Lithium-rich manganese-based cathode materials and their preparation methods, cathode sheets, and secondary batteries

Abstract

This application relates to a lithium-rich manganese-based cathode material, which exhibits high initial coulombic efficiency and specific capacity, along with good storage performance and low gas production. This application also relates to a method for preparing the lithium-rich manganese-based cathode material, which utilizes organic acids and / or their acidic salts to acid-treat the matrix powder, ensuring stable synthesis of a lithium-rich manganese-based cathode material that combines high specific capacity, high initial coulombic efficiency, improved storage performance, and reduced gas production.

Description

Technical Field

[0001] This application belongs to the field of secondary battery technology, specifically relating to a lithium-rich manganese-based cathode material and its preparation method, cathode sheet, secondary battery, battery module, battery pack and power device. Background Technology

[0002] With technological advancements, clean energy sources such as batteries are gradually replacing traditional fossil fuels, providing power for various applications. Lithium-rich manganese-based cathode materials are considered an ideal choice for next-generation high-energy-density power lithium batteries. However, existing lithium-rich manganese-based cathode materials generally suffer from low initial coulombic efficiency and specific capacity, poor storage performance, and high gas production.

[0003] Therefore, there is a need to develop a lithium-rich manganese-based cathode material that has high initial coulombic efficiency and specific capacity, while also exhibiting good storage performance and low gas production. Summary of the Invention

[0004] In view of the problems existing in the background technology, this application provides a lithium-rich manganese-based cathode material, which has high initial coulombic efficiency and specific capacity, while having good storage performance and low gas production.

[0005] The lithium-rich manganese-based cathode material provided in the first aspect of this application includes a matrix powder. The chemical formula of the matrix powder is Li[Li] x Ni a Co b Mn c M d O2, where x+a+b+c+d=1, x>0, c>0, 0<b<0.1, and M includes one or more of V, Nb, Ta, Cr, Mo, B, Al, Ti, Zr, Mg, Ce, Fe, and Sn. The specific surface area of ​​the matrix powder is 0.6-4m². 2 / g.

[0006] In the technical solution of this application embodiment, by controlling the specific surface area of ​​the matrix powder within the above-mentioned range, the first coulombic efficiency and specific capacity of lithium-rich manganese-based cathode materials can be improved, and the storage performance and gas generation problem can be improved.

[0007] In some embodiments, according to the first aspect, a first example of the first aspect is provided, wherein the specific surface area of ​​the matrix powder is 1.0 to 1.7 m². 2 / g.

[0008] Optimizing the specific surface area can help to further improve the initial coulombic efficiency and specific capacity of lithium-rich manganese-based cathode materials, as well as improve storage performance and address gas generation issues.

[0009] In some embodiments, according to the first aspect, a second example of the first aspect is provided, wherein the residual alkali content on the surface of the matrix powder is 550-1200 ppm based on the total weight of the matrix powder. The residual lithium content on the surface of the matrix powder is 300-1000 ppm based on the total weight of the matrix powder.

[0010] Reducing the residual alkali and residual lithium content is beneficial to improving the specific capacity and initial coulombic efficiency of lithium-rich manganese-based cathode materials.

[0011] In some embodiments, according to the first aspect, a third example of the first aspect is provided, wherein the lithium-rich manganese-based cathode material further includes: a coating layer coated on the surface of the matrix powder. The coating layer includes one or more coating elements selected from Zr, F, B, and Al.

[0012] By setting a coating layer on the surface of the matrix powder, the surface of the matrix powder can be modified, avoiding poor storage performance, high gas production and poor circulation performance caused by a large number of oxygen defects on the surface of the matrix powder.

[0013] In some embodiments, according to the first aspect, a fourth example of the first aspect is proposed, wherein the content of each coating element may be 0 to 10,000 ppm based on the total weight of the matrix powder, and the total content of the coating elements is greater than 0.

[0014] Optimizing the content of coating elements can further enhance the modification effect on the substrate surface, improve surface oxygen defects, improve the storage performance of lithium-rich manganese-based cathode materials, and reduce gas production.

[0015] In some embodiments, according to the first aspect, a fifth example of the first aspect is proposed, wherein the thickness of the coating layer is 0.1 to 3 μm.

[0016] Optimizing the thickness of the coating layer can improve the initial coulombic efficiency and specific capacity of lithium-rich manganese-based cathode materials, while reducing gas production.

[0017] In some embodiments, according to the first aspect, a sixth example of the first aspect is provided, wherein the coating elements include Zr, F, and B. Preferably, the molar ratio of Zr, F, and B is 1:(3.5-4.5):(0.01-0.5). Alternatively, the coating elements include Zr, F, and Al. Preferably, the molar ratio of Zr, F, and Al is 1:(3.5-4.5):(0.01-0.5).

[0018] The coating elements Zr, F, B, and Al all play effective roles in improving the initial coulombic efficiency, specific capacity, and storage performance of cathode materials, as well as reducing gas production. However, each of these four elements has its own distinct characteristics. For example, Zr can enhance ionic conductivity and improve the stability of the material during cycling; F can improve oxygen defects on the surface of the matrix powder and prevent electrolyte corrosion of the matrix powder; B can activate the lithium-containing rock salt phase on the surface of the matrix powder, increasing specific capacity; and Al can form a dense passivation layer by dotted coating on the surface of the matrix powder, improving gas production. The combined use of Zr, F, and B, or the combined use of Zr, F, and Al, has a more significant effect on improving initial coulombic efficiency, specific capacity, and storage performance, as well as reducing gas production.

[0019] In some embodiments, according to the first aspect, a seventh example of the first aspect is provided, wherein the specific surface area of ​​the lithium-rich manganese-based cathode material is 0.5-4 m². 2 / g.

[0020] After coating the surface of the matrix powder, by controlling the specific surface area of ​​the lithium-rich manganese-based cathode material within the above-mentioned range, it can promote the specific capacity and at the same time avoid the serious side reactions caused by excessive specific surface area, which would exacerbate capacity decay.

[0021] In some embodiments, according to the first aspect, an eighth example of the first aspect is proposed, wherein the lithium-rich manganese-based cathode material satisfies at least one of the following conditions (1)-(3):

[0022] (1) The oxygen defect index of the lithium-rich manganese-based cathode material is above 1.96. Where I101 and I102 represent the intensity values ​​of the (101) crystal plane diffraction peak and the (102) crystal plane diffraction peak of the lithium-rich manganese-based cathode material in the XRD diffraction pattern, respectively;

[0023] (2) The micro-stress of the lithium-rich manganese-based cathode material is 0.1% to 2%, and the micro-stress = (β) hkl *Cosθ hkl ) / (4sinθ hkl ), where θ hkl β represents the diffraction angle of the crystal plane of the lithium-rich manganese-based cathode material (hkl) described in the XRD diffraction pattern. hkl The full width at half maximum (FWHM) of the crystal plane of the lithium-rich manganese-based cathode material (hkl) described in the XRD diffraction pattern;

[0024] (3) The particle size distribution of the lithium-rich manganese-based cathode material is SPAN = (Dv90-Dv10) / Dv50, and SPAN is in the range of 0.7 to 1.8.

