Sodium-ion battery and electric device

Abstract

Disclosed in the present application are a sodium-ion battery and an electric device. The sodium-ion battery comprises: a positive electrode, a negative electrode and an electrolyte. The negative electrode comprises a negative electrode current collector, a negative electrode active material layer and a metal-philic additive, wherein the negative electrode active material layer is arranged on the negative electrode current collector, the surface density of the negative electrode active material layer is ρ mg / cm2, and the specific surface area of the negative electrode active material layer is A m2 / g; and the metal-philic additive is added to the negative electrode active material layer, and the content of the metal-philic additive is W2% based on the mass of the negative electrode active material layer. The electrolyte comprises a leveling additive, wherein the content of the leveling additive is W1% based on the total mass of the electrolyte. The following relationship is satisfied: 0<(W1+W2) / (A+10 / ρ)≤1. In the present application, the metal-philic additive is introduced into the negative electrode active material layer; the leveling additive is introduced into the electrolyte; and a sodium precipitation risk is relieved by regulating and controlling the relationship between the surface density and the specific surface area of and the metal-philic additive in the negative electrode active material layer and the leveling additive in the electrolyte, thereby improving the charging and discharging performance of the battery.

Description

Sodium-ion batteries and electrical equipment

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on January 23, 2024, with application number 202410099946.1 and application name “Sodium Ion Batteries and Electrical Equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of sodium ion batteries, and in particular to a sodium ion battery and electrical equipment. Background Art

[0003] Lithium-ion batteries are currently the most widely commercialized electrochemical energy storage device. They convert chemical energy into electrical energy through the reversible insertion and extraction of lithium ions between the positive and negative electrodes. Sodium and lithium belong to the same main group, but sodium reserves on Earth are far greater than lithium. my country has abundant sodium resources and sodium extraction technology, so the cost of sodium-ion batteries is significantly lower than that of lithium-ion batteries.

[0004] However, the anodes commonly used in sodium-ion batteries currently suffer from large surface areas and numerous surface defects. This results in the formation of a thicker SEI (Solid Electrolyte Interface) layer on the anode surface, which increases the consumption of active sodium. Furthermore, the electrolytes in commercial sodium-ion batteries primarily use carbonate solvents, which have high viscosity and surface tension, resulting in poor pore wetting. This leads to a higher risk of sodium deposition in the battery and poor charge and discharge performance. Summary of the Invention

[0005] Based on this, the present application provides a sodium ion battery and electrical equipment, introducing metal-philic additives into the negative electrode and leveling additives into the electrolyte. By regulating the surface density, specific surface area, metal-philic additives and the relationship between the leveling additives in the electrolyte of the negative electrode active material layer, the risk of sodium decomposition is mitigated and the high and low temperature charge and discharge performance of the battery is improved.

[0006] In a first aspect, an embodiment of the present application provides a sodium ion battery, the sodium ion battery comprising:

[0007] positive electrode;

[0008] The negative electrode comprises a negative electrode current collector, a negative electrode active material layer and a metal-philic additive, the negative electrode active material layer is arranged on the negative electrode current collector, and the surface density of the negative electrode active material layer is ρ mg / cm 2 , the specific surface area of ​​the negative electrode active material layer is Am 2 / g, the metalloid additive is added to the negative electrode active material layer, and the content of the metalloid additive is W2% based on the mass of the negative electrode active material layer;

[0009] The electrolyte contains a leveling additive, the content of the leveling additive is W1% based on the total mass of the electrolyte, and the following relationship is satisfied: 0<(W1+W2) / (A+10 / ρ)≤1.

[0010] In the embodiment of the present application, the areal density of the negative electrode active material layer and the content of the metal-philic additive satisfy the following relationship: 5<ρ*W2≤20.

[0011] In the embodiment of the present application, the specific surface area of ​​the negative electrode active material layer and the content of the leveling additive satisfy the following relationship: 0<W1 / A≤1.

[0012] In the implementation manner of the present application, W1, W2, ρ, and A satisfy: 0.5<(W1+W2) / (A+10 / ρ)≤1.

[0013] In an embodiment of the present application, the metal-philic additive includes one or more of sodium alginate and sodium rosinate.

[0014] In the embodiment of the present application, the content of the metallophilic additive satisfies 0<W2≤3.

