Multi-gradient multi-layer high-voltage lithium-rich manganese-sulfur-based positive electrode coupling composite material and preparation method thereof

Abstract

The invention relates to a multi-gradient multi-layer high-voltage lithium-rich manganese-sulfur-based positive electrode coupling composite material and a preparation method thereof. The preparation method of the multi-gradient multi-layer high-voltage lithium-rich manganese-sulfur-based positive electrode coupling composite material comprises the following steps: (1) carrying out surface passivation treatment on a lithium-rich manganese-based positive electrode material through a lanthanum permeation or barium permeation process to obtain a perovskite structure coated lithium-rich manganese positive electrode material; and (2) mixing the perovskite structure coated lithium-rich manganese positive electrode material with a sulfur-based conversion positive electrode material and conductive carbon, and heating at high temperature to melt the sulfur-based conversion positive electrode material to obtain the multi-gradient multi-layer high-voltage lithium-rich manganese-sulfur-based positive electrode coupling composite material, wherein the sulfur-based conversion positive electrode material comprises at least one of S8, TiS3, sulfurized polyacrylonitrile or other sulfur group element-based conversion positive electrode materials.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, specifically relating to multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite materials and their preparation methods. Background Technology

[0002] Currently, lithium batteries are widely used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, special equipment, aerospace, and many other fields. These diverse applications place higher demands on the performance of lithium-ion batteries, with high energy density being a primary requirement.

[0003] Ultra-high capacity cathodes are crucial for achieving high energy density in lithium-ion batteries. Lithium-rich manganese materials possess high theoretical capacity, reaching 400 mAh / g under 0.025C micro-current discharge conditions, corresponding to a theoretical energy density exceeding 800 Wh / kg for some devices. However, their rate capacity is poor, with an energy density of less than 550 Wh / kg at 0.2C. Meanwhile, sulfur-based cathode materials offer high energy density, but require a large electrolyte injection volume (>3 g / Ah), limiting the energy density of practical devices. A high-energy lithium-rich manganese-sulfur-based fusion cathode material approach combines the high capacity and voltage of lithium-rich manganese with the high capacity and high rate performance of sulfur-based materials, improving the composite cathode's energy density and rate performance. This approach holds promise for achieving ultra-high specific capacity and high energy density, making it an ideal material for high-performance lithium-ion battery cathodes.

[0004] Although the high-energy-density lithium-rich manganese-sulfur-based coupled cathode material system has significant advantages, the main obstacle to its application in high-energy-density batteries lies in the difficulty of simultaneously achieving high-pressure ester electrolytes for lithium-rich manganese materials and low-pressure ether electrolytes for sulfur-based materials. Furthermore, the structural stability of lithium-rich manganese cathodes is challenged under high voltage, and they also face the problem of reaction with sulfur-based components. Therefore, lithium-rich manganese-sulfur-based coupled cathodes have not yet been reported. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material and its preparation method.

[0006] In a first aspect, the present invention provides a method for preparing a multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material, the method comprising the following steps: (1) The lithium-rich manganese-based cathode material is surface passivated by lanthanum or barium infiltration process to obtain perovskite-structured lithium-rich manganese cathode material. (2) The perovskite-structured lithium-rich manganese cathode material is mixed with sulfur-based conversion cathode material and conductive carbon, and heated at high temperature to melt the sulfur-based conversion cathode material to obtain the multi-gradient multilayer high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material. Wherein: the sulfur-based conversion cathode material includes at least one of S8, TiS3, sulfurized polyacrylonitrile, or other chalcogenide-based conversion cathode materials.

[0007] Preferably, in step (1), the lithium-rich manganese-based cathode material is an O3 phase, an O2 phase, or an O3 / O2 composite phase; The lithium-rich manganese-based cathode material comprises Li[Li] x M y O2, wherein: 0 < x < 1 / 3, 2 / 3 < y < 1, M = Mn and at least one of Ni and Co; preferably, the lithium-rich manganese-based cathode material comprises Li[Li 0.2 Mn 0.54 Co 0.13 Ni 0.13 O2.

