Electrode, and electrode assembly comprising the same

Abstract

The present disclosure relates to an electrode and an electrode assembly including the same. An electrode according to one aspect comprises: a current collector; an intermediate layer laminated on at least one surface of the current collector and comprising a Positive Temperature Coefficient (PTC) material; and an active material layer laminated on the intermediate layer. The PTC material comprises a first PTC material and a second PTC material having different critical temperatures. The intermediate layer may comprise a first intermediate layer comprising the first PTC material and a second intermediate layer comprising the second PTC material.

Description

Technology Field

[0001] The present disclosure relates to an electrode and an electrode assembly comprising the same. Background Technology

[0002] Secondary batteries can easily ignite due to internal short circuits when subjected to external impact or exposed to high-temperature environments, and the heat and flames generated from the ignited battery can easily propagate to adjacent components. This phenomenon can cause critical safety issues, commonly known as thermal runaway.

[0003] One of the causes of the aforementioned thermal runaway phenomenon is the lack of an effective cutoff mechanism to prevent internal short circuits between electrodes when the internal temperature of the secondary battery rises, which consequently allows for the control of rapid temperature increases. To secure such a cutoff mechanism, a method is being attempted to employ a PTC layer containing a Positive Temperature Coefficient (PTC) material as one of the functional layers constituting the electrodes of the secondary battery. The problem to be solved

[0004] According to one aspect of the present disclosure, an electrode can be provided that can interrupt current flow more quickly when the temperature rises, and furthermore, can more effectively interrupt current flow to more effectively prevent short circuits between electrodes.

[0005] According to another aspect of the present disclosure, an electrode assembly with further improved stability and safety can be provided.

[0006] According to another aspect of the present disclosure, battery performance and safety can be further improved, and in particular, a secondary battery capable of effectively delaying or suppressing thermal runaway phenomena can be provided.

[0007] Meanwhile, the present disclosure can be widely applied in the field of green technology, such as electric vehicles, battery charging stations, energy storage systems (ESS), and other photovoltaic and wind power generation that utilize batteries. In addition, the present disclosure can be used in eco-friendly mobility, including electric vehicles and hybrid vehicles, to prevent climate change by suppressing air pollution and greenhouse fluid emissions. means of solving the problem

[0008] An electrode according to the present disclosure comprises: a current collector; an intermediate layer laminated on at least one surface of the current collector and comprising a Positive Temperature Coefficient (PTC) material; and an active material layer laminated on the intermediate layer; wherein the PTC material comprises a first PTC material and a second PTC material having different critical temperatures, and the intermediate layer may comprise a first intermediate layer comprising the first PTC material and a second intermediate layer comprising the second PTC material.

[0009] In an electrode according to one embodiment, the PTC material can satisfy the relationship defined by the following formula 1.

[0010] [Equation 1]

[0011] 10 ≤ R2 / R1 ≤ 1,000,000

[0012] In Equation 1 above, R2 is the resistance value at the critical temperature, and R1 is the resistance value at room temperature.

[0013] In an electrode according to one embodiment, the first intermediate layer is in contact with the current collector, the second intermediate layer is interposed between the first intermediate layer and the active material layer, and the critical temperature of the first PTC material may be higher than the critical temperature of the second PTC material.

[0014] In an electrode according to one embodiment, the critical temperature of the first PTC material may be 120°C or higher.

[0015] In an electrode according to one embodiment, the critical temperature of the second PTC material may be 80°C or higher.

[0016] In an electrode according to one embodiment, the PTC material may include at least one selected from the group consisting of a conductive polymer, a ceramic, and a metal oxide.

[0017] In an electrode according to one embodiment, the conductive polymer may comprise at least one selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polythiophene, polyethylenedioxythiophene (PEDOT), and polyphenylene vinylene (PPV).

[0018] In an electrode according to one embodiment, the ceramic may comprise at least one of zirconium oxide (ZrO2) and barium titanate (BaTiO3).

[0019] In an electrode according to one embodiment, the metal oxide may include at least one of nickel oxide (NiO) and cobalt oxide (CoO).

[0020] In an electrode according to one embodiment, the intermediate layer may further include a conductive material.

[0021] In an electrode according to one embodiment, the conductive material may include at least one selected from the group consisting of carbon nanotubes (CNT), graphite, graphene, carbon black, and silver nanoparticles.

[0022] In an electrode according to one embodiment, the intermediate layer may further include the conductive material when the PTC material includes at least one of the ceramic and the metal oxide.

[0023] In an electrode according to one embodiment, the conductive material may be included in an amount of 1% to 15% by weight relative to the total weight of the solid content of the intermediate layer.

[0024] In an electrode according to one embodiment, the thickness of the intermediate layer may be 7 μm to 15 μm.

[0026] An electrode assembly according to the present disclosure is an electrode assembly comprising an electrode according to the present disclosure, wherein the electrode may include a positive electrode and a negative electrode.

[0027] In an electrode assembly according to one embodiment, the PTC material included in the anode may comprise at least one selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polyethylenedioxythiophene (PEDOT), zirconium oxide (ZrO2), barium titanate (BaTiO3), nickel oxide (NiO), and cobalt oxide (CoO).

[0028] In an electrode assembly according to one embodiment, the PTC material included in the cathode may include at least one selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polythiophene, polyethylenedioxythiophene (PEDOT), polyphenylene vinylene (PPV), and zirconium oxide (ZrO2). Effects of the invention

[0029] According to one aspect of the present disclosure, an electrode can be provided that can interrupt current flow more quickly when the temperature rises, and furthermore, can more effectively interrupt current flow to more effectively prevent short circuits between electrodes.

[0030] According to another aspect of the present disclosure, an electrode assembly with further improved stability and safety can be provided.

[0031] According to another aspect of the present disclosure, battery performance and safety can be further improved, and in particular, a secondary battery capable of effectively delaying or suppressing thermal runaway phenomena can be provided.

