JP2000348729A - Positive electrode plate for lithium secondary battery, its manufacture and lithium secondary battery manufactured by using the positive electrode plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain expansion at high temperature at a low cost and enhance ion conductivity by using polyvinyl chloride for a binder. SOLUTION: Polyvinyl chloride used for a binder serves to allow a positive electrode active material to adhere well to a collector and to reduce contact resistance between the collector and the active material. Since the ion conductivity of the polyvinyl chloride shows a relatively high value of around 10-3 S/cm, it can improve battery performance. The use quantity of the polyvinyl chloride is preferably set to 1-10 wt.% with respect to the total quantity of the active material, the binder and a conductive agent. In order to manufacture this positive electrode plate, slurry prepared by mixing the active material, the conductive agent and the binder in a solvent is applied to a positive electrode collector. Then, it is dried at 80-150 deg.C to remove the solvent. It is pressed by a roll press, and thereafter shaped into a desired size. Aluminum foil is preferably used for the positive electrode collector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode plate for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery manufactured by using the same. And a positive electrode plate for a lithium secondary battery.

[0002]

_2. Description of the Related Art LiCoO ₂ , LiMn ₂ O ₄ , which are positive electrode active materials for producing a positive electrode plate for a lithium secondary battery,
LiMnO ₂ , LiNiO ₂ , LiNi _1-x Co _x O
_{2, LiNi 1-y Co x} M y O z (0 <x <1,0 <y <
A mixed metal oxide such as 1, 0 <x + y <1, M is a metal) is mixed with a solvent together with a binder, a conductor and the like to prepare a slurry, which is then applied to a positive electrode current collector and dried.
At this time, the material used as the binder is a conductive polymer material called vinylidene fluoride resin (PVdF), but this material is expensive and has a problem of swelling at about 150 degrees Celsius. further,
There is a problem that the ionic conductivity is as low as about 10 ⁻⁶ S / cm.

In particular, when a battery employing the electrode plate using a vinylidene fluoride resin as a binder, electrolyte, H _{2 O} and vinylidene fluoride resin present in the positive electrode active material or negative electrode active material to react with the HF gas In some cases, and the performance of the battery was seriously deteriorated.

[0004]

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a positive electrode plate for a lithium secondary battery which is inexpensive, hardly expands even at high temperatures, and has high ion conductivity. That is.

Another object of the present invention is to provide a positive electrode plate for a lithium secondary battery which can ensure excellent battery performance by not generating HF gas.

Another object of the present invention is to provide a method for manufacturing the positive electrode plate and a lithium secondary battery employing the same.

[0007]

In order to achieve these objects of the present invention, the present invention provides a positive electrode for a lithium secondary battery in which a positive electrode active material and a binder are applied in a mixed state on a positive electrode current collector. A positive electrode plate for a lithium secondary battery, wherein the binder is polyvinyl chloride. The positive electrode plate may further include a conductive agent in addition to the positive electrode active material and the binder.

[0008] The present invention also provides a step of mixing a positive electrode active material, polyvinyl chloride and a conductive agent in a solvent, a step of applying the mixture to a positive electrode current collector, and a step of applying the positive electrode current collector to which the mixture is applied. Provided is a method of manufacturing a positive electrode plate for a lithium secondary battery, including a step of drying at 80 to 150 degrees Celsius.

Further, the present invention provides a lithium secondary battery employing the above-mentioned positive electrode plate.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

A first method for producing a positive electrode plate according to the present invention
Is a step of mixing a positive electrode active material, polyvinyl chloride and a conductive agent in a solvent.

As the positive electrode active material, manganese compounds represented by the following chemical formulas 1 to 6 and cobalt or nickel compounds represented by the following formulas 7 to 12 can be used.

Li _x MnA ₂ (chemical formula 1) Li _x MnO _2-z A _z (chemical formula 2) Li _x Mn _{1- y My} A ₂ (chemical formula 3) Li _x Mn ₂ A ₄ (chemical formula 4) Li _x Mn ₂ O _4-z A _z (Chemical formula 5) Li _x Mn _{2- y My} A ₄ (Chemical formula 6) (In formulas 1 to 6, 1.0 ≦ x ≦ 1.1,
0.01 ≦ y ≦ 0.1, 0.01 ≦ z ≦ 0.5,
M is Al, Cr, Co, Mg, La, Ce, Sr and V
And at least one metal selected from the group consisting of transition metals and lanthanoid metals, wherein A is selected from the group consisting of O, F, S and P. )

