JP6625153B2 - Electrode active material for all-solid secondary battery, method for producing the same, and all-solid secondary battery - Google Patents

Description

  The present invention relates to an electrode active material for an all-solid secondary battery having a reduced interfacial resistance with a solid electrolyte (a positive electrode active material, a negative electrode active material, and the like), particularly an electrode active material for an all-solid lithium ion secondary battery, and The present invention relates to a manufacturing method, and an all-solid secondary battery or an 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 for the electrolyte, so they have a structure to prevent short circuits and suppress the temperature rise when a short circuit occurs Safety devices are required. In contrast, an all-solid lithium-ion secondary battery including an oxide-based solid electrolyte such as Li ₇ La ₃ Zr ₂ O ₁₂ and a sulfide-based solid electrolyte such as 75 Li ₂ S · 25P ₂ S ₅ is A lithium ion secondary battery is expected to have a high energy density and simplification of a safety device because it does not use combustibles, 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. This step involves improving the solid-solid interface contact between the solid materials to improve the interface. 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.

Ryo Inada, The 58th Battery Symposium Abstracts, 1C07, 2017

  However, in the all-solid-state lithium-ion secondary battery and the like manufactured by pressing as described above, the expansion and contraction of the electrode active material that is repeated by charging and discharging, and vibration during use, etc., cause the material in the secondary battery to be damaged. There is a possibility that the stacked structure is destroyed and the positive electrode active material and the negative electrode active material come into contact with each other to cause an internal short circuit in the battery. Further, the method of Non-Patent Document 1 has a problem that it is difficult to apply the method to an electrode active material other than lithium metal.

  Therefore, an object of the present invention is to provide an electrode active material for an all-solid secondary battery, particularly for an all-solid lithium ion secondary battery, in which the interfacial resistance with the solid electrolyte is effectively reduced even in continuous use of the secondary battery. An object of the present invention is to provide an electrode active material, a method for producing the same, and an all-solid secondary battery using the same.

  The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, the following objects have been achieved by an all-solid-state secondary battery electrode active material, a method for producing the same, and an all-solid-state secondary battery using them, as described below. We have found that we can achieve this 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 nanofiber 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).

  Further, 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 successively arranged linearly by being induced into 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 nanofiber is used as a shaft or a base material, and a plurality of nanoparticles of a specific solid electrolyte are supported or arranged in a row on this. A solid electrolyte nanoparticle aggregate (b) exhibiting a unique shape formed as described above, or a plurality of linearly arranged nanoparticle arrays (c) of the solid electrolyte obtained using the nanoparticles of the solid electrolyte may be, 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, and the interface resistance is reduced. Even if shrinkage is repeated, effective joining between the electrode active material and the solid electrolyte can be continued.

  In the electrode active material for an all-solid-state 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. With the above configuration, a good packing state having a small porosity with the electrode active material (particles), the electrolyte (particles), and the like can be formed, which is more suitable as an electrode active material for an all-solid-state secondary battery. 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 0.5 nm to 100 nm. With the above configuration, a good packing state having a small porosity with the electrode active material (particles), the electrolyte (particles), and the like can be formed, which is more suitable as an electrode active material for an all-solid 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. In the case where the solid electrolyte nanoparticle aggregate is contained, the mass ratio of the total amount to the total amount thereof (electrode active material particles (A): solid electrolyte nanoparticle aggregate (b) + solid electrolyte nanoparticle aggregate (c)) (B) and the solid electrolyte nanoparticle array (c) when only one of them is included, only one of them) can be 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.

Further, the all-solid secondary battery electrode active material of the present invention, the electrode active material particles (A) _{is, L iNi 1-x-y} Co x Mn y O 2, LiNi 1-x-y Co x Al y At least one of the group consisting of 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 It may contain more than one species. With the above configuration, the electrode active material for an all solid state secondary battery, particularly an electrode active material for an all solid state lithium ion secondary battery can be more suitable.

Further, the all-solid secondary battery electrode active material of the present invention, 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 _A group containing at least one or more members of the group consisting of ₃ may be used. With the above configuration, the electrode active material for an all solid state secondary battery, particularly an electrode active material for an all solid state lithium ion secondary battery can be more suitable.

  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. With the above configuration, it can be suitable as an electrode active material for an all solid state secondary battery.

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

On the other hand, the method for producing an electrode active material for an all-solid secondary battery of the present invention includes:
The following steps (II) to (III):
A slurry containing at least one raw material compound of a solid electrolyte, an alkali solution, and a raw material cellulose nanofiber (hereinafter, also referred to as “CNF”) may be prepared at a temperature of 100 ° C. or more and a pressure of 0.3 MPa. A solid electrolyte nanoparticle aggregate (d) enclosing a part or all of the cellulose nanofiber by being subjected to a hydrothermal reaction of up to 0.9 MPa, and the solid electrolyte enclosing a part or the whole of the cellulose nanofiber A step (II) of producing a nanoparticle aggregate (e) or both comprising a precursor of
At least a solid electrolyte nanoparticle aggregate (d) containing part or all of the raw material CNF obtained in step (II), and a precursor of the solid electrolyte containing part or all of the raw material CNF And the solid electrolyte nanoparticle aggregate (b) by reacting with the nanoparticle aggregate (e) and the nanoparticle aggregate (e) composed of the precursor of the solid electrolyte containing a part or all of the raw material CNF. Calcining the remaining raw material compounds, or both, to produce the solid electrolyte nanoparticle train (c) (III),
It is characterized by including.

Further, another method for producing an electrode active material for an all solid state secondary battery of the present invention,
The following steps (II) to (III '):
A raw material compound of at least one solid electrolyte, an alkaline solution, and a slurry containing cellulose nanofibers as raw materials are subjected to a hydrothermal reaction at a temperature of 100 ° C. or higher and a pressure of 0.3 MPa to 0.9 MPa, A solid electrolyte nanoparticle aggregate (d) containing part or all of the raw material CNF, a nanoparticle aggregate (e) consisting of the solid electrolyte precursor containing part or all of the raw material CNF, or Step (II) of producing both, and
At least a solid electrolyte nanoparticle aggregate (d) containing part or all of the raw material CNF obtained in step (II), and a precursor of the solid electrolyte containing part or all of the raw material CNF Reacts with the nanoparticle aggregate (e) and the nanoparticle aggregate (e) comprising the precursor of the solid electrolyte containing a part or all of the raw material CNF to produce the solid electrolyte nanoparticle aggregate (b) Calcining the remaining raw material compound or both in a reducing atmosphere (III ′),
It is characterized by including.

