A molybdenum disulfide / molybdenum nitride / carbon conductive agent, a preparation method thereof and application thereof in a sulfide all-solid-state battery

Abstract

The application relates to the technical field of solid-state batteries, and provides a MoS2 / MoN / C conductive agent, a preparation method thereof and application of the MoS2 / MoN / C conductive agent in sulfide full solid-state batteries. The MoS2 / MoN / C conductive agent is prepared by the following steps: firstly, preparing formaldehyde-melamine polymer microspheres; then, adsorbing molybdenum salt and ammonia water on the formaldehyde-melamine microspheres through immersion to obtain a polymer precursor; and finally, obtaining the MoS2 / MoN / C conductive agent through a pyrolysis reaction of the polymer precursor and thiourea. Compared with traditional conductive agents, the MoS2 / MoN / C conductive agent prepared by the application does not induce chemical / electrochemical side reactions of sulfide solid-state electrolyte positive electrode materials, has excellent electronic conductivity and ion transference rate, has excellent stability, and can promote the development of sulfide electrolyte full solid-state batteries.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, and in particular to a MoS2 / MoN / C conductive agent, its preparation method, and its application in sulfide all-solid-state batteries. Background Technology

[0002] All-solid-state lithium-ion batteries are considered one of the promising solutions to replace lithium-ion batteries due to their high safety and high energy density. To further improve the cycle stability of all-solid-state batteries, constructing composite cathodes with active materials, sulfide electrolytes, and carbon additives as the main components has become a mainstream approach. However, due to the limited chemical / electrochemical stability of sulfide electrolytes, side reactions can occur at the interface, thus degrading battery performance. Notably, carbon additives, used to improve the electronic conductivity of cathode materials, can promote further decomposition of sulfide electrolytes. Studies have shown that these decomposition products, especially sulfites, can block lithium-ion or electron conduction channels in the cathode, leading to contact losses and reduced battery capacity.

[0003] Currently, most research on carbon materials focuses on their morphology, particle size, and specific surface area. However, these methods still cannot effectively suppress chemical / electrochemical side reactions at the interface to improve interfacial stability. Summary of the Invention

[0004] In view of this, the present invention provides a MoS2 / MoN / C conductive agent, its preparation method, and its application in sulfide all-solid-state batteries. The MoS2 / MoN / C conductive agent provided by the present invention does not induce chemical / electrochemical side reactions between the sulfide solid electrolyte and the cathode material, and exhibits excellent stability.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A method for preparing a MoS2 / MoN / C conductive agent includes the following steps:

[0007] Formaldehyde, melamine, emulsifier, co-emulsifier, and a first solvent are mixed and subjected to a condensation reaction to obtain formaldehyde-melamine polymer microspheres; the emulsifier includes a first emulsifier and a second emulsifier; the first emulsifier is a Span series emulsifier, and the second emulsifier is one or more of the Tween series emulsifier and the OP series emulsifier; the molar ratio of formaldehyde to melamine is greater than or equal to 4:1;

[0008] The formaldehyde-melamine polymer microspheres were mixed with ammonia, molybdenum salt solution, and a second solvent and impregnated to obtain a polymer precursor; the concentration of the molybdenum salt solution was greater than or equal to 0.01 mol / L.

[0009] The polymer precursor and thiourea are subjected to a pyrolysis reaction to obtain a MoS2 / MoN / C conductive agent; the pyrolysis reaction is carried out at a temperature greater than or equal to 600°C and for a time greater than or equal to 5 hours.

[0010] Preferably, the co-emulsifier is an alcohol; the first solvent is a water-in-oil emulsion; and the volume ratio of the continuous oil phase to water in the water-in-oil emulsion is (6~12):1.

[0011] The mass ratio of the emulsifier to the volume of the first solvent is 5~15g:100mL; the volume ratio of the co-emulsifier to the first solvent is 2~10:100.

[0012] The molar ratio of formaldehyde to melamine is (4~12):1; the ratio of melamine to the first solvent is 0.01~0.1mol:100mL.

[0013] Preferably, the polycondensation reaction is carried out at a temperature of 40-60°C for 6-12 hours.

[0014] Preferably, the molybdenum salt in the molybdenum salt solution includes (NH4)2MoO4 and C8H. 12 One or two of Mo2O8; the concentration of the molybdenum salt solution is 0.01~0.1 mol / L; the second solvent is water;

[0015] The volume ratio of the formaldehyde-melamine polymer microspheres to the second solvent is 5~20g:100mL; the volume ratio of the molybdenum salt solution to the second solvent is 30~60:100; the volume fraction of the ammonia water is 4~6%; and the volume ratio of the ammonia water to the second solvent is 5~20:100.

