WO2006098216A1 - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

Disclosed is a nonaqueous electrolyte secondary battery wherein the separator contains a heat-resistant resin having a chlorine atom as a terminal group and the positive electrode active material contains a lithium-containing complex oxide having an aluminum atom in the composition. In this nonaqueous electrolyte secondary battery, even if the chlorine atom is liberated into the nonaqueous electrolyte solution, aluminum contained in the positive electrode active material is selectively dissolved into the nonaqueous electrolyte solution, thereby suppressing dissolution of other constitutional elements. Consequently, there can be obtained a nonaqueous electrolyte secondary battery which is excellent in safety and high-temperature storage characteristics.

Description

 Specification

 Nonaqueous electrolyte secondary battery

 Technical field

 The present invention relates to a non-aqueous electrolyte secondary battery, and in particular to a highly safe non-aqueous electrolyte secondary battery.

 Background art

 [0002] In recent years, portable and cordless electronic devices for consumer use have rapidly progressed. As a power source for driving such electronic devices, there is an increasing demand for a small, lightweight battery having high energy density. In particular, lithium ion secondary batteries are expected to grow significantly as power sources for portable electronic devices such as laptop computers, mobile phones, and AV devices because they have high voltage and high density of technology.

 LiCoO is a positive electrode active material of a lithium ion secondary battery.

 2, LiNiO

 2, LiMnO

 2. Lithium-containing composite oxides such as LiMn 2 o are used. In such a positive electrode active material

Four

 As a result of the expansion and contraction due to charge and discharge, destruction of the crystal structure and cracking of particles occur. Therefore, if the charge and discharge cycle is repeated, the capacity decreases and the internal resistance increases.

 For example, in order to improve the cycle characteristics and safety of the battery, a part of Co and Ni contained in the lithium-containing composite oxide is replaced with an element such as Mg to form a crystal structure of the lithium-containing composite oxide. It is proposed that the solution be stabilized (see Patent Document 1).

 Among the positive electrode active materials as described above, LiNiO has a large theoretical capacity but on the other hand,

 2

 The reversibility of the accompanying crystal structure change is significantly reduced. In order to solve such a problem, a proposal has been made to replace a part of N i with an element such as Co to alleviate the change in the crystal structure! / See (see, for example, Patent Document 2).

 Furthermore, by substituting nickel and Z or cobalt of lithium-containing nickel cobalt oxide with inexpensive Mn, Li (NiMnCo) 0 is obtained, and this oxide is used as a positive electrode active material.

 2

Has been proposed (see, for example, Patent Document 3). This makes it possible to obtain a low cost and high performance battery. For a separator used in a lithium ion secondary battery, a porous film which is also a thermoplastic resin, for example, polyolefin, is often used from the viewpoint of safety. Such a separator is also a force having a so-called shutdown function. Here, the shutdown function means that, for example, when an external short circuit occurs and the battery temperature rises sharply along with it, the separator softens, its pores are blocked, and the ion conductivity decreases. By doing this, it is a function to stop the current flow.

 However, even if the shutdown function works, if the temperature of the battery is further increased, the separator melts and thermally shrinks, causing a problem of so-called melt down, which causes a large-scale short circuit between the positive electrode and the negative electrode. On the other hand, there is also a problem that the meltdown temperature of the separator is lowered if the heat melting property of the separator is improved to improve the shutdown function.

 Therefore, in order to improve both the shutdown property and the meltdown resistance, a large number of composite separators have been proposed that include a porous layer that is also made of polyolefin as described above and a layer made of a heat resistant resin. ing. For example, there has been proposed a separator in which a layer comprising a heat-resistant nitrogen-containing aromatic polymer such as aramid or polyamideimide and a ceramic powder, and a porous film layer are laminated (see, for example, Patent Document 4). ).

 Patent Document 1: Japanese Patent Application Laid-Open No. 2002-198051

 Patent Document 2: Patent No. 3232943

 Patent Document 3: Japanese Patent Application Laid-Open No. 2004-31091

 Patent Document 4: Patent No. 3175730

 Disclosure of the invention

 Problem that invention tries to solve

[0009] When the above heat resistant resin is used, the safety of the battery can be enhanced. There is a problem that the capacity reduction at the time of high temperature storage becomes large. Specifically, since the aramid is obtained by polymerizing an organic substance having an amine group represented by paralep eradiamine and an organic substance having a chlorine group represented by terephthalic acid chloride, the aramid produced is Chlorine groups remain as end groups. Similarly, since polyamideimide is obtained by reacting trimellitic anhydride monohydrate with diamine, a chlorine group remains as an end group in the formed polyamideimide. Such chlorine groups are liberated in the electrolyte under high temperature environment Do. On the other hand, in the positive electrode active material, the main constituent elements (transition metals such as Co) of the positive electrode active material are easily eluted under the environment of high temperature and high potential. When liberated chlorine is present in the vicinity of the positive electrode active material, a complex formation reaction between the transition metal eluted from the positive electrode active material and chlorine continues to occur. As a result, a large amount of constituent elements are eluted from the positive electrode active material into the electrolytic solution, and the number of sites functioning as the positive electrode active material decreases, so that the battery capacity is considered to be significantly reduced.

The present invention has been made in view of the above problems, and has excellent safety.

An object of the present invention is to provide a non-aqueous electrolyte secondary battery capable of suppressing a decrease in capacity during high temperature storage.

 Means to solve the problem

 The present invention comprises a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a non-aqueous electrolytic solution, and a separator, and the separator has a heat resistant resin having a chlorine atom as an end group. The present invention relates to a non-aqueous electrolyte secondary battery including a lithium-containing composite oxide in which the positive electrode active material has an aluminum atom in the composition.

 The heat-resistant resin preferably contains at least one selected from the group consisting of aramid and polyamideimide.

 The above-mentioned separator may have a film containing a heat resistant resin and a film containing a polyolefin laminated thereon. In addition, the separator may have a film containing polyolefin and a layer containing a heat resistant resin and a filler formed on the film.

 [0013] The lithium-containing composite oxide has the following formula:

 Li M AI O (1)

 l 2

 (l ≤ x ≤ l. 05, 0. 001 ≤ y ≤ 0.2, M is preferably at least one selected from the group consisting of Co, Ni, Mn and Mg). .

Among the complex oxides of the formula (1), the above lithium-containing complex oxide is represented by the following formula:

 Li Co Mg Al O (2)

 a 1-b-c b c 2

 The compound acid compound represented by (l≤a≤l. 05, 0. 005 ≤ b ≤ 0. 1, 0. 001 ≤ c ≤ 0.2) may be used.

 The following formula:

Li Ni Co Al O (3) It is a complex acid compound represented by (l≤a≤l. 05, 0. l≤ b ≤ 0. 35, 0. 001 ≤ c ≤ 0.2), and

 The following formula:

 Li Ni Mn Co Al O (4)

 a 1-(b + c + d) b c d 2

 (l≤a≤l. 05, 0. l≤b≤ 0. 5, 0. l≤c≤ 0. 5, 0. 001 0 d ≤ 0. 2, 0. 2 ≤ b + c + d ≤ 0 It may be a complex acid complex represented by 75).

 Effect of the invention

 According to the present invention, even if chlorine atoms are liberated from the heat-resistant resin contained in the separator in the non-aqueous electrolyte during high temperature storage, they react preferentially with aluminum contained in the positive electrode active material. In addition, other components of the positive electrode active material do not elute out of the positive electrode active material. Therefore, it is possible to provide a non-aqueous electrolyte secondary battery excellent in high temperature storage characteristics with high safety.

 Brief description of the drawings

 FIG. 1 is a longitudinal sectional view schematically showing a cylindrical lithium secondary battery produced in an example.

 BEST MODE FOR CARRYING OUT THE INVENTION

 The non-aqueous electrolyte secondary battery of the present invention comprises a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a non-aqueous electrolyte, and a separator. The positive electrode active material includes a lithium-containing composite oxide having an aluminum atom in the composition. The separator contains a heat resistant resin having a chlorine atom as an end group.

