JP2014035874A - Positive-electrode material for lithium secondary battery use, and lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive-electrode material for lithium secondary battery use which enables the enhancement of a high-rate discharge characteristic of a lithium secondary battery, and a lithium secondary battery having a positive electrode arranged by use of the positive-electrode material for lithium secondary battery use.SOLUTION: A positive-electrode material for lithium secondary battery use comprises at least a positive-electrode active material including ferrocenes and at least one of transition metals higher than the ferrocenes in oxidation-reduction potential. The content of the ferrocenes is 2-4 mass% to the total amount of the positive-electrode material for lithium secondary battery use.

Description

  The present invention relates to a positive electrode material for a lithium secondary battery and a lithium secondary battery using the positive electrode material for a lithium secondary battery.

  In addition to being able to discharge chemical energy by converting it into electrical energy, secondary batteries can convert electrical energy into chemical energy and store it (charge) by passing a current in the opposite direction to that during discharge. It is a possible battery. Among secondary batteries, a lithium secondary battery has a high energy density, and thus is widely applied as a power source for mounting on a vehicle or a portable device such as a notebook personal computer or a mobile phone.

Research on lithium secondary batteries has been actively conducted. For example, Patent Document 1 discloses that an oxidation-reduction reaction of a redox shuttle agent itself is performed during charging by using an electrolyte containing a ferrocene as a redox shuttle agent. Discloses a lithium secondary battery that prevents the battery voltage (potential difference between positive and negative electrodes) from exceeding a predetermined value and prevents overcharge.
On the other hand, when a lithium secondary battery is used in a hybrid vehicle (HV) or the like, improvement in high-rate discharge characteristics is required for engine assistance, brake regeneration, and the like.

JP 2012-018775 A

In the lithium secondary battery disclosed in Patent Document 1, ferrocenes are added to the electrolyte solution to prevent overcharge, do not work as an active material, and high-rate discharge of the lithium secondary battery It does not contribute to the characteristics.
In addition, when a conventional positive electrode active material is used in a lithium secondary battery, Li ions move in the solid, so the internal resistance of the positive electrode active material is large, and a high rate discharge reduces the electrode potential due to overvoltage. Since it is large, there is a problem that sufficient high rate discharge characteristics cannot be obtained.

  The present invention has been accomplished in view of the above circumstances, and can provide a positive electrode material for a lithium secondary battery that can improve the high rate discharge characteristics of a lithium secondary battery, and the positive electrode material for the lithium secondary battery as a positive electrode. An object is to provide a lithium secondary battery used in the above.

In the present invention, a positive electrode material for a lithium secondary battery comprising at least a ferrocene and a positive electrode active material containing at least one transition metal having a higher oxidation-reduction potential than the ferrocenes,
The content of the ferrocene is 2 to 4% by mass with respect to the total mass of the positive electrode material for a lithium secondary battery, and provides a positive electrode material for a lithium secondary battery.
In the present invention, the positive electrode active material is preferably a composite oxide containing a transition metal and lithium.
In the present invention, the transition metal is preferably one or more selected from the group consisting of manganese, cobalt, nickel, and combinations thereof.
In the present invention, the positive electrode active material is more preferably LiCoO ₂ .
In the present invention, the ferrocene is preferably ferrocene.

In the present invention, a lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte layer,
Provided is a lithium secondary battery comprising the positive electrode material for a lithium secondary battery in the positive electrode.

  According to the present invention, there is provided a positive electrode material for a lithium secondary battery comprising at least one of ferrocenes and a positive electrode active material containing at least one transition metal having a higher oxidation-reduction potential than the ferrocenes, wherein the ferrocenes Is used for the positive electrode of the lithium secondary battery, using a positive electrode material for the lithium secondary battery containing 2 to 4% by mass with respect to the total mass of the positive electrode material for the lithium secondary battery. Characteristics can be improved.

It is a figure which shows an example of the lithium secondary battery of this invention. It is a figure which shows the relationship between ferrocene content and time to reach | attain 2.5V by the high rate discharge at 30 C from a full charge state.

1. In the present invention, a positive electrode material for a lithium secondary battery comprising at least a ferrocene and a positive electrode active material containing at least one transition metal having a higher oxidation-reduction potential than the ferrocenes. There,
The content of the ferrocene is 2 to 4% by mass with respect to the total mass of the positive electrode material for a lithium secondary battery, and provides a positive electrode material for a lithium secondary battery.

