Negative-electrode-free solid-state battery based on multi-hydrogen-bond polyurethane polymer and preparation method of negative-electrode-free solid-state battery

Abstract

The invention discloses a cathode-free solid-state battery based on a multi-hydrogen-bond polyurethane polymer and a preparation method, and belongs to the technical field of solid-state batteries. The negative-electrode-free solid-state battery comprises a positive electrode, an electrolyte layer and a copper foil current collector, wherein a polyurethane polymer with multiple hydrogen bonds is introduced into the electrolyte layer. The polyurethane polymer with multiple hydrogen bonds forms a dynamic cross-linked hydrogen bond network through a plurality of hydrogen bond donors and hydrogen bond receptors contained in a molecular chain, and has an excellent self-repairing function. The polymer is introduced into an electrolyte layer, real-time protection and repair of an electrolyte-electrode interface are realized by utilizing the self-repairing characteristic of the polymer, generation and expansion of interface cracks are effectively inhibited, and a more uniform and stable electrolyte / copper foil interface is constructed. And the uniform interface can guide lithium to be uniformly deposited on the surface of the copper foil current collector, so that the growth of lithium dendrites and the generation of dead lithium are avoided, and the coulombic efficiency, the rate capability and the long cycle stability of the negative-electrode-free solid-state battery are remarkably improved.

Description

A cathode-free solid-state battery based on polyurethane polymers with multiple hydrogen bonds and its preparation method Technical Field

[0001] This invention relates to the field of solid-state battery technology, and in particular to a negative electrode-free solid-state battery based on a polyurethane polymer with multiple hydrogen bonds and its preparation method. Background Technology

[0002] Electrodeless solid-state batteries, by eliminating the need for traditional negative electrode active materials, offer significant advantages such as high energy density, simple structure, and good safety, making them one of the important development directions for next-generation power batteries. However, during the charging and discharging process of electrodeless solid-state batteries, lithium needs to be deposited and stripped from the surface of the copper foil current collector. The interfacial stability between the electrolyte and the copper foil current collector is a key factor affecting battery performance.

[0003] Currently, traditional solid-state electrolytes and copper foil current collectors suffer from multiple problems at the interface, including poor compatibility, high interfacial impedance, and susceptibility to cracking during cycling. These problems, when combined, severely restrict the performance improvement of electrodeless solid-state batteries. Specifically, the significant difference in surface energy between the solid-state electrolyte and the copper foil current collector leads to poor contact and high interfacial impedance, significantly increasing the resistance to lithium-ion transport at the interface and reducing the battery's rate performance. Simultaneously, during charge-discharge cycles, lithium deposition and stripping on the copper foil surface cause interfacial volume changes, generating periodic mechanical stress. This stress leads to microcracks between the electrolyte layer and the copper foil current collector. As the number of cycles increases, these microcracks expand, further exacerbating the increase in interfacial impedance, creating a vicious cycle of "impedance growth ~ performance degradation." During lithium deposition, an uneven interface leads to inconsistent lithium-ion deposition rates, easily forming lithium nuclei at interfacial defects, which in turn triggers the growth of lithium dendrites. Lithium dendrites not only pierce the electrolyte layer, causing short circuits and posing serious safety hazards, but also react with the electrolyte to form dead lithium, reducing the battery's coulombic efficiency and cycle life. Although researchers have attempted to improve interface performance through methods such as interface modification (e.g., evaporating metal layers, coating functional layers) and electrolyte composition optimization (e.g., introducing inorganic fillers, adjusting lithium salt concentration), most existing technologies can only improve interface stability in the short term and are unable to achieve dynamic interface repair. When new cracks or damage occur at the interface, traditional methods cannot repair them in a timely manner, and cannot maintain the uniformity and stability of the interface in the long term, thus hindering the development of electrodeless solid-state batteries towards high energy density and long cycle life. Therefore, developing a technical solution that can achieve dynamic protection and repair of the electrolyte-electrode interface, thereby guiding uniform lithium deposition, is of great significance for promoting the industrial application of electrodeless solid-state batteries. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of poor electrolyte-copper foil interface stability and uneven lithium deposition in existing electrodeless solid-state batteries. It provides an electrodeless solid-state battery based on a multi-hydrogen bonded polyurethane polymer and its preparation method. By introducing a multi-hydrogen bonded polyurethane polymer with self-healing function, the electrolyte / electrode interface is effectively protected, and lithium is guided to be deposited uniformly on the copper foil, thereby improving the overall performance of the battery.

