JP3196223B2 - Battery pack - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembled battery using a secondary battery.

[0002]

2. Description of the Related Art In recent years, the performance and miniaturization of electronic devices such as video cameras and headphone stereos have been remarkable, and a high energy density is required for a secondary battery serving as a power supply for these electronic devices. Have been.

In order to meet such demands, development of a non-aqueous electrolyte secondary battery having a negative electrode composed of a material which can be doped and de-doped with lithium such as lithium metal, lithium alloy or carbonaceous material has been required. It is being actively conducted. In such a non-aqueous electrolyte secondary battery, the negative electrode is usually connected to a battery can, and a high battery voltage of 3.5 V or more per unit cell can be obtained.

In an electronic device, a secondary battery is rarely used as a single cell in general, and by using an assembled battery obtained by combining a plurality of batteries, a voltage and a capacity corresponding to the electronic device to be used can be obtained. ing.

[0005]

When the above-described battery pack is constructed, the connection between the batteries is made by, for example, welding a lead plate to each electrode of the battery. Therefore, an assembled battery having a large number of cells requires a considerable amount of time for the assembling process, and the assembling workability and productivity of the assembled battery are not good.

In addition, in the battery pack, the insulating tube covering the single cell is broken by the above-mentioned lead plate, causing a problem of causing an external short circuit.

[0007] In order to solve the above-mentioned problems, the present inventors have obtained two types of batteries in which respective battery cans are connected to a positive electrode and a negative electrode, respectively. The idea came to be able to obtain an assembled battery connected in series simply by simply bringing the cans into contact with each other and combining them without using a lead plate.

An object of the present invention is to provide Hisage pairs batteries of simple construction <br/>.

[0009]

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned idea of the present inventors, and comprises an electrode body having a negative electrode and a positive electrode; First and second secondary batteries each including a battery can body housing the body and an electrode terminal portion provided on one end side of the battery can body are electrically connected in series. In the assembled battery, the negative electrode and the positive electrode in the electrode body of the first and second secondary batteries are configured to be capable of doping and undoping lithium, respectively, and the first and second secondary batteries are configured to be capable of doping lithium. A nonaqueous electrolyte is contained in the battery can body of the battery, and the inner surface of the battery can body of the first secondary battery is covered with an aluminum material. The positive electrode in the first secondary battery is The above negative electrode is electrically connected to the battery can body. The negative electrode of the second secondary battery is electrically connected to the battery can, and the positive electrode is electrically connected to the electrode terminal. And the first and second
In the secondary battery of the present invention, a conductive foil is wound around the peripheral surfaces of the battery cans while the peripheral surfaces of the battery cans are in contact with each other.

[0010]

In the battery pack of the present invention , the first and second polarities of the battery can body housing the electrode body and the electrode terminal portion provided at one end of the battery can body are opposite to each other. A conductive foil is wound around these peripheral surfaces in a state where the peripheral surfaces of the battery cans in the secondary battery are in contact with each other, so that the battery cans are integrated, so leads for connecting each electrode are provided. The work of connecting the plate and the lead plate is unnecessary.

The negative electrode and the positive electrode in the electrode bodies of the first and second secondary batteries are respectively configured so as to be capable of doping and undoping lithium. Since the non-aqueous electrolyte is contained in the battery can body, a non-aqueous electrolyte secondary battery having a high battery voltage can be combined.

Further , the secondary battery may be a non-aqueous solution containing a non-aqueous electrolyte.
It is an electrolyte secondary battery, but the battery can body to which the positive electrode is connected
Since the inner surface is covered with aluminum material,
Electrochemical stability is increased.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic longitudinal sectional view of a nonaqueous electrolyte secondary battery in which the battery can 5 is on the positive electrode side and the battery lid 7 is on the negative electrode side.

The negative electrode 1 is formed in a belt-like shape by providing a negative electrode material mainly composed of a carbonaceous material as a negative electrode active material carrier capable of doping and undoping lithium on both sides of a belt-like negative electrode current collector 9. . From this negative electrode 1, a negative electrode lead 1
1 has been derived.

The positive electrode 2 is formed in a band shape by providing a positive electrode material mainly composed of LiCoO ₂ as a positive electrode active material capable of doping and undoping lithium on both sides of a band-shaped positive electrode current collector 10.

The above-mentioned strip-shaped negative electrode 1 and positive electrode 2 are laminated via a pair of separators 3a and 3b made of a microporous polypropylene film, and then spirally wound many times. The electrode body 15 is configured. 33 is a winding core.

The battery can 5 is made of a clad material comprising a stainless steel layer 16 and an aluminum layer 17. The aluminum layer 17 is located on the inner surface side of the battery can 5. As a result, electrochemical stability with respect to the non-aqueous electrolyte is obtained, and the stainless steel layer 16 is located on the outer surface side to obtain sufficient strength. The stainless steel layer 16
Has an outer surface side subjected to nickel plating. Also,
The stainless steel layer 16 may be steel or the like.

The wound electrode body 15 is housed in the battery can 5 as described above, and lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte is mixed with propylene carbonate and 1, 2
1 mol / mol in a non-aqueous solvent mixed in an equal amount with dimethoxyethane.
A non-aqueous electrolyte obtained by dissolving at a rate of 1 liter is injected.

