A non-negative electrode secondary sodium battery and a manufacturing method thereof

Abstract

The application discloses a kind of negative electrode-free secondary sodium batteries and its manufacturing method, negative electrode-free secondary sodium battery includes negative electrode current collector, electrolyte, diaphragm and positive pole, wherein, diaphragm is located between negative electrode current collector and positive pole;Electrolyte is located between negative electrode current collector and positive pole;Positive pole includes positive pole current collector and the positive pole active material coated on the two sides of positive pole current collector;The surface of negative electrode current collector includes microstructure, microstructure is pit or protrusion, microstructure is micrometer or nanometer, by micro-etching treatment to the surface of negative electrode current collector, it is convenient for sodium to deposit at the microstructure of negative electrode current collector surface, and then grow around microstructure, so that sodium deposition is more dense, and more dense sodium deposition can improve the performance such as energy density, cycle stability and safety of battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium battery, more particularly, to a kind of anode-free secondary sodium battery and its manufacturing method. BACKGROUND

[0002] Sodium-ion battery is an electrochemical device that stores and releases energy by moving sodium ions (Na+) between the positive and negative electrodes. Its basic working principle is similar to that of traditional lithium-ion batteries, but sodium ions have a larger ionic radius and lower redox potential, which leads to differences in material selection and electrochemical performance between sodium-ion batteries and lithium-ion batteries. During charging, sodium ions are extracted from the positive electrode material, migrate to the negative electrode through the electrolyte, and are embedded in the negative electrode material. At the same time, to maintain charge balance, electrons flow from the positive electrode to the negative electrode through the external circuit. The discharge process is the opposite, sodium ions are extracted from the negative electrode, return to the positive electrode through the electrolyte, and electrons flow from the negative electrode to the positive electrode through the external circuit to provide power to external devices.

[0003] Anode-free sodium-ion secondary battery has the following advantages compared to ordinary sodium battery:

[0004] 1. No use of high-chemical-activity metal sodium negative electrode, lower production environment requirements, and lower risk of safety production accidents;

[0005] 2. No voltage before first charging, long-term storage without self-discharge, and high safety index;

[0006] 3. No use of negative electrode active material, extremely high volume energy density and mass energy density.

[0007] With anode-free design, it is expected to improve the energy density of the battery, suitable for long-lasting and lightweight application scenarios. SUMMARY

[0008] Therefore, the present application provides an anode-free secondary sodium battery and its manufacturing method to improve the energy density, cycle stability and safety of the battery.

[0009] In one aspect, the present application provides an anode-free secondary sodium battery, comprising a negative electrode current collector, an electrolyte, a separator and a positive electrode, wherein,

[0010] The separator is located between the negative electrode current collector and the positive electrode;

[0011] The electrolyte is located between the negative electrode current collector and the positive electrode;

[0012] The positive electrode comprises a positive electrode current collector and a positive electrode active material coated on both sides of the positive electrode current collector;

[0013] The surface of the negative current collector comprises microstructures, which are pits or protrusions, and the microstructures are micrometer or nanometer.

[0014] The present application can facilitate the deposition of sodium on the microstructures of the surface of the negative current collector and the growth around the microstructures, so that the sodium deposition is more compact, and the more compact sodium deposition can improve the energy density, cycle stability, safety and other performances of the battery.

[0015] Optionally, the surface of the negative current collector is plated with a protective layer, and the protective layer comprises at least one of nickel, tin, antimony, bismuth, zinc, barium, cadmium, chromium, strontium.

[0016] By plating tin on the surface of the copper foil, the nucleation barrier of sodium is reduced. The nucleation barrier is the energy required for atomic crystallization, and the presence of attachment sites can reduce the energy required for crystallization. The protective layer formed on the surface of the negative current collector is relatively rough, which can more easily induce sodium to find deposition sites on the protective layer, and the increase in the number of sodium attachment sites is beneficial to the nucleation of atomic crystallization. Of course, during the deposition process, sodium and elements such as nickel, tin, antimony, bismuth, zinc, barium, cadmium, chromium, and strontium will form an alloy, and the formation of the alloy further reduces the nucleation barrier of sodium, making the deposition of sodium more uniform and stable.

[0017] Optionally, the negative current collector comprises one of a copper foil, a carbon-coated aluminum foil, or a carbon-coated copper foil.

[0018] The present application directly uses the negative current collector as the negative electrode sheet, and the sodium metal is deposited and stripped in situ on the negative current collector by discharging of the positive electrode, thereby forming a negative electrode-free secondary sodium battery. The negative electrode material in the traditional battery is removed, thereby saving the cost of the negative electrode material. The negative current collector as the negative electrode sheet is dissolved in the electrolyte and forms sodium ions, thereby realizing efficient material utilization and avoiding the loss and waste of the traditional negative electrode material during the charging and discharging process. Of course, due to the negative electrode-free design, the battery can accommodate more sodium ions, thereby improving the energy density of the battery.

[0019] The copper foil has excellent electrical conductivity, which can ensure efficient transmission of current in the negative current collector, thereby improving the power output of the battery. In addition, due to the good ductility and flexibility of the copper foil, it can adapt to the volume change that may occur during the charging and discharging process of the battery, thereby preventing the fracture or deformation of the current collector. Of course, the reactivity of the copper foil with sodium ions is low, which can maintain stability in the battery and avoid adverse reactions with the electrolyte.

[0020] The carbon-coated aluminum foil can further improve the conductivity of the current collector and reduce the internal resistance of the battery by coating a layer of carbon material on the surface of the aluminum foil. The carbon coating can enhance the adhesion between the negative active material and the current collector, prevent the active material from falling off during charging and discharging, and improve the cycle stability and service life of the battery. The carbon coating can also protect the aluminum foil from corrosion or oxidation by the electrolyte, prolonging the service life of the current collector.

[0021] The carbon-coated copper foil improves the adsorption capacity of the negative current collector surface, making it easier for the metal sodium to be uniformly deposited on the surface of the negative current collector.

[0022] Optionally, the positive current collector includes one of an aluminum foil, a high-tension aluminum foil, or a carbon-coated aluminum foil.

