A modified current collector and a negative electrode-free sodium metal battery comprising the same

Abstract

The application provides a modified current collector and a negative electrode-free sodium metal battery comprising the same. The application designs a step coating with a certain thickness to reserve space on the current collector, slow down the large volume change of the battery cell caused by the repeated deposition / dissolution of metal sodium, stabilize the structure of the battery cell, and improve the cycle stability of the battery. Importantly, the overall thickness of the battery cell can be uniform by designing the step shape as a corrugated or zigzag shape, avoiding the structural distortion phenomenon caused by the reserved step coating, improving the structural stability of the battery cell with the reserved space, and being beneficial to further improving the electrochemical performance of the negative electrode-free sodium metal battery.

Description

Technical Field

[0001] This invention belongs to the field of secondary ion battery technology, specifically relating to a modified current collector and a sodium metal battery without a negative electrode including the modified current collector. Background Technology

[0002] In the past two years, based on extensive prior research, the industrialization process of sodium-ion batteries has accelerated significantly. Companies such as CATL and Zhongke Haina in China, Faradion in the UK, and Natron Energy in the US have all produced preliminary sodium-ion battery samples or products, greatly stimulating researchers' enthusiasm for sodium-ion battery development. However, the energy density of sodium-ion batteries is relatively low (40–200 Wh / kg). -1 This limits its application scenarios. Sodium metal anodes have a high theoretical capacity (1166 mAh g⁻¹), which restricts their application scenarios. -1 Its low reaction site (-2.73V vs. SHE) has been proposed for constructing high energy density batteries.

[0003] Compared to sodium metal batteries, electrodeless sodium metal batteries represent a more ideal structure. In electrodeless sodium metal batteries, the current collector serves as the negative electrode during assembly, and sodium ions released from the positive electrode during charging are deposited onto the current collector to form the sodium metal negative electrode. Because there is no negative electrode active material layer, the mass and volume of the cell can be significantly reduced, increasing the battery's energy density. However, due to the high chemical / electrochemical activity and deposition nucleation potential of metallic sodium, it readily reacts with the electrolyte and undergoes uneven deposition, causing SEI film instability and sodium dendrite growth, resulting in low coulombic efficiency and short battery cycle life. Furthermore, the direct deposition of sodium metal onto the current collector causes significant changes in cell volume, posing a major challenge to cell structure design and hindering the practical application of electrodeless batteries. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a modified current collector and a negative electrode-free sodium metal battery including the modified current collector. The modified current collector has a corrugated or serrated stepped coating on its substrate surface. This corrugated or serrated stepped coating provides reserved space on the surface of the modified current collector, mitigating the significant volume changes in the cell caused by repeated sodium deposition / dissolution, stabilizing the cell structure, and improving the battery's cycle stability. The corrugated or serrated stepped coating design also ensures uniform overall cell thickness, avoiding structural distortion caused by the reserved stepped coating, improving the structural stability of the cell with reserved space, and further enhancing the electrochemical performance of the negative electrode-free sodium metal battery.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A modified current collector, wherein the modified current collector includes a current collector substrate and a corrugated or serrated stepped coating provided on at least one surface of the current collector substrate.

[0007] According to an embodiment of the present invention, the corrugated or serrated stepped coating is a coating with a certain thickness formed by reciprocally coating at an angle with respect to the width direction of the current collector substrate. For the specific structure, refer to Figure 1 and Figure 2 the top view of the modified current collector shown.

[0008] According to an embodiment of the present invention, the coating path of the corrugated stepped coating is a curve, and the path shape is a water ripple curve, a sine curve or a cosine curve.

[0009] According to an embodiment of the present invention, the coating path of the serrated stepped coating is a broken line.

[0010] According to an embodiment of the present invention, the coating path of the corrugated or serrated stepped coating has the characteristic of periodic distribution.

[0011] According to an embodiment of the present invention, the modified current collector satisfies: 0.05W ≤ L ≤ 2.0W; wherein, L is the length of the cycle period of the corrugated or serrated stepped coating, and W is the width of the current collector substrate.

[0012] Preferably, the modified current collector satisfies: 0.2W ≤ L ≤ 1.0W. Preferably, L = 0.05W, 0.1W, 0.2W, 0.3W, 0.4W, 0.5W, 0.6W, 0.7W, 0.8W, 0.9W, 1W, 1.2W, 1.5W, 1.8W or 2W

[0013] According to an embodiment of the present invention, the width W1 of the corrugated or serrated stepped coating is greater than or equal to the width of the matched positive electrode paste.

