Composite sodium metal negative electrode sheet and preparation method and application thereof

Abstract

The application belongs to the technical field of sodium metal batteries, and discloses a composite sodium metal negative electrode sheet, which is a sodium / sodium-M alloy / sodium halide composite material, wherein the sodium-M alloy is a Na-Sn alloy, a Na-In alloy, a Na-Bi alloy or a Na-Zn alloy, and the sodium halide is NaF, NaCl, NaBr or Nal. The preparation steps are as follows: (1) dry the metal halide powder for standby, and prepare two pieces of sodium foil at the same time; (2) in an inert atmosphere protection glove box, evenly distribute the dried metal halide powder between the two pieces of sodium foil, stack them according to the structure of sodium foil-metal halide-sodium foil "sandwich", cold calendering, folding, cold calendering, and repeat the steps of "cold calendering-folding-cold calendering" for multiple times, to obtain a composite foil; (3) use a punch to punch the composite foil into an electrode sheet with a required diameter, to obtain the composite sodium metal negative electrode sheet. The composite negative electrode sheet has excellent formability, processing performance, excellent rate performance and cycle stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium metal batteries, and particularly relates to a composite sodium metal negative electrode sheet and a preparation method and application thereof. BACKGROUND

[0002] Sodium metal batteries have attracted great attention due to their high energy density, abundant sodium resources and potential low cost, but still face some challenges affecting the commercialization process. On the one hand, the high reducibility of metal sodium leads to continuous side reactions between the negative electrode and the electrolyte, producing unstable solid electrolyte interface (SEI), which will develop into a loose porous layer structure during the cycle process, destroying the Na + diffusion and accelerate the growth of sodium dendrites. On the other hand, metal sodium is usually stored in the form of sodium blocks in kerosene, which is quickly corroded in air, and the low metal bond energy of sodium leads to poor processability and great difficulty in manufacturing electrodes. Due to the low hardness and high viscosity of metal sodium, slight applied pressure will cause deformation and adhesion, which creates difficulties for the storage or transportation of sodium foil. Therefore, it is urgent to develop a sodium metal negative electrode to solve the problem of sodium dendrites and the difficulties in processing, storage, transportation and application of metal sodium. SUMMARY

[0003] In order to overcome the deficiencies in the prior art, the purpose of the present application is to provide a composite sodium metal negative electrode sheet and a preparation method and application thereof.

[0004] To achieve the above-mentioned purpose, the technical solutions adopted by the present application are as follows:

[0005] A composite sodium metal negative electrode sheet, the composite sodium metal negative electrode sheet is a sodium / sodium-M alloy / halide sodium composite material, and the sodium-M alloy and the halide sodium are uniformly dispersed in the metal sodium phase; wherein the sodium-M alloy is a Na-Sn alloy, a Na-In alloy, a Na-Bi alloy or a Na-Zn alloy, and the halide sodium is NaF, NaCl, NaBr or Nal.

[0006] Preferably, the thickness of the composite sodium metal negative electrode sheet is 20-500 μm.

[0007] A preparation method of a composite sodium metal negative electrode sheet, the preparation steps are as follows:

[0008] (1) dry the metal halide powder for standby, and prepare two pieces of sodium foil at the same time; the metal halide is a halide of Sn, In, Bi or Zn;

[0009] (2) In the glove box under inert atmosphere, the dried metal halide powder is evenly distributed between two pieces of sodium foil, stacked together according to the structure of "sandwich" of sodium foil-metal halide-sodium foil, cold rolling→folding in half→cold rolling, repeating the process of "cold rolling→folding in half→cold rolling" for several times, to obtain the composite foil;

[0010] (3) The composite foil is punched into an electrode sheet with a desired diameter using a punch press, to obtain the composite sodium metal negative electrode sheet.

[0011] Preferably, in step (2), the metal halide powder is added in batches, i.e., the specific process of step (2) is as follows: in the glove box under inert atmosphere, a portion of the dried metal halide powder is evenly distributed between two pieces of sodium foil, stacked together according to the structure of "sandwich" of sodium foil-metal halide-sodium foil, cold rolling→further distributing a portion of the metal halide powder on the upper sodium foil after cold rolling→folding in half→cold rolling, repeating the process of "cold rolling→further distributing a portion of the metal halide powder on the upper sodium foil after cold rolling→folding in half→cold rolling" for several times, to obtain the composite foil.

