Ultra-high sulfur loading lithium-sulfur battery and preparation method thereof

Abstract

The present invention discloses an ultra-high sulfur-loading lithium-sulfur battery and its preparation method. The preparation method of the ultra-high sulfur-loading lithium-sulfur battery comprises: fully mixing sublimated sulfur with a carbon nanotube fiber material having a cross-linked structure, and then heating the mixture in a protective atmosphere to obtain a sulfur-carbon composite material; uniformly mixing the sulfur-carbon composite material with a binder, a conductive agent, etc. to obtain a slurry; coating the slurry on the surface of a current collector to obtain a sulfur positive electrode; coating the slurry on the surface of a diaphragm substrate close to the positive electrode to obtain a diaphragm; and combining the sulfur positive electrode, the diaphragm, an electrolyte, and a lithium negative electrode to obtain an ultra-high sulfur-loading lithium-sulfur battery. During operation of the lithium-sulfur battery prepared by the present invention, the positive electrode and the diaphragm work synergistically. The dense layer formed by the active material on the diaphragm can physically adsorb polysulfides and effectively prevent polysulfides from penetrating the diaphragm. At the same time, it acts as a sulfur compensator to increase the sulfur loading, thereby significantly increasing the battery capacity.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-sulfur battery preparation, and particularly relates to an ultra-high sulfur-loading lithium-sulfur battery and a preparation method thereof. Background Art

[0002] The specific capacity of lithium-sulfur batteries can reach 1675mAh g -1 , can provide 2600Wh kg -1 energy, is a potential new energy storage device. Compared with traditional positive electrode materials, sulfur is abundant, cheap and environmentally friendly. However, the development of lithium-sulfur batteries also faces many challenges. The final product of the charge and discharge process is electronic / ionic insulating, which causes serious kinetic difficulties. The volume of the electrode material changes by up to 80% during the cycle, which destroys the integrity of the electrode and causes the rapid loss of active materials. The intermediate product lithium polysulfide (LiPS) dissolves in the electrolyte and shuttles between the cathode and anode, reducing the coulombic efficiency and cycle stability.

[0003] Currently, the capacity of commercial lithium-ion batteries is 4 mAh cm -2 . In order to make lithium-sulfur batteries have higher energy density, it is necessary to increase the sulfur content of the positive electrode material and the loading amount of the active material on the basis of improving the specific capacity of the battery. However, the actual situation is that when the electrode increases to a certain thickness, the wettability, conductivity, shuttle reaction of the electrode and the weak bonding between the electrode and the collector will greatly limit the specific capacity of the battery. In addition, during the battery reaction process, a large amount of polysulfides are produced, which need to be dissolved by electrolyte. The dissolved polysulfides form solvent clusters and interact with ion beams, free solvents, and even lithium salts, thereby reducing the ionic conductivity. Under high sulfur-loaded positive electrode conditions, the increase in polysulfide concentration greatly reduces the ionic conductivity of the electrolyte, thereby resulting in lower energy density. Summary of the Invention

[0004] The main purpose of the present invention is to provide an ultra-high sulfur loading lithium-sulfur battery and a preparation method thereof, so as to overcome the deficiencies in the prior art.

[0005] To achieve the aforementioned purpose of the invention, the technical solutions adopted in the embodiments of the present invention include:

[0006] An embodiment of the present invention provides a method for preparing an ultra-high sulfur-loading lithium-sulfur battery, comprising:

[0007] The sublimated sulfur and the carbon nanotube fiber material with a cross-linked structure are fully mixed in a mass ratio of 3:1 to 9:1, and then heated to 130 to 150° C. at a heating rate of 10° C. / min to 15° C. / min in a protective atmosphere and kept warm for 5 to 20 hours, and then heated to 180 to 240° C. at a heating rate of 3° C. / min to 5° C. / min and kept warm for 0.5 to 2 hours to prepare a sulfur-carbon composite material.

