Sodium ion battery and electric equipment

Abstract

The invention discloses a sodium ion battery and electric equipment. The sodium ion battery comprises a positive electrode and a negative electrode, 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, the surface density of the negative electrode active material layer is rho mg / cm < 2 >, the specific surface area of the negative electrode active material layer is Am < 2 > / g, and the metal-philic additive is added to the negative electrode active material layer. The content of the metallophilic additive is W 2%; the electrolyte comprises a leveling additive, the content of the leveling additive is W < 1% > based on the total mass of the electrolyte, and the following relation is met: 0 lt; (W1 + W2) / (A + 10 / rho) < = 1. The metal-philic additive is introduced into the negative electrode active material layer, the leveling additive is introduced into the electrolyte, and by regulating and controlling the surface density and the specific surface area of the negative electrode active material layer and the relationship between the metal-philic additive and the leveling additive in the electrolyte, the risk of sodium precipitation is relieved, and the charge-discharge performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a sodium ion battery and electrical equipment. Background Art

[0002] Lithium-ion batteries are the most widely commercialized electrochemical energy storage devices. They achieve the conversion of chemical energy and electrical energy through the reversible insertion / extraction of lithium ions between the positive and negative electrodes. Sodium and lithium belong to the same main group, but the reserves of sodium on Earth are much higher than lithium, and my country has abundant sodium resources and sodium extraction technology, so the cost of sodium-ion batteries will be greatly reduced compared to lithium-ion batteries.

[0003] However, the negative electrode commonly used in sodium-ion batteries currently has the disadvantages of large specific surface area and many surface defects, which will cause the electrolyte to form a thicker SEI on the surface of the negative electrode, consuming more active sodium. In addition, the electrolyte of commercial sodium-ion batteries mainly uses carbonate solvents, which have high viscosity and surface tension and poor wettability to pores, resulting in a high risk of sodium precipitation in the battery and poor charge and discharge performance. Summary of the invention

[0004] Based on this, the present invention provides a sodium ion battery and electrical equipment, introduces a metal-philic additive into the negative electrode, introduces a leveling additive into the electrolyte, and regulates the relationship between the surface density, specific surface area, metal-philic additive and leveling additive in the negative electrode active material layer to mitigate the risk of sodium decomposition and improve the high and low temperature charging and discharging performance of the battery.

[0005] In a first aspect, an embodiment of the present invention provides a sodium ion battery, the sodium ion battery comprising:

[0006] 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 ρmg / cm 2 The specific surface area of ​​the negative electrode active material layer is A m 2 / g, 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;

[0007] The electrolyte comprises 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. In an embodiment of the present invention, 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.

[0008] In the embodiment of the present invention, the specific surface area of ​​the negative electrode active material layer and the content of the leveling additive satisfy the following relationship: <W1 / A≦1。

[0009] In the implementation manner of the present invention, W1, W2, ρ, and A satisfy: 0.5<(W1+W2) / (A+10 / ρ)≦1.

[0010] In an embodiment of the present invention, the metal-philic additive includes one or more of sodium alginate and sodium rosinate.

[0011] In the embodiment of the present invention, the content of the metal-philic additive satisfies 0 <W2≦3。

[0012] In the embodiment of the present invention, the content of the leveling additive satisfies 0 <W1≦2。

[0013] In the embodiment of the present invention, the specific surface area of ​​the negative electrode active material layer and the content of the leveling additive satisfy the following relationship: <W1 / A≦1。

[0014] In an embodiment of the present invention, the leveling additive includes one or more of butynediol, a pyridine compound and a quinoline compound.

[0015] In an embodiment of the present invention, the negative electrode current collector is aluminum foil, the negative electrode active material comprises a negative electrode active material capable of embedding and extracting sodium ions, and the negative electrode active material comprises 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,

[0016] The negative electrode active material includes one or more of Si, Ge, Pb, In, Zn, Ca, Sr, Ba, Ru, Rh and other elements alloyed with sodium, oxides and carbides containing these elements; and / or,

[0017] The negative electrode active material includes one or more transition metal oxides and sulfides that can undergo conversion reactions with sodium ions.

