Laminated structure porous intelligent flame-retardant skeleton composite metal lithium negative electrode and preparation and application thereof

Abstract

The invention provides a laminated structure porous intelligent flame-retardant skeleton composite metal lithium negative electrode as well as preparation and application thereof. The preparation method of the composite metal lithium negative electrode comprises the following steps: fully mixing a graphene oxide aqueous dispersion with an ethanol solution of a triphenyl phosphate flame retardant to obtain a TPP-GO mixed solution; then carrying out freeze drying and rolling to obtain porous TPPGO foam; loading ZnO on the surface and in the porous TPPGO foam to obtain a porous flame-retardant framework ZnOTPPGO with a laminated structure; and further loading metal lithium. The laminated structure framework effectively prevents the flame retardant from being decomposed in the preparation process of the composite negative electrode and from being diffused into electrolyte and lithium metal in the cycle process of the battery, and meanwhile, the flame retardant can be successfully heated and released under the high-temperature conditions such as a fire disaster; therefore, the flame retardance of the lithium metal negative electrode is realized while the electrochemical performance of the lithium metal battery is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of high specific energy and high safety lithium metal batteries, and particularly relates to a laminated porous intelligent flame-retardant skeleton composite lithium metal anode and its preparation and application. Background Art

[0002] Among the candidate materials for lithium battery anodes, lithium metal stands out due to its maximum theoretical energy density (3860 mAh g -1 ) and the lowest electrochemical potential (-3.04 V compared to the standard hydrogen electrode), becoming the best choice for lithium battery anode materials. However, due to the high flammability and reactivity of the lithium metal anode and the use of highly flammable organic electrolytes, lithium metal batteries have serious safety problems. In addition, the dendrites growing on the surface of the lithium metal anode may penetrate the separator, causing internal short circuit of the battery, generating a large amount of heat, triggering a series of exothermic reactions, and ultimately leading to thermal runaway, resulting in catastrophic accidents such as fires and explosions. These safety problems limit the large-scale practical application of lithium metal batteries.

[0003] Despite the well-known serious combustion problems of lithium metal anodes, current research on the construction of safe lithium batteries mainly focuses on the development of non-flammable liquid or solid electrolytes, high thermal stability separators, intelligent response separators, and battery management systems, etc. To improve the air stability of lithium metal to a certain extent, other strategies such as artificial fluorinated protective layers have also been developed. However, due to the extremely high flammability and reducibility of lithium metal anodes, all of the above strategies cannot provide sufficient flame-retardant effects to extinguish the fire of lithium metal anodes. In addition, due to the serious corrosion reaction that destroys the electrode function between the flame retardant and lithium metal, the conventional flame retardant mixing strategy also cannot solve this challenge. Since the invention of lithium batteries, this safety problem has been one of the most critical but unsolved 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 is to conduct flame-retardant design for lithium metal anodes without affecting the electrochemical performance of the batteries. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a laminated structure porous intelligent flame-retardant framework composite lithium metal anode and its preparation and application. The laminated structure framework in the present invention effectively prevents the decomposition of the flame retardant during the preparation of the composite anode and its diffusion into the electrolyte and lithium metal during the battery cycling process. At the same time, under high-temperature conditions such as fire, the flame retardant can be successfully released by heating, thereby realizing the 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 heat insulation performance of the three-dimensional structure within the framework, the present invention achieves a remarkable flame retardant effect that the composite anode does not burn within 10 s when ignited by an open flame, and can still maintain the normal operation of the battery after ignition, solving the extreme flammability problem of the lithium metal anode. In addition, the ZnO intermediate layer design can completely seal the flame retardant within the intermediate layer of the anode during the normal cycling of the anode, eliminating the side reaction between the lithium metal and the flame retardant during the operation of the conventional electrode. Combining the inhibitory effect of the three-dimensional structure on the formation of Li dendrites and the lithium affinity of ZnO in the framework resulting in the + uniform deposition, the composite lithium anode exhibits excellent cycling stability. Therefore, the present invention fundamentally solves for the first time the safety problem that has long hindered the large-scale application of lithium metal anodes and has great application prospects.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A preparation method of a laminated structure porous intelligent flame-retardant framework composite lithium metal anode, comprising the steps of:

