High-load sulfur composite positive electrode, preparation method thereof and lithium-sulfur battery

Abstract

The invention relates to a high-load sulfur composite positive electrode, a preparation method thereof and a lithium-sulfur battery. The preparation method comprises the following steps: performing solid-phase mixing on elemental sulfur, an electronic conductive agent, an ionic conductive agent, a binder and a lithium salt to obtain a mixed material; and filling the mixed material into a mold, and performing hot pressing to obtain the high-load sulfur composite positive electrode, a current collector is laid at the bottom of the mold. According to the preparation method provided by the invention, uniform dispersion of the active substances is realized through a preparation process of combining solid-phase mixing with hot pressing, and meanwhile, interface bonding among the active substances is enhanced; meanwhile, an electron conductive agent, an ion conductive agent and lithium salt are introduced and mixed with elemental sulfur, and a stable ion / electron transmission network is constructed. The preparation method provided by the invention does not need any solvent, is simple and convenient to operate, does not need a specific protective atmosphere, can be used for synthesizing the composite positive electrode with high sulfur loading capacity in one step in an air environment, and has a relatively good application prospect in liquid lithium-sulfur batteries and solid lithium-sulfur batteries.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a lithium-sulfur battery, and more particularly to a high-load sulfur composite cathode, a preparation method thereof and a lithium-sulfur battery. BACKGROUND

[0002] With the increasing demand for renewable energy and efficient energy storage solutions worldwide, the development of the next generation of high-energy-density energy storage systems has become a research hotspot in the field of electrochemical energy storage. Lithium-sulfur batteries are considered one of the most promising secondary battery systems due to their extremely high theoretical energy density (up to 2600 Wh / kg), and the active material sulfur in the positive electrode has outstanding advantages such as abundant reserves, low cost, and environmental friendliness.

[0003] However, lithium-sulfur batteries still face a series of severe technical challenges for large-scale commercialization. For example, elemental sulfur and its discharge end product (Li2S2 / Li2S) are both electronically insulating substances, resulting in low utilization of active materials and poor rate performance. In addition, the soluble lithium polysulfide intermediates generated during charging and discharging will undergo "shuttle effect" in the electrolyte, not only causing irreversible loss of active materials, low coulombic efficiency, and rapid capacity decay, but also causing corrosion and failure of the lithium metal negative electrode. Furthermore, sulfur has a huge volume change (about 80%) during the reaction, which will cause the positive electrode structure to collapse and further exacerbate the decline in battery performance. In order to overcome the above difficulties, researchers generally adopt the strategy of constructing a "sulfur composite cathode", which is to composite sulfur with various conductive materials (such as porous carbon, graphene, carbon nanotubes, etc.) and polar catalytic materials (such as metal oxides, sulfides, nitrides, etc.) in order to construct an electronic conduction network, stabilize polysulfides, and buffer volume expansion.

[0004] CN111785930A discloses a large-area coated solid-state lithium-sulfur battery composite sulfur cathode and a preparation method thereof, which includes preparing a composite sulfur cathode containing different proportions of conductive agent / sulfur / solid-state electrolyte; adding the composite sulfur cathode, binder, solvent, and ball milling beads into a ball milling tank in a certain proportion; after high beating, the slurry is coated on an aluminum foil to obtain a large-area coated solid-state lithium-sulfur battery composite sulfur cathode. The composite sulfur cathode coated by this method has the advantages of high uniformity, high load, and high specific capacity. However, the solvent used in this method includes volatile and environmentally unfriendly solvents such as N-methyl pyrrolidone, which can easily cause environmental pollution.

[0005] CN119725360A discloses a lithium-organic sulfur battery composite electrode and its preparation method and application. The lithium-organic sulfur dry electrode is prepared by dry rolling technology under solvent-free conditions by mixing positive active material, conductive agent and binder; the positive active material is a mixture of organic sulfur and sulfur element, and organic polysulfide can be generated in situ by electrochemistry; but in the lithium-organic sulfur dry electrode, the single-sided loading capacity of the positive active material is preferably 25 mg / cm 2 The following is not applicable to the preparation of high loading capacity composite electrode.