[0016] Preferably, the impregnation temperature is 25~35℃ and the time is 6~24h.

[0017] Preferably, the mass ratio of the polymer precursor to thiourea is 100:5~50; the temperature of the pyrolysis reaction is 600~1000℃, the time is 5~10h, and the pyrolysis reaction is carried out in a protective atmosphere.

[0018] The present invention also provides a MoS2 / MoN / C conductive agent prepared by the preparation method described above, wherein the mass fraction of MoS2 in the MoS2 / MoN / C conductive agent is 3~5%, the mass fraction of MoN is 8~10%, and the mass fraction of C is 85~89%.

[0019] The present invention also provides the application of the MoS2 / MoN / C conductive agent described above in sulfide all-solid-state batteries.

[0020] The present invention also provides a positive electrode material, comprising the MoS2 / MoN / C conductive agent, sulfide electrolyte, and active material described in the above scheme.

[0021] The present invention also provides a sulfide all-solid-state battery, comprising a positive electrode, a negative electrode and a sulfide solid electrolyte, wherein the positive electrode is the positive electrode material described in the above-described scheme.

[0022] This invention provides a method for preparing a MoS2 / MoN / C conductive agent, comprising the following steps: mixing formaldehyde, melamine, an emulsifier, a co-emulsifier, and a first solvent to undergo a polycondensation reaction to obtain formaldehyde-melamine polymer microspheres; the emulsifier includes a first emulsifier and a second emulsifier; the first emulsifier is a Span series emulsifier, and the second emulsifier is one or more of a Tween series emulsifier and an OP series emulsifier; the molar ratio of formaldehyde to melamine is greater than or equal to 4:1; impregnating the formaldehyde-melamine polymer microspheres with ammonia, a molybdenum salt solution, and a second solvent to obtain a polymer precursor; the concentration of the molybdenum salt solution is greater than or equal to 0.01 mol / L; and subjecting the polymer precursor to a pyrolysis reaction with thiourea to obtain the MoS2 / MoN / C conductive agent; the temperature of the pyrolysis reaction is greater than or equal to 600°C, and the time is greater than or equal to 5 hours. This invention first prepares formaldehyde-melamine polymer microspheres, then impregnates them with molybdenum salt and ammonia to obtain a polymer precursor. Finally, through the pyrolysis reaction of the polymer precursor and thiourea, the polymer precursor loses H and O elements to form C. The molybdenum salt reacts under sufficient nitrogen source conditions to form MoN. In addition, the molybdenum salt reacts with thiourea at the interface to form MoS2, thus obtaining a MoS2 / MoN / C conductive agent. The doping of Mo can effectively reduce the anti-occupancy defects generated during the material preparation process, thereby reducing the defect density on the material surface. Furthermore, molybdenum sulfide material, as an excellent dual-carrier conductor (with high ion mobility and electronic conductivity), not only facilitates the migration of Li ions and electrons in the cathode material, but also, to a certain extent, prevents direct contact between carbon materials and conductive agents, reducing interfacial side reactions. Compared with traditional conductive agents, the MoS2 / MoN / C conductive agent prepared in this invention does not induce chemical / electrochemical side reactions between the sulfide solid electrolyte and the cathode material, has excellent electronic conductivity and ion mobility, and excellent stability, which can promote the development of sulfide electrolyte all-solid-state batteries. Attached Figure Description

[0023] Figure 1 The equivalent circuit diagram of a sulfide all-solid-state battery;

[0024] Figure 2XPS spectra of the cathode material of a sulfide all-solid-state battery containing conductive carbon black and the MoS2 / MoN / C conductive agent from Example 1 after 100 cycles, where a represents conductive carbon black and b represents the MoS2 / MoN / C conductive agent. Detailed Implementation

[0025] This invention provides a method for preparing a MoS2 / MoN / C conductive agent, comprising the following steps:

[0026] Formaldehyde, melamine, emulsifier, co-emulsifier, and a first solvent are mixed and subjected to a condensation reaction to obtain formaldehyde-melamine polymer microspheres; the emulsifier includes a first emulsifier and a second emulsifier; the first emulsifier is a Span series emulsifier, and the second emulsifier is one or more of the Tween series emulsifier and the OP series emulsifier; the molar ratio of formaldehyde to melamine is greater than or equal to 4:1;

[0027] The formaldehyde-melamine polymer microspheres were mixed with ammonia, molybdenum salt solution, and a second solvent and impregnated to obtain a polymer precursor; the concentration of the molybdenum salt solution was greater than or equal to 0.01 mol / L.

