Negative electrode sheet, sodium battery, and energy storage device

Abstract

The application relates to a negative pole piece, a sodium battery and an energy storage device. The negative pole piece provided by the application comprises a negative pole current collector, a negative pole active layer arranged on the surface of the negative pole current collector, and an infiltration layer arranged on the surface of the negative pole active layer away from the negative pole current collector, wherein the infiltration layer comprises a sodium supplementing binder and an ion conducting agent.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a negative electrode sheet, a sodium battery, and an energy storage device. Background Technology

[0002] To improve the structural stability and safety of sodium batteries, double-sided adhesive separators (i.e., separators with adhesive layers on both sides) are often used. However, double-sided adhesive separators cause the separator to be bonded too tightly to the positive and negative electrode plates, which is not conducive to the wetting of the electrolyte on the negative electrode plate, reduces the electrolyte injection efficiency of the sodium battery, and reduces the kinetic performance of the sodium battery. Summary of the Invention

[0003] This application provides a negative electrode sheet with good wettability, which can improve the liquid injection efficiency of sodium batteries and give sodium batteries better dynamic performance.

[0004] In a first aspect, embodiments of this application provide a negative electrode sheet, the negative electrode sheet comprising: Negative electrode current collector; A negative electrode active layer, wherein the negative electrode active layer is disposed on the surface of the negative electrode current collector; and A wetting layer is disposed on the surface of the negative electrode active layer opposite to the negative electrode current collector, and the wetting layer includes a sodium-replenishing binder and an ion-conducting agent.

[0005] Furthermore, the mass ratio of the sodium-supplementing binder to the ion-conducting agent in the impregnation layer is 3:7 to 6:4.

[0006] Furthermore, the specific surface area of ​​the ion-conducting agent is in the range of 60 m². 2 / g to 300m 2 / g.

[0007] Furthermore, the average particle size of the ion-conducting agent ranges from 1 μm to 12 μm.

[0008] Furthermore, the ion-conducting agent includes at least one of silicon dioxide and aluminum oxide.

[0009] Furthermore, the sodium-supplementing binder is sodium polyacrylate.

[0010] Furthermore, the number-average molecular weight of the sodium polyacrylate ranges from 40,000 to 500,000.

[0011] Furthermore, the thickness of the impregnation layer ranges from 1 μm to 15 μm.

[0012] Secondly, embodiments of this application also provide a sodium battery, the sodium battery comprising: an electrolyte, a positive electrode, a separator, and a negative electrode as described in embodiments of this application, wherein the separator is located between the positive electrode and the negative electrode.

[0013] Thirdly, embodiments of this application also provide an energy storage device, which includes one or more sodium batteries as described in embodiments of this application.

[0014] The negative electrode sheet of this application includes a negative current collector, a negative active layer and a wetting layer stacked sequentially, and the wetting layer includes a sodium-supplementing binder and an ion-conducting agent. Sodium-replenishing binders can replenish sodium in sodium-ion batteries. During the initial charge-discharge cycle, they replenish the sodium consumed by the solid electrolyte interphase (SEI) film on the surface of the negative electrode active layer and by side reactions, compensating for the initial coulombic efficiency loss. By stabilizing the sodium ion supply to the negative electrode, they slow down capacity decay and extend the cycle life of the sodium-ion battery. In addition to replenishing sodium, sodium-replenishing binders also have a bonding effect, which can be used to bond ion-conducting agents, integrating the sodium-replenishing agent and the binder into one unit. This avoids the increase in side reactions caused by the electrochemical instability of the added sodium-replenishing agent. Furthermore, ion-conducting agents can improve the wettability and liquid retention capacity of the negative electrode, enhance its ion-conducting ability, improve the kinetic and rate performance of the sodium-ion battery, and increase the electrolyte filling efficiency. Moreover, the wettability layer can better prevent powder and material shedding from the negative electrode active layer, reducing the proportion of sodium-ion batteries that fail the withstand voltage insulation test (i.e., Hipot failure). Furthermore, when the negative electrode sheet of this application is used in a sodium battery, even if the sodium battery uses a separator with adhesive layers on both sides, it still has high wettability, liquid retention and high liquid injection efficiency, and will not reduce the adhesion between the negative electrode sheet and the separator. Attached Figure Description

[0015] 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.

[0016] Figure 1 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application.

[0017] Figure 2 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0018] Figure 3 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0019] Figure 4This is a schematic diagram of the structure of an electrical system according to an embodiment of this application.

[0020] Figure 5 This is a schematic diagram of the structure of an energy storage device according to an embodiment of this application.

[0021] Figure 6 This is a schematic diagram of the structure of a sodium battery according to an embodiment of this application.

[0022] Figure 7 For the application of an embodiment of a sodium battery Figure 6 A schematic diagram of the cross-sectional structure along the AA direction.

[0023] Figure 8 This is a cross-sectional view of the positive electrode sheet according to one embodiment of the application.

[0024] Figure 9 This is a cross-sectional view of the negative electrode sheet according to an embodiment of this application.

[0025] Figure 10 This is a cross-sectional view of the negative electrode sheet according to another embodiment of this application.

[0026] Explanation of reference numerals in the attached figures: 100 - Energy storage system; 110 - First power conversion device; 120 - First user load; 130 - Second user load; 140 - High-voltage cable; 150 - Second power conversion device; 160 - Photovoltaic-energy storage-charging station; 170 - Automobile; 200 - Energy storage device; 210 - Single cell battery; 100' - Power system; 110' - Power equipment; 300 - Sodium battery; 310 - Positive electrode sheet; 311 - Positive current collector; 312 - Positive active layer; 320 - Separator; 340 - Housing; 341 - Reception cavity; 350 - End cap assembly; 400 - Negative electrode sheet; 410 - Negative current collector; 420 - Negative active layer; 430 - Wetting layer. Detailed Implementation

[0027] 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.