[0018] In an embodiment of the present invention, the positive electrode includes a positive electrode active material that can extract and embed sodium ions, including 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. One or more.

[0019] In an embodiment of the present invention, the electrolyte also includes sodium salt, and the sodium salt includes one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium bisoxalatoborate, sodium difluorooxalatoborate, sodium trifluoromethylsulfonate, sodium bisfluorosulfonyl imide, sodium bistrifluoromethylsulfonyl 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, the content of the sodium salt is W0%, 5≦W0≦30.

[0020] In an embodiment of the present invention, 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%, 70≤Ws<95.

[0021] In an embodiment of the present invention, 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.

[0022] In an embodiment of the present invention, the surfactant includes one or more of stearic acid, sodium dodecylbenzene sulfonate, quaternary ammonium compounds, lecithin, betaine-type compounds, alkyl glucoside, fatty acid glyceride, fatty acid sorbitan, and polysorbate.

[0023] In an embodiment of the present invention, the negative electrode current collector is aluminum foil, the negative electrode material comprises a negative electrode active material capable of embedding and extracting sodium ions, and the negative electrode active material comprises one or more of hard carbon, natural graphite, artificial graphite, soft carbon, carbon black, acetylene black, carbon nanotubes, graphene, carbon nanofibers and other carbon materials and titanium oxide; and / or,

[0024] The negative electrode active material includes one or more of Si, Ge, Pb, In, Zn, H, Ca, Sr, Ba, Ru, Rh and other elements alloyed with sodium, oxides and carbides containing these elements; and / or,

[0025] The negative electrode active material includes one or more transition metal oxides and sulfides that can undergo conversion reactions with sodium ions.

[0026] In an embodiment of the present invention, the positive electrode includes a positive electrode active material that can extract and embed sodium ions, including 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. One or more.

[0027] In an embodiment of the present invention, the sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium bis(oxalatoborate), sodium difluorooxalatoborate, sodium trifluoromethylsulfonate, sodium bis(fluorosulfonyl imide), sodium bis(trifluoromethylsulfonyl imide), sodium perchlorate, 4,5-dicyano-2-(trifluoromethyl)imidazol sodium, and 4,5-dicyano-2-(pentafluoroethyl)imidazol sodium. Based on the total mass of the electrolyte, the content of the sodium salt is Ws%, and 5≦Ws≦30.

[0028] In an embodiment of the present invention, 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, and the content of the solvent is W1% based on the total mass of the electrolyte, 70≤W1<95.

[0029] In an embodiment of the present invention, 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, maleic anhydride, etc., and the total content of the additive is W2%, 0<W2≤10.

[0030] The present invention introduces a leveling additive into the electrolyte, which can even out the charge density on the negative electrode surface, promote the uniform deposition and embedding of sodium ions, and 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 the solvent, reduce the negative electrode SEI impedance, improve the stability of SEI, and thus improve the high and low temperature charging and discharging and storage performance of the whole battery. In addition, a metalloid additive with excellent metalloid performance is introduced into the negative electrode, and 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 charging and discharging efficiency and stability of the battery.

[0031] In a second aspect, an embodiment of the present invention further provides an electric device, the electric device comprising the sodium ion battery described in the first aspect. The electric device provided by the embodiment of the present invention comprises the sodium ion battery described in the second aspect, the sodium ion battery has a long cycle life and good rate performance, so that the electric device can be used stably for a long time, which is conducive to improving the performance of the electric device. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in the present invention includes any and all combinations of one or more of the related listed items.

[0034] Some embodiments of the present invention are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0035] Lithium-ion batteries are the most widely commercialized electrochemical energy storage devices. They achieve the conversion of chemical energy and electrical energy through the reversible insertion / extraction of lithium ions between the positive and negative electrodes. Sodium and lithium belong to the same main group, but the reserves of sodium on Earth are much higher than lithium, and my country has abundant sodium resources and sodium extraction technology, so the cost of sodium-ion batteries will be greatly reduced compared to lithium-ion batteries.

