Electrolytic iron foil and application thereof

Abstract

The invention provides an electrolytic iron foil and application thereof. The electrolytic iron foil comprises an iron base material and a surface layer formed on at least one surface of the iron base material; the surface layer comprises metal elements and non-metal elements, the metal elements comprise non-ferrous metal elements, the non-ferrous metal elements comprise at least one of nickel, copper, manganese, cobalt and molybdenum, and the non-metal elements comprise at least one of phosphorus and boron; in terms of 100 wt% of all metals contained in the electrolytic iron foil, the content of non-ferrous metal elements in the electrolytic iron foil is greater than 0 and 5 wt% or less. The electrolytic iron foil has high-strength tensile resistance, and when the electrolytic iron foil is used for an energy storage device, the prepared electrode has excellent flexibility, lithium dendrites can be inhibited, the interface resistance between an electrode mixture layer and the electrolytic iron foil can be reduced, and the energy storage device can exert excellent low-temperature output characteristics.

Description

Technical Field

[0001] This application belongs to the technical field of energy storage, and specifically relates to an electrolytic iron foil and its application. Background Art

[0002] In recent years, with the rapid development of the new energy industry, energy storage devices such as lithium-ion batteries with graphite as the negative electrode have been widely used in devices such as electric vehicles, smart grids, electric bicycles, smart watches, laptops, and mobile phones. However, the currently commercialized lithium-ion batteries cannot meet people's needs due to their low energy density. Therefore, it is imperative to develop rechargeable batteries with high energy density, high safety, long life, and low cost.

[0003] Lithium metal batteries, sodium metal batteries, potassium metal batteries, calcium metal batteries, magnesium metal batteries, etc. with metal lithium, sodium, potassium, calcium, magnesium, etc. as the negative electrode have received extensive attention from researchers in recent years due to their high energy density. These metal negative electrodes have advantages such as high theoretical specific capacity, low electrochemical potential, and good electrical conductivity. However, these metal negative electrodes often use copper foil, aluminum foil, or titanium foil as the current collector. These current collectors not only have high costs but also easily lead to uncontrollable growth of dendrites. The generation of dendrites not only reduces the life of the battery but also causes serious safety problems. Therefore, the development of a current collector with low cost and the ability to inhibit dendrite growth can promote the rapid progress of rechargeable batteries with high energy density, high safety, long life, and low cost, which is of great significance to the development of the new energy industry. Summary of the Invention

[0004] Problems to be Solved by the Invention The purpose of this application is to provide a high-strength and anti-tensile electrolytic iron foil. When this electrolytic iron foil is used in energy storage devices, the prepared negative electrode has excellent softness and can inhibit lithium dendrites, can reduce the interfacial resistance between the negative electrode binder layer and the electrolytic iron foil, and can enable the energy storage device to exhibit excellent low-temperature output characteristics.

[0005] Means for Solving the Problems From the perspective of the surface layer material of the electrolytic iron foil and the low internal resistance of the device having it, the applicant repeatedly and intensively studied the surface layer material of the electrolytic iron foil. As a result, it was found that by making the surface of the iron substrate of the electrolytic iron foil contain specific metal elements and non-metal elements, and when the content of all metal elements contained in the electrolytic iron foil is set to 100 wt%, the content of metals other than iron is greater than 0 and 5 wt% or less, an electrolytic iron foil with high strength and anti-tensile properties was unexpectedly obtained. At the same time, it was found that the negative electrode using this electrolytic iron foil has excellent softness and can inhibit lithium dendrites, and can reduce the interfacial resistance between the negative electrode binder layer and the electrolytic iron foil, so that the energy storage device can exhibit excellent low-temperature output characteristics.

[0006] That is, the object of the present application is to advantageously solve all or part of the above problems. According to the present application, an electrolytic iron foil for an electrode of an energy storage device, an electrode of an energy storage device, and an energy storage device can be provided.

[0007] A first aspect of the present application provides an electrolytic iron foil, which includes an iron substrate and a surface layer formed on at least one surface of the iron substrate; The surface layer includes a metal element and a non-metal element. The metal element includes a non-ferrous metal element, and the non-ferrous metal element includes at least one of nickel, copper, manganese, cobalt, and molybdenum. The non-metal element includes at least one of phosphorus and boron; Based on the total amount of all metals contained in the electrolytic iron foil being 100 wt%, the content of the non-ferrous metal element in the electrolytic iron foil is greater than 0 and 5 wt% or less.

[0008] By making the surface of the iron substrate of the electrolytic iron foil contain specific non-ferrous metal elements and non-metal elements, and the content of the non-ferrous metal element is within a specified range, an electrolytic iron foil with high strength and tensile resistance can be produced.

[0009] In some embodiments, based on the total amount of all metals contained in the electrolytic iron foil being 100 wt%, the content of the non-ferrous metal element is 0.01 - 3 wt%.

[0010] If the content of the non-ferrous metal element satisfies the above range, the strength and tensile resistance of the electrolytic iron foil can be further improved.

[0011] In some embodiments, the metal element includes at least one of nickel and copper.

[0012] If the above conditions are satisfied, the strength and tensile resistance of the electrolytic iron foil can be further improved.

[0013] Furthermore, based on the total amount of all metals contained in the electrolytic iron foil being 100 wt%, the nickel content is 4 wt% or less, preferably 2 wt% or less.

[0014] Furthermore, based on the total amount of all metals contained in the electrolytic iron foil being 100 wt%, the copper content is 2 wt% or less, preferably 1 wt% or less.

[0015] If the above conditions are satisfied, the strength and tensile resistance of the electrolytic iron foil can be further improved.

[0016] In some embodiments, the non-ferrous metal element includes at least one of manganese and molybdenum.

[0017] Furthermore, based on the total amount of all metals contained in the electrolytic iron foil being 100 wt%, the manganese content is 0.5 wt% or less, preferably 0.3 wt% or less.

[0018] Furthermore, based on the total amount of all metals contained in the electrolytic iron foil being 100 wt%, the molybdenum content is 0.2 wt% or less, preferably 0.1 wt% or less.

[0019] If the above conditions are satisfied, the strength and tensile resistance of the electrolytic iron foil can be further improved.

[0020] In some embodiments, based on the total amount of all metals contained in the electrolytic iron foil being 100 wt%, the content of the non-metallic element is 0.01 - 1.0 wt%.

[0021] In some embodiments, the thickness of the electrolytic iron foil is 1.5 μm - 15 μm, preferably 3 μm - 10 μm. In some embodiments, the single-sided thickness of the surface layer is 0.5 μm - 5 μm, preferably 1 μm - 3 μm.

[0022] If the above conditions are satisfied, the strength and tensile resistance of the electrolytic iron foil can be further improved.

[0023] In some embodiments, the tensile strength of the electrolytic iron foil exceeds 750 MPa, preferably exceeds 800 Mpa.

[0024] In some embodiments, the elongation rate of the electrolytic iron foil is 1.6% or more, preferably the elongation rate is 2.2% or more.

[0025] If the above conditions are satisfied, the strength and tensile resistance of the electrolytic iron foil can be further improved.

[0026] In some embodiments, the surface roughness Ra of the electrolytic iron foil is 0.25 μm - 0.8 μm, preferably the surface roughness Ra is 0.35 μm - 0.65 μm.

[0027] In some embodiments, the surface roughness Rz of the electrolytic iron foil is 1.5 μm - 5 μm, preferably Rz is 2.3 μm - 4.2 μm.

[0028] If the above conditions are satisfied, the strength and tensile resistance of the electrolytic iron foil can be further improved.

[0029] In some embodiments, the method for preparing the electrolytic iron foil includes: forming the surface layer on at least one surface of an iron substrate by electrodeposition, and the plating bath used in the electrodeposition method includes 10 - 50 g / L of a metal sulfamate and 5 - 10 g / L of a metal borate and / or a metal phosphate; the metals contained in the metal sulfamate, the metal borate, and the metal phosphate are at least one of nickel, copper, manganese, cobalt, and molybdenum; the process conditions of the electrodeposition method include: the temperature is 50°C - 65°C, the pH value is 4 - 6, and the electrolytic current density is 8 - 20 A / dm 2 。

[0030] The second aspect of the present application provides an electrode for an energy storage device, which includes the electrolytic iron foil described in any one of the above, and a binder layer formed on a part or all of the surface of the electrolytic iron foil.

[0031] In some embodiments, the electrode for the energy storage device is a negative electrode, and the negative electrode includes the electrolytic iron foil described above, and a negative electrode binder layer formed on a part or all of the surface of the electrolytic iron foil.

[0032] If the above electrolytic iron foil is used, the fabricated negative electrode has excellent flexibility and can inhibit lithium dendrites, and the interfacial resistance between the negative electrode binder layer and the electrolytic iron foil can be reduced.

[0033] The third aspect of the present application provides an energy storage device, including a positive electrode, a negative electrode, and an electrolyte, and at least one of the positive electrode and the negative electrode of the energy storage device is the electrode for the energy storage device described above.

[0034] If the above electrode for the energy storage device is used, an energy storage device with significantly improved low-temperature output performance can be obtained.

[0035] In some embodiments, the energy storage device is a lithium-ion battery or an electric double-layer capacitor.