[0025] When the oxygen defect index of lithium-rich manganese-based cathode materials is within the above range, it can effectively reduce the accelerated oxygen diffusion caused by oxygen defects, reduce gas production, and improve cycle and storage performance.

[0026] When the micro-stress of lithium-rich manganese-based cathode material is within the above range, it can prevent particle pulverization caused by particle cracks generated by residual stress during cycling from the inside to the surface, thereby avoiding battery performance degradation and safety hazards.

[0027] When the particle size distribution of lithium-rich manganese-based cathode materials is within the above range, space utilization can be improved, which is beneficial to the specific capacity.

[0028] The second aspect of this application provides a method for preparing a lithium-rich manganese-based cathode material, comprising the following steps:

[0029] The matrix powder is acid-treated with an acidic solution. The acidic solution includes organic acids and / or their acidic salts. The chemical formula of the matrix powder is Li[Li]. x Ni a Co b Mn c M d O2, where x+a+b+c+d=1, x>0, c>0, 0<b<0.1, and M includes one or more of V, Nb, Ta, Cr, Mo, B, Al, Ti, Zr, Mg, Ce, Fe and Sn.

[0030] The acid treatment method of this application can ensure the stable synthesis of lithium-rich manganese-based cathode materials that combine high specific capacity, high initial coulombic efficiency, improved storage performance, and reduced gas production.

[0031] In some embodiments, according to the second aspect, a first example of the second aspect is provided, wherein the pH value of the acidic solution is ≥2 and <7. Preferably, the organic acid includes citric acid. The acidic salt includes one or more of ammonium citrate, ammonium hydrogen citrate, and diammonium hydrogen citrate. Preferably, the acid treatment time is 0.25 to 4 hours.

[0032] Optimizing the pH value of the acidic solution, the types of organic acids and acidic salts can improve the effectiveness of acid treatment, further enhance the initial coulombic efficiency and specific capacity of lithium-rich manganese-based cathode materials, improve storage performance, and reduce gas production.

[0033] In some embodiments, according to the second aspect, a second example of the second aspect is provided, wherein the preparation method further includes: mixing the acid-treated matrix powder with a coating material and sintering. The coating material includes one or more coating elements selected from Zr, F, B, and Al.

[0034] Research has shown that acid treatment can etch the surface of the matrix powder, resulting in oxygen defects on the surface and affecting performance such as circulation, storage, and gas generation. The inventors solved the above problems by coating and modifying the surface of the acid-treated matrix powder.

[0035] In some embodiments, according to the second aspect, a third example of the second aspect is provided, wherein the coating material includes one or more of zirconium boride, zirconium oxide, zirconium fluoride, aluminum boride, aluminum oxide, aluminum fluoride, and boric acid.

[0036] The inventors noted that excessively high coating temperatures (>500℃) can easily cause the spinel structure of defects on the matrix powder surface to transform into rock salt and lithium-rich phases, which in turn leads to a decrease in initial coulombic efficiency and specific capacity. Therefore, it is necessary to use coating materials that can melt at low temperatures. Zirconium boride, zirconium oxide, zirconium fluoride, aluminum boride, alumina, aluminum fluoride, and boric acid are all coating materials with melting temperatures not exceeding 500℃, which is more conducive to improving initial coulombic efficiency and specific capacity, while also enabling surface coating modification.

[0037] In some embodiments, according to the second aspect, a fourth example of the second aspect is proposed, wherein the sintering temperature is 400-550°C and the sintering time is 8-12 hours.

[0038] Optimizing sintering temperature and time helps to form a uniform and dense coating layer, improves the coating and modification effect on the surface of the matrix powder, and is more conducive to improving circulation, storage, gas generation and other properties.

[0039] In some embodiments, according to the second aspect, a fifth example of the second aspect is proposed, wherein the acid-treated matrix powder is washed with water before being mixed with the coating material.

[0040] Acid treatment followed by water washing can remove residual impurities on the surface of the matrix powder and improve the stability of the surface and interface.

[0041] In some embodiments, according to the second aspect, a sixth example of the second aspect is proposed, wherein the matrix powder is prepared by a method comprising the following steps: mixing a hydroxide precursor, a Li source, an optional Mn source, an optional Co source, an optional Ni source and an optional M source, and sintering the mixture to obtain the matrix powder.

[0042] The above method can be used to prepare lithium-rich manganese-based matrix powder materials.

[0043] The third aspect of this application provides a positive electrode sheet, including the lithium-rich manganese-based positive electrode material of the first aspect of this application or the lithium-rich manganese-based positive electrode material obtained by the preparation method of the second aspect of this application.

[0044] The fourth aspect of this application provides a secondary battery, including the positive electrode sheet of the third aspect of this application.

[0045] The fifth aspect of this application provides a battery module, including the secondary battery of the fourth aspect of this application.

[0046] The sixth aspect of this application provides a battery pack, including a secondary battery according to the fourth aspect of this application or a battery module according to the fifth aspect of this application.

[0047] The seventh aspect of this application provides an electrical device, including at least one of the secondary battery of the fourth aspect of this application, the battery module of the fifth aspect of this application, and the battery pack of the sixth aspect of this application.

[0048] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0051] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0052] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0053] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0054] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0055] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0056] Explanation of reference numerals in the attached figures:

[0057] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0058] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing description of the drawings, are intended to cover non-exclusive inclusion.

[0060] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0061] In this description, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more (including two).

[0062] In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists, A and B exist simultaneously, and B exists.

[0063] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0064] The foregoing description of this invention is not intended to describe every disclosed embodiment or implementation. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are merely representative and should not be construed as exhaustive.

[0065] With technological advancements, clean energy sources such as batteries are gradually replacing traditional fossil fuels, providing power for various applications. Cathode materials are a crucial component of batteries and also constitute the largest proportion of their cost. Among existing cathode materials, lithium-rich manganese-based cathode materials boast a discharge specific capacity as high as 300 mAh / g, approximately twice that of currently commercialized lithium iron phosphate and ternary cathode materials. Lithium-rich manganese-based cathode materials are considered an ideal choice for next-generation high-energy-density power lithium batteries. However, existing lithium-rich manganese-based cathode materials generally suffer from low initial coulombic efficiency and specific capacity, as well as poor storage performance and high gas production.