[0036] In addition to the advantages of reserves and cost, sodium-ion batteries generate less instantaneous heat in safety tests and have higher safety. In addition, the sodium ion desolvation rate in organic solvents is lower, and under the same conditions, it has a higher ion conduction rate and lower charge transfer impedance. In addition, sodium and aluminum will not form alloys at low potentials, so aluminum can be used as the current collector for both the positive and negative electrodes of sodium-ion batteries to increase the energy density of the battery.

[0037] However, the negative electrode commonly used in sodium-ion batteries currently has the disadvantages of large specific surface area and many surface defects, which will cause the electrolyte to form a thicker SEI on the surface of the negative electrode and consume more active sodium. In addition, the electrolyte of commercial sodium-ion batteries mainly uses carbonate solvents, which have high viscosity and surface tension and poor wettability to pores, resulting in poor battery cycle performance and reduced energy density.

[0038] Based on this, the present invention 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 arranged on the negative electrode current collector, and the surface density of the negative electrode active material layer is ρmg / cm 2 The specific surface area of ​​the negative electrode active material layer is Am 2 / g, 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, the electrolyte contains a leveling additive, and 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. In this embodiment, a leveling additive is introduced into the electrolyte, and the leveling additive can evenly distribute the charge density on the negative electrode surface, promote the uniform deposition and embedding of sodium ions, and 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 the solvent, reduce the negative electrode SEI impedance, and improve the stability of the SEI, thereby improving the high and low temperature charging and discharging and storage performance of the whole battery. In addition, metallophilic additives with excellent metallophilic properties are introduced into the negative electrode. Metallophilic additives can effectively complex metal cations, especially in sodium ion batteries, they 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.

[0039] Furthermore, 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, wherein 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. The matching of the two can ensure 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. The interface layer can improve the sodium extraction / insertion kinetics of the negative electrode surface, reduce the sodium insertion 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. 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 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0.

[0040] In one embodiment, 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. When 5 < ρ * W2 ≤ 20, the areal density of the negative electrode and the content of the electrochemically inert components are controlled within a reasonable range, which can improve the negative electrode interface without causing excessive energy density loss of the full cell. Optionally, the value of ρ * W2 can be 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.

[0041] In one embodiment, 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. When 0 < W1 / A ≤ 1, the leveling additive in the electrolyte can form a good adsorption layer on the surface of the negative electrode, promoting the uniform adsorption and insertion of sodium ions, thereby playing a role in uniforming the local current density and retarding the sodium desorption. Optionally, the value of W1 / A can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0.

[0042] In one embodiment, the metalophilic additive is a surfactant containing metal cations, including but not limited to sodium alginate and sodium rosinate. For example, sodium rosinate is an anionic surfactant containing a triphenyl ring structure. Adding it to the negative electrode can not only improve the uniformity of the negative electrode mixture, but also its anions can combine with the 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 the rapid desolvation of sodium ions in the electrolyte at the interface, thereby enhancing the sodium insertion kinetics.

[0043] In one embodiment, the content of the metalophilic additive satisfies 0 < W2 ≤ 3. The appropriate proportion of the metalophilic additive added can improve the battery cycle while avoiding excessive content of electrochemically inert sodium rosinate in the negative electrode, resulting in a decline in the rate discharge performance. Optionally, the value of W2 can be 0.3, 0.6, 0.9, 1.2, 1.5, 1.8, 2.1, 2.4, 2.7, 3.

[0044] In one embodiment, the content of the leveling additive satisfies 0 < W1 ≤ 2. When this range is satisfied, the proportion of the leveling additive can be prevented from being too high, which affects the oxidation stability of the electrolyte, and prevent the product from accumulating on the electrode surface due to the oxidation side reaction of the electrolyte, resulting in a continuous increase in the interfacial impedance, thereby improving the comprehensive cycle performance of sodium ions. Optionally, the value of W1 can be 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0.

