surface of the negative electrode can be suppressed. , suppressing the generation of lithium that does not contribute to the battery reaction, maintaining the discharge capacity, and as a result, Thus, in a secondary battery in which an active material layer is not provided on the negative electrode, When inorganic salts having fluorine are used as electrolytes, new and remarkable effects of inorganic salts having fluorine are obtained. can be obtained.

[0087] By including fluorine in the electrolyte, fluorine can be provided to the lithium deposited on the current collector surface. In addition, an organic compound having fluorine may be added as an additive to the electrolyte. It is possible to suppress the formation of lithium in the form of doped lithium (whiskers), which does not contribute to the battery reaction. This suppresses the generation of ions and maintains the discharge capacity, thereby making it possible to increase the discharge capacity.

[0088] The additive added to the electrolyte is ethylene carbonate containing fluorine, e.g., Fluoro 4-Fluoro-1,3-dioxolan-2-one (FEC) For example, when such an additive is added to the electrolyte, depending on the amount added, It can be seen that the cycle characteristics are improved. In secondary batteries, when an organic compound having fluorine is added to the electrolyte, By adding the compound, new and remarkable effects can be obtained.

[0089] In the above, the case where the carrier ion is lithium ion has been described. Carrier ions other than lithium ions can also be used. Ions include alkali metal ions, alkaline earth metal ions, beryllium ions, and In the case of magnesium ions, the electrolyte is a substitute for lithium in the above lithium salt. Instead, alkali metals (e.g., sodium and potassium) and alkaline earth metals (e.g., , calcium, strontium, barium, etc.), beryllium, or magnesium This is also fine.

[0090] In addition, the electrolyte used in secondary batteries is free of granular waste and elements other than the constituent elements of the electrolyte (hereinafter referred to as single It is preferable to use a highly purified electrolyte solution with a low content of impurities. Specifically, the mass ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less. More preferably, it is 0.01% or less. Additives such as phosphate may also be added.

[0091] Next, the exterior body 106 will be described. The exterior body 106 is made of, for example, polyethylene, polypropylene, etc. On the inner surface made of materials such as propylene, polycarbonate, ionomer, polyamide, etc. A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper, or nickel, is applied. On the metal thin film, an insulating composite such as polyamide resin or polyester resin is applied as the outer surface of the exterior body. A three-layer film having a resin film can be used. This prevents electrolyte and gas from passing through, ensures insulation, and is electrolyte resistant. Fold the exterior body inwards and stack them together, or place the two exterior bodies with their inner faces facing each other. By stacking them together and applying heat, the material on the inside melts and the two exterior bodies are fused together. By this, a sealing structure can be produced.

[0092] If the part where the exterior body is fused or otherwise bonded to form a sealed structure is called the sealed part, the exterior body is folded inward. When the package is folded and folded, a sealing portion is formed at a portion other than the fold, and the first region of the exterior body and The first region and the overlapping second region are fused or otherwise bonded to each other. When the material is kneaded, a sealing portion is formed around the entire outer periphery by a method such as heat fusion.

[0093] When a flexible material is selected from the materials of each member shown in this embodiment, It is possible to fabricate a flexible lithium-ion secondary battery. Research and development of flexible secondary batteries for such devices is currently underway. There is a demand for secondary batteries having the above structure.

[0094] When a secondary battery with electrodes, electrolyte, etc. sandwiched between two sheets of film as the exterior body is bent, In this case, the radius of curvature 1802 of the film 1801 on the side closer to the center of curvature 1800 of the secondary battery is , which is smaller than the radius of curvature 1804 of the film 1803 on the side farther from the center of curvature 1800 (see FIG. 7(A)). When a secondary battery is bent to make its cross section arc-shaped, the filter closest to the center of curvature 180° The surface of the film is subjected to compressive stress, while the surface of the film far from the center of curvature 1800 is subjected to tensile stress. Stress is applied (Figure 7(B)).

[0095] When a flexible lithium-ion secondary battery is deformed, a large stress is applied to the exterior body. However, if a pattern consisting of concave or convex parts is formed on the surface of the exterior body, the secondary battery may become deformed. Even if compressive or tensile stress is applied, the effects of distortion can be suppressed. Therefore, the radius of curvature of the exterior body of the secondary battery on the side closer to the center of curvature is 30 mm, preferably 1 It can be deformed within a range of 0 mm.