[0014] According to an embodiment of the present invention, the modified current collector satisfies: W1 < W; wherein, W1 is the width of the corrugated or serrated stepped coating, and W is the width of the current collector substrate. Wherein, the width W1 of the corrugated or serrated stepped coating refers to the distance between the outermost edges on both sides in the transverse direction of the stepped coating.

[0015] According to an embodiment of the present invention, the width W2 of the corrugated or serrated stepped coating satisfies: 1.0 mm ≤ W2 ≤ 20 mm. Preferably, W2 is 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 12 mm, 13 mm, 15 mm, 18 mm, or 20 mm. Wherein, the width W2 of the corrugated or serrated stepped coating refers to the width of the coating path of the corrugated or serrated stepped coating.

[0016] According to an embodiment of the present invention, the thickness H2 of the corrugated or sawtooth stepped coating can be adjusted according to the areal capacity of the positive electrode of the designed battery cell, and the range of H2 is 5.0 μm ≤ H2 ≤ 50 μm. Preferably, H2 is 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, or 50 μm.

[0017] According to an embodiment of the present invention, the material forming the corrugated or serrated stepped coating includes an adhesive and ceramic particles.

[0018] The adhesives include, but are not limited to: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile rubber (NBR), aqueous acrylic resin, polyvinyl alcohol, polyvinyl butyral, polyurethane, fluorinated rubber, carboxymethyl cellulose (CMC), and polyacrylic acid (PAA).

[0019] The ceramic particles include, but are not limited to, alumina (Al2O3), boehmite (γ-AlOOH), silicon dioxide (SiO2), silicon carbide (SiC), magnesium oxide (MgO), and zirconium oxide (ZrO2).

[0020] According to an embodiment of the present invention, the mass ratio of the binder to the ceramic particles is 3 to 7:7 to 3, for example, 3:7, 4:6, 5:5, 6:4 or 7:3.

[0021] According to an embodiment of the present invention, the corrugated or serrated stepped coating can be achieved by moving extrusion coating or moving spray coating.

[0022] According to an embodiment of the present invention, the current collector substrate includes, but is not limited to: copper foil, perforated copper foil, nickel foil, aluminum foil, perforated aluminum foil, and stainless steel.

[0023] The present invention also provides a sodium metal battery without a negative electrode, which includes the modified current collector described above.

[0024] According to an embodiment of the present invention, the negative electrode-free sodium metal battery further includes a positive electrode, a separator, and an electrolyte.

[0025] According to an embodiment of the present invention, the negative electrode-free sodium metal battery does not include a negative electrode sheet.

[0026] According to embodiments of the present invention, the application of the negative electrode-free sodium metal battery is not particularly limited and can be used for a variety of known applications. Examples include: mobile computers, laptops, portable telephones, e-book players, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, calculators, memory cards, portable recorders, radios, backup power supplies, automobiles, motorcycles, electric boats, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, cameras, large household batteries, energy storage power stations, etc.

[0027] According to an embodiment of the present invention, the cell of the negative electrode-free sodium metal battery can be a stacked structure formed by sequentially stacking a modified current collector, a separator, and a positive electrode sheet, or a wound structure formed by sequentially stacking a modified current collector, a separator, and a positive electrode sheet and then winding them.

[0028] The beneficial effects of this invention are:

[0029] This invention provides a modified current collector for use in a sodium-metal battery without a negative electrode. The invention designs a stepped coating of a certain thickness to create space on the current collector, mitigating the large volume changes in the cell caused by repeated sodium deposition / dissolution, stabilizing the cell structure, and improving the battery's cycle stability. Importantly, the corrugated or serrated stepped shape design also ensures uniform overall cell thickness, avoiding structural distortion caused by the stepped coating, improving the structural stability of the cell with the reserved space, and further enhancing the electrochemical performance of the sodium-metal battery without a negative electrode. Attached Figure Description

[0030] Figure 1 This is a top view of the modified current collector with a corrugated stepped coating of the present invention.

[0031] Figure 2 This is a top view of the modified current collector with a serrated stepped coating of the present invention.

[0032] Figure 3 This is an oblique side view of the modified current collector with a corrugated or serrated stepped coating of the present invention.

[0033] Figure 4 This is a front view of the modified current collector with a corrugated or serrated stepped coating of the present invention.

[0034] Reference numerals: 1 represents the stepped coating; 2 represents the current collector substrate. Detailed Implementation

[0035] <Positive Electrode Tablets>

[0036] According to an embodiment of the present invention, the positive electrode includes a current collector and an active material layer; the active material layer is coated on the surface of the current collector; the active material layer includes an active material.