[0045] In one embodiment, the leveling additive includes one or more of butynediol, pyridine compounds and quinoline compounds. For example, butynediol is a class of small organic molecules that can be adsorbed on the electrode surface to prevent metal ions from being directly reduced on the surface, effectively slowing down the release of sodium.

[0046] 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 will not react to form alloys, and the cost is much lower than copper foil in lithium batteries. The negative electrode material includes a negative electrode active material that can embed and extract sodium ions. The 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 oxides; and / or, the negative electrode active material includes one or more of Si, Ge, Pb, In, Zn, Ca, Sr, Ba, Ru, Rh, etc., which are alloyed with sodium, oxides containing these elements, and carbides; and / or, the negative electrode active material includes one or more of transition metal oxides and sulfides that can undergo conversion reactions with sodium ions. The negative electrode material of the sodium ion battery needs to have the ability to embed and extract sodium ions, which is the key to ensuring that the battery can charge and discharge normally. Among the given negative electrode active materials, carbon materials such as hard carbon, natural graphite, artificial graphite, soft carbon, carbon black, acetylene black, carbon nanotubes, graphene, and carbon nanofibers have good conductivity and plasticity, and can undergo embedding and extraction reactions with sodium ions. These carbon materials can be used alone or in combination in different ways to improve the performance of negative electrode materials. In addition, some metal elements such as Si, Ge, Pb, In, Zn, Ca, Sr, Ba, etc. can undergo alloying reactions with sodium to form sodium alloys, which can also be used as negative electrode materials. In addition, some metal oxides and sulfides can also undergo conversion reactions with sodium ions, and these materials can also be used as negative electrode active materials. Therefore, the negative electrode materials of sodium ion batteries use these materials with different characteristics, aiming to achieve the embedding and extraction of sodium ions through different mechanisms, thereby improving the energy density and cycle life of the battery.

[0047] In one embodiment, the positive electrode of the sodium ion battery includes a positive electrode active material capable of extracting and embedding sodium ions, including 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, sodium vanadium fluorophosphate. One or more of these composite oxides have a variety of crystal structures, such as layered structures, tunnel structures, etc., which are conducive to the embedding and extraction of sodium ions, thereby improving the charge and discharge performance of the battery.

[0048] In one embodiment, the sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium bisoxalate borate, sodium difluorooxalate borate, sodium trifluoromethanesulfonate, sodium bisfluorosulfonyl imide, sodium bistrifluoromethanesulfonyl imide, sodium perchlorate, 4,5-dicyano-2-(trifluoromethyl) imidazole sodium, 4,5-dicyano-2-(pentafluoroethyl) imidazole sodium, and the sodium salt is the main electrolyte in the sodium ion battery, 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 the sodium salt is Ws%, 5≦Ws≦30. The concentration of the sodium salt has an important influence on the performance of the sodium ion battery. The appropriate concentration of the sodium salt can increase the conductivity of the battery, thereby improving the energy density and charge and discharge performance of the battery.

[0049] 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%.

[0050] 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 better transmit them 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%, 95%.

[0051] In one embodiment, the electrolyte further includes additives, and the additives include 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. Some additives 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 adjusting interface properties, thereby improving the electrochemical properties of the electrode. Based on the total mass of the electrolyte, the total content of the 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%, 10%.

[0052] The embodiment of the present invention further provides an electric device, which includes the sodium ion battery in any of the above embodiments. Specifically, the electric device can be an electric car, an electric motorcycle, an electric bicycle, a mobile power supply, an unmanned aerial vehicle, a mobile phone, a computer, a camera, an electric tool, a smart home or a wearable device.

[0053] The electric device provided in the embodiment of the present invention comprises a sodium ion battery, which has a long cycle life and good rate performance, so that the electric device can be used stably for a long time, which is beneficial to improving the performance of the electric device.

[0054] The technical solution of the present invention is further illustrated below through specific embodiments and comparative examples.

