Negative current collector, preparation method thereof and non-negative sodium ion battery

Abstract

The invention relates to the technical field of sodium ion batteries, in particular to a negative electrode current collector, a preparation method of the negative electrode current collector and a negative-electrode-free sodium ion battery. The negative electrode current collector comprises a current collector substrate and a sodium-philic plating layer arranged on the current collector substrate, and the sodium-philic plating layer comprises three metal elements or non-metal elements with gradient sodium alloying potentials. According to the negative electrode current collector provided by the invention, the current collector substrate is modified by utilizing the sodium-philic coating, so that on one hand, the nucleation overpotential of sodium metal on the negative electrode current collector can be effectively reduced, and on the other hand, the alloying potential gradient of the sodium-philic coating is beneficial to guiding the interface reaction kinetics of sodium deposition / stripping of the sodium metal in the charge-discharge process; the overlarge local current density and the generation of dendritic crystals are avoided, the problems of poor reversibility, easy generation of dendritic crystals, excessive use and the like of the traditional negative current collector of the negative-electrode-free sodium ion battery are solved, and the cycling stability of the negative-electrode-free sodium ion battery is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a negative electrode current collector and a preparation method thereof, and a negative electrode-free sodium ion battery. Background Art

[0002] Metallic sodium has a high theoretical capacity (1166 mAh g -1 ) and low redox potential (-2.71Vvs. standard hydrogen electrode), making the sodium metal anode the first choice for high-energy sodium battery anodes. However, traditional sodium metal anodes have problems with dendrite growth and unstable solid / electrolyte interface during the cycle, resulting in the generation of "dead sodium", which increases the internal resistance of the battery, reduces the coulomb efficiency, and continuously consumes the electrolyte, further leading to battery failure. In addition, traditional sodium metal anodes are usually metal pole pieces larger than 300μm, and there is a situation of excessive use of the anode, in which only part of the sodium metal participates in the electrochemical behavior of deposition / stripping, resulting in a decrease in the battery energy density and safety risks.

[0003] The initial active sodium ions of the negative electrode-free sodium ion battery are stored in the positive electrode material. When the battery is charged, the sodium ions are released from the positive electrode and deposited on the negative electrode. When the battery is discharged, the sodium ions are stripped from the negative electrode in situ and embedded in the positive electrode material. The negative electrode-free sodium ion battery with this feature can maximize the mass and volume energy density of the battery, which is of great significance for the development of sodium ion batteries. However, the negative electrode-free sodium ion battery prepared only by conventional negative electrode current collectors faces the problem of uneven deposition of sodium on the negative electrode side, dendrite growth, etc., which leads to battery performance degradation or even failure.

[0004] Therefore, the difficulty in overcoming the negative electrode-free sodium-ion battery at this stage is how to achieve uniform deposition of sodium ions at the negative electrode and highly reversible release, so as to avoid the appearance of sodium dendrites and the production of "dead sodium". Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a negative electrode current collector and a preparation method thereof and a negative electrode-free sodium ion battery. The negative electrode current collector provided by the present invention uses a sodium-philic coating to modify the current collector substrate. On the one hand, it can effectively reduce the nucleation overpotential of sodium metal on the negative electrode current collector. On the other hand, the alloying potential gradient of the sodium-philic coating helps to guide the interface reaction kinetics of sodium deposition / stripping during the charge and discharge process of sodium metal, avoiding excessive local current density and the generation of dendrites, solving the problems of poor reversibility, easy generation of dendrites and excessive use of traditional negative electrode current collectors of negative electrode-free sodium ion batteries, and effectively improving the cycle stability of negative electrode-free sodium ion batteries.

[0006] In a first aspect, the present invention provides a negative electrode current collector, comprising a current collector substrate and a sodium-philic coating disposed on the current collector substrate, wherein the sodium-philic coating comprises three metal elements or non-metal elements having gradient sodium alloying potentials.

[0007] The negative electrode current collector provided by the present invention is modified by using a sodium-philic coating to modify the current collector substrate. On the one hand, the nucleation overpotential of sodium metal on the negative electrode current collector can be effectively reduced. On the other hand, the alloying potential gradient of the sodium-philic coating helps to guide the interface reaction kinetics of sodium deposition / stripping during the charge and discharge process of sodium metal, thereby avoiding excessive local current density and the generation of dendrites. The problems of poor reversibility and easy generation of dendrites in conventional negative electrode current collectors of negative electrode-free sodium ion batteries are solved, and the cycle stability of negative electrode-free sodium ion batteries is effectively improved. Specifically:

[0008] The negative electrode current collector provided by the present invention utilizes a sodium-philic coating layer to modify the current collector substrate, and the sodium-philic coating layer has a gradient-differentiated sodium alloying potential gradient, which can effectively reduce the nucleation overpotential of sodium metal on the negative electrode current collector on the one hand, and can utilize the potential gradient effect of the alloying process on the other hand to promote the uniform deposition of sodium ions, improve the kinetics of sodium deposition / stripping, reduce the local current density, avoid the formation of dendrites and the generation of dead "sodium", promote the reversible deposition and separation of sodium on the negative electrode side, effectively improve the reversibility and stability of the traditional negative electrode current collector of the negative electrode-free sodium ion battery, realize the stable reversible cycle of the negative electrode-free sodium ion battery, and solve the problems of excessive use of the negative electrode of the sodium metal battery and the potential safety hazards of sodium metal, thereby effectively reducing the cost.

[0009] As a preferred technical solution of the present invention, the three metal elements or non-metal elements having gradient sodium alloying potentials are tin, phosphorus and antimony.

[0010] The sodium-philic coating provided by the present invention includes Sn element (0.2V vs Na / Na + ), P element (0.44V vs Na / Na + ) and Sb element (0.58V vs Na / Na + ), the potential gradients of the alloying reaction between Sn, Sb and P and Na were obtained by theoretical calculation, as shown in the following figure: Figure 2 Sn, Sb and P have gradient sodium alloying potential, which helps to improve the interface reaction kinetics of sodium at the negative electrode, reduce the overpotential of sodium nucleation and deposition at the negative electrode, and help guide the uniform deposition / stripping of sodium metal during the charge and discharge process, avoiding excessive local current density and the formation of dendrites.

[0011] As a preferred technical solution of the present invention, the thickness of the sodium-philic coating is 300-900nm, for example, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, etc.

[0012] As a preferred technical solution of the present invention, taking the total molar amount of the tin element, the phosphorus element and the antimony element as 100%, the molar content of each element is 20-50%, for example, 20%, 30%, 40%, 50%, etc.

[0013] As a preferred technical solution of the present invention, the molar ratio of the tin element, the phosphorus element and the antimony element is 1:1:1 ， At this time, the three elements have the best entropy increase effect, which is conducive to the nucleation and uniform deposition of sodium metal.

[0014] As a preferred technical solution of the present invention, the current collector substrate is aluminum foil or copper foil.

[0015] In a second aspect, the present invention provides a method for preparing the negative electrode current collector described in the first aspect, the preparation method comprising: depositing a target material on a current collector substrate by magnetron sputtering, wherein the target material comprises single substances corresponding to the three metal elements or non-metal elements having a gradient sodium alloying potential.

[0016] As a preferred technical solution of the present invention, the power of the magnetron sputtering method is 100-300W, for example, 100W, 150W, 200W, 250W, 300W, etc., preferably 200W.

[0017] As a preferred technical solution of the present invention, the sputtering time of the magnetron sputtering method is 10-30 minutes, for example, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc.

[0018] In a third aspect, the present invention provides a negative electrode-free sodium ion battery, wherein the negative electrode-free sodium ion battery comprises the negative electrode current collector described in the first aspect or the negative electrode current collector prepared by the preparation method described in the second aspect.

[0019] The negative electrode-free sodium ion battery provided by the present invention includes the negative electrode current collector, which can effectively reduce the sodium ion nucleation overpotential, promote the uniform deposition of sodium ions by utilizing the potential gradient effect of the alloying process, avoid the formation of dendrites, and realize the stable reversible cycle of the negative electrode-free sodium ion battery.

[0020] As a preferred technical solution of the present invention, the negative electrode-free sodium ion battery also includes a positive electrode plate, an electrolyte and a separator.

[0021] As a preferred technical solution of the present invention, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and the components of the positive electrode active material layer include a positive electrode active substance, a conductive agent and a binder.

[0022] As a preferred technical solution of the present invention, the positive electrode current collector is selected from aluminum foil.

[0023] As a preferred technical solution of the present invention, the mass ratio of the positive electrode active material, the conductive agent and the binder is (70-90):(5-20):(5-10), for example, 70:20:10, 75:15:10, 80:10:10, 85:8:7, 90:5:5, etc., preferably 80:10:10.

[0024] As a preferred technical solution of the present invention, the positive electrode active material is selected from sodium vanadium phosphate (NVP) and / or composite sodium iron phosphate (NFPP), preferably sodium vanadium phosphate.

[0025] As a preferred technical solution of the present invention, the conductive agent includes any one or more of Super P, Ketjen black, acetylene black and carbon nanotubes, preferably Super P.