In the present invention, the lithium-containing composite oxide, which is a positive electrode active material, contains a predetermined amount of aluminum atoms. The complex composed of an aluminum atom and a chlorine atom is more stable than the complex composed of a main constituent element (for example, a transition metal such as C, Ni, or Mn) of a lithium-containing composite acid complex and a chlorine atom. The constant is high. For this reason, the aluminum atom tends to form a complex with the chlorine atom preferentially. Therefore, even if chlorine atoms which are terminal groups are liberated from the heat resistant resin contained in the separator during storage at high temperatures, the chlorine atoms are in preference to the aluminum atoms contained in the positive electrode active material. Form a complex. Therefore, it is possible to suppress the elution of the constituent elements contained in the positive electrode active material other than the aluminum in the non-aqueous electrolyte solution, and to avoid the decrease in the battery capacity at high temperature storage. it can. The heat-resistant resin having a chlorine atom as a terminal group preferably contains at least one selected from a group consisting of aramid and polyamideimide. Since aramid and polyamideimide are soluble in polar organic solvents, porous films made of these immediately after film formation have extremely high retention and heat resistance of the non-aqueous electrolyte.

 The heat-resistant resin preferably has a glass transition point, a melting point, and a sufficiently high thermal decomposition initiation temperature accompanied with a chemical change, more specifically, preferably has high mechanical strength under high heat. For example, the heat-resistant resin preferably has a heat distortion temperature of 260 ° C. or higher, which is determined by measurement of deflection temperature under load under test method ASTM-D 648, 1. 82 MPa of the American Society for Testing and Materials. This is because the shape of the separator can be maintained even when thermal contraction or the like occurs as the thermal deformation temperature is higher. When the heat distortion temperature is 260 ° C. or higher, the battery can exhibit sufficiently high thermal stability even when the battery temperature is further increased due to heat storage at the time of battery overheating (usually about 180 ° C.).

The amount of chlorine contained in the separator is preferably 300 to 3000 μg per 1 g of the separator. The amount of chlorine contained in a given weight of heat resistant resin is affected by the degree of polymerization of the heat resistant resin. If the amount of chlorine is too low, the degree of polymerization of the heat-resistant resin becomes too high, and its flexibility decreases. For this reason, the processability of heat resistant resin falls. When the amount of chlorine is large, the heat distortion temperature of the heat resistant resin decreases as the degree of polymerization of the heat resistant resin decreases. Therefore, when the amount of chlorine is in the above-mentioned range, it is considered that the function of the heat-resistant resin is sufficiently achieved.

 In the present invention, a porous film containing the above-mentioned heat-resistant resin may be used as a separator. In addition, the separator may be a laminated film in which, for example, a porous film containing polyolefin such as polyethylene and polypropylene and a porous film containing the above-mentioned heat resistant resin are laminated. Furthermore, the separator may be a laminate having a porous film containing polyolefin and a porous layer containing the above-mentioned heat resistant resin and filler formed thereon.

 For example, a porous film containing the above-mentioned heat resistant resin can be produced as follows.

First, the heat-resistant resin is dissolved in a polar solvent such as N-methyl pyrrolidone. Obtained The solution is applied onto a substrate such as a glass plate or stainless plate and dried. The obtained porous membrane is peeled off from the substrate. Thus, a porous film containing the above-mentioned heat resistant resin can be obtained.

 A laminated film in which a porous film containing polyolefin and a porous film containing the above-mentioned heat-resistant resin are laminated, the above-mentioned heat-resistant resin is dissolved in a polar solvent, and the solution is made into a porous material containing polyolefin. It can be prepared by coating on a membrane and drying.

 [0025] A laminate having a porous film containing polyolefin and a porous layer containing the above-mentioned heat-resistant resin and filler formed thereon can be produced as follows. The heat-resistant resin is dissolved in a polar solvent, and a filler is added to the solution. The resulting mixture is coated on a porous membrane containing polyolefin and dried. Thus, a laminate having a porous membrane containing polyolefin and a porous layer containing the above-mentioned heat-resistant resin and filler formed thereon can be obtained.

 [0026] The filler used may be chemically stable and high in purity so as not to adversely affect the battery characteristics even under the immersion potential of the non-aqueous electrolyte and the redox potential of the active material. preferable. Such fillers include, for example, inorganic acid filler. For example, inorganic inorganic fillers such as alumina, zeolite, silicon nitride, silicon carbide, silicon oxide, zirconium oxide, magnesium oxide, zinc oxide, zinc oxide, etc. Porous material is included.

 Among the above, a separator having a laminate having a porous film containing polyolefin and a porous layer containing the above-mentioned heat-resistant resin and filler, which is formed thereon, is used as a separator because it has higher heat resistance. Preferred to use.

[0028] When the separator is a laminate having a porous film containing polyolefin and a porous layer containing heat resistant resin and filler, the thickness of the heat resistant resin layer and the porous layer containing filler is Although it is not particularly limited, from the viewpoint of securing safety by prevention of internal short circuit and balance of battery capacity, it is more preferable to be 1 to 120 111, preferably 2 to 10 m. When the thickness is less than 1 m, in a high temperature environment, the porous layer containing heat resistant resin and filler becomes effective in suppressing the thermal contraction of the porous layer containing polyolefin. When the thickness exceeds 20 m, the porous layer containing the heat resistant resin and the filler is The porosity is relatively low and its ion conductivity is reduced. As a result, the impedance may increase and the charge and discharge characteristics of the battery may be slightly reduced.

 From the viewpoint of securing ion conductivity, the porosity of the porous layer containing the heat resistant resin and the filler is preferably 20 to 70%. The porosity can be controlled by adjusting the coating speed and drying conditions (temperature and air volume) of the mixture containing heat resistant resin and filler, and the particle diameter and shape of the filler.

 [0030] When the separator has a porous film containing polyolefin and a porous layer containing a heat resistant resin and a filler formed thereon, the total thickness of the separator is not particularly limited. If considering safety, various battery characteristics, and battery design capacity, it is preferred to be 5 to 35 μm! /.

 From the viewpoint of achieving both ion conductivity and mechanical strength, the pore diameter of the porous membrane containing the polyolefin is preferably 0.01 to 10 / ζπ か ら.

 In the case of the separator containing the above heat resistant resin, the thickness of the separator is preferably 5 to 20 μm in order to ensure the safety by preventing the internal short circuit and the balance between the battery capacity and 10 to 20 μm. It is more preferable that The porosity of the separator containing heat resistant resin is preferably 20 to 70%. The porosity of the separator can be controlled by adjusting the coating speed and drying conditions of the heat resistant resin solution.

 Next, a lithium-containing composite oxide having an aluminum atom in its composition, which is a positive electrode active material, will be described.

 As described above, even if chlorine atoms remaining as terminal groups are liberated in a heat-resistant resin under high temperature and high potential environment, the chlorine atoms preferentially form complexes with aluminum atoms. As described above, in the present invention, a lithium-containing composite oxide containing a predetermined amount of aluminum is used.

 Among such lithium-containing composite acid compounds, the following formula:

 Li M AI O (1)

 X ly y 2

Lithium-containing composite represented by (l ≤ x ≤ l. 05, 0. 001 ≤ y ≤ 0.2, M is at least one selected from group forces consisting of Co, Ni, Mn, and Mg) An acid food can be used. The lithium-containing composite acid oxide represented by the formula (1) has a large capacity and high voltage. In any case, it is possible to occlude and release lithium ions.

 It is desirable that the molar ratio X of lithium be l≤x 05l. 05. When the molar ratio X of lithium is less than 1, the amount of lithium salt in the raw material mixture for producing the lithium-containing composite oxide decreases. For this reason, electrochemically inactive impurities such as cobalt oxide and the like are present in the obtained product, which may lower the battery capacity. When the molar ratio of lithium X exceeds 1.05, an excess of lithium salt is present in the raw material mixture. For this reason, lithium salt may remain as an impurity in the product, and the battery capacity may be reduced.

 The molar ratio X of lithium is a value immediately after preparation of the lithium-containing composite acid represented by the formula (1). However, the X value changes beyond the range of the above X value due to charge and discharge of the battery

[0036] It is desirable that the thing ktty of the annoleminum is 0. 001 ≤ y ≤ 0.2 ^ desirable, 0. 005 ≤ y ≤ 0.

 It is more desirable that it is 2. When the molar ratio y of aluminum is less than 0.001, a sufficient improvement effect beyond the above-mentioned action may not be expected. When the molar ratio y exceeds 0.2, the amount of metal atoms M contributing to the charge and discharge reaction decreases, so the battery capacity S may decrease.

 The method for producing the lithium-containing composite oxide represented by the formula (1) is not particularly limited, and can be produced, for example, as follows.

