Battery cell manufacturing equipment including rework automation device and rework quantity counting method using the same

Abstract

The present invention relates to a battery cell manufacturing device including a rework automation device and a rework quantity counting method using the same, and more particularly, to a battery cell manufacturing device capable of measuring the number of reworked battery cells while automatically performing rework and a rework quantity counting method using the same.

Description

Technical Field

[0001] This application claims the benefit of priority to Korean Patent Application No. 2020-0185100, filed on December 28, 2020, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to a battery cell manufacturing device including a rework automation device and a rework quantity counting method using the same, and more particularly, to a battery cell manufacturing device capable of measuring the number of reworked battery cells while automatically performing rework and a rework quantity counting method using the same. Background Art

[0003] Lithium secondary batteries have been used as energy sources for mobile devices and wearable devices, and have also been widely used as energy sources for electric vehicles and hybrid electric vehicles.

[0004] Based on the shape of the battery case, lithium secondary batteries are classified into cylindrical secondary batteries having an electrode assembly mounted in a cylindrical metal can, prismatic secondary batteries having an electrode assembly mounted in a prismatic metal can, or pouch-shaped secondary batteries having an electrode assembly mounted in a pouch-shaped case made of an aluminum laminate sheet.

[0005] The electrode assembly may be manufactured by stacking a positive electrode formed with a tab and a negative electrode formed with a tab with a separator interposed therebetween to manufacture a single cell, and stacking a plurality of single cells in a state where the plurality of single cells are disposed on a separator or winding the plurality of single cells.

[0006] The electrode assembly is housed in a battery case and an electrolyte is injected into the battery case, or the electrode assembly using a solid electrolyte layer instead of a separator is housed in the battery case and the battery case is hermetically sealed to form a secondary battery.

[0007] Conventional manufacture of a secondary battery will be described based on a pouch-shaped secondary battery. Figure 1 It is a schematic diagram of a conventional pouch-shaped secondary battery manufacturing device.

[0008] The battery cell 100 is manufactured by the battery cell manufacturing apparatus 200 .

[0009] Generally, the electrode assembly 110 is formed by stacking or winding an electrode plate 111 composed of at least one positive electrode or negative electrode and a separator.

[0010] The electrode assembly 110 may include an electrode tab 112 or an electrode lead 113 for connecting to an external device. The electrode tab 112 may be formed separately and connected to one electrode plate 111, or a portion of the active material layer of the electrode plate 111 may be removed to form the electrode tab. In this case, the electrode tab 112 is formed by the electrode tab forming unit 210 of the battery cell manufacturing equipment 200. The electrode tab forming unit 210 may be a welder configured to weld the electrode tab 112 to the electrode plate 111 or a laser device configured to remove the active material layer from the electrode plate 111 to form the electrode tab 112.

[0011] After forming the electrode tabs 112 on the electrode plates 111 as described above, at least one positive electrode, at least one separator, and at least one negative electrode may be stacked by the unit assembly forming unit 220. Thereafter, the electrode tabs 112 connected to the respective electrode plates 111 are gathered together based on their polarity and connected to electrode leads 113 having the same polarity using the electrode lead welding unit 230.

[0012] The electrode assembly 110 formed as described above is housed in the battery case 120 .

[0013] For a pouch-shaped battery case, for example, the battery case 120 may be composed of a receiving portion 121 configured to receive the electrode assembly 110 and a sealing portion 122 configured to hermetically seal the receiving portion 121 around the receiving portion.

[0014] The electrode assembly 110 is housed in the housing 121, an electrolyte is injected into the housing 121 using the electrolyte injection unit 240, and the battery case 120 is hermetically sealed using the sealing unit 250. When the electrode assembly 110 uses a solid electrolyte layer, the electrolyte injection process may be omitted.

[0015] Figure 2 A conventional defective product quantity measurement system is shown.

[0016] In conventional defective unit measurement methods, when defective units are reworked, the device process for rework is individually selected and the defective units are manually marked. Specifically, conventional defective unit measurement methods only check the initial supply quantity, the number of good units, and the number of defective units. It is not possible to automatically check the number of battery units that have become good units through rework, making it difficult to calculate an accurate defect rate.