[0008] Preferably, in step (1), the lanthanum infiltration process includes: adding lithium-rich manganese cathode material to a LaCl3 solution and mixing, followed by filtration, washing, drying, and annealing; The steps of the barium infiltration process include: adding lithium-rich manganese cathode material to BaCl2 solution and mixing, followed by filtration, washing, drying and annealing.

[0009] Preferably, in step (2), the other chalcogenide-based conversion cathode materials include Se and Nb2CSe2.

[0010] Preferably, in step (2), the conductive carbon includes at least one of carbon nanotubes, graphene, few-layer carbon, and N-doped carbon.

[0011] Preferably, in step (2), the mass ratio of the perovskite structure-coated lithium-rich manganese cathode material, the sulfur-based conversion cathode material, and the conductive carbon is (4-25):(3-4):1.

[0012] Preferably, in step (2), the high-temperature heating temperature is 115-450℃ and the heat preservation time is 5-20h.

[0013] Secondly, the present invention provides a multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material obtained according to the above preparation method.

[0014] Preferably, the multi-gradient, multi-layered high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material comprises: a perovskite structure formed by surface doping with lanthanum or barium covering a lithium-rich manganese cathode body, a composite sulfur cathode filler anchored to the surface of the lithium-rich manganese cathode body, and an electrode-level conductive carbon network; wherein the composite sulfur cathode comprises sulfur-based conversion cathode material particles and a sulfur particle-level conductive carbon network attached to the surface of the sulfur-based conversion cathode material particles.

[0015] Preferably, the multi-gradient multilayer high-voltage lithium-rich manganese-sulfur-based cathode coupling composite material can achieve a discharge capacity of 390-526 mAh / g in the electrolyte at a rate of 0.1C and a voltage range of 1.8-4.8V, and can be stably cycled for 50 cycles with a capacity retention rate of 65-75%.

[0016] Beneficial effects (1) This invention achieves full utilization of the capacity of both by combining lithium-rich manganese-based cathode with a specific ratio of sulfur-based conversion cathode. Furthermore, by using the surface passivation technology of lithium-rich manganese-based cathode and the anchoring of small molecule sulfur-based cathode by its surface transition metal, the stability of the composite cathode is improved, thus realizing the preparation of an ultra-high capacity lithium-ion battery cathode material. (2) This invention fully utilizes the capacity of lithium-rich manganese-based cathode and sulfur-based conversion cathode through structural design, greatly improving the energy density of cathode materials, providing support for high-performance lithium-ion battery systems, and has great potential for large-scale commercial production. (3) The multi-gradient, multi-level high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material provided by the present invention has a composite cathode formed by coupling lithium-rich manganese cathode and sulfur-based cathode; wherein, the lithium-rich manganese cathode is a perovskite structure formed by surface doping with lanthanum or barium; the composite sulfur cathode is a sulfur-based cathode constructed by sulfur-based conversion cathode particles and conductive carbon network at the sulfur-based conversion cathode particle level, and the sulfur-based conversion cathode particles and conductive carbon network construct a fluffy and highly active composite sulfur cathode. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the multi-gradient multilayer high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material prepared in Example 1 of the present invention; Figure 2 The image shows the XRD pattern of the multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material prepared in Example 1 of this invention. Figure 3 The constant current charge-discharge curves of lithium-rich manganese-based cathode, sulfur-based anchored cathode, and multi-gradient multilayer high-voltage lithium-rich manganese-sulfur-based cathode coupling composite material prepared in Example 1 of this invention are shown in an optimized ester-based electrolyte, at a rate of 0.1C, and in a voltage range of 1.8-4.8V. Figure 4This is a schematic diagram of the discharge specific capacity of the multi-gradient multilayer high-voltage lithium-rich manganese-sulfur-based cathode coupling composite material prepared in Example 1 of the present invention, in an optimized ester-based electrolyte, at a rate of 0.1C, and within a voltage range of 1.8-4.8V for 50 cycles. Figure 5 The graph shows the constant current charge-discharge curves of the composite material prepared in Comparative Example 1 of this invention in an optimized ester-based electrolyte, at a rate of 0.1C, and within a voltage range of 1.8-4.8V. Figure 6 This is a constant current charge-discharge curve of the composite material prepared in Comparative Example 2 of the present invention in an optimized ester-based electrolyte, at a rate of 0.1C and a voltage range of 1.8-4.8V. Detailed Implementation

