Lithium battery diaphragm prepared by utilizing retired photovoltaic back plate and preparation method of lithium battery diaphragm

Abstract

The invention relates to the technical field of preparation of lithium battery diaphragms, in particular to a lithium battery diaphragm prepared from a decommissioned photovoltaic backboard and a preparation method of the lithium battery diaphragm, and the preparation method specifically comprises the following steps: firstly, obtaining a main component polyethylene terephthalate material of the decommissioned photovoltaic backboard; a mixed solvent of dichloromethane and trifluoroacetic acid is used for dissolving a polyethylene terephthalate material, polyoxyethylene is further dissolved, a hydrogen bond type polymer network is formed, and the performance of the diaphragm is optimized by subsequently controlling relevant parameters of electrostatic spinning voltage and flow velocity. According to the method, high-valued utilization of the retired photovoltaic back plate is realized, the performance of the diaphragm is improved, a new way is provided for preparation of the lithium battery diaphragm, and cyclic utilization and sustainable development of photovoltaic industry resources are promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery diaphragm preparation, and in particular to a lithium battery diaphragm prepared using retired photovoltaic backboards and a preparation method thereof. Background Art

[0002] With the rapid development of the photovoltaic industry, the number of retired photovoltaic backsheets is increasing, and their recycling has become a pressing issue. Furthermore, existing lithium battery separator manufacturing technology primarily relies on new materials, which are costly and require significant improvements in mechanical strength, thermal stability, and ionic conductivity.

[0003] The current technological gaps are mainly reflected in the following: after about 25 years of outdoor service, the retired backsheet undergoes severe photo-oxidation aging due to ultraviolet radiation and humid and hot environment, resulting in molecular chain breakage and decreased crystallinity, resulting in insufficient melt strength of the recycled material, making it difficult to achieve both mechanical and electrochemical properties of the recycled PET separator, which has become the core bottleneck restricting its industrial application. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a high-performance lithium battery separator prepared using retired photovoltaic backplanes and a preparation method thereof. The new rPET / PEO composite electrospinning process developed in the present invention has opened up a new technical path for the preparation of high-performance separators. This process combines unique material composites with electrospinning technology to construct an rPET-PEO hydrogen bond interpenetrating network, overcoming the many technical bottlenecks faced by traditional processes when rPET materials are used in separator preparation.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for preparing a high-performance lithium battery separator using retired photovoltaic backsheets comprises the following steps:

[0007] Obtain retired photovoltaic backsheets and obtain polyethylene terephthalate to be dissolved.

[0008] The polyethylene terephthalate to be dissolved is placed in a mixed solvent containing dichloromethane and trifluoroacetic acid to dissolve the polyethylene terephthalate. During the dissolution process, a polyethylene oxide spinning aid is added, and the polyethylene oxide molecular chains and the polyethylene terephthalate molecular chains form a hydrogen bond interpenetrating network, which is then processed by electrospinning to obtain polyethylene oxide-polyethylene terephthalate nanofibers.

[0009] The polyethylene oxide-polyethylene terephthalate nanofibers are dried under vacuum conditions to obtain a high-performance lithium battery separator.

[0010] The new rPET / PEO composite electrospinning process developed in this invention has opened up a new technical path for the preparation of high-performance diaphragms. This process overcomes many technical bottlenecks faced by traditional processes when recycling PET materials for diaphragm preparation through the combination of unique material composites and electrospinning technology.

[0011] In a preferred embodiment of the present invention, the polyethylene oxide accounts for 20% to 30% of the total mass of polyethylene terephthalate and polyethylene oxide.

[0012] In a preferred embodiment of the present invention, the mass fraction of ethylene terephthalate in the mixed solvent is controlled to be 5% to 15% during the decomposition process.

[0013] In a preferred embodiment of the present invention, the thermal shrinkage starting temperature of ethylene terephthalate is 120°C to 130°C.

[0014] In a preferred embodiment of the present invention, in the mixed solvent, the mass ratio of dichloromethane to trifluoroacetic acid is 1-3:3-7.

