JP2011146202A - Lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that a lithium ion battery used widely as a power source of a portable electronic equipment is becoming extremely difficult to display a polarity of the terminal electrode while downsizing progresses, and accompanied with downsizing, reduction of unit cost per one battery progresses, however, increase in manufacturing cost in the polarity identification process and polarity display process of the battery has become a great burden. <P>SOLUTION: The battery cell to constitute a battery is made a compound cell consisting of a set of battery cells in which a positive electrode and a negative electrode are mutually connected, and is made a structure in which at least the compound cells are connected in series or in parallel. As a result, the battery becomes a nonpolar secondary battery, and has no distinction in the terminal electrode, thereby, it is not necessary to take care in mounting direction and mounting process is simplified, enabling reduction in manufacturing cost. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a multilayer all solid-state lithium ion secondary battery including a laminate including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer.

  In recent years, the development of electronic technology has been remarkable, and portable electronic devices have been made smaller, lighter, thinner, and multifunctional. Accordingly, it is strongly desired to reduce the size, weight, thickness, and improve the reliability of batteries that serve as power sources for electronic devices. In order to meet these demands, a multilayer lithium ion secondary battery in which a plurality of positive electrode layers and negative electrode layers are laminated via a solid electrolyte layer has been proposed. A multilayer lithium ion secondary battery is assembled by stacking battery cells having a thickness of several tens of μm. Therefore, the battery can be easily reduced in size and weight and reduced in thickness. In particular, parallel or series-parallel stacked batteries are excellent in that a large discharge capacity can be achieved even with a small cell area. In addition, an all-solid-state lithium ion secondary battery using a solid electrolyte instead of the electrolytic solution has high reliability without fear of liquid leakage or liquid depletion. Furthermore, since the battery uses lithium, a high voltage and a high energy density can be obtained.

FIG. 6 is a cross-sectional view of a conventional lithium ion secondary battery (Patent Document 1). A conventional lithium ion secondary battery includes a laminate in which a positive electrode layer 101, a solid electrolyte layer 102, and a negative electrode layer 103 are sequentially laminated, and terminal electrodes 104 and 105 that are electrically connected to the positive electrode layer 101 and the negative electrode layer 103, respectively. Consists of FIG. 6 shows a battery composed of a single laminate for convenience, but an actual battery generally has a large number of positive electrode layers, solid electrolyte layers, and negative electrode layers in order to increase battery capacity. It is formed by laminating in order. Different active materials were used for the positive electrode layer and the negative electrode layer. A material having a higher redox potential was selected as the positive electrode active material, and a lower material was selected as the negative electrode active material. In a battery having such a structure, when the terminal electrode on the negative electrode side is used as a reference voltage, the battery is charged by applying a positive voltage to the terminal electrode on the positive electrode side, and discharged from the terminal electrode on the positive electrode side. A positive voltage is output. On the other hand, if the polarity of the terminal electrode is wrong and the positive terminal electrode is used as a reference voltage and a positive voltage is applied to the negative terminal electrode, the battery is not charged. Therefore, conventionally, the polarity is displayed on the surface of the battery after inspecting the polarity of all the batteries regardless of the size of the battery. Moreover, when mounting the battery, the polarity was identified and the battery was mounted so as to have the correct polarity. However, in particular, in the case of a small battery having a side of 5 mm or less, the manufacturing unit cost per unit is low, and thus the manufacturing cost by these processes has become a very heavy burden.
Furthermore, in addition to manufacturing costs, lithium ion secondary batteries are being miniaturized. In particular, in the case of an all-solid small battery manufactured by batch firing as described in Patent Document 1, It has become technically very difficult to provide a mark for identifying the positive electrode and the negative electrode. In the case of a secondary battery that is used by being mounted on an electronic circuit board, such as a chip-type lithium ion secondary battery, there is a problem that it cannot be easily removed and reattached just because the polarity is wrong.

WO / 2008/099508 Publication

  An object of the present invention is to simplify a manufacturing process of a lithium ion secondary battery and reduce manufacturing cost.

