JP2005197080A - Anode for secondary battery and secondary battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anode material for a secondary battery with high capacity and a long life. <P>SOLUTION: The anode material for the secondary battery used for the anode storing and releasing lithium ion contains a material component 3a larger than a theoretical weight lithium storage volume of carbon, storing less lithium as it comes nearer a current collector 1a. By using the material component not storing lithium with low ductility and malleability, exfoliation from the collector or pulverization of an anode active material is restrained to improve cycle characteristics. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a negative electrode for a secondary battery and a secondary battery using the same, and more particularly to a negative electrode for a secondary battery having high capacity and excellent cycle characteristics and a secondary battery using the same.

With the widespread use of mobile terminals such as mobile phones and laptop computers, the role of the battery serving as the power source has been regarded as important. These batteries are required to have a small size, light weight, high capacity, and performance that does not easily deteriorate even after repeated charge and discharge.
From the viewpoint of high energy density and light weight, metallic lithium may be used for the negative electrode. In this case, acicular crystals (dendrites) are deposited on the lithium surface as the charge / discharge cycle progresses, or the dendrites are collected by current. Peeling from the body may occur. As a result, the dendrite penetrates the separator and causes a short circuit inside, which may cause problems such as shortening the battery life or deteriorating cycle characteristics.

  Therefore, carbon materials that do not have the above problems are used as negative electrode materials in practical batteries. A typical one of these is a graphite-based carbon material, but the amount of lithium ions that can be occluded by this material is limited by the amount that can be inserted between graphite layers, and its specific capacity is 372 Ah / It is generally difficult to set the weight to kg or more. In addition, since the capacity of the carbon negative electrode used in the lithium ion secondary battery has already been used up to near the upper limit of the theoretical capacity, it may not be possible to increase the capacity further. Therefore, a method using an alloy-based negative electrode that can occlude lithium ions and has a larger specific capacity than graphite has been developed. However, since the alloy-based negative electrode has a large volume expansion / contraction during charge / discharge, there are cases where electrical contact cannot be obtained due to pulverization or peeling from the current collector.

For example, Patent Document 1 proposes a method in which a current collector component is diffused in a negative electrode active material to relatively reduce expansion and contraction in the vicinity of the current collector and maintain adhesion. Patent Document 2 discloses a method in which the active material contains a conductive agent that does not alloy with an alkali metal, and the active material conductive agent concentration in the vicinity of the current collector is higher than the active material conductive agent concentration at a position away from the current collector. As an example, a method of mixing Cu powder in a graphite material has been proposed.
International Publication Number WO01 / 031721 Pamphlet (7th to 10th pages) JP-A-9-265976 (pages 3-4)

However, the negative electrode materials disclosed in Patent Documents 1 and 2 sometimes have some problems.
The first problem is that pulverization of the active material accompanying the cycle cannot be suppressed. The reason for this is that copper foil is generally used for the current collector of the negative electrode of lithium ion batteries, but copper is malleable and ductile like gold and silver and has high workability, but it is tough. This is because when the active material repeatedly expands due to charge and discharge, peeling or pulverization from the current collector occurs.

The second problem is that the active material cannot be prevented from being peeled off from the current collector due to the cycle. The reason for this is that even if an active material that does not bind to an alkali metal is added as a conductive agent, the expansion and contraction of the lithium storage material itself cannot be suppressed. End up. The reason raised as the first problem is also a factor that prevents the active material from being separated from the current collector.
An object of the present invention relates to a negative electrode for a secondary battery having a high capacity and excellent cycle characteristics, and a secondary battery using the same.

In order to solve the above problems, the present invention is characterized by having the following configuration. The present invention is a secondary battery negative electrode comprising a current collector and a secondary battery negative electrode material capable of occluding and releasing lithium ions,
The negative electrode material for a secondary battery has a material (A) larger than the theoretical weight lithium occlusion amount of carbon and a material component (B) that does not occlude lithium, and extends from the negative electrode material for secondary battery toward the current collector side. The material component (B) concentration is thus increased.

