Current collector and preparation method and application thereof

Abstract

The invention provides a current collector and a preparation method and application thereof. The current collector comprises a current collector base material; the passivation layer is arranged on the surface of the current collector base material, and metal elements in the passivation layer comprise at least three of titanium, zirconium, tantalum, niobium or chromium. According to the current collector and the preparation method and application thereof provided by the invention, the low interface resistance of the current collector base material can be maintained while the corrosion of the electrolyte to the current collector base material is blocked, and the electron conduction capability of the current collector is ensured.

Description

Technical Field

[0001] This invention relates to the field of power battery technology, specifically to a current collector, its preparation method, and its application. Background Technology

[0002] With the rapid development of high-energy-density lithium-ion batteries, high-voltage (≥4.4V) and high-capacity positive electrode active materials are being used more and more. To reduce electrolyte resistance and improve cycle stability, novel lithium salts such as lithium bisfluorosulfonylimide (LiFSI) have been incorporated into electrolyte systems. However, LiFSI is highly corrosive to aluminum current collectors, especially at high temperatures, causing the aluminum current collector to dissolve and reducing battery cycle life and safety. Summary of the Invention

[0003] This invention proposes a current collector, its preparation method, and its application, which can prevent the electrolyte from corroding the current collector substrate while maintaining the low interfacial resistance of the current collector substrate and ensuring the electron conduction capability of the current collector.

[0004] To solve the above-mentioned technical problems, the present invention provides a current collector, comprising:

[0005] Current collector substrate; and

[0006] A passivation layer is disposed on the surface of the current collector substrate, wherein the metal element in the passivation layer includes at least three of titanium, zirconium, tantalum, niobium, or chromium.

[0007] In one embodiment of the present invention, the thickness of the passivation layer is 5nm-50nm.

[0008] In one embodiment of the present invention, the thickness of the passivation layer is 5nm-20nm.

[0009] In one embodiment of the present invention, when there are four or more types of metal elements in the passivation layer, the proportion of the number of atoms of each metal element to the total number of atoms of all metal elements is 5%-70%.

[0010] When there are three types of metallic elements, the proportion of the number of atoms of each metallic element to the total number of atoms of all metallic elements is 10%-60%.

[0011] In one embodiment of the present invention, the current collector substrate is one or more of aluminum, titanium, zinc, tin, nickel and their respective alloys, and the thickness of the current collector substrate is 10μm-25μm.

[0012] The present invention also provides a method for preparing a current collector, comprising:

[0013] An electrolyte solution is obtained by dissolving at least three of the following salts: titanium salt, zirconium salt, tantalum salt, niobium salt, or chromium salt in a solvent.

[0014] The current collector substrate is placed in the electrolyte solution and electrochemically treated to obtain the current collector.

[0015] In one embodiment of the present invention, the titanium salt includes potassium fluorotitanate, the zirconium salt includes potassium fluorozirconate, the niobium salt includes potassium fluoroniobate, the tantalum salt includes potassium fluorotantalate, and the chromium salt includes chromium sulfate.

[0016] The solvent includes at least one of sulfuric acid, oxalic acid, phosphoric acid, or phytic acid with a concentration of 0.05 mol / L to 0.15 mol / L;

[0017] The electrochemical treatment includes micro-arc oxidation.

[0018] The present invention also provides a positive electrode sheet, characterized in that it includes a current collector and a positive active layer disposed at least on one side surface of the current collector along the thickness direction of the current collector;

[0019] The current collector includes the current collector described above, or the current collector obtained according to the preparation method described above.

[0020] In one embodiment of the present invention, the positive electrode active layer includes a positive electrode active material, which includes one or more of lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, or lithium-rich manganese-based oxide materials.

[0021] The present invention also provides a lithium-ion battery, comprising:

[0022] Positive electrode plate, wherein the positive electrode plate is selected from the positive electrode plates described above;

[0023] Negative electrode sheet;

[0024] A diaphragm is disposed between the positive electrode and the negative electrode;

[0025] The electrolyte includes lithium bisfluorosulfonylimide, wherein the content of lithium bisfluorosulfonylimide in the electrolyte is greater than or equal to 2 wt%.

[0026] In summary, this invention proposes a current collector, its preparation method, and its application. By forming a passivation layer on the current collector substrate, and the passivation layer being a mixed compound composed of multiple metal elements, the passivation layer tends to form a more uniform and stable single-phase solid solution structure. This fundamentally eliminates grain boundaries, which serve as corrosion initiation points in traditional polycrystalline structures, thereby improving the protection of the current collector substrate and reducing its corrosion. The similar atomic radii of the metal elements in the passivation layer are conducive to the formation of a solid solution structure, while also generating a suitable degree of lattice distortion effect, enhancing the lattice stability of the passivation layer. This also increases the configurational entropy of the passivation layer, significantly improving its thermodynamic stability and reducing its reactivity, thus preventing the electrolyte from corroding the current collector substrate. By controlling the thickness of the passivation layer, while preventing electrolyte corrosion of the current collector substrate, the low interfacial resistance of the current collector substrate is maintained, ensuring the electron conductivity of the current collector. Detailed Implementation

[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0028] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0029] The technical solution of the present invention will be further described in detail below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] This invention proposes a current collector, comprising a current collector substrate and a passivation layer, wherein the passivation layer is disposed on the surface of the current collector substrate, and the metal element in the passivation layer includes at least three selected from titanium, zirconium, tantalum, niobium, or chromium. The current collector provided by this application effectively mitigates the corrosive effect of LiFSI-based electrolyte on the current collector substrate while maintaining good electron conductivity.