[0005] To achieve the above objectives, the technical solution adopted in this application is as follows: a negative electrode-free solid-state battery based on a polyurethane polymer with multiple hydrogen bonds, comprising a positive electrode, an electrolyte layer, and a copper foil current collector. The electrolyte layer is composed of a polyurethane polymer with multiple hydrogen bonds and a lithium salt. The mass fraction of the polyurethane polymer with multiple hydrogen bonds is 80% to 95% of the total mass of the electrolyte layer, and the mass fraction of the lithium salt is 5% to 20%. The polyurethane polymer with multiple hydrogen bonds is prepared by using a long-chain compound with terminal hydroxyl groups as raw materials, through the polymerization reaction of terminal hydroxyl groups with isocyanate groups, and by adding a diamine chain extender to regulate the molecular chain structure. The long-chain compound with terminal hydroxyl groups is at least one of polytetrahydrofuran and polyethylene glycol.

[0006] Further, the polyurethane polymer with multiple hydrogen bonds is prepared by the following method: a long-chain compound with terminal hydroxyl groups, a diol containing hydrogen bond donors, and a diisocyanate containing hydrogen bond acceptors are polymerized in a solvent at a reaction temperature of 60-80°C for 4-6 hours to obtain the polyurethane polymer with multiple hydrogen bonds; wherein, the molar ratio of the long-chain compound with terminal hydroxyl groups, the diol containing hydrogen bond donors, and the diisocyanate containing hydrogen bond acceptors is 1:(0.1-0.3):(1.1-1.3); the diol containing hydrogen bond donors is at least one of 4,4'-dihydroxydiphenyl sulfone and 2,2-bis(4-hydroxyphenyl)propane; and the diisocyanate containing hydrogen bond acceptors is at least one of 4,4'-diphenylmethane diisocyanate and isophorone diisocyanate.

[0007] Furthermore, the solid electrolyte matrix is ​​one of a sulfide solid electrolyte, an oxide solid electrolyte, or a polymer solid electrolyte; when the solid electrolyte matrix is ​​a polymer solid electrolyte, it is at least one of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer.

[0008] This invention also provides a method for preparing a negative electrode-free solid-state battery based on a polyurethane polymer with multiple hydrogen bonds, comprising the following steps: 1. Preparing a polyurethane polymer with multiple hydrogen bonds: A long-chain compound with terminal hydroxyl groups (number average molecular weight 1000~4000), a diisocyanate containing hydrogen bond acceptors, and a diamine chain extender are added to an N,N-dimethylformamide solvent at a molar ratio of 1:(1.1~1.3):(0.1~0.3). Under nitrogen protection, the mixture is stirred and reacted at 60~80℃ for 4~6h. After the reaction is completed, the product is poured into deionized water to precipitate, filtered, and dried in a vacuum drying oven at 80℃ for 12~16h to obtain a polyurethane polymer with multiple hydrogen bonds; 2. Preparing an electrolyte layer slurry: The polyurethane polymer with multiple hydrogen bonds prepared in step 1 and a lithium salt are added to an organic solvent at a mass ratio of (80~95):(5~20). 1. Disperse the electrolyte layer for 40-60 min, then stir at 60℃ for 2-3 h to obtain a uniform electrolyte layer slurry; 2. Prepare the positive electrode sheet: Mix the positive electrode active material, conductive agent and binder in a mass ratio of (80-90):(5-10):(5-10), add N-methylpyrrolidone to prepare the positive electrode slurry, coat the positive electrode slurry onto the aluminum foil current collector, dry at 120℃ for 8-10 h, and then roll under a pressure of 10-15 MPa to obtain the positive electrode sheet; 3. Assemble the negative electrode-free solid-state battery: Coat the electrolyte layer slurry prepared in step 2 onto the copper foil current collector, vacuum dry at 80-90℃ for 10-12 h to form an electrolyte layer with a thickness of 40-60 μm; bond the active material side of the positive electrode sheet to the electrolyte layer, and hot press under vacuum conditions at 90-110℃ and 8-12 MPa for 20-40 min to obtain the negative electrode-free solid-state battery.

[0009] Compared with existing technologies, the beneficial effects of this invention are: 1. Significant and rapid interface self-healing function: The polyurethane polymer with multiple hydrogen bonds introduced in this invention is rich in hydrogen bond donor and acceptor groups such as hydroxyl, amino, and carbonyl groups in its molecular chain. These groups can form a large number of dynamically cross-linked hydrogen bond networks between molecules. This hydrogen bond network has good dynamic reversibility. When microcracks appear at the electrolyte-copper foil interface due to mechanical stress caused by lithium deposition / stripping, the hydrogen bonds at the crack will break rapidly to release the stress. At the same time, the hydrogen bond donors and acceptors on the surrounding molecular chains can quickly recombine to form new hydrogen bond connections, achieving immediate repair of the cracks. This self-healing process does not require external stimulation, has a short response time (usually completed within a few seconds to a few minutes), can effectively inhibit the propagation of microcracks, and maintain the integrity and uniformity of the interface for a long time, fundamentally solving the problem of easy damage and difficult repair of the interface in traditional electrodeless solid-state batteries.

