JPH07335262A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To maintain high capacity and high preservation by using a carbon material satisfying a condition that rhoP/rhoHe is smaller than a specific value, when assumed rhoP for true specific gravity measured by a liquid immersion substitution method with n-Bu0H serving as an immersion liquid in a negative electrode and f He for true specific gravity measured by a gas substitution method using Li. CONSTITUTION:In this nonaqueous electrolyte secondary battery, a graphitizationdifficult carbon material is used in a negative electrode, and an Li transition metal compound oxide, represented by a formula LixNiyCo1-yO2 (0.05<=x<=1.10, 0.5<=y<=0.95), is used in a positive electrode active material, to set upper changing limit voltage, for instance, to 4.0V or more. In this negative electrode 1, a graphitization-difficult carbon material, having 0.37nm or more surface space of (002) surface, less than true specific gravity 1.7 further without having a heating analytic peak at 700 deg.C or more by differential thermal analysis in an air stream, is used. Or when assumed rhoP for true specific gravity measured by a liquid immersion method with n-butanol serving as an immersion liquid in the negative electrode and rhoHe for true specific gravity by a gas substitution method using helium gas, a carbon quality material, where a relation rhoP/rhoHe<0.960 is provided, can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery using, as a negative electrode, a carbonaceous material capable of being doped / dedoped with lithium, and having a high capacity and improved storage characteristics. The present invention relates to a liquid secondary battery.

[0002]

2. Description of the Related Art Recent remarkable advances in electronic technology have made electronic devices smaller and lighter one after another. Along with this, there are increasing demands for batteries as portable power sources that are smaller and lighter and have high energy density. Conventionally, aqueous secondary batteries such as lead batteries and nickel-cadmium batteries have been the mainstream as secondary batteries for general use. Although these batteries have excellent cycle characteristics, they were not satisfactory in terms of battery weight and energy density. From the viewpoint of environmental protection, the emergence of new battery system is desired. Under such circumstances, research and development of a non-aqueous electrolyte secondary battery using lithium or a lithium alloy as a negative electrode has been actively conducted. This battery has high energy density, low self-discharge, and excellent characteristics such as light weight. However, since metal lithium is dissolved / precipitated during charging / discharging, lithium grows in a dendrite-like crystal upon charging and reaches the positive electrode. That is, an internal short circuit may occur. Further, this probability tends to increase as the charge / discharge cycle progresses, which is not preferable from the viewpoint of safety and reliability, which is a major obstacle to practical use.

As a battery system that overcomes the problem of having a lithium secondary battery having metal lithium as a negative electrode, a lithium ion secondary battery using a carbon material for the negative electrode has recently been put into practical use. This battery utilizes doping / de-doping of lithium ions between carbon layers for the negative electrode reaction, and by designing an appropriate battery, the charging / discharging cycle or the progress of charging / discharging cycle can be improved. However, no precipitation of metallic lithium is observed. Therefore, good charge / discharge cycle characteristics and safety are exhibited. Further, the rapid charge / discharge characteristics and the low temperature characteristics of the lithium ion secondary battery are also superior to those of the lithium secondary battery. Various carbon materials that can be used as the negative electrode of lithium-ion secondary batteries have been reported, but the batteries that have been commercialized so far have low crystalline properties such as coke and glassy carbon that have been treated at relatively low temperatures. The carbonaceous material is used. In addition, although there are many reports on positive electrode materials, lithium cobalt oxide (LiCoO ₂ ) is used in commercialized batteries. The electrolytes of these batteries have been generally used for non-aqueous electrolyte batteries such as coin type and cylindrical type lithium primary batteries,
Solvents based on propylene carbonate (PC) are used.

In the case of a non-aqueous electrolyte battery in which metallic lithium is used as a negative electrode, PC, which is an electrolyte solvent, reacts with lithium in the outermost surface layer of the negative electrode, and the product thereof serves as a protective film for the negative electrode. Discharge reaction is unlikely to occur. In addition, since the inside except the outermost surface layer that contacts the electrolytic solution consists of a single metal,
It has high stability during storage, and when it is used as the negative electrode of a non-aqueous electrolyte secondary battery, the same capacity as before storage can be obtained by recharging after storage. On the other hand, the lithium-ion secondary battery is
When the battery is stored in the discharged state, the capacity hardly changes, but when it is stored in the charged state, the capacity recovery rate is slightly lowered. The effect of this decrease in capacity recovery rate depends on the battery voltage during storage, and has a large effect when stored at a high voltage. Further, when a graphite material having high crystallinity is used as the negative electrode, the negative electrode in the charged state, that is, the lithium-graphite intercalation compound has high stability, so that the capacity recovery rate is small even when stored in the charged state, In a battery in which a low crystalline carbon material treated at a low temperature of 1000 to 2000 ° C. is used for the negative electrode, this effect tends to be relatively large.

