JP3543437B2 - Positive electrode active material and non-aqueous electrolyte secondary battery using this positive electrode active material - Google Patents

Positive electrode active material and non-aqueous electrolyte secondary battery using this positive electrode active material Download PDF

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JP3543437B2
JP3543437B2 JP20736095A JP20736095A JP3543437B2 JP 3543437 B2 JP3543437 B2 JP 3543437B2 JP 20736095 A JP20736095 A JP 20736095A JP 20736095 A JP20736095 A JP 20736095A JP 3543437 B2 JP3543437 B2 JP 3543437B2
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positive electrode
active material
electrode active
lithium
li
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JPH0935715A (en
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尚之 加藤
佳克 山本
貴夫 韮澤
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ソニー株式会社
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product
    • Y02P70/54Manufacturing of lithium-ion, lead-acid or alkaline secondary batteries

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present inventionFor non-aqueous electrolyte secondary batteriesPositive electrode active material andUsing this positive electrode active materialThe present invention relates to a non-aqueous electrolyte secondary battery.
[0002]
[Prior art]
2. Description of the Related Art With the remarkable progress of electronic technology in recent years, electronic devices have been improved in performance, downsized, and portable, and batteries used in these electronic devices have been required to have high energy.
[0003]
Conventionally, aqueous secondary batteries such as nickel-cadmium batteries and lead batteries have been used as secondary batteries used in electronic devices. However, these aqueous secondary batteries have a low discharge potential and cannot sufficiently meet the recently required improvement in energy density.
[0004]
On the other hand, recently, as a battery system capable of obtaining a high energy density, a lithium secondary battery using lithium metal or a lithium alloy as a negative electrode active material has attracted attention and has been actively studied.
[0005]
However, in this secondary battery, when metal lithium is used as a negative electrode active material, when lithium dissolves and precipitates on the negative electrode, metal lithium grows in a dendritic form from the negative electrode, and finally forms a positive electrode. There is a high possibility that it will reach and cause an internal short. Further, when a lithium alloy is used as the negative electrode active material, lithium is dissolved and precipitated on the negative electrode, so that the negative electrode becomes finer and the performance of the negative electrode deteriorates. In any case, lithium secondary batteries are recognized as having problems in cycle life, safety, rapid charging performance, and the like, and this is a major obstacle to practical application, and some lithium secondary batteries are practically used as coin type. It's just
[0006]
In order to solve such a problem, a non-aqueous electrolyte secondary battery (a lithium ion secondary battery) using a material capable of doping and undoping lithium ions, such as a carbonaceous material, as a negative electrode active material. Research and development of batteries. In this non-aqueous electrolyte secondary battery, since lithium does not exist in a metallic state in the battery system, good cycle characteristics and safety can be obtained without lithium dendrite crystal growth from the negative electrode. become.
[0007]
In addition, in such a nonaqueous electrolyte secondary battery, particularly by using a lithium-containing compound having a high oxidation-reduction potential as the positive electrode active material, the battery voltage is increased and the energy density is increased. Further, the self-discharge is smaller than that of the nickel-cadmium battery, so that the secondary battery exhibits extremely excellent performance. As described above, the nonaqueous electrolyte secondary battery using a carbonaceous material as a negative electrode active material has excellent characteristics. Therefore, for example, 8 m / m VTRs, CD players, laptop computers, cellular telephones, and other portable electronic devices. Commercialization has started as a power source.
[0008]
Meanwhile, in portable electronic devices using secondary batteries, power consumption tends to increase with diversification of functions and the like. For this reason, there is a demand for a battery serving as a power supply to further improve the heavy load cycle characteristics as well as the energy density.
[0009]
Here, the heavy duty cycle characteristics of the battery largely depend on the reaction area at the electrode. That is, in the battery, when the reaction area of the electrode is large, good heavy duty cycle characteristics can be obtained.
