JPH07192718A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To provide a nonaqueous electrolyte secondary battery excellent in recycle characteristic by using a positive electrode composed of transition metal oxide and a conducting agent including a carbon material having a specific (d) value and a negative electrode made of metal lithium. CONSTITUTION:A nonaqueous electrolyte secondary battery using a nonaqueous electrolyte comprises a positive electrode formed of a positive electrode active material composed of transition metal oxide or transition metal composite oxide having a potential of 2V (vs. Li/Li<+>) or higher in an electric charging/ discharging region and including a conducting agent for enhancing conductivity, and a negative electrode made of a negative electrode material capable of storing or discharging metal lithium or a lithium ion. The conducting agent includes at least 10wt.% of a carbon material having a (d) value (d002) of a grid surface (002) is 3.358Angstrom or less by X-ray analysis measurement or 1000Angstrom or more of a size (Lc) of a crystallite in the C axis direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a charging / discharging region.
A transition metal oxide or a transition metal composite oxide showing a potential of V (vs. Li ^/ Li ⁺ ) or more is used as a positive electrode active material, and
The present invention relates to a non-aqueous electrolyte secondary battery including a positive electrode containing a conductive agent, a negative electrode using a material capable of inserting and extracting metal lithium or lithium ions as a negative electrode material, and a non-aqueous electrolyte. The present invention relates to improvement of a conductive agent to be blended in a positive electrode for the purpose of improving cycle characteristics of a water electrolyte secondary battery.

[0002]

2. Description of the Related Art In recent years,
Non-aqueous electrolyte secondary batteries have attracted attention as next-generation secondary batteries because they have advantages such as high energy density and higher voltage because it is not necessary to consider the decomposition voltage of water. ing.

As a positive electrode active material for such a high voltage type non-aqueous electrolyte secondary battery, 2 V (vs.L) in a charge / discharge region is used.
i / Li ⁺ ) or more potential LiNi _x Co _1-x O ₂
A transition metal composite oxide represented by (0 ≦ x ≦ 1) has been proposed. However, since a positive electrode active material of this type generally has low conductivity, a conductive agent such as acetylene black or carbon black is used in the positive electrode. Need to be added to.

However, the conventional non-aqueous electrolyte secondary battery using these conductive agents in the positive electrode has a problem that the cycle characteristics are generally poor, although the reason for this is not clear.

The present invention has been made to solve this problem, and an object thereof is to provide a non-aqueous electrolyte secondary battery having excellent cycle characteristics by using a novel conductive agent for the positive electrode. There is.

[0006]

A non-aqueous electrolyte secondary battery according to the present invention for attaining the above object exhibits a potential of 2 V (vs. Li / Li ⁺ ) or more in a charge / discharge region. A positive electrode containing a transition metal oxide or a transition metal composite oxide as a positive electrode active material, and a positive electrode containing a conductive agent, and a negative electrode containing a material capable of inserting and extracting metal lithium or lithium ions as a negative electrode material. In a non-aqueous electrolyte secondary battery including a water electrolyte, the d-value (d ₀₀₂ ) of a lattice plane (002) plane in X-ray diffraction measurement is used as the conductive agent.
Is a conductive material containing at least 10% by weight of a carbon material having a viscosity of 3.358Å or less.

The non-aqueous electrolyte secondary battery according to the invention of claim 2 has a voltage of 2 V (vs. Li /
Li ⁺ ) a positive electrode active material of a transition metal oxide or a transition metal composite oxide exhibiting a potential of Li ⁺ ) or more, a positive electrode containing a conductive agent, and a substance capable of inserting and extracting metal lithium or lithium ions. A non-aqueous electrolyte secondary battery comprising a negative electrode as a negative electrode material and a non-aqueous electrolyte, wherein the conductive material is a carbon material having a crystallite size (Lc) in the c-axis direction in X-ray diffraction measurement of 1000 Å or more. A conductive agent containing at least 10% by weight is used.

Further, the non-aqueous electrolyte secondary battery according to the invention of claim 3 has a voltage of 2 V (vs. Li) in the charge / discharge region.
/ Li ⁺ ) or more as a positive electrode active material of a transition metal oxide or a transition metal composite oxide showing a potential, and a positive electrode containing a conductive agent and a substance capable of inserting and extracting metal lithium or lithium ions. In a non-aqueous electrolyte secondary battery including a negative electrode having a negative electrode as a negative electrode material and a non-aqueous electrolyte, the conductive agent is a lattice plane (002) in X-ray diffraction measurement.
The d value (d ₀₀₂ ) of the surface is 3.358Å or less, and
Crystallite size in the c-axis direction (L
At least 10 carbon materials whose c) is 1000Å or more
A conductive agent contained in a weight percentage is used.

