JP5602541B2 - All-solid-state lithium ion battery - Google Patents

Description

  The present invention relates to an all solid lithium ion battery.

  An all-solid-state battery that uses an inorganic solid electrolyte and does not use organic substances in the electrode is expected as a safe battery without leakage of organic electrolyte and gas generation. In addition, all solid-state batteries are less likely to undergo reactions other than battery reactions and can be expected to have a longer life compared to liquid batteries.

  As an example, in an all-solid battery, a positive electrode layer and a negative electrode layer are respectively laminated on both sides of a solid electrolyte layer. When using a sintered body as the inorganic solid electrolyte layer, the solid electrolyte or its unfired body and the unfired body of the electrode are stacked and fired at the same time to produce the sintered body of the electrode and solid electrolyte, and at the same time the interface between them. Can be expected to be bonded well. This method can reduce the number of manufacturing steps, reduce the manufacturing cost, and at the same time, can be expected to reduce the ion migration resistance at the electrode layer-solid electrolyte layer junction interface.

However, in general, in a lithium ion secondary battery, the positive electrode active material is a material with high oxidizing power, and the negative electrode active material is a material with high reducing power. In order to provide ionic conductivity in the electrode, it is preferable that the unfired body of the electrode contains a solid electrolyte powder together with the electrode active material powder and is fired, but the grain boundary between both powders during firing is preferred. In some cases, both may chemically react. In addition, even when the unfired body of the electrode layer is fired simultaneously with the solid electrolyte layer or the unfired body thereof, the electrode active material and the solid electrolyte are chemically reacted at the interface between the electrode layer and the solid electrolyte layer.
For this reason, there arises a problem that the electrode active material is decomposed and does not perform its function, or a compound that inhibits ionic conduction is generated.
Accordingly, even if the interface between the electrode layer and the solid electrolyte layer is physically well bonded by firing, the lithium ions are formed by the compound formed at the interface and the grain boundary between the electrode active material and the solid electrolyte in the electrode layer. As a result, the moving resistance increases and the discharge capacity does not reach the theoretical capacity. Furthermore, a design voltage may not be obtained due to the product compound.
Moreover, only the unsintered body of an electrode is baked, and only the sintered body of an electrode layer is produced, Then, it may sinter again with the unsintered body of a solid electrolyte layer, and a solid electrolyte layer may be adhere | attached. Even in such a case, both of them chemically react at the grain boundary between the electrode active material in the electrode layer and the solid electrolyte during sintering of the electrode layer.
This is particularly noticeable in the positive electrode.

  In order to solve such problems, a method of lowering the firing temperature has also been proposed, but the sintering of the electrodes and the solid electrolyte becomes insufficient, a high open circuit voltage is realized, and even near the theoretical capacity. The discharge capacity has not been increased.

Patent Document 1 proposes that the atmosphere in which a laminate made of an electrode precursor, a solid electrolyte precursor, or the like is fired is a low oxygen atmosphere. However, the battery manufactured by these methods is only charging / discharging with a very small current of 0.88 μA / cm ² , and charging / discharging with a large current is not realized. Also, the discharge capacity is very small.
JP 2007-227362 A

  The subject of the present invention is that when the green body of the electrode layer of the all-solid-state lithium ion battery is fired, both the electrode active material powder and the solid electrolyte powder in the electrode layer and the interface between the electrode layer and the solid electrolyte layer are used. All-solid-state lithium with reduced electrode active material decomposition and generation of substances that inhibit ionic conduction, high open circuit voltage, high discharge capacity, and low manufacturing cost It is to provide an ion battery.

  In view of the above problems, the present inventor has conducted extensive research, and as a result of selecting a specific substance as an active material of the positive electrode and making the content of the solid electrolyte mixed in the electrode a specific ratio, It has been found that the above problems can be solved, and the present invention has been completed, and its specific configuration is as follows.