The present invention (1) is a multilayer all solid-state lithium ion secondary comprising a laminate comprising a first terminal electrode and a second terminal electrode, wherein a positive electrode layer and a negative electrode layer are alternately laminated via a solid electrolyte layer. In the battery, n nonpolar battery cells arranged in series connection between the first terminal electrode and the second terminal electrode, and 0 or any arbitrary connected in parallel to each of the nonpolar battery cells A lithium ion battery comprising: a plurality of natural battery cells, wherein the nonpolar battery cell is a cell in which one battery cell and the other battery cell are connected to each other's positive electrode and negative electrode. Secondary battery (where n is an arbitrary natural number).
The present invention (2) is the lithium ion secondary battery of the invention (1), wherein the laminate is formed by batch firing after the laminate is laminated.
The present invention (3) is an electronic device using the lithium ion secondary battery of the invention (1) or the invention (2) as a power source.
The present invention (4) is an electronic device using the lithium ion secondary battery of the invention (1) or the invention (2) as a storage element.

According to the present invention (1), since a nonpolar lithium ion secondary battery can be realized, there is no need to distinguish terminal electrodes, the battery manufacturing process and the mounting process can be simplified, and the manufacturing cost can be reduced. is there. In particular, for a battery whose length, width, and height are all 5 mm or less, a significant effect can be obtained in reducing the manufacturing cost by omitting the polarity identification step.
According to the present invention (2), the manufacturing process of the nonpolar lithium ion secondary battery can be simplified, and the manufacturing cost can be reduced. It is also effective in reducing the size and strength of the battery.
According to the present invention (3), it is possible to use a small battery with a lower cost than in the prior art, which is effective in reducing the size and cost of the electronic device.
According to the present invention (4), since a lithium ion secondary battery can be used as a large-capacity storage element, the degree of freedom in circuit design is increased. For example, an AC / DC converter for power supply, a DC / DC converter, and a load device By connecting in between, it is possible to make a lithium ion secondary battery with a large storage density function as a smoothing capacitor, and to supply stable power with little ripple to the load device and to reduce the number of components. It becomes possible.

(a) is sectional drawing of the lithium ion secondary battery which concerns on the Example of this invention. (b) is a circuit diagram showing connections of battery cells constituting the lithium ion secondary battery shown in (a). (a) And (b) is sectional drawing of the lithium ion secondary battery which concerns on the other Example of this invention. It is a circuit diagram which shows the connection of the battery cell which comprises the lithium ion secondary battery which concerns on the Example of this invention. (a) And (b) is a figure explaining the charging / discharging operation | movement of the lithium ion secondary battery which concerns on the Example of this invention. (a) thru | or (d) is a manufacturing process order sectional drawing of the lithium ion secondary battery concerning the Example of this invention. (e) is sectional drawing of the lithium ion secondary battery which concerns on a comparative example. It is sectional drawing of the conventional lithium ion secondary battery. It is a figure which shows the charging / discharging characteristic of the nonpolar lithium ion secondary battery which concerns on the Example of this invention.

The best mode of the present invention will be described below.
(Battery structure)
FIG. 1A is a cross-sectional view of a lithium ion secondary battery according to an embodiment of the present invention, and is a cross-sectional view showing the most basic battery structure. The battery includes a solid electrolyte layer 1, a current collector layer 2, a positive electrode layer 3, a negative electrode layer 4, a terminal electrode 5, and a terminal electrode 6. A battery in which a plurality of laminates composed of current collector layers each having a positive electrode layer and a negative electrode layer arranged on both sides are connected to either the terminal electrode 5 or the terminal electrode 6 at an end thereof and are alternately laminated via a solid electrolyte layer. Is formed. Moreover, about the arrangement | positioning of a laminated body, it arrange | positions so that the positive electrode layer in each laminated body and the negative electrode layer in another laminated body may face each other through a solid electrolyte layer. As for the uppermost layer and the lowermost layer of the current collector layer, as shown in the figure, the positive electrode layer or the negative electrode layer is disposed only on one side thereof.
FIG.1 (b) is a circuit diagram which shows the connection of the battery cell which comprises the lithium ion secondary battery shown to Fig.1 (a), and four battery cells are connected in parallel. Unlike the conventional lithium ion secondary battery shown in FIG. 5, the battery cells are arranged such that the positive electrode of one battery cell and the negative electrode of another battery cell are connected to the same terminal electrode.

