JP2003242972A - Negative active material and non-aqueous electrolyte secondary battery and their manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve capacity maintenance factor at charge and discharge cycle while maintaining high discharge capacity. <P>SOLUTION: The surface of a negative active material particle containing a transition element, and elements of group 12, group 13, group 14 element excluding carbon, or group 15 is coated by a metal or alloy film containing at least one kind out of cobalt, iron, palladium, platinum, nickel, copper, tin, chromium, and zinc that is formed by plating method, and the cover rate by the metal or alloy film is 5% or more of the total surface area of the negative active material particle, and the weight of the metal or alloy film is in the range 0.01 wt.% or more and 70 wt.% or less of the total weight. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a negative electrode active material containing an alloy or an intermetallic compound capable of electrochemically reacting with lithium as a negative electrode active material, a non-aqueous electrolyte secondary battery using the same, and a method for producing these. .

[0002]

2. Description of the Related Art Recently, a VTR with a built-in camera, a mobile phone,
Many portable electronic devices such as laptop computers have appeared,
Its size and weight are being reduced. Therefore, research and development for improving the energy density of batteries used as portable power sources for these electronic devices, especially secondary batteries, as these key devices are being actively pursued. Above all,
Lithium ion secondary batteries are widely used because they can obtain a larger energy density than lead batteries and nickel-cadmium batteries, which are conventional aqueous electrolyte secondary batteries.

As a negative electrode material used in lithium ion batteries, carbonaceous negative electrode materials such as non-graphitizable carbon and graphite having a relatively high capacity and good cycle characteristics have been generally used. However, with the recent increase in capacity, there has been a challenge to further increase the capacity of carbonaceous negative electrode materials.
In Japanese Unexamined Patent Publication No. 8-315825, although a high capacity is achieved with a carbonaceous material negative electrode by selecting a carbonization raw material and preparation conditions, the negative electrode discharge potential is 0.8 V to 1.
Since it was 0 V, the battery discharge voltage when the battery was constructed was low, and a significant improvement in battery energy density could not be expected.
Further, there is a drawback that the charge / discharge curve shape has a large hysteresis and the energy efficiency in each charge / discharge cycle is low.

On the other hand, as a high-capacity negative electrode exceeding a carbon-based material, a material to which a certain type of metal is electrochemically alloyed with lithium and is reversibly produced / decomposed has been widely studied. . A high-capacity negative electrode using a Li-Al alloy has been widely studied, and a high-capacity negative electrode using a Si alloy is proposed in U.S. Pat. No. 4,950,566.

[0005]

However, Li-Al or Li-Si alloy expands and contracts with charge and discharge,
Since the negative electrode is pulverized every time the charge / discharge cycle is repeated, there is a problem that the cycle characteristics are extremely poor.
Therefore, as a method of improving the cycle characteristics, it has been studied to coat the surface with a material having high conductivity. For example, Japanese Patent Laid-Open Nos. 2000-173669 and 2000-17
In 3670 and JP 2001-68096, the surface of the conductive material is coated with the conductive material by immersing the conductive material in an organic solvent in which the conductive material is dissolved, or by using a mechanochemical reaction such as hybridization. It has been proposed to improve cycle characteristics. Even when these methods are used, the effect of improving the cycle can be seen, but the fact is that the features of the high-capacity negative electrode have not been fully utilized.

The present invention has been proposed in view of such conventional circumstances, and a negative electrode active material and a non-aqueous electrolyte having improved capacity retention rate during charge / discharge cycles while maintaining high discharge capacity. An object of the present invention is to provide a secondary battery and a manufacturing method thereof.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a metal coating is formed on the surface of an alloy or an intermetallic compound or on a negative electrode by using a plating method. It is particularly excellent in suppressing the reaction with the electrolytic solution and improving the conductivity by controlling the coverage and weight of the surface coating, and increasing the contact with the conductive agent by making the surface uneven. It was found that the cycle characteristics can be improved.

That is, in the negative electrode active material of the present invention, the surface of the negative electrode active material particles containing a transition element, a group 12, a group 13, a group 14 element other than carbon or a group 15 element is formed by a plating method. , Iron, palladium, platinum, nickel, copper, tin, chromium, zinc, is coated with a metal or alloy coating containing at least one of the above, the coverage by the metal or alloy coating, the negative electrode active material particles It is 5% or more of the total surface area, and the weight of the metal or alloy coating is in the range of 0.01% by weight or more and 70% by weight or less of the whole.

In the negative electrode active material according to the present invention as described above, since the surface of the negative electrode active material particles is covered with the metal or alloy coating formed by the plating method, the fine powder of the negative electrode active material accompanying the charge / discharge cycle is used. Can be suppressed, the conductivity can be improved, and the reaction with the electrolytic solution can be suppressed.