 At least one selected salt selected from cobalt salt, nickel salt, manganese salt and magnesium salt, lithium salt and magnesium salt are mixed in a predetermined ratio. The lithium-containing composite oxide of the formula (1) can be obtained by calcining the obtained raw material mixture at a high temperature under an oxidizing atmosphere.

Among the lithium-containing composite acid compounds represented by the above formula (1), the following formula:

 Li Co Mg Al O (2)

 a 1-b-c b c 2

 (l≤a≤l. 05, 0. 005 ≤ b ≤ 0. 1, 0. 001 ≤ c ≤ 0. 2)

The lithium-containing composite acid represented by can be used. The lithium-containing composite oxide represented by the formula (2) contains magnesium. Due to the inclusion of magnesium, even if the positive electrode active material repeatedly expands and contracts due to charge and discharge, distortion of the crystal lattice, its structure It is possible to suppress smashing or cracking of active material particles. This alleviates the decrease in discharge capacity and improves the cycle characteristics.

 It is desirable that the molar ratio b of magnesium be in the range of 0.50 ≤ b 1 0.1. The molar ratio b is 0.

 If the ratio is less than 005, the above effect may not be obtained. If the molar ratio b exceeds 0.1, the battery capacity may decrease slightly.

The molar ratio c of aluminum is preferably in the range of 0.10 ≤ c 2 0.2. The molar ratio c is 0.

 If it is less than 001, the effect of A1 is not sufficiently exerted. When the molar ratio c exceeds 0.2, the amount of metal atoms contributing to the charge and discharge reaction is slightly short.

The preferred range of the molar ratio a of lithium and the reason why the range is preferred are the same as in the case of the lithium-containing composite oxide of the formula (1).

The method for producing the lithium-containing composite oxide represented by the formula (2) is not particularly limited, and can be produced, for example, as follows.

 Lithium salt, magnesium salt, cobalt salt and aluminum salt are mixed in a predetermined ratio. The lithium-containing composite acid oxide of the formula (2) can be obtained by calcining the obtained raw material mixture at a high temperature under an oxidizing atmosphere.

[0043] A composite salt containing two or more elements selected from the group consisting of complex, magnesium and aluminum may be used in place of the respective salts of the elements contained in the composite salt. For example, in place of cobalt salt, magnesium salt and aluminum salt, eutectic hydroxides containing cobalt, magnesium and aluminum or their eutectic oxides can be used.

[0044] Similarly, the following equation:

 Li Ni Co Al O (3)

 a 1-b-c b c 2

 (l≤a≤l. 05, 0. l≤b≤0. 35, 0. 001≤c≤0. 2)

 It is also possible to use a lithium-containing composite acid represented by The LiNiO based material is

 2

It is known that the crystal structure change with charge and discharge is large while the high capacity density is large and the reversibility of the structure change is bad. On the other hand, the lithium-containing composite acid of the formula (3) further contains cobalt and aluminum in its composition. Cobalt atom or aluminum nuclear, its complex acid, particularly lithium, by being present in the lithium diffusion layer in its crystal structure At the time of force detachment, contraction of the crystal lattice is suppressed. Therefore, the amount of structural change at the time of charge and discharge can be reduced by / J.

 Also, the lithium-containing composite acid of formula (3) is less expensive than LiCoO-based materials.

 2

 In particular, it is also useful as a positive electrode material for large battery applications.

The molar ratio b of cobalt is preferably in the range of 0.1 ≦ b ≦ 0.35. If the molar ratio b is less than 0.1, it is difficult to obtain the above-mentioned effects. If the molar ratio b exceeds 0.35, the battery capacity decreases slightly.

 The preferable range of the molar ratio a of lithium and the molar ratio c of aluminum and the reason why the range is preferable are the same as in the case of the lithium-containing composite acid of the formula (1).

 The lithium-containing composite oxide of the formula (3) can be produced, for example, as follows.

 The nickel salt, cobalt salt and aluminum salt are dissolved in water at a predetermined mixing ratio. The resulting aqueous solution is neutralized and coprecipitated to precipitate as a nickel-cobalt-aluminum ternary composite hydroxide. The obtained composite hydroxide and lithium salt are mixed at a predetermined mixing ratio, and the mixture is fired to obtain a lithium-containing composite oxide of the formula (3).

 A composite salt containing two or more elements selected from nickel, cobalt and aluminum may be used in place of the respective salts of the elements contained in the composite salt.

Furthermore, the following equation:

 Li Ni Mn Co Al O (4)

 a 1-(b + c + d) b c d 2

 (l≤a≤l. 05, 0. l≤b≤ 0. 5, 0. l≤c≤ 0. 5, 0. 001 ≤ d ≤ 0. 2, 0. 2 ≤ b + c + d ≤ 0 .75)

 It is also possible to use a lithium-containing composite acid represented by The lithium-containing composite oxide represented by the formula (4) can maintain stable battery characteristics while being inexpensive.

It is desirable that the molar ratio b of manganese be in the range of 0.1.b≤0.5. If the molar ratio b is less than 0.1, the amount of manganese contained in the complex oxide is small, so cost reduction is difficult. When the molar ratio b exceeds 0.5, the battery capacity decreases slightly. The molar ratio c of cobalt is preferably in the range of 0.1 0 c ≤ 0.5. If the molar ratio c is less than 0.1, the crystals of the complex oxide may become somewhat unstable, the cycle characteristics may be degraded, and the safety of the battery may be somewhat degraded. If the molar ratio c exceeds 0.5, the battery capacity decreases slightly.

 Further, in order to exhibit various battery characteristics in a well-balanced manner, it is preferable that 0.2≤b + c + d≤0.75.

 The preferable range of the molar ratio a of lithium and the molar ratio d of aluminum is the same as in the case of the lithium-containing composite oxide of the formula (1).

The lithium-containing composite oxide of the formula (4) is prepared, for example, by mixing lithium salt, nickel salt, cobalt salt, manganese salt, aluminum salt and the like in a predetermined mixing ratio, and oxidizing the resulting mixture. It can be obtained by firing at a high temperature under an atmosphere.

In the same manner as described above, a complex salt containing two or more elements selected from the group consisting of nickel, cobalt, manganese and aluminum is used in place of the respective salts of the elements contained in the complex salt. It is also good. For example, nickel salts, cobalt salts, manganese salts, and aluminum

Instead of the um salt, eutectic hydroxides containing cobalt, magnesium, manganese and aluminum or their eutectic oxides can be used.

For example, lithium carbonate, lithium hydroxide, lithium nitrate, lithium sulfate and lithium oxide can be used as a lithium salt used for the synthesis of the above lithium-containing composite acid complex.

 As the magnesium salt, for example, magnesium oxide, basic magnesium carbonate, magnesium chloride, magnesium fluoride, magnesium nitrate, magnesium sulfate, magnesium acetate, magnesium oxalate, magnesium sulfate, magnesium sulfate and hydroxide magnesium hydroxide are used. It can be done.

 As a cobalt salt, for example, cobalt oxide and cobalt hydroxide can be used.

 As the aluminum salt, for example, aluminum hydroxide, aluminum nitrate, aluminum oxide, aluminum fluoride and aluminum sulfate can be used.

As the nickel salt, it is possible to use, for example, acid nickel and hydroxide nickel. Can.

 As the manganese salt, for example, manganese dioxide, manganese dioxide, manganese carbonate, manganese nitrate, manganese sulfate, manganese fluoride, manganese chloride, and hydroxyhydroxylated manganese can be used.

 In the lithium-containing composite acid complex represented by the above-mentioned formula (1), the effects of the present invention can be obtained by using the composite oxide contained therein alone or in combination of two or more. You can earn For example, a mixture containing two or more of lithium-containing composite acids represented by formulas (1) to (4) can be used as a positive electrode active material.

 When a mixture of lithium-containing composite oxide containing no aluminum atom in its composition, for example, a mixture of LiCoO and LiNiMnCoO, is used as the positive electrode active material, charging a 1-b 2 a l- (b + c) bc 2

 The potential of each composite oxide in the charge state is derived from the valence of the included transition metal. this

In the two complex oxides, since the types of transition metals contained are different, the potentials of the respective complex oxides have different values. For this reason, in the mixture, variations in potential distribution are likely to occur. Therefore, when the chlorine atom contained as a terminal group in the heat resistant resin is liberated, there is a possibility that the main constituent elements (transition metals such as Co) of the positive electrode active material may be easily eluted in the non-aqueous electrolyte. . Furthermore, when the charging voltage is high, the transition metal contained in the positive electrode active material is easily oxidized in a high voltage environment, and in particular, the main constituent element (transition metal such as Co) is easily eluted.

