JP2000200625A - Device for evaluating capacity of electrode active material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for evaluating the capacity of an electrode active material, whereby the capacity of only an active material in an electrode can be accurately evaluated. SOLUTION: This device includes a charging means, a voltage detecting means 5 for detecting the voltage changes of a cell having an operating electrode, a counter electrode and a reference electrode connected in parallel to the charging means, a voltage waveform storing means 7 for storing the voltage changes detected by the voltage detecting means 5 in sequence to feedback the storage signal to the charging means 2, a current detecting means 10 for detecting the current changes of the cell having the operating electrode, the counter electrode and the reference electrode connected in parallel to the charging means 2 and a current waveform storing means 14 for storing the current changes detected by the current detecting means 10 in sequence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for evaluating the capacity of an electrode active material.

[0002]

2. Description of the Related Art In recent years, various secondary batteries such as lithium ion secondary batteries have been used as power supplies for small electronic devices. In such a secondary battery, an active material used for an electrode has been developed for the purpose of further increasing the capacity.

A positive electrode and a negative electrode incorporated in a secondary battery generally have a structure in which an electrode layer containing an active material, a conductive material and a binder is supported on a current collector. As a method of evaluating the electrode capacity of such a secondary battery, a voltage change is measured by performing charging and discharging at a constant current, and a current change is measured by performing charging and discharging at a constant voltage. ing.

[0004]

However, the above-described conventional capacity evaluation method is intended for an electrode including a current collector in addition to an active material, a conductive material and a binder, and the capacity of the active material itself is not considered. It was difficult to measure. Therefore, development of a method for accurately evaluating the performance of the active material has been desired.

An object of the present invention is to provide an electrode active material capacity evaluation apparatus capable of accurately evaluating the capacity of only an active material in an electrode.

[0006]

According to the present invention, there is provided an apparatus for evaluating the capacity of an electrode active material, which detects a voltage change of a charging means and a cell having a working electrode, a counter electrode and a reference electrode connected in parallel to the charging means. Voltage detecting means, a voltage waveform storing means for sequentially storing the voltage change detected by the voltage detecting means, and a feedback signal of the stored signal to the charging means, a working electrode connected in parallel to the charging means, Current detection means for detecting a current change in a cell having a counter electrode and a reference electrode, and a current waveform storage means for sequentially storing the current change detected by the current detection means, an active material, and an electrode layer including a binder. A test cell having a working electrode carried by a current collector is connected in parallel to the charging means, and the test cell is charged at a constant current by the charging means. Through the voltage waveform storage means, and a blank cell having a working electrode in which an electrode layer including a binder excluding an active material is carried on a current collector is connected in parallel to the charging means, and the voltage waveform storage circuit And outputs a storage signal to the charging means, and charges the blank cell according to the voltage change stored in the voltage waveform storage circuit by the charging means. The current change at this time is stored in the current waveform storage through the current detection means. It is characterized in that it is sequentially stored in the means.

According to another aspect of the present invention, there is provided a device for evaluating the capacity of an electrode active material, comprising: a discharging means; and a voltage detecting means for detecting a voltage change of a cell having a working electrode, a counter electrode and a reference electrode connected in parallel to the discharging means. A voltage waveform storage means for sequentially storing the voltage change detected by the voltage detection means and feeding back the storage signal to the discharge means; a working electrode, a counter electrode and a reference electrode connected in parallel to the discharge means A current detecting means for detecting a current change in the cell having: and a current waveform storage means for sequentially storing the current change detected by the current detecting means, wherein an active material and an electrode layer containing a binder are used as a current collector. A test cell having a working electrode carried thereon is connected in parallel to the discharging means, and the test cell is discharged at a constant current by the discharging means. A blank cell having a working electrode in which an electrode layer containing a binder excluding an active material is carried on a current collector, which is sequentially stored in a voltage waveform storage unit, is connected in parallel to the discharge unit, and stored from the voltage waveform storage circuit. A signal is output to the discharge means, and the blank cell is discharged by the discharge means in accordance with the voltage change stored in the voltage waveform storage circuit, and the current change at this time is sent to the current waveform storage means through the current detection means. It is characterized by being stored sequentially.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an apparatus for evaluating the capacity of an electrode active material according to the present invention will be described in detail with reference to FIGS.

In FIG. 1, a current setting circuit 1 is connected to a charger 2 through a first switch SW1. The charger 2 charges a test cell connected in parallel to the charger 2 with a predetermined constant current value in response to a signal input from the current setting circuit 1. The current setting circuit 1 includes a second switch S
It is connected to the discharger 3 through W2. This discharger 3
Discharges a test cell connected in parallel to the discharger 3 at a predetermined constant current value in response to a signal input from the current setting circuit 1.

