Sodium-ion battery, energy storage device, power utilization system and energy storage system

Abstract

The application provides a sodium ion battery, an energy storage device, a power utilization system and an energy storage system. The sodium ion battery provided by the application comprises a negative electrode sheet, a positive electrode sheet and a sodium storage layer. The negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer arranged on the surface of the negative electrode current collector. The negative electrode material layer comprises a sodium storage layer and a conductive framework layer. The sodium storage layer is closer to the negative electrode current collector than the conductive framework layer. The positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on the surface of the positive electrode current collector. The ratio of the capacitance of the sodium storage layer to the capacitance of the positive electrode material layer is CB, and 0.8<=CB<=1.4. The sodium ion battery provided by the application has a high cycle capacity retention rate.

Description

Technical Field

[0001] This application relates to the field of energy storage, specifically to a sodium-ion battery, an energy storage device, an electrical system, and an energy storage system. Background Technology

[0002] The development of sodium-ion batteries has attracted the attention of many researchers; however, existing sodium-ion batteries have a low cycle life. Summary of the Invention

[0003] This application provides a sodium-ion battery with a high cycle capacity retention rate.

[0004] In a first aspect, this application provides a sodium-ion battery, comprising:

[0005] A negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on the surface of the negative electrode current collector. The negative electrode material layer includes a sodium storage layer and a conductive framework layer, wherein the sodium storage layer is closer to the negative electrode current collector than the conductive framework layer.

[0006] A positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on the surface of the positive current collector;

[0007] Among them, the ratio of the capacitance of the sodium storage layer to the capacitance of the positive electrode material layer of the same area is CB, then 0.8≤CB≤1.4.

[0008] Furthermore, the sodium-ion battery also satisfies the following relationship: 1.4≤d² / [10000×(1-CB)×L / M]≤3.8, where 0.8≤CB<1, L is the capacitance per unit area of ​​the positive electrode material layer, M is the theoretical volumetric capacity of sodium metal, d² is in μm, and L is in mAh / cm². 2 The unit of M is mAh / cm³. 3 10000 is the conversion constant when converting centimeters to micrometers.

[0009] Furthermore, the sodium-ion battery also satisfies the following relationship: 1.7≤d2+1 / CB≤10.9, where 1≤CB≤1.4, and d2 is the thickness of the conductive framework layer, with the unit of d2 being μm.

[0010] Furthermore, the ratio of the thickness d2 of the conductive framework layer to the thickness d1 of the sodium storage layer is in the range of 0.02≤d2 / d1≤0.22.

[0011] Furthermore, the thickness d1 of the sodium storage layer is in the range of 45μm≤d1≤100μm; the thickness d2 of the conductive framework layer is in the range of 1μm≤d2≤10μm.

[0012] Furthermore, the sodium storage layer includes at least one of hard carbon and soft carbon; the conductive framework layer includes a conductive carbon material, which includes at least one of porous carbon, carbon nanotubes, carbon fibers, and carbon black.

[0013] Furthermore, the conductive framework layer also includes a doping element, which is doped into the conductive carbon material, and the doping element includes at least one of oxygen, sulfur, nitrogen, phosphorus or fluorine.

[0014] Furthermore, in the conductive framework layer, the mass fraction of the dopant element ranges from 0.1 wt% to 1.5 wt%.

[0015] Furthermore, the positive electrode material layer includes a positive electrode active material, which includes one or more of transition metal oxides, polyanionic compounds, and Prussian blue materials.

[0016] Secondly, this application provides an energy storage device, which includes:

[0017] Box;

[0018] The sodium-ion battery described in this application embodiment is housed within the casing, and the multiple sodium-ion batteries are connected in at least one of series and parallel connections.

[0019] Thirdly, this application provides an electrical system comprising:

[0020] Electrical equipment; and

[0021] The energy storage device described in this application embodiment supplies power to the electrical equipment.

[0022] Fourthly, this application provides an energy storage system, which includes:

[0023] An energy conversion device for converting other forms of energy into electrical energy;

[0024] The energy storage device described in this application embodiment is electrically connected to the power conversion device and is used to store the electrical energy of the power conversion device; and

[0025] The electrical load is electrically connected to the power conversion device and the energy storage device, respectively, and is used to operate using the electrical energy of the power conversion device or the energy storage device.

[0026] The sodium-ion battery in the application embodiment includes a positive electrode and a negative electrode. The negative electrode material layer of the negative electrode includes a sodium storage layer and a conductive framework layer. The ratio CB of the capacitance of the sodium storage layer per unit area to the capacitance of the positive electrode material layer per unit area is in the range of 0.8≤CB≤1.4. The sodium storage layer of the negative electrode in this application is used as an active material for sodium ion intercalation, and the conductive framework layer is used as a substrate for sodium metal deposition. When the conductive framework layer includes conductive carbon material, the conductive carbon material has sodium affinity, which can reduce the nucleation overpotential of sodium metal deposition and induce sodium metal to be uniformly deposited on the conductive framework layer. Therefore, it can effectively suppress the formation and growth of sodium dendrites during sodium deposition / dissolution, and improve the cycle life and safety performance of the battery. At the same time, the "intercalation-deposition" hybrid mechanism for sodium storage can achieve a higher sodium storage capacity, thereby improving the energy density of the battery. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is an application scenario diagram of the energy storage system provided in the embodiments of this application.

[0029] Figure 2 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application.

[0030] Figure 3 This is a circuit block diagram of an energy storage system according to an embodiment of this application.

[0031] Figure 4 This is a partial perspective structural diagram of an electrical system according to an embodiment of this application.

[0032] Figure 5 This is a schematic diagram of the structure of an energy storage device according to an embodiment of this application.

[0033] Figure 6 This is a schematic diagram of the structure of a sodium-ion battery according to an embodiment of this application.

[0034] Figure 7 This application describes a sodium-ion battery according to an embodiment of the present application. Figure 6 A schematic diagram of the cross-sectional structure along the A-A direction.

[0035] Figure 8 This is a cross-sectional view of the negative electrode sheet in an embodiment of this application, along the direction perpendicular to the thickness.

