A cellulose-polyacrylonitrile fiber film of a double-layer configuration, and a preparation method and applications thereof

Abstract

This invention provides a bilayer cellulose@polyacrylonitrile fiber film, its preparation method, and its application. Cotton cellulose is repeatedly washed with distilled water and anhydrous ethanol and thoroughly dried. The cotton is then added to an N,N-dimethylacetamide solution. Under an inert atmosphere, the mixture is stirred and heated for a certain time, then cooled and LiCl is rapidly added. The temperature is maintained and the mixture is stirred to obtain a homogeneous cellulose solution. Polyacrylonitrile is then added to the cellulose solution and stirred to obtain a mixed electrospinning solution. A cellulose@polyacrylonitrile film is then prepared using electrospinning technology. Finally, a pre-oxidation treatment is performed to obtain a bilayer cellulose@polyacrylonitrile fiber film with good thermal stability and mechanical properties. This invention applies the cellulose@polyacrylonitrile fiber film to the application of suppressing lithium polysulfide shuttle in lithium-sulfur batteries, thereby improving the cycle stability of sulfur-loaded Li-S batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-sulfur batteries and relates to a strategy that helps suppress the shuttle of soluble lithium polysulfides and prevent the loss of active materials through a bilayer configuration. Specifically, it relates to a bilayer cellulose@polyacrylonitrile fiber film, its preparation method and application. Background Technology

[0002] The rapid growth of the electric vehicle market has sparked widespread research interest in next-generation batteries to meet the increasing demand for high power performance, high energy density, and long cycle life. Environmentally friendly, low-cost lithium-sulfur (Li-S) batteries boast energy densities as high as 2600 Wh / kg. -1 Its capacity is far greater than that of lithium-ion batteries, making it one of the most promising rechargeable battery systems. However, its cycle stability remains a key obstacle to its commercial application. The culprit behind these problems is the shuttle effect of soluble lithium polysulfides, which leads to the loss of active materials and thus extremely poor cycle stability.

[0003] To address the issue of active material loss in Li-S batteries, numerous efforts have been made, primarily focusing on preparing composite materials of sulfur (S) cathode and conductive materials, such as porous carbon, graphene, carbon nanotubes, and conductive polymers, as well as using metal oxides with extremely high adsorption and catalytic capabilities for polysulfides, such as TiO2, Ti4O7, and Al2O3. Unfortunately, these efforts have resulted in complex cathode structure designs, which undoubtedly hinders the practicality of Li-S batteries. Therefore, developing a novel, multifunctional Li-S battery separator is of great significance for its commercialization. Summary of the Invention

[0004] The purpose of this invention is to provide a bilayer cellulose@polyacrylonitrile fiber film, its preparation method, and its application, in order to overcome the problem of poor cycle stability caused by lithium polysulfide shuttle in the prior art. This invention prepares a bilayer cellulose@polyacrylonitrile fiber film using electrospinning technology and uses it in lithium-sulfur batteries that suppress lithium polysulfide shuttle, thereby improving the cycle stability of the battery.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing a bilayer cellulose@polyacrylonitrile fiber film includes the following steps:

[0007] Step 1: Rinse the cotton cellulose repeatedly with distilled water and anhydrous ethanol, and then dry it thoroughly.

[0008] Step 2: Add the cotton obtained in Step 1 to DMAC, stir and heat it for the first preset time under N2 atmosphere and keep it warm, then cool it to the second preset temperature, add LiCl, and then cool it to the third preset temperature to finally obtain a uniform cellulose solution.

[0009] Step 3: Add polyacrylonitrile to the cellulose solution obtained in Step 2 and stir at a preset temperature to obtain a mixed electrospinning solution;

[0010] Step 4: Prepare cellulose@polyacrylonitrile films by electrospinning the mixed electrospinning solution obtained in Step 3.

[0011] Step 5: The cellulose@polyacrylonitrile film obtained in Step 4 is subjected to pre-oxidation treatment to obtain a bilayer cellulose@polyacrylonitrile fiber film.

[0012] Furthermore, the rinsing and drying in step 1 specifically involves rinsing repeatedly with distilled water and anhydrous ethanol 3-5 times, and then drying at 60°C.

[0013] Furthermore, in step 2, 0.5g of cotton is added to every 100mL of DMAC, and the mass ratio of cotton to LiCl is 1:15.6.

