JP3363547B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to selection of a current collector material for a positive electrode and / or a negative electrode for the purpose of improving storage characteristics and cycle characteristics.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
A positive electrode formed by coating an active material layer on a positive electrode current collector;
In a non-aqueous electrolyte secondary battery including a negative electrode formed by coating and forming a carbon layer on a negative electrode current collector, generally, as a material of the positive electrode current collector, even when exposed to a high potential of about 4 V, the electrolyte solution is Aluminum, which does not elute, and copper, which has high conductivity, were used as the material for the negative electrode current collector.

However, the conventional non-aqueous electrolyte secondary battery using each of these current collectors has a problem that storage characteristics and cycle characteristics are generally poor due to the following causes.

(1) Aluminum has poor corrosion resistance, electrochemical stability, and adhesion to the positive electrode active material.

(2) Copper does not elute during normal charge and discharge, but elutes when the negative electrode potential becomes extremely noble during storage or during charge and discharge cycles, so that adhesion with the carbon layer and shape retention of the electrode plate are maintained. Is not good.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a non-aqueous electrolyte secondary battery having excellent storage characteristics and cycle characteristics.

[0007]

[Means for Solving the Problems] To achieve the above object
According to the invention of claim 1,Carbon layer on the negative electrode current collector
Non-aqueous electrolyte secondary battery having a negative electrode formed by coating
(Hereinafter, referred to as “first battery”.)The negative
Surface of a tantalum plate, sheet or foil as a pole collector
Copper-plated is used.

Further, the positive electrode assembly according to the second aspect of the invention.
A positive electrode formed by coating and forming an active material layer on an electric conductor, and a negative electrode collector.
A negative electrode formed by coating a carbon layer on an electric body
In a water electrolyte secondary battery (hereinafter, referred to as “second battery”), a plate made of tantalum, a battery, or the like is used as the positive electrode current collector .
Or a foil is used, and as the negative electrode current collector,
Copper plating on the surface of tantalum plate, sheet or foil
Is used.

[0009]

In the second battery , tantalum (Ta) is used as the material of the positive electrode current collector because tantalum is softer than aluminum and has excellent adhesion to the positive electrode active material and corrosion resistance. Because it is excellent and electrochemically stable. It should be noted that tantalum, like aluminum, is not affected by L when exposed to a high potential of 4 V or more during charging.
It does not react with solutes such as iPF ₆ and LiCF ₃ SO _{3 in} the electrolytic solution.

In the first battery , the plate, sheet or foil made of tantalum is used as the base material of the negative electrode current collector because tantalum has excellent corrosion resistance and electrochemical stability. is there. In addition, highly conductive copper (Cu)
The reason why the base material surface is plated is to suppress the decrease in the conductivity of the negative electrode due to using the tantalum base material, which is inferior in conductivity as compared with conventional copper, as it is by copper plating. is there. In addition, when the negative electrode potential becomes extremely noble, the plated copper becomes ions and elutes, and the adhesiveness is slightly reduced, but since the base material tantalum hardly dissolves, unlike the conventional copper negative electrode current collector. The electrode plate shape does not change significantly.

As the positive electrode active material forming the active material layer formed by coating on the positive electrode current collector, Li ₂ FeO ₃ and TiO ₂ are used.
₂ , oxides having tunnel-like vacancies such as V ₂ and V ₂ O _5, metal chalcogenides having a layered structure such as TiS ₂ and MoS ₂ , LiCoO ₂ , LiMnO ₂ , and LiNiO
₂ , the composition formula Li _{x of} LiCrO ₂ , LiMn ₂ O _4, etc.
MO ₂ or Li _y M ₂ O ₄ (where M is a transition element, 0
The composite oxide represented by ≦ x ≦ 1, 0 ≦ y ≦ 2) is mentioned as a typical one, but is not particularly limited thereto. Active material layer, these positive electrode active material, by a conventional method,
A conductive agent such as graphite, acetylene black or carbon black and a binder solution such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) are kneaded to form a slurry, which is coated on the positive electrode current collector. , Formed by drying and solidifying.