[0036] Figure 9This is a cross-sectional view of the positive electrode sheet of an embodiment of this application along the direction perpendicular to the thickness.

[0037] Explanation of reference numerals in the attached figures:

[0038] 300-Energy storage system, 310-Electrical energy conversion device, 330-Electrical load, 200-Electrical system, 210-Electrical equipment, 400-Energy storage device, 410-Box, 100-Sodium-ion battery, 110-Negative electrode, 111-Negative current collector, 112-Negative electrode material layer, 1121-Sodium storage layer, 1122-Conductive framework layer, 120-Positive electrode, 121-Positive current collector, 122-Positive electrode material layer, 130-Separator. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0040] 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.

[0041] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0042] It should be noted that, for ease of explanation, the same reference numerals denote the same components in the embodiments of this application, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0043] 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.

[0044] Taking electrochemical energy storage as an example, this solution provides an energy storage device. The energy storage device is equipped with a chemical battery, which mainly uses the chemical elements in the battery 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 electricity is released for use, or transferred to places with a shortage of electricity for use.

[0045] Current energy storage applications are quite widespread, including generation-side energy storage, grid-side energy storage, renewable energy grid-connected energy storage, and user-side energy storage. The corresponding types of energy storage devices include:

[0046] (1) Large energy storage containers used in grid-side energy storage scenarios can serve as high-quality active and reactive power regulation power sources in the grid, enabling load matching of electrical energy in time and space, enhancing the absorption capacity of renewable energy, and playing a significant role in grid system backup, alleviating peak load power supply pressure, and peak regulation and frequency regulation.

[0047] (2) Small and medium-sized energy storage cabinets used in commercial and industrial energy storage scenarios (banks, shopping malls, etc.) and small household energy storage boxes used in residential energy storage scenarios primarily operate under the "peak shaving and valley filling" mode. Because there are significant price differences in electricity consumption during peak and off-peak periods, users with energy storage devices typically charge the cabinets / boxes during off-peak hours to reduce costs; during peak hours, they release the stored electricity for use, thus saving on electricity bills. Furthermore, in remote areas and regions prone to natural disasters such as earthquakes and hurricanes, the existence of household energy storage devices effectively provides backup power for users and the power grid, eliminating the inconvenience caused by frequent power outages due to disasters or other reasons.

[0048] Figure 1 This is an application scenario diagram of the energy storage system 300 provided in an embodiment of this application. This application... Figure 1The embodiments are illustrated using a residential energy storage scenario in user-side energy storage as an example. The energy storage device 400 of this application is not limited to residential energy storage scenarios. Figure 2 This is a schematic diagram of the structure of an energy storage system 300 according to an embodiment of this application. Figure 3 This is a circuit block diagram of an energy storage system 300 according to an embodiment of this application.

[0049] Please see Figures 1 to 3 This application provides an energy storage system 300, which is a residential energy storage system. The energy storage system 300 includes a power conversion device 310, an energy storage device 400, and an electrical load 330. The power conversion device 310 converts other forms of energy into electrical energy. The energy storage device 400 is electrically connected to the power conversion device 310 and stores the electrical energy stored in the power conversion device 310. The electrical load 330 is electrically connected to both the power conversion device 310 and the energy storage device 400, and operates using the electrical energy from either the power conversion device 310 or the energy storage device 400. It is understood that a portion of the electrical energy converted by the power conversion device 310 is stored in the energy storage device 400, and a portion is used to supply power to the electrical load 330. The energy storage device 400 stores electrical energy and supplies it to the electrical load 330 during peak electricity price periods. The energy storage system 300 can convert other forms of energy into electrical energy and store the electrical energy in the energy storage device 400 to supply sufficient electrical energy to the electrical load 330.

[0050] Optionally, the power conversion device 310 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy and mechanical energy into electrical energy, providing a stable power supply for the electrical load 330 and the energy storage device 400.

[0051] Optionally, the power conversion device 310 can be a photovoltaic panel, which can convert solar energy into electrical energy during periods of low electricity prices and store it in the energy storage device 400. In other embodiments, it can also be at least one of wind power generation devices, thermal power generation devices, tidal power generation devices, biomass power generation devices, and mechanical power generation devices.

[0052] Optionally, the energy storage device 400 is a small energy storage box that can be wall-mounted on an outdoor wall. In other embodiments, the energy storage device 400 can also be a large energy storage container, a battery used in electronic devices, etc.

[0053] Optionally, the electrical load 330 can be a street light, household appliance, motor vehicle, etc., and the energy storage device 400 is used to store the electrical energy and supply it to the street light and household appliance during peak electricity prices, or to supply power when the power grid is interrupted / out of service.

[0054] It is understood that the energy storage device 400 may include, but is not limited to, at least one of the following: individual cells, battery modules, battery packs, and battery systems. Individual cells may be, but are not limited to, at least one of the following: cylindrical cells, prismatic cells, etc.

[0055] It is understood that the accompanying drawings in this embodiment are merely one form of the energy storage system 300 and should not be construed as limiting the energy storage system 300 provided in this application, nor should they be construed as limiting the energy storage device 400 provided in various embodiments of this application.

[0056] Please see Figure 4 , Figure 4 This is a schematic diagram of the structure of an electrical system 200 according to an embodiment of this application. This application also provides an electrical system 200, which includes: an electrical device 210 and an energy storage device 400, wherein the energy storage device 400 supplies power to the electrical device 210.

[0057] The electrical device 210 in this 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 vehicles such as cars, trucks, sedans, vans, freight cars, bullet trains, high-speed trains, and electric bicycles. Furthermore, it can be various household appliances such as refrigerators, lights, and air conditioners.

[0058] It is understood that the electrical equipment 210 in the accompanying drawings of this application is illustrated using a car as an example. The electrical system 200 illustrated in the accompanying drawings of this application is only one form of the electrical equipment 210 and should not be construed as a limitation on the electrical system 200 and electrical equipment 210 provided in this application.

[0059] Please see Figure 5 This application embodiment also provides an energy storage device 400, which includes a housing 410 and a plurality of sodium-ion batteries 100.