[0010]
From such a point of view, when looking at the cylindrical battery and the coin battery which are mainly adopted as the battery form of the lithium ion secondary battery, first, in the cylindrical battery, the electrode is attached to the surface of the band-shaped metal foil serving as the current collector. A wound electrode body formed by laminating a plurality of thin-film positive electrodes and negative electrodes on which an agent layer is formed with a separator interposed therebetween, and winding this is used, and is a so-called jelly roll type. Note that, in the case of the negative electrode, the electrode mixture layer is formed by applying a negative electrode mixture slurry in which a powder of a carbonaceous material and a binder are dispersed in an organic solvent to the surface of the current collector and drying the slurry. Layer. In the case of the positive electrode, it is a layer formed by applying and drying a positive electrode mixture slurry in which a lithium-containing compound powder, a binder and a conductive agent are dispersed in an organic solvent, on the surface of the current collector.
[0011]
A wound electrode body in which a plurality of such thin-film electrodes are stacked has a relatively large reaction area, is capable of quick charging, and has a long cycle life.
[0012]
On the other hand, in a coin-type battery, a pellet-shaped positive electrode and a negative electrode obtained by compression-molding an electrode mixture according to the shape of a battery can are housed in the battery can in a stacked state with a separator interposed therebetween. .
[0013]
In the case of a battery in which such pellet-shaped electrodes are laminated, it is considered that the electrode reaction easily proceeds from the surfaces of the positive electrode and the negative electrode facing the separator, and the electrode reaction becomes slower as the distance from the surface increases. For this reason, when the electrode thickness is increased, a portion far from the surface facing the separator is likely to be in an apparent overvoltage state, and the active material is deteriorated. For this reason, sufficient cycle characteristics and load characteristics cannot be obtained.
[0014]
In order to increase the reaction area of the coin-type battery, an electrode configuration in which the electrode is divided in the thickness direction and a current collector is interposed therebetween has been considered. However, in this case, since the current collector occupies a part of the capacity of the battery can, there is an inconvenience that the filling rate of the electrode mixture decreases accordingly and the battery capacity decreases.
[0015]
[Problems to be solved by the invention]
As described above, in the conventional nonaqueous electrolyte secondary batteries, the degree differs depending on the electrode form, but there is a problem that the electrode filling property is reduced when trying to secure the reaction area of the electrode, and while maintaining the energy density. It is very difficult to improve heavy load characteristics.
[0016]
Therefore, the present invention has been proposed in view of such a conventional situation. When an electrode is formed, a high electrode filling property is obtained and a wide reaction area is secured.Positive electrode active material for non-aqueous electrolyte secondary battery and using this positive electrode active materialAn object is to provide a non-aqueous electrolyte secondary battery.
[0017]
[Means for Solving the Problems]
To achieve the above objectivesFor non-aqueous electrolyte secondary batteries according to the proposed inventionThe positive electrode active material is LixCoO2, LixNiO2, LixMn2O4, LixCo1-yMyO2, LixNi1-yMyO2, LxMn1-yMyO2(However, M represents at least one element selected from Ti, V, Cr, Mn, Fe, Al, Co, Ni, Cu, Zn, Mo, Bi, and B, and x is 0 <x ≦ 1. 2, y is 0 <y <1), and the surface of a core particle composed of any one of the lithium-containing compounds represented byComposite particlesIt is.
[0018]
In producing the positive electrode active material in this manner, the core particles are coated with fine particles, that is, the average particle diameter r as the composite particles1And the average particle size r of the core particlesTwoAnd the average particle diameter r of the fine particles covering around the core particlesThreeIt is important that is appropriate.
[0019]
That is, the average particle diameter r of the composite particles themselves1And the average particle size r of the core particlesTwoThe ratio r1/ RTwoIs 1.01 ≦ r1/ RTwo≤2, and the average particle diameter r of the fine particlesThreeAnd the average particle diameter r of the core particlesTwoThe ratio rThree/ RTwoIs rThree/ RTwoIt is more preferred that ≦ 1 /. Here, the average particle size is a median size, that is, a particle size with respect to 50% of the integrated distribution.