[0015] In a preferred embodiment of the present invention, the electrospinning voltage is 19.5 kV to 20.01 kV, and the flow rate is 0.0025 mm / s to 0.005 mm / s.

[0016] In a preferred embodiment of the present invention, the dissolution time is 3 h to 6 h.

[0017] In a preferred embodiment of the present invention, the vacuum drying temperature is 50° C. to 80° C., and the vacuum drying time is 6 h to 12 h.

[0018] Another object of the present invention is to provide a lithium battery separator prepared by any of the methods described above.

[0019] To overcome the performance degradation of recycled polyethylene terephthalate (rPET), the present invention uses a hydrogen-bonded interpenetrating network to composite rPET with polyethylene oxide (PEO). Furthermore, a solution system with a methylene chloride and trifluoroacetic acid ratio of 1:3 (by mass) is more effective in dissolving PEO.

[0020] This invention is based on abundant retired photovoltaic resources, uses backboard as raw material, and utilizes electrospinning technology to prepare high-performance fibers. The developed lithium battery separator has the advantages of both low cost and high performance, opening up a closed loop of "solid waste recycling-material regeneration-separator manufacturing".

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

[0022] 1. The present invention places the polyethylene terephthalate (PET) to be dissolved in a mixed solvent containing dichloromethane and trifluoroacetic acid to dissolve the PET. During the dissolution process, a polyethylene oxide spinning aid is added, so that the polyethylene oxide molecular chains form a hydrogen-bonded interpenetrating network with the polyethylene terephthalate molecular chains. The resulting fibers are then electrospun to obtain polyethylene oxide-PET nanofibers. The polyethylene oxide-PET nanofibers are then dried under vacuum conditions to obtain a high-performance lithium battery separator. The novel rPET / PEO composite electrospinning process developed by the present invention opens up a new technical path for the preparation of high-performance separators. By combining unique material compounding with electrospinning technology, the process overcomes many technical bottlenecks faced by traditional processes when recycling PET materials for separator preparation.

[0023] 2. This invention effectively solves the spinnability problem of recycled PET materials, making the fiber spinning process more stable and continuous, significantly improving the fiber's spinnability and uniformity, and reducing spinning defects. In terms of electrochemical performance, by optimizing the material structure and preparation process, key electrochemical performance indicators such as the electrolyte absorption rate of the separator are improved, enhancing the charge-discharge performance and cycle stability of lithium batteries. In terms of mechanical strength and thermal stability, the composite of PET and PEO and the special processing technology give the prepared separator higher mechanical strength and excellent thermal stability, which can better meet the use requirements of lithium batteries under complex operating conditions and provide solid technical support for the preparation of high-performance lithium battery separators.

[0024] 3. This invention successfully realizes the high-value utilization of retired photovoltaic backsheets, converting them into high-performance lithium battery separators. This achievement not only effectively addresses the environmental issues caused by retired photovoltaic backsheets and avoids resource waste, but also, through resource recycling, establishes a new closed-loop industrial chain from retired photovoltaic backsheets to high-performance lithium battery separators. This perfectly aligns with the concept of sustainable development and provides an innovative example for the efficient recycling of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The full-band infrared spectra of rPET / PEO blends with different PEO contents.

[0026] Figure 2 This is a comparison chart of infrared spectra of functional groups in rPET / PEO blend system.

[0027] Figure 3 DSC crystallization curves of rPET / PEO blends with different PEO contents.

[0028] Figure 4 This is the relationship between rPET crystallinity and PEO content in the rPET / PEO blend system.

[0029] Figure 5 This is the relationship between PEO crystallinity and PEO content in the rPET / PEO blend system.

[0030] Figure 6 This is a physical picture of the spinning solution dissolution process.

[0031] Figure 7 The real scenes of the electrospinning process before and after adding PEO, (a) is without addition, and (b) is with addition.

[0032] Figure 8 The morphology of electrospun fiber membrane before and after adding PEO, (a) is without addition, and (b) is with addition.

[0033] Figure 9 Actual pictures of electrospun fiber membranes before and after adding PEO, (a) is without addition, (b) is with addition.

[0034] Figure 10 Engineering stress-strain curves of electrospun fiber membranes before and after adding PEO, (a) is without addition, (b) is with addition.