[0031] In one embodiment of the present invention, the current collector substrate is one or more of aluminum, titanium, zinc, tin, nickel, and their respective alloys, and the thickness of the current collector substrate is 10μm-25μm to match different battery systems and meet the manufacturing requirements of lithium-ion batteries. In this embodiment, the current collector substrate is, for example, aluminum foil.

[0032] In one embodiment of the present invention, a passivation layer is fully coated on the surface of the current collector substrate. The passivation layer comprises a single-phase solid solution composed of oxides and / or fluorides and / or fluorine oxides of at least three metals selected from titanium, zirconium, tantalum, niobium, or chromium. By forming a mixed compound from multiple material components, the passivation layer tends to form a more uniform and stable single-phase solid solution structure, fundamentally eliminating grain boundaries that serve as corrosion initiation points in traditional polycrystalline structures, thereby improving the protection of the current collector substrate and reducing its corrosion.

[0033] In one embodiment of the present invention, the metal elements in the passivation layer include at least three selected from titanium, zirconium, tantalum, niobium, or chromium. The similar atomic radii of these metal elements are beneficial for forming a solid solution structure and also produce a suitable degree of lattice distortion effect, enhancing the lattice stability of the passivation layer. Simultaneously, the similar valence states of the metal elements result in well-matched properties, leading to stable oxides / fluorides / fluorine oxides with high corrosion resistance. When there are four or more types of metal elements in the passivation layer, the proportion of each metal element's atoms to the total number of atoms is, for example, 5%-70%; when there are three types of metal elements, the proportion of each metal element's atoms to the total number of atoms is, for example, 10%-60%. By introducing multiple cations into the solid solution lattice, the configuration entropy of the passivation layer is increased. Where R is the gas constant, n is the number of metal elements in the passivation layer, and xi is the proportion of the number of atoms of the i-th metal element to the total number of atoms of all metal elements. The more types of atoms there are, and the closer the number of atoms of different metal elements are, the greater the entropy of the system, thus greatly increasing the configurational entropy of the passivation layer. According to thermodynamic principles, high entropy significantly reduces the Gibbs free energy of the system, thereby greatly improving the thermodynamic stability of the passivation layer and reducing its reactivity. Compared to passivation layers with a single oxide / fluoride composition, multi-component high-entropy passivation layers exhibit significantly stronger stability, effectively preventing the electrolyte from corroding the current collector substrate.

[0034] In one embodiment of the present invention, the thickness of the passivation film is, for example, 5nm-50nm, or, for example, 5nm-20nm. By controlling the thickness of the passivation layer, the current collector substrate is protected from corrosion by the electrolyte while maintaining a low interfacial resistance, thus ensuring the electron conductivity of the current collector.

[0035] The present invention also provides a method for preparing a current collector, comprising: dissolving at least three of titanium salt, zirconium salt, tantalum salt, niobium salt or chromium salt in a solvent to obtain an electrolyte solution; placing a current collector substrate in the electrolyte solution and obtaining a current collector by electrochemical treatment.

[0036] In one embodiment of the present invention, the titanium salt includes, for example, a fluorinated titanium salt such as potassium fluorotitanate; the zirconium salt includes, for example, a fluorinated zirconium salt such as potassium fluorozirconate; the niobium salt includes, for example, a fluorinated niobium salt such as potassium fluoroniobate; the tantalum salt includes, for example, a fluorinated tantalum salt such as potassium fluorotantalate; and the chromium salt includes, for example, chromium sulfate. During the formation of the passivation layer, metal oxides and / or fluorides and / or fluorine oxides are formed. The solvent includes, for example, at least one aqueous solution of sulfuric acid, oxalic acid, phosphoric acid, or phytic acid with a concentration of 0.05 mol / L to 0.15 mol / L. In the electrolyte solution, the total mass content of the metal salts is, for example, 5 wt% to 10 wt%.

