KR102419885B1 - Positive electrode for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery and system thereof - Google Patents

Abstract

Provided is a system including a nonaqueous electrolyte secondary battery capable of exhibiting excellent charge/discharge cycle characteristics even when the upper limit voltage during charging is increased, a positive electrode for constituting the nonaqueous electrolyte secondary battery, and the nonaqueous electrolyte secondary battery.
The positive electrode for a nonaqueous electrolyte secondary battery of the present invention has a positive electrode mixture layer containing a positive electrode active material, a conductive support agent, and a binder, and as a positive electrode active material, an element M ¹ selected from Al, Ti, etc., Ni, Co, etc. in a specific amount It contains a lithium-containing metal oxide (A) containing 50% by mass or more of particles having a primary particle size of 0.5 µm or more, and when the total amount of the positive electrode active material is 100% by mass, the lithium-containing metal oxide (A) It is characterized in that the content is 5 to 80% by mass. Moreover, the nonaqueous electrolyte secondary battery of this invention has the positive electrode for nonaqueous electrolyte secondary batteries of this invention, a negative electrode, a separator, and a nonaqueous electrolyte.

Description

A positive electrode for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery, and a system thereof

The present invention relates to a non-aqueous electrolyte secondary battery having excellent charge/discharge cycle characteristics, a positive electrode for constituting the non-aqueous electrolyte secondary battery, and a system having the non-aqueous electrolyte secondary battery.

BACKGROUND ART A nonaqueous electrolyte secondary battery such as a lithium ion secondary battery has a high voltage and a high energy density, and therefore demand tends to increase as a driving power source for portable devices or the like. Currently, lithium cobaltate having a large capacity and good reversibility is mainly used as a positive electrode active material for this nonaqueous electrolyte secondary battery.

At present, non-aqueous electrolyte secondary batteries are required to have higher capacity with improvements in applied devices. However, in a battery using lithium cobaltate, the battery capacity is almost near the limit.

For this reason, in order to achieve a higher capacity of the nonaqueous electrolyte secondary battery, the use of a positive electrode active material with a larger capacity, such as LiNiO ₂ , has also been studied _. The used battery also has a problem such as low charge/discharge cycle characteristics.

On the other hand, in Patent Document 1, Ni, Mn, and Mg are essential elements, and at least one element selected from the group consisting of Nb, Mo, Ga, W and V is further included, and Ni, Mn and Mg are further included. A technique has been proposed that enables the provision of an electrochemical device such as a nonaqueous electrolyte secondary battery having a high capacity and excellent charge/discharge cycle characteristics by using a lithium-containing composite oxide having an average valence of a specific value as a positive electrode active material.

Japanese Patent Laid-Open No. 2011-82150

By the way, in recent years, with respect to the request|requirement of the capacity increase of a nonaqueous electrolyte secondary battery, the study to respond to this is made|formed by raising the upper limit voltage at the time of charging compared with the prior art. However, on the other hand, when the charging voltage of the non-aqueous electrolyte secondary battery is increased, the positive electrode active material deteriorates and there is also a problem that the charge/discharge cycle characteristics of the non-aqueous electrolyte secondary battery are deteriorated.

The present invention has been made in view of the above circumstances, and its object is a nonaqueous electrolyte secondary battery capable of exhibiting excellent charge/discharge cycle characteristics even when the upper limit voltage during charging is increased, a positive electrode for constituting the nonaqueous electrolyte secondary battery, and to provide a system having the nonaqueous electrolyte secondary battery.

The positive electrode for a non-aqueous electrolyte secondary battery of the present invention, which has achieved the above object, is used in a non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte, and contains a positive electrode active material, a conductive aid and a binder A lithium-containing metal oxide ( A) is contained, and when the whole amount of the positive electrode active material contained in the said positive mix layer is 100 mass %, content of the said lithium containing metal oxide (A) is 5-80 mass %, It is characterized by the above-mentioned.

Li _a Ni _{1 -bc- d} Co _b Mn _c M ¹ _d Mg _e O ₂ (1)

In the general formula (1), M ¹ is a metal element other than Li, Ni, Co and Mn, and is at least one element selected from the group consisting of Al, Ti, Sr, Zr, Nb, Ag and Ba. , 0.9≤a≤1.10, 0.1≤b≤0.2, 0≤c≤0.2, 0.1≤b+c≤0.25, 0.003≤d≤0.06, and 0≤e≤0.003.

Moreover, the nonaqueous electrolyte secondary battery of this invention has a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, The said positive electrode is the positive electrode for nonaqueous electrolyte secondary batteries of this invention, It is characterized by the above-mentioned.

Further, the system of the nonaqueous electrolyte secondary battery of the present invention comprises the nonaqueous electrolyte secondary battery of the present invention and a charging device, and the nonaqueous electrolyte secondary battery is charged with a voltage of 4.3V or more as an upper limit, characterized in that will be.

According to the present invention, there is provided a system having a nonaqueous electrolyte secondary battery capable of exhibiting excellent charge/discharge cycle characteristics even when the upper limit voltage during charging is increased, a positive electrode for constituting the nonaqueous electrolyte secondary battery, and the nonaqueous electrolyte secondary battery can do.

1 is a partial longitudinal cross-sectional view schematically showing an example of a nonaqueous electrolyte secondary battery of the present invention.
FIG. 2 is a perspective view of FIG. 1 ;

The positive electrode for a nonaqueous electrolyte secondary battery of the present invention (hereinafter simply referred to as "positive electrode") has a positive electrode mixture layer containing a positive electrode active material, a conductive support agent and a binder, for example, the positive electrode mixture layer is one side of the current collector. Or it has a structure formed on both sides.

The positive electrode of this invention uses the lithium containing metal oxide (A) represented by the said General formula (1) and has a specific particle size as a positive electrode active material. Accordingly, in the positive electrode of the present invention, it is possible to construct a nonaqueous electrolyte secondary battery that can exhibit excellent charge/discharge cycle characteristics (especially charge/discharge cycle characteristics at high temperatures (about 40 to 60°C)) even when the upper limit voltage during charging is increased. doing it

In the lithium-containing metal oxide (A), when the total element amounts of Ni, Co, Mn and element M ¹ are 1, the ratio b of Co and the ratio c of Mn are 0.1≤b≤0.2, 0≤c, respectively. ? 0.2 and 0.1 ? b+c ? 0.25, Co or Co and Mn are present in the crystal lattice. Accordingly, when the phase transition of the lithium-containing metal oxide (A) occurs due to the desorption and insertion of Li, the irreversible reaction due to the structural change is relieved by the action of Co or Mn, so space group R3-m The reversibility of the layered crystal structure of the lithium-containing metal oxide (A) represented by .

Moreover, in the lithium containing metal oxide (A), Co is a component contributing to the improvement of the charge/discharge cycle characteristic under high temperature especially at the time of charging which makes an upper limit voltage 4.3V or more. In the general formula (1), the amount b of Co is 0.1 or more, preferably 0.12 or more, from the viewpoint of satisfactorily ensuring the respective effects. However, when the amount of Co in the lithium-containing metal oxide (A) is too large, the amount of other elements decreases and the effect thereof cannot be satisfactorily secured, so the amount of Co in the general formula (1) above. b is 0.2 or less.

Further, it is not necessary to contain Mn in the lithium-containing metal oxide (A), but when it is contained, the amount c of Mn in the general formula (1) is 0.005 or more from the viewpoint of ensuring the above-mentioned effect satisfactorily. desirable. However, when the amount of Mn in the lithium-containing metal oxide (A) is too large, the amount of other elements decreases and the effect thereof cannot be satisfactorily secured, so the amount of Mn in the general formula (1) above c is 0.2 or less, and it is preferable that it is 0.15 or less.

Further, the lithium-containing metal oxide (A) contains, as element M ¹ , at least one element selected from the group consisting of Al, Ti, Sr, Zr, Nb, Ag and Ba, and contains these elements Also by this, the stability can be improved, and the positive electrode which can constitute a battery with high charge/discharge cycle characteristic and safety|security can be obtained. The amount d of the element M ¹ in the general formula (1) is 0.003 or more, preferably 0.01 or more, from the viewpoint of satisfactorily ensuring such an effect by the element M ¹ . However, when the amount of element M ¹ in the lithium-containing metal oxide (A) is too large, the amount of other elements decreases and the effect thereof cannot be satisfactorily secured, so the element in the general formula (1) The quantity d of M< ¹ > is 0.06 or less, and it is preferable that it is 0.04 or less.

Moreover, the lithium containing metal oxide (A) contains Ni. When Ni is present in the crystal lattice of the lithium-containing metal oxide (A), the lithium-containing metal oxide (A) can be easily desorbed and inserted during charging and discharging of the battery, thereby increasing the capacity of the lithium-containing metal oxide (A).

In the above general formula (1) representing the lithium-containing metal oxide (A), the amount of Ni is expressed as “1-bcd” using the amount b of Co, the amount c of Mn and the amount d of the element M ¹ , Specifically, the amount of Ni “1-bcd” is preferably 0.69 or more, and more preferably 0.897 or less.

Further, the lithium-containing metal oxide (A) may contain Mg, but since Mg has a stronger effect of causing the capacity reduction of the lithium-containing metal oxide (A) than other metal elements, it is preferable to limit the amount thereof. Specifically, in the general formula (1) representing the lithium-containing metal oxide (A), the amount e of Mg is 0.003 or less, preferably 0.002 or less. Moreover, since the lithium containing metal oxide (A) does not need to contain Mg, the lower limit of the quantity e of Mg in the said General formula (1) is 0.