[0010] High lithium deposition uniformity and low nucleation barrier: The uniform and stable electrolyte-copper foil interface provides a consistent electrochemical environment and transport channel for lithium ion transport and deposition, significantly reducing lithium ion transport resistance. Simultaneously, the polyurethane polymer with multiple hydrogen bonds exhibits a moderate interaction with lithium, which regulates the distribution of lithium ions at the interface, guiding uniform nucleation and growth of lithium ions on the copper foil current collector surface and preventing excessive accumulation of lithium ions in localized areas. Scanning electron microscopy revealed that the lithium deposition layer on the copper foil surface using the present invention exhibits a dense and uniform lamellar structure with no obvious lithium dendrite formation; in contrast, the copper foil surface of traditional electrodeless solid-state batteries shows a large number of needle-like lithium dendrites. Uniform lithium deposition not only effectively suppresses lithium dendrite growth and the generation of dead lithium, but also reduces side reactions between lithium and the electrolyte, significantly improving battery safety and coulombic efficiency.

[0011] The battery's overall performance is significantly improved, and its stability is excellent: Through the above-mentioned interface optimization, the electrodeless solid-state battery of this invention exhibits excellent overall performance. The battery's coulombic efficiency is significantly increased, and its cycle stability is greatly improved.

[0012] The preparation process is simple, feasible, and highly compatible: The preparation method of this invention adopts conventional processes such as solution coating, vacuum drying, and hot pressing, requiring no special equipment or complex operating steps, resulting in low production costs and easy large-scale production. Polyurethane polymers with multiple hydrogen bonds exhibit good compatibility with various existing solid electrolyte matrices (sulfides, oxides, polymers), allowing for direct addition without significant modifications to existing electrolyte systems. Furthermore, the addition of this polymer does not significantly negatively impact the ionic conductivity of the electrolyte, maintaining the intrinsic properties of the electrolyte while ensuring improved interfacial performance. In addition, the raw materials used in the preparation process are widely available and inexpensive, further reducing the battery manufacturing cost and demonstrating high practical application value. Attached Figure Description

[0013] Figure 1 shows the coulombic efficiency cycling curve of the lithium copper battery corresponding to the multi-hydrogen-bonded polymer electrolyte prepared in Example 1; Figure 2 shows the coulombic efficiency cycling curve of the lithium copper battery corresponding to the multi-hydrogen-bonded polymer electrolyte prepared in Example 2; Figure 3 shows the cycling curve of the electrodeless solid-state battery assembled with the multi-hydrogen-bonded polymer electrolyte prepared in Example 1 and the NCM811 positive electrode; Figure 4 shows the cycling curve of the electrodeless solid-state battery assembled with the multi-hydrogen-bonded polymer electrolyte prepared in Example 2 and the NCM811 positive electrode. Detailed Implementation

[0014] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0015] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0016] A cathodeless solid-state battery based on a polyurethane polymer with multiple hydrogen bonds includes a positive electrode, an electrolyte layer, and a copper foil current collector. The electrolyte layer is composed of a polyurethane polymer with multiple hydrogen bonds and a lithium salt. The mass fraction of the polyurethane polymer with multiple hydrogen bonds is 80% to 95% of the total mass of the electrolyte layer, and the mass fraction of the lithium salt is 5% to 20%. The polyurethane polymer with multiple hydrogen bonds is prepared by using a long-chain compound with terminal hydroxyl groups as raw materials, through the polymerization reaction of terminal hydroxyl groups with isocyanate groups, and by adding a diamine chain extender to regulate the molecular chain structure. The long-chain compound with terminal hydroxyl groups is at least one of polytetrahydrofuran and polyethylene glycol.

[0017] Further, the polyurethane polymer with multiple hydrogen bonds is prepared by the following method: a long-chain compound with terminal hydroxyl groups, a diol containing hydrogen bond donors, and a diisocyanate containing hydrogen bond acceptors are polymerized in a solvent at a reaction temperature of 60-80°C for 4-6 hours to obtain the polyurethane polymer with multiple hydrogen bonds; wherein, the molar ratio of the long-chain compound with terminal hydroxyl groups, the diol containing hydrogen bond donors, and the diisocyanate containing hydrogen bond acceptors is 1:(0.1-0.3):(1.1-1.3); the diol containing hydrogen bond donors is at least one of 4,4'-dihydroxydiphenyl sulfone and 2,2-bis(4-hydroxyphenyl)propane; and the diisocyanate containing hydrogen bond acceptors is at least one of 4,4'-diphenylmethane diisocyanate and isophorone diisocyanate.

