A multi-layer structure lithium-free negative electrode, a preparation method and a solid-state lithium-free negative electrode battery

Abstract

The application discloses a multilayer structure lithium-free negative electrode, a preparation method and a solid-state lithium-free negative electrode battery. The multilayer structure lithium-free negative electrode comprises a first material layer, a second material layer and a third material layer arranged in sequence. The first material layer is a conductive carbon layer. The second material layer is a dense lithiumophilic metal or metal oxide layer. The third material layer is a porous material layer containing Lewis acid sites. The multilayer structure lithium-free negative electrode has good lithiumophilic characteristics. In the process of delithiation, the copper foil and the coating can maintain good structural integrity and maintain a good conductive network, which is conducive to the stable and continuous delithiation reaction. The lithiumophilic metal layer can be alloyed with lithium to form a low nucleation barrier. The porous material layer containing Lewis acid sites can be combined with the electrolyte to form an ionic conductor and form a stable lithiumophilic SEI layer. The large number of Lewis acid sites can effectively improve the lithium deposition morphology and regulate the uniform deposition of lithium. Finally, uniform lithium deposition can be realized, and the cycle performance of the lithium-free negative electrode can be improved.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, specifically relating to a multilayer lithium-free anode, its preparation method, and a solid-state lithium-free anode battery containing the anode. Background Technology

[0002] With the continuous advancement of technology, lithium batteries, as an important energy storage device, have been widely used in electric vehicles, portable electronic devices, and other fields. However, the energy density and cycle life of traditional lithium batteries are gradually becoming insufficient to meet the ever-increasing demands. Lithium-free negative electrode lithium batteries, because they lack initial active materials on the negative electrode side, derive all their active lithium from the lithium extracted from the positive electrode material during the first charge, significantly improving the energy density of the battery system, especially the volumetric energy density, and have become a current research hotspot.

[0003] However, lithium-free anode batteries also face numerous challenges. During cycling, battery polarization continuously intensifies, leading to a sustained decline in specific capacity, which rapidly reaches its minimum value, ultimately resulting in battery failure. The main reasons lie in the continuous generation of dead lithium and the damage and reconstruction of the SEI film during cycling. Among these, anode volume expansion, poor lithium affinity leading to the detachment of active lithium from the substrate, and other side reactions are the primary factors contributing to the reduction in active lithium content. Therefore, developing a lithium-free anode preparation method that can effectively improve the cycling performance of lithium-free anode batteries is of significant practical importance. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a multilayer lithium-free anode that can be used in polymer or sulfide solid-state batteries, a preparation method thereof, and a solid-state lithium-free anode battery containing the anode. The technical problem to be solved is that during the cycling process of the solid-state lithium-free anode battery, the battery polarization continuously increases, limiting the specific capacity, and the poor lithium affinity of the anode leads to the detachment of active lithium from the substrate.

[0005] To solve the above technical problems, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention proposes a multilayer lithium-free anode, comprising a first material layer, a second material layer and a third material layer arranged sequentially, wherein the first material layer is a conductive carbon layer, the second material layer is a dense lithiophilic material layer, and the lithiophilic material is a lithiophilic metal or a metal oxide; the third material layer is a porous metal oxide, molecular sieve material or metal salt layer containing a large number of Lewis acid sites.

[0007] Furthermore, the first material layer is a mixed coating of one of Ketjen black, amorphous carbon, activated carbon, carbon nanotubes, and graphene with a PVDF binder.

[0008] Secondly, this invention proposes a method for preparing a multilayer lithium-free anode as described above, comprising the following processes: dispersing a certain mass of conductive carbon material, binder, and dispersant in a certain mass of NMP, dispersing for a period of time using ultrasound and stirring, uniformly coating the resulting slurry onto the surface of a copper foil, and vacuum drying to obtain a first material layer for later use; depositing a second material layer on the surface of the first material layer using a vacuum evaporation apparatus, and then loading a third material layer onto the second material layer to obtain a multilayer lithium-free anode. The copper foil serves as the current collector for the lithium-free anode.

[0009] Furthermore, the preparation process also includes a copper foil pretreatment step, specifically: selecting copper foil with a purity ≥99.9%, and ultrasonically cleaning it sequentially with acetone, ethanol, and deionized water for 15-30 minutes each to remove surface oil, impurities, etc. The cleaned copper foil is then placed in a vacuum drying oven and dried at 60-80°C for 6-8 hours for later use.

[0010] Furthermore, the binder is PVDF; the dispersant is PVP.

[0011] Furthermore, the lithiophilic layer material in the second material layer is a lithiophilic metal element such as Ag, Mg, Al, Zn, Sn or its compound (such as ZnO, SnO2, etc.) as one of the lithiophilic layer materials.

