Negative electrode current collector and preparation method therefor, negative electrode sheet, and battery

Abstract

The present invention provides a negative electrode current collector and a preparation method therefor, a negative electrode sheet, and a battery. The preparation method for the negative electrode current collector comprises: providing a substrate, the substrate having a first surface and a second surface that are substantially parallel; depositing a first lithiophilic layer on the first surface; depositing a second lithiophilic layer on the second surface; depositing a first induction layer on the first lithiophilic layer; and depositing a second induction layer on the second lithiophilic layer, wherein the first induction layer and the second induction layer are configured to induce lithium ions to form SEI films. In the present invention, by providing lithiophilic layers (i.e., a first lithiophilic layer and a second lithiophilic layer) on two sides of a substrate, a current collector can have a low nucleation overpotential, inducing uniform deposition of lithium ions. In addition, by depositing induction layers (i.e., a first induction layer and a second induction layer) on the surfaces of the lithiophilic layers, formation of SEI films having relatively high mechanical strength can be guided, reducing repeated regeneration of the SEI films and improving the electrochemical performance of a battery.

Description

A negative electrode current collector and its preparation method, a negative electrode sheet, and a battery.

[0001] This application is based on and claims priority to Chinese application CN application number 202411838929.1 filed on December 13, 2024, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] This disclosure relates to the field of battery technology, and more specifically, to a negative electrode current collector and its preparation method, a negative electrode sheet, and a battery. Background Technology

[0003] Lithium-ion batteries are currently one of the dominant energy storage devices on the market, boasting advantages such as high energy density, long cycle life, no memory effect, low self-discharge rate, and a wide operating temperature range. With the rapid popularization of electronic devices such as mobile phones, laptops, and tablets, and the vigorous development of electric vehicles and hybrid vehicles, the demand for lithium-ion batteries is constantly increasing. With the rapid development of the new energy industry, lithium-ion batteries, as one of the main methods of electrochemical energy storage, are developing rapidly. The market is placing higher demands on lithium-ion batteries, with increasing energy density being a primary focus. To improve the energy density and reduce the weight of lithium-ion batteries, current collectors are key auxiliary materials, primarily responsible for carrying the active material and collecting the current generated by the active material for output.

[0004] Currently, lithium-ion batteries typically use copper foil as the negative electrode. With the increasing demand for high-performance energy storage technologies in modern society, especially the development of electric vehicles and portable electronic devices, the demand for high-energy-density rechargeable batteries has increased significantly. However, the theoretical specific capacity of commercially available graphite negative electrodes is only 372 mAh / g, severely restricting the improvement of lithium-ion battery energy density. Therefore, researchers have proposed the concept of a negative electrode-free lithium battery. A negative electrode-free lithium metal battery is simply a special configuration of lithium metal batteries; it does not truly lack a negative electrode. In actual operation, the negative electrode is still lithium metal. A negative electrode-free lithium metal battery consists of a bare negative electrode current collector (usually copper) and a lithiated positive electrode. During battery charging, lithium ions are extracted from the positive electrode and deposited on the copper current collector, forming a lithium negative electrode. During subsequent battery discharge, the deposited lithium metal dissolves and is reinserted into the positive electrode. The weight and thickness of a negative electrode-free lithium battery are significantly reduced, which can greatly improve the battery's energy density, while also simplifying the manufacturing process and reducing costs.

[0005] However, due to the lack of stable host material protection or compensation from excess active lithium at the negative electrode, "dead lithium" is easily generated during battery cycling, leading to irreversible loss of lithium resources and thus capacity loss. Furthermore, because lithium metal has an extremely low redox potential, most organic solvents react chemically on the surface of the lithium negative electrode to generate many unstable chemical substances. These substances cannot passivate the surface of the lithium negative electrode, increasing the resistance to lithium-ion transport and consuming more solvent and electrolyte, resulting in irreversible capacity loss and reduced coulombic efficiency. Finally, the problem of lithium dendrite growth persists, which may lead to puncture of the separator, causing short circuits, fires, or even explosions. Summary of the Invention

[0006] The purpose of this disclosure is to provide a negative electrode current collector and its preparation method, a negative electrode sheet, and a battery, which can solve at least one of the aforementioned technical problems. The specific solution is as follows:

[0007] According to specific embodiments of this disclosure, in one aspect, this disclosure provides a method for preparing a negative electrode current collector, comprising: providing a substrate having a generally parallel first surface and a second surface; depositing a first lithiophilic layer on the surface of the first surface; depositing a second lithiophilic layer on the surface of the second surface; depositing a first induction layer on the surface of the first lithiophilic layer; and depositing a second induction layer on the surface of the second lithiophilic layer; wherein the first induction layer and the second induction layer are configured to induce lithium ions to form an SEI film.

