JP2019012654A - Positive electrode material for nonaqueous electrolyte secondary battery, manufacturing method thereof, and nonaqueous electrolyte secondary battery using positive electrode material - Google Patents

Abstract

To provide a positive electrode material for a nonaqueous electrolyte secondary battery capable of obtaining a high output while suppressing a decrease in capacity when used for a positive electrode.SOLUTION: In a positive electrode material for a nonaqueous electrolyte secondary battery containing a mixture of a powder of a positive electrode active material composed of primary particles and/or secondary particles of lithium metal composite oxide and preferably having a specific surface area of 0.5 to 2.0 m/g, a powder of lithium nitride phosphate preferably having a median diameter D50 of 0.01 to 0.50 μm, and nonaqueous organic solvent, 20 to 40 parts by mass of the nonaqueous organic solvent is contained relative to 100 parts by mass of the powder of the positive electrode active material, and preferably 0.1 to 2.0 parts by mass of the powder of the lithium nitride phosphate is contained in 100 parts by mass of the powder of the positive electrode active material.SELECTED DRAWING: None

Description

  The present invention relates to a positive electrode material for a non-aqueous electrolyte secondary battery, a manufacturing method thereof, and a non-aqueous electrolyte secondary battery using the positive electrode material.

  With the recent popularization of portable electronic devices such as mobile phones and notebook computers, development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density is strongly desired. In addition, development of a high-power secondary battery is strongly desired as a battery for electric vehicles such as hybrid vehicles. As a secondary battery that satisfies these requirements, a lithium ion secondary battery using a material capable of desorption and insertion of lithium ions as an active material for a negative electrode and a positive electrode has been attracting attention, and research and development is actively conducted at present. It has been broken. Among the lithium ion secondary batteries described above, a lithium ion secondary battery using a layered or spinel type lithium metal composite oxide as a positive electrode material can obtain a high voltage of 4V, and therefore has a high energy density. Practical use is progressing.

Examples of active material materials proposed so far include lithium cobalt composite oxide (LiCoO ₂ ) that is relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) using nickel that is cheaper than cobalt, and lithium nickel. Examples thereof include cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese, and the like. Among these, lithium nickel composite oxide and lithium nickel cobalt manganese composite oxide are attracting attention as materials having excellent battery characteristics because they have good cycle characteristics and low resistance and high output. In recent years, the active material of the positive electrode material has been required to further improve the characteristics, and various techniques have been proposed.

  For example, in Patent Document 1, surface modification is performed by coating a lithium cobalt-based composite oxide as a positive electrode active material with a Zr compound, thereby improving battery characteristics, particularly load characteristics, cycle characteristics, and stability. A technique for providing an excellent positive electrode active material is disclosed. In Patent Document 2, after lithium cobaltate particles powder, Zr raw material and Li raw material are mixed, the surface of lithium cobaltate particles is coated with a Zr compound by firing at a high temperature of 600 to 1000 ° C. A technique for providing a positive electrode active material excellent in load characteristics, cycle characteristics, and thermal stability is disclosed. Furthermore, in Patent Document 3, a 5V-grade positive electrode active material (B) and a specific oxide (C) or a solid electrolyte (D) are attached to the surface of particles of a 4V-grade positive electrode active material (A). There is disclosed a lithium secondary battery positive electrode material comprising a composite particle, and a lithium secondary battery comprising a positive electrode using the positive electrode material for a lithium secondary battery of the present invention.

JP 2003-221234 A Japanese Patent No. 5482977 Japanese Patent Laying-Open No. 2015-060767

  However, when the surface of the positive electrode active material is coated with a different compound as in Patent Document 1, the movement (intercalation) of lithium ions is greatly limited, and as a result, the lithium composite oxide has a high capacity. The advantages may be lost. Further, when a different element is dissolved in the lithium composite oxide, the capacity is likely to decrease. On the other hand, the heat treatment such as baking at a high temperature of 600 to 1000 ° C. described in Patent Document 2 may change depending on the material of the positive electrode active material, and the battery characteristics may be deteriorated. Furthermore, in Patent Document 3, it is necessary to perform a mechanofusion process. In addition to capital investment of tens of millions of yen to hundreds of millions of yen, in addition to the initial cost, there is a large increase in running cost and time loss due to increased processes. It becomes a problem. The present invention has been made in view of the above-described conventional problems, and provides a positive electrode material for a non-aqueous electrolyte secondary battery that can obtain a high output while suppressing a decrease in capacity when used in a positive electrode. For the purpose.

  In order to achieve the above object, a positive electrode material for a non-aqueous electrolyte secondary battery according to the present invention comprises a positive electrode active material powder comprising primary particles and / or secondary particles of a lithium metal composite oxide, and a lithium nitride phosphate powder. And a non-aqueous electrolyte secondary battery positive electrode material containing a mixture of a non-aqueous organic solvent, the non-aqueous organic solvent being contained in an amount of 20 to 40 parts by mass with respect to 100 parts by mass of the positive electrode active material powder. It is characterized by being.

