JP2017142997A - Lithium nickelate-carbon composite positive electrode active material particle powder, and manufacturing method thereof, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: lithium nickelate-carbon composite positive electrode active material particle powder having a high electron conductivity and a high mechanical strength; a method for manufacturing the lithium nickelate-carbon composite positive electrode active material particle powder; and a nonaqueous electrolyte secondary battery.SOLUTION: Lithium nickelate-carbon composite positive electrode active material particle powder comprises: a lithium nickelate expressed by the chemical formula, LiNiCoMO(where M represents at least one element of Mn, Al, B, Mg and Zn elements; -0.1≤a≤0.2, 0.05≤b≤0.5, and 0.01≤c≤0.4), which is a composite with carbon having at least a part consisting of carbon nanotube; the content of the carbon is 0.1-5.5 wt%. The average value P/Pof ratios of peak intensities Pof a G prime band to a peak intensity Pof a G band of the carbon is 0.1-0.8. The average value P/Pof ratios of peak intensities Pof the lithium nickelate to a peak intensity Pof the spectra is 0.4-10.SELECTED DRAWING: None

Description

  The present invention relates to a lithium nickelate-carbon composite cathode active material particle powder having a high energy density and excellent charge / discharge repeatability, a method for producing the same, and a nonaqueous electrolyte secondary battery using the same.

  In recent years, electronic devices such as mobile phones and personal computers have been spurred to be smaller and lighter, and the demand for secondary batteries having high energy density as power sources for driving these devices has increased. Under such circumstances, a battery having a large secondary battery weight and charge / discharge capacity per volume and a high charge / discharge repeatability has attracted attention.

Conventionally, lithium nickel oxide LiNiO ₂ having a layered (rock salt type) structure having a voltage of 4 V has been known as one of positive electrode active material particle powders useful for high energy type lithium ion secondary batteries. Since the particle powder is inexpensive and excellent in output characteristics as compared with a general-purpose positive electrode active material lithium cobalt oxide LiCoO ₂ particle powder, it is mainly used for a power tool main power source. In recent years, taking advantage of its characteristics, it is also being used as a drive power source for electric vehicles. However, elution of other than Li ⁺ ions from the active material particle powder and imperfect reaction between raw material powders during synthesis may cause problems such as deterioration of charge / discharge repetition characteristics associated with high voltage charging and gas generation during high temperature storage. Is causing. Therefore, further improvement of powder characteristics is required.

  As is well known, lithium nickelate has been improved in charge / discharge repeatability and thermal stability as a secondary battery by substituting a part of nickel with another element. Typical substitutional elements include transition metal elements that contribute to the capacity obtained by contributing to electrode reactions such as Mn and Co, and metal elements that improve thermal stability and repetitive characteristics such as Mg, Al, B, and Zn.

  Generally, a positive electrode active material particle powder such as lithium nickelate is mixed with an electronic conductive assistant containing carbon black, a polymer binder, and an organic solvent to produce a positive electrode sheet. The presence state of the lithium nickelate and the conductive agent in the positive electrode sheet greatly affects the electric resistance of the positive electrode and thus the battery characteristics. Therefore, in order to improve the conductivity of the positive electrode, for example, an invention in which the surface of the positive electrode active material particle powder is coated with a conductive additive as in Patent Document 1 or a non-oxidizing atmosphere heat treatment of organic matter as in Patent Document 2 is performed. An invention that improves the conductivity by providing film-like carbon on the surface of the active material particles, and an invention that combines with the carbon material by the mechanochemical method on the electrode active material surface as shown in Patent Document 3 are shown. .

By the way, the lithium nickelate positive electrode active material particle powder is often composed of secondary particles of several to several tens of μm in which the submicron primary particles are firmly aggregated. It is reported that with the expansion and contraction of the particles due to the first charge and discharge, cracks are formed in the grain boundaries, and NiO having a rock salt structure due to Ni ²⁺ is formed in the vicinity of the grain boundaries, which adversely affects the charge and discharge characteristics. (Non-patent reference).

JP, 2015-84323, A JP 2013-69566 A Japanese Patent Laying-Open No. 2015-92462

S. Zheng, et al. Electrochem. Soc. vol. 158 (2011) A357-A362.

  However, the technique described in Patent Document 1 only refers to the state of the surface of the positive electrode material layer by optimizing the conditions during coating and sheeting of the conductive carbon material and the positive electrode active material, and collecting current Regarding the thickness direction from the body, it is difficult to say that the contacts between the active material and the conductive agent are sufficiently combined. In addition, the technique described in Patent Document 2 does not increase the number of contact points between particles only by coating the surface of the active material with film-like carbon by thermal decomposition of an organic compound, and the crystallinity of the carbon film is low. For this reason, it cannot be said that the conductivity is sufficiently improved, so there is sufficient room for improvement.

  Furthermore, in the technique described in Patent Document 3, it is difficult to say that the technique is related to the positive electrode active material particle powder combined with the carbon nanotube, and the structure of the conductive additive attached to the surface of the active material is sufficiently controlled. It's hard to say. Accordingly, it is expected that a large amount of carbon black is necessary to sufficiently secure the conductivity of the entire positive electrode active material particle powder.

  In view of the above problems, an object of the present invention is to provide a lithium nickelate-carbon composite cathode active material particle powder that acts as a cathode active material having high electron conductivity and high mechanical strength.

That is, the present invention relates to a lithium nickelate-carbon composite positive electrode active material powder, wherein the lithium nickelate has a chemical formula Li _{1 + a} Ni _1-bc Co _{b McO 2} (M is an element Mn, Al, At least one of B, Mg, and Zn, represented by −0.1 ≦ a ≦ 0.2, 0.05 ≦ b ≦ 0.5, 0.01 ≦ c ≦ 0.4), A part of at least carbon nanotubes, the carbon content is 0.1 to 5.5% by weight, and a carbon G band in a Raman spectrum measured with a green laser having an excitation wavelength of 532 nm. mean value _P a / _{P G} of the ratio of the peak intensity _{P a} G-prime band to the peak intensity _{P G} of is 0.1 to 0.8, the peak intensity of the lithium nickelate to the peak intensity _{P G} of the spectrum Lithium nickelate, wherein the average value _P M / _{P G} of the ratio of the P _M is 0.4 to 10 - is a carbon composite positive electrode active material particles (the present invention 1).

  Further, the present invention is the lithium nickelate-carbon composite cathode active material particle powder according to the present invention 1, wherein the density of the compression molded body under a load of 8 kN is 2.7 to 3.6 g / cc, and It is a lithium nickelate-carbon composite cathode active material particle powder having a volume resistivity of 0.1 to 200 Ω · cm (Invention 2).

Further, the present invention is lithium nickelate according to the present invention 1 or 2 - a carbon composite positive electrode active material particles, the average value _P M / _{P G} of the peak intensity ratio, 4 kN, 6 kN, the 8kN Lithium nickelate-carbon characterized in that the following formula (1) holds between the absolute value | X | of the slope X when plotting the volume resistivity against the density of the compression molded body when a load is applied. This is a composite positive electrode active material particle powder (Invention 3).
| X | / (P _M / P _G ) ≦ 500 (1)

The present invention is the lithium nickelate-carbon composite positive electrode active material powder according to any one of the first to third aspects, wherein the water vapor adsorption amount at P / P ₀ = 0.28 is 1 mg. Lithium nickelate-carbon composite positive electrode active material particles that are less than / g (Invention 4).