[0018] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0019] To address the aforementioned technical problems, the present invention discloses the following technical solution: First, a high-capacity, stable perovskite-structured lithium-rich manganese cathode material is prepared using lanthanum infiltration and barium infiltration passivation techniques. Then, a small-molecule sulfur-based cathode is anchored on the surface of the perovskite-structured lithium-rich manganese cathode material using transition metals. Finally, the composite cathode capacity is increased to 526 mAh / g without sacrificing the cathode plateau voltage. Simultaneously, the excellent rate performance and low-temperature performance of the small-molecule sulfur-based cathode are combined to promote the realization of high-rate and low-temperature discharge capabilities of a multi-gradient, multi-level lithium-rich manganese composite cathode.

[0020] The following exemplarily describes a method for preparing the multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material provided by the present invention. The preparation method may include the following steps: (1) The lithium-rich manganese-based cathode material is surface passivated by lanthanum or barium infiltration process to obtain perovskite-structured lithium-rich manganese cathode material. (2) The perovskite-structured lithium-rich manganese cathode material is mixed with sulfur-based conversion cathode material and conductive carbon, and heated at high temperature under vacuum conditions to melt the sulfur-based conversion cathode material to obtain the multi-gradient multilayer high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material.

[0021] In some embodiments, in step (1), the lithium-rich manganese-based cathode material can be an O3 phase, an O2 phase, or an O3 / O2 composite phase; the components of the lithium-rich manganese-based cathode material may include Li[Li x M y O2, wherein: 0 < x < 1 / 3, 2 / 3 < y < 1, M = Mn and at least one of Ni and Co; preferably, the lithium-rich manganese-based cathode material comprises Li[Li 0.2 Mn0.54 Co 0.13 Ni 0.13 O2.

[0022] In some embodiments, step (1) of the lanthanum infiltration process may include: preparing a 0.1-0.5M DMF solution of LaCl3, adding lithium-rich manganese cathode powder, stirring and dispersing at room temperature to 60℃ for 12-20h, separating the powder by vacuum filtration and washing with DMF, drying at 80℃ for 12h, and annealing at 650℃ for 5-10h.

[0023] In some embodiments, step (1) of the barium infiltration process may include: preparing a 0.1-0.5M BaCl2 DMF solution, adding lithium-rich manganese cathode powder, stirring and dispersing at room temperature to 60℃ for 12-20h, separating the powder by vacuum filtration and washing with DMF, drying at 80℃ for 12h, and annealing at 650℃ for 5-10h.

[0024] This invention is based on the interfacial coating technology of "lanthanum infiltration" and "barium infiltration" to construct a highly conductive coating layer on the surface of a lithium-rich manganese-based cathode. At the same time, by compositing conductive networks at the electrode scale, the overall conductivity is improved, the volume change during the charging and discharging process is mitigated, and the realization of a composite cathode with ultra-high capacity, high rate and high stability is promoted.

[0025] It should be noted that the "lanthanum infiltration" and "barium infiltration" processes used in this invention differ from those using phosphorus and lanthanum for surface modification. The latter typically uses phosphate as the phosphorus source, which cannot be further converted in subsequent processing. Therefore, its effect is phosphate surface coating and near-surface doping of lanthanum ions, fundamentally different from the perovskite surface structure achieved through ion exchange in this invention. Furthermore, the cathodes produced by phosphorus and lanthanum surface modification generally exhibit lower capacity and cutoff voltages, typically lower than the 4.8V described in this invention. At higher voltages, material stability faces greater challenges. Therefore, the perovskite surface structure formed by the lanthanum and barium infiltration processes of this invention provides better structural stability at higher voltages.

