JP2019212637A - Electrode active material for all-solid secondary battery, manufacturing method thereof, and all-solid secondary battery - Google Patents

Abstract

An electrode active material for an all-solid-state secondary battery, a method for manufacturing the same, and an all-solid-state secondary battery, in which the interfacial resistance with a solid electrolyte is effectively reduced even when the secondary battery is continuously used. .
A solid electrolyte nanoparticle aggregate (b) in which a plurality of solid electrolyte nanoparticles (a) are linearly supported on a carbon chain derived from cellulose nanofibers having an average fiber diameter of 50 nm or less is an electrode active material. An electrode active material for an all-solid-state secondary battery, supported on the surface of the particles (A).
[Selection] Figure 1

Description

  The present invention relates to an electrode active material for an all-solid-state secondary battery with reduced interface resistance with a solid electrolyte (a positive electrode active material, an anode active material, etc.), particularly an electrode active material for an all-solid lithium ion secondary battery, and their The present invention relates to a production method, and an all-solid secondary battery or all-solid lithium ion secondary battery using the same.

Secondary batteries such as lithium-ion secondary batteries currently on the market use a flammable organic solvent in the electrolyte solution, so they prevent structures from short-circuiting and prevent temperature rises when short-circuiting occurs. A safety device is required. On the other hand, an all-solid-state lithium ion secondary battery including an oxide-based solid electrolyte such as Li ₇ La ₃ Zr ₂ O ₁₂ or a sulfide-based solid electrolyte such as 75Li ₂ S · 25P ₂ S ₅ is It is expected to be a lithium ion secondary battery that has high energy density and simplifies the safety device because it does not use combustible materials, and is excellent in manufacturing cost and productivity.

  All solid-state lithium ion secondary batteries are composed of solid materials such as a positive electrode current collector such as aluminum foil, a positive electrode active material, a solid electrolyte, a negative electrode active material, and a negative electrode current collector such as copper foil. ing. The production of the all-solid-state lithium ion secondary battery generally includes a step of laminating and pressing these constituent materials, which improves the solid-solid interface contact between the solid materials. This is for reducing the resistance and improving the performance of the obtained lithium ion secondary battery.

Further, Non-Patent Document 1, by performing heat treatment for 5 hours at 175 ° C., a solid electrolyte _{Li 7-x La 3 Zr 2} -x Ta x O 12 and (LLZT) a negative electrode material made of metallic lithium It is disclosed that a good bonding interface can be formed and the interface resistance can be effectively reduced.

Ryoji Inada; Abstract of the 58th Battery Conference, 1C07, 2017

  However, in an all-solid-state lithium ion secondary battery or the like manufactured by pressing as described above, the material in the secondary battery may be affected by expansion and contraction of the electrode active material that is repeatedly charged and discharged, vibration during use, and the like. The laminated structure may be destroyed, and the positive electrode active material and the negative electrode active material may come into contact with each other and the battery may be internally short-circuited. Further, the method of Non-Patent Document 1 has a problem that it is difficult to apply to electrode active materials other than metallic lithium.

  Accordingly, an object of the present invention is to provide an electrode active material for an all-solid secondary battery, particularly an all-solid lithium ion secondary battery, in which the interface resistance with the solid electrolyte is effectively reduced even in continuous use of the secondary battery. It is an object to provide an electrode active material, a manufacturing method thereof, and an all-solid-state secondary battery using the same.

  As a result of intensive studies to solve the above problems, the present inventors have achieved the above object by using the electrode active material for an all-solid secondary battery shown below, a method for producing the same, and an all-solid secondary battery using them. The inventors have found that this can be achieved and have completed the present invention.

  That is, the electrode active material for an all-solid secondary battery of the present invention is a solid electrolyte in which a plurality of solid electrolyte nanoparticles (a) are linearly supported on a carbon chain derived from cellulose nanofibers having an average fiber diameter of 50 nm or less. The nanoparticle aggregate (b) is supported on the surface of the electrode active material particles (A).

  Another electrode active material for an all-solid-state secondary battery according to the present invention is a solid electrolyte in which solid electrolyte nanoparticles (a) are linearly arrayed by being induced by cellulose nanofibers having an average fiber diameter of 50 nm or less. The nanoparticle array (c) is supported on the surface of the electrode active material particles (A).

  According to the electrode active material for an all-solid-state secondary battery of the present invention, as described above, a carbon chain derived from cellulose nanofibers is used as a shaft or a substrate, and a plurality of nanoparticles of a specific solid electrolyte are supported or arranged in series on this. A solid electrolyte nanoparticle aggregate (b) exhibiting a unique shape, or a plurality of solid electrolyte nanoparticle arrays (c) arranged linearly obtained using the solid electrolyte nanoparticles, for example, an electrode By being present at the interface between the active material layer and the solid electrolyte, effective bonding between the electrode active material and the solid electrolyte is sufficiently ensured to reduce the interface resistance, and further, the electrode active material expands due to charge and discharge, Even when the contraction is repeated, it is possible to continue effective bonding between the electrode active material and the solid electrolyte.

  In the electrode active material for an all-solid secondary battery of the present invention, the average secondary particle diameter of the electrode active material particles (A) can be 50 nm to 50 μm. By adopting the above-described configuration, a good packing state with a small porosity with the electrode active material (particles), the electrolyte (particles), etc. can be formed, which is more suitable as an electrode active material for an all-solid-state secondary battery. It can be.

  In the electrode active material for an all-solid secondary battery of the present invention, the average particle diameter of the solid electrolyte nanoparticles (a) can be set to 0.5 nm to 100 nm. By adopting the above configuration, a good packing state with a small porosity can be formed with the electrode active material (particles), the electrolyte (particles), etc., and it becomes more suitable as an electrode active material for an all-solid-state secondary battery. sell.

  Further, in the electrode active material for an all-solid-state secondary battery of the present invention, the electrode active material particles (A), the solid electrolyte nanoparticle aggregate (b), the solid electrolyte nanoparticle array (c), or both The total amount, and the mass ratio (electrode active material particles (A): solid electrolyte nanoparticle aggregate (b) + solid electrolyte nanoparticle array (c)) (however, solid electrolyte nanoparticle aggregate (B) and the solid electrolyte nanoparticle array (c), when only one of them is included, only one of them.)) Can be set to 99.9: 0.1 to 70:30. By doing so, it can be more suitable as an electrode active material for an all-solid-state secondary battery.

In the electrode active material for an all-solid-state secondary battery of the present invention, the electrode active material particles (A) are LiNi _1-xy Co _x Mn _y O ₂ , LiNi _1-xy Co _x Al _y O. ₂ , LiMPO ₄ (M = Ni, Co, Fe, Mn), Li ₂ MSiO ₄ (M = Ni, Co, Fe, Mn), SiO _x , and at least one selected from the group consisting of Li ₄ Ti ₅ O _12. The above may be included. By setting it as the said structure, it can become more suitable as an electrode active material for all-solid-state secondary batteries, especially an electrode active material for all-solid-state lithium ion secondary batteries.

In the electrode active material for an all-solid-state secondary battery according to the present invention, the solid electrolyte nanoparticles (a) are Li ₃ PO ₄ -Li ₄ SiO ₄ , Li _7-x La ₃ Zr _{2 -x} Ta _x O _12. La _0.51 Li _0.34 TiO _2.94 , Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li ₇ La ₃ Zr ₂ O ₁₂ , and 50Li ₄ SiO ₄ .50Li ₃ BO You may include at least 1 sort (s) among the group which consists of _three . By setting it as the said structure, it can become more suitable as an electrode active material for all-solid-state secondary batteries, especially an electrode active material for all-solid-state lithium ion secondary batteries.

  In the electrode active material for an all-solid-state secondary battery of the present invention, the linear shape may be a linear shape or a substantially linear shape. By setting it as the said structure, it can become a suitable thing as an electrode active material for all-solid-state secondary batteries.

  Moreover, the electrode active material for an all-solid-state secondary battery of the present invention can be used for the all-solid-state lithium ion secondary battery. Since the electrode active material for an all-solid-state secondary battery of the present invention has the above characteristics, it is particularly preferable to be used for an all-solid-state lithium ion secondary battery.

