A positive electrode material and a solid-state battery containing the same

Abstract

The application provides a positive electrode material and a solid-state battery containing the positive electrode material; the positive electrode material has a core-shell structure, and the core-shell structure comprises a core and a shell layer; the core comprises carbon and an active material; and the shell layer comprises a covalent organic framework material, which is an organic material with a ring structure. The positive electrode material has good compactness under a microscope, a large interface contact area in the interior of the positive electrode material, small interface impedance between particles, and excellent rate performance.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a positive electrode material and a solid-state battery containing the positive electrode material. Background Technology

[0002] With the dwindling reserves of fossil fuels, represented by the three major energy sources—coal, oil, and natural gas—chemical power sources have gained significant attention in areas such as high-tech devices, green and low-energy transportation, and the development and utilization of renewable energy. Rechargeable batteries are a key technology for clean energy storage and electric vehicle applications. However, traditional lithium-ion batteries (LIBs) use flammable liquid electrolytes, which increases safety risks; simultaneously, graphite anodes reduce energy density compared to lithium metal anodes. Among various alternatives, all-solid-state lithium batteries (ASSBs) based on solid-state electrolytes (SEs) and ideal lithium metal anodes (or anode-free designs) offer the potential to meet the growing demand for high-energy-density and high-safety energy storage systems.

[0003] Liquid lithium-sulfur (Li-S) batteries have attracted attention as a next-generation energy storage technology due to their high theoretical specific capacity. However, their development has been limited by problems such as the shuttle effect, high volatility, and low ignition point, leading to low coulombic efficiency, rapid capacity decay, high self-discharge, and safety issues. Solid-state electrolytes have been extensively studied due to their ability to mitigate the shuttle effect, provide high-speed lithium-ion transport, high mechanical strength, and improved safety. All-solid-state lithium-sulfur batteries (ASSLSBs) exhibit superior electrochemical performance and high safety; however, they still face significant challenges in reversible specific capacity, cycle stability, and rate performance. This is mainly due to the low ion and electron transport rates at the interface between the electrode materials and the solid electrolyte. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a cathode material and a solid-state battery containing the cathode material; the cathode material has the characteristic of good compatibility with solid electrolyte, and the use of the cathode material can obtain a cathode / solid electrolyte interface with high lithium-ion and electron transport, thereby obtaining an all-solid-state lithium-sulfur battery with high reversible specific capacity, high cycle stability and high rate performance.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A cathode material having a core-shell structure, the core-shell structure comprising a core and a shell layer; wherein the core comprises carbon and an active material; and the shell layer comprises a covalent organic framework material, the covalent organic framework material being prepared by reacting an acylhydrazine with an allyl group, an aldehyde with a phenyl and / or triazine group, and a sulfonate with a mercapto group.

[0007] According to an embodiment of the present invention, the organic building blocks of the covalent organic framework material include the structural units shown in Formula 1 and the structural units shown in Formula 2:

[0008]

[0009] In Equation 1, X is C or N; R may be the same or different and are independent of each other, namely H, F, Cl, Br, NH2, NO2, OH, C. 1～6 Alkyl group; * indicates a connecting end;

[0010] In Equation 2, n is an integer greater than or equal to 1; * represents a connection terminal.

[0011] According to an embodiment of the present invention, in Formula 1, X is N; R may be the same or different, and independently represent H, F, Cl, Br, NH2, NO2, OH, C 1～3 Alkyl groups (such as methyl, ethyl or propyl).

[0012] According to an embodiment of the present invention, in Formula 2, n is an integer between 1 and 6.

[0013] According to an embodiment of the present invention, the covalent organic framework material has the structure shown in Formula 3:

[0014] In Equation 3, n is defined as described above; * represents the connection end.

[0015] According to an embodiment of the present invention, the covalent organic framework material is prepared by reacting a compound comprising the compound shown in Formula 4, the compound shown in Formula 5, the compound shown in Formula 6, and lithium carbonate; or, the covalent organic framework material is prepared by reacting a compound comprising the compound shown in Formula 4, the compound shown in Formula 5, and the compound shown in Formula 6'.

[0016]

[0017] In Equation 4, X and R are defined as described above;

[0018] In Equations 6 and 6', n is defined as described above.

