TWI790197B - Lithium copper composite oxide - Google Patents

Abstract

To provide a novel compound effective as a positive electrode active material for lithium ion secondary batteries. A copper-based composite oxide containing lithium represented by the following composition formula (1): Li _m Cu _y X ¹ O _n [in the composition formula (1), X ¹ represents Si or Ge, y represents 0.8~1.2, m represents 1.5 ~2.5, n means 3.9~4.1].

Description

Lithium copper composite oxide

Field of the Invention The present invention relates to lithium copper-based composite oxides.

Background of the Invention Lithium-ion secondary batteries occupy the most important position in energy storage devices, and in recent years their use has gradually expanded to plug-in hybrid car batteries and the like.

Regarding the positive electrode of the lithium-ion secondary battery, currently, positive electrode active materials such as LiCoO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ are the mainstream (Non-Patent Documents 1 and 2). However, these positive electrode materials containing positive electrode active materials contain a large amount of rare metals such as cobalt and nickel, so the price is high, and in addition, they have strong combustion-supporting properties, so they are also one of the main causes of thermal accidents.

Therefore, for the positive electrode active material that can solve this problem at present, iron-based poly(oxy)anion (poly(oxo)anion) materials, especially LiFePO ₄ , have attracted much attention (Non-Patent Document 3). The poly(oxy)anion system utilizes the abundant element iron in nature to greatly suppress the combustion-supporting property with a strong polyvalent anion acid skeleton. Prior art literature Non-patent literature

Non-Patent Document 1: Solid State Ionics, 3-4, 171-174, 1981 Non-Patent Document 2: Electrochem. Soc., 151(6), A914-A921, 2004 Non-Patent Document 3: Electrochem. Soc., 144( 4), 1188-1194, 1997

Summary of the Invention Problems to be Solved by the Invention However, the above-mentioned positive electrode materials such as LiFePO ₄ have polyanion units in the structure that are not involved in the charge-discharge reaction, so the theoretical capacity is higher than that of simple oxides such as LiCoO ₂ (274mAh/g) simple oxides) are low in positive electrode materials, and in addition, when they are put into practical use, they will be micronized or compounded with carbon, so the compactness will inevitably decrease.

The present invention is carried out in view of these current circumstances, and its object is to provide a novel compound that is effective as a positive electrode active material for lithium ion secondary batteries. means to solve problems

In order to solve the above-mentioned problems of the present invention, the inventors of the present invention have repeatedly made intensive studies. As a result, a lithium-copper composite oxide with a specific composition was successfully synthesized. In addition, we have found that this lithium-copper-based composite oxide is capable of insertion and extraction of lithium ions, and exhibits a high theoretical charge-discharge capacity that can be used as a positive electrode active material for lithium-ion secondary batteries. Based on these findings, the inventors of the present invention made further studies and completed the present invention.

That is, the present invention typically includes the subject matter described in the following items. Item 1. A lithium-copper composite oxide, represented by composition formula (1): Li _m Cu _y X ¹ O _n [in composition formula (1), X ¹ represents Si or Ge, y represents 0.8 ~ 1.2, m represents 1.5~2.5, n means 3.9~4.1]. Item 2. The lithium copper-based composite oxide according to item 1 above, which has a monoclinic crystal structure. Item 3. The lithium copper-based composite oxide according to item 1 or 2 above, which has an average particle diameter of 0.1 to 100 μm. Item 4. A method for producing the lithium copper-based composite oxide according to any one of items 1 to 3 above, comprising a step of heating a mixture containing lithium, copper, silicon or germanium, and oxygen. Item 5. The method described in item 4 above, wherein the heating temperature is 600°C or higher. Item 6. A positive electrode active material for a lithium ion secondary battery, containing a lithium-copper composite oxide represented by the following composition formula (2): Li _m Cu _y X ² O _n [in the composition formula (2), X ² represents Si, Ti or Ge, y means 0.8~1.2, m means 1.5~2.5, n means 3.9~4.1]. Item 7. A positive electrode for a lithium ion secondary battery comprising the positive electrode active material for a lithium ion secondary battery as described in the above item 6. Item 8. The positive electrode for a lithium ion secondary battery as described in the above item 7, further comprising a conductive additive. Item 9. A lithium ion secondary battery comprising the positive electrode for a lithium ion secondary battery according to item 7 or 8 above. Invention effect

The lithium-copper composite oxide of the present invention can insert and extract lithium ions, so it can be used as a positive electrode active material for lithium-ion secondary batteries. In particular, by using the lithium copper-based composite oxide of the present invention as a positive electrode active material, a lithium ion secondary battery capable of exhibiting a high charge and discharge capacity can be produced.

Modes for Carrying Out the Invention The present invention will be described in detail below. However, when a numerical range is indicated in this specification, both ends of the numerical range are included.

1. Lithium-copper-based composite oxide The lithium-copper-based composite oxide of the present invention is a compound shown in the following composition formula (1): Li _m Cu _y X ¹ O _n [in the composition formula (1), X ¹ represents Si or Ge, y means 0.8~1.2, m means 1.5~2.5, n means 3.9~4.1]. In addition, below, this compound may be described as a "compound represented by compositional formula (1)".

In the above composition formula (1), X ¹ is silicon (Si) or germanium (Ge).

In the above composition formula (1), y is 0.8~1.2, and 0.8~1.0 is suitable from the viewpoint of high capacity.

In the above-mentioned composition formula (1), m is 1.5-2.5, and from the standpoint of ease of insertion and detachment of lithium ions, capacity, and potential, it is preferably 1.75-2.25. Also, n in the above composition formula (1) is 3.9 to 4.1, and is preferably 3.95 to 4.05 from the standpoint of ease of insertion and removal of lithium ions, capacity, and potential.

The compound represented by the above-mentioned compositional formula (1) specifically includes Li ₂ CuSiO ₄ , Li ₂ CuGeO ₄ , and the like. Among them, Li ₂ CuSiO ₄ is preferable from the viewpoint of performance (especially capacity improvement) when used as a positive electrode active material for a lithium ion secondary battery described later.

