JPH10125317A - Monaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superior performance ensuring high-energy density and a cycle life, free from short-circuits due to dendrite by using a mixture of metallic or semi-metallic powder containing at least a phosphorus, a carbon material and a binding agent as a negative electrode. SOLUTION: Al, Sn, Si, Pb, Cd, Bi, In, Zn, Ga, B, Au and Pt, when made to contain P, improve the cycle characteristic thereof by leaps and bounds. The P content is preferably between 1wt.% and 50wt.%, and the content between 1wt.% and 15wt.% is particularly preferable. The mechanical strength of a metal is improved as a result of containing P, thereby restraining fine pulverization, due to the repetition of light discharge. Also, Mo, Mg, Fe, Mn, Co, Ni, Ta, Cr, W, Ti, V and the like become capable of performing a charging and discharging process by containing P. In this case, the P content is preferably between 1wt.% and 50wt.%, and the content between 5wt.% and 15wt.% is particularly preferable. A new Li storage site is formed when these metals turn into a solid solution state like metallic grating.

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 an improvement of a negative electrode thereof.

[0002]

2. Description of the Related Art A non-aqueous electrolyte secondary battery using lithium or a lithium compound as a negative electrode is expected to have a high voltage and a high energy density, and has been actively studied. Until now, LiCoO ₂ , V ₂
Oxides of transition metals such as O ₅ , Cr ₂ O ₅ , MnO ₂ , TiS ₂ and MoS ₂ and chalcogen compounds are known.
These compounds have a layered or tunnel structure,
It has a crystal structure that allows lithium ions to enter and exit.
On the other hand, as the negative electrode active material, many studies have been made of metallic lithium. However, there is a problem in that lithium is deposited in a dendritic manner on the lithium surface during charging, and the charging / discharging efficiency is reduced or an internal short circuit is caused by contact with the positive electrode.

As means for solving such a problem, studies have been made on the use of a negative electrode made of a lithium alloy plate such as lithium-aluminum which can suppress the dendritic growth of lithium and occlude and release lithium. However,
In the case of using a lithium alloy plate, if the charge and discharge are repeated deeply, the electrode becomes finer, which causes a problem in cycle characteristics. Therefore, for aluminum and the like, a proposal has been made to suppress the miniaturization of the electrode by using an alloy to which another element is added as the electrode (Japanese Patent Laid-Open No. 62-1).
19856, JP-A-4-109562, etc.). However, at present, sufficient characteristics have not been improved.

[0004]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a negative electrode for a non-aqueous electrolyte secondary battery having excellent charge / discharge cycle characteristics. The present invention uses L
An object of the present invention is to provide a negative electrode that does not generate dendrite by absorbing i, has a large electric capacity, and has an excellent cycle life.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a non-aqueous electrolyte secondary battery including a chargeable / dischargeable positive electrode, a nonaqueous electrolyte, and a chargeable / dischargeable negative electrode. It is characterized by using a metal.
By using this negative electrode, with high energy density,
It is possible to obtain a highly reliable secondary battery having excellent cycle life and no short circuit due to dendrite.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Metals or metalloids containing P include Al, Sn, Si, Pb, Cd, Bi, and I.
n, Zn, Ga, B, Au, Pt, Mo, Mg, Fe,
At least one selected from the group consisting of Mn, Co, Ni, Ta, Cr, W, Ti, and V is preferable. P
Is preferably 1 to 50% by weight based on the total weight of the metal or metalloid containing.

Al, Sn, Si, Pb, Cd, Bi, I
n, Zn, Ga, B, Au, and Pt are each independently L
Although it is possible to occlude and release an alkali metal such as i, the cycle characteristics are dramatically improved by containing P. In addition, Mo, Mg, Fe, Mn, Co, Ni,
Conventionally, Ta, Cr, W, Ti, V, and the like have not been able to occlude and release an alkali metal such as Li by themselves, but containing P enables charge and discharge. The details of the effect of containing P are unknown, but Al, Sn, Si, Pb, Cd, and B, which can occlude and release an alkali metal such as Li without containing P conventionally.
Regarding i, In, Zn, Ga, B, Au, and Pt, the mechanical strength of the metal is increased by containing P,
It is considered that pulverization caused by repeating conventional charge and discharge is suppressed. In view of both the capacity characteristics and the cycle characteristics, the P content is preferably 1 to 50% by weight,
1-30 wt% is more preferable, and 1-15 wt% is particularly preferable.

On the other hand, Mo, Mg, Fe, Mn, Co, N
For metals such as i, Ta, Cu, Cr, W, Ti, and V, which have not been able to occlude and release alkali metals such as Li by themselves, a new solution is formed by the solid solution of P in a metal lattice. It is considered that the Li storage site was formed. In view of both the capacity characteristics and the cycle characteristics, the P content is preferably 1 to 50 wt%, more preferably 1 to 30 wt%, and particularly preferably 5 to 15 wt%.