[0036] In some embodiments, the electrolyte of the energy storage device includes component A, and component A includes at least one of lithium difluorophosphate, vinylene sulfate, vinylene carbonate, succinonitrile, 1,3,6-hexanetricarbonitrile, glycerol trinitrile, and crown ether.

[0037] Like this, if the above electrolyte component A is used, the corrosion of the electrolytic iron foil can be inhibited, lithium dendrites can be inhibited, and the interfacial resistance between the negative electrode binder layer and the electrolytic iron foil can be further reduced.

[0038] In some embodiments, the crown ether includes one or a combination of more than one of 15-crown-5, 18-crown-6, 21-crown-7, 24-crown-8, dibenzo-15-crown-5, dibenzo-18-crown-6, dibenzo-21-crown-7, dibenzo-24-crown-8, 1-aza-15-crown-5, 1-aza-18-crown-6, 1-aza-21-crown-7, and 1-aza-24-crown-8.

[0039] If the above crown ether is used, the corrosion of the electrolytic iron foil can be inhibited, lithium dendrites can be inhibited, and the interfacial resistance between the negative electrode binder layer and the electrolytic iron foil can be further reduced.

[0040] In some embodiments, based on 100 parts by mass of the electrolyte, the content of lithium difluorophosphate is 0.01 to 0.8 parts by mass; and / or, the content of vinylene sulfate is 0.01 to 0.8 parts by mass; and / or, the content of vinylene carbonate is 0.01 to 0.5 parts by mass; and / or, the content of succinonitrile is 1.9 to 4.3 parts by mass; and / or, the content of 1,3,6 - hexanetricarbonitrile is 0.9 to 3.5 parts by mass; and / or, the content of glycerol trinitrile is 0.1 to 2.8 parts by mass; and / or, the content of crown ether is 0.1 to 2.5 parts by mass.

[0041] Using the electrolyte component A with the above - mentioned content can inhibit the corrosion of electrolytic iron foil and inhibit lithium dendrites, thereby further reducing the interfacial resistance between the negative electrode binder layer and the electrolytic iron foil.

[0042] Technical effects When the high - strength tensile - resistant electrolytic iron foil of the present application is used in energy storage devices, the fabricated electrode has excellent flexibility and can inhibit lithium dendrites, can reduce the interfacial resistance between the electrode binder layer and the electrolytic iron foil, and can enable the energy storage device to exhibit excellent low - temperature output characteristics. Detailed description of specific embodiments

[0043] The embodiments of the present application are described in detail below. However, these embodiments are exemplary and the present application is not limited thereto.

[0044] The electrolytic iron foil of the present application contains an iron substrate and a surface layer formed on at least one surface of the iron substrate. The surface layer includes a metal element and a non - metal element; the metal element includes a non - iron metal element, and the non - iron metal element includes at least one of nickel, copper, manganese, cobalt, and molybdenum; the non - metal element includes at least one of phosphorus and boron; based on 100 wt% of the total metals contained in the electrolytic iron foil, the content of the non - iron metal element is greater than 0 and 5 wt% or less. When this electrolytic iron foil is used in an energy storage device, the fabricated negative electrode has excellent flexibility and can inhibit lithium dendrites, can reduce the interfacial resistance between the negative electrode binder layer and the current collector, and can enable the energy storage device to exhibit excellent low - temperature output characteristics.

[0045] As the energy storage device in the present application, various energy storage devices such as electric double - layer capacitors, lithium - ion batteries, proton polymer batteries, sodium - ion batteries, aluminum - ion batteries, aluminum solid capacitors, electrolytic capacitors, and lead - acid batteries can be cited. The electrolytic iron foil of the present application is particularly suitable for electric double - layer capacitors and lithium - ion batteries.

[0046] Electrolytic iron foil The electrolytic iron foil in this application includes an iron substrate and a surface layer formed on the surface of the iron substrate. The surface layer includes metal elements and non-metal elements; the metal elements include non-ferrous metal elements, and the non-ferrous metal elements include at least one of nickel, copper, manganese, cobalt, and molybdenum; the non-metal elements include at least one of phosphorus and boron; based on the total amount of all metals contained in the electrolytic iron foil being 100 wt%, the content of non-ferrous metal elements in the electrolytic iron foil is greater than 0 and 5 wt% or less.

[0047] [Iron substrate] The iron substrate used in this application refers to an electrolytic iron substrate foil of pure iron. However, manufacturing errors, etc. are allowed, and even if it contains elements other than iron, as long as it is an extremely small amount that can ignore its influence, it is allowed. Specifically, the iron purity (content) of the electrolytic iron substrate foil is 99.9% or more, preferably 99.95% or more, and more preferably 99.97% or more. Since iron is not likely to cause lithium dendrites, the higher the iron content of the electrolytic iron substrate foil, the more the short circuit inside the electrode can be suppressed.

[0048] [Surface layer] The surface layer on the surface of the iron substrate in this application includes metal elements and non-metal elements; the metal elements include non-ferrous metal elements, and the non-ferrous metal elements include at least one of nickel, copper, manganese, cobalt, and molybdenum; the non-metal elements include at least one of phosphorus and boron; based on the total amount of all metals contained in the electrolytic iron foil being 100 wt%, the content of non-ferrous metal elements in the electrolytic iron foil is greater than 0 and 5 wt% or less.

[0049] The inventors unexpectedly found that the surface layer of this application has the following advantages: Compared with the iron foil without a surface layer, after using the surface layer in this application, stable chemical bonds are formed at the interface between the iron substrate and the surface layer, such as iron-copper, iron-nickel, iron-boron, or iron-phosphorus, etc., which not only improves the overall strength of the electrolytic iron foil, but also significantly improves the surface rust prevention effect of the electrolytic iron foil, facilitating transportation and storage.

[0050] Compared with the iron foil with only metal elements in the surface layer, the surface layer of this application includes metal elements and non-metal elements. The metal elements include at least one of nickel, copper, manganese, cobalt, and molybdenum, and the non-metal elements include at least one of phosphorus and boron. This can significantly improve the strength of the iron foil and make its surface not easily corroded by the electrolyte.

[0051] In this application, from the perspective of reducing the interface resistance between the negative electrode mixture layer and the electrolytic iron foil, when the content of all metal elements contained in the electrolytic iron foil is set to 100 wt%, the content of non-ferrous metal elements is greater than 0 and 5 wt% or less, preferably 0.01 - 3 wt%.

[0052] In the present application, from the perspective of reducing the interfacial resistance between the negative electrode mixture layer and the electrolytic iron foil, the metal elements include nickel and / or copper.

[0053] In the present application, from the perspective of reducing the interfacial resistance between the negative electrode mixture layer and the electrolytic iron foil, when the content of all metal elements contained in the electrolytic iron foil is set to 100 wt%, the nickel content is 4 wt% or less, preferably 2 wt% or less.

[0054] In the present application, from the perspective of reducing the interfacial resistance between the negative electrode mixture layer and the electrolytic iron foil, when the content of all metal elements contained in the electrolytic iron foil is set to 100 wt%, the copper content is 2 wt% or less, preferably 1 wt% or less.

[0055] In the present application, from the perspective of reducing the interfacial resistance between the negative electrode mixture layer and the electrolytic iron foil, when the content of all metal elements contained in the electrolytic iron foil is set to 100 wt%, the manganese content is 0.5 wt% or less, preferably 0.3 wt% or less.

[0056] In the present application, from the perspective of reducing the interfacial resistance between the negative electrode mixture layer and the electrolytic iron foil, when the content of all metal elements contained in the electrolytic iron foil is set to 100 wt%, the molybdenum content is 0.2 wt% or less, preferably 0.1 wt% or less.

[0057] In the present application, the non-metal element preferably includes phosphorus, and a further improved effect can be obtained.

[0058] In the present application, when the content of all metal elements contained in the electrolytic iron foil is set to 100 wt%, the content of the non-metal element is 0.01 - 1.0 wt%, preferably 0.01 - 0.8 wt%, and a further improved effect can be obtained.

[0059] In the present embodiment, as a method for measuring the content of iron and metals other than iron contained in the electrolytic iron foil, for example, inductively coupled plasma (ICP) optical emission spectrometry can be cited. In addition, according to the content of each metal obtained, the mass percentage (wt%) of the metal can be calculated.

[0060] In the present application, from the perspective of improving the strength of the electrolytic iron foil, the thickness of the electrolytic iron foil is 1.5 μm - 15 μm, preferably 3 μm - 10 μm; and / or, the single-sided thickness of the surface layer is 0.5 μm - 5 μm, preferably 1 μm - 3 μm.

[0061] Through SEM cross-section observation, the average value of the thickness at any 5 measured points is used as the thickness of the electrolytic iron foil. The single-sided thickness of the surface layer is measured in the same way.

[0062] In this application, from the perspective of improving the flexibility of the negative electrode, the tensile strength of the electrolytic iron foil exceeds 750 MPa, preferably exceeding 800 MPa.

[0063] In this application, from the perspective of improving the flexibility of the negative electrode, the elongation rate of the electrolytic iron foil is 1.6% or more, preferably 2.2% or more.