FIGS. 4A and 4B are diagrams illustrating the charge / discharge operation of the lithium ion secondary battery according to the embodiment of the present invention. In FIG. 4A, charging is performed by applying a voltage from an external power source so that the terminal 1 is on the positive voltage side and the terminal 2 is on the negative voltage side. At this time, the battery cell 42 and the battery cell 44 arranged in parallel inside the battery are charged. On the other hand, the battery cell 41 and the battery cell 42 are not charged. It is common knowledge that a lithium ion secondary battery will generate abnormal heat and cause explosion and ignition when reverse charged. However, the present inventors have found that such a phenomenon occurs in a lithium ion secondary battery in which the electrolyte is a liquid such as an organic solvent. The positive electrode layer, the electrolyte layer, and the negative electrode as disclosed in Patent Document 1 In the all-solid-state lithium ion secondary battery formed by laminating layers and firing at once, such a dangerous phenomenon does not occur, and it is found that even if reverse charging is performed, it is not simply charged, The present invention has been devised. When the battery shown in FIG. 4A is discharged, the charged battery cell 42 and the battery cell 44 are discharged to supply electric energy to the outside.
On the other hand, FIG. 4B is a diagram when charging is performed by applying a voltage from an external power source so that the terminal 1 is on the negative voltage side and the terminal 2 is on the positive voltage side. In this case, the battery cell 45 and the battery cell 47 are charged, and the battery cell 46 and the battery cell 48 are not charged. At the time of discharging, the charged battery cells 45 and 47 are discharged to supply electric energy to the outside.

FIG. 3 is a circuit diagram showing connection of battery cells constituting the lithium ion secondary battery according to the embodiment of the present invention. The technical idea relating to the lithium ion secondary battery of the present invention is not limited to the battery in which the plurality of battery cells shown in FIG. 1 are connected in parallel, but a plurality of battery cells are connected in series and parallel as shown in FIG. It is possible to apply to a battery that has been used. The battery 21 includes two terminal electrodes, that is, a terminal electrode 22 and a terminal electrode 23. The internal circuit of the battery 21 is configured by connecting a plurality of battery cells. Here, a battery cell in which one battery cell and another battery cell are connected to each other's positive electrode and negative electrode is referred to as a “nonpolar battery cell”. When n is an arbitrary natural number, n nonpolar battery cells 24, 25,..., 26 are connected in series inside the battery 21. Furthermore, in the row (1 row, 2 rows,..., N row) of the battery cells in which the respective nonpolar battery cells are arranged, the terminal electrode 23 is arranged in the i-th row (i = 1,..., N). The a _i battery cells arranged so that the side becomes the positive electrode side and the b _i battery cells arranged so that the terminal electrode 23 side becomes the negative electrode side are connected in parallel. Here, a _i and b _i are 0 or an arbitrary natural number, and a battery cell in which one positive electrode layer, one electrolyte layer, and one negative electrode layer are stacked is simply referred to as a “battery cell”.
The lithium ion secondary battery according to the embodiment of the present invention shown in FIG. 3 includes a first terminal electrode and a second terminal electrode, and a laminate in which a positive electrode layer and a negative electrode layer are alternately laminated via a solid electrolyte layer. A multilayer all solid-state lithium ion secondary battery comprising: n nonpolar battery cells arranged in series between the first terminal electrode and the second terminal electrode; and the nonpolar battery cell It is composed of 0 or any natural number of battery cells connected in parallel to each other, and the nonpolar battery cell is composed of one battery cell and another battery cell connected to each other's positive and negative electrodes. It can also be expressed as a lithium ion secondary battery (where n is an arbitrary natural number) characterized by being a cell.
The battery cell shown in FIG. 3 is a configuration of a general internal circuit of the lithium ion secondary battery according to the embodiment of the present invention, and the lithium ion secondary battery shown in FIG. This corresponds to the case of a _i = 3 and b _i = 3. Even when the battery shown in FIG. 3 is used, it goes without saying that charging can be performed by charging the terminal electrode 23 on the positive voltage side or charging it on the negative voltage side with respect to the terminal electrode 22. Yes.

