Negative current collector, battery and electrical equipment

Abstract

This application relates to a negative electrode current collector, a battery, and an electrical device. The application provides a negative electrode current collector comprising: a substrate, a conductive layer, and a sodium storage layer. The conductive layer is located on the surface of the substrate. The sodium storage layer and the conductive layer are disposed on the same side of the substrate, and the sodium storage layer surrounds at least a portion of the outer periphery of the conductive layer. Along the thickness direction of the negative electrode current collector, the thickness of the sodium storage layer is greater than the thickness of the conductive layer.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a negative electrode current collector, a battery, and an electrical device. Background Technology

[0002] During the charging and discharging process of a battery, there are often problems such as frequent expansion and contraction of the battery thickness and accumulation of metal dendrites in the overhang area of ​​the negative electrode. Dendrites may puncture the separator and cause safety issues. Therefore, it is necessary to improve the current collector of the negative electrode to mitigate the problems of frequent expansion and contraction of the battery during charging and discharging and accumulation of metal dendrites in the overhang area of ​​the negative electrode.

[0003] The overhang region of the negative electrode refers to the area where the negative electrode extends beyond the positive electrode. Summary of the Invention

[0004] In view of this, this application provides a negative electrode current collector, a battery, and an electrical device. The negative electrode current collector can slow down the growth of metal dendrites, and when the negative electrode current collector is applied to a battery, the battery has better safety performance.

[0005] This application provides a negative electrode current collector, which includes: a substrate, a conductive layer, and a sodium storage layer. The conductive layer is located on the surface of the substrate. The sodium storage layer and the conductive layer are disposed on the same side of the substrate, and the sodium storage layer is disposed around at least a portion of the outer periphery of the conductive layer. Along the thickness direction of the negative electrode current collector, the thickness of the sodium storage layer is greater than the thickness of the conductive layer.

[0006] Further, the conductive layer includes a first carbon material and a second carbon material, wherein the first carbon material is a one-dimensional material and the second carbon material is a non-one-dimensional material; the conductive layer satisfies at least one of the following conditions: in the conductive layer, the mass percentage a1 of the first carbon material is in the range of 50% ≤ a1 ≤ 95%; and in the conductive layer, the mass percentage a2 of the second carbon material is in the range of 0% < a2 ≤ 45%.

[0007] Furthermore, the first carbon material includes at least one of carbon nanotubes, carbon nanorods, and carbon fibers; the second carbon material includes at least one of fullerenes, carbon quantum dots, carbon black, graphene, graphyne, carbon nanosheets, graphite, hard carbon, soft carbon, carbon aerogel, and glassy carbon.

[0008] Furthermore, the sodium storage layer includes a sodium storage carbon material, which includes at least one of graphene, graphyne, carbon nanosheets, graphite, hard carbon, soft carbon, carbon aerogel, and glassy carbon.

[0009] Furthermore, the sodium storage capacity of the sodium-storing carbon material is greater than or equal to 200 mAh / g.

[0010] Furthermore, the sodium storage layer also includes a third carbon material, which is a one-dimensional material and includes at least one of carbon nanotubes, carbon nanorods, and carbon fibers.

[0011] Furthermore, the sodium storage layer satisfies at least one of the following conditions: in the sodium storage layer, the mass percentage a3 of the sodium storage carbon material is in the range of 50% ≤ a3 ≤ 90%; and in the sodium storage layer, the mass percentage a4 of the third carbon material is in the range of 5% ≤ a4 ≤ 40%.

[0012] Furthermore, the thickness d1 of the conductive layer is in the range of 0.1μm≤d1≤100μm.

[0013] Furthermore, if the thickness of the sodium storage layer is d2, then the negative electrode current collector satisfies the following relationship: and satisfies the relationship 0. <d2-d1≤50μm。

[0014] This application provides a battery comprising: a positive electrode, a separator, a negative electrode current collector provided in this application, and an electrolyte. The separator is disposed on one side of the positive electrode. The sodium storage layer of the negative electrode current collector is stacked on the positive projection of the separator and partially offset from the positive projection of the positive electrode in the separator.

[0015] Furthermore, the specific capacity of the positive electrode sheet is C, the theoretical volumetric specific capacity of sodium metal is Q, the thickness of the conductive layer is d1, and the thickness of the sodium storage layer is d2. Then the battery satisfies the relationship: 0 < d2 - d1 ≤ 1.5 × C / Q.

[0016] Furthermore, along the preset direction, the width of the positive electrode plate projected onto the sodium storage layer is L1, and the width of the sodium storage layer is L2, which satisfies the relationship: 0 < L2 / L1 ≤ 1; where the preset direction is the arrangement direction of the conductive layer and the sodium storage layer.

[0017] This application provides an electrical device, which includes: a device body and a battery provided in this application, wherein the battery supplies power to the device body.

[0018] In this application, the sodium storage layer and the conductive layer are disposed on the same side of the substrate, and the sodium storage layer is disposed around at least a portion of the outer periphery of the conductive layer. The thickness of the sodium storage layer is greater than the thickness of the conductive layer. Thus, the sodium storage layer and the conductive layer cooperate to form a sodium metal deposition region. When the negative electrode current collector is applied to the battery and the battery is charging, sodium ions are transported to the negative electrode current collector side and deposited as sodium metal on the surface of the conductive layer away from the substrate. In other words, sodium metal is deposited in the sodium metal deposition region. Similarly, when the battery is discharging, the sodium metal is converted into sodium ions and stripped from the negative electrode current collector side, thus reducing the amount of sodium metal located in the sodium metal deposition region. By setting the sodium metal deposition region, the thickness of the negative electrode current collector remains essentially constant during the charging and discharging process of the battery. This avoids repeated increases or decreases in the battery thickness, thereby maintaining the bonding performance between the negative electrode current collector and the separator, mitigating the increase in the battery's interface impedance, and effectively mitigating the problem of local dendrite formation. Furthermore, when the negative electrode current collector is applied to a battery, the sodium storage layer is positioned closer to the edge region of the positive electrode plate. In other words, the overhang region of the negative electrode current collector is located within the sodium storage layer. Compared to the conductive layer, the sodium storage layer has better sodium storage performance and better sodium affinity. The sodium storage layer can provide uniform nucleation sites for the deposition and stripping of sodium metal. Sodium ions can enter and deposit within the sodium storage layer, thereby mitigating the problem of severe dendrite growth in the overhang region of the negative electrode current collector and improving the safety performance of the battery when the negative electrode current collector is applied to the battery. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the implementation will be briefly introduced below. Obviously, the drawings described below are some implementations of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application;

[0021] Figure 2 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application;

[0022] Figure 3 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application;

[0023] Figure 4 This is a cross-sectional structural diagram of a negative electrode current collector according to an embodiment of this application;

[0024] Figure 5This is a schematic diagram illustrating the interaction between the negative electrode current collector and other components when applied to a battery according to an embodiment of this application.

[0025] Figure 6 This is a cross-sectional structural diagram of a battery according to an embodiment of this application;

[0026] Figure 7 This is a schematic diagram of the structure of an electrical device according to an embodiment of this application;

[0027] Figure 8 This is a circuit block diagram of an electrical device according to an embodiment of this application.

[0028] Explanation of reference numerals in the attached figures:

[0029] 100-Negative current collector, 110-Substrate, 120-Conductive layer, 130-Sodium storage layer, 140-Sodium metal deposition area, 200-Battery, 210-Positive electrode sheet, 220-Separator, 230-Electrolyte, 300-Electrical equipment, 310-Equipment body, 400-Energy storage system, 410-First power conversion device, 420-First user load, 430-Second user load, 440-Energy storage device, 450-High voltage cable, 460-Second power conversion device, 470-Energy storage cabinet, 480-Photovoltaic-storage-charging station, 490-Automobile. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0031] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0032] In this document, references to "embodiment" or "implementation" mean that a particular feature, structure, or characteristic described in connection with an embodiment or implementation may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0033] During battery charging and discharging, issues such as frequent expansion and contraction of battery thickness and metal dendrite accumulation in the overhang region of the negative electrode are common. The reasons are as follows: During charging and discharging, alkali metal ions repeatedly deposit or peel off from the negative electrode side, causing repeated increases and decreases in battery thickness. This leads to a deterioration in the interfacial bonding performance between the negative electrode and the separator, resulting in increased interfacial impedance and localized dendrite formation. Secondly, due to differences in local pressure, ion concentration, and electric field distribution, the risk of metal dendrite formation in the overhang region of the negative electrode side, opposite the edge of the positive electrode, is high. Furthermore, dendrites accumulate continuously during cycling, potentially piercing the separator and causing safety issues. Therefore, improvements to the negative electrode current collector are needed to mitigate the problems of frequent expansion and contraction of the battery during charging and discharging, as well as the accumulation of metal dendrites in the overhang region of the negative electrode.

[0034] The overhang region of the negative electrode refers to the area where the negative electrode extends beyond the positive electrode.

[0035] Because the energy we need is highly time- and space-dependent, in order to utilize energy rationally and improve energy efficiency, it is necessary to store one form of energy in the same way or by converting it into another, and then release it in a specific energy form for future applications. Currently, the main way to generate green electricity is to develop green energy sources such as photovoltaics and wind power to replace fossil fuels.

[0036] Currently, the generation of green electricity generally relies on solar, wind, and hydropower. However, wind and solar power are generally characterized by strong intermittency and large fluctuations, which can cause grid instability, insufficient power during peak demand periods, and excessive power during off-peak periods. Unstable voltage can also damage the power grid. Therefore, insufficient electricity demand or insufficient grid capacity may lead to the problem of "wind and solar curtailment." Solving these problems requires energy storage. This involves converting electrical energy into other forms of energy through physical or chemical means and storing it. When needed, this energy can be converted back into electrical energy and released. Simply put, energy storage is like a large "power bank," storing electrical energy when solar and wind power are abundant and releasing the stored electricity when needed.

[0037] Taking electrochemical energy storage as an example, this solution provides an energy storage device 440, which is applied to an energy storage system 400. The energy storage device 440 is equipped with a set of chemical batteries, which mainly use the chemical elements in the battery 200 as the energy storage medium. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage medium. Simply put, the electrical energy generated by wind and solar energy is stored in the chemical battery. When the use of external electrical energy reaches its peak, the stored electrical energy is released for use, or transferred to places with a shortage of electricity for use.