[0008] In an optional embodiment, depositing the first lithiophilic layer on the surface of the first side includes: assembling the substrate in a vacuum evaporation apparatus; placing copper in an evaporation boat; introducing oxygen into the vacuum evaporation apparatus; heating the evaporation boat to react the oxygen and copper at a temperature greater than 1000°C to generate Cu2O, which is then deposited on the first side of the substrate to form the first lithiophilic layer.

[0009] In an optional embodiment, depositing a second lithiophilic layer on the second surface includes: assembling the substrate with the first lithiophilic layer in a vacuum evaporation apparatus; placing copper in an evaporation boat; introducing oxygen into the vacuum evaporation apparatus; heating the evaporation boat to react the oxygen and copper at a temperature greater than 1000°C to generate Cu2O, which is then deposited on the second surface of the substrate to form the second lithiophilic layer.

[0010] In an optional embodiment, depositing the first inducing layer on the surface of the first lithiophilic layer includes: evaporating Li2SiO3 on the surface of the first lithiophilic layer to form the first inducing layer.

[0011] In an optional embodiment, depositing the second inducing layer on the surface of the second lithiophilic layer includes: evaporating Li2SiO3 on the surface of the second lithiophilic layer to form the second inducing layer.

[0012] In an alternative embodiment, the oxygen introduction rate is 1-30 sccm.

[0013] In one alternative embodiment, the oxygen introduction time is 1-300 seconds.

[0014] In one alternative embodiment, the heating time inside the evaporation boat is 5-20 minutes.

[0015] In an optional embodiment, the reaction time for reacting the oxygen and the copper at a temperature greater than 1000°C to generate Cu2O is 1-300 s.

[0016] In one alternative embodiment, the copper is at least one of copper wire, copper granules, copper blocks, and copper powder.

[0017] In a preferred embodiment, the copper is copper granules, and the diameter of the copper granules is less than or equal to 6 mm.

[0018] In an optional embodiment, the substrate is made of copper or a composite copper foil.

[0019] In an alternative embodiment, the thickness of the first lithiophilic layer is 100-5000 nm.

[0020] In one alternative embodiment, the thickness of the second lithiophilic layer is 100-5000 nm.

[0021] In an alternative embodiment, the thickness of the first inducing layer is 10-500 nm.

[0022] In one alternative embodiment, the thickness of the second inducing layer is 10-500 nm.

[0023] In an optional embodiment, the first lithiophilic layer is made of Cu2O.

[0024] In one optional embodiment, the second lithiophilic layer is made of Cu2O;

[0025] In an optional embodiment, the Li2SiO3 raw material used for evaporating Li2SiO3 onto the surface of the first lithiophilic layer is Li2SiO3 powder.

[0026] In an optional embodiment, the vacuum degree within the vacuum evaporation equipment during the Li2SiO3 evaporation process is greater than 10. -3 Pa, the evaporation rate of the evaporated Li2SiO3 is

[0027] According to a specific embodiment of the present disclosure, in another aspect, the present disclosure provides a negative electrode current collector, which is prepared by adopting the preparation method of the negative electrode current collector as described in any of the above technical solutions.

[0028] According to a specific embodiment of the present disclosure, in another aspect, the present disclosure provides a negative electrode sheet, including a negative current collector as described in any of the above technical solutions.

[0029] According to a specific embodiment of the present disclosure, in another aspect, the present disclosure provides a lithium-ion battery, including at least two electrodes that are cross-laminated and have opposite polarities, with a separator disposed between two adjacent electrodes, and at least one of the electrodes being a negative electrode as described in any of the above technical solutions.

[0030] Compared with the prior art, the above-described solutions of this disclosure have at least the following beneficial effects:

[0031] This disclosure enables the current collector to have a lower nucleation overpotential by providing a lithiophilic layer (i.e., a first lithiophilic layer and a second lithiophilic layer) on both sides of the substrate, thereby inducing uniform lithium-ion deposition. In addition, by depositing an induction layer (i.e., a first induction layer and a second induction layer) on the surface of the lithiophilic layer, it can guide the formation of an SEI film with high mechanical strength, reduce the repeated regeneration of the SEI film, and improve the electrochemical performance of the battery. Attached Figure Description

[0032] Figure 1 shows a flowchart of a method for preparing a negative electrode current collector according to an embodiment of the present disclosure.

[0033] Figure 2 shows a flowchart of step S200 according to an embodiment of the present disclosure.