[0028] 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.

[0029] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0030] 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.

[0031] 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 based on future application needs. Currently, the main way to generate green electricity is to develop green energy sources such as photovoltaics and wind power to replace fossil fuels.

[0032] 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.

[0033] Taking electrochemical energy storage as an example, this solution provides an energy storage device for use in energy storage systems. The energy storage device is equipped with a set of chemical batteries, which mainly use the chemical elements in the batteries as energy storage media. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage media. Simply put, the electrical energy generated by wind and solar energy is stored in the chemical batteries. 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.

[0034] 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 include: (1) Large-scale energy storage power stations (composed of multiple prefabricated energy storage modules) 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, the energy storage power station realizes the load matching of power in time and space, enhances the renewable energy absorption capacity, reduces instantaneous power changes, reduces the impact on the power grid, improves the problem of new energy power generation absorption, and is of great significance in power grid system backup, alleviating peak load power supply pressure and peak regulation and frequency regulation. (2) The energy storage prefabricated cabin applied on the grid side mainly functions as peak regulation, frequency regulation and grid congestion relief. In terms of peak regulation, it can realize 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. (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, 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 when the electricity price is low and discharging the energy storage system 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 energy storage systems 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 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.

[0035] In some embodiments, see Figure 1 , Figure 1 This is a schematic diagram of the structure of an energy storage system 100 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 200 of this application is not limited to the home energy storage scenario.

[0036] This application provides an energy storage system 100, which includes a first power conversion device 110 (photovoltaic panel), a first user load 120 (household lighting fixture), a second user load 130 (e.g., household appliances such as air conditioners), and an energy storage device 200. The energy storage device 200 is a small energy storage box that can be wall-mounted on an outdoor wall. However, the energy storage device 200 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 200 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.

[0037] In some embodiments, see Figure 2 , Figure 2 This is a schematic diagram of the structure of an energy storage system 100 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 200 of this application is not limited to its generation / distribution side energy storage scenario.

[0038] This application provides an energy storage system 100, which includes: a high-voltage cable 140, a first power conversion device 110, a second power conversion device 150, and an energy storage device 200 provided in this application. In some embodiments of the power generation scenario, the second power conversion device 150 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 200 through grid connection. The energy storage device 200 is connected to the high-voltage cable 140 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 conversion... The power conversion device is always connected to the high-voltage cable 140. 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 140. 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 200 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 200 together with the high-voltage cable 140 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.

[0039] In some embodiments on the distribution network side, the first power conversion device 110 can be a photovoltaic panel, and the energy storage device 200 is connected to the high-voltage cable 140 and installed downstream of the high-voltage cable 140 between the user load and the photovoltaic power conversion device. The electrical energy output by the photovoltaic power conversion device is stored in the energy storage device 200, 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 140 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.

[0040] In some embodiments, see Figure 3 , Figure 3 This is a schematic diagram of the structure of an energy storage system 100 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 200 of this application is not limited to industrial and commercial energy storage scenarios.

[0041] This application provides an energy storage system 100, which includes: an energy storage device 200, a high-voltage cable 140, a factory equipped with a first power conversion device 110, a photovoltaic-energy storage-charging station 160, and a vehicle 170. In some embodiments of industrial and commercial scenarios, the first power conversion device 110 can be a photovoltaic panel, which converts solar energy into electrical energy and stores it in the energy storage device 200 in the factory. In the event of a power grid failure, the energy storage device 200 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 device 200 in conjunction with the high-voltage cable 140 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 first power conversion device 110 can also convert solar energy into electrical energy and store it in the energy storage device 200 of the photovoltaic-energy storage-charging station 160, which can directly charge the vehicle 170, making it fast and convenient.

[0042] Optionally, the first power conversion device 110 may include, but is not limited to, a photovoltaic panel, and the second power conversion device 150 may include, but is not limited to, a wind power conversion device. The first power conversion device 110 and the second power conversion device 150 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0043] Figure 4 This is a schematic diagram of the structure of an electrical system 100' according to an embodiment of this application.

[0044] Please see Figure 4This application embodiment also provides an electrical system 100', which includes an electrical device 110' and an energy storage device 200 or an energy storage system 100 as described in this application embodiment, wherein the energy storage device 200 or the energy storage system 100 is used to supply power to the electrical device 110'.

[0045] Optionally, the electrical equipment 110' can be, but is not limited to, at least one of the following: power grid, base station, household appliances (such as air conditioners, lamps, refrigerators, etc.), commercial charging equipment (such as photovoltaic storage charging stations).

[0046] It should be noted that when the power system 100' includes the energy storage system 100, the power device 110' is electrically connected to the high-voltage cable 140 of the energy storage system.

[0047] Please see Figure 5 , Figure 5 This is a schematic diagram of the structure of an energy storage device 200 according to an embodiment of this application.

[0048] Optionally, the energy storage device 200 includes one or more individual battery cells 210.

[0049] The term "multiple" refers to two or more, such as, but not limited to, 2, 5, 10, 30, 50, 100, 200, 300, 400, 800, 1000, etc. The number of individual battery cells 210 included in the energy storage device 200 can be determined based on the rated capacity of the individual battery cells 210 and the rated capacity to be achieved by the energy storage device 200.

[0050] Optionally, the energy storage device 200 can be used, but is not limited to, 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 applied in multiple fields such as data centers, military equipment, aerospace, charging piles, and electric vehicles.