[0012] Preferably, in the glove box under inert atmosphere, H2O < 0.1 ppm, O2 < 0.1 ppm.

[0013] Preferably, in step (1), the drying temperature of the metal halide powder is 60-80°C, and the drying time is 48-72 h.

[0014] Preferably, in step (1), the mass ratio of the metal halide powder to two pieces of sodium foil is (5-8):100, more preferably the mass ratio of the metal halide powder to two pieces of sodium foil is (20-60):100, and most preferably the mass ratio of the metal halide powder to two pieces of sodium foil is 40:100.

[0015] A use of the composite sodium metal negative electrode sheet in a sodium metal battery.

[0016] Preferably, the sodium metal battery is a button full cell or a soft pack full cell.

[0017] The assembly process of the button full cell is as follows: in the glove box under inert atmosphere, the positive electrode sheet is placed in the positive electrode shell, electrolyte is added, the separator is placed, electrolyte is further added, then the composite sodium metal negative electrode sheet is placed on the separator, and finally the foam nickel and the negative electrode shell are placed and pressed, to obtain the button full cell.

[0018] The assembly process of the soft pack full cell is as follows: in the glove box under inert atmosphere, the NSF composite sodium metal negative electrode sheet-electrolyte-separator-electrolyte-positive electrode sheet are sequentially stacked, then transferred to two pieces of aluminum foil, the cut ear is placed, and finally the heat sealing machine is used for packaging, to obtain the soft pack full cell.

[0019] The positive electrode sheet is prepared by the following process: taking 70-80% of positive electrode active material, 10-20% of conductive agent and 10-20% of binder respectively, with the total of mass percentage being 100%, adding an appropriate amount of dispersant to form a slurry, grinding uniformly until the slurry is bright, then evenly coating on the aluminum foil, drying, cutting to obtain the positive electrode sheet.

[0020] Preferably, the positive electrode active material is one or a combination of several of sodium vanadium phosphate, sodium vanadium fluoride, sodium iron pyrophosphate, sodium iron sulfate, sodium copper iron manganese acid, sodium nickel iron manganese acid; the conductive agent is one or a combination of several of acetylene black, Super P Li, Ketjen black, carbon nanotube; the binder is one or a combination of several of PVDF, PTFE, polyacrylic acid, styrene-butadiene rubber, polyethylene oxide, sodium carboxymethyl cellulose, alginate; the dispersant is one or a combination of several of 1-methyl-2-pyrrolidone, dimethyl sulfoxide, N-N-dimethylformamide, N-N-dimethylacetamide, acetone, anhydrous ethanol, water; the electrolyte is a soluble salt organic solution; the separator is a composite separator of one or several of polyethylene, polypropylene microporous membrane, glass fiber separator, polyacrylonitrile separator.

[0021] The operating temperature of the cold rolling in the application is room temperature.

[0022] The preparation principle of the composite sodium metal negative electrode sheet in the application is: MX+Na→NaM+NaX (MX represents metal halide, NaM represents sodium-M alloy, M is Sn, In, Bi or Zn, and X is F, Cl, Br or I), the chemical property of metal Na is active, can spontaneously react with metal halide to form sodium-M alloy and sodium halide, which can improve the affinity of sodium ions, adjust the deposition of sodium ions, and at the same time can improve the processability of the composite sodium metal negative electrode sheet.

[0023] Beneficial effects:

[0024] (1) The application utilizes the spontaneous reaction between metal sodium and metal halide to prepare a composite sodium metal negative electrode sheet by a simple repeated cold rolling folding method of sodium foil and metal halide powder, which produces abundant and fresh sodium halide and sodium-M alloy in the process, the sodium-M alloy can adjust the deposition of Na + , and improve the affinity of Na + , while the sodium halide has high mechanical strength and is an effective Na +The high ionic conductivity of the conductor and stabilizer, sodium halide, can realize fast ion transmission and good rate performance on the whole negative sheet, and the low electronic conductivity further inhibits dendrite growth; the synergistic effect of both can not only inhibit the side reaction between the sodium metal negative electrode and the electrolyte and the growth of sodium dendrites, but also promote the fast transmission of Na + Compared with soft and viscous metal sodium, the composite sodium metal negative sheet has higher formability;