[0060] The term "multiple" refers to two or more.

[0061] Understandably, the multiple sodium-ion batteries 100 of the energy storage device 400 can be connected in parallel, or in series, or partially in parallel and partially in series (in other words, mixed connection). This application does not specifically limit the connection method of the multiple sodium-ion batteries 100 of the same energy storage device 400.

[0062] Understandably, the housing 410 has a receiving cavity (not shown) in which a plurality of sodium-ion batteries 100 are received. In some embodiments, each receiving cavity receives one sodium-ion battery 100. In other embodiments, each receiving cavity receives a plurality of sodium-ion batteries 100.

[0063] Please see Figures 6 to 9 In some embodiments, this application also provides a sodium-ion battery 100, which includes a negative electrode 110 and a positive electrode 120. The negative electrode 110 includes a negative current collector 111 and a negative electrode material layer 112 disposed on the surface of the negative current collector 111. The negative electrode material layer 112 includes a sodium storage layer 1121 and a conductive framework layer 1122. The sodium storage layer 1121 is closer to the negative current collector 111 than the conductive framework layer 1122. The positive electrode 120 includes a positive current collector 121 and a positive electrode material layer 122 disposed on the surface of the positive current collector 121. The ratio of the capacitance of the sodium storage layer 1121 to the capacitance of the positive electrode material layer 122 of the same area is CB, and 0.8 ≤ CB ≤ 1.4.

[0064] It should be noted that the ratio of the capacitance of the sodium storage layer 1121 to the capacitance of the positive electrode material layer 122 of the same area is CB. Then, 0.8≤CB≤1.4. It can be understood that the range of the ratio CB of the sodium storage layer 1121 per unit area to the capacitance of the positive electrode material layer 122 per unit area is: 0.8≤CB≤1.4.

[0065] Understandably, the sodium storage layer 1121 and the conductive framework layer 1122 are sequentially stacked on the surface of the negative electrode current collector 111. In other words, the sodium storage layer 1121 is disposed between the negative electrode current collector 111 and the conductive framework layer 1122.

[0066] Specifically, the ratio CB of the capacitance of the sodium storage layer 1121 per unit area to the capacitance of the positive electrode material layer 122 per unit area can be, but is not limited to, 0.8, 0.83, 0.85, 0.88, 0.9, 0.93, 0.95, 0.97, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, etc. If the ratio CB of the capacitance of the sodium storage layer 1121 per unit area to the capacitance of the positive electrode material layer 122 per unit area is too small, the sodium storage capacity of the sodium storage layer 1121 will be too small, resulting in an excess of sodium metal. The conductive framework layer 1122 will not be able to effectively distribute all the sodium metal, and the sodium metal will not be deposited uniformly in the conductive framework layer 1122. If the ratio CB of the capacitance of the sodium storage layer 1121 per unit area to the capacitance of the positive electrode material layer 122 per unit area is too large, the irreversible capacity loss of the battery will be greater, and the energy density of the sodium-ion battery 100 will decrease. When the ratio CB of the capacitance of the sodium storage layer 1121 per unit area to the capacitance of the positive electrode material layer 122 per unit area is between 0.8 and 1.4, both more uniform deposition of sodium metal in the conductive framework layer 1122 and a higher energy density of the sodium-ion battery 100 can be achieved.

[0067] The sodium storage mechanism of the negative electrode 110 in this embodiment is as follows: sodium ions are first intercalated in the sodium storage layer 1121, and then sodium metal is deposited on the surface of the conductive framework layer 1122.

[0068] The sodium-ion battery 100 in the application embodiment includes a positive electrode 120 and a negative electrode 110. The negative electrode material layer 112 of the negative electrode 110 includes a sodium storage layer 1121 and a conductive framework layer 1122. The ratio CB of the capacitance of the sodium storage layer 1121 per unit area to the capacitance of the positive electrode material layer 122 per unit area is in the range of 0.8≤CB≤1.4. The sodium storage layer 1121 of the negative electrode 110 in this application is used as an active material for sodium ion intercalation, and the conductive framework layer 1122 is used as a substrate for sodium metal deposition. When the conductive framework layer 1122 includes conductive carbon material, the conductive carbon material has sodium affinity, which can reduce the nucleation overpotential of sodium metal deposition and induce sodium metal to be uniformly deposited on the conductive framework layer 1122. Therefore, it can effectively suppress the formation and growth of sodium dendrites during sodium deposition / dissolution, and improve the cycle life and safety performance of the battery. At the same time, the "intercalation-deposition" hybrid mechanism for sodium storage can achieve a higher sodium storage capacity, thereby improving the energy density of the battery.

[0069] In some embodiments, the sodium-ion battery 100 also satisfies the following relationship: 1.4 ≤ d² / [10000 × (1-CB) × L / M] ≤ 3.8, where 0.8 ≤ CB < 1, L is the capacitance per unit area of ​​the positive electrode material layer 122, M is the theoretical volumetric capacity of sodium metal, d² is in μm, and L is in mAh / cm². 2 The unit of M is mAh / cm³. 3 10000 is the conversion constant when converting centimeters to micrometers.

[0070] It should be noted that the theoretical reversible specific capacity of sodium metal is 1166 mAh / g, and the theoretical density of sodium metal is 0.97 g / cm³. 3 Therefore, the theoretical volumetric capacity of sodium metal is M = 1166 mAh / g × 0.97 g / cm³. 3 =1131.02mAh / cm 3 .

[0071] Specifically, d2 / [10000×(1-CB)×L / M] can be, but is not limited to, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, etc.