The non-aqueous electrolyte secondary battery of the present invention comprises a negative electrode, a positive electrode, and a non-aqueous electrolyte, and the negative electrode is a transition element, a group 12, a group 13, a group 14 element excluding carbon or 15
The surface of the negative electrode active material particles containing a group element is coated with a metal or alloy film containing at least one selected from cobalt, iron, palladium, platinum, nickel, copper, tin, chromium and zinc formed by a plating method. The coverage of the metal or alloy coating is 5% or more of the total surface area of the negative electrode active material particles, and the weight of the metal or alloy coating is 0.01% by weight or more and 70% by weight of the whole. It is characterized by containing a negative electrode active material in the following range.

In the non-aqueous electrolyte secondary battery according to the present invention as described above, since the surface of the negative electrode active material particles is coated with the metal or alloy coating formed by the plating method, the negative electrode active material accompanying the charge / discharge cycle is It is possible to suppress pulverization of the substance, improve conductivity, and suppress reaction with the electrolytic solution.

The non-aqueous electrolyte secondary battery of the present invention comprises a negative electrode, a positive electrode and a non-aqueous electrolyte, and the negative electrode is a negative electrode active material excluding transition elements, groups 12, 13 and carbon.
A negative electrode active material layer containing a group 4 element and a group 15 element is formed on a negative electrode current collector, and cobalt, iron, palladium, platinum, nickel, and nickel are formed on the surface of the negative electrode active material layer by a plating method.
It is characterized in that a metal or alloy coating containing at least one of copper, tin, chromium and zinc is formed.

In the non-aqueous electrolyte secondary battery according to the present invention as described above, since the surface of the negative electrode active material layer is covered with the metal or alloy film formed by the plating method, the negative electrode active material accompanying the charge / discharge cycle is It is possible to suppress pulverization of the substance, improve conductivity, and suppress reaction with the electrolytic solution.

The method for producing the negative electrode active material of the present invention is
The surface of the negative electrode active material particles containing a transition element, a group 12 element, a group 13 element, a group 14 element other than carbon, or a group 15 element is coated with cobalt, iron, palladium, platinum, nickel, by a plating method.
There is a step of coating with a metal or alloy coating containing at least one of copper, tin, chromium and zinc, and the coverage with the metal or alloy coating is 5% or more of the total surface area of the negative electrode active material particles. It is characterized in that the weight of the metal or alloy coating is in the range of 0.01% by weight or more and 70% by weight or less of the whole.

In the method for producing a negative electrode active material according to the present invention as described above, the surface of the negative electrode active material particles is coated with a metal or alloy coating by a plating method, so that the negative electrode active material is pulverized with a charge / discharge cycle. It is possible to obtain a negative electrode active material in which the conductivity is suppressed, the conductivity is improved, and the reaction with the electrolytic solution is suppressed.

The method for producing a non-aqueous electrolyte secondary battery of the present invention is a method for producing a non-aqueous electrolyte secondary battery including a negative electrode, a positive electrode and a non-aqueous electrolyte, and the negative electrode is produced. At this time, the surface of the negative electrode active material particles containing a transition element, a group 12 element, a group 13 element, or a group 14 element other than carbon or a group 15 element is coated with cobalt, iron, palladium, platinum, nickel, copper, tin or chromium by a plating method. , A step of coating with a metal or alloy coating containing at least one of zinc to obtain a negative electrode active material, and the coverage with the metal or alloy coating is 5% or more of the total surface area of the negative electrode active material particles. And
The weight of the metal or alloy coating is 0.01% by weight of the whole.
As described above, the content is in the range of 70% by weight or less.

In the method of manufacturing a non-aqueous electrolyte secondary battery according to the present invention as described above, by coating the surface of the negative electrode active material particles with a metal or alloy coating by a plating method,
A non-aqueous electrolyte secondary battery having a negative electrode capable of suppressing pulverization of the negative electrode active material due to charge / discharge cycles, improving conductivity, and suppressing reaction with an electrolytic solution can be obtained.

The method for producing a non-aqueous electrolyte secondary battery of the present invention is a method for producing a non-aqueous electrolyte secondary battery comprising a negative electrode, a positive electrode and a non-aqueous electrolyte, the negative electrode being produced. At this time, a negative electrode active material layer containing a transition element, a group 12, a group 13, a group 14 element other than carbon and a group 15 element as a negative electrode active material is formed on the negative electrode current collector, and the surface of the negative electrode active material layer is formed. ,
Depending on the plating method, at least one of cobalt, iron, palladium, platinum, nickel, copper, tin, chromium, zinc
It is characterized in that a metal or alloy coating including a kind is formed.

