JP2005259467A - Secondary battery and manufacturing method of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for a secondary battery having high permeability of an electrolyte into an electrode plate and enhancing battery characteristics. <P>SOLUTION: The electrode of the secondary battery is equipped with current collectors 1, 5, active material layers 2, 6 applied to the current collectors 1, 5, and electrolyte layers 3, 7 formed on the surfaces on the opposite side of the current collectors 1, 5 of the active material layers 2, 6, the electrolyte layers 3, 7 have recessed and projecting parts on the surfaces of the active material layers 2, 6, or on the opposite side of the active material layers 2, 6, and the depth of the recessed part is 1-50 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a secondary battery and a method for manufacturing the secondary battery.

  As a conventional secondary battery, for example, there is one described in Patent Document 1. FIG. 5 shows a cross section of an electrode / electrolyte laminate of a conventional lithium ion secondary battery described in Patent Document 1.

  As shown in FIG. 5, a conventional lithium ion secondary battery includes an insulator layer 503, a negative electrode current collector layer 504 formed on one surface of the insulator layer 503, and a positive electrode current collector formed on the opposite surface. Layer 502.

A positive electrode mixture layer 501 is formed on the opposite surface of the positive electrode current collector layer 502 to the insulator layer 503, and a negative electrode mixture is formed on the opposite surface of the negative electrode collector layer 504 to the insulator layer 503. Layer 505 is formed. An electrolyte layer 506 is formed on the surface of the negative electrode mixture layer 505 opposite to the negative electrode current collector layer 504 (the positive electrode mixture layer 501, the positive electrode current collector layer 502, the insulator layer 503, the negative electrode current collector layer 504). (A laminate of the electric conductor layer 504, the negative electrode mixture layer 505, and the electrolyte layer 506 is referred to as an electrode / electrolyte laminate).
JP-A-10-189050 (for example, page 3, FIG. 1)

  However, in the conventional configuration, when the electrode / electrolyte membrane seat layer in the form of a tape is wound in a spiral shape and inserted into a can such as an aluminum case to inject an electrolyte, the electrolyte layer 506 and the positive electrode or When the permeability of the electrolytic solution into the positive electrode or the negative electrode mixture layer was evaluated by any combination of the negative electrode mixture layers 501 and 505, it was found that the permeability was about 50 to 70%.

  As a result of evaluating rate characteristics, discharge capacity, cycle characteristics, and the like as battery characteristics using this battery, it was confirmed that all of the battery characteristics were fatal defects in terms of battery characteristics.

  This is because the electrolyte membrane 506 of the conventional configuration needs to have sufficient mechanical strength to keep the distance between the electrodes at a stable distance, and the adhesion with the electrodes is very good. The permeability of the electrolyte solution to the electrode was poor.

  In view of the above-described conventional problems, an object of the present invention is to provide a secondary battery capable of further improving battery characteristics and a secondary battery, because the electrolyte has better permeability to the electrode plate. It is to provide a manufacturing method.

In order to achieve the above object, the first present invention provides:
A current collector,
An active material layer coated on the current collector;
An electrolyte layer provided on the surface of the active material layer opposite to the current collector,
The electrolyte layer is a secondary battery having irregularities on the surface of the active material layer side or the opposite side of the active material layer.

The second aspect of the present invention is
The active material layer is formed on both sides of the current collector,
The electrolyte layer is provided on the surface of the two active material layers opposite to the current collector,
At least one of the electrolyte layers is the secondary battery according to the first aspect of the present invention having the irregularities.

The third aspect of the present invention
In the secondary battery according to the first aspect of the present invention, the depth of the recess is 1 μm or more and 50 μm or less.

The fourth aspect of the present invention is
The unevenness is formed by particles,
In the secondary battery according to the first aspect of the present invention, the particle diameter is 1 μm or more and 50 μm or less.

The fifth aspect of the present invention is
The particles are dispersed on the surface of the electrolyte layer;
In the secondary battery according to the fourth aspect of the present invention, the interval between the particles is 5 μm or more and 100 μm or less.

