A laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode and its preparation and application

Abstract

This invention provides a multilayered porous intelligent flame-retardant framework composite lithium metal anode and its preparation and application. The preparation method of the composite lithium metal anode of this invention includes the following steps: thoroughly mixing an aqueous dispersion of graphene oxide with an ethanol solution of triphenyl phosphate flame retardant to obtain a TPP-GO mixed solution; then freeze-drying and rolling to obtain porous TPP||GO foam; loading ZnO onto the surface and interior of the porous TPP||GO foam to obtain a multilayered porous flame-retardant framework ZnO||TPP||GO; and then further loading lithium metal to obtain the final product. The multilayered framework in this invention effectively prevents the flame retardant from decomposing during the preparation of the composite anode and from diffusing into the electrolyte and lithium metal during battery cycling. Simultaneously, under high-temperature conditions such as fires, the flame retardant can be successfully released by heat, thus achieving flame retardancy of the lithium metal anode while ensuring the electrochemical performance of the lithium metal battery.

Description

Technical Field

[0001] This invention belongs to the field of high-energy-density and high-safety lithium metal battery technology, specifically relating to a multi-layered porous intelligent flame-retardant skeleton composite lithium metal anode and its preparation and application. Background Technology

[0002] Among candidate materials for lithium-ion battery anodes, lithium metal is chosen because it has the highest theoretical energy density (3860 mAh g⁻¹). -1 With its low electrochemical potential (-3.04V compared to the standard hydrogen electrode), lithium metal stands out as the optimal choice for lithium-ion battery anode materials. However, due to the high flammability and reactivity of lithium metal anodes, as well as the use of highly flammable organic electrolytes, lithium metal batteries present serious safety issues. Furthermore, dendrites growing on the surface of the lithium metal anode can penetrate the separator, causing internal short circuits, generating significant heat, triggering a series of exothermic reactions, and ultimately leading to thermal runaway, resulting in catastrophic accidents such as fires and explosions. These safety concerns limit the large-scale practical application of lithium metal batteries.

[0003] Despite the well-known serious combustion problem of lithium metal anodes, current research on building safe lithium batteries mainly focuses on developing non-flammable liquid or solid electrolytes, highly thermally stable separators, smart responsive separators, and battery management systems. Other strategies, such as artificial fluoridation protective layers, have also been developed to improve the air stability of lithium metal to some extent. However, due to the extremely high flammability and reducing properties of lithium metal anodes, none of the above strategies can provide sufficient flame retardancy to extinguish ignition. Furthermore, conventional flame retardant mixing strategies cannot address this challenge because of the severe corrosion reaction between flame retardants and lithium metal that damages electrode function. Since the invention of lithium batteries, this safety issue has remained one of the most critical but unresolved challenges, hindering the large-scale practical application of lithium metal batteries for decades. Therefore, the ultimate solution to the safety problem of lithium metal batteries lies in the flame-retardant design of the lithium metal anode without affecting the battery's electrochemical performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a multilayered porous intelligent flame-retardant framework composite lithium metal anode and its preparation and application. The multilayered framework effectively prevents the flame retardant from decomposing during composite anode preparation and diffusing into the electrolyte and lithium metal during battery cycling. Simultaneously, under high-temperature conditions such as fires, the flame retardant can be successfully released by heat, thus achieving flame retardancy of the lithium metal anode while ensuring the electrochemical performance of the lithium metal battery. Through the intelligent release of the flame retardant and the thermal insulation performance of the three-dimensional structure within the framework, this invention achieves a significant flame-retardant effect, ensuring the composite anode does not burn for 10 seconds after ignition under an open flame, and maintains normal battery operation even after ignition, solving the problem of extreme flammability of lithium metal anodes. Furthermore, the ZnO interlayer design completely seals the flame retardant within the interlayer during conventional anode cycling, eliminating side reactions between lithium metal and the flame retardant during conventional electrode operation. Combined with the inhibitory effect of the three-dimensional structure on Li dendrite formation and the lithium affinity of ZnO in the framework, this further enhances the flame retardancy of the lithium metal anode. + Uniform deposition results in excellent cycle stability in the composite lithium anode. Therefore, this invention fundamentally solves the long-standing safety problem hindering the large-scale application of lithium metal anodes, and has great application potential.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for preparing a multilayered porous intelligent flame-retardant framework composite lithium metal anode includes the following steps:

[0007] (1) A TPP-GO mixed solution was obtained by thoroughly mixing an aqueous dispersion of graphene oxide (GO) with an ethanol solution of triphenyl phosphate (TPP) flame retardant; then, porous TPP||GO foam was obtained by freeze drying and roll pressing.

[0008] (2) A multilayered porous flame-retardant skeleton ZnO||TPP||GO is obtained by loading ZnO on the surface and inside of porous TPP||GO foam;

[0009] (3) A composite lithium metal anode (Li||ZnO||TPP||GO) is obtained by loading lithium metal onto a multilayered porous flame-retardant framework ZnO||TPP||GO.

[0010] According to a preferred embodiment of the present invention, in step (1), the mass concentration of the graphene oxide aqueous dispersion is 1-100 mg / g.

[0011] According to a preferred embodiment of the present invention, in step (1), the concentration of the ethanol solution of triphenyl phosphate flame retardant is 0.1-0.5 g / ml.

[0012] According to a preferred embodiment of the present invention, in step (1), the mass ratio of triphenyl phosphate to graphene oxide is 0.5:1-2:1, preferably 2:1.

[0013] According to a preferred embodiment of the present invention, step (1) of the method for preparing porous TPP||GO foam includes the following steps: uniformly coating a TPP-GO mixed solution onto a plastic film, freeze-drying, then removing the plastic film, and rolling to obtain porous TPP||GO foam. The thickness of the porous TPP||GO foam is 50-300 μm.

[0014] According to a preferred embodiment of the present invention, in step (1), the freeze-drying temperature is -40℃ to 0℃; and the freeze-drying time is 24h to 48h.

[0015] According to a preferred embodiment of the present invention, in step (2), the preparation method of the multilayer porous flame-retardant skeleton ZnO||TPP||GO includes the following steps: depositing a 100-200 nm thick ZnO layer on the surface and inside of the porous TPP||GO foam using atomic layer deposition to obtain the multilayer porous flame-retardant skeleton ZnO||TPP||GO; the thickness of the ZnO layer is preferably 150 nm.

[0016] According to a preferred embodiment of the present invention, step (3) of the preparation method of the multilayered porous intelligent flame-retardant framework composite lithium metal anode includes the following steps: contacting the periphery of the multilayered porous flame-retardant framework ZnO||TPP||GO with molten lithium metal, and uniformly diffusing the molten lithium metal into the interior of the multilayered porous flame-retardant framework ZnO||TPP||GO to obtain the multilayered porous intelligent flame-retardant framework composite lithium metal anode. Since the multilayered porous flame-retardant framework ZnO||TPP||GO has a large number of nanopores and a lithium-loving ZnO layer, the molten lithium metal will uniformly diffuse into the interior of the ZnO||TPP||GO framework according to capillary action.

[0017] A multilayered porous intelligent flame-retardant skeleton composite lithium metal anode was prepared by the above method.

[0018] According to a preferred embodiment of the present invention, the microstructure of the composite lithium metal anode with a multi-layered porous structure is a multi-layered porous structure; the composite lithium metal anode is a graphene oxide sheet with a triphenyl phosphate layer and a ZnO layer sequentially coated from the inside to the outside, and lithium metal particles are loaded on the surface of the ZnO layer and fill the pores of the multi-layered porous structure.

[0019] The above-mentioned layered porous intelligent flame-retardant skeleton composite lithium metal anode is used in lithium metal batteries.

