JP2001015177A - Charge and discharge control method for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent deterioration of a battery caused by charging and discharging it, in a charge and discharge control method for a secondary battery in which a winding-up electrode is stored in a battery can and electric power generated by the winding-up electrode body can be taken outside from a positive electrode external terminal and a negative electrode external terminal mounted to a battery can. SOLUTION: In this charge and discharge control method for a secondary battery, a reference electrode 2 independent of a winding-up electrode body 6 is installed in a battery can 5, a potential difference between the reference electrode 2 and an external terminal 16 of a positive electrode and a potential difference between the reference electrode 2 and a negative electrode terminal 17 are always monitored, and when at least either one of the potential differences exceeds a threshold value, charging and/or discharging is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode external terminal and a negative electrode external terminal mounted on a battery can, such as a cylindrical lithium ion secondary battery, in which an electrode body is housed inside a battery can into which an electrolyte is injected. From the secondary battery that can take out the electric power generated by the electrode body from the outside,
Alternatively, the present invention relates to a method for controlling discharge.

[0002]

2. Description of the Related Art As shown in FIG. 1, a cylindrical lithium ion secondary battery (1) has sealing plates (51) and (51) at both openings of a cylindrical body (50).
To form a cylindrical battery can (5).
Inside (5), a separator is placed between the positive electrode (63) and the negative electrode (61).
It accommodates a wound electrode body (6) interposed therebetween (62) and is filled with an electrolytic solution. A positive external terminal (16) and a negative external terminal (17) are attached to both sealing plates (51) and (51) of the battery can (5) through the sealing plate (51). A plurality of positive current collecting tabs (7) extending from the positive electrode (63) of the body (6) are connected to the positive external terminal (16), and a plurality of positive current collecting tabs extending from the negative electrode (61) of the winding electrode body (6). The negative electrode current collecting tab (70) is connected to the negative electrode external terminal (17).

Conventionally, when charging or discharging is performed on a cylindrical lithium ion secondary battery (1) as described above, a potential difference between a positive external terminal (16) and a negative external terminal (17) is monitored. When the potential difference exceeds a predetermined threshold, control is performed to stop charging and discharging.

[0004]

However, in charging / discharging of a lithium ion secondary battery, the positive electrode potential and the negative electrode potential change due to insertion and desorption of lithium, respectively.
At the end of charge or end of discharge, charge / discharge may continue beyond the proper charge / discharge potential of the positive electrode or negative electrode, causing lithium metal to precipitate on the surface of the negative electrode during charge, There has been a problem that the crystal structure of the positive electrode is collapsed due to the transition, and the capacity is deteriorated due to a side reaction such as decomposition of an electrolytic solution on the surface of the negative electrode at the time of discharge, and the cycle characteristics of the battery are deteriorated.

Therefore, a reference electrode is installed inside the battery can, and the potential difference between the negative electrode and the reference electrode during charging is monitored.
A method of controlling charging has been proposed (Japanese Patent Laid-Open No. 11-6 / 1999).
No. 7280). However, even with this method, deterioration of the battery could not be effectively prevented. In addition, there is a problem that the weight of the battery increases due to the provision of the reference electrode, and the weight energy density decreases.

The inventors of the present invention have conducted intensive studies to determine the cause. In the above method, control was performed based only on the potential of the negative electrode during charging.
Deterioration due to changes due to the crystal structure of the positive electrode during charging could not be suppressed, which caused the battery capacity to deteriorate, and even at the end of discharge, charging and discharging due to decomposition of electrolyte etc. on the negative electrode It was determined that the battery was deteriorated by the occurrence of unrelated side reactions, and the present invention was completed.

[0007]

According to the present invention, there is provided a method for controlling charging and discharging of a secondary battery, comprising the steps of: setting a reference electrode (2) independent of an electrode body (6) inside a battery can (5); The potential difference between the pole (2) and the positive electrode external terminal (16) and the potential difference between the reference electrode (2) and the negative electrode external terminal (17) are constantly monitored, and when at least one of the potential differences exceeds a predetermined threshold, Charging and / or discharging is stopped. Here, as the material of the reference electrode (2), for example, lithium metal, lithium alloy, platinum, gold,
A carbon material or a metal oxide can be employed.