[0006] CN117393693A discloses a high surface loading sulfur electrode and its preparation method, a molten salt aluminum battery and its preparation method and an energy storage device, although the high surface loading sulfur electrode can achieve a high sulfur loading capacity, but it needs to use a two-dimensional structure material to react with a sulfur-containing precursor to obtain a self-supporting sulfur composite material without binder, or a three-dimensional structure self-supporting carbon material is mixed with sulfur powder to obtain a self-supporting sulfur composite material without binder, and the preparation method is complex.

[0007] In summary, the existing sulfur composite cathode preparation method is mainly "wet process", and this process usually needs to use a large amount of organic solvent, which is easy to remain in the sulfur composite cathode, and at the same time, the solvent volatilization will cause environmental pollution, facing the problem of recovery and treatment of a large amount of toxic and harmful organic solvents, not only increasing the production cost, but also bringing serious environmental and safety risks, which is contrary to the concept of green manufacturing. Although the "dry method" electrode does not need solvent, the process is simple and the cost is low, but due to the large difference in density between sulfur and conductive medium, phase separation is easy to occur during dry mixing, and uniform compounding is difficult to achieve; and in the solvent-free environment, the film-forming property of dry powder and the adhesion of current collector are poor, and it is difficult to form a self-supporting electrode with mechanical strength and high ion / electron conductivity; in addition, the existing dry process has insufficient regulation ability for porous conductive network, and cannot effectively build an ideal three-dimensional structure that can accommodate a large amount of sulfur and effectively inhibit the shuttle effect and adapt to volume expansion, resulting in "dry method" preparation of high loading (>30 mg / cm 2 ) sulfur composite cathode, which still faces great challenges.

[0008] Therefore, developing a dry preparation method for high loading sulfur composite cathode that can realize uniform dispersion of active material, has strong interface combination, and can build a stable ion / electron transport network, has important practical significance for breaking through the performance bottleneck of lithium-sulfur battery and promoting its industrialization process. SUMMARY

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a high-sulfur-loaded composite cathode, its preparation method, and a lithium-sulfur battery. The preparation method of the high-sulfur-loaded composite cathode provided by the present invention requires no solvent, is simple to operate, and does not require a specific protective atmosphere. It can synthesize a composite cathode with a high sulfur loading in one step in an air environment, showing good application prospects in both liquid and solid-state lithium-sulfur batteries.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a dry preparation method for a highly loaded sulfur composite cathode, the preparation method comprising:

[0012] Solid-phase mixing of elemental sulfur, electronic conductive agent, ionic conductive agent, binder and lithium salt is used to obtain a mixed material; the mixed material is filled into a mold and hot-pressed to obtain the high-load sulfur composite cathode; a current collector is laid at the bottom of the mold.

[0013] The preparation method provided by this invention achieves uniform dispersion of active materials through a solid-phase mixing combined with hot pressing process, which also enhances the interfacial bonding between active materials. Simultaneously, the introduction of electronically conductive agents, ionically conductive agents, and lithium salts mixed with elemental sulfur facilitates the construction of a stable ion / electron transport network. Specifically, the electronically conductive agent improves the electronic conductivity of the composite cathode, while the ionically conductive agent enhances the Li-ion conductivity during charging and discharging. + The diffusion rate of lithium salt can be increased by adding lithium salt to the composite cathode. + The concentration of Li further promotes + This increases the diffusion rate and improves the utilization rate of sulfur.

[0014] This invention prepares a high-load sulfur composite cathode with uniform dispersion of active substances, strong interfacial bonding, and a stable ion / electron transport network in one step by hot pressing mixed materials.

[0015] Preferably, in the mixed material, the mass ratio of elemental sulfur, electronic conductive agent, ionic conductive agent, binder and lithium salt is (30~60):(10~40):(1~25):(1~5):(0~10).

