Anti-pulverization integrated current collector negative electrode and preparation method thereof

Abstract

The application discloses an anti-pulverization integrated current collector negative electrode and a preparation method thereof, and relates to the technical field of current collectors.The integrated current collector negative electrode comprises a PI-Ag functional substrate and a Li-Ag solid solution layer; the preparation method comprises the following steps: the PI film is subjected to KOH hydrolysis activation, silver-ammonia solution ion exchange and L-ascorbic acid reduction in sequence to obtain the PI-Ag functional substrate; and then lithium and silver are spontaneously diffused through an electrochemical deposition method or a roll pressing composite process to form the Li-Ag solid solution layer, so that the integrated current collector negative electrode is prepared.The PI-Ag functional substrate can significantly reduce the surface density, the Li-Ag alloy can guide the uniform deposition of lithium and inhibit the dendrite, and the integrated current collector negative electrode with high energy density, long cycle stability and high safety can be realized.

Description

Technical Field

[0001] This invention relates to the field of current collector technology, specifically to an anti-powdering integrated current collector negative electrode and its preparation method. Background Technology

[0002] Lithium metal batteries, with their high theoretical capacity and low redox potential of lithium metal anodes, have become a core technology for meeting the high energy density requirements of electric vehicles, large-scale energy storage, and other applications. However, their commercialization is mainly constrained by the following two key issues: Firstly, the redundancy of the current collector mass limits energy density: Traditional lithium metal anodes rely on copper foil as the current collector, which has a density as high as 8.9 g / cm³. Even with a composite structure of 20 μm lithium foil and copper foil, the mass ratio of inert copper foil in the anode still exceeds 75%, which significantly offsets the high capacity advantage of lithium metal. Although anode-free batteries reduce the mass ratio of the anode to 16%, this part is still entirely composed of inert copper foil and requires additional process integration, making it difficult for the battery energy density to break through 500 Wh / kg, which cannot meet the needs of next-generation high-energy-density energy storage technologies.

[0003] Secondly, pulverization causes cycling stability failure: Lithium metal is prone to two types of pulverization during deposition and stripping: 1. Lithium dendrites break due to uneven stripping, forming "dead lithium", causing loss of active lithium, and the coulombic efficiency is usually less than 85%; 2. Lithium or lithium alloys undergo volume expansion of more than 300% during cycling, causing electrode delamination and disintegration, especially in high energy density configurations with low positive and negative electrode capacity ratios, the capacity retention rate is often less than 60% after 100 cycles.

[0004] To address the above issues, existing solutions still have significant limitations: although lithium deposition behavior can be controlled by introducing lithium-friendly alloys such as silver and aluminum, the interfacial bonding problem between the alloy layer and the current collector remains unresolved; while porous carbon-based or metal-based lightweight current collectors can reduce mass, additional binders or vapor deposition processes are required, increasing interfacial resistance and manufacturing costs, and they cannot simultaneously and effectively suppress "dead lithium pulverization" and "electrode pulverization".

[0005] Therefore, there is an urgent need to develop an integrated current collector anode structure that combines lightweight design, dual anti-pulverization capabilities, and simplified fabrication process to overcome the current technological bottlenecks in lithium metal batteries. Summary of the Invention

[0006] The purpose of this invention is to provide an anti-powdering integrated current collector negative electrode and its preparation method, so as to solve the problems raised in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: An anti-powdering integrated current collector negative electrode includes the following structure: a PI-Ag functional substrate and a Li-Ag solid solution layer.

[0008] Furthermore, the Li-Ag solid solution layer is prepared by electrochemical deposition or roll forming composite process; the Li-Ag solid solution layer is disposed on the surface of the PI-Ag functional substrate.

[0009] Furthermore, the Ag content in the PI-Ag functional matrix is ​​22-28 wt%.

[0010] Furthermore, in the Li-Ag solid solution layer, the main alloying phase is Li. 20 Ag.

[0011] Furthermore, the thickness of the integrated current collector negative electrode is 20-49 μm.

[0012] A method for preparing an anti-powdering integrated current collector negative electrode includes the following steps: S1: Preparation of PI-Ag functional substrate S1-1: PI hydrolysis activation (PI-K) + Preparation): Take a PI (polyimide) film, immerse it in KOH solution, and soak it at 25℃ for 2-3 hours; use deionized water to ultrasonically clean it at 300-400W for 4-5 minutes until neutral, and blow it dry with high-purity nitrogen to obtain PI-K + film; S1-2: Ion-ligand exchange (PI-Ag) + Preparation): PI-K + The membrane was immersed in silver ammonia solution at 25°C for 2-3 hours; after washing with deionized water 3-5 times, it was dried with nitrogen gas to obtain PI-Ag. + film; S1-3: Silver Reduction (Preparation of PI-Ag Functional Substrate): PI-Ag... + The film was immersed in L-ascorbic acid solution and reacted at 25°C for 2-3 min; after washing with deionized water, it was dried at 60-70°C and vacuum degree -0.09MPa for 10-12 h to obtain PI-Ag functional substrate. S2: Preparation of PI-Ag-Li integrated current collector anode: Lithium is deposited onto the surface of a PI-Ag functional substrate using an electrochemical deposition method, or a roll-pressing composite process is used to roll-press lithium foil onto a PI-Ag functional substrate, where Ag atoms and lithium spontaneously diffuse to form a Li-Ag solid solution layer, thus preparing a PI-Ag-Li integrated current collector anode.