According to the charge / discharge control method of the present invention, both the potential difference between the reference electrode (2) and the positive external terminal (16) and the potential difference between the reference electrode (2) and the negative external terminal (17) are constantly monitored. In addition, since charge and discharge are controlled, lithium metal deposits on the negative electrode surface during charge, collapse of the positive electrode crystal structure during charge and discharge, and side reactions such as decomposition of electrolyte on the negative electrode surface during charge This can suppress the capacity deterioration due to the above, thereby effectively preventing the deterioration of the battery.

The charge / discharge control method for a secondary battery according to the present invention includes a method for controlling the potential difference between the battery can (5) and the positive external terminal (16) and the potential difference between the battery can (5) and the negative external terminal (17). It is characterized in that at least one of the potential differences is constantly monitored, and when the potential difference exceeds a predetermined threshold, charging and / or discharging is stopped. Here, as the material of the battery can (5), aluminum, stainless steel, nickel-plated stainless steel, or a magnesium alloy can be adopted. According to the charge / discharge control method of the present invention, since the battery can (5) is used as the reference electrode, there is no increase in weight due to the installation of the reference electrode.

It should be noted that the charging / discharging control method for a secondary battery according to the present invention has a great effect by being applied to charging / discharging of a lithium secondary battery.

[0011]

According to the charging / discharging control method for a secondary battery according to the present invention, it is possible to effectively prevent the battery from being deteriorated due to charging / discharging. Further, according to the method of controlling charge and discharge of a secondary battery according to the present invention, it is possible to prevent battery deterioration without lowering the weight energy density.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment in which the present invention is applied to a cylindrical lithium ion secondary battery will be specifically described with reference to the drawings.

[0013]First embodiment  As shown in FIG. 1, cylindrical lithium as the object of this embodiment
The ion secondary battery (1) is provided with sealing plates (5) at both openings of the cylindrical body (50).
1) By fixing (51), a cylindrical battery can (5) is constructed,
Inside the pond (5), there is a separator between the positive electrode (63) and the negative electrode (61).
To accommodate the wound electrode body (6) with the
And an electrolyte is injected. Battery can
(5) Both sealing plates (51) and (51) have a positive external terminal (16) and a negative terminal.
The external terminal (17) is attached through the sealing plate (51).
And extending from the positive electrode (63) of the winding electrode body (6).
One positive current collector tab (7) is connected to the positive external terminal (16)
And a plurality extending from the negative electrode (61) of the winding electrode body (6).
The negative current collecting tab (70) is connected to the negative external terminal (17).
I have.

Each of the external terminals (16) and (17) has a pair of packing members (1) in a central hole formed in the sealing plate (51) of the battery can (5).
2) Insulation packing (14) consisting of (13) is attached, and sealing plate (5
Electrical insulation and airtightness between 1) and each external terminal (16) (17) is maintained. At both ends of each external terminal (16) (17), nut (15)
(15) is screwed, and the insulating packing (14) is pressed by tightening the nuts (15) and (15).

A rod (19) penetrates the sealing plate (51) on the negative electrode side of the battery can (5) via an insulating packing (18). Has a reference electrode (2) attached thereto and a reference electrode external terminal (21) attached to the outer end of the can. As the material of the reference electrode (2), the rod (19), and the reference electrode external terminal (21), lithium metal is used. In addition, lithium alloy, platinum, gold,
A carbon material, a metal oxide, or the like can be used.

The positive electrode external terminal (16) and the reference electrode external terminal (21) are connected to a potentiometer (3), and the positive electrode (63) and the reference electrode are connected.
The potential difference of (2) is measured. Further, the negative electrode external terminal (17) and the reference electrode external terminal (21) are connected to a potentiometer (31), and the negative electrode (6
The potential difference between 1) and the reference electrode (2) is measured.

FIG. 3 shows a cylindrical lithium ion secondary battery.
FIG. 3 shows a circuit configuration for controlling charging and discharging of (1), and a positive electrode external terminal of a cylindrical lithium ion secondary battery (1)
(16) and the negative electrode external terminal (17) are connected to a charging / discharging circuit (4), and when discharging, current is supplied from the lithium ion secondary battery (1) to the charging / discharging circuit (4). A current is supplied from the charge / discharge circuit (4) to the lithium ion secondary battery (1).

As described above, the positive external terminal (16) and the reference external terminal (21) of the cylindrical lithium ion secondary battery (1) are connected to the potentiometer (3), and are referred to as the negative external terminal (17). The pole external terminal (21) is connected to a potentiometer (31). Also, the positive external terminal (16) and the negative external terminal of the lithium ion secondary battery (1).
(17) is connected to a potentiometer (32), and the potential difference between the positive external terminal (16) and the negative external terminal (17) is measured. Each potentiometer
(3) The potential difference measured by (31) and (32) is supplied to a control circuit (41) including a microcomputer.