[0015] In the embodiment of the present application, the content of the leveling additive satisfies 0<W1≤2.

[0016] In an embodiment of the present application, the leveling additive includes one or more of butynediol, a pyridine compound, and a quinoline compound.

[0017] In an embodiment of the present application, the negative electrode active material includes a first negative electrode active material capable of inserting and extracting sodium ions, wherein the first negative electrode active material includes one or more carbon materials such as hard carbon, natural graphite, artificial graphite, soft carbon, carbon black, acetylene black, carbon nanotubes, graphene, carbon nanofibers, and titanium oxide; and / or,

[0018] The negative electrode active material includes a second negative electrode active material capable of alloying with sodium, wherein the second negative electrode active material includes a single substance, oxide or carbide of one or more elements selected from the group consisting of Si, Ge, Pb, In, Zn, Ca, Sr, Ba, Ru and Rh; and / or,

[0019] The negative electrode active material includes a third negative electrode active material capable of undergoing a conversion reaction with sodium ions. The third negative electrode active material includes one or more of a transition metal oxide and a transition metal sulfide.

[0020] In an embodiment of the present application, the positive electrode includes a positive electrode active material that can release and embed sodium ions, and the positive electrode active material includes one or more of sodium iron composite oxide, sodium cobalt composite oxide, sodium chromium composite oxide, sodium manganese composite oxide, sodium nickel composite oxide, sodium nickel titanium composite oxide, sodium nickel manganese composite oxide, sodium iron manganese composite oxide, sodium nickel cobalt manganese composite oxide, sodium iron phosphate compound, sodium manganese phosphate compound, sodium cobalt phosphate compound, sodium vanadium phosphate compound, and sodium vanadium fluorophosphate compound.

[0021] In an embodiment of the present application, the electrolyte further includes sodium salt, which includes one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium bis(oxalatoborate), sodium difluorooxalatoborate, sodium trifluoromethylsulfonate, sodium bis(fluorosulfonylimide), sodium bis(trifluoromethylsulfonylimide), sodium perchlorate, 4,5-dicyano-2-(trifluoromethyl)imidazolium sodium, and 4,5-dicyano-2-(pentafluoroethyl)imidazolium sodium. Based on the total mass of the electrolyte, the content of the sodium salt is W0%, 5≤W0≤30.

[0022] In an embodiment of the present application, the electrolyte also includes a solvent, and the solvent includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, ethylene glycol dimethyl ether, dioxolane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Based on the total mass of the electrolyte, the content of the solvent is Ws%, and 70≤Ws<95.

[0023] In an embodiment of the present application, the electrolyte further includes a film-forming additive, and the film-forming additive includes one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, 1-propylene-1,3-sultone, vinyl ethylene carbonate, vinyl sulfate, methylene dicarbonate, tris(trimethylsilyl)phosphate, succinic anhydride, and maleic anhydride, and the total content of the additive is Wa%, 1<Wa≤10.

[0024] The present application introduces a leveling additive into the electrolyte. The leveling additive can even out the charge density on the negative electrode surface and promote the uniform deposition and embedding of sodium ions. The uniform embedding of sodium can not only improve the utilization rate of sodium ions and mitigate the risk of sodium desorption, but also regulate the reduction process of the additive on the negative electrode surface, avoid excessive reduction of the additive and solvent, reduce the negative electrode SEI impedance, improve the stability of SEI, and thus improve the high and low temperature charge and discharge and storage performance of the whole battery. In addition, a metalloid additive with excellent metalloid properties is introduced into the negative electrode. The metalloid additive can effectively complex metal cations, especially in sodium ion batteries, it can effectively bind sodium metal ions, enhance the adhesion of sodium ions on the negative electrode surface and promote the embedding of sodium ions into the negative electrode, which can mitigate the risk of sodium desorption, thereby improving the charge and discharge efficiency and stability of the battery.

[0025] In a second aspect, embodiments of the present application further provide an electrical device comprising the sodium-ion battery of the first aspect. The sodium-ion battery has a long cycle life and good rate performance, enabling the electrical device to be used stably for a long period of time, thereby improving the performance of the electrical device. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0027] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by those skilled in the art to which this application belongs. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used in this application includes any and all combinations of one or more of the relevant listed items.