[0019] According to an embodiment of the present invention, the compound represented by Formula 4 is selected from at least one of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and 1,3,5-tris(4-aldehydephenyl)-benzene.

[0020] According to an embodiment of the present invention, the compound represented by Formula 5 is selected from 2,5-bis(allyloxy)-terephthalohydrazide.

[0021] According to an embodiment of the present invention, the compound represented by Formula 6 is selected from at least one of sodium 2-mercaptoethanesulfonate, sodium 3-mercaptoethanesulfonate, sodium 4-mercaptoethanesulfonate, sodium 5-mercaptoethanesulfonate, sodium 6-mercaptoethanesulfonate, sodium 7-mercaptoethanesulfonate, sodium 3-mercapto-1-propanesulfonate, etc.

[0022] According to an embodiment of the present invention, the compound represented by Formula 6' is selected from at least one of lithium 2-mercaptoethanesulfonate, lithium 3-mercaptoethanesulfonate, lithium 4-mercaptoethanesulfonate, lithium 5-mercaptoethanesulfonate, lithium 6-mercaptoethanesulfonate, lithium 7-mercaptoethanesulfonate, lithium 3-mercapto-1-propanesulfonate, etc.

[0023] According to an embodiment of the present invention, the pore size of the covalent organic framework material is 1.70 nm to 2.65 nm.

[0024] According to an embodiment of the present invention, the carbon accounts for 25% to 35% of the total mass of the core.

[0025] According to an embodiment of the present invention, the active substance is Li2S.

[0026] According to an embodiment of the present invention, the active material accounts for 65% to 75% of the total mass of the core.

[0027] According to an embodiment of the present invention, the mass ratio of the core to the shell in the cathode material is 1 to 5:1.

[0028] According to an embodiment of the present invention, the thickness of the shell layer in the positive electrode material is 2 nm to 20 nm.

[0029] According to an embodiment of the present invention, the median particle size D of the cathode material is... 50 The range is 20nm to 200nm.

[0030] According to an embodiment of the present invention, the thermal decomposition temperature of the positive electrode material is 600–800°C.

[0031] According to an embodiment of the present invention, the ionic conductivity of the positive electrode material is 10. -3 ~10 -4 S / cm.

[0032] According to an embodiment of the present invention, the electronic conductivity of the positive electrode material is 10. -1 ~10 -2 S / cm.

[0033] The present invention also provides a positive electrode sheet, wherein the positive electrode sheet comprises the above-described positive electrode material.

[0034] The present invention also provides a battery comprising the above-described positive electrode material; or comprising the above-described positive electrode sheet.

[0035] The beneficial effects of this invention are specifically manifested as follows:

[0036] This invention provides a cathode material and a solid-state battery containing the cathode material. The cathode material has a core-shell structure, comprising a core and a shell layer. The core comprises carbon and an active material, and the shell layer comprises a covalent organic framework material. The cathode material constructs an ion transport network based on the covalent organic framework material, which has a high lithium-ion charge density. Furthermore, the oscillation of the branched chains (lithium alkyl sulfonate) of the covalent organic framework material can improve the lithium-ion mobility, significantly increasing the ionic conductivity of the cathode material. The core of the cathode material comprises highly conductive carbon, which can partially coat Li₂S particles, improving the conductivity of Li₂S and suppressing its volume expansion, thus greatly enhancing the electronic conductivity of the cathode material. Based on this, the nano-conductive network constructed by the cathode material can form a uniform and efficient ion and electron conduction network, providing effective electron and ion transport channels, alleviating stress during lithium insertion and extraction processes, and enabling the preparation of cathode materials with high loading capacities. The rigid framework of the covalent organic framework material ensures no phase change during thermal decomposition, and its permanent porous structure provides ample space to promote ion diffusion, ensuring ion transport at low temperatures. Batteries assembled from this material exhibit excellent low-temperature performance and can undergo reversible cycling at -30°C. The cathode material exhibits good microscopic density, with a large interfacial contact area and low interfacial impedance between particles, resulting in excellent rate performance.