(Configuration 1)
An all-solid lithium ion battery including a positive electrode layer, an electrolyte layer, and a negative electrode layer made of an inorganic solid,
The positive electrode layer includes a positive electrode active material that is Li _1.3-x A _y MPO ₄ and a lithium ion conductive solid electrolyte,
The all-solid-state lithium ion battery whose mass ratio value with respect to the said positive electrode active material of the said solid electrolyte is 1-9 or more and 9 or less.
However, x satisfies 0 ≦ x ≦ 0.5, y satisfies 0 ≦ y ≦ 0.5, A is one or more selected from Al, Mg, W, Ti, and Na, and M is Fe, Mn , Co, Ni, Cu, Zn.
(Configuration 2)
The all-solid-state lithium ion battery of the structure 1 with which the said positive electrode active material is coat | covered with carbon.
(Configuration 3)
The all-solid-state lithium ion battery of the structure 1 or 2 with which the conductive support agent is contained in the said positive electrode layer 1 mass% or more and 20 mass% or less.
(Configuration 4)
The negative electrode layer includes a negative electrode active material that is Li ₄ Ti _5-x R _y O ₁₂ and a lithium ion conductive solid electrolyte,
The all-solid-state lithium ion battery in any one of the structures 1 to 3 whose mass ratio value with respect to the said negative electrode active material of the said solid electrolyte is 1-9 or more and 10 or less.
However, x satisfies 0 ≦ x ≦ 0.5, y satisfies 0 ≦ y ≦ 0.5, and R is one or more selected from Mg, Al, and W.
(Configuration 5)
The all-solid-state lithium ion battery according to Configuration 4, wherein the negative electrode active material is coated with carbon (Configuration 6).
All-solid-state lithium-ion according to any one of 5 from the configuration 1 the lithium ion conductive solid electrolyte, which comprises a crystal of _{Li 0.8 + x + z E y} G 2-j Si z P 3-z O 12 battery.
However, x, y, z is 0 ≦ x ≦ 0.8, 0 ≦ z ≦ 0.6, y is 0 ≦ y ≦ 0.6, j is 0 ≦ j ≦ 0.6, E is Al, One or more selected from Ga, and G is one or more selected from Ge, Ti, Zr, Y, and Sc.

According to the present invention, when the green body of the electrode layer of the all-solid-state lithium ion battery is fired, at the interface between the solid electrolyte layer and the electrode layer and / or the grain boundary between the electrode active material and the solid electrolyte in the electrode. All-solid-state lithium ion secondary battery that has high discharge capacity and high charge / discharge efficiency even at large operating currents. A battery can be obtained.
Further, as the electromotive force is higher, the positive electrode active material has a higher oxidizing power and the negative electrode active material has a higher reducing power, so that decomposition during firing and generation of a compound that greatly inhibits ion conduction are more likely to occur. However, according to the present invention, an all solid lithium ion secondary battery having a higher electromotive force can be obtained.

It is the figure which showed the relationship between the kind of positive electrode active material, and discharge capacity.

  The all-solid-state lithium ion secondary battery of the present invention has an electrode layer composed of two inorganic solids, a positive electrode and a negative electrode, sandwiching an inorganic solid electrolyte layer, and at least one electrode layer is sintered. A current collector is joined to the. The solid electrolyte layer physically separates the positive electrode layer and the negative electrode layer and carries lithium ion conduction. The two electrode layers are joined to the solid electrolyte layer. The solid electrolyte layer and the two electrode layers are preferably bonded by firing in order to improve physical and electrochemical bonding properties.

The all solid lithium ion secondary battery of the present invention will be described. The all solid lithium ion secondary battery of the present invention is an all solid lithium ion battery including a positive electrode layer made of an inorganic solid, an electrolyte layer, and a negative electrode layer, and the positive electrode layer is Li _1-x A _y MPO ₄ An active material and a lithium ion conductive solid electrolyte are included, and the mass ratio of the solid electrolyte to the positive electrode active material is 1/9 or more and 9 or less.

When the unfired body of the electrode layer is fired by using Li _1-x A _y MPO ₄ as the positive electrode active material and further regulating the amount of the solid electrolyte relative to the positive electrode active material, the solid electrolyte layer and the electrode layer It is possible to effectively suppress the decomposition of the solid electrolyte and the electrode active material and the formation of a compound that greatly inhibits ionic conduction at the interface between the electrode and / or the grain boundary between the electrode active material in the electrode and the solid electrolyte.
Here, in Li _1.3-x A _y MPO ₄ , x _satisfies 0 ≦ x ≦ 0.5, y satisfies 0 ≦ y ≦ 0.5, and A is selected from Al, Mg, W, Ti, and Na. M is one or more selected from Fe, Mn, Co, Ni, Cu, and Zn.
Among these, in the above formula, A may be one selected from Al, Mg, W, Ti, and Na. M may be one selected from Fe, Mn, Co, Ni, Cu, and Zn. In particular, M is most preferably a solid solution of Ni and Co. The ratio of Co and Ni is preferably 1: 1. In the above formula, the range of x is more preferably 0.39 ≦ x ≦ 0.5, and most preferably 0.35 ≦ x ≦ 0.40.
Preferable positive electrode active materials are specifically Li _0.95 Al _0.05 Ni _0.5 Co _0.5 PO ₄ and Li _0.95 Al _0.05 CoPO ₄ .