[0020] According to a preferred embodiment of the present invention, the positive electrode of the lithium metal battery is lithium cobalt oxide, a ternary nickel-cobalt-manganese layered material, lithium iron phosphate, lithium titanate, a layered lithium-rich manganese-based positive electrode material, or a layered lithium manganese oxide (LiMnO2); the separator is selected from one or more combinations of glass-carbon fiber, polypropylene separator, or polyethylene separator; the solute of the electrolyte is selected from one or more combinations of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium nitrate, or lithium polysulfide, and the solvent of the electrolyte is selected from... The lithium metal battery packaging comprises one or more of the following: 1,3-dioxapentane, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethyl carbonate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether, or 1,1,1,2,2,3,4,5,5,5-decafluoropentane; and includes button cell battery cases, pouch cell battery cases, or stainless steel battery cases.

[0021] The technical features and beneficial effects of this invention are as follows:

[0022] (1) The multi-layered porous framework in this invention is the key to achieving excellent flame retardancy of the composite lithium metal anode. It effectively prevents the flame retardant from decomposing during the preparation of the composite anode and from diffusing into the electrolyte and lithium metal during battery cycling. While ensuring the electrochemical performance of the lithium metal battery, the flame retardant design for the lithium metal anode is achieved through the high-temperature release of the flame retardant in situations such as fire and the heat insulation performance of the three-dimensional structure in the framework.

[0023] (2) This invention employs atomic layer vapor deposition (ALVDC) to uniformly deposit ZnO onto the surface and interior of porous TPP||GO foam, not just the surface. This lithium-loving ZnO coating can lower the nucleation barrier, reduce polarization, and promote Li-... + The uniform deposition of ZnO improves the electrochemical performance of the lithium metal anode. Furthermore, the ZnO interlayer design completely seals the TPP component within the interlayer during conventional anode cycling, preventing Li metal corrosion of the TPP and forming an SEI that is beneficial for battery cycling. Additionally, the ZnO layer facilitates the absorption of molten lithium into the framework, avoiding the decomposition of flame retardants during preparation. Moreover, atomic layer vapor deposition (ALV) is a mature process, producing oxide layers with uniform thickness and high stability. Therefore, this invention has the advantage of being suitable for large-scale production.

[0024] (3) This invention successfully developed a multilayer porous intelligent flame-retardant framework composite lithium metal anode with excellent flame retardancy and cycle stability. This composite lithium metal anode exhibits a significant flame-retardant effect, showing no combustion phenomenon after 10 seconds of ignition under an open flame, and can still maintain normal battery operation after ignition, solving the problem of extreme flammability of lithium metal anodes. The ZnO interlayer design can completely seal the TPP component within the interlayer of the anode during conventional anode cycling, eliminating the side reactions between lithium metal and flame retardant during conventional electrode operation. Combined with the inhibition of Li dendrite formation by the three-dimensional structure and the lithium affinity of ZnO in the framework, the Li + With uniform deposition, the composite lithium anode exhibits excellent cycle stability, showing higher cycle stability than the pure lithium anode in electrochemical tests. Attached Figure Description

[0025] Figure 1 These are cross-sectional SEM images of the products obtained in each preparation step of Example 1;

[0026] Figure 2 The self-extinguishing time of the electrodes prepared in Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3;

[0027] Figure 3 Infrared thermographs and physical images of the electrodes prepared in Example 1 and Comparative Examples 1 and 2 during the ignition test process;

[0028] Figure 4 The image shows the actual photos of the pouch cells assembled with the negative electrodes prepared in Example 1 and Comparative Example 1 during the ignition test process.

[0029] Figure 5 The cycle performance of the CR2032 coin lithium metal full cells using the post-combustion negative electrode assembled in Example 1 and Comparative Examples 1 and 2 is shown.