[0014] Furthermore, in step 2, the first preset time is 165℃, the heat preservation time is 30min, the second preset temperature is 100℃, and the third preset temperature is 80℃.

[0015] Furthermore, in step 3, the ratio of the mass of PAN to the mass of cotton in step 2 is 2:1.

[0016] Furthermore, in step 3, the preset temperature is 60℃ and the stirring time is 6h.

[0017] Furthermore, the electrospinning technology in step 4 specifically involves electrospinning at a high voltage of 15 kV and a feed rate of 0.75 mL / min.

[0018] Furthermore, the pre-oxidation treatment conditions in step 5 are: 235℃ under an argon atmosphere for 12 hours.

[0019] A bilayer cellulose@polyacrylonitrile fiber film was prepared using the method described above.

[0020] Application of a bilayer cellulose@polyacrylonitrile fiber film in lithium-sulfur batteries: The bilayer cellulose@polyacrylonitrile fiber film is used as the separator in lithium-sulfur batteries.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] The materials prepared by this invention are inexpensive and abundant. The electrospinning technology used to prepare thin films is relatively mature, easy to implement, and has significant effects, which can greatly improve the long-cycle stability of lithium-sulfur batteries.

[0023] This invention presents a novel strategy for suppressing lithium polysulfide shuttle. It utilizes a cellulose@polyacrylonitrile separator woven from bilayer fibers to inhibit lithium polysulfide shuttle, thereby slowing down the loss of active material and improving battery cycle life. This strategy can achieve a cycle life of ~1.5 mA cm⁻¹. -2 Surface current density, high loading of 9.1 mg S, 6.2 μL mg -1 At the specified electrolyte / S ratio, its areal capacity remains at 4.0 mAh cm⁻¹ after 200 cycles. -2 above.

[0024] Furthermore, this invention uses a bilayer cellulose@polyacrylonitrile fiber film as a separator for lithium-sulfur batteries, thereby suppressing the shuttle of lithium polysulfides and mitigating the loss of active materials, thus improving the cycle stability of the battery. Attached Figure Description

[0025] Figure 1 Here is a SEM image of the cellulose@polyacrylonitrile fiber film prepared according to an embodiment of the present invention;

[0026] Figure 2 This is a TEM image of the cellulose@polyacrylonitrile fiber film prepared in an embodiment of the present invention;

[0027] Figure 3 This is a high-temperature stability test diagram of the cellulose@polyacrylonitrile fiber film prepared in the embodiments of the present invention;

[0028] Figure 4 These are battery performance data graphs obtained from application examples and comparative examples of the present invention. Detailed Implementation

[0029] The embodiments of the present invention will be described in detail below with reference to the examples. These embodiments represent preferred solutions of the present invention and should not be construed as limiting the scope of the invention. Unless otherwise specified, the methods and experimental equipment used in the following embodiments are conventional methods and instruments.

[0030] Example

[0031] Step 1: Wash the cotton cellulose repeatedly with distilled water and anhydrous ethanol 4 times, and then dry it at 60℃;

[0032] Step 2: Add 0.5g of cotton obtained in Step 1 to 100mL of DMAC (Dimethylacetamide, N,N-dimethylacetamide) solution. Under a nitrogen atmosphere, stir and heat to 165℃ for 30min. Then cool to 100℃ and quickly add 7.8g of LiCl. Cool to 80℃ to obtain a homogeneous cellulose solution.

[0033] Step 3: Add 1g of polyacrylonitrile (PAN) to the cellulose solution obtained in step 2 and stir at 60℃ for 6h to obtain a mixed electrospinning solution;

[0034] Step 4: Prepare cellulose@PAN film by electrospinning 5 mL of the electrospinning solution obtained in step 3. Specifically, the electrospinning is carried out at a high voltage of 15 kV and a feed rate of 0.75 ml / min.

[0035] Step 5: The cellulose@PAN film obtained in step 4 is pre-oxidized under an argon atmosphere at a temperature of 235℃ for 12 hours to obtain a bilayer cellulose@polyacrylonitrile fiber film with good thermal stability and mechanical properties.

[0036] The number of rinses in the first step can also be 3 or 5.

[0037] Application examples

[0038] The cellulose@polyacrylonitrile fiber film prepared in the examples directly replaces the traditional commercial PP separator and is used as the separator for lithium-sulfur batteries. This strategy effectively suppresses lithium polysulfide shuttle, thereby ensuring the long-term cycle stability of lithium-sulfur batteries.