The crystal structure of the compound represented by the above formula (1) is preferably a monoclinic crystal structure. In particular, the compound represented by the above composition formula (1) preferably has a monoclinic crystal structure as the main phase. In the compound represented by the above composition formula (1), the amount of the crystal structure of the main phase is not particularly limited, but based on the entire compound represented by the above composition formula (1), it is preferably 80 mol% or more, preferably 90 mol% or more. Therefore, the compound represented by the above composition formula (1) may be made into a material composed of a single-phase crystal structure, or may be made into a material having another crystal structure within the range that does not impair the effect of the present invention. In addition, the crystal structure of the compound represented by the above composition formula (1) can be confirmed by X-ray diffraction measurement.

The compound represented by the above-mentioned compositional formula (1) has peaks at various positions in the X-ray diffraction pattern using CuKα ray.

For example, Li ₂ CuSiO ₄ is suitable to have peaks at the following diffraction angles 2θ: 18.3~19.3°, 26.3~27.0°, 27.1~28.0°, 28.8~29.6°, 29.9~30.5°, 32.3~32.9°, 35.5~36.7° , 38.6~39.9°, 40.8~42.0°, 43.6~45.2°, 45.7~46.8°, 47.1~48.3°, 48.5~49.8°, 50.8~52.7°, 53.7~55.2°, 55.6~58.2°, 62.3~63.4° , 63.8~65.1° and 68.6~71.0°, etc.

For another example, Li ₂ CuGeO ₄ is suitable for peaks at the following diffraction angles 2θ: 17.9~19.2°, 24.9~27.0°, 31.6~33.4°, 35.0~39.2°, 41.2~43.4°, 49.2~51.5°, 53.2~55.4 °, 56.9~58.7°, 60.1~62.7°, 63.7~65.2°, 66.5~68.5°, 69.9~71.7°, 72.7~75.5° and 76.9~78.4°, etc.

The average particle size of the compound represented by the above composition formula (1) is not particularly limited, but it is preferably 0.1-100 μm, more preferably 0.1-50 μm from the viewpoint of shortening the Li ⁺ diffusion path. In addition, the average particle diameter of the compound represented by the said composition formula (1) can be confirmed by the scanning electron microscope (SEM).

2. Manufacturing method of lithium-copper composite oxide In the manufacturing method of the compound represented by the above composition formula (1), as long as the raw material compound used to obtain the mixture containing lithium, copper, silicon or germanium and oxygen is as long as the final mixture Lithium, copper, silicon, or germanium, and oxygen may be contained in predetermined ratios. For example, lithium-containing compounds, copper-containing compounds, silicon-containing compounds or germanium-containing compounds, and oxygen-containing compounds may be used.

There are no special restrictions on the types of compounds such as lithium-containing compounds, copper-containing compounds, silicon-containing compounds, germanium-containing compounds, and oxygen-containing compounds. Each of the four elements containing one lithium, copper, silicon or germanium, and oxygen can be Compounds of two or more types may be used in combination, or compounds containing two or more of lithium, copper, silicon, germanium, and oxygen may be used as a part of the raw materials and less than four compounds may be used in combination.

These raw material compounds are preferably compounds that do not contain metal elements (especially rare metal elements) other than lithium, copper, silicon or germanium and oxygen. In addition, elements other than lithium, copper, silicon, germanium, and oxygen contained in the raw material compound are desirably desorbed or volatilized by heat treatment described later.

Specific examples of such raw material compounds include the following compounds.

Examples of lithium-containing compounds include lithium metal (Li); lithium _bromide (LiBr) _; lithium oxalate (Li ₂ C ₂ O ₄ ); lithium fluoride (LiF); lithium iodide (LiI); ); lithium methoxide (LiOCH ₃ ); lithium ethoxide (LiOC ₂ H ₅ ); lithium hydroxide (LiOH); lithium nitrate (LiNO ₃ ); lithium chloride (LiCl); lithium carbonate (Li ₂ CO ₃ ), etc. .

Copper-containing compounds can be exemplified as: metallic copper (Cu); copper oxide (CuO); copper hydroxide (Cu(OH) ₂ ); copper carbonate (CuCO ₃ ); copper oxalate (CuC ₂ O ₄ ); copper sulfate (CuSO ₄ ); copper chloride (CuCl ₂ ); copper iodide (CuI); copper acetate (Cu(CH ₃ COO) ₂ ), etc.

Examples of silicon-containing compounds include: silicon (Si); silicon oxide (SiO ₂ ); tetraethoxysilane (SiOC ₂ H ₅ ); tetramethoxysilane (SiOCH ₃ ); silicon tetrabromide (SiBr ₄ ); Silicon (SiCl ₄ ), etc.

Germanium compounds can be exemplified as: germanium (Ge); germanium oxide (GeO ₂ ); germanium tetrachloride (GeCl ₄ ); germanium tetrabromide (GeBr ₄ ); germanium tetraiodide (GeI ₄ ); GeF ₄ ); germanium disulfide (GeS ₂ ), etc.

Oxygen-containing compounds can be exemplified: lithium hydroxide (LiOH); lithium carbonate (Li ₂ CO ₃ ); copper oxide (CuO); copper hydroxide (Cu(OH) ₂ ); copper carbonate (CuCO ₃ ); CuC ₂ O ₄ ); silicon oxide (SiO ₂ ); germanium oxide (GeO ₂ ), etc.

In addition, hydrates can also be used for these raw material compounds.

Moreover, the raw material compound used for the manufacturing method of this invention may use a commercial item, and may synthesize|combine it suitably and use. When synthesizing each raw material compound, the synthesis method is not particularly limited, and a known method can be used.

The shape of these raw material compounds is not particularly limited. From the viewpoint of ease of handling and the like, the powder form is preferable. Also, from the viewpoint of reactivity, the particles should be fine, and preferably in the form of a powder with an average particle diameter of 1 μm or less (preferably about 10-500 nm, particularly preferably about 60-80 nm). In addition, the average particle size of the raw material compound can be measured by a scanning electron microscope (SEM).

A mixture containing lithium, copper, silicon or germanium and oxygen can be obtained by mixing necessary materials among the above-mentioned raw material compounds.

The mixing ratio of each raw material compound is not specifically limited, It is preferable to mix so that the compound represented by the said composition formula (1) which becomes a final product may have a composition. The mixing ratio of the raw material compounds is preferably such that the ratio of each element contained in the raw material compound is the same as the ratio of each element in the compound represented by the above composition formula (1) to be produced.

