JP2016023118A - Method for producing surface-treated oxide particles and oxide particles obtained using the production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing surface-treated oxide particles suitably used as an active material layer of a positive or negative electrode in a storage battery (secondary battery).SOLUTION: There are obtained surface-treated oxide particles having a hydrophobic product having a trimethylsilyl group on a part or the whole of the particle surface by bringing oxide particles having an alkaline compound on a part or the whole of the particle surface into contact with gas containing volatile trimethyl silylation agent to form a hydrophobic product having a trimethylsilyl group by a gas reaction. The alkaline compound is at least one selected from compounds containing lithium (Li), sodium (Na) and magnesium (Mg). The oxide particles are an alkaline composite oxide containing at least one transition metals of manganese, cobalt, nickel, iron and titanium.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for producing surface-treated oxide particles. More specifically, in a storage battery (secondary battery) having a current collector (positive electrode, negative electrode), positive electrode active material layer, (solid or liquid) electrolyte, negative electrode active material layer, (positive electrode or negative electrode) active material layer A method for producing surface-treated oxide particles (surface treatment method) that can be used in a very simple method called a vapor phase method for producing oxide particles that can be suitably used in a battery and that can improve various characteristics of a storage battery. And low-cost and high-performance oxide particles obtained by the production method thereof.

  A lithium ion secondary battery (hereinafter referred to as a lithium ion battery) as a storage battery has a large energy density and is excellent in charge / discharge cycle characteristics, and is therefore widely used mainly in electronic devices such as portable devices. Here, lithium ion batteries are roughly classified into (1) electrolyte-based lithium ion batteries and (2) all solid-state lithium ion batteries, depending on the type of electrolyte used.

(1) Electrolyte-based lithium-ion battery An electrolyte-based lithium-ion battery is the most common lithium-ion battery that is widely used at present, and as shown in FIG. The material layer 2), the negative electrode (the negative electrode current collector 6, the negative electrode active material layer 5), the electrolyte solution 4, and the separator 3 are configured as basic elements. The positive electrode and the negative electrode to which the electrode lead 7 (extraction electrode) is attached are immersed in the electrolytic solution 4 with the separator 3 capable of holding the electrolyte interposed between the electrodes, and the container 8 (metal, plastic laminate, etc.) is used. It has a covered cell structure.

  The positive electrode and the negative electrode are respectively active material layers (positive electrode active material layers) mainly composed of crystalline particles of each active material (positive electrode active material, negative electrode active material), conductive additive, binder (binder), and the like. 2, the negative electrode active material layer 5) has a structure formed on each current collector (positive electrode current collector 1: aluminum foil or the like, negative electrode current collector 6: copper foil or the like).

A composite oxide containing lithium and a transition metal is usually used for the positive electrode active material. Specifically, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ) as a layered material, Lithium-nickel-cobalt-aluminum oxide (Li (Ni-Co-Al) O ₂ ), lithium-nickel-manganese-cobalt oxide (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ), spinel system Generally, lithium-manganese oxide (LiMn ₂ O ₄ ) as a material, lithium iron phosphate (LiFePO ₄ ) as an olivine-based material, and the like are common. Furthermore, aiming for higher energy, lithium-manganese-nickel oxide (Li (Mn _3/2 Ni _1/2 ) O ₄ or the like) as a spinel material that charges and discharges at a high voltage (5 V region), Development of solid solution system (also called “excess system”) manganese-containing lithium composite oxide (eg, Li ₂ MnO ₃ —LiMO ₂ [M: Ni, Mn, Co, etc.]) as a layered material having a high capacity It is being advanced. As the negative electrode active material, graphite (graphite), lithium titanate (Li ₄ Ti ₅ O ₁₂ ), or the like is generally used.

  By the way, each active material layer (positive electrode active material layer 2, negative electrode active material layer 5) is formed by using each active material layer forming paste (positive electrode active material layer forming paste, negative electrode active material layer forming paste). The coating is performed on the current collector by coating and drying (dense by pressing if necessary).

  Here, the paste for forming the positive electrode active material layer is, for example, an organic solvent such as N-methylpyrrolidone (NMP) in which a binder (binder) such as polyvinylidene fluoride (PVDF) is dissolved. Non-aqueous pastes in which particles of conductive assistants such as particles, acetylene black (AB) and vapor grown carbon fiber (VGCF) are dispersed are generally used. For the negative electrode active material layer forming paste, for example, In the water containing styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), etc. as an aqueous binder (binder), particles of the above negative electrode active material, and optionally acetylene black (AB) In general, water-based pastes in which conductive auxiliary particles such as vapor grown carbon fiber (VGCF) are dispersed are used.

  In the above-described electrolyte-based lithium ion battery, various improvements have been continuously made in active materials (positive electrode active material, negative electrode active material), electrolytic solution, separator, and the like in order to improve performance and reduce costs. However, in an electrolyte-based lithium ion battery using a liquid electrolyte as an electrolyte, there is a risk of ignition due to the flammability of the organic solvent that is the main component of the electrolyte, and there is also a risk of electrolyte leakage, It cannot be said that the battery has sufficient safety. Further, when the battery voltage is about 4.5 V or more, the electrolytic solution is decomposed, so it is difficult to increase the capacity by increasing the voltage, and the inside of the container (package) Since the cells are electrically connected by an electrolyte solution, it was difficult to increase the voltage and size of the cell by using a bipolar stacked cell structure. . Therefore, in recent years, development of an all-solid-state lithium ion battery using a solid electrolyte instead of the electrolytic solution has been actively promoted.

(2) All-solid-state lithium-ion batteries All-solid-state lithium-ion batteries are characterized by the use of non-flammable and flame-retardant solid electrolytes instead of flammable electrolytes. The bipolar stacked cell structure makes it possible to reduce the package thickness and size, and increase the cell voltage by serializing (stacking) in one cell. There is an advantage that the cost can be reduced. Furthermore, since the potential window of the solid electrolyte can be widened, it is possible to further increase the capacity by applying a positive electrode active material (5 V system) having a higher potential than Li.

  As shown in FIG. 2, the basic cell structure of the all-solid-state lithium ion battery includes a current collector (positive electrode current collector 1, negative electrode current collector 6) and a functional layer (positive electrode active material layer 2, solid electrolyte layer 9, The negative electrode active material layer 5) is a laminated cell structure in which a plurality of the laminated cell structures are stacked to obtain a bipolar type laminated cell structure (n times lamination: current collector / positive electrode active material layer (first layer) / solid Electrolyte layer (first layer) / negative electrode active material layer (first layer) / current collector / positive electrode active material layer (second layer) / solid electrolyte layer (second layer) / negative electrode active material layer (second layer) / Current collector /.../ positive electrode active material layer (nth layer) / solid electrolyte layer (nth layer) / negative electrode active material layer (nth layer) / current collector) can be easily realized. An electrode lead 7 (extraction electrode) is attached to the outermost current collector (positive electrode current collector 1, negative electrode current collector 6) of the laminated cell structure, and is covered with a container 8 (metal, plastic laminate, etc.). Yes. As the current collector, a stainless steel foil, an aluminum foil or the like can be used for the positive electrode current collector 1, and a stainless steel foil or a copper foil can be used for the negative electrode current collector 6.

  The functional layers (positive electrode active material layer 2, solid electrolyte layer 9, negative electrode active material layer 5) are, for example, active material layers (positive electrode active material layer 2, negative electrode active material layer 5). A positive electrode active material, a negative electrode active material) crystalline particles are dispersed in a solid electrolyte matrix, and if necessary, a conductive aid for improving the current collection (electronic conductivity) in the active material layer, A trace amount of a binder (binder) for imparting adhesion and flexibility may be contained. The solid electrolyte layer 9 is a polycrystalline layer densely filled with solid electrolyte particles, or a dense amorphous layer made of a solid electrolyte. If necessary, the solid electrolyte layer 9 is provided for adhesion and flexibility. A small amount of a binder (binder) may be contained.