[0035] Figure 11 is the diaphragm circulation performance. DETAILED DESCRIPTION

[0036] The following is a detailed description of the technical solutions in the embodiments of the present invention, using preferred embodiments and accompanying drawings in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] It should be noted that all professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0038] Example 1

[0039] A method for preparing a high-performance lithium battery separator using retired photovoltaic backsheets comprises the following steps:

[0040] (1) Obtain retired photovoltaic backboards and obtain polyethylene terephthalate to be dissolved.

[0041] (2) The polyethylene terephthalate to be dissolved is placed in a mixed solvent containing dichloromethane and trifluoroacetic acid in a volume ratio of 1:3, and the polyethylene terephthalate is dissolved for 4 hours. During the dissolution process, polyethylene oxide is added, and the mass ratio of polyethylene oxide to polyethylene terephthalate is 1:4. The polyethylene oxide molecular chain and the polyethylene terephthalate molecular chain form a hydrogen bond interpenetrating network, and then the polyethylene terephthalate is processed by electrospinning. The electrospinning voltage is 19.55 kV, the needle is 21G, the receiving distance is 15 cm, and the pushing speed is 0.0050 mm / s to obtain polyethylene oxide-polyethylene terephthalate nanofibers.

[0042] (3) Drying the polyethylene oxide-polyethylene terephthalate nanofibers at 60° C. for 6 h under vacuum conditions to obtain a high-performance lithium battery separator.

[0043] Example 2

[0044] A method for preparing a high-performance lithium battery separator using retired photovoltaic backsheets comprises the following steps:

[0045] (1) Obtain retired photovoltaic backboards and obtain polyethylene terephthalate to be dissolved.

[0046] (2) The polyethylene terephthalate to be dissolved is placed in a mixed solvent containing dichloromethane and trifluoroacetic acid in a volume ratio of 1:3, and the polyethylene terephthalate is dissolved for 4 hours. During the dissolution process, a polyethylene oxide spinning aid is added, and the mass ratio of polyethylene oxide to polyethylene terephthalate is 3:7. The polyethylene oxide molecular chain and the polyethylene terephthalate molecular chain form a hydrogen bond interpenetrating network, and then the polyethylene terephthalate is processed by electrospinning. The electrospinning voltage is 19.55 kV, the needle is 21G, the receiving distance is 15 cm, and the pushing speed is 0.0050 mm / s to obtain polyethylene oxide-polyethylene terephthalate nanofibers.

[0047] (3) Drying the polyethylene oxide-polyethylene terephthalate nanofibers at 60° C. for 6 h under vacuum conditions to obtain a high-performance lithium battery separator.

[0048] Example 3

[0049] A method for preparing a high-performance lithium battery separator using retired photovoltaic backsheets comprises the following steps:

[0050] (1) Obtain retired photovoltaic backboards and obtain polyethylene terephthalate to be dissolved.

[0051] (2) The polyethylene terephthalate to be dissolved is placed in a mixed solvent containing dichloromethane and trifluoroacetic acid in a volume ratio of 1:3, and the polyethylene terephthalate is decomposed for 3 hours. During the dissolution process, a polyethylene oxide spinning aid is added, and the mass ratio of polyethylene oxide to polyethylene terephthalate is 1:4. The polyethylene oxide molecular chain and the polyethylene terephthalate molecular chain form a hydrogen bond interpenetrating network, and then the polyethylene oxide is processed by electrospinning. The electrospinning voltage is 20 kV, the needle is 21 G, the receiving distance is 15 cm, and the pushing speed is 0.0025 mm / s to obtain polyethylene oxide-polyethylene terephthalate nanofibers.

[0052] (3) Drying the polyethylene oxide-polyethylene terephthalate nanofibers at 50° C. for 12 h under vacuum conditions to obtain a high-performance lithium battery separator.

[0053] Example 4

[0054] A method for preparing a high-performance lithium battery separator using retired photovoltaic backsheets comprises the following steps:

[0055] (1) Obtain retired photovoltaic backboards to obtain polyethylene terephthalate to be decomposed.