Further, as a carbon material forming the carbon layer formed by coating on the negative electrode current collector, coke and graphite which can occlude and release cations such as lithium ions electrochemically are typical examples. However, the present invention is not limited to these. Carbon layer, these carbon materials, by a conventional method,
It is formed by kneading with a solution of a binder to form a slurry, applying this on a positive electrode current collector, and drying and solidifying.

[0014]

In the second battery , tantalum is used in place of conventional aluminum as the material for the positive electrode current collector, so it has excellent corrosion resistance, is electrochemically stable, and has a positive electrode active material and a positive electrode current collector. Good adhesion with.

In the first battery , since copper-plated tantalum is used as the material of the negative electrode current collector in place of conventional copper, it has excellent corrosion resistance and is electrochemically stable.
Further, when the negative electrode potential becomes noble, the plated copper elutes but the tantalum hardly dissolves, so that the shape change of the electrode plate due to the elution of the collector metal hardly occurs.

[0016]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by the examples described below, and various modifications may be made without departing from the scope of the invention. Is possible.

Example 1 [Preparation of Positive Electrode] 95 parts by weight of a mixture of LiCoO ₂ as a positive electrode active material and artificial graphite as a conductive agent in a weight ratio of 9: 1 was mixed with polyvinylidene fluoride as a binder. A slurry was prepared by kneading with 5 parts by weight of a 5% by weight N-methylpyrrolidone solution, and the slurry was used as a positive electrode current collector to have a thickness of 2
0 μm tantalum foil (tantalum purity: 99.9% or more)
On both sides of the coating by the doctor blade method, 150 °
It vacuum-dried at C for 2 hours and produced the positive electrode.

[Preparation of Negative Electrode] Carbon lump (d ₀₀₂ = 3.35)
Å; Lc> 1000Å) was sprayed with an air flow to be crushed (jet crushed) to obtain a carbon powder. 95 parts by weight of this carbon powder was added to 5 parts by weight of polyvinylidene fluoride as a binder.
A slurry was prepared by kneading with a wt% N-methylpyrrolidone solution, and this slurry was copper-plated (plating thickness: 2 μm) as a negative electrode current collector with a thickness of 16 μm tantalum foil (tantalum purity: 99.9% or more). Both surfaces were coated with a doctor blade method and vacuum dried at 150 ° C. for 2 hours to prepare a negative electrode.

[Preparation of Electrolyte Solution] An equal volume of a mixed solvent of ethylene carbonate and 1,2-dimethoxyethane was mixed with Li.
An electrolyte was prepared by dissolving PF ₆ at 1 mol / liter.

[Battery Assembly] AA size (AA) is prepared by using the positive and negative electrodes and the electrolytic solution described above.
Type) of the present invention battery BA1 ( second battery ) was assembled. As the separator, an ion-permeable polypropylene microporous film was used.

FIG. 1 is a cross-sectional view of the manufactured battery BA1 of the present invention. The battery BA1 of the present invention shown in FIG. 1 includes a positive electrode 1 and a negative electrode 2, a separator 3 for separating these electrodes, a positive electrode lead 4 and a negative electrode lead 5. , Positive electrode external terminal 6, negative electrode can 7 and the like. The positive electrode 1 and the negative electrode 2 are housed in the negative electrode can 7 in a state of being spirally wound via the separator 3 into which the nonaqueous electrolytic solution is injected, and the positive electrode 1 is connected to the positive electrode external terminal via the positive electrode lead 4. 6, and the negative electrode 2 is connected to the negative electrode can 7 via the negative electrode lead 5 so that the chemical energy generated inside the battery BA1 can be taken out as electric energy to the outside.

Example 2 A battery BA2 ( first battery ) of the present invention was assembled in the same manner as in Example 1 except that an aluminum foil was used instead of the tantalum foil as the positive electrode current collector.