[0030] Figure 6 The cycle performance of the CR2032 coin lithium metal full cells assembled in Example 1 and Comparative Examples 1 and 2;

[0031] Figure 7 The image shows the X-ray photoelectron spectroscopy depth etching pattern of the composite lithium anodes prepared in Example 1 and Comparative Example 2 after cycling. Detailed Implementation

[0032] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] A method for preparing a multilayered porous intelligent flame-retardant framework composite lithium metal anode includes the following steps:

[0035] Step 1: Preparation of TPP-GO mixed solution: Mix 10 mg / g GO aqueous solution and 0.125 g / ml TPP ethanol solution at a mass ratio of 2:1 (i.e., add 4 ml TPP ethanol solution to 25 g GO aqueous solution) and stir until homogeneous to obtain TPP-GO mixed solution.

[0036] Step 2: Preparation of TPP||GO foam: The TPP-GO mixed solution is uniformly coated on a plastic film, and then placed in a freeze dryer and freeze-dried at -20℃ for 24 hours. The plastic film is then removed and rolled to a foam thickness of 80μm to obtain porous TPP||GO foam.

[0037] Step 3: Preparation of ZnO||TPP||GO stacked porous flame-retardant framework: Using an atomic layer deposition (ALD) device, porous TPP||GO foam was placed in a chamber at 150℃ and deposited for 400 cycles, resulting in a 150nm ZnO thin film deposited on its surface and inside, thus obtaining a ZnO||TPP||GO stacked porous flame-retardant framework.

[0038] Step 4: Preparation of the composite lithium metal anode with a multilayered porous intelligent flame-retardant framework: Metallic Li was heated to 350°C on a heating stage, and molten Li droplets were prepared in an argon-filled glove box. Lithium was absorbed into the framework by contacting the edges of the ZnO||TPP||GO multilayered porous flame-retardant framework with the molten lithium droplets for about 20 seconds. Then, the mixture was cooled to room temperature to obtain the (2:1) Li||ZnO||TPP||GO composite lithium metal anode.

[0039] The application of the above-mentioned multilayered porous intelligent flame-retardant framework composite lithium metal anode in lithium metal batteries is as follows:

[0040] Assembly of a full cell using the combustion-exposed negative electrode: The aforementioned composite lithium metal negative electrode (2:1) Li||ZnO||TPP||GO was ignited for 2 seconds. The combustion-exposed material was used as the negative electrode, and assembled into a full cell with a commercially available ternary nickel-cobalt-manganese layered positive electrode (LiNi8Co8Mn8O2(NCM811)), a Celgard 2325 separator, and a locally high-concentration electrolyte (molar ratio of LiFSI:DME:TTE = 1:1.2:3). The positive electrode surface capacity was 1.63 mAh cm⁻¹. -2 The ratio of negative electrode capacity to positive electrode capacity (R) N / P The value was 2.45, resulting in a CR2032 coin cell lithium metal full cell using the negative electrode after combustion.

[0041] Assembly of lithium metal full cell: The above-mentioned composite metal lithium anode (2:1)Li||ZnO||TPP||GO is used as the anode, and the remaining steps are the same as the assembly of the full cell using the combustion anode.

[0042] Example 2

[0043] A method for preparing a multilayered porous intelligent flame-retardant framework composite lithium metal anode is as described in Example 1, except that in step one, the mass ratio of TPP to GO is replaced with 1.5:1 (i.e., 3 ml of TPP ethanol solution is added to 25 g of GO aqueous solution) to obtain a multilayered porous intelligent flame-retardant framework composite lithium metal anode (1.5:1)Li||ZnO||TPP||GO.

[0044] The remaining steps and conditions are the same as in Example 1.

[0045] The application method of the above-mentioned multilayered porous intelligent flame-retardant skeleton composite lithium metal anode in lithium metal batteries is the same as in Example 1.

[0046] Example 3

[0047] A method for preparing a multilayered porous intelligent flame-retardant framework composite lithium metal anode, as described in Example 1, is as follows: in step one, the mass ratio of TPP to GO is replaced with 1:1 (i.e., 2 ml of TPP ethanol solution is added to 25 g of GO aqueous solution) to obtain a multilayered porous intelligent flame-retardant framework composite lithium metal anode (1:1)Li||ZnO||TPP||GO.

