Lithium-rich manganese-based positive electrode material, preparation method, positive electrode sheet, and sulfide solid-state battery

Abstract

The present application relates to a kind of lithium-rich manganese-based positive electrode material, preparation method, positive plate and sulfide solid-state battery.The preparation method includes: mixing lithium-rich manganese-based precursor, lithium source, fast ion conductor material and hard ball milling beads, ball milling activation, obtain mixed material;The mixed material is sintered, and lithium-rich manganese-based positive electrode material is obtained;The fast ion conductor material includes LiNbO3, Li2ZrO3, LiTaO3 or Li3PO4-ZrO2 compound;The hard ball milling bead includes first hard ball milling bead and second hard ball milling bead, and the average diameter of first hard ball milling bead is greater than second hard ball milling bead.The present application is based on ball milling activation process and introduces fast ion conductor in raw material, realizes the body phase doping of lithium-rich manganese-based positive electrode material, while forming nanoscale modification layer on the surface of lithium-rich manganese-based positive electrode material, fundamentally optimizes solid-solid interface contact and ion transport kinetics, provides key material basis for high-performance solid-state battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to sulfide solid-state batteries, and more particularly to a lithium-rich manganese-based cathode material, its preparation method, cathode sheet, and sulfide solid-state battery. Background Technology

[0002] The combination of lithium-rich manganese-based layered oxide cathode materials and sulfide solid electrolytes is considered one of the most promising technological routes for achieving next-generation high-energy-density, high-safety all-solid-state lithium batteries. Lithium-rich manganese-based materials, with their unique synergistic redox mechanism of anions and cations, can provide an ultra-high specific capacity exceeding 250 mAh / g, while sulfide solid electrolytes possess high ionic conductivity comparable to liquid electrolytes.

[0003] However, the solid-solid interface compatibility between lithium-rich manganese-based cathode materials and sulfide solid electrolytes presents serious challenges: When operating at high voltages, lithium-rich manganese-based materials are prone to irreversible oxygen loss, releasing highly oxidizing oxygen species. Meanwhile, sulfide solid electrolytes have a narrow thermodynamic-electrochemical stability window and are easily oxidized and decomposed under high voltages. This results in the oxygen species released by the lithium-rich manganese-based cathode material severely oxidizing the sulfide solid electrolyte when the two are in direct contact, generating high-resistivity interface products containing elemental sulfur and phosphates. Simultaneously, the difference in lithium-ion chemical potential between the lithium-rich manganese-based cathode material and the sulfide solid electrolyte leads to the formation of a lithium-ion-depleted "space charge layer" at the interface, severely hindering ion transport. Furthermore, during charge and discharge, the repeated expansion and contraction of the lithium-rich manganese-based cathode material makes the rigid solid-solid interface susceptible to mechanical failure and contact loss.

[0004] CN117293306A discloses a lithium-rich manganese-based material and its application in sulfide all-solid-state batteries. By employing Ru doping and a sulfur-containing coating layer, not only can the lattice oxygen be stabilized, improving the structural stability of the lithium-rich manganese-based material, but ion diffusion channels can also be constructed within it. Furthermore, the lithium-rich manganese-based material of this invention does not undergo side reactions with the sulfide solid electrolyte and can effectively mitigate the interfacial space charge layer reaction caused by the electrochemical potential difference between the lithium-rich manganese-based basal oxide cathode material and the sulfide solid electrolyte, thereby improving the electrical performance of the lithium-rich manganese-based material.

[0005] CN121172070A discloses a method for constructing an interface between a sulfide solid electrolyte and a lithium-rich manganese-based material, a cathode material, and an all-solid-state lithium battery. The method for constructing the interface between the sulfide solid electrolyte and the lithium-rich manganese-based material employs boron and niobium element surface modification to modify the surface of the lithium-rich manganese-based material, and further constructs a sulfide solid electrolyte modification layer to obtain a sulfide solid electrolyte-surface-modified lithium-rich manganese-based material, forming a sulfide solid electrolyte-lithium-rich manganese-based interface. This improves the structural stability of the sulfide solid electrolyte-lithium-rich manganese-based cathode interface and also enhances the ionic conductivity of the interface.

