JPH10289731A - Nonaqueous electrolytic battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a film on a positive electrode material at an interface with a nonaqueous electrolyte, and restrain reaction between the positive electrode material and the nonaqueous electrolyte by using a composite oxide of lithium transition metal containing at least Co and Mn as the positive electrode material, as well as a nonaqueous electrolyte composed of a solute containing at least one type of fluorine contained compound dissolved in a solvent which contains ethylene carbonate. SOLUTION: A positive electrode material is made of a compound/ expressed by the formula of Lia Cob Mno Md Ni1-(b+o+d) O2 where M stands for B, Al, Si, Ti, Fe, V, Cr, Cu, Zn, Ga and W, 0<(a)<1.2, 0.1<=(b)<1.0, 0.05<=(c)<1.0, 0.05<=(c)<1, 0<=(d)<1, and 0.15<=(b+c+d)<1. A negative electrode is made of a carbonaceous material. Furthermore, a solvent is preferably prepared by mixing another solvent with ethylene carbonate, and LiPF4 , LiBF4 , LiN (C2 F5 S02 )2 or the like is preferable as a fluoride compound for the solute of a nonaqueous electrolyte. As a result, a nonaqueous electrolytic battery with a high preservation characteristic and a high cycle characteristic can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous electrolyte battery comprising a positive electrode using a lithium transition metal composite oxide as a positive electrode material, a negative electrode, and a non-aqueous electrolyte. The present invention relates to a nonaqueous electrolyte battery in which storage characteristics and cycle characteristics are less likely to be reduced by reacting with a positive electrode material and a negative electrode material in a negative electrode.

[0002]

2. Description of the Related Art In recent years, a non-aqueous electrolyte battery using a non-aqueous electrolyte as an electrolyte and utilizing the oxidation and reduction of lithium has been used as one of new batteries with high output and high energy density. It was started.

[0003] In such a non-aqueous electrolyte battery, a lithium transition metal composite oxide capable of obtaining a relatively high voltage has been generally used as a positive electrode material for the positive electrode.

However, when such a lithium transition metal composite oxide is used as a cathode material, the cathode material reacts with the non-aqueous electrolyte to decompose the non-aqueous electrolyte, resulting in poor storage characteristics and cycle characteristics. There was a problem of becoming.

For this reason, in recent years, Japanese Patent Laid-Open No.
As shown in Japanese Patent No. 84872, a mixed solvent of propylene carbonate and diethyl carbonate is used as a solvent in the non-aqueous electrolyte to prevent the above-mentioned reaction between the lithium transition metal composite oxide and the non-aqueous electrolyte. The thing which tried to suppress was thought.

However, when a lithium transition metal composite oxide containing a transition metal such as Co, Ni, or Mn is used as a cathode material, particularly in a charged state, the cathode material still reacts with the nonaqueous electrolyte. However, there is a problem that the charge storage characteristics deteriorate.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a non-aqueous electrolyte battery comprising a positive electrode using a lithium transition metal composite oxide as a positive electrode material, a negative electrode, and a non-aqueous electrolyte. Is to solve the problem,
Even when a lithium transition metal composite oxide containing a transition metal such as Co, Mn, or Ni is used for the cathode material, the reaction between the cathode material and the non-aqueous electrolyte is sufficiently suppressed,
An object of the present invention is to provide a nonaqueous electrolyte battery having excellent storage characteristics and cycle characteristics.

[0008]

According to a first aspect of the present invention, there is provided a nonaqueous electrolyte battery comprising: a positive electrode using a lithium transition metal composite oxide as a positive electrode material; And, in a non-aqueous electrolyte battery comprising a non-aqueous electrolyte, the positive electrode material, while using a lithium transition metal composite oxide containing at least Co, Mn and Ni, the above-mentioned non-aqueous electrolyte, A solvent containing ethylene carbonate is used, and a solute containing at least one fluorine-containing compound is used.

Further, as in the non-aqueous electrolyte battery according to the first aspect, at least Co, Mn and N
While using a lithium transition metal composite oxide containing i
When a solute containing at least one fluorine-containing compound is used together with a solvent containing ethylene carbonate for the non-aqueous electrolyte, a film is formed on the positive electrode material at the interface with the non-aqueous electrolyte, This coating suppresses the reaction between the positive electrode material and the non-aqueous electrolyte even in the charged state, and improves the storage characteristics and cycle characteristics of the non-aqueous electrolyte battery.