[0048] The remaining steps and conditions are the same as in Example 1.

[0049] The application method of the above-mentioned multilayered porous intelligent flame-retardant skeleton composite lithium metal anode in lithium metal batteries is the same as in Example 1.

[0050] Example 4

[0051] A method for preparing a multilayered porous intelligent flame-retardant framework composite lithium metal anode is as described in Example 1, except that in step one, the mass ratio of TPP to GO is replaced with 0.5:1 (i.e., 1 ml of TPP ethanol solution is added to 25 g of GO aqueous solution) to obtain a multilayered porous intelligent flame-retardant framework composite lithium metal anode (0.5:1)Li||ZnO||TPP||GO.

[0052] The remaining steps and conditions are the same as in Example 1.

[0053] The application method of the above-mentioned multilayered porous intelligent flame-retardant skeleton composite lithium metal anode in lithium metal batteries is the same as in Example 1.

[0054] Comparative Example 1

[0055] The negative electrode in this comparative example is pure metallic lithium.

[0056] The application method of the above negative electrode in lithium metal batteries is the same as in Example 1.

[0057] Comparative Example 2

[0058] A method for preparing a composite lithium metal anode with flame-retardant foam tightly attached to a lithium sheet, as described in Example 1, except that step (iii) is omitted, and the porous TPP||GO foam obtained in step (ii) is attached to the lithium sheet to obtain the composite lithium metal anode with flame-retardant foam tightly attached to the lithium sheet; the specific steps are as follows:

[0059] The preparation of the TPP-GO mixed solution is the same as step (I) in Example 1;

[0060] The preparation of porous TPP-GO foam is the same as step (II) in Example 1;

[0061] Step 3: Preparation of lithium metal composite anode: Press and attach porous TPP||GO foam onto the lithium sheet to obtain a composite lithium metal anode (2:1)Li@TPP||GO with flame-retardant foam tightly attached to the lithium sheet.

[0062] The application method of the above negative electrode in lithium metal batteries is the same as in Example 1.

[0063] Comparative Example 3

[0064] A method for preparing a flame-retardant-free multilayer porous framework composite lithium metal anode is as described in Example 1, except that step (i) is omitted, and step (ii) is performed directly by replacing the TPP-GO mixed solution with an aqueous GO solution.

[0065] The remaining steps and conditions are the same as in Example 1, and Li||ZnO||GO is obtained.

[0066] The application method of the above negative electrode in lithium metal batteries is the same as in Example 1.

[0067] Experimental Example 1

[0068] (1) Test SEM images of the cross sections of the materials obtained in each preparation step of Example 1.

[0069] like Figure 1 As shown, the prepared Li||ZnO||TPP||GO composite lithium metal anode has a thickness of approximately 80 μm. The TPP||GO foam and ZnO||TPP||GO framework have a porous layered structure, with lithium metal filling the pores of the composite framework. In the TPP||GO foam, the thickness of the monolayer is 260 nm, and in the ZnO||TPP||GO, the thickness of the monolayer is 560 nm.

[0070] (2) Electrode ignition test

[0071] The electrodes prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to ignition tests. Ignition was performed by open flame for 2 seconds, followed by a 3-second intermittent ignition, and this cycle was repeated. If a sample failed to burn after three ignition cycles, it was defined as non-combustible. The self-extinguishing time SET (s / g) was obtained by dividing the continuous burning time and mass of each sample.

[0072] Depend on Figure 2 It is evident that the self-extinguishing time decreases with increasing TPP flame retardant content. Example 1 exhibits a self-extinguishing time of 0, demonstrating excellent flame retardancy. Comparative Examples 2 and 3 show only a slight decrease in self-extinguishing time compared to Comparative Example 1, proving the crucial role of the layered porous flame-retardant framework in the present invention for the flame retardancy of the composite lithium metal anode. Figure 3 The images shown are infrared thermographs and physical photographs taken during the ignition tests of Example 1 and Comparative Examples 1 and 2, demonstrating the flame retardancy of Example 1 and its small temperature rise during ignition. In a more stringent ignition test, the electrode obtained in Example 1 remained non-combustible under an open flame for 10 seconds.