In the negative electrode for a secondary battery of the present invention, it is preferable that the material (A) having a larger theoretical weight lithium occlusion amount of carbon has at least one element selected from the group consisting of Si, Sn and Al.
In the secondary battery negative electrode of the present invention, the material component (B) that does not occlude lithium further contains at least one element selected from the group consisting of Ti, Fe, Co, Ni, Mo, and W. preferable.

The negative electrode for a secondary battery according to the present invention further includes particles in which the negative electrode material for a secondary battery has a material (A) larger than the theoretical weight lithium occlusion amount of the carbon and a material component (B) that does not occlude lithium. It is preferable to be configured.
In the secondary battery negative electrode of the present invention, it is preferable that the current collector is a copper foil, and the surface roughness (Ra) of the copper foil is 1 to 5 μm.

The present invention provides a material component (B) that supplies a material (A) larger than the theoretical weight lithium occlusion amount of carbon from a first source onto a current collector and does not occlude lithium from a second source. A negative electrode for a secondary battery by forming a film containing a negative electrode material for a secondary battery, and continuously supplying the material (A) onto the current collector. And a method for producing a negative electrode for a secondary battery, wherein the supply amount of the material component (B) is continuously increased.
In the method for producing a negative electrode for a secondary battery according to the present invention, the method for forming a film containing the negative electrode material for a secondary battery is at least one selected from the group consisting of vapor deposition, sputtering, and CVD. It is preferable.

In the production method of the present invention, the film forming method of the material (A) larger than the theoretical weight lithium occlusion amount of carbon and the material component (B) which does not occlude lithium is selected from the group consisting of vapor deposition, sputtering and CVD methods. Preferably, at least one method is used.
The present invention is characterized in that particles having a material (A) larger than the theoretical weight lithium occlusion amount of carbon and a material component (B) that does not occlude lithium are formed, and the particles are laminated on a current collector. The present invention relates to a method for producing a negative electrode for a secondary battery.

In the production method of the present invention, it is preferable that the method for forming the particles is mechanical rimming or firing.
The present invention further relates to a negative electrode for a secondary battery manufactured by the previous manufacturing method.
The present invention further relates to a secondary battery having the secondary battery negative electrode.

  According to the present invention, even when an alloy material having a large amount of occlusion of lithium is used as a negative electrode material, it is possible to obtain high capacity and excellent cycle characteristics in order to suppress separation from the current collector and to suppress pulverization of the active material. .

[Features of the invention]
The negative electrode for a lithium ion secondary battery of the present invention is a negative electrode having a material (A) larger than the theoretical weight lithium occlusion amount of carbon and containing a material component (B) that does not occlude lithium as it is closer to the current collector. Here, carbon represents a crystal of graphite, and the limit is the state in which one atom of lithium is contained per six atoms of carbon. When this state is converted into an amount of electricity, it becomes 372 Ah / g. The material (A) larger than the lithium storage amount preferably contains at least one selected from the group consisting of Si, Sn and Al. By using these materials (A), a secondary battery having a higher energy density can be obtained. Specifically, these metal carbides, nitrides, organic acid salts (for example, acetates), inorganic acid salts (for example, chlorides, carbonates, nitrates) and the like can be used. Examples thereof include SiO, SnO, SnO ₂ , Al ₂ O ₃ , and non-stoichiometric compounds of these oxides. These may be composite oxides with lithium oxide, Li ₂ SnO ₂ , LiSiO, Li ₂ SiO, LiSiO _1.5 , Li ₂ SiO _1.5 . More preferably, a material (A) containing at least one of Si and Al is used.

The material component that does not occlude lithium is a simple substance or a compound containing at least one of Ti, Fe, Co, Ni, Mo, and W.
In one embodiment of the negative electrode for secondary battery of the present invention, the concentration of the material component (B) that does not occlude lithium in the negative electrode material for secondary battery increases from the negative electrode material for secondary battery toward the current collector side. There is a feature. In this case, there may be a portion where the concentration of the material component (B) is constant toward the current collector side in the layer thickness direction in the layer including the negative electrode material for secondary batteries in a part of the negative electrode material.