[0006] CN121546013A discloses a modified lithium-rich manganese-based cathode material, its preparation method, and its application in solid-state lithium batteries. The modified lithium-rich manganese-based cathode material comprises a lithium-rich manganese-based cathode material and a coating layer of LiAl, the LiAl coating layer being formed by the decomposition of LiAlH4. The lithium-rich manganese-based cathode material and LiAlH4 are uniformly mixed using a solid-phase or liquid-phase method, and then annealed under an inert atmosphere to prepare the modified lithium-rich manganese-based cathode material. This invention simultaneously solves the problems of interfacial instability and poor transport kinetics in sulfide-based all-solid-state lithium-ion batteries, and can improve the first-cycle charge-discharge specific capacity and cycle stability of solid-state lithium-ion batteries.

[0007] Existing technologies typically rely on surface engineering to construct a modification layer on the surface of lithium-rich manganese-based cathode materials to optimize the solid-solid interface with the sulfide solid electrolyte. This usually requires complex processes and is costly.

[0008] Therefore, it is of great significance to provide a technical solution that can improve the complex interfacial reaction between lithium-rich manganese-based cathode materials and sulfide solid electrolytes at low cost. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a lithium-rich manganese-based cathode material, its preparation method, cathode sheet, and sulfide solid-state battery. Based on a ball milling activation process, this invention achieves the refinement and uniform, close mixing of raw materials and introduces defects into the crystal lattice of the lithium-rich manganese-based precursor. This facilitates the diffusion of dopant ions from the fast-ion conductor into the lattice interior, enabling bulk doping of the lithium-rich manganese-based cathode material while simultaneously forming a nanoscale modification layer on its surface. This results in the lithium-rich manganese-based cathode material possessing high ionic conductivity, structural stability, and compatibility with sulfide solid electrolytes at its interface, fundamentally optimizing solid-solid interface contact and ion transport kinetics, and providing a key material foundation for high-performance solid-state batteries.

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

[0011] In a first aspect, the present invention provides a method for preparing a lithium-rich manganese-based cathode material, the method comprising:

[0012] A mixture of a lithium-rich manganese-based precursor, a lithium source, a fast-ion conductor material, and hard grinding beads is ball-milled and activated to obtain a mixture. The mixture is then sintered to obtain the lithium-rich manganese-based cathode material. The fast-ion conductor material includes any one or a combination of at least two of LiNbO3, Li2ZrO3, LiTaO3, or a Li3PO4-ZrO2 composite. The hard grinding beads include at least a first hard grinding bead and a second hard grinding bead, wherein the average diameter of the first hard grinding bead is greater than the average diameter of the second hard grinding bead.

[0013] In the preparation method provided by this invention, hard grinding balls with different average diameters are selected for ball milling activation. The first hard grinding ball with a larger average diameter provides high impact force, responsible for breaking large particles and introducing lattice defects; the second hard grinding ball with a smaller average diameter fills the gaps, enhancing the uniformity of the mixing and grinding. Based on the above ball milling activation process, the raw materials are refined and uniformly and tightly mixed. Defects are introduced into the lattice of the lithium-rich manganese-based precursor, which facilitates the diffusion of doped ions from the fast ion conductor into the lattice interior. This allows the lithium-rich manganese-based precursor and the fast ion conductor material to achieve atomic-scale chemical bonding and structural intercalation. Simultaneously, a nanoscale modification layer is formed on the surface of the lithium-rich manganese-based cathode material, enabling the interface of the lithium-rich manganese-based cathode material to possess high ionic conductivity, structural stability, and compatibility with sulfide solid electrolytes. This fundamentally optimizes solid-solid interface contact and ion transport kinetics, providing a key material foundation for high-performance solid-state batteries.

[0014] Preferably, the material of the hard grinding balls includes any one or a combination of at least two of alumina, zirconium oxide, or silicon nitride.

[0015] Preferably, the average diameter of the first hard grinding ball is 6mm to 10mm.

[0016] Preferably, the average diameter of the second hard grinding ball is 2mm to 4mm.

[0017] Preferably, the mass ratio of the first hard grinding ball to the second hard grinding ball is (1.25~3):1.

[0018] Preferably, the ball-to-material ratio for ball milling activation is (4~20):1.

[0019] Preferably, the ball milling speed for ball milling activation is 100 rpm to 450 rpm.

[0020] Preferably, the ball milling time for ball milling activation is 1h to 20h.

[0021] Preferably, the mass ratio of the lithium-rich manganese-based precursor to the fast ion conductor material is 100:(0.2~2).

[0022] Preferably, the molar ratio of Li in the lithium source to the transition metal element TM in the lithium-rich manganese-based precursor is Li / TM = 1.5~1.54.