[0026] In some embodiments, in step (1), the thickness of the coating layer of the perovskite structure coated with lithium-rich manganese cathode material can be 3-10 nm.

[0027] In some embodiments, in step (2), the sulfur-based conversion cathode material may include at least one of S8, TiS3, sulfurized polyacrylonitrile (SPAN), or other chalcogenide-based conversion cathode materials; preferably, the other chalcogenide-based conversion cathode materials may include Se or Nb2CSe2.

[0028] In some embodiments, in step (2), the conductive carbon may include at least one of carbon nanotubes, graphene, few-layer carbon, and N-doped carbon.

[0029] In some embodiments, in step (2), the mass ratio of the perovskite structure-coated lithium-rich manganese cathode material, the sulfur-based conversion cathode material, and the conductive carbon can be (4-25):(3-4):1.

[0030] This invention achieves full capacity utilization of both lithium-rich manganese-based cathodes and sulfur-based conversion cathodes in a specific ratio. Furthermore, by utilizing surface passivation technology of the lithium-rich manganese-based cathode and anchoring small-molecule sulfur-based cathodes with its surface transition metal, the stability of the composite cathode is improved, ultimately leading to the successful preparation of ultra-high capacity lithium-ion battery cathode materials. However, insufficient sulfur-based cathode content results in limited capacity utilization; excessive sulfur-based cathode content prevents the lithium-rich manganese cathode from fully anchoring the sulfur component, especially at high pressures where sulfur is easily oxidized, leading to poor stability.

[0031] In some embodiments, in step (2), the high-temperature heating temperature can be 115-450℃, and the heat preservation time can be 5-20h, preferably 5-10h.

[0032] The lower limit of the high-temperature heating is the melting temperature of sulfur, ensuring that all components melt and mix thoroughly and uniformly. Furthermore, a milder heat treatment temperature promotes the interaction between the metal on the lithium-rich cathode surface and the chalcogen elements in the sulfur-based conversion cathode, achieving structural coupling. Higher temperatures can cause over-sulfidation of the lithium-rich manganese-based cathode, transforming it into sulfides; even higher temperatures may lead to the decomposition of sulfides, resulting in ion-doped structures and the loss of the capacity contribution from the sulfur-based cathode. Simultaneously, too short a heat treatment time will not fully achieve structural coupling, while too long a time will waste resources.

[0033] The multi-gradient, multilayer, high-voltage lithium-rich manganese-sulfur-based cathode coupling composite material prepared by the method provided in this invention combines the high capacity advantages of lithium-rich manganese-based cathodes and sulfur-based cathodes. The lithium-rich cathode serves as the main component, providing mechanical strength to the thick electrode system, while the fluffy and highly active composite sulfur cathode acts as a filler. Specifically, by using a highly conductive, low-dimensional material for coating, and combining it with transition metal-anchored small-molecule sulfur to replace the traditional single S8 cathode molecule, the compatibility of the sulfur cathode in ester electrolytes is improved, promoting electron and ion transport on the sulfur cathode side.

[0034] In some embodiments, the multi-gradient, multi-layered high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material may include: a perovskite structure formed by surface doping with lanthanum or barium covering the lithium-rich manganese cathode body, a composite sulfur cathode filler anchored to the surface of the lithium-rich manganese cathode body, and an electrode-level conductive carbon network; wherein the composite sulfur cathode includes sulfur-based conversion cathode material particles and a sulfur particle-level conductive carbon network attached to the surface of the sulfur-based conversion cathode material particles.