[0051] Optionally, the energy storage device 200 may include, but is not limited to, battery integrated systems comprising a single battery cell 210, or battery modules, battery packs, battery clusters, power banks, energy storage cabinets / prefabricated energy storage containers, etc., composed of single battery cells 210. In other words, when the energy storage device 200 includes a single battery cell 210, the energy storage device 200 may exist in the form of a single battery cell 210. When the energy storage device 200 includes multiple single battery cells 210, the multiple single battery cells 210 may be stacked, arranged, assembled, etc., to form battery integrated systems such as battery modules, battery packs, battery clusters, power banks, energy storage cabinets / energy storage containers, etc.; that is, the energy storage device 200 exists in the form of battery integrated systems such as battery modules, battery packs, battery clusters, power banks, energy storage cabinets / energy storage containers, etc. The actual application form of the energy storage device 200 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 200. This application embodiment only illustrates the case where the energy storage device 200 is a multi-cell battery (i.e., multiple single-cell batteries 210).

[0052] Optionally, the single cell 210 can be, but is not limited to, at least one of cylindrical, square, prismatic, or other shaped cells.

[0053] Optionally, the single cell 210 can be a rechargeable battery, which refers to a single cell 210 that can be recharged after discharge to activate the active materials and continue to be used. The single cell 210 can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium 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.

[0054] Understandably, the single cell 210 can be, but is not limited to, a sodium battery, a lithium battery, a magnesium battery, a nickel-metal hydride battery, a nickel-cadmium battery, a lead-acid battery, etc. In the following embodiments of this application, the single cell 210 is illustrated using a sodium battery 300 as an example.

[0055] To improve the structural stability and safety of sodium batteries, double-sided adhesive separators (i.e., separators with adhesive layers on both sides) are often used. However, double-sided adhesive separators result in excessively tight adhesion between the separator and both the positive and negative electrode plates, which is detrimental to the electrolyte wetting of the negative electrode plate, reducing the electrolyte injection efficiency and kinetic performance of the sodium battery. Therefore, this application also provides a sodium battery and a negative electrode plate.

[0056] Although adding ceramic particles to the adhesive layer of the diaphragm can help retain liquid, it will reduce the adhesion performance of the diaphragm to the positive / negative electrode sheets, affecting the cross-sectional stability of the positive and negative electrode sheets.

[0057] Figure 6 This is a schematic diagram of the structure of a sodium battery 300 according to an embodiment of this application. Figure 7 For example, a sodium battery 300 according to a patent application. Figure 6 A schematic diagram of the cross-sectional structure along the AA direction.

[0058] Please see Figure 6 and Figure 7 This application also provides a sodium battery 300, which includes an electrolyte, a positive electrode 310, a separator 320 and a negative electrode 400, with the separator 320 located between the positive electrode 310 and the negative electrode 400.

[0059] Understandably, the diaphragm 320 serves to separate the positive electrode 310 from the negative electrode 400.

[0060] It should be noted that the positive electrode 310, the separator 320, and the negative electrode 400 are all at least partially immersed in the electrolyte.

[0061] Optionally, the sodium battery 300 of this application may be, but is not limited to, at least one of sodium-ion batteries, sodium metal batteries, lithium sodium-ion batteries, etc.

[0062] Optionally, the sodium battery 300 can be, but is not limited to, a blade battery (laminated battery) or a wound battery.

[0063] In some examples, the sodium battery 300 may include a positive electrode 310 and a negative electrode 400. In other examples, the sodium battery 300 may include multiple positive electrode 310s and multiple negative electrode 400s, with the positive electrode 310s and negative electrode 400s stacked alternately in sequence, and a separator 320 is provided between each adjacent pair of positive electrode 310s and negative electrode 400s.

[0064] Figure 8 This is a cross-sectional view of the positive electrode 310 according to an embodiment of the application.

[0065] Please see Figure 8 Optionally, the positive electrode 310 includes a positive current collector 311 and a positive active layer 312, wherein the positive active layer 312 is disposed on the surface of the positive current collector 311.

[0066] It should be noted that the positive electrode active layer 312 can be disposed on one or more surfaces (greater than or equal to two surfaces) of the positive electrode current collector 311. In the schematic diagram of the accompanying drawings of this application, the positive electrode active layer 312 is disposed on two opposite surfaces of the positive electrode current collector 311 as an example, which should not be construed as a limitation on the positive electrode active layer 312 and the positive electrode sheet 310 of the embodiments of this application.

[0067] Optionally, the positive current collector 311 can be made of a material with good conductivity and mechanical strength. The positive current collector 311 can be, but is not limited to, aluminum sheet, aluminum foil, etc.

[0068] Optionally, the positive electrode active layer 312 includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.

[0069] Optionally, the positive electrode active material can be, but is not limited to, sodium transition metal oxide and its modified materials, wherein the modified material can be a sodium transition metal oxide that has undergone doping modification and / or coating modification. Optionally, the sodium transition metal oxide can be selected from at least one of sodium cobalt oxide, sodium nickel oxide, sodium manganese oxide, sodium nickel manganese oxide, sodium nickel cobalt manganese oxide, and sodium nickel cobalt aluminum oxide. In other embodiments, the positive electrode active material can also be sodium iron pyrophosphate.

[0070] Optionally, the positive electrode conductive agent may be, but is not limited to, at least one of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0071] Optionally, the positive electrode binder may be, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyvinyl ether, polymethyl methacrylate (PMMA), polyhexafluoropropylene, and polymerized styrene-butadiene rubber (SBR).

[0072] Optionally, the electrolyte includes an electrolyte salt, an organic solvent, and a film-forming additive.

[0073] Optionally, the electrolyte salt may include, but is not limited to, sodium salts. Optionally, the sodium salt may be, but is not limited to, at least one of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium dioxalate borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP).