[0023] The aluminum foil, as a product of metallic aluminum, has good electrical conductivity, which can effectively reduce the internal resistance of the battery and improve the power output of the battery. The aluminum foil is relatively thin, which can reduce the mass of the battery and improve the energy density of the battery. At the same time, the aluminum foil has good plasticity, which facilitates the assembly and production of the battery.

[0024] The high-tension aluminum foil may be treated to enhance the surface tension, making it easier for the electrolyte to form a uniform film on its surface, thereby improving the performance of the battery. Due to the enhancement of the surface tension, the high-tension aluminum foil may be more easily coated with active material or other coating materials, thereby improving the manufacturing efficiency and performance of the battery.

[0025] The carbon-coated aluminum foil adds a layer of carbon coating on the surface of the aluminum foil. This layer of carbon material (such as carbon black, graphite sheet, graphene, etc.) can serve as a bridge for electron transmission, improving the conductivity of the positive electrode sheet and reducing the internal resistance of the battery. In addition, the carbon coating layer makes the aluminum foil surface form a uniform concave-convex, increasing the contact area between the active material in the electrolyte and the positive current collector, thereby faster transmission of electrons and collection of current during high-current fast charging and discharging. In addition, the carbon-coated aluminum foil can also reduce the interfacial impedance and polarization phenomenon of the current collector, improving the cycle life and rate performance of the battery. The carbon coating layer can prevent the current collector from being corroded and oxidized, further prolonging the service life of the battery.

[0026] Optionally, the positive active material includes 92-96% of a positive main material, 1-6% of a conductive agent, 1-5% of a binder, and 0.1-1% of a dispersant, wherein the positive main material includes one of sodium iron pyrophosphate and sodium nickel manganese acid.

[0027] The positive electrode preferably uses sodium pyrophosphate iron, because the polyanion system has a more stable discharge voltage, lower exothermic reaction, good electrochemical reversibility, smaller volume change during charging and discharging, stronger structural stability and excellent thermal stability, which helps to improve the safety performance of the battery. Make them safer in high temperature or extreme conditions. Sodium pyrophosphate iron has high electrical conductivity, which helps to improve the discharge performance of the battery, so that the battery can release the stored energy faster.

[0028] Sodium nickel-iron-manganese acid has a higher specific capacity, which means it can store more energy per unit mass or unit volume, thereby increasing the energy density of the battery.

[0029] The addition of conductive agent can improve the conductivity of the positive electrode active material, making the transmission of electrons in the positive electrode material more smooth, which helps to improve the power output and charging and discharging efficiency of the battery.

[0030] The role of the binder is to bond the particles of the positive electrode main material, conductive agent, etc. together to form a stable positive electrode structure, which helps to prevent the shedding and pulverization of the positive electrode material during charging and discharging, and improves the stability and cycle life of the battery.

[0031] The addition of dispersant can improve the dispersibility of the positive electrode material, so that the positive electrode active material is more uniformly distributed in the electrolyte, which helps to improve the charging and discharging efficiency and energy density of the battery.

[0032] The positive electrode active material formula of the present application combines the advantages of multiple materials, making the battery have significant advantages in performance, safety, cost and application prospect, etc.

[0033] Optionally, the separator includes at least one of a polypropylene (PP) film, a polyethylene (PE) film, a non-woven fabric separator, a glass fiber separator, a ceramic separator, a filter membrane, and a solid electrolyte separator.

[0034] The separator in the present application can effectively isolate the electrolyte between the positive and negative electrodes to prevent short circuiting of the battery, while allowing sodium ions to freely shuttle during charging and discharging.

[0035] Polypropylene (PP) film and polyethylene (PE) film have good chemical stability and can resist the corrosion of most acids, bases, organic solvents and hot water, ensuring stable operation of the battery in various environments. Non-woven fabric separator has high porosity, which is beneficial to the rapid transmission of sodium ions and improves the charging and discharging efficiency of the battery. Glass fiber separator can maintain stable performance at high temperature and is not easy to soften and deform, ensuring safe operation of the battery under high temperature conditions. The glass fiber separator has high ion conductivity and can quickly transfer ions, improving the charging and discharging efficiency of the battery.

[0036] Optionally, the electrolyte comprises a solvent and a sodium salt, wherein,

[0037] The solvent is an ether solvent, including at least one of tetrahydrofuran, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and triethylene glycol dimethyl ether.

[0038] The sodium salt includes at least one of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium triflate, sodium bis(trifluoromethylsulfonyl)imide, sodium iodide, sodium bromide, sodium thiocyanate, sodium chlorate, sodium carbonate, sodium oxalate, sodium ketomalonate, sodium diketosuccinate and sodium triketopentanedioate, 2-cyclopropene-1-ketone-2,3-dihydroxy sodium, 3-cyclobutene-1,2-dione-3,4-dihydroxy sodium, 4-cyclopentene-1,2,3-trione-4,5-dihydroxy sodium, 5-cyclohexene-1,2,3,4-tetraone-5,6-dihydroxy sodium.

[0039] Compared with the conventional ester electrolyte, the ether solvent can form a thinner and more stable solid electrolyte interface on the electrode surface, which helps to reduce the first circle irreversible capacity and the decomposition of the electrolyte in subsequent cycles.

[0040] Preferably, the concentration of the sodium salt is 0.5 mol / L to 2.0 mol / L, for example, the concentration of the sodium salt is 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, or any value between 0.5 mol / L and 2.0 mol / L. Among the electrolytes with the same concentration, the sodium salt electrolyte has higher ionic conductivity than the lithium salt electrolyte. Within the concentration range of 0.5 mol / L to 2.0 mol / L of the sodium salt, the electrolyte can more effectively conduct sodium ions, thereby improving the rate performance and power output capability of the battery.

[0041] Preferably, 90% of sodium hexafluorophosphate and 10% of sodium tetrafluoroborate are selected. Here, 10% of the borate helps to form a film on the negative electrode and improve the stability of the battery.

[0042] Optionally, the electrolyte further comprises a functional additive, and the functional additive includes at least one of fluoroethylene carbonate, ethylene carbonate, propylene carbonate, ethyl acetate, gamma-butyrolactone, dimethyl carbonate, diethyl carbonate, methyl acetate, propyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone, phenylacetone, maleic anhydride, citraconic anhydride, succinic anhydride, pyromellitic dianhydride, styrene anhydride, glutaric anhydride, succinic anhydride, azelaic anhydride, N,N-dimethyl trifluoroacetamide, N,N-dimethyl acrylamide, sulfate, sulfite, potassium nitrate, acid triethyl, sodium difluoro oxalate borate, phosphorus oxide, phosphorus sulfide.