When a lithium-containing metal oxide (A) is a composition close|similar to a stoichiometric ratio especially, it improves a true density and reversibility, and it becomes possible to set it as a higher capacity|capacitance material. Therefore, in the above general formula (1) representing the lithium-containing metal oxide (A), the amount a of Li is 0.9 or more and 1.10 or less, and thus the true density and reversibility of the lithium-containing metal oxide (A) can be improved. have.

The lithium-containing metal oxide (A) contains 50 mass% or more, preferably 70 mass% or more, particularly preferably 100 mass% of particles having a primary particle diameter of 0.5 µm or more in 100 mass% of the total amount. By using the lithium-containing metal oxide (A) containing particles having a relatively large primary particle diameter as described above in the above amount, the charge/discharge cycle characteristics of the battery at high temperatures can be improved. In addition, as long as the lithium-containing metal oxide (A) provided for production of the positive electrode of the present invention contains particles having a primary particle diameter of 0.5 µm or more in the specified amount, it may be in the state of primary particles, and the primary particles are aggregated. It may be in the state of the obtained secondary particles, or in a state in which primary particles and secondary particles are mixed.

However, when the primary particle diameter of the lithium-containing metal oxide (A) is too large, the load characteristics deteriorate and the capacity may decrease. Therefore, among the particles (primary particles) contained in the lithium-containing metal oxide (A), the particle diameter It is preferable that the maximum value (the maximum value of the primary particle diameter) of is 5 µm.

The primary particle diameter of a lithium containing metal oxide (A) as used in this specification is a value measured by the following method (a).

(a) Measuring method of primary particle diameter of lithium-containing metal oxide (A) present in positive mix layer

With respect to the cross section of the positive electrode (positive electrode mixture layer) processed by ion milling, using a scanning electron microscope equipped with an EDX apparatus, mapping is performed with an EDX apparatus under the condition of an observation magnification of 500 times, Ni concentration With respect to the particles with high , it is further specified by elemental analysis that they are lithium-containing metal oxides (A). Then, when the particles of the lithium-containing metal oxide (A) present in the field of view are enlarged under the condition of a magnification of 5000 times, the minor axis of the primary particles (the diameter of the portion orthogonal to the portion serving as the maximum diameter in the primary particles) ) to determine the primary particle diameter by measuring the length. Here, the ratio of particles having a primary particle diameter of 0.5 µm or more in the lithium-containing metal oxide (A) is the number of particles of 0.5 µm or more of the lithium-containing metal oxide (A) measured by the method described above, the number of primary particles in the field of view. What is divided by the total number is expressed and calculated|required as a percentage, and let the maximum value of a primary particle diameter be the diameter of the largest primary particle among them. In addition, in the Examples described later, using an "S-3400N type scanning electron microscope" manufactured by Hitachi High-Technologies Co., Ltd. as the scanning electron microscope, the acceleration voltage at the time of mapping is set to 15 kV, and the lithium-containing metal oxide ( The primary particle diameter of the lithium-containing metal oxide (A) in the positive electrode mixture layer was determined by setting the acceleration voltage at the time of observation at 5000 times the magnification of the particles of A) to be 2 kV.

Further, a lithium-containing metal oxide (A) containing 50% by mass or more of particles having a primary particle size of 0.5 µm or more, and further, a lithium-containing metal oxide (A) in which the maximum value of the primary particle size satisfies the above suitable value. The positive mix layer to be made is a lithium-containing metal oxide (A) containing 50 mass % or more of particles having a primary particle diameter of 0.5 µm or more as measured by the method of (b) below, and further by the method of (b) below. It can form by using the lithium containing metal oxide (A) with which the largest value of the measured primary particle diameter satisfy|fills the said suitable value.

(b) Primary particle diameter of lithium-containing metal oxide (A) used for formation of positive mix layer

Lithium used for forming a positive electrode mixture layer by pulverizing the powder of the lithium-containing metal oxide (A) until it becomes primary particles, and measuring the particle size distribution using a laser diffraction scattering type particle size distribution analyzer The ratio of the particle|grains whose primary particle diameter in a containing metal oxide (A) is 0.5 micrometer or more, and the maximum value of the primary particle diameter of a lithium containing metal oxide (A) are calculated|required. Incidentally, in Examples to be described later, "Micro Track HRA" manufactured by Nikkiso Co., Ltd. is used as a laser diffraction scattering type particle size distribution measuring device, and the number of times of disintegration of the lithium-containing metal oxide (A) powder is 20 in order to reduce the error. made the circuit.

Lithium-containing metal oxides (A) include Li-containing compounds (lithium hydroxide, etc.), Ni-containing compounds (nickel sulfate, etc.), Co-containing compounds (cobalt sulfate, etc.), Mn-containing compounds (manganese sulfate, etc.), elements M ¹ or Mg It can be produced by mixing a compound (oxide, hydroxide, sulfate, etc.) containing

In addition, in order to synthesize the lithium-containing metal oxide (A) with higher purity, a complex compound (hydroxide, oxide, etc.) containing a plurality of elements among Ni, Co, Mn, elements M ¹ and Mg, and other raw material compounds ( Li-containing compound, etc.) is mixed and this raw material mixture is preferably calcined.

The firing conditions of the raw material mixture for synthesizing the lithium-containing metal oxide (A) can be, for example, from 800 to 1050° C. for 1 to 24 hours, but at a temperature lower than the firing temperature once (for example, from 250 to 850). ℃), it is preferable to perform preliminary heating by maintaining it at that temperature, and then to advance the reaction by raising the temperature to the calcination temperature. Although there is no restriction|limiting in particular about the time of preheating, Usually, what is necessary is just about 0.5 to 30 hours. In addition, the atmosphere at the time of firing can be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (argon, helium, nitrogen, etc.) and oxygen gas, an oxygen gas atmosphere, etc., but the oxygen concentration at that time It is preferable that (volume basis) is 15 % or more, and it is preferable that it is 18 % or more.

In addition, since the lithium-containing metal oxide (A) contains a large amount of Ni, an alkali component [a non-reacted substance among alkali components that is a raw material for synthesizing a lithium-containing metal oxide (A) or a lithium-containing metal oxide (A) during synthesis Alkaline component] produced by the oxidizer), which decomposes under high temperature or during charging to generate gas, expands the battery, and may cause a decrease in capacity or a decrease in charge/discharge cycle characteristics under high temperature. Therefore, in the positive electrode of the present invention, when the total amount of the positive electrode active material contained in the positive electrode mixture layer is 100% by mass, the content of the lithium-containing metal oxide (A) is 80% by mass or less, preferably 40% by mass or less This makes it possible to reduce the total amount of the alkali component contained in the positive electrode and suppress a decrease in charge/discharge cycle characteristics and capacity under high temperature.

Moreover, in the positive electrode of this invention, when the whole quantity of the positive electrode active material contained in a positive mix layer is 100 mass %, content of lithium containing metal oxide (A) is 5 mass % or more, Preferably 10 mass % or more. In this way, the effect described above by the use of the lithium-containing metal oxide (A) is satisfactorily secured.

The positive electrode of this invention WHEREIN: As a positive electrode active material used together with a lithium containing metal oxide ( _A ), Lithium cobalt oxides, such as LiCoO2; lithium manganese oxides such as LiMnO ₂ and Li ₂ MnO ₃ ; lithium nickel oxide [except those represented by the general formula (1) and those in which the Ni content is equal to or higher than those represented by the general formula (1)); lithium-containing composite oxides having a spinel structure, such as LiMn ₂ O ₄ and Li _{4 /3} Ti _{5 /3} O ₄ ; Lithium-containing metal oxides having an olivine structure, such as LiFePO ₄ ; an oxide in which the oxide is substituted with various elements as a basic composition; and the like.

Among these positive electrode active materials, it is preferable to use together the lithium-containing metal oxide (B) represented by the following general formula (2) with the lithium-containing metal oxide (A). In the case of a non-aqueous electrolyte secondary battery using a positive electrode in which a lithium-containing metal oxide (A) and a lithium-containing metal oxide (B) represented by the following general formula (2) are used together as a positive electrode active material, the lithium-containing metal oxide (A) is used alone Compared with the case and the case where a lithium containing metal oxide (B) is used independently, the charge/discharge cycle characteristic under high temperature in the case of making an upper limit voltage 4.3V or more becomes especially favorable.

Li _f Co _{1 -g- h} M ² _g M ³ _h O ₂ (2)

In the general formula (2), M ² is at least one element selected from the group consisting of Al, Mg and Er, and M ³ is Zr, Ti, Ni, Mn, Na, Bi, Ca, F, At least one element selected from the group consisting of P, Sr, W, Ba, Mo, V, Sn, Ta, Nb and Zn, 0.9≤f≤1.10, 0.010≤g≤0.1, 0≤h≤0.05, g+h≤0.12.

In the lithium-containing metal oxide (B), the elements M ² , Al, Mg, and Er, suppress the elution of Co accompanying charging and discharging of the battery, and in particular, at the time of charging with an upper limit voltage of 4.3 V or more, under high temperature. It is a component that contributes to improvement of charge/discharge cycle characteristics. The lithium-containing metal oxide (B) may contain at least one of Al, Mg, and Er as the element M ² , but may contain a plurality of types.

From a viewpoint of ensuring favorably ^the said effect by element M2, it is preferable that it is 0.010 or more, and, as for the quantity g of element M2 in the said General formula ( ² ), it is more preferable that it is 0.014 or more. However, when the amount of element M ² in the lithium-containing metal oxide (B) is too large, the amount of other elements decreases and the effect by these elements cannot be ensured satisfactorily, so the element in the general formula (2) It is preferable that it is 0.1 or less, and, as for ^the quantity g of M2, it is more preferable that it is 0.05 or less.

