Negative pole piece and preparation method thereof, lithium ion battery and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a negative pole piece, a preparation method of the negative pole piece, a lithium ion battery and an electric device. The negative pole piece comprises a negative current collector, a negative coating arranged on the surface of at least one side of the negative current collector and a pre-lithiation layer arranged on at least part of the surface of the negative coating; the negative current collector comprises a base material and metal foils compounded on the surfaces of the two sides of the base material, and the negative coating comprises a negative active material and a binder; the pre-lithiation layer comprises a pre-lithiation agent; the lithium ion battery comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm, the electrolyte comprises a functional additive, and the functional additive comprises a fluorine-containing carbonic ester additive. According to the negative electrode plate provided by the invention, the first-circle coulombic efficiency, the fast charging capability and the cycling stability of the negative electrode can be remarkably improved, and the negative electrode plate has a good commercial application prospect.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a negative electrode sheet and its preparation method, a lithium-ion battery, and an electrical device. Background Technology

[0002] With the continuous pursuit of high energy density and fast charging capabilities in new energy vehicles and energy storage systems, silicon-based anode materials, with their theoretical specific capacity of up to 3500 mAh / g, have become a strong candidate to replace traditional graphite anodes. However, silicon undergoes volume expansion of over 300% during lithium insertion / extraction, which easily triggers a series of degradation mechanisms such as particle breakage, repeated formation and rupture of the SEI film, loose electrode structure, and interface debonding. This results in low initial coulombic efficiency, poor rate performance, and limited cycle life, severely restricting its application in practical battery systems. Summary of the Invention

[0003] In view of this, the purpose of this invention is to address, to some extent, the problems of low initial coulombic efficiency, poor rate performance, and low cycle stability. To this end, this invention provides a negative electrode sheet and its preparation method, a lithium-ion battery, and an electrical device. Through a high-silicon-graphite negative electrode synergistic design scheme that integrates chemical pre-lithiation, functional additive-assisted interface modification, a plastic copper foil current collector, and a composite binder system, the structure and composition of the negative electrode sheet are improved, significantly enhancing the initial coulombic efficiency, fast-charging capability, and cycle stability of the negative electrode.

[0004] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0005] According to one aspect of the present invention, a negative electrode sheet is provided, comprising a negative electrode current collector, a negative electrode coating disposed on at least one side surface of the negative electrode current collector, and a pre-lithiation layer disposed on at least a portion of the surface of the negative electrode coating;

[0006] The negative electrode current collector includes a substrate and metal foils laminated on both sides of the substrate. The substrate includes at least one of polyethylene terephthalate, polyethylene naphthalate, polyimide, polyethylene, and polypropylene. The metal foils include at least one of copper foil, nickel foil, stainless steel foil, tin foil, and indium foil.

[0007] The negative electrode coating includes a negative electrode active material and a binder; the pre-lithiation layer includes a pre-lithiation agent.

[0008] In some embodiments, the substrate comprises polyethylene terephthalate; the metal foil comprises copper foil; and the X-ray diffraction pattern of the negative electrode current collector exhibits characteristic peaks at 24–28.5°, 43.5–45.0°, 49.5–51.5°, and 73.5–76.0°.

[0009] In some embodiments, the thickness of the substrate is 4 μm to 8.5 μm;

[0010] In some embodiments, the thickness of the metal foil is 0.5 μm to 2.5 μm.

[0011] In some embodiments, the negative electrode active material includes a first negative electrode active material and a second negative electrode active material.

[0012] In some of these embodiments, the first negative electrode active material includes at least one of artificial graphite, natural graphite, soft carbon, and hard carbon.

[0013] In some of these embodiments, the second negative electrode active material includes at least one of deposited silicon carbon and crystalline silicon.

[0014] In some of these embodiments, the mass ratio of the first negative electrode active material to the second negative electrode active material is (3-19):1.

[0015] In some embodiments, the mass of the negative electrode active material accounts for 95% to 99% of the mass of the negative electrode coating.

[0016] In some of these embodiments, the adhesive includes a first adhesive and a second adhesive.

[0017] In some of these embodiments, the first binder comprises sodium carboxymethyl cellulose.

[0018] In some of these embodiments, the second adhesive comprises at least one of polyacrylonitrile, polystyrene-acrylic acid, styrene-butadiene rubber, polyacrylic acid, and pre-sodium-modified polyacrylic acid.

[0019] In some of these embodiments, the mass ratio of the first adhesive to the second adhesive is (1-4):4.

[0020] In some embodiments, the binder accounts for 0.5% to 5% of the mass of the negative electrode coating.

[0021] In some embodiments, the prelithiation agent includes at least one of Li-naphthalene, Li-phenanthrene, Li-anthracene, and Li-tetrahydrofuran complex.

[0022] According to a second aspect of the present invention, the present invention provides a method for preparing the negative electrode sheet described in the above technical solution, comprising the following steps:

[0023] a) After activating both sides of the substrate, metal deposition is performed, followed by surface oxidation to obtain the negative electrode current collector;

[0024] b) The negative electrode current collector obtained in step a) is coated with a negative electrode coating slurry on at least one side surface, and then cured and pressed to form a negative electrode coating. The negative electrode coating is then brought into contact with a pre-lithiation solution to form a pre-lithiation layer on at least a portion of the surface of the negative electrode coating. The negative electrode is then washed and dried to obtain a negative electrode sheet.

[0025] In some embodiments, the process of activating the surfaces on both sides of the substrate in step a) includes the following steps:

[0026] At room temperature, the substrate is contacted with a 20wt% to 40wt% strong alkaline solution and reacted for 2 to 10 minutes. After the reacted substrate is cleaned until neutral, it is vacuum dried at 40℃ to 100℃ for 1 to 4 hours to obtain a substrate with activated surfaces on both sides.

[0027] In some embodiments, the metal deposition in step a) includes metal film deposition using magnetron sputtering.

[0028] In some embodiments, the surface oxidation in step a) includes ultraviolet irradiation for 2 to 20 minutes in the presence of ozone.

[0029] In some embodiments, the negative electrode current collector described in step a) has a tensile strength ≥280MPa and an elongation at break of 6.0% to 18.0% under a tensile rate of 50±0.5mm / min.

[0030] In some embodiments, the negative electrode coating slurry in step b) includes a negative electrode active material, a binder, a conductive agent, and a solvent.

[0031] In some embodiments, the compaction density of the pressing in step b) is 1.40 g / cm³. 3 ~1.65g / cm 3 .

[0032] In some embodiments, the negative electrode coating and the negative electrode current collector described in step b) satisfy the following: 10.2 N / m ≤ peel strength ≤ 21.0 N / m.

[0033] In some embodiments, the prelithiation solution in step b) includes a prelithiation agent with a concentration of 0.5M to 2M.

[0034] In some embodiments, the contact time in step b) is 2 min to 10 min.

[0035] According to a third aspect of the present invention, the present invention provides a lithium-ion battery, comprising a negative electrode, a positive electrode, a separator, and an electrolyte; wherein the negative electrode comprises the negative electrode described in the above-described technical solution or the negative electrode prepared by the preparation method described in the above-described technical solution.

[0036] In some embodiments, the electrolyte includes functional additives; the functional additives include fluorinated carbonate additives.

[0037] In some embodiments, the fluorinated carbonate additive accounts for 0.5% to 10% of the electrolyte concentration by mass.

[0038] According to a fourth aspect of the present invention, the present invention provides an electrical device comprising the lithium-ion battery described above.

[0039] Implementing the technical solution of the present invention has at least the following beneficial effects:

[0040] 1. In the embodiments of the present invention, the negative electrode sheet provided by the present invention adopts a specific structure with a specific composition, especially the negative electrode current collector obtained by combining a flexible polymer substrate with a metal foil. It has good flexibility and mechanical buffering properties, and can adapt to the volume change of expansive negative electrodes such as silicon, thereby achieving better overall interaction. It can effectively alleviate / suppress problems such as cracking, pulverization and detachment of negative electrode sheets during high-pressure compaction and cycling, and improve the performance of negative electrode sheets.

[0041] 2. In this embodiment of the invention, the invention adopts a synergistic design scheme for a high-silicon-graphite anode that integrates chemical pre-lithiation, functional additive-assisted interface modification, plastic copper foil current collector, and composite binder system. This scheme performs three-dimensional synergistic design of the anode sheet and the materials, interface, and structure of the lithium-ion battery, improving the structure and composition of the anode sheet and significantly enhancing the first-cycle coulombic efficiency, fast-charging capability, and cycle stability of the anode. This provides a complete solution for the practical application of the high-silicon anode system, taking into account performance requirements such as high specific capacity, fast-charging capability, and long cycle life.

[0042] 3. In the embodiments of the present invention, the present invention achieves better overall interaction at the negative electrode plate level and the lithium-ion battery level by systematically controlling the Si / C mass ratio of the negative electrode active material in the negative electrode coating, the composition and proportion of the binder, the relevant technical characteristics of polyethylene terephthalate (PET) based plastic Cu foil, the type and concentration of the pre-lithiation agent in the pre-lithiation layer, and the type and amount of additives in the electrolyte of the lithium-ion battery. This significantly improves the first-cycle coulombic efficiency, fast charging capability and cycle stability of the negative electrode.

[0043] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0044] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0045] Figure 1 This is a schematic diagram of the negative electrode current collector provided in an embodiment of the present invention.

[0046] Figure 2 The X-ray diffraction pattern of the negative electrode current collector provided in the embodiment of the present invention.

[0047] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0048] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0049] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0050] In the description of this application, "same chemical composition" should be interpreted broadly, that is, the main components of the two have the same chemical composition, or the two have substantially the same chemical composition, but may have errors or impurities within the acceptable range that can be understood by those skilled in the art.

