JP2013114986A - Secondary battery manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery manufacturing method which can make it possible to detect a short circuit in a secondary battery in a short time.SOLUTION: In the secondary battery manufacturing method, a unit cell 100 which has had its charging finished is heated and subjected to aging in a high temperature environment until a first reference time elapses. After the high temperature aging, a plurality of unit cells to be simultaneously inspected by subsequent aging in a low temperature environment are combined and their battery voltages are equalized. Then, these unit cells 100 are cooled and, after the battery voltages of each unit cell 100 are made uniform, the aging in the low temperature environment (short circuit inspection) is started. Then, after a reference time has elapsed, the battery voltages of each unit cell 100 are measured, and determination of whether each of the unit cells 100 is good or not is made on the basis of the measured values.

Description

  The present invention relates to a method for manufacturing a secondary battery. More specifically, the present invention relates to a technique for inspecting battery performance in the manufacturing process of a secondary battery.

  In recent years, non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries have attracted attention as power sources not only for electronic devices such as portable PCs and mobile phones, but also for hybrid vehicles and electric vehicles. A secondary battery for a vehicle is generally mounted on a vehicle as a battery unit in which a plurality of single cells are connected in series.

  The manufacturing process of the secondary battery described above includes an inspection process for inspecting the battery performance in order to prevent those having inappropriate battery performance from being distributed to the market. As a document disclosing the inspection of battery performance, there is, for example, Patent Document 1. In this Patent Document 1, charging / discharging and aging of the secondary battery to be tested are performed, and further, the voltage of the secondary battery to be tested, the voltage at the time of opening after charging, the voltage at the time of discharging, the voltage at the time of discharging, and the voltage after opening of the circuit It is disclosed that at least one of the open circuit voltages is measured, and if the battery performance predicted from the measured value is within the reference range, it is determined as a non-defective product.

JP 2004-361253 A

However, the conventional technique described above has the following problems. That is, it takes time to inspect the short circuit of the secondary battery. For example, in a lithium ion secondary battery using LiNiCoMnO ₂ fine particles and a conductive material as a positive electrode material and graphite as a negative electrode material, the normal voltage is set to 3.0 V to 4.1 V from the viewpoint of maintaining the performance of the electrode material and the electrolytic solution. Is done. In such a lithium ion secondary battery, in a fully charged state, the potentials of the positive electrode and the negative electrode are near +1.1 V and −3.0 V with respect to the hydrogen reference potential, respectively.

  In the manufacturing process of the lithium ion secondary battery described above, metal foreign matter may be mixed. The metal foreign matter is dissolved or precipitated inside the battery, thereby causing a micro short circuit. Specifically, iron-based and copper-based metals are conceivable as the metal foreign matter, and the ionization tendency is −0.44V and 0.34V, respectively. Therefore, when these metallic foreign matters are mixed in the battery, they are dissolved at the positive electrode and deposited as a metal at the negative electrode, thereby causing a minute short circuit inside the battery. Such a micro short circuit inside the battery can occur even in a battery other than a lithium ion secondary battery.

  In the conventional secondary battery manufacturing process, after the initial charge of the test secondary battery, high temperature aging is performed in which the test secondary battery is stored for a predetermined time in a high temperature environment in order to stabilize the battery reaction. Yes. Then, the secondary battery to be tested is cooled after high temperature aging, and then low temperature aging is performed as a short circuit inspection, which is further stored in a room temperature environment for a predetermined time. Then, the battery voltage value before and after storage at room temperature is measured, and if the voltage change amount is out of the allowable range, it is determined as defective.

  However, the amount of voltage drop due to a short circuit is negligible for a battery with a large capacity. On the other hand, the secondary battery after high-temperature aging has a variation in the voltage drop even if it is a non-defective product due to factors such as variations in the amount of active material applied to the electrode and variations in density. Therefore, in order to clearly distinguish a defective battery that is short-circuited from a non-defective battery, the voltage value immediately after high-temperature aging is measured for each battery, and then long-term low-temperature aging that exceeds 10 days is performed. The voltage value after the measurement is measured, and both measured values are compared to determine whether there is a short circuit.