The method of preparing a mixture containing lithium, copper, silicon, or germanium and oxygen is not particularly limited, and a method capable of uniformly mixing each raw material compound can be used. For example, it is possible to use milk-caster mixing, mechanical grinding, co-precipitation, a method of dispersing and mixing each raw material compound in a solvent, and a method of dispersing and mixing each raw material compound in a solvent together. Among them, the mixture can be obtained in a relatively simple way by mixing milk castor, and a more uniform mixture can be obtained by co-precipitation.

In addition, when performing mechanical grinding treatment as a mixing means, for example, a ball mill, a vibration mill, a turbo mill, a disc mill, etc. can be used as a mechanical grinding device, and a ball mill is preferable among them. In addition, when performing mechanical grinding treatment, mixing and heating are preferably performed simultaneously.

The gas atmosphere during mixing and heating is not particularly limited, and for example, an inert gas atmosphere such as argon or nitrogen, a hydrogen atmosphere, or the like can be used. In addition, mixing and heating may be performed under reduced pressure such as vacuum.

When the mixture containing lithium, copper, silicon or germanium and oxygen is heated, the heating temperature is not particularly limited. From the point of view of further improving the crystallinity and electrode characteristics (capacity and potential) of the compound represented by the above composition formula (1) From the point of view, it is preferable to set it at 600°C or higher, more preferably at 700°C or higher, more preferably at 800°C or higher, and especially preferably at 900°C or higher. In addition, the upper limit of the heating temperature is not particularly limited, and the temperature (for example, about 1500° C.) may be sufficient to easily produce the compound represented by the above-mentioned compositional formula (1). In other words, the heating temperature should be set at 600-1500°C, more preferably at 700-1500°C, more preferably at 800-1500°C, and most preferably at 900-1500°C.

3. Positive electrode active material for lithium ion secondary battery The compound represented by the above composition formula (1) has the above composition and crystal structure, so it can insert and detach lithium ions, so it can be used as a positive electrode active material for lithium ion secondary battery. Therefore, the present invention includes the positive electrode active material for lithium ion secondary batteries containing the compound represented by the above composition formula (1).

Moreover, not only the compound represented by the composition formula (1), but also the lithium-copper composite oxide represented by the following composition formula (2) can intercalate and deintercalate lithium ions, so it can be used as a positive electrode active material for lithium ion secondary batteries. Li _m Cu _y X ² O _n [In composition formula (2), X ² represents Si, Ti or Ge, y represents 0.8~1.2, m represents 1.5~2.5, n represents 3.9~4.1]. In addition, the lithium-copper composite oxide represented by the above composition formula (2) may be described as "the compound represented by the above composition formula (2)" below. Therefore, the present invention includes the positive electrode active material for lithium ion secondary batteries containing the compound represented by the above composition formula (2).

In addition, the positive electrode active material for lithium ion secondary batteries containing the compound represented by the above compositional formula (1) and the positive electrode active material for lithium ion secondary batteries containing the compound represented by the above compositional formula (2) are sometimes collectively described below It is "the positive electrode active material for the lithium ion secondary battery of the present invention".

In the above composition formula (2), X ² is silicon (Si), titanium (Ti) or germanium (Ge).

In the above composition formula (2), y is 0.8~1.2, and 0.8~1.0 is suitable from the viewpoint of high capacity.

In the above compositional formula (2), m is 1.5 to 2.5, and is preferably 1.75 to 2.25 from the viewpoints of the ease of insertion and extraction of lithium ions, capacity, and potential. n is 3.9 to 4.1, preferably 3.95 to 4.05 from the viewpoint of the ease of insertion and removal of lithium ions, capacity, and potential.

The compound represented by the above composition formula (2) specifically includes Li ₂ CuSiO ₄ , Li ₂ CuTiO ₄ , Li ₂ CuGeO ₄ and the like. Among them, Li ₂ CuSiO ₄ is preferable from the viewpoint of performance (especially capacity improvement) when used as a positive electrode active material for lithium ion secondary batteries.

The crystal structure of the compound represented by the above formula (2) is preferably a monoclinic crystal structure. In particular, the compound represented by the above composition formula (2) preferably has a monoclinic crystal structure as the main phase. In the compound represented by the above composition formula (2), the amount of the crystal structure of the main phase is not particularly limited, but it is preferably 80 mol% or more, preferably 90 mol% or more, based on the entire compound represented by the above composition formula (2). Therefore, the compound represented by the above composition formula (2) may be a material composed of a single-phase crystal structure, or may be a material having another crystal structure within the range not impairing the effect of the present invention. In addition, the crystal structure of the compound represented by the above composition formula (2) can be confirmed by X-ray diffraction measurement.

The compound represented by the above-mentioned compositional formula (2) has peaks at various positions in the X-ray diffraction diagram using CuKα ray.

For example, Li ₂ CuSiO ₄ is suitable to have peaks at the following diffraction angles 2θ: 18.3~19.3°, 26.3~27.0°, 27.1~28.0°, 28.8~29.6°, 29.9~30.5°, 32.3~32.9°, 35.5~36.7° , 38.6~39.9°, 40.8~42.0°, 43.6~45.2°, 45.7~46.8°, 47.1~48.3°, 48.5~49.8°, 50.8~52.7°, 53.7~55.2°, 55.6~58.2°, 62.3~63.4° , 63.8~65.1° and 68.6~71.0°, etc.

For another example, Li ₂ CuGeO ₄ is suitable for peaks at the following diffraction angles 2θ: 17.9~19.2°, 24.9~27.0°, 31.6~33.4°, 35.0~39.2°, 41.2~43.4°, 49.2~51.5°, 53.2~55.4 °, 56.9~58.7°, 60.1~62.7°, 63.7~65.2°, 66.5~68.5°, 69.9~71.7°, 72.7~75.5° and 76.9~78.4°, etc.

The average particle size of the compound represented by the above composition formula (2) is not particularly limited, but it is preferably 0.1-100 μm, more preferably 0.1-50 μm from the viewpoint of shortening the Li ⁺ diffusion path. In addition, the average particle size of the compound represented by the above-mentioned compositional formula (2) can be confirmed by a scanning electron microscope (SEM).

The method for producing the compound represented by the above compositional formula (2) includes the step of heating a mixture containing lithium, copper, the above X ² and oxygen.