[0037] In one embodiment of the present invention, the electrochemical treatment includes, for example, micro-arc oxidation, to form a passivation layer on the surface of the current collector substrate. Specifically, the current collector substrate is used as the anode, and an insoluble lead electrode is used as the cathode. A bipolar pulse power supply is connected to both ends of the electrode. The parameters of the power supply are set as follows: positive voltage, for example, 150V-260V; negative voltage, for example, -5V-30V; frequency, for example, 1500Hz-3000Hz; pulse period, for example, 10ms-20ms; duty cycle, for example, 25%-35%; and processing time, for example, 7.5s-75s. During the pulse phase of micro-arc oxidation, the metal element salt solute in the electrolyte ionizes under high voltage to form a plasma. During the pulse intervals, it cools and becomes a solid solution deposited on the surface of the current collector substrate, forming a high-entropy passivation layer. The thickness of the passivation layer is mainly determined by the total energy injected by micro-arc oxidation and the reaction duration. Specifically, increasing the current density / voltage ratio, increasing the duty cycle, and extending the processing time directly increase energy input and reaction rate, thus significantly increasing the passivation layer thickness. Using a lower pulse frequency increases the energy of a single discharge, promoting deeper growth. These parameters work synergistically to determine the final passivation layer thickness.

[0038] In one embodiment of the present invention, after the electrochemical treatment, the current collector substrate after the post-treatment reaction is used to obtain a current collector with a passivation layer. The post-treatment includes, for example, cleaning and drying, such as rinsing the current collector substrate with deionized water and then drying it at 50°C-70°C. Since the metal salt is completely dissolved in the electrolyte solution and the metal ions are uniformly mixed, the concentration ratio of metal ions in the electrolyte solution is the same as the atomic weight ratio of the metal elements. During the micro-arc oxidation process, the probability of deposition for each metal element is the same, so the proportion of metal elements in the final passivation layer is the same as the metal ion concentration ratio in the electrolyte solution, which is also the atomic weight ratio of the metal elements in the raw material.

[0039] The present invention also provides a positive electrode sheet, comprising a current collector and a positive electrode active layer disposed at least on one side surface of the current collector along the thickness direction of the current collector. The current collector is selected from the aforementioned current collectors. The positive electrode active layer includes, for example, a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent. The positive electrode active material includes, for example, one or more of lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, or lithium-rich manganese-based oxide materials. The positive electrode binder is selected from, for example, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinylidene fluoride-tetrafluoroethylene-propylene terpolymer (ETFE), ethylene-vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer (TFE-HFP-VDF), or tetrafluoroethylene-hexafluoropropylene copolymer (FEP). The positive electrode conductive agent is selected from, for example, one or more of conductive carbon black (Super P), acetylene black, Ketjen black, graphene, carbon nanotubes, carbon nanofibers, or porous carbon. The mass ratio of positive electrode active material, positive electrode conductive agent and positive electrode binder in the positive electrode active layer is, for example, (90-98):(1-5):(1-5).

[0040] In one embodiment of the present invention, the positive electrode active material is, for example, LiNi. 0.6 Co 0.1 Mn 0.3 O2, a positive electrode conductive agent (e.g., conductive carbon black), and a positive electrode binder (e.g., polyvinylidene fluoride) are mixed in a mass ratio of 98:1:1, and an organic solvent is added. The mixture is then thoroughly stirred and homogenized under vacuum to obtain a positive electrode slurry. The organic solvent is, for example, N-methylpyrrolidone (NMP). The positive electrode slurry is uniformly coated onto the current collector, air-dried at room temperature, and then transferred to an oven for further drying. The positive electrode sheet is obtained through cold pressing, edge trimming, cutting, and slitting. In this embodiment, the areal density of the positive electrode active layer is, for example, 10 mg / cm³. 2 -20mg / cm 2 This application does not limit the method of preparing the positive electrode sheet. In other embodiments, the positive electrode sheet can also be obtained by any other method of forming the positive electrode sheet.

[0041] This invention also proposes a lithium-ion battery, comprising a casing and an electrode assembly disposed within the casing. The electrode assembly includes a positive electrode, a separator, and a negative electrode. The positive electrode is selected from the aforementioned positive electrode types. The separator is placed between the positive and negative electrodes to prevent short circuits and allow lithium ions to pass through. The positive electrode, separator, and negative electrode are sequentially stacked to ensure that a separator is present between any positive and negative electrode. A multi-layered stack is obtained by winding or folding, and this stack is then incorporated into the battery casing as the electrode assembly. Finally, electrolyte is injected into the casing once or in multiple stages to completely immerse the electrode assembly in the electrolyte, thereby conducting ions between the positive and negative electrodes. In one embodiment of this invention, the lithium-ion battery is, for example, a primary battery or a secondary battery. A secondary battery is, for example, a pouch battery, a hard-shell battery, or a cylindrical battery. This invention does not specifically limit the type of lithium-ion battery. In this embodiment, a pouch battery is used as an example to illustrate the lithium-ion battery.

[0042] In one embodiment of the present invention, the negative electrode sheet includes, for example, a negative electrode current collector and a negative electrode active layer coated at least on one surface of the negative electrode current collector. The negative electrode current collector is selected, for example, from foils treated with nickel, titanium, gold, silver, chromium, molybdenum, copper, stainless steel, or carbon. Besides foils, the negative electrode current collector can also be used in any one or more combinations of various forms such as film, mesh, porous, foam, or nonwoven fabric. The thickness of the negative electrode current collector is, for example, 6 μm-15 μm. In this embodiment, the negative electrode current collector is, for example, copper foil, and the thickness of the copper foil is, for example, 8 μm.

