Apparatus and method for evaluating electrolyte impregnation level of secondary battery

Abstract

Disclosed are an apparatus and method for evaluating an electrolyte impregnation level of a secondary battery. Specifically, an electrolyte is injected into a 3-electrode cell and aged for a first hour. Charging of the 3-electrode cell is initiated, and a first state of charge (SOC) voltage is obtained between a reference terminal and a positive terminal in a first SOC. The 3-electrode cell is aged for a second hour, and then an aging completion voltage is obtained between the reference terminal and the positive terminal. Charging of the 3-electrode cell is resumed, and a second state of charge voltage is obtained between the reference terminal and the positive terminal in a second state of charge. At least one of the first state of charge voltage, the voltage difference between the first state of charge voltage and the aging completion voltage, and the voltage difference between the first state of charge voltage and the second state of charge voltage is determined as an impregnation evaluation voltage. An electrolyte impregnation level corresponding to the impregnation evaluation voltage is identified from reference voltage information for multiple electrolyte impregnation levels, and the identified electrolyte impregnation level is determined as the electrolyte impregnation level of the 3-electrode cell.

Description

Device and method for evaluating electrolyte impregnation level of secondary battery

[0001] The present invention relates to a device and method for evaluating an electrolyte impregnation level of a secondary battery, and more particularly, to a device and method for quantitatively evaluating an electrolyte impregnation level of a secondary battery from a voltage difference between a reference electrode and an anode using a three-electrode cell including a reference electrode.

[0002] This application claims priority from Korean Patent Application No. 10-2024-0044943, filed on April 2, 2024 in the Republic of Korea, the contents of which are the basis of the priority claim and may be incorporated herein as a part of the present specification.

[0003] Recently, with the development of technology and increasing demand for mobile devices, small aircraft, electric vehicles, and power storage devices, the demand for secondary batteries, such as lithium secondary batteries, is rapidly increasing.

[0004] A secondary battery includes an electrode assembly having a cathode and a cathode, each of which has an active material applied to an electrode current collector, and a separator interposed between them. The electrode assembly is impregnated with an electrolyte that transfers operating ions between the cathode and the anode during charging and discharging of the secondary battery.

[0005] The electrode assembly comprises one or more unit cells with a separator interposed between an anode and a cathode. The electrode assembly has various structures, such as a simple stacked type, a jelly-roll type, and a stacked / folded type, depending on whether the unit cells are stacked and / or wound.

[0006] The electrode assembly is inserted into a case, such as a metal can of a certain size and shape or a flexible pouch packaging. The secondary battery is then assembled by injecting electrolyte into the case and sealing it.

[0007] The electrolyte injected into the case permeates between the anode, cathode, and separator through capillary force. The electrolyte impregnates the separator and electrodes until the assembled secondary battery enters the formation process. The performance of the secondary battery is determined by the level of electrolyte impregnation prior to the formation process. In particular, if the separator or electrodes are insufficiently impregnated with electrolyte, the efficiency of the secondary battery deteriorates and its lifespan is shortened. Therefore, a technology for quantitatively assessing the level of electrolyte impregnation during the development or production of secondary batteries is needed.

[0008] Conventional methods for evaluating electrolyte impregnation involve injecting electrolyte into a case containing an electrode assembly, impregnating the electrode assembly with the electrolyte, and then aging the assembly for a specified period of time. The electrode assembly is then disassembled, and the electrode surface is visually observed to qualitatively assess the level of electrolyte impregnation. For example, the greater the number of areas on the electrode surface where no traces of electrolyte impregnation are visible, the lower the level of electrolyte impregnation is assessed.

[0009] However, the method of directly checking the electrolyte-free region of the electrode after disassembling the electrode assembly has limitations in that it is difficult to quantitatively evaluate the impregnation level of the electrode assembly and it is difficult to apply it to an automated secondary battery production process.

[0010] Therefore, in the technical field to which the present invention pertains, there is a need for a method capable of quantitatively and accurately evaluating the electrolyte impregnation level without disassembling the electrode assembly.

[0011] The present invention was created under the background of the above-mentioned prior art, and its purpose is to provide an electrolyte impregnation level evaluation device and method of a secondary battery capable of quantitatively evaluating the electrolyte impregnation level without disassembling an electrode assembly.

[0012] In addition, by providing a system including a device for evaluating an electrolyte impregnation level of a secondary battery and a computer for managing a production line of a secondary battery, another purpose is to adaptively control the process conditions of a pouring process using the evaluated electrolyte impregnation level for a 3-electrode cell manufactured from a semi-finished cell sampled in a production line of a secondary battery, thereby managing the electrolyte impregnation level at an optimal level.

[0013] According to the present invention for achieving the above technical task, a method for evaluating an electrolyte impregnation level of a secondary battery comprises the steps of: (a) preparing a three-electrode cell including a positive terminal, a negative terminal, and a reference terminal; (b) injecting an electrolyte into a case of the three-electrode cell and aging it for a first hour; (c) charging the three-electrode cell to a first state of charge (SOC: State Of Charge) that is preset and obtaining a first state of charge voltage between the reference terminal and the positive terminal in the first state of charge; (d) aging the three-electrode cell for a second hour in a no-load state and then obtaining an aging completion voltage between the reference terminal and the positive terminal; (e) charging the three-electrode cell from the first state of charge to a second state of charge and obtaining a second state of charge voltage between the reference terminal and the positive terminal in the second state of charge; (f) a step of determining at least one of the first state of charge voltage, the voltage difference between the first state of charge voltage and the aging completion voltage, and the voltage difference between the first state of charge voltage and the second state of charge voltage as an impregnation evaluation voltage; and (g) a step of identifying an electrolyte impregnation level corresponding to the impregnation evaluation voltage from reference voltage information for a plurality of predefined electrolyte impregnation levels, and determining the identified electrolyte impregnation level as the electrolyte impregnation level of the three-electrode cell.

[0014] The above reference voltage information may include first to n-th electrolyte impregnation levels (n is a natural number greater than or equal to 2) and first to n-th voltage section information corresponding to each electrolyte impregnation level.

[0015] In the above reference voltage information, the first to nth voltage section information can be set differently depending on the type of the impregnation evaluation voltage.

[0016] In the step (f), the first charge state voltage, the voltage difference between the first charge state voltage and the aging completion voltage, and the voltage difference between the first charge state voltage and the second charge state voltage can be determined as the first impregnation evaluation voltage, the second impregnation evaluation voltage, and the third impregnation evaluation voltage, respectively.

[0017] In the step (g), the first electrolyte impregnation level, the second electrolyte impregnation level, and the third electrolyte impregnation level corresponding to the first impregnation evaluation voltage, the second impregnation evaluation voltage, and the third impregnation evaluation information, respectively, are determined from reference voltage information for a plurality of predefined electrolyte impregnation levels, and an average of the first electrolyte impregnation level, the second electrolyte impregnation level, and the third electrolyte impregnation level can be determined as the electrolyte impregnation level of the three-electrode cell.

[0018] The first time period may be 0 to 48 hours, preferably 24 hours, and the second time period may be 12 to 48 hours, preferably 24 hours.

[0019] The first charge state may be 3% to 7%, preferably 5%, and the second charge state may be 8% to 12%, preferably 10%.