[0064] In this application, from the perspective of improving the adhesion between the binder layer and the electrolytic iron foil, the surface roughness Ra of the electrolytic iron foil is 0.25 μm to 0.8 μm, and the surface roughness Rz is 1.5 μm to 5 μm; preferably, the surface roughness Ra is 0.35 μm to 0.65 μm, and the surface roughness Rz is 2.3 μm to 4.2 μm.

[0065] Here, the surface roughness Ra and Rz are measured in accordance with JIS B0601:2013. The tensile strength and elongation rate are measured in accordance with JIS Z2241 (Test Method for Tensile Properties of Metallic Materials).

[0066] The electrolytic iron foil of this embodiment can be formed by electroplating. Specifically, an iron substrate foil can be first formed using an electroplating bath containing iron ions, and then the iron substrate foil can be electroplated again to form a surface layer.

[0067] Specifically, it can be manufactured as follows: 1) Prepare a Ti material as a support for forming the electrolytic iron foil, clean the Ti material through pretreatment such as pickling or water washing, and then electro-deposit iron on its surface, thereby obtaining an iron substrate.

[0068] The plating bath used for electro-deposition preferably contains 600 - 700 g / L of ferric chloride tetrahydrate and 10 - 20 g / L of hydrochloric acid, and is carried out under the conditions of a temperature of 90 - 110 °C, a pH value of 1.0 or less, and a current density of 8 - 12 A / dm 2 to form an iron substrate foil with a preset thickness.

[0069] 2) Electroplate a surface layer on the iron substrate.

[0070] The plating bath used preferably contains 10 - 50 g / L of a metal sulfamate (the metal is, for example, at least one of nickel, copper, manganese, cobalt, and molybdenum) and 5 - 10 g / L of a metal borate or metal phosphate (the metal is, for example, at least one of nickel, copper, manganese, cobalt, and molybdenum), and under the conditions of 50 °C - 65 °C, a pH value of 4 - 6, and an electrolytic current density of 8 - 20 A / dm 2 to form a surface layer with a preset thickness.

[0071] Energy storage device electrode The energy storage device electrode of this application includes the above-mentioned electrolytic iron foil and an electrode binder layer formed on the electrolytic iron foil, and the binder layer includes an active substance.

[0072] As the positive electrode active material, various active materials conventionally used in electrodes of energy storage devices can be used.

[0073] The positive electrode active material includes, for example, a lithiated intercalation compound that reversibly intercalates and deintercalates lithium ions.

[0074] For example, at least one composite oxide of lithium with a metal such as cobalt, manganese, nickel, or a combination thereof can be used.

[0075] A composite oxide having a coating on its surface can be used, or a mixture of a composite oxide and a composite oxide having a coating can be used. The coating can include a coating element compound selected from the following: an oxide of the coating element, a hydroxide of the coating element, a hydroxyoxide of the coating element, an oxycarbonate of the coating element, or a basic carbonate of the coating element. The compound used for the coating can be amorphous or crystalline. The coating element included in the coating can be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, W, La, Y, Ce, or a mixture thereof. The coating process can include any suitable process commonly used in the art as long as it does not (or substantially does not) cause any side effects (e.g., any undesired side effects) on the characteristics of the positive electrode active material (e.g., spraying, dipping), which will be apparent to those of ordinary skill in the art after reading this application, and thus need not be described in detail herein.

[0076] For example, the positive electrode active material can include lithium cobalt oxide.

[0077] In some embodiments, the positive electrode active material can include a lithium cobalt oxide represented by Chemical Formula 1: Chemical Formula 1: Li a11 Co x11 M 11 y11 O 2 .

[0078] In Chemical Formula 1, 0.9 ≤ a11 ≤ 1.8, 0.9 ≤ x11 ≤ 1, 0 ≤ y11 ≤ 0.1, x11 + y11 = 1, and M 11 is at least one of Al, B, Ce, Cr, F, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, and Zr.

[0079] For example, the positive electrode active material can be LiCoO 2 .

[0080] In some embodiments, the positive electrode active material can include a lithium nickel-based composite oxide represented by Chemical Formula 2: Chemical Formula 2: Lia1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 。

[0081] In Chemical Formula 2, 0.9 ≤ a1 ≤ 1.2, 0.7 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.2, 0 ≤ z1 ≤ 0.2, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1; M 1 and M 2 are each independently selected from one or more elements of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr; and X is selected from one or more elements of F, P, and S.

[0082] In Chemical Formula 2, 0.75 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.18, and 0 ≤ z1 ≤ 0.18; 0.85 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.15, and 0 ≤ z1 ≤ 0.15; or 0.9 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.1, and 0 ≤ z1 ≤ 0.1.

[0083] For example, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 3. The compound represented by Chemical Formula 3 may be referred to as a lithium nickel cobalt-based composite oxide: Chemical Formula 3: Li a2 Ni x2 Co y2 M 3 z2 O 2-b2 X b2 。

[0084] In Chemical Formula 3, 0.9 ≤ a2 ≤ 1.8, 0.7 ≤ x2 < 1, 0 < y2 ≤ 0.2, 0 ≤ z2 ≤ 0.2, 0.9 ≤ x2 + y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 3 is selected from one or more elements of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is selected from one or more elements of F, P, and S.

[0085] In Chemical Formula 3, 0.75 ≤ x2 ≤ 0.99, 0 ≤ y2 ≤ 0.15, and 0 ≤ z2 ≤ 0.15; 0.85 ≤ x2 ≤ 0.99, 0.01 ≤ y2 ≤ 0.15, and 0.01 ≤ z2 ≤ 0.15; or 0.9 ≤ x2 ≤ 0.99, 0.01 ≤ y2 ≤ 0.1, and 0.01 ≤ z2 ≤ 0.1.

[0086] For example, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 4. The compound represented by Chemical Formula 4 may be referred to as a lithium nickel cobalt aluminum-based oxide or a lithium nickel cobalt manganese-based oxide.

[0087] Chemical Formula 4: Li a3 Ni x3 Co y3 M 4 z3 M 5 w3 O 2-b3 X b3 In Chemical Formula 4, 0.9 ≤ a3 ≤ 1.8, 0.7 ≤ x3 ≤ 0.98, 0.01 ≤ y3 ≤ 0.19, 0.01 ≤ z3 ≤ 0.19, 0 ≤ w3 ≤ 0.19, 0.9 ≤ x3 + y3 + z3 + w3 ≤ 1.1, and 0 ≤ b3 ≤ 0.1, M 4 is one or more elements selected from Al and Mn, M 5 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from F, P, and S.

[0088] In Chemical Formula 4, 0.75 ≤ x3 ≤ 0.98, 0 ≤ y3 ≤ 0.16, 0 ≤ z3 ≤ 0.16, and 0 ≤ w3 ≤ 0.16; 0.85 ≤ x3 ≤ 0.98, 0.01 ≤ y3 ≤ 0.14, 0.01 ≤ z3 ≤ 0.14, and 0 ≤ w3 ≤ 0.14; or 0.9 ≤ x3 ≤ 0.98, 0.01 ≤ y3 ≤ 0.09, 0.01 ≤ z3 ≤ 0.09, and 0 ≤ w3 ≤ 0.09.

[0089] For example, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 5. The compound represented by Chemical Formula 5 may be referred to as a cobalt-free lithium nickel manganese-based oxide.

[0090] Chemical Formula 5: Li a4 Ni x4 Mn y4 M 6 z4 O 2-b4 X b4 In Chemical Formula 5, 0.9 ≤ a4 ≤ 1.8, 0.7 ≤ x4 < 1, 0 < y4 ≤ 0.2, 0 ≤ z4 ≤ 0.2, 0.9 ≤ x4 + y4 + z4 ≤ 1.1, and 0 ≤ b4 ≤ 0.1, M 6is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from F, P, and S.

[0091] In some exemplary embodiments of the positive electrode, based on the total weight of the positive electrode binder layer, the content of the positive electrode active material can be 90 wt% to 98 wt%, 50 wt% to 99 wt%, 60 wt% to 99 wt%, 70 wt% to 99 wt%, 80 wt% to 99 wt%, or 90 wt% to 99 wt%.

[0092] In some embodiments of the present application, the positive electrode binder layer includes a conductive material (e.g., a conductivity material) and a binder. In some embodiments, based on the total weight of the positive electrode binder layer, the respective contents of the conductive material and the binder can be 1.0 wt% to 5.0 wt%.

[0093] The conductive material is used to impart conductivity (e.g., electrical conductivity) to the electrode, and any suitable conductivity material can be used as the conductive material (e.g., a conductivity material), unless it causes chemical changes in the battery (e.g., undesired changes in a rechargeable lithium battery). Examples of the conductive material can include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (such as metal powders or metal fibers of copper, nickel, aluminum, silver, etc.), conductive polymers (such as polyphenylene derivatives), or a mixture of these.

[0094] The binder improves the bonding characteristics between the positive electrode active material particles and the bonding characteristics between the positive electrode active material particles and the positive electrode current collector. The binder can be, for example, one or a combination of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc., but is not limited thereto.

[0095] The negative electrode active material can be a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and dedoping lithium, and / or a transition metal oxide.