  As the active material (positive electrode active material, negative electrode active material), a material similar to the active material used in the above-described electrolyte-based lithium ion battery can be applied. Furthermore, high-capacity negative electrode active material materials that cannot be used in electrolyte-based lithium ion batteries, such as metallic lithium and various lithium alloys, can be used because dendrites are deposited on the negative electrode to cause a short circuit. There is also an advantage that it can be applied to a battery.

By the way, solid electrolytes used in all solid lithium ion batteries are roughly classified into oxide solid electrolytes and sulfide solid electrolytes. For example, in oxide solid electrolytes, lithium phosphate (Li ₃ PO ₄ ), phosphoric acid is used. _(. called LiPON) lithium was added with nitrogen _{Li 3 PO 4 N X, LiBO} 2 N X, LiNbO 3, LiTaO 3, Li 2 SiO 3, Li 4 SiO 4 -Li 3 PO 4, Li 4 SiO 4 - Li ₃ VO ₄ , Li ₂ O—B ₂ O ₃ —P ₂ O ₅ , Li ₂ O—SiO ₂ , Li ₂ O—B ₂ O ₃ —ZnO, Li _{1 + X} Al _X Ti _{2 -X} (PO ₄ ) _{3 (.} called LATP or LTAP) (0 ≦ X ≦ 1 ), Li 1 + X Al X Ge 2-X (PO 4) 3 (0 ≦ X ≦ 1; _{Specifically, Li} 1.5 Al _{. .5} called _{Ge 1.5 (PO 4) 3)} (LAGP), LiTi 2 (PO 4) 3, Li 3X La 2 / 3X TiO 3 (0 ≦ X ≦ 2/3; specifically, , Li _0.33 La _0.56 TiO ₃ , Li _0.5 La _0.5 TiO _3, etc. (referred to as LLT or LLTO), Li ₅ La ₃ Ta ₂ O ₁₂ , Li ₇ La ₃ Zr ₂ O ₁₂ (Referred to as LLZ or LLZO), Li ₆ BaLa ₂ Ta ₂ O ₁₂ , Li _3.6 Si _0.6 P _0.4 O _4, etc., in sulfide-based solid electrolytes, Li ₂ S—SiS ₂ , LiI— _{Li 2 S-SiS 2, LiI} -Li 2 S-P 2 S 5, LiI-Li 2 S-B 2 S 3, Li 3 PO 4 -Li 2 S-Si 2 S, Li 3 PO 4 -Li 2 S -SiS ₂ , LiPO _{4 -Li 2 S-SiS, LiI} -Li 2 S-P 2 O 5, LiI-Li 3 PO 4 -P 2 S 5, Li 2 S-P 2 is _{S 5,} and the like, oxide-based solid electrolyte In particular, a sulfide-based solid electrolyte having a higher lithium ion conductivity is suitable. Among them, a Li ₂ S—P ₂ S ₅ -based solid electrolyte has excellent characteristics and is low in cost (expensive metal element Not included) is preferable.

In the all-solid-state lithium ion battery using the sulfide-based solid electrolyte, oxide particles having excellent electron conductivity as an active material (for example, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium-nickel- Cobalt-aluminum oxide (Li (Ni—Co—Al) O ₂ ), lithium-nickel-manganese-cobalt oxide (such as LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ), and electronic conductivity Not so bad oxide particles (lithium-manganese-nickel oxide (Li (Mn _3/2 Ni _1/2 ) O ₄ etc.), solid solution system (excess system) manganese-containing lithium composite oxide (Li ₂ MnO ₃ -LiMO) _{2 [M: Ni, Mn,} Co] applying the like), the active material particles (oxide particles of the active material layer) / sulfide-based solid electrolyte boundary In this case, it is known that a space charge layer deficient in lithium ions is formed on the sulfide-based solid electrolyte side, the interface resistance is greatly increased, and the output characteristics (rate characteristics) of the battery are greatly deteriorated. As a method for effectively reducing the interface resistance, an oxide solid electrolyte with low electronic conductivity (for example, alkaline composite oxidation such as Li ₂ SiO ₃ , LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , Li ₂ Ti ₂ O _5, etc.) Coating of active material particles (oxide particles) with a material has been proposed and widely attempted (see Patent Documents 1 to 3, etc.).

  As described above, the lithium ion battery as the storage battery has been described. In recent years, as a next generation battery (next generation secondary battery) aiming at higher capacity and lower cost of the storage battery, for example, a sodium ion battery, a magnesium ion battery, etc. Development is also actively underway. In these batteries, the basic structure is the same as that of the above-described lithium ion battery, and sodium or magnesium is applied instead of lithium.

JP 2009-266728 A WO2013 / 011871 international pamphlet WO2013 / 046443 International Publication Pamphlet

  In the above-mentioned electrolyte-based lithium ion battery, in order to ensure a high capacity of the positive electrode active material particles to be used, a lithium excess composition is often required. In that case, the positive electrode active material layer forming paste There was a problem that gelation (purination) was likely to occur. As a method for suppressing this gelation (purination), for example, a method has been proposed in which positive electrode active material particles containing excessive lithium are washed in pure water to remove excess lithium on the surface of the positive electrode active material particles. . It is also known that various coatings on the positive electrode active material particles as described above are effective.

  On the other hand, even in an all-solid-state lithium ion battery, the problem of increasing the interfacial resistance between the positive electrode active material particles and the sulfide-based solid electrolyte as described above has become apparent. It is known that coating with positive electrode active material particles with an oxide solid electrolyte (alkali composite oxide) is also effective for reducing the interface resistance.

  As described above, surface coating on the active material particles is effective. However, in conventional wet coating methods such as a method using a rolling flow device, it is difficult to control the coating film thickness and film quality, and an expensive device. High cost because complicated processes are required. For this reason, a manufacturing method for coating oxide particles as active materials (positive electrode active material, negative electrode active material) with an oxide solid electrolyte (alkali composite oxide) in a simpler and lower cost process has been desired. .

  The present invention provides a method for producing surface-treated oxide particles that can be produced by a very simple method called a gas phase method in producing oxide particles for a storage battery active material that can improve various characteristics of the storage battery. Objective.

  In view of such a situation, the inventors have conducted extensive research and as a result, contacted oxide particles having an alkaline compound on part or all of the particle surface with a gas containing a volatile trimethylsilylating agent. A hydrophobic product having a trimethylsilyl group is formed by a reaction between an alkaline compound and the trimethylsilylating agent via a gas phase, and oxide particles having the hydrophobic product having the trimethylsilyl group on part or all of the surface are obtained. Thus, it has been found that high-performance surface-treated oxide particles can be produced at low cost.

That is, according to the first aspect of the present invention, the oxide particles having an alkaline compound on part or all of the particle surface are brought into contact with a gas containing a volatile trimethylsilylating agent, and the alkaline compound, the trimethylsilylating agent, Formed a hydrophobic product having a trimethylsilyl group by a reaction via a gas phase of the product to obtain oxide particles having the hydrophobic product having the trimethylsilyl group on a part or all of the particle surface. A method for producing oxide particles, comprising:
The alkaline compound is any one or more selected from the group of compounds containing lithium (Li), sodium (Na), and magnesium (Mg),
The oxide particles include one or more transition metals selected from the group consisting of manganese, cobalt, nickel, iron, and titanium, and are selected from the group consisting of lithium (Li), sodium (Na), and magnesium (Mg). A method for producing surface-treated oxide particles, which is an alkali composite oxide containing at least one alkali element.

