Electrochemical cell

Abstract

An electrochemical cell comprises a positive electrode, a negative electrode, a first separator between the positive electrode and the negative electrode, and first and second reference electrodes disposed between the positive electrode and the first separator. The first reference electrode is configured to measure the potential of the negative electrode during discharge, and the second reference electrode is configured to measure the potential of the negative electrode during charge.

Description

electrochemical cell

[0001] It's about electrochemical cells.

[0002] Lithium batteries are used in a variety of applications due to their high voltage and high energy density. Examples include home appliances and electric vehicles (HEVs, PHEVs).

[0003] Electric vehicles can operate at high temperatures, must charge or discharge large amounts of electricity, and must be used for long periods of time, so accurate discharge capacity and charge / discharge voltage design are required.

[0004] If the anode and cathode potentials are measured differently from the actual potential during charging and discharging of a lithium battery, the charging and discharging may be stopped at a lower capacity than the actual capacity. As a result, the efficiency of the lithium battery is reduced and the energy density of the lithium battery is reduced. Therefore, by accurately understanding the actual behavior of the anode and cathode potentials during charging and discharging of a lithium battery, the overall voltage change of the lithium battery can be predicted more accurately. By more accurately predicting the voltage change during charging and discharging of a lithium battery, the capacity of the lithium battery can be designed more accurately. Consequently, by more accurately designing the capacity of a lithium battery, the energy density of the lithium battery can be further improved. A method for more accurately measuring the anode and / or cathode potential during charging and discharging of a lithium battery is required.

[0005] One aspect is to provide a novel electrochemical cell capable of preventing errors in cathode potential during charging and discharging of the electrochemical cell by using different reference electrodes during charging and discharging of the electrochemical cell.

[0006] According to the implementation example

[0007] comprising an anode; a cathode; and a first separator between the anode and the cathode,

[0008] It includes a first reference electrode and a second reference electrode disposed between the anode and the first separator,

[0009] The first reference electrode is configured to measure the potential of the cathode during discharge,

[0010] An electrochemical cell is provided, wherein the second reference electrode is configured to measure the potential of the cathode during charging.

[0011] According to one aspect, it is possible to provide a novel electrochemical cell having multiple reference electrodes and preventing errors in cathode potential by using different reference electrodes during charging and discharging of the electrochemical cell.

[0012] Figure 1 is a schematic exploded view of an electrochemical cell according to an exemplary embodiment.

[0013] Figure 2 is a schematic exploded view of an electrochemical cell according to an exemplary embodiment.

[0014] Figure 3 is a schematic diagram of a lithium battery according to an exemplary embodiment.

[0015] Figure 4 is a schematic diagram of a lithium battery according to an exemplary embodiment.

[0016] Figure 5 is a schematic diagram of a lithium battery according to an exemplary embodiment.

[0017] Figure 6 is a schematic diagram of a lithium battery according to an exemplary embodiment.

[0018] Figure 7 is a profile showing the potential of the electrochemical cell, the anode potential with respect to the first reference electrode, the anode potential with respect to the second reference electrode, the cathode potential with respect to the first reference electrode, and the cathode potential with respect to the second reference electrode during the charging process of the electrochemical cell of Example 1.

[0019] Figure 8 is an enlarged view of the cathode potential of Figure 7.

[0020] Figure 9 is a profile showing the potential of the electrochemical cell, the anode potential with respect to the first reference electrode, the anode potential with respect to the second reference electrode, the cathode potential with respect to the first reference electrode, and the cathode potential with respect to the second reference electrode during the discharge process of the electrochemical cell of Example 1.

[0021] Figure 10 is an enlarged view of the cathode potential of Figure 9.

[0022] Unless otherwise defined, all terms (including technical and scientific terms) used in this disclosure have the same meaning as commonly understood by those of ordinary skill in the art to which this disclosure pertains. Furthermore, terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning within the context of the relevant technology and this disclosure, and should not be interpreted in an idealized or overly formal sense.

[0023] Exemplary embodiments are described in this disclosure with reference to cross-sectional drawings that are schematic representations of idealized embodiments. As such, variations from the shapes depicted are to be expected, for example, as a result of manufacturing techniques and / or tolerances. Therefore, the embodiments described in this disclosure should not be construed as limited to the specific shapes of regions as depicted in this disclosure, but should encompass variations in shapes resulting from, for example, manufacturing. For example, regions depicted or described as flat may typically have rough and / or non-linear features. Moreover, angles depicted as sharp may be rounded. Therefore, the regions depicted in the drawings are schematic in nature, and their shapes are not intended to depict the precise shapes of the regions, nor are they intended to limit the scope of the claims.

[0024] This creative idea may be embodied in many different forms and should not be construed as limited to the embodiments described in this disclosure. These embodiments are provided so that this disclosure will be thorough and complete, and so that it will fully convey the scope of the creative idea to those skilled in the art. Like reference numerals in the drawings indicate like elements.

[0025] When a component is referred to as being "on" another component, it can be understood that it is either directly on top of the other component or that other components may be intervening between them. Conversely, when a component is referred to as being "directly on" another component, no intervening components are present.

[0026] Although terms such as "first," "second," "third," etc. may be used herein to describe various components, elements, regions, layers, and / or zones, these components, elements, regions, layers, and / or zones should not be limited by these terms. These terms are only used to distinguish one component, element, region, layer, or zone from another component, element, region, layer, or zone. Thus, a first component, element, region, layer, or zone described below may be referred to as a second component, element, region, layer, or zone without departing from the teachings of this disclosure.

[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms including "at least one," unless the content clearly dictates otherwise. "At least one" should not be construed as limiting to the singular. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items. The terms "comprises" and / or "comprising" as used in the detailed description specify the presence of stated features, regions, integers, steps, operations, components, and / or ingredients, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, components, ingredients, and / or groups thereof.

[0028] Spatially relative terms such as "below," "under," "lower," "above," "upper," and the like may be used herein to readily describe the relationship of one component or feature to another. It will be understood that spatially relative terms are intended to encompass different orientations of the device when in use or operation in addition to the orientations depicted in the drawings. For example, if the device in the drawings were turned over, a component described as "below" or "below" another component or feature would then be oriented "above" the other component or feature. Thus, the exemplary term "below" can encompass both the above and below orientations. The device may be arranged in other orientations (rotated 90 degrees or otherwise rotated), and the spatially relative terms used herein may be interpreted accordingly.

[0029] "Group" means a group in the periodic table of elements according to the International Union of Pure and Applied Chemistry ("IUPAC") Group 1-18 classification system.

[0030] In this disclosure, "particle diameter" refers to the average diameter when the particle is spherical, and refers to the average major axis length when the particle is non-spherical. The particle diameter can be measured using a particle size analyzer (PSA). The "particle diameter" is, for example, the average particle diameter. The "average particle diameter" is, for example, D50, the median particle diameter.

[0031] D50 is the size of the particle corresponding to 50% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0032] D90 is the size of the particle corresponding to 90% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0033] D10 is the size of the particle corresponding to 10% of the cumulative volume, calculated from the particle side with a small particle size in the particle size distribution measured by laser diffraction.

[0034] In the present disclosure, the “weight average molecular weight” of a polymer can be measured, for example, using gel permeation chromatography (GPC), and is a relative value to a polystyrene standard sample.

[0035] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0036] In this disclosure, “alloy” means a mixture of two or more metals.

[0037] In the present disclosure, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0038] In the present disclosure, “positive electrode material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0039] In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0040] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material.

[0041] In the present disclosure, “delithiation” and “delithiate” mean a process of removing lithium from an electrode active material.

[0042] In this disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery.

[0043] In this disclosure, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

[0044] In the present disclosure, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during a discharge process.

[0045] In the present disclosure, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during a discharge process.

[0046] While specific implementations have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are not currently anticipated or unforeseen may occur to the applicant or those skilled in the art. Accordingly, the appended claims, as filed and as amended, are intended to encompass all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0047] Below, electrochemical cells according to exemplary implementation examples are described in more detail.

[0048] [Electrochemical cell]

[0049] An electrochemical cell according to one embodiment includes an anode; a cathode; and a first separator between the anode and the cathode, and includes a first reference electrode and a second reference electrode disposed between the anode and the first separator, wherein the first reference electrode is configured to measure a potential of the cathode during discharge, and the second reference electrode is configured to measure a potential of the cathode during charge.