[0013] Furthermore, in step S1, the thickness of the PI film is 8-10 μm; The concentration of the KOH solution is 5-6M; The purity of high-purity nitrogen is 99.999%.

[0014] Furthermore, in step S1, the concentration of the silver ammonia solution is 0.02-0.03M, and the preparation process is as follows: ammonia water is added dropwise to AgNO3 with a concentration of 0.02-0.03M until the precipitate disappears; the concentration of the ammonia water is 2wt%.

[0015] Furthermore, in step S1, the concentration of the L-ascorbic acid solution is 0.2-0.3M.

[0016] In the above technical solution, the PI film is immersed in KOH solution, which causes the imide ring to open and generate potassium carboxylate and amide groups, thus obtaining PI-K + Thin film; PI-K + The thin film is immersed in silver ammonia solution, and then passed through K + With Ag + Exchange, making Ag + Anchored to the PI surface, PI-Ag is obtained. + Thin film; PI-Ag + The membrane was immersed in L-ascorbic acid solution to allow Ag to... + The nanoparticles were reduced to Ag nanoparticles to obtain the PI-Ag functional substrate.

[0017] Further, in step S2, the specific operation of the electrochemical deposition method is as follows: in an argon glove box (water oxygen <0.1ppm), PI-Ag is used as the working electrode and lithium foil as the counter electrode, and the electrolyte is 1M LiTFSI / DOL-DME (1:1) + 1% LiNO3; 2-10mAh / cm² lithium is deposited, and Ag atoms spontaneously diffuse to form a Li-Ag solid solution layer, thus obtaining a PI-Ag-xLi integrated current collector negative electrode (x is the lithium areal capacity, in mAh / cm²).

[0018] Furthermore, in step S2, the specific operation of the roll-pressing composite process is as follows: in a drying chamber with a dew point of <-40℃, lithium foil and PI-Ag functional substrate are rolled together by roll pressing. The rolling pressure is 15-20MPa. Ag atoms spontaneously diffuse to form a Li-Ag solid solution layer, resulting in a PI-Ag-xLi integrated current collector anode (x is the lithium areal capacity, in mAh / cm²).

[0019] Battery assembly: NCM811 (or Li-rich cathode), Ketjen Black, and PVDF are mixed at a mass ratio of 95:2.5:2.5 or 8:1:1, coated onto a 12μm aluminum foil, and vacuum dried at 120℃ for 12 hours to obtain the cathode sheet (active material loading 7.5-20 mg / cm³). 2In an argon-filled glove box, a positive electrode, an Al2O3-coated separator, a PI-Ag-Li integrated current collector, and a negative electrode are stacked. A locally high-concentration electrolyte (LHCE electrolyte: LiFSI (lithium bisfluorosulfonylimide) / DME (ethylene glycol dimethyl ether) / TTE (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether) = 1:1:3, amount 6g / Ah) is injected to assemble CR2032 coin cells or 0.5Ah pouch cells (N / P = 1.0-5.0).

[0020] Furthermore, a protective layer is provided on the surface of the Li-Ag solid solution layer, which is prepared by the following process: Step 1: Under nitrogen protection, 2-amino-4-hydroxy-6-ethylpyrimidine is mixed with isophorone diisocyanate, heated to 90-100℃, and refluxed for 8-10 h. After precipitation, washing and drying, isocyanate-terminated ureidopyrimidinone is obtained. Step 2: Dissolve hydroxyl-terminated polydimethylsiloxane in toluene, heat to 70-80℃, add isocyanate-terminated ureidopyrimidinone, and react for 10-12 h with stirring at 600-800 r / min. After precipitation, washing, and drying, polydimethylsiloxane containing ureidopyrimidinone is obtained. Step 3: Add polydimethylsiloxane containing ureidopyrimidinone and polypropylene oxide to toluene, add isophorone diisocyanate and dibutyltin dilaurate to obtain a protective layer slurry. Coat the protective layer slurry onto the surface of the Li-Ag solid solution layer and cure it at 80-100℃ for 4-6 hours to form a protective layer.

[0021] Furthermore, in step 1, the molar ratio of 2-amino-4-hydroxy-6-ethylpyrimidine to isophorone diisocyanate is 1:(5-6).