[0032] Meanwhile, the present disclosure can be widely applied in the field of green technology, such as electric vehicles, battery charging stations, energy storage systems (ESS), and other photovoltaic and wind power generation that utilize batteries. In addition, the present disclosure can be used in eco-friendly mobility, including electric vehicles and hybrid vehicles, to prevent climate change by suppressing air pollution and greenhouse fluid emissions. Brief explanation of the drawing

[0033] FIG. 1 is a drawing showing an example of a cross-sectional view of an electrode according to one embodiment of the present disclosure. FIG. 2 is a drawing showing an example of a cross-sectional view of an electrode assembly according to one embodiment of the present disclosure. Figure 3 is a diagram illustrating the comparative example structure set in the simulation. Figure 4 is a graph comparing the electrode resistance behavior at different temperatures in the simulation of the electrodes of the example and comparative example. Figure 5 is a graph comparing the allowable current behavior at different temperatures in the simulation of the electrodes of the example and comparative example. Specific details for implementing the invention

[0034] Since the embodiments described in this specification may be modified in various different forms, the technology according to one embodiment is not limited to the embodiments described below. Furthermore, throughout the specification, the terms "comprising," "having," "containing," or "having" any component do not exclude other components but may include additional components unless specifically stated otherwise, and do not exclude elements, materials, or processes not additionally listed.

[0035] In this specification, "identical or uniform" may mean that they are identical or uniform to one another within an acceptable margin of error, unless otherwise specified. For example, the statement that certain components or physical property measurements are identical may include not only that the two objects being compared are completely identical, but also that they are identical within a margin of error. Meanwhile, the statement that certain physical property measurements are identical may mean that the difference between the measurements between the objects is approximately less than 5%, specifically less than 3%, and more specifically less than 1%.

[0036] In this specification, the angle formed by two objects being perpendicular, or parallel or parallel to each other, may include not only geometrically perpendicular or parallel but also within a slight margin of error.

[0037] The numerical ranges used in this specification include lower and upper limits and all values ​​within the range, increments logically derived from the form and width of the defined range, all of which are limited values, and all possible combinations of upper and lower limits of numerical ranges limited in different forms.

[0038] Unless otherwise specifically defined in this specification, “about” may be considered to be a value within 30%, 25%, 20%, 15%, 10%, or 5% of the specified value.

[0039] In this specification, the use of terms such as "first," "second," or "third" preceding any component is intended solely to avoid confusion regarding the components being referred to, and is unrelated to the order, importance, or hierarchical relationship between the components. For example, an invention comprising only the second component without the first component is also possible.

[0040] As used in this specification, the term "secondary battery" may refer to a battery that generates or stores electrical energy through oxidation and reduction reactions when ions, specifically metal ions such as lithium ions, are inserted and extracted from the positive and negative electrodes. Specifically, the "secondary battery" may refer to any one of a lithium cobalt battery, a lithium high-nickel battery, a lithium iron phosphate battery, a lithium-ion battery, a lithium polymer battery, a lithium-sulfur battery, a nickel-hydrogen battery, a nickel-cadmium battery, a sodium battery, or an all-solid-state battery.

[0042] The present disclosure will be described in detail below. However, this is merely illustrative and the present disclosure is not limited to the specific embodiments described illustratively.

[0044] FIG. 1 is a drawing showing an example of a cross-sectional view of an electrode according to one embodiment of the present disclosure.

[0046] Referring to FIG. 1, an electrode (100) according to one aspect of the present disclosure comprises: a current collector (110); an intermediate layer (120) including a Positive Temperature Coefficient (PTC) material that is laminated on at least one surface of the current collector (110); and an active material layer (130) laminated on the intermediate layer (120), wherein the PTC material includes a first PTC material and a second PTC material having different critical temperatures, and the intermediate layer (120) may include a first intermediate layer (121) including the first PTC material and a second intermediate layer (122) including the second PTC material.

[0047] Meanwhile, the shape, size, color, thickness, shading, width, etc. of each component shown in FIG. 1 above are depicted arbitrarily for convenience of explanation and may be configured in various ways as needed within the scope of not departing from the matters defined in the present disclosure, and it is obvious that the scope of the patent claims is not limited thereby. This applies equally to the drawings to be described later.

[0049] Referring to FIG. 1, in one embodiment, the electrode (100) may include a current collector (110). The current collector (110) may include a known conductive material within a range that does not cause a chemical reaction in the secondary battery.

[0050] Meanwhile, as will be described later, the electrode (100) may be a positive electrode or a negative electrode. Accordingly, the current collector (110) may refer to a positive current collector or a negative current collector. Details regarding this will be described later.

[0051] Referring again to FIG. 1, in one embodiment, the electrode (100) may include an active material layer (130). The active material layer (130) may include an electrode active material, and the electrode active material may be a material capable of inserting and extracting lithium ions within a secondary battery.

[0052] Meanwhile, as described below, the electrode (100) may be a positive electrode or a negative electrode, and accordingly, the active material layer (130) may refer to a positive active material layer or a negative active material layer comprising a positive active material or a negative active material. Details thereof will be described later.

[0053] Referring again to FIG. 1, in one embodiment, the electrode (100) may include an intermediate layer (120). The intermediate layer (120) may be laminated on at least one surface of the current collector (110).

[0054] In one embodiment, the intermediate layer (120) may be interposed between the current collector (110) and the active material layer (130). In such an embodiment, the electrode (100) may be in a form in which the current collector (110), the intermediate layer (120), and the active material layer (130) are stacked along a predetermined stacking direction. In other words, the intermediate layer (120) may be in contact with the current collector (110) on one side and in contact with the active material layer (130) on the other side. Meanwhile, the stacking direction may mean a direction parallel to, for example, the first direction (DR1) based on the illustration in FIG. 1.

[0055] In one embodiment, the intermediate layer (120) may include a PTC (Positive Temperature Coefficient) material.

[0056] In this specification, the PTC material may be defined as a material having a constant temperature coefficient characteristic in which the resistance value increases rapidly with increasing temperature. Due to this characteristic, the PTC material exhibits a low level of intrinsic resistance in a normal environment, but when the temperature rises and reaches a certain level, the resistance value increases rapidly, thereby exhibiting electrical characteristics similar to those of an insulator.

