JP2018092790A - Method for manufacturing lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a battery, which makes it possible to determine whether or not a battery property is good in a range of a second battery voltage V2 to a third battery voltage V3 (V3<V2≤V) under the condition of an environment temperature Ts (Ts≤0°C), and which eliminates the need for lowering a battery voltage to a third battery voltage V3 to perform a confirmatory test.SOLUTION: A method for manufacturing a lithium ion secondary battery 1 comprises: an initially charging step S2; an aging step S3; a first decrease measurement step S5 of measuring a first voltage decrease ΔVa under the condition of an environment temperature Ts; a second decrease estimation step S6 of estimating a second voltage decrease ΔVb; an amount-of-electricity calculation step S7 of calculating an electricity amount Qa charged into the battery 1 until reaching a fourth battery voltage V4 from a third battery voltage V3 in the initially charging step S2; and a determination step S8 of determining that the battery 1 is a conforming article if the second voltage decrease ΔVb is equal to or lower than a reference decrease ΔVs and the electricity amount Qa is equal to or higher than a reference electricity amount Qs.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method of manufacturing a lithium ion secondary battery including an inspection process for confirming the quality of a lithium ion secondary battery in a low temperature environment of 0 ° C. or lower.

Lithium ion secondary batteries for automotive use (hereinafter also simply referred to as “batteries”) are used even in harsh temperature environments, so it is necessary to perform battery performance tests under various temperature environments before shipment. . For example, in a low temperature environment of 0 ° C. or lower (for example, under an environmental temperature of Ts = −30 ° C.), a low battery voltage region having a battery voltage V ₄₀ or lower corresponding to SOC ₄₀ % (for example, the second battery voltage V2 = 3). There is a case where it is desired to check whether or not the battery output can be obtained in the range of .55V to the third battery voltage V3 = 2.70V (between 1.5 seconds and 100 W).
In addition, patent document 1 is mentioned as a related prior art.

JP 2013-084508 A

  When performing the battery output test described above, for example, the battery is initially charged to SOC 100%, left at high temperature for aging, and then the battery is discharged to obtain the battery voltage Ve as the second battery voltage V2 = 3.55 V (SOC30 %). Thereafter, as shown in FIG. 4, the battery is discharged at a current value of 100 W / 3.55 V = 28.2 A at an environmental temperature of Ts = −30 ° C. for a discharge time te = 1.5 seconds. When the battery voltage Ve at the end of discharge (discharge time te = 1.5 seconds) is equal to or higher than the third battery voltage V3 = 2.70 V, the battery is determined to be non-defective. In FIG. 4, since the battery voltage Ve at the end of the discharge is about 2.80 V, this battery is determined to be a non-defective product.

  However, as described above, when the battery output inspection is performed in a state where the battery voltage Ve (SOC) is lowered, the battery is then recharged to, for example, SOC 100% and shipped after the state of charge is increased. To do. As described above, the battery output inspection includes a step of discharging the battery to lower the battery voltage Ve before the battery output inspection, and a step of increasing the battery voltage Ve by recharging the battery after the battery output inspection. Since it is necessary, there exists a subject that inspection time becomes long.

The present invention has been made in view of such a situation, and the second battery voltage V2 to the third battery voltage V3 (less than the battery voltage V40 corresponding to SOC ₄₀ % under an environmental temperature Ts (Ts ≦ 0 ° C.) ( V3 <V2 ≦ V ₄₀ ) A method for producing a lithium ion secondary battery that can confirm the quality of the battery in the range of V3 <V2 ≦ V ₄₀ ) and can perform this confirmation inspection without lowering the battery voltage Ve to the third battery voltage V3. The purpose is to provide.

One aspect of the present invention to solve the above problems, the constant current constant voltage (CCCV) charging, to the initial charging to the first battery voltage V1 above the battery voltage V ₆₀ corresponding lithium ion secondary battery to SOC 60% At the same time, after the initial charging step for obtaining the relationship between the charging time tc and the battery voltage Ve in the initial charging, and after the initial charging step, the lithium ion secondary is used under an environmental temperature Tage (where Tage = 40 to 85 ° C.). In the aging step of leaving the secondary battery, and when the lithium ion secondary battery is discharged at the first current value Ia, the battery voltage Ve rapidly decreases due to the internal resistance of the battery immediately after the start of discharge, Thereafter, the battery voltage Ve has a characteristic of gradually decreasing, and the voltage rapid decrease period from the start of the discharge to the end of the rapid decrease of the battery voltage Ve is defined as a predetermined time ta (seconds). After the aging step, the lithium ion secondary battery is discharged at the first current value Ia for the predetermined time ta at an environmental temperature Ts (where Ts ≦ 0 ° C.), When the lithium ion secondary battery is discharged at the second current value Ib over the predetermined time ta from the first reduction amount measurement step for measuring one voltage reduction amount ΔVa and the measured first voltage reduction amount ΔVa. The second charge amount estimation step for estimating the second voltage drop amount ΔVb generated before and after the discharge, and the charge in the initial charge acquired in the initial charge step in advance after the second decrease amount estimation step. time using the relationship between tc and the battery voltage Ve, in the first charging step, the third battery voltage V3 of the battery voltage V ₄₀ below corresponding to SOC 40%, the battery voltage V ₄₀ below the second battery voltage V From to fourth battery voltage minus the second voltage reduction amount ΔVb V4 (= V2-ΔVb) ( where, V3 <V4 <V2 ≦ V 40 <V 60 ≦ V1), the charging to the lithium ion secondary battery An electric quantity calculating step for calculating the electric quantity Qa, the second voltage drop quantity ΔVb is equal to or less than a reference drop quantity ΔVs (ΔVb ≦ ΔVs), and the electric quantity Qa is equal to or greater than a reference quantity of electricity Qs (Qa ≧ Qs), a determination process for determining the lithium ion secondary battery as a non-defective product is a method for manufacturing a lithium ion secondary battery.

