JP2002050407A - Nonaqueous electrolyte secondary cell and control method of charge and discharge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method of charge and discharge which enables to provide a nonaqueous secondary cell with excellent cycle characteristics by restraining the over charged state caused by the deterioration of charge and discharge cycle, and uneven charge distribution generated on an electrode plate. SOLUTION: An electrode plate of a positive electrode or a negative electrode has a terminal enabled to confirm one or more electric potential, and each terminal charges and discharges individually by referring to the electric potential of each terminal, thus, the unevenness of charging on the electrode plate or the over charge of an activator caused by the lowering of capacity of the cell having an electrode plate with large area, or the cell after the lapse of cycles, are enabled to restrain, and the problem in the past is enabled to solve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge / discharge control method for a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art In recent years, lithium secondary batteries used as main power sources for mobile communication devices and portable electronic devices have the characteristics of high electromotive force and high energy density.
A lithium secondary battery using lithium metal as the negative electrode material has a high energy density, but dendrites are deposited on the negative electrode during charging, and may repeatedly break through the separator to reach the positive electrode side by repeated charging and discharging, causing an internal short circuit. there were. Further, the precipitated dendrite has a high specific activity because of its large specific surface area, and reacts with the solvent in the electrolytic solution on its surface to form a solid electrolyte interface film lacking electron conductivity. For this reason, the internal resistance of the battery is increased, and particles isolated from the electron conduction network are present, and these are factors that lower the charge / discharge efficiency. For these reasons, lithium secondary batteries using lithium metal as the negative electrode material have problems with low reliability and short cycle life.

At present, a carbon material capable of occluding and releasing lithium ions is used as a negative electrode material instead of lithium metal, and has been put to practical use. Normally, metallic lithium does not precipitate at the carbon material negative electrode, so there is no problem of internal short circuit due to dendrite.

[0004] Such a lithium secondary battery is charged with a constant current, and after the battery reaches a set voltage, the charge current is reduced so as not to exceed the set voltage to keep the voltage constant (hereinafter referred to as a charge method). , CVCC charging). This is for the following reasons. In the charging of a nickel-cadmium battery or a nickel-metal hydride battery, when approaching a fully charged state, current is spent on a side reaction in a high charged state, thereby eliminating uneven charging in a low charged state. However, in a lithium secondary battery in which side reactions hardly occur, non-uniform charging in the electrode plate is eliminated by using CVCC charging in which the current value is reduced after reaching a set voltage during charging. That is, CVCC charging has a role of preventing non-uniform charging of the active material on the electrode. Here, the non-uniform charge means that a portion having a different potential is generated in the same electrode plate due to a current distribution generated inside the electrode, whereby active materials having different charge states exist in the same electrode plate. Refers to the state in which

[0005] Further, since the lithium secondary battery uses an organic electrolyte, the ion conductivity is low and the charge and discharge in the electrode are likely to be uneven. Therefore, compared to nickel-cadmium batteries and nickel-metal hydride batteries that have an aqueous electrolyte solution, the electrode area is increased and the thickness of the electrodes is reduced to increase the reactivity of the active material and eliminate uneven charging and discharging inside the electrodes. are doing.

[0006] However, even if the electrode plate area is widened and CVCC charging is used as described above, the elimination of non-uniform charging is not yet complete.

First, the following problems arise because the area of the electrode plate inside the battery is large. Usually, a lithium secondary battery has a pair of positive and negative terminals, and charges and discharges by controlling the voltage obtained from these terminals. However, this terminal merely indicates a representative potential of various potentials existing on the electrode, and the nonuniformity of the potential generated in the electrode is unknown. The non-uniformity of the electric potential increases as the area of the electrode plate inside the battery increases, and the power storage device for home use, a motorcycle powered by a motor, an electric vehicle,
This is an important issue for large batteries used in hybrid electric vehicles and the like. In other words, the distribution of the potential generated in the electrode plate is that charging is unevenly performed in the electrode plate and a portion where charging or discharging is excessively performed and a portion where charging or discharging is insufficient occur in the same electrode plate. become. If overcharged,
Lithium ions occluded in the negative electrode material are deposited on the negative electrode surface as lithium metal. Since the charge and discharge efficiency of the deposited lithium metal is very low, the cycle life of the battery is significantly reduced. In the positive electrode, lithium present in the crystal of the positive electrode is excessively released. As a result, the crystals of the positive electrode become unstable and the cycle life of the battery is significantly reduced.