In a second invention of the present invention, the volatile trimethylsilylating agent in the first invention is ((CH ₃ ) ₃ Si) ₂ NR (R: hydrogen or lower alkyl group) or (CH ₃ ) ₃ A surface-treated oxide that is at least one selected from the group of compounds represented by SiY (a group selected from Y: —OH, —OR, or —NR ₂ (R: hydrogen, or a lower alkyl group)) A method for producing particles.

  According to a third aspect of the present invention, there is provided an oxide in which part or all of the particle surface of the particle surface of the first or second invention is covered with an alkali component. The surface is a particle, and the alkali component is at least one selected from the group consisting of lithium (Li), sodium (Na), magnesium (Mg) hydroxide, carbonate, and oxide. It is a manufacturing method of the processed oxide particle.

In the fourth invention of the present invention, the alkali component in the third invention is at least one selected from the group consisting of lithium hydroxide (LiOH), lithium carbonate (LiCO ₃ ), and lithium oxide (Li ₂ O). This is a method for producing surface-treated oxide particles.

  According to a fifth invention of the present invention, the alkaline compound in any of the first to fourth inventions is selected from the group consisting of oxides of lithium (Li), sodium (Na), and magnesium (Mg) in the alkali composite oxide. A method for producing surface-treated oxide particles, wherein the oxide is an alkali composite oxide containing at least one alkali oxide in excess of the stoichiometric composition.

  A sixth invention of the present invention is a method for producing surface-treated oxide particles, wherein the boiling point of the volatile trimethylsilylating agent in the first to fifth inventions is 250 ° C. or less.

  In a seventh aspect of the present invention, the volatile trimethylsilylating agent in the sixth aspect is one or more of hexamethyldisilazane (boiling point: 125 ° C.) and trimethylsilanol (boiling point: 98.6 to 99 ° C.). It is a manufacturing method of the surface-treated oxide particle characterized by these.

  The eighth invention of the present invention is a surface treatment characterized in that after the formation of the hydrophobic product having a trimethylsilyl group in the first to seventh inventions, a heat treatment is performed at 100 ° C. or more and 500 ° C. or less. It is a manufacturing method of oxide particles.

Ninth aspect of the present invention are alkali composite oxide in the invention of the first to _{eighth, LiMO 2, LiMPO 4, Li} 2 MSiO 4 (M: one of manganese, cobalt, nickel, selected from the group consisting of iron One or more transition metals), LiYaMn ₂ —aO ₄ (Y: cobalt, nickel; 0 ≦ a ≦ 1), Li ₂ MnO ₃ —LiMO ₂ (M: one or more selected from the group of manganese, cobalt, nickel) A transition metal) and Li ₄ Ti ₅ O ₁₂ as a main component, and a method for producing surface-treated oxide particles characterized by comprising at least one selected from the group consisting of Li ₄ Ti ₅ O ₁₂ as a main component.

  The tenth invention of the present invention is an oxide particle obtained by the method for producing surface-treated oxide particles in the first to ninth inventions, and is an oxidation comprising secondary particles composed of primary particles In the product particle, the trimethylsilyl group is present on the surface of the secondary particle and the surface of the primary particle inside the secondary particle and exposed to the open pore side between the primary particles. The oxide particles are characterized in that a hydrophobic product is formed.

  According to the method for producing surface-treated oxide particles of the present invention, since the gas phase method in which a gas containing a volatile trimethylsilylating agent is brought into contact with the oxide particles having an alkaline compound is used, the oxide particles A hydrophobic product having a trimethylsilyl group on the surface can be easily formed, and high-performance surface-treated oxide particles can be produced at low cost.

  In the surface-treated oxide particles according to the present invention, a dense surface treatment layer is formed very easily by a manufacturing method called a vapor phase method, for example, by trimethylsilylating an alkali component on the surface of the oxide particles. It is possible to suppress the gelation of the active material layer forming paste (active material paste) of the electrolyte-based secondary battery and reduce the interface resistance of the active material particles / sulfide-based solid electrolyte of the sulfide-based all-solid-state secondary battery. Therefore, it is suitable for an active material layer (positive electrode, negative electrode) of an electrolyte-based secondary battery or an all-solid secondary battery, and greatly contributes to cost reduction and characteristic improvement of the secondary battery.

It is a schematic diagram which shows an example of the structure of an electrolyte type lithium ion battery. It is a schematic diagram which shows an example of the structure of an all-solid-state lithium ion battery. It is oxide particle | grains, (a) It is a schematic diagram which shows the secondary particle comprised by agglomerating the primary particle, (b) The coating layer was formed by the liquid phase method (wet method), It is a schematic diagram showing oxide particles (secondary particles) formed by agglomerating primary particles, and (c) primary particles having a surface treatment layer formed by a vapor phase method according to the present invention. It is a schematic diagram which shows the surface-treated oxide particle (secondary particle) comprised by being aggregated in the lump shape. It is a schematic diagram which shows an example of the manufacturing method of the surface-treated oxide particle by the gaseous-phase method using the volatile trimethylsilylating agent which concerns on this invention. It is a schematic diagram which shows another example of the manufacturing method of the oxide particle surface-treated by the gaseous-phase method using the volatile trimethylsilylating agent which concerns on this invention. It is a manufacturing method of the oxide particle surface-treated by the gaseous-phase method using the volatile trimethylsilylating agent which concerns on this invention, Comprising: It is a schematic diagram which shows an example performed supplying atmospheric gas in reaction container. It is a manufacturing method of the oxide particle surface-treated by the gaseous-phase method using the volatile trimethylsilylating agent which concerns on this invention, Comprising: It is a schematic diagram which shows an example performed while circulating atmospheric gas within reaction container. It is a manufacturing method of the oxide particle surface-treated by the gas phase method using the volatile trimethylsilylating agent which concerns on this invention, Comprising: It is a schematic diagram which shows an example performed while stirring and flowing an oxide particle. FIG. 4 is a schematic diagram showing another example of a method for producing surface-treated oxide particles by a vapor phase method using a volatile trimethylsilylating agent according to the present invention, which is performed while stirring and flowing the oxide particles. . A method for producing surface-treated oxide particles by a vapor phase method using a volatile trimethylsilylating agent according to the present invention, wherein the oxide particles are stirred and fluidized, and an atmospheric gas is circulated in a reaction vessel. It is a schematic diagram which shows an example to perform. A method for producing surface-treated oxide particles by a vapor phase method using a volatile trimethylsilylating agent according to the present invention, wherein the oxide particles are stirred and fluidized, and an atmospheric gas is circulated in a reaction vessel. It is a schematic diagram which shows another example to perform.

  Hereinafter, embodiments of the present invention will be described in detail. In the method for producing surface-treated oxide particles according to the present invention, surface treatment is performed by a gas phase method in which oxide particles having an alkaline compound on part or all of the particle surface are brought into contact with a gas containing a volatile trimethylsilylating agent. Thus, a dense hydrophobic product is easily formed on the surface of the oxide particles, and high-performance surface-treated oxide particles can be produced at low cost.

  The surface-treated oxide particles can be used, for example, to suppress gelation of an active material paste of an electrolyte-based secondary battery by trimethylsilylating an alkali component on the surface of the oxide particles, or to form a sulfide-based all-solid secondary. In order to reduce the interfacial resistance of the active material particles / sulfide-based solid electrolyte of the battery, it is suitable for the (active electrode, negative electrode) active material layer of an electrolyte-based secondary battery or an all-solid secondary battery.