[0028] The following describes some embodiments of the present application in detail. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0029] Lithium-ion batteries are currently the most widely commercialized electrochemical energy storage device. They convert chemical energy into electrical energy through the reversible insertion and extraction of lithium ions between the positive and negative electrodes. Sodium and lithium belong to the same main group, but sodium reserves on Earth are far greater than lithium. my country has abundant sodium resources and sodium extraction technology, so the cost of sodium-ion batteries is significantly lower than that of lithium-ion batteries.

[0030] In addition to their storage and cost advantages, sodium-ion batteries generate less transient heat during safety testing, offering greater safety. Furthermore, sodium ions have a lower desolvation rate in organic solvents, resulting in higher ion conductivity and lower charge transfer resistance under the same conditions. Furthermore, sodium and aluminum do not form alloys at low potentials, allowing the use of aluminum as current collectors in both the positive and negative electrodes of sodium-ion batteries, increasing the battery's energy density.

[0031] However, the anodes commonly used in current sodium-ion batteries suffer from large surface areas and numerous surface defects. This results in the formation of a thicker SEI layer on the anode surface, which increases the consumption of active sodium. Furthermore, the electrolytes in commercial sodium-ion batteries primarily use carbonate solvents, which have high viscosity and surface tension, resulting in poor pore wetting, leading to poor battery cycling performance and reduced energy density.

[0032] Based on this, the present application provides a sodium ion battery, comprising: a positive electrode; a negative electrode, wherein the negative electrode comprises a negative electrode current collector, a negative electrode active material layer and a metal-philic additive, wherein the negative electrode active material layer is disposed on the negative electrode current collector, and the surface density of the negative electrode active material layer is ρ mg / cm 2 The specific surface area of ​​the negative electrode active material layer is A m 2 / g, the metalloid additive is added to the negative electrode active material layer, and the content of the metalloid additive is W2% based on the mass of the negative electrode active material layer; the electrolyte, the electrolyte contains a leveling additive, and the content of the leveling additive is W1% based on the total mass of the electrolyte, and satisfies the following relationship: 0<(W1+W2) / (A+10 / ρ)≤1.

[0033] This embodiment introduces a leveling additive into the electrolyte. The leveling additive can even out the charge density on the negative electrode surface and promote the uniform deposition and embedding of sodium ions. The uniform embedding of sodium can not only improve the utilization rate of sodium ions and mitigate the risk of sodium desorption, but also regulate the reduction process of the additive on the negative electrode surface, avoid excessive reduction of the additive and solvent, reduce the negative electrode SEI impedance, improve the stability of the SEI, and thus improve the high and low temperature charge and discharge and storage performance of the full battery. In addition, a metalloid additive with excellent metalloid properties is introduced into the negative electrode. The metalloid additive can effectively complex metal cations, especially in sodium ion batteries, it can effectively bind sodium metal ions, enhance the adhesion of sodium ions on the negative electrode surface and promote the embedding of sodium ions into the negative electrode, which can mitigate the risk of sodium desorption, thereby improving the charge and discharge efficiency and stability of the battery.

[0034] When the specific surface area of ​​the negative electrode active material layer, the surface density of the negative electrode active material layer, the content of the leveling additive and the content of the metal-philic additive satisfy the following relationship: 0<(W1+W2) / (A+10 / ρ)≤1, where W1+W2 is positively correlated with the affinity of the electrolyte to the electrode interface, and A+10 / ρ is positively correlated with the electrode / electrolyte contact interface area. Only when the two are matched can it be ensured that the electrolyte has sufficient wettability and affinity for the electrode. When 0<(W1+W2) / (A+10 / ρ)≤1, the metal-philic additive added to the negative electrode and the leveling additive in the electrolyte can form a good metal-philic interface layer on the negative electrode surface. This interface layer can improve the sodium desorption / intercalation kinetics of the negative electrode surface, reduce the sodium intercalation barrier, and prevent sodium ions from being directly reduced on the surface, effectively improving the cycle retention rate and alleviating the sodium precipitation phenomenon of the negative electrode during the cycle, especially under low temperature and high rate charge and discharge conditions. Optionally, the value of (W1+W2) / (A+10 / ρ) can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0.