  For example, when these materials are formed on a copper foil by vapor deposition, CVD, sputtering, etc., the closer to the current collector, the more the material components that do not occlude lithium, and as the distance from the current collector increases, the lithium occlusion material component Form so as to increase. Or particles composed of a material larger than the theoretical weight lithium storage capacity of carbon and a material component that does not occlude lithium, and the closer to the current collector, the more the material component that does not occlude lithium than the lithium occlusion material component. As the distance from the electric body increases, it is composed of particles containing a large amount of lithium storage material components.

  It is preferable to have a concentration gradient such that the concentration of the material component (B) increases from the secondary battery negative electrode material toward the current collector side.

[Action]
The negative electrode of the present invention contains the material (A) larger than the theoretical weight lithium occlusion amount of carbon and contains the material component (B) that does not occlude lithium as it is closer to the current collector. First, the energy density of the battery can be further improved by using a material (A) having a higher theoretical capacity than the carbon material used in the conventional lithium ion secondary battery. In addition, the closer to the current collector, the more the material component (B) that does not occlude lithium is contained, so that the volume expansion / contraction associated with charging / discharging is alleviated and peeling from the current collector can be suppressed. Furthermore, by using a material component (B) that does not occlude lithium and having a lower ductility and malleability than the current collector, pulverization due to stress generated by charging and discharging can be suppressed. Alternatively, the anode material can be composed of particles having a material (A) larger than the lithium storage amount of carbon and a material component (B) that does not store lithium, whereby the pulverization of the active material accompanying charge / discharge can be suppressed.

[Negative electrode structure]
Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an example of the negative electrode structure of the present invention. The current collector 1a is a member that becomes a base when the negative electrode material (active material) is formed, and is a member that exchanges current with the active material during charging and discharging. It consists mainly of a copper foil having a thickness of 5 to 20 μm. The surface roughness Ra of the current collector is suitably from 0.01 to 5 μm, more preferably from 1 to 5 μm. The presence of these surface roughnesses can increase the adhesion between the current collector 1b and the active material. The Li storage material (material (A) larger than the theoretical weight lithium storage amount of carbon) 2a plays a role of storing and releasing Li, and includes at least one element selected from the group consisting of Si, Sn, and Al. The Li non-occlusion material (material component (B) that does not occlude lithium) 3a functions to suppress pulverization of Li storage material 2a accompanying charge / discharge or separation from current collector 1a. Ti, Fe, Co, Ni , At least one element selected from the group consisting of Mo and W. When the Li non-occlusion material contains these elements, a secondary battery having a higher capacity and excellent cycle characteristics can be obtained.

  In the negative electrode of FIG. 1, the concentration of the material component (B) (or the content in the surface direction of the current collector) increases toward the current collector side in the layer thickness direction in the layer containing the negative electrode material for the secondary battery. ing. Further, the Li storage material 2a and the Li non-occlusion material 3a occupy a certain region in the negative electrode material (the Li storage material 2a is a hatched portion: the Li non-occlusion material 3a is a vertical line portion).

  FIG. 3 is a schematic view showing another example of the negative electrode structure of the present invention. Particles having a Li storage material (material (A) larger than the theoretical weight lithium storage amount of carbon (2)) 2b and a non-Li storage material (material component (B) that does not store lithium) 3b are stacked on the current collector 1b. Yes. In the particles, the Li occlusion material 2b and the Li non occlusion material 3b are mixed in a desired ratio, and the Li occlusion material 2b and the Li non occlusion material 3b are uniformly or non-uniformly distributed in the particles. Preferably, as shown in FIG. 3, one material is wrapped with the other material. In this case, the concentration of (B) in the particles increases in the layer containing the negative electrode material for secondary batteries toward the current collector side in the layer thickness direction. A part of the negative electrode material may have a constant concentration of the material component (B) from the negative electrode material for the secondary battery toward the current collector.

  When such particles are used, voids are generated between the particles during lamination, so that the volume expansion / contraction of the material (A) due to charge / discharge can be absorbed by the voids, and the negative electrode material can be separated from the current collector. It can be effectively suppressed.