[0057] In this regard, the above-mentioned PTC material exhibits a low level of intrinsic resistance in a normal environment, but when the temperature rises and reaches a critical temperature, it may exhibit electrical characteristics similar to those of an insulator as described above. Therefore, the above-mentioned critical temperature (Tc) may refer to the temperature at which the electrical characteristics begin to change as the resistance value of the PTC material rises rapidly, as described above. In other words, this critical temperature may also be expressed as the PTC operating temperature, switching temperature, Curie temperature, etc.

[0058] In one embodiment, the PTC material may satisfy the relationship defined by the following formula 1.

[0059] [Equation 1]

[0060] 10 ≤ R2 / R1 ≤ 1,000,000

[0061] In Equation 1 above, R2 is the resistance value at the critical temperature, and R1 is the resistance value at room temperature.

[0062] The above resistance value can be measured by a known method that can measure the resistance of a material, for example, using a 4-point probe meter or an LCR meter. For example, the resistance value can be measured using the method described above after soaking the PTC material in a constant temperature chamber to a predetermined temperature (room temperature or critical temperature).

[0063] That is, in one embodiment, the ratio of the resistance value (Ω) at the critical temperature and the resistance value (Ω) at room temperature of the PTC material may be 10 to 1,000,000.

[0064] In such an embodiment, the PTC material may refer to a material that can satisfy the relationship of Equation 1 in terms of resistance characteristics.

[0065] In such an embodiment, the intermediate layer (120) is interposed between the current collector (110) and the active material layer (130) and may simultaneously include the PTC material. When the temperature rises inside the secondary battery, the electrical characteristics of the intermediate layer (120) may be changed by the PTC material as described above. Accordingly, when the temperature inside the secondary battery reaches the critical temperature, the flow of current passing through the electrode (100) may be controlled or blocked. This prevents short circuits between electrodes and / or controls a rapid rise in temperature inside the secondary battery, thereby suppressing the occurrence of a thermal runaway phenomenon even if one of the battery cells ignites, or suppressing or minimizing the propagation to adjacent battery cells even if a thermal runaway phenomenon occurs.

[0066] Meanwhile, in one embodiment, the PTC material may include a first PTC material and a second PTC material. In one embodiment, the first PTC material and the second PTC material may have different critical temperatures.

[0067] In one embodiment, the intermediate layer (120) may include a first intermediate layer (121) and a second intermediate layer (122). In one embodiment, the first intermediate layer (121) may include the first PTC material, and the second intermediate layer (122) may include the second PTC material. That is, the critical temperatures of the PTC materials included in each of the first intermediate layer (121) and the second intermediate layer (122) may be different from each other.

[0068] Referring again to FIG. 1, in one embodiment, the first intermediate layer (121) is in contact with the current collector (110), and the second intermediate layer (122) is interposed between the first intermediate layer (121) and the active material layer (130), and the critical temperature of the first PTC material may be higher than the critical temperature of the second PTC material.

[0069] As previously described, the intermediate layer (120) may be interposed between the current collector (110) and the active material layer (130), and in such an embodiment, the electrode (100) may be in a form in which the current collector (110), the intermediate layer (120), and the active material layer (130) are stacked along a predetermined stacking direction. In other words, the intermediate layer (120) may be in contact with the current collector (110) on one side and with the active material layer (130) on the other side.

[0070] Referring to FIG. 1, in one embodiment, the intermediate layer (120) may be divided into a first intermediate layer (121) and a second intermediate layer (122) along the stacking direction. In such an embodiment, the first intermediate layer (121) may be in contact with the current collector (110), and the second intermediate layer (122) may be interposed between the first intermediate layer (121) and the active material layer (130).

[0071] That is, in such an embodiment, the electrode (100) may be in the form in which the current collector (110), the first intermediate layer (121), the second intermediate layer (122), and the active material layer (130) are stacked along the stacking direction.

[0072] In an exemplary embodiment, among the two layers separated along the stacking direction, the first intermediate layer (121) may refer to a layer in contact with the current collector (110), and the second intermediate layer (122) may refer to a layer in contact with the active material layer (130).

[0073] Meanwhile, in one embodiment, the critical temperature of the first PTC material may be higher than the critical temperature of the second PTC material. That is, the critical temperature of the PTC material included in the first intermediate layer (121) may be higher than the critical temperature of the PTC material included in the second intermediate layer (122).

[0074] This means that, in an exemplary embodiment, the critical temperature of the PTC material included in the layer in contact with the current collector (110) in the intermediate layer (120) may be relatively high, and the critical temperature of the PTC material included in the layer in contact with the active material layer (130) in the intermediate layer (120) may be relatively low.

[0075] In one embodiment, the critical temperature of the first PTC material may be 120°C or higher. In a specific embodiment, the critical temperature of the first PTC material may be 120°C to 200°C. In a more specific embodiment, the critical temperature of the first PTC material may be 120°C to 190°C, 120°C to 180°C, 150°C to 180°C, 120°C to 150°C, or 120°C to 140°C.

[0076] In one embodiment, the critical temperature of the second PTC material may be 80°C or higher. In a specific embodiment, the critical temperature of the second PTC material may be 80°C to 200°C. In a more specific embodiment, the critical temperature of the second PTC material may be 80°C to 100°C, 90°C to 110°C, 100°C to 120°C, 100°C to 130°C, or 110°C to 130°C.

[0077] In such an embodiment, the intermediate layer (120) interposed between the current collector (110) and the active material layer (130) as described above may be divided into a first intermediate layer (121) and a second intermediate layer (122), each comprising a first PTC material and a second PTC material having different critical temperatures along the stacking direction. Accordingly, the electrode (100) maintains a low level of resistance within the normal operating temperature range of the secondary battery, and when it reaches the critical temperature of the PTC material having a relatively low critical temperature, the resistance increases rapidly first, thereby significantly lowering the allowable current. Subsequently, when it reaches the critical temperature of the PTC material having a relatively high critical temperature, the resistance increases rapidly secondarily, thereby further lowering the allowable current. As a result, faster current interruption is possible compared to an embodiment composed of a single PTC layer, and at the same time, at higher temperatures, the PTC material having a relatively high critical temperature additionally operates to function as a dual safety device, thereby further improving safety.

