Modified lithium-rich manganese positive electrode material, preparation method therefor, positive electrode sheet, secondary battery, battery module, and electrical device

Abstract

The present application relates to a modified lithium-rich manganese positive electrode material, comprising: a lithium-rich manganese matrix material; and a coating layer coated on a surface of the lithium-rich manganese matrix material. The coating layer comprises a first sublayer and a second sublayer. The first sublayer is closer to the lithium-rich manganese matrix material than the second sublayer. The material of the first sublayer comprises a sodium-doped lithium-rich manganese-based material, and the material of the second sublayer comprises a transition metal oxide mesoporous material.

Description

Modified lithium-rich manganese cathode materials and their preparation methods, cathode sheets, secondary batteries, battery modules and electrical devices Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a modified lithium-rich manganese cathode material and its preparation method, cathode sheet, secondary battery, battery module and power device. Background Technology

[0002] Secondary batteries are named for their ability to be cycled through charging and discharging. Among secondary batteries, lithium-ion batteries have advantages such as high voltage platform, good cycle performance, no memory effect, and high specific energy, making them the most widely used power batteries. With the development of smart grid energy storage and the continuous promotion of new energy vehicles, lithium-ion batteries have experienced rapid development, and at the same time, the market's performance requirements for lithium-ion batteries are becoming increasingly stringent.

[0003] Using high-capacity, high-voltage, and low-cost cathode materials is one of the key factors in obtaining low-cost, high-energy power batteries. Among the known cathode materials, lithium-rich manganese cathode materials have a discharge capacity as high as 300 mAh / g, far exceeding that of lithium iron phosphate cathode materials, ternary cathode materials, and other cathode materials. Therefore, lithium-rich manganese cathode materials are considered an ideal choice for the next generation of high-energy-density power batteries. However, they also have some drawbacks, such as low initial coulombic efficiency and severe gas production at high temperatures, which hinder their further commercialization and industrialization. Summary of the Invention

[0004] According to at least one embodiment of this application, a modified lithium-rich manganese cathode material is provided. This application also provides a method for preparing the modified lithium-rich manganese cathode material, as well as a cathode sheet containing the modified lithium-rich manganese cathode material, a secondary battery, a battery module, and an electrical device.

[0005] In a first aspect, a modified lithium-rich manganese cathode material is provided, the modified lithium-rich manganese cathode material comprising: a lithium-rich manganese matrix material, and a coating layer coated on the surface of the lithium-rich manganese matrix material;

[0006] The coating layer includes a first sublayer and a second sublayer. The first sublayer is closer to the lithium-rich manganese matrix material than the second sublayer. The material of the first sublayer includes a sodium-doped lithium-rich manganese matrix material, and the material of the second sublayer includes a transition metal oxide mesoporous material.

[0007] Optionally, the modified lithium-rich manganese cathode material satisfies at least one of the following conditions:

[0008] (1) The chemical formula of the sodium-doped lithium-rich manganese-based material is Li (m-x) Na x Ni a Mn (1-a)O b , where 1.20 ≤ m ≤ 1.40, 0.03 ≤ x ≤ 0.07, 0.30 ≤ a ≤ 0.40, 2.20 ≤ b ≤ 2.40;

[0009] (2) The molar ratio of sodium element to the sum of lithium and sodium elements is 1:46 to 1:17;

[0010] (3) The mass ratio of the transition metal oxide mesoporous material to the lithium-rich manganese matrix material is 0.05% to 0.20%;

[0011] (4) The transition metal oxide mesoporous material is selected from one or more of ZrO2, PbO2, MoO3, Fe2O3, TiO2 and V2O5;

[0012] (5) The chemical formula of the lithium-rich manganese matrix material is yLi2MnO3·(1 - y)LiMO2, where 0 < y < 1, and M is selected from one or more of Co, Nb, W, Zr, Sr, Al, La.

[0013] Second, a preparation method of a modified lithium-rich manganese cathode material is provided, including:

[0014] Preparing a lithium-rich manganese matrix material and forming a coating layer on the surface of the lithium-rich manganese matrix material;

[0015] Among them, the coating layer includes a first sub-layer and a second sub-layer. The first sub-layer is closer to the lithium-rich manganese matrix material than the second sub-layer. The material of the first sub-layer includes a sodium-doped lithium-rich manganese-based material, and the material of the second sub-layer includes a transition metal oxide mesoporous material.

[0016] Optionally, preparing a lithium-rich manganese-based matrix material and forming a coating layer on the surface of the lithium-rich manganese matrix material includes:

[0017] Blending a nickel-manganese precursor with a lithium salt, a sodium salt and a dopant and performing a first sintering to obtain a first sintered product;

[0018] Corroding the first sintered product with an acidic solution to obtain a pickled product, and the pickled product includes a lithium-rich manganese matrix material and a first sub-layer coated on the surface of the lithium-rich manganese matrix material;

[0019] Mixing the pickled product with a transition metal oxide mesoporous material and performing a second sintering to obtain the modified lithium-rich manganese cathode material.