[0043] The application adds a functional additive in the electrolyte, which can improve the electrochemical stability of the electrolyte, improve the interface characteristics between the electrolyte and the electrode, and reduce the interface resistance.

[0044] In another aspect, the application also provides a method for manufacturing the above-mentioned negative electrode-free secondary sodium battery, comprising the steps of:

[0045] The step of assembling the sodium battery cell includes:

[0046] A negative electrode current collector, an electrolyte, a separator, and a positive electrode are provided, wherein the positive electrode includes a positive electrode current collector and a positive electrode active material coated on both sides of the positive electrode current collector;

[0047] The separator is placed between the negative electrode current collector and the positive electrode, and the structure formed by the negative electrode current collector, the separator, and the positive electrode is placed in a cell housing, and the electrolyte is injected to be located between the negative electrode current collector and the positive electrode and around the structure;

[0048] The step of forming a microstructure includes:

[0049] An external circuit is provided, and the positive and negative electrodes of the sodium battery cell are connected in reverse, the positive electrode of the external circuit is electrically connected to the negative electrode of the sodium battery cell, and the negative electrode of the external circuit is electrically connected to the positive electrode of the sodium battery cell, the sodium battery cell is charged, the surface of the negative electrode current collector is formed with a microstructure, and the sodium battery cell is subjected to secondary packaging after degassing.

[0050] The step of formation and capacity distribution includes:

[0051] The positive and negative electrodes of the sodium battery cell are connected in positive, the positive electrode of the external circuit is electrically connected to the positive electrode of the sodium battery cell, and the negative electrode of the external circuit is electrically connected to the negative electrode of the sodium battery cell, and formation and capacity distribution are performed.

[0052] Optionally, in the step of forming a microstructure, charging the sodium battery cell includes charging at 0.01C for 10-60 minutes, or charging from 0V to 1.0V-2.0V.

[0053] And / or, the formation and capacity distribution includes charging at 0.1C constant current and constant voltage to 3.4V for 10 hours, standing for 20 minutes, discharging at 0.2C constant current to 1.5V, standing for 20 minutes, then charging at 0.2C constant current and constant voltage to 3.4V, standing for 20 minutes, discharging at 0.2C constant current to 1.5V, standing for 20 minutes, and then charging at 0.2C constant current and constant voltage to 2.5V.

[0054] Note that "C" represents the capacity of the battery (usually in Ah, or ampere-hours). A 0.1C charge means that the charging current is 0.1 times the capacity of the battery.

[0055] The upper limit of the formation voltage is reduced to 3.4V, decomposition of the ether electrolyte is avoided, since the negative electrode is a foil, aging is not needed to form a stable SEI film interface, the process time of the battery cell is shortened, and the output efficiency is improved.

[0056] Compared with the prior art, the negative electrode-free secondary sodium battery and the manufacturing method thereof provided by the application at least achieve the following beneficial effects:

[0057] The negative electrode-free secondary sodium battery provided by the application comprises a negative electrode current collector, an electrolyte, a separator and a positive electrode, wherein the separator is located between the negative electrode current collector and the positive electrode; the electrolyte is located between the negative electrode current collector and the positive electrode; the positive electrode comprises a positive electrode current collector and a positive electrode active material coated on two sides of the positive electrode current collector; the surface of the negative electrode current collector comprises a microstructure, the microstructure is a pit or a protrusion, and the microstructure is micrometer-level or nanometer-level; the surface of the negative electrode current collector is subjected to micro-etching treatment, so that sodium is deposited at the microstructure on the surface of the negative electrode current collector, and then grows around the microstructure, so that the sodium deposition is more compact. The more compact sodium deposition can improve the energy density, cycle stability and safety performance of the battery.

[0058] Of course, implementing any product of the application does not necessarily need to achieve all the technical effects described above at the same time.

[0059] Other features of the application, and their advantages, will become apparent from the following detailed description of exemplary embodiments of the application with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0060] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and, together with the description, serve to explain the principles of the application.

[0061] Figure 1 is a structural schematic diagram of a negative electrode-free secondary sodium battery provided by the application;

[0062] Figure 2 is a structural schematic diagram of another negative electrode-free secondary sodium battery provided by the application;

[0063] Figure 3 is a structural schematic diagram of another negative electrode-free secondary sodium battery provided by the application;

[0064] Figure 4 is a flowchart of a manufacturing method of a negative electrode-free secondary sodium battery provided by the application;

[0065] Figure 5is a cycle diagram of 0.5C charging and discharging of the sodium battery without negative electrode for 1000 cycles;

[0066] wherein, 1-negative electrode current collector, 10-microstructure, 2-electrolyte, 3-separator, 4-positive electrode, 41-positive electrode current collector, 42-positive electrode active material, 5-protection layer. DETAILED DESCRIPTION

[0067] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of the components and steps, the numerical expressions, and the numerical values set forth in these embodiments are not limiting to the scope of the present application unless otherwise specifically stated.

[0068] The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the scope of the application its application or uses.

[0069] Techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail herein. However, the techniques, methods, and devices should be considered part of the specification.

[0070] In all of the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments can have different values.

[0071] It should be noted that like reference numerals and letters refer to like items in the following drawings, and thus, once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

[0072] Reference Figure 1 and Figure 2 The sodium battery without negative electrode includes a negative electrode current collector 1, an electrolyte 2, a separator 3, and a positive electrode 4, wherein,

[0073] The separator 3 is located between the negative electrode current collector 1 and the positive electrode 4;

[0074] The electrolyte 2 is located between the negative electrode current collector 1 and the positive electrode 4;

[0075] The positive electrode 4 includes a positive electrode current collector 41 and a positive electrode active material coated on both sides of the positive electrode current collector 41;

[0076] The surface of the negative electrode current collector 1 includes a microstructure 10, which is a pit or a protrusion, and the microstructure 10 is micrometer or nanometer level.