[0025] (2) The sodium-M alloy and sodium halide in-situ formed in the present application are uniformly implanted into the metal sodium, the thickness of the composite sodium metal negative sheet can be accurately controlled by adjusting the distance between the two rollers of the cold rolling mill, and different molds can be used to cut various shapes according to actual needs in the later stage, so that the composite sodium metal negative sheet has excellent processing performance;

[0026] (3) The button-type full battery assembled with the composite sodium metal negative sheet provides a high capacity of 108.9 mAh g -1 at 1 C, and a capacity retention rate of up to 97.2% in 300 cycles, showing excellent rate performance; the soft package full battery assembled provides a high capacity of 94.87 mAh g -1 at 1 C and a high capacity retention rate of 95.04%;

[0027] (4) The present application improves the sodium ion deposition kinetics and electrochemical performance, provides a novel alloy strategy for Na metal chemical modification, promotes the commercial development of sodium metal batteries, and shows high technical application value. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 : The preparation flowchart of the NSF composite sodium metal negative sheet in Example 1 of the present application.

[0029] Figure 2 : The XRD spectrum of the NSF composite sodium metal negative sheet prepared in Example 1 of the present application.

[0030] Figure 3 : The influence of different metal halide ratios on battery performance: (a) EIS diagram of NSF|NSF and Na|Na symmetrical batteries under different ratios; (b) deposition / dissolution curves of NSF|NSF and Na|Na symmetrical batteries under different ratios at a current density of 1 mA cm -2 .

[0031] Figure 4 : The cycle performance comparison diagram of the NVP|NSF and NVP|Na button-type full batteries assembled in Example 1 of the present application at 1 C.

[0032] Figure 5Comparison of rate capacity of NVP|NSF and NVP|Na coin cells assembled in Embodiment 1 of this invention.

[0033] Figure 6 Charge-discharge curves of the NVP|NSF button cell assembled in Embodiment 1 of the present invention under different cycle numbers.

[0034] Figure 7 Cycling performance at 1C of the NVP|NSF soft-pack full cell assembled in Embodiment 1 of the present invention. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] Na / Na 15 The preparation steps of Sn4 / NaF (NSF) composite sodium metal anode are as follows:

[0038] (1) After drying SnF2 powder in a 60℃ forced-air drying oven for 48 hours, transfer it to an argon glove box (H2O<0.1ppm, O2<0.1ppm). At the same time, prepare two sodium foils according to the mass ratio of SnF2 powder: two sodium foils = 40:100. The two sodium foils have the same shape and size.

[0039] (2) In an argon glove box, such as Figure 1 As shown (where the composite network refers to the sodium-Sn alloy Na), 15 A composite of Sn4 and sodium fluoride (NaF) is formed by stacking dried SnF2 powder and two sodium foils together to form a Na-SnF2-Na "sandwich" structure. The sandwich is then pressed together mechanically using a roll press (cold rolling), folded in half, and cold rolled again. This process of cold rolling → folding → cold rolling is repeated to obtain a composite foil with a thickness of 50 μm. During this process, the thickness of the composite foil is changed by adjusting the distance between the two rolls of the roll press.

[0040] (3) The obtained composite foil is punched into an electrode sheet with a diameter of 12 mm using a stamping machine. This is the target composite sodium metal negative electrode sheet, marked as NSF, for structural characterization and electrochemical testing.

[0041] Example 2

[0042] The difference from Example 1 is that in step (1), the mass ratio of SnF2 powder and two pieces of sodium foil is changed to SnF2 powder: two pieces of sodium foil = 20:100; and the others are the same as in Example 1.

[0043] Example 3

[0044] The difference from Example 1 is that in step (1), the mass ratio of SnF2 powder and two pieces of sodium foil is changed to SnF2 powder: two pieces of sodium foil = 60:100; and the others are the same as in Example 1.

[0045] Example 4

[0046] The difference from Example 1 is that SnCl2 powder is used instead of SnF2 powder.

[0047] The composite sodium metal negative electrode sheet prepared in this example is Na / Na 15 Sn4 / NaCl (NSC).

[0048] Example 5

[0049] The difference from Example 1 is that SnBr2 powder is used instead of SnF2 powder.

[0050] The composite sodium metal negative electrode sheet prepared in this example is Na / Na 15 Sn4 / NaBr (NSB).

[0051] Example 6

[0052] The difference from Example 1 is that SnI2 powder is used instead of SnF2 powder.