[0038] Current energy storage applications are quite widespread, including generation-side energy storage, grid-side energy storage, and consumption-side energy storage. The corresponding types of energy storage devices 440 include:

[0039] (1) Large-scale energy storage power stations applied to wind power and photovoltaic power stations can help renewable energy power generation meet grid connection requirements and improve the utilization rate of renewable energy. As a high-quality active / reactive power regulation power source on the power supply side, energy storage power stations can achieve load matching of power in time and space, enhance the absorption capacity of renewable energy, reduce instantaneous power changes, reduce the impact on the power grid, improve the absorption of new energy power generation, and are of great significance in power grid system backup, alleviating peak load power supply pressure and peak regulation and frequency regulation.

[0040] (2) Energy storage containers applied on the grid side mainly function as peak shaving, frequency regulation and grid congestion relief. In terms of peak shaving, they can achieve peak shaving and valley filling of electricity load, that is, charging the energy storage battery when the electricity load is low and releasing the stored electricity during the peak electricity load period, thereby achieving a balance between power production and consumption.

[0041] (3) Small energy storage cabinets applied to the electricity consumption side mainly function as self-consumption of electricity, peak-valley price arbitrage, capacity cost management, and improvement of power supply reliability. Depending on the application scenario, electricity consumption side energy storage can be divided into industrial and commercial energy storage cabinets, household energy storage devices 440, energy storage charging piles, etc., which are generally used in conjunction with distributed photovoltaics. Industrial and commercial users can use energy storage for peak-valley price arbitrage and capacity cost management. In the electricity market implementing peak-valley pricing, by charging the energy storage system 400 when the electricity price is low and discharging the energy storage system 400 when the electricity price is high, peak-valley price arbitrage can be achieved, reducing electricity costs. In addition, industrial enterprises subject to two-part tariffs can use the energy storage system 400 to store energy during off-peak hours and discharge during peak loads, thereby reducing peak power and the maximum demand declared, achieving the goal of reducing capacity electricity costs. Household photovoltaics with energy storage can improve the level of self-consumption of electricity. Due to high electricity prices and poor power supply stability, the demand for household photovoltaic installations is driven. Given that photovoltaic power generation occurs during the day, while user load is generally higher at night, configuring energy storage can better utilize photovoltaic power, improve self-consumption levels, and reduce electricity costs. Furthermore, energy storage is needed in areas such as communication base stations and data centers for backup power.

[0042] In some embodiments, see Figure 1 , Figure 1 This is a schematic diagram of the structure of an energy storage system 400 according to an embodiment of this application. Figure 1 The embodiments are illustrated using a home energy storage scenario in user-side energy storage as an example. The energy storage device 440 of this application is not limited to the home energy storage scenario.

[0043] This application provides an energy storage system 400, which includes a first power conversion device 410 (photovoltaic panel), a first user load 420 (household lighting fixture), a second user load 430 (e.g., household appliances such as air conditioners), and an energy storage device 440. The energy storage device 440 is a small energy storage box that can be wall-mounted on an outdoor wall. However, the energy storage device 440 is not limited to wall mounting and can also be placed in a user's residence in other ways. Specifically, the photovoltaic panel can convert solar energy into electrical energy during periods of low electricity prices, and the energy storage device 440 stores this electrical energy and supplies it to lighting fixtures and household appliances during peak electricity prices, or provides power during power outages / power interruptions.

[0044] In some embodiments, see Figure 2 , Figure 2 This is a schematic diagram of the structure of an energy storage system 400 according to another embodiment of this application, and this application Figure 2 The embodiments are illustrated using a shared energy storage scenario on the generation / distribution side as an example. The energy storage device 440 of this application is not limited to the energy storage scenario on the generation / distribution side.

[0045] This application provides an energy storage system 400, which includes: a high-voltage cable 450, a first power conversion device 410, a second power conversion device 460, and an energy storage device 440 provided in this application. In some embodiments of the power generation scenario, the second power conversion device 460 can be a wind power conversion device. Since the electricity generated by wind power conversion is volatile, random, and intermittent, the unstable electricity output by the wind power conversion device can be stored in the energy storage device 440 through grid connection. The energy storage device 440 is connected to the high-voltage cable and outputs smooth electricity to the power consumption side of the distribution network, realizing peak shaving and frequency regulation, and stable grid operation; or, wind power... The conversion device is always connected to the high-voltage cable. Under normal power generation conditions, the power output of the wind power conversion device is supplied to the power consumption side of the distribution network through the high-voltage cable. When the current power load is low and the wind power conversion device generates excess power, the excess power is first stored in the energy storage device 440 to reduce wind and solar curtailment rates and improve the problem of new energy power generation consumption. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 440 together with the high-voltage cable 450 in grid-connected mode to supply power to the power consumption side. This provides the power grid with various services such as peak shaving, frequency regulation, and backup, giving full play to the peak shaving role of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure of the power grid.

[0046] In some embodiments on the distribution network side, the first power conversion device 410 can be a photovoltaic power conversion device, and the energy storage device 440 is connected to the high-voltage cable 450 and installed downstream of the high-voltage cable 450 and between the user load. The power output of the photovoltaic power conversion device is stored in the energy storage device 440, which can respond in a timely manner to act as a backup power source when the power grid / distribution network fails; or, it can provide power supply support to alleviate line congestion when the high-voltage cable 450 transmission line is blocked, and to delay the economic pressure caused by the expansion of the power grid / distribution capacity when the power grid is planned to be expanded.

[0047] Optionally, the first power conversion device 410 may include, but is not limited to, a wind power conversion device, and the second power conversion device 460 may include, but is not limited to, a photovoltaic power conversion device. The first power conversion device 410 and the second power conversion device 460 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0048] Optionally, the battery cell can be a rechargeable battery, which refers to a battery cell that can be recharged after discharge to activate the active materials and continue to be used. The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and this application does not specifically limit it.

[0049] In some embodiments, see Figure 3 , Figure 3 This is a schematic diagram of the structure of an energy storage system 400 according to another embodiment of this application, and this application Figure 3 The embodiments are illustrated using an industrial and commercial energy storage scenario as an example. The energy storage device 440 of this application is not limited to its power generation / distribution side energy storage scenario.

[0050] This application provides an energy storage system 400, which includes: an energy storage cabinet 470, a high-voltage cable 450, a factory equipped with a first power conversion device 410, a photovoltaic-energy storage-charging station 480 equipped with a second power conversion device 460, and a vehicle 490. In some embodiments of industrial and commercial scenarios, the first power conversion device 410 can be a photovoltaic panel, which converts solar energy into electrical energy and stores it in the energy storage cabinet 470 of the factory. In the event of a power grid failure, the energy storage cabinet 470 provides power to ensure the safe and stable operation of the factory without interruption. Alternatively, when the factory's power load is high, the power grid issues an instruction to transmit the electricity stored in the energy storage cabinet 470 in conjunction with the high-voltage cable 450 in a grid-connected mode to supply the factory with electricity, providing various services such as peak shaving / frequency regulation and backup for the power grid operation. In addition, the second power conversion device 460 can also be a photovoltaic panel, which converts solar energy into electrical energy and stores it in the energy storage cabinet 470 of the photovoltaic-energy storage-charging station 480, directly charging the vehicle 490 through the photovoltaic-energy storage-charging station 480, which is fast and convenient.

[0051] Optionally, the first power conversion device 410 and the second power conversion device 460 may include, but are not limited to, photovoltaic power conversion devices. The first power conversion device 410 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0052] Optionally, the energy storage cabinet 470 may include, but is not limited to, energy storage application scenarios such as energy storage power stations, hydropower / thermal / wind power generation systems, solar power generation systems, mobile power systems, smart home systems, or temporary power supply systems, and is also used in multiple fields such as data centers, military equipment, aerospace, charging piles, and electric vehicles.

[0053] Optionally, the energy storage cabinet 470 may include, but is not limited to, individual battery cells, or battery modules composed of individual battery cells, battery packs, battery clusters, power banks, energy storage cabinets / containers, and other integrated battery systems. The actual application form of the energy storage cabinet 470 provided in this application embodiment can be, but is not limited to, the listed products, and can also be other application forms. This application embodiment does not strictly limit the application form of the energy storage cabinet 470. This application embodiment only uses a multi-cell battery in the energy storage cabinet 470 as an example for illustration.

[0054] Optionally, the battery cells constituting the energy storage cabinet 470 can be, but are not limited to, at least one of cylindrical, square, prismatic, or other shaped batteries.

[0055] Optionally, the energy storage device 440 may include, but is not limited to, energy storage applications such as energy storage power stations, hydropower / thermal / wind power generation systems, solar power generation systems, mobile power systems, smart home systems, or temporary power supply systems, and may also be applied in multiple fields such as data centers, military equipment, aerospace, charging piles, and electric vehicles.

[0056] Optionally, the energy storage device 440 may include, but is not limited to, individual battery cells, or battery modules, battery packs, battery clusters, power banks, energy storage cabinets / containers, and other integrated battery systems composed of individual battery cells. The actual application form of the energy storage device 440 provided in this application embodiment may be, but is not limited to, the listed products, and may also be other application forms. This application embodiment does not strictly limit the application form of the energy storage device 440. This application embodiment only uses a multi-cell battery as an example for illustration.

[0057] Optionally, when the energy storage device 440 is a single battery cell, the energy storage device 440 can be, but is not limited to, at least one of cylindrical, square, prismatic, or other shaped batteries.

[0058] Please see Figure 4 and Figure 5 This application provides a negative electrode current collector 100, which includes a substrate 110, a conductive layer 120, and a sodium storage layer 130. The conductive layer 120 is located on the surface of the substrate 110. The sodium storage layer 130 and the conductive layer 120 are disposed on the same side of the substrate 110, and the sodium storage layer 130 is disposed around at least a portion of the outer periphery of the conductive layer 120. Along the thickness direction of the negative electrode current collector 100, the thickness of the sodium storage layer 130 is greater than the thickness of the conductive layer 120.

[0059] Understandably, the sodium storage layer 130 and the conductive layer 120 are disposed in the same layer.