As the negative electrode active material, SiO _z (where z satisfies 0.1 ≦ z ≦ 2.2), Nb ₂ O ₅ , Li ₄ Ti ₅ O ₁₂ , Li _0.1 WO ₂ , MoO ₂ , Li ₂ Mn ₄ O ₉ , Li ₅ Fe ₂ O ₃ , Li ₂ NiVO ₄ , Li _1.5 CoVO ₄ , Li _2.5 ZnVO ₄ , Li ₂ MnV ₂ O _6.96 , Li ₃ Fe ₂ (PO ₄ ) ₃ , LiTi ₂ (PO ₄ ) ₃ , graphite, hard carbon, Sn—Cu, Sn _0.5 B _0.5 O _{3 and the} like can be used, but Li ₄ Ti _5-x R _y O ₁₂ (however, , X satisfies 0 ≦ x ≦ 0.5, y satisfies 0 ≦ y ≦ 0.5, and R is one or more selected from Mg, Al, and W), thereby providing electronic conductivity. Therefore, it is preferable.
More specifically, Li ₄ Ti ₅ O ₁₂ , Li ₄ Ti _4.95 Al _0.05 O ₁₂ , Li ₃ Fe ₂ (PO ₄ ) ₃ , and LiTi ₂ (PO ₄ ) ₃ are preferable.

  The positive electrode layer includes a solid electrolyte as an ion conduction aid in order to satisfactorily form a lithium ion conduction path between the solid electrolyte layer bonded to the positive electrode layer and the active material in the positive electrode layer.

Also in the negative electrode layer, in order to satisfactorily form a lithium ion conduction path between the solid electrolyte layer bonded to the negative electrode layer and the active material in the negative electrode layer, a solid electrolyte is preferably included as an ion conduction aid.

In order to include a solid electrolyte as an ion conduction aid in the electrode layer of the positive electrode layer or the negative electrode layer, the lithium ion conductive solid electrolyte powder or lithium ion conductivity is exhibited after sintering together with the electrode active material and the conductive aid. The inorganic solid powder to be mixed may be mixed and sintered.

The lithium ion conductive solid electrolyte content contained in the positive electrode layer is 1/9 or more and 9 or less in mass ratio with respect to the positive electrode active material in the positive electrode layer. More preferably, they are 2/8 or more and 6/4 or less, More preferably, they are 3/7 or more and 4/6 or less. By including a lithium ion conductive solid electrolyte within this range and limiting the positive electrode active material, the solid electrolyte and electrode active material can be decomposed and the compound active during firing of the electrode layer while obtaining good ion conduction. Generation can be effectively suppressed.

The negative electrode layer also preferably contains a lithium ion conductive solid electrolyte in order to increase the lithium ion conductivity in the negative electrode layer. The content of the lithium ion conductive solid electrolyte contained is preferably 1/9 or more and 10 or less, more preferably 2/8 or more and 6/4 or less, and more preferably 3/7 or more and 4 by mass ratio with respect to the negative electrode active material in the negative electrode layer. / 6 or less is most preferable.

As the solid electrolyte layer located between the positive electrode layer and the negative electrode layer, and the solid electrolyte existing as an ion conduction aid in the electrode material constituting the electrode layer, a compound containing a crystal having lithium ion conductivity can be used. . For example, LiN, LISICON, La _0.55 Li _0.35 TiO ₃ having a perovskite structure, a material having a NASICON type structure (for example, Li _{1 + X} Al _x (Ti, Ge) _{2 -X} (PO ₄ ) ₃ , _{LiTi 2 P 3 O 12, Li} 1.5 Al 0.5 Ge 1.5 (PO 4) 3 , etc.) can be used.

Among them, Li _{1 + x + z} E _y G _{2 -j} Si _z P _{3 -z} O ₁₂ (where j, x, y, and z are 0 ≦ x ≦ 0.8, 0 ≦ z ≦ 0.6, and y is 0) ≦ y ≦ 0.6, j satisfies 0 ≦ j ≦ 0.6, E is one or more selected from Al and Ga, and G is one or more selected from Ge, Ti, Zr, Y, and Sc) A substance containing crystals has an advantage that it has high lithium ion conductivity, is chemically stable, and is easy to handle. Further, this crystal can be precipitated as a crystal in glass ceramics by heat-treating a glass having a specific composition. The glass ceramic particles having the above crystal are preferable in that they have almost no vacancies or crystal grain boundaries that hinder ion conduction in the particles.

Here, the glass ceramic is a substance obtained by precipitating a crystalline phase in a glass phase by heat-treating an amorphous glass, and means a substance composed of an amorphous solid and a crystal. Further, it includes substances in which the entire glass phase is phase-transitioned into a crystalline phase, that is, a substance having a crystal amount (crystallinity) of 100% by mass in the substance. In the case of glass ceramics, there are almost no vacancies between and within the precipitated crystals, which is advantageous in terms of ion conduction.
In order to incorporate a solid electrolyte in the electrode layer in the production of the solid electrolyte layer or in the production of the electrode layer, the glass ceramic powder or the glass ceramic raw glass powder can be used. When the raw glass powder is used, crystals are deposited in the glass powder in the firing process of the solid electrolyte layer and the electrode layer to form glass ceramics. That is, the original glass on which the crystals are precipitated is an inorganic solid that exhibits lithium ion conductivity after sintering.