[0043] In one embodiment of the present invention, the negative electrode active layer is disposed on any one or both surfaces of the negative electrode current collector. The negative electrode active layer includes a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and a thickener. The negative electrode active material is selected from graphite or silicon-containing composite materials, such as natural graphite, artificial graphite, graphite / silicon oxide composite materials, graphite / silicon-carbon composite materials, and graphite / elemental silicon composite materials. The negative electrode binder is selected from at least one of polymerized styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), carboxylated polyvinyl chloride (CPVC), polyvinyl fluoride (PVF), or polyurethane (PU). The thickener may be, for example, sodium carboxymethyl cellulose (CMC-Na) or lithium carboxymethyl cellulose (CMC-Li), and the negative electrode conductive agent may be, for example, one or a combination of two or more selected from conductive carbon black, Ketjen black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, or porous carbon in any proportion. In one embodiment of the present invention, the mass ratio of the negative electrode active material, the negative electrode conductive agent, the negative electrode binder, and the thickener in the negative electrode active layer is, for example, (91-98.5):(0.5-2):(0.5-5):(0.5-2).

[0044] In one embodiment of the present invention, the negative electrode active material is selected from artificial graphite, the negative electrode conductive agent is selected from conductive carbon black, the thickener is selected from sodium carboxymethyl cellulose, and the negative electrode binder is selected from styrene-butadiene rubber. The negative electrode active material, negative electrode conductive agent, thickener, and negative electrode binder are mixed, for example, at a mass ratio of 96:1:1:2. Deionized water is added, and the mixture is thoroughly stirred and homogenized under vacuum to obtain a negative electrode slurry. The negative electrode slurry is coated onto copper foil, then air-dried at room temperature and transferred to an oven for drying. After processes such as rolling, edge trimming, cutting, and slitting, a negative electrode sheet is obtained. The single-sided areal density of the negative electrode active layer is, for example, 8 mg / cm³. 2 -15mg / cm 2 In other embodiments, the negative electrode sheet can also be obtained by any other method of forming the negative electrode sheet.

[0045] In one embodiment of the present invention, the separator is, for example, a polyethylene (PE) membrane, a polypropylene (PP) membrane, a glass fiber membrane, or a composite membrane, and the thickness of the separator is, for example, 9 μm-15 μm. In another embodiment of the present invention, the separator is, for example, selected as an 8 μm-10 μm polyethylene base membrane, and a 2 μm-4 μm thick nano-alumina coating is coated on at least one side of the base membrane.

[0046] In one embodiment of the present invention, the electrolyte includes, for example, an organic solvent and a lithium salt. The organic solvent is selected from one or more of propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), or ethyl methyl carbonate (EMC). The lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), or lithium perchlorate (LiClO4). In this embodiment, the lithium salt is, for example, lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the content of lithium bis(fluorosulfonyl)imide in the electrolyte is greater than or equal to 2 wt% to improve the operating voltage of the battery. The electrolyte may also include additives, such as any one or more selected from vinylene carbonate (VC), ethylene sulfate (1,3,2-Dioxathiolane 2,2-dioxide (DTD), lithium difluorooxalate borate (LiDFOB), or 1,3-propanesultone (1,3-PS). In this embodiment, in a glove box with an inert gas atmosphere such as argon containing less than or equal to 10 ppm of moisture and oxygen, ethylene carbonate and ethyl methyl carbonate are mixed, for example, in a mass ratio. Thoroughly dried LiPF6, LiFSI, VC, PS, and DTD are dissolved in the mixed organic solvent and mixed thoroughly to obtain the electrolyte. The electrolyte contains 24 wt% ethylene carbonate, 58 wt% ethyl methyl carbonate, 6 wt% LiPF6, 9 wt% LiFSI, 1 wt% VC, 1 wt% PS, and 1 wt% DTD.

[0047] In one embodiment of the present invention, the positive electrode, separator, and negative electrode are placed sequentially, with the separator positioned between the positive and negative electrode to act as a separator. The electrode assembly is then obtained by winding. The electrode assembly is placed in an aluminum-plastic film and baked at 80°C-120°C to remove moisture. The electrolyte is then injected into the aluminum-plastic film once or in multiple stages, followed by sealing. After processes such as settling, formation, clamping, and capacity testing, a soft-pack lithium-ion battery is obtained.

[0048] The present invention will be explained in more detail below by referring to embodiments, which should not be construed as limiting. Appropriate modifications can be made within the scope of the invention and all such modifications fall within the technical scope of the invention. Unless otherwise stated, the raw materials and reagents used in the following embodiments are commercially available or can be prepared by conventional methods in the art, and the instruments used in the embodiments are also commercially available.