[0060] Understandably, the negative electrode current collector 100 is applied to the battery 200. When the negative electrode current collector 100 is applied to the battery 200, the sodium storage layer 130 is closer to the edge region of the positive electrode 210 than the conductive layer 120. Active ions such as sodium ions in the battery 200 can be deposited on the side of the negative electrode current collector 100 and form sodium metal.

[0061] Understandably, the sodium storage layer 130 is disposed around at least a portion of the outer periphery of the conductive layer 120, and the thickness of the sodium storage layer 130 is greater than the thickness of the conductive layer 120. Then, the sodium storage layer 130 and the conductive layer 120 cooperate to form a sodium metal deposition region 140.

[0062] Understandably, the thickness direction of the negative electrode current collector 100 can be the arrangement direction of the sodium storage layer 130 and the substrate 110.

[0063] Optionally, the substrate 110 is selected from copper foil and aluminum foil.

[0064] In this embodiment, the sodium storage layer 130 and the conductive layer 120 are disposed on the same side of the substrate 110, and the sodium storage layer 130 is disposed around at least a portion of the outer periphery of the conductive layer 120. The thickness of the sodium storage layer 130 is greater than the thickness of the conductive layer 120. The sodium storage layer 130 and the conductive layer 120 cooperate to form a sodium metal deposition region 140. When the negative electrode current collector 100 is applied to the battery 200 and the battery 200 is charging, sodium ions are transported to the negative electrode current collector 100 side and deposited as sodium metal on the surface of the conductive layer 120 away from the substrate 110. In other words, sodium metal is deposited in the sodium metal deposition region 140. Similarly, when the battery 200 is discharging, the sodium metal is converted into sodium ions and stripped from the negative electrode current collector 100 side, thus reducing the amount of sodium metal located in the sodium metal deposition region 140. By setting the sodium metal deposition region 140, the thickness of the negative electrode current collector 100 remains basically unchanged during the charging and discharging process of the battery 200. This avoids repeated increases or decreases in the thickness of the battery 200, thereby maintaining the bonding performance between the negative electrode current collector 100 and the separator 220, slowing down the increase in the interface impedance of the battery 200, and effectively mitigating the problem of local dendrite formation. Furthermore, when the negative electrode current collector 100 is applied to the battery 200, the sodium storage layer 130 is located closer to the edge region of the positive electrode plate 210. In other words, the overhang region of the negative electrode current collector 100 is within the sodium storage layer 130. The sodium storage layer 130 has better sodium storage performance than the conductive layer 120. The sodium storage layer 130 has better sodium affinity. The sodium storage layer 130 can provide uniform nucleation sites for the deposition and stripping of sodium metal. Sodium ions can enter into the sodium storage layer 130 and deposit within it, thereby mitigating the problem of severe dendrite growth in the overhang region of the negative electrode current collector 100 and improving the safety performance of the battery 200 when the negative electrode current collector 100 is applied to the battery 200.

[0065] Understandably, if the thickness of the sodium storage layer 130 is greater than the thickness of the conductive layer 120, then when the negative electrode current collector 100 is assembled into the battery 200, the preload of the sodium storage layer 130 is higher than that of the conductive layer 120. Consequently, the growth rate of metal dendrites in the region with high preload is lower than that in the region with low preload. In other words, by setting the thickness of the sodium storage layer 130 to be greater than that of the conductive layer 120, the formation of metal dendrites on the surface of the sodium storage layer 130 can be effectively slowed down, thus effectively solving the problem of severe dendrite growth in the overhang region of the negative electrode current collector 100. This embodiment, by setting the thickness of the sodium storage layer 130 and by setting the sodium storage layer 130 to surround at least a portion of the outer periphery of the conductive layer 120, suppresses the formation of metal dendrites on the surface of the sodium storage layer 130 from multiple angles.

[0066] Understandably, in the negative electrode current collector 100 of this application embodiment, the sodium storage layer 130 and the conductive layer 120 are disposed in the same layer. Compared with the scheme of first disposing of the conductive layer 120 on the surface of the substrate 110 and then disposing of the sodium storage layer 130 on the surface of the conductive layer 120 away from the substrate 110, the scheme of this embodiment has the following advantages: First, the sodium storage layer 130 is directly connected to the substrate 110, so that the bonding performance between the sodium storage layer 130 and the substrate 110 is better, and the interface impedance between the sodium storage layer 130 and the substrate 110 is smaller, which facilitates the transport of electrons and ions. Secondly, if the sodium storage layer 130 and the conductive layer 120 are disposed in different layers, the structural integrity of the conductive layer 120 will be damaged when the sodium storage layer 130 is coated on the surface of the conductive layer 120. This embodiment can avoid damaging the conductive layer 120 during the coating process, and can avoid increasing the internal resistance of the battery 200 when the negative electrode current collector 100 is applied to the battery 200. Thirdly, in the process of preparing the negative electrode current collector 100, the conductive layer 120 can be coated on the surface of the substrate 110 first, the sodium storage layer 130 can be coated on the outer periphery of the conductive layer 120, and then air-dried, which has a high preparation efficiency. If the sodium storage layer 130 and the conductive layer 120 are disposed in different layers, a second drying process is required. First, the conductive layer 120 is coated on the surface of the substrate 110. After the conductive layer 120 is dried, the sodium storage layer 130 is coated on the surface of the conductive layer 120, which results in a lower production efficiency of the negative electrode current collector 100.

[0067] In some embodiments, the conductive layer 120 includes a first carbon material and a second carbon material, wherein the first carbon material is a one-dimensional material and the second carbon material is a non-one-dimensional material.

[0068] Understandably, in the terminology of this application, a one-dimensional material refers to a material with two dimensions having dimensions at the nanometer level (typically less than 100 nm) and a relatively large dimension in the third dimension, exhibiting a “linear” or “fibrous” structure.

[0069] In this embodiment, the conductive layer 120 includes a first carbon material and a second carbon material. The first carbon material is a one-dimensional material. The first carbon material is stacked in an interleaved manner within the conductive layer 120 to form a three-dimensional network structure. On the one hand, this can improve the structural stability of the conductive layer 120. On the other hand, it can provide a three-dimensional channel for the transport of sodium ions and electrons, thereby improving the wetting performance of the electrolyte 230 on the conductive layer 120. This allows sodium ions and electrons to pass through the conductive layer 120 and complete the electron transfer, thereby realizing the deposition or deintercalation of sodium metal on the negative electrode current collector 100, and thus slowing down the formation of local dendrites. Furthermore, the second carbon material is a non-one-dimensional material, dispersed within the three-dimensional network structure formed by the first carbon material. The second carbon material enhances the conductivity of areas not covered by the first carbon material; in other words, it fills the conductive gaps in the three-dimensional network formed by the first carbon material, thereby improving the conductivity of the conductive layer 120 and increasing its electron transport speed. This improves the efficiency of sodium ion deposition of sodium metal on the surface of the conductive layer 120, preventing dendrite formation due to excessive local impedance. Furthermore, the surface of the non-one-dimensional material has numerous defects. The functional groups on the surface of the second carbon material, such as C-OH and C=O, have good sodium affinity, providing more nucleation sites for sodium metal deposition. This also helps to mitigate dendrite formation and ultimately improves the safety performance of the battery 200 when the negative electrode current collector 100 is applied.

[0070] Optionally, the conductive layer 120 satisfies at least one of the following conditions: in the conductive layer 120, the mass percentage a1 of the first carbon material is in the range of 50% ≤ a1 ≤ 95%; and in the conductive layer 120, the mass percentage a2 of the second carbon material is in the range of 0% < a2 ≤ 45%.

[0071] Understandably, in one embodiment of the conductive layer 120, the mass percentage a1 of the first carbon material satisfies the range 50% ≤ a1 ≤ 95%; in another embodiment of the conductive layer 120, the mass percentage a2 of the second carbon material satisfies the range 0% < a2 ≤ 45%; in still some embodiments, the mass percentage a1 of the first carbon material satisfies the range 50% ≤ a1 ≤ 95%, while the mass percentage a2 of the second carbon material satisfies the range 0% < a2 ≤ 45%.

[0072] In some embodiments, in the conductive layer 120, the mass percentage a1 of the first carbon material ranges from 50% to a1 to 95%.

[0073] Specifically, in the conductive layer 120, the mass percentage a1 of the first carbon material can be, but is not limited to, 50%, 55%, 58%, 60%, 65%, 58%, 70%, 75%, 78%, 80%, 82%, 85%, 89%, 90%, 92%, and 95%.

[0074] Specifically, in the conductive layer 120, the mass percentage a2 of the second carbon material can be, but is not limited to, 1%, 2%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, and 45%.

[0075] In some embodiments of this application, when the mass percentage a1 of the first carbon material is within the range of 50% ≤ a1 ≤ 95%, the mass percentage of the first carbon material is within a reasonable range. On the one hand, the first carbon material is staggered and stacked within the conductive layer 120 to construct a three-dimensional network structure, providing a three-dimensional channel for the transport of sodium ions and electrons, improving the wetting performance of the electrolyte 230 on the conductive layer 120, so that sodium ions and electrons can pass through the conductive layer 120 and complete electron transfer, thereby realizing the deposition or deintercalation of sodium metal on the negative electrode current collector 100, thus slowing down the formation of local dendrites. On the other hand, the mass percentage of the second carbon material is also within a reasonable range, so that the second carbon material can further improve the conductivity of the conductive layer 120, which is beneficial to electron transport, and thus beneficial to the deposition of sodium ions on the conductive layer 120 and the formation of sodium metal. When the mass percentage of the first carbon material is too large, correspondingly, the mass percentage of the second carbon material is too small, and the second carbon material is unable to improve the conductivity of the three-dimensional network structure formed by the first carbon material, which may lead to an increase in the local impedance of the conductive layer 120, increasing the probability of dendrite formation. When the mass percentage of the first carbon material is too small, the interleaved stacking of the first carbon material makes it difficult to form a three-dimensional network structure, which is insufficient to provide three-dimensional channels for the transport of sodium ions and electrons. This is detrimental to the deposition of sodium ions on the conductive layer 120 and the formation of sodium metal. Furthermore, the structural stability of the conductive layer 120 is also poor. During the deposition and stripping of sodium metal, the structure of the conductive layer 120 may be damaged, shortening the service life of the negative electrode current collector 100 and thus reducing the cycle performance of the battery 200 when the negative electrode current collector 100 is used.