[0077] Figure 1 The microstructure 10 is a protrusion is schematically illustrated as an example, Figure 2The microstructure 10 is taken as a concave pit as an example for illustration. Optionally, the difficulty of manufacturing the microstructure 10 in nanoscale is greater than that of manufacturing the microstructure 10 in micrometer scale.

[0078] The present application can facilitate the deposition of sodium at the microstructure 10 on the surface of the negative current collector 1 by micro-etching treatment on the surface of the negative current collector 1, and the sodium can grow around the microstructure 10, so that the sodium deposition is more compact. The more compact sodium deposition can improve the energy density, cycle stability, safety and other performances of the battery.

[0079] Referring to Figure 3 The negative electrode-free secondary sodium battery includes a negative current collector 1, an electrolyte 2, a separator 3 and a positive electrode 4, wherein,

[0080] The separator 3 is located between the negative current collector 1 and the positive electrode 4.

[0081] The electrolyte 2 is located between the negative current collector 1 and the positive electrode 4.

[0082] The positive electrode 4 includes a positive current collector 41 and a positive active material coated on both sides of the positive current collector 41.

[0083] The surface of the negative current collector 1 includes a microstructure 10, the microstructure 10 is a concave pit or a convex, the microstructure 10 is in micrometer scale or nanometer scale, the surface of the negative current collector 1 is plated with a protective layer 5, and the protective layer 5 includes at least one of nickel, tin, antimony, bismuth, zinc, barium, cadmium, chromium and strontium.

[0084] Figure 3 The negative electrode-free secondary sodium battery in the present application can reduce the sodium nucleation barrier by plating the protective layer 5 on the surface of the negative current collector 1.

[0085] Referring to Figure 4 , Figure 4 The manufacturing method of the negative electrode-free secondary sodium battery in the present application includes the following steps:

[0086] S101, the step of assembling the sodium battery cell, including:

[0087] The negative current collector, the electrolyte, the separator and the positive electrode are provided, and the positive electrode includes a positive current collector and a positive active material coated on both sides of the positive current collector;

[0088] The separator is placed between the negative current collector and the positive electrode, and the structure formed by the negative current collector, the separator and the positive electrode is placed in the cell shell, and the electrolyte is injected to be located between the negative current collector and the positive electrode and around the structure;

[0089] S102, the step of forming a microstructure, including:

[0090] An external circuit is provided, and the positive and negative electrodes of the sodium battery cell are connected in reverse connection, the positive electrode of the external circuit is electrically connected to the negative electrode of the sodium battery cell, and the negative electrode of the external circuit is electrically connected to the positive electrode of the sodium battery cell, so as to charge the sodium battery cell, form a microstructure on the surface of the negative electrode current collector, and perform secondary packaging by degassing.

[0091] S103, a formation and dispensing step, comprising:

[0092] The positive and negative electrodes of the external circuit are connected in positive connection, the positive electrode of the external circuit is electrically connected to the positive electrode of the sodium battery cell, and the negative electrode of the external circuit is electrically connected to the negative electrode of the sodium battery cell, and formation and dispensing are performed.

[0093] The following is a specific embodiment:

[0094] Embodiment 1:

[0095] The embodiment provides a negative electrode-free secondary sodium battery, which comprises a negative electrode current collector, an electrolyte, a separator, a positive electrode material and a positive electrode current collector, the positive electrode active material is coated on both surfaces of the positive electrode current collector, the positive electrode current collector and the negative electrode current collector are separated by the separator, the surface of the negative electrode current collector comprises a microstructure, the microstructure is a protrusion, and the microstructure is micron-level.

[0096] The positive electrode current collector is selected from a carbon-coated aluminum foil; the positive electrode active material comprises 92% of a positive electrode main material, 6% of a conductive agent, 1% of a binder and 1% of a dispersing agent.

[0097] The positive electrode main material is selected from sodium iron pyrophosphate. The separator is selected from a polyethylene ceramic separator.

[0098] The electrolyte comprises an ether solvent, a sodium salt and a functional additive, wherein the ether solvent is selected from diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether; the sodium salt has a concentration of 0.5 mol / L and comprises 90% of sodium hexafluorophosphate and 10% of sodium tetrafluoroborate; and the functional additive has a concentration of 0.01 mol / L and is selected from N,N-dimethyl trifluoroacetamide.

[0099] The negative electrode current collector is selected from a carbon-coated copper foil.

[0100] The method for manufacturing the negative electrode-free secondary sodium battery comprises the following steps:

[0101] The negative electrode current collector, the electrolyte, the separator and the positive electrode are provided, and the positive electrode comprises a positive electrode current collector and positive electrode active material coated on both surfaces of the positive electrode current collector;

[0102] The separator is arranged between the negative electrode current collector and the positive electrode, and the structure formed by the negative electrode current collector, the separator and the positive electrode is arranged in a cell shell, and the electrolyte is injected to be located between the negative electrode current collector and the positive electrode and around the structure;

[0103] The step of forming the microstructure comprises:

[0104] The external circuit is connected to the positive and negative electrodes of the sodium battery cell in a positive connection mode, the positive electrode of the external circuit is electrically connected to the negative electrode of the sodium battery cell, and the negative electrode of the external circuit is electrically connected to the positive electrode of the sodium battery cell.

[0105] The formation and capacity distribution process comprises the following steps: the external circuit is connected to the positive and negative electrodes of the sodium battery cell in a positive connection mode, the positive electrode of the external circuit is electrically connected to the positive electrode of the sodium battery cell, and the negative electrode of the external circuit is electrically connected to the negative electrode of the sodium battery cell.

[0106] Example 2

[0107] The negative electrode-free secondary sodium battery comprises a negative electrode current collector, an electrolyte, a separator, a positive electrode material, and a positive electrode current collector.

[0108] The positive electrode current collector is a carbon-coated aluminum foil.

[0109] The electrolyte comprises an ether solvent, a sodium salt, and a functional additive.

[0110] The negative electrode current collector is a carbon-coated copper foil.

[0111] The method for manufacturing the negative electrode-free secondary sodium battery comprises the following steps:

[0112] The positive electrode comprises a positive electrode current collector and positive electrode active material coated on both sides of the positive electrode current collector.

[0113] The separator is arranged between the negative current collector and the positive electrode, and the structure formed by the negative current collector, the separator and the positive electrode is arranged in the battery case, and the electrolyte is injected to be located between the negative current collector and the positive electrode and around the structure.