[0096] Materials that can reversibly embed / extract lithium ions include carbon materials. The carbon materials can be any suitable carbonaceous negative electrode active materials commonly used in rechargeable lithium batteries. Examples of the carbon materials include crystalline carbon, amorphous carbon, and combinations thereof. The crystalline carbon can be amorphous natural graphite and / or artificial graphite, such as flaky, sheet-like, spherical, and / or fibrous natural graphite and / or artificial graphite. The amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0097] Lithium metal alloys include, for example, lithium and also include one or more metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0098] Materials that can be doped and de-doped with lithium can include Si, SiO x (0 < x < 2), Si-Q alloys (where Q is selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements other than Si, Group 15 elements, Group 16 elements, transition metals, rare earth elements, or combinations thereof), Sn, SnO 2 , Sn-R alloys (where R is selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements other than Sn, Group 15 elements, Group 16 elements, transition metals, rare earth elements, or combinations thereof), etc. At least one of them can be mixed with SiO 2 together.

[0099] The element Q and the element R can further be independently selected from one or more of 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 (the element R does not include Sn), In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po.

[0100] The transition metal oxides can be vanadium oxides, lithium vanadium oxides, etc.

[0101] In some exemplary embodiments, the negative electrode active material can be selected from at least one of graphite and Si composites.

[0102] The Si composite includes a core of Si particles and amorphous carbon, and, for example, the Si particles can be selected from at least one of Si-C composites, SiO k (0 < k ≤ 2), and Si alloys.

[0103] For example, the Si-C composite can include a core of Si particles and amorphous carbon.

[0104] The central part of the core may include pores, and the radius of the central part may correspond to about 30% to about 50% of the radius of the Si composite.

[0105] The Si particles may have a median particle size of 10 nm to 200 nm.

[0106] As used herein, the median particle size (D50) may be the particle size at which the volume ratio is 50% in the cumulative size distribution curve.

[0107] When the median particle size of the Si particles is within the above range, volume expansion occurring during charging and discharging can be suppressed or reduced, and disconnection of the conduction path due to particle pulverization during charging and discharging can be prevented or reduced.

[0108] Based on the total weight of the Si composite, the amount of Si particles included may be 1 wt% to 60 wt%, for example 3 wt% to 60 wt%.

[0109] The central part may not include amorphous carbon, and amorphous carbon may only be present in the surface part of the negative electrode active material.

[0110] As used herein, the surface part refers to the region from the central part of the negative electrode active material (for example, the region just outside the central part) to the outermost surface of the negative electrode active material.

[0111] In some embodiments, Si particles are included substantially uniformly throughout the negative electrode active material. For example, the Si particles are present in the central part and the surface part of the negative electrode active material at a substantially uniform concentration.

[0112] The amorphous carbon may be one or a combination of soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke.

[0113] The negative electrode active material may further include crystalline carbon.

[0114] When the negative electrode active material includes both the Si composite and crystalline carbon, the Si composite and crystalline carbon may be included in the form of a mixture, and in some embodiments, the Si composite and crystalline carbon may be included in a weight ratio of 1:99 to 50:50. In some embodiments, the Si composite and crystalline carbon may be included in a weight ratio of 3:97 to 20:80 or 5:95 to 20:80.

[0115] The crystalline carbon may be, for example, graphite, such as natural graphite, artificial graphite, or a mixture thereof.

[0116] The crystalline carbon may have a median particle size of 5 μm to 30 μm.

[0117] The amorphous carbon precursor may include coal tar pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil, and / or polymer resins (such as phenolic resin, furan resin, and / or polyimide resin).

[0118] In the negative electrode binder layer, based on the total weight of the negative electrode binder layer, the amount of the negative electrode active material included may be 95 wt% to 99 wt%.

[0119] In some exemplary embodiments, the negative electrode binder layer may further include a binder, and optionally may include a conductive material (e.g., a conductivity material). In the negative electrode binder layer, based on the total weight of the negative electrode binder layer, the amount of the binder may be 1 wt% to 5 wt%. When the negative electrode binder layer further includes a conductive material, the negative electrode binder layer may include 90 wt% to 98 wt% of the negative electrode active material, 1 wt% to 5 wt% of the binder, and 1 wt% to 5 wt% of the conductive material.

[0120] The binder improves the binding characteristics between the negative electrode active material particles and the binding characteristics between the negative electrode active material and the current collector. The binder may include one or a combination of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide. The binder may also include a rubber binder and / or a polymer resin binder. The rubber binder may be selected from one or a combination of styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber. The polymer resin binder may be selected from one or a combination of polytetrafluoroethylene, ethylene-propylene copolymer, poly(ethylene oxide), polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol.

[0121] The conductive material provides electrode conductivity (e.g., conductivity), and any suitable conductivity material may be used as the conductive material (e.g., the conductivity material), unless it causes an undesired chemical change (e.g., unless it causes an undesired change in a rechargeable lithium battery). The conductive material may be a carbon material (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), a metal material (such as metal powder or metal fiber of copper, nickel, aluminum, silver, etc.), a conductive polymer (such as polyphenylene derivatives, etc.), or a mixture thereof.

[0122] In addition, in the case where the energy storage device is an electric double layer capacitor, the active material can be a carbonaceous material. Examples of the carbonaceous material include activated carbon, such as activated carbon obtained by carbonizing and activating phenolic resin.

[0123] Energy storage device The energy storage device involved in the present application has the above-mentioned energy storage device electrode. More specifically, it includes at least one pair of positive and negative electrodes, a separator and an electrolyte existing between the positive and negative electrodes, and at least one of the positive and negative electrodes is composed of the above-mentioned energy storage device electrode.

[0124] This energy storage device uses the above-mentioned energy storage device electrode as the electrode, and components such as the separator and electrolyte, which are other components of the device, can be appropriately selected from known materials for use.

[0125] The separator can be a porous substrate or a composite porous substrate.

[0126] The porous substrate can be a substrate including pores, and lithium ions can move through the pores. The porous substrate includes, for example, a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multilayer structure formed by these separators (such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, and a polypropylene / polyethylene / polypropylene trilayer separator).

[0127] The composite porous substrate can include a porous substrate and a functional layer formed on the porous substrate. From the perspective of ensuring additional functions, the functional layer can be selected from at least one of a heat-resistant layer and a bonding layer. For example, the heat-resistant layer can include a heat-resistant resin and optionally include a filler.

[0128] In some embodiments, the bonding layer can include a binder resin and optionally include a filler.

[0129] The filler can be an organic filler and / or an inorganic filler.

[0130] As the electrolyte, both liquid and solid are acceptable, and both aqueous and non-aqueous are acceptable. When the energy storage device electrode of the present application is applied to a device using a non-aqueous electrolyte, it can also exhibit practically sufficient performance.

[0131] As the non-aqueous electrolyte, a non-aqueous electrolyte solution obtained by dissolving an electrolyte salt in a non-aqueous organic solvent can be cited.

[0132] In some embodiments, the electrolyte includes component A, and component A includes at least one of lithium difluorophosphate, ethylene sulfate, vinylene carbonate, succinonitrile, 1,3,6-hexanetricarbonitrile, glycerol trinitrile, and crown ether. At this time, the corrosion of the electrolytic iron foil can be further reduced, lithium dendrites can be inhibited, and the improvement effect is beyond expectation.

[0133] The description of the electrolyte including Component A above is as follows.

[0134] The electrolyte includes a non-aqueous organic solvent, an electrolyte salt, Component A, and optionally other additives.

[0135] As the electrolyte salt, LiPF 6 、LiBF 4 、LiDFOP, LiDFOB, LiPO 2 F 2 、LiSbF 6 、LiAsF 6 、LiN(SO 2 C 2 F 5 ) 2 、Li(CF 3 SO 2 ) 2 N, LiN(SO 3 C 2 F 5 ) 2 、Li(FSO 2 ) 2 N (lithium bis(fluorosulfonyl)imide: LiFSI), LiC 4 F 9 SO 3 、LiClO 4 、LiAlO 2 、LiAlCl 4 、LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ) (where x and y are natural numbers, for example, integers from 1 to 20), LiCl, LiI, and LiB(C 2 O 4 ) 2 (lithium bis(oxalato)borate: LiBOB). The concentration of the electrolyte salt can be in the range of about 0.1 M to about 2.0 M. When the lithium salt is included in the above concentration range, appropriate or optimal electrolyte conductivity and viscosity can be generated, so that the electrolyte can have excellent performance and lithium ion mobility.

[0136] The non-aqueous organic solvent can be used as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0137] The non-aqueous organic solvent can include one or a combination of more of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, and aprotic solvents.

[0138] Carbonate solvents may include ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, decanolide, mevalonolactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. Ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and examples of aprotic solvents include nitriles (such as R-CN, where R is a C2-C20 straight-chain hydrocarbon group, branched-chain hydrocarbon group or cycloalkyl group, and may include double bonds, aromatic rings or ether bonds), amides (such as dimethylformamide), dioxolanes (such as 1,3-dioxolane), sulfolane, etc.

[0139] A single non-aqueous organic solvent or a combination of one or more of them may be used, and when a combination of one or more is used, the mixing ratio may be appropriately or suitably adjusted according to the appropriate or desired battery performance, which should be fully understood by those skilled in the art after reading this application.

[0140] Component A can effectively inhibit the corrosion of electrolytic iron foil, thereby inhibiting the breakage of electrolytic iron foil generated during charge and discharge cycles, and further improving the low-temperature output performance of energy storage devices.