[0076] Preferably, in the conductive layer 120, the mass percentage a1 of the first carbon material is in the range of 60% ≤ a1 ≤ 80%.

[0077] In some embodiments, in the conductive layer 120, the mass percentage a2 of the second carbon material ranges from 0% to a2 ≤ 45%.

[0078] In some embodiments of this application, when the mass percentage a2 of the second carbon material satisfies the range 0% < a2 ≤ 45%, the mass percentage of the second carbon material is within a reasonable range. On the one hand, the second carbon material can be dispersed in the three-dimensional network formed by the first carbon material to improve the conductivity of the areas not covered by the first carbon material, thereby further improving the conductivity of the conductive layer 120, facilitating the transport of sodium ions and electrons in the conductive layer 120, improving the efficiency of sodium metal deposition on the surface of the conductive layer 120, reducing the interfacial impedance of the negative electrode current collector 100, and slowing down the formation of interfacial dendrites. When the mass percentage of the second carbon material is too large, the defects on the surface of the second carbon material will increase the side reactions between the second carbon material and the electrolyte 230, which will reduce the capacity retention rate of the battery 200 when the negative electrode current collector 100 is applied to the battery 200. When the mass percentage of the second carbon material is too small, the second carbon material is difficult to improve the conductivity of the three-dimensional network structure formed by the first carbon material, which may lead to an increase in the local impedance of the conductive layer 120 and increase the probability of dendrite formation.

[0079] Preferably, in the conductive layer 120, the mass percentage a2 of the second carbon material is in the range of 10% ≤ a2 ≤ 20%.

[0080] In some embodiments, the first carbon material includes at least one of carbon nanotubes, carbon nanorods, and carbon fibers; the second carbon material includes at least one of fullerenes, carbon quantum dots, carbon black, graphene, graphyne, carbon nanosheets, graphite, hard carbon, soft carbon, carbon aerogel, and glassy carbon.

[0081] In this embodiment, carbon nanotubes, carbon nanorods, and carbon fibers are one-dimensional materials. The first carbon material is staggered and stacked in the conductive layer 120 to construct a three-dimensional network that facilitates the transport of sodium ions and electrons, thereby improving the efficiency of sodium metal deposition on the surface of the conductive layer 120. The second carbon material includes at least one of fullerene, carbon quantum dots, carbon black, graphene, graphynylene, carbon nanosheets, graphite, hard carbon, soft carbon, carbon aerogel, and glassy carbon, dispersed in the three-dimensional network formed by the first carbon material. In the three-dimensional network formed by the first carbon material, the second carbon material can conduct electricity through the hollow regions in the three-dimensional network, further improving the electron and ion conduction properties of the conductive layer 120, reducing the impedance of the conductive layer 120, and thus slowing down dendrite formation.

[0082] In this embodiment, the conductive layer 120 further includes a first adhesive, which includes at least one of polyvinylidene fluoride, polyacrylonitrile, polyimide, carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, sodium alginate, polytetrafluoroethylene, and polyvinyl alcohol.

[0083] In this embodiment, the first adhesive is used to bond the first carbon material and the second carbon material. On one hand, the first adhesive can improve the bonding performance between the first carbon material and the first carbon material, between the second carbon material and the second carbon material, and between the first carbon material and the second carbon material, thereby solving the material interface separation problem and improving the mechanical properties of the conductive layer 120, which is beneficial to extending the service life of the negative electrode current collector 100. On the other hand, the first adhesive can promote the uniform distribution of the first carbon material and the second carbon material and form a continuous conductive path, constructing a stable conductive network, which facilitates the transport of sodium ions and electrons.

[0084] In some embodiments, the sodium storage layer 130 includes a sodium storage carbon material, which includes at least one of graphene, graphyne, carbon nanosheets, graphite, hard carbon, soft carbon, carbon aerogel, and glassy carbon.

[0085] Understandably, the sodium storage capacity of the sodium-storing carbon material is greater than that of the first carbon material, and the sodium storage capacity of the sodium-storing carbon material is greater than that of the second carbon material.

[0086] In this embodiment, the sodium storage carbon material of the sodium storage layer 130 includes at least one of graphene, graphynylene, carbon nanosheets, graphite, hard carbon, soft carbon, carbon aerogel, and glassy carbon. This sodium storage carbon material significantly enhances the sodium affinity of the sodium storage layer 130 and provides uniform nucleation sites for sodium metal deposition and stripping. When the negative electrode current collector 100 is applied to the battery 200, the sodium storage layer 130 is at least partially disposed corresponding to the edge region of the positive electrode 210. Sodium ions transported from the positive electrode 210 to the negative electrode current collector 100 can enter the sodium storage layer 130 and be converted into sodium metal, which is deposited in the sodium storage carbon material. This prevents sodium metal from accumulating on the surface of the sodium storage layer 130 away from the substrate 110 and forming dendrites, effectively reducing the number of dendrites in the overhang region of the negative electrode current collector 100. Secondly, the reversible sodium storage capacity of the sodium-storing carbon material is higher than that of the first carbon material in the conductive layer 120, which allows sodium metal to be deposited or stripped in the sodium storage layer 130 during charge-discharge cycles. This avoids sodium metal from depositing on the surface of the sodium storage layer 130 and increasing the thickness of the negative electrode current collector 100, thereby slowing down the expansion and contraction of the battery 200 during charge-discharge cycles, slowing down dendrite growth, and improving the safety performance of the battery 200 when the negative electrode current collector 100 is used.

[0087] In some embodiments, the sodium storage capacity of the sodium-storing carbon material is greater than or equal to 200 mAh / g.

[0088] In this embodiment, the sodium storage capacity of the sodium-storing carbon material is greater than or equal to 200 mAh / g, and the reversible sodium capacity of the sodium-storing carbon material is relatively large. When the negative electrode current collector 100 is applied to the battery 200 and the battery 200 is in a charging state, sodium ions in the region where the positive electrode 210 and the sodium storage layer 130 are directly opposite each other are transported to the sodium storage layer 130. The sodium-storing carbon material can provide sufficient nucleation sites for the sodium ions, so that the sodium ions are deposited as sodium metal in the sodium storage layer 130, avoiding the deposition of sodium ions on the surface of the sodium storage layer 130, thereby slowing down the formation of dendrites.

[0089] In some embodiments, the sodium storage layer 130 further includes a third carbon material, which is a one-dimensional material and includes at least one of carbon nanotubes, carbon nanorods, and carbon fibers.

[0090] Understandably, the third carbon material and the sodium-storing carbon material are dispersed within the sodium-storing layer 130.

[0091] In this embodiment, the sodium storage layer 130 includes the sodium storage carbon material and the third carbon material. The third carbon material is a one-dimensional material, comprising at least one of carbon nanotubes, carbon nanorods, and carbon fibers. It can construct a three-dimensional conductive network within the sodium storage layer 130, dispersing the sodium storage carbon material between the three-dimensional conductive networks. The third carbon material provides three-dimensional transport channels for sodium ion and electron transport, improving the wetting effect of the electrolyte 230 on the sodium storage layer 130, thus facilitating the deposition or stripping of sodium metal within the sodium storage layer 130. Furthermore, the three-dimensional network constructed by the third carbon material enhances the structural stability of the sodium storage layer 130, thereby extending the service life of the negative electrode current collector 100.

[0092] In some embodiments, the sodium storage layer 130 satisfies at least one of the following conditions: in the sodium storage layer 130, the mass percentage a3 of the sodium storage carbon material is in the range of 50% ≤ a3 ≤ 90%; and in the sodium storage layer 130, the mass percentage a4 of the third carbon material is in the range of 5% ≤ a4 ≤ 40%.

[0093] Understandably, in some embodiments of the sodium storage layer 130, the mass percentage a3 of the sodium storage carbon material satisfies the range of 50% ≤ a3 ≤ 90%; in other embodiments of the sodium storage layer 130, the mass percentage a4 of the third carbon material satisfies the range of 5% ≤ a4 ≤ 40%; and in still other embodiments of the sodium storage layer 130, the mass percentage a3 of the sodium storage carbon material satisfies the range of 50% ≤ a3 ≤ 90%, while the mass percentage a4 of the third carbon material satisfies the range of 5% ≤ a4 ≤ 40%.

[0094] In some embodiments, in the sodium storage layer 130, the mass percentage a3 of the sodium storage carbon material ranges from 50% to a3% to 90%.

[0095] Specifically, in the sodium storage layer 130, the mass percentage a3 of the sodium storage carbon material can be, but is not limited to, 50%, 52%, 55%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 85%, and 90%.

[0096] In the sodium storage layer 130 provided in this embodiment, when the mass percentage a3 of the sodium storage carbon material meets the range of 50% ≤ a3 ≤ 90%, the mass percentage of the sodium storage carbon material is within a reasonable range, and the nucleation sites in the sodium storage layer 130 that can be used for sodium metal deposition or stripping are within a reasonable range. On the one hand, when the negative electrode current collector 100 is applied to the battery 200, sodium ions transported from the positive electrode plate 210, which is directly opposite to the sodium storage layer 130, to the sodium storage layer 130 can enter the sodium storage layer 130 and be deposited in the sodium storage carbon material, thereby avoiding sodium metal deposition on the surface of the sodium storage layer 130 and reducing the probability of dendrite formation. On the other hand, the mass percentage of the third carbon material is also within a reasonable range, so that the sodium storage layer 130 has good conductivity, ion conduction performance, and structural stability, which facilitates the deposition or stripping of sodium metal. When the mass percentage (a3) ​​of the sodium-storage carbon material is too large, on the one hand, when the negative electrode current collector 100 is applied to the battery 200, the number of sodium ions transported from the positive electrode plate 210, which is directly opposite the sodium storage layer 130, to the sodium storage layer 130 is relatively small, thus requiring less sodium-storage carbon material and avoiding design redundancy. However, if the mass percentage of the sodium-storage carbon material is too large, it may lead to waste of the sodium-storage carbon material. Furthermore, the presence of numerous defects on the surface of the sodium-storage carbon material may increase side reactions between the sodium storage layer 130 and the electrolyte 230, thereby reducing the capacity retention rate of the battery 200. On the other hand, correspondingly, the mass percentage of the third carbon material is relatively small, resulting in decreased conductivity, ion conduction, and structural stability of the sodium storage layer 130, which is detrimental to sodium metal deposition and stripping. If the interfacial impedance of the sodium storage layer 130 is high, it may lead to an increase in the number of dendrites on the surface of the sodium storage layer 130, reducing the performance of the negative electrode current collector 100. When the mass percentage a3 of the sodium-carbon material is too small, there are too few nucleation sites for sodium metal deposition or stripping within the sodium storage layer 130. When the negative electrode current collector 100 is applied to the battery 200, not all sodium ions transported from the positive electrode plate 210, which is directly opposite the sodium storage layer 130, can enter the sodium storage layer 130. Some sodium ions are directly deposited on the surface of the sodium storage layer 130. Under the influence of factors such as local pressure, ion concentration, and electric field distribution differences, the risk of metal dendrites forming in the overhang region of the negative electrode current collector 100 is high. If dendrites continue to accumulate, they may puncture the separator 220 and cause safety problems, reducing the performance of the negative electrode current collector 100.