[Method for producing secondary battery]
In an example of the method for producing a negative electrode of the present invention, a material (A) larger than the theoretical weight lithium occlusion amount of carbon and a material component (B) that does not occlude lithium are supplied from different sources, respectively. It can be manufactured by continuously reducing the amount of film and continuously increasing the amount of film formation of the material component (B).

  Next, an example of the manufacturing method of the negative electrode of this invention is demonstrated. FIG. 2 shows a manufacturing method of the negative electrode having the structure of FIG. In this manufacturing method, an electrode material is formed by forming a negative electrode material on the copper foil to be the current collector 1a. It is preferable to use a copper foil as the current collector 1a, and the thickness is preferably 5 to 20 μm, and more preferably 1 to 5 μm. The surface roughness Ra of the current collector 1a is suitably 0.01 to 5 μm. As a film formation method, a vacuum film formation method such as a sputtering method, a CVD method, or an evaporation method can be used. These methods can be used alone or in combination of a plurality of film forming methods. By using these methods, a desired material can be formed with high accuracy. The Li non-occlusion material supply source 4a supplies the Li non-occlusion material (material component (B) that does not occlude lithium) 3a to the current collector 1a, and is composed of a material mainly composed of the Li non-occlusion material 3a. . The Li storage material supply source 5a supplies a Li storage material (material (A) larger than the theoretical weight lithium storage amount of carbon) 2a to the current collector 1a, and is composed of a material mainly composed of the Li storage material 2a. The In this manufacturing method, the surface of the foil-like current collector 1a is perpendicular to the supply direction of the Li non-occlusion material 3a from the Li non-occlusion material supply source 4a and the supply direction of the Li storage material 2a from the Li storage material supply source 5a. The current collector 1a is moved from one end 7 to the other end 8 in a direction 6 perpendicular to the material supply direction from the supply sources 3a and 5a. Immediately after the current collector 1a starts moving from one end portion 7, the current collector 1a is present in the vicinity of the Li non-occlusion material supply source 4a and is far from the Li storage material supply source 5a. For this reason, the ratio of the Li non-occlusion material 3a formed on the current collector 1a in the Li non-occlusion material 3a supplied from the Li non-occlusion material supply source 4a is large. On the other hand, the proportion of the Li storage material 2a formed on the current collector 1a in the Li storage material 2a supplied from the Li storage material supply source 5a is small. Therefore, the concentration of the material component (B) increases in the portion close to the current collector 1a. Note that the film deposition amount of the Li storage material 2a from the Li storage material supply source 5a immediately after the start of the movement of the current collector 1a may be zero.

  On the other hand, when a long time has elapsed after the start of the movement of the current collector 1a, the current collector 1a is present in the vicinity of the Li storage material supply source 5a and is far from the Li non-storage material supply source 4a. For this reason, the proportion of the Li storage material 2a formed on the current collector 1a in the Li storage material 2a supplied from the Li storage material supply source 5a is large, whereas the supply is from the Li non-storage material supply source 4a. The ratio of the Li non-occlusion material 3a formed on the current collector 1a in the Li non-occlusion material 3a is large. Accordingly, the concentration of the material component (B) decreases as the distance from the current collector 1a increases. Note that the film formation amount of the Li non-occlusion material 3a from the Li non-occlusion material supply source 4a when a long time has elapsed after the start of the movement of the current collector 1a may be zero.

  Further, the current collector 1a is fixed, the amount of the Li storage material 2a supplied from the Li storage material supply source 5a is continuously reduced, and the amount of the Li non storage material 3a supplied from the Li non storage material supply source 4a is continuously reduced. Similarly, the negative electrode material can be manufactured by increasing the number of the negative electrodes.

  In this way, it is possible to obtain a negative electrode in which the concentration of the material component (B) (Li non-occlusion material 3a) is large in the vicinity of the current collector 1a, and the concentration decreases as the distance from the current collector 1a increases. In these manufacturing methods, the concentration of the Li non-occlusion material 3a in the material can be easily controlled by changing the supply amount of the raw material and the moving speed of the current collector.