[0051] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0052] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0053] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0054] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0055] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0056] Generally, silicon-based anode materials, with their theoretical specific capacity of up to 3500 mAh / g, have become strong candidates to replace traditional graphite anodes. However, silicon undergoes volume expansion exceeding 300% during lithium insertion / extraction, easily triggering a series of degradation mechanisms such as particle breakage, repeated formation and rupture of the SEI film, loose electrode structure, and interface debonding. This results in low initial coulombic efficiency, poor rate performance, and limited cycle life, severely restricting its application in practical battery systems. To address the problem of rapid battery performance degradation caused by the large volume change of silicon-based anode materials before and after lithium insertion / extraction, this invention prepares a silicon-carbon composite material by mixing silicon (alloy) with graphite in a certain proportion. While ensuring a large capacity of silicon, the large specific surface area of ​​graphite is utilized to buffer the volume expansion and contraction of silicon (alloy) materials during charge and discharge. Compared with carbon materials, the silicon-carbon composite material improves lithium insertion capacity through the addition of silicon (alloy); on the other hand, the introduction of carbon buffers the expansion of silicon, improving electronic conductivity.

[0057] Based on this, the negative electrode sheet provided by this invention adopts a specific structure with a specific composition, especially the negative electrode current collector obtained by combining a flexible polymer substrate with a metal foil. This current collector possesses good flexibility and mechanical buffering properties, adapting to the volume changes of expansive negative electrodes such as silicon, thereby achieving better overall interaction. This effectively alleviates / suppresses problems such as cracking, pulverization, and detachment of the negative electrode sheet during high-pressure compaction and cycling, thus improving the performance of the negative electrode sheet. Furthermore, this invention constructs a flexible metal-organic interface structure rich in CO / C=O functional groups between the substrate and the metal foil through magnetron sputtering and UV ozone catalysis. This gives the negative electrode current collector excellent elongation at break and current collector adaptability, effectively mitigating the problem of electrode detachment during high-pressure compaction and cycling.

[0058] Furthermore, by selecting a composite binder system, the present invention enables the binder to have both elastic buffering and chemical anchoring effects, thereby improving the constraint and interfacial integrity of silicon-based particles at the electrode structure level. By using an electrolyte containing specific types of functional additives, an artificial SEI film rich in inorganic phases such as LiF can be induced to form on the negative electrode surface. This film has good thermal stability and ion selectivity, and can effectively suppress electrolyte side reactions and reduce interfacial impedance.

[0059] In summary, this invention adopts a synergistic design scheme for a high-silicon-graphite anode that integrates chemical pre-lithiation, functional additive-assisted interface modification, plastic copper foil current collector, and composite binder system. Through three-dimensional synergistic design of materials, interface, and structure, it provides a complete solution for the practical application of high-silicon anode systems, taking into account performance requirements such as high specific capacity, fast charging capability, and long cycle life, thereby solving the above-mentioned technical problems to a certain extent and improving battery performance.

[0060] Through in-depth research, the inventors have discovered that, in addition to meeting the above-mentioned design conditions, the performance of the product can be further improved if it optionally meets one or more of the following conditions. Specifically, the present invention adopts the following technical solution:

[0061] According to a first aspect of the present invention, a negative electrode sheet is provided, comprising a negative electrode current collector, a negative electrode coating, and a pre-lithiation layer; wherein the negative electrode coating is disposed on at least one surface of the negative electrode current collector, and the pre-lithiation layer is disposed on at least a portion of the surface of the negative electrode coating.

[0062] In this invention, the negative electrode current collector includes a substrate and metal foils laminated on both sides of the substrate; wherein, the substrate includes at least one of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polyethylene (PE), and polypropylene (PP), preferably PET; the metal foil includes at least one of copper foil, nickel foil, stainless steel foil, tin foil, and indium foil, preferably copper foil.

[0063] In this invention, the negative electrode coating comprises a negative electrode active material and a binder; the pre-lithiation layer comprises a pre-lithiation agent.

[0064] This invention forms a negative electrode sheet by combining a negative electrode current collector with a specific composition and structure, along with a negative electrode coating and a pre-lithiation layer of a specific composition. This enables three-dimensional synergy of materials, interfaces, and structures, providing a complete solution for the practical application of high-silicon negative electrode systems. It achieves stable construction of the SEI film and comprehensive optimization of interface performance. Furthermore, the lithium-ion battery including this negative electrode sheet can meet the performance requirements of high specific capacity, fast charging capability, and long cycle life, making this lithium-ion battery a promising candidate for commercial application.

[0065] [Negative electrode current collector]

[0066] In this invention, the negative electrode current collector comprises a substrate and metal foils laminated to both surfaces of the substrate; wherein the substrate comprises at least one selected from polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polyethylene (PE), and polypropylene (PP), preferably PET; the metal foil comprises at least one selected from copper foil, nickel foil, stainless steel foil, tin foil, and indium foil, preferably copper foil. This invention does not impose any special restrictions on the source of the substrate and metal foil; commercially available products or homemade products well known to those skilled in the art can be used.

[0067] In this invention, the aforementioned metal foils, such as copper foil, nickel foil, and tin foil, are not only widely available and easy to obtain, but also have strong lithium affinity, which is more conducive to promoting the uniform deposition of lithium ions, improving the lithium dendrite problem, and thus improving the safety of the battery.

[0068] In a preferred embodiment of the present invention, the substrate comprises polyethylene terephthalate; the metal foil comprises copper foil; and the negative electrode current collector is a three-layer composite PET-based Cu foil current collector (denoted as Cu@PET@Cu), whose X-ray diffraction pattern shows characteristic peaks at 24–28.5°, 43.5–45.0°, 49.5–51.5°, and 73.5–76.0°. The characteristic peak at 24–28.5° belongs to the middle PET substrate, while the characteristic peaks at 43.5–45.0°, 49.5–51.5°, and 73.5–76.0° belong to the upper and lower Cu foil layers. The X-ray diffraction pattern of the negative electrode current collector provided in this embodiment of the present invention is shown below. Figure 2 As shown.

[0069] In a preferred embodiment of the present invention, PET is used as the substrate. As a flexible polymer, PET imparts superior flexibility and mechanical cushioning to the entire Cu@PET@Cu structure, enabling it to adapt to volume changes in expansive negative electrodes such as silicon and suppressing electrode cracking and pulverization. Based on this, the tensile strength of the aforementioned Cu@PET@Cu is preferably ≥280MPa and the elongation at break is preferably 6.0%–18.0% under a tensile rate of 50±0.5mm / min.

[0070] In this invention, the thickness of the substrate is preferably 4μm to 8.5μm, specifically 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, and most preferably 6μm; the thickness of the metal foil is preferably 0.5μm to 2.5μm, specifically 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, and most preferably 1μm. By controlling the thickness of each layer in the negative electrode current collector within the above range, this invention can further improve the first-cycle coulombic efficiency, fast-charging capability, and cycle stability of the negative electrode.

[0071] See the schematic diagram of the negative electrode current collector provided in this embodiment of the invention. Figure 1 As shown.

[0072] [Negative electrode coating]

[0073] In this invention, the negative electrode coating comprises a negative electrode active material and a binder; wherein, the negative electrode active material preferably comprises a first negative electrode active material and a second negative electrode active material.

[0074] In this invention, the first negative electrode active material preferably includes at least one of artificial graphite, natural graphite, soft carbon, and hard carbon, more preferably artificial graphite and / or natural graphite; the second negative electrode active material preferably includes at least one of deposited silicon carbon and crystalline silicon, more preferably deposited silicon carbon. This invention does not impose any special restrictions on the source of the first and second negative electrode active materials; commercially available products or self-made products well known to those skilled in the art can be used.

[0075] This invention uses the above-mentioned graphite and silicon-containing materials as negative electrode active materials, which enables the lithium-ion battery to form a stable conductive network. At the same time, while ensuring the large capacity of the silicon-containing materials, the large specific surface area of ​​graphite is used to buffer the expansion and contraction of the silicon-containing materials during charging and discharging.

[0076] In this invention, the mass ratio of the first negative electrode active material to the second negative electrode active material is preferably (3-19):1, specifically it can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, or any range of two of the above ratios, more preferably (3-4):1.

[0077] By controlling the mass ratio of the first negative electrode active material to the second negative electrode active material within the above-mentioned range, this invention can further improve the first-cycle coulombic efficiency, fast charging capability, and cycle stability of the negative electrode.

[0078] In this invention, the mass of the negative electrode active material preferably accounts for 95% to 99% of the total mass of the negative electrode coating, specifically 95%, 96%, 97%, 98%, 99%, or any two of the above values, and more preferably 96%.

[0079] By controlling the mass ratio of the negative electrode active material within the above-mentioned range, this invention can further improve the first-cycle coulombic efficiency, fast-charging capability, and cycle stability of the negative electrode.

[0080] In this invention, the adhesive preferably comprises a first adhesive and a second adhesive; wherein the first adhesive preferably comprises sodium carboxymethyl cellulose (CMC); the second adhesive preferably comprises at least one selected from polyacrylonitrile (PAN), polystyrene-acrylic acid, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), and pre-sodium-modified polyacrylic acid, more preferably styrene-butadiene rubber (SBR) and polyacrylic acid (PAA); in a preferred embodiment of this invention, the second adhesive is a composite system of styrene-butadiene rubber (SBR) and polyacrylic acid (PAA), wherein the mass ratio of styrene-butadiene rubber (SBR) to polyacrylic acid (PAA) is preferably 3:1 to 1:3. This invention does not impose any special restrictions on the source of the first and second adhesives; commercially available products or homemade products well known to those skilled in the art can be used.