As a result of intensive studies, the present inventor has found that the lithium secondary battery includes at least a positive electrode active material containing at least one transition metal and ferrocene as a material that does not involve movement of Li ions and is oxidized and reduced only by electron transfer. It has been found that the high rate discharge characteristics or the high rate charge characteristics of the lithium secondary battery can be improved by using the positive electrode material for a positive electrode of the lithium secondary battery.
Specifically, a high-rate discharge characteristic of a lithium secondary battery is improved by using a positive electrode material for a lithium secondary battery including a positive electrode active material having a higher oxidation-reduction potential than ferrocenes as a positive electrode of the lithium secondary battery. On the other hand, by using a positive electrode material for a lithium secondary battery containing a positive electrode active material having a lower oxidation-reduction potential than ferrocenes for the positive electrode of the lithium secondary battery, the high rate charging characteristics of the lithium secondary battery are improved. Found that you can.

Ferrocenes exist as ferrocenes having divalent iron when the potential of the positive electrode is lower than the oxidation-reduction potential of the ferrocenes in the positive electrode, and when the potential of the positive electrode exceeds the oxidation-reduction potential of the ferrocenes, It exists as ferricinium ion with trivalent iron.
Therefore, when ferrocenes are mixed with a positive electrode active material having a higher oxidation-reduction potential than ferrocenes, the potential of the positive electrode exceeds the oxidation-reduction potential of ferrocenes, so that ferrocenes are oxidized and exist as ferricinium ions. Become.
When a positive electrode material for a lithium secondary battery containing a positive electrode active material having a higher oxidation-reduction potential than ferrocenes is used for the positive electrode of the lithium secondary battery, the potential of the positive electrode may be maintained during low rate charge / discharge. Therefore, the potential of the positive electrode does not fall below the oxidation-reduction potential of ferrocenes, and ferrocenes are always present as ferricinium ions. However, when high-rate discharge is performed, the potential of the positive electrode is reduced due to a large overvoltage. Below. At this time, it is considered that ferricinium ions are reduced to ferrocenes, and the reduction current contributes to the discharge current of the battery, leading to improvement in output time, that is, improvement in high rate discharge characteristics.

On the other hand, when ferrocene is mixed with a positive electrode active material having a lower oxidation-reduction potential than ferrocenes, the potential of the positive electrode is lower than the oxidation-reduction potential of ferrocenes, so that ferrocenes are not oxidized and always exist as ferrocenes. Become.
Therefore, when a positive electrode material for a lithium secondary battery containing a positive electrode active material having a lower oxidation-reduction potential than ferrocenes is used for the positive electrode of the lithium secondary battery, even if an overvoltage occurs during high-rate discharge, an overvoltage is generated. Since the potential of the positive electrode has already been lower than the oxidation-reduction potential of ferrocene from before, there is no ferricinium ion, and no reduction reaction of ferricinium ion to ferrocene occurs, so the effect of improving the high rate discharge characteristics is I can't get it.
However, during high rate charging, the redox potential of the positive electrode active material exceeds the redox potential of ferrocenes due to a large overvoltage. At this time, ferrocenes are oxidized to ferricinium ions, and the oxidation current contributes to the charging current of the battery, leading to a reduction in charging time, that is, an improvement in high rate charging characteristics.

In addition, since the oxidation-reduction potential of ferrocenes is relatively high, ferrocenes are preferably present in the positive electrode.
In addition, if ferrocenes move away from the positive electrode due to diffusion into the electrolyte layer or move to the negative electrode, the redox current cannot be effectively used for high-rate charge / discharge. Is preferably fixed to at least one of a positive electrode active material in a positive electrode material for a lithium secondary battery and a conductive material described later.

  Hereinafter, the configuration and embodiments of the present invention will be described in detail. Although the present invention will be described in detail with reference to the drawings and examples, the present invention is not limited to these drawings and examples.

