JP2003197265A - Nonaqueous electrolytic solution battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution battery wherein an abundant electrolytic solution is put into a sheath can in a shorter time than a conventional one, and wherein development of superior battery performance is possible. <P>SOLUTION: This is the nonaqueous electrolytic solution battery wherein a bending in which the electrolytic solution is circulated from the short part to the center part in the width direction at least at one of a separator, a positive electrode plate and a negative electrode plate, and wherein the bending is formed preferably in the depth of 1 μm to 1 mm in the thickness direction. For example, on the surface of the positive electrode 1, plural semilunar grooves (bendings) 1a are formed by means of bending work in parallel with the width direction of the positive electrode. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for abundantly containing an electrolytic solution in an outer casing in a non-aqueous electrolytic solution battery such as a lithium ion battery.

[0002]

2. Description of the Related Art In recent years, mobile phones and personal digital assistants (PDs)
Small electronic devices such as A) are rapidly spreading. A non-aqueous electrolyte battery such as a lithium ion battery is often used as a power source with a high energy density that can withstand long-term use in these small electronic devices. The non-aqueous electrolyte battery has a structure in which a power generation element body is housed in an exterior body (exterior can) and the inside of the battery is sealed by a sealing body. The power generation element body is, for example, an electrode body formed by stacking a strip-shaped separator, a positive electrode, and a negative electrode, and impregnating the electrolytic solution. The electrolytic solution is injected mainly so that the active material in the electrode body is impregnated after the electrode body is put in the outer can. The electrolyte injected into the outer can does not easily impregnate the active material immediately after injection, so generally, it takes a long time to repeat the process of gradually impregnating the active material in the electrode body, It is necessary to depressurize the can and inject the electrolytic solution.

[0003]

By the way, with the recent increase in the energy density of batteries, it is required to secure the volume of the electrode body and the amount of the active material as much as possible. However, this increases the packing density of the active material in the electrode body housed in the outer can, which makes it more difficult to inject the electrolytic solution and reduces working efficiency. Further, in some cases, the electrolyte may not be sufficiently injected.

Such a problem may occur in all non-aqueous electrolyte batteries, but particularly in the field of lithium ion batteries widely used as a power source for small electronic devices, urgent countermeasures are required. It is rare. In order to solve such a problem, Japanese Unexamined Patent Publication No. 9-298057 discloses that a surface of an electrode plate is partially compressed to form a groove, and an electrolytic solution is circulated in the groove. However, due to the higher energy density of the battery, the electrode plate is filled closer to the limit, and further compression force applied by this method causes damage to the electrode plate. This is even more so in batteries that use thin plates such as lithium-ion batteries. Further, in order to form the groove, it is considered to scrape off a part of the active material layer of the electrode plate to form the groove, but the battery capacity is reduced, and the treatment of powder generated when scraping is performed. Is a problem.

The present invention has been made in view of the above problems, and an object thereof is to be able to inject abundant electrolytic solution into an outer can in a shorter time than in the conventional case and to obtain a good battery. It is to provide a non-aqueous electrolyte battery that can be expected to exhibit its performance.

[0006]

In order to solve the above-mentioned problems, the present invention is a non-consolidated case in which an electrode body formed by stacking a positive electrode plate and a negative electrode plate via a separator is housed in an outer package together with an electrolytic solution. In a water electrolyte battery, an electrode body formed by stacking a positive electrode and a negative electrode via a separator, in a sealed battery formed by accommodating in an outer package together with an electrolytic solution, in at least one of the separator, the positive electrode plate and the negative electrode plate. In the above, a bend in which the electrolytic solution flows is formed from the end portion in the width direction to the central portion.

According to this structure, the bending formed in at least one of the positive electrode, the separator, and the negative electrode forms at least one minute passage of the separator, the positive electrode plate, and the negative electrode plate inside the electrode body. Therefore, when injecting the electrolytic solution into the electrode body housed in the exterior body, the electrolytic solution circulates through at least one minute passage of the separator, the positive electrode plate, and the negative electrode plate, and the electrode active material is swiftly absorbed. As a result, abundant amount of electrolyte is injected into the outer casing. Therefore, there is no need to repeat the step of impregnating the electrode body with the electrolytic solution many times as in the conventional case. Therefore, in the present invention, the time required for the step of injecting the electrolyte solution is significantly shorter than that of the conventional one, although the structure is very simple, and the work efficiency is improved, so that the number of manufacturing steps is reduced. Such an effect is produced.