[0018] Furthermore, the solid electrolyte matrix is ​​one of a sulfide solid electrolyte, an oxide solid electrolyte, or a polymer solid electrolyte; when the solid electrolyte matrix is ​​a polymer solid electrolyte, it is at least one of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer.

[0019] This invention also provides a method for preparing a negative electrode-free solid-state battery based on a polyurethane polymer with multiple hydrogen bonds, comprising the following steps: 1. Preparing a polyurethane polymer with multiple hydrogen bonds: A long-chain compound with terminal hydroxyl groups (number average molecular weight 1000~4000), a diisocyanate containing hydrogen bond acceptors, and a diamine chain extender are added to an N,N-dimethylformamide solvent at a molar ratio of 1:(1.1~1.3):(0.1~0.3). Under nitrogen protection, the mixture is stirred and reacted at 60~80℃ for 4~6h. After the reaction is completed, the product is poured into deionized water to precipitate, filtered, and dried in a vacuum drying oven at 80℃ for 12~16h to obtain a polyurethane polymer with multiple hydrogen bonds; 2. Preparing an electrolyte layer slurry: The polyurethane polymer with multiple hydrogen bonds prepared in step 1 and a lithium salt are added to an organic solvent at a mass ratio of (80~95):(5~20). 1. Disperse the electrolyte layer for 40-60 min, then stir at 60℃ for 2-3 h to obtain a uniform electrolyte layer slurry; 2. Prepare the positive electrode sheet: Mix the positive electrode active material, conductive agent and binder in a mass ratio of (80-90):(5-10):(5-10), add N-methylpyrrolidone to prepare the positive electrode slurry, coat the positive electrode slurry onto the aluminum foil current collector, dry at 120℃ for 8-10 h, and then roll under a pressure of 10-15 MPa to obtain the positive electrode sheet; 3. Assemble the negative electrode-free solid-state battery: Coat the electrolyte layer slurry prepared in step 2 onto the copper foil current collector, vacuum dry at 80-90℃ for 10-12 h to form an electrolyte layer with a thickness of 40-60 μm; bond the active material side of the positive electrode sheet to the electrolyte layer, and hot press under vacuum conditions at 90-110℃ and 8-12 MPa for 20-40 min to obtain the negative electrode-free solid-state battery.

[0020] Example 1: A method for preparing a negative electrode-free solid-state battery based on a polyurethane polymer with multiple hydrogen bonds, comprising the following steps: 1. Preparation of a polyurethane polymer with multiple hydrogen bonds: Polytetrahydrofuran (number average molecular weight 2000, 0.1 mol), 4,4'-diphenylmethane diisocyanate (0.12 mol), and ethylenediamine (0.02 mol) are added to 100 mL of N,N-dimethylformamide solvent. Under nitrogen protection, the mixture is stirred and reacted at 70 °C for 5 h. After the reaction is complete, the product is poured into 500 mL of deionized water to precipitate. After filtration, the precipitate is dried in a vacuum drying oven at 80 °C for 12 h to obtain a polyurethane polymer with multiple hydrogen bonds; 2. Preparation of an electrolyte layer slurry: The polyurethane polymer with multiple hydrogen bonds prepared in step 1 (85 g) and lithium bis(trifluoromethanesulfonylimide) (15 g) are added to 200 mL of ethanol, ultrasonically dispersed for 45 min, and then stirred at 60 °C for 12 h. Stirring at ℃ for 2.5h yields a uniform electrolyte slurry; 3. Assemble the electrodeless solid-state battery: Coat the electrolyte slurry prepared in step 2 onto a copper foil current collector, and vacuum dry at 85℃ for 11h to form an electrolyte layer with a thickness of 50μm; Lithium metal and NCM811 positive electrodes are used as positive electrodes respectively, and the surface of the positive electrode sheet is bonded to the electrolyte layer. Under vacuum conditions, hot-pressing is performed at 100℃ and 10MPa pressure for 30min to obtain electrodeless solid-state batteries with lithium copper battery and NCM811 positive electrode respectively.