According to the above-described method for manufacturing a lithium ion secondary battery, after performing the initial charging step and the aging step, the first reduction amount measuring step is performed without discharging the battery and lowering the battery voltage Ve to the second battery voltage V2. The first voltage drop amount ΔVa is measured as described above. Thereafter, in the second decrease amount estimation step, the second voltage decrease amount ΔVb is estimated from the measured first voltage decrease amount ΔVa as described above.
Further, in the first charging step performed previously, the third battery is used by using the relationship between the second voltage drop amount ΔVb and the charging time tc and the battery voltage Ve obtained in the initial charging step in advance. voltage V3~ fourth battery voltage V4 (= V2-ΔVb) until the (V3 <V4 <V2 ≦ V 40 <V 60 ≦ V1), the electric quantity Qa charged in the battery, calculated after the second decrease amount estimation step (Electric quantity calculation step).

In the determination step, if the second voltage drop amount ΔVb is equal to or less than the reference drop amount ΔVs (ΔVb ≦ ΔVs) and the amount of electricity Qa is equal to or greater than the reference amount of electricity Qs (Qa ≧ Qs), the battery is determined to be a good product. Is determined. This determination process, as will be described later, ambient temperature Ts (Ts ≦ 0 ℃) under a second battery voltage below the battery voltage V ₄₀ corresponding to SOC40% V2~ third battery voltage V3 (V3 <V2 ≦ V ₄₀ ), The quality of the battery can be determined.

Moreover, in the above-described method for manufacturing a lithium ion secondary battery, the first reduction amount measurement step, the second reduction amount estimation step, the electric quantity calculation step, and the determination step are performed without reducing the battery voltage Ve to the third battery voltage V3. It can be carried out. That is, without lowering the battery voltage Ve to the third battery voltage V3, environment temperature Ts, check the quality of the characteristics of the battery in the range of the second battery voltage V2~ third battery voltage _{V3 (V3 <V2 ≦ V 40} ) it can.

The positive electrode active material of the “lithium ion secondary battery” is preferably a lithium transition metal composite oxide, and further includes nickel (Ni), manganese (Mn), and cobalt (Co) as transition metals. Lithium nickel manganese cobalt composite oxide is preferable. Further, the negative electrode active material is preferably a carbon material, and more preferably graphite.
The “initial charging step” is preferably performed at room temperature (25 ± 5 ° C.).
The “environmental temperature Ts” which is 0 ° C. or lower is preferably −40 to −10 ° C., more preferably −40 to −20 ° C.

The “first battery voltage V1” which is a battery voltage V ₆₀ or higher corresponding to SOC 60% is preferably a battery voltage V ₈₀ or higher corresponding to SOC ₈₀ %, and further a battery voltage V ₉₀ or higher corresponding to SOC ₉₀ %. Is preferable. “First battery voltage V1” is preferably set to a value close to the upper limit SOC which is the upper limit in the SOC range in which the battery is actually used. On the other hand, when the battery is actually used by being mounted on a vehicle (plug-in hybrid car, electric vehicle, etc.) or a battery-equipped device (personal computer, mobile phone, electric tool, etc.), the upper limit SOC is, for example, SOC100. This is because there are many cases where the SOC is 80% or more, and further, the SOC is 90% or more.
SOC40 is battery voltage V ₄₀ below corresponding to% "second battery voltage V2 'is preferably equal to the battery voltage V ₃₅ below, which corresponds to SOC35%. “Second battery voltage V2” is preferably set to a value close to the lower limit SOC which is the lower limit in the SOC range in which the battery is actually used. On the other hand, when the battery is mounted and actually used in the above-described vehicle or battery-equipped device, the lower limit SOC is often set to SOC 35% or less, such as SOC 0%.

The “first current value Ia” is preferably 0.5 C to 10 C, and more preferably 2 C to 5 C.
The “second current value Ib” is preferably 2C to 10C, and more preferably 4C to 7C.