[0023] Preferably, the lithium-rich manganese-based precursor comprises Mn a Ni b Co c M d (OH)2 and / or Mn a Ni b Co c M d CO3, a+b+c+d=1, a>b, and a>0.5, M is one or more elements selected from Co, Al, Mo, Mg, Fe, Nb, W, Zr, and Ti.

[0024] Preferably, the lithium source includes any one or a combination of at least two of lithium carbonate, lithium hydroxide, lithium nitrate, lithium sulfate, or lithium acetate.

[0025] Preferably, the sintering atmosphere includes air.

[0026] Preferably, the sintering heating rate is 2℃ / min to 5℃ / min.

[0027] Preferably, the sintering temperature is 800℃~980℃.

[0028] Preferably, the sintering time is 8h to 20h.

[0029] In a second aspect, the present invention provides a lithium-rich manganese-based cathode material, which is prepared by the preparation method described in the first aspect.

[0030] Thirdly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising the lithium-rich manganese-based positive electrode material as described in the second aspect; the positive electrode sheet further comprises a sulfide solid electrolyte.

[0031] Preferably, the sulfide solid electrolyte includes Li3PS4 and Li7P3S. 11 Any one or a combination of at least two of Li6PS5Cl or Li6PS5Br.

[0032] Fourthly, the present invention provides a sulfide solid-state battery, the sulfide solid-state battery comprising a positive electrode as described in the third aspect.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) In the preparation method provided by the present invention, hard grinding balls with different average diameters are selected to be used in combination for ball milling activation, which realizes the refinement and uniform and tight mixing of raw materials, and introduces defects in the lattice of lithium-rich manganese-based precursor, which is conducive to the diffusion of doped ions in fast ion conductor into the lattice, so that the lithium-rich manganese-based precursor and fast ion conductor material are chemically bonded and structurally interlocked at the atomic scale. While realizing the bulk doping of lithium-rich manganese-based cathode material, a nanoscale modification layer is formed on the surface of lithium-rich manganese-based cathode material, so that the interface of lithium-rich manganese-based cathode material has high ionic conductivity, structural stability and compatibility with sulfide solid electrolyte, fundamentally optimizing solid-solid interface contact and ion transport dynamics, and providing a key material basis for high-performance solid-state batteries.

[0035] (2) This invention utilizes Nb in fast ion conductors 5+ Zr 4+ Or Ta 5+ Mn in lithium-rich manganese-based cathode materials 2+ The close radius characteristic allows the lattice defects introduced by ball milling activation to enter the transition metal layer, forming bulk phase reinforcement. It can also widen the lithium-ion diffusion channels, improve the bulk ionic conductivity, and fundamentally suppress oxygen loss, manganese migration and harmful phase transitions during cycling, alleviate voltage decay, and significantly reduce the risk of side reactions between lithium-rich manganese-based cathode materials and sulfide electrolytes.

[0036] (3) In this invention, the fast ion conductor material forms a dense nanoscale modification layer on the surface of the lithium-rich manganese-based cathode material under the action of ball milling, which can reduce the contact resistance and ion transport impedance. Moreover, the dense structure of the nanoscale modification layer can act as a physical barrier to effectively isolate the lithium-rich manganese-based cathode material from the sulfide solid electrolyte, further suppress the side reaction between the lithium-rich manganese-based cathode material and the sulfide solid electrolyte, reduce the generation of high impedance by-products, avoid the formation of a "space charge layer" that depletes lithium ions, and reduce the risk of mechanical failure and contact loss caused by rigid contact. Attached Figure Description

[0037] Figure 1 These are the initial charge-discharge curves of the sulfide solid-state batteries in Example 1 and Comparative Example 1. Detailed Implementation

[0038] 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.

[0039] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0040] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The 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" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0041] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. 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 in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. Those skilled in the art can understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology.

[0042] In this invention, the ordinal numbers “first,” “second,” “third,” and “fourth” used in expressions such as “first aspect,” “second aspect,” “third aspect,” and “fourth aspect” 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. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0043] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0044] In one specific embodiment, the present invention provides a method for preparing a lithium-rich manganese-based cathode material, the method comprising:

[0045] A mixture of a lithium-rich manganese-based precursor, a lithium source, a fast-ion conductor material, and hard grinding beads is ball-milled and activated to obtain a mixture. The mixture is then sintered to obtain the lithium-rich manganese-based cathode material. The fast-ion conductor material includes any one or a combination of at least two of LiNbO3, Li2ZrO3, LiTaO3, or a Li3PO4-ZrO2 composite. The hard grinding beads include at least a first hard grinding bead and a second hard grinding bead, wherein the average diameter of the first hard grinding bead is greater than the average diameter of the second hard grinding bead.