Next, a description will be given of a problem of the conventional CVCC charging when the battery is deteriorated due to the repetition of the charge / discharge cycle. In a battery system, such as a lithium ion battery, in which a battery is formed by lithium ions moving between the positive and negative electrodes, it is necessary to consider the balance of the lithium storage / release capacity (hereinafter abbreviated as capacity) of the positive and negative electrodes. is there. For example, when the positive electrode capacity is larger than the negative electrode capacity,
When the battery is charged, the lithium ions released from the positive electrode are not entirely occluded by the negative electrode, and are deposited on the negative electrode surface as lithium metal. Since the charge and discharge efficiency of the deposited lithium metal is very low, the cycle life of the battery is significantly reduced.

On the other hand, when the capacity of the negative electrode is significantly larger than the capacity of the positive electrode, lithium present in the crystal of the positive electrode is excessively released. As a result, the crystals of the positive electrode become unstable, and the cycle life of the battery is significantly reduced. In order to solve such a problem, Japanese Patent Application Laid-Open No. 5-62712 proposes to specify an optimum value of a capacity balance between a positive electrode capacity and a negative electrode capacity.

However, even when the capacity balance between the positive electrode and the negative electrode is designed optimally at the initial stage of the production of the battery, the battery deteriorates and the capacity balance between the positive electrode and the negative electrode is lost due to the lapse of charge / discharge cycles. Come. In this case, even if the positive electrode deteriorates quickly or the negative electrode deteriorates quickly, one of the capacities becomes significantly larger than the other, so that an excessive load is applied to the deteriorated electrode plate, and the cycle life is accelerated. There is also a problem that it becomes shorter.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and is intended to be used even when the electrode area is large or when the battery is deteriorated due to repeated charge / discharge cycles. It is an object of the present invention to provide a charge / discharge control method for a lithium secondary battery in which a non-uniform charge state generated on an electrode is eliminated by performing the above-mentioned steps optimally, and charge / discharge efficiency and cycle characteristics are improved.

[0012]

Means for Solving the Problems In order to solve the above problems,
In the method for controlling charge and discharge of a nonaqueous electrolyte secondary battery according to the present invention, the positive or negative electrode plate has one or more terminals capable of confirming a potential, and each terminal is referred to a potential obtained from each terminal. It performs charging and discharging independently. That is, instead of controlling charging / discharging only by the voltage of the battery as in the related art, the non-uniform charging state generated on the electrode is eliminated by directly measuring the potential of the electrode plate by each terminal.

In a conventional battery having only a pair of terminals, the voltage obtained from the pair of terminals alone is not sufficient to correct the above-described nonuniform charge state (potential) generated in the electrode plate. On the other hand, according to the present invention, the positive electrode and the negative electrode can be measured and charged independently at various points on the electrode plate where the electric potential becomes non-uniform. Similarly, in a battery in which the capacity balance has been lost due to the charge / discharge cycle, the potential can be measured independently at each part of the electrode, and the battery can be charged in accordance with the deterioration state.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The non-aqueous electrolyte secondary battery of the present invention
A positive electrode plate and a negative electrode plate capable of inserting and extracting lithium are formed via a separator, and include a nonaqueous electrolyte in which a lithium salt is dissolved in a solvent, and a reference electrode for measuring the electrode potential of the positive electrode or the negative electrode. On the positive electrode plate, one or more terminals, preferably a plurality of terminals, for directly checking the potential of the electrode plate are provided. In the case of one, the positive electrode terminal used in the conventional battery can be used as it is as the terminal of the present invention. When there are a plurality of terminals, the terminals are arranged so as not to be in direct contact with each other. Each terminal installed is charged and discharged independently with reference to the potential of the electrode plate obtained from the terminal. One or more, preferably a plurality of terminals capable of directly confirming the potential of the electrode plate may be provided on the negative electrode plate instead of on the positive electrode plate. Further, the terminals may be provided on both the positive and negative electrode plates. However, when a plurality of terminals are provided on each electrode plate, it is necessary to control so that the total current flowing through each electrode plate becomes equal.