[0078] Meanwhile, the first PTC material included in the first intermediate layer (121) in contact with the current collector (110) has a higher critical temperature than the second PTC material included in the second intermediate layer (122) in contact with the active material layer (130). As a result, the PTC material in the second intermediate layer (122) in contact with the active material layer (130) can operate first during the initial temperature rise, thereby reducing the current flow inside the active material layer (130) and rapidly suppressing side reactions. Consequently, the safety improvement effect can be even more excellent.

[0080] In one embodiment, the PTC material may include at least one selected from the group consisting of conductive polymers, ceramics, and metal oxides.

[0081] In one embodiment, the conductive polymer may include an aromatic ring comprising a conjugated system. In such an embodiment, the conductive polymer may basically exhibit electrical conductivity, and at a temperature above a certain level, a change in properties may occur to have electrical characteristics similar to those of an insulator as described above.

[0082] In one embodiment, the conductive polymer may include, without limitation, any known conductive polymer capable of exhibiting the above characteristics.

[0083] In one embodiment, the conductive polymer may comprise at least one selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polythiophene, polyethylenedioxythiophene (PEDOT), and polyphenylene vinylene (PPV).

[0084] Meanwhile, in one embodiment, the ceramic and metal oxide may be any ceramic or metal oxide that can be used as a PTC material exhibiting the aforementioned electrical properties, without limitation.

[0085] In one embodiment, the ceramic may include at least one of zirconium oxide (ZrO2) and barium titanate (BaTiO3).

[0086] In one embodiment, the metal oxide may include at least one of nickel oxide (NiO) and cobalt oxide (CoO).

[0087] Meanwhile, in one embodiment, the intermediate layer (120) may further include a conductive material.

[0088] In one embodiment, a known conductive material capable of exhibiting conductive performance can be used as the conductive material without limitation.

[0089] In one embodiment, the conductive material may include at least one selected from the group consisting of carbon nanotubes (CNT), graphite, graphene, carbon black, and silver nanoparticles.

[0090] Meanwhile, as described above, the intermediate layer (120) may include a conductive polymer, a ceramic, and a metal oxide. In one embodiment, the ceramic and the metal oxide may have low electrical conductivity or exhibit non-conductivity.

[0091] In such an embodiment, the intermediate layer (120) includes the conductive material, and may further include the conductive material if the PTC material includes at least one of the ceramic and metal oxide. That is, in one embodiment, the intermediate layer (120) may further include the conductive material if the PTC material includes at least one of the ceramic and metal oxide.

[0092] In one embodiment, when the PTC material includes the ceramic, the intermediate layer (120) may further include the conductive material.

[0093] In one embodiment, when the PTC material includes the metal oxide, the intermediate layer (120) may further include the conductive material.

[0094] In one embodiment, when the PTC material comprises the conductive polymer, the intermediate layer (120) may optionally further comprise the conductive material. Meanwhile, in an exemplary embodiment, when the conductive polymer is polyphenylene vinylene (PPV), the intermediate layer (120) may optionally further comprise the conductive material. In an exemplary embodiment, when the conductive polymer comprises at least one of polyaniline (PANI), polypyrrole (PPy), polythiophene, and polyethylenedioxythiophene (PEDOT), the intermediate layer (120) may optionally further comprise the conductive material.

[0095] That is, in one embodiment, if the PTC material comprises the ceramic, and / or the metal oxide, and / or the polyphenylene vinylene (PPV), the intermediate layer (120) may further comprise the conductive material.

[0096] Meanwhile, in an exemplary embodiment, if the PTC material is essentially composed of the ceramic, metal oxide and / or PPV, the intermediate layer (120) may further include the conductive material.

[0097] In one embodiment, if the PTC material exhibits a somewhat high level of room temperature resistance, degradation of battery cell performance in a general environment (e.g., room temperature environment) may be observed. In such a case, the degradation of battery cell performance can be suppressed by further adding the conductive material.

[0098] In one embodiment, the conductive material may be included in an amount of 1% to 15% by weight relative to the total weight of the solid content of the intermediate layer (120).

[0099] If the above-mentioned conductive material is included in an amount less than the aforementioned numerical range, the room temperature resistance of the electrode (100) is high, and a decrease in battery cell performance may be observed; if it is included in an amount exceeding the aforementioned numerical range, the aforementioned PTC characteristics of the intermediate layer (120) by the PTC material may not be sufficiently realized.

[0100] In a specific embodiment, the conductive material may be included in an amount of 1.1 wt% or more, 1.2 wt% or more, 1.3 wt% or more, 1.4 wt% or more, 1.5 wt% or more, 1.6 wt% or more, 1.7 wt% or more, 1.8 wt% or more, 1.9 wt% or more, or 2 wt% or more with respect to the total weight of the solid content of the intermediate layer (120), or 14.5 wt% or less, 14 wt% or less, 13.5 wt% or less, 13 wt% or less, 12.5 wt% or less, 12 wt% or less, 11.5 wt% or less, 11 wt% or less, 10.5 wt% or less, or 10 wt% or less.

[0101] In an exemplary embodiment, the first PTC material may comprise at least one selected from the group consisting of polythiophene, polyethylenedioxythiophene (PEDOT), polyphenylene vinylene (PPV), zirconium oxide, and barium titanate.

[0102] In an exemplary embodiment, the second PTC material may comprise at least one selected from the group consisting of polyaniline, polypyrrole, nickel oxide, and cobalt oxide.

[0103] In one embodiment, the thickness of the intermediate layer (120) may be 7 μm to 15 μm. In a specific embodiment, the thickness of the intermediate layer (120) may be 7.5 μm or more, 8 μm or more, 8.5 μm or more, 9 μm or more, or 9.5 μm or more, or 14 μm or less, 13 μm or less, 12 μm or less, or 11 μm or less.

[0104] Meanwhile, the thickness of the intermediate layer (120) may refer to the length in the stacking direction described above. For example, based on the illustration in FIG. 1, it may refer to the length in the first direction (DR1).

[0105] If the thickness of the intermediate layer (120) is less than the aforementioned numerical range, the aforementioned PTC characteristics of the intermediate layer (120) may not be sufficiently realized, and if it exceeds the aforementioned numerical range, a degradation of battery cell performance may be observed.