[0016] Preferably, the electronic conductive agent includes any one or a combination of at least two of carbon nanotubes, Ketjen black, acetylene black, conductive carbon black, or graphene.

[0017] Preferably, the ionic conductive agent comprises any one or a combination of at least two of the following: lithium lanthanum zirconium oxide, lithium titanium aluminum phosphate, lithium germanium aluminum phosphate, lithium lanthanum titanate, polyethylene oxide, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, or polyvinylidene fluoride.

[0018] Preferably, the adhesive comprises polyvinylidene fluoride and / or polyethylene oxide.

[0019] Preferably, the lithium salt comprises any one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluoroylanyl)imide, or lithium perchlorate.

[0020] Preferably, the hot pressing temperature is 110℃~200℃.

[0021] Preferably, the hot pressing pressure is 10MPa~40MPa.

[0022] Preferably, the areal density of sulfur in the highly loaded sulfur composite cathode is 30 mg / cm³. 2 ~50mg / cm 2 .

[0023] Preferably, the preparation method further includes pretreatment of elemental sulfur, electronically conductive agent, ionicly conductive agent, binder and lithium salt, wherein the pretreatment includes vacuum drying and dehydration.

[0024] In a second aspect, the present invention provides a high-load sulfur composite cathode, which is prepared by the preparation method described in the first aspect.

[0025] Thirdly, the present invention provides a lithium-sulfur battery, the lithium-sulfur battery comprising a high-load sulfur composite cathode as described in the second aspect.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) In the preparation method provided by the present invention, the active material is uniformly dispersed by solid-phase mixing combined with hot pressing, and the interfacial bonding between the active materials is enhanced. At the same time, electronic conductive agent, ionic conductive agent and lithium salt are introduced and mixed with elemental sulfur to construct a stable ion / electron transport network.

[0028] (2) The method for preparing the high-sulfur-loaded composite cathode provided by the present invention does not require any solvent, is easy to operate, and does not require a specific protective atmosphere. It can synthesize a composite cathode with high sulfur loading in one step in an air environment, and has good application prospects in both liquid lithium-sulfur batteries and solid lithium-sulfur batteries. Detailed Implementation

[0029] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0030] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0031] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0032] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0033] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0034] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0035] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0036] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0037] In this invention, the terms "first aspect," "second aspect," "third aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0038] In this invention, "optional" means that something is optional, that is, it refers to either "with" or "without". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0039] In this invention, unless otherwise specified, it is assumed that the experiments are conducted at room temperature or a temperature conventionally set in the art. "Room temperature" generally refers to 4°C to 35°C, and may refer to 20°C ± 5°C. In some embodiments of this invention, room temperature refers to 20°C to 30°C.

[0040] In one specific embodiment, the present invention provides a dry preparation method for a highly loaded sulfur composite cathode, the preparation method comprising:

[0041] Solid-phase mixing of elemental sulfur, electronic conductive agent, ionic conductive agent, binder and lithium salt is used to obtain a mixed material; the mixed material is filled into a mold and hot-pressed to obtain the high-load sulfur composite cathode; a current collector is laid at the bottom of the mold.

[0042] The preparation method provided by this invention achieves uniform dispersion of active materials through a solid-phase mixing combined with hot pressing process, which also enhances the interfacial bonding between active materials. Simultaneously, the introduction of electronically conductive agents, ionically conductive agents, and lithium salts mixed with elemental sulfur facilitates the construction of a stable ion / electron transport network. Specifically, the electronically conductive agent improves the electronic conductivity of the composite cathode, while the ionically conductive agent enhances the Li-ion conductivity during charging and discharging. + The diffusion rate of lithium salt can be increased by adding lithium salt to the composite cathode. + The concentration of Li further promotes + This increases the diffusion rate and improves the utilization rate of sulfur.

[0043] This invention prepares a high-load sulfur composite cathode with uniform dispersion of active substances, strong interfacial bonding, and a stable ion / electron transport network in one step by hot pressing mixed materials.