[0008] uniformly mixing at least the sulfur-carbon composite material with a binder and a conductive agent which may or may not be added to prepare a slurry;

[0009] coating the slurry on the surface of the current collector to prepare a sulfur positive electrode;

[0010] coating the slurry on the surface of a separator substrate close to the positive electrode to prepare a separator having an active material coating;

[0011] The sulfur positive electrode, the separator, the electrolyte and the lithium negative electrode are combined to prepare an ultra-high-load lithium-sulfur battery.

[0012] Furthermore, the method for preparing the ultra-high sulfur-loading lithium-sulfur battery specifically includes:

[0013] uniformly mixing the sulfur-carbon composite material, the conductive agent, the binder and the diluent to prepare the slurry;

[0014] The slurry is coated on the surface of the current collector and the separator substrate respectively, and then vacuum dried at 50-60° C. for 10-24 hours to obtain the sulfur positive electrode and separator.

[0015] Furthermore, the method for preparing the ultra-high sulfur-loading lithium-sulfur battery comprises:

[0016] The slurry is coated on the surface of the current collector to a coating thickness of 50 to 600 μm, and then vacuum dried to obtain the sulfur positive electrode;

[0017] The slurry is coated on the surface of one side of the separator substrate close to the positive electrode with a coating thickness of 5 to 150 μm, and then vacuum drying is performed to obtain the separator.

[0018] Furthermore, the mass ratio of the sulfur-carbon composite material, the conductive agent and the binder is 7:2:1 to 8:1:1.

[0019] Furthermore, the sulfur loading of the sulfur positive electrode is 1.0 to 8 mg / cm 2 The sulfur loading of the diaphragm is 1-6 mg / cm 2 .

[0020] Furthermore, the electrolyte comprises a solvent, a lithium salt with a concentration of 0.1 to 3.0 mol / L, and an additive with a concentration of 0.1 to 1.0 mol / L, wherein the solvent comprises 1,3-dioxolane and ethylene glycol dimethyl ether in a volume ratio of 1:9 to 9:1, the lithium salt comprises a combination of any one or more of lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium hexafluorophosphate, and lithium trifluoromethanesulfonate, and the additive comprises lithium nitrate.

[0021] An embodiment of the present invention further provides an ultra-high sulfur loading lithium-sulfur battery, which is prepared by the aforementioned method.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) In the preparation method of the ultra-high sulfur-loading lithium-sulfur battery of the present invention, by arranging an active material coating on the diaphragm, the positive electrode and the diaphragm can work synergistically during the operation of the battery. For example, on the one hand, the dense layer formed by the active material on the diaphragm can be used to physically adsorb polysulfides and effectively prevent polysulfides from penetrating the diaphragm, thereby overcoming the defect of the existing diaphragm in effectively inhibiting the diffusion and shuttling of polysulfides. At the same time, it can also serve as a sulfur compensator to increase the sulfur loading, thereby greatly improving the battery capacity. On the other hand, by coating the active material on the current collector to make the positive electrode, the sulfur loading of the battery positive electrode can also be increased, which is beneficial to the electrolyte infiltration, enhances the transmission of electrons / ions during the battery charging and discharging process, and reduces the battery polarization.

[0024] (2) In the preparation method of the ultra-high sulfur-loading lithium-sulfur battery of the present invention, sublimated sulfur and carbon nanotube fiber material with a cross-linked structure are mixed in a mass ratio of 3:1 to 9:1, which can not only ensure the full recombination of sulfur and carbon, but also avoid excessive sulfur accumulation on the carbon surface. At the same time, by first rapidly heating and keeping the temperature for a long time, the sulfur can be quickly diffused in the carbon material and less accumulated on the surface of the carbon material. Then, the temperature is slowly increased and kept for a short time. On the one hand, the sulfur on the carbon surface can be fully sublimated, and on the other hand, the sulfur inside the carbon can be further diffused, thereby improving the utilization rate of sulfur, so that the final composite material has a high sulfur loading, and the combination of sulfur and carbon is stable and will not be easily lost.