[0072] In this embodiment, when 0.8 ≤ CB < 1, d2 / [10000 × (1-CB) × L / M] is too small, indicating that the thickness of the conductive framework layer 1122 is too small or the capacitance L per unit area of ​​the positive electrode material layer 122 is too large. A thin conductive framework layer 1122 will result in insufficient nucleation sites for sodium metal, failing to effectively improve the sodium deposition overpotential, easily causing the formation and growth of sodium dendrites, and reducing the cycle performance of the sodium-ion battery 100. Conversely, a large capacitance L per unit area of ​​the positive electrode material layer 122 will result in insufficient nucleation sites for sodium metal, failing to effectively improve the sodium deposition overpotential, easily causing the formation and growth of sodium dendrites, and reducing the cycle performance of the sodium-ion battery 100. The excessive thickness of both layer 122 and negative electrode material layer 112 makes electrolyte wetting difficult, increases sodium ion transport resistance, and leads to excessive sodium metal, preventing the conductive framework layer 1122 from effectively utilizing all the sodium metal. The excessively large d2 / [10000×(1-CB)×L / M] indicates that the thickness of the conductive framework layer 1122 is too large or the capacitance L per unit area of ​​the positive electrode material layer 122 is too small. Both of these will result in insufficient sodium deposition in the conductive framework layer 1122, thus causing a decrease in the energy density of the sodium-ion battery 100. When 1.4≤d2 / [10000×(1-CB)×L / M]≤3.8, the carbon material in the conductive framework layer 1122 has a sodium affinity, which can reduce the nucleation overpotential of sodium metal deposition and induce uniform sodium metal deposition. Therefore, it can effectively suppress the formation and growth of sodium dendrites during sodium deposition / dissolution, and improve the cycle life and safety performance of sodium-ion battery 100. At the same time, the "intercalation-deposition" hybrid mechanism for sodium storage can achieve a higher sodium storage capacity, thereby improving the energy density of sodium-ion battery 100.

[0073] Optionally, the capacitance L per unit area of ​​the positive electrode material layer 122 ranges from 1.6 mAh / cm². 2 ≤L≤2.8mAh / cm 2 Specifically, the capacitance L per unit area of ​​the positive electrode material layer 122 can be, but is not limited to, 1.6 mAh / cm². 2 1.7mAh / cm 2 1.8mAh / cm 2 1.9mAh / cm 2 2.0mAh / cm 2 2.1mAh / cm 2 2.2mAh / cm 2 2.3mAh / cm 2 2.4mAh / cm 2 2.5mAh / cm 2 2.6mAh / cm 2 2.7mAh / cm 2 2.8mAh / cm 2If the capacitance L per unit area of ​​the positive electrode material layer 122 is too small, the energy density of the sodium-ion battery 100 will be low; if the capacitance L per unit area of ​​the positive electrode material layer 122 is too large, both the positive electrode material layer 122 and the negative electrode material layer 112 will be too thick, making electrolyte wetting difficult, increasing sodium ion transport resistance, causing a decrease in the kinetic performance of the positive electrode 120 and the negative electrode 110, and affecting the rate performance of the sodium-ion battery 100.

[0074] Furthermore, the capacitance L per unit area of ​​the positive electrode material layer 122 ranges from 1.9 mAh / cm². 2 ≤L≤2.4mAh / cm 2 This allows the sodium-ion battery 100 to have a high energy density and good kinetic performance.

[0075] In some embodiments, the sodium-ion battery 100 also satisfies the following relationship: 1.7 ≤ d² + 1 / CB ≤ 10.9, where 1 ≤ CB ≤ 1.4, and d² is the thickness of the conductive framework layer 1122, with the unit of d² being μm. Specifically, d² + 1 / CB can be, but is not limited to, 1.7, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10.9, etc. In this embodiment, when 1 ≤ CB ≤ 1.4, d² + 1 / CB is too small, indicating that the thickness of the conductive framework layer 1122 is too small. A small thickness of the conductive framework layer 1122 will result in too few sodium metal nucleation sites, making it impossible for sodium precipitated during long-cycle processes or high-rate charging of the sodium-ion battery 100 to be uniformly deposited, causing a decrease in the cycle performance of the sodium-ion battery 100. A large thickness of d² + 1 / CB indicates that the thickness of the conductive framework layer 1122 is too large. A large thickness of the conductive framework layer 1122 will lead to a decrease in the energy density of the sodium-ion battery 100. When 1.7≤d2+1 / CB≤10.9, the carbon material in the conductive framework layer 1122 has a sodium affinity, which enables the sodium that is precipitated due to increased polarization during long cycles or high-rate charging to be deposited uniformly, effectively suppressing the formation and growth of sodium dendrites, thereby improving the cycle life and safety performance of the battery.

[0076] In some embodiments, the ratio of the thickness d2 of the conductive framework layer 1122 to the thickness d1 of the sodium storage layer 1121 is in the range of 0.02 ≤ d2 / d1 ≤ 0.22.

[0077] Specifically, the ratio d2 / d1 of the thickness d2 of the conductive framework layer 1122 to the thickness d1 of the sodium storage layer 1121 can be, but is not limited to, 0.01, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, etc. A small d2 / d1 ratio indicates either an insufficient thickness of the conductive framework layer 1122 or an excessive thickness of the sodium storage layer 1121. Insufficient thickness of the conductive framework layer 1122 results in too few nucleation sites for sodium metal, failing to effectively improve the overpotential of sodium deposition and easily leading to the formation and growth of sodium dendrites, thus reducing the cycle performance of the sodium-ion battery 100. Excessive thickness of the sodium storage layer 1121 makes electrolyte wetting of the negative electrode material layer 112 difficult, increasing sodium ion transport resistance and reducing the kinetic performance of the negative electrode 110, thus affecting the rate performance of the sodium-ion battery 100. Conversely, a large d2 / d1 ratio indicates either an insufficient thickness of the sodium storage layer 1121 or an excessive thickness of the conductive framework layer 1122, leading to a decrease in the energy density of the sodium-ion battery 100. A ratio of 0.01 ≤ d2 / d1 ≤ 0.22 allows the sodium-ion battery 100 to achieve both good cycle and rate performance, as well as a high energy density.

[0078] Furthermore, the ratio of the thickness d2 of the conductive framework layer 1122 to the thickness d1 of the sodium storage layer 1121 is in the range of 0.05 ≤ d2 / d1 ≤ 0.16. This allows the sodium-ion battery 100 to have better cycle performance and rate performance, as well as higher energy density.