[0020] The step (c) above may include: (c1) a step of repeatedly measuring a voltage difference between the reference terminal and the positive terminal at time intervals while charging the three-electrode cell to a preset first charge state to generate a first voltage profile; and (c2) a step of obtaining a terminal voltage of the first voltage profile as the first charge state voltage.

[0021] The step (d) above may include: (d1) a step of repeatedly measuring a voltage difference between the reference terminal and the positive terminal at time intervals while aging the 3-electrode cell for a second time in a no-load state to generate a second voltage profile; and (d2) a step of obtaining a terminal voltage of the second voltage profile as the aging completion voltage.

[0022] The step (e) above may include: (e1) a step of repeatedly measuring the voltage difference between the reference terminal and the positive terminal at time intervals while charging the 3-electrode cell from the first charge state to the second charge state to obtain a third voltage profile; and (e2) a step of obtaining the terminal voltage of the third voltage profile as the second charge state voltage.

[0023] The method for evaluating the electrolyte impregnation level of a secondary battery according to the present invention may further include a step of displaying the electrolyte impregnation level through a display; and / or a step of transmitting the electrolyte impregnation level to a computer.

[0024] The above electrode assembly may be an electrode assembly in which a core and an outer surface are defined by winding a positive electrode and a negative electrode and a separator interposed therebetween around a winding axis, wherein the positive electrode and the negative electrode each include an active material portion coated with an active material along a winding direction and a non-coated portion not coated with an active material, and the non-coated portion of the positive electrode and the non-coated portion of the negative electrode are exposed to the outside of the separator so as to face each other along the winding axis direction, and the non-coated portion of the positive electrode is bent toward the core to form a first bent surface area, and the non-coated portion of the negative electrode is bent toward the core to form a second bent surface area.

[0025] The case is a cylindrical can having a bottom portion in which a first side is open and a through hole is formed on a second side opposite the first side in the winding axis direction, and the three-electrode cell includes a rivet terminal fastened to the through hole so as to be electrically insulated from the cylindrical can, a positive electrode collector connecting the first folded surface area and the rivet terminal, and a negative electrode collector connecting the second folded surface area and the inner surface of the cylindrical can, and the reference electrode is installed in the core of the electrode assembly so that one end can be exposed to the outside of the electrode assembly or is installed between the outer peripheral surface of the electrode assembly and the inner peripheral surface of the case, and the positive terminal may be the rivet terminal, the negative terminal may be the case, and the reference terminal may be a lead connected to the reference electrode.

[0026] According to another aspect of the present invention for achieving the above technical task, a device for evaluating an electrolyte impregnation level of a secondary battery comprises: a mount portion into which a three-electrode cell aged for a first hour after electrolyte injection is loaded, wherein the three-electrode cell includes a positive terminal, a negative terminal, and a reference terminal; a charging portion for applying a charging current to the three-electrode cell; a voltage measuring portion for measuring a voltage difference between the reference terminal and the positive terminal; a storage medium for storing reference voltage information regarding a plurality of electrolyte impregnation levels; And a control unit operably coupled with the charging unit, the voltage measuring unit, and the storage medium, wherein the control unit controls the charging unit to charge the three-electrode cell to a first charging state and obtains a first charging state voltage through the voltage measuring unit in the first charging state, stops the operation of the charging unit for a second time, and obtains an aging completion voltage through the voltage measuring unit, controls the charging unit to charge the three-electrode cell from the first charging state to a second charging state and obtains a second charging state voltage through the voltage measuring unit in the second charging state, determines at least one of the first charging state voltage, the voltage difference between the first charging state voltage and the aging completion voltage, and the voltage difference between the first charging state voltage and the second charging state voltage as an impregnation evaluation voltage, identifies an electrolyte impregnation level corresponding to the impregnation evaluation voltage from the reference voltage information, and determines the identified electrolyte impregnation level as the electrolyte impregnation level of the three-electrode cell. It can be configured to decide.

[0027] The device further comprises a display operably coupled to the control unit, wherein the control unit may be configured to display the electrolyte impregnation level via the display.

[0028] The device may include a communication interface operably coupled to the control unit, wherein the control unit may be configured to transmit the electrolyte impregnation level to a computer via the communication interface.

[0029] The above technical task can be achieved by a system including an electrolyte impregnation level evaluation device of the secondary battery; and a computer that receives the electrolyte impregnation level from the electrolyte impregnation level evaluation device through a network.

[0030] Preferably, the computer can control process conditions applied to the pouring process of the secondary battery by referring to the electrolyte impregnation level.

[0031] According to the present invention, the electrolyte impregnation level of an electrode assembly can be quantitatively and accurately evaluated without disassembling the electrode assembly of a secondary battery.

[0032] Additionally, by monitoring the temporal change in the electrolyte impregnation level using a three-electrode cell manufactured from a semi-finished cell sampled from a secondary battery production line and adaptively controlling the electrolyte injection process, the electrolyte impregnation level can be optimized to a desired level.

[0033] The following drawings attached to this specification illustrate one embodiment of the present invention, and together with the detailed description described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0034] Figure 1 is a block diagram showing a schematic configuration of an electrolyte impregnation level evaluation device (10) of a secondary battery according to an embodiment of the present invention.

[0035] FIG. 2 illustrates tables including reference voltage information for multiple electrolyte impregnation levels by type of impregnation evaluation voltage according to an embodiment of the present invention.

[0036] Figure 3 is a graph showing voltage profiles measured for a 3-electrode cell with a normal electrolyte impregnation level (example) and a 3-electrode cell with a poor electrolyte impregnation level (comparative example).

[0037] FIG. 4 is a drawing specifically illustrating a state in which a cylindrical 3-electrode cell is loaded into an electrolyte impregnation level evaluation device of a secondary battery according to an embodiment of the present invention immediately after charging and aging.

[0038] Figure 5a is a plan view showing an electrode structure according to an embodiment of the present invention.

[0039] Figure 5b is a process diagram showing a winding process of an electrode assembly according to an embodiment of the present invention.

[0040] FIG. 5c is a perspective view of an electrode assembly manufactured according to an embodiment of the present invention.

[0041] Figure 6 is a flowchart showing the flow of a method for evaluating the electrolyte impregnation level of a secondary battery according to an embodiment of the present invention.

[0042] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, it should be noted that the terms and words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that aligns with the technical spirit of the present invention.

[0043] Therefore, it should be understood that the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention, and that there may be various equivalents and modified examples that can replace them at the time of filing this application.

[0044] Additionally, to facilitate understanding of the invention, the attached drawings are not drawn to scale and the dimensions of some components may be exaggerated. Furthermore, identical components may be assigned the same reference numbers in different embodiments.

[0045] The statement that two compared objects are "identical" means "substantially identical." Therefore, "substantially identical" may include deviations considered low in the art, such as deviations of less than 5%. Furthermore, uniformity of a parameter within a region may mean uniformity on average within that region.

[0046] Although terms like "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless otherwise specified, a "first" component may also be a "second" component.

[0047] Throughout the specification, unless otherwise specifically stated, each element may be singular or plural.

[0048] Any configuration being placed "on (or below)" a component or "on (or below)" a component may mean not only that any configuration is placed in contact with the upper surface (or lower surface) of said component, but also that other configurations may intervene between said component and any configuration placed on (or below) said component.