Further, in the lithium-containing metal oxide (B), as elements M ³ , Zr, Ti, Ni, Mn, Na, Bi, Ca, F, P, Sr, W, Ba, Mo, V, Sn, Ta, Nb and At least one element selected from the group consisting of Zn may be contained. These elements ^M3 also contribute to the improvement of the charge/discharge cycle characteristic under high temperature especially at the time of charging which sets an upper limit voltage to 4.3V or more.

However, if the amount of element M ³ in the lithium-containing metal oxide (B) is too large, the amount of other elements decreases and the effect by these elements cannot be ensured satisfactorily, so the element in the general formula (2) It is preferable that it is 0.05 or less, and, as for the quantity h of ^M3 , it is more preferable that it is 0.01 or less. In addition, the lithium-containing metal oxide (B) does not need to contain the element M ³ , but in the case of containing these elements, from the viewpoint of more favorably securing the effect due to the element M ³ , in the general formula (2), The amount h of the element M ³ of is preferably 0.0005 or more.

In addition, in the lithium-containing metal oxide (B), since Co is a component contributing to capacity improvement, the amount of element M ² or element M ³ is limited and a sufficient amount of Co is contained, so that the lithium-containing metal oxide From a viewpoint of maintaining the capacity|capacitance of (B) large, it is preferable that the sum total g+h of the amount g of element M2 ^and the amount h of element M3 in the said General formula ( ² ) is 0.12 or less.

Similarly to the lithium-containing metal oxide (A), the lithium-containing metal oxide (B) also has a composition close to the stoichiometric ratio, improves true density and reversibility, and makes it possible to obtain a material with a higher capacity. Therefore, in the above general formula (2) representing the lithium-containing metal oxide (B), the amount f of Li is preferably 0.9 or more and 1.10 or less, and thus the true density and reversibility of the lithium-containing metal oxide (B) are improved. can be raised

The lithium-containing metal oxide (B) is a mixture of a Li-containing compound (lithium hydroxide, etc.), a Co-containing compound (cobalt sulfate, etc.), and a compound containing an element M ² or an element M ³ (oxide, hydroxide, sulfate, etc.) , it can be produced by calcining this raw material mixture.

In addition, in order to synthesize the lithium-containing metal oxide (B) with higher purity, a complex compound (hydroxide, oxide, etc.) containing a plurality of elements among Co, element M ² and element M ³ and other raw material compounds (containing Li) compound, etc.) and calcining this raw material mixture.

The firing conditions of the raw material mixture for synthesizing the lithium-containing metal oxide (B) can be, for example, from 800 to 1050° C. for 1 to 24 hours, but at a temperature lower than the firing temperature once (for example, from 250 to 850). ℃), it is preferable to perform preliminary heating by maintaining it at that temperature, and then to advance the reaction by raising the temperature to the calcination temperature. Although there is no restriction|limiting in particular about the time of preheating, Usually, what is necessary is just about 0.5 to 30 hours. In addition, the atmosphere at the time of firing can be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (argon, helium, nitrogen, etc.) and oxygen gas, an oxygen gas atmosphere, etc., but the oxygen concentration at that time It is preferable that (volume basis) is 15 % or more, and it is preferable that it is 18 % or more.

It is preferable that content of the positive electrode active material in a positive mix layer is 94-98 mass %.

To the conductive support agent of a positive electrode, For example, Graphites, such as natural graphite (scaly graphite etc.) and artificial graphite; carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; carbon fiber; It is preferable to use carbon materials, such as, and conductive fibers, such as a metal fiber; carbon fluoride; metal powders such as aluminum; zinc oxide; conductive whiskers such as potassium titanate; conductive metal oxides such as titanium oxide; organic conductive materials such as polyphenylene derivatives; etc. can also be used.

The content of the conductive additive in the positive electrode mixture layer suppresses the rate of desorption of lithium ions from the positive electrode during charging, improves the balance with the rate of importation of lithium ions from the negative electrode, and the battery It is preferable that it is 2.0 mass % or less, and it is more preferable that it is 1.5 mass % or less from a viewpoint of highly suppressing generation|occurrence|production of lithium dendrite on the surface of a negative electrode accompanying charging/discharging of a battery, and further improving the charge/discharge cycle characteristic of a battery. However, when the amount of the conductive additive in the positive mixture layer is too small, the conductivity in the positive mixture layer decreases and there is a risk of causing a decrease in battery capacity, etc., so the content of the conductive auxiliary in the positive mixture layer is 0.5 mass It is preferable that it exceeds %, and it is more preferable that it is 1.0 mass % or more.

Examples of the positive electrode binder include acrylonitrile, acrylic acid esters (methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc.) and methacrylic acid esters (methyl methacrylate, ethyl methacrylate, methacrylic acid). butyl, etc.) a copolymer formed of two or more monomers including at least one monomer selected from the group consisting of; hydrogenated nitrile rubber; PVDF; vinylidene fluoride-tetrafluoroethylene copolymer (VDF-TFE); vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer (VDF-HFP-TFE); vinylidene fluoride-chlorotrifluoroethylene copolymer (VDF-CTFE); These etc. are mentioned, Only 1 type may be used among these, and 2 or more types may be used together.

The content of the binder in the positive electrode material layer is such that the positive electrode active material and the conductive auxiliary in the positive electrode material layer can be satisfactorily bound, the detachment of the positive electrode material layer is prevented, and the reliability of the battery in which this positive electrode is used It is preferable that it is 1 mass % or more from a viewpoint of raising more favorably. However, when there is too much quantity of the binder in a positive mix layer, the quantity of a positive electrode active material and the quantity of a conductive support agent decrease, and there exists a possibility that the effect of capacity increase may become small. Therefore, it is preferable that content of the binder in a positive mix layer is 1.6 mass % or less.

In manufacturing the positive electrode, the positive electrode mixture including the positive electrode active material, the conductive auxiliary and the binder is uniformly dispersed using a solvent such as N-methyl-2-pyrrolidone (NMP), a paste or slurry composition. Prepared (a binder may be dissolved in a solvent), apply|coating this composition to the positive electrode collector surface, drying, and the method of adjusting the thickness and density of a positive electrode mixture layer by a press process as needed can be employ|adopted. However, the manufacturing method of the positive electrode of this invention is not limited to the said method, You may employ|adopt another method.

The material of the positive electrode current collector is not particularly limited as long as it is an electron conductor that is chemically stable in the battery. For example, in addition to aluminum or an aluminum alloy, stainless steel, nickel, titanium, carbon, a conductive resin, and the like, a composite material in which a carbon layer or a titanium layer is formed on the surface of aluminum, an aluminum alloy or stainless steel can be used. Among the positive electrode current collectors composed of these materials, foils, films, and the like composed of aluminum or an aluminum alloy are preferable.

The positive electrode current collector has a thickness of 11 µm or less, preferably 10 µm or less. By making the positive electrode current collector thin, the ratio occupied by the positive electrode current collector among the internal volume of the non-aqueous electrolyte secondary battery can be made as small as possible. In a non-aqueous electrolyte secondary battery formed using such a positive electrode, It becomes possible to further increase the amount of non-aqueous electrolyte introduced therein.

When high capacity is achieved by setting the upper limit voltage of charging to 4.3 V or more, since the potential of the positive electrode in a charged state of the non-aqueous electrolyte secondary battery becomes very high, oxidative decomposition of the non-aqueous electrolyte occurs, and the non-aqueous electrolyte in the positive electrode becomes insufficient. By doing so, decomposition products may be deposited on the surface layer of the positive electrode active material contained in the positive electrode, or the ion conduction path between particles may decrease, and these may cause a decrease in the charge/discharge cycle characteristics of the battery. However, when the amount of non-aqueous electrolyte introduced into the non-aqueous electrolyte secondary battery is increased using the above-described thin positive electrode current collector, the occurrence of the above problem is suppressed, and the charge/discharge cycle characteristics resulting from the occurrence of this problem decrease can be suppressed.

However, when the positive electrode current collector is too thin, the strength is insufficient and there is a risk that the productivity of the positive electrode or the battery may be impaired. Therefore, the thickness of the positive electrode current collector is preferably 6 µm or more.

It is preferable that the thickness of the positive mix layer is 30-80 micrometers per single side|surface of an electrical power collector. Moreover, in a positive mix layer, it is preferable that the filling rate is 75 % or more from a viewpoint of setting it as higher capacity|capacitance. However, if the filling rate of the positive mix layer is too high, the number of voids in the positive mix layer is too small, and the permeability of the nonaqueous electrolyte (nonaqueous electrolyte) in the positive mix layer may decrease. It is preferably 83% or less. The filling rate of the positive mix layer is calculated|required by the following formula.

Filling factor (%) = 100 x (actual density of positive mixture layer/theoretical density of positive mixture layer)

The "theoretical density of the positive mixture layer" in the above formula for calculating the filling rate of the positive mixture layer is a density calculated from the density and content of each component of the positive mixture layer (the absence of voids in the positive mixture layer) and calculated|required density), and "the actual density of the positive mix layer" is measured by the following method. First, the positive electrode is cut to a size of 1 cm × 1 cm, and the thickness (l ₁ ) is measured with a micrometer, and the mass (m ₁ ) is measured with a precision balance. Next, the positive electrode mixture layer is removed, only the current collector is taken out, and the thickness ( _{lc) and mass (m c )} of the current collector are measured in the same manner as the positive electrode. From the obtained thickness and mass, the actual density (d _ca ) of the positive electrode material layer is obtained by the following formula (the unit of the thickness is cm, the unit of the mass is g).

d _ca =(m ₁ -m _c )/(l ₁ -l _c )

Moreover, you may form the lead body for electrically connecting with other members in a nonaqueous electrolyte secondary battery according to a normal method in a positive electrode as needed.

The nonaqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, and just needs to have the positive electrode of the present invention as a positive electrode, and there is no particular limitation on other configurations and structures. Each configuration and structure employed in the electrolyte secondary battery may be applied.

For the negative electrode related to the nonaqueous electrolyte secondary battery of the present invention, for example, a negative electrode mixture layer containing a negative electrode active material, a binder, and, if necessary, a conductive aid, etc. can be used on one or both surfaces of the current collector. have.

As a negative electrode active material, For example, graphite [natural graphite, such as flaky graphite; artificial graphite obtained by graphitizing carbon easily graphitized at 2800°C or higher, such as pyrolytic carbons, mesophase carbon microbeads (MCMB), and carbon fibers; etc.], pyrolysis carbons, cokes, glassy carbons, sintered bodies of organic high molecular compounds, mesocarbon microbeads, carbon fibers, activated carbon, metals capable of alloying with lithium (Si, Sn, etc.) or their alloys, oxides, etc. and one or two or more of them may be used.

Among the negative electrode active materials, materials containing Si and O as constituent elements (however, the atomic ratio x of O to Si is 0.5≤x≤1.5. It is preferable to use the material "SiOx" ₎ . In addition, by using such a high-capacity negative electrode active material, it is possible to increase the capacity of the battery while making the negative electrode mixture layer thin.

SiO _x may contain the microcrystal or amorphous phase of Si, and in this case, the atomic ratio of Si and O becomes the ratio which included the microcrystal or amorphous phase of Si of Si. That is, SiO _x includes a structure in which Si (eg, microcrystalline Si) is dispersed in an amorphous SiO ₂ matrix, and the amorphous SiO ₂ and Si dispersed therein are combined, and the atomic ratio It is sufficient that x satisfies 0.5≤x≤1.5. For example, in the case of a material having a molar ratio of SiO ₂ and Si of 1:1 in a structure in which Si is dispersed in an amorphous SiO ₂ matrix, x=1, and therefore, the structural formula is expressed as SiO. In the case of a material having such a structure, for example, in X-ray diffraction analysis, a peak due to the presence of Si (microcrystalline Si) may not be observed in some cases, but when observed with a transmission electron microscope, the presence of fine Si can be confirmed. have.

And, it is preferable that _SiOx is the composite_body|complex formed with the carbon material, for example, it is preferable that the surface of _SiOx is coat|covered with the carbon material. Since SiO _x lacks conductivity, when using it as a negative electrode active material, a conductive material (conductive aid) is used from the viewpoint of ensuring good battery characteristics, and mixing and dispersing of SiO _x and conductive material in the negative electrode is satisfactory. Therefore, it is necessary to form an excellent conductive network. In the case of a composite obtained by complexing SiO _x with a carbon material, for example, a conductive network in the negative electrode is formed more favorably than when a material obtained by merely mixing SiO _x and a conductive material such as a carbon material is used.

As a composite_body|complex of _SiOx and a carbon material, as mentioned above, besides what coat|covered the surface of _SiOx with a carbon material, granules of _SiOx and a carbon material, etc. are mentioned.

In addition, by using the above-mentioned composite in which the surface of SiO _x is covered with a carbon material, in combination with a conductive material (carbon material, etc.), a better conductive network can be formed in the negative electrode, so that it has a higher capacity, It becomes possible to realize a lithium secondary battery having more excellent battery characteristics (eg, charge/discharge cycle characteristics). Examples of the composite of SiO _x coated with a carbon material and a carbon material include granules obtained by further granulating a mixture of SiO _x coated with a carbon material and a carbon material.

Further, as SiO _x whose surface is coated with a carbon material, one in which the surface of a composite (for example, granulated body) of SiO _x and a carbon material having a lower resistivity value than that is further coated with a carbon material can be preferably used. have. In a nonaqueous electrolyte secondary battery having a negative electrode containing SiO _x as a negative electrode active material, since a better conductive network can be formed when SiO _x and the carbon material are dispersed in the assembly, heavy load discharge characteristics, etc. Battery characteristics can be further improved.

As said carbon material which can be used for formation of the composite_body|complex with SiOx, for example, carbon materials, such as low crystalline carbon, carbon nanotube, vapor _- phase growth carbon fiber, are mentioned as a preferable thing.

As the details of the carbon material, at least one selected from the group consisting of fibrous or coiled carbon material, carbon black (including acetylene black and Ketjen black), artificial graphite, easily graphitized carbon, and hardly graphitized carbon. material is preferred. A fibrous or coil-like carbon material is preferable in that it is easy to form a conductive network and has a large surface area. Carbon black (including acetylene black and Ketjen black), graphitizable carbon, and non-graphitizable carbon have high electrical conductivity and high liquid retention, and even if SiO _x particles expand and contract, their It is preferable in that it has the property of being easy to maintain contact with particle|grains.

When using _SiOx as a negative electrode active material, it is preferable to use graphite together as a negative electrode active material as mentioned later, but this graphite can also be used as a carbon material concerning the composite_body|complex of _SiOx and a carbon material. Like graphite, carbon black, etc., it has high electrical conductivity and high liquid retention, and also has a property of easily maintaining contact with the SiO _x particles even if they expand and contract, so it is important for forming a complex with SiO _x . It can be used preferably.

Among the carbon materials exemplified above, fibrous carbon materials are particularly preferable as those used when the composite with SiO _x is granules. Since the _fibrous carbon material has a thin thread shape and high flexibility, it can follow the expansion and contraction of SiO _x accompanying charging and discharging of the battery. because you can have Examples of the fibrous carbon include polyacrylonitrile (PAN)-based carbon fibers, pitch-based carbon fibers, vapor-grown carbon fibers, and carbon nanotubes, and any of these may be used.

The fibrous carbon material may be formed on the surface of the SiO _x particles by, for example, a vapor phase method.

While the specific resistance value of SiO _x is usually 10 ³ to 10 ⁷ kΩcm, the specific resistance value of the carbon material exemplified above is usually 10 ^-5 to 10 kΩcm. Moreover, the composite_body|complex of SiOx and a carbon material may further have the material layer (material layer containing non _- graphitizable carbon) which covers the carbon material coating layer of the particle|grain surface.

In the case of using a composite of SiO _x and a carbon material for the negative electrode, the ratio of SiO _x and the carbon material is SiO _x : 100 parts by mass of the carbon material from the viewpoint of favorably exhibiting the action due to the composite with the carbon material. It is preferable that it is 5 mass parts or more, and it is more preferable that it is 10 mass parts or more. Further, in the composite, when the ratio of SiO _x and the carbon material to be composited is too large, it leads to a decrease in the amount of SiO _x in the negative electrode mixture layer, and there is a possibility that the effect of increasing the capacity becomes small, so SiO _x : 100 parts by mass On the other hand, it is preferable that it is 50 mass parts or less, and, as for a carbon material, it is more preferable that it is 40 mass parts or less.

The composite of the SiO _x and the carbon material can be obtained, for example, by the following method.

First, the manufacturing method in the case of compounding _SiOx is demonstrated. A dispersion liquid in which SiO _x is dispersed in a dispersion medium is prepared, sprayed and dried to prepare composite particles including a plurality of particles. As a dispersion medium, ethanol etc. can be used, for example. It is appropriate to perform spraying of a dispersion liquid in 50-300 degreeC atmosphere normally. In addition to the above method, the same composite particles can be produced also in a granulation method by a mechanical method using a vibrating or planetary ball mill, rod mill, or the like.

In addition, when manufacturing granules of SiO _x and a carbon material having a specific resistance smaller than that of SiO _x , the carbon material is added to a dispersion in which SiO _x is dispersed in a dispersion medium, and using this dispersion, SiO _x is complexed. What is necessary is just to set it as a composite particle (granulated body) by the same method as the case. Moreover, the granulated body of SiOx and a carbon material can be manufactured also _by the granulation method by the mechanical method similar to the above.

Next, when the surface of the SiO _x particles (SiO _x composite particles or granules of SiO _x and carbon material) is coated with a carbon material to form a composite, for example, the SiO _x particles and hydrocarbon gas are heated in the gas phase. Thus, carbon generated by thermal decomposition of hydrocarbon gas is deposited on the surface of the particles. As described above, according to the vapor phase growth (CVD) method, the hydrocarbon-based gas spreads to every corner of the composite particles, and a thin and uniform film (carbon material coating layer) containing a conductive carbon material is formed on the surface of the particles or in the pores on the surface. ), it is possible to impart conductivity to the SiO _x particles with good uniformity with a small amount of the carbon material.

In the production of SiO _x coated with a carbon material, the processing temperature (ambient temperature) of the vapor phase growth (CVD) method varies depending on the type of hydrocarbon gas, but is usually 600 to 1200° C. , preferably 700°C or higher, and more preferably 800°C or higher. This is because the higher the treatment temperature, the less residual impurities and the higher conductive carbon-containing coating layer can be formed.

Although toluene, benzene, xylene, mesitylene, etc. can be used as a liquid source of hydrocarbon type gas, Toluene which is easy to handle is especially preferable. By vaporizing them (for example, bubbling with nitrogen gas), a hydrocarbon-based gas can be obtained. Moreover, methane gas, acetylene gas, etc. can also be used.

