Self-repairing lithium-conducting binder as well as preparation method and application thereof

Abstract

The invention relates to the technical field of battery material preparation, in particular to a self-repairing lithium-conducting binder and a preparation method and application thereof. The self-repairing lithium-conducting binder comprises a matrix polymer, a phase change material and a filler, the phase change point of the phase change material is not less than 30 DEG C. The self-repairing lithium-conducting binder disclosed by the invention can enhance the interface stability, not only can repair cracks or gaps generated on an electrode interface, but also can prevent the cracks or gaps from appearing on the electrode interface, improve the capacity retention ratio and the cycling stability of a sulfide all-solid-state battery, and reduce the capacity fading; the binder has a lithium conducting effect, so that lithium ions can be conducted uniformly, overlarge local current density is reduced, and dendritic crystals are inhibited. The phase-change material is subjected to phase change when the battery is locally overheated, so that the fluidity is enhanced, the phase-change material permeates into gaps between the filler and electrode active material particles, interface pores are eliminated, and tight physical contact is formed; and the phase change material can carry the filler to migrate to a crack repair area or a poor contact area, so that an ion transmission path is repaired.

Description

Technical Field

[0001] The present invention relates to the technical field of battery material preparation, and in particular to a self-repairing lithium-conducting binder and a preparation method and application thereof. Background Art

[0002] All-solid-state batteries, due to their high energy density and excellent safety, are considered a core technology for next-generation energy storage devices. However, the contact issues between the solid electrolyte and the electrode interface in all-solid-state batteries limit the battery's performance and lifespan. During long-term cycling, the binder in all-solid-state batteries experiences significant stress changes due to the volume changes of the electrode material. This can lead to pulverization and flaking of the active material, fracture of the solid-electrolyte interface film, and cracks within the solid electrolyte. These problems can degrade battery cycling performance and even cause short circuits.

[0003] Sulfide all-solid-state batteries have high ionic conductivity (>10 -2 While high density (S / cm) and flexibility have received widespread attention, cracks easily form at the electrode interface due to volume expansion, hindering ion transport and causing capacity degradation. Traditional binders, such as PVDF, lack self-healing capabilities, are unable to provide lithium conductivity, and are incompatible with sulfide electrolytes, failing to address these cracking issues. Summary of the Invention

[0004] The purpose of the present invention is to provide a self-healing lithium-conducting binder and its preparation method and application, so as to solve the problem that cracks are generated at the electrode interface due to volume expansion in existing sulfide all-solid-state batteries, which cannot be repaired, resulting in obstruction of ion transmission and affecting battery performance.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a self-healing lithium-conducting binder comprising a matrix polymer, a phase change material, and a filler; the phase change point of the phase change material is ≥30° C. The phase change point of the present invention refers to the critical point at which the phase change material undergoes phase change, such as the melting point.

[0007] According to the above technical means, the electrode interface in the sulfide all-solid-state battery produces cracks and voids due to volume expansion, causing interface contact problems between the sulfide electrolyte and the positive and negative electrodes. The sulfide electrolyte and the positive electrode are easily separated at the interface due to volume expansion, causing cracks or voids, causing the battery capacity to decay. In order to solve these problems, on the one hand, when the self-healing lithium-conducting binder of the present invention is applied to the sulfide all-solid-state battery, when the temperature changes due to battery operation, the local overheating temperature is 50-70°C, and the binder phase transition point of the present invention is ≥30°C. The cracks or voids at the electrode interface are filled through solid-liquid phase transition, realizing dynamic repair of the problem of microcracks on the interface caused by volume change during lithium deposition or stripping, reducing interface impedance, and avoiding uneven precipitation of lithium ions. On the other hand, the phase change material can also alleviate the mechanical stress generated by the lithium deposition or stripping process, preventing the solid electrolyte from generating mechanical cracks due to stress concentration, thereby blocking the penetration path of lithium dendrites. On the third aspect, the binder contains fillers that can form continuous lithium ion transmission channels. The ion transmission channels can guide lithium ions to diffuse evenly to the negative electrode surface, reduce local current density, and inhibit the nucleation and growth of lithium dendrites. The self-healing lithium-conducting binder of the present invention can enhance interface stability, not only repair cracks or voids generated at the electrode interface, but also prevent cracks or voids from occurring at the electrode interface, improve the capacity retention and cycle stability of sulfide all-solid-state batteries, reduce capacity decay, and maintain a higher effective capacity during long-term cycles; the binder has a lithium-conducting effect, which can make lithium ion conduction uniform, reduce excessive local current density, and inhibit dendrites. The present invention uses phase change materials to undergo phase change when the battery is locally overheated, thereby enhancing fluidity, penetrating into the gaps between the filler and the electrode active material particles, eliminating interface pores, and forming close physical contact; the phase change material can also carry the filler to migrate to the crack repair area or the poor contact area to repair the ion transmission path. The binder of the present invention is insensitive to air and can achieve solvent recycling, especially the recycling and reuse of the solvent added when the binder is made into a pole piece.