[0037] Furthermore, if the covalent organic framework material prepared in this invention has a triazine structure, it facilitates the chemical adsorption of sulfur (S) during preparation, adsorbing the active material Li₂S within the core-shell structure. The raw materials for the cathode material are widely available organic materials, abundant in the Earth's crust for energy storage. In addition, the cathode material is prepared by a liquid-phase mixing method, which results in a uniform distribution of ionic and electronic conductive networks within the carbon and active material composite, leading to a higher discharge specific capacity than current solid-state lithium-sulfur batteries. Attached Figure Description

[0038] Figure 1 The image shows a transmission electron microscope image of the cathode material prepared in Example 1.

[0039] Figure 2 The image shows a SEM image of the positive electrode sheet prepared in Example 2, which reveals that the positive electrode sheet has a dense structure. Detailed Implementation

[0040] <Cathode Materials>

[0041] A cathode material having a core-shell structure, the core-shell structure comprising a core and a shell layer; wherein the core comprises carbon and an active material; and the shell layer comprises a covalent organic framework material, the covalent organic framework material being prepared by reacting an acylhydrazine with an allyl group, an aldehyde with a phenyl and / or triazine group, and a sulfonate with a mercapto group.

[0042] According to an embodiment of the present invention, the organic building blocks of the covalent organic framework material include the structural units shown in Formula 1 and the structural units shown in Formula 2:

[0043]

[0044] In Equation 1, X is C or N; R may be the same or different and are independent of each other, namely H, F, Cl, Br, NH2, NO2, OH, C. 1～6 Alkyl group; * indicates a connecting end;

[0045] In Equation 2, n is an integer greater than or equal to 1; * represents a connection terminal.

[0046] According to an embodiment of the present invention, in Formula 1, X is N; R may be the same or different, and independently represent H, F, Cl, Br, NH2, NO2, OH, C 1～3 Alkyl groups (such as methyl, ethyl or propyl).

[0047] According to an embodiment of the present invention, in Formula 1, X is N; R is H.

[0048] According to an embodiment of the present invention, in Formula 2, n is an integer between 1 and 6.

[0049] According to an embodiment of the present invention, in Formula 2, n is 1, 2, 3, 4, 5 or 6.

[0050] According to an embodiment of the present invention, the covalent organic framework material has the structure shown in Formula 3:

[0051] In Equation 3, n is defined as described above; * represents the connection end.

[0052] According to an embodiment of the present invention, the covalent organic framework material is prepared by reacting a compound comprising the compound shown in Formula 4, the compound shown in Formula 5, the compound shown in Formula 6, and lithium carbonate; or, the covalent organic framework material is prepared by reacting a compound comprising the compound shown in Formula 4, the compound shown in Formula 5, and the compound shown in Formula 6'.

[0053]

[0054] In Equation 4, X and R are defined as described above;

[0055] In Equations 6 and 6', n is defined as described above.

[0056] According to an embodiment of the present invention, the compound represented by Formula 4 is selected from at least one of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and 1,3,5-tris(4-aldehydephenyl)-benzene.

[0057] According to an embodiment of the present invention, the compound shown in Formula 5 is 2,5-bis(allyloxy)-terephthalohydrazide.

[0058] According to an embodiment of the present invention, the compound represented by Formula 6 is selected from at least one of sodium 2-mercaptoethanesulfonate, sodium 3-mercaptoethanesulfonate, sodium 4-mercaptoethanesulfonate, sodium 5-mercaptoethanesulfonate, sodium 6-mercaptoethanesulfonate, sodium 7-mercaptoethanesulfonate, sodium 3-mercapto-1-propanesulfonate, etc.

[0059] According to an embodiment of the present invention, the compound represented by Formula 6' is selected from at least one of lithium 2-mercaptoethanesulfonate, lithium 3-mercaptoethanesulfonate, lithium 4-mercaptoethanesulfonate, lithium 5-mercaptoethanesulfonate, lithium 6-mercaptoethanesulfonate, lithium 7-mercaptoethanesulfonate, lithium 3-mercapto-1-propanesulfonate, etc.

[0060] According to an embodiment of the present invention, the covalent organic framework material has a two-dimensional planar structure.

[0061] According to an embodiment of the present invention, the aldehyde group in the compound shown in Formula 4 and the acylhydrazine in the compound shown in Formula 5 are covalently linked by a Schiff base reaction; the mercapto group in the compound shown in Formula 6 or Formula 6' can be linked to the carbon-carbon double bond in the allyloxy group in the compound shown in Formula 5 by a Michael addition reaction.