  The present invention has been made to solve the above-described problems of the prior art. That is, the problem is to provide a method for manufacturing a secondary battery that can be expected to detect a short circuit of the secondary battery in a short time.

  A method for manufacturing a secondary battery for the purpose of solving this problem includes a temperature raising step of raising a temperature of a single battery in a state where initial charging is completed to a first temperature, and after the temperature raising step, A high-temperature aging step for performing aging at the first temperature until a first reference time elapses, and an equalizing step for equalizing battery voltages of the plurality of single cells after the first reference time has elapsed. And a cooling step for cooling the plurality of single cells to a second temperature lower than the first temperature after the equalizing step, and a second reference time after the cooling step. A low temperature aging step of aging the single cells with the second temperature at the second temperature, and a measurement of measuring the battery voltages of the plurality of single cells after the second reference time has elapsed. And step, after said measuring step is characterized by including a determination step of determining good or not to the plurality of unit cells each on the basis of the measured value.

  In the method for manufacturing a secondary battery according to the present invention, the temperature of the unit cell that has been initially charged is increased, and high-temperature aging is performed until the first reference time elapses. After the high temperature aging, a plurality of single cells are combined to equalize the battery voltage. Thereafter, each unit cell is cooled, and low-temperature aging is started for each unit cell in a state where the cell voltages of the unit cells are aligned. Then, after the low temperature aging is completed, the battery voltage of each unit cell is measured, and the quality of each unit cell is determined based on the measured value.

  That is, in the method for manufacturing a secondary battery according to the present invention, before starting a short-circuit inspection by low-temperature aging, the battery voltages that have varied due to high-temperature aging are evenly aligned. For this reason, there is no need for long-term aging until it becomes distinguishable from battery voltage variations due to high-temperature aging as in the past, and even if the amount of self-discharge due to short-circuit is small, It can be expected to distinguish. Therefore, it is possible to shorten the time for the short circuit inspection.

  Further, in the method for manufacturing a secondary battery according to the present invention, after the start of the high temperature aging step and before the start of the equalization step, the cell voltage of the unit cell is measured, and the measured value is within an allowable range as a non-defective product. When it exceeds, it is good to include the exclusion step which excludes the said cell as a defective article. If you attempt to equalize the battery voltage, including defective products that have undergone a significant voltage drop due to high-temperature aging, the amount of discharge of other cells required to charge the defective product will increase, and it will take time to equalize the battery voltage. It takes. Therefore, it is preferable to equalize by excluding defective products.

Moreover, the said determination step is good to determine the said cell as a good product, when the measured value of the said measurement step is in the tolerance | permissible_range as a good product. That is, as the pass / fail judgment, for example, the voltage change amount is calculated by measuring the battery voltage twice, that is, the battery voltage immediately before the start of the low temperature aging and the battery voltage immediately after the end of the low temperature aging, and the voltage change amount is acceptable. Although it may be determined based on whether or not it is within the range, in the present invention, the battery voltage immediately before the start of low-temperature aging is set to a substantially constant voltage value. Therefore, the quality of the unit cell can be determined from the battery voltage after the end of the low temperature aging without acquiring the battery voltage immediately before the start of the low temperature aging. As in this configuration, the number of measurements can be reduced by determining the quality of the unit cell by the battery voltage after the end of the low temperature aging, that is, by measuring the battery voltage once.

  In the low temperature aging step, aging may be performed in a state where the plurality of single cells are constrained. By constraining a plurality of cells in the same manner as in actual use, and by reducing the distance between the positive electrode and the negative electrode of each cell, it is possible to further promote the voltage drop of the cells that are short-circuited.

  In the high temperature aging step, aging may be performed in a state where the unit cell is constrained. By constraining the cell in the same manner as in the actual use state, the battery reaction can be promoted more in line with the actual use state.

  In the equalizing step, the positive electrode of one unit cell and the positive electrode of the other unit cell are electrically connected by a first connecting member, and the negative electrode of the one unit cell and the negative electrode of the other unit cell are connected. Are preferably electrically connected by a second connecting member. With this configuration, each unit cell is connected in parallel, a unit cell with a low battery voltage is charged from another unit cell, and a unit cell with a high battery voltage is discharged to charge another unit cell. As a result, the battery voltages of the single cells connected to the first and second connection members can be equalized.