There is no particular limitation on the types of compounds such as lithium-containing compounds, copper-containing compounds, ^X2- containing compounds, and oxygen-containing compounds, and four or more of each element containing one lithium, copper, ^X2 , and oxygen may be used. Compounds of different types may be used in combination, or a compound containing two or more elements of lithium, copper, ^X2 , and oxygen may be used as a part of the raw materials and less than four types of compounds may be used in combination.

These raw material compounds are preferably compounds that do not contain metal elements (especially rare metal elements) other than lithium, copper, X ² and oxygen. In addition, elements other than lithium, copper, ^X2 , and oxygen contained in the raw material compound are desirably desorbed or volatilized by heat treatment described later.

Specific examples of such raw material compounds include the following compounds.

Examples of _lithium -containing compounds include: lithium oxalate (Li ₂ C ₂ O ₄ ); lithium hydroxide ₍ LiOH); lithium nitrate (LiNO ₃ ); lithium chloride (LiCl);

Copper-containing compounds can be exemplified as: metallic copper (Cu); copper oxide (CuO); copper hydroxide (Cu(OH) ₂ ); copper carbonate (CuCO ₃ ); copper oxalate (CuC ₂ O ₄ ); II) (CuCl ₂ ); copper (II) sulfate (CuSO ₄ ); copper (II) nitrate (Cu(NO ₃ ) ₂ ); copper (II) sulfate (CuSO ₄ ), etc.

Examples of titanium-containing compounds include: titanium tetrachloride (TiCl ₄ ); titanium hydroxide (Ti(OH) ₂ ), and the like. Examples of silicon-containing compounds include silicon (Si); silicon oxide (SiO ₂ ), and the like.

Examples of germanium compounds include germanium (Ge); germanium oxide (GeO ₂ ), and the like.

Oxygen-containing compounds can be exemplified: lithium hydroxide (LiOH); lithium carbonate (Li ₂ CO ₃ ); copper oxide (CuO); copper hydroxide (Cu(OH) ₂ ); copper carbonate (CuCO ₃ ); CuC ₂ O ₄ ); Silicon oxide (SiO ₂ ); Titanium oxide (TiO ₂ ); Titanium hydroxide (Ti(OH) ₂ ); Germanium oxide (GeO ₂ ), etc.

In addition, hydrates can also be used for these raw material compounds.

Moreover, the raw material compound used in the manufacturing method of the compound represented by the said composition formula (2) may use a commercial item, and may synthesize|combine suitably and use it. When synthesizing each raw material compound, the synthesis method is not particularly limited, and a known method can be used.

The shape of these raw material compounds is not particularly limited. From the viewpoint of ease of handling and the like, the powder form is preferable. Also, from the viewpoint of reactivity, the particles should be fine, and preferably in the form of a powder with an average particle diameter of 1 μm or less (preferably about 10 to 100 nm, particularly preferably about 60 to 80 nm). In addition, the average particle size of the raw material compound can be measured by a scanning electron microscope (SEM).

A mixture containing lithium, copper, X ² and oxygen can be obtained by mixing the necessary materials among the above-mentioned raw material compounds.

The mixing ratio of each raw material compound is not specifically limited, It is preferable to mix so that the compound represented by the said composition formula (2) which becomes a final product may have a composition. The mixing ratio of the raw material compounds is preferably such that the ratio of each element contained in the raw material compound is the same as the ratio of each element in the compound represented by the above composition formula (2) to be produced.

The method of preparing a mixture containing lithium, copper, X ² and oxygen is not particularly limited, and a method capable of uniformly mixing each raw material compound can be used. For example, it is possible to use milk-caster mixing, mechanical grinding, co-precipitation, a method of dispersing and mixing each raw material compound in a solvent, and a method of dispersing and mixing each raw material compound in a solvent together. Among them, the mixture can be obtained in a relatively simple way by mixing milk castor, and a more uniform mixture can be obtained by co-precipitation.

In addition, when performing mechanical grinding treatment as a mixing means, for example, a ball mill, a vibration mill, a turbo mill, a disc mill, etc. can be used as a mechanical grinding device, and a ball mill is preferable among them. In addition, when performing mechanical grinding treatment, mixing and heating are preferably performed simultaneously.

The gas atmosphere during mixing and heating is not particularly limited, and for example, an inert gas atmosphere such as argon or nitrogen, a hydrogen atmosphere, or the like can be used. In addition, mixing and heating may be performed under reduced pressure such as vacuum.

When the mixture containing lithium, copper, ^X2 and oxygen is heated, the heating temperature is not particularly limited, if from the point of view of further improving the crystallinity and electrode characteristics (capacity and potential) of the compound represented by the above composition formula (2) obtained Look, it is better to set it above 600°C, preferably above 700°C, more preferably above 800°C, and especially preferably above 900°C. In addition, the upper limit of the heating temperature is not particularly limited, and the temperature (for example, about 1500° C.) may be sufficient to easily produce the compound represented by the above-mentioned compositional formula (2). In other words, the heating temperature should be set at 600-1500°C, more preferably at 700-1500°C, more preferably at 800-1500°C, and most preferably at 900-1500°C.

The positive electrode active material for lithium-ion secondary batteries of the present invention may also form a complex with a compound represented by the above formula (1) or a compound represented by formula (2) and a carbon material (such as carbon black such as acetylene black). Thereby, since the carbon material suppresses particle growth during firing, a fine particle positive electrode active material for lithium ion secondary batteries having excellent electrode characteristics can be obtained. At this time, the content of the carbon material in the positive electrode active material for lithium ion secondary batteries of the present invention is preferably 1-30% by mass, more preferably 3-20% by mass, especially preferably 5-15% by mass.

The positive electrode active material for lithium ion secondary batteries of the present invention contains the compound represented by the above compositional formula (1) or the compound represented by the compositional formula (2). The positive electrode active material for lithium ion secondary battery of the present invention can only be made of the compound shown in the above-mentioned compositional formula (1) or the compound shown in the compositional formula (2), or can also contain the compound shown in the above-mentioned compositional formula (1) or In addition to the compound represented by the compositional formula (2), unavoidable impurities are contained. Such unavoidable impurities include the above-mentioned raw material compounds and the like. The content of unavoidable impurities is less than 10 mol%, preferably less than 5 mol%, more preferably less than 2 mol%, within the range that does not impair the effect of the present invention.