On the other hand, the method for producing an electrode active material for an all-solid-state secondary battery of the present invention includes:
Next steps (II) to (III):
A slurry containing at least one solid electrolyte raw material compound, an alkaline solution, and cellulose nanofibers (hereinafter also referred to as “CNF”) as a raw material has a temperature of 100 ° C. or higher and a pressure of 0.3 MPa. The solid electrolyte nanoparticle aggregate (d) enclosing part or all of the cellulose nanofibers by subjecting to a hydrothermal reaction of ˜0.9 MPa, and the solid electrolyte enclosing part or all of the cellulose nanofibers A step (II) of producing a nanoparticle aggregate (e) consisting of precursors of
At least from the solid electrolyte nanoparticle aggregate (d) enclosing part or all of the raw material CNF obtained in step (II), the precursor of the solid electrolyte encapsulating part or all of the raw material CNF A solid electrolyte nanoparticle aggregate (b) which reacts with the nanoparticle aggregate (e) and the nanoparticle aggregate (e) comprising the precursor of the solid electrolyte encapsulating part or all of the raw material CNF Step (III) of firing the remaining raw material compounds for producing the solid electrolyte nanoparticle array (c), or both,
It is characterized by including.

In addition, another method for producing an electrode active material for an all-solid-state secondary battery of the present invention,
Next steps (II) to (III ′):
A slurry containing at least one raw material compound of a solid electrolyte, an alkali solution, and cellulose nanofibers as a raw material is subjected to a hydrothermal reaction at a temperature of 100 ° C. or higher and a pressure of 0.3 MPa to 0.9 MPa, Solid electrolyte nanoparticle aggregate (d) encapsulating part or all of the raw material CNF, nanoparticle aggregate (e) comprising the solid electrolyte precursor encapsulating part or all of the raw material CNF, or Steps (II) for producing both, and
At least from the solid electrolyte nanoparticle aggregate (d) enclosing part or all of the raw material CNF obtained in step (II), the precursor of the solid electrolyte encapsulating part or all of the raw material CNF A solid electrolyte nanoparticle aggregate (b) by reacting with the nanoparticle aggregate (e) comprising the above-mentioned solid electrolyte precursor encapsulating part or all of the raw material CNF and the nanoparticle aggregate (e) A step (III ′) of firing the remaining raw material compounds to be used, or both in a reducing atmosphere,
It is characterized by including.

In addition, another method for producing an electrode active material for an all-solid-state secondary battery of the present invention,
Next steps (II) to (III ″):
A slurry containing at least one raw material compound of a solid electrolyte, an alkali solution, and cellulose nanofibers as a raw material is subjected to a hydrothermal reaction at a temperature of 100 ° C. or higher and a pressure of 0.3 MPa to 0.9 MPa, Solid electrolyte nanoparticle aggregate (d) encapsulating part or all of the raw material CNF, nanoparticle aggregate (e) comprising the solid electrolyte precursor encapsulating part or all of the raw material CNF, or Steps (II) for producing both, and
At least from the solid electrolyte nanoparticle aggregate (d) enclosing part or all of the raw material CNF obtained in step (II), the precursor of the solid electrolyte encapsulating part or all of the raw material CNF Reacting with the nanoparticle aggregate (e) and the nanoparticle aggregate (e) comprising the precursor of the solid electrolyte enclosing part or all of the raw material CNF to produce a solid electrolyte nanoparticle array (c) A step (III ″) of firing the remaining raw material compound for the purpose, or both in an oxidizing atmosphere,
It is characterized by including.

  Since the method for producing an electrode active material for an all-solid-state secondary battery of the present invention has the above configuration, the above-described electrode active material for an all-solid-state secondary battery can be more easily produced. Furthermore, as described above, by having the step (III ′) or the step (III ″), a plurality of solid electrolyte nanoparticles (a) are linearly supported on the carbon chains derived from cellulose nanofibers. An electrode active material comprising the solid electrolyte nanoparticle aggregate (b), and the solid electrolyte nanoparticle array (c) in which the solid electrolyte nanoparticles (a) are linearly arranged continuously by being induced by cellulose nanofibers. It is possible to easily obtain each desired electrode active material comprising

  In the method for producing a solid electrolyte for an all-solid-state secondary battery of the present invention, the electrode active material particles (A) are further added during firing in the step (III), (III ′), or (III ″). Can be included. For example, by including the electrode active material particles (A) in advance in the raw material mixture before firing, either the solid electrolyte nanoarray (b) or the solid electrolyte nanoparticle array (c) can be used as an electrode. It may be possible to more easily obtain an electrode active material for an all-solid-state secondary battery supported on the surface of the active material particles (A).

  In the method for producing an electrode active material for an all-solid-state secondary battery of the present invention, the electrode active material particles (A) are produced prior to the step (III), (III ′), or (III ″). Step (I).

  Moreover, in the manufacturing method of the electrode active material for all-solid-state secondary batteries of this invention, content of the cellulose nanofiber in the slurry of process (II) is carbon atom conversion amount with respect to 100 mass parts of water in slurry. It can be 0.01 mass part-10 mass parts. By adopting the above-described configuration, the solid electrolyte nanoparticle aggregate (d) enclosing part or all of the raw material CNF is more reliably obtained from the precursor of the solid electrolyte including part or all of the raw material CNF. It is possible to obtain the above-mentioned electrode active material for an all-solid-state secondary battery by converting into the nanoparticle aggregate (e) or both.

  Moreover, in the manufacturing method of the electrode active material for all-solid-state secondary batteries of this invention, the hydrothermal reaction in process (II) is temperature 100 degreeC or more, pressure is 0.3 Mpa-0.9 Mpa, reaction time is 0.00. It can be from 5 hours to 24 hours. By adopting the above-described configuration, the solid electrolyte nanoparticle aggregate (d) enclosing part or all of the raw material CNF is more reliably obtained from the precursor of the solid electrolyte including part or all of the raw material CNF. It is possible to obtain the above-mentioned electrode active material for an all-solid-state secondary battery by converting into the nanoparticle aggregate (e) or both.

  Moreover, in the manufacturing method of the electrode active material for all-solid-state secondary batteries of this invention, the calcination temperature in process (III), (III '), or (III' ') shall be 500 to 1200 degreeC. be able to. By the above configuration, the nanoparticle aggregate (e) composed of the precursor of the solid electrolyte encapsulating part or all of the raw material CNF while carbonizing or burning out the cellulose nanofibers more reliably is included. In the case where the solid electrolyte nanoparticle aggregate (b) or the solid electrolyte nanoparticle array (c) is converted, the electrode active material for an all-solid-state secondary battery can be obtained.

  On the other hand, the all-solid-state secondary battery of the present invention includes the above-described electrode active material for all-solid-state secondary batteries.

  Since the all-solid-state secondary battery includes the solid electrolyte for all-solid-state secondary batteries having the above characteristics as a constituent element, the charge / discharge capacity, durability, and the like can be further improved.

  Moreover, it is preferable that the all-solid-state secondary battery of this invention is an all-solid-state lithium ion secondary battery. Since it has the above characteristics, it can be an all-solid-state lithium ion secondary battery with further improved charge / discharge capacity and durability.

  According to the electrode active material for an all-solid-state secondary battery of the present invention, the solid electrolyte nanoparticle aggregate (b) or the nanoparticle array (c) of solid electrolyte particles is supported on the surface of the electrode active material particles (A). Therefore, the interfacial resistance between the electrode active material particles and the solid electrolyte particles in an all-solid secondary battery using the same, particularly an all-solid lithium ion secondary battery is sufficiently reduced, and the charge / discharge capacity of the secondary battery is Can be further increased.

  Moreover, according to the manufacturing method of the electrode active material for all-solid-state secondary batteries of this invention, the solid electrolyte nanoparticle aggregate | assembly (b) on the surface of the above-mentioned electrode active material particle (A), or the nanoparticle of solid electrolyte particle Each desired solid electrolyte carrying the row (c) can be easily obtained.

  In addition, according to the all-solid secondary battery or the all-solid lithium ion secondary battery of the present invention, the electrode active material for the all-solid-state secondary battery having the above characteristics is provided. The all-solid-state secondary battery, or the all-solid-state lithium ion secondary battery, in which the interfacial resistance of the secondary battery is sufficiently reduced and the durability associated with repeated charge / discharge capacity and charge / discharge of the secondary battery can be further increased. sell.