[0037] According to an embodiment of the present invention, the active material in the positive electrode includes one or more of Prussian blue-based materials, polyanionic materials, and transition metal layered oxides.

[0038] According to embodiments of the present invention, the transition metal layered oxide is selected, for example, from NaCoO2 and Na... 2 / 3 [Cu 1 / 3Mn 2 / 3 O2, Na 2 / 3 [Fe 1 / 3 Mn 2 / 3 O2, Na 2 / 3 [Li 1 / 3 Ni 2 / 3 O2, Na[Ni 0.5 Co 0.5 O2, Na 7 / 9 [Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 O2, Na 2 / 3 [Li 1 / 3 Mn 1 / 2 Ti 1 / 6 O2, Na[Ni 0.5 Fe 0.5 O2, Na[Co 0.5 Fe 0.5 O2, Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na[Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 O2, etc.

[0039] According to an embodiment of the present invention, the chemical formula of the Prussian blue-like material is A. x M[Fe(CN)6] y Where A is an alkali metal cation, M is a transition metal cation, 1≤x≤2, and 0.9≤y≤1.

[0040] According to an embodiment of the present invention, the Prussian blue material also contains water of crystallization.

[0041] According to an embodiment of the present invention, A can specifically be Li, Na, K, Rb, Cs, or Fr.

[0042] According to embodiments of the present invention, M can specifically be one or more of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr and Mo.

[0043] According to embodiments of the present invention, the Prussian blue material is selected from one or more of LiFe2(CN)6, LiCoFe(CN)6, LiMnFe(CN)6, NaFe2(CN)6, KFe2(CN)6, NaCuFe(CN)6, NaNiFe(CN)6, Na2Fe2(CN)6, Na2MnFe(CN)6, Na2CoFe(CN)6, and Na2NiFe(CN)6.

[0044] According to an embodiment of the present invention, the chemical formula of the polyanionic material is A' x’ M' y’ (X n’ O m ) z F w In this context, A' is Li or Na, M' is one or more transition metal ions with variable valence states, X is P, S, V or Si, and x'≥1, y'>0, z≥1, w≥0, and the values ​​of n' and m conform to the principle of charge conservation.

[0045] According to an embodiment of the present invention, M' is Ti, Fe or Mn.

[0046] According to an embodiment of the present invention, the polyanionic material is selected from one or more of NaFePO4, Na3V2(PO4)3, Na2MnP2O7, Na2FeP2O7, and Na2FePO4F.

[0047] According to an embodiment of the present invention, the average particle size Dv50 of the Prussian blue material is 1 μm to 15 μm.

[0048] According to an embodiment of the present invention, the average particle size Dv50 of the polyanionic material is 1 μm to 10 μm.

[0049] According to an embodiment of the present invention, the positive electrode is used in a sodium metal battery without a negative electrode.

[0050] According to an embodiment of the present invention, the active material layer in the positive electrode further includes a conductive agent and a binder.

[0051] According to embodiments of the present invention, the conductive agent includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, or mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0052] According to embodiments of the present invention, the adhesive includes, but is not limited to: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile rubber (NBR), aqueous acrylic resin, polyvinyl alcohol, polyvinyl butyral, polyurethane, fluorinated rubber, carboxymethyl cellulose (CMC), and polyacrylic acid (PAA).

[0053] According to an embodiment of the present invention, the mass percentage of each component in the active material layer of the positive electrode is as follows:

[0054] 75–98 wt% active material, 1–15 wt% conductive agent, and 1–10 wt% binder.

[0055] Preferably, the mass percentage of each component in the active material layer of the positive electrode is:

[0056] 82–96 wt% active material, 2–10 wt% conductive agent, and 2–8 wt% binder.

[0057] According to embodiments of the present invention, the current collector includes, but is not limited to: aluminum foil, carbon-coated aluminum foil, perforated aluminum foil, stainless steel foil, polymer substrate coated with conductive metal, and any combination thereof.

[0058] According to embodiments of the present invention, the positive electrode sheet can be prepared according to conventional methods in the art. Typically, active materials and optional conductive agents and binders are dispersed in a solvent (e.g., NMP) to form a uniform positive electrode slurry. The positive electrode slurry is then coated onto a current collector, and after drying and other processes, the positive electrode sheet is obtained.