[0008] Furthermore, the phase change point of the phase change material is ≥50°C;

[0009] Preferably, the phase change point of the phase change material is 50-70°C; illustratively, the phase change point of the phase change material is 30°C, 40°C, 50°C, 55°C, 60°C, 65°C, 70°C, etc.

[0010] Preferably, the phase change material comprises polyethylene glycol and / or paraffin.

[0011] Based on the above technical means, the present invention regulates the phase change point of the phase change material to ≥50°C, especially to 50-70°C, which is conducive to further improving the problems of interfacial separation between the sulfide electrolyte and the positive electrode due to volume expansion, causing cracks or voids, and further improving the battery capacity and cycle performance. The phase change material of the present invention is preferably polyethylene glycol and / or paraffin. When the battery temperature rises, the polyethylene glycol and / or paraffin undergoes a phase change, filling the cracks generated at the electrode interface, achieving dynamic repair, reducing interfacial impedance and buffering stress, and thus improving battery performance.

[0012] Furthermore, the molecular weight of the polyethylene glycol is 2000-6000 g / mol. Exemplarily, the molecular weight of the polyethylene glycol is 2000 g / mol, 4000 g / mol, 6000 g / mol, etc.

[0013] According to the above technical means, the present invention regulates the molecular weight of polyethylene glycol to adjust the phase transition point of polyethylene glycol, which is beneficial for the adhesive to achieve the effect of dynamically adjusting the interface cracks.

[0014] Furthermore, the carbon chain length of the paraffin wax is C18-C30;

[0015] and / or, the molecular weight of the paraffin wax is 250-450 g / mol;

[0016] And / or, the melting point of the paraffin wax is 30-70°C.

[0017] According to the above technical means, the carbon chain length of the paraffin wax of the present invention is C18-C30, the molecular weight is 250-450g / mol, and the melting point is 30-70°C, which can make the adhesive have both flexibility and melt fluidity, soften and flow when the battery is locally overheated, and repair the resulting cracks; it has solid supporting force at room temperature.

[0018] Furthermore, the filler includes sulfur and lithium;

[0019] Optionally, the filler includes at least one of lithium disulfide, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0020] According to the above technical means, due to the volume change of the positive electrode material itself, during the charge and discharge process of the battery, the stress change blocks the lithium ion transmission path. After the dynamic self-repair of the binder is completed, the filler in the binder diffuses to the self-repair area, re-forming a uniformly distributed ion transmission channel, guiding the lithium ions to diffuse evenly to the negative electrode surface, reducing the local current density, and inhibiting the nucleation and growth of lithium dendrites. The present invention preferably uses the above-mentioned substances to better form continuous lithium ion transmission channels, guide lithium ions to diffuse evenly to the negative electrode surface, further reduce the local current density, inhibit the nucleation and growth of lithium dendrites, improve ionic conductivity, reduce interfacial impedance, improve capacity retention and cycle stability, and are more suitable for sulfide all-solid-state batteries.

[0021] Furthermore, the matrix polymer includes polyisobutylene.