[0022] Furthermore, in step 2, the ratio of hydroxyl-terminated polydimethylsiloxane, toluene, and isocyanate-terminated ureidopyrimidinone is 1g:(2-3)mL:(0.15-0.3)g.

[0023] Furthermore, in step 3, the protective layer slurry comprises the following components by weight: 1 part of polydimethylsiloxane containing ureidopyrimidinone, 0.8-1.2 parts of polypropylene oxide, 0.15-0.2 parts of isophorone diisocyanate, 0.005-0.01 parts of dibutyltin dilaurate, and 150-350 parts of toluene; The thickness of the protective layer is 0.3-0.5 μm.

[0024] Furthermore, the protective layer slurry should be used within 0.5-1 hour after preparation.

[0025] Compared with the prior art, the beneficial effects of the present invention are: 1. The areal density of the PI-Ag-Li integrated current collector anode of this invention is ≤0.035g / cm², which is only 22.6% of that of the traditional Cu-20Li anode. The energy density of the pouch battery (soft-pack lithium battery) based on this anode is ≥620Wh / kg, which is about 10.7% higher than the existing anode-less battery. No additional integration steps are required, breaking through the bottleneck of mass redundancy in traditional current collectors. The Li-Ag solid solution layer provides strong lithium-affinity sites (binding energy with Li -2.57eV), guiding uniform lithium deposition. After 50 cycles, the dendrite length is ≤2.5μm, and the average coulombic efficiency is ≥99.9%, solving the problem of dead lithium pulverization. The PI film and the Li-Ag solid solution layer form a strong interfacial bond (binding energy 1.59eV) through van der Waals forces (Li-Ag…O=C), buffering volume changes and avoiding electrode pulverization. At N / P=1.0, the capacity retention rate is ≥90% after 170 cycles at 0.5C rate, which is significantly better than the traditional Cu-4Li anode.

[0026] 2. The thermal insulation of the PI film of this invention can block the propagation of heat during thermal runaway. The total heat release by DSC (scanning calorimetry) is only -33.5 kJ / g (62.6% of Cu-20Li); the self-heating onset temperature tested by ARC (accelerated calorimeter) is 135℃, with no thermal runaway; the maximum temperature of the needle penetration test is ≤40℃, with no smoke or fire, meeting the safety requirements for practical application; the PI-Ag functional substrate of this invention is prepared by a three-step chemical method, without the need for complex equipment; the integrated current collector negative electrode can be achieved by electrochemical deposition or roll-pressing composite process. Roll-pressing composite is suitable for roll-to-roll production, reducing the preparation cost by 40% compared to porous carbon-based current collectors, and the batch deviation of the product is ≤5%.

[0027] 3. In this invention, polydimethylsiloxane containing ureidinone is prepared by reacting isocyanate-terminated ureidinone with hydroxyl-terminated polydimethylsiloxane. The ureidinone group can spontaneously coordinate with lithium to form a protective layer with self-stabilizing and self-healing properties, significantly enhancing the protection of the Li-Ag solid solution layer and adapting to volume changes during cycling. Furthermore, the quadruple hydrogen bonds of the ureidinone group can spontaneously break and recombine at room temperature. When microcracks are generated in the protective layer during cycling, the hydrogen bond network can automatically repair the cracks, effectively preventing the protective layer from failing due to crack propagation, thereby significantly inhibiting the failure caused by interface damage. The Si-O-Si backbone of polydimethylsiloxane imparts excellent flexibility and high elongation at break to the protective layer, effectively buffering the volume expansion of the Li-Ag solid solution layer during charging and discharging, alleviating interfacial stress concentration, and fundamentally suppressing "electrode pulverization" caused by electrode delamination and disintegration. Simultaneously, the low surface energy of polydimethylsiloxane forms a highly efficient hydrophobic barrier on the protective layer surface, effectively suppressing electrolyte side reactions and moisture erosion, and extending battery cycle life. Furthermore, the excellent thermal stability of polydimethylsiloxane complements the thermal insulation of the PI film, further enhancing battery safety.

[0028] 4. In this invention, polypropylene oxide in the protective layer serves as an ion-conducting component, providing a rapid diffusion pathway for lithium ion transport. The ether oxygen atoms in the polypropylene oxide segments form coordination bonds with lithium ions, constructing continuous ion transport channels and significantly reducing the interfacial impedance between the electrode and the electrolyte. Simultaneously, the electrostatic interaction between the polar segments of polypropylene oxide and lithium ions in the electrolyte can delay and homogenize the lithium ion flux on the lithium metal surface, making the local current density distribution more uniform, thereby effectively inhibiting the initiation and growth of lithium dendrites. Polypropylene oxide reacts with isophorone diisocyanate to form a cross-linked network. Polydimethylsiloxane containing ureidopyrimidinone is physically entangled with the cross-linked network and fixed within the protective layer. The cross-linked network provides a stable structural framework, and the four hydrogen bonds of ureidopyrimidinone endow the protective layer with self-healing capabilities. The synergistic effect of both provides the Li-Ag solid solution layer with long-term interfacial protection that combines structural stability and damage repair functions, thus fundamentally solving the problem of pulverization failure of lithium metal anodes caused by interfacial damage and volume expansion during cycling. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the following specific implementation: All numbers of parts mentioned below refer to parts by weight, unless otherwise specified.