Li _x BA ₂ (chemical formula 7) Li _x BO _2-z A _z (chemical formula 8) Li _x B _{1 -y My} A ₂ (chemical formula 9) Li _x NiCoA ₂ (chemical formula 10) Li _x NiCoO _{2- z} A _z (formula _{11) Li x Ni 1-yz} Co y M z A 2 ( formula 12) (in formula 7~12, 1.0 ≦ x ≦ 1.1,
0.01 ≦ y ≦ 0.1, 0.01 ≦ z ≦ 0.5,
M is Al, Cr, Mn, Fe, Mg, La, Ce, Sr
And at least one metal selected from the group consisting of transition metals and lanthanoid metals selected from the group consisting of
Is selected from the group consisting of O, F, S and P, and B is Ni
Or Co. )

The polyvinyl chloride used as a binder serves to make the positive electrode active material adhere well to the aluminum foil serving as the positive electrode current collector, and to reduce the contact resistance between the current collector and the active material. Further, since polyvinyl chloride has a relatively high ionic conductivity value of about 10 ⁻³ S / cm, a battery having excellent performance can be provided.

The amount of the polyvinyl chloride used as the binder is 1 to the combined amount of the positive electrode active material, the binder and the conductive agent.
It is preferable to use 10% by weight.

When the amount of the binder exceeds 10% by weight, the amount of the active material is relatively reduced, so that there is a problem that the capacity of the battery is reduced. If the amount of the binder used is 1% by weight or less, the power for binding the active material of the current collector is weak, and it is difficult to easily manufacture an electrode plate.

As the conductive agent, it is preferable to use a carbon-based conductive agent such as Ketjen black or carbon black, and it is preferable to use 2 to 4% by weight of the combined amount of the positive electrode active material, the binder and the conductive agent. preferable. It is not always necessary to use a conductive agent when manufacturing the electrode plate, but it is preferable to use a small amount of the conductive agent in order to further improve the conductivity of the electrode plate. As a solvent, n-methylpyrrolidone can be used.

A slurry prepared by mixing a positive electrode active material, a conductive agent, and a binder with a solvent is applied to a positive electrode current collector. Aluminum foil can be used as the positive electrode current collector. The slurry is coated on a current collector to make it evenly thin and flat, and then dried at 80 to 150 degrees Celsius to volatilize n-methylpyrrolidone. Preferably, n-methylpyrrolidone is volatilized at about 120 degrees Celsius. Next, after pressurizing with a roll press, cutting with an appropriate size is performed, and this is used for assembling a battery.

A person skilled in the art can easily manufacture a lithium secondary battery according to a known battery manufacturing method using the positive electrode plate according to the present invention.

In the above lithium secondary battery, the negative electrode active material is lithium metal, lithium alloy (alloy).
y), graphite capable of inserting and removing lithium ions,
A carbon material active material such as carbon can be used, and a non-aqueous liquid electrolyte, a polymer electrolyte, or the like can be used as the electrolytic solution.

Next, a preferred embodiment will be presented for understanding the present invention. However, the following examples are provided for better understanding of the present invention, and the present invention is not limited to the following examples.

Example 1 Nikki Co., Ltd. was used as a positive electrode active material. LiMn ₂ O ₄
(Trade name LM4), polyvinyl chloride as binder,
A slurry was prepared by mixing super P as a conductive agent with N-methylpyrrolidone. At this time,
The amount of polyvinyl chloride used was 3% by weight of the total amount of the positive electrode active material, polyvinyl chloride, and superpy.
Superpy was made up to 3% by weight of the combined amount. After applying the produced slurry to aluminum foil,
After drying at 20 degrees, a positive electrode plate was manufactured. A coin-type half-cell was manufactured using lithium metal as a counter electrode to the positive electrode plate. As an electrolyte, a mixture of ethylene carbonate and dimethyl carbonate in a 1: 1 volume ratio was used.
A solution of M LiPF ₆ was used, and a polyethylene porous film was used as a separator.

Example 2 In Example 1, the amount of polyvinyl chloride used was changed to the total amount of the positive electrode active material, polyvinyl chloride and superpy.
The procedure was performed in the same manner as in Example 1 except that the content was changed to% by weight.

