Sodium-ion battery, preparation method thereof and electric equipment

Abstract

The invention provides a sodium ion battery, a preparation method thereof and electric equipment, the sodium ion battery comprises a sodium supplementing agent and an accelerant, and the accelerant is suitable for promoting the sodium supplementing agent to decompose to generate sodium ions. The sodium ion battery provided by the invention can effectively promote the decomposition of the sodium supplement agent, reduce the probability of side reaction caused by the undecomposed sodium supplement agent in the battery, and generate more active sodium ions to supplement sodium to the negative electrode, thereby effectively improving the cycling stability of the battery.

Description

Technical Field

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

[0002] Sodium-ion batteries have the advantages of high energy density, long cycle life, high reliability and low cost, and are widely considered to be an effective alternative to lithium-ion batteries.

[0003] The coulombic efficiency of the negative electrode materials used in sodium-ion batteries is generally lower than that of the positive electrode materials. By adding sodium supplements, the coulombic efficiency difference between the positive and negative electrodes can be effectively compensated, thereby improving the energy density of the battery cell.

[0004] However, the decomposition rate of commonly used sodium supplements is low. Not only does the capacity increase fall short of demand, but the undecomposed sodium supplement will trigger side reactions inside the battery during subsequent cycles, thereby causing deterioration of battery performance. Summary of the Invention

[0005] The present invention provides a sodium ion battery. By introducing a promoter, the sodium ion battery can effectively promote the decomposition of a sodium supplement, reduce the probability of undecomposed sodium supplement inducing side reactions inside the battery, and generate more active sodium ions to supplement sodium for the negative electrode.

[0006] The present invention also provides a method for preparing the above-mentioned sodium ion battery, which can prepare the above-mentioned sodium ion battery and has a simple process.

[0007] The present invention also provides an electrical device. Since the electrical device includes the battery or battery pack, the electrical device has higher energy output and longer service life.

[0008] In a first aspect, the present invention provides a sodium ion battery, comprising a sodium supplement and a promoter, wherein the promoter is suitable for promoting the decomposition of the sodium supplement to produce sodium ions.

[0009] According to one embodiment of the present invention, the promoter is suitable for undergoing a redox reaction.

[0010] According to one embodiment of the present invention, the promoter is suitable for undergoing an oxidation reaction at a potential of 3.4V to 4.3V relative to sodium and generating free radical cations, and the free radical cations are suitable for decomposing the sodium supplement to generate the sodium ions.

[0011] According to one embodiment of the present invention, the accelerator includes at least one of phenothiazine and its derivatives, triphenylamine and its derivatives, bisphenol A and its derivatives, and dimethoxybenzene and its derivatives.

[0012] According to one embodiment of the present invention, the sodium supplement includes at least one of Na2O, Na2O2, NaNO2, Na2CO3, Na2C4O4, Na2C2O4, Na2C3O5, Na2C6O6, Na2C6H2O6, CH3COONa, Na2NiO2, and NaCrO2.

[0013] According to one embodiment of the present invention, the particle size distribution of the sodium supplement meets the following condition: 100nm≤Dv99≤5000nm.

[0014] According to one embodiment of the present invention, the sodium ion battery includes a positive electrode sheet, the positive electrode sheet includes a current collector and a positive electrode active material layer arranged on at least one surface of the current collector, and the sodium supplement is provided inside and / or on at least part of the surface of the positive electrode active material layer.

[0015] According to one embodiment of the present invention, the positive electrode active material layer includes a positive electrode active material, and the mass of the sodium supplement is 0.1 wt % to 10 wt % of the mass of the positive electrode active material.

[0016] According to one embodiment of the present invention, the sodium ion battery includes a diaphragm, and the sodium supplement is provided inside and / or on at least a portion of the surface of the diaphragm.

[0017] According to one embodiment of the present invention, the sodium ion battery includes an electrolyte, the electrolyte includes the promoter, and the mass fraction of the promoter in the electrolyte is 0.05wt%-2wt%.

[0018] In a second aspect, the present invention provides a method for preparing a sodium ion battery as described in the first aspect, comprising the following steps:

[0019] The sodium supplement, the accelerator and the battery raw materials are mixed to prepare the sodium ion battery.

[0020] According to one embodiment of the present invention, the mixing of the sodium supplement, the accelerator and the battery raw material specifically includes the following process:

[0021] preparing an electrolyte containing the accelerator;

[0022] preparing a diaphragm and / or a positive electrode sheet containing the sodium supplement;

[0023] The separator, the positive electrode sheet, the negative electrode sheet and the electrolyte are assembled.