Further, the present invention is the lithium nickelate-carbon composite positive electrode active material powder according to any one of the first to fourth aspects, wherein the BET specific surface area is 10 m ² / g or less. It is a carbon composite cathode active material particle powder (Invention 5).

  The present invention is the lithium nickelate-carbon composite cathode active material powder according to any one of the present inventions 1 to 5, wherein the carbon nanotube has a node, and the tube outer diameter is 5 nm. It is a lithium nickelate-carbon composite positive electrode active material particle powder of ˜50 nm (Invention 6).

  Moreover, this invention is a manufacturing method of lithium nickelate-carbon composite positive electrode active material particle powder of any one of this invention 1-6, Comprising: Lithium nickelate and carbon are added in inert gas atmosphere. This is a method for producing a lithium nickelate-carbon composite positive electrode active material particle powder characterized in that the lithium nickelate surface is coated by mechanochemical treatment (Invention 7).

  Moreover, this invention is a secondary battery provided with the lithium nickelate-carbon composite positive electrode active material particle powder of any one of this invention 1-6 as a secondary battery electrode active material (this invention 8). .

  According to the lithium nickelate-carbon composite positive electrode active material particle powder according to the present invention, at least a portion of carbon nanotube carbon and lithium nickelate are composited, and a small amount of carbon is used to form an electron in the entire particle powder. Increases conductivity and mechanical strength. Accordingly, the obtained electrode sheet has a high electrode density and a low electric resistance, and the lithium ion secondary battery having the electrode sheet has a high energy density and excellent charge / discharge repetition characteristics.

It is the secondary electron (SE) image of the lithium nickelate-carbon composite cathode active material particle powder of Example 1, and EDX mapping of Ni element and C element. It is a Raman spectrum including the background of Example 1 and Comparative Example 3. It is the secondary electron (SE) image of the lithium nickelate-carbon composite positive electrode active material powder of Comparative Example 2, and EDX mapping of Ni element and C element. It plots the volume resistivity with respect to the compression molding body density when applying the load of 0.5-18 kN of Examples 1, 2, 3, Comparative Examples 1, 2, 3, and lithium nickelate.

  The configuration of the present invention will be described in more detail as follows.

  First, the lithium nickelate-carbon composite positive electrode active material powder according to the present invention will be described.

Lithium nickelate according to the present invention - the lithium nickelate of carbon composite positive electrode active material particles is the chemical formula _{Li 1 + a Ni 1-b} -c Co b M c O 2 (M is an element Mn, Al, B, Mg, Zn At least one of them, -0.1≤a≤0.2, 0.05≤b≤0.5, 0.01≤c≤0.4). It may contain defects in transition metals and oxygen at the atomic level.

  Part of the carbon of the lithium nickelate-carbon composite cathode active material particles according to the present invention is at least carbon nanotubes. The carbon nanotube is a tube-like carbon fiber material, and the tube diameter is nano-sized. Even if a defect occurs in the outermost layer, the carbon nanotubes are more preferably multi-layered, because the conductivity is easily ensured by the inner tube.

  The lithium nickelate-carbon composite cathode active material particle powder according to the present invention may contain carbon other than carbon nanotubes. The carbon is preferably fine particles, and can be selected from the group consisting of graphite, graphene, hard carbon, soft carbon, amorphous carbon, amorphous carbon, glassy carbon, carbon nanofiber, and fullerene, for example.

  In the present invention, the weight ratio of the carbon nanotubes in the carbon of the lithium nickelate-carbon composite cathode active material powder is preferably 5% or more. The upper limit is 100% by weight. If it is less than 5% by weight, the electronic conductivity and mechanical strength of the positive electrode active material particle powder tend not to be sufficiently maintained. More preferably, it is 10 to 95 weight%, More preferably, it is 20 to 90 weight%.

  The composite state of the lithium nickelate-carbon composite positive electrode active material particle powder according to the present invention is expressed as carbon having at least a part of the surface of the lithium nickelate particle adhered mechanochemically. In other words, the degree of compounding of the lithium nickelate particles and carbon may be such that they are not separated in the coating step when manufacturing the electrode body. It is sufficient that the carbon adheres to the surface of the lithium nickelate particles to the extent that the electron conductivity is ensured, and the lithium nickelate particles may be buried or protruded as a carbon aggregate, and one or more of them are mixed It may be. In particular, in order to ensure high electronic conductivity and mechanical strength with a small amount of the carbon, the lithium nickelate particles are encased in a network and stretched toward the outside of the lithium nickelate-carbon composite cathode active material particles. The shape of the carbon nanotube is preferable. One lithium nickelate-carbon composite cathode active material particle may contain a plurality of lithium nickelate particles and a plurality of carbon particles.

  The carbon content in the lithium nickelate-carbon composite positive electrode active material powder according to the present invention is 0.1 to 5.5% by weight. If the carbon content exceeds 5.5% by weight, the electrode density when used as a positive electrode is lowered, which is not preferable. Further, if the carbon content is less than 0.1% by weight, the effects such as electrical conductivity imparted by carbon cannot be sufficiently obtained, which is not preferable. A more preferable range of the carbon content is 0.2 to 4.5% by weight, and a particularly preferable content is 0.3 to 3.5% by weight.

Lithium nickel oxide according to the present invention - carbon composite positive electrode active material particles, in the Raman spectrum measured with green laser excitation wavelength 532 nm, and the peak intensity P _A G-prime band to the peak intensity P _G of the G band of carbon mean value _P a / _{P G} ratio of 0.1 to 0.8. Here, the G band of carbon is a peak appearing in the range of 1470 to 1700 cm ⁻¹ represented by the stretching mode E _2g2 between carbons of sp ² hybrid orbitals. The G prime band is also called a 2D band, and is a peak existing in the range of 2550 to 2850 cm ⁻¹ . The intensity of the band varies depending on the interaction between the carbon network surfaces and the influence of the layered layer structure. For example, in the monolayer graphene, the intensity of the G prime band is higher than that of the G band. On the other hand, almost no G prime band is seen in amorphous carbon having low crystallinity in the layer direction, that is, in which the periodicity of the crystal is disturbed. Therefore, also it means that it is to contain an indirect carbon nanotube P _A has a finite value. If P A _/ P _G is larger than 0.8, the carbon net plane crystallinity is too high poor flexibility, since hardly adheres to the surface of the lithium nickelate is not preferable. If P A _/ P _G is less than 0.1, free of carbon nanotubes, so is poor overall conductivity of the particles it is not preferable. A more preferable range of P _A / _{P G} is 0.15 to 0.7, furthermore preferably from 0.2 to 0.65.

Reference materials: Carbon nanotube graphene handbook ”Corona (2011) P171.

