Electrolyte suitable for high-capacity organic sulfur-based battery, organic sulfur-based battery and preparation method of organic sulfur-based battery

Abstract

The invention provides an electrolyte suitable for a high-capacity organic sulfur-based battery, the organic sulfur-based battery and a preparation method of the organic sulfur-based battery, and belongs to the technical field of secondary batteries. The electrolyte comprises a copper salt and an organic solvent, the concentration of the copper salt in the electrolyte is 1-4 mol / L. According to the electrolyte prepared by the invention, the copper salt is dissolved in the organic solvent, so that cations Cu < 2 + > in the electrolyte and elemental sulfur in the positive electrode active material are uniquely reacted to generate Cu2S and promote a four-electron transfer reaction, and the reaction mechanism breaks through the limitation that a sulfur positive electrode in a traditional organic sulfur-based battery only can be subjected to a two-electron transfer reaction; the capacity and the electrochemical performance of the battery are obviously improved; according to the prepared organic sulfur-based battery, by introducing a multi-electron transfer reaction mechanism, the specific capacity of the sulfur positive electrode is remarkably improved in the charging and discharging process.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to an electrolyte suitable for high-capacity organic sulfur-based batteries, an organic sulfur-based battery and a preparation method thereof. Background Art

[0002] With the rapid development of portable electronic devices, electric vehicles, and large-scale energy storage systems, the demand for high-energy-density, long-life, and low-cost energy storage devices has become increasingly urgent. Among numerous energy storage technologies, sulfur-based batteries have attracted significant attention due to their advantages, including the high theoretical specific capacity (1675 mAh / g) of the sulfur cathode, its abundant resources, and its environmental friendliness. In organic electrolyte systems, sulfur-based batteries typically pair a sulfur cathode with a metal anode, such as lithium, sodium, or potassium, to store energy through the redox reaction between sulfur and metal ions. However, despite the high theoretical capacity of sulfur cathodes, they face numerous challenges in practical applications, resulting in actual capacities far below their theoretical values, making them difficult to meet the demands of high-energy-density batteries. First, sulfur's inherent poor conductivity leads to poor rate performance, hindering the realization of high energy output. Furthermore, sulfur undergoes significant volume changes during charge and discharge, which can disrupt the electrode structure and further reduce the battery's capacity and cycling stability. Second, the intermediate polysulfides readily dissolve in the electrolyte, resulting in a shuttle effect that leads to irreversible loss of active materials and capacity decay, severely shortening the battery's cycle life and reducing its actual capacity. Finally, the sulfur cathode in traditional organic sulfur-based batteries usually undergoes a two-electron conversion reaction. This reaction mechanism limits the specific capacity and energy density of the sulfur cathode, making it difficult to meet the needs of high energy density batteries.

[0003] Currently, common methods for improving the capacity of organic sulfur-based batteries include optimizing the structural design of sulfur (e.g., sulfur-carbon composites) to alleviate the problem of poor conductivity, and introducing additives into the electrolyte to inhibit the dissolution of polysulfides. However, these methods mainly focus on improving sulfur conductivity and inhibiting the shuttle effect, and it is difficult to fundamentally solve the problem of low capacity of organic sulfur-based batteries.

[0004] Therefore, it is of great significance to provide an organic sulfur-based battery that can break through the limitations of traditional elemental sulfur two-electron transfer reaction and achieve high capacity. Summary of the Invention

[0005] The purpose of the present invention is to provide an electrolyte, an organic sulfur-based battery and a preparation method thereof suitable for high-capacity organic sulfur-based batteries, so as to solve the technical problems in the prior art of organic sulfur-based batteries such as dissolution of active substances in the positive electrode material and severe interfacial side reactions during the charge and discharge process, resulting in low capacity.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides an electrolyte suitable for a high-capacity organic sulfur-based battery, wherein the electrolyte comprises a copper salt and an organic solvent;

[0008] The concentration of the copper salt in the electrolyte is 1-4 mol / L.

[0009] Furthermore, the copper salt includes one or more of CuCl2, Cu(NO3)2, Cu(ClO4)2 and Cu(CF3SO3)2.

[0010] Furthermore, the organic solvent includes one or more of ethylene glycol dimethyl ether, 1,3-dioxolane, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.

[0011] The present invention provides a method for preparing an electrolyte suitable for a high-capacity organic sulfur-based battery. The specific steps are: dissolving a copper salt in an organic solvent under the protection of an argon atmosphere to obtain the electrolyte.