Here, as described above, at least Co and M
When a nickel transition metal composite oxide containing n and Ni is used for a positive electrode material, as the lithium transition metal composite oxide, Li _a Co _b M n _c M
_d Ni _{1- (b + c + d)} O ₂ (M is B, Al, Si, Ti, F
e, at least one metal selected from V, Cr, Cu, Zn, Ga and W, and 0 <a <1.2, 0.1 ≦
b <1, 0.05 ≦ c <1, 0 ≦ d <1, 0.15 ≦ b
The condition of + c + d <1 is satisfied. When () is used, the reaction with the non-aqueous electrolyte is further suppressed, and the storage characteristics and the cycle characteristics are further improved.

In the non-aqueous electrolyte battery according to the present invention, as the negative electrode material used for the negative electrode, a known negative electrode material generally used conventionally can be used. In particular, graphite, coke and the like can be used. In the case of a carbon material having a large surface area and a high reactivity with a non-aqueous electrolyte, by combining the non-aqueous electrolyte as described above, the non-aqueous electrolyte and the carbon material as a negative electrode material Is also suppressed, and the cycle characteristics and storage characteristics are further improved.

Further, in the nonaqueous electrolyte battery according to the present invention, the solvent in the nonaqueous electrolyte may be a solvent containing at least ethylene carbonate as described above. It is preferable to use a mixture of solvents.

Here, when mixing the ethylene carbonate with another solvent as described above, if the amount of the ethylene carbonate is small, the ionic conductivity in the non-aqueous electrolyte becomes poor, and the amount of the ethylene carbonate increases. If too long, the viscosity of the non-aqueous electrolyte increases, and the ionic conductivity also decreases in this case. Therefore, the amount of ethylene carbonate in the solvent is 20 to 80 vol by volume.
%.

Further, the solute in the non-aqueous electrolyte described above also
As long as at least one fluorine-containing compound is used as described above, a known fluorine-containing compound generally used as a solute can be used as the fluorine-containing compound. For example, LiPF ₆ , LiBF ₄ , Li
N (C ₂ F ₅ SO ₂ ) ₂ , LiAsF ₆ or the like can be used, and such a fluorine-containing compound can be used in combination with another known solute.

Here, when adding the solute containing at least one fluorine-containing compound to the non-aqueous electrolyte, if the amount of the solute added is too large or too small, the ionic conductivity of the non-aqueous electrolyte decreases. To do so, preferably
The total amount of solute in the non-aqueous electrolyte is 0.5 to 2.0 m
ol / l.

[0016]

The non-aqueous electrolyte battery of the present invention will be described below.
A specific example will be described with reference to examples, and in the non-aqueous electrolyte battery of this example, a decrease in the discharge capacity when stored in a charged state is reduced and the cycle characteristics are improved. I will clarify it. The non-aqueous electrolyte battery according to the present invention is not limited to those shown in the following examples, but can be implemented by appropriately changing the scope of the invention without changing its gist.

(Examples 1 to 8 and Comparative Examples 1 to 3) In these examples, a positive electrode, a negative electrode and a non-aqueous electrolyte prepared as described below were used, and an AA size as shown in FIG. Was manufactured.

[Preparation of Positive Electrode] In preparing the positive electrode, LiNi _0.7 Co _0.2 Mn _0.1 O ₂ was used as a positive electrode material.
After mixing the positive electrode material with artificial graphite as a conductive agent using powder, polyvinylidene fluoride as a binder is mixed with N-methyl-2-pyrrolidone (NM).
A solution dissolved in P) is added, and the above positive electrode material, artificial graphite, and polyvinylidene fluoride are kneaded at a weight ratio of 85: 10: 5 to prepare a slurry. Was coated on both sides of an aluminum foil by a doctor blade method and dried to prepare a positive electrode.

[0019] The order to prepare the Preparation of Negative Electrode] negative electrode, as an anode material, using natural graphite powder surface spacing d ₀₀₂ in the lattice plane (002) is 3.35 Å, with respect to the natural graphite powder, a binder A solution prepared by dissolving polyvinylidene fluoride as an agent in the above NMP is added, and the mixture is kneaded so that the weight ratio of natural graphite powder and polyvinylidene fluoride becomes 95: 5 to prepare a slurry. A negative electrode was prepared by applying the powder to both surfaces of a copper foil as an electric body by a doctor blade method and drying the applied copper foil.