[Oxide particle having alkaline compound on part or all of particle surface]
First, the oxide particles before surface treatment used in the present invention will be described. The oxide particles used in the present invention are oxide particles having an alkaline compound on part or all of the particle surface. The oxide particles are roughly classified into oxide particles for a positive electrode active material and oxide particles for a negative electrode active material, which will be specifically described below.

(A) Oxide Particles for Positive Electrode Active Material For example, in the case of a lithium ion battery, the positive electrode active material is a substance that can easily release and adsorb lithium ions and can release and occlude many lithium ions. Well, lithium-cobalt oxide (LiCoO ₂ [lithium cobaltate], LiCo ₂ O ₄ etc.) (referred to as LCO), lithium-nickel oxide (LiNiO ₂ [lithium nickelate], LiNi ₂ O ₄ etc.) ( Called LNO.), Lithium-manganese oxide (LiMnO ₂ [lithium manganate], LiMn ₂ O ₄ , Li ₂ Mn ₂ O ₄ etc.) (called LMO), lithium-manganese-cobalt oxide (LiMnCoO ₄ , _Li 2 MnCoO _4, etc.), lithium - nickel - manganese - cobalt oxide (Li (Ni _Mn-Co) called _{O 2, LiNi 1/3 Mn 1/3 Co} 1/3 O 2 , etc.) (NMC or NCM), lithium -. Nickel - cobalt - aluminum oxide (Li (Ni-Co-Al ) O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ etc.) (referred to as NCA), lithium-manganese-nickel oxide (Li (Mn _3/2 Ni _1/2 ) O ₄ etc.), Solid solution system (excess system) manganese-containing lithium composite oxide (for example, Li ₂ MnO ₃ —LiMO ₂ [M: Ni, Mn, Co, etc.]), lithium-titanium oxide (Li ₄ Ti ₅ O ₁₂ , LiTi ₂ O _4, etc.) are referred to as (LTO.), and other lithium oxide containing a transition metal _{(Li 2 CuO 2, LiCuO 2} , LiVO 2, LiV 2 O 4, LiCrO 2, Li _{eO 2, LiTiO 2, LiScO 2} , LiYO 2, LiMnCrO 4, LiNiVO 4, LiCoVO 4 , etc.), lithium phosphates including various transition metals (LiFePO ₄ [lithium iron phosphate] called (LFP.), LiCuPO ₄ , LiNiPO ₄ , LiCoPO ₄ , LiMnPO ₄ , Li ₂ NiPO ₄ F, Li ₂ CoPO ₄ F, Li ₂ MnPO ₄ F, Li ₂ FePO ₄ F, LiVOPO ₄ , Li ₃ V ₂ (PO ₄ ) _3, etc. Lithium silicate containing transition metals (Li ₂ MnSiO ₄ , Li ₂ FeSiO ₄ , Li ₂ CoSiO ₄ , Li ₂ NiSiO ₄ etc.), sulfides of various transition metals (TiS ₂ , MoS ₂ , FeS, FeS ₂ , CuS) , _Ni 3 _S 2), various oxides of transition metals (Bi _{2 3, Bi 2 Pb 2 O 5} , CuO, may be used _{V 2 O 5, V 6 O} 13, Nb 2 O 5 , etc.) and the like. Moreover, you may mix and use these.

In addition, for example, in sodium ion battery applications, any substance that can easily release and adsorb sodium ions and can release and occlude many sodium ions may be used. Sodium-iron oxide (NaxFeO ₂ ; 2/3) ≦ X ≦ 1), sodium-nickel-manganese oxide (Nax (Ni—Mn) O ₂ ; 2/3 ≦ X ≦ 1, Na _0.67 Ni _0.5 Mn _0.5 O ₂ , NaNi _0.5 Mn _0.5 O ₂ etc.), sodium-iron-manganese-nickel oxide (Na (Fe—Mn—Ni) O ₂ , NaFe _0.4 Mn _0.3 Ni _0.3 O ₂ etc.), various transition metals Sodium phosphate (NaFePO ₄ , Na ₂ FeP ₂ O ₇ , Na ₄ M ₃ (PO ₄ ) ₂ P ₂ O ₇ [M: Mn, Co, Ni], etc.) and the like can be used. Moreover, you may mix and use these.

  Here, there is no clear distinction between the positive electrode active material and the negative electrode active material, the charge / discharge potentials of the two types of compounds are compared, the positive potential is the positive electrode active material, and the base potential is the negative electrode active material. Can be used.

Among the many positive electrode active materials described above, for lithium ion battery applications, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium-nickel-cobalt-aluminum oxide (Li (Ni -Co-Al) O ₂ etc.), lithium-nickel-manganese-cobalt oxide (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ), lithium-manganese oxide (LiMn ₂ O as a spinel material) ₄ ) Lithium iron phosphate (LiFePO ₄ ) or the like as an olivine-based material is suitable and is generally used. Furthermore, lithium-manganese-nickel oxide (Li (Mn _3/2 Ni _1/2 ) as a spinel material that is charged and discharged at a high voltage (5 V region), which is being developed for higher energy. O _{4 and the} like, and a solid solution system (also called “excess system”) manganese-containing lithium composite oxide as a layered material having a high capacity (for example, Li ₂ MnO ₃ —LiMO ₂ [M: Ni, Mn, Co, etc.) ]) Etc. can also be used suitably.

(B) Oxide particles for negative electrode active material As described above, there is no clear distinction between the negative electrode active material and the positive electrode active material, and the material forming the negative electrode active material is, for example, a lithium ion battery. Any substance can be used as long as it is easy to adsorb and desorb, and can absorb and desorb a large amount of lithium ions. For example, lithium-titanium oxide (Li ₄ Ti ₅ O ₁₂ , LiTi ₂ O ₄ etc.), lithium-titanium - niobium oxide _{(Li 4 (T i2 Nb 3} ) O 12 , etc.), various metal oxides _{(Nb 2 O 5, V 2} O 5, NiO, In 2 O 3, SnO 2, ZnO, TiO 2 , etc.), etc. Can be used. Moreover, you may mix and use these. Among the many oxide particles of the negative electrode active material, lithium titanate (Li ₄ Ti ₅ O ₁₂ ) or the like is widely used.

In addition, for example, in sodium ion battery applications, any substance that can easily adsorb and desorb sodium ions and can occlude and desorb many sodium ions may be used. For example, sodium-titanium oxide (Na ₂ Ti ₃ O ₇ etc.), metal oxides (SnO ₂ etc.), etc. can be used.

In the present invention, as oxide particles having an alkaline compound on part or all of the particle surface, (1) hydroxylation of lithium (Li), sodium (Na), or magnesium (Mg) is part or all of the particle surface. Oxide particles coated with one or more selected from the group of products, carbonates, oxides (for example, lithium hydroxide (LiOH), lithium carbonate (LiCO ₃ ), lithium oxide (Li ₂ O), etc.), And (2) any one or more alkali oxides selected from the group of oxides of lithium (Li), sodium (Na), and magnesium (Mg) are in excess of the stoichiometric composition. Alkali composite oxides (for example, oxides containing excessive lithium in the positive electrode active materials such as LNO, NCA, NMC, etc. and manganese containing solid solution (excess system)) Oxide particles of a lithium composite oxide or the like). In the case of the latter (2), the presence of the alkaline compound on the surface of the oxide particles is naturally increased even if the alkaline coating or the like is not applied as in the former (1), and the trimethylsilylation reaction on the surface of the oxide particles is performed. Is promoted to enable more uniform surface treatment, which is preferable.

