A porous current collector and its preparation method and application

Abstract

The present invention discloses a porous current collector and its preparation method and application. The porous current collector comprises a conductive substrate, a porous polymer disposed on the conductive substrate, and a lithium-philic fluoride MF dispersed on the surface of the porous polymer. x , where M is an element capable of forming an alloy with Li, and x satisfies valence balance. The porous current collector of the present invention, when applied to lithium metal batteries, can effectively improve the electrochemical performance of the battery, particularly the cycling performance. This is because the porous current collector of the present invention can effectively mitigate the growth of lithium dendrites, inhibit the expansion of the lithium metal negative electrode, and avoid the formation of dead lithium.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium metal batteries and relates to a porous current collector and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have attracted great interest as power storage systems for electric vehicles and smart grids. To break through the limits of lithium-ion batteries, lithium metal anodes (with an ultra-high theoretical specific capacity of 3860 mAh g) have been used. -1 ) is matched with a high-capacity / high-voltage positive electrode and is the research direction of the next generation of high-energy batteries.

[0003] However, highly reactive lithium metal anodes often easily cause a large number of side reactions, forming unstable solid electrolyte interface films, leading to lithium dendrite growth and even volume expansion and the generation of dead lithium, which affects battery performance and brings serious safety hazards, thus limiting their commercialization.

[0004] Suppressing the growth and volume expansion of lithium dendrites is an urgent problem to be solved in lithium metal batteries. Researchers have suppressed the growth of lithium dendrites by constructing artificial solid electrolyte interface membranes. For example, CN113690485A discloses a solid electrolyte interface membrane, an alkali metal electrode and a preparation method thereof. The solid electrolyte interface membrane includes a polymer layer formed by the reaction of polyoxometallic clusters and 1,3-dioxolane. By polymerizing the polyacid anions in the polyoxometallic clusters with the cations of 1,3-dioxolane, a flexible, self-healing polymer layer is generated to inhibit the growth of alkali metal dendrites. The realization of the entire preparation process is similar to the response to biological information stimulation. It is a preparation method of a self-healing artificial solid electrolyte interface membrane that mimics the response of gene editing technology. At the same time, due to its flexible characteristics, it reduces the risk of SEI membranes with poor mechanical properties rupturing with long-term cycling of alkali metal batteries, thereby avoiding the safety problems caused by the growth of alkali metal dendrites, which is beneficial to improving the electrochemical performance of the battery. CN110512306A discloses a method for preparing an electrolyte membrane for inhibiting lithium dendrite growth in solid-state lithium batteries. The method comprises the following steps: coaxially spinning polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and a linear polymer to prepare spinning solutions; heat-treating the formed membrane during the spinning process, stretching it, and then rapidly cooling and solidifying it, with the flow rates of the solutions during the spinning process being PMMA > linear polymer > PAN; then immersing the membrane in a lithium-ion battery electrolyte; and finally treating the membrane at 80-90°C for 14.5-15.5 minutes to obtain the desired solid electrolyte membrane, which is a multilayer core-shell fiber composite film of PMMA / linear polymer / PAN. This patent effectively addresses the shortcomings of PMMA's poor mechanical properties, which make it difficult to inhibit lithium dendrite growth, and PAN's instability toward lithium metal.

[0005] However, the method of suppressing the growth of lithium dendrites by constructing an artificial solid electrolyte interface film is often prone to more serious side reactions and interface instability. Dendrite growth can also be alleviated by regulating the liquid electrolyte or designing a solid electrolyte. CN116979157A discloses a preparation method and application of an aqueous composite electrolyte for suppressing the growth of zinc dendrites, comprising the following steps: S1), taking a certain amount of aqueous soluble zinc salt and a saccharide additive and mixing them evenly; S2), adding deionized water, fixing the volume, and stirring continuously until dissolved, and standing until the pH value of the composite aqueous electrolyte is stable to obtain a stable aqueous composite electrolyte containing a saccharide organic additive that suppresses dendrite growth. However, regulating the composition of the electrolyte may also cause the interfacial impedance to become larger, and the volume expansion cannot be effectively suppressed.