 However, since the lithium-containing composite acid oxide used in the present invention contains A1, even if the chlorine atom contained in the heat-resistant resin is liberated in the non-aqueous electrolyte, the positive electrode can be selectively selected. A1 selectively elutes from the complex acid product of and the elution of the other main components is suppressed. Therefore, it is possible to obtain a battery which is excellent in safety and in which the capacity reduction at the time of high temperature storage is suppressed.

Next, the positive electrode, the negative electrode, and the non-aqueous electrolyte will be described.

 The positive electrode includes, for example, a positive electrode current collector and a positive electrode mixture layer supported thereon. / / ...

 The positive electrode mixture layer contains a positive electrode active material, a conductive agent, a binder and the like. As described above, the positive electrode active material includes a lithium-containing composite oxide having an aluminum atom in the composition.

[0060] Examples of the binder used for the positive electrode include polytetrafluoroethylene and modified atari. Examples include oral-tolyl rubber particles (eg, BM-500B manufactured by Nippon Zeon Co., Ltd.), and polyfluorinated bi-idene having both binding property and thickening property and modified products thereof. These may be used alone or in combination of two or more.

 The above-mentioned polytetrafluoroethylene and modified acrylonitrile rubber particles are combined with carboxymethyl cellulose, polyethylene oxide, and soluble modified atari port 2 tolyl rubber (for example, BM-720H manufactured by Nippon Zeon Co., Ltd.) having a thickening effect. You may use it.

 As the conductive agent, acetylene black, ketjen black, and various graphites can be used. These may be used alone or in combination of two or more.

 Similar to the positive electrode, the negative electrode may also include a negative electrode current collector and a negative electrode mixture layer supported thereon. The negative electrode mixture layer contains a negative electrode active material. The negative electrode mixture layer may contain a binder, a conductive agent, and the like, as necessary.

 As the negative electrode active material, lithium metal, a material capable of alloying with lithium, various natural graphites and artificial graphites, silicon-based composite materials such as silicides, and a group force consisting of tin, aluminum, zinc and magnesium are also selected. Lithium alloys containing one element and various alloy materials can be used. These may be used alone or in combination of two or more.

Among the above, from the viewpoint of increasing the capacity, it is desirable to use, for example, at least one selected from a substance that can be alloyed with lithium, lithium metal, and a group power of lithium alloys described above as a negative electrode active material. .

 As materials that can be alloyed with lithium, a single substance of silicon, an oxide of silicon (for example, SiO (0 <x <2)), a single substance of tin, an oxide of tin (for example, SnO), Ti, etc. Be mentioned

The negative electrode mixture layer may be formed by direct deposition of the negative electrode active material on a current collector. Alternatively, a negative electrode mixture layer may be formed by applying a mixture containing a negative electrode active material and a small amount of optional components on a current collector and drying.

The binder used in the negative electrode is, like the positive electrode, poly-biphenylidene difluoride and the like. Various resin materials can be used including denatured products.

 Among them, from the viewpoint of improving overcharge safety, it is more preferable to use a mixture of a water-soluble binder containing, for example, a styrene-butadiene copolymer or a modified product thereof and a cellulose-based resin such as carboxymethylcellulose. preferable.

 The non-aqueous electrolyte contains a non-aqueous solvent and a solute dissolved in the non-aqueous solvent. As the non-aqueous solvent, solvents generally used in the relevant field can be used. Such solvents include, for example, ethylene carbonate, dimethinole carbonate, getinole carbonate, and ethyl methyl carbonate. These may be used alone or in combination of two or more.

As a solute, a lithium salt generally used in the relevant field can be used. Such lithium salts include, for example, LiPF and LiBF. like this

 6 4

 The lithium salts may be used alone or in combination of two or more.

The non-aqueous electrolytic solution may also contain, for example, biphenyl carbonate, cyclohexyl benzene, and Z or their modified products in order to form a good film on the positive and negative electrodes.

 Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these.

 Example 1

Example 1 1

 (a) Production of positive electrode

 An aqueous solution containing cobalt sulfate at a concentration of 0.999 mol / L and containing aluminum sulfate at a concentration of 0.10 molmol ZL was continuously fed to the reaction vessel. Add CoAl 2 (OH) 2 by adding sodium hydroxide solution dropwise to the reaction vessel so that the pH of the aqueous solution becomes 10 to 13.

 It was made 0.999 0.001 2. Thereafter, the hydroxide was thoroughly washed with water and dried to obtain a precursor of a positive electrode active material.

[0072] The obtained precursor and lithium carbonate were mixed so that the molar ratio of lithium: cobalt: aluminum was 1.02: 0.0999: 0.00U. The mixture was calcined at 600 ^° C. for 10 o'clock and crushed. Then, the calcined product is calcined again at 900 ° C. for 10 hours and pulverized. The resultant was classified to obtain a lithium-containing composite oxide represented by the formula Li 2 Co 3 Al 2 O 3. This

 1.02 0.999 0.001 2

 The lithium-containing composite oxide was used as the positive electrode active material 11.

3 kg of the obtained positive electrode active material and N-methylpyrrolidone (hereinafter, NMP) solution containing 12% by weight of a poly (vinyl fluoride) as a positive electrode binder (manufactured by Toha Chemical Industry Co., Ltd.) A positive electrode mixture paint was prepared by stirring 1 kg of # 1320 (trade name), 90 g of acetylene black as a conductive agent, and an appropriate amount of NMP with a double-arm mixer.

This paint was applied to both sides of a 15 μm thick aluminum foil as a positive electrode current collector. At this time, the paint was not applied to the connection portion of the positive electrode lead.

Next, the applied paint was dried and rolled with a roller to form a positive electrode mixture layer having an active material density (active material weight Z mixture layer volume) of 3.3 g Z cm ³ . The total thickness of the positive electrode current collector and the positive electrode mixture layer was 160 m.

Thereafter, the obtained electrode plate precursor was slit into a width that can be inserted into a battery case of a cylindrical battery (diameter 18 mm, length 65 mm) to obtain a positive electrode plate.

(B) Production of Negative Electrode

 An aqueous dispersion containing 3% of artificial graphite as a negative electrode active material and 40% by weight of a modified product of a styrene butadiene copolymer as a negative electrode binder ("BM-400B (trade name)" manufactured by Nippon Zeon Co., Ltd.) A negative electrode mixture paint was prepared by stirring 75 g, carboxymethyl cellulose 30 g as a thickener, and an appropriate amount of water with a double-arm mill. The obtained paint was applied to both sides of a 10 m-thick copper foil as a negative electrode current collector. At this time, this paint was not applied to the connection portion of the negative electrode lead.

The applied paint was dried and rolled with a roller to form a negative electrode mixture layer with an active material density of 1.4 gZ cm ³ . The total thickness of the copper foil and the negative electrode mixture layer was controlled to 180 m.

 Thereafter, the obtained electrode plate precursor was slit to a width that can be inserted into the above-described battery can of the cylindrical battery, to obtain a negative electrode plate.

(C) Preparation of Separator

A laminated film including a 16 m thick polyethylene (PE) porous thin film and a film made of aramid resin which is a heat-resistant resin formed thereon was prepared, and this laminated film was used as a separator. . Below, the manufacturing method of the said laminated film is shown.

 6. 5 parts by weight of dry anhydrous sodium chloride was added to 100 parts by weight of NMP. The mixture was heated to 80 ° C. in a reaction vessel to completely dissolve anhydrous calcium chloride in NMP.

 The resulting solution was allowed to cool to room temperature, and 3.2 weight parts of paraphenylene diamine was added to this solution to completely dissolve it. After this, the reaction vessel containing the solution containing paradylene diamine was placed in a thermostat at 20.degree. While maintaining the temperature at 20 ° C., 5.8 parts by weight of diphthalic acid terephthalic acid is added dropwise to the solution over 1 hour, and reacted to obtain polyparaphenylene terephthalate (hereinafter referred to as “PPTA”). The

 Thereafter, the solution containing PPTA was allowed to stand in a thermostat at 20 ° C. for 1 hour, and after completion of the reaction, the solution containing PTCA was put into a vacuum chamber and degassed for 30 minutes while stirring under reduced pressure.