[0049] Example 1

[0050] Preparation of the current collector: Potassium fluorotitanate, potassium fluorozirconate, potassium fluoroniobate, and potassium fluorotantalate were dissolved in a 0.1 mol / L sulfuric acid aqueous solution to obtain an electrolyte solution. The content of potassium fluorotitanate was 1.57 wt%, potassium fluorozirconate was 1.86 wt%, potassium fluoroniobate was 1.99 wt%, and potassium fluorotantalate was 2.57 wt%. The atomic ratio of Ti, Zr, Nb, and Ta in the electrolyte solution was 1:1:1:1. A 12 μm thick aluminum foil was used as the anode and immersed in the electrolyte solution. An insoluble lead electrode was used as the cathode. A bipolar pulsed power supply was connected to both ends of the electrode. The power supply parameters were set as follows: positive voltage 200 V, negative voltage -25 V, frequency 2000 Hz, pulse period (e.g., 10 ms), duty cycle 30%, and processing time 15 s. After processing, the aluminum foil was removed, rinsed with deionized water, and dried at 60 °C to obtain the current collector.

[0051] Positive electrode preparation: LiNi 0.6 Co 0.1 Mn 0.3 O2, conductive carbon black, and polyvinylidene fluoride were mixed in a mass ratio of 98:1:1, and NMP was added. The mixture was thoroughly stirred and homogenized under vacuum to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated onto the aforementioned current collector, air-dried at room temperature, and then transferred to an oven for further drying. The positive electrode sheet was then obtained through cold pressing, edge trimming, cutting, and slitting processes. The single-sided areal density of the positive electrode active layer was 17 mg / cm³. 2 .

[0052] Preparation of the negative electrode sheet: Artificial graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber were mixed in a mass ratio of 97:1:1:2. Deionized water was added, and the mixture was thoroughly stirred and homogenized under vacuum to obtain a negative electrode slurry. The negative electrode slurry was coated onto copper foil, then air-dried at room temperature before being transferred to an oven for drying. After rolling, edge trimming, cutting, and slitting, the negative electrode sheet was obtained. The single-sided areal density of the negative electrode active layer was 11 mg / cm³. 2 .

[0053] Electrolyte preparation: In a glove box with an argon atmosphere containing 10 ppm moisture and 10 ppm oxygen, ethylene carbonate and ethyl methyl carbonate were mixed in a specific mass ratio. Thoroughly dried LiPF6, LiFSI, VC, PS, and DTD were dissolved in the mixed organic solvent. After thorough mixing, the electrolyte was obtained. The electrolyte contained 24 wt% ethylene carbonate, 58 wt% ethyl methyl carbonate, 6 wt% LiPF6, 9 wt% LiFSI, 1 wt% VC, 1 wt% PS, and 1 wt% DTD.

[0054] Selection of diaphragm: A 12μm thick polypropylene membrane was selected as the diaphragm.

[0055] Battery fabrication: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to act as a separator. The stacked electrodes form the electrode assembly. The electrode assembly is then placed in an aluminum-plastic film, baked at 120°C to remove moisture, and then injected with electrolyte at a rate of 3 g / Ah. After sealing, the battery undergoes settling, formation, clamping, and capacity testing to obtain a 1Ah soft-pack lithium-ion battery.

[0056] The present invention also provides Examples 2-8, wherein the total content of metal salts in the electrolyte solution is 8 wt%, and the selection of metal salts and the metal elements and their proportions are shown in Table 1. Then, the content C of each metal salt in the electrolyte solution... n It is obtained by calculation using the following formula:

[0057]

[0058] Among them, C n M n N n These represent the content, molecular weight, and metal element percentage of the nth metal salt in the electrolyte solution, respectively, along with the stoichiometric coefficient of the metal element in one molecule.

[0059] Example 9

[0060] When preparing the current collector, the micro-arc oxidation process took 7.5 seconds, and the other steps were the same as in Example 1.

[0061] Example 10

[0062] When preparing the current collector, the micro-arc oxidation process time is 30 seconds, and the other steps are consistent with those in Example 1.

[0063] Example 11

[0064] When preparing the current collector, the micro-arc oxidation process time was 75 seconds, and the other steps were the same as in Example 1.

[0065] Example 12

[0066] When preparing the current collector, the micro-arc oxidation process took 3.5 seconds, and the other steps were the same as in Example 1.

[0067] Example 13

[0068] When preparing the current collector, the micro-arc oxidation process time was 150s, and the other steps were the same as in Example 1.

[0069] Example 14

[0070] In preparing the electrolyte, the content of LiPF6 was 10 wt% and the content of LiFSI was 5 wt%, and the other steps were the same as in Example 1.

[0071] Example 15

[0072] In preparing the electrolyte, the content of LiPF6 was 13 wt% and the content of LiFSI was 2 wt%, and the other steps were the same as in Example 1.

[0073] Example 15

[0074] In preparing the electrolyte, the content of LiPF6 was 14 wt% and the content of LiFSI was 1 wt%, and the other steps were the same as in Example 1.

[0075] Example 17

[0076] In the preparation of the positive electrode sheet, the positive electrode active material LiNi 0.6 Co 0.1 Mn 0.3 O2 replaced with LiNi 0.5 Mn 0.5 O2, and the other steps are consistent with those in Example 1.