4. Positive electrode for lithium ion secondary battery and lithium ion secondary battery The positive electrode material for lithium ion secondary battery of the present invention and lithium ion secondary battery are except using the compound shown in above-mentioned composition formula (1) or composition formula (2) In addition to the compound shown as the positive electrode active material, the basic structure can be the same as that of the known nonaqueous electrolyte (nonaqueous) lithium ion secondary battery positive electrode and nonaqueous electrolyte (nonaqueous) lithium ion secondary battery. For example, the positive electrode, the negative electrode, and the separator may be arranged in the battery container in such a manner that the positive electrode and the negative electrode are separated from each other through the separator. Then, the lithium ion secondary battery of the present invention is produced by filling the battery container with a non-aqueous electrolytic solution and then sealing the battery container. In addition, the lithium ion secondary battery of the present invention may also be a lithium secondary battery. In this specification, a "lithium ion secondary battery" refers to a secondary battery using lithium ions as carrier ions, and a "lithium secondary battery" refers to a secondary battery using lithium metal or lithium alloy as a negative electrode active material.

The positive electrode for the lithium ion secondary battery of the present invention may have a structure in which the positive electrode active material containing the compound represented by the above composition formula (1) or the compound represented by the composition formula (2) is carried on a positive electrode current collector. For example, it can be produced by coating the positive electrode material containing the compound represented by the above composition formula (1) or the compound represented by composition formula (2), a conductive additive, and a binder as required.

As the conductive aid, for example, carbon materials such as acetylene black, Ketjen black, carbon nanotubes, vapor-phase-processed carbon fibers, carbon nanofibers, black lead, and cokes can be used. The shape of the conductive additive is not particularly limited, for example, a powder form can be used.

As the binder, for example, fluororesins such as polyvinylidene fluoride and polytetrafluoroethylene can be used.

The contents of various components in the positive electrode material are not particularly limited, and can be appropriately determined within a wide range. For example, it is suitable to contain 50-95% by volume (especially 70-90% by volume) of the compound shown in the above composition formula (1) or the compound shown by composition formula (2), 2.5-25% by volume (especially 5-15% by volume) %) and 2.5~25% by volume (especially 5~15% by volume) of binder.

Examples of materials constituting the positive electrode current collector include aluminum, platinum, molybdenum, and stainless steel. Examples of the shape of the positive electrode current collector include a porous body, foil, plate, and mesh made of fibers.

In addition, the coating amount of the positive electrode material of the positive electrode current collector is not particularly limited, and should be appropriately determined according to the application of the lithium ion secondary battery and the like.

The negative electrode active material constituting the negative electrode can be exemplified: lithium metal; silicon; silicon-containing clathrate compound; lithium alloy; M ¹ M ² ₂ O ₄ (M ¹ : Co, Ni, Mn, Sn, etc., M ² : Mn, Fe, Zn, etc.); M ³ ₃ O ₄ (M ³ : Fe, Co, Ni, Mn, etc.), M ⁴ ₂ O ₃ (M ⁴ : Fe, Co, Oxidation of metals such as Ni, Mn, etc.), MnV ₂ O ₆ , M ⁵ O ₂ (M ⁵ : Sn, Ti, etc.), M ⁶ O (M ⁶ : Fe, Co, Ni, Mn, Sn, Cu, etc.) materials; black lead, hard carbon, soft carbon, graphene; the above-mentioned carbon materials; organic compounds such as Li ₂ C ₆ H ₄ O ₄ , Li ₂ C ₈ H ₄ O ₄ , Li ₂ C ₁₆ H ₈ O _{4 ,} etc.

Lithium alloys include, for example, alloys containing lithium and aluminum as constituent elements, alloys containing lithium and zinc as constituent elements, alloys containing lithium and lead as constituent elements, alloys containing lithium and manganese as constituent elements, lithium and bismuth Alloys containing lithium and nickel as constituent elements, alloys containing lithium and antimony as constituent elements, alloys containing lithium and tin as constituent elements, alloys containing lithium and indium as constituent elements; metals (scandium , titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, etc.) and MXene alloys with carbon as constituent elements, M ⁷ _x BC ₃ -series alloys (M ⁷ : Sc, Ti, V, Cr, Zr, Nb , Mo, Hf, Ta, etc.) and other quaternary layered carbide or nitride compounds.

The negative electrode can be composed of negative electrode active material, and can also be composed of negative electrode material loaded on the negative electrode current collector. The negative electrode material contains negative electrode active material, conductive additive and binder if required. When the negative electrode material is carried on the negative electrode current collector, it can be manufactured by applying the negative electrode mixture containing the negative electrode active material, the conductive additive and the binder as required to the negative electrode current collector.

When the negative electrode is composed of a negative electrode active material, it can be obtained by molding the above negative electrode active material into a shape (plate shape, etc.) conforming to the electrode.

In addition, when the negative electrode current collector is used to carry the negative electrode material, the types of the conductive auxiliary agent and the binder, and the contents of the negative electrode active material, conductive auxiliary agent, and binder can be applied to the above-mentioned positive electrode. Examples of materials constituting the negative electrode current collector include aluminum, copper, nickel, and stainless steel. Examples of the shape of the negative electrode current collector include porous bodies, foils, plates, meshes made of fibers, and the like. In addition, the coating amount of the negative electrode material on the negative electrode current collector should be appropriately determined according to the application of the lithium ion secondary battery and the like.

The separator is not limited as long as it is made of a material that can separate the positive electrode and the negative electrode in the battery, hold the electrolyte, and ensure ion conductivity between the positive electrode and the negative electrode. For example, it can be made of polyolefin resins such as polyethylene, polypropylene, polyimide, polyvinyl alcohol, and terminally aminated polyethylene oxide; fluorine resins such as polytetrafluoroethylene; acrylic resin; nylon; aromatic aramid; Composed of inorganic glass, ceramics and other materials, materials in the form of porous membranes, non-woven fabrics, and woven fabrics are used.

The non-aqueous electrolyte is preferably one containing lithium ions. Examples of such electrolytes include lithium salt solutions, ionic liquids made of lithium-containing inorganic materials, and the like.

Lithium salts can be exemplified: lithium halides such as lithium chloride, lithium bromide, and lithium iodide; inorganic lithium salt compounds such as lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium hexafluoroarsenate; bis(trifluoromethylsulfonate) Lithium acyl)imide, lithium bis(perfluoroethanesulfonyl)imide, lithium benzoate, lithium salicylate, lithium phthalate, lithium acetate, lithium propionate, Grignard reagent and other organic lithium salt compounds etc.