[0039] Comparative Example

[0040] A Li-S battery using a commercially available PP separator was used as a comparison sample.

[0041] like Figure 1 and Figure 2 As shown, TEM and SEM analyses reveal that the cellulose@polyacrylonitrile electrospun film is a network structure composed of interwoven fibers with a diameter of approximately several hundred nanometers. This interwoven network structure provides abundant pores, significantly improving wettability to organic electrolytes and offering numerous ion transport pathways, thereby enhancing the rate performance of Li-S batteries. Furthermore, the cellulose@polyacrylonitrile electrospun fibers exhibit a bilayer structure. Figure 3The results showed that commercial PP membranes began to shrink, curl, and deform after being held at 100℃ for 30 minutes. When the temperature reached 150℃, the originally white commercial PP membranes became transparent and melted. However, the cellulose@polyacrylonitrile electrospun membranes did not show obvious deformation, curling, or melting after being held at 100℃ and 150℃ for 30 minutes respectively. Figure 4 For ~1.5mA cm -2 The Li-S battery was subjected to cycle stability testing under conditions of surface current density and 9.1 mg S load. The initial surface discharge capacity of the battery was 5.67 mAh cm⁻¹. -2 After 200 long-cycle cycles, its areal capacity still remains at 4.0 mAh cm⁻¹. -2 That's all. In contrast, commercially available PP membrane Li-S batteries only underwent 100 cycles, and their areal capacity decreased from approximately 4.0 mAh / cm². -2 Rapidly decays to ~0.3mAh cm⁻¹ -2 .

[0042] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing a bilayer cellulose@polyacrylonitrile fiber film, characterized in that, Includes the following steps: Step 1: Rinse the cotton cellulose repeatedly with distilled water and anhydrous ethanol, and then dry it thoroughly. Step 2: Add the cotton obtained in Step 1 to DMAC, stir and heat to the first preset temperature under N2 atmosphere and keep warm, then cool to the second preset temperature, add LiCl, and then cool to the third preset temperature to finally obtain a uniform cellulose solution. Step 3: Add polyacrylonitrile to the cellulose solution obtained in Step 2 and stir at a preset temperature to obtain a mixed electrospinning solution; Step 4: Prepare cellulose@polyacrylonitrile films by electrospinning the mixed electrospinning solution obtained in Step 3. Step 5: The cellulose@polyacrylonitrile film obtained in Step 4 is subjected to pre-oxidation treatment to obtain a bilayer cellulose@polyacrylonitrile fiber film; the bilayer cellulose@polyacrylonitrile fiber film is used as the separator of lithium-sulfur battery. In step 2, 0.5g of cotton is added to every 100 mL of DMAC, and the mass ratio of cotton to LiCl is 1:15.

6. The first preset temperature is 165 ℃, the holding time is 30 min, the second preset temperature is 100 ℃, and the third preset temperature is 80 ℃. In step 4, the electrospinning technology is specifically performed at a high voltage of 15 kV and a feed rate of 0.75 mL / min. In step 5, the pre-oxidation treatment conditions are: under an argon atmosphere, the temperature is 235℃, and the time is 12 h.

2. The method for preparing a bilayer cellulose@polyacrylonitrile fiber film according to claim 1, characterized in that, The specific steps of rinsing and drying in step 1 are as follows: rinse repeatedly with distilled water and anhydrous ethanol 3-5 times, and then dry at 60°C.

3. The method for preparing a bilayer cellulose@polyacrylonitrile fiber film according to claim 1, characterized in that, In step 3, the mass ratio of polyacrylonitrile to cotton in step 2 is 2:

1.

4. The method for preparing a bilayer cellulose@polyacrylonitrile fiber film according to claim 1, characterized in that, The preset temperature in step 3 is 60℃, and the stirring time is 6 hours.

5. A bilayer cellulose@polyacrylonitrile fiber film, characterized in that, It is prepared by the preparation method according to any one of claims 1-4.

6. The application of the bilayer cellulose@polyacrylonitrile fiber film according to claim 5 in lithium-sulfur batteries, characterized in that, A bilayer cellulose@polyacrylonitrile fiber film was used as a separator in a lithium-sulfur battery.

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