[0114] The step of forming the microstructure comprises:

[0115] An external circuit is provided, and the positive and negative electrodes of the sodium battery cell are reversely connected. The positive electrode of the external circuit is electrically connected to the negative electrode of the sodium battery cell, and the negative electrode of the external circuit is electrically connected to the positive electrode of the sodium battery cell. The sodium battery cell is charged from 0 V to 1.0 V, so that the surface of the negative current collector forms a microstructure. The sodium battery cell is subjected to secondary packaging by degassing.

[0116] The formation and capacity process is as follows: 0.1 C constant current and constant voltage charging to 3.4 V for 10 h, 0.2 C constant current discharging to 1.5 V after standing for 20 min, then 0.2 C constant current and constant voltage charging to 3.4 V, standing for 20 min, 0.2 C constant current discharging to 1.5 V, standing for 20 min, and then 0.2 C constant current and constant voltage charging to 2.5 V.

[0117] Example 3

[0118] The embodiment provides a negative electrode-free secondary sodium battery, which comprises a negative current collector, an electrolyte, a separator, a positive electrode material and a positive current collector. The positive electrode active material is coated on both surfaces of the positive current collector. The positive current collector and the negative current collector are separated by the separator. The surface of the negative current collector comprises a microstructure. The microstructure is a protrusion, and the microstructure is micron-level.

[0119] The positive current collector is selected from a carbon-coated aluminum foil. The positive electrode active material comprises 93% of a positive electrode main material, 1.5% of a conductive agent, 5% of a binder and 0.5% of a dispersant. The positive electrode main material is selected from sodium iron pyrophosphate. The separator is selected from a polyethylene ceramic separator.

[0120] The electrolyte comprises an ether solvent, a sodium salt and a functional additive. The ether solvent is selected from diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether. The sodium salt has a concentration of 1 mol / L and comprises 90% of sodium hexafluorophosphate and 10% of sodium tetrafluoroborate. The functional additive has a concentration of 0.1 mol / L. The functional additive is selected from N,N-dimethyl trifluoroacetamide (which improves the electrochemical stability of the electrolyte, improves the interface properties between the electrolyte and the electrode, and reduces the interface resistance).

[0121] The negative current collector is selected from a carbon-coated copper foil.

[0122] The method for manufacturing the negative electrode-free secondary sodium battery comprises the following steps:

[0123] A negative electrode current collector, an electrolyte, a separator, and a positive electrode are provided, the positive electrode including a positive electrode current collector and a positive electrode active material coated on both sides of the positive electrode current collector;

[0124] The separator is placed between the negative electrode current collector and the positive electrode, and the structure formed by the negative electrode current collector, the separator, and the positive electrode is placed in a battery case, electrolyte is injected, and the electrolyte is located between the negative electrode current collector and the positive electrode and around the structure;

[0125] The step of forming the microstructure includes:

[0126] An external circuit is provided, and the positive and negative electrodes of the sodium battery cell are reversely connected. The positive electrode of the external circuit is electrically connected to the negative electrode of the sodium battery cell, and the negative electrode of the external circuit is electrically connected to the positive electrode of the sodium battery cell. The sodium battery cell is charged at 0.01C for 60 min, so that a microstructure is formed on the surface of the negative electrode current collector. The sodium battery cell is subjected to secondary packaging by degassing.

[0127] The formation and capacity process is as follows: 0.1C constant current and constant voltage charging to 3.4V for 10h, standing for 20min, then 0.2C constant current discharging to 1.5V, standing for 20min, then 0.2C constant current and constant voltage charging to 3.4V, standing for 20min, then 0.2C constant current discharging to 1.5V, standing for 20min, and then 0.2C constant current and constant voltage charging to 2.5V.

[0128] Example 4

[0129] The embodiment provides a negative electrode-free secondary sodium battery, which comprises a negative electrode current collector, an electrolyte, a separator, a positive electrode material, and a positive electrode current collector. The positive electrode active material is coated on both sides of the positive electrode current collector. The positive electrode current collector and the negative electrode current collector are separated by the separator. The surface of the negative electrode current collector comprises a microstructure. The microstructure is a pit, and the microstructure is nanoscale. The surface of the negative electrode current collector is plated with tin.

[0130] The positive electrode current collector is selected from a carbon-coated aluminum foil. The positive electrode active material comprises 94.7% of a positive electrode main material, 2% of a conductive agent, 3% of a binder, and 0.3% of a dispersing agent. The positive electrode main material is selected from sodium iron pyrophosphate. The separator is selected from a polyethylene ceramic separator.

[0131] The electrolyte comprises an ether solvent, a sodium salt, and a functional additive. The ether solvent is selected from diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether. The sodium salt has a concentration of 1mol / L and comprises 90% of sodium hexafluorophosphate and 10% of sodium tetrafluoroborate. The functional additive has a concentration of 0.04mol / L and is selected from N,N-dimethyl trifluoroacetamide (which improves the electrochemical stability of the electrolyte, improves the interface properties between the electrolyte and the electrode, and reduces the interface resistance).

[0132] The negative electrode current collector is selected from a carbon-coated copper foil.

[0133] The manufacturing method of the negative electrode-free secondary sodium battery comprises the following steps:

[0134] A negative electrode current collector, an electrolyte, a separator and a positive electrode are provided, the positive electrode comprises a positive electrode current collector and a positive electrode active material coated on both sides of the positive electrode current collector, and the surface of the negative electrode current collector is plated with tin;

[0135] The separator is arranged between the negative electrode current collector and the positive electrode, and the structure formed by the negative electrode current collector, the separator and the positive electrode is arranged in a battery case, and the electrolyte is injected to be located between the negative electrode current collector and the positive electrode and around the structure;

[0136] The step of forming the microstructure comprises:

[0137] An external circuit is provided, the positive and negative electrodes of the sodium battery cell are reversely connected, the positive electrode of the external circuit is electrically connected to the negative electrode of the sodium battery cell, the negative electrode of the external circuit is electrically connected to the positive electrode of the sodium battery cell, the sodium battery cell is charged from 0 V to 2.0 V, so that the surface of the negative electrode current collector forms a microstructure, and the sodium battery cell is subjected to secondary packaging after degassing.