In addition, after the surface of the SiO _x particles (SiO _x composite particles, or granules of SiO _x and carbon material) is covered with a carbon material by a vapor phase growth (CVD) method, petroleum-based pitch, coal-based pitch, thermosetting resin, and naphthalenesulfonic acid After making at least 1 sort(s) of organic compound selected from the group which consists of a condensate of salt and aldehydes adhere to the coating layer containing a carbon material, you may bake the particle|grains to which the said organic compound adhered.

Specifically, a dispersion in which SiO _x particles (SiO _x composite particles, or an assembly of SiO _x and a carbon material) coated with a carbon material and the organic compound are dispersed in a dispersion medium are prepared, and the dispersion is sprayed and dried, The particles coated with the organic compound are formed, and the particles coated with the organic compound are fired.

An isotropic pitch can be used as said pitch, and a phenol resin, a furan resin, furfural resin, etc. can be used as a thermosetting resin. As a condensate of a naphthalenesulfonic acid salt and aldehydes, a naphthalenesulfonic acid formaldehyde condensate can be used.

As a dispersion medium for dispersing the SiO _x particles coated with the carbon material and the organic compound, for example, water or alcohols (such as ethanol) can be used. It is appropriate to perform spraying of a dispersion liquid in 50-300 degreeC atmosphere normally. Although 600-1200 degreeC is suitable normally, as for a calcination temperature, 700 degreeC or more is preferable especially, and it is more preferable that it is 800 degreeC or more. This is because the higher the treatment temperature, the less impurities remain and a coating layer made of a high-quality carbon material with high conductivity can be formed. However, the treatment temperature is required to be below the melting point of SiO _x .

When using SiOx ₍ preferably the composite_body|complex of SiOx and a carbon material ₎ for a negative electrode active material, it is preferable to also use graphite together. SiO _x has a high capacity compared to a carbon material commonly used as a negative electrode active material for a nonaqueous electrolyte secondary battery, _but has a large volume change accompanying charging and discharging of the battery. In a nonaqueous electrolyte secondary battery, there is a fear that the negative electrode (negative electrode mixture layer) is deteriorated due to a large volume change due to repeated charging and discharging, resulting in a decrease in capacity (that is, a decrease in charge/discharge cycle characteristics). Graphite is widely used as a negative electrode active material of a nonaqueous electrolyte secondary battery, and while it has a comparatively large capacity|capacitance, the volume change accompanying charging/discharging of a battery is small compared with _SiOx . Therefore, by using SiO _x and graphite in combination as the negative electrode active material, it is possible to suppress the decrease in the capacity improvement effect of the battery as much as possible along with the reduction in the amount of SiO _x used, while the decrease in the charge/discharge cycle characteristics of the battery can be well suppressed. Therefore, it becomes possible to set it as the nonaqueous electrolyte secondary battery which has a higher capacity|capacitance and is excellent in charge/discharge cycling characteristics.

As graphite used as a negative electrode active material with the said _SiOx , For example, Natural graphite, such as flaky graphite; artificial graphite obtained by graphitizing easily graphitized carbon such as pyrolytic carbons, mesophase carbon microbeads (MCMB), and carbon fibers at 2800° C. or higher; and the like.

When a composite of SiOx and a carbon material and graphite are used together for the negative electrode active material, the content of the composite of SiO _x and the carbon material in the total negative electrode active material from the viewpoint of securing favorably the effect of increasing the capacity by using SiO _x It is preferable that this is 0.01 mass % or more, It is more preferable that it is 1 mass % or more, It is more preferable that it is 3 mass % or more. In addition, from the viewpoint of better avoiding the problem due to the volume change of SiO _x accompanying charging and discharging, the content of the composite of SiO _x and carbon material in the total negative electrode active material is preferably 20% by mass or less, 15 It is more preferable that it is mass % or less.

The binder of the negative electrode can be used for the positive electrode and is the same as the one exemplified above, but styrene-butadiene rubber (SBR), ethylene-acrylic acid copolymer or Na ⁺ ion crosslinked product of the copolymer, ethylene-methacrylic acid copolymer, or the same A cross-linked Na ⁺ ion copolymer, an ethylene-methyl acrylate copolymer or a cross-linked Na ⁺ ion of the copolymer, an ethylene-methyl methacrylate copolymer or a cross-linked Na ⁺ ion of the copolymer may be used. Moreover, the thing similar to what was previously illustrated as a thing which can be used for a positive electrode as a conductive support agent of a negative electrode can be used.

For the negative electrode, for example, a negative electrode active material and a binder, and further, if necessary, a conductive auxiliary agent used as needed is dispersed in a solvent such as NMP or water to prepare a composition containing a negative electrode mixture in the form of a paste or slurry (however, the binder is dissolved in a solvent It is manufactured through the process of apply|coating this to one side or both surfaces of an electrical power collector, drying, and performing press processing, such as a calendering process, if necessary. However, a negative electrode is not limited to what was manufactured by the said manufacturing method, The thing manufactured by another method may be sufficient.

Moreover, you may form the lead body for electrically connecting with the other member in a nonaqueous electrolyte secondary battery in a normal method in a negative electrode as needed.

It is preferable that the thickness of the negative mix layer is, for example, 10 to 100 µm per single side of the current collector. Moreover, as a composition of a negative mix layer, it is preferable that the negative electrode active material shall be 80.0-99.8 mass %, and the binder shall be 0.1-10 mass %, for example. Moreover, when making a negative mix layer contain a conductive support agent, it is preferable to make the quantity of the conductive support agent in a negative mixture layer into 0.1-10 mass %.

As the current collector of the negative electrode, copper or nickel foil, punching metal, net, expanded metal, etc. can be used, but copper foil is usually used. In this negative electrode current collector, when the overall thickness of the negative electrode is made thin in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 µm, and the lower limit is preferably 5 µm to ensure mechanical strength.

As the non-aqueous electrolyte, for example, a solution (non-aqueous electrolyte solution) prepared by dissolving a lithium salt in the following solvent can be used.

Examples of the solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (MEC), γ-butyrolactone (γ-BL), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, dimethylsulfoxide (DMSO), 1,3-dioxolane, formamide, dimethyl Formamide (DMF), dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, 3-methyl-2-oxazolidinone, propylene Non-protic organic solvents such as carbonate derivatives, tetrahydrofuran derivatives, diethyl ether and 1,3-propane sultone can be used alone or as a mixed solvent in which two or more kinds are mixed.

Examples of the lithium salt related to the non-aqueous electrolyte include LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN ( CF ₃ SO ₂ ) ₂ , LiC(CF ₃ SO ₂ ) ₃ , LiC _n F _2n+1 SO ₃ (n≥2), LiN(RfOSO ₂ ) ₂ [wherein Rf is a fluoroalkyl group] at least one of them can be mentioned. The concentration of these lithium salts in the non-aqueous electrolyte is preferably 0.6 to 1.8 mol/l, more preferably 0.9 to 1.6 mol/l.

Nonaqueous electrolytes For the nonaqueous electrolyte used in secondary batteries, vinylene carbonate, vinylethylene carbonate, anhydride, sulfonic acid ester, Additives (including derivatives thereof) such as nitrile, 1,3-propanesultone, diphenyldisulfide, cyclohexylbenzene, biphenyl, fluorobenzene and t-butylbenzene may be appropriately added.

In addition, as the nonaqueous electrolyte of the nonaqueous electrolyte secondary battery, a gel formed by adding a known gelling agent such as a polymer to the above nonaqueous electrolyte (gel electrolyte) can also be used.

In the nonaqueous electrolyte secondary battery of the present invention, a separator containing the nonaqueous electrolyte is disposed between the positive electrode and the negative electrode. As the separator, an insulating microporous thin film having high ion permeability and predetermined mechanical strength is used. Moreover, it is preferable to have a function (that is, to have a shutdown function) that a hole is blocked by melting of a constituent material at a certain temperature or higher (for example, 100 to 140°C) and increases resistance.

Specific examples of such a separator include a sheet (porous sheet), a nonwoven fabric or a woven fabric made of a material such as a polyolefin polymer such as polyethylene or polypropylene having organic solvent resistance and hydrophobicity, or glass fiber; a porous body in which the fine particles of the polyolefin-based polymer exemplified above are fixed with an adhesive; and the like.

The pore size of the separator is preferably such that the active material, conductive auxiliary, binder, etc. of the positive and negative electrodes detached from the positive and negative electrodes do not pass, and for example, it is preferably 0.01 to 1 µm. Although it is common to set the thickness of a separator as 8-30 micrometers, in this invention, it is preferable to set it as 10-20 micrometers. Moreover, although the porosity of a separator is determined with a constituent material and thickness, it is common that it is 30 to 80 %.

In the nonaqueous electrolyte secondary battery of the present invention, the positive electrode and the negative electrode of the present invention are formed by a stacked electrode body stacked with the separator interposed therebetween, or by laminating the stacked electrode body with the separator interposed therebetween and then winding in a spiral shape. It is used as a single wound electrode body.

In the nonaqueous electrolyte secondary battery of the present invention, for example, a stacked electrode body or a wound electrode body is loaded in an exterior body, a nonaqueous electrolyte is injected into the exterior body, and the electrode body is immersed in the nonaqueous electrolyte, and then the opening of the exterior body is closed. It is manufactured by sealing. As the exterior body, an exterior can of steel, aluminum, or an aluminum alloy can be used, such as an exterior can having a cylindrical shape or a cylindrical shape, or an exterior body composed of a laminate film on which a metal is vapor-deposited.