[0081] In this invention, the mass ratio of the first adhesive to the second adhesive is preferably (1-4):4, specifically it can be 1:4, 1.5:4, 2:4, 2.5:4, 3:4, 3.5:4, 4:4, or any range of two of the above values.

[0082] By controlling the mass ratio of the first binder and the second binder within the aforementioned range, this invention can further improve the first-cycle coulombic efficiency, fast-charging capability, and cycle stability of the negative electrode.

[0083] In this invention, the mass of the binder preferably accounts for 0.5% to 5% of the mass of the negative electrode coating, specifically it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any two of the above values, more preferably 2.5% to 3%.

[0084] By controlling the mass ratio of the binder within the above-mentioned range, this invention can further improve the first-cycle coulombic efficiency, fast-charging capability, and cycle stability of the negative electrode.

[0085] In this invention, in order to improve the electronic conductivity of the electrode, construct an electronic conduction network, and reduce the internal resistance of the electrode, the negative electrode coating preferably further includes a conductive agent; this invention does not have any special restrictions on the type and source of the conductive agent, and commercially available conventional conductive agents known to those skilled in the art can be used; in a preferred embodiment of this invention, the conductive agent preferably includes at least one of single-walled carbon nanotubes, multi-arm carbon nanotubes, carbon black, carbon fiber, and graphene, and more preferably single-walled carbon nanotubes.

[0086] In this invention, the content of the conductive agent in the negative electrode coating can be selected within a wide range, preferably 0.5% to 2%, specifically 0.5%, 1%, 1.5%, 2%, or any two of the above values.

[0087] In a preferred embodiment of the present invention, the mass ratio of the negative electrode active material, conductive agent, and binder in the negative electrode coating is preferably (95%–99%):(0.5%–2%):(0.5%–5%); specifically, it can be 95%:2%:3%, 96%:1.5%:2.5%, 97%:1%:2%, 98%:0.5%:1.5%, 99%:0.5%:0.5%, or any range of two of the above values.

[0088] By controlling the mass ratio of the negative electrode active material, conductive agent, and binder within the above-mentioned range, this invention can further improve the first-cycle coulombic efficiency, fast-charging capability, and cycle stability of the negative electrode.

[0089] [Pre-lithiation layer]

[0090] In this invention, the pre-lithiation layer is disposed on at least a portion of the surface of the negative electrode coating, preferably on the entire surface of the negative electrode coating on the side away from the negative electrode current collector; the purpose of the pre-lithiation layer is to compensate for the initial irreversible lithium loss, improve the initial coulombic efficiency, and increase the battery energy density.

[0091] In this invention, the pre-lithiation layer includes a pre-lithiation agent, which preferably includes at least one selected from Li-naphthalene, Li-phenanthrene, Li-anthracene, and Li-tetrahydrofuran complexes, more preferably Li-naphthalene. This invention does not impose any particular restriction on the source of the pre-lithiation agent; commercially available products or homemade products well-known to those skilled in the art can be used.

[0092] [Negative electrode plate]

[0093] In this invention, "the negative electrode sheet includes a negative current collector, a negative electrode coating disposed on at least one side surface of the negative current collector, and a pre-lithiation layer disposed on at least a portion of the surface of the negative electrode coating" means that a negative electrode coating is disposed on one or both sides surface of the negative current collector, preferably both sides surface of the negative current collector are provided with a negative electrode coating; a pre-lithiation layer is disposed on at least a portion surface of the negative electrode coating, preferably the side surface of the negative electrode coating away from the negative current collector is provided with a pre-lithiation layer; specifically, the negative current collector, negative electrode coating, and pre-lithiation layer are the same as those described in the above technical solution, and will not be repeated here.

[0094] [Preparation of the negative electrode sheet]

[0095] According to a second aspect of the present invention, the present invention provides a method for preparing the negative electrode sheet described in the above technical solution, comprising the following steps:

[0096] a) After activating both sides of the substrate, metal deposition is performed, followed by surface oxidation to obtain the negative electrode current collector;

[0097] b) The negative electrode current collector obtained in step a) is coated with a negative electrode coating slurry on at least one side surface, and then cured and pressed to form a negative electrode coating. The negative electrode coating is then brought into contact with a pre-lithiation solution to form a pre-lithiation layer on at least a portion of the surface of the negative electrode coating. The negative electrode is then washed and dried to obtain a negative electrode sheet.

[0098] This invention first activates both surfaces of a substrate, then deposits metal, followed by surface oxidation to obtain a negative electrode current collector. In this invention, the substrate is the same as described in the above-mentioned technical solutions, and will not be repeated here.

[0099] In this invention, the process of activating the surfaces on both sides of the substrate preferably includes the following steps:

[0100] At room temperature, the substrate is contacted with a 20wt% to 40wt% strong alkaline solution and reacted for 2 to 10 minutes; the reacted substrate is then cleaned until neutral and vacuum dried at 40℃ to 100℃ for 1 to 4 hours to obtain a substrate with activated surfaces on both sides.

[0101] More preferably:

[0102] At room temperature, the substrate was contacted with a 30wt% strong alkaline solution and reacted for 5 minutes. After the reacted substrate was cleaned until neutral, it was vacuum dried at 60°C for 2 hours to obtain a substrate with activated surfaces on both sides.

[0103] The strong alkaline solution preferably includes NaOH solution and / or KOH solution, more preferably NaOH solution; the present invention does not have any special restrictions on the source of the strong alkaline solution, and commercially available products well known to those skilled in the art can be used; the cleaning is preferably done with deionized water.

[0104] In this invention, the contact method is preferably as follows:

[0105] A strong alkaline solution is used to treat the substrate surface, which initiates a hydrolysis reaction and introduces polar groups such as carboxyl groups (-COOH) and hydroxyl groups (-OH) onto the substrate surface, thereby activating the substrate surface.

[0106] After obtaining the substrate with activated surfaces on both sides, the present invention further performs metal deposition;

[0107] The metal deposition preferably includes metal film deposition using magnetron sputtering technology.

[0108] In a preferred embodiment of the present invention, the metal film deposition preferably includes metal film deposition using magnetron sputtering technology, specifically including the following steps:

[0109] The substrate with activated surfaces on both sides is fixed on a stage inside a vacuum chamber, and a metal film is deposited using a DC or RF magnetron sputtering system in an inert atmosphere; wherein the vacuum base pressure is maintained at <5×10 -4 The working pressure was 0.5 Pa to 1.5 Pa, and the sputtering power was controlled between 200 W and 400 W. Using a metal target with a purity ≥99.99%, a metal layer with a single-sided thickness of 0.5 μm to 2.5 μm was obtained on a rotating stage at a uniform deposition rate (50 nm / min to 150 nm / min). Subsequently, the same method was used to deposit a metal layer on the other side of the substrate with activated surfaces on both sides. After deposition, the sample was cooled to room temperature and removed, resulting in a metal@substrate@metal composite current collector.

[0110] In this invention, the metal selected during the metal film deposition process can be at least one of copper, nickel, stainless steel, aluminum, tin, and indium; in a preferred embodiment of this invention, the metal selected is copper, and the single-sided thickness of the metal film deposition is preferably 1 μm.

[0111] After obtaining the aforementioned metal@substrate@metal composite current collector, the present invention further performs surface oxidation on it to obtain a negative electrode current collector. In the present invention, the surface oxidation preferably includes ultraviolet light irradiation in the presence of ozone for 2 min to 20 min, specifically 2 min, 5 min, 10 min, 15 min, 20 min, or any combination of two of the above values.

[0112] In this invention, the surface oxidation process specifically includes the following steps:

[0113] The obtained metal@substrate@metal composite current collector was placed in a UV ozone catalytic oxidation device and irradiated for 2 to 20 minutes under ozone concentrations of 10 ppm to 50 ppm and temperatures of 15°C to 35°C. Based on this, high-energy UV induced the conversion of O2 in the air into O3, which then decomposed to form active oxygen atoms. These active oxygen atoms can react with small carbon molecules on the metal surface (a very small portion of the carbon monomers released from the substrate during magnetron sputtering deposition adsorbed on the metal surface) to form polar oxygen-containing functional groups such as metal=O, carboxyl groups (-COOH), and carbon groups (C=O).

[0114] The negative electrode current collector provided by this invention achieves the presence of COC and C=O functional groups on its surface through the synergistic effect of magnetron sputtering and UV ozone catalysis. The mechanism for generating COC and C=O in this invention is as follows:

[0115] UV-induced ozone generation and reactive oxygen decomposition reaction: Short-wave ultraviolet light first decomposes O2 in the air into oxygen free radicals (O·): O2 + hν → 2O·; Oxygen free radicals react with O2 to generate ozone (O3): O· + O2 → O3; During magnetron sputtering, some PET will release a small amount of carbon-containing molecules onto the copper layer, such as monomers terephthalic acid or ethylene glycol O· and O3 reacting with Cu to generate Cu2O or CuO, which will also convert these small carbon-containing molecules into functional groups such as -COOH or COC.

[0116] In this invention, the negative electrode current collector, under a tensile rate of 50±0.5mm / min, preferably has a tensile strength of ≥280MPa and a breaking elongation of 6.0% to 18.0%.

[0117] After obtaining the negative electrode current collector, the present invention coats at least one side of the obtained negative electrode current collector with a negative electrode coating slurry, and then cures and presses it to form a negative electrode coating. The negative electrode coating is then brought into contact with a pre-lithiation solution to form a pre-lithiation layer on at least a portion of the surface of the negative electrode coating. After cleaning and drying, a negative electrode sheet is obtained.