[0006] Therefore, providing an improved strategy for the current collector so that it can effectively suppress the dendrite problem in lithium metal batteries and effectively reduce the volume expansion of the negative electrode is a technical problem that needs to be solved urgently. Summary of the Invention

[0007] In view of the above technical problems existing in the prior art, the object of the present invention is to provide a porous current collector and a preparation method and application thereof.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a porous current collector, comprising a conductive substrate, a porous polymer disposed on the conductive substrate, and a lithium-philic fluoride MF dispersed on the surface of the porous polymer. x , where M is an element that can form an alloy with Li, and x satisfies the valence balance.

[0010] The present invention constructs a porous polymer on a conductive substrate and disperses a lithiophilic fluoride on its surface, forming a three-dimensional porous current collector with a porous mixed conductive structure. This current collector can be used in lithium metal batteries to effectively alleviate lithium dendrite growth, inhibit lithium metal anode expansion, and avoid the generation of dead lithium. The technical principle is as follows:

[0011] First, the porous structure allows lithium to be deposited preferentially inside the current collector, achieving dense lithium metal deposition, reducing negative electrode volume expansion and avoiding surface dendrite growth and dead lithium formation. Second, lithiophilic fluoride (MF x ) can react with lithium metal to form LiM alloy and LiF, LiF has good Li + Conductivity, LiM alloy has high mechanical strength, which helps to construct a stable SEI film and inhibit the growth of lithium dendrites.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0013] Preferably, the conductive substrate is selected from at least one of a carbon material film layer having a porous structure or a metal substrate, and is preferably a carbon material film layer having a porous structure.

[0014] In the present invention, by adopting a carbon material film layer with a porous structure and forming a porous polymer and a lithium-philic fluoride on its surface, the battery can achieve better performance. This is because: a conductive network with a porous skeleton structure is formed in the current collector, which is beneficial to the transmission and diffusion of lithium ions, effectively reducing the local current density on the surface, thereby alleviating the growth of lithium dendrites, and at the same time facilitating high-rate charging and discharging of the battery.

[0015] Preferably, the porous carbon material film layer comprises at least one of carbon fabric, carbon nanotube film, carbon paper, and graphene film. A carbon nanotube film is a porous skeleton structure formed by overlapping one-dimensional carbon nanotubes. A graphene film is a porous skeleton structure formed by overlapping two-dimensional graphene.

[0016] Preferably, the metal substrate comprises at least one of copper foil, copper mesh and carbon-coated copper foil.

[0017] Preferably, the thickness of the conductive substrate is 40μm-100μm, for example, it can be 40μm, 42μm, 44μm, 45μm, 47μm, 48μm, 50μm, 52μm, 55μm, 56μm, 58μm, 60μm, 65μm, 67μm, 70μm, 80μm, 90μm or 100μm, etc.

[0018] Preferably, the thickness of the porous polymer is 5μm-30μm, for example, it can be 5μm, 6μm, 8μm, 9μm, 10μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 20μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm or 30μm, etc.

[0019] Preferably, the lithiophilic fluoride MF x The thickness is 3μm-10μm, for example, it can be 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm or 10μm, etc.

[0020] As a preferred technical solution of the porous current collector of the present invention, the porous polymer is prepared by non-solvent induced phase separation technology.

[0021] Preferably, the polymer in the porous polymer includes at least one of polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polypropylene oxide, polymethyl methacrylate and polyvinylidene chloride.

[0022] Preferably, the MF x M in Mg is selected from at least one of Mg, Al, In, Si, Ag, Bi, Fe, Co, Cu and Ni, preferably at least one of Mg, Al and In. For example, MF x Specifically, it can be MgF2, AlF3, InF3, SiF4, AgF, BiF3, FeF3, CoF3, CuF2, NiF2, etc.

