Porous lithium-sulfur battery positive electrode material and preparation method thereof, and soft package battery and preparation method thereof

Abstract

The invention belongs to the technical field of lithium-sulfur batteries, and particularly relates to a porous lithium-sulfur battery positive electrode material and a preparation method thereof as well as a soft package battery and a preparation method thereof. The preparation method of the porous lithium-sulfur battery positive electrode material comprises the following steps: adding polyacrylonitrile powder, nitrogen-doped graphene and sulfur powder into a ball milling tank, adding absolute ethyl alcohol for ball milling, taking out the slurry after ball milling, performing vacuum drying, calcining the dried powder for sulfur loading treatment, and grinding the calcined powder to obtain the porous lithium-sulfur battery positive electrode material. S (at) PAN / NGr powder is obtained; and performing porous treatment on the S-coated PAN / NGr powder: dispersing the dried S-coated PAN / NGr powder and PVP (Polyvinyl Pyrrolidone) into DMF (Dimethyl Formamide), stirring and mixing, then putting into deionized water, ultrasonically washing off PVP, and drying in a drying oven to obtain the porous lithium-sulfur battery positive electrode material marked as porous S-coated PAN / NGr. The overall performance and stability of the lithium-sulfur battery can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-sulfur batteries, and particularly relates to a porous lithium-sulfur battery cathode material and a preparation method thereof, as well as a soft-pack battery and a preparation method thereof. Background Art

[0002] Due to its ultra-high theoretical capacity of 1675 mAh / g, the assembled battery has an energy density as high as 2600 Wh / kg, and the lithium-sulfur battery is considered to be the most promising next-generation high-energy density battery. At the same time, the cathode material sulfur of the lithium-sulfur battery has the characteristics of large reserves, low cost, and environmental friendliness, and is one of the most promising cathode materials. Sulfur as the cathode has disadvantages such as poor conductivity, polysulfide shuttle effect, and slow kinetics. Lithium as the anode also has risks of polarization and dendrite formation, and the electrolyte also has safety problems. Therefore, constructing stable anodes, cathodes, and electrolytes is the key to the development of lithium-sulfur soft-pack batteries. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides a porous lithium-sulfur battery cathode material, which can improve the overall performance and stability of the lithium-sulfur battery. The present invention also provides a preparation method of the porous lithium-sulfur battery cathode material, as well as a soft-pack battery and a preparation method thereof.

[0004] The preparation method of the porous lithium-sulfur battery cathode material of the present invention includes the following steps:

[0005] Take polyacrylonitrile powder, nitrogen-doped graphene, and sulfur powder and add them to a ball-milling tank, add absolute ethanol for ball milling, take out the ball-milled slurry, dry it in vacuum, calcine the dried powder for sulfur loading treatment, grind the calcined powder, and obtain S@PAN / NGr powder; perform porous treatment on the S@PAN / NGr powder: disperse the dried S@PAN / NGr powder and PVP in DMF, stir and mix, then put it into deionized water and ultrasonically wash off PVP, and dry it in an oven to obtain the porous lithium-sulfur battery cathode material, denoted as porous S@PAN / NGr.

[0006] Preferably, the mass ratio of polyacrylonitrile, nitrogen-doped graphene, and sulfur powder is (1-2):(1-2):(8-16).

[0007] Preferably, wet ball milling is performed using a planetary ball mill, using agate balls as grinding balls, the ball-to-material mass ratio is (4-6):1, the ball milling speed is 200-600 rpm, and the ball milling time is 6-10 h.

[0008] Preferably, the vacuum drying conditions are 16-24 h at 60-80 °C.

[0009] Preferably, the calcination is carried out in a muffle furnace under an argon or nitrogen atmosphere at 150 - 300 °C for 6 - 10 h, and the heating rate is 2 - 5 °C / min. -1 .

[0010] Preferably, the S@PAN / NGr powder and PVP are dispersed in a DMF solution at a mass ratio of (1 - 4):1.

[0011] The present invention also provides a porous lithium - sulfur battery cathode material prepared by the above - mentioned preparation method.

[0012] The preparation method of the soft - package battery according to the present invention includes the following steps:

[0013] Coat the above - mentioned porous lithium - sulfur battery cathode material, cathode conductive agent, and cathode binder onto an aluminum foil to obtain a cathode sheet, coat the anode material, anode conductive agent, and anode binder onto a copper foil to obtain an anode sheet, roll - press the anode sheet and a lithium foil for pre - lithium supplementation, and then assemble a lithium - sulfur soft - package battery with the cathode sheet, anode sheet, PP separator, and electrolyte in a drying room.