The sixth aspect of the present invention
The secondary battery according to the first aspect of the present invention further includes a separator formed on a surface of the electrolyte layer that is not in contact with the active material layer.

The seventh aspect of the present invention
Applying and forming an active material layer on the surface of the current collector;
A step of dispersing particles of a predetermined size in an electrolyte coating;
And a step of forming an electrolyte layer by applying a coating material in which the particles are dispersed on the active material layer.

  ADVANTAGE OF THE INVENTION According to this invention, since the permeability of the electrolyte solution to an electrode plate is more favorable, the secondary battery which can improve a battery characteristic more, and the manufacturing method of a secondary battery can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the following embodiment is merely a preferred embodiment of the present invention, and the present invention is not limited to the following embodiment.

(Embodiment 1)
FIG. 1A is a cross-sectional view of an electrode / electrolyte laminate of a lithium ion secondary battery according to Embodiment 1 of the present invention. Moreover, FIG.1 (b) is an external view of the lithium ion secondary battery in Embodiment 1 concerning this invention. An enlarged view of the S part in FIG. 1B corresponds to FIG.

As shown in FIG. 1, the lithium ion secondary battery of Embodiment 1 includes a positive electrode current collector 1 such as an aluminum foil, which is an example of the current collector of the present invention, and the front and back surfaces of the positive electrode current collector 1. And a positive electrode active material layer 2 such as LiCoO ₂ which is an example of the active material layer of the present invention. On the surface of the two positive electrode active material layers 2, a positive electrode side electrolyte layer 3, which is an example of the electrolyte layer of the present invention, is formed of a material such as a fluorine-based resin. Further, a separator 4 made of polyethylene or the like, which is an insulator provided with a predetermined gap for conducting ion conduction from the positive and negative electrodes, is provided on the surface of one positive electrode side electrolyte layer 3.

  A configuration similar to that of the positive electrode current collector 1, the positive electrode active material layer 2, and the positive electrode side electrolyte layer 3 is also formed on the negative electrode side with the separator 4 interposed therebetween. This negative electrode side includes a negative electrode current collector 5 which is an example of the current collector of the present invention, a negative electrode active material layer 6 which is an example of the active material layer of the present invention, and a negative electrode side electrolyte layer which is an example of the electrolyte layer of the present invention. 3 and 7. The negative electrode current collector 5 is a copper foil or the like, and the negative electrode active material layer 6 is made of a carbon material or the like. Further, a separator 8 is further provided above the negative electrode side electrolyte layers 3 and 7.

  In addition, minute irregularities are formed on the surfaces of the positive electrode and negative electrode side electrolyte layers 3 and 7 provided on the surfaces of the positive electrode active material layer 2 and the negative electrode active material layer 6.

  Positive electrode current collector 1, positive electrode active material layer 2, positive electrode side electrolyte layer 3, separator 4, negative electrode current collector 5, negative electrode active material layer 6, negative electrode side electrolyte layers 3 and 7, and separator laminated as described above 8 is an electrode / electrolyte laminate 9. As shown in FIG. 1B, the lithium ion secondary battery according to Embodiment 1 has a structure in which a wound electrode / electrolyte laminate 9 is inserted into a can such as an aluminum case. The electrolyte is injected.

  Below, the manufacturing method of the lithium ion secondary battery of the said structure which is an example of the manufacturing method of the secondary battery of this invention is described.

Taking the positive electrode side as an example, the front and back of the cathode current collector 1 of aluminum foil or the like, is formed by coating a positive electrode active material layer 2 such as LiCoO _2.

  Next, as a method of providing minute irregularities on the surface of the positive electrode electrolyte layer 3, for example, a powder such as a resin having an average particle diameter of about 1 to 50 μm is uniformly obtained by a mill using a medium such as beads as an electrolyte paint. To disperse. And it forms on the positive electrode active material layer 2 using various coating apparatuses, such as a die | dye and a gravure. At this time, the interval between the particles dispersed in the surface area of the positive electrode electrolyte layer 3 is 5 to 100 μm.

