WO2018181578A1 - Solid electrolyte and all-solid secondary battery - Google Patents

Abstract

Provided are: a solid electrolyte having a high lithium ion conductivity and an all-solid secondary battery using the same. The solid electrolyte is characterized by comprising a main component represented by general formula Li_aM1_xR_2-bM2_bP_3-cM3_cO₁₂. (where, 0<a≤3, 0≤b<2, 0<c<3, 0≤x<0.5; M1 is K or an element having a valence number of at least 2; R is Zr or Hf; M2 is at least one selected from the group consisting of Co, V, Sn and B; and M3 is at least one selected from the group consisting of Si, B, V, Nb, Mo and W.)

Description

Solid electrolyte and all-solid secondary battery

The present invention relates to a solid electrolyte and an all-solid secondary battery.

With the spread of small electronic devices, the performance of lithium ion secondary batteries has greatly improved. However, since the Great East Japan Earthquake, storage batteries that exhibit high safety and reliability have been strongly desired. Under such circumstances, practically used lithium ion secondary batteries use flammable organic electrolytes, so there are problems in safety and reliability such as abnormal heat generation and liquid leakage. there were.
Therefore, research and development of all-solid-state secondary batteries in which the organic electrolyte solution is replaced with a nonflammable solid electrolyte and the other constituent members are also made solid are being actively conducted.

Solid electrolytes of all-solid secondary batteries mainly include sulfide-based solid electrolytes and oxide-based solid electrolytes. Since sulfide-based solid electrolytes generate hydrogen sulfide when they react with water, it is necessary to produce a battery in a glove box with a controlled dew point. In addition, since it is difficult to form a sheet, it is a problem to reduce the thickness of the solid electrolyte layer and to increase the battery stack.

An all-solid secondary battery has a problem that its output is small compared to a battery using an electrolytic solution. Therefore, it is required to increase the ionic conductivity of the all solid state secondary battery.

For example, Patent Document 1 describes an all-solid-state secondary battery using oxide-based Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ as a solid electrolyte. Patent Document 2 describes an all-solid-state secondary battery using LiZr ₂ (PO ₄ ) ₃ containing Zr having excellent reduction resistance as a solid electrolyte. Further, Patent Document 3 uses particles having excellent reduction resistance and complexed with rhombohedral Li _1.55 Al _0.2 Zr _1.7 Y _0.1 Si _0.25 P _2.75 O ₁₂ . All-solid-state secondary batteries were described.

Japanese Unexamined Patent Publication No. 2016-1595 JP 2001-143754 A JP 2012-246196 A

However, the all-solid-state secondary battery using the solid electrolyte described in Patent Documents 1 to 3 cannot be said to have sufficient ion conductivity.

In order to produce a solid electrolyte having high ion conductivity, heat treatment at a high temperature of 1300 ° C. or higher is required. However, when the treatment is performed at a high temperature, it reacts with the active material of the positive electrode or the negative electrode, and the ionic conductivity decreases.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a solid electrolyte having high lithium ion conductivity and an all-solid-state secondary battery using the same.

The present inventors have improved the lithium ion conductivity of the solid electrolyte by substituting a part of Li, Zr, and P constituting the solid electrolyte of the LiZr ₂ (PO ₄ ) ₃ composition with other elements. I found it. Further, by using a solid electrolyte in which a part of Li, Zr, and P is substituted with another element, lithium ion conductivity of the all-solid secondary battery can be improved and the discharge capacity can be improved.
Therefore, the present invention provides the following means in order to solve the above problems.

The solid electrolyte according to the present invention are represented by the general formula _{Li a M1 x R 2-b} M2 b P 3-c M3 c O 12, M1 in the formula, R, M2, M3 represents the following: . M1: an element having K and a valence of 2 or more; M2: at least one selected from the group consisting of Co, V, Sn and B; M3: Si, B, V, Nb, Mo and W At least one selected from the group consisting of: R: Zr or Hf, and the relationship of a, b, c and x in the general formula is 0 <a ≦ 3, 0 ≦ b <2, 0 <C <3, 0 ≦ x <0.5.

According to such a configuration, it is possible to generate a defect in the crystal structure by substituting an element having a valence different from that of the solid electrolyte constituent element or an element having a different ionic radius. Due to this defect, holes or ions that are carriers of the solid electrolyte are generated in order to maintain charge neutrality, resulting in an increase in the number of carriers. As a result, the number of movable carriers increases, so that ion conductivity can be improved.

The solid electrolyte according to the present invention is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Al, Ga, Y and Nb for M1 in the general formula.

According to such a configuration, the number of carriers contributing to lithium ion conduction can be increased by introducing defects at the Li site. Therefore, it is thought that lithium ion conductivity can be further improved.

The all solid state secondary battery using the solid electrolyte can reduce the lithium ion resistance of the solid electrolyte layer. Therefore, energy loss in the solid electrolyte layer is reduced, and energy can be used in the active material layer that contributes to the capacity, so that the capacity of the all-solid-state secondary battery can be improved.

An all solid state secondary battery according to the present invention is characterized in that a pair of electrode layers and a solid electrolyte layer having the solid electrolyte provided between the pair of electrode layers have a relative density of 80% or more. To do.

ADVANTAGE OF THE INVENTION According to this invention, the solid electrolyte which has high lithium ion conductivity, and the all-solid-state secondary battery using the same can be provided.

It is the cross-sectional schematic diagram which expanded the principal part of the all-solid-state secondary battery of this embodiment.

Hereinafter, the present invention will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, in order to make the characteristics of the present invention easier to understand, there are cases where the characteristic parts are enlarged for the sake of convenience, and the dimensional ratios of the respective components are different from actual ones. is there. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately modified and implemented without departing from the scope of the invention.