[0079] In some embodiments, the thickness d1 of the sodium storage layer 1121 ranges from 45 μm ≤ d1 ≤ 100 μm. Specifically, the thickness of the sodium storage layer 1121 can be, but is not limited to, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc. If the thickness of the sodium storage layer 1121 is too small, the energy density of the sodium-ion battery 100 is reduced. If the thickness of the sodium storage layer 1121 is increased, the energy density of the sodium-ion battery 100 will also increase accordingly. However, if the thickness of the sodium storage layer 1121 is too thick, it makes electrolyte wetting difficult, increases sodium ion transport resistance, reduces the kinetic performance of the negative electrode 110, and thus reduces the rate performance of the sodium-ion battery 100. When the thickness d1 of the sodium storage layer 1121 is in the range of 45μm≤d1≤100μm, the electrolyte can well wet the sodium storage layer 1121 of the negative electrode 110, which increases the liquid phase transport rate of sodium ions and reduces the resistance to sodium ion transport, and also enables the sodium-ion battery 100 to have a high energy density.

[0080] Furthermore, the thickness d1 of the sodium storage layer 1121 is in the range of 50μm≤d1≤80μm. This allows the electrolyte to effectively wet the sodium storage layer 1121 of the negative electrode 110, resulting in a faster liquid phase transport rate of sodium ions and lower sodium ion transport resistance, while also enabling the sodium-ion battery 100 to have a higher energy density.

[0081] Furthermore, the thickness d1 of the sodium storage layer 1121 is in the range of 55μm≤d1≤75μm. This allows the electrolyte to effectively wet the sodium storage layer 1121 of the negative electrode 110, resulting in a faster liquid phase transport rate of sodium ions and lower sodium ion transport resistance, while also enabling the sodium-ion battery 100 to have a higher energy density.

[0082] In some embodiments, the thickness d2 of the conductive framework layer 1122 is in the range of 1 μm ≤ d2 ≤ 10 μm. Specifically, the thickness d2 of the conductive framework layer 1122 can be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. If the thickness d2 of the conductive framework layer 1122 is too small, there will be too few nucleation sites for sodium metal, which will not effectively improve the overpotential of sodium deposition and will easily cause the formation and growth of sodium dendrites, resulting in a decrease in the cycle performance of the sodium-ion battery 100. If the thickness d2 of the conductive framework layer 1122 is too large, the energy density of the sodium-ion battery 100 will decrease. When the thickness d2 of the conductive framework layer 1122 is in the range of 1 μm ≤ d2 ≤ 10 μm, the growth of sodium dendrites can be effectively prevented, resulting in good cycle performance of the sodium-ion battery 100 and a high energy density of the sodium-ion battery 100.

[0083] Furthermore, the thickness d2 of the conductive framework layer 1122 is in the range of 2μm≤d2≤9μm, which can effectively prevent the growth of sodium dendrites, giving the sodium-ion battery 100 good cycle performance and high energy density.

[0084] Furthermore, the thickness d2 of the conductive framework layer 1122 is in the range of 2.5μm≤d2≤8μm. This can effectively prevent the growth of sodium dendrites, giving the sodium-ion battery 100 good cycle performance and high energy density.

[0085] In some embodiments, the sodium storage layer 1121 includes a first active material, a first binder, and a first conductive agent.

[0086] Optionally, the first active material can be an amorphous carbon material, including at least one of hard carbon and soft carbon.

[0087] Optionally, the hard carbon may include at least one of the following: hard carbon produced by carbonization using coconut shell, fruit shell, rice husk, straw, bamboo, lignin, starch, cellulose, sucrose, phenolic resin, asphalt, etc. as precursors.

[0088] Optionally, the soft carbon may include at least one of bitumen, anthracite, petroleum coke, etc.

[0089] Optionally, the first binder may include at least one of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyacrylate, carboxymethyl cellulose (CMC), sodium alginate, etc. These binders can better bond the first active material and the first conductive agent, making the sodium storage layer 1121 less prone to pulverization or flaking.

[0090] Optionally, the first conductive agent may include at least one of acetylene black, conductive carbon black (Super-P), carbon nanotubes, carbon fibers, graphene, etc. These conductive agents can better reduce the contact resistance of the negative electrode 110, accelerate the electron mobility and sodium ion migration rate in the negative electrode material layer 112, and improve the electronic conductivity, thereby improving the charge and discharge efficiency of the negative electrode 110.

[0091] In some embodiments, the conductive framework layer 1122 includes a conductive carbon material and a second binder. The conductive carbon material has good conductivity, mechanical properties, and flexibility, which is beneficial for sodium metal deposition, and it is lightweight, enabling the sodium-ion battery 100 to have a higher energy density.

[0092] Optionally, the conductive carbon material includes at least one of porous carbon, carbon nanotubes, carbon fibers, and carbon black. These conductive carbon materials have a high degree of graphitization and high electronic conductivity, resulting in better electronic conductivity of the conductive framework layer 1122, thereby allowing sodium metal to be uniformly deposited on the conductive framework layer 1122. Optionally, the mass fraction of the conductive carbon material in the conductive framework layer 1122 is 90% to 98%. Specifically, the mass fraction of the conductive carbon material in the conductive framework layer 1122 can be, but is not limited to, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, etc. If the mass fraction of the conductive carbon material in the conductive framework layer 1122 is too high, the proportion of the second binder will be too low, easily leading to a decrease in the adhesion of the conductive framework layer 1122, and problems such as coating peeling and cracking may occur during processing. If the mass fraction of the conductive carbon material in the conductive framework layer 1122 is too low, the conductivity of the conductive framework layer 1122 will decrease, which will not effectively improve the sodium deposition overpotential and will easily form sodium dendrites, thus reducing the cycle performance of the sodium-ion battery 100.

[0093] In some embodiments, the conductive framework layer 1122 further includes a dopant element, which is doped into the conductive carbon material. The dopant element includes at least one of oxygen, sulfur, nitrogen, phosphorus, or fluorine. Doping the conductive framework layer 1122 with a dopant element allows for preferential deposition of sodium metal in the conductive framework layer 1122 and results in more uniform deposition of sodium metal in the conductive framework layer 1122. This can better suppress the formation and growth of sodium dendrites, thereby improving the cycle life and safety performance of the battery.