  Moreover, the method for producing a positive electrode material for a non-aqueous electrolyte secondary battery of the present invention includes a positive electrode active material powder composed of primary particles and / or secondary particles of a lithium metal composite oxide, a lithium nitride phosphate powder, It includes a step of mixing 20 to 40 parts by mass of a non-aqueous organic solvent with respect to 100 parts by mass of the positive electrode active material powder.

  According to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery having high capacity and high output battery characteristics.

It is a schematic diagram which shows the measurement result of the impedance spectrum of the electrode using the positive electrode material which concerns on embodiment of this invention. It is explanatory drawing of the equivalent circuit used for the analysis. It is a partial cross section front view of the battery using the positive electrode material which concerns on embodiment of this invention.

  The positive electrode material of the embodiment of the present invention includes primary particles of a lithium metal composite oxide, secondary particles having a structure in which the primary particles are aggregated, or a mixture of these primary particles and secondary particles (hereinafter referred to as lithium metal composite for simplicity. A mixture of a powder composed of an oxide primary particle and / or a secondary particle), preferably a lithium nitride phosphate powder having a median diameter D50 of 0.01 to 0.50 μm, and a non-aqueous organic solvent. It is characterized by including. Hereinafter, the positive electrode material, its constituent elements, the non-aqueous electrolyte secondary battery using the positive electrode material, and the manufacturing method thereof will be described in detail.

(1) positive electrode material for a nonaqueous electrolyte secondary battery of the embodiment of the positive electrode material the invention is represented by the general formula _{Li z Ni 1-x-y} Co x M y O 2 ( however, 0.01 ≦ x ≦ 0.35 , 0 ≦ y ≦ 0.35, 0.97 ≦ z ≦ 1.20, M is an additive element and is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al) A powder composed of primary particles and / or secondary particles of a lithium metal composite oxide, preferably a lithium nitride phosphate powder having a median diameter D50 of 0.01 to 0.50 μm, and a non-aqueous organic solvent. Contains the mixture and has the form of a paste.

  In this way, the non-aqueous organic solvent is added to the positive electrode material to form a paste, thereby suppressing aggregation of the lithium nitride phosphate powder composed of fine particles, and further adding a non-aqueous organic solvent when creating the subsequent positive electrode In this case, uniform mixing becomes possible, and the dispersibility of the lithium lithium phosphate in the positive electrode becomes extremely high. The specific composition of the non-aqueous organic solvent is not particularly limited as long as it does not adversely affect the battery characteristics. However, in consideration of the possibility of suppressing the cost and the possibility of contamination, the positive electrode described later is used. It is preferable to use the same non-aqueous organic solvent used at the time of preparation, for example, N-methyl-2-pyrrolidinone. In the positive electrode material according to the embodiment of the present invention, the non-aqueous organic solvent is contained in an amount of 20 to 40 parts by mass with respect to 100 parts by mass of the positive electrode active material.

As described above, a high charge / discharge capacity can be obtained by using the lithium metal composite oxide represented by the above general formula for the positive electrode active material serving as a base material of the positive electrode material. Furthermore, charging and discharging is performed by mixing lithium nitride phosphate powder having a median diameter D50 in the range of 0.01 to 0.50 μm with the powder composed of primary particles and secondary particles of the above lithium metal composite oxide. Output characteristics can be improved while suppressing a decrease in capacity. The reason why the output characteristics of the battery are thus improved is that LiPON, Li ₃ PO ₄ , Li ₃ BO ₃ , LiNbO ₃ , LiTaO ₃ , Li ₂ SiO ₃ , Li ₄ SiO ₄ , Li ₂ WO ₄ , Li ₂ MoO ₄ This is because lithium compounds such as Li ₂ ZrO ₃ and Li ₂ TiO ₃ are highly lithium conductive materials that promote the conductivity of lithium ions. That is, since the lithium compound has a high lithium ion conductivity, the presence of such a high lithium conductive material on the surface of the positive electrode active material promotes the movement of lithium ions, and the lithium ion on the surface of the positive electrode active material. Intercalation is promoted.

Among the above high lithium conductive materials, lithium nitride phosphate (LiPON) is a compound having extremely high lithium ion conductivity. Therefore, this lithium nitride phosphate powder is simply obtained by using lithium metal in the presence of a non-aqueous organic solvent. The positive electrode resistance can be greatly reduced without impairing the high capacity characteristics of the lithium metal composite oxide simply by mixing with the composite oxide powder and allowing it to exist in a dispersed state between the particles of the lithium metal composite oxide. As described above, the mechanism in which the output characteristics are improved by the uniform presence of the lithium nitride phosphate powder in the positive electrode material is that the lithium nitride phosphate particles are in contact with the active material surface and thus act on the electrolyte and the positive electrode active material. This is because a lithium ion conduction path is formed between the electrolyte solution and the positive electrode active material interface, thereby reducing the reaction resistance of the active material. In addition, this lithium nitride phosphate can be prepared by nitriding a part or all of lithium phosphate Li ₃ PO ₄ , for example.

