JP2002075441A - Nonaqueous electrolyte cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte cell enabled to aim at a cost reduction and high energy density, by disusing a protection circuit according to the improvement of an over discharge characteristics. SOLUTION: For the nonaqueous electrolyte cell, a positive pole 1 containing a positive pole activator, a negative pole 2 containing a negative pole activator enabled to occlude and release lithium, and an electrolyte liquid containing solute and solvent, are arranged inside a laminate outer casing 6. Vinylene carbonate is added to the solvent of the electrolyte liquid, and the solute of the electrolyte liquid contains lithium salt shown by the general formula; LiPF6-X (CnF2n+1)X (here, X is an integer chosen from 1-5, n fulfils n=1 or n=2, preferably X=2 or X=3, most preferably, X=2 or X=3 and n=2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a non-aqueous battery comprising a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material capable of inserting and extracting lithium, and an electrolyte solution containing a solvent and a solute. The present invention relates to a water electrolyte battery.

[0002]

2. Description of the Related Art In recent years, a non-aqueous electrolyte battery using lithium cobalt oxide as a positive electrode active material and a carbon material capable of occluding and releasing lithium ions as a negative electrode active material has attracted attention.

[0003] When lithium cobaltate is used as the positive electrode active material in this manner, the battery characteristics during normal operation such as cycle characteristics and load characteristics are excellent, but the battery characteristics during abnormalities such as overcharge tests and high-temperature storage tests are improved. In terms of reliability, measures using batteries alone are insufficient. Therefore, in order to improve the reliability of the battery in the event of an abnormality, a means of providing a protection circuit or a protection element outside the battery (hereinafter referred to as a protection circuit or the like) and packing the protection circuit and the like and the battery is adopted. ing. If the protection circuit and the like are packed in a battery as described above, the reliability of the battery at the time of abnormality is improved, but the protection circuit and the like are expensive, which leads to an increase in cost. Since an extra space is required for arranging a protection circuit and the like in the pack, there is a problem that high energy density cannot be achieved. Therefore, in order to increase the energy density at a low cost, it is necessary to provide characteristics of a single battery that does not require a protection circuit or the like even in an abnormal situation.

Therefore, in order to improve the reliability of the battery alone at the time of abnormality, for example, with respect to overcharge characteristics and thermal stability, lithium manganate which has excellent resistance to these is used as a positive electrode active material, and a separator is used. Although certain effects have been achieved by improving the above, at present, no measures have been taken for overdischarge characteristics. This is due to overcharge characteristics and thermal stability.
Active research is being conducted at companies and universities because it is an issue directly related to battery safety, but overdischarge characteristics are not directly linked to battery safety. It is considered that this is due to the fact that the process has not been performed.

However, when an overdischarge abnormality is caused, a decrease in the battery voltage causes a decrease in the potential of the positive electrode and an increase in the potential of the negative electrode, and the problem that the electrolyte is decomposed and a large amount of gas is generated in the battery. If the positive electrode is over-discharged to the region, the crystal structure of the positive electrode active material changes, which causes a problem that charging and discharging cannot be performed again. That is,
Even if the overcharge characteristics and the thermal stability are improved, if the overdischarge characteristics are not improved, a protection circuit or the like is required, so that there is a problem that the cost and the energy density of the battery cannot be reduced. .

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and eliminates the need for a protection circuit or the like by improving overdischarge characteristics, thereby reducing costs and increasing energy consumption. It is an object of the present invention to provide a non-aqueous electrolyte battery capable of increasing the density.

[0007]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 of the present invention provides a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material capable of inserting and extracting lithium. And a non-aqueous electrolyte battery in which an electrolyte containing a solvent and a solute is disposed in an outer package, wherein vinylene carbonate (hereinafter abbreviated as VC) is added to the solvent of the electrolyte, and the electrolyte is Of the general formula LiP
F _6-X (C _n F _{2n + 1} ) _X [where X is an integer of 1 to 5 and satisfies n = 1 or 2, preferably X = 2 or 3, particularly preferably X = 2 Or 3 and n = 2 is satisfied].

As described above, VC is added to the solvent of the electrolytic solution, and the solute of the electrolytic solution contains the general formula LiPF _6-X
(C _n F _{2n + 1)} if it contains a lithium salt represented by _X, VC and LiPF _6-X (C _n F _{2n + 1) X} and good composite decomposition product on the anode active material consisting of Because it forms a film,
Since cobalt and manganese are dissolved at the time of overdischarge, and direct damage to the negative electrode active material due to deposition on the negative electrode can be suppressed, overdischarge characteristics are improved.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, the positive electrode active material contains spinel-type lithium manganate. When lithium cobaltate is used as the positive electrode active material,
Due to the low reversibility of lithium cobaltate during overdischarge, no remarkable improvement in overdischarge characteristics is observed even when the present invention is applied to lithium cobaltate. On the other hand, in the case where the positive electrode active material contains lithium manganate whose positive electrode potential is unlikely to fall, the decrease in the positive electrode potential can be suppressed to a potential region where the influence on the positive electrode active material is small, and As described above, VC and LiPF _6-X (C _n
F _{2n + 1} ) _X can suppress direct damage to the negative electrode active material with a good composite coating composed of F _{2n + 1} ) _X , so that the overdischarge characteristics are dramatically improved.