[0020]
The generated composite particles may be subjected to a heat treatment thereafter.
[0021]
In addition, the present inventionPertain toNon-aqueous electrolyte secondary batteries areThe positive electrode active material described above is used for the positive electrode. The negative electrode of this non-aqueous electrolyte secondary battery isIt is mainly composed of a lithium metal, a lithium alloy or a carbon material capable of doping and undoping lithium.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
A specific embodiment of the present invention will be described below.
[0023]
The present inventionPertain toThe positive electrode active material isIt is composed of composite particles 36 as shown in FIG. The composite particles 36LixCoO2, LixNiO2, LixMn2O4, LixCo1-yMyO2, LixNi1-yMyO2, LxMn1-yMyO2(However, M represents at least one element selected from Ti, V, Cr, Mn, Fe, Al, Co, Ni, Cu, Zn, Mo, Bi, and B, and x is 0 <x ≦ 1. 2, y is 0 <y <1), and the surface of a core particle composed of any of the lithium-containing compounds represented by the following formula is coated with fine particles composed of any of these lithium-containing compounds.It was done.
[0024]
As a method for coating the surface of the core particles 34 made of the lithium-containing compound with the fine particles 35 made of the lithium-containing compound, there is a high-speed airflow impact method. With the high-speed airflow impact method, a mixture in which powder and fine particles are uniformly mixed is dispersed in a high-speed airflow, and mechanical energy is given to the powder by repeating the impact operation. Things. By this action, fine particles are uniformly attached to the surface of the powder, and the surface of the powder is reformed. For reference, LiCoO not coated with fine particlesTwoFIG. 2 shows a scanning micrograph of the core particles.TwoFIG. 3 shows a scanning micrograph of the composite particles coated with the fine particles. In this case, the average particle diameter r of the core particlesTwoAnd the average particle diameter r of the fine particlesThreeThe ratio rThree/ RTwoIs 0.05. The core particles and the fine particles may be the same kind of lithium-containing compound as described above, or may be different kinds of lithium-containing compounds.
[0025]
When the composite particles of the lithium-containing compound in which the core particle surface is coated with the fine particles are used as the positive electrode active material, the following effects can be obtained.
[0026]
That is, generally, the packing density of the powder particles tends to increase as the particle diameter increases. This tendency also applies to the case where the positive electrode is composed of a lithium-containing compound, and the use of a lithium-containing compound having a larger particle diameter leads to a positive electrode having a higher active material filling property.
[0027]
However, although a lithium-containing compound having a simply large particle diameter can have high electrode filling properties, its effective surface area contributing to an electrode reaction is small due to its small specific surface area. Therefore, in a positive electrode using a lithium-containing compound having only such a large particle diameter, a portion far from the surface facing the negative electrode is likely to be in an overvoltage state, and the active material is deteriorated.
[0028]
On the other hand, the composite particles of the lithium-containing compound in which the surface of the core particle is coated with the fine particles have a larger specific surface area than a normal lithium-containing compound having the same particle size. For this reason, the reaction area which effectively contributes to the electrode reaction is sufficiently secured while increasing the filling property by increasing the particle size. Therefore, when this composite powder is used for the positive electrode, a battery having high energy and excellent heavy load characteristics and cycle characteristics can be realized at the same time.
[0029]
In order to obtain such an effect effectively, the core particles are coated with the fine particles, that is, the average particle diameter r as the composite particles.1And the average particle size r of the core particlesTwoAnd the average particle diameter r of the fine particles covering around the core particlesThreeIt is important that is appropriate.