[All-solid secondary battery]
FIG. 1 is a schematic cross-sectional view enlarging a main part of the all solid state secondary battery of the present embodiment. As shown in FIG. 1, the all solid state secondary battery 10 includes a laminate 4 having a first electrode layer 1, a second electrode layer 2, and a solid electrolyte 3.

Each first electrode layer 1 is connected to a first external terminal 5, and each second electrode layer 2 is connected to a second external terminal 6. The first external terminal 5 and the second external terminal 6 are electrical contacts with the outside.

(Laminate)
The stacked body 4 includes a first electrode layer 1, a second electrode layer 2, and a solid electrolyte 3. One of the first electrode layer 1 and the second electrode layer 2 functions as a positive electrode, and the other functions as a negative electrode. The polarity of the electrode layer varies depending on which polarity is connected to the external terminal. Hereinafter, in order to facilitate understanding, the first electrode layer 1 is referred to as a positive electrode layer 1, and the second electrode layer 2 is referred to as a negative electrode layer 2.

In the laminate 4, the positive electrode layers 1 and the negative electrode layers 2 are alternately laminated via the solid electrolyte 3. The charging / discharging of the all-solid-state secondary battery 10 is performed by exchanging lithium ions between the positive electrode layer 1 and the negative electrode layer 2 via the solid electrolyte 3.

[Solid electrolyte]
The solid electrolyte 3 according to the present embodiment is preferably a material excellent in lithium ion conductivity, and is preferably represented by the following general formula (1).
Li _a M1 _x R _2-b M2 _b P _3-c M3 _c O ₁₂ (1)
General formula (1) satisfies 0 <a ≦ 4, 0 ≦ b <2, 0 <c <3, 0 ≦ x <0.5,
M1, M2, M3 and R in the general formula (1) are as follows.
M1: an element having K and a valence of 2 or more,
M2: at least one element selected from the group consisting of Co, V, Sn and B,
M3: At least one element selected from the group consisting of Si, B, V, Nb, Mo and W R: Zr or Hf.

According to such a configuration, it is possible to generate a defect in the crystal structure by substituting an element having a valence different from that of the solid electrolyte constituent element or an element having a different ionic radius. Due to this defect, holes or ions that are carriers of the solid electrolyte are generated in order to maintain charge neutrality, resulting in an increase in the number of carriers. Thereby, since the movable carrier increases, lithium ion conductivity can be improved.

The solid electrolyte 3 according to this embodiment is characterized in that M1 is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Al, Ga, Y, and Nb.

According to such a configuration, the number of carriers contributing to ionic conduction can be increased by introducing defects into the Li site. Therefore, lithium ion conductivity can be further improved.

The crystal structure of the substance represented by the general formula (1) is preferably monoclinic, orthorhombic, triclinic, or rhombohedral, more preferably triclinic or rhombohedral. And most preferably rhombohedral. These crystal structures are excellent in ionic conductivity because paths contributing to ionic conductivity exist three-dimensionally.

The all-solid-state secondary battery 10 according to the present embodiment uses the solid electrolyte 3 represented by the general formula (1).

According to this configuration, by using the solid electrolyte represented by the general formula (1), it is possible to reduce the lithium ion resistance of the solid electrolyte in the all-solid secondary battery 10. Therefore, voltage loss (energy loss) in the solid electrolyte is reduced, and more energy can be used in the active material layer contributing to the capacity, so that the capacity of the all-solid-state secondary battery can be improved.

X-ray diffraction (XRD) is used to confirm the desired solid electrolyte. It can be confirmed by fitting the spectrum obtained by XRD with the XRD spectrum of the known rhombohedral LiZr ₂ (PO ₄ ) ₃ . Furthermore, the lattice constant of the produced solid electrolyte can be estimated by performing Rietveld analysis of the spectrum obtained by XRD. The presence or absence of substitution in the crystal structure can be confirmed from the change in the lattice constant.

In general, the lattice constant increases if the ionic radius of the element to be substituted is larger than that of the constituent element, and the lattice constant decreases if the ionic radius of the element to be substituted is smaller than that of the constituent element.

Further, the inductively coupled plasma emission spectroscopy (ICP-AES) can be used to identify the contained elements and confirm whether a solid electrolyte having a desired composition has been produced.

[Positive electrode layer and negative electrode layer]
The positive electrode layer 1 includes a positive electrode current collector layer 1A and a positive electrode active material layer 1B containing a positive electrode active material. The negative electrode layer 2 includes a negative electrode current collector layer 2A and a negative electrode active material layer 2B containing a negative electrode active material.

The positive electrode current collector layer 1A and the negative electrode current collector layer 2A preferably have high electrical conductivity. Therefore, it is preferable to use, for example, silver, palladium, gold, platinum, aluminum, copper, nickel or the like for the positive electrode current collector layer 1A and the negative electrode current collector layer 2A. Among these materials, copper hardly reacts with the positive electrode active material, the negative electrode active material, and the solid electrolyte. Therefore, when copper is used for the positive electrode current collector layer 1A and the negative electrode current collector layer 2A, the internal resistance of the all-solid-state secondary battery 10 can be reduced. The materials constituting the positive electrode current collector layer 1A and the negative electrode current collector layer 2A may be the same or different.

The positive electrode active material layer 1B is formed on one side or both sides of the positive electrode current collector layer 1A. For example, the positive electrode layer 1 located in the uppermost layer in the stacking direction of the all-solid-state secondary battery 10 does not have the opposing negative electrode layer 2. Therefore, in the positive electrode layer 1 located at the uppermost layer of the all-solid-state secondary battery 10, the positive electrode active material layer 1B only needs to be on one side on the lower side in the stacking direction. Similarly to the positive electrode active material layer 1B, the negative electrode active material layer 2B is formed on one or both surfaces of the negative electrode current collector layer 2A.
The positive electrode active material layer 1B and the negative electrode active material layer 2B include a positive electrode active material and a negative electrode active material that transfer and receive electrons. In addition, a conductive auxiliary agent, a binder, and the like may be included. It is preferable that the positive electrode active material and the negative electrode active material can efficiently insert and desorb lithium ions.