[0096] The radius of curvature of a surface will be described with reference to FIG. 8. In FIG. 8(A), a curved surface 1700 is cut. In a cross-sectional plane 1701, a part of a curve 1702, which is a curved surface shape, is approximated to an arc of a circle. The radius of the circle is the radius of curvature 1703, and the center of the circle is the center of curvature 1704. 8(C) shows a top view of the curved surface 1700. When a curved surface is cut with a plane, the shape of the curved surface is determined by the plane. The radius of curvature of the lines will be different, but the surface can be divided into two planes with the curve with the smallest radius of curvature. When cut, the radius of curvature of the curve that is the cross-sectional shape of the curved surface is defined as the radius of curvature of the surface.

[0097] The cross-sectional shape of the secondary battery is not limited to a simple arc shape, and may be a shape that includes a partial arc. For example, the shape shown in FIG. 7(C), a wavy shape (FIG. 7(D)), an S-shape, etc. In the case where the curved surface of the secondary battery has a shape having a plurality of centers of curvature, The radius of curvature at each center of curvature is the smallest, and the two outer surfaces The radius of curvature of the exterior body closest to the center of curvature of the exterior body is 30 mm, preferably 10 mm. The secondary battery can be deformed.

[0098] In this embodiment, the present invention is applied to a lithium ion secondary battery as an example. However, one aspect of the present invention is not limited thereto. lithium ion polymer secondary battery, nickel-hydrogen secondary battery, nickel-cadmium secondary battery nickel-iron secondary battery, nickel-zinc secondary battery, silver oxide-zinc secondary battery, solid-state battery It is also possible to apply the present invention to various electric storage devices. This is applicable to, for example, primary batteries, capacitors, lithium ion capacitors, etc. It is also possible.

[0099] This embodiment mode can be implemented in appropriate combination with other embodiment modes and examples. .

[0100] (Embodiment 2) In this embodiment, an example of an electronic device having the secondary battery described in the previous embodiment will be described. This will be explained with reference to FIG.

[0101] Examples of electronic devices that use secondary batteries include digital cameras, digital video cameras, Digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable games Examples of such electronic devices include digital cameras, portable information terminals, and audio playback devices. As shown in.

[0102] FIG. 9A shows an example of a mobile phone. A mobile phone 800 is assembled in a housing 801. In addition to the built-in display unit 802, the device is equipped with operation buttons 803, a speaker 805, a microphone 806, etc. Note that the secondary battery 804 of one embodiment of the present invention is used in the mobile phone 800. This reduces the weight.

[0103] The mobile phone 800 shown in FIG. 9A allows users to input information by touching a display unit 802 with a finger or the like. In addition, operations such as making a phone call or composing an email can be performed by inputting the This can be done by touching the portion 802 with a finger or the like.

[0104] The screen of the display unit 802 has three main modes. The first is a display mode that mainly displays images. The first is a display mode, the second is an input mode for inputting information such as characters, and the third is a display mode. This is a display + input mode that combines the two modes, display and input mode.

[0105] For example, when making a call or composing an e-mail, the display unit 802 is used mainly for inputting characters. The user may then enter a character input mode in which the character is displayed on the screen and perform an input operation for the character.

[0106] In addition, the mobile phone 800 includes sensors for detecting tilt, such as a gyro sensor and an acceleration sensor. By providing a detection device having a sensor, the orientation of the mobile phone 800 (portrait or landscape) can be determined, The screen display on the display unit 802 can be automatically switched.

[0107] The screen mode can be changed by touching the display unit 802 or by pressing the operation button on the housing 801. The image display is performed by operating the button 803. Also, the image display is changed depending on the type of image displayed on the display unit 802. For example, if the image signal to be displayed on the display unit is video data, If there is, switch to display mode; if there is text data, switch to input mode.

[0108] In the input mode, a signal detected by the optical sensor of the display unit 802 is detected. If there is no input from the touch of the 802 for a certain period of time, the screen mode will change from input mode to The display mode may be switched to the display mode.

[0109] The display unit 802 can also function as an image sensor. By touching the device with your palm or fingers and capturing an image of your palm print or fingerprint, you can authenticate your identity. The display uses a backlight that emits near-infrared light or a sensing light source that emits near-infrared light. If a person has a fingerprint, it is also possible to image finger veins, palm veins, etc.

[0110] FIG. 9B shows the mobile phone 800 in a bent state. When the force of the part is applied to deform the device and bend the entire device, the secondary battery 804 disposed inside the device is deformed and bent. The bent secondary battery 804 is also bent as shown in FIG. The secondary battery 804 is a stacked type secondary battery.

[0111] FIG. 9D shows an example of a wristband-type display device. The wristband-type display device 7200 has a housing. The armband-type display device 7200 has a flexible armband type display device 7201 and a display unit 7202. The armband-type display device 7200 has a secondary battery having a flexible structure in response to changes in shape of the armband-type display device 7200. Secondary batteries also change shape.