[0066] To address the aforementioned issues, the inventors, through in-depth research, designed a lithium-rich manganese-based cathode material comprising a matrix powder. By controlling the specific surface area of ​​this matrix powder within a certain range, the specific capacity of the cathode material was effectively promoted, and the initial coulombic efficiency of the cathode material was improved. Furthermore, by controlling the specific surface area of ​​the matrix powder, excessive contact area between the surface and the electrolyte due to an excessively large specific surface area can be avoided, reducing side reactions and thus improving the storage performance and gas generation issues of the cathode material. The inventors also noted that lithium-rich manganese-based cathode materials are prone to oxygen defects, which are related to gas generation and storage performance. By controlling the specific surface area of ​​the matrix powder, surface oxygen defects can be reduced to a certain extent, improving storage performance and alleviating gas generation problems.

[0067] The technical solutions described in the embodiments of this application are applicable to lithium-rich manganese-based cathode materials, and also to the preparation process of lithium-rich manganese-based cathode materials, cathode plates using lithium-rich manganese-based cathode materials, secondary batteries using cathode plates, battery modules using secondary batteries, battery packs using secondary batteries or battery modules, and electrical devices using at least one of secondary batteries, battery modules, and battery packs.

[0068] Firstly, according to some embodiments of this application, this application provides a lithium-rich manganese-based cathode material. It comprises a matrix powder. The chemical formula of the matrix powder is Li[Li] x Ni a Co b Mn c M dO2, where x+a+b+c+d=1, x>0, c>0, 0<b<0.1, and M includes one or more of V, Nb, Ta, Cr, Mo, B, Al, Ti, Zr, Mg, Ce, Fe, and Sn. The specific surface area of ​​the matrix powder is 0.6-4m². 2 / g.

[0069] This application does not impose any special restrictions on the specific type of matrix powder. Any matrix powder that meets the above chemical formula can be used in this application and can achieve the purpose of this application.

[0070] In some embodiments, the specific surface area of ​​the matrix powder may be 1.0-1.7 m². 2 / g.

[0071] Optimizing the specific surface area can help to further improve the initial coulombic efficiency and specific capacity of lithium-rich manganese-based cathode materials, as well as improve storage performance and address gas generation issues.

[0072] In some specific embodiments, the specific surface area of ​​the matrix powder can be 1.0 m². 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g or 1.7m 2 / g. The specific surface area of ​​the matrix powder can be within the range formed by taking any two of the values ​​listed above as endpoints.

[0073] In some embodiments, the residual alkali content on the surface of the matrix powder can be 550-1200 ppm based on the total weight of the matrix powder. The residual lithium content on the surface of the matrix powder can be 300-1000 ppm based on the total weight of the matrix powder.

[0074] Reducing the residual alkali and residual lithium content is beneficial to improving the specific capacity and initial coulombic efficiency of lithium-rich manganese-based cathode materials.

[0075] In some specific embodiments, the residual alkali content on the surface of the matrix powder can be 550 ppm, 600 ppm, 650 ppm, 700 ppm, 750 ppm, 800 ppm, 850 ppm, 900 ppm, 950 ppm, 1000 ppm, 1050 ppm, 1100 ppm, 1150 ppm, or 1200 ppm. The residual alkali content on the surface of the matrix powder can be within a numerical range formed by using any two of the values ​​listed above as endpoints.

[0076] In some specific embodiments, the residual lithium content on the surface of the matrix powder can be 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, 550 ppm, 600 ppm, 650 ppm, 700 ppm, 750 ppm, 800 ppm, 850 ppm, 900 ppm, 950 ppm, or 1000 ppm. The residual lithium content on the surface of the matrix powder can be within a numerical range formed by using any two of the values ​​listed above as endpoints.

[0077] In some embodiments, the lithium-rich manganese-based cathode material further includes a coating layer coated on the surface of the matrix powder. The coating layer includes one or more coating elements selected from Zr, F, B, and Al.

[0078] By applying a coating layer to the surface of the matrix powder, the surface of the matrix powder can be modified, avoiding poor storage performance, high gas production, and poor cycle performance caused by a large number of oxygen defects on the matrix powder surface. As coating elements, Zr, F, B, and Al can all play an effective role in improving the initial coulombic efficiency, specific capacity, and storage performance of the cathode material, as well as reducing gas production.

[0079] In some embodiments, the content of each coating element may be 0 to 10,000 ppm based on the total weight of the matrix powder, and the total content of the coating elements is greater than 0.

[0080] Optimizing the content of coating elements can further enhance the modification effect on the substrate surface, improve surface oxygen defects, improve the storage performance of lithium-rich manganese-based cathode materials, and reduce gas production.

[0081] Preferably, the content of each coating element can be 100-5000 ppm, based on the total weight of the matrix powder. The content of the coating element reflects the amount of coating material used, and thus affects the coating thickness. Too high a content of coating elements will result in an excessively thick coating, which is not conducive to lithium-ion insertion / extraction; too low a content of coating elements will result in poor coating effect and insignificant improvement to the material.

[0082] In some specific embodiments, the contents of the coating elements Zr, F, B, and Al can be independently 100 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, or 5000 ppm. The contents of the coating elements Zr, F, B, and Al can be independently within a numerical range formed by using any two of the values ​​listed above as endpoints.

[0083] In some embodiments, the total content of all coated elements can be 0 to 20,000 ppm, and the total content of coated elements is greater than 0. For example, the total content of all coated elements can be 100-5,000 ppm or 500-5,000 ppm.

[0084] In some embodiments, the thickness of the coating layer may be 0.1 to 3 μm.

[0085] When the coating thickness is within the above-mentioned range, it is beneficial to improve the initial coulombic efficiency and specific capacity of lithium-rich manganese-based cathode materials and reduce gas production. Excessive coating thickness is detrimental to improving battery energy density; insufficient coating thickness results in inadequate surface modification of the substrate powder, failing to effectively improve the initial coulombic efficiency, specific capacity, and storage performance of the cathode material, and thus hindering gas production. A reasonable coating thickness can fully function as a protective layer, mitigating side reactions between the cathode material and the electrolyte, while simultaneously avoiding adverse effects on lithium-ion insertion / extraction.

[0086] In some specific embodiments, the thickness of the coating layer can be 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm. The thickness of the coating layer can be within a numerical range formed by using any two of the values ​​listed above as endpoints.

[0087] In some embodiments, the coating elements include Zr, F, and B. Preferably, the molar ratio of Zr, F, and B is 1:(3.5-4.5):(0.01-0.5). Alternatively, the coating elements include Zr, F, and Al. Preferably, the molar ratio of Zr, F, and Al is 1:(3.5-4.5):(0.01-0.5).