For the positive electrode active material and the negative electrode active material, for example, a transition metal oxide or a transition metal composite oxide is preferably used. Specifically, lithium manganese composite oxide Li ₂ Mn _a Ma _1-a O ₃ (0.8 ≦ a ≦ 1, Ma = Co, Ni), lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂₎ ), Lithium manganese spinel (LiMn ₂ O ₄ ), general formula: LiNi _x Co _y Mn _z O ₂ (x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1) Complex metal oxide, lithium vanadium compound (LiV ₂ O ₅ ), olivine type LiMbPO ₄ (where Mb is one or more elements selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr) ), lithium vanadium phosphate _{(Li 3 V 2 (PO 4} ) 3 or _{LiVOPO 4), Li 2 MnO 3} -LiMcO 2 (Mc = Mn, Co, represented by Ni) L Table with excess solid solution positive electrode, lithium titanate _{(Li 4 Ti 5 O 12)} , Li s Ni t Co u Al v O 2 (0.9 <s <1.3,0.9 <t + u + v <1.1) The composite metal oxide etc. which can be used can be used.

Further, a negative electrode active material and a positive electrode active material may be selected according to the solid electrolyte 3.
For example, when using the compound of the general formula (1) for the solid electrolyte 3, it is preferable to use one or both of LiVOPO ₄ and Li ₃ V ₂ (PO ₄ ) _{3 for} the positive electrode active material and the negative electrode active material. Bonding at the interface between the positive electrode active material layer 1B and the negative electrode active material layer 2B and the solid electrolyte 3 becomes strong. Moreover, it is preferable at the point which can make the contact area in the interface of the positive electrode active material layer 1B and the negative electrode active material layer 2B, and the solid electrolyte 3 wide.

There is no clear distinction between the active materials constituting the positive electrode active material layer 1B or the negative electrode active material layer 2B, the potentials of two kinds of compounds are compared, and a compound showing a more noble potential is used as the positive electrode active material. A compound exhibiting a base potential can be used as the negative electrode active material.

The positive electrode current collector layer 1A and the negative electrode current collector layer 2A may include a positive electrode active material and a negative electrode active material, respectively. The content ratio of the active material contained in each current collector is not particularly limited as long as it functions as a current collector. For example, the positive electrode current collector / positive electrode active material or the negative electrode current collector / negative electrode active material preferably has a volume ratio in the range of 90/10 to 70/30.

The positive electrode current collector layer 1A and the negative electrode current collector layer 2A contain a positive electrode active material and a negative electrode active material, respectively, so that the positive electrode current collector layer 1A, the positive electrode active material layer 1B, the negative electrode current collector layer 2A, and the negative electrode active material It is preferable at the point which adhesiveness with layer 2 B improves.

(Terminal)
The first external terminal 5 and the second external terminal 6 of the all-solid-state secondary battery 10 are preferably made of a material having a high conductivity. For example, silver, gold, platinum, aluminum, copper, tin, or nickel can be used. The first external terminal 5 and the second external terminal 6 may be a single layer or a plurality of layers.

(Protective layer)
The all-solid-state secondary battery 10 may have a protective layer on the outer periphery of the multilayer body 4 that electrically, physically, and chemically protects the multilayer body 4 and the terminals. The material constituting the protective layer is preferably excellent in insulation, durability and moisture resistance and environmentally safe. For example, it is preferable to use glass, ceramics, thermosetting resin, or photocurable resin. Only one type of material for the protective layer may be used, or a plurality of materials may be used in combination. Further, the protective layer may be a single layer, but it is preferable to provide a plurality of layers. Among these, an organic-inorganic hybrid in which a thermosetting resin and ceramic powder are mixed is particularly preferable.

[Production method]
(Method for manufacturing all-solid-state secondary battery)
The method for manufacturing the all-solid-state secondary battery 10 may use a simultaneous firing method or a sequential firing method.
The co-firing method is a method in which materials for forming each layer are laminated and a laminated body is manufactured by batch firing. The sequential firing method is a method of sequentially producing each layer, and a firing step is included every time each layer is produced. Using the co-firing method can reduce the work steps of the all-solid-state secondary battery 10. Moreover, the laminate 4 obtained becomes denser when the co-firing method is used. Hereinafter, the manufacturing method of the all-solid-state secondary battery 10 will be described taking the case of using the simultaneous firing method as an example.

The simultaneous firing method includes a step of producing a paste of each material constituting the laminate 4, a step of applying and drying the paste to produce a green sheet, and a step of laminating the green sheets and simultaneously firing the produced laminated sheet. And have.

First, each material of the positive electrode current collector layer 1A, the positive electrode active material layer 1B, the solid electrolyte 3, the negative electrode active material layer 2B, and the negative electrode current collector layer 2A constituting the laminate 4 is made into a paste.

The method of pasting is not particularly limited. For example, a paste can be obtained by mixing powder of each material in a vehicle. Here, the vehicle is a general term for the medium in the liquid phase. The vehicle includes a solvent and a binder. By this method, the paste for the positive electrode current collector layer 1A, the paste for the positive electrode active material layer 1B, the paste for the solid electrolyte 3, the paste for the negative electrode active material layer 2B, and the paste for the negative electrode current collector layer 2A Is made.

Next, a green sheet is produced. For green sheets, the paste produced is PET
It is obtained by applying the coating material in a desired order on a base material such as (polyethylene terephthalate) and drying it as necessary. The method for applying the paste is not particularly limited. For example, known methods such as screen printing, coating, transfer, doctor blade, etc. can be employed.

The produced green sheets are stacked in the desired order and the number of layers. Alignment, cutting, etc. are performed as necessary to produce a laminate. In the case of producing a parallel type or series-parallel type battery, it is preferable to align and stack the end surfaces of the positive electrode current collector layer and the negative electrode current collector layer so as not to coincide with each other.