2 (a) and 2 (b) are cross-sectional views of a lithium ion secondary battery according to another embodiment of the present invention.
The battery shown in FIG. 2 (a) has a structure in which the current collector is removed from the lithium ion secondary battery shown in FIG. The battery includes a solid electrolyte layer 11, a positive electrode layer 12, a negative electrode layer 13, a terminal electrode 14, and a terminal electrode 15. A battery in which a plurality of laminates in which the positive electrode layer and the negative electrode layer are directly connected without being connected to the current collector layer is connected to either the terminal electrode 14 or the terminal electrode 15 at an end thereof and alternately stacked via the solid electrolyte layer. Is formed. Moreover, about the arrangement | positioning of a laminated body, it arrange | positions so that the positive electrode layer in each laminated body and the negative electrode layer in another laminated body may face each other through a solid electrolyte layer. As for the uppermost layer and the lowermost layer of the laminate, only the positive electrode layer or the negative electrode layer is arranged as shown in the figure. Since the battery shown in FIG. 2A does not have a current collector layer, the manufacturing process can be reduced by simplifying the process.
The battery shown in FIG. 2B includes a solid electrolyte layer 16, a positive electrode layer 17, a negative electrode layer 18, a terminal electrode 19, and a terminal electrode 20. A battery in which a plurality of laminates in which a positive electrode layer and a negative electrode layer are directly connected without being connected to a current collector layer is connected to either the terminal electrode 19 or the terminal electrode 20 at an end thereof and alternately stacked via a solid electrolyte layer Is formed. Moreover, about the arrangement | positioning of a laminated body, it arrange | positions so that the positive electrode layer in each laminated body and the negative electrode layer in another laminated body may face each other through a solid electrolyte layer. As for the uppermost layer and the lowermost layer of the laminate, only the positive electrode layer or the negative electrode layer is arranged as shown in the figure. In the battery shown in FIG. 2B, a positive electrode layer and a negative electrode layer are formed by mixing a conductive material with an active material constituting the positive electrode layer and the negative electrode layer in order to reduce internal resistance. In the battery, the positive electrode layer and the negative electrode layer have a structure in which an active material is supported on a conductive matrix made of a conductive material after the batch firing step.

(Battery material)
(Active material)
As an active material constituting the electrode layer of the lithium ion secondary battery of the present invention, it is preferable to use a material that efficiently releases and adsorbs lithium ions. For example, it is preferable to use a transition metal oxide or a transition metal composite oxide. Specifically, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium vanadium composite oxide, lithium titanium composite oxide, manganese dioxide, titanium oxide, niobium oxide, vanadium oxide, tungsten oxide, It is preferable to use a polyanion oxide containing lithium and a halide thereof. Furthermore, lithium manganese composite oxide and lithium titanium composite oxide are particularly suitable for use as an active material material because the volume change due to adsorption and release of lithium ions is particularly small, and the electrode is not pulverized or peeled off easily. Can do.
Here, there is no clear distinction between the positive electrode active material and the negative electrode active material, the potential of two kinds of compounds is compared, a compound showing a more noble potential is used as a positive electrode active material, and a compound showing a lower potential Can be used as the negative electrode active material.

(Conductive material)
As the conductive substance constituting the electrode layer of the lithium ion secondary battery of the present invention, it is preferable to use a material having a high conductivity. For example, it is preferable to use a metal or alloy having high oxidation resistance. Here, the metal or alloy having high oxidation resistance is a metal or alloy having a conductivity of 1 × 10 ¹ S / cm or more after firing in an air atmosphere. Specifically, it is preferable to use silver, palladium, gold, platinum, aluminum or the like as long as it is a metal. As an alloy, an alloy composed of two or more metals selected from silver, palladium, gold, platinum, copper, and aluminum is preferable. For example, AgPd is preferably used. AgPd is preferably a mixed powder of Ag powder and Pd powder or AgPd alloy powder.
The conductive material mixed with the active material to produce the electrode layer may be the same for the positive electrode and the negative electrode, or may be different. That is, it is preferable to select a material, a mixing ratio, a manufacturing condition, and the like of the conductive substance as suitable for each of the positive electrode and the negative electrode.

(Material of solid electrolyte)
As the solid electrolyte constituting the solid electrolyte layer of the lithium ion secondary battery of the present invention, it is preferable to use a material having low electron conductivity and high lithium ion conductivity. Moreover, it is preferable that it is an inorganic material which can be baked at high temperature in an atmospheric condition. For example, oxides of lithium, lanthanum, titanium, oxides of lithium, lanthanum, tantalum, barium, titanium, polyanion oxides that do not contain lithium-containing polyvalent transition elements, lithium silicate (Li _3.5 Si _0.5 P _0.5 O ₄ ), lithium titanium phosphate (LiTi ₂ (PO ₄ ) ₂ ), lithium germanium phosphate (LiGe ₂ (PO ₄ ) ₃ ), Li ₂ O-SiO ₂ , Li ₂ OV ₂ O ₅ -SiO ₂ , Li _It is preferable to use at least one material selected from the group consisting of ₂ O—P ₂ O ₅ —B ₂ O ₃ and Li ₂ O—GeO ₂ . Furthermore, a material doped with a different element, Li ₃ PO ₄ , LiPO ₃ , Li ₄ SiO ₄ , Li ₂ SiO ₃ , LiBO ₂ or the like may be used for these materials. The material of the solid electrolyte layer may be crystalline, amorphous, or glassy.