[0074] Sodium bis(oxalate)borate, sodium difluoro(oxalate)phosphate, sodium difluorophosphate (NaPO2F2), etc.

[0075] Optionally, the organic solvent may include, but is not limited to, at least one of the following: dimethyl ethylene glycol (DME), dioxolane (DOL), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0076] Optionally, the film-forming additive may include at least one of the positive electrode film-forming additive and the negative electrode film-forming additive. Optionally, the film-forming additive may include, but is not limited to, at least one of the following: propargylbenzenesulfonic acid, vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), methanedisulfonate (MMDS), butyl sulfonate lactone (BS), and 1,3-propenyl sulfonate lactone (PST).

[0077] Optionally, the electrolyte may also include additives that improve certain properties of the sodium battery 300, such as additives that improve the overcharge performance of the sodium battery 300, additives that improve the high-temperature performance of the sodium battery 300, and additives that improve the low-temperature performance of the sodium battery 300.

[0078] Optionally, the diaphragm 320 can be a porous diaphragm 320 with good chemical and mechanical stability. Optionally, it can be at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0079] Optionally, the separator 320 can be a single-layer film or a multi-layer composite film. When the separator 320 is a multi-layer composite film, the materials of the multi-layer composite films can be the same or different.

[0080] Optionally, the diaphragm 320 may be, but is not limited to, a diaphragm 320 having adhesive layers on both sides. That is, the diaphragm 320 includes a base film and an adhesive layer, the adhesive layer being disposed on two opposite surfaces of the diaphragm 320.

[0081] Please see again Figure 6 and Figure 7 Optionally, the sodium battery 300 further includes a housing 340 and an end cap assembly 350, the housing 340 and the end cap assembly 350 forming a closed receiving cavity 341 for housing the electrolyte, the positive electrode 310, the separator 320, and the negative electrode 400. Understandably, the end cap assembly 350 electrically connects the positive electrode 310 and the negative electrode 400, leading them out for electrical connection to external devices or other sodium batteries 300.

[0082] Figure 9 This is a cross-sectional view of a negative electrode 400 according to an embodiment of this application. Figure 10 This is a cross-sectional view of the negative electrode 400 according to another embodiment of this application.

[0083] Please see Figure 9 and Figure 10 This application also provides a negative electrode sheet 400, which includes a negative electrode current collector 410, a negative electrode active layer 420, and a wetting layer 430. The negative electrode active layer 420 is disposed on the surface of the negative electrode current collector 410; the wetting layer 430 is disposed on the surface of the negative electrode active layer 420 opposite to the negative electrode current collector 410, and the wetting layer 430 includes a sodium-supplementing binder and an ion-conducting agent.

[0084] Understandably, the negative electrode current collector 410, the negative electrode active layer 420, and the wetting layer 430 are stacked sequentially. The negative electrode active layer 420 can be disposed on one or more surfaces (greater than or equal to two surfaces) of the negative electrode current collector 410. In the schematic diagram of this application, the negative electrode active layer 420 is disposed on two opposite surfaces of the negative electrode current collector 410, and both surfaces of the two negative electrode active layers 420 facing away from the negative electrode current collector 410 are provided with the wetting layer 430. This should not be construed as a limitation on the negative electrode sheet 400 of the embodiments of this application.

[0085] It should be noted that the wetting layer 430 can cover all of the negative electrode active layer 420, or it can only cover a portion of the negative electrode active layer 420. Compared to the solution where the wetting layer 430 covers only a portion of the negative electrode active layer 420, the solution where the wetting layer 430 covers all of the negative electrode active layer 420 can better prevent the problem of material shedding and powder shedding from the negative electrode active layer 420.

[0086] Understandably, the sodium-replenishing binder is used to replenish sodium and to bind the ion-conducting agent, and the sodium-replenishing binder and the ion-conducting agent are uniformly dispersed.

[0087] The negative electrode 400 of this application includes a negative electrode current collector 410, a negative electrode active layer 420, and a wetting layer 430 stacked sequentially. The wetting layer 430 includes a sodium-replenishing binder and an ion-conducting agent. The sodium-replenishing binder can replenish sodium in the sodium battery 300. During the first charge and discharge process, it can replenish the sodium consumed by the solid electrolyte interphase (SEI) film on the surface of the negative electrode active layer 420 and by side reactions, compensating for the loss of initial coulombic efficiency of the sodium battery 300. By stabilizing the sodium ion supply of the negative electrode 400, it slows down capacity decay and extends the cycle life of the sodium battery 300. In addition, besides replenishing sodium, the sodium-replenishing binder also has a bonding effect, which can be used to bond the ion-conducting agent, integrating the sodium-replenishing agent and the binder into one unit. This avoids the increase in side reactions caused by the electrochemical instability of the added sodium supplement. Furthermore, the ion-conducting agent can improve the wettability and liquid retention of the negative electrode 400, enhance its ion-conducting ability, improve the kinetic and rate performance of the sodium battery 300, and increase its electrolyte filling efficiency. Moreover, the wetting layer 430 can better prevent powder and material shedding from the negative electrode active layer 420, reducing the proportion of sodium batteries 300 failing the withstand voltage insulation test (i.e., hipot defects). Furthermore, when the negative electrode 400 of this application is used in the sodium battery 300, even if the sodium battery 300 uses a separator 320 with adhesive layers on both sides, it still maintains high wettability, liquid retention, and electrolyte filling efficiency, without reducing the adhesion between the negative electrode 400 and the separator 320.