[0030]
That is, the average particle size r of the composite particles1And the average particle diameter r of the core particlesTwoThe ratio r1/ RTwoIs 1.01 ≦ r1/ RTwoIt is preferred that ≦ 2. r1/ RTwoIs smaller than 1.01, that is, when the proportion of the coating layer formed by the fine particles is too small, the heavy duty cycle characteristics cannot be sufficiently improved. Conversely r1/ RTwoIs larger than 2, that is, when the proportion of the coating layer formed by the fine particles is too large, the heavy duty cycle characteristics are rather poor.
[0031]
Also, the average particle diameter r of the fine particlesThreeAnd the average particle diameter r of the core particlesTwoThe ratio rThree/ RTwoIs preferably 1/5 or less. rThree/ RTwoIs larger than 1/5, that is, when the particle size of the fine particles is too large relative to the particle size of the core particles, a large gap is left between the core particles and the fine particles, and there is a high possibility that the composite particle structure is broken.
[0032]
The average particle size r of the core particles isTwoIs specifically 3 μm ≦ rTwo≦ 30 μm is desirable for handling.
[0033]
The lithium composite oxide composite powder having the core particle surface coated with fine particles may be subjected to a heat treatment at a more appropriate temperature. Thereby, the properties such as conductivity of the composite powder are improved, and the composite powder becomes more excellent as a positive electrode active material.
[0034]
The nonaqueous electrolyte secondary battery of the present invention uses the lithium-containing compound produced as described above as a positive electrode active material. Therefore, a high electrode filling property is obtained, a sufficient electrode reaction area is secured, a high energy density is obtained, and good heavy load cycle characteristics are obtained.
[0035]
On the other hand, as the negative electrode active material of the battery, lithium, a lithium alloy, or a carbon material capable of doping / dedoping lithium is used. Examples of the carbon material include a low-crystalline carbon material obtained by calcining at a relatively low temperature of 2000 ° C. or less, and artificial graphite and natural graphite obtained by heat-treating a raw material that easily crystallizes at a high temperature of about 3000 ° C. Is used. Specifically, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, and organic polymer compound fired bodies (furan resin, etc.) ), Carbon fiber, activated carbon and the like. In particular, carbon having a characteristic that the spacing between (002) planes is 0.370 nm or more, the true specific gravity is less than 1.70 g / cc, and that it has no exothermic peak at 700 ° C. or more in differential thermal analysis in an air stream. Materials are preferred.
[0036]
Further, as the electrolytic solution, an electrolytic solution in which a lithium salt is used as a supporting electrolyte and this is dissolved in an organic solvent is used.
[0037]
Examples of the organic solvent include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, and 4-methyl-1,3. -Dioxolan, sulfolane, methylsulfolane, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate and the like can be used.
[0038]
LiClO is used as a supporting electrolyte.Four, LiAsF6, LiPF6, LiBFFour, LiB (C6HFive)Four, CHThreeSOThreeLi, CFThreeSOThreeLi, LiN (CFThreeSOTwo)Two, LiC (CFThreeSOTwo)Three, LiCl, LiBr and the like.
[0039]
【Example】
Examples of the present invention will be described based on experimental results.
[0040]
Configuration of fabricated battery
FIG. 4 shows the structure of the battery manufactured in each of the experimental examples described later.
[0041]
As shown in FIG. 4, the nonaqueous electrolyte secondary battery has a negative electrode 1 formed by applying a negative electrode active material to a negative electrode current collector 10 and a positive electrode formed by applying a positive electrode active material to a positive electrode current collector 11. 2 is wound through a separator 3 and the wound body is housed in a battery can 5 with an insulator 4 placed on top and bottom.
[0042]
A battery lid 7 is attached to the battery can 5 by caulking via a sealing gasket 6, and is electrically connected to the negative electrode 1 or the positive electrode 2 via a negative electrode lead 12 and a positive electrode lead 13, respectively. It is configured to function as a positive electrode.