As a positive electrode active material used for the positive electrode material for lithium secondary batteries of the present invention, any positive electrode active material that can occlude and release lithium ions and contains at least one transition metal having a higher redox potential than ferrocenes can be used. Although not particularly limited, the positive electrode active material is preferably a composite oxide containing lithium from the viewpoint of improving high rate discharge characteristics.
Although it does not specifically limit as a transition metal, It is preferable that it is 1 or more types chosen from the group which consists of manganese, cobalt, nickel, and these combination.
Specific examples of the positive electrode active material include LiCoO ₂ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNiPO ₄ , LiMnPO ₄ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoMnO ₄ , and Li ₂ NiMn ₃ O. _{8 and the} like, and LiCoO ₂ is particularly preferable.
In order to obtain an effect of improving the high rate charging characteristics, a positive electrode active material containing at least one transition metal having a lower oxidation-reduction potential than ferrocenes may be selected.
Although it does not specifically limit as a transition metal used in order to acquire a high rate charge characteristic improvement effect, Iron etc. are mentioned.
Specific examples of the positive electrode active material used to obtain the effect of improving the high rate charging characteristics include Li ₃ Fe ₂ (PO ₄ ) ₃ , LiFe (PO ₄ ), etc., and Li ₃ Fe ₂ (PO ₄ ). ₃ is particularly preferred.
In order to obtain a high rate discharge characteristic improvement effect or a high rate charge characteristic improvement effect, the redox potential of the positive electrode active material may have a difference of at least ± 0.5 V or more than the redox potential of ferrocenes. preferable.

  The average particle diameter of the positive electrode active material is, for example, preferably 1 to 50 μm, particularly 1 to 20 μm, and more preferably 3 to 5 μm. If the average particle size of the positive electrode active material is too small, the handleability may be deteriorated. If the average particle size of the positive electrode active material is too large, it may be difficult to obtain a flat positive electrode active material layer. Because. The average particle diameter of the positive electrode active material can be determined by measuring and averaging the particle diameter of the active material carrier observed with, for example, a scanning electron microscope (SEM).

Examples of ferrocenes include ferrocene or ferrocene derivatives. The positive electrode material for a lithium secondary battery of the present invention may contain at least one of ferrocene and ferrocene derivatives, and includes ferrocene. It is more preferable.
In addition, ferrocene is a complex represented by the following general formula (Formula 1), and a ferrocene derivative is a complex represented by the following general formula (Formula 2).

Here, at least one of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ is an alkyl group, acetyl group, alkoxy group, acetonitrile group, carboxyl group And a compound substituted with a substituent such as a hydroxyl group. Specifically, ethyl ferrocene, i-propyl ferrocene, t-butyl ferrocene, n-butyl ferrocene, acetyl ferrocene, methoxy ferrocene, ethoxy ferrocene, propoxy ferrocene, ferrocene acetonitrile, hydroxyl ethyl ferrocene, ferrocene carboxylic acid, 1,1 ′ -Ferrocene dicarboxylic acid, 1,1'-diisopropyl ferrocene, 1,1'-diethyl ferrocene and the like.
The content of ferrocene may be 2 to 4% by mass with respect to the total mass of the positive electrode material for a lithium secondary battery, and more preferably 3 to 4% by mass.

The positive electrode material for a lithium secondary battery of the present invention may contain a conductive material, a binder and the like as necessary.
The conductive material is not particularly limited as long as the conductivity of the positive electrode material for a lithium secondary battery can be improved, and examples thereof include carbon black such as acetylene black and ketjen black. Moreover, although the content rate of the electrically conductive material in the positive electrode material for lithium secondary batteries is different depending on the type of conductive material, when the total mass of the positive electrode material for lithium secondary batteries is 100% by mass, usually 1 to 30% by mass.
Examples of the binder include polyvinylidene fluoride (PVdF) and polytetrafluoroethylene (PTFE). Moreover, the content rate of the binder in the positive electrode material for lithium secondary batteries should just be a grade which can fix a positive electrode active material etc., and it is preferable that it is less. The content ratio of the binder is usually 1 to 10% by mass when the total mass of the positive electrode material for a lithium secondary battery is 100% by mass.

  The method for producing the positive electrode material for a lithium secondary battery used in the present invention is not particularly limited, and can be obtained, for example, by mixing the positive electrode active material and ferrocenes in a mortar or the like.

2. Lithium secondary battery The lithium secondary battery of the present invention is a lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte layer,
The positive electrode includes the positive electrode material for a lithium secondary battery.

FIG. 1 is a diagram showing an example of a lithium secondary battery according to the present invention, and is a schematic view of a cross section cut in the stacking direction. The lithium secondary battery of the present invention is not necessarily limited to this example.
The lithium secondary battery 100 is sandwiched between the positive electrode 6 including the positive electrode active material layer 2 and the positive electrode current collector 4, the negative electrode 7 including the negative electrode active material layer 3 and the negative electrode current collector 5, and the positive electrode 6 and the negative electrode 7. The electrolyte layer 1 is provided. Hereinafter, the negative electrode, the positive electrode, and the electrolyte layer used in the lithium secondary battery of the present invention, and the separator and battery case suitably used for the lithium secondary battery of the present invention will be described in detail.