The invention according to claim 3 is the invention according to claim 1 or 2, wherein the compound represented by the general formula LiPF _6-X (C
_n F _{2n + 1} ) _X has a molar concentration of 0.
It is characterized by being at least 3 mol / l. As described above, the reason why the molar concentration of the lithium salt represented by the general formula LiPF _6-X (C _n F _{2n + 1} ) _X is restricted to 0.3 mol / l or more is that LiPF ₃ (C ₂ F ₅ ) ₃ 0.3m molar concentration
If it is less than ol / l, the capacity recovery rate after overdischarge is not sufficiently ensured.

[0011] The invention described in claim 4 is based on claim 1,
In the invention described in 2 or 3, when the mass ratio of the VC to the solvent of the electrolytic solution is defined as y (wt%), the mass ratio y satisfies 0 <y ≦ 5, preferably 0 <y ≦ 3. It is characterized by the following. As described above, the addition amount of VC is regulated because if the addition amount of VC exceeds 5% by weight, the internal resistance of the battery becomes extremely large, and the battery characteristics in a normal use region are greatly reduced. Things. In particular, if the added amount of VC is 2 wt% or less, the increase in the internal resistance of the battery is sufficiently suppressed, so that the added amount of VC is 2 wt%.
It is particularly desirable that the content be not more than wt%.

[0012] Further, the invention according to claim 5 is based on claim 2,
In the invention described in 3 or 4, the mass ratio of the spinel-type lithium manganate to the total amount of the positive electrode active material is z
(Wt%), the mass ratio z is 20 ≦ z. As described above, the ratio of the spinel-type lithium manganate is regulated by the fact that the ratio of the lithium manganate to the total amount of the positive electrode active material is 20 wt%.
%, The capacity recovery rate after overdischarge is not significantly improved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First to fourth embodiments of the present invention will be described below. (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. 1 is a front view of a non-aqueous electrolyte battery according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line AA of FIG. 1, and FIG. 3 is a non-aqueous electrolyte according to the first embodiment of the present invention. FIG. 4 is a perspective view of a power generating element used for a battery, and FIG. 4 is a cross-sectional view of a laminate exterior body.

As shown in FIG. 3, the nonaqueous electrolyte battery of the present invention comprises a positive electrode 1 mainly composed of LiCoO ₂ , a negative electrode 2 mainly composed of a carbon material, and a polyethylene separator which separates these two electrodes. (Not shown in FIG. 3). A positive electrode tab 8 made of aluminum is connected to the positive electrode 1, and a negative electrode tab 9 made of nickel is connected to the negative electrode 2. I have.

As shown in FIGS. 1 and 2, the power generation element 4 is disposed in a storage space 5.
Are formed by sealing the upper and lower ends and the central portion of the laminate exterior body 6 with sealing portions 7a, 7b, and 7c, respectively. The storage space 5 contains ethylene carbonate (E
C) and diethyl carbonate (DEC) mixed at a ratio of 3: 7 by volume to a mixture of 2 wt% VC and LiPF ₅ (CF ₃ ) at 1 mol / l.
The electrolyte solution dissolved in the ratio of is injected.

As shown in FIG. 4, a specific structure of the laminate outer package 6 is an aluminum layer (thickness: 30 μm).
m) A nylon layer (thickness: 2 μm) on one side of 21 via an adhesive layer (thickness: 2 μm) 25 made of a urethane-based adhesive.
25 μm) 22 is adhered, and a polyethylene terephthalate layer (thickness: 12 μm) is bonded to the nylon layer 22 via an adhesive layer (thickness: 2 μm) 26 made of a urethane-based adhesive.
m) 23 is adhered, and on the other surface of the aluminum layer 21 is a polypropylene layer (thickness: 4) via an adhesive layer (thickness: 2 μm) 27 made of modified polypropylene.
0 μm) 24 is bonded.

Here, the positive electrode tab 8 and the negative electrode tab 9
Means projecting from the sealing portion 7a of the laminate exterior body 6. The positive electrode tab 8 also functions as an external terminal on the positive electrode side, while the negative electrode tab 9 also functions as an external terminal on the negative electrode side.
The capacity of the battery having the above structure is 600 mA.