2 is a TEM photograph showing the surface structure of electrode active material particles obtained in Example 1. FIG.

  Hereinafter, the present invention will be described in detail.

[Electrode active material for all-solid-state secondary batteries]
The electrode active material for an all-solid-state lithium ion secondary battery of the present invention is a carbon derived from cellulose nanofibers having an average fiber diameter of 50 nm or less on the surface of electrode active material particles (A) having an average secondary particle diameter of 50 nm to 50 μm. Solid electrolyte nanoparticle aggregate (b) in which a plurality of solid electrolyte nanoparticles (a) having an average particle size of 0.5 nm to 100 nm are linearly supported on a chain (hereinafter referred to as “solid electrolyte nanoarray (b)”) Or a solid electrolyte nanoparticle array (c) in which the solid electrolyte nanoparticles (a) are continuously arranged in a linear form by being induced by the cellulose nanofibers are formed into electrode active material particles (A ).

  Here, the solid electrolyte nanoparticle aggregate (b) in the present invention is the other nanoscale structure on a carbon chain derived from cellulose nanofibers having an average fiber diameter of 50 nm or less, which is a nanoscale structure. A plurality of solid electrolyte nanoparticles having an average particle diameter of 0.5 nm to 100 nm have a unique shape in which they are supported linearly, continuously or intermittently. And since the said solid electrolyte nanoparticle aggregate | assembly (b) does not produce separation of a constituent material easily, it can carry | support on the surface of an electrode active material particle (A), hold | maintaining the said specific shape.

  The electrode active material for an all-solid secondary battery, in particular the electrode active material for an all-solid lithium ion secondary battery, on which the solid electrolyte nanoarray (b) or the solid electrolyte nanoparticle array (c) is supported on the surface, Although the scope of the invention is not limited to the presumed mechanism, the microscopic uneven structure by the support of the solid electrolyte nanoarray (b) or the solid electrolyte nanoparticle array (c) on the surface, for example, by charging and discharging Even when the electrode active material is repeatedly expanded and contracted, the electrode active material particles (A) and the solid electrolyte nanoarray (b) supported on the surface thereof or the solid electrolyte nanoparticle array (c) The bonding between them remains sufficiently effective, and on the surface of the electrode active material particles (A), the coated fine solid electrolyte nanoarray (b) or solid electrolyte nanoparticle array (c) A solid structure formed on the surface of the electrode active material particles (A) and a solid that is in contact with the electrode active material particles (A) in the secondary battery. By being able to maintain a state in which a large amount of effective joints can always exist between the electrolyte particles, all-solid secondary batteries obtained using these, particularly all-solid lithium ion secondary batteries, have electrode active material particles and It is presumed that the interfacial resistance between the solid electrolyte particles is sufficiently reduced and a good charge / discharge capacity can be expressed.

  The supported state of the solid electrolyte nanoarray (b) on the surface of the electrode active material particles (A) or the solid electrolyte nanoparticle array (c) on the surface of the electrode active material particles (A) is not necessarily limited. It need not be physically or chemically strong. This is because, for example, as described above, the electrode active material particles that are the base material repeatedly expand and contract due to charge and discharge, so that the solid electrolyte nanoarray may be destroyed due to the volume change of the electrode active material in a strong support state. For this reason, in the production of an all-solid-state lithium ion secondary battery, the laminated structure of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer is pressed to form a battery. Good contact between the electrode active material particles (A) and the solid electrolyte particles via the electrode, or between the electrode active material particles (A) and the solid electrolyte particles via the solid electrolyte nanoparticle array (c) This is because a state can be formed.

The electrode active material particles (A) used in the present invention can be used for an all-solid secondary battery, particularly an all-solid lithium ion secondary battery, and are solid in the firing step in the production method described later. There is no limitation on the type of the material as long as it is difficult to cause a solid phase reaction with the raw material compound of the electrolyte phase. Specifically, for example, as the positive electrode active material, layered oxide-based LiNi _1-xy Co _x Mn _y O ₂ , LiNi _1-xy Co _x Al _y O ₂ , olivine-based LiMPO ₄ ( M = Ni, Co, Fe, Mn), Li ₂ MSiO ₄ (M = Ni, Co, Fe, Mn), and the like. Examples of the negative electrode active material include oxide-based SiO _x , titanium oxide-based Li ₄ Ti ₅ O _{12, and the} like. The electrode active material particles (A) of the present _{invention, LiNi 1-x-y Co} x Mn y O 2, LiNi 1-x-y Co x Al y O 2, LiMPO 4 (M = Ni, Co, Fe , Mn), Li ₂ MSiO ₄ (M = Ni, Co, Fe, Mn), SiO _x , and Li ₄ Ti ₅ O ₁₂ may be included.

  The average particle diameter of the primary particles of the electrode active material for an all-solid secondary battery is preferably 500 nm or less, more preferably 400 nm or less, and still more preferably 300 nm or less. As described above, when the average particle diameter of the primary particles of the electrode active material is at least 500 nm or less, the amount of expansion and contraction of the electrode active material particles accompanying the insertion and desorption of lithium ions can be suppressed. The lower limit of the average particle size of the primary particles is not particularly limited, but is preferably 10 nm or more from the viewpoint of handling.

  The average particle diameter of the secondary particles of the electrode active material particles (A) formed by aggregation of the primary particles is preferably 50 nm to 50 μm, more preferably 50 nm to 25 μm, and particularly preferably 50 nm. ˜20 μm, or 40 nm to 30 μm. When the average particle diameter of the secondary particles is 50 μm or less, a good packing state having a small porosity with the solid electrolyte particles can be formed inside the obtained all-solid-state secondary battery.

  Here, the average particle diameter in the present invention means an average value of measured values of particle diameters (lengths of major axes) of several tens of particles in observation using an SEM or TEM electron microscope. The average value is calculated using, for example, measured values of 10 particles.

  Cellulose nanofibers, which are raw materials for carbon chains derived from cellulose nanofibers constituting the solid electrolyte nanoarray (b) of the present invention, are skeletal components that occupy about 50% of all plant cell walls, and constitute the cell walls. It is a lightweight, high-strength fiber that can be obtained by defibrating plant fibers to the nano size and has good dispersibility in water. In addition, since the cellulose molecular chain constituting the cellulose nanofiber has a periodic structure formed of carbon, the cellulose nanofiber obtained by baking under reducing conditions is carbonized to form a chain shape. Carbon can be partially or wholly included in the solid electrolyte nanoarray (b) supported on the surface of the electrode active material particles (A) as a good conductive path.

  In addition, as a matter of course, in the firing in an oxygen atmosphere, the cellulose nanofibers are burnt down as carbon dioxide and water, and therefore, a solid electrolyte nanoparticle aggregate (d) containing a part or all of the raw material CNF ) (Hereinafter also referred to as “CNF-encapsulated solid electrolyte nanoparticle aggregate (d)”), or a nanoparticle aggregate composed of a precursor of the solid electrolyte encapsulating part or all of the raw material CNF ( e) (hereinafter, also referred to as “CNF-encapsulated precursor nanoparticle aggregate (e)”) is fired in an oxygen atmosphere to obtain a CNF-encapsulated solid electrolyte nanoparticle aggregate (d) or CNF-encapsulated precursor nanoparticle. Only the solid electrolyte nanoparticle array (c) having the aligned state in the nanoarray obtained by removing the cellulose nanofibers from the particle assembly (e) is used as the electrode active material particles. It is possible to be supported on the surface of A).

  In the present invention, the “inclusive” means a state in which a part or the whole of an object is covered in a fragmentary manner or continuously. In the present invention, for example, the CNF-encapsulated solid electrolyte nanoparticle aggregate (d) refers to a part or all of the raw material CNF, and at least the solid electrolyte nanoparticles (a) are continuously linear or massive. In addition, the CNF-encapsulating precursor nanoparticle aggregate (e) is a nanoparticle composed of at least a part of the raw material CNF and a precursor of the solid electrolyte. The particles are covered linearly or in a lump, continuously or intermittently.