The resulting polymerization solution, further more the Shioi匕calcium be diluted with添Ka卩the NMP solution, PPTA concentration was prepared NMP solution of PTAA of 1.4 weight ^_0/0.

The NMP solution of PTAA thus obtained was thinly coated on a polyethylene porous thin film with a doctor blade, and dried with hot air at 80 ° C. (wind speed: 0.5 mZ seconds). Thereafter, the obtained PTAA membrane was thoroughly washed with pure water to remove calcium chloride, to make the membrane porous and then dried again. Thus, a laminated membrane including a polyethylene porous thin membrane and a PTAA porous membrane formed thereon was produced.

 The amount of residual chlorine in this laminated film was measured by molecular analysis, and the amount of residual chlorine was 650 μg per 1 g of laminated film.

(D) Preparation of Nonaqueous Electrolyte

 LiPF was dissolved at a concentration of ImolZL in a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate mixed in a volume ratio of 2: 3: 3. In this solution

 6

 To this was added vinylene carbonate to prepare a non-aqueous electrolyte. The amount of vinyl carbonate was adjusted to 3 parts by weight per 100 parts by weight of the non-aqueous electrolyte.

(E) Assembly of battery

 A cylindrical battery as shown in FIG. 1 was produced.

The positive electrode plate and the negative electrode plate obtained as described above are respectively cut into predetermined lengths, The positive electrode 11 and the negative electrode 12 were obtained. One end of the positive electrode lead 14 was connected to the positive electrode lead connection portion of the positive electrode 11. Further, in the negative electrode lead connection portion of the negative electrode 12, a separator 13 was disposed between the positive electrode 11 and the negative electrode 12 to which one end of the negative electrode lead was connected, and these were wound to fabricate a cylindrical electrode group. At this time, the separator 13 was disposed between the positive electrode 11 and the negative electrode 12 so that the PTAA layer was disposed on the positive electrode side. The outermost periphery of the electrode assembly was covered with the separator 13.

 The obtained electrode group was sandwiched between the upper insulating ring 16 and the lower insulating ring 17, and these were accommodated in a battery can 18. Then, 5 g of the non-aqueous electrolyte (not shown) was injected into the battery can 18. After that, the inside of the battery can 18 was depressurized to 133 Pa, and the electrode group was impregnated with the non-aqueous electrolyte by leaving it until no residue of the non-aqueous electrolyte was observed on the surface of the electrode group.

 Next, the other end of the positive electrode lead 14 was welded to the back surface of the battery lid 19 having the insulating packing 20 at the periphery, and the other end of the negative electrode lead 15 was welded to the inner bottom surface of the battery can 18. Finally, the open end of the battery can 18 was pressed onto the insulating packing 20 of the battery lid 19 to close the opening of the battery can 18, thereby completing the cylindrical lithium ion secondary battery. The obtained battery was used as the battery of Example 1-1.

 (Examples 1 2 to 4)

 When the precursor of the positive electrode active material is synthesized, the concentration ratio of cobalt sulfate to aluminum sulfate is set to 0.95: 0.5, 0.50: 0.20, or 0.75: 0.25. A battery was manufactured in the same manner as in the f-th row 1-1. The obtained batteries were used as the batteries of Examples 12 to 14, respectively.

 (Example 1 5)

 When synthesizing the precursor of the positive electrode active material, iron sulfate is further added, and the concentration ratio of cobalt sulfate to iron sulfate to aluminum sulfate is set to 0.9: 0. 05: 0. 05 except that A battery was produced in the same manner as Example 1-1. The obtained battery was used as the battery of Example 1-5.

 (Examples 1 6 to 9)

When synthesizing a positive electrode active material, a precursor of the positive electrode active material and lithium carbonate, a mono-ktt force of lithium, a comonomer and an anolemium ^). 98: 0. 95: 0. 05, 1: 0. 95: 0. 05, 1. 05: 0 A battery was fabricated in the same manner as in the f column 12 except that 95: 0. 05 or 1. 08: 0. 95: 0. 05 was mixed. The obtained battery was used as the battery of Examples 16 to 1-9.

 Example 1 10

 A battery was produced in the same manner as in Example 1-2 except that a laminated film in which a film made of polyamideimide resin was formed instead of the PTAA film on a porous film made of polyethylene was used as a separator. The obtained battery was used as the battery of Example 110.

Hereinafter, a method for producing a laminated film including a porous thin film made of polyethylene and a film made of polyamideimide resin formed thereon will be described.

 Trimellitic anhydride monochloride and diamine were added to NMP at room temperature and mixed to obtain an NMP solution of polyamic acid. This NMP solution was thinly applied onto a polyethylene porous thin film by a doctor blade. The coated film was dried with hot air at 80 ° C. (air velocity: 0.5 mZ seconds) to dehydrate the polyamic acid, cyclize it, and convert it to polyamidoimide. Thus, a laminated film including a porous polyethylene thin film and a polyamideimide film formed thereon was produced. The total thickness of this laminated film was 20 m.

 The amount of residual chlorine in this laminated film was measured by molecular analysis, and the amount of residual chlorine was 830 μg per 1 g of laminated film.

Example 1 11

 A battery was fabricated in the same manner as in Example 1-2, except that a porous film which also had only aramid force was used as the separator. The obtained battery is referred to as the battery of Example 1-11.

Hereinafter, a method for producing a porous film which is also effective only with aramid will be shown.

 As described above, a predetermined amount of aramid resin was dissolved in NMP. Next, the NMP solution was applied onto a smooth stainless steel plate using a doctor blade. The resulting coated film was dried with hot air at 80 ° C. (air velocity: 0.5 mZ seconds) to obtain a porous film in which only aramid was active. The thickness of this porous membrane was 20 m.

 The amount of residual chlorine in this porous membrane was measured by molecular analysis, and the amount of residual chlorine was 1800 g per 1 g of the porous membrane.

Example 1 12 A battery was fabricated in the same manner as in Example 1-2, except that a layered product having a porous polyethylene thin film and a layer containing a filler and aramid resin formed thereon was used as a separator. did. The obtained battery was used as a battery of Example 112.

Hereinafter, a method for producing the above laminate will be described.

 Alumina fine particles were added to the NMP solution of aramid resin prepared in the above Example 1-1 and stirred. The amount of alumina fine particles added was 200 parts by weight per 100 parts by weight of the aramid resin contained in the NMP solution.

 The obtained dispersion was thinly coated on a porous polyethylene thin film with a doctor blade, and the coated film was dried by hot air at 80 ° C. (wind velocity: 0.5 mZ seconds). Thus, a laminate having a polyethylene porous membrane and a layer containing a filler and an aramid formed thereon was obtained.

 The amount of residual chlorine in this laminate was measured by molecular analysis, and the amount of residual chlorine was 600 g per 1 g of separator.

Comparative Example 1

 In the same manner as in Example 1-1, cobalt sulfate alone was used to synthesize cobalt hydroxide, and lithium carbonate and cobalt hydroxide were mixed so that the molar ratio force of lithium and cobalt was 1.02: 1. The lithium-containing composite oxide was synthesized. A battery was produced in the same manner as in Example 1-1 except that this lithium-containing composite oxide was used as a positive electrode active material. The obtained battery was used as the battery of Comparative Example 1.

(Comparative Example 2)

 A battery was fabricated in the same manner as in Example 1-2, except that a polyethylene porous film with a thickness of 20 m was used as the separator. The obtained battery was used as the battery of Comparative Example 2.

 [0095] Each obtained battery is discharged at a constant current of 400 mA until the battery cell decreases to 3 V, and then, preliminary charging / discharging is performed until the battery voltage reaches 4.2 V at a constant current of 1400 mA. Served twice. The charged battery was then stored at 45 ° C. for 7 days. The following evaluation was performed on the battery after storage.

 [Evaluation]

(i) Measurement of discharge capacity After storage, charge the battery at 20 ° C with a constant voltage of 4.2 V until the current value decreases to 100 mA, and then charge the battery with a constant current of 2000 mA to a battery voltage of 3 V. One cycle of the first charge / discharge cycle was performed to discharge until it decreased. The discharge capacity at this time was taken as the initial discharge capacity. The results are shown in Table 1.

(Ii) Safety test

 After storage, the battery was charged at a constant voltage of 4.2 V at 20 ° C. until the current value decreased to 100 mA. Thereafter, the charged battery was placed in a 130 ° C. constant temperature bath, and the maximum temperature of the battery surface was measured. The results are shown in Table 1.