(Battery manufacturing method)
In the laminate constituting the lithium ion secondary battery of the present invention, the positive electrode layer, the solid electrolyte layer, and the negative electrode layer constituting the laminate are pasted, applied and dried to produce a green sheet. It laminates and it manufactures by baking the produced laminated body collectively.

Here, as the positive electrode active material, the negative electrode active material, and the solid electrolyte material used for pasting, those obtained by calcining inorganic salts or the like as the respective raw materials can be used. The calcination temperature of the positive electrode active material, the negative electrode active material, and the solid electrolyte are all set to 700 ° C. or higher from the point of proceeding the chemical reaction of the raw materials by calcining and fully exhibiting the respective functions after batch firing. Is preferred.
The method for forming the paste is not particularly limited, and for example, a paste can be obtained by mixing the powder of each of the above materials in a vehicle of an organic solvent and a binder. For example, a positive electrode paste can be prepared by dispersing LiMn ₂ O ₄ powder as a positive electrode active material in a solvent and a vehicle. Similarly, a negative electrode paste can be produced by dispersing Li _4/3 Ti _5/3 O ₄ powder as a negative electrode active material in a solvent and a vehicle. Also, a solid electrolyte paste can be prepared by dispersing Li _3.5 Si _0.5 P _0.5 O ₄ powder as a solid electrolyte in a solvent and a vehicle.
The prepared paste is applied in a desired order on a substrate such as PET and dried as necessary, and then the substrate is peeled off to produce a green sheet. The paste application method is not particularly limited, and a known method such as screen printing, application, transfer, doctor blade, or the like can be employed.
The produced green sheets for the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are stacked in the desired order and the number of layers, and alignment, cutting, etc. are performed as necessary to produce a laminate.
The produced laminate is pressed together. The pressure bonding is performed while heating, and the heating temperature is, for example, 40 to 80 ° C. The pressure-bonded laminated body is heated and fired, for example, in an air atmosphere. Here, firing refers to heat treatment for the purpose of sintering. Sintering refers to a phenomenon in which when a solid powder aggregate is heated at a temperature lower than the melting point, it solidifies into a compact body called a sintered body. In the production of the lithium ion secondary battery of the present invention, the firing temperature is preferably in the range of 600 to 1100 ° C. If the temperature is lower than 600 ° C, no conductive matrix is formed in the electrode layer. If the temperature exceeds 1100 ° C, problems such as melting of the solid electrolyte and changes in the structure of the positive electrode active material and the negative electrode active material occur. . The firing time is, for example, 1 to 3 hours.

As a first specific example of the production method, there is a production method of a multilayer all solid-state lithium ion secondary battery including the following steps (1) to (5).
Step (1): A positive electrode paste containing a metal powder and a positive electrode active material, a negative electrode paste containing a metal powder and a negative electrode active material, and a solid electrolyte paste containing a solid electrolyte powder are prepared.
Step (2): A solid electrolyte paste is applied and dried on a PET substrate to produce a solid electrolyte sheet. Hereinafter, the green sheet is simply referred to as a sheet. Next, a positive electrode paste is applied and dried on the solid electrolyte sheet to produce a positive electrode sheet. Further, a negative electrode paste is applied and dried on the solid electrolyte sheet to produce a negative electrode sheet.
Step (3): The positive electrode unit in which the solid electrolyte sheet and the positive electrode sheet are laminated is peeled from the PET substrate. Further, the negative electrode unit in which the solid electrolyte sheet and the negative electrode sheet are laminated is peeled from the PET substrate. Next, the laminated body which laminated | stacked the positive electrode unit and the negative electrode unit alternately is produced.
Step (4): The laminate is fired to produce a sintered laminate.
Step (5): On the side surface of the laminate, a positive electrode terminal is formed so as to be connected to the positive electrode layer, and a negative electrode terminal is formed so as to be connected to the negative electrode layer. The electrode terminal (positive terminal, negative terminal) is a curing temperature suitable for the paste to be used after applying a terminal electrode paste such as a commonly known thermosetting conductive paste or sintered metal conductive paste to each side of the battery. It is formed by heating at a metal sintering temperature. Although not shown, a protective layer is formed on the outermost part of the laminated body as necessary to complete the battery.