Lithium nickel oxide according to the present invention - carbon composite positive electrode active material particles, in the Raman spectrum, the average value P _{M /} P _G of the ratio of the peak intensity P _M of lithium nickelate to the peak intensity P _G is 0. 4-10. The peak due to lithium nickelate is in the range of 300 to 750 cm ⁻¹ . There are a transition metal-oxygen bond stretching mode A _{1 g} on the high wave number side and an oxygen-transition metal-oxygen bond bending mode E _g on the low wave number side, and an A _{1 g} mode having a high peak intensity is employed. Here, the Raman spectrum at the measurement wavelength is attributed to a crystal phase existing within a depth range of several hundred nm from the sample surface. Therefore, P M _/ P _G can be regarded as a value that reflects the existing ratio of nickel acid lithium and carbon in the deep range. It is preferably a lower P _{M /} P _G from the viewpoint of electron conductivity of the positive electrode active material particle surface, whereas, it is preferable higher P _{M /} P _G in view of electrode reaction of the positive electrode active material particle surfaces. P _M in the Raman _spectrum, a state in which all the peaks can be confirmed in the P _G, and P _A, which means that coexist and carbon lithium nickelate. A more preferable range of P _M / _{P G} is 0.45 to 9.5, more preferably from 0.5 to 9.0.

  The lithium nickelate-carbon composite positive electrode active material powder according to the present invention has a compression molded body density of 2.7 to 3.6 g / cc under a load of 8 kN and a volume resistivity of 0.1 to 200 Ω · cm. When the density of the compression molded body is less than 2.7 g / cc, the volume energy density of the battery is low, which is not preferable. When the density exceeds 3.6 g / cc, voids inside the electrode are reduced, and This is not preferable because the liquid becomes difficult to permeate and the ionic conductivity of the battery as a whole deteriorates. When the volume resistivity exceeds 200 Ω · cm, the performance of the battery is extremely lowered by the resistance. When the volume resistivity is less than 0.1 Ω · cm, the carbon content exceeds the specified value, which causes a decrease in the density of the molded body. More preferably, it is 2.75 to 3.55 g / cc and 0.5 to 150 Ω · cm, and further preferably 2.8 to 3.5 g / cc and 1 to 100 Ω · cm.

  The volume resistivity of the lithium nickelate-carbon composite positive electrode active material powder according to the present invention decreases as it is compressed. For example, when plotting the volume resistivity against the compression molded body density when each load from 0.5 kN to 18 kN is applied, a downwardly convex curve is obtained with a negative slope. Therefore, attention was paid to the relationship between the volume resistivity and the density of the compression-molded body when a load of 4 to 8 kN is obtained that provides a linear relationship. The absolute value | X | of the slope X strongly depends not only on the prescribed carbon content but also on the degree of the composite. A higher molded body density is desirable, and a lower volume resistivity is desirable, so a smaller value of | X | is desirable.

Generally, the carbon material used as a conductive agent is bulky, and it is necessary to minimize the amount of the carbon material used in order to increase the density of the active material when manufacturing the electrode. As described above, | X | values smaller is preferable, the average value P _{M /} P _G peak intensity ratio there is an optimal value. As a result of careful examination of these parameters, it was found that when the following formula (1) is established, the lithium nickelate-carbon composite cathode active material particle powder is suitable.
| X | / (P _M / P _G ) ≦ 500 (1)
When | X | / (P _M / P _G ) exceeds 500, an electrical contact between the lithium nickelate-carbon composite positive electrode active material particles is difficult to form efficiently in the electrode. Absent. A more preferable range of | X | / (P _M / P _G ) is 475 or less, and a more preferable range is 450 or less. The lower limit of | X | / (P _M / P _G ) is about 1.

The lithium nickelate-carbon composite positive electrode active material powder according to the present invention has a water vapor adsorption amount of 1 mg / g or less at a relative pressure condition P / P ₀ = 0.28 with respect to the saturated vapor pressure P ₀ . When the water vapor adsorption amount exceeds 1 mg / g, the hydrophilicity of the lithium nickelate-carbon composite is increased, and the affinity with the organic solvent used for producing the positive electrode may be decreased, which is not preferable. A more preferable range is 0.8 mg / g or less, and a further preferable range is 0.6 mg / g or less. The lower limit of the water vapor adsorption amount is about 0.001 mg / g.

The BET specific surface area of the lithium nickelate-carbon composite cathode active material powder according to the present invention is 10 m ² / g or less. When the BET specific surface area exceeds 10 m ² / g, it may be difficult to slurry the positive electrode active material particle powder for producing the positive electrode, which is not preferable. More preferably, it is 9.5 m < ² > / g or less, More preferably, it is 9.0 m < ² > / g or less. Since it is industrially difficult to produce a lithium nickelate-carbon composite cathode active material particle powder having a BET specific surface area of less than 0.05 m ² / g, the lower limit of the BET specific surface area is about 0.05 m ² / g. It is.

  Next, the manufacturing method of the lithium nickelate-carbon composite cathode active material particle powder in the present invention will be described.

  The lithium nickelate-carbon composite positive electrode active material particle powder in the present invention is obtained by preparing lithium nickelate and carbon, respectively, passing through a predetermined amount, and then press-contacting by mechanochemical treatment under an inert atmosphere. .

The lithium nickelate of the lithium nickelate-carbon composite positive electrode active material particles in the present invention is not particularly limited and can be obtained by a conventional method. For example, it can be obtained by mixing, firing and pulverizing various raw materials. Examples of the Li source include Li ₂ CO ₃ or LiOH.H ₂ O, and Ni, Co, and M (M is at least one of the elements Mn, Al, B, Mg, and Zn) include water containing the element. It is an oxide or a hydrous oxide. A predetermined amount of each raw material is weighed and mixed, and then desired lithium nickelate is obtained by firing in an oxidizing atmosphere in the range of 600 to 1100 ° C. As long as lithium nickelate can topochemically occlude and release lithium ions, there may be atomic unit defects or substitution of different elements in the particles.

  The lithium nickelate used for the raw material of the lithium nickelate-carbon composite positive electrode active material powder in the present invention is preferably spherical or substantially spherical because it is easy to press the carbon uniformly on the surface by mechanochemical treatment.

  The lithium nickelate used for the raw material of the lithium nickelate-carbon composite cathode active material powder in the present invention is not particularly limited in average secondary particle diameter, but is preferably 1 μm or more and 35 μm or less. More preferably, it is 2 μm or more and 30 μm or less, and a particularly preferable range is 3 μm or more and 25 μm or less. It is preferable that the secondary particle size distribution is sharp because complexation with carbon by mechanochemical treatment easily proceeds uniformly.

  At least a part of the carbon used as the raw material for the lithium nickelate-carbon composite cathode active material particles in the present invention is a carbon nanotube. Since the carbon nanotube has both high electronic conductivity and high mechanical strength, the composite particles have the same properties. The carbon nanotubes are produced by a hydrocarbon pyrolysis reaction using catalytic metal compound particles containing Fe, Co, Ni and the like. After the reaction, if necessary, purification for removing the metal compound particles for catalyst and oxidation for hydrophilizing the surface may be performed. Even if a defect occurs in the outermost layer of the tube, the carbon nanotubes are more preferably multi-walled because the conductivity is easily ensured by the inner tube. Since carbon nanotubes are hollow inside, they are distinguished from nanofibers having a dense inside for convenience.