In the following, the non-aqueous electrolyte secondary battery according to each invention of claim 1, 2 or 3 may be collectively referred to as the battery of the present invention.

According to the present invention, in the charging / discharging region, 2V (v
s. Li / Li ⁺ ) A positive electrode that uses a transition metal oxide or a transition metal composite oxide that exhibits a potential of Li / Li ⁺ ) or more as a positive electrode active material, and a negative electrode that uses a material capable of inserting and extracting metal lithium or lithium ions as a negative electrode material. The target of the non-aqueous electrolyte secondary battery including is a high-voltage non-aqueous electrolyte secondary battery in which the positive electrode potential becomes noble to about 4 V (vs. Li ^/ Li ⁺ ) at the end of charging or overcharge. In this case, in particular, the electrolytic solution is easily decomposed on the surface of the positive electrode, and the capacity is significantly reduced when charging and discharging are repeated.

As the transition metal oxide as the positive electrode active material,
MnO ₂ , TiO ₂ , and V ₂ O ₅ , and LiNi _x Co _1-x O ₂ (0 ≦ x ≦ 1) as the transition metal composite oxide,
Examples are LiMnO ₂ , LiCrO ₂ , and LiMn ₂ O ₄ .

As the negative electrode material in the present invention, a substance capable of inserting and extracting metallic lithium or lithium ions is used. Examples of the substance capable of inserting and extracting lithium ions include carbon materials such as coke, graphite, and a fired organic material.

[0013]

In the battery of the present invention, as the positive electrode conductive agent,
d ₀₀₂ and / or 1 for a carbon material having Lc within a predetermined range
Since the one containing 0% by weight or more is used, decomposition of the electrolytic solution on the surface of the positive electrode at the end of charging or overcharging at which the positive electrode potential becomes noble is suppressed.

[0014]

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] LiOH and Co (OH) ₂ were mixed in a mortar and then dried at 850 ° C. in a dry air atmosphere.
Heat treatment for a period of time, and then crushed into powder with an average particle size of about 5 μm in an Ishikawa type mortar, and LiCo as the positive electrode active material.
O ₂ powder was obtained.

LiCoO ₂ powder thus obtained,
Carbon materials shown in Table 1 as a conductive agent (graphite powder; d ₀₀₂
= 3.356Å, Lc = 900Å) and fluororesin powder as a binder are mixed in a weight ratio of 90: 6: 4 to prepare a positive electrode mixture, and this positive electrode mixture is molded at a molding pressure of 2 Tons /
After pressure forming into a disc with a diameter of 20 cm and a diameter of ² cm, 25
It heat-processed at 0 degreeC and produced the positive electrode.

[Production of Negative Electrode] A rolled lithium plate having a diameter of 20
A negative electrode was manufactured by punching out into a disc shape of mm.

[Preparation of Electrolytic Solution] 1 mol / liter of lithium perchlorate was dissolved in an equal volume mixed solvent of propylene carbonate and 1,2-dimethoxyethane to prepare an electrolytic solution (non-aqueous electrolytic solution).

[Production of Battery] A flat type battery BA1 of the present invention was assembled using the above-mentioned positive and negative electrodes and a non-aqueous electrolyte (battery size: diameter 24.0 mm, thickness 3.0 mm). As the separator, a polypropylene microporous film (manufactured by Hoechst Celanese Co., Ltd., trade name “Celgard”) was used and impregnated with the electrolytic solution.

FIG. 1 is a sectional view schematically showing the assembled battery BA1 of the present invention. The battery BA1 of the present invention shown in the same drawing.
Is composed of a positive electrode 1, a negative electrode 2, a separator 3 for separating the electrodes 1 and 2 from each other, a positive electrode can 4, a negative electrode can 5, a positive electrode current collector 6, a negative electrode current collector 7 and an insulating packing 8 made of polypropylene. .

The positive electrode 1 and the negative electrode 2 are housed in a battery case formed by positive and negative bipolar cans 4 and 5 facing each other through a separator 3 impregnated with a non-aqueous electrolyte solution, and the positive electrode 1 is a positive electrode current collector. 6 to the positive electrode can 4 and the negative electrode 2 to the negative electrode current collector 7
It is connected to the negative electrode can 5 via the so that the chemical energy generated inside the battery can be taken out as electric energy from both terminals of the positive electrode can 4 and the negative electrode can 5.