[0012] Furthermore, the material containing Lewis acid sites in the third material layer is one of the following: metal oxide (Al2O3, TiO2 or ZrO2), molecular sieve material (zeolite molecular sieve ZSM-5 or mesoporous molecular sieve MCM-41, SBA-15) or metal salt layer (AlCl3, FeCl3 or BF3), with the preferred material being 200 nm molecular sieve material zeolite.

[0013] Furthermore, the loading method of the third layer material is one of impregnation, hot pressing transfer, or coating scraping.

[0014] Furthermore, the thickness of the first material layer is 1~5μm, preferably 2μm; the thickness of the second material layer is 100~400nm, preferably 100nm; and the thickness of the third material layer is 5~12μm, preferably 10μm.

[0015] Furthermore, in the first material layer, the content of conductive carbon layer material, binder, and dispersant accounts for 87%~96%, 3%~10%, and 1%~3% of the total solid mass, respectively; in the slurry required for the third material layer, the content of material containing Lewis acid sites and binder accounts for 93.7%~98.8% and 1.2%~6.3% of the total solid mass, respectively.

[0016] Furthermore, in the first material layer preparation process, the slurry is uniformly coated on the surface of the copper foil and dried under vacuum at 100-120℃ for 18-24 hours before use; in the third material layer preparation process, the slurry is loaded onto the surface of the second material layer and dried under vacuum at 100-120℃ for 18-24 hours before use.

[0017] Thirdly, the present invention proposes a solid-state lithium-free anode battery, comprising a positive electrode, a solid electrolyte, and a negative electrode, wherein the positive electrode is a dry positive electrode, the solid electrolyte is a polymer solid electrolyte or a sulfide solid electrolyte, and the negative electrode is a multilayer lithium-free anode as described above.

[0018] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (taking the first material layer as Ketjen black conductive carbon layer, the second material layer as Ag metal, and the third material layer as zeolite (D50=200nm), with a mass ratio of zeolite to PVDF of 1:0.1, and taking the coating by scraping as an example to prepare a multilayer lithium-free anode, the following explanation is given. Other materials that can be selected, such as conductive carbon materials, metals, or materials containing Lewis acid sites, have the same effect).

[0019] 1. The conductive carbon material Ketjen black coating can alleviate the volume expansion of the composite coating on the copper foil surface and enhance its structural stability. During the delithiation process, it can maintain the structural integrity of the copper foil and coating, maintain a good conductive network, and facilitate the continuous and stable progress of the delithiation reaction.

[0020] 2. A thinner Ag layer exhibits excellent lithium affinity and can alloy with lithium, forming a lower nucleation barrier. This induces uniform deposition of lithium downwards from the zeolite layer. The Li-Ag alloy formed by the reaction of Ag and Li serves as a rapid lithium transport channel, effectively improving the cycle performance of lithium-free anode batteries.

[0021] 3. The porous zeolite layer containing Lewis acid sites can effectively regulate the uniform deposition of lithium and inhibit the growth and penetration of lithium dendrites. At the same time, the pre-solidified liquid of the polymer electrolyte fully wets the porous zeolite layer, thus constructing a three-dimensional lithium-ion transport pathway.

[0022] 4. This lithium-free anode has the advantages of being thin, lightweight, and low-cost, and has significant advantages in improving battery safety, cycle stability, energy density, and expanding the range of applications.

[0023] 5. The fabrication process of this multi-layer structure is simple, using the traditional liquid lithium-ion battery slurry and electrode coating technology. The process technology is mature, which is conducive to large-scale production and ensures high production efficiency. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the fabrication structure of a multilayer anode for an all-solid-state lithium-free anode battery according to the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of a polymer all-solid-state lithium-free anode battery according to the present invention;

[0026] Figure 3 The rate performance was tested using the lithium-free negative electrode assembled coin cell prepared in Example 1.

[0027] Figure 4 This is a comparison chart of the cycle performance of lithium-free anode assembled coin cells in Comparative Example and Example 1.

[0028] In the figure: 1. First material layer; 2. Second material layer; 3. Third material layer; 4. Copper foil current collector; 5. Positive electrode shell; 6. Spring sheet; 7. Gasket; 8. Positive electrode; 9. Polymer electrolyte; 10. Negative electrode; 11. Negative electrode shell. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0030] Example 1

[0031] Select copper foil with a purity ≥99.9%, and ultrasonically clean it sequentially with acetone, ethanol, and deionized water for 15-30 minutes each to remove surface oil, impurities, etc. Then place the cleaned copper foil in a vacuum drying oven and dry it at 60-80℃ for 6-8 hours for later use.

