JPH09298062A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery of excellent cycle characteristics in which a discharge capacity is not decreased by increase of a charge/discharge cycle number in the case where charging is performed to a higher potential. SOLUTION: This battery is composed of a positive electrode, a negative electrode, and nonaqueous ion conductor. Active material in the positive electrode has a layered rock salt structure belonging to a space group of R-3m, and the electrode coutaius such lithium nickelate that a rate of total of lithium occupying a site 3a and a site 3d determined by sort belt analysis of a diffraction pattern obtained by a powder diffraction method using X-ray to total of nickel occupying the site 3a and the site 3b, that is Li/Ni, is 1.05-1.15.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode, a negative electrode, a non-aqueous ionic conductor, a positive electrode containing lithium nickel oxide and a substance containing lithium, or a substance capable of inserting and releasing lithium, particularly carbon. , A non-aqueous secondary battery comprising a negative electrode containing graphite.

[0002]

2. Description of the Related Art With the miniaturization and power saving of electronic devices,
Research and development of secondary batteries that use lightweight and high-voltage alkaline metals such as lithium are underway. When an alkali metal such as lithium is used alone for the negative electrode, repeated charging and discharging,
That is, by the dissolution-precipitation process of the alkali metal, dendrites (dendritic crystals) are generated on the dissolution-precipitation surface of the metal.
There is a problem in that the growth penetrates the separator and contacts the positive electrode to induce a short circuit inside the battery. It has been found that when an alkali metal alloy is used instead of an alkali metal for a negative electrode for a secondary battery, the generation of dendrites is suppressed and the charge / discharge cycle characteristics are improved as compared with the case of a single substance. However, the use of the alloy does not completely prevent the generation of dendrite, and may cause a short circuit inside the battery. In recent years, instead of using a dissolution-precipitation process or a dissolution-precipitation-diffusion process of a metal such as an alkali metal or an alloy thereof for a negative electrode, carbon or carbon using an absorption-desorption process of an alkali metal ion is used. Organic materials such as conductive polymers have been developed. As a result, the generation of dendrites that occur when using alkali metals or their alloys will no longer occur in principle, and the problem of short circuits inside the battery will be drastically reduced.Currently, carbon or graphite is used for the negative electrode and cobalt oxide for the positive electrode. Lithium ion batteries using lithium have been put to practical use.

However, when lithium cobalt oxide is used for the positive electrode, there are problems that the amount of cobalt is small and the raw material cost is high.

Therefore, lithium nickelate using nickel, which is lower in cost and richer in resources, has been noted since it was proposed by John Bannister Goodenaf et al. (Japanese Patent Publication No. 63-59507).

A lithium secondary battery having a high voltage using an electrode containing a composite oxide in which another element is added to lithium nickelate is disclosed in JP-A-62-90863 (A).
_x M _y N _z O ₂ , A is an alkali metal, M is a transition metal, N is aluminum, indium, tin, and a substance in which a part of the transition metal is replaced with aluminum, indium, tin, x:
0.05-1.10, y: 0.85-1.00, z:
0.001 to 0.10), JP 62-264560 JP _{(LiNi x Co 1-x O} 2), JP-A-4-17165
No. 9 (substitution of lithium with alkaline earth metal), JP-A-5-101827 (substitution of nickel with magnesium, vanadium, chromium, copper), JP-A-5-283076 (nickel). A part of the above is replaced with titanium, vanadium, manganese, and iron), JP-A-6-1.
As disclosed in Japanese Patent No. 24707 (substituting a part of nickel with copper, silver and zinc) and the like, it is proposed.

Regarding the composition of lithium nickelate, Japanese Patent Laid-Open No. 2-40861 discloses Li _y Ni _2-y O ₂ (y: 0.
84-1.22) is proposed, and is disclosed in Japanese Patent Laid-Open No. 5-290851.
In the publication, Li _x NiO _y (x: 1.15 to 1.75, y
By using> 0), the capacity is improved.

In terms of physical properties, Japanese Unexamined Patent Publication No. 5-290845.
JP-A-6-60887 and JP-A-6-96.
By optimizing the peak intensity ratio of the diffraction line obtained from the powder X-ray diffraction pattern as disclosed in JP-A-76928 and JP-A-6-111822.
6 and JP-A-6-124707, hexagonal lattice constants (a-axis and c-axis) of a substance obtained by substituting a part of nickel of lithium nickelate with another element.
Proposal to improve the discharge capacity, high rate discharge, and cycle characteristics by optimizing the half-value width of the peak and the nickel valence related to the (003) plane as disclosed in JP-A-6-267539. was there.

[0008]

However, in the evaluation using the conventional lithium nickel oxide, the termination potential of charging is 4.2 to 4.3 V with respect to the lithium reference electrode, and charging is performed to a higher potential. In this case, although the initial discharge capacity was about 180 mAh / g, there was a problem that the discharge capacity was remarkably reduced as the number of charge / discharge cycles increased, and the life due to charge / discharge cycles was short.

[0009]

Therefore, as a result of intensive research to solve the above problems, the correlation between the site occupancy ratio of lithium and nickel obtained from the powder X-ray diffraction pattern and the charge-discharge cycle characteristics are correlated. We found out that there is a relationship, and found that the problems can be solved by the following methods.

According to the present invention, the positive electrode active material is R-3.
It has a layered rock-salt structure belonging to a space group of m, and is preferably obtained by a method of obtaining a diffraction pattern obtained by a powder diffraction method using X-rays by Rietveld analysis.
A lithium nickelate having a ratio (Li / Ni) of the total lithium occupying the a site and the 3b site and the total nickel occupying the 3a site and the 3b site is 1.05 to 1.15 is included. The above-mentioned problems are solved by the non-aqueous secondary battery, which is the second electrode.

The basic composition formula of lithium nickelate is L
It can be written as iNiO ₂ . When this active material is used as a non-aqueous secondary battery, in particular, a lithium secondary battery, the composition ratio of lithium in the substance changes from 1 to 0 because lithium is inserted and released by charging and discharging.