[0088] Optionally, the negative electrode current collector 410 can be made of a material with good conductivity and mechanical strength. The negative electrode current collector 410 can be, but is not limited to, copper sheet, copper foil, etc. The negative electrode current collector 410 is used to collect the current generated by the negative electrode active material in the negative electrode active material layer to form a larger current output. Therefore, the negative electrode current collector 410 should have sufficient contact with the negative electrode active layer 420, and its internal resistance should be as low as possible.

[0089] Optionally, the negative electrode active material includes at least one of carbon materials and non-carbon materials. Carbon materials may include, but are not limited to, at least one of graphite, mesophase microcarbon spheres (MCMB), hard carbon, and soft carbon. Non-carbon materials include at least one of alloy materials, intermetallic compounds, and nanomaterials for negative electrodes.

[0090] Optionally, the negative electrode active layer 420 may further include at least one of a negative electrode conductive agent, a negative electrode binder, and a negative electrode thickener.

[0091] Optionally, the negative electrode conductive agent may be, but is not limited to, at least one of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0092] Optionally, the negative electrode binder may be, but is not limited to, at least one of polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), sodium alginate (SA), polymethyl methacrylate (PMAA), and carboxymethyl chitosan (CMCS).

[0093] Optionally, the negative electrode thickener may be, but is not limited to, at least one of sodium carboxymethyl cellulose (CMC), polyacrylamide (PAM), and polymethyl methacrylate (PMA).

[0094] Optionally, the negative electrode active layer 420 can be obtained by extrusion coating, and the wetted layer 430 can be obtained by gravure coating.

[0095] Optionally, the negative electrode active layer 420 may also include a sodium replenishing agent. Optionally, the sodium replenishing agent may be, but is not limited to, a sodium-containing binder such as sodium polyacrylate or a conventional sodium replenishing agent (such as a small molecule sodium replenishing agent).

[0096] In some embodiments, the mass ratio of the sodium-supplementing binder to the ion-conducting agent in the impregnation layer 430 is 3:7 to 6:4.

[0097] Understandably, the wetting layer 430 comprises 30% to 60% sodium-supplementing binder and 40% to 70% ion-conducting agent.

[0098] It should be noted that, unless otherwise specified, percentages and "%" in this application refer to mass percentages and mass fractions.

[0099] Specifically, the mass ratio of the sodium-supplementing binder to the ion-conducting agent in the impregnation layer 430 can be, but is not limited to, 3:7, 3:5, 3:4, 3.5:4, 4:4, 4.5:4, 5:4, 5.5:4, 6:4, etc.

[0100] Specifically, the mass fraction of the sodium-replenishing binder in the wetting layer 430 can be, but is not limited to, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, etc. If the mass fraction of the sodium-replenishing binder in the wetting layer 430 is too low, the ion-conducting agent will easily become loosely bonded and prone to powdering. In addition, it will reduce the sodium replenishment effect of the wetting layer 430, resulting in limited improvement in the initial coulombic efficiency of the sodium battery 300. If the mass fraction of the sodium-replenishing binder in the wetting layer 430 is too high, it will increase the impedance of the wetting layer 430, reduce the liquid retention capacity and ion-conducting capacity of the wetting layer 430, and reduce the kinetic performance and energy efficiency of the sodium battery 300.

[0101] Specifically, the mass fraction of the ion-conducting agent in the wetting layer 430 can be, but is not limited to, 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 63%, 65%, 68%, 70%, etc. If the mass fraction of the ion-conducting agent in the wetting layer 430 is too low, it increases the impedance of the wetting layer 430, reduces its liquid retention and ion-conducting capacity, and decreases the kinetic performance and energy efficiency of the sodium battery 300. If the mass fraction of the ion-conducting agent in the wetting layer 430 is too high, it easily leads to weak adhesion of the ion-conducting agent and easy powder shedding. In addition, if the content of the sodium-replenishing binder is too low, it reduces the sodium-replenishing effect of the wetting layer 430, and has limited effect on improving the initial coulombic efficiency of the sodium battery 300.

[0102] In some embodiments, the ion-conducting agent has a porous structure, and the surface of the ion-conducting agent has micropores and mesopores.

[0103] Understandably, the surface of an ion-conducting agent has a large number of micropores and mesopores. "Micropores" refer to pores with a diameter of less than 2 nm. "Mesopores" refer to pores with a diameter of 2 nm to 50 nm.

[0104] In this embodiment, the ion-conducting agent has a porous structure. The surface of the ion-conducting agent has micropores and mesopores. This porous structure can be used to store electrolyte, thereby playing the role of wetting and liquid retention, which can improve the ion-conducting ability of the negative electrode 400, improve the dynamic performance and rate performance of the sodium battery 300, and improve the electrolyte filling efficiency of the sodium battery 300.

[0105] In some embodiments, the specific surface area of ​​the ion-conducting agent is in the range of 60 m². 2 / g to 300m 2 / g.

[0106] In the embodiments of this application, when the numerical range a to b is involved, unless otherwise specified, the numerical value can be any value between a and b, including the endpoint value a and the endpoint value b.

[0107] Specifically, the specific surface area of ​​the ion-conducting agent can be, but is not limited to, 60 m². 2 / g、80m 2 / g, 100m 2 / g, 120m 2 / g, 140m 2 / g, 160m 2 / g、180m 2 / g、200m 2 / g、220m 2 / g、240m 2 / g、260m 2 / g、280m 2 / g、300m 2 / g etc.

[0108] In this embodiment, if the specific surface area of ​​the ion-conducting agent is too small, the liquid retention effect of the ion-conducting agent will be reduced, which is not conducive to improving the ion-conducting ability of the negative electrode 400. As the specific surface area of ​​the ion-conducting agent increases, the contact area between the electrolyte and the ion-conducting agent increases, and the liquid retention ability of the ion-conducting agent increases. However, if the specific surface area of ​​the ion-conducting agent is too large, the particles of the ion-conducting agent may be too small, which may easily lead to agglomeration and uneven dispersion.