  The average length of the cellulose nanofibers used in the present invention is such that the solid electrolyte nanoparticles (a) can be supported linearly, continuously or intermittently while the electrode active material particles (A) From the viewpoint of ensuring good loading, it is preferably 50 nm to 200 μm, more preferably 50 nm to 150 μm, and still more preferably 50 nm to 100 μm. From the same viewpoint, the average fiber diameter of the cellulose nanofiber used is preferably 5 nm to 50 nm, more preferably 5 nm to 30 nm, and further preferably 5 nm to 20 nm.

  Moreover, the average length of the carbon chain derived from the cellulose nanofiber obtained by carbonizing the cellulose nanofiber is such that the solid electrolyte nanoparticle (a) is supported linearly, continuously, or intermittently. From the viewpoint of ensuring a shape that can effectively increase the charge / discharge capacity while enabling the above-mentioned, it is preferably 50 nm to 10 μm, more preferably 50 nm to 5 μm, and still more preferably 50 nm to 1 μm.

  Moreover, the average fiber diameter of the carbon chain derived from the cellulose nanofiber is 50 nm or less, preferably 40 nm or less, and more preferably 30 nm or less. Although there is no restriction | limiting in particular about the lower limit of the average fiber diameter of the carbon chain derived from a cellulose nanofiber, Usually, it is 5 nm or more.

The solid electrolyte nanoarray (b) or the solid electrolyte nanoparticle (a) constituting the solid electrolyte nanoparticle array (c) of the present invention may be used for an all-solid secondary battery, particularly an all-solid lithium ion secondary battery. If the raw material compound used in the firing step in the production method described later is a material that does not cause a solid phase reaction with the electrode active material phase that is fired at the same time, the type of the compound is not limited. Furthermore, it is not necessarily the same as the solid electrolyte particles when forming an all-solid secondary battery. Specifically, it is possible to use an oxide-based solid electrolyte, for _{example, Li 3 PO 4 -Li 4 SiO} 4, Li 7-x La 3 Zr 2-x Ta x O 12, La 0.51 Li 0. ₃₄ TiO _2.94 , Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li ₇ La ₃ Zr ₂ O ₁₂ , 50Li ₄ SiO ₄ .50Li ₃ BO _{3 and the} like can be mentioned. Further, as the solid electrolyte constituting the solid electrolyte Nanoarrays in the present invention (b), or a solid electrolyte nanoparticles column _{(c), Li 3 PO 4} -Li 4 SiO 4, Li 7-x La 3 Zr 2-x Ta x O ₁₂ , La _0.51 Li _0.34 TiO _2.94 , Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li ₇ La ₃ Zr ₂ O ₁₂ , and 50Li ₄ SiO ₄ .50Li _It may contain at least one or more of the group consisting of ₃ BO ₃ .

In the combination of the electrode active material and the solid electrolyte, examples of suitable combinations include the following.
(Positive electrode active material)
_{LiNi 1-x-y Co x} Mn y O 2 -Li 7-x La 3 Zr 2-x Ta x O 12,
_{LiNi 1-x-y Co x} Mn y O 2 -Li 7 La 3 Zr 2 O 12,
_{LiNi 1-x-y Co x} Al y O 2 -Li 7-x La 3 Zr 2-x Ta x O 12,
_{LiNi 1-x-y Co x} Al y O 2 -Li 7 La 3 Zr 2 O 12,
LiMPO ₄ (M = Ni, Co, Mn) -Li ₃ PO ₄ -Li ₄ SiO ₄ ,
LiMPO ₄ (M = Ni, Co, Mn) —Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ ,
Li ₂ MSiO ₄ (M = Ni, Co, Mn) -Li ₃ PO ₄ -Li ₄ SiO ₄ ,
Li ₂ MSiO ₄ (M = Ni, Co, Mn) -50Li ₄ SiO ₄ .50Li ₃ BO ₃ ,
(Negative electrode active material)
SiO _x -50Li ₄ SiO ₄ · 50Li ₃ BO ₃ ,
Li ₄ Ti ₅ O ₁₂ -La _0.51 Li _0.34 TiO _2.94
These positive electrode active materials and negative electrode active materials may be used alone or in combination of two or more.

  The average particle diameter of the solid electrolyte nanoarray (b) or the solid electrolyte nanoparticle (a) constituting the solid electrolyte nanoparticle array (c) has a viewpoint of forming a good interface with the electrode active material, etc. From the viewpoint of favorably supporting the carbon chain derived from the fiber, 0.5 nm to 100 nm is preferable, 1 nm to 80 nm is more preferable, and 1 nm to 50 nm is particularly preferable.

  Moreover, the shape (crystal habit) of the solid electrolyte nanoparticles constituting the solid electrolyte nanoarray (b) or the solid electrolyte nanoparticle array (c) is not particularly limited, but is a plate, needle, cube, cuboid And hexagonal columnar shape. Among these, from the viewpoint of further strengthening the support to the carbon chains derived from cellulose nanofibers, the cuboid particles extending in the axial length direction of the carbon chains are preferable.

  The average length of the solid electrolyte nanoarray (b) composed of the carbon chains derived from the cellulose nanofibers and the solid electrolyte nanoparticles (a) ensures effective improvement of the charge / discharge capacity by exhibiting a unique shape. In view of the above, it is preferably 50 nm to 10 μm, more preferably 50 nm to 5 μm, and still more preferably 50 nm to 1 μm.

  In the electrode active material for an all-solid-state secondary battery of the present invention, the electrode active material particles (A), the solid electrolyte nanoparticle aggregate (b), the solid electrolyte nanoparticle array (c), or both are included. In the case of the total amount, the mass ratio of the total amount, the viewpoint of forming a good interface in which the interface resistance is sufficiently reduced in the packing structure of the electrode active material particles and the solid electrolyte particles in the all-solid secondary battery, and From the viewpoint of increasing the energy density of the all-solid-state secondary battery, electrode active material particles (A): (solid electrolyte nanoarray (b) + solid electrolyte nanoparticle array (c) (provided that solid electrolyte nanoarray (b) and solid electrolyte nano In the case where only one of the particle rows (c) is included, only one of them.)) (Mass ratio) = preferably 99.9: 0.1 to 70:30, 99: 1 to 80: More preferred is 20 There.

  In the electrode active material for an all-solid-state secondary battery of the present invention, the linear shape may be a linear shape or a substantially linear shape. The linear shape means an elongated and linear shape and includes not only a linear shape but also a curved shape or a chain shape. In addition, the term “linear” means that the straight portion has a length ratio of approximately 70% or more in the (approximately) major axis direction of the aggregate (b) or row (c) of the solid electrolyte nanoparticles (a). It may be 80% or more, or 90% or more. Further, the substantially linear shape means a linear shape having a slight curvature or an error in approximate calculation in the (approximately) axial length direction of the aggregate (b) or the row (c) of the solid electrolyte nanoparticles (a). Including.

  Moreover, the electrode active material for an all-solid-state secondary battery of the present invention can be used for the all-solid-state lithium ion secondary battery. In addition, each component, solid electrolyte, etc. relating to the electrode active material for an all solid secondary battery in the present specification is appropriately used for an all solid lithium ion secondary battery, even if not specifically mentioned for lithium ions. Can be.

[Method for producing electrode active material for all-solid-state secondary battery]
On the other hand, the electrode active material for an all-solid-state secondary battery of the present invention includes the following steps (II) to (III):
A slurry containing at least one solid electrolyte raw material compound, an alkaline solution, and cellulose nanofibers is subjected to a hydrothermal reaction at a temperature of 100 ° C. or higher and a pressure of 0.3 MPa to 0.9 MPa to obtain a CNF-encapsulated solid. A step (II) of producing an electrolyte nanoparticle aggregate (d), a CNF-encapsulated precursor nanoparticle aggregate (e), or both, and
Reaction with at least the CNF-encapsulated solid electrolyte nanoparticle aggregate (d), the CNF-encapsulated precursor nanoparticle aggregate (e), and the CNF-encapsulated precursor nanoparticle aggregate (e) obtained in step (II) And firing the remaining raw material compound for producing the solid electrolyte nanoparticle aggregate (b) or the solid electrolyte nanoparticle array (c), or both (III),
Can be obtained by a production method comprising

In addition, as another method for producing an electrode active material for an all-solid-state secondary battery of the present invention,
Next steps (II) to (III ′):
A slurry containing at least one solid electrolyte raw material compound, an alkaline solution, and cellulose nanofibers is subjected to a hydrothermal reaction at a temperature of 100 ° C. or higher and a pressure of 0.3 MPa to 0.9 MPa to obtain a CNF-encapsulated solid. A step (II) of producing an electrolyte nanoparticle aggregate (d), a CNF-encapsulated precursor nanoparticle aggregate (e), or both, and
Reaction with at least the CNF-encapsulated solid electrolyte nanoparticle aggregate (d), the CNF-encapsulated precursor nanoparticle aggregate (e), and the CNF-encapsulated precursor nanoparticle aggregate (e) obtained in step (II) Step (III ′) of firing the remaining raw material compound for producing the solid electrolyte nanoparticle aggregate (b), or both in a reducing atmosphere,
Can be used as appropriate.

