Lithium metal composite negative electrode, preparation method thereof and solid-state battery

Abstract

The present application relates to a kind of lithium metal composite negative electrode and its preparation method and solid-state battery.The lithium metal composite negative electrode of the present application is three-layer structure, it includes in turn: current collector, active material layer and space reinforcement layer, wherein active material layer is continuous or intermittent distribution metal lithium or lithium alloy layer, and space reinforcement layer is metal organic framework material (MOFs) modified three-dimensional graphene film material.During lithium metal battery cycle, space reinforcement layer controls lithium ion deposition and deintercalation, simultaneously act as lithium ion storage layer, improve the cycle and rate performance of solid-state battery.

Description

Technical Field

[0001] This invention relates to the field of lithium metal battery technology, and more specifically to a lithium metal composite anode, its preparation method, and a solid-state battery. Background Technology

[0002] Lithium-ion batteries, as the primary power source for new energy vehicles and portable electronic devices, have always been a focus of industry attention regarding their energy density and safety performance. Currently, commercially available lithium-ion batteries mainly use graphite as the anode material, but graphite's theoretical specific capacity is relatively low, becoming a bottleneck limiting the improvement of battery energy density. Lithium metal, due to its extremely high theoretical specific capacity and the lowest electrochemical potential, is considered an ideal anode material for next-generation high-energy-density batteries. However, lithium metal is prone to side reactions with the electrolyte during cyclic charging and discharging, forming an unstable solid electrolyte interface film. Furthermore, factors such as uneven electric field distribution can lead to the growth of lithium dendrites, causing short-circuit safety hazards and severely affecting the battery's cycle life and safety performance.

[0003] Chinese patent application CN116247215A discloses a lithium metal composite anode and its preparation method, a lithium metal battery, and an electrical device. The lithium metal composite anode includes an anode body, a fluorinated ether filling layer, and a fluorinated ether coating layer. The anode body includes a lithium metal body and a three-dimensional conductive framework located within the lithium metal body. However, there is still a problem in optimizing the type and proportion of fluorinated ether to select a more suitable fluorinated ether to obtain a superior solid electrolyte interface film. Summary of the Invention

[0004] This invention aims to solve the following technical problems: Existing technologies suffer from issues such as side reactions between lithium metal anodes and electrolytes during cyclic charging and discharging, the formation of unstable solid electrolyte interfacial films, and uneven electric field distribution leading to lithium dendrite growth, all of which affect battery cycle life and safety performance. Therefore, to address these problems, this invention provides a lithium metal composite anode, its preparation method, and a solid-state battery.

[0005] The inventors discovered that combining metal-organic frameworks (MOFs) with three-dimensional graphene can fully leverage their synergistic effects, significantly improving material performance. MOF-modified three-dimensional graphene combines the high specific surface area of ​​MOFs with the porous structure of three-dimensional graphene, forming a hierarchical porous system. This structure not only provides numerous active sites but also offers efficient channels for lithium-ion transport and distribution, thereby reducing local current density, suppressing lithium dendrite growth, and improving battery safety and cycle stability. The nanoporous structure of MOFs can restrict lithium-ion deposition behavior, ensuring uniform distribution on the three-dimensional graphene surface and preventing local lithium-ion aggregation and dendrite formation. This confinement effect significantly improves the cycle life and coulombic efficiency of lithium metal anodes.

[0006] Specifically, the present invention provides a lithium metal composite anode, the anode comprising an active material layer and a space reinforcement layer disposed on and in contact with the active material layer; wherein, the active material layer is a continuous or intermittently distributed lithium metal or lithium alloy layer; and the space reinforcement layer is a MOF-modified three-dimensional graphene film.

[0007] Optionally, the MOFs-modified three-dimensional graphene is obtained by in-situ growth of MOFs on the surface or in the pores of three-dimensional graphene, and the MOFs-modified three-dimensional graphene film is formed by coating a MOFs-modified three-dimensional graphene mixture onto a transfer film.

[0008] Optionally, the MOFs material includes MOFs materials with zinc-based, cobalt-based, vanadium-based, iron-based, aluminum-based, chromium-based, zirconium-based or lanthanide metal-based metals as metal ion or metal cluster nodes;

[0009] Preferably, the MOFs material is selected from one or a combination of at least two of the ZIF series, MIL series, UiO series, IRMofF series, PCN series, and NU series. ZIF materials are zeolite imidazole ester framework structure materials, which are porous crystalline materials. The ZIF series is selected from at least one of ZIF-7, ZIF-8, ZIF-63, ZIF-67, ZIF-71, and ZIF-90. MIL materials are synthesized from different transition metal elements and dicarboxylic acid ligands such as succinic acid and glutaric acid, exhibiting a periodic network structure. The MIL series is selected from at least one of MIL-53, MIL-88, MIL-96, MIL-100, MIL-101, and MIL-125. UiO materials are composed of zirconium ions and organic ligands. The UiO series is selected from at least one of UiO-67, UiO-68, UiO-76, UiO-77, and UiO-84. IRMOF materials are composed of separated secondary structural units [Zn,O]. 6+ Microporous crystalline materials are formed by the self-assembly of inorganic groups and a series of aromatic carboxylic acid ligands in an octahedral bridge, wherein the IRMOF series is selected from at least one of IRMOF-1, IRMOF-3, IRMOF-6, IRMOF-8, IRMOF-9, and IRMOF-10; PCN materials contain multiple cubic octahedral nanopore cages and form a cage-channel topological structure in space, wherein the PCN series is selected from at least one of PCN-14, PCN-200, PCN-221, PCN-222, PCN-223, and PCN-250; NU materials are composed of metal ions such as cobalt, magnesium, nickel, zinc, and iron and organic ligands, and have porosity, high specific surface area, and structural tunability, wherein the NU sequence is selected from at least one of NU-100, NU-109, NU-110, NU-111, NU-125, and NU-901.

[0010] Optionally, the three-dimensional graphene structure is a three-dimensional honeycomb graphene.