[0035] Furthermore, when 0.5 < (W1 + W2) / (A + 10 / ρ) ≤ 1, the adsorption layer of the added leveling additive on the negative electrode surface is more complete, reducing the negative electrode polarization. Optionally, the value of (W1 + W2) / (A + 10 / ρ) can be 0.6, 0.7, 0.8, 0.9, or 1.0.

[0036] In one embodiment, the areal density of the negative electrode active material layer and the content of the metalloid additive satisfy the following relationship: 5 < ρ*W2 ≤ 20. When 5 < ρ*W2 ≤ 20, the areal density of the negative electrode and the content of the metalloid additive are controlled within a reasonable range, which means that the negative electrode interface can be improved without causing excessive loss of energy density in the full battery. Alternatively, the value of ρ*W2 can be 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20.

[0037] In one embodiment, the specific surface area of ​​the negative electrode active material layer and the leveling additive content satisfy the following relationship: 0 < W1 / A ≤ 1. When 0 < W1 / A ≤ 1, the leveling additive in the electrolyte can form a good adsorption layer on the negative electrode surface, promoting uniform adsorption and embedding of sodium ions, thereby achieving uniform local current density and slowing sodium release. Optionally, W1 / A can have values ​​of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0.

[0038] In one embodiment, the metallophilic additive is a compound containing a metal cation, and the metallophilic additive includes one or more of sodium alginate and sodium rosinate. For example, sodium rosinate is an anionic surfactant containing a triphenyl ring structure. Adding it to the negative electrode not only improves the uniformity of the negative electrode mixture, but also its anions can bind to surface defects and oxygen-containing functional groups in the hard carbon negative electrode. Its benzene ring structure can improve the wettability between the electrode and the electrolyte, promoting rapid desolvation of sodium ions in the electrolyte at the interface, thereby enhancing the sodium insertion kinetics.

[0039] In one embodiment, the content of the metallophilic additive satisfies 0 < W2 ≤ 3. The appropriate proportion of the metallophilic additive can improve battery cycle life while avoiding excessive levels of the electrochemically inert metallophilic additive in the negative electrode, which can lead to reduced rate discharge performance. Alternatively, W2 can be 0.3, 0.6, 0.9, 1.2, 1.5, 1.8, 2.1, 2.4, 2.7, or 3.

[0040] In one embodiment, the content of the leveling additive satisfies 0<W1≤2. When this range is met, the excessive leveling additive content can be avoided, thereby preventing the electrolyte's oxidative stability from being affected. This prevents the accumulation of products on the electrode surface due to electrolyte oxidation side reactions, which can cause a continuous increase in interfacial impedance, thereby improving the overall sodium ion cycling performance. Alternatively, W1 can be 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, or 2.0.

[0041] In one embodiment, the leveling additive includes one or more of butynediol, a pyridine compound, and a quinoline compound. For example, butynediol, pyridine compounds, and quinoline compounds are small organic molecules that can adsorb on the electrode surface, preventing direct reduction of metal ions on the surface and effectively slowing the release of sodium. Specifically, the pyridine compound may be pyridinium propanesulfonate or pyridinium hydroxypropanesulfonate. The quinoline compound may be 8-hydroxyquinoline or copper quinoline.

[0042] In one embodiment, the negative electrode current collector is aluminum foil. In sodium ion batteries, aluminum foil can be used for both positive and negative electrode current collectors because sodium and aluminum do not react to form alloys, and the cost is much lower than copper foil in lithium batteries.

[0043] In one embodiment, the negative electrode material includes a first negative electrode active material that can embed and de-embed sodium ions, and the first negative electrode active material includes one or more carbon materials such as hard carbon, natural graphite, artificial graphite, soft carbon, carbon black, acetylene black, carbon nanotubes, graphene, carbon nanofibers, and titanium oxide; and / or, the negative electrode active material includes a second negative electrode active material that can undergo an alloying reaction with sodium, and the second negative electrode active material may include a single substance, oxide or carbide of one or more elements of Si, Ge, Pb, In, Zn, Ca, Sr, Ba, Ru, and Rh; and / or, the negative electrode active material includes a third negative electrode active material that can undergo a conversion reaction with sodium ions, and the third negative electrode active material may include one or more transition metal oxides and transition metal sulfides.