[0012] The present invention also provides an organic sulfur-based battery, comprising a positive electrode, a negative electrode, an electrolyte and a separator;

[0013] The active material of the positive electrode is elemental sulfur;

[0014] The negative electrode includes copper foil or lithium sheet;

[0015] The diaphragm includes one or more of filter paper, glass fiber diaphragm and anion exchange membrane.

[0016] Furthermore, the preparation method of the positive electrode is: mixing the sulfur-carbon composite material, the conductive agent, the binder and the solvent and grinding them to obtain an intermediate slurry, and then coating the intermediate slurry on a conductive base material;

[0017] The mass ratio of the sulfur-carbon composite material, the conductive agent, the binder and the solvent is 5-8:0.1-2:0.1-2:50-120.

[0018] Furthermore, the conductive agent includes one or more of conductive carbon black, acetylene black, Ketjen black and graphene;

[0019] The binder includes polyvinylidene fluoride and / or polytetrafluoroethylene;

[0020] The solvent includes N-methylpyrrolidone and / or alcohol;

[0021] The conductive base material includes one or more of stainless steel mesh, carbon cloth and titanium foil.

[0022] Furthermore, the sulfur-carbon composite material is prepared by mixing sulfur powder and carbon nanotubes under a protective atmosphere, and then grinding and heat treating the mixture in sequence to obtain the sulfur-carbon composite material;

[0023] The protective atmosphere is argon;

[0024] The mass ratio of the sulfur powder to the carbon nanotubes is 70-80:20-30.

[0025] Furthermore, the grinding includes first performing dry grinding and then performing wet grinding;

[0026] The dry grinding time is 100 to 150 seconds;

[0027] The solvent for the wet grinding is ethanol, and the wet grinding time is 15 to 25 minutes.

[0028] Furthermore, the heating rate of the heat treatment is 3-7°C / min, the temperature of the heat treatment is 150-160°C, and the time of the heat treatment is 10-14h.

[0029] Beneficial effects of the present invention:

[0030] 1) The electrolyte prepared by the present invention is prepared by dissolving copper salt in an organic solvent so that the cation Cu 2+ It undergoes a unique reaction with elemental sulfur in the cathode active material to generate Cu2S and promote a four-electron transfer reaction. This reaction mechanism breaks the limitation of the sulfur cathode in traditional organic sulfur-based batteries that can only undergo a two-electron transfer reaction, significantly improving the battery's capacity and electrochemical performance.

[0031] 2) The organic sulfur-based battery prepared by the present invention introduces Cu 2+ The carrier-mediated reaction pathway achieves higher specific capacity through electrolyte component design, which not only solves the problem of rapid capacity decay of traditional sulfur-based batteries, but also effectively inhibits the dissolution and shuttle effect of polysulfides, thereby extending the cycle life of the battery;

[0032] 3) The organic sulfur-based battery provided by the present invention provides a new idea for the design of high-capacity sulfur-based batteries in organic systems and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a charge and discharge test diagram of the organic Cu-S battery prepared in Example 1;

[0034] Figure 2 This is a rate performance diagram of the organic Cu-S battery prepared in Example 1;

[0035] Figure 3 This is a cycle performance diagram of the organic Cu-S battery prepared in Example 1;

[0036] Figure 4is an X-ray diffraction pattern of the sulfur cathode in the organic Cu-S battery prepared in Example 1 in a fully discharged state;

[0037] Figure 5 Schematic diagram of the structure of the organic Li-S battery prepared in Example 2;

[0038] Figure 6 This is a charge and discharge test diagram of the organic Li-S battery prepared in Example 2;

[0039] Figure 7 This is a diagram of the cycle performance of the organic Li-S battery prepared in Example 2. DETAILED DESCRIPTION

[0040] The present invention provides an electrolyte suitable for a high-capacity organic sulfur-based battery. The electrolyte comprises a copper salt and an organic solvent.

[0041] In the present invention, the concentration of the copper salt in the electrolyte is 1 to 4 mol / L, preferably 1.5 to 3.5 mol / L, and more preferably 2 to 3 mol / L.

[0042] In the present invention, the copper salt includes one or more of CuCl2, Cu(NO3)2, Cu(ClO4)2 and Cu(CF3SO3)2, preferably one or more of CuCl2, Cu(ClO4)2 and Cu(CF3SO3)2, and further preferably Cu(ClO4)2 and / or Cu(CF3SO3)2.

[0043] In the present invention, the organic solvent includes one or more of ethylene glycol dimethyl ether, 1,3-dioxolane, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate, preferably one or more of ethylene glycol dimethyl ether, 1,3-dioxolane, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, further preferably ethylene glycol dimethyl ether and / or 1,3-dioxolane.