[0023] In a second aspect, the present invention provides a method for preparing the porous current collector according to the first aspect, the preparation method comprising the following steps:

[0024] (1) dissolving a polymer in a first solvent to obtain a polymer solution, coating the polymer solution on a substrate, and then immersing the substrate in a second solvent to exchange the first solvent with the second solvent;

[0025] (2) After the exchange is completed, spray MF on the polymer surface x , and a porous current collector is obtained after drying.

[0026] The method of the present invention uses non-solvent-induced phase separation technology to quickly and easily construct a porous polymer layer, helping to mitigate lithium dendrite growth and dead lithium formation. The lithiophilic fluoride helps to construct a more stable SEI membrane, thereby effectively improving the cycle life and safety of lithium metal batteries. Furthermore, the non-solvent-induced phase separation method is simple and controllable for the production of porous current collectors, eliminating the need for additional pore-forming agents, reducing costs and facilitating large-scale production.

[0027] Preferably, the polymer is soluble in the first solvent but insoluble in the second solvent, and the first solvent and the second solvent are miscible with each other.

[0028] Preferably, in step (1), the mass concentration of the polymer solution is 5wt%-20wt%, for example, it can be 5wt%, 7wt%, 8wt%, 9wt%, 10wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt%, etc.

[0029] Preferably, the conductive substrate is selected from at least one of a carbon material film layer having a porous structure or a metal substrate, and is preferably a carbon material film layer having a porous structure.

[0030] In the method of the present invention, when a porous carbon film is used as the substrate, the porous polymer layer and the porous carbon film interact with each other, with a portion of the porous polymer filling the pores of the carbon film, thereby forming a porous mixed conductive structure for the current collector, which helps to alleviate the growth of lithium dendrites and the formation of dead lithium. Lithiaphilic fluorides help to form a more stable SEI film, thereby effectively improving the cycle life and safety of lithium metal batteries.

[0031] Preferably, the carbon material film layer having a porous structure includes at least one of carbon fabric, carbon nanotube film, carbon paper and graphene film.

[0032] Preferably, the metal substrate comprises at least one of copper foil, copper mesh and carbon-coated copper foil.

[0033] Preferably, in step (1), the coating is immediately immersed in the second solvent.

[0034] Preferably, in step (1), after immersing in the second solvent, the mixture is allowed to stand for 5-8 hours, for example, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours.

[0035] As a preferred technical solution of the method for preparing the porous current collector of the present invention, in the spraying step (2), MF x The spraying is carried out in the form of a solution, and the mass concentration of the solution is 3wt%-10wt%, for example, it can be 3wt%, 4wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt% or 10wt%, etc.

[0036] Preferably, the drying in step (2) is vacuum drying.

[0037] Preferably, the drying temperature in step (2) is 80°C-90°C, for example, it can be 80°C, 82°C, 83°C, 84°C, 85°C, 86°C, 88°C or 90°C; the drying time is 4h-5h, for example, it can be 4h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h or 5h.

[0038] In a third aspect, the present invention provides a negative electrode, comprising the porous current collector described in the first aspect and lithium deposited on the porous current collector.

[0039] In a fourth aspect, the present invention provides a lithium metal negative electrode, wherein the lithium metal battery comprises the negative electrode described in the third aspect.

[0040] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The present invention forms a three-dimensional porous current collector with a porous mixed conductive structure by constructing a porous polymer on a conductive substrate and dispersing a lithium-philic fluoride on its surface. The current collector can be used in lithium metal batteries to effectively alleviate the growth of lithium dendrites, inhibit the expansion of lithium metal negative electrodes, and avoid the generation of dead lithium.

[0043] (2) In the present invention, by adopting a carbon material film layer with a porous structure and forming a porous polymer and a lithium-philic fluoride on its surface, the battery can obtain better performance. This is because: a conductive network with a porous skeleton structure is formed in the current collector, which is beneficial to the transmission and diffusion of lithium ions, effectively reducing the local current density on the surface, thereby alleviating the growth of lithium dendrites, and at the same time facilitating high-rate charging and discharging of the battery.