[0011] Optionally, the MOFs-modified three-dimensional graphene slurry includes MOFs-modified three-dimensional graphene powder, lithium salt, binder, and hydrophilic additive.

[0012] Optionally, the lithium salt includes one or more combinations of lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisfluorosulfonylimide, lithium bistrifluoromethanesulfonylimide, lithium dioxalateborate, lithium difluorooxalateborate, lithium carbonate, lithium oxalate, lithium bicarbonate, lithium acetate, lithium halides, lithium sulfate, and lithium hydroxide.

[0013] Optionally, the adhesive comprises one or a combination of at least two of the following: polyvinyl alcohol, polyethylene oxide, polybutene-styrene, polystyrene-butadiene copolymer, polyvinylidene fluoride, polystyrene, polycarboxylic cellulose, cyanoacrylate, cyclodextrin, cyclic ether derivatives, polyurethane, methacrylate, epoxy resin, vinyl acetate polymer, polyimide, organofluoropolymer, organosiloxane, polyethylene glycol, polyethylene, polyvinyl chloride, polypropylene, glycerol, ethylparaben, and their derivatives.

[0014] Optionally, the hydrophilic additive includes one or more combinations of carboxylates, sulfonates, sulfates, phosphates, imidazole ionic liquids, pyridine ionic liquids, quaternary ammonium ionic liquids, quaternary phosphonium ionic liquids, pyrrolidine ionic liquids, and piperidine ionic liquids.

[0015] Optionally, the transfer film material includes an organic material selected from one or more of polyvinylidene fluoride, polyvinyl chloride, polyethylene, polypropylene, polystyrene, styrene-butadiene-vinyl nitrile copolymer, polyimide, polycarbonate, phenolic plastics, polyoxymethylene, polyethylene terephthalate, styrene-modified polymethacrylic acid, polysulfone, polytetrafluoroethylene, amino plastics, and epoxy resin, or their homopolymers or copolymers.

[0016] Optionally, in the MOFs-modified three-dimensional graphene, the mass ratio of MOFs material to three-dimensional graphene is 1:(1-10).

[0017] When the MOF content is low, the conductivity and mechanical properties of three-dimensional graphene are well maintained, but the functionality of MOFs may be insufficient; when the MOF content is high, the functionality of MOFs is strong, but it may affect the conductivity and structural stability.

[0018] Optionally, the MOFs-modified three-dimensional graphene mixed slurry has a mass ratio of (1-20):(1-5):(1-5):(0.5-2) of MOFs-modified three-dimensional graphene, lithium salt, binder and hydrophilic additive.

[0019] Optionally, the MOFs material is in particulate form with a particle size D50 of 100-500 nm, a pore size of 0.1-10 Å, a density of 0.3-0.5 g / cm2, and a porosity of 70%-90%.

[0020] Optionally, the pore size of the three-dimensional graphene is 1-1000 nm, and the specific surface area is 500-5000 m². 2 / g.

[0021] Optionally, the adhesion of the transfer film is 1-8 g / inch, and the thickness is 20-100 μm.

[0022] The thickness of the space reinforcement layer is 1-100 μm and the Young's modulus is ≥6 GPa.

[0023] Optionally, the active material layer includes one or a combination of a lithium metal layer and a lithium alloy layer; preferably, the lithium alloy layer includes an alloy of lithium with one or more of silicon, indium, silver, carbon, magnesium, aluminum, boron, tin, gallium, cobalt, gold, barium, bismuth, calcium, germanium, mercury, platinum, zinc, lead, antimony, cadmium, and cobalt.

[0024] Optionally, the thickness of the active material layer is 3μm-300μm, preferably 10μm-100μm.

[0025] Optionally, the thickness ratio of the space reinforcement layer to the active material layer is (0.001-1):1, preferably (0.01-0.1):1.

[0026] Optionally, the lithium metal composite negative electrode further includes a current collector, which includes at least one of copper foil, aluminum foil, stainless steel foil, nickel foil, tin foil, carbon nanotube paper, carbon fiber paper, copper mesh, aluminum mesh, stainless steel mesh, nickel foam, and organic fiber film with metal plating on the surface.

[0027] Another aspect of the present invention provides a method for preparing a lithium metal composite anode as described above, the method comprising:

[0028] (1) Preparation of MOFs-modified three-dimensional graphene: Three-dimensional graphene (3DG) is immersed in a solution containing MOF precursor. The reaction is carried out at 80-120℃ for several hours to several days to allow MOF to grow on the surface or in the pores of 3DG; the residual solvent is removed by vacuum drying at 60-80℃ to obtain MOF-3DG composite material, i.e., MOFs-modified three-dimensional graphene;

[0029] (2) Weigh the MOF-3DG composite material powder, refine the powder, and mix it evenly;

[0030] (3) Weigh a certain amount of solvent, add lithium salt, binder and hydrophilic additive according to the corresponding mass fraction, mix and stir, then add MOF-3DG composite material powder obtained in step (2), mix and stir to obtain a uniform and viscous slurry;

[0031] (4) The slurry obtained in step (3) is placed on the transfer film and dried to obtain the MOF-3DG composite material film;

[0032] (5) The film material obtained in step (4) is rolled and transferred onto the surface of the active material layer to form a spatial reinforcement layer, thereby obtaining the lithium metal composite anode.

[0033] Optionally, before immersing 3DG in a solution containing MOF precursor in step (1), 3DG is cleaned with ethanol and surface active sites are increased by plasma cleaning.

[0034] Optionally, the MOF precursor described in step (1) comprises metal ions and organic ligands (metal ions and organic ligands that form MOFs).

[0035] Optionally, the gas used for plasma cleaning includes one of hydrogen, oxygen, nitrogen, argon, and helium; the plasma cleaning time is 3-5 minutes.

[0036] Optionally, the refining method in step (2) includes ball milling, chemical precipitation, sol-gel method, and ultrasonic mixing method, wherein the ball milling speed is 100-600 rpm and the ball milling time is 3-6 h.