[0050] By measuring the potential of the cathode with respect to the first reference electrode during discharge, errors due to potential changes of the cathode electrode can be prevented. For example, the second reference electrode may distort the potential of the cathode measured with respect to the second reference electrode because its own potential increases as the discharge capacity increases during discharge. That is, errors may occur in the cathode potential measured during discharge. In contrast, the first reference electrode may have little change in its own potential even though the cathode potential increases during discharge.

[0051] By measuring the potential of the negative electrode during charging with respect to the second reference electrode, errors due to changes in the negative electrode potential can be prevented. For example, as the charge capacity of the first reference electrode increases during charging, there may be a section where the negative electrode potential measured with respect to the first reference electrode has a negative value (i.e., a value less than 0). This negative negative electrode potential can be interpreted as being due to lithium deposited on the negative electrode. However, in reality, this negative negative electrode potential is due to a change in the potential of the first reference electrode due to the formation of a film on the surface of the first reference electrode, and not due to a change in the potential of the negative electrode. That is, errors may occur in the negative electrode potential measured with respect to the first reference electrode during charging. In contrast, by measuring the potential of the negative electrode during charging with respect to the second reference electrode, the negative electrode potential always has a positive value as the potential of the negative electrode decreases, so this error can be prevented.

[0052] As a result, the electrochemical cell includes a first reference electrode and a second reference electrode disposed between the positive electrode and the first separator, wherein the first reference electrode is configured to measure the potential of the negative electrode during discharge, and the second reference electrode is configured to measure the potential of the negative electrode during charge, thereby allowing more accurate measurement of the potential change of the negative electrode during charge and discharge of the electrochemical cell. Accordingly, the capacity of the electrochemical cell can be designed more accurately, and the energy density of the electrochemical cell can be further improved.

[0053] [Reference electrode]

[0054] Referring to FIGS. 1 and 2, an electrochemical cell (1) includes an anode (10); a cathode (20); and a first separator (40) between the anode (10) and the cathode (20). A first reference electrode (50) and a second reference electrode (60) are disposed between the anode (10) and the first separator (40). The first reference electrode (50) is configured to measure the potential of the cathode (20) during discharge. The second reference electrode (60) is configured to measure the potential of the cathode (20) during charge.

[0055] The potential measurement of the cathode (20) can be performed more accurately when the first reference electrode (50) and the second reference electrode (60) are placed between the anode (10) and the first separator (40). When the first reference electrode (50) and the second reference electrode (60) are placed between the cathode (20) and the first separator (40), an error may occur in the potential measurement of the cathode (20) due to mutual interference between the first reference electrode (50) and the second reference electrode (60) and the cathode (20) due to the first reference electrode (50) and the second reference electrode (60) being too close to the cathode (20).

[0056] In the electrochemical cell (1), the first reference electrode (50) and the second reference electrode (60) may be spaced apart from each other, for example, on the first separator (40). By spaced apart from each other, for example, on the first separator (40), the first reference electrode (50) and the second reference electrode (60) can prevent mutual interference between the first reference electrode (50) and the second reference electrode (60). The distance at which the first reference electrode (50) and the second reference electrode (60) are spaced apart from each other may be 2 times or more, 3 times or more, 5 times or more, or 10 times or more the width of the first reference electrode (50). By spaced apart from each other within this range, mutual interference between the first reference electrode (50) and the second reference electrode (60) can be more effectively prevented. As a result, the potential of the cathode (20) during charging and discharging of the electrochemical cell (1) can be measured more accurately.

[0057] In the electrochemical cell (1), the first reference electrode (50) may be a plate-shaped electrode. Since the first reference electrode (50) is plate-shaped, it has a stable contact area with the electrolyte, thereby more effectively preventing measurement errors due to overcurrent and / or overvoltage during the charge and discharge process of the electrochemical cell (1). Since the first reference electrode (50) is plate-shaped, the influence of film formation, etc. due to local side reactions on the surface of the first reference electrode (50) during the charge and discharge process can be relatively alleviated compared to a rod-shaped electrode. The smaller the area of ​​the plate-shaped electrode, the lower the resistance, thereby minimizing interference caused by the introduction of the first reference electrode (50) during the charge and discharge of the electrochemical cell (1). Alternatively, the first reference electrode (50) may be a wire-shaped electrode.

[0058] In the electrochemical cell (1), the first reference electrode (60) may be a wire-shaped electrode or a plate-shaped electrode.

[0059] Since the first reference electrode (60) is a wire-shaped electrode, interference caused by the introduction of the first reference electrode (60) during charging and discharging of the electrochemical cell (1) can be minimized. For example, the amount of current between the positive electrode (10) and / or negative electrode (20) and the first reference electrode (60) can be minimized. Accordingly, a measurement error when measuring the potential between the positive electrode (10) and / or negative electrode (20) and the first reference electrode (60) can be minimized. The wire-shaped electrode can have a reduced resistance compared to, for example, a plate-shaped electrode.

[0060] Since the first reference electrode (60) is a plate-shaped electrode, it is easy to handle and can be more easily placed within the electrochemical cell (1). Since the first reference electrode (60) is plate-shaped, errors due to local side reactions on the surface of the first reference electrode (60) can be relatively alleviated compared to a rod-shaped electrode.

[0061] In the electrochemical cell (1), for example, the first reference electrode (50) may include lithium metal. Since the first reference electrode (50) is lithium metal, there is no need to additionally compensate the potential of the positive electrode (10) and / or negative electrode (20) for lithium, so that the potential measurement of the positive electrode (10) and / or negative electrode (20) can be performed more easily. The first reference electrode (50) may be, for example, lithium metal foil. A plate-shaped first reference electrode (50) can be easily manufactured using lithium metal foil.

[0062] In the electrochemical cell (1), the potential change of the first reference electrode (50) may be smaller than the potential change of the first reference electrode (60), for example, when the electrochemical cell is discharged at a depth of discharge (Depth of Discharge) of 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more. The DOD is the percentage of the actual discharged capacity with respect to the designed discharge capacity. In the electrochemical cell (1) using lithium metal as the first reference electrode (50), in the process of discharging to 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more of the designed discharge capacity of the electrochemical cell (1), the film on the surface of the lithium metal is all removed, so that the potential of the negative electrode (20) with respect to pure lithium metal can be measured. Therefore, the potential of the negative electrode (20) with respect to the first reference electrode (50) can be measured relatively accurately. Since the first reference electrode (60) uses a material other than lithium metal, the self-potential of the first reference electrode (60) increases during the discharge process, so the accuracy of the cathode (20) potential for the first reference electrode (60) may be relatively lower than that of the first reference electrode (50).

[0063] In the electrochemical cell (1), for example, the first reference electrode (60) may include an electrode active material. The electrode active material may include, but is not limited to, a metal oxide, a lithium transition metal oxide, or a combination thereof, and any material having a stable operating potential and low resistance in the art may be used. The lithium transition metal oxide may include, for example, lithium vanadium oxide, lithium titanium oxide, or a combination thereof. The lithium vanadium oxide may be, for example, Li3VO4, LiV3O8, LiVO3. The lithium titanium oxide may be, for example, Li4Ti5O. 12(LTO). The metal oxide may include, for example, vanadium oxide, titanium oxide, or a combination thereof. The vanadium oxide may be, for example, V2O5, VO2. The titanium oxide may be, for example, TiO2.

[0064] The first reference electrode (60) may further include, for example, a binder, a conductive material, or a combination thereof. The first reference electrode (60) may be prepared by, for example, mixing an electrode active material, a binder, and a conductive material, and then coating an electrode active material slurry prepared by mixing the mixture with a solvent on a conductive substrate. The binder may include, for example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene, and mixtures thereof, or a styrene butadiene rubber-based polymer. The binder is not limited thereto, and any binder that can be used in the art may be used. The conductive material may include, for example, acetylene black, Ketjen black, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powders such as copper, nickel, aluminum, and silver, metal fibers, etc. The binder may also include one or a mixture of one or more conductive materials such as a polyphenylene derivative. The conductive material is not limited to these, and any conductive material that can be used in the relevant technical field may be used. The solvent may include, for example, N-methylpyrrolidone, acetone, or water. The solvent is not limited to these, and any conductive material that can be used in the relevant technical field may be used. The contents of the electrode active material, conductive material, binder, and solvent are at levels typically used in the electrochemical cell (1). Depending on the purpose and configuration of the electrochemical cell (1), one or more of the conductive material, binder, and solvent may be omitted.