  The weight ratio of carbon nanotubes in the carbon used as a raw material for the lithium nickelate-carbon composite cathode active material particles in the present invention is preferably 5% or more. The upper limit is 100% by weight. If it is less than 5% by weight, the electronic conductivity and mechanical strength of the positive electrode active material particle powder tend not to be sufficiently maintained. When carbon nanotubes and carbon other than carbon nanotubes are used together, they may be mixed in advance before the mechanochemical treatment, or may be added separately while performing the mechanochemical treatment.

  The carbon nanotube used for the raw material of the lithium nickelate-carbon composite cathode active material powder in the present invention preferably has a tube outer diameter of 5 to 50 nm. The diameter can be confirmed, for example, by observing a sample obtained by drying the dispersion with a transmission electron microscope or a high-resolution scanning electron microscope. When the outer diameter of the tube exceeds 50 nm, the number of fibers per unit weight decreases and sufficient conductivity cannot be obtained. Further, when the tube outer diameter is less than 5 nm, the carbon nanotubes easily form bundles, and dispersion becomes difficult, resulting in deterioration of characteristics. (Fiber length) / (Fiber diameter) is not particularly limited, but is preferably 100,000 or less. When (fiber length) / (fiber diameter) exceeds 100,000, the single fibers are easily entangled with each other, and it is difficult to make a composite with lithium nickelate, which is not preferable.

  The carbon nanotubes used as the raw material for the lithium nickelate-carbon composite cathode active material particles in the present invention are preferably easily dispersible carbon nanotubes that are easily dispersed. The easy dispersibility of the carbon nanotubes can be confirmed by, for example, a transmission electron microscope, and it is preferable that the ratio of the carbon nanotubes in a bundle shape is small and that the nodes and constricted portions are seen in the fiber length direction of the carbon nanotubes. Can be mentioned.

  Specifically, a 0.1% dispersion is placed on a sample stage and dried, and an image taken at 20,000 times with a transmission electron microscope is divided into 100 nm square sections, and carbon nanotubes occupy the sections. When 300 sections having an area of 10 to 80% are selected, 10% of sections have at least one constricted portion with a tube outer diameter of 90% or less with respect to the fiber diameter of the carbon nanotube in one section. The carbon nanotube which exists above is mentioned. More preferably, it is 30% or more, and most preferably 60% or more.

  A node or a constricted portion is a discontinuous portion of a crystal created by changing the growth direction of carbon nanotubes, and an easily breakable portion that can be easily cut with a small mechanical energy. In order to disperse carbon nanotubes, it is necessary to make single fibers and shorten fibers, and in order to disperse carbon nanotubes with few easily breakable portions, it is necessary to break and cut the continuous tube wall surface. In dry dispersion that imparts mechanical energy to the entire carbon nanotube with high linearity, the crystal structure of the entire carbon nanotube is destroyed more than necessary before the tube is divided, and electrical conductivity is a characteristic of the carbon nanotube. There is a risk that the characteristics such as will deteriorate. When carbon nanotubes with many easily breakable parts are used, the easily breakable parts are preferentially cut by absorbing the impact, so the mechanical energy required to complete the dispersion is small, and the graphite network surface other than the cut parts It is preferable because there is little damage. Carbon nanotubes having a node or a constriction can be obtained by slowing the production rate of carbon nanotubes depending on various conditions such as reaction temperature, raw material gas concentration and flow rate in the carbon nanotube production process.

  Carbon other than carbon nanotubes used as a raw material for the lithium nickelate-carbon composite cathode active material particles in the present invention is not particularly limited, but graphite, graphene, hard carbon, soft carbon, amorphous carbon, amorphous carbon, It can be selected from the group consisting of glassy carbon, carbon nanofibers and fullerenes.

  The shape of carbon other than carbon nanotubes used as the raw material for the lithium nickelate-carbon composite cathode active material particles in the present invention is, for example, spherical, scaly, needle-like, polygonal, columnar, plate-like, fiber-like, or these Mixtures are preferred. Among these, a three-dimensional structure structure in which fine particles are continuous is preferable. Specific examples include acetylene black (AB) and ketjen black. The carbon preferably has a minor axis diameter of 500 nm or less. Both the minor axis diameter and the major axis diameter can be confirmed by observing a sample obtained by drying the dispersion with a transmission electron microscope. In the case of a granular material, the aspect ratio determined by (major axis diameter) / (minor axis diameter) is not particularly limited, but is preferably 2 or less. A granular material with an aspect ratio exceeding 2 is not preferable because it tends to be bulky.

  The treatment by the mechanochemical method of the method for producing the lithium nickelate-carbon composite cathode active material particle powder in the present invention can be adjusted to the atmosphere, and stress such as shearing, compression, and collision can be simultaneously applied. Although an apparatus can be used, the processing apparatus is not limited to an apparatus using such a structure and principle. Examples of the apparatus used for the mechanochemical process include a ball-type kneader such as a rotary ball mill, a wheel-type kneader such as an edge runner, a hybridization system (manufactured by Nara Machinery Co., Ltd.), and mechano-fusion (Hosokawa Micron). Nobilta (manufactured by Hosokawa Micron Corporation), COMPOSI (manufactured by Nippon Coke Industries Co., Ltd.), and the like.

The mechanochemical treatment is preferably performed in an inert atmosphere. When lithium nickelate is handled in an oxidizing atmosphere or a high-humidity atmosphere that is not an inert atmosphere, the inter-layer Li is leached to the surface and changed to Li ₂ CO _3, etc., and the charge / discharge capacity of a lithium ion secondary battery Is unfavorable because it decreases.

  In order to suppress hydrophilization as the positive electrode active material particle powder by mechanochemical treatment, and to suppress deterioration of crystallinity of carbon and lithium nickelate, it is desirable to adjust the force applied to the mixed powder. As a specific method, the rotational speed of the processing apparatus may be reduced or the processing time may be shortened.

  When the lithium nickelate-carbon composite cathode active material powder according to the present invention is produced, mechanochemical treatment is performed on a mixture of lithium nickelate and carbon in advance under an inert atmosphere. In some cases, mechanochemical treatment may be performed on a part of the mixture, and then lithium nickelate and / or carbon may be added and repeated mechanochemical treatment. In particular, it is preferable to divide and add carbon because carbon is uniformly compounded on the lithium nickelate surface. However, if the mechanochemical treatment is performed with 0.8% by volume or less of carbon, the crystallinity deterioration and chipping of lithium nickelate are caused by frictional heat and impact, which is not preferable. Moreover, you may add carbon not as a dry powder state but as a dispersion liquid. As the dispersion medium, it is preferable to use an organic solvent that does not contain water so as not to affect the lithium nickelate. When added as a dispersion, it is more preferable to spray the mixture. It is preferable to keep the reaction field in an inert atmosphere during the divided charging and the dispersion spraying.

  After the above treatment, carbon that has not been complexed with lithium nickelate may be removed by classification, but it is desirable to carry out by a method that does not give much impact force to the powder, and it is desirable not to classify. Examples of the classifier include a precision air classifier such as a turbo classifier (manufactured by Nisshin Engineering Co., Ltd.), an elbow jet (manufactured by Nittetsu Mining Co., Ltd.), a class seal (manufactured by Seishin Enterprise Co., Ltd.), and the like.