[0031] The raw materials involved in this invention are not subject to any special limitations, and include, for example: The PI film thickness is 8 μm; the CAS number of KOH is 1310-58-3, and its purity is 95%; the CAS number of AgNO3 is 7761-88-8, and its purity is 99%; the CAS number of ammonia is 1336-21-6; the CAS number of L-ascorbic acid is 50-81-7, and its purity is 99%; the CAS number of 2-amino-4-hydroxy-6-ethylpyrimidine is 5734-66-7, and its purity is... The purity is 98%; isophorone diisocyanate CAS number is 4098-71-9, purity is 99%; hydroxyl-terminated polydimethylsiloxane type is MDH, molecular weight is 2000; toluene CAS number is 108-88-3, purity is 99.8%; polypropylene oxide type is HC3567, molecular weight is 2000; dibutyltin dilaurate CAS number is 77-58-7, purity is 98%.

[0032] Example 1: A method for preparing an anti-powdering integrated current collector negative electrode, comprising the following steps: S1: Preparation of PI-Ag functional substrate S1-1: PI hydrolysis activation (PI-K) + Preparation): An 8 μm thick PI film was immersed in a 5 M KOH solution at 25 °C for 2 h; it was then ultrasonically cleaned with deionized water at 300 W for 5 min until neutral, and dried with high-purity nitrogen to obtain PI-K + Thin film; the purity of high-purity nitrogen gas is 99.999%; S1-2: Ion-ligand exchange (PI-Ag) + Preparation): PI-K + The membrane was immersed in a 0.02M silver ammonia solution at 25°C for 2 hours; after washing three times with deionized water, it was dried with nitrogen to obtain PI-Ag. + The thin film; the preparation process of the silver ammonia solution is as follows: ammonia water is added dropwise to 0.02M AgNO3 until the precipitate disappears; the concentration of ammonia water is 2wt%. S1-3: Silver Reduction (Preparation of PI-Ag Functional Substrate): PI-Ag... + The thin film was immersed in a 0.2M L-ascorbic acid solution and reacted at 25°C for 2 min. After washing with deionized water, it was dried at 60°C and a vacuum of -0.09 MPa for 12 h to obtain the PI-Ag functional substrate. The Ag content in the PI-Ag functional substrate was 24 wt%. S2: Preparation of PI-Ag-Li integrated current collector anode: Lithium was deposited onto the surface of a PI-Ag functional substrate using an electrochemical deposition method. Ag atoms and lithium spontaneously diffused to form a Li-Ag solid solution layer, thus preparing a PI-Ag-8Li integrated current collector anode with a thickness of 48 μm. The specific operation of the electrochemical deposition method was as follows: in an argon glove box (water and oxygen <0.1 ppm), PI-Ag was used as the working electrode and lithium foil as the counter electrode. The electrolyte was 1 M LiTFSI / DOL-DME (1:1) + 1% LiNO3. Lithium of 8 mAh / cm² was deposited at 0.5 mA / cm². Battery assembly: NCM811, Ketjen Black, and PVDF were mixed at a mass ratio of 95:2.5:2.5, coated onto a 12μm aluminum foil, and vacuum dried at 120℃ for 12 hours to obtain a positive electrode sheet (active material loading 7.5 mg / cm³). 2 In an argon glove box, a CR2032 coin cell (N / P=5.0) was assembled by stacking the positive electrode, Al2O3 coated separator, PI-Ag-8Li integrated current collector, and negative electrode, and injecting LHCE electrolyte at a rate of 6 g / Ah.