In addition, for example, when a lithium composite oxide is used as the alkali composite oxide in which the alkali oxide is contained in excess of the stoichiometric composition, excessive lithium oxide (alkali compound) on the surface of the oxide particles is used. Is expected to come into contact with moisture in the atmosphere (even if very little) in the course of particle handling, and some or all of it may be lithium hydroxide (alkaline compound) (LiO _{0). .5} + 0.5H ₂ O → LiOH) is fully conceivable. Of course, the alkaline compound in the present invention includes the above hydroxides.

[Volatile trimethylsilylating agent]
Next, the volatile trimethylsilylating agent used in this embodiment will be described. The volatile trimethylsilylating agent used in the present embodiment is a compound whose vapor reacts with an alkaline compound existing on the surface of the oxide particles via a gas phase, and needs to be a compound containing a trimethylsilyl group. is there. Specifically, ((CH ₃ ) ₃ Si) ₂ NR (R: hydrogen or lower alkyl group) or (CH ₃ ) ₃ SiY (Y: —OH, —OR, or —NR _{2 is} selected. It is preferably any one or more selected from the group of compounds represented by a group (R: hydrogen or lower alkyl group).

  Further, the volatile trimethylsilylating agent used in the present embodiment preferably has a boiling point of 250 ° C. or lower, more preferably 150 ° C. or lower.

The volatile trimethylsilylating agent used in this embodiment is more specifically hexamethyldisilazane (other names: 1,1,1,3,3,3-hexamethyldisilazane, bis (trimethylsilyl). ) Amine, HMDS) (boiling point: 125 ° C., melting point: −78 ° C .; vapor pressure: 2.7 kPa [20 ° C.]), N-methyl-hexamethyldisilazane, N-ethyl-hexamethyldisilazane, hexamethyl-N -Propyldisilazane and the like can be mentioned, and it is particularly preferable to use hexamethyldisilazane because of its good reactivity. On the other hand, as an example of a trimethylsilylating agent represented by (CH ₃ ) ₃ SiY, trimethylsilanol (another name: trimethylhydroxysilane) (boiling point: 98.6 to 99 ° C., melting point: −9.8 ° C .; vapor pressure: 1.84 kPa [25 ° C.]), triethylsilanol (triethylhydroxysilane) (boiling point: 154 ° C.), methoxytrimethylsilane, ethoxytrimethylsilane, propoxytrimethylsilane, dimethylaminotrimethylsilane, diethylaminotrimethylsilane, etc. Hexamethyldisilazane, trimethylsilanol, and the like, which have relatively high volatility (relatively low boiling point) and low risk and toxicity, are preferable.

  The volatile trimethylsilylating agent used in the present invention is not particularly limited to the above compound as long as the vapor reacts with the alkaline compound present on the surface of the oxide particles via the gas phase.

[Method for producing surface-treated oxide particles]
The manufacturing method of the surface-treated oxide particle of this invention is demonstrated in detail. In the method for producing surface-treated oxide particles according to the present invention, the volatile trimethylsilylating agent vapor is brought into contact with oxide particles having an alkaline compound on part or all of the particle surface, and the volatile A dense hydrophobic product having a trimethylsilyl group is formed by a vapor phase method in which the vapor of the trimethylsilylating agent is selectively or preferentially reacted with the alkaline compound portion on the particle surface.

  As described above, the production method of the present invention uses a gas phase method, and unlike the liquid phase method (wet method) in which a coating layer is formed on the particle surface in the liquid, the oxide particle surface has, for example, a single molecule. Thus, a uniform surface treatment layer having a single nano-level thickness can be formed.

  As a result, as shown in FIG. 3A, the oxide particles are composed of primary particles 10 (for example, average particle size: 0.1 to 1 μm) aggregated in a lump shape, for example, secondary particles 11 (for example, 3 (average particle diameter: several to several tens of μm), and when there are open pores (open pores) 12 between the primary particles 10, the open pores (open) as shown in FIG. There is also a feature that a single nano (nm) level uniform surface treatment layer 13b can be formed on the surface of the primary particle 10 through the pores 12.

  On the other hand, in the surface treatment by the liquid phase method (wet method), usually, as shown in FIG. 3B, the coating layer 13a can be mainly formed mainly on the surface of the secondary particles 11, and the primary particles 10 are particularly small ( For example, when the particle size is nano (nm) to sub-micron order, the surface treatment layer 13b can hardly be formed on the surface of the primary particle 10 in the open pores 12 (open pores).

  When the rolling fluidized bed coating, which is one of the dry coatings described above, is used, unlike the surface treatment by the liquid phase method (wet method), the nano (nm) level uniform surface treatment layer (coating layer). However, since the precipitation reaction (coating layer formation) occurs mainly in the vicinity of the surface of the secondary particles 11, the primary in the open pores (open pores) 12 as in the surface treatment of the vapor phase method of the present invention. The surface treatment layer 13b cannot be formed every corner of the particle 10 surface.

  Not only the surface of the secondary particles 11 of the oxide particles described above, but also the surface of the open pores 12 between the primary particles 10, more specifically, the primary in the secondary particles 11. According to the present invention, a uniform surface treatment layer 13b of nano (nm) level can be formed on the surface of the particle 10 and the surface exposed to the open pores 12 between the primary particles 10. The feature is that in the electrolyte-based lithium ion battery, all contact surfaces (the surface of the secondary particles 11 and the surface of the open pores 12) of the electrolyte and the positive electrode active material are protected by the surface treatment layer. This leads to an advantage that deterioration of the positive electrode active material material due to charge / discharge can be further suppressed. On the other hand, in the surface treatment by a liquid phase method (wet method), the surface of the open pores (open pores) 12 is not protected by the surface treatment layer, and the positive electrode active material in that portion is deteriorated by charge / discharge by contacting with the electrolyte Therefore, suppression of deterioration of the positive electrode active material becomes insufficient. The characteristics of the present invention are also effective from the viewpoint of suppressing elution of the positive electrode active material component into the electrolyte solution. For example, positive electrode active material particles containing manganese (Mn) that are easily eluted into the electrolyte solution are used. In the case of an electrolyte-based lithium ion battery, the surface treatment by the vapor phase method of the present invention can significantly suppress manganese elution into the electrolyte compared to the surface treatment by a liquid phase method (wet method).

  In the method for producing surface-treated oxide particles according to the present invention, the oxide particles having an alkaline compound on part or all of the particle surface are brought into contact with a gas containing a volatile trimethylsilylating agent. (A) a surface treatment step for forming a hydrophobic product having a trimethylsilyl group on the surface, and (b) a heat treatment step for heating the oxide particles having the hydrophobic product having a trimethylsilyl group on the surface, if necessary. After that.

(A) Surface treatment process As shown in FIG. 4, for example, the surface treatment process includes an oxide particle storage container 15 and a volatile trimethylsilylating agent storage container 17 in a reaction container 14. Predetermined amounts of the oxide particles 16 and the volatile trimethylsilylating agent 18 are put in a storage container and left in an atmosphere gas.

  The reaction container 14 needs a highly sealed container so that atmospheric gas and vapor of the volatile trimethylsilylating agent do not leak to the outside, and the material thereof is a plastic such as polyethylene, polypropylene, Teflon (registered trademark), Examples thereof include ceramics such as alumina, quartz, and glass, stainless steel (SUS304, SUS316, etc.), metals such as titanium, and the like, as long as they do not react with the vapor of the volatile trimethylsilylating agent. .

  The oxide particle storage container 15 and the volatile trimethylsilylating agent storage container 17 do not react with the oxide particles having an alkaline compound or the volatile trimethylsilylating agent 18 and need to be durable. Examples thereof include plastics such as polyethylene, polypropylene, and Teflon, ceramics such as alumina, quartz, and glass, metals such as stainless steel and titanium, and the kind of oxide particles having an alkaline compound and volatile trimethylsilylating agent 18 to be used. It is possible to select appropriately according to.