[0022] According to the above technical means, the matrix polymer of the present invention includes polyisobutylene, which firstly has an inert non-polar structure, is resistant to sulfide reduction, and will not affect the performance of sulfide electrolyte; secondly, it has good adaptability of mechanical properties, which is conducive to maintaining high flexibility and elasticity within the operating temperature range of the battery; the matrix polymer can also provide beneficial mechanical strength and chemical stability for the self-healing lithium-conducting binder, ensuring the reliability of the self-healing lithium-conducting binder in long-term circulation.

[0023] Furthermore, the mass ratio of the matrix polymer, the phase change material, and the filler is (70-90):(5-25):(5-25); optionally, (70-90):(5-15):(5-15). Exemplary ratios include 70:5:25, 70:10:20, 70:20:10, 80:10:10, 80:12:8, 85:5:10, 80:15:5, and 90:5:5.

[0024] According to the above technical means, the present invention optimizes the amount of the matrix polymer, phase change material and filler in the binder, and further optimizes the lithium conductivity, bonding strength and thermal phase change characteristics of the binder.

[0025] A second aspect of the present invention provides a method for preparing the self-repairing lithium-conducting binder, comprising mixing various raw materials.

[0026] The third aspect of the present invention provides a positive electrode material, comprising a positive electrode active material and the above-mentioned self-repairing lithium-conducting binder.

[0027] Furthermore, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide or lithium cobalt oxide;

[0028] And / or, the mass ratio of the positive electrode active material to the self-repairing lithium-conducting binder is (70-80):(3-5).

[0029] Furthermore, the positive electrode material also includes a sulfide solid electrolyte, such as Li6PS5Cl, Li6PS5Br, Li6PS5I, Li10GeP2S 12 At least one of the above.

[0030] Optionally, the positive electrode material further includes a conductive agent, such as at least one of Super P and carbon nanotubes.

[0031] Optionally, the positive electrode material includes a positive electrode active material, a sulfide solid electrolyte, a conductive agent, and a self-healing lithium conductive binder in a mass ratio of (70-80):(15-30):(3-5):(3-5).

[0032] When preparing the positive electrode sheet, a method known in the art is used, which exemplarily includes the following steps:

[0033] (1) All raw materials are dried in advance, for example, vacuum dried at 120°C for 12 hours to remove moisture. This operation is carried out in a glove box (H2O / O2<1ppm). The positive electrode active material, sulfide solid electrolyte, and conductive agent are placed in a ball mill, and an organic solvent and a solution containing a self-healing lithium conductive binder are added. Zirconia balls with a diameter of 3-5mm are used, and the rotation speed is 300-500rpm. Ball milling and dispersion are performed for 4-6 hours to form a uniform slurry with a solid content of 50-60%. The organic solvent uses a type of solvent known in the art. The specific type of organic solvent can be determined according to the raw materials, such as anisole. The amount of organic solvent added is adjusted according to the viscosity of the positive electrode slurry.

[0034] (2) Pre-dry the aluminum foil current collector, use a scraper or coater to evenly coat the slurry on the current collector, let it stand at room temperature for 1 hour, and vacuum dry it at 60-95℃ for 12 hours to remove the solvent.

[0035] (3) Use a double-roll press or a flat plate press, maintain a pressure of 10-30 MPa for 1-5 minutes, cut to the required size, and obtain the electrode.

[0036] A fourth aspect of the present invention provides a sulfide all-solid-state battery, comprising a positive electrode plate, wherein the positive electrode plate comprises the above-mentioned positive electrode material.

[0037] The sulfide all-solid-state battery is prepared according to the method in the art, and the negative electrode plate is a conventional negative electrode in the art, such as a lithium plate, indium-lithium alloy, etc.