[0065] When charging the electrochemical cell (1), the potential of the cathode (20) with respect to the first reference electrode (60) can be maintained at, for example, 0 V (vs. Li) or more in the range of SOC (State of Charge) from 10% to 100%, 20 to 100%, 30 to 100%, 40 to 100%, or 50 to 100%. When charging the electrochemical cell (1), the potential of the cathode (20) with respect to the first reference electrode (60) can be maintained at, for example, 0 V (vs. Li) or more, 0.1 V or more, 0.2 V or more, or 0.5 V or more in the range of SOC (State of Charge) from 10% to 100%. During the charging process of the electrochemical cell (1), the potential of the cathode (20) with respect to the first reference electrode (60) can always have such a positive value. Since the potential of the cathode (20) with respect to the first reference electrode (60) always has a positive value during the charging process, errors such as the potential of the cathode (20) having a negative value can be prevented. For example, when the first reference electrode is lithium metal, there may be a case where the potential of the cathode (20) with respect to the first reference electrode (50) has a negative value in the SOC range of 10 to 100% during charging of the electrochemical cell (1). In this case, the accuracy of the potential of the cathode (20) is reduced. SOC is the percentage of the currently charged capacity compared to the designed charging capacity.

[0066] In the electrochemical cell (1), the redox potential of the first reference electrode (60) may be higher than the redox potential of the first reference electrode (50). For example, the difference between the redox potential of the second reference electrode and the redox potential of the first reference electrode may be 2.0 V or less, 1.6 V or less, 1.0 V or less, or 0.5 V or less. Lithium metal is used as the first reference electrode (50), and Li4Ti5O is used as the first reference electrode (60). 12In the electrochemical cell (1) using, the difference between the redox potential of the first reference electrode (50) and the redox potential of the first reference electrode (60) is, for example, 1.55 V (vs. Li / Li + ) is. Since the first reference electrode (50) and the first reference electrode (60) have redox potentials in this range, the potential change of the negative electrode (20) can be measured more easily during the charge / discharge process. If the difference between the first reference electrode (50) and the first reference electrode (60) increases excessively, the error in the potential of the negative electrode (20) measured during the charge / discharge process may increase.

[0067] [Separator]

[0068] Referring to FIGS. 1 and 2, an electrochemical cell (1) includes an anode (10); a cathode (20); and a first separator (40) between the anode (10) and the cathode (20). The electrochemical cell (1) may further include a second-first separator (41) disposed between the anode (10) and a first reference electrode (50). The electrochemical cell (1) may further include a second-second separator (42) disposed between the anode (10) and a second reference electrode (60).

[0069] In the electrochemical cell (1), interference, side reactions, etc. between the anode (10) and the first reference electrode (50) and / or the first reference electrode (60) can be more easily prevented by further including the second-1 separator (41) and the second-2 separator (42).

[0070] In the electrochemical cell (1), the 2-1 separator (41) and the 2-2 separator (42) can be arranged spaced apart from each other on the first separator. By the 2-1 separator (41) and the 2-2 separator (42) being arranged spaced apart from each other on the first separator, interference between the first reference electrode (50) and the first reference electrode (60) can be more easily prevented.

[0071] In the electrochemical cell (1), the first separator, the second-first separator (41), and the second-second separator (42) may be, for example, porous membranes.

[0072] Any separator commonly used in electrochemical cells (1) can be used. The separator may have, for example, low resistance to ion migration of the electrolyte and excellent electrolyte absorption capacity. The separator may be selected from, for example, glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof. The separator may be in the form of, for example, non-woven fabric or woven fabric. The electrochemical cell (1) may use a rollable separator such as, for example, polyethylene, polypropylene, or a separator having excellent organic electrolyte absorption capacity.

[0073] The membrane can be manufactured, for example, according to the following method.

[0074] A separator composition is prepared by mixing a polymer, a filler, and a solvent. The separator composition may be directly coated on the positive electrode (10) and / or the negative electrode (20) and dried to prepare a separator. Alternatively, the separator composition may be cast on a support and dried, and then the separator film peeled from the support and laminated on the positive electrode (10) and / or the negative electrode (20) to prepare a separator. The polymer used in the manufacture of the separator is not particularly limited, and any material used as an electrode binder may be used. The polymer used in the manufacture of the separator may include, for example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof.

[0075] In the electrochemical cell (1), the first reference electrode (50) and the first reference electrode (60) may be free between the cathode (20) and the first separator. The first reference electrode (50) and the first reference electrode (60) may not be disposed between the cathode (20) and the first separator. By not disposing the first reference electrode (50) and the first reference electrode (60) between the cathode (20) and the first separator, the measurement error of the cathode (20) potential with respect to the first reference electrode (50) and / or the first reference electrode (60) may be reduced. In the electrochemical cell (1) in which the first reference electrode (50) and the first reference electrode (60) are disposed too close to the cathode (20), the error of the measured cathode (20) potential may increase due to interference between the first reference electrode (50) and the first reference electrode (60) and the cathode (20).

[0076] In the electrochemical cell (1), a plurality of first reference electrodes (50), a plurality of first reference electrodes (60), or a combination thereof, which are spaced apart from each other between the positive electrode (10) and the first separator, may be included. The number of first reference electrodes (50) may be 2 or more, 3 or more, or 5 or more. By using a plurality of first reference electrodes (50), the potential of the negative electrode (20) during discharge can be measured at various locations between the positive electrode (10) and the first separator, and an average value thereof can be obtained. Therefore, by using a plurality of first reference electrodes (50), the reliability of the potential of the negative electrode (20) measured during discharge can be improved. The number of first reference electrodes (60) may be 2 or more, 3 or more, or 5 or more. By using a plurality of first reference electrodes (60), the potential of the negative electrode (20) during charge can be measured at various locations between the positive electrode (10) and the first separator, and an average value thereof can be obtained. Therefore, by using multiple first reference electrodes (60), the reliability of the negative electrode (20) potential measured during charging can be improved.

[0077] In the electrochemical cell (1), a first electrode lead (51) electrically connected to a first reference electrode (50) may be further included. The first reference electrode (50) may be connected to an external circuit through the first electrode lead (51) to measure a potential for the anode (10) and / or the cathode (20). A second electrode lead (61) electrically connected to the first reference electrode (60) may be further included. The first reference electrode (60) may be connected to an external circuit through the second electrode lead (61) to measure a potential for the anode (10) and / or the cathode (20). The first electrode lead (51) and the second electrode lead (61) may be arranged parallel to the first separator and may be extended to the outside of the electrochemical cell (1).

[0078] The first electrode lead (51) and the second electrode lead (61) may be, for example, in the form of wires. Since the first electrode lead (51) and the second electrode lead (61) have the form of wires, the influence on the volume of the electrochemical cell (1) can be minimized.

[0079] The first electrode lead (51) and the second electrode lead (61) may be coated with, for example, an insulator. When the first electrode lead (51) and / or the second electrode lead (61) is extended outside the electrochemical cell (1), an internal short circuit may occur due to electrical contact with the positive lead tab (13) and / or the negative lead tab (23). By coating the first electrode lead (51) and / or the second electrode lead (61) with an insulator, a short circuit between the first electrode lead (51) and / or the second electrode lead (61) and the positive lead tab (13) and / or the negative lead tab (23) can be effectively prevented. The insulator may be, for example, a fluorinated polymer. The insulator may be, for example, Teflon.

[0080] [anode]

[0081] Referring to FIGS. 1 and 2, an electrochemical cell (1) according to one embodiment includes a positive electrode (10). The positive electrode (10) includes a positive electrode current collector (11) and a positive electrode active material layer (12) disposed on one surface of the positive electrode current collector (11).

[0082] [Anode: Anode active material layer]

[0083] The cathode active material layer (12) includes a cathode active material, which is a cathode active material that can reversibly absorb and desorb lithium ions. The cathode active material includes, for example, an oxide-based cathode active material, a sulfide-based cathode active material, or a combination thereof.

[0084] The oxide-based cathode active material includes, for example, a lithium transition metal oxide, a metal oxide, or a combination thereof. The lithium transition metal oxide includes, for example, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt mangense oxide, lithium manganate, lithium iron phosphate, or a combination thereof. The metal oxide includes, for example, iron oxide, vanadium oxide, or a combination thereof.

[0085] Sulfide-based cathode active materials include, for example, nickel sulfide, copper sulfide, Li2S, Li2S-containing complexes, or combinations thereof.

[0086] The oxide-based cathode active material may be, for example, at least one compound oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof, and specific examples thereof include Li a A 1-b B' b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B' b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B' b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B' c O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Mn b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B'c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni b E c G d O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) A compound represented by any one of the chemical formulas Fe2(PO4)3(0 ≤ f ≤ 2); LiFePO4 can be used.