[0046] In the preparation method provided by this invention, hard grinding balls with different average diameters are selected for ball milling activation. The first hard grinding ball with a larger average diameter provides high impact force, responsible for breaking large particles and introducing lattice defects; the second hard grinding ball with a smaller average diameter fills the gaps, enhancing the uniformity of the mixing and grinding. Based on the above ball milling activation process, the raw materials are refined and uniformly and tightly mixed. Defects are introduced into the lattice of the lithium-rich manganese-based precursor, which facilitates the diffusion of doped ions from the fast ion conductor into the lattice interior. This allows the lithium-rich manganese-based precursor and the fast ion conductor material to achieve atomic-scale chemical bonding and structural intercalation. Simultaneously, a nanoscale modification layer is formed on the surface of the lithium-rich manganese-based cathode material, enabling the interface of the lithium-rich manganese-based cathode material to possess high ionic conductivity, structural stability, and compatibility with sulfide solid electrolytes. This fundamentally optimizes solid-solid interface contact and ion transport kinetics, providing a key material foundation for high-performance solid-state batteries.

[0047] The crystal parameters of the fast ion conductor introduced in this invention have a high degree of matching with lithium-rich manganese-based cathode materials, which is beneficial for achieving low-stress bonding and rapid ion conduction at the interface; utilizing Nb in the fast ion conductor 5+ Zr 4+ Or Ta 5+ Mn in lithium-rich manganese-based cathode materials 2+ The close radius characteristic allows the lattice defects introduced by ball milling activation to enter the transition metal layer, forming bulk phase reinforcement. It can also widen the lithium-ion diffusion channels, improve the bulk ionic conductivity, and fundamentally suppress oxygen loss, manganese migration and harmful phase transitions during cycling, alleviate voltage decay, and significantly reduce the risk of side reactions between lithium-rich manganese-based cathode materials and sulfide electrolytes.

[0048] When the fast ion conductor material is a Li3PO4-ZrO2 composite, the mass ratio of Li3PO4 to ZrO2 is 1:(1~4), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4. Among them, Li3PO4, as a fast ion conductor, can provide an efficient lithium ion transport channel, improve the interfacial contact between lithium-rich manganese-based cathode materials and sulfide electrolytes, reduce interfacial impedance, and at the same time, Li3PO4 can synergistically stabilize the interfacial structure with ZrO2.

[0049] Furthermore, the fast ion conductor material, under ball milling, can form a dense nanoscale modification layer on the surface of the lithium-rich manganese-based cathode material. This layer has good structural compatibility with the solid electrolyte, which can reduce contact resistance. At the same time, the high ionic conductivity of the fast ion conductor material itself can act as a "bridge" for lithium-ion transport, significantly reducing the ion transport impedance at the interface. More importantly, the dense structure of this nanoscale modification layer can act as a physical barrier, effectively isolating the lithium-rich manganese-based cathode material from the sulfide solid electrolyte, further suppressing side reactions between the lithium-rich manganese-based cathode material and the sulfide solid electrolyte, reducing the generation of high-resistance byproducts, avoiding the formation of a "space charge layer" that depletes lithium ions, and reducing the risk of mechanical failure and contact loss caused by rigid contact.

[0050] In some embodiments, the hard grinding balls are made of any one or a combination of at least two of alumina, zirconium oxide, or silicon nitride. Hard grinding balls possess high hardness, excellent wear resistance, and extremely low wear rate during high-speed grinding, thus minimizing the introduction of foreign contaminants.

[0051] In some embodiments, the average diameter of the first hard grinding ball is 6mm to 10mm, for example, it can be 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm or 10mm.

[0052] In some embodiments, the average diameter of the second hard grinding ball is 2mm to 4mm, for example, it can be 2mm, 2.5mm, 3mm, 3.5mm or 4mm.