[0007] (1) A graphene oxide (GO) aqueous dispersion is fully mixed with an ethanol solution of a triphenyl phosphate (TPP) flame retardant to obtain a TPP-GO mixed solution; then it is freeze-dried and roll-pressed to obtain a porous TPP||GO foam;

[0008] (2) ZnO is loaded on the surface and inside of the porous TPP||GO foam to obtain a laminated structure porous flame-retardant framework ZnO||TPP||GO;

[0009] (3) The laminated structure porous flame-retardant framework ZnO||TPP||GO is loaded with lithium metal to obtain a laminated structure porous intelligent flame-retardant framework composite lithium metal anode (Li||ZnO||TPP||GO).

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

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

[0012] Preferably according to 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] Preferably according to the present invention, in step (1), the preparation method of the porous TPP||GO foam includes the steps of: uniformly coating the TPP-GO mixed solution on a plastic film, freeze-drying, then removing the plastic film, and rolling to obtain the porous TPP||GO foam. The thickness of the porous TPP||GO foam is 50 - 300 μm.

[0014] Preferably according to the present invention, in step (1), the freeze-drying temperature is -40°C - 0°C; the freeze-drying time is 24 h - 48 h.

[0015] Preferably according to the present invention, in step (2), the preparation method of the laminated porous flame-retardant framework ZnO||TPP||GO includes the steps of: depositing a ZnO layer with a thickness of 100 - 200 nm on the surface and inside of the porous TPP||GO foam by atomic layer deposition to obtain the laminated porous flame-retardant framework ZnO||TPP||GO; the thickness of the ZnO layer is preferably 150 nm.

[0016] Preferably according to the present invention, in step (3), the preparation method of the laminated porous intelligent flame-retardant framework composite lithium metal anode includes the steps of: bringing the four peripheral edges of the laminated porous flame-retardant framework ZnO||TPP||GO into contact with molten lithium metal, and the molten lithium metal uniformly diffuses into the interior of the laminated porous flame-retardant framework ZnO||TPP||GO framework to obtain the laminated porous intelligent flame-retardant framework composite lithium metal anode. Since there are a large number of nano-pores and lithiumophilic ZnO layers inside the laminated porous flame-retardant framework ZnO||TPP||GO, according to capillary action, the molten lithium metal will uniformly diffuse into the interior of the ZnO||TPP||GO framework.

[0017] A laminated porous intelligent flame-retardant framework composite lithium metal anode is prepared by the above method.

[0018] Preferably according to the present invention, the microscopic morphology of the laminated porous intelligent flame-retardant framework composite lithium metal anode is a laminated porous structure; the composite lithium metal anode is such that a triphenyl phosphate layer and a ZnO layer are sequentially coated on the surface of the graphene oxide sheet 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 laminated porous structure.

[0019] The application of the above laminated porous intelligent flame-retardant framework composite lithium metal anode in a lithium metal battery.

[0020] Preferably according to the present invention, the positive electrode of the lithium metal battery is lithium cobaltate, ternary nickel cobalt manganese layered material, lithium iron phosphate, lithium titanate, layered lithium-rich manganese-based positive electrode material or layered lithium manganate (LiMnO 2 ); the separator is selected from one or a combination of two or more of glass fiber, polypropylene separator or polyethylene separator; the solute of the electrolyte is selected from one or a combination of two or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium nitrate or lithium polysulfide, and the solvent of the electrolyte is selected from one or a combination of two or more of 1,3-dioxolane, 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 package includes a button cell case, a soft package cell case or a stainless steel cell case.

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

[0022] (1) The laminated porous framework in the present invention is the key to achieving excellent flame retardancy of the composite lithium metal negative electrode, effectively preventing the decomposition of the flame retardant during the preparation of the composite negative electrode and the diffusion into the electrolyte and lithium metal during the battery cycling process. While ensuring the electrochemical performance of the lithium metal battery, through the high-temperature release of the flame retardant in case of fire and the heat insulation performance of the three-dimensional structure inside the framework, the flame retardant design for the lithium metal negative electrode is realized.