[0141] Component A includes at least one of lithium difluorophosphate, vinylene sulfate, ethylene carbonate, succinonitrile, 1,3,6-hexanetricarbonitrile, glycerol trinitrile, crown ether.

[0142] The crown ether includes one or more of 15-crown-5, 18-crown-6, 21-crown-7, 24-crown-8, dibenzo-15-crown-5, dibenzo-18-crown-6, dibenzo-21-crown-7, dibenzo-24-crown-8, 1-aza-15-crown-5, 1-aza-18-crown-6, 1-aza-21-crown-7 and 1-aza-24-crown-8.

[0143] Among them, based on 100 parts by mass of the electrolyte, the content of lithium difluorophosphate is 0.01 to 0.8 parts by mass; and / or, the content of vinylene sulfate is 0.01 to 0.8 parts by mass; and / or, the content of vinylene carbonate is 0.01 to 0.5 parts by mass; and / or, the content of succinonitrile is 1.9 to 4.3 parts by mass; and / or, the content of 1,3,6 - hexanetricarbonitrile is 0.9 to 3.5 parts by mass; and / or, the content of glycerol trinitrile is 0.1 to 2.8 parts by mass; and / or, the content of crown ether is 0.1 to 2.5 parts by mass.

[0144] Using the electrolyte components with the above contents can further suppress the breakage of the current collector substrate generated during charge - discharge cycles and further improve the low - temperature output performance of the energy storage device.

[0145] There is no particular limitation on the form of the energy storage device. For example, various conventionally known forms of batteries such as cylindrical, flat - wound rectangular, laminated rectangular, coin - type, flat - wound laminated, laminated - laminated type, etc. can be adopted.

[0146] Examples The following examples and comparative examples are listed in this application to illustrate the technical solutions of this application more specifically, but this application is not limited to the following examples.

[0147] Manufacture of electrolytic iron foil

[0148] Example 1 - 1 1) Using a Ti material as the support for forming the iron base foil, placing it in a plating bath containing 600 g / L of ferric chloride tetrahydrate and 10 g / L of hydrochloric acid, and performing electro - deposition under the conditions of a temperature of 90 °C, a pH value of 0.8, and a current density of 8 A / dm 2 to form the iron base foil and stripping it from the support; 2) Placing the obtained iron base foil in a plating bath containing 10 g / L of nickel sulfamate and 5 g / L of nickel borate, and performing electro - deposition under the conditions of 50 °C, a pH value of 4, and an electrolysis current density of 8 A / dm 2 to form the surface layer.

[0149] The obtained electrolytic iron foil has a Ni content of 0.01 wt%, a B content of 0.3 wt%. The thickness of the iron base is 1.5 μm, and the single - side thickness of the surface layer is 0.5 μm. The tensile strength of the electrolytic iron foil is 750 MPa, the elongation rate is 1.6%, Ra is 0.25 μm, and Rz is 1.5 μm.

[0150] Example 1 - 2A 1) Using Ti material as the support for forming the iron base foil, place it in a plating bath containing 700 g / L of ferric chloride tetrahydrate and 20 g / L of hydrochloric acid, and perform electrodeposition under the conditions of a temperature of 110 °C, a pH value of 0.9, and a current density of 12 A / dm 2 to form the iron base foil; 2) Place the iron base foil prepared above in a plating bath containing 50 g / L of nickel sulfamate and 10 g / L of nickel borate, and perform electrodeposition under the conditions of 65 °C, a pH value of 6, and an electrolytic current density of 20 A / dm 2 to form the surface layer.

[0151] The obtained electrolytic iron foil contains 5 wt% of Ni and 0.6 wt% of B. The thickness of the iron base is 15 μm, and the single-sided thickness of the surface layer is 5 μm. The tensile strength of the electrolytic iron foil is 850 MPa, the elongation at break is 2.2%, Ra is 0.8 μm, and Rz is 5 μm.

[0152] Example 1-2B 1) Using Ti material as the support for forming the iron base foil, place it in a plating bath containing 700 g / L of ferric chloride tetrahydrate and 20 g / L of hydrochloric acid, and perform electrodeposition under the conditions of a temperature of 110 °C, a pH value of 0.9, and a current density of 12 A / dm 2 to form the iron base foil; 2) Place the iron base foil prepared above in a plating bath containing 50 g / L of nickel sulfamate and 20 g / L of nickel borate, and perform electrodeposition under the conditions of 65 °C, a pH value of 6, and an electrolytic current density of 20 A / dm 2 to form the surface layer.

[0153] The obtained electrolytic iron foil contains 5 wt% of Ni and 1.2 wt% of B. The thickness of the iron base is 15 μm, and the single-sided thickness of the surface layer is 5 μm. The tensile strength of the electrolytic iron foil is 830 MPa, the elongation at break is 2.1%, Ra is 0.7 μm, and Rz is 3.6 μm.

[0154] Example 1-2C 1) Using Ti material as the support for forming the iron base foil, place it in a plating bath containing 700 g / L of ferric chloride tetrahydrate and 20 g / L of hydrochloric acid, and perform electrodeposition under the conditions of a temperature of 110 °C, a pH value of 0.9, and a current density of 12 A / dm 2 to form the iron base foil; 2) Place the iron base foil prepared above in a plating bath containing 50 g / L of nickel sulfamate and 14 g / L of nickel borate, and perform electrodeposition under the conditions of 65 °C, a pH value of 6, and an electrolytic current density of 20 A / dm 2 to form the surface layer.

[0155] The obtained electrolytic iron foil has a Ni content of 5 wt% and a B content of 1.0 wt%. The thickness of the iron substrate is 15 μm, and the single-sided thickness of the surface layer is 5 μm. The tensile strength of the electrolytic iron foil is 830 MPa, the elongation at break is 2.1%, Ra is 0.7 μm, and Rz is 3.6 μm.

[0156] Example 1-2D 1) Using a Ti material as the support for forming the iron substrate foil, place it in a plating bath containing 700 g / L of ferric chloride tetrahydrate and 20 g / L of hydrochloric acid, and perform electrodeposition at a temperature of 110 °C, a pH value of 0.9, and a current density of 12 A / dm 2 to form the iron substrate foil; 2) Place the obtained iron substrate foil in a plating bath containing 50 g / L of nickel sulfamate and 12 g / L of nickel borate, and perform electrodeposition at 65 °C, a pH value of 6, and an electrolytic current density of 20 A / dm 2 to form the surface layer.

[0157] The obtained electrolytic iron foil has a Ni content of 5 wt% and a B content of 0.8 wt%. The thickness of the iron substrate is 15 μm, and the single-sided thickness of the surface layer is 5 μm. The tensile strength of the electrolytic iron foil is 830 MPa, the elongation at break is 2.1%, Ra is 0.7 μm, and Rz is 3.6 μm.

[0158] Example 1-3 1) Using a Ti material as the support for forming the iron substrate foil, place it in a plating bath containing 620 g / L of ferric chloride tetrahydrate and 12 g / L of hydrochloric acid, and perform electrodeposition at a temperature of 95 °C, a pH value of 0.8, and a current density of 10 A / dm 2 to form the iron substrate foil; 2) Place the obtained iron substrate foil in a plating bath containing 30 g / L of nickel sulfamate and 8 g / L of nickel borate, and perform electrodeposition at 60 °C, a pH value of 5, and an electrolytic current density of 15 A / dm 2 to form the surface layer.

[0159] The obtained electrolytic iron foil has a Ni content of 1 wt% and a B content of 0.4 wt%. The thickness of the iron substrate is 3 μm, and the single-sided thickness of the surface layer is 1 μm. The tensile strength of the electrolytic iron foil is 906 MPa, the elongation at break is 2.5%, Ra is 0.35 μm, and Rz is 2.3 μm.

[0160] Example 1-4 1) Using a Ti material as the support for forming the iron substrate foil, place it in a plating bath containing 680 g / L of ferric chloride tetrahydrate and 14 g / L of hydrochloric acid, and perform electrodeposition at a temperature of 95 °C, a pH value of 0.8, and a current density of 10 A / dm2 Electrodeposition is carried out under the following conditions to form an iron base foil; 2) The iron base foil obtained above is placed in a plating bath containing 10 g / L nickel sulfamate, 30 g / L copper sulfamate and 6 g / L nickel borate, and electrodeposition is carried out at 65 °C, pH value of 5, and electrolytic current density of 13 A / dm 2 to form a surface layer.

[0161] In the obtained electrolytic iron foil, the Ni content is 3 wt%, the Cu content is 1 wt%, and the B content is 0.4 wt%. The thickness of the iron base material is 5 μm, and the single-sided thickness of the surface layer is 2 μm. The tensile strength of the electrolytic iron foil is 975 MPa, the elongation rate is 3.4%, Ra is 0.57 μm, and Rz is 2.6 μm.

[0162] Example 1 - 5 1) Using Ti material as the support for forming the iron base foil, it is placed in a plating bath containing 680 g / L ferric chloride tetrahydrate and 14 g / L hydrochloric acid, and electrodeposition is carried out at a temperature of 95 °C, pH value of 0.8 and current density of 10 A / dm 2 to form an iron base foil; 2) The iron base foil obtained above is placed in a plating bath containing 8 g / L nickel sulfamate, 20 g / L manganese sulfamate and 6 g / L nickel borate, and electrodeposition is carried out at 65 °C, pH value of 5, and electrolytic current density of 15 A / dm 2 to form a surface layer.