[0044] The anode materials of sodium-ion batteries must possess the ability to intercalate and deintercalate sodium ions, which is crucial for ensuring normal charge and discharge. Among a given set of anode active materials, carbon materials such as hard carbon, natural graphite, artificial graphite, soft carbon, carbon black, acetylene black, carbon nanotubes, graphene, and carbon nanofibers possess excellent conductivity and plasticity, and are capable of intercalating and deintercalating sodium ions. These carbon materials can be used alone or in combination to enhance the performance of the anode materials. Furthermore, some metal elements such as Si, Ge, Pb, In, Zn, Ca, Sr, and Ba can alloy with sodium to form sodium alloys, which can also serve as anode materials. Furthermore, some metal oxides and sulfides can also undergo conversion reactions with sodium ions, and these materials can also serve as anode active materials. Therefore, the anode materials of sodium-ion batteries utilize these diverse properties, aiming to achieve sodium ion intercalation and deintercalation through different mechanisms, thereby improving the battery's energy density and cycle life.

[0045] In one embodiment, the positive electrode of the sodium ion battery includes a positive electrode active material capable of extracting and inserting sodium ions, and the positive electrode active material includes one or more of sodium iron composite oxide, sodium cobalt composite oxide, sodium chromium composite oxide, sodium manganese composite oxide, sodium nickel composite oxide, sodium nickel titanium composite oxide, sodium nickel manganese composite oxide, sodium iron manganese composite oxide, sodium nickel cobalt manganese composite oxide, sodium iron phosphate, sodium manganese phosphate, sodium cobalt phosphate, sodium vanadium phosphate, and sodium vanadium fluorophosphate. These composite oxides have a variety of crystal structures, such as layered structures and tunnel structures, which are conducive to the insertion and extraction of sodium ions, thereby improving the charge and discharge performance of the battery.

[0046] In one embodiment, the electrolyte may further include a sodium salt, which may include one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium bis(oxalatoborate), sodium difluorooxalatoborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonylimide), sodium bis(trifluoromethylsulfonylimide), sodium perchlorate, sodium 4,5-dicyano-2-(trifluoromethyl)imidazolium, and sodium 4,5-dicyano-2-(pentafluoroethyl)imidazolium. Sodium salt is the main electrolyte in sodium ion batteries, which can conduct sodium ions and enable the battery to perform charge and discharge reactions. Based on the total mass of the electrolyte, the content of sodium salt is W0%, 5≤W0≤30. The concentration of sodium salt has a significant impact on the performance of sodium ion batteries. An appropriate concentration of sodium salt can increase the conductivity of the battery, thereby improving the energy density and charge and discharge performance of the battery. Optionally, based on the total mass of the electrolyte, the content of sodium salt in the sodium ion battery electrolyte can be 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, 27%, or 30%.

[0047] In one embodiment, the solvent in the sodium ion battery electrolyte includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, ethylene glycol dimethyl ether, dioxolane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. The solvent can combine with sodium ions to form solvated ions, which helps to stabilize the sodium ions and enable them to be better transported in the electrode material. Based on the total mass of the electrolyte, the content of the solvent is Ws%, 70≤Ws<95. Optionally, the content of sodium salt in the sodium ion battery electrolyte can be 70%, 75%, 80%, 85%, 90%, or 95%.

[0048] In one embodiment, the electrolyte further includes a film-forming additive, and the film-forming additive includes one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, 1-propylene-1,3-sultone, vinyl ethylene carbonate, vinyl sulfate, methylene dicarbonate, tris(trimethylsilyl)phosphate, succinic anhydride, and maleic anhydride. The film-forming additive can increase the conductivity of the electrolyte, thereby accelerating the transmission speed of electrons and ions, improving the charge and discharge performance of the battery, inhibiting side reactions and regulating interface properties, thereby improving the electrochemical performance of the electrode. Based on the total mass of the electrolyte, the total content of the film-forming additive is Wa%, 0<Wa≤10. Optionally, the content of sodium salt in the sodium ion battery electrolyte can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0049] The present application also provides an electrical device comprising a sodium-ion battery according to any of the above embodiments. Specifically, the electrical device may be an electric vehicle, an electric motorcycle, an electric bicycle, a power bank, an unmanned aerial vehicle, a mobile phone, a computer, a camera, a power tool, a smart home device, or a wearable device.

[0050] The electrical equipment provided in the embodiment of the present application includes a sodium ion battery, which has a long cycle life and good rate performance, so that the electrical equipment can be used stably for a long time, which is beneficial to improving the performance of the electrical equipment.