Furthermore, as another method for producing an electrode active material for an all-solid-state secondary battery of the present invention,
Next steps (II) to (III ″):
A slurry containing at least one solid electrolyte raw material compound, an alkaline solution, and cellulose nanofibers is subjected to a hydrothermal reaction at a temperature of 100 ° C. or higher and a pressure of 0.3 MPa to 0.9 MPa to obtain a CNF-encapsulated solid. A step (II) of producing an electrolyte nanoparticle aggregate (d), a CNF-encapsulated precursor nanoparticle aggregate (e), or both, and
Reaction with at least the CNF-encapsulated solid electrolyte nanoparticle aggregate (d), the CNF-encapsulated precursor nanoparticle aggregate (e), and the CNF-encapsulated precursor nanoparticle aggregate (e) obtained in step (II) Step (III ″) of firing the remaining raw material compounds for producing the solid electrolyte nanoparticle array (c), or both in an oxidizing atmosphere,
Can be used as appropriate.

Moreover, in the method for producing an electrode active material for an all-solid-state secondary battery of the present invention,
Furthermore, prior to the step (III), (III ′) or (III ″), a production method including the step (I) for producing the electrode active material particles (A) can be appropriately used.

  Step (I) is a step of obtaining electrode active material particles (A) for all-solid-state secondary batteries. What is necessary is just to manufacture about the said electrode active material particle (A) using the existing arbitrary manufacturing methods that the average particle diameter of the electrode active material particle (A) obtained will be 50 nm-50 micrometers. Specifically, for example, for the layered oxide system of the positive electrode active material, a solid phase method and pulverization and classification as required are used, and for the olivine system, a hydrothermal method or a coprecipitation method is preferably used. In addition, a solid phase method or a hydrothermal method is suitably used for the oxide type and titanium oxide type negative electrode active materials.

  In addition, the specific electrode active material obtained in step (I), specifically, the olivine system of the positive electrode active material, may carry a conductive material on the surface of the electrode active material particles as necessary.

  Examples of the conductive substance include carbon or metal fluorides. More specifically, examples of carbon include water-insoluble conductive carbon materials other than carbon derived from water-soluble carbon materials and carbon derived from cellulose nanofibers. And carbon derived from cellulose nanofibers.

  The amount of the conductive material supported is preferably 0.1% by mass to 20% by mass in 100% by mass of the total amount of the electrode active material particles (A) on which the conductive material is supported, More preferably, the content is 3% by mass to 15% by mass, and particularly preferably 0.5% by mass to 10% by mass.

  The water-soluble carbon material used as the carbon source of carbon derived from the water-soluble carbon material is dissolved in 100 g of water at 25 ° C. in an amount of 0.4 g or more, preferably 1.0 g or more in terms of carbon atom of the water-soluble carbon material. This means a carbon material that is carbonized, so that it is present as carbon on the surface of the electrode active material particles.

  Examples of the water-soluble carbon material include one or more selected from saccharides, polyols, polyethers, and organic acids. More specifically, for example, monosaccharides such as glucose, fructose, galactose and mannose; disaccharides such as maltose, sucrose and cellobiose; polysaccharides such as starch and dextrin; ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol and butane Examples thereof include polyols and polyethers such as diol, propanediol, polyvinyl alcohol, and glycerin; and organic acids such as citric acid, tartaric acid, and ascorbic acid. Of these, glucose, fructose, sucrose, and dextrin are preferred, and glucose is more preferred from the viewpoint of enhancing solubility in a solvent and dispersibility to effectively function as a carbon material. These may be used singly or in combination of two or more.

  Examples of water-insoluble conductive carbon materials other than carbon derived from cellulose nanofiber include graphite, amorphous carbon (Ketjen black, acetylene black, etc.), nanocarbon (graphene, fullerene, etc.), conductive polymer powder (polyaniline). Powder, polyacetylene powder, polythiophene powder, polypyrrole powder, etc.) and the like. Of these, graphite, acetylene black, graphene, and polyaniline powder are preferred, and graphite is more preferred from the viewpoint of reinforcing the degree of contact between the electrode active material particles and the solid electrolyte particles. The graphite may be any of artificial graphite (scaly, massive, earthy, graphene) or natural graphite. These may be used singly or in combination of two or more.

  The average particle diameter of the water-insoluble conductive carbon material other than carbon derived from cellulose nanofibers is preferably 0.5 to 20 μm, more preferably 1 from the viewpoint of being favorably supported on the secondary particles of the electrode active material. 0.0 to 15 μm.

  The carbon derived from the cellulose nanofiber refers to a carbon chain derived from the cellulose nanofiber.

  In addition, the atomic conversion amount (carbon carrying amount) of carbon derived from water-soluble carbon material or carbon derived from cellulose nanofiber existing on the surface of the electrode active material particles (A) is the carbon for the electrode active material particles. -It can be confirmed as the amount of carbon measured using a sulfur analyzer.

  As the metal of the metal fluoride, Li, Na, Mg, Ca, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ta, Sn, W, K , Ba, and Sr. Among these, from the viewpoint of improving Li ion conductivity, a metal selected from Li, Na, Mg, Ca, and Al is preferable, and a metal selected from Li and Mg is more preferable.

  In step (II), a slurry containing at least one solid electrolyte raw material compound, an alkali solution, and cellulose nanofibers is subjected to a hydrothermal reaction at a temperature of 100 ° C. or higher and a pressure of 0.3 MPa to 0.9 MPa. Then, the CNF-encapsulating solid electrolyte nanoparticle aggregate (d), the CNF-encapsulating precursor nanoparticle aggregate (e), or both are produced.

The hydrothermal reactant obtained in this step (II) is CNF-encapsulated solid electrolyte nanoparticle aggregate (d), CNF-encapsulated precursor nanoparticle aggregate (e), or both depending on the solid electrolyte to be produced. Or Specifically, for example, in a solid-state _{electrolyte, Li 3 PO 4 -Li 4 SiO} 4 and _{50Li 4 SiO 4 · 50Li 3 BO} 3 is, CNF containing solid electrolyte nano by one hydrothermal reaction step (II) Although it is possible to obtain particles aggregates (d), _{whereas, Li 7-x La 3 Zr} 2-x Ta x O 12, La 0.51 Li 0.34 TiO 2.94, Li 1.3 Al 0. ₃ Ti _1.7 (PO ₄ ) ₃ and Li ₇ La ₃ Zr ₂ O ₁₂ are difficult to obtain a CNF-encapsulated solid electrolyte nanoparticle aggregate (d) by one hydrothermal reaction, and therefore, step (II) In the hydrothermal reaction, a CNF-encapsulated precursor nanoparticle aggregate (e) can be obtained.

Here, the precursor of the solid electrolyte is, for example, Li _7-x La ₃ Zr _2-x Ta _x O ₁₂ , LiTaO ₃ , La _0.51 Li _0.34 TiO _2.94 , TiO ₂ , Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ is Li ₃ PO ₄ , and Li ₇ La ₃ Zr ₂ O ₁₂ is ZrO ₂ . These may be used singly or in combination of two or more.

  In the step (II), the amount of the raw material compound of at least one solid electrolyte used can prepare a predetermined proportion of the raw material compound depending on the solid electrolyte to be produced or the precursor of the solid electrolyte.