[0088] The coating elements Zr, F, B, and Al can all play an effective role in improving the initial coulombic efficiency, specific capacity, and storage performance of cathode materials, as well as reducing gas production. However, each of these four elements has its own prominent characteristics. For example, Zr can improve ionic conductivity and enhance the stability of the material during cycling; F can improve oxygen defects on the surface of the matrix powder and prevent electrolyte corrosion of the matrix powder; B can activate the lithium-containing rock salt phase on the surface of the matrix powder, thereby increasing the specific capacity; and Al can form a dense passivation layer by dotted coating on the surface of the matrix powder, thus improving gas production. The combined use of Zr, F, and B, or the combined use of Zr, F, and Al, has a more significant effect on improving the initial coulombic efficiency, specific capacity, and storage performance, as well as reducing gas production.

[0089] In some specific embodiments, the molar ratio of Zr, F, and B can be 1:(3.8-4.2):(0.01-0.1), 1:(3.8-4.2):(0.1-0.3), 1:(3.8-4.2):(0.3-0.5), or 1:(3.8-4.2):(0.2-0.4). Preferably, the molar ratio of Zr, F, and B can be 1:4:(0.01-0.5), 1:4:(0.01-0.1), 1:4:(0.1-0.3), 1:4:(0.3-0.5), or 1:4:(0.2-0.4).

[0090] In some specific embodiments, the molar ratio of Zr, F, and Al can be 1:(3.8-4.2):(0.01-0.1), 1:(3.8-4.2):(0.1-0.3), 1:(3.8-4.2):(0.3-0.5), or 1:(3.8-4.2):(0.2-0.4). Preferably, the molar ratio of Zr, F, and Al can be 1:4:(0.01-0.5), 1:4:(0.01-0.1), 1:4:(0.1-0.3), 1:4:(0.3-0.5), or 1:4:(0.2-0.4).

[0091] When the molar ratios of Zr, F, and B, and Zr, F, and Al are within the aforementioned ranges, it is beneficial to improve the initial coulombic efficiency, specific capacity, and storage performance, while reducing gas production. The molar ratios between elements are related to the element content, which in turn is related to the amount of coating material used, thus affecting the coating thickness. Therefore, by controlling the element molar ratios, the coating thickness is indirectly controlled. A reasonable coating thickness is beneficial to improving the initial coulombic efficiency and specific capacity of lithium-rich manganese-based cathode materials, and reducing gas production.

[0092] In some embodiments, the specific surface area of ​​the lithium-rich manganese-based cathode material is 0.5-4 m². 2 / g.

[0093] After coating the surface of the matrix powder, by controlling the specific surface area of ​​the lithium-rich manganese-based cathode material within the above-mentioned range, it can promote the specific capacity and at the same time avoid the serious side reactions caused by excessive specific surface area, which would exacerbate capacity decay.

[0094] In some specific embodiments, the specific surface area of ​​the lithium-rich manganese-based cathode material can be 0.5 m². 2 / g, 1m 2 / g, 1.5m 2 / g、2m 2 / g, 2.5m 2 / g、3m 2 / g, 3.5m 2 / g or 4m 2 / g. The specific surface area of ​​lithium-rich manganese-based cathode materials can be within the range of any two of the values ​​listed above as endpoints.

[0095] In some embodiments, the oxygen defect index of the lithium-rich manganese-based cathode material can be above 1.96. Where I101 and I102 represent the intensity values ​​of the (101) crystal plane diffraction peak and the (102) crystal plane diffraction peak of the lithium-rich manganese-based cathode material in the XRD diffraction pattern, respectively.

[0096] When the oxygen defect index of lithium-rich manganese-based cathode materials is within the above range, it can effectively reduce the accelerated oxygen diffusion caused by oxygen defects, reduce gas production, and improve cycle and storage performance.

[0097] In some specific embodiments, the oxygen defect index of the lithium-rich manganese-based cathode material can be 1.96-4, for example, 1.96-2, 2-2.5, 2.5-3, 3-3.5 or 3.5-4.

[0098] In some embodiments, the microstress of the lithium-rich manganese-based cathode material is 0.1% to 2%, and the microstress = (β) hkl *Cosθ hkl ) / (4sinθ hkl ), where θ hkl β represents the diffraction angle of the crystal plane of the lithium-rich manganese-based cathode material (hkl) described in the XRD diffraction pattern. hkl The full width at half maximum (FWHM) of the crystal plane of the lithium-rich manganese-based cathode material (hkl) described in the XRD diffraction pattern is shown.

[0099] When the micro-stress of lithium-rich manganese-based cathode material is within the above range, it can prevent particle pulverization caused by particle cracks generated by residual stress during cycling from the inside to the surface, thereby avoiding battery performance degradation and safety hazards.

[0100] Preferably, the microstress of the lithium-rich manganese-based cathode material can be 0.2% to 1%.

[0101] In some specific embodiments, the microstress of the lithium-rich manganese-based cathode material can be 0.1%-0.2%, 0.2%-0.4%, 0.4%-0.6%, 0.6%-0.8%, or 0.8%-1.0%.

[0102] 1.0%-1.2%, 1.2%-1.4%, 1.4%-1.6%, 1.6%-1.8%, or 1.8%-2.0%.

[0103] In some embodiments, the particle size distribution of the lithium-rich manganese-based cathode material is SPAN = (Dv90-Dv10) / Dv50, and SPAN is in the range of 0.7 to 1.8.

[0104] When the particle size distribution of lithium-rich manganese-based cathode materials is within the above range, space utilization can be improved, which is beneficial to the specific capacity.

[0105] In some specific embodiments, the particle size distribution (SPAN) of the lithium-rich manganese-based cathode material can be 0.7-0.9, 0.9-1.1, 1.1-1.3, 1.3-1.5, 1.5-1.7, or 1.7-1.8. Both excessively large and excessively small particle size distributions (SPAN) are detrimental to capacity utilization.

[0106] The second aspect of this application provides a method for preparing a lithium-rich manganese-based cathode material, comprising the following steps:

[0107] The matrix powder is acid-treated with an acidic solution. The acidic solution includes organic acids and / or their acidic salts. The chemical formula of the matrix powder is Li[Li]. x Ni a Co b Mn c M d O2, where x+a+b+c+d=1, x>0, c>0, 0<b<0.1, and M includes one or more of V, Nb, Ta, Cr, Mo, B, Al, Ti, Zr, Mg, Ce, Fe and Sn.