Lithium nickelate is hexagonal R-3m.
It is a layered rock-salt type structure belonging to the space group, and its basic structure is shown in FIG. Both lithium and nickel are present in the hexacoordinated position in the cubic closest packing of oxygen. Furthermore, all the oxygen of the NiO ₆ octahedron is shared by the three sides,
An O ₂ layer structure is formed, and lithium is present at the 6-coordinate site between the layers to form LiNiO ₂ . Here, the sites occupied by oxygen are 6c sites, the sites occupied by lithium are 3a sites, and the sites occupied by nickel are 3b sites.

In the present invention, Rietveld analysis is performed using a diffraction pattern obtained by a powder X-ray diffraction method of lithium nickel oxide to refine the lattice constant and the structural parameter, and the lattice constant and the occupation rate of each site are calculated. Ask.

The Rietveld analysis uses a powder diffraction pattern using X-rays and neutron rays, and in order to extract the information contained therein, a diffraction pattern obtained by actual measurement,
This is a method for refining parameters relating to the crystal structure by fitting with a diffraction pattern expected from the crystal structure model.

In practice, for the reflections that contribute to each diffraction point, the integrated intensity obtained from the structural model is multiplied by a function that approximates the shape of the peak, and the sum is calculated to obtain the diffraction intensity at each diffraction point by actual measurement. Various structural parameters are refined by the nonlinear least squares method so as to fit the obtained diffraction intensity as much as possible.

Lithium nickelate as the positive electrode active material used in the present invention has a lithium and nickel site occupancy obtained by Rietveld analysis of a diffraction pattern obtained by a powder diffraction method using X-rays. The occupancy rate of lithium 3b site (g ₁ ) is 0.03 to 0.10, preferably 0.05 to 0.09, and the occupancy rate of nickel 3a site (g ₃ ) is 0 to 0.07. Preferably 0.02-
0.06, which is the total of lithium occupying the 3a site (occupancy g ₁ ) and the 3b site (occupancy g ₂ ) (g ₁ +
g ₂ = a _Li ) is 1.02 to 1.07, the total of nickel (g ₃ + g ₄ = a _Ni ) occupying 3a site (occupancy g ₃ ) and 3b site (occupancy g ₄ ) is 0.93 to 0.98, from which the ratio of lithium and nickel occupying 3a site and 3b site (Li / Ni, (g ₁ + g ₂ )
_{/ (G 3 + g 4)} ) is 1.05 to 1.15. It is difficult to synthesize lithium nickelate having a ratio of lithium and nickel (Li / Ni) occupying 3a sites and 3b sites of more than 1.15. When the lithium-nickel ratio (Li / Ni) occupying the 3a site and the 3b site is less than 1.05, when the battery is charged to a higher potential, the discharge capacity remarkably increases as the number of charge / discharge cycles increases. It is not preferable because it decreases.

Specific surface area by BET method is 0.2-10 m
More preferably, it is ² / g of lithium nickel oxide. B
When the specific surface area by the ET method is smaller than 0.2 m ² / g, the discharge capacity is small, and when it is larger than 10 m ² / g,
Cycle characteristics are not desirable. More preferably 0.2
~ ⁵ m ² / g. When it is larger than 5 m ² / g, self-discharge becomes large, which is not preferable.

With the above structure, excess lithium occupies nickel sites, the crystal structure is stabilized, the discharge capacity is stabilized, and when charging to a higher potential, excellent cycle characteristics are obtained. Can be obtained.

Lithium nickelate can be manufactured as follows. The lithium compounds that are the lithium source include lithium carbonate, lithium hydroxide, lithium peroxide, lithium oxide, lithium nitrate, lithium sulfate, lithium acetate, lithium benzoate, lithium chloride, lithium bromide, lithium citrate, lithium formate, and iodide. Examples include lithium, lithium lactate, lithium oxalate, lithium pyruvate, lithium stearate, and lithium tartrate. The nickel compound as the nickel source is nickel carbonate, nickel hydroxide, nickel oxyhydroxide, nickel oxide, nickel nitrate, nickel sulfate, nickel acetate, nickel benzoate,
Nickel chloride, nickel bromide, nickel citrate, nickel formate, nickel iodide, nickel oxalate, nickel stearate, nickel tartrate, etc. are used. Lithium in excess of the composition ratio is added to and mixed with these raw materials, and the mixture is fired at a temperature of 600 to 900 ° C. in an oxygen atmosphere or air. It is also possible to perform pressure molding and firing after mixing.

A positive electrode using lithium nickel oxide as an active material is formed by using a mixture of lithium nickel oxide obtained as described above, a conductive material, a binder and, in some cases, a solid electrolyte. To be done. As the conductive material, carbons such as carbon black, acetylene black and Ketjen black, graphite powder (natural graphite, artificial graphite), metal powder, metal fiber and the like can be used, but are not limited thereto. . As the binder, a fluoropolymer such as polytetrafluoroethylene or polyvinylidene fluoride, a polyolefin polymer such as polyethylene, polypropylene or ethylene-propylene-diene terpolymer, or a styrene-butadiene rubber can be used, but the binder is not limited thereto. It is not something that will be done. The mixing ratio can be 1 to 50 parts by weight of the conductive material and 1 to 30 parts by weight of the binder with respect to 100 parts by weight of the active material. When the amount of the conductive material is less than 1 part by weight, the resistance or polarization of the electrode increases and the discharge capacity decreases, so that a practical secondary battery cannot be manufactured. When the amount of the conductive material is more than 50 parts by weight (the weight part changes depending on the kind of the mixed conductive material), the amount of the active material contained in the electrode is reduced, so that the discharge capacity as the positive electrode becomes small.
If the binder is less than 1 part by weight, the binding ability will be lost, and if it is more than 30 parts by weight, the amount of the active material contained in the electrode will be reduced as in the case of the conductive material. As described above, the resistance or polarization of the electrode increases and the discharge capacity decreases, which is not practical.