  The positive electrode used in the present invention comprises a positive electrode active material layer containing the positive electrode material for a lithium secondary battery of the present invention. In addition to the positive electrode active material layer, the positive electrode used in the present invention preferably includes a positive electrode current collector and a positive electrode lead connected to the positive electrode current collector.

  The thickness of the positive electrode active material layer used in the present invention varies depending on the intended use of the lithium secondary battery, etc., preferably 10 to 250 μm, more preferably 20 to 200 μm, More preferably, it is 30-150 micrometers.

  The positive electrode current collector has a function of collecting the positive electrode active material layer. Examples of the material for the positive electrode current collector include copper, aluminum, SUS, nickel, iron, and titanium. Examples of the shape of the positive electrode current collector include a foil shape, a plate shape, and a mesh shape.

The method for producing the positive electrode used in the present invention is not particularly limited. Examples thereof include a method of preparing a slurry by dispersing the positive electrode material for a lithium secondary battery of the present invention in a dispersion medium, and applying, drying, and rolling the slurry on a positive electrode current collector.
The dispersion medium is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone.
Examples of the coating method include a doctor blade method, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a gravure coating method, and a screen printing method.
In addition, after forming a positive electrode active material layer, in order to improve an electrode density, you may press a positive electrode active material layer.

  The negative electrode includes a negative electrode active material layer containing a negative electrode active material. The negative electrode used in the present invention usually comprises a negative electrode current collector and a negative electrode lead connected to the negative electrode current collector in addition to the negative electrode active material layer.

The negative electrode active material is not particularly limited as long as it can occlude and release lithium ions. Examples thereof include metal lithium, lithium alloy, metal oxide containing lithium element, metal sulfide containing lithium element, metal nitride containing lithium element, and carbon materials such as graphite.
Examples of the lithium alloy include a lithium aluminum alloy, a lithium tin alloy, a lithium lead alloy, and a lithium silicon alloy. Moreover, as a metal oxide containing a lithium element, lithium titanium oxide etc. can be mentioned, for example. Examples of the metal nitride containing a lithium element include lithium cobalt nitride, lithium iron nitride, and lithium manganese nitride. Also, metallic lithium coated with a solid electrolyte can be used.

The negative electrode active material layer may contain a conductive material, a binder, and the like as necessary.
The details of the conductive material and the binder are the same as the conductive material and the binder in the positive electrode material described above.
Although it does not specifically limit as a layer thickness of a negative electrode active material layer, For example, it is preferable that it is 10-100 micrometers, especially 10-50 micrometers.

  The negative electrode current collector has a function of collecting current from the negative electrode active material layer. As the material for the negative electrode current collector, the same materials as those for the positive electrode current collector described above can be used. Moreover, as a shape of a negative electrode collector, the thing similar to the shape of the positive electrode collector mentioned above is employable.

  The method for producing the negative electrode is not particularly limited as long as the negative electrode is obtained. In addition, after forming a negative electrode active material layer, in order to improve an electrode density, you may press a negative electrode active material layer.

The electrolyte layer used in the present invention is held between the positive electrode and the negative electrode, and has a function of exchanging lithium ions between the positive electrode and the negative electrode.
For the electrolyte layer, an electrolytic solution, a gel electrolyte, a solid electrolyte, or the like can be used. These may be used alone or in combination of two or more.

As the electrolytic solution, a non-aqueous electrolytic solution can be used.
As the non-aqueous electrolyte, one containing a lithium salt and a non-aqueous solvent is usually used.
Examples of lithium salts include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ ; LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ (Li-TFSI), LiN (SO ₂ C ₂ F ₅ ) ₂ and organic lithium salts such as LiC (SO ₂ CF ₃ ) ₃ .
Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone, sulfolane, Acetonitrile (AcN), dimethoxymethane, 1,2-dimethoxyethane (DME), 1,3-dimethoxypropane, diethyl ether, tetraethylene glycol dimethyl ether (TEGDME), tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide (DMSO) and these And the like. The concentration of the lithium salt in the nonaqueous electrolytic solution is, for example, in the range of 0.5 to 3 mol / L.