Here, the battery having the above structure was manufactured as follows. First, LiCoO ₂ as a positive electrode active material
, A carbon conductive agent, graphite, and a fluororesin binder in a mass ratio of 92: 3: 2: 3 to prepare a positive electrode mixture, and then mixing the positive electrode mixture with a strip of aluminum. The positive electrode 1 was produced by applying the coating on both sides of the positive electrode core, further rolling and drying.

In parallel with this, a carbon material as a negative electrode active material and a styrene-based binder are mixed at a mass ratio of 98: 2 to prepare a negative electrode mixture. Negative electrode 2 was produced by coating on both sides of a strip-shaped negative electrode core made of copper, followed by drying and rolling. Next, after attaching the positive electrode tab 8 and the negative electrode tab 9 to these positive and negative electrodes 1 and 2, respectively, the positive and negative electrodes 1 and 2 are arranged via a separator.
Thereafter, the positive and negative electrodes 1 and 2 and the separator were wound in a flat spiral shape to produce a power generating element 4 as shown in FIG. 3 (the separator is omitted in FIG. 3).

Next, after preparing a laminated material having a seven-layer structure, the polypropylenes at both ends of the laminated material were overlapped with each other, and the overlapped portion was welded by an impulse heating method to form a sealing portion 7c. Next, the power generating element 4 was inserted into the storage space 5 of the cylindrical laminate material. At this time, the power generating element 4 was arranged so that the tabs 8 and 9 protruded from one opening of the cylindrical laminate. Next, in this state, the laminated material in the opening from which both tabs 8 and 9 protrude was welded and sealed to form a sealed portion 7a. At this time, welding was performed using a high-frequency induction heating device.

Next, in this state, drying by heating under vacuum (temperature:
105 ° C.) for 2 hours, and the laminate material and the power generation element 4
Of water was removed. Thereafter, ethylene carbonate (E
C) and diethyl carbonate (DEC) mixed at a ratio of 3: 7 by volume to a mixture of 2 wt% VC and LiPF ₅ (CF ₃ ) at 1 mol / l.
Of the dissolved electrolyte was injected at a rate of Thereafter, the end of the laminate material opposite to the sealing portion 7a was welded using a high-frequency induction welding device to form a sealing portion 7b, thereby producing a non-aqueous electrolyte battery.

(Second Embodiment) A battery was fabricated in the same manner as in the first embodiment except that spinel-type lithium manganate was used instead of lithium cobaltate as the positive electrode active material.

(Third Embodiment) As the positive electrode active material, a magnesium-substituted lithium manganate (a spinel-type lithium manganate in which a part of a crystal lattice is substituted with magnesium) is used in place of lithium cobaltate. A battery was produced in the same manner as in the first embodiment.

(Fourth Embodiment) As the positive electrode active material, a lithium-substituted lithium manganate (a spinel-type lithium manganate in which a part of a crystal lattice is substituted with aluminum) is used instead of lithium cobaltate. A battery was produced in the same manner as in the first embodiment.

The solvent of the electrolytic solution used in the present invention is not limited to the above-mentioned ones. For example, ethylene carbonate and dimethyl carbonate, ethyl methyl carbonate, tetrahydrofuran, 1,2-dimethoxyethane,
A solvent obtained by mixing a low-viscosity, low-boiling solvent such as 1,3-dioxolan, 2-methoxytetrahydrofuran, diethyl ether or the like at an appropriate ratio can be used.

As the solute of the electrolyte, the above-mentioned LiP
In addition to F ₅ (CF ₃ ), LiPF ₄ (CF ₃ ) ₂ , LiP
F ₃ (CF ₃ ) ₃ , LiPF ₂ (CF ₃ ) ₄ , LiPF
(CF ₃ ) ₅ , LiPF ₅ (C ₂ F ₅ ), LiPF
₄ (C ₂ F ₅ ) ₂ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiP
_{F 2 (C 2 F 5)} 4, LiPF (C 2 F 5) can be used ₅ or the like.

Further, the solute of the electrolytic solution contains the above-mentioned LiPF
₅ (CF ₃ ) and the like need only be contained, and the solute of the electrolytic solution does not necessarily need to be composed entirely of LiPF ₅ (CF ₃ ). In addition, the exterior body is not limited to the aluminum laminate exterior body, but may be an exterior can made of SUS or an exterior can made of aluminum or an aluminum alloy.

[0028]

EXAMPLES (First Example) [Example 1] In Example 1, a battery manufactured by the method described in the first embodiment was used. The battery fabricated in this manner is hereinafter referred to as Battery A1 of the invention.

Examples 2 to 10 As a solute of an electrolytic solution,
Instead of LiPF ₅ (CF ₃ ), LiPF ₄
(CF ₃ ) ₂ , LiPF ₃ (CF ₃ ) ₃ , LiPF
₂ (CF ₃ ) ₄ , LiPF (CF ₃ ) ₅ , LiPF
₅ (C ₂ F ₅ ), LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF
₃ (C ₂ F ₅ ) ₃ , LiPF ₂ (C ₂ F ₅ ) ₄ , LiP
A battery was fabricated in the same manner as in Example 1 except that F (C ₂ F ₅ ) ₅ was used. The battery fabricated in this way is
Hereinafter, these batteries are referred to as present invention batteries A2 to A10, respectively.