1 is a perspective view of a lithium ion secondary battery according to an embodiment. It is a longitudinal cross-sectional view of the lithium ion secondary battery which concerns on embodiment. It is a flowchart which shows the manufacturing process of the lithium ion secondary battery which concerns on embodiment. The graph which shows the relationship between the discharge time te and battery voltage Ve when discharging the lithium ion secondary battery adjusted to battery voltage Ve = 3.55V over 1.5 second under environmental temperature of Ts = -30 degreeC. It is. Discharge time te and voltage drop when a lithium ion secondary battery adjusted to battery voltage Ve = 3.90V or Ve = 3.50V is discharged for 0.2 seconds at an environmental temperature of Ts = −30 ° C. It is a graph which shows the relationship with (DELTA) V. Discharge time te and battery voltage Ve when a lithium ion secondary battery adjusted to battery voltage Ve = 3.55 V was discharged for 1.5 seconds at an environmental temperature of Ts = 20 ° C. or Ts = −30 ° C. It is a graph which shows the relationship. It is a graph which shows the relationship between the electric current value I discharged in the 1st fall amount measurement process, and the voltage fall amount (DELTA) V.

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are a perspective view and a longitudinal sectional view of a lithium ion secondary battery (hereinafter also simply referred to as “battery”) 1 according to the present embodiment. In the following description, the battery thickness direction BH, the battery lateral direction CH, and the battery vertical direction DH of the battery 1 are defined as the directions shown in FIGS. 1 and 2.
The battery 1 is a rectangular and sealed lithium ion secondary battery mounted on a vehicle such as a hybrid car, a plug-in hybrid car, or an electric car. The battery 1 includes a battery case 10, an electrode body 20 accommodated therein, a positive terminal member 50 and a negative terminal member 60 supported by the battery case 10, and the like. In addition, an electrolytic solution 17 is accommodated in the battery case 10, and a part thereof is impregnated in the electrode body 20.

  Among these, the battery case 10 has a rectangular parallelepiped box shape and is made of metal (in this embodiment, aluminum). The battery case 10 is composed of a bottomed rectangular tube-shaped case main body member 11 that is open only on the upper side, and a rectangular plate-shaped case lid member 13 that is welded in a form that closes the opening of the case main body member 11. The A positive terminal member 50 made of aluminum is fixed to the case lid member 13 while being insulated from the case lid member 13. The positive electrode terminal member 50 is connected to the positive electrode plate 21 of the electrode body 20 in the battery case 10 to be conductive, and extends through the case lid member 13 to the outside of the battery. Further, a negative electrode terminal member 60 made of copper is fixed to the case lid member 13 while being insulated from the case lid member 13. The negative electrode terminal member 60 is connected to and conductive with the negative electrode plate 31 of the electrode body 20 in the battery case 10, and extends through the case lid member 13 to the outside of the battery.

  The electrode body 20 has a flat shape and is accommodated in the battery case 10 in a laid-down state. Between the electrode body 20 and the battery case 10, a bag-shaped insulating film enclosure 19 made of an insulating film is disposed. The electrode body 20 includes a belt-like positive electrode plate 21 and a belt-like negative electrode plate 31 that are overlapped with each other via a pair of separators 41 and 41 made of a resin-made porous film and wound around an axis to be flat. Compressed. The positive electrode plate 21 is provided with a positive electrode active material layer in a band shape at predetermined positions on both main surfaces of a positive electrode current collector foil made of a band-shaped aluminum foil. The positive electrode active material layer includes a positive electrode active material (lithium transition metal composite oxide in this embodiment, specifically lithium nickel manganese cobalt composite oxide), a conductive material (acetylene black in this embodiment), and a binder ( In the present embodiment, it is made of polyvinylidene fluoride). Moreover, the negative electrode plate 31 is provided with a negative electrode active material layer in a strip shape at predetermined positions on both main surfaces of a negative electrode current collector foil made of a strip-shaped copper foil. This negative electrode active material layer is composed of a negative electrode active material (carbon material in the present embodiment, specifically graphite), a binder (styrene butadiene rubber in the present embodiment), and a thickener (carboxymethyl cellulose in the present embodiment). Become.

  Next, a method for manufacturing the battery 1 will be described (see FIG. 3). First, in the “assembly process S1”, the battery 1 is assembled. Specifically, the positive electrode plate 21 and the negative electrode plate 31 are overlapped with each other via a pair of separators 41 and 41 and wound into a flat shape to form the electrode body 20. Next, the case lid member 13 is prepared, and the positive electrode terminal member 50 and the negative electrode terminal member 60 are fixed thereto (see FIGS. 1 and 2). Thereafter, the positive electrode terminal member 50 and the negative electrode terminal member 60 are welded to the positive electrode plate 21 and the negative electrode plate 31 of the electrode body 20, respectively. Next, the electrode body 20 is covered with the insulating film enclosure 19, and these are inserted into the case main body member 11, and the opening of the case main body member 11 is closed with the case lid member 13. The case body member 11 and the case lid member 13 are welded to form the battery case 10. Thereafter, the electrolytic solution 17 is injected into the battery case 10 through the injection hole 13 h and impregnated in the electrode body 20. Thereafter, the injection hole 13 h is sealed with the sealing member 15.

  Next, the battery 1 is restrained prior to performing the “initial charging step S2”. Specifically, the side surface 10c, 10c having the largest area of the battery case 10 is sandwiched in the battery thickness direction BH by a pair of plate-shaped pressing jigs (not shown), and the battery 1 is pressed in the battery thickness direction BH. Restrain with. In the present embodiment, the process from the “initial charging step S2” to the “first reduction amount measuring step S5” described below is performed in a state where the battery 1 is thus restrained.