The raw glass on which the crystals are precipitated by heat treatment is expressed in mol% based on the oxide,
Li ₂ O: 10~25%, and _{Al 2 O 3 + Ga 2 O} 3: 0.5~15%, and _{TiO 2 + GeO 2 + ZrO 2} + Y 2 O 3 + Sc 2 O 3: 25~50%, and SiO ₂ 0 to 15% and _P 2 _O 5: _26~40%
It can be obtained by melting and quenching a glass containing each of the components.

The positive electrode active material and the negative electrode active material may be coated with carbon in order to smoothly transfer and receive electrons associated with insertion and extraction of lithium ions in the active material. The fact that the active material is coated with carbon means that a carbon layer exists at the crystal grain boundary of the active material. In order to obtain the effect, the thickness of the carbon layer is preferably 1 nm to 1 μm, more preferably 3 nm to 100 nm, and most preferably 5 nm to 10 nm. Similarly, in order to obtain the above effect, it is not necessary to cover the entire periphery of the active material crystallites, and it is sufficient to cover a certain area or more. Specifically, 5% to 100% of the area of the crystallite is preferable, 40% to 100% is more preferable, and 60% to 100% is most preferable.
Here, the thickness of the coating layer around the active material in the electrode layer can be confirmed by scraping the electrode layer and observing the sample in a fine powder state with a TEM (transmission electron microscope). Further, since the three-dimensional measurement is difficult for the existing area ratio of the coating layer, the ratio of the length of the protective layer to the total length of the grain boundary lines appearing in the TEM image is defined as the area ratio of the coating layer. When observation with TEM is not possible, observation is performed by mapping analysis with EPMA, and the ratio of the existing area is obtained in the same manner. The area ratio of the protective layer does not need to be measured for all parts of the battery, and a value measured in a TEM observation image of an arbitrarily selected part can be used. In addition, even if only a specific limited part (for example, 3% or less of the volume of the electrode layer) is different from the other part, the other part is defined in the present invention. If the area ratio of the covering layer to be matched is satisfied, the battery can obtain the effects of the present invention.

In the positive electrode material constituting the positive electrode layer or the negative electrode material constituting the negative electrode layer, an electron conduction path between the current collector bonded to the electrode layer of the positive electrode layer or the negative electrode layer and the electrode active material in the electrode layer is provided. In order to form well, it is preferable that a conductive support agent is contained.
The content of the conductive assistant is 1% by mass or more and 20% by mass with respect to the entire electrode material (that is, the positive electrode material or the negative electrode material) of the electrode layer in consideration of the balance between the battery capacity and the electron conductivity of the electrode layer. The content is preferably 2% by mass or more, more preferably 15% by mass or less, and most preferably 4% by mass or more and 10% by mass or less. The conductive additive can include metals such as carbon, titanium, nickel, chromium, iron, stainless steel, and aluminum, and noble metals such as platinum, gold, and rhodium.

The laminate of the electrode layer and solid electrolyte layer of the all solid lithium ion battery of the present invention can be produced by firing the electrode layer precursor and the solid electrolyte layer precursor. Various modes can be used for the firing method.
That is, the electrode layer precursor and the solid electrolyte layer precursor are respectively fired and then stacked and fired again to join the layers, or after firing any of the layers into a sintered body, A method in which the precursors are stacked on each other, and the sintered body and the precursor are simultaneously fired and bonded, and a method in which two or more layers of precursors are stacked and simultaneously fired to form a sintered body to bond the layers. .
The electrode layer precursor and the solid electrolyte layer precursor mean a green body of the electrode layer and a green body of the solid electrolyte layer, respectively.

  Further, a current collector is laminated on the electrode layer, but a thin metal layer may be joined, or may be formed by firing from a precursor. Note that the current collector may not be provided as long as the electrode layer itself has high electron conductivity.

  The solid electrolyte layer precursor may be formed using a solid electrolyte powder as a material powder. The average particle diameter of the solid electrolyte powder is preferably 0.1 μm to 3 μm, more preferably 0.1 μm to 1 μm, and most preferably 0.1 μm to 0.6 μm in order to increase the ionic conductivity by densifying the solid electrolyte layer.