[0038] Beneficial effects of the present invention:

[0039] (1) The self-healing lithium-conducting binder provided by the present invention comprises a matrix polymer, a phase change material and a filler; the phase change point of the phase change material is ≥30°C. In the first aspect, when the self-healing lithium-conducting binder of the present invention is applied to a sulfide all-solid-state battery, when the temperature changes during battery operation, the local overheating temperature is between 50-70°C, and the binder of the present invention has a phase change point of ≥30°C. The cracks or gaps at the electrode interface are filled through solid-liquid phase transition, thereby dynamically repairing the problem of microcracks at the interface caused by volume changes during lithium deposition or stripping, reducing interface impedance, and avoiding uneven precipitation of lithium ions. In the second aspect, the phase change material can also alleviate the mechanical stress generated during lithium deposition or stripping, preventing the solid electrolyte from generating mechanical cracks due to stress concentration, thereby blocking the penetration path of lithium dendrites. In the third aspect, the binder contains fillers that can form continuous lithium ion transmission channels. The ion transmission channels can guide lithium ions to diffuse evenly to the negative electrode surface, reduce local current density, and inhibit the nucleation and growth of lithium dendrites. The self-healing lithium-conducting binder of the present invention can enhance interface stability, not only can repair cracks or voids generated at the electrode interface, but also can prevent cracks or voids from occurring at the electrode interface, thereby improving the capacity retention and cycle stability of sulfide all-solid-state batteries, reducing capacity attenuation, and maintaining a higher effective capacity during long-term cycles; the binder has a lithium-conducting effect, which can make lithium ion conduction uniform, reduce excessive local current density, and inhibit dendrites. The present invention uses a phase change material to undergo a phase change when the battery is locally overheated, thereby enhancing fluidity, penetrating into the gaps between the filler and the electrode active material particles, eliminating interface pores, and forming close physical contact; the phase change material can also carry the filler to migrate to the crack repair area or the poor contact area to repair the ion transmission path. The binder of the present invention is insensitive to air and can achieve solvent recycling.

[0040] (2) The self-healing lithium-conducting binder provided by the present invention regulates the phase change point of the phase change material to ≥50°C, especially to meet 50-70°C, which is conducive to further improving the problems of interfacial separation between the sulfide electrolyte and the positive electrode due to volume expansion, causing cracks or voids, and further improving the battery capacity and cycle performance. The phase change material of the present invention is preferably polyethylene glycol and / or paraffin. When the battery temperature rises, the polyethylene glycol and / or paraffin undergoes a phase change, filling the cracks generated at the electrode interface, achieving dynamic repair, reducing the interface impedance and buffering stress, and thus improving the battery performance.

[0041] (3) The self-healing lithium-conducting binder provided by the present invention can adjust the phase transition point of polyethylene glycol by regulating the molecular weight of polyethylene glycol, which is beneficial for the binder to achieve the effect of dynamically adjusting the interface cracks.

[0042] (4) The self-healing lithium-conducting binder provided by the present invention has a carbon chain length of C18-C30, a molecular weight of 250-450g / mol, and a melting point of 30-70°C, which can make the binder have both flexibility and melt fluidity, soften and flow when the battery is locally overheated, and repair the resulting cracks; it has solid support force at room temperature.

[0043] (5) The self-healing lithium-conducting binder provided by the present invention has a volume change of the positive electrode material itself. During the charge and discharge process of the battery, the stress change blocks the lithium ion transmission path. After the dynamic self-repair of the binder is completed, the filler in the binder diffuses to the self-repairing area, re-forming a uniformly distributed ion transmission channel, guiding the lithium ions to diffuse evenly to the negative electrode surface, reducing the local current density, and inhibiting the nucleation and growth of lithium dendrites. The present invention preferably uses the above-mentioned material to better form a continuous lithium ion transmission channel, guide the lithium ions to diffuse evenly to the negative electrode surface, further reduce the local current density, inhibit the nucleation and growth of lithium dendrites, improve ionic conductivity, reduce interfacial impedance, improve capacity retention and cycle stability, and is more suitable for sulfide all-solid-state batteries.