[0106] Meanwhile, in one embodiment, the thickness of the intermediate layer (120) may be equal to the sum of the thickness of the first intermediate layer (121) and the thickness of the second intermediate layer (122). In such an embodiment, the thickness of the first intermediate layer (121) and the thickness of the second intermediate layer (122) may not be particularly limited, and, for example, the thicknesses of the first intermediate layer (121) and the second intermediate layer (122) may be equal to each other.

[0108] FIG. 2 is a drawing showing an example of a cross-sectional view of an electrode assembly according to one embodiment of the present disclosure.

[0110] Referring to FIG. 2, an electrode assembly (10) according to one aspect of the present disclosure is an electrode assembly (10) including an electrode according to one aspect of the present disclosure, wherein the electrode may include a positive electrode (100a) and a negative electrode (100b).

[0111] In one embodiment, the anode (100a) may include an anode current collector (110a), an anode intermediate layer (120a) including a PTC material that is laminated on at least one surface of the anode current collector (110a), and an anode active material layer (130a) laminated on the anode intermediate layer (120a).

[0112] In an exemplary embodiment, the positive current collector (110a) may include stainless steel, nickel, aluminum, titanium, or an alloy thereof as a non-limiting example. The positive current collector (110a) may include carbon, nickel, titanium, aluminum or stainless steel surface-treated with silver. The thickness of the positive current collector (110a) may be, for example, 10 to 50 μm, although not limited thereto.

[0113] In one embodiment, the positive active material layer (130a) may include a positive active material. The positive active material may include a compound capable of reversibly intercalating and deintercalating metal ions, specifically lithium ions.

[0114] The above-mentioned cathode active material may include a lithium-nickel metal oxide. The lithium-nickel metal oxide may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0115] In some embodiments, the positive electrode active material or the lithium-nickel metal oxide may comprise a layered structure or a crystalline structure represented by the following chemical formula 1.

[0116] [Chemical Formula 1]

[0117] Li x Ni a M b O 2+z

[0118] In Chemical Formula 1, 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b≤0.4, and -0.5≤z≤0.1 may be used. As described above, M may include Co, Mn, and / or Al.

[0119] The chemical structure represented by Chemical Formula 1 represents the bonding relationships contained within the layered or crystal structure of the cathode active material and does not exclude other additional elements. For example, M includes Co and / or Mn, and Co and / or Mn may be provided as the main active element of the cathode active material together with Ni. Chemical Formula 1 is provided to express the bonding relationships of the main active elements and should be understood as encompassing the introduction and substitution of additional elements.

[0120] In one embodiment, auxiliary elements may be further included to be added to the main active element to enhance the chemical stability of the cathode active material or the layered structure / crystal structure. The auxiliary elements may be incorporated together within the layered structure / crystal structure to form bonds, and in this case, it should be understood that they are also included within the range of the chemical structure represented by Chemical Formula 1.

[0121] The above auxiliary element may include, for example, at least one of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. The above auxiliary element may also act as an auxiliary active element that contributes to the capacity / output activity of the cathode active material together with Co or Mn, such as Al.

[0122] For example, the above-mentioned positive active material or the above-mentioned lithium-nickel metal oxide may include a layered structure or a crystal structure represented by the following chemical formula 1-1.

[0123] [Chemical Formula 1-1]

[0124] Li x Ni a M1 b1 M2 b2 O 2+z

[0125] In Chemical Formula 1-1, M1 may include Co, Mn and / or Al. M2 may include the auxiliary element described above. In Chemical Formula 1-1, 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b1+b2≤0.4, and -0.5≤z≤0.1.

[0126] The above-described cathode active material may further include a coating element or a doping element. For example, elements substantially identical or similar to the auxiliary elements described above may be used as coating elements or doping elements. For example, any of the elements described above may be used alone or in combination of two or more as coating elements or doping elements.

[0127] The coating element or doping element may be present on the surface of the lithium-nickel metal oxide particles or penetrate through the surface of the lithium-nickel metal composite oxide particles and be included within the bonding structure represented by Formula 1 or Formula 1-1.

[0128] The above-mentioned cathode active material may include a nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, an NCM-based lithium oxide with an increased nickel content may be used.

[0129] Ni can be provided as a transition metal associated with the output and capacity of a lithium secondary battery. Therefore, by adopting a high-Ni composition in the cathode active material as described above, a high-capacity cathode and a high-capacity secondary battery can be provided.

[0130] However, as the Ni content increases, the long-term storage stability and lifespan stability of the anode or secondary battery may relatively decrease, and side reactions with the electrolyte may also increase. However, according to exemplary embodiments, electrical conductivity can be maintained by including Co, while lifespan stability and capacity retention characteristics can be improved through Mn.

[0131] The content of Ni in the above NCM-based lithium oxide (e.g., the mole fraction of nickel in the total moles of nickel, cobalt, and manganese) may be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the content of Ni may be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0132] In some embodiments, the positive electrode active material may include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate (LFP)-based active material (e.g., LiFePO4).

[0133] The above positive active material layer (130a) may further include a binder and a conductive material. If necessary, the above positive active material layer (130a) may further include a thickener. In some embodiments, polyvinylidenefluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (Poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, polymethylmethacrylate, butadiene rubber, etc. may be used as the binder. In one embodiment, a PVDF-based binder may be used as the positive binder.

[0134] The above conductive material may be added to enhance the conductivity of the positive active material layer (130a) and / or the mobility of lithium ions or electrons. For example, the conductive material may include, but is not limited to, carbon-based conductive materials such as graphite, carbon black, acetylene black, ketjen black, graphene, carbon nanotubes (CNT), vapor-grown carbon fiber (VGCF), carbon fiber, etc., and / or metal-based conductive materials such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc.

[0135] If necessary, the above positive active material layer (130a) may further include known thickeners and / or dispersants, etc.

[0136] In one embodiment, the PTC material included in the anode (100a) may include at least one selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polyethylenedioxythiophene (PEDOT), zirconium oxide (ZrO2), barium titanate (BaTiO3), nickel oxide (NiO) and cobalt oxide (CoO).