[0026] As a preferred technical solution of the present invention, the binder includes any one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, carboxymethyl cellulose and sodium alginate, preferably polyvinylidene fluoride.

[0027] As a preferred technical solution of the present invention, the electrolyte includes sodium salt and an organic solvent.

[0028] As a preferred technical solution of the present invention, the concentration of the sodium salt in the electrolyte is 0.1-10 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 5 mol / L, 10 mol / L, etc., preferably 1 mol / L.

[0029] As a preferred technical solution of the present invention, the sodium salt includes NaClO 4 、NaPF 6 , NaTFSI and NaCF 3 SO 3 Any one or more of, preferably NaClO 4 .

[0030] As a preferred technical solution of the present invention, the organic solvent includes any one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, fluoroethylene carbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate and vinylene carbonate.

[0031] As a preferred technical solution of the present invention, the organic solvent comprises ethylene carbonate and propylene carbonate in a volume ratio of 1:1.

[0032] As a preferred technical solution of the present invention, the organic solvent further comprises fluoroethylene carbonate, and the ratio of the mass of the fluoroethylene carbonate to the mass sum of ethylene carbonate and propylene carbonate is 5:100.

[0033] As a preferred technical solution of the present invention, the diaphragm is selected from any one or more of a glass fiber diaphragm, a PE diaphragm or a PP diaphragm, preferably a glass fiber diaphragm.

[0034] The technical solution provided by the embodiment of the present invention has the following advantages compared with the prior art:

[0035] The negative electrode current collector provided by the present invention utilizes a sodium-philic coating to modify the current collector substrate, which can effectively reduce the nucleation overpotential of sodium metal on the negative electrode current collector on the one hand, and on the other hand, the alloying potential gradient of the sodium-philic coating helps to guide the interface reaction kinetics of sodium deposition / stripping during the charge and discharge process of sodium metal, thereby avoiding excessive local current density and the generation of dendrites, thereby solving the problems of poor reversibility, easy generation of dendrites and excessive use of traditional negative electrode current collectors in negative electrode-free sodium ion batteries, and effectively improving the cycle stability of negative electrode-free sodium ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 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.

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0038] Figure 1 The negative electrode current collector in Example 1 of the present invention and Comparative Example 1 is 2 mA / cm 2 Potential diagram of sodium deposition under current density;

[0039] Figure 2 Schematic diagram of the potential gradient for alloying reactions between Sn, Sb, and P and Na respectively. DETAILED DESCRIPTION

[0040] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0041] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0042] Preparation Example 1

[0043] This preparation example provides a negative electrode current collector and a preparation method thereof, the preparation method comprising:

[0044] The three elements Sn, Sb and P were mixed in equal molar amounts as a target material, and Al foil was used as a substrate material. Magnetron sputtering was performed at a power of 200 W for 20 minutes to obtain the negative electrode current collector named SnSbP@Al. The thickness of the sodium-philic coating was about 600 nm, and then the negative electrode current collector was cut into pieces to obtain the negative electrode current collector of the required size.

[0045] Preparation Example 2

[0046] This preparation example provides a negative electrode current collector and a preparation method thereof. The preparation method is the same as Preparation Example 1. The difference from Preparation Example 1 is that in this preparation example, the magnetron sputtering time is 10 minutes and the thickness of the sodium plating layer is about 300 nm.

[0047] Preparation Example 3

[0048] This preparation example provides a negative electrode current collector and a preparation method thereof. The preparation method is the same as Preparation Example 1. The difference from Preparation Example 1 is that in this preparation example, the magnetron sputtering time is 30 minutes and the thickness of the sodium plating layer is about 900 nm.

[0049] Preparation Example 4

[0050] This preparation example provides a negative electrode current collector and a preparation method thereof. The preparation method is the same as that of Preparation Example 1. The difference from Preparation Example 1 is that the molar ratio of the three elements Sn, Sb, and P in this preparation example is 3:2:5.

[0051] Preparation Example 5

[0052] This preparation example provides a negative electrode current collector and a preparation method thereof. The preparation method is the same as that of Preparation Example 1. The difference from Preparation Example 1 is that the molar ratio of the three elements Sn, Sb, and P in this preparation example is 5:2.5:2.5.

[0053] Comparative Preparation Example 1

[0054] This comparative preparation example provides a negative electrode current collector and a preparation method thereof. The preparation method is the same as that of Preparation Example 1, and the difference from Preparation Example 1 is that the target material in this comparative preparation example is only Sb single substance.