(Examples 2 to 7) Batteries BA2 to BA7 of the present invention were assembled in the same manner as in Example 1 except that the carbon materials shown in Table 1 were used as the conductive agent.

(Examples 8 to 16) Specific d as a conductive agent
Example 1 except that the mixture shown in Table 1 consisting of a carbon material having ₀₀₂ and Lc and acetylene black was used.
Inventive batteries BA8 to BA16 were assembled in the same manner as in.

(Comparative Examples 1 to 3) Specific d as a conductive agent
Comparative batteries BC1 to BC3 were made in the same manner as in Example 1 except that the carbon materials shown in Table 2 having ₀₀₂ and Lc were used.
Assembled.

(Comparative Examples 4 to 6) Specific d as a conductive agent
Example 1 except using the mixture shown in Table 2 consisting of a carbon material having ₀₀₂ and Lc and acetylene black.
Comparative batteries BC4 to BC6 were assembled in the same manner as in.

[0026]

[Table 1]

[0027]

[Table 2]

[Charge / Discharge Cycle Characteristics of Each Battery] The batteries BA1 to BA16 of the present invention and the comparative batteries BC1 to BC6 were charged at a charging current density of 1 mA / cm ² to 4.3 V and then at a discharging current density of 3 mA / cm ² . A charging / discharging cycle test in which the step of discharging up to 2.5 V was set as one cycle was performed, and the capacity deterioration rate was calculated when the discharge capacity at the first cycle of the discharge capacity at the 100th cycle was 100. The results are shown in Tables 1 and 2 above.

From Table 1 and Table 2, d ₀₀₂ and / or Lc
However, the battery of the present invention using a conductive agent containing at least 10% by weight of a carbon material within the range regulated by the present invention as the conductive agent of the positive electrode has a smaller capacity deterioration rate than the comparative battery, and therefore has excellent cycle characteristics. I understand that.

2, 3 and 4 are graphs showing the results shown in Tables 1 and 2, and FIG. 2 shows the relationship between d ₀₀₂ and the capacity deterioration rate of the carbon material used as the conductive agent. , Fig. 3
Shows the relationship between Lc of the carbon material used as the conductive agent and the capacity deterioration rate, and FIG. 4 shows the relationship between the ratio of the carbon material in the conductive agent regulated by the present invention and the capacity deterioration rate.

FIG. 2 is a graph in which the vertical axis represents the capacity deterioration rate (%) at the 100th cycle, and the horizontal axis represents d ₀₀₂ (Å) of the carbon material, where Lc is Inventive batteries BA1 and BA using 900Å carbon material as a conductive agent
2 and comparative batteries BC1 and BC2, comparing the respective capacity deterioration rates, d ₀₀₂ is 3.35 even if Lc is less than 1000Å.
By using a carbon material of 8 Å or less (the present invention battery B
It can be seen that a battery having a small capacity deterioration rate can be obtained.

Further, since the capacity deterioration rates of the batteries BA5 and BA6 of the present invention having d ₀₀₂ of 3.358 Å or less and Lc of 1000 Å are extremely smaller than those of the batteries BA1 and BA2 of the present invention, d ₀₀₂ of 3. It can be seen that a battery having an extremely small capacity deterioration rate can be obtained by using a carbon material having 358 Å or less and Lc of 1000 Å or more.

FIG. 3 is a graph in which the vertical axis shows the capacity deterioration rate (%) at the 100th cycle, and the horizontal axis shows Lc (Å) of the carbon material. In the figure, d ₀₀₂ is 3.360
The battery BA3 of the present invention using the carbon material of Å as a conductive agent,
From the comparison of the capacity deterioration rates of BA4 and comparative batteries BC1 and BC3, Lc is 1 even if d ₀₀₂ is larger than 3.358Å
It can be seen that by using a carbon material of 000 Å or more (invention batteries BA3 and BA4), batteries having a small capacity deterioration rate can be obtained.

Further, since the capacity deterioration rates of the batteries BA6 and BA7 of the present invention having Lc of 1000 Å or more and d ₀₀₂ of 3.358 Å are extremely smaller than those of the batteries BA3 and BA4 of the present invention, d ₀₀₂ of 3. It can be seen that a battery having an extremely small capacity deterioration rate can be obtained by using a carbon material having 358 Å or less and Lc of 1000 Å or more.