In order to mold the above mixture into a positive electrode, it is compressed into pellets, or a paste prepared by adding a suitable solvent to the mixture is applied on a current collector, dried and compressed into a sheet. However, the method is not limited to this.

The transfer of electrons from or to the positive electrode is performed through a current collector. As the current collector, a simple metal, an alloy, carbon or the like is used. For example, titanium, aluminum, stainless steel, etc. are available. In addition, those obtained by treating the surface of copper, aluminum, or stainless steel with carbon, titanium, and silver, and those obtained by oxidizing the surface of these materials are also used. As the shape, besides foil, a film, a sheet, a net, a punched product, a lath body, a porous body, a foamed body, a molded body of a fiber group, or the like is used. Although the thickness is 1 μm to 1 mm, it is not particularly limited.

As the negative electrode, lithium, a lithium alloy, and / or a substance capable of inserting and extracting lithium is used. For example, lithium metal, lithium / aluminum alloy, lithium /
Lithium alloys such as zuzu alloys, lithium / lead alloys, and wood alloys, as well as substances that can be electrochemically doped or dedoped with lithium ions, such as conductive polymers (polyacetylene, polythiophene, polyparaphenylene, etc.), pyrolytic carbon , Pyrolytic carbon that was pyrolyzed in the gas phase in the presence of a catalyst,
Carbon calcined from pitch, coke, tar, etc., carbon calcined from polymers such as cellulose and phenol resin, and graphite capable of intercalating / deintercalating lithium ions (natural graphite, artificial graphite, expanded graphite) Etc.), inorganic compounds (WO ₂ , MoO _2, etc.) capable of doping and dedoping with lithium ions, etc., or a composite of these substances can be used. Of these negative electrode active materials, pyrolytic carbon, pyrolytic carbon vapor-decomposed in the presence of a catalyst, carbon fired from pitch, coke, tar, etc., carbon fired from a polymer, graphite (natural Graphite, artificial graphite, expanded graphite, etc.) have battery characteristics, especially safety,
From this viewpoint, a preferable secondary battery can be manufactured. In particular, graphite is preferably used for manufacturing a high voltage secondary battery.

As the negative electrode active material, conductive polymer, carbon, graphite,
When the negative electrode is made of an inorganic compound or the like, a conductive material and a binder may be added. The conductive material is carbon black,
Carbons such as acetylene black and Ketjen black, graphite powder (natural graphite, artificial graphite), metal powder, metal fiber and the like can be used, but not limited thereto. As the binder, a fluoropolymer such as polytetrafluoroethylene or polyvinylidene fluoride, a polyolefin polymer such as polyethylene, polypropylene or ethylene-propylene-diene terpolymer, or a styrene-butadiene rubber can be used, but the binder is not limited thereto. It is not something that will be done.

The ionic conductor is, for example, an organic electrolytic solution,
Solid electrolytes (polymer solid electrolytes, inorganic solid electrolytes), molten salts and the like can be used, and among these, organic electrolytes can be preferably used. The organic electrolyte is composed of an organic solvent and an electrolyte. As the organic solvent, propylene carbonate, ethylene carbonate, butylene carbonate, diethyl carbonate, which are aprotic organic solvents,
Dimethyl carbonate, methyl ethyl carbonate, γ
-Esters such as butyrolactone, tetrahydrofuran, substituted tetrahydrofuran such as 2-methyltetrahydrofuran, dioxolane, diethyl ether, ethers such as dimethoxyethane, diethoxyethane, methoxyethoxyethane, dimethyl sulfoxide, sulfolane, methylsulfolane, acetonitrile, formic acid Methyl,
Methyl acetate and the like can be mentioned, and they are used as a mixed solvent of one kind or two or more kinds thereof. Examples of the electrolyte include lithium salts such as lithium perchlorate, lithium borofluoride, lithium phosphorofluoride, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium halides and lithium chloroaluminate. One of these or Two or more kinds are mixed and used. An electrolyte solution is prepared by dissolving the electrolyte in the solvent selected above. The solvent and the electrolyte used when preparing the electrolytic solution are not limited to those listed above.

Li-nitrides, halides, oxyacid salts and the like are known as inorganic solid electrolytes. For example, Li
_{3 N, LiI, Li 3 N} -LiI-LiOH, LiSiO
₄ , LiSiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li
₄ SiO ₄ , phosphorus sulfide compounds, Li ₂ SiS _{3 and the} like.

Examples of the organic solid electrolyte include a substance composed of the above-mentioned electrolyte and a polymer that dissociates the electrolyte, a substance in which the polymer has an ionic dissociation group, and the like. Examples of the polymer that dissociates the electrolyte include a polyethylene oxide derivative or a polymer containing the derivative, a polypropylene oxide derivative, a polymer containing the derivative, and a phosphate ester polymer. In addition, a polymer matrix material containing the aprotic polar solvent, a mixture of a polymer containing an ionic dissociative group and the aprotic electrolytic solution,
There is also a method of adding polyacrylonitrile to the electrolytic solution.
In addition, a method of using an inorganic and an organic solid electrolyte in combination is also known.

As the separator for holding these electrolytic solutions, electrically insulating synthetic resin fiber, glass fiber,
Examples include non-woven fabrics such as natural fibers, woven fabrics or micropore structure materials, and powder compacts such as alumina. Of these, non-woven fabrics of synthetic resins such as polyethylene and polypropylene, and micropore structures are preferable from the viewpoint of quality stability. Some of these synthetic resin non-woven fabrics / micropore structures have the function of separating the positive electrode and negative electrode by melting the separator due to heat when the battery abnormally heats up, and these are also suitable for safety. can do. The thickness of the separator is not particularly limited, but it is sufficient if it can hold a necessary amount of electrolytic solution and has a thickness that prevents a short circuit between the positive electrode and the negative electrode, and is usually 0.01.
Approximately 1 mm can be used, and preferably approximately 0.02 to 0.05 mm.