[0062] According to an embodiment of the present invention, the covalent organic framework material has a microporous structure.

[0063] According to an embodiment of the present invention, the pore size of the covalent organic framework material is 1.70 nm to 2.65 nm, for example, 1.70 nm, 1.75 nm, 1.80 nm, 1.90 nm, 2.00 nm, 2.10 nm, 2.20 nm, 2.30 nm, 2.40 nm, 2.50 nm, 2.60 nm or 2.65 nm.

[0064] According to an embodiment of the present invention, the carbon is amorphous carbon. Specifically, it can be generated through an in-situ reaction of carbon disulfide.

[0065] According to an embodiment of the present invention, the carbon accounts for 25% to 35% of the total mass of the core, for example, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or 35%.

[0066] According to an embodiment of the present invention, the active substance is Li2S.

[0067] According to an embodiment of the present invention, the active substance accounts for 65% to 75% of the total mass of the core, for example, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74% or 75%.

[0068] According to an embodiment of the present invention, the mass ratio of the core to the shell in the positive electrode material is 1 to 5:1, for example, 1:1, 2:1, 3:1, 4:1 or 5:1.

[0069] According to an embodiment of the present invention, the thickness of the shell layer in the positive electrode material is 2nm to 20nm, for example, 2nm, 3nm, 4nm, 5nm, 6nm, 8nm, 10nm, 12nm, 15nm, 16nm, 18nm or 20nm.

[0070] According to an embodiment of the present invention, the median particle size D of the cathode material is... 50 The range is 20nm to 200nm, for example, 20nm, 30nm, 40nm, 50nm, 60nm, 80nm, 90nm, 100nm, 120nm, 130nm, 140nm, 150nm, 165nm, 180nm or 200nm.

[0071] According to an embodiment of the present invention, the thermal decomposition temperature of the positive electrode material is 600–800°C.

[0072] According to an embodiment of the present invention, the ionic conductivity of the positive electrode material is 10. -3 ~10 -4 S / cm.

[0073] According to an embodiment of the present invention, the electronic conductivity of the positive electrode material is 10. -1 ~10 -2 S / cm.

[0074] <Preparation Methods of Cathode Materials>

[0075] This invention also provides a method for preparing the above-mentioned cathode material, the method comprising the following steps:

[0076] The cathode material is prepared by mixing lithium metal, carbon disulfide, and a covalent organic framework material and reacting them.

[0077] According to an embodiment of the present invention, the reaction temperature is 250 to 350°C, for example, 250°C, 280°C, 300°C, 320°C or 350°C; the reaction time is 3 to 8 hours, for example, 3h, 5h or 8h.

[0078] According to an embodiment of the present invention, the reaction is carried out under an inert atmosphere. The inert atmosphere is, for example, nitrogen or argon.

[0079] According to an embodiment of the present invention, the covalent organic framework material is prepared by reacting an acylhydrazine with an allyl group, an aldehyde with a phenyl and / or triazine group, and a sulfonate with a mercapto group.

[0080] According to an embodiment of the present invention, the covalent organic framework material is prepared by the following method:

[0081] 1) Mix the compound shown in Formula 4 and the compound shown in Formula 5, react them, and prepare intermediate A;

[0082] 2) Intermediate A and the compound shown in Formula 6 are mixed and reacted under light irradiation to prepare intermediate B; intermediate B is mixed with Li₂CO₃ and reacted to prepare the covalent organic framework material; or,

[0083] 2') Intermediate A and the compound shown in Formula 6' are mixed and reacted under light irradiation to prepare the covalent organic framework material.

[0084] According to an embodiment of the present invention, in step 1), the molar ratio of the compound shown in Formula 4 to the compound shown in Formula 5 is 2:3.

[0085] According to an embodiment of the present invention, in step 1), the temperature of the reaction is 110 to 150°C, for example, 110°C, 120°C, 140°C or 150°C; the reaction time is 0.5 to 2 hours, for example, 0.5h, 1h or 2h.