Further, in the present invention, since the surfaces of the electrodes and the separators are finely processed without using anything other than the power generating element as described above, there is no fear of lowering the energy density of the battery. Specifically, the flow passage can be formed as a groove (flexure) by processing at least one surface of the separator, the positive electrode, and the negative electrode. By this processing, while maintaining the amount of active material as it is,
There is an advantage that the groove can be formed without damaging the electrode plate. According to experiments conducted by the inventors, it has been found that the groove preferably has a depth of 1 μm or more and 1 mm or less.

However, when the depth is about 1 μm, it is desirable to increase the number of grooves as described later in detail. Further, the present invention can be generally applied to a non-aqueous electrolyte battery having an outer package of any shape. However, as in a type in which the electrode body is wound in a spiral shape and is housed in a cylindrical outer can. The effect is particularly large in the case where the electrode body is wound with a relatively strong winding force.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION 1. First Embodiment 1-1. Configuration of Lithium Ion Battery FIG. 1 is a sectional perspective view of a cylindrical lithium ion battery as an application example of the present invention.

The lithium ion battery (diameter 18 mm, height
65 mm) has a cylindrical outer can 6, an electrode body 4 in which a positive electrode 1 and a negative electrode 2 are spirally wound around a separator 3, and an electrolytic solution impregnated in the electrode body 4. It has a configuration in which etc. are stored. A non-aqueous electrolyte is used as the electrolyte,
Here, as an example, EC (ethylene carbonate) and EMC
An electrolytic solution is used in which LiPF ₆ (lithium hexafluorophosphate) is dissolved as an electrolyte in a mixed solvent of (ethyl methyl carbonate).

The positive electrode 1 is a positive electrode composite in which a conductive material (carbon black) and a binder (polyvinylidene fluoride) are mainly mixed with lithium cobalt oxide LiCoO ₂ which is a positive electrode active material on the surface of a strip-shaped core made of aluminum. It is formed by applying an agent and is connected to the positive electrode current collector 11. Negative electrode 2
Is a cylinder that doubles as a negative electrode terminal by applying a negative electrode mixture that is a mixture of a negative electrode active material mainly composed of graphite and a binder to the surface of a copper strip-shaped core, and a negative electrode current collector (not shown). It is connected to the inner bottom surface of the outer can 6.

The separator 3 is a microporous polyethylene film and is used for insulating the positive electrode 1 and the negative electrode 2. Electrode body
A center pin 5 is arranged at the center of 4 to prevent deformation of the electrode body 4 and to secure a gas flow passage that is generated in an abnormal state (such as being dropped in a fire). A pressing plate 7 is arranged on the electrode body 4 housed in the outer can 6, and a positive electrode current collector 11 is arranged through the central opening of the pressing plate 7. The positive electrode current collector 11 includes a rupture disk (thin film valve plate) 8 and a positive electrode terminal 1.
Connected to 0.

In the battery 1 having such a structure, the following reactions occur during charging and discharging. That is, at the time of charging, in the positive electrode 1, cobalt in the crystal lattice of lithium cobalt oxide, which is the positive electrode active material, is oxidized, and along with this, lithium ions are released. The released lithium ions move to the negative electrode side through the separator 3 impregnated with the electrolytic solution. On the negative electrode side, lithium ions are incorporated into the graphite crystal lattice.

At the time of discharging, a reaction opposite to that at the time of charging occurs, and electric energy can be taken out to the outside. Here, the first embodiment is characterized by the structure of the positive electrode 1. FIG. 2 is a partial perspective view of the positive electrode. As shown in the figure, the positive electrode 1 according to the first embodiment has a plurality of half-moon shaped grooves (flexures) formed on its surface in parallel with the width direction of the positive electrode from the end in the width direction to the center.
1a is installed side by side at regular intervals. As an example, the groove 1a has a depth of 300 μm in the thickness direction of the electrode plate and a width of 1 mm, and is formed at a pitch of 4 mm in the width direction of the positive electrode 1.

The groove 1a of the positive electrode 1 forms a minute passage with the separator 3 after the electrode body 4 is molded. At least one minute passage of the separator, the positive electrode plate, and the negative electrode plate allows the electrolytic solution to quickly and satisfactorily penetrate into the active material of the electrode (particularly near the center of the electrode body) when the battery is manufactured. Note that the positive electrode 1 in FIG. 1 has a groove size larger than the actual size for reasons of explanation.