The nonaqueous electrolyte secondary battery of the present invention can be used with an upper limit voltage set to about 4.2V as in the conventional nonaqueous electrolyte secondary battery. good charging/discharging cycle characteristics (especially charging/discharging cycle characteristics under high temperature) can be exhibited even if it is used in this way. Therefore, the nonaqueous electrolyte secondary battery of the present invention can maintain a large capacity over a long period of time even if charging and discharging are repeatedly performed under these conditions while achieving high capacity by increasing the upper limit voltage during charging. Moreover, it is preferable that the upper limit voltage of charging of the nonaqueous electrolyte secondary battery of this invention is 4.7 V or less.

The system for a nonaqueous electrolyte secondary battery of the present invention includes the nonaqueous electrolyte secondary battery of the present invention and a charging device, wherein the upper limit of the voltage applied by the charging device to the nonaqueous electrolyte secondary battery is 4.3 V or more (preferably In most cases, it is charged under the condition that it is 4.7V or less). By such a system, use at a larger capacity of the nonaqueous electrolyte secondary battery of the present invention becomes possible. As for the charging device related to the system of the nonaqueous electrolyte secondary battery of the present invention, as long as it can charge the nonaqueous electrolyte secondary battery of the present invention under the condition that the upper limit voltage is 4.3V or more (preferably 4.7V or less), A charging device for a non-aqueous electrolyte secondary battery known in the art can be used, for example, a charging device capable of performing constant voltage charging after constant current charging, a charging device capable of performing pulse charging, and the like.

Since the nonaqueous electrolyte secondary battery of the present invention has a high capacity and excellent charge/discharge cycle characteristics (especially charge/discharge cycle characteristics under high temperature), conventionally known nonaqueous electrolyte secondary batteries are employed, including applications in which these characteristics are particularly required. It can be preferably applied to various uses that have been made.

[Example]

Hereinafter, the present invention will be described in detail based on Examples. However, the following examples do not limit the present invention.

Example 1

<Production of positive electrode>

_{LiNi 0.78} Co _0.20 Al _{0.02 O 2} [ _Lithium -containing metal oxide (A), the proportion of particles having a primary particle diameter of 0.5 μm or more determined by the measurement method of (b) above is 50 mass%, and , the particle diameter of the largest primary particle is ₂ μm] and a mixture of _{LiCo 0.984} Al _0.008 Mg _0.006 Ti _{0.001 Zr 0.001 O 2} [lithium _- containing metal oxide (B)] (mass ratio 20: 80):97.3 parts by mass, conductive aid (carbon black and graphite, the use ratio is 80:20 by mass): 1.5 parts by mass and PVDF: 1.2 parts by mass as a binder are mixed to make a positive mix, and the positive mix is added with a solvent Phosphorus NMP was added, and using "Clairmix CLM0.8 (brand name)" made by M Technics, it processed for 30 minutes at rotation speed: 10000 min ^-1 , and it was set as the paste-like mixture. NMP as a solvent was further added to this mixture, and it processed for 15 minutes at rotation speed:1000min ^-1 , and the positive mix containing composition was prepared.

The positive mix-containing composition is applied to both surfaces of an aluminum alloy foil (thickness: 10.0 µm) serving as a current collector, vacuum dried at 80° C. for 12 hours, and further press-treated to provide a thickness on both surfaces of the current collector. A positive electrode having a positive electrode mixture layer having a value of 56 µm was prepared. The density (actual density) of the positive mix layer after the press process calculated|required by the said method was 3.85 g/cm<3>, and the filling rate was 77.7 %.

In addition, a sample for measuring the primary particle size of the lithium-containing metal oxide (A) is taken from a part of the obtained positive electrode, and by the method (a) above, the primary particle diameter of the lithium-containing metal oxide (A) is 0.5 µm or more. The ratio and the particle diameter of the largest primary particle (the maximum value of a primary particle diameter) were calculated|required.

<Production of negative electrode>

Natural graphite: 97.5 mass %, SBR: 1.5 mass %, and carboxymethyl cellulose (CMC, thickener): 1 mass % were mixed using water, and the slurry-like negative electrode mixture containing composition was prepared. This negative mix-containing composition is applied to both surfaces of a copper foil (thickness: 8 μm) as a current collector, vacuum dried at 120° C. for 12 hours, and further press-treated, so that both sides of the current collector have a thickness A negative electrode having a negative electrode mixture layer of 63 µm was prepared.

<Production of electrode body>

The positive electrode and the negative electrode are superimposed with a separator (a polyethylene porous film having a thickness of 17 μm and an air permeability of 300 seconds/100 cm 3 ) and wound in a spiral shape, and then the cross section becomes flat It was pressed and crushed to manufacture a flat wound electrode body.

<Preparation of non-aqueous electrolyte>

LiPF ₆ was dissolved in a mixed solvent of methyl ethyl carbonate, diethyl carbonate, and ethylene carbonate (volume ratio 0.5:2:1) at a concentration of 1.2 mol/l, and LiBF ₄ :0.05 mass %, vinylene carbonate: 2 Mass %, propane sultone: 0.2 mass % was added, and the non-aqueous electrolyte solution (non-aqueous electrolyte) was prepared.

<Assembly of the battery>

The electrode body was inserted into a rectangular battery case made of an aluminum alloy having an outer dimension of 3.75 mm in thickness, 52.8 mm in width, and 61.3 mm in height, the lead body was welded, and the aluminum alloy cover plate was attached to the battery case. Welded to the open end. Thereafter, the nonaqueous electrolyte is injected from the injection port provided on the cover plate, and after standing for 1 hour, the injection port is sealed, and a prismatic nonaqueous electrolyte secondary battery having the structure illustrated in FIG. Manufactured.

1 is a partial cross-sectional view thereof, wherein the positive electrode 1 and the negative electrode 2 are wound in a spiral shape with a separator 3 interposed therebetween, and then pressed to form a flat shape to form a flat wound electrode body 6, which is a square shape. It is accommodated together with the non-aqueous electrolyte in the battery case 4 (square-shaped). However, in FIG. 1, in order to avoid complication, the metal foil, nonaqueous electrolyte, etc. used as an electrical power collector used in manufacture of the positive electrode 1 and the negative electrode 2 are not shown.

The battery case 4 is made of an aluminum alloy and constitutes an exterior body of the battery, and the battery case 4 also serves as a positive electrode terminal. Then, an insulator 5 made of a polyethylene sheet is disposed at the bottom of the battery case 4, and from the flat wound electrode body 6 comprising the positive electrode 1, the negative electrode 2 and the separator 3, A positive electrode lead body 7 and a negative electrode lead body 8 respectively connected to one end of the positive electrode 1 and the negative electrode 2 are drawn out. In addition, a stainless steel terminal 11 is attached to the aluminum alloy sealing cover plate 9 that seals the opening of the battery case 4 through an insulating packing 10 made of polypropylene, and this terminal ( 11), a lead plate 13 made of stainless steel is attached with an insulator 12 interposed therebetween.

And this cover plate 9 is inserted into the opening part of the battery case 4, and by welding the junction part of both, the opening part of the battery case 4 is sealed, and the inside of a battery is sealed. In addition, in the battery of FIG. 1 , a non-aqueous electrolyte injection port 14 is provided in the cover plate 9, and a sealing member is inserted into the non-aqueous electrolyte injection port 14, for example, by laser welding or the like. It is sealed, and the airtightness of the battery is ensured. In addition, the cover plate 9 is provided with a cleavage vent 15 as a mechanism for discharging internal gas to the outside when the temperature of the battery rises.

In the battery of Example 1, the battery case 4 and the cover plate 9 function as a positive electrode terminal by directly welding the positive electrode lead body 7 to the cover plate 9, and the negative electrode lead body 8 is connected to the lead. By welding to the plate 13 and conducting the negative electrode lead 8 and the terminal 11 through the lead plate 13, the terminal 11 functions as a negative electrode terminal. Depending on the material and the like, the government may be the opposite.

2 is a perspective view schematically showing the appearance of the battery shown in FIG. 1, and FIG. 2 is shown for the purpose of showing that the battery is a prismatic battery, and in this FIG. 2, the battery is schematically shown, Among the constituent members of the battery, only specific ones are shown. Also in Fig. 2, the portion on the inner peripheral side of the electrode body is not cross-sectioned.

Example 2

_{LiNi 0.82} Co _{0.15 Al 0.03 O 2 [} The ratio of particles having a primary particle size of 0.5 μm or more is 50 mass%, and the largest primary particle size is 2 μm. ], a positive electrode was manufactured in the same manner as in Example 1, and a prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this positive electrode was used.

Example 3

_{LiNi 0.75} Co _{0.10 Mn 0.14 Al 0.01 O 2} [The ratio of particles _having a primary particle size of 0.5 µm or more is 50 mass %, A positive electrode was manufactured in the same manner as in Example 1 except that the particle diameter was changed to 2 µm], and a prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this positive electrode was used.

Example 4

_{LiNi 0.80} Co _{0.10 Mn 0.10} Al _{0.02 O 2} [The ratio of particles _having a primary particle size of 0.5 µm or more is 50 mass %, A positive electrode was manufactured in the same manner as in Example 1 except that the particle diameter was changed to 2 µm], and a prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this positive electrode was used.

Example 5

_{LiNi 0.80} Co _0.10 Mn _{0.097 Nb 0.003 O 2} [The ratio of particles _having a primary particle size of 0.5 µm or more is 50 mass %, A positive electrode was manufactured in the same manner as in Example 1 except that the particle diameter was changed to 2 µm], and a prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this positive electrode was used.

Example 6

The lithium-containing metal oxide (A) was the same as in Example 1, except that the ratio of particles having a primary particle diameter of 0.5 µm or more was 80 mass % and the largest primary particle diameter was 3 µm. was manufactured, and a prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this positive electrode was used.