In a conventional battery having only a pair of terminals for measuring a battery voltage, when a non-uniform potential occurs in a positive electrode plate or a negative electrode plate, it is not controlled. However, as in the present invention, a plurality of terminals are present on the positive electrode plate and / or the negative electrode plate, and not the battery voltage, which is the difference between the potentials of the positive electrode and the negative electrode, but the direct measurement of the potential of the electrode plate to accurately measure the active material. By grasping the charging state, uniform charging can be performed without causing non-uniform potential on the electrode plate. That is, the charging current is reduced in the terminals in the excessively charged region, and the current is continuously supplied in the terminals in the insufficiently charged region, whereby the uneven charging caused in the electrode plate is eliminated.

In the prior art, since the battery is charged based on the battery voltage obtained from the pair of positive and negative electrodes, even the battery deteriorated by the charge / discharge cycle is charged to the initial set voltage. However, if the deterioration of the battery is a decrease in the capacity of the positive electrode, the positive electrode reaches a fully charged potential before the potential of the negative electrode does not decrease. That is, the positive electrode is fully charged even though the battery voltage, which is the potential difference between the positive electrode and the negative electrode, has not reached the set value. When the battery in this state is charged to the set voltage, the positive electrode becomes overcharged. In this case, if the charging method is such that the potential of the positive electrode is measured, and after the positive electrode reaches the set potential, the charging current is reduced so as not to exceed the set potential, the positive electrode does not become overcharged. On the other hand, when the deterioration of the battery is a decrease in the capacity of the negative electrode, lithium is supplied from the positive electrode beyond the capacity of the negative electrode, and lithium is deposited on the surface of the negative electrode. In this case, the potential of the negative electrode is measured, and the charging current is reduced so as not to exceed the potential at which lithium is deposited, whereby the deposition of lithium metal on the negative electrode can be suppressed.

As described above, whether charging is controlled with the positive electrode or with the negative electrode depends on whether the cause of deterioration of the cycle life of the battery is caused by the positive electrode or the negative electrode. Therefore, it is only necessary that the pole having the cause has a terminal for measuring the potential of the electrode plate.

Whether the cause of deterioration of the cycle life of the battery is caused by the positive electrode or the negative electrode depends on the charge / discharge capacity per unit area of the positive electrode and the negative electrode. Can be estimated. Specifically, in an electrochemical cell using a positive electrode plate as a working electrode and lithium metal as a counter electrode, 10 kHz to 10 m
The impedance of a semicircular arc drawn when measuring the impedance in the frequency domain of Hz and describing the result on a complex plane is R1,
In an electrochemical cell using a negative electrode plate as a working electrode and lithium metal as a counter electrode, impedance is measured in a frequency range of 10 kHz to 10 mHz, and the diameter of a semicircular arc drawn when the result is described on a complex plane is R2. The diameter R of the semicircle represents the magnitude of the resistance generated when the electrode plate exchanges ions and electrons at the interface with the electrolytic solution. FIG. 3 shows an example in which the diameter R of a semicircular arc drawn on this complex plane is measured.

When the value of R1 / R2 is 1 or more, the charge / discharge capacity of the positive electrode is lower than that of the negative electrode and tends to be deteriorated at the positive electrode. The positive electrode plate is provided with a terminal capable of confirming the potential of the electrode plate. By regulating charging and discharging, ideal charging and discharging can be performed.