[0034] Figure 3 shows a flowchart of step S300 according to an embodiment of the present disclosure.

[0035] Figure 4 shows a flowchart of a method for preparing a negative electrode current collector according to another embodiment of the present disclosure.

[0036] Figure 5 shows a schematic diagram of the negative electrode current collector according to an embodiment of the present disclosure.

[0037] Reference numerals: 100: substrate; 210: first lithiophilic layer; 220: second lithiophilic layer; 310: first inducing layer; 320: second inducing layer. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this disclosure clearer, the disclosure will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0039] The terminology used in the embodiments of this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The singular forms “a,” “the,” and “the” as used in the embodiments of this disclosure and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0040] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0041] It should be understood that although the terms first, second, third, etc., may be used to describe structures in the embodiments of this disclosure, these structures should not be limited to these terms. These terms are only used to distinguish different structures. For example, without departing from the scope of the embodiments of this disclosure, a first component may also be referred to as a second component, and similarly, a second component may also be referred to as a first component.

[0042] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0043] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0044] In related technologies, "negative electrode-less" lithium batteries suffer from capacity loss due to the lack of stable host material protection or compensation from excess active lithium at the negative electrode, leading to the formation of "dead lithium" during cycling. Furthermore, because lithium metal has an extremely low redox potential, most organic solvents react chemically on the lithium negative electrode surface to generate many unstable chemical substances. These substances cannot passivate the lithium negative electrode surface, increasing resistance to lithium-ion transport and consuming more solvent and electrolyte, resulting in irreversible capacity loss and reduced coulombic efficiency. Finally, the problem of lithium dendrite growth persists, potentially causing the separator to be punctured, leading to short circuits, fires, or even explosions.

[0045] The main solutions to this problem are: 1. By adjusting the composition of the electrolyte, reducing side reactions between the electrolyte and lithium metal, and further suppressing lithium dendrite growth. 2. Surface modification of the current collector: through structural design on the substrate surface, more uniform sites can be provided for lithium ion deposition / stripping, effectively improving the cycle stability of the negative electrode. 3. Coating the substrate surface with a layer of ion-conducting polymer and framework material, achieving rapid lithium ion conduction and uniform deposition.

[0046] While related technologies can promote uniform lithium deposition, inhibit lithium dendrite growth, and improve battery performance, they are either based on alloying reactions, which result in large volume changes during cycling and make it difficult to maintain a stable interface, or they involve surface coating modification of copper foil, which results in insufficient stability.

[0047] To address at least one of the aforementioned technical problems, this disclosure provides a negative electrode current collector and its preparation method, a negative electrode sheet, and a battery. The preparation method of the negative electrode current collector includes: providing a substrate 100, the substrate 100 having a generally parallel first surface and a second surface; depositing a first lithiophilic layer 210 on the surface of the first surface; depositing a second lithiophilic layer 220 on the surface of the second surface; depositing a first induction layer 310 on the surface of the first lithiophilic layer 210; and depositing a second induction layer 320 on the surface of the second lithiophilic layer 220; wherein the first induction layer 310 and the second induction layer 320 are present. The negative electrode current collector prepared by the preparation method of this disclosure forms a lithiophilic layer on the surface of the substrate 100, and an induction layer on the surface of the lithiophilic layer. An SEI film (solid electrolyte interface film) is a thin film naturally formed on the electrode surface during the charging and discharging process of a lithium-ion battery. Its main function is to prevent direct contact between the electrode and the electrolyte, thereby protecting the electrode material and ensuring the safe and stable operation of the battery. The SEI film possesses ionic conductivity, allowing lithium ions to shuttle freely but preventing electrons from passing through, making it a crucial component of lithium-ion batteries. The formation mechanism of the SEI film involves the reaction of organic or inorganic substances in the electrolyte with the negative electrode material, resulting in deposition on the negative electrode surface. The reaction that forms the SEI film releases a significant amount of heat, potentially leading to thermal runaway at high temperatures. The SEI film formation process also results in lithium ion loss from the electrolyte, increasing the battery's irreversible capacity. Therefore, this invention discloses a method for forming a mechanically stronger SEI film on the negative electrode current collector, preventing the reaction of organic or inorganic substances in the electrolyte with the negative electrode material and their deposition on the negative electrode surface, thereby preventing lithium ion loss and eliminating the heat generated during the real-time formation of the SEI film.

[0048] The optional embodiments of this disclosure are described in detail below with reference to the accompanying drawings.