[0051] The technical solution of the present application is further illustrated below through specific examples and comparative examples.

[0052] Example 1

[0053] (1) Preparation of electrolyte

[0054] In an argon glove box with a water content of <1 ppm and an oxygen content of <1 ppm, propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were uniformly mixed with a leveling additive (specifically, butynediol) in a mass ratio of 4:4:2. Sodium hexafluorophosphate (NaPF6) was then added to prepare a 1 mol / L electrolyte. The content of the leveling additive (specifically, butynediol) is shown in Table 1.

[0055] (2) Preparation of positive electrode sheet

[0056] The positive electrode active material sodium manganese composite oxide (NaMnO2), the conductive agent carbon nanotubes (CNT, Carbon Nanotubes), and the specific binder polyvinylidene fluoride are mixed in a mass ratio of 95:2:3, and N-methylpyrrolidone (NMP, N-Methylpyrrolidone) is added. The mixture is stirred into a uniform positive electrode slurry under the action of a vacuum mixer, and then the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil; after drying at 85°C, it is cold pressed, cut into pieces, and slit, and then dried under vacuum conditions at 85°C for 4 hours to obtain a positive electrode sheet.

[0057] (3) Negative electrode preparation

[0058] The negative electrode active material, hard carbon, the conductive agent, acetylene black, the binder, polymerized styrene butadiene rubber (SBR), the dispersant, carboxymethylcellulose (CMC), and a metalloid additive (specifically sodium rosinate) were thoroughly mixed in a deionized water solvent system at a mass ratio of 93.5:2:2.5:2. The mixture was then added to the mixture, coated onto aluminum foil, dried, and cold-pressed to produce a negative electrode sheet. The layer density, specific surface area, and metalloid additive selection for the negative electrode active material are shown in Table 1.

[0059] (4) Diaphragm preparation

[0060] The diaphragm is made of polypropylene.

[0061] (5) Preparation of sodium ion batteries

[0062] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role. Then they are wound and placed in the outer packaging foil. The prepared electrolyte is injected into the dried electrode core. After vacuum packaging, standing, formation, shaping and other processes, the preparation of the sodium ion battery is completed.

[0063] Examples 2 to 16

[0064] The types and contents of the leveling additives and metal-philic additives, the surface density and specific surface area of ​​the negative electrode sheets of Examples 2 to 16 are shown in Table 1. The remaining steps are the same as those of Example 1.

[0065] Comparative Examples 1 to 7

[0066] The types and contents of the leveling additives and metalloid additives, the surface density and specific surface area of ​​the negative electrode sheets of Comparative Examples 1 to 7 are shown in Table 1. The remaining steps are the same as those of Example 1.

[0067] Table 1 Layer density, specific surface area of ​​negative electrode active materials and selection of metal-philic additives and leveling additives

[0068] Test Method

[0069] (1) Surface density test

[0070] The surface density of the negative electrode sheet is tested by punching and weighing. A small punching machine (model T-06) is used to punch the coated and rolled negative electrode sheet into a circle (generally with a diameter of 12mm or 13mm). Then a high-precision analytical balance (model MS-TS) is used to weigh the mass of the small round electrode sheet and the mass of the empty current collector without active material coating, and the surface density is obtained as (electrode sheet mass - empty current collector mass) / area.

[0071] (2) Specific surface area test

[0072] The specific surface area of ​​the powder material was tested by gas adsorption method. A specific surface area tester (model ASAP2020) was used to obtain the specific surface area of ​​the material to be tested according to the BET (Brunauer-Emmett-Teller) model.

[0073] (3) Normal temperature cycle test

[0074] Take the prepared sodium ion battery and charge it to 3.95V at a constant current of 0.5C at room temperature (25±3℃), then charge it to a current of 0.05C at a constant voltage at 3.95V, let it sit for 5min, and then discharge it to 1.5V at a constant current of 0.5C, let it sit for 5min, which is one cycle. Record the capacity retention rate and thickness expansion rate (1000 full-charge thickness / first full-charge thickness) after 1000 cycles at room temperature. The cycle uses a test cabinet (NEWARE brand, model CTE-4080D-5V30A). To ensure that the battery temperature is constant during the cycle test, the battery is placed in a high and low temperature test chamber (model CH1000T). The battery thickness test uses a PPG (Panel Pressure Gap) tester (model ATMPPGSH200).