[0005]

As described above, the lithium ion secondary battery shows almost no capacity change when stored in a discharged state, but has a capacity recovery rate when stored in a charged state. The drawback is that it is slightly reduced. Considering practicality, it is considered that a rechargeable battery is generally charged and stored for immediate use rather than stored in a discharged state and charged immediately before use. Further, as a negative electrode material of a lithium ion secondary battery, it is often advantageous to use a low crystalline carbon material for the negative electrode because it has excellent low temperature characteristics and heavy load characteristics.

For the above reasons, it is very important to improve the capacity recovery rate of a lithium ion secondary battery using a low crystalline carbon material for the negative electrode when stored at a high battery voltage. It is an issue. An object of the present invention is to provide a non-aqueous electrolyte secondary battery having high capacity and excellent storage characteristics. Another object of the present invention is to provide a non-aqueous electrolyte secondary battery capable of improving the capacity recovery rate when stored in a state of high battery voltage. Also,
An object of the present invention is to provide a lithium ion secondary battery using a low crystalline carbon material for the negative electrode, which can improve the capacity recovery rate when stored at a high battery voltage.

[0007]

The above objects of the present invention can be achieved by the following constitutions. That is, a carbonaceous material capable of doping and dedoping lithium is used for the negative electrode, a composite oxide of lithium and a transition metal is used for the positive electrode, and a nonaqueous electrolytic solution obtained by dissolving an electrolyte in an organic solvent is used as the electrolytic solution. In a water electrolyte secondary battery, a non-graphitizable carbonaceous material is used for the negative electrode, and a positive electrode active material of the general formula Li _x Ni _y Co _1-y O
₂ (0.05 ≦ x ≦ 1.10, 0.5 ≦ y ≦ 0.95)
It is a non-aqueous electrolyte secondary battery which is used by using the lithium-transition metal composite oxide represented by the following, and setting the charging upper limit voltage to 4.0 V or more. In the non-aqueous electrolyte secondary battery of the present invention, the negative electrode has a (002) plane spacing of 0.37 nm or more, a true specific gravity of less than 1.7, and a differential thermal analysis of 700 ° C. or more in an air stream. A non-graphitizable carbonaceous material having no exothermic peak is used, or the true specific gravity measured by a liquid immersion displacement method using n-butanol as an immersion liquid for the negative electrode is ρp, and a gas displacement method using helium gas is used. When the measured true specific gravity is ρHe, ρp / ρHe <0.
A carbonaceous material satisfying the condition of 960 can be used.

In a non-aqueous electrolyte secondary battery (so-called lithium ion secondary battery) using a carbon material for the negative electrode and a lithium-containing transition metal composite oxide for the positive electrode of the present invention, a low crystalline carbon material is used for the negative electrode, By using a lithium-nickel-cobalt composite oxide in which the atomic ratio of nickel and cobalt is specified as the positive electrode active material, a battery having high capacity and excellent storage characteristics is provided. Since the lithium-ion secondary battery of the present invention is intended to have a high capacity, the charging upper limit voltage is set to 4.0 V or more before use. A battery having a higher energy density can be obtained by designing on the assumption that the upper limit voltage is 4.2 V or higher and charging the battery at 4.2 V or higher.

The negative electrode material according to the present invention is 200
It is possible to use a carbonaceous material having low crystallinity such as a graphitizable carbonaceous material or a non-graphitizable carbonaceous material that has been heat-treated at a temperature of 0 ° C. or less. Here, the carbonaceous material having low crystallinity means a carbon material having a (002) plane spacing of 0.340 nm or more measured by a powder X-ray diffraction method. Among carbonaceous materials having low crystallinity, JP-A-2-66.
The surface spacing of the (002) plane shown in Japanese Patent No. 856 is 0.3.
A non-graphitizable carbonaceous material having a true specific gravity of 7 nm or more and a true specific gravity of less than 1.7 and having no exothermic peak at 700 ° C or more in a differential thermal analysis in an air stream has a large chargeable / dischargeable capacity per unit weight and a high This is effective because a lithium ion secondary battery having a capacity can be obtained. When this carbonaceous material is used for the negative electrode, by combining a lithium-nickel-cobalt composite oxide having a composition range specified in the present invention as a positive electrode active material, a lithium ion electrode having high capacity and excellent storage stability is obtained. The next battery is obtained.