  As described above, the lithium nitride phosphate powder is uniformly dispersed in the positive electrode material in order to form a lithium ion conduction path. Conversely, the dispersion of the lithium nitride phosphate powder in the positive electrode material is not dispersed. When uniform, the movement of lithium ions between the particles of the lithium metal composite oxide becomes non-uniform. As a result, a load is applied to the specific lithium metal composite oxide particles, which tends to deteriorate cycle characteristics and increase reaction resistance. Thus, in order to uniformly distribute the lithium nitride phosphate powder in the positive electrode material, the median diameter D50 of the lithium nitride phosphate powder is preferably in the range of 0.01 to 0.50 μm.

  When the median diameter D50 of the lithium nitride phosphate powder is less than 0.01 μm, fine lithium nitride phosphate particles having insufficient lithium ion conductivity are excessively contained. In a portion where a lot of fine particles are present, the above effect is difficult to obtain, and as a result, the cycle characteristics may be deteriorated and the reaction resistance may be increased as in the case of non-uniform dispersion. In addition, the grinding cost may be too high. On the other hand, when the median diameter D50 exceeds 0.50 μm, it becomes difficult to uniformly disperse the lithium nitride phosphate powder in the positive electrode material, and the effect of reducing the reaction resistance may not be sufficiently obtained.

  The median diameter D50 is obtained by accumulating the number of particles in each particle diameter obtained by measuring the powder to be measured using a laser diffraction scattering method from the smaller particle diameter side, and the accumulated volume is It means a particle size that is 50% of the total volume of the particles. In addition, when a particle size remove | deviates from the said range, it can be made into the said range by grind | pulverizing or sieving before mixing.

  In the positive electrode material according to the embodiment of the present invention, mixing may be performed so that the lithium nitride phosphate powder includes 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the lithium metal composite oxide powder. preferable. Thereby, it is possible to achieve both high charge / discharge capacity and excellent output characteristics. If the amount of the lithium nitride phosphate powder is less than 0.1 parts by mass, the effect of improving the output characteristics may not be sufficiently obtained. Conversely, if the amount exceeds 2.0 parts by mass, the amount of lithium nitride phosphate powder is large. Thus, the lithium conduction between the lithium metal composite oxide and the electrolytic solution may be hindered, and the charge / discharge capacity, particularly the charge / discharge capacity per unit mass of the positive electrode material may be reduced.

  The lithium metal composite oxide contained in the positive electrode material according to the embodiment of the present invention is a ratio of the number of atoms of lithium (Li) to the sum of the number of atoms of nickel (Ni), cobalt (Co) and M (Me). (Li / Me) is preferably 0.97 or more and 1.20 or less. If the Li / Me value is less than 0.97, the reaction resistance of the positive electrode in the non-aqueous electrolyte secondary battery using the amount of the positive electrode material is increased, which may reduce the battery output. On the other hand, if the Li / Me value exceeds 1.20, the discharge capacity of the positive electrode active material may decrease, or the reaction resistance of the positive electrode may increase. The value of Li / Me is more preferably 1.10 or less in order to obtain a larger discharge capacity.

  Co and additive element M are added to improve battery characteristics such as cycle characteristics and output characteristics, and when x and y indicating these addition amounts exceed 0.35, they contribute to the Redox reaction. Since Ni decreases, the battery capacity may decrease. On the other hand, if x indicating the amount of Co added is less than 0.01, the cycle characteristics and thermal stability may not be sufficiently obtained. Therefore, in order to obtain a sufficient battery capacity when used in a battery, it is more preferable that y indicating the amount of addition of M is 0.15 or less. Further, since increasing the contact area with the electrolytic solution is advantageous for improving the output characteristics, lithium metal composite oxide particles composed of primary particles and / or secondary particles are used.

The lithium metal composite oxide powder composed of primary particles and / or secondary particles preferably has a specific surface area of 0.5 to 2.0 m ² / g. When the specific surface area is less than 0.5 m ² / g, sufficient contact with the electrolytic solution may not be obtained, and output characteristics and battery capacity may be reduced. On the other hand, when the specific surface area exceeds 2.0 m ² / g, decomposition of the electrolytic solution is promoted and thermal stability may be lowered. That is, by making the specific surface area within the range of 0.5 to 2.0 m ² / g, the contact with the electrolytic solution is enhanced, the output characteristics and the battery capacity are improved, and the thermal stability is also ensured. can do.