[0112] Note that the structure described in this embodiment may be used in appropriate combination with structures described in other embodiments. There can be.

[0113] (Embodiment 3) In this embodiment, a lithium ion secondary battery obtained by using the first embodiment is incorporated. 10A shows an example of an electronic device. FIG. 10(B) is a photograph showing the appearance of an electronic device incorporating a secondary battery. FIG. 10(C) is a photograph of the electronic device taken from the rear. 1 is a schematic diagram of the structure of the electronic device as viewed from the side.

[0114] The electronic device shown in FIGS. 10 and 11 is a display device that can be worn on the arm. It can display images and information. The lithium-ion secondary battery is flexible, so it can be worn on the wrist. It is possible to realize a shape that matches the design of the product. It can also be used as a prop.

[0115] The electronic device shown in FIGS. 10 and 11 includes a support structure 1001, a secondary battery 1002, a control board, 1004, a display module 1011, a protective member 1013, and a cover 1012. Specifically, a support structure 1001 has a secondary battery 1002, and a control board 1003 is placed on the secondary battery 1002. 1004, a protective member 1013 is provided on the control board 1004, and The electronic device includes a display module 1011 and a cover 1012. It has an antenna 1005 for wireless charging, and can perform wireless charging according to the Qi standard. The electronic device can also be equipped with a communication device for wirelessly communicating data used for display with external devices. The sensor 1007 has a sensing element 1007.

[0116] The secondary battery 1002 according to the first embodiment has a thin and flexible exterior. The film is attached to a curved support structure 1001, and the curved surface of the support structure 1001 is It is possible to deform the surface in accordance with the curved surface portion in an area with a large radius of curvature.

[0117] As shown in FIGS. 10B and 10C, the electronic device has a support structure 1001 having a light-transmitting property. When a plastic substrate is used, the secondary battery 1002 can be seen from the back side of the electronic device. The embossed film surface of the secondary battery 1002 can be observed.

[0118] In addition, the support structure 1001 has flexibility. Therefore, the support structure 1001 can be easily It should be noted that the support structure 1001 can be made of a material other than plastic. The shape of the support structure 1001 is a bracelet-like shape made by bending a belt-like structure. In addition, at least a part of the support structure 1001 is flexible. You can transform 001 and fit it onto your wrist.

[0119] The protective member 1013 protects the internal structure of the electronic device, especially the control board, from unexpected external shocks. 1004. Since it is deformed as a part of the electronic device, the same structure as the support structure 1001 is used. However, the material of the protective member 1013 may be different from that of the support structure 1001. Different materials may be used.

[0120] The cover 1012 is a light-shielding film with an adhesive applied on one side, and is used to protect the electronic device. It has the function of enveloping the entire structure and integrating each structure into one unit, and has an opening in the display section 1015 . The cover 1012 has a light-shielding property, so that the internal structure can be hidden, and the design of the electronic device can be improved. However, it is important to note that electronic devices are designed so that the internal structure can be seen from the outside. If such a design is adopted, the cover 1012 is The protective member 1013 does not have to have a light-shielding property. The bar 1012 does not have to have light-shielding properties.

[0121] The control board 1004 has a slit for bending, and is connected to Bluetooth (registered trademark) Same as EEE802.15.1.) standard communication device 1007, microcomputer, storage device, FP It is configured with a GA, a DA converter, a charge control IC, a level shifter, etc. The control board 1004 is connected to a display module having a display unit 1015 via an input / output connector 1014. The control board 1004 is connected to an antenna module 1011 via a wiring 1008. 1005, and is connected to the secondary battery 1002 through the wiring 1003 and the connection part 1010. A power supply control circuit 1006 controls the charging and discharging of the secondary battery 1002.

[0122] The display module 1011 is a display panel with at least the FPC 1009 attached. The electronic device shown in FIG. 11 includes a display unit 1015, an FPC 1009, and a driving circuit. It is preferable to further provide a converter for supplying power from the secondary battery 1002. .

[0123] The display module 1011 has a display unit 1015 that is flexible and is made of a flexible film. The secondary battery 1002 and the display unit are arranged so that they overlap each other. It is preferable that the display is arranged in a partially or completely overlapping position. This shortens the power path to the unit 1015, i.e., the wiring distance, and reduces power consumption. By providing the display module between the protective member 1013 and the cover 1011, wrinkles and twists can be prevented. The display module 1011 can be protected from unexpected deformation such as cracks and other damages, and the electronic device can be manufactured more efficiently. The life span of the device as a whole can be improved.