Further, among the above-mentioned non-graphitizable carbonaceous materials, the true specific gravity measured by the liquid immersion displacement method using n-butanol as an immersion liquid as shown in Japanese Patent Application No. 05-267253 is ρp, and helium is helium. When the true specific gravity measured by the gas displacement method using gas is ρHe, ρp / ρHe <0.9
The carbonaceous material satisfying the condition of 60 has a larger chargeable / dischargeable capacity per unit weight and is effective in increasing the capacity of the lithium ion secondary battery. When this carbonaceous material is used for the negative electrode, by combining the lithium-nickel-cobalt composite oxide having the composition range specified in the present invention as the positive electrode active material, a lithium ion having higher capacity and excellent storage stability is obtained. A secondary battery can be obtained. Furthermore, since the chargeable / dischargeable capacity per unit weight is larger,
It is preferable to use a non-graphitizable carbonaceous material satisfying the condition of ρp / ρHe <0.900, and ρp / ρHe <
It is preferable to use a non-graphitizable carbonaceous material satisfying the condition of 0.850.

Organic materials such as coal and pitch are typical as a starting material for producing the graphitizable carbonaceous material. As pitch, tars obtained by high-temperature pyrolysis of coal tar, ethylene bottom oil, crude oil, etc., distillation of asphalt (vacuum distillation, atmospheric distillation, steam distillation), thermal polycondensation, extraction, chemical polycondensation, etc. Examples include those obtained by operation and those produced during carbonization of wood. Further, it is possible to use a high molecular compound such as polyvinyl chloride resin, polyvinyl acetate, polyvinyl butyrate, or 3,5-dimethylphenol resin as a starting material for pitch. These coals, pitches, and polymer compounds exist in a liquid state up to around 400 ° C. during carbonization, and by storing at that temperature, aromatic rings are condensed and polycyclic, and are in a laminated orientation. Then, when the temperature becomes higher than about 500 ° C., a solid carbon precursor (semi-coke) is formed. Such a process is called a liquid-phase carbonization process, which is a typical formation process of graphitizable carbon.

Further, condensed polycyclic hydrocarbon compounds such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, perylene, pentaphene and pentacene, other derivatives (for example, carboxylic acids, carboxylic acid anhydrides, carboxylic acid imides thereof), or Mixture, acenaphthylene, indole, isoindole, quinoline,
Fused heterocyclic compounds such as isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine and phenanthridine, and derivatives thereof can also be used as raw materials. For the graphitizable carbonaceous material, the above-mentioned starting materials are used, for example, in a stream of an inert gas such as nitrogen for 300
After carbonization at ~ 700 ° C, 9 at a rate of 1-100 ° C / min
The temperature is raised to 00 to 1500 ° C, and the reached temperature is 0 to 30
Obtained by holding for a time. Of course, the carbonization operation may be omitted in some cases.

Also, since the lithium doping ability can be improved by efficiently removing various volatile components generated during firing, the atmospheric conditions during firing are also important. The atmosphere during firing is preferably an inert gas atmosphere, and more preferably 0.1 cm ³ / min or more per 1 g of the raw material in an inert gas stream. Furthermore, the method of firing while evacuating is the most preferable method because it is hardly affected by volatile components (Japanese Patent Application No. 4-1).
37846). As a starting material for producing the non-graphitizable carbonaceous material, furfuryl alcohol resin, furfural resin, furan resin, phenol resin, acrylic resin,
Vinyl halide resin, polyimide resin, polyamide-imide resin, polyamide resin, polyacetylene, poly (p
-Phenylene) and other conjugated resins, and organic polymer compounds such as cellulose and its derivatives can be used.

Further, a so-called oxygen-crosslinking product, in which a functional group containing oxygen is introduced into a petroleum pitch having a specific hydrogen atom / carbon (H / C) atomic ratio, is also carbonized at a temperature of 400 ° C. or higher. Without melting in the process, solid-phase carbonization results in a non-graphitizable carbonaceous material. The oil pitch is
It can be obtained by operations such as distillation (vacuum distillation, atmospheric distillation, steam distillation), thermal polycondensation, extraction, chemical polycondensation, etc., obtained by high-temperature thermal decomposition of coal tar, ethylene bottom oil, crude oil, etc., and asphalt. . In order to obtain a non-graphitizable carbonaceous material, the H / C atomic ratio of petroleum pitch is important and needs to be 0.6 to 0.8.