[0094] In some embodiments, the mass fraction of the dopant element in the conductive framework layer 1122 ranges from 0.1 wt% to 1.5 wt%. Specifically, the mass fraction of the dopant element in the conductive framework layer 1122 can be, but is not limited to, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, and 1.5 wt%. If the mass fraction of the dopant element in the conductive framework layer 1122 is too low, it is not conducive to the formation of uniform sodium metal nuclei by sodium ions, and it is not conducive to improving the uniformity of sodium metal deposition. When the mass fraction of the dopant element is too high, it leads to an increase in defects in the conductive carbon material, an increase in side reactions with the electrolyte, and a decrease in the conductivity of the conductive carbon material, which is not conducive to uniform sodium metal deposition. In this embodiment, by controlling the content of doped elements in the conductive framework layer 1122, the nucleation overpotential of sodium metal deposition can be effectively reduced, and uniform deposition of sodium metal can be induced, which is beneficial to suppressing the formation and growth of sodium dendrites and improving the cycle life and safety performance of the battery.

[0095] Optionally, the negative electrode current collector 111 can be, but is not limited to, at least one of aluminum foil, copper foil, carbon-coated aluminum foil, and stainless steel foil.

[0096] Optionally, the positive current collector 121 can be, but is not limited to, at least one of aluminum foil, carbon-coated aluminum foil, and stainless steel foil.

[0097] In some embodiments, the positive electrode material layer 122 includes a positive electrode active material, which includes one or more of transition metal oxides, polyanionic compounds, and Prussian blue materials.

[0098] Optionally, the transition metal oxide may include a sodium transition metal oxide. The sodium transition metal oxide may include at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The chemical formula of the sodium transition metal oxide is Na. xMO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1. In a specific embodiment, the sodium transition metal oxide can be Na[Ni] 1 / 3 Fe 1 / 3 Mn 1 / 3 O2.

[0099] Optionally, the polyanionic compound refers to a compound containing sodium ions, transition metal ions, and a tetrahedral (YO4) structure. n A class of compounds with an anionic unit, wherein Y can be at least one of P, S, and Si; n represents (YO4). n The valence state. The transition metal in the polyanionic compound can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. In some embodiments, the polyanionic compound is at least one of Na3V2(PO4)3.

[0100] Optionally, the Prussian blue compounds refer to a class of compounds containing sodium ions, transition metal ions, and cyanide ions (CN). The general chemical formula of the Prussian blue compounds is Na. x M1[M2(CN)6], where 0<x≤2, M1 can be at least one of Ni, Cu, Fe, Mn, Co and Zn, and M2 can be at least one of Ni, Cu, Fe, Mn, Co and Zn.

[0101] Optionally, the positive electrode material layer 122 further includes a third binder and a second conductive agent.

[0102] Optionally, the third binder can be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyacrylic acid (PAA), etc. These binders can better bond the positive electrode active material and the second conductive agent, making the positive electrode material layer 122 less prone to pulverization or flaking.

[0103] Optionally, the second conductive agent can be at least one of acetylene black, conductive carbon black, carbon nanotubes, carbon fibers, graphene, etc. These conductive agents can better reduce the contact resistance of the positive electrode 120, accelerate the electron mobility and sodium ion migration rate in the positive electrode material layer 122, and improve the electronic conductivity, thereby improving the charge and discharge efficiency of the positive electrode 120.

[0104] Please see again Figure 7 The sodium-ion battery 100 of this application also includes a separator 130, which is disposed between the positive electrode 120 and the negative electrode 110.

[0105] Optionally, the diaphragm 130 includes one or more of polypropylene (PP), polyethylene (PE), and ceramic diaphragm 130.

[0106] The sodium-ion battery 100 of this application further includes an electrolyte (not shown), which wets at least a portion of the positive electrode material layer 122 of the positive electrode 120 and the negative electrode material layer 112 of the negative electrode 110. In other words, both the positive electrode material layer 122 of the positive electrode 120 and the negative electrode material layer 112 of the negative electrode 110 are at least partially immersed in the electrolyte.

[0107] Optionally, the electrolyte includes electrolyte salts, organic solvents, and additives.

[0108] Optionally, the electrolyte salt may include, but is not limited to, sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), and sodium perchlorate (NaClO). 4) At least one of the following: sodium bis(fluorosulfonyl)imide (NaN(CF3SO2)2), sodium bis(fluorosulfonyl)imide (NaN(SO2F)2), sodium bis(oxalateborate)borate (NaB(C2O4)2), sodium difluorooxalateborate (NaBF2C2O4).

[0109] Optionally, the organic solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethylene glycol dimethyl ether (DEGDME), ethylene glycol dimethyl ether (DME), and 1,3-dioxolane (DOL).

[0110] Optionally, the additives may include, but are not limited to, at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), sodium nitrate, etc.

[0111] The sodium-ion battery 100 of this application will be further described below through specific embodiments.

[0112] Examples 1 to 12, Comparative Examples 1 to 2

[0113] The sodium-ion batteries 100 of each embodiment and comparative example were prepared by the following steps:

[0114] (1) Preparation of negative electrode sheet 110: Hard carbon (first active material), conductive carbon black (first conductive agent), sodium hydroxymethyl cellulose (CMC, first binder) and styrene-butadiene rubber (SBR, first binder) are mixed in a mass ratio of 95.5:1:1.5:2. The mixed powder is placed in a vacuum mixer, deionized water is added and stirred to obtain a first negative electrode slurry. The first negative electrode slurry is uniformly coated on the opposite two sides of the negative electrode current collector 111 to form a first negative electrode slurry layer. The negative electrode current collector 111 coated with the first negative electrode slurry layer is transferred to an oven to dry, obtaining a negative electrode sheet 110. A negative electrode current collector 111 with a sodium storage layer 1121 is prepared. Carbon nanotubes (conductive carbon material, doped with nitrogen at a doping amount of 0.5 wt%), sodium hydroxymethyl cellulose (CMC, the second binder) and styrene-butadiene rubber (SBR, the second binder) are mixed in a mass ratio of 95:2:3. The mixed powder is placed in a vacuum mixer, deionized water is added and stirred to obtain a second negative electrode slurry. The second negative electrode slurry is uniformly coated on the surface of the sodium storage layer 1121 and transferred to an oven for drying to obtain a conductive framework layer 1122. Then, after rolling and slitting, a negative electrode sheet 110 is obtained.