The gel electrolyte is usually gelled by adding a polymer to a non-aqueous electrolyte solution.
As a gel electrolyte, specifically, a polymer such as polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride (PVdF), polyurethane, polyacrylate, or cellulose is added to the above non-aqueous electrolyte solution to form a gel. Can be obtained.

As the solid electrolyte, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer electrolyte, or the like can be used.
Specific examples of the sulfide-based solid electrolyte include Li ₂ S—P ₂ S ₅ , Li ₂ S—P ₂ S ₃ , Li ₂ S—P ₂ S ₃ —P ₂ S ₅ , and Li ₂ S—SiS. _{2, Li 2 S-Si 2} S, Li 2 S-B 2 S 3, Li 2 S-GeS 2, LiI-Li 2 S-P 2 S 5, LiI-Li 2 S-SiS 2 -P 2 S 5 _{, Li 2 S-SiS 2 -Li} 4 SiO 4, Li 2 S-SiS 2 -Li 3 PO 4, Li 3 PS 4 -Li 4 GeS 4, Li 3.4 P 0.6 Si 0.4 S 4, Examples include Li _3.25 P _0.25 Ge _0.76 S ₄ , Li _4-x Ge _1-x P _x S _{4, and the} like.
Specifically, as the oxide-based solid electrolyte, LiPON (lithium phosphate oxynitride), Li _1.3 Al _0.3 Ti _0.7 (PO ₄ ) ₃ , La _0.51 Li _0.34 TiO Examples include _0.74 , Li ₃ PO ₄ , Li ₂ SiO ₂ , Li ₂ SiO _{4 and the} like.
The polymer electrolyte usually contains a lithium salt and a polymer.
As lithium salt, the inorganic lithium salt, organic lithium salt, etc. which were mentioned above can be used. The polymer is not particularly limited as long as it forms a complex with a lithium salt, and examples thereof include polyethylene oxide.

A separator can be used in the lithium secondary battery of the present invention. A separator is arrange | positioned between a positive electrode and a negative electrode, and has a function which prevents a contact with a positive electrode active material layer and a negative electrode active material layer, and hold | maintains electrolyte normally. Examples of the material for the separator include resins such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Among these, polyethylene and polypropylene are preferable. The separator may have a single layer structure or a multilayer structure. Examples of the separator having a multilayer structure include a separator having a two-layer structure of PE / PP, or a separator having a three-layer structure of PP / PE / PP or PE / PP / PE.
In the present invention, the separator may be a nonwoven fabric such as a resin nonwoven fabric or a glass fiber nonwoven fabric. Moreover, the film thickness of the said separator is not specifically limited, It is the same as the film thickness of the separator used for a general lithium secondary battery.
The separator may be used by being impregnated with an electrolyte such as the electrolytic solution described above.

  The lithium secondary battery of the present invention may include a battery case that houses a positive electrode, an electrolyte layer, a negative electrode, and the like. Specific examples of the shape of the battery case include a coin type, a flat plate type, a cylindrical type, and a laminate type.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples.

Example 1
Commercially available LiCoO ₂ powder (redox potential 3.7 V vs Li / Li ⁺ , average particle size 10 μm) was used as the positive electrode active material, this LiCoO ₂ powder, polyvinylidene fluoride (PVdF) as the binder, ketjen black as the conductive agent, Ferrocene (redox potential 3.6 V vs Li / Li ⁺ ) was mixed at a mass ratio of 80: 5: 13: 2 as shown in Table 1 below to prepare a positive electrode material for a lithium secondary battery, and a solvent N A slurry was prepared by dispersing in -methyl-2-pyrrolidone (NMP). The positive electrode was prepared by applying the slurry on an Al foil having a thickness of 10 μm.
Ketjen black and ferrocene were mixed in a mortar for 15 minutes or more before mixing with other materials to prepare a mixed powder of ketjen black and ferrocene, and this mixed powder was mixed with other materials. .
Li metal was used for the negative electrode.
As the electrolytic solution, 1M LiPF ₆ / (EC + DMC) (manufactured by Mitsubishi Chemical Corporation, Sollite (registered trademark)) was used. Here, 1M LiPF ₆ / (EC + DMC) is a solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) are mixed at a volume ratio of 1: 1 so that LiPF ₆ as a lithium salt has a concentration of 1M. It is dissolved.
A lithium secondary battery (coin type) was produced in the glove box using the positive electrode, the negative electrode, the electrolytic solution, and the coin cell.