[0108] This application employs weakly acidic organic acids and / or their acidic salts for acid treatment. Compared to inorganic acids, organic acids and / or their acidic salts have a weaker etching effect on the substrate powder surface, which can prevent a significant increase in the specific surface area of ​​the substrate powder, reduce the presence of surface oxygen defects, thereby promoting the effective utilization of the cathode material's specific capacity, improving the initial coulombic efficiency of the cathode material, and improving storage performance and gas generation issues. Furthermore, acid treatment can remove residual alkali and lithium from the substrate powder surface, further improving the specific capacity and initial coulombic efficiency of the cathode material. Acid washing can remove residual lithium and alkali from the surface, pre-activating Li2MnO3 in the lithium-rich manganese-based cathode material, extracting Li2O from the material surface, leaving a structurally stable spinel-like structure. Through the 3D diffusion channels of the spinel-like structure, the lithium-ion insertion / extraction rate is enhanced, improving the specific capacity and initial coulombic efficiency. In addition, during the acid washing process, H... + / Li + Exchange can stabilize the surface structure of materials, improve material stability, and thus enhance gas generation and storage performance. Using the acid treatment method of this application, it is possible to ensure the stable synthesis of lithium-rich manganese-based cathode materials that possess high specific capacity, high initial coulombic efficiency, improved storage performance, and reduced gas generation. This method is simple to operate, highly reproducible, and conducive to large-scale industrial production.

[0109] In some embodiments, the pH value of the acidic solution may be ≥2 and <7, for example, it may be 2-3, 3-4, 4-5, 5-6 or 6-6.9.

[0110] In some embodiments, the organic acid includes citric acid. The acidic salt includes one or more of ammonium citrate, ammonium hydrogen citrate, and diammonium hydrogen citrate.

[0111] In some embodiments, the ratio of the volume of the acidic solution to the mass of the matrix powder (hereinafter referred to as the liquid-solid ratio) may be 10 to 40, for example, 10, 15, 20, 25, 30, 35 or 40, wherein the volume unit is mL and the mass unit is g.

[0112] In some embodiments, the acid treatment time can be 0.25 to 4 hours, for example, 0.25 hours, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0113] Optimizing the pH value of the acidic solution, the types of organic acids and acidic salts, the volume ratio of the acidic solution to the mass of the matrix powder, and the acid treatment time can improve the effect of acid treatment and further enhance the initial coulombic efficiency and specific capacity of lithium-rich manganese-based cathode materials.

[0114] In some embodiments, the preparation method further includes: mixing the acid-treated matrix powder with a coating material and sintering it. The coating material includes one or more coating elements selected from Zr, F, B, and Al.

[0115] Research has shown that acid treatment can etch the surface of the matrix powder, resulting in oxygen defects on the surface and affecting performance such as circulation, storage, and gas generation. The inventors solved the above problems by coating and modifying the surface of the acid-treated matrix powder.

[0116] In some embodiments, the coating material includes one or more of zirconium boride, zirconium oxide, zirconium fluoride, aluminum boride, aluminum oxide, aluminum fluoride, and boric acid.

[0117] The inventors noted that excessively high coating temperatures (>500℃) can easily cause the spinel structure of defects on the matrix powder surface to transform into rock salt and lithium-rich phases, which in turn leads to a decrease in initial coulombic efficiency and specific capacity. Therefore, it is necessary to use coating materials that can melt at low temperatures. Zirconium boride, zirconium oxide, zirconium fluoride, aluminum boride, alumina, aluminum fluoride, and boric acid are all coating materials with melting temperatures not exceeding 500℃, which is more conducive to improving initial coulombic efficiency and specific capacity, while also enabling surface coating modification.

[0118] In some embodiments, the sintering temperature can be 400-550℃ and the sintering time can be 8-12h.

[0119] Optimizing sintering temperature and time facilitates the formation of a uniform and dense coating layer, improving the coating and modification effect on the surface of the matrix powder, and further enhancing performance in cycling, storage, and gas generation. Excessively high sintering temperatures can lead to surface densification of lithium-rich manganese-based cathode materials, hindering capacity utilization; excessively low sintering temperatures hinder crystallization, resulting in low crystallinity. Conversely, excessively long sintering times can lead to overly large particle growth in lithium-rich manganese-based cathode materials; insufficient sintering times can result in incomplete growth.

[0120] In some specific embodiments, the sintering temperature may be 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, or 550℃. The sintering temperature can be within a range formed by using any two of the values ​​listed above as endpoints.

[0121] In some specific embodiments, the sintering time can be 8h, 9h, 10h, 11h, or 12h. The sintering time can be within a range formed by using any two of the values ​​listed above as endpoints.

[0122] Preferably, the acid-treated matrix powder and the coating material can be mixed for 5-15 hours (e.g., 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, or 15 hours), and then the mixture of matrix powder and coating material can be heated to the sintering temperature at a heating rate of 2-5 °C / min for sintering. The sintering atmosphere can be air.

[0123] After acid treatment, organic acids and / or their acidic salts may remain on the surface of the matrix powder. These substances are removed by volatilization at high temperature during sintering, leaving no impurities and improving the stability of the surface and interface.

[0124] In some embodiments, the acid-treated matrix powder is washed with water before being mixed with the coating material.

[0125] Acid treatment followed by water washing can remove residual acidic impurities from the surface of the matrix powder and improve the stability of the surface and interface.

[0126] In some embodiments, the matrix powder is prepared by a method comprising the following steps: mixing a hydroxide precursor, a Li source, an optional Mn source, an optional Co source, an optional Ni source, and an optional M source, followed by sintering to obtain the matrix powder.

[0127] The ratios of the hydroxide precursor, Li source, Co source, Mn source, Ni source, and M source are usually determined by referring to the proportions of each element in the matrix powder. The above method can be used to prepare lithium-rich manganese-based matrix powder materials.

[0128] In some embodiments, the ratio of the amount of Li element in the Li source to the total amount of metal elements in the Co source, Mn source, Ni source and M source (hereinafter referred to as the Li / Me molar ratio) can be (1.3-1.4):1, for example, it can be 1.3:1, 1.31:1, 1.32:1, 1.33:1, 1.34:1, 1.35:1, 1.36:1, 1.37:1, 1.38:1, 1.39:1 or 1.4:1.

[0129] Optimizing the Li / Me molar ratio is beneficial for capacity utilization. A molar ratio that is too small is not conducive to capacity release, while a molar ratio that is too large will cause blockage of lithium-ion diffusion channels, resulting in a decrease in capacity.

[0130] In some specific embodiments, the hydroxide precursor may include a low-cobalt hydroxide precursor, such as a Ni 0.33 Co 0.01 Mn 0.66 (OH)2, Ni 0.34 Mn 0.66 (OH)2, Ni 0.35 Mn 0.65 (OH)2, Ni 0.30 Mn 0.4 (OH)2, etc.