  In the equalizing step, a resistor may be connected to at least one of the first connection member and the second connection member. With this configuration, it can be expected to avoid discharge caused by a potential difference between adjacent unit cells, and the safety of inspection is increased.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the secondary battery which can anticipate detecting the short circuit of a secondary battery in a short time is implement | achieved.

It is a perspective perspective view which shows the external appearance and internal structure of the lithium ion secondary battery concerning embodiment. It is a flowchart which shows the manufacture procedure of the lithium ion secondary battery concerning embodiment. It is a graph which shows the time change of a voltage and temperature of a lithium ion secondary battery. It is a figure which shows the state which mounted | wore the voltage equalization circuit with the lithium ion secondary battery. FIG. 5 is a schematic diagram of the voltage equalization circuit shown in FIG. 4. It is a figure which shows the restraint state of a lithium ion single battery. It is a graph which shows the relationship between the voltage variation | change_quantity and time in a self-discharge test | inspection.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a secondary battery according to the present invention will be described in detail with reference to the accompanying drawings. In the following embodiment, the present invention is applied to a lithium ion secondary battery mounted on a hybrid vehicle.

[Configuration of lithium ion secondary battery]
First, a lithium ion secondary battery 100 constituting a battery unit will be described with reference to FIG.

As shown in FIG. 1, the lithium ion secondary battery 100 of this embodiment is a sealed rectangular secondary battery having a rectangular exterior portion 50 that forms the outer shell of the lithium ion single battery 100. FIG. 1 shows a state in which the exterior portion 50 is seen through. In the following description, for convenience of explanation, the width direction (X direction in FIG. 1) of the exterior portion 50 is “width direction”, and the height direction (Y direction in FIG. 1) of the exterior portion 50 is “height direction”. The depth direction of the exterior portion 50 (the Z direction in FIG. 1) is defined as the “row placement direction”.

  The exterior portion 50 includes a battery case 10 serving as a container and a sealing lid 20 that seals an opening of the battery case 10. The battery case 10 is made of a metal material such as aluminum, an aluminum alloy, a plated steel plate, or a stainless steel plate. The sealing lid 20 is made of a metal material such as aluminum, a plated steel plate, or a stainless steel plate. The metal material used for the battery case 10 and the sealing lid 20 may be any material that can be easily molded and has rigidity. An insulating film (not shown) is attached to the entire inner surface of the exterior portion 50.

  The battery case 10 is a bottomed rectangular box, that is, a rectangular parallelepiped having an upper surface opened. The battery case 10 houses the power generation element 60 and seals the power generation element 60 by closing the opening with a rectangular plate-shaped sealing lid 20. Specifically, in the exterior part 50, the battery case 10 and the sealing lid 20 are integrated by laser welding.

  A positive electrode collector terminal 31 and a negative electrode collector terminal 32 are attached to the sealing lid 20 so as to penetrate the sealing lid 20 and protrude from the sealing lid 20 toward the outside of the exterior portion 50. An insulating member 33 made of resin is interposed at a position where the positive current collecting terminal 31 is attached to the sealing lid 20 to insulate the positive current collecting terminal 31 from the sealing lid 20. Similarly, an insulating member 34 made of resin is interposed at a location where the negative electrode current collecting terminal 32 is attached to the sealing lid 20 to insulate the negative electrode current collecting terminal 32 from the sealing lid 20. Further, the sealing lid 20 is provided with a liquid injection hole 24 penetrating the sealing lid 20, and an electrolytic solution is injected from the liquid injection hole 24. A rectangular plate-shaped safety valve 23 is also welded to the sealing lid 20.