Heat treatment may be added to the above step as long as the structure of the lithium nickelate-carbon composite cathode active material particle powder is not significantly changed. Heat treatment is performed using a tubular furnace, a gas flow-type box muffle furnace, a gas flow-type rotary furnace, a roller hearth kiln, etc. at 600 ° C. or lower, an inert gas such as Ar, Cl, CO ₂ , CO, the atmosphere, O _2, etc. One or more selected from an oxidizing gas, a hydrocarbon gas such as CH ₄ , C ₂ H ₄ , or C ₂ H ₂ may be used. In some cases, a lithium compound such as LiOH or Li ₂ CO ₃ is mixed. May be. By this heat treatment, the hydrophilicity, crystallinity, and composition of the lithium nickelate particle-carbon composite cathode active material particles can be adjusted.

  Two or more types of lithium nickelate-carbon composite cathode active material particles may be mixed, or lithium nickelate particle-carbon composite cathode active material particles and lithium nickelate alone may be mixed. By mixing powders having different processing histories, for example, the electrode density and charge / discharge capacity can be adjusted.

  Next, a non-aqueous electrolyte secondary battery using the lithium nickelate-carbon composite cathode active material powder according to the present invention will be described.

  The secondary battery in the present invention includes a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator.

  When manufacturing the positive electrode containing the positive electrode active material particle powder according to the present invention, a conductive agent and a binder are added and mixed according to a conventional method. As the conductive agent, carbon materials such as acetylene black, carbon black, carbon nanofiber, and graphite can be applied. However, since the positive electrode active material particle powder according to the present invention is a particle powder combined with carbon, it is not always necessary to mix the conductive material. As the binder, polyamideimide, polyimide, polytetrafluoroethylene, polyvinylidene fluoride, acrylic resin, and the like are preferable. For example, N-methyl-pyrrolidone (NMP) is preferably used as the solvent.

  As the negative electrode active material, lithium metal, lithium / aluminum alloy, lithium / tin alloy, graphite or the like can be used, and the negative electrode sheet is produced by the same doctor blade method or metal rolling as the positive electrode.

Further, the solvent is not particularly limited as long as it can be used for a non-aqueous electrolyte. Generally, aprotic high dielectric constant solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, dipropyl carbonate, diethyl ether, tetrahydrofuran, 1,2, -Aprotic low viscosity such as acetate ester or propionate ester such as dimethoxyethane, 1,2-diethoxyethane, 1,3-dioxolane, sulfolane, methylsulfolane, acetonitrile, propionitrile, anisole, methyl acetate A solvent is mentioned. These aprotic high-dielectric constant solvents and aprotic low-viscosity solvents are desirably used in combination at an appropriate mixing ratio. Furthermore, ionic liquids using imidazolium, ammonium, and pyridinium type cations can be used. The counter anion is not particularly limited, and examples thereof include BF ⁴⁻ , PF ⁶⁻ , (CF ₃ SO ₂ ) ₂ N ^{− and the} like. The ionic liquid can be used by mixing with the aforementioned non-aqueous electrolyte solvent.

Further, examples of the electrolyte salt include LiPF ₆ , (CF ₃ SO ₂ ) ₂ NLi, LiBF ₄ , LiClO ₄ , LiAsF ₆ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, and CF ₃ CO, which are lithium salts. ₂ Li, (CF ₃ CO ₂ ) ₂ NLi, C ₆ F ₅ SO ₃ Li, C ₈ F ₁₇ SO ₃ Li, (C ₂ F ₅ SO ₂ ) ₂ NLi, (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) NLi, (FSO ₂ C ₆ F ₄ ) (CF ₃ SO ₂ ) NLi, ((CF ₃ ) ₂ CHOSO ₂ ) ₂ NLi, (CF ₃ SO ₂ ) ₃ CLi, (3,5- (CF ₃ ) ₂ C ₆ F ₃ ) ₄ BLi, LiCF ₃ , LiAlCl ₄ , C ₄ BO ₈ Li and the like, and any one or two or more of these may be used in combination.

<Action>
The lithium nickelate-carbon composite cathode active material powder according to the present invention is appropriately composited with carbon, and a part of the carbon is at least a carbon nanotube. Therefore, it is a positive electrode active material particle powder having a high electron conductivity, an appropriate electrode reaction field, a high compact density, and a high mechanical strength, and a secondary battery composed of the particle powder has a high energy density. In addition, it is presumed that the charge / discharge repetition characteristics are excellent.

  Hereinafter, although the example of the concrete implementation of this invention is shown below, this invention is not limited to a following example at all.

  The powder evaluation of the lithium nickelate-carbon composite cathode active material particle powder of the present invention was performed as follows.

(A) Measurement of Raman spectrum Using a green laser with an excitation wavelength of 532 nm using a micro-Raman spectrometer innoRam (manufactured by B & W Tek), measurement is performed on 10 arbitrary particles at a magnification of 100 times and 10 times of integration. The average ratio was calculated.

(B) Measurement of powder resistivity The density of the compacted compact of the particle powder was 0.5, 1, 2, 4, 6, 8, 10, 12, 14, using a 2.00 g sample with a 20 mm diameter jig. The powder was compacted by applying a load of 16, 18 kN, the thickness of the molded body was measured for each pressure, and the volume / weight ratio of the obtained molded body was calculated. At the same time, the volume resistivity was measured with a resistivity meter Loresta GP (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) using the 4-terminal method and 10V.

(C) Measurement of water vapor adsorption amount After the sample was vacuum dried at 120 ° C., the water vapor adsorption isotherm was measured using BELSORP-aqua3 (Microtrack Bell Co., Ltd.), and P / P ₀ = 0.28. The value at was taken as the amount of water vapor adsorption.

(D) Measurement of BET specific surface area The BET specific surface area was measured using a fully automatic specific surface area meter Macsorb model-1201 (manufactured by Mountec Co., Ltd.).

(E) Evaluation of composite of particle powder by shape observation and EDX mapping A sheet dispersed and fixed so that particles are not stacked was photographed from directly above the sheet with a high-resolution scanning electron microscope (S-4800 manufactured by Hitachi High-Tech). . Ni element and C element were mapped with EDX (manufactured by Edax Japan) as it was. As a judgment of the appearance uniformity and the degree of compounding of carbon, when segregation of C element is not confirmed in 10 visual fields where about 10 particles are observed, ○ when 1 visual field is observed Δ, 2 visual fields or more are observed It was determined to be ×.

(F) Measurement of carbon content The carbon content in the sample was measured using a carbon / sulfur analyzer EMIA-2200 (manufactured by Horiba, Ltd.).

(G) Measurement of secondary particle diameter The secondary particle diameter of the sample was a laser diffraction / scattering particle size distribution analyzer LMS-2000e (manufactured by Seishin Enterprise Co., Ltd.).