[0023] (2) The method of atomic layer chemical vapor deposition is adopted in the present invention, which can deposit ZnO uniformly on the surface and inside of the porous TPP||GO foam, not limited to the surface only. This lithium-philic ZnO coating can reduce the nucleation barrier, reduce polarization, and promote the uniform deposition of Li + , thereby improving the electrochemical performance of the lithium metal negative electrode. In addition, the ZnO intermediate layer design can completely seal the TPP component inside the intermediate layer of the negative electrode during the normal negative electrode cycling, prevent the Li metal corrosion reaction of TPP, and form a SEI beneficial to battery cycling. In addition, the ZnO layer is conducive to the absorption of molten lithium into the framework interior, avoiding the decomposition of the flame retardant during the preparation process. And the atomic layer chemical vapor deposition method has a mature process, and the deposited oxide layer has a uniform thickness and high stability. Therefore, the present invention has the advantage of large-scale preparation.

[0024] (3) The present invention has successfully developed a laminated porous intelligent flame-retardant framework composite lithium metal anode with excellent flame retardancy and cycle stability. This composite lithium metal anode has a remarkable flame retardant effect that it does not burn within 10 s when ignited in an open flame, and can still maintain the normal operation of the battery after ignition, solving the problem of extreme flammability of lithium metal anodes. The ZnO intermediate layer design can completely seal the TPP component within the intermediate layer of the anode during the cycling of a conventional anode, eliminating the side reaction between lithium metal and the flame retardant during the operation of a conventional electrode. Combining the inhibitory effect of the three-dimensional structure on the formation of Li dendrites and the lithiophilicity of ZnO in the framework resulting in the + uniform deposition, the composite lithium anode exhibits excellent cycle stability and shows higher cycle stability than a pure lithium anode in electrochemical tests. Description of the Drawings

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

[0026] Figure 2 Self-extinguishing times of the electrodes prepared in Example 1, 2, 3, 4 and Comparative Examples 1, 2, 3;

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

[0028] Figure 4 Physical images during the ignition test of the soft-pack full battery assembled with the anodes prepared in Example 1 and Comparative Example 1;

[0029] Figure 5 Cycling performance of the CR2032 coin-type lithium metal full batteries assembled with the burned anodes in Example 1 and Comparative Examples 1, 2;

[0030] Figure 6 Cycling performance of the CR2032 coin-type lithium metal full batteries assembled in Example 1 and Comparative Examples 1, 2;

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

[0032] The present invention will be further explained and described below with reference to the drawings and specific embodiments. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] A preparation method of a laminated structure porous intelligent flame-retardant framework composite lithium metal anode, comprising the steps:

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

[0036] Step 2, preparation of a TPP||GO foam: Uniformly coat the TPP-GO mixed solution on a plastic film, then place it in a freeze dryer, freeze-dry at -20 °C for 24 h, then remove the plastic film, and roll it to a foam thickness of 80 μm to obtain a porous TPP||GO foam.

[0037] Step 3, preparation of a ZnO||TPP||GO laminated structure porous flame-retardant framework: Using an atomic layer deposition (ALD) device, place the porous TPP||GO foam in a chamber at 150 °C and deposit 400 cycles to deposit a 150 nm ZnO thin film on its surface and inside to obtain a ZnO||TPP||GO laminated structure porous flame-retardant framework.

[0038] Step 4, preparation of a laminated structure porous intelligent flame-retardant framework composite lithium metal anode: Heat metal Li on a heating table to 350 °C, and prepare molten Li droplets in a glove box filled with argon. Absorb lithium into the framework by contacting the four peripheral edges of the ZnO||TPP||GO laminated structure porous flame-retardant framework with the molten lithium droplets for about 20 s, and then cool to room temperature to obtain a laminated structure porous intelligent flame-retardant framework composite lithium metal anode (2:1) Li||ZnO||TPP||GO.