[0077] Example 18

[0078] In the preparation of the positive electrode sheet, the positive electrode active material LiNi 0.6 Co 0.1 Mn 0.3 O2 is replaced with Li[Li 0.2 Mn0.54 Ni 0.13 Co 0.13 O2, the other steps are consistent with Example 1.

[0079] Comparative Example 1

[0080] The current collector is selected as a 12μm thick aluminum foil, and no passivation layer is formed. The other steps are consistent with those in Example 1.

[0081] Comparative Example 2

[0082] In preparing the current collector, only potassium fluorotitanate was added to the electrolyte solution, with a potassium fluorotitanate content of 8 wt%, and the other steps were consistent with those in Example 1.

[0083] Comparative Example 3

[0084] In preparing the current collector, only potassium fluorozirconate was added to the electrolyte solution, with a potassium fluorozirconate content of 8 wt%, and the other steps were consistent with those in Example 1.

[0085] Comparative Example 4

[0086] In preparing the current collector, only potassium fluoroniobate was added to the electrolyte solution, with a potassium fluoroniobate content of 8 wt%, and the other steps were consistent with those in Example 1.

[0087] Comparative Example 5

[0088] In preparing the current collector, only potassium fluorotantalate was added to the electrolyte solution, with a potassium fluorotantalate content of 8 wt%, and the other steps were consistent with those in Example 1.

[0089] Comparative Example 6

[0090] In preparing the current collector, only chromium sulfate was added to the electrolyte solution, with a chromium sulfate content of 8 wt%, and the other steps were consistent with those in Example 1.

[0091] Comparative Example 7

[0092] In preparing the current collector, only potassium fluorotitanate and potassium fluorozirconate were added to the electrolyte solution, with the content of potassium fluorotitanate being 3.66 wt% and the content of potassium fluorozirconate being 4.34 wt%. Other steps were consistent with those in Example 1.

[0093] Comparative Example 8

[0094] In preparing the current collector, only potassium fluoroniobate and potassium fluorotantalate were added to the electrolyte solution, with the content of potassium fluoroniobate being 3.49 wt% and the content of potassium fluorotantalate being 4.51 wt%. Other steps were consistent with those in Example 1.

[0095] Comparative Example 9

[0096] In preparing the current collector, only potassium fluorotitanate and chromium sulfate were added to the electrolyte solution. The content of potassium fluorotitanate was 4.39 wt%, and the content of chromium sulfate was 3.61 wt%. The other steps were the same as in Example 1.

[0097] Comparative Example 10

[0098] In preparing the electrolyte, the content of LiPF6 was 13 wt%, the content of LiFSI was 2 wt%, and other steps were the same as those in Comparative Example 1.

[0099] Comparative Example 11

[0100] In preparing the electrolyte, the content of LiPF6 was 14 wt%, the content of LiFSI was 1 wt%, and other steps were the same as those in Comparative Example 1.

[0101] Comparative Example 12

[0102] In the preparation of the positive electrode sheet, the positive electrode active material LiNi 0.6 Co 0.1 Mn 0.3 O2 replaced with LiNi 0.5 Mn 0.5 O2, and the other steps are the same as those in Comparative Example 1.

[0103] Comparative Example 13

[0104] In the preparation of the positive electrode sheet, the positive electrode active material LiNi 0.6 Co 0.1 Mn 0.3 O2 is replaced with Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 O2, and the other steps are the same as those in Comparative Example 1.

[0105] In this invention, in Examples 1-18 and Comparative Examples 1-13, different current collectors were used to prepare positive electrode sheets and lithium-ion batteries, and the performance of the lithium batteries was tested. The test results are shown in Tables 1-3.

[0106] In one embodiment of the present invention, the passivation layer thickness is measured using X-ray photoelectron spectroscopy (XPS) combined with ion beam sputtering. Specifically, the current collectors of the examples and comparative examples are prepared into 2mm × 2mm samples and cleaned and dried with deionized water. The samples are fixed on the sample stage, and under ultra-high vacuum conditions, a full-spectrum scan of the sample surface is first performed to determine the main elemental species, using an ion beam (such as Ar). +The sample surface was progressively sputtered, with XPS measurements performed every 5 minutes to obtain elemental signal variation curves at different sputtering depths. Time was converted to depth based on the sputtering rate. The location where the metal element transitions from the oxide state to the metallic state is the interface between the passivation layer and the substrate, thus determining the passivation layer thickness. The sputtering rate was calibrated using a standard film. The standard film is a titanium dioxide film of known thickness formed on a current collector substrate. The titanium dioxide film has similar properties to the passivation films obtained in the examples and comparative examples and can be used as a reference. Calibration process: First, the sputtering rate was determined using the standard film. The standard film was sputtered under specific sputtering conditions until the titanium dioxide film was completely etched. The sputtering rate was obtained by calculating the film thickness / sputtering time. The examples and comparative samples were sputtered at the same sputtering rate until the passivation layer on the sample surface was etched, i.e., a metallic signal was detected. The sputtering time was measured, and the passivation layer thickness was calculated by multiplying the sputtering time by the sputtering rate.