Further, another method for producing an electrode active material for an all solid state secondary battery of the present invention,
The following steps (II) to (III ″):
A raw material compound of at least one solid electrolyte, an alkaline solution, and a slurry containing cellulose nanofibers as raw materials are subjected to a hydrothermal reaction at a temperature of 100 ° C. or higher and a pressure of 0.3 MPa to 0.9 MPa, A solid electrolyte nanoparticle aggregate (d) containing part or all of the raw material CNF, a nanoparticle aggregate (e) consisting of the solid electrolyte precursor containing part or all of the raw material CNF, or Step (II) of producing both, and
At least a solid electrolyte nanoparticle aggregate (d) containing part or all of the raw material CNF obtained in step (II), and a precursor of the solid electrolyte containing part or all of the raw material CNF Reacts with the nanoparticle aggregate (e) comprising the precursor of the solid electrolyte and enclosing a part or all of the raw material CNF and the raw material CNF to form a solid electrolyte nanoparticle array (c) Baking the remaining raw material compounds or both in an oxidizing atmosphere (III ″),
It is characterized by including.

  The method for producing an electrode active material for an all-solid secondary battery of the present invention having the above-described configuration makes it possible to more easily produce the above-mentioned electrode active material for an all-solid secondary battery. Furthermore, as described above, the presence of the step (III ′) or the step (III ″) allows the plurality of solid electrolyte nanoparticles (a) to be linearly supported on the carbon chain derived from the cellulose nanofiber. 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 guided by cellulose nanofibers and are continuously arranged in a linear manner. It is possible to easily obtain desired ones of the electrode active materials provided with:

  Further, in the method for producing a solid electrolyte for an all-solid secondary battery of the present invention, in the step (III), (III ′), or (III ″), the electrode active material particles (A) may be further added when firing. Can be included. For example, by preliminarily including the electrode active material particles (A) in the raw material mixture before firing, one of the solid electrolyte nanoarray (b) and 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 according to the present invention, the electrode active material particles (A) are produced before the step (III), (III ′) or (III ″). (I).

  Further, in the method for producing an electrode active material for an all-solid secondary battery according to the present invention, the content of the cellulose nanofibers in the slurry in the step (II) is expressed in terms of carbon atoms with respect to 100 parts by mass of water in the slurry. It can be 0.01 to 10 parts by mass. With the above configuration, the solid electrolyte nanoparticle aggregate (d) containing part or all of the raw material CNF, and the solid electrolyte precursor containing part or all of the raw material CNF can be more reliably obtained. Into a nanoparticle aggregate (e), or both, to obtain the electrode active material for an all-solid secondary battery.

  In the method for producing an electrode active material for an all-solid-state secondary battery according to the present invention, the hydrothermal reaction in the step (II) has a temperature of 100 ° C. or more, a pressure of 0.3 MPa to 0.9 MPa, and a reaction time of 0.1 MPa. It can be from 5 hours to 24 hours. With the above configuration, the solid electrolyte nanoparticle aggregate (d) containing part or all of the raw material CNF, and the solid electrolyte precursor containing part or all of the raw material CNF can be more reliably obtained. Into a nanoparticle aggregate (e), or both, to obtain the electrode active material for an all-solid secondary battery.

  In the method for producing an electrode active material for an all-solid-state secondary battery of the present invention, the firing temperature in the step (III), (III ′), or (III ″) is 500 ° C. to 1200 ° C. be able to. With the above configuration, the cellulose nanofibers are more reliably carbonized or burned out, and the nanoparticle aggregate (e) including the solid electrolyte precursor containing a part or all of the raw material CNF is included. In this case, it can be converted into a solid electrolyte nanoparticle aggregate (b) or a solid electrolyte nanoparticle array (c) to obtain the above-mentioned electrode active material for an all-solid secondary battery.

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

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

  Further, the all solid state secondary battery of the present invention is preferably an all solid state lithium ion secondary battery. Since the battery 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 secondary battery of the present invention, the solid electrolyte nanoparticle aggregate (b) or the nanoparticle array (c) of the 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 in an all-solid lithium ion secondary battery, is sufficiently reduced, and the charge / discharge capacity of the secondary battery is reduced. Can be further increased.

  Further, according to the method for producing an electrode active material for an all-solid-state secondary battery of the present invention, a solid electrolyte nanoparticle aggregate (b) or a solid electrolyte nanoparticle is formed on the surface of the above-mentioned electrode active material particles (A). It is possible to easily obtain desired solid electrolytes on which the row (c) is supported.

  Further, according to the all solid state secondary battery or the all solid state lithium ion secondary battery of the present invention, since the electrode active material for an all solid state secondary battery having the above characteristics is provided, the electrode active material particles and the solid electrolyte particles The interface resistance of the secondary battery is sufficiently reduced, and the all-solid-state secondary battery or the all-solid-state lithium-ion secondary battery further improves the charge and discharge capacity of the secondary battery and the durability with repeated charge and discharge. sell.

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

  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 includes a carbon nanocell-derived carbon having an average fiber diameter of 50 nm or less on the surface of the electrode active material particles (A) having an average secondary particle diameter of 50 nm to 50 μm. A 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 a “solid electrolyte nanoarray (b)”) ), Or a row of solid electrolyte nanoparticles (c) in which the solid electrolyte nanoparticles (a) are linearly and continuously arranged by being guided by the cellulose nanofibers, and the electrode active material particles (A ).

  Here, the solid electrolyte nanoparticle aggregate (b) in the present invention refers to a nanoscale structure, a carbon chain derived from cellulose nanofiber having an average fiber diameter of 50 nm or less, and another nanoscale structure. A plurality of solid electrolyte nanoparticles having an average particle size of 0.5 nm to 100 nm are supported linearly, continuously or intermittently, and have a unique shape. Since the solid electrolyte nanoparticle aggregate (b) hardly separates constituent materials, the solid electrolyte nanoparticle aggregate (b) can be supported on the surface of the electrode active material particles (A) while maintaining the unique shape.