In addition, the solvent can be exemplified: carbonate compounds such as propylene carbonate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate; γ-butyrolactone, γ-valerolactone, etc. Lactone compounds; tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, diisopropyl ether, dibutyl ether, methoxymethane, ethylene glycol dimethyl ether (glyme), dimethoxyethane, dimethoxyethane Methoxymethane, diethoxymethane, diethoxyethane, propylene glycol dimethyl ether and other ether compounds; acetonitrile; N,N-dimethylformamide; N-propyl-N-methylpyrrolidinium bis (Trifluoromethanesulfonyl)imide, etc.

In addition, instead of the above-mentioned non-aqueous electrolytic solution, a solid electrolyte may also be used. Examples of solid electrolytes include lithium ion conductors such as Li ₁₀ GeP ₂ S ₁₂ , Li ₇ P ₃ S ₁₁ , Li ₇ La ₃ Zr ₂ O ₁₂ , La _0.51 Li _0.34 TiO _2.94 , and the like.

This lithium ion secondary battery of the present invention can ensure higher potential and energy density during oxidation-reduction reaction (charge-discharge reaction) due to the use of the compound represented by the composition formula (1) or the compound represented by the composition formula (2). , and good safety (polyvalent anion skeleton) and practicability. Therefore, the lithium ion secondary battery of the present invention is suitable for use in, for example, devices that require miniaturization and high performance. Example

Hereinafter, examples are given to further describe the present invention in detail, but the present invention is not limited by the following examples.

Example 1: Li ₂ CO ₃ (manufactured by RARE METALLIC Co., Ltd.; 99.9% (3N)) and CuO (manufactured by High Purity Chemical Research Institute Co., Ltd.; 99.99% (4N)) were used for the synthesis of Li ₂ CuSiO ₄ raw material powder ) and precipitated amorphous SiO ₂ (manufactured by Kanto Chemical Co., Ltd.; 3N). Weigh Li ₂ CO ₃ , CuO and SiO ₂ so that lithium:copper:silicon (molar ratio) becomes 2:1:1, put them into a chromium steel container together with zirconia balls (15mmΦ×10), add acetone The mixture was pulverized and mixed at 400 rpm for 24 hours with a planetary ball mill (manufactured by Fritsch, trade name: P-6). Then, after removing acetone under reduced pressure, the recovered powder was hand-kneaded into granules, and fired at 600°C, 700°C, 800°C, 900°C or 1000°C for 1 hour under argon flow. At this time, the temperature increase rate was set at 400° C./h. In addition, the cooling rate was set to 100° C./h up to 300° C., and then left to cool to room temperature by natural cooling. The obtained products (Li ₂ CuSiO ₄ ) were confirmed by powder X-ray diffraction (XRD). The results are shown in Figure 1.

Figure 2 shows the comparison results of the X-ray diffraction patterns of Li ₂ CuSiO ₄ and Li ₂ SiO ₃ obtained when the firing temperature is set to 900°C. The Li ₂ SiO ₃ is composed of CuO and Li ₂ CO ₃ and SiO ₂ generators.

In addition, an X-ray diffraction measurement device (manufactured by Rigaku Corporation, trade name: RINT2200) was used in the powder X-ray diffraction (XRD) measurement system, and CuKα monochromatized by a monochromator was used as the X-ray source. Measurement conditions were set to a tube voltage of 5 kV and a tube current of 300 mA, and data collection was performed. At this point, the scan rate was set so that the intensity was about 10,000 counts. In addition, the sample used for the measurement has been pulverized sufficiently to make the particles uniform. The structural analysis system uses Rietveld analysis, and the analysis software uses JANA-2006.

It is confirmed from Fig. 1 that when the firing temperature is 800°C or higher, many main peaks can be seen at least at the 2θ value of 15° to 70°. It is also known that the peak seen at the 2θ value of 15~70° is stronger when the firing temperature is higher, so the firing temperature should be higher.

From Figure 1, the main peaks confirmed at the 2θ value of 15~70° correspond to the single-phase Li ₂ CuSiO ₄ . It can be seen that the product has a single-phase Li ₂ CuSiO ₄ . In addition, no peak originating from _Li 2 SiO ₃ formed from the raw material compound CuO and the raw material compounds Li ₂ CO ₃ and SiO ₂ was not confirmed in Fig. 2 , which also shows that a single-phase Li ₂ CuSiO ₄ is obtained.

Also, as can be seen from Figure 1, when the firing temperature is set to 900°C, the obtained Li ₂ CuSiO ₄ crystal has a peak at the diffraction angle indicated by the following 2θ in the X-ray diffraction pattern obtained by powder X-ray diffraction: 18.31~ 19.24°, 26.39~26.96°, 27.22~27.39°, 28.90~29.59°, 38.65~39.82°, 40.88~41.92°, 43.63~45.12°, 45.72~46.70°, 47.21~48.23°, 48.56~49.7 1°, 50.87~ 52.69°, 53.81~55.14°, 55.66~58.17°, 62.40~63.33°, 63.88~65.04° and 68.67~70.90°. From this result, it can be known that the obtained Li ₂ CuSiO ₄ crystal system has a monoclinic crystal structure (space group C2/m), and the lattice constants are a=6.457~6.484Å, b=3.340~3.345Å, c=9.504~11.183Å , β=93.65~121.78° and the unit lattice volume (V) is 205.1~206.0Å ³ crystals.

In addition, Li ₂ CuSiO ₄ obtained when the firing temperature was set to 900° C. was observed with a scanning electron microscope (SEM). The results are shown in Figure 3. In addition, the scale bar in FIG. 3 shows 11.7 micrometers. It can be seen from Fig. 3 that Li ₂ CuSiO ₄ with a particle size of about 3-10 μm can be obtained.

Also, the chemical composition of the product obtained at a firing temperature of 900°C was measured by ICP-AES (measuring device: iCAP6500, manufactured by Thermo Fisher Scientific Inc.), and Li _2.08 Cu _1.05 Si _1.00 O ₄ was obtained.