[0118] In this invention, the negative electrode coating slurry preferably includes a negative electrode active material, a conductive agent, a binder, and a solvent; wherein, the negative electrode active material, conductive agent, and binder are the same as those described in the above technical solutions, and will not be repeated here; the solvent can be any commercially available conventional solvent known to those skilled in the art for preparing negative electrode coating slurries, and this invention does not have any special restrictions on it; in a preferred embodiment of this invention, the solvent is deionized water.

[0119] In this invention, the negative electrode coating slurry is coated on at least one side of the obtained negative electrode current collector, preferably on both sides of the obtained negative electrode current collector, and then cured and pressed in sequence to form a negative electrode coating; wherein, the curing method can be a drying technique known to those skilled in the art.

[0120] In this invention, the pressing process is preferably specifically as follows:

[0121] The material is cold-pressed using a roller press; the preferred compaction density is 1.40 g / cm³. 3 ~1.65g / cm 3 Specifically, it can be 1.40 g / cm³ 3 1.45g / cm 3 1.50g / cm 3 1.55g / cm 3 1.60g / cm 3 1.65g / cm 3 Or a range consisting of any two of the above values, more preferably 1.45 g / cm³. 3 ~1.65g / cm 3 More preferably 1.55 g / cm³ 3 .

[0122] This invention controls the compaction density of the negative electrode sheet within the aforementioned range, enabling the negative electrode active material layer to have a dense structure with low porosity and high particle contact. This simultaneously strengthens the conductive network and bonding interface, and shortens the electron and lithium-ion transport paths, resulting in reduced interface resistance and improved peel strength. When the compaction density of the negative electrode sheet is too high, the internal pore structure of the negative electrode active material layer closes, leading to restricted electrolyte penetration, hindered SEI formation, and decreased lithium-ion diffusion rate. Consequently, both the capacity retention and cycle stability of the lithium-ion battery decrease, demonstrating the defects of the synergistic mechanism of "diffusion restriction" and "interface deterioration" caused by excessive compaction.

[0123] In this invention, the formed negative electrode coating and the negative electrode current collector preferably satisfy the following conditions: 10.2 N / m ≤ peel strength ≤ 21.0 N / m; specifically, it can be 10.2 N / m, 10.5 N / m, 11.5 N / m, 12.5 N / m, 13.5 N / m, 14.5 N / m, 15.5 N / m, 16.5 N / m, 18 N / m, 19 N / m, or any range of two of the above values. Therefore, the negative electrode sheet provided by this invention has an excellent bonding interface.

[0124] Subsequently, the present invention contacts the negative electrode coating with a pre-lithiation solution to form a pre-lithiation layer on at least a portion of the surface of the negative electrode coating. It is understood that all the features and advantages described above regarding the "pre-lithiation layer" also apply to this "method for preparing the negative electrode sheet", and the present invention will not repeat them here.

[0125] In this invention, the pre-lithiation solution preferably includes a pre-lithiation agent; it should be understood that the pre-lithiation solution is composed of a pre-lithiation agent and a solvent, wherein the characteristics and advantages of the "pre-lithiation agent" are the same as those described in the above technical solutions, and will not be repeated here; the solvent refers to a conventional solvent that can dissolve the pre-lithiation agent, including but not limited to 2-methyltetrahydrofuran (2-MTHF), and commercially available sources well known to those skilled in the art can be used.

[0126] In this invention, the concentration of the pre-lithiation agent is preferably 0.5M to 2M, specifically 0.5M, 1M, 1.5M, 1.8M, 2M, or any two of the above values, more preferably 1M to 1.8M, and even more preferably 1.5M.

[0127] This invention, by controlling the concentration of the aforementioned pre-lithiation agent, can precisely compensate for the amount of lithium required for SEI formation, thereby constructing a stable and dense LiF / Li2CO3-rich interface film on the silicon-carbon surface, reducing lithium loss, and improving interface stability and Li... + Diffusion efficiency.

[0128] In this invention, the contact time is preferably 2 min to 10 min, specifically 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or any two of the above values, and more preferably 5 min.

[0129] In this invention, the process of the negative electrode coating contacting the pre-lithiation solution is preferably as follows:

[0130] The negative electrode sheet with the negative electrode coating is immersed in a pre-lithiation solution with a concentration of 0.5M to 2M and allowed to stand at room temperature for 2 to 10 minutes. This allows lithium ions in the pre-lithiation solution to be released through chemical reduction and penetrate to the surface of the electrode sheet, reacting with silicon-carbon active particles and interfacial functional groups to pre-construct a partial SEI layer and compensate for the initial lithium loss. A pre-lithiation layer is formed on at least part of the surface of the negative electrode coating. Immediately after pre-lithiation, the electrode sheet is removed and rapidly rinsed 2 to 4 times with anhydrous 2-MTHF to remove residual solution from the surface. Then, it is dried in a vacuum drying oven at 50°C to 70°C for 1 to 3 hours to obtain the pre-lithiated negative electrode sheet.

[0131] More preferably:

[0132] The negative electrode sheet with the negative electrode coating is immersed in a pre-lithiation solution with a concentration of 1M to 1.8M and allowed to stand at room temperature for 5 minutes to form a pre-lithiation layer on at least part of the surface of the negative electrode coating. After the pre-lithiation is completed, the electrode sheet is immediately removed and rinsed three times with anhydrous 2-MTHF to remove residual solution on the surface. Then it is dried in a vacuum drying oven at 60°C for 2 hours to obtain the pre-lithiated negative electrode sheet.

[0133] According to a third aspect of the present invention, a lithium-ion battery is provided, comprising a negative electrode, a positive electrode, a separator, and an electrolyte; the negative electrode comprises the negative electrode described in the above-described technical solution or the negative electrode prepared by the preparation method described in the above-described technical solution. Therefore, the lithium-ion battery possesses all the features and advantages of the negative electrode described in the above-described technical solution, which will not be repeated here.

[0134] [Positive electrode plate]

[0135] This invention does not impose any particular limitation on the positive electrode sheet; any positive electrode sheet known to those skilled in the art for use in lithium-ion batteries may be used. In a preferred embodiment of this invention, the positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector, wherein the positive electrode coating is preferably disposed on both surfaces of the positive current collector. The positive electrode coating is preferably a layer of positive active material coated on at least one surface of the positive current collector by a mixture of positive active material, conductive agent, and binder. The positive active material includes, but is not limited to, lithium nickel cobalt manganese oxide (Li1Ni). x Co y Mn z M b O2) and / or lithium iron phosphate, wherein 0.70≤x≤0.95, 0.15≤y<0.45, 0.05≤z<0.45, 0.0≤b≤0.25, x+y+z+b=1, and M includes at least one of zirconium (Zr), tungsten (W), titanium (Ti), aluminum (Al), strontium (Sr), boron (B), and neodymium (Nd), preferably Li1Ni 0.8 Co 0.1 Mn 0.1 O2; the conductive agent and binder are materials well known to those skilled in the art, wherein the conductive agent includes, but is not limited to, conductive carbon black and / or carbon nanotubes, and the binder includes, but is not limited to, polyvinylidene fluoride (PVDF). In this invention, the mass ratio of the above components can adopt the conventional mass ratio of raw materials in a positive electrode coating well known to those skilled in the art, the purpose of which is to achieve the basic performance of the positive electrode sheet, and this invention does not have any special limitations in this regard. In a preferred embodiment of this invention, the positive electrode coating includes Li1Ni in a mass ratio of 96:1:1:2. 0.8 Co 0.1 Mn0.1 O2, conductive carbon black, carbon nanotubes, and polyvinylidene fluoride (PVDF).

[0136] Meanwhile, the positive current collector is a commercially available, conventional current collector well-known to those skilled in the art for preparing positive electrode sheets, including but not limited to aluminum foil. This invention does not impose any particular limitation on the thickness of either the positive current collector or the positive electrode coating; thicknesses conventional in the art are permissible.

[0137] [Preparation of the positive electrode sheet]

[0138] In this invention, the positive electrode sheet can be prepared using conventional methods in the art. As an example, the preferred method for preparing the positive electrode sheet includes the following steps:

[0139] The positive electrode active material, conductive agent and binder are thoroughly mixed in an N-methylpyrrolidone solvent system to obtain a positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and after drying and cold pressing, a positive electrode sheet is obtained.

[0140] Electrolyte

[0141] In this invention, the electrolyte preferably includes functional additives; to achieve the basic functions of the electrolyte in a lithium-ion battery, it preferably also includes an electrolyte salt and a solvent; wherein, the functional additives include fluorinated carbonate additives, preferably fluoroethylene carbonate (FEC); the electrolyte salt preferably includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate, more preferably lithium hexafluorophosphate (LiPF6); the solvent preferably includes one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC), more preferably dimethyl carbonate (DMC) and ethylene carbonate (EC); this organic solvent system can significantly reduce the viscosity of the electrolyte and greatly improve the lithium-ion migration rate. In this invention, the electrolyte preferably further includes other functional additives, including but not limited to butylene carbonate (BC) and vinylene carbonate (VC). This invention does not impose any special restrictions on the source of the above-mentioned functional additives, electrolyte salts, and solvents; commercially available products well known to those skilled in the art can be used.

[0142] In a preferred embodiment of the present invention, the electrolyte comprises lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC); the mass ratio of lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC) is preferably 16:22:52:5:5.

[0143] In this invention, the fluorinated carbonate additive accounts for 0.5% to 10% of the electrolyte concentration by mass, specifically 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any combination of two of the above values; preferably 2% to 7.5%. By adding a specific amount of fluorinated carbonate additive, this invention can preferentially decompose and form a dense, uniform, LiF-rich artificial SEI during the first charging process, exhibiting excellent chemical stability and ion conductivity, and significantly suppressing electrolyte side reactions and active particle pulverization.