[0056] (2) The polyethylene terephthalate to be dissolved is placed in a mixed solvent containing dichloromethane and trifluoroacetic acid in a volume ratio of 1:3, and the polyethylene terephthalate is dissolved for 6 hours. During the dissolution process, a polyethylene oxide spinning aid is added, and the mass ratio of polyethylene oxide to polyethylene terephthalate is 1:4. The polyethylene oxide molecular chain and the polyethylene terephthalate molecular chain form a hydrogen bond interpenetrating network, and then the polyethylene terephthalate is processed by electrospinning. The electrospinning voltage is 19.55 kV, the needle is 21G, the receiving distance is 15 cm, and the pushing speed is 0.005 mm / s to obtain polyethylene oxide-polyethylene terephthalate nanofibers.

[0057] (3) Drying the polyethylene oxide-polyethylene terephthalate nanofibers at 80° C. for 10 h under vacuum conditions to obtain a high-performance lithium battery separator.

[0058] Comparative Example 1

[0059] A method for preparing a lithium battery separator using retired photovoltaic backsheets comprises the following steps:

[0060] (1) Obtain retired photovoltaic backboards and obtain polyethylene terephthalate to be dissolved.

[0061] (2) The polyethylene terephthalate to be dissolved is placed in a mixed solvent containing dichloromethane and trifluoroacetic acid in a volume ratio of 1:3, and the polyethylene terephthalate is dissolved for 4 hours. The polyethylene terephthalate is then processed by electrospinning. The electrospinning voltage is 19.55 kV, the needle is 21 G, the receiving distance is 15 cm, and the pushing speed is 0.0050 mm / s to obtain polyethylene oxide-polyethylene terephthalate nanofibers.

[0062] (3) Drying the polyethylene oxide-polyethylene terephthalate nanofibers at 60° C. for 6 h under vacuum conditions to obtain a lithium battery separator.

[0063] Result Analysis

[0064] Figure 1 The full-band infrared spectra of rPET / PEO blends with different PEO contents are shown in Figure 2. Figure 2 This is a comparison of infrared spectra of key functional groups in the rPET / PEO blend system. By comparing the Fourier transform infrared spectra (FTIR) of materials with different PEO addition amounts (0%, 20%, 30%, and 100%), the hydrogen bond interaction between rPET and PEO macromolecules is clarified: the characteristic peak of PET ester group (C=O): pure rPET at 1712 cm -1 A strong absorption peak (C=O stretching vibration) appears at 1700 cm-1. As the amount of PEO increases, the peak gradually shifts to a lower wave number of 1700 cm-1. -1 , and the peak width increased significantly, indicating that the H in PEO formed intermolecular hydrogen bonds with the ester group (C=O) of PET, weakening the internal hydrogen bonding of rPET, resulting in red shift and broadening of the characteristic peak. The experimental characterization sample information and name settings are shown in Table 1.

[0065] Table 1 Experimental characterization sample information and name settings

[0066]

[0067] Figure 3 is the DSC crystallization curve of rPET / PEO blend system with different PEO contents, Figure 4 This is the relationship between the crystallinity of rPET and the content of PEO in the rPET / PEO blend system. Figure 5The figure shows the relationship between the crystallinity of PEO and the content of PEO in the rPET / PEO blend system. Due to the formation of the rPET-PEO hydrogen bond interpenetrating network structure, the crystallization behavior of rPET and PEO will be inhibited when PEO is added. By comparing the crystallinity data of the pure components and the blend system, the inhibitory effect of the PET-rPEO hydrogen bond interpenetrating network on the crystallization behavior can be clearly verified: the crystallinity of the pure PEO diaphragm was measured to be 72.17% (no interaction), and after being added to the rPET matrix (Sample A and Sample B), its actual crystallinity dropped to 15.43% and 24.25%, respectively. The difference between the assumed non-interaction crystallinity and the crystallinity of the rPET-PEO interpenetrating network indicates that the hydrogen bond interaction between PEO and PET macromolecules destroys the regular arrangement of the PEO molecular chains and inhibits its crystallization.