[0131] In some specific embodiments, the Li source can be a lithium-containing compound, including but not limited to one or more of LiOH·H2O, LiOH, Li2CO3, and Li2O.

[0132] In some specific embodiments, the Co source can be a cobalt-containing compound, including but not limited to CoOH, Co(OH)2, and CoO.

[0133] In some specific embodiments, the Mn source can be a manganese-containing compound, including but not limited to MnO, Mn3O4, MnC2O4·2H2O, and C4H6MnO4.

[0134] In some specific embodiments, the Ni source can be a nickel-containing compound, including but not limited to NiO, NiC4H6O4·4H2O, and NiC2O4·2H2O.

[0135] In some specific embodiments, the M source can be a compound containing the M element, such as one or more of the following: oxides containing the M element, nitrates containing the M element, and carbonates containing the M element.

[0136] In some specific embodiments, the hydroxide precursor, Li source, and Me source are mixed, and the resulting mixture is heated at a heating rate of 2–5 °C / min. The sintering temperature is controlled at 780–900 °C, for example, 780 °C, 790 °C, 800 °C, 810 °C, 820 °C, 830 °C, 840 °C, 850 °C, 860 °C, 870 °C, 88 °C, 890 °C, or 900 °C. The sintering time is controlled at 10–15 h, for example, 10 h, 11 h, 12 h, 13 h, 14 h, or 15 h. The sintering atmosphere can be air.

[0137] The third aspect of this application provides a positive electrode sheet, including the lithium-rich manganese-based positive electrode material of the first aspect of this application or the lithium-rich manganese-based positive electrode material obtained by the preparation method of the second aspect of this application.

[0138] The fourth aspect of this application provides a secondary battery, including the positive electrode sheet of the third aspect of this application.

[0139] The fifth aspect of this application provides a battery module, including the secondary battery of the fourth aspect of this application.

[0140] The sixth aspect of this application provides a battery pack, including a secondary battery according to the fourth aspect of this application or a battery module according to the fifth aspect of this application.

[0141] The seventh aspect of this application provides an electrical device, including at least one of the secondary battery of the fourth aspect of this application, the battery module of the fifth aspect of this application, and the battery pack of the sixth aspect of this application.

[0142] The secondary battery, battery module, battery pack, and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0143] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0144] [Positive electrode plate]

[0145] The positive electrode includes a positive current collector and a positive electrode film disposed on at least one surface of the positive current collector. The positive electrode film includes the lithium-rich manganese-based positive electrode material of the first aspect of this application or the lithium-rich manganese-based positive electrode material obtained by the preparation method according to the second aspect of this application.

[0146] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0147] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0148] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0149] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0150] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0151] [Negative electrode plate]

[0152] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0153] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0154] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0155] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0156] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0157] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0158] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0159] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0160] [Electrolytes]

[0161] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0162] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0163] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0164] In some embodiments, the solvent may include at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0165] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0166] [Isolation membrane]

[0167] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0168] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0169] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0170] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0171] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0172] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0173] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0174] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0175] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0176] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0177] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0178] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0179] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0180] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0181] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0182] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0183] The present invention will be further illustrated below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0184] Preparation of lithium-rich manganese-based cathode materials

[0185] Example 1

[0186] Weigh the low-cobalt hydroxide precursor Mn according to stoichiometric ratio. 0.66 Ni 0.33 Co 0.01 (OH)₂, LiOH·H₂O, and (NH₄)₆Mo₇O 12·4H2O, weighed raw materials and ball-milled zirconium beads are mixed in a drum-type ball mill mixer at a ball-to-material ratio of 60 to obtain a mixture. The Li / Me molar ratio (i.e., the ratio of the amount of Li element to the total amount of Co, Mn, Ni, and Mo in the cathode material) is 1.35. The mixture is then sintered in a muffle furnace at 800℃, a heating rate of 2℃ / min, and a sintering time of 10 hours in an air atmosphere. After sintering, the mixture is mechanically ground and sieved to obtain the matrix powder, the chemical formula of which is [missing information].

[0187] Li[Li 0.35 Ni 0.33 Co 0.01 Mo 0.05 Mn 0.61 O2.

[0188] Citric acid was dissolved in deionized water to prepare an acid solution with a pH of 2.57. The matrix powder was then weighed at a liquid-to-solid ratio of 15:1 (i.e., the volume of the acid solution to the mass of the matrix powder, with volume in mL and mass in g). The matrix powder was then placed in the acid solution and acid-washed with stirring for 0.5 h at a stirring rate of 900 r / min. After acid washing, the powder was filtered, rinsed with deionized water, filtered again, and then dried at 80℃ for 10 h. After mechanical grinding and sieving, the acid-treated matrix powder, i.e., the lithium-rich manganese-based cathode material, was obtained.

[0189] Example 2

[0190] The acid-treated matrix powder was prepared according to the method described in Example 1.

[0191] The raw material ratio was determined based on a theoretical total coating element content of 2000 ppm (i.e., the total content of all coating elements, based on the total weight of the matrix powder). The weighed acid-treated matrix powder (obtained from the previous step) and coating materials were mixed in a drum ball mill for 10 hours. The coating materials were ZrF4 and H3BO3, with a Zr:F:B molar ratio of 1:4:0.25. The mixture was then placed in a muffle furnace for secondary sintering at 450℃, a heating rate of 2℃ / min, and a sintering time of 10 hours. The sintering atmosphere was air. After sintering, the material was mechanically ground and sieved to obtain the coated lithium-rich manganese-based cathode material. (Note: The effects of acid treatment and secondary sintering on the weight of the matrix powder are negligible.)

[0192] Examples 3-25

[0193] Examples 3-25 were carried out according to the method described in Example 2, except that the parameters listed in Table 1 below are different from those in Example 2.

[0194] Comparative Example 1

[0195] Comparative Example 1 was carried out according to the method described in Example 2, except that acid treatment and coating sintering were not performed.

[0196] Comparative Example 2

[0197] Comparative Example 2 was carried out according to the method described in Example 2, except that after acid treatment, no coating was performed, but sintering was performed.

[0198] Comparative Example 3

[0199] Comparative Example 3 was carried out according to the method described in Example 2, except that acid treatment was not performed, but coating and sintering were performed.

[0200] Comparative Example 4

[0201] Comparative Example 4 was carried out according to the method described in Example 2, except that the parameters listed in Table 1 below are different from those in Example 2.

[0202] Comparative Example 5

[0203] Comparative Example 5 was carried out according to the method described in Example 2, except that the parameters listed in Table 1 below are different from those in Example 2.

[0204] Table 1

[0205]

[0206]

[0207]

[0208] Using the coated lithium-rich manganese-based cathode materials prepared in Examples 1-25 and Comparative Examples 1-5, full cells were prepared according to the following general preparation method.