After the battery 1 is restrained, the battery 1 is initially charged in the “initial charging step S2”. Specifically, by connecting a charging / discharging device to the battery 1 and charging at a constant current and constant voltage (CCCV) at room temperature (25 ± 5 ° C.), the battery voltage V ₆₀ or more corresponding to SOC 60% or more, SOC 80 % to the corresponding battery voltage V ₈₀ above, further to the initial charge of the battery 1 to the first battery voltage V1 = 4.10 V is the battery voltage V ₉₀ or more, which corresponds to SOC90%. Incidentally, the first battery voltage V1 = 4.10V = V ₁₀₀ is a battery voltage V ₁₀₀ when the SOC 100%. In the present embodiment, the battery voltage Ve is charged at a constant current of 4C = 20.0A until the battery voltage Ve reaches the first battery voltage V1 = 4.10V, and then the first current is charged until the charge current value becomes 0.2C = 1.0A. 1 Battery voltage V1 was maintained at 4.10V. During the initial charging in the initial charging step S2, the battery voltage Ve is measured every 0.1 seconds, and the relationship between the charging time tc and the battery voltage Ve in the initial charging is acquired.

  Next, in the “aging step S3”, the battery 1 is left to age under an environmental temperature Tage of 40 to 85 ° C. Specifically, the battery 1 after the initial charge is aged by leaving it to stand for 20 hours with the terminal open at an environmental temperature Tage = 63 ° C.

  Next, in the “short circuit detection step S4”, the battery 1 is left to be discharged with its terminals open (self-discharged), and the voltage drop amount ΔVh of the battery voltage Ve being left is measured. Detects whether there is an internal short circuit. Specifically, the battery voltage Vh1 measured after 2.0 days from the end of the aging step S3 (at the start of the short-circuit detection step S4) is left with the terminal opened at a temperature of 20 ° C. Then, a voltage drop amount ΔVh = Vh1−Vh2 is calculated from the battery voltage Vh2 measured after 7.0 days from the end of the aging step S3 (at the start of the short circuit detection step S4).

  Then, the obtained voltage decrease amount ΔVh of the battery 1 is compared with a predetermined reference decrease amount ΔVr. When the voltage decrease amount ΔVh is larger than the reference decrease amount ΔVr (ΔVh> ΔVr), The battery 1 is removed by determining that the short circuit has occurred. On the other hand, when the voltage drop amount ΔVh of the battery 1 is smaller than the reference drop amount ΔVr (ΔVh ≦ ΔVr), the battery 1 is determined to be a good product without an internal short circuit, and the next “first drop amount measurement step S5” is performed. "I do.

In the subsequent “first reduction amount measurement step S5” to “determination step S8”, the battery voltage corresponding to ₄₀ % SOC or less, and further the battery corresponding to 35% SOC, in a low temperature environment with an environmental temperature Ts = −30 ° C. in the region of the voltage V ₃₅ or lower battery voltage (range of the second battery voltage V2 = 3.55V~ third battery voltage V3 = 2.70V), the battery output is the reference or more (1.5 seconds, 100W or higher) in It is confirmed by a substitute inspection without discharging the battery 1 to the low battery voltage region.
That is, originally, as described above (see FIG. 4), the battery 1 adjusted to the second battery voltage V2 = 3.55 V (SOC 30%) is set to 100 W / 30 at an environmental temperature of Ts = −30 ° C. A discharge time te = 1.5 seconds is discharged at a current value of 3.55V = 28.2 A (second current value Ib described later). When the battery voltage Ve at the end of discharge (discharge time te = 1.5 seconds) is equal to or higher than the third battery voltage V3 = 2.70 V, the battery 1 is determined to be non-defective.
On the other hand, in the present embodiment, the battery output inspection described above is substituted by performing the following “first reduction amount measurement step S5” to “determination step S8”. Thereby, the quality of the battery 1 can be determined without lowering the battery voltage Ve to the second battery voltage V2 = 3.55 V (SOC 30%).

  First, in the “first reduction amount measurement step S5”, the battery 1 is discharged at a first current value Ia for a predetermined time ta under an environmental temperature Ts of 0 ° C. or less, and a first voltage reduction amount before and after the discharge. ΔVa is measured. Specifically, a charging / discharging device is connected to the battery 1, and the battery 1 is set to a first current value Ia = 0.5C to 10C, and further within a range of 2C to 5C at an environmental temperature Ts = −30 ° C. The battery is discharged at 4C (20.0 A) for a predetermined time ta = 0.2 seconds, and the first voltage drop amount ΔVa before and after the discharge is measured. For example, ΔVa = 0.50 V is measured as the first voltage drop amount ΔVa.