[0024] According to one embodiment of the present invention, the preparation of the diaphragm containing the sodium supplement comprises the following process:

[0025] A material comprising the sodium supplement and a binder is coated on at least a portion of the surface of the diaphragm.

[0026] According to one embodiment of the present invention, the preparation of the positive electrode sheet containing the sodium supplement comprises any one of the following steps ac:

[0027] a. coating a positive electrode slurry containing the sodium supplement and the positive electrode active material on at least one surface of a current collector and drying the slurry to prepare the positive electrode sheet;

[0028] b. coating a first positive electrode slurry containing a positive electrode active material on at least one surface of a current collector, and then coating a slurry containing the sodium supplement agent on the side coated with the first positive electrode slurry, and drying to prepare the positive electrode sheet;

[0029] c. The second positive electrode slurry containing the sodium supplement agent and the positive electrode active material is coated on at least one surface of the current collector, and then the slurry containing the sodium supplement agent is continuously coated on the side coated with the second positive electrode slurry, and dried to prepare the positive electrode sheet.

[0030] In a third aspect, the present invention provides an electrical device comprising the sodium ion battery described in the first aspect, or the sodium ion battery prepared by the preparation method described in the second aspect.

[0031] The sodium ion battery provided by the present invention can effectively promote the decomposition of the sodium supplement agent by introducing a accelerator, reduce the probability of undecomposed sodium supplement agent triggering side reactions inside the battery, and generate more active sodium ions to supplement sodium to the negative electrode, thereby effectively improving the cycle stability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0033] Figure 1 This is a schematic diagram of a promoter promoting the decomposition of a sodium supplement according to a specific embodiment of the present invention;

[0034] Figure 2 This is a molecular decomposition diagram of a promoter according to a specific embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of a sodium supplement according to a specific embodiment of the present invention being restored to its initial state. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific embodiments listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present invention.

[0037] In a first aspect, the present invention provides a sodium ion battery, comprising a sodium supplement and a promoter, wherein the promoter is suitable for promoting the decomposition of the sodium supplement to produce sodium ions.

[0038] By introducing a sodium supplement agent into a sodium ion battery, active sodium ions can be generated to supplement the negative electrode with sodium, thereby compensating for the coulombic efficiency difference between the positive and negative electrodes and improving the energy density and cycle life of the battery cell. However, adding a sodium supplement agent to the positive electrode sheet and / or separator has the problem of a low decomposition rate of the sodium supplement agent. Therefore, the present invention has found that the introduction of a promoter can promote the decomposition of the sodium supplement agent, thereby replenishing more active sodium ions to the negative electrode, helping to maintain the structural integrity of the electrode material, reducing the volume change and structural damage caused by the insertion and extraction of sodium ions, and thus improving the cycle stability of the battery.

[0039] It should be noted that, compared with the prior art method of directly adding a sodium supplement, the sodium ion battery of the present invention can effectively improve the decomposition rate of the sodium supplement by simultaneously introducing a sodium supplement and a promoter. Therefore, the sodium ion battery of the present invention has universal applicability, and its specific structure can be adjusted accordingly according to the application scenario, and the present invention is not particularly limited to this.

[0040] In one embodiment of the present invention, the promoter is suitable for undergoing a redox reaction.

[0041] In a specific embodiment of the present invention, the accelerator is suitable for undergoing an oxidation reaction at a potential of 3.4V to 4.3V relative to sodium and generating free radical cations, and the free radical cations are suitable for decomposing the sodium supplement to generate sodium ions.

[0042] The potential relative to sodium can be understood as the potential difference relative to sodium metal. Specifically, sodium metal is used as the reference electrode. At this time, the potential of the working electrode obtained by testing is the potential relative to sodium.

[0043] In the embodiment described above, when the redox voltage (3.4-4.3V vs Na + / Na), the oxidation of the promoter (A) begins to appear on the positive electrode, forming free radical cations (A *+ ), see formula (1) and schematic Figure 1 ; Radical cations can react with sodium supplements, see schematic Figure 2, so that the sodium supplement decomposes oxidatively to release sodium ions and decomposition products (PS *- ), and restored to the initial state A, see formula (2) and see schematic diagram Figure 3 ; Then, the next redox cycle is carried out to complete the reversible reaction.

[0044] A→A *+ + e - ; (1),

[0045] A *+ +PS→A+ Na + + PS *- ; (2).

[0046] In a specific embodiment of the present invention, the accelerator includes at least one of phenothiazine and its derivatives, triphenylamine and its derivatives, bisphenol A and its derivatives, and dimethoxybenzene and its derivatives.