[0044] (6) The self-healing lithium-conducting binder provided by the present invention comprises a matrix polymer comprising polyisobutylene, which firstly has an inert non-polar structure, is resistant to sulfide reduction, and will not affect the performance of the sulfide electrolyte; secondly, has good adaptability of mechanical properties, which is conducive to maintaining high flexibility and elasticity within the operating temperature range of the battery; thirdly, has good compatibility with the polar surface of the sulfide electrolyte, can form close physical contact, reduce interfacial pores, and reduce lithium ion transmission resistance; the matrix polymer can also provide beneficial mechanical strength and chemical stability for the self-healing lithium-conducting binder, ensuring the reliability of the self-healing lithium-conducting binder in long-term cycles.

[0045] (7) The self-healing lithium-conducting adhesive provided by the present invention optimizes the amount of matrix polymer, phase change material and filler in the adhesive, and further optimizes the lithium-conducting performance, bonding strength and thermal phase change characteristics of the adhesive. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram of the state after the raw materials in the self-repairing lithium-conducting binder of Example 1 of the present invention are mixed.

[0047] Figure 2 Schematic diagram of the interface before and after the self-healing adhesive repairs it. DETAILED DESCRIPTION

[0048] The following describes the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art will readily appreciate the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the various details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are intended only to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0049] It should be noted that the illustrations provided in the following embodiments are merely schematic illustrations of the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0050] Example 1

[0051] This embodiment provides a self-healing lithium-conducting binder, comprising a phase change material PEG-2000, a lithium-conducting filler Li2S, and a matrix polymer PIB in a mass ratio of 15:15:70. A method for preparing the self-healing lithium-conducting binder comprises: uniformly mixing the raw materials. Figure 1 This is a schematic diagram of the self-repairing adhesive after mixing.

[0052] This embodiment provides a sulfide solid-state battery, including:

[0053] Positive electrode: Combine the active material (NCM811), sulfide solid electrolyte (Li6PS5Cl), conductive agent (Super P), and the aforementioned self-healing lithium-conducting binder in a mass ratio of 75:20:3:2 in an argon glove box (H2O / O2 <1ppm). Vacuum dry at 120°C for 12 hours to remove moisture and set aside. Heat anisole to 70°C and magnetically stir at 800 rpm. Slowly add the aforementioned self-healing lithium-conducting binder and continue stirring for 5 hours until completely dissolved to form a transparent, viscous gel with a solids content of 5%.

[0054] The active material, sulfide solid electrolyte and conductive agent were premixed in an argon glove box at a speed of 300 rpm. Zirconia balls with a diameter of 3-5 mm were used for ball milling for 5 minutes. Then the above-mentioned viscous glue was added, and anisole solvent was added to adjust the solid content of the slurry to 60%. Zirconia grinding balls were continued to be used for dispersion for 6 hours at a speed of 500 rpm to obtain the positive electrode slurry.

[0055] The aluminum foil current collector was dried in advance, and the positive electrode slurry was coated on the aluminum foil current collector with a wet film thickness of 200 μm. It was allowed to stand at room temperature (25°C) for 1 hour, and then vacuum dried at 85°C for 24 hours. After drying, it was maintained at a pressure of 30 MPa for 3 minutes and cut into discs with a diameter of 10 mm to obtain positive electrode sheets.

[0056] Assemble the battery: Place the sulfide electrolyte powder in a mold and use a tablet press to maintain the pressure at 3 MPa for 3 minutes to make a dense disc; then place the positive electrode on one side of the mold battery electrolyte membrane and maintain the pressure at 3 MPa for 3 minutes; place the lithium indium alloy on the other side of the mold battery containing the electrolyte and use a tablet press to maintain the pressure at 1 MPa for 5 minutes to obtain the battery. Figure 2 Schematic diagram of the interface before and after the self-healing adhesive repairs it.

[0057] Example 2

[0058] This embodiment provides a sulfide solid-state battery, which is basically the same as Example 1, with the main difference being a different self-healing lithium-conducting binder. The self-healing lithium-conducting binder of this embodiment includes a phase change material PEG-2000, a lithium-conducting filler Li2S, and a matrix polymer PIB in a mass ratio of 5:25:70.