1-2. Effects of Embodiments In general, in a battery manufacturing process, an electrode body in which a positive electrode, a separator and a negative electrode are stacked is housed in an outer casing (outer can), and then an electrolytic solution is placed in the outer can. inject. The injected electrolytic solution mainly permeates from the upper and lower end surfaces of the electrode body to the central portion, but this impregnation requires a long time. In recent years, in non-aqueous electrolyte batteries, in order to achieve a high energy density, an attempt has been made to increase the volume ratio (active material density) of the electrode body to the volume of the outer package. Therefore, when such an electrode body is put into an outer can, there is almost no space left inside the outer can, and it becomes very difficult to inject the electrolytic solution more than ever before.

As a method for injecting the electrolytic solution, other than the method of repeating the injecting step of gradually injecting the electrolytic solution, the internal can is decompressed while the external can is rotated by centrifugal force and the electrolytic solution is applied to the electrode body. There is a method of sucking it in, but the former takes a long time and the latter takes time. In order to solve such a problem, in Embodiment 1, since a plurality of minute grooves 1a are formed on the surface of the positive electrode 1, the positive electrode 1, the separator 3 and the negative electrode are formed.
When the electrode body 4 is wound by winding 2 and is housed in the outer can 6, the groove 1a becomes a minute passage between the positive electrode 1 and the separator 3. Since the stripes of the minute passages are open to the end surface of the electrode body 4, when the electrolytic solution is injected into the outer can 6 accommodating the electrode body 4, the electrolytic solution of the electrode body 4 flows from the opening of the minute passage. It rapidly penetrates deep inside and penetrates the active material of the positive electrode 1 and the negative electrode 2 all the way. This allows the electrolytic solution to soak into the electrode body 4 in a short time, and abundant electrolytic solution can be injected into the outer can 6. In Embodiment 1, since groove 1a is formed in the electrode width direction, the electrolytic solution can be satisfactorily permeated into the electrode active material particularly near the center of electrode body 4.

Further, in the method of forming the groove by scraping or compressing the active material layer of the electrode, there is only the effect of flowing the electrolytic solution for the one groove for one groove, but this embodiment In the embodiment, as shown in the electrode body partial cross-sectional view of FIG. 5, when the electrode body is wound, the vicinity of the bend is bent and wound, so that several bends of the electrolyte flow path are formed for one bend. Therefore, it is possible to more rapidly impregnate the electrolytic solution.

In Japanese Patent Application No. 11-228728, a thread-shaped or plate-shaped member is inserted between the electrode and the separator to form a gap inside the electrode body, and the gap is formed while decompressing the inside of the outer can. Although a method of injecting an electrolytic solution is disclosed in, the energy density is considered to be reduced by that much when a member other than the power generating element is put in the outer can. On the other hand, in the present invention, in order to secure the flow passage of the electrolytic solution, since the groove is directly formed by pressing at least one surface of the positive electrode, the separator, and the negative electrode, the decrease in energy density is basically not decreased. .

2. Example 2-1. Performance Comparison Experiment of Example and Comparative Example Next, a battery of the example was prepared and a performance measurement experiment was conducted.
When manufacturing the positive electrode, length 600 mm, width 55 mm, thickness 20
A positive electrode mixture slurry containing lithium cobalt oxide as a main component, graphite as a conductive agent, and polyvinylidene fluoride as a binder on the surface of a conductive core made of an aluminum foil of μm (solvent is N-methyl-2-pyrrolidone). ) Is applied. After that, the solvent is dried and volatilized, and pressed to a thickness of 165 μm to prepare an electrode plate.

Then, a groove (flexure) is formed on the surface of the electrode plate by using a roller with a convex portion as shown in the process diagram of FIG. The shape and pitch of the groove can be freely set by changing the shape and pitch of the convex portion of the roller. In this process, 0 or more per 200 mm of positive electrode length
It was changed within 110 lines. In addition, the groove depth is from 0 μm
It was changed between 1500 μm. The positive electrode having no groove corresponds to the conventional example. The depth of the groove is the depth of the electrode body in a wound state, and it was confirmed by seeing through the cross section with an X-ray CT apparatus (for example, Micro Focus 3D X-ray CT apparatus ELESCAN manufactured by Nittetsu Ellex Co., Ltd.).