  There is no limitation in particular about the manufacturing method of said lithium metal complex oxide, It can produce | generate with a well-known manufacturing method. The powder properties such as the particle size and tap density of the lithium metal composite oxide may be in the range of the positive electrode active material that is usually used, but the median diameter D50 is in the range of 4.0 to 15.0 μm. Preferably within. The median diameter D50 can be measured by, for example, Microtrack MT3300EXII manufactured by Microtrack Bell Co., Ltd. This measuring device measures the particle size using the laser diffraction scattering method while circulating the slurry obtained by adding a liquid to the powder to be measured. Since the particles are crushed, the particles to be measured are almost primary particles.

  In the above-described positive electrode material according to the embodiment of the present invention, the case where the lithium nickel cobalt composite oxide is used as the positive electrode active material has been described. However, the positive electrode material of the present invention is not limited to this, for example, lithium cobalt Similar effects can be expected even when a lithium-based composite oxide, a lithium-manganese-based composite oxide, a lithium-nickel-cobalt-manganese-based composite oxide, or the like is used.

(2) Method for Producing Positive Electrode Material Next, a method for producing the positive electrode material for a non-aqueous electrolyte secondary battery according to the embodiment of the present invention will be described. First, as the positive electrode active material comprising a base material, the general formula _{Li z Ni 1-x-y} Co x M y O 2 ( however, 0.01 ≦ x ≦ 0.35,0 ≦ y ≦ 0.35,0. 97 ≦ z ≦ 1.20, M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al) Lithium metal composite oxide powder comprising primary particles and / or secondary particles And lithium nitride phosphate powder as a high lithium conductive material and a non-aqueous organic solvent are prepared.

  Then, the lithium metal composite oxide powder and the lithium nitride phosphate powder are sufficiently mixed with the non-aqueous organic solvent added. As a result, while suppressing aggregation of the lithium nitride phosphate powder, the fine particles of lithium nitride phosphate, which is a high lithium conductive material, are uniformly dispersed between the positive electrode active material particles, and the fine particles are spread on the surface of the positive electrode active material. Can be contacted. Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, but are not limited thereto as described above.

  For the above mixing, a general mixer can be used. For example, using a shaker mixer, a Roedige mixer, a Julia mixer, a V blender, etc., primary particles of the lithium metal composite oxide powder are used. It is sufficient that lithium nitride nitride is sufficiently mixed under such a condition that is not destroyed. Thereby, the fine particles of lithium nitride phosphate can be distributed substantially uniformly on the surface of the lithium metal composite oxide powder.

  In the method for producing the positive electrode material, a step of washing the lithium metal composite oxide powder with water may be provided before the mixing step in order to improve the battery capacity and thermal stability of the positive electrode material. As long as lithium is not excessively eluted from the lithium metal composite oxide powder and the battery characteristics are not deteriorated in this water washing step, a known water washing method or water washing conditions can be employed. The lithium metal composite oxide powder after washing with water may be subjected to a drying treatment before mixing with lithium nitride phosphate, or after being mixed with lithium nitride phosphate without being dried only by solid-liquid separation. May be applied. In any case, a known drying method or drying condition can be used for this drying treatment as long as the battery characteristics of the lithium metal composite oxide do not deteriorate.

(3) Non-aqueous electrolyte secondary battery A positive electrode using the positive electrode material according to the above-described embodiment of the present invention, and a negative electrode, a separator, a non-aqueous electrolyte, and the like used in a general non-aqueous electrolyte secondary battery A non-aqueous electrolyte secondary battery can be constructed from the elements. Hereinafter, specific examples of the non-aqueous electrolyte secondary battery and its constituent elements will be described. However, the present invention is not limited to the following specific examples, and various modifications based on the knowledge of those skilled in the art. And alternatives can be implemented. Moreover, it does not specifically limit about the use of the non-aqueous electrolyte secondary battery using the positive electrode material of embodiment of this invention.

(A) Positive electrode Using the positive electrode material of the above-described embodiment of the present invention, for example, a positive electrode of a nonaqueous electrolyte secondary battery can be produced by the following method. That is, first, to the above-described paste-like positive electrode material (first paste), a binder that plays a role of connecting the conductive material and the active material particles is added, and activated carbon is added to increase the electric double layer capacity as necessary. After the addition, these positive electrode active materials, conductive materials and the like are dispersed, and an organic solvent having the purpose of dissolving the binder and adjusting the viscosity is added and kneaded. Thereby, a paste-like positive electrode mixture is obtained (second paste).

  The mixing ratio of the constituent elements in the positive electrode mixture of the second paste is also an important factor that determines the performance of the non-aqueous electrolyte secondary battery. Therefore, when the total mass of the solid content of the positive electrode mixture excluding the organic solvent is 100 parts by mass, the content of the positive electrode active material is 60 to 95 parts by mass in the same manner as the positive electrode of a general non-aqueous electrolyte secondary battery. It is desirable that the content of the conductive material is in the range of 1 to 20 parts by mass and the content of the binder is in the range of 1 to 20 parts by mass. In addition, it is preferable that the content rate of the organic solvent contained in the positive electrode compound material of said 2nd paste exists in the range of 20-60 mass%, and 30-50 mass% is more preferable.