Further, as a second specific example of the manufacturing method, a method for manufacturing a multilayer all solid-state lithium ion secondary battery including the following steps (i) to (iii) may be mentioned.
Step (i): A positive electrode paste containing a metal powder and a positive electrode active material, a negative electrode paste containing a metal powder and a negative electrode active material, and a solid electrolyte paste containing a powder of a lithium ion conductive inorganic material are prepared.
Step (ii): A positive electrode paste, a solid electrolyte paste, a negative electrode paste, and a solid electrolyte paste are applied and dried in this order to produce a laminate composed of green sheets.
Step (iii): If necessary, the substrate used for producing the green sheet is peeled off, and the laminate is fired to produce a sintered laminate.
Step (iv): A terminal electrode is formed on the side surface of the laminate so that the end faces extending from the active material layers can be electrically joined. If necessary, a protective layer is formed on the outermost part of the laminate to complete the battery.

(Applications other than power supply)
The lithium ion secondary battery according to the present invention can be used for applications other than the power source. As a background to this, there is a problem of increase in power supply wiring resistance due to miniaturization of wiring width accompanying reduction in size and weight of electronic devices. For example, when the power consumption of the CPU in a notebook computer increases, if the power supply wiring resistance is high, the power supply voltage supplied to the CPU may be lower than the minimum drive voltage, which may cause problems such as signal processing errors and function stoppages. For this reason, a power storage device consisting of a smoothing capacitor is placed between the power supply device such as an AC / DC converter or DC / DC converter and a load device such as a CPU, suppressing ripples in the power line and temporarily reducing the power supply voltage. In consideration of this, consideration is given to supplying a certain amount of power to the load device. However, power storage elements such as aluminum electrolytic capacitors and tantalum electrolytic capacitors have a drawback that the power storage density is small because the power storage principle is based on the polarization of the dielectric. In addition, since these power storage elements use an electrolytic solution, it is difficult to mount them by solder reflow near the components on the substrate.
On the other hand, the lithium ion secondary battery according to the present invention can be mounted in the vicinity of a component (load device) on a substrate. In particular, when the lithium ion secondary battery according to the present invention is mounted in the vicinity of a component with large power consumption and used as a power storage element, the function as a power storage device can be maximized. Furthermore, since the lithium ion secondary battery according to the present invention is an extremely small nonpolar battery, it can be easily attached to a mounting board. In particular, those using an inorganic solid electrolyte have high heat resistance and can be mounted by solder reflow. In addition, the lithium ion secondary battery has a high storage density because the storage principle is the movement of lithium ions between electrodes. Therefore, by using such a nonpolar lithium ion secondary battery as a storage element, it is possible to function as an excellent smoothing capacitor and / or backup power source and to supply stable power to the load device. Effects such as improvement in the degree of freedom in circuit design and mounting board design and reduction in the number of parts can also be obtained.

(Example)
EXAMPLES The present invention will be described in detail below using examples, but the present invention is not limited to these examples. In addition, unless otherwise indicated, a part display is a weight part.

(Preparation of positive electrode paste)
LiMn ₂ O ₄ produced by the following method was used as the positive electrode active material.
Li ₂ CO ₃ and MnCO ₃ were used as starting materials, these were weighed so as to have a molar ratio of 1: 4, wet-mixed with a ball mill for 16 hours using water as a solvent, and then dehydrated and dried. The obtained powder was calcined in air at 800 ° C. for 2 hours. The calcined product was coarsely pulverized, wet mixed with a ball mill for 16 hours using water as a solvent, and then dehydrated and dried to obtain a positive electrode active material powder. The average particle size of this powder was 0.30 μm. It was confirmed using an X-ray diffractometer that the composition of the produced powder was LiMn ₂ O ₄ .
The positive electrode paste was prepared by mixing 100 parts of Ag / Pd with a weight ratio of 85/15 used as a metal powder and LiMn ₂ O ₄ used as a positive electrode active material powder in a volume ratio of 60:40, and ethyl cellulose as a binder. 15 parts and 65 parts of dihydroterpineol as a solvent were added, and the mixture was kneaded and dispersed with three rolls to prepare a positive electrode paste. Here, as Ag / Pd having a weight ratio of 85/15, a mixture of Ag powder (average particle size 0.3 μm) and Pd powder (average particle size 1.0 μm) was used.