When the battery 1 is discharged at the first current value Ia = 4C (20.0 A) (see FIG. 4), the battery voltage Ve rapidly decreases due to the internal resistance of the battery 1 immediately after the discharge starts, and thereafter The battery voltage Ve gradually decreases. The predetermined time ta = 0.2 seconds described above is a voltage rapid decrease period from the start of discharge until the rapid decrease of the battery voltage Ve ends. FIG. 4 is a graph when the battery 1 is discharged at the second current value Ib = 28.2A as described above, but when the battery 1 is discharged at the first current value Ia = 20.0A, FIG. A graph having the same shape as that shown in FIG. 6 is obtained, and it is known from the graph that the voltage rapid decrease period is 0.2 seconds.
In addition, after finishing 1st fall amount measurement process S5, the restraining jig | tool which restrains the battery 1 is removed, and the restraint state of the battery 1 is cancelled | released.

Next, in the “second reduction amount estimation step S6”, the battery 1 is within the range of 2C to 10C, further 4C to 7C, from the first voltage reduction amount ΔVa obtained in the first reduction amount measurement step S5. When the second current value Ib = 5.64C (28.2A) is discharged for the predetermined time ta = 0.2 seconds, the second voltage drop amount ΔVb generated before and after the discharge is estimated.
FIG. 7 shows the relationship between current value I and voltage drop amount ΔV when battery 1 is discharged for a predetermined time ta = 0.2 seconds using non-defective battery 1 having average characteristics. From the slope of this approximate line (−0.0124), it can be seen that the voltage drop amount ΔV per 1 A of the discharge current value is 0.0124 V / A.

Therefore, by using the following equation (1), when discharging at the second current value Ib = 28.2A from the first voltage drop amount ΔVa when discharging at the first current value Ia = 20.0A: The second voltage drop amount ΔVb can be estimated.
ΔVb = 0.0124 (Ib−Ia) + ΔVa (1)
For example, if the first voltage drop amount ΔVa = 0.50 V as described above, the second voltage drop amount ΔVb is ΔVb = 0.124 (28.2-20.0) + 0.50 = 0. Estimated to be 60V.

  Here, the relationship between the magnitude of the battery voltage Ve before the start of discharge and the magnitude of the voltage drop amount ΔV due to discharge will be described. For the battery 1 adjusted to the battery voltage Ve = 3.90V and the battery 1 adjusted to the battery voltage Ve = 3.50V, respectively, the environmental current Ts = −30 ° C. and the second current value Ib = 28.2A. FIG. 5 shows the relationship between the discharge time te and the voltage drop amount ΔV when discharging for a predetermined time ta = 0.2 seconds.

  As apparent from the graph of FIG. 5, the voltage drop amount ΔV during the period from the discharge time te to 0 to 0.2 seconds is the battery 1 with the battery voltage Ve = 3.90V and the battery voltage Ve = 3.50V. It can be seen that there is almost no difference with the battery 1. That is, it can be seen that during the period from 0 to 0.2 seconds of the discharge time te, the magnitude of the voltage drop ΔV due to discharge is substantially constant regardless of the magnitude of the battery voltage Ve before the start of discharge. Accordingly, in obtaining the first voltage drop amount ΔVa and the second voltage drop amount ΔVb (after the short circuit detection step S4 and before the first drop amount measurement step S5), the battery voltage Ve is set to the second battery voltage V2 = 3. There is no need to reduce the voltage to 55 V, and the first reduction amount measurement step S5 can be performed while the battery voltage Ve after the short-circuit detection step S4 remains high.

Next, in the “electricity calculation step S7”, using the “relationship between the charging time tc in the initial charging and the battery voltage Ve” acquired in the initial charging step S2, the SOC 40 in the initial charging step S2 is obtained. % from the third battery voltage V3 = 2.70V cell voltage V ₄₀ below corresponding to fourth battery by subtracting the second voltage reduction amount ΔVb from the battery voltage V ₄₀ below the second battery voltage V2 = 3.55 V The amount of electricity Qa charged in the battery 1 up to the voltage V4 (= V2−ΔVb) is calculated.

  For example, as described above, if the second voltage drop amount ΔVb = 0.60 V, the battery voltage Ve is changed from the third battery voltage V3 = 2.70 V to the fourth battery voltage V4 = V2 in the initial charging step S2. The amount of electricity Qa charged in the battery 1 is calculated until −ΔVb = 3.55−0.60 = 2.95V. First, from the “relationship between the charging time tc and the battery voltage Ve in the initial charging”, the time tg required for the battery voltage Ve to change from the third battery voltage V3 = 2.70V to the fourth battery voltage V4 = 2.95V. (Hr) is obtained. In the initial charging step S2, since charging is performed at a constant current of 20.0 A as described above, from the third battery voltage V3 = 2.70V to the fourth battery voltage V4 = 2.95V. The amount of electricity Qa stored in the battery 1 is calculated by Qa = 20.0 × tg (Ahr).

Here, the relationship between the environmental temperature Ts at the time of discharge and the battery voltage Ve will be described. When the battery 1 adjusted to the battery voltage Ve = 3.55 V is discharged for 1.5 seconds at the second current value Ib = 28.2 A under the environmental temperature of Ts = 20 ° C. or Ts = −30 ° C. The relationship between the discharge time te and the voltage drop amount ΔV is shown in FIG.
As is clear from the graph of FIG. 6 (see the portion surrounded by the alternate long and short dash line in FIG. 6), the change amount (decrease amount) of the battery voltage Ve during the discharge time te is 0.2 to 1.5 seconds. It can be seen that there is almost no difference between the case where the environmental temperature is Ts = 20 ° C. and the case where Ts = −30 ° C. That is, it can be seen that the amount of decrease in the battery voltage is substantially constant regardless of the environmental temperature during the period from the discharge time te to 0.2 to 1.5 seconds. Therefore, it is not necessary to set the environmental temperature to Ts = −30 ° C. in obtaining the electric quantity Qa, and the data of the initial charging process performed at room temperature can be used as described above.