[0087] In the chemical formula representing the above-described compound, A is Ni, Co, Mn, or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F' is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I' is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound having a coating layer added to the surface of the above-described compound, or it is also possible to use a mixture of the above-described compound and the compound having a coating layer added. The coating layer added to the surface of the above-mentioned compound includes a coating element compound of, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method includes, for example, spray coating and dipping. Since the specific coating method is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0088] The oxide-based cathode active material may include, for example, a lithium transition metal oxide represented by the following chemical formulas 1 to 8:

[0089] <Chemical Formula 1>

[0090] Li a Ni x Co y Mz O 2-b A b

[0091] In the above chemical formula 1,

[0092] 1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0≤y≤0.3, 0 <z≤0.3, 및 x+y+z=1이고,

[0093] M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof,

[0094] A is F, S, Cl, Br or a combination thereof,

[0095] <Chemical Formula 2>

[0096] LiNi x Co y Mn z O2

[0097] <Chemical Formula 3>

[0098] LiNi x Co y Al z O2

[0099] In the above chemical formulas 2 and 3, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1이며,

[0100] <Chemical Formula 4>

[0101] LiNi x Co y Mn z Al w O2

[0102] In the above chemical formula 4, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1이며,

[0103] <Chemical Formula 5>

[0104] Li a Co x M y O2-b A b

[0105] In the above chemical formula 5,

[0106] 1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1,

[0107] M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof,

[0108] A is F, S, Cl, Br or a combination thereof,

[0109] <Chemical Formula 6>

[0110] Li a Ni x Mn y M' z O 2-b A b

[0111] In the above chemical formula 6,

[0112] 1.0≤a≤1.2, 0≤b≤0.2, 0 <x≤0.3, 0.5≤y<1, 0<z≤0.3, 및 x+y+z=1이고,

[0113] M' is cobalt (Co), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof,

[0114] A is F, S, Cl, Br or a combination thereof,

[0115] <Chemical Formula 7>

[0116] Li a M1 x M2 y PO 4-b X b

[0117] In the above chemical formula 7, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2 이며,

[0118] M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof,

[0119] M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y) or a combination thereof, and X is O, F, S, P or a combination thereof.

[0120] <Chemical Formula 8>

[0121] Li a M3 z PO4

[0122] In the above chemical formula 8, 0.90≤a≤1.1, 0.9≤z≤1.1,

[0123] M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

[0124] The content of the positive electrode active material included in the positive electrode active material layer (12) may be 80 wt% to 99 wt%, 90 wt% to 99 wt%, or 95 wt% to 99 wt% of the total weight of the positive electrode active material layer (12).

[0125] The positive electrode active material layer (12) may further include a conductive material. Examples of the conductive material include, but are not limited to, carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers; carbon nanotubes; metal powders or metal fibers or metal tubes such as copper, nickel, aluminum, and silver; and conductive polymers such as polyphenylene derivatives. Alternatively, the positive electrode (10) may not include a separate conductive material, for example. The content of the conductive material included in the positive electrode active material layer (12) may be 0.1 wt% to 10 wt% or 0.1 wt% to 5 wt% of the total weight of the positive electrode active material layer (12).

[0126] The positive electrode active material layer (12) may further include, for example, a binder. The binder may be a vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), a mixture of the above-mentioned polymers, a styrene butadiene rubber-based polymer, or the like. The binder content included in the positive electrode active material layer (12) may be 0.1 wt% to 10 wt% or 0.1 wt% to 5 wt% of the total weight of the positive electrode active material layer (12).

[0127] The contents of the cathode active material, conductive material, and binder contained in the cathode are at levels typically used in an electrochemical cell (1). Depending on the purpose and configuration of the electrochemical cell (1), one or more of the conductive material and binder may be omitted.

[0128] [Anode: Anode current collector]

[0129] The material constituting the positive electrode current collector (11) can be any material that does not react with lithium, that is, any material that does not form an alloy or compound with lithium and has conductivity. The positive electrode current collector (11) is, for example, a metal or an alloy. The positive electrode current collector (11) can be made of, for example, aluminum (Al), indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), germanium (Ge) or an alloy thereof. The positive electrode current collector (11) can have a shape selected from, for example, a sheet, a foil, a film, a plate, a porous body, a mesoporous body, a body containing through-holes, a polygonal ring body, a mesh body, a foam body, and a non-woven body, but is not necessarily limited to these shapes, and any shape used in the relevant technical field can be used.

[0130] Alternatively, the cathode current collector (11) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may be an insulating polymer. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and suppressing a sudden increase in current. The metal layer may include, for example, aluminum (Al), indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), germanium (Ge), or an alloy thereof. The positive electrode current collector (11) may additionally include a metal piece and / or a lead tab. For more specific details regarding the base film, metal layer, metal piece (metal chip), and lead tab of the positive electrode current collector (11), refer to the negative electrode current collector (21) described above. By having such a structure, the positive electrode current collector (11) can reduce the weight of the positive electrode, thereby improving the energy density of the positive electrode and the electrochemical cell (1).

[0131] [cathode]

[0132] Referring to FIGS. 1 and 2, an electrochemical cell (1) according to one embodiment includes a negative electrode (20). The negative electrode (20) includes a negative electrode current collector (21) and a negative electrode active material layer (22) disposed on one surface of the negative electrode current collector (21).

[0133] [Cathode: Cathode active material layer]

[0134] The negative electrode active material layer (22) includes a negative electrode active material. Any negative electrode active material that can be used as a negative electrode active material of an electrochemical cell (1) in the relevant technical field can be used. The negative electrode active material can include, for example, lithium metal, a metal alloyable with lithium, a transition metal oxide, a non-transition metal oxide, a carbon-based material, or a combination thereof. Metals alloyable with lithium are, for example, Si, Sn, Al, Ge, Pb, Bi, Sb Si-X alloy (wherein X is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, a rare earth element, or a combination thereof, and is not Si), Sn-X alloy (wherein X is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, a rare earth element, or a combination thereof, and is not Sn), etc. The element X is, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof. The transition metal oxide is, for example, lithium titanium oxide, vanadium oxide, lithium vanadium oxide, etc. The non-transition metal oxide is, for example, SnO2, SiO x(0 <x≤2) 등이다. 탄소계 재료는 예를 들어 결정질 탄소, 비정질 탄소 또는 이들의 혼합물이다. 결정질 탄소는 예를 들어 무정형, 판상, 린편상(flake), 구형 또는 섬유형의 천연 흑연 또는 인조 흑연과 같은 흑연이다. 비정질 탄소는 예를 들어 소프트 카본(soft carbon: 저온 소성 탄소) 또는 하드 카본(hard carbon), 메조페이스 피치(mesophase pitch) 탄화물, 소성된 코크스 등이다. 음극활물질층(22)이 포함하는 음극활물질 함량은 음극활물질층(12) 전체 중량의 60 wt% 내지 99 wt%, 80 wt% 내지 99 wt% 또는 90 wt% 내지 99 wt%일 수 있다.

[0135] The negative electrode active material layer (22) may include, for example, a binder. The binder may include, for example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene and mixtures thereof, or a styrene butadiene rubber-based polymer. The binder is not limited thereto and may be any binder that can be used as a binding agent in the art. The binder content may be, for example, 0.1 to 5 wt%, 0.1 to 3 wt%, or 0.1 to 2 wt% of the total weight of the negative electrode active material layer. When the negative electrode active material layer has a binder content in this range, the internal resistance of the negative electrode active material layer may be reduced. The cycle characteristics of the electrochemical cell (1) may be further improved.