  The paste-like positive electrode mixture obtained above is applied to the surface of a current collector made of, for example, an aluminum foil, and subjected to a drying treatment to scatter the organic solvent. Thereby, a sheet-like positive electrode can be produced. In addition, you may raise an electrode density by compressing with a roll press etc. as needed after the said drying process. The sheet-shaped positive electrode produced as described above is formed into an appropriate shape by cutting or the like in accordance with the secondary battery as the final product, and then incorporated into the secondary battery.

  Examples of the conductive agent include carbon black materials such as graphite (natural graphite, artificial graphite, expanded graphite, etc.), acetylene black, and ketjen black. Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluorine rubber, ethylene propylene diene rubber, styrene butadiene, cellulose resin, and polyacrylic acid. . Moreover, as an organic solvent, N-methyl-2-pyrrolidone etc. can be used, for example.

(B) Negative electrode In the negative electrode serving as the counter electrode of the positive electrode, a negative electrode mixture prepared by mixing a negative electrode active material capable of inserting and extracting lithium ions with a binder and adding a suitable solvent to form a paste is used. It can be applied to the surface of a metal foil current collector, etc., dried, and compressed to increase the electrode density as necessary. As the negative electrode active material, for example, natural graphite, artificial graphite, a fired organic compound such as a phenol resin, or a powdery carbon material such as coke can be used. May be used. Further, as the binder, a fluorine-containing resin such as PVDF similar to that of the positive electrode can be used, and as a solvent for dispersing the negative electrode active material and the binder, organic solvents such as N-methyl-2-pyrrolidone are used. A solvent can be used.

(C) Separator The separator disposed in a state of being sandwiched between the positive electrode and the negative electrode is isolated so as not to cause a short circuit between the positive electrode and the negative electrode, and has a role of allowing electrolytes and ions to pass therethrough. Yes. As the material of the separator, a thin film such as polyethylene or polypropylene having countless fine holes can be used.

(D) Non-aqueous electrolyte solution The non-aqueous electrolyte solution serves as a transport medium for ions moving between the positive electrode and the negative electrode, and uses a solution obtained by dissolving a lithium salt as a supporting salt in an organic solvent. be able to. Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate; chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate; and tetrahydrofuran, 2- One kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc. are used alone or in admixture of two or more. be able to. As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and complex salts thereof can be used. The nonaqueous electrolytic solution may further contain a radical scavenger, a surfactant, a flame retardant, and the like.

(E) Form and manufacturing method of non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery mainly composed of the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte described above has various types such as a cylindrical type and a laminated type. It can be in the form of In any case, in the manufacturing method, a positive electrode and a negative electrode are laminated with a separator interposed therebetween to form an electrode body, and the electrode body is impregnated with a non-aqueous electrolyte, and the positive electrode terminal communicates with the positive electrode current collector. And between the negative electrode current collector and the negative electrode terminal communicating with the outside using a current collecting lead or the like, and sealing in a battery case, whereby a non-aqueous electrolyte secondary battery is Can be completed.

(F) Characteristics The non-aqueous electrolyte secondary battery using the positive electrode material according to the above-described embodiment of the present invention has a high capacity and high output battery characteristics. For example, when the positive electrode material of the embodiment of the present invention is used for the positive electrode of a 2032 type coin battery, a high initial discharge capacity of 165 mAh / g or more and a low positive electrode resistance are obtained, and a high capacity and a high output are obtained. In addition, it has high thermal stability, and thus is excellent in safety.

  The non-aqueous electrolyte secondary battery using the positive electrode material according to the above-described embodiment of the present invention is suitable for a power source of a small portable electronic device such as a notebook personal computer or a mobile phone terminal that always requires a high capacity. It is also suitable for batteries for electric vehicles that require output. In particular, the non-aqueous electrolyte secondary battery using the positive electrode material according to the embodiment of the present invention has excellent safety, and can be downsized and increased in output. It is suitable as a power source for use. Furthermore, the non-aqueous electrolyte secondary battery using the positive electrode material according to the embodiment of the present invention is used not only for a power source for an electric vehicle that is driven purely by electric energy but also for a so-called combustion engine such as a gasoline engine or a diesel engine. It can also be used as a power source for hybrid vehicles.

  The positive electrode material of the Example of this invention and the comparative example was prepared, the non-aqueous electrolyte secondary battery which each has a positive electrode using these was produced, and those positive electrode interface resistances were evaluated. The median diameter D50 of the positive electrode active material powder and the lithium nitride phosphate powder was assumed using Microtrac MT3300EXII, which is a particle size distribution measuring apparatus using a laser diffraction scattering method manufactured by Microtrac Bell. The specific surface area of the powder of the positive electrode active material was measured using a Maxsorb 1200 series manufactured by Mountec Co., Ltd., which is a specific surface area measuring apparatus using a nitrogen gas adsorption / desorption flow method. The composition of the lithium ion composite oxide was analyzed using Agilent 730-ES, which is an ICP-OES manufactured by Agilent Technologies, which is a measuring device by the ICP method.