[0044] The present invention provides a method for preparing an electrolyte suitable for a high-capacity organic sulfur-based battery. The specific steps are: dissolving a copper salt in an organic solvent under the protection of an argon atmosphere to obtain the electrolyte.

[0045] The present invention also provides an organic sulfur-based battery, comprising a positive electrode, a negative electrode, an electrolyte and a separator;

[0046] The active material of the positive electrode is preferably elemental sulfur;

[0047] The negative electrode comprises copper foil or lithium sheet, preferably lithium sheet;

[0048] The diaphragm includes one or more of filter paper, glass fiber diaphragm and anion exchange membrane, preferably glass fiber diaphragm and / or anion exchange membrane, more preferably anion exchange membrane.

[0049] In the present invention, the positive electrode and the negative electrode both exist in the form of pole pieces.

[0050] In the present invention, the positive electrode is prepared by mixing a sulfur-carbon composite material, a conductive agent, a binder and a solvent, grinding the mixture and obtaining an intermediate slurry, and then coating the intermediate slurry on a conductive base material.

[0051] In the present invention, the mass ratio of the sulfur-carbon composite material, the conductive agent, the binder and the solvent is 5-8:0.1-2:0.1-2:50-120, preferably 6-8:0.5-1.5:0.5-1.5:60-100, and more preferably 7-8:1:1:70-80.

[0052] In the present invention, the conductive agent includes one or more of conductive carbon black, acetylene black, Ketjen black and graphene, preferably one or more of conductive carbon black, acetylene black and graphene, more preferably conductive carbon black and / or graphene;

[0053] The binder comprises polyvinylidene fluoride and / or polytetrafluoroethylene, preferably polyvinylidene fluoride;

[0054] The solvent includes N-methylpyrrolidone and / or alcohol, preferably N-methylpyrrolidone;

[0055] The conductive base material includes one or more of stainless steel mesh, carbon cloth and titanium foil, preferably stainless steel mesh and / or carbon cloth, more preferably stainless steel mesh.

[0056] In the present invention, after the intermediate slurry is coated on the conductive base material, a drying step is also included; the drying temperature is 50 to 70°C, preferably 55 to 65°C, and more preferably 60°C; the drying time is 11 to 13 hours, preferably 11.5 to 12.5 hours, and more preferably 12 hours.

[0057] In the present invention, the sulfur-carbon composite material is prepared by mixing sulfur powder and carbon nanotubes under a protective atmosphere, and then grinding and heat treating them in sequence to obtain the sulfur-carbon composite material;

[0058] The protective atmosphere is preferably argon;

[0059] The mass ratio of the sulfur powder to the carbon nanotubes is 70-80:20-30, preferably 72-78:22-28, and more preferably 75:25.

[0060] In the present invention, the grinding includes first performing dry grinding and then performing wet grinding;

[0061] The dry grinding time is 100 to 150 seconds, preferably 110 to 140 seconds, and more preferably 120 to 130 seconds;

[0062] The solvent for the wet grinding is preferably ethanol, and the wet grinding time is 15 to 25 minutes, preferably 18 to 23 minutes, and more preferably 20 minutes.

[0063] In the present invention, the heating rate of the heat treatment is 3 to 7°C / min, preferably 4 to 6°C / min, and more preferably 5°C / min; the temperature of the heat treatment is 150 to 160°C, preferably 152 to 158°C, and more preferably 155°C; the time of the heat treatment is 10 to 14h, preferably 10.5 to 13.5h, and more preferably 11 to 13h.

[0064] In the present invention, the purpose of heat treatment is to fully melt the sulfur powder and uniformly load it on the surface of the carbon nanotubes.

[0065] In the present invention, the mechanism of action of the positive electrode material is: sulfur reacts with Cu in the organic electrolyte. 2+ Reaction, a four-electron transfer reaction can occur, so its capacity is greatly improved;

[0066] The reaction mechanism of the positive electrode is:

[0067] S+4e - +2Cu 2+ →Cu2S.

[0068] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0069] Example 1

[0070] Preparation of the electrolyte: In an argon atmosphere glove box, copper perchlorate (Cu(ClO4)2) was dissolved in an organic solvent (ethylene glycol dimethyl ether and 1,3-dioxolane in a volume ratio of 1:1) and stirred to fully dissolve the copper salt in the organic solvent. The concentration of Cu(ClO4)2 in the electrolyte was 3 mol / L.