[0014] Preferably, the cathode conductive agent is one of Super P carbon, Ketjen black, and acetylene black; the cathode binder is one of PVDF5130, sodium alginate, sodium carboxymethylcellulose, and polyacrylamide.

[0015] Preferably, the anode material is one of graphene, silicon - carbon, silicon - oxygen - carbon, and vapor - deposited silicon - carbon; the anode conductive agent is Super P carbon or aqueous carbon nanotubes; the anode binder is styrene - butadiene rubber or sodium carboxymethylcellulose.

[0016] Preferably, the thickness of the lithium foil is 5 μm - 20 mm; for pre - lithium supplementation roll - pressing, a roll - press machine is used, and the roll - press gap of the roll - press machine is set to 170 - 200 μm, and the roll - press speed is set to 5 - 10 mm / s.

[0017] The present invention also provides a soft - package battery prepared by the above - mentioned preparation method.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. Based on the problem of poor sulfur conductivity of polyacrylonitrile, the present invention prepares a composite material of polyacrylonitrile and graphene, effectively improving the overall conductivity of the material and greatly enhancing its rate performance;

[0020] 2. The nitrogen-doped graphene of the present invention has a network structure, nanopores and rich defects, which greatly improves the conductivity of the cathode material. By designing a suitable pore structure, polysulfides can be physically restricted, thereby reducing the volume expansion of sulfur. The porous structure has a high specific surface area, effectively alleviating the shuttle effect. Porous S@PAN / NGr as the cathode material of a lithium-sulfur battery can improve the electron and ion transport conditions inside the lithium-sulfur battery, alleviate volume expansion, inhibit the shuttle effect, and improve the overall performance and stability of the lithium-sulfur battery;

[0021] 3. The preparation of a soft-pack battery with porous S@PAN / NGr requires prelithiation. The present invention adopts a simple in-situ lithiation method. During the assembly of the soft-pack battery, a thin lithium foil is attached to the surface of the negative electrode. When the battery is assembled, the anode can be spontaneously lithiated; when the thin lithium foil is attached to the negative electrode sheet, the soft-pack battery should be discharged first. During the first discharge process, the porous S@PAN / NGr cathode undergoes the first lithiation, and some Li + is irreversibly consumed in the cathode and shows an increase in the voltage plateau during subsequent cycles. Detailed Embodiments

[0022] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments.

[0023] All raw materials used in the embodiments are commercially available unless otherwise specified. The nitrogen content in the nitrogen-doped graphene is 20%; the electrolyte in the soft-pack battery uses the MJS-LiS-01 electrolyte of Nanjing Mojiesi Energy Technology Co., Ltd., and the lithium foil is purchased from Tianjin Zhongneng Lithium Industry Co., Ltd.

[0024] Example 1

[0025] The preparation method of the porous lithium-sulfur battery cathode material includes the following steps:

[0026] Take 0.2 g of polyacrylonitrile powder, 0.2 g of nitrogen-doped graphene, and 1.6 g of sulfur powder and add them to the ball milling tank of a planetary ball mill. Add 15 mL of absolute ethanol for wet ball milling. Use agate balls as grinding balls, with a ball-to-material mass ratio of 4:1, a ball milling speed of 200 rpm, and a ball milling time of 10 h. Take out the ball-milled slurry and dry it in vacuo at 60 °C for 24 h. Place the dried powder in a muffle furnace and calcine it at 150 °C for 10 h in an inert gas argon atmosphere, with a heating rate of 5 °C / min -1 , and then cool it to 25 °C at a cooling rate of 5 °C / min -1, grind the calcined powder to obtain S@PAN / NGr powder; perform porous treatment on the S@PAN / NGr powder: disperse the dried S@PAN / NGr powder and PVP in a mass ratio of 2:1 into 50 mL of DMF, stir and mix for 16 h, then put it into deionized water and ultrasonically wash for 2 h to remove PVP, and dry it in an oven at 60 °C to obtain the porous lithium-sulfur battery cathode material, denoted as porous S@PAN / NGr.