[0109] In some embodiments, the average particle size of the ion-conducting agent ranges from 1 μm to 12 μm.

[0110] Specifically, the average particle size of the ion-conducting agent can be, but is not limited to, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, etc.

[0111] In this embodiment, if the average particle size of the ion-conducting agent is too small, it will easily agglomerate and disperse unevenly; if the average particle size of the ion-conducting agent is too large, it will reduce the specific surface area of ​​the ion-conducting agent, reduce the liquid retention effect of the ion-conducting agent, and be detrimental to improving the ion-conducting ability of the negative electrode 400.

[0112] In some embodiments, the ion-conducting agent includes at least one of silicon oxide and aluminum oxide. In this embodiment, using silicon oxide and aluminum oxide as ion-conducting agents can improve the wettability and liquid retention of the wetting layer 430, thereby improving the ion-conducting capability of the negative electrode 400, enhancing the kinetic performance and rate performance of the sodium battery 300, and increasing the electrolyte filling efficiency of the sodium battery 300. Furthermore, silicon oxide and aluminum oxide have good electrochemical stability and are less prone to side reactions with the electrolyte.

[0113] In some embodiments, the sodium-supplementing binder is sodium polyacrylate. In this embodiment, sodium polyacrylate is used as the sodium-supplementing binder. The raw material of sodium polyacrylate, polyacrylic acid, is a commonly used binder in sodium batteries 300. It has good compatibility with the binders in sodium batteries 300. In addition, it has good electrochemical stability and is not prone to side reactions with electrolytes, etc.

[0114] In some embodiments, the number-average molecular weight of the sodium polyacrylate ranges from 40,000 to 500,000.

[0115] Specifically, the number-average molecular weight of the sodium polyacrylate can be, but is not limited to, 40,000, 60,000, 80,000, 100,000, 120,000, 140,000, 160,000, 180,000, 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, 500,000, etc.

[0116] In this embodiment, if the number average molecular weight of the sodium polyacrylate is too low, the adhesion of the sodium polyacrylate will be low. When the sodium polyacrylate and the ion-conducting agent are used to make a coating slurry, the viscosity of the coating slurry will be too low, and the suspension of the ion-conducting agent will be poor, affecting the coating of the coating slurry. If the number average molecular weight of the sodium polyacrylate is too high, when the sodium polyacrylate and the ion-conducting agent are used to make a coating slurry, the viscosity of the coating slurry will be too high, the dispersion of the ion-conducting agent will be poor, and it will be easy to locally agglomerate.

[0117] In some embodiments, the thickness of the impregnation layer 430 ranges from 1 μm to 15 μm.

[0118] Specifically, the thickness of the impregnation layer 430 can be, but is not limited to, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, etc.

[0119] In this embodiment, if the thickness of the wetting layer 430 is too small, the improvement on the wettability, liquid retention capacity, and ion conduction capacity of the negative electrode 400 will be limited, which is detrimental to improving the kinetic performance, rate performance, and liquid injection efficiency of the sodium battery 300. Furthermore, it is not conducive to reducing the problem of material loss due to folding at the winding corner of the negative electrode 400. If the thickness of the wetting layer 430 is too thick, it increases the impedance of the negative electrode 400, thus worsening the energy efficiency of the sodium battery 300.

[0120] Optionally, the wetting layer 430 is prepared by the following steps: (1) Provide sodium polyacrylate and ion-conducting agent; (2) Disperse sodium polyacrylate and ion-conducting agent in water to prepare a coating slurry with a solid content of 15% to 30% and a viscosity of 200 Pa·s to 1000 Pa·s. Specifically, the viscosity of the coating slurry can be, but is not limited to, 200 Pa·s, 400 Pa·s, 600 Pa·s, 800 Pa·s, 1000 Pa·s, etc. If the viscosity of the coating slurry is too low, the suspension of the ion-conducting agent will be reduced, and it will easily settle; if the viscosity of the coating slurry is too high, the gravure coating will easily be uneven.

[0121] (3) A layer of impregnation slurry is formed on the surface of the negative electrode active layer 420 away from the negative electrode current collector 410 by a gravure coating process, and dried at 110°C to 150°C (e.g., 110°C, 120°C, 130°C, 140°C, 150°C, etc.) to obtain the impregnation layer 430.

[0122] The negative electrode 400 and sodium battery 300 of this application will be further described below through specific embodiments.