The negative electrode lead 11 derived from the negative electrode 1 of the wound electrode body 15 is welded to the projection 34a of the safety valve 34, and the positive electrode lead 12 derived from the positive electrode 2 is welded to the bottom of the battery can 5. Have been. The wound electrode body 15
The upper and lower end faces of the circular-shaped insulating plate 4 a, 4 b are respectively arranged.

The metal safety valve 34 and the stripper 36 are provided integrally with the intermediate fitting 35. The safety valve 34 and the metal battery cover 7 are closely attached to each other at their outer circumferences, and are provided at the upper end of the battery can 5 via an insulating sealing gasket 6. By caulking the battery can 5 at this upper end, the battery cover 7 as the negative electrode terminal and the battery can 5 on the positive electrode side are electrically insulated, and the battery can 5 is hermetically sealed. The lower end of the insulating sealing gasket 6 is in contact with the insulating plate 4a, and the insulating plate 4a and the wound electrode
5 is in close contact with the upper end surface.

When the internal pressure of the sealed battery rises for some reason, the safety valve 34 is moved upward in FIG.
4a, the negative electrode lead 11 and the projection 34
It is configured so that the connection with a is disconnected. Further, the safety valve 34 is provided with a not-shown cleavage portion that is opened when the internal pressure of the battery rises and the safety valve 34 is deformed, and a hole (not shown) is formed in the battery lid 7. As described above, the battery of this embodiment is provided with a dual safety device including the current interrupting device and the internal pressure releasing device.

The above-mentioned non-aqueous electrolyte secondary battery can be formed in a cylindrical shape having a diameter of 15 mm and a height of 50 mm, for example. This battery can be used after being charged with the upper limit voltage of 4.1 V.

For the negative electrode 1 in the non-aqueous electrolyte secondary battery as described above, various materials that can be doped with lithium and dedoped can be used. For example, lithium metal,
Conductive polymers such as lithium alloy and polyacetylene, carbonaceous materials such as coke, and carbon materials can be used.

As the positive electrode active material, a material capable of doping and undoping lithium is used, and a material containing a sufficient amount of lithium is preferably used. For example, lithium such as LiCoO ₂ represented by the general formula LixMO ₂ (M is at least one of Co and Ni)
Cobalt composite oxide, lithium nickel composite oxide,
Lithium-cobalt-nickel composite oxide is preferred,
Lithium-manganese composite oxide such as LiMnO ₄ ,
Vanadium oxide such as V ₂ O ₅ may be used.

As the non-aqueous electrolyte, for example, a solution obtained by dissolving lithium salt as an electrolyte in an organic solvent (non-aqueous solvent) can be used.

Here, the organic solvent is not particularly limited. For example, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-
Diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-diexolan, 4-methyl-1,3-
Dioxolan, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile and the like can be used alone or in combination of two or more. As the electrolyte, any of conventionally known electrolytes can be used.
ClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , L
iB (C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO
₃ Li, CF ₃ SO ₃ Li and the like.

EXPERIMENTAL EXAMPLE A non-aqueous electrolyte secondary battery shown in FIG. 1 and a nickel-plated iron battery can 5 as a battery can 5 in FIG. 1 for comparison (an aluminum layer is not provided on the inner surface) Except that the same non-aqueous electrolyte secondary batteries as in FIG. 1 were produced.

The above two types of batteries were charged at a constant current of 100 mA for 8 hours at an upper limit voltage of 4.1 V. Thereafter, a cycle life test was performed in which discharging was performed at a constant current of 80 mA to a final voltage of 2.75 V and then charging was performed at a constant current of 400 mA to an upper limit voltage of 4.1 V as one cycle. Then, the discharge capacity was measured for each cycle.

FIG. 2 shows how the discharge capacity changes with the cycle in the cycle life test described above. As is clear from FIG. 2, the battery of the present example did not cause any problem even after 100 cycles, but the battery of the comparative example had its life at the 20th cycle. When the battery of this comparative example was disassembled and observed, the iron battery can body corroded,
It was observed that the precipitate penetrated the separator of the wound electrode body. It is estimated that iron and nickel ions were dissolved out of the battery can body, and this precipitate was deposited in the separator. It is considered that an internal short circuit occurred due to the penetration of the precipitate in the separator, and the battery life was shortened.

As described above, in the non-aqueous electrolyte secondary battery having a discharge voltage of 3.5 V or more with the battery can body 5 side as the positive electrode, the aluminum layer 1 is formed on the inner surface of the battery can 5.
Providing 7 makes it possible to electrochemically stabilize the non-aqueous electrolyte and to prevent capacity deterioration due to charge / discharge cycles. It is preferable to use an aluminum-stainless steel clad material (ply plate) in order to make the above-mentioned battery can 5, and with such a clad material, the strength of the battery body can be obtained.