[0039] The application of the above laminated structure porous intelligent flame-retardant framework composite lithium metal anode in a lithium metal battery is as follows:

[0040] Assembly of a full cell using the anode after combustion: Ignite the above composite lithium metal anode (2:1) Li||ZnO||TPP||GO for 2 s, and use the material after combustion as the anode, and assemble a full cell with a commercial ternary nickel cobalt manganese layered cathode (LiNi 8 Co 8 Mn 8 O 2 (NCM811)), a Celgard 2325 separator, and a locally high-concentration electrolyte (molar ratio of LiFSI:DME:TTE = 1:1.2:3). The cathode areal capacity is 1.63 mAh cm -2 , and the anode:cathode capacity ratio (R N / P) is 2.45, and a CR2032 button-type lithium metal full cell using the post-combustion negative electrode is obtained.

[0041] Assembly of the lithium metal full cell: Using the above composite metal lithium negative electrode (2:1) Li||ZnO||TPP||GO as the negative electrode, and the remaining steps are the same as those for the assembly of the full cell using the post-combustion negative electrode above.

[0042] Example 2

[0043] A preparation method of a laminated structure porous intelligent flame-retardant skeleton composite metal lithium negative electrode is as described in Example 1, except that: in Step 1, the mass ratio of TPP to GO is replaced with 1.5:1 (i.e., 3 ml of ethanol solution of TPP is added to 25 g of GO aqueous solution), and a laminated structure porous intelligent flame-retardant skeleton composite metal lithium negative electrode (1.5:1) Li||ZnO||TPP||GO is obtained.

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

[0045] The application method of the above laminated structure porous intelligent flame-retardant skeleton composite metal lithium negative electrode in a lithium metal battery is the same as that in Example 1.

[0046] Example 3

[0047] A preparation method of a laminated structure porous intelligent flame-retardant skeleton composite metal lithium negative electrode is as described in Example 1, except that: in Step 1, the mass ratio of TPP to GO is replaced with 1:1 (i.e., 2 ml of ethanol solution of TPP is added to 25 g of GO aqueous solution), and a laminated structure porous intelligent flame-retardant skeleton composite metal lithium negative electrode (1:1) Li||ZnO||TPP||GO is obtained.

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

[0049] The application method of the above laminated structure porous intelligent flame-retardant skeleton composite metal lithium negative electrode in a lithium metal battery is the same as that in Example 1.

[0050] Example 4

[0051] A preparation method of a laminated structure porous intelligent flame-retardant skeleton composite metal lithium negative electrode is as described in Example 1, except that: in Step 1, the mass ratio of TPP to GO is replaced with 0.5:1 (i.e., 1 ml of ethanol solution of TPP is added to 25 g of GO aqueous solution), and a laminated structure porous intelligent flame-retardant skeleton composite metal lithium negative electrode (0.5:1) Li||ZnO||TPP||GO is obtained.

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

[0053] The application method of the above laminated structure porous intelligent flame-retardant skeleton composite lithium metal anode in a lithium metal battery is the same as that 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 a lithium metal battery is the same as that in Example 1.

[0057] Comparative Example 2

[0058] A preparation method of a composite lithium metal anode with a flame-retardant foam closely attached to a lithium sheet is 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 a composite lithium metal anode with a flame-retardant foam closely 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) of Example 1;

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

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

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

[0063] Comparative Example 3

[0064] A preparation method of a laminated structure porous skeleton composite lithium metal anode without a flame retardant is as described in Example 1, except that: step (i) is omitted, and the TPP-GO mixed solution is directly replaced with an aqueous GO solution for step (ii).

[0065] The remaining steps and conditions are the same as those in Example 1 to obtain Li||ZnO||GO.

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

[0067] Test Example 1

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

[0069] As Figure 1As shown, the prepared Li||ZnO||TPP||GO composite lithium metal anode has a thickness of about 80 μm. The TPP||GO foam and ZnO||TPP||GO framework have a porous layered structure, and metallic lithium is filled in the pores of the composite framework. In the TPP||GO foam, the thickness of the single layer is 260 nm, and in ZnO||TPP||GO, the thickness of the single layer 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. The ignition method was to ignite with an open flame for 2 s and then interrupt for 3 s, and this cycle was repeated. If the sample did not burn after 3 ignitions, it was defined as non-flammable. The self-extinguishing time SET (s / g) was obtained by dividing the continuous burning time of each sample by its mass.