The shape of the battery can be any of coins, buttons, sheets, cylinders, corners and the like. In the case of a coin or button type battery, it is common to form the positive electrode and the negative electrode in the form of pellets, put them in a can, and crimp the lid with an insulating packing.

In a cylindrical or prismatic battery, a sheet electrode is mainly inserted into a can, the can and the sheet are electrically connected, an electrolytic solution is injected, and a sealing plate is sealed via an insulating packing or a hermetic seal is used. Insulate the plate and the can and seal them to make a battery. At this time, a safety valve provided with a safety element can be used as a sealing plate. Safety elements include, for example:
Fuse, bimetal, PTC as overcurrent protection element
There are elements, etc. In addition to the safety valve, as a measure for increasing the internal pressure of the battery can, a method of cracking the gasket, a method of cracking the sealing plate, a method of making a cut in the battery can, etc. are used. Also, an external circuit incorporating measures against overcharge and overdischarge may be used.

Pellets and sheet electrodes are dried in advance,
It is preferably dehydrated. As a drying and dehydrating method, a general method can be used. For example, there is a method of using hot air, vacuum, infrared rays, far infrared rays, electron beams, low humidity air, etc., alone or in combination. Temperature is 50
The range of ~ 380 ° C is preferred.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to Examples. The Rietveld analysis method is a known method, for example, "The Rietvelt Methode", ed. By RAYoung, Ox.
It can be performed by the method described in ford University Press, Oxford (1993), and the procedure was as follows.

When actually carrying out the Rietveld analysis, it is necessary to apply the calculated pattern based on the predicted structural model to the actually measured diffraction pattern.

Therefore, a structural model must first be created. The parameters of this structural model are 1)
Parameters for adjusting the intensity of the diffraction peak (scale factor, selective orientation parameter), 2) Parameters relating to the position of the diffraction peak (lattice constant, zero point shift),
3) Parameters related to profile (half-width parameter), 4) Parameters related to structure (atomic coordinate,
Occupancy rate, isotropic thermal vibration parameter), and 5) background parameter. The initial values for 1), 2), 3), and 5) can be obtained from the information obtained from the measured X-ray diffraction pattern. As for the initial value regarding the structure of 4), the space group of the crystal phase is R-3 in the case of the LiNiO ₂ sample.
m, and each constituent atom is a Li-3a site, Ni
-3b site and O-6c site.

The Rietveld analysis is performed by setting the initial values according to the procedure described above. After that, the parameters are sequentially set again from the obtained analysis result so that the R factor is smoothly decreased, and the parameters are refined.

When analyzing a LiNiO ₂ sample, 3
It is considered that substitution of lithium and nickel at the a site and the 3b site is likely to occur. In the portion, the occupancy was set assuming that Ni was present at the 3a site and Li was present at the 3b site, and analysis was performed. The end of analysis is
The R factor is small, and the residual value between the measured value and the calculated value (R _wp value)
Was set to about 10% or less as a guide when all parameters converged to values physically considered appropriate. From the above, the lattice constant and the occupation rate of each atom at each site were obtained. At that time, the R _e value which is the best statistically expected R _wp value was added. In addition, the electrodes and batteries were evaluated at 20 ° C.

(Example 1) Synthesis of lithium nickel oxide Lithium hydroxide and nickel oxyhydroxide (NiOO)
H) has a lithium to nickel ratio of Li: Ni of 1.2: 1
To 100kg /
A pressure of cm ² was applied to make pellets. This is 60
By firing at 0 ° C. for 15 hours in an oxygen atmosphere, lithium nickel oxide as an active material could be obtained. This active material was subjected to powder X-ray diffraction using CuKα ray as an X-ray source, and Rietveld analysis was performed as described above. Table 1 shows the results. Further, the parameter I (003) / I (104) or I obtained by powder X-ray diffraction
(104) / I (103) ((003) plane strength and (1
(04) intensity ratio), half width relative to (003) plane peak, L determined by chemical analysis (ICP emission spectroscopy)
Table 1 also shows the i / Ni ratio and the specific surface area obtained by the nitrogen adsorption BET method.

[0038]

[Table 1]

Production of Electrode The active material obtained as described above was mixed with acetylene black and polytetrafluoroethylene in an amount of 10
After mixing in a mortar at a ratio of 0:10:10, pressure molding was performed to prepare pellets having a diameter of 20 mm and a weight of 0.10 g. A titanium mesh that acts as a current collector was also added during pressure molding. A titanium wire was spot-welded from the titanium mesh to collect current, and used as an electrode for evaluation.

Evaluation of Electrode For evaluation, a three-pole method was used, and lithium was used for the counter electrode and the reference electrode. The electrolytic solution used was a 1: 1 mixed solvent of ethylene carbonate and dimethyl carbonate in which 1 mol / l of lithium perchlorate (LiClO ₄ ) was dissolved. Two
First, the lithium of the reference electrode was charged to 4.5 V at a current density of 7.4 mA / g, and then 2. at the same current.
Discharged to 7V. The same potential range from the second time onward,
Charging and discharging were repeated at the same current density.

The results are shown in Table 2 and FIG. In order to evaluate self-discharge, after repeating charging and discharging 10 times under the above conditions with another electrode, charging was performed and the holding capacity after standing for 30 days at 20 ° C. was measured. I asked.
The results are shown in FIG. 5 as the relationship of the specific surface area.

[0042]

[Table 2]

(Example 2) Lithium oxide (L
i ₂ O) and nickel oxyhydroxide (NiOOH),
Table 1 shows the results obtained by synthesizing an active material in the same manner as in Example 1 except that the firing temperature and time were 700 ° C. for 24 hours and performing Rietveld analysis in the same manner as in Example 1. . Further, the parameter I obtained from powder X-ray diffraction
(003) / I (104) or I (104) / I (1
03) (intensity ratio of (003) plane and intensity of (104) plane), half width to peak of (003) plane, Li / Ni ratio determined by chemical analysis (ICP emission spectroscopy), nitrogen adsorption BET method Table 1 also shows the specific surface area obtained by.