[0086] According to an embodiment of the present invention, in step 2), the molar ratio of intermediate A and the compound shown in Formula 6 is 1:8 to 1:12.

[0087] According to an embodiment of the present invention, in step 2'), the molar ratio of intermediate A and the compound shown in formula 6' is 1:8 to 1:12.

[0088] According to an embodiment of the present invention, in step 2), the temperature at which the reaction is carried out under the light conditions is room temperature; the reaction time under the light conditions is 5 to 10 hours; and the light conditions are sunlight with a power of 300W.

[0089] According to an embodiment of the present invention, in step 2'), the temperature at which the reaction is carried out under the light conditions is room temperature; the reaction time under the light conditions is 5 to 10 hours, and the light conditions are sunlight with a power of 300W.

[0090] For example, the covalent organic framework material is prepared by the following method:

[0091] 1: To a mixture of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and 2,5-bis(allyloxy)-terephthalohydrazide, n-butanol, o-DCB and acetic acid were added; the mixture was heated at 120°C for 30 minutes with vigorous stirring; the mixture was then cooled to room temperature, filtered, and thoroughly washed with THF and acetone; the product was dried under vacuum overnight to give a yellow solid compound A;

[0092] 2: A methanol solution of sodium 2-mercaptoethanesulfonate was added to compound A and 1,1'-azobis(cyclohexanecarboxynitrile). The mixture was rapidly frozen at 77 K and subjected to three freeze-thaw cycles to remove air. The mixture was then irradiated with a solar simulator (300 W) for 5 hours with stirring; the suspension was filtered, thoroughly washed with water, ethanol, and tetrahydrofuran, and dried to give compound B as a bright yellow solid.

[0093] 3: Mix compound B with an aqueous solution of Li2CO3; stir at room temperature for 5 h to obtain a red solid suspension, filter, and vacuum dry to obtain red solid compound C.

[0094] <Positive Electrode Tablets>

[0095] The present invention also provides a positive electrode sheet, wherein the positive electrode sheet comprises the above-described positive electrode material.

[0096] According to an embodiment of the present invention, the positive electrode includes a current collector and an active material layer located on at least one side of the current collector, the active material layer including the aforementioned positive electrode material.

[0097] According to an embodiment of the present invention, the mass of the positive electrode material accounts for 70-98 wt% of the total mass of the active material layer, preferably 82-93 wt%, such as 90 wt%.

[0098] According to an embodiment of the present invention, the active material layer further includes a solid electrolyte.

[0099] According to an embodiment of the present invention, the mass of the solid electrolyte accounts for 1 to 10 wt% of the total mass of the active material layer, preferably 2 to 8 wt%, such as 2 wt%.

[0100] According to an embodiment of the present invention, the solid electrolyte is selected from LLZO, LLZTO, LiPS4, and Li7P3S. 11 Li6PS5Cl, Li 3.25 Ge 0.25 P 0.75 S4, Li 3.25 Ge 0.25 P 0.75S4, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 At least one of the following.

[0101] According to an embodiment of the present invention, the active material layer further includes a conductive agent and a binder.

[0102] According to an embodiment of the present invention, the mass percentage of each component in the active material layer is as follows:

[0103] 70–98 wt% positive electrode material, 1–10 wt% solid electrolyte, 0.5–10 wt% conductive agent, and 0.5–10 wt% binder.

[0104] According to an embodiment of the present invention, the mass percentage of each component in the active material layer is as follows:

[0105] 82–93 wt% positive electrode material, 2–8 wt% solid electrolyte, 1–5 wt% conductive agent, and 1–5 wt% binder.

[0106] Preferably, the mass percentage of each component in the active material layer is:

[0107] 90wt% positive electrode material, 6wt% solid electrolyte, 2wt% conductive agent, 2wt% binder;

[0108] Preferably, the mass percentage of each component in the active material layer is:

[0109] 90wt% positive electrode material, 2wt% solid electrolyte, 4wt% conductive agent, and 4wt% binder.

[0110] According to an embodiment of the present invention, the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, and metal powder.