Example 7

Positive electrode in the same manner as in Example 1 except that the lithium-containing metal oxide (A) was changed to have a ratio of particles having a primary particle diameter of 0.5 μm or more to 100% by mass and a particle diameter of the largest primary particle to 4 μm. was manufactured, and a prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this positive electrode was used.

Example 8

Positive electrode in the same manner as in Example 1, except that the lithium-containing metal oxide (A) was changed to a particle having a primary particle diameter of 0.5 µm or more in a ratio of 100 mass % and a particle diameter of the largest primary particle of 5 µm. was manufactured, and a prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this positive electrode was used.

Example 9

A positive electrode was manufactured in the same manner as in Example 1 except that the mixing ratio of the lithium-containing metal oxide (A) and the lithium-containing metal oxide (B) was changed to 5:95 by mass ratio. Moreover, it carried out similarly to Example 1 except having changed the thickness of the negative mix layer to 72 micrometers, and manufactured the negative electrode. A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the positive electrode and the negative electrode were used. The density (actual density) of the positive mix layer after the press process calculated|required by the said method was 3.90 g/cm<3>, and the filling rate was 78.4 %.

Example 10

A positive electrode was manufactured in the same manner as in Example 1 except that the mixing ratio of the lithium-containing metal oxide (A) and the lithium-containing metal oxide (B) was changed to 40:60 by mass, and the thickness of the positive electrode mixture layer was 57 µm. did. Moreover, it carried out similarly to Example 1 except having changed the thickness of the negative mix layer to 72 micrometers, and manufactured the negative electrode. A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the positive electrode and the negative electrode were used, and a positive electrode was manufactured in the same manner as in Example 1, and this positive electrode was used. The density (actual density) of the positive mix layer after the press process calculated|required by the said method was 3.80 g/cm<3>, and the filling rate was 77.3 %.

Example 11

A positive electrode was manufactured in the same manner as in Example 1, except that the amount of the positive electrode active material used for preparation of the positive mixture-containing composition was 96.5 parts by mass, the amount of the conductive aid was 2 parts by mass, and the amount of the binder was 1.5 parts by mass. did. Moreover, it carried out similarly to Example 1 except having changed the thickness of the negative mix layer to 72 micrometers, and manufactured the negative electrode. A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the positive electrode and the negative electrode were used. The density (actual density) of the positive mix layer after the press process calculated|required by the said method was 3.83 g/cm<3>, and the filling rate was 77.8 %.

Example 12

Example 1 except that the amount of the positive electrode active material used for preparation of the positive mixture-containing composition was 98.7 parts by mass, only carbon black was used as the conductive aid, the amount was 0.5 parts by mass, and the amount of the binder was 0.8 parts by mass. A prismatic non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that a positive electrode was manufactured in the same manner as described above, and this positive electrode was used. The density (actual density) of the positive mix layer after the press process calculated|required by the said method was 3.87 g/cm<3>, and the filling rate was 77.3 %.

Example 13

A composite (the amount of carbon material in the composite is 10% by mass; hereinafter referred to as SiO/carbon material composite) and an average particle _diameter of _d50 This 16 µm graphite is mixed in an amount such that the amount of the SiO/carbon material composite is 1.5% by mass: 97.5 parts by mass, SBR as a binder: 1.5 parts by mass, and CMC as a thickener: 1 part by mass, water was added and mixed to prepare a slurry-like negative electrode mixture-containing composition. This negative mix-containing composition is applied to both surfaces of a copper foil (thickness: 8 μm) as a current collector, vacuum dried at 120° C. for 12 hours, and further press-treated, so that both sides of the current collector have a thickness A negative electrode having a negative electrode mixture layer of 72 µm was prepared.

Moreover, except having changed the thickness of the positive mix layer per single side|surface of an electrical power collector to 58 micrometers, it carried out similarly to Example 1, and manufactured the positive electrode. A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this positive electrode and the negative electrode were used.

Example 14

In the same manner as in Example 13, the mixture used as the negative electrode active material was changed to one in which the amount of the SiO/carbon material composite was 3.0% by mass, and the thickness of the negative electrode mixture layer per one side of the current collector was changed to 71 µm. A negative electrode was manufactured. Moreover, except having changed the thickness of the positive mix layer per single side|surface of an electrical power collector to 59 micrometers, it carried out similarly to Example 1, and manufactured the positive electrode. A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this positive electrode and the negative electrode were used.

Example 15

A positive electrode was manufactured in the same manner as in Example 10 except that the thickness of the positive electrode mixture layer was 58 µm. Then, a prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 14 except that this positive electrode was used.

Example 16

The lithium-containing metal oxide (A) is changed to one in which the proportion of particles having a primary particle diameter of 0.5 μm or more is 100% by mass and the largest primary particle has a particle diameter of 4 μm, and this lithium-containing metal oxide (A) and lithium A positive electrode was manufactured in the same manner as in Example 1 except that the mixing ratio of the containing metal oxide (B) was changed to 60:40 by mass, and the thickness of the positive mixture layer was 58 µm. In addition, a negative electrode was manufactured in the same manner as in Example 14 except that the thickness of the negative electrode mixture layer was changed to 72 µm. A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the positive electrode and the negative electrode were used. The density (actual density) of the positive mix layer after the press process calculated|required by the said method was 3.75 g/cm<3>, and the filling rate was 76.9 %.

Example 17

The lithium-containing metal oxide (A) is changed to one in which the proportion of particles having a primary particle diameter of 0.5 μm or more is 100% by mass and the largest primary particle has a particle diameter of 5 μm, and this lithium-containing metal oxide (A) and lithium A positive electrode was manufactured in the same manner as in Example 1 except that the mixing ratio of the containing metal oxide (B) was changed to 80:20 by mass, and the thickness of the positive electrode mixture layer was 58 µm. In addition, a negative electrode was manufactured in the same manner as in Example 14 except that the thickness of the negative electrode mixture layer was changed to 72 µm. A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the positive electrode and the negative electrode were used. The density (actual density) of the positive mix layer after the press process calculated|required by the said method was 3.70 g/cm<3>, and the filling rate was 75.9%.

Comparative Example 1

_{LiNi 0.47} Co _0.19 Mn _0.29 Mg _{0.05 O 2} was used instead of the lithium-containing metal oxide (A ₎ , _and the thickness of the positive electrode mixture layer per side of the current collector was changed to 58 µm, It carried out similarly to Example 1, and manufactured the positive electrode. Moreover, it carried out similarly to Example 1, except having changed the thickness of the negative mix layer per single side|surface of an electrical power collector to 72 micrometers, and manufactured the negative electrode. A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this negative electrode and the positive electrode were used. The density (actual density) of the positive mix layer after the press process calculated|required by the said method was 3.80 g/cm<3>, and the filling rate was 77.3 %.

Comparative Example 2

A _positive electrode was prepared in the same manner as in Example ₁ except that _{LiNi 0.91} Co _0.03 Mn _0.02 Al _{0.02 Mg 0.02 O 2 was} used instead of the lithium-containing metal oxide (A), and this positive electrode A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that .

Comparative Example 3

Instead of the lithium-containing metal oxide (A), _{LiNi 0.78} Co _{0.20 Al 0.02 O 2 ,} the proportion of particles having a primary particle size of 0.5 μm or more is 30% by mass, and the largest primary particle size is A positive electrode was manufactured in the same manner as in Example 1 except that a 1 µm thing was used, and a prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this positive electrode was used.

Comparative Example 4

A _positive electrode was prepared in the same manner as in Comparative Example ₃ except that LiCo _0.992 Mg _0.006 Ti _0.001 Zr _{0.001 O 2} was used instead of the lithium-containing metal oxide (B) _. In the same manner as in Example 1, a prismatic nonaqueous electrolyte secondary battery was manufactured.

Comparative Example 5

The positive electrode active material was changed to only LiCo _0.984 Al _0.008 Mg _0.006 Ti _{0.001 Zr 0.001 O 2} , which is a lithium-containing metal oxide (B ₎ , _and the thickness of the positive electrode mixture layer per one side of the current collector was changed to 55 μm _. Except having changed to, it carried out similarly to Example 1, and manufactured the positive electrode. Moreover, it carried out similarly to Example 1, except having changed the thickness of the negative mix layer per single side|surface of an electrical power collector to 72 micrometers, and manufactured the negative electrode. A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this negative electrode and the positive electrode were used. The density (actual density) of the positive mix layer after the press process calculated|required by the said method was 3.95 g/cm<3>, and the filling rate was 79.0 %.

Comparative Example 6

The positive electrode active material was changed only to _{LiNi 0.78} Co _0.20 Al _{0.02 O 2} which is a lithium-containing metal oxide (A), _and the thickness of the positive electrode mixture layer per side of the current collector was changed to 57 μm. A positive electrode was manufactured in the same manner as in Example 1. Moreover, it carried out similarly to Example 1, and manufactured the negative electrode except having changed the thickness of the negative mix layer per single side|surface of an electrical power collector to 76 micrometers. A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this negative electrode and the positive electrode were used. The density (actual density) of the positive mix layer after the press process calculated|required by the said method was 3.60 g/cm<3>, and the filling rate was 75.1 %.

Reference Experimental Example 1

A positive electrode was manufactured in the same manner as in Example 1 except that the thickness of the positive electrode mixture layer per single side of the current collector was changed to 60 µm. Moreover, it carried out similarly to Example 1, and manufactured the negative electrode except having changed the thickness of the negative mix layer per single side|surface of an electrical power collector to 68 micrometers. A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that this negative electrode and the positive electrode were used.