[0021] Example 2: A method for preparing a negative electrode-free solid-state battery based on a polyurethane polymer with multiple hydrogen bonds, comprising the following steps: 1. Preparation of a polyurethane polymer with multiple hydrogen bonds: Polyethylene glycol (number average molecular weight 3000, 0.1 mol), isophorone diisocyanate (0.13 mol), and 1,4-butanediamine (0.03 mol) are added to 100 mL of N,N-dimethylformamide solvent. Under nitrogen protection, the mixture is stirred and reacted at 80 °C for 4 h. After the reaction is complete, the product is poured into 500 mL of deionized water to precipitate. After filtration, the precipitate is dried in a vacuum drying oven at 80 °C for 12 h to obtain a polyurethane polymer with multiple hydrogen bonds; 2. Preparation of an electrolyte layer slurry: The polyurethane polymer with multiple hydrogen bonds prepared in step 1 (90 g) and lithium bis(trifluoromethanesulfonylimide) (10 g) are added to 200 mL of ethanol, ultrasonically dispersed for 60 min, and then... Stirring at 0℃ for 2 hours yields a uniform electrolyte slurry; 3. Assemble the electrodeless solid-state battery: Coat the electrolyte slurry prepared in step 2 onto a copper foil current collector, and vacuum dry at 80℃ for 12 hours to form an electrolyte layer with a thickness of 60μm; Use lithium metal and NCM811 positive electrodes as positive electrodes respectively, with the surface of the positive electrode sheet bonded to the electrolyte layer, and hot-press at 100℃ and 10MPa pressure for 30 minutes under vacuum conditions to obtain electrodeless solid-state batteries with lithium copper battery and NCM811 positive electrode respectively.

[0022] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0023] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A cathodeless solid-state battery based on a polyurethane polymer with multiple hydrogen bonds, characterized in that, The device includes a positive electrode, an electrolyte layer, and a copper foil current collector. The electrolyte layer is composed of a polyurethane polymer with multiple hydrogen bonds and a lithium salt. The polymer has a mass fraction of 80% to 95%, and the lithium salt has a mass fraction of 5% to 20%. The polymer is prepared by polymerizing at least one hydroxyl-terminated long-chain compound selected from polytetrahydrofuran and polyethylene glycol with isocyanate groups and adding a diamine chain extender.

2. The battery according to claim 1, characterized in that, The polymer is prepared by reacting a terminal hydroxyl long-chain compound, isocyanate, and diamine chain extender in a molar ratio of 1:(1.1~1.3):(0.1~0.3) in a solvent at 60~80℃ for 4~6h.

3. The battery according to claim 2, characterized in that, The isocyanate is at least one of 4,4'-diphenylmethane diisocyanate and isophorone diisocyanate; the diamine chain extender is at least one of ethylenediamine and 1,4-butanediamine.

4. The battery according to claim 1, characterized in that, The lithium salt is at least one of lithium bis(trifluoromethanesulfonylimide), lithium hexafluorophosphate, and lithium perchlorate; the number-average molecular weight of the terminal hydroxyl long-chain compound is 1000~4000.

5. A method for preparing a negative electrode-free solid-state battery based on a polyurethane polymer with multiple hydrogen bonds, characterized in that, include: (1) Polymer preparation: A long-chain compound with terminal hydroxyl groups (molecular weight 1000~4000), isocyanate, and diamine chain extender are added to N,N-dimethylformamide in proportion, and the reaction is carried out under nitrogen protection at 60~80℃ for 4~6h. The polymer is then precipitated and dried. (2) Electrolyte slurry preparation: The polymer and lithium salt are added to an organic solvent at a ratio of (80~95):(5~20), and the mixture is ultrasonically dispersed for 40~60min and then stirred at 60℃ for 2~3h. (3) Positive electrode preparation: Positive electrode active material, conductive agent, and binder are mixed at a ratio of (80~90):(5~10):(5~10) to form a slurry, coated with aluminum foil, dried, and rolled. (4) Battery assembly: The electrolyte slurry is coated with copper foil and vacuum dried at 80~90℃ to form a 40~60μm electrolyte layer. After being bonded to the positive electrode, it is hot-pressed at 90~110℃ and 8~12 MPa for 20~40min.

6. The method according to claim 5, characterized in that, In step (1), the terminal hydroxyl long-chain compound is at least one of polytetrahydrofuran and polyethylene glycol; the isocyanate is at least one of 4,4'-diphenylmethane diisocyanate and isophorone diisocyanate; and the chain extender is at least one of ethylenediamine and 1,4-butanediamine.

7. The method according to claim 5, characterized in that, In step (2), the organic solvent is at least one of acetonitrile and ethanol; in step (3), the positive electrode active material is at least one of LiCoO2 and LiFePO4, the conductive agent is Super P, and the binder is polyvinylidene fluoride.

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