[0020] Optionally, the nickel-manganese precursor is selected from at least one of Ni a Mn (1-a) CO3 and Ni a Mn (1-a) (OH)2, where 0.30 ≤ a ≤ 0.40; and / or,

[0021] The lithium salt is selected from one or both of Li₂CO₃ and LiOH; and / or,

[0022] The sodium salt is selected from one or more of Na₂CO₃, NaCl, Na₂SO₄, CH₃COONa, and Na₂C₂O₄; and / or,

[0023] The dopant is selected from at least one of oxides, hydroxides, and sulfides of metal M, wherein M is selected from one or more of Co, Nb, W, Zr, Sr, Al, and La; and / or,

[0024] The acid in the acidic solution is selected from one or more of sulfuric acid, oxalic acid, and boric acid; and / or,

[0025] The transition metal oxide mesoporous material is selected from one or more of ZrO2, PbO2, MoO3, Fe2O3, TiO2, and V2O5.

[0026] Optionally, the first sintering temperature is 800℃~950℃, and the time is 10h~15h; and / or,

[0027] The second sintering temperature is 300℃~600℃, and the time is 5h~10h.

[0028] Thirdly, a positive electrode sheet is provided, comprising: a modified lithium-rich manganese positive electrode material as described in the first aspect, or a modified lithium-rich manganese positive electrode material prepared by the preparation method described in the second aspect.

[0029] Fourthly, a secondary battery is provided, comprising a positive electrode, a separator, and a negative electrode stacked together, wherein the positive electrode is the positive electrode as described in the third aspect.

[0030] Fifthly, a battery module is provided, comprising a plurality of batteries connected in series and / or in parallel, wherein at least one battery is a secondary battery as described in the fourth aspect.

[0031] In a sixth aspect, an electrical device is provided, comprising a battery module as described in the fifth aspect.

[0032] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the disclosed drawings without creative effort.

[0034] Figure 1 is a cross-sectional view of a modified lithium-rich manganese cathode material provided in an embodiment of this application;

[0035] Figure 2 is a scanning electron microscope image of the modified lithium-rich manganese cathode material provided in Example 1 of this application;

[0036] Figure 3 is a scanning electron microscope image of the modified lithium-rich manganese cathode material provided in Comparative Example 3 of this application. Detailed Implementation

[0037] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0038] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as open-ended and encompassing, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "exemplary," or "some examples," etc., are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0039] This document describes exemplary embodiments with reference to cross-sectional views and / or plan views, which are idealized exemplary drawings. In the drawings, the thickness of layers and regions is enlarged for clarity. Therefore, variations in shape relative to the drawings are contemplated due to, for example, manufacturing techniques and / or tolerances. Thus, exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing processes. For example, etched regions shown as rectangular would typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to show the actual shapes of the regions of the device, nor are they intended to limit the scope of the exemplary embodiments.

[0040] In this document, unless otherwise stated, "one or more" means one or more.

[0041] In this document, terms such as "for example," "like," "example," and "exemplary" are used for descriptive purposes to indicate a connection in the content covered by different technical solutions presented earlier and later. However, they should not be construed as limitations on the preceding technical solution or as restrictions on the scope of protection of this document. In this document, unless otherwise specified, A (like B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0042] In this article, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "options" in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "option" is independent.

[0043] In this document, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features.

[0044] 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 the application.

[0045] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0046] In this article, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of the selectable numerical values within this numerical interval is considered continuous, and it includes the two numerical endpoints of this numerical interval (i.e., the minimum value and the maximum value), as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within this numerical interval, it includes the two endpoint integers of this numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When providing multiple numerical ranges to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed in this article should be understood to include any and all sub-ranges subsumed therein. The "numerical values" in this numerical interval can be any quantitative values, such as numbers, percentages, ratios, etc. The "numerical interval" is allowed to broadly include numerical interval types such as percentage intervals, ratio intervals, and ratio value intervals.

[0047] In this article, when a method process involves multiple steps, unless there are clear different descriptions in this article, the execution of these steps has no strict order limit, and it can be executed in other orders than the described one. Moreover, any step can include multiple sub-steps or multiple stages. These sub-steps or stages do not necessarily need to be completed at the same moment, but can be executed at different moments, and their execution order does not necessarily need to be sequential, but can be executed alternately or simultaneously with other steps or a part of the sub-steps or stages of other steps.