[0027] The preparation method of the soft-pack battery includes the following steps:

[0028] Make a slurry by mixing porous S@PAN / NGr, the cathode conductive agent Ketjenblack (Shenzhen Kejing Zhida Technology Co., Ltd., ECP-600JD), and the cathode binder PVDF5130 in a mass ratio of 8:1:1. Coat the slurry on aluminum foil and dry it in an oven at 70 °C to obtain a positive electrode sheet. Make a slurry by mixing the anode material graphene, the anode conductive agent Super P carbon (Timcal, battery grade), and the anode binder sodium carboxymethyl cellulose (Sinopharm Chemical Reagent Co., Ltd., viscosity 600 - 3000 mPa·s) in a mass ratio of 96:1:3. Coat the slurry on copper foil to obtain a negative electrode sheet. Roll the negative electrode sheet and a 5-mm-thick thin lithium foil with a rolling press for pre-lithiation. The rolling gap of the rolling press is set to 175 μm, and the rolling speed is set to 5 mm / s. Then assemble a lithium-sulfur soft-pack battery with the positive electrode sheet, negative electrode sheet, PP separator, and electrolyte in a dry room.

[0029] Example 2

[0030] The preparation method of the porous lithium-sulfur battery cathode material includes the following steps:

[0031] Take 0.2 g of polyacrylonitrile powder, 0.4 g of nitrogen-doped graphene, and 1.6 g of sulfur powder and add them to the ball mill jar of a planetary ball mill. Add 25 mL of anhydrous ethanol for wet ball milling. Use agate balls as grinding balls, with a ball-to-material mass ratio of 5:1, a ball milling speed of 300 rpm, and a ball milling time of 8 h. Take out the ball-milled slurry and dry it in vacuo at 70 °C for 24 h. Place the dried powder in a muffle furnace and calcine it at 200 °C for 8 h in an inert gas argon atmosphere, with a heating rate of 4 °C / min -1 , then cool it to 25 °C, with a cooling rate of 5 °C / min -1 , grind the calcined powder to obtain S@PAN / NGr powder; perform porous treatment on the S@PAN / NGr powder: disperse the dried S@PAN / NGr powder and PVP in a mass ratio of 1:1 into 50 mL of DMF, stir and mix for 16 h, then put it into deionized water and ultrasonically wash for 2 h to remove PVP, and dry it in an oven at 60 °C to obtain the porous lithium-sulfur battery cathode material, denoted as porous S@PAN / NGr.

[0032] The preparation method of the soft-pack battery includes the following steps:

[0033] Mix porous S@PAN / NGr, positive electrode conductive agent Super P carbon (Timcal, battery grade), and positive electrode binder polyacrylamide (Sinopharm Chemical Reagent Co., Ltd., analytical pure) in a mass ratio of 6:2:1 to form a slurry. Coat the slurry onto aluminum foil and dry it in an oven at 70°C to obtain a positive electrode sheet. Mix negative electrode material silicon carbide (BTR New Materials Group Co., Ltd., SiC-600), negative electrode conductive agent aqueous carbon nanotubes (Qingdao Huagao Graphene Technology Co., Ltd., HGFS05), and negative electrode binder styrene-butadiene latex (Shenzhen Kejing Zhida Technology Co., Ltd., MS-SBR-S2919) in a mass ratio of 96:1:3 to form a slurry. Coat the slurry onto copper foil to obtain a negative electrode sheet. Roll the negative electrode sheet and a 100-μm-thick thin lithium foil with a roll press for pre-lithiation. The roll press gap is set to 185 μm, and the roll press speed is set to 8 mm / s. Then assemble the positive electrode sheet, negative electrode sheet, PP separator, and electrolyte in a drying room to form a lithium-sulfur soft-pack battery.

[0034] Example 3

[0035] The preparation method of the porous lithium-sulfur battery positive electrode material includes the following steps:

[0036] Take 0.4 g of polyacrylonitrile powder, 0.4 g of nitrogen-doped graphene, and 1.6 g of sulfur powder and add them to the ball milling tank of a planetary ball mill. Add 30 mL of absolute ethanol for wet ball milling. Use agate balls as grinding balls. The ball-to-material mass ratio is 6:1, the ball milling speed is 500 rpm, and the ball milling time is 6 h. Take out the ball-milled slurry and dry it in a vacuum at 80°C for 24 h. Place the dried powder in a muffle furnace and calcine it at 300°C for 6 h in an inert gas argon atmosphere with a heating rate of 3°C / min -1 , and then cool it to 25°C with a cooling rate of 5°C / min -1 , grind the calcined powder to obtain S@PAN / NGr powder; perform porous treatment on the S@PAN / NGr powder: Disperse the dried S@PAN / NGr powder and PVP in a mass ratio of 3:1 into 50 mL of DMF and stir and mix for 16 h, then put it into deionized water and ultrasonically wash it for 2 h to remove PVP, and dry it in an oven at 60°C to obtain the porous lithium-sulfur battery positive electrode material, denoted as porous S@PAN / NGr.