[0136] The negative electrode active material layer (22) may include, for example, a conductive material. The porous structure may further include, for example, a conductive material. The porous structure may include a fibrous polymer, and the conductive material may be disposed on the surface and / or inside the fibrous polymer. The conductive material may include, for example, a carbon-based conductive material, a metal-based conductive material, or a combination thereof. The carbon-based conductive material may include, for example, carbon black, acetylene black, furnace black, ketjen black, graphene, graphene oxide, reduced graphene oxide, carbon fiber, carbon nanotubes (CNT), or a combination thereof. The carbon-based conductive material may include, for example, a doped carbon-based conductive material. The doped carbon-based conductive material may include a dopant. The dopant may include, for example, nitrogen (N), sulfur (S), fluorine (F), chlorine (Cl), or a combination thereof. The doped carbon-based conductive material may include, for example, nitrogen-doped graphene, nitrogen-doped graphene oxide, nitrogen-doped reduced graphene oxide, nitrogen-doped carbon fibers, nitrogen-doped carbon nanotubes (CNTs), or a combination thereof. The doped carbon-based conductive material may include, for example, fluorine-doped graphene, fluorine-doped graphene oxide, fluorine-doped reduced graphene oxide, fluorine-doped carbon fibers, fluorine-doped carbon nanotubes (CNTs), or a combination thereof. The doped carbon-based conductive material may include, for example, sulfur-doped graphene, sulfur-doped graphene oxide, sulfur-doped reduced graphene oxide, sulfur-doped carbon fibers, sulfur-doped carbon nanotubes (CNTs), or a combination thereof. The metal-based conductive material may be, for example, metal powder, metal fiber, or a combination thereof, but is not limited thereto, and any material used as a metal-based conductive material in the relevant technical field may be used.The conductive material content may be, for example, 0.1 to 5 wt%, 0.1 to 3 wt%, or 0.1 to 2 wt% of the total weight of the negative electrode active material layer. When the negative electrode active material layer has a conductive material content within this range, the internal resistance of the negative electrode active material layer can be reduced. The cycle characteristics of the electrochemical cell (1) can be further improved.

[0137] [Cathode: Negative current collector]

[0138] The negative electrode current collector (21) is composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound. The material constituting the negative electrode current collector (21) is, for example, copper, nickel, nickel-coated copper, stainless steel (SUS), iron (Fe), cobalt (Co), etc., but is not necessarily limited thereto, and any material that is used as an electrode current collector in the relevant technical field may be used. The negative electrode current collector (21) may be composed of one type of the above-described metal, or may be composed of an alloy or a coating material of two or more types of metals. The negative electrode current collector (21) is, for example, in the form of a plate or foil.

[0139] The negative electrode current collector (21) is not shown in the drawing, but may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), or a combination thereof. Since the base film includes a thermoplastic polymer, the base film may melt when a short circuit occurs, thereby suppressing a rapid increase in current. The base film may be, for example, an insulator. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. In particular, the metal layer may include, for example, copper (Cu), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni) or an alloy thereof. The metal layer may act as an electrochemical fuse and be cut off in the event of an overcurrent to prevent a short circuit. The limit current and the maximum current may be controlled by adjusting the thickness of the metal layer. The metal layer may be plated or deposited on the base film. As the thickness of the metal layer decreases, the limit current and / or the maximum current of the negative electrode current collector (21) decrease, thereby improving the stability of the electrochemical cell (1) in the event of a short circuit. A lead tab may be added on the metal layer for connection to the outside. The lead tab may be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, or the like. When welding, the base film and / or the metal layer may be melted, so that the metal layer may be electrically connected to the lead tab.In order to make the welding between the metal layer and the lead tab more robust, a metal chip may be added between the metal layer and the lead tab. The metal chip may be a thin piece of the same material as the metal of the metal layer. The metal chip may be, for example, a metal foil, a metal mesh, etc. The metal chip may be, for example, copper foil, nickel foil, etc. By placing the metal chip on the metal layer and then welding it with the lead tab, the lead tab may be welded to the metal chip / metal layer laminate or the metal chip / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal chip may melt, so that the metal layer or the metal layer / metal chip laminate may be electrically connected to the lead tab. The metal chip and / or the lead tab may be added to a portion of the metal layer. The thickness of the base film may be, for example, 1 to 50 ㎛, 1.5 to 50 ㎛, 1.5 to 40 ㎛, or 1 to 30 ㎛. By having a thickness of the base film in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film can be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. By having a melting point in this range, the base film can be melted during the process of welding the lead tab and easily bonded to the lead tab. A surface treatment, such as corona treatment, can be performed on the base film to improve the adhesion between the base film and the metal layer. The thickness of the metal layer can be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. By having a thickness of the metal layer in this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece can be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. By having the metal piece in this range of thickness, the connection between the metal layer and the lead tab can be performed more easily.By having this structure, the negative electrode current collector (21) can reduce the weight of the negative electrode and consequently improve the energy density of the electrochemical cell (1).

[0140] [Electrolyte]

[0141] Referring to FIGS. 1 and 2, the electrochemical cell (1) includes an electrolyte (30) between an anode (10) and a cathode (20). The electrolyte may be, for example, a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0142] Liquid electrolytes are, for example, organic electrolytes. Organic electrolytes are manufactured by dissolving lithium salts in organic solvents.

[0143] Any organic solvent used in the relevant technical field may be used. Examples of the organic solvent include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof.

[0144] Lithium salts are all possible if they are used as lithium salts in the relevant technical field. Lithium salts include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiDFOB, LiN(C x F 2x+1 SO2)(C y F 2y+1SO2)(1≤x≤20, 1≤y≤20), LiCl, LiI or a mixture thereof. The concentration of the lithium salt is, for example, 0.1 M to 5.0 M.

[0145] The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0146] Solid electrolytes are, for example, oxide-based solid electrolytes. Oxide-based solid electrolytes are Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(O≤x<1, O≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12(M = Te, Nb, or Zr, x is an integer from 1 to 10) is one or more selected from. The solid electrolyte is manufactured by a sintering method, etc. An oxide-based solid electrolyte is, for example, Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 A garnet-type solid electrolyte selected from (M doped LLZO, M=Ga, W, Nb, Ta, or Al, x is an integer from 1 to 10).

[0147] The sulfide-based solid electrolyte may include, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or a combination thereof. The sulfide-based solid electrolyte particles may include Li2S, P2S5, SiS2, GeS2, B2S3, or a combination thereof. The sulfide-based solid electrolyte particles may be Li2S or P2S5. Sulfide-based solid electrolyte particles are known to have high lithium ion conductivity compared to other inorganic compounds. For example, the sulfide-based solid electrolyte includes Li2S and P2S5. When the sulfide solid electrolyte material constituting the sulfide-based solid electrolyte includes Li2S-P2S5, the mixing molar ratio of Li2S to P2S5 may be, for example, in a range of about 50:50 to about 90:10. In addition, Li3PO4, halogen, halogen compound, Li 2+2x Zn 1-x GeO4("LISICON", 0≤x<1), Li 3+y PO 4-x N x( "LIPON", 0 <x<4, 0<y<3), Li 3.25 Ge 0.25 P 0.75 S4("ThioLISICON"), Li2O-Al2O3-TiO2-P2O 5(An inorganic solid electrolyte prepared by adding "LATP") etc. to an inorganic solid electrolyte of Li2S-P2S5, SiS2, GeS2, B2S3, or a combination thereof can be used as a sulfide solid electrolyte. Non-limiting examples of sulfide solid electrolyte materials include Li2S-P2S5; Li2S-P2S5-LiX (X=halogen element); Li2S-P2S5-Li2O; Li2S-P2S5-Li2O-LiI; Li2S-SiS2; Li2S-SiS2-LiI; Li2S-SiS2-LiBr; Li2S-SiS2-LiCl; Li2S-SiS2-B2S3-LiI; Li2S-SiS2-P2S5-LiI; Li2S-B2S3; Li2S -P2S5-Z m S n (0 <m<10, 0<n<10, Z=Ge, Zn 또는 Ga); Li2S-GeS2; Li2S-SiS2-Li3PO4; 및 Li2S-SiS2-Li p MO q (0 <p<10, 0<q<10, M=P, Si, Ge, B, Al, Ga 또는 In)을 포함한다. 이와 관련하여, 황화물계 고체전해질 재료는 황화물계 고체전해질 물질의 원료 시작 물질(예를 들면, Li2S, P2S5, 등)을 용융 담금질법(melt quenching method), 기계적 밀링법 등에 의해 처리함으로써 제조될 수 있다. 또한, 소성(calcinations) 공정이 상기 처리 후에 수행될 수 있다. 황화물계 고체전해질은 비정질이거나, 결정질이거나, 이들이 혼합된 상태일 수 있다.