[0072] As Figure 2 can be seen, as the content of the flame retardant TPP increases, the self-extinguishing time decreases. The self-extinguishing time of Example 1 is 0, indicating excellent flame retardancy. Compared with Comparative Example 1, the self-extinguishing times of Comparative Example 2 and Comparative Example 3 only slightly decrease, demonstrating the important role of the laminated structure porous flame retardant framework in the present invention for the flame retardancy of the composite lithium metal anode. Figure 3 Figs. are the infrared thermal images and physical images during the ignition tests of Example 1 and Comparative Examples 1 and 2, showing the flame retardancy of Example 1 and the smaller temperature rise during the ignition process. In a more severe ignition test, the electrode obtained in Example 1 can remain non-flammable under an open flame for 10 s.

[0073] (3) Soft-pack full cell ignition test

[0074] The anodes prepared in Example 1 and Comparative Example 1 were assembled into NCM811 soft-pack full cells for ignition tests. Using Example 1 and Comparative Example 1 as the anodes, they were respectively assembled with a commercial ternary nickel cobalt manganese layered cathode (LiNi 8 Co 8 Mn 8 O 2 (NCM811)), a PE separator, and a locally high-concentration electrolyte (molar ratio of LiFSI:DME:TTE = 1:1.2:3) to assemble full cells. The effective area of the electrode was 4.5 cm × 5.7 cm to obtain soft-pack lithium metal full cells. Then, an LED lamp was lit with them, and the battery case was cut open to expose part of the electrode for ignition tests. The ignition method was the same as that for the electrode ignition test.

[0075] As Figure 4It can be seen that the soft-pack battery 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 strongly. The soft-pack battery assembled with the negative electrode prepared in Example 1 did not burn during the 3 ignition processes, and the LED light did not go out throughout the process. In a more stringent ignition test, the soft-pack battery assembled with the negative electrode obtained in Example 1 could remain non-combustible under an open flame for 20 s.

[0076] (4) Performance test of the full battery assembled with the burned negative electrode

[0077] For the CR2032 coin-type lithium metal full batteries assembled with the burned negative electrodes in Example 1 and Comparative Examples 1 and 2, a cycle performance test was carried out at a cycle rate of 0.5C.

[0078] It can be seen from Figure 5 that the capacity retention rate of the full battery in Example 1 after 250 cycles was 93.72%, which was better than that of the full batteries in Comparative Example 1 and Comparative Example 2 (the capacity retention rates were 36.03% after 80 cycles and 35.08% after 50 cycles, respectively).

[0079] (5) Performance test of the full battery

[0080] For the CR2032 coin-type lithium metal full batteries assembled in Example 1 and Comparative Examples 1 and 2, a cycle performance test was carried out at a cycle rate of 0.5C.

[0081] It can be seen from Figure 6 that the capacity retention rate of the full battery in Example 1 after 500 cycles was 79.09%, which was better than that of the full batteries in Comparative Example 1 and Comparative Example 2 (43.13% and 14.15% after 500 cycles, respectively).

[0082] (6) The negative electrodes in Example 1 and Comparative Example 2 after the symmetric battery assembled with ion beam etching with different etching times was cycled for 5 laps.

[0083] CR2032 coin-type lithium metal symmetric batteries were assembled with the electrodes prepared in Example 1 and Comparative Example 2, and the electrode surfaces were etched after 5 cycles. The X-ray photoelectron spectroscopy depth etching pattern shows ( Figure 7 ) that there are a large number of Li 3 PO 4 species in the SEI of the negative electrode in Comparative Example 2. Since there are no phosphorus-related elements in the electrolyte, this result proves that the TPP in the unprotected TPP||GO matrix dissolves into the electrolyte and corrodes the Li metal negative electrode, which is not conducive to the uniform lithium deposition and the SEI of the reversible lithium negative electrode cycle. In contrast, there is no Li 3 PO 4, indicating that the ZnO interlayer design can completely seal the TPP component within the interlayer of the anode during the normal anode cycling, prevent the Li metal corrosion reaction of TPP, and form a SEI that is beneficial to the battery cycling.