Comparative Examples 1 to 10 Batteries were produced in the same manner as in Examples 1 to 10 except that VC was not added. The batteries fabricated in this manner are hereinafter referred to as comparative batteries W1 to W10, respectively.

[Comparative Examples 11 to 13] Instead of LiPF ₅ (CF ₃ ), LiP
A battery was fabricated in the same manner as in Example 1 except that F ₆ , LiBF ₄ , and LiClO ₄ were used. The batteries fabricated in this manner are hereinafter referred to as comparative batteries W11 to W13.

Comparative Examples 14 to 16 Batteries were produced in the same manner as in Comparative Examples 11 to 13 except that VC was not added. The batteries fabricated in this manner are hereinafter referred to as comparative batteries W14 to W16, respectively.

[Experiment] The batteries A1 to A10 of the present invention and the comparative batteries W1 to W16 were charged, discharged, and overdischarged under the following conditions. Further, a capacity recovery rate represented by the following equation 1 was calculated. The results are shown in Table 1 below.

Charging conditions Charging is performed at a constant current at a charging current of 500 mA until the battery voltage reaches 4.2 V, and after the battery voltage reaches 4.2 V, charging is performed at a constant voltage until the current value becomes 25 mA or less. Conditions-Discharge conditions Conditions for discharging at a constant current up to a battery voltage of 3.0 V at a discharge current of 500 mA. The interval (pause time) between charge and discharge was set to 10 minutes. -Overdischarge condition A condition in which the battery is discharged at a small current of 10 mA until the battery voltage becomes 1.0 V, and then left at 60 ° C for 5 days.

[0035]

(Equation 1)

[0036]

[Table 1]

As apparent from Table 1, VC was added to the solvent, and the solute was represented by the general formula LiPF _6-X (C _n F
_{2n + 1} ) _X [where X is an integer of 1 to 5 and n = 1 or 2
The present invention battery A comprising a lithium salt represented by the following formula:
1 to A10 have the same lithium salt as a solute, but V
Compared with comparative batteries W1 to W10 to which C was not added,
It can be seen that the capacity recovery rate after overdischarge is high.

Although the details of this cause are not clear, part of the lithium salt and VC decompose and react in the initial charge / discharge reaction after battery assembly, resulting in a high quality composite material on the negative electrode active material. This is considered to be due to the formation of a coating (hereinafter referred to as a composite coating). Specifically, the comparative battery W1
At ~ W10, an abnormal reaction called overdischarge forcibly lowers the potential of the positive electrode, and cobalt dissolves as ions from the positive electrode active material, which precipitates on the negative electrode active material, increasing the potential of the negative electrode. I do. As a result, decomposition of the electrolytic solution and deterioration of the active material itself occur, so that a sufficient discharge capacity cannot be obtained by recharging and discharging after overdischarging. In particular, since the damage of the negative electrode active material due to the deposition of cobalt becomes extremely large, the discharge capacity at the time of the recharge / discharge remarkably decreases. On the other hand, in the batteries A1 to A10 of the present invention, since the composite film is deposited on the negative electrode active material, damage to the negative electrode active material is greatly reduced, and a decrease in discharge capacity during recharge / discharge is reduced. Is suppressed. The composite coating may also be formed on the positive electrode active material and may suppress the dissolution of cobalt itself, which is currently under investigation.

The properties of the composite film are considered to be different depending on the type of the lithium salt, ie, -P (C _n F _{2n + 1} ).
It is considered that the composite coating formed by the decomposition reaction between the-part and VC has a great effect on the affinity with the negative electrode active material and the suppression of the deposition of cobalt ions. Specifically, VC is added and LiPF ₆ , LiBF ₄ , LiC
In Comparative Battery W11~W13 with either lO _4,
No VC was added, but LiPF was used as a solute in the electrolyte.
₆ , it is recognized that the capacity recovery rate after overdischarge hardly changes as compared with the comparative batteries W14 to W16 using either LiBF ₄ or LiClO ₄ . Thus, as the lithium _{salt, -P (C n F 2n +} 1) - LiP having portions
It can be seen that it is necessary to include those represented by F _6-X (C _n F _{2n + 1} ) _X.