[0035] It should be noted that this invention differs from those that utilize molybdenum disulfide or tungsten disulfide as raw materials to achieve uniform doping of sulfur and tungsten or molybdenum through prolonged high-temperature treatment. The latter approach typically involves relatively small amounts of molybdenum and tungsten disulfide (≤2%) due to limitations in doping levels. Furthermore, after prolonged high-temperature treatment, the added molybdenum and tungsten disulfide no longer maintain their initial structure but are uniformly doped into the lithium-rich manganese cathode material in atomic form, thereby improving the stability of the lithium-rich manganese cathode. However, the addition of a sulfur-based conversion cathode in this invention is primarily to leverage its capacity contribution in the low-voltage region; therefore, the amount of sulfur-based conversion cathode material added is greater (the mass ratio relative to the lithium-rich manganese cathode can be 20-100%). Moreover, to ensure the sulfur-based conversion cathode can achieve its capacity, its structure needs to be maintained. This invention employs a mild processing temperature (115-450℃) to allow for better fusion of the lithium-rich manganese cathode conversion cathode and conductive carbon, constructing an electron-ion pathway. In addition, the present invention uses a voltage range of 1.8-4.8V, which is within the capacity utilization range of sulfur-based conversion cathodes. Therefore, the capacity contribution of the combination of lithium-rich manganese cathode and sulfur-based conversion cathode is much higher than that of the latter technical solution.

[0036] In some embodiments, the multi-gradient, multilayer, high-voltage lithium-rich manganese-sulfur-based cathode coupling composite material, in an optimized ester-based electrolyte, can achieve a discharge capacity of 390-526 mAh / g at a 0.1C rate and a voltage range of 1.8-4.8V, preferably 500-526 mAh / g; it can be stably cycled for 50 cycles at a 0.1C rate and a voltage range of 1.8-4.8V with a capacity retention rate of 65-75%; preferably, the optimized ester-based electrolyte can be 1M LiPF6 / EC:DMC:EMC (volume ratio 1:1:1, 5wt% FEC added).

[0037] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0038] Example 1

[0039] The lithium-rich manganese-based cathode Li[Li] provided in this embodiment 0.2 Mn 0.54 Co 0.13 Ni 0.13 The preparation method of O2 and S8 (or TiS3) (3:1) multi-gradient multilayer high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material includes the following steps: To prepare a 0.1M DMF solution of LaCl3, add 1.2g of Li[Li] 0.2 Mn 0.54 Co 0.13 Ni 0.13 O2 powder was stirred and dispersed at room temperature -60℃ for 12-20 hours, separated by vacuum filtration and washed with DMF, dried at 80℃ for 12 hours, and annealed at 650℃ for 5-10 hours for lanthanum infiltration. The above passivated lithium-rich manganese powder was then mixed with 0.4g S8 (or TiS3) and 0.1g carbon nanotubes (CNTs) by ball milling at 350rpm for 6 hours. The mixture was then vacuum-sealed in a quartz tube and heat-treated at 155℃ for 5 hours to obtain the final product. The mixture was then sieved for later use.

[0040] The above composite positive electrode was mixed with Super P and PVDF in a ratio of 8:1:1, and a slurry was prepared using NMP as a dispersant and coated onto aluminum foil. The mixture was then vacuum dried at 60°C for 24 hours to obtain the composite positive electrode sheet.

[0041] Figure 1 This is a schematic diagram of the multi-gradient, multi-layered, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material prepared in Example 1 of the present invention. As can be seen from the figure, the composite cathode material has a multi-gradient, multi-layered structural design, constructing a good ion-electron transport pathway.

[0042] Figure 2 The image shows the XRD pattern of the multi-gradient, multilayer, high-voltage lithium-rich manganese-sulfur-based cathode (S8) coupling composite material prepared in Example 1 of this invention. As can be seen from the image, the lithium-rich manganese-based material Li[Li 0.2 Mn 0.54 Co0.13 Ni 0.13 O2 can coexist stably with S.