[Preparation of Non-Aqueous Electrolyte] In preparing a non-aqueous electrolyte, in Examples 1 to 7, as shown in Table 1 below, at least ethylene carbonate was used as a solvent and a solute was used. At least one fluorine-containing compound was used.

Here, in Example 1, LiPF ₆ as a solute was dissolved at a ratio of 1 mol / l in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) mixed at a volume ratio of 50:50. In Example 2, Li was used as a solute in the same mixed solvent as in Example 1.
BF ₄ was dissolved at a rate of 1 mol / l, and in Example 3, LiN (C
₂ F ₅ SO ₂ ) ₂ was dissolved at a rate of 1 mol / l. In Example 4, LiAsF ₆ was dissolved as a solute in the same mixed solvent as in Example 1 at a rate of 1 mol / l. And dimethyl carbonate (DMC) were mixed at a volume ratio of 50:50 to dissolve LiPF ₆ as a solute at a ratio of 1 mol / l. In Example 6, EC and γ-butyrolactone (G-BL) were dissolved. And LiPF at a volume ratio of 50:50.
₆ was dissolved at a rate of 1 mol / l. In Example 7, LiPF ₆ and LiClO ₄ were mixed in the same mixed solvent as in Example 1.
Was dissolved at a ratio of 0.5 mol / l, and in Example 8, 1 mol / l of LiPF ₆ was added to a mixed solvent in which EC, propylene carbonate (PC), and DEC were mixed at a volume ratio of 25:25:50. Dissolve in the proportion of
Each non-aqueous electrolyte was prepared.

On the other hand, in Comparative Example 1, 1 LiClO ₄ was used as a solute in the same mixed solvent of EC and DEC as in Example 1.
mol / l, and in Comparative Example 2, PC
And DEC were mixed at a volume ratio of 50:50 to dissolve LiPF ₆ at a ratio of 1 mol / l. In Comparative Example 3, PC and 1,2-dimethoxyethane (DM
E) and LiP at a 1: 1 volume ratio.
F ₆ was dissolved at a rate of 1 mol / l to prepare each non-aqueous electrolyte.

[Preparation of Battery] In preparing the battery, as shown in FIG. 1, a lithium ion-permeable microporous membrane as a separator 3 was placed between the positive electrode 1 and the negative electrode 2 prepared as described above. After winding these in a spiral shape and accommodating them in the battery can 4, each of the non-aqueous electrolyte solutions prepared as described above is injected into the battery can 4 and sealed, and the positive electrode 1 is closed. Is connected to a positive electrode external terminal 6 via a positive electrode lead 5, the negative electrode 2 is connected to a battery can 4 via a negative electrode lead 7, and the positive electrode external terminal 6 and the battery can 4 are electrically separated by an insulating packing 8. Was.

Next, the first embodiment manufactured as described above was used.
-8 and each of the lithium secondary batteries of Comparative Examples 1 to 3,
After each battery was charged to a charge end voltage of 4.2 V at a charge current of 200 mA, the battery was discharged to a discharge end voltage of 2.75 V at a discharge current of 200 mA, and the discharge capacity of each lithium secondary battery before storage was measured. Are charged at a charging current of 200 mA to a charging end voltage of 4.2 V, and the thus charged lithium secondary batteries are stored in a 60 ° C. atmosphere for 20 days, and then each lithium secondary battery is charged. After the battery was returned to room temperature, discharge was performed at a discharge current of 200 mA to a discharge end voltage of 2.75 V, the discharge capacity after storage was measured, and the capacity remaining rate after storage was obtained. Indicated according to

[0025]

[Table 1]

As is evident from the results, Ni was added to the positive electrode.
In the case where a lithium transition metal composite oxide containing Co and Mn was used, Examples 1 to 3 in which a solvent containing ethylene carbonate was used as a solvent of the non-aqueous electrolyte and a solute containing a fluorinated compound was used as the solute 8 are the lithium secondary batteries of Comparative Example 1 in which the solute in the non-aqueous electrolyte does not contain the fluorine-containing compound, and the lithium secondary batteries of Comparative Examples 2 and 3 in which the solvent in the non-aqueous electrolyte does not contain ethylene carbonate. As compared with the lithium secondary batteries, the reduction in the discharge capacity after storage was small, and the residual capacity ratio was significantly improved.