  The electrode active material for an all-solid secondary battery, particularly the electrode active material for an all-solid lithium ion secondary battery, having the solid electrolyte nanoarray (b) or the solid electrolyte nanoparticle array (c) supported on the surface thereof according to the present invention is the present invention. Although the scope of the invention is not limited to the mechanism of the presumption, a fine uneven structure by supporting the solid electrolyte nanoarray (b) or the solid electrolyte nanoparticle array (c) on the surface thereof, for example, by charging and discharging Even when the electrode active material repeatedly expands and contracts, the electrode active material particles (A) and the solid electrolyte nanoarray (b) or the solid electrolyte nanoparticle array (c) supported on the surface of the electrode active material particles (A). The junction between them remains sufficiently effective, and the surface of the electrode active material particles (A) is further coated with a small solid electrolyte nanoarray (b) or a row of solid electrolyte nanoparticle (c). Are formed on the surface of the electrode active material particles (A), and the solid electrolyte that is in contact with the electrode active material particles (A) in the secondary battery. By being able to maintain a state where a large amount of effective junctions can always exist between the electrolyte particles, the all-solid secondary battery obtained by using these, particularly the all-solid lithium-ion secondary battery, It is presumed that the interfacial resistance between the solid electrolyte particles is sufficiently reduced and a good charge / discharge capacity can be exhibited.

  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 supported. It need not be physically or chemically robust. Because, for example, as described above, since the electrode active material particles as the base material are repeatedly expanded and contracted by charging and discharging, the solid electrolyte nanoarray may be destroyed by a volume change of the electrode active material in a firmly supported state. Therefore, in the production of an all-solid lithium ion secondary battery, a stacked structure of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer is pressed into a battery. Good contact between the electrode active material particles (A) and the solid electrolyte particles through the solid electrolyte particles, or between the electrode active material particles (A) and the solid electrolyte particles through 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 can be used in a firing step in a manufacturing method described later. The type is not limited as long as it does not easily cause a solid phase reaction with the raw material compound of the electrolyte phase. Specifically, for example, as a positive electrode active material, _LiNi layered oxide system _{1-x-y Co x Mn} y O 2, LiNi 1-x-y Co x Al y O 2, LiMPO 4 of olivine ( M = Ni, Co, Fe, Mn) and Li ₂ MSiO ₄ (M = Ni, Co, Fe, Mn). 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 .

  The average particle size 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. By setting the average particle size of the primary particles of the electrode active material to at least 500 nm or less, the amount of expansion and contraction of the electrode active material particles accompanying 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 size of the secondary particles of the electrode active material particles (A) formed by agglomeration of the primary particles is preferably 50 nm to 50 μm, more preferably 50 nm to 25 μm, and particularly preferably 50 nm. To 20 μm, or 40 nm to 30 μm. When the average particle size of the secondary particles is 50 μm or less, a favorable packing state having a small porosity with the solid electrolyte particles can be formed inside the obtained all-solid 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 electron microscope of SEM or TEM. The calculation of the average value is performed using, for example, the measured values of 10 particles.

  The cellulose nanofiber which is a raw material of the carbon chain derived from the cellulose nanofiber constituting the solid electrolyte nanoarray (b) of the present invention is a skeletal component which accounts for about 50% of all plant cell walls, and constitutes the cell wall. It is a lightweight, high-strength fiber that can be obtained by defibrating plant fibers to 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, a chain-like chain formed by carbonizing the cellulose nanofiber obtained by firing under reducing conditions or the like. Carbon can be partially or entirely included in the solid electrolyte nanoarray (b) supported on the surface of the electrode active material particles (A) as a good conductive path.

  Naturally, in the calcination in an oxygen atmosphere, the cellulose nanofibers become carbon dioxide and water and burn off. Therefore, the solid electrolyte nanoparticle aggregate (d (Hereinafter sometimes referred to as “CNF-encapsulated solid electrolyte nanoparticle aggregate (d)”), or a nanoparticle aggregate composed of a precursor of the above-mentioned solid electrolyte that includes part or all of the raw material CNF ( e) (hereinafter sometimes referred to as “CNF-encapsulated precursor nanoparticle aggregate (e)”) is fired in an oxygen atmosphere to obtain CNF-encapsulated solid electrolyte nanoparticle aggregate (d) or CNF-encapsulated precursor nanoparticle. Only the solid electrolyte nanoparticle row (c), which maintains the alignment state in the nanoarray obtained by removing the cellulose nanofibers from the particle aggregate (e), is used as the electrode active material particles. It is possible to be supported on the surface of A).

  Note that, in the present invention, “inclusion” means a state in which a part or the whole of an object is covered in a fragmentary or continuous manner. In the present invention, for example, the CNF-encapsulated solid electrolyte nanoparticle aggregate (d) refers to a part or the whole of the raw material CNF, in which at least the solid electrolyte nanoparticles (a) are linear or massive. And the CNF-encapsulated precursor nanoparticle aggregate (e) is a nanoparticle assembly comprising at least a part or the whole of the raw material CNF and at least a precursor of the solid electrolyte. The particles are in a linear or agglomerated, continuous or intermittent manner.

  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, and the electrode active material particles (A) It is preferably from 50 nm to 200 μm, more preferably from 50 nm to 150 μm, and still more preferably from 50 nm to 100 μm, from the viewpoint of ensuring good support with the above. In addition, 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 still more preferably 5 nm to 20 nm.

  Further, the average length of the carbon chain derived from the cellulose nanofiber obtained by carbonizing the cellulose nanofiber is such that the solid electrolyte nanoparticles (a) are supported linearly, continuously, or intermittently. From the viewpoint of ensuring a shape capable of effectively increasing the charge / discharge capacity while enabling the above, the thickness is preferably 50 nm to 10 μm, more preferably 50 nm to 5 μm, and further preferably 50 nm to 1 μm.

  Further, 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. The lower limit of the average fiber diameter of the carbon chains derived from cellulose nanofibers is not particularly limited, but is usually 5 nm or more.

The solid electrolyte nanoarray (b) or the solid electrolyte nanoparticles (a) constituting the solid electrolyte nanoparticle array (c) of the present invention can be used for an all-solid secondary battery, particularly, an all-solid lithium ion secondary battery. There is no limitation on the type of the raw material compound as long as the raw material compound used in the firing step in the manufacturing method described below does not cause a solid-phase reaction with the electrode active material phase that is fired at the same time. Further, it is not always necessary to be the same as the solid electrolyte particles when forming the 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. 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 include at least one or more of the group consisting of ₃ BO ₃ .