[0138] The formation and capacity process is as follows: 0.1 C constant current and constant voltage charging to 3.4 V for 10 h, 0.2 C constant current discharging to 1.5 V after standing for 20 min, then 0.2 C constant current and constant voltage charging to 3.4 V, standing for 20 min, 0.2 C constant current discharging to 1.5 V, standing for 20 min, and then 0.2 C constant current and constant voltage charging to 2.5 V.

[0139] Example 5:

[0140] The negative electrode-free secondary sodium battery comprises a negative electrode current collector, an electrolyte, a separator, a positive electrode material and a positive electrode current collector, the positive electrode active material is coated on both sides of the positive electrode current collector, the positive electrode current collector and the negative electrode current collector are separated by the separator, the surface of the negative electrode current collector comprises a microstructure, the microstructure is a protrusion, the microstructure is micron-level, and the surface of the negative electrode current collector is plated with tin.

[0141] The positive electrode current collector is selected from high-durability aluminum foil; the positive electrode active material comprises 94.7% of a positive electrode main material, 2% of a conductive agent, 3% of a binder and 0.3% of a dispersing agent. The positive electrode main material is selected from sodium nickel-iron-manganese acid. The separator is selected from a polyethylene ceramic separator.

[0142] The electrolyte includes an ether solvent, a sodium salt, and a functional additive. The ether solvent is selected from diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether; the sodium salt has a concentration of 1 mol / L and includes 90% sodium hexafluorophosphate and 10% sodium tetrafluoroborate; and the functional additive has a concentration of 0.1 mol / L. The functional additive is selected from N,N-dimethyl trifluoroacetamide (to improve the electrochemical stability of the electrolyte, improve the interface properties between the electrolyte and the electrode, and reduce the interface resistance).

[0143] The negative current collector is a carbon-coated copper foil.

[0144] The method for manufacturing the negative electrode-free secondary sodium battery includes:

[0145] The negative electrode current collector, the electrolyte, the separator, and the positive electrode are provided, the positive electrode includes a positive electrode current collector and a positive electrode active material coated on both sides of the positive electrode current collector, and the surface of the negative electrode current collector is plated with tin;

[0146] The separator is arranged between the negative electrode current collector and the positive electrode, and the structure formed by the negative electrode current collector, the separator, and the positive electrode is arranged in the battery cell shell, the electrolyte is injected, and the electrolyte is located between the negative electrode current collector and the positive electrode and around the structure;

[0147] The step of forming the microstructure includes:

[0148] The external circuit is provided, the positive and negative electrodes of the sodium battery cell are reversely connected, the positive electrode of the external circuit is electrically connected to the negative electrode of the sodium battery cell, the negative electrode of the external circuit is electrically connected to the positive electrode of the sodium battery cell, the sodium battery cell is charged at 0.01C for 35 min, the surface of the negative electrode current collector is formed with a microstructure, and the sodium battery cell is subjected to vacuum packaging.

[0149] The formation and capacity measurement process includes: charging at 0.1C constant current and constant voltage to 3.4V for 10h, standing for 20min, discharging at 0.2C constant current to 1.5V, standing for 20min, then charging at 0.2C constant current and constant voltage to 3.4V, standing for 20min, discharging at 0.2C constant current to 1.5V, standing for 20min, and then charging at 0.2C constant current and constant voltage to 2.5V.

[0150] Example 6

[0151] The negative electrode-free secondary sodium battery includes a negative electrode current collector, an electrolyte, a separator, a positive electrode material, and a positive electrode current collector, the positive electrode active material is coated on both sides of the positive electrode current collector, the positive electrode current collector and the negative electrode current collector are separated by the separator, the surface of the negative electrode current collector includes a microstructure, the microstructure is a pit, and the microstructure is nanoscale.

[0152] The positive electrode current collector is selected from a carbon-coated aluminum foil; the positive electrode active material includes 94.7% of a positive electrode main material, 2% of a conductive agent, 3% of a binder, and 0.3% of a dispersing agent. The positive electrode main material is selected from sodium iron pyrophosphate. The separator is selected from a polyethylene ceramic separator.

[0153] The electrolyte includes an ether solvent, a sodium salt, and a functional additive. The ether solvent is selected from diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether; the sodium salt has a concentration of 1 mol / L and includes 90% of sodium hexafluorophosphate and 10% of sodium tetrafluoroborate; and the functional additive has a concentration of 0.1 mol / L and is selected from N,N-dimethyl trifluoroacetamide (to improve the electrochemical stability of the electrolyte, improve the interface properties between the electrolyte and the electrode, and reduce the interface resistance).

[0154] The negative electrode current collector is selected from a carbon-coated aluminum foil.

[0155] The method for manufacturing the negative electrode-free secondary sodium battery includes:

[0156] The negative electrode current collector, the electrolyte, the separator, and the positive electrode are provided, and the positive electrode includes a positive electrode current collector and a positive electrode active material coated on both sides of the positive electrode current collector.

[0157] The separator is arranged between the negative electrode current collector and the positive electrode, and the structure formed by the negative electrode current collector, the separator, and the positive electrode is arranged in the battery cell shell. The electrolyte is injected to be located between the negative electrode current collector and the positive electrode and around the structure.

[0158] The step of forming the microstructure includes:

[0159] An external circuit is provided, and the positive and negative electrodes of the sodium battery cell are reversely connected. The positive electrode of the external circuit is electrically connected to the negative electrode of the sodium battery cell, and the negative electrode of the external circuit is electrically connected to the positive electrode of the sodium battery cell. The sodium battery cell is charged from 0 V to 1.5 V, so that a microstructure is formed on the surface of the negative electrode current collector. The sodium battery cell is subjected to vacuum packaging.

[0160] The formation and capacity distribution process includes: charging at 0.1 C constant current and constant voltage to 3.4 V for 10 h, standing for 20 min, discharging at 0.2 C constant current to 1.5 V, standing for 20 min, then charging at 0.2 C constant current and constant voltage to 3.4 V, standing for 20 min, discharging at 0.2 C constant current to 1.5 V, standing for 20 min, and then charging at 0.2 C constant current and constant voltage to 2.5 V.