[0043]
In the battery of the present embodiment, the positive electrode lead 13 is welded and attached to a safety valve device 8 having a current cutoff mechanism, and an electrical connection with the battery lid 7 is achieved through the safety valve device 8.
[0044]
In a battery having such a configuration, when the pressure inside the battery increases, the safety valve device 8 is pushed up and deformed. Then, the positive electrode lead 13 is cut leaving a portion welded to the safety valve device 8, and the current is cut off.
[0045]
Example 1
First, a positive electrode active material was produced as follows.
[0046]
Cobalt carbonate and lithium carbonate were mixed so that the Li / Co ratio = 1, and fired in air at 900 ° C. for 5 hours. As a result of X-ray diffraction measurement of the fired product, it was found that LiCoOTwoWell matched the diffraction pattern. This LiCoOTwoWas ground to obtain core particles having an average particle size of 3.0 μm and fine particles having an average particle size of 0.1 μm. And this LiCoOTwoLiCoO on the surface of the core particlesTwoThe particles are coated by a high-speed air-flow impact method, and LiCoOTwoWas prepared. The average particle size of the produced composite particles was 5.9 μm. The average particle diameter is a volume-based median diameter, and was measured with a laser diffraction particle size analyzer (trade name LA-50, manufactured by Horiba, Ltd.).
[0047]
And this LiCoOTwoUsing the composite particles as a positive electrode active material, a positive electrode was produced as follows.
[0048]
LiCoOTwo91% by weight of composite particles, 6% by weight of graphite as a conductive agent, and 3% by weight of polyvinylidene fluoride are mixed to prepare a positive electrode mixture, and the mixture is dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode mixture slurry. did.
[0049]
The positive electrode mixture slurry was applied to both sides of an aluminum foil serving as the positive electrode current collector 11, dried, and then compression-molded with a roller press to produce a belt-shaped positive electrode 2.
[0050]
Next, a negative electrode active material was produced.
[0051]
A petroleum pitch was used as a starting material, and after introducing 10 to 20% of a functional group containing oxygen (oxygen crosslinking), the mixture was fired in an inert gas at a temperature of 1000C. As a result, a non-graphitizable carbon material having properties close to those of a glassy carbon material was obtained.
[0052]
The negative electrode 1 was produced as follows using this non-graphitizable carbon material as a negative electrode active material.
[0053]
A negative electrode mixture was prepared by mixing 90% by weight of a carbon material and 10% by weight of polyvinylidene fluoride as a binder, and dispersed in N-methyl-2-pyrrolidone to prepare a negative electrode mixture slurry.
[0054]
Then, the negative electrode mixture slurry was applied to both surfaces of a copper foil serving as the negative electrode current collector 10, dried, and then compression-molded with a roller press to produce a band-shaped negative electrode 1.
[0055]
The strip-shaped negative electrode 1 and the positive electrode 2 manufactured as described above were laminated via a microporous polypropylene film having a thickness of 25 μm as a separator, and were wound many times to obtain a spiral electrode body.
[0056]
Next, the spiral electrode body was housed in an iron battery can 5 plated with nickel, and insulating plates 4 were arranged on both upper and lower surfaces of the spiral electrode body. Then, in order to collect the current of the positive electrode 2 and the negative electrode 1, the positive electrode lead 13 made of aluminum is led out from the positive electrode current collector 11 and welded to the safety valve device 8 having a current interrupting device, and nickel is collected from the negative electrode current collector 10. The negative electrode lead 12 made of was made and was welded to the battery can 5.
[0057]
Then, LiPF was mixed in the battery can 5 with a mixed solvent of 50% by volume of propylene carbonate and 50% by volume of methyl ethyl carbonate.6Was dissolved at a concentration of 1 mol. Then, the battery lid 7 and the battery can 5 were fixed by caulking via the gasket 6 coated with asphalt, thereby producing a cylindrical battery having a diameter of 18 mm and a height of 65 mm.