[0107] In one embodiment of the present invention, the lithium-ion battery can be tested by the following method:

[0108] (1) Float charge (chronoamperometry) test

[0109] A three-electrode setup was used. The positive electrode sheet from the examples and comparative examples was cut to 5cm x 5cm and used as the working electrode. The negative electrode sheet of the same size was used as the counter electrode. A lithium sheet was used as the reference electrode, and the electrolyte was the lithium-ion battery electrolyte described above. The working electrode and counter electrode were placed parallel to each other, with a distance of 0.5cm between them. The leakage current of the three-electrode setup under high voltage was used to evaluate the corrosion current. The working electrode of the three-electrode setup was used as the positive electrode, and the counter electrode as the negative electrode. The device was charged to voltage U1 (vs.Ref), and then the voltage was kept constant for 12 hours. The average current in the last hour was recorded as the corrosion current. For lithium nickel cobalt manganese oxide, U1 = 4.4V; for lithium nickel manganese oxide, U1 = 4.85V; and for lithium-rich manganese-based oxide materials, U1 = 4.6V. The corrosion current represents the degree of corrosion. In electrolytes with high LiFSI content, aluminum foil will undergo a corrosion reaction under high voltage, generating current. The smaller the current, the better the passivation layer's effect in inhibiting the corrosion reaction.

[0110] (2) DCR test

[0111] At 25°C, when the batteries in the examples and comparative examples were discharged to 50% State of Charge (50% SOC) at a 1C current, the current was increased to 4C and maintained for 30 seconds. The difference between the updated stable voltage and the original platform voltage was measured, and the ratio of this difference to the 4C current value is the battery's Direct Current Resistance (DCR). The DCR test result performed after the battery's first full charge is the battery's initial DCR. During the DCR test, the charge / discharge cutoff voltage for lithium nickel cobalt manganese oxide was 2.8V-4.4V; for lithium nickel manganese oxide, it was 3.4V-4.85V; and for lithium-rich manganese-based oxide materials, it was 2.5V-4.6V.

[0112] Table 1. Partial characteristics of the current collectors and performance of the lithium-ion batteries in Examples 1-13 and Comparative Examples 1-9.

[0113]

[0114] Please refer to Table 1. Comparing Examples 1-13 with Comparative Example 1, it can be seen that when a passivation layer is provided on the current collector in the positive electrode, the corrosion current of the lithium-ion battery is significantly reduced. This indicates that by providing a passivation layer on the current collector, the corrosion resistance of the current collector can be improved, reducing the corrosion current by three orders of magnitude, while not significantly affecting the battery's DCR.

[0115] Please refer to Table 1. Comparing Examples 1-6, it can be seen that the more types of metal elements and the more uniform the proportion of each metal element in the passivation layer, the lower the corrosion current. This is because when there are more types of metal elements and the proportion of each metal element is more uniform, the configuration entropy of the resulting passivation layer is higher, the passivation layer is more stable, and therefore the corrosion resistance is better. Comparing Examples 7-8, it can be seen that even when the number of metal elements is sufficient, if the proportions of each element differ significantly, the corrosion resistance of the current collector will still be poor. This is because a high configuration entropy depends on the uniform distribution of metal elements. If the proportions of metal elements are unbalanced, the configuration entropy will also be insufficient, affecting the corrosion resistance of the current collector. Therefore, the metal element proportion structure needs to be reasonable.

[0116] Please refer to Table 1. Comparing with Comparative Examples 2-9, it can be seen that when the passivation layer contains only one or two metal elements, neither of them can effectively inhibit corrosion. This is because when there are few types of metal elements, the configurational entropy of the passivation layer is too low, its thermodynamic stability is insufficient, and it is difficult to achieve a good corrosion resistance effect.

[0117] Please refer to Table 1. Comparing Examples 1 and 9-13, it can be seen that as the passivation layer thickness increases, the battery's current resistance (DCR) increases, while the corrosion current decreases and tends to stabilize. This is because the metal oxides and / or fluorides and / or fluorine oxides of the passivation layer have a certain influence on the conductivity of the current collector; the thicker the passivation layer, the greater the resistance. Therefore, it is necessary to control the passivation layer thickness within a reasonable range to reduce corrosion without significantly degrading the battery's DCR.

[0118] Table 2 shows some characteristics and performance of lithium-ion batteries in Examples 1, 14-16 and Comparative Examples 10-11.

[0119]

[0120] Please refer to Table 2. Comparing Examples 1, 14-16, and Comparative Examples 10-11, it can be seen that when the LiFSI content in the electrolyte is not less than 2 wt%, ordinary aluminum foil exhibits significant corrosion. When the LiFSI content is less than 2 wt%, even ordinary aluminum foil shows little corrosion, and corrosion-resistant aluminum foil is not needed to address the corrosion problem. However, by forming a passivation layer on the aluminum foil, it still exhibits good corrosion resistance even with a high LiFSI content. Therefore, the current collector of this invention is more suitable for electrolytes with high LiFSI content, thereby improving the performance of lithium-ion batteries.