[0055] Example 1

[0056] (1) Preparation of electrolyte

[0057] In an argon atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and a leveling additive (specifically butynediol) were uniformly mixed at a mass ratio of 4:4:2, and NaPF6 was added to prepare a 1 mol / L electrolyte. The content of the leveling additive (specifically butynediol) is shown in Table 1.

[0058] (2) Preparation of positive electrode

[0059] The positive electrode active material sodium manganese composite oxide (NaMnO2), the conductive agent carbon nanotube (CNT), and the specific binder polyvinylidene fluoride are mixed in a mass ratio of 95:2:3, and N-methylpyrrolidone (NMP) 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 Al 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.

[0060] (3) Negative electrode preparation

[0061] The negative electrode active material hard carbon, conductive agent acetylene black, binder SBR: dispersant CMC in a mass ratio of 93.5:2:2.5:2 and a metal-philic additive (specifically sodium rosin acid) were fully stirred and mixed in a deionized water solvent system, and then added, coated on Al foil, dried, and cold pressed to obtain a negative electrode sheet. The layer density, specific surface area and metal-philic additive of the negative electrode active material are shown in Table 1.

[0062] (4) Diaphragm preparation

[0063] The diaphragm is made of polypropylene.

[0064] (5) Preparation of sodium ion batteries

[0065] The positive electrode sheet, the separator, and the 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, and then they are wound and placed in an outer packaging foil. The prepared electrolyte is injected into the dried electrode core, and after vacuum packaging, standing, formation, shaping and other processes, the preparation of the sodium ion battery is completed.

[0066] Embodiments 2 to 16

[0067] 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, and the remaining steps are the same as those of Example 1.

[0068] Comparative Examples 1 to 7

[0069] 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 Comparative Examples 1 to 7 are shown in Table 1, and the remaining steps are the same as those of Example 1.

[0070] Table 1 Layer density, specific surface area of ​​negative electrode active materials and selection of metal-philic additives and leveling additives

[0071]

[0072]

[0073] Test Method

[0074] (1) Surface density test

[0075] 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 negative electrode sheet after coating and rolling (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. The surface density is obtained as (electrode sheet mass - empty current collector mass) / area

[0076] (2) Specific surface area test

[0077] The specific surface area of ​​the powder material was tested by gas adsorption method, and 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 model.

[0078] (3) Normal temperature cycle test

[0079] 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 0.05C at a constant voltage at 3.95V, let it stand for 5min, and then discharge it to 1.5V at a constant current of 0.5C, let it stand 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 NEWARE test cabinet (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 box (model CH1000T). The battery thickness test uses a PPG tester (model ATMPPGSH200).

[0080] (4) Low temperature (12 degrees) cycle test

[0081] The prepared sodium ion battery was charged to 3.95V at 0.5C rate at 12 degrees Celsius (12±3℃), then charged to 0.05C at 3.95V, left for 5 minutes, and then discharged to 1.5V at 0.5C rate, left for 5 minutes, which was considered a cycle. The capacity retention rate (ratio of discharge capacity after 1000 cycles to discharge capacity in the first cycle) and thickness expansion rate (600 full charge thickness / first full charge thickness) after 600 high-temperature cycles were recorded.

[0082] (5) Normal temperature rate test

[0083] Take the prepared sodium ion battery at room temperature (25±3℃) and charge it to 3.95V at 0.2C rate constant current and constant voltage, cut off at 0.05C, let it stand for 5min, then discharge it to 1.5V at 0.2C rate constant current and let it stand for 5min, which is one cycle. After two 0.2C cycles, the second cycle discharge capacity is taken as the 0.2C discharge capacity. Then the battery is charged to 3.95V at 0.5C rate constant current and constant voltage, cut off at 0.05C, let it stand for 5min, then discharge it to 1.5V at 2C rate constant current and let it stand for 5min, which is one cycle. After two 2C cycles, the second cycle discharge capacity is taken as the 2C discharge capacity. The ratio of the discharge capacity recorded twice is the room temperature 2C / 0.1C capacity retention rate.