[0037] The preparation method of the soft-pack battery includes the following steps:

[0038] The porous S@PAN / NGr, the positive electrode conductive agent acetylene black (Timcal, battery grade), and the positive electrode binder sodium alginate (Sinopharm Chemical Reagent Co., Ltd., analytical pure) are made into a slurry according to a mass ratio of 7:2:1. The slurry is coated on an aluminum foil and dried in an oven at 70 °C to obtain a positive electrode sheet. The negative electrode material silicon oxycarbide (BTR New Materials Group Co., Ltd., BSO-1), the negative electrode conductive agent aqueous carbon nanotubes (Qingdao Huagao Graphene Technology Co., Ltd., HGFS05), and the negative electrode binder styrene-butadiene latex (Shenzhen Kejing Zhida Technology Co., Ltd., MS-SBR-S2919) are made into a slurry according to a mass ratio of 96:1:3. The slurry is coated on a copper foil to obtain a negative electrode sheet. The negative electrode sheet and a 20-mm-thick thin lithium foil are roll-pressed by a roll press for pre-lithiation. The roll-pressing gap of the roll press is set to 195 μm, and the roll-pressing speed is set to 10 mm / s. Then, the positive electrode sheet, the negative electrode sheet, the PP separator, and the electrolyte are assembled into a lithium-sulfur soft-pack battery in a drying room.

[0039] Example 4

[0040] The preparation method of the porous lithium-sulfur battery positive electrode material includes the following steps:

[0041] Take 0.4 g of polyacrylonitrile powder, 0.2 g of nitrogen-doped graphene, and 1.6 g of sulfur powder and add them to the ball-milling tank of a planetary ball mill. Add 25 mL of absolute ethanol for wet ball milling. Use agate balls as grinding balls. The ball-to-material mass ratio is 4:1. The ball-milling speed is 400 rpm, and the ball-milling time is 8 h. Take out the ball-milled slurry and dry it in a vacuum at 80 °C for 24 h. Place the dried powder in a muffle furnace and calcine it at 250 °C for 8 h in an inert gas argon atmosphere. The heating rate is 2 °C / min -1 , and then cool it to 25 °C. The cooling rate is 5 °C / min -1 , grind the calcined powder to obtain S@PAN / NGr powder; perform porous treatment on the S@PAN / NGr powder: disperse the dried S@PAN / NGr powder and PVP in a mass ratio of 4:1 into 50 mL of DMF, stir and mix for 16 h, then put it into deionized water and ultrasonically wash for 2 h to remove PVP, and dry it in an oven at 60 °C to obtain the porous lithium-sulfur battery positive electrode material, denoted as porous S@PAN / NGr.

[0042] The preparation method of the soft-pack battery includes the following steps:

[0043] The porous S@PAN / NGr, the positive electrode conductive agent Super P carbon (Timcal, battery grade), and the positive electrode binder sodium carboxymethylcellulose (Sinopharm Chemical Reagent Co., Ltd., viscosity 600 - 3000 mPa·s) were made into a slurry according to a mass ratio of 8:1:2. The slurry was coated on an aluminum foil and dried in an oven at 70 °C to obtain a positive electrode sheet. The negative electrode material, vapor deposition silicon carbon, the negative electrode conductive agent Super P carbon (Timcal, battery grade), and the negative electrode binder sodium carboxymethylcellulose (Sinopharm Chemical Reagent Co., Ltd., viscosity 600 - 3000 mPa·s) were made into a slurry according to a mass ratio of 96:1:3. The slurry was coated on a copper foil to obtain a negative electrode sheet. The negative electrode sheet and a 20-μm-thick thin lithium foil were roll-pressed by a roll press to pre-lithiate. The roll-press gap was set to 185 μm and the roll-press speed was set to 6 mm / s. Then, the positive electrode sheet, the negative electrode sheet, the PP separator, and the electrolyte were assembled into a lithium-sulfur soft-pack battery in a drying room.

[0044] Comparative Example 1

[0045] The difference between this Comparative Example 1 and Example 1 is only that in the preparation of the positive electrode material of the porous lithium-sulfur battery, wet ball milling is not carried out in the planetary ball mill, but dry ball milling is directly carried out, that is, ethanol is not added.