[0044] (3) The non-solvent-induced phase separation method for manufacturing porous current collectors is simple and controllable, does not require the addition of additional pore-forming agents, reduces costs, and facilitates large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic structural diagram of the porous current collector of Example 1, wherein: 1. a conductive substrate; 2. a porous polymer; 3. a lithium-philic fluoride. DETAILED DESCRIPTION

[0046] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0047] The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] Example 1

[0049] This embodiment provides a porous current collector, the structural diagram of which is shown in FIG. Figure 1 , including a conductive substrate 1 (thickness 50 μm), a porous polymer 2 (thickness 20 μm) arranged on the conductive substrate 1, and a lithiophilic fluoride 3 (thickness 5 μm) dispersed on the surface of the porous polymer 2, wherein the conductive substrate 1 is a carbon nanotube film, the polymer in the porous polymer 2 is polyvinyl alcohol, and the lithiophilic fluoride 3 is MgF2.

[0050] This embodiment also provides a method for preparing the above-mentioned porous current collector, comprising the following steps:

[0051] Polyvinyl alcohol (PVA) was added to a certain amount of water and stirred at 80°C for 5 hours to prepare a polymer solution with a concentration of 10wt%. The evenly stirred polymer solution was scraped onto a carbon nanotube film (CF) with a thickness of 50μm, and then immediately immersed in a propanol solution and allowed to stand for 6 hours. After the solvent and the non-solvent were fully exchanged, a layer of porous polymer was formed on the carbon nanotube film. Then, a 5wt% MgF2 dimethyl sulfoxide solution was sprayed on the current collector. Finally, the current collector was placed in an 80°C oven and vacuum dried for 5 hours to completely remove the residual solvent, thereby obtaining a porous current collector, referred to as MgF2 / PVA / CF porous current collector.

[0052] Example 2

[0053] This embodiment provides a porous current collector, including a conductive substrate (50 μm thick), a porous polymer (25 μm thick) arranged on the conductive substrate, and a lithiophilic fluoride (3 μm thick) dispersed on the surface of the porous polymer, wherein the conductive substrate is a carbon nanotube film, the polymer in the porous polymer is polyethylene oxide, and the lithiophilic fluoride is AlF3.

[0054] This embodiment also provides a method for preparing the above-mentioned porous current collector, comprising the following steps:

[0055] Polyethylene oxide (PEO) was added to a certain amount of water and stirred at 60°C for 5 hours to prepare a polymer solution with a concentration of 8wt%. The evenly stirred polymer solution was scraped onto a carbon nanotube film (CF) with a thickness of 50μm, and then immediately immersed in an ethylene glycol solution and allowed to stand for 6 hours. After the solvent and the non-solvent were fully exchanged, a layer of porous polymer was formed on the carbon nanotube film. Then, a 3wt% AlF3 dimethyl sulfoxide solution was sprayed on the current collector. Finally, the current collector was placed in an 80°C oven and vacuum dried for 5 hours to completely remove the residual solvent, thereby obtaining a porous current collector, referred to as AlF3 / PEO / CF porous current collector.

[0056] Example 3

[0057] This embodiment provides a porous current collector, including a conductive substrate (thickness 50 μm), a porous polymer (thickness 10 μm) arranged on the conductive substrate, and a lithiophilic fluoride (thickness 8 μm) dispersed on the surface of the porous polymer, wherein the conductive substrate is carbon paper, the polymer in the porous polymer is polyvinylidene fluoride, and the lithiophilic fluoride is InF3.