[0071] Under an argon atmosphere, sulfur powder and carbon nanotubes in a mass ratio of 75:25 were mixed, and then dry-ground for 120 seconds. Anhydrous ethanol was then added as a solvent for wet grinding. Anhydrous ethanol was added three times, 1 mL each time, and the wet grinding time was 20 minutes. The fully ground material was transferred to a crucible, placed in a muffle furnace, and heated to 155°C at a heating rate of 5°C / min for heat treatment for 12 hours. The material was then naturally cooled to room temperature to obtain a sulfur-carbon composite material.

[0072] A sulfur-carbon composite material, carbon black, polyvinylidene fluoride, and N-methyl-2-pyrrolidone in a mass ratio of 8:1:1:80 were mixed and ground uniformly to prepare a positive electrode slurry, the positive electrode slurry was evenly coated on a 400-mesh stainless steel mesh, and dried under vacuum at 60°C for 12 hours to obtain a positive electrode sheet. The positive electrode is composed of a positive electrode sheet;

[0073] The copper foil is cut into copper metal discs with a diameter of 16 mm to obtain the negative electrode sheet. The negative electrode is composed of the negative electrode sheet;

[0074] Cut the glass fiber into discs to obtain a diaphragm;

[0075] In a glove box with an argon atmosphere, the above-mentioned positive electrode, negative electrode, separator and electrolyte containing 3 mol / L Cu(ClO4)2 were assembled into an organic Cu-S battery. Specifically, CR2032 standard button cells were used to assemble the button cells, and the amount of electrolyte added was 120 μL. The organic Cu-S battery was assembled.

[0076] The performance of the organic sulfur-based battery prepared in Example 1 was tested using the Newwell battery testing system. The test results are as follows: Figures 1 to 4 As shown. Figure 1 It can be seen that the discharge capacity of the sulfur cathode at a current density of 0.1A / g is as high as 2034mAh / g, and the charge-discharge curve polarization is 0.09V. Figure 2 It can be seen that the battery prepared in Example 1 exhibits excellent kinetics, with a discharge capacity of up to 1062 mAh / g at a current density of 2 A / g. Figure 3 It can be seen that at a current density of 0.5A / g, the average charge and discharge efficiency can reach more than 98.6%. After 100 cycles, the discharge capacity of the battery based on the positive electrode active material sulfur is still maintained at 1362mAh / g, showing good cycle stability. Figure 4 It can be seen that the conversion process of sulfur to cuprous sulfide occurred at the positive electrode.

[0077] Example 2

[0078] Preparation of electrolyte: The electrolyte in Example 2 includes a positive electrode side electrolyte and a negative electrode side electrolyte;

[0079] The positive electrode electrolyte was prepared by dissolving copper perchlorate (Cu(ClO4)2) in an organic solvent (ethylene glycol dimethyl ether and 1,3-dioxolane in a volume ratio of 1:1) in an argon atmosphere glove box, stirring to fully dissolve the copper salt in the organic solvent. The concentration of Cu(ClO4)2 in the electrolyte was 1 mol / L.

[0080] The negative electrode electrolyte was prepared by dissolving lithium perchlorate in an organic solvent (ethylene glycol dimethyl ether and 1,3-dioxolane in a volume ratio of 1:1) in an argon atmosphere glove box, stirring to fully dissolve the lithium salt in the organic solvent. The concentration of LiClO4 in the electrolyte was 1.5 mol / L.

[0081] Under an argon atmosphere, sulfur powder and carbon nanotubes in a mass ratio of 75:25 were mixed, and then dry-ground for 120 seconds. Anhydrous ethanol was then added as a solvent for wet grinding. Anhydrous ethanol was added three times, 1 mL each time, and the wet grinding time was 20 minutes. The fully ground material was transferred to a crucible, placed in a muffle furnace, and heated to 155°C at a heating rate of 5°C / min for heat treatment for 12 hours. The material was then naturally cooled to room temperature to obtain a sulfur-carbon composite material.

[0082] A sulfur-carbon composite material, carbon black, polyvinylidene fluoride, and N-methyl-2-pyrrolidone in a mass ratio of 8:1:1:80 were mixed and ground uniformly to prepare a positive electrode slurry, the positive electrode slurry was evenly coated on a 400-mesh stainless steel mesh, and dried under vacuum at 60°C for 12 hours to obtain a positive electrode sheet. The positive electrode is composed of a positive electrode sheet;

[0083] A lithium metal disc with a diameter of 16 mm is used as the negative electrode plate, and the negative electrode is composed of a negative electrode plate;

[0084] Cutting the anion exchange membrane into discs to obtain a diaphragm;

[0085] In an argon atmosphere glove box, Figure 5 As shown, first, an anion exchange membrane is placed between the two electrolyte chambers. The use of an anion exchange membrane prevents crosstalk between the different types of electrolytes in the positive and negative electrodes. Then, the sulfur positive electrode and lithium negative electrode are installed, ensuring that the positive and negative electrodes are located between the ion exchange membranes. 6mL of positive electrode electrolyte is added to the positive electrode chamber and 6mL of negative electrode electrolyte is added to the negative electrode chamber. The device is sealed to assemble the organic Li-S battery.