Example 1
Lithium metal composite represented by Li _1.02 Ni _0.82 Co _0.15 Al _0.03 O ₂ obtained by a known technique in which an oxide containing nickel as a main component and lithium hydroxide are mixed and fired Prepare a powder of oxide, wash water by adding water at room temperature at a rate of 1 ml of water to 1.5 g of the powder and stir, then dehydrate and dry to form a cathode of the cathode material The active material was used. This positive electrode active material had a specific surface area of 1.35 m ² / g and a median diameter D50 of 8.7 μm.

  Next, lithium nitride phosphate powder as an additive material was prepared, and this was sufficiently pulverized using a rotation / revolution mixer to obtain lithium nitride phosphate powder having a median diameter D50 of 0.16 μm. To 20 g of the lithium metal composite oxide powder as the positive electrode active material, 0.020 g of this lithium nitride phosphate powder is added (corresponding to 0.1 part by mass with respect to 100 parts by mass of the positive electrode active material), and N -A paste-like positive electrode material (first paste) was prepared by adding 6.0 g of methyl-2-pyrrolidone and kneading for 30 minutes using a rotation / revolution mixer.

(Production of battery)
After forming a positive electrode using the positive electrode material prepared by the above method, a coin-type secondary battery 10 as shown in FIG. 3 was assembled using the positive electrode material, and the battery characteristics were evaluated by a method described later. Specifically, first, 26.02 g of the positive electrode material in the form of the first paste was added to 5.72 g of acetylene black, 2.86 g of polytetrafluoroethylene resin (PTFE), and 10.0 g of N-methyl- A second paste was prepared by adding 2-pyrrolidone and kneading for 30 minutes using a rotation / revolution mixer. When this paste was visually confirmed, it was well mixed.

  This second paste was applied to the surface of a current collector made of aluminum foil and dried in an vacuum dryer at an ambient temperature of 120 ° C. for 12 hours. After the drying treatment, the film was pressed to a thickness of 100 μm at a pressure of 100 MPa, and further punched out to a diameter of 11 mm to produce a positive electrode (evaluation electrode) 1. In addition, the desired weight was ensured after the punching by finely adjusting the thickness at the time of application. Next, in the glove box of Ar atmosphere in which the dew point was controlled at −80 ° C., the produced positive electrode 1 was subjected to dry treatment of the positive electrode (evaluation electrode) 1, the negative electrode 2, the separator 3, and the electrolytic solution. A coin-type battery 10 as shown in FIG. 3 was prepared by placing the positive electrode can 4 and the negative electrode can 5 inside.

The negative electrode 2 is a negative electrode sheet obtained by punching a negative electrode sheet in which a graphite powder having an average particle diameter of about 20 μm and polyvinylidene fluoride are applied to a copper foil into a disk shape having a diameter of 14 mm, and 1M LiPF ₆ is supported as an electrolyte An equal volume mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (manufactured by Ube Industries) was used as the electrolyte, and a 25 μm thick polyethylene porous film was used for the separator 3. A gasket 6 was provided at the joint between the positive electrode can 4 and the negative electrode can 5, and the upper surface of the negative electrode 2 was fixed with a wave washer 7.

(Example 2)
Instead of 0.020 g, the amount of lithium nitride phosphate powder added to 20 g of lithium metal composite oxide powder as the positive electrode active material is 0.060 g (corresponding to 0.3 parts by mass with respect to 100 parts by mass of the positive electrode active material). Except for the above, a coin-type secondary battery 10 was produced in the same manner as in Example 1, and the battery evaluation was performed by the method described later.

(Example 3)
Instead of 0.020 g of lithium nitride phosphate powder added to 20 g of lithium metal composite oxide powder as the positive electrode active material, 0.20 g (corresponding to 1.0 part by mass with respect to 100 parts by mass of the positive electrode active material). The coin-type secondary battery 10 was produced in the same manner as in Example 1 except that the battery evaluation was performed, and the battery evaluation was performed by the method described later.

(Example 4)
Instead of 0.020 g of lithium nitride phosphate powder added to 20 g of lithium metal composite oxide powder as the positive electrode active material, 0.40 g (corresponding to 2.0 parts by mass with respect to 100 parts by mass of the positive electrode active material). The coin-type secondary battery 10 was produced in the same manner as in Example 1 except that the battery evaluation was performed, and the battery evaluation was performed by the method described later.

(Example 5)
The amount of N-methyl-2-pyrrolidone added during preparation of the first paste is 6.0 g to 4.0 g, and the amount of N-methyl-2-pyrrolidone added during preparation of the second paste is 10.0 g. In addition, a coin-type secondary battery 10 was prepared in the same manner as in Example 3 except that the amount was 12.0 g, and the battery evaluation was performed by the method described later.