[0049] Additionally, when it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the components may be directly connected or connected to one another, but that other components may also be "interposed" between the components, or that each component may be "connected," "coupled," or "connected" through another component.

[0050] Throughout the specification, when we refer to "A and / or B", this means A, B, or A and B, unless otherwise stated, and when we refer to "C to D", this means C or more and D or less, unless otherwise stated.

[0051] Figure 1 is a block diagram showing a schematic configuration of an electrolyte impregnation level evaluation device (10) of a secondary battery according to an embodiment of the present invention.

[0052] Referring to FIG. 1, a device (10) for evaluating an electrolyte impregnation level of a secondary battery may include a mount unit (18 of FIG. 4) into which a three-electrode cell (20) into which an electrolyte is injected is loaded, a charging unit (11) for applying a charging current to the three-electrode cell (20), a voltage measuring unit (12) for measuring a voltage difference between a reference terminal (22) and a positive terminal (211t) of the three-electrode cell (20), a storage medium (13) for pre-storing reference voltage information for a plurality of electrolyte impregnation levels, and a control unit (14) operably connected to the charging unit (11), the voltage measuring unit (12), and the storage medium (13).

[0053] The above three-electrode cell (20) may include an electrode assembly (21) including an anode (211) and a cathode (212) and a separator (213) interposed therebetween, a case (23) that houses a reference electrode (22) together with the electrode assembly (21), a cathode terminal (211t) electrically connected to the anode (211), a cathode terminal (212t) electrically connected to the cathode (212), and a reference terminal (22t) electrically connected to the reference electrode (22).

[0054] There is no particular limitation on the structure of the above positive electrode terminal (211t) as long as it is electrically connected to the positive electrode (211) included in the electrode assembly (21) and exposed to the outside.

[0055] There is no particular limitation on the structure of the above negative terminal (212) as long as it is electrically connected to the negative electrode (212) included in the electrode assembly (21) and exposed to the outside.

[0056] In one example, the positive terminal (211t) may be a lead terminal of a pouch cell, a rivet terminal installed on the cap or can bottom of a cylindrical cell, a terminal installed on the cap of a square cell, etc. The negative terminal (212t) may be a lead terminal of a pouch cell, a terminal installed on the can of a cylindrical cell, a cap of a square cell, etc.

[0057] The above electrode assembly (21) may have a structure known in the art, such as a laminated structure, a jelly-roll structure, or a stack / folding structure.

[0058] The above case (23) is widely used in the industry and may be a square can, a cylindrical can, or a pouch packaging material.

[0059] The above reference electrode (22) is an electrode having a potential of 0 volts and may be additionally included in the case (23) to quantitatively evaluate the electrolyte impregnation level. The material of the reference electrode (22) may vary depending on the type of the three-electrode cell (20). If the three-electrode cell (20) is a lithium ion cell, the reference electrode (22) may be made of lithium metal.

[0060] The above reference electrode (22) may be installed in a position where it is separated from the positive electrode (211) and negative electrode (212) included in the electrode assembly (21) and can only contact the separator. In one example, when the electrode assembly (21) is an electrode assembly having a jelly-roll structure, the reference electrode (22) may be installed in a core, which is an empty space at the center of the electrode assembly (21), or may be installed between the outer surface of the electrode assembly (21) and the inner surface of the case (23).

[0061] There is no particular limitation on the structure of the above-mentioned reference terminal (22t) as long as it is electrically connected to the reference electrode (22) installed in the case (23) and exposed to the outside. In one example, the above-mentioned reference terminal (22t) may be a lead connected to the reference electrode (22).

[0062] It is obvious to those skilled in the art that any structure of the above three-electrode cell known in the art can be employed.

[0063] The above three-electrode cell can be loaded onto the mount (18 in FIG. 4) after aging for a first hour after electrolyte injection. The first hour can be 0 to 48 hours. In one example, the first hour can be 24 hours.

[0064] The control unit (14) controls the charging unit (11) to charge the three-electrode cell (20) to a first state of charge (SOC: State Of Charge) and obtains the first state of charge voltage through the voltage measuring unit (12) in the first state of charge. The magnitude of the charging current can be preset. In one example, the magnitude of the charging current can be 0.3C (c-rate). The first state of charge voltage is the voltage difference between the reference terminal (22t) and the positive terminal (211t).

[0065] In one embodiment, the control unit (140) may be configured to control the charging unit (11) to repeatedly acquire a voltage difference between the reference terminal (22t) and the positive terminal (211t) at time intervals through the voltage measuring unit (12) while charging the three-electrode cell (20) to a preset first charging state, generate a first voltage profile according to time, record the first voltage profile in the storage medium (13), and acquire the terminal voltage of the first voltage profile as the first charging state voltage.

[0066] The above first charging state is not particularly limited, but can be set in the range of SOC 3% to 7% based on the full charge capacity of the 3-electrode cell (20).

[0067] Preferably, the first charge state can be set to a SOC level of 5%, which is the initial charge state of the 3-electrode cell (20).

[0068] The above control unit (14) also suspends the operation of the charging unit (11) for a second time to age the three-electrode cell (20) and then obtains the aging completion voltage through the voltage measuring unit (12). The aging completion voltage is the voltage difference between the reference terminal (22t) and the positive terminal (211t) after aging is completed for the second time.

[0069] In one embodiment, the control unit (14) may be configured to repeatedly acquire a voltage difference between the reference terminal (22t) and the positive terminal (211t) at time intervals through the voltage measuring unit (12) while the operation of the charging unit (11) is stopped for a second time, generate a second voltage profile according to time, record the second voltage profile in the storage medium (13), and acquire the terminal voltage of the second voltage profile as the aging completion voltage.

[0070] When the operation of the charging unit (11) is stopped, the charging of the 3-electrode cell (20) is stopped and it ages. While the 3-electrode cell (20) is aging, it is preferable that the temperature of the 3-electrode cell (20) be maintained at room temperature. To this end, the mount unit (18 in FIG. 4) may include a fluid circulation mechanism for temperature control and a temperature control mechanism for heating or cooling the fluid.

[0071] The second time period may be set within a range of 12 to 48 hours so that the electrolyte can be sufficiently impregnated into the interior of the electrode assembly (21). Preferably, the second time period may be 24 hours.

[0072] The control unit (14) also controls the charging unit (11) to charge the three-electrode cell (20) from the first charging state to the second charging state, and obtain the second charging state voltage through the voltage measuring unit (12) in the second charging state. The size of the charging current can be preset. In one example, the size of the charging current can be 0.3 C (c-rate). The second charging state voltage is the voltage difference between the reference terminal (22t) and the positive terminal (211t) after the three-electrode cell (20) is charged to the second charging state.

[0073] In one embodiment, the control unit (14) may be configured to control the charging unit (11) to repeatedly acquire a voltage difference between the reference terminal (22t) and the positive terminal (211t) at time intervals through the voltage measuring unit (12) while charging the three-electrode cell (20) from the first charging state to the second charging state, generate a third voltage profile according to time, record the same in a storage medium (13), and acquire the terminal voltage of the third voltage profile as the second charging state voltage.

[0074] The above second charging state is not particularly limited, but may be set to a percentage value greater than the first charging state within the range of SOC 8% to 12% based on the full charge capacity of the three-electrode cell (20).

[0075] Preferably, the second charging state can be set to a SOC 10% level.