[0058] This embodiment also provides a method for preparing the above-mentioned porous current collector, comprising the following steps:

[0059] Polyvinylidene fluoride (PVDF) was added to a certain amount of N,N-dimethylformamide and stirred at 60°C for 5 hours to prepare a polymer solution with a concentration of 15wt%. The evenly stirred polymer solution was scraped onto carbon paper (CP) with a thickness of 50μm, and then immediately immersed in an aqueous solution and allowed to stand for 6 hours. After the solvent and the non-solvent were fully exchanged, a layer of porous polymer was formed on the carbon paper. Then, an 8wt% InF3 dimethyl sulfoxide solution was sprayed on the current collector. Finally, the current collector was placed in an 80°C oven and vacuum dried for 5 hours to completely remove the residual solvent, thereby obtaining a porous current collector, referred to as InF3 / PVDF / CP porous current collector.

[0060] Example 4

[0061] This embodiment provides a porous current collector. The difference between its preparation method and that of Example 1 is that the carbon nanotube film is replaced by a copper foil of the same thickness (50 μm).

[0062] Example 5

[0063] This embodiment provides a porous current collector, and its preparation method is different from that of Example 1 in that MgF2 is replaced by NiF2.

[0064] Example 6

[0065] This embodiment provides a porous current collector. The difference between the preparation method thereof and that of Example 1 is that the concentration of the polymer solution is adjusted to 3 wt %.

[0066] Example 7

[0067] This embodiment provides a porous current collector. The difference between the preparation method thereof and that of Example 1 is that the concentration of the polymer solution is adjusted to 22 wt %.

[0068] Example 8

[0069] This embodiment provides a porous current collector, and its preparation method is different from that of Example 1 in that the standing time is 4 hours.

[0070] Example 9

[0071] This embodiment provides a porous current collector, and its preparation method is different from that of Example 1 in that the standing time is 9 hours.

[0072] Comparative Example 1

[0073] This comparative example provides a current collector. The difference in the preparation method from Example 1 is that the following operation of "immediately immersing in a propanol solution and letting it stand for 6 hours" is omitted.

[0074] Comparative Example 2

[0075] This comparative example provides a current collector. The difference in preparation method from Example 2 is that the lithiophilic fluoride is replaced by aluminum oxide.

[0076] Application Example 1

[0077] A lithium metal negative electrode is provided, and its preparation method is as follows:

[0078] The porous current collector prepared in Example 1 was assembled with a lithium sheet into a battery. The separator used was a 9 μm polyethylene film. The electrolyte used was a 1 mol / L LiTFSI solution in 1,3-dioxolane / ethylene glycol dimethyl ether (DOL / DME volume ratio was 1:1, and the solution contained 1.0 wt% LiNO3 additive). The flow rate was 2 mA cm -1 The lithium was deposited on the porous current collector by constant current discharge for 3 h at a current density of 100 nm to obtain the negative electrode, which is referred to as Li-MgF2 / PVA / CF electrode.

[0079] Application Example 2-9

[0080] A lithium metal negative electrode is provided. The preparation method thereof is different from that of Application Example 1 in that the porous current collectors prepared in Examples 2-9 are respectively used to assemble a battery with a lithium sheet. The rest of the contents are the same as those of Application Example 1.

[0081] Comparative Application Examples 1-2

[0082] A lithium metal negative electrode is provided. The difference between its preparation method and that of Application Example 1 is that the porous current collector prepared in Comparative Example 1-2 is assembled with a lithium sheet into a battery. The rest of the contents are the same as those of Application Example 1.

[0083] Making and testing lithium metal batteries:

[0084] (1) Production of lithium metal batteries:

[0085] The positive electrode material NCM811 (chemical formula LiNi 0.8 Co 0.1 Mn 0.1 O2), carbon black Super P, and PVDF were mixed in a mass ratio of 98:1:1, and NMP was added to prepare a positive electrode slurry. The slurry was coated on aluminum foil and dried to obtain a positive electrode sheet. The positive electrode sheet was assembled into a battery with the lithium metal negative electrode of Application Examples 1-9 and Comparative Application Example 1. The separator used was a 9μm polyethylene film, and the electrolyte used was a 1.0mol / L LiTFSI solution in 1,3-dioxolane / ethylene glycol dimethyl ether (DOL / DME volume ratio of 1:1, the solution contained 1.0wt% LiNO3 additive).