[0144] [Preparation of Electrolyte]

[0145] This invention does not impose any particular limitation on the preparation method of the electrolyte; conventional methods well-known to those skilled in the art can be used. In a preferred embodiment of this invention, the electrolyte is obtained by uniformly mixing the various components. As an example, the preparation method of the electrolyte includes the following steps: in an argon glove box, the solvent components are first mixed to form a homogeneous solvent system, and then a lithium salt electrolyte is slowly added to avoid local overheating and decomposition of the lithium salt; after complete dissolution, electrolyte additives are added and stirred; finally, the electrolyte is obtained by pressure filtration through a 0.2 μm PTFE filter membrane to remove trace particulate impurities.

[0146] [Septum]

[0147] In this invention, the separator is a commercially available separator for lithium-ion batteries that is well known to those skilled in the art; as an example, the separator is generally selected as a high porosity separator (typically 40% to 60%), and the separator includes a base film, a ceramic coating and a PVDF coating; wherein, the base film includes, but is not limited to, polyethylene (PE).

[0148] [Battery Assembly]

[0149] In this invention, the lithium-ion battery includes, but is not limited to, button cells, pouch cells, and cylindrical cells. A cylindrical cell is used as an example in this invention. The positive and negative electrode sheets are rolled and slit, then wound together with a separator according to a set process to form a 21700 cylindrical battery core. Subsequently, the battery core is fixed to a pre-made connecting piece by welding and then installed into a metal battery casing. After completing electrolyte injection, sealing, and formation processes, a cylindrical lithium-ion battery is obtained. The assembly of the cylindrical battery can also be performed using other conventional methods in the art, which will not be elaborated upon here.

[0150] In this invention, the preferred charging characteristics of the lithium-ion battery are as follows: after discharging the lithium-ion battery to 2.5V at 25°C and letting it stand for 6 hours, it is charged to 4.2V at constant current with charging rates of 1C and 6C, respectively. The corresponding constant current charging capacities are Q1 and Q6, wherein the charging capacity is maintained to satisfy Q6 / Q1≥85%.

[0151] In this invention, the lithium-ion battery exhibits a capacity decay rate of less than 10% after 1000 cycles at 25°C and a 1C rate.

[0152] According to a fourth aspect of the present invention, an electrical device is provided, comprising the lithium-ion battery described in the above-described technical solution. Thus, the electrical device possesses all the features and advantages of the lithium-ion battery described in the above-described technical solution, which will not be repeated here. Specifically, the lithium-ion battery can serve as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships and satellites, and energy storage systems.

[0153] In the context of this specification, including the following embodiments and comparative examples, tests were conducted as follows:

[0154] Preprocessing:

[0155] First, discharge the lithium-ion battery to a constant current of 2.5V to ensure it is in a safe state, reducing the risk of short circuits or thermal runaway during disassembly. Carefully disassemble the battery within a glove box (protected by argon or other inert atmosphere) and remove the negative electrode from the cylindrical cell. Use tweezers or suitable tools to peel off the electrode, avoiding damage to the active material layer. Next, cut the removed negative electrode to an appropriate size and soak it in anhydrous dimethyl carbonate (DMC) solution for 30 minutes to dissolve and remove residual electrolyte and possible byproducts. After removing the electrode, gently wipe the surface with lint-free paper, then replace with fresh DMC solution, repeating the soaking-wiping process three times to ensure no residual contaminants remain on the electrode surface. Subsequently, rinse the electrode with anhydrous ethanol and wipe again to further remove solvent and impurities. After cleaning, place the electrode in a glove box and let it stand for 48 hours to ensure it is completely dry, preventing interference from residual solvent in subsequent testing. After drying, the electrode sheets were subjected to subsequent compaction density and peel strength tests, and the copper foil was subjected to XRD tests.

[0156] X-ray diffraction (XRD) test:

[0157] A copper target X-ray diffractometer (Cu-Kα radiation) was used. With a tube voltage of 40kV and a tube current of 40mA, the current collector was uniformly dispersed on a silicon substrate, and XRD patterns were acquired at a scan rate of 2° / min within the range of 2θ = 10° to 80°.

[0158] Test method for compaction density of negative electrode sheet:

[0159] First, the negative electrode sheet, after being washed with dimethyl carbonate and vacuum dried, was cut into six standard-sized square samples (2.0cm × 2.0cm). Next, the active material on both sides of three of these square samples was removed, and they were rinsed with ethanol, dried, weighed, and their average mass M1 was calculated. Simultaneously, the average thickness L1 of the samples was measured using a micrometer. Then, the mass of the remaining three square samples was weighed, and their average mass M2 was calculated. The average thickness L2 of these samples was also measured. The electrode sheet thickness was calculated as L2 - L1 (in cm). The compaction density of the electrode sheet was also calculated.

[0160] Unit g / cm 3 .

[0161] Test method for peel strength of negative electrode sheet:

[0162] First, use double-sided tape to fix the strip sample onto a flat, thin steel plate, ensuring the tape is centered on the plate. Then, peel off the protective layer of the double-sided tape and attach the strip sample to be tested onto it. Use a pressure roller to evenly press the strip sample to ensure good adhesion. Next, tear off the unattached end, bend the torn end upwards, and clamp it in the upper fixture of a tensile testing machine for a 180° peel test. Record the tensile force curve. The segment where the tensile force changes by no more than 10% is selected as the stable peel segment. Finally, divide the average tensile force of this segment by the width of the strip sample electrode to calculate the peel strength of the negative electrode. Peel force tests are conducted on the front, middle, and rear segments of the electrode, and the obtained values ​​are recorded as N1, N2, and N3, respectively. Finally, the arithmetic mean of these values ​​is calculated to obtain the average peel force N of the actual tested negative electrode (N = (N1 + N2 + N3) / 3).

[0163] First-time effectiveness test method for button circuit:

[0164] In an argon-protected environment, the pre-lithiated negative electrode was assembled with a lithium metal sheet, electrolyte, and Celgard separator to form a CR2032 coin cell. After standing for 12 hours, the first constant current constant voltage charge-discharge test was conducted at 25°C within a 0.1C rate range (0.01–1.5V). The first charge-discharge capacity was recorded, and the initial coulombic efficiency was calculated using ICE = (first charge capacity / first discharge capacity) × 100%. All electrode operations must be performed in a glove box to avoid interference from oxygen and water.

[0165] Ratio performance testing method:

[0166] The lithium battery was discharged to 2.5V and placed in a 25℃ constant temperature chamber for 6 hours, and then tested according to the following steps:

[0167] (1) Under 1C conditions, constant current and constant voltage charging to 4.2V, cutoff current is 0.1C, and stand for 30 minutes. The capacity of constant current charging to 4.2V is Q1 (constant current segment capacity).

[0168] (2) Discharge under constant current at 1C until 2.5V cutoff, cutoff current is 0.1C, and let stand for 30 minutes.

[0169] (3) Under 6C conditions, constant current and constant voltage charging to 4.2V, cutoff current is 0.1C, and stand for 30 minutes. The capacity of constant current charging to 4.2V is Q6.

[0170] (4) Discharge under constant current at 1C until 2.5V cutoff, with a cutoff current of 0.1C, and let stand for 30 minutes.

[0171] The capacity retention rate of a lithium battery at 25℃ is calculated as: Q1 / Q6×100.

[0172] Cyclic performance testing methods:

[0173] Place the battery in a 25°C constant temperature chamber for 6 hours and test it according to the following steps:

[0174] (1) First round of constant current and constant voltage charging: Charge at a constant current of 0.1C to 4.2V, then switch to constant voltage charging until the current drops to 0.01C.

[0175] (2) Let it stand for 30 minutes after charging is complete.

[0176] (3) Perform constant current discharge, and discharge to 2.5V at a rate of 0.1C.

[0177] (4) Cyclic charge and discharge process: Charge at a constant current rate of 1C to 4.2V. Let stand for 30 minutes again. Discharge at a constant current rate of 1C to 2.5V.

[0178] (5) Repeat the above charging and discharging process for a total of 1000 cycles.

[0179] Statistical analysis of the battery discharge capacity Q1 and Q after 1 cycle and 1000 cycles. 1000 Calculate the battery capacity decay rate: (Q1-Q 1000 ) / Q1×100.

[0180] The present application will be described in detail below with reference to the accompanying drawings and embodiments. However, the implementation and protection of the present invention are not limited thereto. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0181] Example 1

[0182] 1. Method for manufacturing positive electrode plates:

[0183] Take the positive electrode active material (Li1Ni) 0.8 Co 0.1 Mn 0.1 O2), conductive carbon black, carbon nanotubes and polyvinylidene fluoride (PVDF) were thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 96:1:1:2 to obtain a positive electrode coating material. The positive electrode coating material was then coated onto a 12.0 μm thick aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.

[0184] 2. Method for manufacturing the negative electrode:

[0185] The negative electrode sheet comprises a three-layer composite PET-based Cu foil current collector (1.0 μm Cu@6.0 μm PET@1.0 μm Cu) and a negative electrode coating applied to both sides of the three-layer composite PET-based Cu foil current collector. The negative electrode coating comprises 20.0 wt% deposited silicon carbon, 76.0 wt% graphite (the mass ratio of deposited silicon carbon to graphite is 5:19), 1.5 wt% single-walled carbon nanotubes, 0.9 wt% sodium carboxymethyl cellulose (CMC), 0.8 wt% pre-sodiumized polyacrylic acid (Na-PAA), and 0.8 wt% styrene-butadiene rubber (SBR). These substances are added to deionized water and stirred to form a negative electrode coating slurry. This slurry is then coated onto both sides of the PET-based Cu foil current collector. After drying and cold pressing, the negative electrode sheet is formed with a compaction density of 1.55 g / cm³. 3 .