[0028] The polymer precursor and thiourea are subjected to a pyrolysis reaction to obtain a MoS2 / MoN / C conductive agent; the pyrolysis reaction is carried out at a temperature greater than or equal to 600°C and for a time greater than or equal to 5 hours.

[0029] This invention involves mixing formaldehyde, melamine, emulsifier, co-emulsifier, and a first solvent to undergo a polycondensation reaction, thereby obtaining formaldehyde-melamine polymer microspheres. In this invention, the emulsifier includes a first emulsifier and a second emulsifier; the first emulsifier is a Span series emulsifier, and the second emulsifier is one or more of a Tween series emulsifier and an OP series emulsifier; the Span series emulsifier preferably includes one or more of Span-85, Span-80, Span-65, Span-60, Span-40, and Span-20; the Tween series emulsifier preferably includes one or more of Tween-20, Tween-40, Tween-60, and Tween-80; the OP series emulsifier preferably includes one or more of OP-4, OP-7, OP-9, OP-10, OP-13, OP-15, OP-20, OP-30, OP-40, and OP-50; this invention combines Span series emulsifiers with Tween series emulsifiers, or combines Span series emulsifiers with OP series emulsifiers, which is beneficial to improving the stability of the oil-water interface.

[0030] In this invention, the co-emulsifier is preferably an alcohol; the alcohol preferably includes one or more of n-butanol, n-hexanol, and isobutanol; the introduction of the co-emulsifier is beneficial to reducing the diameter of droplets in the water-in-oil emulsion and to the formation of micro / nano polymer microspheres.

[0031] In this invention, the first solvent is preferably a water-in-oil emulsion; the volume ratio of the continuous oil phase to water in the water-in-oil emulsion is preferably (6~12):1, specifically 6:1, 8:1, 9:1, 10:1, or 12:1; the continuous oil phase is preferably one or both of white oil and kerosene, and the water is preferably deionized water. This invention limits the volume ratio of the continuous oil phase to water within the above range, which enables the formation of a water-in-oil emulsion with good results. If the volume ratio of the continuous oil phase to water is too low, for example, in the case of a ratio of 1:1, it is difficult to form a water-in-oil emulsion.

[0032] In this invention, the mass ratio of the emulsifier to the volume ratio of the first solvent is preferably 5~15g:100mL, more preferably 8~15g:100mL; the volume ratio of the co-emulsifier to the first solvent is preferably 2~10:100, more preferably 2.5~6:100.

[0033] In this invention, the molar ratio of formaldehyde to melamine is greater than or equal to 4:1, preferably (4~12):1, more preferably (6~12):1; the ratio of melamine to the first solvent is preferably 0.01~0.1mol:100mL, more preferably 0.05~0.1mol:100mL.

[0034] In this invention, the temperature of the polycondensation reaction is preferably 40~60℃, more preferably 45~55℃, and the time of the polycondensation reaction is preferably 6~12h, more preferably 8~10h; the polycondensation reaction is preferably carried out under nitrogen protection.

[0035] In a specific embodiment of the present invention, preferably, a first solvent, an emulsifier, and a co-emulsifier are added sequentially to a three-necked round-bottom flask equipped with a stirring rod, a thermometer, and a nitrogen inlet tube. After stirring at room temperature for 20-60 minutes, formaldehyde and melamine are added sequentially, and then the temperature is raised to the temperature for polycondensation reaction. After the reaction is complete, the resulting product liquid is preferably centrifuged, and the resulting solid product is washed and vacuum dried to obtain formaldehyde-melamine polymer microspheres; the formaldehyde-melamine polymer microspheres have a micro-nano scale, specifically 2-5 μm.