The control circuit (41) generates a charge / discharge control signal C for controlling the charge operation and the discharge operation of the charge / discharge circuit (4) based on the measured data of the potential difference, and
(4).

FIGS. 4 and 5 show a control procedure at the time of charging and discharging by the control circuit (41). At the time of charging, as shown in FIG. 4, first, in step S1, it is determined whether or not the potential difference (battery voltage) between the positive electrode and the negative electrode is 4.2 V or less, and if yes (Y), the process proceeds to step S2. The potential difference between the positive electrode and the reference electrode (positive electrode potential based on lithium)
Is determined to be 4.3 V or less, and if yes, the process further proceeds to step S3 to determine whether or not the potential difference between the negative electrode and the reference electrode (the negative electrode potential based on lithium) is 0.1 V or more. I do. Here, when it is judged yes,
After recording the potential data in the hard disk in step S4, the process returns to step S1 to repeat the same determination.
Thereafter, charging proceeds, and steps S1, S2,
Alternatively, when it is determined NO (N) in step S3,
In step S5, the charging is terminated, and the state shifts to the charging suspension state.

On the other hand, at the time of discharging, as shown in FIG. 5, first, in step S11, it is determined whether or not the potential difference (battery voltage) between the positive electrode and the negative electrode is 2.7 V or more.
In the case of, the process proceeds to step S12 to determine whether or not the potential difference between the positive electrode and the reference electrode (lithium-based positive electrode potential) is 3.6 V or more.
Then, it is determined whether or not the potential difference between the negative electrode and the reference electrode (the negative electrode potential based on lithium) is 1.0 V or less. If the determination is yes, the potential data is recorded in the hard disk in step S14, and the process returns to step S11 to repeat the same determination. Thereafter, the discharge proceeds, and when it is determined as No (N) in step S11, step S12, or step S13, the discharge is terminated in step S15, and the state shifts to the discharge pause state.

According to the charge / discharge control method of the first embodiment, the potential difference between the reference electrode (2) and the positive electrode external terminal (16) is determined by
(2) The potential difference between the negative terminal (17) and the external terminal (17) is constantly monitored to control charging and discharging, so that lithium metal deposits on the negative electrode surface during charging, collapse of the positive electrode crystal structure during charging and discharging, Further, it is possible to suppress capacity deterioration due to side reactions such as decomposition of an electrolytic solution on the surface of the negative electrode during charging, thereby effectively preventing battery deterioration.

[0023]Second embodiment  As shown in FIG. 2, the charge / discharge control method of the present embodiment is an object.
Cylindrical lithium ion secondary battery (1)
Of the cylindrical lithium ion secondary battery (1) and the battery itself
Same structure, but using battery can (5) as reference electrode
Have been. The material of the battery can (5) is aluminum
But stainless steel, nickel
Kel-plated stainless steel, magnesium alloy
Etc. can be adopted.

The reference electrode external terminal (22) is directly attached to the sealing plate (51) of the battery can (5), and the positive electrode external terminal (1) is attached.
6) and the reference electrode external terminal (22) are connected to a potentiometer (3),
The potential difference between the positive electrode (63) and the battery can (5) is measured. Further, the negative electrode external terminal (17) and the reference electrode external terminal (22) are connected to a potentiometer (31), and the potential difference between the negative electrode (61) and the battery can (5) is measured.

The circuit configuration for controlling charging and discharging of the cylindrical lithium ion secondary battery (1) is basically the same as that shown in FIG. 3, and is measured by the potentiometers (3) and (31). The charge / discharge control based on the potential difference is basically the same as that shown in FIGS.

According to the charge / discharge control method of the second embodiment, since the weight is not increased by the provision of the reference electrode, the charge / discharge control method of the first embodiment can be used without lowering the weight energy density. Similarly, deterioration of the battery can be effectively prevented.

Table 1 shows the reference electrodes in the first embodiment.
Table 2 shows various materials that can be used in (2).
Various materials that can be used for the battery can (5) in the embodiment are shown. Table 3 shows an appropriate potential range based on the reference electrode when each material is used as the reference electrode (2) and the battery can (5). When the potential deviates from this range, it is necessary to stop charging and discharging. There is.