  Moreover, after spraying only the powder with an average particle diameter of about 1-50 micrometers on an active material with a spray apparatus etc., it can also provide on the positive electrode active material layer 2 by a roll press or a flat plate press at a very low pressure. The roll press or flat plate press may be heat-treated.

  In addition, it is important that the height of minute irregularities on the surface of the positive electrode electrolyte layer 3 is 1 μm or more and 50 μm or less. When the height of the minute unevenness on the surface of the positive electrode electrolyte layer 3 is 1 μm or less, the unevenness is small and the adhesion with the portion facing the positive electrode electrolyte layer 3 is improved, so that the permeability of the electrolytic solution to the electrode is remarkably deteriorated. As a result, battery characteristics deteriorate.

  In addition, when the height of the minute unevenness on the surface of the positive electrode side electrolyte layer 3 is 50 μm or more, the gap in the portion facing the surface of the positive electrode side electrolyte layer 3 becomes large, so that the conductivity deteriorates and the battery characteristics deteriorate. To do.

  The negative electrode side is also manufactured in the same manner as the positive electrode side, and minute irregularities are formed on the surfaces of the two negative electrode electrolyte layers 7.

  The positive electrode side, the negative electrode side, and the separators 4 and 8 are laminated to form an electrode / electrolyte laminate 9. Then, the electrode / electrolyte laminate 9 is wound, inserted into a can such as an aluminum case, and the electrolytic solution is injected.

  Finally, the upper part is closed by a sealing plate or the like connected to the positive electrode, whereby a lithium ion secondary battery is produced.

  As described above, by providing minute irregularities on the surfaces of the positive electrode and negative electrode side electrolyte layers 3 and 7, when the electrode is inserted into a can such as an aluminum case by winding, the surface facing the electrolyte layer surface is minute. As a result, an electrolyte solution is injected into the minute space, and the permeability of the electrolyte solution into the active material can be significantly improved.

  Further, as the secondary battery of the present invention, the lithium ion secondary battery is described as an example in the first embodiment. However, the configuration of the present invention is not limited to the lithium ion secondary battery, for example, nickel-hydrogen secondary battery. It can also be applied to secondary batteries. In short, the present invention can be applied to a secondary battery including a current collector, an active material layer, and an electrolyte layer.

  Taking the positive electrode as an example, the electrode according to the first embodiment has fine irregularities formed on both of the two positive electrode-side electrolyte layers 3, but the minute irregularities are formed only on one electrolyte layer. May be. In this case, the permeability of the electrolytic solution is worse than that of the first embodiment, but the permeability of the electrolytic solution is increased as compared with the conventional case. The same applies to the negative electrode.

  In addition, minute irregularities may be provided between the positive electrode active material layer 2 and the positive electrode side electrolyte layer 3, but as in the first embodiment, between the separators 4 and 8 and the positive electrode and negative electrode side electrolyte layers 3 and 7. It is preferable to provide it because it is easy to manufacture. Similarly, the negative electrode may be provided between the negative electrode active material layer 6 and the negative electrode side electrolyte layers 3 and 7. In addition, when minute irregularities are provided on both the separator side and the active material layer side of the electrolyte layer, the conductivity may be deteriorated, so the height of the minute irregularities needs to be considered.

  In the electrode of the first embodiment, the active material layer is formed on both sides of the current collector for both the positive electrode and the negative electrode, but the active material layer is formed only on one side as in the conventional electrode shown in FIG. It may be configured to do so. In this case, minute irregularities may be formed on the surface of the electrolyte layer 506 on the negative electrode mixture layer 505 side and / or on the opposite side of the negative electrode mixture layer 505.

  Further, in the first embodiment, as shown in FIG. 1A, a cylindrical battery is manufactured by inserting a wound electrode into a cylindrical aluminum case. A square battery in which an electrode is inserted into a case or the like may be used.

  Next, the first embodiment will be described more specifically in Example 1.