(Iii) High temperature storage characteristics

 First, the initial discharge capacity was measured as described above. After this, the battery was charged at 20 ° C. with a constant voltage of 4.2 V until the current value decreased to 100 mA. Next, the battery after charging was placed in a thermostat of 90 ° C. and stored for 24 hours. After storage, the battery was discharged at a constant current of 2000 mA, and the discharge capacity after storage was determined. The ratio of the discharge capacity after storage to the initial discharge capacity as a percentage was taken as the capacity recovery rate. The results are shown in Table 1.

 Table 1 also shows the composition of the positive electrode active material and the type of separator used in Examples and Comparative Examples.

[0099] [Table 1]

Li _a Co, _ _b . _C Fe _b Al _c 0 ₂ separete initial discharge cell surface capacity capacity recovery rate

(mAh)

 (° C)

 a 1-b-c b c

 Example 1-1 1.02 0.999 0 0.001 aramid + PE 2050 142 66 Example 1-2 1.02 0.95 0 0.05 aramid + PE 2020 139 70 Example 1-3 1.02 0.8 0 0.2 aramid + PE 2000 140 71 Example 4 1.02 0.75 0 0.25 Fara SD + PE 1890 139 73 Example 5 1.02 0.9 0.05 0.05 aramid + PE 2015 141 72 Example 1-6 0.98 0.95 0 0.05 aramid + PE 1900 144 71 Example 1-7 1 0.95 0 0.05 Aramid + PE 1950 143 70 Example 1-8 1.05 0.95 0 0.05 Aramid + PE 1970 141 72 Example 1-9 1.08 0.95 0 0.05 Aramid + PE 1880 142 70 Example 1-10 1.02 0.95 0 0.05 Polyamide imm 2020 144 69

 H + PE

 Example 1-Π 1.02 0.95 0 0.05 aramid 2020 137 72 Example 1-12 1.02 0.95 0 0.05 (aramid + flame 2020 142 71 ir) + PE

 Comparative example 1 1.02 1 0 0 aramid + PE 2050 141 50 Comparative example 2 1.02 0.95 0 0.05 PE 2020 156 72

From Table 2, in the battery of Comparative Example 2 in which the separator does not contain the heat resistant resin, the maximum temperature of the battery surface is 156. It had risen to C. Therefore, it is understood that the safety of the battery is lowered when the separator does not contain the heat resistant resin.

 Even when the separator contains a heat-resistant resin, in the case where the positive electrode active material does not contain an aluminum atom, the result of Comparative Example 1 shows that the capacity recovery rate is significantly reduced. The cause of this is that the chlorine group contained as a terminal group in the heat resistant resin is liberated in the non-aqueous electrolyte under high temperature environment, and the elution of the main constituent element (cobalt in the case of Comparative Example 1) of the positive electrode active material is It is thought that this was due to promotion.

On the other hand, when the separator contains a heat-resistant resin and a positive electrode active material containing an aluminum atom in the composition as in the batteries of Examples 1 1 to 1 12, the safety under high temperature environment is high. It can be seen that the integrity and preservation characteristics can be compatible. The aluminum atom in the positive electrode active material forms a stable complex ion with the liberated chlorine from the aramid (or polyamide imide). The positive electrode active material power is considered to be because the aluminum atoms were selectively eluted, and the elution of other components of the positive electrode active material was suppressed. Such an effect is the same as in the case of the battery of Example 15 when a positive electrode active material containing a metal such as iron in addition to cobalt in the composition is used.

 As shown in the results of Examples 1 to 14, as the amount of aluminum contained in the positive electrode active material increases, the maximum temperature of the battery decreases and the capacity recovery rate improves. However, as shown in Example 14, when the amount of aluminum is too large, the proportion of main constituent elements in the positive electrode active material is reduced, and the initial discharge capacity is reduced.

 Further, from the results of Examples 1-2 and 1-6 to 1-8, it can be seen that the initial discharge capacity is reduced if the amount of lithium contained in the positive electrode active material is small or large. If the amount of lithium in the positive electrode active material is small, it is considered that the amount of impurities does not contribute to the battery capacity, such as cobalt oxide, and the battery capacity decreases. If the amount of lithium is too large, it is considered that an excess of lithium remains as an impurity in the positive electrode active material and the initial discharge capacity is reduced.

 Therefore, in the lithium-containing composite oxide represented by Li Co Al 2 O, l≤x≤l. 05

 X ly y 2

 And the force that 0. 001 ≤ y ≤ 0.2 is preferred! / ヽ.

Furthermore, according to the results of Examples 1-10-1-12, the above-described effects can be obtained even when the laminated film including the porous thin film and the film made of the heat resistant resin is used as the separator. It can be seen that even when using a porous membrane made of resin, it can be obtained even when using a laminate having a porous thin film and a layer containing a filler and an aramid resin.

 Example 2

(Example 2—1-2—12)

When synthesizing a precursor of the positive electrode active material, magnesium sulfate is further added, and the concentration ratio of cobalt sulfate, magnesium sulfate and aluminum sulfate is changed as shown in Table 2, and Example 1-1 and In the same manner, precursors 2-1 to 2-12 were synthesized. Further, the mixing ratio of the obtained precursor 2-1 to 2-12 and lithium carbonate is changed as shown in Table 2, and the positive electrode active material 2-is obtained in the same manner as in Example 1-1. 1-2-12 were synthesized. A battery was produced using these positive electrode active materials in the same manner as in Example 1-1. The resulting batteries were used as the batteries of Examples 2-1 to 2-12, respectively. Each of the obtained batteries was subjected to the same preliminary charge and discharge as in Example 1 twice. The charged battery was stored at 45 C for 7 days. The initial discharge capacity, the maximum temperature of the battery surface and the capacity recovery rate were measured in the same manner as in Example 1 for the battery after storage. The results are shown in Table 2.

 (Iv) Capacity maintenance rate

 In this example, the capacity retention rate was further measured for the battery after storage at 45 ° C. for 7 days. The capacity retention rate was measured as follows. The first charge and discharge cycle was repeated 200 times at 5 ° C. for the battery after storage. The ratio of the discharge capacity of the 200th cycle to the discharge capacity of the first cycle as a percentage value was taken as the capacity retention ratio. The results are shown in Table 2.

 [Table 2]

In Table 2, the capacity retention rate of each battery is 80% or more. Therefore, when the h electrode active material contains magnesium, expansion and contraction of the positive electrode active material due to charge and discharge are alleviated, and a decrease in discharge capacity is suppressed.

From the results of Example 2-2 and 2-5 2-8, magnesium in the positive electrode active material was As the molar ratio b increases, the capacity retention rate is improved. However, in the case of Example 2-5 in which the molar ratio b is 0.01, the capacity retention ratio is 80%, and sufficient cycle characteristics can not be obtained.

 In addition, when the molar ratio b of magnesium increases, the ratio of main constituent elements in the positive electrode active material tends to decrease, and the initial discharge capacity tends to decrease. That is, in the case of Example 2-8 in which the molar ratio b is 0.15, a sufficient initial discharge capacity can not be obtained.

 [0112] Further, with regard to the aluminum amounts and lithium amounts shown in Examples 2-1 to 2-4 and Examples 2-9 to 2-12, the same as Example 1 can be applied. Tend.

 Therefore, in the lithium-containing complex acid complex represented by Li Co Mg Al O O, l≤a≤a 1-b-c b c 2

 1. 05, 0. 005 ≤ b ≤ 0. 1, 0. 001 ≤ c ≤ 0.2.

 Example 3

Example 3 1 to 12

 When a precursor of a positive electrode active material is synthesized, nickel sulfate, cobalt sulfate and aluminum sulfate are used, and the concentration ratio of these is changed as shown in Table 3, to obtain Example 1-1 and In the same manner, precursors 3-1 to 3-12 were synthesized. In addition, the mixing ratio of the obtained precursor 3-1 to 3-12 and lithium carbonate is changed as shown in Table 3, and the positive electrode active material 3- is obtained in the same manner as in Example 1-1. 1 to 3-12 were synthesized. A battery was produced using these positive electrode active materials in the same manner as in Example 1-1. The obtained batteries were used as the batteries of Examples 3-1 to 12 respectively.

 Each battery thus obtained was subjected to the same preliminary charge and discharge as in Example 1 twice. The charged battery was stored at 45 ° C. for 7 days. With respect to the battery after storage, the initial discharge capacity, the maximum temperature of the battery surface, the capacity recovery rate and the capacity retention rate were measured in the same manner as in Example 2. The results are shown in Table 3.