The method of introducing a functional group containing oxygen is not limited, but for example, a wet method using an aqueous solution of nitric acid, mixed acid, sulfuric acid, hypochlorous acid, a dry method using an oxidizing gas such as air or oxygen, or sulfur. , A reaction method using a solid reagent such as ammonia nitrate, ammonium persulfate, and ferric chloride is used. The oxygen content is not particularly limited, but it is disclosed in Japanese Patent Laid-Open No.
It is preferably 3% or more, more preferably 5% or more, as shown in Japanese Patent No. 252053. The non-graphitizable carbonaceous material is obtained by carbonizing the above starting materials at 300 to 700 ° C. in a stream of an inert gas such as nitrogen, and then
It is obtained by raising the temperature to 900 to 1500 ° C. at a rate of 100 ° C./min and holding at the reached temperature for 0 to 30 hours. Of course, the carbonization operation may be omitted in some cases.

Among these non-graphitizable carbonaceous materials, furan resins composed of furfuryl alcohol or furfural homopolymers or copolymers and starting materials obtained by oxygen-crosslinking petroleum pitch having a specific H / C atomic ratio are used. The used one has a (002) plane spacing of 0.37 nm or more,
It has a true specific gravity of less than 1.7, has no oxidation exothermic peak at 700 ° C. or higher in differential thermal analysis in an air stream, has a large chargeable / dischargeable capacity, and exhibits very good characteristics as a load material for a battery. Further, when carbonizing the furan resin, petroleum pitch or the like, a phosphorus compound as described in JP-A-3-137010, or JP-A-3-24.
A carbon material having a large lithium doping amount by adding a boron compound as described in Japanese Patent No. 5458 is also suitable as a negative electrode material.

Examples of the phosphorus compound include phosphorus oxides such as phosphorus pentoxide and oxo acids such as orthophosphoric acid and salts thereof. Among them, phosphorus oxide and phosphoric acid are preferable from the viewpoint of easy handling. Is. The amount of the phosphorus compound added is 0.2 to 30% by weight, preferably 0.5 to 15% by weight, in terms of phosphorus, based on the organic material or the carbon material, and the proportion of phosphorus remaining in the negative electrode carbon material is 0. 2-9.
It is 0% by weight, preferably 0.3 to 5% by weight. As the boron compound, boron oxide or boric acid can be added in the form of an aqueous solution. The amount of the boron compound added is 0.2 to 30% by weight, preferably 0.5 to 15% by weight, in terms of boron with respect to the organic material or the carbon material, and the proportion of boron remaining in the negative electrode carbon material is 0. ．
The content is 2 to 9.0% by weight, preferably 0.3 to 5% by weight.

Further, since the lithium doping ability can be improved by efficiently removing various volatile components generated during firing, the atmospheric conditions during firing are also important. The atmosphere during firing is preferably an inert gas atmosphere, and more preferably 0.1 cm ³ / min or more per 1 g of the raw material in an inert gas stream. Furthermore, the method of firing while evacuating is the most preferable method because it is hardly affected by volatile components (Japanese Patent Application No.
137846). The non-graphitizable carbonaceous material obtained by such a method has a true specific gravity of ρp measured by a liquid immersion displacement method using n-butanol as an immersion liquid, and a gas displacement method using helium gas. When the true specific gravity is ρHe, the condition of ρp / ρHe <0.960 is satisfied, the chargeable / dischargeable capacity is large, and excellent properties are exhibited as a negative electrode material of a lithium ion secondary battery.

The positive electrode material for a lithium ion secondary battery of the present invention has the general formula Li _x Ni _y Co _{1 -y} O ₂ (provided that
The lithium-nickel-cobalt composite oxide represented by 0.05 ≦ x ≦ 1.10 and 0.5 ≦ y ≦ 0.95) is used. This material contains a large amount of lithium that can be dedoped / doped, and by combining it with the above-mentioned negative electrode material, a lithium ion secondary battery having high capacity and excellent storage stability can be obtained. Among these lithium-nickel-cobalt composite oxides, using a material having a composition represented by 0.65 ≦ y ≦ 0.92 in the general formula Li _x Ni _y Co _1-y O ₂ makes it The recovery rate after storage of the secondary battery can be further increased, which is preferable, and 0.75 ≦ y ≦ 0.
It is most preferable to use the material having the composition shown by 90. The lithium-nickel-cobalt composite oxide is
For example, a salt such as a hydroxide, oxide, or carbonate of a transition metal such as lithium, cobalt, or nickel is used as a starting material, and each compound is mixed at a predetermined composition ratio to obtain 600 to 1
It is obtained by firing in the temperature range of 000 ° C.