[0076] The control unit (14) may also determine at least one of the first charge state voltage, the voltage difference between the first charge state voltage and the aging completion voltage, and the voltage difference between the first charge state voltage and the second charge state voltage as the impregnation evaluation voltage.

[0077] The above control unit (14) can also identify an electrolyte impregnation level corresponding to the impregnation evaluation voltage from reference voltage information for a plurality of electrolyte impregnation levels pre-recorded in the storage medium (13) and quantitatively determine the identified electrolyte impregnation level as the electrolyte impregnation level of the 3-electrode cell (20).

[0078] Preferably, the reference voltage information may include first to nth electrolyte impregnation levels (n is a natural number greater than or equal to 2) and first to nth voltage section information corresponding to each electrolyte impregnation level.

[0079] Preferably, in the reference voltage information, the first to nth voltage section information can be set differently for each type of the impregnation evaluation voltage.

[0080] FIG. 2 illustrates tables including reference voltage information for multiple electrolyte impregnation levels by type of impregnation evaluation voltage according to an embodiment of the present invention.

[0081] The reference voltage information shown in the tables was set based on the case where the 3-electrode cell (20) is a lithium ion cell, the first and second charge states are 5% and 10%, respectively, and the aging time (second hour) after charging of the 3-electrode cell (20) is 24 hours.

[0082] The 3-electrode cell (20) uses lithium transition metal oxide (LiNi) as the positive electrode active material. 1 / 3 Co 1 / 3 Mn 1 / 3 An electrolyte containing O2) as a cathode active material, graphite as a negative electrode active material, lithium salt LiPF6 as an electrolyte, and solvents DMC (DiMethyl Carbonate) and EC (Ethylene Carbonate) was used.

[0083] Referring to (a) of Fig. 2, the impregnation evaluation voltage (V po ) is the first state of charge voltage, the electrolyte impregnation level can be classified into three stages.

[0084] As shown, the first electrolyte impregnation level is when the first state of charge voltage exceeds 4.0 V, and the electrolyte impregnation level is less than 70%. The second electrolyte impregnation level is when the first state of charge voltage is greater than 3.7 V and less than or equal to 4.0 V, and the electrolyte impregnation level is greater than or equal to 70% and less than or equal to 90%. The third electrolyte impregnation level is when the first state of charge voltage is less than or equal to 3.7 V, and the electrolyte impregnation level is greater than or equal to 90%, which is a normal impregnation level.

[0085] The electrolyte impregnation level of the 3-electrode cell (20) decreases as the first state of charge voltage increases. This is because the lower the electrolyte impregnation level, the smaller the amount of lithium ions moving from the positive electrode to the negative electrode, thereby increasing the first state of charge voltage. The voltages of 3.7 V and 4.0 V, which are the boundaries of the electrolyte impregnation levels, can be determined based on a standard 3-electrode cell in which the electrolyte impregnation level is accurately evaluated as 90% or more, 70% or more and less than 90%, and less than 70% through a decomposition analysis method. The electrolyte impregnation level through the decomposition analysis method can be determined as the area ratio of the electrolyte-impregnated area to the total area of ​​the positive electrode. The distinction between the electrolyte-impregnated area and the electrolyte-non-impregnated area can be made by examining the color change of the positive electrode surface due to electrolyte impregnation. The voltages that divide the boundaries of the electrolyte impregnation levels can vary depending on the types of the positive electrode active material, the negative electrode active material, and the electrolyte. The number of electrolyte impregnation levels can be increased beyond the three stages shown.

[0086] Referring to (b) of Fig. 2, the impregnation evaluation voltage (V po ) is the voltage difference between the first charge state voltage and the aging completion voltage, the electrolyte impregnation level can be classified into three stages.

[0087] As shown, the first electrolyte impregnation level is when the voltage difference between the first state of charge voltage and the aging completion voltage exceeds 0.8 V, and the electrolyte impregnation level is less than 70%. The second electrolyte impregnation level is when the voltage difference between the first state of charge voltage and the aging completion voltage is greater than 0.5 V and less than 0.8 V, and the electrolyte impregnation level is 70% or more and less than 90%. The third electrolyte impregnation level is when the voltage difference between the first state of charge voltage and the aging completion voltage is less than 0.5 V, and the electrolyte impregnation level is 90% or more, which is a normal impregnation level.

[0088] The larger the voltage difference between the first state of charge voltage and the aging completion voltage, the lower the electrolyte impregnation level can be quantitatively evaluated. During aging in a no-load state after the charging of the 3-electrode cell (20) is stopped, lithium ions can move to the electrolyte-free region of the positive electrode. The greater the amount of lithium ion movement, the larger the voltage difference between the first state of charge voltage and the aging completion voltage. Therefore, the larger the voltage difference, the more electrolyte-free region there is in the positive electrode that induces the movement of lithium ions.

[0089] The voltages dividing the boundaries of the electrolyte impregnation levels, 0.5 V and 0.8 V, can be determined based on a standard three-electrode cell, in which the electrolyte impregnation levels are accurately evaluated as 90% or more, 70% or more but less than 90%, and less than 70%, through the decomposition analysis method described above. The voltages dividing the boundaries of the electrolyte impregnation levels can vary depending on the types of the positive active material, negative active material, and electrolyte. The number of electrolyte impregnation levels is not limited to three stages as illustrated and can be increased further.

[0090] Referring to (c) of Fig. 2, the impregnation evaluation voltage (V po ) is the voltage difference between the first state of charge voltage and the second state of charge voltage, the electrolyte impregnation level can be classified into three stages.

[0091] As shown, the first electrolyte impregnation level is when the voltage difference between the first state of charge voltage and the second state of charge voltage exceeds 0.2 V, and the electrolyte impregnation level is less than 70%. The second electrolyte impregnation level is when the voltage difference between the first state of charge voltage and the second state of charge voltage is greater than 0.0 V and less than 0.2 V, and the electrolyte impregnation level is greater than 70% and less than 90%. The third electrolyte impregnation level is when the voltage difference between the first state of charge voltage and the second state of charge voltage is less than 0.0 V, and the electrolyte impregnation level is greater than 90%, which is a normal impregnation level.

[0092] The larger the voltage difference between the first state of charge voltage and the second state of charge voltage, the lower the electrolyte impregnation level can be evaluated. This is because the larger the voltage difference between the first state of charge voltage and the second state of charge voltage, the lower the electrolyte impregnation level of the 3-electrode cell (20) in the initial state of charge (SOC 5%).

[0093] The voltages dividing the boundaries of the electrolyte impregnation levels, 0.0 V and 0.2 V, can be determined based on a standard three-electrode cell, in which the electrolyte impregnation levels are accurately evaluated as 90% or more, 70% or more but less than 90%, and less than 70%, through the decomposition analysis method described above. The voltages dividing the boundaries of the electrolyte impregnation levels can vary depending on the types of the positive active material, negative active material, and electrolyte. The number of electrolyte impregnation levels is not limited to three stages as illustrated and can be increased further.

[0094] Figure 3 is a graph showing voltage profiles measured for a 3-electrode cell (example) with a normal electrolyte impregnation level of 90% or higher and a 3-electrode cell (comparative example) with a defective electrolyte impregnation level of 70%.