(Example 1)
As the negative electrode, the negative electrode current collector 5 is a copper foil having a thickness of 10 μm and a width of 500 mm, and the negative electrode paste for forming the negative electrode active material layer 6 is coated and dried using a kneaded carbon material, CMC and water. .

Further, as the positive electrode, the positive electrode current collector 1 is an aluminum foil having a thickness of 20 μm and a width of 500 mm, and the positive electrode paste forming the positive electrode active material layer 2 is kneaded with LiCoO ₂ , conductive carbon black, fluorine resin, CMC and water. What was done was used. Also, as the anchor agent, conductive carbon black, a binder and water were kneaded and dispersed, and then coated and dried.

  Further, as the positive electrode and negative electrode side electrolyte layers 3 and 7, a fluorine resin in which particles such as resin having an average particle diameter of 1 to 50 μm are uniformly dispersed is formed on the surfaces of the positive electrode active material layer 2 and the negative electrode active material layer 6. The coating was formed at 5 μm.

  The separators 4 and 8 are ceramic separators having a thickness of 25 μm, and are opposite to the positive electrode side electrolyte layer 3 between the positive electrode side electrolyte layer 3 and the negative electrode side electrolyte layer 7 and the negative electrode side electrolyte layer 7. Installed on the side surface.

  The obtained electrode / electrolyte laminate 9 was rolled to a predetermined thickness and then slit to a predetermined width. And as demonstrated in Embodiment 1, it wound and inserted in cans, such as an aluminum case. Thereafter, an electrolytic solution was injected to prepare a lithium ion secondary battery.

(Comparative Example 1)
As a comparative example, using the electrode having the conventional configuration shown in FIG. 5, the obtained positive and negative plates were rolled to a predetermined thickness, then slit to a predetermined width, and wound to form a cylindrical aluminum case, etc. Inserted into the can. Thereafter, an electrolytic solution was injected to prepare a lithium ion secondary battery of Comparative Example 1 using a conventional electrode.

  The following evaluation was performed on the above battery to confirm the effect of the secondary battery of the present invention.

(1) Discharge capacity The two types of secondary batteries of Example 1 and Comparative Example 1 that have been charged with a constant current (160 mA) and a final voltage (4.2 V) at room temperature are constant currents (160 mA to 3200 mA). The discharge capacity was compared when the voltage dropped from the start of discharge reached the end voltage (3 V). The results are shown in FIG. The horizontal axis of the graph in FIG. 2 indicates the discharge current (mA), and the vertical axis indicates the discharge capacity (mAh). In addition, the solid line indicates Example 1, and the dotted line indicates Comparative Example 1. As shown in FIG. 2, the discharge capacity of the battery according to Example 1 is clearly higher than that of the battery according to the conventional example.

(2) Cycle characteristics Constant conditions at normal temperature (discharge: current 2000 mA, final voltage 3 V, charge: current 160 mA, final voltage 4.2 V) The charge capacity was measured repeatedly, and the discharge capacity was 90% of the initial capacity. The secondary batteries of Example 1 and Comparative Example 1 were compared by the number of times of charge / discharge (cycle). The results are shown in FIG. The horizontal axis of the graph in FIG. 3 indicates the number of cycles, and the vertical axis indicates the discharge capacity (mAh). As shown in FIG. 3, the battery according to the first embodiment has clearly improved cycle characteristics as compared with the battery according to the conventional example.

(3) Rate characteristics At normal temperature, the secondary battery of Example 1 and Comparative Example 1 were compared according to the ratio of the discharge time of 30 minutes (2C) and the discharge time of 5 hours (0.2C). The results are shown in FIG. The vertical axis of the graph in FIG. 4 indicates the ratio of the discharge capacity at 2C to the discharge capacity at 0.2C. As shown in FIG. 4, the value of Example 1 is almost 1.0, which is higher than that of Comparative Example 1. This indicates that the secondary battery of Example 1 can obtain a discharge capacity equivalent to that at the time of low load (0.2 C) even at the time of high load (2 C). It can be seen that the rate characteristics are clearly improved compared to.