In the method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention as described above, by coating the surface of the negative electrode active material layer with a metal or alloy coating by a plating method, the negative electrode active material accompanying the charging / discharging cycle. It is possible to obtain a non-aqueous electrolyte secondary battery having a negative electrode capable of suppressing the pulverization of the powder, improving the conductivity, and suppressing the reaction with the electrolytic solution.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a negative electrode active material and a non-aqueous electrolyte secondary battery to which the present invention is applied will be described in detail below.

FIG. 1 shows a constitutional example of a non-aqueous electrolyte battery to which the present invention is applied. The non-aqueous electrolyte battery 1 includes a negative electrode 2 and
The negative electrode can 3 includes the negative electrode can 3, which accommodates the negative electrode 2, the positive electrode 4, the positive electrode can 5 which accommodates the positive electrode 4, the separator 6 disposed between the positive electrode 4 and the negative electrode 2, and the insulating gasket 7. Also, the positive electrode can 5 is filled with a non-aqueous electrolytic solution.

The negative electrode 2 is made of, for example, a metallic lithium foil which serves as a negative electrode active material. When a material capable of being doped with lithium and dedoped from lithium is used as the negative electrode active material, the negative electrode 2 has the negative electrode active material layer containing the negative electrode active material formed on the negative electrode current collector. As the negative electrode current collector, for example, nickel foil or the like is used.

In the present invention, the negative electrode active material is formed by depositing and coating a metal on the surface of the negative electrode active material particles by a plating method. The negative electrode active material particles include transition elements, group 12,
It contains at least one element capable of forming an alloy with lithium among Group 13 and Group 14 and 15 elements other than carbon. In particular, those containing Sn or Si are preferable, and those containing Sn are more preferable. Examples of such active material particles include MxSny or MxS
iy (M is one or more elements other than Li element, x,
y is a numerical value larger than 0. ) And the like. This may include a phase which is electrochemically inactive with lithium.

The average particle size of the negative electrode active material particles is 0.
It is preferably in the range of 1 μm or more and 100 μm or less. Although the discharge capacity of these materials is remarkably reduced from the beginning of the cycle and the theoretical capacity exceeds that of the carbon-based negative electrode material,
After 0 cycles, there are some that decrease to about 10% of the initial capacity, and it is difficult to develop a high capacity. Each time these materials are cycled, they expand and contract due to the reaction with lithium and become fine powder. Therefore, it is considered that the contact with the conductive agent is lost.

The metal coated on the surface of the negative electrode active material particles includes cobalt, iron, palladium, platinum, nickel,
Examples include copper, tin, chromium, zinc, and alloys containing at least one of these elements.

Such a negative electrode active material is manufactured by a plating method. Although the effect can be obtained by either the electrolytic plating method or the electroless plating method, the plating on the powder by the electrolytic plating method tends to cause variations in the coverage rate and coating weight of each powder, and it is difficult to uniformly control the weight. Is. On the other hand, in the electroless plating method, since the current density distribution is not generated, the surface of the active material can be uniformly coated, and both the coverage and the coating weight can be easily controlled.

It is also possible to control the roughness of the film surface by adding various organic compounds such as organic acids and alcohols as additives to the plating bath. As an example of the manufacturing method, the negative electrode active material particles made of the above-mentioned metal are activated with dilute acid after removing the oxide film on the particle surface with phosphoric acid or the like. Then, it is catalyzed by immersing it in tin, a palladium solution or the like, and by immersing it in an electroless plating solution, a metal film is formed on the surface of the particles. After filtering this, alcohol substitution was performed and 4
The negative electrode active material of the present invention can be obtained by drying in a vacuum of 0 to 60 ° C. It is also possible to form a plating film without going through the steps of pretreatment and catalysis.

When the negative electrode active material particles are subjected to electroless plating, the coverage of the plated metal coating is preferably 5% or more of the total surface area of the negative electrode active material particles, and the weight of the plated coating is based on the entire active material. 0.01% by weight or more, 70
It is preferably in the range of not more than wt%.

As for the coverage, it is not always necessary to cover the entire surface, and it may be 5% or more of the entire surface.
This is because the detached metal coating is present in the electrode and has the effect of acting as a conductive auxiliary agent. Further, the desorbed portion of the active material serves as a passage for metal ions, and ions are easily passed through during charge / discharge. To obtain the same effect, etching may be performed using dilute acid. In addition, as a conductive additive, Cu, Ni,
At least one metal powder selected from Fe, Co, Ag, Au, Al and Mn may be added.