[0032] 990 mg of nano-Ketjen black powder, 112.5 mg of PVDF (5 wt% solution) and 22.5 mg of PVP (2 wt% solution) were dispersed in 1 g of NMP and ultrasonically stirred for 3 h. The resulting slurry was coated on the surface of copper foil and dried under vacuum at 100 °C for 12 h for later use.

[0033] A 100 nm Ag layer was first deposited on a copper foil with a 2 μm Ketjen Black conductive carbon layer using a vacuum evaporation apparatus as a second material layer. Then, 1 g of zeolite powder and 2 g of PVDF (5 wt% solution) were dispersed in 2.5 g of NMP and ultrasonically stirred for 2 h. The resulting slurry was coated onto the 10 μm thick Ag / KB / Cu deposited on the surface and dried under vacuum at 100 °C for 24 h to serve as a multilayer lithium-free anode.

[0034] Example 2

[0035] A 100 nm Al layer was first deposited on a copper foil with a 2 μm Ketjen Black conductive carbon layer using a vacuum evaporation apparatus as a second material layer. Then, 1 g of zeolite powder and 2 g of PVDF (5 wt% solution) were dispersed in 2.5 g of NMP and ultrasonically stirred for 2 h. The resulting slurry was coated onto the 10 μm thick Al / KB / Cu deposited surface and dried under vacuum at 100 °C for 24 h as a multilayer lithium-free anode. Other steps were the same as in Example 1.

[0036] Example 3

[0037] A 100 nm Sn layer was first deposited on a copper foil with a 2 μm Ketjen Black conductive carbon layer using a vacuum evaporation apparatus as a second material layer. Then, 1 g of zeolite powder and 2 g of PVDF (5 wt% solution) were dispersed in 2.5 g of NMP and ultrasonically stirred for 2 h. The resulting slurry was coated onto the 10 μm thick Sn / KB / Cu deposited surface and dried under vacuum at 100 °C for 24 h as a multilayer lithium-free anode. Other steps were the same as in Example 1.

[0038] Example 4

[0039] A 100 nm Ag layer was first deposited on a copper foil with a 2 μm Ketjen Black conductive carbon layer using a vacuum evaporation apparatus as a second material layer. Then, 1 g of zeolite powder and 2 g of PVDF (5 wt% solution) were dispersed in 2.5 g of NMP and ultrasonically stirred for 2 h. The resulting slurry was coated onto the 100 nm Ag / KB / Cu deposited surface to a thickness of 5 μm, and dried under vacuum at 100 °C for 24 h as a multilayer lithium-free anode. Other steps were the same as in Example 1.

[0040] Comparative Example

[0041] 1. Directly use copper foil coated with Ketjen black as the negative electrode;

[0042] 2. Directly use the evaporated lithium-loving layer / Ketjen black composite copper foil as the negative electrode;

[0043] 3. A zeolite layer / Ketjen black composite copper foil was coated as the negative electrode;

[0044] The button cell assembly method in the above comparative examples is the same as that in the examples.

[0045] Battery assembly method:

[0046] Example: Dry-process positive electrode sheet, polymer electrolyte pre-solidified solution, and lithium-free negative electrode are prepared according to... Figure 2 Assemble the cells into button cells and apply a pressure of 50 MPa to the button cells using a sealing machine. Figure 2Both the spring contacts and gaskets play a supporting role in assembling button cells. The spring contacts are responsible for the "conductive path": eliminating gaps through elastic contact to ensure continuous current transmission; the gaskets are responsible for "safety protection": preventing leakage through sealing, preventing short circuits through insulation, buffering against damage, and also helping to optimize assembly dimensions.

[0047] Comparative examples: only the lithium-affinity Ag / Ketjen black layer, only the zeolite / Ketjen black layer, and the Ketjen black composite copper foil were used as negative electrodes, and their assembly methods and encapsulation pressures were the same as those described above.

[0048] Figure 1 The schematic diagram illustrates the structure of a multilayer anode for a lithium-free all-solid-state battery according to the present invention. The structure consists of three material layers. The first material layer is loaded on a copper foil. The first material layer can be selected as a Ketjen black conductive carbon layer. The second material layer can be selected as Ag metal. The third material layer can be selected as zeolite (D50=200nm). Taking the coating method as an example, the multilayer lithium-free anode is prepared. Other materials such as conductive carbon materials, metals (oxides) or materials containing Lewis acid sites can have the same effect.

[0049] In terms of rate performance, from Figure 3 As can be seen, the coin cell using a zeolite layer / lithophile layer / Ketjen black anode can adapt to different charge / discharge rates (0.1C~1C). Regarding cycle performance, from... Figure 4 It can be seen that at a charge / discharge rate of 0.2C, its discharge specific capacity remains stable at over 200mAh / g, and it can cycle stably for over 20 cycles without any short circuits occurring (e.g.). Figure 4 Lithium-free anode batteries that do not combine zeolite and a lithiophilic layer, from Figure 4 The data shows that when cyclically charged at 0.2C, the discharge capacity decreases with each cycle, making stable cycling difficult.