[0037] Optionally, the particle size D50 of the refined powder is 500nm-5μm.

[0038] Optionally, the solvent mentioned in step (3) includes any one or a combination of at least two of N-methylpyrrolidone, tetrahydrofuran, dimethyl ethyl ether, dichloromethane, ethylene carbonate, dimethyl carbonate, diethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, dimethyl sulfate, and polyetherketone.

[0039] Optionally, the mass ratio of MOF-3DG composite material powder, lithium salt, binder, hydrophilic additive and solvent in step (3) is (1-10): (1-5): (1-2): (0.5-1): (81-97).

[0040] Optionally, the method of setting the slurry from step (3) onto the transfer film in step (4) includes any one or a combination of at least two of coating, spraying, spin coating, rolling, and impregnation.

[0041] Optionally, the drying temperature in step (4) is 80-100℃ and the drying time is 8-12h.

[0042] Optionally, in step (5), the pressure at which the membrane material obtained in step (4) is rolled onto the active material layer is 10-20 kN.

[0043] Another aspect of the present invention provides a solid-state battery, the solid-state battery comprising a positive electrode, a negative electrode and a solid electrolyte disposed between the positive electrode and the negative electrode; wherein the negative electrode is a lithium metal composite negative electrode as described above.

[0044] Optionally, the active material of the positive electrode is any one or a combination of at least two of layered oxides, polyanionic active materials, lithium-rich oxides, or spinel oxides.

[0045] Optionally, the solid-state battery includes lithium-sulfur solid-state batteries, bipolar solid-state batteries, sulfide solid-state batteries, polymer solid-state batteries, halide solid-state batteries, oxide solid-state batteries, and organic-inorganic composite solid-state batteries.

[0046] Optionally, the solid-state battery is a bipolar solid-state battery, which is composed of n (n=2-20) layers stacked in the structure of "current collector-positive electrode-solid electrolyte-composite negative electrode-current collector-positive electrode-solid electrolyte-composite negative electrode".

[0047] This invention has at least one of the following beneficial technical effects:

[0048] 1. The lithium metal composite anode adopts a three-layer structure design of current collector / active material layer / space reinforcement layer. The active material layer is lithium metal or lithium alloy, and the space reinforcement layer is MOFs modified three-dimensional graphene film, which can effectively control the deposition and deintercalation behavior of lithium ions, avoid the growth of lithium dendrites, and improve the cycle stability and safety performance of the battery.

[0049] 2. MOFs-modified three-dimensional graphene films have excellent ion transport performance and mechanical strength, which can effectively buffer the volume change of lithium metal during charging and discharging, and extend the battery cycle life.

[0050] 3. The space reinforcement layer also serves as a lithium-ion storage layer, which can alleviate the contact loss problem during lithium insertion and extraction, and improve the cycle and rate performance of solid-state batteries;

[0051] 4. The three-layer structure design is simple and does not require additional processes to construct an artificial solid electrolyte interface membrane, which is conducive to large-scale production;

[0052] 5. This lithium metal composite negative electrode structure design can effectively suppress side reactions between lithium metal and electrolyte, form a stable solid electrolyte interface film, and improve the safety performance of the battery. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of lithium-ion deposition when the lithium metal composite anode of the present invention is applied to a solid-state battery;

[0054] Figure 2 This is a 1000x magnified SEM image of the MOFs-modified three-dimensional graphene structure in the spatial reinforcement layer of Example 1.

[0055] Figure 3 This is a 3000x magnified SEM image of the MOFs-modified three-dimensional graphene structure in the spatial reinforcement layer of Example 1.

[0056] Figure 4 The lithium metal composite anodes in Examples 1, 2, 3 and Comparative Example 1 are the cycle test curves at a charge-discharge current of 0.3C.

[0057] Among them, 1-current collector, 2-active material layer, 3-space reinforcement layer. Detailed Implementation

[0058] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0059] An example illustrating the structure of the lithium metal composite anode provided by this invention is shown in the schematic diagram below. Figure 1 As shown. The lithium metal composite anode includes a current collector 1, an active material layer 2, and a space reinforcement layer 3.

[0060] Example 1

[0061] This embodiment provides a lithium metal composite anode, wherein the anode structure is stacked in the order of current collector, active material layer and space reinforcement layer;

[0062] The space enhancement layer has a D50 of 200 nm, a pore size of 0.4 Å, and a density of 0.3 g / cm³. 2 ZIF-8 material with a porosity of 80%; pore size of 1000 nm; specific surface area of ​​1000 m². 2The composition comprises: 3D graphene with a honeycomb framework structure; lithium hexafluorophosphate (LiPF6); polyethylene oxide (PEO); hydrophilic additive N-ethylpyridine bromide; solvent NMP; wherein the mass ratio of ZIF-8-3DG and 3DG is 1:3; and the mass ratio of ZIF-8-3DG, LiPF6, PEO, N-ethylpyridine bromide, and NMP is 10:3:2:1:84. The spatial layer has a thickness of 5 μm and a Young's modulus of 6 GPa. The active site layer is a 50 μm lithium metal layer, and the current collector is copper foil.

[0063] The preparation method of the lithium metal composite anode includes the following steps:

[0064] (1) In-situ growth of ZIF-8 on the surface or in the channels of three-dimensional graphene: 3DG was cleaned with ethanol to remove impurities, and nitrogen plasma cleaning was performed to increase surface active sites. 3DG was then immersed in a solution containing ZIF-8 precursor. The reaction was carried out at 80-120℃ for 24 h to allow ZIF-8 to grow on the surface or in the channels. Vacuum drying was performed at 60-80℃ to remove residual solvent, yielding ZIF8-3DG composite material;

[0065] (2) Weigh 10g of ZIF8-3DG composite material, refine the powder particles, and mix them evenly;

[0066] (3) Weigh 84g NMP, 3g LiPF6, 2g PEO and 1g N-ethylpyridine bromide, mix and stir, then add the ZIF8-3DG composite material obtained in step (2), mix and stir to obtain a uniform and viscous slurry;

[0067] (4) The slurry obtained in step (3) is coated onto a PET film and dried to obtain a ZIF8-3DG composite film.