  In addition, a well-known thing can be used for the raw material and film-forming conditions at the time of sputtering method, CVD method, and vapor deposition.

  Next, a method for manufacturing the battery having the structure shown in FIG. 3 will be described as another example of the manufacturing method of the present invention. The particles constituting the negative electrode material of the battery of FIG. 3 can be obtained by mixing and granulating the Li occlusion material 2b and the Li non-occlusion material 3b by mechanical milling, or by firing a mixture of these materials. By using these methods, the concentration of the Li non-occlusion material 3b in the particles can be easily controlled. At this time, the ratio of the Li storage material 2b and the Li non-storage material 3b in the particles can be changed by adjusting the mixing ratio of the Li storage material 2b and the Li non-storage material 3b in advance. Moreover, it is preferable that the average particle diameter of particle | grains is 0.1-5 micrometers. When the average particle diameter is within these ranges, voids can be provided between the particles with an appropriate distribution and size, and volume changes due to expansion and contraction of the material (A) can be absorbed in the voids. Peeling of the negative electrode material from the electric body can be effectively prevented.

  The negative electrode powder material thus obtained is made into a solution form dispersed and kneaded with a conductive substance, a conductivity-imparting agent, a binder and a solvent, and a material having a high Li non-occlusion material 3b concentration in the powder is placed on the current collector 1b. Apply sequentially. A well-known thing can be used for a conductive provision agent and a binder. The content of the conductivity-imparting agent in the solution is preferably 1 to 5% by mass. Moreover, it is preferable that the content of a binder is 1-10 mass%. As a coating method, a doctor blade method or spray coating is used. These manufacturing methods can be performed in a short time with a simple apparatus. When the specific gravity of the Li non-occlusion material 3b is larger than that of the Li occlusion material 2b, a plurality of types of particles having different ratios between the Li non-occlusion material 3b and the Li occlusion material 2b were mixed and applied in a solvent. By leaving it later, particles whose specific gravity of the Li non-occlusion material 3b is larger than that of the Li occlusion material 2b are first settled on the current collector 1b side, and a negative electrode containing a material component that does not occlude lithium is obtained as it is closer to the current collector. be able to.

[Secondary battery]
A secondary battery can be obtained by using the negative electrode and combining it with a positive electrode, a separator and an electrolytic solution.

As the positive electrode for _{example, LiCoO 2, Li x Co 1} -y M y O 2, Li 2 NiO 2, Li x MnO 2, Li x MnF 2, Li x MnS 2, Li x Mn 1-y M y O 2, _{Li x Mn 1-y M y} O 2, Li x Mn 1-y M y O 2-z F z, Li x Mn 1-y MyO 2-z S z, Li x Mn 2 O 4, Li x Mn 2 _{F 4, Li x Mn 2 S} 4, Li x Mn 2-y M y O 4, Li x Mn 2-y M y O 4-z F z , and _{Li x Mn 2-y MyO 4} -z S z (0 <X ≦ 1.5, 0 <y <1.0, Z ≦ 1.0, and M represents at least one transition metal), and the thickness thereof is 10 to 500 μm. Similarly to the negative electrode, the positive electrode active material is a conductive material such as carbon black, and a binder such as polyvinylidene fluoride (PVDF) is dispersed and kneaded with a solvent such as N-methyl-2, multi-pyrrolidone (NMP) such as fluororesin. Is applied to the positive electrode current collector.

There is an insulating and ionic conductive separator between the negative electrode and the positive electrode, and it is made of a polyolefin porous film such as polypropylene or polyethylene.
Moreover, as electrolyte solution, cyclic carbonates, such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl Linear carbonates such as carbonate (EMC) and dipropyl carbonate (DPC), aliphatic carboxylic acid esters such as methyl formate, methyl acetate and ethyl propionate, γ-lactones such as γ-butyrolactone, 1,2- Chain ethers such as ethoxyethane (DEE) and ethoxymethoxyethane (EME), cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, acetamide, dimethyl Formamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2- An aprotic organic solvent such as oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propane sultone, anisole, N-methylpyrrolidone, etc. is used, or a mixture of two or more of these organic solvents. The lithium salt that dissolves in the solvent is dissolved.

Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiAlCl ₄ , LiClO ₄ , LiBF ₄ , LiSbF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ). ₂ , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium carboxylate, lithium chloroborane, lithium tetraphenylborate, LiBr, LiI, LiSCN, LiCl, imides and the like. Further, a polymer electrolyte may be used instead of the electrolytic solution.

  FIG. 4 shows a form of a coin type cell as an example of the battery. The present invention is not limited in battery shape, and can take the form of a positive electrode and a negative electrode facing each other with a separator in between, a wound type, a laminated type, etc. A cell or a cylindrical cell can be used.

  Below, an example of the assembly method of a battery is demonstrated. After laminating the positive electrode, separator, and negative electrode, or winding the laminated one, it is placed in a container made of a flexible film made of a metal can or a laminate of synthetic resin and metal foil, and then the electrolyte is injected and sealed By doing so, a battery can be manufactured.

[Example 1], [Reference Example 1]
(First embodiment)
Next, the first embodiment will be described using Example 1 and Reference Example 1. In Example 1 and Reference Example 1, a secondary battery having the structure of FIG. 1 is manufactured by a film forming method (manufacturing method of FIG. 2). The film formation method at this time was performed by vapor deposition, sputtering, or CVD. For the vapor deposition, the film was formed by properly using an electron beam, an ion beam, a resistance heating method, etc. depending on the melting point and physical properties of the material. Sputtering was performed by forming an inert gas into plasma on a target made of a material and sputtering with an acceleration voltage. In the case of the CVD method, the chambers of the Li non-occlusion material supply source 4a and the Li occlusion material supply source 5a are isolated so that the reaction gases are not mixed.

  In these film forming methods, the tip of the Li non-occlusion material supply source 4a and the Li occlusion material supply source 5a and the current collector were arranged apart from each other. Next, the current collector is moved from one end (corresponding to 7 in FIG. 2) to the other end (corresponding to 7 in FIG. 2) in the direction perpendicular to the supply direction of the Li non-occlusion material supply source 4a and the Li storage material supply source 5a. (Corresponding to 8 in FIG. 2). The density | concentration of the material component (B) in the negative electrode manufactured by the said manufacturing method was 0 mass% near the separator, increased as it went to the collector side, and was 100 mass% near the negative electrode collector.

In order to confirm the cycle characteristics of the negative electrode thus obtained, a battery was evaluated in combination with the positive electrode. An electrode composed mainly of LiCoO ₂ was used as a positive electrode as a counter electrode, and the coating amount was controlled so that the capacity ratio between the positive electrode and the negative electrode was 1.0 to 1.1 with respect to the positive electrode 1. A cylindrical cell was fabricated by winding a separator between the negative electrode and the positive electrode and evaluated. The results of the cycle characteristics are shown in Table 1. The cycle characteristics were evaluated by the number of charge / discharge cycles at which the initial discharge capacity was reduced to 80%. From this result, it was found that when gold or copper having high ductility or malleability was used as the Li non-occlusion material 3a, the capacity deterioration due to the charge / discharge cycle was severe. This is because the Li storage material 2a is peeled off or pulverized from the current collector 1a due to volume expansion / contraction due to charge / discharge.

[Example 2], [Reference Example 2]
Next, a second embodiment will be described using Example 2 and Reference Example 2. In the present embodiment, the negative electrode material is composed of particles having a Li storage material 2b and a Li non-storage material 3b. First, particles were formed by mechanical milling or firing. Mechanical milling was performed in an argon atmosphere, and a desired type of particles prepared by changing the mass ratio of the Li storage material 2b and the Li non-storage material 3b were prepared. The Li occlusion material 2b and the Li non-occlusion material 3b were fired until they became an alloy under inert gasification, and in some cases, pulverized after firing, and the obtained particles were used as the negative electrode.

