JP3456354B2 - Method for producing electrode for non-aqueous electrolyte battery and non-aqueous electrolyte battery using the electrode - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an electrode for a non-aqueous electrolyte battery and a non-aqueous electrolyte battery having an electrode manufactured by the manufacturing method.

[0002]

2. Description of the Related Art Recent remarkable advances in electronic technology have made electronic devices smaller and lighter one after another. Along with this, further miniaturization, weight reduction, and higher energy density are also required for batteries that are power sources.

Conventionally, lead batteries have been used as batteries for general use,
Aqueous solution batteries such as nickel-cadmium batteries were the mainstream. However, although these aqueous solution type batteries are excellent in cycle characteristics, they cannot be said to be sufficiently satisfactory in terms of battery weight and energy density.

Therefore, recently, non-aqueous electrolyte batteries having a high battery voltage, a high energy density and excellent cycle characteristics have begun to be used. A typical non-aqueous electrolyte battery is a lithium ion battery using a material capable of reversibly intercalating lithium ions as an electrode material.

Comparing the approximate energy densities of various small secondary batteries used for power sources of portable equipment,
20-40 Wh / kg, 50-100 Wh / for lead batteries
1, 30-60 Wh / k for nickel-cadmium battery
g, 100 to 160 Wh / l, 4 for nickel metal hydride batteries
5 to 65 Wh / kg, 160 to 200 Wh / l, while lithium ion batteries have 60 to 125 Wh / kg,
It is said to be 190-310 Wh / l.

[0006]

Since the lithium ion battery is excellent in energy density and charge / discharge cycle characteristics as described above, it is expected to be used as a power supply for a portable device which consumes a relatively large amount of power. However, further improvement of load characteristics is one of the important issues.

Generally, one of the methods for improving the load characteristics of a battery is to improve the electron conductivity in the electrode to facilitate the movement of electrons. In particular, the metal oxides and metal composite oxides used as the positive electrode active material are themselves substances having relatively high electric resistance. Therefore,
When the electrode is composed of only these active materials, the electron conductivity is insufficient. Therefore, electronic conductivity is enhanced by adding a conductive agent composed of carbon atoms such as highly conductive graphite or carbon (hereinafter, carbon-based conductive agent) to the electrode.

In such an electrode, a powdery (scale-like, for example) carbonaceous conductive agent, an active material powder, a binder, and a dispersion solvent are kneaded to form a paste, and the paste is applied to an electrode substrate. Are manufactured by the following method (for example, JP-A-5-174811 and JP-A-6-33355).
(See No. 8).

However, in the case of the method of kneading the powdery carbon-based conductive agent, the active material powder, the binder, and the dispersion solvent into a paste, and applying this paste to the electrode substrate,
There are problems that the carbon-based conductive agent is mixed unevenly and the expected conductive effect cannot be obtained, the packing density of the electrodes is lowered, and the production process is complicated.

The present invention has been made to solve the above conventional problems, and an object of the present invention is to provide a method for manufacturing an electrode having excellent load characteristics, and to provide an excellent battery. .

[0011]

[Means for Solving the Problems] That is, the first aspect of the present invention is a ball mill after a carbon-based conductive agent and a dispersion solvent other than water are kneaded in a method for producing an electrode for a non-aqueous electrolyte battery. A step of dispersing a carbon-based conductive agent using, a step of adding an active material and a binder to the paste obtained in the step, kneading these to form an active material paste, and the active material paste is an electrode And a step of applying to a substrate.

A second aspect of the present invention is a method for producing an electrode for a non-aqueous electrolyte battery, wherein a carbon-based conductive agent, a dispersion solvent excluding water, and a binder are kneaded, and then a carbon is produced using a ball mill. A step of dispersing the system conductive agent, a step of adding an active material to the paste obtained in the step, kneading these to form an active material paste, and a step of applying the active material paste to an electrode substrate It is characterized by having.

[0013]

[0014]

[0015]

The third invention is a non-aqueous electrolyte battery,
An electrode manufactured by the manufacturing method according to the first or second invention is provided.