[0009]

Embodiments of the present invention will be described below. << Example 1 >> First, Al having different P contents shown in Table 1 was used.
Sn, Si, Pb, Cd, Bi, In, Zn, Ga,
In order to study the characteristics of B, Au, and Pt as a negative electrode active material, a test cell shown in FIG. 1 was manufactured. To 6 g of the active material powder, 3 g of graphite powder as a conductive agent and 1 g of polyethylene powder as a binder were mixed to form a mixture. 0.1 g of this mixture was pressed into a disk having a diameter of 17.5 mm to obtain an electrode 1. The electrode 1 was placed at the center of the case 2, and a separator 3 made of a microporous polypropylene film was placed thereon. 1 mol / l of lithium perchlorate (LiCl
A mixed solution of ethylene carbonate and dimethoxyethane in which O4) was dissolved at a volume ratio of 1: 1 was injected as a non-aqueous electrolyte onto the separator. After this, the inside diameter is 17.5mm
A metal lithium plate 4 was attached, and a sealing plate 6 having a gasket 5 made of polypropylene on the outer periphery was combined with the case, and sealed to form a test cell.

The test cell is subjected to cathodic polarization at a constant current of 2 mA until the electrode becomes 0 V with respect to the Li counter electrode (corresponding to charging when the electrode 1 is viewed as a negative electrode),
Next, anodic polarization (corresponding to discharge) was performed until the electrode reached 1.0 V. The electrode characteristics were evaluated by repeating this cathodic polarization and anodic polarization. As comparative examples, various metals or metalloids not containing P were also examined. Also for this comparative example, a test cell was prepared in the same manner as described above, and the electrode characteristics were examined under the same conditions. Table 1 shows the discharge capacity per 1 g of the active material in the first cycle.

[0011]

[Table 1]

It has been found that all of the P-containing electrodes of this embodiment charge and discharge. Al, S containing P
n, Si, Pb, Cd, Bi, In, Zn, Mg, G
For a, B, Au, and Pt alloys, as the P content increases, the discharge capacity in the first cycle decreases, but the P content is 50% by weight or more of the P-free metal. showed that. After the cathode polarization in the tenth cycle of this test cell was completed, the test cell was disassembled, and no deposition of lithium metal was observed in any case. As described above, in the active material electrode of the present invention, Li was occluded in the electrode by the cathodic polarization, and L absorbed by the anodic polarization.
It was found that i was released and no metal Li was deposited.

<< Example 2 >> Here, Mo, Mg, Fe, Mn, Co, Ni, T having different P contents shown in Table 2 were used.
In order to study the characteristics of a, Cu, Cr, W, Ti, and V as a negative electrode active material, a test cell shown in FIG. 1 was prepared in the same manner as in Example 1, and tested under the same conditions as in Example 1. .
Table 2 shows the results. As comparative examples, various metals not containing P were also examined. Table 2 shows the discharge capacity per 1 g of the active material in the first cycle.

[0014]

[Table 2]

It has been found that the electrode of this embodiment charges and discharges by containing P. Mo, Mg, Fe, Mn, C
The o, Ni, Ta, Cu, Cr, W, Ti, and V metals alone have almost no capacity, whereas the presence of a small amount of P significantly increased the capacity. After the cathode polarization of the 10th cycle of this test cell is completed,
When the test cells were disassembled, no deposition of metallic lithium was observed in any case. As described above, in the active material electrode of the present invention, Li is occluded in the electrode by cathodic polarization, and the occluded Li is released by anodic polarization, and there is no deposition of metallic Li. Further, it was found that the charge / discharge capacity became extremely large by containing P.

<< Example 3 >> Here, Al, Sn, Si, Pb, Cd, Bi, and I having different P contents shown in Table 3 were used.
n, Zn, Mg, Ga, B, Au, Pt, Mo, Fe,
The cylindrical battery shown in FIG. 2 having Mn, Co, Ni, Ta, Cr, W, Ti, and V as negative electrodes was constructed and its characteristics were examined. A battery was manufactured according to the following procedure. LiMn _1.8 Co _0.2 O ₄ , which is a positive electrode active material, is composed of Li ₂ CO ₃ and Mn ₃ O ₄
And CoCO ₃ were mixed at a predetermined molar ratio and heated at 900 ° C. to synthesize. Furthermore, what classified this into 100 mesh or less was used as the positive electrode active material. With respect to 100 g of the positive electrode active material, 10 g of a carbon powder as a conductive agent, 8 g of an aqueous dispersion of polytetrafluoroethylene as a binder, and pure water were added to form a paste, which was applied to a titanium core material, After drying and rolling, a positive electrode was obtained. On the other hand, a graphite powder as a conductive agent and a Teflon binder as a binder were added to a negative electrode active material composed of various alloy powders containing P at a weight ratio of 60:
The mixture was mixed at a ratio of 30:10, made into a paste using a petroleum solvent, applied to a copper core material, and then dried at 100 ° C. to obtain a negative electrode plate. A microporous polypropylene film was used as a separator.