[0017] In patent document 1, a marking device is provided, which is configured to mark the records of secondary batteries to mark the occurrence of defective secondary batteries or their rework; however, this is not for defect rate calculation, and there is a problem that the ratio of the number of defective products to the input number must be verified in units of secondary batteries.

[0018] Therefore, there is a need for a battery cell manufacturing device that can automatically check the ratio of the number of defective products to the input number.

[0019] (Patent Document 1) Korean Patent Application Publication No. 2016-0061756 Summary of the Invention

[0020] Technical issues

[0021] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a battery cell manufacturing apparatus capable of automatically checking the ratio of the number of defective products to the input number.

[0022] Another object of the present invention is to provide a battery cell manufacturing apparatus capable of automatically performing reworking based on a defect type of the reworked battery cells and measuring the number of reworked battery cells.

[0023] Technical Solution

[0024] In order to achieve the above-mentioned object, a battery cell manufacturing apparatus according to the present invention includes a rework automation device configured to automatically rework a battery cell determined to be defective.

[0025] The rework automation device may include: a classification unit configured to classify the battery cells based on the rework type to which the battery cells belong, which is pre-specified by a user; and a rework unit configured to automatically rework the battery cells classified by the classification unit according to the rework type.

[0026] The classification unit may include a quantity measurement section by type configured to check the quantity of the battery cells while classifying the battery cells based on a rework type to which the battery cells belong.

[0027] The rework automation device may further include: a detection unit, which is configured to determine whether the battery cell reworked by the rework unit is defective; a separation unit, which is configured to separate the battery cell determined to be defective according to the result of the detection unit; and a defective product quantity measurement unit, which is configured to verify the number of battery cells determined to be defective by the detection unit among the battery cells reworked by the rework unit according to the rework type.

[0028] The defective product number measurement unit may measure the number of battery cells according to defect types of the battery cells.

[0029] The classification unit may include a button configured to automatically classify the defect type of the battery cell or to be manually operated according to the defect type.

[0030] The rework types may be classified according to work steps such as a battery cell input step, a tab welding step, a cell assembly forming step, an electrolyte injection step, and a sealing step, or the rework types may be classified by rework methods based on defect types.

[0031] Rework can be performed once or multiple times.

[0032] The number of battery cells determined by the classification unit as being unreworkable may be measured as the number of defective products.

[0033] The present invention provides a method for counting the number of reworks, comprising the following steps: (S1) a user sets a rework type for each battery cell determined to be defective, and inputs the battery cells determined to be defective; (S2) a classification unit classifies the battery cells based on the rework type of the battery cells and checks the number of battery cells according to the rework type; (S3) a rework unit reworks the battery cells to be reworked according to the rework type; (S4) a detection unit determines whether the reworked battery cells are defective, a separation unit separates the battery cells determined to be defective, and a defective product quantity measurement unit checks the number of the battery cells determined to be defective to obtain the final number of defective battery cells.

[0034] Step (S2) and step (S3) may be performed once or multiple times.

[0035] The defective rate may be determined based on the number of the final defective battery cells and the number of initially input battery cells in step (S4), and the rework defective rate may be determined by the number of the battery cells by rework type in step (S2).

[0036] In the present invention, one or more configurations that do not conflict with each other may be selected and combined from among the above configurations.

[0037] Beneficial effects

[0038] The battery cell manufacturing apparatus according to the present invention can automatically rework defective battery cells according to rework types, thereby improving battery cell production time and battery cell quality.

[0039] In addition, the number of reworked battery cells can be mechanically checked, thereby making it possible to check the defect rate by type when manufacturing battery cells and easily obtain improvements by defect type. In addition, the ratio of the number of defective products to the total input number can be easily checked. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of a conventional pouch-shaped secondary battery manufacturing device.

[0041] Figure 2 A conventional defective product quantity measurement system is shown.

[0042] Figure 3 is a schematic diagram of a pouch-shaped secondary battery manufacturing apparatus according to the present invention.

[0043] Figure 4 A defective product number measuring system according to the present invention is shown. DETAILED DESCRIPTION

[0044] In this application, it should be understood that the terms "include", "have", "comprises", etc. specify the existence of the stated features, quantities, steps, operations, elements, parts or their combinations, but do not exclude the existence or addition of one or more other features, quantities, steps, operations, elements, parts or their combinations.