[0028]

[Table 1]

[Table 2]

[Table 3]

[0029]Charge / discharge test  The cylindrical lithium ion secondary battery (1) according to the present invention is
Prototype through the following process, charge and discharge test,
It was confirmed.

[Preparation of Positive Electrode] Lithium hydroxide and cobalt hydroxide were mixed and fired in air at 80 ° C. for 24 hours to obtain LiCoO ₂ as a positive electrode active material.
The weight ratio of this positive electrode active material to artificial graphite as a conductive agent was 9
The mixture was mixed at 0: 5 to obtain a positive electrode mixture. Further, polyvinylidene fluoride as a binder is replaced with N-methyl-2-pyrrolidone (N
MP) to prepare an NMP solution. And
The slurry was prepared by kneading the positive electrode mixture and the NMP solution so that the weight ratio of the positive electrode mixture and polyvinylidene fluoride became 95: 5. This slurry was applied to both sides of an aluminum foil as a positive electrode current collector by a doctor blade method,
Vacuum drying was performed at 50 ° C. for 2 hours to produce a positive electrode.

[Preparation of Negative Electrode] Graphite lump (d002 = 3.356)
{; Lc> 1000}), jet pulverization was performed, and the resulting powder was sieved to obtain a graphite powder having an average particle diameter of 18 μm. Further, polyvinylidene fluoride as a binder is dissolved in NMP, and NM
A P solution was prepared. Then, the graphite powder and polyvinylidene fluoride were kneaded so that the weight ratio was 90:10 to prepare a slurry. This slurry is applied to both sides of a copper foil as a negative electrode current collector by a doctor blade method,
Vacuum drying was performed at 150 ° C. for 2 hours to produce a negative electrode.

[Preparation of electrolyte solution] A solvent obtained by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1
LiPF ₆ was dissolved at a rate of 1 mol / L to prepare an electrolytic solution.

[Assembly of Battery] A separator made of a microporous polyethylene membrane having ion permeability is interposed between the positive electrode and the negative electrode prepared as described above, and the separator is spirally wound. An electrode body was prepared. And
The wound electrode body was housed inside a battery can having a diameter of 40 mm and a length of 150 mm, and the battery of Example 1 having the structure shown in FIG.
(A1 to A7) and Example battery 2 (B1
To B4). Further, Comparative Example batteries 1 to 3 having the same structure as the example battery 1 (A1) were assembled.

[Charge / Discharge Test Method] Charge / discharge was performed at a constant current of 4.0 A, and a charge / discharge cycle test in which a cycle of charge → pause for 30 minutes → discharge → pause for 30 minutes was repeated was performed.

In the charge / discharge cycle test, the following Table 4
The following conditions were used. In addition, under the conditions in Table 4,
(a) represents control based on the battery voltage (step S1 in FIG. 4, step S11 in FIG. 5), and (b) represents control based on the positive electrode potential (step S2 in FIG. 4, step S12 in FIG. 5).
(C) represents control based on the negative electrode potential (step S3 in FIG. 4, step S13 in FIG. 5).

[0036]

[Table 4]

As shown in Table 4, all the controls shown in FIGS. 4 and 5 were executed for the battery of the embodiment 1 (A1) and the battery of the embodiment 2 (B1).
At the time of charging and discharging, only the control based on the battery voltage alone (steps S1 and S11) was performed. For the comparative example battery 2, at the time of charging and discharging, control based on the battery voltage (steps S1 and S11) and control based on the negative electrode potential (steps S3 and S13) are executed. Omitted. Further, for the comparative example battery 3, at the time of charging, control based on the battery voltage (step S1) and control based on the negative electrode potential (step S3)
And the control based on the positive electrode potential was omitted. At the time of discharging, only control based on the battery voltage (step S11) was executed, and control based on the positive electrode potential and control based on the negative electrode potential were omitted.

A charge / discharge cycle test was performed under the above conditions, the initial discharge capacity and the discharge capacity after 200 cycles were measured, and the deterioration rate was calculated. Table 5 shows the results.

[Table 5]

As is clear from Table 5, Comparative Example 3 in which charge control based on the negative electrode potential was added to Comparative Example 1, and Comparative Example 2 in which discharge control based on the negative electrode potential was added to Comparative Example 3
Although some effects are recognized, the effects are insufficient. The reason that the cycle characteristics of Comparative Example 3 are better than that of Comparative Example 1 is that deposition of lithium metal on the negative electrode surface during charging is suppressed, and that the cycle characteristics of Comparative Example 2 are better than Comparative Example 3. This is probably because capacity deterioration due to side reactions such as decomposition of the electrolyte on the negative electrode surface during discharge was suppressed.