(H) Battery evaluation test Preparation of positive electrode:
96 parts by weight of the sample and 4 parts by weight of Kurewa Chemical KF polymer W # 1300 are added to the NMP solvent and kneaded with a planetary mixer and a thin-film swirl type high speed mixer to adjust the solid content concentration to about 68.5% by weight. Then, it was coated on a high-purity aluminum foil using a 140 μm doctor blade. After drying the electrode sheet after coating at 80 ° C., the electrode sheet was pressed with a linear pressure of 0.06 kN / mm using a roll press, punched out to a size of 40 mm × 50 mm, and further 120 The mixture was vacuum-dried at 12 ° C. for 12 hours.
Production of laminate cell for full cell:
The following operations were performed in a dry atmosphere with a dew point of −50 ° C. or lower.
In the aluminum laminate foil for lithium ion batteries, each positive electrode and a negative electrode obtained by applying artificial graphite to a copper foil were sandwiched and laminated. In this laminate, an electrolyte (EC (ethylene carbonate) and EMC (ethyl methyl carbonate) mixed at a volume ratio of 1: 2) was used as a solvent, and LiPF ₆ was dissolved as an electrolyte at a concentration of 1 mol / L. To obtain a test cell.
Charge / discharge test:
Charging was performed by constant current charging (CC charging) at 0.2 C, and charging was completed at 4.3 V. The discharge was a constant current discharge (CC discharge) at 0.2 C and cut off at 3.0 V.
Cycle test:
In a thermostatic bath at 25 ° C., CC charging up to 4.1 V at 1 C and CC discharging up to 3.0 V at 1 C were repeated 35 cycles.

In the following examples and comparative examples, carbon used as a raw material for mechanochemical treatment is carbon (I) obtained by mixing 5% by weight of carbon (II) described later with AB Denka Black HS-100, which is a non-bundle type. Is the carbon (II) of the multi-walled carbon nanotube having a larger number, carbon (III) of the multi-walled carbon nanotube having less nodes and less nodes, and carbon (IV) of the bundle-type carbon nanotube. The raw material lithium nickelate used in the treatment was Li _1.03 Ni _0.8 Co _0.15 Al _0.05 O ₂ (A) having an average secondary particle diameter of 10 μm and a BET of 0.2 m ² / g, and average secondary particles. Li _1.05 Ni _0.333 Co _0.333 Mn _0.333 O ₂ (M) having a diameter of 5 μm and a BET of 0.4 m ² / g was used.

  For comparison, only lithium nickelate (A) was subjected to mechanochemical treatment in a nitrogen gas atmosphere for 1, 5, and 30 minutes to obtain lithium nickelate (A-1), (A-2), ( A-3) was prepared, and the volume resistivity and density at a BET specific surface area and a load of 6 kN were measured. The results are shown in Table 1.

As the mechanochemical treatment time was extended, the BET specific surface area did not change, but the molded body density at 6 kN decreased and the volume resistivity increased significantly. Further, the water vapor adsorption amount of lithium nickelate (A) at P / P ₀ = 0.28 was 0.45 mg / g, and P / P _{0 of} lithium nickelate (A-1) treated for 1 minute = 0. The water vapor adsorption amount at 28 was 0.50 mg / g. With the mechanochemical treatment, the surface structure slightly changed to easily adsorb water vapor. When the obtained sample surface was observed with a scanning electron microscope (SEM), it was estimated that the sample surface became amorphous and electrochemically inactive because the smoothness of the sample surface was improved after the treatment. did.

<Example 1>
A mixture of lithium nickelate (M) and carbon (II) 2% by weight is compounded by a mechanochemical treatment for 1 minute in a nitrogen gas atmosphere, and lithium nickelate-carbon having a carbon content of 1.98% by weight. A composite positive electrode active material particle powder 1 was obtained. When observed by SEM and EDX, as shown in FIG. 1, Ni element derived from lithium nickelate and C element derived from carbon were confirmed in all particles. Since there was no carbon segregation in observation of several fields of view, it was judged that the appearance uniformity and the degree of particle complexation were ○. In addition, the presence of carbon nanotubes was confirmed from the shape by high-magnification SEM observation. In the Raman spectrum of one arbitrary particle shown in FIG. 2, a peak corresponding to the vibration mode was confirmed. Both peaks derived from lithium nickelate and carbon were observed in all 10 particles. Intensity ratio average value _P A / _{P G} in the Raman spectrum for the 10 particles _{0.56, P} M / P _G was 0.97.

<Example 2>
A mixture of lithium nickelate (M) and carbon (IV) 2% by weight is compounded by mechanochemical treatment for 1 minute in a nitrogen gas atmosphere, and lithium nickelate-carbon having a carbon content of 2.00% by weight A composite positive electrode active material particle powder 2 was obtained. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 fields of view. Mean value _P A / _{P G} in the Raman spectrum of the 10 field are _{0.28, P} M / P _G was 4.01.

<Example 3>
Except that the mechanochemical treatment time was changed to 5 minutes, the same procedure as in Example 2 was performed to obtain a lithium nickelate-carbon composite cathode active material particle powder 3 having a carbon content of 1.99% by weight. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 visual fields, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.22, the P M / _{P G} was 0.66.

<Example 4>
A mixture of lithium nickelate (A) and carbon (I) 2% by weight is compounded by a mechanochemical treatment for 1 minute in a nitrogen gas atmosphere, and lithium nickelate-carbon having a carbon content of 2.03% by weight. A composite positive electrode active material particle powder 4 was obtained. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 visual fields, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.19, the P M / _{P G} was 0.50.

<Example 5>
A mixture of lithium nickelate (A) and carbon (II) 5% by weight is compounded by mechanochemical treatment for 1 minute in a nitrogen gas atmosphere, and lithium nickelate-carbon having a carbon content of 4.48% by weight. A composite positive electrode active material particle powder 5 was obtained. In the Raman spectrum, all the peaks derived from carbon and lithium nickelate were confirmed in all 10 fields of view. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.58, the P M / _{P G} was 4.09.

<Example 6>
Except for changing the mechanochemical treatment time to 5 minutes, the same procedure as in Example 5 was performed to obtain lithium nickelate-carbon composite positive electrode active material powder 6 having a carbon content of 4.75% by weight. In the Raman spectrum, all the peaks derived from carbon and lithium nickelate were confirmed in all 10 fields of view, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.40, the P M / _{P G} was 0.73.

<Example 7>
A mixture of lithium nickelate (A) and carbon (II) 2% by weight is compounded by mechanochemical treatment for 1 minute in a nitrogen gas atmosphere, and lithium nickelate-carbon having a carbon content of 2.02% by weight A composite positive electrode active material particle powder 7 was obtained. In the Raman spectrum, all the peaks derived from carbon and lithium nickelate were confirmed in all 10 fields of view. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.58, the P M / _{P G} was 1.14.

<Example 8>
Except that the mechanochemical treatment time was changed to 3 minutes, the same procedure as in Example 7 was performed to obtain a lithium nickelate-carbon composite cathode active material particle powder 8 having a carbon content of 1.90% by weight. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 visual fields, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.54, the P M / _{P G} was 1.01.

<Example 9>
Except for changing the mechanochemical treatment time to 5 minutes, the same procedure as in Example 7 was performed to obtain a lithium nickelate-carbon composite positive electrode active material particle powder 9 having a carbon content of 1.98 wt%. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 visual fields, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.49, the P M / _{P G} was 0.40.