[0017]

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The first invention according to the present invention is, in a method for producing an electrode for a non-aqueous electrolyte battery, a carbon-based conductive agent and a dispersion solvent other than water are kneaded and then carbonized using a ball mill. The step of dispersing the system conductive agent, the step of adding the active material and the binder to the paste obtained in the step, kneading them to form the active material paste, and applying the active material paste to the electrode substrate. The second invention according to the present invention is a method for producing an electrode for a non-aqueous electrolyte battery, in which a carbon-based conductive agent, a dispersion solvent other than water, and a binder are kneaded. , A step of dispersing a carbon-based conductive agent using a ball mill, a step of adding an active material to the paste obtained in the above step and kneading these to form an active material paste, and the active material paste as an electrode substrate Applied to Characterized in that a that step.

[0019]

In the conventional method for manufacturing a battery electrode of this type, it is general that a carbon-based conductive agent, an active material, a binder, and a solvent are kneaded to manufacture an active material paste, which is applied to an electrode substrate. However, in the course of battery performance improvement research, the inventors of the present invention first knead a carbon-based conductive agent or / and a binder and a dispersion solvent other than water, and kneaded the active material. It was found that the battery characteristics can be dramatically improved by dividing into a step of kneading with a binder or an active material and a step of dispersing a carbon-based conductive agent by a ball mill during this step.

The reason why an electrode excellent in load characteristics is provided by adopting such a constitution is not necessarily understood by the present inventors, but the carbon-based conductive agent is dispersed in suitable fine particles. Therefore, when kneading and forming a paste together with the active material, there is no unevenness in dispersion, uniform dispersion, improved adhesion with the active material, and some synergistic effect with the binder and active material. It is thought that this is due to things. In addition, when the dispersion medium of the ball mill is a sphere having a diameter of 30 mm or less and / or a shape corresponding to the sphere, the above effect is further exhibited.

Further, the shape and material of the dispersion medium of the ball mill are not particularly limited, but preferably spherical or / and a shape corresponding thereto. Examples of the conformable shape here include an ellipse and an ellipse, and the material may be natural stone, agate stone, Ottawa sand or the like. A continuous disperser such as a sand grinder similar to a ball mill can also be used.

Further, the binder is added in a more uniform state by adding the binder after the dispersing step or by kneading the active material and then kneading the binder. And shows better battery performance.

[0024]

EXAMPLES The present invention will be described in detail below based on examples, but the invention is not limited to the following examples, and various modifications can be made without departing from the scope of the invention. Needless to say.

<Example 1> [Positive electrode] 0.3 parts by weight, 1.5 parts by weight, 3.0 parts by weight of acetylene black, which is a carbon-based conductive agent, based on 100 parts by weight of LiCoO ₂ , 4.
5 parts by weight and 6.0 parts by weight, and polyvinylidene fluoride (PVd
3 parts by weight of F) and NMP (N- as a dispersion solvent).
Methylpyrrolidone) was added to 40 parts by weight, and they were added and kneaded. Next, the obtained paste was dispersed using a medium type dispersing machine, here a ball mill. At this time, the medium is spherical and has a diameter of 5 mm, 1
Zirconia balls of 0 mm, 30 mm, 40 mm and 50 mm were used.

Then, an active material was added to the obtained paste and kneaded to obtain a positive electrode paste. Next, this active material paste was applied to an electrode base made of aluminum foil and dried to obtain a lithium battery positive electrode. Therefore, the types of positive electrodes adjusted here are 2 types of 5 types of medium × 5 types of carbon-based conductive agent.
There are five types.

In the case of producing a positive electrode for a non-aqueous electrolyte battery according to the present invention, the active material may be any material capable of inserting and extracting lithium ions. Other than the above, metal oxides (MnO ₂ , modified MnO ₂ , heavy MnO ₂ , Li-containing MnO ₂ , MoO ₂ , CuO, Cr ₂ O ₃ , CrO ₃ , V ₂
O ₅ , LiNiO ₂ , NiOOH, etc., metal sulfide (F
eS, TiS ₂ , or MoS _2, etc.), metal selenides (TiSe _2, etc.), MnCo, Ni, V, Cr, Cu
And a composite oxide of at least two metals selected from the group consisting of Ti and Ti. Further, as the electrode substrate, other than the above, an aluminum lath plate,
Examples thereof include a stainless steel plate and a resin substrate on which a metal thin film such as aluminum or copper is formed.