When producing a laminated body, you may prepare the positive electrode active material layer unit and negative electrode active material layer unit which are demonstrated below, and may produce a laminated body.

First, a solid electrolyte 3 paste is formed into a sheet shape on a PET film by a doctor blade method, and dried to form the solid electrolyte 3. On the solid electrolyte 3 obtained, the positive electrode active material layer 1B paste is printed by screen printing and dried to form the positive electrode active material layer 1B.

Next, the positive electrode current collector layer 1A paste is printed on the produced positive electrode active material layer 1B paste by screen printing and dried to form the positive electrode current collector layer 1A. On the obtained positive electrode current collector layer 1A, the positive electrode active material layer 1B paste is printed again by screen printing and dried to form the positive electrode active material layer 1B. And a positive electrode active material layer unit is produced by peeling a PET film. In the positive electrode active material layer unit, solid electrolyte 3 / positive electrode active material layer 1B / positive electrode current collector layer 1A / positive electrode active material layer 1B are laminated in this order.

A negative electrode active material layer unit is also produced in the same procedure. In the negative electrode active material layer unit, solid electrolyte 3 / negative electrode active material layer 2B / negative electrode current collector layer 2A / negative electrode active material layer 2B are laminated in this order.

One positive electrode active material layer unit and one negative electrode active material layer unit are laminated. At this time, the solid electrolyte 3 of the positive electrode active material layer unit and the negative electrode active material layer 2B of the negative electrode active material layer unit, or the positive electrode active material layer 1B of the positive electrode active material layer unit and the solid electrolyte 3 of the negative electrode active material layer unit are in contact. Laminate as follows. Thus, the positive electrode active material layer 1B / the positive electrode current collector layer 1A / the positive electrode active material layer 1B / the solid electrolyte 3 / the negative electrode active material layer 2B / the negative electrode current collector layer 2A / the negative electrode active material layer 2B / the solid electrolyte 3 A laminated body laminated in order is obtained. The positive electrode current collector layer 1A of the first positive electrode active material layer unit extends only to one end surface, and the negative electrode current collector layer 2A of the second negative electrode active material layer unit extends only to the other surface. As you move the units, stack them. Sheets for solid electrolyte 3 having a predetermined thickness are further stacked on both surfaces of the stacked units to prepare a laminate.

The produced laminate is pressed together. The pressure bonding is performed while heating, and the heating temperature is, for example, 40 to 95 ° C.

The laminated body that has been pressure-bonded is heated to, for example, 600 ° C. to 1000 ° C. in a nitrogen atmosphere and fired to obtain a sintered body. The firing time is, for example, 0.1 to 3 hours.
The sintered body may be put into a cylindrical container together with an abrasive such as alumina and barrel-polished. Thereby, the corners of the laminate can be chamfered. As another method, polishing may be performed by sandblasting. This method is preferable because only a specific portion can be removed.

(Terminal formation)
The first external terminal 5 and the second external terminal 6 are attached to the laminate 4. The first external terminal 5 and the second external terminal 6 are formed so as to be in electrical contact with the positive electrode current collector layer 1A and the negative electrode current collector layer 2A, respectively. For example, the positive electrode current collector layer 1A and the negative electrode current collector layer 2A exposed from the side surface of the laminate 4 can be formed by using a known method such as a sputtering method, a dipping method, or a spray coating method. When forming only on a predetermined part, it forms by masking etc. with a tape, for example.

80% or more may be sufficient as the relative density of the solid electrolyte layer which has a solid electrolyte provided between a pair of electrode layer and this pair of electrode layer of the said laminated body 4 sintered. The higher the relative density, the easier it is for the mobile ion diffusion path in the crystal to be connected, and the ionic conductivity is improved.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the configurations and combinations of the embodiments in the embodiments are examples, and the addition and omission of configurations are within the scope not departing from the gist of the present invention. , Substitutions, and other changes are possible.

In the solid electrolyte represented by the general formula _{Li a M1 x R 2-b} M2 b P 3-c M3 c O 12, a portion of P B, Si, the lithium ion conductivity when substituted with V or Mo Values are shown in Table 1.

[Example 1]
About the raw material of the solid electrolyte, 1.419 g of Li ₂ CO ₃ , 7.886 g of ZrO ₂ , 10.67 g of NH ₄ H ₂ PO _4, and 0.198 g of H ₃ BO ₃ were weighed.

The weighed raw materials, ethanol and zirconia balls were put into a polyethylene pot mill, and mixed and pulverized at 120 rpm for 16 hours.

After mixing and grinding, the slurry and zirconi balls were separated, and the slurry was dried to obtain mixed powder. The obtained mixed powder was put into a MgO container and baked in the air atmosphere at 800 ° C. for 2 hours and further at 1000 ° C. for 2 hours to obtain a baked powder.

The fired powder, ethanol and zirconia balls were put into a pot mill and pulverized at 120 rpm for 16 hours.

After pulverization, the slurry was separated into zirconia balls and the slurry was dried to obtain a solid electrolyte powder.

[Evaluation]
Each of the obtained solid electrolyte powders was measured for chemical composition, crystal structure, and lithium ion conductivity by the following methods.

(Chemical composition)
The solid electrolyte powder was dissolved in acid. The contents of Li, Zr, P, and B in the obtained solution were measured by IC P-AES and converted to the contents in the solid electrolyte powder.

(Crystal structure)
The X-ray diffraction pattern of the solid electrolyte powder was measured by a powder X-ray diffraction method. The crystal structure of the solid electrolyte powder was identified using the obtained X-ray diffraction pattern. It was the same X-ray diffraction pattern as lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ .

(Lithium ion conductivity)
A solid electrolyte powder 0.5 g was put into a mold having a diameter of 12 mm, cold-pressed at a pressure of 2.0 t / cm ² , and then fired at 900 ° C. for 2 hours to obtain a solid electrolyte sintered body. Gold electrodes were formed on both surfaces of the obtained solid electrolyte sintered body by performing gold sputtering. The lithium ion conductivity was measured using an impedance measuring device (model number SI1260 manufactured by Solartron) under the conditions of an amplitude of 50 mV and a frequency of 0.1 Hz to 1 MHz.

[Example 2]
Example 1 except that 1.655 g of Li ₂ CO ₃ , 7.886 g of ZrO ₂ , 10.302 g of NH ₄ H ₂ PO ₄ , and 0.396 g of H ₃ BO ₃ were weighed for the solid electrolyte raw material. Similarly, preparation and evaluation were performed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Example 3]
Example 1 except that 1.891 g of Li ₂ CO ₃ , 7.886 g of ZrO ₂ , 9.934 g of NH ₄ H ₂ PO _4, and 0.593 g of H ₃ BO ₃ were weighed as the solid electrolyte raw material. Similarly, preparation and evaluation were performed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Example 4]
Example 1 except that 2.128 g of Li ₂ CO ₃ , 7.886 g of ZrO ₂ , 9.566 g of NH ₄ H ₂ PO _4, and 0.791 g of H ₃ BO ₃ were weighed as the solid electrolyte raw material. Similarly, preparation and evaluation were performed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Example 5]
Except for weighing 2.364 g of Li ₂ CO ₃ , 7.886 g of ZrO ₂ , 9.198 g of NH ₄ H ₂ PO ₄ and 0.989 g of H ₃ BO ₃ for the raw material of the solid electrolyte, Example 1 and Similarly, preparation and evaluation were performed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Example 6]
Except for weighing the solid electrolyte raw material 3.546 g of Li ₂ CO ₃ , 7.886 g of ZrO ₂ , 7.359 g of NH ₄ H ₂ PO _4, and 1.978 g of H ₃ BO ₃ , Example 1 and Similarly, preparation and evaluation were performed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Example 7]
Except that 4.09 g of Li ₂ CO ₃ , 7.886 g of ZrO ₂ , 6.623 g of NH ₄ H ₂ PO _4, and 2.374 g of H ₃ BO ₃ were weighed as the solid electrolyte raw material, and Example 1 Similarly, preparation and evaluation were performed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Example 8]
The raw material of the solid electrolyte was the same as in Example 1 except that 4.728 g of Li ₂ CO ₃ , 7.886 g of ZrO ₂ , 5.519 g of NH ₄ H ₂ PO _4, and 2.967 g of H ₃ BO ₃ were weighed. Similarly, preparation and evaluation were performed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Example 9]
Except for weighing 1.300 g of Li ₂ CO ₃ , 7.886 g of ZrO ₂ , 10.302 g of NH ₄ H ₂ PO ₄ and 0.385 g of SiO ₂ for the solid electrolyte raw material, the same as in Example 1 Fabrication and evaluation were performed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Example 10]
Example 1 except that 1.182 g of Li ₂ CO ₃ , 7.886 g of ZrO ₂ , 10.302 g of NH ₄ H ₂ PO _4, and 0.582 g of V ₂ O ₅ were weighed for the solid electrolyte raw material. Similarly, preparation and evaluation were performed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Example 11]
About the raw material of the solid electrolyte, 1.064 g of Li ₂ CO ₃ , 7.886 g of ZrO ₂ , 10.302 g of NH ₄ H ₂ PO ₄ , 1.130 g of (NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O Except for weighing, production and evaluation were performed in the same manner as in Example 1. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Example 12]
Example 1 except that 1.064 g of Li ₂ CO ₃ , 13.472 g of HfO ₂ , 10.302 g of NH ₄ H ₂ PO ₄ , and 0.396 g of H ₃ BO ₃ were weighed for the raw material of the solid electrolyte. Similarly, preparation and evaluation were performed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiHf ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Comparative Example 1]
Each raw material was weighed and mixed so as to have a general formula LiZr ₂ P ₃ O _{12 in} which a part of P was not substituted.
The solid electrolyte raw material was prepared and evaluated in the same manner as in Example 1 except that 1.182 g of Li ₂ CO ₃ , 7.886 g of ZrO _2, and 11.0838 NH ₄ H ₂ PO ₄ were weighed. The X-ray diffraction pattern was lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

[Comparative Example 2]
The solid electrolyte material was prepared and evaluated in the same manner as in Example 1 except that 1.182 g of Li ₂ CO ₃ , 13.472 g of HfO _2, and 11.038 g of NH ₄ H ₂ PO ₄ were weighed. The X-ray diffraction pattern was lithium zirconium phosphate: LiHf ₂ (PO ₄ ) ₃ . Table 1 shows the values of lithium ion conductivity.

From Examples 1 to 8 and Comparative Example 1, it was clear that in the solid electrolyte represented by the general formula Li _a Zr ₂ P _3-c B _c O ₁₂ , when c> 0, the lithium ion conductivity was improved. is there. Further, in the range of c> 0.2, the lithium ion conductivity tended to be low. This revealed that c is more preferably in the range of 0.1 to 0.2.

From Examples 9 to 11 and Comparative Example 1, in the solid electrolyte represented by the general formula LiZr ₂ P _2.8 M3 _0.2 O ₁₂ , the lithium ion conductivity was improved by substituting the element. It was. Among these, it became clear that the substitution element is more preferably B or V.

From Example 12 and Comparative Example 2, even in the solid electrolyte represented by the general formula LiHf ₂ P _3-c B _c O ₁₂ , the lithium ion conductivity was improved in the range of c> 0.

As a result, it was revealed that lithium ion conductivity was improved by substituting a part of P with an element, more preferably substituting a part of P with B.

In the solid electrolyte represented by the general formula _{Li a M1 x R 2-b} M2 b P 3-c M3 c O 12, a solid electrolyte obtained by substituting a part of P B or V, and a part of Zr in Co Fabrication was performed. Table 2 shows the amount of substitution, composition, and lithium ion conductivity.