[0095] In Fig. 3, the dotted line graph is a voltage profile for a 3-electrode cell of an example with a normal electrolyte impregnation level, and the solid line graph is a voltage profile for a 3-electrode cell of a comparative example with a poor electrolyte impregnation level.

[0096] Also, in Fig. 3, the voltage profile between the reference terminal and the positive terminal measured during aging after pouring the electrolyte into the 3-electrode cell is profile ①. The voltage profile between the reference terminal and the positive terminal measured during charging the 3-electrode cell to SOC 5% (first state of charge) at a charging rate of 0.3C is profile ②. The voltage profile between the reference terminal and the positive terminal measured during aging the 3-electrode cell at room temperature for 24 hours after stopping charging the 3-electrode cell is profile ③. The voltage profile between the reference terminal and the positive terminal measured during charging the 3-electrode cell again from SOC 5% to SOC 10% (second state of charge) at a charging rate of 0.3C is profile ④.

[0097] Referring to Fig. 3, a 3-electrode cell with a normal electrolyte impregnation level has a first state of charge voltage of 3.7 V, and a 3-electrode cell with a poor electrolyte impregnation level has a first state of charge voltage of 4.0 V.

[0098] Additionally, a 3-electrode cell with a normal electrolyte impregnation level has a voltage difference of 0.5 V between the first charge state voltage and the aging completion voltage, and a 3-electrode cell with a poor electrolyte impregnation level has a voltage difference of 0.8 V between the first charge state voltage and the aging completion voltage.

[0099] Additionally, a 3-electrode cell with a normal electrolyte impregnation level has a voltage difference of -0.1 V between the first state of charge voltage and the second state of charge voltage, and a 3-electrode cell with a poor electrolyte impregnation level has a voltage difference of 0.2 V between the first state of charge voltage and the second state of charge voltage.

[0100] The graph of FIG. 3 supports that the reference voltage information for multiple electrolyte impregnation levels defined by impregnation evaluation voltage according to the embodiment of the present invention shown in FIG. 2 is well consistent with actual experiments.

[0101] Meanwhile, reference voltage information for multiple electrolyte impregnation levels, as illustrated in FIG. 2, can be stored in advance in a storage medium (13) as a lookup table.

[0102] In another embodiment, the control unit (14) may quantitatively determine a plurality of electrolyte impregnation levels by comparing each of a plurality of impregnation evaluation voltages obtained for the three-electrode cell (20) with corresponding reference voltage information, and may determine an average of the plurality of electrolyte impregnation levels as the electrolyte impregnation level of the three-electrode cell.

[0103] Specifically, the control unit (14) can determine the first charge state voltage, the voltage difference between the first charge state voltage and the aging completion voltage, and the voltage difference between the first charge state voltage and the second charge state voltage as the first impregnation evaluation voltage, the second impregnation evaluation voltage, and the third impregnation evaluation voltage, respectively.

[0104] The control unit (14) may also quantitatively determine a first electrolyte impregnation level corresponding to the first impregnation evaluation voltage from first reference voltage information for a plurality of electrolyte impregnation levels (e.g., a table of (a) in FIG. 2), quantitatively determine a second electrolyte impregnation level corresponding to the second impregnation evaluation voltage from second reference voltage information for a plurality of electrolyte impregnation levels (e.g., a table of (b) in FIG. 2), quantitatively determine a third electrolyte impregnation level corresponding to the third impregnation evaluation voltage from third reference voltage information for a plurality of electrolyte impregnation levels (e.g., a table of (c) in FIG. 2), and determine an average of the first electrolyte impregnation level, the second electrolyte impregnation level, and the third electrolyte impregnation level as the electrolyte impregnation level of the 3-electrode cell.

[0105] In this way, if the average of multiple electrolyte impregnation levels determined from multiple impregnation evaluation voltages is determined as the electrolyte impregnation level of the 3-electrode cell, the reliability of the impregnation evaluation result can be improved.

[0106] Referring again to FIG. 1, the electrolyte impregnation level evaluation device (10) of a secondary battery according to an embodiment of the present invention may further include a display (15) and / or a communication interface (16).

[0107] The above control unit (14) can be operably coupled with the display (15) and / or the communication interface (16).

[0108] The control unit (14) may also be configured to visually display the electrolyte impregnation level of the three-electrode cell through a display (15). Preferably, the electrolyte impregnation level may be quantitatively displayed as a number or graph.

[0109] The control unit (14) may also be configured to transmit the electrolyte impregnation level for the three-electrode cell to a computer (17) via the communication interface (16). The computer (17) may be a server that manages the production process of the secondary battery. If the electrolyte impregnation level for the three-electrode cell is lower than a reference level, the server may adjust process variables applied to the electrolyte injection process of the secondary battery to increase the electrolyte impregnation level to a required level. In one example, the server may adjust the electrolyte injection amount and / or the electrolyte injection pressure and / or the electrolyte temperature and / or the internal pressure of the electrolyte injection facility.

[0110] In the above embodiment, the three-electrode cell can be manufactured from semi-finished products of secondary battery cells randomly sampled from a secondary battery production line. In addition, the computer (17) can be connected to the electrolyte impregnation level evaluation device (10) of the secondary battery via a network.

[0111] In this way, the electrolyte impregnation level can be optimized to a desired level by monitoring the change over time in the electrolyte impregnation level using a three-electrode cell manufactured from a semi-finished cell sampled from a secondary battery production line and adaptively controlling the electrolyte injection process.

[0112] FIG. 4 is a drawing specifically showing a state in which a three-electrode cell manufactured in a cylindrical cell structure is loaded into an electrolyte impregnation level evaluation device (10) of a secondary battery according to an embodiment of the present invention immediately after the injection and aging of the electrolyte.

[0113] Referring to FIG. 4, the 3-electrode cell (20) may have a structure of a cylindrical cell including an electrode assembly (21) of a jelly-roll structure.

[0114] The electrode assembly (21) has a jelly-roll structure in which a core (C) and an outer surface (S) are defined by winding the positive and negative electrodes and the separator interposed therebetween around a winding axis. The core (C) may be a hollow space at the center of the electrode assembly (21). A core member (not shown) used in the winding process may be inserted into the core (C).

[0115] Figures 5a to 5c are drawings showing a manufacturing process for an electrode assembly (21) of a jelly-roll structure included in a three-electrode cell (20) according to an embodiment of the present invention. Figure 5a shows the structure of the electrode, Figure 5b shows a winding process of the electrode, and Figure 5c is a perspective view of the manufactured electrode assembly (21).

[0116] Referring to FIGS. 5a to 5c, the positive electrode (211) and the negative electrode (212) have a structure in which an active material (31) is coated on a sheet-shaped current collector (30), and include a non-coated portion (32) on one long side along the winding direction (X). The non-coated portion (32) may be divided into a plurality of segments (32a). A notched groove or a cutting line may be formed between the segments (32a). The shape of the segments (32a) may be a square, a trapezoid, or a parallelogram. The core-side adjacent region of the non-coated portion (32) may have a relatively low height. Optionally, the outer peripheral adjacent region of the non-coated portion (32) may also have a relatively low height.