[0137] That is, in one embodiment, the anode (100a) may include an anode intermediate layer (120a), and the anode intermediate layer (120a) may be interposed between the anode current collector (110a) and the anode active material layer (130a). Meanwhile, the anode intermediate layer (120a) may include an anode PTC material, and the anode PTC material may include at least one selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polyethylenedioxythiophene (PEDOT), zirconium oxide (ZrO2), barium titanate (BaTiO3), nickel oxide (NiO), and cobalt oxide (CoO).

[0138] The above positive PTC material can be easily coated onto the positive current collector (110a) and the positive active material layer (130a) as described above, or can exhibit excellent adhesion. In such an embodiment, the structural stability of the positive intermediate layer (120a) can be improved by including the above positive PTC material in the positive intermediate layer (120a), and furthermore, the battery performance can be improved.

[0139] In one embodiment, the anode intermediate layer (120a) may further include a conductive material.

[0140] In one embodiment, the conductive material included in the anode intermediate layer (120a) may include at least one selected from the group consisting of carbon nanotubes (CNT), graphite, graphene, and silver nanoparticles.

[0141] Meanwhile, the anode intermediate layer (120a) may include a first anode intermediate layer (121a) and a second anode intermediate layer (122a) as described above with reference to FIG. 1. In addition to the description regarding the PTC material or conductive material described above, the description regarding the anode intermediate layer (120a), the first anode intermediate layer (121a), and the second anode intermediate layer (122a) can be applied as described above with reference to FIG. 1, so redundant descriptions will be omitted below.

[0143] In one embodiment, the cathode (100b) may include a cathode current collector (110b), a cathode intermediate layer (120b) including a PTC material that is laminated on at least one surface of the cathode current collector (110b), and a cathode active material layer (130b) laminated on the cathode intermediate layer (120b).

[0144] In an exemplary embodiment, non-limiting examples of the negative current collector (110b) include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, and a polymer substrate coated with a conductive metal. The thickness of the negative current collector (110b) is not necessarily limited thereto, but, for example, may have a thickness of 10 μm to 50 μm.

[0145] In one embodiment, the negative electrode active material layer (130b) may include a negative electrode active material. The negative electrode active material may include a compound capable of reversibly intercalating and deintercalating metal ions, specifically lithium ions.

[0146] In one embodiment, the negative electrode active material may include at least one selected from the group consisting of carbon-based active materials, silicon-based active materials, and lithium metal. As an example, the negative electrode active material may be a carbon-based material such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber; lithium metal; lithium alloy; silicon (Si)-containing material or tin (Sn)-containing material.

[0147] In one embodiment, the negative electrode active material may be a mixture of at least two selected from the group consisting of carbon-based active materials, silicon-based active materials, and lithium metal.

[0148] In one embodiment, the negative electrode active material may include a carbon-based active material.

[0149] Examples of the above carbon-based active materials include carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, and carbon fibers.

[0150] Examples of the above-mentioned amorphous carbon include hard carbon, soft carbon, coke, mesocarbon microbeads (MCMB), and mesophase pitch-based carbon fiber (MPCF).

[0151] Examples of the above-mentioned crystalline carbon include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, and graphitized MPCF.

[0152] The carbon-based active material may include both crystalline carbon and amorphous carbon. Without limitation, an example in which amorphous carbon is coated on the surface of the crystalline carbon may be exemplified.

[0153] In one embodiment, the negative electrode active material may include a silicon-based active material.

[0154] The above silicon-containing material can provide increased capacity characteristics. The above silicon-containing material is Si, SiO x (0 <x<2), 금속 도핑된 SiO x (0 <x<2), 실리콘-탄소 복합체 등을 포함할 수 있다. 상기 금속은 리튬 및 / 또는 마그네슘을 포함할 수 있으며, 금속 도핑된 SiO x (0 <x<2)는 금속 실리케이트를 포함할 수 있다.

[0155] In one embodiment, the negative electrode active material may include lithium metal.

[0156] The above lithium metal may be pure lithium metal or lithium metal in the form of an alloy for inhibiting dendrite growth, etc.

[0157] Examples of elements included in the above lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium.

[0158] When the above-mentioned negative electrode active material layer (130b) is formed by a wet process, non-limiting examples of solvents for the negative electrode active material include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, t-butanol, etc.

[0159] Meanwhile, the above-mentioned negative electrode active material layer (130b) may include a binder. As the binder included in the above-mentioned negative electrode active material layer (130b), a binder having good binding strength with the negative electrode current collector (110b) may be used.

[0160] In some embodiments, the binder may be a rubber-based binder, a cellulose-based binder, a polyacrylic acid-based binder, a poly(3,4-ethylenedioxythiophene), PEDOT-based binder, etc.

[0161] In one embodiment, the rubber-based binder may include butadiene rubber (BR), nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (H-NBR) or styrene butadiene rubber (SBR), or other butadiene-based rubbers substituted with functional groups such as fluorine, alkyl, or acrylate.

[0162] In one embodiment, the cellulose-based binder may include a cellulose-based polymer.

[0163] In exemplary embodiments, the cellulosic polymer may, without limitation, refer to a polymer comprising a structure of cellulose or a derivative thereof. Examples of such cellulosic polymers include carboxymethylcellulose (CMC), carboxyethylcellulose (CEC), hydroxymethylcellulose (HMC), hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC), hydroxyethylmethylcellulose (HEMC), hydroxypropylmethylcellulose (HPMC), nitrocellulose (NC), etc.

[0164] Additionally, as needed, the above-mentioned negative electrode active material layer (130b) may optionally further include a conductive material, a thickener, etc.

[0165] The above conductive material may be added to enhance the conductivity of the negative electrode active material layer (130b) and / or the mobility of lithium ions or electrons. For example, the conductive material may include, but is not limited to, carbon-based conductive materials such as carbon nanotubes including graphite, carbon black, acetylene black, ketjen black, graphene, single-walled carbon nanotubes (SWCNT) or multi-walled carbon nanotubes (MWCNT), vapor-grown carbon fiber (VGCF), carbon fiber, etc., and / or metal-based conductive materials such as perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3.

[0166] If necessary, the above negative electrode active material layer (130b) may further include known thickeners and / or dispersants, etc.