When the value of R1 / R2 is 3 or less, the charge / discharge capacity of the negative electrode is lower than that of the positive electrode and tends to be deteriorated at the positive electrode. The negative electrode plate is provided with a terminal capable of confirming the potential of the electrode plate. Ideal charging and discharging can be performed by regulating charging and discharging by the potential.

Further, when the value of R1 / R2 is 1 or more and 3 or less, there may be a case where deterioration occurs at the positive electrode and a case where deterioration occurs at the negative electrode. Which pole the deterioration starts from depends on the shape of the electrode plate of the battery, the type of the binder, the conductive material, and the like, and further depends on the use conditions. As described above, in the region where the charge and discharge capacities of the positive electrode and the negative electrode are close to each other (region where the value of R1 / R2 is 1 or more and 3 or less), the potentials of both the positive electrode and the negative electrode are measured, and the deterioration state of the battery is measured. It is desirable to regulate charging and discharging in accordance with the requirements.

It is desirable to provide one or more terminals capable of confirming the potential of the electrode per electrode plate area of 0.1 m ² / g. If the amount is small, the effect of the charge / discharge control method becomes small.

This charge / discharge control is performed for a battery having a large electrode plate area, for example, a battery having a discharge capacity of 4 Ah for an electric vehicle.
The effect is particularly great when used in the above batteries.

[0024]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.

(Example 1) FIG. 1 is a longitudinal sectional view of a cylindrical battery according to the present invention.

The negative electrode plate is prepared by mixing 95% by weight of graphite and 5% by weight of polyvinylidene fluoride resin as a binder and dispersing them in a 1% aqueous solution of carboxymethylcellulose to form a slurry. It was applied on an electric body, dried and then rolled. Graphite is Timcal SF
G44 is subjected to pulverization by a turbo mill and particle size adjustment to have a specific surface area of 3 m ² / g and a particle size of 15 to 22 μm by a wet laser particle size meter.

On the other hand, for the positive electrode plate, 10% by weight of carbon powder as a conductive agent and 5% by weight of polyvinylidene fluoride resin as a binder were mixed with 85% by weight of lithium cobalt oxide powder, and these were mixed with 1% of carboxymethyl cellulose. A slurry was prepared by dispersing the slurry in an aqueous solution, applied on a positive electrode current collector made of aluminum foil, dried, and then rolled. Here, lithium cobaltate having a specific surface area of 0.4 m ² / g was used.

The positive electrode plate and the negative electrode plate prepared as described above were spirally wound a plurality of times with a separator interposed therebetween to form an electrode plate group 4 and housed in the battery case 1. Further, the positive electrode lead 5 was pulled out from the positive electrode plate and connected to the sealing plate 2, and the negative electrode lead 6 was drawn out from the negative electrode plate and connected to the bottom of the battery case 1. Further, insulating rings 7 were provided on the upper and lower portions of the electrode plate group 4 respectively.

A reference electrode 8 was inserted between the electrode group 4 and the battery case 1. The reference electrode 8 is made of lithium metal foil, and electrical insulation is performed by covering the surface of the metal foil and the lead with a separator.

Then, LiP was added to a mixed solvent of ethylene carbonate and ethyl methyl carbonate at a volume ratio of 1: 1.
An organic electrolyte solution in which 1.5 mol / l of F ₆ was dissolved was injected, and a battery was formed using the sealing plate 2. Thus, a cylindrical battery having a diameter of 18 mm and a height of 650 mm was produced. When the ratio of R1 / R2 was measured using the electrode plate of this battery, R1 / R2 = 4.6.

Using this cylindrical battery, CVCC charging was performed in which the upper limit of the potential of the positive electrode measured by the reference electrode was 4.3 V, the maximum limiting current was 1 A, and the charging was terminated when the current reached 100 mA. Discharge was performed at a constant current of 1400 mA until the battery voltage reached 3.0 V, and a cycle test was performed with a pause time of 20 minutes during switching between charge and discharge.
The charge and discharge were performed in a constant temperature bath at 20 ° C. The upper limit of the positive electrode potential was determined with reference to the positive electrode potential when the battery of Comparative Example 1 described later was charged.