[0097] Preferably, in the sodium storage layer 130, the mass percentage a3 of the sodium storage carbon material is in the range of 70% ≤ a3 ≤ 80%.

[0098] In some embodiments, in the sodium storage layer 130, the mass percentage a4 of the third carbon material ranges from 5% to a4% to 40%.

[0099] Specifically, in the sodium storage layer 130, the mass percentage a4 of the third carbon material can be, but is not limited to, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, and 40%.

[0100] In the sodium storage layer 130 provided in this embodiment, when the mass percentage a4 of the third carbon material meets the range of 5% ≤ a4 ≤ 40%, the mass percentage of the third carbon material is within a reasonable range. The third carbon material can construct a three-dimensional network structure within the sodium storage layer 130 to improve the conductivity and structural strength of the sodium storage layer 130, facilitating the deposition and stripping of sodium metal. The third carbon material and the sodium storage carbon material cooperate with each other so that sodium ions transported from the positive electrode 210, which is positioned opposite to the sodium storage layer 130, can enter the interior of the sodium storage layer 130 and deposit within it, effectively mitigating the formation of dendrites in the overhang region of the negative electrode current collector 100 and improving the safety performance of the negative electrode current collector 100 when applied to the battery 200. When the mass percentage a4 of the third carbon material is too large, correspondingly, the mass percentage of the sodium storage carbon material in the sodium storage layer 130 is too small, reducing the nucleation sites available for sodium metal deposition in the sodium storage layer 130. When the negative electrode current collector 100 is applied to the battery 200, sodium ions transported from the positive electrode plate 210, which is positioned directly opposite the sodium storage region, to the sodium storage layer 130 may directly deposit on the surface of the sodium storage layer 130, increasing the risk of metal dendrite formation in the overhang region of the negative electrode current collector 100. When the mass percentage a4 of the third carbon material is too small, it is difficult for the third carbon material to form a three-dimensional network within the sodium storage layer 130, reducing the conductivity of the sodium storage layer 130 and hindering the deposition or stripping of sodium metal within the sodium storage layer 130. This also reduces the structural stability of the sodium storage layer 130, shortening its lifespan after multiple charge-discharge cycles.

[0101] Preferably, in the sodium storage layer 130, the mass percentage a4 of the third carbon material is in the range of 10% ≤ a4 ≤ 20%.

[0102] Optionally, in this embodiment, the sodium storage layer 130 further includes a second adhesive, which includes at least one of polyvinylidene fluoride, polyacrylonitrile, polyimide, carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, sodium alginate, polytetrafluoroethylene, and polyvinyl alcohol.

[0103] In this embodiment, the second adhesive is used to bond the sodium-storing carbon material and the third carbon material. The second adhesive can improve the bonding performance between the sodium-storing carbon materials, between the third carbon materials, and between the sodium-storing carbon materials and the third carbon materials, so as to solve the material interface separation problem and improve the mechanical properties of the sodium-storing layer 130, which is beneficial to extending the service life of the negative electrode current collector 100.

[0104] In some embodiments, the thickness d1 of the conductive layer 120 is in the range of 0.1 μm ≤ d1 ≤ 100 μm.

[0105] Specifically, the thickness d1 of the conductive layer 120 can be, but is not limited to, 0.1μm, 0.5μm, 1μm, 5μm, 8μm, 10μm, 15μm, 20μm, 30μm, 35μm, 40μm, 50μm, 55μm, 60μm, 65μm, 70μm, 80μm, 90μm, and 100μm.

[0106] In this embodiment, when the thickness d1 of the conductive layer 120 satisfies the range of 0.1μm≤d1≤100μm, the thickness of the conductive layer 120 is within a reasonable range. On the one hand, the conductive layer 120 has a sufficiently complete electronic conduction network and ion conduction network, so that sodium ions and electrons can be rapidly transported within the conductive layer 120, which is beneficial for the deposition and stripping of sodium metal on the surface of the conductive layer 120. On the other hand, when the thickness of the sodium storage layer 130 is constant, the thickness of the conductive layer 120 is within a reasonable range, so that the height of the sodium metal deposition region 140 formed by the sodium storage layer 130 and the conductive layer 120 is also within a reasonable range. During the charging and discharging process of the battery 200, sodium metal can be deposited or stripped in the sodium metal deposition region 140, so as to avoid the thickness of the negative electrode current collector 100 continuously increasing and decreasing, so that the negative electrode current collector 100 and the separator 220 have better bonding performance and slow down the generation of metal dendrites. When the thickness of the conductive layer 120 is too large, it may increase the side reactions between the conductive layer 120 and the electrolyte 230, thereby reducing the capacity retention rate of the negative electrode current collector 100 when applied to the battery 200. Furthermore, with a fixed thickness of the sodium storage layer 130, the height of the sodium metal deposition region 140 formed by the sodium storage layer 130 and the conductive layer 120 may be too small. During the charging and discharging process of the battery 200, repeated deposition or stripping of sodium metal will cause the thickness of the negative electrode current collector 100 to continuously expand or contract, resulting in poor bonding performance between the negative electrode current collector 100 and the separator 220, increasing the internal resistance of the battery 200, and promoting the growth of metal dendrites. When the thickness of the conductive layer 120 is too small, it is difficult for the conductive layer 120 to form a sufficiently complete electronic conduction network, which is detrimental to the transport of sodium ions and electrons in the conductive layer 120, potentially increasing the internal resistance of the battery 200 and thus increasing the probability of dendrite formation. Furthermore, the conductive layer 120 has insufficient mechanical strength, which may prevent it from providing adequate support for the sodium metal. During the deposition and stripping of the sodium metal, the conductive layer 120 is prone to breakage, shortening the service life of the negative electrode current collector 100. Moreover, with a fixed thickness of the sodium storage layer 130, the height of the sodium metal deposition region 140 formed by the sodium storage layer 130 and the conductive layer 120 may be excessive. During the sodium metal deposition process, the pre-tightening force between the negative electrode current collector 100 and the separator 220 is too low, reducing the density of sodium metal deposition on the surface of the conductive layer 120, increasing the contact area between the sodium metal and the electrolyte 230, potentially increasing side reactions between the sodium metal and the electrolyte 230, and ultimately reducing the capacity retention rate of the battery 200 when the negative electrode current collector 100 is used.

[0107] Preferably, the thickness d1 of the conductive layer 120 is in the range of 0.5μm≤d1≤30μm.

[0108] In some embodiments, the thickness of the sodium storage layer 130 is d2, then the negative electrode current collector 100 satisfies the following relationship: 0 <d2-d1≤50μm。

[0109] Specifically, the values ​​of d2-d1 can be, but are not limited to, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 32μm, 35μm, 38μm, 40μm, 42μm, 45μm, 48μm and 50μm.

[0110] In this embodiment, when the negative electrode current collector 100 satisfies the relationship 0 < d2 - d1 ≤ 50μm, the difference between the thickness of the sodium storage layer 130 and the thickness of the conductive layer 120 is within a reasonable range. Then, along the thickness direction of the negative electrode current collector 100, the height of the sodium metal deposition region 140 enclosed by the sodium storage layer 130 and the conductive layer 120 is within a reasonable range, which facilitates deposition or stripping of sodium metal in the sodium metal deposition region 140, so as to slow down the change in thickness of the negative electrode current collector 100 during charging and discharging, keep the impedance between the negative electrode current collector 100 and the separator 220 relatively low, and slow down the generation of dendrites. Furthermore, it can avoid reducing the density of sodium metal deposited on the conductive layer 120 due to low pre-tightening force between the negative electrode current collector 100 and the separator 220, thereby slowing down the side reaction between sodium metal and the electrolyte 230, and finally, when the negative electrode current collector 100 is applied to the battery 200, the battery 200 has a long service life and a high capacity retention rate. When the value of d2 - d1 is too large, along the thickness direction of the negative electrode current collector 100, the height of the sodium metal deposition region 140 enclosed by the sodium storage layer 130 and the conductive layer 120 is too large. During the deposition of sodium metal, the pre-tightening force between the negative electrode current collector 100 and the separator 220 is low, which reduces the density of sodium metal deposited on the surface of the conductive layer 120, increases the contact area between sodium metal and the electrolyte 230, may increase side reactions between sodium metal and the electrolyte 230, and ultimately reduces the capacity retention rate of the battery 200 when the negative electrode current collector 100 is applied to the battery 200. When the value of d2 - d1 is too small, along the thickness direction of the negative electrode current collector 100, the height of the sodium metal deposition region 140 enclosed by the sodium storage layer 130 and the conductive layer 120 is too small. When the negative electrode current collector 100 is applied to the battery 200, on one hand, sodium ions extracted from the positive electrode sheet 210 are deposited on the surface of the conductive layer 120 to form sodium metal. If the space of the sodium metal deposition region 140 is too small, during the charging and discharging of the battery 200, the deposition and stripping of sodium metal will cause a significant increase or decrease in the thickness of the negative electrode current collector 100, thereby increasing the impedance between the negative electrode current collector 100 and the separator 220, and increasing the probability of metal dendrite growth between the conductive layer 120 and the separator 220. On the other hand, if the difference between the thickness of the sodium storage layer 130 and the thickness of the conductive layer 120 is too small, the difference between the pre-tightening force of the sodium storage layer 130 and the pre-tightening force of the conductive layer 120 is not significant. In other words, the thickness difference between the sodium storage layer 130 and the conductive layer 120 is too small to inhibit the growth rate of metal dendrites on the surface of the sodium storage layer 130.