The electrode layer precursor may be formed by using an electrode active material powder and, if necessary, a solid electrolyte powder and an electron conduction aid powder as an electrode material powder. The average particle diameter of the electrode active material powder is preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 3 μm, and most preferably 0.1 μm to 1 μm in order to increase the electrode reaction area.
The average particle size of the solid electrolyte powder contained in the electrode layer precursor is preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 1 μm, and most preferably 0.1 μm to 0.6 μm in order to increase the reaction area.
The average particle size of the electron conduction aid powder is preferably 10 nm to 3 μm, more preferably 10 nm to 1 μm, most preferably 10 nm to 50 nm in order to increase the conductivity. The average particle size is D50 when measured by a laser diffraction method. Specifically, a value measured with a particle size analyzer Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd. or a submicron particle analyzer N5 manufactured by Beckman Coulter, Inc. can be used. The average particle diameter is a value expressed on a volume basis.

  In order to form the coating layer on the particles of the electrode active material, it is preferable to coat the surface of the raw material powder of the electrode layer precursor with a substance that becomes the coating layer, and to use this as the electrode material powder. For example, when the surface of the electrode active material particles is coated with carbon, the water is dried while mixing the electrode active material and an aqueous solution of saccharides such as sucrose and glucose, and heat treatment is performed in a graphite crucible in an inert atmosphere.

The electrode layer precursor and the solid electrolyte layer precursor may be formed by pressure-molding the above-mentioned raw material powder, but it is preferable to use a green sheet as a precursor because it can be easily formed into a thin plate shape or an arbitrary shape.
Here, the green sheet is a mixture of an organic binder, a plasticizer, a solvent, and the like mixed with powder before firing, glass, glass ceramics, ceramics, etc. to form a slurry, and after forming the slurry into a thin plate shape, the solvent is volatilized. It can mean a fired body. This molding can be performed by a doctor blade, a calendar method, a coating method such as spin coating or dip coating, a printing method, a die coater method, a spray method, or the like. The green sheet before firing is flexible and can be cut into an arbitrary shape or laminated.

  As the organic binder, a general-purpose binder commercially available as a molding aid for press molding, rubber press, extrusion molding, or injection molding can be used. Specifically, acrylic resin, ethyl cellulose, polyvinyl butyral, methacrylic resin, urethane resin, butyl methacrylate, vinyl copolymer and the like can be used. The lower limit of the content of the organic binder is 1% by weight with respect to the amount of the mixed slurry composed of the electrode active material powder, the solid electrolyte powder, the organic binder, the plasticizer, the solvent, etc. in order to easily maintain the sheet shape. Preferably, the content is preferably 3% by weight or more, and more preferably 5% by weight or more.

  Further, the upper limit of the content of the organic binder is preferably 50% by weight or less, more preferably 40% by weight or less with respect to the amount of the mixed slurry in order to easily reduce voids after degreasing. 30% by weight or less is most preferable.

  A solvent may be used to uniformly disperse the powder. As the solvent, known materials such as PVA, IPA, butanol, toluene, xylene, acetonitrile, NMP can be used, but alcohol or water is preferable from the viewpoint of environment. In order to obtain a more homogeneous and dense solid electrolyte, an appropriate amount of a dispersant can be added together with an electrode active material, a solid electrolyte powder, and an organic binder, and a surfactant for improving foam removal during mixing and drying. It is also possible to add an appropriate amount.

In addition, the green sheet can contain an inorganic compound containing Li at the same time. This is because an inorganic compound containing Li functions as a sintering aid (binder) and has a function of bonding particles during sintering. Examples of the inorganic compound containing Li include Li ₃ PO ₄ , LiPO ₃ , LiI, LiN, Li ₂ O, Li ₂ O ₂ , and LiF.

  The green sheet is formed into a sheet using a known method such as a doctor blade method or a calendar method. The lower limit of the thickness of the green sheet after molding is preferably 300 μm or less, more preferably 150 μm or less, and most preferably 100 μm or less in order to minimize the amount of residual solvent in the drying step and prevent cracks on the surface. preferable. Further, the lower limit of the thickness of the green sheet is preferably 1 μm or more, more preferably 5 μm or more, and most preferably 10 μm or more in order to provide stable handling properties. Furthermore, you may process into arbitrary shapes as needed. In order to obtain the desired thickness of the solid electrolyte, electrode, and the like after firing, the same type of green sheets may be laminated. In order to further improve the density of the solid electrolyte after firing, the green sheet may be pressed by a roll press, uniaxial, isotropic pressurization, or the like.

  When the green sheets of the positive electrode, the solid electrolyte, and the negative electrode are laminated, the upper limit of the thickness of the green sheet after lamination is preferably 2 mm or less, more preferably 1 mm or less, and most preferably 800 μm or less for shortening the firing time. Further, the lower limit of the thickness of the green sheet is preferably 30 μm or more, more preferably 100 μm or more, and most preferably 200 μm or more in order to reduce the degree of undulation. Further, in order to prevent the green sheet laminate from being bent or damaged when fired, these green sheets may be laminated on the support and fired.