The above-mentioned positive electrode plate 11 and negative electrode plate 12 were superposed on each other with a separator 13 wider than the electrode plates interposed therebetween, and these were spirally wound to form an electrode plate group. This electrode plate group is provided with insulating plates 16 and 17 made of polypropylene on the upper and lower sides thereof, respectively, and inserted into the battery case 18. After forming a step on the upper portion of the battery case 18, a non-aqueous electrolyte is injected. The battery was sealed as shown in FIG. 2 with a sealing plate 19. In addition,
As the electrolytic solution, an equivolume mixed solution of ethylene carbonate and dimethoxyethane in which 1 mol / l of lithium perchlorate was dissolved was used. Reference numeral 14 denotes a positive electrode lead made of the same material as the core material of the positive electrode, and is connected to a positive electrode terminal 20 provided on the sealing plate 19. Reference numeral 15 denotes a negative electrode lead made of the same material as the negative electrode, and is connected to the battery case 18. As a comparative example, a negative electrode was prepared and a battery was assembled in the same manner as described above except that various metal or metalloid powders not containing P were used as the negative electrode active material.

These batteries were charged at a temperature of 30 ° C. at a charge / discharge current of 1 mA / cm ² and a charge / discharge voltage range of 4.2 V to 3.0 V.
Charge / discharge was repeated at V, and the life (cycle number) until the discharge capacity was reduced to 50% of the initial capacity was examined. Table 3 shows the results.

[0019]

[Table 3]

Al, Sn, Si, Pb, Cd, Bi, I
For n, Zn, Ga, B, Au and Pt, up to a P content of 50 wt%, the cycle characteristics were improved as the P content increased. In view of both the capacity characteristic and the cycle characteristic shown in Example 1, P containing Al, Sn, Si,
The P content of Pb, Cd, Bi, In, Zn, Ga, B, Au, and Pt is preferably 1 to 50 wt%, and 1 to 50 wt%.
30 wt% is more preferable, and 1 to 15 wt% is particularly preferable. On the other hand, Mo, Mg, Fe, Mn, Co, Ni, T
a, Cu, Cr, W, Ti, and V also became capable of charging and discharging by containing P, and exhibited good cycle characteristics. In view of both the capacity characteristic and the cycle characteristic shown in Example 2, the P content is preferably 1 to 50% by weight,
1-30 wt% is more preferable, and 5-15 wt% is particularly preferable.

In the above embodiment, a cylindrical battery was described. However, the present invention is not limited to this structure, and the same applies to a secondary battery having a coin shape, a square shape, a flat shape, or the like. Needless to say, an effect can be obtained.

[0022]

According to the present invention, a negative electrode having a high capacity and an extremely excellent cycle life can be obtained. By using this negative electrode, a highly reliable non-aqueous electrolyte secondary battery having a high energy density and no short circuit due to dendrite can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a test cell used in an example of the present invention.

FIG. 2 is a longitudinal sectional view of a cylindrical battery used in another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test electrode 2 Case 3 Separator 4 Metal lithium 5 Gasket 6 Sealing plate 11 Positive electrode plate 12 Negative electrode plate 13 Separator 14 Positive electrode lead 15 Negative electrode lead 16 Upper insulating plate 17 Lower insulating plate 18 Battery case 19 Sealing plate 20 Positive electrode terminal

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toyoguchi ▲ Yoshi ▼ Toku 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A non-aqueous electrolyte secondary battery comprising a chargeable / dischargeable positive electrode, a non-aqueous electrolyte, and a chargeable / dischargeable negative electrode, wherein the negative electrode is made of a P-containing metal or metalloid. 2. A chargeable / dischargeable positive electrode, a nonaqueous electrolyte, and a chargeable / dischargeable negative electrode, wherein the negative electrode is made of a mixture of a P-containing metal powder or semimetal powder, a carbon material, and a binder. Non-aqueous electrolyte secondary battery characterized by the following. 3. The method according to claim 1, wherein the metal or metalloid containing P is Al, Sn, Si, Pb, Cd, Bi, In, Z
n, Ga, B, Au, Pt, Mo, Mg, Fe, Mn,
3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the secondary battery is at least one selected from the group consisting of Co, Ni, Ta, Cr, W, Ti, and V. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the metal or metalloid containing P has a P content of 1 to 50 wt%.