Next, in the “determination step S8”, the second voltage decrease amount ΔVb obtained in the second decrease amount estimation step S6 is compared with a predetermined reference decrease amount ΔVs, and the second voltage decrease amount ΔVb is compared with the reference decrease amount ΔVs. Is greater than (ΔVb> ΔVs), the battery 1 is determined to be defective.
Further, the electric quantity Qa (Ahr) obtained in the electric quantity calculation step S7 is compared with a predetermined reference electric quantity Qs (Ahr), and when the electric quantity Qa is smaller than the reference electric quantity Qs (Qa <Qs). The battery 1 is determined as a defective product. In this embodiment, the reference electric quantity Qs is 100 W / V3 = 100 W / 2.70 V = 37.0 A, and the electric quantity when discharging for 1.5 seconds−0.2 seconds = 1.3 seconds = It was set to 37.0 * 1.3 / 3600 = 0.134Ahr.

On the other hand, when the second voltage drop amount ΔVb is smaller than the reference drop amount ΔVs (ΔVb ≦ ΔVs) and the amount of electricity Qa is larger than the reference amount of electricity Qs (Qa ≧ Qs), the battery 1 is regarded as a good product. judge. As a result, as will be described later, the battery 1 in the state of the second battery voltage V2 = 3.55 V is discharged at 100 W / 3.55 V = 28.2 A for 1.5 seconds at an environmental temperature of Ts = −30 ° C. It is considered that it is possible to ensure that the battery voltage Ve after discharge is equal to or higher than the third battery voltage V3 = 2.70V.
Thus, the battery 1 is completed.

The determination step (.DELTA.Vb ≦ .DELTA.Vs and,, Qa ≧ Qs) by, Ts = -30 ° C. under an environment temperature, the battery voltage V ₄₀ below the second battery voltage V2 = 3.55V~ third battery voltage V3 = 2 The reason why the quality of the battery 1 in the range of 70 V can be judged is considered to be as follows.
That is, as described above, the second battery voltage V2 = 3.55 V to the third battery voltage V3 = 2.70 V at the second current value Ib = 28.2 A under the environmental temperature of Ts = −30 ° C. When the battery output inspection in the range is performed, the relationship between the discharge time te and the battery voltage Ve is as shown in the graph of FIG. That is, immediately after the start of discharge, the battery voltage Ve rapidly decreases due to the internal resistance of the battery 1, and then the battery voltage Ve gradually decreases.

  In this graph, a section where the discharge time te is 0 to 0.2 seconds is a rapid voltage drop period from the start of discharge until the rapid drop of the battery voltage Ve ends. During this period, the battery voltage Ve is the second battery. The voltage V2 decreases from 3.55V to 2.95V. The voltage drop amount ΔVc = 3.55V−2.95V = 0.60V during this voltage rapid drop period is mainly the amount of voltage drop caused by the internal resistance of the battery 1 at the environmental temperature Ts = −30 ° C. Conceivable.

In the manufacturing method of the battery 1 of the present embodiment, the first reduction amount measurement step S5 and the second reduction amount estimation step S6 are performed, and the battery 1 is connected to the second current value Ib = 28 at the ambient temperature Ts = −30 ° C. The second voltage drop amount ΔVb is estimated when discharging is performed for a predetermined time ta = 0.2 seconds at .2A. As described above (see FIG. 5), it is known that the second voltage drop amount ΔVb does not depend on the value of the battery voltage Ve before the start of discharge. Therefore, in the state where the battery voltage Ve after the short circuit detection step S4 is high, the first decrease amount measurement step S5 is performed to measure the first voltage decrease amount ΔVa, and further in the second decrease amount estimation step S6, the second voltage decrease amount ΔVb. Is calculated, the second voltage drop amount ΔVb is substantially the same value as the voltage drop amount ΔVc = 0.60 V described above when the discharge is actually performed from the second battery voltage V2 = 3.55V.
In the determination step S8, since it is determined whether or not the second voltage drop amount ΔVb is equal to or less than the reference drop amount ΔVs (ΔVb ≦ ΔVs), the second battery voltage V2 = 3.55V to the fourth battery voltage V4. It is considered that the quality of the battery in the range of the second voltage drop amount ΔVb = 0.60 V up to 2.95V (substantially the same as the above-described voltage drop amount ΔVc) can be determined.

  On the other hand, in the graph of FIG. 4, when the discharge time te is 0.2 seconds or later, the battery voltage Ve gradually decreases from the fourth battery voltage V4 = 2.95V at an almost constant rate. The voltage drop amount ΔVd after the discharge time te = 0.2 seconds is considered to be a voltage drop amount mainly due to a decrease in the amount of electricity Qa stored in the battery 1 due to discharge.