[0048] The lithium-rich manganese-based material yLi2MnO3·(1-y)LiMO2 (0 < y < 1, M = transition metals such as Ni, Co, Mn and their combinations, hereinafter referred to as LMR) uses inexpensive manganese as the main transition metal element, and its discharge specific capacity can reach more than 250 mAh / g, so it has attracted extensive attention from researchers. Compared with commercial cathode materials such as lithium manganate (LMO), lithium iron phosphate (LFP), lithium cobalt oxide (LCO), lithium nickel cobalt manganese oxide (NCM) and lithium nickel cobalt aluminum oxide (NCA), LMR has a higher energy density. However, since this material was discovered nearly 30 years ago, it has never been truly commercially applied. The main reasons are as follows: ① During the cycling process, Mn 3+ migrates into the lithium vacancies, causing the layered structure to transform into a spinel structure, resulting in a continuous decrease in the average discharge voltage, serious energy loss and posing a huge challenge to battery management; ② The low electronic conductivity of Li2MnO3 makes the LMR material have poor rate performance; ③ The density of the LMR material is relatively low, resulting in a relatively low volumetric energy density of the material; ④ The LMR material needs to operate at a high voltage (>4.55 V) to exhibit high capacity, but at high voltages, the electrolyte is prone to oxidative decomposition, and at the same time, lattice oxygen is oxidized to O2 and escapes, resulting in a large irreversible capacity loss and a decrease in the initial Coulomb efficiency.

[0049] Therefore, how to provide a lithium-rich manganese cathode material that can improve initial coulombic efficiency, cycle performance, rate performance, high-temperature storage performance, and effectively alleviate voltage drop and oxygen release during cycling has become an urgent technical problem to be solved.

[0050] To address the above-mentioned technical problems, in a first aspect, some embodiments of this application provide a modified lithium-rich manganese cathode material, as shown in FIG1. ​​The modified lithium-rich manganese cathode material includes: a lithium-rich manganese substrate material 1, and a coating layer 2 covering the surface of the lithium-rich manganese substrate material 1. The coating layer 2 includes a first sublayer 21 and a second sublayer 22. The first sublayer 21 is closer to the lithium-rich manganese substrate material 1 than the second sublayer 22. The material of the first sublayer 21 includes a sodium-doped lithium-rich manganese substrate material, and the material of the second sublayer 22 includes a transition metal oxide mesoporous material.

[0051] The inventors of this application have discovered that by surface coating the lithium-rich manganese substrate material 1, since the coating layer 2 includes a first sublayer 21 and a second sublayer 22, with the first sublayer 21 being closer to the lithium-rich manganese substrate material 1 than the second sublayer 22, and the material of the first sublayer 21 comprising a sodium-doped lithium-rich manganese substrate material, and the material of the second sublayer 22 comprising a transition metal oxide mesoporous material, therefore, in a first aspect, the coating layer 2 can effectively suppress side reactions between the lithium-rich manganese substrate material and the electrolyte, improve the surface structural stability of the lithium-rich manganese substrate material, reduce surface oxygen loss, and suppress SEI (Solid Electrolyte). The interphase (solid electrolyte interface) layer continues to grow during cycling; secondly, the sodium-doped lithium-rich manganese material in the first sublayer 21 of the coating layer 2 can, on the one hand, impart a higher lithium-ion diffusion rate to the modified lithium-rich manganese cathode material, thereby improving rate performance and cycle performance; on the other hand, while maintaining the lithium-rich manganese matrix material 1 with lithium-rich manganese two phases (i.e., Li2MnO3 phase and LiMO2 phase), it can replace part of the high-cost lithium salt with low-cost sodium salt, thereby effectively reducing costs; thirdly, the transition metal oxide mesoporous material in the second sublayer 22 of the coating layer 2 has an adsorption effect on O2 released during the redox reaction between the inner first sublayer 21 and the lithium-rich manganese matrix material 1, which can reduce irreversible oxygen loss, thereby effectively improving the first coulombic efficiency, cycle performance, rate performance, high-temperature storage performance, and effectively mitigating voltage drop and O2 release.

[0052] The chemical formula of the aforementioned lithium-rich manganese matrix material is not specifically limited, and all lithium-rich manganese materials with lithium-rich manganese two phases are within the scope of protection of this application.

[0053] In some embodiments, the chemical formula of the lithium-rich manganese matrix material 1 is yLi2MnO3·(1-y)LiMO2, where 0 < y < 1, and M is selected from one or more of Co, Nb, W, Zr, Sr, Al, and La.