[0036] After obtaining formaldehyde-melamine polymer microspheres, the present invention impregnates the formaldehyde-melamine polymer microspheres, ammonia water, molybdenum salt solution, and a second solvent to obtain a polymer precursor. In the present invention, the second solvent is preferably water, specifically deionized water; the concentration of the molybdenum salt solution is greater than or equal to 0.01 mol / L, preferably 0.01~0.1 mol / L, and more preferably 0.03~0.08 mol / L; the molybdenum salt in the molybdenum salt solution preferably includes (NH4)2MoO4 (ammonium molybdate) and C8H2O. 12 One or two of Mo2O8 (molybdenum(II) acetate dimer); the volume ratio of the molybdenum salt solution and the second solvent is preferably 30~60:100, more preferably 45~60:100; the volume ratio of the formaldehyde-melamine polymer microspheres and the second solvent is preferably 5~20g:100mL, more preferably 8~15g:100mL; the volume fraction of the ammonia water is preferably 4~6%, more preferably 5%; the volume ratio of the ammonia water and the second solvent is preferably 5~20:100.

[0037] In this invention, the impregnation temperature is preferably 25~35℃, specifically 30℃, and the impregnation time is preferably 6~24h, specifically 6h, 8h, 12h or 24h; the impregnation is preferably carried out under static conditions; during the impregnation process, molybdenum salt and ammonia water are adsorbed into formaldehyde-melamine polymer microspheres.

[0038] After impregnation, the impregnated product is preferably freeze-dried. The freeze-drying temperature is preferably -60°C, the pressure is preferably 12 Pa, and the drying time is preferably 12~24 h.

[0039] After obtaining the polymer precursor, the present invention performs a pyrolysis reaction between the polymer precursor and thiourea to obtain a MoS2 / MoN / C conductive agent. In this invention, the mass ratio of the polymer precursor to thiourea is preferably 100:5~50, more preferably 100:30~50; the temperature of the pyrolysis reaction is greater than or equal to 600℃, preferably 600~1000℃, more preferably 800~1000℃; the time of the pyrolysis reaction is greater than or equal to 5h, preferably 5~10h, more preferably 8~10h; the pyrolysis reaction is preferably carried out under a protective atmosphere, preferably Ar; the pyrolysis reaction is preferably carried out in a tube furnace. During the pyrolysis reaction, the polymer precursor loses H and O elements to form C; the molybdenum salt reacts under sufficient nitrogen source conditions to form MoN; furthermore, the molybdenum salt reacts with thiourea at the interface to form MoS2, thus obtaining the MoS2 / MoN / C conductive agent.

[0040] The present invention also provides a MoS2 / MoN / C conductive agent prepared by the preparation method described above, wherein the mass fraction of MoS2 in the MoS2 / MoN / C conductive agent is 3~5%, the mass fraction of MoN is 8~10%, and the mass fraction of C is 85~89%.

[0041] In this invention, the average particle size of the MoS2 / MoN / C conductive agent is preferably 800~6500nm, more preferably 800~1600nm.

[0042] This invention also provides the application of the MoS2 / MoN / C conductive agent described above in sulfide all-solid-state batteries. The MoS2 / MoN / C conductive agent prepared by this invention does not induce chemical / electrochemical side reactions in the cathode material of the sulfide solid electrolyte, exhibits excellent electronic conductivity and ion mobility, and demonstrates excellent stability, thus showing broad application prospects in sulfide all-solid-state batteries.

[0043] This invention also provides a positive electrode material, comprising the MoS2 / MoN / C conductive agent, sulfide electrolyte, and active material described in the above scheme; this invention does not have special requirements for the sulfide electrolyte and active material, and any material well known to those skilled in the art can be used; in a specific embodiment of this invention, the sulfide electrolyte can be LPSC, and the active material can be lithium cobalt oxide (LCO); the preferred weight ratio of the MoS2 / MoN / C conductive agent, sulfide electrolyte, and active material is 8:22:70.

[0044] This invention also provides a sulfide all-solid-state battery, comprising a positive electrode, a negative electrode, and a sulfide solid electrolyte, wherein the positive electrode is the positive electrode material described in the above-described scheme. This invention does not impose special requirements on the specific structure and assembly method of the sulfide all-solid-state battery; methods well known to those skilled in the art can be used. Figure 1 This is the equivalent circuit diagram of a sulfide all-solid-state battery.

[0045] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0046] Example 1

[0047] (1) In a three-necked round-bottom flask equipped with a stir bar, thermometer, and nitrogen inlet tube, 20 mL of deionized water, 27.5 g of Span 60, 5.5 g of Tween 20, and 10 mL of n-butanol were added sequentially to 200 mL of white oil. The mixture was stirred at room temperature for 60 min, and then 2.64 mol of formaldehyde and 0.22 mol of melamine were added sequentially. The mixture was heated to 60 °C and reacted for 10 h. After the reaction was completed, the mixture was centrifuged, washed, and vacuum dried to obtain formaldehyde-melamine polymer microspheres.