[0084] In summary, the present invention provides a preparation method of a laminated structure porous intelligent flame-retardant framework composite lithium metal anode material and its application in a lithium metal battery, achieving an excellent flame-retardant effect that the lithium metal anode does not burn within 10 s when ignited in an open flame, and improving the cycling stability of the lithium metal battery, having great practical application prospects.

[0085] The above are only the preferred embodiments of the present invention. The implementation manners of the present invention are not limited by the above embodiments. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode, comprising the steps of: (1) A graphene oxide (GO) aqueous dispersion and an ethanol solution of a triphenyl phosphate (TPP) flame retardant are fully mixed to obtain a TPP-GO mixed solution; then, a porous TPP||GO foam is obtained by freeze drying and roller pressing; (2) ZnO is loaded on the surface and inside of porous TPP||GO foam to obtain a laminated porous flame-retardant skeleton ZnO||TPP||GO; (3) The layered porous flame-retardant skeleton ZnO||TPP||GO is loaded with metallic lithium to obtain a layered porous intelligent flame-retardant skeleton composite metallic lithium anode (Li||ZnO||TPP||GO).

2. The method for preparing the laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode according to claim 1, characterized in that: In step (1), the mass concentration of the graphene oxide aqueous dispersion is 1-100 mg / g.

3. The method for preparing the laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode 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 method for preparing the laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode according to claim 1, characterized in that: In step (1), the mass ratio of triphenyl phosphate to graphene oxide is 0.5:1-2:1, preferably 2:

1.

5. The method for preparing the laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode according to claim 1, characterized in that: In step (1), the method for preparing porous TPP||GO foam includes the steps of: uniformly coating the TPP-GO mixed solution on 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.

6. The method for preparing the laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode according to claim 1, characterized in that: In step (1), the freeze-drying temperature is -40°C to 0°C; and the freeze-drying time is 24h to 48h.

7. The method for preparing the laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode according to claim 1, characterized in that: In step (2), the method for preparing a laminated porous flame-retardant skeleton ZnO||TPP||GO includes the steps of: using atomic layer deposition to deposit a 100-200 nm thick ZnO layer on the surface and inside of the porous TPP||GO foam to obtain a laminated porous flame-retardant skeleton ZnO||TPP||GO; the thickness of the ZnO layer is preferably 150 nm.

8. The method for preparing the laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode according to claim 1, characterized in that: In step (3), the preparation method of the laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode includes the steps of: contacting the edges of the laminated porous flame-retardant skeleton ZnO||TPP||GO with molten metal lithium, and uniformly diffusing the molten metal lithium into the interior of the laminated porous flame-retardant skeleton ZnO||TPP||GO skeleton to obtain the laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode.

9. A laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode, prepared by the method according to any one of claims 1 to 8; Preferably, the microscopic morphology of the laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode is a laminated porous structure; the composite metal lithium negative electrode is a graphene oxide sheet whose surface is sequentially coated with a triphenyl phosphate layer and a ZnO layer from the inside to the outside, and the lithium metal particles are loaded on the surface of the ZnO layer and filled in the pores of the laminated porous structure.

10. Application of the laminated porous intelligent flame-retardant skeleton composite metal lithium negative electrode as claimed in claim 9 in lithium metal batteries; Preferably, 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 diaphragm is selected from one or a combination of two or more of glass carbon fiber, polypropylene diaphragm or polyethylene diaphragm; the solute of the electrolyte is selected from one or a combination of two or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium nitrate or lithium polysulfide, and the solvent of the electrolyte is selected from 1, 3-Dioxolane, 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, or a combination of two or more thereof; lithium metal battery packaging includes button battery case, soft pack battery case or stainless steel battery case.

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