[0049] Figure 1 shows a flowchart of a method for preparing a negative electrode current collector according to an embodiment of the present disclosure. As shown in Figure 1, according to a specific embodiment of the present disclosure, in one aspect, a method for preparing a negative electrode current collector is provided, the method for preparing the negative electrode current collector including at least the following steps:

[0050] S100, Provide a substrate 100 having a generally parallel first surface and a second surface.

[0051] S200, deposit a first lithiophilic layer 210 on the surface of the first surface.

[0052] S300, deposit a second lithiophilic layer 220 on the surface of the second surface.

[0053] S400, deposit a first induction layer 310 on the surface of the first lithiophilic layer 210.

[0054] S500, deposit a second induction layer 320 on the surface of the second lithiophilic layer 220.

[0055] The first induction layer 310 and the second induction layer 320 are configured to induce lithium ions to form an SEI film. This disclosure, by providing lithiophilic layers (i.e., the first lithiophilic layer 210 and the second lithiophilic layer 220) on both sides of the substrate 100, can give the current collector a lower nucleation overpotential, induce uniform lithium ion deposition, and avoid the growth of lithium dendrites. Furthermore, by depositing induction layers (i.e., the first induction layer 310 and the second induction layer 320) on the surface of the lithiophilic layers, the inductive effect of Li2SiO3 is utilized to form a high-mechanical-strength SEI film on the negative electrode current collector, reducing repeated regeneration of the SEI film and improving the cycle performance of the battery.

[0056] In step S100, the substrate 100 is made of copper or composite copper foil.

[0057] Figure 2 shows a flowchart of step S200 according to an embodiment of the present disclosure. As shown in Figure 2, step S200 includes:

[0058] S210. The substrate 100 is assembled in a vacuum evaporation equipment.

[0059] S220. Place the copper into the evaporation boat.

[0060] S230. Introduce oxygen into the vacuum evaporation equipment.

[0061] S240. The evaporation boat is heated so that the oxygen and copper react at a temperature greater than 1000°C to generate Cu2O, which is then deposited on the first side of the substrate 100 to form the first lithiophilic layer 210.

[0062] It should be noted that, in addition to the vacuum in-situ reaction in steps S210-S240, the first lithiophilic layer 210 can also be formed by magnetron sputtering, vacuum evaporation or other methods to deposit a layer of Cu2O on the surface of the first surface.

[0063] In step S210, the substrate 100 may be made of copper or composite copper foil.

[0064] In step S220, in an optional embodiment, the copper is at least one of copper wire, copper granules, copper blocks, and copper powder. In a preferred embodiment, the copper may be copper granules. In a preferred embodiment, the diameter of the copper granules is less than or equal to 6 mm. In another optional embodiment, the evaporation boat may be a crucible.

[0065] In step S230, in one optional embodiment, the oxygen introduction rate is 1-30 sccm. In another optional embodiment, the reaction time for reacting the oxygen and copper at a temperature greater than 1000°C to generate Cu2O is 1-300 s.

[0066] In step S240, in one optional embodiment, the copper inside the evaporation boat is heated using resistance heating. In another optional embodiment, an auxiliary heating lamp is used while heating the evaporation boat. In yet another optional embodiment, the evaporation rate is... In another alternative embodiment, the heating temperature of the heat lamp is 50-200°C.

[0067] Figure 3 shows a flowchart of step S300 according to an embodiment of the present disclosure. As shown in Figure 3, step S300 includes:

[0068] S310, The substrate 100 with the first lithiophilic layer 210 is assembled in a vacuum evaporation apparatus.

[0069] S320. Place the copper into the evaporation boat.

[0070] S330. Introduce oxygen into the vacuum evaporation equipment.

[0071] S340. The evaporation boat is heated so that the oxygen and copper react at a temperature greater than 1000°C to generate Cu2O, which is then deposited on the second side of the substrate 100 to form the second lithiophilic layer 220.

[0072] It should be noted that, in addition to the vacuum in-situ reaction in steps S310-S340, the second lithiophilic layer 220 can also be formed by magnetron sputtering, vacuum evaporation or other methods to deposit a layer of Cu2O on the surface of the first surface.

[0073] In step S310, the substrate 100 may be made of copper or composite copper foil.

[0074] In step S320, in one optional embodiment, the copper may be copper granules. In another optional embodiment, the evaporation boat may be a crucible.

[0075] In step S330, in one optional embodiment, the oxygen introduction rate is 1-30 sccm. In another optional embodiment, the reaction time for reacting the oxygen and copper at a temperature greater than 1000°C to generate Cu2O is 1-300 s.

[0076] In step S340, in one optional embodiment, the copper inside the evaporation boat is heated using resistance heating. In another optional embodiment, an auxiliary heating lamp is used while heating the evaporation boat. In yet another optional embodiment, the evaporation rate is... In another alternative embodiment, the heating temperature of the heat lamp is 50-200°C.