<Example 10>
Under a nitrogen gas atmosphere, while adding 2% by weight of carbon fine particles (II) to lithium nickelate (A) in three portions, it was compounded by mechanochemical treatment for 3 minutes, and the carbon content was 2.02% by weight. A lithium nickelate-carbon composite cathode active material particle powder 10 was obtained. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 visual fields, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.41, the P M / _{P G} was 0.61.

<Example 11>
After a mechanochemical treatment for 29 minutes with respect to lithium nickelate (A) in a nitrogen gas atmosphere, 2% by weight of carbon (II) was added and further compounded by a mechanochemical treatment for 1 minute to obtain a carbon content. A 2.22 wt% lithium nickelate-carbon composite positive electrode active material powder 11 was obtained. In the Raman spectrum, all the peaks derived from carbon and lithium nickelate were confirmed in all 10 fields of view. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.57, the P M / _{P G} was 1.01.

<Example 12>
A mixture of lithium nickelate (A) and carbon (II) 1% by weight is compounded by mechanochemical treatment for 2 minutes in a nitrogen gas atmosphere, and lithium nickelate-carbon having a carbon content of 1.01% by weight. A composite positive electrode active material particle powder 12 was obtained. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 visual fields, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.51, the P M / _{P G} was 0.67.

<Example 13>
A mixture of lithium nickelate (A) and carbon fine particle (II) 0.3% by weight is compounded by a mechanochemical treatment for 1 minute in a nitrogen gas atmosphere, and a carbon content of 0.34% by weight lithium nickelate -Carbon composite positive electrode active material particle powder 13 was obtained. In the Raman spectrum, all the peaks derived from carbon and lithium nickelate were confirmed in all 10 fields of view. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.63, the P M / _{P G} was 8.61.

<Example 14>
Except for changing the mechanochemical treatment time to 5 minutes, a lithium nickelate-carbon composite positive electrode active material particle powder 14 having a carbon content of 0.35 wt% was obtained in the same manner as in Working Example 13. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 visual fields, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.37, the P M / _{P G} was 2.27.

<Example 15>
Except for changing the treatment time to 30 minutes, the same procedure as in Example 13 was performed to obtain a lithium nickelate-carbon composite positive electrode active material particle powder 15 having a carbon content of 0.28 wt%. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 visual fields, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.18, the P M / _{P G} was 1.35.

<Example 16>
In a nitrogen gas atmosphere, 2 wt% of carbon fine particles (III) were dividedly added to lithium nickelate (A) in three portions and combined by mechanochemical treatment for 3 minutes, resulting in a carbon content of 1.98 wt%. Of lithium nickelate-carbon composite cathode active material particles 16 were obtained. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 fields of view. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.35, the P M / _{P G} was 0.57.

  Table 2-1 shows the manufacturing conditions and the results of the measured powder properties for the lithium nickelate-carbon composite cathode active material particles produced in the above examples. Appearance uniformity and degree of particle complexation are due to SEM-EDX mapping.

<Comparative Example 1>
In a nitrogen gas atmosphere, lithium nickelate (A) and carbon (I) 2% by weight are combined by mixing in an agate mortar, and a lithium nickelate-carbon composite cathode active material having a carbon content of 1.99% by weight Material particle powder 21 was obtained. As a result of confirmation by SEM and EDX, segregation of C element as an AB aggregate was observed in several fields, and only a carbon peak was confirmed in a Raman spectrum, and a peak derived from lithium nickelate was not observed. was there. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.22, the P M / _{P G} was 16.79.

<Comparative example 2>
In a nitrogen gas atmosphere, lithium nickelate (M) and carbon fine particles (II) 2% by weight are combined by mixing in an agate mortar, and a lithium nickelate-carbon composite having a carbon content of 1.98% by weight Positive electrode active material particle powder 22 was obtained. As a result of confirmation by SEM and EDX, segregation of C element was observed as a carbon nanotube aggregate in several fields of view (see FIG. 3), and in the Raman spectrum, only the carbon peak was confirmed, and the peak derived from lithium nickelate There was a field of vision that could not be seen. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.58, the P M / _{P G} was 7.55.

<Comparative Example 3>
Except for changing the mechanochemical treatment time to 30 minutes, the same procedure as in Example 1 was performed to obtain a lithium nickelate-carbon composite cathode active material particle powder 23 having a carbon content of 2.01 wt%. All peaks derived from carbon and lithium nickelate were confirmed in all 10 fields of the Raman spectrum, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} 0.13 in the Raman spectrum of the 10 fields from lithium G band and nickelate carbon to indicate the Raman spectrum of the arbitrary field of view in FIG. _{3, P} M / P _G 0. It was 12.

<Comparative Example 4>
A mixture of lithium nickelate (A) and carbon (I) 5% by weight is compounded by mechanochemical treatment for 1 minute in a nitrogen gas atmosphere, and lithium nickelate having a carbon content of 4.98% by weight Carbon composite positive electrode active material particle powder 24 was obtained. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 visual fields, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.23, the P M / _{P G} was 0.27.

<Comparative Example 5>
Except for changing the mechanochemical treatment time to 5 minutes, the same procedure as in Comparative Example 4 was carried out to obtain a lithium nickelate-carbon composite positive electrode active material particle powder 25 having a carbon content of 4.60% by weight. In the Raman spectrum, all the peaks derived from both carbon and lithium nickelate were confirmed in all 10 fields of view, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.17, the P M / _{P G} was 0.26.

<Comparative Example 6>
A lithium nickelate-carbon composite positive electrode active material powder 26 having a carbon content of 4.76% by weight was obtained except that the treatment time was changed to 30 minutes. In the Raman spectrum, all the peaks derived from both carbon and lithium nickelate were confirmed in all 10 fields of view, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.09, the P M / _{P G} 0.17.

<Comparative Example 7>
In a nitrogen gas atmosphere, lithium nickelate (A) and carbon fine particles (I) 2% by weight are combined by mixing in an agate mortar, and the lithium nickelate-carbon composite having a carbon content of 2.01% by weight A positive electrode active material particle powder 27 was obtained. As a result of confirmation by SEM and EDX, segregation of C was observed as AB aggregates in several visual fields, and in the Raman spectrum, only a carbon peak was confirmed, and there was a visual field in which no peak derived from lithium nickelate was observed. It was.

<Comparative Example 8>
Except for changing the treatment time to 5 minutes, the same procedure as in Example 4 was performed to obtain a lithium nickelate-carbon composite cathode active material particle powder 28 having a carbon content of 1.96 wt%. In the Raman spectrum, the peaks of both carbon and NCA were confirmed in all 10 fields of view, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.12, the P M / _{P G} was 0.21.

<Comparative Example 9>
Except for changing the treatment time to 30 minutes, the same procedure as in Example 4 was performed to obtain a lithium nickelate-carbon composite positive electrode active material powder 29 having a carbon content of 2.01 wt%. In the Raman spectrum, all the peaks derived from both carbon and lithium nickelate were confirmed in all 10 fields of view, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.08, the P M / _{P G} was 0.12.

<Comparative Example 10>
Except for changing the treatment time to 30 minutes, the same procedure as in Example 5 was performed to obtain a lithium nickelate-carbon composite positive electrode active material particle powder 30 having a carbon content of 4.97% by weight. In the Raman spectrum, all peaks derived from carbon and lithium nickelate were confirmed in all 10 visual fields, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.22, the P M / _{P G} was 0.05.