[0033] Example 2: A method for preparing an anti-powdering integrated current collector negative electrode, comprising the following steps: S1: Preparation of PI-Ag functional substrate S1-1: PI hydrolysis activation (PI-K) + Preparation): An 8 μm thick PI film was immersed in a 5 M KOH solution at 25 °C for 2 h; it was then ultrasonically cleaned with deionized water at 300 W for 5 min until neutral, and dried with high-purity nitrogen to obtain PI-K + Thin film; the purity of high-purity nitrogen gas is 99.999%; S1-2: Ion-ligand exchange (PI-Ag) + Preparation): PI-K + The membrane was immersed in a 0.02M silver ammonia solution at 25°C for 2 hours; after washing three times with deionized water, it was dried with nitrogen to obtain PI-Ag. + The thin film; the preparation process of the silver ammonia solution is as follows: ammonia water is added dropwise to 0.02M AgNO3 until the precipitate disappears; the concentration of ammonia water is 2wt%. S1-3: Silver Reduction (Preparation of PI-Ag Functional Substrate): PI-Ag... + The thin film was immersed in a 0.2M L-ascorbic acid solution and reacted at 25°C for 2 min. After washing with deionized water, it was dried at 60°C and a vacuum of -0.09 MPa for 12 h to obtain the PI-Ag functional substrate. The Ag content in the PI-Ag functional substrate was 24 wt%. S2: Preparation of PI-Ag-Li integrated current collector anode: A roll-pressing composite process was used to roll-press lithium foil with a PI-Ag functional substrate, allowing Ag atoms to spontaneously diffuse with lithium to form a Li-Ag solid solution layer, thus preparing a PI-Ag-4Li integrated current collector anode with a thickness of 28 μm. The specific operation of the roll-pressing composite process was as follows: in a drying chamber with a dew point < -40℃, a 20 μm lithium foil and a PI-Ag functional substrate were rolled-pressed together at a rolling pressure of 15 MPa. Battery assembly: NCM811, Ketjen Black, and PVDF were mixed in a mass ratio of 8:1:1, coated onto a 12μm aluminum foil, and vacuum dried at 120℃ for 12 hours to obtain a positive electrode (active material loading 7.5 mg / cm³). 2 In an argon glove box, a 0.5Ah pouch battery (N / P=1.0) is assembled by stacking the positive electrode, Al2O3 coated separator, PI-Ag-4Li integrated current collector, and negative electrode, and injecting LHCE electrolyte at a rate of 6 g / Ah.

[0034] Example 3: A method for preparing an anti-powdering integrated current collector negative electrode, comprising the following steps: S1: Preparation of PI-Ag functional substrate S1-1: PI hydrolysis activation (PI-K) + Preparation): An 8 μm thick PI film was immersed in a 5 M KOH solution at 25 °C for 2 h; it was then ultrasonically cleaned with deionized water at 300 W for 5 min until neutral, and dried with high-purity nitrogen to obtain PI-K + Thin film; the purity of high-purity nitrogen gas is 99.999%; S1-2: Ion-ligand exchange (PI-Ag) + Preparation): PI-K + The membrane was immersed in a 0.03M silver ammonia solution at 25°C for 2 hours; after washing three times with deionized water, it was dried with nitrogen to obtain PI-Ag. + The thin film; the preparation process of the silver ammonia solution is as follows: ammonia water is added dropwise to 0.03M AgNO3 until the precipitate disappears; the concentration of ammonia water is 2wt%. S1-3: Silver Reduction (Preparation of PI-Ag Functional Substrate): PI-Ag... + The thin film was immersed in a 0.2M L-ascorbic acid solution and reacted at 25°C for 2 min. After washing with deionized water, it was dried at 60°C and a vacuum of -0.09 MPa for 12 h to obtain a PI-Ag functional substrate. The Ag content in the PI-Ag functional substrate was 28 wt%. S2: Preparation of PI-Ag-Li integrated current collector anode: Lithium was deposited onto the surface of a PI-Ag functional substrate using electrochemical deposition. Ag atoms spontaneously diffused with lithium to form a Li-Ag solid solution layer, resulting in a PI-Ag-4Li integrated current collector anode with a thickness of 28 μm. The specific operation of the electrochemical deposition method was as follows: in an argon glove box (water and oxygen <0.1 ppm), PI-Ag was used as the working electrode and lithium foil as the counter electrode. The electrolyte was 1 M LiTFSI / DOL-DME (1:1) + 1% LiNO3. Lithium was deposited at 0.5 mA / cm², with a Li-Ag alloy phase accounting for 35%. Battery assembly: NCM811, Ketjen Black, and PVDF were mixed at a mass ratio of 95:2.5:2.5 and coated onto a 12μm aluminum foil. The mixture was then vacuum dried at 120℃ for 12 hours to obtain a positive electrode. In an argon glove box, a CR2032 coin cell (N / P=2.0) was assembled by stacking the positive electrode, Al2O3 coated separator, PI-Ag-4Li integrated current collector, and negative electrode, and injecting LHCE electrolyte at a rate of 6 g / Ah.