Further, even when the weight percentage of the metal coating is small, that is, when the surface coating layer is thin, the effect of suppressing the conductivity and the reaction with the electrolytic solution can be recognized, but it is large in suppressing the pulverization. This is because the effect cannot be obtained. For the same reason, when electroless plating is performed on the surface of the negative electrode as described later, the film thickness is preferably in the range of 0.01 μm or more and 10 μm or less.

Further, by adding an organic additive to the electroless plating solution or performing plating in a static bath, it is possible to form fine irregularities or spherical or acicular projections on the surface of the coating. As a result, the contact property with the conductive agent is improved and the cycle characteristics can be improved. If the height of the protrusions is about 0.1 nm to 5 μm, the effect can be exhibited.

Such a negative electrode active material of the present invention can be used as a mixture with a carbon-based negative electrode material, and can be used within a range in which the capacity of the negative electrode is superior to that of the carbon-based negative electrode. The carbon material in this case may have a function as a negative electrode material that reacts electrochemically with lithium or as a conductive additive, but it can be used in any combination of two or more kinds in order to obtain predetermined battery characteristics. . As the carbon material, at least one kind of hard carbon, soft carbon and graphite can be used. Further, as the shape thereof, at least one kind of fibrous, spherical, granular, and scaly can be used. The amount of the carbon-based material mixed with the plating-coated active material is preferably 1 to 95% by weight.

In addition to the above active materials, carbonaceous materials such as pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, activated carbons and carbon blacks can be used for the negative electrode. Further, a material that does not contribute to charge / discharge may be included.

As the binder contained in the negative electrode active material layer, a known resin material or the like usually used as a binder for the negative electrode active material layer of this type of non-aqueous electrolyte battery can be used.

The negative electrode can 3 accommodates the negative electrode 2 and serves as an external negative electrode of the non-aqueous electrolyte battery 1.

The positive electrode 4 is formed by forming a positive electrode active material layer containing a positive electrode active material on a positive electrode current collector. As the positive electrode current collector, for example, aluminum foil or the like is used.

As the positive electrode active material, a mixture of a metal oxide, a metal sulfide or a specific polymer, which is known as a positive electrode active material, is mixed with a conductive agent and a binder, depending on the type of the intended battery. It can be prepared by applying it on the body. As the positive electrode active material, a lithium composite mainly composed of LixMO2 (wherein M represents one or more transition metals, x varies depending on the charging / discharging state of the battery, and usually 0.05 ≦ x ≦ 1.10.) Oxides and the like can be used.
As the transition metal M constituting the lithium composite oxide, Co, Ni, Mn and the like are preferable. Specific examples of such a lithium composite oxide include LiCoO2 and LiN.
iO2, LixNiyCo1-yO2 (where x, y,
Is usually 0 <x <1,
0.7 <y <1.02), and lithium manganese composite oxide having a spinel structure can be used. Since these lithium composite oxides can obtain a high voltage, they become a positive electrode active material excellent in energy density. In addition, lithium-free TiS2, MoS
It is also possible to use a metal sulfide or oxide such as 2, NbSe2 or V2O5. Further, as the positive electrode active material, plural kinds thereof may be mixed and used.

As the binder contained in the positive electrode active material layer, a known resin material or the like usually used as a binder for the positive electrode active material layer of this type of non-aqueous electrolyte battery can be used.

The positive electrode can 5 accommodates the positive electrode 4 and serves as an external positive electrode of the non-aqueous electrolyte battery 1.

The separator 6 separates the positive electrode 4 and the negative electrode 2 from each other, and may be made of a known material that is commonly used as a separator for a non-aqueous electrolyte battery of this type. For example, polypropylene or the like may be used. A polymer film is used. Further, the thickness of the separator needs to be as thin as possible in view of the relationship between lithium ion conductivity and energy density. Specifically, the thickness of the separator is preferably 50 μm or less.

The insulating gasket 7 is incorporated in and integrated with the negative electrode can 3. The insulating gasket 7 is for preventing leakage of the nonaqueous electrolytic solution filled in the negative electrode can 3 and the positive electrode can 5.

As the non-aqueous electrolyte, a solution prepared by dissolving an electrolyte in an aprotic non-aqueous solvent is used.

Any non-aqueous solvent can be used as long as it is used in a lithium secondary battery.
Propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,
3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile,
Examples thereof include anisole, acetic acid ester, butyric acid ester, propionic acid ester and the like.

As the lithium salt used in the electrolyte, any lithium salt can be used as long as it is used in a lithium secondary battery. For example, LiClO4, LiAsF6, L
iPF6, LiBF4, LiB (C6H5) 4, CH3
SO3Li, CF3SO3Li, LiCl, LiBr and the like can be mentioned.