[0115] (2) Preparation of positive electrode 120:

[0116] Na3V2(PO4)3 (positive electrode active material), conductive carbon black (second conductive agent, Super-P), and PVDF (third binder) are mixed in a mass ratio of 95:2.5:2.5. The mixed powder is placed in a vacuum mixer, N-methylpyrrolidone (NMP) is added, and the mixture is stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on the opposite two sides of the aluminum foil of the positive electrode current collector 121. The positive electrode current collector 121 coated with the positive electrode slurry is transferred to an oven for drying. After rolling and slitting, the positive electrode sheet 120 is obtained.

[0117] (3) Electrolyte preparation

[0118] Dry sodium salt NaPF6 was added to diethylene glycol dimethyl ether (DEGDME) solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0119] (4) Secondary battery preparation

[0120] The positive electrode 120, polypropylene separator 130 and negative electrode 110 are stacked in sequence and then wound to obtain a bare cell. The bare cell is placed in an aluminum-plastic film soft package, dried and injected with electrolyte. After vacuum sealing, standing, formation and shaping processes, a secondary sodium-ion battery 100 is obtained.

[0121] Example 13

[0122] The difference between this embodiment 13 and embodiment 1 is that the positive electrode active material of the positive electrode material layer 122 is replaced with Na[Ni] 1 / 3 Fe 1 / 3 Mn 1 / 3 O2.

[0123] Example 14

[0124] The difference between this embodiment 14 and embodiment 3 is that the positive electrode active material of the positive electrode material layer 122 is replaced with Na[Ni] 1 / 3 Fe 1 / 3 Mn 1 / 3 O2.

[0125] Comparative Example 5, Examples 15-17

[0126] The difference between Comparative Example 5, Examples 15-17 and Example 2 is that the content of doped elements in the conductive framework layer 1122 is different.

[0127] Comparative Example 3

[0128] The main difference between Comparative Example 3 and Example 1 is that the negative electrode material layer 112 of Comparative Example 3 only includes the sodium storage layer 1121 and does not include the conductive framework layer 1122.

[0129] Comparative Example 4

[0130] The main difference between Comparative Example 4 and Example 3 is that the negative electrode material layer 112 of Comparative Example 4 only includes the sodium storage layer 1121 and does not include the conductive framework layer 1122.

[0131] The parameters of the sodium-ion batteries 100 in each embodiment and comparative example are shown in Table 1 below.

[0132] Table 1. Parameters of sodium-ion batteries 100 in various embodiments and comparative examples.

[0133]

[0134]

[0135] Performance testing:

[0136] (1) Measurement of the thickness of sodium storage layer 1121 and conductive framework layer 1122: The negative electrode sheet 110 was cut by liquid nitrogen quenching and the cross-sectional image was obtained by scanning electron microscope (SEM) to obtain the thickness of sodium storage layer 1121 and conductive framework layer 1122.

[0137] (2) Energy density test: At 25°C, the sodium-ion batteries 100 of each embodiment and comparative example were weighed using an electronic balance; at 25°C, each sodium-ion battery 100 was charged and discharged at a rate of 0.33C, and the actual discharge energy was recorded; the ratio of the actual discharge energy of the sodium-ion battery 100 to the weight of the sodium-ion battery 100 is the actual energy density of the sodium-ion battery 100.

[0138] (3) Cyclic performance test: The sodium-ion batteries 100 of each embodiment and comparative example were charged at a rate of 0.33C and discharged at a rate of 0.33C to conduct a full charge and discharge cycle test, and the capacity retention rate after 500 cycles was recorded.

[0139] The energy density and cycle capacity retention of the sodium-ion batteries 100 of each embodiment and comparative example are shown in Table 2 below.

[0140] Table 2 Parameters of sodium-ion batteries 100 in various embodiments and comparative examples

[0141] Example Energy density (Wh / kg) Capacity retention rate after 500 cycles Example 1 131 83.2％ Example 2 124 84.3％ Example 3 122 94.7％ Example 4 106 95.9％ Example 5 127 84.1％ Example 6 114 86.2％ Example 7 106 93.9％ Example 8 112 95.4％ Example 9 111 94.0％ Example 10 104 93.5％ Example 11 103 95.3％ Example 12 103 94.4％ Example 13 145 81.4％ Example 14 136 90.1％ Example 15 125 80.9％ Example 16 121 85.2％ Example 17 119 82.4％ Comparative Example 1 110 84.8％ Comparative Example 2 114 90.4％ Comparative Example 3 98 41.6％ Comparative Example 4 122 89.3％ Comparative Example 5 107 57.1％

[0142] The test data from Examples 1 to 17 show that when 0.8 ≤ CB ≤ 1.4, the obtained sodium-ion batteries 100 all have high energy density and cycle capacity retention. The test data from Examples 1 to 4 show that as CB increases, the energy density of the sodium-ion battery 100 decreases, while the cycle capacity retention gradually increases.

[0143] The test data from Examples 1 and 5 show that the CB of Example 1 is relatively smaller, and the energy density of the sodium-ion battery 100 in Example 1 is higher than that in Example 5, but the difference is not significant. The cycle capacity retention rates of the sodium-ion batteries 100 in Examples 1 and 5 are also not significantly different, indicating that when d2 and d2 / d1 are within a certain range, their impact on the cycle capacity retention rate is relatively small.

[0144] As can be seen from the test data of Examples 5 and 6, when the capacity L of the positive electrode material layer 122 per unit area is large, the sodium-ion battery 100 has a higher energy density, but the cycle capacity retention rate is slightly reduced.