In the combination of the above-mentioned electrode active material and the above-mentioned solid electrolyte, a preferred combination is as follows.
(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) is determined from the viewpoint of forming a good interface with an electrode active material and the like, and In light of favorably supporting the carbon chain derived from the fiber, the thickness is preferably 0.5 nm to 100 nm, more preferably 1 nm to 80 nm, and particularly preferably 1 nm to 50 nm.

  The shape (crystal habit) of the solid electrolyte nanoarray (b) or the solid electrolyte nanoparticles constituting the solid electrolyte nanoparticle array (c) is not particularly limited, but may be plate-like, needle-like, cubic, or rectangular parallelepiped. , Hexagonal columnar shape and the like. Among them, cuboid particles extending in the axial direction of the carbon chain are preferable from the viewpoint of more firmly supporting the carbon chain derived from the cellulose nanofiber.

  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 an effective improvement in charge / discharge capacity due to its unique shape. From the viewpoint of performing, it is preferably 50 nm to 10 μm, more preferably 50 nm to 5 μm, and still more preferably 50 nm to 1 μm.

  The electrode active material for an all-solid-state secondary battery of the present invention includes the electrode active material particles (A), the solid electrolyte nanoparticle aggregate (b), the solid electrolyte nanoparticle array (c), or both. In that case, the total amount thereof, and the mass ratio, the viewpoint of forming a good interface in which the interface resistance is sufficiently reduced in the packing structure between 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, the electrode active material particles (A): (solid electrolyte nanoarray (b) + solid electrolyte nanoparticle array (c)) (however, solid electrolyte nanoarray (b) and solid electrolyte nanoparticle When only one of the particle rows (c) is included, only one of them is included.)) (Mass ratio) = 99.9: 0.1 to 70:30, preferably 99: 1 to 80: 20 is more preferred 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 term “linear” refers to an elongated 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 linear portion has a length ratio of about 70% or more in the (generally) major axis direction of the aggregate (b) or the row (c) of the solid electrolyte nanoparticles (a). May be present, may be 80% or more, or may be 90% or more. The term “substantially linear” refers to a line having some curvature or an error in the approximate calculation in the (approximate) axial direction of the aggregate (b) or row (c) of the solid electrolyte nanoparticles (a). Including.

  Further, the electrode active material for an all-solid secondary battery of the present invention can be used for the all-solid lithium-ion secondary battery. Further, in the present specification, the constituent components and the solid electrolyte, etc. relating to the electrode active material for an all solid state secondary battery, even if not particularly specified for lithium ions, are appropriately used for an all solid state lithium ion secondary battery. 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 comprises the following steps (II) to (III):
A slurry containing at least one raw material compound of a solid electrolyte, an alkali solution, and cellulose nanofibers is subjected to a hydrothermal reaction at a temperature of 100 ° C. or more and a pressure of 0.3 MPa to 0.9 MPa to obtain a CNF-containing solid. Step (II) of producing an electrolyte nanoparticle assembly (d), a CNF-encapsulated precursor nanoparticle assembly (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) Baking the remaining raw material compounds for producing the solid electrolyte nanoparticle aggregate (b) or the solid electrolyte nanoparticle array (c), or both;
Can be obtained by a production method including:

Further, as another method for producing an electrode active material for an all solid state secondary battery of the present invention,
The following steps (II) to (III '):
A slurry containing at least one raw material compound of a solid electrolyte, an alkali solution, and cellulose nanofibers is subjected to a hydrothermal reaction at a temperature of 100 ° C. or more and a pressure of 0.3 MPa to 0.9 MPa to obtain a CNF-containing solid. Step (II) of producing an electrolyte nanoparticle assembly (d), a CNF-encapsulated precursor nanoparticle assembly (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) Baking the remaining raw material compounds for producing the solid electrolyte nanoparticle aggregate (b) or both in a reducing atmosphere (III ′),
Can be used as appropriate.

Further, as another method for producing an electrode active material for an all solid state secondary battery of the present invention,
The following steps (II) to (III ″):
A slurry containing at least one raw material compound of a solid electrolyte, an alkali solution, and cellulose nanofibers is subjected to a hydrothermal reaction at a temperature of 100 ° C. or more and a pressure of 0.3 MPa to 0.9 MPa to obtain a CNF-containing solid. Step (II) of producing an electrolyte nanoparticle assembly (d), a CNF-encapsulated precursor nanoparticle assembly (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) Calcining the remaining raw material compound or both in order to produce the solid electrolyte nanoparticle row (c) in an oxidizing atmosphere (III ″),
Can be used as appropriate.

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

  Step (I) is a step of obtaining electrode active material particles (A) for an all solid state secondary battery. The above-mentioned electrode active material particles (A) may be manufactured using any existing manufacturing method such that the average particle size of the obtained electrode active material particles (A) is 50 nm to 50 μm. Specifically, for example, in the case of a layered oxide system of the positive electrode active material, a solid phase method and pulverization and classification as necessary are used, and for the olivine system, a hydrothermal method or a coprecipitation method is suitably used. Further, a solid phase method or a hydrothermal method is suitably used for the oxide system and the titanium oxide system of the negative electrode active material.

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

  Examples of the conductive substance include carbon, or metal fluoride, and more specifically, as the carbon, carbon derived from a water-soluble carbon material, a water-insoluble conductive carbon material other than carbon derived from cellulose nanofiber, And carbon derived from cellulose nanofibers.

  In addition, the amount of the conductive material to be supported is preferably 0.1% by mass to 20% by mass based on 100% by mass of the total amount of the electrode active material particles (A) on which the conductive material is carried. It is more preferably from 0.3% by mass to 15% by mass, and particularly preferably from 0.5% by mass to 10% by mass.

  The water-soluble carbon material as a carbon source of the 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 atoms of the water-soluble carbon material. Is carbonized, and is present as carbon on the surface of the electrode active material particles by being carbonized.

  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, butane Polyols and polyethers such as diol, propanediol, polyvinyl alcohol and glycerin; and organic acids such as citric acid, tartaric acid and ascorbic acid. Among them, glucose, fructose, sucrose, and dextrin are preferred, and glucose is more preferred, from the viewpoint of enhancing the solubility and dispersibility in a solvent and effectively functioning as a carbon material. These may be used alone or as a mixture of two or more.