[0148] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 19:

[0149] <Chemical Formula 19>

[0150] Li + 12-n-x A n+ X 2- 6-x Y - x

[0151] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN or N3, and 1≤n≤5, 0≤x≤2. The sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , may be an argyrodite-type compound including at least one selected from 0≤x≤2. The sulfide-based solid electrolyte may be, for example, an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0152] The density of the argyrodite-type solid electrolyte may be 0.1 to 2.0 g / cc, 0.5 to 2.0 g / cc, 1.0 to 2.0 g / cc, or 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density in this range, the internal resistance of the solid secondary battery (1) is reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

[0153] The polymer solid electrolyte may, for example, comprise a mixture of a lithium salt and a polymer, or a polymer having an ion-conducting functional group. The polymer solid electrolyte may be, for example, a polymer electrolyte that is solid at 25°C and 1 atm. The polymer solid electrolyte may not, for example, comprise a liquid.The polymer solid electrolyte comprises a polymer, and the polymer is, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA, poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), Polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi. +) or a combination thereof, but is not limited thereto, and any lithium salt that can be used in polymer electrolytes in the relevant technical field is possible. The lithium salt can be any lithium salt that can be used in the relevant technical field. The lithium salt is, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are each 1 to 20), LiCl, LiI or a mixture thereof, etc. The polymer included in the polymer solid electrolyte may be, for example, a compound including 10 or more, 20 or more, 50 or more or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer solid electrolyte may be, for example, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more or 1,000,000 Dalton or more.

[0154] A gel electrolyte is, for example, a polymer gel electrolyte. A gel electrolyte can have a gel state without containing a polymer, for example.

[0155] A polymer gel electrolyte may include, for example, a liquid electrolyte and a polymer, or an organic solvent and a polymer having an ion-conducting functional group. The polymer gel electrolyte may be, for example, a polymer electrolyte that is in a gel state at 25°C and 1 atm. The polymer gel electrolyte may, for example, have a gel state without containing a liquid. The liquid electrolyte used in the polymer gel electrolyte may be, for example, a mixture of an ionic liquid, a lithium salt, and an organic solvent; a mixture of a lithium salt and an organic solvent; a mixture of an ionic liquid and an organic solvent; or a mixture of a lithium salt and an ionic liquid. The polymer used in the polymer gel electrolyte may be selected from among the polymers used in solid polymer electrolytes. The organic solvent may be selected from among the organic solvents used in liquid electrolytes. The lithium salt may be selected from among the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt that has a melting point below room temperature, is composed solely of ions, and is liquid at room temperature or a molten salt at room temperature. The ionic liquid may include, for example, one or more cations selected from among a) ammonium compounds, pyrrolidinium compounds, pyridinium compounds, pyrimidinium compounds, imidazolium compounds, piperidinium compounds, pyrazolium compounds, oxazolium compounds, pyridazinium compounds, phosphonium compounds, sulfonium compounds, triazolium compounds, and mixtures thereof, and b) one or more anions selected from among BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, Cl-, Br-, I-, BF4-, SO4-, CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N-. A polymer solid electrolyte can form a polymer gel electrolyte, for example, by being impregnated into a liquid electrolyte in a secondary battery. The polymer gel electrolyte may further include inorganic particles. The polymer included in the polymer gel electrolyte may be, for example, a compound containing 10 or more, 20 or more, 50 or more, or 100 or more repeating units.The weight average molecular weight of the polymer included in the polymer gel electrolyte may be, for example, 500 Dalton or more, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0156] The polymer gel electrolyte may include, for example, a crosslinking product of a crosslinking monomer and a liquid electrolyte. The polymer gel electrolyte may be obtained, for example, by heat treating a precursor composition including a crosslinking monomer and a liquid electrolyte.

[0157] The crosslinking monomer may comprise, for example, 3 to 20, 3 to 10, 3 to 8, or 4 to 6 reactive functional groups. The crosslinking monomer may comprise, for example, an acrylic monomer comprising a plurality of acrylic groups, a methacrylic monomer comprising a plurality of methacrylic groups, or a combination thereof. Acrylic monomers include, for example, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, Dipentaerythritol hexaacrylate or a combination thereof may be included. The liquid electrolyte may be selected from the liquid electrolytes described above.

[0158] Electrochemical Cell: Assembly

[0159] Referring to FIGS. 3 to 6, an anode, a cathode, and a first separator may be assembled to form an electrode assembly. A first separator may be disposed between the anode and the cathode to prepare a laminate. A first reference electrode (50) and a first reference electrode (60) are disposed between the anode and the first separator. The electrode assembly may be, for example, in a jellyroll shape, a stack shape, or a folding shape. Referring to FIGS. 3 and 5, a jellyroll shape electrode assembly may be prepared by winding a laminate. Referring to FIGS. 4 and 6, a plurality of laminates may be stacked to prepare a star shape electrode assembly. Referring to FIG. 5, a folded shape electrode assembly may be prepared by alternately bending the laminate in one direction.

[0160] An electrochemical cell may include the electrode assembly described above. The electrochemical cell may be, for example, an alkaline metal battery. The electrochemical cell may be, for example, a lithium battery, a sodium battery, or the like. The electrochemical cell may be, for example, a primary battery or a secondary battery. The electrochemical cell may be, for example, a lithium ion battery, a lithium solid-state battery, a lithium semi-solid-state battery, or a lithium hybrid battery.

[0161] Electrochemical Cell: Manufacturing Method

[0162] A method for manufacturing an electrochemical cell according to one embodiment includes a step of preparing an assembly by laminating a cathode, a first separator, and a cathode; and a step of preparing an electrochemical cell (1) by injecting an electrolyte into the assembly and sealing it.

[0163] A positive electrode is prepared. For example, a positive electrode active material composition is prepared by mixing a positive electrode active material, a conductive agent, a binder, and a solvent. The prepared positive electrode active material composition is directly coated on a positive electrode current collector and dried to produce a positive electrode plate having a positive electrode active material layer formed thereon. Alternatively, the positive electrode active material composition is cast on a separate support, and then the film obtained by peeling from the support is laminated on a positive electrode current collector to produce a positive electrode plate having a positive electrode active material layer formed thereon. The solvent is, for example, N-methylpyrrolidone, but is not particularly limited. It is also possible to form pores inside the electrode plate by further adding a plasticizer or a pore forming agent to the positive electrode active material composition. The positive electrode can be prepared by the methods described above, but is not necessarily limited thereto. The types and contents of the positive electrode active material, conductive agent, and binder refer to the positive electrode active material layer described above.

[0164] A negative electrode is prepared. For example, a negative electrode active material composition is prepared by mixing a negative electrode active material, a conductive agent, a binder, and a solvent. The prepared negative electrode active material composition is directly coated on a negative electrode current collector and dried to produce a negative electrode plate having a negative electrode active material layer formed thereon. Alternatively, the negative electrode active material composition is cast on a separate support, and then peeled from the support to obtain a film, which is laminated on a negative electrode current collector to produce a negative electrode plate having a negative electrode active material layer formed thereon. The solvent is, for example, N-methylpyrrolidone, but is not particularly limited. It is also possible to form pores inside the electrode plate by further adding a plasticizer or a pore forming agent to the negative electrode active material composition. The negative electrode can be prepared by the methods described above, but is not necessarily limited thereto. The types and contents of the negative electrode active material, conductive agent, and binder refer to the negative electrode active material layer described above.

[0165] Prepare the first separator. The first separator is, for example, a polyethylene separator. For more specific details about the first separator, refer to the separator described above.

[0166] A first reference electrode and a first reference electrode (60) are spaced apart from each other on one side adjacent to the anode of the first separator. A second-first separator (41) and a second-second separator (42) are respectively placed on the first reference electrode and the first reference electrode (60).

[0167] An assembly is prepared by stacking a positive electrode, a first separator, and a negative electrode. The assembly is contained in a can or pouch. An electrolyte is injected into the assembly and sealed. By injecting the electrolyte into the assembly contained in the can or pouch, the electrolyte impregnates the first separator.

[0168] The electrochemical cell (1) may have, for example, a structure as shown in FIGS. 3 to 6 below. In FIGS. 3 to 6, the illustrations of the first reference electrode, the first reference electrode (60), the second-first separator (41), and the second-second separator (42) are omitted.

[0169] Referring to FIG. 3, an electrochemical cell (1) according to an embodiment includes a positive electrode (3), the above-described negative electrode (2), and a first separator (4). The positive electrode (3), the negative electrode (2), and the first separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). A composition for forming a positive electrode electrolyte is injected into the battery case (5), cross-linked, and sealed with a cap assembly (6), thereby completing the electrochemical cell (1)(1). The battery case (5) is cylindrical, but is not necessarily limited to this shape, and may be, for example, square, thin-film, etc.