[0047] The promoters described above can exist stably in the electrolyte in an unused state. When the battery starts to charge and discharge, these promoters undergo redox reactions, thereby promoting the decomposition of the sodium supplement.

[0048] In a specific embodiment of the present invention, the sodium supplement includes at least one of Na2O, Na2O2, NaNO2, Na2CO3, Na2C4O4, Na2C2O4, Na2C3O5, Na2C6O6, Na2C6H2O6, CH3COONa, Na2NiO2, and NaCrO2.

[0049] The sodium supplement as described above can add more active sodium ions to the negative electrode, help maintain the structural integrity of the electrode material, reduce the volume change and structural damage caused by the insertion and extraction of sodium ions, and thus further ensure the cycle stability of the battery.

[0050] In order to ensure the surface density of the positive electrode and / or the separator, the particle size distribution of the sodium supplement meets the following requirements: 100nm≤Dv99-Dv50≤5000nm, where Dv99-Dv50 can be 100nm, 120nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1200nm, 1500nm, 1800nm, 2000nm, 2500nm, 3000nm, 3500nm, 4000nm, 4500nm, 5000nm. In one embodiment of the present invention, 100 nm ≤ Dv99 - Dv50 ≤ 2000 nm; 300 nm ≤ Dv99 - Dv10 ≤ 3000 nm, wherein Dv99 - Dv10 can be 350 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1200 nm, 1500 nm, 1800 nm, 2000 nm, or 2500 nm. In another embodiment of the present invention, 300 nm ≤ Dv99 - Dv10 ≤ 1500 nm.

[0051] In order to further ensure the surface density of the positive electrode sheet and / or separator, in a specific embodiment of the present invention, the sodium supplement is a spherical or quasi-spherical particle.

[0052] Among them, Dv99 represents the particle size corresponding to the cumulative curve when the volume passing percentage is 99%, Dv50 represents the particle size corresponding to the cumulative curve when the volume passing percentage is 50%, and Dv10 represents the particle size corresponding to the cumulative curve when the volume passing percentage is 10%.

[0053] It is understood that Dv50 can be the average particle size of the sodium supplement, indicating that particles smaller than this value and larger than this value each account for 50% of the sample. Dv10 and Dv99 can be the boundary particle sizes of the sodium supplement, which are closer to the maximum and minimum particle sizes in the popular sense. Meeting the above ranges can further ensure the gradation of large and small particles in the sodium supplement, effectively fill the pores between particles, ensure the areal density of the positive electrode sheet and / or separator, and thus improve the volumetric energy density of the battery.

[0054] In some embodiments, the cumulative distribution curve of the sodium supplement is tested by the following method:

[0055] Malvern Mastersizer 3000 was used for analysis by wet dispersion-laser derivatization. Specifically, 0.20±0.01 g of the sodium supplement sample was weighed into a 100 mL beaker, 3 mL of a surfactant was added dropwise, and deionized water was added to 20.0±0.1 mL. The beaker was sealed with sealing film and placed in an ultrasonic machine (40 kHz / 210 W, output power 70%) for 5 minutes. The laser intensity was 70-90%, and the detector light energy was <100. The test was started when the shading reached 5-15%, and the cumulative distribution curve of the sodium supplement was obtained.

[0056] In a specific embodiment of the present invention, a sodium ion battery includes a positive electrode sheet, which includes a positive electrode collector and a positive electrode active material layer arranged on at least one surface of the positive electrode collector, and a sodium supplement is provided inside and / or on at least a portion of the surface of the positive electrode active material layer.

[0057] The present invention has no particular restrictions on the positive electrode current collector, as long as it is a material with electrical conductivity and high electrochemical stability. In some specific embodiments, the positive electrode current collector can be a metal foil or a composite current collector. Metal foil includes but is not limited to aluminum, nickel, titanium, stainless steel, or aluminum or stainless steel coated with carbon, nickel, etc.; the composite current collector can include a resin layer and a conductive layer disposed on at least one side of the resin layer, wherein the resin layer can be made of polypropylene, polybutylene terephthalate, or polyethylene terephthalate, and the conductive layer can be made of a metal material such as aluminum, nickel, titanium, stainless steel, or aluminum or stainless steel coated with carbon, nickel, etc. In addition, the surface state of the positive electrode current collector can also include rough particles or a network structure, which can further improve the bonding strength of the positive electrode active material. For example, the positive electrode current collector can be applied in various forms such as a film, sheet, foil, mesh, porous body, etc.