[0050] In summary, the preparation of the multilayer lithium-free anode in this embodiment of the invention involves uniformly coating a slurry containing a conductive carbon layer and a binder onto a copper foil, drying it, and then depositing a metal layer (such as an Ag, Al, or Sn coating) onto the surface of the conductive carbon layer composite copper foil using vacuum evaporation technology. The Ag metal, acting as a lithiophilic interlayer, can improve the interfacial interaction between lithium and the substrate, regulating lithium nucleation and growth behavior, thereby preventing lithium dendrite growth, stabilizing the interface, reducing side reactions, lowering the capacity decay rate during cycling, and improving the battery's cycle life and coulombic efficiency. Furthermore, the formation of the Ag-Li alloy phase can mitigate substrate cracking or interfacial peeling caused by drastic volume changes during lithium deposition and stripping through lattice buffering. Subsequently, a slurry of zeolite and binder is uniformly loaded onto the second material layer. The porous zeolite layer containing Lewis acid sites effectively regulates the uniform deposition of lithium, inhibiting lithium dendrite growth and penetration. Simultaneously, the pre-solidified polymer electrolyte fully wets the porous zeolite layer, constructing a three-dimensional lithium-ion transport pathway.

[0051] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-layered structure lithium-free negative electrode, characterized by, The multilayer structure lithium-free negative electrode comprises a first material layer, a second material layer and a third material layer arranged in sequence, wherein the first material layer is a conductive carbon layer, the second material layer is a compact lithiumophilic material layer, the lithiumophilic material is a lithiumophilic metal or a metal oxide, and the third material layer is a zeolite molecular sieve ZSM-5 with a porous structure and a large number of Lewis acid sites; the metal in the lithiumophilic metal or the metal oxide in the second material layer is one of Ag, Mg, Al, Zn and Sn.

2. The multi-layered structure lithium-free negative electrode of claim 1, wherein, The first material layer is a mixed coating layer of one of Ketjenblack, amorphous carbon, activated carbon, carbon nanotube and graphene and a PVDF binder.

3. The multi-layered structure lithium-free negative electrode of claim 1, wherein, The coating thickness of the first material layer is 1-5 μm, the thickness of the second material layer is 100-400 nm, and the thickness of the third material layer is 5-12 μm.

4. The method of producing a multi-layer structure lithium-free negative electrode according to any one of claims 1 to 3, wherein The preparation process comprises the following steps: dispersing a conductive carbon layer material, a binder and a dispersant in NMP, dispersing for a period of time by using ultrasonic agitation, uniformly coating the obtained slurry on the surface of a copper foil, and vacuum drying to obtain the first material layer for standby; using a vacuum evaporation instrument to evaporate the second material layer on the surface of the first material layer, then dispersing the third material layer powder and a binder in a certain mass of NMP, ultrasonic agitation and dispersion for a period of time, loading the obtained slurry on the second material layer, and vacuum drying to obtain the multilayer structure lithium-free negative electrode.

5. The method of claim 4, wherein the multilayer structure lithium-free negative electrode is prepared by the steps of: The binder in the preparation process of the first material layer and the third material layer is PVDF with a concentration of 5 wt%, and the dispersant in the preparation process of the first material layer is PVP; the material loading method of the third material layer is one of impregnation, hot-press transfer printing and coating blade coating.

6. The method of claim 4, wherein the multilayer structure lithium-free negative electrode is prepared by the steps of: The content of the conductive carbon layer material, the binder and the dispersant in the first material layer accounts for 87-96%, 3-10% and 1-3% of the total mass of solids respectively; the content of the material with Lewis acid sites and the binder in the slurry required by the third material layer accounts for 93.7-98.8% and 1.2-6.3% of the total mass of solids respectively.

7. The method of claim 4, wherein the multilayer structure lithium-free negative electrode is prepared by the steps of: In the preparation process of the first material layer, the obtained slurry is uniformly coated on the surface of a copper foil, and vacuum drying is performed at 100-120 ℃ for 18-24 h to obtain the first material layer for standby; in the preparation process of the third material layer, the obtained slurry is loaded on the surface of the second material layer, and vacuum drying is performed at 100-120 ℃ for 18-24 h to obtain the third material layer for standby.

8. A solid-state lithium-free negative electrode battery, characterized by The battery comprises a positive electrode, a solid-state electrolyte and a negative electrode, wherein the solid-state electrolyte is one of a polymer solid-state electrolyte and a sulfide solid-state electrolyte, and the negative electrode is the multilayer structure lithium-free negative electrode according to any one of claims 1-3.

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