[0044] In some embodiments, the mass ratio of elemental sulfur, electronically conductive agent, ionicly conductive agent, binder, and lithium salt in the mixed material is (30~60):(10~40):(1~25):(1~5):(0~10), for example, it can be 30:40:25:1:4, 35:35:20:2:8, 40:30:15:5:10, 45:25:20:2.5:7.5, 50:20:19:1:10, 55:15:22:4:4, 55.5:40:1:3:0.5, or 60:10:25:5:0.

[0045] In some embodiments, the electronically conductive agent includes any one or a combination of at least two of carbon nanotubes, Ketjen black, acetylene black, conductive carbon black, or graphene. Typical but non-limiting combinations include combinations of carbon nanotubes and Ketjen black, combinations of acetylene black and conductive carbon black, combinations of graphene and carbon nanotubes, combinations of Ketjen black and acetylene black, or combinations of conductive carbon black and graphene.

[0046] In some embodiments, the ionic conductive agent comprises any one or a combination of at least two of lithium lanthanum zirconium oxide, lithium titanium aluminum phosphate, lithium germanium aluminum phosphate, lithium lanthanum titanate, polyethylene oxide, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, or polyvinylidene fluoride. Typical but non-limiting combinations include combinations of lithium lanthanum zirconium oxide and lithium titanium aluminum phosphate, combinations of lithium germanium aluminum phosphate and lithium lanthanum titanate, combinations of polyethylene oxide and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, combinations of polyvinylidene fluoride and lithium lanthanum zirconium oxide, combinations of lithium titanium aluminum phosphate and lithium germanium aluminum phosphate, combinations of lithium lanthanum titanate and polyethylene oxide, or combinations of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer and polyvinylidene fluoride.

[0047] In some embodiments, the adhesive comprises polyvinylidene fluoride and / or polyethylene oxide.

[0048] In some embodiments, the lithium salt comprises any one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluoroylanyl)imide, or lithium perchlorate. Typical but non-limiting combinations include combinations of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluoroylanyl)imide, combinations of lithium perchlorate and lithium bis(trifluoromethanesulfonyl)imide, or combinations of lithium bis(fluoroylanyl)imide and lithium perchlorate.

[0049] In some embodiments, the hot pressing temperature is 110°C to 200°C, for example, it can be 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C.

[0050] In some embodiments, the hot pressing pressure is 10MPa to 40MPa, for example, it can be 10MPa, 15MPa, 20MPa, 25MPa, 30MPa, 35MPa or 40MPa.

[0051] In some embodiments, the areal density of sulfur in the highly loaded sulfur composite cathode is 30 mg / cm³. 2 ~50mg / cm 2 For example, it could be 30 mg / cm³ 2 35mg / cm 2 40mg / cm 2 45mg / cm 2 Or 50mg / cm2 .

[0052] In another specific embodiment, the present invention provides a high-load sulfur composite cathode, which is prepared by the preparation method described in one of the preceding specific embodiments.

[0053] In yet another embodiment, the present invention provides a lithium-sulfur battery comprising a high-load sulfur composite cathode as described in another preceding embodiment.

[0054] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0055] Example 1

[0056] This embodiment provides a method for preparing a highly loaded sulfur composite cathode, the method comprising the following steps:

[0057] 45% elemental sulfur, 10% acetylene black, 10% carbon nanotubes, 10% Ketjen black, 15% polyethylene oxide, 3% polyvinylidene fluoride, and 7% lithium bis(trifluoromethanesulfonyl)imide were weighed out according to mass percentage. After vacuum drying and dehydration, the mixture was mixed in a solid phase to obtain a composite material. An aluminum current collector was laid at the bottom of a hot press mold, and the composite material was filled into the hot press mold. The mold was then hot-pressed at 160℃ and 30MPa to obtain a sulfur surface density of 40mg / cm³. 2 An integrated composite positive electrode.