The power generation element 60 is obtained by winding a belt-like positive electrode plate 61 and a belt-like negative electrode plate 62 with a separator made of polyethylene interposed therebetween to make it flat. The positive electrode plate 61 carries a positive electrode active material layer (not shown) on both surfaces of an aluminum foil. The positive electrode active material layer includes, for example, a positive electrode active material (for example, LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ), a conductive agent acetylene black, a binder polyvinylidene fluoride (PVdF), a dispersion The agent polyvinylpyrrolidone (PVP) is included. The negative electrode plate 62 carries a negative electrode active material layer (not shown) on both sides of the copper foil. This negative electrode active material layer contains, for example, graphite and a binder. In addition, the electrolyte solution (not shown) was added lithium hexafluorophosphate (LiPF ₆ ) as a solute to a mixed organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed. An organic electrolyte having a lithium ion concentration of 1 mol / l. The materials used for the positive electrode plate 61, the positive electrode active material layer, the negative electrode plate 62, the negative electrode active material layer, and the electrolytic solution are merely examples, and materials generally used for lithium ion batteries may be appropriately selected.

  The positive electrode plate 61 is joined to a plate-like positive electrode current collecting terminal 31 bent in a crank shape, and the negative electrode plate 62 is joined to a plate-like negative electrode current collecting terminal 32 also bent in a crank shape. Specifically, the positive electrode current collecting terminal 31 is joined to the positive electrode plate 61 exposed at one end in the width direction of the power generation element 60. On the other hand, the negative electrode current collecting terminal 32 is joined to the negative electrode plate 62 exposed at the other end in the width direction of the power generation element 60.

[Method for producing lithium ion secondary battery]
Next, a method for manufacturing the above-described lithium ion secondary battery 100 will be described by paying attention to the inspection process after the unit cell is manufactured. FIG. 2 is a flowchart showing a manufacturing procedure of the lithium ion secondary battery 100. FIG. 3 is a graph showing changes over time in the battery voltage and temperature of the lithium ion secondary battery 100. In FIG. 3, the upper diagram shows the transition of the battery voltage, and the lower diagram shows the transition of the battery temperature.

  In the manufacturing procedure of the lithium ion secondary battery 100, first, the lithium ion secondary battery 100 is manufactured alone (S01). In S01, for example, the power generation element 60 is accommodated in the battery case 10, the sealing lid 20 is welded to the opening of the battery case 10, and the power generation element 60 is sealed in the exterior part 50. Thereafter, an electrolytic solution is injected into the exterior portion 50 from the liquid injection hole 24 and stored for a predetermined time until the electrolytic solution penetrates into the power generation element 60. Thereby, a unit cell of the lithium ion secondary battery 100 (hereinafter referred to as “lithium ion unit cell 100”) is manufactured. A visual inspection is performed on the manufactured lithium ion unit cell 100, and defective products are removed.

  Next, initial charge is performed with respect to the lithium ion single cell 100 produced by S01 (S02). Specifically, in S02, charging is performed at a constant current and a constant voltage up to a battery use upper limit voltage (in this embodiment, for example, 4.10 V). In S02, charging of the lithium ion unit cell 100 may be performed individually or may be performed collectively.

  In the state where the initial charge is completed, the lithium ion unit cell 100 has a degree of penetration of the electrolyte and a gas generated by charging due to variations in the amount and density of the active material of the electrode and variations in the binding force that restrains the power generation element 60. Variation occurs in the degree of omission, the degree of lithium ion intercalation, the degree of SEI film formation, and the like. For this reason, after the initial charge is completed, aging is performed in a high temperature environment to promote the cell reaction mainly of diffusion and to stabilize the battery.

  Specifically, the charged lithium ion unit cell 100 is housed in a heating chamber, and the temperature of the lithium ion unit cell 100 is raised to a first temperature (in this embodiment, for example, 60 ° C.) (S03, temperature increasing step). One case). A plurality of lithium ion unit cells 100 are accommodated in the heating chamber, and the plurality of lithium ion unit cells 100 are heated together.

  After raising the temperature to the first temperature, an aging test in a high temperature environment is started (S04, an example of a high temperature aging step). That is, the lithium ion unit cell 100 is stored in the high temperature aging chamber until the first reference time (in this embodiment, for example, 10 hours to 30 hours) elapses while the lithium ion unit cell 100 is maintained at the first temperature.