[0046] Comparative Example 2

[0047] The difference between this Comparative Example 2 and Example 1 is only that in the preparation of the positive electrode material of the porous lithium-sulfur battery, the nitrogen-doped graphene is replaced with pure graphene (Qingdao Huagao Graphene Technology Co., Ltd., analytical pure) having the same mass as the graphene component in the nitrogen-doped graphene, and the obtained battery positive electrode material is denoted as S@PAN / Gr.

[0048] Comparative Example 3

[0049] The difference between this Comparative Example 3 and Example 1 is only that the S@PAN / NGr powder is used as the positive electrode material to prepare a soft-pack battery without being porous-treated.

[0050] Comparative Example 4

[0051] The difference between this Comparative Example 4 and Example 2 is only that in the preparation of the soft-pack battery, the negative electrode sheet and the thin lithium foil are not roll-pressed, but directly attached.

[0052] Performance Test

[0053] The soft-pack batteries of Examples 1 - 4 and Comparative Examples 1 - 4 were subjected to charge and discharge tests at a current of 0.1C.

[0054] The positive electrodes in Example 1, Comparative Example 2, and Comparative Example 3 were subjected to AC impedance tests, and the results are shown in Table 1. The batteries of Examples 1-4 and Comparative Examples 1-4 were charged and discharged, and the discharge capacities and capacity retention rates after 100 cycles are shown in Table 2.

[0055] Table 1 Impedance Table of the Cathode Materials in Example 1, Comparative Example 2, and Comparative Example 3

[0056] Example Cathode material Impedance / Ω Example 1 Porous S@PAN / NGr 35.5 Comparative Example 2 S@PAN / Gr 60 Comparative Example 3 S@PAN / NGr 45

[0057] As can be seen from Table 1, the impedance of porous S@PAN / NGr is the smallest, that of S@PAN / NGr is the second, and that of S@PAN / Gr is the largest. This is because the introduction of nitrogen atoms in porous S@PAN / NGr breaks the original electronic structure of graphene, improving the carrier mobility and thus significantly enhancing the conductivity of porous S@PAN / NG. While S@PAN / NGr has a low sulfur loading, sluggish redox reaction kinetics, and a relatively weak active material loading capacity, resulting in an impedance slightly worse than that of porous S@PAN / NGr.

[0058] Table 2 Test Results of the Discharge Specific Capacity and Capacity Retention Rate of Examples 1-4 and Comparative Examples 1-4

[0059]

[0060] As can be seen from Table 2, the discharge capacity and capacity retention rate of Comparative Example 1 after 100 cycles are both lower than those of Example 1. This is because wet ball milling with ethanol results in fine and uniform grinding particle size and less environmental pollution to the workplace. Ethanol, as a ball milling medium, has a cooling effect and can effectively reduce the heat generated during grinding, thus avoiding property changes of the material due to high temperature. In addition, the fluidity of ethanol helps the material to be evenly stressed during grinding, thereby improving the grinding efficiency. During wet ball milling, ethanol can help the material to disperse better, and the addition of ethanol helps to prevent agglomeration between particles, resulting in a finer and more uniform final product. Wet ball milling can maintain the low temperature state of the material during grinding and effectively improve the dispersibility of the material. Therefore, the final product usually has a finer particle distribution and higher material properties, which is beneficial to the cycle stability of the soft-pack battery.

[0061] The discharge capacity and capacity retention rate of Comparative Example 2 after 100 cycles are both lower than those of Example 1. This is because porous S@PAN / NGr has enhanced adsorption ability, and nitrogen doping can provide lone pair electrons to form dipole-dipole (S xThe (Li-N bond) interaction significantly enhances the adsorption of sulfur species on the graphene substrate, inhibits the dissolution of polysulfides, reduces the loss of active materials, achieves higher specific capacity and Coulombic efficiency, and inhibits the shuttle effect. Nitrogen-doped graphene improves the conductivity of the cathode material, enabling rapid transfer of lithium ions and electrons, reducing the lithium ion diffusion barrier, and improving the rate performance of the soft-pack battery. Nitrogen doping can also improve the chemical stability of graphene, enhancing its adaptability and durability to chemical reactions.