[0068] (5) The film material obtained in step (4) is rolled and transferred onto the surface of the active material layer to form a spatial reinforcement layer, thereby obtaining the lithium metal composite anode.

[0069] The prepared negative electrode is used to assemble an all-solid-state battery.

[0070] Example 2

[0071] This embodiment provides a lithium metal composite anode, wherein the anode structure is stacked in the order of current collector, active material layer and space reinforcement layer;

[0072] The space enhancement layer has a D50 of 300 nm, a pore size of 2 Å, and a density of 0.3 g / cm³. 2 MIL-96 material with a porosity of 80%; pore size of 800 nm; specific surface area of ​​1500 m². 2The composition comprises: 3D graphene with a honeycomb framework structure (g); lithium bis(fluorosulfonyl)imide (LiFSI); polystyrene-butadiene copolymer (SBR); hydrophilic additive sodium dodecylbenzenesulfonate (SDBS); solvent DME; wherein the mass ratio of MIL-96 to 3DG is 1:5; and the mass ratio of MIL-96-3DG, LiFSI, SBR, SDBS, and DME is 10:3:2:1:84. The space layer has a thickness of 5 μm and a Young's modulus of 8 GPa. The active site layer is a 50 μm lithium metal layer, and the current collector is copper foil.

[0073] The preparation method of the lithium metal composite anode includes the following steps:

[0074] (1) In-situ growth of MIL-96 on the surface or in the channels of three-dimensional graphene: 3DG was cleaned with ethanol to remove impurities, and nitrogen plasma cleaning was performed to increase surface active sites. 3DG was then immersed in a solution containing the MIL-96 precursor. The reaction was carried out at 80-120℃ for 24 h to allow MIL-96 to grow on the surface or in the channels. Vacuum drying was performed at 60-80℃ to remove residual solvent, yielding the MIL96-3DG composite material;

[0075] (2) Weigh 10g of MIL96-3DG composite material, refine the powder particles, and mix them evenly;

[0076] (3) Weigh 84g DME, 3g LiFSI, 2g SBR and 1g SDBS, mix and stir, then add the MIL96-3DG composite material obtained in step (2), mix and stir to obtain a uniform and viscous slurry;

[0077] (4) The slurry obtained in step (3) is coated onto a PET film and dried to obtain a MIL96-3DG composite film.

[0078] (5) The film material obtained in step (4) is rolled and transferred onto the surface of the active material layer to form a spatial reinforcement layer, thereby obtaining the lithium metal composite anode.

[0079] The prepared negative electrode is used to assemble an all-solid-state battery.

[0080] Example 3

[0081] This embodiment provides a lithium metal composite anode, wherein the anode structure is stacked in the order of current collector, active material layer and space reinforcement layer;

[0082] The space enhancement layer has a D50 of 500 nm, a pore size of 5 Å, and a density of 0.5 g / cm³. 2 UiO-67 material with a porosity of 85%; pore size of 1000 nm; specific surface area of ​​2000 m². 2The composition comprises: 3D graphene with a honeycomb framework structure; lithium bis(trifluoromethanesulfonyl)imide (LiTFSI); polyvinylidene fluoride (PVDF); hydrophilic additive 1-methylimidazolium chloride; and dimethyl carbonate as solvent; wherein the mass ratio of UiO67-3DG to 3DG is 1:5; and the mass ratio of UiO67-3DG, LiTFSI, PVDF, 1-methylimidazolium chloride, and dimethyl carbonate is 10:3:1:1:85. The space layer has a thickness of 5 μm and a Young's modulus of 10 GPa. The active site layer is a 50 μm lithium metal layer, and the current collector is copper foil.

[0083] The preparation method of the lithium metal composite anode includes the following steps:

[0084] (1) In-situ growth of UiO-67 on the surface or in the channels of three-dimensional graphene: 3DG was cleaned with ethanol to remove impurities, and nitrogen plasma cleaning was performed to increase surface active sites. 3DG was then immersed in a solution containing UiO-67 precursor. The reaction was carried out at 80-120℃ for 24 h to allow UiO-67 to grow on the surface or in the channels. Vacuum drying was performed at 60-80℃ to remove residual solvent, yielding UiO67-3DG composite material;

[0085] (2) Weigh 10g of UiO67-3DG composite material, refine the powder particles, and mix them evenly;

[0086] (3) Weigh 85g of dimethyl carbonate, 3g of LiFSI, 1g of SBR and 1g of SDBS, mix and stir, then add the UiO67-3DG composite material obtained in step (2), mix and stir to obtain a uniform and viscous slurry;

[0087] (4) The slurry obtained in step (3) is coated onto a PET film and dried to obtain a UiO67-3DG composite film.

[0088] (5) The film material obtained in step (4) is rolled and transferred onto the surface of the active material layer to form a spatial reinforcement layer, thereby obtaining the lithium metal composite anode.

[0089] The prepared negative electrode is used to assemble an all-solid-state battery.

[0090] Example 4

[0091] Compared with Example 1, the only difference is that the mass ratio of ZIF-8 to 3DG in ZIF8-3DG is replaced with 1:1, while the other conditions remain the same.

[0092] Example 5

[0093] Compared with Example 1, the only difference is that the mass ratio of ZIF-8 to 3DG in ZIF8-3DG is replaced with 1:10, while the other conditions remain unchanged.

[0094] Example 6

[0095] Compared with Example 1, the only difference is that the ZIF8-3DG content in the slurry is replaced with 20% by mass, while the other conditions remain unchanged.

[0096] Example 7

[0097] Compared with Example 1, the only difference is that the ZIF8-3DG content in the slurry is replaced with 1% by mass, while the other conditions remain unchanged.

[0098] Example 8

[0099] Compared with Example 1, the only difference is that the proportion of LiPF6 in the slurry is replaced with 5% by mass, while the other conditions remain the same.