[0124] As a method for producing a display element on a flexible film, There are two methods: directly fabricating a display element on a substrate, and fabricating a display element on a substrate with rigidity such as a glass substrate. After forming the layer containing the display element, the substrate is removed by etching or polishing. A method of bonding a flexible film to a layer of the material, or a method of bonding a rigid substrate such as a glass substrate A peeling layer is provided on the display device, and a layer including a display element is formed thereon. After that, the peeling layer is used to form a rigid substrate. The layer including the display element is separated from the substrate, and the layer including the display element and a flexible film are There are ways to glue it on.

[0125] In addition, a touch panel is mounted on the display unit 1015, and information can be input to the electronic device through the touch panel. It may be possible to apply force or perform an operation.

[0126] Note that the structure described in this embodiment may be used in appropriate combination with structures described in other embodiments. There can be.

[0127] In addition, the contents (or even a part of the contents) described in one embodiment may be used in the embodiment. Another content (or a part of the content) described in the embodiment, and / or one or more other embodiments The application, combination, or replacement of the contents (or part of the contents) described in the form It is possible to do the following:

[0128] The contents described in the embodiments are explained in detail with reference to various figures in each embodiment. This refers to the content that is stated or stated using the text in the specification.

[0129] In addition, a figure (or a part thereof) described in one embodiment may be different from another part of the figure, Another figure (or a part thereof) described in the embodiment, and / or one or more By combining with the figure (or a part of it) described in another embodiment of the present invention , and many more diagrams can be constructed.

[0130] In addition, regarding the contents not specified in the drawings or text in the specification, Alternatively, the upper limit of a certain value may be set. If a numerical range is listed, such as a lower limit, you can narrow the range arbitrarily. Or, by excluding one point within the scope, a mode of the invention that excludes a part of the scope is specified. As a result, for example, the prior art can be considered to be within the technical scope of one aspect of the present invention. It may be stipulated that no entry will be allowed.

[0131] In this specification, etc., in a drawing or text described in a certain embodiment, When at least one specific example is described, it is not possible to derive a generic concept of that specific example. It will be easily understood by those skilled in the art. When at least one specific example is described in a figure or text, the general outline of that specific example is The invention is also disclosed as an embodiment of the invention and may constitute an embodiment of the invention. And one aspect of the invention can be said to be clear.

[0132] In this specification, at least the contents shown in the drawings (or even a part of the drawings) This is disclosed as one aspect of the invention and can constitute one aspect of the invention. Therefore, if something is shown in a diagram, it does not need to be explained in words. However, the contents are disclosed as one aspect of the invention and constitute one aspect of the invention. Similarly, a part of the drawings may be regarded as an embodiment of the invention. This is disclosed as one embodiment of the present invention. It can be said that one aspect of the invention is clear. Example 1

[0133] Example 1 In this example, a lithium-ion secondary battery, which is one embodiment of the present invention, is used in which an active material is not used in a negative electrode. The results of SEM observation of lithium deposited on the negative electrode current collector surface during charging. Explain.

[0134] [Preparation of positive and negative electrodes] First, the negative electrode will be described. A rolled copper foil current collector (18 μm) is used as the current collector for the negative electrode. there was.

[0135] Note that in the secondary battery of one embodiment of the present invention, an active material layer is not formed over the current collector. The apparatus required for the step of providing an active material on a negative electrode current collector, that is, the apparatus for preparing a slurry, a kneading machine for mixing the slurry, a coater for applying the slurry, and a dryer for drying the slurry. Therefore, there is no need for machines or other equipment. In addition, the cost of materials such as active materials, conductive additives, and binders was reduced. Furthermore, considering the yield of the process of providing the active material on the negative electrode current collector, This eliminates the need for a separate process, thereby increasing the yield throughout the entire secondary battery manufacturing process.

[0136] Next, the manufacturing process of the positive electrode will be described. 4 , Conductive assistant The material is graphene oxide (GO) and the binder is PVDF. 4 :G The mixture was O:PVDF=94.4:0.6:5 ​​(weight%), and the solvent was N-methyl A slurry for the electrodes was prepared using N-2-pyrrolidone (NMP).

[0137] Next, the prepared slurry was applied to an aluminum current collector (20 μm The coating was performed using a continuous coating machine and a slot coating method. The coating speed was 1.0 m / min. The NMP was dried until it was completely evaporated. Then, the graphene oxide was chemically reduced. .

[0138] Regarding the chemical reduction conditions, the reaction was carried out in a solvent containing a reducing agent to reduce graphene oxide. The reduction treatment was carried out at 60°C for 4.5 hours. Ascorbic acid was used as the reducing agent. The solvent used was ethanol, and the concentration of the reducing agent was 13.5 g / L. The substrate was washed with ethanol and dried at 70° C. for 10 hours in a vacuum atmosphere.

[0139] Next, the mixture was pressed and compacted by a roll press method to form a positive electrode active material layer.