[Example 13]
The material of the solid electrolyte, _Li 2 CO ₃ to 1.891G, the ZrO _{2 7.492g,} the _{NH 4 H 2 PO 4 10.302g,} 0.396g of _{H 3 BO 3, Co (NO} 3) 2 · 6H Production and evaluation were performed in the same manner as in Example 1 except that 0.931 g of ₂ O was weighed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 2 shows the values of lithium ion conductivity.

[Example 14]
The material of the solid electrolyte, _Li 2 CO ₃ to 1.655G, the ZrO _{2 7.097g,} the _{NH 4 H 2 PO 4 10.302g,} 0.396g of _{H 3 BO 3, Co (NO} 3) 2 · 6H Production and evaluation were performed in the same manner as in Example 1 except that 1.862 g of ₂ O was weighed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 2 shows the values of lithium ion conductivity.

[Example 15]
The material of the solid electrolyte, _Li 2 CO ₃ to 1.419G, the ZrO _{2 6.703g,} the _{NH 4 H 2 PO 4 10.302g,} 0.396g of _{H 3 BO 3, Co (NO} 3) 2 · 6H Preparation and evaluation were performed in the same manner as in Example 1 except that 2.793 g of ₂ O was weighed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 2 shows the values of lithium ion conductivity.

[Example 16]
The material of the solid electrolyte, _Li 2 CO ₃ to 1.182G, the ZrO _{2 6.309g,} the _{NH 4 H 2 PO 4 10.302g,} 0.396g of _{H 3 BO 3, Co (NO} 3) 2 · 6H Production and evaluation were performed in the same manner as in Example 1 except that 3.724 g of ₂ O was weighed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 2 shows the values of lithium ion conductivity.

[Example 17]
The material of the solid electrolyte, 1.419G the _Li 2 CO _3, the _{ZrO 2 7.492g, NH 4 H 2} PO 4 and _10.302g, V 2 _{O 5} and _{0.582g, Co (NO 3) 2} · 6H Production and evaluation were performed in the same manner as in Example 1 except that 0.931 g of ₂ O was weighed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 2 shows the values of lithium ion conductivity.

[Example 18]
The material of the solid electrolyte, 1.182G the _Li 2 CO _3, the _{ZrO 2 7.097g, NH 4 H 2} PO 4 and _10.302g, V 2 _{O 5} and _{0.582g, Co (NO 3) 2} · 6H Production and evaluation were performed in the same manner as in Example 1 except that 1.862 g of ₂ O was weighed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 2 shows the values of lithium ion conductivity.

[Example 19]
The material of the solid electrolyte, 0.946 g of _Li 2 CO _3, the _{ZrO 2 6.703g, NH 4 H 2} PO 4 and _10.302g, V 2 _{O 5} and _{0.582g, Co (NO 3) 2} · 6H Preparation and evaluation were performed in the same manner as in Example 1 except that 2.793 g of ₂ O was weighed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 2 shows the values of lithium ion conductivity.

[Example 20]
The material of the solid electrolyte, 0.709 g of _Li 2 CO _3, the _{ZrO 2 6.309g, NH 4 H 2} PO 4 and _10.302g, V 2 _{O 5} and _{0.582g, Co (NO 3) 2} · 6H Production and evaluation were performed in the same manner as in Example 1 except that 3.724 g of ₂ O was weighed. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 2 shows the values of lithium ion conductivity.

[Comparative Example 3]
Each raw material was weighed and mixed so as to be a general formula Li _1.2 Zr _1.9 Co _0.1 P ₃ O _{12 in} which a part of Zr was substituted with Co and a part of P was not substituted.
The material of the solid electrolyte, 1.419G the _Li 2 CO _3, except the ZrO _{2 7.492g,} to 11.038g of NH ₄ H 2 PO _4, Co and _{(NO 3) 2 · 6H 2} O and 0.931g weighed Were produced and evaluated in the same manner as in Example 1. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 2 shows the values of lithium ion conductivity.

From Example 2, Examples 13 to 16, and Comparative Example 3, in the solid electrolyte represented by the general formula Li _a Zr _2-b Co _b P _2.8 B _0.2 O ₁₂ , c> 0 and b> 0 It is clear that the lithium ion conductivity was improved at that time. Further, in the range of b> 0.1, the lithium ion conductivity tended to be low. This revealed that b is more preferably in the range of 0 to 0.1.

From Example 10 and Examples 17 to 20, the solid electrolyte represented by the general formula Li _a Zr _2-b Co _b P _2.8 V _0.2 O ₁₂ was also used when c> 0 and b> 0. It was clear that the lithium ion conductivity was improved and b was more preferably in the range of 0 to 0.1.

In the solid electrolyte represented by the general formula _{Li a M1 x R 2-b} M2 b P 3-c M3 c O 12, a solid electrolyte obtained by substituting a part of P B or V, and a part of Li in Ca Fabrication was performed. Table 3 shows the values of substitution amount, composition, and lithium ion conductivity.

[Example 21]
For the preparation of the solid electrolyte, Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and Ca _0.5 Zr ₂ (PO ₄ ) ₃ of Example 2 were used as raw materials.

[Preparation of Ca _0.5 Zr ₂ (PO ₄ ) ₃ ]
The raw materials were prepared in the same manner as in Example 1 except that 7.886 g of ZrO ₂ , 11.038 g of NH ₄ H ₂ (PO ₄ ) ₃ and 1.601 g of CaCO ₃ were weighed.

[Evaluation of Ca _0.5 Zr ₂ (PO ₄ ) ₃ ]
(Chemical composition)
The solid electrolyte powder was dissolved in acid. The contents of Ca, Zr, and P in the obtained solution were measured by ICP-AES and converted to the contents in the solid electrolyte powder.