[0111] According to an embodiment of the present invention, the adhesive is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0112] <Preparation Method of Positive Electrode>

[0113] The present invention also provides a method for preparing the above-mentioned positive electrode sheet, the method comprising the following steps:

[0114] The positive electrode material, solid electrolyte, binder and conductive agent are mixed evenly in a solvent and coated onto the surface of the current collector. After drying to remove the solvent, the mixture is repeatedly rolled under a pressure of over 100 MPa to form a positive electrode sheet.

[0115] <Battery>

[0116] The present invention also provides a battery comprising the above-described positive electrode material; or comprising the above-described positive electrode sheet.

[0117] According to an embodiment of the present invention, the battery is a solid-state battery. Preferably, it is a solid-state lithium-sulfur battery.

[0118] According to an embodiment of the present invention, the battery further includes a negative electrode.

[0119] According to an embodiment of the present invention, the negative electrode is metallic lithium and its alloys, and the negative electrode is prepared, for example, by rolling.

[0120] According to an embodiment of the present invention, the battery further includes a solid electrolyte layer located between the positive electrode and the negative electrode.

[0121] According to an embodiment of the present invention, the solid electrolyte layer includes a solid electrolyte selected from LLZO, LLZTO, LiPS4, and Li7P3S. 11 Li6PS5Cl, Li 3.25 Ge 0.25 P 0.75 S4, Li 3.25 Ge 0.25 P 0.75 S4, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 At least one of them.

[0122] According to an embodiment of the present invention, the solid electrolyte layer and the positive electrode sheet in the battery can be bonded together by rolling.

[0123] According to an embodiment of the present invention, the solid electrolyte layer and the negative electrode sheet in the battery can be bonded together by rolling.

[0124] <Battery Manufacturing Methods>

[0125] The present invention also provides a method for preparing the above-mentioned battery, the method comprising the following steps: preparing a battery by stacking a positive electrode sheet, a solid electrolyte layer and a negative electrode sheet, and then welding and encapsulating the battery to obtain the battery.

[0126] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0127] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0128] Example 1

[0129] To a mixture of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine (CAS: 443922-06-3) (589.9 mg, 1.75 mmol) and 2,5-bis(allyloxy)-terephthalohydrazide (CAS: 2227151-69-9) (804.1 mg, 2.15 mmol), n-butanol (17.5 mL), o-DCB (17.5 mL), and 6 mol / L acetic acid (0.7 mL) were added. The mixture was heated at 120 °C for 30 minutes with vigorous stirring. The mixture was then cooled to room temperature, filtered, and thoroughly washed with THF and acetone. The product was dried under vacuum overnight to give compound A as a yellow solid.

[0130] A methanol (30 mL) solution of sodium 2-mercaptoethanesulfonate (492.5 mg, 3 mmol) was added to compound A (180 mg) and 1,1'-azobis(cyclohexanecarboxynitrile) (36 mg, 0.15 mmol). The mixture was rapidly frozen at 77 K and de-aired using three freeze-thaw cycles. The mixture was then irradiated with a solar simulator (300 W) for 5 hours with stirring. The suspension was filtered, thoroughly washed with water, ethanol, and tetrahydrofuran, and dried to give compound B (252 mg) as a bright yellow solid.

[0131] Compound B (180 mg) was mixed with a 0.1 M Li₂CO₃ (aq, 20 mL) aqueous solution. The mixture was stirred at room temperature for 5 h to obtain a red solid suspension, which was then filtered and dried under vacuum to obtain a red solid compound C.

[0132] Take 0.2g of lithium metal, 0.43ml of carbon disulfide, and 0.05g of compound C, seal them in a stainless steel tube, and heat at 300℃ for 5h to complete the reaction, forming the positive electrode material D.

[0133] Preparation of positive electrode:

[0134] 0.9g of positive electrode material D, 0.02g of commercial solid electrolyte (LLZTO (particle size 20nm)) powder, 0.04g of conductive agent Super-P, 0.04g of binder PTFE, and 1g of NMP were added and wet-milled in a ball mill at 230r / min for 2h until a homogeneous and fluid positive electrode slurry was formed. The positive electrode slurry was uniformly coated onto an aluminum foil with a thickness of 12μm. The coated aluminum foil was baked in an oven with five different temperature gradients, and then dried in an oven at 120℃ for 8h. After drying, the foil was repeatedly rolled three times at room temperature under a pressure of 100MPa in a roller press to obtain the positive electrode sheet.