The maximum temperature when firing the electrode layer precursor is preferably 750 ° C to 1100 ° C, more preferably 900 ° C to 1050 ° C, and most preferably 950 ° C to 1000 ° C.
The maximum temperature when firing the solid electrolyte layer precursor is preferably 850 ° C to 1100 ° C, more preferably 900 ° C to 1050 ° C, and most preferably 950 ° C to 1000 ° C.

In the step of firing the electrode layer precursor, or the step of firing the laminate of the electrode layer precursor containing at least one electrode layer precursor and the solid electrolyte layer precursor, N ₂ , H ₂ , He, Ar, CO Firing in an atmosphere containing at least one gas selected from ₂ , CO, and CH ₄ is preferred. By setting it as such an atmosphere, it becomes easy to acquire the effect which suppresses the quality change and burning of a protective layer, and a protective layer suppresses the decomposition reaction of a solid electrolyte or an electrode active material.

In addition to the above, the protective layer can be prevented from being altered or burned by the step of firing while the molded body made of a material that can reduce the oxygen partial pressure in the firing atmosphere is in contact with the electrode layer precursor. The material can easily obtain an effect of suppressing the decomposition reaction between the electrode active material and the solid electrolyte. This may be performed while firing in an atmosphere containing the gas described above.
The material capable of reducing the oxygen partial pressure is preferably a material capable of causing a combustion reaction with oxygen in the atmosphere. Specifically, a carbon material or a sheet in which metal particles are dispersed in a carbon material is preferable, and a setter made of graphite or a setter made of graphite in which Fe fine particles are dispersed is most preferable.

The thickness of the electrode layer after sintering is preferably 5 μm to 1 mm, more preferably 10 μm to 500 μm, and most preferably 20 to 100 μm from the balance of the ion transfer resistance in the electrode layer and the battery capacity. In the case where one electrode (for example, the negative electrode) is provided with a function as a support, the thickness of the electrode may be 2 mm as an upper limit.
The thickness of the solid electrolyte layer after sintering is sufficient if the negative electrode and the positive electrode can be separated, and is preferably thinner, but is preferably 1 μm to 100 μm, more preferably 1 μm to 50 μm in view of mechanical strength. Most preferred is 1 to 20 μm.

Hereinafter, the all-solid-state lithium ion battery according to the present invention will be described with specific examples.
[Production of lithium ion conductive glass ceramics]
H ₃ PO ₄ , Al (PO ₃ ) ₃ , Li ₂ CO ₃ , SiO ₂ , and TiO ₂ are used as raw materials, and these are mol% in terms of oxide, P ₂ O ₅ is 35.0%, Al ₂ O ₃ is 7.5%, Li ₂ O is 15.0%, TiO ₂ is 38.0% and SiO ₂ is 4.5%. The glass melt was heated and melted at 1500 ° C. for 4 hours in an electric furnace while stirring. Thereafter, the glass melt was dropped into running water to obtain flaky glass.
Each of the flaky glasses was pulverized by a lab scale jet mill and classified by a zirconia rotating roller to obtain a powder having an average particle diameter of 20 μm. This powder was further pulverized with a planetary ball mill, an attritor, a bead mill, etc. to obtain an original glass powder of lithium ion conductive glass ceramics (hereinafter referred to as an original glass powder) having an average particle diameter of 0.6 μm.

[Preparation of Lithium Ion Conductive Glass Ceramic Substrate]
To the raw glass powder, a dispersant was added to an acrylic resin dispersed in water, and a slurry was prepared by stirring with a ball mill for 12 hours. The content of glass fine particles in this slurry was 65.5% by mass, and the content of acrylic resin was 13.5% by mass. Such a slurry was molded to a thickness of 20 μm on a PET film which had been subjected to a release treatment by the doctor blade method, and was subjected to primary drying at 80 ° C. and further secondary drying at 95 ° C. to obtain a sheet-like material. .
A dense green sheet was prepared by superimposing 26 sheets after peeling the PET film and applying pressure at 196.1 MPa for 10 minutes using an isotropic pressure device (CIP). .
The green sheet was cut into 59.5 mm and fired at 1000 ° C. for 1 hour. When the fired product was examined by X-ray diffraction, the main crystal phase was Li _{1 + x + y} Al _x Ti _2-x Si _y P _3-y O ₁₂ (where 0 ≦ x ≦ 0.4, 0 <y ≦ 0.6) was confirmed. Moreover, the ionic conductivity obtained by performing impedance measurement was 2.0 × 10 ⁻⁴ Scm ⁻¹ . The thickness was 380 μm and the diameter was 50 mm.