An electrode was prepared in the same manner as in Example 1 except that the ratio of the active material, acetylene black and polytetrafluoroethylene was 100: 30: 25.

The electrolytic solution was added to a 1: 1 mixed solvent of propylene carbonate and methyl ethyl carbonate at 1 mol / l.
The electrodes were evaluated in the same manner as in Example 1 except that the one obtained by dissolving the lithium phosphate fluoride (LiPF ₆ ) of was used. The results are shown in Table 2 and FIG. In order to evaluate self-discharge, after repeating charging and discharging 10 times under the above conditions with another electrode, charging was performed and the holding capacity after standing for 30 days at 20 ° C. was measured. I asked. The results are shown in FIG. 5 as the relationship of the specific surface area.

Example 3 An active material was prepared in the same manner as in Example 1 except that lithium hydroxide (LiOH) and nickel oxide (NiO) were used as main raw materials, and the firing temperature and time were 700 ° C. for 10 hours. The results obtained by synthesizing and performing Rietveld analysis in the same manner as in Example 1 are shown in Table 1. Furthermore, the parameter I (00
3) / I (104) or I (104) / I (103)
(Ratio of strength of (003) plane to strength of (104) plane), (0
03) Full width at half maximum with respect to the surface peak, Li / Ni ratio determined by chemical analysis (ICP emission spectroscopy), nitrogen adsorption BE
Table 1 also shows the specific surface area obtained by the T method.

An electrode was prepared in the same manner as in Example 1 except that the active material, acetylene black and polytetrafluoroethylene were mixed in the ratio of 100: 4: 3.

The electrodes were evaluated in the same manner as in Example 1 except that 1 mol / l of lithium phosphorus fluoride was dissolved in a 1: 1 mixed solvent of propylene carbonate and dimethyl carbonate as the electrolytic solution. The results are shown in Table 2 and FIG. To evaluate self-discharge, after repeating charging and discharging 10 times under the above conditions with another electrode, charging was performed, and the storage capacity after standing at 20 ° C. for 30 days was measured,
The capacity retention rate was calculated. The results are shown in FIG. 5 as the relationship of the specific surface area.

(Example 4) The firing temperature and time were set to 650 ° C.
Table 1 shows the results obtained by synthesizing the active material in the same manner as in Example 3 except that the heating time was 15 hours, and performing Rietveld analysis in the same manner as in Example 1. Further, the parameters I (003) / I (104) or I (104) / I (103) (the intensity of the (003) plane and the intensity of the (104) plane) obtained by powder X-ray diffraction, the (003) plane Table 1 also shows the full width at half maximum with respect to the peak, the Li / Ni ratio determined by chemical analysis (ICP emission spectroscopy), and the specific surface area determined by the nitrogen adsorption BET method.

An electrode was prepared in the same manner as in Example 1 except that the active material, acetylene black and polytetrafluoroethylene were mixed in the ratio of 100: 10: 10.

Example 1 except that 1 mol / l of lithium perchlorate was dissolved in a 1: 1 mixed solvent of propylene carbonate and diethyl carbonate was used as the electrolytic solution.
The electrodes were evaluated in the same manner as in. The results are shown in Table 2 and FIG.
Shown in In order to evaluate self-discharge, charging and discharging were repeated 10 times under the above conditions with another electrode, and then charged.
The storage capacity after standing for 30 days at 20 ° C. was measured to determine the capacity retention rate. The result is shown in FIG.
Shown in

(Example 5) Ratio L of lithium to nickel
An active material was synthesized in the same manner as in Example 3 except that i: Ni was set to 1.3: 1 and the firing temperature and time were changed to 750 ° C. for 10 hours. Table 1 shows the results obtained by performing the belt analysis. Furthermore, the parameter I (003) / I obtained from powder X-ray diffraction
(104) or I (104) / I (103) ((00
(3) intensity of plane and intensity ratio of (104) plane), full width at half maximum to peak of (003) plane, Li / Ni ratio determined by chemical analysis (ICP emission spectroscopy), ratio determined by nitrogen adsorption BET method The surface area is also shown in Table 1.

An electrode was prepared in the same manner as in Example 1 except that the active material, acetylene black, and polytetrafluoroethylene were used in the ratio of 100: 10: 7.

Example 1 except that 1 mol / l of lithium phosphorus fluoride was dissolved in a 1: 1 mixed solvent of ethylene carbonate and diethyl carbonate was used as the electrolytic solution.
The electrodes were evaluated in the same manner as in. The results are shown in Table 2 and FIG.
Shown in In order to evaluate self-discharge, charging and discharging were repeated 10 times under the above conditions with another electrode, and then charged.
The storage capacity after standing for 30 days at 20 ° C. was measured to determine the capacity retention rate. The result is shown in FIG.
Shown in

Example 6 The main raw material was lithium oxide (L
i ₂ O) and nickel hydroxide (Ni (OH) ₂ ), the ratio Li: Ni of lithium to nickel is 1.3: 1, and the firing temperature and time are 750 ° C. for 10 hours. Table 1 shows the results obtained by synthesizing an active material in the same manner as in Example 1 and performing Rietveld analysis in the same manner as in Example 1.
Shown in Furthermore, the parameter I (003) / I (104) or I (104) / I obtained by powder X-ray diffraction is used.
(103) (strength ratio of (003) plane to (104) plane), half width to peak of (003) plane, Li / Ni ratio determined by chemical analysis (ICP emission spectroscopy), nitrogen adsorption BET The specific surface area obtained by the method is also shown in Table 1.

An electrode was prepared in the same manner as in Example 1 except that the active material, acetylene black and polytetrafluoroethylene were mixed in the ratio of 100: 20: 10.