Example 2: Li ₂ CO ₃ (manufactured by RARE METALLIC Co., Ltd.; 99.9% (3N)) and CuO (manufactured by High Pure Chemical Research Institute Co., Ltd.; 99.99% (4N)) were used for the synthesis of Li ₂ CuGeO ₄ raw material powder ) and GeO ₂ (manufactured by Kanto Chemical Co., Ltd.; 99.99% (4N)). Weigh Li ₂ CO ₃ , CuO and GeO ₂ so that lithium: copper: germanium (molar ratio) becomes 2:1:1, put them together with zirconia balls (15mmΦ×10 pieces) into a chrome steel container, add acetone The mixture was pulverized and mixed at 400 rpm for 24 hours with a planetary ball mill (manufactured by Fritsch, trade name: P-6). Then, after the acetone was removed under reduced pressure, the recovered powder was hand-kneaded into granules and fired at 700°C, 800°C or 900°C for 1 hour under argon flow. At this time, the temperature increase rate was set at 400° C./h. In addition, the cooling rate was set to 100° C./h up to 300° C., and then left to cool to room temperature by natural cooling. Each of the obtained products (Li ₂ CuGeO ₄ ) was confirmed by powder X-ray diffraction (XRD) in the same manner as in Example 1. The results are shown in Figure 4.

It is confirmed from Fig. 4 that when the firing temperature is 700°C or higher, many main peaks can be seen at least at the 2θ value of 15° to 80°. These peaks correspond to single-phase Li ₂ CuGeO ₄ , so it can be seen that single-phase Li ₂ CuGeO ₄ is obtained in the product. It is also known that the peak seen at the 2θ value of 15~80° is stronger when the firing temperature is higher, so the higher firing temperature is suitable.

Also, it can be seen from Fig. 4 that when the calcination temperature is set to 700°C, the Li ₂ CuSiO ₄ crystal obtained by powder X-ray diffraction has a peak at the diffraction angle indicated by the following 2θ in the X-ray diffraction pattern: 17.94~19.15 °, 24.96~26.91°, 31.65~33.32°, 35.07~39.17°, 41.30~43.39°, 49.29~51.44°, 53.24~55.30°, 56.92~58.63°, 60.16~62.63°, 63.79~65.19°, 66 .57~68.44 °, 69.92~71.64°, 72.80~75.41° and 76.94~78.33°. From this result, it can be known that the obtained Li ₂ CuGeO ₄ crystal system has a monoclinic crystal structure (space group C2/m), and the lattice constants are a=5.491~5.552Å, b=9.645~9.691Å, c=5.491~5.552Å , β=119.69~120.75° and the unit lattice volume (V) is 256.1~256.6Å ³ crystals.

In addition, Li ₂ CuGeO ₄ obtained when the firing temperature was set to 900° C. was observed with a scanning electron microscope (SEM). The results are shown in Figure 5. In addition, the scale bar in Fig. 5 indicates 27.0 μm. It can be seen from Fig. 5 that Li ₂ CuGeO ₄ with a particle size of about 1-50 μm can be obtained.

It was also found that the mass ratio of Cu to Ge was 1:0.956 when the chemical composition of the product obtained at a firing temperature of 900° C. was measured by the EDX method (measurement device: JSM-7800F, manufactured by JEOL Ltd.).

Example 3: Determination of the charge-discharge characteristics of Li ₂ CuSiO ₄ In order to perform the charge-discharge measurement, Li ₂ CuSiO ₄ , polyvinylidene fluoride (PVDF) and acetylene black (AB ) was mixed with an agate mortar at a volume ratio of 85:7.5:7.5, and the resulting slurry was coated on the aluminum foil (thickness 20 μm) of the positive electrode collector, and punched into a circle with a diameter of 8 mm to make the positive electrode. In addition, in order not to separate the sample from the positive electrode current collector, it was crimped at 30 to 40 mPa.

Metal lithium with 14mmφ perforation is used for the negative electrode, and two porous membranes with 18mmφ perforation (trade name: celgard 2500) are used for the separator. The electrolyte system is used: Ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed into a solvent at a volume ratio of 1:2, and LiPF ₆ is dissolved in the solvent at a concentration of 1mol/ ^dm3 as a supporting electrolyte. The prepared electrolyte solution (manufactured by Kishida Chemical Co., Ltd.). Based on the use of lithium metal, and the main cause of the increase in resistance if water is mixed in the electrolyte in the production of the battery, the battery is produced in a glove box under an argon atmosphere. As the battery system, a CR2032 coin-type battery shown in FIG. 6 was used. Before entering the charge-discharge test, the potential (that is, the open circuit potential) in the state where no current is applied to the electrode is measured. Constant current charge and discharge measurement uses a voltage switcher, set to C/20 charge and discharge rate or C/50 charge and discharge rate, current 10mA/g, upper limit voltage 4.8V, lower limit voltage 1.5V, starting from charging. In addition, the charge-discharge measurement was carried out with the battery placed in a 55°C thermostat. The measurement results of the open circuit potential are shown in Figure 7, the measurement results of the charge-discharge characteristics at the C/20 charge-discharge rate (the relationship between each cycle and the discharge capacity) are shown in Figure 8, and the charge-discharge characteristics at the C/50 charge-discharge rate The measurement results are shown in FIG. 9 . In addition, the charge-discharge rate (C-rate) means the current density required to charge and discharge the theoretical capacity from the electrode active material for 1 hour.

It can be seen from FIG. 7 that the open circuit potential of Li ₂ CuSiO ₄ is about 3.0V. Also, it can be seen from Fig. 8 that the initial charge capacity extracted under the C/20 charge-discharge rate is about 110mAh/g. In addition, the theoretical capacity is 316mAh/g, and the initial charge and discharge capacity of Li ₂ CuSiO ₄ corresponds to about 1/3 of the theoretical capacity. As shown in Figure 8, the voltage (average operating voltage) at the intersection point of the charge curve and discharge curve is about 3.3V, which shows that Li ₂ CuSiO ₄ can be effectively used as a high-potential and high-capacity positive electrode material.

In addition, it was confirmed from FIG. 9 that the initial charge capacity of Li ₂ CuSiO ₄ was 220 mAh/g (capacity corresponding to about 70% of the theoretical capacity) at the charge-discharge rate of C/50. From this point of view also, Li ₂ CuSiO ₄ can be expected to be used as a high-capacity material.

Also, except that Li ₂ CuSiO ₄ was not used, a positive electrode was prepared in the same manner as above, and a charge-discharge test was performed at a charge-discharge rate of C/20 under the same conditions as above. The results are shown in Figure 10.