[0140] [Preparation of secondary battery] Next, a secondary battery was fabricated using the fabricated positive and negative electrodes. A coin-type secondary battery of type 32 (diameter 20 mm, height 3.2 mm) was used. The positive electrode of the battery is made of 25 μm thick polypropylene and the negative electrode is made of cellulose fiber. The positive and negative electrodes are 1.13 cm 2 The positive and negative electrode cans were made of stainless steel. The one made of stainless steel (SUS) was used.

[0141] Three types of electrolytes were prepared: electrolyte A, electrolyte B, and comparative electrolyte A. The solvent used for the solution was ethylene carbonate (EC) and diethyl carbonate (DEC). A mixed solvent was used, in which the volume ratio was 1:1. LiPF 6 ) at a concentration of about 1 mol / L to prepare electrolyte A. Secondary battery A was fabricated using solution A. In addition, lithium tetrafluoroborate (Li BF 4 ) at a concentration of about 1 mol / L to prepare electrolyte B. A secondary battery B was thus produced.

[0142] In addition, lithium perchlorate (LiClO 4 ) at a concentration of about 1 mole / liter Comparative electrolyte A was then used to prepare a comparative secondary battery A.

[0143] Next, we performed charge and discharge tests on the three types of thin secondary batteries we had fabricated. The battery was charged and discharged at a constant current of A. The upper limit of the charge and discharge voltage was 4 V and the lower limit was 2 V. Charge and discharge were carried out at a temperature of 25°C.

[0144] [SEM observation] During the initial charge, the battery operation is stopped when the upper voltage limit of 4V is reached, and the battery is disassembled. The negative electrode with the lithium precipitated was then taken out and washed. The surface of this negative electrode was observed using a scanning electron microscope (SEM). The results of the SEM observation were As shown in FIG. 3 and FIG. 12(A).

[0145] Figure 3(A) shows the electrolyte solution containing lithium hexafluorophosphate (LiPF 6 ) a secondary battery The SEM image of the negative electrode taken from the secondary battery A is shown in Fig. 3(B). Lithium tetrafluoroborate (LiBF 4 ) from a secondary battery (secondary battery B) The negative electrode was then subjected to SEM observation. (LiClO 4 SEM of the negative electrode taken out from a secondary battery (comparative secondary battery A) having This is an observation image.

[0146] As shown in Figure 3(A), whisker-shaped lithium particles were found on the current collector taken out of secondary battery A. On the other hand, as shown in Figure 3(B), the current collector taken out of secondary battery B had In the case of the current collector taken from secondary battery A, the dendrite-like (whisker-like) As shown in FIG. 12(A), the amount of lithium in the comparative secondary battery A was 100%. On the current collector taken out from the electrode, the lithium precipitated was mostly in the form of dendrites (whiskers). The results of SEM observations showed that the electrolyte contains fluorine. In the negative electrode of a secondary battery using inorganic salts that It was confirmed that the occurrence of 200 was reduced.

[0147] The relationship between the electrolyte and the deposition of lithium in the form of dendrites (whiskers) will be discussed later. do. Example 2

[0148] Example 1 In this example, a lithium-ion secondary battery, which is one embodiment of the present invention, is used in which an active material is not used in a negative electrode. The lithium deposited on the negative electrode current collector surface during charging was analyzed by XPS. The results are explained.

[0149] The secondary battery produced in this example will be described. The conditions for producing the positive and negative electrodes are the same as those shown in Example 1. The conditions for preparing the positive and negative electrodes are the same as those for the positive and negative electrodes described above, so the explanation will be omitted. The conditions for preparing the secondary battery are the same as those shown in Example 1, so the explanation will be omitted except for a few points. Omitted.

[0150] [Preparation of secondary battery] The electrolyte used in the secondary battery produced in this example will be described. Two types of electrolytes were used: electrolyte C, which was a mixture of EC and DEC in a volume ratio of 3:7. A mixed solvent was used with lithium hexafluorophosphate (LiPF 6 ) to 1 The electrolyte solution C was dissolved at a concentration of 1 mole / liter to prepare a secondary battery C. Electrolyte D is a mixed solvent of EC and DEC in a 1:1 volume ratio. Using lithium tetrafluoroborate (LiBF 4 ) at a concentration of about 1 mole / liter Electrolyte solution D was used to prepare secondary battery D.

[0151] Next, the two types of thin secondary batteries were charged and discharged. The battery was charged and discharged at a constant current of A. The upper limit of the charge and discharge voltage was 4 V and the lower limit was 2 V. Charge and discharge were carried out at a temperature of 25°C.