  As described above, by using the secondary battery electrode of the present invention, the permeability of the electrolytic solution into the active material can be remarkably improved. As battery characteristics, rate characteristics, discharge capacity, cycle characteristics, etc. Has improved dramatically.

(Example 2)
The configuration is the same as that of Example 1, but the heights of minute irregularities formed on the surfaces of the positive and negative electrode electrolyte layers 3 and 7 are 0.8, 1.0, 5.0, 25, 50, and 60 μm, respectively. A secondary battery was prepared using the secondary battery electrode. The six types of secondary batteries were tested in the above (1). The results are shown in (Table 1).

From the data in Table 1, it can be seen that when the height of the unevenness is smaller than 1.0 μm or larger than 50 μm, the value of the discharge capacity is suddenly decreased. Therefore, the height of the minute irregularities formed on the electrolyte layer is preferably 1.0 μm or more and 50 μm or less.

(Example 3)
The structure is the same as that of Example 1, but the intervals between dispersed particles forming minute irregularities on the surfaces of the positive and negative electrode electrolyte layers 3 and 7 are 4.0, 5.0, 15, 50, 100, and 120 μm, respectively. A secondary battery was manufactured using the six types of secondary battery electrodes. The six types of secondary batteries were tested in the above (1). The results are shown in (Table 2).

  From the data in this (Table 2), it can be seen that when the particle spacing is smaller than 5 μm or larger than 100 μm, the value of the discharge capacity suddenly decreases. Accordingly, the particle spacing is preferably 5.0 μm or more and 100 μm or less.

  The secondary battery of the present invention has an effect of improving the battery characteristics because the electrolyte has better permeability to the electrode plate, and is useful as a lithium ion secondary battery, a nickel hydride secondary battery, or the like. is there.

(A) Sectional drawing which shows the electrode and electrolyte laminated body of the lithium ion secondary battery in Embodiment 1 concerning this invention (b) The external view of the lithium ion secondary battery in Embodiment 1 concerning this invention The figure which shows the graph of the measurement result of the lithium discharge capacity of the lithium ion secondary battery in Example 1 concerning this invention, and the lithium ion secondary battery in the comparative example 1 The figure which shows the graph of the measurement result of the cycle characteristic of the lithium ion secondary battery in Example 1 concerning this invention, and the lithium ion secondary battery in the comparative example 1 The figure which shows the graph of the measurement result of the rate characteristic of the lithium ion secondary battery in Example 1 concerning this invention, and the lithium ion secondary battery in the comparative example 1 Sectional drawing which shows the electrode and electrolyte laminated body of the conventional lithium ion secondary battery

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode collector 2 Positive electrode active material layer 3 Positive electrode side electrolyte layer 4 Separator 5 Negative electrode collector 6 Negative electrode active material layer 7 Negative electrode side electrolyte layer 8 Separator 9 Electrode / electrolyte laminated body

Claims (7)

A current collector,
An active material layer coated on the current collector;
An electrolyte layer provided on the surface of the active material layer opposite to the current collector,
The said electrolyte layer is a secondary battery which has an unevenness | corrugation in the surface of the said active material layer side or the other side of the said active material layer. The active material layer is formed on both sides of the current collector,
The electrolyte layer is provided on the surface of the two active material layers opposite to the current collector,
The secondary battery according to claim 1, wherein at least one of the electrolyte layers has the unevenness.   The secondary battery according to claim 1, wherein a depth of the recess is 1 μm or more and 50 μm or less. The unevenness is formed by particles,
The secondary battery according to claim 1, wherein the particle diameter is 1 μm or more and 50 μm or less. The particles are dispersed on the surface of the electrolyte layer;
The secondary battery according to claim 4, wherein an interval between the particles is 5 μm or more and 100 μm or less.   The secondary battery according to claim 1, further comprising a separator formed on a surface of the electrolyte layer that is not in contact with the active material layer. Applying and forming an active material layer on the surface of the current collector;
A step of dispersing particles of a predetermined size in an electrolyte coating;
And a step of forming an electrolyte layer by applying a paint in which the particles are dispersed on the active material layer.

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