In such a non-aqueous electrolyte battery 1, since the surface of the negative electrode active material particles is coated with a metal material by a plating method, pulverization of the negative electrode active material is suppressed and the conductivity is improved. At the same time, the reaction with the electrolytic solution is suppressed.
This makes it possible to improve the capacity retention rate during charge / discharge cycles while maintaining a high discharge capacity, and to provide a battery with a higher capacity and superior cycle characteristics than a lithium secondary battery using a conventional graphite material. Become.

Then, such a non-aqueous electrolyte battery 1 is manufactured, for example, as follows.

The negative electrode active material is, as described above, a negative electrode active material containing at least one element capable of forming an alloy with lithium among transition elements, group 12, group 13 and group 14 and 15 elements other than carbon. The surface of the particles is produced by depositing / coating cobalt, iron, palladium, platinum, nickel, copper, tin, chromium, zinc or an alloy containing at least one of these elements by a plating method.

For the negative electrode 2, first, the negative electrode active material and the binder obtained as described above are dispersed in a solvent to prepare a slurry negative electrode mixture. Next, the obtained negative electrode mixture is uniformly applied onto the negative electrode current collector and dried to form a negative electrode active material layer, whereby the negative electrode 2 is produced. As the binder for the negative electrode mixture, a known binder can be used, and a known additive or the like can be added to the negative electrode mixture. Further, metallic lithium serving as the negative electrode active material can be used as it is as the negative electrode 2.

As the positive electrode 4, first, a positive electrode active material and a binder are dispersed in a solvent to prepare a slurry positive electrode mixture. Next, the obtained positive electrode mixture is uniformly applied onto the positive electrode current collector and dried to form a positive electrode active material layer, thereby forming the positive electrode 4
Is created. As the binder of the positive electrode mixture, a known binder can be used, and a known additive or the like can be added to the positive electrode mixture.

The non-aqueous electrolytic solution is prepared by dissolving an electrolyte salt in a non-aqueous solvent.

Then, the negative electrode 2 is accommodated in the negative electrode can 3, the positive electrode 4 is accommodated in the positive electrode can 5, and the separator 6 made of a polypropylene porous film or the like is disposed between the negative electrode 2 and the positive electrode 4. The nonaqueous electrolytic solution battery 1 is completed by injecting the nonaqueous electrolytic solution into the negative electrode can 3 and the positive electrode can 5, and caulking and fixing the negative electrode can 3 and the positive electrode can 5 via the insulating gasket 7.

Non-aqueous electrolyte battery 1 thus obtained
Is, since the metal material is deposited on the surface of the negative electrode active material particles by a plating method, pulverization of the negative electrode active material is suppressed,
In addition, the conductivity is improved and the reaction with the electrolytic solution is suppressed. This makes it possible to improve the capacity retention rate during charge / discharge cycles while maintaining a high discharge capacity, and to provide a battery with a higher capacity and superior cycle characteristics than a lithium secondary battery using a conventional graphite material. Become.

In the above-mentioned embodiment, the case where a metal or alloy coating film is formed on the surface of the negative electrode active material particles by a plating method has been described as an example. However, the effect of the present invention is as follows.
It can be obtained even when a metal or alloy coating is formed on the surface of the negative electrode by a plating method instead of the negative electrode active material particles.

That is, in the negative electrode in this case, a negative electrode active material layer containing a transition element, a group 12, a group 13, a group 14 element other than carbon and a group 15 element as a negative electrode active material is formed on the negative electrode current collector, On the surface of the negative electrode active material layer, by a plating method, cobalt, iron, palladium, platinum, nickel, copper,
A metal or alloy coating containing at least one of tin, chromium and zinc is formed. Furthermore, the surface of the negative electrode active material particles is coated with a metal or alloy coating containing at least one selected from cobalt, iron, palladium, platinum, nickel, copper, tin, chromium, and zinc formed by a plating method. May be.

Also in this case, since the metal material is deposited on the surface of the negative electrode by the plating method, the pulverization of the negative electrode active material is suppressed, the conductivity is improved, and the reaction with the electrolytic solution is also achieved. Suppressed. This makes it possible to improve the capacity retention rate during charge / discharge cycles while maintaining a high discharge capacity, and to provide a battery with a higher capacity and excellent cycle characteristics than a lithium secondary battery using a conventional graphite material. Can be realized.

The method of forming the metal or alloy coating on the surface of the negative electrode by the plating method can be performed in the same manner as the method of forming the metal or alloy coating on the surface of the negative electrode active material particles described above.

Further, in the above-described embodiment, the non-aqueous electrolyte battery using the non-aqueous electrolyte was described as an example, but the present invention is not limited to this, and the conductive polymer compound is used. The present invention is also applicable to a solid electrolyte battery using a polymer solid electrolyte containing a single substance or a mixture thereof, and a gel electrolyte battery using a gel electrolyte in which a non-aqueous electrolyte is gelled by a matrix polymer.