[0025] (3) In the preparation method of the ultra-high sulfur-loading lithium-sulfur battery of the present invention, the carbon material in the sulfur-carbon composite material adopts a carbon nanotube fiber material with a cross-linked structure, and its hollow tubular structure can provide a certain buffer for the volume expansion of the sulfur positive electrode during the charge and discharge process, which is better than the carbon nanofiber material; the tube length of the carbon nanotube fiber material with a cross-linked structure is longer than that of ordinary carbon nanotubes, which can reach the centimeter level, and can provide a longer-range conductive network, thereby improving the electronic conductivity of the electrode coating. In addition, the unique cross-linked structure between the tubes increases the lateral conductive channel, which is conducive to constructing a richer electronic conductive channel and improving the electronic conductivity of the electrode coating, thereby improving the utilization and capacity of sulfur, and then the entire electrode forms a good plane mechanical strength under the action of this cross-linked carbon nanotube fiber, which is conducive to achieving thick coating of the slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a scanning electron microscope image of a carbon nanotube fiber material having a cross-linked structure in one embodiment of the present application.

[0028] Figure 2 Schematic diagram of the structure of an ultra-high sulfur-loading lithium-sulfur battery in one embodiment of the present application.

[0029] Figure 3 This is a trend diagram of the charge and discharge cycle capacity retention rate and charge and discharge efficiency of the ultra-high sulfur loading lithium-sulfur battery in Example 1 of the present application.

[0030] Figure 4 This is a digital photo of the surface of the separator and negative lithium sheet after battery cycling prepared in Example 1 of the present application.

[0031] Figure 5 This is a trend diagram of the cycle capacity retention rate and charge and discharge efficiency of the ultra-high sulfur-loading lithium-sulfur battery in Example 2 of the present application.

[0032] Figure 6 This is a trend diagram of the cycle capacity retention rate and charge and discharge efficiency of the lithium-sulfur battery in comparative example 1 of the present application.

[0033] Explanation of the accompanying reference numerals: 1. negative electrode shell, 2. positive electrode plate, 3. diaphragm, 4. lithium sheet, 5. gasket, 6. spring, 7. positive electrode shell. DETAILED DESCRIPTION

[0034] One aspect of an embodiment of the present invention provides a method for preparing an ultra-high sulfur-loading lithium-sulfur battery, comprising:

[0035] The sublimated sulfur and the carbon nanotube fiber material with a cross-linked structure are fully mixed in a mass ratio of 3:1 to 9:1, and then heated to 130 to 150° C. at a heating rate of 10° C. / min to 15° C. / min in a protective atmosphere and kept warm for 5 to 20 hours, and then heated to 180 to 240° C. at a heating rate of 3° C. / min to 5° C. / min and kept warm for 0.5 to 2 hours to prepare a sulfur-carbon composite material.

[0036] uniformly mixing at least the sulfur-carbon composite material with a binder and a conductive agent which may or may not be added to prepare a slurry;

[0037] coating the slurry on the surface of the current collector to prepare a sulfur positive electrode;

[0038] coating the slurry on the surface of a separator substrate close to the positive electrode to prepare a separator having an active material coating;

[0039] The sulfur positive electrode, the separator, the electrolyte and the lithium negative electrode are combined to prepare an ultra-high-load lithium-sulfur battery.

[0040] In some preferred embodiments, the protective atmosphere may be an inert atmosphere or a nitrogen atmosphere, but is not limited thereto.

[0041] In some preferred embodiments, the method for preparing the ultra-high sulfur-loading lithium-sulfur battery specifically includes:

[0042] uniformly mixing the sulfur-carbon composite material, the conductive agent, the binder and the diluent to prepare the slurry;

[0043] The slurry is coated on the surface of the current collector and the separator substrate respectively, and then vacuum dried at 50-60° C. for 10-24 hours to obtain the sulfur positive electrode and separator.