(Preparation of negative electrode paste)
Li _4/3 Ti _5/3 O ₄ produced by the following method was used as the negative electrode active material.
Using Li ₂ CO ₃ and TiO ₂ as starting materials, these were weighed so as to have a molar ratio of 2: 5, wet-mixed in a ball mill for 16 hours using water as a solvent, and then dehydrated and dried. The obtained powder was calcined in air at 800 ° C. for 2 hours. The calcined product was coarsely pulverized, wet mixed with a ball mill for 16 hours using water as a solvent, and then dehydrated and dried to obtain a negative electrode active material powder. The average particle size of this powder was 0.32 μm. It was confirmed using an X-ray diffractometer that the composition of the produced powder was Li _4/3 Ti _5/3 O ₄ .
The negative electrode paste was prepared by mixing Ag / Pd with a weight ratio of 85/15 previously used as a metal powder and Li _4/3 Ti _5/3 O ₄ used as a negative electrode active material powder in a volume ratio of 60:40. Part, 15 parts of ethyl cellulose as a binder, and 65 parts of dihydroterpineol as a solvent were added and kneaded and dispersed with a three roll to prepare a negative electrode paste. Here, as Ag / Pd having a weight ratio of 85/15, a mixture of Ag powder (average particle size 0.3 μm) and Pd powder (average particle size 1.0 μm) was used.

(Preparation of solid electrolyte sheet)
As a solid electrolyte, Li _3.5 Si _0.5 P _0.5 O ₄ produced by the following method was used.
Using Li ₂ CO ₃ , SiO ₂ and Li ₃ PO ₄ as starting materials, these were weighed to a molar ratio of 2: 1: 1, wet mixed with a ball mill for 16 hours using water as a solvent, and then dehydrated and dried. did. The obtained powder was calcined in air at 950 ° C. for 2 hours. The calcined product was coarsely pulverized, wet mixed in a ball mill for 16 hours using water as a solvent, and then dehydrated and dried to obtain a lithium ion conductive inorganic substance powder. The average particle size of this powder was 0.54 μm. It was confirmed using an X-ray diffractometer that the composition of the produced powder was Li _3.5 Si _0.5 P _0.5 O ₄ .
Next, 100 parts of this powder is mixed with 100 parts of ethanol and 200 parts of toluene with a ball mill and wet-mixed. Then, 16 parts of polyvinyl butyral binder and 4.8 parts of benzylbutyl phthalate are further added and mixed to form lithium. An ion conductive inorganic material paste was prepared. This lithium ion conductive inorganic substance paste was formed into a sheet using a PET film as a base material by a doctor blade method to obtain a lithium ion conductive inorganic substance sheet having a thickness of 13 μm.

(Preparation of terminal electrode paste)
Silver fine powder, epoxy resin, and solvent were kneaded and dispersed with three rolls to produce a thermosetting conductive paste.

  Using these pastes, a multilayer all solid-state lithium ion secondary battery having the structure shown in FIG. 2 was produced.

(Preparation of positive electrode unit)
A positive electrode paste was printed at a thickness of 8 μm by screen printing on the surface opposite to the PET film of the lithium ion conductive inorganic material sheet having a thickness of 13 μm. Next, the printed positive electrode paste was dried at 80 to 100 ° C. for 5 to 10 minutes. In this way, a sheet of the positive electrode unit of FIG. 5A in which the positive electrode paste was printed on the lithium ion conductive inorganic material sheet was obtained.

(Preparation of negative electrode unit)
A negative electrode paste was printed at a thickness of 8 μm by screen printing on the opposite side of the 13 μm thick lithium ion conductive inorganic material sheet from the PET film. In this way, a negative electrode unit sheet of FIG. 5B in which the negative electrode paste was printed on the lithium ion conductive inorganic material sheet was obtained.

(Production of laminate)
After the PET film was peeled off from each of the positive electrode unit and the negative electrode unit, surface bonding was performed so that the surfaces made of the lithium ion conductive inorganic material sheets of each unit were bonded together to obtain the composite unit shown in FIG. 5 (c). . At this time, the printed positive electrode paste was extended only to one end surface, and the printed negative electrode paste was extended only to the other surface. Two sets of this composite unit were produced, and the positive electrode paste printing surface of one composite unit and the negative electrode paste printing surface of another composite unit were overlapped so as to be in surface contact with each other, and extended to the same end surface. Further, a laminate of lithium ion conductive sheets was provided on both sides of the composite unit so as to sandwich the composite unit. Thereafter, this was molded at a temperature of 80 ° C. and a pressure of 1000 kgf / cm ² , and then cut to produce a laminated block. Thereafter, the laminated block was fired to obtain a laminated body. Firing was performed by raising the temperature in air to 1000 ° C. at a rate of temperature rise of 200 ° C./hour, maintaining that temperature for 2 hours, and naturally cooling after firing. In the thus obtained sintered laminate, the thickness of each lithium ion conductive inorganic substance was 15 μm, the thickness of the positive electrode unit was 8 μm, and the thickness of the negative electrode unit was 7 μm. Moreover, the vertical, horizontal, and height of the laminate were 3.7 mm, 3.2 × mm × 0.13 mm, respectively. A terminal electrode paste is applied to the end surface of the laminated body where the electrodes are extended, and thermosetting is performed at 150 ° C. for 30 minutes to form a pair of terminal electrodes. The nonpolar all solid lithium ion secondary battery of FIG. Obtained.