[0100] Example 9

[0101] Compared with Example 1, the only difference is that the proportion of LiPF6 in the slurry is replaced with 1% by mass, while the other conditions remain the same.

[0102] Example 10

[0103] Compared with Example 1, the only difference is that the proportion of PEO in the slurry is replaced with 5%, while the other conditions remain the same.

[0104] Example 11

[0105] Compared with Example 1, the only difference is that the proportion of PEO in the slurry is replaced with 1%, while the other conditions remain the same.

[0106] Example 12

[0107] Compared with Example 1, the only difference is that the hydrophilic additive is replaced with 2% of the slurry mass, while the other conditions remain the same.

[0108] Example 13

[0109] Compared with Example 1, the only difference is that the hydrophilic additive is replaced with 0.5% of the slurry mass, while the other conditions remain the same.

[0110] Example 14

[0111] Compared with Example 1, the only difference is that the thickness of the space reinforcement layer is replaced with 1 μm, while the other conditions remain the same.

[0112] Example 15

[0113] Compared with Example 1, the only difference is that the thickness of the space reinforcement layer is replaced with 50 μm, while the other conditions remain the same.

[0114] Example 16

[0115] Compared with Example 1, the only difference is that the thickness of the active material layer is replaced with 5 μm, while the other conditions remain the same.

[0116] Example 17

[0117] Compared with Example 1, the only difference is that the thickness of the active material layer is replaced with 100 μm, while the other conditions remain the same.

[0118] Example 18

[0119] Compared with Example 1, the only difference is that the lithium metal strip of the active material layer is replaced with a lithium aluminum alloy strip, while the other conditions remain the same.

[0120] Example 19

[0121] Compared with Example 1, the only difference is that the space reinforcement layer is applied to the transfer film using a spraying method, while the other conditions remain the same.

[0122] Example 20

[0123] Compared with Example 1, the only difference is that the prepared lithium metal composite anode is used to assemble a bipolar battery.

[0124] Comparative Example 1

[0125] This comparative example provides an all-solid-state battery that directly uses a 50μm lithium metal strip as the negative electrode.

[0126] Comparative Example 2

[0127] This comparative example provides an all-solid-state battery that directly uses a 50μm lithium-aluminum alloy strip as the negative electrode.

[0128] Comparative Example 3

[0129] This comparative example provides an all-solid-state battery. Compared with Example 1, its lithium metal composite anode does not contain three-dimensional graphene, while the other conditions are the same as in Example 1.

[0130] Comparative Example 4

[0131] This comparative example provides an all-solid-state battery. Compared with Example 1, its lithium metal composite anode does not contain ZIF-8 modification, and the other conditions are the same as those in Example 1.

[0132] Comparative Example 5

[0133] This comparative example provides an all-solid-state battery. Compared with Example 1, no lithium salt is added to its lithium metal composite negative electrode, and the other conditions are the same as those in Example 1.

[0134] Comparative Example 6

[0135] This comparative example provides an all-solid-state battery. Compared with Example 1, no binder is added to its lithium metal composite negative electrode, and the other conditions are the same as those in Example 1.

[0136] Comparative Example 7

[0137] This comparative example provides an all-solid-state battery. Compared with Example 1, no hydrophilic additives are added to its lithium metal composite anode, and the other conditions are the same as those in Example 1.

[0138] Comparative Example 8

[0139] This comparative example provides an all-solid-state battery. Compared with Example 1, the three-dimensional graphene is replaced with graphene nanosheets, and the other conditions are the same as in Example 1.

[0140] Comparative Example 9

[0141] This comparative example provides an all-solid-state battery. Compared with Example 1, its space enhancement layer is replaced with a transfer Al2O3 coating, and the other conditions are the same as those in Example 1.

[0142] Comparative Example 10

[0143] This comparative example provides a bipolar solid-state battery with the same anti-dendritic anode configuration as Comparative Example 1.

[0144] Fabrication of all-solid-state batteries:

[0145] The resulting battery is a mold battery with an electrode active area of ​​0.8 cm². 2 .

[0146] The solid electrolyte is prepared as follows: 100 mg of lithium phosphorus sulfide chloride (LSPCl) electrolyte is pressed into a Teflon tablet mold at a pressure of 300 MPa to obtain an electrolyte layer.

[0147] The preparation method of the positive electrode is as follows: 20 mg LiNi 0.8 Co 0.1 Mn 0.1 O2, small-particle-size LSPCl electrolyte, and carbon black are mixed evenly in a mass ratio of 75:25:2, and then pressed into a Teflon pressing mold under a pressure of 300MPa to obtain the positive electrode sheet of the battery.

[0148] The preparation method of all-solid-state battery is as follows: the obtained positive electrode sheet is pressed onto one side of the LSPCl electrolyte at a pressure of 300MPa, and then the lithium metal negative electrode is pressed onto the other side of the electrolyte layer at a pressure of 20MPa to obtain an all-solid-state battery.

[0149] The fabrication method of a bipolar solid-state battery is as follows: A positive electrode sheet is pressed onto one side of a solid electrolyte layer under a pressure of 300 MPa, and a lithium metal negative electrode is pressed onto the other side of the electrolyte layer to obtain a repeating structural unit. Current collectors are placed between multiple repeating structural units, and the repeating structural units are stacked. An external pressure of 20 MPa is applied to assemble the bipolar solid-state battery.

[0150] Solid-state battery negative electrode performance test:

[0151] The negative electrodes provided in Examples 1-19 and Comparative Examples 1-9 were used to assemble solid-state batteries for cycle performance testing. The specific testing method was as follows: at 25°C, constant current charging and constant current discharging were used, with a charging and discharging voltage range of 2.7-4.3V and a charging and discharging rate of 0.3C or 2C. The initial capacity of the battery was recorded as C0. One full charge and discharge cycle was recorded as one cycle. The charging and discharging were performed according to the above method, and the capacity of the battery was tested after each cycle until the battery capacity was 80% of C0, or the battery experienced a short circuit or the charging and discharging efficiency was less than 98%. The number of cycles at this point was recorded.