[0044] In some more preferred embodiments, the method for preparing the ultra-high sulfur-loading lithium-sulfur battery comprises:

[0045] The slurry is coated on the surface of the current collector to a coating thickness of 50 to 600 μm, and then vacuum dried to obtain the sulfur positive electrode;

[0046] The slurry is coated on the surface of one side of the separator substrate close to the positive electrode with a coating thickness of 5 to 150 μm, and then vacuum drying is performed to obtain the separator.

[0047] In some preferred embodiments, the adhesive may include polyvinylidene fluoride (PVDF), but is not limited thereto.

[0048] In some preferred embodiments, the diluent may include N-methylpyrrolidine, but is not limited thereto.

[0049] In some preferred embodiments, the mass ratio of the sulfur-carbon composite material, the conductive agent and the binder is 7:2:1 to 8:1:1.

[0050] In some preferred embodiments, the current collector may include carbon-coated aluminum foil, but is not limited thereto.

[0051] In some preferred embodiments, the membrane substrate may include a polypropylene membrane, but is not limited thereto.

[0052] In some preferred embodiments, the lithium negative electrode may include a lithium sheet, but is not limited thereto.

[0053] In some preferred embodiments, the sulfur loading of the sulfur cathode is 1.0 to 8 mg / cm 2 The sulfur loading of the diaphragm is 1-6 mg / cm 2 .

[0054] In some preferred embodiments, the electrolyte comprises a solvent, a lithium salt with a concentration of 0.1 to 3.0 mol / L, and an additive with a concentration of 0.1 to 1.0 mol / L, wherein the solvent comprises 1,3-dioxolane and ethylene glycol dimethyl ether in a volume ratio of 1:9 to 9:1, the lithium salt may include any one or more combinations of lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium hexafluorophosphate, lithium trifluoromethanesulfonate, etc., but is not limited thereto; the additive may include lithium nitrate, but is not limited thereto.

[0055] Another aspect of the embodiments of the present invention further provides an ultra-high sulfur loading lithium-sulfur battery, wherein the ultra-high sulfur loading lithium-sulfur battery is prepared by the aforementioned method.

[0056] The present invention provides a method for preparing an ultra-high sulfur-loading lithium-sulfur battery. During the preparation process, the principle of increasing the sulfur content of the positive electrode of the lithium-sulfur battery by using a sulfur-carbon composite material diaphragm is as follows: (1) the sulfur active material is directly coated on the polypropylene diaphragm, and the dense layer formed can physically adsorb polysulfides and effectively prevent polysulfides from penetrating the diaphragm; (2) the diaphragm coated with the active material can act as a sulfur compensator, and the positive electrode and the diaphragm work synergistically to promptly compensate for the loss of sulfur on the electrode during the charge and discharge process, thereby increasing the sulfur loading.

[0057] In order to better understand the present invention, the following examples are provided to further illustrate the present invention, but the present invention is not limited to the following examples. Unless otherwise specified, the raw materials and reagents used in the examples of the present invention were purchased from general commercial sources.

[0058] Example 1

[0059] A method for preparing an ultra-high sulfur-loading lithium-sulfur battery comprises the following steps:

[0060] (1) Weigh sublimed sulfur and carbon nanotube fibers with a cross-linked structure (such as Figure 1 The carbon nanotube fibers were cross-linked and ground in a mortar for 15 min.

[0061] (2) The ground mixture was placed in a porcelain boat, and in an argon atmosphere, the temperature was first increased to 140°C at a heating rate of 12°C / min and kept warm for 12 hours, and then the temperature was increased to 210°C at a heating rate of 4°C / min and kept warm for 1 hour to obtain a sulfur-carbon composite material, i.e., an active material.