[0186] The preparation method of the three-layer composite PET-based Cu foil current collector:

[0187] (1) PET substrate surface pretreatment:

[0188] A 6.0 μm thick PET film was treated with a 30 wt% NaOH solution at room temperature for 5 min to initiate a hydrolysis reaction, introducing polar groups such as carboxyl (-COOH) and hydroxyl (-OH) groups onto the PET surface. The film was then thoroughly washed with deionized water until neutral and dried in a vacuum oven at 60 °C for 2 h to obtain a surface-activated PET substrate.

[0189] (2) Upper and lower copper (1.0μm) magnetron sputtering deposition:

[0190] The surface-activated PET substrate was fixed on a stage within a vacuum chamber, and copper film deposition was performed using a DC or RF magnetron sputtering system in a pure argon (Ar, 99.9%) atmosphere. The vacuum base pressure was maintained at <5 × 10⁻⁶. - 4 The working pressure was approximately 1.0 Pa, and the sputtering power was controlled at 300 W. Using a copper target with a purity ≥99.99%, a 1.0 μm thick Cu layer was obtained on one side of a rotating substrate at a uniform deposition rate (approximately 100 nm / min). The same method was used to deposit the same layer on the other side of the PET substrate. After deposition, the sample was cooled to room temperature and removed, resulting in the Cu@PET@Cu current collector.

[0191] (3) Post-processing:

[0192] The Cu@PET@Cu current collector prepared above was placed in a UV ozone catalytic oxidation device and irradiated for 10 minutes under the conditions of ozone concentration of 30ppm and temperature of 25℃. In this way, O2 in the air is induced to be converted into O3 by high-energy UV and decomposed to form active oxygen atoms. These active oxygens can react with carbon-containing small molecules on the copper surface (a very small part of PET decomposes and releases monomers adsorbed on the copper surface during magnetron sputtering deposition) to generate polar oxygen-containing functional groups such as Cu=O, carboxyl (-COOH) and carbonyl (C=O).

[0193] 3. Method for pre-lithiation of negative electrode:

[0194] The dried and shaped negative electrode sheet was immersed in a 1.5M concentration of Li-naphthalene 2-methyltetrahydrofuran (2-MTHF) pre-lithiation solution and allowed to stand at room temperature for 5 minutes. This allowed lithium ions in the Li-naphthalene complex to be released through chemical reduction and permeate to the electrode surface, reacting with silicon-carbon active particles and interfacial functional groups to pre-construct a partial SEI layer and compensate for the initial lithium loss. Immediately after pre-lithiation, the electrode sheet was removed and rapidly rinsed three times with anhydrous 2-MTHF to remove residual solution. It was then dried in a vacuum drying oven at 60°C for 2 hours to obtain the pre-lithiated silicon-carbon negative electrode.

[0195] 4. Preparation of electrolyte:

[0196] An electrolyte was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC) in a mass percentage ratio of 16.0:22.0:52.0:5.0:5.0.

[0197] 5. Diaphragm:

[0198] A high-porosity membrane is selected, in which the thickness of the PE base membrane is 9μm, the thickness of the ceramic coating on both sides of the base membrane is 1.0μm, and the thickness of the PVDF coating is 1.0μm.

[0199] 6. Assembly of lithium-ion batteries:

[0200] After the positive and negative electrode sheets are rolled and slit, they are wound together with the separator according to a set process to form a 21700 cylindrical battery core. Subsequently, the battery core is fixed to a pre-made connecting piece by welding and then installed into a metal battery casing. After completing key processes such as electrolyte injection, sealing, and formation, the lithium-ion battery described in Example 1 is obtained. This lithium-ion battery uses a cylindrical casing with an external dimension of 21.0 mm in diameter and 70.0 mm in length, conforming to the 21700 standard specification.

[0201] Example 2

[0202] The method of Example 1 was followed, except that the concentration of the Li-naphthalene 2-methyltetrahydrofuran solution immersed in the negative electrode sheet was 0.5M; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peeling force of the negative electrode sheet, the first coin cell efficiency, the capacity retention rate at 6C charging, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0203] Example 3

[0204] The method of Example 1 was followed, except that the concentration of the Li-naphthalene 2-methyltetrahydrofuran solution immersed in the negative electrode sheet was 1.0 M; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peeling force of the negative electrode sheet, the first coin cell efficiency, the capacity retention rate at 6C charging, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0205] Example 4

[0206] The method of Example 1 was followed, except that the concentration of the 2-methyltetrahydrofuran solution of Li-naphthalene immersed in the negative electrode was 1.8M; the negative electrode and the corresponding lithium-ion battery were finally prepared. The peeling force of the negative electrode, the first coin cell efficiency, the capacity retention rate at 6C charging, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0207] Example 5

[0208] The method of Example 1 was followed, except that the concentration of the 2-methyltetrahydrofuran solution of Li-naphthalene immersed in the negative electrode was 2.0 M; the negative electrode and the corresponding lithium-ion battery were finally prepared. The peeling force of the negative electrode, the first coin cell efficiency, the capacity retention rate at 6C charging, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0209] Example 6

[0210] The method of Example 1 was followed, except that the FEC content in the electrolyte was 0.5 wt% and the DMC content was 56.5 wt%; the negative electrode and the corresponding lithium-ion battery were finally prepared. The negative electrode peeling force, first coin cell efficiency, 6C charging capacity retention rate, and capacity decay rate after 1000 cycles are shown in Table 1.

[0211] Example 7

[0212] The method of Example 1 was followed, except that the FEC content in the electrolyte was 2.0 wt% and the DMC content was 55.0 wt%. The negative electrode and the corresponding lithium-ion battery were finally prepared. The negative electrode peeling force, first-time coin cell efficiency, 6C charging capacity retention rate, and capacity decay rate after 1000 cycles are shown in Table 1.

[0213] Example 8

[0214] The method of Example 1 was followed, except that the FEC content in the electrolyte was 7.5 wt% and the DMC content was 49.5 wt%. The negative electrode and the corresponding lithium-ion battery were finally prepared. The negative electrode peeling force, first-time coin cell efficiency, 6C charging capacity retention rate, and capacity decay rate after 1000 cycles are shown in Table 1.

[0215] Example 9

[0216] The method of Example 1 was followed, except that the FEC content in the electrolyte was 10.0 wt% and the DMC content was 47.0 wt%. The negative electrode and the corresponding lithium-ion battery were finally prepared. The negative electrode peeling force, first-time coin cell efficiency, 6C charging capacity retention rate, and capacity decay rate after 1000 cycles are shown in Table 1.

[0217] Example 10

[0218] The method of Example 1 was followed, except that the Cu@PET@Cu current collector was irradiated in a UV ozone catalytic oxidation device for 2.0 min; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peeling force of the negative electrode sheet, the first coin cell efficiency, the capacity retention rate at 6C charging, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0219] Example 11

[0220] The method of Example 1 was followed, except that the Cu@PET@Cu current collector was irradiated in a UV ozone catalytic oxidation device for 5.0 min; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peeling force of the negative electrode sheet, the first coin cell efficiency, the 6C charging capacity retention rate, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0221] Example 12

[0222] The method of Example 1 was followed, except that the Cu@PET@Cu current collector was irradiated in a UV ozone catalytic oxidation device for 15.0 min; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peeling force of the negative electrode sheet, the first coin cell efficiency, the 6C charging capacity retention rate, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0223] Example 13

[0224] The method of Example 1 was followed, except that the Cu@PET@Cu current collector was irradiated in a UV ozone catalytic oxidation device for 20.0 min; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peeling force of the negative electrode sheet, the first coin cell efficiency, the 6C charging capacity retention rate, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0225] Example 14

[0226] The method of Example 1 was followed, except that the binder in the negative electrode coating consisted of 0.9 wt% CMC, 1.2 wt% Na-PAA, and 0.4 wt% SBR; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peel force of the negative electrode sheet, the first coin cell efficiency, the capacity retention rate at 6C charging, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0227] Example 15

[0228] The method of Example 1 was followed, except that the binder in the negative electrode coating consisted of 0.9 wt% CMC, 1.0 wt% Na-PAA, and 0.6 wt% SBR; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peel force of the negative electrode sheet, the first coin cell efficiency, the 6C charging capacity retention rate, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0229] Example 16

[0230] The method of Example 1 was followed, except that the binder in the negative electrode coating consisted of 0.9 wt% CMC, 0.6 wt% Na-PAA, and 1.0 wt% SBR; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peel force of the negative electrode sheet, the first coin cell efficiency, the 6C charge capacity retention rate, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0231] Example 17

[0232] The method of Example 1 was followed, except that the binder in the negative electrode coating consisted of 0.9 wt% CMC, 0.4 wt% Na-PAA, and 1.2 wt% SBR; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peel strength of the negative electrode sheet, the first coin cell efficiency, the 6C charge capacity retention rate, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0233] Example 18

[0234] The method is the same as in Example 1, except that the compaction of the negative electrode sheet is 1.45 g / cm³. 3 The negative electrode and the corresponding lithium-ion battery were finally prepared. The negative electrode peeling force, first coin cell efficiency, 6C charging capacity retention rate, and capacity decay rate after 1000 cycles are shown in Table 1.

[0235] Example 19

[0236] The method is the same as in Example 1, except that the compaction of the negative electrode sheet is 1.65 g / cm³. 3 The negative electrode and the corresponding lithium-ion battery were finally prepared. The negative electrode peeling force, first coin cell efficiency, 6C charging capacity retention rate, and capacity decay rate after 1000 cycles are shown in Table 1.