  Examples of the water-insoluble conductive carbon material other than carbon derived from cellulose nanofiber include graphite, amorphous carbon (Ketjen black, acetylene black, etc.), nanocarbon (graphene, fullerene, etc.), and conductive polymer powder (polyaniline). Powder, polyacetylene powder, polythiophene powder, polypyrrole powder, etc.). Among these, graphite, acetylene black, graphene, and polyaniline powder are preferable, and graphite is more preferable, from the viewpoint of reinforcing the degree of contact between the electrode active material particles and the solid electrolyte particles. As the graphite, any of artificial graphite (flaky, massive, earthy, graphene) and natural graphite may be used. These may be used alone or as a mixture 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 to 20 μm, 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 the carbon chain derived from the cellulose nanofiber.

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

  Examples of the metal of the metal fluoride include Li, Na, Mg, Ca, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ta, Sn, W, and K. , Ba, and Sr. Above all, 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 the step (II), the slurry containing at least one raw material compound of the solid electrolyte, the alkali solution, and the cellulose nanofiber is subjected to a hydrothermal reaction at a temperature of 100 ° C. or more and a pressure of 0.3 MPa to 0.9 MPa. Then, a CNF-encapsulated solid electrolyte nanoparticle aggregate (d), a CNF-encapsulated precursor nanoparticle aggregate (e), or both are manufactured.

The hydrothermal reaction product obtained in this step (II) is a CNF-encapsulated solid electrolyte nanoparticle aggregate (d), a CNF-encapsulated precursor nanoparticle aggregate (e), or both, depending on the solid electrolyte to be manufactured. 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. _{Since 3} Ti _1.7 (PO ₄ ) ₃ and Li ₇ La ₃ Zr ₂ O ₁₂ are difficult to obtain CNF-encapsulated solid electrolyte nanoparticle aggregate (d) by one hydrothermal reaction, step (II) Can yield a CNF-encapsulated precursor nanoparticle aggregate (e).

Here, the precursor of the solid electrolyte, for _example, in _{Li 7-x La 3 Zr 2} -x Ta x O 12, in _{LiTaO 3, La 0.51 Li 0.34 TiO} 2.94, TiO 2, Li _{For 1.3} Al _0.3 Ti _1.7 (PO ₄ ) ₃ , it is Li ₃ PO ₄ , and for Li ₇ La ₃ Zr ₂ O ₁₂ , it is ZrO ₂ . These may be used alone or as a mixture of two or more.

  In the step (II), at least one kind of the raw material compound of the solid electrolyte is used, and a predetermined ratio of the raw material compound can be prepared according to the solid electrolyte to be manufactured or the precursor of the solid electrolyte.

  Specific examples of the raw material compound for the solid electrolyte include a zirconium compound, a titanium compound, an aluminum compound, and a silicon compound. Among them, sulfates, nitrates, carbonates, acetates, oxalates, oxides, hydroxides, halides and the like of these elements can be suitably used. These may be used alone or as a mixture of two or more.

  When preparing the slurry by mixing the raw material compound and cellulose nanofiber, water is usually used. The amount of the water used is 10 mol to 300 mol per 1 mol of the metal element of the raw material compound in view of the solubility or dispersibility of each raw material compound, the ease of stirring, the efficiency of the hydrothermal reaction, and the like. Mole, and more preferably 50 mole to 200 mole.

  Examples of the alkaline solution used in the step (II) include an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia and the like. Above all, from the viewpoint of increasing the efficiency of the hydrothermal reaction, and from the viewpoint of minimizing the obtained CNF-encapsulated solid electrolyte nanoparticle aggregate (d) or the CNF-encapsulated precursor nanoparticle aggregate (e), sodium hydroxide; It is preferable to use sodium carbonate or a mixed solution thereof. The amount of the alkali solution used in the slurry may be an amount sufficient to keep the pH of the slurry at 7 to 12 by dropping. These may be used alone or as a mixture of two or more.

  Further, the content of cellulose nanofibers in the slurry is preferably 0.01 parts by mass to 10 parts by mass, more preferably 0.05 parts by mass, in terms of carbon atoms, relative to 100 parts by mass of water in the slurry. Parts to 8 parts by mass.

  The order of adding these raw materials is not particularly limited. After the addition, the mixing time is preferably from 1 minute to 12 hours, more preferably from 5 minutes to 6 hours. Further, the mixing temperature is preferably 5C to 60C, more preferably 5C to 50C.

  In the mixing of the slurry, from the viewpoint of sufficiently dispersing the cellulose nanofibers, it is preferable to disintegrate the aggregated cellulose nanofibers by a treatment using a disperser (homogenizer). Examples of the disperser include a disintegrator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short-screw extruder, a twin-screw extruder, an ultrasonic stirrer, and a household juicer mixer. I can give it. Among them, 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 spectrometer or viscosity using an E-type viscometer. By confirming that the degree is uniform, the evaluation can be easily performed. The processing time in 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 the cellulose nanofibers still in the aggregated state. A sieve or a commercially available wet classifier can be used for the wet classification. The opening of the sieve may vary depending on the fiber length of the cellulose nanofiber used, but is preferably 25 μm to 160 μm from the viewpoint of working efficiency.

  Next, the obtained slurry is subjected to a hydrothermal reaction. The hydrothermal reaction may be at least 100 ° C, preferably from 130 ° C to 180 ° C. 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 at which this is performed is preferably from 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 comprising a cellulose nanofiber and a solid electrolyte or a precursor of a cellulose nanofiber and a solid electrolyte, and is filtered, washed with water, and repulped (resuspended). In addition, reduced pressure filtration, pressure filtration, centrifugal filtration, etc. can be used as a filtration means, but pressure filtration such as a filter press is preferred from the viewpoint of simplicity of operation.

  When washing the complex after filtration 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) composed 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 still more preferably 1.5% by mass. １２12% by mass.

  Steps (III), (III ′), and (III ″) are each performed using the electrode active material particles (A) (in the case of including the step (I), the electrode active material particles ( A)), the CNF-encapsulated precursor nanoparticle aggregate (e), and the solid electrolyte nanoparticle aggregate (b) or the solid electrolyte nanoparticle array by reacting with the CNF-encapsulated precursor nanoparticle aggregate (e) ( This is a step of mixing a predetermined amount of the remaining raw material compounds for producing c) or both, and firing the mixture.