[0117] The electrode assembly (21) is manufactured by sequentially stacking a positive electrode (211) and a negative electrode (212) together with two separators (213) as illustrated in Fig. 5b, and then winding them in one direction (X). At this time, the non-coated portions of the positive electrode (211) and the negative electrode (212) are arranged in opposite directions in the winding axis direction, and when the winding of the electrode assembly (21) is completed, the separator (213) is exposed to the outside along the winding axis direction. The negative electrode (212) is longer than the positive electrode (211). In addition, the positive electrode (211) overlaps the negative electrode (212) in the longitudinal direction over its entire area.

[0118] After the electrode assembly (21) is wound, the segments (32a) included in the uncoated portion (32) of the positive electrode (211) are bent in the direction of the core (C) to form a first bent surface area (F1) at the upper portion of the electrode assembly (21), as shown in FIG. 5C. Similarly, the segments (32a, not shown) included in the uncoated portion (32) of the negative electrode (212) are also bent in the direction of the core (C) to form a second bent surface area (F2) at the lower portion of the electrode assembly (21).

[0119] Referring again to FIG. 4, the case (23) may be a cylindrical can with an upper first side that is open and a lower second side opposite to the first side that may have a bottom portion (23b) in which a through hole (23h) is formed.

[0120] The 3-electrode cell (20) may also include a rivet terminal (25) installed in the through hole (23h) with a gasket (25a) interposed therebetween so as to be electrically insulated from the case (23). An insulator (29) may be interposed between the inner surface of the bottom portion (23b) of the case (23) and the first folded surface area (F1). In addition, the electrode assembly (21) may be inserted into the case (23) such that the first folded surface area (F1) faces the bottom portion (23b) of the case (23).

[0121] The 3-electrode cell (20) may also include a positive electrode collector (26) electrically connecting the first folded surface area (F1) and the rivet terminal (25), and a negative electrode collector (27) electrically connecting the second folded surface area (F2) and the inner surface of the case (23).

[0122] The flat portion of the rivet terminal (25) facing the positive electrode collector plate (26) may be welded to the positive electrode collector plate (26) by penetrating the insulator (29). In addition, at least a portion (e.g., an edge) of the negative electrode collector plate (27) may be in contact with the inner surface of the beading portion (28) formed near the opening of the case (23). Of course, the negative electrode collector plate (27) may also be in contact with the flat inner surface of the case (23).

[0123] In the 3-electrode cell (20), the reference electrode (22) may be attached to the inner surface of the core (C) using an adhesive material so that one end may be exposed to the outside of the electrode assembly (21). Alternatively, the reference electrode (22) may be installed between the outer surface (S) of the electrode assembly (21) and the inner surface of the case (23).

[0124] The electrolyte can be injected through an opening at the top of the case (23). The three-electrode cell (20) is designed for the purpose of quantitatively evaluating the electrolyte impregnation level. Therefore, after injecting the electrolyte into the case (23), the opening of the case (23) may not be sealed to facilitate easy connection of the reference electrode (22) and the voltage measurement probe.

[0125] Alternatively, the opening of the case (23) may be sealed by a cap assembly (not shown) after electrolyte injection. When sealing the opening of the case (23), a sealing gasket (not shown) may be interposed between the upper end of the case (23) and the cap assembly (not shown), and the upper end of the case (23) may be crimped to integrally secure the sealing gasket and the cap assembly to the upper end of the case (23).

[0126] The structure of a cell including a rivet terminal (25) illustrated in FIG. 4 is disclosed in detail in Korean Patent No. 10-2446797 of the applicant of the present invention. Therefore, the cell structure disclosed in the above-mentioned patent can be equally applied to the three-electrode cell (20) of the present invention.

[0127] The 3-electrode cell (20) can be mounted on a mount portion (18). The mount portion (18) can include a groove (18a) that accommodates an externally exposed portion of a rivet terminal (25), a positive probe (18b) that contacts the lower surface of the rivet terminal (25) corresponding to the positive terminal, and a negative probe (18c) that contacts the lower surface of a case (23) that functions as a negative terminal located around the rivet terminal (25).

[0128] Voltage measurement lines can be wired between the voltage measurement unit (12) and the mount unit (18). In addition, voltage measurement lines can also be wired between the voltage measurement unit (12) and a reference terminal (22t) connected to the reference electrode (22).

[0129] In the present invention, the charging unit (11) can apply charging power through the positive probe (18b) and the negative probe (18c) of the mount unit (18). The charging unit (11) can support various charging protocols such as constant current-constant voltage charging, step charging, and pulse charging. Since the H / W configuration and operating mechanism of the charging unit (11) are widely known in the art, a detailed description thereof will be omitted.

[0130] The charging unit (11) determines the amount of change in the state of charge through the ampere counting method and can charge the 3-electrode cell (20) to the desired state of charge according to the request of the control unit (14).

[0131] The voltage measuring unit (12) may include a voltage measuring circuit capable of measuring the voltage difference between the reference terminal (22t) and the positive terminal (211t). Since the voltage measuring circuit is widely known in the art, a detailed description thereof will be omitted.

[0132] There is no particular limitation on the type of storage medium (13) as long as it can record and erase data and / or information. As an example, the storage medium (13) may be RAM, ROM, a register, a flash memory, a hard disk, or a magnetic recording medium.

[0133] The storage medium (13) can be electrically connected to the control unit (14) via, for example, a data bus so that it can be accessed by the control unit (14).

[0134] The storage medium (13) stores and / or updates and / or erases and / or transmits a program including various control logics performed by the control unit (14), and / or data generated when the control logic is executed, and / or preset data or lookup information / tables, etc.

[0135] The control unit (14) may optionally include a processor, an application-specific integrated circuit (ASIC), other chipsets, logic circuits, registers, communication modems, data processing devices, etc. known in the art to execute the various control logics described above. In addition, when the control logic is implemented as software, the control unit (14) may be implemented as a set of program modules. In this case, the program modules may be stored in a memory and executed by the processor. The memory may be located inside or outside the processor, and may be connected to the processor by various well-known computer components. In addition, the memory may be included in the storage medium (14) of the present invention. In addition, the memory is a general term for a device in which information is stored regardless of the type of device, and does not refer to a specific memory device.

[0136] At least one or more of the various control logics of the control unit (14) are combined, and the combined control logics can be written in a computer-readable code system and stored in a computer-readable storage medium. There is no particular limitation on the type of the storage medium as long as it can be accessed by a processor included in the computer. As an example, the storage medium includes at least one selected from the group including a ROM, a RAM, a register, a CD-ROM, a magnetic tape, a hard disk, a floppy disk, and an optical data recording device. In addition, the code system can be distributed and stored and executed in a network-connected computer. In addition, functional programs, codes, and code segments for implementing the combined control logics can be easily inferred by programmers in the technical field to which the present invention pertains.

[0137] The electrolyte impregnation level evaluation device (10) and the computer (17) of the secondary battery according to the present invention can constitute a system for managing the injection process of a secondary battery production line.

[0138] Below, a method for evaluating the electrolyte impregnation level of a secondary battery will be described in detail.

[0139] Figure 6 is a flowchart showing the flow of a method for evaluating the electrolyte impregnation level of a secondary battery according to an embodiment of the present invention.

[0140] Referring to FIG. 6 together with FIG. 1, first, in step S10, a 3-electrode cell (20) is prepared. The 3-electrode cell (20) can be manufactured by randomly sampling a semi-finished cell before the sealing process is performed in a secondary battery production line.