[0048] (2) 15g of formaldehyde-melamine polymer microspheres, 20mL of 5wt% ammonia water and 60mL of (NH4)2MoO4 solution with a concentration of 0.08mol / L were added to 100mL of deionized water. The mixture was allowed to stand at 35℃ for 24h, and then freeze-dried (-60℃, 12Pa) for 24h to finally obtain the polymer precursor.

[0049] (3) In a tube furnace filled with Ar atmosphere, 50g of polymer precursor and 25g of thiourea are mixed evenly, and the temperature is raised to 1000℃ for pyrolysis for 10h to finally obtain MoS2 / MoN / C conductive agent (the mass fraction of MoS2 is 3.5%, the mass fraction of MoN is 8.5%, and the mass fraction of C is 88.0%).

[0050] The resulting product was named Conductive Agent-1, with an average particle size of 842 nm.

[0051] Example 2

[0052] (1) In a three-necked round-bottom flask equipped with a stirrer, thermometer, and nitrogen inlet tube, 20 mL of deionized water, 12.3 g of Span 85, 2.1 g of OP-10, and 5 mL of n-hexanol were added sequentially to 160 mL of kerosene. The mixture was stirred at room temperature for 20 min, and then 0.54 mol of formaldehyde and 0.09 mol of melamine were added sequentially. The mixture was heated to 40 °C and reacted for 8 h. After the reaction was completed, the mixture was centrifuged, washed, and vacuum dried to obtain formaldehyde-melamine polymer microspheres.

[0053] (2) Add 16g of formaldehyde-melamine polymer microspheres, 10mL of ammonia, and 90mL of C8H4 solution with a concentration of 0.03mol / L to 200mL of deionized water in sequence. 12 The Mo2O8 solution was left to stand at 25°C for 6 hours, and then freeze-dried (-60°C, 12 Pa) for 12 hours to finally obtain the polymer precursor.

[0054] (3) In a tube furnace filled with Ar atmosphere, 50g of polymer precursor and 15g of thiourea were mixed evenly and the temperature was raised to 800℃ for 8h to pyrolyze, and finally MoS2 / MoN / C conductive agent was obtained (the mass fraction of MoS2 was 4.5%, the mass fraction of MoN was 9.2%, and the mass fraction of C was 86.3%).

[0055] The resulting product was named Conductive Agent-2, with an average particle size of 1549 nm.

[0056] Example 3

[0057] (1) In a three-necked round-bottom flask equipped with a stirrer, thermometer, and nitrogen inlet tube, 20 mL of deionized water, 8.0 g of Span 60, 2.0 g of OP-40, and 8 mL of isobutanol were added sequentially to 180 mL of kerosene. The mixture was stirred at room temperature for 40 min, and then 1.28 mol of formaldehyde and 0.16 mol of melamine were added sequentially. The mixture was heated to 50 °C and reacted for 9 h. After the reaction was completed, the mixture was centrifuged, washed, and vacuum dried to obtain formaldehyde-melamine polymer microspheres.

[0058] (2) 24g of formaldehyde-melamine polymer microspheres, 20mL of ammonia and 100mL of (NH4)2MoO4 solution with a concentration of 0.05mol / L were added to 200mL of deionized water. The mixture was allowed to stand at 30℃ for 12h, and then freeze-dried (-60℃, 12Pa) for 18h to finally obtain the polymer precursor.

[0059] (3) In a tube furnace filled with Ar atmosphere, 100g of polymer precursor and 40g of thiourea were mixed evenly and the temperature was raised to 900℃ for pyrolysis for 9h to finally obtain MoS2 / MoN / C conductive agent (the mass fraction of MoS2 is 4.8%, the mass fraction of MoN is 9.8%, and the mass fraction of C is 85.4%).

[0060] The resulting product was named Conductive Agent-3, with an average particle size of 1054 nm.

[0061] Example 4

[0062] (1) In a three-necked round-bottom flask equipped with a stirrer, thermometer, and nitrogen inlet tube, 10 mL of deionized water, 4.4 g of Span65, 2.2 g of OP-50, and 6 mL of n-butanol were added sequentially to 120 mL of white oil. The mixture was stirred at room temperature for 60 min, and then 0.052 mol of formaldehyde and 0.013 mol of melamine were added sequentially. The mixture was heated to 60 °C and reacted for 6 h. After the reaction was completed, the mixture was centrifuged, washed, and vacuum dried to obtain formaldehyde-melamine polymer microspheres.