[0059] Example 3

[0060] This embodiment provides a sulfide solid-state battery, which is basically the same as Example 1, with the main difference being a different self-healing lithium-conducting binder. The self-healing lithium-conducting binder of this embodiment includes a phase change material PEG-2000, a lithium-conducting filler Li2S, and a matrix polymer PIB in a mass ratio of 25:5:70.

[0061] Example 4

[0062] This embodiment provides a sulfide solid-state battery, which is basically the same as Example 1, with the main difference being the filler in the self-healing lithium-conducting binder. In this embodiment, the filler is LiTFSI.

[0063] Example 5

[0064] This embodiment provides a sulfide solid-state battery, which is basically the same as Example 1, with the main difference being a different self-healing lithium-conducting binder. The self-healing lithium-conducting binder of this embodiment includes a phase change material PEG, a lithium-conducting filler LiTFSI, and a matrix polymer PIB in a mass ratio of 5:25:70.

[0065] Example 6

[0066] This embodiment provides a sulfide solid-state battery, which is basically the same as Example 1, with the main difference being a different self-healing lithium-conducting binder. The self-healing lithium-conducting binder of this embodiment includes a phase change material PEG, a lithium-conducting filler LiTFSI, and a matrix polymer PIB in a mass ratio of 25:5:70.

[0067] Example 7

[0068] This embodiment provides a sulfide solid-state battery, which is basically the same as Example 1, with the main difference being the phase change material in the self-healing lithium-conducting binder. The phase change material in this embodiment is paraffin wax, which has a carbon chain length of C25, a melting point of approximately 55°C, and a molecular weight of approximately 350 g / mol.

[0069] Example 8

[0070] This embodiment provides a sulfide solid-state battery, which is basically the same as Example 1, with the main difference being a different self-healing lithium-conducting binder. The self-healing lithium-conducting binder of this embodiment includes a phase change material PEG-6000, a lithium-conducting filler Li2S, and a matrix polymer PIB in a mass ratio of 5:5:90.

[0071] Example 9

[0072] This embodiment provides a sulfide solid-state battery, which is basically the same as Example 1, with the main difference being the filler in the self-healing lithium-conducting binder. In this embodiment, the filler is LiPF6.

[0073] Example 10

[0074] This embodiment provides a sulfide solid-state battery, which is basically the same as Example 1, with the main difference being a different self-healing lithium-conducting binder. The self-healing lithium-conducting binder of this embodiment is different, including succinonitrile, lithium-conducting filler Li2S, and matrix polymer PIB in a mass ratio of 15:15:70.

[0075] Comparative Example 1

[0076] This comparative example provides a sulfide solid-state battery, which is basically the same as Example 1, with the main difference being the binder in the slurry. This comparative example uses PIB as the binder.

[0077] Comparative Example 2

[0078] This comparative example provides a sulfide solid-state battery, which is basically the same as Example 1, with the main difference being that the matrix polymer in the self-healing lithium-conducting binder is different. In this comparative example, the matrix polymer is PVDF, and the organic solvent is NMP instead of anisole.

[0079] Test Case

[0080] This test example provides performance tests of sulfide solid-state batteries in various embodiments and comparative examples, and the results are as follows:

[0081] Test method of ionic conductivity: put the prepared positive electrode into the mold battery, and use an electrochemical workstation to measure the ionic conductivity at an amplitude of 10mV and a frequency of 0.1-10 -6 Hz, and the total ionic conductivity was obtained; then, the DC polarization method was used to obtain the electronic conductivity at a voltage of 10 mV for 1800 s, and then the ionic conductivity was obtained.

[0082] The test method for 1C / 0.1C rate discharge capacity retention rate is as follows: charge the mold battery at 0.1C and discharge it at 0.1C to obtain the 0.1C discharge capacity; charge the mold battery at 0.1C and discharge it at 1C to obtain the 1C discharge capacity; divide the 1C discharge capacity by the 0.1C discharge capacity to obtain the 1C / 0.1C rate discharge capacity retention rate.