In addition, the general formula LiPF _6-X (C _n F
_{2n + 1} ) _X [where X is an integer of 1 to 5 and n = 1 or 2
Of the present invention, the batteries A2, A3, A7, and A8 of the present invention in which X is 2 or 3 are preferable.
Among these, it is recognized that the batteries A7 and A8 of the present invention in which n is 2 are particularly good. I'm not sure why,
It is considered that the form in which the lithium salt is decomposed and combined with VC is most favorable when n is 2 and X is 2 or 3 (that is, the portion mainly contributing to the decomposition is -P (C
_n F _{2n + 1} ) _-part and its quantity [value of X]
It is considered that if the amount is too large or too small, the originally required composite film is not formed). Although not shown in the above experiments, it has been confirmed by experiments that lithium nickel oxide having the same layer structure as lithium cobalt oxide has the same effect.

(Second Example) [Example 1] In Example 1, a battery manufactured by the method described in the second embodiment was used. The battery fabricated in this manner is hereinafter referred to as Battery B1 of the invention.

Examples 2 to 10 As a solute of an electrolytic solution,
Instead of LiPF ₅ (CF ₃ ), LiPF ₄
(CF ₃ ) ₂ , LiPF ₃ (CF ₃ ) ₃ , LiPF
₂ (CF ₃ ) ₄ , LiPF (CF ₃ ) ₅ , LiPF
₅ (C ₂ F ₅ ), LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF
₃ (C ₂ F ₅ ) ₃ , LiPF ₂ (C ₂ F ₅ ) ₄ , LiP
A battery was fabricated in the same manner as in Example 1 except that F (C ₂ F ₅ ) ₅ was used. The battery fabricated in this way is
Hereinafter, these batteries are referred to as present invention batteries B2 to B10, respectively.

Comparative Examples 1 to 10 Batteries were produced in the same manner as in Examples 1 to 10 except that VC was not added. The batteries fabricated in this manner are hereinafter referred to as comparative batteries X1 to X10, respectively.

[Comparative Examples 11 to 13] Instead of LiPF ₅ (CF ₃ ), LiP
A battery was fabricated in the same manner as in Example 1 except that F ₆ , LiBF ₄ , and LiClO ₄ were used. The batteries manufactured in this manner are hereinafter referred to as comparative batteries X11 to X13.

Comparative Examples 14 to 16 Batteries were produced in the same manner as in Comparative Examples 11 to 13 except that VC was not added. The batteries fabricated in this manner are hereinafter referred to as comparative batteries X14 to X16, respectively.

[Experiment] The batteries B1 to B10 of the present invention and the comparative batteries X1 to X16 were charged, discharged and overdischarged under the same conditions as in the experiment of the first embodiment. The recovery rate was calculated, and the results are shown in Table 2 below.

[0047]

[Table 2]

As is clear from Table 2, even when lithium manganate is used as the positive electrode active material, VC is added to the solvent, and the solute has the general formula LiPF _6-X (C _n F
_{2n + 1} ) _X [where X is an integer of 1 to 5 and n = 1 or 2
The present invention battery B1 containing a lithium salt represented by the following formula:
To B10, the same lithium salt is used as a solute, but VC
It is recognized that the capacity recovery rate after overdischarge is higher than that of the comparative batteries X1 to X10 to which no is added. This is considered to be due to the same reason as that shown in the experiment of the first embodiment.

However, when lithium manganate is used as the positive electrode active material, manganese ions (cobalt ions) from the crystal lattice in the overdischarged state are lower than when lithium cobalt oxide is used as the positive electrode active material. It is clear from Tables 1 and 2 that the dissolution is more likely to occur and the deterioration of the negative electrode active material due to the dissolution of ions is further increased, so that the improvement effect by forming the composite coating is also increased.

Further, lithium cobalt oxide is used as a positive electrode active material.
As in the case where the electrolyte is used, VC is added and
LiPF as solute₆, LiBF_Four, LiClO_FourWhat
In the comparative batteries X11 to X13 using these, VC was added.
LiPF as a solute of the electrolytic solution₆, LiB
F_Four, LiClO_FourComparative battery X14 using any one of
The capacity recovery rate after overdischarge is almost the same as X16
Is recognized. Therefore, as lithium salt
Is -P (C_nF_{2n + 1}LiPF having a)-moiety _6-X(
C_nF_{2n + 1})_XMust be included.
It turns out that it is important.

In addition, the general formula LiPF _6-X (C _n F
_{2n + 1} ) _X [where X is an integer of 1 to 5 and n = 1 or 2
Of the present invention, the batteries B2, B3, B7, and B8 of the present invention in which X is 2 or 3 are favorable,
Among them, it is recognized that the batteries B7 and B8 of the present invention in which n is 2 are particularly good. This reason is considered to be the same as the reason described in the experiment of the first embodiment.

(Third Example) [Example 1] In Example 1, a battery manufactured by the method described in the third embodiment was used. The battery fabricated in this manner is hereinafter referred to as Battery C1 of the invention.