[0058] Example 2

[0059] This embodiment provides a method for preparing a highly loaded sulfur composite cathode, the method comprising the following steps:

[0060] Weigh out 30% elemental sulfur, 20% carbon nanotubes, 14% Ketjen black, 20% polyethylene oxide, 5% lithium lanthanum titanate, 1% polyvinylidene fluoride, and 10% lithium bis(trifluoromethanesulfonyl)imide by mass percentage. After vacuum drying and dehydration, mix the solid phases to obtain a mixed material. Lay an aluminum current collector at the bottom of a hot press mold, fill the mold with the mixed material, and hot press at 170℃ and 10MPa to obtain a sulfur surface density of 50mg / cm³. 2 An integrated composite positive electrode.

[0061] Example 3

[0062] This embodiment provides a method for preparing a highly loaded sulfur composite cathode, the method comprising the following steps:

[0063] 60% elemental sulfur, 10% acetylene black, 25% lithium aluminum titanium phosphate, and 5% polyvinylidene fluoride were weighed out by mass percentage, vacuum dried and dehydrated, and then mixed in a solid state to obtain a mixed material. An aluminum current collector was laid at the bottom of a hot press mold, and the mixed material was filled into the hot press mold. The mold was then hot-pressed at 110℃ and 40MPa to obtain a sulfur surface density of 30mg / cm³. 2 An integrated composite positive electrode.

[0064] Example 4

[0065] This embodiment provides a method for preparing a highly loaded sulfur composite cathode, the method comprising the following steps:

[0066] Weigh out 55.5% elemental sulfur, 20% graphene, 20% Ketjen black, 1% ethylene oxide-propylene oxide-ethylene oxide triblock copolymer, 3% polyvinylidene fluoride, and 0.5% lithium difluorosulfonate imide by mass percentage. After vacuum drying and dehydration, mix the solid phases to obtain a mixed material. Lay an aluminum current collector at the bottom of a hot press mold, fill the mold with the mixed material, and hot press at 200℃ and 20MPa to obtain a sulfur surface density of 45mg / cm³. 2 An integrated composite positive electrode.

[0067] Example 5

[0068] This embodiment provides a method for preparing a high-load sulfur composite cathode. Except for the hot-pressing temperature of 100°C, the preparation method is the same as that in Example 1.

[0069] Example 6

[0070] This embodiment provides a method for preparing a high-load sulfur composite cathode. Except for the hot-pressing temperature of 210°C, the preparation method is the same as that in Example 1.

[0071] Example 7

[0072] This embodiment provides a method for preparing a high-load sulfur composite cathode. The preparation method is the same as in Example 1, except that the hot pressing pressure is 8 MPa.

[0073] Example 8

[0074] This embodiment provides a method for preparing a high-load sulfur composite cathode. Except for the hot-pressing pressure of 42 MPa, the preparation method is the same as that in Example 1.

[0075] Comparative Example 1

[0076] This comparative example provides a method for preparing a high-load sulfur composite cathode. The preparation method is the same as in Example 1, except that elemental sulfur is used to replace the ionic conductive agent polyethylene oxide with an equal mass in the mixed materials.

[0077] Performance testing:

[0078] Liquid lithium-sulfur batteries and all-solid-state lithium-sulfur batteries were prepared using the high-load sulfur composite cathodes provided in all the above embodiments and comparative examples, respectively. The actual areal capacity was tested, and the utilization rate was calculated by comparing the measured actual areal capacity with the theoretical areal capacity. The assembly and testing methods for liquid lithium-sulfur batteries and all-solid-state lithium-sulfur batteries are as follows:

[0079] Liquid lithium-sulfur battery testing: A CR2025 coin cell was assembled using a commercially available lithium-sulfur electrolyte containing 2% lithium nitrate (1 mol / L LiTFSI dissolved in a 1:1 volume ratio of DOL and DME), a highly loaded sulfur composite cathode, a Celgard 2400 separator, and a lithium metal anode. The test voltage range was 1.7V~2.8V, the test temperature was 25℃, and the test current density was 0.1 mA / cm². 2 .