For example, a voltage detection circuit 5 comprising a pair of resistors 4a and 4b is connected in parallel to the charger 2 and the discharger 3. The charger 2 and the discharger 3
Are connected to the voltage detector 5 through a third switch SW3. The voltage detector 5 includes an A / D conversion circuit 6
Is connected to a voltage waveform RAM 7 as voltage waveform storage means. The voltage waveform RAM 7 has a function of sequentially storing a voltage change during charging or discharging of a test cell connected in parallel to the charger and the discharger.

The voltage waveform RAM 7 includes a fourth switch S
It is connected to the charge voltage control circuit 8 and the discharge voltage control circuit 9 through W4. The charging voltage control circuit 8 is connected to the charger 2 through a fifth switch SW5, and controls a charging voltage of the charger 2 based on a stored signal from the RAM 7. The discharge voltage control circuit 9 is connected to the discharger 3 through a sixth switch SW6, and controls a discharge voltage of the discharger 3 based on a storage signal from the RAM 7.

The current detector 10 comprises, for example, a resistor 11 connected in series to the charger 2 and the discharger 3, and a comparator 12 connected before and after the resistor 11. The current detector 10 includes an A / D conversion circuit 13
Is connected to a current waveform RAM 14 as current waveform storage means.

Next, the evaluation of the active material capacity during charging by the above-described evaluation device will be described with reference to FIGS.

As shown in FIG. 1, a working electrode 15a containing an active material, a binder, and a conductive material, a counter electrode 15b, and a reference electrode 15c.
Is prepared, the working electrode 15a and the counter electrode 15b are connected in parallel to the charger 3,
The working electrode 15a and the reference electrode 15c are connected in parallel to the voltage detector 5. Second, fifth, and sixth
Switches SW2, SW5, and SW6 are open, SW1
Is connected to the charger 2, and the third switch SW3 is connected to the charger 2.
And the switch SW4 is temporarily connected to the charging voltage control circuit 8.

In this state, a signal is output from the current setting circuit 1 to the charger 2 and the charger 2 outputs the test cell 15.
When a constant current charge is performed at a predetermined value, the voltage (charge voltage) of the test cell 15 sequentially changes with time as shown in FIG. 2 showing the relationship between time, charge voltage, and current. This voltage change is detected by the voltage detector 5 and the A / D
The data is stored as a digital signal in the voltage waveform RAM 7 through the conversion circuit 6.

As shown in FIG. 3, the test cell is removed from the evaluation apparatus, and a blank cell 16 having a working electrode 16a containing a conductive material, a counter electrode 16b, and a reference electrode 16c is removed in the same manner as the test cell. Connecting. The first switch SW1 is opened, and the fifth switch SW5 is connected to the charger 2 side.

In this state, when the voltage waveform signal stored from the voltage waveform RAM 7 is output to the charging voltage control circuit 8 and a control signal is output from the charging voltage control circuit 8 to the charger 2, 2, the blank cell 16 is charged according to the voltage change stored in the RAM 7, that is, the voltage change at the time of charging the test cell 15 (charging curve in FIG. 2). The current change (current curve shown by the broken line in FIG. 2) at this time is detected by the current detector 10 and the A / A
It is stored as a digital signal in the current waveform RAM 14 through the D conversion circuit 13.

As described above, the change in current with respect to the charging time of the blank cell 16 stored in the current waveform RAM 14 is obtained when the test cell 15 is charged according to the change in charging voltage. It can be regarded as a current change in a blank portion (including a current collector) excluding the active material in the 15 working electrodes.

Therefore, based on the current change during the charging of the blank cell 16 stored in the current waveform RAM 14, the integrated current value of the blank cell 16 up to a predetermined charging time is obtained, and this is calculated as BC _A , A current integrated value up to the charging time is obtained based on the current (constant current) at the time of charging of No. 15 and the obtained value is defined as SC _A. The capacity C _A (Ah) of only the active material in the working electrode of the test cell is , Can be calculated from the following equation.

AC _A = SC _A -BC _A Also, the current change during charging of the blank cell 16 stored in the current waveform RAM 14 and the voltage waveform RAM 7
The blank cell 16 based on the voltage change stored in
(A · V · h = W)
h) is obtained, and based on BC _W , the current (constant current) when charging the test cell 15 and the voltage change stored in the voltage waveform RAM 7, the integrated power value (A · V · h = Wh), and this is SC _W ,
The electric energy C _W (W) of only the active material in the working electrode of the test cell
h) can be calculated from the following equation.

C _W = SC _W −BC _W Next, the evaluation of the active material capacity at the time of discharge by the above-described evaluation device will be described with reference to FIGS.