[0063] (2) Add 5g of formaldehyde-melamine polymer microspheres, 5mL of ammonia, and 30mL of 0.01mol / L C8H2O to 100mL of deionized water in sequence. 12 The Mo2O8 solution was left to stand at 25°C for 24 hours, and then freeze-dried (-60°C, 12 Pa) for 20 hours to finally obtain the polymer precursor.

[0064] (3) In a tube furnace filled with Ar atmosphere, 50g of polymer precursor and 2.5g of thiourea were mixed evenly and the temperature was raised to 600℃ for 5h to obtain MoS2 / MoN / C conductive agent (the mass fraction of MoS2 is 3.3%, the mass fraction of MoN is 8.1%, and the mass fraction of C is 88.6%).

[0065] The resulting product was named Conductive Agent-4, with an average particle size of 6284 nm.

[0066] Example 5

[0067] (1) In a three-necked round-bottom flask equipped with a stirrer, thermometer, and nitrogen inlet tube, 20 mL of deionized water, 7.35 g of Span20, 2.45 g of OP-10, and 8 mL of isobutanol were added sequentially to 120 mL of kerosene. The mixture was stirred at room temperature for 30 min, and then 0.28 mol of formaldehyde and 0.056 mol of melamine were added sequentially. The mixture was heated to 40 °C and reacted for 12 h. After the reaction was completed, the mixture was centrifuged, washed, and vacuum dried to obtain formaldehyde-melamine polymer microspheres.

[0068] (2) 20g of formaldehyde-melamine polymer microspheres, 16mL of ammonia and 40mL of (NH4)2MoO4 solution with a concentration of 0.1mol / L were added to 100mL of deionized water. The mixture was allowed to stand at 35℃ for 6h, and then freeze-dried (-60℃, 12Pa) for 14h to finally obtain the polymer precursor.

[0069] (3) In a tube furnace filled with Ar atmosphere, 50g of polymer precursor and 14.5g of thiourea were mixed evenly and the temperature was raised to 700℃ for 7h to pyrolyze, and finally MoS2 / MoN / C conductive agent was obtained (the mass fraction of MoS2 was 4.5%, the mass fraction of MoN was 8.2%, and the mass fraction of C was 87.3%).

[0070] The resulting product was named Conductive Agent-5, with an average particle size of 2854 nm.

[0071] Example 6

[0072] (1) In a three-necked round-bottom flask equipped with a stirring rod, thermometer, and nitrogen inlet tube, 20 mL of deionized water, 6.72 g of Span20, 1.68 g of Tween-870, and 7 mL of n-hexanol were added sequentially to 120 mL of kerosene. The mixture was stirred at room temperature for 45 min, and then 0.23 mol of formaldehyde and 0.042 mol of melamine were added sequentially. The mixture was heated to 50 °C and reacted for 7 h. After the reaction was completed, the mixture was centrifuged, washed, and vacuum dried to obtain formaldehyde-melamine polymer microspheres.

[0073] (2) Add 7g of formaldehyde-melamine polymer microspheres, 11mL of ammonia, and 35mL of 0.02mol / L C8H2O to 100mL of deionized water in sequence. 12 The Mo2O8 solution was left to stand at 33°C for 16 hours, and then freeze-dried (-60°C, 12 Pa) for 22 hours to finally obtain the polymer precursor.

[0074] (3) In a tube furnace filled with Ar atmosphere, 50g of polymer precursor and 10g of thiourea are mixed evenly, and the temperature is raised to 650℃ for 6h to pyrolyze, finally obtaining MoS2 / MoN / C conductive agent (the mass fraction of MoS2 is 4.8%, the mass fraction of MoN is 8.8%, and the mass fraction of C is 86.4%).

[0075] The resulting product was named Conductive Agent-6, with an average particle size of 4219 nm.

[0076] Comparative Example 1

[0077] The TMoS2 / MoN / C conductive agent was prepared using the same method as in Example 1, except that "27.5g Span60" was not added in step (1).

[0078] The resulting product was labeled D-1, with an average particle size of 7751 nm.

[0079] Comparative Example 2

[0080] The MoS2 / MoN / C conductive agent was prepared using the same method as in Example 1, except that "5.5g Tween20" was not added in step (1).

[0081] The resulting product was labeled D-2, with an average particle size of 6982 nm.

[0082] Comparative Example 3

[0083] The MoS2 / MoN / C conductive agent was prepared using the same method as in Example 1, except that "10 mL of n-butanol" was not added in step (1).