[0058] In some specific embodiments, the thickness of the current collector is 1 μm-50 μm. A current collector with a thickness between 1 μm and 50 μm can provide sufficient mechanical strength while maintaining good electrical conductivity.

[0059] Illustratively, the thickness of the current collector is any value selected from the group consisting of 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, and 50 μm, or a range consisting of both values.

[0060] In some embodiments, the positive electrode active material layer includes a positive electrode active material, a binder, and a conductive agent; the positive electrode active material includes sodium nickel iron manganese oxide (Na a Mn b Ni c Fe d M eOne or more of O2 cathode materials (a≥0.67, b + c + d = 1 and e = 0, or b + c + d + e = 1, where M is a doping element such as Cu, Zn, Ti, Ca, etc.), Prussian blue, sodium iron phosphate, sodium pyrophosphate iron, sodium phosphate pyrophosphate iron, sodium iron sulfate; the conductive agent includes one or several of acetylene black, conductive carbon black, carbon nanotubes, graphene; the binder includes one or several of polyvinylidene fluoride, vinylidene fluoride - hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, polyacrylic acid, polyethylene oxide polytetrafluoroethylene, hydrogenated nitrile rubber.

[0061] In some specific embodiments, to ensure the binding effect of the binder, the weight - average molecular weight of the binder is 50000 g / mol - 500000 g / mol. In some specific embodiments, the weight - average molecular weight of the binder is 100000 g / mol - 250000 g / mol.

[0062] The present invention has no special limitation on the negative electrode sheet. In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector.

[0063] Exemplarily, the above - mentioned negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material includes hard carbon (including biomass - based, resin - based, and coal - based and their mixtures), Si单质, Sn单质, SiO x (0 < x < 2), SnO y (0 < y < 2), Si alloy (i.e., an alloy material formed by Si and one or several of Ti, Fe, Co, Ni, Cu), Sn alloy (i.e., an alloy material formed by Sn and one or several of Ti, Fe, Co, Ni, Cu) one or several; the conductive agent includes one or several of carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotubes, metal powder, graphene; the binder includes one or several of carboxymethyl cellulose, styrene - butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyvinyl alcohol, sodium polyacrylate.

[0064] The negative electrode active material layer may further include a dispersant, where the dispersant includes one or several of sodium carboxymethyl cellulose, triethylhexyl phosphate, sodium dodecyl sulfate.

[0065] The material of the negative electrode current collector can be selected from any one or several of copper foil, nickel foam, copper foam, or copper foil, nickel foam, copper foam with carbon - coated surfaces, etc.

[0066] In a specific embodiment of the present invention, the positive electrode active material layer includes a positive electrode active material, and the mass of the sodium supplement is 0.1 wt % to 10 wt % of the mass of the positive electrode active material.

[0067] Among them, the sodium supplement agent mentioned above can produce more active sodium ions to supplement the negative electrode, thereby making up for the difference in coulombic efficiency between the positive and negative electrodes and improving the energy density and cycle life of the battery cell.

[0068] Exemplarily, the mass of the sodium supplement is 0.1wt%, 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt%, 8.0wt%, 8.5wt%, 9.0wt%, 9.5wt%, 10.0wt% or the like of the mass of the positive electrode active material, or a range consisting of any two of the values.

[0069] In a specific embodiment of the present invention, the sodium ion battery includes a separator, and a sodium supplement is provided inside and / or on at least a portion of the surface of the separator.

[0070] The present invention does not particularly limit the material of the separator. Any known porous structure separator with electrochemical and chemical stability can be selected, for example, at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator can be single-layer or multi-layer.

[0071] In a specific embodiment of the present invention, the sodium ion battery includes an electrolyte, the electrolyte includes a promoter, and the mass fraction of the promoter in the electrolyte is 0.05wt%-2wt%.

[0072] The above-mentioned promoter can further promote the decomposition of the sodium supplement agent and reduce the residual sodium supplement agent or promoter, thereby reducing the probability of the undecomposed sodium supplement agent or promoter inducing side reactions inside the battery.

[0073] Illustratively, the mass fraction of the promoter in the electrolyte is any value of 0.05 wt%, 0.07 wt%, 0.1 wt%, 0.12 wt%, 0.15 wt%, 0.17 wt%, 0.2 wt%, etc., or a range consisting of any two of the values.

[0074] It is understood that the electrolyte of the above-mentioned battery also includes an organic solvent and an electrolyte salt. The organic solvent serves as a medium for transporting ions in the electrochemical reaction and can be any organic solvent known in the art for battery electrolytes, such as one or a mixture of cyclic esters such as ethylene carbonate, propylene carbonate, and fluoroethylene carbonate, and linear esters such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The electrolyte sodium salt can be one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bisoxalatoborate, sodium bistrifluoromethanesulfonimide, and sodium bisfluorosulfonimide.