[0035] Example 4: Based on Example 1, the difference from Example 1 is that a protective layer is provided on the surface of the Li-Ag solid solution layer, and the protective layer is prepared by the following process: Step 1: Under nitrogen protection, 2-amino-4-hydroxy-6-ethylpyrimidine and isophorone diisocyanate were mixed at a molar ratio of 1:5.5, heated to 95°C, and refluxed for 9 hours. After precipitation, washing, and drying, isocyanate-terminated ureidopyrimidinone was obtained. Step 2: Dissolve hydroxyl-terminated polydimethylsiloxane in toluene, heat to 75°C, add isocyanate-terminated ureapyrimidine ketone, and react for 11 h with stirring at 700 r / min. After precipitation, washing, and drying, polydimethylsiloxane containing ureapyrimidine ketone is obtained; the ratio of hydroxyl-terminated polydimethylsiloxane, toluene, and isocyanate-terminated ureapyrimidine ketone is 1 g: 2.5 mL: 0.2 g. Step 3: Mix polydimethylsiloxane containing ureidopyrimidinone, polypropylene oxide, and toluene, add isophorone diisocyanate and dibutyltin dilaurate to obtain a protective layer slurry. Coat the protective layer slurry onto the surface of the Li-Ag solid solution layer and cure at 90°C for 5 hours to form a protective layer with a thickness of 0.4 μm. The protective layer slurry comprises the following components by weight: 1 part polydimethylsiloxane containing ureidopyrimidinone, 1 part polypropylene oxide, 0.18 parts isophorone diisocyanate, 0.008 parts dibutyltin dilaurate, and 200 parts toluene; The protective layer slurry should be used within 0.5 hours after preparation.

[0036] Example 5: Based on Example 1, the difference from Example 1 is that a protective layer is provided on the surface of the Li-Ag solid solution layer, and the protective layer is prepared by the following process: Step 1: Under nitrogen protection, 2-amino-4-hydroxy-6-ethylpyrimidine and isophorone diisocyanate were mixed in a molar ratio of 1:5, heated to 90°C, and refluxed for 10 h. After precipitation, washing and drying, isocyanate-terminated ureidopyrimidinone was obtained. Step 2: Dissolve hydroxyl-terminated polydimethylsiloxane in toluene, heat to 70°C, add isocyanate-terminated ureapyridinium ketone, and react for 12 h with stirring at 600 r / min. After precipitation, washing, and drying, polydimethylsiloxane containing ureapyridinium ketone is obtained; the ratio of hydroxyl-terminated polydimethylsiloxane, toluene, and isocyanate-terminated ureapyridinium ketone is 1 g: 2 mL: 0.15 g. Step 3: Mix polydimethylsiloxane containing ureidopyrimidinone, polypropylene oxide, and toluene, add isophorone diisocyanate and dibutyltin dilaurate to obtain a protective layer slurry. Coat the protective layer slurry onto the surface of the Li-Ag solid solution layer and cure at 80°C for 6 hours to form a protective layer with a thickness of 0.5 μm. The protective layer slurry comprises the following components by weight: 1 part polydimethylsiloxane containing ureidopyrimidinone, 1.2 parts polypropylene oxide, 0.2 parts isophorone diisocyanate, 0.01 parts dibutyltin dilaurate, and 150 parts toluene; The protective layer slurry should be used within 0.5 hours after preparation.

[0037] Example 6: Based on Example 1, the difference from Example 1 is that a protective layer is provided on the surface of the Li-Ag solid solution layer, and the protective layer is prepared by the following process: Step 1: Under nitrogen protection, 2-amino-4-hydroxy-6-ethylpyrimidine and isophorone diisocyanate were mixed in a molar ratio of 1:6, heated to 100°C, and refluxed for 8 hours. After precipitation, washing, and drying, isocyanate-terminated ureidopyrimidinone was obtained. Step 2: Dissolve hydroxyl-terminated polydimethylsiloxane in toluene, heat to 80°C, add isocyanate-terminated ureapyridinium ketone, and react for 10 h with stirring at 800 r / min. After precipitation, washing, and drying, polydimethylsiloxane containing ureapyridinium ketone is obtained; the ratio of hydroxyl-terminated polydimethylsiloxane, toluene, and isocyanate-terminated ureapyridinium ketone is 1 g: 3 mL: 0.3 g. Step 3: Mix polydimethylsiloxane containing ureidopyrimidinone, polypropylene oxide, and toluene, add isophorone diisocyanate and dibutyltin dilaurate to obtain a protective layer slurry. Coat the protective layer slurry onto the surface of the Li-Ag solid solution layer and cure at 100°C for 4 hours to form a protective layer with a thickness of 0.3 μm. The protective layer slurry comprises the following components by weight: 1 part polydimethylsiloxane containing ureidopyrimidinone, 0.8 parts polypropylene oxide, 0.15 parts isophorone diisocyanate, 0.005 parts dibutyltin dilaurate, and 350 parts toluene; The protective layer slurry should be used within 1 hour after preparation.

[0038] Comparative Example 1: Based on Example 1, the only difference from Example 1 is that a 15μm copper foil is used instead of the PI-Ag functional substrate, and the other parameters are the same.

[0039] Comparative Example 2: Based on Example 2, the only difference from Example 2 is that a 15μm copper foil and a 20μm lithium foil are rolled together (Cu-4Li) under a rolling pressure of 20MPa to obtain a negative electrode.

[0040] Comparative Example 3: Based on Example 2, the only difference from Example 2 is that 1 μm Ag foil and 20 μm lithium foil are rolled together (Ag-4Li) under a rolling pressure of 20 MPa to obtain a negative electrode.