[0152] The negative electrodes provided in Example 20 and Comparative Example 10 were used to assemble bipolar solid-state batteries for cycle performance testing. The specific testing method was as follows: constant current charging and constant current discharging were performed at 25°C, with a charging and discharging voltage range of 5.0-8.5V and a charging and discharging rate of 0.3C or 2C. The initial capacity of the battery was recorded as C1. One full charge and discharge cycle was recorded as one cycle. The charging and discharging were performed according to the above method, and the capacity of the battery was tested after each cycle until the battery capacity was 80% of C1, or the battery experienced a short circuit or the charging and discharging efficiency was lower than 98%. The number of cycles at this point was recorded.

[0153] Young's modulus test:

[0154] A space layer was placed on a lithium metal anode, and Young's modulus was measured at the anode interface. Using an atomic force microscope, one end of a microcantilever, highly sensitive to minute forces, was fixed, while the other end had a tiny needle tip that gently contacted the interface. During scanning, the repulsive force between the tip and the interface was kept constant. The microcantilever with the tip moved undulating perpendicular to the interface, corresponding to the equipotential surface of the interatomic forces between the tip and the interface. Using optical detection or tunneling current detection, the positional changes of the microcantilever at various scanning points could be measured, thus obtaining the sample morphology and calculating the Young's modulus.

[0155] The cycle performance test results of all-solid-state batteries assembled using the functional lithium metal anodes prepared in Examples 1-20 and Comparative Examples 1-10 are shown in Table 1.

[0156] Table 1 Battery Cycle Performance Test Results

[0157]

[0158]

[0159] Battery cycle performance test analysis results:

[0160] (1) Comparison of Examples 1-3 and Comparative Example 1

[0161] Examples 1-3 illustrate the improvement in cycle performance of all-solid-state batteries achieved by adding the space reinforcement layer of the present invention to the surface of the lithium metal anode. The space reinforcement layer in Examples 1-3 consists of MOF-3DG, lithium salt, binder, and hydrophilic additives, such as... Figure 1 As shown in the schematic diagram, the MOF-modified three-dimensional graphene structure combines the high specific surface area and porous properties of MOF with the high conductivity and mechanical strength of three-dimensional graphene, forming a composite material with hierarchical porosity, high stability, and fast ion / electron transport properties. Figure 2 and Figure 3 The highly ordered porous structure of MOF provides abundant transport channels and storage sites for lithium ions, while suppressing lithium dendrite growth through physical confinement. The continuous conductive network of three-dimensional graphene not only uniformly distributes current density but also mitigates the volume changes of lithium metal during charge and discharge, enhancing the mechanical stability of the structure. Compared to Comparative Example 1 using pure lithium metal strips as the anode, the lithium metal anode with added spatial layers significantly improves the cycle performance of the battery at both 0.3C and 2C charge / discharge rates. (Based on Table 1 and...) Figure 4 According to the data, at a charge / discharge rate of 0.3C, the pure lithium electrode can only cycle 60 times, while the lithium metal composite anode can cycle about 300 times; at a charge / discharge rate of 2C, the pure lithium electrode can cycle 30 times, while the lithium metal composite anode can cycle more than 200 times.

[0162] (2) Comparison of Example 1 and Examples 4-13

[0163] Examples 4-13 illustrate the impact of variations in the content of MOFs, 3D graphene, lithium salt, binder, and hydrophilic additives in the space reinforcement layer on the cycle life of all-solid-state batteries. Data from Table 1 demonstrates that the highly ordered porous structure of MOFs provides abundant lithium-ion transport channels and storage sites, while simultaneously suppressing lithium dendrite growth through physical confinement. 3D graphene, acting as a framework, not only provides high mechanical strength but also mitigates lithium metal volume changes through its continuous network structure and uniform current density distribution. Lithium salt, as the core component of the electrolyte, provides the lithium-ion source, ensuring the smooth electrochemical reaction of the battery. The binder ensures the slurry's viscosity, maintaining the structural integrity of the space reinforcement layer. The hydrophilic additive improves the wettability and uniformity of the slurry, ensuring good contact between the slurry and the transfer film, thereby optimizing ion transport and electrochemical performance. The synergistic effect of these components enhances the overall performance of the electrode.

[0164] (3) Comparison of Example 1 and Examples 14-17

[0165] Examples 14-17 illustrate the effects of the thickness of the space reinforcement layer and the active material layer on the cycle life of all-solid-state batteries. If the space reinforcement layer is too thick, the lithium metal battery interface impedance increases, affecting the battery energy density; if the space reinforcement layer is too thin, the lithium storage space is small, resulting in weak protection of the lithium anode interface. If the active material layer is too thin, the anode interface modification layer is relatively thicker, increasing battery impedance; if the active material layer is too thick, it will reduce the battery's energy density.

[0166] (4) Comparison of Example 1 and Example 19

[0167] Example 19 illustrates the impact of different coating processes on the performance of all-solid-state batteries. The coating method is replaced with a spraying method. The spraying method requires ensuring the uniformity of the space reinforcement layer slurry sprayed onto the active material layer and controlling the surface tension of the lithium metal strip during drying. By controlling the process parameters, different coating processes can be substituted.

[0168] (5) Comparison of Example 18 and Comparative Example 2

[0169] Example 18 and Comparative Example 2 illustrate the effect of incorporating a space reinforcement layer on the lithium alloy layer on the cycle performance of all-solid-state batteries. By introducing other metallic elements (such as magnesium, aluminum, and zinc), the lithium alloy layer alters the deposition behavior of lithium, making it more uniform and effectively suppressing lithium dendrite formation, thus reducing the risk of short circuits. Simultaneously, alloying improves the mechanical strength of the material, enabling it to better withstand volume changes during charge and discharge, maintaining the integrity of the electrode structure. As shown in Table 1, the cycle performance of the lithium metal battery is improved after incorporating a space reinforcement layer on the alloy layer, with an improvement of 232 cycles at a 0.3C charge / discharge rate and 173 cycles at a 2C charge / discharge rate.