[0075] In one embodiment, the molar concentration of the electrolyte sodium salt in the electrolyte is 0.5 to 2 mol / L.

[0076] In a second aspect, the present invention provides a method for preparing a sodium ion battery according to the first aspect, comprising the following steps:

[0077] The sodium supplement agent, the accelerator and the battery raw materials are mixed to prepare a sodium ion battery.

[0078] In one embodiment, the sodium supplement, the accelerator and the battery raw materials are mixed, specifically comprising the following process:

[0079] preparing an electrolyte containing a accelerator;

[0080] preparing a separator and / or a positive electrode sheet containing a sodium supplement;

[0081] The sodium ion battery of the present invention can be assembled according to conventional methods in the art, such as stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence, assembling the battery cell through a winding process or a stacking process, and then packaging and baking, injecting the electrolyte, and then hot pressing and forming to obtain a sodium ion battery.

[0082] According to one embodiment of the present invention, preparing a membrane containing a sodium supplement comprises the following steps:

[0083] A material comprising a sodium supplement and a binder is applied to at least a portion of the surface of the diaphragm.

[0084] In a specific embodiment, the binder in the material including the sodium supplement and the binder can be selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylate, polyimide, and chlorinated rubber.

[0085] According to one embodiment of the present invention, preparing a positive electrode sheet containing a sodium supplement comprises any one of the following steps ac:

[0086] a. coating a positive electrode slurry containing a sodium supplement and a positive electrode active material on at least one surface of a current collector and drying the slurry to prepare a positive electrode sheet;

[0087] b. Applying a first positive electrode slurry containing a positive electrode active material on at least one surface of a current collector, and then applying a slurry containing a sodium supplementing agent on the side coated with the first positive electrode slurry, and drying to prepare a positive electrode sheet;

[0088] c. The second positive electrode slurry containing a sodium supplement and a positive electrode active material is coated on at least one surface of the current collector, and then the slurry containing a sodium supplement is continuously coated on the side coated with the second positive electrode slurry, and dried to prepare a positive electrode sheet.

[0089] In a third aspect, the present invention provides an electrical device comprising the sodium ion battery of the first aspect, or the sodium ion battery prepared by the preparation method of the second aspect.

[0090] It should be noted that the above-mentioned electrical equipment can be any conventional equipment that requires electricity, such as but not limited to computers, electric cars, air conditioners, refrigerators, washing machines, microwave ovens, printers, fax machines, etc.

[0091] To further understand the present invention, the following will clearly and completely describe the technical solutions of the present invention in conjunction with specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0092] Unless otherwise specified, all reagents involved in the embodiments of the present invention are commercially available products and can be purchased through commercial channels.

[0093] Example 1

[0094] This example provides a sodium ion battery, including a positive electrode, a negative electrode, a separator and an electrolyte. The positive electrode includes sodium ferric pyrophosphate (Na4Fe3(PO4)(P2O7), NFPP) and a sodium supplement sodium oxalate (Na2C2O4). The amount of the sodium supplement added is 1wt% of the mass of the sodium ferric pyrophosphate. The electrolyte includes 0.5wt% of the promoter phenothiazine, and the sodium supplement particles have a Dv99-Dv50 of 800nm.

[0095] The preparation method thereof comprises the following steps:

[0096] Preparation of positive electrode sheet: The binder PVDF was dissolved in N-methylpyrrolidone (NMP), and then the positive electrode active materials sodium ferric pyrophosphate, sodium oxalate, and conductive agent (carbon black SP and carbon nanotubes CNT with a mass ratio of 1:1) were added thereto, and the positive electrode slurry was obtained after thorough mixing. The mass ratio of the binder, the positive electrode active material, and the conductive agent was 3:100:2. The positive electrode slurry was then coated on the front and back sides of a 16 μm thick positive electrode current collector aluminum foil, and then dried at 85 ° C for 24 h, cold pressed, and vacuum dried to obtain a surface density of 25 g / cm 2 The positive electrode;

[0097] Preparation of negative electrode sheet: The negative electrode active material hard carbon, conductive agent SP, binder SBR, and thickener CMC were dissolved in deionized water at a mass ratio of 97:1:1.5:0.5 to prepare a negative electrode slurry, which was then coated on both sides of the negative electrode current collector aluminum foil. The slurry was then dried at 80°C for 20 hours, cold pressed, and vacuum dried to obtain a negative electrode sheet.