[0041] Comparative Example 4: Based on Example 4, the only difference from Example 4 is that the polydimethylsiloxane containing ureidopyrimidinone in the protective layer slurry is replaced with an equal mass of polydimethylsiloxane.

[0042] Comparative Example 5: Based on Example 4, the only difference from Example 4 is that polypropylene oxide was not added to the protective layer slurry.

[0043] Experiment: PI-Ag-Li integrated current collector negative electrodes obtained in Examples 1-6 and Comparative Examples 1-5 were used to prepare samples. Their performance was tested and the results were recorded. Thickness and areal density testing: The thickness of the sample was measured using a laser thickness gauge (accuracy ±0.1μm), and the weight of the sample was measured using an electronic balance (accuracy 0.1mg). The areal density was then calculated.

[0044] The batteries prepared in Examples 1-6 and Comparative Examples 1-5 were used to test their performance. Electronic conductivity test: The electronic conductivity of the battery was tested using the four-probe method. The test conditions were: 25±1℃ and applied current of 10mA. Electrochemical performance testing: The electrochemical performance of the battery negative electrode was tested using a Neware CT-4008 testing system. The test conditions were: charge / discharge voltage 2.8-4.3V, 1C=200mAh / g; Safety performance testing: DSC testing was conducted using a Netzsch DSC 214 Polyma with a heating rate of 10℃ / min; ARC testing was conducted using Thermal Hazard Technology EV-ARC; Needle penetration testing: in accordance with GB 38031-2020, the steel needle diameter was 1mm.

[0045]

[0046]

[0047] Conclusion: A comparison of the data in Tables 1 and 2 shows that the performance of the batteries prepared in Comparative Examples 1-5 is significantly lower than that of the batteries prepared in Examples 1-6.

[0048] To further verify the overall performance of the technical solution of the present invention, supplementary electrochemical tests were conducted on some embodiments and comparative examples, and the results are as follows: The battery in Example 1 retained 82% of its capacity after 500 cycles at 0.5C, with an average coulombic efficiency of 99.92%; and had a discharge specific capacity of 126 mAh / g at a high rate of 5C, demonstrating good rate performance.

[0049] The battery in Example 2 retained 90% of its capacity after 170 cycles at 0.5C, meeting the long-cycle requirement under a high energy density configuration (N / P=1.0).

[0050] The battery in Example 3 retained 88% of its capacity after 300 cycles at 0.5C rate, and its lithium nucleation overpotential was 35mV, which was significantly lower than that of conventional lithium metal anodes, indicating that high Ag content is beneficial to reducing the nucleation barrier.

[0051] The battery in Comparative Example 1 (Cu-8Li) completely failed after 120 cycles at 0.5C, with an average coulombic efficiency of only 83.3%, which is far lower than that of the embodiments of the present invention. This further confirms the key role of the PI-Ag functional substrate and the Li-Ag solid solution layer in cycle stability.

[0052] The above supplementary test results are consistent with the trend of the basic performance data in Tables 1 and 2, which fully demonstrates the comprehensive advantages of the anti-powdering integrated current collector negative electrode of the present invention in terms of long cycle life, high rate performance and low overpotential.

[0053] Examples 1-3 verified the effectiveness of the PI-Ag-Li integrated current collector anode in conventional, high-load, and high-Ag-content scenarios. In particular, Examples 2 (roll-pressed composite) and 3 (high-Ag content) showed outstanding performance in terms of cycle stability and safety. Comparative Examples 1-3 showed that the absence of the PI film or the use of traditional copper foil would lead to a significant decrease in performance, confirming the innovation and superiority of the present invention.

[0054] Examples 4-6 added a protective layer to Example 1, and their battery performance was better than that of Examples 1-3. This shows that the protective layer formed by polydimethylsiloxane containing ureidopyrimidinone and polypropylene oxide can effectively inhibit dendrite growth, repair microcracks and improve interface stability.

[0055] Comparative Example 4: Based on Example 4, the polydimethylsiloxane containing ureidopyrimidinone in the protective layer slurry was replaced with polydimethylsiloxane. The battery performance was worse than that of Example 4, indicating that the self-healing effect of the ureidopyrimidinone group is the key to the long-term stable protection of the protective layer.

[0056] Comparative Example 5: Based on Example 4, no polyoxypropylene was added to the protective layer slurry, which resulted in obstructed lithium-ion conduction, intensified dendrite growth, and inferior battery performance compared to Example 4. This indicates that the ion conduction and flux equalization effects of polyoxypropylene are indispensable key components for achieving efficient anti-powdering protection.

[0057] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A pulverized integrated current collector negative electrode, characterized in that: It includes the following structure: PI-Ag functional substrate and Li-Ag solid solution layer; The Li-Ag solid solution layer is prepared by electrochemical deposition or roll pressing composite process; The Li-Ag solid solution layer is disposed on the surface of the PI-Ag functional substrate.