[0145] As can be seen from the test data of Example 6 and Comparative Example 1, when the thickness d2 of the conductive framework layer 1122 is too large, and d2 / [10000×(1-CB)×L / M] is too large, the sodium deposition amount of the conductive framework layer 1122 is insufficient, the energy density of the sodium-ion battery 100 decreases, and the cycle capacity retention rate also decreases.

[0146] As can be seen from the test data of Example 3 and Comparative Example 2, when the thickness d2 of the conductive framework layer 1122 is too large and d2+1 / CB is too large, the energy density and cycle capacity retention of the sodium-ion battery 100 will both decrease.

[0147] As can be seen from the test data of Example 1 and Comparative Example 3, when the negative electrode material layer 112 only includes the sodium storage layer 1121, the energy density and cycle capacity retention of the sodium-ion battery 100 are greatly reduced.

[0148] As can be seen from the test data of Example 3 and Comparative Example 4, when the negative electrode material layer 112 only includes the sodium storage layer 1121, the cycle capacity retention rate of the sodium-ion battery 100 will decrease, but the energy density of the sodium-ion battery 100 will remain almost unchanged.

[0149] Test data from Examples 10 to 12 show that when the ratio CB of the capacitance of the sodium storage layer 1121 to the capacitance of the positive electrode material layer 122 of the same area remains constant, and the capacitance L per unit area of ​​the positive electrode material layer 122 remains constant, the energy density of the sodium-ion battery 100 decreases slightly with the increase of d2 / d1 and d2, but the cycle capacity retention rate increases slightly. However, when d2 / d1 and d2 are controlled within a certain range, their impact on the energy density and cycle capacity retention rate of the sodium-ion battery 100 is relatively small.

[0150] The test data from Examples 1 and 13, and Examples 3 and 14 show that when the doping amount, CB, d2, L, d2 / d1, and d2 / [10000×(1-CB)×L / M] are all the same, compared to Examples 1 and 3 which use Na3V2(PO4)3 as the positive electrode active material, Examples 13 and 14 which use Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 Using O2 as the positive electrode active material, sodium-ion batteries have higher energy density, but lower cycle capacity retention.

[0151] The test data from Examples 2, 15 to 17, and Comparative Example 5 show that when the conductive framework layer 1122 does not include any doping elements (Comparative Example 5), the sodium-ion battery 100 has a lower energy density and a lower cycle capacity retention rate. As the doping element content increases, the energy density of the sodium-ion battery 100 first gradually increases and then gradually decreases, and the cycle capacity retention rate also first gradually increases and then gradually decreases. When the mass fraction of the doping element in the conductive framework layer ranges from 0.1 wt% to 1.5 wt%, the sodium-ion battery 100 has a higher energy density and a higher cycle capacity retention rate.

[0152] 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.

[0153] 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 sodium-ion battery, characterized in that, include: A negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on the surface of the negative electrode current collector. The negative electrode material layer includes a sodium storage layer and a conductive framework layer. The sodium storage layer is closer to the negative electrode current collector than the conductive framework layer. The conductive framework layer includes a conductive carbon material. A positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on the surface of the positive current collector; Wherein, the ratio of the capacitance of the sodium storage layer to the capacitance of the positive electrode material layer of the same area is CB, then 0.8≤CB≤1.4; When 0.8 ≤ CB < 1, the sodium-ion battery also satisfies the following relationship: 1.4 ≤ d2 / [10000×(1-CB)×L / M] ≤ 3.8; When 1≤CB≤1.4, the sodium-ion battery also satisfies the following relationship: 1.7≤d2+1 / CB≤10.9; Where L is the capacitance per unit area of ​​the positive electrode material layer, M is the theoretical volumetric capacitance of sodium metal, d2 is the thickness of the conductive framework layer, d2 is in μm, and L is in mAh / cm². 2 The unit of M is mAh / cm³. 3 10000 is the conversion constant when converting centimeters to micrometers.

2. The sodium-ion battery according to claim 1, characterized in that, The ratio of the thickness d2 of the conductive framework layer to the thickness d1 of the sodium storage layer is in the range of 0.02≤d2 / d1≤0.

22.

3. The sodium-ion battery according to claim 1, characterized in that, The thickness d1 of the sodium storage layer is in the range of 45μm≤d1≤100μm; the thickness d2 of the conductive framework layer is in the range of 1μm≤d2≤10μm.

4. The sodium-ion battery according to any one of claims 1-3, characterized in that, The sodium storage layer includes at least one of hard carbon and soft carbon; the conductive carbon material includes at least one of porous carbon, carbon nanotubes, carbon fibers, and carbon black.

5. The sodium-ion battery according to claim 4, characterized in that, The conductive framework layer further includes a doping element, which is doped into the conductive carbon material. The doping element includes at least one of oxygen, sulfur, nitrogen, phosphorus, or fluorine.

6. The sodium-ion battery according to claim 5, characterized in that, In the conductive framework layer, the mass fraction of the doping element ranges from 0.1 wt% to 1.5 wt%.

7. The sodium-ion battery according to any one of claims 1-3 and 5-6, characterized in that, The positive electrode material layer includes a positive electrode active material, which includes one or more of transition metal oxides, polyanionic compounds, and Prussian blue materials.

8. An energy storage device, characterized in that, include: Box; The sodium-ion battery according to any one of claims 1-7, wherein the plurality of sodium-ion batteries are housed in the casing, and the plurality of sodium-ion batteries are connected in at least one of series and parallel connection.

9. An electrical system, characterized in that, include: Electrical equipment; as well as The energy storage device of claim 8, wherein the energy storage device supplies power to the electrical equipment.

10. An energy storage system, characterized in that, include: An energy conversion device for converting other forms of energy into electrical energy; The energy storage device of claim 9, wherein the energy storage device is electrically connected to the power conversion device for storing the electrical energy of the power conversion device; and The electrical load is electrically connected to the power conversion device and the energy storage device, respectively, and is used to operate using the electrical energy of the power conversion device or the energy storage device.

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