The electrolytic solution was added to propylene carbonate at 1 mo
The electrodes were evaluated in the same manner as in Example 1 except that 1 / l of lithium phosphorus fluoride was dissolved. The results are shown in Table 2 and FIG. In order to evaluate self-discharge, after repeating charging and discharging 10 times under the above conditions with another electrode, charging was performed and the holding capacity after standing for 30 days at 20 ° C. was measured. I asked. The results are shown in FIG. 5 as the relationship of the specific surface area.

(Comparative Example 1) Ratio L of lithium to nickel
An active material was synthesized in the same manner as in Example 1 except that i: Ni was set to 1.1: 1 and the firing temperature and time were set to 900 ° C. for 5 hours. Table 1 shows the results obtained by performing the belt analysis. Furthermore, powder X
Parameter I (003) / I (1
04) or I (104) / I (103) ((003)
Plane intensity and (104) plane intensity ratio), full width at half maximum with respect to (003) plane peak, chemical analysis (ICP emission spectroscopy)
Table 1 also shows the Li / Ni ratio obtained by the above and the specific surface area obtained by the nitrogen adsorption BET method.

An electrode was prepared in the same manner as in Example 1 except that the active material, acetylene black and polytetrafluoroethylene were mixed in the ratio of 100: 20: 15.

The electrodes were evaluated in the same manner as in Example 1 except that 1 mol / l of lithium perchlorate was dissolved in a 1: 1 mixed solvent of ethylene carbonate and diethyl carbonate as the electrolytic solution. The results are shown in Table 2.

(Comparative Example 2) The firing temperature and time were set to 650 ° C.
Table 1 shows the results obtained by synthesizing the active material in the same manner as in Comparative Example 1 except that the heating time was 5 hours, and performing Rietveld analysis in the same manner as in Example 1. Further, the parameters I (003) / I (104) or I (104) / I (103) (the intensity of the (003) plane and the intensity of the (104) plane) obtained by powder X-ray diffraction, the (003) plane Table 1 also shows the full width at half maximum with respect to the peak, the Li / Ni ratio determined by chemical analysis (ICP emission spectroscopy), and the specific surface area determined by the nitrogen adsorption BET method.

An electrode was prepared in the same manner as in Example 1 except that the active material, acetylene black and polytetrafluoroethylene were mixed in the ratio of 100: 10: 10.

The electrodes were evaluated in the same manner as in Example 1 except that 1 mol / l of lithium perchlorate was dissolved in a 1: 1 mixed solvent of ethylene carbonate and diethyl carbonate as the electrolytic solution. The results are shown in Table 2.

(Comparative Example 3) Lithium hydroxide (LiOH) and nickel hydroxide (Ni (OH) ₂ ) were used as the main raw materials, and the ratio Li: Ni of lithium and nickel was set to 1: 1 at the firing temperature. Table 1 shows the results obtained by synthesizing the active material in the same manner as in Example 1 except that the heating time was set to 750 ° C. for 5 hours and performing Rietveld analysis in the same manner as in Example 1. Furthermore, the parameter I (003) / I (104) or I (104) / determined by powder X-ray diffraction
I (103) (strength ratio of (003) plane to (104) plane), half width to peak of (003) plane, Li / Ni ratio determined by chemical analysis (ICP emission spectroscopy),
Table 1 also shows the specific surface area obtained by the nitrogen adsorption BET method.

An electrode was prepared in the same manner as in Example 1 except that the active material, acetylene black and polytetrafluoroethylene were mixed in the ratio of 100: 7: 5.

The electrolyte solution was added to propylene carbonate at 1 mo.
The electrodes were evaluated in the same manner as in Example 1 except that one in which 1 / l of lithium perchlorate was dissolved was used. The results are shown in Table 2.

Comparative Example 4 Lithium oxide (L
i ₂ O) and nickel oxide (NiO), the active material was synthesized in the same manner as in Comparative Example 1 except that the firing temperature and time were 650 ° C. for 10 hours, and Rietveld analysis was performed in the same manner as in Example 1. The results obtained by carrying out are shown in Table 1. Furthermore, the parameter I (003) / I obtained from powder X-ray diffraction
(104) or I (104) / I (103) ((00
(3) intensity of plane and intensity ratio of (104) plane), full width at half maximum to peak of (003) plane, Li / Ni ratio determined by chemical analysis (ICP emission spectroscopy), ratio determined by nitrogen adsorption BET method The surface area is also shown in Table 1.

An electrode was prepared in the same manner as in Example 1 except that the active material, acetylene black and polytetrafluoroethylene were mixed in a ratio of 100: 10: 10.

The electrodes were evaluated in the same manner as in Example 1 except that 1 mol / l of lithium phosphorus fluoride was dissolved in a 1: 1 mixed solvent of propylene carbonate and diethyl carbonate as the electrolytic solution. The results are shown in Table 2.

(Comparative Example 5) Lithium hydroxide (LiOH) and nickel oxide (NiO) were used as the main raw materials, the ratio Li: Ni of lithium to nickel was 1: 1, and the firing temperature and time were 650. Table 1 shows the results obtained by synthesizing the active material in the same manner as in Example 1 except that the temperature was 24 hours, and performing Rietveld analysis in the same manner as in Example 1.
Furthermore, the parameter I (0
03) / I (104) or I (104) / I (10
3) (strength ratio of (003) plane to (104) plane),
Full width at half maximum for (003) plane peak, chemical analysis (IC
Table 1 also shows the Li / Ni ratio determined by P emission spectroscopy and the specific surface area determined by the nitrogen adsorption BET method.

An electrode was prepared in the same manner as in Example 1 except that the ratio of the active material, acetylene black and polytetrafluoroethylene was 100: 10: 10.

The electrolytic solution was added to a 1: 1 mixed solvent of propylene carbonate and methyl ethyl carbonate at 1 mol / l.
The electrodes were evaluated in the same manner as in Example 1 except that the one obtained by dissolving the lithium phosphate fluoride was used. The results are shown in Table 2.