[0152] [XPS analysis] During the initial charge, the battery operation is stopped when the upper voltage limit of 4V is reached, and the battery is disassembled. The negative electrode with the lithium precipitated was then taken out and washed. The surface of this negative electrode was analyzed using X-ray photoelectron spectroscopy (XPS). The results are shown in Figure 2.

[0153] Figure 2 shows the XPS spectrum of the region where the peaks attributed to lithium fluoride appear. A peak attributable to lithium fluoride was strongly observed on the surface of the negative electrode taken out of the secondary battery D. In addition, relatively small particles were observed on the surface of the negative electrode taken out of secondary battery C. A peak attributed to lithium fluoride was observed. It was confirmed that the surface of the lithium ionized material contained lithium fluoride. Lithium fluoride phosphate (LiPF 6 ) than the negative electrode of secondary battery C using lithium tetrafluoroborate. LiBF 4 It was confirmed that the negative electrode of secondary battery D, which used the

[0154] The relationship between the electrolyte and the lithium fluoride deposited on the surface of the negative electrode will be described later. Example 3

[0155] Example 1 In this example, a lithium-ion secondary battery, which is one embodiment of the present invention, is used in which an active material is not used in a negative electrode. The charge and discharge characteristics will be described.

[0156] The secondary battery produced in this example will be described. The negative electrode was produced under the conditions shown in Example 1. The conditions for preparing the secondary battery other than the electrolyte solution are the same as those in the embodiment. The fabrication conditions are the same as those shown in 1, so the explanation will be omitted except for a few points.

[0157] [Preparation of positive electrode] First, LiFePO 4 , acetylene black (hereinafter referred to as AB) and PVDF, ePO 4:AB:PVDF = 90:5:5 (weight%), and used as a solvent. The slurry for the positive electrode was prepared using NMP.

[0158] Next, the prepared slurry was applied to an aluminum current collector (2 Drying was performed at 80°C under atmospheric pressure until NMP was completely removed. The positive electrode active material layer was then pressed by a roll press method. It became dense.

[0159] Next, the values ​​used in calculating the capacity of the positive electrode will be explained. LifePO 4 A capacity of 170 mAh / g was used.

[0160] [Preparation of secondary battery] The electrolyte used in the secondary battery produced in this example will be described. Two types of electrolytes were used: electrolyte E and electrolyte F. Electrolyte E contains EC and DEC in a volume ratio of 1:1 as a solvent. A mixed solvent was used in which lithium hexafluorophosphate (LiPF 6 ) The electrolyte solution E was used to prepare a secondary battery E. Electrolyte F was prepared by mixing EC and DEC in a 1:1 volume ratio. The mixture was dissolved in lithium tetrafluoroborate (LiBF 4 ) at a concentration of 1 mole / liter The electrolyte solution F was used to prepare a secondary battery F.

[0161] [Charge / discharge characteristics] Next, the secondary battery was charged and discharged at a constant current of 1.7 mA. The upper and lower limit voltages for charging and discharging were set to 4 V and 2 V, respectively. The charging and discharging were performed at a temperature of 25°C. The initial charge-discharge characteristics are shown in Figure 4.

[0162] As shown in Figure 4, the initial discharge capacity was 100% when the electrolyte was lithium tetrafluoroborate (LiBF 4 The secondary battery F uses lithium hexafluorophosphate (LiPF 6 ) using the secondary It was confirmed that the discharge capacity was higher than that of battery E.

[0163] In lithium-ion secondary batteries, which use an active material in the negative electrode, lithium tetrafluoroborate (L iBF 4 ) is lithium hexafluorophosphate (LiPF 6 ) is chemically less stable and less decomposable. It is easy to break down and has a relatively low discharge capacity when used in an electrolyte. The results showed the opposite: the electrolyte was lithium tetrafluoroborate (LiBF 4 ) using secondary battery F The electrolyte is lithium hexafluorophosphate (LiPF 6 ) than secondary battery E, which uses The results showed that the amount was relatively high.

[0164] The results shown in Examples 1 to 3 are summarized below. That is, the lithium tetrafluoroborate ( LiBF 4 When the fluorine is partially decomposed, it provides fluorine to the lithium deposited on the surface of the negative electrode current collector. The lithium fluoride formed on the surface of the negative electrode is used to form a secondary battery. It suppresses the formation of lithium dendrites (whiskers) during battery charging. As a result, the base of the whiskers dissolves during discharge, resulting in lithium that does not contribute to the battery reaction. The generation of hexafluorophosphate was suppressed, and the discharge capacity was maintained without loss. Lithium (LiPF 6 ) has a larger discharge capacity.