[0043] Figure 3 The graphs show the constant current charge-discharge curves of the lithium-rich manganese-based cathode, the sulfur-based anchored cathode, and the multi-gradient multilayer high-voltage lithium-rich manganese-sulfur-based cathode (S8) coupling composite material prepared in Example 1 of this invention, in an optimized ester-based electrolyte, at a rate of 0.1C and a voltage range of 1.8-4.8V. As can be seen from the graphs, the composite cathode can achieve a discharge capacity of 526 mAh / g in the optimized ester-based electrolyte at a rate of 0.1C and a voltage range of 1.8-4.8V.

[0044] Figure 4 This diagram illustrates the discharge specific capacity of the multi-gradient, multilayer, high-voltage lithium-rich manganese-sulfur-based cathode (S8) coupling composite material prepared in Example 1 of this invention, after 50 cycles in an optimized ester-based electrolyte at a 0.1C rate and a voltage range of 1.8-4.8V. As can be seen from the figure, the composite cathode can stably cycle for 50 cycles in the optimized ester-based electrolyte at a 0.1C rate and a voltage range of 1.8-4.8V, maintaining a capacity retention of 72%.

[0045] Example 2

[0046] The preparation method of the multi-gradient multilayer high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material provided in this embodiment is the same as that in Example 1, the main difference being: the lithium-rich manganese-based cathode Li[Li 0.2 Mn 0.54 Co 0.13 Ni 0.13 The mass ratio of O2 to S8 is 5:1 (the raw materials weighed are 1g each of Li[Li 0.2 Mn 0.54 Co 0.13 Ni 0.13 [O2, 0.2g sublimed sulfur S8 and 0.05g carbon nanotubes (CNTs)].

[0047] Tests show that the composite cathode prepared in this embodiment can achieve a discharge capacity of 455 mAh / g in the optimized ester electrolyte at a rate of 0.1C and a voltage range of 1.8-4.8V. It can also be stably cycled for 50 cycles at a rate of 0.1C and a voltage range of 1.8-4.8V, with a capacity retention rate of 65%.

[0048] Example 3

[0049] The preparation method of the multi-gradient multilayer high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material provided in this embodiment is the same as that in Example 1, the main difference being: (1) the sulfur-based cathode material is Se; (2) the high-temperature heating temperature is 250℃.

[0050] Tests show that the composite cathode prepared in this embodiment can achieve a discharge capacity of 398 mAh / g in the optimized ester electrolyte at a rate of 0.1C and a voltage range of 1.8-4.8V. It can also be stably cycled for 50 cycles at a rate of 0.1C and a voltage range of 1.8-4.8V, with a capacity retention rate of 68%.

[0051] Example 4

[0052] The preparation method of the multi-gradient multilayer high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material provided in this embodiment is the same as that in Example 1, the main difference being that the high-temperature heating temperature is 250℃.

[0053] Tests show that the multi-gradient, multilayer high-voltage lithium-rich manganese-sulfur-based cathode (TiS3) coupling composite material prepared in this embodiment can achieve a discharge capacity of 410 mAh / g at a rate of 0.1C and a voltage range of 1.8-4.8V in an optimized ester-based electrolyte. It can also be stably cycled for 50 cycles at a rate of 0.1C and a voltage range of 1.8-4.8V, with a capacity retention rate of 75%.

[0054] Comparative Example 1

[0055] The preparation method of the multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material provided in this comparative example is the same as in Example 1, the main difference being: the lithium-rich manganese-based cathode Li[Li] used... 0.2 Mn 0.54 Co 0.13 Ni 0.13 O2 was not subjected to lanthanum passivation treatment.

[0056] Tests showed that the composite cathode prepared in this comparative example could not achieve normal charge-discharge in the optimized ester-based electrolyte at a rate of 0.1C and a voltage range of 1.8-4.8V. It also underwent an irreversible reaction with sulfur at high voltage, as indicated by the charge-discharge curves shown below. Figure 5 As shown.