[0111] Optionally, in some embodiments, the thickness d2 of the sodium storage layer 130 satisfies the range: 0.1μm < d2 ≤ 150μm.

[0112] Specifically, the thickness of the sodium storage layer 130 can be, but is not limited to, 0.1 μm, 3 μm, 8 μm, 12 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 85 μm, 90 μm, 100 μm, 110 μm, 120 μm, 125 μm, 130 μm, 140 μm, and 150 μm.

[0113] In this embodiment, when the thickness d2 of the sodium storage layer 130 satisfies the range 0.1μm<d2≤150μm, the thickness of the sodium storage layer 130 is within a reasonable range. This allows the height of the sodium metal deposition region 140 formed by the sodium storage layer 130 and the conductive layer 120 to be within a reasonable range, facilitating the deposition or stripping of sodium metal in the sodium metal deposition region 140. This reduces the change in the thickness of the negative electrode current collector 100 during charging and discharging, resulting in a smaller impedance between the negative electrode current collector 100 and the separator 220, thereby reducing dendrite formation.

[0114] Please see also Figure 6 This application provides a battery 200, which includes: a positive electrode 210, a separator 220, a negative electrode current collector 100 provided in this application, and an electrolyte 230. The separator 220 is disposed on one side of the positive electrode 210. The sodium storage layer 130 of the negative electrode current collector 100 is stacked on the positive projection of the separator 220 and the positive projection of the positive electrode 210 on the separator 220, and is partially staggered.

[0115] Understandably, the electrolyte 230 is used to wet at least a portion of the positive electrode 210, at least a portion of the separator 220, and at least a portion of the negative electrode.

[0116] Understandably, the positive electrode 210, the diaphragm 220, and the negative electrode current collector 100 are arranged in sequence and then wound together.

[0117] Understandably, the orthogonal projection of the positive electrode 210 onto the diaphragm 220 falls within the range of the orthogonal projection of the negative electrode current collector 100 onto the diaphragm 220.

[0118] Understandably, the conductive layer 120 of the negative current collector 100 is completely superimposed on the orthogonal projection of the diaphragm 220 with the orthogonal projection of the positive electrode 210 on the diaphragm 220.

[0119] Understandably, the portion of the sodium storage layer 130 of the negative electrode current collector 100 whose orthogonal projection on the diaphragm 220 is offset from the orthogonal projection of the positive electrode plate 210 on the diaphragm 220 constitutes the overhang region of the negative electrode current collector 100.

[0120] Understandably, the portion of the positive electrode 210 whose orthogonal projection onto the diaphragm 220 is stacked with the portion of the sodium storage layer 130 whose orthogonal projection onto the diaphragm 220 corresponds to the edge region of the positive electrode 210.

[0121] In this embodiment, the positive electrode 210 and the negative current collector 100 are disposed on opposite sides of the separator 220. The electrolyte 230 at least partially wets the positive electrode 210, the separator 220, and the negative current collector 100. During the charging process of the battery 200, sodium ions are released from the positive electrode 210, pass through the separator 220, and enter the negative current collector 100. Some of the sodium ions enter the conductive layer 120 and are converted into sodium metal, which is deposited on the surface of the conductive layer 120. Other sodium ions enter the sodium storage layer 130 and are converted into sodium metal, which is deposited inside the sodium storage layer 130. Similarly, during the discharging process of the battery 200, sodium metal is converted into sodium ions and stripped from the negative current collector 100 to enter the positive electrode 210. The sodium storage layer 130 of the negative electrode current collector 100 is overlapped with the positive electrode plate 210 in the portion of the positive electrode plate 210 projected onto the separator 220, but partially staggered. On one hand, the negative electrode current collector 100 has an overhang region to increase its area. When the battery 200 expands during charging and discharging, the separator 220 can better enclose the negative electrode current collector 100, preventing direct contact between the positive electrode plate 210 and the sodium metal layer on the negative electrode current collector 100, thus preventing short circuits and improving the safety performance of the battery 200. On the other hand, during charging, sodium ions from the positive electrode plate 210, which corresponds to the sodium storage layer 130, pass through the separator 220 and enter the sodium storage layer 130, preventing sodium metal from depositing on the surface of the sodium storage layer 130 and generating more metal dendrites. Furthermore, even if excess sodium ions enter the overhang region of the sodium storage layer 130, they can be converted into sodium metal and stored within the negative electrode current collector 100, thus preventing dendrite formation during the deposition of sodium metal on the surface of the overhang region of the negative electrode current collector 100. The battery 200 of this embodiment exhibits good safety performance.

[0122] Optionally, in some embodiments, the battery 200 is a sodium metal battery, and the surface of the negative electrode current collector 100 is loaded with sodium metal. Specifically, the sodium metal is loaded on the surface of the conductive layer 120 opposite to the substrate 110. In other embodiments, the battery 200 is a negative electrodeless battery. During charging and discharging, sodium ions are converted into sodium metal on the surface of the negative electrode current collector 100 and deposited. Charge storage is achieved through the deposition or stripping of sodium metal.

[0123] In some embodiments, the specific capacity of the positive electrode 210 is C, the theoretical volumetric specific capacity of sodium metal is Q, the thickness of the conductive layer 120 is d1, and the thickness of the sodium storage layer 130 is d2. Then the battery 200 satisfies the relationship: 0 < d2 - d1 ≤ 1.5 × C / Q.

[0124] Specifically, the value of d2-d1 can be, but is not limited to, 0.1×C / Q, 0.3×C / Q, 0.5×C / Q, 0.8×C / Q, C / Q, 1.1×C / Q, d1+1.2×C / Q, 1.3×C / Q, and 1.5×C / Q.

[0125] In this embodiment, the battery 200 satisfies the relationship 0 < d2 - d1 ≤ 1.5 × C / Q. The thickness of the conductive layer 120 is matched with the thickness of the sodium storage layer 130 to form a sodium metal deposition region 140. The height of the sodium metal deposition region 140 is related to the specific capacity of the single-sided area of ​​the positive electrode 210 and the theoretical volumetric specific capacity of sodium metal. Specifically, when the battery 200 satisfies the relationship 0 < d2 - d1 ≤ 1.5 × C / Q, the thickness of the conductive layer 120 and the thickness of the sodium storage layer 130 are both within a reasonable range, so that sodium ions released from the positive electrode 210 can be deposited or stripped in the sodium metal deposition region 140, thereby avoiding repeated expansion or contraction of the negative electrode current collector 100 and the battery 200. At the same time, the pre-tightening force between the negative electrode current collector 100 and the separator 220 is also within a reasonable range, so that sodium metal can be densely deposited in the sodium metal deposition region 140, and ultimately slow down the formation of metal dendrites, thereby improving the safety performance of the battery 200. If d2-d1 is greater than 1.5×C / Q, then with a fixed thickness of conductive layer 120, the excessive thickness of sodium storage layer 130 results in an excessively large height of sodium metal deposition region 140. Consequently, during sodium metal deposition in sodium metal deposition region 140, the pre-tightening force between negative electrode current collector 100 and separator 220 is insufficient, making dense sodium metal deposition difficult and potentially leading to the formation of metal dendrites. Furthermore, an excessively large thickness of sodium storage layer 130 may cause volume expansion during sodium intercalation, making it difficult to release internal stress. This can lead to cracking, pulverization, or even separation of sodium storage layer 130 from conductive layer 120 and substrate 110, shortening the service life of negative electrode current collector 100.

[0126] In some embodiments, along a preset direction (such as...) Figure 5 In the X direction (as shown), the width of the sodium storage layer 130 projected onto the diaphragm 220 is L1, and the width of the area where the sodium storage layer 130 is superimposed on the diaphragm 220 and the positive electrode 210 is superimposed on the diaphragm 220 is L2. Then, the following relationship is satisfied: 0 < L2 / L1 ≤ 1; where the preset direction is the arrangement direction of the conductive layer 120 and the sodium storage layer 130.

[0127] Understandably, the sodium storage layer 130 is disposed around at least a portion of the outer periphery of the conductive layer 120, and the preset direction is parallel to the radial direction of the negative electrode current collector 100, that is, the direction from the inner conductive layer 120 to the outer sodium storage layer 130.

[0128] Understandably, the preset direction is perpendicular to the thickness direction of the negative electrode current collector 100.

[0129] Understandably, the value of L1 is Figure 5 In this embodiment, L1' and L1" are sums, in other words, L1 = L1' + L1"; the value of L2 is... Figure 5 In the embodiment, the sum of L2' and L2" is, in other words, L2 = L2' + L2".

[0130] Specifically, the value of L2 / L1 can be, but is not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.

[0131] In this embodiment, when the negative electrode current collector 100 satisfies the relationship 0 < L2 / L1 ≤ 1, the width of the area where the sodium storage layer 130 is superimposed on the positive electrode plate 210 in the positive projection of the separator 220 is within a reasonable range. During the charging and discharging process of the battery 200, most of the sodium ions released from the positive electrode plate 210 corresponding to the sodium storage layer 130 pass through the separator 220 and enter the sodium storage layer 130 for storage inside. Excess sodium ions can also enter the overhang region of the sodium storage layer 130 to allow sodium metal deposition or stripping, which can effectively solve the problem of severe dendrite growth in the overhang region of the negative electrode current collector 100, thereby giving the battery 200 better safety performance.

[0132] Preferably, the value of L2 / L1 satisfies the range of 0.3≤L2 / L1≤0.7, which can more effectively solve the problem of severe dendrite growth in the overhang region of the negative electrode current collector 100, thereby enabling the battery 200 to have better safety performance.

[0133] The technical solution of this application will be further described below with reference to several embodiments:

[0134] Examples 1 to 14, Comparative Example 1 and Comparative Example 2:

[0135] 1. Preparation of negative electrode current collector 100:

[0136] A first carbon material, a second carbon material, a first binder (polyvinylidene fluoride), and a solvent (ammidine pyrrolidone) are mixed in a certain proportion to form a first slurry (the viscosity of the first slurry ranges from 5000 mPa·s to 8000 mPa·s). A sodium-storing carbon material, a third carbon material, a second binder (polyvinylidene fluoride), and a solvent (ammidine pyrrolidone) are mixed in a certain proportion to form a second slurry (the viscosity of the second slurry ranges from 5000 mPa·s to 8000 mPa·s). The first slurry is coated on the middle region of the substrate 110 to form a conductive layer 120, and the second slurry is coated on both sides of the edge region of the substrate 110 (copper foil) to form a sodium-storing layer 130. The sodium-storing layer 130 is connected to the conductive layer 120, and the overhang region of the negative electrode current collector 100 is included in the sodium-storing layer 130. After the coated electrode is dried, the negative electrode current collectors 100 of Examples 1 to 14, Comparative Example 1, and Comparative Example 2 are formed.