[0237] Example 20

[0238] The method of Example 1 was followed, except that the binder in the negative electrode coating consisted of 0.9 wt% CMC and 1.6 wt% SBR; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peel force of the negative electrode sheet, the first coin cell efficiency, the capacity retention rate at 6C charging, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0239] Example 21

[0240] The method of Example 1 was followed, except that the binder in the negative electrode coating consisted of 0.9 wt% CMC and 1.6 wt% polystyrene-acrylic acid; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The peel force of the negative electrode sheet, the first coin cell efficiency, the 6C charge capacity retention rate, and the capacity decay rate after 1000 cycles are shown in Table 1.

[0241] Example 22

[0242] The method of Example 1 was followed, except that the negative electrode was immersed in a 1.5M Li-phenanthrene 2-methyltetrahydrofuran (2-MTHF) pre-lithiation solution; the negative electrode and the corresponding lithium-ion battery were finally prepared. The negative electrode peeling force, first coin cell efficiency, 6C charging capacity retention rate, and 1000-cycle capacity decay rate are shown in Table 1.

[0243] Example 23

[0244] The method of Example 1 was followed, except that the negative electrode sheet was immersed in a 1.5M concentration of Li-anthracene 2-methyltetrahydrofuran (2-MTHF) pre-lithiation solution; the negative electrode sheet and the corresponding lithium-ion battery were finally prepared. The negative electrode sheet peel strength, coin cell first efficiency, 6C charging capacity retention rate, and 1000-cycle capacity decay rate are shown in Table 1.

[0245] Example 24

[0246] The method of Example 1 was followed, except that the negative electrode was immersed in a 1.5M concentration of 2-methyltetrahydrofuran (2-MTHF) pre-lithiation solution; the negative electrode and the corresponding lithium-ion battery were finally prepared. The negative electrode peeling force, first coin cell efficiency, 6C charging capacity retention rate, and 1000-cycle capacity decay rate are shown in Table 1.

[0247] Comparative Example 1

[0248] Following the method of Example 1, the difference between this comparative example and Example 1 is that the negative electrode sheet is not immersed in a Li-naphthalene 2-methyltetrahydrofuran solution; the negative electrode sheet and the corresponding lithium-ion battery are finally prepared. The negative electrode sheet peeling force, coin cell first efficiency, 6C charging capacity retention rate, and 1000-cycle capacity decay rate are shown in Table 1.

[0249] Comparative Example 2

[0250] The difference between this comparative example and Example 1 is that the Cu@PET@Cu current collector is not treated with a UV ozone catalytic oxidation device; the negative electrode sheet and the corresponding lithium-ion battery are finally prepared according to the method of Example 1. The negative electrode sheet peeling force, coin cell first efficiency, 6C charging capacity retention rate, and 1000-cycle capacity decay rate are shown in Table 1.

[0251] Comparative Example 3

[0252] The difference between this comparative example and Example 1, following the method of Example 1, is that the compaction density of the negative electrode sheet is 1.75 g / cm³. 3 The negative electrode and the corresponding lithium-ion battery were finally prepared. The negative electrode peeling force, first coin cell efficiency, 6C charging capacity retention rate, and capacity decay rate after 1000 cycles are shown in Table 1.

[0253] Table 1. Performance results of negative electrode sheets and lithium-ion batteries in the examples and comparative examples.

[0254]

[0255]

[0256] As can be seen from the test results of Examples 1 to 24 and Comparative Examples 1 to 3, the negative electrode sheet provided by the present invention enables the lithium-ion battery to maintain structural stability and excellent electrochemical performance under high rate and long cycle conditions: the first coin cell efficiency is 86% to 99%, the 6C charging capacity retention rate is 85% to 95%, and the capacity decay rate after 1000 cycles is 4% to 10%. The reason for this success is that the present invention employs a synergistic design scheme for a high-silicon-graphite anode that integrates chemical pre-lithiation, functional additive-assisted interface modification, a plastic metal foil current collector, and a composite binder system. By systematically controlling the Si / C mass ratio of the anode active material in the anode coating, the composition and proportion of the binder, the relevant technical characteristics of the polyethylene terephthalate (PET)-based plastic Cu foil, the type and concentration of the pre-lithiation agent in the pre-lithiation layer, and the type and amount of additives in the electrolyte of the lithium-ion battery, a better overall interaction is achieved at both the anode electrode level and the lithium-ion battery level. This significantly improves the first-cycle coulombic efficiency, fast-charging capability, and cycle stability of the anode. This synergistic optimization scheme significantly improves the comprehensive performance of lithium-ion batteries under high-rate charge-discharge and long-cycle conditions, achieving a multiple balance between high specific capacity, fast-charging capability, and long cycle life of the silicon-containing anode, and has good prospects for commercial application.

[0257] Specifically:

[0258] Comparing Examples 1 to 5 (the study of the effect of Li-naphthalene solution concentration on lithium-ion battery performance in this application), it is evident that as the concentration of pre-lithiated Li-naphthalene gradually increases from 0.5M to 1.5M, the first-cycle coulombic efficiency significantly improves, increasing from 86% to 96%; the 6C rate retention rate increases from 85% to 90%, cycle stability is enhanced, and the capacity decay rate after 1000 cycles decreases from 7.8% to 5%. Simultaneously, the peeling force slightly decreases but remains at a good level. This trend is attributed to the fact that at appropriate concentrations, Li-naphthalene can precisely compensate for the amount of lithium required for SEI formation, constructing a stable and dense LiF / Li2CO3-rich interface film on the silicon-carbon surface, reducing lithium loss, and improving interface stability and Li... + Diffusion efficiency. When the concentration is further increased to 1.8M and above, the Li reduction reaction rate is too fast, which may lead to uneven lithium metal precipitation or an excessively thick SEI structure on the electrode surface. This results in the destruction of the bonding interface and an increase in resistance, which in turn reduces the peel strength and induces performance fluctuations in the later stages of cycling. This exhibits a typical pre-lithiation overcompensation phenomenon, which in turn leads to a decrease in the kinetic performance and cycle performance of the lithium battery.

[0259] According to the data from Examples 1, 6 to 9 (the investigation of the effect of FEC concentration on lithium-ion battery performance in this application), as the FEC addition amount increases from 0.5 wt% to 5.0 wt%, the first-cycle efficiency (CEE) significantly increases from 88% to 96%; the 6C rate retention rate increases from 86% to 91%; and the capacity decay rate decreases from 8.7% to 5.3%. The peel strength decreases slightly but remains within a reasonable range. This performance improvement is attributed to the preferential decomposition of appropriate amounts of FEC during the first charge to form a dense, uniform, LiF-rich artificial SEI, which possesses excellent chemical stability and ion conductivity, significantly suppressing electrolyte side reactions and active particle pulverization. Further increasing the FEC to 7.5 wt% to 10.0 wt%, although the CEE does not change significantly, excessive SEI growth restricts ion diffusion, resulting in non-uniform electron / ion channels, which in turn leads to a decline in rate performance and cycle stability, and causes a decrease in binder wettability, manifested as a significant drop in peel strength. This indicates that the optimal addition window for FEC is 5.0 wt%.

[0260] According to Examples 1, 10-13 (the investigation of the effect of O3 treatment on the performance of copper current collectors on lithium-ion batteries in this application), as the O3 treatment time increased from 2 min to 10 min, the electrode peeling force increased from 15.4 N / cm to 20.5 N / cm, the initial efficiency increased to 96.5%, and the 6C retention rate and cycle decay performance also improved simultaneously. This trend is attributed to the fact that O3 oxidation treatment can introduce high-density C=O and COC polar functional groups on the PET-Cu foil surface, enhancing the interfacial bonding between the binder and the current collector, improving adhesion strength and electrolyte wettability, and contributing to interfacial ion exchange and electron continuity. When the treatment time exceeds 10 min, the PET surface may undergo peroxidation and structural aging, while the Cu layer becomes rough or oxidized, resulting in discontinuous interfacial contact, decreased adhesion, and uneven electrochemical reaction, ultimately causing capacity decline at high rates and poor cycle consistency.

[0261] According to Examples 1, 14 to 17 (the study on the effect of the ratio of binder SBR to Na-PAA on the performance of lithium-ion batteries in this application), as the mass ratio of SBR to Na-PAA is adjusted from 3:1 to 1:1, the electrode peeling force gradually increases to 20.5 N / cm, the first-cycle coulombic efficiency significantly improves to 96.5%, and the 6C rate retention rate and 1000-cycle degradation rate also improve to 91.0% and 5.0%, respectively. This improvement stems from the fact that at the 1:1 ratio, SBR provides stronger flexible buffering and wettability, while Na-PAA, rich in carboxyl groups, can form chemical bonds with the -OH / oxide layer on the surface of Si / C particles and construct a good Li-C composite. +The conductive network and the two work together to construct a highly stable "bonding-transmission" dual-network structure. When the ratio deviates further from 1:1, the binder system becomes unbalanced. Too much SBR leads to strong adhesion but insufficient bonding stability; too much Na-PAA causes electrode embrittlement and increased breakage of the adhesive layer, ultimately impairing interface integrity and reducing cycle stability.