Using the positive electrode thus produced, a separator and a negative electrode were sequentially stacked to form an electrode assembly, which was then housed in a cylindrical outer can. EC (ethylene carbonate) and
Volume ratio of EMC (ethyl methyl carbonate) EC: EMC = 3
A solution prepared by dissolving LiPF ₆ (lithium hexafluorophosphate) as an electrolyte in a mixed solvent mixed at 0:70 was used. As a result, a cylindrical lithium-ion battery (diameter 18 mm, height 65 mm) with a designed capacity of 1800 mAh was produced.

Next, the cylindrical lithium-ion battery prepared above is charged at a constant current at room temperature with a charging current of 1800 mA until the battery voltage reaches 4.2 V, and is reduced to 4.2 mA at a charging current value of 36 mA. Voltage charging was performed. Then disassemble the battery,
The amount of Li deposited on the negative electrode surface was observed. In order to evaluate the ease of impregnation of the electrode body with the electrolytic solution, pour propylene carbonate (PC) into a beaker, immerse only the electrode body in the beaker for 5 minutes, and then pull up the electrolytic solution with the mass difference before and after impregnation. Was taken as the amount impregnated with (absorption amount).

Table 1 shows the data regarding the amount (absorption amount) of the electrolytic solution impregnated in the electrode body and the amount of Li deposited on the surface of the positive electrode of these manufactured batteries.

[0026]

【table 1】

2-2. Consideration of Experimental Results As is apparent from this figure, while the amount of electrolyte absorption of the conventional positive electrode (0 flexure) is 3.0 g, the number of grooves (flexure) is
In the case of 1 piece / 200 mm to 5 pieces / 200 mm, if the bending depth is 3 μm or more, the amount of electrolyte absorbed is kept at 3.2 g or more. Also,
When the number of grooves (flexure) is 10 / 200mm-100 / 200mm,
When the bending depth is 1 μm or more, the amount of electrolyte absorbed is kept at least 3.1 g or more.

As described above, it can be seen that by providing the groove (bending) as in the present invention with respect to the conventional liquid absorption amount of the electrolytic solution of the positive electrode, an excellent liquid absorption amount of the electrolytic solution is secured.
On the other hand, the groove (deflection) of the positive electrode is 1 / 200mm to 100 / 200mm
In the range of the number of, the excellent performance such as a small amount of Li precipitation or no Li precipitation is exhibited. However, the bending depth is 1500 μm
As a result, the Li precipitation amount increased.
This is because the balance of the electrode reaction between the positive electrode and the negative electrode is lost,
It is considered that Li is likely to precipitate here.

Generally, in a lithium ion battery, when the battery is fully charged, Li ions desorbed from the positive electrode are inserted into the active material of the negative electrode. Here, if the positive electrode or the negative electrode has some trouble (for example, the negative electrode is excessively compressed or the impregnation of the electrolyte is insufficient), it becomes difficult for Li ions to insert into the active material in the negative electrode. , Li dendrite (dendritic deposit) is generated on the surface of the negative electrode. When this Li dendrite is generated, the active material corresponding to the deposited portion is deactivated, resulting in a loss of electrode performance (battery performance). In addition, the Li dendrite of the negative electrode may break through the separator and short-circuit with the positive electrode.
Therefore, it can be said that the smaller the amount of Li deposited on the surface of the positive electrode, the better the electrode performance (battery performance).

From the above, in order to avoid the precipitation of Li dendrite, the bending depth is set to Li on the positive electrode surface.
It can be said that a range of 1 μm or more and 1000 μm (1 mm) or less, which is a small amount or less, is suitable. When forming 1 μm of the flexure, the flexure is relatively shallow, so the number of flexures is set to a high density of 10/200 mm to 100/200 mm to compensate for this.
It is desirable to ensure a good flow passage for the electrolyte.

It should be noted that when the number of flexures is high such as 100/200 mm, it may be difficult to store the electrode body in the exterior body depending on the depth of flexure. 3. Other Matters In the above embodiment, an example in which a groove is formed on the surface of the positive electrode has been shown, but naturally the present invention is not limited to this, and it is formed on at least one surface of the positive electrode, the negative electrode and the separator. do it. Of these, when forming a groove in each of the overlapping parts after being formed as an electrode body, be careful that the grooves do not overlap each other and at least one minute passage of the separator, the positive electrode plate and the negative electrode plate is not lost. There is a need. Specifically, for example, there is a method of changing the pitch of the grooves formed in each of the positive electrode and the separator.