[0137] The types of the first carbon material, the mass percentage (a1) of the first carbon material in the conductive layer 120, the types of the second carbon material, the mass percentage (a2) of the second carbon material in the conductive layer 120, the thickness of the conductive layer 120, the types of the sodium-storing carbon material, the mass percentage (a3) ​​of the sodium-storing carbon material in the sodium-storing layer 130, the types of the third carbon material, the mass percentage (a4) of the third carbon material in the sodium-storing layer 130, and the thickness of the sodium-storing layer 130 are shown in Table 1.

[0138] 2. Preparation of positive electrode 210:

[0139] The positive electrode active material (sodium vanadium phosphate), conductive agent (Ketjen Black), and binder (polyvinylidene fluoride) were mixed evenly in a mass ratio of 80:10:10. Then, a solvent (N-methylpyrrolidone) was added and stirred to form a uniform positive electrode slurry with a solid content of 40%. The positive electrode slurry was coated onto an aluminum foil positive electrode current collector, dried, and cold-pressed to obtain the positive electrode sheet 210. The areal specific capacity of the positive electrode active material was controlled to be 2 mAh / cm². 2 .

[0140] 3. Preparation of electrolyte 230:

[0141] In an argon-protected glove box, take 1L of solvent (diethylene glycol dimethyl ether) into a volumetric flask; weigh 168g of solute (sodium hexafluorophosphate) and dissolve it in the above solvent; stir thoroughly until completely dissolved to obtain the required electrolyte 230.

[0142] 4. Preparation of diaphragm 220:

[0143] A 16μm polyethylene film was used as the diaphragm 220.

[0144] 5. Assembly of battery 200:

[0145] The negative electrode current collector 100, the separator 220 and the positive electrode 210 are stacked in sequence, and the electrolyte 230 is added to assemble them into the experimental cells 1 to 14, the control cell 1 and the control cell 2.

[0146] In this embodiment, the negative electrode current collector 100 of Example 1 is applied to the implementation battery 1, the negative electrode current collector 100 of Example 2 is applied to the implementation battery 2, the negative electrode current collector 100 of Comparative Example 1 is applied to the control battery 1, the negative electrode current collector 100 of Comparative Example 2 is applied to the control battery 2, and so on.

[0147] Table 1 below shows the performance parameters of the negative electrode current collector 100 of Examples 1 to 14, Comparative Example 1 and Comparative Example 2.

[0148] Table 1: Performance parameters of negative electrode current collector 100 in Examples 1 to 14, Comparative Examples 1 and 2.

[0149]

[0150]

[0151] Understandably, in the negative electrode current collector 100 of Comparative Example 1 and Comparative Example 2, the negative electrode current collector 100 only includes the conductive layer 120 and does not include the sodium storage layer 130.

[0152] Understandably, in the conductive layer 120, the total mass percentage of the first carbon material and the second carbon material is less than 100%, and the conductive layer 120 also includes other substances such as the first adhesive; in the sodium storage layer 130, the total mass percentage of the sodium storage carbon material and the third carbon material is less than 100%, and the sodium storage layer 130 also includes other substances such as the second adhesive.

[0153] Battery 200 performance test:

[0154] 1. Test of the thickness change rate of battery 200:

[0155] After the experimental batteries 1 to 14, control battery 1, and control battery 2 were assembled, they were charged to 3.8V at a constant current of 1C on a charge-discharge tester, and the thickness T of battery 200 was measured. 充 Subsequently, the same type of battery 200 was discharged at a constant current of 1C to 2.0V, and the thickness T of battery 200 was measured. 放 ; Specify T 放 As the reference thickness for battery 200, then (T) 充 -T 放 ) / T 放 The absolute value is the battery thickness change rate of 200.

[0156] The thickness change rates of implementation batteries 1 to 14, comparison battery 1 and comparison battery 2 are shown in Table 2.

[0157] 2. Test on the metal dendrite formation on the surface of the negative electrode current collector 100 after 100 cycles of battery 200:

[0158] After the assembly of batteries 1 to 14, control battery 1, and control battery 2, constant current charge-discharge tests were performed on battery 200 using a charge-discharge tester (charge-discharge at a constant current of 1C between 2.0V and 3.8V). After the 100th discharge cycle, battery 200 was transferred to an argon-protected glove box for disassembly. The deposition of metal dendrites on the surface of the negative electrode current collector 100 was visually observed. The degree of dendrite formation in the negative electrode current collector 100 was determined based on the amount of metal dendrites, and was classified into five categories: severe dendrites, obvious dendrites, moderate dendrites, slight dendrites, and invisible dendrites.

[0159] The metal dendrite formation on the surface of the negative electrode current collector 100 of the experimental cells 1 to 14, the comparative cell 1, and the comparative cell 2 is shown in Table 2.

[0160] In Table 2, the data on the metal dendrites on the surface of the negative electrode current collector 100 are as follows: 1-2 indicates severe dendrites, 3-5 indicates obvious dendrites, 6-8 indicates moderate dendrites, 9-10 indicates slight dendrites, and 11-12 indicates inconspicuous dendrites.

[0161] 3. Cycle capacity retention test of battery 200:

[0162] After the implementation batteries 1 to 14, control battery 1 and control battery 2 are assembled, the battery 200 is subjected to constant current charge and discharge test on the charge and discharge tester (charge and discharge at a constant current of 1C between 2.0V and 3.8V); the ratio of the discharge capacity of the battery 200 in the 100th cycle to the discharge capacity in the 1st cycle is the cycle capacity retention rate.

[0163] The capacity retention rates of implementation batteries 1 to 14, control battery 1, and control battery 2 after 100 cycles are shown in Table 2.

[0164] Table 2: Performance parameters of implementation batteries 1 to 14, comparison battery 1 and comparison battery 2.

[0165]

[0166] Please refer to Tables 1 and 2. As can be seen from Comparative Examples 1 and 2, the negative electrode current collector 100 of Comparative Example 1 and Comparative Example 2 both include only the conductive layer 120 and do not include the sodium storage layer 130. Furthermore, the conductive layer 120 of Comparative Example 1 only includes the first carbon material, while the conductive layer 120 of Comparative Example 2 includes both the first carbon material and the second carbon material. This results in: the thickness change rate of both Comparative Battery 1 and Comparative Battery 2 being relatively large, and the metal dendrite situation on the surface of the negative electrode current collector 100 being severe. The capacity retention rate of Comparative Battery 1 after 100 cycles is lower than that of Comparative Battery 2 after 100 cycles. This is because: neither the negative electrode current collector 100 of Comparative Example 1 nor Comparative Example 2 is provided with a sodium storage layer 130, making it impossible to form a sodium metal deposition region 140. When sodium ions are transported to the surface of the negative electrode current collector 100, metal dendrites are easily generated. Furthermore, the conductive layer 120 of Comparative Example 1 only includes the first carbon material, while the conductive layer 120 of Comparative Example 2 includes both the first carbon material and the second carbon material. The second carbon material can be dispersed in the three-dimensional network structure formed by the first carbon material and improve the conductivity of the areas not covered by the first carbon material, thereby making the conductivity and cycle performance of the comparative battery 2 better than those of the comparative battery 1.

[0167] As can be seen from the data of Examples 1 to 3 and Comparative Example 2, the negative electrode current collector 100 of Examples 1 to 3 includes a conductive layer 120 and a sodium storage layer 130, while the negative electrode current collector 100 of Comparative Example 2 only includes a conductive layer 120. This results in: the thickness change rate of the implemented battery 1 to the implemented battery 3 being less than the thickness change rate of the comparative battery 2; the metal dendrites on the surface of the negative electrode current collector 100 of the implemented battery 1 to the implemented battery 3 being obvious, while the metal dendrites on the surface of the negative electrode current collector 100 of the comparative battery 2 being severe; and the capacity retention rate of the implemented battery 1 to the implemented battery 3 after 100 cycles being better than that of the comparative battery 2 after 100 cycles. This is because: the sodium storage layer 130 cooperates with the conductive layer 120 to form a sodium metal deposition region 140. During the charging process of the battery 200, sodium ions are transported to the negative electrode current collector 100 side and deposited as sodium metal on the surface of the conductive layer 120 opposite to the substrate 110. Similarly, during the discharging process of the battery 200, the sodium metal is converted into sodium ions and stripped from the negative electrode current collector 100 side, thus reducing the amount of sodium metal in the sodium metal deposition region 140. By setting the sodium metal deposition region 140, the thickness of the negative electrode current collector 100 remains essentially constant during the charging and discharging process of the battery 200, avoiding repeated increases or decreases in the thickness of the battery 200. This maintains the bonding performance between the negative electrode current collector 100 and the separator 220, slows down the increase in the interface impedance of the battery 200, and effectively mitigates the problem of local dendrite formation. Furthermore, when the negative current collector 100 is applied to the battery 200, the sodium storage layer 130 is disposed closer to the edge region of the positive electrode 210. In other words, the overhang region of the negative current collector 100 is within the sodium storage layer 130. The sodium storage layer 130 has better sodium storage performance than the conductive layer 120. The sodium storage layer 130 has better sodium affinity. The sodium storage layer 130 can provide uniform nucleation sites for the deposition and stripping of sodium metal. Sodium ions can enter into the sodium storage layer 130 and deposit within it, thereby mitigating the problem of severe dendrite growth in the overhang region of the negative current collector 100, so that the implemented batteries 1 to 3 have better electrical performance and cycle performance.

[0168] Furthermore, in Examples 1 to 3, under the same conditions, the types of the first carbon materials in Examples 1 to 3 are different. The first carbon material in Example 1 is selected from carbon nanorods, the first carbon material in Example 2 is selected from carbon fibers, and the first carbon material in Example 3 is selected from carbon nanotubes. Among the cells 1 to 3, the thickness change of cell 3 is the smallest, and the capacity retention rate after 100 cycles is the best, indicating that when the first carbon material is selected from carbon nanotubes, it has better performance in improving the conductivity of the conductive layer 120.