[0170] (6) Comparison of Example 1 and Comparative Examples 3-7

[0171] Comparative Examples 3-7 illustrate the importance of the space reinforcement layer composition materials provided by this invention, and the impact of different materials on the cycle performance of all-solid-state batteries. As shown in Table 1, the lack of different space reinforcement layer materials resulted in a decrease in battery cycle performance. If ZIF8 (Comparative Example 4) is missing, the material loses its highly ordered porous structure and physical confinement effect, leading to uneven lithium-ion deposition and intensified lithium dendrite growth, thereby reducing the battery's cycle stability and safety. Simultaneously, the absence of ZIF8 also reduces lithium-ion transport channels and storage sites, affecting electrochemical kinetics performance. If 3DG (Comparative Example 3) is missing, the material loses its high conductivity and mechanical support, resulting in uneven current distribution and decreased electrode structure stability, failing to effectively mitigate the volume change of lithium metal during charge and discharge, further exacerbating electrode pulverization and capacity decay. The lack of lithium salts, binders, or hydrophilic additives (Comparative Examples 5-7) affects ion transport, network structure stability, and hydrophilicity on the transfer film, leading to a decrease in the cycle performance of the solid-state battery.

[0172] (7) Comparison of Example 1 and Comparative Examples 8-9

[0173] Comparative Examples 8-9 illustrate the impact of replacing three-dimensional graphene in the space reinforcement layer with two-dimensional graphene nanosheets and replacing the space reinforcement layer with an inorganic coating on the performance of all-solid-state batteries. While two-dimensional graphene nanosheets possess high conductivity and a large specific surface area, their lack of a three-dimensional continuous network structure leads to uneven current distribution, failing to effectively mitigate lithium metal volume expansion and easily causing electrode pulverization and structural damage. Furthermore, the combination of two-dimensional graphene nanosheets and ZIF-8 may not form a hierarchical porous structure, thus weakening the physical confinement effect and exacerbating lithium dendrite growth and electrolyte side reactions. Therefore, replacing three-dimensional graphene with two-dimensional graphene nanosheets significantly reduces the cycle stability, rate performance, and safety of all-solid-state batteries. Although inorganic alumina coatings possess certain mechanical strength and chemical stability, their lack of porous structure and conductivity prevents them from providing sufficient lithium-ion transport channels and electron conduction pathways, resulting in performance far inferior to the ZIF8-3DG composite structure under high-rate charge-discharge and long-cycle conditions.

[0174] (7) Comparison of Example 20 and Comparative Example 10

[0175] Example 20 and Comparative Example 10 illustrate the application of the space reinforcement layer provided by the present invention to a bipolar battery, thereby improving the cycle performance of the bipolar battery. As shown in Table 1, at a charge / discharge rate of 0.3C, the battery cycle performance is improved by 91 cycles, and at a charge / discharge rate of 2C, the cycle performance is improved by 68 cycles. The space reinforcement layer isolates and reduces side reactions caused by direct contact between lithium metal and the solid electrolyte, while simultaneously improving the consistency of the multilayer interface. The combined effect of suppressing dendrite growth and regulating lithium-ion deposition significantly enhances the cycle performance.

[0176] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A lithium metal composite anode, characterized in that, The negative electrode includes an active material layer and a space enhancement layer disposed on and in contact with the active material layer; The active material layer is a continuous or intermittently distributed layer of metallic lithium or lithium alloy. The space reinforcement layer is a three-dimensional graphene film modified with metal-organic framework (MOF) materials.

2. The lithium metal composite anode according to claim 1, characterized in that, MOFs-modified three-dimensional graphene is obtained by in-situ growth of MOFs on the surface or in the pores of three-dimensional graphene, wherein the three-dimensional graphene is a three-dimensional honeycomb graphene, and the mass ratio of the MOFs material to the three-dimensional graphene is 1:(1-10). The MOFs-modified three-dimensional graphene film is formed by coating a MOFs-modified three-dimensional graphene mixture onto a transfer film; The MOFs-modified three-dimensional graphene slurry comprises MOFs-modified three-dimensional graphene powder, lithium salt, binder, and hydrophilic additive; The mass ratio of MOFs-modified three-dimensional graphene powder, lithium salt, binder and hydrophilic additive is (1-20):(1-5):(1-5):(0.5-2).

3. The lithium metal composite anode according to claim 2, characterized in that, The MOFs materials include MOFs materials with zinc-based, cobalt-based, vanadium-based, iron-based, aluminum-based, chromium-based, zirconium-based, or lanthanide metal-based metals as metal ion or metal cluster nodes. Preferably, the MOFs material is selected from one or a combination of at least two of the ZIF series, MIL series, UiO series, IRMOF series, PCN series, and NU series; the ZIF series is selected from at least one of ZIF-7, ZIF-8, ZIF-63, ZIF-67, ZIF-71, and ZIF-90; the MIL series is selected from at least one of MIL-53, MIL-88, MIL-96, MIL-100, MIL-101, and MIL-125; and the UiO series is selected from UiO-67, UiO-68, and UiO-7.