  By the above-mentioned step (III), (III ′) or (III ″), the solid electrolyte nanoarray (b) or the linearly arranged plurality of solid electrolyte nanoparticle rows (c) is converted into the all-solid-state nanoparticle array. It will be carried on the surface of the secondary battery electrode active material particles (A). Further, since the sintering can improve the crystallinity of both the solid electrolyte particles (b) for the all-solid secondary battery and the nanoparticle array (c) of the solid electrolyte, the obtained all-solid secondary battery has The charge / discharge characteristics of the electrode active material can be effectively improved.

  Here, the solid electrolyte carried on the surface of the electrode active material particles (A) for an all-solid-state secondary battery uses a carbon chain derived from cellulose nanofiber as a shaft or a base material, and a specific solid electrolyte nanoparticle ( a) is a solid electrolyte nanoparticle aggregate (solid electrolyte nanoarray) (b) exhibiting a unique shape formed by linearly carrying or arranging a plurality of solids, or a plurality of solids continuously arranged in a linear manner Whether it is the electrolyte nanoparticle row (c) is determined by the firing atmosphere in the above firing. When firing under an inert atmosphere or a reducing atmosphere, the CNF-encapsulated solid electrolyte nanoparticle aggregate (d) or the CNF-encapsulated precursor nanoparticle aggregate (e) obtained in step (II) is carried. The cellulose nanofibers are carbonized into carbon chains derived from the cellulose nanofibers to obtain the solid electrolyte nanoarray (b). On the other hand, when fired in an oxygen atmosphere, the cellulose nanofibers are burned off and a plurality of solid electrolyte nanoparticle rows (c) having a specific arrangement can be obtained. As the solid electrolyte of the present invention, the obtained solid electrolyte nanoparticle aggregate (solid electrolyte nanoarray) (b) and the solid electrolyte nanoparticle array (c) may be appropriately combined and used.

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

Step (III) is more specifically described in the following steps (III-1) to (III-3):
The above-mentioned electrode active material particles (A) (electrode active material particles (A) obtained in step (I) when step (I) is included), and CNF-encapsulated solid electrolyte nanoparticles obtained in step (II) Mixing the aggregate (d),
The above-mentioned electrode active material particles (A) (in the case of including the step (I), the electrode active material particles (A) obtained in the step (I)), and the CNF-encapsulated precursor nanoparticles obtained in the step (II) Mixing the slurry containing the body (e) and the remaining raw material compounds of the solid electrolyte, or
The electrode active material particles (A) (in the case of including the step (I), the electrode active material particles (A) obtained in the step (I)), and the CNF-encapsulated solid electrolyte nanoparticle obtained in the step (II). Mixing the slurry containing the particle aggregate (d), the CNF-encapsulated precursor nanoparticle aggregate (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 to obtain a mixture of the electrode active material particles for an all-solid secondary battery (A) and the CNF-encapsulated solid electrolyte nanoparticle aggregate (d),
A mixture of the electrode active material particles for an all-solid secondary battery (A), the CNF-encapsulated precursor nanoparticle aggregate (e) and the remaining raw material compound of the solid electrolyte, or
A mixture comprising the electrode active material particles for an all-solid secondary battery (A), the CNF-encapsulated solid electrolyte nanoparticle aggregate (d), and the CNF-encapsulated precursor nanoparticle aggregate (e) and the remaining raw material compound of the solid electrolyte Obtaining step (III-2), and
Baking the mixture obtained in the step (III-2) to obtain an electrode active material for an all-solid-state secondary battery (III-3).

  In the step (III-1), specifically, the electrode obtained in the step (I) when the slurry obtained in the step (II) includes the electrode active material particles (A) (the step (I) is included). The active material particles (A)) or the remaining raw material compounds of the solid electrolyte may be further mixed to form a slurry. In addition, an example of a method for producing an electrode active material for an all-solid secondary battery in which the slurry contains the electrode active material particles (A) is described. After producing the electrolyte nanoarray (b) or the solid electrolyte nanoparticle row (c), one or both of them are appropriately combined with a known method on the surface of the electrode active material particles (A). The electrode active material for all-solid-state secondary batteries may be obtained by carrying.

  The mixing ratio between the slurry obtained in the step (II) and the electrode active material particles for an all-solid-state secondary battery (A) is determined based on the electrode active material particles in the finally obtained all-solid-state secondary-electrode electrode active material. (A) and the solid electrolyte nanoparticle aggregate (b), the solid electrolyte nanoparticle array (c), or the total amount thereof when both are included (electrode active material particles (A) : Solid electrolyte nanoparticle aggregate (b) + solid electrolyte nanoparticle array (c) (provided that the solid electrolyte nanoparticle aggregate (b) and the solid electrolyte nanoparticle array (c) include only one of them) , One of them) is preferably 99.9: 0.1 to 70:30.

  The remaining raw material compounds of the solid electrolyte mixed with the slurry obtained in the step (II) together with the CNF-encapsulated precursor nanoparticle aggregate (e) are nitrate, carbonate, acetate, oxalate of a predetermined element , Oxides, hydroxides and the like can be suitably used. These may be used alone or as a mixture 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 from 1 minute to 12 hours, more preferably from 5 minutes to 6 hours. Further, the mixing temperature is preferably 5C to 60C, more preferably 5C to 50C.

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

The particle size of the mixture obtained by drying is a D50 value in a particle size distribution based on a laser diffraction / scattering method, and is preferably 5 nm to ₅₀ μm, and more preferably 5 nm to 25 μm. Here, the ₅₀ value D in the particle size distribution measurement, a value obtained by volume-based particle size distribution based on the laser diffraction scattering method, D ₅₀ value means a particle diameter at cumulative 50% (median diameter) .

  Examples of the drying method include spray drying, box type drying, fluidized bed drying, external heating type drying, medium fluidized drying, freeze drying, vacuum drying and the like. Of these, freeze-drying, freeze-drying, or spray-drying is preferred from the viewpoint of effectively controlling the particles of the obtained mixture to unnecessarily increase to achieve finer particles.

  In the following step (III-3), the mixture obtained in step (III-2) is fired to obtain an electrode active material for an all-solid-state secondary battery. By this calcination, the cellulose nanofabric contained in the composite is carbonized or burned off, and when the CNF-encapsulated precursor nanoparticle aggregate (e) and the remaining raw material compound of the solid electrolyte are included, the solid electrolyte nanoparticles ( A solid-state 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.

  The firing is performed in an optional 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.