[0053] In some embodiments, the mass ratio of the first hard grinding ball to the second hard grinding ball is (1.25~3):1, for example, it can be 1.25:1, 1.5:1, 1.75:1, 2:1, 2.25:1, 2.5:1, 2.75:1, or 3:1. This invention utilizes a combination of larger diameter hard grinding balls and smaller diameter grinding balls. The larger diameter grinding balls provide high impact force, breaking up large particles and introducing lattice defects, while the smaller diameter grinding balls fill the gaps, enhancing the uniformity of the mixing and grinding. If there are too many large diameter grinding balls, the impact force will be too strong, leading to excessive refinement or even amorphization of the raw material particles, making it impossible to obtain a lithium-rich manganese-based cathode material with a good lattice structure. If there are too many large and small diameter grinding balls, and the large diameter grinding balls are too small, the impact force will be insufficient, making it difficult to effectively generate defects and failing to create sufficient ion diffusion channels.

[0054] In some embodiments, the ball-to-material ratio for ball milling activation is (4~20):1, for example, it can be 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1, or 20:1. In this invention, the ball-to-material ratio refers to the ratio of the mass of the hard grinding balls to the total mass of the lithium-rich manganese-based precursor, lithium source, and fast ion conductor material. The ball-to-material ratio directly affects the intensity of ball milling activation. If the ball-to-material ratio is too low, i.e., the amount of hard grinding balls is too small, the impact energy is insufficient, resulting in limited effects on particle refinement and defect introduction; while if the ball-to-material ratio is too high, too many hard grinding balls will result in excessive impact energy, leading to over-grinding of the sample and generating excessively high surface energy, which is detrimental to subsequent sintering.

[0055] In some embodiments, the ball milling speed for activation is 100 rpm to 450 rpm, for example, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, or 450 rpm. In this invention, the ball milling speed is matched with the ball-to-material ratio and the size of the hard grinding balls, working synergistically to achieve the effects of raw material refinement and close mixing, as well as introducing lattice defects. If the ball milling speed is too low, sufficient impact and shear force cannot be provided, resulting in poor ball milling activation; if the ball milling speed is too high, it will lead to excessive particle breakage.

[0056] In some embodiments, the ball milling activation time is 1 hour to 20 hours, for example, 1 hour, 3 hours, 5 hours, 7 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, or 20 hours. If the ball milling activation time is too short, the activation is insufficient, leading to inadequate formation of defects and diffusion channels; if the ball milling activation time is too long, it will cause excessive nano-sizing of particles, a surge in surface activity, and an increased likelihood of abnormal grain growth and severe agglomeration during subsequent sintering, which in turn reduces the ionic conductivity and tap density of the material.

[0057] In some embodiments, the mass ratio of the lithium-rich manganese-based precursor to the fast ion conductor material is 100:(0.2~2), for example, 100:0.2, 100:0.4, 100:0.6, 100:0.8, 100:1, 100:1.2, 100:1.4, 100:1.6, 100:1.8, or 100:2. This mass ratio is beneficial for achieving a balance between the modification effect and the intrinsic properties of the material. When the mass ratio of the fast ion conductor material is too small, it is difficult to form a completely covered nano-modification layer on the particle surface, and the modification effect is not obvious; while when the mass ratio of the fast ion conductor material is too large, excessive ion doping may cause lattice distortion, which may reduce the overall ionic conductivity of the material.

[0058] In some embodiments, the molar ratio of Li in the lithium source to the transition metal element TM in the lithium-rich manganese-based precursor is Li / TM = 1.5~1.54, for example, it can be 1.5, 1.51, 1.52, 1.53 or 1.54. In this invention, the molar amount of the transition metal element TM is the total molar amount of Mn, Ni, Co and M in the lithium-rich manganese-based precursor.

[0059] In some embodiments, the lithium-rich manganese-based precursor includes Mn a Ni b Co c M d (OH)2 and / or Mn a Ni b Co c M d CO3, a+b+c+d=1, a>b, and a>0.5, M is one or more elements selected from Co, Al, Mo, Mg, Fe, Nb, W, Zr, and Ti.

[0060] In some embodiments, the lithium source includes any one or a combination of at least two of lithium carbonate, lithium hydroxide, lithium nitrate, lithium sulfate, or lithium acetate.

[0061] In some embodiments, the sintering atmosphere includes air.

[0062] In some embodiments, the heating rate of the sintering is 2°C / min to 5°C / min, for example, it can be 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min or 5°C / min.

[0063] In some embodiments, the sintering temperature is 800°C to 980°C, for example, it can be 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 920°C, 940°C, 960°C or 980°C.

[0064] In some embodiments, the sintering time is 8h to 20h, for example, it can be 8h, 10h, 12h, 14h, 16h, 18h or 20h.

[0065] In another specific embodiment, the present invention provides a lithium-rich manganese-based cathode material, which is prepared by the preparation method described in one of the preceding specific embodiments.