[0123] Examples 1 to 22, Comparative Examples 1 to 4 The sodium batteries 300 of each embodiment and comparative example were prepared by the following steps: (1) Preparation of non-aqueous electrolyte: Under an environment with a water content of less than 10 ppm, propylene carbonate (PC, cyclic carbonate) and diethyl carbonate (DEC, chain carbonate) are mixed at a mass ratio of 30:50 to obtain a mixed solvent. Then, sodium hexafluorophosphate, an electrolyte salt, and fluoroethylene carbonate (FEC), a film-forming additive, are added to the mixed solvent to obtain an electrolyte. The molar concentration of sodium hexafluorophosphate in the electrolyte is 1 mol / L, and the mass fraction of fluoroethylene carbonate is 2%. (2) Preparation of positive electrode 310: Sodium iron pyrophosphate, acetylene black and polyvinylidene fluoride are mixed in N-methylpyrrolidone solution in a weight ratio of 97:1:2 to form positive electrode slurry; aluminum foil is used as positive electrode current collector 311, the positive electrode slurry is coated on the positive electrode current collector 311, and after drying, cold pressing and die cutting, positive electrode 310 is obtained; (3) Preparation of negative electrode sheet 400: Hard carbon (negative electrode active material), acetylene black, styrene-butadiene rubber, and sodium carboxymethyl cellulose were dissolved in deionized water in a weight ratio of 95:1:3:1 and stirred to obtain a negative electrode slurry; aluminum foil was used as the negative electrode current collector 410, and the negative electrode slurry was coated on the negative electrode current collector 410 and dried to obtain a negative electrode active layer 420; sodium polyacrylate and an ion-conducting agent were made into a slurry and coated on the surface of the negative electrode active layer 420 away from the negative electrode current collector 410 and dried to obtain a wetting layer 430; after cold pressing and die cutting, a negative electrode sheet 400 was obtained; the performance parameters of the wetting layer 430 of each embodiment and comparative example are shown in Table 1 and Table 2 below; (4) Separator 320: The separator 320 includes a base membrane and an adhesive layer. The adhesive layer is disposed on two opposite surfaces of the base membrane. The base membrane is a 9μm thick porous polyethylene polymer film. The thickness of the adhesive layer on one side is 1μm. (5) Assembly of hard-shell sodium battery 300: The positive electrode 310, separator 320 and negative electrode 400 prepared above are stacked in sequence, so that the separator 320 is placed between the positive electrode 310 and the negative electrode 400 to play a role in isolation. The bare cell is obtained by winding. The middle area, top area and bottom area of ​​the termination part of the bare cell (i.e. the end of the bare cell) are respectively pasted with termination tape. Then the bare cell is put into the aluminum shell and injected with electrolyte. After formation, standing, sealing, helium detection and coating processes, the hard-shell sodium battery 300 is obtained.

[0124] Comparative Example 5 The difference between Comparative Example 5 and Comparative Example 1 is that the diaphragm 320 of Comparative Example 5 is a 9μm thick porous polyethylene polymer film without an adhesive layer.

[0125] The following performance tests were performed on the negative electrode 400 and sodium battery 300 of each embodiment and comparative example: (1) Peel strength (also known as bonding strength) of diaphragm 320 and negative electrode 400: Peel strength 180° peel test method, the steps are as follows: 1) Sampling: Take a sample from the complete negative electrode 400-diaphragm 320 composite. The sample size is 25*120mm. Ensure that the sample edge is free of burrs, wrinkles and damage. 2) Pre-peeling: At one end of the sample (length ≥ 20 mm), carefully peel the diaphragm 320 from the negative electrode 400 manually to form a clampable "separation end". Avoid damaging the coating of the negative electrode 400 or the diaphragm 320 during the peeling process. 3) Testing: Fix the "separation end" of the negative electrode 400 flat in the lower clamp of the tensile testing machine, ensuring that the negative electrode 400 is parallel to the edge of the clamp and is not skewed; fix the "separation end" of the diaphragm 320 flat in the upper clamp, strictly ensuring that the peeling angle between the diaphragm 320 and the negative electrode 400 is 180° and that the sample axis coincides with the force direction of the clamp. Adjust the clamp spacing to make the initial force on the sample 0 (preload ≤ 0.1N) to avoid initial tension or relaxation of the sample; start the testing machine, the upper clamp moves upward at a uniform speed, driving the diaphragm 320 and the negative electrode 400 to peel off in a 180° direction, and the system automatically records the force value and displacement data in real time during the peeling process.

[0126] (2) Hipot defect test after hot pressing of bare cells: 1) Preparation before test: After hot pressing is completed and cooled to room temperature (23±2℃), the bare cells should be placed in a dry, clean test area free from electrostatic interference to avoid excessive humidity (recommended ≤40%RH) causing condensation on the surface and affecting the test results; first, perform a full visual inspection of the bare cells, specifically including: checking whether the tabs are bent / short-circuited, whether there are burrs on the positive electrode 310 / negative electrode 400 at the edge of the winding / stacking, and whether the separator 320 is 1) Check for damage / wrinkles / misalignment; check for obvious deformation (such as bulging or delamination) in the bare cells after hot pressing. Bare cells with abnormal appearance must be isolated and not allowed to enter the Hipot testing stage; 2) Inter-electrode insulation test: Connect the high voltage terminal (HV) of the Hipot tester to the positive electrode tab of the bare cell, and the low voltage terminal (GND) to the negative electrode tab, ensuring good contact between the electrode tab and the test clamp and no risk of short circuit; start the tester, press 200V, test for 5 seconds, and observe its resistance value. If the resistance value is <3MΩ, it is judged as a short circuit. 3000 bare cells were tested in each embodiment and comparative example, and the Hipot failure rate of 3000 bare cells was calculated.

[0127] (3) Energy efficiency test at 25℃: The initialized sodium battery 300 was left to stand for 5 hours at 25℃; it was then charged to 3.3V at a constant power rate of 1P and left to stand for 10 minutes; it was then discharged to 1.5V at a constant power rate of 1P and left to stand for 10 minutes; this one-cycle charging-discharging process is called one cycle or one loop, and the charging capacity and discharging capacity are recorded. Energy efficiency at 25℃ = (discharge capacity of the first cycle / charge capacity of the first cycle) × 100%.

[0128] (4) Electrolyte injection efficiency test: Weigh 1kg of electrolyte and inject 1000g of electrolyte into the assembled sodium battery 300. Calculate the time t for 1kg of electrolyte to be injected. Then the injection efficiency = 1000g / t.

[0129] The performance parameters of the negative electrode 400 and sodium battery 300 of each embodiment and comparative example are shown in Table 1 and Table 2 below.

[0130] Table 1. Performance parameters of the ion-conducting agent and sodium polyacrylate in each embodiment and comparative example.