<Comparative Example 11>
In a nitrogen gas atmosphere, lithium nickelate (A) and carbon fine particles (II) 2% by weight are combined by mixing in an agate mortar, and a lithium nickelate-carbon composite having a carbon content of 1.99% by weight A positive electrode active material particle powder 31 was obtained. As a result of confirmation by SEM and EDX, segregation of the C element was observed as the carbon nanotube aggregate, and in the Raman spectrum, only the carbon peak was confirmed, and there was a field of view in which the peak derived from lithium nickelate was not observed. .

<Comparative Example 12>
Except for changing the treatment time to 30 minutes, the same procedure as in Example 7 was performed to obtain a lithium nickelate-carbon composite positive electrode active material particle powder 32 having a carbon content of 1.95% by weight. In the Raman spectrum, all the peaks derived from both carbon and lithium nickelate were confirmed in all 10 fields of view, and it was confirmed that there was no segregation of carbon. Mean value _P A / _{P G} in the Raman spectrum of the 10 field is _0.14, the P M / _{P G} was 0.18.

  Table 2-2 shows the manufacturing conditions and the results of the measured powder properties for the lithium nickelate-carbon composite cathode active material particles produced in the above comparative example. Appearance uniformity and degree of particle complexation are due to SEM-EDX mapping.

  As for the amount of water vapor adsorption, comparing the treatments under the same conditions, the water vapor adsorption amount increases as the treatment time increases, and when the amount of carbon addition is different, the water vapor adsorption amount tends to increase as the carbon amount increases. It was. As the amount of carbon increases, the number of adsorption sites increases, and it is assumed that the amount of water vapor adsorption increased.

FIG. 4 plots data on the volume resistivity dependence of the powder compact density. In the examples, the volume resistivity around 3.0 g / cc was low, and the volume resistivity of the comparative example and lithium nickelate (M) was high. Comparative Example 3 showed a high compact density and volume resistivity close to the third embodiment, a low ratio of P M _/ P _G, good initial cell characteristics are presumed not obtained.

Tables 3-1 and 3-2 show the values of volume resistivity, molded body density, and | X | / (P _M / P _G ) of Examples and Comparative Examples, respectively. The examples tended to have low volume resistivity, high molded body density, and low | X | / (P _M / P _G ) values. On the other hand, the comparative example tended to have a high volume resistivity, a low molding density, and a high value of | X | / (P _M / P _G ).

  3 of untreated lithium nickelate (A), lithium nickelate-carbon composite cathode active material particle powder 10 (Example 10), lithium nickelate-carbon composite cathode active material particle powder 12 (Example 12) About the point, the electrode sheet was produced and the evaluation was performed. Electrode (a) prepared by adding 3% by weight of AB to untreated lithium nickelate (A), electrode prepared by adding 1% by weight of AB to lithium nickelate-carbon composite cathode active material particle powder 10 (B) An electrode (c) prepared by adding 2% by weight of AB to the lithium nickelate-carbon composite positive electrode active material particle powder 12 was adjusted to have a thickness of each electrode of about 47 μm. The electrical resistivity of the sheet was measured. The results are shown in Table 4. Since the mixture density of the electrode (a) and the electrode (c) became equal and the added AB was bulky, the difference was not as great as the compression density measured only with the lithium nickelate-carbon composite cathode active material powder. However, regarding the electrical resistivity of the electrode, the electrode (b) in which about 2% by weight of carbon nanotubes were combined was the lowest.

  The results of the initial charge / discharge test and the 30-cycle charge / discharge test in the full cell using the electrode (a), the electrode (b), and the electrode (c) with the electrode mixture density adjusted to about 2.85 g / cc are also shown in the table. 4 shows. It was confirmed that the electrode (c) was the best, followed by the electrode (b) and the electrode (a) in this order, and the effect of combining carbon appeared in the improvement of the cycle characteristics.

  The lithium nickelate-carbon composite positive electrode active material particle powder according to the present invention has high electron conductivity, high molded body density, appropriate electrode reaction field, and high mechanical strength. Therefore, the obtained nonaqueous electrolyte secondary battery has a high energy density and is excellent in charge / discharge repetition characteristics.

Claims (8)

Lithium nickelate - a carbon composite positive electrode active material particles, wherein the lithium nickelate formula _{Li 1 + a Ni 1-b} -c Co b M c O 2 (M is an element Mn, Al, B, Mg, and Zn At least one of them, -0.1 ≦ a ≦ 0.2, 0.05 ≦ b ≦ 0.5, 0.01 ≦ c ≦ 0.4), and a part of the carbon is at least a carbon nanotube , and the said carbon content is from 0.1 to 5.5 wt%, in the Raman spectrum measured by using the positive electrode active material particles in the green laser excitation wavelength 532 nm, to the peak intensity P _G of the G band of carbon mean value _P a / _{P G} of the ratio of the peak intensity _{P a} G-prime band is 0.1 to 0.8, the ratio of the peak intensity _{P M} of lithium nickelate to the peak intensity _{P G} of the spectrum flat Lithium nickelate value _P M / _{P G} is characterized in that 0.4 to 10 - carbon composite positive electrode active material particles.   The lithium nickelate-carbon composite cathode active material powder according to claim 1, wherein the density of the compression molded body under a load of 8 kN is 2.7 to 3.6 g / cc, and the volume resistivity is 0.00. A lithium nickelate-carbon composite positive electrode active material particle powder having a particle size of 1 to 200 Ω · cm. Lithium nickelate according to claim 1 or 2 - a carbon composite positive electrode active material particles, the average value P _{M /} P _G of the peak intensity ratio, 4 kN, 6 kN, at the time of applying a load of 8kN Lithium nickelate-carbon composite positive electrode active material particles, wherein the following formula (1) holds between the absolute value | X | of the slope X when plotting the volume resistivity against the compression molded body density Powder.
| X | / (P _M / P _G ) ≦ 500 (1) The nickel nickelate-carbon composite cathode active material powder according to any one of claims 1 to 3, wherein the water vapor adsorption amount at P / P ₀ = 0.28 is 1 mg / g or less. Lithium acid-carbon composite cathode active material particle powder. 5. The lithium nickelate-carbon composite cathode active material powder according to claim 1, wherein the lithium nickelate-carbon composite cathode active material has a BET specific surface area of 10 m ² / g or less. Particle powder.   The nickel nickelate-carbon composite cathode active material powder according to any one of claims 1 to 5, wherein the carbon nanotube has a node and the outer diameter of the tube is 5 nm to 50 nm. Lithium-carbon composite cathode active material particle powder.   It is a manufacturing method of lithium nickelate-carbon composite positive electrode active material particle powder of any one of Claims 1-6, Comprising: Nickel acid by mechanochemical treatment of lithium nickelate and carbon in inert gas atmosphere A method for producing a lithium nickelate-carbon composite cathode active material particle powder, wherein the lithium surface is coated.   A secondary battery comprising the lithium nickelate-carbon composite cathode active material particle powder according to any one of claims 1 to 6 as at least a part of a cathode active material of a secondary battery for nonaqueous electrolyte.