[Pretreatment of positive electrode active material and negative electrode active material]
(Treatment of positive electrode active material)
Each positive electrode active material described in Table 1 was subjected to surface treatment. 10 g of the positive electrode active material, 40 g of denatured ethanol, 200 g of 10 mm zirconia balls (YTZ balls, Tosoh) were placed in a 250 cc zirconia pot, and pulverized at 250 rpm for 100 minutes in a planetary ball mill. Thereafter, the zirconia balls were changed to 0.5 mm and 300 g, and pulverization was performed at 300 rpm for 100 minutes. The sample particle diameter after pulverization was 0.5 μm at D50.
2.5 g of a 20 wt% sucrose solution was added to the pulverized sample, mixed in a mortar, dried, placed in a carbon crucible, a dish containing graphite powder was placed above, and baked at 600 ° C. for 3 hours in an N ₂ atmosphere.

(Treatment of negative electrode active material)
The negative electrode active material Li ₄ Ti ₅ O ₁₂ was subjected to surface treatment. Add 2.5g of 20wt% sucrose solution to 10g of negative electrode active material (Ishihara Sangyo Co., Ltd., LC855-17C, D50 20µm), mix in a mortar, dry and place in a carbon crucible. And firing at 600 ° C. for 3 hours under N ₂ atmosphere.

[Preparation of electrode slurry and firing of cell]
As shown in Table 1, each surface-treated positive electrode active material, raw glass powder, electron conduction aid (carbon nanofiber, manufactured by VGCF (registered trademark) Showa Denko KK), binder (Oricox KC250, Kyoei) Chemistry), a dispersant (Floren G700, Kyoei Chemical) and a solvent (modified ethanol, Wako Pure Chemical Industries) were mixed to prepare six types of positive electrode slurries.
Each positive electrode slurry was applied to one side of a 50 mm diameter lithium ion conductive glass ceramic substrate fired in the above, and the slurry at the peripheral edge of the substrate was wiped with a waste cloth and allowed to dry in the atmosphere. Baking for 10 minutes in ₂ atmospheres.
The raw glass powder contained in the positive electrode slurry became a lithium ion conductive solid electrolyte after firing.

As shown in Table 2, the surface-treated negative electrode active material Li ₄ Ti ₅ O ₁₂ , binder (Oricox KC250, Kyoei Chemical), dispersant (Floren G700, Kyoei Chemical), solvent (modified ethanol, Wako Pure Chemical) ) To prepare a negative electrode slurry.
Applying a respective positive electrode slurry, the negative electrode slurry was coated on the opposite surface of the fired lithium ion conductive glass-ceramic substrate, after the slurry of the peripheral portion is dried slurry with air left wiping waste cloth, 500 ° C. in a N ₂ atmosphere, Baked for 10 minutes.

  An aluminum foil and a copper foil having a thickness of 25 μm were cut into a circular shape of φ45 with a lead having a width of 5 mm and a length of 35 mm to obtain a current collector. The aluminum foil current collector was disposed on the positive electrode side, and the copper foil current collector was disposed on the negative electrode side, and the positive electrode and the positive electrode current collector were brought into contact with each other by vacuum bonding.

[Charge / discharge test]
CC-CV charge was performed about 6 types of produced batteries. The battery was charged at a charging rate of 0.1 C until the charging voltage reached 6 V, and then the charging was terminated when the charging capacity reached the theoretical capacity while maintaining the charging voltage of 6 V. After charging, CC discharge was performed. The battery was discharged at a discharge rate of 0.025C, and the discharge was terminated when the discharge voltage reached 0.01V. The charge and discharge were set as one cycle, and charge / discharge of 4 cycles was performed, and the open circuit voltage was measured after completion of the charge of the 5th cycle. The environmental temperature and the measurement temperature at the environmental temperature of charge / discharge were 120 ° C.

[result]
The relationship between the positive electrode active material and the charge / discharge capacity is shown in Table 3 and FIG. All of the Li _1-x MNPO ₄ positive electrode active materials showed high open circuit voltage and high discharge capacity.

(Comparative example of positive electrode active material)
Evaluation was performed when LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ were used as the positive electrode active material as a material other than Li _1.3-x A _y MPO ₄ .
As shown in Table 4, each positive electrode active material, raw glass powder, electron conduction aid (carbon nanofiber, VGCF (registered trademark) manufactured by Showa Denko KK), binder (Oricox KC250, Kyoei Chemical), dispersion An agent (Floren G700, Kyoei Chemical) and a solvent (modified ethanol, Wako Pure Chemical Industries) were mixed to prepare three types of positive electrode slurries.
Each positive electrode slurry was applied to one side of a 50 mm diameter lithium ion conductive glass ceramic substrate fired in the above examples, the slurry at the periphery of the substrate was wiped off with a waste cloth, and the slurry was allowed to stand in the air. And baked in an N ₂ atmosphere for 10 minutes.
The raw glass powder contained in the positive electrode slurry became a lithium ion conductive solid electrolyte after firing.