(Crystal structure)
The X-ray diffraction pattern of the solid electrolyte powder was measured by a powder X-ray diffraction method. The crystal structure of the solid electrolyte powder was identified using the obtained X-ray diffraction pattern. Zirconium calcium phosphate: The same X-ray diffraction pattern as Ca _0.5 Zr ₂ (PO ₄ ) ₃ .

Example 1 except that 13.623 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 1.560 g of Ca _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. Were prepared and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Example 22]
Example 1 except that 12.110 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 3.119 g of Ca _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. It produced similarly and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Example 23]
Example 1 except that 9.082 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 6.239 g of Ca _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. It produced similarly and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Example 24]
Example 1 except that 7.569 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 7.798 g of Ca _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. It produced similarly and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Example 25]
For production of the solid electrolyte, Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and Sr _0.5 Zr ₂ (PO ₄ ) ₃ of Example 2 were used as raw materials.

[Production of Sr _0.5 Zr ₂ (PO ₄ ) ₃ ]
The raw materials were prepared in the same manner as in Example 1 except that 7.886 g of ZrO ₂ , 11.038 g of NH ₄ H ₂ (PO ₄ ) ₃ and 2.362 g of SrCO ₃ were weighed.

[Evaluation of Sr _0.5 Zr ₂ (PO ₄ ) ₃ ]
(Chemical composition)
The solid electrolyte powder was dissolved in acid. The contents of Sr, Zr, and P in the obtained solution were measured by ICP-AES and converted to the contents in the solid electrolyte powder.

(Crystal structure)
The X-ray diffraction pattern of the solid electrolyte powder was measured by a powder X-ray diffraction method. The crystal structure of the solid electrolyte powder was identified using the obtained X-ray diffraction pattern. It was the same X-ray diffraction pattern as strontium zirconium phosphate: Sr _0.5 Zr ₂ (PO ₄ ) ₃ .

Example 1 except that 13.623 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 1.636 g of Sr _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. Were prepared and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Example 26]
Example 1 except that 12.110 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 3.271 g of Sr _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. Were prepared and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Example 27]
Example 1 except that 9.082 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 6.543 g of Sr _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. It produced similarly and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Example 28]
Example 1 except that 7.569 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 8.179 g of Sr _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. It produced similarly and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Example 29]
For the production of the solid electrolyte, Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and Ba _0.5 Zr ₂ (PO ₄ ) ₃ of Example 2 were used as raw materials.

[Preparation of Ba _0.5 Zr ₂ (PO ₄ ) ₃ ]
The raw materials were prepared in the same manner as Example 1 except that 7.886 g of ZrO ₂ , 11.038 g of NH ₄ H ₂ (PO ₄ ) ₃ and 3.157 g of BaCO ₃ were weighed.

[Evaluation of Ba _0.5 Zr ₂ (PO ₄ ) ₃ ]
(Chemical composition)
The solid electrolyte powder was dissolved in acid. The contents of Ba, Zr, and P in the obtained solution were measured by ICP-AES and converted to the contents in the solid electrolyte powder.

(Crystal structure)
The X-ray diffraction pattern of the solid electrolyte powder was measured by a powder X-ray diffraction method. The crystal structure of the solid electrolyte powder was identified using the obtained X-ray diffraction pattern. It was the same X-ray diffraction pattern as barium zirconium phosphate: Ba _0.5 Zr ₂ (PO ₄ ) ₃ .

Example 1 except that 1.623 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 1.715 g of Ba _0.5 Zr ₂ (PO ₄ ) ³ were weighed as raw materials. Were prepared and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Example 30]
Example 1 except that 12.110 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 3.430 g of Ba _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. Were prepared and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Example 31]
Example 1 except that 9.082 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 6.861 g of Ba _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. It produced similarly and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Example 32]
Example 1 except that 7.569 g of Li _1.4 Zr _2.0 P _2.8 B _0.2 O ₁₂ and 8.576 g of Ba _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. It produced similarly and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Comparative Example 4]
The same as Example 1 except that 12.142 g of Li _1.0 Zr _2.0 P _3.0 O ₁₂ of Comparative Example 1 and 3.119 g of Ca _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. Were prepared and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Comparative Example 5]
The same as Example 1 except that 12.142 g of Li _1.0 Zr _2.0 P _3.0 O ₁₂ of Comparative Example 1 and 3.271 g of Sr _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. Were prepared and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

[Comparative Example 6]
The same as Example 1 except that 12.142 g of Li _1.0 Zr _2.0 P _3.0 O ₁₂ of Comparative Example 1 and 3.430 g of Ba _0.5 Zr ₂ (PO ₄ ) ₃ were weighed as raw materials. Were prepared and evaluated. The X-ray diffraction pattern was the same as that of lithium zirconium phosphate: LiZr ₂ (PO ₄ ) ₃ . Table 3 shows the values of lithium ion conductivity.

From Examples 21 to 32 and Comparative Examples 4 to 6, in the solid electrolyte represented by the general formula Li _a M1 _x Zr ₂ P ₃ —cB _c O ₁₂ , when c> 0 and x> 0, It is clear that it has improved. Moreover, in the range of x <0.05 and x> 0.1, the lithium ion conductivity tended to be low. This revealed that x is more preferably in the range of 0.05 to 0.1.

Further, regarding the element type of M1, it has become clear that substitution of an element having a small ionic radius is more preferable among the homologous elements in the periodic table.

[Examples 33 to 35]
Of the solid electrolytes described above, all-solid secondary batteries were produced using the solid electrolytes of Example 2, Example 13, and Example 22. Li ₃ V ₂ (PO ₄ ) ₃ was used as the positive electrode active material, and Li ₄ Ti ₅ O ₁₂ was used as the negative electrode active material.

(Preparation of solid electrolyte layer forming paste)
The solid electrolyte powder produced in Example 2, Example 13, and Example 22 was used as the solid electrolyte. This solid electrolyte powder was dispersed in a vehicle containing terpineol as a solvent, a non-aqueous dispersant as a dispersant, and ethyl cellulose as a binder to prepare a solid electrolyte layer forming paste.