[0077] Figure 4 shows a flowchart of a method for preparing a negative electrode current collector according to another embodiment of the present disclosure. As shown in Figure 4, step S400 includes:

[0078] S410, Li2SiO3 is vapor-deposited on the surface of the first lithiophilic layer 210 to form the first induction layer 310.

[0079] In step S410, in an optional embodiment, the vacuum degree inside the vacuum evaporation equipment during the evaporation process is greater than 10. -3 Pa. In another alternative embodiment, the evaporation rate is...

[0080] In step S500, step S500 includes:

[0081] S510. Li2SiO3 is vapor-deposited on the surface of the second lithiophilic layer 220 to form the second induction layer 320.

[0082] In step S510, in an optional embodiment, the vacuum degree within the vacuum evaporation equipment during the evaporation process is greater than 10. -3 Pa. In another alternative embodiment, the evaporation rate is...

[0083] In some embodiments, depositing a first lithiophilic layer 210 on the surface of the first side includes: assembling the substrate 100 in a vacuum evaporation apparatus; placing copper in an evaporation boat; introducing oxygen into the vacuum evaporation apparatus; heating the evaporation boat to react the oxygen and copper at a temperature greater than 1000°C to generate Cu2O, which is then deposited onto the first side of the substrate 100 to form the first lithiophilic layer 210. In an optional embodiment, depositing a second lithiophilic layer 220 on the surface of the second side includes: assembling the substrate 100 with the first lithiophilic layer 210 in a vacuum evaporation apparatus; placing copper in an evaporation boat; introducing oxygen into the vacuum evaporation apparatus; heating the evaporation boat to react the oxygen and copper at a temperature greater than 1000°C to generate Cu2O, which is then deposited onto the second side of the substrate 100 to form the second lithiophilic layer 220. The vacuum evaporation method facilitates industrial mass production of the first lithiophilic layer 210 and the second lithiophilic layer 220.

[0084] In some embodiments, depositing the first inducing layer 310 on the surface of the first lithiophilic layer 210 includes: vapor-depositing Li₂SiO₃ on the surface of the first lithiophilic layer 210 to form the first inducing layer 310. In an optional embodiment, depositing the second inducing layer 320 on the surface of the second lithiophilic layer 220 includes: vapor-depositing Li₂SiO₃ on the surface of the second lithiophilic layer 220 to form the second inducing layer 320. The first inducing layer 310 and the second inducing layer 320 are fabricated using vacuum vapor deposition, which facilitates industrial mass production.

[0085] In some embodiments, the oxygen introduction rate is 1-30 sccm. In an optional embodiment, the oxygen introduction time is 1-300 s. In an optional embodiment, the heating time inside the evaporation boat is 5-20 min. In an optional embodiment, the reaction time for reacting the oxygen and the copper at a temperature greater than 1000°C to generate Cu2O is 1-300 s. In an optional embodiment, the copper is at least one of copper wire, copper granules, copper blocks, and copper powder; the copper is preferably copper granules with a diameter of less than or equal to 6 mm.

[0086] In some embodiments, the substrate 100 is made of copper or a composite copper foil.

[0087] In some embodiments, the thickness of the first lithiophilic layer 210 is 100-5000 nm. In an optional embodiment, the thickness of the second lithiophilic layer 220 is 100-5000 nm. In a preferred embodiment, the thickness of the first lithiophilic layer 210 is 2000 nm. In another preferred embodiment, the thickness of the second lithiophilic layer 220 is 2000 nm.

[0088] In some embodiments, the thickness of the first inducing layer 310 is 10-500 nm. In an optional embodiment, the thickness of the second inducing layer 320 is 10-500 nm. In a preferred embodiment, the thickness of the first inducing layer 310 is 100 nm. In another preferred embodiment, the thickness of the second inducing layer 320 is 100 nm.

[0089] In some embodiments, the Li2SiO3 raw material used for depositing Li2SiO3 on the surface of the first lithiophilic layer is Li2SiO3 powder. In an optional embodiment, the vacuum degree in the vacuum evaporation equipment during the Li2SiO3 deposition is greater than 10. -3 Pa, the evaporation rate of the evaporated Li2SiO3 is

[0090] Example 1

[0091] 1. Take a 10cm*10cm copper foil, attach it to the base plate, and assemble it in the vacuum evaporation equipment.