[0163] In the obtained electrolytic iron foil, the Ni content is 2 wt%, the Mn content is 0.5 wt%, and the B content is 0.4 wt%. The thickness of the iron base material is 8 μm, and the single-sided thickness of the surface layer is 3 μm. The tensile strength of the electrolytic iron foil is 929 MPa, the elongation rate is 4.7%, Ra is 0.65 μm, and Rz is 3.7 μm.

[0164] Example 1 - 6 1) Using Ti material as the support for forming the iron base foil: it is placed in a plating bath containing 680 g / L ferric chloride tetrahydrate and 14 g / L hydrochloric acid, and electrodeposition is carried out at a temperature of 95 °C, pH value of 0.8 and current density of 10 A / dm 2 to form an iron base foil; 2) The iron base foil obtained above is placed in a plating bath containing 8 g / L copper sulfamate, 10 g / L molybdenum sulfamate and 6 g / L nickel borate, and electrodeposition is carried out at 65 °C, pH value of 5, and electrolytic current density of 15 A / dm 2 to form a surface layer.

[0165] The obtained electrolytic iron foil has a Cu content of 1.5 wt%, a Mo content of 0.2 wt%, and a B content of 0.4 wt%. The thickness of the iron substrate is 10 μm, and the single-sided thickness of the surface layer is 2 μm. The tensile strength of the electrolytic iron foil is 898 MPa, the elongation rate is 4.4%, Ra is 0.57 μm, and Rz is 2.5 μm.

[0166] Examples 1 - 7 1) Using a Ti material as the support for forming the iron substrate foil, place it in a plating bath containing 600 g / L of ferric chloride tetrahydrate and 10 g / L of hydrochloric acid, and perform electroplating under the conditions of a temperature of 90 °C, a pH value of 0.8, and a current density of 8 A / dm 2 to form the iron substrate foil; 2) Place the above-prepared iron substrate foil in a plating bath containing 10 g / L of nickel sulfamate and 5 g / L of nickel phosphate, and form the surface layer under the conditions of 50 °C, a pH value of 4, and an electrolysis current density of 8 A / dm 2 ;

[0167] The obtained electrolytic iron foil has a Ni content of 0.5 wt% and a P content of 0.3 wt%. The thickness of the iron substrate is 1.5 μm, and the single-sided thickness of the surface layer is 0.5 μm. The tensile strength is 776 MPa, the elongation rate is 1.8%, Ra is 0.23 μm, and Rz is 1.6 μm.

[0168] Examples 1 - 8 1) Using a Ti material as the support for forming the iron substrate foil, place it in a plating bath containing 700 g / L of ferric chloride tetrahydrate and 20 g / L of hydrochloric acid, and perform electroplating under the conditions of a temperature of 110 °C, a pH value of 0.9, and a current density of 12 A / dm 2 to form the iron substrate foil; 2) Place the above-prepared iron substrate foil in a plating bath containing 50 g / L of nickel sulfamate and 10 g / L of nickel phosphate, and perform electroplating under the conditions of 65 °C, a pH value of 6, and an electrolysis current density of 20 A / dm 2 to form the surface layer.

[0169] The obtained electrolytic iron foil has a Ni content of 3 wt% and a P content of 0.5 wt%. The thickness of the iron substrate is 15 μm, and the single-sided thickness of the surface layer is 5 μm. The tensile strength of the electrolytic iron foil is 891 MPa, the elongation rate is 2.8%, Ra is 0.7 μm, and Rz is 4.2 μm.

[0170] Examples 1 - 9 1) Using a Ti material as the support for forming the iron substrate foil, place it in a plating bath containing 620 g / L of ferric chloride tetrahydrate and 12 g / L of hydrochloric acid, and perform electroplating under the conditions of a temperature of 95 °C, a pH value of 0.8, and a current density of 10 A / dm 2Electrodeposition is carried out under the following conditions to form an iron base foil; 2) The iron base foil obtained above is placed in a plating bath containing 30 g / L of nickel sulfamate and 8 g / L of nickel phosphate, and electrodeposition is carried out at 60 °C, pH value of 5, and electrolysis current density of 15 A / dm 2 to form a surface layer.

[0171] In the obtained electrolytic iron foil, the Ni content is 1 wt%, and the P content is 0.4 wt%. The thickness of the iron base is 3 μm, and the single-sided thickness of the surface layer is 1 μm. The tensile strength of the electrolytic iron foil is 953 MPa, the elongation rate is 3.2%, Ra is 0.38 μm, and Rz is 2.7 μm.

[0172] Example 1 - 10 1) Using a Ti material as the support for forming the iron base foil, it is placed in a plating bath containing 680 g / L of ferric chloride tetrahydrate and 14 g / L of hydrochloric acid, and electrodeposition is carried out at a temperature of 95 °C, pH value of 0.8, and current density of 10 A / dm 2 to form an iron base foil; 2) The iron base foil obtained above is placed in a plating bath containing 10 g / L of nickel sulfamate, 30 g / L of copper sulfamate, and 6 g / L of nickel phosphate, and electrodeposition is carried out at 65 °C, pH value of 5, and electrolysis current density of 13 A / dm 2 to form a surface layer.

[0173] In the obtained electrolytic iron foil, the Ni content is 3 wt%, the Cu content is 1 wt%, and the P content is 0.4 wt%. The thickness of the iron base is 5 μm, and the single-sided thickness of the surface layer is 2 μm. The tensile strength of the electrolytic iron foil is 1075 MPa, the elongation rate is 5.3%, Ra is 0.52 μm, and Rz is 2.3 μm.

[0174] Example 1 - 11 1) Using a Ti material as the support for forming the iron base foil, it is placed in a plating bath containing 680 g / L of ferric chloride tetrahydrate and 14 g / L of hydrochloric acid, and electrodeposition is carried out at a temperature of 95 °C, pH value of 0.8, and current density of 10 A / dm 2 to form an iron base foil; 2) The iron base foil obtained above is placed in a plating bath containing 8 g / L of nickel sulfamate, 20 g / L of manganese sulfamate, and 6 g / L of nickel phosphate, and electrodeposition is carried out at 65 °C, pH value of 5, and electrolysis current density of 15 A / dm 2 to form a surface layer.

[0175] The obtained electrolytic iron foil contains 2 wt% of Ni, 0.5 wt% of Mn, and 0.4 wt% of P. The thickness of the iron substrate foil is 8 μm, and the single-sided thickness of the surface layer is 3 μm. The tensile strength of the electrolytic iron foil is 1009 MPa, the elongation rate is 5.4%, Ra is 0.61 μm, and Rz is 3.2 μm.

[0176] Examples 1 - 12 1) Using Ti material as the support for forming the iron substrate foil, place it in a plating bath containing 680 g / L of ferric chloride tetrahydrate and 14 g / L of hydrochloric acid, and perform electroplating under the conditions of a temperature of 95 °C, a pH value of 0.8, and a current density of 10 A / dm 2 to form the iron substrate foil; 2) Place the obtained iron substrate foil in a plating bath containing 8 g / L of copper sulfamate, 10 g / L of molybdenum sulfamate, and 6 g / L of nickel phosphate, and perform electroplating under the conditions of a temperature of 65 °C, a pH value of 5, and an electrolytic current density of 15 A / dm 2 to form the surface layer.

[0177] The obtained electrolytic iron foil contains 1.5 wt% of Cu, 0.2 wt% of Mo, and 0.4 wt% of P. The thickness of the iron substrate is 10 μm, and the single-sided thickness of the surface layer is 2 μm. The tensile strength of the electrolytic iron foil is 992 MPa, the elongation rate is 4.9%, Ra is 0.53 μm, and Rz is 2.7 μm.

[0178] Examples 1 - 13A 1) Using Ti material as the support for forming the electrolytic iron foil, place it in a plating bath containing 680 g / L of ferric chloride tetrahydrate and 14 g / L of hydrochloric acid, and perform electroplating under the conditions of a temperature of 95 °C, a pH value of 0.8, and a current density of 10 A / dm 2 to form the iron substrate foil.

[0179] 2) Place the obtained iron substrate foil in a plating bath containing 10 g / L of nickel sulfamate, 30 g / L of copper sulfamate, 6 g / L of nickel borate, and 6 g / L of nickel phosphate, and perform electroplating under the conditions of a temperature of 65 °C, a pH value of 5, and an electrolytic current density of 13 A / dm 2 to form the surface layer.

[0180] The obtained electrolytic iron foil contains 3 wt% of Ni, 1 wt% of Cu, 0.44 wt% of B, and 0.35 wt% of P. The thickness of the iron substrate is 5 μm, and the single-sided thickness of the surface layer is 2 μm. The tensile strength is 1225 MPa, the elongation rate is 7.2%, Ra is 0.59 μm, and Rz is 2.8 μm.

[0181] Examples 1 - 13B 1) Using Ti material as the support for forming the electrolytic iron foil, place it in a plating bath containing 680 g / L of ferric chloride tetrahydrate and 14 g / L of hydrochloric acid, and perform electrodeposition under the conditions of a temperature of 95 °C, a pH value of 0.8, and a current density of 10 A / dm 2 to form an iron substrate foil.