The general formula Li _x Ni _y Co _1-y O ₂ (where x is
An example using a lithium-nickel-cobalt composite oxide of ≦ 1, 0.5 ≦ y ≦ 0.9) is described in Japanese Patent Application No. 2-92697 (JP-A-3-49155). When the battery is overcharged due to equipment failure or malfunction, the present invention promotes the decomposition of the electrolyte solution and the generated decomposition gas raises the internal pressure of the battery. To secure. Therefore, it relates to the relationship between the positive electrode alone or the positive electrode and the electrolytic solution, and it aims to improve the storage characteristics by combining a specific negative electrode material and a specific lithium-nickel-cobalt composite oxide positive electrode material. It is completely different from the invention.

Further, an example using a lithium-nickel-cobalt composite oxide of the general formula Li _x Ni _y Co _1-y O ₂ (where x ≦ 1, 0.5 ≦ y ≦ 1.0 is disclosed in Japanese Patent Application Laid-Open No. 4-26). 4915
No. 5 publication. In the present invention, Li _x Ni _y Co _1-y O ₂ (where x ≦ 1, 0 ≦ y <0.
If the battery is overcharged due to device failure or malfunction due to addition of the above materials as an auxiliary active material to 50), the decomposition gas of the electrolyte is promoted and the generated decomposition gas causes the internal pressure of the battery to increase. Rises and the safety valve is activated to ensure safety. Therefore, the positive electrode alone or the relationship between the positive electrode and the electrolytic solution is involved, and the specific negative electrode material and the specific lithium nickel
This is completely different from the present invention in which storage characteristics are improved by combining with a cobalt composite oxide positive electrode material.

Further, an example using a lithium-nickel-cobalt composite oxide of the general formula LiNi _y Co _1-y O ₂ (where 0 <y <0.8) is described in JP-A-63-299056. There is. The present invention is intended to increase the deintercalation amount of Li of the lithium-transition metal composite oxide and is intended to increase the capacity of the positive electrode material. Therefore, the present invention is concerned only with the positive electrode, and is completely different from the present invention in which the storage characteristics are improved by combining a specific negative electrode material and a specific lithium-nickel-cobalt composite oxide positive electrode material.

Next, the non-aqueous electrolyte used in the lithium ion secondary battery of the present invention will be described. As the electrolyte,
An electrolytic solution in which a lithium salt is used as a supporting electrolyte and this is dissolved in a non-aqueous solvent is used. The non-aqueous solvent species is not particularly limited, but for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, Sulfolane, methylsulfolane, etc. may be used alone, or two or more kinds of solvents may be mixed at an appropriate ratio.

In forming an electrolytic solution having high conductivity,
A mixed solvent containing a chain carbonic acid ester (ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methylpropyl carbonate) is suitable, and an asymmetric chain carbonic acid ester (methylethyl carbonate, methylpropyl carbonate) is particularly preferable. It is one of the optimum mixed solvent components. By using the mixed solvent, the current characteristics and low temperature characteristics of the lithium ion secondary battery are improved, the reactivity with lithium metal is lowered, and the safety is improved. LiPF ₆ is suitable as the electrolyte, but any of those used in this type of battery can be used, for example, LiClO ₄ , LiAsF ₆ ,
LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiC
l, LiBr, LiSO ₃ CH ₃ , LiSO ₃ CF ₃ , Li
Examples include N (SO ₂ CF ₃ ) ₂ and LiC (SO ₂ CF ₃ ) ₃ .

[0025]

EXAMPLES Examples and comparative examples of the present invention will be described in detail below with reference to FIG. Needless to say, the present invention is not limited to this embodiment. Negative electrode materials and positive electrode materials used in Examples and Comparative Examples were manufactured as follows. The carbon material for the negative electrode of the experimental battery was produced as follows. The starting material has an H / C atomic ratio of 0.6 to 0.
Using a petroleum pitch appropriately selected from the range of 8, a carbon precursor was obtained by oxidation treatment in an air stream. The quinoline insoluble matter of this carbon precursor (JIS centrifugal method: K2425-198
3) was 80%, and the oxygen content (by organic elemental analysis) was 16% by weight. Carbon precursor in various inert gas streams at various flow rates, or in some cases 20 kP
Carbonaceous materials A to D having properties close to glassy carbon by firing at 1000 to 1200 ° C. under reduced pressure below a
Got The obtained carbon material was pulverized to obtain a carbon material powder for a negative electrode of an experimental battery. Table 1 shows the physical properties of these materials. The interplanar spacing of the (002) plane was determined by a powder X-ray diffraction method, and the average grain size was determined by using a laser diffraction type grain size distribution measuring device. The true specific gravity is determined by two methods, a liquid immersion substitution method using n-butanol as an immersion solvent (pycnometer method) and a gas substitution method using He gas (helium method), and the true specific gravity (ρHe) by the helium method is determined by the pycnometer method. The ratio (ρp / ρHe) of the true specific gravity (ρp) was calculated.