[0092] 2. Place copper particles in a crucible, introduce O2 into a vacuum evaporation device, and evaporate Cu using resistance evaporation. Turn on the baking lamp to allow O2 and Cu to react at high temperature to form a Cu2O layer (i.e., the first lithiophilic layer 210) on the first surface. The thickness of Cu2O is controlled to be 2μm by a crystal oscillator.

[0093] 3. Repeat step 2 to generate the same Cu2O layer (i.e., the second lithiophilic layer 220) on the second surface.

[0094] 4. Replace the electron gun evaporation source, control the vacuum level and evaporation rate to deposit a Li2SiO3 layer (i.e. the first induction layer 310) on the surface of Cu2O (the first lithiophilic layer 210), and control the thickness of Li2SiO3 to 100nm through a crystal oscillator.

[0095] 5. Repeat step 4 to generate the same Li2SiO3 layer (i.e. the second induction layer 320) on the second lithiophilic layer 220 to obtain the negative electrode current collector 1.

[0096] Example 2

[0097] 1. Take a 10cm*10cm copper foil, attach it to the base plate, and assemble it in the vacuum evaporation equipment.

[0098] 2. Place copper granules with a diameter of 4 mm into a crucible. In a vacuum evaporation apparatus, introduce O2 at a flow rate of 20 sccm. Evaporate Cu using resistance evaporation. The evaporation rate of Cu is... Turn on the heating lamp, which is set to 150°C, so that O2 and Cu react at high temperature to form a Cu2O layer (i.e., the first lithiophilic layer 210) on the first surface. The thickness of Cu2O is controlled to be 2μm by a crystal oscillator.

[0099] 3. Repeat step 2 to generate the same Cu2O layer (i.e., the second lithiophilic layer 220) on the second surface.

[0100] 4. Replace the electron gun evaporation source with Li2SiO3 powder, and control the vacuum level to be greater than 10. -3 Pa, evaporation rate is A Li2SiO3 layer (i.e., the first induction layer 310) is deposited on the surface of Cu2O (the first lithiophilic layer 210), and the thickness of Li2SiO3 is controlled to be 100nm by a crystal oscillator.

[0101] 5. Repeat step 4 to generate the same Li2SiO3 layer (i.e. the second induction layer 320) on the second lithiophilic layer 220 to obtain the negative electrode current collector 2.

[0102] Example 3

[0103] In this embodiment, the thickness of both Cu2O layers is 100 nm, and the other parameters are the same as in Example 1, resulting in negative electrode current collector 3.

[0104] Example 4

[0105] In this embodiment, the thickness of both Li2SiO3 layers is 500nm, and the other parameters are the same as in Example 1, resulting in negative electrode current collector 4.

[0106] Comparative Example 1

[0107] This embodiment uses pure copper foil without any surface treatment, resulting in Comparative Sample 1.

[0108] Comparative Example 2

[0109] In this embodiment, Cu2O layers are applied to both sides of the copper foil surface. The preparation method is the same as steps 1, 2 and 3 in Example 1, resulting in comparative sample 2.

[0110] Comparative Example 3

[0111] In this embodiment, Li2SiO3 layers are applied to both sides of the copper foil surface. The preparation method is the same as steps 4 and 5 in Example 1, resulting in comparative sample 3.

[0112] Comparative Example 4

[0113] In this embodiment, the evaporation rate of Cu is controlled to be... The oxygen flow rate is 50 sccm; the evaporation rate of Li₂SiO₃ is controlled at... Vacuum degree less than 10 -3 Pa; other parameters are the same as in Example 1, and comparative sample 4 is obtained.

[0114] Manufacturing button batteries:

[0115] 1. The positive electrode uses NCM811 material as the active material, and the negative electrode uses the copper foil with the composite structure prepared above, wherein the diameter of the negative electrode is 14 mm, the diameter of the positive electrode is 12 mm, and the diameter of the separator is 16 mm.

[0116] 2. The electrolyte used is 1 mmol / L LiPF6 (lithium hexafluorophosphate), with a solvent ratio of EC (ethylene carbonate): DEC (diethyl carbonate): EMC (methyl ethyl carbonate) = 1:1:1

[0117] 3. Assemble the CR2032 battery in the following order: negative electrode shell - negative electrode - separator - positive electrode - gasket - spring contact - positive electrode shell.

[0118] Negative electrode current collector 1, negative electrode current collector 2, negative electrode current collector 3 and negative electrode current collector 4 are respectively prepared according to steps 1-3 of the button cell preparation process to obtain corresponding battery 1, battery 2, battery 3 and battery 4.

[0119] Comparative samples 1, 2, 3, and 4 were used to prepare corresponding batteries 5, 6, 7, and 8, respectively, following steps 1-3 of button battery preparation.