Further, the acetylene black used here has a specific surface area of 30 m ² / g, and as the conductive agent, in addition to acetylene black, Ketjen black, furnace black or the like may be used alone or in combination. Are used in combination. Here, polyvinylidene fluoride is used as a binder, but examples of other materials include polytetrafluoroethylene, rubber-based polymers or mixtures of these with cellulose-based polymers, and copolymers mainly composed of polyvinylidene fluoride. To be done.

In addition, as the medium of the ball mill, other than those mentioned above, zircon beads, titania beads,
Alumina beads or the like may be used.

The ball mill itself is described in detail in, for example, "Chemical Equipment Handbook" (edited by the Chemical Engineering Society of Japan, published in June 1970), and therefore its explanation is omitted, but in this embodiment, the drum capacity is 300 l. Use a ball mill with a drum rotation speed of 33 rpm, and prepare 3 balls for the drum capacity.
The powder was crushed under the conditions of 0%, granule charged amount 35%, and space 35%.

[Negative Electrode] Mesocarbon microbeads made of mesophase microspheres produced in the carbonization process of pitch are used as lithium ion intercalation members,
A negative electrode was prepared by kneading styrene-butadiene rubber as a binder and adding NMP as appropriate to form a paste, which was applied to a copper foil substrate and dried. The mesocarbon microbeads at this time have a particle size of 5 to 50 μm and a surface area of 4 to ²⁰ m ² / g.

[Non-Aqueous Electrolyte] LiClO ₄ was dissolved in a mixed solvent of propylene carbonate and 1,2 dimethoxyethane in a volume ratio of 1: 1 to prepare a non-aqueous electrolyte. The non-aqueous electrolyte solution is not limited to the above, and ethylene carbonate, 1,2-
LiP is used as a solvent such as butylene carbonate, dimethyl carbonate, and diethyl carbonate, or a mixed solvent thereof with a low boiling point solvent such as 1,2-dimethoxyentane.
Various solutions such as a solution in which a solute such as F ₆ or LiClO ₄ is dissolved can be used.

[Separator] Thickness 10 μm, porosity 5
A polyethylene microporous membrane having 0%, an average through-pore diameter of 0.01 μm, and a breaking strength of 0.7 mm in a width of 10 mm was used as a separator. The separator is also not particularly limited, and various conventionally used separators can be used.

[Lithium ion battery] The positive and negative electrodes,
The separator and the electrolytic solution were housed in a rectangular battery container, and 25 types of non-aqueous electrolytic solution batteries having different positive electrode formulations were produced.
A schematic diagram of this battery is shown in FIG. The main constituent elements of this battery are a positive electrode 1, a negative electrode 2, a separator 3, a positive electrode terminal 4, a case 5 also serving as a negative electrode terminal, an electrolytic solution (not shown), and the like.

[Conventional Example] In the production of a positive electrode, 100 parts by weight of LiC of acetylene black, which is a carbon-based conductive agent, was used.
Polyvinylidene fluoride (a total of 3 parts by weight) of 0.3 parts by weight, 1.5 parts by weight, 3.0 parts by weight, 4.5 parts by weight, and 6.0 parts by weight with respect to oO ₂ , respectively. Parts by weight), NMP (total 40 parts by weight) and the active material were added and kneaded to obtain a positive electrode active material paste.

Next, this active material paste was applied to an electrode substrate made of aluminum foil and dried to obtain a positive electrode for a lithium battery. The negative electrode and the electrolytic solution were the same as those described above, and the manufactured battery had the same structure.

[Test Method] Ten above-mentioned batteries and five conventional batteries were subjected to a cycle test under the following conditions.

Charge: 200 mA constant current / 4.1 V constant voltage × 5 h (25 ° C.) Discharge: 400 mA
Constant current end constant voltage (25 ° C.) [Test result] FIG. 2 is a diagram showing discharge characteristics (average value of batteries for each used ball diameter) at the 500th cycle of a battery having a conductive agent amount of 0.3 wt%. is there. As is clear from this example, the characteristics of the battery using balls having a diameter of 30 mm or less are superior to those of the batteries using balls having a diameter of 30 mm or less.

FIG. 3 is a diagram showing the discharge characteristics (average value of the battery for each used ball diameter) at the 500th cycle of a battery having a conductive agent amount of 1.5 wt%. As is clear from this example, the characteristics of the battery using balls having a diameter of 30 mm or less are superior to those of the batteries using balls having a diameter of 30 mm or less.