  Specific examples of the solid electrolyte raw material compound include a zirconium compound, a titanium compound, an aluminum compound, and a silicon compound. Of these, sulfates, nitrates, carbonates, acetates, oxalates, oxides, hydroxides, halides, and the like of these elements can be preferably used. These may be used singly or in combination of two or more.

  When preparing the slurry by mixing the raw material compound and cellulose nanofiber, water is usually used. The amount of water used is from 10 mol to 300 mol with respect to 1 mol of the metal element of the raw material compound from the viewpoints of solubility or dispersibility of each raw material compound, easiness of stirring, efficiency of hydrothermal reaction, and the like. It is preferable that it is mol, and it is further preferable that it is 50 mol-200 mol.

  Examples of the alkaline solution used in step (II) include aqueous solutions of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia and the like. Among these, from the viewpoint of increasing the efficiency of the hydrothermal reaction, and from the viewpoint of making the resulting CNF-encapsulated solid electrolyte nanoparticle aggregate (d) or CNF-encapsulated precursor nanoparticle aggregate (e) fine, sodium hydroxide, It is preferable to use sodium carbonate or a mixed solution thereof. Moreover, what is necessary is just to use the quantity which dripped the quantity sufficient to hold | maintain the pH of the said slurry to 7-12 as the usage-amount of the alkaline solution to a slurry. These may be used alone or in combination of two or more.

  Moreover, content of the cellulose nanofiber in a slurry is a carbon atom conversion amount with respect to 100 mass parts of water in a slurry, Preferably it is 0.01 mass part-10 mass parts, More preferably, it is 0.05 mass. Part to 8 parts by mass.

  The order of adding these raw materials is not particularly limited. After the addition, the mixing time is preferably 1 minute to 12 hours, more preferably 5 minutes to 6 hours. Moreover, the temperature to mix becomes like this. Preferably it is 5 to 60 degreeC, More preferably, it is 5 to 50 degreeC.

  In the mixing of the slurry, from the viewpoint of sufficiently dispersing the cellulose nanofibers, it is preferable to crush the aggregated cellulose nanofibers by a treatment using a disperser (homogenizer). Examples of the disperser include a disaggregator, a beater, a low pressure homogenizer, a high pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short shaft extruder, a twin screw extruder, an ultrasonic stirrer, a household juicer mixer, and the like. I can give you. Among these, an ultrasonic stirrer is preferable from the viewpoint of dispersion efficiency. The degree of dispersion uniformity of the obtained slurry can be quantitatively evaluated by, for example, light transmittance using a UV / visible light spectroscope or viscosity using an E-type viscometer. It can also be easily evaluated by confirming that the degree is uniform. The processing time with the disperser is preferably 30 seconds to 6 minutes, more preferably 2 minutes to 5 minutes.

  The slurry is preferably further subjected to wet classification from the viewpoint of effectively removing cellulose nanofibers that are still in an aggregated state. A sieve or a commercially available wet classifier can be used for wet classification. The opening of the sieve may vary depending on the fiber length of the cellulose nanofiber to be used, but is preferably 25 μm to 160 μm from the viewpoint of work efficiency.

  Next, the obtained slurry is subjected to a hydrothermal reaction. Hydrothermal reaction should just be 100 degreeC or more, and 130 to 180 degreeC is preferable. The hydrothermal reaction is preferably performed in a pressure vessel. When the reaction is performed at 130 ° C to 180 ° C, the pressure at this time is preferably 0.3 MPa to 0.9 MPa, and the reaction is performed at 140 ° C to 160 ° C. The pressure in carrying out is preferably 0.3 MPa to 0.6 MPa. The hydrothermal reaction time is preferably 0.5 hours to 24 hours, more preferably 0.5 hours to 15 hours.

  The obtained hydrothermal reaction product is a composite composed of cellulose nanofibers and a solid electrolyte, or a cellulose nanofiber and a solid electrolyte precursor, and after filtration, washed with water and repulped (resuspended). The filtration means may be vacuum filtration, pressure filtration, centrifugal filtration or the like, but pressure filtration such as a filter press is preferred from the viewpoint of simplicity of operation.

  When the complex after filtration is washed with water, it is preferable to use 5 to 100 parts by mass of water with respect to 1 part by mass of the complex.

  Next, the washed composite is repulped. From the viewpoint of generating a solid electrolyte nanoarray (b) or a solid electrolyte nanoparticle array (c) consisting of uniform solid electrolyte nanoparticles in the next step (III), (III ′) or (III ″), The content of the composite in the slurry obtained by repulping is preferably 0.5% by mass to 20% by mass, more preferably 1% by mass to 15% by mass, and even more preferably 1.5% by mass. ˜12% by mass.

  Steps (III), (III ′), and (III ″) are each an electrode active material particle (A) (if the step (I) is included, the electrode active material particles obtained in step (I) ( A)), the CNF inclusion precursor nanoparticle aggregate (e), and the CNF inclusion precursor nanoparticle aggregate (e) to react with the solid electrolyte nanoparticle aggregate (b) or the solid electrolyte nanoparticle array ( This is a step of mixing a predetermined amount of the remaining raw material compounds for producing c), or both, and baking them.

  By the step (III), (III ′), or (III ″), the solid electrolyte nanoarray (b) or the nanoparticle array (c) of a plurality of linearly arranged solid electrolytes is converted into the all solid state It will carry | support on the surface of the electrode active material particle (A) for secondary batteries. Furthermore, since the crystallinity of both the solid electrolyte particles (b) for an all-solid secondary battery and the nanoparticle array (c) of the solid electrolyte can be improved by this firing, the obtained all-solid-state secondary battery use The charge / discharge characteristics of the electrode active material can be effectively enhanced.

  Here, the solid electrolyte supported on the surface of the electrode active material particle (A) for the all-solid-state secondary battery is a specific solid electrolyte nanoparticle (with a carbon chain derived from cellulose nanofiber as a shaft or a base material) a) is a solid electrolyte nanoparticle aggregate (solid electrolyte nanoarray) (b) having a unique shape formed by supporting or arranging a plurality of lines in a line, or a plurality of solids continuously arranged in a line Whether it is the electrolyte nanoparticle array (c) is determined by the firing atmosphere in the firing. When firing in an inert atmosphere or a reducing atmosphere, the CNF-encapsulated solid electrolyte nanoparticle aggregate (d) or CNF-encapsulated precursor nanoparticle aggregate (e) obtained in step (II) is supported. The cellulose nanofiber is carbonized to become a carbon chain derived from the cellulose nanofiber, and the solid electrolyte nanoarray (b) can be obtained. In contrast, when firing in an oxygen atmosphere, a plurality of solid electrolyte nanoparticle arrays (c) in which the cellulose nanofibers are burned out and have a unique arrangement can be obtained. As the solid electrolyte of the present invention, the obtained solid electrolyte nanoparticle aggregate (solid electrolyte nanoarray) (b) and solid electrolyte nanoparticle array (c) may be used in appropriate combination.

  The atmosphere in the firing is determined by the oxidation resistance of the electrode active material particles (A) (or the electrode active material particles (A) obtained in the step (I) when the step (I) is included). In the olivine system of the active material, an inert atmosphere is preferable, and in the layered oxide system of the positive electrode active material, the oxide system of the negative electrode active material, and the titanium oxide system, an oxygen atmosphere is preferable.

More specifically, the step (III) includes the following steps (III-1) to (III-3):
The electrode active material particles (A) (the electrode active material particles (A) obtained in the step (I) when the step (I) is included) and the CNF-encapsulated solid electrolyte nanoparticles obtained in the step (II) Mixing the assembly (d),
Electrode active material particles (A) (electrode active material particles (A) obtained in step (I) when step (I) is included), CNF-encapsulated precursor nanoparticle aggregates obtained in step (II) Mixing the slurry containing the body (e) and the remaining raw material compound of the solid electrolyte, or
The electrode active material particles (A) (the electrode active material particles (A) obtained in the step (I) when the step (I) is included) and the CNF-encapsulated solid electrolyte nanoparticle obtained in the step (II) A step (III-1) of mixing a slurry containing the particle assembly (d), the CNF inclusion precursor nanoparticle assembly (e) and the remaining raw material compound of the solid electrolyte to form a slurry (III-1);
The slurry obtained in the step (III-1) is dried, and is a mixture composed of the electrode active material particles for all-solid-state secondary battery (A) and the CNF-encapsulated solid electrolyte nanoparticle aggregate (d),
A mixture of electrode active material particles for all solid state secondary battery (A), CNF-encapsulated precursor nanoparticle aggregate (e) and the remaining raw material compound of the solid electrolyte, or
A mixture comprising electrode active material particles (A) for all-solid-state secondary batteries, CNF-encapsulated solid electrolyte nanoparticle aggregates (d), and CNF-encapsulated precursor nanoparticle aggregates (e) and the remaining raw material compounds of the solid electrolyte Obtaining step (III-2), and
Calcination of the mixture obtained in step (III-2) to obtain an electrode active material for an all-solid-state secondary battery (III-3).