[0058]
Example 2
When producing the positive electrode active material, LiCoO having an average particle size of 15.1 μm is used as a core particle.TwoAs LiCoO having an average particle diameter of 0.7 μm as fine particles.TwoAnd a cylindrical battery was produced in the same manner as in Example 1 except that composite particles having an average particle size of 18.4 μm were produced.
[0059]
Example 3
In producing the positive electrode active material, LiCoO having an average particle diameter of 30.3 μm is used as a core particle.TwoAs LiCoO having an average particle size of 3.0 μm as fine particles.TwoAnd a cylindrical battery was produced in the same manner as in Example 1 except that composite particles having an average particle size of 34.0 μm were produced.
[0060]
Example 4
In producing the positive electrode active material, LiCoO having an average particle diameter of 30.3 μm is used as a core particle.TwoAs LiCoO having an average particle diameter of 0.7 μm as fine particles.TwoAnd a cylindrical battery was produced in the same manner as in Example 1 except that composite particles having an average particle size of 33.4 μm were produced.
[0061]
Comparative Example 1
LiCoO having an average particle size of 3.0 μmTwoA cylindrical battery was produced in the same manner as in Example 1, except that was used as a positive electrode active material.
[0062]
Comparative Example 2
LiCoO with an average particle size of 15.1 μmTwoA cylindrical battery was produced in the same manner as in Example 1, except that was used as a positive electrode active material.
[0063]
Comparative Example 3
LiCoO having an average particle size of 30.3 μmTwoA cylindrical battery was produced in the same manner as in Example 1, except that was used as a positive electrode active material.
[0064]
A heavy load is applied to the battery manufactured in this manner, under the condition that the charging voltage is 4.20 V, the charging current is 1000 mA, the charging time is 2.5 hours, and the discharging is 1200 mA and the final voltage is 2.75 V. The charge / discharge cycle under the discharge conditions was repeated, and the ratio (capacity retention) between the initial discharge capacity (initial discharge capacity) and the 200th cycle discharge capacity was determined. Table 1 shows the measurement results of the initial discharge capacity and the capacity retention ratio.
[0065]
[Table 1]
[0066]
In Table 1, first, LiCoO not coated with fine particles was used.TwoCompared with the batteries of Comparative Examples 1 to 3 using the same as the positive electrode active material, in this case, as the average particle size of the positive electrode active material increases, the capacity retention under heavy load discharge conditions deteriorates. You can see it coming.
[0067]
In contrast, LiCoO coated with fine particlesTwoCompared with Examples 1 to 4 in which was used as the positive electrode active material, the battery of Example 3 in which the average particle size of the positive electrode active material was 34.0 μm and the average particle size of the positive electrode active material were 33.4 μm. Even in the battery of Example 4, a sufficient capacity retention ratio was obtained under heavy load discharge conditions.
[0068]
Thus, LiCoO coated with fine particlesTwoIt has been found that can provide good heavy load cycle characteristics to the battery even if the average particle size is large, and make it possible to achieve both electrode filling properties and heavy load discharge characteristics.
[0069]
Example 5
A positive electrode active material was produced as follows.
[0070]
Cobalt oxide, nickel oxide and lithium hydroxide are mixed so that the Li / Ni / Co ratio = 1 / 0.8 / 0.2, and calcined at 750 ° C. for 5 hours in an oxygen-containing atmosphere to obtain LiNi.0.8Co0.2OTwoGenerated.
[0071]
This LiNi0.8Co0.2OTwoWas ground to obtain core particles having an average particle size of 15.1 μm. And this LiNi0.8Co0.2OTwoLiCoO having an average particle size of 0.7 μmTwoFine particles are coated by a high-speed air impact method, and LiNi0.8Co0.2OTwoAnd LiCoOTwoWas prepared. The average particle size of the composite particles was 18.6 μm.
[0072]
A cylindrical battery was produced in the same manner as in Example 1, except that the composite particles thus produced were used as a positive electrode active material.