[0098] Preparation of electrolyte: Sodium hexafluorophosphate is dissolved in a solution of ethylene carbonate and linear dimethyl carbonate (v 酯碳酸乙烯酯 :v 线状酯碳酸二甲酯 =1:1), adjust the concentration of sodium hexafluorophosphate to 1 mol / L, then add 0.5 wt% phenothiazine and stir evenly;

[0099] Assembling the battery: stack the positive electrode sheet, separator, and negative electrode sheet prepared above in order, so that the separator is placed between the positive and negative electrode sheets to play an isolating role, and then wind them to obtain a bare battery cell; place the bare battery cell in an outer packaging aluminum-plastic film, inject the above-prepared electrolyte into the dried battery cell, and then go through vacuum packaging, standing, formation, shaping, capacity division and other processes to obtain a sodium ion battery.

[0100] Example 2

[0101] This example provides a sodium ion battery, which differs from Example 1 in that the sodium supplement is sodium carbonate (Na2CO3), the amount of the sodium supplement added is 1.5wt% of the mass of sodium ferric pyrophosphate, and the Dv99-Dv50 of the sodium supplement particles is 100nm.

[0102] Example 3

[0103] This example provides a sodium ion battery, which differs from Example 2 in that the sodium supplement particles have a diameter of Dv99-Dv50=5000 nm.

[0104] Example 4

[0105] This example provides a sodium ion battery, which differs from Example 1 in that the amount of sodium supplement added is 0.1%wt of the mass of sodium ferric pyrophosphate.

[0106] Example 5

[0107] This example provides a sodium ion battery, which differs from Example 1 in that the amount of sodium supplement added is 10 wt % of the mass of sodium ferric pyrophosphate.

[0108] Example 6

[0109] This example provides a sodium ion battery, which differs from Example 1 in that the electrolyte includes 0.05 wt% of a promoter phenothiazine.

[0110] Example 7

[0111] This example provides a sodium ion battery, which differs from Example 1 in that the electrolyte includes 2 wt % of a promoter, phenothiazine.

[0112] Example 8

[0113] This example provides a sodium ion battery, which differs from Example 1 in that the accelerator is dimethoxybenzene.

[0114] Example 9

[0115] This example provides a sodium ion battery, which differs from Example 1 in that the accelerator is a derivative of bisphenol A: 2,2-bis-(4-methoxyphenyl)propane (DBMB), and the amount added to the electrolyte is 0.05 wt%.

[0116] Example 10

[0117] This example provides a sodium ion battery, which differs from Example 1 in that the accelerator is triphenylamine (C 18 H 15 N), the addition amount in the electrolyte is 2 wt%.

[0118] Example 11

[0119] This example provides a sodium ion battery, which differs from Example 10 in that: triphenylamine (C 18 H 15 N) is added in an amount of 2.5 wt% in the electrolyte.

[0120] Example 12

[0121] This example provides a sodium ion battery, which differs from Example 1 in that: the positive electrode does not include a sodium supplement, and the surface of the separator is coated with a sodium supplement, sodium oxalate, and the amount of the sodium supplement added is 1 wt% of the mass of sodium ferric pyrophosphate.

[0122] The preparation method thereof refers to Example 1, except that: no sodium supplement is added to the positive electrode sheet, and the sodium supplement is added by diaphragm coating, specifically comprising: mixing the sodium supplement and the binder polyvinylidene fluoride in a mass ratio of 100:1, dissolving them in an NMP solvent, and applying the obtained slurry on the surface of the diaphragm substrate facing the positive electrode sheet by oil-based roller coating gravure roller coating.

[0123] Example 13

[0124] This example provides a sodium ion battery. The difference from Example 1 is that the positive electrode active material is sodium nickel iron manganese oxide (NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, NNFM).

[0125] Example 14

[0126] This example provides a sodium ion battery, which differs from Example 1 in that the sodium supplement is on the surface of the active material layer of the positive electrode sheet, and the amount of the sodium supplement added relative to the sodium ferric pyrophosphate is 10 wt %.

[0127] The preparation method is as follows: Preparation of positive electrode sheet: Dissolve the binder PVDF in N-methylpyrrolidone (NMP), then add the positive electrode active material sodium ferric pyrophosphate and a conductive agent, wherein the conductive agent is composed of conductive carbon black (SP) and carbon nanotubes (CNT) in a mass ratio of 1:1, and mix thoroughly to obtain a positive electrode slurry, wherein the mass ratio of the binder, the positive electrode active material, and the conductive agent is 3:100:2. The positive electrode slurry is then coated on both sides of a 16μm thick positive electrode current collector aluminum foil, and then dried at 85°C for 24h, cold pressed, and vacuum dried to obtain a surface density of 25g / cm 2 a positive electrode sheet; a sodium supplement agent, polyvinylidene fluoride and SP are mixed in a ratio of 90:5:5, dissolved in an NMP solvent to obtain a sodium supplement agent slurry, and then the sodium supplement agent slurry is applied to the surface of the positive electrode sheet, and after drying, a positive electrode sheet containing the sodium supplement agent on the surface is obtained.