In the manufacturing method of the battery 1 of the present embodiment, the amount of electricity Qa charged in the battery 1 is calculated from the third battery voltage V3 = 2.70 V to the fourth battery voltage V4 = 2.95 V in the amount calculation step S7. Calculated. As described above (see FIG. 6), it is known that this quantity of electricity Qa does not depend on the environmental temperature Ts. Therefore, the measurement of the quantity of electricity Qa does not need to be performed at an ambient temperature of Ts = −30 ° C., and the quantity of electricity is utilized by utilizing the relationship between the charging time tc and the battery voltage Ve in the initial charging step S2 performed at room temperature. Qa can be calculated.
Since it is determined whether or not the electric quantity Qa is greater than or equal to the reference electric quantity Qs (Qa ≧ Qs) in the determination step S8, the fourth battery voltage = 2.95V to the third battery voltage V3 = 2.70V. It is considered that the quality of the battery 1 in the range up to this can be determined.

  Therefore, when ΔVb ≦ ΔVs and Qa ≧ Qs are satisfied, the second battery voltage V2 = 3.55V to the fourth battery voltage V4 = 2.95V to the third battery at an environmental temperature of Ts = −30 ° C. It is considered that the quality of the battery 1 can be determined in the range of the voltage V3 = 2.70V.

(Examples and Comparative Examples)
Subsequently, the result of the test conducted in order to verify the effect of this invention is demonstrated. As Example 1, a battery 1 was manufactured by the manufacturing method of the above-described embodiment.
On the other hand, as Comparative Example 1, the battery 1 manufactured in Example 1 was discharged to lower the battery voltage Ve to the second battery voltage V2 = 3.55V. Thereafter, the battery 1 was discharged to a third battery voltage V3 = 2.70 V at a second current value Ib of 100 W / 3.55 V = 28.2 A under an environmental temperature of Ts = −30 ° C. In this discharge, the voltage drop amount ΔVbh at the discharge time te = 0 to 0.2 seconds was measured. In addition, the amount of electricity Qah discharged from the battery 1 was calculated from the time when the discharge time te = 0.2 seconds until the battery voltage Ve reached the third battery voltage V3 = 2.70V.

Then, the second voltage drop amount ΔVb calculated in the second drop amount estimation step S6 in Example 1 is compared with the voltage drop amount ΔVbh measured in Comparative Example 1, and | (ΔVb−ΔVbh) / ΔVbh | From x100 (%), the error of the voltage drop amount ΔV in the discharge time te = 0 to 0.2 seconds of the first example with respect to the first comparative example was obtained. As a result, the error of the voltage drop amount ΔV in the discharge time te = 0 to 0.2 seconds was only 7%.
Further, the electric quantity Qa calculated in the electric quantity calculation step S7 in Example 1 is compared with the electric quantity Qab calculated in Comparative Example 1, and the comparison example is given by | (Qa−Qab) / Qab | × 100. The error of the electric quantity Qa of Example 1 with respect to 1 was obtained. As a result, the error in the amount of electricity Qa was only 1%.
From these results, even when the first reduction amount measurement step S5 to the determination step S8 of Example 1 were performed instead of the method of Comparative Example 1, the environmental temperature of Ts = −30 ° C. was obtained as in Comparative Example 1. Below, it turns out that the quality of the battery 1 in the range of 2nd battery voltage V2 = 3.55V-3rd battery voltage V3 = 2.70V can be confirmed.

In addition, as Example 2, the battery 1 was manufactured by changing the environmental temperature Ts in which the first reduction amount measurement step S5 is performed from Ts = −30 ° C. to Ts = −10 ° C. in the above-described embodiment. Other than that, it was the same as the embodiment.
On the other hand, as Comparative Example 2, in Comparative Example 1 described above, the environmental temperature Ts during discharge was changed from Ts = −30 ° C. to Ts = −10 ° C. Otherwise, it was the same as Comparative Example 1.

Then, as described above, the second voltage drop amount ΔVb calculated in the second drop amount estimation step S6 of the second embodiment is compared with the voltage drop amount ΔVbh measured in the second comparative example. The error of the voltage drop amount ΔV in the discharge time te = 0 to 0.2 seconds in Example 2 was obtained. As a result, the error of the voltage drop amount ΔV in the discharge time te = 0 to 0.2 seconds was only 7%.
Further, as described above, the electric quantity Qa calculated in the electric quantity calculation step S7 of Example 2 is compared with the electric quantity Qab calculated in Comparative Example 1, and the electric quantity of Example 2 relative to Comparative Example 2 is compared. The Qa error was determined. As a result, the error in the amount of electricity Qa was only 2%.
From these results, even when the environmental temperature Ts is changed to Ts = −10 ° C., instead of the method of the comparative example 2, the first reduction amount measurement step S5 to the determination step S8 of the example 2 is performed. As in Example 2, it can be seen that the quality of the battery 1 can be confirmed in the range of the second battery voltage V2 = 3.55 V to the third battery voltage V3 = 2.70 V under an environmental temperature of Ts = −10 ° C.