[0209] The prepared coated lithium-rich manganese-based cathode material was premixed in a 5L stirred tank for 30 min, followed by a second dry mixing process of 30 min with conductive agent acetylene black (SP) and binder polyvinylidene fluoride (PVDF). Finally, N-methylpyrrolidone (NMP) solvent was added and the mixture was rapidly stirred under vacuum to form a slurry. The mass ratio of cathode material to acetylene black to PVDF was 96:2:2, and the solid content of the slurry was 70% by weight. The slurry was uniformly coated onto both sides of a 12μm thick aluminum foil. The coated electrode was then dried in an oven at 100℃ for half an hour. The cathode material loading of the electrode was 21.5 mg / cm³. 2 The removed electrode sheets are cold-pressed through rollers to obtain the positive electrode sheet.

[0210] The negative electrode active material, artificial graphite, hard carbon, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are thoroughly mixed in a deionized water solvent system at a weight ratio of 90:5:2:2:1. The mixture is then coated onto copper foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0211] Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in this solution to obtain the electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0212] A porous polyethylene polymer film is used as the separator. The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The resulting cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging, filled with the prepared basic electrolyte, and sealed to obtain a full cell.

[0213] Characterization and testing of lithium-rich manganese-based cathode materials and battery performance testing

[0214] 1. Specific surface area test of the matrix powder after acid treatment

[0215] The specific surface area of ​​the matrix powder was measured according to the gas adsorption BET method in GB / T 19587-2004. The test results are shown in Table 2 below.

[0216] 2. Test of residual alkali content in the matrix powder after acid treatment

[0217] The test was conducted according to GB / T 9736-2008, which specifies the potentiometric titration of free lithium. The test results are shown in Table 2 below.

[0218] 3. Test of residual lithium content in the matrix powder after acid treatment

[0219] The test was conducted according to GB / T 9736-2008, which specifies the potentiometric titration of free lithium. The test results are shown in Table 2 below.

[0220] 4. Test of total coated element content in the coating layer

[0221] The contents of Zr, F, B, and Al in the coating layer were tested according to EPA 6010D-2014 elemental analysis—inductively coupled plasma atomic emission spectrometry. The total content of coating elements is equal to the sum of the contents of each coating element. The test results are shown in Table 2 below.

[0222] 5. Coating thickness test

[0223] The thickness of the coating layer was measured using transmission electron microscopy (TEM). The test results are shown in Table 2 below.

[0224] 6. Oxygen defect index testing of lithium-rich manganese-based cathode materials

[0225] The oxygen defect index of the lithium-rich manganese-based cathode material was obtained by analyzing the diffraction peak intensities of the (101) and (102) crystal planes using XRD patterns and calculating according to the formula described above. The test results are shown in Table 2 below.

[0226] 7. Micro-stress testing of lithium-rich manganese-based cathode materials

[0227] The micro-stress of the lithium-rich manganese-based cathode material was obtained by analyzing the diffraction angle and full width at half maximum (FWHM) of the (hkl) crystal plane using XRD patterns, and calculated according to the formula described above. The test results are shown in Table 2 below.

[0228] 8. SPAN test of particle size distribution of lithium-rich manganese-based cathode material

[0229] Referring to GB / T 19077-2016 Particle Size Analysis by Laser Diffraction, the volume distribution particle sizes Dv10, Dv50, and Dv90 of the negative electrode active material were measured using a Mastersizer 3000 laser particle size analyzer. The particle size distribution SPAN was calculated using the formula described above, where Dv10 represents the particle size corresponding to a cumulative volume distribution percentage of 10%, Dv50 represents the particle size corresponding to a cumulative volume distribution percentage of 50%, and Dv90 represents the particle size corresponding to a cumulative volume distribution percentage of 90%. The test results are shown in Table 2 below.

[0230] 9. Specific surface area test of lithium-rich manganese-based cathode materials prepared in Examples 2-25

[0231] The specific surface area of ​​lithium-rich manganese-based cathode materials was measured according to the gas adsorption BET method in GB / T 19587-2004. The test results are shown in Table 2 below.

[0232] 10. First Coulombic Efficiency Test of Lithium-Rich Manganese-Based Cathode Material

[0233] Under a constant temperature environment of 25℃, (1) the sample was left to stand for 5 minutes; (2) it was charged at 0.1C to 4.55V; (3) it was charged at a constant voltage of 4.55V, and the charging capacity at this time was recorded as the initial charging capacity, denoted as C0; (4) it was left to stand for 5 minutes; (5) it was discharged at 0.1C to 2.5V, and the discharge capacity at this time was recorded as the initial specific capacity, denoted as D0. The initial specific capacity retention rate was calculated as: D0 / C0*100%. The test results are shown in Table 2 below.

[0234] 11. Specific capacity testing of lithium-rich manganese-based cathode materials

[0235] Under a constant temperature environment of 25℃, (1) let stand for 30 min; (2) charge to 4.5V at 0.05C; (3) let stand for 5 min; (4) discharge to 2.5V at 1 / 3C; (5) let stand for 5 min. The discharge capacity at this time is the initial specific capacity, denoted as D1. Repeat steps (2) to (5). The capacity after 300 cycles is denoted as D300, and the capacity retention rate after 300 cycles is calculated as: D300 / D1*100%. The test results are shown in Table 2 below.

[0236] 12. Full cell volume expansion rate test

[0237] The battery was discharged to 2V at 0.1C and left to stand for 30 minutes, then fully charged to 4.4V at 0.33C and left to stand for 30 days. The battery's initial volume and volume after 30 days of standing were measured using the water displacement method to obtain the battery volume expansion rate. The volume expansion rate (%) = (volume after 30 days of standing / initial volume - 1) × 100%. The test results are shown in Table 2 below.

[0238] 13. Full-cell capacity retention test

[0239] Under constant temperature of 25℃, the battery was left to stand for 5 minutes, then discharged at 1 / 3C to 2.5V, left to stand for 5 minutes, charged at 1 / 3C to 4.5V, and then charged at 4.5V with constant voltage until the current ≤0.05mA. After standing for 5 minutes, the charged capacity was recorded as C0. Then, the battery was discharged at 1 / 3C to 2.8V, and the discharged capacity was recorded as the initial specific capacity, recorded as D0. The battery was then charged at a constant current of 0.33C to 4.5V and then charged with constant voltage until the current ≤0.05mA. After standing for 5 minutes, the battery was placed in a high and low temperature chamber at 60℃ and left to stand for 1 hour until the battery temperature reached the target temperature before storage. After 15 days, the battery was removed and the above process was repeated under constant temperature of 25℃, with the capacity Dn (n=0,1,2…) recorded every 15 days. The capacity retention rate after 60 days of storage was calculated as (D4-D0) / D0*100%. The test results are shown in Table 2 below.