[Examples 2 to 10] As a solute of the electrolytic solution,
Instead of LiPF ₅ (CF ₃ ), LiPF ₄
(CF ₃ ) ₂ , LiPF ₃ (CF ₃ ) ₃ , LiPF
₂ (CF ₃ ) ₄ , LiPF (CF ₃ ) ₅ , LiPF
₅ (C ₂ F ₅ ), LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF
₃ (C ₂ F ₅ ) ₃ , LiPF ₂ (C ₂ F ₅ ) ₄ , LiP
A battery was fabricated in the same manner as in Example 1 except that F (C ₂ F ₅ ) ₅ was used. The battery fabricated in this way is
Hereinafter, these batteries are referred to as present invention batteries C2 to C10, respectively.

[Comparative Examples 1 to 10] Batteries were produced in the same manner as in Examples 1 to 10 except that VC was not added. The batteries fabricated in this manner are hereinafter referred to as comparative batteries Y1 to Y10, respectively.

[Comparative Examples 11 to 13] Instead of LiPF ₅ (CF ₃ ), LiP
A battery was fabricated in the same manner as in Example 1 except that F ₆ , LiBF ₄ , and LiClO ₄ were used. The batteries manufactured in this manner are hereinafter referred to as comparative batteries Y11 to Y13.

[Comparative Examples 14 to 16] Batteries were produced in the same manner as in Comparative Examples 11 to 13 except that VC was not added. The batteries fabricated in this manner are hereinafter referred to as comparative batteries Y14 to Y16, respectively.

[Experiment] The batteries of the present invention C1 to C10 and the comparative batteries Y1 to Y16 were charged, discharged and overdischarged under the same conditions as in the experiment of the first embodiment. The recovery rate was calculated, and the results are shown in Table 3 below.

[0058]

[Table 3]

As is evident from Table 3, the same tendency as in the case of using unsubstituted lithium spinel-type manganate was obtained when spinel-type lithium manganate in which a part of the crystal lattice was substituted with magnesium was used. It was confirmed that there was.

Fourth Example [Example 1] In Example 1, a battery manufactured by the method described in the fourth embodiment was used. The battery fabricated in this manner is hereinafter referred to as Battery D1 of the invention.

Examples 2 to 10 As solutes of the electrolyte,
Instead of LiPF ₅ (CF ₃ ), LiPF ₄
(CF ₃ ) ₂ , LiPF ₃ (CF ₃ ) ₃ , LiPF
₂ (CF ₃ ) ₄ , LiPF (CF ₃ ) ₅ , LiPF
₅ (C ₂ F ₅ ), LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF
₃ (C ₂ F ₅ ) ₃ , LiPF ₂ (C ₂ F ₅ ) ₄ , LiP
A battery was fabricated in the same manner as in Example 1 except that F (C ₂ F ₅ ) ₅ was used. The battery fabricated in this way is
Hereinafter, these batteries are referred to as present invention batteries D2 to D10, respectively.

[Comparative Examples 1 to 10] Batteries were produced in the same manner as in Examples 1 to 10 except that VC was not added. The batteries fabricated in this manner are hereinafter referred to as comparative batteries Z1 to Z10, respectively.

[Comparative Examples 11 to 13] Instead of LiPF ₅ (CF ₃ ), LiP
A battery was fabricated in the same manner as in Example 1 except that F ₆ , LiBF ₄ , and LiClO ₄ were used. The batteries fabricated in this manner are hereinafter referred to as Comparative Batteries Z11 to Z13.

Comparative Examples 14 to 16 Batteries were produced in the same manner as in Comparative Examples 11 to 13 except that VC was not added. The batteries fabricated in this manner are hereinafter referred to as comparative batteries Z14 to Z16, respectively.

[Experiment] The batteries D1 to D10 of the present invention and the comparative batteries Z1 to Z16 were charged, discharged and overdischarged under the same conditions as in the experiment of the first embodiment. The recovery rate was calculated, and the results are shown in Table 4 below.

[0066]

[Table 4]

As is clear from Table 4, the same tendency as in the case of using unsubstituted spinel-type lithium manganate was obtained when spinel-type lithium manganate in which a part of the crystal lattice was substituted with aluminum was used. It was confirmed that there was. As is clear from Tables 3 and 4, the same effect is obtained when spinel-type lithium manganate is used, regardless of whether a part of the crystal lattice is replaced with a different element.

The different elements that can be substituted in the crystal lattice include magnesium, aluminum, lithium, calcium, vanadium, titanium, chromium, copper, niobium, cobalt, nickel, zirconium, zinc, iron, and the like.
There are molybdenum and tin, among which lithium,
Magnesium and aluminum are optimal.

Fifth Embodiment [Experiment 1] The battery A8 of the present invention shown in the eighth embodiment of the first embodiment, except that a mixture of lithium manganate and lithium cobaltate is used as the positive electrode active material. EC and DE
C in a mixed solvent of 3: 7 by volume.
wt% VC added to LiPF ₃ (C
Batteries having an electrolyte solution in which ₂ F ₅ ) ₃ was dissolved at a rate of 1 mol / l], and various kinds of batteries were manufactured by changing the mixing ratio of lithium manganate and lithium cobaltate. These batteries were charged, discharged and overdischarged under the same conditions as in the experiment of the first embodiment.
Table 5 shows the results of the calculation.
And FIG.