As the solid electrolyte, either an inorganic solid electrolyte or a polymer solid electrolyte can be used as long as it is a material having lithium ion conductivity. Examples of the inorganic solid electrolyte include lithium nitride and lithium iodide. The solid polymer electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt, and the polymer compound is an ether polymer such as poly (ethylene oxide) or its cross-linked product, a poly (methacrylate) ester system, or an acrylate system. They can be used alone, or can be copolymerized or mixed in the molecule.

As the matrix of the gel electrolyte, various polymers can be used as long as they absorb the above non-aqueous electrolyte and gel. For example, fluorine-based polymers such as poly (vinylidene fluoride) and poly (vinylidene fluoride-co-hexafluoropropylene), ether-based polymers such as poly (ethylene oxide) and its cross-linked products, and poly (acrylonitrile), etc. Can be used. In particular, it is desirable to use a fluoropolymer because of its redox stability. Ionic conductivity is imparted by containing an electrolyte salt.

Further, in the above-described embodiment, the secondary battery has been described as an example, but the present invention is not limited to this and can be applied to a primary battery. Further, all the lithium present in the battery system does not necessarily have to be supplied from the positive electrode or the negative electrode, and may be electrochemically doped into the positive electrode or the negative electrode during the manufacturing process of the electrode or the battery. Further, the battery of the present invention is not particularly limited in its shape such as a cylindrical type, a square type, a coin type and a button type, and may be various sizes such as thin and large.

[0061]

EXAMPLES Next, examples carried out to confirm the effects of the present invention will be described. It should be noted that, in the examples shown below, specific substance names, numerical values, and the like are described, but it goes without saying that the present invention is not limited to these examples. Further, the effect of the present invention was confirmed using a coin-type battery having a lithium metal as a counter electrode, but the effect of the present invention can be similarly obtained in a cylindrical battery.

<Sample 1> First, after a step of catalyzing negative electrode active material particles made of a metal mixed powder of 50% by weight of Cu powder and 50% by weight of Sn powder, an electroless copper plating solution I put it in. By immersing the negative electrode active material particles in a bath while stirring, C on the surface of the negative electrode active material particles
A plated layer of u was formed. A negative electrode active material was obtained by filtering and drying this.

The weight of the plated metal coating is 30% by weight of the whole.
The plating time was adjusted so that The coverage is 50
%. Regarding the surface roughness, protrusions having an average height of 0.2 μm were formed, and the same was applied to all the examples. In addition, the average height is calculated by observing the cross section using SEM, but AFM (atomic force microscope)
Can also be measured using.

Next, 46% by weight of the negative electrode active material obtained as described above and 46% by weight of graphite were mixed, and 2% by weight of a conductive agent and polyvinylidene fluoride as a binder were mixed in the mixture. Was mixed with 6% by weight to prepare a slurry negative electrode mixture using n-methylpyrrolidone as a solvent. This negative electrode mixture was applied on a copper foil current collector, dried and punched into pellets having a diameter of 15.2 mm to prepare a negative electrode.

As a counter electrode of the obtained negative electrode, metal lithium having a diameter of 15.5 mm was punched out, and a separator was sandwiched to form a coin-type battery. As the electrolytic solution, a solution obtained by dissolving LiPF6 as an electrolyte salt in a mixed solvent of ethylene carbonate, propylene carbonate and dimethyl carbonate was used.

<Sample 2> A negative electrode active material and a coin-type battery were produced in the same manner as in Sample 1, except that the weight of the plated metal coating was 80% by weight and the coverage was 50%.

<Sample 3> A negative electrode active material and a coin-type battery were produced in the same manner as in Sample 1, except that the weight of the plated metal coating was 30% by weight of the whole and the coverage was 95%.

<Sample Example 4> Except that the weight of the plated metal coating was 4% by weight and the coverage was 4%.
A negative electrode active material and a coin battery were produced in the same manner as in Sample 1.

<Sample 5> Cu on the surface of the negative electrode active material particles
Instead of Ni, the surface was plated with Ni. A negative electrode active material and a coin-type battery were produced in the same manner as in Sample 1 except that the weight of the plated metal coating was 15% by weight of the whole and the coverage was 50%.

<Sample 6> A Cu coating was formed on the surface of the negative electrode active material particles by electrolytic plating. A negative electrode active material and a coin-type battery were produced in the same manner as in Sample 1 except that the weight of the plated metal coating was 30% by weight and the coverage was 50%.

<Sample 7> 15 wt% of Cu powder was added to the non-plated negative electrode active material particles, and a mixture with graphite was used as a negative electrode active material in the same manner as in Sample 1 to obtain a coin type. A battery was made.