[0240] Table 2

[0241]

[0242]

[0243]

[0244] Note: The contents in Table 2 are based on the total weight of the matrix powder.

[0245] The comparative examples show that Comparative Examples 1 and 2 indicate that the un-acid-washed materials have poor stress and oxygen defects, which easily leads to decreased material stability and insufficient specific capacity, resulting in deterioration of long-term storage and gas generation performance. Comparative Examples 1 and 3 show that the material stability is improved after coating, but the resulting decrease in lithium-ion kinetics leads to a relatively average specific capacity. Comparative Examples 1 and 4 show that the acidity of the organic acid is too high. Even if the capacity increases after treatment, the deterioration of storage and gas generation performance due to the increase in specific surface area is serious. Comparative Examples 1 and 5 show that the coating material with a high melting temperature has a poor coating effect at low temperatures and does not significantly improve the material.

[0246] As can be seen from the examples, by rationally selecting the type of organic acid, acid pH, pickling time, coating material, coating amount, sintering time, etc., the surface of the material can be improved, the interface can be stabilized, the side reactions between the material and the electrolyte can be reduced, and the micro-stress and oxygen defects can be improved, thus improving the storage and gas generation performance.

[0247] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A lithium-rich manganese-based positive electrode material, characterized in that, Comprising: Li[Li x Ni a Co b Mn c M d ]O2, wherein x + a + b + c + d = 1, x > 0, c > 0, 0 < b < 0.1, and M includes one or more of V, Nb, Ta, Cr, Mo, B, Al, Ti, Zr, Mg, Ce, Fe, and Sn. The specific surface area of the base powder is 0.6-4 m 2 / g; The lithium-rich manganese-based positive electrode material satisfies the following conditions: (1) the oxygen defect index of the lithium-rich manganese-based positive electrode material is 1.96 or more, and the oxygen defect index = I101 / I102 wherein I101 and I102 represent the (101) crystal face diffraction peak intensity value and the (102) crystal face diffraction peak intensity value of the lithium-rich manganese-based positive electrode material in the XRD diffraction chart, respectively. (2) the micro stress of the lithium-rich manganese-based positive electrode material is 0.1% to 2%, the micro stress = (β hkl *Cosθ hkl ) / (4sinθ hkl ), wherein θ hkl is the diffraction angle of the (hkl) crystal face of the lithium-rich manganese-based positive electrode material in the XRD diffraction chart, and β hkl is the half-height width of the (hkl) crystal face of the lithium-rich manganese-based positive electrode material in the XRD diffraction chart.

2. The lithium-rich manganese-based positive electrode material according to claim 1, characterized in that, The specific surface area of the base powder is 1.0-1.7 m 2 / g. 3.The lithium-rich manganese-based cathode material of claim 1 or 2, characterized in that, The residual alkali amount on the surface of the base powder is 550-1200 ppm based on the total weight of the base powder, and the residual lithium amount on the surface of the base powder is 300-1000 ppm. 4.The lithium-rich manganese-based cathode material of claim 1 or 2, characterized in that, Further comprising: A coating layer coated on the surface of the base powder, the coating layer comprising one or more coating elements of Zr, F, B and Al.

5. The lithium-rich manganese-based positive electrode material according to claim 4, characterized in that, The content of each of the coating elements is 0-10000 ppm based on the total weight of the base powder, and the total content of the coating elements is greater than 0. 6.The lithium-rich manganese-based cathode material of claim 4, characterized in that, The thickness of the coating layer is 0.1-3 μm.

7. The lithium-rich manganese-based positive electrode material of claim 4, wherein, The coating elements comprise Zr, F and B; Or, the coating elements comprise Zr, F and Al.

8. The lithium-rich manganese-based positive electrode material according to claim 7, characterized in that, The molar ratio of Zr, F and B is 1:(3.5-4.5):(0.01-0.5). 9.The lithium-rich manganese-based cathode material of claim 7, wherein, The molar ratio of Zr, F and Al is 1:(3.5-4.5):(0.01-0.5).

10. The lithium-rich manganese-based positive electrode material according to claim 1 or 2, characterized in that, The particle size distribution SPAN of the lithium-rich manganese-based positive electrode material is (Dv90-Dv10) / Dv50, and SPAN is in the range of 0.7-1.

8.

11. A method of producing the lithium-rich manganese-based positive electrode material according to any one of claims 1 to 10, characterized in that, Comprising the following steps: The base powder is acid treated using an acid solution, wherein the acid solution comprises an organic acid and / or an acid salt thereof, the base powder having a chemical formula of Li[Li x Ni a Co b Mn c M d ]O2, wherein x + a + b + c + d = 1, x > 0, c > 0, 0 < b < 0.1, and M comprises one or more of V, Nb, Ta, Cr, Mo, B, Al, Ti, Zr, Mg, Ce, Fe, and Sn.

12. The method of claim 11, wherein, The pH value of the acid solution is ≥2 and <7.

13. The preparation method according to claim 11, characterized in that, The organic acid comprises citric acid, and the acid salt comprises one or more of ammonium citrate, hydrogen ammonium citrate, and hydrogen diammonium citrate.

14. The method of claim 11, wherein, The acid treatment time is 0.25-4 h.

15. The method of claim 11, wherein, Further comprising: Mixing the base powder after acid treatment with a coating material, and sintering, wherein the coating material comprises one or more coating elements of Zr, F, B and Al.

16. The method of claim 15, wherein, The coating material comprises one or more of zirconium boride, zirconium oxide, zirconium fluoride, aluminum boride, aluminum oxide, aluminum fluoride, and boric acid.

17. The preparation method according to claim 15, characterized in that, The sintering temperature is 400-550 ℃, and the sintering time is 8-12 h.

18. The method of claim 15, wherein, The base powder after acid treatment is washed with water before being mixed with the coating material.

19. The method of claim 11, wherein, The base powder is prepared by a method comprising the following steps: mixing a hydroxide precursor, a Li source, a Mn source, a Co source, an optional Ni source, and an optional M source, and sintering to obtain the base powder.

20. A positive electrode sheet characterized by comprising: The lithium-rich manganese-based positive electrode material according to any one of claims 1-10 or obtained by the preparation method according to any one of claims 11-19.

21. A secondary battery characterized by comprising: The positive electrode tab according to claim 20.

22. A battery module, comprising: The secondary battery according to claim 21.

23. A battery pack, characterized by The secondary battery according to claim 21 or the battery module according to claim 22.

24. An electrical device, comprising: At least one of the secondary battery according to claim 21, the battery module according to claim 22, and the battery pack according to claim 23.

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