As described above, in the manufacturing method of the battery 1, after performing the initial charging step S2, the aging step S3, and the short circuit detection step S4, the battery 1 is discharged and the battery voltage Ve is set to the second battery voltage V2 = 3. The first voltage drop amount ΔVa is measured as described above in the first drop amount measurement step S5 while the battery voltage Ve is kept high without being lowered to 55V. Thereafter, in the second decrease amount estimation step S6, the second voltage decrease amount ΔVb is estimated from the measured first voltage decrease amount ΔVa as described above.
Further, using the relationship between the second voltage drop amount ΔVb and the charging time tc and the battery voltage Ve obtained in the initial charging step S2 in advance, The amount of electricity Qa charged in the battery 1 from 3 battery voltage V3 = 2.70 V to 4th battery voltage V4 = 2.95 V is calculated after the second reduction amount estimating step S6 (electric amount calculating step S7).

In the determination step S8, when the second voltage decrease amount ΔVb is equal to or less than the reference decrease amount ΔVs and the amount of electricity Qa is equal to or greater than the reference amount of electricity Qs, the battery 1 is determined to be a non-defective product. By this determination step S8, as described above, under the environmental temperature Ts (Ts ≦ 0 ° C.), the second battery voltage V2 equal to or lower than the battery voltage V40 corresponding to SOC ₄₀ % = 3.55V to the third battery voltage V3 = 2. The quality of the battery 1 in the range of .70 V can be determined.

  Moreover, in the manufacturing method of the battery 1, the first decrease amount measurement step S5, the second decrease amount estimation step S6, the electric amount calculation step S7, and the determination step S8 are performed, and the battery voltage Ve is changed to the third battery voltage V3 = 2.70V. Can be done without lowering. That is, without lowering the battery voltage Ve to the third battery voltage V3, the battery 1 in the range of the second battery voltage V2 = 3.55V to the third battery voltage V3 = 2.70V at the ambient temperature Ts = −30 ° C. The quality of the characteristics can be confirmed.

In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.
For example, in the embodiment, the initial charging step S2 to the second decrease amount estimation step S6 are performed in a state where the battery 1 is restrained, but these steps S2 to S6 can be performed without restraining the battery 1. .

1 Lithium ion secondary battery (battery)
S2 Initial charging step S3 Aging step S5 First reduction amount measurement step S6 Second reduction amount estimation step S7 Electricity amount calculation step S8 Determination step Ve Battery voltage V1 First battery voltage V2 Second battery voltage V3 Third battery voltage V4 Fourth Battery voltage V ₄₀ (corresponding to SOC ₄₀ %) Battery voltage V ₆₀ (corresponding to SOC 60%) Battery voltage ΔV Voltage drop amount ΔVa First voltage drop amount ΔVb Second voltage drop amount ΔVc Voltage drop amount ΔVd Voltage drop amount Ia First 1 current value Ib second current value tc charge time te discharge time ta predetermined time Tage (performs aging process) environmental temperature Ts (performs first decrease measurement process) environmental temperature Qa electric quantity

Claims (1)

With the constant current and constant voltage (CCCV) charging, the lithium ion secondary battery is initially charged to the first battery voltage V1 equal to or higher than the battery voltage V ₆₀ corresponding to SOC 60%, and the charging time tc and the battery voltage Ve in the initial charging are Initial charging process to acquire the relationship,
After the initial charging step, an aging step in which the lithium ion secondary battery is left under an environmental temperature Tage (where Tage = 40 to 85 ° C.),
When the lithium ion secondary battery is discharged at the first current value Ia, the battery voltage Ve drops rapidly due to the internal resistance of the battery immediately after the start of discharge, and then the battery voltage Ve gradually increases. When the voltage rapid decrease period from the start of discharge to the end of the rapid decrease of the battery voltage Ve is a predetermined time ta (seconds), after the aging step, the environmental temperature Ts (Where Ts ≦ 0 ° C.), the first lithium ion secondary battery is discharged at the first current value Ia for the predetermined time ta, and a first voltage drop ΔVa before and after the discharge is measured. A reduction amount measuring step;
From the measured first voltage drop amount ΔVa, when the lithium ion secondary battery is discharged at the second current value Ib for the predetermined time ta, the second voltage drop amount ΔVb generated before and after the discharge is estimated. A second reduction amount estimation step;
After the second reduction amount estimating step, using the relationship between the charging time tc in the initial charging and the battery voltage Ve acquired in the initial charging step in advance, the initial charging step corresponds to SOC 40%. from the battery voltage V ₄₀ following third battery voltage V3, until the fourth battery voltage minus the second voltage reduction amount .DELTA.Vb from the second battery voltage V2 below the battery voltage _{V 40 V4 (= V2-ΔVb} ) ( However, V3 <V4 <V2 ≦ V 40 <V 60 ≦ V1), the electric quantity calculating step of calculating the quantity of electricity Qa charged in the lithium ion secondary batteries,
When the second voltage drop amount ΔVb is equal to or less than the reference drop amount ΔVs (ΔVb ≦ ΔVs) and the amount of electricity Qa is equal to or greater than the reference amount of electricity Qs (Qa ≧ Qs), the lithium ion secondary battery is A method of manufacturing a lithium ion secondary battery comprising: a determination step for determining that the product is non-defective.

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