[0128] Example 15

[0129] This example provides a sodium ion battery, which differs from Example 14 in that the amount of sodium supplement added to the surface of the positive electrode is 12 wt % relative to the amount of sodium ferric pyrophosphate added.

[0130] Comparative Example 1

[0131] This example provides a sodium ion battery, which differs from Example 1 in that no accelerator is added.

[0132] Comparative Example 2

[0133] This example provides a sodium ion battery, which differs from Example 1 in that no accelerator and sodium supplement are added.

[0134] Test Case

[0135] (1) Calculation of the decomposition rate of sodium ion battery sodium supplement

[0136] A charge and discharge tester was used to test the battery charge and discharge specific capacity. Specifically, the battery was set to a charging state, i.e., the working electrode was desodiumed, the charging current density was 0.1C, and the battery was charged to a cut-off voltage of 3.6V or 3.85V. After that, the battery was charged at a constant voltage until the current reached 0.05C, and then the operation was stopped. The first charge specific capacity was calculated. After the first desodiumization was completed, the battery was set to a discharge state, i.e., the working electrode was embedded with sodium, the discharge current density was 0.2C, and the discharge was terminated when the cut-off voltage reached 2.0V. Among them, the first charge specific capacity (mAh / g) = first charge capacity / (mass of active material + mass of sodium supplement); theoretical first charge specific capacity (mAh / g) = theoretical total sodium release capacity in the material / mass of the material; record the charge specific capacity C1mAh of the sodium ion battery, and calculate the decomposition rate (%) according to the theoretical first charge specific capacity C2mAh of the positive electrode active material, the theoretical first charge specific capacity C3mAh of the sodium supplement, and the amount of sodium supplement added P (P = mass of sodium supplement / mass of positive electrode active material): decomposition rate (%) of sodium supplement (%) = C1 / (C2+C3*P)×100%.

[0137] (2) Rate performance test of sodium ion batteries

[0138] The sodium-ion secondary battery was left at rest for 5 minutes at 25°C, then charged at a constant current of 0.1C to the upper voltage limit. It was then charged at a constant voltage to a current of 0.05C, left at rest for 5 minutes, and then discharged at constant currents of 0.1C and 1C, respectively, to a voltage of 3.0V. Four sodium-ion batteries were tested in each group, and the average value was taken.

[0139] Discharge rate performance of sodium ion battery (%) = discharge capacity of the second cycle of sodium ion battery at 1 C / discharge capacity of the first cycle of sodium ion battery at 0.1 C×100%.

[0140] (3) Low temperature performance test of sodium ion batteries

[0141] The sodium-ion battery was left at rest for 5 minutes at 25°C, then charged at a constant current of 0.1C to the upper voltage limit. It was then charged at a constant voltage to a current of 0.05C and left at rest for 5 minutes. The lithium-ion battery was left at rest for 60 minutes at -20°C, then discharged at a constant current of 1C to a voltage of 3.0V. Four lithium-ion batteries were tested in each group, and the average value was calculated.

[0142] Low temperature performance of lithium-ion battery (%) = discharge capacity of lithium-ion battery at -20°C, 1C / discharge capacity of lithium-ion battery in the first cycle at 0.1C × 100%.

[0143] (4) High temperature cycle test of sodium ion batteries

[0144] The lithium-ion battery was left at rest at 45°C for 60 minutes, then charged at a constant current of 0.5C to the upper cutoff voltage. It was then charged at a constant voltage to a current of 0.05C and left at rest for 5 minutes. It was then discharged at a constant current of 0.5C to a voltage of 3.0V. This cycle was repeated 200 times. Four sodium-ion batteries were tested in each group, and the average value was calculated.

[0145] High-temperature cycle retention rate of sodium ion battery (%) = discharge capacity of sodium ion battery at 0.5C after 200 cycles / discharge capacity of sodium ion battery at 0.5C in the first cycle × 100%.

[0146] The above test results are summarized in Table 1.

[0147] Table 1:

[0148]

[0149] As shown in Table 1, compared with the comparative example, the decomposition rate of the sodium supplement agent in Examples 1-15 is significantly improved due to the introduction of the promoter, which helps to improve the rate capability and high / low temperature cycle performance of the sodium ion battery.