Next, FIGS. 3A, 3B and 4 show two examples of the assembled battery. In the assembled battery 50 shown in FIG.
The non-aqueous electrolyte secondary battery shown in FIG. The non-aqueous electrolyte secondary battery is substantially the same as the battery shown in FIG. 1 except that the positive electrode lead 12 is welded to the projection 34a of the safety valve 34 and the negative electrode lead 11 is welded to the bottom surface of the battery can 5. Is referred to as a second battery 42. The battery can in the second battery 42 may be made of stainless steel or steel instead of the clad material shown in FIG.

In the first battery 41, the battery can 5 is a positive electrode portion 41a, and the battery cover 7 is a negative electrode terminal portion 41b. In the second battery 42, the battery can 5 'is
2b, and the battery lid 7 is the positive electrode terminal portion 42a.

As shown in FIGS. 3A and 3B, the battery 5
In the case of 0, the battery can 5 of the first battery 41 and the battery can 5 'of the second battery 42 are wound around by the metal foil 45 so that they are in contact with each other and are integrated. Thereby, the positive electrode side 41a of the first battery 41 and the second battery 42
Is electrically connected to the negative electrode portion 42b. In this case, as shown in FIG. 3B, the electrical connection between the battery can 5 of the first battery 41 and the battery can 5 'of the second battery 42 is made by widening the battery can 5, 5'. Covering metal foil 45 ensures this.
As described above, the assembled battery 50 is configured such that the positive terminal portion 42a is on the positive side and the negative terminal portion 41b is on the negative side.

According to the assembled battery 50 using the non-aqueous electrolyte secondary battery as shown in FIG. 1, the battery voltage between the negative terminal 41b and the positive terminal 42a is 8.2V. It is preferable to further cover the outer surface of the metal foil 45 with an insulating sheet material or the like in order to eliminate an external short circuit. Alternatively, the outer surface of the metal foil 45 may be subjected to a process for obtaining insulation.

FIG. 4 shows another example of an assembled battery. In this assembled battery 51, the negative terminal 41b of the first battery 41 is used.
And the positive electrode terminal portion 42a of the second battery 42 are configured to face in opposite directions. Other than this, battery pack 50
This is the same configuration as.

According to the assembled batteries 50 and 51 described above,
A pair of nonaqueous electrolyte secondary batteries 41 and 42 are simply
, A battery pack connected in series can be easily obtained. This eliminates the need to connect lead plates to each electrode, which has conventionally been required in the manufacturing process of an assembled battery, thereby reducing man-hours and improving productivity. Further, the coating tube for insulation by the lead plate is not broken, and external short circuit can be prevented.

Although the secondary battery in this embodiment is a cylindrical nonaqueous electrolyte secondary battery, the present invention can be applied to other secondary batteries, and may be a prismatic type. You may.

[0038]

According to the battery pack of the present invention , the lead plate for connecting each electrode and the work of connecting the lead plates are not required, so that the cost, the number of steps and the productivity in the manufacturing process of the battery pack are reduced. Improvement can be achieved. Further, the problem of external short circuit caused by the lead plate is eliminated. Also, a non-aqueous electrolyte secondary battery having a high battery voltage can be combined ,
Duck, because that have electrochemical stability is increased in a battery can, a battery pack of high battery voltage and high capacity, lower costs,
It can be obtained while reducing man-hours and improving productivity.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a change in the discharge capacity of a battery obtained by performing a cycle life test on the secondary battery of the embodiment shown in FIG. 1 and the secondary battery of the comparative example, depending on the cycle.

3A and 3B are a front view (A) and a side view (B) of an assembled battery according to an embodiment including the secondary battery shown in FIG. 1 and a conventional secondary battery having a battery can body on the negative electrode side.

FIG. 4 is a front view showing a modification of the battery pack shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 negative electrode 2 positive electrode 5 battery can 15 wound electrode body (electrode body) 17 aluminum layer 41 first battery 41 b negative electrode terminal (electrode terminal) 42 second battery 50, 51 assembled battery

Continuation of the front page (56) References JP-A-2-51847 (JP, A) JP-A-2-297860 (JP, A) JP-A-1-294350 (JP, A) JP-A-63-237349 (JP) JP-A-63-102158 (JP, A) JP-A-63-121269 (JP, A) JP-A-63-121268 (JP, A) JP-A-59-181580 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 10/40 H01M 2/22 H01M 2/30 H01M 4/64

Claims (1)

(57) [Claims] An electrode having a negative electrode and a positive electrode, a battery can housing the electrode, and an electrode terminal provided at one end of the battery can. 1
And a second secondary battery, wherein the negative electrode and the positive electrode in the electrode assembly of the first and second secondary batteries are doped with lithium and undoped. The first and second secondary batteries each include a non-aqueous electrolyte in the battery can bodies, and the inner surface of the battery can body of the first secondary battery is made of an aluminum material. Wherein the positive electrode of the first secondary battery is electrically connected to the battery can and the negative electrode is electrically connected to the electrode terminal; The negative electrode of the battery is electrically connected to the battery can, and the positive electrode is electrically connected to the electrode terminal portion. The periphery of the battery can in the first and second secondary batteries Surface contact Conductive foil is wound in these peripheral surfaces at and are state assembled battery in which the battery can body is integrated.