[0055] Comparative Preparation Example 2

[0056] This comparative preparation example provides a negative electrode current collector and a preparation method thereof. The preparation method is the same as that of Preparation Example 1, and the difference from Preparation Example 1 is that the target material in this comparative preparation example is only a single substance of Sn.

[0057] Comparative Preparation Example 3

[0058] This comparative preparation example provides a negative electrode current collector and a preparation method thereof. The preparation method is the same as that of Preparation Example 1, and the difference from Preparation Example 1 is that the target material in this comparative preparation example is only P single substance.

[0059] Example 1

[0060] This embodiment provides a negative electrode-free sodium ion battery and a preparation method thereof, the preparation method comprising the following steps:

[0061] (1) Positive electrode sheet: Sodium vanadium phosphate (NVP), Super P, and polyvinylidene fluoride are mixed in a ratio of 8:1:1 and then mixed with N-methylpyrrolidone to prepare a slurry, and then the slurry is coated on the surface of the Al current collector, and after drying, the slurry is cut into pieces to obtain a positive electrode sheet;

[0062] (2) Electrolyte: Sodium salt is NaClO 4 , with a concentration of 1 mol / L; the organic solvent is ethylene carbonate and propylene carbonate in a volume ratio of 1:1, and fluoroethylene carbonate is added in an amount of 5% of the total weight of the two; the sodium salt and the organic solvent are evenly mixed to obtain an electrolyte.

[0063] (3) Diaphragm: Cut the fiberglass diaphragm into appropriate size for later use.

[0064] The above-mentioned positive electrode plate, the negative electrode current collector prepared in Preparation Example 1, the separator and the electrolyte were assembled into a negative electrode-free sodium ion battery in a glove box with water and oxygen contents less than 0.1 ppm.

[0065] Example 2-3

[0066] This embodiment provides a negative electrode-free sodium ion battery and a preparation method thereof. The preparation method is the same as that of Example 1. The difference from Example 1 is that in this embodiment, the negative electrode collector is replaced by the negative electrode collector prepared in Preparation Example 2 (Example 2) and the negative electrode collector prepared in Preparation Example 3 (Example 3).

[0067] Embodiment 4-5

[0068] This embodiment provides a negative electrode-free sodium ion battery and a preparation method thereof. The preparation method is the same as that of Example 1. The difference from Example 1 is that in this embodiment, the negative electrode collector is replaced by the negative electrode collector prepared in Preparation Example 4 (Example 4) and the negative electrode collector prepared in Preparation Example 5 (Example 5).

[0069] Example 6

[0070] This embodiment provides a negative electrode-free sodium ion battery and a preparation method thereof. The preparation method is the same as that of Example 1. The difference from Example 1 is that in this embodiment, sodium vanadium phosphate is replaced by composite sodium iron phosphate (NFPP).

[0071] Example 7

[0072] This embodiment provides a negative electrode-free sodium ion battery and a preparation method thereof. The preparation method is the same as that of Example 1. The difference from Example 1 is that in this embodiment, the electrolyte is replaced by: the sodium salt is NaPF 6 , concentration is 3 mol / L, and the organic solvent is ethylene glycol dimethyl ether.

[0073] Example 8

[0074] This embodiment provides a negative electrode-free sodium ion battery and a preparation method thereof. The preparation method is the same as that of Example 1. The difference from Example 1 is that in this embodiment, the glass fiber separator is replaced by a PE film.

[0075] Comparative Example 1

[0076] This comparative example provides a negative electrode-free sodium ion battery and a preparation method thereof. The preparation method is the same as that of Example 1, and the difference from Example 1 is that in this comparative example, the negative electrode current collector is replaced with pure aluminum foil that has not been modified with a sodium-philic coating.

[0077] Comparative Example 2

[0078] This comparative example provides a negative electrode-free sodium ion battery and a preparation method thereof. The preparation method is the same as that of Example 1, and the difference from Example 1 is that in this comparative example, the negative electrode current collector is replaced with the negative electrode current collector prepared in Comparative Preparation Example 1.

[0079] Comparative Example 3

[0080] This comparative example provides a negative electrode-free sodium ion battery and a preparation method thereof. The preparation method is the same as that of Example 1. The difference from Example 1 is that in this comparative example, the negative electrode current collector is replaced with the negative electrode current collector prepared in Comparative Preparation Example 2.

[0081] Comparative Example 4

[0082] This comparative example provides a negative electrode-free sodium ion battery and a preparation method thereof. The preparation method is the same as that of Example 1, and the difference from Example 1 is that in this comparative example, the negative electrode current collector is replaced with the negative electrode current collector prepared in Comparative Preparation Example 3.