[0084] (6) Low temperature circulation sodium precipitation

[0085] The battery was disassembled in a fully charged state after 600 cycles of low-temperature cycling, and the sodium precipitation on the surface of the negative electrode was observed. If there was obvious silvery-white metallic product deposition on the large surface, tab or crease of the negative electrode, it was considered as sodium precipitation. In the case of severe sodium precipitation, the sodium metal will react with the electrolyte to cause the sodium metal to change from silvery white to yellow.

[0086] Table 2 Results of cyclic tests and sodium stripping tests

[0087]

[0088]

[0089] It can be seen from Table 1 and Table 2 that, compared with the electrolyte without a leveling agent additive, after introducing butynediol as a leveling additive, the cyclic capacity retention rate has been significantly improved, and the thickness swelling rate has also decreased. By introducing sodium rosinate additive with an affinity for metals into the negative electrode, the long-term cycling performance has been significantly improved, and it is found by disassembling the battery that the sodium stripping phenomenon in the negative electrode has been alleviated. Further, 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 metalophilic additive satisfy the following relationship: 0 < (W1 + W2) / (A + 10 / ρ) ≤ 1, the room-temperature cycling performance, low-temperature cycling performance, and room-temperature rate performance are good, and the sodium stripping situation during low-temperature cycling is improved. When further satisfying 0 < W1 / A ≤ 1 or 0 < W1 ≤ 2 in the present application, it is possible to avoid an excessive proportion of the leveling agent butynediol, which may affect the oxidation stability of the electrolyte, prevent the accumulation of products caused by oxidation side reactions of the electrolyte on the electrode surface, resulting in a continuous increase in the interfacial impedance, and thus improve the comprehensive cycling performance of sodium ions.

[0090] Further, when 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 or 0 < W2 ≤ 3, the proportion of sodium rosinate added is appropriate, which can improve the battery cycling while avoiding an excessive content of electrochemically inert sodium rosinate in the negative electrode and preventing a decline in the rate discharge performance.

[0091] The above are the preferred embodiments of the present application, but it should not be construed as limiting the scope of the present application. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present application, several improvements and refinements can still be made, and these improvements and refinements are also regarded as the protection scope of the present application.

Claims

1. A sodium ion battery, characterized in that: The sodium ion battery comprises: 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 ρmg / cm 2 The specific surface area of ​​the negative electrode active material layer is Am 2 / g, 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; An electrolyte, wherein the electrolyte comprises a leveling additive, wherein 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.

2. The sodium ion battery according to claim 1, characterized in that: 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.

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: <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 metal-philic 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 metalloid 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, a pyridine compound, and a quinoline compound.

9. The sodium ion battery according to claim 1, characterized in that: The negative electrode active material layer comprises a first negative electrode active material capable of embedding and extracting sodium ions, wherein the first negative electrode active material comprises 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 layer includes a second negative electrode active material capable of alloying with sodium, wherein the second negative electrode active material includes a single substance, an oxide or a carbide of one or more elements selected from Si, Ge, Pb, In, Zn, Ca, Sr, Ba, Ru and Rh; and / or, The negative electrode active material layer includes a third negative electrode active material capable of undergoing a conversion reaction with sodium ions, and the third negative electrode active material includes one or more of a transition metal oxide and a transition metal sulfide.

10. The sodium ion battery according to claim 1, characterized in that: The positive electrode includes a positive electrode active material capable of extracting and embedding sodium ions, including 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 also includes sodium salt, which includes one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium bisoxalatoborate, sodium difluorooxalatoborate, sodium trifluoromethylsulfonate, sodium bisfluorosulfonyl imide, sodium bistrifluoromethylsulfonyl 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, the content of the sodium salt is W0%, 5≦Ws≦30.

12. The sodium ion battery according to claim 1, characterized in that: The electrolyte also 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%, 70≤Ws<95.

13. The sodium ion battery according to claim 1, characterized in that: The electrolyte also includes a film-forming additive, which 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. Based on the total mass of the electrolyte, the total content of the additive is Wa%, 1<Wa≤10.

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

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