[0165] However, lithium hexafluorophosphate (LiPF 6 The XPS results also showed that The results confirmed the formation of lithium fluoride on the surface, so although the amount was relatively small, lithium fluoride was It can be confirmed that the benefits of the formation of thium are being enjoyed.

[0166] By using an inorganic salt containing fluorine as the electrolyte, it is possible to form a dendritic structure (whisker This suppresses the formation of lithium (in the form of lithium ions) that does not contribute to the battery reaction, and prevents the discharge The capacity was maintained, and as a result, the discharge capacity of the secondary battery was increased. Example 4

[0167] In this embodiment, the electrolyte solution contains fluorine-containing ethylene carbonate, which is one embodiment of the present invention. This article describes a lithium-ion secondary battery that does not use an active material in the negative electrode, and uses an additive. do.

[0168] The secondary battery produced in this example will be described. The negative electrode was produced under the conditions shown in Example 1. The conditions for the positive electrode are the same as those shown in Example 3. The conditions for preparing the secondary battery other than the conditions for preparing the electrolyte were the same as those in Example 1. Since the manufacturing conditions are the same as those of the conventional method, the explanation will be omitted except for a few points.

[0169] [Preparation of secondary battery] The electrolyte G used in the secondary battery produced in this example will be described. C (propylene carbonate) and lithium tetrafluoroborate (LiBF 4 )of The solution was dissolved at a concentration of 1 mol / L. FEC (fluorescence emission spectrometry) was performed under four different conditions. ethylene carbonate) was added as an additive to prepare electrolyte solutions G-1 to G-4. Ta.

[0170] That is, electrolyte G-2 was prepared by adding FEC at a weight of 2 wt% based on the weight of the solution and mixing it. Electrolyte G-3 was prepared by adding FEC at a weight of 20 wt% based on the weight of the solution. Electrolyte G-4 was prepared by adding FEC at a weight of 50 wt% based on the weight of the solution. The electrolyte G-1 was prepared by mixing the electrolytes without adding FEC.

[0171] Secondary batteries G-1 to G-4 were prepared using electrolytic solutions G-1 to G-4. .

[0172] [Charge / discharge characteristics] Next, the secondary battery was charged and discharged at a constant current of 1.7 mA. The upper and lower limit voltages for charging and discharging were set to 4 V and 2 V, respectively. The charging and discharging were performed at a temperature of 25°C. The initial charge-discharge characteristics are shown in Fig. 5, and the cycle characteristics are shown in Fig. 6. show.

[0173] As shown in Figure 5, adding FEC to the electrolyte of a secondary battery significantly increased the discharge capacity. The effect of adding FEC becomes apparent from an addition weight of 2 wt%, The effect is more pronounced at 20 wt% added weight. At 50 wt% added weight, the effect becomes saturating. However, the discharge capacity improved with an increase in the weight of FEC added. It was confirmed that:

[0174] This is because FEC reacts with fluorine to lithium that is deposited on the surface of the negative electrode current collector during charging. Lithium fluoride is formed on the surface of the deposited lithium, which then When lithium is deposited during charging, it deposits in the form of dendrites (whiskers). This suppresses the lithium loss caused by the lithium not contributing to the battery reaction, and reduces the amount of lithium lost. This is because the decrease in discharge capacity is suppressed.

[0175] From the cycle characteristics shown in Figure 6, it is clear that the cycle characteristics improved with increasing FEC weight. The addition of FEC reduces the amount of lithium lost as lithium that does not contribute to the battery reaction. This is because the discharge capacity is reduced while maintaining the discharge capacity.

[0176] [Observation by SEM] In addition, a secondary battery was produced under the same conditions as secondary battery G-3, and the upper limit voltage was 1000V for the first charge. When the battery voltage reaches 4V, the battery is stopped, disassembled, and the negative electrode with lithium precipitated is The negative electrode was taken out and washed. Dimethyl carbonate was used as the washing solution. The surface was examined using a scanning electron microscope (SEM). The results of the SEM observation are shown in Figure 12(B). In addition, dendrite-like (whisker-like) lithium was found on the current collector removed from the secondary battery G-3. No deposition of lithium was observed. 4 )is In addition, fluorine is supplied from the FEC to the lithium on the surface of the negative electrode, forming lithium fluoride. This suppressed the formation of lithium dendrites (whiskers).