[0054] In these embodiments, the lithium-rich manganese matrix material is doped with one or more elements of Co, Nb, W, Zr, Sr, Al, and La, which can effectively regulate the properties of the lithium-rich manganese matrix material. For example, through research, it is found that: Al doping can inhibit cation migration and the transformation of the layered structure into the spinel structure, reduce the cyclic voltage drop of the material, and improve the capacity and cyclic performance. W doping increases the layer spacing of the structure of the lithium-rich manganese matrix material, promotes the diffusion of lithium ions, reduces the electrochemical impedance of the lithium-rich manganese matrix material, and effectively improves the cyclic stability and rate performance of the lithium-rich manganese matrix material. The Nb element stabilizes the structure of the lithium-rich manganese matrix material and inhibits the increase of its impedance. La doping can not only broaden the lithium ion transport channels but also stabilize the structure of the lithium-rich manganese matrix material.

[0055] In some embodiments, the chemical formula of the above sodium-doped lithium-rich manganese-based material is Li (m-x) Na x Ni a Mn (1-a) O b , where 1.20 ≤ m ≤ 1.40, 0.03 ≤ x ≤ 0.07, 0.30 ≤ a ≤ 0.40, and 2.20 ≤ b ≤ 2.40.

[0056] In these embodiments, the sodium doping in the sodium-doped lithium-rich manganese-based material in the first sublayer is at the Li site, which can effectively increase the lithium ion diffusion coefficient and delay the formation of the spinel phase, thereby improving the capacity retention rate and rate performance. At the same time, the doping of sodium ions can also reduce the cost.

[0057] In some embodiments, the molar ratio of sodium element to the sum of lithium and sodium elements is 1:46 to 1:17.

[0058] In these embodiments, by controlling the molar ratio of the sodium-doped lithium-rich manganese-based material to the lithium-rich manganese matrix material within the range of 1:19 to 1:9, it is possible to ensure that no impurity phase is generated and a better two-phase structure is formed.

[0059] In some embodiments, the mass ratio of the transition metal oxide mesoporous material to the lithium-rich manganese matrix material is 0.05% to 0.20%.

[0060] In these embodiments, the transition metal oxide mesoporous material accounts for 0.05% to 0.20% of the mass of the lithium-rich manganese matrix material, which means that, based on 100 parts by weight of the lithium-rich manganese matrix material, the transition metal oxide mesoporous material accounts for 0.05 to 0.20 parts by weight.

[0061] In some embodiments, the transition metal oxide mesoporous material is selected from one or more of ZrO2, PbO2, MoO3, Fe2O3, TiO2, and V2O5.

[0062] In these embodiments, these materials can adsorb O2 released during the redox reaction of the inner layer, thereby reducing oxygen ion loss and stabilizing the internal structure. For example, when ZrO2 is used as the second sublayer for coating, the synergistic effect of the double coating can effectively reduce electrochemical polarization, structural changes, and surface side reactions during cycling, thereby effectively improving the discharge capacity, cycle performance, and rate performance of the modified lithium-rich manganese cathode material. TiO2 surface coating can physically block the inner lithium-rich manganese matrix material and the first sublayer from contact with the electrolyte, preventing high-valence metal cations such as Mn from the surface of the lithium-rich manganese matrix material and the first sublayer. 3+ It reacts with reactive oxygen species such as Li2O in the electrolyte and can inhibit the corrosion of the inner lithium-rich manganese matrix material and the first sublayer by electrolyte decomposition products, thereby improving the cycle performance and high-temperature storage performance of the modified lithium-rich manganese cathode material.

[0063] Secondly, some embodiments of this application provide a method for preparing a modified lithium-rich manganese cathode material, the method comprising:

[0064] A lithium-rich manganese matrix material is prepared, and a coating layer is formed on the surface of the lithium-rich manganese matrix material;

[0065] The coating layer includes a first sublayer and a second sublayer. The first sublayer is closer to the lithium-rich manganese matrix material than the second sublayer. The material of the first sublayer includes a sodium-doped lithium-rich manganese matrix material, and the material of the second sublayer includes a transition metal oxide mesoporous material.

[0066] In some embodiments, preparing a lithium-rich manganese-based matrix material and forming a coating layer on the surface of the lithium-rich manganese-based matrix material includes:

[0067] S11) The nickel-manganese precursor is blended with lithium salt, sodium salt and dopant and subjected to first sintering to obtain the first sintered product;

[0068] S12) The first sintered product is etched with an acidic solution to prepare an acid pickling product, which includes a lithium-rich manganese matrix material and a first sublayer coated on the surface of the lithium-rich manganese matrix material.

[0069] S13) The pickling product is mixed with a transition metal oxide mesoporous material and subjected to a second sintering to obtain a modified lithium-rich manganese cathode material.