[0045] In addition, throughout the drawings, the same reference numerals will be used to represent components that perform similar functions or operations. In the present application, when a component is referred to as being connected to another component, not only can the component be directly connected to the other component, but the component can also be indirectly connected to the other component via another component. In addition, unless otherwise mentioned, the inclusion of a certain element does not mean the exclusion of other elements, but rather means that other elements may be further included.

[0046] Hereinafter, a battery cell manufacturing apparatus and a rework number counting method using the same according to the present invention will be described in detail with reference to the accompanying drawings.

[0047] The battery cell manufacturing apparatus according to the present invention is applicable to all kinds of batteries, such as cylindrical secondary batteries, prismatic secondary batteries, and pouch-shaped secondary batteries; however, for convenience of description, a pouch-shaped secondary battery manufacturing apparatus will be described hereinafter.

[0048] Figure 3 is a schematic diagram of a pouch-shaped secondary battery manufacturing apparatus according to the present invention.

[0049] The battery cell 1000 according to the present invention is manufactured by a battery cell manufacturing apparatus 2000 including a heavy-work automation device 2600 .

[0050] When the electrode plate 1110 is input to the battery cell manufacturing apparatus 2000 , the electrode tab forming unit 2100 of the battery cell manufacturing apparatus 2000 welds the electrode tab 1120 to the electrode plate 1110 or removes a portion of the active material layer of the electrode plate 1110 and punches out the uncoated portion to form the electrode tab 1120 .

[0051] The electrode plate 1110 can be a positive electrode or a negative electrode.

[0052] For example, a positive electrode can be manufactured by applying a positive electrode mixture of a positive electrode active material composed of positive electrode active material particles, a conductive agent, and a binder to a positive electrode current collector. A filler may be further added to the positive electrode mixture as needed.

[0053] Typically, the positive electrode collector is manufactured to have a thickness of 3μm to 500μm. There is no particular limitation on the positive electrode collector, as long as the positive electrode collector exhibits high electrical conductivity and the positive electrode collector does not cause any chemical changes in the battery to which the positive electrode collector is applied. For example, the positive electrode collector may be made of stainless steel, aluminum, nickel or titanium. Alternatively, the positive electrode collector may be made of aluminum or stainless steel whose surface is treated with carbon, nickel, titanium or silver. Specifically, aluminum can be used. The positive electrode collector may have a micro-scale concave-convex pattern formed on its surface to increase the adhesion of the positive electrode active material. The positive electrode collector may be configured in any of various forms such as a film, a sheet, a foil, a mesh, a porous body, a foam body and a non-woven fabric body.

[0054] In addition to the positive electrode active material particles, the positive electrode active material can also be composed of the following materials: layered compounds, such as lithium nickel oxide (LiNiO2), or compounds substituted by one or more transition metals; 1+x Mn 2- x Lithium manganese oxide represented by LiMnO4 (wherein x=0 to 0.33) or lithium manganese oxide such as LiMnO3, LiMn2O3 or LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide such as LiV3O8, LiV3O4, V2O5, or Cu2V2O7; 1- x M x Ni-site lithium nickel oxide represented by O2 (wherein M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3); 2-x M x A lithium manganese composite oxide represented by the formula LiMnO2 (wherein M=Co, Ni, Fe, Cr, Zn, or Ta, and x=0.01 to 0.1) or LiMnO8 (wherein M is Fe, Co, Ni, Cu, or Zn); LiMnO4 in which a portion of the Li in the chemical formula is replaced by an alkaline earth metal ion; a disulfide compound; or Fe(MoO4)3. However, the present invention is not limited thereto.

[0055] The conductive agent is generally added so that the conductive agent accounts for 0.1 to 30% by weight of the total weight of the mixture including the positive electrode active material. The conductive agent is not particularly limited as long as the conductive agent exhibits high conductivity and does not cause any chemical changes in the battery to which the conductive agent is applied. For example, the following materials can be used as the conductive agent: graphite, such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black or thermal black; conductive fibers, such as carbon fibers or metal fibers; metal powders, such as carbon fluoride powder, aluminum powder or nickel powder; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; or conductive materials, such as polyphenylene derivatives.