Reference Experimental Example 2

A _positive electrode was prepared in the same manner as in Reference Experimental Example ₁ except that _{LiNi 0.91} Co _0.03 Mn _0.02 Al _{0.02 Mg 0.02 O 2 was} used instead of the lithium-containing metal oxide (A), and this A prismatic nonaqueous electrolyte secondary battery was manufactured in the same manner as in Reference Experimental Example 1 except that a positive electrode was used.

Table 1 shows the configuration of the positive electrode active material related to the positive electrode used in the nonaqueous electrolyte secondary battery of the Examples, Table 2 shows the configuration of the negative electrode active material related to the negative electrode used in the nonaqueous electrolyte secondary battery of the Examples, and the nonaqueous electrolyte secondary batteries of Comparative Examples and Reference Experimental Examples Table 3 shows the configuration of the positive electrode active material related to the positive electrode used for , and Table 4 shows the configuration of the negative electrode active material related to the negative electrode used for the nonaqueous electrolyte secondary batteries of Comparative Examples and Reference Experimental Examples, respectively. In addition, _{LiNi 0.47} Co _0.19 Mn _0.29 Mg _{0.05 O 2} used as a positive electrode for the battery of Comparative Example ₁ , _LiNi 0.91 used as a positive electrode for the battery of Comparative Example ₂ and Reference Experimental Example _{2 LiNi 0.78} Co _0.20 Al _{0.02 O 2} used as a _positive electrode related to Co _{0.03 Mn 0.02} Al _{0.02 Mg 0.02 O 2 and} Comparative Examples ₃ and 4 batteries contains lithium Although it does not correspond to a metal oxide (A), in Table 3, these are also described in the column of "lithium containing metal oxide (A)" for convenience. In addition, LiCo _0.992 Mg _0.006 Ti _0.001 Zr _{0.001 O 2} used as the _positive electrode related to the battery of Comparative Example ₄ does not correspond to _the lithium-containing metal oxide (B), but in Table 3, for convenience, These are also described in the column of "lithium containing metal oxide (B)".

In Table 1 and Table 3, the "ratio" of a lithium containing metal oxide (A) and a lithium containing metal oxide (B) means these content in positive electrode active material whole quantity. In addition, in Tables 1 and 2, "the ratio of particles having a primary particle diameter of 0.5 µm or more" and "the largest primary particle diameter" of the lithium-containing metal oxide (A) are the values obtained by the method (a) above. .

Moreover, each of the following evaluations was performed about the nonaqueous electrolyte secondary battery of an Example and a comparative example.

<Measurement of 1C discharge capacity>

Each of the batteries of Examples 1 to 17 and Comparative Examples 1 to 6 were charged at a constant current of 1 C to 4.4 V under an environment of 25° C., then charged at a constant voltage until the total charging time reached 2.5 hours, followed by 1 C In the furnace, constant current discharge was performed until the battery voltage reached 2.75 V, and the discharge capacity (1C discharge capacity) was measured. In addition, for each battery of Reference Experimental Examples 1 and 2, 1C discharge capacity was measured under the same conditions as the battery of Example 1, except that the charging voltage was 4.2 V.

<45℃ charge/discharge cycle characteristic evaluation>

Each of the batteries of Examples 1 to 17 and Comparative Examples 1 to 6 were charged at a constant current of 1 C to 4.4 V under an environment of 45° C., then charged at a constant voltage until the total charging time reached 2.5 hours, and then continued at 1 C A series of operations of performing constant current discharge with a battery voltage of 3.3 V as one cycle were repeated many of these, and the discharge capacity at the 300th cycle was measured. In addition, for each battery of Reference Experimental Examples 1 and 2, the discharge capacity at the 300th cycle was measured under the same conditions as the battery of Example 1 and the like, except that the charging voltage was set to 4.2 V. Then, for each battery, the value obtained by dividing the discharge capacity at the 300th cycle by the 1C discharge capacity described above was expressed as a percentage to determine the capacity retention rate.

Each of the above evaluation results is shown in Tables 5 and 6. In addition, in Tables 5 and 6, the 1C discharge capacity of each nonaqueous electrolyte secondary battery and the capacity retention rate at the time of the 45°C charge/discharge cycle characteristic evaluation are respectively relative values when the result of the battery of Example 1 is 100. indicates.

As shown in Tables 1 to 6, a positive electrode having a positive electrode mixture layer containing a lithium-containing metal oxide (A) having an appropriate composition and containing particles having a primary particle diameter of 0.5 µm or more in an appropriate ratio in an appropriate amount The nonaqueous electrolyte secondary batteries of Examples 1 to 17 using

On the other hand, the battery of Comparative Example 1 using a positive electrode active material having a large amount of Mn and Mg instead of the lithium-containing metal oxide (A), a positive electrode active material having a small amount of Co and a large amount of Mg instead of the lithium-containing metal oxide (A) The batteries of Comparative Example 2 using a lithium-containing metal oxide (A), the batteries of Comparative Examples 3 and 4 using a battery having a low ratio of particles having a primary particle diameter of 0.5 µm or more, and a lithium-containing metal oxide (A) were not used. The battery of Comparative Example 5 and Comparative Example 6 using only the lithium-containing metal oxide (A) had a low capacity retention rate in the evaluation of charge/discharge cycle characteristics at 45°C, and were poor in charge/discharge cycle characteristics under high temperature.

In addition, the nonaqueous electrolyte secondary battery of Reference Experimental Example 1 had the same configuration as the battery of Example 1 except that the thicknesses of the positive electrode mixture layer and the negative electrode mixture layer were slightly different, and the nonaqueous electrolyte secondary battery of Reference Experimental Example 2 was , the battery of Comparative Example 2 had the same configuration as the battery of Comparative Example 2, except that the thicknesses of the positive mixture layer and the negative electrode mixture layer were slightly different. For the batteries of these Reference Experimental Examples 1 and 2, as described above, the 1C discharge capacity was measured with the upper limit voltage during charging of 4.2 V, but as shown in Table 3, the capacity was small. That is, as can be seen from the comparison of the battery of Comparative Example 2 and the battery of Reference Experimental Example 2, if the upper limit voltage during charging is increased from 4.2V to 4.3V or more (4.4V), it is possible to increase the 1C discharge capacity On the other hand, although the charge/discharge cycle characteristics under high temperature decrease, as can be seen from the evaluation results of the battery of Example 1, a lithium-containing metal having an appropriate composition and containing particles having a primary particle diameter of 0.5 µm or more in an appropriate proportion By using the positive electrode provided with the positive electrode mixture layer containing the oxide (A) in an appropriate amount, it was possible to achieve high capacity while suppressing the decrease in charge/discharge cycle characteristics under high temperature.

1: positive electrode 2: negative electrode
3: separator

Claims (8)

A positive electrode used in a nonaqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator and a nonaqueous electrolyte, the positive electrode comprising:
It has a positive electrode mixture layer containing a positive electrode active material, a conductive support agent, and a binder,
The said positive mix layer, as said positive electrode active material, following General formula (1)
Li _a Ni _1-bcd Co _b Mn _c M ¹ _d Mg _e O ₂ (1)
[In the general formula (1), M ¹ is a metal element other than Li, Ni, Co and Mn, and at least one element selected from the group consisting of Al, Ti, Sr, Zr, Nb, Ag and Ba. and 0.9≤a≤1.10, 0.1≤b≤0.2, 0≤c≤0.2, 0.1≤b+c≤0.25, 0.003≤d≤0.06, and 0≤e≤0.003], and the primary particle diameter Lithium-containing metal oxide (A) containing 50 mass % or more of this 0.5 micrometer or more particle|grains;
The following general formula (2)
Li _f Co _1-gh M ² _g M ³ _h O ₂ (2)
[In the general formula (2), M ² is at least one element selected from the group consisting of Al, Mg and Er, and M ³ is Zr, Ti, Ni, Mn, Na, Bi, Ca, F , P, Sr, W, Ba, Mo, V, Sn, Ta, Nb, and at least one element selected from the group consisting of Zn, 0.9≤f≤1.10, 0.010≤g≤0.1, 0.0005≤h≤0.05 , g+h≤0.12] contains a lithium-containing metal oxide (B) represented by
When the total amount of the positive electrode active material contained in the positive mixture layer is 100% by mass, the content of the lithium-containing metal oxide (A) is 5 to 80% by mass. The positive electrode for a nonaqueous electrolyte secondary battery. delete The method of claim 1,
The positive electrode for nonaqueous electrolyte secondary batteries whose content of the said conductive support agent in the said positive mix layer exceeds 0.5 mass % and is 2.0 mass % or less. 4. The method of claim 1 or 3,
The positive electrode for a nonaqueous electrolyte secondary battery in which the said positive mix layer is formed on both surfaces of the metal collector whose thickness is 11 micrometers or less. A nonaqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, wherein the positive electrode is the positive electrode for a nonaqueous electrolyte secondary battery according to claim 1 or 3. 6. The method of claim 5,
The negative electrode includes a material containing Si and O as constituent elements (however, the atomic ratio x of O to Si is 0.5≤x≤1.5), and a non-water having a negative electrode mixture layer containing graphite as a negative electrode active material electrolyte secondary battery. 6. The method of claim 5,
A non-aqueous electrolyte secondary battery in which the upper limit voltage during charging is set to 4.3 V or higher. A non-aqueous electrolyte secondary battery according to claim 5 and a charging device,
A system for a non-aqueous electrolyte secondary battery, characterized in that the non-aqueous electrolyte secondary battery is charged with a voltage of 4.3 V or higher as an upper limit.

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