Example 2 A cylindrical battery was manufactured in the same manner as in Example 1, and the lower limit of the potential of the negative electrode measured by the reference electrode was CVCC charged at a lower limit of 0.1 V. The charging was terminated when the current reached 100 mA.
The cycle test was performed under the same conditions as in Example 1 except for the above conditions. The upper limit of the potential of the positive electrode was determined with reference to the negative electrode potential when the battery of Comparative Example 1 described later was charged.

Comparative Example 1 A cylindrical battery was manufactured in the same manner as in Example 1, and the upper limit of the voltage of the battery itself was 4.2 V.
Charge the battery, set the maximum current limit to 1A, and set the current to 100m
The charging was terminated when the battery reached A. The cycle test was performed under the same conditions as in Example 1 except for the above conditions. Note that the reference electrode 8 was not provided.

Example 3 A cylindrical battery was manufactured in the same manner as in Example 1 except that the lithium cobaltate used as the positive electrode material had a specific surface area of 1.2 m ² / g. A cycle test was performed under the same charging conditions as in No. 1.
When the ratio of R1 / R2 was measured using the electrode plate of this battery, R1 / R2 = 1.1.

Example 4 A cylindrical battery was manufactured in the same manner as in Example 3, and a cycle test was performed under the same charging conditions as in Example 2.

Comparative Example 2 A cylindrical battery was manufactured in the same manner as in Example 3, and a cycle test was performed under the same charging conditions as in Comparative Example 1. Note that the reference electrode 8 was not provided.

Example 5 FIG. 2 shows a configuration diagram of a sheet-shaped battery according to the present invention.

The positive electrode plate 9 and the negative electrode plate 10 were manufactured in the same manner as the positive electrode plate and the negative electrode plate of Example 1, and were cut into predetermined dimensions. The size of the positive electrode is 220 cm in length and 22 c in width.
m, the size of the negative electrode is 220.5 cm in length and 22.5 in width
cm (electrode plate area: 0.484 m ^{2 to} 0.496
m ² ).

The positive electrode plate 9 and the negative electrode plate 10 were overlapped via the separators 12a and 12b, and inserted into a laminate bag made of aluminum as a core material so as to cover the entire electrode plate.
In addition, the positive electrode lead 9a is pulled out from the long side of the positive electrode plate 9,
A negative electrode lead 10a was drawn out from the long side of the negative electrode plate 10. The positive electrode lead 9a and the negative electrode lead 10a were arranged at positions facing each other with the separators 12a and 12b interposed therebetween. Furthermore, a pair of the positive electrode lead 9a and the negative electrode lead 10a
The reference electrode 11 is disposed between the
a, inserted between 12b. One pair of the positive electrode lead 9a, the negative electrode lead 10a, the reference electrode 11, and the reference electrode lead 11a is hereinafter referred to as a lead pair.

A total of two pairs of the lead pairs were arranged at the A and B ends. These leads were all connected to a device that controls the charge / discharge drawn out of the laminate bag. For the laminate bag or the lead plate, a metal or an alloy having an organic electrolyte resistance and electron conductivity can be used. For example, metals such as iron, nickel, titanium, chromium, molybdenum, copper, and aluminum or alloys thereof are used. Then, an electrolytic solution was injected, and the opening of the laminate bag was heat-sealed to seal, thereby producing a sheet-shaped battery.

Since a battery using a laminated bag as a case has poor adhesion to the electrode plates, the battery was sandwiched and fixed between two stainless steel plates from the outside of the bag. In this case, a laminate bag is used as a battery case, but a case in which the shape as shown in the first embodiment is fixed may be used as long as it has the above-described structure. The shape of the battery is not limited to the sheet battery, but may be a cylindrical battery in which an electrode plate is spirally wound a plurality of times, or a rectangular battery formed by weaving a plurality of times.