[0182] 2) Place the iron substrate foil obtained above in a plating bath containing 10 g / L of nickel sulfamate, 30 g / L of cobalt sulfamate, 6 g / L of nickel borate, and 6 g / L of nickel phosphate, and perform electrodeposition under the conditions of a temperature of 65 °C, a pH value of 5, and an electrolytic current density of 13 A / dm 2 to form a surface layer.

[0183] In the obtained electrolytic iron foil, the Ni content is 3 wt%, the Co content is 1 wt%, the B content is 0.45 wt%, and the P content is 0.35 wt%. The thickness of the iron substrate is 5 μm, and the single-sided thickness of the surface layer is 2 μm. The tensile strength is 1223 MPa, the elongation at break is 7.1%, Ra is 0.57 μm, and Rz is 2.7 μm.

[0184] Example 1 - 13C 1) Using Ti material as the support for forming the electrolytic iron foil, place it in a plating bath containing 680 g / L of ferric chloride tetrahydrate and 14 g / L of hydrochloric acid, and perform electrodeposition under the conditions of a temperature of 95 °C, a pH value of 0.8, and a current density of 10 A / dm 2 to form an iron substrate foil.

[0185] 2) Place the iron substrate foil obtained above in a plating bath containing 10 g / L of manganese sulfamate, 30 g / L of cobalt sulfamate, 10 g / L of molybdenum sulfamate, 6 g / L of manganese borate, and 6 g / L of manganese phosphate, and perform electrodeposition under the conditions of a temperature of 65 °C, a pH value of 5, and an electrolytic current density of 13 A / dm 2 to form a surface layer.

[0186] In the obtained electrolytic iron foil, the manganese content is 2 wt%, the Co content is 1 wt%, the Mo content is 1 wt%, the B content is 0.45 wt%, and the P content is 0.35 wt%. The thickness of the iron substrate is 5 μm, and the single-sided thickness of the surface layer is 2 μm. The tensile strength is 1213 MPa, the elongation at break is 6.7%, Ra is 0.55 μm, and Rz is 2.5 μm.

[0187] Comparative Example 1 - 1 Comparative Example 1 - 1 is an iron-based foil material without a surface layer.

[0188] The preparation method of the iron-based substrate foil is as follows: Using Ti material as the support for forming the iron-based substrate foil, place it in a plating bath containing 600 g / L of ferric chloride tetrahydrate and 10 g / L of hydrochloric acid, and carry out electro-deposition under the conditions of a temperature of 90 °C, a pH value of 0.8, and a current density of 8 A / dm 2 to form the iron-based substrate foil and peel it off from the support. The thickness of the obtained iron-based substrate is 1.5 μm, the tensile strength is 506 MPa, the elongation at break is 1.15%, Ra is 0.45 μm, and Rz is 1.2 μm.

[0189] Comparative Example 1-2 The surface layer of the electrolytic iron foil provided by Comparative Example 1-2 does not contain non-metallic elements.

[0190] Using Ti material as the support for forming the iron-based substrate foil, place it in a plating bath containing 600 g / L of ferric chloride tetrahydrate and 10 g / L of hydrochloric acid, and carry out electro-deposition under the conditions of a temperature of 90 °C, a pH value of 0.8, and a current density of 8 A / dm 2 to form the iron-based substrate foil and peel it off from the support; Use a plating bath containing 10 g / L of nickel sulfamate, and form the surface layer under the conditions of 50 °C, a pH value of 4, and an electrolytic current density of 8 A / dm 2 .

[0191] The Ni content in the obtained electrolytic iron foil is 0.01 wt%. The thickness of the iron-based substrate is 1.5 μm, and the single-sided thickness of the surface layer is 0.5 μm. The tensile strength of the electrolytic iron foil is 629 MPa, the elongation at break is 1.32%, Ra is 0.67 μm, and Rz is 1.18 μm.

[0192] Comparative Example 1-3 1) Using Ti material as the support for forming the electrolytic iron foil, place it in a plating bath containing 700 g / L of ferric chloride tetrahydrate and 20 g / L of hydrochloric acid, and carry out electro-deposition under the conditions of a temperature of 110 °C, a pH value of 0.9, and a current density of 12 A / dm 2 to form the iron-based substrate foil; 2) Place the above-prepared iron-based foil in a plating bath containing 100 g / L of nickel sulfamate and 10 g / L of nickel borate, and carry out electro-deposition under the conditions of 65 °C, a pH value of 6, and an electrolytic current density of 20 A / dm 2 to form the surface layer.

[0193] The Ni content in the obtained electrolytic iron foil is 8 wt% and the B content is 0.6 wt%. The thickness is 15 μm, and the single-sided thickness of the surface layer is 5 μm. The tensile strength of the electrolytic iron foil is 650 MPa, the elongation at break is 3.2%, Ra is 0.9 μm, and Rz is 3.8 μm.

[0194] Table 1 Composition and related properties of electrolytic iron foils in the above examples and comparative examples ;

[0195] Fabrication of lithium-ion batteries Preparation of the positive electrode sheet: Lithium cobaltate, conductive agent Super-P carbon black, and binder polyvinylidene fluoride were stirred and mixed evenly at a weight ratio of 97:2:1, and solvent N-methylpyrrolidone was added to obtain the positive active film layer slurry with a solid content of 73%; then the positive active film layer slurry was evenly coated on aluminum foil, and after drying, cold pressing, and slitting, the positive electrode sheet was obtained.

[0196] Preparation of the negative electrode sheet: Artificial graphite and silicon-carbon material with a mass ratio of 90:10 were used as the negative active material. The negative active material, conductive agent Super-P carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were dissolved in deionized water at a weight ratio of 98:0.5:1.5, and after mixing evenly, the negative active film layer slurry was prepared; the negative slurry was evenly coated on the electrolytic iron foils prepared in the above examples and comparative examples, and after drying, cold pressing, and slitting, the negative electrode sheet was obtained.

[0197] Separator: A polypropylene film was used as the separator.

[0198] Preparation of the electrolyte: In a glove box under an argon atmosphere (H 2 O < 0.1 ppm, O 2 < 0.1 ppm), organic solvents ethylene carbonate (EC) / propylene carbonate (PC) / propyl propionate (PP) were mixed evenly at a mass ratio of 2:1.5:2.5, 12.5 mass% LiPF 6 lithium salt was dissolved in the organic solvent, and then 7 mass% fluoroethylene carbonate and 3 mass% 1,3-propane sultone were added to obtain the basic electrolyte (denoted as EL-0). Component A was added to the basic electrolyte to obtain a further optimized electrolyte, where component A was selected from at least one of lithium difluorophosphate, vinylene sulfate, vinylene carbonate, succinonitrile, 1,3,6-hexanetricarbonitrile, glycerol trinitrile, 18-crown-6, dibenzo-18-crown-6, 1-aza-18-crown-6. The electrolytes used in different examples are shown in Table 2, where the mass parts of component A are calculated based on 100 mass parts of the electrolyte.

[0199] Table 2 Electrolyte additive A used in the battery ; Preparation of the wound structure battery cell: The prepared negative electrode sheet, positive electrode sheet and separator are wound together to form a wound structure battery cell (hereinafter referred to as the core). After hot pressing and shaping the prepared wound structure battery cell, it is packaged with an aluminum-plastic film, baked to remove moisture, and then electrolyte is injected. The obtained battery cell is formed to obtain a lithium-ion battery.

[0200] Examples 2-1 to 2-34 Examples 2-1 to 2-34 were prepared into lithium-ion batteries based on the same method as above, except that the electrolytic iron foil and electrolyte used were changed as shown in Table 3.

[0201] Comparative Examples 2-1 to 2-5 Comparative Examples 2-1 to 2-5 were prepared into lithium-ion batteries based on the same method as above, except that the electrolytic iron foil and electrolyte used were changed as shown in Table 3.

[0202] Table 3 Composition and Related Properties of Lithium-Ion Batteries ;

[0203] The battery performance in Table 3 above was tested by the following method: (1) Flexibility The negative electrode with a single-sided adhesive layer was wound around a stainless steel cylinder with a diameter of 3.0 mm (in addition, the current collector electrolytic iron foil was used as the inner side). Then, it was visually observed to confirm whether cracks occurred on the surface of the negative electrode adhesive layer after winding. In the case where no cracks were confirmed to occur, the diameter of the stainless steel cylinder was successively reduced to 2.5 mm, 2.0 mm, and 1.5 mm, and the same operation was performed. Then, the diameter of the cylinder when cracks were first confirmed on the surface of the negative electrode adhesive layer of this negative electrode (the cylinder diameter when cracks occurred) was recorded and evaluated according to the following criteria. The smaller the cylinder diameter when cracks occurred, the better the flexibility of the negative electrode. Moreover, in the case where no cracks occurred even when using a cylinder with a diameter of 1.5 mm, it indicated that the flexibility of the negative electrode was very excellent. In Table 3, A, B, C, D, and E in the "Flexibility" column represent: A: No cracks were confirmed to occur even when the cylinder diameter was 1.5 mm; B: The cylinder diameter when cracks occurred was 1.5 mm; C: The cylinder diameter when cracks occurred was 2.0 mm; D: The cylinder diameter when cracks occurred was 2.5 mm; E: The cylinder diameter when cracks occurred was 3.0 mm.