[0086] The performance of the organic sulfur-based battery prepared in Example 2 was tested using the Newwell battery testing system. The test results are as follows: Figures 6-7 As shown. Figure 6It can be seen that at a current density of 0.5A / g, the battery's discharge capacity is as high as 1757mAh / g. Due to the low redox potential of the lithium negative electrode, the average discharge platform voltage of the constructed organic Li-S battery is 3.2V. Figure 7 It can be seen that at a current density of 0.6 A / g, the Li-S battery prepared in Example 2 has good cycle stability.

[0087] As can be seen from the above examples, the present invention provides an electrolyte suitable for high-capacity organic sulfur-based batteries, an organic sulfur-based battery and a preparation method thereof. The electrolyte prepared by the present invention is prepared by dissolving copper salt in an organic solvent so that the cation Cu in the electrolyte is 2+ It undergoes a unique reaction with the elemental sulfur in the positive electrode active material to generate Cu2S and promote a four-electron transfer reaction. This reaction mechanism breaks the limitation of the sulfur positive electrode in traditional organic sulfur-based batteries that can only undergo a two-electron transfer reaction, significantly improving the capacity and electrochemical performance of the battery. The organic sulfur-based battery prepared by the present invention significantly improves the specific capacity of the sulfur positive electrode during the charge and discharge process by introducing a multi-electron transfer reaction mechanism.

[0088] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An electrolyte suitable for high-capacity organic sulfur-based batteries, characterized in that: The electrolyte comprises a copper salt and an organic solvent; The concentration of the copper salt in the electrolyte is 1-4 mol / L.

2. The electrolyte suitable for high-capacity organic sulfur-based batteries according to claim 1, characterized in that: The copper salt includes one or more of CuCl2, Cu(NO3)2, Cu(ClO4)2 and Cu(CF3SO3)2.

3. The electrolyte suitable for high-capacity organic sulfur-based batteries according to claim 2, characterized in that: The organic solvent includes one or more of ethylene glycol dimethyl ether, 1,3-dioxolane, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.

4. A method for preparing an electrolyte suitable for a high-capacity organic sulfur-based battery according to claims 1 to 3, characterized in that: The specific steps are: dissolving copper salt in an organic solvent under the protection of an argon atmosphere to obtain an electrolyte.

5. An organic sulfur-based battery, characterized in that: comprising a positive electrode, a negative electrode, the electrolyte according to any one of claims 1 to 3, and a separator; The active material of the positive electrode is elemental sulfur; The negative electrode includes copper foil or lithium sheet; The diaphragm includes one or more of filter paper, glass fiber diaphragm and anion exchange membrane.

6. The organic sulfur-based battery according to claim 5, characterized in that The positive electrode is prepared by mixing a sulfur-carbon composite material, a conductive agent, a binder and a solvent, grinding the mixture and obtaining an intermediate slurry, and then coating the intermediate slurry on a conductive base material. The mass ratio of the sulfur-carbon composite material, the conductive agent, the binder and the solvent is 5-8:0.1-2:0.1-2:50-120.

7. The organic sulfur-based battery according to claim 6, characterized in that: The conductive agent includes one or more of conductive carbon black, acetylene black, Ketjen black and graphene; The binder includes polyvinylidene fluoride and / or polytetrafluoroethylene; The solvent includes N-methylpyrrolidone and / or alcohol; The conductive base material includes one or more of stainless steel mesh, carbon cloth and titanium foil.

8. The organic sulfur-based battery according to claim 6 or 7, characterized in that: The preparation method of the sulfur-carbon composite material comprises: mixing sulfur powder and carbon nanotubes under a protective atmosphere, and then sequentially grinding and heat treating to obtain the sulfur-carbon composite material; The protective atmosphere is argon; The mass ratio of the sulfur powder to the carbon nanotubes is 70-80:20-30.

9. The organic sulfur-based battery according to claim 8, characterized in that The grinding includes first performing dry grinding and then performing wet grinding; The dry grinding time is 100 to 150 seconds; The solvent for the wet grinding is ethanol, and the wet grinding time is 15 to 25 minutes.

10. The organic sulfur-based battery according to claim 9, characterized in that: The heating rate of the heat treatment is 3-7° C. / min, the temperature of the heat treatment is 150-160° C., and the time of the heat treatment is 10-14 hours.

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