Using this sheet-shaped battery, CVCC charging was performed with the upper limit of the potential of the positive electrode measured by the reference electrode being 4.3 V, the maximum limiting current was set to 8 A, and the charging was terminated when the current reached 800 mA. Discharge was performed at a constant current of 11.2 A until the voltage reached 3.0 V, and a cycle test was performed with a pause time of 20 minutes during switching between charge and discharge. However, charge and discharge were controlled independently for each terminal. The charge / discharge was performed in a thermostat at 20 ° C. (positive electrode area per terminal: 0.242 m ² ).

(Example 6) A sheet-shaped battery was produced in the same manner as in Example 5, except that four pairs of lead pairs were arranged at equal intervals between the end A and the end B. The cycle test was also performed in the same manner as in Example 5 (the positive electrode area per terminal was 0.1 mm).
161 m ² ).

Example 7 A sheet-shaped battery was manufactured in the same manner as in Example 5, except that five pairs of lead pairs were arranged at equal intervals between the end A and the end B. The cycle test was also performed in the same manner as in Example 5 (the positive electrode area per terminal was 0.1 mm).
097 m ² ).

(Example 8) A sheet-shaped battery was manufactured in the same manner as in Example 5, except that six pairs of lead pairs were arranged at equal intervals between the end A and the end B. The cycle test was also performed in the same manner as in Example 5 (the positive electrode area per terminal was 0.1 mm).
081 m ² ).

(Example 9) A sheet-shaped battery was manufactured in the same manner as in Example 5, except that eight pairs of lead pairs were arranged at equal intervals between the end A and the end B. The cycle test was also performed in the same manner as in Example 5 (the positive electrode area per terminal was 0.1 mm).
061 m ² ).

(Example 10) A sheet-shaped battery was produced in the same manner as in Example 5, except that only one pair of the lead pairs was arranged at the end A. The cycle test was also performed in the same manner as in Example 5 (positive electrode area per terminal: 0.484 m ² ).

<< Evaluation >> Examples 1, 2 and Comparative Example 1
(Table 1) shows the results of the cycle test. The cycle under the above charge / discharge conditions is repeated, and the number of cycles when the discharge capacity of the battery is reduced to 50% when the discharge capacity in the first cycle is 100% is defined as the cycle life of the battery. And

[0049]

[Table 1]These batteries use the lithium cobaltate used for the cathode material.
0.4m specific surface area ^Two/ G and very small
R1 / R2 for comparing the charge and discharge capacity of the pole and the anode is
4.6, the deterioration of the positive electrode occurs before the negative electrode.
It is designed to work. So it goes through a cycle
The capacity of the positive electrode is smaller than the capacity of the negative electrode. like this
And a conventional charging method as in Comparative Example 1
When CVCC charging is performed, the positive electrode becomes overcharged,
As a result, the deterioration of the material is promoted. In contrast, the first embodiment
In such a charge / discharge control method of the present invention, the positive electrode potential is used as a reference.
To charge according to the decrease in the capacity of the positive electrode.
Noh. In other words, the excess
Cycle life characteristics
It was confirmed that it had improved. In the second embodiment, the negative
Reduces the capacity of the positive electrode because charging is performed based on the potential of the electrode
Can not be charged according to. Therefore, the positive electrode is
Batteries that deteriorate earlier also have a longer cycle life.
Cycle life characteristics similar to Comparative Example 1.
Shows sex.

Next, the results of the cycle tests of Example 3, Example 4, and Comparative Example 2 are shown in Table 2. The index for evaluating the cycle characteristics is as described above.

[0051]

[Table 2]These batteries use the lithium cobaltate used for the cathode material.
1.2m specific surface area ^Two/ G and very large
R1 / R2 for comparing the charge and discharge capacity of the pole and the anode is
1.1, the negative electrode deteriorates before the positive electrode.
It is designed to work. So it goes through a cycle
The capacity of the negative electrode is smaller than the capacity of the positive electrode. like this
The conventional charging method as in Comparative Example 2 is applied to a battery in a good state.
When CVCC charging is performed, the negative electrode becomes overcharged and the negative electrode becomes overcharged.
As a result, the deterioration of the material is promoted. In contrast, the third embodiment
In such a charge / discharge control method of the present invention, the negative electrode potential is used as a reference.
To charge according to the capacity reduction of the negative electrode.
Noh. In other words, the excess
Cycle life characteristics
It was confirmed that it had improved. In the fourth embodiment,
Reduces the capacity of the negative electrode because charging is performed based on the potential of the electrode
Can not be charged according to. Therefore, the negative electrode is
Batteries that deteriorate earlier also have a longer cycle life.
Cycle life characteristics similar to Comparative Example 2
Shows sex.