Comparative Example 6 Lithium hydroxide (LiOH) and nickel oxide (NiO) were used as the main raw materials, the ratio Li: Ni of lithium to nickel was set to 1.2: 1, and the firing temperature and time were changed. Table 1 shows the results obtained by synthesizing the active material in the same manner as in Example 1 except that the temperature was 700 ° C. for 3 hours and performing Rietveld analysis in the same manner as in Example 1. Further, the parameter I obtained from powder X-ray diffraction
(003) / I (104) or I (104) / I (0
03) (intensity ratio of (003) plane to (104) plane), half width to peak of (003) plane, Li / Ni ratio determined by chemical analysis (ICP emission spectroscopy), nitrogen adsorption method BET The specific surface area obtained by the method is also shown in Table 1.

An electrode was prepared in the same manner as in Example 1 except that the ratio of the active material, acetylene black and polytetrafluoroethylene was 100: 10: 10.

The electrolytic solution was added to a 1: 1 mixed solvent of propylene carbonate and methyl ethyl carbonate at 1 mol / l.
The electrodes were evaluated in the same manner as in Example 1 except that the one obtained by dissolving the lithium phosphate fluoride was used. The results are shown in Table 2.
Shown in In order to evaluate self-discharge, charging and discharging were repeated 10 times under the above conditions with another electrode, and then charged.
The storage capacity after standing for 30 days at 20 ° C. was measured to determine the capacity retention rate. The result is shown in FIG.
Shown in

From Examples 1 to 6 and Comparative Examples 1 to 6, it was found that the active material of the present invention was excellent even at high potential. Also,
Discharge Performance preferably in specific surface area of 0.2 to 10 m ² / g, yet when 0.2~5m ² / g, that self-discharge characteristic is excellent found.

Example 7 Synthesis of Positive Electrode Active Material and Production of Positive Electrode Synthesis of a positive electrode active material and lithium nickel oxide and production of a positive electrode were carried out in the same manner as in Example 1, and the diameter was 15 mm and the weight was 5 mm.
0 mg pellets were made.

Preparation of Negative Electrode The negative electrode is pyrolytic carbon, and nickel is used as a substrate (surface area 4 c
m ² ), and was produced by the atmospheric pressure gas phase pyrolysis method using propane as a starting material. At this time, it was deposited at 750 ° C. for 2 hours. This pyrolytic carbon was obtained by X-ray diffraction (0
The interplanar spacing d002 of the (02) plane is 0.337 nm, and (00
2) surface thickness of crystallite size in direction of Lc is 15 nm, also 1360 cm ^-1 vicinity of the peak intensity ratio of the relative peak around 1580 cm ^-1 due to the argon laser Raman, i.e. R value is 0.46. A nickel wire was spot-welded to this electrode to collect current. This was dried under reduced pressure at 200 ° C. to remove water and used as a negative electrode. The weight of the active material of this negative electrode was 28 mg.

Evaluation of Battery For the evaluation of the battery, a beaker cell was used, and the positive electrode and the negative electrode manufactured as described above were used. The electrolyte used was a 1: 1 mixed solvent of propylene carbonate and diethyl carbonate in which 1 mol / l of lithium perchlorate was dissolved. In the charge / discharge test, a current of 0.2 mA was first charged to 4.4 V, and then a discharge of the same current was performed to 2.5 V. After the second time, charging and discharging were repeated in the same voltage range and current density to evaluate the battery.

As a result, one of the batteries prepared as described above was
The discharge capacity at the 10th time was 7.0 mAh, and the discharge capacity at the 100th time was 6.3 mAh.

Example 8 Synthesis of Positive Electrode Active Material and Production of Positive Electrode A positive electrode active material and lithium nickel oxide were synthesized in the same manner as in Example 3 and a positive electrode was produced in the same manner as in Example 1. Diameter 15 mm, thickness 0.77 mm, weight of active material 2
00 mg pellets were made.

Manufacture of Negative Electrode As the negative electrode active material, natural graphite (scale-like, particle size 11 μm, d002 0.337 nm, Lc 27 n) produced in Madagascar
m, La is 17 nm, R value is 0, specific surface area 8 m ² / g)
1 with polytetrafluoroethylene
After mixing at a ratio of 0: 1, pressure molding was performed to prepare pellets having a diameter of 15 mm, a thickness of 0.57 mm and an active material weight of 95 mg. A nickel mesh that acts as a current collector was also added during pressure molding. What was dried under reduced pressure at 200 ° C. to remove water was used as a negative electrode.

Assembly of Battery As shown in FIG. 2, the positive electrode 3 including the positive electrode current collector 2 was pressure-bonded to the positive electrode can 1 on which the insulating packing 8 was placed. next,
A polypropylene non-woven separator 7 is placed on this, ethylene carbonate and propylene carbonate,
An electrolytic solution in which an electrolyte salt LiPF ₆ is dissolved in a mixed solvent having a volume ratio of 2: 1: 3 with diethyl carbonate so as to be 1 mol / l is impregnated. On the other hand, the negative electrode 6 is stacked on the separator 7 so that the negative electrode 6 including the negative electrode current collector 5 is pressure-bonded to the inner surface of the negative electrode can 4. Then, the positive electrode can 1 and the negative electrode can 4 are caulked with the insulating packing 8 interposed therebetween and hermetically sealed to manufacture a coin-type battery.

Evaluation of Battery All the coin type batteries produced were charged and discharged at a current of 1 mA.
The battery was charged up to a charge upper limit voltage of 4.45V, and then discharged up to a discharge lower limit voltage of 2.5V. For evaluation, the discharge capacity of the battery was measured. After the second time, charging and discharging were repeated in the same voltage range and current density to evaluate the battery.

As a result, the discharge capacity in the first cycle discharge was 29.5 mAh, and the discharge capacity in the 100th cycle was 25.2 mAh.

Example 9 The cylindrical battery shown in FIG. 3 was manufactured as follows.