It was confirmed from FIG. 10 that the charge-discharge capacity could not be obtained in the electrode not using Li ₂ CuSiO ₄ . Comparing FIG. 8 and FIG. 10 shows that the high charge-discharge capacity shown in FIG. 8 is derived from Li ₂ CuSiO ₄ .

Example 4: Determination of the charge-discharge characteristics of Li ₂ CuGeO ₄ In order to perform the charge-discharge measurement, Li ₂ CuGeO ₄ , polyvinylidene fluoride (PVDF) and acetylene black (AB ) was mixed with an agate mortar at a volume ratio of 85:7.5:7.5, and the resulting slurry was coated on the aluminum foil (thickness 20 μm) of the positive electrode collector, and punched into a circle with a diameter of 8 mm to make the positive electrode. In addition, in order not to separate the sample from the positive electrode current collector, it was crimped at 30 to 40 mPa.

Metal lithium with 14mmφ perforation is used for the negative electrode, and two porous membranes with 18mmφ perforation (trade name: celgard 2500) are used for the separator. The electrolyte system is used: Ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed into a solvent at a volume ratio of 1:2, and LiPF ₆ is dissolved in the solvent at a concentration of 1mol/ ^dm3 as a supporting electrolyte. The prepared electrolyte solution (manufactured by Kishida Chemical Co., Ltd.). For the following reasons, the battery is produced in a glove box under an argon atmosphere: Based on the use of lithium metal, and the reason that the increase in resistance will be caused by the mixing of water in the electrolyte in the battery production, etc., it is in an argon atmosphere. Make batteries in the lower glove box. As the battery system, a CR2032 coin-type battery shown in FIG. 6 was used. Before entering the charge-discharge test, the potential (that is, the open circuit potential) in the state where no current is applied to the electrode is measured. The constant current charge and discharge measurement system uses a voltage switcher, which is set to C/50 charge and discharge rate, current 10mA/g, upper limit voltage 4.8V, lower limit voltage 1.5V, and starts from charging. In addition, the charge-discharge measurement was carried out with the battery placed in a 55°C thermostat. The measurement results of the open circuit potential are shown in FIG. 11 , and the measurement results of the charge-discharge characteristics (the relationship between each cycle and the discharge capacity) are shown in FIG. 12 .

It can be seen from Fig. 11 that the open circuit potential of Li ₂ CuGeO ₄ is about 2.7V. Also, as can be seen from Fig. 12, the extracted initial capacity was about 120mAh/g. In addition, the theoretical capacity is 250mAh/g, and the initial charge and discharge capacity of Li ₂ CuGeO ₄ corresponds to about 1/2 of the theoretical capacity. From the above results, it can be seen that Li ₂ CuGeO ₄ can be effectively used as a high-potential and high-capacity cathode material.

1‧‧‧Lithium-ion secondary battery 2‧‧‧Negative terminal 3‧‧‧Negative electrode 4‧‧‧Separator soaked with electrolyte 5‧‧‧Insulating pad 6‧‧‧Positive electrode 7‧‧‧Positive electrode can

FIG. 1 is a graph showing the X-ray diffraction pattern of Li ₂ CuSiO ₄ obtained in Example 1. FIG. Fig. 2 is a diagram showing the comparison results of the following patterns: the X-ray diffraction pattern of Li ₂ CuSiO ₄ and the X-ray diffraction pattern of Li ₂ SiO ₃ obtained when the firing temperature was set at 900°C in Example 1, the Li ₂ SiO ₃ is produced from CuO as the raw material compound and Li ₂ CO ₃ and SiO ₂ as the raw material compound. FIG. 3 is a diagram showing the result of observing Li ₂ CuSiO ₄ obtained when the firing temperature in Example 1 is set to 900° C. with a scanning electron microscope (SEM). FIG. 4 is a graph showing the X-ray diffraction pattern of Li ₂ CuGeO ₄ obtained in Example 2. FIG. FIG. 5 is a graph showing the result of observing Li ₂ CuGeO ₄ obtained when the firing temperature is set to 900° C. in Example 2 with a scanning electron microscope (SEM). FIG. 6 is a cross-sectional view of a test battery used in Examples 3 and 4. FIG. FIG. 7 is a graph showing the results of open circuit potential measurements performed in Example 3. FIG. FIG. 8 is a graph showing the measurement results (C/20 charge-discharge rate) of charge-discharge characteristics performed in Example 3. FIG. FIG. 9 is a graph showing the measurement results (C/50 charge-discharge rate) of charge-discharge characteristics performed in Example 3. FIG. Figure 10 is a graph showing the charge and discharge results of carbon only and PVdF. FIG. 11 is a graph showing the results of measurement of open circuit potential performed in Example 4. FIG. FIG. 12 is a graph showing the measurement results (C/50 charge-discharge rate) of charge-discharge characteristics performed in Example 4. FIG.

Claims (8)

A lithium-copper composite oxide, which has a monoclinic structure, the monoclinic structure is the main phase, and it is represented by the composition formula (1): Li _m Cu _y X ¹ O _n [in the composition formula (1), X ¹ means Si or Ge, y means 0.8~1.2, m means 1.5~2.5, n means 3.9~4.1]. For example, the lithium-copper composite oxide of Claim 1 has an average particle size of 0.1-100 μm. A method for producing a lithium-copper-based composite oxide is to manufacture the lithium-copper-based composite oxide according to claim 1 or 2. The method includes the step of heating a mixture containing lithium, copper, silicon or germanium, and oxygen. As the method of claim 3, the heating temperature is above 600°C. A positive electrode active material for a lithium-ion secondary battery, containing a lithium-copper composite oxide represented by the following composition formula (2): Li _m Cu _y X ² O _n [in the composition formula (2), X ² represents Si, Ti or Ge, y represents 0.8~1.2, m represents 1.5~2.5, n represents 3.9~4.1]; and the lithium-copper composite oxide has a monoclinic structure, and the monoclinic structure is the main phase. A positive electrode for a lithium ion secondary battery, comprising the positive electrode active material for a lithium ion secondary battery as claimed in claim 5. The positive electrode for a lithium ion secondary battery as claimed in claim 6, which further contains a conductive additive. A lithium ion secondary battery, comprising the positive electrode for lithium ion secondary battery according to claim 6 or 7.

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