[0057] Comparative Example 2

[0058] The preparation method of the multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material provided in this comparative example is the same as that in Example 1. The main difference is that the lithium-rich manganese-based cathode Li[Li] after lanthanum infiltration passivation treatment... 0.2 Mn 0.54 Co 0.13 Ni 0.13 The mass ratio of O2 to S8 is 1:2 (the raw materials weighed are 0.5g each of Li[Li 0.2 Mn 0.54 Co 0.13 Ni 0.13 [O2, 1g sublimed sulfur S8 and 0.25g carbon nanotubes (CNTs)].

[0059] Tests showed that the composite cathode prepared in this comparative example could not be charged normally in the optimized ester-based electrolyte at a rate of 0.1C and a voltage range of 1.8-4.8V. Excessive sulfur oxidation at high voltage prevented discharge. Its charge-discharge curves are shown below. Figure 6 As shown.

[0060] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material, characterized in that, The preparation method includes the following steps: (1) The lithium-rich manganese-based cathode material is surface passivated by lanthanum or barium infiltration process to obtain perovskite-structured lithium-rich manganese cathode material. (2) The perovskite-structured lithium-rich manganese cathode material is mixed with sulfur-based conversion cathode material and conductive carbon, and heated at high temperature to melt the sulfur-based conversion cathode material to obtain the multi-gradient multilayer high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material. Wherein: the sulfur-based conversion cathode material includes at least one of S8, TiS3, sulfurized polyacrylonitrile, or other chalcogenide-based conversion cathode materials.

2. The preparation method according to claim 1, characterized in that, In step (1), the lithium-rich manganese-based cathode material is an O3 phase, an O2 phase, or an O3 / O2 composite phase; The lithium-rich manganese-based cathode material comprises Li[Li] x M y O2, wherein: 0 < x < 1 / 3, 2 / 3 < y < 1, M = Mn and at least one of Ni and Co; preferably, the lithium-rich manganese-based cathode material comprises Li[Li 0.2 Mn 0.54 Co 0.13 Ni 0.13 O2.

3. The preparation method according to claim 1 or 2, characterized in that, In step (1), the lanthanum infiltration process includes: adding lithium-rich manganese cathode material to a LaCl3 solution and mixing, followed by filtration, washing, drying, and annealing; The steps of the barium infiltration process include: adding lithium-rich manganese cathode material to BaCl2 solution and mixing, followed by filtration, washing, drying and annealing.

4. The preparation method according to any one of claims 1-3, characterized in that, In step (2), the other chalcogenide-based conversion cathode materials include Se and Nb2CSe2.

5. The preparation method according to any one of claims 1-4, characterized in that, In step (2), the conductive carbon includes at least one of carbon nanotubes, graphene, few-layer carbon, and N-doped carbon.

6. The preparation method according to any one of claims 1-5, characterized in that, In step (2), the mass ratio of the perovskite structure-coated lithium-rich manganese cathode material, the sulfur-based conversion cathode material, and the conductive carbon is (4-25):(3-4):

1.

7. The preparation method according to any one of claims 1-6, characterized in that, In step (2), the high-temperature heating temperature is 115-450℃ and the heat preservation time is 5-20h.

8. A multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material obtained by the preparation method according to any one of claims 1-7.

9. The multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material according to claim 8, characterized in that, The multi-gradient, multi-layered high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material includes: a perovskite structure formed by surface doping with lanthanum or barium covering a lithium-rich manganese cathode body, a composite sulfur cathode filler anchored to the surface of the lithium-rich manganese cathode body, and an electrode-level conductive carbon network; wherein, the composite sulfur cathode includes sulfur-based conversion cathode material particles and a sulfur particle-level conductive carbon network attached to the surface of the sulfur-based conversion cathode material particles.

10. The multi-gradient, multilayer, high-pressure lithium-rich manganese-sulfur-based cathode coupling composite material according to claim 8 or 9, characterized in that, The multi-gradient, multilayer, high-voltage lithium-rich manganese-sulfur-based cathode coupling composite material can achieve a discharge capacity of 390-526 mAh / g in electrolyte at a rate of 0.1C and a voltage range of 1.8-4.8V, and can be stably cycled for 50 cycles with a capacity retention rate of 65-75%.

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