Further, in the above embodiment, the groove has a half-moon shape, but the present invention is not limited to this, and other shapes such as a triangular shape and a rectangular shape may be used. Good. Here, FIGS. 4 (a) to 4 (c) are
It is a positive electrode front view which shows the form variation of a groove.

FIG. 3A shows a pattern in which a row of a plurality of cohesive grooves (here, three rows) is repeatedly formed at regular intervals. In this figure (b), a short groove reaching the central portion of the electrode surface is formed from both ends in the electrode width direction. FIG. 3C shows a pattern in which a plurality of rows of grooves (here, three rows) are obliquely formed at regular intervals along the electrode width direction.

The same effect as in the above-described embodiment can be obtained by any of these groove variations, but if the groove reaches from the end portion in the electrode width direction to the center portion of the electrode surface, the electrode body is It is desirable that the electrolytic solution quickly penetrates into the active material in the electrode body when the electrolytic solution is injected after being housed in the outer can. Further, the present invention is not limited to the cylindrical outer can and may be applied to a non-aqueous electrolyte battery having another type of outer can (exterior body) such as a rectangular outer can.

[0035]

As is apparent from the above, the present invention is a nonaqueous electrolytic solution in which an electrode body formed by stacking a positive electrode plate and a negative electrode plate with a separator interposed therebetween is housed in an outer package together with an electrolytic solution. In a battery, an electrode body formed by stacking a positive electrode and a negative electrode via a separator, in a sealed battery that is housed in an outer package together with an electrolytic solution, wherein at least one of the separator, the positive electrode plate, and the negative electrode plate has a width. Since a groove through which the electrolytic solution flows from the end portion to the central portion in the direction is formed, when the electrolytic solution is injected into the outer can containing the electrode body,
The electrolytic solution quickly enters the inside of the electrode body using the groove as a flow path and permeates the entire active material of the positive electrode and the negative electrode. Therefore, the electrolytic solution can be impregnated into the electrode body in a significantly shorter time than in the conventional case, and abundant electrolytic solution can be injected into the outer can, so that high battery performance is realized.

[Brief description of drawings]

FIG. 1 is a sectional perspective view of a cylindrical lithium ion battery according to a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional perspective view of a positive electrode.

FIG. 3 is a diagram showing a manufacturing process of a positive electrode.

FIG. 4 is a diagram showing variations of a positive electrode.

FIG. 5 is a partial cross-sectional view of an electrode body.

[Explanation of symbols]

1 Positive electrode 1a groove (deflection) 2 Negative electrode 3 separator 4 electrode body 6 outer can

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomokazu Yamanaka             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. (72) Inventor Yukihiro Oki             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. F-term (reference) 5H011 AA03 AA09 KK01                 5H021 AA01 BB04 CC09 HH03 HH10                 5H029 AJ01 AJ14 AK03 AL07 AM03                       AM05 AM07 CJ03 EJ04 EJ12                       HJ04 HJ12                 5H050 AA01 AA19 BA17 CA08 CB08                       FA15 GA03 HA04

Claims (4)

[Claims] 1. A non-aqueous electrolyte battery in which an electrode body obtained by stacking a positive electrode plate and a negative electrode plate with a separator interposed between the positive electrode plate and the negative electrode plate is housed in an outer package together with an electrolytic solution. In a non-aqueous electrolyte battery in which an electrode body made of the same is housed in an outer package together with an electrolytic solution, at least one of the separator, the positive electrode plate, and the negative electrode plate has an electrolytic solution from the end portion in the width direction to the central portion. A non-aqueous electrolyte battery, characterized in that it has a flexure that flows. 2. The flexure through which the electrolytic solution flows is a flexure formed by bending at least one of the separator, the positive electrode, and the negative electrode in the thickness direction. Non-aqueous electrolyte battery. 3. The spirally wound electrode body is housed in the outer casing of a cylindrical outer can.
Alternatively, the non-aqueous electrolyte battery described in 2. 4. The non-aqueous electrolyte battery according to claim 1, wherein the bending is formed with a depth in a thickness direction of 1 μm or more and 1 mm or less.