Similarly to Table 2 of the above-mentioned Examples, the surface-treated negative electrode active material Li ₄ Ti ₅ O ₁₂ , a binder (Oricox KC250, Kyoei Chemical), a dispersant (Floren G700, Kyoei Chemical), a solvent (modified ethanol, Wako Pure Chemical) was mixed to prepare a negative electrode slurry.
The negative electrode slurry was applied to the opposite surface of the lithium ion conductive glass ceramic substrate coated and fired with each positive electrode slurry, the slurry at the peripheral edge was wiped off with a waste cloth, and the slurry was dried in the atmosphere, and then at 500 ° C. in an N ₂ atmosphere. Baked for minutes.
CC-CV charge was performed about three types of produced batteries. The battery was charged at a charge rate of 0.1 C until the charge voltage reached 4 V, and then the charge was terminated when the charge capacity reached the theoretical capacity while maintaining the charge voltage of 4 V. After charging, CC discharge was performed. The battery was discharged at a discharge rate of 0.025C, and the discharge was terminated when the discharge voltage reached 0.01V. The charge and discharge were set as one cycle, and charge / discharge of 4 cycles was performed, and the open circuit voltage was measured after completion of the charge of the 5th cycle. The environmental temperature and the measurement temperature at the environmental temperature of charge / discharge were 120 ° C.
The evaluation results are shown in Table 5. Even in LiCoO ₂ which showed the highest open circuit voltage, the open circuit voltage after charging was 0.4 V, and discharge could not be confirmed. The function of the positive electrode active material was not recognized.

(Examination of the ratio of electrolyte to positive electrode active material)
Batteries were prepared in the same manner as in the above Example except that the ratio between the solid electrolyte and the positive electrode active material in the electrode was changed, and the discharge capacity was measured. The electrode active material used was LiFePO ₄ . The results are shown in Table 6.

When the solid electrolyte / positive electrode active material ratio exceeds 9/1, the positive electrode active material is buried in the solid electrolyte in the electrode due to diffusion during sintering, and as a result, the discharge capacity rapidly decreases, and the output as a battery is reduced. You can't expect.
When the ratio of solid electrolyte / positive electrode active material is less than 1/9, the solid electrolyte that functions in the electrode is almost lost due to the reaction during firing, so that the discharge capacity is drastically reduced and the battery functions. Cannot be expected.

Claims (5)

An all solid lithium ion battery including a positive electrode layer, an electrolyte layer, and a negative electrode layer made of an inorganic solid, wherein the positive electrode layer includes a positive electrode active material that is Li _1.3-x Al _y Ni PO ₄ and a lithium ion conductive solid. contains an electrolyte, the lithium ion conductive solid electrolyte comprises a crystal of _{Li 0.8 + x + z E y} G 2-j Si z P 3-z O 12, the mass ratio relative to the positive electrode active material of the solid electrolyte All-solid-state lithium ion battery whose value is 1/9 or more and 9 or less.
However, in the formula of Li _1.3-x Al _y NiPO ₄ , x satisfies 0 ≦ x ≦ 0.5, y satisfies 0.05 ≦ y ≦ 0.5, and Li _{0.8 + x + z} E _y G _{2 -j} Si _z P _3-z wherein the _{O 12,} x, y, z is 0 ≦ x ≦ 0.8,0 ≦ z ≦ 0.6, y is 0 ≦ y ≦ 0.6, j is 0 ≦ j ≦ 0.6 is satisfied, E is one or more selected from Al and Ga, and G is one or more selected from Ge, Ti, Zr, Y, and Sc. The all-solid-state lithium ion battery according to claim 1, wherein the positive electrode active material is coated with carbon. The all-solid-state lithium ion battery of Claim 1 or 2 with which the conductive support agent is contained in the said positive electrode layer 1 mass% or more and 20 mass% or less. The negative electrode layer includes a negative electrode active material that is Li ₄ Ti _5-x R _y O ₁₂ and a lithium ion conductive solid electrolyte, and the mass ratio of the solid electrolyte to the negative electrode active material is 1/9. The all solid lithium ion battery according to any one of claims 1 to 3, which is 10 or more.
However, x satisfies 0 ≦ x ≦ 0.5, y satisfies 0 ≦ y ≦ 0.5, and R is one or more selected from Mg, Al, and W. The all-solid-state lithium ion battery of Claim 4 with which the said negative electrode active material is coat | covered with carbon.