<Sample 8> A coin-type battery was manufactured in the same manner as in Sample 1, using a mixture of non-plated negative electrode active material particles and graphite as a negative electrode active material.

A charge / discharge test was conducted on each of the sample batteries manufactured as described above. 23 for each battery
After constant-current constant-voltage charging at 2 ° C. at 2 ° C., constant-current discharging at 2 A was performed. Repeat this for 10 cycles, 10
The discharge capacity retention rate (%) at the cycle was obtained. Table 1 shows the measurement results of the discharge capacity at the first cycle and the discharge capacity retention rate at the tenth cycle.

[0074]

[Table 1]

As is clear from Table 1, in Sample 1 in which the negative electrode active material particles were formed with the plated metal film, the plated metal film was formed at the discharge capacity (initial capacity) at the first cycle and the capacity retention rate after 10 cycles. It was confirmed that there was a significant improvement over sample 8 which was not formed.
It is considered that this is because the formation of the plated metal film on the surface suppressed the pulverization of the negative electrode active material particles and improved the conductivity. Further, the same effect was confirmed also in Sample 5 in which Ni plating was performed instead of Cu.

However, in Sample 2 in which the weight of the plated metal film was large, the capacity was small but the capacity retention rate was small. In addition, the initial capacity of Sample 3 in which the coverage with the plated metal coating is increased also decreases. On the other hand, in Sample 4 having a small coverage, the initial capacity was high, but no large effect was observed on the capacity retention rate. When the coverage of the plated metal coating is 5% or more and the weight of the plating coating is in the range of 0.01% by weight or more and 70% by weight or less, the initial capacity and the capacity retention rate can be well balanced. .

Further, it was confirmed that the sample 6 subjected to electrolytic plating and the sample 7 to which the metal powder was added had an effect on the capacity retention rate although it did not reach that of the sample 1.

Finally, FIG. 2 shows the relationship between the height of the protrusions formed on the surface of the plating film and the capacity retention rate. As is apparent from FIG. 2, the height of the surface protrusions is 0.1 nm to 5 μm.
It was confirmed that the capacity retention ratio was greatly improved in the range of.

[0079]

According to the present invention, since the metal or alloy coating is formed on the surface of the negative electrode active material particles or the negative electrode by the plating method, it is possible to suppress the pulverization of the negative electrode active material due to the charge / discharge cycle. In addition, the conductivity can be improved and the reaction with the electrolytic solution can be suppressed. Thus, in the present invention, while maintaining a high discharge capacity, it is possible to improve the capacity retention rate during charge / discharge cycles, and has a higher capacity and cycle characteristics than a lithium secondary battery using a conventional graphite material. An excellent non-aqueous electrolyte secondary battery can be realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one structural example of a non-aqueous electrolyte battery to which the present invention is applied.

FIG. 2 is a diagram showing the relationship between the height of protrusions formed on the surface of a plating film and the capacity retention rate of the batteries manufactured in Examples.

[Explanation of Codes] 1 non-aqueous electrolyte battery, 2 negative electrode, 3 negative electrode can, 4
Positive electrode, 5 positive electrode can, 6 separator, 7 insulating gasket

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Keiichi Nishino             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F-term (reference) 5H029 AJ05 AL01 AL07 AM11 AM16                       CJ24 DJ08 EJ01 HJ01 HJ04                 5H050 AA07 AA08 BA18 CA02 CA07                       CA10 CB11 DA10 EA02 EA03                       EA04 GA24 HA01 HA04

Claims (21)