[0070]

[Table 5]

As is clear from Table 5 and FIG. 5, when the ratio of lithium manganate to the total amount of the positive electrode active material is 20 wt% or more by mass, the capacity recovery rate after overdischarge can be significantly improved. Admitted.

As shown in FIG. 6, the spinel-type lithium manganate has the characteristic that the discharge curve has a plateau in the 2.8 V voltage region in addition to the 4 V voltage region, as shown in FIG. It is considered that the reason is that the potential of the positive electrode is hardly reduced even when the lithium becomes excessive during the overdischarge. That is, in the mixed positive electrode, lithium manganate suppresses a decrease in the positive electrode potential during overdischarge,
It is considered that the potential drops only to the voltage range where the reversibility of lithium cobaltate can be maintained, and as a result, the deterioration of lithium cobaltate is suppressed and the capacity retention ratio is improved. More specifically, in lithium cobalt oxide, there is no place where the discharge curve becomes a plateau in a voltage range below the range of normal use, so that there is a risk that lithium cobalt oxide is easily overdischarged to a region where the crystal structure is completely destroyed. In contrast to this, lithium manganate has a plateau potential near 2.8 V, so that a change in crystal structure can be temporarily suppressed at this stage. For this reason, a change in the crystal structure due to overdischarge can be suppressed as much as possible, and deterioration of the positive electrode active material is suppressed. This can be similarly considered in a mixed system. When the mixing ratio of lithium manganate increases, the potential that becomes a plateau near 2.8 V increases in proportion to this, so that the deterioration of the positive electrode active material is reduced. Will be suppressed.

The reason why the capacity retention ratio varies depending on the amount of lithium manganate mixed is that the load ratio of lithium manganate during overdischarge increases in the mixed type positive electrode. It is considered that the reason is that the degree of deterioration becomes too large in a battery with a small amount of mixed. Therefore, the ratio of lithium manganate to the total amount of the positive electrode active material is desirably 20% by weight or more by mass ratio.

The above effect is obtained by using LiP as a lithium salt.
The present invention is not limited to the case where F ₃ (C ₂ F ₅ ) ₃ is used, but the general formula LiPF _6-X (C _n F _{2n + 1} ) _X [where X is 1
It has been confirmed by experiments that the same effect as described above can be obtained when a lithium salt represented by the following formula is used: n is an integer of 5 and n = 1 or 2.

In the above experiment, lithium cobaltate was used as the positive electrode active material mixed with lithium manganate. However, the present invention is not limited to this. For example, lithium nickelate, or lithium cobaltate and lithium nickelate may be used. It has been confirmed by experiments that the same effect as above can be obtained even when the mixture of the above is used.

[Experiment 2] A battery similar to the battery A8 of the present invention shown in Example 8 of the first embodiment was manufactured in various manners except that the amount of VC added was changed, and these batteries were replaced with those of the first embodiment. The battery was charged, discharged, and overdischarged under the same conditions as in the experiment, and the capacity recovery rate represented by the above equation 1 was calculated. The results are shown in Table 6 and FIG. 7 below.

[0077]

[Table 6]

As is clear from Table 6 and FIG. 7, as the amount of VC added to the solvent of the electrolytic solution increases, the capacity recovery rate after overdischarge increases, but the amount of VC increases. As a result, it is recognized that the internal resistance of the battery at the time of manufacturing the battery increases. In particular, when the added amount of VC exceeds 5 wt%, the internal resistance of the battery is significantly increased. When the internal resistance of the battery is increased as described above, the battery characteristics in a normal use region are greatly reduced. Therefore, it is desirable that the amount of VC added is 5 wt% or less, and particularly 2 wt%.
% Is desirable.

The above effect is obtained by using LiP as a lithium salt.
The present invention is not limited to the case where F ₃ (C ₂ F ₅ ) ₃ is used, but the general formula LiPF _6-X (C _n F _{2n + 1} ) _X [where X is 1
It has been confirmed by experiments that the same effect as described above can be obtained when a lithium salt represented by the following formula is used: n is an integer of 5 and n = 1 or 2.

[Experiment 3] Changing the molar concentration of LiPF ₃ (C ₂ F ₅ ) ₃ [However, in order to maintain the charge / discharge performance of the battery, the molar concentration of LiPF ₃ (C ₂ F ₅ ) ₃ was reduced. LiPF ₆ as a substitute is added as much as the amount added, and the total lithium salt concentration is adjusted to be 1 mol / l.] Other than the above, the battery A8 of the present invention shown in Example 8 of the first embodiment. Various batteries were manufactured in the same manner as described above, and these batteries were charged, discharged, and discharged under the same conditions as in the experiment of the first embodiment.
And overdischarge, and the capacity recovery rate represented by the above equation 1 was calculated. The results are shown in Table 7 and FIG. 8 below.