[Table 3] Li _a Ni, _-b - _c Co _b Al _c 0 ₂ Initial discharge surface surface Capacity Capacity Capacity recovery factor Maintenance rate (mAh) 问 / dish (3⁄4) (3⁄4)

 (° c)

 a 1-b-c b c

 Example 3-1 1.01 0.849 0.15 0.001 2250 144 48 87 Example 3-2 1.01 0.8 0.15 0.05 2100 141 77 88 Example 3-3 1.01 0.65 0.15 0.2 2069 142 83 89 Example 3-4 1.01 0.64 0.15 0.21 2030 141 85 91 Example 3-5 1.01 0.945 0.005 0.05 2350 143 73 81 Example 3-6 6 1.01 0.85 0.1 0.05 2150 145 74 87 Example 3-7 1.01 0.6 0.35 0.05 2100 145 73 91 Example 3-8 1.01 0.5 0.45 0.05 1950 143 74 93 Example 3-9 0.98 0.8 0.15 0.05 2009 141 82 87 Example 3-10 1 0.8 0.15 0.05 2082 142 83 88 Example 3-11 1.05 0.8 0.15 0.05 2054 142 84 89 Example 3-12 1.08 0.8 0.15 0.05 1917 141 81 88

From the results in Table 3, it can be seen that when the positive electrode active material contains nickel and cobalt and the amount of nickel is large, the initial discharge capacity and the capacity retention rate are improved.

 Further, as is clear from the results of Example 3-5, the initial discharge capacity increases as the amount of nickel contained in the positive electrode active material increases, that is, as the amount of cobalt decreases. It is However, in the case of Examples 3-8 in which the molar ratio b of cobalt is 0.45, sufficient initial discharge capacity may not be obtained.

 Further, in Example 3-5 in which the molar ratio b of cobalt was 0.005, the capacity retention rate was slightly reduced. This is considered to be because expansion and contraction of the positive electrode active material due to charge and discharge can not be sufficiently relaxed.

Furthermore, as shown in Example 3- :! to 3-4 and Example 3-9 to 3-12, the aluminum amount and the lithium amount also tend to be the same as in Example 1.

Therefore, in the lithium-containing composite acid complex represented by Li Ni Co Al 2 O 3, l≤a a 1-b-c b c 2

好 ま 1.05, 0.1 ≤ b ≤ 0.35, and 0.001 ≤ c ≤ 0.2. Example 4 (Example 4 1:! To 19)

 When a precursor of a positive electrode active material is synthesized, nickel sulfate, manganese sulfate, cobalt sulfate, and aluminum sulfate are used, and the concentration ratio thereof is changed as shown in Table 4 to obtain Example 1-1. In the same manner, precursors 4 1 to 4 19 were synthesized. In addition, the mixing ratio of the obtained precursor 4- 14 19 to lithium carbonate was changed as shown in Table 4, and the positive electrode active material 41 was prepared in the same manner as in Example 11. 4-19 were synthesized. A battery was produced using these positive electrode active materials in the same manner as in Example 1-1. The obtained batteries were used as the batteries of Example 4-14, respectively.

 The resulting battery was subjected twice to the same preliminary charge and discharge as in Example 1. The charged battery was stored at 45 ° C. for 7 days. With respect to the battery after storage, the initial discharge capacity, the maximum temperature of the battery surface, and the capacity recovery rate were measured in the same manner as in Example 1. The results are shown in Table 4.

 Table 4 also shows the values of b + c + d.

 [Table 4]

Li _a Ni, — _{(btc + d} ) Mn _b Co _c Al _d 0 ₂ Initial discharge; 53 53⁄4 Capacitance Capacity recovery rate

(mAh) (%)

 (.C)

 a 1-(b + c + d) b c d b + c + d

Example 4-1 1.01 0.339 0.33 0.33 0.001 0.661 1890 141 69 Example 4-2 1.01 0.31 0.32 0.32 0.05 0.69 1862 133 73 Example 4-3 1.01 0.26 0.27 0.27 0.2 D.74 1710 139 74 Example 4-4 1.01 0.27 0.26 0.26 0.21 0.73 1690 138 76 Example 4-5 1.01 0.44 0.19 0.32 0.05 0.56 1950 141 72 Example 4-6 1.01 0.19 0.57 0.19 0.05 0.81 1650 143 73 Example -7 0.98 0.31 0.32 0.32 0.32 0.36 0 Example 4-8 1 0.31 0.32 0.32 0.05 0.69 1846 137 73 Example 4-9 1.05 0.31 0.32 0.32 0.05 0.69 1822 137 72 Example 4-10 1.08 0.31 0.32 0.32 0.32 0.32 137 138 Example 3 4-11 1.01 0.85 0.05 0.05 0.05 0.15 2100 148 T6 Example 4-12 1.01 0.75 0.10 0.10 0.05 0.25 1972 143 75 Example 4-13 1.01 0.5 0.20 0.25 0.05 0.5 1930 142 73 Example 4-14 1.01 0.25 0.50 0.20 0.05 0.75 1700 139 72 Example 4 -15 1.01 0.25 0.20 0.50 0.05 0.75 1750 140 71 Example 4-16 1.01 0.25 0.60 0.10 0.05 1630 138 71 Example 4-17 1.01 0.25 0.10 0.60 0.05 0.75 1695 141 73 Example 4-18 1.01 0.15 0.60 0.20 0.00 5 0.85 1620 137 72 Example 4-19 1.01 0.15 0.20 0.60 0.05 0.85 1640 142 72 When the positive electrode active material contains manganese in addition to nickel and cobalt, an inexpensive positive electrode active material can be obtained while maintaining stable battery characteristics. A certain amount or more of manganese is required to reduce costs. In the case of Example 4 1 1 in which the molar ratio b of manganese is 0. 05, the maximum temperature of the battery surface is increased, and the battery safety is somewhat reduced. In Examples 4-16 and 4-18 in which the molar ratio b of the Gunn gun is 0.6, the initial discharge capacity decreases.

 Further, as seen from Example 4-11, when the molar ratio c of cobalt is 0.05, the maximum temperature of the battery surface is high. In Examples 4-17 and 419 in which the molar ratio c of cobalt is 0.6, the initial discharge capacity is reduced.

 Furthermore, as shown in Examples 4-1 to 4-4 and Examples 4-7 to 4-10, the amounts of aluminum and lithium tend to be the same as in Example 1. .

 Therefore, in the lithium-containing composite oxide represented by Li Ni Mn Co AI O, a 1-(b + c + d) b c d 2

 It is preferable that l≤a≤l. 05, 0. l≤b≤0.5, and 0. l≤c≤0.5, 0. 001≤d≤0.2.

 Further, in Examples 4-18 and 4-19 in which b + c + d force .85, there was a tendency for the initial discharge capacity to decrease. In Example 4-11 in which b + c + d force ^). 15, the maximum temperature on the battery surface was increased, and the battery safety tended to be slightly reduced. Thus, it can be seen that when 0.2≤b + c + d≤0.75, a battery with an excellent balance of the above three characteristics can be obtained.

 In the following examples, when a mixture of a plurality of lithium-containing composite oxides is used as the positive electrode active material, when the positive electrode active material is exposed to a high voltage environment, and when the type of the negative electrode active material is When changed, the battery characteristics were evaluated.

 Example 5

 Example 5-1

 50 parts by weight of the positive electrode active material (Li Co Al 2 O 3) used in Example 1-2 and Example 4-2

 1.02 0.95 0.05 2

 Obtained by mixing 50 parts by weight of the positive electrode active material (Li Ni Mn Co Al 2 O 3) used in

 1.01 0.32 0.32 0.32 0.05 2

The resulting powder was designated as a positive electrode active material 5-1. A battery was fabricated in the same manner as Example 1-1 except that this positive electrode active material was used. The obtained battery is referred to as the battery of Example 5-1. Example 5-2

A battery was fabricated in the same manner as in Example 1-2, except that the active material density of the positive electrode mixture layer was 3.3 gZ cm ^3, and the thickness of the positive electrode plate was 144 m. The obtained battery was used as a battery of Example 5-1.

 Example 5-3

A battery was produced in the same manner as in Example 4-2 except that the active material density of the positive electrode mixture layer was 3.3 gZ cm ^3, and the thickness of the positive electrode plate was 144 m. The obtained battery was used as the battery of Example 5-3.