  Specifically, in the step (III-1), in the slurry obtained in the step (II), the electrode active material particles (A) (the electrode obtained in the step (I) when the step (I) is included) The active material particles (A)) or the remaining raw material compound of the solid electrolyte may be mixed to form a slurry. Moreover, although the manufacturing method example of the electrode active material for all-solid-state secondary batteries in case the electrode active material particle (A) is included in the said slurry is described, it is solid with components other than electrode active material particle (A). After the electrolyte nanoarray (b) or the solid electrolyte nanoparticle array (c) is produced, any one or both of them are appropriately combined on the surface of the electrode active material particles (A) by combining known methods. It may be supported to obtain an electrode active material for an all-solid secondary battery.

  Moreover, the mixing ratio of the slurry obtained in the step (II) and the electrode active material particles (A) for all-solid-state secondary batteries is the electrode active material particles in the electrode active material for all-solid-state secondary batteries finally obtained. (A) and the total amount of the solid electrolyte nanoparticle aggregate (b), the solid electrolyte nanoparticle array (c), or a combination thereof, if included (electrode active material particles (A) : Solid electrolyte nanoparticle aggregate (b) + solid electrolyte nanoparticle array (c) (However, when solid electrolyte nanoparticle aggregate (b) and solid electrolyte nanoparticle array (c) contain only one of them) , Only one of them.))) Is preferably 99.9: 0.1 to 70:30.

  The remaining raw material compound of the solid electrolyte mixed with the slurry obtained in the step (II) together with the CNF inclusion precursor nanoparticle aggregate (e) is nitrate, carbonate, acetate, oxalate of a predetermined element Oxides, hydroxides and the like can be preferably used. These may be used singly or in combination of two or more.

  The order of adding these raw materials to the slurry obtained in step (II) is not particularly limited. After the addition, the mixing time is preferably 1 minute to 12 hours, more preferably 5 minutes to 6 hours. Moreover, the temperature to mix becomes like this. Preferably it is 5 to 60 degreeC, More preferably, it is 5 to 50 degreeC.

In the subsequent step (III-2), the slurry obtained in the step (III-1) is dried to collect the electrode active material particles for all solid state secondary battery (A) and the CNF-encapsulated solid electrolyte nanoparticle aggregate (d Or a mixture of
A mixture of electrode active material particles for all solid state secondary battery (A), CNF-encapsulated precursor nanoparticle aggregate (e) and the remaining raw material compound of the solid electrolyte, or
A mixture comprising electrode active material particles (A) for all-solid-state secondary batteries, CNF-encapsulated solid electrolyte nanoparticle aggregates (d), and CNF-encapsulated precursor nanoparticle aggregates (e) and the remaining raw material compounds of the solid electrolyte obtain.

The particle size of the mixture obtained by drying is a D ₅₀ value in the particle size distribution based on the laser diffraction / scattering method, preferably 5 nm to ₅₀ μm, more preferably 5 nm to 25 μm. Here, the D ₅₀ value in the particle size distribution measurement is a value obtained by a volume-based particle size distribution based on the laser diffraction / scattering method, and the D ₅₀ value means a particle size (median diameter) at a cumulative 50%. .

  Examples of the drying method include spray drying, box drying, fluidized bed drying, external heat drying, medium fluidized drying, freeze drying, and vacuum drying. Of these, freeze-drying, freeze-drying, or spray-drying is preferred from the viewpoint of effectively controlling the increase in the particles of the resulting mixture more than necessary to achieve finer particles.

  In the subsequent step (III-3), the mixture obtained in the step (III-2) is fired to obtain an electrode active material for an all-solid secondary battery. By this carbonization, carbon nanofibers contained in the composite are carbonized or burnt out, and when the CNF inclusion precursor nanoparticle aggregate (e) and the remaining raw material compound of the solid electrolyte are included, solid electrolyte nanoparticles ( A solid-phase reaction that generates a) also occurs, and an electrode active material for an all-solid-state secondary battery in which the solid electrolyte nanoarray (b) or the solid electrolyte nanoparticle array (c) is supported on the surface can be obtained.

  Firing is performed under any firing atmosphere, and the firing temperature is preferably 500 ° C to 1200 ° C, more preferably 600 ° C to 1100 ° C. The firing time is preferably 10 minutes to 12 hours, more preferably 30 minutes to 8 hours.

  Further, the step (III ′) and the step (III ″) can be performed by appropriately replacing the above-described step (III).

[All-solid secondary battery]
The all-solid-state secondary battery or the all-solid-state lithium ion secondary battery of the present invention includes the above-described electrode active material for an all-solid-state secondary battery.

  In the all solid state secondary battery or the all solid state lithium ion secondary battery of the present invention, the above-described electrode active material for all solid state secondary batteries can be appropriately applied. In addition, the configuration and manufacturing method of the all-solid secondary battery or all-solid lithium ion secondary battery of the present invention are appropriately combined with known methods except that the electrode active material for the all-solid secondary battery of the present invention is used. Can do. The all-solid-state secondary battery to which the electrode active material for an all-solid-state secondary battery of the present invention can be applied as appropriate has a positive electrode, a negative electrode, and a solid electrolyte as essential components, and includes a positive electrode active material layer, a solid electrolyte layer , And the negative electrode active material layer are not particularly limited as long as a laminated body is formed in the order of lamination.

  In the production of a laminate in which the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer are laminated in this order, for example, as the solid electrolyte layer, carbon fibers derived from cellulose nanofibers having an average fiber diameter of 50 nm or less are used. A solid electrolyte nanoparticle aggregate (b) formed by linearly supporting a plurality of solid electrolyte nanoparticles (a) is supported on the surface of the solid electrolyte particles, or a solid electrolyte having an average fiber diameter of 50 nm or less The solid electrolyte nanoparticle array (c), in which the solid electrolyte nanoparticles (a) are linearly arranged in a linear manner induced by cellulose nanofibers, is supported on the surface of the solid electrolyte particles, or both. It can also be used. In the case of having any of the above-described configurations, the all-solid-state lithium ion secondary battery can be further improved in charge / discharge capacity, durability, and the like.

  The solid electrolyte nanoparticle aggregate (b) in which a plurality of solid electrolyte nanoparticles (a) are linearly supported on a carbon chain derived from cellulose nanofibers having an average fiber diameter of 50 nm or less is the solid electrolyte particles. A solid electrolyte nanoparticle array (c) in which solid electrolyte nanoparticles and a solid electrolyte nanoparticle (a) are continuously arranged in a linear form are guided by cellulose nanofibers having an average fiber diameter of 50 nm or less. Each component in the solid electrolyte supported on the surface of the solid electrolyte particles, that is, the solid electrolyte nanoparticles (a), the solid electrolyte nanoparticle aggregate (b), the solid electrolyte nanoparticle array (c), and the solid electrolyte particles These manufacturing methods, various conditions, and the like can be performed by appropriately replacing the description in the present invention described above.

  The shape of the all-solid-state secondary battery having the above-described configuration, particularly the all-solid-state lithium ion secondary battery, is not particularly limited, and various shapes such as a coin shape, a cylindrical shape, and a square shape, and a laminate exterior body can be used. The enclosed irregular shape may be sufficient.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

[Production Example 1] (Production of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ positive electrode active material particles)
After mixing 263 g of nickel sulfate hexahydrate, 281 g of cobalt sulfate heptahydrate, 241 g of manganese sulfate pentahydrate, and 3 L of water so that the molar ratio of Ni: Co: Mn is 1: 1: 1. Then, 25% aqueous ammonia was added dropwise to the mixture at a dropping rate of 300 ml / min to obtain a slurry A1 containing a metal composite hydroxide having a pH of 11.