[0062] (3) The active material, the conductive agent and the binder PVDF were mixed in a mass ratio of 8:1:1, an appropriate amount of N-methylpyrrolidone (NMP) solution was added, and the mixture was stirred evenly to obtain a slurry.

[0063] (4) Use a scraper or push rod to apply the slurry to the carbon-coated aluminum foil and the commercial polypropylene separator, respectively. The coating thickness on the carbon-coated aluminum foil is 300 μm, and the coating thickness on the commercial polypropylene separator is 80 μm. Vacuum drying is carried out at 60°C for 12 h to obtain the positive electrode and separator 3. Then, the positive electrode is cut into 12 mm diameter discs and the separator 3 is cut into 16 mm diameter discs using a tablet press. The sulfur loading of the positive electrode sheet 2 is controlled to be 1.28 mg / cm 2 , diaphragm 3 sulfur loading 1.36mg / cm 2 .

[0064] (5) The lithium sheet 4 is used as the negative electrode, and the electrolyte is a mixed solvent of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) with a volume ratio of 1:1, and the 1,3-dioxolane (DOL) contains 1M lithium bis(trifluoromethanesulfonyl)imide and 0.2M lithium nitrate, such as Figure 2 As shown, a CR2025 battery is assembled in the order of the negative electrode shell 1, the gasket 5, the lithium sheet 4, the separator 3, the positive electrode sheet 2, the gasket 5, the spring 6, and the positive electrode shell 7.

[0065] After the battery was assembled and left to rest for 3 hours, a 0.1C charge and discharge test was performed using a Blue Electric test device in a 30°C constant temperature chamber with a discharge range of 1.7-2.8V.

[0066] Depend on Figure 3 It can be seen that there is good electrical contact between the assembled battery positive electrode and the separator, which can promote the battery capacity. The initial discharge capacity reaches 1007mAh / g at a 0.1C rate, and the subsequent 1C discharge cycle for 80 weeks still maintains a high capacity.

[0067] Figure 4 This is a digital photograph of the separator and negative electrode lithium metal surface after cycling in the battery prepared in Example 1. As can be seen from the image, after multiple cycles using the separator coated with active material, the separator becomes slightly yellow, while the negative electrode lithium metal surface is smooth, demonstrating that this solution alleviates the negative electrode surface corrosion problem caused by the shuttle effect in lithium-sulfur batteries.

[0068] Example 2

[0069] A method for preparing an ultra-high sulfur-loading lithium-sulfur battery comprises the following steps:

[0070] (1) Sublimed sulfur and cross-linked carbon nanotube fibers were weighed in a mass ratio of 3:1 and ground in a mortar for 15 minutes.

[0071] (2) The ground mixture was placed in a porcelain boat, and in an argon atmosphere, the temperature was first increased to 130°C at a rate of 10°C / min and kept warm for 20 hours, and then the temperature was increased to 180°C at a rate of 3°C / min and kept warm for 2 hours to obtain a sulfur-carbon composite material, i.e., an active material.

[0072] (3) The active material, the conductive agent and the binder PVDF were mixed in a mass ratio of 8:1:1, an appropriate amount of N-methylpyrrolidone (NMP) solution was added, and the mixture was stirred evenly to obtain a slurry.

[0073] (4) Use a scraper or push rod to apply the slurry to the carbon-coated aluminum foil and the commercial polypropylene separator, respectively. The coating thickness on the carbon-coated aluminum foil is 300 μm, and the coating thickness on the commercial polypropylene separator is 80 μm. Dry under vacuum at 60 ° C for 12 h to obtain the positive electrode and the separator. Then, use a tablet press to cut the positive electrode into 12 mm diameter discs and the separator into 16 mm diameter discs. The sulfur loading of the positive electrode is controlled to 1.24 mg / cm 2 , the sulfur loading of the diaphragm is 1.36 mg / cm 2 .