[0070] In the preparation method of the modified lithium-rich manganese cathode material provided in this application embodiment, a nickel-manganese precursor is blended with lithium salt, sodium salt, and dopant and subjected to a first sintering. A portion of the high-cost lithium salt is replaced with low-cost sodium salt. This ensures that the lithium-rich manganese matrix material can form a lithium-rich manganese two-phase structure while simultaneously forming a lithium-sodium composite material on the surface of the lithium-rich manganese matrix material, thereby improving the lithium-ion diffusion rate. This ensures both high material performance and cost advantages. By etching the first sintering product with an acidic solution, an etched morphology is formed on the surface of the first sintering product, reducing residual alkali on the surface of the lithium-rich manganese matrix material and forming a porous structure, facilitating lithium-ion insertion and extraction. Subsequently, the acid-washed product with the porous structure is subjected to a first sintering process... The transition metal oxide mesoporous material is blended and then subjected to a second sintering. During the second sintering process, the anionic groups on the surface of the lithium-rich manganese matrix material form a complex structure with the transition metal oxide mesoporous material, making the modified lithium-rich manganese cathode material more stable. At the same time, the transition metal oxide mesoporous material can form a more complete coating on the surface of the pickling product, thereby better suppressing the side reactions between the electrolyte and the lithium-rich manganese matrix material, further improving the structural stability of the modified lithium-rich manganese cathode material. Meanwhile, the transition metal oxide mesoporous material has an adsorption effect on active oxygen substances such as O2 generated by the decomposition of Li2O generated in the inner layer (such as pickling products), which can reduce irreversible oxygen loss and thus improve the first coulombic efficiency of the battery.

[0071] In some embodiments, in S11), the nickel-manganese precursor is selected from Ni a Mn (1-a) CO3 and Ni a Mn (1-a) At least one of (OH)2, wherein 0.30 ≤ a ≤ 0.40.

[0072] In some embodiments, the lithium salt is selected from one or both of Li2CO3 and LiOH.

[0073] In some embodiments, the sodium salt is selected from one or more of Na2CO3, NaCl, Na2SO4, CH3COONa, and Na2C2O4.

[0074] In these embodiments, one or more of Na2CO3, NaCl, Na2SO4, CH3COONa, and Na2C2O are used as sodium salts, which can be melted at low temperatures.

[0075] In some embodiments, the doped precursor is selected from at least one of oxides, hydroxides and sulfides of metal M, and M is selected from one or more of Co, Nb, W, Zr, Sr, Al and La.

[0076] For example, the oxide of the metal M may include: CoO3, Nb2O, WO2, ZrO2, SrO2, Al2O3 and La2O3, etc.

[0077] In some embodiments, the temperature of the first sintering is 800°C to 950°C, and the time is 10h to 15h.

[0078] In these embodiments, by controlling the temperature of the first sintering to be 800°C to 950°C and the time to be 10h to 15h, the grain growth can be more complete and the crystallinity can be higher.

[0079] In some embodiments, in S12), the acid in the acidic solution may be selected from one or more of sulfuric acid, oxalic acid, and boric acid.

[0080] In these embodiments, the use of one or more of sulfuric acid, oxalic acid, and boric acid can effectively neutralize the residual alkali on the surface of the first sintered product and has a certain etching effect on the first sintered product, resulting in a porous structure on the surface of the first sintered product. This increases the porosity of the lithium-rich manganese matrix material and the first sublayer, thereby benefiting Li + Rapid insertion and extraction.

[0081] In some embodiments, in S13), the transition metal oxide mesoporous material is selected from one or more of ZrO2, PbO2, MoO3, Fe2O3, TiO2, and V2O5.

[0082] In these embodiments, the transition metal oxide mesoporous material can uniformly coat the surface of the first sublayer, preventing the inner first sublayer and the lithium-rich manganese matrix material from reacting with the electrolyte, and can absorb the released O2, reducing the safety hazards caused by gas generation.

[0083] In some embodiments, the second sintering temperature is 300°C to 600°C, and the time is 5 to 10 hours.

[0084] In these embodiments, by controlling the temperature of the second sintering to be 300℃~600℃ and the time to be 5~10h, the water of crystallization and possible organic groups such as oxalic acid residual groups in the dried lithium-rich manganese matrix material can be removed, resulting in a modified lithium-rich manganese cathode material with good processing performance and good batch stability.

[0085] Thirdly, some embodiments of this application provide a positive electrode sheet, which may include: a modified lithium-rich manganese positive electrode material as described in the first aspect, or a modified lithium-rich manganese positive electrode material prepared by the preparation method described in the second aspect.

[0086] Fourthly, some embodiments of this application provide a secondary battery, which includes a positive electrode, a separator, and a negative electrode stacked together, wherein the positive electrode is the positive electrode as described in the third embodiment.

[0087] Fifthly, some embodiments of this application provide a battery module comprising a plurality of batteries connected in series and / or in parallel, wherein at least one battery is a secondary battery as described in the fourth aspect.

[0088] Sixthly, some embodiments of this application provide an electrical device that includes a battery module as described in the fifth aspect.