[0066] In yet another embodiment, the present invention provides a positive electrode sheet comprising the lithium-rich manganese-based positive electrode material described in another preceding embodiment; the positive electrode sheet further comprises a sulfide solid electrolyte.

[0067] In some embodiments, the sulfide solid electrolyte includes Li3PS4 and Li7P3S. 11 Any one or a combination of at least two of Li6PS5Cl or Li6PS5Br.

[0068] In yet another embodiment, the present invention provides a sulfide solid-state battery, the sulfide solid-state battery comprising a positive electrode as described in yet another embodiment above.

[0069] 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.

[0070] Example 1

[0071] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, the method comprising:

[0072] (1) Mix Mn according to a ball-to-material ratio of 8:1. 0.66 Ni 0.17 Co 0.17 (OH)2, lithium carbonate, LiNbO3, and alumina grinding beads, Mn 0.66 Ni 0.17 Co 0.17 The mass ratio of (OH)₂ to LiNbO₃ is 100:2. The Li and Mn groups in lithium carbonate... 0.66 Ni 0.17 Co 0.17 The molar ratio of Mn, Ni and Co in (OH)2 is 1.52. The alumina grinding balls include first alumina grinding balls with an average diameter of 8 mm and second alumina grinding balls with an average diameter of 3 mm. The mass ratio of the first alumina grinding balls to the second alumina grinding balls is 3:1. The grinding speed is set to 300 rpm, and the grinding activation is carried out for 3 hours to obtain the mixture.

[0073] (2) Under air atmosphere, the mixture is heated to 900°C at a heating rate of 3°C / min and sintered for 12 hours to obtain the lithium-rich manganese-based cathode material.

[0074] Example 2

[0075] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, the method comprising:

[0076] (1) Mix Mn according to a ball-to-material ratio of 4:1. 0.66 Ni 0.17 Co 0.17 CO3, lithium hydroxide, LiZrO3, and zirconium oxide grinding beads, Mn 0.66 Ni 0.17 Co 0.17 The mass ratio of CO3 to LiZrO3 is 100:1. The Li and Mn groups in lithium hydroxide... 0.66 Ni 0.17 Co 0.17 The molar ratio of transition metal element TM in CO3 is Li / TM=1.5. The zirconia grinding balls include a first zirconia grinding ball with an average diameter of 6 mm and a second zirconia grinding ball with an average diameter of 2 mm. The mass ratio of the first zirconia grinding ball to the second zirconia grinding ball is 1.25:1. The ball milling speed is set to 450 rpm, and the ball milling activation is carried out for 1 hour to obtain the mixture.

[0077] (2) Under air atmosphere, the mixture is heated to 800°C at a heating rate of 2°C / min and sintered for 20h to obtain the lithium-rich manganese-based cathode material.

[0078] Example 3

[0079] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, the method comprising:

[0080] (1) Mix Mn according to a ball-to-material ratio of 20:1. 0.75 Ni 0.15 Co 0.1 (OH)2, nitric acid, Li3PO4-ZrO2 complex, and silicon nitride ball milling beads, Mn 0.75 Ni 0.15 Co 0.1 The mass ratio of (OH)₂ to the Li₃PO₄-ZrO₂ complex is 100:0.2, and the mass ratio of Li₃PO₄ to ZrO₂ in the Li₃PO₄-ZrO₂ complex is 1:2. The Li and Mn in the nitric acid solution... 0.75 Ni 0.15 Co 0.1The molar ratio of transition metal element TM in (OH)2 is Li / TM=1.52. The silicon nitride grinding balls include a first silicon nitride grinding ball with an average diameter of 10 mm and a second silicon nitride grinding ball with an average diameter of 4 mm. The mass ratio of the first silicon nitride grinding ball to the second silicon nitride grinding ball is 2:1. The grinding speed is set to 100 rpm, and the grinding activation is carried out for 20 h to obtain the mixture.

[0081] (2) Under air atmosphere, the mixture is heated to 980°C at a heating rate of 5°C / min and sintered for 8 hours to obtain the lithium-rich manganese-based cathode material.

[0082] Example 4

[0083] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material. Except for the mass ratio of the first alumina ball milling beads to the second alumina ball milling beads being 1:1, the rest is the same as in Example 1.

[0084] Example 5

[0085] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material. Except for the mass ratio of the first alumina ball milling beads to the second alumina ball milling beads being 1:3.5, the rest is the same as in Example 1.