[0161] Referring to Table 1 below, Table 1 is the detection result of the negative electrode-free secondary sodium battery of Example 1 to Example 6.

[0162] Table 1 is the detection result of the negative electrode-free secondary sodium battery of Example 1 to Example 6.

[0163]

[0164] In summary, the peel strength, adhesion, resistivity and sheet resistance of Example 4 are high, the capacity and initial efficiency are high, and the comprehensive performance is the best.

[0165] Comparative Example 1

[0166] Comparative Document 1 provides a negative electrode-free secondary sodium battery, which comprises a negative electrode current collector, an electrolyte, a separator, a positive electrode material and a positive electrode current collector, the positive electrode active material is coated on both sides of the positive electrode current collector, and the positive electrode current collector and the negative electrode current collector are separated by the separator.

[0167] The positive electrode current collector is selected from high-purity aluminum foil; the positive electrode active material comprises 94.7% of a positive electrode main material, 2% of a conductive agent, 3% of a binder and 0.3% of a dispersing agent. The positive electrode main material is selected from sodium iron pyrophosphate. The separator is selected from a polyethylene ceramic separator.

[0168] The electrolyte solvent is selected from an ester solvent. The ester solvent is selected from dimethyl carbonate. The sodium salt concentration is 1 mol / L, and the composition is 90% sodium hexafluorophosphate and 10% sodium tetrafluoroborate.

[0169] The negative electrode current collector is selected from carbon-coated copper foil.

[0170] The method for manufacturing the negative electrode-free secondary sodium battery comprises:

[0171] providing a negative electrode current collector, an electrolyte, a separator and a positive electrode, the positive electrode comprising a positive electrode current collector and a positive electrode active material coated on both sides of the positive electrode current collector;

[0172] placing the separator between the negative electrode current collector and the positive electrode, and placing the structure formed by the negative electrode current collector, the separator and the positive electrode in the battery case, and injecting the electrolyte to make the electrolyte located between the negative electrode current collector and the positive electrode and around the structure;

[0173] The formation and capacity process is as follows: 0.1C constant current and constant voltage charging to 3.4V for 10h, standing for 20min, then 0.2C constant current discharging to 1.5V, standing for 20min, then 0.2C constant current and constant voltage charging to 3.4V, standing for 20min, then 0.2C constant current discharging to 1.5V, standing for 20min, and then 0.2C constant current and constant voltage charging to 2.5V.

[0174] Comparative Example 2

[0175] Comparative Document 2 provides a negative electrode-free secondary sodium battery, which comprises a negative electrode current collector, an electrolyte, a separator, a positive electrode material and a positive electrode current collector, the positive electrode active material is coated on both sides of the positive electrode current collector, and the positive electrode current collector and the negative electrode current collector are separated by the separator.

[0176] The positive electrode current collector is selected from high-durability aluminum foil; the positive electrode active material comprises 94.7% of a positive electrode main material, 2% of a conductive agent, 3% of a binder and 0.3% of a dispersant. The positive electrode main material is selected from sodium iron pyrophosphate; and the separator is selected from a polyethylene ceramic separator.

[0177] The electrolyte comprises an ether solvent, a sodium salt and a functional additive. The ether solvent is selected from diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether. The sodium salt has a concentration of 1 mol / L and comprises 90% of sodium hexafluorophosphate and 10% of sodium tetrafluoroborate.

[0178] The functional additive has a concentration of 0.1 mol / L. The functional additive is selected from N,N-dimethyl trifluoroacetamide.

[0179] The negative electrode current collector is selected from carbon-coated copper foil.

[0180] The method for manufacturing the negative electrode-free secondary sodium battery comprises the following steps:

[0181] The negative electrode current collector, the electrolyte, the separator and the positive electrode are provided, and the positive electrode comprises a positive electrode current collector and positive electrode active material coated on both sides of the positive electrode current collector;

[0182] The separator is arranged between the negative electrode current collector and the positive electrode, and the structure formed by the negative electrode current collector, the separator and the positive electrode is arranged in the battery cell shell. The electrolyte is injected to be located between the negative electrode current collector and the positive electrode and around the structure.

[0183] The formation and capacity distribution process comprises the following steps:

[0184] 0.1C constant current and constant voltage charging is performed to 3.9V, which takes 10h. After 20min of standing, 0.2C constant current discharging is performed to 1.5V. After 20min of standing, 0.2C constant current and constant voltage charging is performed to 3.6V. After 20min of standing, 0.2C constant current discharging is performed to 1.5V. After 20min of standing, 0.2C constant current and constant voltage charging is performed to 2.5V.

[0185] Comparative Example 3

[0186] Comparative Document 3 provides a negative electrode-free secondary sodium battery, which comprises a negative electrode current collector, an electrolyte, a separator, a positive electrode material and a positive electrode current collector. The positive electrode active material is coated on both sides of the positive electrode current collector. The positive electrode current collector and the negative electrode current collector are separated by the separator.

[0187] The positive electrode current collector is selected from high-durability aluminum foil; the positive electrode active material comprises 94.7% of a positive electrode main material, 2% of a conductive agent, 3% of a binder and 0.3% of a dispersant. The positive electrode main material is selected from sodium iron pyrophosphate. The separator is selected from a polyethylene ceramic separator.

[0188] The electrolyte comprises an ether solvent and a sodium salt. The ether solvent is selected from diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether. The sodium salt has a concentration of 1 mol / L and comprises 90% sodium hexafluorophosphate and 10% sodium tetrafluoroborate.

[0189] The negative current collector is selected from an aluminum foil.

[0190] The method for manufacturing the negative electrode-free secondary sodium battery comprises the following steps:

[0191] The method for manufacturing the negative electrode-free secondary sodium battery comprises the following steps:

[0192] The method for manufacturing the negative electrode-free secondary sodium battery comprises the following steps:

[0193] The formation and capacity-determination process comprises the following steps: charging at a constant current and a constant voltage of 0.1 C to 3.4 V for 10 h, resting for 20 min, discharging at a constant current of 0.2 C to 1.5 V, resting for 20 min, then charging at a constant current and a constant voltage of 0.2 C to 3.4 V, resting for 20 min, discharging at a constant current of 0.2 C to 1.5 V, resting for 20 min, and then charging at a constant current and a constant voltage of 0.2 C to 2.5 V

[0194] Reference is made to Figure 5 , Figure 5 The cycle diagram of the battery for 1000 cycles of charging and discharging at 0.5 C, Figure 5 In the cycle diagram, different colors are used to represent the capacity retention rates of different examples, Figure 5 In the cycle diagram, the horizontal axis represents the cycle number, and the vertical axis represents the capacity retention rate, Figure 5 It can be clearly seen that the cycle performance of Example 4 is the best, and the capacity retention rates of Examples 5 and 6 after 1000 cycles are both greater than 90%, and are basically about 95%, and the long-term performance of the battery is excellent. The capacity retention rates of Comparative Examples 1, 2 and 3 after 1000 cycles all decrease greatly.