[0135] Preparation of negative electrode:

[0136] Commercially available lithium foil with a thickness of 20 μm was used as the negative electrode.

[0137] Fabrication of solid-state lithium-sulfur batteries:

[0138] A 10mm diameter polycarbonate hollow tube was used, and lithium foil was cut into 10mm diameter discs and placed at the bottom. 30mg of commercially available LLZTO powder was added to the hollow tube, and the lithium foil discs and solid electrolyte were cold-pressed together under a pressure of 300MPa, resulting in a solid electrolyte layer with a thickness of 250μm. The prepared positive electrode sheet was then cut into 10mm diameter discs and rolled under a pressure of 360MPa to form an all-solid-state lithium-sulfur battery. The resulting battery was assembled into a CR2016 coin cell for testing.

[0139] Example 2

[0140] The other operations are the same as in Example 1, the only difference being the preparation of the positive electrode material:

[0141] To a mixture of 1,3,5-tris(4-aldehydephenyl)-benzene (CAS: 118688-53-2) (585 mg, 1.75 mmol) and 2,5-bis(allyloxy)-terephthalohydrazide (CAS: 2227151-69-9) (804.1 mg, 2.15 mmol), n-butanol (17.5 mL), o-DCB (17.5 mL), and 6 mol / L acetic acid (0.7 mL) were added. The mixture was heated at 120 °C for 30 minutes with vigorous stirring. The mixture was then cooled to room temperature, filtered, and thoroughly washed with THF and acetone. The product was dried under vacuum overnight to give a yellow solid, compound E.

[0142] A methanol (30 mL) solution of sodium 2-mercaptoethanesulfonate (492.5 mg, 3 mmol) was added to compound E (180 mg) and 1,1'-azobis(cyclohexanecarboxynitrile) (36 mg, 0.15 mmol). The mixture was rapidly frozen at 77 K and de-aired using three freeze-thaw cycles. The mixture was then irradiated with a solar simulator (300 W) for 5 hours with stirring. The suspension was filtered, thoroughly washed with water, ethanol, and tetrahydrofuran, and dried to give compound F (252 mg) as a bright yellow solid.

[0143] Compound F (180 mg) was mixed with a 0.1 M Li₂CO₃ aqueous solution (1 aq, 20 mL). The mixture was stirred at room temperature for 5 h to obtain a red solid suspension, which was then filtered and dried under vacuum to obtain a red solid compound G.

[0144] Take 0.2g of lithium metal, 0.43ml of carbon disulfide, and 0.05g of compound G, seal them in a stainless steel tube, and heat at 300℃ for 5h to complete the reaction, forming the positive electrode material H.

[0145] Comparative Example 1

[0146] Take 0.2g of lithium metal and 0.43ml of carbon disulfide, seal them in a stainless steel tube, and heat at 300℃ for 5h to complete the reaction, forming the positive electrode material L.

[0147] Comparative Example 2

[0148] The other operations are the same as in Example 1, the only difference being the preparation of the positive electrode material:

[0149] To a mixture of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine (CAS: 443922-06-3) (589.9 mg, 1.75 mmol) and 2,5-bis(allyloxy)-terephthalohydrazide (CAS: 2227151-69-9) (804.1 mg, 2.15 mmol), n-butanol (17.5 mL), o-DCB (17.5 mL), and 6 mol / L acetic acid (0.7 mL) were added. The mixture was heated at 120 °C for 30 minutes with vigorous stirring. The mixture was then cooled to room temperature, filtered, and thoroughly washed with THF and acetone. The product was dried under vacuum overnight to give a yellow solid compound M.

[0150] Take 0.2g of lithium metal, 0.43ml of carbon disulfide, and 0.05g of compound M, seal them in a stainless steel tube, and heat at 300℃ for 5h to complete the reaction, forming the positive electrode material N.

[0151] The solid-state lithium-sulfur batteries prepared in the above embodiments and comparative examples were subjected to the following performance tests:

[0152] (1) Cyclic performance test: The test results are shown in Table 1. Specifically, after the solid-state lithium-sulfur battery was assembled, the LAND Blue Battery Test System was used at 0.2 mA / cm². 2 0.5mA / cm 2 1.0 mA / cm 2 1.5mA / cm 2 and 2.0 mA / cm 2 Cyclic performance tests were conducted at a current density of 25°C and a charge / discharge voltage of 1.5V-3.0V. The discharge capacity of the second cycle was the reversible specific capacity.