[0073]
Example 6
A positive electrode active material was produced as follows.
[0074]
1 mol of manganese dioxide and 0.25 mol of lithium carbonate are mixed, and calcined in air at a temperature of 850 ° C. for 5 hours to obtain LiMn.TwoOFourGenerated.
[0075]
This LiMnTwoOFourWas ground to obtain core particles having an average particle size of 15.1 μm. And this LiMnTwoOFourLiCoO having an average particle size of 0.7 μmTwoIs coated by a high-velocity air impact method, and LiMnTwoOFourAnd LiCoOTwoWas prepared. The average particle size of the composite particles was 18.5 μm.
[0076]
A cylindrical battery was produced in the same manner as in Example 1, except that the composite particles thus produced were used as a positive electrode active material.
[0077]
Comparative Example 4
LiNi with an average particle size of 15.1 μm0.8Co0.2OTwoA cylindrical battery was produced in the same manner as in Example 1, except that was used as a positive electrode active material.
[0078]
Comparative Example 5
LiMn having an average particle size of 15.1 μmTwoOFourA cylindrical battery was produced in the same manner as in Example 1, except that was used as a positive electrode active material.
[0079]
With respect to the battery manufactured as described above, the initial discharge capacity under the heavy load discharge condition and the discharge capacity at the 200th cycle were measured in the same manner as described above, and the capacity retention rate was obtained. Table 2 shows the results.
[0080]
[Table 2]
[0081]
As can be seen from Table 2, LiNi coated with fine particles0.8Co0.2OTwoOr LiMnTwoOFourThe batteries of Examples 5 and 6 in which LiNi was used as the positive electrode active material were LiNi not coated with fine particles.0.8Co0.2OTwoOr LiMnTwoOFourOf Comparative Example 4 and Comparative Example 5, each of which was used as a positive electrode active material as it was, a large initial capacity was obtained, and the capacity retention ratio was a high value.
[0082]
From this, LiCoOTwoNot limited to LiNi0.8Co0.2OTwo, LiMnTwoOFourAlso, it was found that coating with fine particles was effective in enhancing the performance as a positive electrode.
[0083]
Average particle size r of composite particles 1 , Average particle size r of core particles Two And the average particle diameter r of the fine particles Three Examination of
In producing the positive electrode active material, LiCoO 2 having an average particle diameter shown in Table 3 as core particles and fine particles was used.TwoWas used to produce a cylindrical battery in the same manner as in Example 1 except that composite particles having an average particle size shown in the same table were produced.
[0084]
Then, the initial discharge capacity under the heavy load discharge condition and the discharge capacity at the 200th cycle were measured in the same manner as described above, and the capacity retention rate was obtained. Table 3 shows the results.
[0085]
[Table 3]
[0086]
As shown in Table 3, the average particle size r of the composite particles1And the average particle diameter r of the core particlesTwoThe ratio r1/ RTwoIs less than 1.01, and the battery of Experimental Example 7 in which this value exceeds 2 has a lower capacity retention ratio than the others. From this, r1/ RTwoIs 1.01 ≦ r1/ RTwoIt can be seen that it is desirable to be within the range of ≦ 2.
[0087]
Also, r1/ RTwoIs within this range, the average particle diameter r of the fine particlesThreeAnd the average particle diameter r of the core particlesTwoThe ratio rThree/ RTwoThe battery of Experimental Example 5 in which the ratio exceeds 1/5 cannot be said to have a sufficient capacity retention rate.
[0088]
Therefore, when producing composite particles, r1/ RTwoIs 1.01 ≦ r1/ RTwo≦ 2 and rThree/ RTwoIt can be seen that it is preferable to set the average particle diameter of the core particles and the fine particles and the conditions of the high-speed impact in a gas stream so that the ratio becomes 1/5 or less.