[0170] Referring to FIG. 4, an electrochemical cell (1) according to an embodiment includes a positive electrode (3), the above-described negative electrode (2), and a first separator (4). The positive electrode (3), the negative electrode (2), and the first separator (4) are wound, folded, or laminated to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). A composition for forming a positive electrode electrolyte is injected into the battery case (5), cross-linked, and sealed, thereby completing the electrochemical cell (1)(1). The battery case (5) is square, but is not necessarily limited to this shape, and may be, for example, cylindrical, thin-film, etc. A positive electrode lead tab (3') and a positive electrode terminal (3") are electrically connected to the positive electrode (3). A negative electrode lead tab (2') and a negative electrode terminal (2") are electrically connected to the negative electrode (2).

[0171] Referring to FIG. 5, an electrochemical cell (1) according to an embodiment includes a positive electrode (3), the aforementioned negative electrode (2), and a first separator (4). A first separator (4) is disposed between the positive electrode (3) and the negative electrode (2), and the positive electrode (3), the negative electrode (2), and the first separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). An electrode tab (8) that serves as an electrical path for guiding the current formed in the battery structure (7) to the outside may be included. A composition for forming a positive electrode electrolyte is injected into the battery case (5), crosslinked, and sealed to complete the electrochemical cell (1) (1). The battery case (5) is not necessarily limited to a square shape, and may be, for example, a cylindrical shape, a thin film shape, etc.

[0172] Referring to FIG. 6, an electrochemical cell (1) according to an embodiment includes a positive electrode (3), the aforementioned negative electrode (2), and a first separator (4). The first separator (4) is disposed between the positive electrode (3) and the negative electrode (2), thereby forming a battery structure. The battery structure (7) is stacked in a bi-cell structure and then accommodated in a battery case (5). An electrode tab (8) serving as an electrical path for guiding the current formed in the battery structure (7) to the outside may be included. A composition for forming a positive electrode electrolyte is injected into the battery case (5), crosslinked, and sealed, thereby completing the lithium metal battery (1). The battery case (5) is not necessarily limited to a square shape, but may be, for example, a cylindrical shape, a thin film shape, etc.

[0173] A pouch-type electrochemical cell (1) uses a pouch as a case for the electrochemical cell (1) of FIGS. 3 to 6. The pouch-type electrochemical cell (1) may include one or more battery structures. A first separator is disposed between an anode and a cathode to form a battery structure. A plurality of battery structures are laminated in the thickness direction, then impregnated with an organic electrolyte, and accommodated and sealed in a pouch to complete the pouch-type electrochemical cell (1). For example, although not shown in the drawing, the above-described anode, cathode, and first separator may be simply laminated and accommodated in a pouch in the form of an electrode assembly, or may be wound or folded into a jelly-roll-shaped electrode assembly and then accommodated in a pouch. Subsequently, a composition for forming a cathode electrolyte is injected into the pouch, and thermal cross-linking and sealing are performed to complete the electrochemical cell (1).

[0174] The electrochemical cell (1) of the present disclosure has excellent lifespan characteristics and high energy density, and is therefore used, for example, in electric vehicles (EVs). For example, it is used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). It is also used in fields requiring large amounts of power storage. For example, it is used in electric bicycles, power tools, and the like.

[0175] A plurality of electrochemical cells (1) are stacked to form a battery module, and the plurality of battery modules form a battery pack. Such a battery pack can be used in all devices requiring high capacity and high output. For example, it can be used in laptops, smartphones, electric vehicles, etc. The battery module includes, for example, a plurality of batteries and a frame that holds them. The battery pack includes, for example, a plurality of battery modules and a bus bar that connects them. The battery module and / or the battery pack may further include a cooling device. The plurality of battery packs are controlled by a battery management system. The battery management system includes a battery pack and a battery control device connected to the battery pack.

[0176] The present invention is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0177] (electrochemical cell)

[0178] Example 1: Plate-shaped first reference electrode (Li metal), rod-shaped second reference electrode (LTO)

[0179] (Polar electrode manufacturing)

[0180] LiNi 0.8 Co 0.15 Al 0.05 O2(NCA) powder and carbon conductive material (Super-P; Timcal Ltd.) were uniformly mixed at a weight ratio of 90:5, and then a PVDF (polyvinylidene fluoride) binder solution was added to obtain a weight ratio of active material:carbon conductive material:binder = 90:5:5 to prepare a positive electrode active material slurry. The prepared slurry was coated on a 20 ㎛ thick aluminum substrate using a doctor blade, dried under reduced pressure at 120 ℃, and then rolled into a sheet shape using a roll press to manufacture a positive electrode. The thickness of the positive electrode active material layer was 80 ㎛.

[0181] (Cathode manufacturing)

[0182] Artificial graphite (AG-1, ShanShan Co., Ltd.), natural graphite (C-SNG, Tianjin BTR New Energy Technology Co., Ltd.), styrene-butadiene rubber (SBR) binder (ZEON), and carboxymethyl cellulose (CMC, NIPPON A&L) were mixed in a weight ratio of 49:49:1:1, distilled water was added, and further mixed to prepare a negative electrode active material slurry. The prepared slurry was coated on a 10 ㎛ thick copper substrate using a doctor blade, dried under reduced pressure at 120 ℃, and then rolled using a roll press to form a sheet to prepare a negative electrode.

[0183] (Manufacture of the first reference electrode and the second reference electrode)

[0184] Referring to FIGS. 1 and 2, a first reference electrode was prepared by connecting a copper wire as a first electrode lead to a square-shaped lithium metal foil plate. The portion of the copper wire that is not directly connected to the first reference electrode was coated with Teflon.

[0185] Li4Ti5O as an electrode active material 12 (LTO) 95 wt%, Denka Black 1 wt% as a conductive agent, and polyvinylidene fluoride (PVDF) 1 wt% as a binder were added to NMP (N-methyl pyrrolidone) to prepare an electrode active material slurry, which was coated on the end of a copper wire and dried to prepare a second reference electrode. A copper wire was connected to the second reference electrode as a second electrode lead. The portion of the copper wire that is not in direct contact with the second reference electrode was coated with Teflon.

[0186] (Electrochemical cell manufacturing)

[0187] Referring to FIGS. 1 and 2, a first reference electrode and a second reference electrode are placed spaced apart from each other on one surface of a first polyethylene separator.

[0188] The distance between the first reference electrode and the second reference electrode was more than twice the width of the first reference electrode. The first electrode lead (51) and the second electrode lead were attached to the first separator using double-sided tape.

[0189] A polyethylene 2-1 separator was placed on the first reference electrode and the double-sided tape to cover the first reference electrode and the double-sided tape.

[0190] A polyethylene 2-2 separator was placed on the second reference electrode and the double-sided tape to cover the second reference electrode and the double-sided tape.

[0191] A laminate was prepared by placing a first separator between the anode and the cathode so that the first reference electrode and the second reference electrode are positioned between the anode and the first separator.

[0192] A jelly-roll-shaped electrode assembly was prepared by winding the laminate. The electrode assembly was placed in a square case, the first reference electrode lead and the second reference electrode lead were pulled out of the square case, a liquid electrolyte was injected, and the cell was sealed to manufacture an electrochemical cell.

[0193] The liquid electrolyte was prepared by adding 1.0 M LiPF6 as a lithium salt to a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 3:5:2.

[0194] Comparative Example 1: Plate-shaped first reference electrode (Li metal) alone

[0195] An electrochemical cell was manufactured in the same manner as in Example 1, except that a plate-shaped first reference electrode was used and a rod-shaped second reference electrode was omitted.

[0196] Comparative Example 2: Rod-type second reference electrode (LTO) alone

[0197] An electrochemical cell was manufactured in the same manner as in Example 1, except that a rod-shaped second reference electrode was used and the plate-shaped first reference electrode was omitted.

[0198] Evaluation Example 1: Charge / Discharge Test

[0199] (Example 1)

[0200] A charge-discharge test was performed at room temperature (25°C) on the electrochemical cell of Example 1 under the following conditions.

[0201] (Charging stage)

[0202] The electrochemical cell was charged at a constant current rate of 0.2 C at 45°C until the voltage reached 4.2 V (vs. Li), and then charged at a constant voltage rate until the current decreased to 0.05 C at 4.2 V (vs. Li).

[0203] During the charging process of the electrochemical cell, the potential of the electrochemical cell, the anode potential with respect to the first reference electrode (Li metal), the anode potential with respect to the second reference electrode (LTO), the cathode potential with respect to the first reference electrode (Li metal), and the cathode potential with respect to the second reference electrode (LTO) are shown in Fig. 7.