Example 3 Example 3 was carried out in the same manner as in Example 1 except that the amount of polyvinyl chloride used was 1% by weight of the total amount of the positive electrode active material, polyvinyl chloride and superpy. did.

Example 4 In Example 1, Nikki Co. was used as the positive electrode active material.
Nip instead of LiMn ₂ O ₄ (trade name: LM4)
pon Chemical's LiCoO ₂ (trade name: C
Example 10 was carried out in the same manner as in Example 1 except that -10) was used.

Example 5 In Example 1, Nikki Co., Ltd. was used as the positive electrode active material.
Instead of LiMn ₂ O ₄ (trade name: LM4)
jo Co. LiNi _0.9 Co _0.1 Sr _{0
. The same} operation as in Example 1 was performed except that ₀₀₂ O ₂ was used.

Comparative Example 1 Example 1 was carried out in the same manner as in Example 1 except that polyvinylidene fluoride resin was used instead of polyvinyl chloride as a binder.

Comparative Example 2 The procedure of Example 4 was repeated, except that polyvinylidene fluoride resin was used instead of polyvinyl chloride as the binder.

Comparative Example 3 The same procedure was performed as in Example 5 except that polyvinylidene fluoride resin was used instead of polyvinyl chloride as the binder.

FIG. 1 shows Example 1 (b) and Comparative Example 1 (a).
4 is a graph showing characteristics of initial charge and discharge of a battery according to the present invention.
As shown in FIG. 1, it can be seen that Example 1 using polyvinyl chloride as the binder and Comparative Example 1 using vinylidene fluoride resin as the binder show almost the same initial discharge capacity.

FIG. 2 shows Example 1 (b) and Comparative Example 1 (a).
5 is a graph showing characteristics of the life of a battery at a normal temperature cycle according to the present invention. As shown in FIG. 2, it can be seen that Example 1 using polyvinyl chloride as the binder and Comparative Example 1 using vinylidene fluoride resin as the binder have almost the same cycle life characteristics at room temperature.

FIG. 3 shows Example 1 (b) and Comparative Example 1 (a).
4 is a graph showing characteristics of a high temperature cycle life of a battery according to the present invention. As shown in FIG. 3, Example 1 using polyvinyl chloride as the binder had a higher temperature (50 degrees Celsius) than Comparative Example 1 using polyvinylidene fluoride resin as the binder.
Degree), the cycle life was found to be very good. In the case of Comparative Example 1 in which the polyvinylidene fluoride resin is used, it is considered that the expansion phenomenon of the polyvinylidene fluoride resin is likely to occur, and the cycle life characteristics are reduced.

FIG. 4 shows Example 4 (b) and Comparative Example 2 (a).
5 is a graph showing characteristics of the life of a high-rate cycle of a battery according to the present invention. As shown in FIG. 4, it can be seen that Example 4 using polyvinyl chloride as a binder during high-rate charge / discharge shows much better cycle life characteristics than Comparative Example 2 using polyvinylidene fluoride resin as a binder. I understand.

[0035]

The positive electrode plate using polyvinyl chloride as a binder can have almost the same level of electrochemical characteristics as the positive electrode plate by using a vinylidene fluoride resin as a binder. Also, at high temperatures, cycle life and high rate cycle life can have better properties than when using vinylidene fluoride resin.

In particular, polyvinyl chloride is less expensive than vinylidene fluoride resin, so that the manufacturing cost of the battery can be reduced, and the conductivity of ions is also high, and the conductivity is higher than other positive electrode active materials. Can be usefully applied to a lithium secondary battery using a LiMn ₂ O ₄ active material having a low density.

[Brief description of the drawings]

FIG. 1 is a graph showing initial charge and discharge characteristics of batteries according to one embodiment and a comparative example of the present invention.

FIG. 2 is a graph showing a normal temperature cycle life characteristic of a battery according to an example and a comparative example of the present invention.

FIG. 3 is a graph showing characteristics of a high-temperature cycle life of batteries according to an example and a comparative example of the present invention.