A test cell 15 having a working electrode 15a, a counter electrode 15b, and a reference electrode 15c containing an active material, a binder, and a conductive material which has been charged in advance by the charger 2 is prepared, as shown in FIG. The working electrode 15a and the counter electrode 15b are connected in parallel to the discharger 3;
a and the reference electrode 15 c are connected in parallel to the voltage detector 5. First, fifth, and sixth switches SW1,
SW5 and SW6 are opened, SW2 is connected to the discharger 3, the third switch SW3 is connected to the discharger 3, and SW4 is temporarily connected to the discharge voltage control circuit 9.

In this state, a signal is outputted from the current setting circuit 1 to the discharger 3 and the discharger 3 outputs the signal to the test cell 15.
Is subjected to a constant current discharge of a predetermined value (a current flows in a direction opposite to that during charging as shown in FIG. 4), the voltage (charging voltage) of the test cell 15 gradually decreases with time.
This voltage change is detected by the voltage detector 5 and stored as a digital signal in the voltage waveform RAM 7 through the A / D conversion circuit 6.

The test cell is detached from the evaluation device, and as shown in FIG. 5, a working electrode 16a containing a binder, a conductive material, and a counter electrode 16 excluding an active material previously charged by the charger 2.
The blank cell 16 having b and the reference electrode 16c is connected in the same manner as the test cell. The second switch SW2 is opened, and the sixth switch SW6 is connected to the discharger 3 side.

In this state, when the voltage waveform signal stored from the voltage waveform RAM 7 is output to the discharge voltage control circuit 9, and a control signal is output from the discharge voltage control circuit 9 to the discharge device 3, In step 3, the blank cell 16 is discharged according to the voltage change stored in the RAM 7, that is, the voltage change when the test cell 15 is discharged. The current change at this time is detected by the current detector 10, and A / A
It is stored as a digital signal in the current waveform RAM 14 through the D conversion circuit 13.

As described above, the current change with respect to the discharge time of the blank cell 16 stored in the current waveform RAM 14 is obtained when the test cell 15 is discharged in accordance with the discharge voltage change. It can be regarded as a current change in a blank portion (including a current collector) excluding the active material in the 15 working electrodes.

[0027] Thus, the current based on the current change during discharge of the stored blank cell 16 in the waveform RAM14 seek current integrated value up to a predetermined discharge time of the blank cell 16, which BD _A, the test cell obtains a current integrated value up to the discharge time on the basis of the 15 discharge when the current (constant current), when this and SD _a, the volume of only the active material during operation pole test cells D _a (Ah) are , Can be calculated from the following equation.

D _A = SD _A -BD _{A Further} , the current change when the blank cell 16 stored in the current waveform RAM 14 is discharged and the voltage waveform RAM 7
The blank cell 16 based on the voltage change stored in
Power integrated value up to a predetermined discharge time (A · V · h = W
h) is obtained, and is calculated based on BD _W , the current (constant current) at the time of discharge of the test cell 15 and the voltage change stored in the voltage waveform RAM 7 until the discharge time (A · V · h = Wh), and this is defined as SD _W.
The electric energy D _W (W) of only the active material in the working electrode of the test cell
h) can be calculated from the following equation.

[0029] D _W = According to the capacity evaluation device of the electrode active material according to the present invention as described above SD _W -BD _W, precisely the volume of only the active material in the electrode has been difficult to evaluate ever Therefore, it can greatly contribute to the promotion of the development of the active material involved in the performance improvement of the electrode and the secondary battery.

In the above-described embodiment, one charging means and one discharging means are provided. However, the present invention is not limited to this. For example, the charging means and the discharging means comprise two chargers and two dischargers, respectively. One charger (first charger) is connected to voltage detection means and the other charger (second charger) is connected to voltage waveform storage means for feeding back a storage signal, and the second charger is connected to the current detection means and The current waveform storage means is connected. One of the dischargers (first discharger) is connected to the voltage detection means and the other discharger (second discharger) is connected to the voltage waveform storage means for feeding back a storage signal, and the second discharger is connected to the current detection means. Means and current waveform storage means.

According to such a configuration, a test cell is connected in parallel to the first charger (or the first discharger), and a blank cell is connected in parallel to the second charger (or the second discharger). . In this state, the test cell is charged (or discharged) in the same procedure as described above, and the voltage change at that time is detected and stored in the voltage waveform storage means. The voltage of the second charger (or the second discharger) is controlled through the charge voltage control circuit (or the discharge voltage control circuit) using the storage signal of the voltage waveform storage means, and the blank cell is charged with the charge voltage of the test cell (or the charge voltage of the test cell). Alternatively, charge (or discharge) is performed in accordance with the discharge voltage) to detect a change in current, and stored in the current waveform storage means. Therefore, the first charger (or first discharger)
Detecting and storing a voltage change at the time of charging (or discharging) the test cell, feeding back the stored data to the second charger (or the second discharger), and charging the blank cell by the current waveform storage means. It is possible to continuously measure the current change at the time (or at the time of discharging).