[0026]

[Table 1]

The lithium-transition metal composite oxide for the positive electrode of the experimental battery was prepared as follows. After mixing lithium hydroxide, nickel oxide, and cobalt oxide so that the lithium: nickel: cobalt atomic ratio as shown in Table 2 was obtained, the mixture was burned in an oxygen atmosphere at 700 to 800 ° C. for 12 hours to obtain various lithium. A transition metal composite oxide was synthesized.
These materials were crushed to produce positive electrode materials AJ. X-ray diffraction measurement was performed on these materials. Positive electrode material A
Is in good agreement with the peak of LiCoO ₂ registered in the JCPDS file, confirming the synthesis of LiCoO ₂ . For the positive electrode material J, it was confirmed that LiNiO ₂ having the same crystal structure was synthesized. Further, the positive electrode materials B to I have diffraction positions,
Although the intensity is slightly different, it has a single-phase diffraction pattern very similar to that of the positive electrode material A or the positive electrode material J.
It was confirmed that a part of nickel in ₂ was replaced with cobalt to form a solid solution.

[0028]

[Table 2]

Example 1 FIG. 1 shows a sectional structural view of a battery of the present invention. In this example, carbon material C was used as a negative electrode material, and 90 parts by weight of this was mixed with 10 parts by weight of vinylidene fluoride resin as a binder to prepare a negative electrode mixture. This negative electrode mixture was dispersed in a solvent, N-methyl-2-pyrrolidone, to obtain a slurry (paste form). A strip-shaped copper foil having a thickness of 10 μm was used as the negative electrode current collector 10. The negative electrode mixture slurry was uniformly applied to both surfaces of the current collector 10, dried and then pressure-molded to produce the strip negative electrode 1. did. N-methyl-2 was prepared by mixing 91 parts by weight of the positive electrode material C, 6 parts by weight of graphite as a conductive agent, and 3 parts by weight of vinylidene fluoride resin as a binder to prepare a positive electrode mixture.
Dispersed in pyrrolidone to make a slurry (paste). A strip-shaped aluminum foil having a thickness of 20 μm is used as the positive electrode current collector 11, the positive electrode mixture slurry is uniformly applied to both surfaces of the current collector 11, dried and then pressure-molded to produce the band-shaped positive electrode 2. did.

A strip-shaped negative electrode 1, a strip-shaped positive electrode 2, and a separator 3 composed of a microporous polyolefin film are laminated in this order on the negative electrode 1, the separator 3, the positive electrode 2, and the separator 3 and then wound many times to form the outermost winding end portion. Was fixed with an adhesive tape to produce a spiral electrode body having an outer diameter of 18 mm. A center pin 14 is provided at the center of the spiral electrode body. The spiral electrode thus produced was housed in a nickel-plated iron battery can 5. Insulating plates 4 are provided on the upper and lower surfaces of the spirally wound electrode body, and the aluminum positive electrode lead 13 is led out from the positive electrode current collector 11 so that the battery lid 7 is electrically connected to the protrusion of the safety valve device 8. The nickel negative electrode lead 12 was led out from the negative electrode current collector 10 and welded to the bottom of the battery can 5. As the electrolytic solution, a supporting electrolyte LiPF ₆ dissolved in a mixed solvent of propylene carbonate and methyl ethyl carbonate at a ratio of 1 mol / liter was used.

By caulking the battery can 5 through the insulating sealing gasket 6 whose surface is coated with asphalt, the safety valve device 8 having a current cutoff mechanism, the PTC element 9 and the battery lid 7 are fixed, and the airtightness inside the battery is improved. Was held. With the above structure, a cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced (invention battery 1). The battery was charged for 2.5 hours with the upper limit voltage set at 4.2V and the current in the constant current region set at 1A, and then charged at 0.7A constant current for 2.5 hours.
Discharged to V and recorded discharge capacity up to 2.75V.
After measuring the initial capacity, the battery was fully discharged again under the above-mentioned conditions and left in a 45 ° C. environment for 1 month. After storing the battery, discharge it to the final voltage and then charge and discharge it under the above conditions.
Went cycle. The ratio of the discharge capacity in each cycle after storage to the initial capacity was determined as a percentage, and the maximum value was defined as the capacity recovery rate.