[0056] The binder included in the positive electrode is a component that assists the bonding between the active material and the conductive agent and assists the bonding with the current collector. The binder is usually added in an amount of 0.1 to 30 weight % based on the total weight of the mixture including the positive active material. As an example of a binder, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers can be used.

[0057] The negative electrode is manufactured by applying the negative electrode active material to the negative electrode current collector and drying it. The above components may be further selectively included as needed.

[0058] The negative electrode current collector is generally manufactured to have a thickness of 3μm to 500μm. There is no particular limitation on the negative electrode current collector as long as the negative electrode current collector exhibits high conductivity and the negative electrode current collector does not cause any chemical changes in the battery to which the negative electrode current collector is applied. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium or sintered carbon. Alternatively, the negative electrode current collector may be made of copper or stainless steel whose surface is treated with carbon, nickel, titanium or silver; or an aluminum-cadmium alloy. In addition, in the same manner as the positive electrode current collector, the negative electrode current collector may have a micro-scale concave-convex pattern formed on its surface to increase the adhesion of the negative electrode active material. The negative electrode current collector may be configured in any of various forms such as a film, a sheet, a foil, a mesh, a porous body, a foam body and a non-woven fabric body.

[0059] As the negative electrode active material, for example, carbon such as non-graphitizable carbon or graphite-based carbon; metal composite oxides such as Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of Groups 1, 2 and 3 of the periodic table, halogen; 0≤x≤1; 1≤y≤3; 1≤z≤8); lithium metal; lithium alloy; silicon alloy; tin alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, or Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni based materials.

[0060] Thereafter, the electrode plate 1110 formed with the electrode tab 1120 is stacked with the separator by the unit assembly forming unit 2200 to form a unit assembly, and the electrode lead 1130 is welded to the unit assembly by the lead welding unit 2300, or a bundle of the electrode tab 1120 is formed to be connected to an external device.

[0061] The electrode assembly 1100 formed with the electrode lead 1130 is housed in the housing 1210 of the battery case 1200. Thereafter, the electrolyte is injected into the battery case 1200 housing the electrode assembly 1100 using the electrolyte injection unit 2400. When the electrode assembly 1100 uses a solid electrolyte layer, the electrolyte injection process can be omitted.

[0062] Thereafter, the sealing portion 1220 of the battery case 1200 accommodating the electrode assembly 1100 is sealed using the sealing unit 2500 to form the battery cell 1000 .

[0063] The present invention includes a rework automation device 2600 configured to determine whether the electrode plate 1110, cell assembly, electrode assembly 1100, or battery cell 1000 formed in each of the above steps is defective, and automatically rework the battery cell 1000 determined to be defective.

[0064] The rework automation device 2600 includes: a classification unit 2610, which is configured to classify the battery cells 1000 based on the rework type to which the battery cells belong, as pre-specified by the user; and a rework unit 2620, which is configured to automatically rework the battery cells 1000 classified by the classification unit 2610 according to the rework type.

[0065] The classification unit 2610 may include a button configured to automatically classify the defect type of the battery cell 1000 or to be manually operated according to the defect type.

[0066] When the classification unit 2610 operates automatically, it may be equipped with a sensor configured to determine the type of defect. The sensor may include a transmitter configured to transmit a signal and a receiver configured to receive the signal and determine whether the battery cell 1000 is defective based on the light or wavelength transmitted by the transmitter. Alternatively, the sensor may include a digital camera configured to capture the shape of the battery cell 1000 for comparison with pre-stored data. Furthermore, the weight of the battery cell 1000 may be measured, and if the measured weight exceeds a weight error range, the battery cell 1000 may be determined to be defective.

[0067] When the classification unit 2610 is manually operated, the classification unit 2610 may be provided for each step to allow the user to determine the defect type.

[0068] The classification unit 2610 may include a quantity measurement part by type configured to check the quantity of the battery cells 1000 while classifying the battery cells 1000 based on the rework type to which the battery cells belong.