[0075] (4) Low temperature cycle test

[0076] The prepared sodium ion battery was charged at a constant current of 0.5C to 3.95V at 12°C (12±3°C), then charged at a constant voltage to a current of 0.05C at 3.95V, left for 5 minutes, and then discharged at a constant current of 0.5C to 1.5V, left for 5 minutes. This was considered a cycle. The capacity retention rate (the ratio of the discharge capacity after 1000 cycles to the discharge capacity at the first cycle) and the thickness expansion rate (600 fully charged thickness / first fully charged thickness) after 600 high-temperature cycles were recorded.

[0077] (5) Normal temperature rate test

[0078] The prepared sodium ion battery was charged to 3.95V at a constant current and constant voltage rate of 0.2C at room temperature (25±3℃), cut off at 0.05C, and left for 5 minutes, then discharged to 1.5V at a constant current rate of 0.2C and left for 5 minutes, which was considered as one cycle. After two 0.2C cycles, the discharge capacity of the second cycle was taken as the 0.2C discharge capacity. The battery was then charged to 3.95V at a constant current and constant voltage rate of 0.5C, cut off at 0.05C, and left for 5 minutes, then discharged to 1.5V at a constant current rate of 2C and left for 5 minutes, which was considered as one cycle. After two 2C cycles, the discharge capacity of the second cycle was taken as the 2C discharge capacity. The ratio of the discharge capacity recorded twice is the room temperature 2C / 0.1C capacity retention rate.

[0079] (6) Low-temperature circulation sodium precipitation

[0080] After 600 cycles of low-temperature cycling, the battery is disassembled in a fully charged state and the sodium precipitation on the negative electrode surface is observed. If there is obvious silvery-white metallic product deposition on the large surface of the negative electrode, the tab or the crease, it is considered as sodium precipitation. In the case of severe sodium precipitation, sodium metal will react with the electrolyte to cause the sodium metal to change from silvery white to yellow.

[0081] Table 2 Cyclic test and sodium precipitation test results

[0082] Tables 1 and 2 show that, compared to the electrolyte without a leveler additive, the introduction of butynediol as a leveler significantly improved cycle capacity retention and reduced thickness expansion. The introduction of a metal-philic sodium rosinate additive into the negative electrode significantly improved long-term cycling performance, and battery disassembly revealed that sodium deposition at the negative electrode was alleviated.

[0083] Furthermore, when the specific surface area of ​​the negative electrode active material layer, the areal density of the negative electrode active material layer, the content of the leveling additive, and the content of the metalloid additive satisfy the following relationship: 0 < (W1 + W2) / (A + 10 / ρ) ≤ 1, the room temperature cycle performance, low temperature cycle performance, and room temperature rate performance are good, and the low temperature cycle sodium precipitation situation is improved. When the conditions of 0 < W1 / A ≤ 1 or 0 < W1 ≤ 2 in the present application are further satisfied, the proportion of the leveling agent butynediol can be avoided from being too high, thereby affecting the oxidative stability of the electrolyte, and the electrolyte oxidation side reaction can be prevented from causing the product to accumulate on the electrode surface, causing the interfacial impedance to continue to increase, thereby improving the comprehensive sodium ion cycling performance.

[0084] Furthermore, when the surface density of the negative electrode active material layer and the content of the metal-philic additive satisfy the following relationship: 5<ρ*W2≤20 or 0<W2≤3, the proportion of sodium rosinate added is appropriate, which can improve the battery cycle while avoiding the excessive content of electrochemically inert sodium rosinate in the negative electrode, thereby avoiding the decline of rate discharge performance.

[0085] The above are preferred embodiments of the present application, but they should not be construed as limiting the scope of the present application. It should be noted that those skilled in the art may make improvements and modifications without departing from the principles of the present application, and such improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A sodium-ion battery, characterized in that, The sodium-ion battery includes: Positive electrode; negative electrode, the negative electrode comprising a negative current collector, a negative active material layer, and a metalophilic additive, the negative active material layer being disposed on the negative current collector, the areal density of the negative active material layer being ρ mg / cm 2 , the specific surface area of the negative active material layer being A m 2 / g, the metalophilic additive being added to the negative active material layer, the content of the metalophilic additive being W2% based on the mass of the negative active material layer; An electrolyte solution, the electrolyte solution contains a leveling additive, based on the total mass of the electrolyte solution, the content of the leveling additive is W1%, and the following relationship is satisfied: 0 < (W1 + W2) / (A + 10 / ρ) ≤ 1.