[0167] In one embodiment, the PTC material included in the cathode (100b) may include at least one selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polythiophene, polyethylenedioxythiophene (PEDOT), polyphenylene vinylene (PPV), and zirconium oxide (ZrO2).

[0168] That is, in one embodiment, the cathode (100b) may include a cathode intermediate layer (120b), and the cathode intermediate layer (120b) may be interposed between the cathode current collector (110b) and the cathode active material layer (130b). Meanwhile, the cathode intermediate layer (120b) may include a cathode PTC material, and the cathode PTC material may include at least one selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polythiophene, polyethylenedioxythiophene (PEDOT), polyphenylene vinylene (PPV), and zirconium oxide (ZrO2).

[0169] The above-described negative PTC material can be easily coated onto the negative current collector (110b) and the negative active material layer (130b) as described above, or can exhibit excellent adhesion. In such an embodiment, the negative intermediate layer (120b) can have its structural stability improved and, furthermore, its battery performance can be improved by including the above-described negative PTC material in the negative intermediate layer (120b).

[0170] In one embodiment, the cathode intermediate layer (120b) may further include a conductive material.

[0171] In one embodiment, the conductive material included in the cathode intermediate layer (120b) may include at least one of graphene and carbon black.

[0172] Meanwhile, the above-mentioned cathode intermediate layer (120b) may include a first cathode intermediate layer (121b) and a second cathode intermediate layer (122b) as described above with reference to FIG. 1. In addition to the description regarding the PTC material or conductive material described above, the description regarding the cathode intermediate layer (120b), the first cathode intermediate layer (121b), and the second cathode intermediate layer (122b) can be applied as described above with reference to FIG. 1, so redundant descriptions will be omitted below.

[0174] Referring again to FIG. 2, in one embodiment, the electrode assembly (10) may further include a separator (200) interposed between the anode (100a) and the cathode (100b).

[0175] In one embodiment, the separator (200) may be configured to be interposed between the anode (100a) and the cathode (100b) to prevent an electrical short circuit between the anode (100a) and the cathode (100b) and to allow ion flow. According to an embodiment, the thickness of the separator (200) may be 10 μm to 20 μm, but the present disclosure is not limited thereto.

[0176] For example, the separator (200) may include a porous polymer film or a porous nonwoven fabric. The porous polymer film may include polyolefin-based polymers such as ethylene polymer, propylene polymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer. The porous nonwoven fabric may include high-melting-point glass fibers, polyethylene terephthalate fibers, etc. The separator (200) may also include a ceramic-based material. For example, inorganic particles may be coated on the polymer film or dispersed within the polymer film to improve heat resistance.

[0177] The above-described separator (200) may have a single-layer or multi-layer structure including the polymer film and / or nonwoven fabric described above.

[0178] Unlike the above embodiment, a solid electrolyte may be used in the electrode assembly (10), and in such case, it may be manufactured in the form of an all-solid-state battery. Additionally, a solid electrolyte layer may be disposed between the positive electrode (100a) and the negative electrode (100b) instead of, or together with, the separator (200) described above.

[0179] According to exemplary embodiments, an electrode assembly may be formed by repeatedly arranging a positive electrode (100a), a negative electrode (100b), and a separator (200) (a solid electrolyte layer in the case of the all-solid-state battery described above). In some embodiments, the electrode assembly may be winding, stacking, zigzag folding, or stack-folding.

[0181] A secondary battery according to one aspect of the present disclosure may comprise: an electrode assembly according to one aspect of the present disclosure; an outer casing that accommodates the electrode assembly; and an electrolyte that is accommodated together with the electrode assembly within the outer casing.

[0182] For an electrode assembly according to one aspect of the present disclosure, the configuration and description of the electrode assembly (10) described above with reference to FIG. 2 may be applied as is.

[0183] In one embodiment, the outer casing may include an internal receiving space and be configured to isolate objects received in the receiving space from the outside. The electrode assembly may be received and sealed within the receiving space of the outer casing.

[0184] The above-mentioned outer material may be appropriately selected and used as a pouch-type case, a can-type case, a coin-type outer material, etc., depending on the embodiment of the electrode assembly described above.

[0185] In one embodiment, the electrolyte may be accommodated together with the electrode assembly within the outer casing. Specifically, the electrolyte may be accommodated together with the electrode assembly within the receiving space of the outer casing and may come into contact with at least a portion of the electrode assembly within the receiving space.

[0186] According to exemplary embodiments, a non-aqueous electrolyte may be used as the electrolyte.

[0187] The above-mentioned non-aqueous electrolyte comprises a lithium salt as an electrolyte and an organic solvent, and the lithium salt is, for example, Li + X - It is expressed as and the anion (X) of the above lithium salt - As F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 -, PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - Examples of the back can be given.

[0188] The above organic solvent may include an organic compound that has sufficient solubility for the lithium salt and additive and does not have reactivity in the battery. For example, the above organic solvent may include at least one of a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, and an aprotic solvent.

[0189] The above-mentioned non-aqueous electrolyte may further include additives. The additives may include, for example, cyclic carbonate compounds, fluorine-substituted carbonate compounds, sulfone compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, and borate compounds.

[0191] A secondary battery according to one aspect of the present disclosure can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a battery module of a medium-to-large device comprising a plurality of battery cells. Examples of the small device include mobile phones, laptop computers, cameras, etc., and examples of the medium-to-large device include electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, etc., but are not limited to these.

[0193] In the following, embodiments of the present disclosure are further described with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are merely illustrative of the present invention and are not intended to limit the appended claims. It is obvious to those skilled in the art that various changes and modifications to the embodiments are possible within the scope and spirit of the present disclosure, and that such variations and modifications fall within the scope of the appended claims.

[0195] Examples

[0196] 1. Examples

[0197] Using the MSMD (Multi-Scale Multi-Domain) Battery Equivalent Circuit Model (ECM), an electrochemical-thermal coupling analysis model from FLUENT (ANSYS), the electrical behavior was simulated when an intermediate layer containing a PTC material between the current collector and the active material layer in the electrode of a lithium secondary battery was implemented as a double layer (a first intermediate layer and a second intermediate layer, each with a thickness of 5 μm).