[0059] <Septum>

[0060] According to an embodiment of the present invention, the separator is one of the following: polypropylene separator (PP), polyethylene separator (PE), polypropylene / polyethylene double-layer composite membrane (PP / PE), polypropylene / polyethylene / polypropylene triple-layer composite membrane (PP / PE / PP), polyimide electrospun separator (PI), cellulose nonwoven separator, polyethylene terephthalate nonwoven separator (PET), and separator with ceramic coating.

[0061] According to an embodiment of the present invention, the separator serves as an interlayer between the positive electrode and the modified current collector, acting as a separator.

[0062] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0063] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0064] For simplicity, this invention only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0065] In this description, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more.

[0066] The present invention is not intended to describe every disclosed embodiment or implementation. Instead, the following description provides more specific examples of exemplary embodiments. Throughout this application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0067] Example 1

[0068] (1) Preparation of modified current collectors

[0069] PVDF and Al2O3 powders were weighed in a 1:1 weight ratio, mixed evenly, and then an appropriate amount of N-methylpyrrolidone (NMP) was added. The mixture was thoroughly stirred to form a uniform slurry. This slurry was then coated onto an aluminum foil (380 mm wide) using a moving extrusion coating method. The shape parameters of the steps are as follows: corrugated stepped coating, L = 0.5, W = 190 mm, W1 = 350 mm, W2 = 3 mm, H2 = 30 μm. After drying, rolling, and cutting, the modified current collector was obtained.

[0070] (2) Preparation of positive electrode

[0071] Weigh out the positive electrode active material (Na[Ni) 1 / 3 Fe 1 / 3 Mn 1 / 3 O2), binder (PVDF), and conductive agent carbon black (Super P) are mixed in a mass ratio of 95:2.5:2.5. An appropriate amount of N-methylpyrrolidone (NMP) is then added and thoroughly stirred to form a uniform slurry. This slurry is coated onto a carbon-coated aluminum foil for the positive electrode current collector, then dried, rolled, and slit to obtain the positive electrode sheet. The designed areal capacity is 2.5 mAh / cm². 2 .

[0072] (3) Preparation of the diaphragm

[0073] A 9μm wet-process polyethylene membrane was selected as the substrate. First, a 2μm thick alumina ceramic coating was applied to one surface of the substrate. Then, a 1μm thick PVDF-HFP adhesive layer was applied to both sides of the membrane to obtain a membrane with a total thickness of 13μm. The membrane was then cut into the required width for later use.

[0074] (4) Electrolyte preparation

[0075] In an argon-filled glove box with a water content of <1ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed in a mass ratio of 0.5:1.5:1.5. Sodium hexafluorophosphate (NaPF6) with a concentration of 1.0mol / L was added and stirred until homogeneous. Then, 1.0wt% sodium nitrate (NaNO3) was added and stirred thoroughly to obtain the electrolyte.

[0076] (5) Preparation of sodium metal batteries without negative electrodes

[0077] The modified current collector, separator, and positive electrode are stacked in sequence, with the separator positioned between the positive electrode and the modified current collector. Then, the electrode tabs are welded and the core is wound. The core is then placed in an aluminum-plastic film packaging bag. Finally, the electrolyte is injected and the battery undergoes vacuum sealing, settling, formation, and shaping processes to prepare a sodium metal battery without a negative electrode.

[0078] (6) Performance testing of sodium metal batteries without negative electrode

[0079] First-cycle discharge capacity and first-cycle coulombic efficiency: The sodium metal battery without negative electrode was placed at 25°C and charged at a constant current of 0.5C to the upper limit voltage (4.0V). Then it was charged at a constant voltage of 4.0V to a current of 0.05C and left to stand for 5 minutes. Next, it was discharged at a constant current of 0.5C to a voltage of 2.0V. The discharge capacity was recorded as the first-cycle discharge capacity. The first-cycle coulombic efficiency is the ratio of the first-cycle discharge specific capacity to the charging specific capacity.

[0080] Volume change rate: The thickness of the original cell is measured and recorded as h1. Then, at 25℃, it is charged at a constant current of 0.5C to the upper limit voltage (4.0V), and then charged at a constant voltage of 4.0V to a current of 0.05C. After standing for 5 minutes, the cell thickness is measured again and recorded as h2. Volume change rate = h2 / h1*100%.

[0081] Room temperature cycle life: The sodium metal battery without a negative electrode is placed at 25°C and charged at a constant current of 0.5C to the upper limit voltage (4.0V), then charged at a constant voltage of 4.0V to a current of 0.05C, and left to stand for 5 minutes; then discharged at a constant current of 0.5C to a voltage of 2.0V, and left to stand for 5 minutes. This constitutes one charge-discharge cycle. This charging / discharging process is repeated, and the ratio of the discharge capacity after the 100th cycle to the discharge capacity of the first cycle is recorded, which is the capacity retention rate after 100 cycles.