FIG. 4 is a graph in which the vertical axis shows the capacity deterioration rate (%) at the 100th cycle, and the horizontal axis shows the ratio (% by weight) of the carbon material regulated by the present invention in the conductive agent. From the figure, the ratio of the carbon material regulated by the present invention is 10
It is understood that a battery having a small capacity deterioration rate can be obtained by using the conductive agent in an amount of 30% by weight or more, preferably 30% by weight or more.

In the above embodiments, the case where the present invention is applied to the flat type battery has been described as an example, but the shape of the battery is not particularly limited, and the present invention has various shapes such as a cylindrical shape and a square shape. It is applicable to the non-aqueous electrolyte secondary battery of.

Although LiCoO ₂ was used as the positive electrode active material, it was 2 V (vs. Li / L) in the charge / discharge region.
Any transition metal oxide or transition metal composite oxide exhibiting a potential of i ⁺ ) or higher can be used without particular limitation.

Further, although the non-aqueous electrolytic solution is used as the electrolytic solution, it is naturally possible to use a solid electrolyte.

[0039]

EFFECT OF THE INVENTION As the positive electrode conductive agent, a material containing 10% by weight or more of a carbon material having d ₀₀₂ and / or Lc within a predetermined range is used, and thus the positive electrode potential becomes noble at the end of charging or overcharge. The decomposition of the electrolytic solution on the surface of the positive electrode at that time is suppressed, resulting in excellent cycle characteristics.

[Brief description of drawings]

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

FIG. 2 is a graph showing a relationship between d _{002 of a} carbon material and a capacity deterioration rate.

FIG. 3 is a graph showing a relationship between Lc of a carbon material and a capacity deterioration rate.

FIG. 4 is a graph showing the relationship between the ratio of the carbon material regulated by the present invention in the conductive agent and the capacity deterioration rate.

[Explanation of symbols]

 BA1 Inventive battery 1 Positive electrode 2 Negative electrode 3 Separator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Koji 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (72) Koji Nishio 2-5 Keihanhondori, Moriguchi City, Osaka Prefecture No. 5 Sanyo Electric Co., Ltd. (72) Inventor Toshihiko Saito 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A charging / discharging region of 2 V (vs. Li / L)
i ⁺ ) a positive electrode active material of a transition metal oxide or a transition metal composite oxide exhibiting a potential of not less than, and a positive electrode containing a conductive agent, and a substance capable of inserting and extracting metal lithium or lithium ions. In a non-aqueous electrolyte secondary battery comprising a negative electrode as a negative electrode material and a non-aqueous electrolyte, the conductive agent has a d-value (d ₀₀₂ ) of a lattice plane (002) plane of 3.358 Å or less in X-ray diffraction measurement. A non-aqueous electrolyte secondary battery, wherein a conductive agent containing at least 10% by weight of a certain carbon material is used. 2. A charging / discharging region of 2 V (vs. Li / L)
i ⁺ ) a positive electrode active material of a transition metal oxide or a transition metal composite oxide exhibiting a potential of not less than, and a positive electrode containing a conductive agent, and a substance capable of inserting and extracting metal lithium or lithium ions. A non-aqueous electrolyte secondary battery comprising a negative electrode as a negative electrode material and a non-aqueous electrolyte, wherein the conductive material is a carbon material having a crystallite size (Lc) in the c-axis direction in X-ray diffraction measurement of 1000 Å or more. A non-aqueous electrolyte secondary battery, wherein a conductive agent containing at least 10% by weight is used. 3. A charge / discharge region of 2 V (vs. Li / L)
i ⁺ ) a positive electrode active material of a transition metal oxide or a transition metal composite oxide exhibiting a potential of not less than, and a positive electrode containing a conductive agent, and a substance capable of inserting and extracting metal lithium or lithium ions. In a non-aqueous electrolyte secondary battery comprising a negative electrode as a negative electrode material and a non-aqueous electrolyte, the conductive agent has a d-value (d ₀₀₂ ) of a lattice plane (002) plane of 3.358 Å or less in X-ray diffraction measurement. And at least 10% by weight of a carbon material having a crystallite size (Lc) in the c-axis direction of 1000 Å or more in X-ray diffraction measurement
A non-aqueous electrolyte secondary battery comprising a conductive agent contained therein.