[0121] Table 3 shows some characteristics and performance of lithium-ion batteries in Examples 1, 17-18 and Comparative Examples 12-13.

[0122]

[0123] Please refer to Table 3. Comparing Examples 1, 17-18, and 12-13, it can be seen that when different positive electrode active materials are selected, the current collector provided by this invention can suppress corrosion current under high voltage. Therefore, the current collector provided by this application can be applied to a variety of positive electrode active materials to significantly suppress corrosion current under high voltage.

[0124] This invention also provides an electronic device comprising at least one of the aforementioned lithium-ion batteries, which provides electrical energy. The electronic device can be a vehicle, mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, or power tool, etc. In one embodiment of this invention, the vehicle is, for example, a new energy vehicle, which can be a pure electric vehicle, a hybrid electric vehicle, or a range-extended electric vehicle, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The electronic device includes the aforementioned lithium-ion battery, and therefore the advantages of including the aforementioned lithium-ion battery are not elaborated here.

[0125] In summary, this invention proposes a current collector, its preparation method, and its application. By forming a passivation layer on the current collector substrate, and the passivation layer being a mixed compound composed of multiple metal elements, the passivation layer tends to form a more uniform and stable single-phase solid solution structure. This fundamentally eliminates grain boundaries, which serve as corrosion initiation points in traditional polycrystalline structures, thereby improving the protection of the current collector substrate and reducing its corrosion. The similar atomic radii of the metal elements in the passivation layer are conducive to the formation of a solid solution structure, while also generating a suitable degree of lattice distortion effect, enhancing the lattice stability of the passivation layer. This also increases the configurational entropy of the passivation layer, significantly improving its thermodynamic stability and reducing its reactivity, thus preventing the electrolyte from corroding the current collector substrate. By controlling the thickness of the passivation layer, while preventing electrolyte corrosion of the current collector substrate, the low interfacial resistance of the current collector substrate is maintained, ensuring the electron conductivity of the current collector.

[0126] The above description is merely a preferred embodiment of this application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by replacing the above-mentioned features with technical features with similar functions disclosed in this application (but not limited to) each other.

[0127] Apart from the technical features described in the specification, the other technical features are known to those skilled in the art. To highlight the innovative features of this invention, the other technical features will not be described in detail here.

Claims

1. A current collector characterized by comprising: The collector substrate comprises: a collector substrate; and a passivation layer disposed on a surface of the collector substrate, the metal elements in the passivation layer comprising at least three of titanium, zirconium, tantalum, niobium, or chromium. The thickness of the passivation layer is 5 nm to 50 nm.

2. The current collector of claim 1, wherein The thickness of the passivation layer is 5 nm to 20 nm.

3. The current collector of claim 1, wherein When the number of types of metal elements in the passivation layer is greater than or equal to four, the proportion of the number of atoms of each metal element to the total number of atoms of all metal elements is 5% to 70%; 4. The current collector of claim 1, wherein When the number of types of metal elements is three, the proportion of the number of atoms of each metal element to the total number of atoms of all metal elements is 10% to 60%. The collector substrate is one or more of aluminum, titanium, zinc, tin, nickel, and alloys of each thereof, and the thickness of the collector substrate is 10 μm to 25 μm.

5. The current collector of claim 1, wherein The method comprises:

6. A method of making a current collector, characterized by, dissolving at least three of a titanium salt, a zirconium salt, a tantalum salt, a niobium salt, or a chromium salt in a solvent to obtain an electrolyte solution; placing a collector substrate in the electrolyte solution to obtain a collector by electrochemical treatment.

7. The method for preparing a collector according to claim 6, wherein the titanium salt comprises potassium fluorotitanate, the zirconium salt comprises potassium fluorozirconate, the niobium salt comprises potassium fluoroniobate, the tantalum salt comprises potassium fluorotantalate, and the chromium salt comprises chromium sulfate; the solvent comprises at least one of sulfuric acid, oxalic acid, phosphoric acid, or phytic acid with a concentration of 0.05 mol / L to 0.15 mol / L; the electrochemical treatment comprises a micro-arc oxidation method. The positive electrode active layer comprises a positive electrode active material, and the positive electrode active material comprises one or more of lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, or a lithium-rich manganese-based oxide material.

8. A positive electrode sheet characterized by comprising: The positive electrode active layer comprises a positive electrode active material, and the positive electrode active material comprises one or more of lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, or a lithium-rich manganese-based oxide material. The method comprises:

9. The cathode electrode plate of claim 8, wherein, a positive electrode tab selected from the positive electrode tab according to any one of claims 8-9; 10. A lithium-ion battery, characterized by, a negative electrode tab; a separator disposed between the positive electrode tab and the negative electrode tab; an electrolyte, and the electrolyte comprises lithium bisfluorosulfonylimide, and the content of lithium bisfluorosulfonylimide in the electrolyte is greater than or equal to 2 wt%. ​ ​

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