[0082] Examples 1-9 and Comparative Examples 1-4

[0083] The other operations are the same as in Example 1, except that the morphology of the stepped coating is different, as shown in Table 1.

[0084] Table 1. Morphology of the stepped coatings in the examples and comparative examples.

[0085]

[0086] Table 2 Electrochemical performance of different embodiments and comparative examples

[0087] First lap Coulomb efficiency % Volume change rate % 100-cycle capacity retention % Example 1 79 22 86 Example 2 78 26 83 Example 3 83 19 89 Example 4 81 19 88 Example 5 76 21 82 Example 6 79 22 78 Example 7 72 15 72 Example 8 73 23 77 Example 9 72 25 70 Comparative Example 1 48 29 55 Comparative Example 2 54 22 51 Comparative Example 3 58 35 42 Comparative Example 4 70 30 60

[0088] The results of Tables 1 and 2 are analyzed as follows:

[0089] Comparing Examples 1, 3, and 4 above, it can be seen that the optimization effect of ordinary corrugations and steps with regular sinusoidal structures is better than that of straight serrated structures. This may be attributed to the fact that the straight serrated structure has sharp points at the inflection points, which can easily cause tip discharge and generate metal dendrites, which is not conducive to the uniform deposition of sodium metal.

[0090] Comparing Examples 3 and 6 and Comparative Examples 1 and 2, it can be seen that a moderate ripple period length of the stepped coating is better. Excessive spacing will not provide good support, while too dense a step distribution will affect the deposition of metallic sodium.

[0091] Furthermore, if a non-wavy or non-serrated straight-line stepped coating is selected, since the position of this straight-line stepped coating is generally fixed on both sides of the current collector, the thickness on both sides of the core will be significantly thicker than the thickness in the middle due to cumulative stacking. This easily leads to the formation of a hollow structure in the middle, resulting in poor structural stability. This makes the core prone to deformation under stress during the transfer process, causing wrinkles in the internal current collector, which is not conducive to the uniform deposition of sodium metal and affects the performance of the battery.

[0092] In summary, a corrugated or serrated stepped coating of a certain thickness can create reserved spaces on the surface of the current collector substrate, mitigating the large volume changes in the cell caused by repeated deposition / dissolution of metallic sodium, stabilizing the cell structure, and improving the cycle stability of the battery. Importantly, the corrugated or serrated stepped shape design ensures uniform overall cell thickness, avoiding structural distortion caused by the reserved steps, improving the structural stability of the cell with reserved spaces, and further enhancing the electrochemical performance of sodium-metal batteries without negative electrodes.

[0093] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A negative electrode-free sodium metal battery, comprising a modified current collector, the modified current collector comprising a current collector substrate and a corrugated or serrated stepped coating disposed on at least one side surface of the current collector substrate; wherein the width W1 of the corrugated or serrated stepped coating is greater than or equal to the width of the matching positive electrode paste. The stepped coating has a cycle period length; The material for forming the corrugated or serrated stepped coating includes a binder and ceramic particles.

2. The sodium metal battery without a negative electrode according to claim 1, characterized in that, The coating path of the corrugated stepped coating is a wavy curve, a sine curve or a cosine curve.

3. The sodium metal battery without a negative electrode according to claim 1, characterized in that, The coating path of the serrated stepped coating is a broken line.

4. The sodium metal battery without a negative electrode according to any one of claims 1-3, characterized in that, The modified current collector satisfies: 0.05W ≤ L ≤ 2.0 W; where L is the length of the cycle period of the corrugated or serrated stepped coating, and W is the width of the current collector substrate.

5. The sodium metal battery without a negative electrode according to any one of claims 1-3, characterized in that, The modified current collector satisfies: W1 < W; where W1 is the width of the corrugated or serrated stepped coating, and W is the width of the current collector substrate.

6. The sodium metal battery without a negative electrode according to any one of claims 1-3, characterized in that, The width W2 of the corrugated or serrated stepped coating satisfies: 1.0 mm ≤ W2 ≤ 20 mm.

7. The sodium metal battery without a negative electrode according to any one of claims 1-3, characterized in that, The thickness H2 of the corrugated or serrated stepped coating ranges from 5.0 μm ≤ H2 ≤ 50 μm.

8. The sodium metal battery without a negative electrode according to any one of claims 1-3, characterized in that, The mass ratio of the binder to the ceramic particles is 3~7:7~3.

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