FIG. 4 is a graph showing characteristics of a high rate cycle life of batteries according to another example and a comparative example of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/40 H01M 10/40 Z

Claims (8)

[Claims] 1. A positive electrode plate for a lithium secondary battery, comprising a positive electrode current collector and a composition of a positive electrode active material containing a positive electrode active material and a binder, wherein the binder is polyvinyl chloride. Positive electrode plate for secondary battery. 2. The positive electrode plate for a lithium secondary battery according to claim 1, wherein the composition of the positive electrode active material further includes a conductive agent. 3. The positive electrode plate for a lithium secondary battery according to claim 2, wherein the content of the polyvinyl chloride is 1 to 10% by weight of the total weight of the positive electrode active material, the binder and the conductor. 4. The positive electrode active material has the following chemical formulas 1 to 1
2. The positive electrode plate for a lithium secondary battery according to claim 1, wherein the positive electrode current collector is selected from the group consisting of 2, and the positive electrode current collector is an aluminum foil. Li _x MnA ₂ (chemical formula 1) Li _x MnO _2-z A _z (chemical formula 2) Li _x Mn _{1- y My} A ₂ (chemical formula 3) Li _x Mn ₂ A ₄ (chemical formula 4) Li _x Mn ₂ O _{4 -z} A _z (formula _{5) Li x Mn 2-y} M y A 4 ( chemical formula 6) (in formula 1~6, 1.0 ≦ x ≦ 1.1,
0.01 ≦ y ≦ 0.1, 0.01 ≦ z ≦ 0.5,
M is Al, Cr, Co, Mg, La, Ce, Sr and V
And at least one metal selected from the group consisting of transition metals and lanthanoid metals, wherein A is selected from the group consisting of O, F, S and P. ) Li _x BA ₂ (Formula _{7) Li x BO 2-z} A z ( Formula _{8) Li x B 1-y} M y A 2 ( Chemical 9) Li _x NiCoA ₂ (Formula _{10) Li x NiCoO 2-z} A _z (Chemical formula 11) Li _x Ni _1-yz Co _y M _z A ₂ (Chemical formula 12) (In formulas 7 to 12, 1.0 ≦ x ≦ 1.1,
0.01 ≦ y ≦ 0.1, 0.01 ≦ z ≦ 0.5,
M is Al, Cr, Mn, Fe, Mg, La, Ce, Sr
And at least one metal among transition metals or lanthanoid metals selected from the group consisting of
A is selected from the group consisting of O, F, S and P, and B is N
i or Co. ) 5. The positive electrode plate for a lithium secondary battery according to claim ₄ , wherein the positive electrode active material is LiMn ₂ O ₄ . 6. A step of mixing a positive electrode active material, polyvinyl chloride, and a conductor with a solvent; a step of applying the mixture to a positive electrode current collector; and a step of applying a positive electrode current collector coated with the mixture to a temperature of 80 degrees Celsius. A method for producing a positive electrode plate for a lithium secondary battery, comprising a step of drying at a temperature of from 150 to 150 degrees. 7. The positive electrode active material has the following chemical formulas 1 to 1
7. The positive electrode plate for a lithium secondary battery according to claim 6, wherein the positive electrode current collector is selected from the group consisting of 2, and the positive electrode current collector is an aluminum foil. Li _x MnA ₂ (chemical formula 1) Li _x MnO _2-z A _z (chemical formula 2) Li _x Mn _{1- y My} A ₂ (chemical formula 3) Li _x Mn ₂ A ₄ (chemical formula 4) Li _x Mn ₂ O _{4 -z} A _z (formula _{5) Li x Mn 2-y} M y A 4 ( chemical formula 6) (in formula 1~6, 1.0 ≦ x ≦ 1.1,
0.01 ≦ y ≦ 0.1, 0.01 ≦ z ≦ 0.5,
M is Al, Cr, Co, Mg, La, Ce, Sr and V
And at least one metal selected from the group consisting of transition metals and lanthanoid metals, wherein A is selected from the group consisting of O, F, S and P. Li _x BA ₂ (chemical formula 7) Li _x BO _2-z A _z (chemical formula 8) Li _x B _{1- y My} A ₂ (chemical formula 9) Li _x NiCoA ₂ (chemical formula 10) Li _x NiCoO _2-z A _z (Chemical formula 11) Li _x Ni _1-yz Co _y M _z A ₂ (Chemical formula 12) (In formulas 7 to 12, 1.0 ≦ x ≦ 1.1,
0.01 ≦ y ≦ 0.1, 0.01 ≦ z ≦ 0.5,
M is Al, Cr, Mn, Fe, Mg, La, Ce, Sr
And at least one metal among transition metals or lanthanoid metals selected from the group consisting of
A is selected from the group consisting of O, F, S and P, and B is N
i or Co. ) 8. The lithium secondary battery according to claim 1, wherein a positive electrode plate is used.