[0120] The performance of batteries 1-6 was tested, and the data is shown in the table below:

[0121] Based on the results from button cells, when there are no Cu2O lithiophilic layers and no Li2SiO3 layers, the nucleation overpotential of pure copper foil is the highest, and the cycle retention rate is the lowest. If there is only a Cu2O layer and no Li2SiO3 layer, the nucleation overpotential can be reduced, but because the quality of the SEI film cannot be guaranteed, the cycle retention rate will also decrease. When the Cu2O layer is too thin, its ability to guide uniform lithium deposition is limited, and the reduction in overpotential is also limited. When the Li2SiO3 layer is too thick, it will increase the internal resistance of the battery, affect the conduction of lithium ions, and be detrimental to the cycle.

[0122] As can be seen from battery 8, in the preparation method of the negative electrode current collector provided in this disclosure, Cu2O and Li2SiO3 are evaporated at rates not specified in this disclosure. Simultaneously, the oxygen flow rate is increased and the vacuum degree is decreased. The resulting negative electrode current collector (comparative sample 4) has CuO impurities in its Cu2O layer. Furthermore, the Cu2O and Li2SiO3 layers are not deposited uniformly. Consequently, the performance of the prepared battery is slightly worse than that of batteries 1, 2, 3, and 4, but slightly better than that of batteries 5, 6, and 7 in related technologies. Therefore, even with slightly lower quality due to unfavorable preparation conditions, the negative electrode current collector prepared by the method of this disclosure still exhibits slightly better internal resistance and cycle performance than those in related technologies. This demonstrates the significant advantages of the preparation method disclosed in this disclosure.

[0123] As can be seen from battery 2, in the preparation method of the negative electrode current collector provided in this disclosure, by controlling the evaporation rate of Cu2O and Li2SiO3, using copper particles and Li2SiO3 powder, and finely adjusting the heating temperature of the target material by adjusting the heating temperature of the baking lamp, the quality of the prepared negative electrode current collector is better, resulting in a battery with lower internal resistance and better cycle performance.

[0124] Figure 5 shows a schematic diagram of the negative electrode current collector according to one embodiment of the present disclosure. As shown in Figure 5, according to a specific embodiment of the present disclosure, another aspect provides a negative electrode current collector prepared by the method described in any of the above embodiments. The negative electrode current collector of the present disclosure introduces a lithiophilic Cu2O layer on the surface of the substrate 100, and forms an induction layer, namely a Li2SiO3 layer, on the surface of the lithiophilic layer; this enables uniform deposition of lithium metal and facilitates the formation of a high-mechanical-strength SEI film, thereby improving the cycle life of the lithium-free negative electrode battery.

[0125] According to a specific embodiment of this disclosure, in another aspect, a negative electrode sheet is provided, including a negative current collector as described in any of the above embodiments.

[0126] According to a specific embodiment of this disclosure, in another aspect, a lithium-ion battery is provided, comprising at least two electrodes that are cross-laminated and have opposite polarities, with a separator disposed between two adjacent electrodes, and at least one of the electrodes being a negative electrode as described in any of the above embodiments.

[0127] This disclosure aims to protect a negative electrode current collector and its preparation method, a negative electrode sheet, and a battery. The preparation method of the negative electrode current collector includes: providing a substrate 100, the substrate 100 having a generally parallel first surface and a second surface; depositing a first lithiophilic layer 210 on the surface of the first surface; depositing a second lithiophilic layer 220 on the surface of the second surface; depositing a first induction layer 310 on the surface of the first lithiophilic layer 210; and depositing a second induction layer 320 on the surface of the second lithiophilic layer 220; wherein the first induction layer 310 and the second induction layer 320 are configured to induce lithium ions to form an SEI film. The negative electrode current collector prepared by the preparation method of this disclosure forms a lithiophilic layer on the surface of the substrate 100, and an induction layer is formed on the surface of the lithiophilic layer. The SEI film (solid electrolyte interphase film) is a thin film that naturally forms on the electrode surface during the charging and discharging process of a lithium-ion battery. Its main function is to prevent the electrode from directly contacting the electrolyte, thereby protecting the electrode material and ensuring the safe and stable operation of the battery. The SEI film possesses ionic conductivity, allowing lithium ions to shuttle freely but preventing electrons from passing through, making it a crucial component of lithium-ion batteries. The formation mechanism of the SEI film involves the reaction of organic or inorganic substances in the electrolyte with the negative electrode material, resulting in deposition on the negative electrode surface. The reaction that forms the SEI film releases a significant amount of heat, potentially leading to thermal runaway at high temperatures. The SEI film formation process also results in lithium ion loss from the electrolyte, increasing the battery's irreversible capacity. Therefore, this invention discloses a method for forming a mechanically stronger SEI film on the negative electrode current collector, preventing the reaction of organic or inorganic substances in the electrolyte with the negative electrode material and their deposition on the negative electrode surface, thereby preventing lithium ion loss and eliminating the heat generated during the real-time formation of the SEI film. This disclosure provides a lithium-loving layer (i.e., a first lithium-loving layer 210 and a second lithium-loving layer 220) on both sides of the substrate 100, which can enable the current collector to have a lower nucleation overpotential and induce uniform lithium-ion deposition. In addition, by depositing an induction layer (i.e., a first induction layer 310 and a second induction layer 320) on the surface of the lithium-loving layer, it can guide the formation of an SEI film with high mechanical strength, reduce the repeated regeneration of the SEI film, and improve the electrochemical performance of the battery.