[0083] Performance Testing

[0084] The performance of the negative electrode-free sodium ion batteries prepared in the examples and comparative examples was tested:

[0085] (1) Overpotential of deposition of sodium metal by negative electrode current collector:

[0086] The negative electrode current collectors in the embodiment and the comparative example were used as the positive electrode and the sodium metal was used as the negative electrode, respectively, and the button cells were assembled with the glass fiber separator and the electrolyte (the same as the electrolyte in the embodiment 1) in a glove box with water and oxygen contents less than 0.1 ppm. 2 The battery is discharged for sodium deposition at a current density of , and the sodium deposition potential curves of different current collectors can be obtained. Finally, the deposition overpotentials are statistically summarized based on the curves.

[0087] Among them, the negative electrode current collector in Example 1 and Comparative Example 1 is 2mA / cm 2 The sodium deposition potential diagram under current density is shown in Figure 1 shown.

[0088] (2) Cycle performance:

[0089] The negative electrode-free sodium ion batteries obtained in the examples and comparative examples were subjected to a 0.5C rate charge and discharge test to obtain their discharge specific capacity and capacity retention rate after 300 cycles.

[0090] The test results are shown in Table 1:

[0091] Table 1

[0092]

[0093] It can be found from Table 1 that the negative electrode current collector modified with a sodium-philic coating provided by the present invention has a lower sodium ion deposition overpotential and better cycle stability than the Al foil negative electrode current collector (Comparative Example 1), and compared with the sodium-philic coating with only one metal element or non-metallic element (Comparative Examples 2-4), the sodium-philic coating provided by the present invention has a lower sodium ion deposition overpotential and better cycle stability.

[0094] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0095] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments described herein, but should conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A negative electrode current collector, characterized in that: The negative electrode current collector comprises a current collector substrate and a sodium-philic coating layer disposed on the current collector substrate, wherein the sodium-philic coating layer comprises three metal elements or non-metal elements with gradient sodium alloying potentials.

2. The negative electrode current collector according to claim 1, characterized in that: The three metal elements or non-metal elements having gradient sodium alloying potentials are tin, phosphorus and antimony; And / or, the thickness of the sodium-philic coating is 300-900 nm.

3. The negative electrode current collector according to claim 2, characterized in that: Taking the total molar amount of the tin element, the phosphorus element and the antimony element as 100%, the molar content of each element is 20-50%.

4. The negative electrode current collector according to any one of claims 1 to 3, characterized in that: The current collector substrate is aluminum foil or copper foil.

5. The method for preparing the negative electrode current collector according to any one of claims 1 to 4, characterized in that: The preparation method comprises: depositing a target material on a current collector substrate by magnetron sputtering, wherein the target material comprises single substances corresponding to the three metal elements or non-metal elements having gradient sodium alloying potentials.

6. The preparation method according to claim 5, characterized in that: The power of the magnetron sputtering method is 100-300W; And / or, the sputtering time of the magnetron sputtering method is 10-30 minutes.

7. A negative electrode-free sodium ion battery, characterized in that: The negative electrode-free sodium ion battery comprises the negative electrode current collector according to any one of claims 1 to 4 or the negative electrode current collector prepared by the preparation method according to claim 5 or 6.

8. The negative electrode-free sodium ion battery according to claim 7, characterized in that: The negative electrode-free sodium ion battery also includes a positive electrode plate, an electrolyte and a separator; Preferably, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and the components of the positive electrode active material layer include a positive electrode active material, a conductive agent and a binder; Preferably, the electrolyte comprises a sodium salt and an organic solvent; Preferably, the diaphragm is selected from any one or more of a glass fiber diaphragm, a PE diaphragm or a PP diaphragm.

9. The negative electrode-free sodium ion battery according to claim 8, characterized in that: The positive electrode current collector is selected from aluminum foil; And / or, the mass ratio of the positive electrode active material, the conductive agent and the binder is (70-90):(5-20):(5-10); And / or, the positive electrode active material is selected from sodium vanadium phosphate and / or composite sodium iron phosphate; And / or, the conductive agent includes any one or more of Super P, Ketjen black, acetylene black and carbon nanotubes; And / or, the binder includes any one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, carboxymethyl cellulose and sodium alginate.

10. The negative electrode-free sodium ion battery according to claim 8, characterized in that: The concentration of the sodium salt in the electrolyte is 0.1-10 mol / L; And / or, the sodium salt includes any one or more of NaClO4, NaPF6, NaTFSI and NaCF3SO3; And / or, the organic solvent includes any one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, fluoroethylene carbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate and vinylene carbonate.

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