  Also, the steps (III ′) and (III ″) can be performed by appropriately reading the above-mentioned step (III).

(All-solid secondary battery)
An all-solid secondary battery or an all-solid lithium ion secondary battery of the present invention includes the above-mentioned electrode active material for an all-solid 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 an all-solid-state secondary battery can be appropriately applied. In addition, the configuration of the all-solid secondary battery or the all-solid lithium-ion secondary battery of the present invention, and the manufacturing method thereof may be appropriately combined with known methods except that the electrode active material for the all-solid secondary battery of the present invention is used. Can be. In addition, the all-solid secondary battery to which the electrode active material for an all-solid secondary battery of the present invention can be appropriately applied includes a positive electrode, a negative electrode, and a solid electrolyte as essential components, and includes a positive electrode active material layer and a solid electrolyte layer. , And a negative electrode active material layer is not particularly limited as long as a stacked body is formed in this order.

  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, the average fiber diameter is reduced to 50 nm or less from a carbon chain derived from cellulose nanofiber. A solid electrolyte nanoparticle aggregate (b) in which a plurality of solid electrolyte nanoparticles (a) are supported linearly is supported on the surface of the solid electrolyte particles, and has a solid electrolyte or an average fiber diameter of 50 nm or less. A solid electrolyte nanoparticle array (c) in which the solid electrolyte nanoparticles (a) are continuously arranged linearly and guided by cellulose nanofibers is used as a solid electrolyte supported on the surface of the solid electrolyte particles, or both. It could also be used. In the case of having any one of the above configurations, an all-solid-state lithium ion secondary battery having further improved charge / discharge capacity and durability can be obtained.

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

  The shape of the all-solid secondary battery having the above-described configuration, particularly the shape of the all-solid lithium-ion secondary battery, is not particularly limited. An enclosed irregular shape may be used.

  Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[Production Example 1] (Production of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ cathode 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 such that the molar ratio of Ni: Co: Mn is 1: 1: 1. Then, 25% aqueous ammonia was dropped into 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 provisionally fired at 800 ° C. for 5 hours in an air atmosphere to be disintegrated, and then fired at 800 ° C. for 10 hours in an air atmosphere as main firing to obtain an NCM-based composite oxide (LiNi _1/3). Secondary particles of Co _1/3 Mn _1/3 O ₂ ) were obtained. (Average particle size 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)
5.17 g of lithium carbonate, 11.40 g of lanthanum hydroxide, and 4.93 g of zirconium oxide were pulverized and mixed in a planetary ball mill at 200 rpm for 2 hours to obtain a mixture A2. The obtained mixture A2 was formed into pellets, fired 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] (All-solid-state lithium-ion secondary battery electrode active material composed of NMC + solid electrolyte nanoarray)
1.81 g of zirconium sulfate tetrahydrate, 19.29 g of cellulose nanofiber (manufactured by Sugino Machine Co., Ltd., TMa-10002, water content of 98% by mass), and 55 mL of water were mixed for 60 minutes to prepare a slurry A3. To the obtained slurry A3, 12.0 g of a 10% by mass aqueous NaOH solution was added and mixed for 5 minutes to prepare a slurry B3. The obtained slurry B3 was charged into an autoclave, and a hydrothermal reaction was performed at 140 ° C. for 1 hour. After allowing the obtained hydrothermal reaction product C3 to cool, it is filtered, washed with water, and repulped with water to contain 10% by mass of a ZrO ₂ nanoarray in which a plurality of ZrO ₂ nanoparticles are linearly supported on cellulose nanofibers. A slurry D3 was obtained.

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

  FIG. 1 shows a TEM photograph of the surface 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-based composite oxide secondary particles obtained in Production Example 1 were directly used as the electrode active material B for an all-solid lithium ion secondary battery.

≫Evaluation of discharge capacity of all solid lithium ion secondary battery イ オ ン
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 order to make the same ratio between the positive electrode active material for an all solid lithium ion secondary battery and the solid electrolyte, in Example 1 using the electrode active material A for an all solid lithium ion secondary battery, Comparative Example 1 using the electrode active material B for an all-solid-state lithium ion secondary battery with the solid electrolyte (mass ratio) of 75:25 and the electrode active material: solid electrolyte (mass ratio) of 71.3: 28. After mixing at a mixing ratio of 7, the mixture was charged into a pressing jig to form a positive electrode active material layer, and only LLZ solid electrolyte particles were further charged thereon and laminated as a solid electrolyte layer. By pressing for 2 minutes, a disk-shaped positive electrode having a diameter of 14 mm was obtained. Next, an all-solid lithium-ion secondary battery was fabricated by attaching a lithium foil as a negative electrode to the solid electrolyte layer side.

  Using the fabricated all-solid-state lithium ion secondary battery, charging conditions were 10 mA / g, constant-current charging at a voltage of 4.2 V, discharging conditions were 10 mA / g, and constant-current discharging at a final voltage of 3.0 V. The discharge capacity at 10 mA / g was determined. The charge and discharge tests were all performed at 45 ° C.

  Table 1 shows the results of the above evaluation.

  As is clear from Table 1, the all-solid-state lithium ion secondary battery using the cathode active material particles for the all-solid-state lithium ion secondary battery using the cathode active material in which the solid electrolyte nanoparticles are supported on the particle surface of Example 1 Is compared with the all solid lithium ion secondary battery using the positive electrode active material particles for the all solid lithium ion secondary battery using the common positive electrode active material not supporting the solid electrolyte nanoparticles in Comparative Example 1. Is very large.