[0062] After 100 cycles, both the discharge capacity and capacity retention rate of Comparative Example 3 are lower than those of Example 1. Due to the different dissolution degrees of PVP and PAN in water and DMF, a large number of micropores are created in PAN. The porous structure is beneficial for the storage and penetration of the lithium-sulfur electrolyte and provides a more efficient Li + transport channel. The design of the porous structure helps reduce the volume change of the electrode material, maintain the stability of the electrode structure, and thus improve the conductivity of electrons and ions. This helps enhance the charge-discharge performance of the battery. The porous structure can provide sufficient space to accommodate the significant volume expansion of the sulfur electrode during discharge, relieve the volume expansion, reduce the mechanical degradation of the electrode material, and thereby extend the cycle life of the battery. The porous structure can also inhibit the shuttle effect of polysulfides, improve the energy density and cycle stability, providing strong support for the commercial application of lithium-sulfur batteries.

[0063] After 100 cycles, both the discharge capacity and capacity retention rate of Comparative Example 4 are lower than those of Example 2. This is because by rolling an uncompacted anode with an ultra-thin lithium foil under a roll press, the lithium metal contacts the anode active material layer to achieve prelithiation. This can effectively avoid problems such as anode deformation and incomplete transfer of metallic lithium, improving the cycle life and safety of the battery. While directly attaching a lithium foil to the surface of the anode can avoid the graphite peeling phenomenon, improve the stability of the SEI film on the anode surface, improve the cycle performance of the battery, and rapidly enhance the first charge-discharge performance of the anode.

Claims

1. A method for preparing a porous lithium-sulfur battery positive electrode material, characterized in that: The following steps are involved: Take polyacrylonitrile powder, nitrogen-doped graphene and sulfur powder and add them to a ball mill, add anhydrous ethanol for ball milling, take out the slurry after ball milling, vacuum dry, calcine the dried powder, grind the calcined powder to obtain S@PAN / NGr powder; perform porous treatment on the S@PAN / NGr powder: disperse the dried S@PAN / NGr powder and PVP in DMF, stir and mix, then put them into deionized water to ultrasonically wash off PVP, and dry them in an oven to obtain.

2. The method for preparing a porous lithium-sulfur battery positive electrode material according to claim 1, characterized in that: The mass ratio of polyacrylonitrile, nitrogen-doped graphene and sulfur powder is (1-2):(1-2):(8-16).

3. The method for preparing a porous lithium-sulfur battery positive electrode material according to claim 1, characterized in that: Calcination: Calcine in a muffle furnace under argon or nitrogen atmosphere at 150-300℃ for 6-10h, with a heating rate of 2-5℃min -1 .

4. The method for preparing a porous lithium-sulfur battery positive electrode material according to claim 1, characterized in that: S@PAN / NGr powder and PVP were dispersed into DMF solution in a mass ratio of (1-4):

1.

5. A porous lithium-sulfur battery positive electrode material prepared by the preparation method according to any one of claims 1 to 4.

6. A method for preparing a soft-pack battery, characterized in that: The steps include: The porous lithium-sulfur battery positive electrode material, positive electrode conductive agent, and positive electrode binder described in claim 5 are coated on aluminum foil to obtain a positive electrode sheet, and the negative electrode material, negative electrode conductive agent, and negative electrode binder are coated on copper foil to obtain a negative electrode sheet. The negative electrode sheet and lithium foil are rolled to pre-supplement lithium, and then the positive electrode sheet, negative electrode sheet, PP separator, and electrolyte are assembled into a lithium-sulfur soft-pack battery in a drying room.

7. The method for preparing a soft pack battery according to claim 6, characterized in that: The positive electrode conductive agent is one of Super P carbon, Ketjen black, and acetylene black; the positive electrode binder is one of PVDF5130, sodium alginate, sodium carboxymethyl cellulose, and polyacrylamide.

8. The method for preparing a soft pack battery according to claim 6, characterized in that: The negative electrode material is one of graphene, silicon carbon, silicon oxygen carbon, and vapor deposited silicon carbon; the negative electrode conductive agent is Super P carbon or water-based carbon nanotubes; and the negative electrode binder is styrene-butadiene rubber or sodium carboxymethyl cellulose.

9. The method for preparing a soft-pack battery according to claim 6, characterized in that: The thickness of the lithium foil is 5 μm-20 mm; the pre-lithium filling rolling is performed using a roller press, the roller press gap is set to 170-200 μm, and the roller press speed is set to 5-10 mm / s.

10. A soft-pack battery prepared by the preparation method according to any one of claims 6 to 9.

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