[0086] (2) Cycle test of lithium metal batteries:

[0087] The assembled lithium metal battery was charged at a constant current of 0.01C to 3.4V, then at a constant current of 0.05C to 3.8V, and then at a constant current and voltage of 0.1C to 4.2V. It was then discharged at a constant current of 0.2C to 2.8V for three cycles to form a complete SEI film. Cycling tests were then performed at a constant current and voltage of 0.3C to 4.2V and then at a constant current of 1C to 2.8V. The initial efficiency, capacity retention, and coulombic efficiency were recorded. The test results are shown in Table 1.

[0088] Table 1

[0089] First effect / % Number of cycles Capacity retention rate / % Coulombic efficiency / % Application Example 1 89.90 200 98.5 99.92 Application Example 2 89.69 200 97.2 99.94 Application Example 3 90.17 200 98.0 99.94 Application Example 4 88.77 200 90.2 99.32 Application Example 5 88.02 200 86.1 99.07 Application Example 6 86.78 100 80.0 94.28 Application Example 7 84.50 100 73.7 93.97 Application Example 8 88.39 200 75.5 98.81 Application Example 9 89.19 200 77.3 98.40 Comparative Application Example 1 82.49 100 65.9 92.67 Comparative Application Example 2 87.20 100 78.9 98.11

[0090] As can be seen from Table 1, the porous current collector of the present invention is applied to lithium metal batteries, which can effectively improve the electrochemical performance of the battery, especially the cycle performance is greatly improved. This is because the porous current collector of the present invention can effectively alleviate the growth of lithium dendrites, inhibit the expansion of the lithium metal negative electrode, and avoid the generation of dead lithium.

[0091] By comparing Application Example 1 with Application Example 4, it can be seen that compared with the two-dimensional planar current collector (copper foil), the three-dimensional porous current collector (carbon nanotube film) can induce lithium metal to deposit inside the current collector, alleviate surface dendrite growth, and thus improve the cycle performance of lithium metal batteries.

[0092] By comparing Application Example 1 with Application Example 5, it can be seen that MgF2 has better lithium affinity than NiF2, which helps to construct a more stable SEI film and inhibit the growth of lithium dendrites.

[0093] By comparing Application Example 1 with Application Examples 6-7, it can be seen that if the concentration of the polymer solution is too low, it is not conducive to forming a uniform porous polymer layer; if the concentration of the polymer solution is too high, it will affect the electronic conductivity of the current collector, which is not conducive to the battery cycle.

[0094] By comparing Application Example 1 with Application Examples 8-9, it can be seen that if the exchange time with the second solvent is too short, it is not conducive to the formation of pores; if the exchange time is too long, it is not conducive to the formation of uniform pores, thus deteriorating the performance of the current collector in the battery.

[0095] By comparing Application Example 1 with Comparative Application Example 1, it can be seen that if the polymer is not exchanged with the second solvent, a porous polymer cannot be formed, and only a polymer layer is formed on the surface of the current collector, which is not conducive to lithium ion conduction, thereby deteriorating battery performance.

[0096] By comparing Application Example 1 with Comparative Application Example 2, it can be seen that aluminum oxide has no lithium affinity and cannot form an alloy layer and a LiF-rich SEI layer on the negative electrode surface in lithium metal batteries, and has no effect on improving battery performance.

[0097] The applicant states that the present invention is intended to illustrate the detailed methods of the present invention through the above-described embodiments, but the present invention is not limited to the above-described detailed methods, that is, it does not mean that the present invention must rely on the above-described detailed methods in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for various raw materials in the products of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A porous current collector, characterized in that: The porous current collector includes a conductive substrate, a porous polymer disposed on the conductive substrate, and a lithium-philic fluoride MF dispersed on the surface of the porous polymer. x , where M is an element that can form an alloy with Li, and x satisfies the valence balance; The porous current collector is prepared by the following method, which comprises the following steps: (1) dissolving a polymer in a first solvent to obtain a polymer solution, coating the polymer solution on a conductive substrate, and then immersing the conductive substrate in a second solvent to exchange the first solvent with the second solvent; (2) After the exchange is completed, spray MF on the polymer surface x , after drying, a porous current collector is obtained; In step (1), the polymer is soluble in a first solvent but insoluble in a second solvent, and the first solvent and the second solvent are miscible with each other; The polymer in the porous polymer includes at least one of polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polypropylene oxide, polymethyl methacrylate and polyvinylidene chloride.