[0053] The composite sodium metal negative electrode sheet prepared in this example is Na / Na 15 Sn4 / NaI (NSI).

[0054] Product structure characterization

[0055] The NSF composite sodium metal negative electrode sheet prepared in Example 1 of the application is subjected to XRD phase characterization, and the results are shown in Figure 2 As can be seen from Figure 2 Na and SnF2 are successfully converted into Na 15 Sn4 and NaF, and at the same time, due to the stoichiometric excess of metallic sodium, strong diffraction peaks of metallic sodium are still observed in the XRD spectrum of NSF, indicating the synthesis of NSF.

[0056] Product performance characterization

[0057] (1) Effect of different metal halide ratios on battery performance

[0058] The NSF composite sodium metal negative electrode sheet prepared in embodiments 1-3 of the present application was used to assemble NSF|NSF symmetric batteries (button type): in an argon glove box, the NSF composite sodium metal negative electrode sheet was placed in the positive electrode shell, 55 μL of electrolyte was added, then the separator was added, 55 μL of electrolyte was added again, then the NSF composite sodium metal negative electrode sheet was placed on the separator, and finally the foam nickel and negative electrode shell were placed, and the entire battery was pressed; the electrolyte was a 1M NaClO4 organic solution, the solvent was a mixed solvent of EC (ethylene carbonate) and PC (propylene carbonate) in a volume ratio of 1:1, and 5 wt% FEC (fluoroethylene carbonate) was added to the mixed solvent; the separator was a glass fiber separator.

[0059] A Na|Na symmetric battery (button type) was assembled according to the above process using a pure sodium sheet instead of the NSF composite sodium metal negative electrode sheet as a control battery.

[0060] Figure 3 The effects of different metal halide ratios on battery performance: (a) EIS plots of NSF|NSF and Na|Na symmetric batteries at different ratios; (b) deposition / dissolution curves of NSF|NSF and Na|Na symmetric batteries at 1 mA cm -2 current density; in the figure, 20% NSF, 40% NSF, and 60% NSF correspond to NSF|NSF symmetric batteries assembled using NSF composite sodium metal negative electrode sheets obtained in embodiments 2, 1, and 3, respectively, and Na corresponds to a Na|Na symmetric battery assembled using a pure sodium sheet. Figure 3 a shows that the interfacial impedance of NSF|NSF symmetric batteries assembled at three ratios of 20% NSF, 40% NSF, and 60% NSF is 68.1 Ω, 32.78 Ω, and 71.1 Ω, respectively, all of which exhibit smaller interfacial impedance than the Na|Na symmetric battery (125.7 Ω), and the interfacial impedance of the NSF|NSF symmetric battery assembled at a ratio of 40% NSF is the smallest (32.78 Ω). Figure 3 b shows that at 1 mA cm -2The Na|Na symmetric battery shows the maximum overpotential (0.12 V) at a current density of 0.1 mA / cm2, and a short circuit phenomenon occurs after 125 h; the NSF|NSF symmetric batteries with three mass ratios of 20% NSF, 40% NSF and 60% NSF all show lower charge-discharge overpotential of 0.10 V, 0.05 V and 0.08 V, wherein the NSF|NSF symmetric battery with a mass ratio of 40% NSF shows the lowest cycle overpotential (0.05 V) and can stably charge and discharge for more than 400 h. In summary, the impedance and polarization voltage of the NSF|NSF symmetric batteries with three mass ratios (20% NSF, 40% NSF and 60% NSF) are all smaller than those of the Na|Na, indicating the superiority of the NSF negative electrode. The mass ratio of 40% NSF has the smallest impedance, the lowest polarization voltage and the longest cycle life, and shows the best cycle stability.