Claims (15)

The following steps (II) to (III):
A slurry containing at least one raw material compound of the solid electrolyte, an alkali solution, and cellulose nanofibers is subjected to a hydrothermal reaction at a temperature of 100 ° C. or more and a pressure of 0.3 MPa to 0.9 MPa, whereby the cellulose nano A solid electrolyte nanoparticle aggregate (d) containing a part or all of the fiber, a nanoparticle aggregate (e) consisting of the solid electrolyte precursor containing a part or all of the cellulose nanofiber, or Step (II) of producing both, and
At least the solid electrolyte nanoparticle aggregate (d) containing a part or all of the cellulose nanofiber obtained in the step (II), and the solid electrolyte containing part or all of the cellulose nanofiber. A solid electrolyte nanoparticle aggregate which reacts with a nanoparticle aggregate (e) composed of a precursor and a nanoparticle aggregate (e) composed of a precursor of the above-mentioned solid electrolyte that includes part or all of the cellulose nanofiber. (B) or baking the remaining raw material compounds for producing the solid electrolyte nanoparticle train (c), or both, (III),
including,
The solid electrolyte nanoparticle aggregate (b), in which a plurality of solid electrolyte nanoparticles (a) are linearly supported on a carbon chain derived from the cellulose nanofiber having an average fiber diameter of 50 nm or less, is an electrode active material particle ( An electrode active material for an all-solid-state secondary battery supported on the surface of A), or
The solid electrolyte nanoparticle row (c) in which the solid electrolyte nanoparticles (a) are linearly and continuously arranged by being guided by the cellulose nanofibers having an average fiber diameter of 50 nm or less, and the cellulose nanofibers are burned out. The method for producing an electrode active material for an all-solid-state secondary battery , wherein the solid electrolyte nanoparticle array (c) is supported on the surface of the electrode active material particles (A). The following steps (II) to (III '):
A slurry containing at least one raw material compound of the solid electrolyte, an alkali solution, and cellulose nanofibers is subjected to a hydrothermal reaction at a temperature of 100 ° C. or more and a pressure of 0.3 MPa to 0.9 MPa, whereby the cellulose nano A solid electrolyte nanoparticle aggregate (d) containing a part or all of the fiber, a nanoparticle aggregate (e) consisting of the solid electrolyte precursor containing a part or all of the cellulose nanofiber, or Step (II) of producing both, and
At least the solid electrolyte nanoparticle aggregate (d) containing a part or all of the cellulose nanofiber obtained in the step (II), and the solid electrolyte containing part or all of the cellulose nanofiber. A solid electrolyte nanoparticle aggregate which reacts with a nanoparticle aggregate (e) composed of a precursor and a nanoparticle aggregate (e) composed of a precursor of the above-mentioned solid electrolyte that includes part or all of the cellulose nanofiber. Calcining the remaining raw material compounds for producing (b), or both, in a reducing atmosphere (III ′),
including,
The solid electrolyte nanoparticle aggregate (b), in which a plurality of solid electrolyte nanoparticles (a) are linearly supported on a carbon chain derived from the cellulose nanofiber having an average fiber diameter of 50 nm or less, is an electrode active material particle ( A method for producing an electrode active material for an all-solid-state secondary battery supported on the surface of A). The following steps (II) to (III ′ ′):
A slurry containing at least one raw material compound of the solid electrolyte, an alkali solution, and cellulose nanofibers is subjected to a hydrothermal reaction at a temperature of 100 ° C. or more and a pressure of 0.3 MPa to 0.9 MPa, whereby the cellulose nano A solid electrolyte nanoparticle aggregate (d) containing a part or all of the fiber, a nanoparticle aggregate (e) consisting of the solid electrolyte precursor containing a part or all of the cellulose nanofiber, or Step (II) of producing both, and
At least the solid electrolyte nanoparticle aggregate (d) containing a part or all of the cellulose nanofiber obtained in the step (II), and the solid electrolyte containing part or all of the cellulose nanofiber. Reacting with a nanoparticle aggregate (e) composed of a precursor and a nanoparticle aggregate (e) composed of the precursor of the solid electrolyte containing a part or all of the cellulose nanofibers, and reacting with the solid electrolyte nanoparticle array ( calcining the remaining raw material compounds, or both, to produce c) in an oxidizing atmosphere (III ″),
including,
The solid electrolyte nanoparticle row (c) in which the solid electrolyte nanoparticles (a) are linearly and continuously arranged by being guided by the cellulose nanofibers having an average fiber diameter of 50 nm or less, and the cellulose nanofibers are burned out. The method for producing an electrode active material for an all-solid-state secondary battery , wherein the solid electrolyte nanoparticle array (c) is supported on the surface of the electrode active material particles (A).   The all-solid-state secondary battery according to any one of claims 1 to 3, further comprising an electrode active material particle (A) when firing in the step (III), (III '), or (III' '). Production method of electrode active material for use.   5. The method according to claim 1, further comprising a step (I) of producing the electrode active material particles (A) prior to the step (III), (III ′), or (III ″). The method for producing an electrode active material for an all-solid secondary battery according to the above.   The content of the cellulose nanofibers in the slurry of the step (II) is 0.01 part by mass to 10 parts by mass in terms of carbon atoms with respect to 100 parts by mass of water in the slurry. 13. The method for producing an electrode active material for an all-solid secondary battery according to   The hydrothermal reaction in the step (II) according to any one of claims 1 to 6, wherein the temperature is 100 ° C or higher, the pressure is 0.3 MPa to 0.9 MPa, and the reaction time is 0.5 hours to 24 hours. A method for producing an electrode active material for an all-solid secondary battery.   8. The electrode active material for an all-solid-state secondary battery according to claim 1, wherein the firing temperature in the step (III), (III ′), or (III ″) is 500 ° C. to 1200 ° C. 9. Manufacturing method.   The method for producing an electrode active material for an all-solid secondary battery according to any one of claims 1 to 8, wherein the average secondary particle diameter of the electrode active material particles (A) is 50 nm to 50 µm.   The method for producing an electrode active material for an all-solid secondary battery according to any one of claims 1 to 9, wherein the average particle diameter of the solid electrolyte nanoparticles (a) is 0.5 nm to 100 nm.   The mass ratio of the electrode active material particles (A) to the solid electrolyte nanoparticle aggregate (b), the solid electrolyte nanoparticle array (c), or the total amount thereof when both are included, is 99. The method for producing an electrode active material for an all-solid secondary battery according to any one of claims 1 to 10, wherein the ratio is from 0.9: 0.1 to 70:30. 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), _{12. The method according} to claim 1, wherein at least one of a group consisting of Li ₂ MSiO ₄ (M = Ni, Co, Fe, Mn), SiO _x , and Li ₄ Ti ₅ O ₁₂ is included. 13. A method for producing an electrode active material for a solid secondary battery. 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 , comprising at least one or more of the group consisting of: 13. The method for producing an electrode active material for an all-solid secondary battery according to any one of claims to 12.   The method for producing an electrode active material for an all-solid secondary battery according to any one of claims 1 to 13, wherein the linear shape is a linear shape or a substantially linear shape.   The method for producing an electrode active material for an all solid state secondary battery according to any one of claims 1 to 14, which is for an all solid state lithium ion secondary battery.