As the positive electrode, the positive electrode active material lithium nickel oxide synthesized in Example 1 was used, and 100 parts by weight of the positive electrode active material, 7 parts by weight of acetylene black powder as a conductive material, and 10 parts by weight of polyvinylidene fluoride as a binder were used. Part, N-
Methyl-2-pyrrolidone was mixed as a dispersant to obtain a positive electrode paste. Then, this positive electrode paste has a thickness of 20 μm.
The aluminum foil of m was coated on both sides of the current collector, dried, rolled, and cut into strips.

The positive electrode lead 1 is attached to one end of the cut electrode.
The aluminum tab of No. 5 was attached by spot welding to obtain the positive electrode 14. The positive electrode active material in the positive electrode, lithium nickel oxide, was 40 mg / cm ² .

The negative electrode is made of artificial graphite (particle size 8 μm, d002 is 0.337 nm, Lc is 25 nm, which is a negative electrode active material).
La is 13 nm, R value is 0, specific surface area is 12 m ² / g) 1
00 parts by weight and polyvinylidene fluoride 10 as a binder
By weight, N-methyl-2-pyrrolidone was mixed as a dispersant to prepare a negative electrode paste. Then, this negative electrode paste was applied to both surfaces of a copper foil current collector having a thickness of 18 μm, dried, rolled, and cut into strips. The nickel tab of the negative electrode lead 17 was attached to one end of the cut electrode by spot welding to obtain the negative electrode 16. The amount of graphite, which is the negative electrode active material in the negative electrode, was 20 mg / cm ² .

The positive electrode 14 and the negative electrode 16 were arranged so as to face each other with the microporous separator 18 made of polyethylene sandwiched therebetween, and spirally wound to form a winding element.
With the positive electrode lead 15 on the upper side and the negative electrode lead 17 on the lower side,
Insert into a battery can 13 (diameter 17 mm, height 500 mm, made of stainless steel), spot-weld the negative electrode lead 17 to the bottom of the battery can 13, and attach the positive electrode lead 1 to the positive electrode lid 11 with a safety valve.
5 was spot welded. A center pin 19 (diameter: 3.4 mm, length: 4 mm) is provided at the center of the winding element to prevent winding collapse.
0 mm stainless steel tube) was inserted. after that,
Lithium phosphorofluoride as an electrolyte in a 1: 1 mixed solvent of ethylene carbonate and diethyl carbonate at 1 mol /
A cylindrical battery was manufactured by injecting an electrolyte solution dissolved in a ratio of 1 and caulking the positive electrode lid 11 through the insulating packing 12.

In the charge / discharge test, charging is performed with a charging current of 500 m.
A, upper limit voltage 4.45V, constant current constant voltage charge for 3 hours,
The discharge was carried out in a constant temperature bath at 25 ° C. with a constant current discharge having a discharge current of 100 mA and a lower limit voltage of 2.75V.

As a result, the initial discharge capacity was 873 mAh.
And the battery capacity after 50 cycles is 743
It was in the mAh range.

[0093]

According to the present invention, the active material of the positive electrode is R-
It has a layered rock-salt type structure belonging to a space group of 3 m, and is preferably obtained by a method of obtaining a diffraction pattern obtained by a powder diffraction method using X-rays by Rietveld analysis,
Includes lithium nickelate having a ratio (Li / Ni) of total lithium occupying 3a site and 3b site and total nickel occupying 3a site and 3b site of 1.05 to 1.15. By using the positive electrode, when the battery is charged to a higher potential, the discharge capacity does not decrease significantly with the increase in the number of charge / discharge cycles, and a non-aqueous secondary battery that exhibits excellent cycle characteristics, especially lithium A secondary battery can be provided. Therefore, a non-aqueous secondary battery, especially a lithium secondary battery, which is resistant to overcharge, that is, the charging voltage can be regulated in the unit of 0.1V without being strictly regulated in the unit of 0.01V when charging the battery, Can be provided. Further, by setting the specific surface area to 0.2 to 5 m ² / g, an active material and a battery having excellent self-discharge characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic structure of lithium nickelate belonging to a hexagonal R-3m space group.

FIG. 2 is a cross-sectional view of a coin-type battery used in the embodiment.

FIG. 3 is a sectional view of a cylindrical battery used in the embodiment.

FIG. 4 is a diagram showing cycle dependence of discharge capacities obtained in Examples 1 to 6 and Comparative Examples 1 to 5 of the embodiment.

FIG. 5 is a diagram showing the relationship between the capacity retention rate by self-discharge and the specific surface area obtained in Examples 1 to 9 of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode can 2 Positive electrode current collector 3 Positive electrode 4 Negative electrode can 5 Negative electrode current collector 6 Negative electrode 7 Separator 8 Insulating packing 11 Positive electrode lid with safety valve 12 Insulating packing 13 Battery can 14 Positive electrode 15 Positive electrode lead 16 Negative electrode 17 Negative electrode lead 18 Separator 19 Center pin

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Yamada 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (4)

[Claims] 1. A non-aqueous secondary battery comprising a positive electrode, a negative electrode and a non-aqueous ionic conductor, wherein the negative electrode active material is formed of a lithium-containing material or a lithium insertable / desorbable material. The active material of the positive electrode has a layered rock-salt type structure belonging to the R-3m space group, and has 3a sites and 3a sites.
Ratio of total lithium occupying b site to total nickel occupying 3a site and 3b site (L
A non-aqueous secondary battery which is an electrode containing lithium nickel oxide having i / Ni of 1.05 to 1.15. 2. The non-aqueous secondary battery according to claim 1, wherein the specific surface area of lithium nickel oxide according to the BET method is 0.2 to 10 m ² / g. 3. The non-aqueous secondary battery according to claim 1, wherein the negative electrode active material capable of inserting and releasing lithium is carbon. 4. The non-aqueous secondary battery according to claim 1, wherein the negative electrode active material into / from which lithium can be inserted / desorbed is graphite capable of intercalating / deintercalating lithium.