[0153] Table 1 Performance test results of the examples and comparative examples

[0154]

[0155] (2) Low-temperature performance test: The test results are shown in Table 2. Specifically, after the solid-state lithium-sulfur battery was assembled, the LAND Blue Battery Test System was used at 0.5 mA / cm². 2 The current density was measured at -30℃, and the charging and discharging voltage was 1.5V-3.0V. The low-temperature cycling performance was tested at -30℃. The discharge capacity of the second cycle was the reversible discharge specific capacity.

[0156] Table 2 Performance test results of the examples and comparative examples

[0157]

[0158] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cathode material for all-solid-state lithium-sulfur batteries, characterized in that, The positive electrode material has a core-shell structure, and the core-shell structure comprises a core and a shell layer; wherein the core comprises carbon and an active material; the active material is Li2S; the shell layer comprises a covalent organic framework material, and the covalent organic framework material is prepared by reaction of a hydrazide with an allyloxy group, an aldehyde with a triazine group, and a sulfonate with a mercapto group; The covalent organic framework material has a structure shown in formula 3 as follows: Formula 3 In formula 3, n is an integer greater than or equal to 1; and * is a connecting end.

2. A cathode material for all-solid-state lithium-sulfur batteries, characterized in that, The positive electrode material has a core-shell structure, and the core-shell structure comprises a core and a shell layer; wherein the core comprises carbon and an active material; the active material is Li2S; the shell layer comprises a covalent organic framework material; The covalent organic framework material is prepared by reaction of a compound shown in formula 4, a compound shown in formula 5, a compound shown in formula 6, and lithium carbonate; or, the covalent organic framework material is prepared by reaction of a compound shown in formula 4, a compound shown in formula 5, and a compound shown in formula 6'; Formula 4 Formula 5 Formula 6 Formula 6' In formula 4, X is N; R is the same or different, each independently H, F, Cl, Br, NH2, NO2, OH, C 1~6 alkyl; In formula 6 and formula 6', n is an integer greater than or equal to 1.

3. The positive electrode material according to claim 2, characterized in that, In formula 4, X is N; R is the same or different, each independently H, F, Cl, Br, NH2, NO2, OH, C 1~3 alkyl; In formula 6 and formula 6', n is an integer between 1 and 6.

4. The positive electrode material of claim 2, wherein, The compound shown in formula 4 is selected from 2,4,6-tris(4-formylphenyl)-1,3,5-triazine; And / or, the compound shown in formula 6 is selected from at least one of 2-mercaptoethanesulfonic acid sodium, 3-mercapto-1-propanesulfonic acid sodium; And / or, the compound shown in formula 6' is selected from at least one of 2-mercaptoethanesulfonic acid lithium, 3-mercapto-1-propanesulfonic acid lithium.

5. The cathode material according to any one of claims 1-4, characterized in that, The mass of the carbon accounts for 25% to 35% of the total mass of the core; And / or, the mass of the active material accounts for 65% to 75% of the total mass of the core.

6. The cathode material of any one of claims 1-4, wherein, The mass ratio of the core to the shell layer in the positive electrode material is 1 to 5:1; And / or, the thickness of the shell layer in the positive electrode material is 2 nm to 20 nm; and / or the median particle size D50 of the positive electrode material is 20 nm to 200 nm. 50 20 nm to 200 nm. And / or, the thermal decomposition temperature of the positive electrode material is 600 to 800 DEG C; and / or the ionic conductivity of the positive electrode material is 10 -3 ~10 -4 S / cm; and / or the electronic conductivity of the positive electrode material is 10 -1 ~10 -2 S / cm.

7. A positive electrode sheet for an all-solid-state lithium-sulfur battery, characterized by comprising: The positive electrode sheet comprises the positive electrode material according to any one of claims 1 to 6.

8. An all-solid-state lithium-sulfur battery, characterized by comprising: The positive electrode material according to any one of claims 1 to 6; or, the positive electrode sheet according to claim 7.

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