[0131] Table 2 Performance parameters of sodium battery 300 in each embodiment and comparative example

[0132] The test results from Examples 1 to 6, and Comparative Examples 1 and 2 show that when the negative electrode 400 does not have a wetting layer 430 (as in Comparative Example 1), the peel strength between the separator 320 and the negative electrode 400 in the sodium battery 300 is low, the electrolyte injection efficiency of the sodium battery 300 is low, the hitt defect rate of the sodium battery 300 is relatively high, and the energy efficiency of the sodium battery 300 is relatively low. When a wetting layer 430 is provided on the surface of the negative electrode active layer 420 of the negative electrode sheet 400 (as in Examples 1 to 6 and Comparative Example 2), the peel strength between the separator 320 and the negative electrode sheet 400 in the sodium battery 300 increases, the electrolyte injection efficiency of the sodium battery 300 improves, the hit-pot defect rate of the sodium battery 300 decreases, and the energy efficiency of the sodium battery 300 increases. In addition, as the thickness of the wetting layer 430 increases, the peel strength between the separator 320 and the negative electrode sheet 400 in the sodium battery 300 generally shows an increasing trend, the electrolyte injection efficiency of the sodium battery 300 first increases and then decreases, the hit-pot defect rate of the sodium battery 300 gradually decreases, and the energy efficiency of the sodium battery 300 first increases and then decreases.

[0133] The test results from Comparative Examples 1 and 5 show that when a separator 320 without an adhesive layer (Comparative Example 5) is used, there is no adhesive force between the separator 320 and the negative electrode 400 in the sodium battery 300. This results in higher electrolyte filling efficiency, higher hit-pot failure rate, and higher energy efficiency in the sodium battery 300. However, when a separator 320 with adhesive layers on both sides (Comparative Example 1) is used, the peel strength between the separator 320 and the negative electrode 400 in the sodium battery 300 is significantly increased. This leads to a significant decrease in electrolyte filling efficiency, a significant decrease in hit-pot failure rate, and a decrease in energy efficiency in the sodium battery 300.

[0134] The test results from Examples 4, 7 to 10, Comparative Example 3 and Comparative Example 4 show that as the content of sodium-containing binder (sodium polyacrylate) in the impregnation layer 430 increases and the content of ion-conducting agent decreases, the peel strength between the separator 320 and the negative electrode 400 in the sodium battery 300 gradually increases, the electrolyte injection efficiency of the sodium battery 300 gradually decreases, the hit-pot defect rate of the sodium battery 300 gradually decreases, and the energy efficiency of the sodium battery 300 first gradually increases and then gradually decreases.

[0135] As can be seen from the test results of Examples 4 and 11, using alumina and silicon oxide as ion-conducting agents can improve the peel strength between the separator 320 and the negative electrode 400, improve the electrolyte injection efficiency, and reduce the failure rate of the sodium battery 300 in the Hipot test and the energy efficiency of the sodium battery 300.

[0136] The test results from Examples 12 to 15 show that as the specific surface area of ​​the ion-conducting agent increases, the peel strength between the separator 320 and the negative electrode 400 in the sodium battery 300 does not change much, the electrolyte injection efficiency of the sodium battery 300 gradually increases, the hitt defect rate of the sodium battery 300 increases slightly, and the energy efficiency of the sodium battery 300 gradually decreases.

[0137] The test results of Examples 14, 16 and 17 show that increasing the particle size of the ion-conducting agent is beneficial to improving the peel strength between the separator 320 and the negative electrode 400, reducing the hitt defect rate of the sodium battery 300, and also reducing the energy efficiency of the sodium battery 300.

[0138] The test results from Examples 18 to 22 show that as the number-average molecular weight of sodium polyacrylate increases, the peel strength between the separator 320 and the negative electrode 400 in the sodium battery 300 gradually increases, the electrolyte injection efficiency of the sodium battery 300 gradually decreases, the hitt defect rate of the sodium battery 300 gradually decreases, and the energy efficiency of the sodium battery 300 gradually decreases.

[0139] 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.

[0140] 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 sheet, characterized in that, The negative electrode sheet includes: Negative electrode current collector; A negative electrode active layer, wherein the negative electrode active layer is disposed on the surface of the negative electrode current collector; and A wetting layer is disposed on the surface of the negative electrode active layer away from the negative electrode current collector. The wetting layer includes a sodium-replenishing binder and an ion-conducting agent. The ion-conducting agent has a porous structure and includes at least one of silicon oxide and aluminum oxide.

2. The negative electrode sheet according to claim 1, characterized in that, The mass ratio of the sodium-supplementing binder to the ion-conducting agent in the impregnation layer is 3:7 to 6:

4.

3. The negative electrode sheet according to claim 1, characterized in that, The specific surface area of ​​the ion-conducting agent is in the range of 60m². 2 / g to 300m 2 / g; and / or, the ion-conducting agent has micropores and mesopores.

4. The negative electrode sheet according to claim 1, characterized in that, The average particle size of the ion-conducting agent ranges from 1 μm to 12 μm.

5. The negative electrode sheet according to claim 1, characterized in that, The sodium-containing binder is sodium polyacrylate.

6. The negative electrode sheet according to claim 5, characterized in that, The number-average molecular weight of the sodium polyacrylate ranges from 40,000 to 500,000.

7. The negative electrode sheet according to any one of claims 1-6, characterized in that, The thickness of the impregnation layer ranges from 1 μm to 15 μm.

8. A sodium battery, characterized in that, The sodium battery includes: an electrolyte, a positive electrode, a separator, and a negative electrode as described in any one of claims 1-7, wherein the separator is located between the positive electrode and the negative electrode.

9. An energy storage device, characterized in that, The energy storage device includes one or more sodium batteries as described in claim 8.

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