FIG. 4 is a diagram showing the discharge characteristics (average value of the battery for each used ball diameter) at the 500th cycle of the battery having a conductive agent amount of 3.0 wt%. As is clear from this example, the characteristics of the battery using balls having a diameter of 30 mm or less are superior to those of the batteries using balls having a diameter of 30 mm or less.

The amount of conductive agent is 5.0 wt%, 10.0
Similar results were obtained with a battery of wt%. However,
When the amount of conductive agent exceeds 3.0 wt%, the electrode plate thickness naturally increases, and even if a certain level or more of conductive agent is added, the effect reaches the equilibrium value. It is suitable for the battery to be 3 wt% or less.

In these figures, it was shown that the diameters of 50 mm and 40 mm were superior to the characteristics of the conventional battery, but were slightly inferior to the others.

<Example 2> Next, the specific surface area was 10, 2
Using 0, 30, 40 and 50 m ² / g of acetylene black, the effect of the specific surface area of the conductive agent on the battery characteristics was investigated.

Here, based on the above results, the diameter of 3
Dispersion was carried out using 0 mm balls. Other conditions are the same as above.

As a result, the specific surface area of the conductive agent was 30 m ² /
Those of g or less tended to be inferior in characteristics to those of g or more. It is presumed that this is because those having a specific surface area of 30 m ² / g or less have a larger particle diameter than those having a specific surface area of less than that, and the contact area with the active material and the contact area between the conductive agents are small. . This was also the case when Ketjen black, furnace black or the like was used as the conductive agent.

Therefore, a process in which a carbon-based conductive agent, a binder, and a dispersion solvent are kneaded is used as a dispersion medium in the form of spheres having a diameter of 30 mm or less, and the active material is added to the paste obtained in the above process. The conductive agent used in the invention of the method for producing an electrode for a non-aqueous electrolyte battery, which comprises a step of kneading and kneading to form an active material paste, and a step of applying the active material paste to an electrode substrate is 30 m
Those of ² / g or more are preferable.

Further, the charging amount (in the case of a batch type) or supply amount (in the case of a continuous type) and / or the number of rotations of the drum, etc. to the medium type disperser are limited to those described in this embodiment. Without departing from the spirit of the present invention, those skilled in the art can easily think of making appropriate changes in order to bring out the best effect.

In addition, the binder is added after the dispersing step, or after the active material is added and kneaded, the binder is added and kneaded to bond the active material and the conductive agent in a more uniform state. It was worn and showed better cell performance.

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

As described above in detail, according to the present invention, the conductive effect is reduced due to the uneven mixing of the carbon-based conductive agent, which is found in the conventional method for manufacturing the electrode for the non-aqueous electrolyte battery, and the filling of the electrode. It is possible to provide a method for manufacturing an electrode for a non-aqueous electrolyte battery, which has excellent density characteristics and a complicated manufacturing process, and an excellent battery.

[Brief description of drawings]

FIG. 1 shows a battery that is an embodiment of the present invention.

FIG. 2 is a diagram showing discharge characteristics at a 500th cycle when a conductive agent amount is 0.3 wt%.

FIG. 3 is a diagram showing discharge characteristics at the 500th cycle when the amount of conductive agent is 1.5 wt%.

FIG. 4 is a diagram showing discharge characteristics at the 500th cycle when the amount of a conductive agent is 3.0 wt%.

[Explanation of symbols]

1 positive electrode 2 Negative electrode 3 separator 4 Positive terminal 5 cases

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01M 4/00-4/62

Claims (3)

(57) [Claims] 1. A step of kneading a carbon-based conductive agent and a dispersion solvent excluding water and then dispersing the carbon-based conductive agent by using a ball mill, and a step of adding an active material and a binder to the paste obtained in the above step. A method for producing an electrode for a non-aqueous electrolyte battery, comprising: a step of adding and kneading these to form an active material paste; and a step of applying the active material paste to an electrode substrate. 2. A step of kneading a carbon-based conductive agent, a binder and a dispersion solvent excluding water and then dispersing the carbon-based conductive agent using a ball mill, and an active material in the paste obtained in the above step. A method for producing an electrode for a non-aqueous electrolyte battery, which comprises: a step of adding and kneading these to form an active material paste; and a step of applying the active material paste to an electrode substrate. 3. A manufacturing method according to claim 1 or 2.
Non-aqueous electrolyte battery characterized by having a built-in electrode
pond.