[0083] The test method for capacity retention after 300 cycles at 25°C and 0.5C is as follows: the mold battery is charged at 0.1C and discharged at 0.1C for activation; then, it is charged and discharged at 0.5C for 300 cycles, and the capacity retention after 300 cycles is obtained by dividing the discharge capacity after 300 cycles by the discharge capacity after 1 cycle.

[0084] Table 1 Test results of various embodiments and comparative examples

[0085]

[0086]

[0087] It can be seen from the above results that the self-healing lithium-conducting binder of the present invention includes a matrix polymer, a phase change material and a filler; the phase change point of the phase change material is 50-70°C, and its application in batteries can improve ionic conductivity, capacity and cycle performance.

[0088] From the comparative example 1, it can be seen that directly using PIB as a binder results in poor battery capacity and cycle performance. Comparative example 2 uses PVDF instead of the phase change material PIB. Due to the poor viscoelasticity of PVDF, it is difficult to adapt to the volume change and stress concentration of the solid-solid interface in the sulfide all-solid-state battery, which can easily lead to separation of the electrode and electrolyte interface. In addition, PVDF needs to be used in conjunction with NMP. This type of solvent produces nucleophilic attacks on sulfide solid electrolytes, which can easily cause electrolyte decomposition or interfacial side reactions, affecting battery stability. In addition, PVDF is prone to decomposition under high voltage or high voltage cycles, especially in sulfide systems. Its electrochemical window is narrow, which may cause interface degradation and battery performance to decline.

[0089] Based on the examples, the phase change material of the present invention is preferably polyethylene glycol or paraffin wax, which helps improve battery electrical performance, such as rate capability and cycling performance. However, using succinonitrile as a phase change material, due to its strong molecular structure and poor thermoplasticity, slow crack repair, results in minimal improvement in battery performance. The filler of the present invention, which includes both sulfur and lithium, can further enhance the electrical properties of sulfide all-solid-state batteries, such as ionic conductivity, capacity, and cycling performance.

[0090] The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitution or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention.

Claims

1. A self-repairing lithium-conducting binder, characterized in that: The invention comprises a matrix polymer, a phase change material and a filler; the phase change point of the phase change material is ≥30°C.

2. The self-repairing lithium-conducting binder according to claim 1, characterized in that The phase change point of the phase change material is ≥50°C; Preferably, the phase change point of the phase change material is 50-70°C; Preferably, the phase change material comprises polyethylene glycol and / or paraffin.

3. The self-repairing lithium-conducting binder according to claim 2, characterized in that The molecular weight of the polyethylene glycol is 2000-6000 g / mol; and / or, the carbon chain length of the paraffin wax is C18-C30; and / or, the molecular weight of the paraffin wax is 250-450 g / mol; And / or, the melting point of the paraffin wax is 30-70°C.

4. The self-repairing lithium-conducting binder according to claim 1, characterized in that The filler includes sulfur and lithium; Optionally, the filler includes at least one of lithium disulfide, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

5. The self-repairing lithium-conducting binder according to claim 1, characterized in that The base polymer includes polyisobutylene.

6. The self-repairing lithium-conducting binder according to any one of claims 1 to 5, characterized in that: The mass ratio of the matrix polymer, the phase change material and the filler is (70-90):(5-25):(5-25).

7. The method for preparing the self-repairing lithium-conducting binder according to any one of claims 1 to 6, characterized in that: Involves mixing the raw materials.

8. A positive electrode material, characterized in that The invention comprises a positive electrode active material, the self-repairing lithium-conducting binder according to any one of claims 1 to 6, or the self-repairing lithium-conducting binder prepared by the preparation method according to claim 7.

9. The positive electrode material according to claim 8, characterized in that The positive electrode active material includes at least one of lithium nickel cobalt manganese oxide or lithium cobalt oxide; And / or, the mass ratio of the positive electrode active material to the self-repairing lithium-conducting binder is (70-80):(3-5).

10. A sulfide all-solid-state battery, characterized in that: It comprises a positive electrode plate, and the positive electrode plate comprises the positive electrode material according to claim 8 or 9.

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