 Example 5-4

 An aqueous dispersion containing 3 kg of silicon (Si) powder (median diameter 10 μm), which is a negative electrode active material, and 40 wt% of modified styrene butadiene rubber particles, which is a binder (BM-400B manufactured by Nippon Zeon Co., Ltd.) (Trade name) 750 g of acetylene black which is a conductive agent, 300 g of carboxymethyl cellulose which is a thickening agent, and an appropriate amount of water which is a dispersion medium are stirred by a double-arm type mixer, and a negative electrode mixture The paste was prepared. The negative electrode mixture paste was applied to both sides of a strip-shaped negative electrode current collector made of copper foil having a thickness of 10 m. The applied negative electrode material mixture paste was dried and rolled by a rolling roll to produce a negative electrode plate. A battery was produced in the same manner as in Example 3-2 except that this negative electrode plate was used. The obtained battery was used as the battery of Example 5-4.

 (Example 5-5)

 A battery was fabricated in the same manner as in Example 5-4, except that SiO powder (median diameter 8 μm) was used instead of silica powder, and the dimensions of the positive electrode and the negative electrode were changed as appropriate. The obtained battery was used as the battery of Example 5-5.

Example 5-6

 The following negative electrode was produced using a vacuum evaporation system provided with a water-cooled roller in the vacuum chamber.

An electrolytic Cu foil (manufactured by Furukawa Circuit Oil Co., Ltd., thickness 20 μm) as a current collector was attached and fixed to a water-cooled roller in a vacuum deposition apparatus. Immediately below that, a graphite crucible in which a carbon (Flutch Chemical Co., Ltd., ingot having a purity of 99. 999%) was placed was placed. Between chopsticks and Cu foil The nozzle was installed in the vacuum chamber 1 so that oxygen gas was introduced into the chamber. The flow rate of oxygen gas (manufactured by Nippon Oxygen Co., Ltd., purity 99.7%) of the nozzle force was set to 20 sccm (flow rate of 20 cm ³ flow per minute). In order to prevent the deposition of excess carbon, a stainless steel shield plate having an opening was placed between the crucible and the water-cooled roller. In the direction of rotation of the roller

The width of this opening was 10 mm. A shutter was placed at the opening of this shield to prevent evaporation and adhesion until the evaporation temperature was reached.

A carbon was vapor-deposited on the current collector using an electron gun. Electron beam acceleration voltage is 8k

The electron beam emission was 150 mA.

 At this time, the degree of vacuum in the vacuum chamber was set to 1.5 × 10− &, and the water-cooled roller was rotated at a speed of lOcmZ. The surface temperature of the water-cooled roller was 20 ° C.

After an active material containing carbon and oxygen was vapor-deposited on one side of the current collector, the active material was similarly vapor-deposited on the other side. Thus, a negative electrode carrying a thin film of active material on both sides of the current collector was produced.

 The composition of the negative electrode active material was quantified by elemental analysis. As a result, the composition of the negative electrode active material was Si o.

 0.6

 A battery was produced in the same manner as in Example 5-4 except that the dimensions of the positive electrode and the negative electrode were appropriately changed using such a negative electrode. The obtained battery was used as the battery of Example 5-6.

 The batteries of Examples 5-1 and 5-4 to 5-6 were subjected twice to the same preliminary charge and discharge as in Example 1. The charged battery was stored at 45 ° C. for 7 days. With respect to the battery after storage, the initial discharge capacity, the maximum temperature of the battery surface and the capacity recovery rate were measured in the same manner as in Example 1. The results are shown in Table 5.

 The batteries of Examples 5-2 and 5-3 were subjected twice to the same preliminary charge and discharge as in Example 1 except that the charge termination voltage was changed to 4.4 V. The charged battery was stored at 45 ° C. for 7 days. Next, the following evaluation was performed about the battery after preservation | save.

 (V) Measurement of Discharge Capacity

After storage, the battery was charged at a constant voltage of 4.4 V at 20 ° C. until the current value decreased to 100 mA. Thereafter, the charged battery was discharged at a constant current of 2000 mA until the battery voltage decreased to 3 V, and the initial discharge capacity was determined. The results are shown in Table 5. (Vi) Safety test

 After storage, the battery was charged at a constant voltage of 4.4 V at 20 ° C. until the current value decreased to 100 mA. Thereafter, the charged battery was placed in a 130 ° C. constant temperature bath, and the maximum temperature of the battery surface was measured. The results are shown in Table 5.

 (Vii) High temperature storage characteristics

 First, the initial discharge capacity was measured as described above. After this, the battery was charged at 20 ° C. with a constant voltage of 4.4 V until the current value decreased to 100 mA. Then, after charging the battery, 90. It was placed in a thermostatic bath C and stored for 24 hours. After storage, the battery was discharged at a constant current of 2000 mA, and the discharge capacity after storage was determined. The ratio of the discharge capacity after storage to the initial discharge capacity as a percentage is taken as the capacity recovery rate. The results are shown in Table 5.

 [Table 5]

表 5に示されるように、いずれの実施例の電池においても、初期放電容量および容 量回復率が優れた値を示し、電池表面の最高温度も、それほど高くなかった。よって

As shown in Table 5, in each of the batteries of Examples, the initial discharge capacity and the capacity recovery rate showed excellent values, and the maximum temperature of the battery surface was not so high. Therefore

When a mixture containing two lithium-containing composite oxides is used as a positive electrode active material (Example 5-1), when the positive electrode active material is exposed to a high voltage environment (Examples 5-2 to 5-5) — 3), Also in the case of using a high capacity negative electrode active material (Examples 5-4 to 5-6), it is understood that a battery excellent in safety and high temperature storage characteristics can be obtained.

Industrial applicability

 According to the present invention, since the positive electrode active material contains an appropriate amount of aluminum, the main component of the positive electrode active material is obtained even if the chlorine atom contained as an end group in the heat resistant resin contained in the separator is liberated in the non-aqueous electrolyte. It is possible to suppress the elution of the component into the non-aqueous electrolyte. Therefore, it is possible to provide a non-aqueous electrolyte secondary battery having excellent safety and improved high-temperature storage characteristics. Such a battery can be used, for example, as a power source for devices that require excellent battery characteristics even in a high temperature environment.

Claims

The scope of the claims  [1] A positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a non-aqueous electrolytic solution, and a separator.  The said separator is a non-aqueous-electrolyte secondary battery containing the heat-resistant resin which has a chlorine atom as an end group, and the said positive electrode active material contains the lithium containing complex oxide which has an aluminum atom in a composition.  [2] The non-aqueous electrolyte secondary battery according to claim 1, wherein the heat-resistant resin contains at least one selected from a group consisting of aramid and polyamideimide. [3] The non-aqueous electrolyte secondary battery according to claim 1, wherein the separator comprises a film containing the heat-resistant resin and a film containing polyolefin laminated on the film containing the heat-resistant resin. [4] The non-aqueous electrolyte secondary battery according to claim 1, wherein the separator has a film containing polyolefin and a layer containing the heat-resistant resin and filler formed on the film containing polyolefin. [5] The lithium-containing composite acid has the following formula:  Li M AI O (1)  l 2  (l 記載 x≤l. 05, 0. 001≤y≤ 0.2, M is at least one selected from group forces consisting of Co, Ni, Mn and Mg). Non-aqueous electrolyte secondary battery. [6] The lithium-containing composite acid has the following formula:  Li Co Mg Al O (2)  a 1-b-c b c 2  The non-aqueous electrolyte secondary battery according to claim 5, represented by (l (a≤l. 05, 0. 005≤b≤0.1, 0. 001≤c≤ 0.2). [7] The lithium-containing composite acid has the following formula:  Li Ni Co Al O (3)  a 1-b-c b c 2  The non-aqueous electrolyte secondary battery according to claim 5, represented by (l (a≤l. 05, 0. 1≤b≤ 0. 35, 0. 001≤c≤ 0.2). [8] The lithium-containing composite acid has the following formula:  Li Ni Mn Co Al O (4)  a 1-(b + c + d) b c d 2 (l≤a≤l. 05, 0. l≤b≤ 0. 5, 0. l≤c≤ 0. 5, 0. 001 ≤ d ≤ 0.2, 0. 2 + b + c The non-aqueous electrolyte secondary battery according to claim 5, represented by + d≤0.75).