2. The porous current collector according to claim 1, characterized in that The conductive substrate is selected from at least one of a carbon material film layer with a porous structure or a metal substrate.

3. The porous current collector according to claim 2, characterized in that The conductive substrate is a carbon material film layer with a porous structure.

4. The porous current collector according to claim 2, characterized in that The carbon material film layer with a porous structure includes at least one of carbon fabric, carbon nanotube film, carbon paper and graphene film.

5. The porous current collector according to claim 2, characterized in that: The metal substrate includes at least one of copper foil, copper mesh and carbon-coated copper foil.

6. The porous current collector according to claim 1, characterized in that The thickness of the conductive substrate is 40 μm-100 μm.

7. The porous current collector according to claim 1, characterized in that The thickness of the porous polymer is 5 μm-30 μm.

8. The porous current collector according to claim 1, wherein: The lithiophilic fluoride MF x The thickness is 3μm-10μm.

9. The porous current collector according to claim 1, characterized in that: The porous polymer is prepared by a non-solvent induced phase separation technique.

10. The porous current collector according to claim 1, characterized in that: The MF x Here, M is selected from at least one of Mg, Al, In, Si, Ag, Bi and Cu.

11. The porous current collector according to claim 10, characterized in that: The MF x The M is selected from at least one of Mg, Al and In.

12. A method for preparing a porous current collector according to any one of claims 1 to 11, characterized in that: The preparation method comprises the following steps: (1) dissolving a polymer in a first solvent to obtain a polymer solution, coating the polymer solution on a conductive substrate, and then immersing the conductive substrate in a second solvent to exchange the first solvent with the second solvent; (2) After the exchange is completed, spray MF on the polymer surface x , after drying, a porous current collector is obtained; In step (1), the polymer is soluble in a first solvent but insoluble in a second solvent, and the first solvent and the second solvent are mutually soluble.

13. The preparation method according to claim 12, characterized in that In step (1), the mass concentration of the polymer solution is 5wt%-20wt%.

14. The preparation method according to claim 12, characterized in that The conductive substrate is selected from at least one of a carbon material film layer with a porous structure or a metal substrate.

15. The preparation method according to claim 14, characterized in that The conductive substrate is a carbon material film layer with a porous structure.

16. The preparation method according to claim 14, characterized in that The carbon material film layer with a porous structure includes at least one of carbon fabric, carbon nanotube film, carbon paper and graphene film.

17. The preparation method according to claim 14, characterized in that The metal substrate includes at least one of copper foil, copper mesh and carbon-coated copper foil.

18. The preparation method according to claim 12, characterized in that: In step (1), the coating is immediately immersed in the second solvent.

19. The preparation method according to claim 12, characterized in that: In step (1), the sample is immersed in the second solvent and then allowed to stand for 5-8 hours.

20. The preparation method according to claim 12, characterized in that In the spraying step (2), MF x The spraying is carried out in the form of a solution with a mass concentration of 3wt%-10wt%.

21. The preparation method according to claim 12, characterized in that The drying in step (2) is vacuum drying.

22. The preparation method according to claim 12, characterized in that The drying temperature in step (2) is 80°C-90°C, and the drying time is 4h-5h.

23. A negative electrode, characterized in that The negative electrode comprises the porous current collector according to any one of claims 1 to 11 and lithium deposited on the porous current collector.

24. A lithium metal battery, characterized in that The lithium metal battery comprises the negative electrode according to claim 23.

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