[0086] Example 6

[0087] This embodiment provides a method for preparing lithium-rich manganese-based cathode material. Except for the ball-to-material ratio of 3:1 during ball milling activation, the rest is the same as in Example 1.

[0088] Example 7

[0089] This embodiment provides a method for preparing lithium-rich manganese-based cathode material. Except for the ball-to-material ratio of 22:1 during ball milling activation, the rest is the same as in Example 1.

[0090] Example 8

[0091] This embodiment provides a method for preparing lithium-rich manganese-based cathode material. Except for the ball milling speed of 500 rpm for ball milling activation, the rest is the same as in Example 1.

[0092] Comparative Example 1

[0093] This comparative example provides a method for preparing lithium-rich manganese-based cathode materials, except that only Mn is used. 0.66 Ni 0.17 Co 0.17 (OH)2, lithium carbonate and LiNbO3 are stirred and mixed evenly, but without ball milling activation, the rest is the same as in Example 1.

[0094] Comparative Example 2

[0095] This comparative example provides a method for preparing a lithium-rich manganese-based cathode material. Except for the grinding balls, which only include alumina grinding balls with an average diameter of 8 mm, the rest is the same as in Example 1.

[0096] Comparative Example 3

[0097] This comparative example provides a method for preparing a lithium-rich manganese-based cathode material. Except for replacing LiNbO3 with an equal mass of Nb2O5, the method is the same as in Example 1.

[0098] Performance testing:

[0099] The electrochemical performance of the lithium-rich manganese-based cathode materials prepared by the methods provided in all the above examples and comparative examples was tested when applied to sulfide solid-state batteries. The specific test methods are as follows:

[0100] (a) Preparation of sulfide solid-state battery: In an argon-filled glove box, Li6PS5Cl was weighed and poured into a mold, and pre-pressed to form a dense electrolyte sheet with a thickness of 60μm; then the top cover of the mold was opened, and lithium-rich manganese-based positive electrode material, Li6PS5Cl and conductive carbon black, which had been uniformly mixed in a mass ratio of 1:0.3:0.05, were added to one side of the electrolyte sheet; next, a lithium indium alloy negative electrode was placed on the other side of the electrolyte sheet; finally, the mold was closed, and cold-pressed at 200MPa and held for 10 minutes to form a tight solid-solid contact between the positive electrode layer, the electrolyte membrane layer and the negative electrode layer, thus completing the assembly of the all-sulfide solid-state battery.

[0101] (b) The sulfide solid-state battery was subjected to 0.1C charge-discharge at 45°C and a voltage range of 1.4V to 4.2V. The initial efficiency and 0.1C discharge specific capacity were tested. Then, it was charged and discharged for 50 cycles at a 0.1C rate to test the cycle capacity retention. The test results are shown in Table 1. The initial charge-discharge curves of the sulfide solid-state batteries prepared in Example 1 and Comparative Example 1 are shown in Table 1. Figure 1 .

[0102] Table 1

[0103]

[0104] In summary, based on the test results in Table 1, this invention achieves the refinement and uniform, close mixing of raw materials through ball milling activation. It also introduces defects into the lattice of the lithium-rich manganese-based precursor, facilitating the diffusion of doped ions from the fast-ion conductor into the lattice. This allows for bulk doping of the lithium-rich manganese-based cathode material while simultaneously forming a nanoscale modification layer on its surface. This results in the lithium-rich manganese-based cathode material possessing high ionic conductivity, structural stability, and compatibility with sulfide solid electrolytes at its interface. This fundamentally optimizes solid-solid interface contact and ion transport kinetics, leading to a sulfide solid-state battery with high discharge specific capacity and significantly improved initial efficiency.

[0105] Based on the test results of Examples 1 and 4 to 5, the mass ratio of the first alumina grinding ball to the second alumina grinding ball affects the balance between the impact force provided by the large-diameter first alumina grinding ball and the grinding effect provided by the small-diameter second alumina grinding ball during the ball milling activation process. If the mass ratio is too large or too small, it is impossible to achieve effective refinement and tight bonding of the raw materials, and it is impossible to introduce suitable lattice defects into the lithium-rich manganese-based cathode material, resulting in a decline in the performance of the lithium-rich manganese-based cathode material.

[0106] According to the test results of Examples 1, 6 and 7, if the ball-to-material ratio of ball milling activation is too small, the refining effect will be unsatisfactory and sufficient lattice defects cannot be introduced. If the ball-to-material ratio is too large, the material will be over-refined and the surface energy will be too high, which is not conducive to subsequent sintering and will degrade the performance of lithium-rich manganese-based cathode materials.