[0032]

As described above in detail, according to the electrode active material capacity evaluation apparatus according to the present invention, the capacity of only the active material in the electrode can be accurately evaluated, which contributes to the performance improvement of the electrode, and eventually the secondary battery. It has remarkable effects such as greatly contributing to the promotion of development of active materials.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an electrode active material capacity evaluation device (state during charging) according to the present invention.

FIG. 2 is a characteristic diagram showing a voltage change when a test cell is charged at a constant current by the capacity evaluation apparatus according to the present invention and a current change when a blank cell is charged by voltage control.

FIG. 3 is a circuit diagram showing a state when a blank cell is charged by the capacity evaluation device of FIG. 1;

FIG. 4 is a circuit diagram showing a state when a test cell is discharged by the capacity evaluation device of FIG. 1;

FIG. 5 is a circuit diagram showing a state when a blank cell is discharged by the capacity evaluation device of FIG. 1;

[Explanation of symbols]

 2 ... charger, 3 ... discharger, 5 ... voltage detector, 7 ... voltage waveform RAM, 8 ... charge voltage control circuit, 9 ... discharge voltage control circuit, 10 ... current detector acid, 14 ... current waveform RAM, 15 ... test cell, 16 ... blank cell.

Claims (7)

[Claims] A voltage detecting means for detecting a voltage change of a cell having a working electrode, a counter electrode, and a reference electrode connected in parallel to the charging means; and detecting a voltage change detected by the voltage detecting means. Memorize sequentially,
A voltage waveform storage unit for feeding the storage signal back to the charging unit; a current detection unit for detecting a current change in a cell having a working electrode, a counter electrode, and a reference electrode connected in parallel to the charging unit; Current waveform storage means for sequentially storing current changes detected by the means, and a test cell having a working electrode in which an electrode layer containing an active material and a binder is carried on a current collector is connected in parallel to the charging means. And
The test cell is charged at a constant current by the charging means, and the voltage change at this time is sequentially stored in the voltage waveform storage means through the voltage detection means, and the current collector carries an electrode layer containing a binder excluding an active material. The blank cell having the working electrode was connected in parallel to the charging means, a storage signal was output from the voltage waveform storage circuit to the charging means, and the charging means stored the blank cell in the voltage waveform storage circuit. An apparatus for evaluating the capacity of an electrode active material, wherein the battery is charged according to a voltage change, and the current change at this time is sequentially stored in the current waveform storage means through the current detection means. 2. The battery charger according to claim 1, wherein the test cell and the blank cell are sequentially attached to and detached from the charger in parallel to perform voltage detection and current detection. The capacity evaluation device for an electrode active material according to claim 1. 3. The charging means comprises two chargers, one of which is connected to the voltage detection means and the other of the voltage waveform storage means for feeding back a storage signal to the other charger, and the other charging means. 2. An apparatus for evaluating the capacity of an electrode active material according to claim 1, wherein said current detecting means and said current waveform storing means are connected to a detector. 4. The capacity evaluation apparatus for an electrode active material according to claim 1, wherein the discharging means is provided so as to be switchable with respect to the charging means by a switching means. 5. A discharging unit, a voltage detecting unit for detecting a voltage change of a cell having a working electrode, a counter electrode and a reference electrode connected in parallel to the discharging unit, and a voltage change detected by the voltage detecting unit. Memorize sequentially,
A voltage waveform storage unit for feeding the storage signal back to the discharge unit; a current detection unit for detecting a change in the current of a cell having a working electrode, a counter electrode, and a reference electrode connected in parallel to the discharge unit; A current waveform storage means for sequentially storing current changes detected by the means, and a test cell having a working electrode in which an electrode layer containing an active material and a binder is carried on a current collector is connected in parallel to the discharge means. And
The test cell is discharged at a constant current by the discharging means, and the voltage change at this time is sequentially stored in the voltage waveform storing means through the voltage detecting means, and the current collector carries an electrode layer including a binder excluding an active material. The blank cell having the working electrode was connected in parallel to the discharge means, a storage signal was output from the voltage waveform storage circuit to the discharge means, and the discharge means stored the blank cell in the voltage waveform storage circuit. A capacity evaluation device for an electrode active material, characterized in that discharge is performed in accordance with a voltage change, and the current change at this time is sequentially stored in the current waveform storage means through the current detection means. 6. The discharge means comprises a single discharger, wherein the test cell and the blank cell are sequentially attached to and detached from the discharger in parallel to perform voltage detection and current detection. The capacity evaluation device for an electrode active material according to claim 4. 7. The discharge means comprises two dischargers. One discharger is connected to the voltage detection means and the other discharger is connected to the voltage waveform storage means for feeding back a storage signal, and the other discharger is connected to the other discharger. 5. An apparatus according to claim 4, wherein said current detection means and said current waveform storage means are connected to an electric appliance.