[0023]

Comparative Example 1 The same as Example 1 except that an aluminum foil was used as the positive electrode current collector instead of the tantalum foil, and a copper foil was used as the negative electrode current collector instead of the copper-plated tantalum foil. Thus, a comparative battery BC1 was produced.

(Storage characteristics and cycle characteristics of each battery) The batteries BA1 and BA2 of the present invention and the comparative battery BC1 were stored at 60 ° C for 10 days (corresponding to storage at room temperature for 6 months) and then 200 mA. Discharge end voltage 2
The capacity remaining ratio to the capacity before storage when discharged to V was examined. The results are shown in Table 1. In addition, after charging to the final voltage of charge of 5V at 200mA and resting for 1 hour, 200m
A charging / discharging cycle test in which one cycle includes a step of discharging at A to a discharge end voltage of 2 V and resting for 1 hour was performed to examine the cycle characteristics of each battery. The results are shown in Figure 2. Figure 2
Cycle characteristics of each battery, discharge capacity (mAh) on the vertical axis
And the horizontal axis represents the number of cycles (times).

[0026]

[Table 1]

From Table 1, the batteries BA1 and BA2 of the present invention (remaining capacity ratio: 88 to 91% ) are comparative batteries B which are conventional batteries.
It can be seen that the storage characteristics are superior to C1 (capacity remaining ratio: 85%). In particular, it is understood that the battery BA1 of the present invention (capacity remaining ratio: 91%) has extremely excellent storage characteristics.

Further, from FIG. 2, the batteries BA1 and BA of the present invention are shown.
It can be seen that the battery No. 2 has a smaller decrease in the discharge capacity with the progress of the charging / discharging cycle than the comparative battery BC1 and has excellent cycle characteristics. In particular, it is understood that the battery BA1 of the present invention has extremely excellent cycle characteristics.

In the above embodiment, a specific example in which the present invention is applied to a cylindrical battery has been described. However, the shape of the battery is not particularly limited, and the present invention has various shapes such as flat type and square type. It is applicable to non-aqueous electrolyte secondary batteries.

[0030]

EFFECT OF THE INVENTION A battery using a plate, sheet or foil made of tantalum as the positive electrode current collector has a closer contact between the positive electrode active material and the positive electrode current collector than a conventional battery using an aluminum foil as the positive electrode current collector. Because of its good performance, a battery using a tantalum plate, sheet or foil with copper plating on the surface of the negative electrode current collector has a higher current collector than a conventional battery using a copper foil as the negative electrode current collector. Since there is little change in the shape of the electrode plate due to the elution of metal,
Both are superior in storage characteristics and cycle characteristics to conventional batteries.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a battery of the present invention manufactured in an example.

FIG. 2 is a graph showing cycle characteristics of a battery of the present invention and a comparative battery.

[Explanation of symbols]

BA1 battery of the present invention 1 positive electrode 2 Negative electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikiya Yamazaki 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (56) Reference JP 62-272458 (JP, A) JP Sho 50-110029 (JP, A) JP-A-4-28163 (JP, A) Patent 3263430 (JP, B2) Proceedings of the 32nd battery discussion meeting, 1991, 1B2, pp. 31-32 (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4/02-4/04 H01M 4/66 H01M 10/40

Claims (2)

(57) [Claims] 1. A carbon layer is formed by coating on a negative electrode current collector.
In a non-aqueous electrolyte secondary battery including a negative electrode,
As a collector, on the surface of tantalum plate, sheet or foil
Non-characterized by using copper plated
Water electrolyte secondary battery . 2. An active material layer is formed by coating on a positive electrode current collector.
The positive electrode and the negative electrode current collector are coated with a carbon layer.
A non-aqueous electrolyte secondary battery comprising a negative electrode
A tantalum plate, sheet or foil is used as the pole collector.
And a plate made of tantalum as the negative electrode current collector,
Sheet or foil with copper plating on the surface is used
A non-aqueous electrolyte secondary battery characterized by the following.