Example 2 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced in the same manner as in Example 1 except that the positive electrode material D was used as the positive electrode active material (the present invention battery 2 ) And battery characteristics were evaluated under the same conditions. Example 3 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced in the same manner as in Example 1 except that the positive electrode material E was used as the positive electrode active material (the present battery 3), and the same. The battery characteristics were evaluated under the above conditions. Example 4 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced in the same manner as in Example 1 except that the positive electrode material F was used as the positive electrode active material (invention battery 4). The battery characteristics were evaluated under the above conditions.

Example 5 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced in the same manner as in Example 1 except that the positive electrode material G was used as the positive electrode active material (the battery of the present invention 5 ) And battery characteristics were evaluated under the same conditions. Example 6 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced in the same manner as in Example 1 except that the positive electrode material H was used as the positive electrode active material (invention battery 6). The battery characteristics were evaluated under the above conditions. Example 7 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced in the same manner as in Example 1 except that the positive electrode material I was used as the positive electrode active material (invention battery 7). The battery characteristics were evaluated under the above conditions.

Example 8 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was manufactured in the same manner as in Example 1 except that the carbon material A was used as the negative electrode material and the positive electrode material F was used as the positive electrode active material. Was produced (invention battery 8), and battery characteristics were evaluated under the same conditions. Example 9 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced in the same manner as in Example 1 except that the carbon material B was used as the negative electrode material and the positive electrode material F was used as the positive electrode active material. (Invention Battery 9) The battery characteristics were evaluated under the same conditions. Example 10 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced in the same manner as in Example 1 except that the carbon material D was used as the negative electrode material and the positive electrode material F was used as the positive electrode active material. (Invention Battery 10) The battery characteristics were evaluated under the same conditions.

Comparative Example 1 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced in the same manner as in Example 1 except that the positive electrode material A was used as the positive electrode active material (Comparative Battery 1). ,
Battery characteristics were evaluated under the same conditions. Comparative Example 2 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced in the same manner as in Example 1 except that the positive electrode material B was used as the positive electrode active material (Comparative Battery 2).
Battery characteristics were evaluated under the same conditions. Comparative Example 3 A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was produced in the same manner as in Example 1 except that the positive electrode material J was used as the positive electrode active material (Comparative Battery 3).
Battery characteristics were evaluated under the same conditions. Table 3 shows the initial capacities and storage recovery rates of the present batteries 1 to 10 and the comparative batteries 1 to 3. Further, in FIG. 2, a non-graphitizable carbonaceous material was used for the negative electrode and the general formula Li _x N was used for the positive electrode, which was determined from the results of the storage recovery rates of the present batteries 1 to 7 and the comparative batteries 1 to 3.
i _y Co _{1 -y} O ₂ (0.05 ≦ x ≦ 1.10) shows the relationship between the y value and the storage recovery rate in a lithium-ion secondary battery using a lithium-transition metal composite oxide. It was

[0036]

[Table 3]

Comparative battery 1 using LiCoO ₂ which is a general positive electrode material in a conventional lithium ion secondary battery, comparison using a lithium-nickel-cobalt composite oxide containing 0.2 of nickel in atomic ratio. Battery 2, Li
The present invention using a lithium-nickel-cobalt composite oxide (positive electrode material C to I) containing nickel in an atomic ratio of 0.5 to 0.95 as a positive electrode, as compared with the comparative battery 3 using NiO _2. Batteries 1 to 7 have a large capacity recovery rate after storage,
The value is above%. In particular, from the curve in FIG. 2, a material having a nickel atomic ratio of 0.65 or more and 0.92 or less is a preferable material because the capacity recovery rate becomes higher at 92% or more, and the nickel atomic ratio is 0.75. ~ 0.9
The material in the range of 0 has a capacity recovery rate of 93% or more, and is a more desirable material.

The non-graphitizable carbonaceous material used for the negative electrode has a (002) plane spacing of 0.37 nm or more, a true specific gravity of less than 1.7, and a differential thermal analysis in an air stream of 700 ° C. or more. A material having no exothermic peak is used, and among them, a material satisfying ρp <ρHe <0.960 is desirable. In particular, the battery 4 of the present invention and the batteries 8 to 8 of the present invention
From the results of 10, it is preferable to use a material satisfying ρp <ρHe <0.89 because a high capacity can be obtained, and ρp <ρHe <
A material satisfying 0.86 is more preferable because a higher capacity can be obtained. By using the above-mentioned lithium-nickel-cobalt composite oxide for the positive electrode in the negative electrode of these non-graphitizable carbonaceous materials, a lithium ion secondary battery having high capacity and excellent storage stability can be achieved.