When comparing the lithium secondary batteries of Examples 1 to 8 above, the lithium secondary batteries of Examples 1 to 6 and 8 using only a fluorine-containing compound as a solute in the non-aqueous electrolytic solution are: The decrease in discharge capacity after storage was smaller than that of the lithium secondary battery of Example 7 in which a fluorine-containing compound and other solutes were added.
Each lithium secondary battery using PF ₆ , LiBF ₄ , and LiN (C ₂ F ₅ SO ₂ ) ₂ has a discharge capacity after further storage compared to the lithium secondary battery of Example 4 using LiAsF ₆ as a solute. The decline of the was reduced.

(Examples 9 to 17 and Comparative Examples 4 to 9) In these Examples and Comparative Examples, only the positive electrode material used for the positive electrode and the lithium secondary battery of Example 1 were changed. The above-mentioned natural graphite was used as the negative electrode material of the negative electrode, and LiPF ₆ dissolved at a ratio of 1 mol / l in a mixed solvent in which EC and DEC were mixed at a volume ratio of 50:50 with a non-aqueous electrolyte was used. Each lithium secondary battery was produced in the same manner as in Example 1 described above.

Here, in these Examples and Comparative Examples, as shown in Table 2 below,
Li, Ni, Co, and Mn were used in the proportions shown in the same table. In Comparative Examples 4 to 9,
A material that does not include at least one of Ni, Co, and Mn is used.

The lithium secondary batteries of Examples 9 to 17 and Comparative Examples 4 to 9 manufactured using such a positive electrode material also had the same discharge capacity and storage capacity as before in the same manner as described above. The discharge capacity after storage was measured, and the remaining capacity ratio after storage was determined. The results are shown in Table 2 below.

[0031]

[Table 2]

As is apparent from the results, when a non-aqueous electrolyte in which a solute containing a fluorinated compound is dissolved in a solvent containing ethylene carbonate is used, Ni, Co, and Mn are used as the positive electrode material in the positive electrode. Each of the lithium secondary batteries of Examples 9 to 17 using the lithium transition metal composite oxide containing: a lithium transition metal composite oxide not containing at least one of Ni, Co, and Mn as a positive electrode material. As compared with each of the lithium secondary batteries of Comparative Examples 4 to 9 used in Example 1, the decrease in the discharge capacity after storage was small, and the residual capacity ratio was improved.

Further, when comparing the lithium secondary batteries of Examples 9 to 17, the positive electrode material Li shown in claim 2 above _{a Co b Mn c M d Ni} 1- (b + c + d) O ₂ (M is B,
Al, Si, Ti, Fe, V, Cr, Cu, Zn, G
a, at least one metal selected from W,
<A <1.2, 0.1 ≦ b <1, 0.05 ≦ c <1, 0
<D <1, 0.15 ≦ b + c + d <1. ) Wherein each of the lithium secondary batteries of Examples 9 to 16 using a positive electrode material containing no M and having d equal to 0 is the same as the lithium secondary battery of Example 17 using a positive electrode material that does not satisfy this condition. As compared with the battery, the decrease in the discharge capacity after storage was further reduced, and the remaining capacity ratio was significantly improved.

(Examples 18 to 28) In these examples, only the positive electrode material used for the positive electrode and the case of the lithium secondary battery of Example 1 were changed, and the above-mentioned natural graphite was used as the negative electrode material in the negative electrode. And use EC for non-aqueous electrolyte
And DEC in a volume ratio of 50:50, in which LiPF ₆ was dissolved at a ratio of 1 mol / l, and each lithium secondary battery was used in the same manner as in Example 1 above. Was prepared.

Here, in these examples and comparative examples,
LiNi as the cathode material _0.6Co_0.2Mn
_0.1M_0.1O_TwoWhere M is the gold of the formula
Use the genus type changed as shown in Table 3 below
I was there.