[0061] (II) Full battery performance test

[0062] The NSF composite sodium metal negative electrode sheet prepared in Example 1 of the present application is used for the assembly of NVP|NSF button-type full battery: in an argon glove box, the NVP positive electrode sheet is placed in the positive electrode shell, 55 μL of electrolyte is added, then the separator is added, 55 μL of electrolyte is added again, then the NSF composite sodium metal negative electrode sheet is placed on the separator, and finally the foam nickel and the negative electrode shell are placed, and the whole battery is pressed; the electrolyte is a 1M NaClO4 organic solution, the solvent is a mixed solvent of EC (ethylene carbonate) and PC (propylene carbonate) in a volume ratio of 1:1, and 5 wt% of FEC (fluoroethylene carbonate) is added to the mixed solvent; the separator is a glass fiber separator; the NVP positive electrode sheet is prepared according to the following process: according to a mass ratio of 8:1:1, the positive electrode active material, the conductive agent and the binder are weighed, an appropriate amount of dispersant is added to form a slurry, the slurry is ground uniformly until it is bright, then it is evenly coated on an aluminum foil and placed in a 60°C air drying oven for 6 h, a mold with a diameter of 13 mm is selected for cutting, and the NVP positive electrode sheet is obtained; wherein the positive electrode active material is sodium vanadium phosphate (NVP), the conductive agent is conductive carbon black (Super PLi), the binder is polyvinylidene fluoride, and the dispersant is 1-methyl-2-pyrrolidone.

[0063] A pure sodium sheet is used instead of the NSF composite sodium metal negative electrode sheet to assemble a NVP|Na button-type full battery according to the above process as a control battery.

[0064] The NSF composite sodium metal anode sheet prepared in Example 1 of this invention was used for the assembly of NVP|NSF pouch cells: In an argon-filled glove box, the NSF composite sodium metal anode sheet, 55 μL electrolyte, separator, 55 μL electrolyte, and NVP positive electrode sheet were stacked layer by layer in sequence. The stacked cells were then picked up with plastic tweezers and transferred to two aluminum foils, where the cut tabs were placed. Finally, the cells were sealed using a heat sealer. The NVP positive electrode sheet, electrolyte, and separator were the same as those used in the aforementioned NVP|NSF coin cell.

[0065] Charge-discharge tests were conducted on NVP|NSF coin cells and NVP|Na coin cells at different current densities using a blue electric tester to examine the charge-discharge specific capacity and cycle stability of the coin cells.

[0066] Figure 4 This is a comparison chart of the cycle performance of the NVP|NSF and NVP|Na coin cells assembled in Embodiment 1 of the present invention at 1C. Figure 4 It can be seen that the NVP|NSF coin cell provides 108.9 mAh g at a rate of 1 C in the first cycle. -1 It has a high capacity and provides 107.9 mAh g during the 100th cycle. -1 High capacity, with a capacity of 106.6 mAhg at 200 cycles. -1 The capacity was 105.9 mAh g after the 300th cycle. -1 The capacity retention rate is as high as 97.2%. Furthermore, the capacity-coulombic efficiency curve of the NVP|NSF coin cell remains stable during cycling. In contrast, the NVP|Na coin cell exhibits a much lower capacity and significant capacity decay during cycling, with a capacity of only 66.0 mAh g⁻¹ at 300 cycles. -1 The capacity retention rate is only 65.6%. The coulombic efficiency of the NVP|Na coin cell is not much different from that of the NVP|NSF coin cell.

[0067] Figure 5 This is a comparison chart of the rate capacity of the NVP|NSF and NVP|Na coin cells assembled in Embodiment 1 of the present invention. Figure 5 It can be seen that the NVP|NSF coin cell full cell has a capacity of 100.8 mAh g at the initial 0.1C. -1 At 0.5C, it has a capacity of 94.3 mAh g. -1 At 1C, it has a capacity of 90.0 mAh g. -1 At 2C, it has a capacity of 83.9 mAh g. -1 At 5C, it has a capacity of 76.9 mAh g. -1 At 10C, it is 67.6 mAh g. -1and the capacity at the 50th rate cycle back to 0.1C is 95.3 mAh g -1 , with a capacity retention of 94.5%, indicating that it has good rate performance. In contrast, the capacity of the NVP|Na battery is much lower, especially at high rates, with a capacity of 93.7 mAh g -1 at 0.1C, 84.05 mAh g -1 at 0.5C, 79.3 mAh g -1 at 1C, 74.7 mAh g -1 at 2C, 68.8 mAh g -1 at 5C, and 60.5 mAh g -1 at 10C, with only a capacity retention of 64.5%.

[0068] Figure 6 The charge-discharge curves of the NVP|NSF button full cell assembled in Example 1 of the present application at different cycle numbers. From Figure 6 it can be seen that the cut-off voltage of the 10th and 100th cycles is similar, indicating that this button full cell has good cycle stability.