[0073] (3) Ignition test of soft-pack full battery

[0074] Ignition tests were conducted on NCM811 pouch cells assembled with the negative electrodes prepared in Example 1 and Comparative Example 1. Using Example 1 and Comparative Example 1 as negative electrodes, pouch lithium metal cells were assembled with commercially available ternary nickel-cobalt-manganese layered positive electrodes (LiNi8Co8Mn8O2(NCM811)), PE separators, and locally high-concentration electrolytes (molar ratio of LiFSI:DME:TTE = 1:1.2:3), respectively. The effective electrode area was 4.5 cm × 5.7 cm. These cells were then used to illuminate an LED light, and the battery casing was cut open to expose part of the electrodes for ignition tests. The ignition method was the same as for electrode ignition tests.

[0075] Depend on Figure 4 As can be seen, the pouch cell assembled with the negative electrode prepared in Comparative Example 1 burned after being ignited by a flame for 2 seconds, and then the flame spread rapidly and intensely. In contrast, the pouch cell assembled with the negative electrode prepared in Example 1 did not burn in any of the three ignition attempts, and the LED light remained on throughout. In a more stringent ignition test, the pouch cell assembled with the negative electrode obtained in Example 1 remained unburnt under a continuous open flame for 20 seconds.

[0076] (4) Performance testing of full cells assembled using the post-combustion negative electrode

[0077] Cyclic performance tests were conducted on the CR2032 coin-type lithium metal full batteries assembled in Example 1 and Comparative Examples 1 and 2 using the post-combustion negative electrode, with a cycle rate of 0.5C.

[0078] Depend on Figure 5It can be seen that the full cell in Example 1 has a capacity retention rate of 93.72% after 250 cycles, which is better than the full cells in Comparative Example 1 and Comparative Example 2 (capacity retention rates of 36.03% after 80 cycles and 35.08% after 50 cycles, respectively).

[0079] (5) Full battery performance test

[0080] Cyclic performance tests were conducted on the CR2032 coin cell lithium metal full cells assembled in Example 1 and Comparative Examples 1 and 2, with a cycle rate of 0.5C.

[0081] Depend on Figure 6 It can be seen that the full cell in Example 1 has a capacity retention of 79.09% after 500 cycles, which is better than the full cells in Comparative Example 1 and Comparative Example 2 (43.13% and 14.15% respectively after 500 cycles).

[0082] (6) The negative electrode in Example 1 and Comparative Example 2 was etched with ion beams of different etching times for 5 cycles.

[0083] CR2032 coin-type lithium metal symmetric cells were assembled using the electrodes prepared in Example 1 and Comparative Example 2. After 5 cycles, the electrode surface was etched. X-ray photoelectron spectroscopy depth etching pattern shows ( Figure 7 In Comparative Example 2, the SEI of the negative electrode contained a large amount of Li3PO4. Since phosphorus-related elements were absent in the electrolyte, this result demonstrates that the unprotected TPP||GO matrix dissolved into the electrolyte and corroded the Li metal negative electrode, which is detrimental to uniform lithium deposition and reversible lithium negative electrode cycling. In contrast, the SEI of the negative electrode in Example 1 was completely free of Li3PO4, indicating that the ZnO interlayer design can completely seal the TPP component within the interlayer of the negative electrode during conventional negative electrode cycling, preventing Li metal corrosion of the TPP and forming an SEI that is beneficial for battery cycling.

[0084] In summary, this invention provides a method for preparing a multilayered porous intelligent flame-retardant skeleton composite lithium metal anode material and its application in lithium metal batteries. It achieves excellent flame-retardant effect, with the lithium metal anode not burning for 10 seconds after being ignited in an open flame, and improves the cycle stability of lithium metal batteries, showing great potential for practical application.