[0141] Next, in step S20, an electrolyte is injected into the 3-electrode cell (20), aged for a first hour (e.g., 24 hours), and the 3-electrode cell (20) is loaded onto the mount portion (18 in FIG. 4).

[0142] Next, in step S30, the control unit (14) controls the charging unit (11) to charge the 3-electrode cell (20) to the first charging state (e.g., SOC 5%), and obtains the first charging state voltage corresponding to the voltage difference between the reference terminal (22t) and the positive terminal (211t) through the voltage measuring unit (12).

[0143] In one embodiment, the control unit (14) controls the charging unit (11) in step S30 to repeatedly measure the voltage difference between the reference terminal (22t) and the positive terminal (211t) at time intervals while charging the three-electrode cell (20) to the first charging state, generate a first voltage profile according to time, and record it in the storage medium (13), and obtain the terminal voltage of the first voltage profile as the first charging state voltage.

[0144] Next, in step S40, the control unit (14) suspends the operation of the charging unit (11) for a second time (e.g., 24 hours) to age the 3-electrode cell (20) at room temperature for a second time, and after aging is completed, an aging completion voltage corresponding to the voltage difference between the reference terminal (22t) and the positive terminal (211t) is obtained.

[0145] In one embodiment, the control unit (14) repeatedly measures the voltage difference between the reference terminal (22t) and the positive terminal (211t) at time intervals while aging the three-electrode cell (20) in a no-load state for a second time in step S40, generates a second voltage profile according to time, and records the same in the storage medium (13), and obtains the terminal voltage of the second voltage profile as the aging completion voltage.

[0146] Next, in step S50, the control unit (14) controls the charging unit (11) to charge the 3-electrode cell (20) from the first charging state (e.g., SOC 5%) to the second charging state (e.g., SOC 10%), and obtains the second charging state voltage corresponding to the voltage difference between the reference terminal (22t) and the positive terminal (211t) through the voltage measuring unit (12).

[0147] In one embodiment, the control unit (14) controls the charging unit (11) in step S50 to repeatedly measure the voltage difference between the reference terminal (22t) and the positive terminal (211t) at time intervals while charging the three-electrode cell (20) from the first charging state to the second charging state, generate a third voltage profile according to time, and record it in the storage medium (13), and obtain the terminal voltage of the third voltage profile as the second charging state voltage.

[0148] Next, in step S60, the control unit (14) determines at least one of the first charge state voltage, the voltage difference between the first charge state voltage and the aging completion voltage, and the voltage difference between the first charge state voltage and the second charge state voltage as the impregnation evaluation voltage.

[0149] Next, in step S70, the control unit (14) identifies an electrolyte impregnation level corresponding to the impregnation evaluation voltage from reference voltage information for a plurality of predefined electrolyte impregnation levels, and quantitatively determines the identified electrolyte impregnation level as the electrolyte impregnation level of the 3-electrode cell.

[0150] Preferably, the reference voltage information may include first to n-th electrolyte impregnation levels (n is a natural number greater than or equal to 2) and first to n-th voltage section information corresponding to each electrolyte impregnation level.

[0151] Preferably, in the reference voltage information, the first to nth voltage section information can be set differently for each type of the impregnation evaluation voltage (see FIG. 2).

[0152] According to another embodiment, the control unit (14) may determine the first charge state voltage, the voltage difference between the first charge state voltage and the aging completion voltage, and the voltage difference between the first charge state voltage and the second charge state voltage as the first impregnation evaluation voltage, the second impregnation evaluation voltage, and the third impregnation evaluation voltage, respectively, in step S60.

[0153] In addition, the control unit (14) quantitatively determines the first electrolyte impregnation level, the second electrolyte impregnation level, and the third electrolyte impregnation level corresponding to the first impregnation evaluation voltage, the second impregnation evaluation voltage, and the third impregnation evaluation information, respectively, from reference voltage information for a plurality of electrolyte impregnation levels predefined for each type of impregnation evaluation voltage in step S70, and determines the average of the first electrolyte impregnation level, the second electrolyte impregnation level, and the third electrolyte impregnation level as the electrolyte impregnation level of the 3-electrode cell.

[0154] The method of using multiple impregnation evaluation voltages as described above can further improve the reliability of the electrolyte impregnation evaluation results.

[0155] An embodiment of the present invention may further include a step in which the control unit (14) outputs the electrolyte impregnation level of the three-electrode cell (20) through a display (15); and / or a step in which the control unit (14) transmits the electrolyte impregnation level of the three-electrode cell (20) to a computer (17) through a communication interface (16). The computer (17) may be a server that manages a production line of secondary batteries. As described above, the server may adaptively adjust and optimize the process variables of the electrolyte injection process by referring to the electrolyte impregnation level received from the control unit (14).

[0156]

[0157] In describing various embodiments of the present invention, components designated as "parts" should be understood as functionally distinct elements rather than physically distinct elements. Therefore, each component may be selectively integrated with other components or divided into sub-components for efficient execution of control logic(s). However, it will be apparent to those skilled in the art that even if components are integrated or divided, if the same functionality can be recognized, the integrated or divided components should be interpreted as falling within the scope of the present invention.

[0158] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

Claims

1. (a) A step of preparing a three-electrode cell including a positive terminal, a negative terminal, and a reference terminal; (b) a step of injecting electrolyte into the case of the three-electrode cell and aging it for a first hour; (c) a step of charging the three-electrode cell to a preset first state of charge (SOC: State Of Charge) and obtaining a first state of charge voltage between the reference terminal and the positive terminal in the first state of charge; (d) A step of aging the three-electrode cell for a second time in a no-load state, and then obtaining an aging completion voltage between the reference terminal and the positive terminal; (e) a step of charging the three-electrode cell from the first charge state to the second charge state, and obtaining a second charge state voltage between the reference terminal and the positive terminal in the second charge state; (f) a step of determining at least one of the first charge state voltage, the voltage difference between the first charge state voltage and the aging completion voltage, and the voltage difference between the first charge state voltage and the second charge state voltage as an impregnation evaluation voltage; and (g) A method for evaluating an electrolyte impregnation level of a secondary battery, comprising: a step of identifying an electrolyte impregnation level corresponding to the impregnation evaluation voltage from reference voltage information for a plurality of predefined electrolyte impregnation levels, and determining the identified electrolyte impregnation level as the electrolyte impregnation level of the three-electrode cell; 2. In paragraph 1, A method for evaluating an electrolyte impregnation level of a secondary battery, wherein the reference voltage information includes first to n-th electrolyte impregnation levels (n is a natural number greater than or equal to 2) and first to n-th voltage section information corresponding to each electrolyte impregnation level.

3. In paragraph 2, A method for evaluating an electrolyte impregnation level of a secondary battery, wherein, in the above reference voltage information, the first to nth voltage section information is set differently for each type of the impregnation evaluation voltage.

4. In paragraph 1, In step (f) above, The first charge state voltage, the voltage difference between the first charge state voltage and the aging completion voltage, and the voltage difference between the first charge state voltage and the second charge state voltage are determined as the first impregnation evaluation voltage, the second impregnation evaluation voltage, and the third impregnation evaluation voltage, respectively. In the above step (g), A method for evaluating an electrolyte impregnation level of a secondary battery, comprising: determining a first electrolyte impregnation level, a second electrolyte impregnation level, and a third electrolyte impregnation level corresponding to the first impregnation evaluation voltage, the second impregnation evaluation voltage, and the third impregnation evaluation information, respectively, from reference voltage information for a plurality of predefined electrolyte impregnation levels, and determining an average of the first electrolyte impregnation level, the second electrolyte impregnation level, and the third electrolyte impregnation level as the electrolyte impregnation level of the three-electrode cell.