[0069] Figure 7 The cycle performance of the NVP|NSF soft pack full cell assembled in Example 1 of the present application at 1C. From Figure 7 it can be seen that a high capacity of 94.87 mAh g -1 is provided at 1C in the first cycle, and a high capacity of 90.16 mAh g -1 is provided in the 100th cycle, with stable curves and coulombic efficiency throughout the cycle process, and a capacity retention of up to 95.04%. The inset shows that the assembled full cell can successfully light up a light bulb.

Claims

1. A composite sodium metal anode sheet, characterized by: The composite sodium metal negative electrode sheet is a sodium / sodium-M alloy / sodium halide composite material, and the sodium-M alloy and the sodium halide are uniformly dispersed in the metal sodium phase; wherein the sodium-M alloy is a Na-Sn alloy, a Na-In alloy, a Na-Bi alloy or a Na-Zn alloy, and the sodium halide is NaF, NaCl, NaBr or Nal.

2. The composite sodium metal anode sheet of claim 1, wherein: The thickness of the composite sodium metal negative electrode sheet is 20-500 μm.

3. The method of producing the composite sodium metal negative electrode sheet according to claim 1, characterized by, The preparation steps are as follows: (1) dry the metal halide powder for standby, and prepare two pieces of sodium foil at the same time; the metal halide is a halide of Sn, In, Bi or Zn; (2) in an inert atmosphere glove box, uniformly distribute the dried metal halide powder between the two pieces of sodium foil, stack them together according to the "sandwich" structure of sodium foil-metal halide-sodium foil, cold calendering→folding→cold calendering, repeat the "cold calendering→folding→cold calendering" multiple times, and obtain a composite foil; (3) use a punch to punch the composite foil into an electrode sheet of the required diameter, and obtain the composite sodium metal negative electrode sheet.

4. The method of producing a composite sodium metal negative electrode sheet according to claim 3, characterized by, In step (2), the metal halide powder is added in batches, i.e. the specific process of step (2) is: in an inert atmosphere glove box, take part of the dried metal halide powder, uniformly distribute it between the two pieces of sodium foil, stack them together according to the "sandwich" structure of sodium foil-metal halide-sodium foil, cold calendering→uniformly distribute part of the metal halide powder on the upper sodium foil after cold calendering→folding→cold calendering, repeat the "cold calendering→uniformly distribute part of the metal halide powder on the upper sodium foil after cold calendering→folding→cold calendering" multiple times, and obtain a composite foil.

5. The method of producing a composite sodium metal negative electrode sheet according to claim 3 or 4, characterized by: In the inert atmosphere glove box, H2O <0.1 ppm, O2<0.1 ppm.

6. The method of producing a composite sodium metal negative electrode sheet according to claim 3 or 4, characterized by: In step (1), the drying temperature of the metal halide powder is 60-80°C, and the time is 48-72 h.

7. The method of producing a composite sodium metal negative electrode sheet according to claim 3 or 4, characterized by: In step (1), the mass ratio of the metal halide powder to the two pieces of sodium foil is (5-80):

100.

8. The method of manufacturing a composite sodium metal negative electrode sheet according to claim 7, characterized by: In step (1), the mass ratio of the metal halide powder to the two pieces of sodium foil is (20-60):

100.

9. Use of the composite sodium metal negative electrode sheet according to claim 1 or 2 in a sodium metal battery.

10. Use of the composite sodium metal anode sheet according to claim 9 in a sodium metal battery, characterized by: The sodium metal battery is a button full cell or a soft pack full cell; The assembly process of the button full cell is: in an inert atmosphere glove box, place the positive electrode sheet in the positive electrode shell, add electrolyte, place the separator, add electrolyte again, then place the composite sodium metal negative electrode sheet on the separator, and finally place the foam nickel and the negative electrode shell, and press, to obtain the button full cell; The assembly process of the soft pack full cell is: in an inert atmosphere glove box, stack the NSF composite sodium metal negative electrode sheet-electrolyte-separator-electrolyte-positive electrode sheet in sequence, then transfer to two aluminum foils, place the cut-out tab, and finally use a heat sealing machine for packaging, to obtain the soft pack full cell; The positive electrode sheet is prepared by the following process: taking 70-80% of positive electrode active material, 10-20% of conductive agent and 10-20% of binder by mass percentage, adding appropriate amount of dispersant to form slurry, grinding uniformly until the slurry is bright, then coating uniformly on aluminum foil, drying, cutting to obtain the positive electrode sheet.

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