  Next, 37 g of lithium carbonate was mixed with the obtained slurry A1, and the obtained slurry B1 was filtered and dried to obtain a metal composite hydroxide mixture C1.

The obtained mixture C1 was calcined at 800 ° C. for 5 hours in an air atmosphere and pulverized, and then calcined at 800 ° C. for 10 hours in the air atmosphere as main firing, to obtain an NCM complex oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) secondary particles were obtained. (Average particle diameter of NCM-based composite oxide secondary particles: 10 μm)

[Production Example 2] (Production of Li ₇ La ₃ Zr ₂ O ₁₂ solid electrolyte particles)
Lithium carbonate 5.17 g, lanthanum hydroxide 11.40 g, and zirconium oxide 4.93 g were pulverized and mixed at 200 rpm for 2 hours in a planetary ball mill to obtain a mixture A2. The obtained mixture A2 was formed into pellets, calcined at 900 ° C. for 12 hours in an air atmosphere, and then crushed in a mortar to obtain LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) solid electrolyte particles. (Average particle size of LLZ solid electrolyte particles B: 1 μm)

[Example 1] (Electrode active material for an all solid lithium ion secondary battery comprising NMC + solid electrolyte nanoarray)
A slurry A3 was prepared by mixing 1.81 g of zirconium sulfate tetrahydrate, 19.29 g of cellulose nanofiber (manufactured by Sugino Machine Co., Ltd., TMa-1202, water content 98 mass%), and 55 mL of water for 60 minutes. To the obtained slurry A3, 12.0 g of a 10 mass% NaOH aqueous solution was added and mixed for 5 minutes to prepare a slurry B3. The obtained slurry B3 was put into an autoclave and subjected to a hydrothermal reaction at 140 ° C. for 1 hour. The obtained hydrothermal reaction product C3 is allowed to cool, then filtered, washed with water, repulped with water, and contains 10% by mass of ZrO ₂ nanoarrays in which a plurality of ZrO ₂ nanoparticles are linearly supported on cellulose nanofibers. A slurry D3 was obtained.

  The total amount of slurry D3 obtained was mixed with lithium nitrate 1.21 g, lanthanum nitrate hexahydrate 3.25 g, and 39.7 g of NCM composite oxide secondary particles obtained in Production Example 1 to obtain slurry E3. Obtained. The obtained slurry E3 was freeze-dried to obtain a raw material mixed powder F3. All-solid lithium in which a plurality of LLZ solid electrolyte nanoparticles are supported linearly and continuously on the surface of NCM composite oxide secondary particles by firing raw material mixed powder F3 at 1100 ° C. for 1 hour in an air atmosphere An electrode active material A for ion secondary batteries was obtained. The content rate of the LLZ solid electrolyte nanoparticle in 100 mass% of obtained electrode active materials A for all-solid-state lithium ion secondary batteries was 5 mass%.

  FIG. 1 shows a TEM photograph of the surface portion of the obtained electrode active material A for an all solid lithium ion secondary battery. The TEM used was JEM-ARM200F manufactured by JEOL Ltd.

[Comparative Example 1]
The NCM composite oxide secondary particles obtained in Production Example 1 were used as the electrode active material B for an all solid lithium ion secondary battery as it was.

≪Evaluation of discharge capacity in all solid-state lithium ion secondary battery≫
Using the positive electrode active material for an all solid lithium ion secondary battery obtained in Example 1 and Comparative Example 1 and the LLZ solid electrolyte particles obtained in Production Example 2, a positive electrode for an all solid lithium ion battery was produced. More specifically, in Example 1 using the electrode active material A for all-solid-state lithium ion secondary battery in order to make the positive electrode active material for all-solid-state lithium ion secondary battery and the solid electrolyte have the same ratio, In the first comparative example in which the solid electrolyte (mass ratio) was 75:25 and the electrode active material B for an all solid lithium ion secondary battery was used, the electrode active material: solid electrolyte (mass ratio) was 71.3: 28. After mixing at a blending ratio of 7, the mixture was put into a pressing jig to form a positive electrode active material layer, and only LLZ solid electrolyte particles were further added thereon to form a solid electrolyte layer, which was then stacked at 16 MPa using a hand press. It pressed for 2 minutes and obtained the disk-shaped positive electrode of (phi) 14mm. Next, an all-solid lithium ion secondary battery was fabricated by attaching a lithium foil as the negative electrode to the solid electrolyte layer side.

  Using the produced all solid lithium ion secondary battery, the charging condition is 10 mA / g, constant current charging with a voltage of 4.2 V, the discharging condition is 10 mA / g, and the constant current discharging with a final voltage of 3.0 V is performed. The discharge capacity at 10 mA / g was determined. All charge / discharge tests were conducted at 45 ° C.

  The results of the evaluation are shown in Table 1.

  As is clear from Table 1, the all-solid-state lithium ion secondary battery using positive-electrode active material particles for the all-solid-state lithium ion secondary battery using the positive-electrode active material in which solid electrolyte nanoparticles are supported on the particle surface of Example 1 Compared with the all-solid-state lithium ion secondary battery using the positive electrode active material particles for the all-solid-state lithium ion secondary battery using the general cathode active material not supporting the solid electrolyte nanoparticles in Comparative Example 1, the discharge capacity Can be seen to be very large.

Claims (11)

  A solid electrolyte nanoparticle aggregate (b) in which a plurality of solid electrolyte nanoparticles (a) are linearly supported on a carbon chain derived from cellulose nanofibers having an average fiber diameter of 50 nm or less is an electrode active material particle (A). An electrode active material for an all-solid-state secondary battery, which is supported on the surface of the battery.   A solid electrolyte nanoparticle array (c) in which the solid electrolyte nanoparticles (a) are linearly arranged in a linear manner and are induced by cellulose nanofibers having an average fiber diameter of 50 nm or less is formed on the surface of the electrode active material particles (A). An electrode active material for an all-solid secondary battery, which is supported.   The electrode active material for an all-solid-state secondary battery according to claim 1 or 2, wherein an average secondary particle diameter of the electrode active material particles (A) is 50 nm to 50 µm.   4. The electrode active material for an all-solid-state secondary battery according to claim 1, wherein an average particle size of the solid electrolyte nanoparticles (a) is 0.5 nm to 100 nm.   When the electrode active material particles (A) and the solid electrolyte nanoparticle aggregate (b), the solid electrolyte nanoparticle array (c), or both are included, the mass ratio thereof is 99. It is 9: 0.1-70: 30, The electrode active material for all-solid-state secondary batteries in any one of Claims 1-4. The electrode active material particles (A) _{is, LiNi 1-x-y Co} x Mn y O 2, LiNi 1-x-y Co x Al y O 2, LiMPO 4 (M = Ni, Co, Fe, Mn), The whole of any one of claims 1 to 5, comprising at least one of the group consisting of Li ₂ MSiO ₄ (M = Ni, Co, Fe, Mn), SiO _x , and Li ₄ Ti ₅ O _12. Electrode active material for solid secondary batteries. The solid electrolyte nanoparticles (a) _{is, Li 3 PO 4 -Li 4 SiO} 4, Li 7-x La 3 Zr 2-x Ta x O 12, La 0.51 Li 0.34 TiO 2.94, Li 1 _.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li ₇ La ₃ Zr ₂ O ₁₂ , and 50Li ₄ SiO ₄ .50Li ₃ BO _3. The electrode active material for all-solid-state secondary batteries in any one of -6.   The electrode active material for an all-solid-state secondary battery according to any one of claims 1 to 7, wherein the linear shape is linear or substantially linear.   The electrode active material for an all-solid-state secondary battery according to any one of claims 1 to 8, which is used for an all-solid-state lithium ion secondary battery.   An all-solid secondary battery comprising the electrode active material for an all-solid secondary battery according to claim 1.   The all-solid-state secondary battery of Claim 10 whose said secondary battery is an all-solid-state lithium ion secondary battery.