[0089] The electrical devices include, but are not limited to: laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries or lithium-ion capacitors, etc.

[0090] In order to objectively evaluate the technical effects of this application, the application will be described in detail through the following embodiments and comparative examples.

[0091] In the following examples and comparative examples, all raw materials were commercially available, and to maintain the reliability of the experiments, the raw materials used in the following examples and comparative examples had the same physical and chemical parameters or were prepared by the same processing method.

[0092] Example 1

[0093] Example 1 provides a modified lithium-rich manganese cathode material, the molecular formula of which is ZrO2@Li 1.184 Na 0.051 Ni 0.40 Mn 0.60 O 2.235 @Li 1.30 Ni 0.40 Mn 0.60 W 0.00085 O 2.30 Its preparation method includes the following steps:

[0094] (1) Ni manganese hydroxide precursor Ni 0.40 Mn 0.60 (OH)2, Li2CO3, Na2SO4, Na2C2O4 and dopant (WO3) are uniformly mixed. The molar ratio of the sum of lithium and sodium elements to the sum of nickel and manganese elements is 1.30:1, and the molar ratio of sodium element to the sum of lithium and sodium elements is 1:32.

[0095] (2) The mixture obtained in step (1) is sintered at 950℃ for 12 hours. The sintered product is then sieved to obtain the first sintered product Li, which has uniform particle dispersion and good flowability. 1.219 Na 0.081 Ni 0.40 Mn 0.60 O 2.30 @Li 1.30 Ni 0.40 Mn 0.60 W 0.00085 O 2.30 ;

[0096] (3) Place the first sintered product obtained after step (2) in H + The product was pickled in an acidic solution of oxalic acid and sulfuric acid at a concentration of 0.8 mol / L for 15 min. The pickling product was filtered and then baked in an oven at 150℃ for 12 h to obtain the pickling product.

[0097] (4) The acid-washed product obtained in step (3) is mixed with ZrO2 nanopowder, wherein the mass of ZrO2 nanopowder is 0.15% of the mass of the dried product. After sintering at 500℃ for 8 hours, the sintered product is sieved to obtain a low-cost, high-performance lithium-rich manganese ZrO2@Li with uniform particle dispersion and good flowability. 1.184 Na 0.051 Ni 0.40 Mn 0.60 O 2.235 @Li 1.30 Ni 0.40 Mn 0.60 W 0.00085 O 2.30 .

[0098] Example 2

[0099] The modified lithium-rich manganese cathode material provided in Example 2 has the molecular formula ZrO2@Li 1.215 Na 0.11 Ni 0.30 Mn 0.70 O 2.325 @Li 1.40 Ni 0.30 Mn0.70 W 0.00085 O 2.40 The preparation method is basically the same as in Example 1, except that:

[0100] In step (1), Ni a Mn (1-a) (OH)2 is replaced with Ni a Mn (1-a) CO3, where a is 0.3, the molar ratio of the sum of lithium and sodium to the sum of nickel and manganese is 1.40:1, and the molar ratio of sodium to the sum of lithium and sodium is 1:20.

[0101] In step (2), the mixture is sintered at 850℃ for 10 hours;

[0102] In step (4), the mass of ZrO2 is 0.05% of the mass of the dried product, the sintering temperature is 300℃, and the time is 10h.

[0103] Example 3

[0104] The modified lithium-rich manganese cathode material provided in Example 3 has the molecular formula ZrO2@Li 1.17 Na 0.03 Ni 0.35 Mn 0.65 O 2.20 @Li 1.26 Ni 0.35 Mn 0.65 W 0.00085 O 2.26 The preparation method is basically the same as in Example 1, except that:

[0105] In step (1) Ni a Mn (1-a) In (OH)2, the value of a is 0.35, the molar ratio of the sum of lithium and sodium to the sum of nickel and manganese is 1.26:1, and the molar ratio of sodium to the sum of lithium and sodium is 1:42.

[0106] In step (2), the mixture is sintered at 800℃ for 15 hours;

[0107] In step (4), the mass of ZrO2 is 0.20% of the mass of the dried product, the sintering temperature is 600℃, and the time is 5h.

[0108] Example 4

[0109] The modified lithium-rich manganese cathode material provided in Example 4 has the molecular formula ZrO2@Li. 1.17 Na 0.03 Ni 0.30 Mn 0.70 O 2.20 @Li 1.26Ni 0.30 Mn 0.70 W 0.00085 O 2.26 The preparation method is basically the same as in Example 1, except that:

[0110] In step (1), Ni a Mn (1-a) (OH)2 is replaced with Ni a Mn (1-a) CO3, where a is 0.3, the molar ratio of the sum of lithium and sodium to the sum of nickel and manganese is 1.26:1, the molar ratio of sodium to the sum of lithium and sodium is 1:42, and Na2SO4 is replaced with Na2CO3.