[0069] A detection unit 2630 configured to determine whether the battery cells 1000 reworked by the rework unit 2620 are defective, a separation unit 2640 configured to separate the battery cells determined to be defective based on the results of the detection unit, and a defective product number measurement unit 2650 configured to check the number of battery cells 1000 determined to be defective by the detection unit 2630 among the battery cells 1000 reworked by the rework unit 2620 according to the rework type, thereby measuring the number N of battery cells 1000 finally determined to be defective. The number of battery cells 1000 classified as defective battery cells to be reworked by the classification unit 2610 may be the number of battery cells finally determined to be defective.

[0070] Rework may be performed one or more times. Therefore, the number of input battery cells 1000 increases to the sum of the number of initially input battery cells 1000 and the number n of re-input battery cells 1000, thereby measuring a number different from the number of initially input battery cells 1000. However, when calculating the defective rate, the number n of re-input battery cells 1000 may not be included, so the number of initially input battery cells 1000 may be measured. Therefore, the defective rate may be calculated using only the initially input number excluding the number of re-input battery cells 1000 and the number N of battery cells 1000 ultimately determined to be defective.

[0071] In addition, the defective product number measurement unit 2650 may measure the number of battery cells 1000 by defect type, and thus may provide statistics showing which portion has a high defect rate.

[0072] As examples, defect types may include: errors in the input direction of the electrode plate 1110, abnormal application of the active material layer, errors in the direction of the electrode tab 1120, welding errors of the electrode tab 1120, non-attachment of the electrode lead 1130, errors in the injection capacity of the electrolyte, non-insulating state, and lack of sealing force of the battery case 1200.

[0073] Figure 4 A defective product number measuring system according to the present invention is shown.

[0074] from Figure 4 As can be seen, the defective product quantity measurement system according to the present invention can be connected to the rework automation device 2600 to measure the number of re-inputs and the number of defective products. The number of re-inputs and the number of defective products can be checked for each job, and the parts with high defect rates for each defect type can be checked, and the parts that have been improved can be checked.

[0075] The rework quantity counting method according to the present invention includes the following steps: (S1) the user sets the rework type for each battery cell determined to be defective, and inputs each battery cell determined to be defective; (S2) the classification unit classifies the battery cells based on the rework type of the battery cells and checks the number of battery cells according to the rework type; (S3) the rework unit reworks the battery cells to be reworked according to the rework type; (S4) the detection unit determines whether the reworked battery cells are defective, the separation unit separates the battery cells determined to be defective, and the defective product quantity measurement unit checks the number of battery cells determined to be defective to obtain the final number of defective battery cells.

[0076] At this time, step (S2) and step (S3) may be performed once or multiple times.

[0077] The type of heavy work can be adjusted according to the user's convenience.

[0078] As an example, the rework types may be classified according to steps of forming an electrode assembly or a battery case of a battery cell, or may be classified by a rework method based on each defect type.

[0079] At this time, although the defect type may vary according to each set value, a case where the difference between the stored value and the average value is 10% or more may be classified as a defect.

[0080] As an example, when punching an electrode plate using a punch press to form an electrode having an uncoated portion and a coated portion, a deviation exceeding a value of ±0.1 mm to 0.15 mm from an average value of a conventional electrode plate may be determined as defective.

[0081] Furthermore, when a defect is determined using a method of determining a matching rate with a registered program, a case where the matching rate with regular data is less than 80% may be determined as a defect.

[0082] At this point, one or more defect detection methods may be used to reduce errors.

[0083] In the rework step, work may be performed separately for each type of battery cell separated. For example, the battery cell to be reworked may be reworked on a separate rework station and subjected to the same process as other battery cells, or the battery cell to be reworked may be placed in the process before the defect occurred and the work may be performed again.

[0084] Afterwards, the battery cells that cannot be reworked or the battery cells that are still defective even after rework are determined to be defective. At this time, marking may be performed to clearly indicate whether the battery cell is defective.

[0085] The defective rate may be determined based on the number of final defective battery cells and the number of initially input battery cells in step ( S4 ), and the rework defective rate may be determined by the number of battery cells by rework type in step ( S2 ).

[0086] That is, a step of calculating the total defective rate and the rework defective rate by rework type may be performed.