In the present embodiment, the maximum charging current is set to 1 A, and the charging voltage is set to 4.2 V. The constant current and constant voltage charging is used. However, the same applies to other charging voltages and charging current values and pulse charging. Was obtained.

Further, when the specific surface area of lithium cobalt oxide as the positive electrode material was changed and several electrode plates having different R1 / R2 were prepared, one or more, particularly 2.5, which was designed so that the positive electrode deteriorated earlier When it exceeded, a remarkable effect was shown.
In the third embodiment, the cycle characteristic was improved by only several% in the method of controlling the positive electrode potential using the electrode plate having R1 / R2 of 1.1, but the electrode plate shape (length, width, etc.) was not improved. )
When the same experiment was performed by changing the value and controlling the positive electrode potential using an electrode plate having R1 / R2 of 1.05, an improvement in cycle characteristics of about 30% was found. On the other hand, the negative electrode exhibited a remarkable effect when it was designed to deteriorate earlier than 3 or less, especially when it was 2 or less.

Next, the results of the cycle tests of Examples 5 to 10 are shown in Table 3. However, in Examples 5 to 7 in which there are a plurality of lead pairs, charging / discharging control is performed independently for each terminal, and (maximum current at the time of charging flowing to each terminal) = 8 / (disposed on the electrode plate). Number of lead pairs) A (discharge current flowing through each terminal) = 11.2 / (number of lead pairs arranged on electrode plate) A The index for evaluating the cycle characteristics is as described above. Table 3 shows the results of the cycle characteristic test.

[0055]

[Table 3] Although the cycle life characteristics of Examples 5 to 10 are improved, the cycle life characteristics of Examples 5 to 7 and Example 6 are remarkably improved as compared with Example 8. When the size of the electrode plate is increased, a potential distribution generated in the electrode plate by flowing a current becomes large, and it becomes difficult to maintain a uniform charged state in one electrode plate. Then, Example 5
By arranging a plurality of lead pairs on the electrode plate as shown in FIG. 7 and performing independent charging in accordance with different charging states existing in the electrode plate, uniform charging can be performed as the entire electrode plate. Thus, it was confirmed that the deterioration of the cycle life of the battery was prevented from being reduced due to accelerated deterioration in only a part of the region, and the cycle life characteristics of the battery could be significantly improved.

[0056]

According to the present invention, the positive electrode or the negative electrode has one plate.
In the case of a battery having a large plate area or a battery after a cycle, the terminal has at least one terminal capable of confirming a potential, and each terminal independently charges and discharges with reference to the potential obtained from each terminal. Non-uniform charging on the plate and overcharging of the active material due to a decrease in capacity can be suppressed, and a nonaqueous electrolyte secondary battery with excellent cycle characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylindrical battery of the present invention.

FIG. 2 is a structural diagram of a sheet battery of the present invention.