2. The sodium-ion battery according to claim 1, wherein, The areal density of the negative electrode active material layer and the content of the metalophilic additive satisfy the following relationship: 5 < ρ*W2 ≤ 20.

3. The sodium-ion battery according to claim 1, characterized in that, The specific surface area of the negative electrode active material layer and the content of the leveling additive satisfy the following relationship: 0 < W1 / A ≤ 1.

4. The sodium-ion battery according to claim 1, characterized in that, The W1, W2, ρ, and A satisfy: 0.5 < (W1 + W2) / (A + 10 / ρ) ≤ 1.

5. The sodium ion battery according to claim 1, characterized in that, The metalophilic additive includes one or more of sodium alginate and sodium rosinate.

6. The sodium ion battery according to claim 1, characterized in that, The content of the metalophilic additive satisfies 0 < W2 ≤ 3.

7. The sodium ion battery according to claim 1, characterized in that, The content of the leveling additive satisfies 0 < W1 ≤ 2.

8. The sodium ion battery according to claim 1, characterized in that, The leveling additive includes one or more of butynediol, pyridine compounds, and quinoline compounds.

9. The sodium ion battery according to claim 1, characterized in that, The negative electrode active material layer contains a first negative electrode active material capable of intercalating and deintercalating sodium ions, the first negative electrode active material includes one or more of carbon materials such as hard carbon, natural graphite, artificial graphite, soft carbon, carbon black, acetylene black, carbon nanotubes, graphene, carbon nanofibers, and titanium oxides; and / or, The negative electrode active material layer includes a second negative electrode active material capable of alloying reaction with sodium, the second negative electrode active material includes one or more of elements such as Si, Ge, Pb, In, Zn, Ca, Sr, Ba, Ru, and Rh in the form of simple substances, oxides, or carbides; and / or, The negative electrode active material layer includes a third negative electrode active material capable of conversion reaction with sodium ions, the third negative electrode active material includes one or more of transition metal oxides and transition metal sulfides.

10. The sodium-ion battery according to claim 1, characterized in that, The positive electrode includes a positive electrode active material capable of deintercalating and intercalating sodium ions, the positive electrode active material includes one or more of sodium iron composite oxides, sodium cobalt composite oxides, sodium chromium composite oxides, sodium manganese composite oxides, sodium nickel composite oxides, sodium nickel titanium composite oxides, sodium nickel manganese composite oxides, sodium iron manganese composite oxides, sodium nickel cobalt manganese composite oxides, sodium iron phosphate compounds, sodium manganese phosphate compounds, sodium cobalt phosphate compounds, sodium vanadium phosphate compounds, and sodium vanadium fluorophosphate compounds.

11. The sodium ion battery according to claim 1, characterized in that, The electrolyte solution also includes a sodium salt, the sodium salt includes one or several of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, sodium perchlorate, 4,5-dicyano-2-(trifluoromethyl)imidazole sodium, and 4,5-dicyano-2-(pentafluoroethyl)imidazole sodium. Based on the total mass of the electrolyte solution, the content of the sodium salt is W0%, 5 ≤ W0 ≤ 30.

12. The sodium ion battery according to claim 1, wherein The electrolyte further includes a solvent, which includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, ethylene glycol dimethyl ether, dioxolane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Based on the total mass of the electrolyte, the content of the solvent is Ws%, and 70 ≤ Ws < 95.

13. The sodium-ion battery according to claim 1, characterized in that, The electrolyte further includes a film-forming additive, which includes one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, 1-propene-1,3-sultone, ethylene vinylene carbonate, vinyl sulfate, methylene methanedisulfonate, tris(trimethylsilyl) phosphate, succinic anhydride, and maleic anhydride. Based on the total mass of the electrolyte, the total content of the film-forming additive is Wa%, and 1 < Wa ≤ 10.

14. An electrical device, characterized in that, A sodium ion battery comprising any one of claims 1 to 13.

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