[0128] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0129] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit it. Although this disclosure 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. Such 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 this disclosure.

Claims

1. A method for preparing a negative electrode current collector, characterized in that, include: A substrate is provided, the substrate having a generally parallel first surface and a second surface; A first lithiophilic layer is deposited on the surface of the first surface; A second lithiophilic layer is deposited on the surface of the second surface; A first induction layer is deposited on the surface of the first lithiophilic layer; A second induction layer is deposited on the surface of the second lithiophilic layer; The first induction layer and the second induction layer are configured to induce lithium ions to form an SEI film.

2. The method for preparing the negative electrode current collector according to claim 1, characterized in that, The deposition of the first lithiophilic layer on the surface of the first side includes: assembling the substrate in a vacuum evaporation apparatus; placing copper in an evaporation boat; introducing oxygen into the vacuum evaporation apparatus; heating the evaporation boat to react the oxygen and copper at a temperature greater than 1000°C to generate Cu2O, which is then deposited on the first side of the substrate to form the first lithiophilic layer. The deposition of the second lithiophilic layer on the second surface includes: assembling the substrate with the first lithiophilic layer in a vacuum evaporation apparatus; placing copper in an evaporation boat; introducing oxygen into the vacuum evaporation apparatus; heating the evaporation boat to react the oxygen and copper at a temperature greater than 1000°C to generate Cu2O, which is then deposited on the second surface of the substrate to form the second lithiophilic layer.

3. The method for preparing the negative electrode current collector according to claim 1, characterized in that, The deposition of the first inducing layer on the surface of the first lithiophilic layer includes: depositing Li2SiO3 on the surface of the first lithiophilic layer to form the first inducing layer; The deposition of the second inducing layer on the surface of the second lithiophilic layer includes: depositing Li2SiO3 on the surface of the second lithiophilic layer to form the second inducing layer.

4. The method for preparing the negative electrode current collector according to claim 2, characterized in that, The rate at which oxygen is introduced is 1-30 sccm; The oxygen introduction time is 1-300 seconds; The heating time inside the evaporation boat is 5-20 minutes; The reaction time for reacting the oxygen and copper at a temperature greater than 1000°C to produce Cu2O is 1-300 seconds. The copper is at least one of copper wire, copper granules, copper blocks, and copper powder; the copper is preferably copper granules, and the diameter of the copper granules is less than or equal to 6 mm.

5. The method for preparing the negative electrode current collector according to claim 1, characterized in that, The substrate is made of copper or composite copper foil.

6. The method for preparing the negative electrode current collector according to claim 1, characterized in that, The thickness of the first lithiophilic layer is 100-5000 nm; The thickness of the second lithiophilic layer is 100-5000 nm; The thickness of the first inducing layer is 10-500 nm; The thickness of the second inducing layer is 10-500 nm.

7. The method for preparing the negative electrode current collector according to claim 3, characterized in that, The Li2SiO3 raw material used for evaporating Li2SiO3 on the surface of the first lithiophilic layer is Li2SiO3 powder; The vacuum degree in the vacuum evaporation equipment during the Li2SiO3 evaporation process is greater than 10. -3 Pa, the evaporation rate of the evaporated Li2SiO3 is 8. A negative electrode current collector, characterized in that, Prepared by the method for preparing the negative electrode current collector as described in any one of claims 1-7.

9. A negative electrode sheet, characterized in that, Includes the negative electrode current collector as described in claim 8.

10. A lithium-ion battery, characterized in that, It includes at least two electrodes that are cross-laminated and have opposite polarities, with a diaphragm disposed between two adjacent electrodes, and at least one of the electrodes is a negative electrode as described in claim 9.

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