  During the high temperature aging, the stabilized battery voltage varies due to the above-described various variation factors. However, even if the battery voltages are stabilized at different battery voltages as in samples X1 and X2 in FIG. 3, both single cells are treated as non-defective products at the high temperature aging stage as long as they are within acceptable tolerances. In addition, during this high temperature aging, the lithium ion unit cell 100 whose voltage is remarkably lowered as in the sample X3 in FIG. 3 is discharged as a defective product.

  Next, after the high-temperature aging is completed, that is, after the battery voltage of each lithium ion cell 100 is stabilized, a battery voltage equalization circuit is connected to a plurality of lithium ion cells 100 that simultaneously execute a short-circuit inspection described later. (S05, example of equalization step). By this S05, the battery voltages of the plurality of lithium ion cells 100 are equalized, and the battery voltage deviation caused during high temperature aging is eliminated.

  Specifically, in S05, the above-described plurality of lithium ion cells 100 are arranged so that the flat surfaces are opposed to each other as shown in FIG. In particular, the positive electrode current collecting terminal 31 of the lithium ion cell 100 is arranged on one side in the width direction, and the negative electrode current collecting terminal 32 is arranged on the other side. And the positive electrode current collection terminal 31 of all the lithium ion single cells 100 equalized simultaneously is connected to the bus bar 91. FIG. On the other hand, the negative electrode current collecting terminal 32 of all the lithium ion cells 100 to be equalized at the same time is connected to the bus bar 92.

  By connecting the bus bar 91 and the bus bar 92 as described above, all the lithium ion cells 100 are connected in parallel as shown in the schematic diagram of the voltage equalization circuit 90 of FIG. By connecting in this way, the lithium ion single battery whose battery voltage is lower than that of the other lithium ion single battery is charged from the other lithium ion single battery. On the other hand, a lithium ion cell having a higher battery voltage than other lithium ion cells is discharged to charge the other lithium ion cell. Thereby, the battery voltage of all the lithium ion cells 100 constituting the voltage equalization circuit 90 is equalized.

  In the voltage equalization circuit 90 of this embodiment, as shown in FIG. 5, a resistor 93 is connected to the positive terminal of each lithium ion unit cell 100, and a resistor connected to the positive terminal of each lithium ion unit cell 100. 93 are connected in parallel. The resistor 93 is connected to suppress discharge based on the potential difference between the adjacent lithium ion cells 100 and 100. If the resistance value of the resistor 93 is too small, the effect of suppressing discharge is reduced, and if it is too large, it takes time to equalize the battery voltage. In this embodiment, each resistor 93 is 1 kΩ. The resistor 93 is not limited to the connection to the positive electrode side, but may be connected to the negative electrode side. Also, both sides may be connected.

  Moreover, in S03-S05, it is good to make each lithium ion cell 100 restrained. By restraining the lithium ion cell 100, the battery reaction can be promoted in an environment close to the mounting state.

  For example, as shown in FIG. 6, a rectangular case 71 that accommodates a plurality of lithium ion single cells 100, and a rectangular case 71 that is positioned in the rectangular case 71 are used as a method for bringing each lithium ion single cell 100 into a restrained state. A restraining jig 70 having a restraining force applying plate 73 for applying a restraining force from one end of the head toward the other end is utilized.

  Specifically, the lithium ion cells 100 are arranged in a rectangular case 71 of the restraining jig 70 as shown in FIG. A flame retardant resin spacer 75 is inserted between the adjacent lithium ion cells 100, 100. In this state, the restraining force applying plate 73 is urged toward the lithium ion unit cell 100 side by blades or screw tightening. Thereby, the restraining force in the row direction is equally applied to each lithium ion unit cell 100 arranged in the rectangular case 71.

  Further, as in the sample X3 in FIG. 3, the lithium ion unit cell 100 in which the voltage is remarkably lowered is previously removed as a defective product before being connected to the voltage equalizing circuit 90 (an example of a removal step). ). If the battery voltage is equalized, including defective products that have noticeably reduced voltage, the amount of discharge of other cells required for charging the defective products increases, and it takes time to equalize the battery voltage. In addition, in the short circuit inspection after S07, the reference voltage before low-temperature aging is too low, and there is a risk of erroneous determination of short circuit. Therefore, defective products are excluded and useless charging time is saved.