[0081]

[Table 7]

As is clear from Table 7 and FIG.
F_Three(C_TwoF_Five)_ThreeAs the molarity of
As a result, the capacity recovery rate after overdischarge decreases, but the LiPF
_Three(C _TwoF_Five)_ThreeIs more than 0.3mol / l
If any, the capacity recovery rate after overdischarge is sufficiently ensured
It is recognized that.

Although the details of this factor are unknown, LiPF
_If the molar concentration of ₃ (C ₂ F ₅ ) ₃ is 0.3 mol / l or more, even if a lithium salt other than LiPF ₃ (C ₂ F ₅ ) ₃ is mixed, L decomposed at the early stage of charging.
This is probably because a composite coating of iPF ₃ (C ₂ F ₅ ) ₃ and VC was formed on the negative electrode active material, and the effect of suppressing manganese deposition was sufficiently exhibited. On the other hand, LiPF
_When the molar concentration of ₃ (C ₂ F ₅ ) ₃ is less than 0.3 mol / l, the effect is greatly reduced because the interaction with other lithium salts (LiPF _{6 in the} above experiment) causes LiPF ₃ ( This is considered to be because the composite film of C ₂ F ₅ ) ₃ and VC was not sufficiently formed on the negative electrode active material. Therefore, LiPF ₃ (C ₂ F ₅ ) ₃
Is preferably 0.3 mol / l or more.

The above effect is obtained by using LiP as a lithium salt.
The present invention is not limited to the case where F ₃ (C ₂ F ₅ ) ₃ is used, but the general formula LiPF _6-X (C _n F _{2n + 1} ) _X [where X is 1
It has been confirmed by experiments that the same effect as described above can be obtained when a lithium salt represented by the following formula is used: n is an integer of 5 and n = 1 or 2.

[0085]

As described above, according to the present invention,
Since the overdischarge characteristic is dramatically improved, a protective circuit or the like is not required, thereby providing an excellent effect that the cost and the energy density of the nonaqueous electrolyte battery can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view of a nonaqueous electrolyte battery according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a perspective view of a power generation element used in the nonaqueous electrolyte battery according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of a laminate exterior body.

FIG. 5 is a graph showing a relationship between a mixed amount of lithium manganate and a capacity recovery rate.

FIG. 6 is a graph showing a relationship between capacity and positive electrode potential in lithium manganate, lithium cobaltate, and a mixture of lithium manganate and lithium cobaltate.

FIG. 7 is a graph showing the relationship between the amount of VC added and the capacity recovery rate and internal resistance.

FIG. 8 is a graph showing the relationship between the molar concentration of LiPF ₃ (C ₂ F ₅ ) ₃ and the capacity recovery rate.

[Explanation of symbols]

 1: Positive electrode 2: Negative electrode 4: Power generation element 5: Storage space 6: Laminate exterior body 8: Positive electrode tab 9: Negative electrode tab

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ikukawa Nori 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 5H029 AJ02 AK03 AL06 AM03 AM04 AM05 AM07 BJ04 BJ14 HJ01 HJ02 HJ10 HJ11 5H050 AA04 BA17 CA09 CB07 DA13 HA01 HA02 HA10 HA11

Claims (5)

[Claims] 1. A non-aqueous electrolyte battery in which a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material capable of inserting and extracting lithium, and an electrolytic solution including a solvent and a solute are arranged in an outer package. Vinylene carbonate is added to the solvent of the electrolytic solution, and the solute of the electrolytic solution has a general formula LiPF _6-X
(C _n F _{2n + 1} ) _X [where X is an integer of 1 to 5 and n =
1 or 2, preferably X = 2 or 3, particularly preferably X = 2 or 3, and n = 2]. Electrolyte battery. 2. The non-aqueous electrolyte battery according to claim 1, wherein the positive electrode active material contains spinel-type lithium manganate. 3. The general formula LiPF _6-X (C _n F _{2n + 1} )
The molar concentration of the lithium salt represented by _X is 0.3 mol /
The nonaqueous electrolyte battery according to claim 1, wherein the number is 1 or more. 4. When the mass ratio of the vinylene carbonate to the solvent of the electrolytic solution is defined as y (wt%),
4. The nonaqueous electrolyte battery according to claim 1, wherein the mass ratio y satisfies 0 <y ≦ 5, preferably 0 <y ≦ 3. 5. When the mass ratio of the spinel-type lithium manganate to the total amount of the positive electrode active material is defined as z (wt%), the mass ratio z satisfies 20 ≦ z. The non-aqueous electrolyte battery according to the above.