[0084] The resulting product was labeled D-3, with an average particle size of 10.6 μm.

[0085] Comparative Example 4

[0086] The MoS2 / MoN / C conductive agent was prepared using the same method as in Example 1, except that in step (1), the "2.64 mol formaldehyde" was changed to "0.264 mol formaldehyde".

[0087] The resulting product was labeled D-4, with an average particle size of 1314 nm.

[0088] Comparative Example 5

[0089] The MoS2 / MoN / C conductive agent was prepared in the same manner as in Example 1, except that in step (2), the “0.08 mol / L (NH4)2MoO4 solution” was changed to “0.001 mol / L (NH4)2MoO4 solution”.

[0090] The resulting product was labeled D-5, with an average particle size of 882 nm.

[0091] Comparative Example 6

[0092] The MoS2 / MoN / C conductive agent was prepared using the same method as in Example 1, except that "25g thiourea" was not added in step (3).

[0093] The resulting product was labeled D-6 and had an average particle size of 924 nm.

[0094] Comparative Example 7

[0095] The MoS2 / MoN / C conductive agent was prepared using the same method as in Example 1, except that in step (3), “1000℃” was changed to “100℃”.

[0096] The resulting product was labeled D-7, with an average particle size of 8457 nm.

[0097] Comparative Example 8

[0098] The MoS2 / MoN / C conductive agent was prepared using the same method as in Example 1, except that in step (3), the "carbonization at 1000°C for 10 hours" was changed to "carbonization at 1000°C for 1 hour".

[0099] The resulting product was labeled D-8 and had an average particle size of 4258 nm.

[0100] Test Example 1

[0101] Assembly method of sulfide all-solid-state batteries:

[0102] (1) Preparation of positive electrode material: The conductive agent, sulfide electrolyte LPSC and active material LCO are placed in an agate mortar in a weight ratio of 8:22:70 and mixed evenly for 50 min to obtain a composite positive electrode. The conductive agent is the conductive agent or conductive carbon black (Super P) prepared in Examples 1-6 and Comparative Examples 1-8.

[0103] (2) Assembly of sulfide all-solid-state battery: 100 mg of sulfide electrolyte LPSC was added to a mold with a diameter of 10 mm and pressed at 50 MPa for 10 min to form a solid electrolyte layer. Then, 10 mg of composite positive electrode was evenly spread on one side of the electrolyte layer and pressed at 200 MPa for 10 min to make it in close contact with the solid electrolyte. Finally, 16 mg of Li / In negative electrode was evenly spread on the other side of the solid electrolyte and pressed at 30 MPa for 1 min to complete the assembly of the solid-state battery.

[0104] The first-cycle coulombic efficiency and first-cycle discharge capacity (0.1C) of solid-state batteries with different conductive carbon materials were tested. The test data are shown in Table 1.

[0105] Table 1. First-cycle coulombic efficiency and discharge capacity of sulfide all-solid-state batteries with different conductive agents.

[0106]

[0107] As shown in Table 1, the sulfide all-solid-state battery containing MoS2 / MoN / C conductive agent exhibits higher first-cycle coulombic efficiency and discharge capacity, which are much higher than those of conductive carbon black and the conductive agents obtained in Comparative Examples 1-8.

[0108] Test Example 2

[0109] The discharge capacity and capacity retention of sulfide all-solid-state batteries with different conductive agents were tested after 100 cycles at a current density of 0.1C. The results are shown in Table 2.

[0110] Table 2. Discharge capacity and capacity retention of sulfide all-solid-state batteries with different conductive agents after 100 cycles.

[0111]

[0112] As can be seen from the data in Table 2, the sulfide all-solid-state battery containing MoS2 / MoN / C conductive agent exhibits a higher capacity retention rate, which is much higher than that of conductive carbon black and the conductive agents obtained in Comparative Examples 1 to 8.

[0113] Test Example 3

[0114] The EIS impedance data of sulfide all-solid-state batteries with different conductive agents were tested before and after 100 cycles at a current density of 0.1C. The test results are shown in Table 3.

[0115] Table 3. Impedance changes of sulfide all-solid-state batteries with different conductive agents before and after 100 cycles.