The atmospheric gas needs not to react with the oxide particles having an alkaline compound or the volatile trimethylsilylating agent 18, and examples thereof include air, nitrogen, and argon. Carbon dioxide gas (CO ₂ ) and moisture (H ₂ O) are generally easily removed from the atmospheric gas because they easily react with the oxide particles having an alkaline compound and the volatile trimethylsilylating agent 18. Desirably, for example, dry air (dew point temperature: −30 ° C. or lower, preferably −50 ° C. or lower), dry air treated with decarbonation gas, high purity nitrogen, high purity argon, or the like is preferable. Depending on the type of volatile trimethylsilylating agent 18, there is a risk of explosion depending on the mixing ratio of steam with air or the like, or it may be oxidized and deteriorated by oxygen. Nitrogen or argon must be used, but in any case, it may be appropriately selected according to the type of the oxide particles having an alkaline compound to be used and the volatile trimethylsilylating agent 18.

  In the reaction vessel 14, the vapor of the volatile trimethylsilylating agent 18 diffuses from the storage vessel 17 of the volatile trimethylsilylating agent into the atmospheric gas, while the volatile trimethylsilylating agent 18 diffused into the atmospheric gas. Is consumed by reacting with an alkaline compound on the surface of the oxide particles 16 in the oxide particle storage container 15, and therefore the oxide from the volatile trimethylsilylating agent storage container 17 with the passage of the reaction time. The volatile trimethylsilylating agent 18 is mass transferred into the particle storage container 15.

  For example, when the alkaline compound is lithium hydroxide (LiOH), the reaction between the vapor of the volatile trimethylsilylating agent 18 and the oxide particles having an alkaline compound may be performed by adding hexamethyldisulfide to the volatile trimethylsilylating agent 18. Assuming that silazane (other names: 1,1,1,3,3,3-hexamethyldisilazane, bis (trimethylsilyl) amine, HMDS) and trimethylsilanol (trimethylhydroxysilane) were used, Reaction formulas (1) to (2) shown are conceivable.

  Here, the control of the surface treatment amount (or the thickness of the surface treatment layer) of the oxide particles having an alkaline compound by the volatile trimethylsilylating agent 18 can be performed as follows, for example. First, the oxide particles 16 having a predetermined amount of an alkaline compound are placed in a container 15 for oxide particles, and an amount of the volatile trimethylsilylating agent 18 that is desired to be surface-treated with respect to the oxide particles having the alkaline compound is added. After being put in the storage container 17 for the volatile trimethylsilylating agent, the atmosphere gas is filled in the reaction container 14 and left as it is, and the volatile trimethylsilylating agent 18 in the storage container 17 for the volatile trimethylsilylating agent is obtained. The reaction is terminated when it disappears completely.

  By this method, all of the volatile trimethylsilylating agent 18 charged into the reaction vessel 14 is consumed for the surface treatment of the oxide particles having an alkaline compound. The blending ratio of the trimethylsilylating agent 18 (oxide particles having an alkaline compound: volatile trimethylsilylating agent 18 [weight ratio]) is the same as the oxide particles having an alkaline compound of the oxide particles after the surface treatment and volatile trimethylsilyl. The mixing ratio of the agent 18 is obtained.

In the surface treatment by the vapor phase method of the present invention, as described above, a surface treatment layer (coating layer) is also formed on the surface of the primary particles 10 in the open pores (open pores) 12, so that a predetermined surface is formed. The blending ratio of the oxide particles having an alkaline compound and the volatile trimethylsilylating agent 18 to obtain a treatment layer (coating layer) is determined by the specific surface area (BET value [unit: m ₂ / g] of the oxide particles to be used. ) Is desirable.

  In carrying out the surface treatment step, it is preferable to forcibly convection the atmospheric gas containing the volatile trimethylsilylating agent 18 vapor in the reaction vessel 14 using a fan 19 or the like, as shown in FIG. Due to the convection of the atmospheric gas, the volatile trimethylsilylating agent 18 vapor moves in a shorter time from the inside of the volatile trimethylsilylating agent storage container 17 to the oxide particles having the alkaline compound (oxide particles 16). This is because the surface treatment time can be greatly shortened.

  Further, as shown in FIG. 6, an atmospheric gas containing volatile trimethylsilylating agent 18 vapor is supplied into the reaction vessel 14 at a predetermined flow rate to have an alkaline compound in the oxide particle storage vessel 15. It is also possible to perform surface treatment of the oxide particles (oxide particles 16).

  Further, as shown in FIG. 7, the atmosphere gas containing the vapor of the volatile trimethylsilylating agent 18 supplied into the reaction vessel 14 in FIG. The surface treatment of the oxide particles 16 having an alkaline compound within 15 can also be performed.

  Moreover, as shown in FIGS. 8-11, it is preferable that the oxide particle (oxide particle | grains 16) which have an alkaline compound in the storage container 15 of an oxide particle is stirred and fluidized. The flow of the oxide particles having an alkaline compound significantly increases the substantial area of the surface of the oxide particles that can be reacted with the vapor of the volatile trimethylsilylating agent 18, and at the same time, the contact opportunity becomes uniform. This is because the reaction rate can be greatly increased, and at the same time, a hydrophobic product having a trimethylsilyl group generated by the reaction can be uniformly formed on the oxide particles. That is, the flow of the oxide particles increases the surface treatment speed of the oxide particles by the volatile trimethylsilylating agent 18, and at the same time, can suppress variations in the surface treatment within and between the oxide particles. have.

  In FIG. 11, in the method for performing the surface treatment by circulating the atmospheric gas shown in FIG. 10, the volatilization vessel 21 for volatilizing the volatile trimethylsilylating agent 18 is independent of the reaction vessel 14 for performing the surface treatment. It is installed in the atmospheric gas circulation path. The oxide particle storage container 15 is also used as the reaction container 14, and the reaction container 14 is slowly rotated to stir and flow the oxide particles (oxide particles 16) having an alkaline compound. In this system, for example, a volatile trimethylsilylating agent can be obtained by using a transparent member such as glass in the storage container 17 or the volatile container 21 of the volatile trimethylsilylating agent or by installing a transparent window for visual recognition. There is an advantage that the volatilization amount of 18 (ie, surface treatment amount) can be easily grasped.

  Further, when a heater or the like is installed at an arbitrary place in the circulation path of the atmospheric gas and the atmospheric gas is heated and heated, the volatile container 21, the volatile trimethylsilylating agent 18, the reaction container 14, and the alkaline compound are contained. Since the temperature of the oxide particles (oxide particles 16) can be increased, the surface treatment in a heated state can be easily performed. In the surface treatment in the heated state, since the volatile trimethylsilylating agent 18 which is not so volatile can be applied to the surface treatment, there is an advantage that the degree of freedom of the volatile trimethylsilylating agent 18 that can be utilized is widened.

(B) Heat treatment step The next heat treatment step may be performed at 100 to 500 ° C, preferably 120 to 300 ° C, as necessary. By applying a heat treatment step, the crystallinity of the hydrophobic product having trimethylsilyl groups formed on the surface of the oxide particles is increased, and impurities such as organic components and trace moisture are removed from the hydrophobic product having trimethylsilyl groups. There are cases where it is possible.

  The surface-treated oxide particles obtained by the above method are prepared as a conventionally known (positive electrode, negative electrode) active material layer forming paste or solid electrolyte layer forming coating solution. The application of the paste or the coating liquid is preferably performed in a clean atmosphere such as a clean room where temperature and humidity are controlled. The temperature is generally room temperature (25 ° C.) and the humidity is generally 40 to 60% RH.