[0089]
In this embodiment, LiCoOTwo, LiNi0.8CO0.2OTwo, LiMnTwoOFourWas used as a lithium-containing compound.xCoOTwo, LixNiOTwo, LixMnTwoOFour, LixCo1-yMyOTwo, LixNi1-yMyOTwo, LixMn1-yMyOTwo(However, M represents at least one selected from Ti, V, Cr, Mn, Fe, Al, Co, Ni, Cu, Zn, Mo, Bi, and B, x is 0 <x ≦ 1.2, y Has been confirmed by experiments that the same effect can be obtained even when a lithium-containing compound represented by 0 <y <1 is used.
[0090]
Further, in this embodiment, the positive electrode active material is applied to a cylindrical battery. However, the same effect can be naturally obtained when the positive electrode active material is applied to a square, flat, coin, or button battery.
[0091]
【The invention's effect】
As described above, by using the positive electrode active material according to the present invention,A secondary battery that can secure a large reaction area while increasing the electrode filling property of the positive electrode, has high energy, and has excellent heavy load cycle characteristicsObtainable.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a state in which a composite powder is coated on a core particle surface.
FIG. 2 LiCoOTwo4 is a scanning micrograph showing a particle structure of a core particle.
FIG. 3 LiCoOTwo4 is a scanning micrograph showing the particle structure of a composite powder.
FIG. 4 is a longitudinal sectional view showing one configuration example of a nonaqueous electrolyte secondary battery to which the present invention is applied.
[Explanation of symbols]
34 core particles
35 fine particles
36 Composite powder

Claims (4)

  1. Li x CoO 2, Li x NiO 2, Li x Mn 2 O 4, Li x Co 1-y M y O 2, Li x Ni 1-y M y O 2, L x Mn 1-y M y O 2 ( Here, M represents at least one element selected from Ti, V, Cr, Mn, Fe, Al, Co, Ni, Cu, Zn, Mo, Bi, and B, and x is 0 <x ≦ 1.2. , Y is 0 <y <1), wherein the composite particles are obtained by coating the surface of a core particle composed of any of the lithium-containing compounds represented by the following formula with fine particles composed of any of these lithium-containing compounds. Positive electrode active material for non-aqueous electrolyte secondary batteries .
  2. Claim the ratio r 1 / r 2 of the average particle diameter r 2 of the mean particle size r 1 and the core particles of the positive electrode active material, characterized in that it is a 1.01 ≦ r 1 / r 2 ≦ 2 1 The positive electrode active material for a nonaqueous electrolyte secondary battery according to the above .
  3. The ratio r 3 / r 2 having an average particle diameter r 2 of the average particle diameter r 3 and the core particles of the fine particles is, for a non-aqueous electrolyte secondary battery according to claim 2, wherein a is 1/5 or less of the positive electrode active material.
  4. Non-aqueous electrolysis comprising a negative electrode using a lithium metal, lithium alloy or a carbon material capable of doping / dedoping lithium as a negative electrode active material, a positive electrode using a lithium-containing compound as a positive electrode active material, and a non-aqueous electrolyte In liquid secondary batteries,
    The positive electrode active material, Li x CoO 2, Li x NiO 2, Li x Mn 2 O 4, Li x Co 1-y M y O 2, Li x Ni 1-y M y O 2, L x Mn 1- y M y O 2 (where M represents at least one element selected from Ti, V, Cr, Mn, Fe, Al, Co, Ni, Cu, Zn, Mo, Bi and B, and x is 0 <X ≦ 1.2, y is 0 <y <1) Composite particles obtained by coating the surface of a core particle made of any one of lithium-containing compounds with fine particles made of any of these lithium-containing compounds non-aqueous electrolyte secondary battery, characterized in that it.
JP20736095A 1995-07-24 1995-07-24 Positive electrode active material and non-aqueous electrolyte secondary battery using this positive electrode active material Expired - Lifetime JP3543437B2 (en)

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