[0169] Furthermore, data from Examples 3 to 5 show that, under the same conditions, as the mass proportion of the first carbon material gradually increases, the mass proportion of the second carbon material gradually decreases, resulting in a decreasing trend in the thickness change rate of the corresponding battery 200. The metal dendrite formation on the surface of the negative electrode current collector 100 gradually improves, and the capacity retention rate of the corresponding battery 200 after 100 cycles shows a trend of first increasing and then decreasing. This is because the first carbon material can form a three-dimensional network structure in the conductive layer 120, providing a channel for sodium ion transport. The second carbon material is dispersed in the three-dimensional network, further enhancing the conductivity of the conductive layer 120. Simultaneously, an excessively large proportion of the first carbon material may lead to an increase in local impedance of the conductive layer 120, increasing the probability of dendrite formation.

[0170] Data from Examples 4, 6, and 7 show that, under the same conditions, the types of sodium-storing carbon materials in the sodium storage layer 130 of Examples 4, 6, and 7 are different. The sodium-storing carbon material in Example 4 is selected from graphene, in Example 6 from soft carbon, and in Example 7 from hard carbon. Among Implemented Batteries 4, 6, and 7, Implemented Battery 7 exhibits the smallest thickness change rate, the greatest improvement in metal dendrite formation on the surface of the negative electrode current collector 100, and the best capacity retention rate after 100 cycles. This indicates that when the sodium-storing carbon material is selected from hard carbon, it has better performance in improving the sodium affinity of the negative electrode current collector 100, facilitating sodium ion deposition and reducing the number of dendrites in the overhang region of the negative electrode current collector 100.

[0171] Furthermore, data from Examples 8 to 10 show that, under the same conditions, the types of the third carbon material in the sodium storage layer 130 of Examples 8 to 10 are different. The third carbon material in Example 8 is selected from carbon nanorods, the third carbon material in Example 9 is selected from carbon fibers, and the third carbon material in Example 10 is selected from carbon nanotubes. Among the cells 8 to 10, the thickness change of cell 10 is the smallest, the metal dendrite condition on the surface of the negative electrode current collector 100 of cell 10 is improved the most, and the capacity retention rate after 100 cycles is the best. This indicates that when the third carbon material is selected from carbon nanotubes, the third carbon material constructs a three-dimensional conductive network in the sodium storage layer 130, thereby significantly improving the conductivity and ion conduction performance of the sodium storage layer 130.

[0172] Furthermore, data from Examples 10 to 12 show that, under the same conditions, as the mass percentage a3 of the sodium-carbon material in the sodium storage layer 130 continuously increases, the thickness change rate of the corresponding battery 200 shows an increasing trend, and the capacity retention rate of the corresponding battery 200 after 100 cycles shows a trend of first increasing and then decreasing. This is because: when the mass percentage of the sodium-carbon material is within a reasonable range, the nucleation sites available for sodium metal deposition or stripping in the sodium storage layer 130 are within a reasonable range. On the one hand, when the negative electrode current collector 100 is applied to the battery 200, sodium ions transported from the positive electrode 210, which is directly opposite to the sodium storage layer 130, to the sodium storage layer 130 can all enter the sodium storage layer 130 and be deposited in the sodium-carbon material, thereby avoiding sodium metal deposition on the surface of the sodium storage layer 130 and reducing the probability of dendrite formation. On the other hand, the mass ratio of the third carbon material is also within a reasonable range so that the sodium storage layer 130 has good electrical conductivity, ion conduction performance and structural stability, which facilitates the deposition or stripping of sodium metal. In other words, if the mass ratio a3 of the sodium storage carbon material is too large or too small, it will affect the electrical conductivity and ion conduction performance of the sodium storage layer 130.

[0173] Furthermore, data from Examples 11, 13, and 14 show that, under the same conditions, as the thickness d2 of the sodium storage layer 130 continuously increases, the value of d2-d1 also gradually increases, the thickness change rate of the corresponding battery 200 gradually decreases, and the metal dendrite situation on the surface of the negative electrode current collector 100 gradually improves. The capacity retention rate of the corresponding battery 200 after 100 cycles gradually increases. This is because, as the thickness of the energy storage layer 130 increases, the height of the sodium metal deposition region 140 formed by the sodium storage layer 130 and the conductive layer 120 is within a reasonable range and gradually increases, which facilitates the deposition or stripping of sodium metal in the sodium metal deposition region 140, thereby slowing down the change in the thickness of the negative electrode current collector 100 during charging and discharging, resulting in a smaller impedance between the negative electrode current collector 100 and the separator 220, thus slowing down the formation of dendrites. Furthermore, it can avoid reducing the density of sodium metal deposited on the conductive layer 120 due to the low pre-tightening force between the negative electrode current collector 100 and the separator 220, thereby slowing down the side reaction of sodium metal with electrolyte 230, and ultimately enabling the corresponding battery 200 to have a longer service life and a higher capacity retention rate.

[0174] Please see Figure 7 and Figure 8 This application provides an electrical device 300, which includes a device body 310 and a battery 200 provided in this application, wherein the battery 200 supplies power to the device body 310.

[0175] Understandably, the battery 200 is electrically connected to the electrical device 300.

[0176] In this embodiment, the battery 200 includes the negative electrode current collector 100 provided in this application. The negative electrode current collector 100 can slow down the growth of metal dendrites, thus giving the battery 200 better safety performance and a longer service life. When the battery 200 is applied to the electrical device 300, the battery 200 can provide stable power to the device body 310, which is beneficial to improving the user experience.

[0177] Optionally, the electrical device 300 in this application embodiment can be, but is not limited to, portable electronic devices such as mobile phones, tablets, laptops, desktop computers, smart bracelets, smartwatches, e-readers, and game consoles. It can also be a vehicle such as a car, truck, sedan, van, freight train, high-speed train, or electric vehicle. Furthermore, it can be various household appliances. Figure 7 In this embodiment, the electrical equipment 300 is a storage battery 200 cabinet.

[0178] It is understood that the electrical device 300 described in this embodiment is merely one form of the electrical device 300 used by the battery 200, and should not be construed as a limitation on the electrical device 300 provided in this application, nor should it be construed as a limitation on the electrical device 300 provided in various embodiments of this application.

[0179] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0180] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A negative electrode current collector, characterized in that, The negative electrode current collector includes: Substrate; A conductive layer is located on the surface of the substrate; the conductive layer comprises a first carbon material and a second carbon material, wherein the first carbon material is a one-dimensional material and the second carbon material is a non-one-dimensional material; the conductive layer satisfies at least one of the following conditions: in the conductive layer, the mass percentage a1 of the first carbon material is in the range of 50% ≤ a1 ≤ 95%; and in the conductive layer, the mass percentage a2 of the second carbon material is in the range of 0% < a2 ≤ 45%; and A sodium storage layer is disposed on the same side of the substrate as the conductive layer, and the sodium storage layer is disposed around at least a portion of the outer periphery of the conductive layer. Along the thickness direction of the negative electrode current collector, the thickness of the sodium storage layer is greater than the thickness of the conductive layer. The sodium storage layer comprises a sodium storage carbon material.

2. The negative electrode current collector according to claim 1, characterized in that, The first carbon material includes at least one of carbon nanotubes, carbon nanorods, and carbon fibers; the second carbon material includes at least one of fullerenes, carbon quantum dots, carbon black, graphene, graphyne, carbon nanosheets, graphite, hard carbon, soft carbon, carbon aerogel, and glassy carbon.

3. The negative electrode current collector according to claim 1, characterized in that, The sodium-storing carbon material includes at least one of graphene, graphyne, carbon nanosheets, graphite, hard carbon, soft carbon, carbon aerogel, and glassy carbon.

4. The negative electrode current collector according to claim 3, characterized in that, The sodium storage capacity of the sodium-containing carbon material is greater than or equal to 200 mAh / g.

5. The negative electrode current collector according to claim 3, characterized in that, The sodium storage layer also includes a third carbon material, which is a one-dimensional material and includes at least one of carbon nanotubes, carbon nanorods, and carbon fibers.

6. The negative electrode current collector according to claim 5, characterized in that, The sodium storage layer satisfies at least one of the following conditions: In the sodium storage layer, the mass percentage a3 of the sodium storage carbon material ranges from 50% to a3% to 90%. In the sodium storage layer, the mass percentage a4 of the third carbon material ranges from 5% to 40%.

7. The negative electrode current collector according to any one of claims 1 to 6, characterized in that, The thickness d1 of the conductive layer is in the range of 0.1μm≤d1≤100μm.

8. The negative electrode current collector according to claim 7, characterized in that, If the thickness of the sodium storage layer is d2, then the negative electrode current collector satisfies the following relationship: 0 <d2-d1≤50μm。 9. A battery, characterized in that, The battery includes: Positive electrode sheet; A diaphragm is disposed on one side of the positive electrode plate; The negative electrode current collector according to any one of claims 1 to 8, wherein the sodium storage layer of the negative electrode current collector is stacked on the positive projection portion of the separator and partially offset from the positive electrode sheet on the separator; and Electrolyte.

10. The battery according to claim 9, characterized in that, The specific capacity of the positive electrode sheet is C, the theoretical volumetric specific capacity of sodium metal is Q, the thickness of the conductive layer is d1, and the thickness of the sodium storage layer is d2. Then the battery satisfies the relationship: 0 < d2 - d1 ≤ 1.5 × C / Q.

11. The battery according to claim 9, characterized in that, Along a preset direction, the width of the sodium storage layer projected onto the diaphragm is L1, and the width of the area where the sodium storage layer and the positive electrode plate overlap in the region where the sodium storage layer and the positive electrode plate overlap in the region where the positive electrode plate and the positive electrode plate overlap in the region where the sodium storage layer and the positive electrode plate overlap in the region satisfying the relationship: 0 < L2 / L1 ≤ 1; where the preset direction is the arrangement direction of the conductive layer and the sodium storage layer.

12. An electrical appliance, characterized in that, The electrical equipment includes: The equipment itself; and The battery according to any one of claims 9 to 11, wherein the battery supplies power to the device body.

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