[0074] (5) A lithium sheet is used as the negative electrode, and the electrolyte is a mixed solvent of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) with a volume ratio of 1:1, and 1,3-dioxolane (DOL) contains 1M lithium bis(trifluoromethanesulfonyl)imide and 0.2M lithium nitrate, such as Figure 2 As shown, a CR2025 battery is assembled in the order of the negative electrode shell 1, the gasket 5, the lithium sheet 4, the separator 3, the positive electrode sheet 2, the gasket 5, the spring 6, and the positive electrode shell 7.

[0075] After the battery is assembled and left to stand for 3 hours, a 0.1C charge and discharge test is performed in a 30°C constant temperature chamber using a blue electric test device. Figure 5 It can be seen that the initial discharge capacity is 942 mAh / g at a 0.1C rate, and the subsequent 1C discharge cycle still maintains a high capacity for more than 80 weeks.

[0076] Example 3

[0077] A method for preparing an ultra-high sulfur-loading lithium-sulfur battery comprises the following steps:

[0078] (1) Sublimed sulfur and cross-linked carbon nanotube fibers were weighed in a mass ratio of 9:1 and ground in a mortar for 15 minutes.

[0079] (2) The ground mixture was placed in a porcelain boat, and in an argon atmosphere, the temperature was first increased to 150°C at a rate of 15°C / min and kept warm for 5 hours, and then the temperature was increased to 240°C at a rate of 5°C / min and kept warm for 0.5 hours to obtain a sulfur-carbon composite material, i.e., an active material.

[0080] (3) The active material, the conductive agent and the binder PVDF were mixed in a mass ratio of 7:2:1, an appropriate amount of N-methylpyrrolidone (NMP) solution was added, and the mixture was uniformly stirred to obtain a slurry.

[0081] (4) Use a scraper or push rod to apply the slurry to the carbon-coated aluminum foil and the commercial polypropylene separator, respectively. The coating thickness on the carbon-coated aluminum foil is 50 μm, and the coating thickness on the commercial polypropylene separator is 5 μm. Dry under vacuum at 50 ° C for 24 h to obtain the positive electrode and the separator. Then use a tablet press to punch the positive electrode into a 12 mm disc and the separator into a 16 mm diameter disc. The sulfur loading of the positive electrode is controlled to 1.0 mg / cm 2 , sulfur loading on the diaphragm is 1 mg / cm 2 .

[0082] (5) A lithium sheet is used as the negative electrode, and the electrolyte is a mixed solvent of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) with a volume ratio of 1:1, and 1,3-dioxolane (DOL) contains 1M lithium bis(trifluoromethanesulfonyl)imide and 0.2M lithium nitrate, such as Figure 1 As shown, a CR2025 battery is assembled in the order of the negative electrode shell 1, the gasket 5, the lithium sheet 4, the separator 3, the positive electrode sheet 2, the gasket 5, the spring 6, and the positive electrode shell 7.

[0083] After the battery assembly was completed and allowed to stand for 3 hours, a 0.1C charge and discharge test was carried out in a constant temperature chamber at 30°C using a Blue Electric test device. The initial discharge capacity at a 0.1C rate was 936mAh / g.

[0084] Comparative Example 1

[0085] The negative electrode and electrolyte are the same as those in Example 1, and the sulfur loading of the positive electrode is 2.5 mg / cm 2 The diaphragm is a common commercial polypropylene diaphragm (a diaphragm not coated with active material), and the battery assembly and charge-discharge cycle test methods are the same as those in Example 1.

[0086] The initial 0.1C discharge capacity of the battery is only 606mAh / g, and after 50 cycles of 1C cycling, the capacity drops significantly. Figure 6 .

[0087] Comparative Example 2

[0088] The preparation method of the lithium-sulfur battery of this comparative example is basically the same as that of Example 1, the main difference being that the sublimed sulfur and the carbon nanotube fibers with a cross-linked structure in a mass ratio of 4:1 in Example 1 are replaced with sublimed sulfur and the carbon nanotube fibers with a cross-linked structure in a mass ratio of 2:1.