[0150] Furthermore, compared with Example 11, Example 10 can further improve the electrochemical performance of the sodium ion battery because the promoter is controlled at 0.05-2wt%;

[0151] Furthermore, compared with Example 15, Example 14 can further ensure the decomposition rate of the sodium supplement agent to further improve the performance of the sodium ion battery because the sodium supplement agent is controlled at 0.1-10 wt %.

[0152] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sodium ion battery, characterized in that The invention comprises a sodium supplement and a promoter, wherein the promoter is suitable for promoting the decomposition of the sodium supplement to generate sodium ions.

2. The sodium ion battery according to claim 1, characterized in that The accelerator is suitable for performing a redox reaction.

3. The sodium ion battery according to claim 2, characterized in that The promoter is suitable for undergoing an oxidation reaction when the potential relative to sodium is 3.4V to 4.3V and generating free radical cations, and the free radical cations are suitable for decomposing the sodium supplement to generate the sodium ions.

4. The sodium ion battery according to any one of claims 1 to 3, characterized in that The accelerator includes at least one of phenothiazine and its derivatives, triphenylamine and its derivatives, bisphenol A and its derivatives, and dimethoxybenzene and its derivatives.

5. The sodium ion battery according to any one of claims 1 to 4, characterized in that The sodium supplement includes at least one of Na2O, Na2O2, NaNO2, Na2CO3, Na2C4O4, Na2C2O4, Na2C3O5, Na2C6O6, Na2C6H2O6, CH3COONa, Na2NiO2, and NaCrO2.

6. The sodium ion battery according to any one of claims 1 to 5, characterized in that The particle size distribution of the sodium supplement meets the following conditions: 100nm≤Dv99-Dv50≤5000nm.

7. The sodium ion battery according to any one of claims 1 to 6, characterized in that The sodium ion battery includes a positive electrode sheet, which includes a current collector and a positive electrode active material layer arranged on at least one surface of the current collector, and the sodium supplement is provided inside and / or on at least part of the surface of the positive electrode active material layer.

8. The sodium ion battery according to claim 7, characterized in that The positive electrode active material layer includes a positive electrode active material, and the mass of the sodium supplement is 0.1 wt % to 10 wt % of the mass of the positive electrode active material.

9. The sodium ion battery according to any one of claims 1 to 8, characterized in that The sodium ion battery includes a diaphragm, and the sodium supplement is provided inside and / or on at least a portion of the surface of the diaphragm.

10. The sodium ion battery according to any one of claims 1 to 9, characterized in that: The sodium ion battery includes an electrolyte, the electrolyte includes the promoter, and the mass fraction of the promoter in the electrolyte is 0.05wt%-2wt%.

11. A method for preparing a sodium ion battery according to any one of claims 1 to 10, characterized in that: The following steps are involved: The sodium supplement, the accelerator and the battery raw materials are mixed to prepare the sodium ion battery.

12. The preparation method according to claim 11, characterized in that The mixing of the sodium supplement, the accelerator and the battery raw materials specifically includes the following process: preparing an electrolyte containing the accelerator; preparing a diaphragm and / or a positive electrode sheet containing the sodium supplement; The separator, the positive electrode sheet, the negative electrode sheet and the electrolyte are assembled.

13. The preparation method according to claim 12, characterized in that The preparation of the diaphragm containing the sodium supplement comprises the following steps: A material comprising the sodium supplement and a binder is coated on at least a portion of the surface of the diaphragm.

14. The preparation method according to claim 12, characterized in that The preparation of the positive electrode sheet containing the sodium supplement comprises any one of the following steps ac: a. coating a positive electrode slurry containing the sodium supplement and the positive electrode active material on at least one surface of a current collector and drying the slurry to prepare the positive electrode sheet; b. coating a first positive electrode slurry containing a positive electrode active material on at least one surface of a current collector, and then coating a slurry containing the sodium supplement agent on the side coated with the first positive electrode slurry, and drying to prepare the positive electrode sheet; c. The second positive electrode slurry containing the sodium supplement agent and the positive electrode active material is coated on at least one surface of the current collector, and then the slurry containing the sodium supplement agent is continuously coated on the side coated with the second positive electrode slurry, and dried to prepare the positive electrode sheet.

15. An electrical device, characterized in that: The invention relates to a sodium ion battery comprising the sodium ion battery according to any one of claims 1 to 10, or a sodium ion battery prepared by the preparation method according to any one of claims 11 to 14.

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