[0198] The structure of the electrode implemented above can be referenced to the structure shown in FIG. 1, wherein the PTC material included in the first intermediate layer (121) has a critical temperature of 120°C or higher, and the PTC material included in the second intermediate layer (122) has a critical temperature of 80°C or higher and less than 120°C.

[0200] 2. Comparative Example

[0201] Figure 3 is a diagram illustrating the comparative example structure set in the simulation.

[0203] The simulation was performed in the same manner as the example, except that an intermediate layer (2) containing a PTC material having a critical temperature of 100°C to 120°C between the current collector (1) and the active material layer (3) in the electrode of a lithium secondary battery was implemented as a single layer with a thickness of 10 μm. The structure of the electrode implemented above can be referenced from the structure shown in FIG. 3.

[0205] Evaluation example

[0206] Figure 4 is a graph comparing the electrode resistance behavior at different temperatures in the simulation of the electrodes of the example and comparative example.

[0207] Figure 5 is a graph comparing the allowable current behavior at different temperatures in the simulation of the electrodes of the example and comparative example.

[0209] Referring to Figure 4, it was confirmed that in the case of the comparative example electrode, the normal resistance of 1 mΩ was maintained in the normal temperature range, but the resistance began to increase rapidly from the critical temperature (around 100°C), and the resistance value converged to 40 mΩ from about 140°C.

[0210] Meanwhile, in the case of the electrode of the example, as with the electrode of the comparative example, it maintained a normal resistance of 1 mΩ in the normal temperature range, but it was confirmed that the resistance increased rapidly first from the critical temperature (around 80°C) of the PTC material having a relatively low critical temperature included in the second intermediate layer, showing a resistance value of 20 mΩ, and then the resistance increased rapidly again secondarily from the critical temperature (around 120°C) of the PTC material having a relatively high critical temperature included in the first intermediate layer, converging the resistance value to 50 mΩ.

[0211] Meanwhile, referring to FIG. 5, according to the electrode resistance behavior described with reference to FIG. 4, in the case of the comparative example, a decrease in the allowable current was observed near the critical temperature mentioned above, whereas in the case of the example, the allowable current decreased sharply primarily near 80°C and further decreased sharply near 120°C, resulting in a lower level of allowable current compared to the comparative example.

[0212] Consequently, in the case of an electrode composed of a double layer in which an intermediate layer interposed between a current collector and an active material layer according to one aspect of the present disclosure includes PTC materials having different critical temperatures, it was confirmed that faster current interruption is possible compared to a comparative example electrode in which the intermediate layer is composed of a single layer, and at the same time, at higher temperatures, a PTC material having a relatively higher critical temperature additionally operates to function as a dual safety device, and furthermore, exhibits a lower allowable current. Accordingly, it was confirmed that the electrode according to one aspect of the present disclosure can ensure excellent safety.

[0214] The above description is merely an example of applying the principles of the present disclosure, and other configurations may be included without departing from the scope of the present disclosure. Explanation of the symbols

[0215] 10: Electrode assembly 100: Electrode 100a: Anode 100b: Cathode 110: Whole house 120: Middle layer 121: First intermediate layer 122: Second middle layer 130: Active material layer 200: Separator

Claims

Claim 1 An electrode comprising: a current collector; an intermediate layer laminated on at least one surface of the current collector and comprising a Positive Temperature Coefficient (PTC) material; and an active material layer laminated on the intermediate layer; wherein the PTC material comprises a first PTC material and a second PTC material having different critical temperatures, and the intermediate layer comprises a first intermediate layer comprising the first PTC material and a second intermediate layer comprising the second PTC material. Claim 2 In claim 1, the PTC material is an electrode satisfying the relationship defined by the following Equation 1: [Equation 1] 10 ≤ R2 / R1 ≤ 1,000,000 In the above Equation 1, R2 is the resistance value at critical temperature and R1 is the resistance value at room temperature. Claim 3 In claim 1, the first intermediate layer is in contact with the current collector, the second intermediate layer is interposed between the first intermediate layer and the active material layer, and the electrode has a critical temperature of the first PTC material higher than the critical temperature of the second PTC material. Claim 4 In claim 3, the electrode having a critical temperature of the first PTC material of 120°C or higher. Claim 5 In claim 3, the electrode having a critical temperature of the second PTC material of 80°C or higher. Claim 6 In claim 1, the PTC material comprises an electrode including at least one selected from the group consisting of conductive polymers, ceramics, and metal oxides. Claim 7 In claim 6, the electrode comprises at least one conductive polymer selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polythiophene, polyethylenedioxythiophene (PEDOT), and polyphenylene vinylene (PPV). Claim 8 In claim 6, the ceramic is an electrode comprising at least one of zirconium oxide (ZrO2) and barium titanate (BaTiO3). Claim 9 In claim 6, the metal oxide comprises at least one of nickel oxide (NiO) and cobalt oxide (CoO). Claim 10 In claim 6, the intermediate layer is an electrode further comprising a conductive material. Claim 11 In claim 10, the conductive material comprises at least one selected from the group consisting of carbon nanotubes (CNT), graphite, graphene, carbon black, and silver nanoparticles. Claim 12 In claim 10, the intermediate layer is an electrode further comprising the conductive material when the PTC material comprises at least one of the ceramic and metal oxide. Claim 13 An electrode according to claim 10, comprising 1% to 15% by weight of the conductive material relative to the total weight of the solid content of the intermediate layer. Claim 14 An electrode according to claim 1, wherein the thickness of the intermediate layer is 7 μm to 15 μm. Claim 15 An electrode assembly comprising an electrode of any one of claims 1 to 14, wherein the electrode comprises an anode and a cathode. Claim 16 In claim 15, the PTC material included in the anode comprises at least one selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polyethylenedioxythiophene (PEDOT), zirconium oxide (ZrO2), barium titanate (BaTiO3), nickel oxide (NiO) and cobalt oxide (CoO). Claim 17 In claim 15, the PTC material included in the cathode comprises at least one selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polythiophene, polyethylenedioxythiophene (PEDOT), polyphenylene vinylene (PPV), and zirconium oxide (ZrO2).

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