5. In paragraph 1, The above first hour is 0 to 48 hours, A method for evaluating the electrolyte impregnation level of a secondary battery, wherein the second time is 12 to 48 hours.

6. In paragraph 1, A method for evaluating the electrolyte impregnation level of a secondary battery, wherein the first state of charge is 3% to 7% and the second state of charge is 8% to 12%.

7. In paragraph 1, Step (c) above, (c1) a step of generating a first voltage profile by repeatedly measuring the voltage difference between the reference terminal and the positive terminal at time intervals while charging the three-electrode cell to a preset first charge state; and (c2) A method for evaluating an electrolyte impregnation level of a secondary battery, comprising: a step of obtaining the terminal voltage of the first voltage profile as the first charge state voltage.

8. In paragraph 1, Step (d) above, (d1) a step of generating a second voltage profile by repeatedly measuring the voltage difference between the reference terminal and the positive terminal at time intervals while aging the 3-electrode cell for a second time in a no-load state; and (d2) A method for evaluating an electrolyte impregnation level of a secondary battery, comprising: a step of obtaining the terminal voltage of the second voltage profile as the aging completion voltage.

9. In paragraph 1, Step (e) above, (e1) a step of repeatedly measuring the voltage difference between the reference terminal and the positive terminal at time intervals while charging the 3-electrode cell from the first charge state to the second charge state to obtain a third voltage profile; and (e2) A method for evaluating an electrolyte impregnation level of a secondary battery, comprising: a step of obtaining the terminal voltage of the third voltage profile as the second charge state voltage.

10. In paragraph 1, A method for evaluating an electrolyte impregnation level of a secondary battery, further comprising a step of displaying the electrolyte impregnation level through a display.

11. In paragraph 1, A method for evaluating an electrolyte impregnation level of a secondary battery, further comprising the step of transmitting the electrolyte impregnation level to a computer.

12. In paragraph 1, The above electrode assembly is an electrode assembly in which a core and an outer surface are defined by winding a positive electrode and a negative electrode and a separator interposed therebetween around a winding axis, wherein the positive electrode and the negative electrode each include an active material portion coated with an active material along a winding direction and a non-coated portion not coated with an active material, and the non-coated portion of the positive electrode and the non-coated portion of the negative electrode are exposed to the outside of the separator so as to face each other along the winding axis direction, and the non-coated portion of the positive electrode is bent toward the core to form a first bent surface area, and the non-coated portion of the negative electrode is bent toward the core to form a second bent surface area. The case is a cylindrical can having a bottom portion having a first side open and a through hole formed on a second side opposite to the first side in the direction of the winding axis, The above three-electrode cell includes a rivet terminal fastened to the through hole so as to be electrically insulated from the cylindrical can, a positive electrode collector connecting the first folded surface area and the rivet terminal, and a negative electrode collector connecting the second folded surface area and the inner surface of the cylindrical can. The above reference electrode is installed in the core of the electrode assembly so that one end can be exposed to the outside of the electrode assembly or is installed between the outer surface of the electrode assembly and the inner surface of the case, A method for evaluating an electrolyte impregnation level of a secondary battery, wherein the positive terminal is the rivet terminal, the negative terminal is the case, and the reference terminal is a lead connected to the reference electrode.

13. A mount portion into which a 3-electrode cell aged for a first hour after electrolyte injection is loaded, wherein the 3-electrode cell includes a positive terminal, a negative terminal, and a reference terminal; A charging unit that applies a charging current to the above 3-electrode cell; A voltage measuring unit for measuring the voltage difference between the reference terminal and the positive terminal; A storage medium storing reference voltage information regarding multiple electrolyte impregnation levels; and It includes a control unit operably connected to the charging unit, the voltage measuring unit, and the storage medium, The above control unit, Controlling the charging unit to charge the 3-electrode cell to the first charging state and obtaining the first charging state voltage through the voltage measuring unit in the first charging state, After stopping the operation of the above charging unit for a second time, the aging completion voltage is obtained through the voltage measuring unit, Controlling the charging unit to charge the 3-electrode cell from the first charging state to the second charging state, and obtaining the second charging state voltage through the voltage measuring unit in the second charging state, At least one of the first charge state voltage, the voltage difference between the first charge state voltage and the aging completion voltage, and the voltage difference between the first charge state voltage and the second charge state voltage is determined as the impregnation evaluation voltage, An electrolyte impregnation level evaluation device for a secondary battery, configured to identify an electrolyte impregnation level corresponding to the impregnation evaluation voltage from the reference voltage information and determine the identified electrolyte impregnation level as the electrolyte impregnation level of the three-electrode cell.

14. In paragraph 13, A secondary battery electrolyte impregnation level evaluation device, wherein the reference voltage information includes first to nth electrolyte impregnation levels (n is a natural number greater than or equal to 2) and first to nth voltage section information corresponding to each electrolyte impregnation level.

15. In paragraph 14, A secondary battery electrolyte impregnation level evaluation device, wherein the above reference voltage information is set differently for each type of impregnation evaluation voltage.

16. In paragraph 13, The above control unit, A secondary battery electrolyte impregnation level evaluation device configured to repeatedly acquire a voltage difference between the reference terminal and the positive terminal at time intervals through the voltage measuring unit while controlling the charging unit to charge the 3-electrode cell to a preset first charge state, generate a first voltage profile according to time, and record the generated first voltage profile in the storage medium, and acquire the terminal voltage of the first voltage profile as the first charge state voltage.

17. In paragraph 13, The above control unit, A device for evaluating an electrolyte impregnation level of a secondary battery, configured to repeatedly acquire a voltage difference between the reference terminal and the positive terminal at time intervals through the voltage measuring unit while the operation of the charging unit is stopped for a second time, generate a second voltage profile according to time, record the same in a storage medium, and acquire the terminal voltage of the second voltage profile as the aging completion voltage.

18. In paragraph 13, The above control unit, A secondary battery electrolyte impregnation level evaluation device configured to repeatedly acquire a voltage difference between the reference terminal and the positive terminal at time intervals through the voltage measuring unit while controlling the charging unit to charge the 3-electrode cell from the first charging state to the second charging state, generate a third voltage profile according to time, record the generated voltage profile in a storage medium, and acquire the terminal voltage of the third voltage profile as the second charging state voltage.

19. In paragraph 13, Further comprising a display operably coupled to the control unit, A device for evaluating an electrolyte impregnation level of a secondary battery, wherein the control unit is configured to display the electrolyte impregnation level through the display.

20. In paragraph 13, comprising a communication interface operably coupled to the control unit; A device for evaluating an electrolyte impregnation level of a secondary battery, wherein the control unit is configured to transmit the electrolyte impregnation level to a computer through the communication interface.

21. A device for evaluating the electrolyte impregnation level of a secondary battery according to Article 13; and A computer that receives an electrolyte impregnation level from the electrolyte impregnation level evaluation device through a network; A system characterized in that the computer controls process conditions applied to the secondary battery injection process by referring to the electrolyte impregnation level.

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