[0080] All-solid-state lithium-sulfur battery testing: CR2025 coin cells were assembled using a polyoxyethylene composite solid electrolyte (polyoxyethylene:lithium bis(trifluoromethanesulfonyl)imide:lithium lanthanum zirconium oxide:lithium nitrate = 100:45:15:5 by mass), a high-load sulfur composite positive electrode, and a lithium metal negative electrode. The test voltage range was 1.7V~2.8V, the test temperature was 60℃, and the test current density was 0.1mA / cm². 2 .

[0081] The test results are shown in Table 1.

[0082] Table 1

[0083]

[0084] In summary, based on the test results of Examples 1 to 4 in Table 1, the present invention achieves uniform dispersion of active materials through a solid-phase mixing combined with hot pressing preparation process, while enhancing the interfacial bonding between active materials; at the same time, it introduces electronic conductive agents, ionic conductive agents and lithium salts to mix with elemental sulfur to construct a stable ion / electron transport network, thereby improving the utilization rate of sulfur in the high-load sulfur composite cathode.

[0085] According to the test results of Examples 1, 5, and 6, if the hot pressing temperature is too low, the elemental sulfur cannot be fully integrated with the electronic conductive agent, ionic conductive agent, binder, and lithium salt, and the interfacial bonding cannot be enhanced, resulting in a decrease in the utilization rate of sulfur in the high-load sulfur composite cathode. If the hot pressing temperature is too high, sulfur volatilization will occur, leading to the loss of active materials, which in turn will result in a lower measured areal capacity and a decrease in sulfur utilization.

[0086] According to the test results of Examples 1, 7, and 8, if the hot pressing pressure is too low, it is not conducive to the close contact between elemental sulfur and electronic conductive agent, ionic conductive agent, binder and lithium salt, and the interfacial bonding cannot be enhanced, resulting in a decrease in the utilization rate of sulfur in the high-load sulfur composite cathode. If the hot pressing pressure is too high, it will cause polymer extrusion and uneven component distribution, thus failing to form an efficient ionic and electronic conductive network, which will also lead to a decrease in sulfur utilization.

[0087] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A dry preparation method for a highly loaded sulfur composite cathode, characterized in that, The preparation method includes: Solid-phase mixing of elemental sulfur, electronically conductive agent, ionicly conductive agent, binder and lithium salt yields a mixed material; the mixed material is filled into a mold and hot-pressed to obtain the high-load sulfur composite cathode. A current collector is laid at the bottom of the mold.

2. The preparation method according to claim 1, characterized in that, In the mixed material, the mass ratio of elemental sulfur, electronic conductive agent, ionic conductive agent, binder and lithium salt is (30~60):(10~40):(1~25):(1~5):(0~10).

3. The preparation method according to claim 1, characterized in that, The electronically conductive agent includes any one or a combination of at least two of carbon nanotubes, Ketjen black, acetylene black, conductive carbon black, or graphene.

4. The preparation method according to claim 1, characterized in that, The ionic conductive agent includes any one or a combination of at least two of the following: lithium lanthanum zirconium oxide, lithium titanium aluminum phosphate, lithium germanium aluminum phosphate, lithium lanthanum titanate, polyethylene oxide, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, or polyvinylidene fluoride.

5. The preparation method according to claim 1, characterized in that, The adhesive includes polyvinylidene fluoride and / or polyethylene oxide.

6. The preparation method according to claim 1, characterized in that, The lithium salt includes any one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluoroxanthione)imide, or lithium perchlorate.

7. The preparation method according to claim 1, characterized in that, The hot pressing temperature is 110℃~200℃; And / or, the hot pressing pressure is 10MPa~40MPa.

8. The preparation method according to claim 1, characterized in that, The areal density of sulfur in the high-load sulfur composite cathode is 30 mg / cm³. 2 ~50mg / cm 2 .

9. A high-load sulfur composite cathode, characterized in that, The high-load sulfur composite cathode is prepared by the preparation method according to any one of claims 1 to 8.

10. A lithium-sulfur battery, characterized in that, The lithium-sulfur battery includes the high-load sulfur composite cathode as described in claim 9.

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