Then, in each of the lithium secondary batteries of Examples 18 to 28 produced using such a positive electrode material, the discharge capacity before storage and the discharge capacity after storage were determined in the same manner as described above. In addition to the measurement, the residual capacity ratio after storage was determined.
Indicated according to

[0037]

[Table 3]

As is clear from the results, Example 18
As in each of the lithium secondary batteries of Nos.
A non-aqueous electrolytic solution in which a solute containing a fluorinated compound is dissolved in a solvent containing ethylene carbonate even when a lithium transition metal composite oxide containing a metal represented by M is used in addition to Co and Mn. When used, the decrease in discharge capacity after storage was smaller than that of the lithium secondary batteries of the comparative examples described above, and the residual capacity ratio was significantly improved.

Next, the above-mentioned embodiments 1 to 16 and embodiment 18
Of each of the lithium secondary batteries of Comparative Examples 2 to 3 and Comparative Examples 2 and 3 under a 60 ° C. atmosphere, respectively.
After charging at 0 mA to a charging end voltage of 4.2 V, discharging was performed at a discharging current of 200 mA to a discharging end voltage of 2.75 V, and charging and discharging were repeated as one cycle, and the number of cycles in each lithium secondary battery was determined. The relationship with the discharge capacity was examined, and the results are shown in FIG.

As a result, each of the lithium secondary batteries of Examples 1 to 16 and Examples 18 to 28 has a discharge capacity with an increase in the number of cycles, as compared with the lithium secondary batteries of Comparative Examples 2 and 3. And the cycle characteristics of the lithium secondary battery were improved.

[0041]

As described above in detail, in the nonaqueous electrolyte battery according to the first aspect of the present invention, a lithium transition metal composite oxide containing at least Co, Mn, and Ni is used for a positive electrode material, and ethylene oxide is used. Because a non-aqueous electrolyte in which a solute containing at least one fluorine-containing compound is dissolved in a solvent containing carbonate is used, a film is formed on the positive electrode material at the interface with the non-aqueous electrolyte,
This coating suppressed the reaction between the positive electrode material and the non-aqueous electrolyte even in the charged state, and significantly improved the storage characteristics and cycle characteristics of the non-aqueous electrolyte battery.

_{Further, Li a Co b Mn c M} d Ni 1- (b + c + d) indicating a lithium transition metal composite oxide in claim 2
O ₂ (M is B, Al, Si, Ti, Fe, V, Cr, C
at least one metal selected from u, Zn, Ga, and W, and 0 <a <1.2, 0.1 ≦ b <1, 0.05
Satisfies the conditions of ≦ c <1, 0 ≦ d <1, and 0.15 ≦ b + c + d <1. When) was used as the positive electrode material, the reaction with the non-aqueous electrolyte was further suppressed, and the storage characteristics and cycle characteristics of the non-aqueous electrolyte battery were further improved.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view showing the internal structure of each nonaqueous electrolyte secondary battery produced in an example of the present invention and a comparative example.

FIG. 2 is a diagram showing the relationship between the number of charge / discharge cycles and the discharge capacity of each of the lithium secondary batteries of Examples 1 to 16, Examples 18 to 28, and Comparative Examples 2 and 3.

[Explanation of symbols]

 1 Positive electrode 2 Negative electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahisa Fujimoto 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Toshiyuki Noma 2-chome Keihanhondori, Moriguchi-shi, Osaka No.5-5 Sanyo Electric Co., Ltd. (72) Inventor Koji Nishio 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A non-aqueous electrolyte battery comprising a positive electrode using a lithium transition metal composite oxide as a positive electrode material, a negative electrode, and a non-aqueous electrolyte, wherein at least Co is added to the positive electrode material.
And a lithium transition metal composite oxide containing Mn and Ni, while using a solvent containing ethylene carbonate and a solute containing at least one fluorine-containing compound in the nonaqueous electrolyte. Non-aqueous electrolyte battery. 2. A non-aqueous electrolyte cell according to claim 1, as the positive electrode _{material, Li a Co b Mn c M} d
Ni _{1- (b + c + d)} O ₂ (M is B, Al, Si, Ti, F
e, at least one metal selected from V, Cr, Cu, Zn, Ga and W, and 0 <a <1.2, 0.1 ≦
b <1, 0.05 ≦ c <1, 0 ≦ d <1, 0.15 ≦ b
The condition of + c + d <1 is satisfied. A non-aqueous electrolyte battery characterized by using (1). 3. The non-aqueous electrolyte battery according to claim 1, wherein a carbon material is used as a negative electrode material in the negative electrode.