(Example 2, Comparative Examples 1-6)
As shown in Table 1 below, the mass ratio of LiCoO ₂ powder, polyvinylidene fluoride (PVdF), ketjen black, and ferrocene (commercially available reagent) is 80: 5: 11: 4 in Example 2, 80: 5: 15: 0 in Comparative Example 1, 80: 5: 9: 6 in Comparative Example 2, 80: 5: 7: 8 in Comparative Example 3, and 80: 5: 5: 10 in Comparative Example 4 In addition, a lithium secondary battery was manufactured in the same manner as in Example 1 except that the ratio was 80: 5: 3: 12 in Comparative Example 5 and 80: 5: 1: 14 in Comparative Example 6. .

[Evaluation method]
The high-rate discharge characteristics of the lithium secondary batteries produced in Examples 1-2 and Comparative Examples 1-6 were evaluated.
Constant current constant voltage (CCCV) charge / discharge was performed at 25 ° C. in a voltage range of 4.2 to 2.5 V and a current rate of 1C. Thereafter, the battery was charged at a constant current and a constant voltage (CCCV) up to an upper limit voltage of 4.2 V at a current rate of 30 C. After charging, the battery was held at a constant voltage (CV) state for 30 minutes, then discharged at a current rate of 30 C, and the output time until reaching the lower limit voltage of 2.5 V was measured. The results are shown in Table 1 and FIG.

[Evaluation results]
As shown in Table 1 and FIG. 2, in comparison with Comparative Example 1, Example 1 which is a lithium secondary battery using a positive electrode material for a lithium secondary battery containing 2% by mass of ferrocene as a positive electrode, and ferrocene In Example 2, which is a lithium secondary battery using a positive electrode material for a lithium secondary battery containing 4% by mass for the positive electrode, the output time (seconds) until the lower limit voltage of 2.5 V is reached is 8. As compared with 6 seconds, it can be seen that Example 1 is improved to 9.1 seconds and Example 2 is improved to 9.8 seconds.
In Comparative Example 2, which is a lithium secondary battery using a positive electrode material for lithium secondary battery containing 6% by mass of ferrocene as a positive electrode, the positive electrode material for lithium secondary battery containing 8% by mass of ferrocene is 7.6 seconds. It can be seen that Comparative Example 3 which is the lithium secondary battery used in the example has 5.5 seconds, which is shorter than Comparative Example 1.
Moreover, the lithium secondary battery of Comparative Examples 4-6 which used the positive electrode material for lithium secondary batteries whose ferrocene amount is 10 mass% or more for a positive electrode short-circuited, and could not measure output time.
From the above results, a positive electrode material for a lithium secondary battery comprising at least one of ferrocenes and a positive electrode active material containing at least one transition metal having a higher oxidation-reduction potential than the ferrocenes, the ferrocenes being The output time of a lithium secondary battery is increased by using a positive electrode material for a lithium secondary battery, which is contained in an amount of 2 to 4% by mass, based on the total mass of the positive electrode material for a lithium secondary battery. It can be seen that the high rate discharge characteristics are improved.

DESCRIPTION OF SYMBOLS 1 Electrolyte layer 2 Positive electrode active material layer 3 Negative electrode active material layer 4 Positive electrode collector 5 Negative electrode collector 6 Positive electrode 7 Negative electrode 100 Lithium secondary battery

Claims (6)

A positive electrode material for a lithium secondary battery comprising at least a ferrocene and a positive electrode active material containing at least one transition metal having a higher oxidation-reduction potential than the ferrocene,
The positive electrode material for a lithium secondary battery, wherein a content of the ferrocene is 2 to 4% by mass with respect to a total mass of the positive electrode material for the lithium secondary battery.   The positive electrode material for a lithium secondary battery according to claim 1, wherein the positive electrode active material is a composite oxide containing a transition metal and lithium.   The positive electrode material for a lithium secondary battery according to claim 1 or 2, wherein the transition metal is one or more selected from the group consisting of manganese, cobalt, nickel, and combinations thereof. The positive electrode material for a lithium secondary battery according to claim 1, wherein the positive electrode active material is LiCoO ₂ .   The positive electrode material for a lithium secondary battery according to any one of claims 1 to 4, wherein the ferrocene is ferrocene. A lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte layer,
A lithium secondary battery comprising the positive electrode material for a lithium secondary battery according to any one of claims 1 to 5 in the positive electrode.

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