[0116]

[0117] As shown in Table 3, the sulfide all-solid-state batteries with added conductive carbon black and the conductive agents of Comparative Examples 1-8 exhibited significant changes in interfacial impedance after cycling. This is attributed to the presence of sulfites leading to interfacial instability, which in turn inhibits electron migration and degrades battery performance. In contrast, the sulfide all-solid-state batteries with the MoS2 / MoN / C conductive agent described in this invention showed less impedance change after cycling, indicating that the conductive agent of this invention does not induce chemical / electrochemical side reactions in the sulfide solid electrolyte cathode material.

[0118] Figure 2 XPS spectra of the cathode material of a sulfide all-solid-state battery containing conductive carbon black and the MoS2 / MoN / C conductive agent from Example 1 after 100 cycles, where a represents conductive carbon black and b represents the MoS2 / MoN / C conductive agent. Figure 2 It can be seen that the composite cathode of the sulfide all-solid-state battery containing conductive carbon black produces sulfite after cycling, which inhibits interfacial ion / electron migration, while the composite cathode of the sulfide all-solid-state battery containing MoS2 / MoN / C conductive agent does not exhibit this byproduct. This indicates that the conductive agent of the present invention is beneficial for suppressing the formation of the interfacial byproduct sulfite.

[0119] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a MoS2 / MoN / C conductive agent, characterized in that, The method comprises the following steps: mixing formaldehyde, melamine, an emulsifier, a co-emulsifier and a first solvent to perform a polycondensation reaction to obtain formaldehyde-melamine polymer microspheres; the emulsifier comprises a first emulsifier and a second emulsifier; the first emulsifier is a Span series emulsifier, and the second emulsifier is one or more of a Tween series emulsifier and an OP series emulsifier; a molar ratio of the formaldehyde and the melamine is greater than or equal to 4:1; the co-emulsifier is an alcohol; and the first solvent is a water-in-oil emulsion; mixing the formaldehyde-melamine polymer microspheres, ammonia water, a molybdenum salt solution and a second solvent to perform impregnation to obtain a polymer precursor; a concentration of the molybdenum salt solution is greater than or equal to 0.01 mol / L; performing a pyrolysis reaction on the polymer precursor and thiourea to obtain a MoS2 / MoN / C conductive agent; a temperature of the pyrolysis reaction is greater than or equal to 600 DEG C, and a time of the pyrolysis reaction is greater than or equal to 5 h.

2. The production method according to claim 1, characterized by, A volume ratio of a continuous oil phase to water in the water-in-oil emulsion is (6-12):

1. A mass of the emulsifier to a volume of the first solvent is 5-15 g:100 mL; a volume ratio of the co-emulsifier to the first solvent is 2-10:

100. A molar ratio of the formaldehyde to the melamine is (4-12):1; and a ratio of the melamine to the first solvent is 0.01-0.1 mol:100 mL.

3. The preparation method according to claim 1, characterized in that, A temperature of the polycondensation reaction is 40-60 DEG C, and a reaction time is 6-12 h.

4. The method of claim 1, wherein, The molybdenum salt in the molybdenum salt solution includes one or both of (NH4)2MoO4 and C8H 12 Mo2O8; the concentration of the molybdenum salt solution is 0.01-0.1 mol / L; and the second solvent is water. A volume ratio of the formaldehyde-melamine polymer microspheres to the second solvent is 5-20 g:100 mL; a volume ratio of the molybdenum salt solution to the second solvent is 30-60:100; a volume fraction of the ammonia water is 4-6%; and a volume ratio of the ammonia water to the second solvent is 5-20:

100.

5. The preparation method according to claim 1, characterized in that, A temperature of the impregnation is 25-35 DEG C, and a time of the impregnation is 6-24 h.

6. The method of claim 1, wherein, A mass ratio of the polymer precursor to thiourea is 100:5-50; a temperature of the pyrolysis reaction is 600-1000 DEG C, and a time of the pyrolysis reaction is 5-10 h; and the pyrolysis reaction is performed in a protective atmosphere.

7. The MoS2 / MoN / C conductive agent prepared by the method of any one of claims 1-6, characterized in that, A mass fraction of MoS2 in the MoS2 / MoN / C conductive agent is 3-5%, a mass fraction of MoN is 8-10%, and a mass fraction of C is 85-89%.

8. Application of the MoS2 / MoN / C conductive agent in claim 7 in a sulfide full-solid-state battery.

9. A positive electrode material, characterized in that, The MoS2 / MoN / C conductive agent in claim 7, a sulfide electrolyte and an active material.

10. A sulfide all-solid-state battery comprising a positive electrode, a negative electrode, and a sulfide solid electrolyte, characterized by, The positive electrode is the positive electrode material in claim 9.

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