  The negative electrode powder material thus obtained was dispersed and kneaded with carbon black, polyvinylidene fluoride (PVDF), N-methyl-2-pyrrolidone (NMP), and Li non-occlusion material (material component (B) in the powder) ) The material having a high concentration of 3b was sequentially applied onto the current collector 1b. The density | concentration of the material component (B) in the negative electrode manufactured by the said manufacturing method was 0 mass% near the separator, increased as it went to the collector side, and was 100 mass% near the negative electrode collector.

  The characteristics of each sample are shown below.

  In order to confirm the cycle characteristics of the negative electrode thus obtained, a positive electrode and a combination battery were evaluated. From this result, it was found that the capacity deterioration due to the cycle was severe in the negative electrode in which the Li non-occlusion material 3b and the Li occlusion material 2b were not alloyed by mechanical milling or firing. This is because the Li storage material 2b is peeled off or pulverized from the current collector 1b by volume expansion / contraction due to charge / discharge.

It is a schematic diagram of the negative electrode material which shows an example of 1st embodiment of this invention. It is a figure showing the manufacturing method of the negative electrode material which shows an example of 1st embodiment of this invention. It is a schematic diagram of the negative electrode material which shows an example of 2nd embodiment of this invention. It is a figure showing the manufacturing method of the negative electrode material which shows an example of 2nd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode material layer 2 Negative electrode material layer 3 Positive electrode collector 4 Negative electrode collector 5 Separator 6 Positive electrode outer can 7 Negative electrode outer can 8 Insulation packing 1a, 1b Current collector 2a, 2b Li occlusion material 3a, 3b Li non Occlusion material 4a Li non-occlusion material source 5a Li occlusion material source

Claims (11)

A secondary battery negative electrode comprising a current collector and a secondary battery negative electrode material capable of occluding and releasing lithium ions,
The negative electrode material for a secondary battery has a material (A) larger than the theoretical weight lithium occlusion amount of carbon and a material component (B) that does not occlude lithium, and extends from the negative electrode material for secondary battery toward the current collector side. And the concentration of the material component (B) is increased.   2. The negative electrode for a secondary battery according to claim 1, wherein the material (A) larger than the theoretical weight lithium occlusion amount of carbon has at least one element selected from the group consisting of Si, Sn and Al. .   The material component (B) that does not occlude lithium has at least one element selected from the group consisting of Ti, Fe, Co, Ni, Mo, and W. 3. Negative electrode for secondary battery.   The said negative electrode material for secondary batteries is comprised by the particle | grains which have a material (A) larger than the theoretical weight lithium occlusion amount of the said carbon, and the material component (B) which does not occlude the said lithium. The negative electrode for a secondary battery according to any one of 1 to 3.   The negative electrode for a secondary battery according to any one of claims 1 to 4, wherein the current collector is a copper foil, and the surface roughness (Ra) of the copper foil is 1 to 5 µm. Supplying a material (A) larger than the theoretical weight lithium occlusion amount of carbon from the first source onto the current collector, and supplying a material component (B) that does not occlude lithium from the second source; A method for producing a negative electrode for a secondary battery by forming a film containing a negative electrode material for a secondary battery by:
A method for producing a negative electrode for a secondary battery, wherein the supply amount of the material (A) onto the current collector is continuously reduced, and the supply amount of the material component (B) is continuously increased.   The method for forming a film containing the negative electrode material for a secondary battery is at least one method selected from the group consisting of vapor deposition, sputtering, and CVD methods. Manufacturing method of negative electrode.   For a secondary battery, characterized by forming particles having a material (A) larger than the theoretical weight lithium storage capacity of carbon and a material component (B) that does not store lithium, and laminating the particles on a current collector Manufacturing method of negative electrode.   The method for producing a negative electrode for a secondary battery according to claim 8, wherein the method for forming the particles is mechanical rimming or firing.   A negative electrode for a secondary battery manufactured by the manufacturing method according to claim 6. The secondary battery which has the negative electrode for secondary batteries of any one of Claims 1 thru | or 5 or Claim 10.

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