[0262] According to the data from Examples 1, 18, and 19 (examination of the effect of electrode compaction density on lithium-ion battery performance in this application), it can be seen that as the electrode compaction density increases from 1.45 g / cm³, the performance of lithium-ion batteries increases. 3 Gradually increase to 1.55 g / cm³ 3 The active particles are in close contact, increasing the electrode peel strength and enhancing the compaction of the conductive network. Simultaneously, the moderate porosity facilitates thorough electrolyte wetting and uniform SEI formation, reducing interfacial resistance and significantly improving the first-cycle coulombic efficiency and fast-charging capacity retention. Furthermore, moderate compaction (1.55 g / cm³) further enhances the performance. 3 It can also improve the overall mechanical rigidity of the electrode and enhance the binding capacity of the binder network, thereby effectively improving peel strength and reducing long-cycle capacity decay. However, when the compaction density continues to increase to 1.65 g / cm³, 3 When the porosity of the electrode is too low, the electrolyte cannot fully penetrate, the ion diffusion path is restricted, and a "lithium-poor zone" is formed at the local interface, resulting in uneven SEI and fatigue accumulation in the electrode structure. This manifests as a decrease in rate performance and cycle stability, a sharp drop in peeling force, and exhibits typical "over-compaction failure" characteristics.

[0263] Based on the results of Examples 1, 20, and 21 (the evaluation of the performance of lithium-ion batteries using the binder system in this application), Example 1 (CMC+SBR+Na-PAA) is slightly superior to Examples 20 (CMC+SBR) and 21 (CMC+polystyrene-acrylic acid) in terms of peel strength, first-time efficiency, rate performance, and cycle stability. Analysis shows that the pre-sodium-modified polyacrylic acid (Na-PAA) in Example 1 contains a high proportion of carboxyl functional groups, which enhances the interfacial forces between the binder, active material, and current collector, improving the stability and adhesion of the electrode structure. Simultaneously, Na-PAA, CMC, and SBR synergistically form a flexible and continuous conductive-ion network, buffering silicon expansion and inducing stable SEI film formation, thus more effectively suppressing capacity decay and achieving high first-time efficiency, high rate capacity retention, and excellent long-cycle stability. The experimental data in the table show that the batteries prepared in Examples 20 and 21 also meet the objectives of this invention in terms of peel strength, first-time efficiency, rate performance, and cycle stability.

[0264] Based on the data from Examples 1, 20-24 (an examination of the impact of different pre-lithiation agents on lithium-ion battery performance in this application), it is evident that different pre-lithiation agent systems have a certain impact on the performance of the negative electrode. Example 1, using Li-naphthalene as the pre-lithiation agent, showed the best performance, with superior peel strength, first-time efficiency, rate performance, and cycle stability compared to other systems. Analysis reveals that Li-naphthalene possesses a high reduction potential and strong electron donor capability, enabling it to quickly and fully pre-embed lithium uniformly into the negative electrode material, forming a stable SEI film, improving first-time efficiency, and mitigating lithium consumption and structural damage during cycling. When the pre-lithiation agent was replaced with that of Example 22 (Li-phenanthrene), Example 23 (Li-anthracene), or Example 24 (Li-tetrahydrofuran), the lithium replenishment efficiency and interface stability were slightly weaker than those of Example 1 (Li-naphthalene), resulting in a slight decrease in capacity retention and cycle life. However, the batteries prepared in Examples 22-24 all met the objectives of this invention.

[0265] Analysis of the tabular data from Example 1 and Comparative Examples 1 to 3 shows that Example 1 significantly outperforms the three comparative examples in terms of peel strength, first-efficiency performance, rate performance, and cycle stability, indicating that its comprehensive optimization effect of pre-lithiation treatment, UV / O3 treatment, and suitable compaction density is significant. Comparative Example 1, lacking pre-lithiation treatment, resulted in a large initial irreversible capacity and a significant decrease in first-efficiency, while insufficient lithium source during cycling exacerbated capacity decay. Comparative Example 2, lacking UV / O3 treatment, had a lack of polar oxygen-containing functional groups on the Cu@PET@Cu current collector surface, making it difficult for the binder to adhere firmly, resulting in the lowest peel strength and poor interface stability. Comparative Example 3 had an excessively high compaction density (1.75 g / cm³). 3 This restricts ion diffusion channels and results in insufficient structural buffering capacity, leading to decreased rate performance and increased cycle decay. The above results indicate that synergistic optimization of pre-lithiation, current collector surface polarity modification, and appropriate compaction density is key to achieving high-performance silicon-based anodes.

[0266] In summary, this invention achieves comprehensive optimization of silicon-carbon anodes from structural construction to interface stability, ion transport capability, and mechanical properties by systematically controlling key parameters such as the type and concentration of pre-lithiation agent, the amount of fluoroethylene carbonate added, the O3 treatment time of Cu@PET@Cu foil, the mass ratio and system selection of binder, and the electrode compaction density. This results in a high-silicon anode system with high initial efficiency, low attenuation, and excellent fast-charging performance, exhibiting significant technical advantages such as structural stability, strong interface bonding, and feasible processes.

[0267] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0268] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0269] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0270] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A negative electrode sheet, characterized in that, It includes a negative electrode current collector, a negative electrode coating disposed on at least one side surface of the negative electrode current collector, and a pre-lithiation layer disposed on at least a portion of the surface of the negative electrode coating; The negative electrode current collector includes a substrate and metal foils laminated on both sides of the substrate. The substrate includes at least one of polyethylene terephthalate, polyethylene naphthalate, polyimide, polyethylene, and polypropylene. The metal foils include at least one of copper foil, nickel foil, stainless steel foil, tin foil, and indium foil. The negative electrode coating includes a negative electrode active material and a binder; the pre-lithiation layer includes a pre-lithiation agent.

2. The negative electrode sheet according to claim 1, characterized in that, The substrate includes polyethylene terephthalate; the metal foil includes copper foil; the X-ray diffraction pattern of the negative electrode current collector shows characteristic peaks at 24–28.5°, 43.5–45.0°, 49.5–51.5° and 73.5–76.0°. And / or, the thickness of the substrate is 4 μm to 8.5 μm; And / or, the thickness of the metal foil is 0.5 μm to 2.5 μm.

3. The negative electrode sheet according to claim 1, characterized in that, The negative electrode active material includes a first negative electrode active material and a second negative electrode active material; the first negative electrode active material includes at least one of artificial graphite, natural graphite, soft carbon, and hard carbon, and the second negative electrode active material includes at least one of deposited silicon carbon and crystalline silicon; the mass ratio of the first negative electrode active material to the second negative electrode active material is (3-19):

1. And / or, the mass of the negative electrode active material accounts for 95% to 99% of the mass of the negative electrode coating.

4. The negative electrode sheet according to claim 1, characterized in that, The adhesive comprises a first adhesive and a second adhesive; the first adhesive comprises sodium carboxymethyl cellulose; the second adhesive comprises at least one of polyacrylonitrile, polystyrene-acrylic acid, styrene-butadiene rubber, polyacrylic acid, and pre-sodium-modified polyacrylic acid; the mass ratio of the first adhesive and the second adhesive is (1-4):4; And / or, the mass of the binder accounts for 0.5% to 5% of the mass of the negative electrode coating.

5. The negative electrode sheet according to claim 1, characterized in that, The pre-lithiation agent includes at least one of Li-naphthalene, Li-phenanthrene, Li-anthracene, and Li-tetrahydrofuran complex.

6. A method for preparing a negative electrode sheet according to any one of claims 1 to 5, characterized in that, Includes the following steps: a) After activating both sides of the substrate, metal deposition is performed, followed by surface oxidation to obtain the negative electrode current collector; b) The negative electrode current collector obtained in step a) is coated with a negative electrode coating slurry on at least one side surface, and then cured and pressed to form a negative electrode coating. The negative electrode coating is then brought into contact with a pre-lithiation solution to form a pre-lithiation layer on at least a portion of the surface of the negative electrode coating. The negative electrode is then washed and dried to obtain a negative electrode sheet.

7. The method for preparing the negative electrode sheet according to claim 6, characterized in that, The preparation method satisfies at least one of the following characteristics (1) to (9): (1) The process of activating the surfaces on both sides of the substrate as described in step a) Includes the following steps: At room temperature, the substrate is contacted with a 20wt% to 40wt% strong alkaline solution and reacted for 2 to 10 minutes; the reacted substrate is then cleaned until neutral and vacuum dried at 40℃ to 100℃ for 1 to 4 hours to obtain a substrate with activated surfaces on both sides. (2) The metal deposition described in step a) includes metal film deposition using magnetron sputtering technology; (3) The surface oxidation described in step a) includes ultraviolet light irradiation for 2 min to 20 min in the presence of ozone; (4) The negative electrode current collector described in step a) has a tensile strength ≥280MPa and an elongation at break of 6.0% to 18.0% under the condition of a tensile rate of 50±0.5mm / min; (5) The negative electrode coating slurry mentioned in step b) includes negative electrode active material, binder, conductive agent and solvent; (6) The compaction density described in step b) is 1.40 g / cm³. 3 ~1.65g / cm 3 ; (7) The negative electrode coating and the negative electrode current collector described in step b) satisfy the following: 10.2 N / m ≤ peel strength ≤ 21.0 N / m; (8) The pre-lithiation solution in step b) includes a pre-lithiation agent, the concentration of which is 0.5M to 2M; (9) The contact time described in step b) is 2 min to 10 min.

8. A lithium-ion battery, characterized in that, It includes a negative electrode, a positive electrode, a separator, and an electrolyte; the negative electrode includes the negative electrode as described in any one of claims 1 to 5 or the negative electrode prepared by the preparation method described in any one of claims 6 to 7.

9. The lithium-ion battery according to claim 8, characterized in that, The electrolyte includes functional additives; the functional additives include fluorinated carbonate additives; the fluorinated carbonate additives account for 0.5% to 10% of the mass of the electrolyte.

10. An electrical device, characterized in that, Includes the lithium-ion battery as described in any one of claims 8 to 9.

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