FIG. 3 is a complex surface diagram of impedance measurement.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulating packing 4 Electrode plate group 5 Positive electrode lead 6 Negative electrode lead 7 Insulating ring 8 Reference electrode 9 Positive electrode plate 9a Positive electrode lead 10 Negative electrode plate 10a Negative electrode lead 11 Reference electrode 11a Reference electrode lead 12a Separator 12b Separator

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hirokazu Kimiya 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Terms (reference) 5H022 AA09 BB08 BB27 CC02 CC21 5H029 AJ02 AJ05 AK03 AL07 AM03 AM07 BJ02 BJ14 CJ16 CJ28 DJ05 HJ00 HJ07 HJ16 HJ20 5H030 AA03 AA10 AS05 BB02 BB18 BB21 FF41

Claims (10)

[Claims] 1. A charge / discharge control method for a nonaqueous electrolyte secondary battery having a positive electrode and a negative electrode capable of inserting and extracting lithium, wherein the positive electrode plate has one or more terminals capable of confirming a potential. A charge / discharge control method for a non-aqueous electrolyte secondary battery, wherein each terminal independently charges and discharges with reference to a potential obtained from each terminal. 2. An electrochemical cell using a positive electrode plate as a working electrode and lithium metal as a counter electrode.
The impedance of a semicircular arc drawn when measuring the impedance in the frequency domain of mHz and describing the result on a complex plane is defined as R1, the negative electrode plate is used as a working electrode, and an electrochemical cell using lithium metal as a counter electrode is from 10 kHz to 10 mHz. When the diameter of the semicircular arc drawn when measuring the impedance in the frequency domain of and describing the result on the complex plane is R2, R
2. The value of 1 / R2 is 1 or more.
The charge / discharge control method of the nonaqueous electrolyte secondary battery according to the above. 3. A charge / discharge control method for a nonaqueous electrolyte secondary battery having a positive electrode and a negative electrode capable of inserting and extracting lithium, wherein the negative electrode plate has one or more terminals capable of confirming a potential. A charge / discharge control method for a non-aqueous electrolyte secondary battery, wherein each terminal independently charges and discharges with reference to a potential obtained from each terminal. 4. An electrochemical cell using a positive electrode plate as a working electrode and lithium metal as a counter electrode has a frequency of 10 kHz to 10 kHz.
The impedance of a semicircular arc drawn when measuring the impedance in the frequency domain of mHz and describing the result on a complex plane is defined as R1, the negative electrode plate is used as a working electrode, and an electrochemical cell using lithium metal as a counter electrode is from 10 kHz to 10 mHz. When the diameter of the semicircular arc drawn when measuring the impedance in the frequency domain of and describing the result on the complex plane is R2, R
4. The value of 1 / R2 is 3 or less.
The charge / discharge control method of the nonaqueous electrolyte secondary battery according to the above. 5. A charge / discharge control method for a non-aqueous electrolyte secondary battery having a positive electrode and a negative electrode capable of inserting and extracting lithium, wherein the positive and negative electrode plates can confirm one or more pairs of potentials. A charge / discharge control method for a non-aqueous electrolyte secondary battery, comprising: a terminal pair, wherein each terminal pair independently charges and discharges with reference to a potential obtained from each terminal. 6. An electrochemical cell using a positive electrode plate as a working electrode and lithium metal as a counter electrode, from 10 kHz to 10 kHz.
The impedance of a semicircular arc drawn when measuring the impedance in the frequency domain of mHz and describing the result on a complex plane is defined as R1, the negative electrode plate is used as a working electrode, and an electrochemical cell using lithium metal as a counter electrode is from 10 kHz to 10 mHz. When the diameter of the semicircular arc drawn when measuring the impedance in the frequency domain of and describing the result on the complex plane is R2, R
6. The value of 1 / R2 is 3 or less.
The charge / discharge control method of the nonaqueous electrolyte secondary battery according to the above. 7. A non-aqueous electrolyte secondary battery using the charge / discharge control method according to claim 1. 8. A non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium, wherein the battery has one or more reference electrodes, and two non-aqueous electrodes are provided on the positive or negative electrode plate. A non-aqueous electrolyte secondary battery having terminals capable of confirming the above potentials, wherein the terminals are not in contact with each other and are independent. 9. A terminal provided on a positive electrode plate or a negative electrode plate,
9. The non-aqueous electrolyte secondary battery according to claim 8, wherein (electrode plate area) / (0.1 m ² ) or more. 10. The non-aqueous electrolyte secondary battery according to claim 8, wherein the battery has a discharge capacity of 4 Ah or more.