[0204] The cathode potential of Fig. 7 is enlarged and illustrated in Fig. 8. As shown in Fig. 8, the cathode potential of the first reference electrode decreased to a negative value and then increased to a positive value during the process of charging more than 10% of the state of charge (SOC). In other words, an error in the cathode potential of the first reference electrode occurred. It was determined that this was because the potential of the first reference electrode was distorted by a film formed on the surface of the first reference electrode.

[0205] In contrast, the second reference electrode maintained a positive cathode potential during the charging process of more than 10% of the state of charge (SOC). In other words, the second reference electrode did not exhibit any distortion of the cathode potential.

[0206] Therefore, it was confirmed that the first reference electrode is more suitable for measuring the potential change of the negative electrode during the process of charging more than 10% of the state of charge (SOC).

[0207] (Discharge stage)

[0208] Subsequently, the electrochemical cell was discharged at a constant current of 0.2 C rate until the voltage reached 2.7 V (vs. Li).

[0209] The potential of the electrochemical cell, the anode potential with respect to the first reference electrode (Li metal), the anode potential with respect to the second reference electrode (LTO), the cathode potential with respect to the first reference electrode (Li metal), and the cathode potential with respect to the second reference electrode (LTO) during the discharge process of the electrochemical cell are shown in Fig. 9.

[0210] The cathode potential of Fig. 9 is enlarged and illustrated in Fig. 10. As shown in Fig. 10, the cathode potential of the first reference electrode rapidly increased during the process of discharging to more than 80% of the depth of discharge (DOD). In other words, the first reference electrode sensitively displayed changes in the cathode potential.

[0211] In contrast, the cathode potential of the second reference electrode increased more gradually than that of the first reference electrode during the process of discharging more than 80% of the depth of discharge (DOD). In other words, the first reference electrode was insensitive to changes in the cathode potential.

[0212] It was determined that the second reference electrode distorted the potential change of the cathode due to the change in its own potential during the process of discharging more than 80% of the depth of discharge (DOD).

[0213] Therefore, it was confirmed that the first reference electrode is more suitable for measuring the potential change of the cathode during the process of discharging more than 80% of the depth of discharge (DOD).

[0214] (Comparative examples 1 and 2)

[0215] A room temperature charge / discharge test was performed on the electrochemical cells of Comparative Examples 1 and 2 under the same conditions as Example 1.

[0216] The electrochemical cell of Comparative Example 1 did not have a second reference electrode, which resulted in a problem in which the cathode potential had a negative value when the electrochemical cell was charged.

[0217] The electrochemical cell of Comparative Example 2 did not have a first reference electrode, so the potential of the second reference electrode changed during discharge of the electrochemical cell, resulting in a problem in which the sensitivity of the cathode potential decreased.

[0218] While exemplary embodiments have been described in detail with reference to the attached drawings, the present invention is not limited to these examples. It is self-evident that those skilled in the art to which the present invention pertains can devise various modifications or variations within the scope of the technical concepts described in the patent claims, and these also naturally fall within the technical scope of the present invention.

[0219] [Explanation of symbols]

[0220] 1 electrochemical cell 2, 20 cathode

[0221] 2', 23 negative lead tab 2" negative terminal

[0222] 3, 10 positive lead tab 3', 13 positive lead tab

[0223] 3" positive terminal 4 separator

[0224] 5 Battery case 6 Cap assembly

[0225] 7 Battery structure 8 Electrode tab

[0226] 11. Cathode current collector 12. Cathode active material layer

[0227] 21 Negative current collector 22 Negative active material layer

[0228] 30 Electrolyte 40 First Separator

[0229] 41 Membrane 2-1 42 Membrane 2-2

[0230] 50 First reference electrode 51 First electrode lead

[0231] 60 Second reference electrode 61 Second electrode lead

[0232] According to one aspect, it is possible to provide a novel electrochemical cell having multiple reference electrodes and preventing errors in cathode potential by using different reference electrodes during charging and discharging of the electrochemical cell.

Claims

1. A positive electrode; a negative electrode; and a first separator between the positive electrode and the negative electrode, It includes a first reference electrode and a second reference electrode disposed between the anode and the first separator, The first reference electrode is configured to measure the potential of the cathode during discharge, An electrochemical cell, wherein the second reference electrode is configured to measure the potential of the negative electrode during charging.

2. An electrochemical cell in accordance with claim 1, wherein the first reference electrode and the second reference electrode are spaced apart from each other on the first separator.

3. In the first paragraph, the first reference electrode is a plate-shaped electrode, An electrochemical cell wherein the second reference electrode is a wire-shaped electrode or a plate-shaped electrode.

4. In the first paragraph, the first reference electrode includes lithium metal, An electrochemical cell wherein the first reference electrode is a lithium metal foil.

5. An electrochemical cell in the first paragraph, wherein the potential change of the first reference electrode is smaller than the potential change of the second reference electrode when the depth of discharge (DOD) of the electrochemical cell is 50% or more during discharge.

6. In the first paragraph, the second reference electrode includes an electrode active material, An electrochemical cell, wherein the electrode active material comprises a metal oxide, a lithium transition metal oxide, or a combination thereof.

7. In paragraph 6, the lithium transition metal oxide includes lithium vanadium oxide, lithium titanium oxide, or a combination thereof, An electrochemical cell, wherein the metal oxide comprises vanadium oxide, titanium oxide, or a combination thereof.

8. An electrochemical cell according to claim 6, wherein the second reference electrode further comprises a binder, a conductive material, or a combination thereof.

9. An electrochemical cell in which, in the first paragraph, the potential of the negative electrode with respect to the second reference electrode is maintained at 0 V (vs. Li) or higher in the range of SOC (State of Charge) 10% to 100% during charging of the electrochemical cell.

10. An electrochemical cell in which the redox potential of the second reference electrode is higher than the redox potential of the first reference electrode in the first paragraph.

11. An electrochemical cell in which the difference between the redox potential of the second reference electrode and the redox potential of the first reference electrode is 2.0 V or less in the 10th paragraph.

12. In the first paragraph, it further includes a 2-1 separator disposed between the anode and the first reference electrode and a 2-2 separator disposed between the anode and the second reference electrode, The above 2-1 separator and the above 2-2 separator are arranged spaced apart from each other on the first separator, An electrochemical cell in which the above-mentioned 2-1 separator and the above-mentioned 2-2 separator are porous membranes.

13. An electrochemical cell in which a first reference electrode and a second reference electrode are free between the cathode and the first separator in the first paragraph.

14. An electrochemical cell comprising a plurality of first reference electrodes, a plurality of second reference electrodes, or a combination thereof, spaced apart from each other between the anode and the first separator in the first paragraph.

15. In the first paragraph, a first electrode lead and a second electrode lead each electrically connected to the first reference electrode and the second reference electrode are further included, An electrochemical cell, wherein the first electrode lead and the second electrode lead are arranged parallel to the first separator and extended outside the electrochemical cell.

16. In the 15th paragraph, the first electrode lead and the second electrode lead are in the form of wires, An electrochemical cell, wherein the first electrode lead and the second electrode lead are covered with an insulator.

17. In the first paragraph, the positive electrode comprises a positive electrode current collector; and a positive electrode active material layer on one surface of the positive electrode current collector, The above cathode active material layer includes a cathode active material, The above cathode active material includes a sulfide-based cathode active material, an oxide-based cathode active material, or a combination thereof, The above sulfide-based cathode active material includes nickel sulfide, copper sulfide, Li2S, a Li2S-containing complex, or a combination thereof. A lithium battery, wherein the oxide-based cathode active material comprises a lithium transition metal oxide, a metal oxide, or a combination thereof, and the lithium transition metal oxide comprises lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt mangense oxide, lithium manganate, lithium iron phosphate, or a combination thereof, and the metal oxide comprises iron oxide, vanadium oxide, or a combination thereof.

18. In the first paragraph, an electrolyte is included between the positive and negative electrodes, The above electrolyte comprises a liquid electrolyte, a solid electrolyte, a gel electrolyte or a combination thereof, The above liquid electrolyte comprises a lithium salt, an organic solvent, an ionic liquid or a combination thereof, The above solid electrolyte includes a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof, An electrochemical cell wherein the gel electrolyte comprises a polymer gel electrolyte.

19. In the first paragraph, the positive electrode, negative electrode and first separator are assembled to form an electrode assembly, An electrochemical cell wherein the electrode assembly is in a jelly roll shape, a stack shape or a folding shape.

20. An electrochemical cell according to claim 1, wherein the electrochemical cell is a lithium ion battery, a lithium solid-state battery, a lithium semi-solid-state battery, or a lithium hybrid battery.

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