[0177] From the above examples, it was found that the fluorine supply from the electrolyte to the negative electrode surface during charging This prevents lithium from precipitating in the form of dendrites (whiskers) on the surface. Therefore, it was confirmed that a lithium-ion secondary battery can be fabricated without using a negative electrode active material. Fluorine may be contained in the salt of the electrolyte, or may be contained as an additive to the electrolyte. [Explanation of symbols]

[0178] 101 Positive electrode 101a Positive electrode current collector 101b Positive electrode active material layer 102 Negative electrode current collector 104 Separator 105 Electrolyte 106 Exterior body 108 Spacer 110 Lithium-ion secondary battery 115 Lead Electrode 116 Sealing part 200 Dendrite (whiskers) 800 Mobile Phones 801 Case 802 Display section 803 Operation button 804 Secondary battery 805 Speaker 806 Mike 1001 Support structure 1002 Secondary battery 1003 Wiring 1004 Control board 1005 Antenna 1006 Power supply control circuit 1007 Communication equipment 1008 Wiring 1009 FPC 1010 Connection 1011 Display module 1012 Cover 1013 Protective materials 1014 Input / Output Connector 1015 Display section 1700 curved surface 1701 Plane 1702 Curve, which is the shape of a surface 1703 Radius of curvature 1704 Center of curvature 1800 Center of curvature 1801 Film 1802 radius of curvature 1803 Film 1804 radius of curvature 1805 Electrodes, electrolytes, etc. 7100 Portable display devices 7101 Case 7102 Display section 7103 Operation button 7104 Secondary battery 7200 Armband type display device 7201 Case 7202 Display section

Claims

1. A positive electrode, a negative electrode, and an electrolyte solution, a separator between the positive electrode and the negative electrode; a spacer between the separator and the negative electrode, The negative electrode has a negative electrode current collector containing copper and does not have a negative electrode active material layer, the negative electrode current collector has a region in contact with the spacer, The electrolytic solution comprises a fluorine-containing inorganic salt and fluorine-containing ethylene carbonate, The negative electrode current collector has a function of allowing a lithium-containing deposit to be deposited on its surface during charging.

2. A positive electrode, a negative electrode, and an electrolyte solution, a separator between the positive electrode and the negative electrode; a spacer between the separator and the negative electrode, The negative electrode has a negative electrode current collector containing copper and does not have a negative electrode active material layer, the negative electrode current collector has a region in contact with the spacer and a region in contact with at least one of the electrolytic solution and the separator, The electrolytic solution comprises a fluorine-containing inorganic salt and fluorine-containing ethylene carbonate, The negative electrode current collector has a function of allowing a lithium-containing deposit to be deposited on its surface during charging.

3. A positive electrode, a negative electrode, and an electrolyte solution, a separator between the positive electrode and the negative electrode; a spacer between the separator and the negative electrode, The negative electrode has a negative electrode current collector containing copper and does not have a negative electrode active material layer, the negative electrode current collector has a region in contact with the spacer, The electrolytic solution comprises a fluorine-containing inorganic salt and fluorine-containing ethylene carbonate, A lithium ion secondary battery having a function of allowing a lithium-containing deposit to be deposited in the region between the separator and the negative electrode current collector.

4. A positive electrode, a negative electrode, and an electrolyte solution, a separator between the positive electrode and the negative electrode; a spacer between the separator and the negative electrode, The negative electrode has a negative electrode current collector containing copper and does not have a negative electrode active material layer, the negative electrode current collector has a region in contact with the spacer and a region in contact with at least one of the electrolytic solution and the separator, The electrolytic solution comprises a fluorine-containing inorganic salt and fluorine-containing ethylene carbonate, A lithium ion secondary battery having a function of allowing a lithium-containing deposit to be deposited in the region between the separator and the negative electrode current collector.

5. A positive electrode, a negative electrode, and an electrolyte solution, a separator between the positive electrode and the negative electrode; a sheet-like spacer between the separator and the negative electrode, the sheet-like spacer has a higher porosity than the separator, The negative electrode has a negative electrode current collector containing copper and does not have a negative electrode active material layer, the negative electrode current collector has a region in contact with the spacer, The electrolytic solution comprises a fluorine-containing inorganic salt and fluorine-containing ethylene carbonate, A lithium ion secondary battery having a function of allowing a lithium-containing deposit to be deposited in the region between the separator and the negative electrode current collector.

6. A positive electrode, a negative electrode, and an electrolyte solution, a separator between the positive electrode and the negative electrode; a spacer between the separator and the negative electrode, The negative electrode has a negative electrode current collector containing copper and does not have a negative electrode active material layer, the negative electrode current collector has a region in contact with the spacer, The electrolytic solution comprises a fluorine-containing inorganic salt and fluorine-containing ethylene carbonate, the positive electrode, the negative electrode, the separator, and the spacer are flexible; A lithium ion secondary battery having a function of allowing a lithium-containing deposit to be deposited in the region between the separator and the negative electrode current collector.

7. In any one of claims 1 to 6, The positive electrode has a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer has a region in contact with the separator, The separator has an area in contact with the spacer.

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