[0089] After the battery was assembled and left to stand for 3 hours, a 0.1C charge and discharge test was carried out in a constant temperature chamber at 30°C using a blue electric test equipment. The initial discharge capacity at a 0.1C rate was 886mAh / g.

[0090] Comparative Example 3

[0091] The preparation method of the lithium-sulfur battery of this comparative example is basically the same as that of Example 1, with the main difference being that the sublimed sulfur and the carbon nanotube fibers with a cross-linked structure in a mass ratio of 4:1 in Example 1 are replaced with sublimed sulfur and the carbon nanotube fibers with a cross-linked structure in a mass ratio of 10:1.

[0092] After the battery was assembled and left to stand for 3 hours, a 0.1C charge and discharge test was carried out in a constant temperature chamber at 30°C using a blue electric test equipment. The initial discharge capacity at a 0.1C rate was 873mAh / g.

[0093] Comparative Example 4

[0094] The preparation method of the lithium-sulfur battery in this comparative example is basically the same as that in Example 1, with the main difference being that the heating in step (2) of Example 1 is directly replaced by a heat treatment, specifically, the ground mixture is placed in a porcelain boat and kept warm at 170°C in an argon atmosphere for 13 hours to obtain a sulfur-carbon composite material, i.e., an active material.

[0095] After the battery was assembled and left to stand for 3 hours, a 0.1C charge and discharge test was carried out in a constant temperature chamber at 30°C using a blue electric test device. The initial discharge capacity at a rate of 0.1C was 601mAh / g, and the sulfur utilization rate was only 47%, indicating that some sulfur volatilized during the high-temperature maintenance process.

[0096] Comparative Example 5

[0097] The preparation method of the ultra-high sulfur loading sulfur battery of this comparative example is basically the same as that of Example 1, the main difference being that the carbon material in Example 1 is replaced by Ketjen black instead of carbon nanotube fibers with a cross-linked structure.

[0098] After the battery was assembled and left to stand for 3 hours, a 0.1C charge and discharge test was carried out in a constant temperature chamber at 30°C using a blue electric test equipment. The initial discharge capacity at a 0.1C rate was 742mAh / g.

[0099] Comparative Example 6

[0100] The preparation method of the ultra-high sulfur loading sulfur battery of this comparative example is basically the same as that of Example 1, the main difference being that the carbon material in Example 1 is replaced by carbon nanotube fibers with a cross-linked structure with carbon nanotubes.

[0101] After the battery was assembled and left to stand for 3 hours, a 0.1C charge and discharge test was carried out in a constant temperature chamber at 30°C using a blue electric test equipment. The initial discharge capacity at a 0.1C rate was 857mAh / g.

[0102] Comparative Example 7

[0103] The preparation method of the ultra-high sulfur loading sulfur battery of this comparative example is basically the same as that of Example 1, the main difference being that the carbon material in Example 1 is replaced by carbon nanofibers with carbon nanotube fibers having a cross-linked structure.

[0104] After the battery was assembled and left to stand for 3 hours, a 0.1C charge and discharge test was carried out in a constant temperature chamber at 30°C using a blue electric test equipment. The initial discharge capacity at a 0.1C rate was 819mAh / g.

[0105] Comparative Example 8

[0106] The preparation method of the lithium-sulfur battery of this comparative example is basically the same as that of Example 1, the main difference being that the carbon material in Example 1 is replaced by conductive carbon black (SuperP) instead of carbon nanotube fibers with a cross-linked structure.

[0107] After the battery was assembled and left to stand for 3 hours, a 0.1C charge and discharge test was carried out in a constant temperature chamber at 30°C using a blue electric test equipment. The initial discharge capacity at a 0.1C rate was 512mAh / g.