[0085] The above description is only a preferred embodiment of the present invention. The implementation of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a layered porous intelligent flame-retardant framework composite lithium metal anode in lithium metal batteries, characterized in that the microstructure of the layered porous intelligent flame-retardant framework composite lithium metal anode is a layered porous structure; the composite lithium metal anode is a graphene oxide sheet surface coated with a triphenyl phosphate layer and a ZnO layer from the inside to the outside, and lithium metal particles are loaded on the surface of the ZnO layer and filled in the pores of the layered porous structure; A method for preparing a multilayered porous intelligent flame-retardant framework composite lithium metal anode includes the following steps: (1) A TPP-GO mixed solution was obtained by thoroughly mixing an aqueous dispersion of graphene oxide (GO) with an ethanol solution of triphenyl phosphate (TPP) flame retardant; then, porous TPP||GO foam was obtained by freeze drying and roll pressing; the mass ratio of triphenyl phosphate to graphene oxide was 2:

1. (2) A porous flame-retardant skeleton ZnO||TPP||GO is obtained by loading ZnO on the surface and inside of porous TPP||GO foam; (3) A composite lithium metal anode with a multilayered porous flame-retardant framework ZnO||TPP||GO loaded with lithium metal is obtained by multilayered porous intelligent flame-retardant framework Li||ZnO||TPP||GO.

2. The application according to claim 1, characterized in that, In step (1), the mass concentration of the graphene oxide aqueous dispersion is 1-100 mg / mL.

3. The application according to claim 1, characterized in that, In step (1), the concentration of the ethanol solution of triphenyl phosphate flame retardant is 0.1-0.5 g / ml.

4. The application according to claim 1, characterized in that, In step (1), the preparation method of porous TPP||GO foam includes the following steps: uniformly coating the TPP-GO mixed solution onto a plastic film, freeze-drying, then removing the plastic film, and rolling to obtain porous TPP||GO foam; the thickness of the porous TPP||GO foam is 50-300 µm.

5. The application according to claim 1, characterized in that, In step (1), the freeze-drying temperature is -40℃ to 0℃; the freeze-drying time is 24h to 48h.

6. The application according to claim 1, characterized in that, In step (2), the preparation method of the multilayer porous flame-retardant skeleton ZnO||TPP||GO includes the following steps: depositing a 100-200nm thick ZnO layer on the surface and inside of the porous TPP||GO foam using atomic layer deposition to obtain the multilayer porous flame-retardant skeleton ZnO||TPP||GO.

7. The application according to claim 1, characterized in that, In step (3), the preparation method of the composite lithium metal anode with a multilayered porous intelligent flame-retardant skeleton includes the following steps: contacting the four edges of the multilayered porous flame-retardant skeleton ZnO||TPP||GO with molten lithium metal, and uniformly diffusing the molten lithium metal into the interior of the multilayered porous flame-retardant skeleton ZnO||TPP||GO to obtain the multilayered porous intelligent flame-retardant skeleton composite lithium metal anode.

8. The application according to claim 1, characterized in that, The positive electrode of the lithium metal battery is lithium cobalt oxide, ternary nickel-cobalt-manganese layered material, lithium iron phosphate, lithium titanate, layered lithium-rich manganese-based positive electrode material, or layered lithium manganese oxide (LiMnO2); the separator is selected from one or more combinations of glass fiber, polypropylene separator, or polyethylene separator; the solute of the electrolyte is selected from one or more combinations of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium nitrate, or lithium polysulfide; the solvent of the electrolyte is selected from one or more combinations of 1,3-dioxapentane, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethyl carbonate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether, or 1,1,1,2,2,3,4,5,5,5-decafluoropentane; the lithium metal battery packaging includes button cell casings, pouch cell casings, or stainless steel cell casings.

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