[0111] Example 5

[0112] This embodiment provides a method for preparing a modified lithium-rich manganese cathode material, which differs from the method in Example 1 in that:

[0113] In step (1), Na2SO4 is replaced with NaCl and Na2C2O4 is replaced with CH3COONa.

[0114] Example 6

[0115] This embodiment provides a method for preparing a modified lithium-rich manganese cathode material, which differs from the method in Example 1 in that:

[0116] In step (3), the acid in the acidic solution is replaced with oxalic acid and boric acid.

[0117] Example 7

[0118] This embodiment provides a method for preparing a modified lithium-rich manganese cathode material, which differs from the method in Example 1 in that:

[0119] No acid washing was performed in step (3), and the resulting modified lithium-rich manganese cathode material has the molecular formula ZrO2@Li. 1.219 Na 0.081 Ni 0.40 Mn 0.60 O 2.30 @Li 1.30 Ni 0.40 Mn 0.60 W 0.00085 O 2.30 .

[0120] Comparative Example 1

[0121] This comparative example provides a method for preparing a modified lithium-rich manganese cathode material, the difference of which is that the preparation method differs from that in Example 1:

[0122] In step (1), Na2SO4 and Na2C2O4 are removed, and the molar ratio of lithium to nickel and manganese in the raw materials is adjusted to 1.30:1. The resulting modified lithium-rich manganese cathode material has the molecular formula ZrO2@Li. 1.24 Ni 0.40 Mn 0.60 W 0.00085 O 2.24 .

[0123] Comparative Example 2

[0124] This comparative example provides a method for preparing a modified lithium-rich manganese cathode material, the difference of which is that the preparation method differs from that in Example 1:

[0125] Removing step (4), the molecular formula of the resulting modified lithium-rich manganese cathode material is Li. 1.184 Na 0.051 Ni 0.40 Mn 0.60 O 2.235 @Li 1.30 Ni 0.40 Mn 0.60 W 0.00085 O 2.30 .

[0126] Test case

[0127] 1. The appearance morphology of the modified lithium-rich manganese cathode materials provided in Example 1 and Comparative Example 2 was observed using a scanning electron microscope. Figure 2 shows a scanning electron microscope image of the modified lithium-rich manganese cathode material provided in Comparative Example 2 without the coating of transition metal oxide mesoporous material. Figure 3 shows a scanning electron microscope image of the modified lithium-rich manganese cathode material with double coating provided in Example 1.

[0128] 2. The modified lithium-rich manganese cathode materials provided in Examples 1-6 and Comparative Examples 1-3 were mixed with conductive carbon black and PVDF at a mass ratio of 80:10:10 to prepare cathode sheets. The compaction density of the cathode materials was 2.55 g / cc to 2.65 g / cc. Then, these cathode sheets were used to prepare coin cells, with lithium metal as the negative electrode and a 1 mol / L LiPF6 solution as the electrolyte. Charge-discharge tests were conducted on the coin cells at 25°C, a voltage range of 2.5 V to 4.55 V, and at 0.1 C. The test results are shown in Table 1 below. In the electrolyte, LiPF6 was used as the electrolyte, and the solvent was a mixture of DMC, EMC, and EC (DMC, EMC, and EC in a volume ratio of 1:1:1). The compaction density was tested by loading 2 g of cathode material powder into a mold, applying a pressure of 20 kN to the powder and holding it at that pressure for a period of time, and calculating the compaction density based on the volume-to-mass ratio.

[0129] Table 1

[0130] As shown in Table 1, compared with Comparative Example 1 and Comparative Example 2, the modified lithium-rich manganese cathode materials provided in Examples 1 to 7 have higher initial discharge specific capacity and initial coulombic efficiency, while the gas production is smaller, indicating that the electrochemical performance of the modified lithium-rich manganese cathode materials provided in the examples of this application has been greatly improved.

[0131] Compared to Examples 1-6, Example 7 did not use acidic solution etching, resulting in a decrease in both its initial discharge specific capacity and initial coulombic efficiency. Examples 1-6, after acidic solution etching, effectively reduced the residual alkali content on the surface and formed a porous structure on the lithium-rich manganese matrix. This improved battery capacity, increasing both the initial discharge specific capacity and initial coulombic efficiency. Furthermore, the porous structure facilitated lithium-ion insertion and extraction, enhancing lithium-ion transport performance and thus improving cycle performance and rate capability. Simultaneously, compared to Example 7 without acid washing, the second sublayer coating in Examples 1-6 was more complete, further reducing gas production.

[0132] Compared to Example 1, Comparative Example 1 did not have a first sublayer coated. Although the gas production was reduced, the first discharge specific capacity and the first coulombic efficiency were significantly reduced, which was not conducive to the effective utilization of the battery capacity.