[Claims] 1. Cobalt, iron, palladium, platinum, nickel in which the surface of a negative electrode active material particle containing a transition element, a group 12, a group 13, a group 14 element other than carbon or a group 15 element is formed by a plating method. , Copper, tin, chromium, or zinc, which is coated with a metal or alloy coating containing at least one selected from the group consisting of the metal or alloy coating, and the coverage of the metal or alloy coating is 5% or more of the total surface area of the anode active material particles. The weight of the metal or alloy coating is 0.01% by weight of the whole.
As described above, the negative electrode active material is in the range of 70% by weight or less. 2. The negative electrode active material according to claim 1, comprising a metal or alloy powder desorbed from the surface of the negative electrode active material particles. 3. The film thickness of the metal or alloy coating is 1 nm
The negative electrode active material according to claim 1, wherein the negative electrode active material is in the range of 5 μm or less. 4. A height of 0.
The negative electrode active material according to claim 1, wherein the negative electrode active material has a spherical or acicular projection having a diameter of 1 nm to 5 μm. 5. Further, Cu, Ni, Fe, Co, A
The negative electrode active material according to claim 1, further comprising at least one metal powder selected from g, Au, Al, and Mn. 6. A negative electrode, a positive electrode, and a nonaqueous electrolyte, wherein the negative electrode is a transition element, a group 12, a group 13 and a carbon excluding carbon.
A metal containing at least one selected from the group consisting of cobalt, iron, palladium, platinum, nickel, copper, tin, chromium and zinc, in which the surface of the negative electrode active material particles containing a Group 4 element or a Group 15 element is formed by a plating method. Alternatively, the coating rate of the metal or alloy coating is 5% or more of the total surface area of the negative electrode active material particles, and the weight of the metal or alloy coating is 0.01% by weight of the whole. The nonaqueous electrolyte secondary battery is characterized by containing the negative electrode active material in the range of 70% by weight or less. 7. The non-aqueous electrolyte secondary battery according to claim 6, wherein the negative electrode contains a metal or alloy powder desorbed from the surface of the negative electrode active material particles. 8. The negative electrode further contains Cu, Ni, F
7. The non-aqueous electrolyte secondary battery according to claim 6, wherein at least one metal powder selected from e, Co, Ag, Au, Al and Mn is added. 9. A negative electrode, a positive electrode, and a nonaqueous electrolyte, wherein the negative electrode is a transition element, a group 12, or 13 as a negative electrode active material.
A negative electrode active material layer containing a group 14 element and a group 15 element other than carbon is formed on a negative electrode current collector, and cobalt, iron, palladium, platinum, nickel is plated on the surface of the negative electrode active material layer by a plating method. A non-aqueous electrolyte secondary battery comprising a metal or alloy coating containing at least one of copper, tin, chromium, and zinc. 10. The metal or alloy coating has a thickness of 0.
The non-aqueous electrolyte secondary battery according to claim 9, wherein the range is from 01 μm to 10 μm. 11. The surface of a negative electrode active material particle containing a transition element, a group 12 element, a group 13 element, or a group 14 element other than carbon or a group 15 element is coated with cobalt, iron, palladium, platinum, nickel, copper or tin by a plating method. , A coating of a metal or alloy coating containing at least one of chromium and zinc, the coverage of the metal or alloy coating being 5% or more of the total surface area of the negative electrode active material particles, The weight of the metal or alloy coating is 0.01% by weight of the whole.
The method for producing a negative electrode active material is in the range of 70% by weight or less. 12. The method for producing a negative electrode active material according to claim 11, wherein the plating method is an electroless plating method. 13. The method for producing a negative electrode active material according to claim 12, wherein a catalytic treatment is applied in the electroless plating method. 14. The method for producing a negative electrode active material according to claim 12, wherein an organic additive is used in the electroless plating method. 15. The pretreatment for removing an oxide film existing on the surface of the negative electrode active material particles is performed.
A method for producing the negative electrode active material described. 16. The method for producing a negative electrode active material according to claim 11, wherein the negative electrode active material particles coated with the metal or alloy coating are subjected to an acid treatment. 17. A method for manufacturing a non-aqueous electrolyte secondary battery comprising a negative electrode, a positive electrode, and a non-aqueous electrolyte, wherein a transition element, a group 12, a group 13,
The surface of the negative electrode active material particles containing a Group 14 element or a Group 15 element excluding carbon is plated with a metal containing at least one of cobalt, iron, palladium, platinum, nickel, copper, tin, chromium and zinc, or A step of coating with an alloy coating to obtain a negative electrode active material, the coverage with the metal or alloy coating is 5% or more of the total surface area of the negative electrode active material particles, and the weight of the metal or alloy coating is A method for producing a non-aqueous electrolyte secondary battery, which is in the range of 0.01% by weight or more and 70% by weight or less of the whole. 18. The method for producing a non-aqueous electrolyte secondary battery according to claim 17, wherein the plating method is an electroless plating method. 19. A method of manufacturing a non-aqueous electrolyte secondary battery comprising a negative electrode, a positive electrode, and a non-aqueous electrolyte, wherein a transition element is used as a negative electrode active material when the negative electrode is manufactured.
A negative electrode active material layer containing a group 12 element, a group 13 element, and a group 14 element other than carbon and a group 15 element is formed on a negative electrode current collector, and cobalt, iron, or palladium is formed on the surface of the negative electrode active material layer by a plating method. A method for producing a non-aqueous electrolyte secondary battery, which comprises forming a metal or alloy coating containing at least one of platinum, nickel, copper, tin, chromium and zinc. 20. The method for producing a non-aqueous electrolyte secondary battery according to claim 19, wherein the plating method is an electroless plating method. 21. The method for producing a non-aqueous electrolyte secondary battery according to claim 19, wherein the negative electrode coated with the metal or alloy coating is subjected to acid treatment.