  After equalizing the battery voltage of each lithium ion cell 100 in S05, the bus bars 91 and 92 are removed, and each lithium ion cell 100 is taken out from the high temperature aging chamber. Then, each lithium ion unit cell 100 is housed in a cooling chamber and simultaneously cooled to a second temperature (in this embodiment, for example, 20 ° C.) (S06, an example of a cooling step).

  After each lithium ion unit cell 100 is cooled, a self-discharge test is performed on each lithium ion unit cell 100 to determine whether or not a short circuit has occurred in each lithium ion unit cell 100.

  Specifically, in the self-discharge test, first, a second reference time (for example, 1 to 4 days in this embodiment) has elapsed since the completion of cooling of each lithium ion unit cell 100 to be tested at the same time in the low-temperature aging chamber. (S07, an example of a low temperature aging step). At the start of S07, the battery voltages of the lithium ion cells 100 are substantially equal due to the effect of connecting the voltage equalization circuit 90.

  After the second reference time has elapsed, the battery voltage of each lithium ion single cell 100 is measured (S08, an example of a measurement step). FIG. 7 shows the transition of the change amount of the battery voltage in the self-discharge test. As shown in FIG. 7, in the lithium ion single cell 100, a minute voltage drop occurs due to self-discharge. At this time, if a short circuit occurs in the lithium ion unit cell 100, the amount of voltage drop is larger than that of a non-defective product.

  Conventionally, the difference between the voltage drop due to this internal short circuit and the voltage drop of non-defective products is greater than the deviation of the battery voltage during high-temperature aging so that it can exceed 10 days before the internal short circuit can be clearly distinguished. Long self-discharge was required. On the other hand, in this embodiment, since the voltage equalization circuit 90 eliminates the deviation of the battery voltage during high temperature aging, the difference between the voltage drop due to the internal short circuit and the voltage drop due to the non-defective product is clarified at an early stage. Can be expected to distinguish. That is, in this embodiment, the storage time of S08 in the self-discharge inspection is shortened compared to the conventional case.

  Next, from the measurement result in S08, it is determined whether or not a short circuit has occurred in each lithium ion cell 100 (S09, an example of a determination step). For example, if the voltage value in S08 is less than or equal to the threshold value, it is determined that a short circuit has occurred. Or when it remove | deviates from the normal distribution calculated | required from all the lithium ion single cells 100 measured simultaneously, you may determine with the short circuit having generate | occur | produced.

  Conventionally, considering that there is a variation in the voltage of each lithium ion unit cell 100 immediately after high temperature aging due to battery voltage deviation, the voltage immediately after high temperature aging is applied to each lithium ion battery 100 before the start of self-discharge inspection. The voltage was measured again after a lapse of a predetermined time, the amount of voltage change was obtained from the difference between the two measured values, and the presence or absence of a short circuit was determined based on the amount of voltage change. On the other hand, in this embodiment, the battery voltage of each lithium ion cell 100 immediately after high-temperature aging is uniform, and the battery voltage value after equalization is substantially constant. Therefore, only the voltage value measured after a predetermined time has elapsed. Even if it exists, the variation in the amount of voltage change can be determined. That is, the number of voltage measurements can be reduced to one.

  As a result of the determination in S08, the lithium ion unit cell 100 determined to have a short circuit is removed as a defective product. The remaining lithium-ion cell 100 is shipped as a non-defective product.

  In addition, the manufacturing method of the lithium ion secondary battery 100 mentioned above is a method of manufacturing a single battery to the last. The manufactured lithium ion unit cell 100 is then combined with a plurality of lithium ion unit cells 100 manufactured in the same manner and connected in series to form a battery unit. And when it is put on the market, it is mounted on an electric vehicle or a hybrid vehicle as a battery unit.