(Example 6)
The amount of N-methyl-2-pyrrolidone added during the preparation of the first paste is 6.0 g to be 8.0 g, and the amount of N-methyl-2-pyrrolidone added during the preparation of the second paste is 10.0 g. In addition, a coin-type secondary battery 10 was produced in the same manner as in Example 3 except that the amount was 8.0 g, and the battery evaluation was performed by the method described later.

(Example 7)
A coin-type secondary battery in the same manner as in Example 3 except that the lithium phosphate phosphor powder having a median diameter D50 of 0.013 μm was used instead of the lithium nitride phosphate powder having a median diameter D50 of 0.16 μm. 10 was produced, and the battery evaluation was performed by the method described later.

(Example 8)
A coin-type secondary battery in the same manner as in Example 3 except that lithium nitride phosphate powder having a median diameter D50 of 0.49 μm was used instead of the lithium nitride phosphate powder having a median diameter D50 of 0.16 μm. 10 was produced, and the battery evaluation was performed by the method described later.

Example 9
The positive electrode active material, median diameter D50 of 8.7 .mu.m, median diameter D50 specific surface area in place of the lithium metal composite oxide powder of 1.35 m ² / g is 14.8Myuemu, specific surface area of 0.52 m ² / A coin-type secondary battery 10 was produced in the same manner as in Example 3 except that g lithium metal composite oxide powder was used, and the battery evaluation was performed by the method described later.

(Example 10)
The positive electrode active material, median diameter D50 of 8.7 .mu.m, median diameter D50 specific surface area in place of the lithium metal composite oxide powder of 1.35 m ² / g is 4.2 .mu.m, specific surface area of 1.97m ² / A coin-type secondary battery 10 was produced in the same manner as in Example 3 except that g lithium metal composite oxide powder was used, and the battery evaluation was performed by the method described later.

(Example 11)
A coin-type secondary battery in the same manner as in Example 3 except that lithium nitride phosphate powder having a median diameter D50 of 0.005 μm was used instead of the lithium nitride phosphate powder having a median diameter D50 of 0.16 μm. 10 was produced, and the battery evaluation was performed by the method described later.

(Example 12)
A coin-type secondary battery in the same manner as in Example 3 except that the lithium nitride phosphate powder having a median diameter D50 of 0.72 μm was used instead of the lithium nitride phosphate powder having a median diameter D50 of 0.16 μm. 10 was produced, and the battery evaluation was performed by the method described later.

(Example 13)
The positive electrode active material, median diameter D50 of 8.7 .mu.m, median diameter D50 specific surface area in place of the lithium metal composite oxide powder of 1.35 m ² / g is 16.2, a specific surface area of 0.38 m ² / A coin-type secondary battery 10 was produced in the same manner as in Example 3 except that g lithium metal composite oxide powder was used, and the battery evaluation was performed by the method described later.

(Example 14)
The positive electrode active material, median diameter D50 of 8.7 .mu.m and a specific surface area of 1.35 m ² / g of lithium metal composite oxide powder having a median diameter D50 of 2.5μm instead of a specific surface area of 2.64 M ² / A coin-type secondary battery 10 was produced in the same manner as in Example 3 except that g lithium metal composite oxide powder was used, and the battery evaluation was performed by the method described later.
(Comparative Example 1)
No lithium nitride phosphate powder was added, 20 g of lithium metal composite oxide powder as a positive electrode active material without passing through the first paste, 5.72 g of acetylene black, and polytetrafluoroethylene resin (PTFE) 2 A coin-type secondary battery 10 was produced in the same manner as in Example 1 except that .86 g and 16.0 g of N-methyl-2-pyrrolidone were added at a time to prepare a paste, and the battery evaluation will be described later. Went in the way.

(Comparative Example 2)
20 g of lithium metal composite oxide powder as the positive electrode active material without passing through the first paste, 0.020 g of lithium nitride phosphate powder, 5.72 g of acetylene black, 2.86 g of polytetrafluoroethylene resin (PTFE), A coin-type secondary battery 10 was produced in the same manner as in Example 1 except that 16.0 g of N-methyl-2-pyrrolidone was added at a time to prepare a paste, and the battery evaluation was performed by the method described later. .

(Comparative Example 3)
20 g of lithium metal composite oxide powder as a positive electrode active material without passing through the first paste, 0.20 g of lithium nitride phosphate powder, 5.72 g of acetylene black, 2.86 g of polytetrafluoroethylene resin (PTFE), A coin-type secondary battery 10 was produced in the same manner as in Example 3 except that 16.0 g of N-methyl-2-pyrrolidone was added at a time to prepare a paste, and the battery evaluation was performed by the method described later. .