[0204] (2) Negative electrode lithium precipitation amount The fabricated battery was charged at a constant current of 1C to a charge depth (SOC) of 100% at -10°C. Then, the battery was disassembled, the negative electrode was taken out, the area of lithium deposited on the surface of the negative electrode mixture layer was determined, and the lithium deposition area ratio was calculated (= (area of deposited lithium / area of the surface of the negative electrode mixture layer) × 100%). Then, the evaluation was carried out according to the following criteria. In Table 3, "Lithium precipitation amount", A+, A, B, C, D, E represent: A+: The lithium deposition area ratio is less than 1%; A: The lithium deposition area ratio is 1% or more and less than 3%; B: The lithium deposition area ratio is 3% or more and less than 5%; C: The lithium deposition area ratio is 5% or more and less than 8%; D: The lithium deposition area ratio is 8% or more and less than 10%; E: The lithium deposition area ratio is 10% or more.

[0205] (3)Interface resistance For the fabricated negative electrode, in an environment of 25°C, the resistivity (Ω·cm2) of the interface between the negative electrode mixture layer and the electrolytic iron foil was measured using an electrode resistance system ("RM2610" manufactured by Hioki Electric Co., Ltd.), and the evaluation was carried out according to the following criteria. In the column of "Interface resistance" in Table 3, A, B, C, D represent: A: The resistivity is greater than 0.01 Ω·cm 2 and is 0.05 Ω·cm 2 or less; B: The resistivity is greater than 0.05 Ω·cm 2 and is 0.1 Ω·cm 2 or less; C: The resistivity is greater than 0.1 Ω·cm 2 and is 0.3 Ω·cm 2 or less; D: The resistivity is greater than 0.3 Ω·cm 2 .

[0206] (4)Low-temperature output performance After the fabricated lithium-ion battery was left standing for 24 hours at 25°C, it was charged under the condition of CC-CV charging at a charging rate of 0.2C (terminated at 0.02C) to 4.6V in an environment of 25°C. Then, it was discharged at 0.2C in CC mode to 3.0V. The discharge capacity at this time was taken as the initial capacity. Then, it was charged to make the capacity 50% of the initial capacity, and the voltage at this time was V 0 . Then, a discharge operation was carried out at a discharge rate of 1C in an environment of -10°C, and the voltage V was measured 0.1 seconds after the start of discharge 1. Then, the low-temperature output characteristic is evaluated by the voltage change ΔV shown in 0 -V 1 . The smaller the value of the voltage change ΔV, the better the low-temperature characteristic. In Table 3, A+, A, B, C, and D in the "Low-temperature Output" column represent: A+: The voltage change ΔV is less than 0.3V; A: The voltage change ΔV is less than 0.5V; B: The voltage change ΔV is 0.5 or more and less than 0.8V; C: The voltage change ΔV is 0.8 or more and less than 1.0V; D: The voltage change ΔV is 1.0V or more.

[0207] In this application, by making the surface of the electrolytic iron foil iron substrate contain specific metal elements and non-metal elements, and the metal content other than iron is within a specified range, an electrolytic iron foil with high strength and tensile resistance can be produced. The produced negative electrode has excellent flexibility and can inhibit lithium dendrites, can reduce the interfacial resistance between the negative electrode binder layer and the electrolytic iron foil, and can enable the energy storage device to exhibit excellent low-temperature output characteristics.

[0208] The applicant of this application also found that when the surface layer includes nickel and / or copper, a further improved effect is obtained; when the non-metal element includes phosphorus, a further improved effect is obtained; when the electrolyte system includes at least one of lithium difluorophosphate, ethylene sulfate, vinylene carbonate, succinonitrile, 1,3,6-hexanetricarbonitrile, glycerol trinitrile, and crown ether, lithium dendrites are further significantly inhibited and the low-temperature output characteristic is improved.

[0209] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same structure and the same function and effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that those skilled in the art can think of to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. An electrolytic iron foil, characterized in that: The electrolytic iron foil includes an iron substrate and a surface layer formed on at least one surface of the iron substrate; The surface layer includes metal elements and non-metal elements, the metal elements include non-ferrous metal elements, the non-ferrous metal elements include at least one of nickel, copper, manganese, cobalt, and molybdenum, and the non-metal elements include at least one of phosphorus and boron; Based on 100 wt % of all metals contained in the electrolytic iron foil, the content of non-ferrous metal elements in the electrolytic iron foil is greater than 0 and less than 5 wt %.

2. The electrolytic iron foil according to claim 1, characterized in that: Taking the amount of all metals contained in the electrolytic iron foil as 100wt%, the content of the non-ferrous metal element is 0.01-3wt%; And / or, based on 100wt% of all metals contained in the electrolytic iron foil, the content of the non-metallic element is 0.01-1.0wt%; And / or, the non-metallic element includes phosphorus.

3. The electrolytic iron foil according to claim 1, characterized in that: The non-ferrous metal element includes at least one of nickel and copper; Preferably, based on 100wt% of all metals contained in the electrolytic iron foil, the nickel content is 4wt% or less, preferably 2wt% or less; Preferably, based on 100 wt % of all metals contained in the electrolytic iron foil, the copper content is 2 wt % or less, preferably 1 wt % or less.

4. The electrolytic iron foil according to claim 1 or 3, characterized in that: The non-ferrous metal element includes at least one of manganese and molybdenum; Preferably, based on 100wt% of all metals contained in the electrolytic iron foil, the manganese content is 0.5wt% or less, preferably 0.3wt% or less; Preferably, based on 100 wt % of all metals contained in the electrolytic iron foil, the molybdenum content is 0.2 wt % or less, preferably 0.1 wt % or less.

5. The electrolytic iron foil according to claim 1, characterized in that: The thickness of the electrolytic iron foil is 1.5 μm to 15 μm, preferably 3 μm to 10 μm; And / or, the single-side thickness of the surface layer is 0.5 μm to 5 μm, preferably 1 μm to 3 μm; And / or, the tensile strength of the electrolytic iron foil is 750 MPa or more, preferably 800 MPa or more; and / or, the elongation of the electrolytic iron foil is greater than 1.6%, preferably greater than 2.2%; And / or, the surface roughness Ra of the electrolytic iron foil is 0.25 μm to 0.8 μm, preferably Ra is 0.35 μm to 0.65 μm; And / or, the surface roughness Rz of the electrolytic iron foil is 1.5 μm to 5 μm, preferably Rz is 2.3 μm to 4.2 μm.

6. The electrolytic iron foil according to claim 1, characterized in that: The preparation method comprises: forming the surface layer on at least one surface of an iron substrate by an electrodeposition method, wherein the plating bath used in the electrodeposition method comprises 10-50 g / L of a sulfamate metal salt and 5-10 g / L of a metal borate and / or a metal phosphate; the metal contained in the sulfamate metal salt, the metal borate and the metal phosphate is at least one of nickel, copper, manganese, cobalt and molybdenum; The process conditions of the electrodeposition method include: temperature of 50°C to 65°C, pH value of 4 to 6, electrolytic current density of 8 to 20 A / dm 2 .

7. An electrode for an energy storage device, characterized in that: The invention comprises the electrolytic iron foil according to any one of claims 1 to 6, and a mixture layer formed on a part or all of the surface of the electrolytic iron foil; Preferably, the electrode for the energy storage device is a negative electrode, and the negative electrode comprises the electrolytic iron foil and a negative electrode mixture layer formed on a part or all of the surface of the electrolytic iron foil.

8. An energy storage device comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: At least one of the positive electrode and the negative electrode of the energy storage device is the electrode for the energy storage device according to claim 7; Preferably, the energy storage device is a lithium-ion battery or an electric double-layer capacitor.

9. The energy storage device according to claim 8, characterized in that: The electrolyte of the energy storage device includes component A, and the component A includes at least one of lithium difluorophosphate, vinyl sulfate, vinylene carbonate, succinonitrile, 1,3,6-hexanetrinitrile, glycerol trinitrile, and crown ether.

10. The energy storage device according to claim 9, characterized in that: The crown ether includes one or more combinations of 15-crown-5, 18-crown-6, 21-crown-7, 24-crown-8, dibenzo-15-crown-5, dibenzo-18-crown-6, dibenzo-21-crown-7, dibenzo-24-crown-8, 1-aza-15-crown-5, 1-aza-18-crown-6, 1-aza-21-crown-7 and 1-aza-24-crown-8; And / or, based on the mass of the electrolyte as 100 parts by mass, the content of the lithium difluorophosphate is 0.01 to 0.8 parts by mass; and / or, the content of the vinyl sulfate is 0.01 to 0.8 parts by mass; and / or, the content of the vinylene carbonate is 0.01 to 0.5 parts by mass; and / or, the content of the succinonitrile is 1.9 to 4.3 parts by mass; and / or, the content of the 1,3,6-hexanetrinitrile is 0.9 to 3.5 parts by mass; and / or, the content of the glycerol trinitrile is 0.1 to 2.8 parts by mass; and / or, the content of the crown ether is 0.1 to 2.5 parts by mass.

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