On the other hand, in Example 1 (A1) and Example 2 (B1) in which charge control and discharge control based on the positive electrode potential were further added to Comparative Example 2, the cycle characteristics were greatly improved. The effectiveness of charge / discharge control of GaN was demonstrated. still,
It is considered that the cycle characteristics of Examples 1 and 2 were superior to Comparative Example 2 because the collapse of the positive electrode crystal structure during charge and discharge was suppressed. In particular, since the battery of Example 2 (B1) employs the battery can itself as the reference electrode, there is no increase in weight due to the installation of the reference electrode, which is advantageous in terms of weight energy density. In addition, about battery A2-A7 and B2-B4,
It was confirmed that the batteries A1 and B1 exhibited the same characteristics.

The configuration of each part of the present invention is not limited to the above-described embodiment, and various modifications can be made within the technical scope described in the claims. For example, the measurement of the potential difference serving as the basis of the charge / discharge control is not limited to the method using the actually measured value as described above, but may be a method that predicts from the past potential difference data.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a cylindrical lithium ion secondary battery according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a circuit configuration for charge / discharge control according to the present invention.

FIG. 4 is a flowchart showing a procedure of charge control according to the present invention.

FIG. 5 is a flowchart showing a procedure of discharge control according to the present invention.

[Explanation of symbols]

 (1) Cylindrical lithium ion secondary battery (5) Battery can (50) Cylindrical body (51) Sealing plate (6) Winding electrode body (63) Positive electrode (61) Negative electrode (16) Positive external terminal (17) Negative electrode External terminal (2) Reference electrode (21) Reference electrode external terminal (3) Potentiometer (31) Potentiometer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/40 H01M 10/40 Z (72) Inventor Atsushi Yanai 2-5-5 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Atsuhiro Funabashi 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Inventor Toshiyuki Noma 2 Keihanhondori, Moriguchi-shi, Osaka 5-5-5 Sanyo Electric Co., Ltd. (72) Inventor Ikuro Yonezu 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 5G003 AA01 BA01 CA11 DA07 DA13 EA06 5H011 AA07 AA13 CC06 DD07 EE01 FF04 5H014 AA06 EE05 EE07 EE10 5H029 AJ05 AK03 AL07 AM03 AM05 AM07 BJ02 BJ14 BJ27 DJ01 DJ02 EJ01 EJ04 EJ05 HJ12 5H030 AA03 AA04 AS20 BB01 BB21 FF43 FF44 FF44

Claims (5)

[Claims] 1. An electrode body (6) is accommodated in a battery can (5) into which an electrolytic solution has been injected, and is connected to a positive external terminal (16) and a negative external terminal (17) attached to the battery can (5). A method for controlling charging and / or discharging for a secondary battery capable of taking out the electric power generated by the electrode body (6) to the outside,
A reference electrode (2), which is electrically independent from the electrode body (6), is installed inside the battery can (5), and the potential difference between the reference electrode (2) and the positive electrode external terminal (16) and the reference electrode (2) Charge and / or discharge control of a secondary battery, wherein the charge and / or discharge is stopped when at least one of the potential differences exceeds a predetermined threshold. Method. 2. The method according to claim 1, wherein the reference electrode is formed of a lithium metal, a lithium alloy, platinum, gold, a carbon material, or a metal oxide. 3. A battery can (5) into which an electrolyte is injected, an electrode body (6) which is electrically independent from the battery can (5) is housed, and a positive electrode outside attached to the battery can (5). A method for controlling charging and / or discharging of a secondary battery capable of extracting power generated by an electrode body (6) from a terminal (16) and a negative electrode external terminal (17), comprising: The potential difference between the can (5) and the positive external terminal (16), and the battery can (5) and the negative external terminal (1)
7) Charge / discharge control of a secondary battery, characterized in that at least one of the potential differences among the potential differences is constantly monitored and charging and / or discharging is stopped when the potential difference exceeds a predetermined threshold. Method. 4. The method according to claim 3, wherein the battery can is formed of aluminum, stainless steel, nickel-plated stainless steel, or a magnesium alloy. 5. The charge / discharge control method for a secondary battery according to claim 1, wherein the charge / discharge of the lithium secondary battery is performed.