[0107] According to the test results of Examples 1 and 8, the ball milling speed was too high, which was not matched with the ball-to-material ratio and the size of the hard grinding balls. In addition, the impact force was too large, which led to excessive crushing of the raw materials and deterioration of their performance.

[0108] Based on the test results of Example 1, Comparative Examples 1 and 2, if only the raw materials are mixed without ball milling activation, or if only one type of ball milling bead is used, the ball milling activation process lacks the synergistic effect of impact and grinding. Therefore, it is impossible to simultaneously achieve the goals of refining and tightly binding the raw materials, as well as introducing crystal nucleation defects. This results in the doping elements in the fast ion conductor failing to effectively diffuse into the crystal lattice, failing to achieve bulk strengthening of the lithium-rich manganese-based cathode material, and failing to form a dense nano-modification layer on the surface of the lithium-rich manganese-based cathode material. Consequently, it is impossible to optimize the solid-solid interface contact and ion transport kinetics, resulting in poor material performance.

[0109] Based on the test results of Example 1 and Comparative Example 3, this application selects fast ion conductors as additives. Compared with traditional oxide additives, they are easier to diffuse into lithium-rich manganese-based lattices. Moreover, fast ion conductors have lower melting points and are less likely to form residual phases. The prepared lithium-rich manganese-based cathode has a more complete lattice structure and better performance.

[0110] 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 method for preparing a lithium-rich manganese-based cathode material, characterized in that, The preparation method includes: A mixture of lithium-rich manganese-based precursor, lithium source, fast ion conductor material, and hard ball milling beads is ball-milled and activated to obtain a mixture; the mixture is then sintered to obtain the lithium-rich manganese-based cathode material. The fast ion conductor material includes any one or a combination of at least two of LiNbO3, Li2ZrO3, LiTaO3, or Li3PO4-ZrO2 composite. The hard grinding balls include at least a first hard grinding ball and a second hard grinding ball, wherein the average diameter of the first hard grinding ball is 6mm to 10mm and the average diameter of the second hard grinding ball is 2mm to 4mm; the mass ratio of the first hard grinding ball to the second hard grinding ball is (1.25 to 3):

1.

2. The preparation method according to claim 1, characterized in that, The hard grinding balls are made of any one or a combination of at least two of alumina, zirconium oxide, or silicon nitride.

3. The preparation method according to claim 1, characterized in that, The ball-to-material ratio for ball milling activation is (4~20):1; And / or, the ball milling speed for ball mill activation is 100 rpm to 450 rpm; And / or, the ball milling activation time is 1h to 20h.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the lithium-rich manganese-based precursor to the fast ion conductor material is 100:(0.2~2); And / or, the molar ratio of Li in the lithium source to the transition metal element TM in the lithium-rich manganese-based precursor is Li / TM = 1.5~1.

54.

5. The preparation method according to claim 1, characterized in that, The lithium-rich manganese-based precursor includes Mn a Ni b Co c M d (OH)2 and / or Mn a Ni b Co c M d CO3, a+b+c+d=1, a>b, and a>0.5, M is one or more elements selected from Co, Al, Mo, Mg, Fe, Nb, W, Zr, and Ti; And / or, the lithium source includes any one or a combination of at least two of lithium carbonate, lithium hydroxide, lithium nitrate, lithium sulfate, or lithium acetate.

6. The preparation method according to claim 1, characterized in that, The sintering atmosphere includes air; And / or, the heating rate of the sintering is 2℃ / min to 5℃ / min; And / or, the sintering temperature is 800℃~980℃; And / or, the sintering time is 8h~20h.

7. A lithium-rich manganese-based cathode material, characterized in that, The lithium-rich manganese-based cathode material is prepared by the preparation method described in any one of claims 1 to 6.

8. A positive electrode plate, characterized in that, The positive electrode includes the lithium-rich manganese-based positive electrode material as described in claim 7; the positive electrode also includes a sulfide solid electrolyte.

9. The positive electrode sheet as described in claim 8, characterized in that, The sulfide solid electrolyte includes Li3PS4 and Li7P3S. 11 Any one or a combination of at least two of Li6PS5Cl or Li6PS5Br.

10. A sulfide solid-state battery, characterized in that, The sulfide solid-state battery includes the positive electrode as described in claim 8 or 9.

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