As is clear from the above description, according to the present invention, the non-aqueous electrolyte secondary battery (so-called lithium ion secondary battery) having the carbon material as the negative electrode is used by setting the charging upper limit voltage to 4.0 V or more. Battery), a non-graphitizable carbonaceous material is used for the negative electrode, and the general formula Li _x Ni _y Co _1-y is used for the positive electrode active material.
O ₂ (0.05 ≦ x ≦ 1.10, 0.5 ≦ y ≦ 0.9
It is characterized by using the lithium-nickel-cobalt composite oxide represented by 5), and compared with a battery using LiCoO ₂ which is a general positive electrode material of a lithium-ion secondary battery. It provides a battery having excellent properties. Further, by using a lithium-nickel-cobalt composite oxide represented by 0.65 ≦ y ≦ 0.92 for the positive electrode, the storability is further improved, and particularly 0.75 ≦
The lithium-nickel-cobalt composite oxide represented by y ≦ 0.90 exhibits excellent storability.

Further, the (002) plane spacing of the negative electrode is 0.37 nm or more and the true specific gravity is less than 1.7, and the non-graphitization does not have an exothermic peak at 700 ° C. or more in differential thermal analysis in an air stream. A battery having a high capacity and excellent storability can be obtained by using the organic carbonaceous material. Among them, when the true specific gravity measured by the liquid immersion displacement method using n-butanol as the immersion liquid is ρp and the true specific gravity measured by the gas displacement method using helium gas is ρHe, ρp /
Using a carbonaceous material satisfying the condition of ρHe <0.960 is advantageous for increasing the capacity of the battery. Also, ρ
Higher capacity batteries can be obtained by using materials satisfying p <ρHe <0.89, and higher capacity batteries can be obtained by using materials satisfying ρp <ρHe <0.86.

[0041]

According to the present invention, it is possible to obtain a battery having a high capacity and excellent storability as compared with a battery using LiCoO ₂ , which is a general positive electrode material for lithium ion secondary batteries.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention.

FIG. 2 shows a storage recovery rate of a non-aqueous electrolyte secondary battery of an example of the present invention and a battery of a comparative example, and a general formula Li _x Ni _y Co _{1 -y} O ₂ (0.05) used for a positive electrode active material. ≦ x ≦ 1.10,
FIG. 3 is a relational diagram with the y value of the lithium-nickel-cobalt composite oxide represented by 0.5 ≦ y ≦ 0.95).

[Explanation of symbols]

1 ... Negative electrode, 2 ... Positive electrode, 3 ... Separator, 4 ... Insulating plate, 5
... Battery can, 6 ... Sealing gasket, 7 ... Battery lid, 8 ... Safety valve device, 9 ... PTC element, 10 ... Negative electrode current collector, 11 ... Positive electrode current collector, 12 ... Negative electrode lead, 13 ... Positive electrode lead, 14
… Center pin

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Imoto 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Atsushi Komaru 2-32-3, Shibuya, Shibuya-ku, Tokyo Stocks Within Sony Energy Tech Inc. (72) Inventor Naoyuki Nakajima 2-32 Shibuya, Shibuya-ku, Tokyo Inside Sony Energy Tech Inc. (72) Inventor Yu Suzuki 22-22 Shibuya, Shibuya-ku, Tokyo No. 3 Stock Company Sony Energy Tech

Claims (3)

[Claims] 1. A non-aqueous electrolytic solution in which a carbonaceous material capable of doping and dedoping lithium is used for the negative electrode, a composite oxide of lithium and a transition metal is used for the positive electrode, and an electrolyte is dissolved in an organic solvent as an electrolytic solution. In a non-aqueous electrolyte secondary battery using, a non-graphitizable carbonaceous material is used for the negative electrode, and a positive electrode active material of the general formula Li _x Ni _y Co _1-y O ₂ (0.05 ≦ x ≦ 1.1
0, 0.5 ≦ y ≦ 0.95), and a lithium-transition metal composite oxide is used, and the charging upper limit voltage is set to 4.0 V or more for use. Next battery. 2. The negative electrode has a (002) plane spacing of 0.37.
2. A non-graphitizable carbonaceous material having a specific gravity of not less than 1.7 nm and a true specific gravity of less than 1.7 and having no exothermic peak at 700 ° C. or higher in a differential thermal analysis in an air stream is used. Water electrolyte secondary battery. 3. When the true specific gravity measured by the liquid immersion displacement method using n-butanol as an immersion liquid for the negative electrode is ρp and the true specific gravity measured by the gas displacement method using helium gas is ρHe, ρp The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein a carbonaceous material satisfying a condition of /ρHe<0.960 is used.