[0087] Although the specific details of the present invention have been described in detail, it will be understood by those skilled in the art that the detailed description thereof only discloses the preferred embodiments of the present invention and thus does not limit the scope of the present invention. Therefore, it will be understood by those skilled in the art that various changes and modifications are possible without departing from the scope and technical concept of the present invention, and it will be apparent that such changes and modifications fall within the scope of the appended claims.

[0088] (Explanation of Reference Numbers)

[0089] 100, 1000: battery cells

[0090] 110, 1100: electrode assembly

[0091] 111, 1110: electrode plate

[0092] 112, 1120: electrode tabs

[0093] 113, 1130: Electrode leads

[0094] 120, 1200: battery housing

[0095] 121, 1210: Accommodation

[0096] 122, 1220: Sealing part

[0097] 2000: Battery cell manufacturing equipment

[0098] 210, 2100: splice forming unit

[0099] 220, 2200: Unit components form a unit

[0100] 230, 2300: Electrode lead welding unit

[0101] 240, 2400: electrolyte injection unit

[0102] 250, 2500: Sealed unit

[0103] 2600: Heavy industry automation equipment

[0104] 2610: Taxonomic unit

[0105] 2620: Heavy Industry Unit

[0106] 2630: Detection unit

[0107] 2640: Separation unit

[0108] 2650: Unit of measurement for the number of defective products.

[0109] Industrial Applicability

[0110] The present invention relates to a battery cell manufacturing device including a rework automation device and a rework quantity counting method using the same. More specifically, it relates to a battery cell manufacturing device that can measure the number of reworked battery cells while automatically performing rework and a rework quantity counting method using the same. Therefore, the present invention has industrial applicability.

Claims

1. A battery cell manufacturing apparatus comprising a rework automation device configured to automatically rework a battery cell determined to be defective. The heavy industry automation device includes: a classification unit configured to classify the battery cells based on a rework type to which the battery cells belong, which is pre-specified by a user; a reworking unit configured to automatically rework the battery cells sorted by the sorting unit according to a reworking type; a detection unit configured to determine whether the battery cell reworked by the rework unit is defective; a separation unit configured to separate a battery cell determined to be defective based on a result of the detection unit; as well as A defective product number measuring unit is configured to check the number of battery cells determined to be defective by the inspection unit, among the battery cells reworked by the rework unit according to the rework type. 2 . The battery cell manufacturing apparatus according to claim 1 , wherein the classification unit includes a quantity measurement section by type configured to check the quantity of the battery cells while classifying the battery cells based on the rework type to which the battery cells belong. 3 . The battery cell manufacturing apparatus according to claim 1 , wherein the defective product number measuring unit measures the number of battery cells according to defect types of the battery cells. 4 . The battery cell manufacturing apparatus according to claim 1 , wherein the classification unit comprises a button configured to automatically classify the defect type of the battery cell or to be manually operated according to the defect type.

5. The battery cell manufacturing equipment according to claim 1, wherein the rework type is classified according to a battery cell input step, a tab welding step, a cell assembly forming step, an electrolyte injection step and a sealing step, or the rework type is classified according to a rework method based on a defect type. The battery cell manufacturing equipment according to claim 1 , wherein the reworking is performed one or more times. 7 . The battery cell manufacturing apparatus according to claim 1 , wherein the number of battery cells determined by the classification unit as being unreworkable is measured as the number of defective products.

8. A method for counting the number of reworks, comprising the following steps: (S1) A user sets a rework type for each battery cell determined to be defective, and inputs the number of each battery cell determined to be defective; (S2) checking the number of battery cells by rework type while classifying the battery cells based on the rework type of the battery cells by the classification unit; (S3) reworking the battery cells sorted by the sorting unit according to a reworking type by a reworking unit; (S4) The detection unit determines whether the battery cells reworked by the rework unit are defective, the separation unit separates the battery cells determined to be defective according to the result of the detection unit, and the defective product quantity measurement unit checks the number of battery cells reworked by the rework unit according to the rework type and determined to be defective by the detection unit to obtain the final number of defective battery cells.

9. The rework quantity counting method according to claim 8, wherein step (S2) and step (S3) are performed once or multiple times.

10. The rework quantity counting method according to claim 8, wherein the defective rate is determined based on the final number of defective battery cells and the number of initially input battery cells in step (S4), and the rework defective rate is determined by the number of battery cells by rework type in step (S2).

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