2. A method for preparing an anti-powdering integrated current collector negative electrode, characterized by comprising the following steps: S1: Preparation of PI-Ag functional substrate S1-1: PI-K + Preparation: Take a PI film, immerse it in KOH solution, and soak it at 25℃ for 2-3 hours; then ultrasonically clean it with deionized water at 300-400W for 4-5 minutes until neutral, and dry it with high-purity nitrogen to obtain PI-K + film; S1-2: PI-Ag + Preparation: PI-K + The membrane was immersed in silver ammonia solution at 25°C for 2-3 hours; after washing with deionized water 3-5 times, it was dried with nitrogen gas to obtain PI-Ag. + film; S1-3: Preparation of PI-Ag functional substrate: PI-Ag... + The film was immersed in L-ascorbic acid solution and reacted at 25°C for 2-3 min; after washing with deionized water, it was vacuum dried at 60-70°C for 10-12 h to obtain the PI-Ag functional substrate. S2: Preparation of PI-Ag-Li integrated current collector anode: Lithium is deposited onto the surface of a PI-Ag functional substrate using an electrochemical deposition method, or a roll-pressing composite process is used to roll-press lithium foil onto a PI-Ag functional substrate, where Ag atoms and lithium spontaneously diffuse to form a Li-Ag solid solution layer, thus preparing a PI-Ag-Li integrated current collector anode.

3. The method for preparing an anti-powdering integrated current collector negative electrode according to claim 2, characterized in that: In step S1, the thickness of the PI film is 8-10 μm.

4. The method for preparing an anti-powdering integrated current collector negative electrode according to claim 2, characterized in that: In step S1, the concentration of the KOH solution is 5-6M; the concentration of the silver ammonia solution is 0.02-0.03M; and the concentration of the L-ascorbic acid solution is 0.2-0.3M.

5. The method for preparing an anti-powdering integrated current collector negative electrode according to claim 2, characterized in that: In step S1, the Ag content in the PI-Ag functional matrix is ​​22-28 wt%.

6. The method for preparing an anti-powdering integrated current collector negative electrode according to claim 2, characterized in that: In step S2, the specific operation of the electrochemical deposition method is as follows: in an argon glove box, using PI-Ag as the working electrode and lithium foil as the counter electrode, the electrolyte is 1M LiTFSI / DOL-DME + 1% LiNO3; deposit 2-10 mAh / cm² lithium.

7. The method for preparing an anti-powdering integrated current collector negative electrode according to claim 2, characterized in that: In step S2, the specific operation of the roll forming composite process is as follows: in a drying chamber with a dew point of <-40℃, lithium foil and PI-Ag functional substrate are rolled together by roll forming, and the roll forming pressure is 15-20MPa.

8. The method for preparing an anti-powdering integrated current collector negative electrode according to claim 2, characterized in that: A protective layer is provided on the surface of the Li-Ag solid solution layer, and the protective layer is prepared by the following process: Step 1: Under nitrogen protection, 2-amino-4-hydroxy-6-ethylpyrimidine is mixed with isophorone diisocyanate, heated to 90-100℃, and refluxed for 8-10 h. After precipitation, washing and drying, isocyanate-terminated ureidopyrimidinone is obtained. Step 2: Dissolve hydroxyl-terminated polydimethylsiloxane in toluene, heat to 70-80℃, add isocyanate-terminated ureidopyrimidinone, and react for 10-12 h with stirring at 600-800 r / min. After precipitation, washing, and drying, polydimethylsiloxane containing ureidopyrimidinone is obtained. Step 3: Mix polydimethylsiloxane containing ureidopyrimidinone, polypropylene oxide, and toluene, add isophorone diisocyanate and dibutyltin dilaurate to obtain a protective layer slurry. Coat the protective layer slurry onto the surface of the Li-Ag solid solution layer and cure it at 80-100℃ for 4-6 hours to form a protective layer.

9. The method for preparing an anti-pulverization integrated current collector negative electrode according to claim 8, characterized in that: In step 1, the molar ratio of 2-amino-4-hydroxy-6-ethylpyrimidine to isophorone diisocyanate is 1:(5-6); In step 2, the ratio of hydroxyl-terminated polydimethylsiloxane, toluene, and isocyanate-terminated ureidopyrimidinone is 1g:(2-3)mL:(0.15-0.3)g.

10. The method for preparing an anti-pulverization integrated current collector negative electrode according to claim 8, characterized in that: In step 3, the protective layer slurry comprises the following components by weight: 1 part polydimethylsiloxane containing ureidopyrimidinone, 0.8-1.2 parts polypropylene oxide, 0.15-0.2 parts isophorone diisocyanate, 0.005-0.01 parts dibutyltin dilaurate, and 150-350 parts toluene; The thickness of the protective layer is 0.3-0.5 μm.

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