[0108] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0109] Although the present invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions, and / or additions may be made and that substantial equivalents may be substituted for the elements of the embodiments without departing from the spirit and scope of the present invention. Additionally, many modifications may be made to adapt specific circumstances or materials to the teachings of the present invention without departing from the scope of the present invention. Therefore, it is not intended herein to limit the present invention to the disclosed specific embodiments for carrying out the present invention, but rather to include all embodiments within the scope of the appended claims. Furthermore, unless specifically stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather uses the terms first, second, etc. to distinguish one element from another.

Claims

1. A method for preparing an ultra-high sulfur-loading lithium-sulfur battery, characterized in that: include: The sublimated sulfur and the cross-linked carbon nanotube fiber material are fully mixed in a mass ratio of 3:1 to 9:1, and then heated to 130-150°C at a heating rate of 10-15°C / min in a protective atmosphere and kept at this temperature for 5-20 hours, and then heated to 180-240°C at a heating rate of 3-5°C / min and kept at this temperature for 0.5-2 hours to prepare a sulfur-carbon composite material. uniformly mixing the sulfur-carbon composite material with a binder and a conductive agent which is optionally added to prepare a slurry; The slurry is coated on the surface of the current collector with a coating thickness of 50-600 μm to prepare a sulfur positive electrode with a sulfur loading of 1.0-8 mg / cm 2 ; The slurry is coated on the surface of the side of the separator substrate close to the positive electrode with a coating thickness of 5 to 150 μm to prepare a separator with an active material coating, and the sulfur loading of the separator is 1 to 6 mg / cm 2 ; The sulfur positive electrode, the separator, the electrolyte and the lithium negative electrode are combined to prepare an ultra-high-load lithium-sulfur battery.

2. The method for preparing an ultra-high sulfur-loading lithium-sulfur battery according to claim 1, wherein: The protective atmosphere includes an inert atmosphere or a nitrogen atmosphere.

3. The method for preparing an ultra-high sulfur-loading lithium-sulfur battery according to claim 1, wherein: Specifically include: uniformly mixing the sulfur-carbon composite material, the conductive agent, the binder and the diluent to prepare the slurry; The slurry is coated on the surface of the current collector and the separator substrate respectively, and then vacuum dried at 50-60° C. for 10-24 hours to obtain the sulfur positive electrode and separator.

4. The method for preparing an ultra-high sulfur-loading lithium-sulfur battery according to claim 3, wherein: The binder includes polyvinylidene fluoride; and / or the diluent includes N-methylpyrrolidone.

5. The method for preparing an ultra-high sulfur-loading lithium-sulfur battery according to claim 1, 3 or 4, characterized in that: The mass ratio of the sulfur-carbon composite material, the conductive agent and the binder is 7:2:1-8:1:

1.

6. The method for preparing an ultra-high sulfur-loading lithium-sulfur battery according to claim 1, 3 or 4, characterized in that: The current collector includes a carbon-coated aluminum foil, and / or the separator substrate includes a polypropylene separator, and / or the lithium negative electrode includes a lithium sheet.

7. The method for preparing an ultra-high sulfur-loading lithium-sulfur battery according to claim 1, wherein: The electrolyte includes a solvent, a lithium salt with a concentration of 0.1 to 3.0 mol / L, and an additive with a concentration of 0.1 to 1.0 mol / L, wherein the solvent includes 1,3-dioxolane and ethylene glycol dimethyl ether in a volume ratio of 1:9 to 9:1, the lithium salt includes any one or more combinations of bistrifluoromethanesulfonyl imide lithium, bisfluorosulfonyl imide lithium salt, lithium hexafluorophosphate, and lithium trifluoromethanesulfonate, and the additive includes lithium nitrate.

8. An ultra-high sulfur loading lithium-sulfur battery, characterized in that: The ultra-high sulfur loading lithium-sulfur battery is prepared by the method according to any one of claims 1 to 7.

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