(Preparation of electrode active material layer forming paste)
Using the Li ₃ V ₂ (PO ₄ ) ₃ powder as the positive electrode active material and the Li ₄ Ti ₅ O ₁₂ powder as the negative electrode active material, the electrode active material layer forming paste was prepared in the same manner as the solid electrolyte layer forming paste. Prepared.

(Preparation of current collector layer forming paste)
A mixed powder obtained by mixing copper powder and Li ₃ V ₂ (PO ₄ ) ₃ powder at a volume ratio of 80/20 as a paste for forming a positive electrode current collector, and copper powder as a paste for forming a negative electrode current collector A current collector layer forming paste was prepared in the same manner as the above electrode active material layer forming paste, using a mixed powder obtained by mixing Li ₄ Ti ₅ O ₁₂ powder in a volume ratio of 80/20.

(Preparation of positive electrode unit)
A positive electrode unit was prepared using the solid electrolyte layer forming paste, positive electrode active material layer forming paste, and positive electrode current collector layer forming paste prepared as described above.
First, a solid electrolyte layer forming paste was formed into a sheet shape on a PET film by a doctor blade method and dried to form a solid electrolyte layer. Next, an electrode active material electrode layer forming paste was printed thereon by screen printing and dried to form a positive electrode active material layer. Next, a current collector layer forming paste was printed thereon by screen printing and dried to form a positive electrode current collector layer. Furthermore, an electrode active material layer forming paste was printed on the screen again by screen printing and dried to form a positive electrode active material layer. Then, the PET film was peeled off to produce a positive electrode unit in which a solid electrolyte layer / positive electrode active material layer / positive electrode current collector layer / positive electrode active material layer was laminated in this order.

(Preparation of negative electrode unit)
A negative electrode unit was prepared using the solid electrolyte layer forming paste, negative electrode active material layer forming paste, and negative electrode current collector layer forming paste prepared as described above.
First, a solid electrolyte layer forming paste was formed into a sheet shape on a PET film by a doctor blade method and dried to form a solid electrolyte layer. Next, an electrode active material layer forming paste was printed thereon and dried to form a negative electrode active material layer. Next, a current collector layer forming paste was printed thereon by screen printing and dried to form a negative electrode current collector layer. Furthermore, the electrode active material layer forming paste was printed on the screen again by screen printing, and dried to form a negative electrode active material layer. Then, the PET film was peeled off to produce a negative electrode unit in which a solid electrolyte layer / negative electrode active material layer / negative electrode current collector layer / negative electrode active material layer was laminated in this order.

(Preparation of all-solid-state lithium ion secondary battery)
The positive electrode unit and the negative electrode unit produced as described above were alternately stacked to form a green sheet laminate composed of the positive electrode unit and the negative electrode unit, and fired simultaneously to obtain a sintered body. The co-firing temperature was 800 ° C., and the firing time was 1 hour.

Then, an InGa electrode paste is applied to each of the positive electrode current collector layer and the negative electrode current collector layer of the obtained sintered body and dried to provide the first external terminal on the positive electrode current collector layer, and the negative electrode current collector. A second external terminal was attached to the layer to produce an all-solid secondary battery.

[Comparative Examples 7 and 8]
A positive electrode unit and a negative electrode unit were produced in the same manner as in Examples 33 to 35, except that the solid electrolyte powder produced in Comparative Examples 1 and 4 was used as the solid electrolyte. An all-solid secondary battery was produced in the same manner as in Examples 33 to 35 except that this positive electrode unit and negative electrode unit were used.

[Evaluation]
The charging / discharging of the all solid state secondary batteries produced in Examples 33 to 35 and Comparative Examples 7 to 8 was performed at a constant current of 2 μA. The cut-off voltages during charging and discharging were set to 3.0 V and 0 V, respectively. The rest time after charging and discharging was 1 minute. The results are shown in Table 4.

In the all solid state secondary batteries of Examples 33 to 35, a high discharge capacity could be obtained. On the other hand, the all solid secondary batteries of Comparative Examples 7 and 8 resulted in a low discharge capacity.

As described above, the solid electrolyte according to the present invention is effective in improving the lithium ion conductivity of the solid electrolyte. In addition, the all solid state secondary battery using the solid electrolyte according to the present invention is effective in improving the discharge capacity.
Providing improved lithium ion conductivity and high capacity contributes significantly, especially in the field of electronics.

DESCRIPTION OF SYMBOLS 1 ... 1st electrode layer, positive electrode layer 1A ... Positive electrode collector layer 1B ... Positive electrode active material layer 2 ... 2nd electrode layer, negative electrode layer 2A ... Negative electrode collector layer 2B ... Negative electrode active material layer 3 ... Solid electrolyte 4 ... Laminate 5 ... first external terminal 6 ... second external terminal 10 ... all solid state secondary battery

Claims (4)

1. Formula _{Li a M1 x R 2-b} M2 b P 3-c M3 solid electrolyte which comprises a main component represented by _{c O 12.}
   However, 0 <a ≦ 3, 0 ≦ b <2, 0 <c <3, 0 ≦ x <0.5
   M1: an element having K and a valence of 2 or more R: Zr or Hf
   M2: at least one selected from the group consisting of Co, V, Sn and B M3: at least one selected from the group consisting of Si, B, V, Nb, Mo and W
2. The solid electrolyte according to claim 1, wherein M1 of the solid electrolyte is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Al, Ga, Y, and Nb.
3. An all-solid secondary battery comprising the solid electrolyte according to any one of claims 1 and 2.
4. 
   The all-solid secondary according to claim 3, wherein the pair of electrode layers and the solid electrolyte layer having the solid electrolyte provided between the pair of electrode layers have a relative density of 80% or more. battery.

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