(Comparative Example 4)
20 g of lithium metal composite oxide powder as the positive electrode active material without passing through the first paste, 0.40 g of lithium nitride phosphate powder, 5.72 g of acetylene black, 2.86 g of polytetrafluoroethylene resin (PTFE), A coin-type secondary battery 10 was produced in the same manner as in Example 4 except that 16.0 g of N-methyl-2-pyrrolidone was added at a time to prepare a paste, and the battery evaluation was performed by the method described later. .

(Evaluation)
The positive electrode interface resistances of the coin-type secondary batteries 10 of Examples 1 to 14 and Comparative Examples 1 to 4 manufactured above were evaluated by the following methods. That is, each coin-type battery 10 was charged at a charging potential of 4.0 V, and the impedance spectrum shown in FIG. In the obtained impedance spectrum, two semicircles are observed in the high frequency region and the intermediate frequency region, and a straight line is observed in the low frequency region. Therefore, the equivalent interface model shown in FIG. Was analyzed. Here, Rs is a bulk resistance, R1 is a positive electrode film resistance, Rct is an electrolyte / positive electrode interface resistance (Li + movement resistance at the interface), W is a Warburg component, and CPE1 and CPE2 are constant phase elements. The “positive electrode interface resistance ratio” shown in Table 1 is a “resistance ratio” when the resistance value of Comparative Example 1 (without adding LiPON) is normalized to 1.

  The non-aqueous electrolyte secondary batteries of Examples 1 to 14 have an initial discharge capacity larger than that of Comparative Examples 1 to 4, and a positive electrode interface resistance that is lower than that of Comparative Examples 1 to 4, and excellent characteristics. It was confirmed that a battery having On the other hand, the secondary battery of Comparative Example 1 has a high positive electrode interface resistance, which is considered to be due to the fact that lithium nitride phosphate is not mixed, and the entire raw material is not passed through the first paste. Since they were mixed at the same time, they were not sufficiently mixed to the extent that they could be visually observed at the time of producing the positive electrode, and it is considered that the lithium ion conduction path was not formed well. In Comparative Examples 2 to 4, since all the raw materials were mixed at once without passing through the first paste, portions that were not mixed to the extent that they could be visually observed during the production of the positive electrode were observed. From the above results, it was confirmed that the non-aqueous electrolyte secondary battery using the positive electrode material of the present invention has a low positive electrode interface resistance, and thus a secondary battery having excellent characteristics can be obtained.

  In addition, Examples 11 to 14 have higher positive electrode interface resistance than Example 3, because in Examples 12 and 13, the particle size of the positive electrode active material or lithium nitride phosphate is that of Example 3. This is considered to be due to the fact that the contact area with each other became narrower. On the other hand, in Examples 11 and 14, the particle diameter of the positive electrode active material or lithium nitride phosphate is significantly smaller than that in Example 3, so that the formation of the lithium ion conduction path becomes insufficient, and the positive electrode interface resistance is low. Probably higher.

1 Positive electrode (Evaluation electrode)
2 Negative electrode 3 Separator 4 Positive electrode can 5 Negative electrode can 6 Gasket 7 Wave washer 10 Coin-type battery

Claims (7)

  A positive electrode material for a non-aqueous electrolyte secondary battery comprising a mixture of a positive electrode active material powder comprising primary particles and / or secondary particles of a lithium metal composite oxide, a lithium nitride phosphate powder, and a non-aqueous organic solvent. A positive electrode material for a non-aqueous electrolyte secondary battery, wherein the non-aqueous organic solvent is contained in an amount of 20 to 40 parts by mass with respect to 100 parts by mass of the positive electrode active material powder.   2. The non-aqueous electrolyte 2 according to claim 1, wherein 0.1 to 2.0 parts by mass of the lithium nitride phosphate powder is included with respect to 100 parts by mass of the positive electrode active material powder. Positive electrode material for secondary batteries. The median diameter D50 of the lithium nitride phosphate powder is 0.01 to 0.50 μm, and the specific surface area of the powder of the positive electrode active material composed of the primary particles and / or secondary particles is 0.5 to 2.0 m. ^The positive electrode material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the positive electrode material is ² / g.   It has a positive electrode containing the positive electrode material for nonaqueous electrolyte secondary batteries of any one of Claims 1-3, The nonaqueous electrolyte secondary battery characterized by the above-mentioned.   20-40 parts by mass of positive electrode active material powder composed of primary particles and / or secondary particles of lithium metal composite oxide, lithium nitride phosphate powder, and 100 parts by mass of the positive electrode active material powder The manufacturing method of the positive electrode material for non-aqueous electrolyte secondary batteries characterized by including the process of mixing an aqueous organic solvent.   The method for producing a positive electrode material for a non-aqueous electrolyte secondary battery according to claim 5, comprising a step of washing the powder of the positive electrode active material with water before the step of mixing.   The non-aqueous electrolyte secondary according to claim 5, wherein 0.1 to 2.0 parts by mass of the lithium nitride phosphate powder is mixed with 100 parts by mass of the positive electrode active material powder. A method for producing a positive electrode material for a battery.

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