[0133] Compared to Example 1, Comparative Example 2 did not have a second sublayer, resulting in a significant amount of gas production. This made it impossible to effectively suppress the side reactions between the lithium-rich manganese matrix material and the electrolyte, leading to poor structural stability of the modified lithium-rich manganese cathode material and preventing the battery capacity from being fully utilized.

[0134] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0135] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A modified lithium-rich manganese cathode material, comprising: A lithium-rich manganese-based material, and a coating layer coated on a surface of the lithium-rich manganese-based material; The coating layer comprises a first sub-layer and a second sub-layer, the first sub-layer is closer to the lithium-rich manganese-based material than the second sub-layer, the material of the first sub-layer comprises a sodium-doped lithium-rich manganese-based material, and the material of the second sub-layer comprises a transition metal oxide mesoporous material.

2. The modified lithium-rich manganese cathode material of claim 1, wherein, The modified lithium-rich manganese positive electrode material satisfies at least one of the following conditions: (1) the sodium-doped lithium-rich manganese-based material has a chemical formula of Li (m-x) Na x Ni a Mn (1-a) O b wherein 1.20≤m≤1.40, 0.03≤x≤0.07, 0.30≤a≤0.40, 2.20≤b≤2.40; (2) The molar ratio of sodium element to the sum of lithium and sodium elements is 1:46-1:17; (3) The mass ratio of the transition metal oxide mesoporous material to the lithium-rich manganese-based material is 0.05%-0.20%; (4) The transition metal oxide mesoporous material is selected from one or more of ZrO2, PbO2, MoO3, Fe2O3, TiO2, and V2O5; (5) The chemical formula of the lithium-rich manganese-based material is yLi2MnO3·(1-y)LiMO2, wherein 0 3. A method of preparing a modified lithium-rich manganese cathode material, wherein, It comprises: Preparation of a lithium-rich manganese-based material, and formation of a coating layer on a surface of the lithium-rich manganese-based material; The coating layer comprises a first sub-layer and a second sub-layer, the first sub-layer is closer to the lithium-rich manganese-based material, the material of the first sub-layer comprises a sodium-doped lithium-rich manganese-based material, the material of the second sub-layer comprises a transition metal oxide mesoporous material.

4. The method of preparing a modified lithium-rich manganese cathode material according to claim 3, wherein, Preparation of a lithium-rich manganese-based material, and formation of a coating layer on a surface thereof, comprises: Mixing a nickel-manganese precursor with a lithium salt, a sodium salt, and a dopant, and performing first sintering to obtain a first sintering product; Corrosion of the first sintering product with an acidic solution to prepare an acid-washed product; the acid-washed product comprises a lithium-rich manganese-based material and the first sub-layer coated on a surface of the lithium-rich manganese-based material; Mixing the acid-washed product with a transition metal oxide mesoporous material and performing second sintering to obtain the modified lithium-rich manganese positive electrode material.

5. The preparation method of the modified lithium-rich manganese positive electrode material according to claim 4, wherein The nickel-manganese precursor is selected from Ni a Mn (1-a) CO3and Ni a Mn (1-a) at least one of (OH)2, wherein 0.30 < a < 0.40; and / or, The lithium salt is selected from one or both of Li2CO3 and LiOH; and / or The sodium salt is selected from one or more of Na2CO3, NaCl, Na2SO4, CH3COONa, and Na2C2O4; and / or The dopant is selected from at least one of an oxide, a hydroxide, and a sulfide of a metal M, the M being selected from one or more of Co, Nb, W, Zr, Sr, Al, and La; and / or The acid in the acidic solution is selected from one or more of sulfuric acid, oxalic acid, and boric acid; and / or The transition metal oxide mesoporous material is selected from one or more of ZrO2, PdO2, MoO3, Fe2O3, TiO2, and V2Os.

6. The preparation method of the modified lithium-rich manganese positive electrode material according to claim 4 or 5, wherein The temperature of the first sintering is 800-950°C, and the time is 10-15h; and / or The second sintering temperature is 300-600 DEG C, and the time is 5-10 h.

7. A positive electrode sheet, wherein, Comprising: The modified lithium-rich manganese cathode material of any one of claims 1-2, or the modified lithium-rich manganese cathode material prepared by the preparation method of any one of claims 3-6.

8. A secondary battery, wherein Comprising a positive electrode sheet, a separator, and a negative electrode sheet which are stacked, the positive electrode sheet being the positive electrode sheet of claim 7.

9. A battery module, wherein, Comprising a plurality of batteries connected in series and / or in parallel, at least one battery being the secondary battery of claim 8.

10. An electrical device, comprising: Comprising the battery module of claim 9.

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