[0068] At the same time, the crystallinity of rPET also decreased. The crystallinity of pure rPET is 37.75% (no interaction), while after the introduction of PEO (Sample A and Sample B), its actual crystallinity dropped to 35.41% and 30.90%, respectively, indicating that the hydrogen bond network restricts the movement of rPET molecular chains and inhibits its crystallization ability.

[0069] Therefore, the addition of PEO significantly inhibited the crystallization behavior of PEO and rPET, confirming that the hydrogen bonding network restricts the regular stacking of PEO and rPET macromolecular chain segments, which is beneficial for the preparation of lithium battery separators. Ultimately, a stable interpenetrating network with both rigidity and flexibility was constructed within the PEO-rPET nanofibers, providing the structural foundation for the separator to simultaneously possess excellent mechanical properties and electrochemical stability.

[0070] Figure 6 This figure shows the actual dissolution process of the spinning solution. By optimizing the formulation, rPET and PEO were co-dissolved using a mixed solution of dichloromethane (DCM) and trifluoroacetic acid (TFA). The optimal ratio of DCM to TFA was 1:3, which not only achieved the best dissolution effect but also the best fiber membrane morphology (average fiber diameter 3μm). By optimizing the spinning parameters, the morphological transformation from spherical defects to uniform fibers was successfully achieved using a voltage of 19.55kV, a 21G needle, a receiving distance of 15cm, and a feed speed of 0.0050mm / s.

[0071] Figure 7 The real scene of the electrospinning process before and after adding PEO, (a) is without adding, (b) is with adding, Figure 8The morphology of electrospun fiber membranes before and after adding PEO, (a) is without addition, and (b) is with addition. By introducing PEO as a spinning aid, a hydrogen-bonded interpenetrating network is established. During the electrospinning process, the flexible chain segments of PEO can cooperate with the electric field stretching effect to guide the rPET molecules to arrange in an orderly manner along the fiber axis, inhibiting the tendency of droplets to split. At the same time, the hydrophilic groups of PEO can adjust the surface tension of the solution and promote the uniform volatilization of the solvent. Actual experiments have shown that after adding PEO, the jet is eventually promoted to be uniformly stretched during the electrospinning process, forming a continuous and dense nanofiber structure. The present invention cleverly utilizes the "bridging" effect of polymer additives to transform the performance shortcomings of recycled materials into controllable structural advantages, and with the optimized instrument parameters, a more ideal fiber membrane morphology is obtained.

[0072] Figure 9 The following are the actual pictures of electrospun fiber membranes before and after adding PEO, (a) is without addition, and (b) is with addition. In the absence of PEO, the film-forming performance of the rPET solution is significantly limited. When the concentration of the solution is lower than 8wt%, the intermolecular force is insufficient, resulting in the inability of the fibers to continuously cross-link, and only a fragmented structure is formed or no film can be formed at all. In addition, the resulting film layer is extremely brittle and breaks when subjected to a slight external force, which is far from achieving the expected effect and actual application requirements. Even the electrochemical performance test of the diaphragm is extremely difficult. By introducing 20% ​​to 30% PEO as a co-spinning agent, the viscoelasticity and film-forming stability of the solution are greatly enhanced ( Figure 9 ). Under the same spinning conditions, the addition of PEO formed a uniform and dense interconnected structure between the fibers, and the integrity and mechanical properties of the membrane were significantly improved.

[0073] Figure 10 The engineering stress-strain curves of electrospun fiber membranes before and after adding PEO, (a) is without adding, (b) is with adding. Taking samples Pure PET and Sample A as examples, Figure 10 Engineering stress-strain curves show that the maximum tensile strength of the composite fiber membrane increased from 2.66 MPa to 5.78 MPa, and the elongation at break increased from 4.02% to 15.59%, with toughness nearly 60 times higher than that of pure rPET membrane. This breakthrough improvement stems from the buffering effect of PEO on local stress and its suppression of fiber slippage, ultimately achieving the membrane's high strength, high toughness, and scalable processing.

[0074] During the electrospinning process, this invention achieves precise control of fiber diameter, porosity, and membrane thickness through precise control of formulation and spinning parameters. This precise control overcomes the challenge of microstructural control, enabling the structural properties of the separator to be tailored to specific application requirements. Currently, the apparent porosity of the separator is approximately 25%, and the electrolyte absorption rate is approximately 130%.