6. At least one of UiO-77 and UiO-84; the IRMOF series is selected from at least one of IRMOF-1, IRMOF-3, IRMOF-6, IRMOF-8, IRMOF-9, and IRMOF-10; the PCN series is selected from at least one of PCN-14, PCN-200, PCN-221, PCN-222, PCN-223, and PCN-250; the NU sequence is selected from at least one of NU-100, NU-109, NU-110, NU-111, NU-125, and NU-901; The lithium salts include one or more combinations of lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxalateborate, lithium difluorooxalateborate, lithium carbonate, lithium oxalate, lithium bicarbonate, lithium acetate, lithium halides, lithium sulfate, and lithium hydroxide. The adhesive comprises one or a combination of at least two of the following: polyvinyl alcohol, polyethylene oxide, polybutene-styrene, polystyrene-butadiene copolymer, polyvinylidene fluoride, polystyrene, polycarboxylic cellulose, cyanoacrylate, cyclodextrin, cyclic ether derivatives, polyurethane, methacrylate, epoxy resin, vinyl acetate polymer, polyimide, organofluoropolymer, organosiloxane, polyethylene glycol, polyethylene, polyvinyl chloride, polypropylene, glycerol, ethylparaben, and their derivatives; The hydrophilic additives include one or more combinations of carboxylates, sulfonates, sulfates, phosphates, imidazole ionic liquids, pyridine ionic liquids, quaternary ammonium ionic liquids, quaternary phosphorus ionic liquids, pyrrolidine ionic liquids, and piperidine ionic liquids. The transfer film material includes organic materials, which are selected from one or more of polyvinylidene fluoride, polyvinyl chloride, polyethylene, polypropylene, polystyrene, styrene-butadiene-vinyl nitrile copolymer, polyimide, polycarbonate, phenolic plastics, polyoxymethylene, polyethylene terephthalate, styrene-modified polymethacrylic acid, polysulfone, polytetrafluoroethylene, amino plastics, and epoxy resin, or their homopolymers or copolymers.

4. The lithium metal composite anode according to any one of claims 1-3, characterized in that, The MOFs material is in particulate form with a particle size D50 of 100-500 nm, a pore size of 0.1-10 Å, and a density of 0.3-0.5 g / cm³. 2 The porosity is 70%-90%; The three-dimensional graphene has a pore size of 500-2000 nm and a specific surface area of ​​500-5000 m². 2 / g; The adhesion of the transfer film is 1-8 g / inch, and the thickness is 20-100 μm; The thickness of the space reinforcement layer is 1-100 μm and the Young's modulus is ≥6 GPa.

5. The lithium metal composite anode according to any one of claims 1-4, characterized in that, The active material layer includes one or a combination of a lithium metal layer and a lithium alloy layer; preferably, the lithium alloy layer includes an alloy of lithium with one or more of silicon, indium, silver, carbon, magnesium, aluminum, boron, tin, gallium, cobalt, gold, barium, bismuth, calcium, germanium, mercury, platinum, zinc, lead, antimony, cadmium, and cobalt. The thickness of the active material layer is 3μm-300μm, preferably 10μm-100μm; The thickness ratio of the space reinforcement layer to the active material layer is (0.001-1):1, preferably (0.01-0.1):

1.

6. The lithium metal composite anode according to any one of claims 1-5, characterized in that, The lithium metal composite anode further includes a current collector, which includes at least one of copper foil, aluminum foil, stainless steel foil, nickel foil, tin foil, carbon nanotube paper, carbon fiber paper, copper mesh, aluminum mesh, stainless steel mesh, nickel foam, and organic fiber film with metal plating on the surface.

7. A method for preparing a lithium metal composite anode as described in any one of claims 1-6, characterized in that, The method includes: (1) Preparation of MOFs modified three-dimensional graphene: Three-dimensional graphene (3DG) is immersed in a solution containing MOF precursor and reacted at 80-120℃ for several hours to several days to allow MOF to grow on the surface or in the pores of 3DG; the residual solvent is removed by vacuum drying at 60-80℃ to obtain MOF-3DG composite material, i.e. MOFs modified three-dimensional graphene. (2) Weigh the MOF-3DG composite material powder, refine the powder, and mix it evenly; (3) Weigh a certain amount of solvent, add lithium salt, binder and hydrophilic additive according to the corresponding mass fraction, mix and stir, then add MOF-3DG composite material powder obtained in step (2), mix and stir to obtain a uniform and viscous slurry; (4) The slurry obtained in step (3) is placed on the transfer film and dried to obtain the MOF-3DG composite material film; (5) The film material obtained in step (4) is rolled and transferred onto the surface of the active material layer to form a spatial reinforcement layer, thereby obtaining the lithium metal composite anode.

8. The method according to claim 7, characterized in that, Before immersing 3DG in a solution containing MOF precursor in step (1), 3DG is cleaned with ethanol and surface active sites are increased by plasma cleaning.

9. The method according to claim 8, characterized in that, The gas used for plasma cleaning includes one of hydrogen, oxygen, nitrogen, argon, and helium; the plasma cleaning time is 3-5 minutes. The MOF precursor described in step (1) comprises metal ions and organic ligands; The refining methods in step (2) include ball milling, chemical precipitation, sol-gel method, and ultrasonic mixing. The ball milling speed is 100-600 rpm and the ball milling time is 3-6 h. The particle size D50 of the refined powder is 500 nm-5 μm. The solvent mentioned in step (3) includes any one or a combination of at least two of N-methylpyrrolidone, tetrahydrofuran, dimethyl ethyl ether, dichloromethane, ethylene carbonate, dimethyl carbonate, diethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, dimethyl sulfate, and polyetherketone; The mass ratio of MOF-3DG composite material powder, lithium salt, binder, hydrophilic additive and solvent in step (3) is (1-10):(1-5):(1-2):(0.5-1):(81-97); The method of applying the slurry from step (3) onto the transfer film as described in step (4) includes any one or a combination of at least two of the following: coating, spraying, spin coating, rolling, and impregnation. The drying temperature in step (4) is 80-100℃ and the drying time is 8-12h; In step (5), the pressure at which the membrane material obtained in step (4) is rolled onto the active material layer is 10-20 kN.

10. A solid-state battery, characterized in that, The solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte disposed between the positive and negative electrodes; wherein, the negative electrode is a lithium metal composite negative electrode as described in any one of claims 1-6, and the active material of the positive electrode is any one or a combination of at least two of layered oxides, polyanionic active materials, lithium-rich oxides, or spinel oxides; the solid-state battery includes lithium-sulfur solid-state batteries, bipolar solid-state batteries, sulfide solid-state batteries, polymer solid-state batteries, halide solid-state batteries, oxide solid-state batteries, and organic-inorganic composite solid-state batteries.

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