(Comparative example)
As a comparative example, an all solid lithium ion secondary battery having polarity was produced using a positive electrode unit and a negative electrode unit produced by the same method as in the example.
After peeling the PET film from the positive electrode unit and the negative electrode unit, two units were alternately stacked with the lithium ion conductive inorganic material interposed therebetween. At this time, the positive electrode unit and the negative electrode unit were shifted and stacked so that the printed positive electrode paste extended only to one end surface and the printed negative electrode paste extended only to the other surface. Thereafter, this was molded at a temperature of 80 ° C. and a pressure of 1000 kgf / cm ² , and then cut to produce a laminated block. Thereafter, the laminated block was fired to obtain a laminated body. Firing was performed by raising the temperature in air to 1000 ° C. at a rate of temperature rise of 200 ° C./hour, maintaining that temperature for 2 hours, and naturally cooling after firing. In the laminated body thus obtained, each lithium ion conductive inorganic material had a thickness of 7 μm, a positive electrode unit thickness of 5 μm, and a negative electrode unit thickness of 6 μm. Moreover, the vertical, horizontal, and height of the laminate were 3.2 mm × 2.7 mm × 0.11 mm, respectively. The terminal electrode was formed by the same method as in the example, and an all solid lithium ion secondary battery having the polarity shown in FIG. 5 (e) was obtained.

(Evaluation of battery characteristics)
Lead wires were attached to the respective terminal electrodes, and repeated charge / discharge tests were conducted. The current at the time of charging and discharging was 0.1 μA, the cutoff voltages at the time of charging and discharging were 4.5 V and −4.5 V, respectively, and the charging / discharging time was within 300 minutes. As shown in FIG. 7, the nonpolar lithium ion secondary battery according to the embodiment of the present invention has normal charge and discharge in the forward direction and the reverse direction while the capacity increases as the charge and discharge cycle increases. It was confirmed that this was done. The forward discharge capacity in the fourth cycle was 2.2 μAh, and the reverse discharge capacity was 2.3 μAh. On the other hand, in the case of the battery having the polarity of the comparative example, it was not charged even when reverse charging was performed. However, it was confirmed that charging / discharging in the forward direction was normally performed by repeating a plurality of forward and reverse charging / discharging operations. This means that a secondary battery using a lithium ion conductive solid electrolyte has high resistance to reverse charging, unlike a lithium ion secondary battery using a liquid electrolyte, regardless of whether it is polar or nonpolar. This indicates that there is no risk of fire etc.

  As described in detail above, the present invention solves the problems associated with downsizing of portable electronic devices, and greatly contributes to the field of electronics.

1, 11, 16, 201 Solid electrolyte layer 2 Current collector layer 3, 12, 17, 202 Positive electrode layer 4, 13, 18, 203 Negative electrode layer 5, 6, 14, 15, 19, 20 Terminal electrode 21 Lithium ion two Secondary battery 22, 23 Terminal 24, 25, 26 Nonpolar battery cell 27, 28, 29, 30, 31, 32 Battery cell 41, 42, 43, 44, 45, 46, 47, 48 Battery cell 101 Positive electrode layer 102 Solid Electrolyte layer 103 Negative electrode layer 104, 105 Terminal electrode 204 Positive electrode unit 205 Negative electrode unit 206 Composite unit

Claims (4)

In the multilayer all solid-state lithium ion secondary battery comprising a laminate comprising a first terminal electrode and a second terminal electrode, wherein a positive electrode layer and a negative electrode layer are alternately laminated via a solid electrolyte layer, N nonpolar battery cells arranged in series connection between the terminal electrode and the second terminal electrode, and zero or any natural number of battery cells connected in parallel to each of the nonpolar battery cells The lithium ion secondary battery is characterized in that the nonpolar battery cell is a cell in which one battery cell and the other battery cell are connected to each other's positive electrode and negative electrode (where n is Any natural number). 2. The lithium ion secondary battery according to claim 1, wherein the laminated body is formed by batch firing after being laminated. An electronic device using the lithium ion secondary battery according to claim 1 as a power source. The electronic device which uses the lithium ion secondary battery of any one of Claim 1 or 2 as an electrical storage element.

Images