  As described above, the method for producing surface-treated oxide particles according to the present invention is a simple method using a gas phase method, and the surface of the oxide particles (the surface of the secondary particles and the space between the primary particles). Since a dense and uniform nano-order surface treatment layer can be formed on the surface of the open pores (open pores), high-performance oxide particles can be produced at low cost. In addition, the oxide particles obtained by this method are used to suppress gelation of an active material layer forming paste (active material paste) of an electrolyte-based secondary battery, or active material particles / sulfurization of a sulfide-based all-solid secondary battery. It is effective for reducing the interfacial resistance of solid electrolytes, and is applied to the active material layer (positive electrode, negative electrode) of electrolyte-based secondary batteries and all-solid secondary batteries to reduce the cost and improve characteristics of secondary batteries It can make a big contribution.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to these Examples.

<Example 1>
[Oxide particles]
The oxide particles are made of lithium-nickel-cobalt-aluminum oxide (Li _{1 + x} Ni _0.82 Co _0.15 Al _0.03 O ₂ ; x = 0.05) used for the positive electrode active material of the lithium ion battery. Oxide particles were used. The above composition contains 0.05 times (molar ratio) lithium oxide (LiO _0.5 ) in excess of the stoichiometric composition (LiNi _0.82 Co _0.15 Al _0.03 O ₂ ). Therefore, the oxide particles are hereinafter referred to as lithium oxide excess containing NCA particles. The excessively contained lithium oxide seems to be dissolved in the NCA particles, and therefore, the excess lithium oxide (alkaline compound) is uniformly distributed on the surface of the lithium oxide excessively containing NCA particles. Presumed to exist. The oxide particles are secondary particles having a particle size of 5 to 15 μm and composed of primary particles having a particle size of 0.3 to 1 μm, and an open space of 10 nm to several hundreds of nm is formed between the primary particles. It has a hole (open pore).

[Surface treatment of oxide particles]
As shown in FIG. 5, 120 g of the lithium oxide-excess-containing NCA particles as oxide particles 16 are placed in an oxide particle storage container 15 (glass petri dish), and hexamethyldisilazane ( Other names: 1,1,1,3,3,3-hexamethyldisilazane, bis (trimethylsilyl) amine, HMDS) [((CH ₃ ) ₃ Si) ₂ NH] (boiling point: 125 ° C., melting point: −78 2.8 g of vapor pressure: 2.7 kPa [20 ° C.]) is placed in a storage container 17 (glass petri dish) of volatile trimethylsilylating agent, and they are placed in a reaction container 14 (glass desiccator). After filling the atmosphere gas with nitrogen (dew point temperature: −60 ° C.), the fan 19 circulates the atmosphere gas in the reaction vessel 14 and releases it at room temperature (25 ° C.) for 12 hours. Then, the lithium oxide (or lithium hydroxide) (alkaline compound) present on the surface of the NCA particles containing excessive lithium oxide is reacted with the vapor of hexamethyldisilazane through the gas phase to obtain an excess of lithium oxide. The surface according to Example 1, in which a hydrophobic product having a trimethylsilyl group is formed on the surface of the contained NCA particles, and then heat treatment is performed at 120 ° C. for 30 minutes in dry air (dew point temperature: −60 ° C.). Surface-treated oxide particles according to Example 1 whose surface was coated with the above-described hydrophobic product having a trimethylsilyl group by the method for producing treated oxide particles (NCA particles as a positive electrode active material of a lithium ion battery) )

  The hexamethyldisilazane in the volatile trimethylsilylating agent storage container 17 (glass petri dish) completely disappeared after standing for 12 hours, and all have trimethylsilyl groups on the surface of the lithium oxide-excess-containing NCA particles. It is believed that it was consumed in forming the hydrophobic product.

  The surface treated oxide particles coated with the hydrophobic product having the trimethylsilyl group (the NCA particles as the positive electrode active material of the lithium ion battery) were observed with a scanning microscope (SEM). There was no significant difference in the particle surface shape before and after the treatment, and since silicon (Si) was detected on the particle surface by secondary ion mass spectrometry (SIMS), a monomolecular trimethylsilyl group reacted on the particle surface. It was confirmed that a uniform coating layer having a single nano-level thickness was formed.

[Characteristic evaluation]
Next, using the prepared oxide particles (NCA particles as a positive electrode active material of a lithium ion battery) coated with a hydrophobic product having a trimethylsilyl group, a paste for forming a positive electrode active material layer was prepared. However, it was confirmed that even if it was allowed to stand at room temperature (25 ° C.) for 7 days, it did not gel (purinate) and maintained fluidity.

  The paste for forming the positive electrode active material layer includes oxide particles subjected to surface treatment as a positive electrode active material, acetylene black (AB) as a conductive additive, polyvinylidene fluoride (PVDF) as a binder (binder), N-methylpyrrolidone (NMP) as an organic solvent is mixed and dispersed so as to be oxide particles: AB: PVDF: NMP = 45: 2.5: 2.5: 50 (weight ratio). (Oxide particles and AB are dispersed in NMP in which PVDF is dissolved).

  In addition, in a coin cell (positive electrode active material / electrolytic solution (separator) / negative electrode active material (Li foil)) using a positive electrode active material layer obtained by applying, drying, and pressurizing the paste for forming a positive electrode active material layer. The positive electrode capacity was measured and found to be 195 mAh / g (rate: 0.05C).

<Example 2>
The method for producing surface-treated oxide particles according to Example 2 is performed in the same manner as in Example 1 except that heat treatment is performed at 200 ° C. for 30 minutes instead of 30 minutes at 120 ° C. Thus, surface-treated oxide particles (NCA particles as a positive electrode active material of a lithium ion battery) according to Example 2 whose surface was coated with the hydrophobic product having the trimethylsilyl group were obtained.

[Characteristic evaluation]
Next, using the surface-treated oxide particles (NCA particles as a positive electrode active material of a lithium ion battery) coated with a hydrophobic product having a trimethylsilyl group, the positive electrode active material layer was formed in the same manner as in Example 1. When the forming paste was produced, it was confirmed that even if it was left at room temperature (25 ° C.) for 7 days, it did not gel (purinate) and maintained fluidity.

  In addition, in a coin cell (positive electrode active material / electrolytic solution (separator) / negative electrode active material (Li foil)) using a positive electrode active material layer obtained by applying, drying, and pressurizing the paste for forming a positive electrode active material layer. When the positive electrode capacity was measured, it was 193 mAh / g.

<Example 3>
In Example 1, trimethylsilanol (another name: trimethylhydroxysilane) (boiling point: 98.6 to 99 ° C., melting point: −9.8 ° C .; vapor pressure: 1.84 kPa [25 ° C.) as the volatile trimethylsilylating agent 18. The surface was coated with the above-mentioned hydrophobic product having a trimethylsilyl group by the method for producing surface-treated oxide particles according to Example 3 except that 3.1 g was used. The surface-treated oxide particle (NCA particle as a positive electrode active material of a lithium ion battery) according to Example 3 was obtained.

  The surface treated oxide particles coated with the hydrophobic product having the trimethylsilyl group (the NCA particles as the positive electrode active material of the lithium ion battery) were observed with a scanning microscope (SEM). There was no significant difference in the particle surface shape before and after the treatment, and since silicon (Si) was detected on the particle surface by secondary ion mass spectrometry (SIMS), a monomolecular trimethylsilyl group reacted on the particle surface. It was confirmed that a uniform coating layer having a single nano-level thickness was formed.