  As described in detail above, in the method of manufacturing the lithium ion secondary battery 100 of this embodiment, the battery voltage has shifted due to the high temperature aging in S04 before the short circuit inspection by the low temperature aging in S07 is started. The voltages are evenly arranged by connecting the voltage equalization circuit 90 in S05. Therefore, in the short-circuit inspection, there is no need for long-term aging until it can be distinguished from battery voltage deviation due to high-temperature aging as in the past, and even if the amount of self-discharge due to short-circuit is small, a short-circuit occurs. The lithium ion cell 100 can be clearly distinguished. Therefore, the inspection time can be shortened.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the lithium ion secondary battery is not limited to being mounted on a vehicle, but may be used for home appliances and personal computers. Further, the secondary battery is not limited to the lithium ion secondary battery. That is, the present invention can be applied to a secondary battery such as a nickel metal hydride battery or a nickel cadmium battery.

  In the embodiment, a plurality of lithium ion unit cells 100 are connected in parallel to equalize the battery voltages of the plurality of lithium ion unit cells 100. It is not limited to. For example, the battery voltage of each lithium ion unit cell 100 to be equalized is measured, and the battery voltage of each lithium ion unit cell is aligned with the lithium ion unit cell 100 having the lowest voltage among them. The battery 100 may be discharged.

  In the embodiment, the pass / fail determination is made only from the battery voltage at the completion of the low-temperature aging, but the present invention is not limited to this. That is, after completion of equalization, the battery voltage at the start of low-temperature aging may also be measured, and pass / fail judgment may be made from the difference between the battery voltage at the start and the battery voltage at the completion. Even in this case, the measurement of the battery voltage at the start may be performed by only one of the plurality of lithium ion single cells 100, and it is not necessary to measure all the lithium ion single cells 100.

  In the embodiment, the lithium ion unit cell 100 is moved to the cooling chamber at the time of cooling in S06, but it may be cooled at room temperature. Moreover, although the battery voltage equalization of each lithium ion single cell 100 of S05 is performed in a high temperature environment, it may be performed in a normal temperature environment.

60 Power generation element 90 Voltage equalization circuit 91, 92 Bus bar 93 Resistance 100 Lithium ion cell (secondary battery)

Claims (7)

A temperature raising step for raising the temperature of the unit cell in the initial charge state to the first temperature;
A high temperature aging step for aging the unit cell at the first temperature until a first reference time elapses after the temperature raising step;
An equalizing step for equalizing battery voltages of the plurality of single cells after the first reference time has elapsed;
A cooling step for cooling the plurality of single cells to a second temperature lower than the first temperature after the equalizing step;
A low temperature aging step of aging the single cells at the second temperature until the second reference time elapses after the cooling step;
A measurement step of measuring a battery voltage of each of the plurality of unit cells after the second reference time has elapsed;
A determination step for determining whether each of the plurality of single cells is a non-defective product based on the measurement value after the measurement step;
The manufacturing method of the secondary battery characterized by including. In the manufacturing method of the secondary battery according to claim 1,
After the start of the high temperature aging step and before the start of the equalization step, the cell voltage of the unit cell is measured, and if the measured value exceeds the allowable range as a non-defective product, the unit cell is replaced with a defective unit. The manufacturing method of the secondary battery characterized by including the exclusion step excluded as. In the manufacturing method of the secondary battery according to claim 1 or 2,
The method of manufacturing a secondary battery, wherein the determining step determines that the single cell is a non-defective product when a measurement value of the measuring step is within an allowable range as a non-defective product. In the manufacturing method of the rechargeable battery given in any 1 paragraph of Claims 1-3,
In the low temperature aging step, aging is performed in a state where the plurality of single cells are constrained. In the manufacturing method of the rechargeable battery given in any 1 paragraph of Claims 1-4,
In the high temperature aging step, aging is performed in a state where the unit cell is constrained. In the manufacturing method of the rechargeable battery given in any 1 paragraph of Claims 1-5,
In the equalizing step, the positive electrode of one unit cell and the positive electrode of the other unit cell are electrically connected by a first connecting member, and the negative electrode of the one unit cell and the negative electrode of the other unit cell are connected. A method for manufacturing a secondary battery, wherein the second connection member is electrically connected. In the manufacturing method of the secondary battery according to claim 6,
In the equalizing step, a resistance is connected to at least one of the first connection member and the second connection member.

Images