[0195] Although some specific embodiments of the present application have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, and are not intended to limit the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A method for manufacturing a negative electrode-free secondary sodium battery, characterized in that, The method comprises the steps of: The step of assembling the sodium battery cell comprises: providing a negative current collector, an electrolyte, a separator and a positive electrode, the positive electrode comprising a positive current collector and a positive active material coated on both sides of the positive current collector; placing the separator between the negative current collector and the positive electrode, and placing the structure formed by the negative current collector, the separator and the positive electrode into a cell shell, and injecting the electrolyte to make the electrolyte located between the negative current collector and the positive electrode and around the structure; The step of forming a microstructure comprises: providing an external circuit, reversely connecting the positive and negative electrodes of the sodium battery cell with the external circuit, electrically connecting the positive electrode of the external circuit with the negative electrode of the sodium battery cell, electrically connecting the negative electrode of the external circuit with the positive electrode of the sodium battery cell, charging the sodium battery cell, so that the surface of the negative current collector forms a microstructure, the microstructure is a pit or a protrusion, the microstructure is micron or nanometer, and the sodium battery cell is vacuumized and secondarily packaged; The step of formation and capacity distribution comprises: positively connecting the positive and negative electrodes of the sodium battery cell with the external circuit, electrically connecting the positive electrode of the external circuit with the positive electrode of the sodium battery cell, and electrically connecting the negative electrode of the external circuit with the negative electrode of the sodium battery cell, and performing formation and capacity distribution.

2. The method of manufacturing according to claim 1, wherein, In the step of forming a microstructure, charging the sodium battery cell comprises charging at 0.01C for 10-60 minutes, or charging from 0V to 1.0V-2.0V; And / or, the formation and capacity distribution comprises constant current and constant voltage charging at 0.1C to 3.4V for 10 hours, discharging at 0.2C to 1.5V after standing for 20 minutes, then constant current and constant voltage charging at 0.2C to 3.4V after standing for 20 minutes, discharging at 0.2C to 1.5V after standing for 20 minutes, and then constant current and constant voltage charging at 0.2C to 2.5V.

3. A non-negative electrode secondary sodium battery, characterized by, The negative electrode-free secondary sodium battery is manufactured by the method of any one of claims 1-2, and comprises a negative current collector, an electrolyte, a separator and a positive electrode, wherein the separator is located between the negative current collector and the positive electrode; the electrolyte is located between the negative current collector and the positive electrode; the positive electrode comprises a positive current collector and a positive active material coated on both sides of the positive current collector; the surface of the negative current collector comprises a microstructure, the microstructure is a pit or a protrusion, and the microstructure is micron or nanometer.

4. The negative electrode-free secondary sodium battery according to claim 3, characterized in that, The surface of the negative current collector is plated with a protective layer, and the protective layer comprises at least one of nickel, tin, antimony, bismuth, zinc, barium, cadmium, chromium and strontium.

5. The negative electrode-free secondary sodium battery according to claim 3, characterized in that, The negative current collector comprises one of copper foil, carbon-coated aluminum foil or carbon-coated copper foil.

6. The negative electrode-free secondary sodium battery according to claim 3, characterized in that, The positive current collector comprises one of aluminum foil, high-durability aluminum foil or carbon-coated aluminum foil.

7. The negative electrode-free secondary sodium battery according to claim 3, characterized in that, The positive active material comprises 92-96% of a positive main material, 1-6% of a conductive agent, 1-5% of a binder and 0.1-1% of a dispersing agent, and the positive main material comprises one of sodium iron pyrophosphate and sodium nickel manganese acid.

8. The negative electrode-free secondary sodium battery according to claim 3, characterized in that, The diaphragm comprises at least one of a polypropylene (PP) film, a polyethylene (PE) film, a non-woven fabric diaphragm, a glass fiber diaphragm, a ceramic diaphragm, a filter membrane, and a solid electrolyte diaphragm. 9.The sodium metal anode-free secondary battery of claim 3, wherein, The electrolyte comprises a solvent and a sodium salt, wherein, The solvent is an ether solvent, comprising at least one of tetrahydrofuran, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and triethylene glycol dimethyl ether; The sodium salt comprises at least one of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium triflate, sodium bis(trifluoromethylsulfonyl)imide, sodium iodide, sodium bromide, sodium thiocyanate, sodium chlorate, sodium carbonate, sodium oxalate, sodium ketomalonate, sodium diketosuccinate, and sodium triketopentanedioate, 2-cyclopropene-1-ketone-2,3-dihydroxy sodium, 3-cyclobutene-1,2-dione-3,4-dihydroxy sodium, 4-cyclopentene-1,2,3-trione-4,5-dihydroxy sodium, and 5-cyclohexene-1,2,3,4-tetrone-5,6-dihydroxy sodium.

10. The no-negative-electrode secondary sodium battery according to claim 3, characterized in that, The electrolyte further comprises a functional additive, wherein, The functional additive comprises at least one of fluoroethylene carbonate, ethylene carbonate, propylene carbonate, ethyl acetate, gamma-butyrolactone, dimethyl carbonate, diethyl carbonate, methyl acetate, propyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone, phenylacetone, maleic anhydride, citraconic anhydride, succinic anhydride, pyromellitic dianhydride, styrene anhydride, glutaric anhydride, succinic anhydride, azelaic anhydride, N,N-dimethyl trifluoroacetamide, N,N-dimethyl acrylamide, sulfate, sulfite, potassium nitrate, acid triethyl ester, sodium difluoro oxalate borate, phosphorus oxide, and phosphorus sulfide.

Images