[Characteristic evaluation]
Next, using the surface-treated oxide particles (NCA particles as a positive electrode active material of a lithium ion battery) coated with a hydrophobic product having a trimethylsilyl group, the positive electrode active material layer was formed in the same manner as in Example 1. When the forming paste was produced, it was confirmed that even if it was left at room temperature (25 ° C.) for 7 days, it did not gel (purinate) and maintained fluidity.

  In addition, in a coin cell (positive electrode active material / electrolytic solution (separator) / negative electrode active material (Li foil)) using a positive electrode active material layer obtained by applying, drying, and pressurizing the paste for forming a positive electrode active material layer. When the positive electrode capacity was measured, it was 194 mAh / g.

<Comparative Example 1>
In Example 1, the surface treatment of the oxide particles was not performed, and the lithium oxide-excess-containing NCA particles of Example 1 were formed as oxide particles 16 at 120 ° C. for 30 minutes in dry air (dew point temperature: −60 ° C.). The oxide particles (NCA particles as a positive electrode active material of a lithium ion battery) according to Comparative Example 1 whose surface was not coated with a hydrophobic product having a trimethylsilyl group were obtained.

[Characteristic evaluation]
Next, using the prepared non-surface-treated oxide particles (NCA particles as a positive electrode active material of a lithium ion battery), a positive electrode active material layer forming paste was prepared in the same manner as in Example 1. After standing for 8 hours at (° C.), it was confirmed that it had already gelled (pudding) and lost fluidity.

  In addition, a coin cell (positive electrode active material / electrolytic solution (separator) //) using a positive electrode active material layer obtained by applying, drying, and pressurizing before the above-mentioned positive electrode active material layer forming paste is gelled (pudding) When the positive electrode capacity was measured with a negative electrode active material (Li foil)), it was 194 mAh / g (rate: 0.05C).

  Comparing Examples 1 to 3 with Comparative Example 1, all use NCA particles containing excessive lithium oxide as oxide particles, and the same positive electrode capacity (193 to 195 mAh / g (rate: 0.05C)) is obtained. However, when the surface treatment is performed by the vapor phase method of each example, the produced paste for forming the positive electrode active material layer is gelled (purinized) even if it is left at room temperature (25 ° C.) for 7 days or longer. In the case where the surface treatment was not performed by the vapor phase method of Comparative Example 1, the gelation (purification) was already performed after standing for 8 hours at room temperature (25 ° C.). It was confirmed that the liquidity was lost. The reason for this is that in the surface-treated oxide particles of the present invention, elution of alkali components from the oxide particles into the positive electrode active material layer forming paste is suppressed by the surface treatment, and the binder (binder) in the paste It is presumed that the PVDF as is difficult to be polymerized by the alkali component and gelation can be suppressed.

  According to the method for producing surface-treated oxide particles according to the present invention, a dense and uniform nano-order surface treatment layer can be obtained by a simple method using a gas phase method, so that high-performance oxide particles can be produced at low cost. it can. Further, the oxide particles obtained by this method are used for suppressing gelation of the active material layer forming paste (active material paste) of the electrolyte-based secondary battery, and for the active material particles / sulfide-based all-solid secondary battery. Effective in reducing the interfacial resistance of sulfide-based solid electrolytes, when applied to the active material layer (positive electrode, negative electrode) of electrolyte-based secondary batteries and all-solid secondary batteries, the cost of secondary batteries can be reduced. Improvement in characteristics can be expected.

DESCRIPTION OF SYMBOLS 1 Positive electrode collector 2 Positive electrode active material layer 3 Separator 4 Electrolyte 5 Negative electrode active material layer 6 Negative electrode collector 7 Electrode lead (extraction electrode)
8 Container 9 Solid electrolyte layer 10 Primary particles of oxide particles 11 Oxide particles composed of aggregated primary particles (secondary particles)
12 Open pores between primary particles of oxide particles
13a Coating layer 13b Surface treatment layer 14 Reaction vessel 15 Oxide particle storage container 16 Oxide particle 17 Volatile trimethylsilylating agent storage container 18 Volatile trimethylsilylating agent 19 Fan (for atmospheric gas circulation or atmospheric gas blowing for)
20 Stirring blade (for stirring oxide particles)
21 Volatile containers

Claims (10)

Oxide particles having an alkaline compound on part or all of the particle surface are brought into contact with a gas containing a volatile trimethylsilylating agent, and trimethylsilyl groups are formed by a reaction between the alkaline compound and the trimethylsilylating agent via a gas phase. A method for producing surface-treated oxide particles, which forms an oxide particle having a hydrophobic product having a trimethylsilyl group on part or all of the particle surface,
The alkaline compound is any one or more selected from the group of compounds containing lithium (Li), sodium (Na), and magnesium (Mg),
The oxide particles include one or more transition metals selected from the group consisting of manganese, cobalt, nickel, iron, and titanium, and are selected from the group consisting of lithium (Li), sodium (Na), and magnesium (Mg). A method for producing surface-treated oxide particles, which is an alkali composite oxide containing at least one alkali element. The volatile trimethylsilylating agent is ((CH ₃ ) ₃ Si) ₂ NR (R: hydrogen or lower alkyl group) or (CH ₃ ) ₃ SiY (Y: —OH, —OR, or —NR). _{2. The} method for producing surface-treated oxide particles according to claim 1, which is at least one selected from the group of compounds represented by a group selected from ₂ (R: hydrogen or lower alkyl group).   The oxide particles having an alkaline compound on part or all of the particle surface are oxide particles in which part or all of the particle surface is coated with an alkali component, and the alkali component is lithium (Li), sodium ( The production of surface-treated oxide particles according to claim 1 or 2, wherein the particles are any one or more selected from the group consisting of Na), magnesium (Mg) hydroxide, carbonate, and oxide. Method. The surface treatment according to claim 3, wherein the alkaline component is at least one selected from the group consisting of lithium hydroxide (LiOH), lithium carbonate (LiCO ₃ ), and lithium oxide (Li ₂ O). Method for producing oxide particles.   In the alkali composite oxide, the alkaline compound is one or more alkali oxides selected from the group of lithium (Li), sodium (Na), and magnesium (Mg) oxides in excess of the stoichiometric composition. The method for producing surface-treated oxide particles according to any one of claims 1 to 4, wherein the oxide is an alkali composite oxide.   The method for producing surface-treated oxide particles according to any one of claims 1 to 5, wherein the boiling point of the volatile trimethylsilylating agent is 250 ° C or lower.   The volatile trimethylsilylating agent is at least one of hexamethyldisilazane (boiling point: 125 ° C) and trimethylsilanol (boiling point: 98.6 to 99 ° C). A method for producing surface-treated oxide particles.   The surface-treated oxide particles according to any one of claims 1 to 7, wherein after the formation of the hydrophobic product having the trimethylsilyl group, heat treatment is performed at 100 ° C to 500 ° C. Manufacturing method. The alkaline composite _{oxide, LiMO 2, LiMPO 4, Li} 2 MSiO 4 (M: manganese, cobalt, nickel, any one or more transition metals selected from the group consisting of _{iron), LiYaMn 2 -aO 4 (Y} : Cobalt , Nickel; 0 ≦ a ≦ 1), Li ₂ MnO ₃ —LiMO ₂ (M: one or more transition metals selected from the group consisting of manganese, cobalt, and nickel) and Li ₄ Ti ₅ O ₁₂ The method for producing surface-treated oxide particles according to any one of claims 1 to 8, wherein any one or more of them is a main component.   The oxide particles obtained by the method for producing surface-treated oxide particles according to claim 1, wherein the oxide particles are secondary particles composed of primary particles. The hydrophobic product having the trimethylsilyl group is formed on the surface of the primary particle inside the secondary particle and exposed on the open pore side between the primary particles. Oxide particles characterized by.

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