[0075] Figure 11 The cycling performance of the separator was evaluated. Cyclic tests showed that the separator exhibited excellent stability in a limited number of charge and discharge cycles. The cycling performance test results based on a half-cell (LFP positive electrode / lithium metal negative electrode) showed that the rPET-PEO separator with a hydrogen bond interpenetrating network structure exhibited a gentle capacity decay characteristic. After 30 charge and discharge cycles, the discharge capacity was stably maintained from the initial 75mAh / g to 65mAh / g, with a capacity retention rate of 86.7%. The average capacity loss per cycle was only 0.33%, which has preliminarily verified the feasibility of the application of the hydrogen bond interpenetrating strategy in new energy devices and shows good development potential.

[0076] The development of lithium battery separators using retired photovoltaic recycled materials is one of the important measures for the sustainable development of photovoltaics. However, the backplane polymer material (rPET) is used outdoors for a long time, and the macromolecular chains are weakly entangled, which limits the effective spinning of recycled materials. The present invention proposes a rPET-PEO hydrogen bond interpenetrating network structure, combines it with a TFA-DCM mixed solvent system, and successfully develops nanofibers using electrospinning technology, providing technical support for the application of lithium battery separators. Moreover, due to the hydrogen bonding between macromolecules, the crystallization behavior of PET and PEO is significantly inhibited. Furthermore, a separator with a balance of rigidity and toughness and excellent cycle performance is obtained, providing an experimental basis for the application of lithium battery separators. Therefore, the present invention effectively solves the key problems of the spinnability, insufficient electrochemical properties, and insufficient mechanical strength and thermal stability of recycled PET materials. The method of converting retired photovoltaic backplanes into lithium battery separators not only represents a typical circular economy model, but also achieves a win-win situation in economic and environmental benefits.

[0077] It should be noted that when numerical ranges are mentioned in the present invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints may be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes preferred embodiments. Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0078] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing lithium battery separators using retired photovoltaic backsheets, characterized in that: The following steps are involved: Obtaining retired photovoltaic backsheets to obtain polyethylene terephthalate to be dissolved; The polyethylene terephthalate to be dissolved is placed in a mixed solvent containing dichloromethane and trifluoroacetic acid to dissolve the polyethylene terephthalate, and polyethylene oxide is added during the dissolution process, so that the polyethylene oxide molecular chains and the polyethylene terephthalate molecular chains form a hydrogen bond interpenetrating network, and then the polyethylene terephthalate-polyethylene oxide nanofibers are obtained by electrospinning. The polyethylene terephthalate-polyethylene oxide nanofiber is dried under vacuum conditions to obtain a high-performance lithium battery separator.

2. The method for preparing a lithium battery separator using retired photovoltaic backsheet according to claim 1, characterized in that: The polyethylene oxide accounts for 20% to 30% of the total mass of polyethylene terephthalate and polyethylene oxide.

3. The method for preparing a lithium battery separator using retired photovoltaic backsheet according to claim 1, characterized in that: During the dissolution process, the mass fraction of polyethylene terephthalate in the mixed solvent is controlled to be 5% to 15%.

4. The method for preparing a lithium battery separator using retired photovoltaic backsheet according to claim 1, characterized in that: In the mixed solvent, the mass ratio of dichloromethane to trifluoroacetic acid is 1-3:3-7.

5. The method for preparing a lithium battery separator using retired photovoltaic backsheet according to claim 1, characterized in that: The electrospinning voltage is 19.5 kV to 20.01 kV, and the flow rate is 0.0025 mm / s to 0.005 mm / s.

6. The method for preparing a lithium battery separator using retired photovoltaic backsheet according to claim 1, characterized in that: The dissolution time is 3h to 6h.

7. The method for preparing a lithium battery separator using retired photovoltaic backsheet according to claim 1, characterized in that: The vacuum drying temperature is 50℃~80℃, and the vacuum drying time is 6h~12h.

8. A lithium battery separator prepared by the method according to any one of claims 1 to 7.

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